JP3176700B2 - Regenerative hydraulic circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit of a construction machine such as a hydraulic shovel or the like, and in particular, improves a working efficiency and an energy saving by preventing a sudden decrease in speed of a low-load side actuator during a combined operation. To a regenerative hydraulic circuit that can be used.

[0002]

2. Description of the Related Art Generally, construction machines such as hydraulic excavators are
For example, various actuators such as a bucket, a boom, and an arm are provided, and these actuators are each configured to be driven by hydraulic oil from a hydraulic pump (preferably a variable displacement pump) supplied via a directional control valve. ing. By the way, in such a hydraulic circuit, when performing a combined operation of the actuators, if the sum of the required pressure oil flow rates of the individual actuators exceeds the discharge flow rate of the hydraulic pump, the flow rate distribution to each actuator is not performed well, Oil flows preferentially to the low-load-side actuator, which often makes it impossible to drive the high-load-side actuator. For this reason, the present applicant has previously developed a technique for solving such a drawback and filed a patent application (Japanese Patent Application No. 2-89134).

[0003] The above-mentioned technique (hereinafter referred to as "prior art") will now be described with reference to Fig. 3. This hydraulic circuit is driven by a variable displacement pump 10 having displacement control means 10a and pressure oil of the pump 10. A plurality of (two in the figure) actuators 12, 14, a tank 16,
The pressure oil supply lines 20 and 22 branched from the pump line 18 of the pump 10 and the actuator 1
2, 14 respectively actuator lines 24a, 2
4b, 26a, 26b, the pressure oil of the pump 10 is supplied to the respective actuators 12, 14, and the return oil from the actuators 12, 14 is supplied to the tank 16 via the respective return lines 28, 30. Direction switching valves 34, 36 discharging to the connected tank line 32
It is composed of Further, the respective directional control valves 34, 36
Detecting means (load pressure detecting lines) 38 and 40 for detecting the load pressures of the actuator lines 24 and 26 as unit signal pressures, and the highest pressure among the detected unit signal pressures 38 and 40 as the highest signal. Means for selecting pressure (check valve 42 and maximum pressure detection line 44), directional control valves 34, 36 and tank line 16
And auxiliary valves 46 and 48 for adjusting the degree of opening between the return lines 28 and 30 and the tank line 32, respectively. One end of the auxiliary valves 46 and 48 is connected to the auxiliary valves 4 and 40 by unit signal pressures 38 and 40 and springs 50 and 52, respectively.
6 and 48 are operated in the opening direction, and the other end is configured to operate the maximum signal pressure 44 so as to be controlled in the closing direction.
2, a bypass line 54 is provided.
A flow control valve with pressure compensation 56 and a pressure generating means 58 are provided on the
0, the maximum signal pressure 44 and the spring 62 force act on the pressure-compensated flow control valve 56 in the closing direction, and the pressure-compensated flow control on the opening direction. The upstream pressure of valve 56 is configured to act via signal line 64. The reference numerals 66 and 68 in the figure are pressure oil supply lines 20 and 22 respectively.
Indicates a load check valve provided at
Reference numerals 0 and 72 denote throttles provided in the direction switching valves 34 and 36, respectively.

Next, the operation of the hydraulic circuit having such a configuration will be described. Here, the actuator 12
On the low load side and the actuator 14 on the high load side. First, when the directional control valve 34 is operated to the left to drive the actuator 12 on the low load side, the variable displacement pump 1 is operated.
8 is supplied to the actuator 12 via the pump line 18, the pressure oil supply line 20, the load check valve 66, the throttle 70 of the direction switching valve 34, and the actuator line 24a. At this time, when the directional control valve 34 is fully operated, the pressure loss at the throttle 70 is relatively small, and thus the flow control valve 56 with pressure compensation on the bypass line 54 is provided.
If the force due to the difference between the pressures of the two detection lines 64 and 44 acting on the flow rate control valve 56 is set to be smaller than or substantially equal to the force of the differential pressure setting spring 62, Since it is closed , the entire amount of the pressure oil discharged from the pump 10 flows to the actuator 12. Further, in this state, the forces of the two detection lines 38 and 44 acting on the auxiliary valve 46 are equal, and the auxiliary valve 46 is held at the fully open position by the force of the spring 50, so that the pressure in the return line 28 is low. Therefore, the pressure oil is returned from the tank line 32 to the tank 16 without pressure loss. That is, the low-load actuator 12 is driven at a high speed by the entire discharge flow rate of the pump 10.

When the other directional control valve 36 is operated in the state where the directional control valve 34 is fully operated, the pressure oil flows into the actuator 14 instantaneously because the load of the actuator 14 is higher than that of the actuator 12. not so in the directional control valve 36 of the high pressure side, it is detected transmitted to the detection line 40 without causing any pressure loss in the pressure diaphragm 7 2 of the pressure oil supply line 22. On the other hand, since the pressure oil flows to the actuator 12, the pressure in the pressure oil supply line 20 is reduced at the low load side direction switching valve 34 by the detection pressure of the detection line 3 at the pressure lower by the pressure loss in the throttle 70.
8 is transmitted. Thus, the auxiliary valve 4 on the high load side
8 is maintained fully open by the force of the spring 52 because the same signal pressure acts on the two ends thereof via the detection lines 40 and 44, while the auxiliary valve 46 on the low load side
Since a signal pressure corresponding to the pressure difference between the detection lines 44 and 38 is applied to the end in the closing direction, the member moves in the closing direction by overcoming the relatively weak force of the spring 50. In this case, since the flow control valve 56 with pressure compensation acts on the high-pressure signal pressure in the closing direction via the detection line 44, the pump 10 is in the full discharge state via the signal line 60 and the capacity control means 10a. Has been maintained. As a result, the pressure in the return line 28 of the low-load-side actuator 12 increases, causing a resistance to the flow of the pressure oil to the actuator 12 side, and the pressure in the pressure-oil supply line 20 increases. To drive. That is, the high and low load actuators 12 and 14 are simultaneously driven by the entire discharge flow rate of the pump 10. In this case, the distribution of the pump discharge pressure oil to both actuators 12 and 14 is performed in proportion to the operation amounts of the respective auxiliary valves 46 and 48.

As described above, according to the above-mentioned prior art, a low-load actuator can be driven independently at a high speed, and a plurality of actuators having different load pressures can be simultaneously and reliably driven.

[0007]

However, the above-mentioned prior art still has the following drawbacks, especially during a combined operation.

That is, in the above prior art, in particular, when the actuator on the high load side is fully operated while the actuator on the low load side is fully operated alone, the pump supplied to the low load side actuator As described above, the discharge pressure oil is divided into the two actuators. As a result, the flow rate of the pressure oil to the low-load-side actuator is reduced by half, so that the driving speed is rapidly reduced. Shock with cavitation often occurred.

Accordingly, an object of the present invention is to provide a construction machine such as a hydraulic shovel that, when a low-load-side actuator is operated independently from another high-load-side actuator in a combined operation, a sharp decrease in the speed of the low-load-side actuator is achieved. An object of the present invention is to provide a regenerative hydraulic circuit capable of improving workability and energy saving by preventing and maintaining as high a speed as possible.

[0010]

In order to achieve the above object, a regeneration hydraulic circuit according to the present invention comprises a variable displacement pump having displacement control means and a plurality of actuators driven by pressure oil of the pump. A tank, a pump line of the pump, and a pressure oil of the pump provided between the actuator lines of the plurality of actuators are supplied to the respective actuators, and return oil from the actuators is supplied through the respective return lines. Detecting means for detecting a load pressure of an actuator line of each directional switching valve as a unit signal pressure, comprising: a plurality of directional switching valves discharging to a tank line connected to the tank; Means for selecting the highest pressure among the signal pressures as the highest signal pressure;
An auxiliary valve disposed between each of the directional control valves and the tank line to adjust an opening between each return line and the tank line; and the unit signal pressure and the spring force are provided at one end of the auxiliary valve. With this, the auxiliary valve is operated in the opening direction, the other end is configured to operate to control the maximum signal pressure in the closing direction, and a bypass line is provided from the pump line to the tank line. A pressure control valve with pressure compensation and pressure generating means are provided, and the pressure on the upstream side of the pressure generating means is applied to the capacity control means of the pump. In a hydraulic circuit configured to apply a signal pressure and a spring force and apply a pressure upstream of the pressure compensating flow control valve in the opening direction, a specific one of the plurality of actuators is provided. A return line between the directional switching valve and the auxiliary valve of the heater and a pressure oil supply line from the pump line are connected via a regeneration check valve, and the regeneration check valve transfers the return oil from the return line to the The return to the pressure oil supply line and the flow in the opposite direction are arranged in a blocking direction, and a variable throttle is provided upstream of the connection point of the regeneration check valve on the pressure oil supply line of the specific actuator. By adjusting the opening degree of the variable throttle based on the pressure on the return line, the maximum opening degree of the variable throttle is reduced as the pressure on the return line increases.

In this case, the variable throttle provided on the pressure oil supply line of the specific actuator is formed by a load check valve on the pressure oil supply line, and the load check valve is connected to the direction switching valve of the specific actuator and the auxiliary valve. The stroke is adjusted by the pressure on the return line between the valve and the valve.

[0012]

[Function] When another high-load actuator is combined with a single operation of the low-load actuator, pressure oil does not flow instantaneously to the high-load actuator as described above.
As a result, the pressure in the return line of the low-load-side actuator increases. However, according to the present invention, at this time, the opening of the variable throttle provided on the pressure oil supply line is reduced by the pressure increase of the return line, and at the same time, the variable throttle provided between the return line and the pressure oil supply line is closed. Since the provided regeneration check valve is opened, the return oil in the return line is returned to the low load side actuator via the pressure oil supply line. However, since the actuator has inertia, and particularly the descending arm or the like descends by its own weight, such a low-load-side actuator can continue driving at a relatively high speed without cavitation.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a regeneration hydraulic circuit according to the present invention. For convenience of description, the same components as those of the conventional structure shown in FIG. 3 are denoted by the same reference numerals, and detailed description is omitted.

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a regenerative hydraulic circuit according to the present invention, and its basic configuration is the same as that of the conventional hydraulic circuit shown in FIG. In addition, although it overlaps, it demonstrates again for convenience of understanding. That is, the hydraulic circuit includes the variable displacement pump 10 having the displacement control means 10a.
A plurality of (two in the figure) actuators 12 and 14 driven by the pressure oil of the pump 10, a tank 16 and respective pressure oil supply lines 20 branched from a pump line 18 of the pump 10. 22 and the actuator lines 24 of the actuators 12, 14 respectively.
a, 24b, 26a, 26b
Directional switching valves for supplying pressure oil to the respective actuators 12 and 14 and discharging return oil from the actuators 12 and 14 to a tank line 32 connected to the tank 16 via respective return lines 28 and 30. 34 and 36. Detecting means (load pressure detecting lines) 38, 40 for detecting the load pressures of the actuator lines 24, 26 of the respective directional control valves 34, 36 as respective unit signal pressures; , 40 as the maximum signal pressure (check valve 42 and maximum pressure detection line 44), and each return line 28, disposed between each directional control valve 34, 36 and the tank line 16, 3
Auxiliary valve 4 for adjusting the opening between tank 0 and tank line 32
6 and 48 are provided. At one end of the auxiliary valves 46 and 48, the auxiliary valves 46 and 48 are caused to act in the opening direction by the unit signal pressures 38 and 40 and the springs 50 and 52 forces. It is configured to act to control the maximum signal pressure in the closing direction, and a bypass line 54 is provided from the pump line 18 to the tank line 32. On this bypass line 54, a flow control valve 56 with pressure compensation and pressure generating means 58 And pressure generating means 58
Is applied to the displacement control means 10a of the pump 10 via the signal line 60, and the maximum signal pressure of the detection line 44 and the elasticity of the spring 62 are applied to the pressure compensating flow control valve 56 in the closing direction. And in the opening direction, the upstream pressure of the flow control valve 56 with pressure compensation is applied to the signal line 64.
It is configured to act via The reference numerals 66 and 68 in the figure denote the pressure oil supply lines 20 and 2 respectively.
2 indicates a load check valve provided at 2
Reference numerals 0 and 72 denote throttles provided in the direction switching valves 34 and 36, respectively.

In the present invention, however, the return line 28 between the directional control valve 34 and the auxiliary valve 46 of a specific (low load side) actuator 12 among the plurality (two in the figure) of the actuators 12 and 14 is used. And the pressure oil supply line 20 from the pump line 18 are connected by a bypass line 80 via a regeneration check valve 82. The regeneration check valve 82 transfers the return oil from the return line 28 to the pressure oil supply line 20, the flow in the opposite direction is arranged in a blocking direction, and a variable throttle 84 is provided upstream of the connection point of the regeneration check valve 82 on the pressure oil supply line 20 of the specific actuator 12. This variable aperture 8
By adjusting the opening degree of the variable throttle 84 through the signal line 86 by the pressure on the return line 28, the maximum opening degree of the variable throttle 84 is reduced as the pressure on the return line 28 increases.

The operation of the regenerative hydraulic circuit according to the present invention having such a configuration will now be described. Here, as for the actuator, as in FIG. 3, the actuator 12 is on the low load side, and the actuator 14 is on the high load side.
First, when the directional control valve 34 is operated to the left to drive the actuator 12 on the low load side, the pressure oil discharged from the variable displacement pump 18 is supplied to the pump line 18 and the pressure oil supply line 2.
0, the variable throttle 84, the load check valve 66, the throttle 70 of the direction switching valve 34, and the actuator 12 via the actuator line 24a. At this time, the directional control valve 3
When the valve 4 is fully operated, the pressure loss at the restrictor 70 is relatively small, and therefore, the force caused by the difference between the pressures of the two detection lines 64 and 44 acting on the flow rate control valve 56 with pressure compensation on the bypass line 54 is reduced. smaller than the force of the spring 62 for pressure setting, or this and if you set substantially equal, the pressure compensated flow control valve 56 is fully closed, flows total amount of discharge pressure oil of the pump 10 to the actuator 12 . In this state, both detection lines 38, 4
4 are equal and the auxiliary valve 46 is held in the fully open position by the force of the spring 50, so that the pressure in the return line 28 is maintained at a low pressure, so that the variable restrictor 84 is connected via the signal line 86. Since the regeneration check valve 82 prevents the backflow in the bypass line 80, the pressure oil flows from the tank line 32 to the tank 1 without pressure loss.
Returned to 6. That is, the low load side actuator 12
However, as in the prior art shown in FIG. Even if the opening of the direction switching valve 34 is not fully opened, the same signal pressure always acts on both ends of the auxiliary valve 46 to maintain the fully open state. As a result, the variable throttle 84 is also constantly opened. It is kept fully open.

Next, when the other directional control valve 36 is operated in the state where the directional control valve 34 is fully operated, when the load of the actuator 14 is higher than that of the actuator 12, pressure oil is applied to the actuator 14. It does not instantly flow, in the direction switching valve 36 of the high pressure side, without causing pressure loss in the pressure diaphragm 7 2 of the pressure oil supply line 22, is detected transmitted to the detection line 40 as it is. on the other hand,
Since the pressure oil flows to the actuator 12, the pressure of the pressure oil supply line 20 is detected and transmitted to the detection line 38 at the low load side direction switching valve 34 at a pressure lower by the pressure loss at the throttle 70. You. In this way, since the equal signal pressure acts on the both ends of the auxiliary valve 48 on the high load side via the detection lines 40 and 44, the auxiliary valve 48 is maintained in the fully open state by the force of the spring 52, while the low valve is on the low side. Since the signal pressure corresponding to the pressure difference between the detection lines 44 and 38 is applied to the end of the load-side auxiliary valve 46 in the closing direction, the auxiliary valve 46 moves in the closing direction by overcoming the relatively weak force of the spring 50. I do. In this case, since the high-pressure signal pressure acts on the flow rate control valve with pressure compensation 56 in the closing direction via the detection line 44, the pump 10 is connected to the signal line 60 and the capacity control means 10a.
Is maintained in a full discharge state. As a result, the pressure in the return line 28 of the low-load-side actuator 12 increases, causing a resistance to the flow of the pressure oil to the actuator 12 side, and the pressure in the pressure-oil supply line 20 increases. Since the opening degree of the variable throttle 84 is reduced via the signal line 86 due to the increase in the pressure, the pressure of the pressure oil supply line 20 (pump discharge pressure) further increases, and the high-load-side actuator 14 is driven. That is,
Both high and low load actuators 12, 14 are simultaneously driven by the total discharge flow rate of the pump 10.

However, in the present invention, when assuming a case in which the arm is lowered by the low-load actuator 12 and the turning operation is performed by the high-load actuator 14 during the combined operation, the pressure connected to the bypass line 80 is assumed. Since the pressure in the downstream portion 20a of the oil supply line 20 is lower than the pressure in the return line 28 due to the throttle effect of the variable throttle 84 and the effect of the arm's own weight falling, the regeneration check valve 82 is opened, and the return line 28 is opened. The internal pressure oil flows back to the actuator 12 via the line 20a, the direction switching valve 34, and the actuator line 24a. Therefore, the arm (actuator 12) is driven (falls under its own weight) at a relatively high speed without cavitation. Further, since the discharge pressure oil from the pump 10 hardly flows to the arm side due to the throttle effect of the variable throttle 84, most of the oil flows to the turning side (actuator 14), and thus the turning is driven at a relatively high speed. .

As described above, according to the present invention, by providing a regeneration check valve and a variable throttle at a predetermined position for a specific (low load side) actuator, the operation of the low load side actuator can be changed from a single operation to a high load side. When the actuator is operated in a combined manner, the low-load-side actuator is configured to be driven mainly by the regeneration pressure oil. Can be prevented from abruptly decreasing the speed of the vehicle and the accompanying shock. Therefore, workability and energy saving can be greatly improved.

FIG. 2 shows another embodiment of the regeneration hydraulic circuit according to the present invention. This embodiment is different from the embodiment shown in FIG. 1 in that a variable throttle is not separately formed but is combined with a load check valve originally provided in a hydraulic circuit. That is, the variable throttle / load check valve 90 is configured such that the stroke of the load check valve 66 is adjusted by the piston 92 to which the pressure of the return line 28 acts via the signal line 86. It should be noted that it is clear that the above configuration operates in the same manner as the embodiment shown in FIG.
Detailed description is omitted.

[0021]

As described above, the regeneration hydraulic circuit according to the present invention comprises a variable displacement pump having displacement control means, a plurality of actuators driven by the pressure oil of the pump, A tank, and a pump oil provided between the pump line of the pump and each of the actuators of the plurality of actuators. Detecting means for detecting a load pressure of an actuator line of each of the directional control valves as a unit signal pressure, comprising: a plurality of directional control valves discharging to a tank line connected to the tank; Means for selecting the highest pressure among the above as the highest signal pressure, each of the directional control valves and the tank And an auxiliary valve arranged between the return line and the tank line to adjust the opening between each return line and the tank line. The auxiliary valve is opened at one end of the auxiliary valve by the unit signal pressure and spring force. And the other end is configured to act to control the maximum signal pressure in the closing direction, and a bypass line is provided from the pump line to the tank line, and the flow rate with pressure compensation is provided on the bypass line. A control valve and a pressure generating means are provided, and an upstream pressure of the pressure generating means is applied to a displacement control means of the pump, and the maximum signal pressure and a spring force are applied to the pressure compensating flow control valve in a closing direction. And a hydraulic circuit configured to apply an upstream pressure of the flow control valve with pressure compensation in the opening direction, wherein a specific one of the plurality of actuators A return line between the switching valve and the auxiliary valve and a pressure oil supply line from the pump line are connected via a regeneration check valve, and the regeneration check valve supplies the return oil from the return line to the pressure oil supply line. The return to the line and the flow in the opposite direction are arranged in a blocking direction, and a variable throttle is provided upstream of the connection point of the regeneration check valve on the pressure oil supply line of the specific actuator. By adjusting the opening degree of the throttle by the pressure on the return line, the maximum opening degree of the variable throttle is reduced in accordance with an increase in the pressure on the return line. When the high load side actuator is operated in a combined manner, the low load side actuator can be driven mainly by the regenerated pressure oil, and as a result,
It is possible to prevent a sudden decrease in the speed of the low-load-side actuator during the combined operation, which has been a drawback of a conventional hydraulic circuit of this type, and the occurrence of a shock associated with this. Therefore, workability and energy saving can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing one embodiment of a regeneration hydraulic circuit according to the present invention.

FIG. 2 is a sectional structural view showing another embodiment of the variable throttle applied to the regeneration hydraulic circuit shown in FIG.

FIG. 3 is a circuit diagram showing a configuration of a conventional hydraulic circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Variable displacement pump 10a Capacity control means 12,14 Actuator 16 Tank 18 Pump line 20,22 Pressure oil supply line 24a, 24b, 26a, 26b Actuator line 28,30 Return line 32 Tank line 34,36 Direction switching valve 38,40 Detection line 42 Check valve 44 Detection line 46, 48 Auxiliary valve 50, 52 Spring 54 Bypass line 56 Flow control valve with pressure compensation 58 Pressure generating means 60 Signal line 62 Spring 64 Signal line 66, 68 Load check valve 70, 72 Throttle 80 Bypass line 82 regeneration check valve 84 variable throttle 86 signal line 90 variable throttle and load check valve 92 piston

Claims (2)

(57) [Claims] 1. A variable displacement pump having displacement control means, a plurality of actuators driven by pressure oil of the pump, a tank, a pump line of the pump and an actuator line of each of the plurality of actuators. A plurality of directional control valves which are provided between the pumps to supply pressure oil of the pump to respective actuators and discharge return oil from the actuators to tank lines connected to the tank via respective return lines, Detecting means for detecting the load pressure of the actuator line of each direction switching valve as a unit signal pressure; means for selecting the highest pressure among the detected unit signal pressures as the maximum signal pressure; The opening between each return line and the tank line is located between the valve and the tank line. An auxiliary valve to be adjusted is provided, the auxiliary signal is acted on one end of the auxiliary valve by the unit signal pressure and the spring force in the opening direction, and the maximum signal pressure is controlled on the other end by the closing direction. And a bypass line is provided from the pump line to the tank line, and a flow control valve with pressure compensation and a pressure generation unit are provided on the bypass line, and the upstream pressure of the pressure generation unit is controlled by the pump. Applying the pressure to the capacity control means, the maximum signal pressure and the spring force are applied to the pressure-compensated flow control valve in the closing direction, and the upstream pressure of the pressure-compensated flow control valve is applied to the opening direction. In the hydraulic circuit configured as described above, a return line between a direction switching valve and an auxiliary valve of a specific actuator among the plurality of actuators and a pressure oil supply line from the pump line are provided. The regeneration check valve is arranged in such a way that the return oil from the return line is returned to the pressure oil supply line and the flow in the opposite direction is blocked. Further, a variable throttle is provided upstream of the connection point of the regeneration check valve on the pressure oil supply line of the specific actuator, and the opening degree of the variable throttle is adjusted by the pressure on the return line, whereby the return is achieved. A regeneration hydraulic circuit configured to reduce the maximum opening of the variable throttle as the pressure on the line increases. 2. A variable throttle provided on a pressure oil supply line of a specific actuator comprises a load check valve on the pressure oil supply line. The load check valve is provided between a direction switching valve and an auxiliary valve of the specific actuator. 2. The regenerative hydraulic circuit according to claim 1, wherein the stroke can be adjusted by the pressure on the return line between them.