Fluid pressure circuit

Abstract

The present invention provides a fluid pressure circuit having high pressure accumulation efficiency.　A fluid pressure circuit 100 comprises: a plurality of drive parts 5, 6, 7 that are connected to a single load 4; and a pressure accumulator 10 capable of accumulating pressure. A return flow passage 23-2 of at least one drive part 7 is branched and connected to the accumulator 10.

Description

Fluid Pressure Circuit

[0001] The present invention relates to a hydraulic circuit, and more particularly to a hydraulic circuit having an accumulator for storing hydraulic fluid.

[0002] In various fields, fluid pressure circuits are known that drive actuators using a working fluid such as hydraulic oil delivered from a fluid supply device such as a pump. In such fluid pressure circuits, for example, oil discharged from a hydraulic cylinder device as an actuator is stored in an accumulator as the hydraulic cylinder device contracts, and the oil is regenerated when the hydraulic cylinder device extends.

[0003] For example, the hydraulic circuit disclosed in Patent Document 1 mainly includes a pump, a control valve, two boom cylinders, an accumulator, and a valve. When the operating lever is operated to the down position, the control valve switches to the down position, and oil from the pump is supplied to the rod-side oil chambers of the two boom cylinders, and oil is discharged from the head-side oil chamber. This causes the two boom cylinders to descend, driving the boom downward. Some of the oil discharged from the head-side oil chamber is stored in the accumulator through the valve, and the other part is discharged to a tank.

[0004] When the operating lever is operated to the up position, the control valve switches to the up position, oil from the pump is supplied to the head-side oil chambers of the two boom cylinders, and oil in the rod-side oil chamber is discharged to the tank. At this time, the valve opens, and the stored oil in the accumulator is regenerated and sent to the head-side oil chambers of the two boom cylinders. This reduces the pump discharge flow rate.

[0005] JP 2009-150462 A (page 13, Figure 2)

[0006] In a fluid pressure circuit such as that described in Patent Document 1, the head-side oil chambers of the two boom cylinders join together and are connected to an accumulator. With this, when the boom is raised, the pump discharge pressure acts on the total pressure-receiving area of ​​the two pistons, increasing the thrust when the boom is raised. However, when the boom is lowered, the load on the boom is distributed across the total pressure-receiving area of ​​the two pistons, resulting in a problem of low efficiency in storing pressure in the accumulator.

[0007] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a fluid pressure circuit with high pressure accumulation efficiency.

[0008] In order to solve the above problems, the present invention provides a fluid pressure circuit including a plurality of drive units connected to a single load and a pressure accumulator capable of accumulating pressure, wherein a return flow path of at least one of the drive units is branched and connected to the pressure accumulator. With this, when the load is released from being driven, the force acting from the load is concentrated on one drive unit, the number of which is smaller than the number of drive units that work when the load is driven, so that fluid can be accumulated at high pressure in the accumulator.

[0009] The return flow path of at least one of the drive units may be branched and connected to the pressure accumulator, and the return flow paths of the other drive units may be connected to the tank. In this way, when the load is driven, the load can be driven by at least the other drive unit, and when the drive of the load is released, the return fluid flows from the other drive unit to the tank, and the force acting from the load is concentrated on one drive unit, so that the fluid can be accumulated in the pressure accumulator at high pressure.

[0010] A pressure intensifier may be provided between the return flow path of the one drive unit and the pressure accumulator. This allows the pressure accumulator to maintain a high fluid pressure due to the pressure intensifier. This increases the flexibility in the size and combination of the drive units.

[0011] A plurality of the drive units may be provided, whereby even if the flow rate of the return fluid per drive unit is small, a large flow rate of the return fluid can be ensured for all drive units.

[0012] The size of the pressure receiving surface of the one drive unit may be smaller than the size of the pressure receiving surface of the other drive unit, which allows the installation space of the one drive unit to be reduced, thereby increasing the degree of installation freedom.

[0013] The driving unit may be a cylinder device, which allows for accurate driving control of a plurality of cylinder devices.

[0014] The number of the one drive units may be less than the number of the other drive units. In this case, the reaction of the load acting on the one drive unit becomes larger, and therefore the fluid can be accumulated in the accumulator at a higher pressure.

[0015] Fig. 1 is a schematic diagram showing a fluid pressure circuit according to a first embodiment of the present invention; Fig. 2 is a schematic diagram showing a fluid pressure circuit according to a second embodiment of the present invention; Fig. 3 is a schematic diagram showing a fluid pressure circuit according to a third embodiment of the present invention; Fig. 4 is a schematic diagram showing a fluid pressure circuit according to a fourth embodiment of the present invention;

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fluid pressure circuit according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0017] A fluid pressure circuit according to a first embodiment will be described with reference to FIG.

[0018] The fluid pressure circuit according to the first embodiment is configured to accumulate in an accumulator the working fluid discharged from a cylinder device of a work machine, a construction machine, a cargo handling vehicle, an automobile, an industrial machine, or the like, and to regenerate the working fluid in the hydraulic cylinder device.

[0019] 1, the fluid pressure circuit 100 is mainly composed of a hydraulic pump 1, a drive source 2 that drives the hydraulic pump 1, a switching valve 3, a load 4, cylinder devices 5, 6, and 7 as drive units, a check valve 8, a pressure-accumulation switching valve 9, an accumulator 10 as a pressure accumulator, a regeneration switching valve 11, and a tank 14. Here, the cylinder device 7 is one drive unit in the present invention, and the cylinder devices 5 and 6 are other drive units in the present invention.

[0020] The switching valve 3 is connected to the hydraulic pump 1 by a flow path 20 and to the tank 14 by a flow path 21 .

[0021] The three cylinder devices 5, 6, and 7 are connected in parallel to a single load 4. Since the specifications of these cylinder devices 5, 6, and 7 are the same, the load 4 can be driven and controlled simply and accurately.

[0022] The first oil chambers 5-1, 6-1, 7-1 of the three cylinder devices 5, 6, 7 are connected in parallel to a flow path 23 extending from the switching valve 3. A check valve 8 is provided at the portion extending from the flow path 23 to the first oil chamber 7-1.

[0023] A flow path 23-1 connecting the check valve 8 and the first oil chamber 7-1 is connected to the pressure-accumulation switching valve 9 by a flow path 23-2 serving as a return flow path.

[0024] The pressure-accumulation switching valve 9 is connected to the flow path 23 on the switching valve 3 side of the cylinder devices 5, 6, and 7 by a flow path 23-5.

[0025] In addition, a branch flow path 23-3 is connected to the pressure-accumulation switching valve 9 in addition to the flow path 23-5, and the branch flow path 23-3 is connected to the accumulator 10. The accumulator 10 is also connected to the flow path 23 via a flow path 23-4 and the regeneration switching valve 11.

[0026] The second oil chambers 5-2, 6-2, and 7-2 of the cylinder devices 5, 6, and 7 are connected in parallel to a flow path 24 extending from the switching valve 3.

[0027] When the switching valve 3 is in the raised position R, oil discharged from the hydraulic pump 1 is supplied to the first oil chambers 5-1, 6-1, and 7-1 of the cylinder devices 5, 6, and 7 through the flow paths 20 and 23, and oil in the second oil chambers 5-2, 6-2, and 7-2 is discharged to the tank 14 through the flow paths 24 and 21. This causes the cylinder devices 5, 6, and 7 to perform an upward movement, i.e., the load 4 is driven to ascend.

[0028] When the cylinder devices 5, 6, 7 are in the ascending operation, the pressure accumulation switching valve 9 is in a position that connects the flow path 23-2 and the flow path 23-5, and the regeneration switching valve 11 is in an open position, connecting the flow path 23-4 with the flow path 23.

[0029] As a result, oil stored in an accumulator 10 (described later) is regenerated into the first oil chambers 5-1, 6-1, and 7-1 of the cylinder devices 5, 6, and 7 through a regenerative switching valve 11. This allows the flow rate of the hydraulic pump 1 to be reduced, thereby achieving energy savings. For example, if the hydraulic pump 1 is a swash plate type variable displacement pump as shown in FIG. 1, the flow rate can be adjusted by controlling the pump swash plate.

[0030] On the other hand, when the switching valve 3 is in the lowered position D, the oil discharged from the hydraulic pump 1 is supplied to the second oil chambers 5-2, 6-2, 7-2 of the cylinder devices 5, 6, 7 through the flow paths 20, 24, and the oil in the first oil chambers 5-1, 6-1 of the cylinder devices 5, 6 is discharged to the tank 514 through the flow paths 23, 21. This causes the cylinder devices 5, 6, 7 to perform a lowering operation, i.e., the upward drive of the load 4 is released.

[0031] When each of the cylinder devices 5, 6, and 7 is lowering, the pressure accumulation switching valve 9 switches to connect the flow path 23-2 to the branch flow path 23-3, the regeneration switching valve 11 is in a closed position, and the flow path 23-4 is not connected to the flow path 23.

[0032] As a result, oil in the first oil chamber 7-1 of the cylinder device 7 passes through the flow paths 23-1 and 23-2, the pressure accumulation switching valve 9, and the branch flow path 23-3, and is accumulated in the accumulator 10.

[0033] Furthermore, when the switching valve 3 is in the neutral position N, the operation of the hydraulic pump 1 stops, and the first oil chambers 5-1 and 6-1 of the cylinder devices 5, 6 and 7 are connected to the tank 14 through the flow paths 23 and 21, the first oil chamber 7-1 of the cylinder device 7 is connected to the tank 14 through the flow path 23-2, the pressure accumulator switching valve 9 and the flow paths 23-5 and 21, and the second oil chambers 5-2, 6-2 and 7-2 of the cylinder devices 5, 6 and 7 are connected to the tank 14 through the flow paths 24 and 21.

[0034] When the switching valve 3 is in the neutral position N, the cylinder devices 5, 6, and 7 hardly move. For example, after the load 4 has been driven upward, the switching valve 3 is switched to the neutral position N when the drive is stopped. Strictly speaking, when the switching valve 3 is in the neutral position N, the pressure-accumulation switching valve 9 switches so as to communicate the flow paths 23-2 and 23-5, and the flow rate of the oil in the first oil chamber 7-1 of the cylinder device 7 is throttled by the throttle flow path of the pressure-accumulation switching valve 9, so that the cylinder devices 5, 6, and 7 move downward very slowly.

[0035] In the fluid pressure circuit 100 as shown in FIG. 1, the area of ​​the piston heads as the pressure-receiving surfaces of the cylinder devices 5 and 6 is A1, the area of ​​the piston head as the pressure-receiving surface of the cylinder device 7 is A2, the pressure in the first oil chambers 5-1 and 6-1 of the cylinder devices 5 and 6 when the pistons are descending is P1, the pressure in the first oil chamber 7-1 of the cylinder device 7 when the pistons are descending is P2, the pressure in the second oil chambers 5-2 and 6-2 when the pistons are ascending is P1', the pressure in the second oil chamber 7-2 when the pistons are ascending is P2', and the total load on the cylinder devices 5, 6, and 7 is W1.

[0036] The balance of forces when the piston rises is expressed by the relationship A1×P1′×2+A2×P2′=W1.

[0037] On the other hand, when the pistons descend, the first oil chambers 5-1, 6-1 of the cylinder devices 5, 6 are connected to the tank 14, so P1 = 0, and a certain load is applied to P2 due to the throttle flow path of the pressure-accumulation switching valve 9. Therefore, P2 > 0. Therefore, A2 × P2 = W1.

[0038] In this way, when the piston rises, pressures P1' and P2' act on the total area of ​​the piston head (A1 x 2 + A2), increasing the thrust force when the piston rises. Also, when the piston falls, the total load W1 is concentrated on the total area A2 of the piston head, allowing oil to be stored in the accumulator 10 at high pressure.

[0039] In addition, one cylinder device 7 is provided as one drive unit used for pressure accumulation, and two cylinder devices 5 and 6 are provided as other drive units for driving the load 4. In other words, the number of one drive units is fewer than the number of other drive units. This allows the total area of ​​the piston head when the piston is descending to be reduced, so that oil can be efficiently stored in the accumulator 10.

[0040] Incidentally, one or three or more cylinder devices for driving the load may be provided.

[0041] Furthermore, the cylinder device 7 is preferably disposed in a position where it can support the load 4 in a balanced manner when the piston descends, for example, directly below the center of gravity of the load 4.

[0042] Next, a fluid pressure circuit according to a second embodiment will be described with reference to Fig. 2. Note that the description of the same configuration as in the first embodiment will be omitted.

[0043] 2, a flow dividing valve 29 is provided between the flow paths 223-2 and 223-5. The flow dividing valve 29 and the accumulator 210 are connected by a branch flow path 223-3. A pressure booster 215 is provided in this branch flow path 223-3.

[0044] When each of the cylinder devices 25, 26, and 27 is lowered, oil in the first oil chamber 27-1 of the cylinder device 27 flows through the flow paths 223-1 and 223-2 into the flow dividing valve 29. The oil that has flowed into the flow dividing valve 29 is divided into the flow path 223-5 and the branch flow path 223-3.

[0045] The oil flowing in branch flow path 223-3 is introduced into pressure intensifier 215. Pressure intensifier 215 is a cylinder device that includes, for example, a stepped cylindrical case having a large diameter portion and a small diameter portion, and a piston having a large diameter portion and a small diameter portion, and inputs oil from first oil chamber 27-1 into an input chamber on the large diameter portion side to move the piston, and increases the pressure of oil in an output chamber on the small diameter portion side before sending it out.

[0046] The oil pressurized by the pressure booster 215 is stored in the accumulator 210 .

[0047] In this way, the pressure intensifier 215 allows the accumulator 210 to secure a high accumulated pressure, which increases the degree of freedom in the diameters of the piston heads of the cylinder devices 25, 26, and 27 and their combinations.

[0048] More specifically, if the pressure intensifier 215 is not provided, it is necessary to reduce the piston head diameter of the cylinder device 27 in order to accumulate oil at high pressure in the accumulator 210. If the piston head diameter of the cylinder device 27 is reduced, A1×P1′×2+A2×P2′<W1 is satisfied, and it is therefore necessary to increase the flow rate of the hydraulic pump 1 in order to raise the piston.

[0049] On the other hand, in order to increase the thrust when the piston rises, it is necessary to increase the piston head diameter of the cylinder device 27. Increasing the piston head diameter of the cylinder device 27 has the disadvantage that P2 = W1 / A2 decreases, lowering the efficiency of pressure accumulation in the accumulator 210. Therefore, there is a limit to the degree of freedom in designing the piston head diameter that satisfies both pressure accumulation and load driving.

[0050] In the fluid pressure circuit 200 of the second embodiment, since the pressure intensifier 215 is provided, the accumulator 210 can accumulate high fluid pressure even if the diameter of the piston head of the pressure accumulating cylinder device 27 is increased to improve the thrust during the upward movement of the cylinder device 27. In other words, there is a high degree of freedom in the diameter of the piston head of each of the cylinder devices 25, 26, 27 and their combination.

[0051] In the second embodiment, the pressure booster 215 uses the return oil of the pressure-accumulating cylinder device 27 as the primary pressure, but the present invention is not limited to this. The return oil of the pressure-accumulating cylinder device 27 may be introduced into the oil chamber, pressurized by a piston operated by another drive source, and output to the accumulator as the secondary pressure.

[0052] Furthermore, the pressure intensifier is not limited to a hydraulic cylinder device, but may be a cylinder device driven by a fluid other than hydraulic pressure, or may be a cylinder device driven by a motor.

[0053] Next, a fluid pressure circuit according to a third embodiment will be described with reference to Fig. 3. Note that the description of the same configuration as in the second embodiment will be omitted.

[0054] 3, the piston diameters serving as the pressure-receiving surfaces of the cylinder devices 35 and 36 are different from those of the cylinder device 37. Specifically, the piston diameter D1 of the cylinder device 37 alone is smaller than the piston diameters D2, D2 of the cylinder devices 35 and 36 alone.

[0055] This makes it possible to efficiently increase the pressure of the oil flowing from the first oil chamber 37-1 of the cylinder device 37 toward the accumulator 310 when the cylinder devices 35, 36, and 37 are lowered.

[0056] Furthermore, since the cylinder device 37 can be made compact, the degree of freedom in mounting the cylinder device 37 is high.

[0057] Furthermore, since the return oil from the first oil chamber 37-1 of the cylinder device 37 can be increased to an extremely high pressure by the pressure booster 315 in addition to the small piston diameter D1 of the cylinder device 37, high-pressure oil can be stored in the accumulator 310. This makes it possible to regenerate oil using high-pressure stored oil in the small accumulator 310.

[0058] Although the third embodiment exemplifies a configuration in which the cylinder devices 35, 36, and 37 are pre-installed in the fluid pressure circuit 300, the cylinder device 37 may be additionally installed in an existing fluid pressure circuit in which the cylinder devices 35 and 36 are installed. In this case, by additionally installing the compact cylinder device 37 in the existing fluid pressure circuit, the pressure of the oil stored in the accumulator 310 can be increased.

[0059] Moreover, this embodiment 3 can also be applied to embodiment 1. For example, the cylinder device 37 and the pressure booster 315 of this embodiment 3 may be applied in place of the cylinder device 7 of embodiment 1.

[0060] Next, a fluid pressure circuit according to a fourth embodiment will be described with reference to Fig. 4. Note that the description of the same configuration as in the second embodiment will be omitted.

[0061] In the fluid pressure circuit 400 shown in FIG. 4, four cylinder devices 45 , 46 , 47 , and 48 are connected to a load 44 .

[0062] The cylinder device 48 has the same specifications as the cylinder devices 45, 46, and 47 and is arranged in parallel. The first oil chamber 48-1 of this cylinder device 48 is connected to the flow path 43 via a flow path 423-1′ and a check valve 8′.

[0063] The flow path 423-1′ is connected to a flow path 423-2 that extends from the flow path 423-1 of the cylinder device 47 to the flow dividing valve 49. That is, the first oil chamber 48-1 of the cylinder device 48 is connected to the accumulator 410 together with the first oil chamber 47-1 of the cylinder device 47.

[0064] This allows the accumulator 410 to store oil using two pressure-accumulating cylinder devices 47, 48, so that even if the return oil flow rate of each of the cylinder devices 47, 48 is small, a large total return oil flow rate can be secured.

[0065] The number of pressure accumulating cylinder devices provided may be three or more.

[0066] Moreover, the fourth embodiment can also be applied to the first and third embodiments. For example, the cylinder device 48 of the fourth embodiment may be added to the fluid pressure circuit 100 of the first embodiment and the fluid pressure circuit 200 of the third embodiment.

[0067] In addition, in the fourth embodiment, the pressure accumulation cylinder devices 47, 48 have the same specifications, but the piston head diameters of the plurality of pressure accumulation cylinder devices may be different. In this case, it is preferable to adjust the pressures introduced from the pressure accumulation cylinder devices to the accumulator so that they are the same using a pressure regulating valve or the like.

[0068] 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.

[0069] For example, in the first to fourth embodiments, a cylinder device is used as the driving unit, but this may be freely changed as long as it is an actuator that uses a fluid.

[0070] Furthermore, in the above-described Examples 1 to 4, a configuration in which one drive unit and another drive unit both drive the load upward is exemplified, but as long as at least the other drive unit drives the load upward, the one drive unit does not need to contribute to driving the load upward.

[0071] Furthermore, in Examples 1 to 3, the number of one drive unit is smaller than the number of other drive units, and in Example 4, a configuration is exemplified in which the number of one drive unit is the same as the number of other drive units, but the number of one drive units may be larger than the number of other drive units, as long as the number of drive units contributing to pressure accumulation is smaller than the number of drive units contributing to driving the load upward.

[0072] Furthermore, in the above-described first to fourth embodiments, the fluid pressure circuit has been described as a hydraulic circuit in which oil is pumped, but this is not limited thereto, and the working fluid may be a fluid other than oil, and the fluid to be applied may be changed as appropriate.

[0073] In addition, in the first to fourth embodiments, one drive unit is connected to the accumulator, and the other drive units are connected to the tank but not to the accumulator, but the return flow paths of all the drive units may be connected to the accumulator. For example, a flow path switching valve may be provided between each return flow path and the accumulator so that the connection destination of each return flow path can be selected as appropriate between the accumulator or the tank.

[0074] REFERENCE SIGNS LIST 1 Hydraulic pump 3 Switching valve 4 Load 5, 6 Cylinder device (another driving part) 5-1, 6-1 First oil chamber 5-2, 6-2 Second oil chamber 7 Cylinder device (one driving part) 7-1 First oil chamber 7-2 Second oil chamber 8, 8' Check valve 9 Accumulator switching valve 10 Accumulator (pressure accumulator) 11 Regenerative switching valve 14 Tank 23-2, 23-5 Flow path (return flow path) 100 Fluid pressure circuit

Claims

1. A hydraulic circuit comprising a plurality of driving units connected to a single load and a pressure accumulator capable of accumulating pressure, wherein a return flow path of at least one of the driving units is branched off and connected to the pressure accumulator.

2. A hydraulic circuit as claimed in claim 1, wherein the return flow passage of at least one of the driving sections is branched and connected to the pressure accumulator, and the return flow passages of the other driving sections are connected to the tank.

3. A fluid pressure circuit as claimed in claim 2, further comprising a pressure booster provided between the return flow path of said one driving section and said pressure accumulator.

4. The fluid pressure circuit according to claim 3, wherein a plurality of said driving sections are provided.

5. The fluid pressure circuit according to claim 2, wherein the size of the pressure receiving surface of said one driving portion is smaller than the size of the pressure receiving surface of said other driving portion.

6. The fluid pressure circuit according to claim 1, wherein the drive unit is a cylinder device.

7. The fluid pressure circuit according to claim 2, wherein the number of said one driving parts is smaller than the number of said other driving parts.

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