WO1995009092A1

WO1995009092A1 - Suspension for motor vehicles, mainly for low-floor buses

Info

Publication number: WO1995009092A1
Application number: PCT/HU1994/000042
Authority: WO
Inventors: László EISZRICH; Károly PINTÉR
Original assignee: Ikarus Jármügyártó Rt
Priority date: 1993-09-27
Filing date: 1994-09-23
Publication date: 1995-04-06
Also published as: HU9302715D0; HUT69895A

Abstract

The invention relates to suspension for motor vehicles, mainly for the steered axle of low-floor buses, having pneumatic springs connected to the body or frame of the vehicle and radius rods for guiding the running gear. The upper armature (11) of the pneumatic spring (10), connected to the vehicle body (2) has an articulated - expediently a ball-and-socket - joint to which one telescope stalk (53) of a linear guide path telescope (12) is coupled, while its other telescope stalk (13) of the telescope (12) is fixed in, and - in a sealed way - passed through, a piston crown (58) of piston (47) of the pneumatic spring (10), this other telescope stalk (13) being linked again through a joint - expediently through a ball-and-socket joint (67) - with the axle element guided by a radius rod (37).

Description

Suspension for motor vehicles, mainly for low-floor buses

The invention relates to suspension for motor vehicles, mainly for the steered axle of low-floor buses, having pneumatic springs connected to the body or frame of the vehicle and radius rods for guiding the running gear.

The invention is equally suitable for rigid-axle transmissions and for transmissions

comprising independently suspended wheels. The aim of the invention is, mainly, to

propose a transmission suspension suited to low-floor town busses, the floor of which

is sufficiently low to render possible the omission of steps or step-boards normally required for passenger convenience.

For the fulfillment of this aim new constructional features have to be introduced, together with setting the object of providing a corridor of min. 950 mm width in the middle of the vehicle body. The step-free floor height is max. 350 mm. With these dimensional limits the permissible loading of the front axle and rubber tires should

be 7000 kg.

For satisfying the above conditions, there are known running-gear arrangements, both of the independently suspended and of the rigid-axle designs. An arrangement of independent suspension is described in the Patent Specification DE-3734212, where instead of the usual single pneumatic spring two smaller ones are used, the two being linked through a linearly guiding telescope assembly, and a separate shock damper is provided. That solution is extremely expensive. Rigid axle transmissions have also been proposed for low-floor busses. Such an arrangement is described in the Patent Specification No. GB-1,355,843, where two longitudinal radius rods are rigidly attached - for rigid torque transmission, - to the rigid bridge which is guided by these and a queer rod, commonly known as Panhard rod is attached as well.

The required spring action is provided by a pneumatic spring on either side, bearing up against the tie points of the radius rods. Neither this arrangement can provide a limited height sufficient to allow complete omission of steps nor stepboard and the 900 mm width of the middle passage corridor between the proposed pneumatic springs can be provided. Neither of these arrangements is suitable for accomplishing the floor-height (350 mm) aimed at and the required width (900 mm) of the corridor between passenger seats, due to the dimensions of the rigid-axle arrangement, and to the prohibitive costs of an independent suspension.

Therefore our efforts have been to find a construction that satisfies the requirements laid down in the present patent specification. The aim have been accomplished by a solution according the claims, by adopting a pneumatic spring suspension that can be fit in the wheel box and provides a telescopic guide for the piston of the pneumatic spring eliminating or reducing the additional eccentric distortion of the resilient jacket of the pneumatic spring. The invention relates to a novel suspension for motor vehicles, mainly for the steered axles of low-floor buses, said axles being provided with pneumatic springs attached to the vehicle body or to the frame of the latter, comprising radius rods guiding the transmission.

According to the invention: The upper armature of the pneumatic spring, connected to the vehicle body as an

articulated - expediently a ball-and-socket - joint to which one telescope stalk of a linear guide path telescope is coupled, while its other telescope stalk of the telescope is fixed in, and - in a sealed way - passed through, a piston crown of piston of the pneumatic spring, this other telescope stalk being linked again through a joint - expediently through a ball-and-socket joint - with the axle element guided by a radius

rod.

In an advantageous embodiment of the invention:

The length of the telescope stalk provided with a rolling diaphragm and protruding from the pneumatic spring is approximately equal to the nominal distance between the upper armature of the pneumatic spring and lower rim of piston. The axle element is a rigid bridge to which at each of both ends - near the steering bolts - a radius rod is rigidly attached, the radius rods being spring-steel plate arranged approximately parallel with the bottom plane of the vehicle body and coupled to the vehicle body by means of a bolt with its axis parallel to said plane, and with the telescope stalk of the pneumatic spring being connected to the upper part of the rigid bridge.

In the embodiment of the invention adaptable to the steered front axle: The rigid bridge is a reversed Elliot axle and an angle of approx. 15° is enclosed by the radius arm and the longitudinal axis of the vehicle body, the radius rod is accommodated on the forward side of the front-side rigid bridge which is of deepened (gantry) shape, the radius rod being connected to the deepened axle body of the rigid bridge, the centerline of the pneumatic spring enclosing an angle of about 8° when tilted forward with respect to the direction of travel, and its upper armature is clamped to a support provided within the wheel box of the vehicle body: to the rigid bridge and to the vehicle body a telescopic shock damper is connected behind

said rigid bridge.

Since no transverse radius rods (Panhard rods) are required, very low floor heights can be accomplished. The space requirement of steps is reduced so that no "boots" have to be added to the transmission for supporting the pneumatic springs resulting in reduced weight and unsprung masses. There is no need to use a curve stabilizer, since the longitudinal radius rods fulfil the duty of curve stabilization. Thus, they act

as curve stabilizers, although normally no curve stabilizers are installed in town buses. The curve stabilizer ensures extremely favorable conditions for passenger convenience while getting off and into a bus in its "kneeling" position, i.e. when the pneumatic springs are discharged on one side to reduce sidewise tilt that would cause inconvenience to the passengers sitting in the bus, through compressing the pneumatic spring on the other side of the bus while it is staying in the bus stop. This method results in sparing the quantity of air required for subsequent recharging of the spring.

In the following, the invention is explained in detail on the figures representing an embodiment serving as an example. Figure 1 is a side view of rigid portal axle suspension. Figure 2 is a rear view of the suspension according to Fig. 1, Figure 3 is a top view of the suspension according to Fig.1 , Figure 4 is a longitudinal section of a linear guide path telescope, Figure 5 is a side view of a suspension with radius rods of spring-steel plate, Figure 6 is a top view of the suspension according to Fig.5. The side view of the rigid-axle portal suspension of the vehicle body 2 of a low-floor bus 1 is shown in Figure 1. The height of floor 4 above ground level is 350 mm with the floor 4 directly mounted on beams 5. The front wheel 6 is surrounded by a wheel box 7 which is a load carrying part of the vehicle body too. On its inner side 8 a support 9 is provided to which the upper armature 11 of a pneumatic spring 10 is

attached. A lower stalk 13 of telescope 12 of the pneumatic spring 10 is connected to a supporting block 19 by a connecting bolt 20 reeved through the ball-and-socket

joint 21, where said supporting block 19 is attached to an upper surface 18 of a

swanneck section 15 of the axle body 14. The supporting block 19 is fixed near the suspension bolt 16 located in the swanneck section, the swivelling part 17 being supported by said supporting block 19 and wheel 6. On the rear side of the swanneck section 15 a bearing surface 22 is provided, to which a telescopic cylinder 16 of a

hydraulic shock damper 25 connected to a 24 consol of the swivelling part 17 of the suspension is attached, and the piston rod 27 of said cylinder is connected to a supporting bracket 28 provided on the inner side of the wheel box 7.

To the swivelling part 17 a steering arm 29 and a trapezoid arm 30 are attached with a steering connecting rod 31, the latter serving for linking the trapezoid arms 30. The swivelling part 17 carries a brake support 33, with a brake diaphragm 32 mounted to it through a clamp plate 35 and clamping bolts 36.

The radius rod 37 is made of flat spring-steel, with its flat surface being arranged parallel with the lower plane of the vehicle body 2 i.e. with the floor surface. The other end 39 of the radius rod is rigidly clamped in a pressure-plate spring eye 40 and is coupled through pin 42 located in it to spring trestle 41 the latter being attached to the connection of beam 5 and spreader 46. The radius rods 37 enclose an angle of

about 15° with the longitudinal axis of the body 2, forming hinged joints with the

latter through bolts 42 or - in an advantageous embodiment - through rubber hinges ("silent blocks"). So, the axle body 14 with radius arms (these being leaf springs) functions as a torsional curve stabilizer, since the axle body 14 and the radius rod are rigidly fixed to each other through trestles 34. A wide passenger corridor 44 is arranged above axle body 14 confined by the side walls 45 of the wheel boxes 7.

It can be seen in Figures 1 to 3 than an 8° angle is enclosed by pneumatic spring 10 with the vertical axis being "tilted forward" with respect to the longitudinal vertical plane of the body. Consequently, it exerts on the rigid bridge 3 a constant torque that considerably increases during braking, so that a counter-torque develops acting against the torque causing bending of leaf springs of radius rods, during braking. Due to this 8° forward tilt the angular displacement of the lower stalk 13 of pneumatic spring 10 approaches tangential direction relative to the displacement of the rigid bridge 3, since this angular displacement takes place around the bolt 42 at the end 39 of the radius rod 37. Fundamentally, this is rendered possible by the shape of the pneumatic spring 10 shown in cross-section in Figure 4.

The rolling diaphragm 48 of the pneumatic spring 10 is connected to the upper armature 11 and to a piston 47 of the pneumatic spring 10 in a sealed way, it rolls off along a piston skirt 57. On a piston crown 58 an annular inner rubber buffer 49 is located as inner stop within the inner air space 65 of the rolling diaphragm 48. A bore 59 is provided in piston crown 58, through which a linear guide path telescope 12 is reeved, the telescope stalk 53 of which, with the ball-and-socket joint 50, is connected to the inner side 69 of the upper armature 11. The spherical shell 51 of the ball-and-socket joint 50 is attached to the upper armature 11. The spherical end 52 is fixed into the telescope stalk 53 through a threaded joint not shown. The cylindrical jacket 56 of telescope stalk 53 is displaceably guided in groves 55 provided in the sleeve 54 of the lower stalk 53. Between the outer jacket surface 56 of sleeve 54 and boring 59 of the piston crown 58 a gap 63 is provided, through

which the inner space 65 is connected with the otherwise closed internal space 64 of

piston 47, being sealed by piston shoe 60 from below.

The sleeve 54 and lower stalk 13, respectively, is led through the boring 61 of the piston shoe 60. The external jacket surface 62 of the lower stalk 13 is fitted in a

sealed way into the boring 61. The lower stalk 13 is rigidly fixed to the piston shoe

60, and into its end 66 the spherical joint 67 is fixed through its thread. A connecting bolt 20 is reeved through the spherical joint 67 and is indirectly linked with the rigid axle 3. The upper armature 11 of pneumatic spring 10 leans with its outer side 68 against the support 9 located in wheel box 11. The upper armature 11 of the

pneumatic spring 10 is provided with a known compressed-air connection not shown in the figures.

Swinging arms 43 (radius rods) of the suspension according to Figs. 5 and 6 are

made of a piece of spring-steel plate, because they are less expensive and more durable than the radius rods 37 in the first example. The swinging arm 43 is clamped by its clamp arm 71 and bolts 75 threaded in openings 72 to the axle body 14. The clamp arm 71 is a continuing part of the swinging arm, bended in an angle about 90°

of the spring-steel plate at bending 70. On the other end of the swinging arm 43 there is a spring eye 73 made of the spring-steel plate, by which spring eye and the bolt 42 linking up with the spring eye the swining arm 43 is connected to the spring trestle

41. Near to the spring eye 73 the swinging arm 43 is bended in its plain at bending

74 to get a spring eye 73 parallel to the bearing surface 76 of the clamp arm 71.

The telescope 12 of the pneumatic spring 10 ensures that the rolling diaphragm 48 rolls down along the skirt 57 of piston 47, always remaining in the longitudinal axis during its displacement. This prevents occurrence of objectionable deformations common with known pneumatic spring applications where lateral displacement of the axle bridge when running on a bumpy road causes eccentric distortion of the rolling diaphragm. In addition, because of the ball-and-socket attachment of the telescope, the jacket of the rolling diaphragm can adjust itself by an angular displacement around its longitudinal axis, corresponding to the position of minimum stress.

The dimensions of the pneumatic spring 10 are selected to make the distance equal

between upper armature 11 and piston shoe 60 and spherical head of the ball-socket joint 67 with the pneumatic spring 10 in normal mounting position. With that spacing ratio, sufficient space is available for the brake operating diaphragms 32 even in extreme positions of steering.

Claims

1. Suspension for motor vehicles, mainly for the steered axle of low-floor buses, having pneumatic springs connected to the body or frame of the vehicle and radius rods for guiding the running gear, characterized in that the upper armature ( 11 ) of the pneumatic spring (10), connected to the vehicle body (2) has an articulated -

expediently a ball-and-socket - joint to which one telescope stalk (53) of a linear

guide path telescope (12) is coupled, while its other telescope stalk (13) of the

telescope (12) is fixed in, and - in a sealed way - passed through, a piston crown (58) of piston (47) of the pneumatic spring (10), this other telescope stalk (13) being linked again through a joint - expediently through a ball-and-socket joint (67) - with the axle element guided by a radius rod (37).

2. Suspension as claimed in claim 1 characterized in that the length of the telescope stalk (13) provided with a rolling diaphragm (48) and protruding from the pneumatic spring (10) is approximately equal to the nominal distance between the upper armature (11) of the pneumatic spring (10) and lower rim (60) of piston (47).

3. Transmission suspension as claimed in claim 1 wherein the axle element is a rigid bridge (3) to which at each of both ends - near the steering bolts (16) - a radius rod

(37) is rigidly attached, the radius rods (37) being spring-steel plate arranged

approximately parallel with the bottom plane of the vehicle body (2) and coupled to the vehicle body (2) by means of a bolt (42) with its axis parallel to said plane, and with the telescope stalk (13) of the pneumatic spring (10) being connected to the upper part (18) of the rigid bridge (3).

4. Suspension as claimed in claim 3 characterized in that the rigid bridge (3) is a reversed Elliot axle and an angle of approx. 15° is enclosed by the radius arm (37) and the longitudinal axis of the vehicle body (2), the radius rod (37) is accommodated on the forward side of the front-side rigid bridge (3), which is of deepened (gantry) shape, the radius rod (37) being connected to the deepened axle body (14) of the rigid bridge (3), the centerline of the pneumatic spring (10) enclosing an angle of about 8° when tilted forward with respect to the direction of travel, and its upper armature (11) is clamped to a support provided within the wheel box (7) of the vehicle body (2): to the rigid bridge (3) and to the vehicle body (2) a telescopic shock damper (25) is connected behind said rigid bridge (3).