JP6514522B2 - Hydraulic drive system of unloading valve and hydraulic shovel - Google Patents

Description

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

  In construction machines such as hydraulic shovels and hydraulic cranes, various operations are performed by a hydraulic drive system. For example, Patent Document 1 discloses a hydraulic drive system of a construction machine using 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 disposed on the first circulation line extending from the first discharge port and on the second circulation line extending from the second discharge port. The regulator has a lower pressure which is the pressure on the upstream side of the throttle provided on the downstream side of the control valve in the first circulation line and the pressure on the upstream side of the throttle provided on the downstream side of the control valve in the second circulation line. Led.

  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 operating (the operation valve that outputs the pilot pressure to the control valve is not operated At the same time, a configuration is adopted in which the hydraulic oil discharged from the split pump is released from the upstream side of the throttle to the tank. Specifically, a first unloading valve is provided in the first circulation line, and a second unloading valve is provided in the second circulation line.

JP, 2014-59015, A

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

  Therefore, the present invention aims to provide a single unload valve provided in the first circulation line and the second circulation line, and to provide a hydraulic drive system of a hydraulic shovel using the unload valve. Do.

  In order to solve the above-mentioned subject, the present invention is an unloading valve provided in the 1st circulation line and the 2nd circulation line in a hydraulic drive system of construction machinery, and the 1st which becomes the pump side of the 1st circulation line A pump port, a first output port on the throttling 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 throttling 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 moving between an unloading position communicating 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 fluid in the first circulation line and the second circulation line can be released to the tank from the upstream side of the throttle when the control valve is not operating with a single unload valve.

  The spool may move the first pump port into communication with the first output port and move the second pump port to a cutting position for separating the second pump port from the second output port and the tank port. According to this configuration, when the spool is at the cut position, the second circulation line is blocked while the first circulation line is open. For this reason, for example, when a replenishment path for supplying hydraulic fluid from the upstream side portion of the unload valve in the second circulation line to a specific control valve on the first circulation line is provided, the specific control valve Hydraulic fluid 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 passage.

  For example, the housing has a sliding chamber slidably fitted with the spool, and the first pump port and the tank port are disposed between the inner circumferential surface of the sliding chamber and the spool. A second unloading flow passage communicating with the tank port as an internal flow passage is formed in the spool, and the normal position and the normal position are formed in the spool. The first land portion which closes the first unloading flow path at the cutting position and opens the first unloading flow path at the unloading position; and the second pump port at the normal position and the cutting position. A second land portion separating the second pump port from the second unloading channel at the unloading position; and a second land 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.

  Further, according to the present invention, 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 a downstream of the plurality of control valves A throttle provided in the first circulation line on the side, a first regulator for changing the tilt angle of the first pump, a second pump of variable displacement type, and a second circulation extending from the second pump to the tank A plurality of control valves disposed on a line, a throttle provided on the second circulation line downstream of the plurality of control valves, a second regulator for changing a tilt angle of the second pump, and A standby solenoid valve for switching whether or not 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 on the upstream side of the throttle in the first circulation line Control pressure and the waiting A first selection valve for guiding the higher one of the standby pressure outputted from the solenoid valve to the first regulator, a second negative control pressure which is a pressure on the upstream side of the throttle in the second circulation line, and the standby A second selection valve for guiding the higher one of the standby pressure outputted from the solenoid valve to the second regulator, and the above-mentioned ann provided on the first circulation line and the second circulation line upstream of the throttle. A loading valve, comprising: 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 A solenoid valve for unloading, and a control device for controlling the solenoid valve for standby and the solenoid valve for unloading, When all of the plurality of control valves on the circulation line and 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. The standby solenoid valve is not output when the output is made and the standby solenoid valve is not output when at least one of the plurality of control valves on the first circulation line and the second circulation line is not in the neutral position. A hydraulic drive system of a hydraulic shovel, comprising: a control device that does not output a pilot pressure from a solenoid valve.

  According to the above configuration, when at least one control valve is in operation, the spool of the unload valve is in the normal position, and the first negative control pressure and the second negative control pressure are respectively set to the first regulator and It is led to the second regulator. Therefore, the discharge flow rates of the first pump and the second pump can be controlled by the usual negative control method. On the other hand, when all the control valves are not operating, the unload valve spool is located at the unload position. Therefore, 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. Furthermore, when all the control valves are not operating, a standby pressure that minimizes the tilt angle of the first pump and the second pump is introduced to the first regulator and the second regulator. Pump discharge flow can be kept to a minimum.

  The present invention also controls, from another aspect, the supply and discharge of hydraulic fluid to a variable displacement first pump and a bucket cylinder disposed on 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 on 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 a mold type, a plurality of control valves disposed on a second circulation line extending from the second pump to the tank, and a throttle provided on the second circulation line downstream of the plurality of control valves A second regulator that changes the tilt angle of the second pump, and a standby solenoid valve that switches whether to output a standby pressure that minimizes the tilt angle of the first pump and the second pump; Said first circulation line First selection valve for guiding the higher one of the first negative control pressure which is the pressure on the upstream side of the throttle and the standby pressure outputted 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 on the upstream side of the throttle, and the standby pressure outputted from the solenoid valve for standby, to the second regulator; The unloading valve provided on the first circulation line and the second circulation line, for unloading the spool from the normal position, which is a neutral position, to the unloading position And an unloading valve having a cutting pilot port for moving the spool from the normal position to the cutting position; For unloading, which switches whether or not to output a pilot pressure to the replenishment path for supplying hydraulic fluid from the upstream side portion of the unloading valve in the second circulation line to the bucket control valve, and to the unloading pilot port A control device for controlling a solenoid valve, a bucket control valve for outputting a pilot pressure to a pilot port of the bucket control valve and the pilot port for cutting, a solenoid valve for standby, and a solenoid valve for unloading, When all of the plurality of control valves on the first circulation line and the second circulation line are at the neutral position, the standby pressure is output from the standby solenoid valve, and the pilot from the unloading solenoid valve Pressure, and at least one of the plurality of control valves on the first circulation line and the second circulation line is There is provided a hydraulic drive system of a hydraulic shovel, comprising: a control device which does not output a standby pressure from the standby solenoid valve and does not output a pilot pressure from the unload solenoid valve when not in a standing position. Alternatively, in this configuration, in place of the bucket cylinder, the bucket control valve and the bucket control valve, an option actuator, an option control valve and an option control valve may be employed.

  According to the above configuration, when at least one control valve is in operation, the spool of the unload valve is in the normal position, and the first negative control pressure and the second negative control pressure are respectively set to the first regulator and It is led to the second regulator. Therefore, the discharge flow rates of the first pump and the second pump can be controlled by the usual negative control method. On the other hand, when all the control valves are not operating, the unload valve spool is located at the unload position. Therefore, 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. Furthermore, when all the control valves are not operating, a standby pressure that minimizes the tilt angle of the first pump and the second pump is introduced to the first regulator and the second regulator. Pump discharge flow can be kept to a minimum.

  When the bucket control valve is operated and the bucket control valve is operated, or when the option operation valve is operated and the option control valve is operated, the unload valve spool is in the cut position, While the first circulation line is open, the second circulation line is shut off. As a result, hydraulic fluid is supplied to the bucket cylinder or the option actuator not only from the first circulation line but also from the second circulation line through the replenishment path. Therefore, not only the energy of the first pump but also the energy of the second pump can be used to drive the bucket cylinder or the optional actuator.

  According to the present invention, there is provided a single unload valve provided in the first circulation line and the second circulation line, and a hydraulic drive system of a hydraulic shovel using the unload valve.

FIG. 5 is a cross-sectional view of an unload valve according to an embodiment of the present invention, showing the spool in a normal position. It is sectional drawing of the said unloading valve, and shows the state which a spool is in an unloading position. It is sectional drawing of the said unloading valve, and the state which has a spool in a cut position is shown. It is a schematic block diagram of the hydraulic drive system of the hydraulic shovel in which the said unloading valve was used. It is sectional drawing of the unloading valve of a modification, and the state which has a spool in a normal position is shown. It is sectional drawing of the unloading valve of a modification, and the state where a spool is in an unloading position is shown. It is a schematic block diagram of the hydraulic drive system of the hydraulic shovel which used the option operation valve instead of a 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 of a hydraulic shovel using the unload valve 7. However, the unloading valve 7 may be used in a hydraulic drive system of another construction machine such as a hydraulic crane.

  First, with reference to FIG. 4, a hydraulic drive system 10 of a hydraulic shovel will be described. The hydraulic drive system 10 includes, as hydraulic actuators, a boom cylinder, an arm cylinder, a bucket cylinder, a swing motor, a traveling left motor, and a traveling right motor (all not shown). The boom cylinder, arm cylinder, bucket cylinder, swing motor, running left motor and running right motor are respectively the boom control valve 42, arm control valve 46, bucket control valve 43, swing control valve 45, running left control valve 41 and running It is connected to the right control valve 44. The hydraulic drive system 10 also drives the first pump 12 and the second pump 14 for supplying hydraulic fluid to the actuators via the control valves 41 to 46, and the first pump 12 and the second pump 14 The engine 11 is included. In addition, when the hydraulic shovel is not a self-propelled type, elements for traveling (the traveling left control valve 41 and the traveling right control valve 44 and the like) 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 the negative control method.

  Specifically, a first circulation line 21 extends from the first pump 12 to the tank. The traveling left control valve 41, the boom control valve 42, and the bucket control valve 43 described above are disposed on the first circulation line 21. These control valves 41 to 43 may be arranged in any order. The travel left control valve 41 controls the supply and discharge of hydraulic fluid to the travel left motor, the boom control valve 42 controls the supply and drain of hydraulic fluid 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 the hydraulic oil discharged from the first pump 12 is led to all the control valves 41 to 43 on the first circulation line 21 through the parallel line 24. A tank line 25 is connected to the traveling left 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. The traveling right control valve 44, the turning control valve 45, and the arm control valve 46 described above are disposed on the second circulation line 31. 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 fluid to the traveling right motor, the swing control valve 45 controls the supply and discharge of hydraulic fluid to the swing motor, and the arm control valve 46 operates to the arm cylinder Control oil supply and discharge. A parallel line 34 branches from the second circulation line 31, and the hydraulic oil discharged from the second pump 14 is led 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. A pilot pressure corresponding to the amount of operation by the operator is output from the operation valve to the pilot port of each of the control valves 41 to 46. In FIG. 4, only the bucket control valve 47 that outputs the pilot pressure to the pilot port of the bucket control valve 43 is illustrated as a representative.

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

  The first regulator 13 described above reduces the tilt angle of the first pump 12 if the pressure input is high, and increases the tilt angle of the first pump 12 if the pressure input is low. When the tilting angle of the first pump 12 decreases, the discharge flow rate of the first pump 12 decreases, and when the tilting 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 the standby solenoid valve 67 by a standby pressure passage 66. The standby solenoid valve 67 switches whether or not to output a standby pressure that minimizes the tilt angle of the first pump 12 and the second pump 14.

  Further, the first selection valve 27 is connected to the upstream side 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 sets the higher one of the standby pressure output from the standby solenoid valve 67 and the first negative control pressure, which is the pressure on the upstream side of the throttle 22 in the first circulation line 21, to the first regulator 13. The second selection valve 37 sends the second negative control pressure, which is the standby pressure output from the standby solenoid valve 67 and the pressure on the upstream side 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 above-described standby pressure is the discharge pressure of the auxiliary pump 16. The auxiliary pump 16 is driven by the engine 11.

  An unloading valve 7 is provided on the first circulation line 21 and the second circulation line 31 on the upstream side of the throttles 22 and 32. In the present embodiment, as shown in FIG. 1, a 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 unloading valve 7 is disposed downstream of the control valves 41 to 46. The structures of the unloading 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.

  Referring back to FIG. 4, the first unloading flow path 61 bypassing the throttle 22 is connected to the first circulation line 21, and the second unloading flow bypassing the throttle 32 is connected to the second circulation line 31. The path 62 is connected. The first unloading flow passage 61 and the second unloading flow passage 62 are provided in the unloading valve 7 as shown in FIG.

  As shown in FIG. 1, the unloading valve 7 includes a housing 8 and a spool 9 held by the housing 8. The relief unit 100 integrated with the unloading valve 7 includes a main body 101 integrally formed with the housing 8 of the unloading valve 7, and a pair of cylindrical members 28 and 38 attached to the main body 101. One end of each of the cylindrical members 28, 38 is in communication with the inflow path 102, 103 provided in the main body 101, and the other end of each of the cylindrical members 28, 38 is closed by a cap (the 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 the relief valves 23 and 33 are disposed in the cylindrical members 28 and 38. Further, the main body 101 is provided with outflow passages 104 and 105 which merge the downstream side of the throttles 22 and 32 and the downstream side of the relief valves 23 and 33.

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

  When the spool 9 is in the normal position, the first circulation line 21 and the second circulation line 31 are opened, and the first unloading flow passage 61 and the second unloading flow passage 62 are blocked. When the spool 9 moves to the unloading position, the first circulation line 21 communicates with the first unloading channel 61, and the second circulation line 31 communicates with the second unloading channel 62. In the present embodiment, in the unloading 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 the second circulation. It is disconnected from the upstream portion of line 31. However, at the unloading position, the downstream portion of the first circulation line 21 may be separated from the upstream portion of the first circulation line 21. In the unloading position, the upstream portion of the second circulation line 31 may be kept in communication with the downstream portion of the second circulation line 31.

  When the spool 9 moves to the cut position, the second circulation line 31 is shut off while the first circulation line 21 remains open. The hydraulic drive system 10 is provided with a replenishment path 63 for supplying hydraulic fluid from the upstream side 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 passage 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 unloading valve 7 moves to the cutting position only when the bucket operating valve 47 is operated and the bucket control valve 43 is operated. When the bucket operation valve 47 is operated and the spool 9 of the unload valve 7 moves to the cut position, the hydraulic fluid discharged from the second pump 14 passes through the second circulation line 31 and the supply passage 63 to the bucket cylinder not shown. Supplied.

  The unloading pilot port 71 is connected to the unloading solenoid valve 56 by a first pilot line 57. The unloading solenoid 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 or not. 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. Connected to the valve 58. That is, the pilot pressure is output from the bucket control valve 47 to the cutting pilot port 72.

  The standby solenoid valve 67 and the unloading solenoid valve 56 described above are controlled by the controller 17. In addition, in FIG. 4, only a part of control line is drawn for simplification of the drawing. In this 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 is provided which extends from the auxiliary pump 16 to the tank via the travel right control valve 44 and the travel left control valve 41 in this order. 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. Also, one detection line may pass through all the control valves 41 to 46. Furthermore, whether or not each control valve has been activated may be detected based on the pilot pressure output from the operation valve corresponding to that 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 operated. A throttle 52 for holding the auxiliary pump pressure is provided on the first detection line 51 upstream of the boom control valve 42 positioned most upstream, and a first pressure gauge 19 is provided 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 traveling left control valve 41 and the traveling right control valve 44 is operated. A throttle 54 for holding the auxiliary pump pressure is provided on the second detection line 53 on the upstream side of the travel right control valve 44 located most upstream, and a second pressure gauge is provided between the travel right control valve 44 and the throttle 54 18 are 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, at least one control valve is operating) And the standby solenoid valve 67 do not output the standby pressure, and the unload solenoid valve 56 does not output the pilot pressure. As a result, the spool 9 of the unload valve 7 is located 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. Therefore, the discharge flow rates of the first pump 12 and the second pump 14 can be controlled by the 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 at the neutral position (in other words, when all the control valves 41 to 46 are not operated) The controller 17 causes the unloading solenoid valve 56 to output a pilot pressure. As a result, since the spool 9 of the unload valve 7 is located 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 operated, the control device 17 causes the standby solenoid valve 67 to output the standby pressure. As a result, the standby pressure that minimizes the tilt angle of the first pump 12 and the second pump 14 is introduced 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 can be reduced. It can be kept to a minimum.

  When the bucket control valve 47 is operated and the bucket control valve 43 is operated, the pilot pressure of the bucket control valve 47 is also output to the cut 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 shut off 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 passage 63. Therefore, not only the energy of the first pump 12 but also the energy of the second pump 14 can be used to drive the bucket cylinder.

  Next, the structure of the unloading valve 7 will be described in detail with reference to FIGS. 1 to 3.

  The housing 8 of the unloading 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 throttling 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 control valve on the most downstream side on the first circulation line 21 and has a first output. The port 82 is in communication with the inflow path 102 of the relief unit 100. Further, the housing 8 has a first intermediate port 83 communicating with the outflow passage 104 of the relief unit 100 and a first tank port 84 connected with 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 throttling 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 is in communication with the inflow path 103 of the relief unit 100. Further, the housing 8 has a second intermediate port 87 communicating with the outflow passage 105 of the relief unit 100, and a second tank port 88 connected with 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, the second output port are arranged from one end of the spool 9 to the other end. 86, a second intermediate port 87 and a second tank port 88 are arranged in this order. However, the order of the ports 81 to 88 can be changed as appropriate. Further, the housing 8 does not necessarily have to have the first intermediate port 83 and the second intermediate port 87, and the outflow paths 104 and 105 of the relief unit 100 may be directly connected to the tank. Furthermore, in the case where the second unloading 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 necessarily required. Need not be provided, but only one of them may be provided.

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

  The housing 8 has a first chamber member 73 forming a first pressure chamber 74 for applying a pilot pressure to one end face of the spool 9 on the first tank port 84 side, and the second tank port 88 side of the spool 9 A second chamber member 76 is attached which forms a second pressure chamber 77 for applying a pilot pressure to the other end face of the second chamber. The first chamber member 73 is formed with the unloading pilot port 71 described above, and the second chamber member 76 is formed with the cutting pilot port 72 described above. The spool 9 is urged toward the second chamber member 76 by the first spring 75 disposed in the first pressure chamber 74 and is firstly biased by the second spring 78 disposed in the second pressure chamber 77. It is biased toward the room member 73. In addition, if the reaction force receiving member is attached to the spool 9, by disposing either one of the first spring 75 and the second spring 78 in the same pressure chamber as the other, biasing in both directions as described above is also possible. It is possible.

  At both end portions of the spool 9, sliding portions 95, 96 fitted with the sliding chambers 80 of the housing 8 are provided. 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 divide 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 91 are directed from the 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 connecting 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 unloading flow passage 61 is configured by 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 provided with a second unloading flow passage 62 communicating with the first tank port 84 and the second tank port 88 as an internal flow passage. More specifically, the spool 9 is provided, between the fourth land portion 94 and the second land portion 92, with a central lateral hole 9a which penetrates the spool 9 in a direction perpendicular to the axial direction. Further, the spool 9 is provided with a first horizontal hole 9 b penetrating the spool 9 in a direction orthogonal to the axial direction between the first land portion 91 and the sliding portion 95, and a third land portion 93 and Between the sliding portions 96, a second horizontal hole 9c is provided which penetrates the spool 9 in a direction perpendicular to the axial direction. Furthermore, 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. It is provided. A second unloading flow path 62 is formed by the horizontal holes 9a to 9c and the vertical holes 9d and 9e. However, the first horizontal holes 9 b and the first vertical holes 9 d may not be provided.

  The spool 9 moves between the normal position, the unload position and the cut position as described above. As shown in FIGS. 1 to 3, in any of the normal position, the unloading position, and the cutting position, the first intermediate port 83 is a first tank port through the annular cell between the first land portion 91 and the sliding portion 95. The second intermediate port 87 communicates with the second tank port 88 through the annular cell between the third land 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 the annular cell between the fourth land portion 94 and the first land portion 91. In the present embodiment, as shown in FIG. 2 and FIG. 3, the first pump port 81 is not limited to the first through the annular cell between the fourth land portion 94 and the first land portion 91 even in the unloading position and the cutting position. It communicates with the output port 82. Further, in the normal position, the first land portion 91 cuts off between the first output port 82 and the first intermediate port 83. That is, at the normal position, the first land portion 91 closes the first unloading flow passage 61.

  Also, in the normal position, the fourth land portion 94 cuts off between the first pump port 81 and the second pump port 85. That is, in the normal position, the fourth land portion 94 disconnects the first pump port 81 from the second unloading flow passage 62. In the present embodiment, as shown in FIGS. 2 and 3, the fourth land portion 94 disconnects the first pump port 81 from the second unloading flow passage 62 even at the unloading position and the cutting position.

  In the normal position, the spool 9 makes the second pump port 85 communicate with the second output port 86 through the annular cell between the second land portion 92 and the third land portion 93. Also, in the normal position, the third land portion 93 cuts off between the second output port 86 and the second intermediate port 87. That is, in the normal position, the third land portion 93 makes the second pump port 85 communicate with the second output port 86 and separates 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 unloading position and the cutting position. Also, in the normal position, the second land portion 92 cuts off between the second pump port 85 and the first pump port 81. That is, in the normal position, the second land portion 92 disconnects the second pump port 85 from the second unloading flow passage 62.

  As shown in FIG. 2, in the unloading position, the spool 9 has the first pump port 81, the annular cell between the fourth land portion 94 and the first land portion 91, the first land portion 91, and the sliding portion 95. And communicate with the first tank port 84 through the annular cell between them. That is, at the unloading position, the first land portion 91 opens the first unloading flow passage 61. In the unloading position, the spool 9 further includes the second pump port 85, an annular cell between the fourth land portion 94 and the second land portion 92, a central horizontal hole 9a, a second vertical hole 9e, a second horizontal hole 9c and a second The annular cell between the third land portion 93 and the sliding portion 96 is in communication with the second tank port 88, and the annular cell between the fourth land portion 94 and the second land portion 92, the central horizontal hole 9a, the first vertical hole 9d The first horizontal port 9 b communicates with the first tank port 84 through the annular cell between the first land portion 91 and the sliding portion 95. That is, in the unloading position, the second land portion 92 causes the second pump port 85 to communicate with the second unloading flow channel 62.

  In the present embodiment, in the unloading position, the second land portion 92 cuts off between the second pump port 85 and the second output port 86, and the second land portion 92 functions as the second pump port 85. Disconnect from However, the second land portion 92 may place the second pump port 85 in communication with the second output port 86 at the unloading 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 addition, at the cut position, the first land portion 91 cuts off between the first output port 82 and the first intermediate port 83. That is, at the cut position, the first land portion 91 closes the first unloading flow passage 61.

  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. By disconnecting between the ports 86, the second pump port 85 is disconnected from the second output port 86, the first tank port 84 and the second tank port 88. That is, in the cut position, the second land portion 92 disconnects the second pump port 85 from the second unloading flow passage 62, and the third land portion 93 disconnects the second pump port 85 from the second output port 86.

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

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

  For example, the unloading solenoid valve 56 and the standby solenoid valve 67 do not necessarily have to be on-off valves, and may be solenoid proportional pressure reducing valves. As a result, when at least one of the control valves 41 to 43 on the first circulation line 21 operates from the unloaded state, or all the control valves 41 to 46 stop operating and shift to the unloaded state. Can be reduced.

  For example, when the unloading solenoid valve 56 is an electromagnetic proportional pressure reducing valve, only when all the control valves 41 to 46 are detected to be in the neutral position by the first detection line 51 and the second detection line 53. Alternatively, a pilot hydraulic 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 at the neutral position, A pilot hydraulic signal may be generated and supplied to the standby pressure passage 66.

  Furthermore, the spool 9 of the unload valve 7 need not necessarily move to the cut position, and may move only between the normal position and the unload position. Further, the second unloading flow channel 62 does not necessarily have to be formed as an internal flow channel in the spool 9. For example, in the case where the spool 9 moves only between the normal position and the unloading position, as shown in FIGS. 5 and 6, the second unloading flow path 62 includes the inner peripheral surface of the sliding chamber 80 and the spool. It may be formed between nine.

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

  Further, as a means for moving the spool 9 of the unloading valve 7 to the cutting position, a cutting solenoid valve (not shown) may be used instead of the bucket operating valve 47. Alternatively, as shown in FIG. 7, an option operating valve 49 may be used instead of the bucket operating valve 47.

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

  In this configuration, when the option operation valve 49 is operated and the option control valve 48 is operated, 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, 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 passage 63. Therefore, not only the energy of the first pump 12 but also the energy of the second pump 14 can be used to drive 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, 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.

Reference Signs List 10 hydraulic drive system 12 first pump 13 first regulator 14 second pump 15 second regulator 17 control device 21 first circulation line 22 throttle 27 first selection valve 31 second circulation line 32 throttle 37 second selection valve 41 to 46 , 48 Control valve 47, 49 Operating valve 56 Solenoid valve for unloading 61 1st unloading flow path 62 2nd unloading flow path 63 Refilling path 67 Solenoid valve for standby 7 Unloading valve 71 Pilot port for unloading 72 For cutting Pilot port 8 housing 80 sliding chamber 81 first pump port 82 first output port 84 first tank port 85 second pump port 86 second output port 88 second tank port 9 spool 91 first land portion 92 second land portion 93 3rd land section

Claims (6)

An unloading valve provided in a first circulation line and a second circulation line in a hydraulic drive system of a construction machine, comprising:
A first pump port on the pump side of the first circulation line, a first output port on the throttling 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 throttling side of the
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 moving between an unloading position communicating the second pump port with the tank port;
Equipped with an unloading valve.   2. The en according to claim 1, wherein the spool moves the first pump port into communication with the first output port and moves the second pump port to a cutting position for separating the second pump port from the second output port and the tank port. Load valve. The housing has a sliding chamber slidably fitted with the spool;
A first unloading flow path connecting the first pump port and the tank port is formed between the inner peripheral surface of the sliding chamber and the spool.
The spool is formed with a second unloading flow passage communicating with the tank port as an internal flow passage,
The spool includes a first land portion which closes the first unloading channel at the normal position and the cutting position, and which opens the first unloading channel at the unloading position, the normal position and the cutting position. A second land portion for separating the second pump port from the second unloading flow path and communicating the second pump port with the second unloading flow path at the unloading position; 3. The unload valve according to claim 2, further comprising a third land portion for communicating the two pump ports with the second output port and separating the second pump port from the second output port at the cut position. An unloading valve according to claim 1;
A variable displacement first pump,
A plurality of control valves disposed in the first circulation line on extending to the tank from the first pump,
A throttle provided in the first circulation line downstream of the plurality of control valves;
A first regulator that changes a tilt angle of the first pump;
A variable displacement second pump,
A plurality of control valves disposed in the second circulation line on extending to the tank from the second pump,
A throttle provided in the second circulation line downstream of the plurality of control valves;
A second regulator that changes the tilt angle of the second pump;
A standby solenoid valve that switches 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 a higher one of a first negative control pressure, which is a pressure on the upstream side of the throttle in the first circulation line, and the standby pressure output from the standby solenoid valve to the first regulator;
A second negative control pressure, which is a pressure upstream of the throttle in the second circulation line, and a second selection valve for guiding the higher one of the standby pressure output from the standby solenoid valve to the second regulator Equipped
The unloading valve is provided in the first circulation line and the second circulation line on the upstream side of the diaphragm, for unloading for moving from a is the normal position neutral position the spool to the unloading position have a pilot port,
An unloading solenoid valve that switches whether to output a pilot pressure to the unloading pilot port;
A control device for controlling the standby solenoid valve and the unloading solenoid valve, wherein all of the plurality of control valves on the first circulation line and the second circulation line are at neutral positions. Outputting the waiting pressure from the waiting solenoid valve and outputting the pilot pressure from the unloading solenoid valve, and at least one of the plurality of control valves on the first circulation line and the second circulation line The hydraulic drive system of a hydraulic shovel, further comprising: 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. 4. The unloading valve according to claim 2 or 3;
A variable displacement first pump,
A plurality of control valves including the above extending from the first pump to a tank disposed in the first circulation line on the bucket control valve for controlling supply and discharge of hydraulic oil to the bucket cylinder,
A throttle provided in the first circulation line downstream of the plurality of control valves;
A first regulator that changes a tilt angle of the first pump;
A variable displacement second pump,
A plurality of control valves disposed in the second circulation line on extending to the tank from the second pump,
A throttle provided in the second circulation line downstream of the plurality of control valves;
A second regulator that changes the tilt angle of the second pump;
A standby solenoid valve that switches 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 a higher one of a first negative control pressure, which is a pressure on the upstream side of the throttle in the first circulation line, and the standby pressure output from the standby solenoid valve to the first regulator;
A second negative control pressure, which is a pressure upstream of the throttle in the second circulation line, and a second selection valve for guiding the higher one of the standby pressure output from the standby solenoid valve to the second regulator Equipped
The unloading valve is provided in the first circulation line and the second circulation line on the upstream side of the diaphragm, for unloading for moving from a is the normal position neutral position the spool to the unloading position pilot port, and the spool have a pilot port, for cutting to move to the cutting position from the normal position,
A supply passage for supplying hydraulic fluid from the upstream portion of the unload valve in the second circulation line to the bucket control valve;
An unloading solenoid valve that switches whether to output a pilot pressure to the unloading pilot port;
A bucket control valve that outputs a pilot pressure to a pilot port of the bucket control valve and the pilot port for cutting;
A control device for controlling the standby solenoid valve and the unloading solenoid valve, wherein all of the plurality of control valves on the first circulation line and the second circulation line are at neutral positions. Outputting the waiting pressure from the waiting solenoid valve and outputting the pilot pressure from the unloading solenoid valve, and at least one of the plurality of control valves on the first circulation line and the second circulation line The hydraulic drive system of a hydraulic shovel, further comprising: 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. 4. The unloading valve according to claim 2 or 3;
A variable displacement first pump,
Wherein disposed on the first extending from the pump to the tank the first circulation line on a plurality of control valves including optional control valve for controlling supply and discharge of hydraulic fluid for the option actuator,
A throttle provided in the first circulation line downstream of the plurality of control valves;
A first regulator that changes a tilt angle of the first pump;
A variable displacement second pump,
A plurality of control valves disposed in the second circulation line on extending to the tank from the second pump,
A throttle provided in the second circulation line downstream of the plurality of control valves;
A second regulator that changes the tilt angle of the second pump;
A standby solenoid valve that switches 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 a higher one of a first negative control pressure, which is a pressure on the upstream side of the throttle in the first circulation line, and the standby pressure output from the standby solenoid valve to the first regulator;
A second negative control pressure, which is a pressure upstream of the throttle in the second circulation line, and a second selection valve for guiding the higher one of the standby pressure output from the standby solenoid valve to the second regulator Equipped
The unloading valve is provided in the first circulation line and the second circulation line on the upstream side of the diaphragm, for unloading for moving from a is the normal position neutral position the spool to the unloading position pilot port, and the spool have a pilot port, for cutting to move to the cutting position from the normal position,
A supply passage for supplying hydraulic fluid from an upstream portion of the unload valve in the second circulation line to the option control valve;
An unloading solenoid valve that switches whether to output a pilot pressure to the unloading pilot port;
A pilot port of the option control valve and an option control valve for outputting a pilot pressure to the cutting pilot port;
A control device for controlling the standby solenoid valve and the unloading solenoid valve, wherein all of the plurality of control valves on the first circulation line and the second circulation line are at neutral positions. Outputting the waiting pressure from the waiting solenoid valve and outputting the pilot pressure from the unloading solenoid valve, and at least one of the plurality of control valves on the first circulation line and the second circulation line The hydraulic drive system of a hydraulic shovel, further comprising: 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.

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