JP2019183980A - Hydraulic circuit of construction machine - Google Patents

Abstract

An object of the present invention is to provide a hydraulic circuit of a construction machine in which workability during a boom operation is ensured. A hydraulic circuit includes a first pump, a center bypass line, a flow rate adjusting member, and a hydraulic oil that is supplied to both the boom cylinder and the center bypass line based on input of a boom lowering operation. Boom direction control valve that supplies the boom lowering operation is input, and when a turning operation is input, the pressure oil flows into the flow rate adjusting member, and the boom lowering operation is input, and A switching unit that shuts down or reduces the pressure oil that flows into the flow rate adjustment member when the turning operation is not input. [Selection diagram] Fig. 1

Description

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

  Patent Document 1 discloses a hydraulic circuit of a hydraulic excavator as an operation circuit of a construction machine. In this hydraulic circuit, an operation valve is disposed in a flow path from the hydraulic pump to an actuator such as a boom cylinder or an arm cylinder. In the hydraulic circuit, hydraulic pressure is supplied to the boom cylinder and the arm cylinder by inputting an operation for operating the operation valve. When the operation for operating the operation valve is not input, the pressure oil from the hydraulic pump flows out to the tank through the center bypass pipe line.

  When the boom is operated in the lowering direction, the operating force for operating the boom may be smaller than when the boom is operated in the raising direction. For this reason, when operating the boom in the lowering direction, pressure oil is supplied to the boom cylinder, pressure oil is supplied to the center bypass pipe, and part of the pressure oil flows out to the tank through the center bypass pipe. Let As a result, when the boom cylinder is operated in the lowering direction, the amount of oil supplied to the boom cylinder is smaller than when the boom cylinder is operated in the upward direction, and energy is efficiently consumed.

Japanese Patent No. 2599775

  During maintenance of the construction machine disclosed in Patent Document 1, the body may be jacked up by operating the boom. In this case, the vehicle body is raised by operating the boom in the lowering direction with the bucket grounded. In addition, a rolling operation may be performed in order to compress earth and sand discharged from the bucket or soft ground. In the rolling operation, by operating the boom in the downward direction, the back portion of the bucket is strongly pressed against the soft ground or the discharged earth and sand, thereby compressing the soft ground or the discharged earth and sand. When a part of the pressure oil from the hydraulic pump flows out to the tank when the boom is operated in the downward direction during jack-up or rolling operation, the pressure oil supplied to the boom cylinder is reduced. For this reason, the operating force for operating the boom in the downward direction is insufficient, which may affect the workability of jack-up and rolling work.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a hydraulic circuit that ensures workability during boom operation.

  In order to achieve the above object, an aspect of the present invention provides a traveling body, a revolving body that can swivel relative to the traveling body, a boom that is attached to the revolving body, and pressure oil that is supplied to the boom. Is a hydraulic circuit provided in a construction machine including a boom cylinder that operates the revolving body, and a first pump that discharges the pressure oil supplied to the boom cylinder; A center bypass pipe that flows out to the tank and a boom direction control valve that is displaced from a neutral position when an operation for operating the boom is input, and in the state that is positioned at the neutral position, By supplying the pressure oil and displacing from the neutral position based on the input of the boom lowering operation, the boom cylinder and the center viper are displaced. A boom direction control valve that supplies the pressure oil to both of the pipelines, an adjustment valve that is provided in the center bypass pipeline and that switches the state of the center bypass pipeline, and in the center bypass pipeline from the regulation valve A flow rate adjusting member that is provided on the downstream side and reduces the discharge amount of the pressure oil from the first pump when the pressure oil flows in, and a switching unit that switches a state of the adjustment valve, When a boom lowering operation is inputted and a turning operation for turning the turning body with respect to the traveling body is inputted, the pressure oil is caused to flow into the flow rate adjusting member, and the boom lowering operation is inputted, And a switching unit that blocks or reduces the pressure oil flowing into the flow rate adjusting member when the turning operation is not input.

  ADVANTAGE OF THE INVENTION According to this invention, the hydraulic circuit with which workability | operativity at the time of boom operation was ensured can be provided.

FIG. 1 is a schematic diagram illustrating a configuration of a hydraulic circuit according to the first embodiment. FIG. 2 is a diagram schematically illustrating a hydraulic excavator provided with the hydraulic circuit according to the first embodiment. FIG. 3 is a diagram illustrating a relationship between the operation state of the turning operation in the operation of the boom according to the first embodiment and the flow rate of the pressure oil supplied to the boom cylinder. FIG. 4 is a diagram schematically illustrating a state where the hydraulic excavator provided with the hydraulic circuit according to the first embodiment is jacked up. FIG. 5 is a schematic diagram illustrating a configuration of a hydraulic circuit according to the second embodiment. FIG. 6 is a diagram illustrating a relationship between the operation state of the turning operation in the operation of the boom according to the second embodiment and the flow rate of the pressure oil supplied to the boom cylinder.

(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 1 of the present embodiment. The hydraulic circuit 1 is used for construction machines such as a hydraulic excavator.

  FIG. 2 is a diagram showing a hydraulic excavator 60 as an example of a construction machine provided with the hydraulic circuit 1 of the present embodiment. As shown in FIG. 2, the excavator 60 includes a vehicle body 61 and a work device 64 attached to the vehicle body. The vehicle body 61 includes a lower traveling body (running body) 62 and an upper revolving body (revolving body) 63. The lower traveling body 62 includes an endless track (crawler) 65. The upper swing body 63 includes a cabin 66. The upper turning body 63 is provided on the lower traveling body 62 and can turn (rotate) with respect to the lower traveling body 62. The work device 64 is connected to the upper swing body 63.

  The work device 64 includes a boom 67, an arm 68, and a bucket 69. The boom 67 is attached to the upper swing body 63. A boom cylinder 5 for operating the boom 67 is attached to the upper swing body 63. The boom cylinder 5 is a hydraulic cylinder. The boom 67 is rotated (raised) with respect to the upper swing body 63 by driving the boom cylinder 5.

  An arm 68 and an arm cylinder 71 for operating the arm 68 are attached to the tip of the boom 67. The arm cylinder 71 is a hydraulic cylinder. The arm 68 rotates relative to the boom 67 when the arm cylinder 71 is driven.

  A bucket 69 that is a work attachment and a bucket cylinder 72 for operating the bucket 69 are attached to the tip of the arm 68. The bucket cylinder 72 is a hydraulic cylinder. The bucket 69 rotates with respect to the arm 68 when the bucket cylinder 72 is driven.

  The boom 67, the arm 68, the bucket 69, and each hydraulic cylinder (5, 71, 72) pivot with respect to the lower traveling body 62 together with the upper swing body 63. The excavator 60 is a hydraulic work vehicle that uses a bucket 69 to excavate earth and sand.

  As shown in FIG. 1, the hydraulic circuit 1 includes a boom actuation hydraulic circuit A and a turning hydraulic circuit B. The boom operation hydraulic circuit A is a hydraulic circuit that supplies pressure oil for operating the boom 67 to the boom cylinder 5. The turning hydraulic circuit B is a hydraulic circuit that supplies pressure oil for turning the upper turning body 63 with respect to the lower traveling body 62 to the turning motor 35. The hydraulic circuit 1 also includes a tank (oil tank) 10 in which pressure oil (hydraulic oil) used in the boom actuation hydraulic circuit A and the turning hydraulic circuit B is stored.

  The boom actuation hydraulic circuit A includes a first pump 2. The first pump 2 is a hydraulic pump. The first pump 2 is a variable capacity pump whose capacity (discharge amount) can be changed. By operating the first pump 2, hydraulic oil is supplied from the tank 10 to the first pump 2, and pressure oil is discharged from the first pump 2.

  The boom actuation hydraulic circuit A includes a boom direction control valve 3. The boom direction control valve 3 is connected to the first pump 2 via the first discharge flow path 11. The pressure oil discharged from the first pump 2 is supplied to the boom direction control valve 3 through the first discharge flow path 11. In the boom actuation hydraulic circuit A, a center bypass pipe line 19 extends from the boom direction control valve 3. The center bypass pipe line 19 extends to the tank 10.

  The boom actuation hydraulic circuit A includes a boom cylinder 5 as an actuator. The boom cylinder 5 is connected to the boom direction control valve 3 via a boom cylinder reduction side pipe line 16 and a boom cylinder extension side pipe line 17. The boom cylinder 5 is reduced when pressure oil is supplied from the boom direction control valve 3 via the boom cylinder reduction side pipe line 16. Further, the boom cylinder 5 extends when pressure oil is supplied from the boom direction control valve 3 via the boom cylinder extension side pipe line 17. In this embodiment, when the boom cylinder 5 extends, the boom 67 is operated in the raising direction. Further, when the boom cylinder 5 is reduced, the boom 67 is operated in the lowering direction.

  The boom direction control valve 3 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). In the state in which the boom direction control valve 3 is located at the neutral position, the first discharge flow path 11 and the center bypass pipe line 19 communicate with each other in the boom direction control valve 3. For this reason, pressure oil flows from the boom direction control valve 3 into the center bypass conduit 19. Further, in a state where the boom direction control valve 3 is located at the neutral position, the communication between the first discharge flow path 11 and the boom cylinder extension side pipe line 17 and the first discharge flow path 11 and the boom cylinder reduction side pipe line 16 are performed. Each communication with is blocked. Therefore, in a state where the boom direction control valve 3 is positioned at the neutral position, no pressure oil is supplied to the boom cylinder 5 and the boom cylinder 5 is not operated.

  When the boom direction control valve 3 is displaced from the neutral position in the first displacement direction, the first discharge passage 11 communicates with the boom cylinder extension side conduit 17 and the boom cylinder reduction side conduit 16 communicates with the tank 10. For this reason, the pressure oil is supplied from the boom direction control valve 3 to the boom cylinder 5 through the boom cylinder extension side pipe line 17 and is also collected from the boom cylinder 5 to the tank 10 through the boom cylinder reduction side pipe line 16. . At this time, the boom cylinder 5 is extended by supplying pressure oil to the boom cylinder 5 through the boom cylinder extension side pipe line 17. Then, when the boom cylinder 5 is extended, the boom 67 is operated in the boom raising direction.

  Further, as the amount of displacement in the first displacement direction from the neutral position of the boom direction control valve 3 increases, the opening area of the boom direction control valve 3 with respect to the center bypass conduit 19 decreases, and the boom direction control valve 3 The opening area with respect to the boom cylinder reduction side pipe line 16 and the boom cylinder extension side pipe line 17 becomes large. Therefore, as the amount of displacement from the neutral position of the boom direction control valve 3 increases, the flow rate of the pressure oil flowing from the boom direction control valve 3 into the center bypass pipe 19 decreases, and the boom direction control valve 3 The flow rate of the pressure oil supplied to 5 increases.

  Then, in the state where the displacement amount of the boom direction control valve 3 in the first displacement direction is maximized, the communication between the first discharge flow path 11 and the center bypass pipe line 19 is blocked in the boom direction control valve 3. . Thereby, the pressure oil does not flow into the center bypass conduit 19 from the boom direction control valve 3. Therefore, in a state where the displacement amount of the boom direction control valve 3 in the first displacement direction is maximized, the pressure oil does not flow out to the tank 10 through the center bypass conduit 19.

  When the boom direction control valve 3 is displaced from the neutral position in the second displacement direction, the first discharge flow path 11 communicates with the boom cylinder reduction side pipe line 16 in the boom direction control valve 3, and the boom cylinder extension side pipe line 17. Communicates with the tank 10. As a result, the pressure oil is supplied from the boom direction control valve 3 to the boom cylinder 5 through the boom cylinder reduction side pipe line 16, and the pressure oil is recovered from the boom cylinder 5 to the tank 10 through the boom cylinder extension side pipe line 17. . At this time, the boom cylinder 5 is reduced by supplying pressure oil to the boom cylinder 5 through the boom cylinder reduction side pipe line 16. Then, when the boom cylinder 5 is reduced, the boom 67 is operated in the lowering direction.

  Further, as the amount of displacement from the neutral position of the boom direction control valve 3 to the second displacement direction increases, the opening area of the boom direction control valve 3 with respect to the center bypass conduit 19 decreases, and the boom direction control valve 3 The opening area with respect to the boom cylinder reduction side pipe line 16 and the boom cylinder extension side pipe line 17 is increased. For this reason, as the amount of displacement from the neutral position of the boom direction control valve 3 increases, the flow rate of the pressure oil supplied from the boom direction control valve 3 to the boom cylinder 5 increases.

  In the state in which the displacement amount of the boom direction control valve 3 in the second displacement direction is maximized, the first discharge flow path 11 and the center bypass pipe line 19 communicate with each other via the restriction 25 in the boom direction control valve 3. . Therefore, the pressure oil flowing into the boom direction control valve 3 from the first pump 2 can be supplied to the boom cylinder 5 through the boom cylinder reduction side pipe line 16, and the pressure oil flowing into the boom direction control valve 3 can be supplied to the center bypass. It can flow into the pipeline 19.

  The boom actuation hydraulic circuit A includes a remote control valve (operation valve) 7 and an operation lever (first operation unit) 8 which is an operation input unit. The remote control valve 7 is connected to the operation lever 8. In the operation lever 8, an operation for operating the boom 67 in the boom raising direction or the boom lowering direction is input. The remote control valve 7 is in a neutral state when no operation input is performed on the operation lever 8. The remote control valve 7 is displaced from the neutral state based on the operation input from the operation lever 8.

  The boom actuation hydraulic circuit A includes a boom raising pilot path 13 and a boom lowering pilot path 14. Each of the boom raising pilot path 13 and the boom lowering pilot path 14 extends from the remote control valve 7 to the boom direction control valve 3. The remote control valve 7 is connected to a sub pump (not shown) that discharges pilot oil. By performing an operation input with the operation lever 8, the remote control valve 7 switches the communication state between each of the boom raising pilot path 13 and the boom lowering pilot path 14 and the sub pump.

  When no operation is input at the operation lever 8, the remote control valve 7 is in a neutral state. In the remote control valve 7, the communication between the sub pump and the boom raising pilot path 13 and the communication between the sub pump and the boom lowering pilot path 14 are blocked. Is done. For this reason, pilot oil is not supplied to the boom direction control valve 3, and the boom direction control valve 3 is maintained in the neutral position.

  When an operation for operating the boom 67 in the boom raising direction is input at the operation lever 8, the remote control valve 7 is displaced from the neutral position, and the sub pump and the boom raising pilot path 13 communicate with each other at the remote control valve 7. Thus, pilot oil from the sub pump is supplied to the boom direction control valve 3 through the boom raising pilot path 13. When the boom direction control valve 3 is displaced from the neutral position in the first displacement direction, the boom cylinder extension side pipe line 17 and the first discharge flow path 11 are communicated with each other. Thereby, pressure oil is supplied to the boom cylinder 5 from the boom direction control valve 3, and the boom cylinder 5 is extended. At this time, as the displacement amount of the operation lever 8 increases, the hydraulic pressure of the pilot oil supplied to the boom direction control valve 3 increases, and the displacement amount of the boom direction control valve 3 in the first displacement direction increases.

  When the boom direction control valve 3 moves to the maximum displacement position in the first displacement direction, the communication between the first discharge flow path 11 and the center bypass pipe line 19 is blocked. For this reason, pressure oil does not flow into the center bypass pipe 19 in the boom direction control valve 3, and pressure oil does not flow out from the center bypass pipe 19 to the tank 10. For this reason, the entire amount of pressure oil supplied from the first pump 2 to the boom direction control valve 3 is supplied to the boom cylinder 5.

  When an operation for operating the boom 67 in the boom lowering direction is input from the operation lever 8, the remote control valve 7 is displaced from the neutral position, and the sub pump and the boom lowering pilot path 14 communicate with each other in the remote control valve 7. Thus, pilot oil from the sub pump is supplied to the boom direction control valve 3 through the boom lowering pilot path 14. When the boom direction control valve 3 is displaced from the neutral position in the second displacement direction, the boom cylinder reduction side conduit 16 and the first discharge passage 11 are communicated with each other. Thereby, pressure oil is supplied to the boom cylinder 5 from the boom direction control valve 3, and the boom cylinder 5 contracts. At this time, as the displacement amount of the operation lever 8 increases, the hydraulic pressure of the pilot oil supplied to the boom direction control valve 3 increases, and the displacement amount of the boom direction control valve 3 in the second displacement direction increases.

  A center cut valve (adjustment valve) 9 is provided in the center bypass pipe line 19. The center cut valve 9 is provided on the downstream side of the boom direction control valve 3. The center cut valve 9 can be displaced between a reference position and a displacement position. The center cut valve 9 switches between the open and closed states of the center bypass pipe line 19 by being displaced between the reference position and the displacement position.

  In the state in which the center cut valve 9 is located at the reference position, the center bypass pipe 19 is in an open state (open state) in the center cut valve 9. When the center bypass pipe 19 is in an open state, the boom direction control valve 3 and the tank 10 are communicated with each other via the center bypass pipe 19. In the state where the center cut valve 9 is located at the displacement position, the center bypass conduit 19 is closed (closed state) in the center cut valve 9. When the center bypass line 19 is closed, the communication between the boom direction control valve 3 and the tank 10 is blocked.

  The boom actuation hydraulic circuit A is provided with a branch line 24 through which pilot oil can flow from the boom lowering pilot path 14. The center cut valve 9 includes a pilot signal receiving unit 20. The branch pipe 24 branches from the boom lowering pilot path 14 and is connected to the pilot signal receiver 20 of the center cut valve 9. The branch line 24 is a hydraulic line that guides the pilot oil flowing in from the boom lowering pilot path 14 to the pilot signal receiver 20 of the center cut valve 9.

  When pilot oil is not supplied from the branch pipeline 24 to the pilot signal receiving unit 20 of the center cut valve 9, the center cut valve 9 is located at the reference position. For this reason, in the center cut valve 9, the center bypass pipe 19 is opened, and the boom direction control valve 3 and the tank 10 are communicated with each other via the center bypass pipe 19. On the other hand, when the pilot oil is supplied from the branch pipe 24 to the pilot signal receiving unit 20 of the center cut valve 9, the center cut valve 9 is displaced to the displacement position. For this reason, in the center cut valve 9, the center bypass conduit 19 is closed, and the communication between the boom direction control valve 3 and the tank 10 is blocked.

  In the center bypass line 19, a negative control throttle (flow rate adjusting member) 21 is provided downstream of the center cut valve 9. The negative control throttle 21 is provided between the center cut valve 9 and the tank 10 in the center bypass conduit 19.

  In the boom actuation hydraulic circuit A, a discharge capacity control unit (discharge adjustment unit) 23 that adjusts the discharge amount of the pressure oil from the first pump 2 is provided. The discharge capacity control unit 23 changes the discharge amount of the pressure oil from the first pump 2 by changing the capacity of the first pump 2. In the present embodiment, the discharge capacity control unit 23 performs so-called negative control. In the negative control, the discharge capacity control unit 23 decreases the discharge amount from the first pump 2 when the control pressure supplied to the discharge capacity control unit 23 increases.

  In the boom actuation hydraulic circuit A, the negative control pressure path (control flow path) 22 branches off from the center bypass line 19. The negative control pressure path 22 diverges from the center bypass pipe 19 on the downstream side of the center cut valve 9 and on the upstream side of the negative control throttle 21, and extends to the discharge capacity control unit 23. When the pressure oil that has passed through the center cut valve 9 in the center bypass pipe 19 passes through the negative control throttle 21, hydraulic pressure is generated in the negative control throttle 21. The hydraulic pressure generated in the negative control throttle 21 changes according to the flow rate of the pressure oil passing through the negative control throttle 21. The hydraulic pressure generated in the negative control throttle 21 is guided to the discharge capacity control unit 23 via the negative control pressure path 22 and acts on the discharge capacity control unit 23. When the hydraulic pressure (control pressure) generated in the negative control throttle 21 is transmitted to the discharge capacity control unit 23, the discharge capacity control unit 23 decreases the discharge amount of the pressure oil from the first pump 2.

  The turning hydraulic circuit B includes a second pump (hydraulic pump) 32. The second pump 32 is a variable capacity pump whose capacity (discharge amount) is variable. By operating the second pump 32, hydraulic oil is supplied from the tank 10 to the second pump 32, and pressure oil is discharged from the second pump 32.

  The turning hydraulic circuit B includes a turning direction control valve 33. The turning direction control valve 33 is connected to the second pump 32 via the second discharge channel 41. The pressure oil discharged from the second pump 32 is supplied to the turning direction control valve 33 through the second discharge passage 41. The turning direction control valve 33 has a neutral position, and can be displaced from the neutral position in the first displacement direction (the direction of arrow Z1 in FIG. 1) and the second displacement direction (the direction of arrow Z2 in FIG. 1).

  In the turning hydraulic circuit B, a center bypass conduit 49 extends from the turning direction control valve 33. The center bypass conduit 49 extends to the tank 10.

  The turning hydraulic circuit B includes a turning motor 35 as an actuator. The turning motor 35 is connected to the turning direction control valve 33 through a right turning conduit 46 and a left turning conduit 47. The turning motor 35 turns the upper turning body 63 in the right turning direction when pressure oil is supplied from the turning direction control valve 33 via the right turning pipe 46. Further, the turning motor 35 turns the upper turning body 63 in the left turning direction by being supplied with the pressure oil from the turning direction control valve 33 through the left turning pipeline 47.

  The turning hydraulic circuit B includes a remote control valve 37 and an operation lever (second operation unit) 38 as an operation input unit. The remote control valve 37 is connected to the operation lever 38. In the operation lever 38, an operation for turning the upper turning body 63 in the right turning direction or the left turning direction is input. The remote control valve 37 is displaced based on an operation input from the operation lever 38.

  The turning hydraulic circuit B includes a right turning pilot path 44 and a left turning pilot path 43. Each of the right turning pilot path 44 and the left turning pilot path 43 extends from the remote control valve 37 to the turning direction control valve 33. Each of the right turn pilot path 44 and the left turn pilot path 43 is connected to a sub pump (not shown) via a remote control valve 37. By performing an operation input with the operation lever 38, the remote control valve 37 switches the communication state between each of the right turn pilot path 44 and the left turn pilot path 43 and the sub pump.

  In a state where no operation is input at the operation lever 38, pilot oil is not supplied to the turning direction control valve 33, and the turning direction control valve 33 is maintained at the neutral position. In a state where the turning direction control valve 33 is located at the neutral position, the second discharge passage 41 and the center bypass conduit 49 communicate with each other, and the second discharge passage 41 and the left turn conduit 47 communicate with each other. And each of the communication with the 2nd discharge flow path 41 and the pipe line 46 for right rotation is interrupted | blocked. Therefore, when no operation is input through the operation lever 38, the pressure oil supplied to the turning direction control valve 33 flows into the center bypass conduit 49 and is not supplied to the turning motor 35.

  When an operation for turning the upper turning body 63 is input through the operation lever 38, one of the right turning pilot path 44 and the left turning pilot path 43 is communicated with the sub pump in the remote control valve 37. Thus, pilot oil is supplied to the turning direction control valve 33 through one of the right turning pilot path 44 and the left turning pilot path 43. When the pilot oil is supplied, the turning direction control valve 33 moves from the neutral position to the first displacement direction (the direction of the arrow Z1 in FIG. 1) or the second displacement direction (the direction of the arrow Z2 in FIG. 1). Displace. When the turning direction control valve 33 is displaced in the first displacement direction or the second displacement direction, one of the right turning pipeline 46 and the left turning pipeline 47 communicates with the second discharge flow channel 41. The other of the right turning pipeline 46 and the left turning pipeline 47 communicates with the tank 10. Then, pressure oil is supplied from the turning direction control valve 33 to the turning motor 35 through one of the right turning pipe line 46 and the left turning pipe line 47 and from the turning motor 35 to the right turning pipe 46 and the left turning line. Pressure oil is recovered in the tank 10 through the other of the recirculation pipes 47. Thereby, the turning motor 35 is operated, and the upper turning body 63 turns with respect to the lower traveling body 62.

  In the center bypass pipe 49, a negative control throttle 50 is provided on the downstream side of the turning direction control valve 33. Pressure oil flows from the center bypass line 49 into the tank 10 through the negative control throttle 50. In addition, the turning hydraulic circuit B is provided with a discharge capacity control unit (discharge adjustment unit) 52 that adjusts the discharge amount of the pressure oil from the second pump 32. The discharge capacity control unit 52 changes the discharge amount of the pressure oil from the second pump 32 by changing the capacity of the second pump 32.

  In the turning hydraulic circuit B, a negative control pressure path (control flow path) 51 branches from the center bypass conduit 49 on the downstream side of the turning direction control valve 33 and on the upstream side of the negative control throttle 50. The negative control pressure path 51 extends to the discharge capacity control unit 52. When the hydraulic pressure (control pressure) generated in the negative control throttle 50 is transmitted to the discharge capacity control unit 52 via the negative control pressure path 51, the discharge amount of the pressure oil from the second pump 32 decreases.

  A switching valve 53 is provided in the branch pipeline 24. The switching valve 53 can be displaced between a reference position and a displacement position. The switching valve 53 switches the open / closed state of the branch pipe line 24 by being displaced between the reference position and the displacement position. The switching valve 53 is a switching unit in the present embodiment.

  In the state where the switching valve 53 is located at the reference position, the branch pipe line 24 is opened (opened) in the switching valve 53. When the branch pipe 24 is in an open state, the boom lowering pilot path 14 and the center cut valve 9 are communicated with each other via the branch pipe 24.

  On the other hand, in the state where the switching valve 53 is located at the displacement position, the branch pipe 24 is closed (closed state) in the switching valve 53. When the branch pipe 24 is in the closed state, the communication between the boom lowering pilot path 14 and the center cut valve 9 is blocked.

  A branch pipe (pilot channel) 58 extends between the switching valve 53 and the remote control valve 37. The switching valve 53 includes a pilot signal receiving unit 54. The branch pipe 58 is connected to the pilot signal receiver 54. A hydraulic signal of pilot oil from the right turning pilot path 44 or the left turning pilot path 43 is transmitted to the switching valve 53 via the branch pipe 58.

  Each of the right turn pilot path 44 and the left turn pilot path 43 is connected to the branch pipe 58 via the shuttle valve 59. In the shuttle valve 59, pressure oil can flow into the branch pipeline 58 from each of the right turn pilot route 44 and the left turn pilot route 43. Further, in the shuttle valve 59, inflow of pressure oil from the right turn pilot path 44 to the left turn pilot path 43 and inflow of pressure oil from the left turn pilot path 43 to the right turn pilot path 44 are prevented. The A hydraulic signal of pilot oil from the right turning pilot path 44 or the left turning pilot path 43 is transmitted to the switching valve 53 via the branch pipe 58 by the shuttle valve 59.

  When the hydraulic signal of the pilot oil is not transmitted from the branch pipeline 58 to the switching valve 53, the switching valve 53 is located at the reference position. In this case, the branch line 24 is opened in the switching valve 53. On the other hand, when the hydraulic signal of the pilot oil is transmitted from the branch pipe 58 to the switching valve 53, the switching valve 53 is located at the displacement position. In this case, the branch pipe 24 is closed in the switching valve 53.

  In the state where the turning operation is not input at the operation lever 38, the remote control valve 37 is located at the neutral position. At this time, since the pilot oil is not supplied to the switching valve 53, the switching valve 53 is located at the reference position. For this reason, in the switching valve 53, the branch conduit 24 is opened.

  When a turning operation is input through the operation lever 38, the remote control valve 37 is displaced from the neutral position, and pilot oil is supplied to the turning direction control valve 33 through the right turning pilot path 44 or the left turning pilot path 43. . The turning direction control valve 33 is displaced from the neutral position when pilot oil is supplied from the right turning pilot path 44 or the left turning pilot path 43. The second discharge passage 41 and the turning motor 35 are communicated with each other, and pressure oil supplied from the second pump 32 to the turning direction control valve 33 is supplied to the turning motor 35. As a result, the turning motor 35 operates and the upper turning body 63 turns with respect to the lower traveling body 62.

  At this time, when the pilot oil flows in the right turn pilot path 44 or the left turn pilot path 43, the pilot oil is supplied to the switching valve 53 via the shuttle valve 59 and the branch pipe 58. The switching valve 53 is displaced to the displacement position when the pilot oil is supplied. Thereby, in the switching valve 53, the branch pipe line 24 is closed.

  Next, the operation and effect of the hydraulic circuit 1 of the present embodiment will be described.

  The hydraulic circuit 1 of the present embodiment is provided in a construction machine such as a hydraulic excavator. In a state where the operation of the boom 67 is not performed on the operation lever 8, the remote control valve 7 and the boom direction control valve 3 are located at the neutral position. In the state where the boom direction control valve 3 is located at the neutral position, the first discharge flow path 11 and the center bypass pipe line 19 communicate with each other, and the communication between the first discharge flow path 11 and the boom cylinder 5 is blocked. For this reason, the pressure oil supplied from the first pump 2 to the boom direction control valve 3 flows into the center bypass pipe 19 without being supplied to the boom cylinder 5. Each of the center cut valve 9 and the switching valve 53 is located at the reference position. For this reason, each of the center bypass conduit 19 and the branch conduit 24 is in an open state. For this reason, the pressure oil flows out from the boom direction control valve 3 to the tank 10 through the center bypass conduit 19.

(Boom raising operation)
FIG. 3 is a diagram showing the relationship between the operation of the boom 67 and the flow rate of the pressure oil supplied to the boom cylinder 5. When the raising operation of the boom 67 is performed alone, the branch conduit 24 is in the open state in the switching valve 53. When a turning operation is input with the operation lever 38 along with the raising operation of the boom 67, the branch conduit 24 is closed in the switching valve 53.

  Further, when the raising operation of the boom 67 is input through the operation lever 8, the boom direction control valve 3 moves in the first displacement direction. When the boom direction control valve 3 moves to the maximum displacement position in the first displacement direction, the communication between the first discharge flow path 11 and the center bypass pipe 19 is cut off and supplied from the first pump 2 to the boom direction control valve 3. The entire amount of the pressurized oil is supplied to the boom cylinder 5.

  Thus, in the raising operation of the boom 67, the communication between the first discharge flow path 11 and the center bypass pipe line 19 is interrupted. Therefore, the negative control throttle 21 regardless of the presence or absence of the turning operation, the state of the switching valve 53, and the like. Pressure oil does not flow into. For this reason, the hydraulic pressure generated in the negative control throttle 21 is not transmitted to the discharge capacity control unit 23, and the discharge amount of the pressure oil from the first pump 2 is not reduced. For this reason, the state where the flow volume of the pressure oil supplied to the boom cylinder 5 is large is maintained.

(Simultaneous operation of boom lowering operation and turning operation)
When the lowering operation of the boom 67 is input by the operation lever 8, the remote control valve 7 is displaced from the neutral state, and the pilot oil is supplied to the boom direction control valve 3 through the boom lowering pilot path 14. The boom direction control valve 3 is displaced from the neutral position in the second displacement direction when the pilot oil is supplied from the boom lowering pilot path 14. When the boom direction control valve 3 moves from the neutral position in the second displacement direction, the space between the first discharge passage 11 and the center bypass conduit 19 is throttled, and the boom cylinder reduction side conduit 16 and the first discharge flow are The road 11 is communicated. Thereby, pressure oil is supplied to the boom cylinder 5 from the boom direction control valve 3, and the boom cylinder 5 contracts. Then, when the boom cylinder 5 contracts, the boom 67 is operated in the boom lowering direction. Even in the state where the displacement amount of the boom direction control valve 3 in the second displacement direction is maximized, the first discharge flow path 11 and the center bypass pipe line 19 are not blocked and are brought into a communication state by the throttle 25. Become. At this time, a part of the pressure oil supplied from the first pump 2 to the boom direction control valve 3 flows into the center bypass pipe 19 and the remainder that does not flow into the center bypass pipe 19 is supplied to the boom cylinder 5. .

  When the lowering operation of the boom 67 and the turning operation are performed simultaneously, the turning operation is input by the operation lever 38, whereby the remote control valve 37 is displaced from the neutral position, and the upper turning body 63 is moved with respect to the lower traveling body 62. Turn. At this time, when the pilot oil flows in the right turn pilot path 44 or the left turn pilot path 43, the pilot oil is supplied to the switching valve 53 through the shuttle valve 59 and the branch pipe 58. The switching valve 53 is displaced to the displacement position when the pilot oil is supplied, and thereby the branch pipe line 24 is closed in the switching valve 53.

  Thus, in the simultaneous operation of the lowering operation of the boom 67 and the turning operation, the pilot oil flows through the boom lowering pilot path 14. On the other hand, since the branch pipe 24 is in a closed state, pilot oil is not supplied to the center cut valve 9. Since the pilot oil is not supplied, the center cut valve 9 is not displaced from the reference position. For this reason, in the center cut valve 9, the center bypass pipe line 19 is maintained in an open state. Therefore, the pressure oil flowing into the center bypass pipe 19 from the boom direction control valve 3 flows out to the tank 10 through the center cut valve 9 and the negative control throttle 21.

  At this time, when the pressure oil flows into the negative control throttle 21, hydraulic pressure is generated in the negative control throttle 21. The hydraulic pressure generated in the negative control throttle 21 is transmitted to the discharge capacity control unit 23 via the negative control pressure path 22. For this reason, the discharge capacity control unit 23 decreases the discharge amount of the pressure oil from the first pump 2. When the discharge amount of the pressure oil from the first pump 2 decreases, the flow rate of the pressure oil supplied to the boom cylinder 5 via the boom direction control valve 3 decreases.

(Single boom lowering operation)
When the lowering operation of the boom 67 is performed independently, the turning operation with the operation lever 38 is not performed. In this case, the remote control valve 37 and the turning direction control valve 33 are maintained in the neutral position. Since pilot oil does not flow in the right turn pilot path 44 and the left turn pilot path 43, the switching valve 53 is not displaced from the reference position. For this reason, the branch pipe 24 is maintained in the open state in the switching valve 53.

  As described above, pilot oil flows through the boom lowering pilot path 14 in the operation of lowering the single boom 67. Since the branch line 24 is in the open state, the pilot oil flowing in the boom lowering pilot path 14 is supplied to the center cut valve 9 via the branch line 24. The center cut valve 9 is displaced to the displacement position when the pilot oil is supplied. Thereby, in the center cut valve 9, the center bypass conduit 19 is closed. Therefore, the pressure oil that has flowed from the boom direction control valve 3 into the center bypass pipe 19 is blocked by the center cut valve 9. For this reason, the pressure oil that has flowed into the center bypass pipe 19 from the boom direction control valve 3 does not flow into the negative control throttle 21 and does not flow out into the tank 10. For this reason, the boom cylinder 5 is supplied with the entire amount of the hydraulic oil flowing into the boom direction control valve 3. Further, since the pressure oil does not flow into the negative control throttle 21, the hydraulic pressure generated in the negative control throttle 21 is not transmitted to the discharge capacity control unit 23, and the discharge amount of the pressure oil from the first pump 2 is not reduced. For this reason, the state where the flow volume of the pressure oil supplied to the boom cylinder 5 is large is maintained.

(Function and effect)
As described above, in this embodiment, when the boom lowering operation and the turning operation are performed at the same time in the operation of operating the boom 67, a part of the pressure oil supplied to the boom direction control valve 3 is centered. The oil flows out into the tank 10 through the bypass line 19 and the negative control throttle 21, and the discharge amount of the pressure oil from the first pump 2 decreases. For this reason, when the boom lowering operation and the turning operation are performed at the same time, the flow rate of the pressure oil supplied to the boom cylinder 5 is smaller than in other cases.

  Here, when the boom 67 is activated, an operation for turning the upper swing body 63 is usually performed simultaneously with an operation for operating the boom 67. That is, when the boom 67 is operated, the operation of the boom 67 and the turning operation of the upper turning body 63 are usually performed simultaneously.

  Further, in the lowering operation of the boom 67, the operating force required to operate the boom 67 is smaller than in the raising operation of the boom 67. In this embodiment, when the boom 67 lowering operation and the turning operation are performed simultaneously, the flow rate of the pressure oil supplied to the boom cylinder 5 is reduced. For this reason, an appropriate amount of pressure oil can be supplied to the boom cylinder 5, and energy consumption can be reduced by minimizing unnecessary energy loss. Thereby, energy saving is implement | achieved and a fuel consumption reduces.

  Further, when the lowering operation and the turning operation of the boom 67 are performed at the same time, a part of the pressure oil supplied to the boom direction control valve 3 flows out to the tank 10 through the center bypass conduit 19. For this reason, even when the operation of operating the boom 67 in the lowering direction is suddenly performed, the sudden rise in pressure is alleviated and the rapid operation of the boom 67 is prevented. Thereby, the vibration of the excavator 60 due to the sudden operation of the boom 67 is suppressed, and the operability is improved.

  On the other hand, as shown in FIG. 4, when performing maintenance or repair of the excavator 60, the vehicle body 61 may be jacked up using the boom 67. In this case, the boom 67 is lowered by the operation lever 8 while the bucket 69 is grounded. During this operation, the operation lever 38 is not operated to turn the upper swing body 63. Therefore, the lowering operation of the boom 67 is performed independently. When the operation of lowering the boom 67 is performed independently while the bucket 69 is grounded, the vehicle body 61 rotates relative to the work device 64 including the boom 67 while the grounded portion of the bucket 69 is fixed. At the same time, the vehicle body 61 rotates around the ground contact portion of the endless track 65 far from the connecting portion with the boom 67, and the endless track 65 close to the connecting portion with the boom 67 moves upward from the ground. This facilitates maintenance such as repair.

  Moreover, in the rolling work using the hydraulic excavator 60, the soft ground or the discharged earth and sand may be pressed and hardened. In this case, the boom 67 is lowered by the operation lever 8 in a state where the back surface of the bucket 69 is in contact with the object to be pressed and hardened. During this operation, the operation lever 38 is not operated to turn the upper swing body 63. Therefore, the lowering operation of the boom 67 is performed independently. By performing the lowering operation of the boom 67 alone with the back surface of the bucket 69 in contact with the work target, the soft ground and the discharged earth and sand are compacted.

  In the present embodiment, when the lowering operation of the boom 67 is performed alone and the lowering operation of the boom 67 is performed to the maximum position with the operation lever 8, all of the hydraulic pressure supplied to the boom direction control valve 3 is the boom. It is supplied to the cylinder 5. Further, the flow rate of the pressure oil supplied to the boom cylinder 5 does not decrease. For this reason, the operating pressure in the boom cylinder 5 can be ensured, and sufficient jack-up work and rolling work can be performed. This prevents a shortage of the operating force for operating the boom 67 due to a decrease in the flow rate of the pressure oil supplied to the boom cylinder 5, and the shortage of the operating force affects jack-up work and rolling work. It is prevented.

  Moreover, even when performing simultaneous operation with the boom 67 and the bucket 69 or the like in jack-up work or rolling work by supplying all of the hydraulic pressure supplied to the boom direction control valve 3 to the boom cylinder 5, A sufficient operating pressure can be ensured in the corresponding hydraulic cylinder, and workability is ensured.

  Further, in the present embodiment, in the operation of lowering the single boom 67, the center cut valve 9 switches the open / close state of the center bypass conduit 19 to prevent the pressure oil from flowing out to the tank 10. For this reason, the flow of pressure oil from the boom direction control valve 3 to the tank 10 can be prevented regardless of the size (setting) of the throttle 25 provided in the boom direction control valve 3. Therefore, the throttle 25 provided in the boom direction control valve 3 can be enlarged. By increasing the throttle 25, the flow of the pressure oil flowing out from the boom direction control valve 3 to the tank 10 increases when the boom 67 lowering operation and the turning operation are performed simultaneously, and the pressure supplied to the boom cylinder 5 is increased. The oil can be made smaller. Thereby, the fall of the operating force of the boom cylinder 5 in the operation of lowering the boom 67 alone can be prevented, and the energy saving effect in the simultaneous operation of the operation of lowering the boom 67 and the turning operation can be increased.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIG. In the present embodiment, the configuration of the first embodiment is modified as follows. In addition, about the part same as 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  FIG. 5 is a diagram showing the hydraulic circuit 1 of the present embodiment. In the present embodiment, the hydraulic circuit 1 includes a control unit (control device) 57 instead of the switching valve 53. The control unit 57 switches the position of the center cut valve 9 by controlling the supply of electric power to the center cut valve 9. And the control part 57 switches the open / close state of the center bypass pipe line 19 by switching the position of the center cut valve 9. The control unit 57 is a switching unit in the present embodiment.

  The control unit 57 includes a power control unit 57a, a displacement detection unit 57b, and a displacement detection unit 57c. Each of the power control unit 57a, the displacement detection unit 57b, and the displacement detection unit 57c is formed of, for example, an electronic circuit that constitutes a processor in the control unit 57. The power control unit 57 a controls the supply of power to the center cut valve 9. The displacement detector 57b detects a displacement from the neutral position of the boom direction control valve 3 in the second displacement direction, and determines whether or not the boom direction control valve 3 has been displaced in the second displacement direction. The displacement detection unit 57b transmits the determination result regarding the displacement of the boom direction control valve 3 in the second displacement direction to the power control unit 57a. The displacement detector 57c detects the displacement from the neutral position of the turning direction control valve 33, and determines whether or not the turning direction control valve 33 has been displaced from the neutral position. The displacement detection unit 57c transmits the determination result regarding the displacement of the turning direction control valve 33 to the power control unit 57a.

  The hydraulic circuit 1 includes a pressure sensor 55 and a pressure switch 56. The pressure sensor 55 is a hydraulic pressure detection unit that detects the hydraulic pressure of the pilot oil in the boom lowering pilot path 14. The pressure sensor 55 transmits a detection signal indicating the detected oil pressure to the displacement detector 57b. The displacement detection unit 57b acquires the hydraulic pressure of the boom lowering pilot path 14 when the detection result is transmitted from the pressure sensor 55. The displacement detector 57b calculates the amount of displacement from the neutral position of the boom direction control valve 3 in the second displacement direction based on the acquired hydraulic pressure. The displacement amount from the neutral position of the boom direction control valve 3 in the second displacement direction corresponds to, for example, the operation amount of the boom lowering operation by the operation lever 8. The displacement detector 57b determines whether or not the boom direction control valve 3 has been displaced from the neutral position to the second displacement direction based on the amount of displacement from the neutral position of the boom direction control valve 3 to the second displacement direction. To do. For example, the displacement detection unit 57b moves the boom direction control valve 3 from the neutral position to the second displacement direction based on the fact that the displacement amount from the neutral position of the boom direction control valve 3 to the second displacement direction is larger than zero. Based on the fact that the amount of displacement from the neutral position of the boom direction control valve 3 to the second displacement direction is zero, the boom direction control valve 3 is displaced from the neutral position to the second displacement direction. Judge that it is not. When it is determined that the boom direction control valve 3 is displaced in the second displacement direction, the displacement detection unit 57b outputs an electric signal indicating the amount of displacement of the boom direction control valve 3 in the second displacement direction to the power control unit 57a. To communicate.

  The pressure switch 56 is a hydraulic pressure detection unit that detects the hydraulic pressure of pilot oil in the right-turn pilot path 44 and the left-turn pilot path 43. The pressure switch 56 transmits a detection signal indicating the detected oil pressure to the displacement detection unit 57c. The displacement detection unit 57 c acquires the hydraulic pressure of the right turn pilot path 44 and the left turn pilot path 43 by transmitting the detection result from the pressure switch 56. The displacement detector 57c determines whether or not the turning direction control valve 33 has been displaced from the neutral position based on the acquired hydraulic pressure. At this time, the displacement detector 57c determines that the turning direction control valve 33 has been displaced from the neutral position based on the acquired hydraulic pressure being greater than a predetermined value. The predetermined value is, for example, the hydraulic pressure of the right turning pilot path 44 and the left turning pilot path 43 in a state where the turning direction control valve 33 is located at the neutral position. Further, the predetermined value may be a value larger than the hydraulic pressure of the right turning pilot path 44 and the left turning pilot path 43 in a state where the turning direction control valve 33 is located at the neutral position. When the displacement detection unit 57c determines that the turning direction control valve 33 has been displaced, the displacement detection unit 57c transmits an electrical signal to the power control unit 57a.

  A shuttle valve 59 is provided in the vicinity of the pressure switch 56. The shuttle valve 59 guides the hydraulic pressure in the right turn pilot path 44 or the left turn pilot path 43 to the pressure switch 56 and causes the hydraulic pressure to act on the pressure switch 56. As a result, the hydraulic pressure of the right turn pilot path 44 or the left turn pilot path 43 can be detected by the pressure switch 56.

  In the present embodiment, an electromagnetic valve is used as the center cut valve 9. The center cut valve 9 is electrically connected to the control unit 57. The power control unit 57 a transmits an electric signal by supplying power to the center cut valve 9.

  In the state where electric power is not supplied from the control unit 57 to the center cut valve 9, no electrical signal is transmitted to the center cut valve 9. In a state where an electric signal is not transmitted to the center cut valve 9, the center bypass pipe 19 is opened in the center cut valve 9. By opening the center bypass pipe line 19 in the center cut valve 9, pressure oil can flow into the tank 10 through the center cut valve 9.

  In the state where electric power is supplied from the control unit 57 to the center cut valve 9, an electrical signal is transmitted to the center cut valve 9. In a state where an electrical signal is transmitted to the center cut valve 9, the center bypass pipe 19 is closed in the center cut valve 9. When the center bypass pipe 19 is closed in the center cut valve 9, the pressure oil does not flow downstream from the center cut valve 9.

  The power control unit 57a determines whether or not the displacement amount from the neutral position of the boom direction control valve 3 to the second displacement direction and the electrical signal indicating that the turning direction control valve 33 is displaced from the neutral position are detected. Based on this, the supply of electric power to the center cut valve 9 is controlled. That is, the power control unit 57a is based on whether the boom direction control valve 3 is displaced from the neutral position in the second displacement direction and whether the turning direction control valve 33 is displaced from the neutral position. The transmission of an electric signal to the center cut valve 9 is controlled. The power control unit 57a controls the transmission of the electrical signal to the center cut valve 9 based on the calculation result of the displacement amount of the boom direction control valve 3 in the displacement detection unit 57b and the determination result in the displacement detection unit 57c. It is a control part.

  FIG. 6 is an example of a table used in the process in which the power control unit 57 a controls the supply of power to the center cut valve 9. In the example shown in FIG. 6, when the electrical signal from the displacement detection unit 57 b is not detected and the electrical signal from the displacement detection unit 57 c is not detected, the power control unit 57 a sends the electrical signal to the center cut valve 9. Do not output. That is, it is determined that the boom direction control valve 3 is not displaced from the neutral position in the second displacement direction in the displacement detection unit 57b, and the turning direction control valve 33 is not displaced from the neutral position in the displacement detection unit 57c. If it is determined, the power control unit 57a does not output an electrical signal to the center cut valve 9. In this case, an electrical signal is not transmitted to the center cut valve 9, and the center cut valve 9 is not displaced from the reference position. For this reason, in the center cut valve 9, the center bypass conduit 19 is opened.

  When the electric signal from the displacement detection unit 57b is detected and the electric signal from the displacement detection unit 57c is not detected, the power control unit 57a displaces the boom direction control valve 3 in the second displacement direction. The output of the electrical signal to the center cut valve 9 is controlled based on the above. That is, it is determined in the displacement detector 57b that the boom direction control valve 3 has been displaced from the neutral position in the second displacement direction, and the displacement detector 57c has determined that the turning direction control valve 33 has not been displaced from the neutral position. In the case where it is done, the power control unit 57a outputs an electric signal to the center cut valve 9. When the electric signal is transmitted to the center cut valve 9, the center cut valve 9 is displaced from the reference position to the displacement position in accordance with the amount of displacement of the boom direction control valve 3 in the second displacement direction. As a result, the center bypass pipe 19 is throttled or closed in the center cut valve 9.

  In addition, when the electrical signal from the displacement detection unit 57b is not detected and the electrical signal from the displacement detection unit 57c is detected, the power control unit 57a does not output the electrical signal to the center cut valve 9. That is, it is determined in the displacement detector 57b that the boom direction control valve 3 is not displaced from the neutral position in the second displacement direction, and the displacement detector 57c determines that the turning direction control valve 33 is displaced from the neutral position. When it is done, the power control unit 57a does not output an electrical signal to the center cut valve 9. In this case, no electrical signal is transmitted to the center cut valve 9, and the center cut valve 9 is not displaced from the reference position. For this reason, in the center cut valve 9, the center bypass conduit 19 is opened.

  In addition, when an electrical signal from the displacement detector 57b is detected and an electrical signal from the displacement detector 57c is detected, the power controller 57a does not output an electrical signal to the center cut valve 9. That is, it is determined in the displacement detector 57b that the boom direction control valve 3 has been displaced from the neutral position in the second displacement direction, and the displacement detector 57c has determined that the turning direction control valve 33 has been displaced from the neutral position. In this case, the power control unit 57a does not output an electric signal to the center cut valve 9. In this case, no electrical signal is transmitted to the center cut valve 9, and the center cut valve 9 is not displaced from the reference position. For this reason, in the center cut valve 9, the center bypass conduit 19 is opened.

  Next, the operation and action of the hydraulic circuit 1 of the present embodiment will be described.

  In the present embodiment, the power control unit 57a of the control unit 57 determines the power to the center cut valve 9 based on the determination result in the displacement detection unit 57b, the determination result in the displacement detection unit 57c, and the table in FIG. To control the supply. Thereby, the position of the center cut valve 9 is switched. By switching the position of the center cut valve 9, the open / close state of the center bypass pipe 19 is switched in the center cut valve 9. That is, the power control unit 57a switches the open / close state of the center bypass conduit 19 based on the detection result of the displacement detection unit 57b and the detection result of the displacement detection unit 57c.

(Boom raising operation)
Also in this embodiment, when the raising operation of the boom 67 is performed, the boom direction control valve 3 is moved in the first displacement direction by inputting the raising operation of the boom 67 through the operation lever 8. When the boom direction control valve 3 moves to the maximum displacement position in the first displacement direction, the communication between the first discharge flow path 11 and the center bypass pipe 19 is cut off and supplied from the first pump 2 to the boom direction control valve 3. The entire amount of the pressurized oil is supplied to the boom cylinder 5.

  In the raising operation of the boom 67, since the communication between the first discharge flow path 11 and the center bypass pipe 19 is blocked, the hydraulic pressure supplied to the boom direction control valve 3 does not flow into the center cut valve 9. Accordingly, the pressure oil does not flow into the negative control throttle 21 regardless of the presence or absence of the turning operation and the state of the center cut valve 9. For this reason, the hydraulic pressure generated in the negative control throttle 21 is not transmitted to the discharge capacity control unit 23, and the discharge amount of the pressure oil from the first pump 2 is not reduced. For this reason, the state where the flow volume of the pressure oil supplied to the boom cylinder 5 is large is maintained.

(Simultaneous operation of boom lowering operation and turning operation)
When a lowering operation of the boom 67 is input by the operation lever 8, pressure oil is supplied from the boom direction control valve 3 to the boom cylinder 5 and the boom cylinder 5 contracts in the same manner as in the first embodiment. Then, when the boom cylinder 5 contracts, the boom 67 is operated in the boom lowering direction. At this time, a part of the pressure oil supplied from the first pump 2 to the boom direction control valve 3 flows into the center bypass pipe 19 and the remainder that does not flow into the center bypass pipe 19 is supplied to the boom cylinder 5. .

  At this time, the displacement detection unit 57b determines that the boom direction control valve 3 has been displaced from the neutral state in the second displacement direction. Then, an electrical signal indicating the amount of displacement in the second displacement direction from the neutral state of the boom direction control valve 3 is transmitted from the displacement detector 57b to the power controller 57a.

  When the lowering operation of the boom 67 and the turning operation are performed at the same time, the turning operation is input by the operation lever 38, whereby the remote control valve 37 is displaced from the neutral position, and the upper turning body 63 is moved to the lower traveling body 62. Turn against. At this time, the displacement detector 57c determines that the turning direction control valve 33 has been displaced from the neutral state. Then, an electrical signal indicating that the turning direction control valve 33 has been displaced from the neutral state is transmitted from the displacement detector 57c to the power controller 57a.

  Based on the detection of the electrical signal from the displacement detector 57b, the detection of the electrical signal from the displacement detector 57c, and the center cut valve 9 based on the table in FIG. By controlling the supply of electric power, the center bypass valve 19 is opened in the center cut valve 9.

  As described above, in the simultaneous operation of the lowering operation and the turning operation of the boom 67, a part of the pressure oil supplied from the first pump 2 to the boom direction control valve 3 flows into the center bypass conduit 19 and the center cut. In the valve 9, the center bypass pipe line 19 is opened. Therefore, the pressure oil flowing into the center bypass pipe 19 from the boom direction control valve 3 flows out to the tank 10 through the center cut valve 9 and the negative control throttle 21.

  At this time, when the pressure oil flows into the negative control throttle 21, hydraulic pressure is generated in the negative control throttle 21. The hydraulic pressure generated in the negative control throttle 21 is transmitted to the discharge capacity control unit 23 via the negative control pressure path 22. For this reason, the discharge capacity control unit 23 decreases the discharge amount of the pressure oil from the first pump 2. When the discharge amount of the pressure oil from the first pump 2 decreases, the flow rate of the pressure oil supplied to the boom cylinder 5 via the boom direction control valve 3 decreases.

(Single boom lowering operation)
When the lowering operation of the boom 67 is performed independently, the turning operation with the operation lever 38 is not performed. In this case, the displacement detection unit 57c determines that the turning direction control valve 33 is not displaced from the neutral state. For this reason, an electrical signal is not transmitted from the displacement detector 57c to the power controller 57a.

  The power control unit 57a detects that the electrical signal from the displacement detection unit 57b is detected, the electrical signal from the displacement detection unit 57c is not detected, and the power to the center cut valve 9 based on the table of FIG. The center bypass pipe 19 is throttled or closed in the center cut valve 9 by controlling the supply of.

  Therefore, when the lowering operation of the boom 67 is performed alone, a part of the pressure oil supplied from the first pump 2 to the boom direction control valve 3 flows into the center bypass pipe 19 and the center cut valve In FIG. 9, the center bypass line 19 is throttled or closed. Therefore, the pressure oil flowing into the center bypass pipe 19 from the boom direction control valve 3 is reduced or blocked at the center cut valve 9. For this reason, the inflow to the negative control throttle 21 and the tank 10 of the pressure oil which flowed into the center bypass pipe line 19 from the boom direction control valve 3 is reduced or blocked. For this reason, the quantity supplied to boom cylinder 5 among the pressure oil which flowed into boom direction control valve 3 is maintained. Further, since the pressure oil flowing into the negative control throttle 21 is reduced or cut off, the hydraulic pressure transmitted from the negative control throttle 21 to the discharge capacity control unit 23 is reduced, and the discharge amount of the pressure oil from the first pump 2 is reduced. The amount is suppressed. For this reason, the state where the flow volume of the pressure oil supplied to the boom cylinder 5 is large is maintained.

(Function and effect)
As described above, also in the present embodiment, when the boom lowering operation and the turning operation are simultaneously performed in the operation of operating the boom 67, a part of the pressure oil supplied to the boom direction control valve 3 is It flows out into the tank 10 through the center bypass pipe line 19 and the negative control throttle 21, and the discharge amount of the pressure oil from the first pump 2 decreases. For this reason, when the boom lowering operation and the turning operation are performed at the same time, the flow rate of the pressure oil supplied to the boom cylinder 5 is smaller than in other cases. Therefore, also in this embodiment, the same effect as the first embodiment can be obtained.

(Modification of the second embodiment)
In a modification of the present embodiment, in the state where an electrical signal is transmitted to the center cut valve 9, the center bypass pipe 19 is opened in the center cut valve 9, and no electrical signal is transmitted to the center cut valve 9. Then, the center bypass conduit 19 is closed in the center cut valve 9. In this case, the power control unit 57a is connected to the center cut valve 9 only when the electrical signal from the pressure sensor 55 is detected in the displacement detection unit 57b and the electrical signal from the pressure switch 56 is not detected in the displacement detection unit 57c. In other cases, the electric power control unit 57 a outputs an electric signal to the center cut valve 9. Thereby, also in this embodiment, when boom lowering operation and turning operation are performed simultaneously, the flow volume of the pressure oil supplied to boom cylinder 5 is small compared with the case where boom lowering operation is performed independently. Become.

  In another modification of the present embodiment, each of the operation lever 8 and the boom direction control valve 3 is electrically connected to the control unit 57. In this case, an electromagnetic valve is used as the boom direction control valve 3. An electric signal indicating that an operation input has been performed with the operation lever 8 is input to the control unit 57. The control unit 57 controls the boom direction control valve 3 based on the operation signal input from the operation lever 8. The displacement detector 57b determines whether the boom direction control valve 3 has been displaced in the second displacement direction based on the operation signal from the operation lever 8.

(Other embodiments)
In another embodiment, the center bypass pipe 19 is throttled by the throttle provided in the center cut valve 9 in a state where the center cut valve 9 is located at the displacement position. In this embodiment, when the lowering operation of the boom 67 is performed alone, the pressure oil flowing into the center bypass pipe 19 from the boom direction control valve 3 is throttled by the center cut valve 9. For this reason, when the lowering operation of the boom 67 is performed independently, the flow rate of the pressure oil flowing out to the tank 10 is compared with the case where the lowering operation of the boom 67 is performed simultaneously with the turning operation of the upper swing body 63. Becomes smaller. For this reason, when the lowering operation of the boom 67 is performed independently, the hydraulic oil supplied to the boom cylinder 5 is compared with the case where the lowering operation of the boom 67 is performed simultaneously with the turning operation of the upper swing body 63. The flow rate increases. Thereby, sufficient jack-up work and rolling work can be performed.

  In addition, this invention is not limited to the said embodiment, In the implementation stage, it can change variously in the range which does not deviate from the summary. Further, the embodiments may be implemented in combination as appropriate, and in that case, the combined effect can be obtained. Furthermore, the present invention includes various inventions, and various inventions can be extracted by combinations selected from a plurality of disclosed constituent elements. For example, even if several constituent requirements are deleted from all the constituent requirements shown in the embodiment, if the problem can be solved and an effect can be obtained, the configuration from which the constituent requirements are deleted can be extracted as an invention.

DESCRIPTION OF SYMBOLS 1 ... Hydraulic circuit, 2 ... 1st pump, 3 ... Boom direction control valve, 5 ... Boom cylinder, 7 ... Remote control valve, 9 ... Center cut valve, 10 ... Tank, 19 ... Center bypass line, 21 ... Negative control throttle, DESCRIPTION OF SYMBOLS 23 ... Discharge capacity control part, 32 ... 2nd pump, 33 ... Turning direction control valve, 35 ... Turning motor, 37 ... Remote control valve, 53 ... Switching valve, 60 ... Hydraulic excavator, 62 ... Lower traveling body, 63 ... Upper turning Body, 67 ... Boom.

Claims (3)

A traveling body, a swiveling body that can swivel with respect to the traveling body, a boom that is attached to the swiveling body, and a boom cylinder that operates the boom with respect to the swiveling body by being supplied with pressure oil. A hydraulic circuit provided in a construction machine comprising:
A first pump that discharges the pressure oil supplied to the boom cylinder;
A center bypass line for discharging the pressure oil flowing into the tank;
A boom direction control valve that is displaced from a neutral position when an operation for operating the boom is input, and in a state in which the boom is positioned at the neutral position, the pressure oil is supplied to the center bypass pipe, and a boom lowering operation is performed. A boom direction control valve that supplies the pressure oil to both the boom cylinder and the center bypass conduit by displacing from the neutral position based on the input of
An adjustment valve that is provided in the center bypass pipeline and switches the state of the center bypass pipeline;
A flow rate adjusting member that is provided downstream of the adjustment valve in the center bypass pipe, and reduces the discharge amount of the pressure oil from the first pump when the pressure oil flows in;
A switching unit that switches a state of the adjustment valve, and when the boom lowering operation is input and a turning operation for turning the turning body with respect to the traveling body is input, A switching unit that allows pressure oil to flow in, and when the boom lowering operation is input and the turning operation is not input, shuts or reduces the pressure oil flowing into the flow rate adjustment member;
Hydraulic circuit comprising. The adjustment valve blocks or reduces the pressure oil flowing into the flow rate adjusting member by supplying pilot oil from the switching unit,
The switching unit is a switching valve that is provided in a hydraulic line that supplies the pilot oil to the adjustment valve, and that switches a state of the hydraulic line.
When the boom lowering operation is input and the turning operation is not input, the switching valve supplies the pilot oil to the adjustment valve, the boom lowering operation is input, and the turning operation is input. The pilot oil supply to the regulator valve is shut off when
The hydraulic circuit according to claim 1. The switching unit is a control device electrically connected to the regulating valve,
The control device acquires a displacement amount of the boom direction control valve from the neutral position when the boom lowering operation is input, determines whether or not the turning operation is input, and the displacement amount, and And controlling the state of the regulating valve based on the determination result about the turning operation.
The hydraulic circuit according to claim 1.