JP2016223551A - Hydraulic circuit unit of construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic circuit unit capable of surely preventing a large amount of hydraulic fluid from being suddenly supplied to an actuator when a control valve is displaced from a neutral position.SOLUTION: A hydraulic circuit unit 1 can switch opening/closing of a center bypass flow channel 11 at a downstream side with respect to a control valve 10, by an opening/closing valve 50, and a hydraulic pressure of the hydraulic fluid in a discharge flow channel 8 or a hydraulic pressure of the hydraulic fluid supplied to an actuator from the control valve is detected by a hydraulic pressure detection portion 27. When a displacement amount from a neutral position, of the control valve is a reference displacement amount or more, the center bypass flow channel is kept in an opened state by the opening/closing valve during a time when the hydraulic pressure detected by the hydraulic pressure detection portion is a reference value or more, and the center bypass flow channel is switched to a closed state by the opening/closing valve on the basis of the fact that the detected hydraulic pressure is lowered to a range smaller than the reference value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydraulic circuit unit provided in a construction machine.

  Patent Document 1 discloses a hydraulic circuit unit for a construction machine including a hydraulic pump that discharges hydraulic oil toward a discharge flow path. In this hydraulic circuit unit, hydraulic oil is supplied to the control valve through the discharge flow path, and the control valve can be displaced from the neutral position based on the operation with the valve operation lever. In the hydraulic circuit unit, hydraulic oil is supplied to a hydraulic motor that is an actuator through a control valve, and hydraulic oil that is not supplied to the actuator flows into the center bypass flow path from the control valve. In a state where the control valve is located at the neutral position, the supply of hydraulic oil to the hydraulic motor is interrupted, and the hydraulic oil is supplied to the hydraulic motor when the control valve is displaced from the neutral position. Further, the bypass opening through which hydraulic oil flows from the control valve to the center bypass flow path is in an open state when the control valve is located at the neutral position, and the opening area increases as the amount of displacement from the neutral position of the control valve increases. Get smaller. However, even when the amount of displacement from the neutral position of the control valve becomes maximum, the bipal opening is kept open, and hydraulic oil flows into the center bypass flow path.

  In the hydraulic circuit unit, an opening / closing valve is provided downstream of the control valve in the center bypass passage, and the opening / closing of the center bypass passage is switched downstream of the control valve by the opening / closing valve. When the pilot oil is supplied to the control valve through the pilot pipe line based on the operation with the valve operation lever, the control valve is displaced from the neutral position. Pilot oil is supplied to the throttle from the pilot pipe line. When the pilot oil that has passed through the throttle is supplied to the on-off valve, the center bypass channel in the on-off valve is switched from the open state to the closed state. Here, it takes time for the pilot oil to pass through the throttle. For this reason, it takes time from the time when the control valve is displaced from the neutral position to the time when the center bypass channel is closed in the on-off valve. Therefore, even if the control valve is displaced from the neutral position, a large amount of hydraulic fluid is prevented from being supplied to the hydraulic motor suddenly, and rapid acceleration of the hydraulic motor (actuator) at the start of operation or the like is prevented.

Japanese Patent No. 3643193

  In the hydraulic circuit unit of Patent Document 1, the time for the pilot oil to pass through the throttle varies depending on the temperature, viscosity, etc. of the pilot oil. By shortening the time for the pilot oil to pass through the throttle, the time from when the control valve is displaced from the neutral position to when the center bypass flow path is closed in the on-off valve is also shortened. In this case, when the control valve is displaced from the neutral position, a large amount of hydraulic oil is suddenly supplied to the actuator, and the actuator may accelerate rapidly.

  The present invention has been made paying attention to the above-mentioned problems, and the purpose thereof is to reliably prevent a large amount of hydraulic oil from being supplied suddenly to the actuator when the control valve is displaced from the neutral position. It is to provide a hydraulic circuit unit.

  In order to achieve the above object, a hydraulic circuit unit of a construction machine according to an aspect of the present invention includes a hydraulic pump having a discharge port, a discharge passage through which hydraulic oil is discharged from the discharge port of the hydraulic pump, A control valve that is supplied with the hydraulic oil through a discharge passage and is displaceable from a neutral position; an actuator that is operated by supplying the hydraulic oil through the control valve; and an actuator that extends from the control valve, A center bypass flow path through which the hydraulic oil not supplied to the control valve flows from the control valve, and a bypass opening through which the hydraulic oil flows from the control valve toward the center bypass flow path, the control valve being in the neutral position In the open position, the opening area decreases as the displacement amount of the control valve from the neutral position increases. A bypass opening that is kept open even when the amount of displacement of the control valve from the neutral position is maximized, and a supply opening that allows the hydraulic oil supplied to the actuator to flow into the control valve, When the control valve is in the neutral position, the control valve is closed, and when the control valve is displaced from the neutral position, the supply opening is opened. An opening / closing valve provided on the downstream side of the control valve and capable of switching the opening and closing of the center bypass flow path; a displacement detection unit that detects the displacement of the control valve from the neutral position; and the discharge flow path. A hydraulic pressure detection unit that detects a hydraulic pressure of the hydraulic fluid or a hydraulic pressure of the hydraulic fluid supplied from the control valve to the actuator; and a displacement detection unit and a hydraulic pressure detection unit A control unit that controls the on-off valve based on a result of output, wherein the hydraulic pressure detected by the hydraulic pressure detection unit when the displacement amount of the control valve from the neutral position is equal to or greater than a reference displacement amount; In the on-off valve, the center bypass flow path is kept open in the on-off valve for a reference value or more, and the oil pressure detected by the oil pressure detecting unit is lowered to a range smaller than the reference value. And a control unit that switches the center bypass channel to a closed state.

  ADVANTAGE OF THE INVENTION According to this invention, when a control valve displaces from a neutral position, the hydraulic circuit unit which can prevent reliably reliably supplying a large quantity of hydraulic fluid to an actuator can be provided.

It is the schematic which shows the structure of the hydraulic circuit unit which concerns on 1st Embodiment. It is a flowchart which shows the process in the control part at the time of operating the hydraulic motor which concerns on 1st Embodiment. It is a flowchart which shows the process in the control part at the time of operating the hydraulic motor which concerns on a 1st modification. It is the schematic which shows the structure of the hydraulic circuit unit which concerns on a 2nd modification.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a hydraulic circuit unit 1 of the present embodiment. The hydraulic circuit unit 1 is applied to a construction machine such as a power shovel or a crane.

  As shown in FIG. 1, the hydraulic circuit unit 1 includes an engine 2, an oil tank 3 in which oil is stored, and a main pump (hydraulic pump) 5 connected to the engine 2. When the engine 2 is activated, the main pump 5 is operated. The main pump 5 has a discharge port 6 and is a variable capacity pump that can change its capacity (discharge amount). A main supply passage 7 extends between the oil tank 3 and the main pump 5. A main discharge channel (discharge channel) 8 extends from the discharge port 6 of the main pump 5. By operating the main pump (hydraulic pump) 5, oil is supplied from the oil tank 3 to the main pump 5, and oil is discharged from the discharge port 6 of the main pump 5 to the main discharge flow path 8 as hydraulic oil.

  The hydraulic circuit unit 1 includes a control valve 10, and the main discharge flow path 8 extends from the main pump 5 to the control valve 10. The hydraulic oil discharged to the main discharge flow path 8 is supplied to the control valve 10. In the hydraulic circuit unit 1, a center bypass passage 11 extends from the control valve 10. The center bypass passage 11 has a bypass opening 12 and is connected to the control valve 10 by the bypass opening 12. Further, the center bypass channel 11 communicates with the main discharge channel 8 via the bypass opening 12. On the downstream side of the center bypass channel 11, a main recovery channel 13 is extended. The main recovery flow path 13 extends to the oil tank 3.

  A relay supply flow path 15 branches from the main discharge flow path 8, and the relay supply flow path 15 extends to the control valve 10. The relay supply channel 15 has a supply opening 16 and is connected to the control valve 10 through the supply opening 16. Further, a relay recovery channel 17 extends from the control valve 10, and the relay recovery channel 17 merges with the main recovery channel 13. The relay collection channel 17 has a collection opening 18 and is connected to the control valve 10 through the collection opening 18.

  The hydraulic circuit unit 1 includes a hydraulic motor 20 as an actuator. The hydraulic motor 20 is an actuator that is actuated when, for example, a turning body is turned in a construction machine. In a modification, a cylinder (not shown) that is operated when raising and lowering a boom (not shown) in a construction machine, and a cylinder (not shown) that is operated when excavating with a bucket (not shown) in a power shovel. ) May be provided as an actuator instead of or in addition to the hydraulic motor 20. In the hydraulic circuit unit 1, a first actuator channel 21 and a second actuator channel 22 extend from the control valve 10 to the hydraulic motor 20.

  The control valve 10 has a neutral position, and can be displaced from the neutral position in a first displacement direction (direction of arrow Y1 in FIG. 1) and a second displacement direction (direction of arrow Y2 in FIG. 1). When the control valve 10 is in the neutral position, the bypass opening 12 is opened, and the main discharge flow path 8 and the center bypass flow path 11 communicate with each other. For this reason, hydraulic fluid flows from the control valve 10 through the bypass opening 12 toward the center bypass passage 11. Further, when the control valve 10 is in the neutral position, the supply opening 16 and the recovery opening 18 are closed. For this reason, the relay supply channel 15 and the relay recovery channel 17 are disconnected from both the first actuator channel 21 and the second actuator channel 22. Therefore, when the control valve 10 is in the neutral position, the hydraulic oil is not supplied to the hydraulic motor 20 and the operation of the hydraulic motor 20 is stopped.

  When the control valve 10 is displaced from the neutral position in the first displacement direction or the second displacement direction, the supply opening 16 and the recovery opening 18 are opened. As a result, hydraulic oil is supplied to the hydraulic motor 20 and the hydraulic motor 20 is operated. When the control valve 10 is displaced from the neutral position in the first displacement direction, the relay supply flow path 15 communicates with the first actuator flow path 21 and the relay recovery flow path 17 is the second actuator in the control valve 10. It communicates with the flow path 22. As a result, hydraulic fluid is supplied from the relay supply channel 15 to the hydraulic motor 20 through the first actuator channel 21, and hydraulic fluid is supplied from the hydraulic motor 20 to the relay recovery channel 17 through the second actuator channel 22. The hydraulic motor 20 is actuated. At this time, the hydraulic motor 20 rotates toward the first rotation direction that is one of the rotation directions. On the other hand, when the control valve 10 is displaced from the neutral position in the second displacement direction, the relay supply flow path 15 communicates with the second actuator flow path 22 in the control valve 10, and the relay recovery flow path 17 is the first. It communicates with the actuator flow path 21. As a result, hydraulic fluid is supplied from the relay supply channel 15 to the hydraulic motor 20 through the second actuator channel 22, and hydraulic fluid is supplied from the hydraulic motor 20 to the relay recovery channel 17 through the first actuator channel 21. The hydraulic motor 20 is actuated. At this time, the hydraulic motor 20 rotates in the second rotation direction opposite to the first rotation direction. Note that a shuttle valve 23 that prevents backflow of hydraulic oil from the control valve 10 to the main discharge flow path 8 through the relay supply flow path 15 is disposed in the relay supply flow path 15.

  When the control valve 10 is displaced from the neutral position in the first displacement direction or the second displacement direction, the opening area of the bypass opening 12 decreases as the displacement amount (εa; εb) from the neutral position of the control valve 10 increases. Become. However, even if the control valve 10 is displaced from the neutral position, the bypass opening 12 is kept open. The bypass opening 12 is opened in the state where the displacement amount εa of the control valve 10 in the first displacement direction is maximized and in the state where the displacement amount εb of the control valve 10 in the second displacement direction is maximized. It becomes a state. Therefore, even when the displacement amount εa of the control valve 10 in the first displacement direction is maximized and when the displacement amount εb of the control valve 10 in the second displacement direction is maximized, the hydraulic motor 20 The hydraulic oil that is not supplied can flow from the control valve 10 toward the center bypass passage 11 through the bypass opening 12.

  In the hydraulic circuit unit 1, the main relief flow path 25 branches from the main discharge flow path 8 and joins the main recovery flow path 13. A relief valve (main relief valve) 26 is disposed in the main relief flow path 25. The relief valve 26 has a predetermined operating pressure P0. While the hydraulic pressure P in the main discharge flow path 8 is smaller than the operating pressure P0 of the relief valve 26, the relief valve 26 is not operated, and the hydraulic oil does not pass through the relief valve 26. On the other hand, when the hydraulic pressure P in the main discharge passage 8 becomes equal to or higher than the operating pressure P0 of the relief valve 26, the relief valve 26 is actuated, and the relief valve 26 is moved from the main discharge passage 8 toward the main recovery passage 13. Pass through. At this time, when the hydraulic oil is released by the relief valve 26, the pressure energy of the hydraulic oil is converted into thermal energy, and energy loss occurs.

  The hydraulic circuit unit 1 includes a pressure sensor 27 as a hydraulic pressure detection unit that detects the hydraulic pressure P of the hydraulic oil in the main discharge flow path 8. The hydraulic circuit unit 1 includes a control unit 30 that controls the entire construction machine. The control unit 30 includes a processor having a central processing unit (CPU) or an application specific integrated circuit (ASIC), and a storage medium such as a memory. From the pressure sensor 27, a detection signal (electric signal) indicating the detection result of the hydraulic oil pressure P is transmitted to the control unit 30.

  The hydraulic circuit unit 1 includes a sub pump (hydraulic pump) 31 connected to the engine 2. When the engine 2 is started, the sub pump 31 is operated. The sub pump 31 has a discharge port 32. A sub supply channel 33 branches from the main supply channel 7, and the sub supply channel 33 extends to the sub pump 31. Further, a sub-discharge channel 35 extends from the discharge port 32 of the sub-pump 31. By operating the sub pump 31, oil is supplied from the oil tank 3 to the sub pump 31, and the oil is discharged from the discharge port 32 of the sub pump 31 to the sub discharge passage 35 as pilot oil.

  The hydraulic circuit unit 1 includes an operation lever 36 which is an operation input unit to which an operation for displacing the control valve 10 from the neutral position is input, an operation valve 37 whose operation state is switched based on an operation input at the operation lever 36, Is provided. The sub discharge channel 35 extends from the sub pump 31 to the operation valve 37. The pilot oil discharged to the sub discharge channel 35 is supplied to the operation valve 37. Further, in the hydraulic circuit unit 1, the sub collection passage 38 is extended to the oil tank 3.

  In the hydraulic circuit unit 1, the sub relief channel 41 branches from the sub discharge channel 35 and merges with the sub recovery channel 38. A relief valve (sub relief valve) 42 is disposed in the sub relief channel 41. The relief valve 42 has a predetermined operating pressure P′0. While the hydraulic pressure P ′ of the sub discharge passage 35 is smaller than the operating pressure P ′ 0 of the relief valve 42, the relief valve 42 is not actuated and the pilot oil does not pass through the relief valve 42. On the other hand, when the hydraulic pressure P ′ of the sub-discharge passage 35 becomes equal to or higher than the operating pressure P ′ 0 of the relief valve 42, the relief valve 42 is operated and the relief valve 42 is moved from the sub-discharge passage 35 toward the sub-collection passage 38. Pilot oil passes through.

  In the hydraulic circuit unit 1, a first pilot flow path 45 and a second pilot flow path 46 are extended between the operation valve 37 and the control valve 10. When the operating state of the operation valve 37 is switched based on an operation input from the operation lever 36, the sub-discharge channel 35 communicates with the first pilot channel 45 and the second pilot channel 46 at the operation valve 37. The state is switched. In the state where the sub discharge passage 35 does not communicate with either the first pilot passage 45 or the second pilot passage 46 in the operation valve 37, pilot oil is not supplied to the control valve 10, and the control valve 10 is in the neutral position. Held in.

  On the other hand, in the state where the sub discharge flow path 35 communicates with the first pilot flow path 45 in the operation valve 37, the pilot oil is supplied to the control valve 10 through the first pilot flow path 45, and the control valve 10 is moved from the neutral position. Displacement in the first displacement direction (the direction of arrow Y1 in FIG. 1). At this time, if the displacement amount of the operation lever 26 increases, the hydraulic pressure ρ′a of the pilot oil in the first pilot flow path 45 increases, and the displacement amount in the first displacement direction from the neutral position of the control valve 10. εa also increases.

  In the state where the sub discharge flow path 35 communicates with the second pilot flow path 46 in the operation valve 37, the pilot oil is supplied to the control valve 10 through the second pilot flow path 46, and the control valve 10 is moved from the neutral position. Displacement in the second displacement direction (the direction of arrow Y2 in FIG. 1). At this time, if the displacement amount of the operation lever 26 increases, the hydraulic pressure ρ′b of the pilot oil in the second pilot flow path 46 increases, and the displacement amount from the neutral position of the control valve 10 in the second displacement direction. εb also increases.

  The hydraulic circuit unit 1 includes a pressure switch 47 as a hydraulic pressure detection unit that detects the hydraulic pressure (ρ′a, ρ′b) of pilot oil in the first pilot flow path 45 and the second pilot flow path 46. Further, the control unit 30 includes a displacement detection unit 48 that detects a displacement from the neutral position of the control valve 10. The displacement detection unit 48 is formed of an electronic circuit that constitutes a processor in the control unit 30, for example. From the pressure switch 47, detection signals (electric signals) indicating the detection results of the pilot oil pressure (ρ′a, ρ′b) are transmitted to the displacement detection unit 48. The displacement detector 48 detects the displacement from the neutral position of the control valve 10 based on the detection result of the pressure switch 47. A shuttle valve 54 is provided in the vicinity of the pressure switch 47, and the hydraulic pressure in the first pilot flow path 45 or the second pilot flow path 46 is applied (guided) to the pressure switch 47. The hydraulic pressure of the first pilot channel 45 or the second pilot channel 46 can be detected.

  When the pilot oil pressure (ρ′a; ρ′b) in the first pilot flow path 45 or the second pilot flow path 46 becomes equal to or higher than the reference value ρ′ref, the pressure switch 47 changes from the OFF state to the ON state. Switch. By detecting that the pressure switch 47 is in the ON state, the displacement detector 48 has a displacement amount (εa; εb) in the first displacement direction or the second displacement direction from the neutral position of the control valve 10. It is detected that the displacement is greater than or equal to the reference displacement amount εref.

  In the center bypass channel 11, an on-off valve (center cut valve) 50 is provided on the downstream side of the control valve 10. The on-off valve 50 can switch opening and closing of the center bypass channel 11 on the downstream side of the control valve 10. The hydraulic circuit unit 1 is provided with a relay pilot channel 51 through which pilot oil can flow from the first pilot channel 45 and the second pilot channel 46. Note that a hydraulic signal of pilot oil from the first pilot flow path 45 or the second pilot flow path 46 is transmitted to the relay pilot flow path 51 by the shuttle valve 54.

  The hydraulic circuit unit 1 is provided with an electromagnetic valve 52, and the relay pilot flow path 51 extends to the electromagnetic valve 52. The sub collection channel 38 extends from the electromagnetic valve 52 toward the oil tank 3. Further, a third pilot flow path (additional pilot flow path) 53 extends between the electromagnetic valve 52 and the on-off valve 50. The control unit 30 is provided with a power control unit 55 that controls the supply of power to the electromagnetic valve 52. The power control unit 55 is formed of an electronic circuit that constitutes a processor in the control unit 30, for example.

  In a state where electric power is not supplied from the power control unit 55 to the electromagnetic valve 52, the sub recovery flow path 38 communicates with the third pilot flow path 53 and the relay pilot flow path 51 is connected to the third pilot in the electromagnetic valve 52. It does not communicate with the flow path 53. For this reason, pilot oil is not supplied from the relay pilot channel 51 to the on-off valve 50 through the third pilot channel 53, and the center bypass channel 11 is opened in the on-off valve 50. On the other hand, in the state where electric power is supplied from the power control unit 55 to the electromagnetic valve 52, the relay pilot flow path 51 communicates with the third pilot flow path 53 in the electromagnetic valve 52. For this reason, pilot oil is supplied from the relay pilot channel 51 to the on-off valve 50 through the third pilot channel 53, and the center bypass channel 11 is closed in the on-off valve 50. When the center bypass passage 11 is closed in the on-off valve 50, the hydraulic oil does not flow downstream from the on-off valve 50.

  Based on the detection result of the hydraulic oil pressure P by the pressure sensor 27 and the detection result of the displacement from the neutral position of the control valve 10 by the displacement detection unit 48, the power control unit 55 supplies power to the electromagnetic valve 52. The supply is controlled. Actually, the electric power control unit 55 determines whether or not the hydraulic pressure P of the hydraulic oil detected by the pressure sensor 27 is greater than or equal to the reference value Pref, and the amount of displacement (εa; εb) from the neutral position of the control valve 10. The supply of electric power to the electromagnetic valve 52 is controlled based on whether or not the reference displacement amount εref is greater than or equal to. The reference value Pref of the hydraulic oil pressure P is smaller than the operating pressure P0 of the relief valve 26, and is set to, for example, a value that is 80% to 95% of the operating pressure P0. The reference value Pref of the hydraulic oil pressure P is stored in the storage medium of the control unit 30. Details of the control by the power control unit 55 will be described later.

  In the center bypass channel 11, a throttle 56 is provided on the downstream side of the on-off valve (center cut valve) 50. From the center bypass channel 11, the hydraulic oil flows into the main recovery channel 13 through the throttle 56. In the hydraulic circuit unit 1, a discharge adjustment unit 57 that adjusts the discharge amount of hydraulic oil from the main pump (hydraulic pump) 5 is provided. The discharge adjusting unit 57 changes the discharge amount of the hydraulic oil from the main pump 5 by changing the capacity of the main pump 5. In the present embodiment, the discharge amount adjustment unit 57 performs so-called negative control that reduces the discharge amount from the main pump 5 when the control pressure for controlling the discharge amount adjustment unit 57 increases.

  In the hydraulic circuit unit 1, the control flow path 58 branches from the center bypass flow path 11 on the downstream side of the on-off valve 50 and on the upstream side of the throttle 56. The control flow path 58 extends toward the discharge adjustment unit 57. When the hydraulic oil that has passed through the on-off valve 50 passes through the throttle 56 in the center bypass passage 11, hydraulic pressure (according to the flow rate of hydraulic oil passing through the throttle 56) is generated. The hydraulic pressure (control pressure) generated in the throttle 56 is transmitted (acted) to the discharge adjustment unit 57 via the control flow path 58, whereby the discharge amount of the hydraulic oil from the main pump 5 is reduced.

  Next, the operation and effect of the hydraulic circuit unit 1 of the present embodiment will be described. FIG. 2 is a flowchart showing processing in the control unit 30 when operating the hydraulic motor 20 as an actuator. As shown in FIG. 2, in a state where the operation of the hydraulic motor 20 before the operation of the hydraulic motor 20 is stopped, the power control unit 55 of the control unit 30 does not supply power to the electromagnetic valve 52 ( Step S101). When starting the operation of the hydraulic motor 20, the displacement detection unit 48 of the control unit 30 determines whether or not the pressure switch 47 is in an ON state (step S102). Accordingly, it is determined whether or not the hydraulic pressure (ρ′a; ρ′b) of the pilot oil in the first pilot flow path 45 or the second pilot flow path 46 is equal to or higher than the reference value ρ′ref, and the control is performed. It is determined whether or not the displacement amount (εa; εb) in the first displacement direction or the second displacement direction from the neutral position of the valve 10 is greater than or equal to the reference displacement amount εref. As long as the pressure switch 47 is in the OFF state (step S <b> 102 -No), the power control unit 55 maintains a state in which power is not supplied to the electromagnetic valve 52.

  Then, when the pressure switch 47 is turned on by an operation input from the operation lever 36 (step S102-Yes), the control unit 30 elapses a predetermined time T0 from when the pressure switch 47 is switched to the on state. It is determined whether or not it has been done (step S103). Before the time T0 elapses from when the pressure switch 47 is switched to the ON state (step S103-No), the power control unit 55 maintains a state where power is not supplied to the electromagnetic valve 52.

  When the time T0 has elapsed from when the pressure switch 47 is switched to the ON state (step S103-Yes), the control unit 30 determines that the hydraulic pressure P of the hydraulic oil in the main discharge flow path 8 detected by the pressure sensor 27 is increased. It is determined whether or not it is smaller than a reference value (hydraulic oil reference value) Pref (step S104). When the hydraulic pressure P of the hydraulic oil is greater than or equal to the reference value Pref (step S104—No), the power control unit 55 maintains a state where power is not supplied to the electromagnetic valve 52. For this reason, even when the displacement amount (εa; εb) from the neutral position of the control valve 10 is equal to or larger than the reference displacement amount εref, the hydraulic pressure P of the hydraulic oil detected by the pressure sensor (hydraulic pressure detection unit) 27 is the reference value. During Pref or more, communication between the relay pilot flow path 51 and the third pilot flow path is blocked in the electromagnetic valve 52, and pilot oil is not supplied to the on-off valve 50. For this reason, while the hydraulic pressure P of the hydraulic oil in the main discharge flow path 8 detected by the pressure sensor 27 is greater than or equal to the reference value Pref, the center bypass flow path 11 is kept open in the on-off valve 50.

  When the hydraulic pressure P of the hydraulic oil in the main discharge flow path 8 falls to a range smaller than the reference value Pref (step S104-Yes), the power control unit 55 switches to a state where power is supplied to the electromagnetic valve 52 ( Step S105). As a result, the relay pilot flow path 51 and the third pilot flow path communicate with each other in the electromagnetic valve 52, and pilot oil is supplied to the on-off valve 50. Therefore, the center bypass passage 11 is switched to the closed state in the on-off valve 50 based on the fact that the hydraulic pressure P detected by the pressure sensor (hydraulic pressure detecting unit) has fallen to a range smaller than the reference value Pref.

  When the state is switched to a state where electric power is supplied to the electromagnetic valve 52 (step S105), the displacement detection unit 48 determines whether or not the pressure switch 47 is in an OFF state (step S106). Thereby, it is determined whether or not the hydraulic pressure (ρ′a; ρ′b) of the pilot oil in the first pilot flow path 45 or the second pilot flow path 46 is smaller than the reference value ρ′ref, and the control valve It is determined whether or not the displacement amount (εa; εb) from the 10 neutral position in the first displacement direction or the second displacement direction is smaller than the reference displacement amount εref. As long as the pressure switch 47 is in the ON state (No at Step S <b> 106), the power control unit 55 maintains a state where power is supplied to the electromagnetic valve 52. That is, even when the hydraulic pressure P of the hydraulic oil in the main discharge passage 8 becomes smaller than the reference value Pref after the hydraulic pressure P of the hydraulic oil becomes smaller than the reference value Pref, the displacement amount (εa; As long as εb) is equal to or larger than the reference displacement amount εref, the pilot oil is supplied to the on-off valve 50, and the center bypass passage 11 is maintained in the closed state in the on-off valve 50.

  When the pressure switch 47 is turned off (step S106—Yes), the power control unit 55 switches to a state where power is not supplied to the electromagnetic valve 52 (step S107). As a result, communication between the relay pilot flow path 51 and the third pilot flow path in the electromagnetic valve 52 is blocked, and pilot oil is not supplied to the on-off valve 50. Therefore, based on the fact that the displacement amount (εa; εb) from the neutral position of the control valve 10 is smaller than the reference displacement amount εref, the center bypass passage 11 is switched to the open state in the on-off valve 50. If the work is to be continued (No at Step S108), the process returns to Step S102 and the above-described processing is performed.

  When the control valve 10 is in the neutral position, hydraulic oil is not supplied to the hydraulic motor 20 that is an actuator, and the operation of the hydraulic motor 20 is stopped. From this state, the control valve 10 is displaced from the neutral position by a displacement (εa; εb) equal to or greater than the reference displacement εref from the neutral position to the first displacement direction or the second displacement direction by an operation input from the operation lever 36. The hydraulic oil is supplied to the motor 20 and the operation of the hydraulic motor 20 is started. At this time, the hydraulic pressure P of the hydraulic oil in the main discharge flow path 8 may increase until a certain amount of time elapses after the hydraulic motor 20 starts operating. In this embodiment, even when the displacement (εa; εb) becomes maximum from the neutral position of the control valve 10, the bypass opening 12 of the center bypass passage 11 is kept open. For this reason, even when the displacement amount (εa; εb) is greater than or equal to the reference displacement amount εref from the neutral position of the control valve 10, the opening area of the bypass opening 12 is smaller than when the control valve 10 is positioned at the neutral position. However, hydraulic oil can flow into the center bypass passage 11 from the control valve 10 through the bypass opening 12.

  Further, since the above-described control is performed, when the hydraulic pressure P of the hydraulic oil in the main discharge flow path 8 is equal to or higher than the reference value Pref, the center bypass flow path 11 is opened in the on-off valve 50. Therefore, even if the control valve 10 is displaced from the neutral position by the reference displacement amount εref or more, if the hydraulic oil pressure P in the main discharge flow path 8 is high, a part of the hydraulic oil is controlled from the main discharge flow path 8. It flows downstream from the on-off valve 50 through the valve 10 and the center bypass passage 11. For this reason, even when the hydraulic pressure P of the hydraulic oil in the main discharge flow path 8 is high, a large amount of hydraulic oil is prevented from being supplied to the hydraulic motor 20 at the start of operation. As a result, rapid acceleration of the hydraulic motor 20 and the revolving body operated by the operation of the hydraulic motor 20 is prevented, and the hydraulic motor 20 starts to operate appropriately.

  When a certain amount of time has elapsed since the hydraulic motor 20 started to operate, the hydraulic pressure P of the hydraulic oil in the main discharge flow path 8 decreases. In the present embodiment, the center bypass flow path 11 is switched to the closed state in the on-off valve 50 based on the fact that the hydraulic pressure P detected by the pressure sensor 27 has fallen to a range smaller than the reference value Pref. When the center bypass passage 11 is blocked in the on-off valve 50, the hydraulic oil does not flow downstream from the on-off valve 50. Thereby, the hydraulic oil discharged from the main pump 5 to the main discharge flow path 8 is entirely supplied to the hydraulic motor 20. Therefore, the operating speed can be secured in a state where the hydraulic motor (actuator) 20 is operating.

  For example, a pilot oil is supplied by passing a throttle or the like through the on-off valve (50), and the time difference from the time when the pilot oil is supplied to the control valve (10) to the time when the pilot oil is supplied to the on-off valve (50). In the structure which has, the influence of the temperature and viscosity of pilot oil becomes large. For this reason, since the time for the pilot oil to pass through the throttle is shortened due to the temperature and viscosity of the pilot oil, the center bypass flow path (50) in the on-off valve (50) after the control valve (10) is displaced from the neutral position. The time until 11) is closed is also shortened. In this case, when the control valve (10) is displaced from the neutral position, a large amount of hydraulic oil is suddenly supplied to the hydraulic motor (20), and the hydraulic motor (20) is not operated properly.

  On the other hand, in the present embodiment, the opening and closing of the center bypass passage 11 at the on-off valve 50 is switched based on the hydraulic pressure P of the hydraulic oil in the main discharge passage 8. For this reason, when the hydraulic pressure P in the main discharge flow path 8 is high, the center bypass flow path 11 is reliably opened by the on-off valve 50, and hydraulic oil flows downstream from the on-off valve 50. For this reason, even if the hydraulic pressure P in the main discharge flow path 8 is increased, a large amount of hydraulic oil is prevented from being supplied to the hydraulic motor 20 abruptly. When the hydraulic motor 20 starts to operate and the hydraulic pressure P in the main discharge flow path 8 decreases to a certain level, the on-off valve 50 is closed, and all of the hydraulic oil discharged to the main discharge flow path 8 is transferred to the hydraulic motor 20. Supplied. For this reason, when the control valve 10 is displaced from the neutral position by a displacement amount (εa; εb) equal to or larger than the reference displacement amount εref, supply of the hydraulic oil in the main discharge flow path 8 to the hydraulic motor 20 is performed. The amount is adjusted appropriately and the hydraulic motor 20 is operated properly.

  Further, when the operation input at the operation lever (operation input unit) 36 becomes unstable due to the upper body of the driver shaking, the displacement amount (εa; εb) from the neutral position of the control valve 10 is the reference displacement amount. Oscillate (fluctuate) in the vicinity of εref. In this case, the displacement amount (εa; εb) from the neutral position of the control valve 10 repeatedly changes over time between a state smaller than the reference displacement amount εref and a state larger than the reference displacement amount εref. In the present embodiment, when the hydraulic pressure P in the main discharge flow path 8 is equal to or greater than the reference value Pref, the reference displacement amount from the state where the displacement amount (εa; εb) from the neutral position of the control valve 10 is smaller than the reference displacement amount εref. Even when the state is switched to a state equal to or higher than εref, the center bypass channel 11 is maintained in the open state in the on-off valve 50. Therefore, even when the displacement amount (εa; εb) from the neutral position of the control valve 10 vibrates in the vicinity of the reference displacement amount εref due to an unstable operation input at the operation lever (operation input unit) 36, the hydraulic motor 20 is prevented from being supplied with a large amount of hydraulic oil. As a result, the rapid acceleration of the hydraulic motor 20 is mitigated, and the rapid acceleration of the revolving structure or the like that is operated by the operation of the hydraulic motor 20 is mitigated. Therefore, even when the displacement amount (εa; εb) from the neutral position of the control valve 10 vibrates in the vicinity of the reference displacement amount εref due to an unstable operation input at the operation lever (operation input unit) 36, Occurrence of a hunting phenomenon in which rapid acceleration and rapid deceleration are repeated over time during turning is suppressed.

  Further, while the hydraulic pressure P of the hydraulic oil in the main discharge flow path 8 is greater than or equal to the reference value Pref, the hydraulic oil flows downstream from the on-off valve 50 and the hydraulic pressure generated by the throttle 56 is adjusted for discharge through the control flow path 58. Acts on (transmits to) the portion 57. Thereby, the discharge amount of the hydraulic oil from the main pump 5 decreases. Therefore, while the hydraulic pressure P of the hydraulic oil in the main discharge flow path 8 is greater than or equal to the reference value Pref, the flow rate (flow) of the hydraulic oil is controlled to be small.

  In addition, the reference value Pref of the hydraulic pressure P of the main discharge flow path 8 serving as a reference for switching the center bypass flow path 11 to the closed state by the opening / closing valve 50 is set to a value smaller than the operating pressure P0 of the relief valve (main relief valve) 26. Has been. As described above, the flow rate of the hydraulic oil is controlled to be small while the hydraulic pressure P of the hydraulic oil in the main discharge flow path 8 is equal to or higher than the reference value Pref. For this reason, the amount of hydraulic oil opened by the relief valve 26 (passing through the relief valve 26) is reduced, and energy loss due to the pressure energy of the hydraulic oil being converted into thermal energy by the relief valve 26 is reduced. .

  Further, the hydraulic pressure P of the hydraulic oil in the main discharge flow path 8 vibrates (fluctuates) in the vicinity of the reference value Pref, and the hydraulic pressure P in the main discharge flow path 8 is smaller than the reference value Pref and the reference value Pref or more. May change repeatedly over time. In the present embodiment, after the hydraulic pressure P of the hydraulic oil in the main discharge flow path 8 becomes smaller than the reference value Pref and the center bypass flow path 11 is closed in the on-off valve 50, the hydraulic pressure P becomes the reference value Pref again. Even in this case, as long as the displacement amount (εa; εb) from the neutral position of the control valve 10 is equal to or larger than the reference displacement amount εref, the center bypass channel 11 is maintained in the closed state in the on-off valve 50. Therefore, even when the hydraulic pressure P in the main discharge flow path 8 vibrates in the vicinity of the reference value Pref, as long as the displacement amount (εa; εb) from the neutral position of the control valve 10 is equal to or larger than the reference displacement amount εref, In the on-off valve 50, the center bypass flow path 11 is maintained in a closed state, and hydraulic oil does not flow downstream from the on-off valve 50. Therefore, when the hydraulic pressure P in the main discharge flow path 8 vibrates in the vicinity of the reference value Pref, a rapid increase in the amount of hydraulic oil supplied to the hydraulic motor 20 is prevented and the hydraulic oil to the hydraulic motor 20 is prevented. A sudden decrease in the amount of supply of water is prevented. As a result, even when the hydraulic pressure P in the main discharge flow path 8 vibrates in the vicinity of the reference value Pref, the occurrence of a hunting phenomenon in which rapid acceleration and rapid deceleration are repeated over time in the turning of the turning body is suppressed. The

(Modification)
In the first modification, when the hydraulic motor 20 is operated, the processing shown in FIG. Also in this modification, the processes of steps S101 to S103 are performed as in the first embodiment. However, in this modification, the mode of the construction machine that is switched by operating the mode switching button or the like is detected. That is, in this modification, when the pressure switch 47 is turned on (step S102-Yes) and the time T0 has elapsed since the time when the pressure switch 47 is switched to the on state (step S103-Yes), the control unit 30 It is determined whether or not the mode of the construction machine (power shovel) is the crane mode (step S109). When it is not the crane mode (step S109-Yes), the control unit 30 determines whether or not the mode of the construction machine (power shovel) is the high power mode (step S110). And when it is not hyper mode (step S110-Yes), the process of step S104-S108 is performed similarly to 1st Embodiment.

  When it is determined in step S109 that the construction machine is in the crane mode (step S109-No), the power control unit 55 maintains a state where power is not supplied to the electromagnetic valve 52 (step S111), and the on-off valve. At 50, the center bypass passage 11 is maintained in an open state. And the displacement detection part 48 judges whether the pressure switch 47 is an OFF state (step S112). When the pressure switch 47 is in the OFF state (step S112—Yes), the process proceeds to step S108 while maintaining the state where power is not supplied to the electromagnetic valve 52. Then, when the work is continued (No at Step S108), the process returns to Step S102.

  In the crane mode of the construction machine, it is necessary to stably move the lifted load, and thus it is necessary to operate the swivel body at a low speed. For this reason, it is necessary to operate the hydraulic motor 20 as an actuator at a low speed, and it is necessary to keep the amount of hydraulic oil supplied to the hydraulic motor 20 small. In this modification, since the center bypass passage 11 is always kept open in the on-off valve 50 in the crane mode of the construction machine, the hydraulic oil discharged to the main discharge passage 8 is always downstream from the on-off valve 50. The amount of hydraulic oil supplied to the hydraulic motor 20 is kept small. Thereby, in the crane mode, the hydraulic motor 20 can always be stably operated at a low speed. Further, in the crane mode, the center bypass passage 11 is always kept open in the on-off valve 50, so that a large amount of hydraulic oil is prevented from being suddenly supplied to the hydraulic motor 20. As a result, the rapid acceleration of the hydraulic motor 20 is alleviated, so that the rapid acceleration of the swivel body or the like that is operated by the operation of the hydraulic motor 20 is mitigated. Occurrence of the hunting phenomenon repeated repeatedly is suppressed.

  When it is determined in step S110 that the construction machine is in the high power mode (step S110-No), the power control unit 55 switches to a state in which power is supplied to the electromagnetic valve 52 (step S113), and the on-off valve 50 The center bypass passage 11 is switched to the closed state. Then, the displacement detector 48 determines whether or not the pressure switch 47 is in an OFF state (step S114). As long as the pressure switch 47 is in the ON state (No at Step S <b> 114), the power control unit 55 maintains a state where power is supplied to the electromagnetic valve 52. When the pressure switch 47 is in the OFF state (step S114—Yes), the power control unit 55 switches to a state where power is not supplied to the electromagnetic valve 52 (step S107). As a result, the center bypass passage 11 is switched to the open state in the on-off valve 50. Then, when the work is continued (No at Step S108), the process returns to Step S102.

  Since the high power mode of the construction machine is used when the driving force increases in the operation of the revolving structure or the like, in the high power mode, the amount of hydraulic oil supplied to the hydraulic motor 20 that is an actuator is increased, and the hydraulic motor 20 It is necessary to increase the driving force for operating the. In this modification, since the center bypass passage 11 is always kept closed in the on-off valve 50 during the high power mode of the construction machine, all of the hydraulic fluid discharged to the main discharge passage 8 is always hydraulic motor. 20 is supplied. Further, in the high power mode, hydraulic oil does not flow downstream from the on-off valve 50, so that no hydraulic pressure (pressure) is generated by the throttle 56. Therefore, in the high power mode, the amount of hydraulic oil discharged from the main pump 5 increases, and the operating pressure (relief pressure) P0 of the relief valve 26 increases due to the override characteristics of the relief valve 26. Therefore, in the high power mode, the amount of hydraulic oil supplied to the hydraulic motor 20 is kept large, and the driving force for operating the hydraulic motor 20 is increased. For this reason, even when the driving force is increased in the operation of the revolving structure or the like, the revolving structure can be appropriately operated.

  In the second modified example shown in FIG. 4, the relay pilot flow path 51, the electromagnetic valve 52, and the third pilot flow path 53 are not provided in the hydraulic circuit unit 1, and pilot oil is not supplied to the on-off valve 50. In this modification, the on-off valve 50 is an electromagnetic valve, and the power control unit 55 controls the supply of power to the on-off valve 50. In a state where power is not supplied from the power control unit 55 to the on-off valve 50, the center bypass passage 11 is opened in the on-off valve 50. On the other hand, in the state where electric power is supplied from the power control unit 55 to the on-off valve 50, the center bypass passage 11 is closed in the on-off valve 50.

  Also in this modification, when the hydraulic motor 20 is operated, the control unit 30 performs the same processing as the processing shown in FIG. Accordingly, in the present modification as well, as in the first embodiment, the pressure sensor (hydraulic pressure detecting unit) 27 is also used when the displacement amount (εa; εb) from the neutral position of the control valve 10 is equal to or larger than the reference displacement amount εref. As long as the hydraulic pressure P of the hydraulic oil detected in step S1 is equal to or greater than the reference value Pref, the state in which no electric power is supplied to the on-off valve 50 is maintained, and the center bypass passage 11 is kept open in the on-off valve 50. Then, on the basis of the fact that the hydraulic pressure P detected by the pressure sensor (hydraulic pressure detection unit) has fallen to a range smaller than the reference value Pref, the state is switched to a state where electric power is supplied to the on-off valve 50. The flow path 11 is switched to a closed state.

  In the above-described embodiment, the pressure switch 47 serves as a hydraulic pressure detection unit that detects the hydraulic pressure (ρ′a, ρ′b) of the pilot oil in the first pilot flow path 45 and the second pilot flow path 46. Although provided, in some variations, a pressure sensor may be provided instead. In this case, the reference value ρ′ref serving as a reference in the pilot oil pressure (ρ′a, ρ′b) in the first pilot flow path 45 and the second pilot flow path 46 is stored in the storage medium of the control unit 30. Is remembered. Then, when the hydraulic pressure (ρ′a; ρ′b) of the pilot oil in the first pilot channel 45 or the second pilot channel 46 becomes equal to or higher than the reference value ρ′ref, the displacement detector 48 is It is detected that the displacement amount (εa; εb) in the first displacement direction or the second displacement direction from the neutral position of the control valve 10 is equal to or larger than the reference displacement amount εref.

  In the above-described embodiment and the like, the hydraulic pressure P of the hydraulic oil in the main discharge flow path 8 is detected by the pressure sensor 27. However, in a modification, instead of the control valve 10 to the first actuator flow path 21. Alternatively, a pressure sensor that detects the hydraulic pressure ρ of the hydraulic fluid supplied to the hydraulic motor (actuator) 20 through the second actuator flow path 22 may be provided as the hydraulic pressure detection unit. In this case, the reference value ρref of the hydraulic pressure ρ between the control valve 10 and the hydraulic motor 20 is stored in the storage medium of the control unit 30 instead of the reference value Pref of the hydraulic pressure P in the main discharge flow path 8. . Even when the displacement amount (εa; εb) from the neutral position of the control valve 10 is equal to or larger than the reference displacement amount εref, the hydraulic pressure ρ of the hydraulic oil supplied from the control valve 10 to the hydraulic motor 20 is equal to or larger than the reference value ρref. In the meantime, the center bypass passage 11 is kept open in the on-off valve 50. Then, based on the fact that the hydraulic pressure ρ between the control valve 10 and the hydraulic motor 20 detected by the pressure sensor (hydraulic detector) has fallen to a range smaller than the reference value ρref, the center bypass flow path 11 in the on-off valve 50. Is switched to the closed state.

  In the above-described embodiment and the like, the hydraulic circuit unit (1) includes a hydraulic pump (5) having a discharge port (6), and a discharge passage through which hydraulic oil is discharged from the discharge port (6) of the hydraulic pump (5). (8), hydraulic oil is supplied through the discharge flow path (8), the control valve (10) is displaceable from the neutral position, and the actuator is operated by supplying hydraulic oil through the control valve (10) ( 20) and a center bypass passage (11) that extends from the control valve (10) and into which hydraulic oil that is not supplied to the actuator (20) flows from the control valve (10). Hydraulic fluid flows from the control valve (10) into the center bypass flow path (11) through the bypass opening (12), and the bypass opening (12) is in an open state when the control valve (10) is located at the neutral position. As the displacement amount (εa; εb) from the neutral position of the control valve (10) increases, the opening area decreases. Even when the displacement amount (εa; εb) from the neutral position of the control valve (10) is maximized, the bypass opening (12) is kept open. The hydraulic fluid supplied to the actuator (20) flows into the control valve (10) through the supply opening (16), and the supply opening (16) is closed when the control valve (10) is in the neutral position. At the same time, the control valve (10) is opened by being displaced from the neutral position. On the downstream side of the control valve (10) in the center bypass channel (11), an on-off valve (50) capable of switching opening and closing of the center bypass channel (11) on the downstream side of the control valve (10) is provided. ing. The displacement from the neutral position of the control valve (10) is detected by the displacement detector (48), and the hydraulic oil pressure (P) in the discharge passage (8) or from the control valve (10) to the actuator (20). The hydraulic pressure (ρ) of the supplied hydraulic oil is detected by the hydraulic pressure detector (27). The control unit (30) controls the on-off valve (50) based on the detection results of the displacement detection unit (48) and the hydraulic pressure detection unit (27). When the displacement (εa; εb) from the neutral position of the control valve (10) is greater than or equal to the reference displacement (εref), the control unit (30) detects the hydraulic pressure (P While ρ) is greater than or equal to the reference value (Pref; ρref), the center bypass channel (11) is kept open in the on-off valve (50) and the hydraulic pressure (P; ρ) detected by the hydraulic pressure detection unit (27). ) Is lowered to a range smaller than the reference value (Pref; ρref), the center bypass passage (11) is switched to the closed state in the on-off valve (50).

  The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.

  DESCRIPTION OF SYMBOLS 1 ... Hydraulic circuit unit, 5 ... Main pump, 6 ... Discharge port, 8 ... Main discharge flow path, 10 ... Control valve, 11 ... Center bypass flow path, 12 ... Bypass opening, 16 ... Supply opening, 20 ... Hydraulic motor, 27 ... Pressure sensor, 30 ... Control unit, 48 ... Displacement detection unit, 50 ... Open / close valve.

Claims (2)

A hydraulic pump having a discharge port;
A discharge passage through which hydraulic oil is discharged from the discharge port of the hydraulic pump;
A control valve that is supplied with the hydraulic oil through the discharge passage and is displaceable from a neutral position;
An actuator that is actuated by being supplied with the hydraulic oil through the control valve;
A center bypass passage that extends from the control valve and into which the hydraulic oil that is not supplied to the actuator flows from the control valve;
A bypass opening through which the hydraulic oil flows from the control valve toward the center bypass flow path, and is open when the control valve is positioned at the neutral position, and from the neutral position of the control valve; An opening area decreases as the displacement amount increases, and a bypass opening that is maintained in an open state even when the displacement amount from the neutral position of the control valve is maximized,
A supply opening for allowing the hydraulic oil supplied to the actuator to flow into the control valve; the control valve is closed when the control valve is in the neutral position, and the control valve is displaced from the neutral position; A supply opening that is open by
An on-off valve provided on the downstream side of the control valve in the center bypass channel, and capable of switching opening and closing of the center bypass channel on the downstream side of the control valve;
A displacement detector for detecting the displacement of the control valve from the neutral position;
A hydraulic pressure detection unit that detects a hydraulic pressure of the hydraulic oil in the discharge flow path or a hydraulic pressure of the hydraulic oil supplied to the actuator from the control valve;
A control unit that controls the on-off valve based on detection results of the displacement detection unit and the hydraulic pressure detection unit, and when the displacement amount from the neutral position of the control valve is equal to or greater than a reference displacement amount, While the hydraulic pressure detected by the hydraulic pressure detection unit is greater than or equal to a reference value, the center bypass channel is kept open in the on-off valve, and the hydraulic pressure detected by the hydraulic pressure detection unit is smaller than the reference value A control unit that switches the center bypass passage to a closed state in the on-off valve based on the fact that
A hydraulic circuit unit for a construction machine, comprising: A discharge adjusting unit that adjusts a discharge amount of the hydraulic oil from the hydraulic pump;
A control flow path branched from the center bypass flow path on the downstream side of the open / close valve and extending toward the discharge adjusting section, wherein the hydraulic pressure generated by the hydraulic oil passing through the open / close valve is A control flow path for reducing the discharge amount of the hydraulic oil from the hydraulic pump by acting on the discharge adjustment unit;
The hydraulic circuit unit of the construction machine according to claim 1, further comprising: