JPH10338947A - Method and device for controlling travel speed of working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize low car speed, where a service car is easy to be operated at the time of the selection of low-speed travelling, while ensuring car speed and driving force at the time of the selection of high-speed travelling by reducing the maximum discharge of a variable displacement pump when a variable capacity hydraulic motor for travelling is driven at low speed. SOLUTION: Variable displacement hydraulic pumps 2A, 2B are connected to a variable-speed variable capacity hydraulic motor 3 for travelling, and a variable speed means 4 changing over the hydraulic motor 3 at low speed and at high speed is installed. A travel-speed control means 6 reducing the maximum discharge of the hydraulic pump 2 by detecting the forward and backward movement operation of an operating member 5 is mounted, and the variable speed means 4 and the travel-speed control means 6 are interlocked for bringing the travel-speed control means 6 to an unoperated state by operation on the high speed side of the variable speed means 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling a traveling speed of a working vehicle such as a backhoe for construction and civil engineering.

[0002]

2. Description of the Related Art In a backhoe, for example, a variable displacement hydraulic pump is driven by an engine, and oil discharged from the hydraulic pump is supplied to a swing motor, a boom cylinder, an arm cylinder, etc. This hydraulic motor is of a variable displacement type capable of shifting between high and low speeds in order to efficiently perform excavation work, site movement, and the like.

[0003] In recent years, there has been a further demand for faster on-site movement, and as shown in the table of FIG. 3, model B2 has a larger pump capacity than model B1 so that both first and second speeds can be speeded up. In order to improve the turn performance even during high-speed movement, the driving force is increased. Generally, high flow rate and high pressure are used for traveling.

[0004]

If the speed and the driving force of the second speed are secured as in the above-mentioned model B2, the driving force becomes excessive at the first speed, and the strength of the crawler and the underbody is increased. It is difficult to follow the driving force, and it is necessary to appropriately suppress the driving force. Therefore, as shown in the table of FIG. 3, the driving force in the first speed is set to be the same as the driving force in the second speed.

However, if the driving force is suppressed while the pump capacity is increased in this way, the running speed increases, and it becomes difficult to carry out fishing work, dozer work, unloading work on a truck, and the like. Occurs. The present invention
When the variable displacement hydraulic motor for traveling is driven at low speed,
By reducing the maximum displacement of the variable displacement pump, while ensuring the vehicle speed and driving force when high speed traveling is selected,
An object of the present invention is to provide a traveling speed control method and a device for a working vehicle, which are capable of realizing a low vehicle speed at which low-speed traveling can be easily performed.

[0006]

A concrete means for solving the problems in the method of the present invention is to supply the discharge oil of the variable displacement hydraulic pump 2 to a variable displacement hydraulic motor 3 for traveling, and to control this hydraulic motor 3. This is to decrease the maximum discharge amount of the hydraulic pump 2 when the vehicle is running at a low speed. As a result, the maximum discharge amount is reduced only when the low-speed traveling is selected, without changing the maximum discharge amount of the hydraulic pump 2 when the high-speed traveling is selected, and traveling at a low vehicle speed while securing the driving force can be performed.

[0007] The first solution for solving the problem in the device of the present invention.
Specifically, the traveling speed control of a work vehicle having a variable displacement hydraulic pump 2 connected to a variable displacement hydraulic motor 3 for traveling capable of shifting and having a shifting means 4 for switching the hydraulic motor 3 between low speed and high speed is provided. In the apparatus, traveling speed control means 6 for detecting the forward / backward operation of the operation member 5 and reducing the maximum discharge amount of the hydraulic pump 2 is provided, and the traveling speed control means 6 is deactivated by operating the transmission means 4 on the high-speed side. That is, the speed change means 4 and the traveling speed control means 6 are linked to each other.

Thus, when the operating member 5 is moved forward and backward to run at a low speed, the maximum discharge amount of the hydraulic pump 2 is reduced to enable running during operation at a low vehicle speed. At this time, high-speed traveling can be performed without reducing the maximum discharge amount of the hydraulic pump 2. The second specific means for solving the problem in the device of the present invention is, in addition to the first specific means, the traveling speed control means 6
A sensor 7 for detecting the forward / backward operation of the operation member 5, a pump control member 8 for reducing the maximum discharge amount of the variable displacement pump 2 by a detection signal of the sensor 7, and a sensor 7 and the pump control member 8 And a switch 9 which is provided and is cut off by the operation of the speed change means 4.

Thus, the reduction of the maximum discharge amount when the low-speed traveling is selected can be realized with a simple configuration.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a hydraulic circuit of a mini backhoe, in which an engine 11 drives a main hydraulic pump 2A, a sub hydraulic pump 2B and a pilot hydraulic pump 13 of a multi-hydraulic pump.
A employs a double variable displacement hydraulic pump.

The hydraulic oil of the main hydraulic pump 2A and the sub hydraulic pump 2B is supplied to control valves 14, 1 having a number of control valve bodies.
5, and can be supplied to actuators such as a traveling hydraulic motor 3 of a pair of right and left crawler traveling devices, a swing motor, a boom cylinder, an arm cylinder, a bucket cylinder, a dozer cylinder, and a service port. The motor 3 is of a variable displacement type.

There are backhoes of the type in which the arm is offset to the left and right. In this type, the pressure oil from the sub hydraulic pump 2B is also supplied to the offset cylinder, and the pressure oil from the sub hydraulic pump 2B is When the vehicle travels in a straight line, the actuator merges with the pressure oil from the main hydraulic pump 2A, so that various actuators can be simultaneously operated. The pressure oil of the pilot hydraulic pump 13 is supplied to a pilot valve 18 operated by a left / right operation lever 17 via an unload valve 16, and is supplied to the control valve 14 by operating the pilot valve 18. Control it.

Each of the left and right operation levers 17 can operate each pilot valve 18 by swinging back and forth and right and left, and includes a swing motor, a boom cylinder, an arm cylinder,
Controls bucket cylinders and the like. The backhoe is provided with a pair of left and right traveling operation levers (operation members) 5 separately from the operation lever 17, and the left and right traveling operation levers 5 operate the control valve 15 via a link or a wire, and a left and right hydraulic pressure is applied. The motor 3 is rotated forward and backward.

The hydraulic motor 3 is of a variable displacement type, and the maximum displacement can be changed by changing the angle of the swash plate with the cylinder 21 so that the speed can be changed between high and low. The switching valve 22 connects and disconnects the pressure oil supplied from the hydraulic pump 2 to the cylinder 21.
The switching operation is performed by operating 3. The second-speed solenoid valve 23 is excited by the on-operation of the second-speed switch 24 to be in the second (high-speed) state.

The shifting means 4 is constituted by the cylinder 21, the switching valve 22, the second-speed solenoid valve 23, the second-speed switch 24 and the like, and the second-speed switch 24 is operated by an operating member 25 such as a petal, lever or button. In the vicinity of the travel operation lever 5, a sensor 7 for detecting the forward / reverse operation is provided. On the other hand, the variable displacement pump 2 is provided with a swash plate so as to reduce the maximum displacement (maximum discharge amount). A solenoid (pump control member) 8 for changing the angle is provided, and the solenoid 8 is connected to the sensor 7 via a switch 9.

The switch 9 is a closed contact switch located in the vicinity of the second speed switch 24.
The switch 9 can be operated simultaneously with the speed switch 24, and when the second speed switch 24 is turned on by operating the operating member 25, the switch 9 is turned off, and the signal transmission circuit connecting the sensor 7 and the solenoid 8 is disconnected. The traveling speed control means 6 for detecting the forward / backward operation of the traveling operation lever 5 and reducing the maximum discharge amount of the hydraulic pump 2 is constituted by the sensor 7, the solenoid 8, the switch 9 and the operating member 25. The speed control means 6 is interlocked with the speed change means 4 such that the speed control means 6 is deactivated by the high-speed operation of the speed change means 4.

Next, a running speed control method in the running speed control device configured as described above will be described. In the first speed (low speed) state in which the traveling speed control means 6 and the second speed operating member 25 are not operated, the operation lever 17 is operated,
When hydraulic oil is supplied to various actuators through the control of the control valve 14 to perform turning, raising / lowering of a boom, or scraping / dumping of an arm or a bucket, the hydraulic pump 2A supplies hydraulic oil of the maximum capacity and the maximum discharge amount. Supply those actuators.

When the traveling operation lever 5 is operated for traveling from this state, the sensor 7 detects forward or backward movement to excite the solenoid 8 and changes the swash plate angle of the variable displacement pump 2 to the maximum. The discharge amount is reduced, and as shown in FIG. 2, the maximum discharge amount S shown by a solid line is changed to a reduced discharge amount M shown by a dotted line. In the case of the first speed, if the maximum discharge amount is reduced by almost half by using the same hydraulic pump 2 as the model B2,
As shown in the table of FIG. 3, in the model A of the present invention, since the set pressure of the relief valve is constant, the driving force is maintained as required.
Only the vehicle speed decreases.

The vehicle speed in this case may be the same as or around the model B1, and may be any speed that can withstand the strength of the crawler traveling device and the underbody. When high-speed traveling is selected by operating the operating member 25 during bucket work or traveling, 2
When the speed switch 24 is turned on, the second speed solenoid valve 23 is excited, and the switching valve 22 is switched to switch the hydraulic pump 13 to the first position.
The speed is changed from the second speed to the second speed, and at the same time, the switch 9 is turned off, the transmission of the detection signal from the sensor 7 to the solenoid 8 is stopped (inactive state), and the variable displacement pump 2 is Return to maximum discharge.

At the second speed, the vehicle speed and the driving force of the model A of the present invention are maintained at the same high speed and high driving force as the model B2, and the capacity of the hydraulic pump 2 is made larger than that of the model B1. Fully demonstrates the capacity enhancement effect. This second
In the high-speed state, even if the traveling operation lever 5 is operated to turn on the sensor 7, the switch 9 is in the off state, so that the solenoid 8 is not excited.

The present invention is not limited to the above embodiment, but can be variously modified. For example,
The traveling vehicle may be other than a backhoe, and the traveling speed control means 6 may be hydraulic as long as it can detect the operation of the hydraulic motor 3 in the first speed state. Also,
Although the vehicle speed is reduced even if one of the left and right traveling operation levers 5 is operated, the vehicle speed may be reduced only when operated simultaneously. The traveling speed control means 6 may operate the solenoid valve based on the detection signal of the sensor 7 to change the angle of the swash plate of the main hydraulic pump 22A with the hydraulic cylinder. Further, the operation member 5 may be a pedal for switching between forward and backward movement.

[0022]

According to the present invention described in detail above, it is possible to realize a low vehicle speed at which low-speed traveling is easy to work while securing the vehicle speed and driving force when high-speed traveling is selected. Further, the reduction of the maximum discharge amount when the low-speed traveling is selected can be realized with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a hydraulic and electric circuit diagram showing an embodiment of a traveling speed control device according to the present invention.

FIG. 2 is a pressure flow chart showing a maximum discharge amount and a decrease discharge amount.

FIG. 3 is a table comparing the vehicle speed and the driving force of the present invention and the prior art.

[Explanation of symbols]

 2 Hydraulic pump 3 Hydraulic motor 4 Transmission means 5 Traveling operation lever (operation member) 6 Traveling speed control means 7 Sensor 8 Solenoid (pump control member) 9 Switch

Claims (3)

[Claims] An oil supply from a variable displacement hydraulic pump (2) is supplied to a traveling variable displacement hydraulic motor (3), and when the hydraulic motor (3) is brought into a low speed traveling state, the hydraulic pump (2) is driven. A) reducing the maximum discharge rate of the working vehicle. 2. A variable displacement hydraulic pump (2) is connected to a variable displacement hydraulic motor for traveling (3) capable of shifting, and a speed change means (4) for switching the hydraulic motor (3) between low speed and high speed is provided. A traveling speed control device (6) for detecting a forward / reverse operation of the operating member (5) and reducing a maximum discharge amount of the hydraulic pump (2); The speed change means (4) and the running speed control means (6) are interlocked so that the running speed control means (6) is deactivated in the high-speed side operation of (1). apparatus. The traveling speed control means (6) detects a forward / reverse operation of the operating member (5), and detects a maximum discharge of the hydraulic pump (2) based on a detection signal of the sensor (7). A pump control member (8) for reducing the amount and a switch (9) provided between the sensor (7) and the pump control member (8) and cut off by the operation of the speed change means (4). The traveling speed control device for a work vehicle according to claim 2, wherein: