JP4703418B2 - Control circuit for hydraulic actuator - Google Patents

Description

  The present invention relates to a control circuit that controls hydraulic actuators such as a boom, an arm, and a bucket of a power shovel.

As a circuit for controlling a hydraulic actuator of a construction machine such as a hydraulic excavator, there is a circuit as shown in Patent Document 1. In such a circuit, a control valve is provided between the main hydraulic pump and the actuator, and the supply amount and direction of the pressure oil supplied from the main pump to the actuator are controlled by the switching position of the control valve. .
A pilot passage is provided separately from the supply passage for supplying hydraulic oil from the main pump to the actuator, and the pilot pressure generated in the pilot passage is supplied to the pilot chamber according to the amount of operation of the operation lever provided in the pilot passage. The control valve is switched.
The pilot passage is connected with a pilot pump different from the main pump that supplies the working fluid to the actuator as a pilot pressure source that leads to the pilot chamber of the control valve.
JP 2003-49810 A

In the above circuit, a pilot pump, which is different from the main pump for working fluid for supplying the working fluid to the actuator, is used as a pilot pressure source for switching the control valve.
Since two pumps are used in this way, a drive source for driving the two pumps is required, and energy corresponding to that is required.

  An object of the present invention is to provide a hydraulic actuator control circuit that eliminates the need for a dedicated pump for a pilot pressure source in order to realize energy saving.

  The first invention includes a pump, a supply passage connected to the pump, and a control valve connected to the supply passage and controlling the direction and amount of the working fluid supplied to the actuator, and all the control valves are neutral. When the position is maintained, the fluid discharged from the pump is guided to the tank via each control valve and the neutral passage connecting them, and when any of the control valves is switched to a position other than the neutral position, In the control circuit for a hydraulic actuator configured so that the neutral passage is blocked and the working fluid is supplied to the actuator connected to the switched control valve, the control valves are connected in series, and the pilot primary pressure is connected to each control valve. A pilot primary pressure passage, a high pressure selection circuit for selecting the highest load pressure among the load pressures of the actuators connected to each control valve, and the neutral passage. A connection path connecting the downstream side of the control valve and the high pressure selection circuit, and the pilot primary pressure passage is connected between the connection paths, and when the neutral passage is in communication with each control valve In the state where the neutral passage is generated by generating a pressure in the neutral passage and the pressure is led to the pilot primary pressure passage through the connection passage, and the neutral passage is shut off by switching the control valve, the high pressure selection circuit This is characterized in that it is configured as a pilot pressure source that guides the pressure to the pilot primary pressure passage through the connection path.

The second invention is based on the first invention,
A relief valve provided in the neutral passage downstream of the connection point of the pilot primary pressure passage; a bypass route that bypasses the relief valve and communicates with the tank; and a first open / close valve that opens and closes the bypass route; A second on-off valve provided between the connection path and the high-pressure selection circuit, and the neutral passages of the control valves are in communication with each other and the actuator is in operation after the actuator is prepared for operation. 1 By keeping the on-off valve in the closed position, the bypass is closed and a pressure based on the set pressure of the relief valve is generated in the neutral passage, and the pressure is used as a pilot pressure source, while the neutral passage is switched by switching the control valve. At a predetermined timing until the valve is completely shut off, the high pressure selection circuit and the pilot primary pressure passage are communicated with each other through the connection path by opening the second on-off valve. The pressure of 択回 path has a feature in that a configuration of the pilot pressure source and vacuum through the vacuum valve.

In the first and second inventions, as the pilot pressure source for controlling the control valve for the actuator, the pressure generated by using the flow rate flowing through the neutral passage is used at the neutral time, and the neutral passage is blocked. In this case, since the load pressure of the actuator is used, it is not necessary to provide a dedicated pump as a pilot pressure source.
Therefore, a driving source for the pilot pump is not required, and energy can be saved as compared with the case where two pumps are used as in the prior art.
In particular, since the actuator load pressure can be used as a pilot pressure source, energy can be used effectively.

FIG. 1 is a control circuit for a hydraulic excavator according to an embodiment of the present invention.
As shown in FIG. 1, the control circuit C connects a pump passage 1 to a pump P driven by a motor M, and a traveling motor 2, a bucket cylinder 3, and a boom cylinder 4 are disposed downstream of the pump passage 1. Is provided. The traveling motor 2, the bucket cylinder 3 and the boom cylinder 4 correspond to the hydraulic actuator of the present invention.
Further, the pump passage 1 is branched into a neutral passage 5 and a supply passage 6. In the neutral passage 5 and the supply passage 6, the motor control valve 7 that controls the traveling motor 2, the bucket control valve 8 that controls the bucket cylinder 3, and the boom control that controls the boom cylinder 4. The control valve 9 is connected.
The control valves 7, 8, 9 are connected to the passages 6 a, 6 b, 6 branched from the supply passage 6.

The control valve 7 is connected to the ports 2a and 2b of the motor 2 by passages 12a and 12b, the control valve 8 is connected to the ports 3a and 3b of the bucket cylinder 3 by passages 13a and 13b, and the control valve 9 is The passages 14a and 14b are connected to the ports 4a and 4b of the boom cylinder 4.
Therefore, when each of the control valves 7, 8 and 9 is switched from the neutral position shown in the drawing to the left and right switching positions, the actuator connected to the control valve to be switched is driven and controlled.

Each of the control valves 7, 8, 9 is an electrohydraulic pilot switching spool valve, and the primary pressure generated in the pilot primary pressure passage 10 or 11 is controlled by the electromagnetic valves 7c, 8c, 9c, The controlled pilot pressure is guided to the pilot chambers 7a, 7b, 8a, 8b, 9a, 9b to switch the spool position.
The operation of generating a primary pressure serving as a pilot pressure source in the pilot primary pressure passages 10 and 11 will be described in detail later.
Further, in order to control the control valves 7, 8, and 9, the electromagnetic valves 7c, 8c, and 9c are controlled through an operating means such as an operating lever (not shown).

  For example, when pilot pressure is introduced into one pilot chamber 7a of the control valve 7 and this control valve 7 is switched from the illustrated state to the left switching position, the primary pressure generated in the pilot primary pressure passage 10 is The pilot pressure is controlled by the valve 7c to guide the pilot pressure to the pilot chamber 7a. If this pilot pressure overcomes the pressing force from the other pilot chamber 7b side, it switches to the left switching position. On the contrary, the primary pressure of the pilot primary pressure passage 11 is controlled by the electromagnetic valve 7c and led to the pilot chamber 7b, so that the control valve 7 can be switched to the switching position on the right side of the drawing. In short, each control valve is switched to a position where the spring force acting on both sides of the spool and the pressing force in both directions by the pilot pressure are balanced.

  When the control valve 7 is switched from the neutral position shown in the drawing to the left / right switching position, the discharge fluid of the pump P is an actuator for travel that is an actuator from the branch passage 6a of the supply passage 6 via the control valve 7. Supplied to the motor 2. Then, the return fluid from the motor 2 is returned to the return passage 15 via the control valve 7, and the motor 2 can be driven.

Similarly, the other control valves 8 and 9 can be switched.
When the control valve 8 is switched, the working fluid via the control valve 8 is supplied to the bucket cylinder 3 from the branch path 6 b of the supply passage 6, and the return fluid from the bucket cylinder 3 is supplied to the control valve 8. Is returned to the tank T via the return passage 15.
Further, if the control valve 9 is controlled, the boom cylinder 4 connected thereto can be controlled.

Further, in the neutral passage 5, on the downstream side of the control valves 7, 8, and 9, a bypass 5a is provided from the branch point A, and the first open / close valve 16 of the present invention is provided in the bypass 5a. A relief valve 17 is provided in a neutral passage portion parallel to the bypass 5a. The set pressure of the relief valve 17 is Pr.
Further, all the fluid passages 12a, 12b, 13a, 13b, 14a, 14b connected to the motor 2, the bucket cylinder 3 and the boom cylinder 4 are provided with a high pressure selection circuit 18 for selecting the highest pressure in all the passages. Connected. In this high pressure selection circuit 18, the load pressure is selected from a pair of passages connected to each actuator, and as a result, the maximum load pressure of all the actuators is selected.

A connection path 19 that connects the high-pressure selection circuit 18 and the branch point A of the neutral passage 5 is provided, and the pilot primary pressure paths 10 and 11 are connected to a connection point B in the middle. Further, the second on-off valve 20, the pressure reducing valve 21, and the check valve 22 of the present invention are connected in the order shown in the figure between the connection path 19 and the high pressure selection circuit 18, and the set pressure of the pressure reducing valve 21 is set to Pd. To do.
The first on-off valve 16 and the second on-off valve 20 are each switched by an external signal.

Specifically, before driving the traveling motor 2, when the operator releases the brake, the release signal and when the operation lever is started to switch the other control valves 8 and 9. A control signal for switching the first on-off valve 16 to the open position is output in conjunction with the operation signal.
Further, when it is detected that any one of the control valves 7, 8 and 9 is completely switched to a position other than the neutral position, the second on-off valve 20 is switched to the open position in conjunction with the detection signal. A control signal is output.

  On the other hand, when all the control valves 7, 8, 9 are in the neutral position from the control state, and the control valves 8, 9 are no longer in the operation start state with the brake applied, the first on-off valve A control signal for switching to the open position shown in FIG. 16 is input, and a control signal for switching to the closed position is input to the second on-off valve 20.

In this embodiment, the set value Pr of the relief valve 17 is greater than the set value Pd of the pressure reducing valve 21.
Further, a lock valve 23 is provided in the passage 14a. This lock valve 23 is for preventing fluid from leaking from the port 4a when it is desired to maintain the boom position. The lock valve 23 is a valve that allows only flow from the control valve 9 to the port 4a and restricts backflow. However, when necessary, such as when the boom is contracted, it is opened by an external signal to allow backflow.
In the figure, reference numeral 24 denotes a filter. Reference numeral 25 denotes a main relief valve which prevents the pump passage 1 from becoming a high pressure that exceeds its set pressure.

The operation of this embodiment will be described below.
When it is not necessary to operate any of the actuators, as shown in FIG. 1, each of the control valves 7, 8, 9 is maintained at the neutral position shown in the figure, the first on-off valve 16 is opened, The on-off valve 20 is kept in the closed position. Thus, when all the control valves 7, 8, 9 are in the neutral position, the standby flow rate discharged by the pump P is recirculated from the neutral passage 5 to the tank T via the first on-off valve 16. In this state, the pressure in the neutral passage 5 is substantially the tank pressure.

When it is necessary to switch any one of the control valves 7, 8, 9 from this state, that is, when one or more of the motor 2, the bucket cylinder 3 and the boom cylinder 4 are to be controlled, the control valve 7, A pilot pressure for switching between 8 and 9 is required.
For example, when switching the control valve 7 to drive the traveling motor 2, the operator releases the brake, and the first on-off valve 16 closes from the state shown in the figure in conjunction with the brake release signal. Switch to position. As a result, the connection between the neutral passage 5 and the tank T is interrupted at one end.

When the neutral passage 5 is disconnected from the tank T, the pressure in the neutral passage 5 increases. When the pressure exceeds the set pressure Pr of the relief valve 17, the relief valve 17 is opened to keep the neutral passage 5 at the set pressure Pr.
On the other hand, the pressure in the neutral passage 5 acts on the pilot primary pressure passages 10 and 11 through the connection passage 19. Therefore, the pressure controlled by the relief valve 17 can be used as a pilot primary pressure, that is, a pilot pressure source. Then, the control valves 7, 8, and 9 can be switched by keeping the first on-off valve 16 in the closed position and using the pressure in the neutral passage 5 as a pilot pressure source.

As described above, when the control valve 7, 8, 9 is switched using the pressure in the neutral passage 5 as a pilot pressure source and any one of the control valves is completely switched to a position other than the neutral position, the neutral passage 5 Is blocked by the switched control valve.
When any one of the control valves is completely switched, this is detected by a sensor (not shown). As described above, the second valve provided between the high pressure selection circuit 18 and the connection path 19 in conjunction with this detection signal. The on-off valve 20 is switched from the illustrated closed position to the open position.

As described above, when the second on-off valve 20 is switched to the open position, at least one of the control valves 7, 8, and 9 is switched to a position other than the neutral position before that. That is, any one of the traveling motor 2, the bucket cylinder 3, and the boom cylinder 4 is controlled, and a load pressure should be generated.
Therefore, the high pressure selection circuit 18 selects the highest load pressure from the passages 12a, 12b, 13a, 13b, 14a, 14b connected to the motor 2, the bucket cylinder 3, and the boom cylinder 4, which are the actuators. The load pressure acts on the connection path 19 via the second on-off valve 20.

In the connection path 19, the load pressure is lowered to the set pressure Pd by the pressure reducing valve 21, and this set pressure Pd functions as a pilot pressure source for the pilot primary pressure passages 10 and 11 connected to the connection point B.
In this embodiment, since the relationship between the set pressures Pr and Pd of the relief valve 17 and the pressure reducing valve 21 is Pr> Pd, the relief valve 17 is opened when the second on-off valve 20 is switched to the open position. Thus, the fluid is not returned to the tank T. That is, there is no concern that the fluid on the actuator side will flow to the tank T via the high pressure selection circuit 18, the connection path 19 and the relief valve 17.

  However, if a check valve that allows only the flow from the branch point A to the connection point B is provided between the connection point B and the branch point A in the connection path 19, the relief valve 17 and the pressure reducing valve 21 are provided. The relationship between the set pressures does not allow fluid to flow from the actuator to the tank T via the relief valve 17, even if not as described above.

As described above, in the circuit of this embodiment, in the standby state, the pressure generated using the fluid passing through the neutral passage 5 is used as the pilot pressure source, and when the flow of the neutral passage 5 is interrupted, The load pressure is used as a pilot pressure source.
Therefore, unlike the conventional circuit, there is no need to provide a pilot pressure source for controlling the control valve separately from the fluid supply source. Moreover, since the load pressure can be effectively used as a pilot pressure source, energy saving can be realized.

  In the above embodiment, the timing for switching the pilot pressure source from the pressure of the neutral passage 5 to the load pressure is set when the neutral passage 5 is blocked by the control valve, but the switching timing is not limited to this. When the neutral passage 5 is completely shut off, the load pressure must be switched so that the load pressure can be used. For example, even if the neutral passage 5 is not completely shut off, the actuator is being controlled and As long as the pressure is higher than the pressure required for the pilot pressure, it may be switched at any timing.

In FIG. 1, if the electromagnetic relief valve 26 shown in FIG. 2 is used instead of the relief valve 17 provided in the neutral passage 5 and the bypass 5a and the first on-off valve 16, the bypass 5a is There is no need to provide it.
The electromagnetic relief valve 26 is a valve that can adjust the relief set pressure by an electromagnetic solenoid. When the neutral pressure is set to almost zero, the electromagnetic relief valve 26 is opened at a low pressure, and the operation is the same as when the first on-off valve 16 in FIG. 1 is in the open position.
In a situation where a pilot pressure source is required, if the set pressure is set to Pr by the electromagnetic solenoid, the pressure Pr can be generated as a pilot pressure source in the neutral passage 5.
Therefore, it can function in the same manner as the circuit shown in FIG.

1 is a circuit diagram showing an embodiment of the present invention. It is the example of a change of FIG.

Explanation of symbols

P Pump T Tank 1 Pump passage 2 Motor 3 Bucket cylinder 4 Boom cylinder 5 Neutral passage 5a Detour 6 Supply passage 7 Control valve 7a, 7b Pilot chamber 8 Control valve 8a, 8b Pilot chamber 9 Control valve 9a, 9b Pilot chamber 10, 11 Pilot Primary Pressure Passage 15 Return Passage 16 First Open / Close Valve 17 Relief Valve 18 High Pressure Selection Circuit 19 Connection 20 Second Open / Close Valve 21 Pressure Reducing Valve 26 Electromagnetic Relief Valve

Claims (2)

  A pump, a supply passage connected to the pump, and a control valve connected to the supply passage and controlling the direction and amount of the working fluid supplied to the actuator, when all the control valves are kept in the neutral position The discharge fluid from the pump is guided to the tank via each control valve and the neutral passage connecting them, and when any control valve is switched to a position other than the neutral position, the neutral passage is blocked. In addition, in the hydraulic actuator control circuit configured to supply the working fluid to the actuator connected to the switched control valve, the pilot primary for connecting each control valve in series and leading the pilot primary pressure to each control valve A pressure passage, a high pressure selection circuit for selecting the highest load pressure among the load pressures of the actuators connected to each control valve, and the neutral passage below the control valve. And a connection path that connects the high-pressure selection circuit, and the pilot primary pressure passage is connected to the middle of the connection path. When the neutral passage is in communication with each control valve, a pressure is applied to the neutral passage. In the state where the neutral passage is blocked by switching the control valve, the pressure of the high pressure selection circuit is connected to the connection. A control circuit for a hydraulic actuator configured as a pilot pressure source that leads to a pilot primary pressure passage through a passage.   A relief valve provided in the neutral passage downstream of the connection point of the pilot primary pressure passage; a bypass route that bypasses the relief valve and communicates with the tank; and a first open / close valve that opens and closes the bypass route; A second on-off valve provided between the connection path and the high-pressure selection circuit, and the neutral passages of the control valves are in communication with each other and the actuator is in operation after the actuator is prepared for operation. 1 By keeping the on-off valve in the closed position, the bypass is closed and a pressure based on the set pressure of the relief valve is generated in the neutral passage, and the pressure is used as a pilot pressure source. At a predetermined timing until the valve is completely shut off, the high pressure selection circuit and the pilot primary pressure passage are communicated with each other through the connection path by opening the second on-off valve. The pressure of 択回 path, a hydraulic actuator control circuit according to claim 1 which is a structure in which a pilot pressure source and vacuum through the vacuum valve.

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