JP2000079883A - Hydraulic transmission-type working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the easy steering operation of a hydraulic transmission-type working vehicle capable of communicating and cutting off the discharge ports of the left and right hydraulic pumps, and improving the straight-advancing characteristic by communicating the discharge ports in the straight-advancing operation of a working machine. SOLUTION: The discharge ports 18L, 18R and the intake ports 19L, 19R of left and right hydraulic pumps PL, PR are independently communicated and connected to left and right hydraulic motors ML, MR through left and right going and returning oil passages 20L, 20R, 21L, 21R to form left and right static hydraulic continuously variable transmissions TL, TR. When a steering wheel 9 is operated to a straight-advancing position, the left and right going oil passages 20L, 20R and the left and right returning oil passages 21L, 21R are communicated to one another, and the equal oil pressure is supplied to the left and right hydraulic motors ML, MR, so that the equal driving force is generated on the left and right travelling parts 1L, 1R, and the straight-advancing characteristic of a hydraulic transmission-type working vehicle can be improved. When the steering wheel 9 is operated to a position excluding the straight-advancing position, the communication of the left and right going oil passages 20L, 20R and the loft and right returning oil passages 21L, 21R are cut off, and the different oil pressure is supplied to the left and right hydraulic motors ML, MR to perform turning travelling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a hydraulically driven work vehicle.

[0002]

2. Description of the Related Art Conventionally, left and right traveling units are individually driven by a left and right hydrostatic continuously variable transmission, and the driving speed of the left and right hydrostatic continuously variable transmission is varied by operating a steering device. There is a hydraulically driven work vehicle that performs turning travel. Each hydrostatic continuously variable transmission is configured by connecting a variable displacement type hydraulic pump and a hydraulic motor in communication.

[0003]

However, since the left and right traveling parts are individually driven by the left and right hydrostatic continuously variable transmissions, the difference between the left and right hydraulic pumps and the difference between the steering device and the left and right hydraulic pumps are different. There is a problem that the straightness is not good due to an error of the interlocking mechanism between them.

[0004]

Therefore, in the present invention, a left and right hydrostatic stepless transmission constituted by a left and right hydraulic pump and a left and right hydraulic motor is configured to individually drive the left and right traveling parts, and the operation is performed. In the hydraulically driven work vehicle, which is configured to make a turn by varying the driving speed of the left and right hydrostatic continuously variable transmission by operating the directional device, the discharge ports of the left and right hydraulic pumps can be connected and shut off freely, It is an object of the present invention to provide a hydraulically driven work vehicle characterized in that the straight port is communicated with a discharge port during straight running to enhance straight running.

[0005] The present invention also has the following features.

[0006] The discharge ports of the left and right hydraulic pumps are communicated via a bypass valve that can be opened and closed.

The bypass valve is linked with the steering device, and is opened when the steering device is operated in the straight traveling state, and is closed in other states.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention are as follows.

The left and right hydraulic pumps and the left and right hydraulic motors constitute left and right hydrostatic continuously variable transmissions, respectively, and the hydrostatic continuously variable transmissions drive the left and right traveling units individually.
By operating the shift lever, the output rotational speed of each hydrostatic continuously variable transmission is increased or decreased by a fixed amount, and by operating the steering device, the drive speed of the left and right hydrostatic continuously variable transmission is made different to reduce the traveling speed. The gears can be shifted in stages, and turning can be performed.

Particularly, in this embodiment, the discharge ports of the left and right hydraulic pumps are connected to each other through a bypass oil passage and a bypass valve, and when the steering device is in a straight running state, the bypass valve is opened and the left and right hydraulic pumps are opened. By operating the pump as a single hydraulic pump and equally supplying hydraulic oil to the left and right hydraulic motors, the aforementioned individual differences in hydraulic pumps and errors in the interlocking mechanism between the steering device and the left and right hydraulic pumps are eliminated. Then, the same driving force is output to the left and right hydraulic motors, and the hydraulically driven work vehicle is caused to travel straight.

When the steering device is in a state other than straight traveling, the bypass valve is closed to enable turning traveling.

[0012]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a hydraulically driven working vehicle A according to the present invention.
In the hydraulically driven work vehicle A, an airframe 2 is mounted above a pair of left and right crawler-type left and right traveling units 1L, 1R, and a hood 3 is provided on the front upper surface of the airframe 2 to cover the airframe. And a cabin 6 enclosing an operation unit 5 behind the motor unit 4.
A three-point link mechanism 10 is provided at the rear of the vehicle so that a working machine such as a tiller can be connected.

In the driving section 5, a speed change steering mechanism 7 is disposed at a lower front portion of the floor surface, and a steering column 8 is erected on the upper surface of the speed change steering mechanism 7, and is disposed above the steering column 8. The steering wheel 9 is arranged to be steerable and rotatable.

The left and right traveling units 1L and 1R are provided with left and right traveling unit frames.
The left and right driving sprockets 13L, 13R driven by the left and right hydraulic motors ML, MR are arranged at the front ends of the left and right traveling section frames 12L, 12R. The left and right idler wheels 14L, 14R are supported at the rear ends of the running unit frames 12L, 12R, respectively.
A plurality of left and right rolling wheels 15L, 15R are arranged on the lower surface of 12L, 12R, respectively, and left and right crawler tracks 16L, Crawler type left and right traveling part with 16R wound 1
L, 1R.

As shown in FIG. 2, the motor unit 4 includes an engine 17 and swash plate type variable displacement left and right hydraulic pumps PL and PR interlocked with the engine 17. The discharge ports 18L, 18R and the suction ports 19L, 19R of the PR are individually connected to the above-mentioned left and right hydraulic motors ML, MR via left and right reciprocating oil passages 20L, 20R, 21L, 21R, respectively. It constitutes a continuously variable transmission TL, TR.

The left and right swash plates 22L and 22R for controlling the discharge amounts of the left and right hydraulic pumps PL and PR are connected to the speed change steering mechanism 7 in an interlocked manner. The left and right operation rods 23L, which output the rotation amount of the shift lever 9 and the operation amount of the shift lever 11 to the left and right swash plates 22L, 22R, are synthesized.
The signals are output to the left and right swash plates 22L and 22R via 23R.

That is, the speed change steering mechanism 7 includes a speed change lever.
The operation of operating the left and right swash plates 22L and 22R so as to increase and decrease the discharge amounts of the left and right hydraulic pumps PL and PR in accordance with the increase and decrease of the operation amount of 11, and the operation amount of the steering wheel 9 as the steering device S Correspondingly, the operation of operating the left and right swash plates 22L and 22R so as to decrease the discharge amount of the hydraulic pump inside the turn and increase the discharge amount of the hydraulic pump outside the turn is combined, and the left and right swash plates 22L and 22R are combined. Output function.

Particularly, in this embodiment, the left and right reciprocating oil passages 20 are provided.
Electromagnetically operated bypass valve V in the middle of L, 20R, 21L, 21R
By opening and closing the bypass valve V, the left and right oil passages 20L, 20R and the left and right oil return passages 21L, 21R can be communicated or shut off, respectively.

In the drawing, reference numeral C denotes a controller. On the input side of the controller C, a switch 25 provided on the steering column 8 for detecting the straight traveling position of the steering column 8, and the rotation of the left and right driving sprockets 13L, 13R. Left and right rotation sensors 50L and 50 for detecting the number are connected, and the solenoid 24 of the bypass valve V is connected to the output side of the controller C.

When the switch 25 detects that the steering wheel 9 is at the straight traveling position, the bypass valve V is opened to open the left and right oil passages 20L, 20R and the left and right oil return passages 21L, 21R.
When the switch 25 is at a position other than straight ahead, the switch 25 does not conduct, the bypass valve V is closed, and communication between the left and right oil passages 20L, 20R and the left and right oil return passages 21L, 21R is established. Even when the steering wheel 9 is in the straight position,
If the difference between the detection values of the left and right rotation sensors 50L, 50 is larger than a predetermined value, the bypass valve V is closed and the left and right oil passages 20L,
The communication between 20R and the left and right oil return passages 21L, 21R is cut off.

Therefore, when the steering wheel 9 is operated to the straight traveling position in order to move the hydraulically driven work vehicle A straight, the left and right oil passages 20L and 20R and the left and right oil recovery passages 21L and 21R communicate with each other. Since the same hydraulic pressure is supplied to the hydraulic motors ML and MR, the same driving force is generated in the left and right traveling portions 1L and 1R, and the straight traveling of the hydraulically driven work vehicle A can be improved. In the figure, 26 is a charge pump, 27 is a hydraulic oil tank, 28
Is a hydraulic pump for driving other hydraulic equipment, 29 is a choke, 30 is a relief valve, and 31 is a check valve.

When the steering wheel 9 is operated to a position other than straight ahead for turning, the left and right oil passages
Since the communication between 20L, 20R and the left and right oil return passages 21L, 21R is interrupted and different hydraulic pressures are supplied to the left and right hydraulic motors ML, MR,
Different driving forces are generated in the left and right traveling portions 1L, 1R, and the vehicle can perform turning traveling.

FIGS. 3 to 5 show that the operation amount of the shift lever 40 is electrically detected and the continuously variable transmission 41 is detected based on the detected value.
In this embodiment, the gear-type three-stage transmission 42 is connected in series with the continuously variable transmission 41 to perform the gear shifting operation. , And electromagnetic actuators 43 and 44 for performing gear shifting operations, respectively.
In addition, a potentiometer 45 is interlockedly connected to the base end of the shift lever 40 to output a voltage proportional to the operation amount of the shift lever 40.
And the speed ratio of the gear type three-speed transmission 42 is changed from neutral N to first speed in accordance with the operation amount of the shift lever 40, that is, the traveling speed.
At the same time as shifting between V1-2nd speed V2-3rd speed V3,
By changing the gear ratio 48 of the continuously variable transmission 41 into a saw-tooth shape, and making the final output rotational speed match before and after the speed change operation of the gear type three-stage transmission 42, the gear type three-stage transmission 42
The speed change can be performed without a shock, so that the ride comfort can be improved, and the speed control up to the maximum speed can be performed only by operating the shift lever 40.

[0025]

According to the present invention, the following effects can be obtained.

According to the first aspect of the present invention, the left and right traveling units are individually driven by the left and right hydrostatic stepless transmissions constituted by the left and right hydraulic pumps and the left and right hydraulic motors, respectively. In the hydraulically driven work vehicle that is configured to make a turning motion by varying the drive speed of the left and right hydrostatic continuously variable transmission, the discharge ports of the left and right hydraulic pumps can be freely connected and shut off, and the discharge port is used when the work machine goes straight , The steering operation of the hydraulically driven work vehicle can be facilitated.

According to the second aspect of the present invention, the discharge ports of the left and right hydraulic pumps are communicated via a bypass valve which can be freely opened and closed. By operating the left and right hydraulic pumps as a single hydraulic pump and equally supplying hydraulic oil to the left and right hydraulic motors, individual differences between hydraulic pumps and errors in the interlocking mechanism between the steering device and the left and right hydraulic pumps are eliminated. However, it is possible to output the same driving force to the left and right hydraulic motors and to improve the straightness.

According to the third aspect of the present invention, the bypass valve is operated in conjunction with the steering device so that the valve is opened when the steering device is operated in a straight-ahead state and closed in other states. The bypass valve can be opened and closed only by operating the steering device, so that high straightness can be maintained and the steering operation can be facilitated.

[Brief description of the drawings]

FIG. 1 is a side view of a hydraulically driven work vehicle according to the present invention.

FIG. 2 is a diagram of a power transmission system to a traveling unit.

FIG. 3 is an explanatory diagram showing a configuration of a transmission mechanism of another embodiment.

FIG. 4 is a side view of a shift lever.

FIG. 5 is an explanatory diagram showing a configuration of a transmission controller according to another embodiment.

[Explanation of symbols]

 A Hydraulic drive type work vehicle ML, MR Left and right hydraulic motor PL, PR Left and right hydraulic pump S Steering device TL, TR Left and right hydrostatic continuously variable transmission V Bypass valve 1L, 1R Left and right traveling part 18L, 18R Discharge port

Claims (3)

[Claims] A left-right traveling unit (1L) is provided by a left-right hydrostatic continuously variable transmission (TL) (TR) composed of a left-right hydraulic pump (PL) (PR) and a left-right hydraulic motor (ML) (MR). ) (1R) are configured to be driven individually, and by operating the steering device (S), the left and right hydrostatic continuously variable transmissions (TL) (TR) are configured to make different driving speeds for turning. In the hydraulically driven work vehicle (A), the discharge ports (18L) and (18R) of the left and right hydraulic pumps (PL) and (PR) can be connected and disconnected freely, and the discharge port (18L ) (18R) is communicated to improve the straightness. 2. The hydraulic drive according to claim 1, wherein the discharge ports (18L) and (18R) of the left and right hydraulic pumps (PL) and (PR) communicate with each other via a bypass valve (V) that can be opened and closed. Work vehicle. 3. The bypass valve (V) is linked with the steering device (S), and opens when the steering device (S) is operated in a straight-ahead state, and closes in other states. The hydraulically driven work vehicle according to claim 1 or 2, wherein: