JP2983120B2 - Backhoe hydraulic circuit structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backhoe load control type hydraulic circuit structure and, more particularly, to a technique for suppressing fluctuations in running speed caused by raising and lowering a dozer during dozer work.

[0002]

2. Description of the Related Art As an example of a load control type hydraulic circuit, there is a closed center system as shown in FIG. In this circuit, for example, when the load on the traveling hydraulic motors 6c and 9c increases and exceeds a predetermined circuit pressure, the on-off valve 3 is switched to the open position, and the adjusting cylinder 2 decreases the discharge amount of the hydraulic pump 1. That is, the operation is performed such that the pressure is increased and the on-off valve 3 is closed when the pressure oil corresponding to the load is discharged. That is, when the load increases, the discharge pressure is automatically adjusted so as to increase,
This is a means that is easy to operate and can reduce the power loss by reducing the excessive pump output state. Other forms of the load control circuit include a negative control system and a load sensing system.

[0003]

The backhoe mainly performs excavation work, but also performs dozer work for moving and leveling earth and sand by using a dozer while traveling. However, the following inconveniences have been found during the dozer operation. That is, when the dozer is lifted and lowered during the dozer work, the traveling speed may be slow, and when the lifting and lowering operation is stopped, the traveling speed may be increased. It is difficult to work and the work efficiency decreases.

[0004] This phenomenon tends to occur during heavy loads such as a lot of dislodged earth and sand, and a similar phenomenon occurs during front work with a separate working device mounted on the service port. There are cases.
SUMMARY OF THE INVENTION An object of the present invention is to provide a backhoe employing a load control type hydraulic circuit, in which a change in traveling speed does not occur even when a dozer is lifted and lowered during a dozer operation, thereby suppressing a decrease in maneuverability and work efficiency. It is in.

[0005]

According to a first aspect of the present invention, there are provided a plurality of hydraulically driven actuators, a variable displacement type hydraulic pump for supplying pressure oil thereto, and a supply direction of pressure oil discharged from the hydraulic pump. A control valve for controlling the hydraulic oil supply to the actuator, an adjusting actuator for variably setting the discharge oil amount per unit time of the hydraulic pump, and a hydraulic oil supply lower side of the hydraulic pump and a hydraulic oil supply upper side of the actuator Pressure detection means for detecting the circuit pressure of the oil passage located in the hydraulic circuit, the discharge pressure of the hydraulic pump is increased when the pressure detected by the pressure detection means is high, and the discharge pressure of the hydraulic pump is reduced when the detection pressure is low In the load control state, in the hydraulic circuit structure of the backhoe in which the pressure detecting means and the adjusting actuator are linked, the maximum oil supply amount per unit time to the traveling control valve is determined. The maximum amount of oil supplied to the traveling control valve per unit time by the operation of the speed reducing unit is changed from the maximum discharge oil amount per unit time of the hydraulic pump to the dozer control valve or the service control valve. The throttle amount of the speed reduction means is set to a value obtained by reducing the maximum supply oil amount per unit time of or a value near the value, and the state in which the speed reduction means operates and the state in which the speed reduction means does not operate are selected alternatively. A switching means for selecting and setting is provided.

A second aspect of the present invention is a control valve on the downstream side of the pressure oil supply.
And pressure compensation on the side of the actuator that supplies the hydraulic oil well
Valves are installed, and left and right traveling pressure compensating valves are attached to the oil path disconnection side.
A biasing spring is provided, and the speed reduction means is provided at a position on the fixed side of the spring.
And the control valves for them.
And control the switching means to compress the spring
Dozer mode position to open the valve and control valve to open
Consists of an adjustable switch that can be switched between the OFF position and the OFF position
It is characterized by having been done.

[0007]

When the cause of the above-described inconvenience is examined, it is found that the inconvenience is caused by the relationship between the hydraulic pump capacity and the load control. In other words, load control is an energy-saving method that adjusts the pump capacity as needed. To take advantage of this feature, the maximum required flow rate of the actuator that requires the most amount of oil (for example, a boom cylinder) is usually set to the maximum required flow rate. In many cases, the hydraulic pump itself is set to the minimum necessary, such as setting the discharge amount together.
Therefore, when simultaneously supplying hydraulic oil to the left and right hydraulic motors and a plurality of actuators of the dozer cylinder (or the front working cylinder), the total required flow rate exceeds the maximum supply and discharge amount of the hydraulic pump, As a result, the traveling speed is reduced.

Therefore, according to the configuration of claim 1 based on this recognition, the maximum oil supply amount per unit time to the traveling control valve by the deceleration means in advance is set to the maximum discharge amount per unit time of the hydraulic pump. Since the value is reduced to the value obtained by subtracting the maximum supply oil amount per unit time from the oil amount to the dozer control valve, or a value near the value, even if the dozer cylinder is driven at its maximum output during dozer work There is little or no effect on the amount of oil supplied to the hydraulic motor for traveling, and therefore the maximum traveling speed is slowed down, but no or little speed change occurs.

For example, in the leveling work (dozer work) of raising and lowering the dozer while traveling, in order to make the dozer in the ascending state touch the ground at the target point, the dozer corresponding to the running speed that is present is displayed. Since the lever is operated in consideration of the descending movement speed, if the traveling speed decreases with the dozer operation, the operation feeling will be disturbed, and it will touch the ground in front of the target point, There is a possibility that a problem such as digging may occur.

That is, in the actual work, it is easier for the working efficiency to be adversely affected when the running speed is changed in accordance with the operation of the working device than when the maximum speed is reduced. The same applies to work using a service port that involves traveling. Therefore, at the time of the combined operation of the dozer work and the work using the service port, the operation speed does not change, so that the deterioration of the work efficiency and the work accuracy can be greatly reduced.

Since the switching means for selectively selecting and setting the operating state and the non-operating state of the decelerating means is provided, if the operating state is switched, the above-described favorable action can be obtained. If the state is switched to the non-operating state, the running speed can be increased and the working efficiency can be increased at times other than the dozer work such as traveling and the work using the service port.

According to the configuration of the second aspect, when the adjustment switch is set to the dozer mode position, the control valve is opened, the position cylinder is operated to compress the spring, and the traveling pressure compensating valve is switched to the open side. The required operating pressure is increased, that is, the differential pressure that is the load control reference for the traveling control valve is made higher than a predetermined value. Then, the maximum oil supply amount per unit time to the traveling hydraulic motor is reduced, and even if the dozer is raised and lowered at the maximum speed during the dozer work, the total required flow rate can be kept below the maximum discharge oil amount of the hydraulic pump. Can, and as a result,
Even if the dozer moves up and down during the dozer work, it is possible to prevent the speed fluctuation from occurring.

[0013]

Accordingly, the bag according to the first and second aspects is provided.
By reducing the maximum traveling speed in advance by using the deceleration means, the backhoe that excels in operability and performs reasonable load control eliminates speed fluctuations during dozer work and work using the service port, which would require traveling. In addition, the hydraulic circuit structure which can be almost eliminated and contributes to the improvement of work efficiency can be provided. In addition, since it is possible to select whether the deceleration means does not work or not, there is an advantage that the maximum traveling speed can be increased and the efficiency can be improved at times other than the dozer work and the work using the service port.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 6 is a side view of the backhoe, and FIGS.
2 shows a load control hydraulic circuit including a hydraulic drive unit A, a valve block B, and a plurality of hydraulic actuators. The hydraulic drive unit A includes two variable displacement hydraulic pumps 1 driven by the engine En, an adjusting cylinder 2 for changing the angle of a swash plate of the hydraulic pump 1 to adjust a discharge amount per unit time, and an adjusting cylinder 2. It is composed of a pressure compensation type pressure control valve (pilot pressure reducing valve) 3 and the like.

The valve block B comprises a dozer control valve 4, a bucket control valve 5, a left running control valve 6, a boom control valve 7, an arm control valve 8, a right running control valve 9, and a turning control valve. 10, control valves for swing control valve 11 and service port control valve 12, and compensators (pressure compensating valves) 4a, 5a, 6a, 7 provided for each of these control valves.
a, 8a, 9a, 10a, 11a, 12a, a dozer lifting / lowering cylinder 4c, a bucket cylinder 5c, left and right traveling hydraulic motors 6c, 9c, a boom cylinder 7c, an arm cylinder 8c, and a turning cylinder. The hydraulic motor 10c, the swing cylinder 11c, and the service actuator 12c are connected to respective actuators.

Each of the control valves has a throttle valve 4s, 5
s, 6s, 7s, 8s, 9s, 10s, 11s, 12s
Is equipped. Each control valve is provided with a pair of switching cylinders 5b, 7b, 8b, 10b, 1 that are operated by a pilot pressure, which will be described later, in order to switch these spools.
1b is equipped.

Each of the compensators 4a to 12a is on the lower side of the pressure oil supply to each of the throttle valves 4s to 12s, and
It is arranged on the upstream side of the pressure oil supply to each of the actuators 4c to 12c. And each compensator 4a-1
2a spring-side oil chambers 4x to 12x and each actuator 4c
Low-pressure-side oil passages 4t to 12t that communicate the pressure oil supply lower-side portion with respect to -12c, and compensators 4a to 12c
a spring-side oil chamber 4 opposing the spring-side oil chambers 4x to 12x of FIG.
The high-pressure side oil passages 4k-1 which communicate with the hydraulic oil supply side for each of the compensators 4a-12a and the hydraulic oil supply side for each of the throttle valves 4s-12s.
2k are provided respectively. This constitutes an after-orifice type load sensing circuit.

A low-pressure side oil passage 3t is provided for communicating the spring-side oil chamber 3x of the pressure control valve 3 with the lower side of the pressure oil supply to each of the throttle valves 4s to 12s, and the pressure oil of each of the control valves 4 to 12 is provided. An input port 15 to the valve block B in a communication oil passage 13 between the valve block B and the hydraulic drive unit A connected to the supply ports 4p to 12p, and a spring-side oil chamber 3 of the pressure control valve 3.
x is connected to a non-spring side oil chamber 3y opposed to x.
Are in communication. The connection oil passage 14 makes it possible to make the pressure loss value in the external piping constant even if the hydraulic drive unit A and the valve block B have different pipe lengths for each model. This is convenient because there is no need to fine-tune the force.

As shown in FIG. 4, the bucket control valve 5,
Boom control valve 7, arm control valve 8, turning control valve 1
For the control valve 11 for swing and swing, a hydraulic pilot operation structure operated by the pilot pressure of the auxiliary pump 16 is adopted, a first lever 17 for a bucket / boom that can be freely operated in cross direction, their pilot valve 18, arm / rotation. A second lever 19 and a pilot valve 20 thereof are provided, and a third lever 21 for a swing and a pilot valve 22 thereof are provided.

As shown in FIGS. 1 to 3 and 5, a speed reducing means H for reducing the maximum oil supply amount per unit time to the traveling control valves 6, 9 is provided. The maximum supply oil amount per unit time to the control valves 6 and 9 for
The throttle amount of the speed reduction means H is set to a value obtained by subtracting the maximum oil supply amount per unit time from the maximum discharge oil amount per unit time of the hydraulic pump 1 to the dozer control valve 4.

That is, the deceleration means H includes springs 6d, 9d for urging the left and right traveling compensators 6a, 9a to a switching position on the oil path disconnection side, and a position cylinder provided at a fixed side position of these springs 6d, 9d. 26, 26, and an electromagnetic pressure control valve 27 for the position cylinder 26, and the like. A control device 29 connected to the electromagnetic pressure control valve 27 includes an adjustment switch (an example of switching means) 28 and an engine E
The detection means 30 for detecting the number of rotations of n is connected to form a dozer operation control circuit. In addition, in FIG. 5, for simplicity, only a circuit for left traveling is shown.

To explain the operation, when the adjustment switch 28 is set to the dozer mode position, the electromagnetic pressure control valve 27 is opened, the position cylinder 26 is operated to compress the springs 6d and 9d, and the traveling compensators 6a and 9a The operating pressure required for switching to the opening side is increased, that is, the differential pressure serving as a load control reference for the traveling control valves 6 and 9 is set higher than a predetermined value.

For example, the maximum discharge or oil consumption of each of the hydraulic pump 1, the traveling hydraulic motors 6c and 9c, and the dozer cylinder 4c is determined as follows: Hydraulic pump 1: 120L Traveling hydraulic motors 6c and 9c: 60L Dozer cylinder 4c: 30L Then, if the dozer is moved up and down at the maximum speed during the dozer work at the maximum traveling speed, the required flow rate will be 60 + 60 + 30 =
Since the absolute oil amount becomes 150 L and the absolute oil amount becomes insufficient, the oil amount is distributed by the load sensing control operation so that the total oil amount becomes 120 L or less (for example,
50 L to each hydraulic motor and 20 L to the dozer cylinder), and the traveling speed decreases.

However, when the switch 28 is set to the dozer mode position in advance to increase the differential pressure, the maximum oil supply amount per unit time to the traveling hydraulic motor, that is, to the traveling control valves 6 and 9 becomes, for example, Even if the dozer is moved up and down at the maximum speed during the dozer operation, the total required flow rate becomes 110 L, which can be suppressed below the maximum discharge oil amount of the hydraulic pump. The speed can be prevented from occurring even when the vehicle moves up and down.

When the service port is used, the adjustment switch 28 is operated to the service mode position, and the maximum amount of oil supplied to the traveling control valves 6 and 9 per unit time is reduced to, for example, 45 L. Then, even if the engine speed fluctuates and the discharge amount of the hydraulic pump 1 changes, the traveling speed suppression function of each mode by the operation of the adjustment switch 28 is maintained, that is, the differential pressure increases as the engine speed increases. The control device 29 is configured so that the rate of increase is lower and the rate of increase in differential pressure is higher as the rotational speed decreases.

The compensators 4a, 4b,
The springs 4d, 5d, 7d, 8d, 10d, and 11d for setting a differential pressure are also provided on 5a, 7a, 8a, 10a, and 11a. In the claims, the boom cylinder 7c, the swing motor 10c, and the like are collectively referred to as a hydraulically-driven actuator D, the bucket control valve 5, the arm control valve 8, and the like are collectively referred to as a control valve E. It is to express each.

[Another Embodiment] The operation of the adjustment switch 28 restricts the maximum movement amount of the spool of the traveling control valves 6 and 9 to reduce the maximum traveling speed in advance (for example, the stopper for the spool with the position cylinder 26 described above). The means for regulating the amount of spool movement of the control valve and the means for adjusting the set differential pressure of the compensator are collectively defined as "deceleration means H".

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a hydraulic circuit, part 1

FIG. 2 is a system diagram showing a hydraulic circuit, part 2

FIG. 3 is a system diagram showing a hydraulic circuit, part 3

FIG. 4 is a system diagram showing a pilot circuit.

FIG. 5 is a system diagram showing a differential pressure adjusting structure for the traveling control valve.

FIG. 6 is a side view of the backhoe.

FIG. 7 is a circuit diagram of a closed center type load control.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Variable displacement hydraulic pump 2 Adjustment actuator 3 Pressure adjustment valve 4 Dozer control valves 4a to 12a Pressure compensating valves 6, 9 Traveling control valves 6d, 9d Spring 12 Service control valve 26 Position cylinder 27 Control valve 28 Switching means D Actuator E Control valve H Deceleration means

Claims (2)

(57) [Claims] 1. A plurality of hydraulically driven actuators (D), a variable displacement hydraulic pump (1) for supplying pressure oil thereto, and a supply direction of pressure oil discharged from the hydraulic pump (1). A control valve (E) that controls the hydraulic pump (1) to control the oil supply to the actuator (D), an adjusting actuator (2) that variably sets a discharge oil amount per unit time of the hydraulic pump (1), and the hydraulic pump (1). Pressure detection means (3) for detecting a circuit pressure of an oil passage located on the lower side of the pressure oil supply of the actuator and on the upper side of the pressure oil supply of the actuator (D), wherein the pressure detection means (3) When the detected pressure increases, the discharge pressure of the hydraulic pump (1) increases, and when the detected pressure decreases, the discharge pressure of the hydraulic pump (1) decreases. The adjustment actuator (2 And a speed reducing means (H) for reducing the maximum amount of oil supplied per unit time to the traveling control valves (6) and (9). The maximum oil supply amount per unit time to the traveling control valves (6) and (9) by the operation of (H) is determined from the maximum discharge oil amount per unit time of the hydraulic pump (1) from the dozer control valve. (4) The throttle amount of the speed reduction means (H) is set to a value obtained by subtracting the maximum amount of oil supplied per unit time to the service control valve (12) or to a value in the vicinity thereof. And a switching circuit (28) for selectively selecting and setting a state in which the deceleration means (H) operates and a state in which the speed reduction means (H) does not operate. 2. A control oil supply side of the control valve (E).
And the pressure oil supply side of the actuator (D)
With pressure compensating valves (4a-12a) for left and right traveling
The pressure compensating valves (6a) and (9a) are urged toward the oil path disconnection side.
Provide springs (6d) and (9d) The deceleration means (H) is connected to the springs (6d) and (9d).
Position cylinders (26), (2
6) and a control valve (27) for them
In both cases, the switching means (28) is connected to the spring (6d),
Compress (9d) Open the control valve (27) as much as possible
And the control valve (27) is opened.
Consists of an adjustable switch that can be switched between the OFF position and the OFF position
The hydraulic circuit structure for a backhoe according to claim 1, wherein the hydraulic circuit structure is provided.