JP2016156426A - Unload valve and hydraulic driving system of hydraulic shovel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single unload valve provided on a first circulation line and a second circulation line.SOLUTION: An unload valve 7 provided on a first circulation line and a second circulation line in a hydraulic drive system of a building machine, includes: a housing 8 which has a first pump port 81 on a pump side of the first circulation line, a first output port 82 on a throttle side of the first circulation line, a second pump port 85 on a pump side of the second circulation line, a second output port 86 on a throttle side of the second circulation line, and a tank port; and a spool 9 held by the housing, and moved between a normal position communicating the first pump port to the first output port and communicating the second pump port to the second output port, and an unload position communicating the first pump port and the second pump port to the tank port.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an unload valve used for a hydraulic drive system of a construction machine. The present invention also relates to a hydraulic drive system for a hydraulic excavator using the unload valve.

  In a construction machine such as a hydraulic excavator or a hydraulic crane, various operations are performed by a hydraulic drive system. For example, Patent Document 1 discloses a hydraulic drive system for a construction machine that uses a split pump having a first discharge port and a second discharge port.

  The split pump in the hydraulic drive system is a variable displacement pump, and the tilt angle of the split pump is changed by a regulator. The discharge flow rate of the split pump is controlled by a negative control method. Specifically, a plurality of control valves are arranged on a first circulation line extending from the first discharge port and on a second circulation line extending from the second discharge port. The regulator includes a lower pressure on the upstream side of the throttle provided on the downstream side of the control valve in the first circulation line and a lower pressure on the upstream side of the throttle provided on the downstream side of the control valve in the second circulation line. Is guided.

  Further, in the hydraulic drive system disclosed in Patent Document 1, when the control valves on the first circulation line and the second circulation line are not operated (the operation valve that outputs the pilot pressure to the control valve is not operated). In other words, a configuration is adopted for allowing hydraulic oil discharged from the split pump to escape from the upstream side of the throttle to the tank. Specifically, a first unload valve is provided in the first circulation line, and a second unload valve is provided in the second circulation line.

JP 2014-59015 A

  However, the configuration using two unload valves as in the hydraulic drive system disclosed in Patent Document 1 increases the cost.

  Therefore, an object of the present invention is to provide a single unload valve provided in the first circulation line and the second circulation line, and to provide a hydraulic drive system for a hydraulic excavator using the unload valve. To do.

  In order to solve the above-described problems, the present invention provides an unload valve provided in a first circulation line and a second circulation line in a hydraulic drive system for a construction machine, the first load line being a pump side of the first circulation line. A pump port, a first output port on the throttle side of the first circulation line, a second pump port on the pump side of the second circulation line, a second output port on the throttle side of the second circulation line, and a tank A housing having a port, and a spool held by the housing, wherein the first pump port communicates with the first output port and the second pump port communicates with the second output port; A spool that moves between an unload position that communicates the first pump port and the second pump port with the tank port; Provided, to provide a unload valve.

  According to the above configuration, the hydraulic oil in the first circulation line and the second circulation line can be released from the upstream side of the throttle to the tank with a single unload valve when the control valve is not operating.

  The spool may be moved to a cut position where the first pump port communicates with the first output port and the second pump port is separated from the second output port and the tank port. According to this configuration, when the spool is located at the cut position, the second circulation line is shut off while the first circulation line remains open. For this reason, for example, when a replenishment passage for supplying hydraulic oil from the upstream portion of the unload valve in the second circulation line to the specific control valve on the first circulation line is provided, the specific control valve The hydraulic oil can be supplied to the connected hydraulic actuator not only from the first circulation line but also from the second circulation line through the supply path.

  For example, the housing has a sliding chamber that is slidably fitted to the spool, and the first pump port and the tank port are provided between an inner peripheral surface of the sliding chamber and the spool. A first unload flow path is formed, the second unload flow path communicating with the tank port as an internal flow path is formed in the spool, and the spool has the normal position and A first land portion that closes the first unload flow path at the cut position and opens the first unload flow path at the unload position; and the second pump port at the normal position and the cut position. A second land portion separated from the unload flow path and communicating the second pump port with the second unload flow path at the unload position; and the second pump port at the normal position. Output port and communicates, the second pump port with the cutting position may be the third land portion is provided to separate from said second output port.

  In addition, the present invention provides, from one aspect, a variable displacement first pump, a plurality of control valves disposed on a first circulation line extending from the first pump to the tank, and downstream of the plurality of control valves. On the side of the first circulation line, a first regulator for changing the tilt angle of the first pump, a variable displacement second pump, and a second circulation extending from the second pump to the tank. A plurality of control valves disposed on the line, a throttle provided in the second circulation line on the downstream side of the plurality of control valves, a second regulator for changing a tilt angle of the second pump, A standby solenoid valve for switching whether to output a standby pressure that minimizes the tilt angle of the first pump and the second pump, and a first negative that is the pressure upstream of the throttle in the first circulation line Control pressure and waiting A first selection valve that guides the higher standby pressure output from the solenoid valve to the first regulator, a second negative control pressure that is a pressure upstream of the throttle in the second circulation line, and the standby valve A second selection valve that guides the higher standby pressure output from the solenoid valve to the second regulator, and the above-described amplifier provided in the first circulation line and the second circulation line upstream of the throttle. An unloading valve having an unloading pilot port for moving the spool from the normal position, which is a neutral position, to the unloading position, and outputting a pilot pressure to the unloading pilot port An unloading solenoid valve for switching whether or not, a control device for controlling the standby solenoid valve and the unloading solenoid valve, When all of the plurality of control valves on the circulation line and on the second circulation line are in the neutral position, the standby pressure is output from the standby solenoid valve, and the pilot pressure is output from the unload solenoid valve. When the at least one of the plurality of control valves on the first circulation line and the second circulation line is not in a neutral position, a standby pressure is not output from the standby solenoid valve, and the unloading A hydraulic drive system for a hydraulic excavator is provided that includes a control device that does not output pilot pressure from a solenoid valve.

  According to the above configuration, when the at least one control valve is operating, the spool of the unload valve is positioned at the normal position, and the first negative control pressure and the second negative control pressure are respectively set to the first regulator and Guided to the second regulator. For this reason, the discharge flow rates of the first pump and the second pump can be controlled by a normal negative control method. On the other hand, when all the control valves are not operating, the spool of the unload valve is located at the unload position. For this reason, the hydraulic oil discharged from the first pump and the second pump can be released to the tank from the upstream side of the throttle. Further, when all the control valves are not operating, the standby pressure that minimizes the tilt angle of the first pump and the second pump is guided to the first regulator and the second regulator, so the first pump and the second pump The discharge flow rate of the pump can be kept to a minimum.

  In another aspect, the present invention controls supply and discharge of hydraulic fluid to and from a bucket cylinder disposed on a variable displacement first pump and a first circulation line extending from the first pump to the tank. A plurality of control valves including a bucket control valve; a throttle provided in the first circulation line downstream of the plurality of control valves; a first regulator for changing a tilt angle of the first pump; and a variable capacity A second pump of the type, a plurality of control valves disposed on a second circulation line extending from the second pump to the tank, and a throttle provided in the second circulation line downstream of the plurality of control valves; A second regulator that changes a tilt angle of the second pump; a standby solenoid valve that switches whether to output a standby pressure that minimizes the tilt angles of the first pump and the second pump; The first circulation la A first selection valve that guides the first negative control pressure, which is the pressure upstream of the throttle in the engine, and the standby pressure output from the standby solenoid valve to the first regulator, and the second circulation line A second selection valve for guiding the higher one of the second negative control pressure, which is the pressure upstream of the throttle, and the standby pressure output from the standby solenoid valve to the second regulator, and the upstream side of the throttle An unloading pilot port provided in the first circulation line and the second circulation line, for moving the spool from the normal position which is a neutral position to the unload position. And an unloading valve having a cutting pilot port for moving the spool from the normal position to the cutting position; A replenishment path for supplying hydraulic oil from the upstream portion of the unload valve in the second circulation line to the bucket control valve, and an unload for switching whether to output pilot pressure to the unload pilot port A control device that controls the solenoid valve, a bucket operation valve that outputs pilot pressure to a pilot port of the bucket control valve and the pilot port for cut, and the standby solenoid valve and the unload solenoid valve, When all of the plurality of control valves on the first circulation line and the second circulation line are in the neutral position, the standby solenoid valve outputs a standby pressure, and the unload solenoid valve outputs a pilot. Pressure is output, and at least one of the plurality of control valves on the first circulation line and the second circulation line is in the middle. There is provided a hydraulic drive system for a hydraulic excavator, comprising: a control device that does not output a standby pressure from the standby electromagnetic valve and does not output a pilot pressure from the unloading electromagnetic valve when not in a standing position. Alternatively, in this configuration, an option actuator, an option control valve, and an option operation valve may be employed instead of the bucket cylinder, the bucket control valve, and the bucket operation valve.

  According to the above configuration, when the at least one control valve is operating, the spool of the unload valve is positioned at the normal position, and the first negative control pressure and the second negative control pressure are respectively set to the first regulator and Guided to the second regulator. For this reason, the discharge flow rates of the first pump and the second pump can be controlled by a normal negative control method. On the other hand, when all the control valves are not operating, the spool of the unload valve is located at the unload position. For this reason, the hydraulic oil discharged from the first pump and the second pump can be released to the tank from the upstream side of the throttle. Further, when all the control valves are not operating, the standby pressure that minimizes the tilt angle of the first pump and the second pump is guided to the first regulator and the second regulator, so the first pump and the second pump The discharge flow rate of the pump can be kept to a minimum.

  When the bucket control valve is operated and the bucket control valve is operating, or when the option operation valve is operated and the option control valve is operating, the spool of the unload valve is located at the cut position, The second circulation line is shut off while the first circulation line remains open. As a result, hydraulic oil is supplied to the bucket cylinder or the optional actuator not only from the first circulation line but also from the second circulation line through the supply path. Therefore, not only the energy of the first pump but also the energy of the second pump can be used for driving the bucket cylinder or the optional actuator.

  According to the present invention, a single unload valve provided in the first circulation line and the second circulation line, and a hydraulic drive system for a hydraulic excavator using the unload valve are provided.

It is sectional drawing of the unloading valve which concerns on one Embodiment of this invention, and shows the state which has a spool in a normal position. It is sectional drawing of the said unloading valve, and shows the state which has a spool in an unloading position. It is sectional drawing of the said unloading valve, and shows the state which has a spool in a cut position. It is a schematic block diagram of the hydraulic drive system of the hydraulic shovel using the said unload valve. It is sectional drawing of the unload valve of a modification, and shows the state which has a spool in a normal position. It is sectional drawing of the unload valve of a modification, and shows the state which has a spool in an unload position. It is a schematic block diagram of the hydraulic drive system of the hydraulic shovel which used the option operation valve instead of the bucket operation valve as a means to move a spool to a cut position.

  1 to 3 show an unload valve 7 according to an embodiment of the present invention, and FIG. 4 shows a hydraulic drive system 10 for a hydraulic excavator using the unload valve 7. However, the unload valve 7 may be used in a hydraulic drive system of other construction machines such as a hydraulic crane.

  First, a hydraulic drive system 10 for a hydraulic excavator will be described with reference to FIG. The hydraulic drive system 10 includes a boom cylinder, an arm cylinder, a bucket cylinder, a turning motor, a travel left motor, and a travel right motor (all not shown) as hydraulic actuators. The boom cylinder, arm cylinder, bucket cylinder, swing motor, travel left motor, and travel right motor are respectively a boom control valve 42, an arm control valve 46, a bucket control valve 43, a swing control valve 45, a travel left control valve 41, and a travel. A right control valve 44 is connected. Further, the hydraulic drive system 10 drives the first pump 12 and the second pump 14 and the first pump 12 and the second pump 14 for supplying hydraulic oil to the actuators via the control valves 41 to 46. An engine 11 is included. If the excavator is not self-propelled, elements for traveling (such as the traveling left control valve 41 and the traveling right control valve 44) are unnecessary.

  Each of the first pump 12 and the second pump 14 is a variable displacement pump (swash plate pump or oblique shaft pump) whose tilt angle can be changed. The tilt angle of the first pump 12 is changed by the first regulator 13, and the tilt angle of the second pump 14 is changed by the second regulator 15. In the present embodiment, the discharge flow rates of the first pump 12 and the second pump 14 are controlled by a negative control method.

  Specifically, a first circulation line 21 extends from the first pump 12 to the tank. On the first circulation line 21, the above-described travel left control valve 41, boom control valve 42, and bucket control valve 43 are arranged. These control valves 41 to 43 may be arranged in any order. The travel left control valve 41 controls supply and discharge of hydraulic oil to the travel left motor, the boom control valve 42 controls supply and discharge of hydraulic oil to the boom cylinder, and the bucket control valve 43 operates to the bucket cylinder. Control oil supply and discharge. A parallel line 24 branches from the first circulation line 21, and hydraulic oil discharged from the first pump 12 is guided to all the control valves 41 to 43 on the first circulation line 21 through the parallel line 24. The tank line 25 is connected to the left travel control valve 41, the boom control valve 42, and the bucket control valve 43.

  Similarly, a second circulation line 31 extends from the second pump 14 to the tank. On the second circulation line 31, the traveling right control valve 44, the turning control valve 45, and the arm control valve 46 described above are arranged. These control valves 44 to 46 may be arranged in any order. The traveling right control valve 44 controls the supply and discharge of hydraulic oil to the traveling right motor, the turning control valve 45 controls the supply and discharge of hydraulic oil to the turning motor, and the arm control valve 46 operates to the arm cylinder. Control oil supply and discharge. A parallel line 34 is branched from the second circulation line 31, and hydraulic oil discharged from the second pump 14 is guided to all the control valves 44 to 46 on the second circulation line 31 through the parallel line 34. A tank line 35 is connected to the traveling right control valve 44, the turning control valve 45, and the arm control valve 46.

  Each of the boom control valve 42, the arm control valve 46, the bucket control valve 43, the turning control valve 45, the traveling left control valve 41, and the traveling right control valve 44 has a pair of pilot ports. The pilot pressure corresponding to the operation amount by the operator is output from the operation valve to the pilot port of each control valve 41 to 46. In FIG. 4, only the bucket operation valve 47 that outputs the pilot pressure to the pilot port of the bucket control valve 43 is shown as a representative.

  The first circulation line 21 is provided with a throttle 22 on the downstream side of the control valves 41 to 43. The first circulation line 21 is connected to a bypass path that bypasses the throttle 22, and a relief valve 23 is provided in the bypass path. Similarly, the second circulation line 31 is provided with a throttle 32 on the downstream side of the control valves 44 to 46. The second circulation line 31 is connected to a bypass path that bypasses the throttle 32, and a relief valve 33 is provided in the bypass path.

  The first regulator 13 described above reduces the tilt angle of the first pump 12 if the input pressure is high, and increases the tilt angle of the first pump 12 if the input pressure is low. When the tilt angle of the first pump 12 decreases, the discharge flow rate of the first pump 12 decreases, and when the tilt angle of the first pump 12 increases, the discharge flow rate of the first pump 12 increases. Similarly, the second regulator 15 reduces the tilt angle of the second pump 14 if the input pressure is high, and increases the tilt angle of the second pump 14 if the input pressure is low. When the tilt angle of the second pump 14 decreases, the discharge flow rate of the second pump 14 decreases, and when the tilt angle of the second pump 14 increases, the discharge flow rate of the second pump 14 increases.

  Specifically, the first regulator 13 is connected to the first selection valve 27, and the second regulator 15 is connected to the second selection valve 37. The first selection valve 27 and the second selection valve 37 are connected to a standby electromagnetic valve 67 by a standby pressure path 66. The standby solenoid valve 67 switches whether to output a standby pressure that minimizes the tilt angle of the first pump 12 and the second pump 14.

  The first selection valve 27 is connected to the upstream portion of the throttle 22 in the first circulation line 21 by the first negative control line 26, and the second selection valve 37 is connected by the second negative control line 36. The second circulation line 31 is connected to the upstream portion of the throttle 32. That is, the first selection valve 27 supplies the higher one of the standby pressure output from the standby solenoid valve 67 and the first negative control pressure, which is the pressure upstream of the throttle 22 in the first circulation line 21, to the first regulator 13. The second selection valve 37 guides the higher one of the standby pressure output from the standby solenoid valve 67 and the second negative control pressure, which is the pressure upstream of the throttle 32 in the second circulation line 31, to the second regulator 15. Lead.

  The standby solenoid valve 67 is connected to the auxiliary pump 16 by a pilot line 65. That is, the standby pressure described above is the discharge pressure of the auxiliary pump 16. The auxiliary pump 16 is driven by the engine 11.

  In the first circulation line 21 and the second circulation line 31, an unload valve 7 is provided on the upstream side of the throttles 22 and 32. In this embodiment, as shown in FIG. 1, the relief unit 100 including the throttles 22 and 32 and the relief valves 23 and 33 is integrated with the unload valve 7. For this reason, the unload valve 7 is arrange | positioned in the downstream of the control valves 41-46. The structures of the unload valve 7 and the relief unit 100 will be described later. However, when the relief unit 100 is not integrated with the unload valve 7, the unload valve 7 may be disposed upstream of the control valves 41 to 46.

  Returning to FIG. 4, the first circulation line 21 is connected to the first unload flow path 61 that bypasses the restriction 22, and the second circulation line 31 is connected to the second unload flow that bypasses the restriction 32. A path 62 is connected. The first unload flow path 61 and the second unload flow path 62 are provided in the unload valve 7 as shown in FIG.

  As shown in FIG. 1, the unload valve 7 includes a housing 8 and a spool 9 held by the housing 8. The relief unit 100 integrated with the unload valve 7 includes a main body 101 formed integrally with the housing 8 of the unload valve 7 and a pair of cylindrical members 28 and 38 attached to the main body 101. One end of the cylindrical members 28 and 38 communicates with the inflow passages 102 and 103 provided in the main body 101, and the other end of the cylindrical members 28 and 38 is closed by a cap (for simplification of the drawing). Therefore, the cap is drawn integrally with the cylindrical members 28 and 38). The throttles 22 and 32 are constituted by a plurality of through holes formed in the cylindrical members 28 and 38, and relief valves 23 and 33 are arranged in the cylindrical members 28 and 38. The main body 101 is provided with outflow passages 104 and 105 for joining the downstream side of the throttles 22 and 32 and the downstream side of the relief valves 23 and 33 together.

  In the present embodiment, the spool 9 of the unload valve 7 has a normal position, which is the neutral position shown in FIG. 1, an unload position shown in FIG. 2 (left side position in FIG. 4), and a cut position shown in FIG. 4 to the right position). That is, as shown in FIG. 4, the unload valve 7 has an unloading pilot port 71 for moving the spool 9 from the normal position to the unload position, and an unloading pilot port 71 for moving the spool 9 from the normal position to the cut position. A cutting pilot port 72 is provided.

  When the spool 9 is located at the normal position, the first circulation line 21 and the second circulation line 31 are opened, and the first unload flow path 61 and the second unload flow path 62 are blocked. When the spool 9 moves to the unload position, the first circulation line 21 communicates with the first unload flow path 61 and the second circulation line 31 communicates with the second unload flow path 62. In the present embodiment, at the unload position, the state in which the upstream portion of the first circulation line 21 communicates with the downstream portion of the first circulation line 21 is maintained, and the downstream portion of the second circulation line 31 is in the second circulation. Disconnected from the upstream portion of line 31. However, at the unload position, the downstream portion of the first circulation line 21 may be separated from the upstream portion of the first circulation line 21. Further, at the unload position, a state where the upstream portion of the second circulation line 31 communicates with the downstream portion of the second circulation line 31 may be maintained.

  When the spool 9 moves to the cut position, the second circulation line 31 is blocked while the first circulation line 21 is kept open. The hydraulic drive system 10 is provided with a supply path 63 for supplying hydraulic oil from the upstream portion of the unload valve 7 in the second circulation line 31 to the bucket control valve 43. A check valve 64 is provided in the supply path 63. In the present embodiment, a check valve 65 is provided at a branch portion of the parallel line 24 to the bucket control valve 43, and the supply path 63 is connected to the parallel line 24 on the downstream side of the check valve 65.

  The spool 9 of the unload valve 7 moves to the cut position only when the bucket operation valve 47 is operated and the bucket control valve 43 is activated. When the bucket operation valve 47 is operated and the spool 9 of the unload valve 7 moves to the cut position, the hydraulic oil discharged from the second pump 14 passes through the second circulation line 31 and the replenishment path 63 to the bucket cylinder (not shown). Supplied.

  The unloading pilot port 71 is connected to the unloading electromagnetic valve 56 by the first pilot line 57. The unloading electromagnetic valve 56 is connected to the auxiliary pump 16 by a pilot line 55. The unloading solenoid valve 56 switches whether to output a pilot pressure to the unloading pilot port 71. On the other hand, a high pressure selection valve 58 is provided between a pair of pilot lines extending from the bucket operation valve 47 to the pilot port of the bucket control valve 43, and the cutting pilot port 72 is selected by the second pilot line 59. A valve 58 is connected. That is, the pilot pressure is output from the bucket operation valve 47 to the cutting pilot port 72.

  The standby electromagnetic valve 67 and the unloading electromagnetic valve 56 described above are controlled by the control device 17. In FIG. 4, only some control lines are drawn for the sake of simplicity. In the present embodiment, a configuration for detecting whether or not the traveling left control valve 41, the boom control valve 42, the bucket control valve 43, the traveling right control valve 44, the turning control valve 45, and the arm control valve 46 described above are operated. Is adopted.

  Specifically, the hydraulic drive system 10 includes a first detection line 51 extending from the auxiliary pump 16 to the tank via the boom control valve 42, the bucket control valve 43, the arm control valve 46, and the swing control valve 45 in this order. A second detection line 53 extending from the auxiliary pump 16 to the tank via the traveling right control valve 44 and the traveling left control valve 41 in this order is provided. The order in which the first detection line 51 passes through the control valves 42, 43, 45, and 46 and the order in which the second detection line 53 passes through the control valves 41 and 44 are not particularly limited. One detection line may pass through all the control valves 41 to 46. Further, whether or not each control valve is activated may be detected based on a pilot pressure output from an operation valve corresponding to the control valve.

  The first detection line 51 is configured to be shut off when at least one of the boom control valve 42, the bucket control valve 43, the arm control valve 46, and the turning control valve 45 is activated. The first detection line 51 is provided with a throttle 52 for holding auxiliary pump pressure on the upstream side of the boom control valve 42 located on the most upstream side, and the first pressure gauge 19 between the boom control valve 42 and the throttle 52. Is provided.

  Similarly, the second detection line 53 is configured to be shut off when at least one of the travel left control valve 41 and the travel right control valve 44 is activated. The second detection line 53 is provided with a throttle 54 for holding auxiliary pump pressure on the upstream side of the traveling right control valve 44 located most upstream, and a second pressure gauge between the traveling right control valve 44 and the throttle 54. 18 is provided.

  When at least one of the control valves 41 to 46 on the first circulation line 21 and the second circulation line 31 is not in the neutral position (in other words, when at least one control valve is operating), the control device 17 ) The standby pressure is not output from the standby solenoid valve 67 and the pilot pressure is not output from the unload solenoid valve 56. Thereby, the spool 9 of the unload valve 7 is positioned at the normal position, and the first negative control pressure and the second negative control pressure are led to the first regulator 13 and the second regulator 15, respectively. For this reason, the discharge flow rates of the first pump 12 and the second pump 14 can be controlled by a normal negative control method.

  On the other hand, when all the control valves 41 to 46 on the first circulation line 21 and the second circulation line 31 are in the neutral position (in other words, when all the control valves 41 to 46 are not operating). The control device 17 outputs the pilot pressure from the unloading electromagnetic valve 56. Thereby, since the spool 9 of the unload valve 7 is positioned at the unload position, the hydraulic oil discharged from the first pump 12 and the second pump 14 can be released from the upstream side of the throttles 22 and 32 to the tank. Furthermore, when all the control valves 41 to 46 are not operating, the control device 17 outputs a standby pressure from the standby electromagnetic valve 67. As a result, the standby pressure that minimizes the tilt angle of the first pump 12 and the second pump 14 is guided to the first regulator 13 and the second regulator 15, so the discharge flow rates of the first pump 12 and the second pump 14 are reduced. Can be kept to a minimum.

  When the bucket control valve 47 is operated and the bucket control valve 43 is activated, the pilot pressure of the bucket operation valve 47 is also output to the cutting pilot port 72 of the unload valve 7. As a result, the spool 9 of the unload valve 7 is located at the cut position, and the second circulation line 31 is blocked while the first circulation line 21 remains open. As a result, hydraulic oil is supplied to the bucket cylinder not only from the first circulation line 21 but also from the second circulation line 31 through the supply path 63. Therefore, not only the energy of the first pump 12 but also the energy of the second pump 14 can be used for driving the bucket cylinder.

  Next, the structure of the unload valve 7 will be described in detail with reference to FIGS.

  The housing 8 of the unload valve 7 has a first pump port 81 on the pump side of the first circulation line 21 and a first output port 82 on the throttle side of the first circulation line 21. In the present embodiment, since the relief unit 100 is provided adjacent to the unload valve 7, the first pump port 81 is connected to the most downstream control valve on the first circulation line 21, and the first output The port 82 communicates with the inflow path 102 of the relief unit 100. The housing 8 has a first intermediate port 83 that communicates with the outflow passage 104 of the relief unit 100, and a first tank port 84 that is connected to the tank.

  The housing 8 also has a second pump port 85 on the pump side of the second circulation line 31 and a second output port 86 on the throttle side of the second circulation line 31. In the present embodiment, since the relief unit 100 is provided adjacent to the unload valve 7, the second pump port 85 is connected to the most downstream control valve on the second circulation line 31, and the second output The port 86 communicates with the inflow path 103 of the relief unit 100. The housing 8 has a second intermediate port 87 that communicates with the outflow passage 105 of the relief unit 100 and a second tank port 88 that is connected to the tank.

  In the present embodiment, the first tank port 84, the first intermediate port 83, the first output port 82, the first pump port 81, the second pump port 85, and the second output port from one end of the spool 9 toward the other end. 86, the second intermediate port 87, and the second tank port 88 are arranged in this order. However, the order of the ports 81 to 88 can be changed as appropriate. Moreover, the housing 8 does not necessarily have the 1st intermediate | middle port 83 and the 2nd intermediate | middle port 87, and the outflow paths 104 and 105 of the relief unit 100 may be directly connected with the tank. Further, when the second unload flow path 62 includes first and second horizontal holes 9b and 9c and first and second vertical holes 9d and 9e described later, both the first tank port 84 and the second tank port 88 are not necessarily provided. It is not necessary to be provided, and only one of them may be provided.

  The housing 8 has a sliding chamber 80 slidably fitted to the spool 9. The above-described ports 81 to 88 are open to the sliding chamber 80.

  The housing 8 includes a first chamber member 73 that forms a first pressure chamber 74 for applying a pilot pressure to one end surface of the spool 9 on the first tank port 84 side, and a second tank port 88 side of the spool 9. A second chamber member 76 that forms a second pressure chamber 77 for applying a pilot pressure is attached to the other end surface of the first chamber. The unloading pilot port 71 described above is formed in the first chamber member 73, and the above-described cutting pilot port 72 is formed in the second chamber member 76. The spool 9 is urged toward the second chamber member 76 by the first spring 75 disposed in the first pressure chamber 74, and the first spring 78 is disposed in the second pressure chamber 77. It is biased toward the room member 73. If a reaction force receiving member is attached to the spool 9, either one of the first spring 75 and the second spring 78 may be arranged in the same pressure chamber as the other, so that it can be urged bidirectionally as described above. Is possible.

  Sliding portions 95 and 96 that fit into the sliding chamber 80 of the housing 8 are provided at both ends of the spool 9. The spool 9 has a small diameter between the sliding portions 95 and 96, and an annular space is formed between the inner peripheral surface of the sliding chamber 80 and the spool 9. The spool 9 is provided with first to fourth land portions 91 to 94 that partition the annular space into a plurality of annular cells. In the present embodiment, the first land portion 91, the fourth land portion 94, the second land portion 92, and the third land portion are arranged from one end on the first tank port 84 side of the spool 9 toward the other end on the second tank port 88 side. Land portions 93 are arranged in this order.

  A first unload flow path 61 that connects the first pump port 81 and the first tank port 84 is formed between the inner peripheral surface of the sliding chamber 80 and the spool 9. The first unload flow path 61 includes an annular cell between the fourth land portion 94 and the first land portion 91 and an annular cell between the first land portion 91 and the sliding portion 95.

  On the other hand, the spool 9 is formed with a second unload flow path 62 communicating with the first tank port 84 and the second tank port 88 as an internal flow path. More specifically, the spool 9 is provided with a central lateral hole 9a passing through the spool 9 in a direction perpendicular to the axial direction between the fourth land portion 94 and the second land portion 92. Further, the spool 9 is provided with a first horizontal hole 9b passing through the spool 9 in a direction orthogonal to the axial direction between the first land portion 91 and the sliding portion 95, and the third land portion 93 Between the sliding parts 96, the 2nd horizontal hole 9c which penetrates the spool 9 in the direction orthogonal to an axial direction is provided. Further, the spool 9 has a first vertical hole 9d extending in the axial direction of the spool 9 from the central horizontal hole 9a to the first horizontal hole 9b, and a second vertical hole 9e extending in the axial direction of the spool 9 from the central horizontal hole 9a to the second horizontal hole 9c. Is provided. The second unload flow path 62 is configured by the horizontal holes 9a to 9c and the vertical holes 9d and 9e. However, the 1st horizontal hole 9b and the 1st vertical hole 9d do not need to be provided.

  As described above, the spool 9 moves between the normal position, the unload position, and the cut position. 1 to 3, the first intermediate port 83 is connected to the first tank port through the annular cell between the first land portion 91 and the sliding portion 95 in any of the normal position, the unload position, and the cut position. The second intermediate port 87 communicates with the second tank port 88 through an annular cell between the third land portion 93 and the sliding portion 96.

  As shown in FIG. 1, in the normal position, the spool 9 causes the first pump port 81 to communicate with the first output port 82 through an annular cell between the fourth land portion 94 and the first land portion 91. In the present embodiment, as shown in FIGS. 2 and 3, the first pump port 81 passes through the annular cell between the fourth land portion 94 and the first land portion 91 even in the unload position and the cut position. It communicates with the output port 82. Further, in the normal position, the first land portion 91 blocks between the first output port 82 and the first intermediate port 83. That is, in the normal position, the first land portion 91 closes the first unload flow path 61.

  In the normal position, the fourth land portion 94 blocks between the first pump port 81 and the second pump port 85. That is, in the normal position, the fourth land portion 94 separates the first pump port 81 from the second unload flow path 62. In the present embodiment, as shown in FIGS. 2 and 3, the fourth land portion 94 separates the first pump port 81 from the second unload flow path 62 even at the unload position and the cut position.

  In the normal position, the spool 9 causes the second pump port 85 to communicate with the second output port 86 through an annular cell between the second land portion 92 and the third land portion 93. In the normal position, the third land portion 93 blocks between the second output port 86 and the second intermediate port 87. That is, in the normal position, the third land portion 93 communicates the second pump port 85 with the second output port 86 and disconnects from the second tank port 88. In the present embodiment, as shown in FIGS. 2 and 3, the third land portion 93 separates the second pump port 85 from the second tank port 88 even at the unload position and the cut position. In the normal position, the second land portion 92 blocks between the second pump port 85 and the first pump port 81. That is, in the normal position, the second land portion 92 separates the second pump port 85 from the second unload flow path 62.

  As shown in FIG. 2, in the unload position, the spool 9 causes the first pump port 81, the annular cell between the fourth land portion 94 and the first land portion 91, and the first land portion 91 and the sliding portion 95. The first tank port 84 communicates with the annular cell between the two. That is, in the unload position, the first land portion 91 opens the first unload flow path 61. In the unload position, the spool 9 connects the second pump port 85 to the annular cell between the fourth land portion 94 and the second land portion 92, the central horizontal hole 9a, the second vertical hole 9e, the second horizontal hole 9c, and the second The annular cell between the third land portion 93 and the sliding portion 96 is communicated with the second tank port 88, and the annular cell between the fourth land portion 94 and the second land portion 92, the central lateral hole 9a, and the first vertical hole 9d. The first tank port 84 is communicated with the first lateral hole 9 b and the annular cell between the first land portion 91 and the sliding portion 95. That is, at the unload position, the second land portion 92 causes the second pump port 85 to communicate with the second unload flow path 62.

  In the present embodiment, in the unload position, the second land portion 92 blocks between the second pump port 85 and the second output port 86, and the second land portion 92 connects the second pump port 85 to the second output port 86. Disconnect from. However, the second land portion 92 may cause the second pump port 85 to communicate with the second output port 86 at the unload position.

  As shown in FIG. 3, in the cut position, the spool 9 causes the first pump port 81 to communicate with the first output port 82 through the annular cell between the fourth land portion 94 and the first land portion 91. In the cut position, the first land portion 91 blocks between the first output port 82 and the first intermediate port 83. That is, the first land portion 91 closes the first unload flow path 61 at the cut position.

  In the cut position, the spool 9 shuts off the second pump port 85 and the first pump port 81 at the second land portion 92, and the second pump port 85 and the second output at the third land portion 93. The second pump port 85 is disconnected from the second output port 86, the first tank port 84, and the second tank port 88 by blocking between the ports 86. That is, in the cut position, the second land portion 92 separates the second pump port 85 from the second unload flow path 62 and the third land portion 93 separates the second pump port 85 from the second output port 86.

  As described above, in the unload valve 7 of the present embodiment, the operation of the first circulation line 21 and the second circulation line 31 when the control valves 41 to 46 are not operated by the single unload valve 7. Oil can escape from the upstream side of the throttles 22 and 32 to the tank.

(Modification)
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

  For example, the unloading electromagnetic valve 56 and the standby electromagnetic valve 67 are not necessarily open / close valves, and may be electromagnetic proportional pressure reducing valves. Thereby, when shifting from the unloading state to a state in which at least one of the control valves 41 to 43 on the first circulation line 21 is operated, or when all the control valves 41 to 46 are stopped, the operation is shifted to unloading. It is possible to reduce the shock that occurs when doing this.

  For example, when the unloading electromagnetic valve 56 is an electromagnetic proportional pressure reducing valve, only when it is detected by the first detection line 51 and the second detection line 53 that all the control valves 41 to 46 are positioned at the neutral position. Alternatively, a pilot hydraulic pressure signal may be generated and supplied to the first pilot line 57.

  For example, when the standby solenoid valve 67 is an electromagnetic proportional pressure reducing valve, only when it is detected by the first detection line 51 and the second detection line 53 that all the control valves 41 to 46 are positioned at the neutral position, A pilot hydraulic pressure signal may be generated and supplied to the standby pressure path 66.

  Further, the spool 9 of the unload valve 7 does not necessarily need to move to the cut position, and may move only between the normal position and the unload position. Further, the second unload flow path 62 is not necessarily formed as an internal flow path in the spool 9. For example, when the spool 9 moves only between the normal position and the unload position, the second unload flow path 62 is connected to the inner peripheral surface of the sliding chamber 80 and the spool as shown in FIGS. 9 may be formed.

  5 and 6, a central land portion 97 is provided instead of the fourth land portion 94 and the second land portion 92 shown in FIG. 1, and the third land portion 93 shown in FIG. Instead, a second land portion 98 that is narrower than the third land portion 93 is provided.

  Further, as a means for moving the spool 9 of the unload valve 7 to the cut position, a cut electromagnetic valve (not shown) may be used instead of the bucket operation valve 47. Alternatively, as shown in FIG. 7, an optional operation valve 49 may be used instead of the bucket operation valve 47.

  In the example shown in FIG. 7, an option control valve 48 that controls supply and discharge of hydraulic oil to and from an option actuator (not shown) is disposed on the first circulation line 21. The option actuator may be a hydraulic cylinder or a hydraulic motor. The option operation valve 49 outputs a pilot pressure to the pair of pilot ports of the option control valve 48 and the cutting pilot port 72 of the unload valve 7. In the example shown in FIG. 7, the option control valve 48 in the parallel line 24 is supplied to the option control valve 48 from the upstream portion of the unload valve 7 in the second circulation line 31 through the supply path 63. A check valve 65 is provided at a branching point of the supply valve 63, and the supply path 63 is connected to the parallel line 24 on the downstream side of the check valve 65.

  With this configuration, when the option operation valve 49 is operated and the option control valve 48 is operating, the spool 9 of the unload valve 7 is located at the cut position, and the first circulation line 21 remains open. The second circulation line 31 is shut off. As a result, the hydraulic oil is supplied to the option actuator not only from the first circulation line 21 but also from the second circulation line 31 through the supply path 63. Therefore, not only the energy of the first pump 12 but also the energy of the second pump 14 can be used for driving the option actuator.

  Further, instead of the first pump 12 and the second pump 14, it is also possible to use a split pump having a first discharge port and a second discharge port. In this case, a configuration is adopted in which the first circulation line 21 extends from the first discharge port of the split pump and the second circulation line 31 extends from the second discharge port of the split pump.

DESCRIPTION OF SYMBOLS 10 Hydraulic drive system 12 1st pump 13 1st regulator 14 2nd pump 15 2nd regulator 17 Control device 21 1st circulation line 22 Restriction 27 1st selection valve 31 2nd circulation line 32 Restriction 37 2nd selection valve 41-46 , 48 Control valve 47, 49 Operation valve 56 Unloading solenoid valve 61 First unloading passage 62 Second unloading passage 63 Replenishment passage 67 Standby solenoid valve 7 Unloading valve 71 Unloading pilot port 72 For cutting Pilot port 8 Housing 80 Sliding chamber 81 1st pump port 82 1st output port 84 1st tank port 85 2nd pump port 86 2nd output port 88 2nd tank port 9 Spool 91 1st land part 92 2nd land part 93 Land 3

Claims (6)

An unload valve provided in a first circulation line and a second circulation line in a hydraulic drive system of a construction machine,
A first pump port on the pump side of the first circulation line; a first output port on the throttle side of the first circulation line; a second pump port on the pump side of the second circulation line; and the second circulation line. A housing having a second output port on the throttle side and a tank port;
A spool held by the housing, wherein the first pump port communicates with the first output port and the second pump port communicates with the second output port; and the first pump port and A spool that moves between an unload position that communicates the second pump port with the tank port;
Comprising an unloading valve.   2. The spool according to claim 1, wherein the spool communicates with the first output port and moves to a cut position where the second pump port is disconnected from the second output port and the tank port. Load valve. The housing has a sliding chamber slidably fitted with the spool,
A first unload flow path that connects the first pump port and the tank port is formed between the inner peripheral surface of the sliding chamber and the spool,
A second unload flow path communicating with the tank port as an internal flow path is formed in the spool,
The spool includes a first land portion that closes the first unload flow path at the normal position and the cut position and opens the first unload flow path at the unload position, and the normal position and the cut position. The second pump port is separated from the second unload flow path, and the second land port communicates the second pump port with the second unload flow path at the unload position, and the second land port communicates with the second unload flow path at the normal position. 3. The unloading valve according to claim 2, wherein a third land portion is provided that communicates two pump ports with the second output port and separates the second pump port from the second output port at the cut position. A variable displacement first pump;
A plurality of control valves disposed on a first circulation line extending from the first pump to the tank;
Throttles provided in the first circulation line downstream of the plurality of control valves;
A first regulator for changing a tilt angle of the first pump;
A variable displacement second pump;
A plurality of control valves disposed on a second circulation line extending from the second pump to the tank;
Throttles provided in the second circulation line downstream of the plurality of control valves;
A second regulator for changing a tilt angle of the second pump;
A standby solenoid valve for switching whether to output a standby pressure that minimizes the tilt angle of the first pump and the second pump;
A first selection valve for guiding the higher one of the first negative control pressure, which is the pressure upstream of the throttle in the first circulation line, and the standby pressure output from the standby solenoid valve, to the first regulator;
A second selection valve for guiding the higher one of the second negative control pressure, which is the pressure upstream of the throttle in the second circulation line, and the standby pressure output from the standby solenoid valve, to the second regulator;
2. The unloading valve according to claim 1, wherein the unloading valve is provided in the first circulation line and the second circulation line on the upstream side of the throttle, and the spool is moved from the normal position which is a neutral position to the unload position. An unloading valve having an unloading pilot port for moving to
An unloading solenoid valve for switching whether to output a pilot pressure to the unloading pilot port;
A control device for controlling the electromagnetic valve for standby and the electromagnetic valve for unloading, wherein all of the plurality of control valves on the first circulation line and the second circulation line are located at neutral positions. A standby pressure is output from the standby solenoid valve, a pilot pressure is output from the unload solenoid valve, and at least one of the plurality of control valves on the first circulation line and the second circulation line is A control device that does not output the standby pressure from the standby solenoid valve and does not output the pilot pressure from the unload solenoid valve when not in the neutral position; and
A hydraulic drive system for a hydraulic excavator. A variable displacement first pump;
A plurality of control valves including a bucket control valve disposed on a first circulation line extending from the first pump to the tank and controlling supply and discharge of hydraulic oil to and from the bucket cylinder;
Throttles provided in the first circulation line downstream of the plurality of control valves;
A first regulator for changing a tilt angle of the first pump;
A variable displacement second pump;
A plurality of control valves disposed on a second circulation line extending from the second pump to the tank;
Throttles provided in the second circulation line downstream of the plurality of control valves;
A second regulator for changing a tilt angle of the second pump;
A standby solenoid valve for switching whether to output a standby pressure that minimizes the tilt angle of the first pump and the second pump;
A first selection valve for guiding the higher one of the first negative control pressure, which is the pressure upstream of the throttle in the first circulation line, and the standby pressure output from the standby solenoid valve, to the first regulator;
A second selection valve for guiding the higher one of the second negative control pressure, which is the pressure upstream of the throttle in the second circulation line, and the standby pressure output from the standby solenoid valve, to the second regulator;
The unloading valve according to claim 2 or 3, wherein the unloading valve is provided in the first circulation line and the second circulation line upstream of the throttle, and the spool is moved from the normal position which is a neutral position to the unloading valve. An unloading valve having an unloading pilot port for moving to a loading position and a cutting pilot port for moving the spool from the normal position to the cutting position;
A replenishment path for supplying hydraulic oil from the upstream portion of the unload valve in the second circulation line to the bucket control valve;
An unloading solenoid valve for switching whether to output a pilot pressure to the unloading pilot port;
A bucket operating valve that outputs a pilot pressure to the pilot port of the bucket control valve and the pilot port for cutting;
A control device for controlling the electromagnetic valve for standby and the electromagnetic valve for unloading, wherein all of the plurality of control valves on the first circulation line and the second circulation line are located at neutral positions. A standby pressure is output from the standby solenoid valve, a pilot pressure is output from the unload solenoid valve, and at least one of the plurality of control valves on the first circulation line and the second circulation line is A control device that does not output the standby pressure from the standby solenoid valve and does not output the pilot pressure from the unload solenoid valve when not in the neutral position; and
A hydraulic drive system for a hydraulic excavator. A variable displacement first pump;
A plurality of control valves including an optional control valve disposed on a first circulation line extending from the first pump to the tank and controlling supply and discharge of hydraulic fluid to and from an optional actuator;
Throttles provided in the first circulation line downstream of the plurality of control valves;
A first regulator for changing a tilt angle of the first pump;
A variable displacement second pump;
A plurality of control valves disposed on a second circulation line extending from the second pump to the tank;
Throttles provided in the second circulation line downstream of the plurality of control valves;
A second regulator for changing a tilt angle of the second pump;
A standby solenoid valve for switching whether to output a standby pressure that minimizes the tilt angle of the first pump and the second pump;
A first selection valve for guiding the higher one of the first negative control pressure, which is the pressure upstream of the throttle in the first circulation line, and the standby pressure output from the standby solenoid valve, to the first regulator;
A second selection valve for guiding the higher one of the second negative control pressure, which is the pressure upstream of the throttle in the second circulation line, and the standby pressure output from the standby solenoid valve, to the second regulator;
The unloading valve according to claim 2 or 3, wherein the unloading valve is provided in the first circulation line and the second circulation line upstream of the throttle, and the spool is moved from the normal position which is a neutral position to the unloading valve. An unloading valve having an unloading pilot port for moving to a loading position and a cutting pilot port for moving the spool from the normal position to the cutting position;
A replenishment path for supplying hydraulic oil from an upstream portion of the unload valve in the second circulation line to the option control valve;
An unloading solenoid valve for switching whether to output a pilot pressure to the unloading pilot port;
An optional operation valve that outputs pilot pressure to the pilot port of the option control valve and the pilot port for cutting;
A control device for controlling the electromagnetic valve for standby and the electromagnetic valve for unloading, wherein all of the plurality of control valves on the first circulation line and the second circulation line are located at neutral positions. A standby pressure is output from the standby solenoid valve, a pilot pressure is output from the unload solenoid valve, and at least one of the plurality of control valves on the first circulation line and the second circulation line is A control device that does not output the standby pressure from the standby solenoid valve and does not output the pilot pressure from the unload solenoid valve when not in the neutral position; and
A hydraulic drive system for a hydraulic excavator.

Images