GB2175375A

GB2175375A - Vehicle parking brakes

Info

Publication number: GB2175375A
Application number: GB08607562A
Authority: GB
Inventors: Takeo Yamazaki; Tomio Tachino; Hiroshi Uemura; Masaru Sugawara; Yasuaki Ichiba; Masashi Ohta; Kiyoshi Nishiwaki
Original assignee: Aisin Seiki Co Ltd; Toyota Motor Corp
Current assignee: Toyota Motor Corp; Aisin Corp
Priority date: 1985-03-27
Filing date: 1986-03-26
Publication date: 1986-11-26
Also published as: DE3610525A1; GB8607562D0; GB2175375B

Abstract

An operation mechanism for a parking brake pedal 10 rotatably mounted on a stationary structure 51 in a compartment of a vehicle is connected to a parking brake (not shown). An air damper 40 is interposed between the structure 51 and the pedal 10 to dampen the return of the pedal from a depressed position, upon release of a latching mechanism 20 by a release mechanism 30. The damper 40 includes a cylinder body 41 pivoted to the structure 51, a piston 43 slidable in the body 41, and a piston rod 42. The piston is formed with a throttle of porous material 46 or a cup-shaped element in the piston to permit the flow of air through the piston. Alternatively, the piston may itself be of porous material. Chamber R1 may be open to atmosphere, and seal 45 may be replaced by an O- ring. <IMAGE>

Description

SPECIFICATION Vehicle parking brakes The invention relates to parking brakes for wheeled vehicles, that is to say to an operation mechanism for a parking brake pedal, a lock for the pedal in its depressed position, and a release mechanism.

Such a conventional operation mechanism has been proposed in Japanese Utility Madel Early Publication No. 54-11443, wherein an oil damper is provided for the impact caused by the return movement of the pedal. Use for a long period of time leads to oil leakage caused by wear or the fatigue of seal members, and results in oil stains in the vehicle compartment. In manufacture, it is necessary to form a one-way valve or an orifice in the damper piston in a precise manner, and this results in an increase in cost.

According to the present invention there is provided an operation mechanism for a parking brake pedal of a wheeled vehicle comprising a lock for the pedal in a depressed position, a release mechanism for the lock, a damper for the return of the pedal from the depressed position, a piston slidable in a damper cylinder, and a throttle for permitting a flow of air through the piston.

Preferably, an annular cup seal is provided in the outer periphery of the piston to permit the flow of air on depression of the pedal, and block the flow of air on return of the pedal.

The throttle may comprise an element of porous sintered material, or a cup-shaped element formed with an orifice, or the piston may be made of porous material.

The mechanism of the invention involves no oil which might leak and stain, and is comparatively inexpensive to manufacture to an appropriate standard.

DRAWINGS Figure 1 is a side view of an operation mechanism in accordance with the invention; Figure 2 is a rear view of the mechanism in Fig. 1; Figure 3 is a longitudinal section of an air damper in Figs. 1 and 2; Figure 4 is a similar view of a piston in Fig.

3; Figure 5 is a similar view of a modification of the piston in Fig. 3; Figure 6 is a longitudinal section of a second modification of the air damper in Fig. 3; and Figure 7 is a similar section of a third modification of a piston in Fig. 6.

In Figs. 1 and 2, a pedal 10, a locking mechanism 20, a release mechanism 30, and an air damper 40 are shown. The pedal 10 is arranged to operate a parking brake (not shown) of a wheeled vehicle. The pedal 10 has an arm 11 which is formed at its upper end with a sector gear 12 and provided at its lower end with a pedal 13. The foot pedal arm 11 is placed between a stationary base plate 51 secured to a body structure of the vehicle and an attachment plate 52 secured in parallel to the stationary base plate 51. Thus, the foot pedal arm 11 is rotatably mounted on a stepped lateral bolt 14 which is threaded into the attachment plate 52 through the stationary base plate 51 and fastened by a nut.

The foot pedal arm 11 has a front end portion operatively connected to the parking brake by means of a parking brake cable 60 and is biased counterclockwise by means of a return spring (not shown) assembled within the parking brake. When the foot pedal is in a released position, the foot pedal 11 is in engagement with a rubber stopper 59 which is fixed to a rear portion of the stationary base plate 51. When the pedal 13 is depressed, the foot pedal arm 11 rotates clockwise about the lateral bolt 14 to operate the parking brake through the brake cable 60. A normally closed switch 58 is arranged adjacent the rubber stopper 59 and fixed to the stationary base plate 51 to be opened by engagement with the foot pedal arm 11.

The locking mechanism 20 includes a latch member 21 which is formed at its one end with a pawl 21 engageable with the sector gear 12 of foot pedal arm 11. The latch member 21 is placed between the stationary base plate 51 and the attachment plate 52 and rotatably mounted on a lateral support pin 23 fastened to the stationary base plate 51 through an upper portion of attachment plate 52. A tension spring 22 is fixed at its one end to an outer peripheral flange 51a of stationary base plate 51 and connected at its other end to another end of latch member 21 to bias the latch member 21 clockwise. When the foot pedal 10 is in the released position, the pawl 21a of latch member 21 is resiliently engaged with a non-toothed upper end of foot pedal arm 11 under load of the tension spring 22.When the foot pedal 10 is depressed to cause clockwise rotation of the sector gear 12, the pawl 21a of latch member 21 is brought into engagement with a portion of the sector gear 12 to lock the foot pedal 10 in its depressed position.

The release mechanism 30 is arranged to release the foot pedal 10 from its locked position. The release mechanism 30 includes a release lever 31, a release cable 32, a compression coil spring 33, a release knob 34 and a release stopper 35. The release lever 31 is placed at the outside of attachment plate 52 and rotatably mounted at its upper end on a lateral support pin 36 fastened to the stationary based plate 51 through the attachment plate 52. The release lever 31 has an arm 31 a engageable with the latch member 21. The compression coil spring 33 is anchored at its one end to the attachment plate 52 and engaged at its other end with the lower end of release lever 31 to bias the release lever 31 clockwise.The release lever 31 is further connected at its lower end to the release knob 34 by means of the release cable 32, and the release knob 34 is supported in place by means of the release stopper 35 which is fixedly mounted on a stationary structure in the vehicle compartment.

When the release knob 34 is retained by the release stopper 35 in its inoperative position, the arm 31a of release lever 31 is separated from the latch member 21 under load of the compression coil spring 33. When the release knob 34 is pulled by the driver to cause counterclockwise rotation of the release lever 31 against the compression coil spring 33, the latch member 21 is rotated counterclockwise by engagement with the arm 31a of release lever 31 to disengage the pawl 21 a of latch member 21 from the sector gear 12 of foot pedal arm 11.

As shown in Figs. 1 and 2, the cylinder type air damper 40 is interposed between the foot pedal arm 11 and a bracket 53 secured to a front end portion of the outer peripheral flange 51a of stationary base plate 51.

As shown in Fig. 3, the air damper 40 comprises a cylinder body 41, a piston rod 42 integrally formed with a piston 43, and a closure member 44. The cylinder body 41 has a closed end 41a pivoted to a lateral stepped bolt 54 fixed to the bracket 53 by means of a nut 55 fastened thereto, while the piston rod 42 is provided at its outer end with an end fitting 42a which is pivoted to a lateral stepped bolt 56 secured to an intermediate portion of foot pedal arm 11 by means of a nut 57 fastened thereto. The piston 43 is axially slidably disposed within the cylinder body 41 through an annular seal cup 45 to subdivide the interior of cylinder body 41 into first and second air chambers R, and R,.As shown in Figs. 3 and 4, the piston 43 is formed therein with an L-letter shaped passage H for communication between the first and second air chambers R, and R2 and further formed therein with an end bore Ha in communication with the passage H. A throttle element 46 made of porous material such as porous sintered metal is fixedly coupled within the end bore Ha of piston 43 to permit the flow of air passing therethrough thereby to cause a pneumatic resistance acting on the piston 43. The closure member 44 is disposed within an opening end portion of the cylinder body 41 through an O-ring 47A and fixed in placed by means of a pair of axially spaced annular retainers 48A and 48B. The closure member 44 is provided at its inner periphery with an O-ring 47B through which the portion rod 42 extends outwardly.

In depression of the foot pedal 10, the parking brake cable 60 is pulled by the foot pedal arm 11 to operate the parking brake, and subsequently the locking mechanism 20 acts to lock the foot pedal 10 in its depressed position. In this instance, the piston rod 42 and piston 43 are moved forwards by depression of the foot pedal 10 to compress the air in the first air chamber R1 and to expand the second air chamber R2. During such forward movement of the piston rod 42 and piston 43, the throttle element 46 acts to permit the flow of air passing through the passage H from the first air chamber R1 into the second air chamber R2, and simultaneously the annular seal cup 45 acts to permit the flow of air passing therethrough from the first air chamber R1 into the second air chamber R2.

Thus, the foot pedal 10 is smoothly depressed without any resistance acting thereon.

When the release knob 34 is pulled by the driver to rotate the release lever 31 counterclockwise against the compression coil spring 33, the latch member 21 is rotated counterclockwise by engagement with the arm 31a of release lever 31 to release lock of the foot pedal 10, and subsequently the foot pedal 10 is returned to the release position under load of the return spring of the parking brake. In this instance, the piston rod 42 and piston 43 are moved backwards under the load of the return spring to compress the air in the second air chamber R2 and to expand the first air chamber R1.During such backward movement of the piston rod 42 and piston 43, the annular seal cup 45 acts to block the flow of air from the second air chamber R2 into the first air chamber R,, and the throttle element 46 acts to throttle the flow of air passing therethrough from the second air chamber R2 into the first air chamber R, across the passage H.

Thus, the piston 43 is applied with a pneumatic resistance to retard the backward movement of foot pedal 10 thereby to reduce an impact acting on the rubber stopper 59 caused by abutment against the foot pedal 10.

In the above embodiment, it is to be noted that the cylinder type air damper 40 is adapted as a damper for the foot pedal 10 to avoid problems such as stain of the vehicle compartment caused by oil leakage in use of a conventional cylinder type oil damper. Even if the sealing function of O-rings 47A and 47B is decreased by use for a long period of time, only the dampening function of the air damper will be slightly decreased without causing any other problems. As in the air damper 40 the throttle element 46 is disposed within the end bore Ha formed in the piston 43 for communication between the air chambers R, and R2, it is not necessary to form a conventional orifice in the piston in a precise manner or to provide a conventional one-way valve in the piston. It is, therefore, able to simplify the construction of the air damper so as to reduce the manufacturing cost. In addition, the dampening function of the air damper 40 can be adjusted in a simple manner by replacement of the throttle element 46 with another throttle element having a different throttle property.

In Fig. 5 there is illustrated a modification of the air damper 40 wherein the throttle element 46 of porous sintered metal is replaced with a cup-shaped throttle element 146 which is formed at its center with an orifice 146a. In this modification, the orifice 1 46a in the throttle element 146 may be altered in diameter to adjust the pneumatic resistance acting on the piston. Although in the above embodiment and modification, the annular seal cup 45 has been adapted to the piston 43, it may be replaced with an O-ring. In such a case, it is desirable that the throttle element 46 or 146 is modified in its component or construction in consideration with a pneumatic resistance acting on the piston 43 in depression of the foot pedal 10.Furthermore, although in the above embodiment,the piston 43 has been arranged to reciprocate in the closed cylinder body, the first air chamber R, in the cylinder body may be communicated with the atmospheric air to reduce the resistance acting on the piston in depression of the foot pedal 10. In such a case, it is desirable that an air filter is provided to prevent entry of dust into the first air chamber R,.

In Fig. 6 there is further illustrated another modification of the air damper 40 wherein the piston 43 is replaced with a piston 143 made of porous material such as porous sintered metal which is mounted on the inner end 42b of piston rod 42 through an O-ring 45B and fixed in place by an annular retainer 42c. The piston 143 is axially slidably disposed within the cylinder body 41 through an annular seal cup 45A to subdivide the interior of cylinder body 41 into the first and second air chambers R, and R?. In this modification, each annular groove for the annular seal cup 45A and the O-ring 45B is formed during molding process of the piston 143. Alternatively, the air damper 40 may be.modified as shown in Fig.

7, wherein the piston rod 42 is formed at its inner end with a stepped portion 142b on which the piston 143 is mounted through an annular seal member 145A and fixed in place by an annular retainer 146A.

Claims

1. An operation mechanism for a parking brake pedal of a wheeled vehicle comprising a lock for the pedal in a depressed position, a release mechanism for the lock, a damper for the return of the pedal from the depressed position, a piston slidable in a damper cylinder, and a throttle for permitting a flow of air through the piston.

2. A mechanism as claimed in claim 1 in which the throttle comprises an element of porous sintered metal.

3. A mechanism as claimed in claim 1 in which the throttle comprises a cup-shpoed element formed with an orifice and fixed in the piston.

4. A mechanism as claimed in claim 1 in which the piston is made of porous material.

5. A mechanism as claimed in any preceding claim comprising an annular cup seal in the outer periphery of the piston to permit the flow of air on depression of the pedal, and block the flow of air on return of the pedal.

6. An operation mechanism for a parking brake pedal substantially as herein described with reference to Figs. 1 to 4 of the drawings.

7. An operation mechanism according to claim 6 modified as described with reference to Figs. 5, 6 or 7 of the drawings.