WO2004050454A1

WO2004050454A1 - Electric power steering device

Info

Publication number: WO2004050454A1
Application number: PCT/JP2003/007324
Authority: WO
Inventors: Kazuo Chikaraishi; Manabu Abe
Original assignee: Nsk Ltd.
Priority date: 2002-12-03
Filing date: 2003-06-10
Publication date: 2004-06-17
Also published as: GB0513542D0; DE10393833T5; GB2411874A; AU2003242156A1

Abstract

An electric power steering device in which auxiliary steering force can be outputted by an electric motor. Conical faces (723a, 723a) are provided on cylindrical rollers (723, 723) rolling along a rack shaft (610) so that the rollers can be assembled from an axial direction of a main body (721).

Description

TECHNICAL FIELD The present invention relates to an electric power steering apparatus, and more particularly to an electric power steering apparatus including a rack shaft and a pinion. 2. Description of the Related Art As one type of vehicle steering device, a pinion is combined with rack teeth of a rack shaft to convert the rotational force and the amount of rotation (steering horsepower) of the pinion into axial thrust and stroke of the rack shaft. Pinion type steering devices are known. Here, in a vehicle having a relatively light vehicle weight, a configuration in which a rack and pinion type steering device is incorporated in a so-called manual steering device that does not output auxiliary steering force may be used. In such a case, since the steered wheels must be driven only by the driver's steering, the stroke amount per one pinion (stroke ratio) is reduced to reduce the steering torque and, on the other hand, to reduce the steering amount. Set to be more. Further, in a rack holding mechanism for holding a rack, a holding mechanism for holding the rear surface of the rack shaft (opposite to the tooth side of the rack) is provided with a rolling rack guide (rotating and supporting) with a single mouth. As shown in Fig. 3, the arc surface 73 a of the single mouth 73 is pressed against the rear cylindrical surface of the rack shaft 60 so as to secure the engagement between the pinion 53 and the rack shaft 60). For example, the transmission efficiency has been improved, and the steering torque has been reduced. On the other hand, in a vehicle having a relatively heavy vehicle weight, it is generally necessary to provide a so-called power steering device that outputs an auxiliary steering force in order to reduce the steering horsepower. Here, power steering devices are roughly classified into a hydraulic power steering device and an electric power steering device. The hydraulic power steering system generates hydraulic pressure by a control valve provided on the pinion shaft according to the steering torque applied to the driver's steering wheel, and applies the hydraulic pressure to a hydraulic cylinder provided on the rack shaft. By doing so, thrust is generated directly in the direction of movement of the rack axis. Therefore, the steering torque applied to the steering wheel by the driver is small enough to operate the control valve, and is also larger than the manual steering device in order to reduce the amount of steering. Cresio. Therefore, since the torque transmitted to the rack shaft via the rack and pinion device is extremely small, even if the transmission efficiency is slightly deteriorated, it does not hinder the driver's operation of the rack. In practice, sliding rack guides that are less expensive than rolling rack guides are used (Japanese Utility Model Laid-Open No. 61-18976, Japanese Utility Model Laid-Open No. 61-124, 471). . In contrast, the electric power steering system outputs auxiliary steering force from the electric motor to the steering shaft and the rack shaft according to the steering torque applied to the steering wheel. It has excellent features such as a compact structure, such as no need for hydraulic pumps, hydraulic piping, and hydraulic oil tanks.It was initially used for lightweight vehicles such as mini vehicles, Is also being applied to heavy vehicles. Here, the electric power steering device is a so-called column-assist type electric power steering device that outputs an auxiliary steering force directly to the steering shaft by attaching an electric motor to the steering column. Auxiliary steering force is output directly to the pinion shaft by attaching an electric motor to the pinion device. There is a so-called pinion assist type electric power steering device. According to the latter type of electric power steering device, a large force to which the auxiliary steering force of the electric motor is added is transmitted between the pinion and the rack teeth of the rack shaft. Further, in a vehicle having a relatively heavy vehicle weight, the transmission of a much larger force between the pinion and the rack teeth of the rack shaft, which is much larger than that of a manual steering device or a hydraulic power steering device, becomes stationary. Or, the bending stress and surface pressure acting on the rack teeth increase. On the other hand, bending stress and surface pressure can be reduced by increasing the pressure angle / twist angle. In particular, the variable stroke ratio type rack-and-rack type has a large stroke ratio near the center of the rack teeth and a small stroke ratio at both ends so that the auxiliary steering force can be covered even with the output of a relatively small capacity electric motor. In the pinion type steering device, the pressure angle near the center of the rack tooth, which is most frequently used in normal running, tends to be larger. Here, when a strong force is transmitted between the pinion and the rack teeth of the rack shaft, the separating force for separating the rack from the pinion increases. Also, as the pressure angle increases, the separation force further increases. For example, in the case of a manual steering device or a hydraulic power steering device, the pressure angle is generally about 20 degrees. In an electric power steering device, a rack-and-pinion type steering device of a fixed stroke ratio type is generally used. The pressure angle reaches about 30 degrees even when is applied, and the pressure angle reaches 45 degrees when a variable stroke ratio type rack-and-pinion type steering device is applied. A simple calculation shows that, for the same rack thrust, an electric power steering system using a variable stroke ratio type rack-and-pinion steering system Tan 45 ° no tan 20 ° = 2.75 times compared to a dual steering device, and approximately 10 times the amplification factor of the driver's steering torque by hydraulic assist when compared to a hydraulic power steering device Then, we actually receive 10 X 2.75 = 27.5 times separation force. However, if such a separation force is to be received, the friction force increases and the steering force transmission efficiency decreases if the slide guide is used to support the back of the rack shaft. That is, in a manual steering system or a hydraulic power steering system, a slide guide is sufficient to support the rack shaft, but in an electric power steering system, a rack support system with smaller frictional force is used instead of the slide guide. It will be necessary. Further, in the electric power steering apparatus, in addition to the problem caused by the increase in the separation force, there is also a problem caused by the torsion angle of the rack teeth of the rack shaft. That is, when the torsion angle increases, the rotational force for rotating the rack shaft around its axis also increases, leading to inconveniences such as abrasion of the pinion and rack teeth due to the contact between the rack teeth and the pinion, and an increase in operating torque. I do. In particular, in the case of a so-called rack-assist type electric power steering device in which an electric motor is arranged around the rack shaft and thrust is applied to the rack shaft using a poll screw mechanism including a pole screw and a nut, etc. The rack shaft is further twisted by the reaction force of the nuts and the like, and the contact between the rack teeth and the pinion becomes more remarkable. However, there is a problem that such torsion of the rack shaft cannot be properly supported by the conventional rolling rack guide. Disclosure of the invention An object of the present invention is to provide an electric power steering apparatus capable of suppressing torsion of a rack shaft and supporting low friction, in view of the problems of the related art. To achieve the above object, an electric power steering device according to the present invention is an electric power steering device capable of outputting an auxiliary steering force by an electric motor.

A housing,

A rack shaft having rack teeth and being movable with respect to the housing; a pinion having pinion teeth matching the rack teeth, and transmitting a steering force from a steering wheel to the rack shaft;

A supporting device provided on the housing, for supporting the rack shaft, wherein an axis of the rack shaft and an axis of the pinion intersect at an angle other than 90 degrees;

The rack shaft has a support device guide surface extending in a longitudinal direction at least at two force points on an outer peripheral surface,

The support device includes a rolling element that rolls while pressing each support device guide surface along a direction intersecting with each other when the rack axis is viewed in the longitudinal direction. When the direction of the pressing force applied to the guide surface is indicated by a line, the intersection of the line is shifted from the center of the rack axis. The electric power steering device of the present invention

In an electric power steering device that can output auxiliary steering force by electric motor,

A housing and A rack shaft including a rack tooth and a screw portion, the rack shaft being movable with respect to the eight housings;

A pinion that has pinion teeth that engage with the rack teeth, and that transmits steering force from a steering wheel to the rack shaft;

A support member provided on the housing and supporting the rack shaft; and a conversion member for converting a rotational force of the electric motor into a thrust of the rack shaft using a nut screwed into the screw portion. And

Housing and ''

A rack shaft having rack teeth and being movable with respect to the nosing; a pinion having pinion teeth matching the rack teeth, and transmitting a steering force from a steering wheel to the rack shaft;

A support device provided on the housing, the support device supporting the rack shaft, the rack shaft having a support device guide surface extending in a longitudinal direction at at least two force points on an outer peripheral surface,

Each of the support devices is configured such that, when the rack axis is viewed in the longitudinal direction, A rolling element that rolls while pressing the guide surfaces along directions intersecting with each other; a shaft member having one end swingably supported by the eight housings and rotatably supporting the rolling element; and the shaft. And urging means for urging the other end of the member to press the rolling element toward the support device guide surface of the rack shaft. An electric power steering device according to the present invention is an electric power steering device capable of outputting an auxiliary steering force by an electric motor. The electric power steering device includes a nose, a housing, and rack teeth, and is movable with respect to the housing. A rack shaft, a pinion that includes pinion teeth that match the rack teeth, and transmits a steering force from a steering wheel to the rack shaft; and a support device that is provided in the housing and supports the rack shaft. The axis of the rack shaft and the axis of the pinion intersect at an angle other than 90 degrees, and the rack shaft extends in at least two places on the outer peripheral surface in a longitudinal direction. The support device has a surface, and when the rack axis is viewed in the longitudinal direction, the support devices press the support device guide surfaces along directions intersecting each other. When the direction of the pressing force applied from the rolling element to the support device guide surface is indicated by a line, the intersection of the line is shifted from the center of the rack axis. Therefore, the rack can be supported by the rolling element with low friction, and the supporting device guide surface provided on the outer peripheral surface of the rack shaft is pressed by the rolling element, so that two different directions are provided. Thus, the rack shaft can be supported from the above. Therefore, when the axis of the rack shaft and the axis of the pinion intersect at an angle other than 90 degrees, it is possible to support the rack shaft that generates rotational torque during operation. It has a suitable configuration. Further, when the directions of the pressing forces applied from the rolling elements to the inner surface of the support device plan are indicated by lines, the intersection of the lines is shifted (offset) from the center of the rack axis. The smooth rotation can be maintained by preventing the rotation of the shaft, and a stable state is achieved by the resultant force of the pressing force. With this, the rack teeth can be pressed against the pinion teeth. The axis of the rack shaft refers to a line passing through the center of the cross section perpendicular to the longitudinal direction of the rack shaft (for example, when the rack shaft is formed from a cylindrical material, the axis of the original material). By the way, in a certain type of a so-called rack-assist type electric power steering device, a po / screw and a nut are used to change the rotational force of the electric motor into thrust in the axial direction of the rack shaft. In a rack assist type electric power steering device of this type, a rotational torque is inherently generated around the axis of the rack shaft due to the rotational reaction force of the nut. On the other hand, an electric power steering device according to the present invention is an electric power steering device capable of outputting auxiliary steering force by an electric motor, comprising a housing, a rack tooth and a screw portion, and A rack shaft that is movable with respect to the rack shaft; a pinion that engages with the rack teeth; a pinion that transmits steering force from a steering wheel to the rack shaft; and a housing that is provided on the housing and supports the rack shaft. And a conversion member that converts the rotational force of the electric motor into a thrust of the rack shaft by using a nut screwed into the screw portion, wherein the rack shaft has an outer peripheral surface. A support device guide surface extending in the longitudinal direction is provided in at least two places, and the support device presses each support device guide surface in a direction intersecting each other. When the direction of the pressing force applied from the rolling element to the support device guide surface is indicated by a line, the intersection of the line shifts from the center of the rack axis. Since the rotational force of the electric motor is converted into the thrust of the rack shaft by using a nut screwed into the screw portion, the rotational torque inherently generated around the axis of the rack shaft during operation. Can be received by the rolling elements that come into contact with the support device guide surface from different directions, so that the rack shaft can be appropriately supported while ensuring smooth axial movement. Wear. In other words, without the shifted rolling element, it is not possible to receive the rotating torque around the axis of the rack shaft. By the way, considering the provision of a plurality of the rolling elements as in the first aspect of the present invention, it is necessary to adjust the pressing force for pressing the support device guide surface for each rolling element. On the other hand, an electric power steering device according to the present invention is an electric power steering device capable of outputting an auxiliary steering force by an electric motor, comprising a housing, rack teeth, and movable with respect to the eight housings. A pinion for transmitting a steering force from a steering wheel to the rack shaft; and a support provided on the housing for supporting the rack shaft. The rack shaft has a support device guide surface extending in the longitudinal direction at least at two places on the outer peripheral surface, and the support device has a structure in which the rack shaft is viewed in the longitudinal direction. A rolling element that rolls while pressing each support device guide surface in a direction intersecting with each other, and one end of which is swingably supported with respect to the eight housings. A shaft member rotatably supporting the rolling element; and a biasing means for urging the other end of the shaft member to press the rolling element toward a support device guide surface of the rack shaft. By urging the other end with an appropriate pressing force by the urging means, the rolling element can be pressed against the support device guide surface while oscillating the rolling element. Therefore, smooth operation can be ensured with a simple configuration. In particular, if the urging means has a pressing portion that abuts on the other end of each shaft member and an elastic member that urges the pressing portion visibly, for example, each of the shafts may be formed using a single pressing portion. The member can be urged at one time, and the elastic force of the elastic member is used. Therefore, a stable urging force can be supplied even if wear or the like occurs between the rolling element and the support device guide surface. Furthermore, when the directions of the pressing force applied from the rolling elements to the guide surface of the support device are indicated by respective lines, it is preferable that the intersection of the lines is shifted from the center of the rack axis. Further, it is preferable that the rack shaft has a position regulating portion that regulates the position of the rolling element. Further, it is preferable that an outward conical surface is formed on at least one end surface of the rolling element. Further, it is preferable that at least a portion of the support device that supports the rolling element is formed by die transfer processing. BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B are cross-sectional views of a rack-and-pinion steering apparatus according to a first embodiment. FIG. 2 is a cross-sectional view of a rack and pinion type steering device according to a second embodiment. FIG. 3 is a cross-sectional view of a rack and pinion type steering device according to the related art. FIG. 4 is a partially omitted cross-sectional view of a rack-assist type electric power steering apparatus according to a third embodiment. FIG. 5 is a cross-sectional view showing the configuration of FIG. 4 cut in the axial direction of the input shaft 202. As shown in FIG. FIG. 6 is a sectional view similar to FIG. 5 of the electric power steering device according to the fourth embodiment. FIG. 7 is a sectional view similar to FIG. 5 of the electric power steering device according to the fifth embodiment. FIG. 8 is a sectional view similar to FIG. 5 of the electric power steering device according to the sixth embodiment. 9A to 9D are views showing an electric power steering device according to a seventh embodiment. 10A to 10D are views showing an electric power steering device according to an eighth embodiment. FIG. 11 is a diagram similar to FIG. 9A of a rack and pinion type steering device according to a ninth embodiment applied to a rack assist type electric power steering device. FIG. 12 is a sectional view similar to FIGS. 1A and 1B in the ninth embodiment. FIG. 13 is a sectional view similar to FIG. 2 of the electric power steering apparatus according to the tenth embodiment. FIG. 14 is a cross-sectional view similar to FIG. 2 of the electric power steering device according to the first embodiment. FIG. 15 is a cross-sectional view similar to FIG. 2 of the electric power steering device according to the 12th embodiment. FIG. 16 is a cross-sectional view similar to FIG. 2 of the electric power steering device according to the thirteenth embodiment. FIGS. 17A to 17D are views showing a procedure for assembling the main body according to the embodiment of FIGS. 1A and 1B and 2. FIG. FIG. 18 is a diagram of the configuration of FIG. 17A viewed in the direction of arrow XVI II. FIGS. 19A and 19C are diagrams showing a procedure for assembling the main body according to the embodiment of FIGS. 15 and 16. FIG. FIG. 20 is a diagram of the configuration of FIG. 19A viewed in the direction of arrow XX. FIG. 21 is a diagram of the configuration of FIG. 19A as viewed in the direction of arrow XXI. FIG. 22 is a diagram of the configuration of FIG. 19A viewed in the direction of arrow XXII. FIG. 23 is a view of the main body of FIG. 22 cut along the XXI 11-XXI 11 line and viewed in the direction of the arrow. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1A and 1B are cross-sectional views of a rack-and-pinion steering apparatus according to a first embodiment. FIG. 1A shows a state where a supporting device is assembled, and FIG. 1B shows the supporting device. The disassembled state is shown, but the cross section of each part is combined for easy understanding (the same applies to similar cross sections hereinafter). 1A and 1B, an output shaft (pinion) 3 extending inside the housing 1 is connected to a steering shaft (not shown), and is rotatably supported on the housing 1 by bearings 5 and 6. ing. The inner ring of the bearing 6 is fixed to an end of the output shaft 3 by a nut 7, and the outer ring of the bearing 6 is attached to the housing 1 by screwing a fixing member 8. The housing 1 forms a hollow column 1 c extending leftward in the figure from the periphery of the rack shaft 10. A support device 20 is arranged in the hollow column part lc. The support device 20 includes a substantially cylindrical main body 21, two shafts 22 mounted in a blind hole of the main body 21, and a cylindrical roller as a rolling element mounted on each shaft 22. 23, a screw member 24 for attaching the main body 21 to the hollow column 1c, and a screw member 24 disposed between the screw member 24 and the main body 21 to urge the main body 21 toward the rack shaft 10 side. And a lock member 26 for the screw member 24. Screw member 2 4 By adjusting the displacement amount, the compression amount of the pan panel 25 changes, and the pressing force of the rack shaft 10 can be adjusted. After the adjustment, the screw member 24 can be locked and locked by the lock member 26 to prevent loosening thereof. The surface (referred to as the back surface) of the rack shaft 10 opposite to the rack teeth 10a has a cross-sectional shape in which the upper left and lower left portions are cut out in FIGS. 1A and 1B. In this case, two rolling surfaces (that is, support device guide surfaces extending in the longitudinal direction) 10b and 10b, which extend in the longitudinal direction, are formed, and a raised portion 10c is formed therebetween. . The rolling surfaces 10b, 10b are arranged symmetrically with respect to the center of the rack axis 10 in a cross section. The axis of rack axis 10 intersects the axis of pinion 3 at an angle other than 90 degrees. The rack shaft 10 is formed by machining or cold forming a round bar as a material to form rack teeth 10a. In the case of a rack assist type electric power steering device, a thread groove is formed on the outer peripheral surface of a round bar as a material (not shown). Therefore, the center of the rack shaft 10 refers to the center of the round bar or the center of the thread groove. The two shafts 22 are arranged parallel to the rolling surface 10b and perpendicular to the rack axis, and rotatably support the cylindrical roller 23 via a bearing 22a. The position K where the two bisectors L bisect in the axial direction (corresponding to the direction of the pressing force against the rolling surface 10 b of the cylindrical roller 23) intersects the position K at the center of the rack shaft 10. It is arranged on the rack tooth 10a side from the center O so as to be offset by Δ. The bisectors L are orthogonal to each other here. It is preferable that both ends of the cylindrical roller 23 are subjected to a crowning process in order to reduce an edge load on the rolling surfaces 10b and 10b. Two cylindrical rollers 23 constitute a pressing means for pressing the rack shaft 10 from two directions toward the output shaft 3. The operation of the present embodiment will be described. When a steering force is input to a steering wheel (not shown), the steering force is transmitted via a steering shaft (not shown). The rotational force of the output shaft 3 is converted into the longitudinal thrust of the rack shaft 10 via the pinion teeth 3 a and the rack teeth 10 a which are transmitted to the output shaft 3 and are combined with each other. Since 10 moves in the direction perpendicular to the plane of the paper, the wheels (not shown) are steered. At this time, the cylindrical roller 23 rolls on the rolling surface 10b, and allows the rack shaft 10 to move with low friction. Here, when a strong force is transmitted between the output shaft 3 and the rack shaft 10, a separating force is generated to separate the rack shaft 10 from the output shaft 3. In the present embodiment, the separation force can be appropriately supported by the pair of cylindrical openings 23 arranged symmetrically with respect to the center of the rack shaft 10. On the other hand, when a strong force is transmitted between the output shaft 3 and the rack shaft 10, a rotational force is generated to rotate the rack shaft 10 around its center. Such a rotational force becomes particularly large when the axis of the rack shaft 10 intersects the axis of the pinion 3 at an angle other than 90 degrees. In the present embodiment, this rotational force can be supported by a pair of cylindrical rollers 23 disposed symmetrically with respect to the center of the rack shaft 10. Since the equal lines L of the two cylindrical openings 23 intersect at right angles, the force pressing one of the rolling surfaces 10b is less than that of the other rolling surface 10b. There is also an advantage that the pressing force between them is not affected. Further, in the present embodiment, the position at which the equal lines L of the two cylindrical rollers 23 intersect is offset by Δ from the center O of the rack shaft 10 to the side of the rack teeth 10a. Are arranged so that the resultant force presses the rack shaft 10 in the direction toward the output shaft 3, so that the engagement between the rack shaft 10 and the output shaft 3 can be performed stably. It becomes. In the present embodiment, the main body 21 loosens the hook member 26 and the screw member 24. 1B, and can be removed from the left end of the hollow column 1c integrally with the cylindrical roller 23, as shown in Fig. Easy to disassemble. FIG. 2 is a cross-sectional view of a rack and pinion type steering device according to a second embodiment applied to a rack assist type electric power steering device. In FIG. 2, a housing 101 is composed of a main body 101 a fixed using a polylet (not shown) and a lid member 101 b. In the housing 101, an input shaft 102 and an output shaft 103 extend. The input shaft 102 is hollow, and the upper end of the input shaft 102 shown in the figure is connected to a steering shaft (not shown), and the steering shaft is connected to a steering wheel (not shown). It has become. The input shaft 102 is rotatably supported with respect to the housing 101 by a bearing 104. A torsion bar 105 having the upper end shown in the drawing pin-coupled to the input shaft 102 and the lower end serrated to the output shaft 103 extends in the input shaft 102. A torque sensor 106 that detects the steering torque based on the torsion of the torsion bar 105 in proportion to the received torque is provided around the lower portion of the input shaft 102 shown in the figure (partly). Only shown). The torque sensor 106 mechanically (or electromagnetically) detects the relative angular displacement between the input shaft 102 and the output shaft 103 based on the torsion of the one-shoulder bar 105. This is output to a control circuit (not shown) as a signal. The output shaft 103 is rotatably supported with respect to the housing 101 by bearings 115 and 116, and has a pinion tooth 103a formed at the center thereof. The tooth 103 a is formed by a rack shaft 110 extending perpendicularly to the plane of the paper. The teeth fit 110 1a. Both ends of the rack shaft 110 are connected to a wheel steering device (not shown). The housing 101 forms a hollow column 101c extending leftward in the figure from the periphery of the rack shaft 110c. A support device 120 is disposed in the hollow column portion 101c. The support device 120 includes a substantially cylindrical main body 122, two shafts 122 mounted in the blind hole of the main body 1.21, and rolling elements mounted for each shaft 122. A cylindrical roller 1 2 3, a screw member 1 2 4 for attaching the main body 1 2 1 to the hollow column 1 0 1 c, and a screw roller 1 2 4 disposed between the screw member 1 2 4 and the main body 1 2 1. It is composed of a disc spring 125 for urging the body 121 toward the rack shaft 110 and a lock member 126 for the screw member 124. By adjusting the screwing amount of the screw member 124, the compression amount of the countersunk panel 125 changes, and the pressing force of the rack shaft 110 can be adjusted. After the adjustment, the screw member 124 can be locked and locked by the lock member 126 to prevent the screw member 124 from being loosened. The surface (referred to as the back surface) of the rack shaft 110 opposite to the rack teeth 110a has a cross-sectional shape in which the upper left and lower left portions are cut away in FIG. Two rolling surfaces extending in the longitudinal direction (that is, supporting device guide surfaces extending in the longitudinal direction) 110 b and 110 b are formed, and a raised portion 110 c is formed therebetween. . The rolling surfaces 110b and 110b are arranged symmetrically with respect to the center in the cross section of the rack axis 110. The axis of the rack axis 110 intersects the axis of the pinion 103 at an angle other than 90 degrees.

The two shafts 1 2 2 are arranged parallel to the rolling surface 1 10 b and perpendicular to the rack axis, and rotatably support the cylindrical roller 1 2 3 via the bearing 1 2 2 a. . The position where the equal lines (not shown) of the two cylindrical rollers 123 intersect at a right angle is similar to that of the first embodiment. Both ends of cylindrical roller 1 2 3 It is preferable to have a crowning process to reduce the edge of 0b. The two cylindrical rollers 123 constitute pressing means for pressing the rack shaft 110 from two directions toward the output shaft 103. The operation of the present embodiment will be described. When the steering force is input to the steering wheel (not shown), the torque sensor 106 detects the steering torque from the twist amount of the shawl bar 105, and accordingly, the auxiliary steering force from the electric motor (not shown). Will be output. Here, when the steering force is transmitted to the output shaft 103, the rotation force of the output shaft 103 is changed to the rack shaft 1 via the mutually engaging pinion teeth 103a and rack teeth 110a. The rack thrust 110 is converted into a longitudinal thrust of 10 and the rack thrust 110 moves in a direction perpendicular to the plane of the drawing by the applied longitudinal thrust, whereby a wheel (not shown) is steered. At this time, the cylindrical roller 123 rolls on the rolling surface 110 Ob, and allows the rack shaft 110 to move with low friction. Similarly to the above-described embodiment, when a strong force is transmitted between the output shaft 103 and the rack shaft 110, the rack shaft 110 is separated from the output shaft 103. Separation force occurs. In the present embodiment, the pair of cylindrical rollers 123 arranged symmetrically with respect to the center of the rack shaft 110 can appropriately support this separation force. On the other hand, when a strong force is transmitted between the output shaft 103 and the rack shaft 110, a rotational force is generated to rotate the rack shaft 110 around its center. Such a rotational force becomes particularly large when the axis of the rack shaft 110 intersects the axis of the pinion 103 at an angle other than 90 degrees. In the present embodiment, this rotational force can be supported by a pair of cylindrical rollers 123 disposed symmetrically with respect to the center of the rack shaft 110. In addition, since the equal lines L of the two cylindrical ports — la 1 2 3 intersect at a right angle, the force pressing one rolling surface 110 b is equal to that of the other rolling surface 110 b. Influence on the pressing force between the cylindrical mouth 1 and 2 3 There is also an advantage of not giving. Further, also in the present embodiment, since the two cylindrical openings are arranged so as to be offset from the center of the rack shaft 110 to the rack teeth 110a side, at the position where the equal lines of the two cylindrical openings l intersect each other, the rack shaft Of the rack shaft 110 and the output shaft 103 because the rack shaft 110 is pressed in the direction toward the output shaft 103. Can be performed stably. In the above-described embodiment, the adjustment of the pressing force between the cylindrical rollers 23 and 123 and the rolling surfaces 10b and 110b is performed by tightening or loosening the screw members 24 and 124 with respect to the housings 1 and 101. By changing the amount of elastic deformation of the disc springs 25, 125, the main bodies 21, 121 press the shafts 22, 122 with the elastic force based on the amount of elastic deformation of the disc springs 25, 125, As a result, the cylindrical rollers 23 and 123 are pressed against the rolling surfaces 1013 and 11 Ob. FIG. 4 is a partially omitted cross-sectional view of a rack-assist type electric power steering apparatus according to a third embodiment. In FIG. 4, a lid member 201C is attached to a right end of a rack housing 201A integrally formed with the housing 201 by a port 201D via a spacer member 201B. The rack housing 201A is fixed to a vehicle body (not shown). A rack shaft 210 is inserted into the rack housing 201A, and the rack shaft 210 is connected to tie rods 208 and 209 at both ends. The tie rods 208 and 209 are connected to a wheel steering device (not shown). In the vicinity of the right end in FIG. 4 of the rack shaft 210, a helical outer thread groove 210d is formed on the outer periphery, and a cylindrical pole screw nut 2 is formed around the outer periphery. 30 are arranged, and are rotatably supported by the bearings 2332 with respect to the spacer member 201B, and rotatably supported by the bearings 23, 23 with the lid member 201C. Have been. A helical internal thread groove 230 a is formed on the inner periphery of the pole screw nut 230. A rolling path is formed by the outer thread groove 210d and the inner thread groove 230a, and a number of pawls 231 (only the-part is shown) are accommodated in the rolling path. . The pole 2 31 has a function of reducing the frictional force generated when the ball screw nut 230 and the rack shaft 210 rotate relative to each other. In addition, the pole screw nut 2 31 has a circulation path (not shown), and the pawl screw nut 2 30 can rotate through the circulation path when the pole screw nut 230 rotates. . Rollers 2 36 that are in rolling contact with the outer peripheral surface of the pole screw nut 230 and the outer peripheral surface of the rotating shaft 230 a of the electric motor 230 mounted on the rack housing 201 A, respectively. The rotation torque output from the electric motor 235 is transmitted to the pole screw nut 230 by a so-called traction drive method. Note that the rotation torque may be transmitted by a gear transmission method instead of the truncation drive method. The pole screw nut 230 forms a nut, and the pole screw nut 230 and the rack shaft 210 provided with the outer screw 210 d form a conversion member. FIG. 5 is a cross-sectional view showing the configuration of FIG. 4 cut in the axial direction of the input shaft 202. As shown in FIG. In FIG. 5, an input shaft 202 and an output shaft 203 extend inside the housing 201. The input shaft 202 is hollow, and the upper end of the input shaft 202 shown in the figure is connected to a steering shaft (not shown), and the steering shaft is connected to a steering wheel (not shown). Like I have. The input shaft 202 is rotatably supported with respect to the housing 201 by a bearing 204. A transition par 205 having the upper end shown in the drawing pin-coupled to the input shaft 202 and the lower end selection-coupled to the output shaft 203 extends in the input shaft 202. A torque sensor 206 that detects the steering torque based on the torsion bar 205 being twisted in proportion to the received torque is provided around the lower portion of the input shaft 202 shown in the figure (only a part of the torque sensor is provided). Illustrated). Since the torque sensor 206 is similar to the torque sensor of the above-described embodiment, a detailed description will be omitted. The output shaft 203 is rotatably supported with respect to the housing 201 by bearings 215 and 216, and has a pinion tooth 203a formed in the center thereof. The teeth 203 a are aligned with the rack teeth 210 a of the rack shaft 210 extending in a direction perpendicular to the plane of the drawing. As shown in FIG. 4, both ends of the rack shaft 210 are connected to a wheel steering device (not shown) via tie rods 208 and 209. The housing 201 has a hollow column portion 210 c extending from the periphery of the rack shaft 210 to the lower left in the figure, and a hollow column portion 210 extending to the upper left from the periphery of the rack shaft 210 at the lower part 5 in the figure. Forming 1 e. In the hollow column portions 201c and 201e, supporting devices 220 and 220 having the same configuration are arranged. Each of the support devices 220 includes a substantially cylindrical main body 222, a shaft 222 mounted in a blind hole of the main body 222, and a cylindrical rolling member mounted to the shaft 222. Mouthpiece 2 2 3, screw member 2 2 4 for attaching main body 2 2 1 to hollow column 2 0 1 c or 2 0 1 e, and between screw member 2 2 4 and main body 2 2 1 And a disc spring 225 for urging the main body 222 toward the rack shaft 210 side, and a lock member 222 of a screw member 222. By adjusting the amount of screwing of the screw member 2 24, the amount of compression of the disc spring 2 25 changes, and the pressing forces F l and F 2 against the rack shaft 210 are adjusted so that their vertical components are balanced. However, since the rack shaft 210 is displaced up and down in the figure, the pressing forces F 1 and F 2 become equal to each other). After the adjustment, the screw member 224 can be locked and locked by the lock member 226 to prevent loosening thereof. The surface (rear surface) of the rack shaft 210 opposite to the rack teeth 210a has a cross-sectional shape in which the upper left and lower left portions are cut away in FIG. Two rolling surfaces extending in the longitudinal direction respectively (that is, supporting device guide surfaces extending in the longitudinal direction) 210b and 210b are formed, and a ridge 210c therebetween. Are formed. The rolling surfaces 210b and 210b are arranged symmetrically with respect to the bisector (horizontal line in the figure) in the cross section of the rack shaft 210. The axis of the rack axis 210 intersects the axis of the pinion 203 at an angle other than 90 degrees. The shaft 2 2 2 of each support device 220 is provided with a rolling surface 2 which is perpendicular to and opposes the rack axis.

It is arranged parallel to 1 Ob, and rotatably supports a cylindrical roller 222 through a bearing 222a. The position where the equal line of the two cylindrical openings 2 23 (corresponding to the directions of the pressing forces F l and F 2) intersects at right angles is offset similarly to the above-described embodiment. It is preferable that both ends of the cylindrical opening 223 are subjected to a crowning process in order to ease an edge opening with respect to the rolling surface 210b. The two cylindrical openings 223 constitute pressing means for pressing the rack shaft 210 from two directions toward the output shaft 203. According to the present embodiment, the adjustment of the pressing forces F 1 and F 2 on the rolling surface 2 10 b of the two cylindrical openings 2 2 3 is performed by adjusting the screw member 2 2 4 to the housing 201. Tighten or loosen to change the amount of elastic deformation of the disc spring 225. Can be. In such a case, the direction of the elastic force of the counter panel 2 25 and the direction of the pressing force F l, F 2 are in agreement, so all such fluctuating forces (excluding friction disappearance) are used as the pressing force F 1, F 2 Since it can be used, the structure of the support device 220 can be reduced in size and weight. Further, since the rack shaft 210 is supported in three directions, sufficient support rigidity is ensured, and members such as bushings generally used in the prior art can be omitted, and effective use of space can be achieved. FIG. 6 is a sectional view similar to FIG. 5 of the electric power steering device according to the fourth embodiment. This embodiment is slightly different from the embodiment shown in FIG. 5 only in the configuration of the support device, and the other common components are denoted by the same reference numerals and description thereof is omitted. In this embodiment, the lower support device 220 in FIG. 6 is the same as that according to the embodiment in FIG. 5, but the upper support device 220 omits a disc spring. Therefore, the only difference is that the screw member 224 directly presses the main body 221. According to the present embodiment, the adjustment of the pressing forces F l, F 2 on the rolling surfaces 2 10 b of the two cylindrical openings 2 2 3 is performed in the same manner as in the embodiment of FIG. This is done by tightening or loosening the 24 with respect to the housing 201. For example, due to vibration or the like, the contact part between the screw member 2 24 of the upper support device 220 'and the main body 22 1 etc. When wear occurs, the rack shaft 210 is pushed upward in the figure by the urging force of the disc spring 225 of the lower supporting device 220, thereby causing the upper supporting device 220 to move upward. Since the surface pressure between the screw member 2 2 4 and the main body 2 2 1 is almost maintained, the pressing forces F l and F 2 are not biased and the rack shaft 2 10 The support can be done. FIG. 7 is a diagram similar to FIG. 5 of the electric power steering device according to the fifth embodiment. It is a similar sectional view. This embodiment also differs from the embodiment shown in FIG. 5 only in the configuration of the support device, and the other common components are denoted by the same reference numerals and description thereof is omitted. In this embodiment, the lower supporting device 220 in FIG. 7 is the same as that according to the embodiment of FIG. 5, but the upper supporting device 320 adjusts the pressing force independently. The mechanism for performing this is omitted. More specifically, the support device 320 is provided with a substantially cylindrical main body 321, fixed by a snap ring 3226, in the hollow column portion 201e, and in a blind hole of the main body 321, respectively. And a cylindrical roller 223 as a rolling element rotatably supported on the shaft 222 by an on-axis 222a. The space between the main body 3 2 1 and the hollow column 2 0 1 e is sealed by a 0-ring 3 27. In the present embodiment, the adjustment of the pressing forces F 1 and F 2 on the rolling surface 210 of the two cylindrical rollers 222 is performed by adjusting the screw member 222 of the lower supporting device 220. By tightening or loosening the jig 201, the amount of elastic deformation of the disc spring 225 can be changed. In such a case, the rack shafts 210 are displaced up and down in the figure, so that the pressing forces Fl and F2 become equal. FIG. 8 is a sectional view similar to FIG. 5 of the electric power steering device according to the sixth embodiment. This embodiment also differs from the embodiment shown in FIG. 5 only in the configuration of the support device, and the other common components are denoted by the same reference numerals and description thereof is omitted. In the present embodiment, the lower supporting device 220 in FIG. 8 is the same as that according to the embodiment of FIG. 5, but the upper supporting device 420 It has a fixed configuration. More specifically, the support device 420 includes a shaft 222 that is inserted into a hole 201 f formed in the hollow column 201 e, and a bearing with respect to the shaft 222. And a cylindrical roller 22 3 which is a rolling element rotatably supported by 222 a. The outer end of the hollow column 201 e is sealed with a cover member 426. Also in the present embodiment, the adjustment of the pressing forces F 1 and F 2 on the rolling surfaces 2 10 b of the two cylindrical rollers 2 23 is performed by adjusting the screw members 2 2 4 of the lower supporting device 2 20. By tightening or loosening the housing 201, the amount of elastic deformation of the disc spring 225 can be changed. In such a case, the rack shafts 210 are displaced up and down in the figure, so that the pressing forces Fl and F2 become equal. Also, when each part is worn due to, for example, vibrations, the rack shaft 210 is pushed upward by the urging force of the counterpanel 225 of the lower supporting device 220. F l and F 2 can support the rack shaft 210 stably for a long time without bias. By the way, in order to make the rolling of the cylindrical roller 222 smooth, it is necessary to make the rotation axis of the cylindrical roller 222 orthogonal to the rolling direction with high accuracy. Here, since the hollow column portions 201c and 201e and the main bodies 222 and 321 fitted to the hollow column portions are both cylindrical, the rotation axis of the cylindrical roller 222 is positioned. To do so, it is necessary to prevent the body 2 2 1 from rotating. To prevent rotation, however, it is conceivable to form non-circular inner holes in the hollow column sections 201c and 201e that house the cylindrical rollers 222, but this is labor-intensive and increases costs. Invite. Therefore, in the following embodiment, the rotation of the main body 221 (the description is omitted, but the main body 321 is also possible) is achieved as described later. FIG. 9A is a partial cross-sectional view of the electric power steering device according to the seventh embodiment viewed from the same direction as FIG. 4, and FIG. 9B is a diagram illustrating the configuration of FIG. 9A along line IXB-IXB. FIG. 9C is a view of the structure of FIG. 9B cut along the IXC-IXC line and viewed in the direction of the arrow, and FIG. 9D is a view of the structure of FIG. 9B. Fig. 3 is a view of a section taken along the line IXD-IXD and viewed in the direction of the arrow. Since the embodiment shown in FIGS. 9A to 9D is applied to the embodiment shown in FIG. 7, this embodiment will be described with reference to FIGS. 7 and 9A to 9D. I do. In the seventh embodiment, two cylindrical rollers 222 are provided with a casing corner. More specifically, in FIG. 9A, the axis of the main body 3 21 that supports the cylindrical roller 2 23 of the upper support device 3 20 shown in FIG. It is tilted to the right as viewed in FIG. 9A by an angle 0 with respect to a direction perpendicular to the surface 21Ob. Therefore, the force by which the main body 3 2 1 presses the cylindrical roller 2 23 passes through the center P 1 of the center of the cylindrical roller, and is applied to the center P 2 of the contact between the cylindrical roller 2 2 3 and the rolling surface 2 1 Ob. At the shifted position, it intersects the rolling surface 21Ob. By utilizing this deviation, when the cylindrical roller 2 23 rolls on the rolling surface 2 10 b, the cylindrical roller 2 2 3 is set so that the axis of the cylindrical roller 2 3 is orthogonal to the rolling direction. Since the posture of 3 can be adjusted autonomously, the rotation of the main body 3 2 1 can be achieved without complicated processing or additional parts. Similarly, in FIG. 9A, the axis of the main body 2 21 supporting the cylindrical opening 2 23 of the lower support device 220 in FIG. 9A is, as shown in FIG. 9D, the rolling surface of the rack shaft 210. It is inclined to the left as viewed in FIG. 9A by an angle 0 with respect to the direction perpendicular to 210b. Therefore, the force by which the main body 2 21 presses the cylindrical roller 2 23 passes through the center P 3 of the center of the cylindrical roller and to the center P 4 of the contact between the cylindrical roller 2 23 and the rolling surface 2 10 b. It crosses the raceway 2 10 b at the position shifted from it. Using this deviation, a cylinder is placed on the rolling surface 2 10 b When the roller 223 rolls, the attitude of the cylindrical roller 223 can be adjusted autonomously so that the axis of the cylindrical roller 223 is orthogonal to the rolling direction, so that a complicated force [! The rotation of the main body 221 can be achieved without providing any hardware or other parts. In the present embodiment, each part is arranged such that the central point P5 (FIG. 9A) where the pinion tooth 203a (FIG. 7) and the rack tooth 210a are joined and the points P1 to P4 are on the same plane. Is arranged. FIG. 1 OA is a partial cross-sectional view of the electric power steering device according to the eighth embodiment, viewed from the same direction as FIG. 4, and FIG. 10B is a cross-sectional view of the configuration of FIG. 1 OA taken along line XB-XB. FIG. 10C is a view of the configuration of FIG. 10B taken along line XC-XC and viewed in the direction of the arrow, and FIG. 10D is a view of the configuration of FIG. 10B taken along XD-XD. It is the figure cut | disconnected by the line and seen in the arrow direction. Since the embodiment shown in FIGS. 10A to 10D is also applied to the embodiment shown in FIG. 7, this embodiment will be described with reference to FIG. 7 and FIGS. 1OA to 10D. . Also in the eighth embodiment, the two cylindrical rollers 223 are provided with a casing corner. More specifically, the axis of the main body 321 supporting the cylindrical roller 223 of the upper supporting device 320 in FIG. 1OA is oriented in a direction orthogonal to the rolling surface 210b of the rack shaft 210 as shown in FIG. 10C. It is inclined to the right by an angle of 0 with respect to Figure 1 OA. Accordingly, the force by which the main body 321 presses the cylindrical roller 223 passes through the center P 1 of the center of the cylindrical opening, and is shifted from the center P 2 of the contact between the cylindrical roller 223 and the rolling surface 210 b. Intersects moving surface 210b. By utilizing this deviation, when the cylindrical roller 223 rolls on the rolling surface 210b, the attitude of the cylindrical roller 223 is adjusted autonomously so that the axis of the cylindrical roller 223 is orthogonal to the rolling direction. The rotation of the main body 321 can be achieved without complicated processing or additional parts. Similarly, the axis of the main body 221, which supports the cylindrical roller 223 of the lower support device 220 in FIG. 1OA, is located on the rolling surface of the rack shaft 210, as shown in FIG. 10D. It is tilted to the left by an angle of 0 with respect to the direction perpendicular to 2 1 O b as seen in Figure 1 OA. Therefore, the force of the main body 2 2 1 pressing the cylindrical roller 2 2 3 passes through the center P 3 of the center of the cylindrical roller, and at the contact center P 4 between the cylindrical roller 2 2 3 and the rolling surface 2 10 b. It crosses the raceway 2 110 b at the position shifted from it. By utilizing this deviation, when the cylindrical roller 2 23 rolls on the rolling surface 2 10 b, the cylindrical roller 2 23 is set so that the axis of the cylindrical roller 2 23 is orthogonal to the rolling direction. Since the posture of 23 can be adjusted autonomously, the rotation of the main body 221 can be achieved without complicated processing or additional parts. Note that, in the present embodiment, the points P l,... With respect to the combined center point P 5 (FIG. 10A) between the pinion teeth 203 a (FIG. 7) and the rack teeth 210 a are shown. 1 and point? 3 and P 4 are arranged by shifting the components by a distance に in opposite directions. FIG. 11 is a view similar to FIG. 9A of a rack and pinion type steering apparatus according to a ninth embodiment applied to a rack assist type electric power steering apparatus, and FIG. FIG. 2 is a sectional view similar to FIGS. 1A and 1B of the embodiment. In FIG. 11, an output shaft 503, only a part of which is shown in the housing 501, extends vertically in FIG. 11, and is rotatably supported by a bearing 516. The output shaft 503 has a pinion tooth 503 a formed in the center thereof. The pinion tooth 503 a is a rack tooth 5 of a rack shaft 510 extending in a direction perpendicular to the plane of the drawing. It corresponds to 10 a. Both ends of the rack shaft 501 are connected to a wheel steering device (not shown). The housing 501 forms a hollow column portion 501c extending leftward in FIG. 12 from the periphery of the rack shaft 5110. A supporting device 520 is arranged in the hollow column portion 501c. The supporting device 520 is a swinging shaft which is a shaft member having one end swingably supported by a pin 528 with respect to the substantially disk-shaped main body 521 and the housing 501. 5 2 2, a cylindrical roller 5 2 3 that is rotatably supported or a rolling element with respect to each swing shaft 5 2 2 by a bearing 5 2 a, and a main body 5 2 1 as a hollow column 5 0 1 c Screw member 5 2 4 for attaching the main body 5 2 1 to the rack shaft 5 10 1 side, and a plate as an elastic member disposed between the screw member 5 2 4 and the main body 5 2 1 It comprises a spring 525 and a lock member 526 for the screw member 524.

It is preferable that the two swing shafts 5222 are arranged in parallel with the rolling surface 5110b in an assembled state. At this time, the position at which the equal lines (not shown) of the two cylindrical rollers 52 23 intersect at right angles is off as in the first embodiment. It is preferable that both ends of the cylindrical roller 523 are subjected to a crowning process so as to ease an edge opening with respect to the rolling surface 5110b. Two cylindrical rollers 523 constitute a pressing means for pressing the rack shaft 510 from two directions toward the output shaft 503. In the present embodiment, the free side end 5 2 2b that is the other end of the swing shaft 5 2 2 has a spherical shape, and a frusto-conical surface 5 2 as a pressing portion of the main body 5 2 1 It is in contact with 1a. The swinging shaft 5222 is inserted from the open end of the hollow column portion 501c (the portion to which the screw member 524 is screwed) and attached. The main body 5 2 1, the coned disc spring 5 2 5, and the screw member 5 2 4 constitute the urging means. In this embodiment, two cylindrical rollers 5 2 3 and a rolling surface (support device guide Adjustment of the pressing force F l, F 2 (represented by the reaction force in FIG. 12) of 5 10 b is performed by using a single screw member 5 2 4 of the support device 5 2 0 against the housing 5 0 1 By tightening or loosening it, the amount of elastic deformation of the disc spring 5 25 can be changed. In such a case, based on the biasing force of the countersink 5 25, the main body 5 2 1 is moved to the right in FIG. ), And the frusto-conical surface 5 2 1 a presses the free side end 5 2 2 b of the swing shaft 5 2 2. As a result, the two swinging shafts 5222 swing in opposite directions around the center of the pin 528, and the pressing force F1 of the two cylindrical rollers 523 and the rolling surface 51ob. , F 2 can be adjusted uniformly and appropriately. Also, even when each part is worn due to, for example, vibration, the two swing shafts 5 22 are simultaneously swung by the urging force of the counter panel 5 25 of the support device 5 20, and the pushing is performed. The pressures F 1 and F 2 are not biased, so that the rack shaft 5 10 can be stably supported for a long time. The free end 5 2 2 b is spherical, and the tangent to the free side end 5 2 2 b on the frustoconical surface 5 2 1 a is almost the same as the axis of the swing shaft 5 2 2. Since they are parallel to each other, even if the swing shaft 522 swings, an unnecessary component force (that does not contribute to the pressing of the cylindrical roller 523) caused by the swing is small, and further, the frusto-conical surface No edge load is added to 5 2 1 a. According to the present embodiment, as shown in FIG. 11, the configuration of the supporting device 520 can be reduced to the same extent as the configurations of FIGS. 1A and 1B and 2; There is an advantage that the pressing force can be adjusted only by the screwing of the screw members 5 2 4. In the above embodiment, the main bodies 22 1 and 52 1 constitute a holding member. FIG. 13 is a sectional view similar to FIG. 2 of the electric power steering device according to the tenth embodiment. This embodiment mainly differs from the embodiment shown in FIG. 2 mainly in the configuration of the rack shaft, and the other common configurations are as follows. The same reference numerals are given and the description is omitted. In FIG. 13, a dam 22 formed on a rotating shaft 21 of a motor controlled and driven by a control device (not shown) is connected to a worm wheel 23 mounted near the upper end of an output shaft 103. The auxiliary power of the motor is transmitted to the output shaft 103 via the worm 22 and the worm wheel 23. By the way, in the embodiment of FIG. 2, the pair of cylindrical rollers 123 which are the rolling elements of the support device 120 are rotatably supported on the shaft 122 by the needle bearings 122a, respectively. The direction is not constrained to the axis 122. Therefore, when an axial load is input from the rack shaft 110 to the cylindrical roller 123, the cylindrical roller 123 may come into contact with the main body 121 of the support device 120 and cause the following problem. In particular, as shown in FIG. 2, the rolling surfaces 110b, 110b of the cylindrical rollers 123, 123 of the rack shaft 110 are arranged at a predetermined angle (90 degrees in the figure) with respect to each other. The rotation axes of 123 and 123 are perpendicular to the axis of the rack shaft 110 and parallel to the rolling surfaces 110b and 110b. Furthermore, the two cylindrical rollers 123, 123 are pressed against the rolling surfaces 110b, 11 Ob by being pressed toward the bisector direction of the two rotating shafts by the screw member 124, which is an urging member. I'm making it. That is, since the pressing direction of the screw member 124 does not coincide with the pressing direction of the cylindrical rollers 123, 123 against the rolling surfaces 110b, 110b, the end faces of the cylindrical rollers 123, 123 contact the screw member 124. When they come into contact with each other, the frictional state between the cylindrical roller 123 and the rack shaft 110 generates an axial frictional force corresponding to the pressing force acting on the rolling surfaces 110b, 110b, and the end faces of the cylindrical rollers 123, 123 That Due to the frictional force in the axial direction, the roller is strongly pressed against the main body 121 and frictionally slides, and the smooth rotation of the cylindrical rollers 123 and 123 is hindered, and the operating resistance of the rack shaft 110 increases. , 123 may be worn out or cause abnormal noise. Therefore, in the embodiment shown in FIG. 13, the width of the raised portion 610c of the rack shaft 610 is increased and the roots of both sides 610d and 610d are different from the embodiment shown in FIGS. 1A and 1B. Is used as a position restricting part, which is in contact with the end faces of the cylindrical surfaces 123, 123 (arrow A;). In this way, the movement of the cylindrical rollers 123, 123 in the axial direction is restricted by bringing the end faces of the cylindrical rollers 123, 123 into contact with the movement restricting portions (the roots of the side surfaces 610d and 61 Od) provided on the rack shaft 610. A gap is formed between the cylindrical rollers 123 and 123 and the main body 121 so that frictional sliding of the roller end surfaces does not occur. The rolling surfaces 610 b, 610 b of the rack shaft 610 and the cylindrical rollers 123, 12

3 and the contact radius between the cylindrical rollers 123 and 123 and the side surfaces 61001 and 610d are slightly different, so that the cylindrical rollers 123 and 123 and the movement restricting portion (the root of the side surfaces 610d and 610d) are slightly different. Although a speed difference occurs, which causes sliding, the sliding loss is reduced and the sliding resistance of the rack shaft 610 can be reduced as compared with the case where the entire roller end surface is brought into sliding contact. FIG. 14 is a cross-sectional view of the electric power steering device according to the eleventh embodiment, similar to FIG. The present embodiment differs from the embodiment shown in FIG. 12 mainly in the configuration of the rack shaft. Therefore, other common configurations are denoted by the same reference numerals and description thereof is omitted. In the embodiment shown in FIG. 14, the width of the protruding portion 610c of the rack shaft 610 is increased compared to the embodiment of FIG. It is configured to contact the end face of 123 (arrow B). In this way, the movement of the cylindrical rollers 123, 123 in the axial direction is regulated by bringing the end faces of the cylindrical rollers 123, 123 into contact with the movement restricting portions 610d, 610 provided on the rack shaft 610, and A gap is formed between 123 and 123 and the main body 121 so that frictional sliding of the roller end surface does not occur. FIG. 15 is a cross-sectional view of the electric power steering device according to the twelfth embodiment, similar to FIG. The present embodiment differs from the embodiment shown in FIG. 13 mainly in that the configuration of the cylindrical roller is characteristically different. Therefore, other common configurations are denoted by the same reference numerals and description thereof is omitted. As described above, in the embodiment of FIGS. 1A and 1B, the rack shaft 11

The rolling surfaces 110b, 11 Ob of the cylindrical rollers 123, 123 are arranged at a predetermined angle (90 degrees in the figure) to each other, and the rotation axis of the cylindrical roller 123 is the axis of the rack shaft 110. And are parallel to the rolling surfaces 110b, 110b. Further, the two cylindrical rollers 123, 123 are pressed against the rolling surfaces 110b, 11 Ob by being pressed toward the bisector direction of the two rotating shafts by a screw member 124, which is an urging member. I have. That is, the pressing direction of the screw member 124 does not match the pressing direction of the cylindrical rollers 123, 123 against the rolling surfaces 110b, 110b. The separation force generated by the power transfer between the rack shaft 110 and the pinion 103a to separate the rack shaft 110 from the pinion 103a Since the roller 123 supports the rolling surface 110 b of the rack shaft 110 by the resultant pressing force acting on the rolling surface 110 b, the load applied by the needle bearing 122 a depends on the pressing force acting direction of the cylindrical rollers 123, 123. If the angle formed by the separation force is α, the pressing force will be as large as lZsina times (in the case of = 45 degrees as in this example, “2 times”). Since the rotating shaft is inclined with respect to the direction of the separating force, the main body 121 of the supporting device 120 which is inserted into the mounting hole provided in the housing 101 and supports the cylindrical rollers 123, 123 is moved from the axial direction of the main body 121. As a matter of fact, this is not possible unless the diameter is larger than the circumscribed circle of the cylindrical rollers 123, 123. Therefore, in order to make the rack support ¾5 compact, the cylindrical rollers 123, 123 must be small in both the axial and radial directions. Large, large-capacity needle bearing 122a However, if the configuration is not compact, the mountability to the vehicle will be poor, and if the main body 1 is large and heavy, the followability to the rack shaft will be impaired, and the rack shaft 110 and the There is a danger that an impact sound will be generated between the pinion 103a or the rack shaft 110 and the cylindrical rollers 123, 123. Further, the outer diameter of the cylindrical rollers 123, 123 must be set as small as possible. When the outer diameter of the cylindrical rollers 123, 123 is reduced, the rotational speed of the cylindrical rollers 123, 123 is increased, the load of the dollar bearing 122a is reduced, the rotational life is reduced, and the durability is impaired. On the other hand, according to the embodiment shown in Fig. 15, the rack support portion is made compact, the mounting performance is improved and the followability is improved by reducing the weight, and the durability of the 21 dollar bearing is improved. To improve It is possible. More specifically, in the present embodiment, outward conical surfaces 7 23 a and 7 23 a are formed on the end surfaces of the cylindrical rollers 72 3 and 72 3 by shaving the outer edge. ing. When viewed from the cross section in Fig. 15, the outer shape of the conical surfaces 723a and 723a (the side away from the axis of the main body 712) is parallel to the outer peripheral surface of the main body 7221. Has become. According to such a configuration, even if the outer diameter of the cylindrical rollers 72 3, 72 3 is increased, the cylindrical rollers 72 3, 72 3 viewed from the axial direction of the main body 72 1 The circumscribed circle can be reduced, and the total life of the needle bearings 122a and 122a can be reduced to extend the service life. FIG. 16 is a cross-sectional view similar to FIG. 15 of the electric power steering device according to the thirteenth embodiment. This embodiment differs from the embodiment shown in FIG. 15 mainly in that the configuration of the main body of the supporting device is characteristically different. Therefore, the other common configurations are denoted by the same reference numerals. Omitted. Since the present embodiment has the same features as the embodiment shown in FIG. 15, it is possible to use needle bearings 72 2 a and 72 2 a having a large outer diameter and a large rated load capacity. Therefore, the durability life of the twenty-two dollar bearings 122a and 122a can be further extended. Here, a procedure for assembling the support device will be described. In the embodiment shown in FIGS. 1A and 1B and 2, the shafts 122 and 122 supporting the cylindrical rollers 123 and 123 have both ends supported by the main body 122. Therefore, in order to secure the shaft support on the outer circumference of the main body 1 2 1 without increasing the diameter of the main body 1 2 1, the roller storage section of the main body 1 2 1 needs the shafts 1 2 2 and 1 2 It must be assembled from the direction perpendicular to 2. This will be described more specifically. First, the roller housing 1 2 1 g and shaft hole 1 2 1 h are each formed by forging or machining (Fig. 17A). Fig. 17A shows the main body 1 2 1 in the direction of arrow XVI II in Fig. 17A. Figure 18 shows this. With the main body 1 21 in such a state, the cylindrical roller 1 2 3 incorporating the needle bearing 1 2 2 a is stored in the roller storage section 1 2 1 g while the cylindrical roller 1 2 3 is stored in the shaft hole 1 2 1 h. The shafts 1 and 2 are inserted so that they are skewered (Fig. 17B). In addition, while the other cylindrical mouth 1 2 3 incorporating the needle bearing 1 2 2 a is housed in the other mouth 1 2 1 g, the shaft 1 inserted into the shaft hole 1 2 1 h. 22. Fit so as to skew in 2 (Fig. 17C). In this way, the assembly of the main body 121 is completed (Fig. 17D). However, as is evident from FIG. 18, the main body 122 requires complicated machining, is wasteful, is heavy, and has a high production cost. On the other hand, in the embodiment shown in FIGS. 15 and 16, in the assembled state, the cylindrical rollers 72 3 and 72 3 are provided with the conical surfaces 72 3 a and 72 The roller can be assembled from one axial direction. This will be described more specifically. First, in a single main body 721, one set of a mouthpiece storage section 721g and a shaft storage section 721h are formed (FIG. 19A). Fig. 20 shows the main body 7 2 1 viewed in the direction of the arrow XX in Fig. 19A, Fig. 21 shows the view of the main body 7 2 1 in the direction of the arrow XXI in Fig. 19A, and Fig. 19A. FIG. 22 is a diagram viewed in the direction of the arrow XXI I, and FIG. 23 is a diagram of the main body of FIG. 22 cut along line ΧΧΙΙ-ΠΠΙ and viewed in the direction of the arrow. With the main body 7 21 in such a state, two cylindrical rollers 7 2 3 incorporating the shaft 1 22 and the 21 bearing 12 2 a are arranged in parallel (may be separate), and the roller storage section 7 2 1 g And housed in the shaft housing 7 2 1 h to complete the assembly of the main body 7 2 1 (Fig. 1 9 C) Therefore, the main body 7 2 1 (at least the part supporting the rolling elements) can be formed into a shape that can be molded in the axial direction, and therefore can be cold forged and sintered without machining. As a result, it can be manufactured by die transfer processing such as metal injection molding or resin injection molding, so that it is possible to significantly reduce costs while eliminating waste and reducing weight. In addition, if the meat stealing portion 7 21 s is provided on the back surface of the main body 1 21, the weight of the main body 1 can be further reduced. As described above, the present invention has been described in detail with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be appropriately changed and improved without impairing the spirit thereof. Of course there is. For example, the pressing direction of the pressing portion may be three or more. Further, the present invention is not limited to a variable-stroke, low-cression-type electric power steering device, but also includes a constant-stroke ratio-type electric power steering device, a column assist type, a pinion assist type or a rack assist type electric power steering device. It is also suitable for a power steering device.

Claims

The scope of the claims

(1) In an electric power steering device that can output auxiliary steering force with an electric motor,

A housing,

A rack shaft having a rack tooth and a screw portion, the rack shaft being movable with respect to the nozing;

A pinion that has pinion teeth that match the rack teeth, and that transmits a steering force from a steering wheel to the rack shaft;

A support member provided on the housing and supporting the rack shaft; and a conversion member for converting the rotational force of the electric motor into a thrust of the rack shaft using a nut screwed into the screw portion. And

The support device includes a rolling element that rolls while pressing each support device guide surface along a direction intersecting with each other when the rack axis is viewed in the longitudinal direction. An electric power steering device, wherein when the directions of the pressing force applied to the surface are indicated by lines, the intersections of the lines are shifted from the center of the rack axis.

(2) An electric power steering device capable of outputting an auxiliary steering force by an electric motor, comprising: a rack shaft having rack teeth and being movable with respect to the nosing; and engaging with the rack teeth. A pinion that has pinion teeth and transmits steering force from the steering wheel to the rack shaft; A support device provided on the housing, for supporting the rack shaft, the rack shaft having a support device guide surface extending in a longitudinal direction at at least two force points on an outer peripheral surface,

A rolling element that rolls while pressing the support surfaces along the directions intersecting with each other when the rack shaft is viewed in the longitudinal direction; A shaft member which is freely supported and rotatably supports the rolling element; and by urging the other end of the shaft member, the rolling element is pressed toward a support device guide surface of the rack shaft. An electric power steering device, comprising: a biasing means.

(3) The urging means according to claim 2, characterized in that the urging means includes a pressing portion that contacts the other end of each shaft member, and an elastic member that elastically urges the pressing portion. Onboard electric power steering device.

(4) When the directions of the pressing force applied from the rolling elements to the guide surface of the support device are indicated by respective lines, the intersection of the lines is shifted from the center of the rack axis. 4. The electric power steering apparatus according to claim 2, wherein:

(5) The electric power steering apparatus according to any one of claims 1 to 4, wherein the rack shaft has a position restricting portion that restricts a position of the rolling element.

(6) The electric power steering apparatus according to any one of claims 1 to 5, wherein an outward conical surface is formed on at least one end surface of the rolling element. (7) The electric power steering device according to any one of claims 1 to 6, wherein at least a portion of the support device that supports the rolling element is formed by a mold transfer process. apparatus.