JPH0734489A - Hydraulic circuit structure for construction machinery - Google Patents

Abstract

PURPOSE:To improve the operation performance by allowing the driving speed of a working device to be decreased when engine speed is decreased, in a load sensing system. CONSTITUTION:In a back hoe which carries out the load sensing control for keeping the difference between the load of a boom or a turning actuator and the pump discharge pressure, a pressure compensating valve G is arranged on the pressurized oil feeding downstream side for a throttle valve in each control valve and on the prescrized oil feeding upstream side for the actuator, and an after orifice structure is formed. A valve mechanism B which adjusts the partial pressure in a spring side oil chamber Gx by the application to the spring side oil passage Gt of a pressure compensation valve G is constituted of an electromagnetic high speed response valve 21 which acts to the spring oil passage Gt and an intermittent controller 18 which can set the duty ratio in the intermittent operation time, in a variable manner, and the driving speed of the actuator is increased and decreased in synchronization with the increase/ decrease of the number of engine revolution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit structure of a construction machine such as a backhoe, and more specifically, detecting a load pressure,
The present invention relates to a hydraulic circuit structure for performing control for causing a pump to discharge hydraulic power as much as a load requires, so-called load sensing.

[0002]

2. Description of the Related Art As a hydraulic circuit of this kind, there is an after-orifice type hydraulic circuit shown in Japanese Patent Application No. 5-9674 previously filed. In other words, it is a structure in which the pressure compensating valve is arranged on the pressure oil supply lower side of the throttle in the control valve, and even when the total required flow rate when simultaneously driving a plurality of actuators exceeds the maximum discharge flow rate of the hydraulic pump, The advantage that a flow rate proportional to the opening of the throttle in the control valve appears without the need for a special circuit (anti-saturation function)
There is.

[0003]

In a general backhoe that does not use a load sensing system, when the drive speed of the working device is slowed, such as slowly turning around the wall, the operation of reducing the engine speed is performed. Is common. However, in load sensing in which the differential pressure between the load pressure and the pump pressure is maintained constant, even if the engine speed decreases and the pump discharge amount decreases, the pump discharge amount is within the range higher than the required flow rate of the actuator. If,
It functions to maintain the set drive speed of the actuator. For this reason, when an operator who is accustomed to operating conventional models operates a construction machine equipped with a load sensing system, it is difficult to keep up with the fact that the drive speed of the work equipment does not decrease even if the engine speed is reduced, which improves work efficiency. It is expected to be unfavorable. An object of the present invention is to improve the operability by adopting a load sensing system and adjusting the drive speed of the actuator such that the drive speed of the work device becomes slower if the engine rotation is reduced. The point is to obtain a hydraulic circuit for load sensing.

[0004]

In order to achieve the above object, the present invention provides (1) a hydraulic actuator, a variable displacement hydraulic pump for supplying pressure oil to the hydraulic actuator, and a pressure oil discharged from the hydraulic pump. The control valve that controls the supply direction of the oil to the actuator, the throttle valve that is installed inside this control valve and acts to throttle the pressure oil supply path to the actuator, and the discharge oil amount per unit time of the hydraulic pump A variable flow rate adjusting mechanism is provided, and this flow rate adjusting mechanism is based on the differential pressure between the oil passage communicating with the lower portion of the pressure oil supply to the throttle valve and the oil passage communicating with the pressure oil supply port of the control valve. And (2) a pressure compensating valve is provided on the lower side of the pressure oil supply to the throttle valve and on the upper side of the pressure oil supply to the actuator. Pressure on valve A second oil passage that is on the lower supply side and that communicates the upper pressure oil supply side portion to the actuator and the spring side oil chamber of the pressure compensation valve, and the opposite spring side that faces the spring side oil chamber of the pressure compensation valve. And a first oil passage that connects the oil chamber and the pressure oil supply upper side of the pressure compensating valve and the pressure oil supply lower side of the throttle valve, respectively.
(3) A point that a valve mechanism that adjusts the pressure applied to the spring-side oil chamber by acting on the two oil passages is provided, is provided.

The valve mechanism is a two-position switching type electromagnetic high-speed response valve that acts on the spring-side oil chamber of the pressure compensating valve, and an intermittent control device capable of intermittently operating the valve and variably setting the intermittent time. It is convenient if it is composed of and.

Further, in the electromagnetic high-speed response valve, a normal position for supplying the load pressure of the actuator to the spring side oil chamber of the pressure compensating valve and a hydraulic pressure higher than the load pressure of the actuator are supplied to the spring side oil chamber of the pressure compensating valve. When the engine speed is high, the duty ratio that governs the intermittent operation of the electromagnetic high-speed response valve becomes large, and when the engine speed is low, the duty ratio becomes small. The rotation detecting means for detecting and the intermittent control device may be linked.

Further, the valve mechanism is constructed so that an intermediate pressure between the load pressure and the discharge pressure of the actuator is expressed from the load pressure of the actuator and the discharge pressure of the hydraulic pump and is applied to the spring side oil chamber of the pressure compensating valve. It is convenient if you do.

[0008]

In the structure of claim 1, the characteristic structure (1), (2) forms a load sensing hydraulic circuit having an after-orifice structure, which is a prerequisite structure, and is a control reference in the load sensing. The set differential pressure, that is, the differential pressure between the load pressure of the actuator and the pump pressure is maintained at the set value. By the way, in the above after-orifice structure, the differential pressure between the set load pressure and pump pressure is distributed to (a) pressure loss at the throttle valve (b) pressure loss at the pressure compensating valve (actually, it is extremely small. However, the pressure loss due to the line resistance in the differential pressure path is also included), and the pressure loss in (a) is obtained by the pressure loss in the set differential pressure- (b). Therefore, by providing the above-mentioned characteristic configuration (3), that is, by providing the valve mechanism capable of adjusting the pressure applied to the spring-side oil chamber of the pressure compensating valve by acting on the second oil passage, the required pressure to the pressure compensating valve can be increased. , It can be raised or lowered compared to the case without a valve mechanism. Then, when the total required flow rate of the actuator is less than the maximum discharge flow rate of the pump, the pressure loss of (a) + the pressure loss of (b) = constant, so the pressure loss of (a) is reduced or increased. As a result, the opening of the control valve is automatically adjusted so that the throttling resistance is revealed.As a result, the amount of oil supplied to the actuator is increased or decreased and the drive speed can be increased or decreased. is there. As a result, for example, in a narrow space, the partial pressure at the pressure compensating valve (the pressure loss ratio of (b) in the differential pressure) is increased to reduce the pressure loss of (a), narrowing the opening of the control valve to reduce the swing speed. It becomes possible to adjust and set the drive speed of the actuator while adopting the load sensing system, such as making the speed slower or changing the drive speed of the boom cylinder according to the change of the engine speed.

According to the second aspect of the invention, the action of changing the partial pressure is realized by the electric control means for intermittently operating the high speed electromagnetic response valve.

According to the third aspect of the present invention, since the opening of the control valve increases / decreases in synchronization with the increase / decrease in the engine speed, the higher the engine speed, the faster the drive speed of the work device and the engine speed. When is decreased, the driving speed of the work device is automatically controlled so as to be decreased.
As a result, when operating a construction machine that performs load-sensing control, lowering the engine speed also decreases the drive speed of the work equipment, so that even operators who are accustomed to operating conventional models can operate it without feeling distracted. Become.

By the way, in order to reduce the driving speed of the actuator, it is sufficient to make the pressure applied to the spring-side oil chamber of the pressure compensating valve higher than the load pressure as described above.
During actual work, the load pressure constantly fluctuates, and it is necessary to apply a constant differential pressure to the spring-side oil chamber according to the fluctuation. In the structure of claim 4, the pump pressure is used so that the differential pressure from the load pressure is maintained constant (when the total flow rate required by the actuator is less than the maximum discharge flow rate of the pump). The pump pressure also fluctuates in synchronism with the load fluctuation, and the pressure adjusting action set by the valve mechanism can be maintained regardless of the load fluctuation.

[0012]

As a result, in the hydraulic circuit according to the first and second aspects, the load sensing system capable of maintaining the drive speed of the working device at a predetermined value is adopted, depending on the type of work or the engine speed. It became possible to change the drive speed of the working device in accordance with the above, and it was possible to provide it as a more convenient and excellent operability. In the hydraulic circuit according to the third aspect of the present invention, the engine speed and the drive speed of the work device can be automatically synchronized with each other in accordance with the driving feeling, which is more convenient and excellent in operability, and the usability can be improved. It became so. Further, in the hydraulic circuit according to the fourth aspect, the load sensing function is used to keep the differential pressure between the load pressure and the pump pressure constant, so that the hydraulic circuit can be changed regardless of load fluctuations without requiring a special circuit or the like. A valve mechanism that can maintain the driving speed can be provided.

[0013]

Embodiments of the present invention will be described below with reference to the drawings in the case of a backhoe which is an example of a construction machine.
A backhoe is shown in FIG. 5, 1 is an excavation work device, 2 is a swivel platform, 3 is a traveling platform, 4 is a crawler traveling device, and the excavation work device 1 includes a boom 5, an arm 6, and a bucket 7. It is configured. In this backhoe, the boom cylinder 5c, the arm cylinder 6c, the bucket cylinder 7
c and a load sensing system is used in a hydraulic circuit for driving an actuator such as a traveling hydraulic motor and a swing cylinder (not shown), and the circuit will be described based on the principle diagram shown below.

FIG. 1 shows a principle circuit diagram in which the circuits relating to the boom cylinder 5c and the arm cylinder 6c are extracted. 8 is a variable displacement hydraulic pump driven by the engine En, and A is the hydraulic pump 8 per unit time. Is a flow rate adjusting mechanism that variably sets the amount of discharged oil of. The flow rate adjusting mechanism A is
The adjusting cylinder 13 for adjusting the discharge amount per unit time by changing the angle of the swash plate of the hydraulic pump 8, and the adjusting cylinder 1.
3 and a pressure-compensating control valve 14 for the pressure sensor 3. 9 is a boom control valve, 10 is an arm control valve, 11
Is a boom compensator (pressure compensating valve), 12 is an arm compensator, and throttle valves 9s, 10s are provided in the supply side oil passages of both control valves 9, 10.

The compensators 11, 12 are arranged on the lower side of the pressure oil supply for the throttle valves 9s, 10s and on the upper side of the pressure oil supply for the actuators 5c, 6c. The lower side of the pressure oil supply to the compensators 11 and 12 and the lower side of the pressure oil supply to the actuators 5c and 6c communicates with the spring side oil chambers 11x and 12x of the compensators 11 and 12, respectively. Oil passage (corresponding to the second oil passage Gt) 11t, 12t,
And the spring-side oil chambers 11x of the compensators 11 and 12,
A high-pressure oil passage that connects the opposite spring-side oil chambers 11y and 12y facing 12x, the pressure oil supply upper side to the compensators 11 and 12, and the pressure oil lower supply side to the throttle valves 9s and 10s. (Corresponding to the first oil passage Gk) 11
k and 12k are provided respectively. This constitutes an after-orifice type load sensing circuit.

There is provided a first low pressure side oil passage 14t which connects the spring side oil chamber 14x of the control valve 14 and the pressure oil supply lower side portion to each throttle valve 9s, 10s. That is, the low pressure side oil passages 11t and 12t of the compensators 11 and 12 and the first low pressure side oil passage 14t are connected via the electromagnetic high-speed response valve 21. Further, the communication oil passage 15 connected to the pressure oil supply ports 9p and 10p of the control valves 9 and 10 (corresponding to the pressure oil supply port P), and the spring side oil chamber 14x of the pressure control valve 14.
To the opposite spring-side oil chamber 14y facing the
It is in communication with.

The electromagnetic high-speed response valve 21 communicates with the low-pressure side oil passages 14t, 11t, 12t at the normal position b, and at the high-pressure position a, the low-pressure side oil passages 11t, 1 of the compensator.
2t and the high-pressure communication passage 15 are connected by the communication passage 21a. Therefore, the operation of the electromagnetic high-speed response valve 21 causes the low pressure side oil passages 11t of the compensators 11 and 12,
The hydraulic pressure acting on 12t can be set to an intermediate value between the load pressure of the actuators 5c and 6c and the discharge pressure of the pump, and the supply pressure to the compensators 11 and 12 is changed by the electromagnetic high-speed response by the differential pressure maintaining action of the compensators 11 and 12. Valve 21
Is higher than in the normal position b. Then, in terms of the function of maintaining a constant differential pressure between the first low pressure side oil passage 14t and the discharge pressure of the hydraulic pump 8, the compensators 11, 1 are provided.
2 is controlled so as to reduce the differential pressure between the throttle valves 9s and 10s on the upper side, that is, to reduce the opening degree of the control valves 9 and 10, and as a result, the amount of oil supplied to the actuators 5c and 6c is reduced. It is reduced and the driving speed becomes slower.
This action is maintained even if the load changes due to the control structure based on the differential pressure between the load pressure and the pump pressure.

A tachometer (corresponding to a rotation detecting means) 17 for detecting the number of revolutions of the engine En, the electromagnetic high-speed response valve 21, a setting device 19 for variably adjusting the duty ratio of the intermittent operation time, and an automatic control. An adjustment control device C for connecting the intermittent mode control device 18 to the mode / manual control mode change switch 20 to change and set the partial pressures of the pressure compensation valves 11 and 12 is configured. The intermittent control device 18 has a high pressure position a.
The intermittent operation of intermittently energizing the electromagnetic high-speed response valve 21 which is urged to return to the normal position b for connecting to the high-pressure oil passage which is the discharge oil passage of the hydraulic pump 8, and the intermittent time are variable. It has the function of performing intermittent control that can be set.
Incidentally, here, the electromagnetic high-speed response valve 21 and the intermittent control device 18
And constitute a valve mechanism B.

The operation of the adjustment control device C will be described. First, when the changeover switch 20 is operated in the automatic control mode,
As a result, the electromagnetic high-speed response valve 21 is energized intermittently, and the energization time ratio in one cycle of the intermittent time, that is, the duty ratio is increased when the engine En is at a high rotational speed, and the engine En is rotated. When the number is low, the tachometer 17 and the intermittent control device 1 are set to a small state.
8 and 8 will be linked. Thus, if the driving speed of the actuator is to be slowed, for example, if the turning speed is to be slowed during excavation work, the engine speed can be lowered, and if the driving speed is to be increased, the engine speed can be increased. good.

Next, when it is desired to intentionally change the drive speed of the actuator, the changeover switch 20 is operated in the manual control mode. Then, the connection with the tachometer 17 is cut off, and the duty ratio becomes a control state determined by the setter 19. By adjusting the setter 19, the supply pressure to the compensators 11 and 12 is changed to that of the actuators 5c and 6c. It can be set to an arbitrary value between the load pressure and the discharge pressure of the pump, and the drive speed of the actuators 5c and 6c can be adjusted independently of the engine speed.

In the claims, the boom cylinder 5c, the arm cylinder 6c and the like are collectively referred to as a hydraulically driven actuator D, the boom control valve 9 and the arm control valve 10 are collectively referred to as control. The valve E, the throttle valves 9s, 10s, etc. in each control valve are collectively referred to as a throttle valve F and each pressure compensation valve 1
1, 12 and the like are collectively referred to as a pressure compensating valve G.

[Other Embodiments] (a) As shown by the phantom lines in FIG. 1, the respective second oil passages 11t, 1
It is convenient if the apertures 22 and 23 are additionally set to 2t so as to prevent the hunting phenomenon due to a sudden load change.

(B) The electromagnetic high-speed response valve 21 in this embodiment
2 may be replaced with a manually operated switching valve 28 as shown in FIG. 2 to configure the valve mechanism B. In this case, a pressure reducing throttle 27 for reducing the pressure in the communication oil passage 21a to an appropriate intermediate pressure between this pressure and the load pressure of the actuator is provided.

(C) As shown in FIG. 3, the switching valve 28 of FIG.
May be configured as the electromagnetic high-speed response valve 29, and intermittent control for varying the duty ratio may be performed as in the present embodiment.

(D) In this embodiment, two control valves 9 and 10 are used.
In the above description, the single valve mechanism B is provided, but the valve mechanism B is arranged for each control valve so that a plurality of valves can be provided for each control valve and individually controlled. You can use what you have done. In other words, it is convenient when the engine speed is not synchronized, or when the engine speed is set to the maximum and the turning speed is reduced. When the engine speed is set to the maximum and the boom is raised and the soil is loaded on the dump truck while turning, the boom quickly rises when the turning angle is 90 degrees and the boom when the turning angle is 180 degrees. It is also convenient for determining matching between the turning operation and the boom raising operation according to the work situation, such as slowly raising.

(E) The setting device 19 in the present embodiment may be either a stepwise switch or a stepless switch.

(F) As shown in FIG. 4, the second electromagnetic high-speed response valve 26 is provided between the communication oil passage 15 and a portion of the second oil passage 11t for the boom between the throttle 22 and the compensator 11. And the throttle 25 are connected in series, and the second electromagnetic high-speed response valve 26 and the setting device 24 dedicated thereto are connected to the intermittent control device 1
The adjustment control mechanism C connected to 8 may be used. In this case,
The first setting device 19 adjusts the partial pressures of both compensators 11 and 12, and the second setting device 24 adjusts the boom cylinder 5c.
It is possible to further change and set only the reference differential pressure with respect to.

(G) If the pressure is larger than the value obtained by subtracting the spring pressure for biasing the compensators 11 and 12 to the closed position from the load pressure of the actuators 5c and 6c, for example, the communication oil passage 21a is drained. It is theoretically possible to increase the driving speed of the actuators 5c and 6c by connecting the passages to the electromagnetic fast response valve 21 so that the supply pressure to the compensators 11 and 12 can be reduced.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 Partial hydraulic circuit diagram showing the principle of load sensing

FIG. 2 is a partial hydraulic circuit diagram showing a first different structure of the valve mechanism.

FIG. 3 is a partial hydraulic circuit diagram showing a second different structure of the valve mechanism.

FIG. 4 is a partial hydraulic circuit diagram showing a third different structure of the valve mechanism.

FIG. 5: Side view of backhoe

[Explanation of symbols]

 8 variable displacement hydraulic pump 14t oil passage 15 oil passage 17 rotation detection means 18 intermittent control device 21 electromagnetic high-speed response valve A hydraulic adjustment mechanism B valve mechanism D supply port E output means F throttle valve G pressure compensation valve Gk first oil passage Gt Second oil passage Gx Spring-side oil chamber Gy Anti-spring-side oil chamber P Supply port En Engine a High pressure position b Normal position

Claims (4)

[Claims] 1. A hydraulic actuator (D), a variable displacement hydraulic pump (8) for supplying pressure oil to the hydraulic actuator (D), and a supply direction of pressure oil discharged from the hydraulic pump (8) is controlled to control the hydraulic pressure. A control valve (E) for supplying the actuator (D),
A throttle valve (F) that is installed in the control valve (E) and acts to throttle the pressure oil supply path to the actuator (D) and the discharge oil amount per unit time of the hydraulic pump (8) are variable. A flow rate adjusting mechanism (A) for setting, and an oil passage (14t) communicating the flow rate adjusting mechanism (A) with a lower side portion of the pressure oil supply to the throttle valve (F), and the control valve (E). The hydraulic oil pump (8) is configured to adjust on the basis of the differential pressure between the hydraulic passage (15) communicating with the hydraulic oil supply port (P), and the lower hydraulic oil supply side to the throttle valve (F). And a pressure compensating valve (G) is provided on the pressure oil supply upper side of the actuator (D), and the pressure oil supply lower side of the pressure compensating valve (G) is arranged, and the actuator (D) For supplying pressure oil to the pressure compensation valve ( The second oil path communicating the spring-side oil chamber and (Gx) of) (G
t) and the spring side oil chamber (G) of the pressure compensation valve (G).
x) the opposite spring-side oil chamber (Gy) communicates with the pressure oil supply upstream side of the pressure compensating valve (G) and the pressure oil supply downstream side of the throttle valve (F). 1 oil passage (Gk) is provided, respectively, and acts on the second oil passage (Gt) to cause the spring side oil chamber (G
x) A hydraulic circuit structure for a construction machine, which is provided with a valve mechanism (B) capable of adjusting the pressure applied to it. 2. A two-position switching type electromagnetic high-speed response valve (2) which operates the valve mechanism (B) on the spring side oil chamber (Gx).
2. The hydraulic circuit structure for a construction machine according to claim 1, wherein the hydraulic circuit structure is configured by 1) and an intermittent control device (18) which is intermittently operated and whose intermittent time can be variably set. 3. The load pressure of the actuator (D) is applied to the electromagnetic high-speed response valve (21) by the spring-side oil chamber (Gx).
To the normal position (b) to supply the oil to the spring side oil chamber (G) and a hydraulic pressure higher than the load pressure of the actuator (D).
x) is provided with a high pressure position (a), and the engine (E
When the rotation speed of n) is high, the duty ratio that controls the intermittent operation of the electromagnetic high-speed response valve (21) is large, and when the rotation speed of the engine (En) is low, the duty ratio is small. Rotation detecting means for detecting the number of rotations (1
The hydraulic circuit structure for a construction machine according to claim 2, wherein 7) and the intermittent control device (18) are linked together. 4. The valve mechanism (B) causes the intermediate pressure between the load pressure and the discharge pressure to be developed from the load pressure of the actuator (D) and the discharge pressure of the hydraulic pump (8) to generate the spring. The hydraulic circuit structure for a construction machine according to any one of claims 1 to 3, wherein the hydraulic circuit structure is configured to be applied to the side oil chamber (Gx).