fluid circuit

Abstract

Provided is a fluid circuit that makes it possible to continuously drive an amplification device by means of a simple configuration.　A plurality of amplification devices 10, 10A are connected in parallel in a fluid supply device 6 that delivers a working fluid. The stroke directions of the pistons 120, 120A of each of the plurality of amplification devices 10, 10A are switched by the working fluid, and the phase of the piston 120 in one amplification device 10 is different from that of the piston 120A in the other amplification device 10A.

Description

Technical Field

[0005]

[0001] The present invention relates to a fluid circuit including a pressure boosting device for boosting a working fluid.

Background Art

[0002] In various fields, fluid circuits that drive an actuator using a working fluid such as hydraulic oil sent out from a fluid supply device such as a pump are known. Some of these fluid circuits operate the actuator with a pressure boosting device capable of sending out the boosted working fluid, or can store the boosted working fluid in an accumulator.

[0003] For example, the fluid circuit shown in Patent Document 1 includes a pump that sends out a working fluid, a tank in which the working fluid is stored, a pressure boosting device that can boost the working fluid, and an accumulator that can store the boosted working fluid. The pressure boosting device includes a cylinder having a T-shaped cross-section in front view and a hollow structure, a piston having a T-shaped cross-section in front view, and biasing means for biasing the piston in one axial direction. The piston is provided in the cylinder so as to be reciprocable in the axial direction.

[0004] The space in the cylinder is partitioned by the piston into a back pressure chamber and a pressure boosting chamber. A flow path communicating with the pump and a flow path communicating with the tank are connected to the back pressure chamber, and it is possible to switch whether to communicate with the pump or the tank by a switching valve. A flow path communicating with the tank side and a flow path communicating with the accumulator side are connected to the pressure boosting chamber. The piston has a larger area of the end face facing the back pressure chamber than the area of the end face facing the pressure boosting chamber.

[0005] In this fluid circuit configuration, when working fluid is stored in the pressure-boosting chamber, and working fluid is pumped from the pump into the back pressure chamber, the piston moves axially to the other side. This causes the piston to pressurize the working fluid in the pressure-boosting chamber. The working fluid, pressurized above a predetermined pressure, is then stored in the accumulator. By switching the valve position of the switching valve to connect the back pressure chamber and the tank, the pressurized oil in the back pressure chamber is discharged into the tank, and the pressure in the back pressure chamber gradually decreases. When the biasing force of the biasing means exceeds the force attempting to move the piston axially to the other side, the piston moves axially to the one side.

[0006] The pressure booster described above is what is known as a single-acting type. In contrast, there is also a known double-acting pressure booster that moves a piston back and forth by switching the chamber in the cylinder into which the working fluid flows, according to the valve position of the switching valve. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2011-185417 (page 7, Figure 1) [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] In a pressure boosting device like the one described in Patent Document 1, the valve position of a switching valve is switched according to the reciprocating motion of a piston, allowing for the continuous supply of pressurized working fluid to the accumulator. However, since such switching valves generally use electromagnetic switching valves that enable these switching operations via electrical signals, a device for outputting electrical signals, a device for sensing the valve position, etc., are required, which leads to a large overall size of the device. Furthermore, the control program becomes complex, posing a cost challenge.

[0009] This invention was made in view of these problems, and aims to provide a fluid circuit that can continuously drive a pressure boosting device with a simple configuration. [Means for solving the problem]

[0010] To solve the aforementioned problems, the fluid circuit of the present invention is: It comprises a fluid supply device for delivering working fluid and a pressure boosting device for increasing the pressure of the working fluid, The pressure boosting device comprises a cylinder connected to the fluid supply device and a piston provided in the cylinder so as to be reciprocable in the axial direction, and is a fluid circuit capable of discharging the pressurized working fluid from the cylinder by the working fluid supplied from the fluid supply device, as the piston moves toward the pressure boosting chamber in the cylinder by the working fluid supplied from the fluid supply device. Multiple pressure boosters are connected in parallel to the fluid supply device. The aforementioned multiple pressure boosting devices are configured such that the stroke direction of each piston is switched by the working fluid. At least one of the pistons in the pressure booster has a different phase from the pistons in the other pressure boosters. According to this, the fluid circuit allows each pressure booster to repeatedly move a piston back and forth using the working fluid. Furthermore, because the piston stroke timings of the multiple pressure boosters are staggered, the peak pressure of the working fluid delivered from the multiple pressure boosters is small. Therefore, the fluid circuit can reduce vibrations and noise generated when the working fluid pressure is increased.

[0011] Each of the pressure boosting devices is provided with a pilot switching valve that uses the working fluid supplied from the fluid supply device as the pilot fluid. The pressure boosting device may have its piston stroke direction switched according to the valve position of the corresponding pilot switching valve. According to this, the phases of the pistons in multiple pressure boosting devices can be made different with a simple configuration.

[0012] A throttle is positioned between the fluid supply device and the pilot switching valve, respectively. The aperture settings of at least one aperture may differ from those of the other apertures. According to this, the piston in at least one pressure booster can be phase-shifted relative to the piston in another pressure booster with a simple configuration.

[0013] The aperture may be a variable aperture. According to this, it is easy to adjust the timing of switching the valve position of the switching valve.

[0014] A pilot control valve is provided to switch the flow of pilot fluid in multiple pilot switching valves. The pilot control valve may be switched by the movement of a piston in one of the pressure boosting devices. According to this, the phase of the piston in one pressure booster is precisely shifted relative to the phase of the piston in another pressure booster.

[0015] The aforementioned multiple pressure boosting devices may have their respective pressure boosting chambers connected in parallel. According to this design, when the piston of one of the pressure boosters moves to its terminal position and stops, the peak pressure generated in the booster chamber of that booster can flow into the booster chamber of another booster. The other booster chamber acts as a buffer, dampening the pressure, thereby reducing the vibration and noise generated when the working fluid is pressurized in the fluid circuit. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram showing a fluid circuit equipped with a pressure boosting device according to Example 1 of the present invention. [Figure 2] This is a diagram illustrating the characteristics of a spool valve. [Figure 3] This is a schematic diagram illustrating the pressure boosting cycle of the working fluid by a pressure boosting device. [Figure 4] This is a schematic diagram illustrating the pressure boosting cycle of the working fluid by a pressure boosting device. [Figure 5] It is a schematic diagram for explaining the pressure boosting cycle of the working fluid by the pressure boosting device. [Figure 6] It is a schematic diagram for explaining the pressure boosting cycle of the working fluid by the pressure boosting device. [Figure 7] It is a schematic diagram for explaining the pressure boosting cycle of the working fluid by the pressure boosting device. [Figure 8] It is a schematic diagram for explaining the pressure boosting cycle of the working fluid by the pressure boosting device. [Figure 9] It is a schematic diagram for explaining the pressure boosting cycle of the working fluid by the pressure boosting device. [Figure 10] It is a schematic diagram for explaining the pressure boosting cycle of the working fluid by the pressure boosting device. [Figure 11] It is a diagram for explaining the change of the main part in the fluid circuit during the pressure boosting cycle. [Figure 12] It is a schematic diagram showing the fluid circuit provided with the pressure boosting device of Example 2 according to the present invention.

Embodiment for Carrying Out the Invention

[0017] The embodiment for carrying out the fluid circuit according to the present invention will be described below based on examples.

Example

[0018] The fluid circuit according to Example 1 will be described with reference to FIGS. 1 to 11.

[0019] As shown in FIG. 1, the fluid circuit is applicable to, for example, hydraulic devices such as actuators, brakes, steering, and transmissions in automobiles such as ordinary passenger cars and trucks, and work vehicles such as hydraulic excavators, forklifts, cranes, and garbage collection vehicles. The hydraulic circuit shown in FIG. 1 is an example of the fluid circuit of the present invention and is not limited to the configuration of FIG. 1.

[0020] In this embodiment, the fluid circuit is generally configured to use hydraulic pressure to operate a cylinder 5, which acts as an actuator, in order to move the workpiece W.

[0021] The fluid circuit mainly consists of a main circuit hydraulic pump 2, a switching valve 3, a hydraulic remote control valve 4, a cylinder 5, a pilot circuit hydraulic pump 6 as a fluid supply device, an electromagnetic switching valve 7, switching valves 8, 8A, adjustable slow return valves 9, 9A, pressure boosters 10, 10A, accumulators 11, 12, electromagnetic proportional switching valves 13, 14, a controller C, and various oil passages as flow paths.

[0022] First, the configuration of the main circuit for operating the cylinder 5 using the main circuit hydraulic pump 2 (hereinafter simply referred to as the main pump 2) will be explained. The main pump 2 and the pilot circuit hydraulic pump 6, which are driven by power from the drive mechanism 1 connected to the vehicle's engine or other drive mechanism 1, deliver pressurized oil to the oil passages 20 and 60.

[0023] Pressurized oil delivered from the main pump 2 through oil passages 20 and 21 flows into the switching valve 3.

[0024] The switching valve 3 is a 6-port, 3-position open-center type switching valve. When the switching valve 3 is in the neutral position, it connects the oil passage 21 to the tank-side oil passage 30. The tank-side oil passage 30 is connected to tank T. Therefore, the entire amount of pressurized oil delivered from the main pump 2 is discharged into tank T.

[0025] Furthermore, the switching valve 3, located in the extended position 3E, connects the oil passage 20 and the oil passage 22, which has a check valve, to the head-side oil passage 50, and the rod-side oil passage 51 to the tank-side oil passage 31. The head-side oil passage 50 is connected to the head chamber 5-1 in the cylinder 5. The rod-side oil passage 51 is connected to the rod chamber 5-2 in the cylinder 5. The tank-side oil passage 31 is connected to the tank T.

[0026] Furthermore, the switching valve 3 in the retracted position 3S connects oil passages 20 and 22 to the rod-side oil passage 51, and the head-side oil passage 50 to the tank-side oil passage 31.

[0027] Meanwhile, the pressurized oil supplied from the pilot circuit hydraulic pump 6 (hereinafter simply referred to as the pilot pump 6) is supplied to the hydraulic remote control valve 4 through the oil passage 60. The pressurized oil supplied to the hydraulic remote control valve 4 is not limited to the pressurized oil supplied from the pilot hydraulic pump, but may also be the working fluid supplied from the main pump 2 and cylinder 5, and may be changed as appropriate.

[0028] The variable pressure reducing valve, the hydraulic remote control valve 4, reduces the pressure oil at the pilot primary pressure supplied from the pilot pump 6 to the pilot secondary pressure according to the amount of operation of the operating lever 4-1. The pressure oil at the pilot secondary pressure is supplied to the signal ports 3-1 and 3-2 of the switching valve 3 through the pilot signal oil passages 40 and 41.

[0029] Furthermore, of the pressurized oil discharged from the pilot pump 6, any excess oil other than the hydraulic fluid that is not sent from the hydraulic remote control valve 4 to the signal ports 3-1 and 3-2, and is sent through the oil passage 61 to the first pressure booster 10 (described later), is discharged to the tank T through the relief oil passage 62 which has a relief valve.

[0030] The operation of the cylinder 5 in response to the operation of the hydraulic remote control valve 4 will be explained.

[0031] When the operating lever 4-1 is operated in the extension direction E, the switching valve 3 switches to the extension position 3E. Pressurized oil delivered from the main pump 2 flows into the head chamber 5-1 in the cylinder 5 through oil passages 20, 22, and 50. At the same time, pressurized oil in the rod chamber 5-2 is discharged to the tank T through oil passages 51 and 31. At this time, an electrical signal transmitted from the pressure sensor 42 installed on the pilot signal oil passage 40 is input to the controller C.

[0032] When the operating lever 4-1 is operated in the retraction direction S, the switching valve 3 switches to the retraction position 3S. Pressurized oil delivered from the main pump 2 flows into the rod chamber 5-2 of the cylinder 5 through oil passages 20, 22, and 51. At the same time, pressurized oil in the head chamber 5-1 is discharged to the tank T through oil passages 50 and 31. At this time, an electrical signal transmitted from the pressure sensor 43 installed on the pilot signal oil passage 41 is input to the controller C.

[0033] Furthermore, a relief oil passage 23, which has a relief valve, is branched off and connected to the oil passage 20. When the pressure in the oil passage 20 becomes abnormally high, the relief valve opens, and the pressurized oil is discharged from the relief oil passage 23 to the tank T.

[0034] Next, the configuration of the pilot circuit side, which is connected to the pilot pump 6 and includes the first pressure booster 10, will be described. Note that the oil passage 60, hydraulic remote control valve 4, pilot signal oil passages 40, 41, and relief oil passage 62 mentioned above are included in the configuration of the pilot circuit side.

[0035] An electromagnetic switching valve 7 is provided in oil passage 61, which is branched off from oil passage 60. When switch 15 is in the OFF position, the electromagnetic switching valve 7 shuts off oil passage 61 and oil passage 70.

[0036] Furthermore, when switch 15 is turned ON, the electromagnetic switching valve 7, which receives an electrical signal from controller C through the electrical signal line 72, connects oil passage 61 and oil passage 70.

[0037] The oil passage 70 is provided with a first switching valve 8, which acts as a single switching valve. The first switching valve 8 is a pilot switching valve that switches the oil passage to which it is connected according to the pressure acting on port 8-1. If the pressure acting on port 8-1 is less than a predetermined value, the first switching valve 8 connects oil passages 70 and 80. If the pressure acting on port 8-1 is equal to or greater than the predetermined value, the first switching valve 8 connects oil passages 80 and 81. Oil passage 80 is connected to the back pressure chamber 10-1 of the first pressure booster 10, which will be described later. The tank-side oil passage 81 is connected to tank T.

[0038] Furthermore, a branch oil passage 73 is connected to the oil passage 70. A second switching valve 8A is provided in the branch oil passage 73 as another switching valve. The second switching valve 8A has substantially the same configuration as the first switching valve 8. If the pressure acting on port 8A-1 is less than a predetermined value, the second switching valve 8A connects oil passages 73 and 82. If the pressure acting on port 8-1 is equal to or greater than a predetermined value, the second switching valve 8A connects oil passages 82 and 83. Oil passage 82 is connected to the back pressure chamber 10A of the second pressure booster 10A, which will be described later. The tank-side oil passage 83 is connected to tank T.

[0039] A first pressure booster 10 is provided in the oil passage 80. The first pressure booster 10 is for further increasing the pressure of the pressurized oil sent from the pilot pump 6 and sending it to the oil passage 100. A check valve 100R is provided in the oil passage 100.

[0040] A second pressure booster 10A is provided in oil passage 82. The second pressure booster 10A further increases the pressure of the pressurized oil sent from the pilot pump 6 and sends it to oil passage 100A. Oil passage 100A is branched and connected to oil passage 100. That is, the pressure boosting chamber 10-2 in the first pressure booster 10 and the pressure boosting chamber 10A-2 in the second pressure booster 10A are connected in parallel by oil passages 100 and 100A. The configuration of pressure boosters 10 and 10A will be described later.

[0041] Oil passage 100 is branched and connected to oil passage 101, which has two check valves, and oil passage 102, which has another two check valves.

[0042] In the oil passage 101, an accumulator 11 and a pressure sensor 103 for detecting the pressure of the accumulator 11 are connected between two check valves. Furthermore, an electromagnetic proportional switching valve 13 is connected downstream of the two check valves in the oil passage 101.

[0043] In the oil passage 102, an accumulator 12 and a pressure sensor 104 that detects the pressure of the accumulator 12 are connected between two check valves. Furthermore, an electromagnetic proportional switching valve 14 is connected downstream of the two check valves in the oil passage 102.

[0044] The electromagnetic proportional switching valves 13 and 14 are of the normally closed type and are connected to controller C by an electrical signal line.

[0045] Based on the electrical signals input from pressure sensors 42, 43, 103, and 104, controller C controls the electromagnetic proportional control valves 13 and 14 to either a closed or open state. The following explanation will use electromagnetic proportional control valve 13 as an example.

[0046] The electromagnetic proportional switching valve 13 closes when an electrical signal is received from the controller C when the pressure inside the accumulator 11 decreases. This allows the accumulator 11 to store the pressurized oil that has been pressurized and delivered from the first pressure booster 10.

[0047] Furthermore, when the pressure in the accumulator 11 increases, the controller C inputs an electrical signal to the electromagnetic proportional switching valve 13. The electromagnetic proportional switching valve 13 connects the oil passages 101 and 105 with an opening degree corresponding to the input signal. As a result, the accumulated oil discharged from the accumulator 11 is regenerated in the head chamber 5-1 of the cylinder 5 via the oil passages 107 and 50.

[0048] Furthermore, by alternately switching the electromagnetic proportional switching valves 13 and 14 using controller C, the fluid circuit can store pressure in one of the accumulators 11 and 12 while regenerating the pressurized oil stored in the other to the main circuit.

[0049] Furthermore, a relief oil passage 108, which has a relief valve, is branched and connected to the oil passage 100. When the accumulated oil in the accumulators 11 and 12 reaches its capacity, the excess oil is discharged to the tank T through the relief oil passage 108.

[0050] Next, the pressure boosters 10 and 10A will be described. Since the second pressure booster 10A has almost the same configuration as the first pressure booster 10, redundant explanations will be omitted or simplified. In this embodiment, the spring 140 side of the first pressure booster 10 will be described as the end position side (i.e., the lower side in the figure), and the opposite side as the start position side (i.e., the upper side in the figure). These start and end positions are the positions of the piston 120, which will be described later.

[0051] As shown in Figure 1, the first pressure booster 10 mainly consists of a case 110 as a cylinder, a piston 120, a control valve 130, a spring 140 as a biasing means, and a rod 150. The piston 120 is provided within the case 110 so as to be movable in the axial direction. The spring 140 biases the piston 120 toward the starting position.

[0052] The case 110 is formed in a stepped cylindrical shape that is roughly T-shaped when viewed from the front, and has a large diameter cylindrical portion 111 and a small diameter cylindrical portion 112.

[0053] An oil passage 80 is connected to the large-diameter cylindrical section 111 on the starting end side, and an oil passage 100 is connected to the outer diameter side of the small-diameter cylindrical section 112 at the ending end.

[0054] An oil passage 113, which is connected to the tank T, is connected to the circumferential wall of the small-diameter cylindrical portion 112.

[0055] The piston 120 is formed in a stepped cylindrical shape that is T-shaped when viewed from the front, and has a large diameter portion 121 and a small diameter portion 122.

[0056] The large-diameter portion 121 is formed so that its outer circumferential surface can slide along the inner circumferential surface of the large-diameter cylindrical portion 111 of the case 110. The small-diameter portion 122 is formed so that its outer circumferential surface can slide along the inner circumferential surface of the small-diameter cylindrical portion 112 of the case 110.

[0057] The case 110, which houses the piston 120, has a large diameter cylindrical portion 111 in which the space is defined as a back pressure chamber 10-1 and a pressure boosting chamber 10-2 by the large diameter portion 121 of the piston 120.

[0058] The back pressure chamber 10-1 is faced by the back pressure surface 121a of the large diameter portion 121 of the piston 120. The pressure boosting chamber 10-2 is faced by the annular pressure boosting surface 121b of the large diameter portion 121 of the piston 120.

[0059] An oil passage 80 is connected to the back pressure chamber 10-1, and an oil passage 100 is connected to the pressure boosting chamber 10-2. In addition, a spacer is installed and fixed at the starting end side of the back pressure chamber 10-1 to restrict the movement of the piston 120.

[0060] Furthermore, the back pressure chamber 10-1 and the pressure boosting chamber 10-2 are connected by an oil passage 123 that penetrates the large-diameter portion 121 of the piston 120. The oil passage 123 has a check valve.

[0061] Furthermore, the drain chamber 10-3 is defined by the small-diameter cylindrical portion 112 of the case 110 and the small-diameter portion 122 of the piston 120. The drain oil passage 113 is connected to the drain chamber 10-3.

[0062] The piston 120 is configured to reciprocate between a starting position and an ending position. The starting position is the position where the back pressure surface 121a of the large diameter portion 121 abuts against the spacer in the back pressure chamber 10-1, restricting movement in that direction. The ending position is the position where the end face on the ending position side of the small diameter portion 122 abuts against the inner surface on the ending position side of the drain chamber 10-3, restricting movement in that direction.

[0063] The control valve 130 is a pilot control valve as defined herein, which controls the pilot pressure to ports 8-1 and 8A-1 of the switching valves 8 and 8A, respectively.

[0064] A rod 150 is positioned between the piston 120 and the control valve 130. The rod 150 passes through the bottom of the small-diameter cylindrical portion 112 of the case 110. The piston 120 and the control valve 130 are kept in contact with the rod 150 by the force received from the pressure acting on the back pressure surface 121a of the large-diameter portion 121 of the piston 120 and the biasing force of the spring 140.

[0065] The piston 120 and the control valve 130 may be integrated by, for example, by welding the rod 150 to one or both of the piston 120 and the control valve 130.

[0066] As shown in Figures 1 and 2, the control valve 130 is connected to drain oil passages 131 and 134, pilot oil passages 132 and 135, and pilot oil passages 133 and 136.

[0067] The first drain oil passage 131 and the second drain oil passage 134 are connected to tank T. The first pilot oil passage 132 is connected to port 8-1 of the first switching valve 8. The second pilot oil passage 135 is connected to port 8A-1 of the second switching valve 8A. The first pilot oil passage 133 and the second pilot oil passage 136 are branched and connected to oil passage 70.

[0068] The control valve 130 is configured such that its opening degree increases or decreases in accordance with the stroke of the piston 120, affecting the drain oil passages 131 and 134 and the pilot oil passages 133 and 136. Furthermore, the control valve 130 is always open to approximately a constant degree relative to the pilot oil passages 132 and 135. The detailed operation of the control valve 130 will be described later.

[0069] As shown in Figure 1, the first pilot oil passage 132 is equipped with a first adjustable slow return valve 9, which has a first variable throttle 90 and a first check valve 92 connected in parallel to the first variable throttle 90.

[0070] Furthermore, the second pilot oil passage 135 is also equipped with a second adjustable slow return valve 9A, which has a second variable throttle 90A and a second check valve 92A connected in parallel to the second variable throttle 90A.

[0071] Furthermore, the first variable aperture 90 has a narrower opening than the second variable aperture 90A.

[0072] The second pressure booster 10A mainly consists of a case 110A, a piston 120A, a spring 140A, and a rod 150A, and has the same configuration as the first pressure booster 10 except that it does not have a control valve 130.

[0073] In the second pressure booster 10A, the piston 120A divides the space within the large-diameter cylindrical portion 111 of the case 110A into a back pressure chamber 10A-1 and a pressure boosting chamber 10A-2.

[0074] Oil passage 82 is connected to back pressure chamber 10A-1. Oil passage 101 is connected to pressure boosting chamber 10A-2. Drain oil passage 113A is connected to drain chamber 10A-3.

[0075] The rod 150A, which penetrates the bottom of the small-diameter cylindrical portion 112 of the case 110A, is kept in contact with the piston 120A by the force received from the pressure acting on the back pressure surface 121aA of the piston 120A and the biasing force of the spring 140A.

[0076] Next, the pressure boosting cycle using the pressure boosters 10 and 10A will be explained using Figures 1 to 11. As mentioned above, the pressure boosters 10 and 10A have almost the same configuration and their operation is similar, so redundant explanations will be omitted or simplified. Also, the pressure boosters 10 and 10A and each oil passage in Figures 3 to 10 are schematic diagrams. Furthermore, the pressure boosters 10 and 10A are so-called single-acting pressure boosters.

[0077] First, let's describe the state before the pressure boosting by the pressure boosting devices 10 and 10A is started. As shown in Figure 1, switch 15 is in the OFF position, and the electromagnetic switching valve 7 is shutting off the oil passages 61 and 70.

[0078] In the pressure boosting device 10 before the start of pressure boosting, the piston 120 is positioned at the starting end within the case 110.

[0079] The pressure booster 10 has oil stored in the back pressure chamber 10-1, the pressure booster chamber 10-2, and the drain chamber 10-3, and its pressure is approximately the same as that of the oil stored in the tank T which is open to the outside.

[0080] As shown in Figure 2, when the piston 120 has reached its starting position, the control valve 130 is at its maximum opening on the drain oil passages 131 and 134 side, and at zero opening, i.e., fully closed, on the pilot oil passages 133 and 136 side.

[0081] As a result, the control valve 130 is connected to oil passages 131 and 132. Port 8-1 of the first switching valve 8 is subjected to a pressure approximately the same as that of the oil in tank T. The first switching valve 8 is connected to oil passages 70 and 80. This pressure is the initial value in this embodiment (see Figure 11) and is smaller than the predetermined value at which the position of the switching valve 8 switches.

[0082] Similarly, the control valve 130 is connected to oil passages 134 and 135. Port 8A-1 of the second switching valve 8A is subjected to approximately the same pressure as the oil in tank T. The second switching valve 8A is connected to oil passages 73 and 82.

[0083] To start the pressure boosting by the pressure boosters 10 and 10A, switch 15 is turned ON. This causes the electromagnetic switching valve 7 to connect the oil passages 61 and 70, and as shown in Figure 3, a portion of the pressurized oil sent from the pilot pump 6 passes through oil passage 70, the first switching valve 8, and oil passage 80 to be sent to the back pressure chamber 10-1 of the first pressure booster 10.

[0084] Here, the back pressure surface 121a of the piston 120, which is the effective pressure-receiving area of ​​the back pressure chamber 10-1, has a larger area than the pressure-increasing surface 121b of the piston 120, which is the effective pressure-receiving area of ​​the pressure-increasing chamber 10-2.

[0085] As a result, in the back pressure chamber 10-1, a pressing force is generated by multiplying the fluid pressure of the pressurized oil delivered from the pilot pump 6 by the area of ​​the back pressure surface 121a, which pushes the piston 120 toward the terminal position.

[0086] Consequently, the pressurized oil in the pressure-increasing chamber 10-2 is increased to a pressure calculated by dividing the pressing force by the area of ​​the pressure-increasing surface 121b, and is sequentially sent towards the oil passage 100 as the piston 120 moves.

[0087] In this explanation, the oil pressure in the drain chamber 10-3 remains approximately constant regardless of the movement of the piston 120, and since it repeatedly flows in and out with the movement of the piston 120, its explanation is omitted.

[0088] Also, similar to the first pressure booster 10, the working fluid is also sent to the back pressure chamber 10A-1 of the second pressure booster 10A by passing through the branch oil passage 73, the second switching valve 8A, and the oil passage 82. As a result, in the second pressure booster 10A as well, the pressurized oil in the pressure booster chamber 10A-2 is sequentially sent towards the oil passage 100A as the piston 120A moves.

[0089] As shown in Figure 11, the pistons 120 and 120A in the pressure boosters 10 and 10A move at approximately the same speed.

[0090] As shown in Figure 2, when the piston 120 in the first pressure booster 10 begins to move from the starting position to the ending position, the control valve 130 begins to displace from the minimum stroke st0 to the maximum stroke st5. From stroke st1 onward, the control valve 130 narrows the opening on the first drain oil passage 131 side and widens the opening on the first pilot oil passage 133 side in accordance with the stroke of the piston 120.

[0091] Then, the control valve 130 from stroke st2 onward opens wider on the first pilot oil passage 133 side than on the first drain oil passage 131 side. As a result, the pilot fluid is loaded into port 8-1 of the first switching valve 8 after passing through the first variable throttle 90 (see Figure 11). In addition, the control valve 130 from stroke st2 onward narrows the opening on the second drain oil passage 134 side and widens the opening on the second pilot oil passage 136 side.

[0092] Furthermore, as the piston 120 moves, the control valve 130 from stroke st3 onwards sets the opening degree on the first drain oil passage 131 side to zero, i.e., fully closed, and the opening degree on the first pilot oil passage 133 side to maximum, i.e., fully open. Also, the control valve 130 from stroke st4 onwards sets the opening degree on the second drain oil passage 134 side to fully closed and the opening degree on the first pilot oil passage 136 side to fully open.

[0093] Incidentally, the opening of the first variable aperture 90 is sufficiently narrower than that of the second variable aperture 90A (see Figure 3). As a result, the pilot fluid pressure acting on port 8A-1 of the second switching valve 8A reaches a predetermined value or higher at an earlier timing than the pilot fluid pressure acting on port 8-1 of the first switching valve 8 (see Figure 11).

[0094] Therefore, before the piston 120 reaches its terminal position, the pilot fluid pressure acting on port 8A-1 of the second switching valve 8A becomes greater than or equal to a predetermined value (see Figure 11). As a result, the second switching valve 8A switches to the operating position, as shown in Figure 4, and connects the oil passages 82 and 83.

[0095] As a result, the pressurized oil in the back pressure chamber 10A-1 of the second pressurizing device 10A is discharged to the tank T through the oil passage 82, the second switching valve 8A, and the tank-side oil passage 83.

[0096] Subsequently, the pilot fluid pressure acting on port 8A-1 becomes approximately the same as the pressure of the pressurized oil supplied from the pilot pump 6 (see Figure 11).

[0097] Then, as the pressure in the back pressure chamber 10A-1 decreases, the biasing force of the spring 140A (see Figure 1) causes the piston 120A to begin moving toward its starting position. As this piston 120A moves, some of the oil in the back pressure chamber 10A-1 flows through the oil passage 123A into the pressure boosting chamber 10A-2.

[0098] As shown in Figure 5, as the piston 120A in the second pressure booster 10A moves toward the starting position, the first pressure booster 10 causes the small-diameter portion 122 of the piston 120 to come into contact with the bottom of the small-diameter cylindrical portion 112 in the case 110. As a result, the piston 120 reaches its terminal position and its movement is restricted. At this time, a small volume is maintained in the pressure boosting chamber 10-2. That is, the small-diameter portion 122 of the piston 120 and the small-diameter cylindrical portion 112 in the case 110 function as spacers.

[0099] As described above, the pressure boosters 10 and 10A are connected in parallel to the oil passage 70. As a result, the amount of pressurized oil flowing into each pressure booster 10 and 10A per unit time is reduced compared to a configuration in which the compression efficiency per unit time achieved by the combined action of the pressure boosters 10 and 10A is achieved with a single pressure booster. Therefore, the peak pressure generated in the pressure boosters 10 and 10A when either piston 120 or 120A reaches its terminal position or stops is relatively reduced.

[0100] Furthermore, the pressure-boosting chamber 10-2 in the first pressure booster 10 and the pressure-boosting chamber 10A-2 in the second pressure booster 10A are connected in parallel via oil passages 100 and 100A, allowing them to communicate with each other. As a result, when the piston 120 in the first pressure booster 10 is stopped, the pressure-boosting chamber 10A-2 in the second pressure booster 10A functions as a buffer. Similarly, when the piston 120A in the second pressure booster 10A is stopped, the pressure-boosting chamber 10-2 in the first pressure booster 10 functions as a buffer. In this way, the fluid circuit can reduce vibrations and noise generated when the pressurized oil is increased.

[0101] Subsequently, when the pilot fluid pressure acting on port 8-1 of the first switching valve 8 exceeds a predetermined value, the first switching valve 8 switches to the operating position, connecting the oil passages 80 and 81. As a result, the pressurized oil in the back pressure chamber 10-1 of the first pressure booster 10 is discharged to the tank T through the oil passage 80, the first switching valve 8, and the tank-side oil passage 81.

[0102] Then, as the pressure in the back pressure chamber 10-1 decreases, the biasing force of the spring 140 causes the piston 120 to begin moving toward the starting position. Consequently, the control valve 130 begins to displace from the maximum stroke st5 toward the minimum stroke st0.

[0103] As the piston 120 moves toward its starting position, some of the oil in the back pressure chamber 10-1 flows through the oil passage 123 into the pressure boosting chamber 10-2.

[0104] Referring to Figure 6, the piston 120A in the second pressure booster 10A reaches its starting position before the piston 120 in the first pressure booster 10. On the other hand, the piston 120 in the first pressure booster 10 is in the process of moving toward its starting position.

[0105] Incidentally, the control valve 130 from stroke st4 onwards widens the opening on the second drain oil passage 134 side and narrows the opening on the second pilot oil passage 136 side in accordance with the stroke of the piston 120.

[0106] Furthermore, the control valve 130 from stroke st3 onward opens wider on the second drain oil passage 134 side than on the second pilot oil passage 136 side. As a result, pilot fluid is discharged to tank T through the second variable throttle 90A and the second check valve 92A. In addition, the control valve 130 from stroke st3 onward widens the opening on the first drain oil passage 131 side and narrows the opening on the first pilot oil passage 133 side.

[0107] Furthermore, as the piston 120 moves, the control valve 130 from stroke st2 onwards fully opens on the second drain oil passage 134 side and fully closes on the first pilot oil passage 133 side. Also, the control valve 130 from stroke st1 onwards fully opens on the first drain oil passage 131 side and fully closes on the first pilot oil passage 133 side.

[0108] Therefore, as shown in Figure 6, after the piston 120A in the second pressure booster 10A reaches its starting position, the pilot fluid pressure acting on port 8A-1 of the second switching valve 8A falls below a predetermined value (see Figure 11). As a result, the second switching valve 8A switches to its initial position, connecting the oil passages 73 and 82 (see Figure 11). In other words, the piston 120A in the second pressure booster 10A begins to move toward the terminal position earlier than the piston 120 in the first pressure booster 10 reaches its starting position.

[0109] In this manner, the timing of the valve position switching of the control valve 130, the flow path cross-sectional area of ​​the oil passages 134 and 135, and the opening degree of the second check valve 92A are adjusted so that, after the piston 120A in the second pressure booster 10A reaches its starting position, the pilot fluid pressure acting on port 8A-1 in the second switching valve 8A falls below a predetermined value.

[0110] Furthermore, when the second drain oil passage 134 and the pilot oil passage 135 are connected, the second check valve 92A, which has a wider opening than the second variable throttle 90A, is opened. As a result, the second switching valve 8A switches from the operating position to the initial position in a shorter time than the time it takes to switch from the initial position to the operating position. In other words, compared to a configuration in which the throttle opening and the flow path cross-sectional area in the pilot flow path on the first switching valve 8 side and the second switching valve 8A side are simply different, the adjustable slow return valves 9 and 9A can increase the number of strokes per unit time.

[0111] In this embodiment, as shown in Figure 11, it is explained that the speed at which pistons 120 and 120A move from the end position to the starting position is faster than the speed at which pistons 120 and 120A move from the starting position to the end position. However, the speeds at which pistons 120 and 120A move may be the same.

[0112] Subsequently, as shown in Figure 7, the piston 120 in the first pressure booster 10 reaches its starting position. Also, the pilot fluid pressure acting on port 8-1 of the first switching valve 8 falls below a predetermined value (see Figure 11). As a result, the first switching valve 8 switches to its initial position, connecting the oil passages 70 and 80.

[0113] As shown in Figure 8, the piston 120A in the second pressure booster 10A reaches its terminal position before the piston 120 in the first pressure booster 10. The piston 120A in the second pressure booster 10A waits at the starting position until the valve position of the control valve 130 switches and the valve position of the second switching valve 8A switches from the initial position to the operating position (see Figure 11).

[0114] As shown in Figure 9, the piston 120A in the second pressure booster 10A begins to move toward the starting position when the valve position of the control valve 130 is switched and the valve position of the second switching valve 8A is switched to the operating position (see Figure 11).

[0115] As shown in Figure 10, the first pressure booster 10 begins to move toward the starting position when its piston 120 reaches the terminal position and the valve position of the first switching valve 8 switches to the operating position (see Figure 11).

[0116] Subsequently, as long as switch 15 remains ON, the cycle shown in Figures 6 to 10 can be repeated. In other words, the first pressure booster 10 and the second pressure booster 10A can be continuously driven using fluid pressure.

[0117] Furthermore, by turning switch 15 to the OFF position, the electromagnetic switching valve 7 connects oil passages 61 and 70, as shown in Figure 1. As a result, back pressure chambers 10-1 and 10A-1 are connected to tank T. Therefore, pistons 120 and 120A both move toward their starting positions and stop at those positions.

[0118] As described above, the fluid circuit of this embodiment utilizes the working fluid and, through the cooperation of the switching valves 8, 8A and the control valve 130, which operate by fluid pressure, the two pistons 120, 120A can be repeatedly moved back and forth. In other words, high fluid pressure can be continuously generated without electrical control. This eliminates the need for conventional electrical control and simplifies the configuration of the fluid circuit.

[0119] Furthermore, the two pressure boosters 10 and 10A have staggered stroke timings for their pistons 120 and 120A. In other words, pistons 120 and 120A are prevented from reaching their terminal positions at the same time. As a result, the peak pressure of the pressurized oil delivered from the two pressure boosters 10 and 10A is reduced. Therefore, the fluid circuit can reduce vibrations and noise generated when the oil is pressurized.

[0120] Furthermore, the fluid circuit can be configured to have different phases for the two pistons 120 and 120A by using switching valves 8 and 8A, which switch valve positions using oil as a pilot fluid, to switch the stroke direction of the corresponding pistons 120 and 120A.

[0121] Furthermore, with a simple configuration in which the variable apertures 90 and 90A have different opening degrees, the fluid circuit can shift the phase of pistons 120 and 120A.

[0122] Furthermore, in order to differentiate the phase of the strokes of the two pistons 120 and 120A, adjustments made according to errors in each component when the fluid circuit is first used, and subsequent adjustments made according to temperature, atmospheric pressure, aging, etc., can be achieved in the fluid circuit by adjusting the opening degree of the variable throttles 90 and 90A. Therefore, the fluid circuit makes it easy to adjust the timing of switching the valve positions of the switching valves 8 and 8A.

[0123] Furthermore, for example, if each pressure booster is equipped with a control valve whose valve position switches in accordance with the stroke of its individual piston, it is conceivable that the timing at which one control valve switches relative to the other may change due to aging deterioration, external forces, etc. In contrast, in the fluid circuit of this specification, the control valve 130 switches in accordance with the stroke of the piston 120 in the first pressure booster 10. Therefore, even if the timing at which the valve position of the control valve 130 switches changes, the effect is the same in both the pressure boosters 10 and 10A. As a result, the phase of the piston 120 in the second pressure booster 10A is precisely shifted relative to the piston 120 in the first pressure booster 10. [Examples]

[0124] Next, the fluid circuit according to Example 2 will be described with reference to Figure 12. Note that components identical to those shown in Example 1 are denoted by the same reference numerals, and redundant explanations are omitted.

[0125] As shown in Figure 12, the first adjustable slow return valve 9 includes a first check valve 92' which is opened when the first pilot oil passages 132 and 133 are connected. Similarly, the second adjustable slow return valve 9A also includes a first check valve 92A' which is opened when the second pilot oil passages 135 and 136 are connected.

[0126] Furthermore, when the piston 120 moves from the starting position to the ending position, the control valve 130 first connects the second pilot oil passages 135 and 136, and then connects the first pilot oil passages 132 and 133.

[0127] As a result, pressurized oil delivered from the pilot pump 6 flows into the second pilot oil passage 135 before the first pilot oil passage 132. Therefore, the second switching valve 8A switches to the operating position earlier than the first switching valve 8.

[0128] Furthermore, when the piston 120 moves from the terminal position to the starting position, the control valve 130 first connects the first drain oil passage 131 to the first pilot oil passage 132, and then connects the second drain oil passage 134 to the second pilot oil passage 135.

[0129] As a result, the time required for the pilot fluid pressure to fall below a predetermined value is longer in the first pilot oil passage 132, where the first variable throttle 90 has a sufficiently narrower opening than the second variable throttle 90A, than in the second pilot oil passage 135, where the second variable throttle 90A is located. Therefore, the second switching valve 8A switches to its initial position earlier than the first switching valve 8.

[0130] Thus, the configuration of the adjustable slow return valves 9, 9A and the control valve 130 may be changed as appropriate.

[0131] Although embodiments of the present invention have been described above with reference to the drawings, the specific configurations are not limited to these embodiments, and any changes or additions that do not depart from the spirit of the present invention are also included.

[0132] For example, in the above embodiment, the working fluid was described as oil, but it is not limited to this; any fluid will suffice, and it may be changed as appropriate.

[0133] Furthermore, although the above embodiment was described as having a configuration with two pressure boosting devices, it is not limited to this, and there may be three or more. With such a configuration, the piston in at least one of the multiple pressure boosting devices can be moved from the starting position to the ending position, thereby preventing the generation of peak pressure.

[0134] In the above embodiment, each pressure booster was described as single-acting, but it is not limited to this and may be double-acting. With such a configuration, when the piston is in stroke, the working fluid delivered from the fluid supply device will always flow into one of the pressure boosters, thus preventing the generation of peak pressure. In addition, since only two pressure boosters are required, the fluid circuit can be made compact.

[0135] Furthermore, although the configuration described assumes that the two pressure boosters are connected to corresponding switching valves, the system is not limited to this configuration. For example, in a configuration with three or more pressure boosters, the stroke direction of each piston may be switched by a common switching valve between two of the pressure boosters.

[0136] Furthermore, although the above embodiment was described as having two accumulators arranged downstream of the pressure booster, the configuration is not limited to this, and there may be one accumulator or three or more.

[0137] Furthermore, although the above embodiment described a configuration in which the control valve may connect the flow path on the pump side and the flow path on the drain side to the flow path on the switching valve side at the same time, the configuration is not limited to this, and it may also be configured in which only one of the flow paths on the pump side or the drain side is connected to the flow path on the switching valve side.

[0138] Furthermore, although the above embodiment described the control valve as having a configuration in which the timing at which the opening degree of the first pressure booster reaches its maximum or zero is different from the timing at which the opening degree of the second pressure booster reaches its maximum or zero, it is not limited to this configuration and may occur simultaneously.

[0139] Furthermore, although the above embodiment described a configuration in which the strokes of the two pistons are in different phases according to the opening degree of the throttle, the method for differentiating the phases of the strokes of the two pistons may be appropriately changed, such as by differentiating the opening degree of the control valve, the maximum stroke of each switching valve, the volume of the oil passage connected to each port of the switching valve, the volume of the cylinder in each pressure booster, the maximum stroke of the piston in each pressure booster, or the biasing force of the biasing means that returns each switching valve to its initial position.

[0140] Furthermore, although the throttle was described in the above embodiment as having the configuration of an adjustable slow return valve, it is not limited to this, and the throttle may be a non-variable throttle, various valves with adjustable flow path cross-sectional area, or configurations in which the flow path cross-sectional area is different, and may be changed as appropriate.

[0141] Furthermore, although the fluid supply device in the above embodiment was described as a hydraulic pump for the pilot circuit, it is not limited to this and may be a hydraulic pump for the main circuit, an actuator, an accumulator, etc., and may be changed as appropriate.

[0142] Furthermore, although the above embodiment described the pressurized oil delivered from the pressure booster as being delivered to an accumulator, the configuration is not limited to this, and it may also be delivered to an actuator.

[0143] Furthermore, the shapes of the case and piston are not limited to those described in the above embodiment; the shapes of the case and piston may be changed as appropriate, as long as there is a difference in the effective pressure-receiving area.

[0144] Furthermore, although the biasing means in Examples 1 and 2 was described as being a spring, it is not limited to this and may be changed as appropriate to a magnet or the like. [Explanation of symbols]

[0145] 1. Drive mechanism 6. Hydraulic pump for pilot circuit (fluid supply device) 8. First switching valve (pilot switching valve) 8A Second switching valve (pilot switching valve) 9. First adjustable slow return valve 9A Second adjustable slow return valve 10. First pressure booster (first pressure booster) 10-1 Back pressure chamber 10-2 Pressure Boosting Chamber 10A Second pressure booster (other pressure booster) 10A-1 Back pressure chamber 10A-2 Pressure Boosting Chamber 11,12 Accumulator 90,90A Variable aperture 110, 110A Case (Cylinder) 120, 120A Piston T Tank Double job

Claims

1. It comprises a fluid supply device for delivering working fluid and a pressure boosting device for increasing the pressure of the working fluid, The pressure boosting device comprises a cylinder connected to the fluid supply device and a piston provided in the cylinder so as to be reciprocable in the axial direction, and is a fluid circuit capable of discharging the pressurized working fluid from the cylinder by the working fluid supplied from the fluid supply device, as the piston moves toward the pressure boosting chamber in the cylinder by the working fluid supplied from the fluid supply device. Multiple pressure boosters are connected in parallel to the fluid supply device. The aforementioned multiple pressure boosting devices are configured such that the stroke direction of each piston is switched by the working fluid. At least one of the pistons in the pressure booster has a different phase from the pistons in the other pressure boosters. Each of the pressure boosting devices is provided with a pilot switching valve that uses the working fluid supplied from the fluid supply device as the pilot fluid. The pressure boosting device is a fluid circuit in which the stroke direction of the piston is switched according to the valve position of the corresponding pilot switching valve.

2. A throttle is positioned between the fluid supply device and the pilot switching valve, respectively. The fluid circuit according to claim 1, wherein the opening of at least one aperture and the other apertures are different.

3. The fluid circuit according to claim 2, wherein the aperture is a variable aperture.

4. A pilot control valve is provided to switch the flow of pilot fluid in multiple pilot switching valves. The fluid circuit according to any one of claims 1 to 3, wherein the pilot control valve is switched by the movement of a piston in one of the pressure boosting devices.

5. The fluid circuit according to claim 1, wherein the plurality of pressure boosting devices are connected in parallel to each other's pressure boosting chambers.

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