Valve device and hydraulic system

Abstract

To provide a valve device capable of automatically operating a selective valve for a lock valve and enabling independence metering control.SOLUTION: A valve device 2A according to one embodiment includes a first control valve 4A that switches whether a first actuator passage 51, in which a lock valve 53 is provided, is connected to a pump passage 31 or a tank passage 32, and a second control valve 4B that switches whether a second actuator passage 52 is connected to the pump passage 31 or the tank passage 32. The valve device 2A also includes a first solenoid proportional valve 61 for outputting pilot pressure to the first control valve 4A so that the first actuator passage 51 is connected to the tank passage 32, a second solenoid proportional valve 62 for outputting pilot pressure to the second control valve 4B so that the second actuator passage 52 is connected to the pump passage 31, and a selective valve 55 that receives the pilot pressure output from the first solenoid proportional valve 61 or the second solenoid proportional valve 62 and switches the lock valve 53 from a closed state to an open state.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a valve arrangement for a hydraulic cylinder and to a hydraulic system including said valve arrangement. [Background technology]

[0002] Conventionally, a valve device that controls the supply and discharge of hydraulic oil to a hydraulic cylinder that drives a driven object is used in the hydraulic cylinder. For example, Patent Document 1 discloses a valve device that allows independent metering control on the meter-in side and the meter-out side. In Patent Document 1, the valve device is called an "independent metering valve."

[0003] Specifically, the valve device disclosed in Patent Document 1 includes a first actuator passage and a second actuator passage connected to a hydraulic cylinder, a pump passage connected to a hydraulic pump, and a tank passage connected to a tank. The valve device also includes a first spool valve disposed between the pump passage and the first actuator passage, a second spool valve disposed between the pump passage and the second actuator passage, a third spool valve disposed between the first actuator passage and the tank passage, and a fourth spool valve disposed between the second actuator passage and the tank passage. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-241702 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the first to fourth spool valves are described as being "electrohydraulic displacement controlled." This is presumably meant to mean that an electric signal is converted into a pilot pressure, and the pilot pressure displaces the spool. In such a configuration, an electromagnetic proportional valve is generally used.

[0006] In the valve device of Patent Document 1, the first spool valve and the third spool valve can be integrated as a first control valve, and the second spool valve and the fourth spool valve can be integrated as a second control valve. In this case, the first control valve switches whether the first actuator passage is connected to the pump passage or the tank passage, and the second control valve switches whether the second actuator passage is connected to the pump passage or the tank passage. Independent metering control is possible with this configuration as well.

[0007] Incidentally, there are hydraulic cylinders that drive an object in both the direction of gravity and the direction against gravity. Such hydraulic cylinders include a first working chamber to which hydraulic oil is supplied when the object is driven in the direction against gravity, and a second working chamber to which hydraulic oil is supplied when the object is driven in the direction of gravity.

[0008] When the first actuator passage of the valve device is connected to the first working chamber of the hydraulic cylinder, the first actuator passage is provided with a lock valve that closes the first actuator passage while the hydraulic cylinder is stopped in order to prevent the driven object from moving in the direction of gravity due to its own weight. In general, the lock valve is a poppet valve in which a poppet valve body is separated from a valve seat by the discharge pressure of the pump when the driven object is driven in the direction against gravity.

[0009] When a lock valve is provided, a selection valve may be used to switch the lock valve from a closed state to an open state when the driven object is driven in the direction of gravity. In this case, there is a demand for the selection valve to be automatically operated.

[0010] SUMMARY OF THE DISCLOSURE Accordingly, an object of the present disclosure is to provide a valve device capable of independent metering control that can automatically operate a selection valve for a lock valve. [Means for solving the problem]

[0011] From one aspect, the present disclosure provides a valve device used in a hydraulic cylinder including a first working chamber to which hydraulic oil is supplied when an object to be driven is driven in an antigravity direction, and a second working chamber to which hydraulic oil is supplied when the object to be driven is driven in a gravity direction, the valve device comprising: a first control valve for switching whether a first actuator passage connected to the first working chamber is communicated with a pump passage or a tank passage; a first solenoid proportional valve for outputting a pilot pressure to the first control valve so that the first actuator passage is communicated with the tank passage; a second control valve for switching whether a second actuator passage connected to the second working chamber is communicated with the pump passage or the tank passage; a second solenoid proportional valve for outputting a pilot pressure to the second control valve so that the second actuator passage is communicated with the pump passage; a lock valve provided in the first actuator passage; and a selection valve for receiving pilot pressure output from the first solenoid proportional valve or the second solenoid proportional valve and switching the lock valve from a closed state that closes the first actuator passage to an open state that opens the first actuator passage.

[0012] From another aspect, the present disclosure provides a hydraulic system comprising: a hydraulic cylinder including a first working chamber to which hydraulic oil is supplied when a driven object is driven in an anti-gravity direction, and a second working chamber to which hydraulic oil is supplied when the driven object is driven in the gravity direction, the above-mentioned valve device connected to the hydraulic cylinder, and a hydraulic pump connected to the valve device. Effect of the Invention

[0013] In accordance with the present disclosure, a valve arrangement is provided that allows for independent metering control to automatically operate a selector valve for a lock valve. [Brief description of the drawings]

[0014] [Figure 1] 1 is a circuit diagram of a hydraulic system including a valve device according to a first embodiment. [Diagram 2] FIG. 6 is a circuit diagram of a hydraulic system including a valve device according to a second embodiment. [Diagram 3]FIG. 11 is a circuit diagram of a hydraulic system including a valve device according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 1 shows a hydraulic system 1A including a valve device 2A according to a first embodiment. The hydraulic system 1A includes a main hydraulic pump 11, a sub hydraulic pump 12, a tank 13, and a hydraulic cylinder 8 in addition to the valve device 2A.

[0016] The main hydraulic pump 11 is a variable displacement pump, and the sub hydraulic pump 12 is a fixed displacement pump. For example, the variable displacement pump is an axial piston pump such as a swash plate pump or a bent axis pump. However, the main hydraulic pump 11 may be a fixed displacement pump.

[0017] The hydraulic cylinder 8 drives the driven object in the gravity direction and the antigravity direction. The gravity direction and the antigravity direction do not necessarily have to be vertical, but may be oblique to the vertical. Alternatively, when the driven object swings around a horizontal axis, the gravity direction and the antigravity direction may be circumferential directions around the horizontal axis.

[0018] More specifically, the hydraulic cylinder 8 includes a first working chamber 81 to which hydraulic oil is supplied when the driven object is driven in the antigravity direction, and a second working chamber 82 to which hydraulic oil is supplied when the driven object is driven in the gravity direction. In this embodiment, the rod side chamber is the first working chamber 81 and the head side chamber is the second working chamber 82, but the head side chamber may be the first working chamber 81 and the rod side chamber may be the second working chamber 82, opposite to this embodiment.

[0019] The valve device 2A includes a housing 21, and a first spool 22 and a second spool 23 slidably held in the housing 21. The first spool 22 and a portion of the housing 21 adjacent to the first spool 22 constitute a first control valve 4A, and the second spool 23 and a portion of the housing 21 adjacent to the second spool 23 constitute a second control valve 4B.

[0020] The housing 21 is provided with a pump passage 31, a tank passage 32, a first actuator passage 51, and a second actuator passage 52. The pump passage 31 forms a pump port on the surface of the housing 21, and the pump port is connected to the main hydraulic pump 11 by a pipe 14. The tank passage 32 forms a tank port on the surface of the housing 21, and the tank port is connected to the tank 13 by a pipe 16.

[0021] The housing 21 is also provided with a primary pressure passage 33 and a drain passage 34. The primary pressure passage 33 forms a primary pressure port on the surface of the housing 21, and the primary pressure port is connected to the auxiliary hydraulic pump 12 by piping 15. The drain passage 34 forms a drain port on the surface of the housing 21, and the drain port is connected to the tank 13 by piping 17.

[0022] The first actuator passage 51 and the second actuator passage 52 respectively form a first actuator port and a second actuator port on the surface of the housing 21. The first actuator port is connected to a first working chamber 81 by a pipe 83, and the second actuator port is connected to a second working chamber 82 by a pipe 84.

[0023] The pump passage 31 includes a main passage extending from the pump port and a pair of branch passages branching from the main passage to the first control valve 4A and the second control valve 4B. Similarly, the tank passage 32 includes a main passage extending from the tank port and a pair of branch passages branching from the main passage to the first control valve 4A and the second control valve 4B.

[0024] The first control valve 4A switches whether the first actuator passage 51 is communicated with the pump passage 31 or the tank passage 32. When the first spool 22 is located in the neutral position, the first control valve 4A blocks the pump passage 31, the tank passage 32, and the first actuator passage 51. When the first spool 22 moves from the neutral position in a first direction, the first control valve 4A communicates the first actuator passage 51 with the tank passage 32, and when the first spool 22 moves from the neutral position in a second direction, the first control valve 4A communicates the first actuator passage 51 with the pump passage 31.

[0025] A first pilot chamber 41 for moving the first spool 22 in a first direction and a second pilot chamber 42 for moving the first spool 22 in a second direction are formed in the housing 21. The first pilot chamber 41 and the second pilot chamber 42 are components of the first control valve 4A.

[0026] The second control valve 4B switches whether the second actuator passage 52 is communicated with the pump passage 31 or the tank passage 32. When the second spool 23 is located in the neutral position, the second control valve 4B blocks the pump passage 31, the tank passage 32, and the second actuator passage 52. When the second spool 23 moves from the neutral position in a first direction, the second control valve 4B communicates the second actuator passage 52 with the pump passage 31, and when the second spool 23 moves from the neutral position in a second direction, the second control valve 4B communicates the second actuator passage 52 with the tank passage 32.

[0027] A first pilot chamber 43 for moving the second spool 23 in a first direction and a second pilot chamber 44 for moving the second spool 23 in a second direction are formed in the housing 21. The first pilot chamber 43 and the second pilot chamber 44 are components of the second control valve 4B.

[0028] Furthermore, the valve device 2A includes a first solenoid proportional valve 61, a second solenoid proportional valve 62, a third solenoid proportional valve 63, and a fourth solenoid proportional valve 64. The first solenoid proportional valve 61, the second solenoid proportional valve 62, the third solenoid proportional valve 63, and the fourth solenoid proportional valve 64 may be attached to the housing 21 or may be incorporated into the housing 21.

[0029] The first solenoid proportional valve 61, the second solenoid proportional valve 62, the third solenoid proportional valve 63 and the fourth solenoid proportional valve 64 are connected to the primary pressure passage 33 and the drain passage 34. The first solenoid proportional valve 61 and the third solenoid proportional valve 63 are for operating the first control valve 4A, and the second solenoid proportional valve 62 and the fourth solenoid proportional valve 64 are for operating the second control valve 4B.

[0030] More specifically, the first solenoid proportional valve 61 is connected to the first pilot chamber 41 of the first control valve 4A by a pilot passage 71, and the third solenoid proportional valve 63 is connected to the second pilot chamber 42 of the first control valve 4A by a pilot passage 72. Similarly, the second solenoid proportional valve 62 is connected to the first pilot chamber 43 of the second control valve 4B by a pilot passage 73, and the fourth solenoid proportional valve 64 is connected to the second pilot chamber 44 of the second control valve 4B by a pilot passage 74.

[0031] The first solenoid proportional valve 61 outputs pilot pressure as secondary pressure to the first pilot chamber 41 of the first control valve 4A, or connects the first pilot chamber 41 to the drain passage 34. The third solenoid proportional valve 63 outputs pilot pressure as secondary pressure to the second pilot chamber 42 of the first control valve 4A, or connects the second pilot chamber 42 to the drain passage 34.

[0032] Similarly, the second solenoid proportional valve 62 outputs pilot pressure as secondary pressure to the first pilot chamber 43 of the second control valve 4B, or connects the first pilot chamber 43 to the drain passage 34. The fourth solenoid proportional valve 64 outputs pilot pressure as secondary pressure to the second pilot chamber 44 of the second control valve 4B, or connects the second pilot chamber 44 to the drain passage 34.

[0033] When driving an object to be driven in the direction of gravity, the first solenoid proportional valve 61 outputs pilot pressure to the first pilot chamber 41 of the first control valve 4A, and the second solenoid proportional valve 62 outputs pilot pressure to the first pilot chamber 43 of the second control valve 4B. This allows the pump passage 31 to communicate with the second actuator passage 52, and the first actuator passage 51 to communicate with the tank passage 32. This causes hydraulic oil to be supplied to the second working chamber 82 of the hydraulic cylinder 8 and hydraulic oil to be discharged from the first working chamber 81, and the hydraulic cylinder 8 drives the object to be driven in the direction of gravity.

[0034] Conversely, when the driven object is driven in the anti-gravity direction, the third solenoid proportional valve 63 outputs pilot pressure to the second pilot chamber 42 of the first control valve 4A, and the fourth solenoid proportional valve 64 outputs pilot pressure to the second pilot chamber 44 of the second control valve 4B. This allows the pump passage 31 to communicate with the second actuator passage 52, and the first actuator passage 51 to communicate with the tank passage 32. As a result, hydraulic oil is supplied to the first working chamber 81 of the hydraulic cylinder 8 and hydraulic oil is discharged from the second working chamber 82, and the hydraulic cylinder 8 drives the driven object in the anti-gravity direction.

[0035] A lock valve 53 that closes the first actuator passage 51 while the hydraulic cylinder 8 is stopped is provided in the first actuator passage 51 that communicates with the tank passage 32 when the driven object is driven in the direction of gravity. The lock valve 53 is a poppet valve.

[0036] Specifically, the lock valve 53 includes a poppet valve body 53a that abuts against a valve seat to close the first actuator passage 51, a back pressure chamber 53b that faces the poppet valve body 53a on the side opposite to the valve seat, and a spring 53c that is disposed in the back pressure chamber 53b and biases the poppet valve body 53a toward the valve seat. The back pressure chamber 53b is connected to a selection valve 55 by a first communication passage 54.

[0037] The selection valve 55 is connected to a portion of the first actuator passage 51 between the lock valve 53 and the first actuator port by a second communication passage 56 , and is connected to the drain passage 34 by a third communication passage 57 .

[0038] The selection valve 55 is positioned in a locked position in which the first communication passage 54 communicates with the second communication passage 56 except when the object to be driven is driven in the direction of gravity, and is switched to an unlocked position in which the first communication passage 54 communicates with the third communication passage 57 when the object to be driven is driven in the direction of gravity.

[0039] The selection valve 55 has a pilot port. In this embodiment, the pilot port of the selection valve 55 is connected to a pilot passage 73 between the first pilot chamber 43 of the second control valve 4B and the second solenoid proportional valve 62 via a pilot passage 75.

[0040] When the selection valve 55 is in the locked position, the pressure in the back pressure chamber 53b of the lock valve 53 becomes equal to the pressure in the first working chamber 81 of the hydraulic cylinder 8, so that the lock valve 53 closes the first actuator passage 51 unless the first actuator passage 51 communicates with the pump passage 31. On the other hand, when the third solenoid proportional valve 63 outputs pilot pressure and the first control valve 4A communicates the first actuator passage 51 with the pump passage 31, the poppet valve element 53a of the lock valve 53 is separated from the valve seat by the discharge pressure of the main hydraulic pump 11, and the first actuator passage 51 is opened. In other words, even if the selection valve 55 is in the locked position, it is possible to drive the driven object in the antigravity direction.

[0041] When the first solenoid proportional valve 61 and the second solenoid proportional valve 62 output pilot pressure to drive the driven object in the direction of gravity, the pilot pressure output from the second solenoid proportional valve 62 is introduced to the pilot port of the selection valve 55, and the selection valve 55 is switched from the locked position to the unlocked position. As a result, the pressure in the back pressure chamber 53b of the lock valve 53 becomes substantially zero, and the poppet valve element 53a of the lock valve 53 is separated from the valve seat by the pressure in the first working chamber 81 of the hydraulic cylinder 8, and the first actuator passage 51 is opened. In other words, the selection valve 55 receives the pilot pressure output from the second solenoid proportional valve 62 and switches the lock valve 53 from a closed state in which the first actuator passage 51 is closed to an open state in which the first actuator passage 51 is opened.

[0042] In the valve device 2A having the above-described configuration, independent metering control is possible by the first control valve 4A and the second control valve 4B. In addition, when the hydraulic cylinder 8 drives the driven object in the direction of gravity, the selection valve 55 receives the pilot pressure output from the second electromagnetic proportional valve 62 and switches the lock valve 53 to the open state, so that the selection valve 55 can be automatically operated.

[0043] <Second embodiment> 2 shows a hydraulic system 1B including a valve device 2B according to a second embodiment. In this embodiment and a third embodiment described later, the same components as those in the first embodiment are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0044] The valve device 2B of this embodiment differs from the valve device 2A of the first embodiment only in that the pilot port of the selection valve 55 is connected to a pilot passage 71 between the first pilot chamber 41 of the first control valve 4A and the first solenoid proportional valve 61 by a pilot passage 75.

[0045] In this embodiment, as in the first embodiment, independent metering control is possible by the first control valve 4A and the second control valve 4B. In addition, when the hydraulic cylinder 8 drives the driven object in the direction of gravity, the selection valve 55 receives the pilot pressure output from the first electromagnetic proportional valve 61 and switches the lock valve 53 to the open state, so that the selection valve 55 can be automatically operated.

[0046] Incidentally, in the case where the selection valve 55 operates by receiving pilot pressure output from the first electromagnetic proportional valve 61 as in this embodiment, if a malfunction of the first electromagnetic proportional valve 61 causes the first electromagnetic proportional valve 61 to output pilot pressure while the hydraulic cylinder 8 is stopped, the selection valve 55 switches the lock valve 53 to the open state, causing the driven object to move in the direction of gravity due to its own weight.

[0047] In contrast, when the selection valve 55 operates by receiving the pilot pressure output from the second electromagnetic proportional valve 62 as in the first embodiment, even if the first electromagnetic proportional valve 61 outputs the pilot pressure while the hydraulic cylinder 8 is stopped due to a malfunction of the first electromagnetic proportional valve 61, the lock valve 53 is maintained in the closed state. Therefore, even if a malfunction occurs in the first electromagnetic proportional valve 61, it is possible to prevent the driven object from moving in the direction of gravity due to its own weight. Furthermore, even if the second electromagnetic proportional valve 62 outputs the pilot pressure while the hydraulic cylinder 8 is stopped due to a malfunction of the second electromagnetic proportional valve 62, the first spool 22 is maintained in the neutral position, so that the driven object is prevented from moving in the direction of gravity due to its own weight.

[0048] <Third embodiment> 3 shows a hydraulic system 1C including a valve device 2C according to a third embodiment. In the first and second embodiments, independent metering control can be performed using four solenoid proportional valves, but in the third embodiment, independent metering control can be performed using three solenoid proportional valves.

[0049] Specifically, in this embodiment, the first control valve 4A and the second control valve 4B share the third pilot chamber 45. For example, when the first spool 22 and the second spool 23 are inserted into the same spool hole, a portion of the spool hole between the first spool 22 and the second spool 23 forms the third pilot chamber 45. In addition, the valve device 2C includes a third solenoid proportional valve 65 connected to the third pilot chamber 45 by a pilot passage 76.

[0050] The third solenoid proportional valve 65 outputs pilot pressure as secondary pressure to the third pilot chamber 45, or communicates the third pilot chamber 45 with the drain passage 34. When the pilot pressure is output to the third pilot chamber 45, the first spool 22 and the second spool 23 move in the second direction. In other words, the third solenoid proportional valve 65 outputs pilot pressure to the first control valve 4A and the second control valve 4B such that the first actuator passage 51 communicates with the pump passage 31 and the second actuator passage 52 communicates with the tank passage 32.

[0051] In FIG. 3, the pilot port of the selection valve 55 is connected to the pilot passage 73 by the pilot passage 75 as in the first embodiment, but the pilot port of the selection valve 55 may be connected to the pilot passage 71 by the pilot passage 75 as in the second embodiment.

[0052] In this embodiment, the same effects as those of the first and second embodiments can be obtained.

[0053] <Other embodiments> The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present disclosure.

[0054] <Summary> As a first aspect, the present disclosure provides, from one aspect, a valve device used in a hydraulic cylinder including a first working chamber to which hydraulic oil is supplied when an object to be driven is driven in an antigravity direction, and a second working chamber to which hydraulic oil is supplied when the object to be driven is driven in a gravity direction, the valve device comprising: a first control valve for switching whether a first actuator passage connected to the first working chamber is connected to a pump passage or a tank passage; a first solenoid proportional valve for outputting a pilot pressure to the first control valve so that the first actuator passage is connected to the tank passage; a second control valve for switching whether a second actuator passage connected to the second working chamber is connected to the pump passage or the tank passage; a second solenoid proportional valve for outputting a pilot pressure to the second control valve so that the second actuator passage is connected to the pump passage; a lock valve provided in the first actuator passage; and a selection valve for receiving pilot pressure output from the first solenoid proportional valve or the second solenoid proportional valve and switching the lock valve from a closed state that closes the first actuator passage to an open state that opens the first actuator passage.

[0055] According to the above configuration, independent metering control is possible by the first control valve and the second control valve. When the first solenoid proportional valve outputs pilot pressure to the first control valve and the second solenoid proportional valve outputs pilot pressure to the second control valve, the pump passage communicates with the second actuator passage and the first actuator passage communicates with the tank passage. This causes the hydraulic cylinder to drive the driven object in the direction of gravity. At this time, the selection valve switches the lock valve to an open state upon receiving the pilot pressure output from the first solenoid proportional valve or the second solenoid proportional valve, so that the selection valve can be automatically operated.

[0056] When the selection valve operates by receiving pilot pressure output from the first electromagnetic proportional valve, if a malfunction of the first electromagnetic proportional valve causes the first electromagnetic proportional valve to output pilot pressure while the hydraulic cylinder is stopped, the selection valve switches the lock valve to the open state, causing the driven object to move in the direction of gravity due to its own weight.

[0057] In contrast, when the selection valve operates by receiving pilot pressure output from the second electromagnetic proportional valve, even if a malfunction of the first electromagnetic proportional valve causes the first electromagnetic proportional valve to output pilot pressure while the hydraulic cylinder is stopped, the lock valve is maintained in the closed state. Therefore, even if a malfunction occurs in the first electromagnetic proportional valve, it is possible to prevent the driven object from moving in the direction of gravity due to its own weight.

[0058] As a second aspect, in the first aspect, the valve device may further include a third solenoid proportional valve that outputs a pilot pressure to the first control valve so that the first actuator passage communicates with the pump passage, and a fourth solenoid proportional valve that outputs a pilot pressure to the second control valve so that the second actuator passage communicates with the tank passage. With this configuration, independent metering control can be performed using four solenoid proportional valves.

[0059] As a third aspect, in the first aspect, the valve device may further include a third solenoid proportional valve that outputs a pilot pressure to the first control valve and the second control valve so that the first actuator passage communicates with the pump passage and the second actuator passage communicates with the tank passage. With this configuration, independent metering control can be performed using three solenoid proportional valves.

[0060] As a fourth aspect, the present disclosure provides, from another aspect, a hydraulic system comprising: a hydraulic cylinder including a first working chamber to which hydraulic oil is supplied when a driven object is driven in an anti-gravity direction, and a second working chamber to which hydraulic oil is supplied when the driven object is driven in the gravity direction; a valve device of any of the first to third aspects connected to the hydraulic cylinder; and a hydraulic pump connected to the valve device. [Explanation of symbols]

[0061] 1A, 1B, 1C Hydraulic System 11 Hydraulic pump 2A, 2B, 2C Valve gear 31 Pump passage 32 Tank Passage 4A First control valve 4B Second control valve 51 First Actuator Passage 52 Second Actuator Passage 61 First solenoid proportional valve 62 No. 2 solenoid proportional valve 63 3rd solenoid proportional valve 64 4th solenoid proportional valve 65 3rd solenoid proportional valve 8 Hydraulic Cylinders 81 First working chamber 82 Second working chamber

Claims

1. A valve device used in a hydraulic cylinder including a first working chamber to which hydraulic oil is supplied when an object to be driven is driven in an antigravity direction, and a second working chamber to which hydraulic oil is supplied when the object to be driven is driven in a gravity direction, a first control valve for switching whether a first actuator passage connected to the first working chamber is connected to a pump passage or a tank passage; a first solenoid proportional valve that outputs a pilot pressure to the first control valve so that the first actuator passage communicates with the tank passage; a second control valve that switches whether a second actuator passage connected to the second working chamber is connected to the pump passage or the tank passage; a second electromagnetic proportional valve that outputs a pilot pressure to the second control valve so that the second actuator passage communicates with the pump passage; a lock valve provided in the first actuator passage; a selection valve that switches the lock valve from a closed state that closes the first actuator passage to an open state that opens the first actuator passage in response to a pilot pressure output from the first electromagnetic proportional valve or the second electromagnetic proportional valve; The valve device comprises:

2. a third electromagnetic proportional valve that outputs a pilot pressure to the first control valve so that the first actuator passage communicates with the pump passage; a fourth electromagnetic proportional valve that outputs a pilot pressure to the second control valve so that the second actuator passage communicates with the tank passage; The valve arrangement of claim 1 further comprising:

3. 2. The valve apparatus according to claim 1, further comprising a third solenoid proportional valve outputting a pilot pressure to the first control valve and the second control valve such that the first actuator passage communicates with the pump passage and the second actuator passage communicates with the tank passage.

4. a hydraulic cylinder including a first working chamber to which hydraulic oil is supplied when a driven object is driven in a direction against gravity, and a second working chamber to which hydraulic oil is supplied when the driven object is driven in a direction toward gravity; A valve device according to any one of claims 1 to 3, connected to the hydraulic cylinder; a hydraulic pump connected to the valve device; A hydraulic system comprising:

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