JP2011064015A - Hydraulic circuit of construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic circuit of a construction machine, which inexpensively reduces a passage pressure loss caused till oil returned from a hydraulic actuator is discharged into a tank while maintaining the size of a changeover valve to a conventional level. <P>SOLUTION: A second changeover valve 22 for a second working machine includes a discharge passage 22c for discharging, into a tank T, the oil returned from a hydraulic actuator 80 for a first working machine. The hydraulic circuit 10 includes second changeover valve control mechanisms 30, 32, 34 for the second working machine controlling the changeover position of the second changeover valve 22 for the second working machine. When the first working machine 84 is in a working condition and in a specific working condition meeting with a predetermined condition, the second changeover valve 22 for the second working machine is changed over to communicate with the discharge passage 22c. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydraulic circuit of a construction machine such as a hydraulic excavator.

  The hydraulic excavator includes a plurality of operating parts such as a lower traveling body (base body), an upper swing body, a boom, an arm, and a bucket, and is widely used for construction work and the like.

  Often, these multiple actuation sites of a hydraulic excavator are actuated simultaneously. For example, when performing excavation work or floor digging work, which is a general work of a hydraulic excavator, simultaneous operation (combined operation) in which the boom and the arm are simultaneously operated is often performed. In order to perform such simultaneous operation smoothly, a plurality of hydraulic pumps are provided, and a boom switching valve and an arm switching valve are connected in tandem to each hydraulic pump, and the tandem connected passages are connected in parallel. A provided hydraulic circuit is used (for example, see Patent Document 1).

  An example of such a hydraulic circuit is the hydraulic circuit shown in FIG. The hydraulic circuit 100 includes a plurality of hydraulic pumps (first hydraulic pump 102 and second hydraulic pump 104) for driving hydraulic actuators in parallel. From the upstream to the downstream of the first hydraulic pump 102, the boom second switching valve 112 for adjusting the direction and flow rate of the driving hydraulic oil to the boom cylinder 106, and the driving hydraulic oil to the arm cylinder 108 An arm first switching valve 114 for adjusting the direction and flow rate is provided in tandem. Also, from the upstream side to the downstream side of the second hydraulic pump 104, the first boom switching valve 110 for adjusting the direction and flow rate of the driving hydraulic oil to the boom cylinder 106, and the driving pressure to the arm cylinder 108 An arm second switching valve 116 for adjusting the oil direction and flow rate is provided in tandem. Thereby, in the hydraulic circuit 100, the boom switching valve and the arm switching valve that are tandemly connected are tandemly connected to the hydraulic pumps 102 and 104 and provided in parallel.

  In the excavator 150 having the hydraulic circuit 100 shown in FIG. 5, when performing an arm opening operation, which is a general operation, the arm operation lever 120A of the arm remote control lever device 120 is operated to perform the first arm switching. The valve 114 and the arm second switching valve 116 are switched. Specifically, the arm operation lever 120A of the arm remote control lever device 120 is tilted rightward in FIG. 1, and the first arm switching valve 114 is switched to the p side and the second arm switching valve 116 is switched to the q side. Then, passages 114a and 116a for supplying pressure oil to the rod side of the arm cylinder 108 are opened, and pressure oil is supplied from the first hydraulic pump 102 and the second hydraulic pump 104 to the rod side of the arm cylinder 108. Further, when the arm first switching valve 114 is switched to the p side and the arm second switching valve 116 is switched to the q side, the discharge paths 114b and 116b for conducting the return oil from the bottom side of the arm cylinder 108 to the tank T are provided. Opened, the return oil from the bottom side of the arm cylinder 108 can be discharged to the tank T, and the arm cylinder 108 can contract.

  Therefore, when the arm operation lever 120A of the arm remote control lever device 120 is tilted rightward in FIG. 5 to switch the arm first switching valve 114 to the p side and the arm second switching valve 116 to the q side, the arm cylinder Pressure oil is supplied to the rod side of 108, and return oil from the bottom side of the arm cylinder 108 is discharged to the tank T, the arm cylinder 108 contracts, and the arm 152 performs an opening operation.

  The return oil discharged from the bottom side of the arm cylinder 108 is discharged to the tank T through the passage 108a, the arm switching valves 114 and 116, and the passages 114b and 116b from the bottom side of the arm cylinder 108. Therefore, in the case of the hydraulic circuit shown in FIG. 5 which is a conventional example, the passage where the return oil discharged from the bottom side of the arm cylinder 108 returns to the tank T is the passage 114b via the arm first switching valve 114 and the arm. There are two passages, the passage 116b, passing through the second switching valve 116.

  Note that the second boom switching valve 112 has a function of sending pressure oil for assisting the drive of the boom cylinder 106 from the first hydraulic pump 102 to the bottom side of the boom cylinder 106 when the boom 154 is started up. Among the three switching positions r, s, and t, the switching position r for feeding to the bottom side of the boom cylinder 106, and the switching position for passing the pressure oil downstream without supplying the pressure oil to the boom cylinder 106. Only two switching positions of s are used, and the switching position t is not used.

JP 2002-4339 A

  As described above, in the operation of opening the arm 152, the hydraulic oil is discharged from the bottom side of the arm cylinder 108. This return oil passes through the first and second switching valves 114, 116 for the arm. If the return oil passage is not sufficiently secured, the passage pressure loss tends to increase, and the energy loss in the arm opening operation tends to increase.

  As a measure for reducing the passage pressure loss, it is conceivable to increase the size of the first arm switching valve 114 and the second arm switching valve 116 (the size of the return oil passage). However, this method causes another problem that the manufacturing cost of the arm first switching valve 114 and the arm second switching valve 116 is increased, and that the mounting property to the airframe is deteriorated.

  The present invention has been made in view of such a problem, and reduces the passage pressure loss until the return oil from the hydraulic actuator is discharged into the tank at a low cost while maintaining the size of the switching valve at a conventional level. It is an object of the present invention to provide a hydraulic circuit for a construction machine that can be used.

  The present invention relates to a first switching valve for a first working machine, which is connected to a first hydraulic pump and switches the direction and flow rate of pressure oil supplied to a hydraulic actuator for the first working machine that drives the first working machine. And a first switching valve for the second working machine for switching the direction and flow rate of the pressure oil that is connected to the second hydraulic pump and is supplied to the hydraulic actuator for the second working machine that drives the second working machine, A second working machine second switch is connected in tandem to the first hydraulic pump first switching valve for the first working machine and switches the direction and flow rate of the pressure oil supplied to the second working machine hydraulic actuator. And a second switching valve for the second working machine, the second switching valve for the second working machine includes a discharge passage for discharging the return oil from the hydraulic actuator for the first working machine to the tank. The hydraulic circuit includes the first circuit. A second work valve second switching valve control mechanism for controlling a switching position of the work machine second switching valve; a work state in which the operation of the first work machine is performed, and a specific condition that matches a predetermined condition The above-mentioned problem is solved by switching the second switching valve for the second working machine so that the discharge passage communicates in the working state.

  In the present invention, the second switching valve for the second working machine includes a discharge passage for discharging the return oil from the hydraulic actuator for the first working machine to the tank, and the second switching valve for the second working machine A second switching valve control mechanism for the second working machine that controls the switching position, and is a working state in which the first working machine is operated and in a specific working state that meets a predetermined condition, The second switching valve for the two work machines is switched so that the discharge passage communicates. For this reason, in this invention, the return oil of the hydraulic actuator for 1st working machines can be guide | induced to a tank via the 2nd switching valve for 2nd working machines other than the 1st switching valve for 1st working machines. . Therefore, it is not necessary to increase the size of the switching valve for the first work machine, causing the problem that the manufacturing cost of the switching valve for the first work machine increases and the problem that the mounting property to the machine body is deteriorated. In addition, it is possible to reduce the passage pressure loss until the return oil from the first working machine hydraulic actuator is discharged to the tank. That is, in the present invention, while maintaining the size of the switching valve for the first work machine at a conventional level, the passage pressure loss until the return oil from the hydraulic actuator for the first work machine is discharged to the tank can be reduced at a low cost. Can do.

  In the hydraulic circuit, the second hydraulic pump is further connected in tandem with the first switching valve for the second working machine, to switch the direction and flow rate of the pressure oil supplied to the hydraulic actuator for the first working machine. A second switching valve for the first working machine may be provided.

  In the above hydraulic circuit, the first working machine is an arm, and the first working machine first switching valve and the first working machine second switching valve are an arm first switching valve and an arm second switching valve. The first working machine hydraulic actuator is an arm cylinder, the second working machine is a boom, the second working machine first switching valve and the second working machine second switching valve are An arm that indicates the degree of the opening operation of the arm, whether the first working valve for the boom and the second switching valve for the boom, and the boom hydraulic actuator is a boom cylinder This can be determined by comparing whether at least one of the opening parameters is greater than a predetermined threshold.

  In this case, when the arm operating lever for operating the first arm switching valve and the second arm switching valve is provided, one of the arm opening parameters can be set as the operation amount of the arm operating lever. .

  When arm pilot pressure detecting means for detecting at least one of a pilot pressure for switching the first arm switching valve and a pilot pressure for switching the second arm switching valve is provided, one of the arm opening parameters is provided. Can be a pilot pressure for switching the first switching valve for the arm or a pilot pressure for switching the second switching valve for the arm.

  Further, when arm cylinder rod contraction thrust detecting means for detecting a thrust when the arm cylinder is contracted is provided, one of the arm opening parameters can be a thrust when the arm cylinder is contracted.

  When the arm cylinder pressure difference detecting means for detecting the pressure difference between the pressure oil on the rod side and the bottom side of the arm cylinder is provided, one of the arm opening parameters is set as the pressure difference in the arm cylinder. can do.

  When arm cylinder rod contraction speed detecting means for detecting the contraction speed of the rod of the arm cylinder is provided, one of the arm opening parameters can be the rod contraction speed of the arm cylinder.

  In addition, when arm angular velocity detecting means for detecting an increasing speed of an angle between the arm and the boom is provided, one of the arm opening parameters can be an increasing speed of an angle between the arm and the boom. .

  Further, whether or not the specific work state is present may be determined including a result of comparing whether or not at least one boom raising parameter indicating a degree of the boom raising operation is smaller than a predetermined threshold value. .

  In this case, when the boom operation lever for operating the first boom switching valve and the second boom switching valve is provided, one of the boom raising parameters can be set as the operation amount of the boom operation lever. .

  When a boom pilot pressure detecting means for detecting at least one of a pilot pressure for switching the first boom switching valve and a pilot pressure for switching the second boom switching valve is provided, one of the boom raising parameters is provided. The pilot pressure for switching the first switching valve for the boom or the pilot pressure for switching the second switching valve for the boom.

  Further, when the boom cylinder rod extension thrust detecting means for detecting the thrust when the boom cylinder rod is extended is provided, one of the boom raising parameters can be set as the thrust when the boom cylinder rod is extended.

  When the boom cylinder pressure difference detecting means for detecting the pressure difference between the pressure oil on the rod side of the boom cylinder and the pressure oil on the bottom side is provided, one of the boom raising parameters is set as the pressure difference in the boom cylinder. can do.

  Further, when the boom cylinder rod extension speed detecting means for detecting the extension speed of the rod of the boom cylinder is provided, one of the boom raising parameters can be set as the rod extension speed of the boom cylinder.

  In addition, when a boom angle speed detecting means for detecting an increasing speed of the rising angle from the horizontal direction of the boom is provided, one of the boom raising parameters may be an increasing speed of the rising angle from the horizontal direction of the boom. it can.

  Further, the present invention is connected to the first hydraulic pump, connected to the first hydraulic valve for switching the direction and flow rate of the pressure oil supplied to the arm cylinder that drives the arm, and to the second hydraulic pump. A second switching valve for the arm for switching the direction and flow rate of the pressure oil supplied to the arm cylinder, and the second hydraulic pump is connected in tandem with the second switching valve for the arm to drive the boom. A first switching valve for boom for switching the direction and flow rate of pressure oil supplied to the boom cylinder, and the first hydraulic pump are connected in tandem with the first switching valve for arm and supplied to the boom cylinder. In a hydraulic circuit for a construction machine including a second switching valve for a boom for switching the direction and flow rate of pressure oil, the second switching valve for the boom is a return from the bottom side of the arm cylinder. A discharge passage for discharging oil to the tank, and the hydraulic circuit applies an arm opening pilot pressure for switching the first switching valve for the arm or the second switching valve for the arm in the direction of opening the arm. A first pilot passage that leads to a pilot port at one end of the second switching valve, and a boom raising pilot pressure that switches the first switching valve for the boom in the boom raising direction to the pilot port at the other end of the second switching valve for the boom The above-described problem can also be solved by comprising the second pilot passage.

  Further, by providing a pilot switching valve for switching the degree of communication of the first pilot passage according to the arm opening pilot pressure and the boom raising pilot pressure in the first pilot passage. It becomes easier to ensure smoothness of operation.

  According to the present invention, it is possible to reduce the passage pressure loss until the return oil from the hydraulic actuator is discharged into the tank at a low cost while maintaining the size of the switching valve at a conventional level.

The figure which shows the structure of the hydraulic circuit of the hydraulic shovel which concerns on 1st Embodiment of this invention. The figure which shows the structure of the hydraulic circuit of the hydraulic shovel which concerns on 2nd Embodiment of this invention. The figure which shows the structure of the hydraulic circuit of the hydraulic shovel which concerns on 3rd Embodiment of this invention. The figure which shows the structure of the hydraulic circuit of the hydraulic shovel which concerns on 4th Embodiment of this invention. The figure which shows an example of a structure of the hydraulic circuit of the conventional hydraulic shovel

  Hereinafter, an example of a preferred embodiment of a hydraulic circuit of a hydraulic excavator according to the present invention will be described in detail based on the drawings.

  FIG. 1 is a diagram showing a configuration of a hydraulic circuit of a hydraulic excavator according to the first embodiment of the present invention.

  The hydraulic circuit 10 includes a first hydraulic pump 12, a second hydraulic pump 14, a first switching valve for arm (first switching valve for first working machine) 16, and a second switching valve for arm (first working valve). Second switching valve for machine) 18, first switching valve for boom (first switching valve for second work machine) 20, second switching valve for boom (second switching valve for second work machine) 22, An arm remote control lever device 24, a boom remote control lever device 26, a pilot pressure sensor 28, a controller 30, an electromagnetic proportional valve 32, and a pilot hydraulic pump 34 are provided, and an arm cylinder (hydraulic pressure for the first working machine) is provided. Actuator 80 and boom cylinder (hydraulic actuator for second working machine) 82 are supplied with pressure oil, and arm (first working machine) 84 and boom (second working machine) 86 are operated to perform excavation work and flooring. Various works such as digging work The causes to the hydraulic excavator 78. Reference numeral 88 denotes a bucket. When excavation or floor digging is performed, as the preparation operation, the arm 84 opening operation without the boom 86 raising operation or the arm 84 opening operation and the boom 86 lowering operation operation are performed simultaneously. Must be opened to a predetermined position and the boom 86 must be lowered to a predetermined position as necessary. In the present embodiment, a work state in which the arm is opened and that matches a predetermined condition is referred to as a “specific work state”. The “predetermined condition” will be specifically described as appropriate in the following description.

  The first hydraulic pump 12 and the second hydraulic pump 14 are arranged in parallel. A tandem passage 38 is connected to the first hydraulic pump 12, and pressure oil supplied from the first hydraulic pump 12 through the tandem passage 38 is supplied to the arm cylinder 80 and / or the boom cylinder 82. The tandem passage 38 is provided with the second boom switching valve 22 on the upstream side and the arm first switching valve 16 on the downstream side. The first arm switching valve 16 and the second boom switching valve are provided. 22 is connected in tandem.

  A tandem passage 42 is connected to the second hydraulic pump 14, and pressure oil supplied from the second hydraulic pump 14 via the tandem passage 42 is supplied to the arm cylinder 80 and / or the boom cylinder 82. The tandem passage 42 is provided with the first boom switching valve 20 on the upstream side and the second arm switching valve 18 on the downstream side. The second arm switching valve 18 and the first boom switching valve are provided. 20 is connected in tandem.

  The first arm switching valve 16 is a three-position six-port switching valve, and includes three switching positions A, B, and C. The direction and flow rate of the pressure oil from the first hydraulic pump 12 toward the arm cylinder 80 To control. Pilot ports 16a and 16b are provided at both ends of the spool of the arm first switching valve 16, and pilot pressure is supplied from the pilot passages 24a and 24b, respectively.

  The spool of the arm first switching valve 16 moves when the operator operates the arm remote control lever device 24, and controls the direction and flow rate of the pressure oil supplied from the first hydraulic pump 12 to the arm cylinder 80. The pressure oil supplied from the first hydraulic pump 12 to the arm cylinder 80 passes from the parallel passage 40 or the tandem passage 38 and the parallel passage 40 through the arm first switching valve 16 and the arm passages 80a and 80b. It is supplied to the arm cylinder 80.

  Further, the first arm switching valve 16 is provided with a discharge passage 16 c for discharging return oil from the bottom side of the arm cylinder 80 to the tank T. When the first arm switching valve 16 is in the switching position A, the return oil from the bottom side of the arm cylinder 80 is discharged to the tank T via the arm passage 80b, the discharge passage 16c, and the tank passage 16d.

  A bypass passage 80 h is provided in parallel with the first arm switching valve 16. The bypass passage 80h is a passage that connects the branch point 80g on the arm passage 80b that is connected to the bottom side of the arm cylinder 80 and the port 22d that is the downstream port of the second boom switching valve 22. The bypass passage 80h communicates with the tank passage 22e that communicates with the tank T via the discharge passage 22c of the second boom switching valve 22 when the second boom switching valve 22 is in the switching position I. Thus, when the boom second switching valve 22 is in the switching position I, the return oil from the bottom side of the arm cylinder 80 is tanked via the arm passage 80b, the bypass passage 80h, the discharge passage 22c, and the tank passage 22e. Discharged to T.

  The second arm switching valve 18 is a three-position six-port switching valve, and includes three switching positions D, E, and F. The direction and flow rate of the pressure oil from the second hydraulic pump 14 toward the arm cylinder 80 are as follows. To control. Pilot ports 18a and 18b are respectively provided at both ends of the spool of the arm second switching valve 18, and pilot pressure is supplied from the pilot passages 24a and 24b, respectively.

  Similarly to the spool of the arm first switching valve 16, the spool of the arm second switching valve 18 moves when the operator operates the arm remote control lever device 24, and the direction of the pressure oil supplied to the arm cylinder 80. And control the flow rate. The pressure oil supplied from the second hydraulic pump 14 to the arm cylinder 80 passes from the parallel passage 44 or the tandem passage 42 and the parallel passage 44 through the arm switching valve 18 and the arm joining passages 80c and 80d. At the joining points 80e and 80f, they join the arm passages 80a and 80b and are supplied to the arm cylinder 80.

  Further, the second arm switching valve 18 is provided with a discharge passage 18 c for discharging return oil from the bottom side of the arm cylinder 80 to the tank T. When the arm second switching valve 18 is in the switching position D, the return oil from the bottom side of the arm cylinder 80 is discharged to the tank T via the arm passage 80b, the discharge passage 18c, and the tank passage 18d.

  The first boom switching valve 20 is a three-position six-port switching valve, and includes three switching positions J, K, and L. The direction and flow rate of pressure oil from the second hydraulic pump 14 toward the boom cylinder 82. To control. Pilot ports 20a and 20b are respectively provided at both ends of the spool of the first boom switching valve 20, and pilot pressure is supplied from the pilot passages 26a and 26b, respectively.

  The spool of the first boom switching valve 20 moves when the operator operates the boom remote control lever device 26, and controls the direction and flow rate of the pressure oil supplied from the second hydraulic pump 14 to the boom cylinder 82. The pressure oil supplied from the second hydraulic pump 14 to the boom cylinder 82 is supplied from the tandem passage 42 to the boom cylinder 82 through the boom first switching valve 20 and the boom passages 82a and 82b.

  The second boom switching valve 22 is a three-position six-port switching valve, and has three switching positions G, H, and I. The direction and flow rate of the pressure oil from the first hydraulic pump 12 to the boom cylinder 82. To control. Pilot ports 22a and 22b are provided at both ends of the spool of the second boom switching valve 22, respectively. Pilot pressure is supplied from the pilot passage 26a to the pilot port 22a, and from the pilot passage 34a to the pilot port 22b. Pilot pressure is supplied.

  At the switching position G, the boom junction passage 82 c communicates, and the pressure oil from the first hydraulic pump 12 is supplied to the bottom side of the boom cylinder 82. Further, the return oil from the rod side of the boom cylinder 82 is not so much and only a passage through which the return oil returns to the tank T passes through the first switching valve 20 for the boom is sufficient. Is not provided at the switching position G.

  At the switching position H, the pressure oil from the first hydraulic pump 12 flows through the tandem passage 38 directly downstream, and the pressure oil from the first hydraulic pump 12 is not supplied to the boom cylinder 82. Further, the switching position H is not provided with a passage through which the return oil to the tank T passes.

  At the switching position I, the pressure oil from the first hydraulic pump 12 flows through the tandem passage 38 to the downstream side as it is, and the pressure oil from the first hydraulic pump 12 is not supplied to the boom cylinder 82.

  At the switching position I, a discharge passage 22c through which return oil from the bottom side of the arm cylinder 80 to the tank T passes is provided. Therefore, when the boom second switching valve 22 is in the switching position I, a part of the return oil from the bottom side of the arm cylinder 80 is a passage 80b, a branch point 80g, a bypass passage 80h, a discharge passage 22c, and a tank passage 22e. And then discharged to the tank T.

  Similarly to the spool of the first boom switching valve 20, the spool of the second boom switching valve 22 moves when the operator operates the boom remote control lever device 26, and is supplied from the first hydraulic pump 12 to the boom cylinder 82. Control the direction and flow rate of pressurized oil. The pressure oil supplied from the first hydraulic pump 12 to the boom cylinder 82 passes from the tandem passage 38 through the boom second switching valve 22 (switching position G) to the boom junction passage 82c, and reaches the boom passage at the junction 82d. 82m is supplied to the bottom side of the boom cylinder 82. However, as will be described later in detail, the switching position of the second boom switching valve 22 is determined only by the pilot pressure determined by the amount of operation of the operation lever 26A of the boom remote control lever device 26 performed by the operator. Instead, the controller 30 determines the pilot pressure determined by the operation amount of the operation lever 24A of the arm remote control lever device 24.

  The pilot pressure sensor (arm pilot pressure detecting means) 28 measures the pilot pressure in the pilot passage 24 a supplied to the pilot port 16 a of the arm first switching valve 16 and the pilot port 18 a of the arm second switching valve 18. The obtained pressure data is sent to the controller 30 via the electric signal line 28a.

  Based on the pressure data sent from the pilot pressure sensor 28, the controller 30 determines whether the working state of the hydraulic excavator 78 is a working state in which the arm is opened and is a specific working state that matches a predetermined condition. Based on the determination result, the electromagnetic proportional valve 32 is operated via the electric signal line 30a to adjust the opening of the pilot passage 34a, and the pilot hydraulic pressure is supplied to the pilot port 22b of the second boom switching valve. The switching position of the boom second switching valve 22 is adjusted by adjusting the pilot pressure supplied from the pump 34.

  Here, when the pressure data sent from the pilot pressure sensor 28 indicates a large pilot pressure, the switching amount to the position A side of the arm first switching valve 16 and the position D of the arm second switching valve 18 are shown. Therefore, the amount of oil supplied to the rod side of the arm cylinder 80 is increased, and the amount of return oil from the bottom side of the arm cylinder 80 is also increased.

  Also, from the structure of the hydraulic cylinder, the pressure receiving area on the bottom side is larger than the pressure receiving area on the rod side, and the amount of oil discharged from the bottom side is the ratio of the pressure receiving area on the bottom side to the pressure receiving area on the rod side. It is an amount obtained by multiplying (the pressure receiving area on the bottom side) / (the pressure receiving area on the rod side) by the amount of oil supplied to the rod side. Therefore, the amount of return oil from the bottom side of the arm cylinder 80 is further larger than the amount of oil supplied to the rod side of the arm cylinder 80.

  Therefore, when the pressure data sent from the pilot pressure sensor 28 indicates a large pilot pressure, the controller 30 sends a command to the solenoid portion 32a of the electromagnetic proportional valve 32 via the electric signal line 30a, so that the pilot passage 34a The pilot pressure applied to the pilot port 22b of the second boom switching valve 22 is increased by increasing the opening, and the second boom switching valve 22 is switched to the position I side. When the second boom switching valve 22 is switched to the position I side, the bypass passage 80h, the discharge passage 22c, and the tank passage 22e communicate with each other. As a result, the return oil discharged from the bottom side of the arm cylinder 80 flowing through the arm passage 80b partially flows into the bypass passage 80h at the branch point 80g, and is discharged to the tank T through the discharge passage 22c and the tank passage 22e. Is done.

  The electromagnetic proportional valve 32 receives a command from the controller 30, adjusts the opening degree of the pilot passage 34a, adjusts the pilot pressure supplied to the pilot port 22b of the second boom switching valve 22, and controls the second boom valve. It has the role of adjusting the switching position of the switching valve 22. When an electric signal is sent from the controller 30 to the solenoid portion 32a of the electromagnetic proportional valve 32 via the electric signal line 30a, the electromagnetic proportional valve 32 switches the spool of the electromagnetic proportional valve 32 in accordance with the electric signal, and the pilot passage 34a Adjust the opening. As a result, the pilot pressure supplied to the pilot port 22b of the second boom switching valve 22 is adjusted, and the switching position of the second boom switching valve 22 is adjusted.

  Since the controller 30, the electromagnetic proportional valve 32, and the pilot hydraulic pump 34 control the switching position of the second boom switching valve 22 as described above, the second boom switching valve control mechanism (second working machine first) is controlled. 2 switching valve control mechanism).

  Here, the characteristic points of the configuration of the present embodiment described above are that the bypass passage 80h is provided in parallel with the first switching valve 16 for the arm, and the discharge passage 22c is connected to the second switching valve 22 for the boom. Is provided.

  Thereby, the passage through which the return oil from the bottom side of the arm cylinder 80 is discharged to the tank T is the first passage that leads to the tank T via the discharge passage 16c of the first switching valve 16 for the arm in this embodiment. In addition to the second passage leading to the tank T via the discharge passage 18c of the second switching valve 18 for the arm and the tank via the discharge passage 22c of the bypass passage 80h and the second switching valve 22 for the boom. The third passage leading to T exists, and the passage pressure loss until the return oil from the bottom side of the arm cylinder 80 is discharged to the tank T can be reduced. The provision of the bypass passage 80h and the provision of the discharge passage 22c in the second boom switching valve 22 do not significantly increase the cost and do not impair the mountability to the hydraulic excavator 78.

  Next, the operation and action of the hydraulic circuit 10 according to the first embodiment configured as described above will be described.

  In FIG. 1, when the operator tilts the operation lever 24A of the arm remote control lever device 24 to the left and applies pilot pressure to the pilot ports 16a and 18a via the pilot passage 24a, the arm first switching valve 16 is moved to the position. The arm second switching valve 18 is switched to position D. Thus, the pressure oil from the first hydraulic pump 12 passes through the arm passage 80a from the parallel passage 40, or the tandem passage 38 and the parallel passage 40, through the arm first switching valve 16 (switching position A). The pressure oil supplied to the rod side of the arm cylinder 80 and from the second hydraulic pump 14 passes from the parallel passage 44 or the tandem passage 42 and the parallel passage 44 through the arm second switching valve 18 (switching position D), The gas is supplied to the rod side of the arm cylinder 80 through the arm joining passage 80c, the joining point 80e, and the arm passage 80a. As a result, pressure oil is supplied from both the first hydraulic pump 12 and the second hydraulic pump 14 to the rod side of the arm cylinder 80, the rod of the arm cylinder 80 can be greatly contracted, and the arm 84 performs a large opening operation. It can be carried out.

  On the other hand, as described above, due to the structure of the hydraulic cylinder, the pressure receiving area on the bottom side is larger than the pressure receiving area on the rod side, and the amount of return oil discharged from the bottom side is lower than the pressure receiving area on the rod side. It is an amount obtained by multiplying the amount of oil supplied to the rod side by the ratio of the pressure receiving area (pressure receiving area on the bottom side) / (pressure receiving area on the rod side). Therefore, when the arm 84 opens, a large amount of return oil that exceeds the amount of oil supplied to the rod side of the arm cylinder 80 is discharged from the bottom side.

  For this reason, the passage pressure loss until the return oil from the bottom side of the arm cylinder 80 is discharged to the tank T tends to be large. However, in this embodiment, the return oil from the bottom side of the arm cylinder 80 as described above. Is discharged to the tank T through the discharge passage 16c of the arm first switching valve 16 and the tank through the discharge passage 18c of the arm second switching valve 18 and the first passage leading to the tank T. In addition to the second passage that leads to T, there is a third passage that leads to the tank T via the bypass passage 80h and the discharge passage 22c of the second boom switching valve 22. In the present embodiment, by using these three passages simultaneously, the return oil from the bottom side of the arm cylinder 80 is discharged to the tank, so that the passage pressure loss can be reduced.

  The operation at this time will be specifically described.

  When the operating lever 24A of the arm remote control lever device 24 is tilted to the left in FIG. 1 and pilot pressure is applied to the pilot ports 16a and 18a via the pilot passage 24a, the arm first switching valve 16 is moved as described above. The position is switched to the position A side, the arm second switching valve 18 is switched to the position D side, and pressure oil is supplied from both the first hydraulic pump 12 and the second hydraulic pump 14 to the rod side of the arm cylinder 80, and the arm The rod of the cylinder 80 contracts greatly. At the same time, a large amount of return oil exceeding the amount of oil supplied to the rod side of the arm cylinder 80 is discharged from the bottom side.

  Here, since the first arm switching valve 16 is switched to the position A side and the second arm switching valve 18 is switched to the position D side, the return oil discharged from the bottom side of the arm cylinder 80 is used for the arm. It is discharged to the tank T through the passage 80b, the discharge passage 16c of the first switching valve 16 for the arm, and the tank passage 16d, and is also discharged to the tank T, the discharge passage 18c of the second switching valve for arm 18, the tank passage 18d. To the tank T.

  The pilot pressure sensor 28 measures the pilot pressure data in the pilot passage 24a and sends it to the controller 30, but the first arm switching valve 16 is completely in the position A and the second arm switching valve 18 is completely in the position D. When a pilot pressure to be switched is applied to the pilot ports 16a and 18a, the pilot pressure data sent to the controller 30 indicates a large pilot pressure and exceeds a predetermined threshold (less than the pilot pressure). An appropriate value is set as a predetermined threshold).

  In such a case, the controller 30 sends a command to the solenoid portion 32a of the electromagnetic proportional valve 32 via the electric signal line 30a to increase the opening of the pilot passage 34a, and the pilot port of the boom second switching valve 22 The pilot pressure applied to 22b is increased, and the second boom switching valve 22 is switched to the position I side. When the second boom switching valve 22 is switched to the position I side, the bypass passage 80h, the discharge passage 22c, and the tank passage 22e communicate with each other. As a result, the return oil discharged from the bottom side of the arm cylinder 80 flowing through the arm passage 80b partially flows into the bypass passage 80h at the branch point 80g, and is discharged to the tank T through the discharge passage 22c and the tank passage 22e. Is done.

  In this way, in the present embodiment, the tank passes through the first passage that leads to the tank T via the discharge passage 16c of the first arm switching valve 16 and the discharge passage 18c of the second switching valve 18 for arm. In addition to the second passage leading to T, the third passage leading to the tank T via the bypass passage 80h and the discharge passage 22c of the second boom switching valve 22 is also used from the bottom side of the arm cylinder 80. The return pressure loss can be reduced by discharging the return oil to the tank T.

  In the present embodiment, the pilot pressure data measured by the pilot pressure sensor 28 is used as a parameter to determine whether or not it is in a specific work state. However, the status of the opening operation of the arm 84 is determined. Other indices may be used as parameters as long as the parameters can be used (arm opening parameters). For example, the operation amount of the arm operation lever 24A (the operation amount in the left direction in FIG. 1) may be used as the arm opening parameter. Further, for example, an arm cylinder rod contraction speed detection sensor for detecting the contraction speed of the rod of the arm cylinder 80 may be provided, and the rod contraction speed of the arm cylinder 80 may be used as the arm opening parameter. Further, for example, an arm angular velocity detection sensor for detecting an increasing speed of an angle formed by the arm 84 and the boom 86 may be provided, and an increasing speed of an angle formed by the arm 84 and the boom 86 may be used as an arm opening parameter.

  Next, in this embodiment, when the opening operation of the arm 84 and the raising operation of the boom 86 are performed simultaneously, that is, the arm operation lever 24A of the arm remote control lever device 24 is tilted to the left in FIG. The operation when the boom operation lever 26A of the remote control lever device 26 is tilted to the right in FIG. 1 will be described.

  In FIG. 1, when the operator tilts the operation lever 26A of the boom remote control lever device 26 to the right and applies pilot pressure to the pilot port 20a of the first boom switching valve 20 via the pilot passage 26a, The 1 switching valve 20 is switched to the position J side, the pressure oil from the second hydraulic pump 14 is supplied to the bottom side of the boom cylinder 82 through the tandem passage 42 and the boom passage 82a, and the rod of the boom cylinder 82 is extended. Then, the boom 86 stands up.

  The pilot pressure in the pilot passage 26a is also applied to the pilot port 22a of the second boom switching valve 22 so as to switch the second boom switching valve 22 to the position G side. When the boom second switching valve 22 is switched to the position G side, pressure oil is also supplied from the first hydraulic pump 12 to the bottom side of the boom cylinder 82, and the rod extension speed of the boom cylinder 82 increases. On the other hand, the pilot pressure of the pilot passage 34a is applied to the other pilot port 22b of the second boom switching valve 22. Therefore, the switching position of the second boom switching valve 22 is determined by the magnitude of the pilot pressure applied to the pilot ports 22a and 22b.

  Here, the pilot pressure data (pilot pressure data applied to the pilot ports 16a and 18a) of the pilot passage 24a measured by the pressure sensor 28 is sent to the controller 30 via the electric signal line 28a. When the pilot pressure applied to the pilot ports 16a, 18a of the arm switching valves 16, 18 exceeds a predetermined threshold value, the controller 30 increases the pilot pressure applied to the pilot port 22b of the second boom switching valve 22. Thus, while controlling the electromagnetic proportional valve 32 (so that the second boom switching valve 22 is switched to the position I side), the pilot pressure applied to the pilot port 22b is controlled with a predetermined upper limit. For this reason, during a large rise operation of the boom 86 in which a pilot pressure exceeding the predetermined upper limit pilot pressure is applied to the pilot port 22a of the boom second switching valve 22, the boom second switching valve 22 is positioned at the position G side. The pressure oil from the first hydraulic pump 12 can be supplied to the bottom side of the boom cylinder 82. As a result, the hydraulic oil is supplied from both the first hydraulic pump 12 and the second hydraulic pump 14 to the bottom side of the boom cylinder 82, and the boom 86 can be smoothly raised even in a large rise operation. be able to.

  Next, a hydraulic circuit 70 for a hydraulic excavator according to a second embodiment of the present invention will be described.

  FIG. 2 is a diagram showing a configuration of a hydraulic circuit 70 of a hydraulic excavator according to the second embodiment of the present invention. The same components as those of the hydraulic circuit 10 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The hydraulic circuit 70 according to the second embodiment includes, in the configuration of the hydraulic circuit 10 according to the first embodiment, an arm cylinder pressure sensor 52 that detects pressure of pressure oil on the rod side of the arm cylinder 80, and a bottom of the arm cylinder 80. It is the structure which added the arm cylinder pressure sensor 54 which detects the pressure of the side pressure oil. The cylinder pressure data detected by the arm cylinder pressure sensor 52 is sent to the controller 50 via the electric signal line 52a, and the cylinder pressure data detected by the arm cylinder pressure sensor 54 is sent to the controller 50 via the electric signal line 54a. The controller 50 calculates the thrust when the rod of the arm cylinder 80 contracts based on the two cylinder pressure data sent.

  When the calculated thrust at the time of rod contraction of the arm cylinder 80 exceeds a predetermined threshold value, the controller 50 is in a specific work state (a work state in which the arm is opened and a work state that matches a predetermined condition). It is determined that there is a command, and a command is sent to the electromagnetic proportional valve 32 via the electric signal line 30a so that the opening of the pilot passage 34a is increased, and the pilot pressure applied to the pilot port 22b of the second boom switching valve 22 is increased. . As a result, the second boom switching valve 22 is switched to the position I side, and the bypass passage 80h, the discharge passage 22c, and the tank passage 22e communicate with each other. As a result, the return oil discharged from the bottom side of the arm cylinder 80 flowing through the arm passage 80b partially flows into the bypass passage 80h at the branch point 80g, and is discharged to the tank T through the discharge passage 22c and the tank passage 22e. Therefore, the passage pressure loss when the return oil from the bottom side of the arm cylinder 80 is discharged to the tank T can be reduced.

  Similarly to the first embodiment, since the pilot pressure data of the pilot passage 24a measured by the pilot pressure sensor 28 is also sent to the controller 50, this data is added to the thrust of the arm cylinder 80 when the rod contracts. The controller 50 may determine whether or not it is in a specific work state.

  In the hydraulic circuit 70 according to the second embodiment, the controller 50 controls the arm cylinder 80 based on the cylinder pressure data detected by the arm cylinder pressure sensors 52 and 54 (data on the pressure oil pressure on the rod side and the bottom side). Therefore, the arm cylinder pressure sensors 52 and 54 and the controller 50 can be referred to as arm cylinder rod contraction thrust detection means.

  In the hydraulic circuit 70 according to the second embodiment, the controller 50 calculates the thrust when the rod of the arm cylinder 80 is contracted based on the cylinder pressure data detected by the arm cylinder pressure sensors 52 and 54, and calculates the calculated arm cylinder. When the thrust at the time of 80 rod contraction exceeds a predetermined threshold value, the controller 50 determines that it is in a specific work state (a work state in which the arm is opened and that matches a predetermined condition). However, without calculating the thrust when the rod of the arm cylinder 80 contracts, the pressure difference between the pressure oil on the rod side of the arm cylinder 80 and the pressure oil on the bottom side (from the pressure of the pressure oil on the rod side It may be determined whether or not it is in a specific working state by comparing whether or not the difference obtained by reducing the pressure oil pressure is greater than a predetermined threshold. In this case, the arm cylinder pressure sensors 52 and 54 and the controller 50 can be said to be arm cylinder pressure difference detection means.

  Next, a hydraulic circuit 72 of a hydraulic excavator according to a third embodiment of the present invention will be described.

  FIG. 3 is a diagram showing a configuration of a hydraulic circuit 72 of a hydraulic excavator according to the third embodiment of the present invention. The same components as those of the hydraulic circuit 10 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The hydraulic circuit 72 according to the third embodiment includes a pilot that is added to the pilot port 20a of the first boom switching valve 20 and the pilot port 22a of the second boom switching valve 22 in the configuration of the hydraulic circuit 10 according to the first embodiment. A pilot pressure sensor 56 for detecting the pressure (pilot pressure in the pilot passage 26a) is added. The pilot pressure data detected by the pilot pressure sensor 56 is sent to the controller 58 via the electric signal line 56a. Similarly to the first embodiment, the pilot pressure data of the pilot passage 24a detected by the pilot pressure sensor 28 is also sent to the controller 58.

  The controller 58 grasps the state of the opening operation of the arm 84 based on the pilot pressure data detected by the pilot pressure sensor 28, and grasps the state of the raising operation of the boom 86 based on the pilot pressure data detected by the pilot pressure sensor 56. To determine whether it corresponds to a specific work state. Specifically, it is determined whether or not the pilot pressure based on the pilot pressure data detected by the pilot pressure sensor 28 exceeds a predetermined threshold, and the pilot pressure based on the pilot pressure data detected by the pilot pressure sensor 56 is determined to be the predetermined threshold. It is judged whether it exceeds.

  When the pilot pressure based on the pilot pressure data detected by the pilot pressure sensor 28 exceeds a predetermined threshold value, it can be determined that the opening operation of the arm 84 is large, but the pilot pressure detected by the pilot pressure sensor 56 is detected. If the pilot pressure based on the data exceeds a predetermined threshold value, it can be determined that the boom 86 has been raised. In such a case, if the second switching valve 22 for the boom is switched to the position I side, pressure oil is not supplied from the first hydraulic pump to the boom cylinder 82, and the boom 86 cannot be raised smoothly. Therefore, even if the pilot pressure based on the pilot pressure data detected by the pilot pressure sensor 28 exceeds a predetermined threshold value, the controller 58 determines that the pilot pressure based on the pilot pressure data detected by the pilot pressure sensor 56 is equal to the predetermined threshold value. Is not determined to be in the “specific work state”, the electromagnetic proportional valve 32 is controlled so that the pilot passage 34 a does not communicate with the pilot port 22 b of the second boom switching valve 22. Prevent pilot pressure from being supplied. As a result, the second boom switching valve 22 is switched to the position G side, the pressure oil from the first hydraulic pump 12 is also sent to the bottom side of the boom cylinder 82, and the boom 86 can be raised smoothly. .

  That is, in the hydraulic circuit 72 according to the third embodiment, it is determined whether or not the “specific work state” is satisfied, considering not only the state of the opening operation of the arm 84 but also the state of the lifting operation of the boom 86. When the boom 86 is not hindered (when the boom 86 is stopped or lowered), the second boom switching valve 22 is switched to the position I side. The passage pressure loss when the return oil from the bottom side of the arm cylinder 80 is discharged to the tank T can be reduced within a range that does not hinder the operation of 86.

  In the present embodiment, the pilot pressure data measured by the pilot pressure sensor 56 is also added as a parameter to determine whether or not it is in a specific working state. However, the state of the boom 86 raising operation is determined. Other parameters may be used as parameters as long as the parameters can be set (boom raising parameters). For example, the operation amount of the boom operation lever 26A (the operation amount in the right direction in FIG. 1) may be used as the boom raising parameter. Further, for example, a boom cylinder rod extension speed detection sensor for detecting the extension speed of the rod of the boom cylinder 82 may be provided, and the rod extension speed of the boom cylinder 82 may be used as the boom raising parameter. In addition, for example, a boom angular velocity detection sensor that detects an increasing speed of the rising angle of the boom 86 from the horizontal direction may be provided, and the increasing speed of the rising angle of the boom 86 from the horizontal direction may be used as the boom raising parameter. Further, for example, boom cylinder rod extension thrust detecting means for detecting the thrust of the boom cylinder 82 when the rod is extended may be provided, and the thrust of the boom cylinder 82 when the rod is extended may be used as the boom raising parameter. Further, for example, boom cylinder pressure difference detecting means for detecting a pressure difference between the pressure oil on the rod side of the boom cylinder 82 and the pressure oil on the bottom side may be provided, and the pressure difference in the boom cylinder 82 may be used as a boom raising parameter.

  Next, a hydraulic circuit 74 of a hydraulic excavator according to the fourth embodiment of the present invention will be described.

  FIG. 4 is a diagram showing a configuration of a hydraulic circuit 74 of a hydraulic excavator according to the fourth embodiment of the present invention. The same components as those of the hydraulic circuit 10 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the hydraulic circuit 74 according to the fourth embodiment, the pilot pressure sensors 28 and 56, the cylinder pressure sensors 52 and 54 used in the first to third embodiments, the controllers 30, 50 and 58, the electromagnetic proportional valve 32, and the pilot hydraulic pump. Instead of 34, a pilot passage 24c for applying pilot pressure in the arm opening direction is provided to the pilot port 22b of the second boom switching valve, and a pilot switching valve 60 for switching the degree of communication of the pilot passage 24c to the pilot passage 24c. Is provided.

  The pilot switching valve 60 is a two-position / three-port switching valve, and has two switching positions M and N. The pilot pressure in the pilot passage 24a in the arm opening direction is supplied to the second boom valve via the pilot passage 24c. It has the role of switching the degree of addition to the pilot port 22b of the switching valve. Pilot ports 60 a and 60 b are provided at both ends of the spool of the pilot switching valve 60. Further, a spring 60c is provided at the end on the pilot port 60b side.

  At the switching position M, the pilot passage 24c does not communicate, and no pilot pressure is applied to the pilot port 22b of the second boom switching valve. At the switching position N, the pilot passage 24c communicates, and the pilot pressure of the pilot passage 24a in the arm opening direction (the pilot port 16a of the arm first switching valve 16 and the pilot port 22b of the second boom switching valve) The pilot pressure applied to the pilot port 18a of the second arm switching valve 18 is applied via the pilot passage 24c.

  The pilot pressure of the pilot passage 24a is applied to the pilot port 60a of the pilot switching valve 60 via the pilot passage 24c, and the pilot pressure of the pilot passage 26a passes through the pilot passage 26c to the pilot port 60b of the pilot switching valve 60. Join through. A spring 60c provided at the end of the pilot switching valve 60 on the pilot port 60b side is urged to switch the pilot switching valve 60 to the position M side. Accordingly, the switching position of the pilot switching valve 60 is determined by the magnitude relationship between the force due to the pilot pressure applied to the pilot port 60a and the force obtained by adding the biasing force of the spring 60c to the force due to the pilot pressure applied to the pilot port 60b. Therefore, when the operation amount in the arm opening direction of the operation lever 24A of the arm remote control lever device 24 and the operation amount in the boom opening direction of the operation lever 26A of the boom remote control lever device 26 are approximately the same, the pilot force is applied by the biasing force of the spring 60c. The switching valve 60 is switched to the position M side.

  For this reason, when the raising operation of the boom 86 is performed, the pilot switching valve 60 is switched to the position M side unless the pilot pressure in the raising direction of the arm 84 is particularly large, and the second switching valve for the boom No pilot pressure is applied to the pilot port 22b of 22, and the second boom switching valve 22 is switched to the position G side. For this reason, pressure oil is also supplied from the first hydraulic pump to the bottom side of the boom cylinder 82, and the raising operation of the boom 86 is performed smoothly.

  When the boom 86 is not raised, no pilot pressure is applied to the pilot port 60b, so the arm operating lever 24A is tilted in the arm raising direction (leftward in FIG. 4) to overcome the urging force of the spring 60c. When the pilot pressure is applied to the pilot port 60a, the pilot switching valve 60 is switched to the position N side, the pilot pressure is applied to the pilot port 22b of the second boom switching valve 22, and the second boom switching valve 22 is moved to the position I. Switch to the side.

  As a result, the bypass passage 80h, the discharge passage 22c, and the tank passage 22e communicate with each other, so that the return oil that flows through the arm passage 80b and is discharged from the bottom side of the arm cylinder 80 also reaches the bypass passage 80h at the branch point 80g. It flows into the part T, and is discharged to the tank T through the discharge passage 22c and the tank passage 22e. For this reason, the passage pressure loss at the time of discharging the return oil from the bottom side of the arm cylinder 80 to the tank T can be reduced.

  When the driver manually provides a switch or the like that can specify that the work state is a work state (a work state in which the arm is opened and meets a predetermined condition), the switch is Since it can be determined whether or not it is a specific working state according to the present invention simply by checking whether or not it is turned on, when this switch is turned on, it is only necessary to confirm that the arm is opened, The operation of a sensor or the like that detects the value may be stopped and the second boom switching valve may be switched to the position I side.

  In the embodiment described above, the arm first switching valve 16 is provided on the downstream side of the boom second switching valve 22 in the tandem passage 38. However, the arm first switching valve 16 is switched to the boom second switching valve. It may be provided upstream of the valve 22. Further, in the tandem passage 42, the second arm switching valve 18 is provided on the downstream side of the first boom switching valve 20, but the second arm switching valve 18 is provided on the upstream side of the first boom switching valve 20. May be.

  In addition, as the switching valve for the arm, two switching valves, the first switching valve for arm 16 and the second switching valve for arm 18, were used. However, the switching valve for arm is only one of the first switching valve for arm 16. The present invention can also be applied to a hydraulic circuit. In this case, the passage through which the return oil from the bottom side of the arm cylinder 80 is discharged to the tank T is a bypass passage 80h in addition to the passage leading to the tank T via the discharge passage 16c of the arm first switching valve 16. The passage that communicates with the tank T via the discharge passage 22 c of the boom second switching valve 22 is a passage through which return oil from the bottom side of the arm cylinder 80 is discharged to the tank T. When the present invention is not applied, the passage through which return oil from the bottom side of the arm cylinder 80 is discharged to the tank T is only the passage leading to the tank T via the discharge passage 16c of the first switching valve 16 for arm. It is.

  Further, the present invention can be applied without depending on a pump control system such as a positive control, a negative control, and an open center.

  For example, it can be suitably used for a hydraulic circuit of a hydraulic excavator in which passages connected in tandem are provided in parallel.

DESCRIPTION OF SYMBOLS 10, 70, 72, 74 ... Hydraulic circuit 12 ... 1st hydraulic pump 14 ... 2nd hydraulic pump 16 ... 1st switching valve for arms (1st switching valve for 1st working machines)
18 ... Second switching valve for arm (second switching valve for first work machine)
20 ... Boom first switching valve (second working machine first switching valve)
22 ... Boom second switching valve (second working machine second switching valve)
16c, 18c, 22c ... discharge passage 24 ... arm remote control lever device 24A ... arm operating lever 26 ... boom remote control lever device 26A ... boom operating lever 28 ... pilot pressure sensor (arm pilot pressure detecting means)
30, 50, 58 ... Controller 32 ... Proportional solenoid valve 34 ... Pilot hydraulic pump 38, 42 ... Tandem passage 40, 44, 80h ... Parallel passage 52, 54 ... Cylinder pressure sensor (arm cylinder pressure detecting means)
56. Pilot pressure sensor (boom pilot pressure detecting means)
60 ... Pilot switching valve 78 ... Hydraulic excavator 80 ... Arm cylinder (hydraulic actuator for the first working machine)
82 ... Boom cylinder (hydraulic actuator for the second working machine)
84 ... Arm (first working machine)
86 ... Boom (second working machine)
88 ... bucket

Claims (18)

A first switching valve for the first work machine for switching the direction and flow rate of the pressure oil connected to the first hydraulic pump and supplied to the hydraulic actuator for the first work machine that drives the first work machine;
A first switching valve for the second working machine, which is connected to the second hydraulic pump and switches the direction and flow rate of the pressure oil supplied to the hydraulic actuator for the second working machine that drives the second working machine;
A second working machine second switch is connected in tandem to the first hydraulic pump first switching valve for the first working machine and switches the direction and flow rate of the pressure oil supplied to the second working machine hydraulic actuator. Two switching valves,
In the hydraulic circuit of construction machinery with
The second switching valve for the second work machine includes a discharge passage for discharging the return oil from the hydraulic actuator for the first work machine to the tank,
The hydraulic circuit includes a second switching valve control mechanism for the second working machine that controls a switching position of the second switching valve for the second working machine.
Switching the second switching valve for the second working machine so that the discharge passage is in communication in a working state in which the operation of the first working machine is performed and in a specific working state that meets a predetermined condition. A hydraulic circuit for construction machinery. In claim 1, further comprising:
The first working machine first switch is connected in tandem with the second hydraulic pump first switching valve for the second working machine, and switches the direction and flow rate of the pressure oil supplied to the first working machine hydraulic actuator. A hydraulic circuit for a construction machine, comprising a two-way valve. In claim 1 or 2,
The first work machine is an arm, the first work machine first switching valve and the first work machine second switching valve are an arm first switching valve and an arm second switching valve; The hydraulic actuator for one work machine is an arm cylinder,
The second working machine is a boom, the second working machine first switching valve and the second working machine second switching valve are a boom first switching valve and a boom second switching valve, and The boom hydraulic actuator is a boom cylinder;
The construction machine hydraulic pressure is determined by comparing whether at least one of the arm opening parameters indicating the degree of the arm opening operation is greater than a predetermined threshold value. circuit. In claim 3, further:
An arm operating lever for operating the first arm switching valve and the second arm switching valve;
A hydraulic circuit for a construction machine, wherein one of the arm opening parameters is an operation amount of the arm operating lever. In claim 3 or 4, further
Arm pilot pressure detecting means for detecting at least one of pilot pressure for switching the first arm switching valve and pilot pressure for switching the second arm switching valve;
A hydraulic circuit for a construction machine, wherein one of the arm opening parameters is a pilot pressure for switching the first switching valve for the arm or a pilot pressure for switching the second switching valve for the arm. In any one of Claims 3-5, Furthermore,
Arm cylinder rod contraction thrust detecting means for detecting thrust when the arm cylinder rod contracts,
A hydraulic circuit for a construction machine, wherein one of the arm opening parameters is a thrust force when the rod of the arm cylinder is contracted. In any one of Claims 3-6, Furthermore,
Arm cylinder pressure difference detecting means for detecting the pressure difference between the pressure oil on the rod side and the pressure oil on the bottom side of the arm cylinder;
A hydraulic circuit for a construction machine, wherein one of the arm opening parameters is the pressure difference in the arm cylinder. In any one of Claims 3-7,
Arm cylinder rod contraction speed detecting means for detecting the contraction speed of the rod of the arm cylinder;
A hydraulic circuit for a construction machine, wherein one of the arm opening parameters is a rod contraction speed of the arm cylinder. In any one of Claims 3-8, Furthermore,
Arm angular velocity detecting means for detecting an increasing speed of an angle formed by the arm and the boom,
A hydraulic circuit for a construction machine, wherein one of the arm opening parameters is an increasing speed of an angle formed by the arm and the boom. In any one of Claims 3-9,
A construction machine that determines whether or not the specific working state is included, including a result of comparing whether or not at least one boom raising parameter indicating a degree of the boom raising operation is smaller than a predetermined threshold value. Hydraulic circuit. The claim 10, further comprising:
A boom operation lever for operating the first boom switching valve and the second boom switching valve;
A hydraulic circuit for a construction machine, wherein one of the boom raising parameters is an operation amount of the boom operation lever. In claim 10 or 11, further
A boom pilot pressure detecting means for detecting at least one of a pilot pressure for switching the first boom switching valve and a pilot pressure for switching the second boom switching valve;
One of the boom raising parameters is a pilot pressure for switching the first boom switching valve or a pilot pressure for switching the second boom switching valve. In any of claims 10 to 12, further
A boom cylinder rod extension thrust detection means for detecting a thrust at the time of rod extension of the boom cylinder;
A hydraulic circuit for a construction machine, wherein one of the boom raising parameters is a thrust when the boom cylinder rod is extended. In any of claims 10 to 13, further
A boom cylinder pressure difference detecting means for detecting a pressure difference between the pressure oil on the rod side of the boom cylinder and the pressure oil on the bottom side;
A hydraulic circuit for a construction machine, wherein one of the boom raising parameters is the pressure difference in the boom cylinder. In any of claims 10 to 14, further
A boom cylinder rod extension speed detecting means for detecting the extension speed of the boom cylinder rod;
A hydraulic circuit for a construction machine, wherein one of the boom raising parameters is a rod extension speed of the boom cylinder. In any of claims 10 to 15, further
A boom angle speed detecting means for detecting an increasing speed of a rising angle from a horizontal direction of the boom;
A hydraulic circuit for a construction machine, wherein one of the boom raising parameters is an increasing speed of a rising angle of the boom from a horizontal direction. A first switching valve for an arm that is connected to a first hydraulic pump and switches a direction and a flow rate of pressure oil supplied to an arm cylinder that drives the arm;
A second switching valve for an arm connected to a second hydraulic pump for switching the direction and flow rate of the pressure oil supplied to the arm cylinder;
A first switching valve for a boom which is connected in tandem with the second switching valve for the arm to the second hydraulic pump and which switches the direction and flow rate of pressure oil supplied to a boom cylinder which drives the boom;
A second switching valve for a boom which is connected in tandem with the first switching valve for the arm to the first hydraulic pump, and which switches the direction and flow rate of the pressure oil supplied to the boom cylinder;
In the hydraulic circuit of construction machinery with
The second boom switching valve includes a discharge passage for discharging return oil from the bottom side of the arm cylinder to the tank,
The hydraulic circuit guides an arm opening pilot pressure for switching the arm first switching valve or the arm second switching valve in an arm opening direction to a pilot port at one end of the boom second switching valve. A pilot passage, and a second pilot passage for guiding a boom raising pilot pressure for switching the first boom switching valve in a boom raising direction to a pilot port at the other end of the second boom switching valve;
A hydraulic circuit for a construction machine, comprising: The claim 17, further comprising:
A construction machine characterized in that the first pilot passage is provided with a pilot switching valve that switches a degree of communication of the first pilot passage according to the arm opening pilot pressure and the boom raising pilot pressure. Hydraulic circuit.

Images