JP2018003979A - Hydraulic circuit for hydraulic cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic circuit for a hydraulic cylinder capable of automatically changing-over between a differential circuit and a non-differential circuit by a simple configuration and capable of stabilizing a moving speed of a cylinder rod during establishment of the differential circuit.SOLUTION: A hydraulic circuit of this invention comprises a hydraulic fluid conduit line for connecting a hydraulic power source with a second oil chamber; a direction selector valve for changing-over between a communicating state and a non-communicating state in the hydraulic fluid conduit line; a differential conduit line connected to the hydraulic fluid conduit line between the direction selector valve and the hydraulic power source to merge the hydraulic fluid in a first oil chamber with the hydraulic fluid conduit line; a check valve arranged at the differential conduit line; a differential releasing conduit line formed to be branched from the differential conduit line to discharge the hydraulic fluid in the first oil chamber to a hydraulic fluid tank; an external pilot type sequence valve configured to enable the communicated state and the non-communicated state at the differential releasing conduit line; and a differential releasing pilot conduit line for acting a pressure of the hydraulic fluid at the second oil chamber against the external pilot type sequence valve.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydraulic circuit for a hydraulic cylinder used in a hydraulic cylinder.

  Conventionally, as a hydraulic circuit for a hydraulic cylinder used in a hydraulic cylinder, for example, a hydraulic circuit shown in FIG. 6 is known (Patent Document 1). As shown in FIG. 6, the hydraulic circuit of Patent Document 1 includes a directional switching valve 110 having four ports A, B, P, and R, an A port of the directional switching valve 110, and a head side oil chamber 102 b of the hydraulic cylinder 102. , A second pipe 114 connecting the B port of the direction switching valve 110 and the rod side oil chamber 102a of the hydraulic cylinder 102, a P port of the direction switching valve 110 and the hydraulic pressure. A third line 116 that connects the source 104, a fourth line 118 that connects the R port of the direction switching valve 110 and the hydraulic oil tank 106, a first line 112, and a second line 114 and a return pipeline 122 formed by branching from the second pipeline 114 and connecting the rod-side oil chamber 102a of the hydraulic cylinder 102 and the hydraulic oil tank 106. ing.

  In addition, the hydraulic circuit of Patent Document 1 includes a sequence valve 124 provided in the connection pipe 120, an unload valve 126 provided in the return pipe 122, and a check valve 128 provided in the second pipe 114. A pilot line 130 connecting the pilot port of the unload valve 126 and the first line 112, and a discharge line 132 for discharging leakage fluid inside the sequence valve 124 to the second line 114. Are further provided. The sequence valve 124 opens when the internal pressure of the rod-side oil chamber 102a of the hydraulic cylinder 102 reaches a predetermined set operating pressure, and the difference between the operating oil in the rod-side oil chamber 102a flowing toward the head-side oil chamber 102b. A dynamic circuit is formed. The unload valve 126 is configured to open when the internal pressure of the head side oil chamber 102b of the hydraulic cylinder 102 reaches a predetermined set operating pressure, so that the pressure of the rod side oil chamber 102a of the hydraulic cylinder 102 is unloaded. Has been. The check valve 128 is provided between the connection position of the connection pipe 120 and the return pipe 122 and the connection position of the discharge flow path 132 in the second pipe 114, and the direction from the B port toward the rod-side oil chamber 102a. It is configured to allow only the flow of

  The hydraulic circuit of Patent Document 1 having the above-described configuration can switch the stop, advance (down), and reverse (up) of the cylinder rod 103b of the hydraulic cylinder 102 by the switching operation of the direction switching valve 110.

  Specifically, in the hydraulic circuit of Patent Document 1, the direction switching valve 110 is switched to the neutral position, and the A, B, and R ports are communicated with each other, so that the sequence valve 124, the unload valve 126, and the check valve 128 can be Is also closed. This prevents the hydraulic oil from being discharged from the rod-side oil chamber 102a, so that the cylinder rod 103b of the hydraulic cylinder 102 stops.

  Further, in the hydraulic circuit of Patent Document 1, the direction switching valve 110 is switched to one one-side position, and the A port, the P port, the B port, and the R port are communicated with each other, so that the hydraulic source 102 to the hydraulic cylinder 102 head side. The hydraulic oil is fed toward the oil chamber 102b and presses the piston 103a of the hydraulic cylinder 102 in the forward direction. Thereafter, when the internal pressure of the rod side oil chamber 102a increases and exceeds the set operating pressure of the sequence valve 124, the sequence valve 124 opens and the hydraulic oil in the rod side oil chamber 102a moves toward the head side oil chamber 102b. A flowing differential circuit is formed. Thereby, the cylinder rod 103b moves forward at a low pressure and a high speed. Then, when the cylinder rod 103b is in contact with the workpiece and the internal pressure of the head side oil chamber 102b exceeds the set operating pressure of the unload valve 126 in a state where the cylinder rod 103b is moving forward at low pressure and high speed, The load valve 126 is opened, and the hydraulic oil in the rod side oil chamber 102 a is discharged to the hydraulic oil tank 106. As a result, the rod-side oil chamber 102a enters an unloaded state, and the sequence valve 124 is closed and the differential circuit is released, so that the forward movement of the cylinder rod 103b is switched to a high-pressure and low-speed forward movement.

  Furthermore, in the hydraulic circuit of Patent Document 1, the direction switching valve 110 is switched to the other one side position, and the A port, the R port, the B port, and the P port are communicated with each other, so that the hydraulic source 102 is connected to the rod side of the hydraulic cylinder 102. The hydraulic oil is supplied toward the oil chamber 102 a and the hydraulic oil in the head side oil chamber 102 b is discharged to the hydraulic oil tank 106. Thereby, the cylinder rod 103b of the hydraulic cylinder 102 moves backward.

JP-A-54-158583

  However, in the hydraulic circuit of Patent Document 1, the differential circuit is formed on the secondary side of the direction switching valve 110, the sequence valve 124 is disposed in the differential circuit, and the differential circuit is opened by opening the sequence valve 124. Therefore, when the cylinder rod 103b is advanced, the differential circuit is not established unless the internal pressure (pilot pressure) of the rod side oil chamber 102a exceeds the set operating pressure of the sequence valve 124. In such a hydraulic circuit, when fluctuations occur in the internal pressure of the rod side oil chamber 102a due to load fluctuations, there is a risk that the unintended closing and opening operations of the sequence valve 124 may be repeatedly performed. Since the establishment of the differential circuit becomes unstable, there is a problem that the forward movement speed of the cylinder rod 103b may become unstable.

  Further, since the hydraulic circuit of Patent Document 1 is configured to form a differential circuit on the secondary side of the direction switching valve 110, a pressure control device (sequence valve 124) for establishing the differential circuit; A pressure control device (unload valve 126) for releasing the differential circuit is required. In such a hydraulic circuit, since it is necessary to use at least two pressure control devices, there is a problem that the circuit configuration becomes complicated and the equipment cost may increase. Further, in the hydraulic circuit of Patent Document 1, since it is necessary to set and adjust the operation balance of both pressure control devices (sequence valve 124 and unload valve 126) with high accuracy, there is a problem that installation and maintenance work becomes complicated. There is.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to automatically switch between a differential circuit and a non-differential circuit with a simple configuration, and the differential circuit is being established. An object of the present invention is to provide a hydraulic circuit for a hydraulic cylinder that can stabilize the moving speed of the cylinder rod in the cylinder.

  A hydraulic circuit for a hydraulic cylinder according to the present invention includes a hollow cylinder body, a piston that partitions an internal space of the cylinder body into a first oil chamber and a second oil chamber, and the first oil chamber from the piston. And a hydraulic circuit for a hydraulic cylinder used in a hydraulic cylinder having a cylinder rod extending toward at least one side of the second oil chamber, wherein the piston is moved in a direction from the second oil chamber toward the first oil chamber. A hydraulic oil line connecting the hydraulic oil source and the second oil chamber when moving, a direction switching valve configured to be able to switch between a communication state and a non-communication state of the hydraulic oil line; A differential pipe that joins the hydraulic oil discharged from the first oil chamber to the hydraulic oil pipe, and a hydraulic oil that is formed by branching from the differential pipe and discharged from the first oil chamber. Difference to drain to hydraulic oil tank Hydraulic oil that is provided between the release pipe, a branch point of the differential release pipe in the differential pipe, and a junction of the hydraulic oil pipes and that travels from the first oil chamber toward the hydraulic oil pipe And a check valve configured to prevent the flow of hydraulic oil from the hydraulic oil line toward the first oil chamber, and provided in the differential release pipe, the differential release pipe An external pilot type sequence valve configured to be able to switch between a communication state and a non-communication state of the road, and a differential release pilot pipe for applying the pressure of the hydraulic oil on the second oil chamber side to the external pilot type sequence valve; The differential line is connected to the hydraulic oil line between the direction switching valve and the hydraulic power source, and the external pilot type sequence valve is connected to the differential release pilot line. The second granted through The differential release pipe is configured to be in a communication state while the pressure of the hydraulic oil on the chamber side is equal to or higher than a predetermined pilot pressure, and the hydraulic oil line is in a communication state by the direction switching valve, and When the differential release line is brought into a non-communication state by the external pilot type sequence valve, the hydraulic oil in the first oil chamber is supplied to the second oil by the differential line and the hydraulic oil line. When a differential circuit that flows toward the chamber is formed, the hydraulic fluid conduit is in communication with the direction switching valve, and the differential release conduit is in communication with the external pilot sequence valve In addition, the differential release conduit is configured to form a non-differential circuit in which the hydraulic oil in the first oil chamber flows toward the hydraulic oil tank.

  In the hydraulic cylinder hydraulic circuit according to the present invention, the direction switching valve has an A port, a B port, a P port, and a T port, and at least a first state in which the P port is closed, and the A port and the P port. Can be switched between the second state in which the B port and the T port are connected and the third state in which the A port and the T port are connected and the B port and the P port are connected. The hydraulic oil line includes a P port line that connects the hydraulic power source and the P port, and an A port line that connects the A port and the second oil chamber, The differential line is configured to connect the second oil chamber and the P port line, and the hydraulic circuit for the hydraulic cylinder includes a B port that connects the differential line and the B port. Pipe line, T port and hydraulic oil A T-port pipe that connects to the tank, and a B-port pipe that allows hydraulic fluid to flow from the B-port toward the first oil chamber or the differential pipe; and It is preferable to further include a second check valve configured to prevent the flow of hydraulic oil from one oil chamber or the differential pipe line toward the B port.

  Further, the hydraulic circuit for a hydraulic cylinder according to the present invention according to the present invention is configured such that when the direction switching valve is in the third state, the A port pipe and the T port pipe cause the second oil chamber to It is preferable that a discharge pipe is formed in which the hydraulic oil flows toward the hydraulic oil tank.

  In the hydraulic circuit for a hydraulic cylinder according to the present invention according to the present invention, the hydraulic cylinder may be a single rod type hydraulic cylinder having the cylinder rod extending from the piston toward the first oil chamber, It may be a single rod type hydraulic cylinder having the cylinder rod extending from the piston toward the second oil chamber, and the piston extends from the piston toward the first oil chamber and the second oil chamber, respectively. It may be a double rod type hydraulic cylinder having a cylinder rod.

  According to the present invention, it is possible to automatically switch between a differential circuit and a non-differential circuit with a simple configuration, and it is possible to stabilize the moving speed of the cylinder rod during the establishment of the differential circuit. A hydraulic circuit for a hydraulic cylinder can be provided.

It is a figure showing roughly the composition of the hydraulic circuit for hydraulic cylinders concerning the embodiment of the present invention. It is a figure which shows roughly the circuit structure at the time of stopping a cylinder rod in the hydraulic circuit for hydraulic cylinders concerning this embodiment. It is a figure which shows roughly the circuit structure (differential circuit) at the time of making a cylinder rod advance at low pressure and high speed in the hydraulic circuit for hydraulic cylinders concerning this embodiment. It is a figure which shows roughly the circuit structure (non-differential circuit) at the time of making a cylinder rod advance at high pressure low speed in the hydraulic circuit for hydraulic cylinders concerning this embodiment. It is a figure which shows roughly the circuit structure at the time of retracting a cylinder rod in the hydraulic circuit for hydraulic cylinders concerning this embodiment. It is a figure which shows schematically the structure of the hydraulic circuit for conventional hydraulic cylinders.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments for carrying out the present invention will be described with reference to the drawings. The following embodiments do not limit the invention according to each claim, and all combinations of features described in the embodiments are not necessarily essential to the solution means of the invention. .

  As shown in FIG. 1, the hydraulic circuit 1 for a hydraulic cylinder according to the present embodiment includes, for example, a hollow cylinder body 4 and an inner space of the cylinder body 4 in a first oil chamber (rod side oil chamber). 4a and a second oil chamber (head side oil chamber) 4b and a piston 6 that moves forward or backward in the cylinder body 4 and a cylinder rod (power transmission shaft) that extends from the piston 6 toward the first oil chamber 4a. 8 is used to drive a single rod type hydraulic cylinder 2.

  Specifically, as shown in FIG. 1, the hydraulic circuit 1 for a hydraulic cylinder includes a directional switching valve 10 having an A port, a B port, a P port, and a T port, an A port of the directional switching valve 10, and a second oil. A port line 12 connecting the chamber 4b, a T port line 14 connecting the T port of the direction switching valve 10 and the hydraulic oil tank 32, a hydraulic source (pump) 34, and a P port of the direction switching valve 10 A P port pipe line 16 for connecting the P port pipe line 16, a differential pipe line 18 formed by branching from the P port pipe line 16 and connecting the P port pipe line 16 and the first oil chamber 4 a, and a differential pipe A B port pipe 20 formed by branching from a branch point (pipe merging point) 23 of the path 18 and connecting the differential pipe 18 and the B port of the direction switching valve 10; 18 branching points 23 are formed, and the differential pipe line 18 and the T port pipe line 14 are And a differential release conduit 22 to be connected. In this embodiment, in order to simplify the explanation, both the B port pipe 20 and the differential release pipe 22 are formed by branching from the branch point 23. The path does not necessarily have to be formed by branching from the common branch point 23. Moreover, in this embodiment, since these various pipe lines can use various well-known piping suitably, the detailed description is abbreviate | omitted.

  Further, as shown in FIG. 1, the hydraulic circuit 1 for the hydraulic cylinder includes a first check valve 24 provided in the differential pipe line 18, a second check valve 26 provided in the B port pipe line 20, An external pilot type sequence valve 28 provided in the differential release line 22 and a branch port formed from the A port line 12, and a pilot port (not shown) of the A port line 12 and the external pilot type sequence valve 28 And a pressure gauge 31 that measures and displays the pressure of the hydraulic oil upstream (primary side) of the external pilot type sequence valve 28 in the differential release line 22. I have. In addition, in this embodiment, since the differential cancellation | release pilot pipe line 30 and the pressure gauge 31 can use various well-known piping and structures suitably, the detailed description is abbreviate | omitted.

  The direction switching valve 10 has a first connection state (neutral position state) in which the A port and the T port are connected and the B port and the P port are closed, the A port and the P port are connected, and A second connection state in which the B port and the T port are connected (a state in which the solenoid a is excited), and a third connection state in which the A port and the T port are connected and the B port and the P port are connected. This is a so-called AT connection type three-position valve (solenoid valve) that can be switched by electromagnetic operation (the state in which the solenoid b is excited). In the hydraulic cylinder hydraulic circuit 1 according to the present embodiment, the cylinder rod 8 of the hydraulic cylinder 2 is stopped in the first connection state, and the cylinder rod 8 of the hydraulic cylinder 2 is advanced in the second connection state. In the third connection state, the cylinder rod 8 of the hydraulic cylinder 2 is configured to be in the retracted state. Details of the operation of the hydraulic circuit 1 for the hydraulic cylinder will be described later.

  The A port pipe line 12 and the P port pipe line 16 cooperate with the hydraulic pressure source 34 by the communication between the A port and the P port of the direction switching valve 10 in the second connection state described above. It is comprised so that the hydraulic oil pipe line 11 which connects the 2nd oil chamber 4b may be formed (refer FIG.3 and FIG.4).

  The differential line 18 is connected to the hydraulic oil line 11 between the direction switching valve 10 and the hydraulic source 34, and is in the above-described second connection state and the external pilot type sequence valve 28 is not in communication. In the (closed) state, the hydraulic oil discharged from the first oil chamber 4a is configured to join the hydraulic oil pipe 11 (see FIG. 3).

  The differential release line 22 is a hydraulic oil tank that supplies the hydraulic oil discharged from the first oil chamber 4a when the external pilot type sequence valve 28 is in the communication (open) state in the second connection state described above. 32 (see FIG. 4).

  The A port pipe line 12 and the T port pipe line 14 cooperate with each other when the A port and the T port of the direction switching valve 10 communicate with each other in the third connection state described above. Is formed so as to form a discharge pipe 13 that flows toward the hydraulic oil tank 32 (see FIG. 5).

  The differential release pilot pipe line 30 causes the hydraulic oil pressure in the A port pipe line 12, that is, the pressure (head pressure) in the second oil chamber 4b to act on the pilot port of the external pilot type sequence valve 28 as a pilot pressure. Is configured to be possible.

  The first check valve 24 is provided on the P port line 16 side of the branch point 23 of the B port line 20 and the differential release line 22 in the differential line 18, and is connected to the P port from the first oil chamber 4 a. The hydraulic oil is allowed to flow toward the pipe line 16 and is prevented from flowing from the P port pipe line 16 toward the first oil chamber 4a. The second check valve 26 is provided in the B port pipeline 20, allows the hydraulic oil to flow from the B port of the direction switching valve 10 toward the differential pipeline 18, and is directed from the differential pipeline 18. The flow of hydraulic oil toward the B port of the switching valve 10 is configured to be blocked. As the first check valve 24 and the second check valve 26, it is possible to use a simple and inexpensive known check valve which does not have an adjustment function such as a ball check valve, but is not limited thereto. . For example, it is also possible to employ a special check valve such as a pilot check valve capable of adjusting the pressure for preventing flow.

  The external pilot type sequence valve 28 is provided in the differential release line 22 and is supplied to the pilot port via the differential release pilot line 30 (the pressure in the second oil chamber 4b (head pressure). )) According to the pressure of the hydraulic fluid, it is configured to be able to switch between the communication state and the non-communication state of the differential release line 22. Specifically, the external pilot type sequence valve 28 is configured such that the hydraulic oil pressure in the A port pipeline 12 (that is, the pressure (head pressure) in the second oil chamber 4b) is set to a pilot pressure (that is, external pressure). The differential release line 22 is configured to be in a non-communication state while the pressure is less than the set operating pressure of the pilot type sequence valve 28. Further, the external pilot type sequence valve 28 is configured so that the differential release line 22 is in a communicating state while the hydraulic oil pressure in the A port line 12 is equal to or higher than a preset pilot pressure. .

  The pilot pressure that is the operating condition of the external pilot type sequence valve 28 is, for example, that the hydraulic circuit 1 for the hydraulic cylinder according to the present embodiment is applied to a hydraulic cylinder for a product extrusion device of a die casting machine or an injection molding machine, or a partial pressure of a mold. When used for a pressure squeeze pin, a hydraulic cylinder for driving a movable core, or the like, the pressure can be set according to the pressure received when the cylinder rod 8 contacts the object. In addition, the pressure received by the cylinder rod 8 contacting the object can be specified by actual measurement or calculation.

  As such an external pilot type sequence valve 28, various known external pilot type sequence valves can be appropriately used. For example, it has a valve body, a spring that urges the valve body in the direction of blocking the flow path, and a pilot port that applies pilot pressure in a direction to push back the spring, and the pilot pressure exceeds the urging force of the spring, It is possible to use a general external pilot type sequence valve configured to bring the flow path into a communicating state by being pushed back to a position where the valve body opens the flow path.

  The hydraulic cylinder hydraulic circuit 1 according to the present embodiment has the above-described configuration, so that the direction switching valve 10 is connected to the second connection state (that is, the A port and the P port are connected, and the B port and the When the T port is connected) and the differential release line 22 is not in communication, the differential line 18 and the hydraulic oil line 11 (P port line 16 and A port line 12) Thus, a differential circuit is formed in which the hydraulic oil in the first oil chamber 4a flows toward the second oil chamber 4b (see FIG. 3). Further, the hydraulic cylinder hydraulic circuit 1 is configured so that the differential release line 22 causes the first oil when the direction switching valve 10 is in the second connected state and the differential release line 22 is in communication. A non-differential circuit in which the hydraulic oil in the chamber 4a flows toward the hydraulic oil tank 32 is formed (see FIG. 4).

  Next, the operation of the hydraulic cylinder hydraulic circuit 1 according to the present embodiment will be described with reference to FIGS. 2 is a diagram illustrating a circuit configuration when the cylinder rod 8 is stopped, and FIG. 3 is a diagram illustrating a circuit configuration (differential circuit) when the cylinder rod 8 is advanced at a low pressure and a high speed. FIG. 5 is a diagram showing a circuit configuration (non-differential circuit) when the cylinder rod 8 is advanced at a high pressure and a low speed, and FIG. 5 is a diagram showing a circuit configuration when the cylinder rod 8 is retracted.

  First, in order to stop the cylinder rod 8, as shown in FIG. 2, the direction switching valve 10 is set to the neutral position by electromagnetic operation (releasing the excitation of the solenoids a and b), and the above-described first connection state ( That is, the A port and the T port are connected, and the B port and the P port are closed). As a result, the P port is closed by the direction switching valve 10, and the pipes 18, 20, and 22 are closed by the first check valve 24, the second check valve 26, and the external pilot type sequence valve 28. The hydraulic oil is prevented from flowing into and out of the first oil chamber 4a and the second oil chamber 4b, and the cylinder rod 8 is stopped. The first check valve 24 is kept closed by the pressure of the hydraulic oil applied from the hydraulic power source 34.

  Next, in order to move the cylinder rod 8 forward, as shown in FIG. 3, the direction switching valve 10 is switched from the neutral position to one side position (right side in FIG. 3) by electromagnetic operation (excitation of solenoid a). The second connection state described above (that is, a state where the A port and the P port are connected and the B port and the T port are connected). As a result, the hydraulic oil pipe 11 is formed, and the hydraulic oil fed from the hydraulic source 34 flows into the second oil chamber 4b via the P port pipe 16 and the A port pipe 12, and moves the piston 6 in the forward direction. Press to.

  Here, until the pressure of the hydraulic oil in the A-port pipe line 12 (that is, the pressure (head pressure) of the second oil chamber 4b) becomes equal to or higher than a preset pilot pressure, the differential is performed by the external pilot type sequence valve 28. The non-communication (closed) state of the release pipeline 22 is maintained, and the B port pipeline 20 is closed by the second check valve 26. For this reason, in this state, the hydraulic oil discharged from the first oil chamber 4 a as the piston 6 moves forward merges with the P port pipe 16 via the differential pipe 18 and is sent from the hydraulic source 34. A differential circuit is formed that is fed to the second oil chamber 4b together with the supplied hydraulic oil. That is, in the hydraulic cylinder hydraulic circuit 1 according to the present embodiment, since the direction switching valve 10 itself is included in the differential circuit, the differential circuit is established only by switching the direction switching valve 10 to one side position. To do. By forming the differential circuit in this way, the cylinder rod 8 is advanced at a low pressure and a high speed until the pressure of the hydraulic oil on the second oil chamber 4b side reaches a preset pilot pressure. Can do.

  Specifically, since the flow rate of the hydraulic oil supplied to the second oil chamber 4b is increased by the establishment of the differential circuit, the cylinder rod 8 moves forward in proportion to the increased flow rate of the hydraulic oil. Speed is increased. In other words, the forward speed of the cylinder rod 8 in the establishment of the differential circuit depends on the flow rate Q1 of the hydraulic oil discharged from the hydraulic source 34 and the hydraulic oil returned from the first oil chamber 4a to the second oil chamber 4b by the differential circuit. Since it is determined by the total flow rate Q with the flow rate Q2, the cylinder rod 8 in a state where a differential circuit is not formed (when the hydraulic oil discharged from the first oil chamber 4a is discharged to the hydraulic oil tank 32). The forward speed becomes higher than the forward speed by the flow rate Q2 of the increased amount of hydraulic oil. The flow rate Q2 of the hydraulic oil increased by the differential circuit is the cylinder boost ratio of the hydraulic cylinder 2 (the area of the piston 6 on the second oil chamber 4b side and the area of the piston 6 on the first oil chamber 4a side (first 2) (the ratio of the area of the piston 6 on the oil chamber 4b side to the cross-sectional area of the cylinder rod 8), that is, the specification of the hydraulic cylinder 2.

  On the other hand, when a differential circuit is formed, a closed circuit is formed between the first oil chamber 4a and the second oil chamber 4b, and back pressure is generated on the first oil chamber 4a (rod side oil chamber) side. The forward force of the cylinder rod 8 is “(the area of the piston 6 on the second oil chamber 4b side−the cross-sectional area of the cylinder rod 8) × the pressure of the hydraulic oil”, and the cross-sectional integral and differential circuit of the cylinder rod 8 are formed. This is lower than the forward force in a state where the hydraulic oil is not discharged (when the hydraulic oil discharged from the first oil chamber 4a is discharged to the hydraulic oil tank 32). For this reason, while the differential circuit is formed, the moving speed of the cylinder rod 8 is high, but the forward force (pressing force) is low.

  Then, in a state where the cylinder rod 8 is moving forward at a low pressure and a high speed, a target load is applied to the cylinder rod 8, for example, a pressure received when the cylinder rod 8 comes into contact with the object, and the second oil chamber When the pressure of the hydraulic fluid on the 4b side reaches a preset pilot pressure, the external pilot type sequence valve 28 is brought into communication with the pressure. As a result, as shown in FIG. 4, the hydraulic oil discharged from the first oil chamber 4 a is discharged to the hydraulic oil tank 32 via the differential release line 22. In addition, as a no-load (substantially atmospheric pressure) conduit toward the hydraulic oil tank 32 is formed, the first check valve 24 is closed by the hydraulic oil pressure applied from the hydraulic source 34. Thereby, since the differential circuit is released, the forward movement of the cylinder rod 8 is switched to the forward movement at high pressure and low speed. The “low speed” in this case is “low speed” with respect to the forward speed of the piston 6 (cylinder rod 8) in a state where the differential circuit is formed, and is not intended for speed control. . The forward speed of the piston 6 (cylinder rod 8) in this case is the speed generated as a result of the difference between the pressure of the hydraulic oil fed to the second oil chamber 4b and the target load acting on the cylinder rod 8. Become.

  In the hydraulic cylinder hydraulic circuit 1 according to the present embodiment, the differential is applied while the load applied to the cylinder rod 8 is less than the set operating pressure of the external pilot type sequence valve 28 regardless of the position of the cylinder rod 8. When a circuit is formed and a load higher than the set operating pressure of the external pilot type sequence valve 28 is generated on the cylinder rod 8, the differential circuit is released and a non-differential circuit is formed. For this reason, for example, a non-differential circuit is formed in addition to a mode in which the above-described differential circuit is formed and then switched to a non-differential circuit (a mode in which a target load is generated at the stroke end of the cylinder rod 8). After switching to the differential circuit (a mode in which the target load occurs immediately after the cylinder rod 8 moves and the load disappears later), and after the differential circuit is formed, the mode is switched to the non-differential circuit. After that, it is possible to execute a mode in which the circuit is switched again to the differential circuit (a mode in which a target load is generated during the stroke of the cylinder rod 8).

  Next, in order to retract the cylinder rod 8, the direction switching valve 10 is switched to the neutral position by electromagnetic operation (release of excitation of the solenoids a and b), and the cylinder rod 8 is once stopped, and then shown in FIG. As described above, the direction switching valve 10 is switched from the neutral position to the other one-side position by electromagnetic operation (excitation of the solenoid b), and the third connection state described above (that is, the A port and the T port are connected and the B port is connected) And P port are connected). As a result, hydraulic oil is supplied from the hydraulic power source 34 toward the first oil chamber 4a via a part of the P port pipeline 16, the B port pipeline 20, and the differential pipeline 18, and the discharge pipe Since the hydraulic oil in the second oil chamber 4b is discharged to the hydraulic oil tank 32 via the passage 13 (A port pipeline 12 and T port pipeline 14), the cylinder rod 8 moves backward.

  As described above, in the hydraulic cylinder hydraulic circuit 1 according to the present embodiment, the differential pipe 18 that joins the hydraulic oil discharged from the first oil chamber 4a to the hydraulic oil pipe 11 includes the direction switching valve 10 and the hydraulic pressure. A hydraulic oil line 11 is connected to the source 34. Thus, in the hydraulic cylinder hydraulic circuit 1 according to the present embodiment, the differential circuit is not included in the differential circuit on the secondary side of the direction switching valve 10, but the direction switching valve 10 itself is included in the differential circuit. Therefore, the differential circuit is automatically established only by switching the direction switching valve 10 to the above-described second connection state until a target load acts on the cylinder rod 8. While the differential circuit is established, the flow rate Q1 of the hydraulic oil discharged from the hydraulic source 34, and the flow rate Q2 of the hydraulic oil returned from the first oil chamber 4a to the second oil chamber 4b by the differential circuit The forward speed of the cylinder rod 8 is determined by the total flow rate Q. For this reason, even if the load acting on the cylinder rod 8 slightly fluctuates, the forward speed of the cylinder rod 8 in the differential circuit is not affected, and the total amount of hydraulic oil supplied to the second oil chamber 4b. The moving speed according to the flow rate Q is maintained. Further, in the hydraulic cylinder hydraulic circuit 1 according to the present embodiment, the external pilot type sequence valve 28 is in a non-communication state while the differential circuit is established, and a load acting on the cylinder rod that is moving forward ( Since the circuit is constituted by the first check valve 24 and the second check valve 26 that are not affected by the pressure of the hydraulic oil), there is no element that affects the moving speed of the cylinder rod 8 during the establishment of the differential circuit. As described above, in the hydraulic cylinder hydraulic circuit 1 according to the present embodiment, a differential circuit is formed by the operation of the pressure control device (sequence valve 124) based on the pilot pressure, like the hydraulic circuit of Patent Document 1. However, even if a load less than the target load acts on the cylinder rod 8, it does not affect the establishment of the differential circuit, so that the moving speed of the cylinder rod during the establishment of the differential circuit can be stabilized. Is possible.

  Further, in the hydraulic cylinder hydraulic circuit 1 according to the present embodiment, one direction switching valve 10, one external pilot type sequence valve 28, and two check valves (first check valve 24, second check valve 26). And low-pressure high-speed driving (differential circuit establishment) in a state where a target load is not generated, without using any special sensor or electrical control except for the direction switching valve 10 only in various pipe lines, Thus, it is possible to configure a circuit that can automatically switch between high-pressure and low-speed driving (non-differential circuit establishment) in a state where a load is generated regardless of the position of the cylinder rod. For this reason, according to the hydraulic circuit 1 for a hydraulic cylinder according to the present embodiment, it is possible to provide a simpler and less expensive configuration than the hydraulic circuit of Patent Document 1 in which at least two pressure control devices need to be used. . Further, the hydraulic circuit 1 for the hydraulic cylinder according to the present embodiment does not require setting and adjustment of the operation balance of two pressure control devices (sequence valve 124 and unload valve 126) like the hydraulic circuit of Patent Document 1. Therefore, there is an advantage that installation and maintenance work are easy.

  Further, in the hydraulic cylinder hydraulic circuit 1 according to the present embodiment, as the direction switching valve 10, the A port and the T port are connected in the neutral position state (first connection state), and the B port and the P port are connected. A so-called “AT communication / B, P blockage” type directional switching valve that is closed is used. Generally, the residual pressure on the second oil chamber 4b side (head side) in a state where the cylinder rod 8 is stopped may cause an unintended sudden advance when the stopped cylinder rod 8 is advanced. On the other hand, in the hydraulic cylinder hydraulic circuit 1 according to the present embodiment, by using a direction switching valve of the type “AT communication / B, P blockage” as the direction switching valve 10, when the cylinder rod 8 is stopped, The hydraulic oil pressure (head pressure) in the second oil chamber 4b can be reliably reduced to the hydraulic oil pressure in the T-port pipe line 14 without depending on the hydraulic oil pressure in the P port and B port. It is possible to prevent unintended sudden advance when the cylinder rod 8 is advanced, and there is an advantage that it is safe.

  The hydraulic circuit 1 for a hydraulic cylinder according to the present embodiment includes, for example, a hydraulic cylinder for a product extrusion device of a die casting machine or an injection molding machine, a squeeze pin for partial pressurization of a mold, a hydraulic cylinder for driving a movable core, etc. However, the present invention is not limited to this.

  The preferred embodiment of the present invention has been described above, but the technical scope of the present invention is not limited to the scope described in the above-described embodiment. Various modifications or improvements can be added to the above embodiments.

  For example, in the above-described embodiment, the hydraulic cylinder hydraulic circuit 1 according to the present embodiment is employed in the single rod type hydraulic cylinder 2 in which the cylinder rod 8 extends from the piston 6 toward the first oil chamber 4a side. Although it has been described that the differential circuit is established until the target load is generated when the rod 8 moves forward, the present invention is not limited to this. The hydraulic circuit 1 for a hydraulic cylinder according to the present embodiment may be used, for example, in a one-rod hydraulic cylinder in which a cylinder rod 8 extends from the piston 6 toward the second oil chamber 4b. It may be used for a double rod type hydraulic cylinder in which the cylinder rod 8 extends toward both the oil chamber 4a and the second oil chamber 4b. When used in a single rod type hydraulic cylinder in which the cylinder rod 8 extends from the piston 6 toward the second oil chamber 4b, a differential circuit is formed until a target load is generated when the cylinder rod 8 is retracted. When a high tensile force acts on the rod 8, the differential circuit is released. When the cylinder rod 8 is used in a double rod type hydraulic cylinder in which the cylinder rod 8 extends from the piston 6 toward both the first oil chamber 4a and the second oil chamber 4b, both when the cylinder rod 8 moves forward and backward. Thus, the differential circuit is established until the target load is generated.

  In the above-described embodiment, the direction switching valve 10 has been described as using the “AT communication / B, P blockage” type direction switching valve. However, the present invention is not limited to this, and at least P in the neutral position state. Any direction switching valve that closes the port may be used. As such a direction switching valve, in addition to the above-described “AT communication / B, P blockage” type direction switching valve, for example, an “ABT communication / P blockage” type direction switching valve, A “ABPT total occlusion” type direction switching valve or the like can be exemplified.

  Here, the direction switching valve of the “A-B-T communication / P blockage” type is similar to the direction switching valve 110 described in Patent Document 1 in that the A port, the B port, and the T port are in the neutral position. It is connected and the P port is closed. The cylinder rod 8 can be stopped in the neutral position also by such a direction switching valve of the “ABT communication / P blocking” type. When a direction switching valve of the “A-B-T communication / P blockage” type is used, if a flow is generated in the T port line 14 by driving another actuator or the like, it becomes back pressure and becomes the rod side. As a result, the cylinder rod 8 may move forward due to the difference in the area of the piston 6 between the rod side and the head side. It is preferable to additionally arrange a check valve so as to prevent the flow of gas.

  Further, the direction switching valve of the “ABPT total block” type is configured such that all of the A port, the B port, the P port, and the T port are closed in the neutral position state. In such a direction switch valve of the “ABPT total block” type, sudden jumping that is not intended at the time of forward switching is caused by the residual pressure on the second oil chamber 4b side (head side) when the cylinder rod 8 is stopped. The cylinder rod 8 can be stopped in the neutral position, although there is a possibility that the cylinder rod 8 may move forward a little due to a leak in the valve accompanying a long-time stop.

  Further, in the above-described embodiment, the direction switching valve that switches between the communication state and the non-communication state of the hydraulic oil pipe is described as a three-position valve having an A port, a B port, a P port, and a T port. However, the present invention is not limited to this, and other types of direction switching valves may be used as long as the same function can be exhibited, and a configuration in which the same function is exhibited by a plurality of switching valves may be employed.

  DESCRIPTION OF SYMBOLS 1 Hydraulic circuit for hydraulic cylinders, 2 Hydraulic cylinders, 4 Cylinder main body, 4a 1st oil chamber, 4b 2nd oil chamber, 6 Piston, 8 Cylinder rod, 10 direction switching valve, 11 Hydraulic oil line, 12 A port line, 13 discharge line, 14 T port line, 16 P port line, 18 differential line, 20 B port line, 22 differential release line, 23 branch point, 24 first check valve, 26 second Check valve, 28 External pilot type sequence valve, 30 Differential release pilot line, 31 Pressure gauge, 32 Hydraulic oil tank, 34 Hydraulic source

Claims (6)

A hollow cylinder body, a piston that partitions the internal space of the cylinder body into a first oil chamber and a second oil chamber, and at least one side of the first oil chamber and the second oil chamber from the piston A hydraulic circuit for a hydraulic cylinder used in a hydraulic cylinder having a cylinder rod extending toward the
When moving the piston in the direction from the second oil chamber toward the first oil chamber, a hydraulic oil line connecting the hydraulic oil source and the second oil chamber;
A direction switching valve configured to be able to switch between a communication state and a non-communication state of the hydraulic oil pipe;
A differential pipe for joining the hydraulic oil discharged from the first oil chamber to the hydraulic oil pipe;
A differential release line that is formed by branching from the differential line and discharges the hydraulic oil discharged from the first oil chamber to a hydraulic oil tank;
Provided between the branch point of the differential release pipe and the junction of the hydraulic oil pipe in the differential pipe, and allows the hydraulic oil to flow from the first oil chamber toward the hydraulic oil pipe. And a check valve configured to prevent the flow of hydraulic oil from the hydraulic oil conduit toward the first oil chamber;
An external pilot type sequence valve that is provided in the differential release line and configured to be able to switch between a communication state and a non-communication state of the differential release line;
A differential release pilot pipe for applying the pressure of the hydraulic oil on the second oil chamber side to the external pilot type sequence valve;
The differential pipe line is connected to the hydraulic oil pipe line between the direction switching valve and the hydraulic pressure source,
The external pilot type sequence valve communicates with the differential release line while the pressure of the hydraulic oil on the second oil chamber side applied through the differential release pilot line is equal to or higher than a predetermined pilot pressure. Configured to be in a state,
When the hydraulic oil line is brought into communication with the direction switching valve, and the differential release pipe is brought into non-communication with the external pilot type sequence valve, the differential pipe and the hydraulic oil pipe The path forms a differential circuit in which the hydraulic oil in the first oil chamber flows toward the second oil chamber,
When the hydraulic oil conduit is in communication with the direction switching valve and the differential release conduit is in communication with the external pilot type sequence valve, A hydraulic circuit for a hydraulic cylinder, characterized in that a non-differential circuit is formed in which hydraulic oil in an oil chamber flows toward the hydraulic oil tank. The direction switching valve has an A port, a B port, a P port, and a T port, and at least a first state in which the P port is closed, the A port and the P port are connected, and the B port and the T port Is configured to be switchable between a second state in which the A port and the T port are connected, and a third state in which the B port and the P port are connected.
The hydraulic oil line includes a P port line that connects the hydraulic pressure source and the P port, and an A port line that connects the A port and the second oil chamber,
The differential pipe line is configured to connect the second oil chamber and the P port pipe line,
The hydraulic circuit for the hydraulic cylinder is
A B port pipe connecting the differential pipe and the B port;
A T port line connecting the T port and the hydraulic oil tank;
Provided in the B port pipeline, allowing the hydraulic oil to flow from the B port toward the first oil chamber or the differential pipeline, and from the first oil chamber or the differential pipeline The hydraulic circuit for a hydraulic cylinder according to claim 1, further comprising: a second check valve configured to prevent the flow of hydraulic oil toward the B port. When the direction switching valve is in the third state, the A port pipe and the T port pipe form a discharge pipe through which the hydraulic oil in the second oil chamber flows toward the hydraulic oil tank. The hydraulic circuit for a hydraulic cylinder according to claim 2, wherein the hydraulic circuit is configured as described above. The hydraulic cylinder according to any one of claims 1 to 3, wherein the hydraulic cylinder is a one-rod hydraulic cylinder having the cylinder rod extending from the piston toward the first oil chamber. Hydraulic circuit. The hydraulic cylinder according to any one of claims 1 to 3, wherein the hydraulic cylinder is a one-rod hydraulic cylinder having the cylinder rod extending from the piston toward the second oil chamber. Hydraulic circuit. The said hydraulic cylinder is a double rod type hydraulic cylinder which has the said cylinder rod each extended toward the said 1st oil chamber and the said 2nd oil chamber from the said piston. Hydraulic circuit for hydraulic cylinder as described in item

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