JPH06173902A - Oil pressure regenerating circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] In a hydraulic circuit for load sensing control using a variable pump P and a pressure compensating valve PV ₁ , a cylinder C
When it becomes negative pressure, prevent its escape. Then, when a positive load is applied to the cylinder C, the return oil is smoothly returned to the tank T to minimize energy loss. [Structure] A flow dividing valve FV is provided between the first actuator port 5 of the switching valve DV and the bottom side chamber 8 of the cylinder C. The flow dividing valve FV is switched to the free flow position which is the right side position in the drawing only when the pilot pressure acts on the pilot chamber 18. In the normal state, the branch position shown in the figure is maintained and the branch passage 23 is connected to the second pressure compensation valve PV.
Connect to the inflow side of ₂ . The second pressure compensation valve is in communication with the first inflow port 1 side of the switching valve DV via the check valve 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic regeneration circuit having a cylinder having a bottom side chamber and a rod side chamber and also having a load sensing function.

[0002]

2. Description of the Related Art As a hydraulic circuit having a load sensing function, the one shown in FIG. 2 has been conventionally known, and its configuration is as follows. The switching valve DV connected to the variable pump P has a first inflow port 1, a relay port 2, a second inflow port 3 and a tank port 4 formed on one side thereof. Further, the first actuator port 5, the second actuator port 6 and the load detection port 7 are not formed on the other side.

The first actuator port 5 is communicated with the bottom chamber 8 of the cylinder C, and the second actuator port 6 is communicated with the rod chamber 9. The load detection port 7 is connected to a regulator 10 that controls the tilt angle of the variable pump P. The first inflow port 1 is in communication with the variable pump P, and the relay port 2 is in communication with the inflow side of the pressure compensation valve PV. Further, the second inflow port 3 is communicated with the outflow side of the pressure compensation valve PV. When the switching valve PV as described above is in the illustrated neutral position, only the tank port 4 and the load detection port 7 communicate with each other, and the other ports are closed.

When the switching valve PV is switched to the left or right, the first inflow port 1 and the relay port 2 communicate with each other.
The variable diaphragm 11 is formed in the passage process. The variable throttle 11 increases its opening in proportion to the switching amount of the switching valve PV. Also,
At this switching position, one of the actuator ports communicates with the second inflow port 3 and the other actuator port communicates with the tank port 4. When the switching valve PV is in the switching position, the load detection port 7 is always connected to the second inflow port 3.

Next, the operation of this conventional example will be described. Now, when the switching valve PV is switched from the illustrated state to the right position,
The first inflow port 1 and the relay port 2 communicate with each other, and the opening of the variable throttle 11 is determined according to the switching amount. Further, when the switching valve PV is switched to the right side position as described above, the second inflow port 3 changes to the first actuator port 5
Through the bottom side chamber 8 of the cylinder C, and the tank port 4 communicates with the rod side chamber 9 through the second actuator port 6. Therefore, the high pressure oil of the variable pump P is the first inflow port 1 → the variable throttle 11 → the relay port 2 →
It is supplied to the bottom side chamber 8 via the pressure compensation valve PV → the second inflow port 3 → the first actuator port 5. Also,
Return oil from the rod side chamber 9 is returned to the tank T via the second actuator port 6 and the tank port 4.

As a result, the piston 12 of the cylinder C rises to extend the rod 13 and the load W is rotated clockwise in the drawing. The load pressure at this time acts on the regulator 10 from the load detection port 7. The regulator 10 controls the tilting angle of the variable pump P so that the pump discharge pressure is lower than the load pressure of the cylinder C. Also make it a little higher. The pressure compensating valve PV has one pilot chamber 14 communicated with the relay port 2 and the other pilot chamber 15 communicated with the load detection port 7. Moreover, the spring 16 is provided on the other pilot chamber 15 side.
The spring force of is also acting.

The pressure compensating valve PV calculates the differential pressure between the pressure on the upstream side of the pressure compensating valve and the pressure on the downstream side thereof.
The pressure corresponding to the spring force of the spring 16 is maintained. Therefore, since the pump discharge pressure is controlled to be higher than the load pressure by a constant value by the action of the regulator 10, the differential pressure before and after that is also kept constant by the action of the pressure compensating valve PV. Eventually, the differential pressure before and after the variable throttle 11 is kept constant regardless of the change in the load pressure.
In this way, the variable throttle 11 is irrespective of the fluctuation of the load pressure.
Since the differential pressure between the front and the rear is kept constant, the flow rate supplied to the cylinder C is determined according to the opening degree of the variable throttle 11, that is, the switching amount of the switching valve DV.

When the switching valve DV is switched from the neutral position in the drawing to the left position, the second inflow port 3 and the second actuator port 6 communicate with each other, and the tank port 4 and the first actuator port 5 communicate with each other. . Therefore, the high-pressure oil of the variable pump P is the first inflow port 1 → the variable throttle 11 →
Relay port 2-> pressure compensation valve PV-> 2nd inflow port 3-> 2nd
It is supplied to the rod side chamber 9 via the actuator port 6. Further, the return oil from the bottom side chamber 8 is returned to the tank T via the first actuator port 5 and the tank port 4.

As a result, the piston 12 of the cylinder C descends and the rod 13 contracts, so that the load W rotates counterclockwise in the drawing. When the rod 13 of the cylinder C contracts in this manner, the load direction and the moving direction of the piston 12 coincide with each other, so that the rod side chamber 9, which is the supply side, may have a negative pressure and the cylinder C may escape. There is. Therefore, in this conventional hydraulic circuit, when the switching valve DV is switched to the left side position, the throttle 16 is formed in the passage process that connects the first actuator port 5 and the tank port 4, and by the action of the throttle 16, The cylinder C is prevented from running away.

[0010]

In the conventional apparatus as described above, the throttle 16 is formed in order to prevent the escape of the cylinder when the rod 13 contracts as described above. However, even when the rod 13 contracts, there are times when a positive load acts on the cylinder C. If a positive load acts on the cylinder C when the rod 13 contracts in this way, there is a problem that the throttle 16 provided for preventing escape rather causes energy loss. It is an object of the present invention to provide a hydraulic regeneration circuit that prevents escape even when negative pressure acts on a cylinder and that does not cause energy loss when a positive load acts.

[0011]

According to the present invention, a cylinder having a bottom side chamber and a rod side chamber, a supply direction of pressure oil to the cylinder is controlled, and an opening of a variable throttle is adjusted according to a switching amount. A switching valve to be controlled, a variable pump located upstream of this switching valve that detects the load pressure on the cylinder and discharges a pressure higher than that, and a variable pump downstream of the variable throttle of the switching valve. And a pressure compensating valve that controls the load pressure and the pressure on the downstream side of the variable throttle so as to maintain a constant differential pressure. While assuming the above hydraulic circuit, the present invention is
The diversion valve is provided in a passage connecting the switching valve to the bottom side of the cylinder, and a second pressure compensation valve provided in a passage process for communicating the diversion valve with the upstream side of the switching valve. The valve detects the pressure in the rod side chamber, maintains the branch position when the pressure is negative, and maintains the free flow position when the load is positive.At this branch position, the return position is connected to the return side via the throttle. The second pressure compensating valve is provided with a passage and a branch passage connected to the second pressure compensating valve, and the second pressure compensating valve has a function of maintaining a constant differential pressure between the load pressure and the upstream side of the switching valve. Have.

[0012]

Since the present invention is configured as described above, when a negative pressure is applied when the cylinder is contracted, the shunt valve maintains the branch position, and most of the return oil from the cylinder is supplied to the second pressure compensating valve. Side, and the excess oil is returned to the tank through the throttle. This second pressure compensating valve has a function of keeping the differential pressure between the load pressure and the upstream side of the switching valve constant, so that the return oil from the bottom side chamber maintains a high pressure higher than the load pressure by a constant value. However, it will be regenerated by the switching valve. At this time, since the rod side chamber has a negative pressure, the discharge pressure of the variable pump controlled by this load pressure maintains the minimum.
Further, when the rod-side chamber becomes a positive load, the flow dividing valve is switched to the free flow position, so that the return oil from the bottom-side chamber at that time is smoothly returned to the tank.

[0013]

According to the hydraulic regeneration circuit of the present invention, when the rod side chamber has a negative pressure, the return pressure from the bottom side chamber is maintained at a constant pressure while maintaining the discharge pressure of the variable pump at a minimum. It can be regenerated while being operated and the cylinder's contraction energy can be fully utilized to operate the cylinder, thus improving energy efficiency. Further, since the surplus oil is returned to the tank via the throttle, it is possible to reliably prevent the cylinder from running away. Furthermore, if a positive load is applied to the rod side chamber, the shunt valve switches to the free flow position, so there is no problem of energy loss as in the conventional case.

[0014]

[Embodiment] In the embodiment shown in FIG. 1, the flow dividing valve FV is provided between the bottom side chamber 8 of the cylinder C and the first actuator port 5.
Is provided. This flow dividing valve FV has a spring 17 acting on one side thereof and a pilot chamber 1 formed on the other side thereof.
The pressure of the rod side chamber 9 is applied to the rod 8. In this embodiment, pilot chambers 19 and 20 are provided on the left and right of the switching valve DV, and pilot pressure is applied to the pilot chambers 19 and 20 to switch the switching valve DV. One of the pilot chambers 20 is connected to the pilot chamber 18 of the flow dividing valve.

The shunt valve FV is provided in the pilot chamber 1
Unless a pressure acts on 8, the action of the spring 17 maintains the normal branching position shown. In this branch position, the first actuator port 5 passes through the diaphragm 21.
And a branch passage 23 connected to the _second pressure compensating valve PV ₂ described below. Shunt valve
When pressure acts on the pilot chamber 18 of the FV, this flow dividing valve switches to the free flow position on the right side of the drawing. In this free flow position, the branch passage 23 is closed and
The free flow state without resistance by the throttle 21 is maintained.

The second pressure compensation valve PV ₂ has its inflow side connected to the branch passage 23 and its outflow side connected to the first inflow port 1 side of the switching valve DV via the check valve 24. There is. Then, the pressure on the side of the first inflow port 1 is introduced into one pilot chamber 25 of this second pressure compensation valve PV ₂ , and the pressure on the side of the load detection port 7 is introduced into the other pilot chamber 26. ing. Moreover, the spring force of the spring 27 acts on the other pilot chamber 26. Therefore, in the second pressure compensation valve PV ₂ , when the flow dividing valve FV is in the branch position, the load pressure of the second pressure compensating valve PV ₂ and the pressure of the hydraulic oil regenerated in the first inflow port 1 are the spring force of the spring 27. Is controlled so as to maintain the differential pressure component corresponding to. Since the configuration other than the above is the same as that of the conventional circuit shown in FIG. 2, its details will be omitted, and the same components as those of the conventional one will be described with the same reference numerals.

Next, the operation of this embodiment will be described. Now, when one pilot chamber 19 is set to the tank pressure and the pilot pressure is applied to the other pilot chamber 20, the switching valve DV is switched to the right side position in the drawing. When the switching valve DV is switched in this way, the pilot pressure that acts on the other pilot chamber 20 also acts on the pilot chamber 18 of the diversion valve FV, so this diversion valve FV also resists the spring force of the spring 17. Switch to the free flow position. Therefore, the variable pump P
High pressure oil from the first inflow port 1 → variable throttle 11 → relay port 2 → first pressure compensation valve PV ₁ → second inflow port 3
→ First actuator port 5 → Supply to the bottom side chamber 8 via the free flow position of the flow dividing valve FV. Further, the return oil in the rod side chamber 9 is returned to the tank T via the second actuator port 6 and the tank port 4.

In the above state, the discharge pressure of the variable pump P is
The pressure is maintained at a constant value higher than the load pressure of the cylinder C, and the first pressure compensating valve PV ₁ functions to maintain the pressure on the downstream side of the variable throttle 11 constant. In addition, a constant flow rate according to the switching amount of the switching valve DV is supplied to the cylinder C regardless of the load change of the cylinder C. In the above state, the discharge oil of the variable pump P is
1st inflow port 1-> variable throttle 11-> relay port 2-> 1st
Is supplied to the rod side chamber 9 via the pressure compensating valve PV ₁ → second inflow port 3 → second actuator port 6. When the pilot pressure is applied to one pilot chamber 19 of the switching valve DV and the other pilot chamber 20 is set to the tank pressure, the switching valve DV switches to the left side position in the drawing.

At this time, when a positive load is applied to the cylinder C, the load pressure acts on the pilot pressure of the flow dividing valve FV to switch the flow dividing valve FV to the free flow position. Therefore, the return oil in the bottom side chamber 8 of the cylinder C is smoothly returned to the tank T. When a counter load acts on the cylinder C from this state and the rod side chamber 9 becomes negative pressure, the pressure in the pilot chamber 18 of the flow dividing valve FV also becomes tank pressure. This is because the other pilot chamber 20 of the switching valve DV communicating with the pilot chamber 18 is maintained at the tank pressure. Therefore, the flow dividing valve FV is kept in the illustrated branch position by the action of the spring 17. When the return oil flows out from the bottom side chamber 8 with the branch valve FV kept in the branch position as described above, most of the return oil flows into the _second pressure compensation valve PV ₂ via the branch passage 23. Other excess flow rates are returned to the tank T via the throttle 21.

The second pressure compensating valve PV ₂ is a load pressure and switching valve.
Since it has a function of keeping the differential pressure with the upstream side of DV constant, the return oil from the bottom side chamber 8 is regenerated to the first inflow port 1 of the switching valve DV while maintaining a high pressure higher than the load pressure by a constant value. Will be done. At this time, since the rod side chamber 9 has a negative pressure, the variable pump P controlled by this load pressure is used.
The discharge pressure of keeps the lowest and keeps energy loss to the minimum. Further, in this state, if the rod side chamber 9 becomes a positive load, the pressure acts on the pilot chamber 18 of the flow dividing valve FV and switches it to the free flow position, so that the return oil of the bottom side chamber 8 smoothly flows to the tank T. Returned to. In other words, in this state, there is no problem with energy loss as in the past.

[Brief description of drawings]

FIG. 1 is a hydraulic regeneration circuit diagram showing an embodiment of the present invention.

FIG. 2 is a conventional hydraulic circuit diagram.

[Code]

P Variable pump DV Switching valve C Cylinder 8 Bottom chamber 9 Rod side chamber PV ₁ 1st pressure compensating valve PV ₂ 2nd pressure compensating valve FV Flow dividing valve 11 Variable throttle 21 Throttle 22 Return passage 23 Branch passage

Claims (1)

[Claims] 1. A cylinder provided with a bottom side chamber and a rod side chamber, a switching valve for controlling the supply direction of pressure oil to the cylinder, and for controlling the opening of a variable throttle according to the switching amount, and this switching valve. A variable pump located upstream of the valve that detects the load pressure on the cylinder and discharges a pressure higher than that, and a load downstream of the variable throttle of the switching valve, With the pressure on the downstream side of the variable throttle,
In a hydraulic circuit provided with a pressure compensating valve for controlling to maintain a constant differential pressure, a diversion valve provided in a passage connecting the switching valve and the bottom side of the cylinder, and an upstream side of the diversion valve and the switching valve. And a second pressure compensating valve provided in a passage process that communicates with the above. The flow dividing valve detects the pressure of the rod side chamber, maintains the branch position when the pressure is negative pressure, and freely when the positive load is applied. The flow position is maintained, and at this branch position, a return passage connected to the return side via a throttle and a branch passage connected to the second pressure compensation valve are provided. A hydraulic regeneration circuit having a function of maintaining a constant differential pressure between the switching valve and the upstream side of the switching valve.