US20130142675A1

US20130142675A1 - Fluid control device

Info

Publication number: US20130142675A1
Application number: US13/756,361
Authority: US
Inventors: Tatsushi NABEI; Yukie Nakamura
Original assignee: CKD Corp
Current assignee: CKD Corp
Priority date: 2010-08-20
Filing date: 2013-01-31
Publication date: 2013-06-06
Also published as: TW201211431A; WO2012023342A1; JP5150009B2; KR20130021404A; CN103097789A; TWI427230B; JPWO2012023342A1; KR101250654B1

Abstract

In a fluid control device, a valve body is prevented from being pressed forcefully against a valve seat or the like, and an excessive load is prevented from acting on a motor. A flow rate adjustment device includes a first engagement portion, and a second engagement portion that is capable of moving relative to the first engagement portion and transmitting and receiving rotary force. The flow rate adjustment device includes a valve body that adjusts an opening of a flow passage, and a rod that is coupled to the valve body. The flow rate adjustment device further includes a male screw portion and a female screw portion that are intermeshed so as to be fed relative to each other in the axial direction, a projecting portion that restricts movement of the second engagement portion, and a first cylinder that restricts movement of the rod.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a fluid control device that controls a position of a valve body on the basis of rotation of a motor.
2. Description of the Related Art
In a conventional fluid control device of this type, a position of the valve body in an open condition is determined by rotating a male screw member coupled to a drive shaft of the motor such that a female screw member meshed to the male screw member is fed in an axial direction of the male screw member (see Patent Documents 1 and 2, for example). In the devices described in Patent Documents 1 and 2, a stop position of the valve body in the open condition is determined when a piston coupled to the valve body impinges on the female screw member.

Patent Document 1: Japanese Patent Application Publication No. 2003-083466
Patent Document 2: Japanese Patent Application Publication No. 2007-278514

Incidentally, with the devices described in Patent Documents 1 and 2, the female screw member may impinge on the piston or another member when an opening of the valve body in the open condition is reduced by feeding the female screw member in the axial direction of the male screw member. In this case, the valve body may be pressed forcefully against a valve seat or the like, and an excessive load may be exerted on the motor when feeding of the female screw member is restricted.

BRIEF DESCRIPTION OF THE INVENTION

The present invention has been designed in consideration of these circumstances, and a main object thereof is to prevent a valve body from being pressed forcefully against a valve seat or the like and an excessive load from being exerted on a motor in a fluid control device.
To solve the problem described above, the present invention employs following means.
First means is a fluid control device including: a motor having a drive shaft; a first engagement portion provided on the drive shaft; a second engagement portion configured to move relative to the first engagement portion in an axial direction of the drive shaft and receive a rotary force from the first engagement portion. A valve main body has a flow passage for a fluid and a valve seat portion; a valve body is provided to face the valve seat portion in order to adjust an opening of the flow passage. A moving member is coupled to the valve body of which movement in the axial direction is permitted and of which rotation about the drive shaft is restricted. An elastic member is configured to exert a force on the moving member in a direction for causing the valve body to approach the valve seat portion. A first restricting portion is configured to restrict movement of the second engagement portion to the side of the valve seat portion beyond a first restriction position. And a second restricting portion is configured to restrict movement of the moving member to the side of the valve seat portion beyond a second restricting position. The second engagement portion and the moving member are screwed together such that the second engagement portion and the moving member move relative to each other in the axial direction when rotated relative to each other.
According to the configuration described above, the first engagement portion provided on the drive shaft of the motor is rotated by driving the motor. Rotary force is transmitted from the first engagement portion to the second engagement portion, and as a result, the second engagement portion is rotated. Further, the flow passage for the fluid and the valve seat portion are provided in the valve main body, and the valve body for adjusting the opening of the flow passage is provided to face the valve seat portion. The moving member is coupled to the valve body such that movement thereof in the axial direction of the drive shaft is permitted but rotation thereof about the axis is restricted.
The male screw portion and the female screw portion are provided on either the second engagement portion or the moving member, respectively. The male screw portion and the female screw portion are meshed to each other so as to be fed relative to each other in the axial direction of the drive shaft when rotated relative to each other. When the second engagement portion is rotated, therefore, the moving member that is restricted to rotate and the second engagement portion rotate relative to each other.
At this time, movement of the second engagement portion to the valve seat portion side beyond the first restriction position is restricted by the first restricting portion. Therefore, when the drive shaft is rotated in a direction for causing the second engagement portion and the moving member to approach each other, or in other words a direction for pressing the second engagement portion against the first restricting portion, the moving member is fed in a direction separating away from the valve seat portion. Force is exerted on the moving member by the elastic member in a direction for causing the valve body to approach the valve seat portion. Hence, when the moving member is fed, the moving member is moved against the force of the elastic member. A distance between the valve seat portion and the valve body, or in other words the opening of the flow passage, is adjusted in accordance with an amount by which the moving member is fed.
When the drive shaft is rotated in a direction for causing the second engagement portion and the moving member to head away from each other, on the other hand, the moving member is fed in a direction approaching the valve seat portion. At this time, force is exerted on the moving member by the elastic member in a direction for causing the valve body to approach the valve seat portion. And therefore the second engagement portion is pressed against the first restricting portion via the male screw portion and the female screw portion that are intermeshed each other. When the moving member reaches the second restriction position, movement of the moving member to the valve seat portion side is restricted by the second restricting portion.
Here, the first engagement portion and the second engagement portion are capable of relative movement in the axial direction of the drive shaft. Therefore, by rotating the second engagement portion when movement of the moving member is restricted, the second engagement portion is fed in a direction separating away from the moving member, or in other words a direction separating away from the first restricting portion. Hence, even when the motor is driven further in a condition in which movement of the moving member is restricted, situations in which the valve body is pressed forcefully against the valve seat portion or an excessive load is exerted on the motor can be suppressed. As a result, particle generation from the valve body and the valve seat portion, deformation of and damage to the valve body and the valve seat portion, damage to the motor, or the like can be suppressed.
Further, the first engagement portion and the second engagement portion are capable of transmitting rotary force to each other and capable of moving relative to each other in the axial direction of the drive shaft. Therefore, a reaction to the force for feeding the moving member in the axial direction and a reaction to the force for feeding the second engagement portion in the direction separating away from the first restricting portion can be prevented from acting on the drive shaft of the motor in the axial direction. As a result, an increase in a rotary load of the motor can be suppressed, whereby a reduction in a durability of the motor and an increase in a size of the motor can be suppressed.
In second means pertaining to the first aspect of the invention, the second restricting portion is provided with a spacer for adjusting the second restriction position, and in a condition where movement of the moving member is restricted by the second restricting portion, a gap is formed between the valve seat portion and the valve body.
According to the above configuration, the second restriction position is adjusted by the spacer in the second restricting portion for restricting movement of the moving member to the valve seat portion side beyond the second restriction position. Therefore, the gap between the valve seat portion and the valve body, or in other words a flow condition of the fluid, in a condition of maximum closeness between the valve body and the valve seat portion can be controlled precisely. Further, in the condition where movement of the moving member is restricted by the second restricting portion, the gap is formed between the valve seat portion and the valve body, and therefore the valve body can be prevented from impinging on the valve seat portion. As a result, a situation in which particles are generated from the valve body and the valve seat portion can be suppressed effectively. The above configuration is particularly effective when applied to a flow rate adjustment device or a pressure adjustment device used in a condition where the valve body keeps the opening of the flow passage constant.
In third means pertaining to the second aspect of the invention, a cylinder configured to guide movement of the moving member in the axial direction is further provided, and an insertion port into which the spacer is inserted from outside is formed in the cylinder.
According to the above configuration, movement of the moving member in the axial direction is guided by the cylinder. Further, the spacer can be inserted through the insertion port from the outside of the cylinder. Therefore, the gap between the valve seat portion and the valve body can be adjusted finely by the spacer after assembling the fluid control device. Hence, a high degree of dimensional precision is not required in the valve main body, the cylinder, the moving member, or the like, and as a result, fluid control precision can be maintained while suppressing costs.
In fourth means pertaining to any of the first to third aspects of the inventions, one of the first engagement portion and the second engagement portion includes a rectangular parallelepiped-shaped insertion portion, the other of the first engagement portion and the second engagement portion includes a recessed portion into which the insertion portion is inserted in the axial direction, and outside surfaces of the insertion portion and inside surfaces of the recessed portion are mutually parallel and fitted together with a gap between the surfaces.
According to the above configuration, the rectangular parallelepiped-shaped insertion portion provided on one of the first engagement portion and the second engagement portion can be inserted into the recessed portion provided in the other in the axial direction of the drive shaft. Further, the mutually parallel outside surfaces of the insertion portion and the inside surfaces of the recessed portion are fitted together with a gap therebetween. Hence, the first engagement portion and the second engagement portion can be made capable of relative movement in the axial direction of the drive shaft, and rotary force can be transmitted between the first engagement portion and the second engagement portion. The first engagement portion and the second engagement portion can therefore be realized by a simple configuration.
Moreover, by exposing the second engagement portion and rotating the second engagement portion by hand, the position of the valve body can be adjusted manually. As a result, a maintainability of the fluid control device can be improved.
When the motor is constituted by a stepping motor that rotates in synchronization with pulse power, as in fifth means pertaining to any of the first to fourth aspects of the inventions, an excessive load can be prevented from acting on the motor, and as a result, the stepping motor can be prevented from losing steps. Hence, a stepping motor that exhibits superior position adjustment precision and controllability can be employed while suppressing a reduction in the position adjustment precision due to loss of steps.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial sectional view showing a flow rate adjustment device;

FIG. 2 is a partially enlarged view of FIG. 1;

FIGS. 3A and 3B are a view showing an insertion port and a shim;

FIG. 4 is an exploded perspective view showing a first engagement portion and a second engagement portion;

FIG. 5 is a partially enlarged view showing a valve body opening operation performed in the flow rate adjustment device; and

FIG. 6 is a partially enlarged view showing a valve body closing operation performed in the flow rate adjustment device.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

An embodiment will be described below with reference to the drawings. In this embodiment, the present invention is realized as a flow rate adjustment device that adjusts a flow rate of a fluid in a semiconductor manufacturing apparatus or the like.
FIG. 1 is a partial sectional view showing a flow rate adjustment device 10. The flow rate adjustment device 10 (fluid control device) includes a valve main body 20, a first cylinder 30, a second cylinder 50, a motor 110, and a housing 120.
The valve main body 20 is provided with an inflow port 25 through which a fluid (a liquid) flows in, and an outflow port 26 through which the fluid flows out. The valve main body 20 is formed of a chemical-resistant fluorine resin, for example PTFE (Poly Tetra Fluoro Ethylene). A flow passage 21 connected to the inflow port 25, a flow passage 23 connected to the outflow port 26, and a valve chamber 22 that connects the flow passages 21 and 23 are formed in an interior of the valve main body 20. The valve chamber 22 is formed as a columnar space that opens onto a surface (an upper surface) of the valve main body 20. The fluid flows in at a predetermined pressure through the inflow port 25.
The first cylinder 30 is fixed to the valve main body 20 on the open surface (the upper surface) of the valve chamber 22. The first cylinder 30 is formed of a general purpose resin, for example PP (Poly Propylene). A columnar first housing portion 31 is formed in an interior of the first cylinder 30. The first housing portion 31 penetrates the first cylinder 30, and a central axis of the valve chamber 22 matches a central axis of the first cylinder 30. The first housing portion 31 communicates with the valve chamber 22.
The second cylinder 50 is fixed to a surface (an upper surface) of the first cylinder 30 on an opposite side to the valve main body 20. The second cylinder 50 is formed of a general purpose resin, for example PP (Poly Propylene). A columnar second housing portion 54 and a columnar third housing portion 55 are formed in an interior of the second cylinder 50. The second housing portion 54 and the third housing portion 55 communicate with each other, and respective central axes thereof match a central axis of the first housing portion 31. The second housing portion 54 opens onto a surface (a lower surface) of the second cylinder 50, while the third housing portion 55 opens onto an opposite side surface (an upper surface) of the second cylinder 50. The second housing portion 54 communicates with the first housing portion 31 in the first cylinder 30. A diameter of the second housing portion 54 is larger than a diameter of the first housing portion 31. Therefore, a step is formed between the first housing portion 31 and the second housing portion 54.
Respective inner walls of the second housing portion 54 and the third housing portion 55 project inwardly such that an annular projecting portion 51 is formed between the second housing portion 54 and the third housing portion 55. In other words, the projecting portion 51 serves as a boundary between the second housing portion 54 and the third housing portion 55.
The stepping motor 110 (the motor) is fixed to the second cylinder 50 on the open surface (the upper surface) of the third housing portion 55 with an attachment portion 113. The motor 110 includes a drive circuit 112, and a signal line 132 from a controller (not shown) is connected to the drive circuit 112. A drive control signal (a pulse signal) is input into the drive circuit 112 from the controller, and a rotation position of a drive shaft 111 of the motor 110 is controlled by the drive control signal, which corresponds to a number of steps. Further, a photo sensor 74 is provided on an outer periphery of the second cylinder 50, and a signal line 131 from the controller is connected to the photo sensor 74. The housing 120 is fixed to the surface (the upper surface) of the first cylinder 30 on the opposite side to the valve main body 20. The second cylinder 50, the motor 110, and the photo sensor 74 are covered by the housing 120.
FIG. 2 is a partially enlarged view of FIG. 1. As shown in the drawing, a columnar rod 60 is housed in the first housing portion 31 and the second housing portion 54. The rod 60 is formed from a chemical-resistant fluorine resin, for example PVDF (Poly Vinylidene Di Fluoride). A columnar valve body 41 is coupled to an end portion of the rod 60 on the side of the valve main body 20. A diaphragm 42 is provided on an outer peripheral edge of the valve body 41. An annular support portion 43 is provided on an outer peripheral edge of the diaphragm 42. The support portion 43 is fixed to be sandwiched between the valve main body 20 and the first cylinder 30. The valve chamber 22 is separated from the first housing portion 31 by the diaphragm 42 so that fluid in the valve chamber 22 is prevented from flowing into the first housing portion 31.
The valve body 41 includes an enlarged diameter portion 41 a having a larger diameter than other parts. An annular valve seat portion 24 is formed in the valve main body 20 in a connecting portion that connects the flow passage 21 to the valve chamber 22. The enlarged diameter portion 41 a of the valve body 41 is disposed to face the valve seat portion 24. A wall surface of the valve seat portion 24 is parallel to a wall surface of the enlarged diameter portion 41 a such that a distance between the respective wall surfaces remains constant.
The rod 60 (a moving member) includes a first rod portion 61 housed in the first housing portion 31 and a second rod portion 62 housed in the second housing portion 54. A diameter of the second rod portion 62 is larger than a diameter of the first rod portion 61. In other words, the first rod portion 61 and the second rod portion 62 have dimensions that correspond to the first housing portion 31 and the second housing portion 54, respectively. A central axis of the rod 60 matches the central axis of the valve body 41.
An annular groove portion 65 is formed in an outer peripheral surface of the first rod portion 61. An annular seal member 77 is fitted into the groove portion 65 such that an inner peripheral surface of the first cylinder 30 is sealed from the outer peripheral surface of the first rod portion 61 by the seal member 77. The first rod portion 61 slides in an axial direction thereof while being guided by an inner peripheral surface of the first housing portion 31. At this time, the second rod portion 62 moves in an axial direction thereof in the second housing portion 54.
A groove 52 that extends in the axial direction of the second housing portion 54 is formed in a part of an inner wall of the second housing portion 54. The groove 52 extends from the vicinity of the projecting portion 51 to a first cylinder 30 side. A pin 72 that extends in an outer diameter direction is provided in an outer peripheral edge of the second rod portion 62 of the rod 60. A tip end of the pin 72 is inserted into the groove 52 to enable the second rod portion 62 to move in the axial direction thereof while restricting rotation of the second rod portion 62 about the axis thereof.
A sensor insertion port 53 that penetrates the second cylinder 50 in a radial direction is formed in a part of the second cylinder 50 that opposes the groove 52. A detection portion 74 a provided on a tip end of the photo sensor 74 is inserted into the interior of the second cylinder 50 through the sensor insertion port 53. A pin 73 that extends in the outer diameter direction is provided in the outer peripheral edge of the second rod portion 62 of the rod 60. A tip end of the pin 73 is inserted between a light emitting portion and a light receiving portion of the detection portion 74 a such that light emitted from the light emitting portion is blocked by the pin 73, and as a result, a fully open position of the valve body 41 is detected. Note that FIGS. 1 and 2 show a condition in which the valve body 41 has been moved to a maximally closed side.
A cylindrical groove 63 is formed in an end surface of the second rod portion 62 on the side of the motor 110. A central axis of the groove 63 matches the central axis of the second rod portion 62 (the first rod portion 61). A spring 71 (an elastic member) having a substantially identical diameter to a diameter of the groove 63 is inserted into an interior of the groove 63. One end of the spring 71 contacts a bottom portion of the groove 63, and the other end contacts the projecting portion 51. The spring 71 exerts an elastic force on the rod 60 and the projecting portion 51 in order to move the rod 60 in a direction separating away from the projecting portion 51, or in other words a direction for causing the valve body 41 to approach the valve seat portion 24.
A part of the second rod portion 62 that projects further toward the outer diameter side than the first rod portion 61 faces the upper surface of the first cylinder 30. Therefore, when the rod 60 is moved in the direction separating away from the projecting portion 51, the second rod portion 62 impinges on the first cylinder 30 (a second restricting portion) such that movement of the rod 60 to the valve seat portion 24 side is restricted. At this time, the valve body 41 is in a condition of maximum closeness to the valve seat portion 24, and therefore an opening of the flow passage 21, or in other words a flow rate of the fluid flowing out through the outflow port 26, is at a minimum.
Here, a shim 75 for adjusting a position (a second restriction position) in which movement of the rod 60 to the valve seat portion 24 side is restricted is provided between the second rod portion 62 and the first cylinder 30. FIG. 3A is a side view of the second cylinder 50, and FIG. 3B is a plan view of the shim 75.
As shown in FIG. 3A, an insertion port 56 enabling insertion of the shim 75 (a spacer) from the outside is formed in the second cylinder 50. The insertion port 56 penetrates the second cylinder 50, and is formed in a part where the first cylinder 30 and the second cylinder 50 face each other. As shown in FIG. 3B, the shim 75 is formed in a “U” shape, and includes a two-pronged portion 75 a that is inserted between the first cylinder 30 and the second rod portion 62, and an arc-shaped arc portion 75 b. The shim 75 is inserted through the insertion port 56 until the arc portion 75 b impinges on the first rod portion 61 of the rod 60. Accordingly, the shim 75 can be inserted through the insertion port 56 after assembling the flow rate adjustment device 10.
The position in which movement of the rod 60 to the valve seat portion 24 side is restricted is adjusted by adjusting a thickness of the shim 75 inserted between the second rod portion 62 and the first cylinder 30. A shim having a thickness of 0.2 mm or 0.1 mm is used either singly or in combinations of a plurality as the shim 75. In this embodiment, when the second rod portion 62 is pressed against the first cylinder 30 via the shim 75, a distance (a gap) between the valve seat portion 24 and the valve body 41 in the axial direction of the valve body 41 is adjusted to 0.2 mm. Note that the distance between the valve seat portion 24 and the valve body 41 may be adjusted appropriately in accordance with an application of the flow rate adjustment device 10.
Returning to FIG. 2, a part of the second rod portion 62 surrounded by the groove 63 serves as a female screw portion 64 having a female screw thread cut into an interior thereof. The female screw portion 64 is formed in a cylindrical shape to extend in the axial direction of the second rod portion 62. The female screw portion 64 and the spring 71 (the groove 63) are provided coaxially, and therefore a space for disposing the female screw portion 64 and the spring 71 in the axial direction of the rod 60 can be reduced.
The drive shaft 111 of the motor 110 is inserted into the third housing portion 55. The drive shaft 111 is provided with a first engagement portion 90. A second engagement portion 80 that engages with the first engagement portion 90 is housed in the third housing portion 55 and the second housing portion 54. The first engagement portion 90 and the second engagement portion 80 are formed of a material capable of transmitting driving force from the motor 110, for example stainless steel.
FIG. 4 is an exploded perspective view showing the first engagement portion 90 and the second engagement portion 80. As shown in the drawing, the second engagement portion 80 includes a male screw portion 82 into which a male screw thread is cut, and a head portion 81 having a larger diameter than the male screw portion 82. The second engagement portion 80 has an overall shape that resembles a slotted screw, and the male screw portion 82 extends in an axial direction thereof. A groove portion 83 (a recessed portion) that extends in a radial direction is formed in the head portion 81. A width and a depth of the groove portion 83 are constant, and the depth of the groove portion 83 is substantially equal to a thickness of the head portion 81. Two inside surfaces 80 a of the groove portion 83 are parallel to each other and equidistant from a central axis of the head portion 81. The central axis of the head portion 81 matches a central axis of the male screw portion 82.
The first engagement portion 90 (an insertion portion), which is inserted into the groove portion 83 of the second engagement portion 80, is provided on the drive shaft 111 of the motor 110. The first engagement portion 90 is formed in a rectangular parallelepiped shape, and a central portion of the first engagement portion 90 in a lengthwise direction thereof is fixed to the drive shaft 111. The first engagement portion 90 includes mutually parallel outside surfaces 90 a. A thickness of the outside surface 90 a in an axial direction of the drive shaft 111 is set to be thinner than the thickness of the head portion 81 of the second engagement portion 80.
A lengthwise direction length of the first engagement portion 90 is substantially equal to a diameter of the head portion 81 of the second engagement portion 80. A width of the first engagement portion 90 is slightly narrower than the width of the groove portion 83 in the second engagement portion 80. The first engagement portion 90 is inserted into the groove portion 83 in the central axis direction while the central axis of the drive shaft 111 of the motor 110 is aligned with the central axis of the second engagement portion 80. As a result, the outside surfaces 90 a of the first engagement portion 90 and the inside surfaces 80 a of the groove portion 83 are fitted together with a gap therebetween.
Returning to FIG. 2, the first engagement portion 90 and the second engagement portion 80 are capable of moving relative to each other in the axial direction of the drive shaft 111 and capable of transmitting rotary force to each other. The male screw portion 82 of the second engagement portion 80 meshes with the female screw portion 64 of the second rod portion 62 (the rod 60). The rod 60 is pushed toward the valve seat portion 24 by the spring 71. The second engagement portion 80 is coupled to the rod 60 via the male screw portion 82 and the female screw portion 64. Accordingly, the second engagement portion 80 is pulled toward the valve seat portion 24 by the rod 60. When the second engagement portion 80 is moved toward the valve seat portion 24, the head portion 81 of the second engagement portion 80 impinges on the projecting portion 51 (the first restricting portion) such that movement of the second engagement portion 80 to the valve seat portion 24 side is restricted.
A thrust washer 76 that receives a force acting in the axial direction of the second engagement portion 80 is provided between the second engagement portion 80 and the projecting portion 51. Hence, when the second engagement portion 80 rotates about the male screw portion 82, the head portion 81 and the thrust washer 76 slide smoothly. Further, a force for pulling the second engagement portion 80 toward the valve seat portion 24 is received by the projecting portion 51 and the thrust washer 76. The position in which movement of the second engagement portion 80 is restricted corresponds to a first restriction position.
The respective central axes of the valve body 41, the rod 60, the second engagement portion 80, and the drive shaft 111 all match. The male screw portion 82 of the second engagement portion 80 and the female screw portion 64 of the rod 60 are fed relative to each other in the axial direction of the drive shaft 111 when rotated relative to each other. In other words, when the second engagement portion 80 is rotated by the drive shaft 111 via the first engagement portion 90, the distance between the head portion 81 of the second engagement portion 80 and the second rod portion 62 of the rod 60 is modified. FIG. 2 shows a condition in which a rotation position (a step number) of the drive shaft 111 of the motor 110 corresponds to a reference position (a reference step number). In this condition, the second rod portion 62 of the rod 60 impinges on the shim 75 and the head portion 81 of the second engagement portion 80 impinges on the thrust washer 76. Meanwhile, a gap (a space) is formed between a bottom portion of the first engagement portion 90 and a bottom portion of the groove portion 83 in the second engagement portion 80.
Next, referring to FIG. 5, an operation performed in the flow rate adjustment device 10 to increase the opening of the flow passage 21 using the valve body 41 will be described. Driving of the drive shaft 111 of the stepping motor 110 is controlled by the aforementioned controller.
When the drive shaft 111 is rotated in the direction of an arrow in the drawing, rotary force is transmitted from the first engagement portion 90 to the second engagement portion 80. The second engagement portion 80 is pulled toward the valve seat portion 24 by the elastic force of the spring 71, and movement of the second engagement portion 80 is restricted by the thrust washer 76 and the projecting portion 51. Further, rotation of the rod 60 in a rotary direction of the drive shaft 111 is restricted by the pin 72 inserted into the groove 52 in the second cylinder 50.
Hence, by rotating the male screw portion 82 of the second engagement portion 80, the female screw portion 64 is fed in a direction approaching the drive shaft 111 such that the head portion 81 of the second engagement portion 80 and the second rod portion 62 of the rod 60 approach each other. Accordingly, the rod 60 is moved in the direction of an arrow in the drawing, and in accompaniment therewith, the valve body 41 moves in a direction separating away from the valve seat portion 24. As a result, the distance between the valve seat portion 24 and the valve body 41, or in other words the opening of the flow passage 21, is adjusted such that the flow rate of the fluid flowing out into the flow passage 23 is adjusted.
Here, the first engagement portion 90 and the second engagement portion 80 are capable of relative movement in the axial direction of the drive shaft 111. Therefore, when the rod 60 is fed in the axial direction, a reaction to a force thereof can be prevented from acting on the drive shaft 111 in the axial direction. Further, the rotation position of the drive shaft 111 is controlled precisely on the basis of the step number of the motor 110, and therefore the opening of the flow passage 21 can be controlled precisely.
When the rod 60 is moved further such that the pin 73 is detected by the detection portion 74 a of the photo sensor 74, it is determined that the valve body 41 has reached the fully open position, and rotation of the drive shaft 111 is stopped. At this time, a gap is formed between the second rod portion 62 of the rod 60 and the projecting portion 51. In other words, the rod 60 can be moved in the direction of the arrow in the drawing until the second rod portion 62 impinges on the projecting portion 51, but when the fully open position of the valve body 41 is detected by the detection portion 74 a, further movement of the rod 60 is prohibited. Thus, the rod 60 can be prevented from impinging on the projecting portion 51, and as a result, an excessive load can be prevented from acting on the motor 110.
Referring to FIG. 6, an operation performed in the flow rate adjustment device 10 to reduce the opening of the flow passage 21 using the valve body 41 will be described. Driving of the drive shaft 111 of the stepping motor 110 is controlled by the aforementioned controller.
When the drive shaft 111 is rotated in the direction of an arrow in the drawing (an opposite direction to that of FIG. 5), rotary force is transmitted from the first engagement portion 90 to the second engagement portion 80. In this case, when the male screw portion 82 of the second engagement portion 80 is rotated, the female screw portion 64 is fed in a direction approaching the valve seat portion 24 such that the head portion 81 of the second engagement portion 80 heads away from the second rod portion 62 of the rod 60. Accordingly, the rod 60 is moved in the direction of an arrow in the drawing (an opposite direction to that of FIG. 5), and in accompaniment therewith, the valve body 41 moves in a direction approaching the valve seat portion 24. As a result, the distance between the valve seat portion 24 and the valve body 41, or in other words the opening of the flow passage 21, is adjusted such that the flow rate of the fluid flowing out into the flow passage 23 is adjusted.
When the second rod portion 62 of the rod 60 impinges on the shim 75 such that movement of the rod 60 is restricted by the shim 75 and the first cylinder 30, the valve seat 41 is in the condition of maximum closeness to the valve seat portion 24. When the drive shaft 111 is rotated further from this condition, the head portion 81 of the second engagement portion 80 and the second rod portion 62 of the rod 60 are fed relative to each other in a direction separating away from each other. Here, the first engagement portion 90 and the second engagement portion 80 are capable of relative movement in the axial direction of the drive shaft 111, while movement of the rod 60 in the direction toward the valve seat portion 24 is restricted. Hence, when the drive shaft 111 and the second engagement portion 80 are rotated, the second engagement portion 80 is moved in a direction that causes the head portion 81 to head away from the thrust washer 76 and the projecting portion 51, or in other words the direction of an arrow in the drawing.
Hence, even when movement of the rod 60 is restricted and the valve body 41 is in the condition of maximum closeness to the valve seat portion 24, rotation of the second engagement portion 80 and the drive shaft 111 is not restricted. Therefore, an excessive load can be prevented from acting on the motor 110, and as a result, the motor 110 can be prevented from losing steps. Here, a space is provided between the bottom portion of the first engagement portion 90 and the bottom portion of the groove portion 83, and therefore the second engagement portion 80 can be allowed to move away sufficiently in the direction toward the motor 110 even when the drive shaft 111 is rotated while movement of the rod 60 is restricted.
The second engagement portion 80 can be exposed by detaching the housing 120 and the motor 110 from the flow rate adjustment device 10. In so doing, the second engagement portion 80 can be rotated easily by hand, whereby the position of the valve body 41 can be adjusted manually. As a result, a maintainability of the flow rate adjustment device 10 can be improved.
The embodiment described in detail above exhibits following advantages.
The first engagement portion 90 and the second engagement portion 80 are capable of relative movement in the axial direction of the drive shaft 111. Therefore, by rotating the second engagement portion 80 when movement of the rod 60 is restricted, the head portion 81 of the second engagement portion 80 is fed in the direction separating away from the second rod portion 62 of the rod 60, or in other words a direction separating away from the projecting portion 51. Hence, an excessive load can be prevented from acting on the motor 110 even when the motor 110 is driven further from a condition in which movement of the rod 60 is restricted. As a result, the motor 110 can be prevented from losing steps, and the precision with which the position of the valve body 41 is adjusted can be prevented from decreasing. Further, damage to the motor 110 or the like can be suppressed.
Furthermore, the first engagement portion 90 and the second engagement portion 80 are capable of transmitting rotary force to each other and capable of moving relative to each other in the axial direction of the drive shaft 111. Therefore, a reaction to the force for feeding the rod 60 in the axial direction and a reaction to the force for feeding the head portion 81 of the second engagement portion 80 in the direction separating away from the projecting portion 51 can be prevented from acting on the drive shaft 111 of the motor 110 in the axial direction. As a result, an increase in a rotary load of the motor 110 can be suppressed, whereby a reduction in a durability of the motor 110 and an increase in a size of the motor 110 can be suppressed.
The second restriction position is adjusted by the shim 75 in an upper surface portion of the first cylinder 30, where movement of the rod 60 to the valve seat portion 24 side beyond the second restriction position is restricted. Therefore, the gap between the valve seat portion 24 and the valve body 41, or in other words a flow condition of the fluid, in the condition of maximum closeness between the valve body 41 and the valve seat portion 24, can be controlled precisely. Further, in a condition where movement of the rod 60 is restricted by the upper surface portion of the first cylinder 30, a gap is formed between the valve seat portion 24 and the valve body 41, and therefore the valve body 41 can be prevented from impinging on the valve seat portion 24. As a result, situations in which the valve body 41 is pressed forcefully against the valve seat portion 24, particles are generated from the valve body 41 and the valve seat portion 24, and the valve body 41 and the valve seat portion 24 are deformed or damaged can be suppressed effectively.
Movement of the rod 60 in the axial direction is guided by the first cylinder 30 and the second cylinder 50. Further, the shim 75 can be inserted through the insertion port 56 from the outside of the first cylinder 30. Therefore, the gap between the valve seat portion 24 and the valve body 41 can be adjusted finely by the shim 75 after assembling the flow rate adjustment device 10. Hence, a high degree of dimensional precision is not required in the valve main body 20, the first cylinder 30, the rod 60 or the like, and as a result, fluid control precision can be maintained while suppressing costs.
The rectangular parallelepiped-shaped insertion portion of the first engagement portion 90 can be inserted into the groove portion 83 of the second engagement portion 80 in the axial direction of the drive shaft 111. Further, the mutually parallel outside surfaces 90 a of the first engagement portion 90 and the inside surfaces 80 a of the groove portion 83 are fitted together with a gap therebetween. Hence, functions of the first engagement portion 90 and the second engagement portion 80 can be realized by a simple configuration.
The present invention is not limited to the above embodiment, and may be embodied as follows, for example.
In the above embodiment, the insertion portion is provided in the first engagement portion 90 and the groove portion 83 (the recessed portion) is formed in the second engagement portion 80. However, a groove portion (a recess portion) may be formed in the first engagement portion 90 and an insertion portion may be provided in the second engagement portion 80.
Further, as long as the first engagement portion 90 and the second engagement portion 80 are capable of moving relative to each other in the axial direction of the drive shaft 111 of the motor 110 and transmitting rotary force to each other, their shapes may be modified as desired.
In the above embodiment, the male screw portion 82 is provided on the second engagement portion 80 and the female screw portion 64 is provided in the rod 60. However, a female screw portion may be provided in the second engagement portion 80 and a male screw portion may be provided on the rod 60.
A configuration in which the valve body 41 contacts the valve seat portion 24 when the valve body 41 is in the condition of maximum closeness to the valve seat portion 24 may be employed. With this configuration, by allowing the second engagement portion 80 to move away in the direction toward the motor 110, situations in which the valve body 41 is pressed forcefully against the valve seat portion 24 and an excessive load is exerted on the motor 110 can be suppressed.
Instead of the spring 71, an elastic member made of a rubber material or the like, a configuration using repulsive force generated by a magnet, or the like may be employed.
A motor other than the stepping motor 110, for example a servo motor or a DC motor, may be employed.
The present invention is not limited to the flow rate adjustment device 10, and may be realized as a pressure adjustment device that adjusts a fluid pressure. Further, the fluid is not limited to a liquid, and a gas may be used instead.

Claims

What is claimed is:

1. A fluid control device comprising:

a motor having a drive shaft;

a first engagement portion provided on the drive shaft;

a second engagement portion configured to move relative to the first engagement portion in an axial direction of the drive shaft and receive a rotary force from the first engagement portion;

a valve main body having a flow passage for a fluid and a valve seat portion;

a valve body provided to face the valve seat portion in order to adjust an opening of the flow passage;

a moving member coupled to the valve body of which movement in the axial direction is permitted and of which rotation about the drive shaft is restricted;

an elastic member configured to exert a force on the moving member in a direction for causing the valve body to approach the valve seat portion;

a first restricting portion configured to restrict movement of the second engagement portion to the side of the valve seat portion beyond a first restriction position; and

a second restricting portion configured to restrict movement of the moving member to the side of the valve seat portion beyond a second restricting position,

wherein the second engagement portion and the moving member are screwed together such that the second engagement portion and the moving member move relative to each other in the axial direction when rotated relative to each other.

2. The fluid control device according to claim 1, wherein the second restricting portion is provided with a spacer for adjusting the second restriction position, and

in a condition where movement of the moving member is restricted by the second restricting portion, a gap is formed between the valve seat portion and the valve body.

3. The fluid control device according to claim 2, further comprising a cylinder configured to guide movement of the moving member in the axial direction,

wherein an insertion port into which the spacer is inserted from outside is formed in the cylinder.

4. The fluid control device according to claim 1, wherein one of the first engagement portion and the second engagement portion includes a rectangular parallelepiped-shaped insertion portion,

the other of the first engagement portion and the second engagement portion includes a recessed portion into which the insertion portion is inserted in the axial direction, and

outside surfaces of the insertion portion and inside surfaces of the recessed portion are mutually parallel and fitted together with a gap between the surfaces.

5. The fluid control device according to claim 1, wherein the motor is a stepping motor configured to rotate in synchronization with pulse power.

6. The fluid control device according to claim 2, wherein one of the first engagement portion and the second engagement portion includes a rectangular parallelepiped-shaped insertion portion,

7. The fluid control device according to claim 3, wherein one of the first engagement portion and the second engagement portion includes a rectangular parallelepiped-shaped insertion portion,

8. The fluid control device according to claim 2, wherein the motor is a stepping motor configured to rotate in synchronization with pulse power.

9. The fluid control device according to claim 3, wherein the motor is a stepping motor configured to rotate in synchronization with pulse power.

10. The fluid control device according to claim 4, wherein the motor is a stepping motor configured to rotate in synchronization with pulse power.