JP3362258B2 - Pressure oil recovery and reuse system - Google Patents

Description

Description: TECHNICAL FIELD The present invention stores high-pressure oil with energy of return pressure oil from a hydraulic actuator in a construction machine such as a power shovel, and reuses the stored high-pressure oil as operating energy of the actuator. The present invention relates to a pressure oil recovery and reuse system.

BACKGROUND ART As a power shovel, an upper revolving structure is provided on a lower vehicle body equipped with a traveling structure so that it can be freely rotated by a hydraulic motor for revolving. It is known that an arm is attached by an arm cylinder so as to be vertically swingable, and a bucket is attached to the arm by a bucket cylinder so as to be vertically swingable.

The turning hydraulic motor, boom cylinder, arm cylinder, and bucket cylinder of the power shovel described above supply the hydraulic fluid discharged from the hydraulic pump to one chamber by switching the direction switching valve, and the pressure in the other chamber. Oil is running into the tank and is working.

For example, the boom direction switching valve supplies the hydraulic cylinder discharge pressure oil to the expansion chamber of the boom cylinder, and the pressure oil of the compression chamber flows out into the tank to perform expansion operation, and the hydraulic pump is supplied to the compression chamber of the boom cylinder. While supplying the discharge pressure oil of
The pressure oil in the extension chamber flows out into the tank and contracts.

In this way, the swing hydraulic motor, boom cylinder,
Since the return pressure oil from the arm cylinder and the bucket cylinder has flown into the tank, the energy of the return pressure oil cannot be used.

For example, when the boom cylinder is contracted, pressure is generated in the return pressure oil from the extension chamber due to the weight of the boom, arm, and bucket, but the return pressure oil flows out to the tank. Energy) cannot be reused. On the other hand, there has been proposed a device for recovering and reusing the energy of the return pressure oil of the hydraulic actuator.
For example, a pressure oil recovery and reuse system disclosed in Japanese Patent Publication No. 3-33922 is known.

As shown in FIG. 1, this pressure oil recovery / reuse system connects a chamber 2 of a single-acting cylinder 1 which is an actuator to a port 4 of a first pump / motor 3 so that the first pump / motor 3 mechanically connects The port 6 of the connected second pump / motor 5 is connected to a pressure oil supply circuit 7, and this pressure oil supply circuit 7 is connected to a hydraulic pressure source via a check valve 8 and a pressure accumulator 9 is connected. .

In this system, by supplying the pressure oil from the hydraulic pressure source to the pressure oil supply circuit 7, the second pump / motor 5 operates as a motor to drive the first pump / motor 3, and the first pump / motor 3 The pump acts to supply pressure oil to the chamber 2 of the single-acting cylinder 1 to extend the single-acting cylinder 1.

When the pressure oil supply to the pressure oil supply circuit 7 is stopped, the single-acting cylinder 1 is contracted by an external load to generate pressure in the return pressure oil in the chamber 2 to drive the first pump / motor 3 to operate as a motor. As a result, the second pump / motor 5 acts as a pump to generate high-pressure oil in the pressure oil supply circuit 7, and the high-pressure oil is blocked by the check valve 8 and stored in the pressure accumulator 9.

Then, when the pressure oil is supplied to the pressure oil supply circuit 7 again and the single-acting cylinder 1 is extended and operated, the high pressure oil stored in the pressure accumulator 9 drives the second pump / motor 5. The motor 3 acts as a pump to supply high-pressure oil to the chamber 2, and the pressure oil (energy) stored in the pressure accumulator 9 can be reused.

In the system described above, high pressure oil is stored by the energy of the return pressure oil in the chamber 2 of the single acting cylinder 1, and the stored high pressure oil supplies the pressure oil to the chamber 2 of the single acting cylinder 1 again. The high-pressure oil is reused only for the single-acting cylinder 1 and cannot be reused for other actuators.

Therefore, an object of the present invention is to provide a pressure oil recovery / reuse system capable of solving the above problems.

DISCLOSURE OF THE INVENTION A first invention relates to a main hydraulic pump 10 that supplies pressure oil to an actuator, a first circuit 22 to which return pressure oil from the actuator is supplied, and a first pump to which the first circuit 22 is connected. A pressure converter 18 having a motor 16 and a variable displacement type second pump / motor 17 mechanically connected to the first pump / motor 16 and connected to a second circuit 25, and the first circuit 22.
And a third circuit 29 that connects the discharge passage 11 of the main hydraulic pump 10 to each other,
The pressure accumulator 27 provided in the second circuit 25 and the third circuit 29
Of the regenerative valve 30 for switching between the state in which the pressure oil flow is allowed and the state in which the pressure oil flow is blocked, and the pressure accumulation valve 26 for connecting and disconnecting the second circuit 25.
And a second pump from the pressure accumulation valve 26 in the second circuit 25.
The pressure oil recovery and reuse system is characterized by comprising a sequence valve 28 provided between the motor side and the discharge passage 11 of the main hydraulic pump 10, and a sequence valve 28.

According to the first aspect of the present invention, the regeneration valve 30 switches the third circuit 29 to the state in which the flow of pressure oil is blocked, and the return pressure oil causes the first pump / motor 16 to act as a motor and the second pump / motor 17 to be operated. Since the pump acts as a pump, the high pressure oil can be stored in the pressure reservoir 27.

The regeneration valve 30 switches the third circuit 29 to a state where the pressure oil flow is allowed, so that the high pressure oil stored in the second pump / motor
Since 17 acts as a motor and the first pump / motor 16 acts as a pump, pressure oil is discharged to the first circuit 22 and supplied to the discharge passage 11 of the main hydraulic pump 10 via the third circuit 29.

This allows the energy of the return pressure oil of the actuator to be reused for actuation of other actuators.

Further, by increasing or decreasing the capacity of the second pump / motor 17 when the second pump / motor 17 operates, the output torque of the second pump / motor 17, that is, the first pump / motor 16
Since the torque that drives the motor changes, the first pump / motor
The pumping action of 16 can increase or decrease the pressure in the first circuit 22.

As a result, the pressure in the first circuit 22 is reduced to the main hydraulic pump 10
The pressure in the first circuit 22 can be supplied to the discharge passage 11 of the main hydraulic pump 10 and reused by making it equal to or slightly higher than the pressure in the discharge passage 11.

Further, according to the first aspect of the present invention, if the second circuit 25 is shut off by the pressure storage valve 26 in the state where the high pressure oil has been stored in the pressure storage device 27, the high pressure oil stored in the pressure storage device 27 will not leak. It can be prevented.

When the high pressure oil is fully stored in the pressure reservoir 27, the high pressure oil in the second circuit 25 is supplied from the sequence valve 28 to the discharge passage 11 of the main hydraulic pump 10, so that the capacity of the pressure reservoir 27 is reduced. It is possible.

If the pressure accumulation valve 26 is closed when the second pump / motor 17 acts as a pump and accumulates pressure, the high pressure oil discharged from the second pump / motor 17 is directly supplied from the sequence valve 28 to the main hydraulic pump.
It is supplied to ten discharge paths 11.

As a result, the energy of the recovered return pressure oil can be immediately reused.

A second invention is a first hydraulic pump 10 for supplying pressure oil to an actuator, a first circuit 22 for supplying return pressure oil from an actuator, and a first circuit 22 for allowing a pressure oil flow to the first circuit 22. Of the recovery valve 23 for switching between the second state and the second state for blocking and the first pump / motor connected to the first circuit 22.
16 and a variable displacement type second pump motor mechanically connected to the first pump motor 16 and connected to the second circuit 25.
A pressure converter 18 provided with 17, a third circuit 29 communicating the first circuit 22 with the discharge passage 11 of the main hydraulic pump 10, a pressure reservoir 27 provided in the second circuit 25, and the third circuit. A regenerative valve 30 that switches 29 between a first state in which the flow of pressure oil is allowed and a second state in which the flow of pressure oil is blocked, and a pressure accumulation valve that connects and disconnects the second circuit 25.
26, and a variable set pressure sequence valve 28 provided between the second pump / motor 17 side of the pressure storage valve 26 in the second circuit 25 and the discharge passage 11 of the main hydraulic pump 10. This is a pressure oil recovery and reuse system.

According to the second invention, after the high pressure oil is stored in the pressure reservoir 27, the recovery valve 23 is in the second state (closed), the pressure storage valve 26 is in the communicating state, and the regeneration valve 30 is in the first state (open). By setting the set pressure of the sequence valve 28 to a high pressure, the stored high pressure oil is passed from the third circuit 29 to the main hydraulic pump 10 via the pressure converter 18.
Can be supplied to the discharge path 11.

In addition, the recovery valve 23 and the regeneration valve 30 are in the second state (closed), the pressure accumulation valve 26 is in the communication state, and the set pressure of the sequence valve 28 is set to a low pressure, whereby the accumulated high pressure oil is changed to the sequence valve.
It can be supplied to the discharge passage 11 of the main hydraulic pump 10 via 28.

Because of this, the pressure converter 18 can be driven by the high pressure oil stored in the pressure reservoir 27 to supply the low pressure and large flow rate of pressure oil to the discharge passage 11, and the high pressure oil stored in the pressure reservoir 27 can be sequenced. valve
It can be supplied to the discharge passage 11 via 28.

While the actuator is operating, the recovery valve 23 is in the first state (open), the pressure accumulation valve 26 is in the closed state, the regeneration valve 30 is in the second state (closed), and the set pressure of the sequence valve 28 is low. By doing so, the return pressure oil of the first circuit 22 is fed to the pressure converter 1
8. Can be supplied to the discharge passage 11 via the sequence valve 28.

In addition, the recovery valve 23 and the regeneration valve 30 are in the first state (open), the pressure accumulation valve 26 is in the closed state, and the set pressure of the sequence valve 28 is set to a high pressure, so that the return pressure oil of the first circuit 22 is removed. It can be supplied to the discharge passage 11 through the third circuit 29.

Because of this, the return pressure oil from the actuator can be boosted by the pressure converter 18 and supplied to the discharge path without storing the return pressure oil, and the return pressure oil can be supplied to the discharge path via the third circuit 29 without storing the return pressure oil. 11
Can be supplied efficiently.

A third aspect of the present invention is a first means for detecting the discharge pressure P2 of the main hydraulic pump 10, and a storage pressure of a pressure accumulator 27 of the second circuit 25.
A second means for detecting P1 and a third means for switching the recovery valve 23, the pressure storage valve 26 and the regeneration valve 30 based on the pressures detected by the first and second means and changing the set pressure of the sequence valve 28. The third means includes a recovery valve when the pressure difference between the stored pressure P1 and the discharge pressure P2 is equal to or more than a set pressure difference.
23 to the second state (closed), pressure accumulation valve 26 to the communication state, regeneration valve 30
Is set to the first state (open), the set pressure of the sequence valve 28 is set to a high pressure, and when the differential pressure between the stored pressure P1 and the discharge pressure P2 is less than or equal to the set differential pressure, the recovery valve 23 and the regeneration valve 30 are set to the second state. In this state (closed), the pressure accumulation valve 26 is brought into a communication state, and at the same time, the pressure oil recovery and reuse system of the second invention has a function of reducing the set pressure of the sequence valve 28.

According to the third invention, when the pressure difference between the stored pressure P1 and the discharge pressure P2 is equal to or higher than the set differential pressure, the recovery valve 23 is in the second state (closed), the pressure storage valve 26 is in the communicating state, and the regeneration valve 30 is in the second state. In addition to the state 1 (open), the set pressure of the sequence valve 28 becomes high, and the stored high pressure oil is supplied from the third circuit 29 to the discharge passage 11 of the main hydraulic pump 10 via the pressure converter 18.

Further, when the differential pressure between the stored pressure P1 and the discharge pressure P2 is less than or equal to the set differential pressure, the recovery valve 23 and the regeneration valve 30 are in the second state (closed), and the storage valve
26 becomes a communication state, the set pressure of the sequence valve 28 becomes low, and the stored high pressure oil is supplied to the discharge passage 11 of the main hydraulic pump 10 via the sequence valve 28.

Since this is the case, the high pressure oil stored according to the pressure difference between the stored pressure P1 and the discharge pressure P2 can be supplied via the pressure converter 18 or the sequence valve 28. Can be efficiently supplied to the discharge passage 11 for effective use.

A fourth invention is a first means for detecting a discharge pressure P2 of the main hydraulic pump 10, and a return pressure oil pressure P3 of the first circuit 22.
And a recovery valve 23, a pressure accumulation valve 26, and a regeneration valve 30 based on the pressure detected by the first and third means.
And a third means for changing the set pressure of the sequence valve 28. The third means sets the recovery valve 23 to the first state (open) when the pressure P3 is lower than the discharge pressure P2. When the pressure accumulation valve 26 is closed, the regeneration valve 30 is in the second state (closed), the set pressure of the sequence valve 28 is low, and the pressure P3 is higher than the discharge pressure P2, the recovery valve
23 and the regeneration valve 30 in the first state (open), the pressure accumulation valve 26 in the shut-off state, and the function of increasing the set pressure of the sequence valve 28 to a high pressure. System.

According to the fourth invention, when the pressure P3 of the return pressure oil is lower than the discharge pressure P2, the recovery valve 23 is in the first state (open), the pressure accumulation valve 26 is in the closed state, and the regeneration valve 30 is in the second state. As the state becomes closed (closed), the set pressure of the sequence valve 28 becomes low, and the return pressure oil of the first circuit 22 is supplied to the discharge passage 11 via the pressure converter 18 and the sequence valve 28.

When the pressure P3 of the return pressure oil is higher than the discharge pressure P2, the recovery valve 23 and the regeneration valve 30 are in the first state (open) and the pressure accumulation valve 26.
Is shut off and the set pressure of the sequence valve 28 becomes high, so that the return pressure oil of the first circuit 22 is supplied to the discharge passage 11 through the third circuit 29.

Because of this, when the pressure of the return pressure oil is lower than the discharge pressure, the pressure of the return pressure oil from the actuator can be increased by the pressure converter 18 and stored in the discharge passage without storing the pressure of the return pressure oil. Is higher than the discharge pressure, the return pressure oil can be efficiently supplied to the discharge passage 11 through the third circuit 29 without storing the pressure.

Brief Description of the Drawings The present invention will be better understood from the following detailed description and the accompanying drawings, which show embodiments of the invention.

It should be noted that the embodiments shown in the accompanying drawings are not intended to specify the present invention, but are merely for facilitating the description and understanding.

  In the figure,   1 is a conventional hydraulic circuit diagram.

2 is a hydraulic circuit diagram showing a first embodiment of the present invention.

3 is a hydraulic circuit diagram showing a second embodiment of the present invention.

4 is a hydraulic circuit diagram showing a third embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 2, a first directional switching valve 12 and a second directional switching valve 13 are provided in a discharge passage 11 of a main hydraulic pump 10 to provide a first actuator 14 and a second directional switching valve 13. Pressure oil is supplied to the actuator 15.

The first pump / motor 16 and the second pump / motor 17 are mechanically connected to form a pressure converter 18. The first pump / motor 16 is a variable displacement type whose capacity changes by changing the inclination angle of the swash plate 19, and the second pump / motor 17 is a swash plate 20.
The capacity is variable by changing the tilt angle of the variable capacity type.

The main port 21 of the first pump / motor 16 is the first circuit 22.
This first circuit 22 is connected to the return port 12a of the first directional control valve 12 and the return port 13a of the second directional control valve 13 via the recovery valve 23 to connect the first actuator 14 and the second actuator 15 respectively. Return pressure oil is supplied.

The main port 24 of the second pump / motor 17 is the second circuit 25.
Connected to.

The second circuit 25 is connected to a pressure accumulator 27 via a pressure accumulation valve 26, and is also connected to the main hydraulic pump 10 via a sequence valve 28.
Connected to the discharge passage 11 of.

The first circuit 22 is connected to the discharge passage 11 of the main hydraulic pump 10 by a third circuit 29. This third circuit 29 has a regeneration valve 30
Is provided. The regeneration valve 30, the recovery valve 23, and the pressure accumulation valve 26
Is held in the closed position a by the springs 30a, 23a, 26a, and in the open position b when the solenoids 30b, 23b, 26b are energized.

A first pressure sensor 31 is provided in the discharge passage 11 of the main hydraulic pump 10, and a second pressure sensor 32 is provided in the first circuit 22. The pressures detected by the first pressure sensor 31 and the second pressure sensor 32 are input to the controller 33. The controller 33 inputs the displacement control signal to the displacement control member 34 of the second pump / motor 17 when the reuse signal is input to the first pressure sensor 31.
The capacity of the second pump / motor 17 is controlled so that the pressure detected by the second pressure sensor 32 becomes equal to the pressure detected by the second pressure sensor 32.

  Next, the operation of collecting the return pressure oil and storing it will be described.

The solenoid 23b of the recovery valve 23 is energized to the open position b, and the solenoid 26a of the pressure accumulation valve 26 is energized to the open position b.
Then, in this state, when the first direction switching valve 12 is set to the first position c and pressure oil is supplied to one chamber 14a of the first actuator 14 to perform a contraction operation, the return pressure oil in the other chamber 14b returns to the return port 12a. Then flows into the first circuit 22. At this time, the regeneration valve 30 is in the closed position a.

The pressure oil that has flowed into the first circuit 22 flows into the main port 21 of the first pump / motor 16 and the first pump / motor 16 acts as a motor to drive the second pump / motor 17. At this time, the second
By making the capacity of the pump / motor 17 small, high-pressure oil is discharged when driven by the same drive torque.

This operation may be performed by inputting a recovery signal to the controller 33 and outputting a small capacity signal to the capacity control member 34 by the controller 33.

The controller 33 controls the solenoid of the recovery valve 23.
23b and the solenoid 26b of the pressure accumulation valve 26 may be energized.

As a result, the second pump / motor 17 acts as a pump to discharge the high pressure oil to the second circuit 25 and store the high pressure oil in the pressure reservoir 27. At this time, when the high pressure oil is full in the pressure reservoir 27, the second circuit
The pressure of 25 becomes higher than the set pressure of the sequence valve 28,
The high-pressure oil in the second circuit 25 is supplied to the discharge passage 11 of the main hydraulic pump 10.

Since the regenerative valve 30 is in the closed position a during this operation, the return pressure oil that has flowed into the first circuit 22 does not flow into the discharge passage 11 even if it is higher than the pressure in the discharge passage 11, and the pressure in the discharge passage 11 remains the same. The first circuit 22 even if it is higher than the return pressure oil that has flowed into the first circuit 22.
Does not flow into.

When the recovery operation is completed, the pressure accumulation valve 26 is set to the closed position a and the high pressure oil accumulated in the pressure accumulator 27 is held so as not to flow out.

  Next, the operation of reusing the stored high pressure oil will be described.

Stop the energization of the solenoid 23b of the recovery valve 23 and close the position a
And the solenoid 26 of the pressure accumulation valve 26 and the regeneration valve 30.
Energize b and 30b to open position b respectively.

As a result, the high pressure oil accumulated in the pressure accumulator 27 becomes the second circuit.
It flows into the main port 24 of the second pump / motor 17 from 25, and the second pump / motor 17 operates as a motor, and thus drives the first pump / motor 16.

The second pump / motor 16 acts as a pump to discharge high-pressure oil to the first circuit 22, and the high-pressure oil is supplied from the third circuit 29 to the discharge passage 11 of the main hydraulic pump 10. At this time, the capacity of the second pump / motor 17 is controlled so that the pressure in the discharge passage 11 and the pressure in the first circuit 22 become equal (or the pressure in the first circuit 22 is slightly higher).

Specifically, when the pressure of the first circuit 22 is lower than the pressure of the discharge passage 11, a large displacement signal is output to the displacement control member 34 to increase the displacement of the second pump / motor 17, and the second pump / motor 17 The output torque of 17 (driving torque of the first pump / motor 16) is increased so that the first pump / motor 16 can output high-pressure oil. When the pressure in the first circuit 22 is higher than the pressure in the discharge passage 11, the above is reversed.

Since the first pump / motor 16 is a variable displacement type,
As described above, when the pressure of the first circuit 22 is lower than the pressure of the discharge passage 11 even if the capacity of the second pump / motor 17 is increased, a small capacity signal is input from the controller 33 to the capacity control member 35 to input the first small capacity signal. 1 Reduce the capacity of the pump / motor 16 so that high-pressure oil can be discharged.

That is, the first pump / motor 16 is a variable displacement type in order to enlarge the pressure conversion region, and when the pressure conversion region is small, the first pump / motor 16 may be a fixed displacement type.

A backflow prevention valve 36 may be provided in the third circuit 29 in order to reliably prevent the pressure oil in the discharge passage 11 from backflowing from the third circuit 29 to the first circuit 22.

Next, an operation of immediately reusing the energy of the recovered return pressure oil without storing the energy will be described. By setting the recovery valve 23 to the open position b and the regeneration valve 30 and the pressure accumulation valve 26 to the closed position a, the return pressure oil that has flowed into the first circuit 22 is pressurized by the pressure converter 18 as described above. When it is discharged to the second circuit 25 and becomes equal to or higher than the set pressure of the sequence valve 28, it is directly supplied to the discharge passage 11. When the regeneration valve 30 is set to the open position b in this state, the return pressure oil is supplied to the discharge passage 11 by the third circuit 29.

  Next, a second embodiment of the present invention will be described.

As shown in FIG. 3, by providing the second check valve 37 on the output side of the sequence valve 28, the reverse flow from the discharge passage 11 of the main hydraulic pump 10 to the second circuit 25 is reliably prevented. That is, the sequence valve 28 can prevent the backflow from the discharge passage 11 to the second circuit 25, but in order to reliably prevent the backflow even if internal pressure oil leaks or malfunction of the sequence valve 28, the second backflow prevention valve 37 To provide.

By providing a safety valve 38 between the pressure accumulator valve 26 and the pressure accumulator 27, the maximum internal pressure of the pressure accumulator 27 is regulated. That is, when the internal pressure of the pressure accumulator 27 rises due to a peak pressure due to a sudden switching of the pressure accumulation valve 26 during the pressure accumulation or an increase in the ambient temperature of the pressure accumulator 27, the safety valve 38
Regulates the maximum internal pressure so that the internal pressure does not exceed the set pressure of the safety valve 38 due to the relief operation.

  Next, a third embodiment of the present invention will be described.

As shown in FIG. 4, the sequence valve 28 is a variable set pressure type. For example, an electromagnetic variable set pressure type sequence valve 28 that has a set pressure proportional to the amount of electricity supplied to the solenoid 28a is used. A third pressure sensor 39 that detects the pressure of the second circuit 25 is provided, and the detected pressure is input to the controller 33.

  Next, the operation of collecting the return pressure oil and storing it will be described.

The pressure is stored in the pressure accumulator 27 in the same manner as in the first embodiment. At this time, the energization amount of the solenoid 28 of the sequence valve 28 is made large and the set pressure is made high.

Next, the first operation of reusing the stored high pressure oil will be described.

Stop the energization of the solenoid 23b of the recovery valve 23 and close the position a
And the solenoids 26b, 3 of the pressure accumulation valve 26 and the regeneration valve 30.
Energize 0b to open position b. Sequence valve 28
The set pressure of is high.

As a result, the high pressure oil accumulated in the pressure accumulator 27 becomes the second circuit.
It flows into the main port 24 of the second pump / motor 17 from 25, and the second pump / motor 17 operates as a motor, and thus drives the first pump / motor 16. The second pump / motor 16 acts as a pump to discharge high-pressure oil to the first circuit 22, and the high-pressure oil is supplied from the third circuit 29 to the discharge passage 11 of the main hydraulic pump 10.

That is, the pressure converter is the same as in the first embodiment described above.
18 and the third circuit 29 to supply to the discharge passage 11 of the main hydraulic pump 10 for reuse.

Next, the second operation of reusing the stored high pressure oil will be described.

Stop the energization of the solenoid 23b of the recovery valve 23 and close the position a
At the same time, the solenoid 26b of the pressure accumulation valve 26 is energized to the open position b, and the regeneration valve 30 is set to the closed position a. Sequence valve
The set pressure is set to a low pressure by reducing the amount of electricity supplied to the solenoid 28a of 28.

As a result, the high pressure oil accumulated in the pressure accumulator 27 becomes the second circuit.
25 flows into the main port 24 of the second pump / motor 17 and drives the second pump / motor 17 to drive the first pump / motor 16. The main port 21 of the first pump / motor 16
Since the first circuit 22 connected to is closed by the recovery valve 23 and the regeneration valve 30, the pressure oil discharged from the main port 21 of the first pump / motor 16 becomes a dead end, and the set pressure of the sequence valve 28 is set. Is low pressure, the high pressure oil stored in the pressure reservoir 27 is supplied from the sequence valve 28 to the discharge passage 11 of the main hydraulic pump 10.

Next, an operation of automatically selecting the above-mentioned first operation and second operation will be described.

The controller 33 is a pressure accumulator detected by the third pressure sensor 39.
27 internal pressure (hereinafter referred to as stored pressure) P1 and first pressure sensor
The differential pressure ΔP of the discharge pressure P2 (load pressure) of the main hydraulic pump 10 detected by 31 is calculated, and when this differential pressure ΔP is equal to or higher than the set differential pressure ΔP1, it is judged as the first operation, and the differential pressure △ P is the set differential pressure △
When it is P1 or less, it is determined to be the second operation.

The set differential pressure ΔP1 is a pressure at which the horsepower loss due to the pressure converter 18 and the horsepower loss due to the pressure loss of the sequence valve 28 are substantially equal,
For example, it is about 20 kg / cm ² .

When the controller 33 determines that it is the first operation, the recovery valve 23,
The pressure accumulation valve 26 and the regeneration valve 30 are switched as described above, and the set pressure of the sequence valve 28 is made high.

When the controller 33 determines that it is the second operation, the recovery valve 23,
The pressure accumulation valve 26 and the regeneration valve 30 are switched as described above, and the set pressure of the sequence valve 28 is set to a low pressure.

Because of this, the differential pressure between the stored pressure P1 and the discharge pressure P2
When P is equal to or higher than the set pressure difference ΔP1 (when the discharge pressure P2 is low), the first operation is performed, and the stored high pressure oil is discharged from the main hydraulic pump 10 through the pressure converter 18 and the third circuit 29. Supply to road 11.

As a result, a large amount of low pressure oil can be supplied to the discharge passage 11 using the stored high pressure oil. That is, since the discharge pressure P2 is low, the pressure supplied to the discharge passage 11 may be low, so that the swash plate angle of the second pump / motor 17 of the pressure converter 18 is reduced to rotate at high speed, The swash plate angle of 16 is increased to reduce the discharge pressure, the discharge amount is increased, and a large amount of low-pressure hydraulic pressure is supplied to the discharge passage 11.

Further, the pressure difference ΔP between the stored pressure P1 and the discharge pressure P2 is the set pressure difference ΔP.
When P1 or less (when the discharge pressure P2 is high), the stored high pressure oil is supplied to the discharge passage 11 of the main hydraulic pump 10 via the sequence valve 28.

Next, the first operation for immediately reusing the energy of the recovered return pressure oil without storing the energy will be described.

The recovery valve 23 is set to the open position b, and the regeneration valve 30 and the pressure accumulation valve
26 is set to the closed position a and the set pressure of the sequence valve 28 is set to low pressure. As a result, the return pressure oil that has flown into the first circuit 22 is boosted by the pressure converter 18 as described above and discharged to the second circuit 25. When the pressure reaches or exceeds the set pressure of the sequence valve 28, it is directly supplied to the discharge passage 11. To be done.

By doing so, the pressure converter 18 for the return pressure oil can increase the pressure and supply it to the discharge passage 11. Therefore, even if the pressure of the return pressure oil is lower than the discharge pressure, the pressure is not re-stored immediately and the pressure is restored again. Available.

Next, the second operation for immediately reusing the energy of the recovered return pressure oil without storing it will be described.

The recovery valve 23 and the regeneration valve 30 are in the open position b, the pressure accumulation valve 26 is in the closed position a, and the set pressure of the sequence valve 28 is high.

As a result, the return pressure oil that has flowed into the first circuit 22 is discharged to the second circuit 25 as in the first operation.
Since the set pressure of 28 is high, the return pressure oil flowing into the first circuit 22 is supplied from the regeneration valve 30 and the third circuit 29 to the discharge passage 11 of the main pressure oil pump 10.

By doing so, the return pressure oil can be directly supplied without passing through the pressure converter 18, so that the return pressure oil can be efficiently reused when the pressure of the return pressure oil is higher than the discharge pressure.

Next, an operation of automatically selecting the first operation and the second operation of immediately reusing the return pressure oil will be described.

The controller 33 determines the magnitude of the discharge pressure P2 from the first pressure sensor 31 and the return pressure oil pressure P3 from the second pressure sensor 32. When P3 <P2, the first operation is selected, and P3> P2 Sometimes the second operation is selected.

When the first operation is selected, the controller 33 switches the recovery valve 23, the pressure storage valve 26, and the regeneration valve 30 in the same manner as described above, and sets the sequence valve 28 to a low set pressure, and when the second operation is selected, the controller 33 is selected. 33 is a recovery valve 23, a pressure storage valve
26, the regeneration valve 30 is switched in the same manner as described above, and the set pressure of the sequence valve 28 is increased.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-155999 (JP, A) Actual development Sho 63-9359 (JP, U) International publication 96/11796 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) F15B 21/14

Claims (4)

(57) [Claims] 1. A main hydraulic pump 10 for supplying pressure oil to an actuator, a first circuit 22 for supplying return pressure oil from an actuator, and a first pump connected to the first circuit 22.
The motor 16 and the variable pump type second pump mechanically connected to the first pump / motor 16 and connected to the second circuit 25.
A pressure converter 18 provided with a motor 17, a third circuit 29 communicating the first circuit 22 with the discharge passage 11 of the main hydraulic pump 10, a pressure accumulator 27 provided in the second circuit 25, and the third circuit 29. A regeneration valve 30 that switches the circuit 29 between a state in which the flow of pressure oil is allowed and a state in which the flow of pressure oil is blocked, and a pressure accumulation valve 26 that connects and disconnects the second circuit 25.
A sequence valve 28 provided between the pressure pump valve 17 of the second circuit 25 closer to the second pump / motor 17 and the discharge passage 11 of the main hydraulic pump 10; Utilization system. 2. A main hydraulic pump 10 for supplying pressure oil to an actuator, a first circuit 22 to which return pressure oil from the actuator is supplied, and a first circuit 22 for allowing a flow of pressure oil to the first circuit 22. Recovery valve 23 for switching between the second state and the second state for blocking
And a first pump / motor 16 connected to the first circuit 22 and a second pump / motor 16 mechanically connected to the first pump / motor 16.
A pressure converter 18 having a variable displacement second pump / motor 17 connected to a circuit 25, the first circuit 22 and a main hydraulic pump.
A third circuit 29 communicating the 10 discharge paths 11 and the second circuit 25
And a regenerative valve 30 for switching the third circuit 29 between a first state in which the pressure oil flow is allowed and a second state in which the pressure oil flow is blocked, and the second circuit 25 are connected and disconnected. Storage valve 26
And a variable set pressure sequence valve 28 provided between the second pump / motor 17 side of the pressure storage valve 26 in the second circuit 25 and the discharge passage 11 of the main hydraulic pump 10. A pressure oil recovery and reuse system. 3. A first means for detecting a discharge pressure P2 of the main hydraulic pump 10, a second means for detecting a storage pressure P1 of a pressure accumulator 27 of the second circuit 25, and the first and the second means. The recovery valve 23, the pressure accumulation valve 26, and the regeneration valve based on the pressure detected by the second means.
It is provided with a third means for changing the set pressure of the sequence valve 28 while switching 30, and the third means is the stored pressure.
When the pressure difference between P1 and the discharge pressure P2 is equal to or higher than the set pressure difference, the recovery valve 23 is set to the second state, the pressure accumulation valve 26 is set to the communication state, the regeneration valve 30 is set to the first state, and the sequence valve 28 is set. When the pressure is high, and the differential pressure between the stored pressure P1 and the discharge pressure P2 is less than or equal to the set differential pressure, the recovery valve 23 and the regeneration valve 30 are set to the second state, the storage valve 26 is set to the communication state, and the sequence valve 28 is used. 3. The pressure oil recovery / reuse system according to claim 2, wherein the set pressure is set to a low pressure. 4. A first means for detecting a discharge pressure P2 of the main hydraulic pump 10, a second means for detecting a return pressure oil pressure P3 of the first circuit 22, and the first and second means. The recovery valve 23, the pressure storage valve 26, and the regeneration valve 30 are switched based on the pressure detected by the means of (3), and the third means for changing the set pressure of the sequence valve (28) is provided. When the pressure is lower than the discharge pressure P2, the recovery valve 23 is set to the first state, the pressure accumulation valve 26 is set to the closed state, the regeneration valve 30 is set to the second state, and the set pressure of the sequence valve 28 is set to low pressure.
When P3 is higher than the discharge pressure P2, the recovery valve 23 and the regeneration valve 30 are in the first state, the pressure accumulation valve 26 is in the shut-off state, and the set pressure of the sequence valve 28 has a function of raising the pressure. The pressure oil recovery and reuse system according to claim 2, characterized in that.