JP3369390B2 - Work vehicle brake device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake device for a working vehicle such as a wheel loader. [0002] Conventionally, in a wheel loader, a hydraulic motor is driven by pressure oil from a swash plate type variable displacement hydraulic pump driven by an engine, and drive wheels are rotated by the hydraulic motor. Some are equipped with a hydrostatic transmission. In this apparatus, the inclination angle of a swash plate of a hydraulic pump of a hydrostatic transmission is controlled by a servo cylinder, and the servo cylinder is controlled by a switching operation of a forward / reverse switching valve. The swash plate is tilted to one or the other from a neutral state (a state perpendicular to the power input shaft), and the flow of the hydraulic oil of the hydrostatic transmission is switched so that the wheel loader moves forward and backward. [0003] A valve block in which a forward / backward switching valve is incorporated has a forward oil passage for supplying pressure oil to a servo cylinder so as to advance the wheel loader, and a hydraulic oil to the servo cylinder so as to move the wheel loader backward. Is formed, and a variable throttle valve is interposed in the bypass oil passage. The variable throttle valve gradually shuts off the bypass oil passage from a shut-off state. It is configured such that it is opened and decelerated, and finally the bypass oil passage is fully opened to eliminate the pressure difference between the forward oil passage and the reverse oil passage, so that the swash plate of the hydraulic pump becomes neutral. [0004] In the prior art, a brake pedal and a variable throttle valve are interlocked and connected, and the variable throttle valve is moved by depressing the brake pedal to decelerate, and the bypass oil passage is fully opened. After the swash plate of the hydraulic pump is neutralized, the brake pedal presses the piston of the master cylinder to operate the brake to brake the drive wheels, thereby reducing the number of parts in the operation system, A device that simplifies the operation has been proposed. [0005] However, in this case, the brake pedal can be depressed so that the brake is fully applied between the time when the bypass oil passage is fully opened and the time when the valve element of the variable throttle valve is stopped by the stopper. If the variable throttle valve element is stopped by the stopper and the brake pedal is not depressed, the brake will not be fully actuated. Then, there is a problem that the brake pedal cannot be depressed to a state where the brake is completely applied, and the adjustment is difficult. The range from when the bypass oil passage is fully opened to when the valve body of the variable throttle valve is stopped by the stopper cannot be increased due to restrictions on the valve side. Then, this invention aims at solving the said problem. The technical means taken by the present invention to achieve the above object is to drive a hydraulic motor by a swash plate type variable displacement hydraulic pump, and drive wheels by this hydraulic motor. comprising a transmission for driving, provided with a brake for braking the driving wheels by depression of the brake pedal, comprising a deceleration unit for decelerating by allowing return the swash plate of the hydraulic pump in a neutral position, operating the speed reduction means The operating means and the brake pedal are operated by depressing the brake pedal.
Is pushed to move the swash plate of the hydraulic pump to the neutral position.
Dosu with deceleration means is operatively connected to be operated as, after the swash plate of the hydraulic pump becomes neutral, further blanking
The brake is activated by depressing the rake pedal, and the operating means is such that the swash plate of the hydraulic pump is neutral.
Is pressed after the brake pedal is depressed.
So that it stops in a certain range,
And the operating means is a brake pedal.
It is configured to be pushed through the elastic body when depressed
After the operating means touches the stopper,
With the means being elastically deformed, the brake pedal
It is characterized by being configured to be able to step on. Embodiments of the present invention will be described below with reference to the drawings. In FIG. 4, reference numeral 1 denotes a wheel loader, which is exemplified as a work vehicle. A loader working machine 3 is connected to a front portion of a traveling vehicle body 2 via a hinge portion. The wheel 5 is steered by bending the loader working machine 3 left and right by a hydraulic cylinder. The traveling vehicle body 2 is provided with a driver's seat 6, a steering device 7, an engine, a hydrostatic transmission, and the like. The loader working machine 3 has a pair of left and right frames 8 erected on the machine body, and an upper end of each frame 8 is pivotally connected to an arm 10 vertically pivoted by a lift cylinder 9. 11 is provided with a bucket 12 that is squeezed and dumped. FIG. 5 shows a hydraulic circuit of a traveling system. Reference numeral 13 denotes a hydrostatic transmission, which includes a hydraulic pump 15 driven by an output shaft of an engine 14 and a hydraulic pump 15.
Hydraulic motor 16 driven by the motor to rotate the rear wheel 5
And are connected by oil passages 17 and 18 so as to form a closed circuit. The hydraulic pump 15 is a swash plate type variable displacement pump, and the swash plate of the hydraulic pump 15
Is controlled by the servo cylinder 19 so as to tilt to one or the other from a neutral position orthogonal to the input shaft interlocked with the output shaft. Servo cylinder 1
9 is a forward / reverse switching valve 20 comprising a three-position switching valve.
By the switching operation of the forward / reverse switching valve 20, the flow of the pressure oil of the hydrostatic transmission 13 is switched, and the wheel loader 1 moves forward and backward. Further, a valve block 21 in which a forward / reverse switching valve 20 is incorporated has a forward-side oil passage 22 for supplying pressure oil to a servo cylinder 19 so as to advance the wheel loader 1 and a backward-moving wheel loader 1. A bypass oil passage 24 is formed to communicate with a reverse oil passage 23 that supplies pressure oil to the servo cylinder 19, and a variable throttle valve 25 is interposed in the bypass oil passage 24. As shown in FIG. 6, the variable throttle valve 25 has a communication hole 27 for communicating the bypass oil passage 24 with a valve element 26 inserted from the outside into the valve block 21 so as to cross the bypass oil passage 24 at right angles. Is formed in an orthogonal shape, the bypass oil passage 24 is shut off in a state where the communication hole 27 is orthogonal to or close to the bypass oil passage 24, and the valve body 26 is rotated about the axis from this state. The degree of communication between the bypass oil passage 24 and the communication hole 27 gradually increases, whereby the pressure difference between the forward oil passage 22 and the reverse oil passage 23 gradually disappears, and the swash plate of the hydraulic pump 15 The angle gradually decreases, and the engine speed is reduced without slowing down the engine rotation. Eventually, the bypass oil passage 24 and the communication hole 27 are completely communicated, and the forward oil passage 22 and the reverse oil passage 23 The differential pressure disappears,
The swash plate of the hydraulic pump 15 becomes neutral. Therefore, the bypass oil passage 24 and the variable throttle valve 25 constitute a speed reduction means. The hydraulic motor 16 employs a swash plate type variable displacement motor. The inclination angle of the swash plate of the hydraulic motor 16 is controlled by a high / low speed switching cylinder 29 controlled by a high / low speed switching valve 28 comprising a three-position switching valve. The gear is switched so as to shift between high and low. The speed of the engine 14 is steplessly increased or decreased by increasing or decreasing the rotation speed of the engine 14 by operating the accelerator. The rotational power from the output shaft 30 of the hydraulic motor 16 is transmitted to a differential 32 through a gear transmission 31 and transmitted from the differential 32 to the left and right rear wheels 5. Further, the gear transmission 31 is provided with a negative brake 33 which is also used as a traveling brake and a parking brake. As shown in FIG. 1, the negative brake 33 is housed in a brake case 36 fixed to a gear case 35 fixed to the output shaft 30 of the hydraulic motor 16. A brake shaft 37 is rotatably supported on the gear case 35 so as to protrude from both the case 35 and the brake case 36 around the axis. A transmission gear 38 of a gear transmission 31 interlocked with the output shaft 30 is fixed, and a brake disc 39 is spline-fitted to the brake case 37 side of the brake shaft 37. A support wall 40 is disposed in the brake case 36 so as to face the brake disk 39, and a support portion 41 protrudes from the support wall 40 on a side opposite to the brake disk 39. The support portion 41 secures the brake case 36. It penetrates and projects outside and is fixed to the case 36. In the brake case 36, the brake disc 3 is fitted externally to the support wall 40 and the support portion 41.
An annular piston 42 is provided, which is supported so as to be able to come in contact with and separate from the gear 9. The piston 42 is urged by a plurality of coil springs 43 so as to press the brake disc 39 against the gear case 35. 3
7 (therefore, the rear wheel 5) is braked. As a result, the negative brake 33 functions as a parking brake. The piston 42 is separated from the brake disc 39 against the urging force of the coil spring 43 by supplying pressure oil to a pressure oil chamber 44 formed between the piston 42 and the support wall 40. In the pressure oil chamber 44, a parking valve 45, a supply oil passage 46 formed in the support portion 41, and the parking valve 45 and the supply oil passage 46
Pressure oil is supplied from a charge pump 48 rotated by the engine 14 through an oil passage 47 connecting the parking brake and the parking brake is released. The parking valve 45 is constituted by a two-position switching electromagnetic valve. The parking valve 45 is normally biased by a spring and is set at a position for supplying pressure oil to the pressure oil chamber 44. The pressure oil in the pressure oil chamber 44 is drained by the pushing operation of the parking switch 49 disposed. A throttle 51 is provided in a drain oil passage 50 of the parking valve 45, and is configured to reduce a shock due to braking when the parking switch 49 is pressed to activate the parking brake during traveling. A throttle 51 is provided in the parking valve 45.
The reason why is incorporated is that if the oil passage 47 is throttled, the throttle works even when the parking brake is released.
The gear case 35 is provided with an annular piston 52 that protrudes and retracts into the brake case 36. An oil passage 53 formed in the gear case 35, and an oil passage 53 formed in the gear case 35 are provided on the back surface of the piston 52. Pressure oil is supplied from the master cylinder 55 through an oil passage 54 connecting the cylinder 55 and the piston 52 presses the brake disc 39 so as to press it against the piston 42.
Brake the rotation of Thereby, the function as a traveling brake is achieved. The piston 55a of the master cylinder 55
Is configured to be depressed by an interlocking arm 57 rotated by a depressing operation of a brake pedal 56 to discharge pressure oil. A predetermined interval is provided between the interlocking arm 57 and the piston 55a. 56 is returned to the original non-depressed position by the return spring 58. The tip side of the interlocking arm 57 is interlockingly connected to the valve element 26 of the variable throttle valve 25 via a push-pull cable 59. One end of the inner wire 59 a of the push-pull cable 59 is connected to the tip of the interlocking arm 57. On the other hand, a boss 60 is externally fitted and fixed to a portion of the valve body 26 of the variable throttle valve 25 projecting from the valve block 21 (also shown in FIG. 6).
As shown in FIGS. 2 and 3, the inching lever 61
(Operating means) is fixed so as to protrude radially outward of the valve body 26,
A receiving plate 62 is rotatably supported on a distal end side of the inching lever 61 via a support shaft 63 around an axis parallel to the axis of the valve body 26. The receiving plate 62 has a push-pull cable 59
The other end of the inner wire 59a is penetrated so as to be movable in the axial direction, and is prevented from coming off by a nut 64 screwed to the distal end. A spring receiver 65 is provided on the other end of the inner wire 59a so as to face the receiving plate 62 at a predetermined interval, and the spring receiver 65 is fixed by a nut 66 screwed to the inner wire 59a. Receiving plate 62
Movement in the direction away from the support plate 62 is restricted.
A coil spring 67 is interposed between the coil spring 67 and the spring receiver 65 in a compressed state. Both ends of the outer wire 59b of the push-pull cable 59 are connected to a bracket 6 fixed to the vehicle body 2 side.
8 is fixed. Preferably, the coil spring 67 and the spring receiver 65 are covered with a rubber boot 69. Therefore, when the brake pedal 56 is not depressed, the valve element 26 of the variable throttle valve 25
When the brake pedal 56 is depressed, the receiving plate 62 is pushed via the inner wire 59a and the coil spring 67, and the inching lever 6 is pressed.
The valve body 26 is rotated via 1. In FIG. 2, the inching lever 61 is
It swings from the position to the D position, contacts the stopper at the D position, and stops. In the range E in which the inching lever 61 swings from the position A to the position B, the bypass oil passage 24 is in a closed state, and the communication hole 27 formed in the valve body 26 from the position B to the position C is connected to the bypass oil passage 24. The bypass oil passage 24 is finally fully opened (a state in which the communication hole 27 is completely connected), and the bypass oil passage 24 is fully opened in a range swinging from the C position to the D position. is there. Accordingly, the range F between the position B and the position C is a deceleration region,
A range G from the position to the position D is a neutral region of the swash plate of the hydraulic pump 15. When the inching lever 61 reaches the C position, the interlocking arm 57 contacts the piston 55a of the master cylinder 55, and the brake pedal 56 is depressed until the inching lever 61 moves from the C position to the D position. The operation is adjusted so that the traveling brake works. However, even after the inching lever 61 has reached the D position and the travel brake is not fully effective unless the brake pedal 56 is depressed, the coil spring 67 is compressed. , The brake pedal 56 can be depressed, so that adjustment is easy or adjustment failure does not occur. Further, in the above-described negative brake 33 which serves both as a parking brake and a traveling brake,
As shown in FIG. 7, when the parking brake is released,
The piston 52 does not project into the brake case 36, and the distance between the brake disc 39 and the piston 52 is relatively large. As shown in FIG. 8, when the piston 52 is protruded to press the brake disk 39, the sealing material 70 is elastically deformed, and when the depression operation of the brake pedal 56 is released, as shown in FIG. ,
Since the piston 52 is returned by the restoring force of the seal member 70, it does not completely return to the original position. Therefore, after releasing the parking brake,
The amount of depression of the brake pedal 56 differs between the case where the brake pedal 56 is depressed first and the case where the brake pedal 56 is depressed after the second time. In this sense, the coil spring 6
The amount of depression of the brake pedal 56 due to the compression of 7 has an important significance. Further, as shown in FIG. 10, a tubular body 71 which is loosely fitted to the other end side of the inner wire 59a and penetrates the receiving plate 62 is sandwiched between the spring receiver 65 and a contact plate 72 which comes into contact with the receiving plate 62. Alternatively, the coil spring 67 may be fixed from both sides by nuts 64 and 66 so that the coil spring 67 is fitted to the cylindrical body 71, thereby providing an effect that the setting of the coil spring 67 is facilitated. The elastic body interposed between the receiving plate 62 and the spring receiver 65 is not limited to a spring.
For example, a rubber cylinder may be used. The inching lever 61 can be pushed from the position A to the position D, and the brake pedal 56 is elastically deformed from the position D to allow the brake pedal 56 to be depressed. Anything that can be done is acceptable. According to the present invention, there is provided a transmission in which a hydraulic motor is driven by a swash plate type variable displacement hydraulic pump and drive wheels are driven by the hydraulic motor, and the drive wheels are operated by depressing a brake pedal. provided with a brake for braking by comprising a speed reduction means that decelerates by allowing return the swash plate of the hydraulic pump in a neutral position, the operating means and the brake pedal for operating the deceleration unit, by depressing the brake pedal Operation means
Is pushed to move the swash plate of the hydraulic pump to the neutral position.
Dosu with deceleration means is operatively connected to be operated as, after the swash plate of the hydraulic pump becomes neutral, further blanking
The brake is activated by depressing the rake pedal, and the operating means is such that the swash plate of the hydraulic pump is neutral.
Is pressed after the brake pedal is depressed.
So that it stops in a certain range,
And the operating means is a brake pedal.
It is configured to be pushed through the elastic body when depressed
Have been, after the operation means has been brought into contact with strike Tsu path, elastic
With the means being elastically deformed, the brake pedal
Even when the operating means is stopped by the stopper and the brake is not fully actuated unless the brake pedal is depressed, the elastic member can be depressed. By elastically deforming, it is possible to depress the brake pedal, and it is configured such that adjustment is easy or poor adjustment does not occur.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram showing a main part of the present invention. FIG. 2 is a side view of a main part. FIG. 3 is a plan sectional view of a main part. FIG. 4 is an overall side view of the wheel loader. FIG. 5 is a hydraulic circuit diagram of a traveling system. FIG. 6 is a sectional view of a variable throttle valve. FIG. 7 is a sectional view showing an operation state of a piston of the traveling brake. FIG. 8 is a sectional view showing an operation state of a piston of the traveling brake. FIG. 9 is a sectional view showing an operation state of a piston of the traveling brake. FIG. 10 is a side view showing a modification. [Description of Signs] 5 Rear wheel (drive wheel) 15 Hydraulic pump 16 Hydraulic motor 24 Bypass oil passage 25 Variable throttle valve 33 Negative brake 56 Brake pedal 61 Inching lever (operation means)

────────────────────────────────────────────────── (5) References JP-A-63-305044 (JP, A) JP-A-62-230594 (JP, A) JP-A-48-11723 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B60T 7/04

Claims (1)

(57) [Claims 1] A swash plate type variable displacement hydraulic pump drives a hydraulic motor, and the hydraulic motor drives driving wheels .
Comprising a that transmission, provided with a brake for braking the driving wheels by depression of the brake pedal, comprising a deceleration unit for decelerating by allowing return the swash plate of the hydraulic pump in a neutral position, operating the speed reduction means operating means and the brake pedal, the brake
The operating means is pushed by depressing the pedal
The deceleration hand so that the swash plate of the hydraulic pump is returned to the neutral position.
The gears are linked so that the gears are operated , and the brake pedal is further depressed after the hydraulic pump swash plate becomes neutral.
The brake is configured to operate by
After the hydraulic pump swash plate is neutral,
Pushing operation by depressing the pedal stops within a predetermined range
And the stopper is configured to contact the stopper.
In addition, the operating means is operated by depressing a brake pedal.
It is configured to be pushed through the elastic body,
After the means abuts against the stopper, the elastic means deforms elastically.
By doing so, the brake pedal can be further depressed
A brake device for a work vehicle, wherein the brake device is configured as follows .