JPH0989100A - Brake device for work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relax a shock when a brake is applied, by arranging positions of a brake port and an operating pilot port in a brake valve displaced in a spool sliding direction. SOLUTION: In a brake valve 76, a spool 41 is inserted in a valve case 40, in the peripheral part of the valve case 40, a pump port 42, brake port 43, operating pilot port 44 and a tank port 45 are provided, and each port is arranged by displacing its port position relating to a sliding direction of the spool 41. When a brake pedal is stepped in, the spool 41 is slid to the right, the operating pilot port 44 is closed by a land part 41c, and a feed of oil is stopped. Further, when the spool 41 is slid to move, the operating pilot port 44 communicates with the tank port 45 in a tilt part 41d, a pressure for maintaining a condition turning a forward/reverse advancing lever is gradually decreased, and in a tilt plate angle control means, a tilt plate is moved in a neutral direction by the tension of a neutral spring, so as to decrease a running speed. In this way, a shock can be relieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a brake valve for integrally providing a brake with a hydraulic motor provided in a traveling device and for braking the brake.

[0002]

2. Description of the Related Art Conventionally, a work vehicle such as a tractor is equipped with an HST type transmission device, a crawler type traveling device is driven by a hydraulic motor, and a brake is integrally provided on the hydraulic motor. BACKGROUND ART A technique is known in which a vehicle is urged in a braking direction by a spring or the like and hydraulic pressure is supplied to release the brake so that the vehicle can travel.

[0003]

The brake in the prior art serves both as a running brake for braking by stepping on the brake pedal and a parking brake for stopping the vehicle body when the engine is stopped and the hydraulic pressure is stopped. The braking force when depressing the brake pedal does not directly press the friction plate, so it can be operated with almost the same force from the initial depression to the stroke end, and it is difficult to understand the brake load. The friction plates were pressed against each other and the wear of the friction plates was severe. Further, when the brake is suddenly applied, there is a problem that the speed reducer provided between the hydraulic motor and the drive sprocket is overloaded.

[0004]

The present invention uses the following means in order to solve the above problems. That is, an HS including a variable displacement hydraulic pump and a hydraulic motor
The transmission is shifted by a T-type transmission, the hydraulic pump is provided with swash plate angle control means, the hydraulic motor is internally equipped with a brake that constantly acts on the braking side, and the brake valve is operated by operating the brake pedal. Braking is possible, the brake valve and the swash plate angle control means are interlockingly connected by a pilot oil passage, and the positions of the brake port and the operation pilot port of the brake valve are displaced in the spool sliding direction. It was done. Also,
In the spool, a land portion that separates the pump port and the tank port is provided, and an inclined portion that gradually increases the opening is provided on the tank port side of the land portion.
Further, in the spool of the brake valve, springs having different spring constants are externally fitted so that the pedaling load is changed in two stages during the stroke of the brake pedal.

[0005]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; 1 is an overall side view of the crawler type tractor, FIG. 2 is a plan view of the same, FIG. 3 is a plan view of the interior of the cabin of the operating unit, FIG. 4 is a hydraulic circuit diagram, FIG. 5 is a diagram showing swash plate angle control means, and FIG. Is a sectional view of the brake valve, FIG. 7 is a diagram showing the same hydraulic symbol, FIG. 8 is a sectional view showing the middle of the stroke, FIG. 9 is a side view, and FIG. 10 is a diagram showing the relationship between the stroke of the brake pedal and the load. is there.

The overall structure will be described with reference to FIGS. 1 and 2. In the crawler type tractor, the engine E is mounted on the front of the body frame 1 and housed in the hood 2.
A three-point-link type working machine mounting device A is arranged at the rear end of the machine body frame 1, a working machine B is mounted at the rear end of the working machine mounting device A, and the lifting means 4 allows it to move up and down. The working machine B of this embodiment is a rotary tiller, and the elevating means 4 is a hydraulic cylinder.

A cabin 3 is arranged at the rear of the bonnet 2, and a steering wheel 5 and a driver's seat 6 are provided inside the cabin 3 to form a driving section C. A fuel tank 7 and a hydraulic oil tank 8 are arranged on both left and right sides of the cabin 3. Further, a crawler type traveling device D is arranged below the machine body frame 1.

The crawler type traveling device D has a traveling frame 12 arranged below the machine body, and a drive sprocket 13 driven by a hydraulic motor M at the front end of the traveling frame 12.
, The driven wheel 14 is arranged at the rear end so as to be able to be tensioned, and the rolling wheels 15, 15 ...
And the roller 16 is pivotally supported on the upper part thereof, and these drive sprocket 13, driven wheel 14, rolling wheel 15, roller 1
A crawler 17 is wound around 6 and the left and right drive sprockets 13 and 13 are rotated by hydraulic motors M and M to run.

A front mission case 20 is fixedly mounted on the rear portion of the engine E via a clutch case, and a pair of variable displacement hydraulic pumps P1 and P1 and a working machine hydraulic pump are provided on the rear portion of the front mission case 20. P2
Are arranged in series, and the hydraulic pumps P1 and P1 and the left and right hydraulic motors M and M are respectively connected by pipes to form a closed circuit to form an HST transmission. Hydraulic pump P
Pressure oil is sent from 1 / P1 to the hydraulic motors M / M to drive the hydraulic motors M / M. Further, a rear mission case 21 is arranged at the rear part of the body frame 1, and power is transmitted from the front mission case 20 to the rear mission case 21 via a universal joint 22. A PTO shaft 19 is projected rearward from the rear surface of the rear transmission case 21, and power is transmitted to the work machine B via the universal joint 23 to the PTO shaft 19.

As shown in FIG. 3, a front column 9 is provided in the rear portion of the hood 2 in the driving section C, a driver's seat 6 is arranged behind the front column 9, and a right lever is provided on the right side of the driver's seat 6. By providing the guide 25, the position lever 31
Or draft control lever 33, etc., and P on the left side
TO gear shift levers 34 and 35 are provided. A round handle 5 is projected from the upper surface of the front column 9, an operation panel 27 such as a speedometer and a fuel gauge is arranged on the upper surface of the front column 9, and the front column 9 is further provided.
Accelerator lever 24 on the right side in the direction of travel of the upper surface of
Is projected, and the forward-backward movement lever 30 is projected on the left side. A work machine elevating lever 32 and an auxiliary shift switch 37 are provided on the grip 30a of the forward / backward moving lever 30.
36 is a brake pedal.

Next, referring to FIG. 4, the hydraulic circuit will be described.
As described above, the pair of hydraulic pumps P1 and P1 and the working machine and charging hydraulic pumps P2 are arranged in series at the rear portion of the front transmission case 20, and the hydraulic pumps P1 and P1 and the left and right hydraulic motors M are arranged. -M is connected in communication with each other to form two pairs of closed circuits. Swash plate angle control means G is provided between the hydraulic pumps P1 and P1, and the swash plates of the hydraulic pumps P1 and P1 can be changed by rotating the forward / backward lever 30 and the handle 5. By changing the plate with the forward / backward lever 30, the discharge amount of the hydraulic oil can be changed steplessly, the discharge direction can also be changed, and the forward / backward movement and the main shift can be performed at the same time. Also, handle 5
By rotating the left and right to change the left and right discharge amounts.
-The left and right rotation speeds of M can be changed to make a turn. The drive sprockets 13, 13 are fixedly mounted on the output shafts of the hydraulic motors M, M, so that the crawler 17.1.
7 can be rotated.

Further, the hydraulic motor M is integrally provided with a hydraulic servo type brake 74 and an auxiliary transmission mechanism 75. The brake 74 can be operated by switching the brake valve 76 of the present invention. Switching can be performed by stepping on the brake pedal 36. Further, the engine E is started to turn on the hydraulic pump P1.
The braking is released by driving P1. The pilot oil passage 5 is connected to the brake valve 76.
It is connected to the swash plate angle control means G through 0. The swash plate angle control means G, as shown in FIG.
The base portion of the trunnion arm 92 is fixedly mounted on the swash plate operating shaft 91 that is interlocked with the swash plate, and the pin 94 fixed to the servo spool 93 is inserted into the long hole provided at the other end of the trunnion arm 92. There is. The servo spool 93 is inserted into the servo cylinder 95, the servo spool 93 is biased to the neutral position by the springs 96, 96 in the servo cylinder 95, and the oil passage 93a formed on the peripheral surface of the servo spool 93 is used for the pilot. It is connected to the oil passage 50.
A spool control lever 55 is pivotally supported at one end of the servo spool 93, and the spool control lever 5
A midway portion of the steering wheel 5 is pivotally supported by a pivot shaft 97, and the other end thereof is connected to a steering box provided below the steering wheel 5 via a link, a rod or the like.

The sub-transmission mechanism 75 is capable of changing the flow rate between high and low stages by switching the hydraulic valve 77 for shifting. The shift hydraulic valve 77 is an electromagnetic valve, and can be switched by operating the auxiliary shift switch 37. Reference numerals 78 and 78 are bypass switching valves.
Reference numeral 80 denotes a control valve, which allows the elevating means 4 to be expanded and contracted by operating the position lever 31 and the working machine elevating lever 32, or to feed oil to an external hydraulic device. Reference numeral 79 denotes a motor, which is the work machine lifting lever 32.
When the working machine lifting lever 32 is operated, the motor 79 is driven to change the spool of the control valve 80 so that the lifting means 4 can be expanded and contracted to move the working machine B up and down.

Next, the structure of the brake control valve 76 of the present invention will be described with reference to FIGS. The brake valve 76 has a spool 41 inserted into the valve case 40, and a pump port 42, a brake port 43, an operation pilot port 44, and a tank port 45 are provided on the outer peripheral portion of the valve case 40, and each port is a spool 41. The port position is deviated with respect to the sliding direction of. Pressure oil is sent from the hydraulic pump P2 to the pump port 42, and the brake port 43 is connected to the brake 74.
It is communicated with the cylinder that operates and is released by supplying pressure oil. Operation pilot port 4
4 is communicated with the swash plate angle control means G through the pilot oil passage 50 to send pressure oil so that the swash plate can be maintained at the rotated position and opened to the tank side. Then, the swash plate is moved in the neutral direction by the neutral springs 96. The tank port 45 communicates with the front mission case 20 via a hydraulic motor M.

The spool 41 is formed in a rod shape and forms a connecting portion 41a for connecting one end to the brake pedal 36 via a link or the like, thereby forming a valve case 40.
More protruding. A center portion of the spool 41 has a recess 41b for communicating the pump port 42, the brake port 43, and the operation pilot port 44 when the brake pedal 36 is not depressed, and a land portion 41c for separating the pump port 42 and the tank port 45. , The land portion 41
An inclined portion 41d for enlarging the opening is provided on the side of the tank port 45 side of c, a small diameter step 41e is provided on the other side, and a shaft hole 41f is bored in the axial direction from the other end surface of the spool 41. There is. A stop ring 46 is slidably fitted on the step portion 41e, and a stop ring 47 is fixed on the end of the spool 41. The spring 4 is mounted on the spool 41 between the retaining rings 46 and 47.
8 and the spring 49 longer than the spring 48 (having a different spring constant) is connected to the tank port 45 of the valve case 40.
It is interposed between the wall 40a of the insertion hole bored from the side and the retaining ring 47.

In such a structure, when the brake pedal 36 is not depressed, the pump port 42, the brake port 43, and the operation pilot port 44 have the recess 41.
The hydraulic fluid is communicated via b, the hydraulic oil is sent to the brake 74 and is not braked, and the hydraulic oil is also sent from the operation pilot port 44 to the swash plate angle control means G to move the forward / backward lever 30. It keeps the rotated state of. When the brake pedal 36 is depressed, in FIG.
The spool 41 is slid to the right, and first, the land portion 41c
When the operation pilot port 44 is closed and the oil supply is stopped and the spool 41 is slid further, the operation pilot port 44 communicates with the tank port 45 at the inclined portion 41d, and the forward / reverse lever 30 is rotated. The pressure for maintaining is gradually reduced, and the swash plate angle control means G causes the neutral spring 96
-The force of 96 moves the swash plate in the neutral direction to reduce the traveling speed.

When the spool 41 is further slid,
As shown in FIG. 8, the brake port 43 has the land portion 41.
It is blocked by c, and so far, the depression by the brake pedal 36 pushes against the spring 49, and the load is at the L position in FIG. When the brake pedal 36 is further depressed, it must be depressed against the spring force of the springs 48 and 49, and the operation force feels heavy, resulting in a two-step motion. Then, by sliding the spool 41, the brake port 43 communicates with the tank port 45 via the inclined portion 41d and the shaft hole 41f to gradually reduce the release pressure of the brake 74 to increase the braking force, and at the stroke end. The brake port 43 and the tank port 45 are communicated with each other for full brake braking.

[0018]

According to the present invention having the above-described structure, the following effects can be obtained. That is, since the port position is deviated as in the first aspect, the operation pilot port and the brake port are sequentially connected to the tank port when the brake pedal is operated, and the shock at the time of braking is alleviated.

Further, since the inclined portion is provided on the outer periphery of the spool as in claim 2, abrupt opening from the brake port to the tank port is suppressed, and leaking little by little to prevent sudden braking. I was able to.

Further, as described in claim 3, since the spring for urging the brake pedal in the returning direction is doubled, the operation of depressing the brake pedal is a two-step motion, and it can be suddenly felt heavy at the stroke end. The load of the brake can be easily identified with the foot, and the operation feeling of the slow brake and the hard brake is improved.

[Brief description of drawings]

FIG. 1 is an overall side view of a crawler type tractor.

FIG. 2 is a plan view of the same.

FIG. 3 is a plan view of the inside of a cabin of a driving unit.

FIG. 4 is a hydraulic circuit diagram.

FIG. 5 is a diagram showing swash plate angle control means.

FIG. 6 is a sectional view of a brake valve.

FIG. 7 is a diagram showing a hydraulic pressure symbol.

FIG. 8 is a sectional view showing the middle of a stroke.

FIG. 9 is a side view of the same.

FIG. 10 is a diagram showing a relationship between a stroke of a brake pedal and a load.

[Explanation of symbols]

 P hydraulic pump M hydraulic motor 36 brake pedal 41 spool 41d inclined part 42 pump port 43 brake port 44 operation pilot port 45 tank port 48/49 spring 50 pilot oil passage 76 brake valve

Claims (3)

[Claims] 1. An HST type transmission comprising a variable displacement hydraulic pump and a hydraulic motor is used for traveling speed change, the hydraulic pump is provided with swash plate angle control means, and the hydraulic motor is internally provided with a brake that always acts on the braking side. Then, the brake can be operated by operating a brake valve by operating a brake valve, and the brake valve and the swash plate angle control means are interlockingly connected by a pilot oil passage, and a brake port in the brake valve and an operating pilot. A brake device for a work vehicle, wherein the position with respect to the port is displaced in the sliding direction of the spool. 2. The spool of the brake valve according to claim 1, wherein a land portion that separates the pump port and the tank port is provided, and an inclined portion that gradually increases the opening is provided on the tank port side of the land portion. Brake device for work vehicles that features. 3. The brake valve spool according to claim 1, wherein springs having different spring constants are doubly fitted, and the pedaling load is changed in two steps during the stroke of the brake pedal. Vehicle braking device.