JP4551573B2 - Braking device for work vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a braking device for a work vehicle such as a tractor, and more particularly to a technique that enables adjustment of an assist force (pressure) of a hydraulic assist type braking device.
[0002]
[Prior art]
Conventionally, in a traveling vehicle such as a tractor, if the fuselage becomes large, the braking force may be weak and sufficient stopping accuracy may not be obtained only by the operator's brake pedal operating force. The braking device is used. The hydraulic pressure setting of this hydraulic assist type braking device is fixed, and even if it can be changed by a serviceman or the like, the user can hardly change it.
[0003]
[Problems to be solved by the invention]
As described above, the setting of the braking force is not easy for the user, so if you set a convenient assisting force such as driving on the road or working, it will be too effective or insufficient during braking. Sometimes.
[0004]
For example, if the pressure is set so that it can be braked moderately when driving on the road or lightly working, if a heavy object is pulled, the braking force will be insufficient when stopping or decelerating downhill, and overrun etc. Occurring and causing an accident. Further, when turning as a single brake at the time of work, the pedaling force is insufficient, and a large pedaling force is required to stop the vehicle reliably. On the contrary, if the assist force was increased so as to be able to tow heavy objects, the brakes were too effective when traveling on the road, and it was difficult to operate because the brakes were applied suddenly just by depressing the brake pedal.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention solves the problems by the following means.
[0006]
According to claim 1, in a braking device in which an assist device is provided between a pair of left and right braking operation tools provided in the driving unit and a left and right brake that brakes the left and right traveling wheels, an assist force changing means is provided in the assist device. The assist force changing means is interlocked and connected to the left and right braking operation tool connection detecting means.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment in which the work vehicle of the present invention is a tractor will be described with reference to the drawings.
[0008]
Figure 1 is a whole side view of a tractor, FIG. 2 is a skeleton diagram showing a power transmission system, FIG. 3 is a hydraulic circuit diagram of a configuration example of the assist device, FIG. 4 is also a hydraulic circuit diagram of another configuration example, FIG. 5 is present It is a hydraulic circuit diagram of the Example of invention .
[0009]
In FIG. 1, a description will be given from an overall configuration using a work vehicle as a tractor . A front wheel 1 and a rear wheel 2 which are traveling wheels are supported before and after the machine, an engine 5 is disposed inside the front bonnet 6, and a steering handle 10 is provided behind the bonnet 6. A seat 11 is disposed behind the handle 10. Further, a main speed change lever 3, a sub speed change lever 4, a height change lever and the like are projected on the side portion of the seat 11, and a forward / reverse changeover lever 7 is arranged as a forward / reverse changeover operation tool on the handle column side portion of the steering handle 10. In addition, a brake pedal 13 and a main clutch pedal serving as a braking operation tool are disposed on the lower side of the handle column. These steering handle 10, seat 11, levers, brake pedal 13, and the like are arranged in a driving unit 19 in the cabin 12.
[0010]
A transmission housing is disposed at the rear of the engine 5, a transmission case 9 is disposed at the rear of the transmission housing, and the power from the engine 5 is transmitted to the rear wheels 2 to drive the four-wheel drive switching mechanism 70. The driving force can be transmitted to the front wheel 1 at the same time.
[0011]
Further, the driving force of the engine 5 is transmitted to the PTO shaft 15 protruding from the rear end of the mission case 9, and is mounted from the PTO shaft 15 to the rear end of the machine body via a universal joint or the like (not shown) via a work implement mounting device. The work machine is configured to be driven.
[0012]
Next, the configuration of the power transmission system will be described with reference to FIG. An output shaft (crankshaft) 22 of the engine 5 extends rearward of the machine body and is input to the forward / reverse switching device 20. The forward / reverse switching device 20 is composed of a hydraulic forward clutch 25 and a reverse clutch 26, and can switch the forward / reverse switching valve by operating the forward / reverse switching lever 7 to connect / disconnect the forward clutch 25 and the reverse clutch 26. I am doing so. The forward clutch 25 and the reverse clutch 26 also serve as the main clutch.
[0013]
A high / low switching shaft 21 is horizontally mounted in parallel with the output shaft 22, and a high / low switching mechanism 30 is provided on the rear portion of the high / low switching shaft 21, and the high / low switching mechanism 30 includes a high speed clutch 33, a low speed clutch 34, and the like. The high / low switching valve is switched by the operation of a high / low switching lever arranged in the driving section so that a high / low speed change can be performed.
[0014]
The pipe shaft 16 is loosely fitted on the rear portion of the output shaft 22, and power is transmitted from the height switching mechanism 30 on the pipe shaft 16 to the main transmission 35. The main transmission 35 has a hydraulic first-speed clutch 37, a second-speed clutch 38, and a third-speed clutch 39. By operating the main transmission lever 3, the valve is switched to enable three-speed transmission.
[0015]
Further, power is transmitted to the rear wheel differential device 43 via a gear-selective creep transmission mechanism 40 and a sub-transmission device 41 provided at the rear portion, so that power is transmitted to the rear wheel 2. A four-wheel drive gear 76 and a speed increasing gear 77 are fixed on the front portion of the drive shaft 14 serving as the output shaft of the auxiliary transmission 41, while the front wheel drive shaft 75 is disposed in parallel with the drive shaft 14. The 4-drive gear 73 and the speed-up transmission gear 74 are loosely fitted on the upper side, the 4-drive gear 76 is meshed with the 4-drive gear 73, and the speed-up gear 77 is meshed with the speed-up gear 74. A hydraulic four-wheel drive clutch 78 and a front wheel acceleration clutch 79 are disposed between the gear 76 and the speed increasing gear 77 and the front wheel driving shaft 75. In this way, the four-wheel drive switching mechanism 70 is formed. The power is transmitted from the front end of the front wheel drive shaft 75 to the front wheel 1 via a universal joint, a front wheel differential device, or the like.
[0016]
In the PTO transmission system, a PTO transmission shaft 86 is horizontally mounted on the extension of the rear end of the output shaft 22 via a PTO clutch (or damper) 85, and the PTO transmission shaft 86 is connected to the PTO transmission shaft 86 via a PTO transmission 90. Thus, power is transmitted to the PTO shaft 15.
[0017]
Next, the braking device of the present invention will be described. Differential yoke shafts 44R and 44L project from the rear wheel differential device 43 to the left and right, so that power can be transmitted from the differential yoke shafts 44R and 44L to the axles of the rear wheels 2 and 2 through a final speed reduction mechanism. Brake disks 45, 45... Are fixed on the differential yoke shafts 44R, 44L, and friction plates are arranged on the sides of the brake disks 45, 45. The brake can be braked by being pressed by a brake actuator 46 made of a piston. Thus, wet type multi-plate brakes 47R and 47L are formed.
[0018]
As shown in FIG. 3, the hydraulic brake operating device 50 for supplying pressure oil to the brake actuator 46 is composed of a brake pedal and an assist (boost) device. That is, since the left and right are configured in the same way, a description will be given of one side. A push rod 51 is connected to the brake pedal 13, and the push rod 51 is connected to a piston rod 53 of an assist cylinder 52 that constitutes an assist device, and an interlocking rod 54. Are connected. The interlocking rod 54 is disposed so as to be able to contact the spool 55 a of the assist valve 55 and the spool 56 a of the communication valve 56.
[0019]
The assist valve 55 is a three-port / two-position switching valve, and the pump port of the assist valve 55 is connected to the discharge side of the hydraulic pump 57 via an assist oil passage 67, and a variable relief serving as an assist force (pressure) changing means. An assist pressure can be set by a valve 59. The tank port of the assist valve 55 is connected to the reservoir tank 60, and the output port is connected to the urging side of the assist cylinder 52.
[0020]
In such a configuration, when the assist valve 55 is in a normal state, the pressure oil from the hydraulic pump 57 is blocked, and the hydraulic oil in the bias side chamber of the assist cylinder 52 is drained. When the spool 55a is slid and switched by depressing the brake pedal 13, the tank port is blocked, the pump port and the output port are communicated, and the pressure from the hydraulic pump 57 is supplied to the urging side chamber of the assist cylinder 52. The oil is fed and the push rod 51 is pushed to assist, so that the depressing force of the brake pedal 13 can be reduced.
[0021]
The assist cylinder 52 is a double rod type cylinder, one rod 53 is connected to the push rod 51, and the rod protruding to the other is integrally formed with the piston rod 62 of the master cylinder 61. A return spring is accommodated in the return side chamber of the assist cylinder 52. A return spring is housed in the head side chamber of the master cylinder 61 and is connected to the communication valve 56 and an oil chamber for operating the brake actuator 46 of the brake 47. One port on the primary side of the communication valve 56 is a reservoir tank 60. The other port communicates with the port of the communication valve 56 on the left and right other side.
[0022]
In such a configuration, when the communication valve 56 is in a normal state, the head side chamber is communicated with the reservoir tank 60, the brake pedal 13 is depressed, the spool 56a is slid, and the communication valve 56 is switched. The oil passage to the tank 60 is blocked, and the other port communicates with the port of the communication valve 56 on the left and right other side. However, when the left and right brake pedals 13R and 13L are operated separately by turning at the time of work, etc. When the two brake pedals 13R and 13L are simultaneously operated, the head side chambers of the master cylinder 61 are communicated with each other, and the same pressure is sent to the brakes 47R and 47L for braking.
[0023]
The spring force for setting the relief pressure of the variable relief valve 59 can be changed by an actuator 63. The actuator 63 is composed of a motor, a cylinder, or the like. It is connected to detection means 65 for detecting the position. In this configuration example, the rotation of the auxiliary transmission lever 4 is detected by the angle sensor, but the transmission position is detected by detecting the slider position of the auxiliary transmission device 41 or detecting the link position to be connected. You can also
[0024]
With this configuration, when traveling on the road or the like, when the sub-shift lever 4 is shifted to the high speed side, the actuator 63 is activated, the assist pressure (set relief pressure) is reduced, and the brake pedal 13 is stepped on strongly. But don't apply sudden braking. In addition, when the sub-shift lever 4 is shifted to a low speed position when working, the actuator 63 is actuated to increase the assist pressure, and a high load is applied during the work. Therefore, even if a small pedal force is applied by increasing the assist pressure. Increase the power. Further, even when a single brake is used, a large braking force is obtained so that the turning performance does not deteriorate.
[0025]
As shown in FIG. 4, instead of the variable relief valve 59, the assist force changing means can be an electromagnetic proportional valve 49. In this case, the maximum assist pressure is set by the relief valve 48, and the electromagnetic proportional valve 49 is arranged in the middle of the assist oil passage 67. As described above, the electromagnetic proportional valve 49 may be configured to control so that the electromagnetic proportional valve is throttled when traveling on the road and opened during work, in accordance with the shift stage of the auxiliary transmission, as shown in FIG. In addition, an adjustment tool 17 such as a dial or a switch is provided in the operation unit 19 instead of the detection means 65, the adjustment tool 17 is connected to the controller 64, and an assist force (pressure) is arbitrarily set by operating the adjustment tool 17. It can also be configured to set.
[0026]
Further, when the left and right brake pedals 13R and 13L are connected, it is almost time to drive on the road, and when the left and right brakes are braked independently, the brake is operated as shown in FIG. Detection means 69 is provided for detecting whether the coupling tool 68 disposed on the pedals 13R and 13L is in the coupling position or the non-coupling position. The detection means 69 is connected to the controller 64, and the controller 64 is connected to the solenoid 66a of the switching valve 66 Connecting. The switching valve 66 is constituted by a 3-port 2-position switching electromagnetic valve, and the switching valve 66 is connected to the output side of the hydraulic pump 57 in parallel with the assist oil passage 67.
[0027]
In such a configuration, when traveling on the road, the vehicle travels with the brake pedals 13R and 13L connected. At this time, the detecting means 69 is turned on, the switching valve 66 is not switched, and the pressure oil from the hydraulic pump 57 is drained. Thus, the oil is not fed to the assist cylinder 52 and is operated only by the pedaling force of the operator. During operation, the brake pedals 13R and 13L are disengaged and the vehicle travels. At this time, the detecting means 69 is turned OFF, the switching valve 66 is switched, and the pressure oil from the hydraulic pump 57 is assisted by the relief valve 71. Oil is sent to the assist cylinder 52 with pressure. In place of the switching valve 66 and the relief valve 71, an electromagnetic proportional valve may be used.
[0028]
Further, in the braking device provided with the assist device between the braking operation tool provided in the driving unit and the brake for braking the traveling wheel, an assist force changing unit is provided in the assist device, and the assist force changing unit is provided in the driving unit. Because it is possible to change with the adjustment tool provided in, there is no need to adjust the brake effect while the vehicle is stopped, while driving the brake effect while driving or when not working It is now possible to adjust the brakes to suit the driving when working or not working, and it is possible to prevent sudden braking and long running distance and improve the brake operation feeling. it can.
[0029]
Further, in the braking device provided with the assist device between the braking operation tool provided in the driving unit and the brake for braking the traveling wheel, the assist device is provided with assist force changing means, and the assist force changing means is sub-shifted. Since it is linked with the device, the shift of the sub-transmission device is detected and braking according to the traveling speed can be performed, braking is not overworked or insufficiently braked, improving brake operability and improving safety it can. Further, since the assist force is automatically adjusted, it is not necessary to adjust the assist force in accordance with the work and the traveling speed.
[0030]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
As described in claim 1, between the left and right brake for braking a running wheel and the left and right are provided to the OPERATION section pair of brake operation device, the brake device provided an assist device, the assist to the assist device Since the force change means is provided and the assist force change means is interlocked with the left and right braking operation tool connection detection means, when turning at the time of work, the brake force can be reduced by operating one brake. There is no need to set the brake assist force when disconnected.
[Brief description of the drawings]
FIG. 1 is an overall side view of a tractor.
FIG. 2 is a skeleton diagram showing a power transmission system.
FIG. 3 is a hydraulic circuit diagram of a configuration example of an assist device.
FIG. 4 is a hydraulic circuit diagram of another configuration example .
FIG. 5 is a hydraulic circuit diagram of an embodiment of the present invention .
[Explanation of symbols]
2 Rear wheel 4 Sub transmission lever 13 Brake pedal 17 Adjuster 41 Sub transmission 47 Brake 52 Assist cylinder 59 Variable relief valve 66 Switching valve 69 Detection means

Claims (1)

In a braking device in which an assist device is provided between a pair of left and right braking operation tools provided in the driving unit and a left and right brake that brakes the left and right traveling wheels, the assist device is provided with assist force changing means, A braking device for a work vehicle, wherein the force changing means is linked to the left and right braking operation tool connection detecting means .

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