Control valve unit

Abstract

To provide a control valve unit that can prevent pressure buildup in the oil passage upstream of the check valve when the control valve is operated to the neutral position, while also preventing the actuator, which is stopped in the neutral position, from operating against the user's intention. [Solution] The control valve unit 2 includes a pump oil passage 41, a first control valve 31, a second control valve 32, a first oil passage 42 connecting the first control valve 31 and the first actuator 61, a second oil passage 43 connecting the second control valve 32 and the second actuator 62, a pilot-operated first check valve 33, a pilot-operated second check valve 34, a tank oil passage 44 connected to the tank port 22, and pilot oil passages 45, 461, and 471 through which pilot hydraulic fluid flows. The pilot oil passages 45, 461, and 471 are not connected to the tank oil passage 44 and are not in communication with the tank port 22.

Description

Technical Field

[0001] The present invention relates to a control valve connected to a plurality of actuators.

Background Art

[0002] In a hydraulic control valve unit of an agricultural machine and a construction machine, a check valve may be used for the purpose of suppressing the occurrence of oil leakage from an actuator. For example, Patent Document 1 discloses a control valve unit including a first check valve and a second check valve. Each of the first check valve and the second check valve is configured as a pilot-operated type and operates by pilot hydraulic oil supplied through a pilot oil passage.

[0003] In the control valve unit described in Patent Document 1, the flow of hydraulic oil from the first port in the first oil passage to the control valve is blocked by the first check valve, and the flow of hydraulic oil from the second port in the second oil passage to the control valve is blocked by the second check valve. Thereby, the boom cylinder stops.

[0004] Among such control valve units, there is a control valve unit connected to a plurality of actuators. In a multi-control valve unit that controls the operations of a plurality of actuators, a plurality of check valves are provided in parallel. Further, in order to suppress the occurrence of pressure buildup in the oil passage on the upstream side of the check valve when the control valve is operated to the neutral position, the oil passage on the upstream side of each check valve communicates with the tank port.

[0005] However, in such a multi-control valve unit, when one actuator is operated, back pressure occurs in the tank oil passage connected to the tank port, and the check valve that stops the other actuator in the neutral state may be opened by the back pressure generated in the tank oil passage. Then, there is a possibility that the other actuator that is stopped in the neutral state may operate against the intention of the user of the agricultural machine or the construction machine. In this regard, there is room for improvement. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-184600 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The present invention has been made in view of the above circumstances, and aims to provide a control valve unit that can prevent pressure buildup in the oil passage upstream of the check valve when the control valve is operated to the neutral position, while also preventing the actuator, which is stopped in the neutral position, from operating against the user's intention. [Means for solving the problem]

[0008] One aspect of the present invention includes a pump oil passage connected to a pump port through which hydraulic fluid supplied from a hydraulic pump flows, a first control valve capable of controlling the flow direction of the hydraulic fluid and supplying the hydraulic fluid to a first actuator, a second control valve capable of controlling the flow direction of the hydraulic fluid and supplying the hydraulic fluid to a second actuator, a first oil passage connecting the first control valve and the first actuator, a second oil passage connecting the second control valve and the second actuator, a pilot-operated first check valve provided in the first oil passage which blocks the flow of hydraulic fluid from the first actuator to the first control valve when pilot hydraulic fluid is not supplied and allows the flow of hydraulic fluid from the first actuator to the first control valve when pilot hydraulic fluid is supplied, and a pilot-operated second check valve provided in the second oil passage which blocks the flow of hydraulic fluid from the second actuator to the second control valve when pilot hydraulic fluid is not supplied and allows the flow of hydraulic fluid from the second actuator to the second control valve when pilot hydraulic fluid is supplied, and A tank oil passage connected to a tank port, which guides the hydraulic fluid discharged from the first actuator via the first check valve and the first control valve, and the hydraulic fluid discharged from the second actuator via the second check valve and the second control valve, to the tank; a pilot oil passage connected to a pilot port, through which the pilot hydraulic fluid supplied from a pilot pump flows; a first pilot valve provided in the pilot oil passage, which is capable of supplying the pilot hydraulic fluid to the first check valve; and a pilot oil passage provided, which is capable of supplying the pilot hydraulic fluid to the first check valve. The control valve unit is characterized by comprising a second pilot valve capable of supplying hydraulic fluid to the second check valve, wherein the first control valve is biased to a first neutral position that shuts off the connection between the pump oil passage and the first oil passage and connects the first oil passage and the tank oil passage, the second control valve is biased to a second neutral position that shuts off the connection between the pump oil passage and the second oil passage and connects the second oil passage and the tank oil passage, and the pilot oil passage is not connected to the tank oil passage and is not in communication with the tank port. [Effects of the Invention]

[0009] The present invention, made in view of the above circumstances, provides a control valve unit that can prevent pressure buildup in the oil passage upstream of the check valve when the control valve is operated to the neutral position, while also preventing the actuator, which is stopped in the neutral position, from operating against the user's intention. [Brief explanation of the drawing]

[0010] [Figure 1] This is a hydraulic circuit diagram representing the control valve unit according to this embodiment. [Figure 2] This hydraulic circuit diagram shows the state in which the first check valve of this embodiment is forcibly opened. [Figure 3] This is a hydraulic circuit diagram showing a control valve unit related to a comparative example. [Figure 4] This is a hydraulic circuit diagram showing the state in which the first check valve of the comparative example is forcibly opened. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below are preferred examples of the present invention and are subject to various technically preferred limitations. However, the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description. In addition, similar components are denoted by the same reference numerals in the drawings, and detailed descriptions are omitted as appropriate.

[0012] Figure 1 is a hydraulic circuit diagram representing the control valve unit according to this embodiment. Figure 2 is a hydraulic circuit diagram showing the state in which the first check valve of this embodiment is forcibly opened.

[0013] As shown in Figure 1, the control valve unit 2 according to this embodiment is connected to the first actuator 61 and the second actuator 62, and controls the operation of the first actuator 61 and the second actuator 62 by supplying hydraulic fluid to the first actuator 61 and the second actuator 62, and by discharging hydraulic fluid from the first actuator 61 and the second actuator 62.

[0014] The number of actuators connected to the control valve unit 2 is not particularly limited, as long as there are multiple actuators, and may be three or more. In the following description, we will take the case where the control valve unit 2 is connected to two actuators, namely the first actuator 61 and the second actuator 62, as an example.

[0015] The control valve unit 2 includes a pump port 21, a tank port 22, a pilot port 23, a tank port 24, a first connection port 25, and a second connection port 26. The control valve unit 2 also includes a first control valve 31, a second control valve 32, a first check valve 33, a second check valve 34, a first pilot valve 35, and a second pilot valve 36.

[0016] The pump port 21 is connected to the pump oil passage 41. The pump oil passage 41 is connected to the hydraulic pump 51 via the pump port 21, and also connects the pump port 21 to the first control valve 31 and the second control valve 32. The pump oil passage 41 guides the hydraulic fluid supplied from the hydraulic pump 51 through the pump port 21 to the first control valve 31 and the second control valve 32. In other words, the hydraulic fluid supplied from the hydraulic pump 51 flows through the pump oil passage 41 and is guided to the first control valve 31 and the second control valve 32.

[0017] The tank port 22 is connected to the tank oil passage 44. The tank oil passage 44 is connected to the tank 52 via the tank port 22 and also connects the tank port 22 to the first control valve 31 and the second control valve 32. The tank oil passage 44 guides the hydraulic oil discharged from the first actuator 61 through the first check valve 33 and the first control valve 31 and the hydraulic oil discharged from the second actuator 62 through the second check valve 34 and the second control valve 32 to the tank 52. That is, the hydraulic oil discharged from the first actuator 61 and the second actuator 62 flows through the tank oil passage 44 and is guided to the tank 52 via the tank port 22.

[0018] The pilot port 23 is connected to the pilot oil passage 45. The pilot oil passage 45 is connected to the pilot pump 53 via the pilot port 23 and also connects the pilot port 23 to the first pilot valve 35 and the second pilot valve 36. The pilot oil passage 45 guides the pilot hydraulic oil supplied from the pilot pump 53 through the pilot port 23 to the first pilot valve 35 and the second pilot valve 36. That is, the pilot hydraulic oil supplied from the pilot pump 53 flows through the pilot oil passage 45 and is guided to the first pilot valve 35 and the second pilot valve 36.

[0019] The tank port 24 is connected to the tank oil passage 48. The tank oil passage 48 is connected to the tank 54 via the tank port 24 and also connects the tank port 24 to the first pilot valve 35 and the second pilot valve 36. The tank oil passage 48 guides the pilot hydraulic oil discharged from the first control valve 31 through the first pilot valve 35 and the pilot hydraulic oil discharged from the second control valve 32 through the second pilot valve 36 to the tank 54. That is, the pilot hydraulic oil discharged from the first control valve 31 and the second control valve 32 flows through the tank oil passage 48 and is guided to the tank 54 via the tank port 24. Note that the tank 54 may be the same as the tank 52.

[0020] The hydraulic pump 51 and the pilot pump 53 are mounted on industrial machines such as agricultural machines and construction machines, for example, and are driven by an engine (not shown). The hydraulic pump 51 supplies the lubricating oil stored in a tank 52 such as a mission case mounted on an industrial machine as hydraulic oil to a pump oil passage 41 through a pump port 21. The pilot pump 53 supplies the lubricating oil stored in a tank 54 such as a mission case mounted on an industrial machine as pilot hydraulic oil to a pilot oil passage 45 through a pilot port 23.

[0021] The first connection port 25 is connected to a first oil passage 42. The first oil passage 42 is connected to a first actuator 61 through the first connection port 25 and also connects the first connection port 25 and the first control valve 31. The first oil passage 42 guides the hydraulic oil supplied from the first control valve 31 to the first actuator 61 through a first check valve 33 and the first connection port 25. That is, the hydraulic oil supplied from the first control valve 31 flows through the first oil passage 42, passes through the first check valve 33, and is guided to the first actuator 61 through the first connection port 25. Further, the first oil passage 42 guides the hydraulic oil discharged from the first actuator 61 to the first control valve 31 through the first connection port 25 and the first check valve 33. That is, the hydraulic oil discharged from the first actuator 61 flows through the first oil passage 42 through the first connection port 25, passes through the first check valve 33 in a state where the valve body is forcibly opened, and is guided to the first control valve 31.

[0022] The second connection port 26 is connected to the second oil passage 43. The second oil passage 43 is connected to the second actuator 62 via the second connection port 26, and also connects the second connection port 26 to the second control valve 32. The second oil passage 43 guides the hydraulic fluid supplied from the second control valve 32 to the second actuator 62 via the second check valve 34 and the second connection port 26. That is, the hydraulic fluid supplied from the second control valve 32 flows through the second oil passage 43, passes through the second check valve 34, and is guided to the second actuator 62 via the second connection port 26. In addition, the second oil passage 43 guides the hydraulic fluid discharged from the second actuator 62 to the second control valve 32 via the second connection port 26 and the second check valve 34. In other words, the hydraulic fluid discharged from the second actuator 62 flows through the second oil passage 43 via the second connection port 26, passes through the second check valve 34 which is in a forcibly open state, and is led to the second control valve 32.

[0023] The first actuator 61 and the second actuator 62 are not particularly limited and may include, for example, cylinders or hydraulic motors that drive implements such as loaders or rotary tillers connected to industrial machinery.

[0024] The first control valve 31 is a pilot-operated spool valve that controls the flow direction of the hydraulic fluid supplied from the hydraulic pump 51. The first control valve 31 is connected to the pump oil passage 41, the first oil passage 42, and the tank oil passage 44. In other words, the first control valve 31 is a three-port valve having three connection ports. The first control valve 31 is operable to a first neutral position 311, a first supply position 312, and a first discharge position 313. In other words, the first control valve 31 is a three-position valve having three switching positions. The first control valve 31 is biased to the first neutral position 311 by a pair of springs and is operable to the first supply position 312 and the first discharge position 313 by pilot hydraulic fluid supplied from the pilot pump 53.

[0025] To explain in more detail, as shown in Figure 1, the pilot oil passage 461 is connected to one end of the first control valve 31. The pilot oil passage 462 is connected to the other end of the first control valve 31. When the pilot hydraulic fluid flows only through the pilot oil passage 461 and is supplied to one end of the first control valve 31, the first control valve 31 is operated to the first discharge position 313 by the pilot pressure generated by the pilot hydraulic fluid. On the other hand, when the pilot hydraulic fluid flows only through the pilot oil passage 462 and is supplied to the other end of the first control valve 31, the first control valve 31 is operated to the first supply position 312 by the pilot pressure generated by the pilot hydraulic fluid.

[0026] When the first control valve 31 is operated to the first neutral position 311, it disconnects the connection between the pump oil passage 41 and the first oil passage 42, and connects the first oil passage 42 to the tank oil passage 44. As a result, the first portion 421 of the first oil passage 42, which is located on the primary side (i.e., upstream side) of the first check valve 33, communicates with the tank port 22. This prevents pressure buildup in the first portion 421 of the first oil passage 42 when the first control valve 31 is operated to the first neutral position 311.

[0027] In this specification, "pressure buildup" refers to the undesirable pressure remaining in the hydraulic circuit after the supply of hydraulic fluid to the actuator has been stopped. "Pressure buildup" is sometimes referred to as "residual pressure," etc.

[0028] When the first control valve 31 is operated to the first supply position 312, it connects the pump oil passage 41 and the first oil passage 42, and disconnects the connection between the first oil passage 42 and the tank oil passage 44. As a result, the hydraulic fluid delivered from the hydraulic pump 51 flows through the pump oil passage 41 and the first oil passage 42, passes through the first check valve 33, and is supplied to the first actuator 61.

[0029] When the first control valve 31 is operated to the first discharge position 313, it disconnects the connection between the pump oil passage 41 and the first oil passage 42, and connects the first oil passage 42 to the tank oil passage 44. As a result, with the first check valve 33 forcibly opened by the pilot pressure generated by the pilot hydraulic fluid, the hydraulic fluid discharged from the first actuator 61 flows through the first oil passage 42 and the tank oil passage 44 and is guided to the tank 52.

[0030] The second control valve 32 is a pilot-operated spool valve that controls the flow direction of the hydraulic fluid supplied from the hydraulic pump 51. The second control valve 32 is connected to the pump oil passage 41, the second oil passage 43, and the tank oil passage 44. In other words, the second control valve 32 is a three-port valve with three connection ports. The second control valve 32 is operable to a second neutral position 321, a second supply position 322, and a second discharge position 323. In other words, the second control valve 32 is a three-position valve with three switching positions. The second control valve 32 is biased to the second neutral position 321 by a pair of springs and is operable to the second supply position 322 and the second discharge position 323 by pilot hydraulic fluid supplied from the pilot pump 53.

[0031] To explain in more detail, as shown in Figure 1, the pilot oil passage 471 is connected to one end of the second control valve 32. The pilot oil passage 472 is connected to the other end of the second control valve 32. When the pilot hydraulic fluid flows only through the pilot oil passage 471 and is supplied to one end of the second control valve 32, the second control valve 32 is operated to the second discharge position 323 by the pilot pressure generated by the pilot hydraulic fluid. On the other hand, when the pilot hydraulic fluid flows only through the pilot oil passage 472 and is supplied to the other end of the second control valve 32, the second control valve 32 is operated to the second supply position 322 by the pilot pressure generated by the pilot hydraulic fluid.

[0032] When the second control valve 32 is operated to the second neutral position 321, it disconnects the connection between the pump oil passage 41 and the second oil passage 43, and connects the second oil passage 43 to the tank oil passage 44. As a result, the first portion 431 of the second oil passage 43, which is located on the primary side (i.e., upstream side) of the second check valve 34, communicates with the tank port 22. This prevents pressure buildup in the first portion 431 of the second oil passage 43 when the second control valve 32 is operated to the second neutral position 321.

[0033] When the second control valve 32 is operated to the second supply position 322, it connects the pump oil passage 41 and the second oil passage 43, and disconnects the connection between the second oil passage 43 and the tank oil passage 44. As a result, the hydraulic fluid delivered from the hydraulic pump 51 flows through the pump oil passage 41 and the second oil passage 43, passes through the second check valve 34, and is supplied to the second actuator 62.

[0034] When the second control valve 32 is operated to the second discharge position 323, it disconnects the connection between the pump oil passage 41 and the second oil passage 43, and connects the second oil passage 43 to the tank oil passage 44. As a result, with the second check valve 34 forcibly opened by the pilot pressure generated by the pilot hydraulic fluid, the hydraulic fluid discharged from the second actuator 62 flows through the second oil passage 43 and the tank oil passage 44 and is guided to the tank 52.

[0035] The first check valve 33 has a pilot-operated structure and is located in the first oil passage 42. The first portion 421 of the first oil passage 42, located on the primary side (i.e., upstream side) of the first check valve 33, connects the first control valve 31 and the first check valve 33. The second portion 422 of the first oil passage 42, located on the secondary side (i.e., downstream side) of the first check valve 33, connects the first check valve 33 and the first connection port 25. The first check valve 33 is operable by pilot hydraulic fluid supplied from the pilot pump 53 via the first pilot valve 35.

[0036] To explain in more detail, as shown in Figure 1, the pilot oil passage 461 is connected to the first check valve 33. In other words, the pilot oil passage 461 is connected to both the first check valve 33 and the first control valve 31. When pilot hydraulic fluid flows through the pilot oil passage 461 and is supplied to the first check valve 33, the first check valve 33 is forced to open its valve body in response to the pilot pressure generated by the pilot hydraulic fluid, allowing the flow of hydraulic fluid from the first actuator 61 to the first control valve 31. That is, the first check valve 33 allows reverse free flow of hydraulic fluid. As a result, the hydraulic fluid discharged from the first actuator 61 can pass through the first check valve 33 and flow through the first oil passage 42 toward the first control valve 31.

[0037] In this specification, "reverse free flow" means the flow of hydraulic fluid permitted when the check valve is forcibly opened by pilot pressure, and is a flow in the direction in which the check valve normally blocks the flow. In addition, in this specification, "free flow" means the flow of hydraulic fluid permitted when the check valve is not receiving pilot pressure, and is a flow in the direction in which the check valve normally allows the flow.

[0038] On the other hand, when pilot hydraulic fluid is not supplied to the first check valve 33, the first check valve 33 closes its valve body under the biasing force of the spring, blocking the flow of hydraulic fluid from the first actuator 61 to the first control valve 31. In other words, the first check valve 33 prevents the reverse free flow of hydraulic fluid. As a result, the first check valve 33 prevents hydraulic fluid from leaking from the first actuator 61 and can stop the first actuator 61 in a neutral position.

[0039] The second check valve 34 has a pilot-operated structure and is located in the second oil passage 43. The first portion 431 of the second oil passage 43, located on the primary side (i.e., upstream side) of the second check valve 34, connects the second control valve 32 and the second check valve 34. The second portion 432 of the second oil passage 43, located on the secondary side (i.e., downstream side) of the second check valve 34, connects the second check valve 34 and the second connection port 26. The second check valve 34 is operable by pilot hydraulic fluid supplied from the pilot pump 53 via the second pilot valve 36.

[0040] To explain in more detail, as shown in Figure 1, the pilot oil passage 471 is connected to the second check valve 34. In other words, the pilot oil passage 471 is connected to both the second check valve 34 and the second control valve 32. When pilot hydraulic fluid flows through the pilot oil passage 471 and is supplied to the second check valve 34, the second check valve 34 is forced to open its valve body in response to the pilot pressure generated by the pilot hydraulic fluid, allowing the flow of hydraulic fluid from the second actuator 62 to the second control valve 32. That is, the second check valve 34 allows reverse free flow of hydraulic fluid. As a result, the hydraulic fluid discharged from the second actuator 62 can pass through the second check valve 34 and flow through the second oil passage 43 toward the second control valve 32.

[0041] On the other hand, when pilot hydraulic fluid is not supplied to the second check valve 34, the second check valve 34 closes its valve body under the biasing force of the spring, blocking the flow of hydraulic fluid from the second actuator 62 to the second control valve 32. In other words, the second check valve 34 prevents the reverse free flow of hydraulic fluid. As a result, the second check valve 34 prevents hydraulic fluid from leaking from the second actuator 62 and can stop the second actuator 62 in a neutral position.

[0042] The first pilot valve 35 is an electromagnetically operated spool valve and is connected to the pilot oil passage 45, the pilot oil passage 461, and the tank oil passage 48. In other words, the first pilot valve 35 is a three-port valve having three connection ports. The first pilot valve 35 is operable to a first non-supply position 351 and a first supply position 352. In other words, the first pilot valve 35 is a two-position valve having two switching positions. The first pilot valve 35 is biased to the first non-supply position 351 by a spring and is operable to the first supply position 352 by an electromagnet solenoid.

[0043] When the first pilot valve 35 is operated to the first non-supply position 351, it disconnects the pilot oil passage 45 from the pilot oil passage 461 and connects the pilot oil passage 461 to the tank oil passage 48. As a result, the pilot hydraulic fluid discharged from the first control valve 31 and the first check valve 33 flows through the pilot oil passage 461 and the tank oil passage 48 and is led to the tank 54.

[0044] When the first pilot valve 35 is operated to the first supply position 352, it connects the pilot oil passage 45 and the pilot oil passage 461, and disconnects the connection between the pilot oil passage 461 and the tank oil passage 48. As a result, the pilot hydraulic fluid delivered from the pilot pump 53 flows through the pilot oil passage 45 and the pilot oil passage 461 and is supplied to the first control valve 31 and the first check valve 33.

[0045] The second pilot valve 36 is an electromagnetically operated spool valve and is connected to the pilot oil passage 45, the pilot oil passage 471, and the tank oil passage 48. In other words, the second pilot valve 36 is a three-port valve with three connection ports. The second pilot valve 36 is operable to a second non-supply position 361 and a second supply position 362. In other words, the second pilot valve 36 is a two-position valve with two switching positions. The second pilot valve 36 is biased to the second non-supply position 361 by a spring and is operable to the second supply position 362 by an electromagnet solenoid.

[0046] When the second pilot valve 36 is operated to the second non-supply position 361, it disconnects the pilot oil passage 45 from the pilot oil passage 471 and connects the pilot oil passage 471 to the tank oil passage 48. As a result, the pilot hydraulic fluid discharged from the second control valve 32 and the second check valve 34 flows through the pilot oil passage 471 and the tank oil passage 48 and is led to the tank 54.

[0047] When the second pilot valve 36 is operated to the second supply position 362, it connects the pilot oil passage 45 and the pilot oil passage 471, and disconnects the connection between the pilot oil passage 471 and the tank oil passage 48. As a result, the pilot hydraulic fluid delivered from the pilot pump 53 flows through the pilot oil passage 45 and the pilot oil passage 471 and is supplied to the second control valve 32 and the second check valve 34.

[0048] As shown in Figure 1, the control valve unit 2 further comprises a first throttle valve 371, a second throttle valve 372, a third throttle valve 373, a fourth throttle valve 374, a first branch tank oil passage 423, and a second branch tank oil passage 433.

[0049] The first throttle valve 371 is installed at the connection point between the first oil passage 42 and the tank oil passage 44, and regulates the flow rate of the hydraulic fluid. The second throttle valve 372 is installed at the connection point between the second oil passage 43 and the tank oil passage 44, and regulates the flow rate of the hydraulic fluid. The third throttle valve 373 is installed in the first branch tank oil passage 423, and regulates the flow rate of the hydraulic fluid flowing through the first branch tank oil passage 423. The fourth throttle valve 374 is installed in the second branch tank oil passage 433, and regulates the flow rate of the hydraulic fluid flowing through the second branch tank oil passage 433.

[0050] The first branch tank oil passage 423 is provided by branching off from the first portion 421 of the first oil passage 42, which is located on the primary side of the first check valve 33. The first portion 421 of the first oil passage 42 in this embodiment is an example of the "portion of the first oil passage" in the present invention. The first branch tank oil passage 423 guides at least a portion of the hydraulic fluid flowing through the first portion 421 of the first oil passage 42 to the tank 55. Note that the tank 55 may be the same as tanks 52 and 54.

[0051] The second branch tank oil passage 433 is provided by branching off from the first portion 431 of the second oil passage 43, which is located on the primary side of the second check valve 34. The first portion 431 of the second oil passage 43 in this embodiment is an example of the "portion of the second oil passage" in the present invention. The second branch tank oil passage 433 guides at least a portion of the hydraulic fluid flowing through the first portion 431 of the second oil passage 43 to the tank 56. Note that the tank 56 may be the same as tanks 52 and 54.

[0052] Thus, the first throttle valve 371 and the third throttle valve 373 are positioned to sandwich the upstream and downstream sides of the first portion 421 of the first oil passage 42, which is provided on the primary side of the first check valve 33. The second throttle valve 372 and the fourth throttle valve 374 are positioned to sandwich the upstream and downstream sides of the first portion 431 of the second oil passage 43, which is provided on the primary side of the second check valve 34.

[0053] Next, a control valve relating to a comparative example will be described with reference to the drawings. In cases where the components of the comparative example control valve unit 2A are the same as those of the control valve unit 2 according to the present embodiment described above with respect to Figure 1, redundant explanations will be omitted as appropriate, and the differences will be explained below.

[0054] Figure 3 is a hydraulic circuit diagram showing a control valve unit related to a comparative example. Figure 4 is a hydraulic circuit diagram showing the state in which the first check valve of the comparative example is forcibly opened.

[0055] As shown in Figure 3, the control valve unit 2A of the comparative example includes a pump port 21, a tank port 22, a first connection port 25, and a second connection port 26. The control valve unit 2A also includes a first control valve 31A, a second control valve 32A, a first check valve 33, and a second check valve 34.

[0056] The first control valve 31A is a pilot-operated spool valve that controls the flow direction of the hydraulic fluid supplied from the hydraulic pump 51. The first control valve 31A is connected to the pump oil passage 41, the first oil passage 42, the tank oil passage 44, and the pilot oil passage 491. In other words, the first control valve 31A is a four-port valve with four connection ports. The first control valve 31A is operable to a first neutral position 311A, a first supply position 312A, and a first discharge position 313A. In other words, the first control valve 31A is a three-position valve with three switching positions. The first control valve 31A is biased to the first neutral position 311A ​​by a pair of springs and is operable to the first supply position 312A and the first discharge position 313A by pilot hydraulic fluid supplied from a pilot pump (not shown).

[0057] To explain in more detail, as shown in Figure 3, pilot oil passage 461A is connected to one end of the first control valve 31A. Pilot oil passage 462A is connected to the other end of the first control valve 31A. When pilot hydraulic fluid flows only through pilot oil passage 461A and is supplied to one end of the first control valve 31A, the first control valve 31A is operated to the first discharge position 313A by receiving the pilot pressure generated by the pilot hydraulic fluid. On the other hand, when pilot hydraulic fluid flows only through pilot oil passage 462A and is supplied to the other end of the first control valve 31A, the first control valve 31A is operated to the first supply position 312A by receiving the pilot pressure generated by the pilot hydraulic fluid.

[0058] When the first control valve 31A is operated to the first neutral position 311A, it connects the first oil passage 42 to the tank oil passage 44, and also connects the pilot oil passage 491 to the tank oil passage 44. As a result, the first portion 421 of the first oil passage 42, which is provided on the primary side of the first check valve 33, communicates with the tank port 22. In addition, the pilot oil passage 491 communicates with the tank port 22.

[0059] When the first control valve 31A is operated to the first supply position 312A, it connects the pump oil passage 41 and the first oil passage 42, and also connects the pilot oil passage 491 and the tank oil passage 44. As a result, the hydraulic fluid sent from the hydraulic pump 51 flows through the pump oil passage 41 and the first oil passage 42, passes through the first check valve 33, and is supplied to the first actuator 61. In addition, the pilot hydraulic fluid discharged from the first check valve 33 flows through the pilot oil passage 491 and the tank oil passage 44 and is led to the tank 52.

[0060] When the first control valve 31A is operated to the first discharge position 313A, it connects the pump oil passage 41 to the pilot oil passage 491, and also connects the first oil passage 42 to the tank oil passage 44. As a result, the first check valve 33 is forced open by the pilot pressure generated by the pilot hydraulic fluid, and the hydraulic fluid discharged from the first actuator 61 flows through the first oil passage 42 and the tank oil passage 44 and is guided to the tank 52.

[0061] The second control valve 32A is a pilot-operated spool valve that controls the flow direction of the hydraulic fluid supplied from the hydraulic pump 51. The second control valve 32A is connected to the pump oil passage 41, the second oil passage 43, the tank oil passage 44, and the pilot oil passage 492. In other words, the second control valve 32A is a four-port valve with four connection ports. The second control valve 32A is operable to a second neutral position 321A, a second supply position 322A, and a second discharge position 323A. In other words, the second control valve 32A is a three-position valve with three switching positions. The second control valve 32A is biased to the second neutral position 321A by a pair of springs and is operable to the second supply position 322A and the second discharge position 323A by pilot hydraulic fluid supplied from a pilot pump (not shown).

[0062] To explain in more detail, as shown in Figure 3, pilot oil passage 471A is connected to one end of the second control valve 32A. Pilot oil passage 472A is connected to the other end of the second control valve 32A. When pilot hydraulic fluid flows only through pilot oil passage 471A and is supplied to one end of the second control valve 32A, the second control valve 32A is operated to the second discharge position 323A by receiving the pilot pressure generated by the pilot hydraulic fluid. On the other hand, when pilot hydraulic fluid flows only through pilot oil passage 472A and is supplied to the other end of the second control valve 32A, the second control valve 32A is operated to the second supply position 322A by receiving the pilot pressure generated by the pilot hydraulic fluid.

[0063] When the second control valve 32A is operated to the second neutral position 321A, it connects the first oil passage 42 to the tank oil passage 44, and also connects the pilot oil passage 492 to the tank oil passage 44. As a result, the first portion 431 of the second oil passage 43, which is provided on the primary side of the second check valve 34, communicates with the tank port 22. In addition, the pilot oil passage 492 communicates with the tank port 22.

[0064] When the second control valve 32A is operated to the second supply position 322A, it connects the pump oil passage 41 and the second oil passage 43, and also connects the pilot oil passage 492 and the tank oil passage 44. As a result, the hydraulic fluid sent from the hydraulic pump 51 flows through the pump oil passage 41 and the second oil passage 43, passes through the second check valve 34, and is supplied to the second actuator 62. In addition, the pilot hydraulic fluid discharged from the second check valve 34 flows through the pilot oil passage 492 and the tank oil passage 44 and is led to the tank 52.

[0065] When the second control valve 32A is operated to the second discharge position 323A, it connects the pump oil passage 41 to the pilot oil passage 492, and also connects the second oil passage 43 to the tank oil passage 44. As a result, the second check valve 34 is forced open by the pilot pressure generated by the pilot hydraulic fluid, and the hydraulic fluid discharged from the second actuator 62 flows through the second oil passage 43 and the tank oil passage 44 and is guided to the tank 52.

[0066] The first check valve 33 has a pilot-operated structure and is located in the first oil passage 42. The first portion 421 of the first oil passage 42, located on the primary side of the first check valve 33, connects the first control valve 31A and the first check valve 33. The second portion 422 of the first oil passage 42, located on the secondary side of the first check valve 33, connects the first check valve 33 and the first connection port 25. The first check valve 33 is operable by pilot hydraulic fluid supplied from the hydraulic pump 51 via the first control valve 31A.

[0067] To explain in more detail, as shown in Figure 3, the pilot oil passage 491 is connected to the first check valve 33. When pilot hydraulic fluid flows through the pilot oil passage 491 and is supplied to the first check valve 33, the first check valve 33 is forced to open its valve body in response to the pilot pressure generated by the pilot hydraulic fluid, allowing the flow of hydraulic fluid from the first actuator 61 toward the first control valve 31A. In other words, the first check valve 33 allows reverse free flow of hydraulic fluid. As a result, the hydraulic fluid discharged from the first actuator 61 can pass through the first check valve 33 and flow through the first oil passage 42 toward the first control valve 31A.

[0068] On the other hand, when pilot hydraulic fluid is not supplied to the first check valve 33, the first check valve 33 closes its valve body under the biasing force of the spring, blocking the flow of hydraulic fluid from the first actuator 61 to the first control valve 31A. In other words, the first check valve 33 prevents the reverse free flow of hydraulic fluid. As a result, the first check valve 33 prevents hydraulic fluid from leaking from the first actuator 61 and can stop the first actuator 61 in a neutral position.

[0069] The second check valve 34 has a pilot-operated structure and is located in the second oil passage 43. The first portion 431 of the second oil passage 43, located on the primary side of the second check valve 34, connects the second control valve 32A and the second check valve 34. The second portion 432 of the second oil passage 43, located on the secondary side of the second check valve 34, connects the second check valve 34 and the second connection port 26. The second check valve 34 is operable by pilot hydraulic fluid supplied from the hydraulic pump 51 via the second control valve 32A.

[0070] To explain in more detail, as shown in Figure 3, the pilot oil passage 492 is connected to the second check valve 34. When pilot hydraulic fluid flows through the pilot oil passage 492 and is supplied to the second check valve 34, the second check valve 34 is forced to open its valve body in response to the pilot pressure generated by the pilot hydraulic fluid, allowing the flow of hydraulic fluid from the second actuator 62 toward the second control valve 32A. In other words, the second check valve 34 allows reverse free flow of hydraulic fluid. As a result, the hydraulic fluid discharged from the second actuator 62 can pass through the second check valve 34 and flow through the second oil passage 43 toward the second control valve 32A.

[0071] On the other hand, when pilot hydraulic fluid is not supplied to the second check valve 34, the second check valve 34 closes its valve body under the biasing force of the spring, blocking the flow of hydraulic fluid from the second actuator 62 to the second control valve 32A. In other words, the second check valve 34 prevents the reverse free flow of hydraulic fluid. As a result, the second check valve 34 prevents hydraulic fluid from leaking from the second actuator 62 and can stop the second actuator 62 in a neutral position.

[0072] Here, we will explain, with reference to Figure 4, a case in which the first actuator 61 is operated, such as when lowering the loader. As shown in Figure 4, when the first actuator 61 is activated, for example, the first control valve 31A is operated to the first discharge position 313A. At this time, for example, in order to prevent pressure buildup in the first portion 431 of the second oil passage 43, the second control valve 32A is operated to the second neutral position 321A, connecting the first oil passage 42 to the tank oil passage 44, and also connecting the pilot oil passage 492 to the tank oil passage 44.

[0073] When the first control valve 31A is operated to the first discharge position 313A, the hydraulic fluid sent from the hydraulic pump 51 flows through the pump oil passage 41 and the pilot oil passage 491 and is supplied to the first check valve 33. As a result, the first check valve 33 is forced to open its valve body in response to the pilot pressure generated by the pilot hydraulic fluid. In other words, the first check valve 33 allows reverse free flow of the hydraulic fluid. Then the hydraulic fluid is discharged from the first actuator 61 and flows through the first oil passage 42 and the tank oil passage 44 and is led to the tank 52. This causes the first actuator 61 to operate.

[0074] When the hydraulic fluid discharged from the first actuator 61 flows through the tank oil passage 44 and is guided to the tank 52, back pressure is generated in the tank oil passage 44 due to pressure loss and flow resistance. The back pressure generated in the tank oil passage 44 passes through the second control valve 32A, which is operated to the second neutral position 321A, and is transmitted to the second check valve 34 via the pilot oil passage 492. As a result, the second check valve 34 may be forced to open its valve body due to the back pressure. When the second check valve 34 is forced to open its valve body due to the back pressure, hydraulic fluid is discharged from the second actuator 62, which is stopped in the neutral position. Consequently, the second actuator 62, which is stopped in the neutral position, operates against the intention of the user of the industrial machine.

[0075] For example, when the control valve unit 2A is used as an auxiliary control valve unit, and implements according to the user's requirements are connected to the control valve unit 2A as the first actuator 61 and the second actuator 62, the second actuator 62, which is stopped in a neutral state, may operate against the user's intentions for the reasons mentioned above.

[0076] In contrast, in the control valve unit 2 according to this embodiment, as shown in Figure 1, the pilot oil passages 45, 461, and 471 through which pilot hydraulic fluid that operates the first check valve 33 and the second check valve 34 flows are not connected to the tank oil passage 44 and are not in communication with the tank port 22. Therefore, even when the second control valve 32 is operated to the second neutral position 321, it is possible to prevent the second actuator 62, which is stopped in the neutral position, from operating against the intention of the user of the industrial machine when the first actuator 61 is activated.

[0077] Specifically, the case in which the first actuator 61 of the control valve unit 2 according to this embodiment is operated will be described with reference to Figure 2. As shown in Figure 2, when the first actuator 61 is activated, for example, the first pilot valve 35 is operated to the first supply position 352. At this time, for example, in order to prevent pressure buildup in the first portion 431 of the second oil passage 43, the second control valve 32 is operated to the second neutral position 321, disconnecting the connection between the pump oil passage 41 and the second oil passage 43, and connecting the second oil passage 43 and the tank oil passage 44.

[0078] When the first pilot valve 35 is operated to the first supply position 352, pilot hydraulic fluid sent from the pilot pump 53 flows through the pilot oil passage 45 and pilot oil passage 461 and is supplied to the first control valve 31 and the first check valve 33. As a result, the first control valve 31 is operated to the first discharge position 313 by the pilot pressure generated by the pilot hydraulic fluid. The first check valve 33 is also forced to open by the pilot pressure generated by the pilot hydraulic fluid. In other words, the first check valve 33 allows reverse free flow of hydraulic fluid. As a result, the hydraulic fluid is discharged from the first actuator 61 and flows through the first oil passage 42 and the tank oil passage 44 to the tank 52. This activates the first actuator 61.

[0079] As described above, in the control valve unit 2 according to this embodiment, the pilot oil passages 45, 461, and 471 through which pilot hydraulic fluid that operates the first check valve 33 and the second check valve 34 flows are not connected to the tank oil passage 44 and are not in communication with the tank port 22. Therefore, it is possible to suppress the transmission of back pressure generated in the tank oil passage 44 when the hydraulic fluid discharged from the first actuator 61 flows through the tank oil passage 44 and is led to the tank 52 to the second check valve 34. As a result, even when the second control valve 32 is operated to the second neutral position 321, it is possible to suppress the operation of the second actuator 62, which is stopped in the neutral position, against the intention of the user of the industrial machine when the first actuator 61 is activated.

[0080] Furthermore, in the control valve unit 2A of the comparative example described above with respect to Figures 3 and 4, if, for example, a hydraulic motor operating at a relatively low pressure is connected to the control valve unit 2A as the second actuator 62, the back pressure generated in the tank oil passage 44 may become higher than the pressure in the second portion 432 of the second oil passage 43. That is, when the back pressure generated in the tank oil passage 44 passes through the second control valve 32A, which is operated to the second neutral position 321A, and is transmitted to the first portion 431 of the second oil passage 43, which is provided on the primary side of the second check valve 34, the back pressure transmitted to the first portion 431 of the second oil passage 43 may become higher than the pressure in the second portion 432 of the second oil passage 43.

[0081] In this case, since the second check valve 34 allows free flow of hydraulic fluid, the hydraulic fluid passes through the second check valve 34 and is supplied to the second actuator 62. As a result, the second actuator 62, which is stopped in the neutral position, operates against the intention of the user of the industrial machine.

[0082] As mentioned above, when implements according to the user's requirements of the industrial machine are connected to the control valve unit 2A as the first actuator 61 and the second actuator 62, such as when the control valve unit 2A is used as an auxiliary control valve unit, the back pressure transmitted to the first part 431 of the second oil passage 43 may be higher than the pressure in the second part 432 of the second oil passage 43.

[0083] In contrast, in the control valve unit 2 according to this embodiment, as shown in Figure 1, a second throttle valve 372 is provided at the connection point between the second oil passage 43 and the tank oil passage 44, and regulates the flow rate of the hydraulic fluid. Therefore, even if the pressure in the second portion 432 of the second oil passage 43 is lower than the back pressure generated in the tank oil passage 44, the second throttle valve 372 can regulate the flow rate of the hydraulic fluid and reduce the pressure in the first portion 431 of the second oil passage 43 to be lower than the pressure in the second portion 432 of the second oil passage 43.

[0084] To explain in more detail, the hydraulic fluid that flows through the first section 431 of the second oil passage 43, passing through the second throttle valve 372 due to the back pressure generated in the tank oil passage 44, flows through the first section 431 of the second oil passage 43 and the second branch tank oil passage 433 with its flow rate restricted by the second throttle valve 372, and is then led to the tank 56. As a result, the pressure in the first section 431 of the second oil passage 43 becomes an intermediate pressure between the back pressure generated in the tank oil passage 44 and the pressure in the tank 56 (i.e., atmospheric pressure). This makes it possible to reduce the pressure in the first section 431 of the second oil passage 43 to a level lower than the pressure in the second section 432 of the second oil passage 43.

[0085] Therefore, regardless of the type of first actuator 61 and second actuator 62 connected to the control valve unit 2 (e.g., cylinder and hydraulic motor), it is possible to prevent the hydraulic fluid from flowing to the second actuator 62 via the second check valve 34 against the user's intention. This prevents the second actuator 62, which is stopped in the neutral position, from operating against the user's intention due to back pressure generated in the tank oil passage 44.

[0086] As described above, according to the control valve unit 2 of this embodiment, when the first control valve 31 is operated to the first neutral position 311, it disconnects the connection between the pump oil passage 41 and the first oil passage 42, and connects the first oil passage 42 to the tank oil passage 44. Therefore, when the first control valve 31 is operated to the first neutral position 311, the first portion 421 of the first oil passage 42, which is provided on the primary side of the first check valve 33, is in communication with the tank port 22. This makes it possible to suppress the occurrence of pressure buildup in the first portion 421 of the first oil passage 42 when the first control valve 31 is operated to the first neutral position 311.

[0087] Furthermore, when the second control valve 32 is operated to the second neutral position 321, it disconnects the connection between the pump oil passage 41 and the second oil passage 43, and connects the second oil passage 43 to the tank oil passage 44. Therefore, when the second control valve 32 is operated to the second neutral position 321, the first portion 431 of the second oil passage 43, which is provided on the primary side of the second check valve 34, is in communication with the tank port 22. This prevents pressure buildup in the first portion 431 of the second oil passage 43 when the second control valve 32 is operated to the second neutral position 321.

[0088] Furthermore, the pilot oil passages 45 and 461 through which pilot hydraulic fluid for operating the first check valve 33 flows, and the pilot oil passages 45 and 471 through which pilot hydraulic fluid for operating the second check valve 34 flows, are not connected to the tank oil passage 44 and are not in communication with the tank port 22. Therefore, it is possible to suppress the transmission of back pressure generated in the tank oil passage 44 to the first check valve 33 and the second check valve 34. As a result, even when the second control valve 32 is operated to the second neutral position 321, it is possible to suppress the second actuator 62, which is stopped in the neutral position, from operating against the intention of the industrial machine user when the first actuator 61 is activated. Also, even when the first control valve 31 is operated to the first neutral position 311, it is possible to suppress the first actuator 61, which is stopped in the neutral position, from operating against the intention of the industrial machine user when the second actuator 62 is activated.

[0089] As mentioned earlier with respect to Figure 1, the pilot oil passage 461 is connected to both the first check valve 33 and the first control valve 31. Therefore, the first control valve 31 can be operated to a first neutral position 311, a first supply position 312, and a first discharge position 313 by the pilot hydraulic fluid that operates the first check valve 33. In other words, the pilot hydraulic fluid that operates the first check valve 33 and the pilot hydraulic fluid that operates the first control valve 31 are shared. Also, the pilot oil passage 471 is connected to both the second check valve 34 and the second control valve 32. Therefore, the second control valve 32 can be operated to a second neutral position 321, a second supply position 322, and a second discharge position 323 by the pilot hydraulic fluid that operates the second check valve 34. In other words, the pilot hydraulic fluid that operates the second check valve 34 and the pilot hydraulic fluid that operates the second control valve 32 are shared. This makes it possible to simplify and miniaturize the structure of the control valve unit 2.

[0090] As mentioned above with respect to Figure 2, even if the pressure in the second portion 432 of the second oil passage 43 is lower than the back pressure generated in the tank oil passage 44, the second throttle valve 372 restricts the flow rate of the hydraulic fluid flowing through the first portion 431 of the second oil passage 43, setting the pressure in the first portion 431 of the second oil passage 43 to an intermediate pressure between the back pressure generated in the tank oil passage 44 and the pressure in the tank 56 connected to the second branch tank oil passage 433 (i.e., atmospheric pressure), thereby reducing it to a pressure lower than the pressure in the second portion 432 of the second oil passage 43. Furthermore, even if the pressure in the second portion 422 of the first oil passage 42 is lower than the back pressure generated in the tank oil passage 44, the first throttle valve 371 can regulate the flow rate of the hydraulic fluid through the first portion 421 of the first oil passage 42, setting the pressure in the first portion 421 of the first oil passage 42 to an intermediate pressure between the back pressure generated in the tank oil passage 44 and the pressure in the tank 55 connected to the first branch tank oil passage 423 (i.e., atmospheric pressure), thereby reducing it to a pressure lower than the pressure in the second portion 422 of the first oil passage 42.

[0091] Therefore, regardless of the type of first actuator 61 and second actuator 62 connected to the control valve unit 2 (e.g., cylinder and hydraulic motor), it is possible to prevent the hydraulic fluid from flowing to the second actuator 62 via the second check valve 34 against the user's intention, and to prevent it from flowing to the first actuator 61 via the first check valve 33. This prevents the first actuator 61 and second actuator 62 from operating against the user's intention due to back pressure generated in the tank oil passage 44.

[0092] Furthermore, the third throttle valve 373, provided in the first branch tank oil passage 423, regulates the flow rate of hydraulic fluid through the first branch tank oil passage 423, preventing excessive hydraulic fluid flowing through the first oil passage 42 from being directed to the tank 55 via the first branch tank oil passage 423. This allows the valve body of the first check valve 33 to open more reliably with the pressure generated by the hydraulic fluid flowing through the first oil passage 42, and ensures that the hydraulic fluid flowing through the first oil passage 42 is reliably supplied by the first actuator 61.

[0093] The fourth throttle valve 374, installed in the second branch tank oil passage 433, regulates the flow rate of hydraulic fluid through the second branch tank oil passage 433, preventing excessive hydraulic fluid from being guided to the tank 56 via the second branch tank oil passage 433. This allows the valve body of the second check valve 34 to open more reliably with the pressure generated by the hydraulic fluid flowing through the second oil passage 43, ensuring that the hydraulic fluid flowing through the second oil passage 43 is reliably supplied by the second actuator 62.

[0094] Embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the claims. The configurations of the above embodiments can be partially omitted or combined in any way different from those described above. [Explanation of Symbols]

[0095] 2: Control valve unit, 2A: Control valve unit, 21: Pump port, 22: Tank port, 23: Pilot port, 24: Tank port, 25: First connection port, 26: Second connection port, 31: First control valve, 31A: First control valve, 32: Second control valve, 32A: Second control valve, 33: First check valve, 34: Second check valve, 35: First pilot valve, 36: Second pilot valve, 41: Pump oil passage, 42: First oil passage, 43: Second oil passage, 44: Tank oil passage, 45: Pilot oil passage, 48: Tank oil passage, 51: Hydraulic pump, 52: Tank, 53: Pilot pump, 54: Tank, 55: Tank, 56: Tank, 61: First actuator, 62: Second actuator, 311: First neutral position, 311A: First neutral position, 312: First supply position, 312A: First supply position, 313: First discharge position, 313A: First discharge position, 321: Second neutral position, 321A: Second neutral position, 322: Second supply position, 322A: Second supply position, 323: Second discharge position, 323A: Second discharge position, 351: First non-supply position, 352: First supply position, 361: Second non-supply position, 362: Second supply position, 371: First throttle valve, 372: Second throttle valve, 373: Third throttle valve, 374: Fourth throttle valve, 421: First section, 422: Second section, 423: First branch tank oil passage, 431: First section, 432: Second section, 433: Second branch tank oil passage, 461: Pilot oil passage, 461A: Pilot oil passage, 462: Pilot oil passage, 462A: Pilot oil passage, 471: Pilot oil passage, 471A: Pilot oil passage, 472: Pilot oil passage, 472A: Pilot oil passage, 491: Pilot oil passage, 492: Pilot oil passage

Claims

1. A pump oil passage connected to the pump port, through which hydraulic fluid supplied from the hydraulic pump flows, A first control valve capable of controlling the flow direction of the hydraulic fluid and supplying the hydraulic fluid to the first actuator, A second control valve capable of controlling the flow direction of the hydraulic fluid and supplying the hydraulic fluid to the second actuator, A first oil passage connecting the first control valve and the first actuator, A second oil passage connecting the second control valve and the second actuator, A pilot-operated first check valve is provided in the first oil passage, which blocks the flow of hydraulic fluid from the first actuator to the first control valve when pilot hydraulic fluid is not supplied, and allows the flow of hydraulic fluid from the first actuator to the first control valve when pilot hydraulic fluid is supplied, A pilot-operated second check valve is provided in the second oil passage, which blocks the flow of hydraulic fluid from the second actuator to the second control valve when the pilot hydraulic fluid is not supplied, and allows the flow of hydraulic fluid from the second actuator to the second control valve when the pilot hydraulic fluid is supplied. A tank oil passage connected to a tank port, which guides the hydraulic fluid discharged from the first actuator via the first check valve and the first control valve, and the hydraulic fluid discharged from the second actuator via the second check valve and the second control valve, to the tank, A pilot oil passage connected to a pilot port, through which the pilot hydraulic fluid supplied from the pilot pump flows, A first pilot valve is provided in the pilot oil passage and is capable of supplying the pilot hydraulic fluid to the first check valve, A second pilot valve is provided in the pilot oil passage and is capable of supplying the pilot hydraulic fluid to the second check valve, Equipped with, The first control valve is biased to a first neutral position that disconnects the connection between the pump oil passage and the first oil passage, and connects the first oil passage and the tank oil passage. The second control valve is biased to a second neutral position that disconnects the connection between the pump oil passage and the second oil passage, and connects the second oil passage and the tank oil passage. The control valve unit is characterized in that the pilot oil passage is not connected to the tank oil passage and is not in communication with the tank port.

2. The first control valve is, A first supply position that connects the pump oil passage and the first oil passage, and disconnects the connection between the first oil passage and the tank oil passage, A first discharge position that disconnects the connection between the pump oil passage and the first oil passage, and connects the first oil passage and the tank oil passage, The aforementioned first neutral position and, It is a pilot-operated type that can be operated using the aforementioned pilot hydraulic fluid. The second control valve is, A second supply position that connects the pump oil passage and the second oil passage, and disconnects the connection between the second oil passage and the tank oil passage, A second discharge position that disconnects the connection between the pump oil passage and the second oil passage, and connects the second oil passage and the tank oil passage, The aforementioned second neutral position and, The control valve unit according to claim 1, characterized in that it is a pilot-operated type that can be operated by the pilot hydraulic fluid.

3. A first throttle valve is provided at the connection point between the first oil passage and the tank oil passage, which regulates the flow rate of the hydraulic fluid, A first branch tank oil passage is provided, which branches off from the portion of the first oil passage located on the primary side of the first check valve, and guides at least a portion of the hydraulic fluid that has flowed through the portion of the first oil passage to the tank, A second throttle valve is provided at the connection point between the second oil passage and the tank oil passage, which regulates the flow rate of the hydraulic fluid, A second branch tank oil passage is provided, which branches off from the portion of the second oil passage located on the primary side of the second check valve, and guides at least a portion of the hydraulic fluid that has flowed through the portion of the second oil passage to the tank, The control valve unit according to claim 1, further comprising the features described above.

4. A third throttle valve is provided in the first branch tank oil passage and regulates the flow rate of the hydraulic fluid flowing through the first branch tank oil passage, A fourth throttle valve is provided in the second branch tank oil passage and regulates the flow rate of the hydraulic fluid flowing through the second branch tank oil passage, The control valve unit according to claim 3, further comprising the features described above.

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