Valve device and hydraulic system

Abstract

A valve device (2A) according to one embodiment of the present invention comprises: a first control valve (4A) that switches by communicating a first actuator passage (51) provided with a lock valve (53) with either a pump passage (31) or a tank passage (32); and a second control valve (4B) that switches between the second actuator passage (52) and either the pump passage (31) or the tank passage (32) by connecting the second actuator passage (52) to the pump passage (31) or the tank passage (32). Furthermore, the valve device (2A) is provided with: a first electromagnetic proportional valve (61) that outputs pilot pressure to the first control valve (4A) such that the first actuator passage (51) communicates with the tank passage (32); a second electromagnetic proportional valve (62) that outputs pilot pressure to a second control valve (4B) such that a second actuator passage (52) communicates with the pump passage (31); and a selector valve (55) that receives the pilot pressure output from the first electromagnetic proportional valve (61) or the second electromagnetic proportional valve (62) and switches the lock valve (53) from the closed state to the open state. Therefore, the selection valve used for the lock valve can be automatically operated, and independent metering control can be realized.

Description

Technical Field

[0001] The present disclosure relates to a valve device for a hydraulic cylinder and a hydraulic system including the valve device. Background Art

[0002] At present, a valve device for controlling the supply and discharge of working fluid to a hydraulic cylinder that drives a driven object is used. For example, Japanese Patent Publication No. 11-241702 discloses a valve device that can achieve independent metering control of a liquid inlet (Meter-In) side and a liquid outlet (Meter-Out) side. In addition, Japanese Patent Publication No. 11-241702 refers to the valve device as an "independent metering valve".

[0003] Specifically, the valve device disclosed in Japanese Patent Application Laid-Open No. 11-241702 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. Furthermore, the valve device includes: a first slide valve arranged between the pump passage and the first actuator passage; a second slide valve arranged between the pump passage and the second actuator passage; a third slide valve arranged between the first actuator passage and the tank passage; and a fourth slide valve arranged between the second actuator passage and the tank passage. Summary of the invention

[0004] Problems to be solved by the invention: Japanese Patent Application Laid-Open No. 11-241702 states that the first to fourth slide valves are "electrical hydraulic adjustment control". It is assumed that this means that the electrical signal is converted into a pilot pressure, and the valve core is displaced according to the pilot pressure. In such a structure, an electromagnetic proportional valve is generally used.

[0005] In the valve device of Japanese Patent Application Laid-Open No. 11-241702, the first slide valve and the third slide valve can be integrated as a first control valve, and the second slide valve and the fourth slide valve can be integrated as a second control valve. In this case, the first control valve switches which of the pump passage and the tank passage the first actuator passage is connected to, and the second control valve switches which of the pump passage and the tank passage the second actuator passage is connected to. Independent metering control can also be achieved in such a structure.

[0006] However, the hydraulic cylinder can also drive the driven object in the gravity direction and the counter-gravity direction. Such a hydraulic cylinder includes a first working chamber to which the working fluid is supplied when the driven object is driven in the counter-gravity direction and a second working chamber to which the working fluid is supplied when the driven object is driven in the gravity direction.

[0007] When the first actuator passage of the valve device is connected to the first working chamber of the hydraulic cylinder, a locking valve is provided in the first actuator passage to close the first actuator passage during the stop period of the hydraulic cylinder to prevent the driven object from moving in the direction of gravity due to its own weight. Generally speaking, the locking valve is a lift valve that causes the lift valve body to be separated from the valve seat by the discharge pressure of the pump when the driven object is driven in the direction against gravity.

[0008] When a lock valve is provided, a selector 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, it is desirable to automatically operate the selector valve.

[0009] Therefore, an object of the present disclosure is to provide an independently metering controllable valve device capable of automatically operating a selector valve for a locking valve.

[0010] The present disclosure provides a valve device based on one aspect: a valve device for a hydraulic cylinder, the hydraulic cylinder including a first working chamber for supplying working fluid when driving a driven object in a direction counter to gravity and a second working chamber for supplying working fluid when driving the driven object in a direction of gravity, and comprising: a first control valve for switching a first actuator passage connected to the first working chamber to be connected to either a pump passage or a tank passage; a first electromagnetic proportional valve for outputting a pilot pressure to the first control valve in the form of connecting the first actuator passage to the tank passage; a second control valve for switching a second actuator passage connected to the second working chamber to be connected to either the pump passage or the tank passage; a second electromagnetic proportional valve for outputting a pilot pressure to the second control valve in the form of connecting the second actuator passage to the pump passage; a locking valve provided in the first actuator passage; and a selection valve for receiving a pilot pressure output from the first electromagnetic proportional valve or the second electromagnetic proportional valve to switch the locking valve from a closed state for closing the first actuator passage to an open state for opening the first actuator passage.

[0011] Based on another aspect, the present disclosure provides a hydraulic system comprising: a hydraulic cylinder, which includes: a first working chamber that supplies working fluid when a driven object is driven in a direction counter to gravity; a second working chamber that supplies working fluid when the driven object is driven in a direction of gravity; the above-mentioned valve device, which is connected to the hydraulic cylinder; and a hydraulic pump, which is connected to the valve device.

[0012] According to the present disclosure, a selector valve for a locking valve that can automatically operate and a valve device that can independently meter and control are provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a circuit diagram of a hydraulic system including a valve device according to a first embodiment; Figure 2is a circuit diagram of a hydraulic system including a valve device according to a second embodiment; Figure 3 1 is a circuit diagram of a hydraulic system including a valve device according to a third embodiment. DETAILED DESCRIPTION

[0014] Figure 1 The hydraulic system 1A including the valve device 2A of the first embodiment is shown. 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.

[0015] The main hydraulic pump 11 is a variable displacement pump, and the auxiliary 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 also be a fixed displacement pump.

[0016] The hydraulic cylinder 8 drives the driven object in the direction of gravity and the direction of counter-gravity. The direction of gravity and the direction of counter-gravity do not necessarily have to be the vertical direction, but can also be a direction inclined relative to the vertical direction. Or when the driven object swings around the horizontal axis, the direction of gravity and the direction of counter-gravity can also be a circumferential direction centered on the horizontal axis.

[0017] More specifically, the hydraulic cylinder 8 includes a first working chamber 81 for supplying working fluid when the driven object is driven in the direction counter to gravity, and a second working chamber 82 for supplying working fluid when the driven object is driven in the direction of gravity. In the present 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 in contrast to the present embodiment.

[0018] The valve device 2A includes a housing 21, a first valve core 22 and a second valve core 23 slidably held on the housing 21. The first valve core 22 and the adjacent portion of the first valve core 22 in the housing 21 constitute a first control valve 4A, and the second valve core 23 and the adjacent portion of the second valve core 23 in the housing 21 constitute a second control valve 4B.

[0019] 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 via the 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 via the pipe 16.

[0020] The housing 21 is further 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 via the pipe 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 via the pipe 17.

[0021] The first actuator passage 51 and the second actuator passage 52 form a first actuator port and a second actuator port, respectively, on the surface of the housing 21. The first actuator port is connected to the first working chamber 81 via a pipe 83, and the second actuator port is connected to the second working chamber 82 via a pipe 84.

[0022] The pump passage 31 includes a main passage extending from the pump port and a pair of branch passages branching from the main passage and connected 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 and connected to the first control valve 4A and the second control valve 4B.

[0023] The first control valve 4A switches the first actuator passage 51 to communicate with one of the pump passage 31 and the tank passage 32. The first control valve 4A closes the pump passage 31, the tank passage 32, and the first actuator passage 51 when the first valve element 22 is in the neutral position. The first control valve 4A communicates the first actuator passage 51 with the tank passage 32 when the first valve element 22 moves from the neutral position to the first direction, and communicates the first actuator passage 51 with the pump passage 31 when the first valve element 22 moves from the neutral position to the second direction.

[0024] The housing 21 includes a first pilot chamber 41 for moving the first valve body 22 in a first direction and a second pilot chamber 42 for moving the first valve body 22 in a second direction. The first pilot chamber 41 and the second pilot chamber 42 are components of the first control valve 4A.

[0025] The second control valve 4B switches the second actuator passage 52 to communicate with one of the pump passage 31 and the tank passage 32. The second control valve 4B closes the pump passage 31, the tank passage 32, and the second actuator passage 52 when the second valve element 23 is in the neutral position. The second control valve 4B communicates the second actuator passage 52 with the pump passage 31 when the second valve element 23 moves from the neutral position to the first direction, and communicates the second actuator passage 52 with the tank passage 32 when the second valve element 23 moves from the neutral position to the second direction.

[0026] The housing 21 includes a first pilot chamber 43 for moving the second valve body 23 in the first direction and a second pilot chamber 44 for moving the second valve body 23 in the second direction. The first pilot chamber 43 and the second pilot chamber 44 are components of the second control valve 4B.

[0027] In addition, the valve device 2A includes a first electromagnetic proportional valve 61, a second electromagnetic proportional valve 62, a third electromagnetic proportional valve 63, and a fourth electromagnetic proportional valve 64. The first electromagnetic proportional valve 61, the second electromagnetic proportional valve 62, the third electromagnetic proportional valve 63, and the fourth electromagnetic proportional valve 64 can be installed in the housing 21 or assembled in the housing 21.

[0028] The first electromagnetic proportional valve 61, the second electromagnetic proportional valve 62, the third electromagnetic proportional valve 63 and the fourth electromagnetic proportional valve 64 are connected to the primary pressure passage 33 and the discharge passage 34. The first electromagnetic proportional valve 61 and the third electromagnetic proportional valve 63 are used to operate the first control valve 4A, and the second electromagnetic proportional valve 62 and the fourth electromagnetic proportional valve 64 are used to operate the second control valve 4B.

[0029] In more detail, the first electromagnetic proportional valve 61 is connected to the first pilot chamber 41 of the first control valve 4A through the pilot passage 71, and the third electromagnetic proportional valve 63 is connected to the second pilot chamber 42 of the first control valve 4A through the pilot passage 72. Similarly, the second electromagnetic proportional valve 62 is connected to the first pilot chamber 43 of the second control valve 4B through the pilot passage 73, and the fourth electromagnetic proportional valve 64 is connected to the second pilot chamber 44 of the second control valve 4B through the pilot passage 74.

[0030] The first electromagnetic proportional valve 61 outputs the pilot pressure as the secondary pressure to the first pilot chamber 41 of the first control valve 4A, or communicates the first pilot chamber 41 with the drain passage 34. The third electromagnetic proportional valve 63 outputs the pilot pressure as the secondary pressure to the second pilot chamber 42 of the first control valve 4A, or communicates the second pilot chamber 42 with the drain passage 34.

[0031] Similarly, the second electromagnetic proportional valve 62 outputs the pilot pressure as the secondary pressure to the first pilot chamber 43 of the second control valve 4B, or communicates the first pilot chamber 43 with the drain passage 34. The fourth electromagnetic proportional valve 64 outputs the pilot pressure as the secondary pressure to the second pilot chamber 44 of the second control valve 4B, or communicates the second pilot chamber 44 with the drain passage 34.

[0032] When the driven object is driven in the direction of gravity, the first electromagnetic proportional valve 61 outputs the pilot pressure to the first pilot chamber 41 of the first control valve 4A, and the second electromagnetic proportional valve 62 outputs the pilot pressure to the first pilot chamber 43 of the second control valve 4B. As a result, the pump passage 31 communicates with the second actuator passage 52, and the first actuator passage 51 communicates with the tank passage 32. As a result, the working fluid is supplied to the second working chamber 82 of the hydraulic cylinder 8, and the working fluid is discharged from the first working chamber 81, and the hydraulic cylinder 8 drives the driven object in the direction of gravity.

[0033] On the other hand, when the driven object is driven in the direction against gravity, the third electromagnetic proportional valve 63 outputs the pilot pressure to the second pilot chamber 42 of the first control valve 4A, and the fourth electromagnetic proportional valve 64 outputs the pilot pressure to the second pilot chamber 44 of the second control valve 4B. As a result, the pump passage 31 communicates with the second actuator passage 52, and the first actuator passage 51 communicates with the tank passage 32. As a result, the working fluid is supplied to the first working chamber 81 of the hydraulic cylinder 8, and the working fluid is discharged from the second working chamber 82, and the hydraulic cylinder 8 drives the driven object in the direction against gravity.

[0034] The first actuator passage 51 communicating with the tank passage 32 when the driven object is driven in the gravity direction is provided with a lock valve 53 for closing the first actuator passage 51 while the hydraulic cylinder 8 is stopped. The lock valve 53 is a poppet valve.

[0035] Specifically, the lock valve 53 includes: a lift valve body 53a that closes the first actuator passage 51 by abutting against the valve seat; a back pressure chamber 53b facing the lift valve body 53a on the opposite side of the valve seat; and a spring 53c disposed in the back pressure chamber 53b that urges the lift valve body 53a toward the valve seat. The back pressure chamber 53b is connected to the selector valve 55 through the first communication passage 54.

[0036] The selector valve 55 is connected to a portion of the first actuator passage 51 between the lock valve 53 and the first actuator port via a second communication passage 56 , and is connected to the drain passage 34 via a third communication passage 57 .

[0037] The selector valve 55 is located at the locking position for connecting the first communication passage 54 with the second communication passage 56 when the driven object is not driven in the gravity direction, and is switched to the unlocking position for connecting the first communication passage 54 with the third communication passage 57 when the driven object is driven in the gravity direction.

[0038] The selector valve 55 has a pilot port. In this embodiment, the pilot port of the selector valve 55 is connected to a pilot passage 73 between the first pilot chamber 43 of the second control valve 4B and the second electromagnetic proportional valve 62 via a pilot passage 75 .

[0039] When the selector valve 55 is in the lock position, the pressure in the back pressure chamber 53b of the lock valve 53 is equal to the pressure in the first working chamber 81 of the hydraulic cylinder 8, so the lock valve 53 closes the first actuator passage 51 as long as the first actuator passage 51 is not connected to the pump passage 31. On the other hand, when the third electromagnetic proportional valve 63 outputs the pilot pressure and the first control valve 4A connects the first actuator passage 51 to the pump passage 31, the lift valve body 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. That is, even if the selector valve 55 is in the lock position, it is possible to drive the driven object in the direction against gravity.

[0040] When the first electromagnetic proportional valve 61 and the second electromagnetic proportional valve 62 output pilot pressures in order to drive the driven object in the gravity direction, the pilot pressure output from the second electromagnetic proportional valve 62 is introduced into the pilot port of the selector valve 55 to switch the selector valve 55 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, so that the lift valve body 53a of the lock valve 53 is separated from the valve seat by the pressure of the first working chamber 81 of the hydraulic cylinder 8, and the first actuator passage 51 is opened. That is, the selector valve 55 receives the pilot pressure output from the second electromagnetic proportional valve 62, and switches the lock valve 53 from the closed state of closing the first actuator passage 51 to the open state of opening the first actuator passage 51.

[0041] In the valve device 2A of the structure described above, independent metering control can be performed 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 selector 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 the selector valve 55 can be automatically operated.

[0042] <Second embodiment> Figure 2 A hydraulic system 1B including a valve device 2B according to the second embodiment is shown. 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 duplicate descriptions are omitted.

[0043] The valve device 2B of this embodiment is different from the valve device 2A of the first embodiment only in that the pilot port of the selector valve 55 is connected to the pilot passage 71 between the first pilot chamber 41 of the first control valve 4A and the first electromagnetic proportional valve 61 through a pilot passage 75 .

[0044] In this embodiment, as in the first embodiment, independent metering control can be performed by the first control valve 4A and the second control valve 4B. When the hydraulic cylinder 8 drives the driven object in the gravity direction, the selector 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 the selector valve 55 can be automatically operated.

[0045] However, as in the present embodiment, when the selection valve 55 operates by receiving the pilot pressure output from the first electromagnetic proportional valve 61, when the first electromagnetic proportional valve 61 outputs the pilot pressure during the stop period of the hydraulic cylinder 8 due to a malfunction of the first electromagnetic proportional valve 61, the locking valve 53 can also be switched to an open state through the selection valve 55, so that the driven object moves in the direction of gravity due to its own weight.

[0046] In contrast, when the selector 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 during the stop of the hydraulic cylinder 8 due to a malfunction of the first electromagnetic proportional valve 61, the lock valve 53 can be maintained in a closed state. Therefore, even if a malfunction occurs in the first electromagnetic proportional valve 61, the driven object can be prevented from moving in the direction of gravity due to its own weight. In addition, even if the second electromagnetic proportional valve 62 outputs the pilot pressure during the stop of the hydraulic cylinder 8 due to a malfunction of the second electromagnetic proportional valve 62, the first valve core 22 can be maintained in a neutral position, so that the driven object can be prevented from moving in the direction of gravity due to its own weight.

[0047] <Third Embodiment> Figure 3 A hydraulic system 1C including a valve device 2C according to a third embodiment is shown. In the first and second embodiments, four electromagnetic proportional valves can be used to perform independent metering control, and in the third embodiment, three electromagnetic proportional valves can be used to perform independent metering control.

[0048] Specifically, in the present embodiment, the first control valve 4A and the second control valve 4B share the third pilot chamber 45. For example, when the first valve core 22 and the second valve core 23 are inserted into the same valve core hole, the portion between the first valve core 22 and the second valve core 23 in the valve core hole constitutes the third pilot chamber 45. In addition, the valve device 2C includes a third electromagnetic proportional valve 65 connected to the third pilot chamber 45 via a pilot passage 76.

[0049] The third electromagnetic proportional valve 65 outputs the pilot pressure to the third pilot chamber 45 as the secondary pressure, or communicates the third pilot chamber 45 with the discharge passage 34. When the pilot pressure is output to the third pilot chamber 45, the first valve element 22 and the second valve element 23 move in the second direction. In other words, the third electromagnetic proportional valve 65 outputs the pilot pressure to the first control valve 4A and the second control valve 4B in a manner that the first actuator passage 51 communicates with the pump passage 31 and the second actuator passage 52 communicates with the tank passage 32.

[0050] Figure 3 The pilot port of the selector valve 55 is connected to the pilot passage 73 through the pilot passage 75 as in the first embodiment, but the pilot port of the selector valve 55 may be connected to the pilot passage 71 through the pilot passage 75 as in the second embodiment.

[0051] In this embodiment, the same effects as those of the first embodiment or the second embodiment can be obtained.

[0052] <Other embodiments> The present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present disclosure.

[0053] Summary As a first aspect, the present disclosure provides a valve device based on one aspect, which is a valve device for a hydraulic cylinder, the hydraulic cylinder including a first working chamber for supplying working fluid when driving a driven object in a direction counter to gravity and a second working chamber for supplying working fluid when driving the driven object in a direction of gravity, and comprising: a first control valve, which switches a first actuator passage connected to the first working chamber to be connected to either a pump passage or a tank passage; a first electromagnetic proportional valve, which outputs a pilot pressure to the first control valve in the form of connecting the first actuator passage to the tank passage; a second control valve, which switches a second actuator passage connected to the second working chamber to be connected to either the pump passage or the tank passage; a second electromagnetic proportional valve, which outputs a pilot pressure to the second control valve in the form of connecting the second actuator passage to the pump passage; a locking valve, which is provided in the first actuator passage; and a selection valve, which receives the pilot pressure output from the first electromagnetic proportional valve or the second electromagnetic proportional valve, and switches the locking valve from a closed state of closing the first actuator passage to an open state of opening the first actuator passage.

[0054] According to the above structure, independent metering control can be performed by the first control valve and the second control valve. When the first electromagnetic proportional valve outputs a pilot pressure to the first control valve, and the second electromagnetic proportional valve outputs a pilot pressure to the second control valve, the pump passage is connected to the second actuator passage, and the first actuator passage is connected to the tank passage. As a result, the hydraulic cylinder drives the driven object in the direction of gravity. At this time, the selection valve receives the pilot pressure output from the first electromagnetic proportional valve or the second electromagnetic proportional valve and switches the locking valve to the open state, so the selection valve can be automatically operated.

[0055] When the selector valve receives the pilot pressure output from the first electromagnetic proportional valve and operates, if the first electromagnetic proportional valve outputs the pilot pressure during the stop period of the hydraulic cylinder due to a malfunction of the first electromagnetic proportional valve, the lock valve is switched to an open state through the selector valve, so that the driven object moves in the direction of gravity due to its own weight.

[0056] On the other hand, when the selector valve operates by receiving the pilot pressure output from the second electromagnetic proportional valve, the lock valve can maintain the closed state even if the first electromagnetic proportional valve outputs the pilot pressure during the stop period of the hydraulic cylinder due to a malfunction of the first electromagnetic proportional valve. Therefore, even if a malfunction occurs in the first electromagnetic proportional valve, the driven object can be prevented from moving in the direction of gravity due to its own weight.

[0057] As a second aspect, in the first aspect, the valve device may further include: a third electromagnetic proportional valve that outputs a pilot pressure to the first control valve in a form in which the first actuator passage is connected to the pump passage; and a fourth electromagnetic proportional valve that outputs a pilot pressure to the second control valve in a form in which the second actuator passage is connected to the tank passage. According to this structure, four electromagnetic proportional valves can be used for independent metering control.

[0058] As a third aspect, in the first aspect, the valve device may further include a third electromagnetic proportional valve that outputs a pilot pressure to the first control valve and the second control valve in a manner that the first actuator passage is connected to the pump passage and the second actuator passage is connected to the tank passage. According to this structure, independent metering control can be performed using three electromagnetic proportional valves.

[0059] As a fourth form, the present disclosure provides a hydraulic system based on another aspect, comprising: a hydraulic cylinder, which includes a first working chamber for supplying working fluid when a driven object is driven in a direction counter to gravity and a second working chamber for supplying working fluid when the driven object is driven in a direction of gravity; the above-mentioned valve device, which is connected to the hydraulic cylinder; and a hydraulic pump, which is connected to the valve device.

Claims

1. A valve device, characterized in that: A valve device for a hydraulic cylinder, the hydraulic cylinder comprising a first working chamber for supplying working fluid when a driven object is driven in a direction counter to gravity and a second working chamber for supplying working fluid when the driven object is driven in a direction of gravity, comprising: a first control valve for switching a first actuator passage connected to the first working chamber to communicate with one of a pump passage and a tank passage; a first electromagnetic proportional valve that outputs a pilot pressure to the first control valve in a form in which the first actuator passage is communicated with the tank passage; a second control valve for switching a second actuator passage connected to the second working chamber to communicate with one of the pump passage and the tank passage; a second electromagnetic proportional valve that outputs a pilot pressure to the second control valve in a form in which the second actuator passage is connected to the pump passage; a lock valve disposed in the first actuator passage; and The selector valve receives the pilot pressure output from the first electromagnetic proportional valve or the second electromagnetic proportional valve and switches the lock valve from a closed state that closes the first actuator passage to an open state that opens the first actuator passage.

2. The valve device according to claim 1, characterized in that Also available: a third electromagnetic proportional valve that outputs a pilot pressure to the first control valve in a form in which the first actuator passage is communicated with the pump passage; and The fourth electromagnetic proportional valve outputs a pilot pressure to the second control valve in a manner that the second actuator passage communicates with the tank passage.

3. The valve device according to claim 1, characterized in that A third electromagnetic proportional valve is further provided for outputting a pilot pressure to the first control valve and the second control valve in such a manner that the first actuator passage communicates with the pump passage and the second actuator passage communicates with the tank passage.

4. A hydraulic system, characterized in that: have: A hydraulic cylinder comprising a first working chamber for supplying working fluid when driving a driven object in a direction counter to gravity and a second working chamber for supplying working fluid when driving the driven object in a direction of gravity; The valve device according to any one of claims 1 to 3, connected to the hydraulic cylinder; and A hydraulic pump is connected to the valve device.

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