Hydraulic device

Abstract

In a rod-side passage (22) of a hydraulic device (10), a driving hydraulic oil discharged from a rod chamber (105) of a hydraulic cylinder (100) flows. A control valve (40) of the hydraulic device (10) operates in response to the pressure of a control hydraulic oil supplied by a pump (61), and controls the flow of the driving hydraulic oil in the rod-side passage (22). A controller (70) of the hydraulic device (10) controls the pressure of the control hydraulic oil supplied to the control valve (40) by the pump (61).

Description

Hydraulic system

[0001] The present disclosure relates to hydraulic systems.

[0002] Patent Document 1 discloses a hydraulic device for driving a die-casting machine. In the die-casting machine, a plunger that pushes out molten metal is driven by a hydraulic cylinder. The hydraulic device drives the hydraulic cylinder of the die-casting machine. In this hydraulic device, a servo valve is provided in a pipe connected to a rod chamber of the hydraulic cylinder.

[0003] The hydraulic device disclosed in Patent Document 1 controls the extrusion speed of a hydraulic cylinder rod by meter-out control. Specifically, hydraulic oil is supplied to the head chamber of the hydraulic cylinder with the servo valve closed. When the pressure in the head chamber reaches a predetermined value, the servo valve opens. When the servo valve opens, hydraulic oil is discharged from the rod chamber of the hydraulic cylinder, pushing the rod out. At this time, the extrusion speed of the rod is controlled by adjusting the opening of the servo valve and adjusting the flow rate of hydraulic oil flowing out of the rod chamber.

[0004] Japanese Patent Application Laid-Open No. 2020-142245

[0005] The hydraulic device disclosed in Patent Document 1 can precisely control the extrusion speed of the hydraulic cylinder rod by controlling the opening of the servo valve. However, because the servo valve controls the spool position in very fine steps (e.g., 5 μm), it cannot function properly if foreign matter such as sludge gets into the servo valve. Therefore, when using a servo valve, measures such as installing a filter to capture foreign matter must be taken, which can complicate maintenance work on the hydraulic device.

[0006] An object of the present disclosure is to control the extrusion speed of a rod of a hydraulic cylinder in a hydraulic device that drives a hydraulic cylinder, without complicating maintenance work for the hydraulic device.

[0007] A first aspect of the present disclosure is a hydraulic device (10) that drives a hydraulic cylinder (100), comprising: a head-side passage (21) through which driving hydraulic oil supplied to a head chamber (104) of the hydraulic cylinder (100) flows; a rod-side passage (22) through which driving hydraulic oil discharged from a rod chamber (105) of the hydraulic cylinder (100) flows; a control valve (40) that is provided in the rod-side passage (22) and operates in accordance with the pressure of the supplied control hydraulic oil to control the flow of the driving hydraulic oil in the rod-side passage (22); a pump (61) that supplies control hydraulic oil to the control valve (40); and a controller (70) that controls the pressure of the control hydraulic oil supplied by the pump (61) to the control valve (40).

[0008] In the first aspect, a control valve (40) is provided in the rod-side passage (22). The control valve (40) controls the flow of hydraulic oil flowing out of the rod chamber (105) of the hydraulic cylinder (100). The control valve (40) operates in response to the pressure of the control hydraulic oil supplied by the pump (61). The controller (70) controls the pressure of the hydraulic oil supplied to the control valve (40) by the pump (61). Therefore, the operation of the control valve (40) is controlled by the controller (70), and as a result, the extrusion speed of the rod of the hydraulic cylinder (100) is controlled. Furthermore, since the control valve (40) that operates in response to the pressure of the supplied control hydraulic oil is used, maintenance work on the hydraulic device (10) is not complicated.

[0009] A second aspect of the present disclosure is the first aspect, wherein the control valve (40) is a relief valve (41) whose operating pressure changes depending on the pressure of the supplied control hydraulic oil.

[0010] In the second aspect, a relief valve (41) is provided as the control valve (40) in the hydraulic device (10). The pressure at which the relief valve (41) operates varies depending on the pressure of the control hydraulic oil supplied to the relief valve (41) by the pump (61).

[0011] A third aspect of the present disclosure is the first aspect, wherein the control valve (40) is a flow rate adjustment valve (42) that changes the flow rate of the driving hydraulic oil passing through it depending on the pressure of the supplied control hydraulic oil.

[0012] In the third aspect, the flow rate adjustment valve (42) is provided as the control valve (40) in the hydraulic device (10). The flow rate of the driving hydraulic oil passing through the flow rate adjustment valve (42) varies depending on the pressure of the control hydraulic oil supplied to the flow rate adjustment valve (42) by the pump (61).

[0013] A fourth aspect of the present disclosure is any one of the first to third aspects, wherein the pump (61) performs both the operation of supplying control hydraulic oil to the control valve (40) and the operation of supplying drive hydraulic oil to the hydraulic cylinder (100) through the head side passage (21).

[0014] In the fourth aspect, the pump (61) not only supplies control hydraulic oil to the control valve (40) but also supplies drive hydraulic oil to the head chamber (104) of the hydraulic cylinder (100). The pump (61) is used both to control the operation of the control valve (40) and to drive the hydraulic cylinder (100).

[0015] A fifth aspect of the present disclosure is any one of the first to fourth aspects, further comprising an on-off valve (51) arranged in parallel with the control valve (40) in the rod side passage (22) and controlling the flow of hydraulic oil for driving in the rod side passage (22).

[0016] In the fifth aspect, a control valve (40) and an on-off valve (51) are provided in parallel in the rod side passage (22). The hydraulic oil for driving flowing through the rod side passage (22) passes through the control valve (40) or the on-off valve (51).

[0017] A sixth aspect of the present disclosure is the fifth aspect, wherein the controller (70) opens the control valve (40) and then opens the on-off valve (51) when pushing out the rod (103) of the hydraulic cylinder (100).

[0018] When pushing out the rod (103) of the hydraulic cylinder (100), the controller (70) of the sixth aspect first opens the control valve (40) and then opens the on-off valve (51). As a result, the flow rate of the driving hydraulic oil flowing out from the rod chamber (105) of the hydraulic cylinder (100) to the rod-side passage (22) changes in two stages, and the moving speed of the rod-side passage (22) of the hydraulic cylinder (100) changes in two stages. The moving speed of the rod (103) in the first stage changes depending on the pressure of the control hydraulic oil supplied to the control valve (40) by the pump (61).

[0019] FIG. 1 is a piping diagram of a hydraulic circuit showing the configuration of a hydraulic device of embodiment 1. FIG. 2 is a piping diagram of a hydraulic circuit showing a preparatory operation of the hydraulic device of embodiment 1. FIG. 3 is a piping diagram of a hydraulic circuit showing a low-speed injection operation of the hydraulic device of embodiment 1. FIG. 4 is a piping diagram of a hydraulic circuit showing a high-speed injection operation of the hydraulic device of embodiment 1. FIG. 5 is a piping diagram of a hydraulic circuit showing a stop operation of the hydraulic device of embodiment 1. FIG. 6 is a piping diagram of a hydraulic circuit showing a retraction operation of the hydraulic device of embodiment 1. FIG. 7 is a piping diagram of a hydraulic circuit showing the configuration of a hydraulic device of embodiment 2. FIG. 8 is a piping diagram of a hydraulic circuit showing a preparatory operation of the hydraulic device of embodiment 2. FIG. 9 is a piping diagram of a hydraulic circuit showing a low-speed injection operation of the hydraulic device of embodiment 2. FIG. 10 is a piping diagram of a hydraulic circuit showing a high-speed injection operation of the hydraulic device of embodiment 2. FIG. 11 is a piping diagram of a hydraulic circuit showing a stop operation of the hydraulic device of embodiment 2. FIG. 12 is a piping diagram of a hydraulic circuit showing a retraction operation of the hydraulic device of embodiment 2.

[0020] First Embodiment A first embodiment will be described.

[0021] As shown in Fig. 1, the hydraulic device (10) of this embodiment drives a hydraulic cylinder (100) of a die-casting machine. The hydraulic cylinder (100) driven by the hydraulic device (10) of this embodiment drives a plunger that pushes out molten metal.

[0022] - Hydraulic Cylinder - The hydraulic cylinder (100) is a single-rod cylinder. The hydraulic cylinder (100) includes a cylinder tube (101), a piston (102), and a rod (103). The internal space of the cylinder tube (101) is partitioned by the piston (102) into a head chamber (104) on the piston (102) side and a rod chamber (105) on the rod (103) side.

[0023] -Hydraulic Device- The hydraulic device (10) includes a hydraulic circuit (20) and a controller (70). The hydraulic circuit (20) is connected to a hydraulic cylinder (100) of the die-casting machine. The controller (70) controls the devices provided in the hydraulic device (10).

[0024] <Hydraulic Circuit> The hydraulic circuit (20) includes a pump unit (60), a tank (15), and an accumulator (16). The hydraulic circuit (20) also includes a relief valve (41), a first cartridge valve (51), a second cartridge valve (52), a switching valve (55), a first direction switching valve (56), a second direction switching valve (57), and a third direction switching valve (58).

[0025] In the hydraulic circuit (20), a plurality of components such as a pump unit (60) are connected by piping. In the hydraulic circuit (20), hydraulic oil sucked out from a tank (15) is supplied to a hydraulic cylinder (100), and hydraulic oil discharged from the hydraulic cylinder (100) is returned to the tank (15).

[0026] In the hydraulic circuit (20), the hydraulic pump (61) of the pump unit (60) has an inlet connected to the tank (15). The discharge port of the hydraulic pump (61) is connected to a first port of a switching valve (55). The second port of the switching valve (55) is connected to a second port of a second cartridge valve (52). The piping from the discharge port of the hydraulic pump (61) to the second port of the second cartridge valve (52) forms a supply-side main passage (30).

[0027] A first port of the second cartridge valve (52) is connected to the head chamber (104) of the hydraulic cylinder (100). The piping from the second cartridge valve (52) to the head chamber (104) of the hydraulic cylinder (100) forms a first supply passage (31).

[0028] The first supply passage (31) and the supply-side main passage (30) form a head-side passage (21) through which the hydraulic oil for driving flows and is supplied to the head chamber (104) of the hydraulic cylinder (100). In the head-side passage (21), the selector valve (55) and the second cartridge valve (52) are connected in series.

[0029] The accumulator (16) is connected to a pipe connecting the switching valve (55) and the second cartridge valve (52). A die circuit (not shown) for driving the die of the die-casting machine is connected to a pipe connecting the discharge port of the hydraulic pump (61) and the switching valve (55).

[0030] A first port of the relief valve (41) and a first port of the first cartridge valve (51) are connected to a rod chamber (105) of the hydraulic cylinder (100). The piping connecting the relief valve (41) and the first cartridge valve (51) to the hydraulic cylinder (100) forms a second discharge passage (37). A second port of the relief valve (41) and a second port of the first cartridge valve (51) are connected to the tank (15). The piping connecting the relief valve (41) and the first cartridge valve (51) to the tank (15) forms a discharge-side main passage (35).

[0031] The second discharge passage (37) and the discharge-side main passage (35) form a rod-side passage (22) through which the hydraulic oil discharged from the rod chamber (105) of the hydraulic cylinder (100) flows. In the rod-side passage (22), the relief valve (41) and the first cartridge valve (51) are connected in parallel.

[0032] The third directional control valve (58) has a first port connected to a third port of the second cartridge valve (52) and a second port connected to the rod chamber (105) of the hydraulic cylinder (100). The piping connecting the third directional control valve (58) and the rod chamber (105) of the hydraulic cylinder (100) constitutes the second supply passage (32). The third directional control valve (58) has a third port connected to the head chamber (104) of the hydraulic cylinder (100) and a fourth port connected to the tank (15). The piping connecting the third directional control valve (58) and the head chamber (104) of the hydraulic cylinder (100) constitutes the first discharge passage (36).

[0033] A back pressure port of the relief valve (41) is connected to a pipe connecting the discharge port of the hydraulic pump (61) and the switching valve (55). The pipe connected to the back pressure port of the relief valve (41) forms a first pressure introducing passage (26) for supplying control hydraulic oil to the relief valve (41).

[0034] The back pressure port of the first cartridge valve (51) and the back pressure port of the second cartridge valve (52) are connected via piping between the switching valve (55) and the second cartridge valve (52) in the supply side main passage (30). This piping forms a second pressure introducing passage (27). In the second pressure introducing passage (27), a first directional control valve (56) is connected to the first cartridge valve (51) and a second directional control valve (57) is connected to the second cartridge valve (52).

[0035] In the second pressure introducing passage (27), the first port of the first directional control valve (56) and the first port of the second directional control valve (57) are connected between the switching valve (55) and the second cartridge valve (52) in the supply side main passage (30). The second port of the first directional control valve (56) is connected to the back pressure port of the first cartridge valve (51). The second port of the second directional control valve (57) is connected to the back pressure port of the second cartridge valve (52).

[0036] The fourth port of the first directional control valve (56) and the fourth port of the second directional control valve (57) are connected to the tank (15). The third port of the first directional control valve (56) and the third port of the second directional control valve (57) are each sealed.

[0037] <Pump Unit> The pump unit (60) includes a hydraulic pump (61) and an electric motor (62). The hydraulic pump (61) is a pump that draws hydraulic oil from an inlet and discharges it from a discharge port. The hydraulic pump (61) is a positive displacement fluid machine such as a swash plate pump. The electric motor (62) is connected to a drive shaft of the hydraulic pump (61) and drives the hydraulic pump (61).

[0038] The pump unit (60) includes a pump controller (63). The pump controller (63) controls the rotation speed of the hydraulic pump (61) by adjusting the rotation speed of the electric motor (62). The pump controller (63) controls the rotation speed of the hydraulic pump (61) so that the pressure of the hydraulic oil discharged by the hydraulic pump (61) becomes a set pressure.

[0039] <Relief Valve> The relief valve (41) switches between an open state and a closed state depending on the back pressure. In the open state, the first port is in communication with the second port. In the closed state, the first port is blocked from the second port. The relief valve (41) allows or blocks the flow of hydraulic oil for driving in the rod side passage (22). The maximum value of the flow rate of the hydraulic oil passing through the relief valve (41) is smaller than the maximum value of the flow rate of the hydraulic oil passing through the first cartridge valve (51).

[0040] The back pressure in the relief valve (41) is the pressure of the control hydraulic oil introduced from the first pressure introducing passage (26) to the back pressure port. The pressure at which the relief valve (41) switches from a closed state to an open state varies depending on the back pressure. As the back pressure increases, the pressure at which the relief valve (41) switches from a closed state to an open state increases. The relief valve (41) is "a control valve (40) that operates in response to the pressure of the control hydraulic oil supplied from the hydraulic pump and controls the flow of the drive hydraulic oil in the rod side passage (22)."

[0041] <First Cartridge Valve> The first cartridge valve (51) switches between an open state and a closed state depending on the back pressure. In the open state, the first port communicates with the second port. In the closed state, the first port is blocked from the second port. The first cartridge valve (51) allows or blocks the flow of hydraulic oil for driving in the rod side passage (22).

[0042] The back pressure in the first cartridge valve (51) is the pressure of the control hydraulic oil introduced from the second pressure introducing passage (27) to the back pressure port. When the back pressure is sufficiently higher than the pressure of the hydraulic oil introduced to the first port, the first cartridge valve (51) is held in a closed state. When the back pressure becomes lower to a certain extent than the pressure of the hydraulic oil introduced to the first port, the first cartridge valve (51) switches from a closed state to an open state. The first cartridge valve (51) is "an open / close valve that is arranged in parallel with the relief valve (41) in the rod side passage (22) and controls the flow of the driving hydraulic oil in the rod side passage (22)."

[0043] <Second Cartridge Valve> The second cartridge valve (52) switches between a first state and a second state depending on the back pressure. In the first state, the second port communicates with both the first port and the third port. In the second state, the second port communicates with the third port and is blocked from the first port. The second cartridge valve (52) enables and disables the flow of hydraulic oil for driving in the head side passage (21).

[0044] The back pressure in the second cartridge valve (52) is the pressure of the hydraulic oil for control introduced from the second pressure introducing passage (27) to the back pressure port. When the back pressure is sufficiently higher than the pressure of the hydraulic oil introduced to the second port, the second cartridge valve (52) is held in the second state. When the back pressure becomes lower than the pressure of the hydraulic oil introduced to the second port to a certain extent, the second cartridge valve (52) switches from the second state to the first state.

[0045] <Switching Valve> The switching valve (55) is provided with a driving solenoid and is switchable between an open state and a closed state. In the open state, the first port is connected to the second port. In the closed state, the first port is disconnected from the second port.

[0046] <First Directional Switching Valve, Second Directional Switching Valve> The first direction switching valve (56) and the second direction switching valve (57) each include a driving solenoid and are switchable between a first state and a second state. In the first state, the first port communicates with the second port, and the third port communicates with the fourth port. In the second state, the first port communicates with the third port, and the second port communicates with the fourth port.

[0047] The first directional control valve (56) in the first state connects the back pressure port of the first cartridge valve (51) to the second pressure introducing passage (27). The first directional control valve (56) in the second state connects the back pressure port of the first cartridge valve (51) to the tank (15). By operating the first directional control valve (56), the first cartridge valve (51) is switched from one of the open state and the closed state to the other.

[0048] The second directional control valve (57) in the first state connects the back pressure port of the second cartridge valve (52) to the second pressure introducing passage (27). The second directional control valve (57) in the second state connects the back pressure port of the second cartridge valve (52) to the tank (15). By operating the second directional control valve (57), the second cartridge valve (52) is switched from one of the first state and the second state to the other.

[0049] <Third Direction Switching Valve> The third direction switching valve (58) is provided with a driving solenoid and is switchable between a first state, a second state, and a closed state. In the first state, the first port communicates with the second port, and the third port communicates with the fourth port. In the second state, the first port communicates with the third port, and the second port communicates with the fourth port. In the closed state, each of the first to fourth ports is blocked from the other ports.

[0050] <Accumulator> The accumulator (16) is a hollow container-like member. The interior of the accumulator (16) is divided into an oil chamber and a gas chamber by a rubber bladder. The oil chamber of the accumulator (16) communicates with the supply-side main passage (30) via a pipe.

[0051] <Controller> The controller (70) includes a microcomputer (71) and a memory device (72). The memory device (72) is a semiconductor memory. The memory device (72) stores software for operating the microcomputer (71). The controller (70) controls the switching valve (55), the first directional control valve (56), the second directional control valve (57), and the third directional control valve (58). The controller (70) also controls the pressure of the hydraulic oil discharged by the hydraulic pump (61) by transmitting a set pressure to the pump controller (63) of the pump unit (60).

[0052] --Operation-- The operation of the hydraulic device (10) will be described. The hydraulic device (10) drives the hydraulic cylinder (100) by meter-out control. In one molding process of the die-casting machine, the hydraulic device (10) sequentially performs a preparatory operation, a low-speed injection operation, a high-speed injection operation, a stopping operation, and a retreating operation.

[0053] <Preparatory Operation> The preparatory operation is an operation for holding the relief valve (41) and the first cartridge valve (51) in a closed state and for holding the second cartridge valve (52) in the second state. Here, the preparatory operation will be described with reference to FIG. 2.

[0054] In the preparatory operation, the controller (70) sets the set pressure to the first pressure. The pump controller (63) of the pump unit (60) controls the rotation speed of the hydraulic pump (61) so that the pressure of the hydraulic oil discharged from the hydraulic pump (61) becomes the set pressure (=the first pressure).

[0055] The first pressure introducing passage (26) is connected to the back pressure port of the relief valve (41), so that the back pressure of the relief valve (41) becomes the first pressure, and the relief valve (41) is maintained in a closed state.

[0056] In the preparatory operation, the controller (70) opens the switching valve (55), puts the first directional control valve (56) and the second directional control valve (57) in their first states, and puts the third directional control valve (58) in a closed state.

[0057] The hydraulic oil discharged from the hydraulic pump (61) passes through the selector valve (55) and is stored in the accumulator (16). Note that when the amount of hydraulic oil stored in the accumulator (16) is sufficiently large and the pressure of the hydraulic oil stored in the accumulator (16) is sufficiently high, the selector valve (55) may be in a closed state.

[0058] The pressure of the hydraulic oil in the second pressure introducing passage (27) is substantially equal to the pressure (=first pressure) of the hydraulic oil discharged from the hydraulic pump (61). When the first directional control valve (56) is in the first state, the back pressure of the first cartridge valve (51) becomes the first pressure, and the first cartridge valve (51) is held in a closed state. When the second directional control valve (57) is in the first state, the back pressure of the second cartridge valve (52) becomes the first pressure, and the second cartridge valve (52) is held in the second state.

[0059] <Low-Speed ​​Injection Operation> The low-speed injection operation is an operation in which the rod (103) of the hydraulic cylinder (100) is pushed out at a relatively low speed. The low-speed injection operation is an operation for pushing out molten metal at a low speed. The low-speed injection operation is performed for a very short time (e.g., 50 to 100 ms). Here, the low-speed injection operation will be described with reference to FIG. 3.

[0060] During the low-speed injection operation, the controller (70) changes the set pressure from the first pressure to the second pressure. The second pressure is lower than the first pressure. The pump controller (63) of the pump unit (60) controls the rotation speed of the hydraulic pump (61) so that the pressure of the hydraulic oil discharged from the hydraulic pump (61) becomes the set pressure (= the second pressure). As a result, the back pressure of the relief valve (41) decreases from the first pressure to the second pressure.

[0061] In the low-speed injection operation, the controller (70) switches the switching valve (55) from an open state to a closed state, holds the first directional switching valve (56) in the first state, switches the second directional switching valve (57) from the first state to the second state, and holds the third directional switching valve (58) in the closed state.

[0062] The pressure of the hydraulic oil in the accumulator (16) and the second pressure introducing passage (27) is maintained at the first pressure. The first directional control valve (56) is maintained in the first state. Therefore, the back pressure of the first cartridge valve (51) is maintained at the first pressure, and the first cartridge valve (51) is maintained in the closed state. The second directional control valve (57) switches from the first state to the second state. Therefore, the back pressure of the second cartridge valve (52) becomes the pressure of the hydraulic oil in the tank (15) (substantially equal to atmospheric pressure), and the second cartridge valve (52) switches from the second state to the first state.

[0063] When the second cartridge valve (52) is in the first state, the hydraulic oil in the accumulator (16) flows through the head-side passage (21) and is supplied as driving hydraulic oil to the head chamber (104) of the hydraulic cylinder (100). The pressure of the hydraulic oil supplied to the head chamber (104) of the hydraulic cylinder (100) is substantially the first pressure.

[0064] When the hydraulic pressure in the head chamber (104) of the hydraulic cylinder (100) increases, the hydraulic pressure in the rod chamber (105) also increases. When the hydraulic pressure in the rod chamber (105) exceeds a predetermined pressure, the relief valve (41) switches from a closed state to an open state. As a result, the hydraulic oil in the rod chamber (105) of the hydraulic cylinder (100) is discharged to the tank (15) through the rod-side passage (22), and the rod (103) of the hydraulic cylinder (100) is pushed out.

[0065] As the back pressure (= second pressure) of the relief valve (41) increases, the difference in hydraulic pressure between the head chamber (104) and the rod chamber (105) at the time when the relief valve (41) opens and the rod (103) of the hydraulic cylinder (100) starts to move decreases, resulting in a slower movement speed of the rod (103). Also, as the back pressure (= second pressure) of the relief valve (41) decreases, the difference in hydraulic pressure between the head chamber (104) and the rod chamber (105) at the time when the relief valve (41) opens and the rod (103) of the hydraulic cylinder (100) starts to move increases, resulting in a faster movement speed of the rod (103). In this way, during the low-speed injection operation, the movement speed of the rod (103) of the hydraulic cylinder (100) can be adjusted by changing the back pressure of the relief valve (41).

[0066] <High-Speed ​​Injection Operation> The high-speed injection operation is an operation in which the rod (103) of the hydraulic cylinder (100) is pushed out at a relatively high speed. The high-speed injection operation is an operation for injecting molten metal into the mold of the die-casting machine at a high speed. Here, the high-speed injection operation will be described with reference to FIG. 4.

[0067] In the high-speed injection operation, similarly to the low-speed injection operation, the controller (70) sets the set pressure to the second pressure (< the first pressure). Therefore, the back pressure of the relief valve (41) becomes the second pressure. The relief valve (41) is in the open state, similarly to the low-speed injection operation.

[0068] In the high-speed injection operation, the controller (70) maintains the switching valve (55), the second directional control valve (57), and the third directional control valve (58) in the same states as in the low-speed injection operation, while switching the first directional control valve (56) from the first state to the second state.

[0069] As in the case of the low-speed injection operation, hydraulic oil for driving is supplied to the head chamber (104) of the hydraulic cylinder (100) from the accumulator (16) through the head-side passage (21).

[0070] The first directional control valve (56) switches from the first state to the second state, and therefore the back pressure of the first cartridge valve (51) becomes equal to the pressure of the hydraulic oil in the tank (15) (substantially equal to atmospheric pressure), and the first cartridge valve (51) switches from the closed state to the open state.

[0071] In the high-speed injection operation, both the relief valve (41) and the first cartridge valve (51) are open, and therefore, the flow rate of the hydraulic oil flowing from the rod chamber (105) of the hydraulic cylinder (100) to the rod-side passage (22) increases significantly compared to the low-speed injection operation, and the rod (103) of the hydraulic cylinder (100) is pushed out in one go at high speed.

[0072] <Stopping Operation> The stopping operation is an operation for stopping the rod (103) of the hydraulic cylinder (100) that has been pushed out by the high-speed injection operation. Here, the stopping operation will be described with reference to FIG.

[0073] In the stopping operation, the controller (70) changes the set pressure from the second pressure to the first pressure, so that the back pressure of the relief valve (41) changes from the second pressure to the first pressure, and the relief valve (41) switches from an open state to a closed state.

[0074] In the stopping operation, the controller (70) maintains the switching valve (55) and the third directional switching valve (58) in the same state as in the high-speed injection operation, while switching the first directional switching valve (56) and the second directional switching valve (57) from the second state to the first state.

[0075] When the second directional control valve (57) is in the first state, the back pressure of the second cartridge valve (52) becomes equal to the pressure of the hydraulic oil in the accumulator (≈first pressure), and the second cartridge valve (52) switches from the first state to the second state, thereby stopping the supply of hydraulic oil to the head chamber (104) of the hydraulic cylinder (100).

[0076] When the first directional control valve (56) is in the first state, the back pressure of the first cartridge valve (51) becomes equal to the pressure of the hydraulic oil in the accumulator (16) (≈first pressure), and the first cartridge valve (51) switches from the open state to the closed state. As described above, during the stopping operation, the relief valve (41) is closed. Therefore, the discharge of the hydraulic oil from the rod chamber (105) of the hydraulic cylinder (100) is stopped.

[0077] In this manner, during the stopping operation, the supply of hydraulic oil to the head chamber (104) of the hydraulic cylinder (100) is stopped, and the discharge of hydraulic oil from the rod chamber (105) of the hydraulic cylinder (100) is stopped, thereby stopping the rod (103) of the hydraulic cylinder (100).

[0078] <Retraction Operation> The retreat operation is an operation of pulling back the rod (103) of the hydraulic cylinder (100). Here, the retreat operation will be described with reference to FIG.

[0079] In the retraction operation, the controller (70) maintains the set pressure at the first pressure, so that the back pressure of the relief valve (41) is maintained at the first pressure, and the relief valve (41) is maintained in a closed state.

[0080] In the stop operation, the controller (70) maintains the switching valve (55), the first directional switching valve (56), and the second directional switching valve (57) in the same states as in the stop operation, while switching the third directional switching valve (58) from the closed state to the first state.

[0081] When the third directional control valve (58) is in the first state, the hydraulic oil in the accumulator (16) passes through the second cartridge valve (52) and the third directional control valve (58) in this order and is supplied to the rod chamber (105) of the hydraulic cylinder (100). When the third directional control valve (58) is in the first state, the head chamber (104) of the hydraulic cylinder (100) communicates with the tank (15), and the hydraulic oil in the head chamber (104) is discharged to the tank (15). As a result, the rod (103) of the hydraulic cylinder (100) is pulled back toward the head chamber (104).

[0082] Feature (1) of First Embodiment In the hydraulic device (10) of this embodiment, a control valve (40) is provided in the rod-side passage (22). The control valve (40) controls the flow of hydraulic oil flowing out of the rod chamber (105) of the hydraulic cylinder (100). The control valve (40) operates in response to the pressure of control hydraulic oil supplied by the hydraulic pump (61). The controller (70) controls the pressure of the hydraulic oil supplied to the control valve (40) by the hydraulic pump (61). Therefore, the controller (70) controls the operation of the control valve (40), which in turn controls the extrusion speed of the rod (103) of the hydraulic cylinder (100). Furthermore, the use of the control valve (40) that operates in response to the pressure of the supplied control hydraulic oil does not complicate maintenance of the hydraulic device (10).

[0083] In particular, the hydraulic device (10) of this embodiment is provided with a relief valve (41) as the control valve (40). In this embodiment, by using the relief valve (41), which is easier to maintain and more reliable than a servo valve, it is possible to control the extrusion speed of the rod (103) of the hydraulic cylinder (100) without complicating the maintenance work of the hydraulic device (10).

[0084] Feature (2) of First Embodiment In the hydraulic device (10) of this embodiment, the hydraulic pump (61) supplies hydraulic oil to the accumulator (16) during the pre-injection operation. The hydraulic oil stored in the accumulator (16) is supplied to the head chamber (104) of the hydraulic cylinder (100) as driving hydraulic oil during the low-speed injection operation and the high-speed injection operation. In this manner, the hydraulic pump (61) supplies driving hydraulic oil to the hydraulic cylinder (100) via the accumulator (16). The hydraulic pump (61) also supplies control hydraulic oil to the relief valve (41) during each of the pre-injection operation, the low-speed injection operation, the high-speed injection operation, the stop operation, and the retraction operation. Therefore, in the hydraulic device (10) of this embodiment, the hydraulic pump (61) of the pump unit (60) is used both to control the operation of the relief valve (41), which is the control valve (40), and to drive the hydraulic cylinder (100).

[0085] Second Embodiment A second embodiment will be described.

[0086] 7, the hydraulic device (10) of the present embodiment includes a throttle valve (42) instead of the relief valve (41) of the first embodiment. Here, differences between the hydraulic device (10) of the present embodiment and the hydraulic device (10) of the first embodiment will be described.

[0087] In the hydraulic circuit (20) of this embodiment, a first port of the throttle valve (42) is connected to the rod chamber (105) of the hydraulic cylinder (100) via a second discharge passage (37). A second port of the throttle valve (42) is connected to the tank (15) via a discharge-side main passage (35). In the rod-side passage (22) of the hydraulic circuit (20) of this embodiment, the throttle valve (42) and a first cartridge valve (51) are connected in parallel. A back pressure port of the throttle valve (42) is connected to a pipe connecting a discharge port of the hydraulic pump (61) and a switching valve (55) via a first pressure introducing passage (26).

[0088] <Throttle Valve> The throttle valve (42) switches between an open state and a closed state depending on the back pressure. In the open state, the first port is connected to the second port. In the closed state, the first port is blocked from the second port. The throttle valve (42) allows or blocks the flow of hydraulic oil for driving in the rod side passage (22). In the open state, the opening degree of the throttle valve (42) changes depending on the back pressure. When the opening degree of the throttle valve (42) changes, the flow rate of the hydraulic oil passing through the throttle valve (42) changes. The maximum value of the flow rate of the hydraulic oil passing through the throttle valve (42) is smaller than the maximum value of the flow rate of the hydraulic oil passing through the first cartridge valve (51).

[0089] The back pressure in the throttle valve (42) is the pressure of the control hydraulic oil introduced from the first pressure introducing passage (26) to the back pressure port. The opening of the throttle valve (42) changes depending on the back pressure. As the back pressure of the throttle valve (42) increases, the opening of the throttle valve (42) increases. The throttle valve (42) is a "flow rate control valve that changes the flow rate of the driving hydraulic oil passing through it depending on the pressure of the supplied control hydraulic oil." Similarly to the relief valve (41) of the first embodiment, the throttle valve (42) is a "control valve (40) that operates depending on the pressure of the control hydraulic oil supplied from the hydraulic pump and controls the flow of the driving hydraulic oil in the rod side passage (22)."

[0090] -Operation- The operation of the hydraulic system (10) will be described. The hydraulic system (10) of this embodiment, like the hydraulic system (10) of the first embodiment, performs a preparatory operation, a low-speed injection operation, a high-speed injection operation, a stopping operation, and a retreating operation in that order in one molding process of the die-casting machine. Here, the differences between these operations and the hydraulic system (10) of the first embodiment will be mainly described.

[0091] <Preparatory Operation> The preparatory operation of this embodiment is an operation for holding the throttle valve (42) and the first cartridge valve (51) in a closed state and for holding the second cartridge valve (52) in the second state. Here, the preparatory operation of this embodiment will be described with reference to Fig. 8. Note that Fig. 8 shows the preparatory operation in a state in which a sufficient amount of hydraulic oil at the first pressure is stored in the accumulator (16).

[0092] In the preparatory operation, the controller (70) sets the set pressure to a third pressure, which is lower than the first pressure. The pump controller (63) of the pump unit (60) controls the rotation speed of the hydraulic pump (61) so that the pressure of the hydraulic oil discharged from the hydraulic pump (61) becomes the set pressure (=the third pressure).

[0093] The first pressure introducing passage (26) is connected to the back pressure port of the throttle valve (42), so that the back pressure of the throttle valve (42) becomes the third pressure, and the throttle valve (42) is maintained in a closed state.

[0094] In the preparatory operation, the controller (70) closes the switching valve (55), sets the first directional control valve (56) and the second directional control valve (57) to their first states, and closes the third directional control valve (58).

[0095] The pressure of the hydraulic oil in the second pressure introducing passage (27) is substantially equal to the pressure (=first pressure) of the hydraulic oil stored in the accumulator (16). When the first directional control valve (56) is in the first state, the back pressure of the first cartridge valve (51) becomes the first pressure, and the first cartridge valve (51) is held in a closed state. When the second directional control valve (57) is in the first state, the back pressure of the second cartridge valve (52) becomes the first pressure, and the second cartridge valve (52) is held in the second state.

[0096] <Low-Speed ​​Injection Operation> The low-speed injection operation of this embodiment is an operation of pushing out the rod (103) of the hydraulic cylinder (100) at a relatively low speed, similar to the low-speed injection operation of Embodiment 1. Here, the low-speed injection operation of this embodiment will be described with reference to FIG. 9 .

[0097] In the low-speed injection operation, the controller (70) holds the switching valve (55) in a closed state, holds the first directional control valve (56) in a first state, switches the second directional control valve (57) from the first state to the second state, and holds the third directional control valve (58) in a closed state.

[0098] The first directional control valve (56) is maintained in the first state. Therefore, the back pressure of the first cartridge valve (51) is maintained at the first pressure, and the first cartridge valve (51) is maintained in the closed state. The second directional control valve (57) switches from the first state to the second state. Therefore, the back pressure of the second cartridge valve (52) becomes the pressure of the hydraulic oil in the tank (15) (substantially equal to atmospheric pressure), and the second cartridge valve (52) switches from the second state to the first state.

[0099] During the low-speed injection operation, the controller (70) changes the set pressure from the third pressure to the fourth pressure. The fourth pressure is higher than the third pressure. The pump controller (63) of the pump unit (60) controls the rotation speed of the hydraulic pump (61) so that the pressure of the hydraulic oil discharged from the hydraulic pump (61) becomes the set pressure (=fourth pressure). Therefore, the back pressure of the throttle valve (42) increases from the third pressure to the fourth pressure. When the back pressure of the throttle valve (42) becomes the fourth pressure, the throttle valve (42) switches from a closed state to an open state.

[0100] When the second cartridge valve (52) is in the first state, the hydraulic oil in the accumulator (16) flows through the head-side passage (21) and is supplied to the head chamber (104) of the hydraulic cylinder (100) as driving hydraulic oil. When the throttle valve (42) is opened, the hydraulic oil in the rod chamber (105) of the hydraulic cylinder (100) is discharged to the tank (15) through the rod-side passage (22). As a result, the rod (103) of the hydraulic cylinder (100) is pushed out.

[0101] As described above, the opening degree of the throttle valve (42) changes depending on the back pressure. As the back pressure of the throttle valve (42) increases, the opening degree of the throttle valve (42) increases. As a result, the flow rate of hydraulic oil flowing out of the rod chamber (105) of the hydraulic cylinder (100) increases, and the movement speed of the rod (103) increases. Also, as the back pressure of the throttle valve (42) decreases, the opening degree of the throttle valve (42) decreases. As a result, the flow rate of hydraulic oil flowing out of the rod chamber (105) of the hydraulic cylinder (100) decreases, and the movement speed of the rod (103) decreases. In this way, in the low-speed injection operation, the movement speed of the rod (103) of the hydraulic cylinder (100) can be adjusted by changing the back pressure of the throttle valve (42).

[0102] <High-Speed ​​Injection Operation> The high-speed injection operation of this embodiment is an operation of pushing out the rod (103) of the hydraulic cylinder (100) at a relatively high speed, similar to the high-speed injection operation of Embodiment 1. Here, the high-speed injection operation will be described with reference to FIG.

[0103] In the high-speed injection operation, the controller (70) sets the set pressure to a fifth pressure. The fifth pressure is equal to or greater than the fourth pressure. Therefore, the back pressure of the throttle valve (42) becomes equal to the fifth pressure. The opening of the throttle valve (42) becomes equal to or greater than the opening of the throttle valve (42) in the low-speed injection operation.

[0104] In the high-speed injection operation, the controller (70) maintains the switching valve (55), the second directional control valve (57), and the third directional control valve (58) in the same states as in the low-speed injection operation, while switching the first directional control valve (56) from the first state to the second state.

[0105] As in the case of the low-speed injection operation, hydraulic oil for driving is supplied to the head chamber (104) of the hydraulic cylinder (100) from the accumulator (16) through the head-side passage (21).

[0106] The first directional control valve (56) switches from the first state to the second state, and therefore the back pressure of the first cartridge valve (51) becomes equal to the pressure of the hydraulic oil in the tank (15) (substantially equal to atmospheric pressure), and the first cartridge valve (51) switches from the closed state to the open state.

[0107] During the high-speed injection operation, both the throttle valve (42) and the first cartridge valve (51) are open, and therefore, the flow rate of the hydraulic oil flowing from the rod chamber (105) of the hydraulic cylinder (100) to the rod-side passage (22) increases significantly compared to the low-speed injection operation, and the rod (103) of the hydraulic cylinder (100) is pushed out in one go at high speed.

[0108] <Stopping Operation> The stopping operation of this embodiment is an operation for stopping the rod (103) of the hydraulic cylinder (100) that has been pushed out by the high-speed injection operation, similar to the stopping operation of Embodiment 1. Here, the stopping operation of this embodiment will be described with reference to FIG.

[0109] In the stop operation, the controller (70) outputs a stop command to the pump controller (63) of the pump unit (60). In the pump unit (60), the pump controller (63) receives the stop command and stops the electric motor (62). As a result, the hydraulic pump (61) stops. When the hydraulic pump (61) stops, the back pressure of the throttle valve (42) drops to or below the third pressure. Therefore, the throttle valve (42) switches from the open state to the closed state.

[0110] In the stopping operation, the controller (70) may set the set pressure to the third pressure. In this case, the back pressure of the throttle valve (42) decreases to the third pressure, and the throttle valve (42) switches from the open state to the closed state.

[0111] In the stopping operation, the controller (70) maintains the switching valve (55) and the third directional switching valve (58) in the same state as in the high-speed injection operation, while switching the first directional switching valve (56) and the second directional switching valve (57) from the second state to the first state.

[0112] As in the stopping operation of the first embodiment, when the second directional control valve (57) is in the first state, the second cartridge valve (52) switches from the first state to the second state, and the supply of hydraulic oil to the head chamber (104) of the hydraulic cylinder (100) is stopped. Also, as in the stopping operation of the first embodiment, when the first directional control valve (56) is in the first state, the first cartridge valve (51) switches from the open state to the closed state, and the discharge of hydraulic oil from the rod chamber (105) of the hydraulic cylinder (100) is stopped.

[0113] In this manner, during the stopping operation, the supply of hydraulic oil to the head chamber (104) of the hydraulic cylinder (100) is stopped, and the discharge of hydraulic oil from the rod chamber (105) of the hydraulic cylinder (100) is stopped, thereby stopping the rod (103) of the hydraulic cylinder (100).

[0114] <Retraction Operation> The retreat operation of this embodiment is an operation of pulling back the rod (103) of the hydraulic cylinder (100), similar to the shift operation of Embodiment 1. Here, the retreat operation will be described with reference to FIG.

[0115] In the retreating operation, following the stopping operation, the controller (70) outputs a stop command to the pump controller (63) of the pump unit (60), so that the hydraulic pump (61) is kept stopped and the throttle valve (42) is kept closed.

[0116] In the backward operation, the controller (70) may set the set pressure to the third pressure, as in the stop operation. In this case, the throttle valve (42) is also held in the closed state, as in the case where the hydraulic pump (61) is stopped.

[0117] In the stop operation, the controller (70) maintains the switching valve (55), the first directional switching valve (56), and the second directional switching valve (57) in the same states as in the stop operation, while switching the third directional switching valve (58) from the closed state to the first state.

[0118] When the third directional control valve (58) is in the first state, the hydraulic oil in the accumulator (16) passes through the second cartridge valve (52) and the third directional control valve (58) in this order and is supplied to the rod chamber (105) of the hydraulic cylinder (100). When the third directional control valve (58) is in the first state, the head chamber (104) of the hydraulic cylinder (100) communicates with the tank (15), and the hydraulic oil in the head chamber (104) is discharged to the tank (15). As a result, the rod (103) of the hydraulic cylinder (100) is pulled back toward the head chamber (104).

[0119] Features of the Second Embodiment The hydraulic device (10) of the present embodiment is provided with a throttle valve (42) as the control valve (40). In the present embodiment, by using the throttle valve (42), which is easier to maintain and more reliable than a servo valve, it becomes possible to control the extrusion speed of the rod (103) of the hydraulic cylinder (100) without complicating the maintenance of the hydraulic device (10).

[0120] Other Embodiments The hydraulic devices (10) of the first and second embodiments are used to drive hydraulic cylinders of a die-casting machine, but the use of the hydraulic devices is not limited thereto. The hydraulic devices (10) of the first and second embodiments may be used to drive hydraulic cylinders for injection provided in an injection molding machine.

[0121] Although the embodiments and modifications have been described above, it will be understood that various modifications in form and detail are possible without departing from the spirit and scope of the claims. Furthermore, elements of the above embodiments, modifications, and other embodiments may be combined or substituted as appropriate. Furthermore, the terms "first," "second," "third," etc. in the specification and claims are used to distinguish between terms to which these terms are attached, and do not limit the number or order of those terms.

[0122] As described above, the present disclosure is useful for hydraulic devices.

[0123] 10 Hydraulic device 21 Head side passage 22 Rod side passage 40 Control valve 41 Relief valve 42 Throttle valve (flow rate control valve) 51 First cartridge valve (opening / closing valve) 61 Hydraulic pump (pump) 70 Controller 100 Hydraulic cylinder 104 Head chamber 105 Rod chamber

Claims

1. A hydraulic device (10) for driving a hydraulic cylinder (100), comprising: a head-side passage (21) through which driving hydraulic oil flows and is supplied to a head chamber (104) of the hydraulic cylinder (100); a rod-side passage (22) through which driving hydraulic oil discharged from a rod chamber (105) of the hydraulic cylinder (100) flows; a control valve (40) provided in the rod-side passage (22), which operates in response to the pressure of the supplied control hydraulic oil, and controls the flow of the driving hydraulic oil in the rod-side passage (22); a pump (61) which supplies control hydraulic oil to the control valve (40); and a controller (70) which controls the pressure of the control hydraulic oil supplied to the control valve (40) by the pump (61).

2. A hydraulic device according to claim 1, wherein the control valve (40) is a relief valve (41) whose operating pressure changes in accordance with the pressure of the supplied control hydraulic oil.

3. A hydraulic device according to claim 1, wherein the control valve (40) is a flow rate adjusting valve (42) that changes the flow rate of the driving hydraulic oil passing through it in accordance with the pressure of the supplied control hydraulic oil.

4. A hydraulic device as described in any one of claims 1 to 3, wherein the pump (61) performs both the operation of supplying control hydraulic oil to the control valve (40) and the operation of supplying drive hydraulic oil to the hydraulic cylinder (100) through the head-side passage (21).

5. A hydraulic device as described in any one of claims 1 to 4, further comprising an on-off valve (51) arranged in parallel with the control valve (40) in the rod side passage (22) to control the flow of hydraulic oil for driving in the rod side passage (22).

6. The hydraulic device according to claim 5, wherein the controller (70) opens the control valve (40) and then opens the on-off valve (51) when pushing out the rod (103) of the hydraulic cylinder (100).

Images