WO2024111381A1 - Hydraulic pressure circuit - Google Patents

Abstract

Provided is a hydraulic pressure circuit capable of supplying a fluid to a regeneration system with good responsiveness.　A hydraulic pressure circuit 110 comprises a pressure supply source 2, an actuator device 4 that is actuated by means of a fluid from the pressure supply source 2, a direction switching valve 3 provided in a main flow passage 23 to 29 between the pressure supply source 2 and the actuator device 4, a regeneration system R connected to the main flow passage 25, 26 via a branch flow passage 6, 41, and a control valve 61 for controlling a flow rate from the main flow passage 25, 26 to the branch flow passage 41, wherein: a throttle 60-6 that throttles the fluid from the main flow passage 25, 26 is disposed in the branch flow passage 110; and the control valve 61 accepts a hydraulic pressure P1 of the main flow passage 63 and a hydraulic pressure P2 of the branch flow passage 64 obtained by means of the throttle 60-6, and is controlled by means of a differential pressure ΔP therebetween.

Description

Fluid Pressure Circuit

The present invention relates to a fluid pressure circuit, for example a fluid pressure circuit that controls a fluid actuator in response to an operation command.

Fluid pressure circuits that control fluid actuators in response to operation commands are used in automobiles, construction machinery, loading and unloading vehicles, industrial machinery, etc. For example, the fluid pressure circuit in a hydraulic excavator rotates a hydraulic motor by supplying pressurized fluid from a hydraulic pump.

For example, a fluid pressure circuit such as that in Patent Document 1 rotates an upper structure using a swing motor, which is a hydraulic motor, and is mainly composed of a pump, a swing motor, a control valve, an adjustment valve, and an accumulator. The swing motor is rotated by oil discharged from the pump. The control valve is provided between the pump and the swing motor. The control valve can switch the direction in which the oil discharged from the pump passes through the swing motor. Depending on this flow direction, the rotation direction of the swing motor is switched.

The control valve can also be switched to a neutral position in which no oil is supplied to either the first or second port of the swing motor. For example, when the control valve is switched to the neutral position while the swing motor is being driven, the oil pressure in the motor pipe fluidly connecting the downstream side of the swing motor to the control valve increases. This allows the rotation of the swing motor to be stopped.

An accumulator pipe is branched off and connected to the motor pipe. A control valve and an accumulator are fluidly connected to the accumulator pipe. The control valve is a proportional flow control valve. When the control valve is switched to the neutral position, the opening of the control valve is adjusted, allowing some of the oil in the motor pipe to be stored in the accumulator.

JP2011-514954A (Pages 5 to 8, Figure 2)

In a fluid pressure circuit such as that described in Patent Document 1, the opening of the control valve is adjusted according to the pressure of the accumulator. This allows the hydraulic circuit to store an appropriate amount of oil in the accumulator. However, when the rotation of the swing motor is stopped and the control valve receives very high pressure, the opening momentarily widens, causing a large deviation from the target flow rate, and there is a risk that the fluid pressure used to stop the rotation of the swing motor will be lost.

Therefore, when determining the opening degree of the control valve, there are also known devices that detect not only the pressure on the accumulator side, but also the pressure on the swing motor side that rises when the swing motor is stopped. With this configuration, the opening degree of the control valve can be adjusted using the pressure on the accumulator side and the pressure on the swing motor side. This makes it possible to reliably secure the fluid pressure required to stop the rotation of the swing motor.

However, to adjust the opening of the control valve based on the pressure on the accumulator side and the pressure on the swing motor side, it is necessary to detect each pressure, calculate the opening of the control valve from these pressures, determine the electrical signal to be input to the control valve, and output this electrical signal. This left room for improvement in responsiveness.

The present invention was developed to address these problems, and aims to provide a fluid pressure circuit that can responsively supply fluid to the regenerative system.

In order to solve the above problems, the fluid pressure circuit of the present invention comprises:
A pressure source;
an actuator device actuated by fluid from the pressure source;
a directional control valve provided in a main flow path between the pressure supply source and the actuator device;
a regeneration system connected to the main flow path via a branch flow path;
a control valve for controlling a flow rate from the main flow path to the branch flow path,
A throttle that throttles a fluid from the main flow path is disposed in the branch flow path,
The control valve receives the fluid pressure in the main flow passage and the fluid pressure in the branch flow passage obtained by the restriction, and is controlled by the differential pressure therebetween.
According to this, the control valve is controlled by utilizing the differential pressure between the pressure in the main flow passage and the pressure in the branch flow passage, and therefore the fluid pressure circuit can supply fluid to the regenerative system with good responsiveness.

The throttle may be a variable throttle that is controlled based on information obtained from the regenerative system.
This allows the fluid pressure circuit to supply an appropriate amount of fluid to the regenerative system.

The information obtained from the regenerative system may be an electrical signal obtained from a sensor on the regenerative system side.
According to this, the opening degree of the variable throttle is controlled in response to an electrical signal from a sensor on the regenerative system side, resulting in a simple configuration.

The throttle may be provided at the operating position of a three-port two-position type solenoid valve.
With this, the fluid pressure circuit can smoothly operate the actuator device, and can supply fluid to the regeneration system with good responsiveness during regeneration.

1 is a diagram showing a hydraulic excavator incorporating a hydraulic circuit according to an embodiment of the present invention. FIG. 2 is a diagram showing a hydraulic circuit in the embodiment. 4 is a graph showing the relationship between the lever operation amount and the electrical signal output to the switching valve. 4 is a graph showing the relationship between the lever operation amount and the opening area of the switching valve. 5 is a graph showing the relationship between the lever operation amount and the flow rate of fluid supplied to the hydraulic motor. 4 is a graph showing the relationship between the lever operation amount and the opening characteristic of the solenoid proportional valve. 4 is a graph showing the relationship between the pressure acting on a relief valve and the flow rate of a fluid passing through the relief valve. 5 is a schematic diagram showing the relationship between an electrical signal input to a flow control valve and a priority flow rate. FIG. FIG. 4 is an enlarged view of a control valve and a throttle. FIG. 4 is a diagram for explaining the movement of a control valve. FIG. 4 is a diagram for explaining the movement of a control valve.

The following describes an embodiment of the fluid pressure circuit according to the present invention.

The fluid pressure circuit according to the embodiment of the present invention will be described with reference to Figures 1 to 11.

The hydraulic circuit as a fluid pressure circuit in the embodiment is a hydraulic circuit that controls the rotation of a hydraulic motor in response to an operation command for a work machine, construction machine, cargo handling vehicle, automobile, etc., and is incorporated, for example, in the swing device 101 of a hydraulic excavator 100 shown in FIG. 1.

In the hydraulic excavator 100, a running body 102 and a rotating body 103 are connected via a rotating device 101. The rotating body 103 can rotate in response to the rotation of a hydraulic motor 4 (see FIG. 2) in the rotating device 101. The hydraulic motor 4 is driven by a hydraulic circuit 110 (see FIG. 2). The hydraulic circuit 110 will be described below.

As shown in FIG. 2, the hydraulic circuit 110 is composed of a hydraulic pump 2 as a fluid supply source driven by a drive mechanism 1 such as an engine or an electric motor, a directional control valve 3, a hydraulic motor 4, a remote control 5, flow divider valves 6, 7, an electromagnetic proportional valve 8, relief valves 9, 10, pressure sensors 11-13, an accumulator 14 as an auxiliary device, a controller 15, a tank 16, check valves 17-20, shuttle valves 21, 22, oil passages 23-45, and electrical signal lines 46-52. Note that although the accumulator 14 is shown as an example of an auxiliary device, this is not limited to this.

The hydraulic pump 2 is connected to a drive mechanism 1 such as an internal combustion engine, and is rotated by the power from the drive mechanism 1 to supply pressurized oil downstream through an oil passage 23.

Pressurized oil discharged from hydraulic pump 2 flows into directional control valve 3 through oil passage 24. Directional control valve 3 is a 6-port, 3-position type, closed-center type electromagnetic directional control valve, and when the spool is in the neutral position, all ports are closed.

The remote control 5 is an electric joystick. When the operating lever 5-1 is operated to the right A or to the left B, the remote control 5 outputs an electric signal proportional to the amount of operation. This electric signal is input to the controller 15 via the electric signal line 46.

The arithmetic circuit of the controller 15 outputs an electrical signal corresponding to the electrical signal input from the remote control 5 to the electrical signal line 47 or the electrical signal line 48. As shown in FIG. 3, the electrical signal output from the controller 15 to the electrical signal line 47 or the electrical signal line 48 is proportional to the amount of operation of the operating lever 5-1.

When the operating lever 5-1 of the remote control 5 is operated to the right direction A, the electrical signal output from the controller 15 is applied to the solenoid 3-1 of the directional control valve 3 through the electrical signal line 47. This causes the spool of the directional control valve 3 to move, and the directional control valve 3 switches to the first rotation position 3-3. The pressurized oil delivered from the hydraulic pump 2 flows into the hydraulic motor 4 through the directional control valve 3 and oil passages 25 and 26, and after passing through the hydraulic motor 4, it is discharged into the tank 16 through oil passages 27 and 28, the directional control valve 3, and oil passage 29. At this time, the hydraulic motor 4 is rotated clockwise.

Similarly, when the operating lever 5-1 of the remote control 5 is operated to the left direction B, the electrical signal output from the controller 15 is applied to the solenoid 3-2 of the directional control valve 3 through the electrical signal line 48. This causes the spool of the directional control valve 3 to move, and the directional control valve 3 switches to the second rotation position 3-4. The pressurized oil delivered from the hydraulic pump 2 flows into the hydraulic motor 4 through the directional control valve 3 and oil passages 28 and 27, and after passing through the hydraulic motor 4, it is discharged into the tank 16 through oil passages 26 and 25, the directional control valve 3, and oil passage 29. At this time, the hydraulic motor 4 is rotated in the counterclockwise direction.

In this way, the oil passages 23 to 29 through which the pressurized oil passes to rotate the hydraulic motor 4 are the main flow paths in this embodiment.

As shown in Figure 4, the directional control valve 3 is configured so that the spool strokes approximately in proportion to the electrical signal input from the controller 15 via the electrical signal line 47 or the electrical signal line 48. As a result, the directional control valve 3 increases the P-M (pump → hydraulic motor) opening area and the M-T (hydraulic motor → tank) opening area according to the spool stroke.

The arithmetic circuit of the controller 15 also outputs an electrical signal to the electrical signal line 52 in response to the electrical signal input from the remote control 5.

As shown in FIG. 5, the hydraulic pump 2 is configured so that the amount of pressurized oil discharged varies variably in approximate proportion to the electrical signal input from the controller 15 via the electrical signal line 52.

As a result, as the amount of operation of the remote control 5 increases, the P-M (pump → hydraulic motor) opening area increases, and as the amount of pressurized oil sent from the hydraulic pump 2 increases, the amount of pressurized oil supplied to the hydraulic motor 4 increases, and the rotation speed of the hydraulic motor 4 increases. In other words, it is possible to control the rotation speed of the hydraulic motor 4 according to the inclination of the operating lever 5-1.

Returning to FIG. 2, oil passages 30, 33, and 34 are branched and connected to oil passage 26. Oil passages 31, 32, and 36 are branched and connected to oil passage 27.

A relief valve 10 is provided between oil passage 30 and oil passage 31. The relief valve 10 opens when the pressure in oil passage 30 reaches or exceeds a predetermined pressure, allowing communication between oil passages 30 and 31.

A relief valve 9 is provided between oil passage 32 and oil passage 33. The relief valve 9 opens when the pressure in oil passage 32 reaches or exceeds a predetermined pressure, allowing communication between oil passages 32 and 33.

Oil passage 34 is connected to oil passage 35 via check valve 19. Check valve 19 is configured to allow oil to pass from oil passage 35 to oil passage 34. Oil passage 36 is connected to oil passage 35 via check valve 20. Check valve 20 is configured to allow oil to pass from oil passage 35 to oil passage 36. Oil passage 35 is connected to tank 16.

In addition, pressure sensor 11 is connected to oil passage 26. Pressure sensor 12 is connected to oil passage 27. Pressure sensors 11 and 12 are capable of inputting the detected pressure value Pv or pressure value Pw to controller 15 as an electrical signal.

The hydraulic circuit 110 is also connected to the regenerative system R via a branch flow path that branches off from oil paths 25, 26, 27, and 28, which are part of the main flow path. The branch flow path is made up of diverter valves 6 and 7, shuttle valves 21 and 22, and oil paths 37, 41, 44, and 45. The regenerative system R is mainly made up of the solenoid proportional valve 8, pressure sensor 13, accumulator 14, check valves 17 and 18, and oil paths 38 to 40, 42, and 43.

The flow dividing valve 6 is provided between the oil passages 25 and 26. The flow dividing valve 6 is also connected to the oil passage 41. The flow dividing valve 6 can switch between passing pressurized oil only between the oil passages 25 and 26, or passing pressurized oil between the oil passages 25 and 26 and also allowing the pressurized oil to flow into the oil passage 41. This flow dividing valve 6 will be described later.

The flow dividing valve 7 is provided between the oil passages 27 and 28. The flow dividing valve 7 is also connected to the oil passage 37. The flow dividing valve 7 can switch between passing pressurized oil only between the oil passages 27 and 28, or passing pressurized oil between the oil passages 25 and 26 as well as flowing into the oil passage 37. This flow dividing valve 7 will be described later.

Oil passages 37 and 41 are connected in parallel to shuttle valve 21. In addition, oil passage 38 is connected to shuttle valve 21. Shuttle valve 21 is configured so that the oil passage with the higher internal pressure out of oil passages 37 and 41 can be connected to oil passage 38.

Oil passage 38 is connected to oil passage 39 via check valve 17. Check valve 17 is configured to allow pressurized oil to pass from oil passage 38 to oil passage 39. In addition, accumulator 14, pressure sensor 13, and solenoid proportional valve 8 are connected to oil passage 39. Pressure sensor 13 is capable of inputting the detected pressure value Px to controller 15 as an electrical signal.

The solenoid proportional valve 8 is also connected to the shuttle valve 22 via an oil passage 42, a check valve 18, and an oil passage 43. The check valve 18 is configured to allow pressurized oil to pass from the oil passage 42 to the oil passage 43. The shuttle valve 22 is also connected to oil passages 44 and 45 in parallel. The shuttle valve 22 is configured to allow the oil passage 44, 45, whichever has the higher internal pressure, to communicate with the oil passage 43.

The electromagnetic proportional valve 8 is a two-port, two-position type electromagnetic proportional flow control valve. The calculation circuit of the controller 15 also outputs an electrical signal corresponding to the electrical signal input from the remote control 5 to the electrical signal line 51.

As shown in FIG. 6, the solenoid proportional valve 8 is configured so that the opening area changes variably in approximate proportion to the electrical signal input from the controller 15 via the electrical signal line 51.

When the remote control 5 is being operated and the pressure value Px input from the pressure sensor 13 is equal to or greater than a predetermined value, the controller 15 outputs an electrical signal to the solenoid proportional valve 8 according to the amount of operation of the remote control 5. This adjusts the opening of the solenoid proportional valve 8 so that the opening area corresponds to the electrical signal, allowing pressure oil to be supplied from the accumulator 14 to the oil passage 44 or oil passage 45. This allows the pressure oil in the T portion shown by the diagonal lines in Figure 5 to be supplied from the accumulator 14 to the hydraulic motor 4.

In addition, when the controller 15 outputs an electrical signal to the electromagnetic proportional valve 8, it also outputs an electrical signal to the hydraulic pump 2, reducing the amount of pressurized oil delivered from the hydraulic pump 2. This makes it possible to reduce the energy required to drive the hydraulic pump 2.

Next, we will explain the control of fluid storage in the accumulator 14 in the regenerative system R. Fluid storage in the accumulator 14 is performed by utilizing the fluid pressure P1 that rises in the oil passages 25, 26 or the oil passages 27, 28 when the operating lever 5-1 is suddenly returned to the neutral position, i.e., a sudden stop operation is performed. First, we will explain the rise in this fluid pressure P1.

For example, when the operating lever 5-1 is moved from its maximum position in the left direction B to its neutral position in one go, the directional control valve 3 is switched from the second rotation position 3-4 to the neutral position 3-5. This stops the supply of pressurized oil from the hydraulic pump 2 to the oil passage 28, and also stops the discharge of pressurized oil from the oil passage 25 to the tank 16.

Meanwhile, the rotating body 103, which had been rotating under the rotational force of the hydraulic motor 4 until just before, tries to continue rotating due to inertial force. This inertial force also acts on the hydraulic motor 4, causing it to rotate. When the hydraulic motor 4 rotates, a pumping action occurs and pressure oil is pumped from oil passage 27 to oil passage 26, causing the fluid pressure P1 in oil passages 26 and 25 to rise. The fluid pressure P1 rising in oil passages 26 and 25 acts as resistance to the rotation of the hydraulic motor 4, in other words, the pressure of the pressure oil being pumped to oil passage 26. This causes the rotational speed of the hydraulic motor 4 to decrease, eventually coming to a stop.

On the other hand, in the oil passages 28, 27, the internal fluid pressure decreases as pressurized oil is sucked in in response to the rotation of the hydraulic motor 4. As a result, when the internal pressure falls below the pressure of the oil in the tank 16, the oil in the tank 16 is sucked up into the oil passages 28, 27 through the oil passages 35, 36. This prevents cavitation from occurring in the oil passages 28, 27.

When the operating lever 5-1 is operated to the right A and returned to the neutral position, the process is substantially the same as when the operating lever 5-1 is operated to the left B and returned to the neutral position, except for the change in flow direction as described above, so a detailed explanation will be omitted.

The relief valves 9 and 10 have pressure override characteristics shown by curve C1 in Figure 7. To explain this, we will first explain the pressure override characteristics shown by curve C0 in Figure 7. Curve C0 shows the flow rate Q that passes through the relief valve in approximate proportion to the increase in fluid pressure P1, and the relief valve begins to open at cracking pressure Pcr and can pass flow rate Q1 at set pressure Pst.

The flow rate Q1 is the total flow rate of pressurized oil discharged by the hydraulic motor 4 through pump action due to the inertial force acting on the rotating body 103 when the operating lever 5-1 is quickly returned to the neutral position from the state in which it is operated to the maximum extent. The set pressure Pst is the pressure required to stop the rotating body 103 within a specified angle centered on the axis of the hydraulic motor 4. This prevents accidents due to excessive rotation flow, such as the risk of the rotating body 103 rotating excessively after the operating lever 5-1 is operated to the neutral position or the risk of the hydraulic circuit being damaged due to an excessive pressure rise.

For these reasons, in a hydraulic circuit that uses a relief valve with the pressure override characteristics shown by curve C0, any pressurized oil that exceeds the amount required to maintain the set pressure Pst must be discharged outside the oil passage that is equipped with the relief valve that generates the set pressure Pst.

The pressure override characteristics of the relief valves 9, 10 in this embodiment are set to pass a flow rate Q2 that is less than the flow rate Q1 at the set pressure Pst, as shown by curve C1. Therefore, in the hydraulic circuit 110 of this embodiment, compared to a hydraulic circuit in which a relief valve with the pressure override characteristics shown by curve C0 is used, when the fluid pressure P1 downstream of the hydraulic motor 4 in the flow direction of the pressurized oil reaches the set pressure Pst, an excess oil amount ΔQ (ΔQ = Q1 - Q2) can be generated on the downstream side.

The hydraulic circuit 110 can store the excess oil volume ΔQ in the accumulator 14 by controlling either the flow divider valve 6 or 7, which is located downstream of the hydraulic motor 4 in the flow direction of the pressurized oil. This allows the hydraulic circuit 110 to prevent accidents caused by excessive flow during rotation.

As shown in FIG. 9, the flow dividing valve 6 includes a flow control valve 60, a pressure compensation valve 61 as a control valve, and oil passages 62 to 66.

The flow control valve 60 is a three-port, two-position type electromagnetic proportional flow control valve. The solenoid 60-1 of the flow control valve 60 is connected to the controller 15 via an electrical signal line 49.

Flow control valve 60 is connected to oil passage 26 via oil passage 62. In addition, oil passages 63 and 64 are connected in parallel to flow control valve 60. In addition, oil passages 63 and 64 are also connected in parallel to pressure compensation valve 61. In addition, oil passage 63 can be communicated with oil passage 65 via pressure compensation valve 61. In addition, oil passage 65 is communicated and connected to oil passage 25. Oil passage 64 is connected to oil passage 66 via pressure compensation valve 61. In addition, oil passage 66 is communicated with oil passage 41.

When no electrical signal is input from the controller 15 to the solenoid 60-1, the flow control valve 60 is in the neutral position 60-3. In the neutral position 60-3, the oil passages 62 and 63 are connected, and the oil passages 62 and 64 are not connected. Therefore, in the neutral position 60-3, pressurized oil can flow between the oil passages 25 and 26.

As shown in FIG. 10, the flow control valve 60 switches to the operating position 60-2 when an electrical signal is input from the controller 15 to the solenoid 60-1. In the operating position 60-2, oil passages 60-4, 60-5, variable throttle 60-6, and 60-7 are provided.

In the operating position 60-2, oil passage 60-4 is connected to oil passage 62 and oil passage 63. In addition, oil passage 60-5 is branched and connected to oil passage 60-4. Oil passage 60-5 is connected to oil passage 60-7 via variable throttle 60-6. In the operating position 60-2, oil passage 60-7 is connected to oil passage 64. As a result, in the operating position 60-2, oil passage 62 and oil passage 63 are connected to each other, and oil passage 64 is also connected to them.

As shown in FIG. 8, the flow control valve 60 variably changes the priority flow rate approximately in proportion to the electrical signal from the controller 15. The priority flow rate is the amount of pressurized oil that passes through the variable throttle 60-6 and is supplied to the oil passage 64. In other words, the flow control valve 60 variably changes the opening area of the variable throttle 60-6 approximately in proportion to the electrical signal from the controller 15.

As a result, in the operating position 60-2, not only is pressurized oil able to flow between the oil passages 25 and 26, but pressurized oil can also flow through oil passage 41, branching off from the oil passages 25 and 26 that form the main flow path.

The pressure compensation valve 61 has an oil passage 61-1, an oil passage 61-2, and a spring 61-3.

Oil passage 61-1 communicates with oil passage 63 and a back pressure chamber (not shown) defined on the lower side of the spool in pressure compensation valve 61. Oil passage 61-2 communicates with oil passage 64 and a back pressure chamber (not shown) defined on the upper side of the spool. As a result, fluid pressure P1 acts on the pressure receiving surface (not shown) on the lower side of the spool as the so-called pilot pressure of the pressurized oil supplied from oil passage 63 through oil passage 61-1. Fluid pressure P2 acts on the pressure receiving surface (not shown) on the upper side of the spool as the so-called pilot pressure of the pressurized oil that has passed through variable throttle 60-6 and is supplied from oil passage 64 through oil passage 61-2. The pressure receiving area S1 on the lower side of the spool and the pressure receiving area S2 on the upper side of the spool are approximately the same (S1 = S2).

The spring 61-3 is located above the spool (not shown) on the page, and biases the spool toward the bottom of the page.

As a result, the spool in the pressure compensation valve 61 moves in response to a force Fp (Fp = F2 + Fsp) obtained by adding the biasing force Fsp of the spring 61-3 to the force F1 (F1 = P1 x S1) generated by the fluid pressure P1 acting on the pressure receiving area S1 and the force F2 (F2 = P2 x S2) generated by the fluid pressure P2 acting on the pressure receiving area S2, and comes to rest at a balanced position where the forces F1 and Fp are in equilibrium (F1 = Fp). The force relationship at this time is summarized as follows: the difference between the forces F1 and F2 is constant (P1 x S1 = P2 x S2 + Fsp = constant P1 - P2 = Fsp/S1 = constant).

In response to this movement of the spool, the pressure compensating valve 61 changes the opening between oil passages 63 and 65 and the opening between oil passages 64 and 66. More specifically, referring to FIG. 10, the further the spool moves downward on the page, the wider the opening between oil passages 63 and 65 becomes, and the narrower the opening between oil passages 64 and 66 becomes. Also, referring to FIG. 11, the further the spool moves upward on the page, the narrower the opening between oil passages 63 and 65 becomes, and the wider the opening between oil passages 64 and 66 becomes. Note that FIGS. 10 and 11 are schematic diagrams showing the operation of the pressure compensating valve 61.

Next, the flow dividing valve 6 when pressure accumulation control to the accumulator 14 is performed will be described. When the controller 15 detects that the control lever 5-1, which had been operated to the maximum extent in the left direction B, has been returned to the neutral position in one go, it switches the directional control valve 3 to the neutral position 3-5, closes the solenoid proportional valve 8, and determines the opening degree Ax of the variable throttle 60-6 in the flow control valve 60 by referring to the pressure value Px input from the pressure sensor 13.

In detail, the opening degree Ax of the variable throttle 60-6 is determined in this embodiment by the override characteristics of the relief valves 9 and 10, respectively, in which the excess oil amount ΔQ and the set pressure Pst are preset. For this reason, the calculation circuit of the controller 15 is preset with an electrical signal for each pressure value Px of the accumulator 14 that allows the excess oil amount ΔQ to flow to the accumulator 14 side while leaving pressure oil to ensure the set pressure Pst. Therefore, the controller 15 in this embodiment can output an electrical signal for controlling the opening degree Ax to an appropriate value based only on the pressure value Px of the accumulator 14.

The controller 15 outputs a smaller electrical signal the smaller the pressure value Px of the accumulator 14 is, and outputs a larger electrical signal the larger the pressure value Px of the accumulator 14 is. In other words, the variable throttle 60-6 narrows the opening Ax the smaller the pressure value Px of the accumulator 14 is, and widens the opening Ax the larger the pressure value Px of the accumulator 14 is.

When the opening Ax of the variable throttle 60-6 is a narrow opening Ax1, the pressure difference ΔP between the fluid pressure P1 and the fluid pressure P2 is a large pressure difference ΔP10 (ΔP10 = P1 - P2). In other words, the fluid pressure P2 is low (P2 << P1).

As described above, the pressure difference ΔP10 in the pressure compensation valve 61 when the cylinder is stationary in the balance position is kept constant (ΔP10 = P1 - P2 = Fsp/S1 = constant).

As a result, even if the pressure difference between the set pressure Pst and the pressure value Px on the accumulator 14 side is large, it is possible to store an excess amount of oil ΔQ on the accumulator 14 side (ΔQ = K x Ax1 x √ΔP10 (K is a constant)). Also, the larger the pressure difference ΔP between the fluid pressures P1 and P2, the wider the opening between the oil passages 64, 66 becomes.

In addition, when the opening degree Ax of the variable throttle 60-6 is a wide opening degree Ax2, the pressure difference ΔP between the fluid pressure P1 and the fluid pressure P2 becomes a small pressure difference ΔP20 (ΔP20 = P1 - P2). In other words, the fluid pressure P2 becomes high (P2 < P1).

As described above, the pressure difference ΔP20 in the pressure compensation valve 61 when the cylinder is stationary in the balance position is kept constant (ΔP20 = P1 - P2 = Fsp/S1 = constant).

As a result, even if the pressure difference between the set pressure Pst and the pressure value Px on the accumulator 14 side is small, it is possible to store an excess amount of oil ΔQ on the accumulator 14 side (ΔQ = K x Ax2 x √ΔP20 (K is a constant)). Also, the smaller the pressure difference ΔP between the fluid pressures P1 and P2, the narrower the opening between the oil passages 64, 66.

For more details on the movement of the pressure compensation valve 61, for example, as shown in FIG. 10, when the spool is stationary in the balance position, high pressure acts on the variable throttle 60-6, causing its opening Ax to momentarily widen, and as a result, the flow rate passing through the variable throttle 60-6 increases, and the fluid pressure P2 in the oil passage 64 rises.

As a result, the spool moves downward on the page by the amount of increase in fluid pressure P2, widening the opening between oil passages 63 and 65 and narrowing the opening between oil passages 64 and 66. As a result, fluid pressure P2 rises instantaneously, the differential pressure ΔP between fluid pressures P1 and P2 becomes smaller, and the inflow of pressurized oil from oil passages 25 and 26 into oil passage 64 can be reduced.

Then, by decreasing the fluid pressure P2 or increasing the fluid pressure P1, the differential pressure ΔP according to the opening degree Ax of the variable throttle 60-6 can be adjusted to a constant differential pressure ΔP10 or differential pressure ΔP20, regardless of whether the differential pressure ΔP is ΔP10 or ΔP20.

As a result, the hydraulic circuit 110 can prevent more than the excess oil volume ΔQ from passing between the oil passages 64, 66, and can maintain the amount of oil in the oil passages 25, 26 required to obtain the set pressure Pst.

Also, as shown in FIG. 11, for example, when the spool is stationary in the balance position, if the flow rate passing through the variable throttle 60-6 decreases, the fluid pressure P2 in the oil passage 64 decreases.

As a result, the spool moves upward on the page by the amount of the decrease in fluid pressure P2, narrowing the opening between oil passages 63 and 65 and widening the opening between oil passages 64 and 66. As a result, fluid pressure P2 decreases instantaneously, and the differential pressure ΔP between fluid pressures P1 and P2 increases, allowing the flow of pressurized oil from oil passages 25 and 26 into oil passage 64 to increase.

Then, by decreasing the fluid pressure P1 or increasing the fluid pressure P2, the differential pressure ΔP according to the opening degree Ax of the variable throttle 60-6 can be adjusted to a constant differential pressure ΔP10 or differential pressure ΔP20, regardless of whether the differential pressure ΔP is ΔP10 or ΔP20.

As a result, the hydraulic circuit 110 is able to prevent more pressurized oil than necessary from being discharged from the relief valve 10 to the oil passage 27 side, allowing excess oil volume ΔQ to pass between the oil passages 64 and 66.

The flow dividing valve 7 includes a flow control valve 70 and a pressure compensation valve 71 as a control valve, and the flow control valve 70 is connected to the controller 15 via an electrical signal line 50. The rest of the configuration is the same as that of the flow dividing valve 6, so a duplicated description will be omitted.

As described above, in the hydraulic circuit 110 of this embodiment, the pressure compensation valve 61 is controlled using the differential pressure ΔP between the fluid pressure P1 in the oil passages 25 and 26 and the fluid pressure P2 in the oil passage 64. This allows the hydraulic circuit 110 to responsively supply pressurized oil to the regenerative system R.

In addition, the hydraulic circuit 110 uses a variable throttle 60-6 to control the amount of oil from the oil passages 25 and 26 to the oil passage 64. Therefore, the hydraulic circuit 110 can supply an appropriate amount of pressurized oil to the regenerative system R while maintaining the amount of oil in the oil passages 25 and 26 required to obtain the set pressure Pst.

The hydraulic circuit 110 also has a simple configuration, since an electrical signal corresponding to the pressure value Px on the accumulator 14 side is input from the pressure sensor 13 to the controller 15, and the opening Ax of the variable throttle 60-6 is controlled accordingly.

Furthermore, the flow control valve 60 is a three-port two-position type solenoid valve. Therefore, the hydraulic circuit 110 can prevent inflow into the regenerative system R by placing the flow control valve 60 in the neutral position 60-3 when rotating the hydraulic motor 4. This allows the hydraulic circuit 110 to operate the hydraulic motor 4 smoothly. Furthermore, during regeneration, the flow control valve 60 is switched to the operating position 60-2 by inputting an electrical signal. This allows the hydraulic circuit 110 to supply fluid to the regenerative system R with good responsiveness.

　Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention also includes modifications and additions that do not deviate from the gist of the present invention.

For example, in the above embodiment, the fluid pressure circuit is described as being a hydraulic circuit in which oil is pumped, but this is not limited thereto and may be a fluid other than oil, and the fluid applied may be changed as appropriate.

In addition, in the above embodiment, the actuator is described as being a hydraulic motor, but this is not limited to this and may be a hydraulic cylinder or may be modified as appropriate.

In addition, in the above embodiment, an accumulator is used in the regeneration system, but this is not limited to this, and a generator may be used, and any other suitable configuration may be used as long as it is capable of regenerating energy from the flow of fluid.

In addition, in the above embodiment, the control valve is described as being a pressure compensation valve, but this is not limited thereto, and may be changed as appropriate as long as it is a valve that operates based on a pilot differential pressure. For this reason, the control valve may be configured to be capable of adjusting the opening of the branch flow passage, but not involved in adjusting the opening of the main flow passage, and in such a configuration, the opening of the main flow passage may be maintained at a constant opening that allows the fluid to flow freely.

In addition, in the above embodiment, the aperture is described as being variable, but this is not limited thereto and may be a fixed aperture.

In the above embodiment, the remote control is described as being an electric joystick, but this is not limited thereto, and it may be, for example, a remote control valve for variably controlling the pilot pressure acting on the directional control valve. In this way, fluid pressure may be used as appropriate instead of an electrical signal for control by the controller.

In addition, in the above embodiment, the variable throttle is described as being part of a three-port two-position type solenoid valve, but this is not limited thereto, and the on-off valve and the variable throttle may be arranged in series, or may be separate. Furthermore, if the throttle is a variable throttle, the on-off valve may be omitted.

1 Drive mechanism 2 Hydraulic pump (pressure supply source)
3 Directional switching valve 4 Hydraulic motor (actuator)
6, 7 Diverter valve 13 Pressure sensor (sensor on the regenerative system side)
14 Accumulator 23-29 Oil passage (main passage)
37, 41, 44, 45 Oil passage (branch passage)
60 Flow control valve (3-port 2-position solenoid valve)
60-2 Operating position 60-6 Variable throttle 61 Pressure compensation valve (control valve)
70 Flow control valve (3-port 2-position solenoid valve)
71 Pressure compensation valve (control valve)
110 Hydraulic circuit (fluid pressure circuit)

Claims (4)

1. A pressure source;
   an actuator device actuated by fluid from the pressure source;
   a directional control valve provided in a main flow path between the pressure supply source and the actuator device;
   a regeneration system connected to the main flow path via a branch flow path;
   a control valve for controlling a flow rate from the main flow path to the branch flow path,
   A throttle that throttles a fluid from the main flow path is disposed in the branch flow path,
   The control valve is a fluid pressure circuit that receives fluid pressure in the main flow path and fluid pressure in the branch flow path obtained by the restriction and is controlled by the differential pressure between them.
2. The fluid pressure circuit according to claim 1, wherein the throttle is a variable throttle that is controlled based on information obtained from the regenerative system.
3. The fluid pressure circuit according to claim 2, wherein the information obtained from the regenerative system is an electrical signal obtained from a sensor on the regenerative system side.
4. The fluid pressure circuit according to any one of claims 1 to 3, wherein the throttle is provided at the operating position of a 3-port 2-position type solenoid valve.

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