Fluid circuit

Abstract

Provided is a fluid circuit capable of continuously driving an amplifier with a simple configuration.　The present invention comprises: a first switching valve 8 for switching between flow paths 70, 80 and first flow paths 80, 81 in accordance with a change in fluid pressure to be applied; a second switching valve 130 for switching a flow path that applies a fluid pressure to the first switching valve 8 when a piston 120 reaches a starting end position or reaches a terminating end position; and second flow paths 123, 125. A biasing force FS2 of a biasing means 140 exerted when the piston 120 reaches the terminating end position is smaller than a pressing force FH1 exerted on the piston 120 due to a fluid pressure by a fluid supply device 6, and a biasing force FS1 of the biasing means 140 exerted when the piston 120 reaches the starting end position is larger than a sum of a flow path resistance R1 exerted on the first flow paths 80, 81 and a flow path resistance R2 exerted on the second flow paths 123, 125.

Description

[Technical field]

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

[0002] In various fields, there are known fluid circuits that drive actuators using hydraulic fluid such as hydraulic oil delivered from a fluid supply device such as a pump. Some of these fluid circuits include a booster device capable of delivering pressurized hydraulic fluid, and the actuator is operated by the hydraulic fluid of the booster device, while others accumulate pressure in an accumulator.

[0003] For example, the fluid circuit shown in Patent Document 1 is mainly composed of a pump, a tank, a booster, and an accumulator. The booster includes a cylinder, a piston, and a biasing means. The cylinder has a hollow structure that is T-shaped when viewed from the front. The piston is T-shaped when viewed from the front, and is provided within the cylinder so as to be capable of reciprocating in the axial direction. The biasing means biases the piston to one side in the axial direction.

[0004] The space within the cylinder is divided by the piston into a back pressure chamber and a booster chamber. The pressure-receiving area of ​​the end face of the piston facing the back pressure chamber is larger than the pressure-receiving area of ​​the end face of the piston facing the booster chamber. The back pressure chamber is connected to a flow path that communicates with the pump and a flow path that communicates with the tank. The flow path that communicates with the back pressure chamber can be switched by switching a switching valve. The booster chamber is connected to a flow path that communicates with the tank side and a flow path that communicates with the accumulator side.

[0005] As a result, when the working fluid is stored in the boost chamber and the pump delivers the working fluid to the back pressure chamber, the piston moves to the other axial side. The booster compresses the working fluid in the boost chamber and delivers the boosted working fluid to the accumulator side. The valve position of the switching valve is switched to connect the back pressure chamber to the tank and start discharging the pressurized oil in the back pressure chamber to the tank, so that the pressure in the back pressure chamber gradually decreases. When the biasing force of the biasing means exceeds the force trying to move the piston to the other axial side, the piston moves to one axial side and the working fluid is sucked into the booster chamber from the tank. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2011-185417 A (page 7, figure 1) Summary of the Invention [Problem to be solved by the invention]

[0007] In a pressure booster such as that described in Patent Document 1, the valve position of the switching valve is switched in response to the reciprocating motion of the piston, so that the pressurized working fluid can be continuously sent to the accumulator. However, such a switching valve generally uses an electromagnetic switching valve that enables these switching operations by an electric signal. For this reason, a pressure booster such as that described in Patent Document 1 requires a device for outputting an electric signal, a device for sensing the valve position, and the like. This causes a problem in that the entire pressure booster becomes large. In addition, the control program for such a pressure booster becomes complicated, which also causes a problem in terms of cost.

[0008] The present invention has been made in view of the above problems, and has an object to provide a fluid circuit capable of continuously driving an amplifier with a simple configuration. [Means for solving the problem]

[0009] In order to solve the above problems, the fluid circuit of the present invention comprises: The hydraulic system includes a fluid supply device that delivers a hydraulic fluid, a tank that stores the hydraulic fluid, a pressure booster that boosts the hydraulic fluid, and an accumulator that accumulates the hydraulic fluid boosted by the pressure booster, the pressure booster includes a cylinder, a piston provided in the cylinder so as to be capable of reciprocating in an axial direction, and a biasing means for biasing the piston toward one side in the axial direction, a space within the cylinder is partitioned by the piston into a back pressure chamber that can communicate with the fluid supply device side and the tank side, and a pressure boosting chamber that can communicate with the accumulator side, A fluid circuit in which a working fluid is caused to flow from the fluid supply device into the back pressure chamber to pressurize the piston in the other axial direction, and the working fluid pressurized in the pressure boosting chamber is delivered to the accumulator side, a first switching valve that switches between a flow path that communicates the back pressure chamber with the fluid supply device side and a first flow path that communicates the back pressure chamber with the tank side in response to a change in the loaded fluid pressure, a second switching valve that switches the flow path that loads fluid pressure to the first switching valve when the piston reaches a start position on one axial side or a terminal position on the other axial side, and a second flow path that communicates the back pressure chamber with the booster chamber, The biasing force of the biasing means when the piston reaches the terminal position is smaller than the pressing force acting on the piston by the fluid pressure from the fluid supply device, and the biasing force of the biasing means when the piston reaches the start position is greater than the sum of the flow path resistance force acting on the first flow path and the flow path resistance force acting on the second flow path. According to this, the first and second switching valves can switch between sending the working fluid from the fluid supply device into the back pressure chamber using the fluid pressure and discharging the working fluid from the back pressure chamber to the tank. That is, the fluid circuit can continuously drive the booster using the fluid pressure. Furthermore, the biasing means has just the right amount of biasing force to move the piston to the start end position and the end end position. Therefore, the biasing means can reliably reciprocate the piston between the start end position and the end end position, and the first and second switching valves can be reliably switched.

[0010] The piston may include the second flow passage. This allows the extension of the second flow path to be shortened, thereby reducing the flow path resistance force acting on the second flow path and reducing the biasing force required of the biasing means.

[0011] A check valve having a biasing portion that biases the second flow path in a closing direction may be disposed in the second flow path. According to this, when the piston is moved from the start position to the end position, there is no risk of the working fluid in the booster chamber flowing back into the back pressure chamber, so the boosting efficiency of the booster device is good.

[0012] An area ratio between an effective cross-sectional area of ​​the first flow passage and an effective cross-sectional area of ​​the second flow passage may be greater than an area ratio between an effective pressure-receiving area of ​​the back pressure chamber and an effective pressure-receiving area of ​​the pressure boosting chamber. This allows the working fluid to be stably delivered to the back pressure chamber and the booster chamber, while reducing the resistance when the working fluid passes through the second flow passage, thereby reducing the load acting on the biasing means. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing a fluid circuit including a pressure booster according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic diagram for explaining a pressure boosting cycle of a working fluid by a pressure booster according to a first embodiment of the present invention. [Diagram 3] FIG. 4 is a schematic diagram for explaining changes in the biasing means and the second switching valve of the pressure booster according to the first embodiment of the present invention. [Figure 4] 1 is an enlarged schematic view showing a main part of a pressure booster according to a first embodiment of the present invention. [Diagram 5] FIG. 11 is a schematic diagram showing a fluid circuit including a pressure booster according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fluid circuit according to an embodiment of the present invention will be described below with reference to the accompanying drawings. EXAMPLES

[0015] A fluid circuit according to a first embodiment will be described with reference to FIGS.

[0016] As shown in Fig. 1, the fluid circuit can be applied to hydraulic devices such as actuators, brakes, steering, transmissions, etc. in passenger cars, trucks, hydraulic excavators, forklifts, cranes, garbage trucks, etc. Note that the hydraulic circuit shown in Fig. 1 is one example of the fluid circuit of the present invention, and is not limited to the configuration of Fig. 1.

[0017] The fluid circuit of this embodiment is generally configured to move the workpiece W by operating a cylinder 5 as an actuator using hydraulic pressure.

[0018] The fluid circuit is mainly composed 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, a first switching valve 8, an adjustable slow return valve 9, a pressure booster 10, accumulators 11, 12, electromagnetic proportional switching valves 13, 14, a controller C, and each oil passage.

[0019] First, the configuration of the main circuit side for operating the cylinder 5 by the main circuit hydraulic pump 2 (hereinafter, may be simply referred to as the hydraulic pump 2) will be described. The hydraulic pump 2 and the pilot circuit hydraulic pump 6 are connected to a drive mechanism 1 such as a vehicle engine. As a result, the hydraulic pump 2 and the pilot circuit hydraulic pump 6 driven by power from the drive mechanism 1 send pressure oil to oil passages 20, 60.

[0020] The pressure oil delivered from the hydraulic pump 2 flows into the switching valve 3 through an oil passage 21 that is branched off and connected to the oil passage 20 .

[0021] The switching valve 3 is a 6-port, 3-position, open-center type switching valve. In its neutral position, the switching valve 3 connects the oil passage 21 to the tank-side oil passage 30 and the tank T. Therefore, the entire amount of pressure oil delivered from the hydraulic pump 2 is discharged into the tank T.

[0022] Furthermore, when the switching valve 3 is in its extended position 3E, it connects the oil passage 22 to a head side oil passage 50 in the cylinder 5 (hereinafter simply referred to as the head side oil passage 50). At the same time, the switching valve 3 connects a rod side oil passage 51 in the cylinder 5 (hereinafter simply referred to as the rod side oil passage 51) to the tank side oil passage 31 and the tank T. The oil passage 22 is branched off and connected to the oil passage 20 and has a check valve.

[0023] Furthermore, when the switching valve 3 is in its contraction position 3S, it connects the oil passage 22 to the rod side oil passage 51. At the same time, the switching valve 3 connects the head side oil passage 50 to the tank side oil passage 31 and the tank T.

[0024] On the other hand, the pressure oil delivered from the pilot circuit hydraulic pump 6 is supplied to the hydraulic remote control valve 4 through an oil passage 60. The pressure oil delivered to the hydraulic remote control valve 4 is not limited to the pressure oil delivered from the pilot hydraulic pump, but may be the working fluid delivered from the hydraulic pump 2 and the cylinder 5, and may be changed as appropriate.

[0025] The hydraulic remote control valve 4 is a variable pressure reducing valve. The hydraulic remote control valve 4 reduces the pressure oil of the pilot primary pressure to a pilot secondary pressure according to the amount of operation of the operation lever 4-1. The pilot primary pressure oil here refers to the pressure oil sent from the pilot circuit hydraulic pump 6. The pilot secondary pressure oil passes through pilot signal oil passages 40 and 41 and acts on the signal ports 3-1 and 3-2 of the switching valve 3.

[0026] Incidentally, some of the pressure oil discharged from the pilot circuit hydraulic pump 6 becomes surplus oil that is not supplied from the hydraulic remote control valve 4 to the signal ports 3-1, 3-2. A part of such surplus oil flows as hydraulic oil into the booster device 10 side described later through an oil passage 61. On the other hand, all of the surplus oil other than the hydraulic oil is discharged to the tank T through a relief oil passage 62 having a relief valve.

[0027] The operation of the cylinder 5 in response to the operation of the hydraulic remote control valve 4 will be described. When the operating lever 4-1 is operated in the extension direction E, the switching valve 3 is switched to the extension position 3E. Then, the pressure oil delivered from the hydraulic pump 2 flows into the head chamber 5-1 in the cylinder 5 through the head side oil passage 50 connected to the oil passages 20, 22. At the same time, the pressure oil flowing out from the rod chamber 5-2 is discharged to the tank T through the tank side oil passage 31 connected to the rod side oil passage 51. At this time, an electric signal from the pressure sensor 42 installed on the pilot signal oil passage 40 is input to the controller C.

[0028] Also, by operating the operating lever 4-1 in the retraction direction S, the switching valve 3 is switched to the retraction position 3S. Then, the pressure oil delivered from the hydraulic pump 2 flows into the rod chamber 5-2 in the cylinder 5 through the rod side oil passage 51 connected to the oil passages 20, 22. At the same time, the pressure oil flowing out from the head chamber 5-1 is discharged to the tank T through the tank side oil passage 31 connected to the head side oil passage 50. At this time, the electric signal output from the pressure sensor 43 installed on the pilot signal oil passage 41 is input to the controller C.

[0029] In addition, a relief oil passage 23 having a relief valve is branched and connected to the oil passage 20. When the pressure in the oil passage 20 becomes abnormally high, the relief valve is opened. As a result, the pressurized oil is discharged from the relief oil passage 23 to the tank T.

[0030] Next, a description will be given of the configuration of the pilot circuit side connected to the pilot circuit hydraulic pump 6, including the booster device 10. The above-mentioned oil passage 60, hydraulic remote control valve 4, pilot signal oil passages 40 and 41, and relief oil passage 62 are included in the configuration of the pilot circuit side.

[0031] An electromagnetic switching valve 7 is provided in oil line 61 which is branched off and connected to oil line 60. When switch 15 is in the OFF state, electromagnetic switching valve 7 blocks connection between oil line 61 and oil line 70. At the same time, electromagnetic switching valve 7 connects oil line 70 to oil line 71 which is connected to tank T.

[0032] Furthermore, an electric signal output from the controller C by turning the switch 15 to the ON state is input to the solenoid switching valve 7 through the electric signal line 72. As a result, the solenoid switching valve 7 connects the oil path 61 to the oil path 70. At the same time, the solenoid switching valve 7 cuts off the oil path 70 to the oil path 71 (see FIG. 2).

[0033] A first switching valve 8 is provided in oil passage 70. The first switching valve 8 is a switching valve that switches the connected oil passage in response 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 passage 70 to oil passage 80. At the same time, the first switching valve 8 blocks oil passage 80 from oil passage 81. Oil passage 81 is connected to tank T.

[0034] Furthermore, if the pressure acting on port 8-1 is equal to or greater than a predetermined value, first switching valve 8 blocks oil passage 70 from oil passage 80. At the same time, first switching valve 8 connects oil passage 80 to oil passage 81 (see FIGS. 2(c) and 2(d)).

[0035] A pressure booster 10 is connected to the oil passage 80. The pressure booster 10 is for further boosting the pressure of the pressure oil delivered from the pilot circuit hydraulic pump 6 and delivering it to an oil passage 100 having a check valve. The configuration of the pressure booster 10 will be described later.

[0036] Oil passages 101 and 102 are branched and connected to the oil passage 100. The oil passage 101 has two check valves. The oil passage 102 has two check valves different from the oil passage 101.

[0037] An accumulator 11 and a pressure sensor 103 are connected between the two check valves in the oil passage 101. The pressure sensor 103 detects the pressure of the accumulator 11. In addition, an electromagnetic proportional switching valve 13 is connected downstream of the two check valves in the oil passage 101.

[0038] An accumulator 12 and a pressure sensor 104 are connected between the two check valves in the oil passage 102. The pressure sensor 104 detects the pressure of the accumulator 12. In addition, an electromagnetic proportional switching valve 14 is connected to the oil passage 102 downstream of the two check valves.

[0039] The electromagnetic proportional switching valves 13 and 14 are of a normally closed type, and are connected to a controller C by electric signal lines.

[0040] The controller C controls the electromagnetic proportional switching valves 13, 14 to a closed state or an open state based on the electric signals input from the pressure sensors 42, 43, 103, 104. Hereinafter, the electromagnetic proportional switching valve 13 will be described as an example.

[0041] When the pressure in the accumulator 11 drops, an electric signal is input from the controller C to the electromagnetic proportional switching valve 13, which is closed. This allows the accumulator 11 to accumulate the pressurized oil delivered from the booster 10.

[0042] Furthermore, when the pressure in the accumulator 11 increases, an electric signal is input from the controller C to the electromagnetic proportional switching valve 13. Then, the electromagnetic proportional switching valve 13 connects the oil passages 101, 105 at an opening degree corresponding to the input signal. As a result, the stored oil sent from the accumulator 11 is regenerated to the head chamber 5-1 in the cylinder 5 via the oil passage 107 having a check valve and the head side oil passage 50.

[0043] Furthermore, by alternately switching the electromagnetic proportional switching valves 13, 14 by the controller C, the fluid circuit accumulates pressure in one of the accumulators 11, 12. At the same time, the fluid circuit can regenerate the pressurized oil accumulated in the other one of the accumulators to the main circuit.

[0044] In addition, when the accumulated oil in the accumulators 11, 12 reaches the allowable amount, excess oil is generated in the oil passage 100. A relief oil passage 108 having a relief valve is branched and connected to the oil passage 100. The excess oil is discharged to the tank T through the relief oil passage 108.

[0045] Next, the pressure booster 10 will be described. In this description, the spring 140 side of the pressure booster 10 is the other axial side (i.e., the lower side in the figure), and the opposite side is the one axial side (i.e., the upper side in the figure).

[0046] As shown in Fig. 1 to Fig. 4, the booster 10 is mainly composed of a case 110 as a cylinder, a piston 120, a second switching valve 130, and a spring 140 as a biasing means. The piston 120 is provided in the case 110 so as to be movable in the axial direction. The spring 140 biases the piston 120 toward one side in the axial direction. In Fig. 1 to Fig. 4, the second switching valve 130 is shown enlarged to show the switching of the oil passages. Also, the booster 10 and each oil passage in Fig. 3 and Fig. 4 are shown typically based on the symbols used in Fig. 1 and Fig. 2.

[0047] 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.

[0048] An oil passage 80 is connected to an upper portion of the large diameter cylindrical portion 111. An oil passage 100 is connected to a lower end portion of the large diameter cylindrical portion 111 on the outer diameter side of the small diameter cylindrical portion 112.

[0049] An oil passage 113 connected to a tank T is connected to the peripheral wall of the small diameter cylindrical portion 112.

[0050] 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.

[0051] The outer circumferential surface of large diameter portion 121 is formed so as to be in sliding contact with the inner circumferential surface of large diameter cylindrical portion 111 in case 110. The outer circumferential surface of small diameter portion 122 is formed so as to be in sliding contact with the inner circumferential surface of small diameter cylindrical portion 112 in case 110.

[0052] Further, in the large diameter portion 121, a back pressure chamber side second oil passage 123, a check valve 124, and a boost chamber side second oil passage 125 are formed. The back pressure chamber side second oil passage 123 communicates with the back pressure chamber 10-1, extends axially downward, and extends radially outwardly and generally perpendicularly. The check valve 124 is disposed between the back pressure chamber side second oil passage 123 and the boost chamber side second oil passage 125. The boost chamber side second oil passage 125 extends radially outwardly from the check valve 124, extends radially outwardly and generally perpendicularly, and extends radially outwardly and communicates with the boost chamber 10-2.

[0053] With the piston 120 housed in the case 110, the space within the large diameter cylindrical portion 111 is divided into a back pressure chamber 10-1 and a pressure boosting chamber 10-2 by the large diameter portion 121 of the piston 120. An oil passage 80 communicates with the back pressure chamber 10-1. An oil passage 100 communicates with the pressure boosting chamber 10-2. A spacer that restricts movement of the piston 120 is fixedly disposed at the axial upper end of the back pressure chamber 10-1.

[0054] In addition, when the piston 120 is housed, the case 110 defines a drain chamber 10-3 by the small diameter cylindrical portion 112 of the case 110 and the small diameter portion 122 of the piston 120. An oil passage 113 communicates with the drain chamber 10-3.

[0055] The piston 120 is configured to be able to reciprocate between a start position and a terminal position. At the start position, the upper end of the large diameter portion 121 on the axially upper side abuts against a spacer in the back pressure chamber 10-1, restricting movement in that direction. At the terminal position, the lower end of the large diameter portion 121 on the axially lower side abuts against the lower surface in the pressure boosting chamber 10-2, restricting movement in that direction.

[0056] The rod of the second switching valve 130 passes through the bottom of the small diameter cylindrical portion 112 of the case 110. A force from pressure on an upper end surface 121a of the large diameter portion 121 of the piston 120 acts on the second switching valve 130. In addition, a biasing force of a spring 140 acts on the second switching valve 130. As a result, the rod of the second switching valve 130 is maintained in a state in which its upper end surface is in contact with a lower end surface of the small diameter portion 122 of the piston 120. The upper end surface 121a is the back surface of the large diameter portion 121 in this embodiment.

[0057] Furthermore, when the piston 120 has reached the start end position, i.e., when the movement in the axially upward direction is restricted, the second switching valve 130 connects the drain oil passage 131 to the pilot oil passage 132. At the same time, the second switching valve 130 blocks the pilot oil passage 132 to the pilot oil passage 133. The drain oil passage 131 is connected to the tank T. The pilot oil passage 132 is connected to the port 8-1 of the first switching valve 8. The pilot oil passage 133 is branched and connected to the oil passage 70.

[0058] Furthermore, when the piston 120 has reached its terminal position, i.e., when the movement in the axial direction is restricted on the lower side, the second switching valve 130 connects the pilot oil passages 132 and 133. At the same time, the second switching valve 130 blocks the drain oil passage 131 and the pilot oil passage 132 (see FIGS. 2(b) and 2(c)).

[0059] The spring 140 is made of an elastic material having a constant spring constant k that is expandable and contractible in the axial direction, and is a spring member formed to a natural length L0 (see FIG. 3(a)). The base end (lower end in the figure) of the spring 140 is fixedly installed. The free end (upper end in the figure) of the spring 140 is always in a compressed state and abuts against the lower end surface of the second switching valve 130. The biasing force F generated according to the compressed position is S1 ,F SX ,F S2 As a result, the spring 140 constantly biases the piston 120 axially upward via the second selector valve 130 .

[0060] In the pilot oil passage 132, an adjustable slow return valve 9 is configured from a variable throttle section 90, a pilot oil passage 91, and a check valve 92. The pilot oil passage 91 is connected to the pilot oil passage 132 across the variable throttle section 90. The check valve 92 is provided midway along the pilot oil passage 91.

[0061] Next, the pressure boosting cycle by the pressure booster 10 will be described with reference to FIGS.

[0062] First, there will be described a state before the start of pressure boosting by the pressure booster 10. As shown in Fig. 1, the switch 15 is in an OFF state, and the solenoid controlled directional control valve 7 blocks the oil passages 61, 70.

[0063] In this state before the start of pressure boosting, the piston 120 is disposed at a start end position on the upper axial side inside the case 110. In this manner, the position where the piston 120 reaches before the start of pressure boosting by the pressure booster 10 and where the movement of the piston 120 toward the upper axial side is restricted is the start end position of the piston 120. In the following description, this will simply be referred to as the start end position.

[0064] At this starting position, the spring 140 has a length L1 (see FIG. 3(b)) that is slightly compressed from its natural length L0 (see FIG. 3(a)) (L0>L1).

[0065] As will be described later, the position where the pressure booster 10 starts boosting the pressure, the piston 120 reaches the lower end in the axial direction, and the downward movement in the axial direction is restricted is the end position of the piston 120 (see FIG. 3(d)). In the following description, this position will simply be referred to as the end position.

[0066] At this end position, the spring 140 is compressed to a maximum length L2 (see FIG. 3(d)) (L1>L2). Needless to say, the spring 140 in this state is within its elastic deformation range.

[0067] In the pressure booster 10, oil is stored in a back pressure chamber 10-1, a pressure booster chamber 10-2, and a drain chamber 10-3. The pressures of these chambers are substantially the same as the pressure P of the oil stored in a tank T that is open to the outside. 0 (In this embodiment, 0.1 MPa (= 1.02 kg / cm 2 )) is the result.

[0068] At this time, the biasing force F of the spring 140 at the starting position of the piston 120 S1 (F S1 = k × (L1-L0)) is the pressure P in the back pressure chamber 10-1 0 The piston 120 is pushed axially downward by a pressing force F H0 (F H0 =P 0 × S1). The biasing force F of the spring 140 is larger than the S1 The piston 120 is maintained at the starting position.

[0069] Further, after the piston 120 reaches the start end position, the second switching valve 130 connects the oil passages 131, 132. As a result, a pressure substantially equal to that of the oil in the tank T acts on the port 8-1 of the first switching valve 8. Since this pressure is less than a predetermined value, the first switching valve 8 connects the oil passages 70, 80.

[0070] Fluid pressure P delivered from the pilot circuit hydraulic pump 6 H1 In this embodiment, the pressure is 1 MPa (= 10.2 kg / cm 2 ) Note that each of the above numerical values ​​may be changed as appropriate, and the same applies to the subsequent numerical values.

[0071] When pressure boosting by the booster 10 is to be started, the switch 15 is turned ON. As a result, the solenoid controlled directional control valve 7 connects the oil passages 61 and 70, as shown in Fig. 2(a). Then, a portion of the pressure oil delivered from the pilot circuit hydraulic pump 6 passes through the oil passages 60 and 61, the solenoid controlled directional control valve 7, the oil passage 70, the first directional control valve 8, and the oil passage 80, and flows into the back pressure chamber 10-1 in the booster 10.

[0072] Immediately after the hydraulic pump 6 for the pilot circuit starts to deliver pressure oil to the back pressure chamber 10-1, as described above, the fluid pressure P H1 The pressure in the boost chamber 10-2 is 0.1 MPa. Therefore, a pressure difference occurs between the pressure in the back pressure chamber side second oil passage 123 communicating with the back pressure chamber 10-1 and the pressure in the boost chamber side second oil passage 125 communicating with the boost chamber 10-2.

[0073] This pressure difference opens the check valve 124, and pressure oil flows from the back pressure chamber 10-1 to the boost chamber 10-2. This flow of pressure oil and the movement of the piston 120 causes the pressure in the boost chamber 10-2 to be higher than that in the back pressure chamber 10-1 in an extremely short time. As a result, the check valve 124 is closed.

[0074] 1 and 3(b), area S1 as the effective pressure receiving area of ​​back pressure chamber 10-1 is larger than area S2 as the effective pressure receiving area of ​​pressure boosting chamber 10-2 by area S3 (S1=S2+S3). Area S1 is the area of ​​upper end surface 121a of large diameter portion 121 of piston 120. Area S2 is the area of ​​annular lower end surface 121b of large diameter portion 121 of piston 120. Area S3 is the cross-sectional area of ​​small diameter portion 122 of piston 120.

[0075] The large diameter portion 121 of the piston 120 is subjected to a fluid pressure P of the pressure oil delivered from the pilot circuit hydraulic pump 6 and flowing into the back pressure chamber 10-1. H1 The pressing force F is calculated by multiplying the area S1 of the upper end surface 121a by the pressing force F. H1 (F H1 =P H1 × S1) acts on the pressing force F H1 urges the piston 120 axially downward.

[0076] This pressure F H1 Needless to say, the biasing force F of the spring 140 at the starting position S1 Exceeds (F H1 >F S1 ) This allows the piston 120 to move smoothly toward its axially downward end position.

[0077] Accordingly, the pressing force F H1 The pressure P is calculated by dividing the area S2 of the lower end surface 121b of the piston 120. H2 (P H2 =F H1 The pressure oil in the booster chamber 10-2 is boosted by the axial downward movement of the piston 120. H2 The pressure oil is sequentially sent toward the oil passage 100.

[0078] In this description, the pressure of the oil in the drain chamber 10-3 is substantially constant regardless of the movement of the piston 120. Also, the oil in the drain chamber 10-3 repeatedly flows in and out with the movement of the piston 120. Therefore, a description of the effect of the oil in the drain chamber 10-3 will be omitted.

[0079] As the piston 120 moves axially downward, the spring 140 is compressed, and the biasing force F SX (F SX = k × (Lx - L0)) is increased. Then, when the piston 120 reaches the end position, the biasing force F of the spring 140 S2 (F S2 3(c), the length Lx of the spring 140 when the piston 120 is moving between the start position and the end position is a variable between the lengths L1 and L2 (L1>Lx>L2).

[0080] In addition, the pressure force F due to the fluid pressure of the pressure oil sent from the hydraulic pump 6 for the pilot circuit is H1 Needless to say, the force F S2 Exceeds (F H1 >>>F S2 In other words, when the piston 120 reaches the end position, the spring 140 receives the pressing force F H1 The spring is configured to have a biasing force smaller than

[0081] In order to allow the piston 120 to reach the end position even if the pressure in the boosting chamber 10-2 is boosted, the area ratio S1 of the upper end face 121a of the piston 120 to the area S2 of the lower end face 121b of the piston 120 and the biasing force F of the spring 140 are set to 0.5 mm. S2 has been adjusted.

[0082] In this way, when the piston 120 moves from the start end position to the end end position, as shown in Fig. 3(c), the second switching valve 130 blocks both the oil passages 131, 132 and the oil passages 132, 133. This keeps the pressure acting on the port 8-1 (see Fig. 1) of the first switching valve 8 constant. This prevents the pressure acting on the port 8-1 from fluctuating and unintentionally switching the oil passage.

[0083] 2(b), after the piston 120 reaches the end position, the second switching valve 130 connects the oil passages 132 and 133. As a result, pressure oil flows from the pilot circuit hydraulic pump 6 through the pilot oil passage 133 into the pilot oil passage 132.

[0084] Further, an adjustable slow return valve 9 is provided in the pilot oil passage 132. Pressurized oil that has passed through a variable throttle section 90 in this adjustable slow return valve 9 acts on port 8-1. The variable throttle section 90, which has an adjustable opening, can change the time it takes for the pressure acting on port 8-1 to reach a predetermined value or higher, depending on the opening. In other words, the variable throttle section 90 can adjust the time it takes for the piston 120 to start moving from the terminal position toward the start position.

[0085] When the pressure acting on port 8-1 reaches or exceeds a predetermined value, the first switching valve 8 connects oil passages 80 and 81, as shown in Fig. 2(c). As a result, the pressurized oil in the back pressure chamber 10-1 passes through the oil passage 80, the first switching valve 8, and the oil passage 81 and is discharged to the tank T. In other words, the oil passages 80 and 81 constitute the first flow path of the present invention.

[0086] And the pressure P in the back pressure chamber 10-1 Y becomes smaller, and the pressure P of the oil stored in the tank T mentioned above 0 Approaching (P H1 >>P Y >P 0 Then, the biasing force F of the spring 140 at the end position of the piston 120 S2 is the pressure P Y The piston 120 is pressed axially downward by a pressing force F HY (F HY =P Y ×S1). As a result, as shown by the outlined thick arrow in FIG. 4, the piston 120 starts to move axially upward (F S2 >F HY As the piston 120 moves, a portion of the oil in the back pressure chamber 10-1 flows out into the oil passage 80, as shown by the thick black arrow in FIG. YBut, P 0 When the pressure becomes equal to that of the piston 120, the piston 120 may start to move axially upward.

[0087] Furthermore, as the piston 120 moves axially upward, the pressure in the boost chamber 10-2 becomes lower than the pressure in the back pressure chamber 10-1. This causes the check valve 124 to open, as shown by the thin white arrow in Fig. 4. Then, as shown by the thin black arrow in Fig. 4, some of the oil in the back pressure chamber 10-1 flows out toward the boost chamber 10-2.

[0088] That is, as the piston 120 moves axially upward, the oil in the back pressure chamber 10-1 branches off and flows out into the oil passage 80 and the boost chamber 10-2. At this time, a flow resistance force R1 acts on the oil passing through the oil passage 80, and a flow resistance force R2 acts on the oil passing through the second oil passages 123, 125 and the check valve 124.

[0089] The flow path resistance force R1 is derived from the viscosity of the oil, the friction coefficient, inner diameter, length, etc. of the oil passages 80 and 81. The flow path resistance force R2 is derived from the elasticity of the coil spring 124a (see FIGS. 3 and 4) serving as a biasing part provided in the check valve 124, in addition to the viscosity of the oil, the friction coefficient, inner diameter, length, etc. of the second oil passages 123 and 125.

[0090] As the piston 120 moves axially upward, the spring 140 expands and exerts a biasing force F SX Then, when the piston 120 reaches the starting position, the biasing force F of the spring 140 is weakened. S1 However, the biasing force F of the spring 140 S1 is the pressing force F H0 and exceeds the sum of flow resistance R1 and flow resistance R2 (F S1 >F H0 +R1+R2).

[0091] In other words, when the piston 120 reaches the starting position, the spring 140 receives a pressing force F H0The flow passage resistance force R2 is configured to have a biasing force greater than the sum of the flow passage resistance force R1 and the flow passage resistance force R2.

[0092] In this embodiment, the second oil passages 123, 125 and the check valve 124 are provided inside the piston 120. Therefore, the length of the second oil passages 123, 125 can be shortened compared to a configuration (see FIG. 5) in which the second oil passage and the check valve are disposed outside the case 110, i.e., the second oil passage is bypassed to connect the back pressure chamber 10-1 and the boost chamber 10-2.

[0093] As a result, the second oil passages 123, 125, which are shorter in length, can reduce the flow resistance force R2 acting on the oil passing through the second oil passages 123, 125. S1 can be kept small.

[0094] 3(b), in this embodiment, the inner diameter D1 of the oil passages 80, 81 is larger than the inner diameter D2 of the second oil passages 123, 125 (D1>D2). As a result, the effective cross-sectional area S11 of the oil passages 80, 81 is larger than the effective cross-sectional area S12 of the second oil passages 123, 125 (S11>S12).

[0095] The area ratio between the effective cross-sectional area S11 and the effective cross-sectional area S12 is greater than the area ratio between the area S1 of the upper end surface 121a and the area S2 of the lower end surface 121b (S11 / S12>S1 / S2). This enables a stable supply of oil to the back pressure chamber 10-1 and the booster chamber 10-2.

[0096] In addition, the pressure-receiving area of ​​the valve body of the check valve 124 can be made smaller than in a configuration in which the area ratio between the effective cross-sectional area S11 and the effective cross-sectional area S12 is equal to or smaller than the area ratio between the area S1 of the upper end face 121a and the area S2 of the lower end face 121b. Furthermore, the biasing force of the coil spring 124a can be made smaller by making the pressure-receiving area smaller. That is, the flow path resistance force R2 when the oil passes through the second oil paths 123 and 125 can be made smaller. This reduces the load acting on the spring 140.

[0097] Further, the back pressure chamber 10-1 and the pressure boosting chamber 10-2 are directly connected to each other by the second oil passages 123, 125 and the check valve 124. Therefore, the influence of the tank T side can be reduced.

[0098] Also, as described above, when the piston 120 moves from the terminal position to the start position, the second switching valve 130 blocks both the oil passages 131 and 132 and the oil passages 132 and 133. Therefore, the first switching valve 8 is prevented from operating and unintentionally switching the oil passages.

[0099] As shown in Fig. 2(d), when the piston 120 reaches the start end position, the second switching valve 130 connects the oil passages 132, 131. As a result, the pressure oil acting on the port 8-1 passes through the pilot oil passage 91 and the check valve 92 and is discharged to the tank T. Then, when the pressure acting on the port 8-1 falls below a predetermined value, the first switching valve 8 connects the oil passages 70, 80 as shown in Fig. 2(a).

[0100] Thereafter, as long as the switch 15 is in the ON state, the first switching valve 8 and the second switching valve 130 switch between sending pressurized oil from the pilot circuit hydraulic pump 6 to the back pressure chamber 10-1 using fluid pressure, and discharging oil from the back pressure chamber 10-1 to the tank T, so that the above-mentioned cycle can be repeated. In other words, the pressure booster 10 can be continuously driven using fluid pressure.

[0101] As described above, the fluid circuit in this embodiment can continuously reciprocate the piston 120 through cooperation of the mechanically operated first switching valve 8, second switching valve 130, and spring 140. In other words, high fluid pressure can be continuously generated without electrical control. This eliminates the need for electrical control as in the past, and allows for a simpler configuration of the fluid circuit.

[0102] Moreover, the spring 140 has just the right amount of biasing force to move the piston 120 to the start end position and the end end position, so that the spring 140 can reliably move the piston 120 back and forth between the start end position and the end end position, and the first switching valve 8 and the second switching valve 130 can be reliably switched.

[0103] In addition, a check valve 124 having a coil spring 124a is disposed between the second oil passages 123 and 125. Therefore, when the piston 120 is moved from the start end position to the end end position, there is no risk of the boosted pressure oil in the boost chamber 10-2 flowing back into the back pressure chamber 10-1, and the boosting efficiency is good.

[0104] The pressure oil boosted by the booster 10 is discharged by the movement of the piston 120 downward in the axial direction, and is accumulated in the accumulators 11 and 12. This prevents the occurrence of pulsation due to the reciprocating motion of the piston 120. This allows the booster 10 to deliver a substantially constant amount of pressure oil to the accumulators 11 and 12.

[0105] Oil passage 107 having a check valve provided between accumulators 11, 12 and the main circuit can separate the system into the main circuit side from the check valve and the accumulators 11, 12 side from the check valve, i.e., the upstream side. This makes it possible to send high-pressure fluid to the destination of high fluid pressure without having to specify unnecessarily high pressure specifications, by configuring the accumulators 11, 12 side to the minimum pressure specifications required for regeneration, even if the main circuit side is of high pressure specifications. EXAMPLES

[0106] A fluid circuit according to the second embodiment will be described with reference to Fig. 5. Note that a description of the same configuration as in the first embodiment will be omitted.

[0107] As shown in FIG. 5, in the fluid circuit of the second embodiment, a first flow path connecting the back pressure chamber 10-1 in the pressure booster 210 and the tank T is made up of an oil path 280 and an oil path 81.

[0108] Further, the second flow passage connecting the back pressure chamber 10-1 and the boost chamber 10-2 is constituted by a part of the oil passage 280, an oil passage 82 branched off from the oil passage 280, and an oil passage 84. A check valve 83 is disposed between the oil passages 82 and 84. That is, in the large diameter portion 221 of the piston 220, the back pressure chamber side second oil passage 123, the check valve 124, and the boost chamber side second oil passage 125 of the first embodiment are omitted.

[0109] Even with this configuration, the fluid circuit of the second embodiment can continuously generate high fluid pressure without electrical control.

[0110] Moreover, compared to the first embodiment in which the piston 120 is provided with the back pressure chamber side second oil passage 123, the check valve 124, and the boost chamber side second oil passage 125, the second flow passage can be configured more simply.

[0111] 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.

[0112] For example, in the first and second embodiments, the working fluid is oil, but the working fluid is not limited to this and may be any fluid, and may be changed as appropriate.

[0113] In addition, in the first and second embodiments, the fluid supply device has been described as a hydraulic pump for the pilot circuit, but is not limited to this and may be a hydraulic pump for the main circuit, an actuator, an accumulator, etc., and may be modified as appropriate.

[0114] Further, in the first and second embodiments, the two accumulators are disposed downstream of the pressure booster. However, the present invention is not limited to this, and the number of accumulators may be one, or three or more.

[0115] In addition, in the first and second embodiments, the biasing means has been described as being a spring, but this is not limited thereto. As long as the biasing force when the piston reaches the terminal position is smaller than the pressing force acting on the piston due to the fluid pressure from the pump and the biasing force when the piston reaches the start position is greater than the sum of the flow path resistance force acting on the first flow path and the flow path resistance force acting on the second flow path, the biasing means may be changed as appropriate to various cylinders, etc.

[0116] In the first and second embodiments, the spring biases the piston axially upward via the second selector valve, but the present invention is not limited to this, and the piston may be biased axially upward directly. For example, the pressure booster can be made compact by integrally connecting the piston and the second selector valve and locating the spring in the drain chamber.

[0117] In addition, in the above-mentioned first and second embodiments, the biasing means of the check valve provided in the second flow path is described as being a coil spring, but this is not limited to this and may be a leaf spring, a disc spring, etc., and may be changed as appropriate.

[0118] In addition, in the above-described first and second embodiments, an adjustable slow return valve is provided between the first switching valve and the second switching valve, but this is not limited thereto, and the adjustable slow return valve may be omitted. [Explanation of symbols]

[0119] 1 Drive mechanism 6 Hydraulic pump for pilot circuit (fluid supply device) 8 First switching valve 10 Pressure booster 10-1 Back pressure chamber 10-2 Pressure booster chamber 11,12 Accumulator 80 Oil passage (first passage) 81 Oil passage (first passage) 110 Case (cylinder) 120 Piston 123 Back pressure chamber side second oil passage (second flow passage) 124 Check valve (second flow path check valve) 124a Spring (biasing part of check valve of second flow path) 125 Pressure booster chamber side second oil passage (second flow passage) 130 Second switching valve 140 Spring (biasing means) 210 Pressure booster 82,84 Oil passage (second passage) 83 Check valve (second flow path check valve) 220 Piston 280 Oil passage (first flow path, second flow path) T Tank

Claims

1. The hydraulic system includes a fluid supply device that delivers a hydraulic fluid, a tank that stores the hydraulic fluid, a pressure booster that boosts the hydraulic fluid, and an accumulator that accumulates the hydraulic fluid boosted by the pressure booster, the pressure booster includes a cylinder, a piston provided in the cylinder so as to be capable of reciprocating in an axial direction, and a biasing means for biasing the piston toward one side in the axial direction, a space within the cylinder is partitioned by the piston into a back pressure chamber that can communicate with the fluid supply device side and the tank side, and a pressure boosting chamber that can communicate with the accumulator side, A fluid circuit in which a working fluid is caused to flow from the fluid supply device into the back pressure chamber to pressurize the piston in the other axial direction, and the working fluid pressurized in the pressure boosting chamber is delivered to the accumulator side, a first switching valve that switches between a flow path that communicates the back pressure chamber with the fluid supply device side and a first flow path that communicates the back pressure chamber with the tank side in response to a change in a loaded fluid pressure, a second switching valve that switches a flow path that loads a fluid pressure on the first switching valve when the piston reaches a start position on one axial side or a terminal position on the other axial side, and a second flow path that communicates the back pressure chamber with the booster chamber, the biasing force of the biasing means when the piston reaches the terminal position is smaller than a pressing force acting on the piston by a fluid pressure from the fluid supply device, and the biasing force of the biasing means when the piston reaches the start position is larger than a sum of a flow path resistance force acting on the first flow path and a flow path resistance force acting on the second flow path, A check valve having a biasing portion biasing the second flow path in a closing direction is disposed in the second flow path, a ratio of an effective cross-sectional area of ​​the first flow passage to an effective cross-sectional area of ​​the second flow passage is greater than an effective pressure-receiving area of ​​the back pressure chamber to an effective pressure-receiving area of ​​the pressure boosting chamber;

2. The fluid circuit of claim 1 , wherein the piston includes the second flow passage.

Images