JP6493916B2 - Fluid pressure circuit and work machine - Google Patents

Description

  The present invention relates to a fluid pressure circuit including a fluid pressure cylinder that operates a working device in a vertical direction, and a work machine equipped with the fluid pressure circuit.

  Conventionally, for example, a hydraulic excavator is known as a working machine that performs excavation work. The hydraulic excavator is provided with a boom that can move up and down, a stick connected to the tip of the boom, and a bucket connected to the tip of the stick. Actuated by a hydraulic cylinder.

  During excavation work with a hydraulic excavator, hydraulic oil is supplied to each of these hydraulic cylinders, and after inserting the bucket into the earth and sand, the bucket is closed (stick-in) and the bucket is closed (bucket-in). During such excavation work, the operator normally operates the stick-in and bucket-in at maximum. At this time, if the bucket is inserted too deep into the earth or sand, or if the earth or sand to be excavated is hard and heavy, the reaction force applied to the bucket by the earth and sand will be large, causing a load that lifts the boom and causing stick or Pulling the bucket may not be possible. In such a case, the operator raises the boom to release the load and restarts the excavation operation.

  A configuration is known in which such a so-called watermarking operation for releasing the boom load is automatically performed when an overload such as a bucket or an arm is detected (see, for example, Patent Document 1).

JP 2011-252338 A

  However, at the time of excavation operation in which the stick-in and bucket-in operations are maximized, the head pressure of the boom hydraulic cylinder is substantially zero, whereas the rod pressure of the boom hydraulic cylinder is increased by the excavation reaction force. Therefore, when performing the watermarking operation by raising the boom, the pump pressure that has become high due to the stick and bucket operation flows to the boom cylinder head pressure that has become substantially zero, so the pressure loss is large.

  Also, in the case of control that automatically performs the watermark operation, it is not easy to dig a floor below the work machine, that is, so-called floor digging. Therefore, it is desirable that the operator can perform the watermark operation with his / her own intention.

  The present invention has been made in view of these points, and an object thereof is to provide a fluid pressure circuit and a work machine capable of reducing energy loss and pressure loss during excavation watermark operation.

  According to the first aspect of the present invention, a fluid pressure cylinder that moves up and down the work device by operating with a working fluid pressurized and supplied from a pump according to an operation of an operation body, and a fluid pressure cylinder that is supplied from the pump. An electromagnetic proportional control valve that controls the working fluid, a bypass valve that controls the amount of communication between the rod side of the fluid pressure cylinder and the tank, and an operating state of the working device are detected, and the working device is in an excavation state When detecting this, at least the operation of the control valve and the bypass valve is controlled according to the operation amount of the operating body that moves the work device upward, so that the working fluid supplied from the pump to the fluid pressure cylinder Reduce the flow rate of the fluid from the rod side of the fluid pressure cylinder to the tank and reduce the flow rate of the pump discharged from the pump. And a passage that connects the head side of the fluid pressure cylinder and the tank via a check valve, and at least part of the return fluid from the rod side to the pump is bypassed to the tank by the bypass valve, and the fluid pressure cylinder And a makeup circuit for replenishing the working fluid from the tank on the head side of the fluid pressure circuit.

Invention described in claim 2, Turkey controller put in the fluid pressure circuit according to claim 1, wherein the pilot pressure is set according to the operation amount of the operating body on the basis of the head pressure of the pump pressure and the fluid pressure cylinder It is the fluid pressure circuit which detects the operation state of a working device.

  The invention described in claim 3 includes an airframe, a boom provided to be rotatable in the vertical direction with respect to the airframe, a stick provided to be rotatable inward and outward with respect to the boom, and an inward / outward direction with respect to the stick. A working apparatus having a bucket provided so as to be rotatable, and a fluid pressure circuit according to claim 1 or 2, wherein at least a boom cylinder that rotates the boom is used as a fluid pressure cylinder. It is a working machine equipped.

  According to the first aspect of the present invention, when it is detected that the working device is in the excavation state, the fluid pressure cylinder is supplied from the pump at least according to the operation amount of the operating body that moves the working device upward. Reducing the working fluid, bypassing at least part of the return fluid from the rod side of the fluid pressure cylinder to the tank, reducing the pump flow rate discharged from the pump, limiting the operation of the electromagnetic proportional control valve, and By replenishing the working fluid from the tank to the head side of the fluid pressure cylinder, it is possible to reduce energy loss and pressure loss during the watermark operation in which the working device is operated upward during excavation to release the load.

According to the second aspect of the present invention, the controller detects the operating state of the work device based on the pilot pressure, the pump pressure, and the fluid pressure cylinder head pressure set according to the operation amount of the operation body. The excavation state can be easily detected with a simple configuration.

  According to the third aspect of the present invention, it is possible to reduce the pressure loss during the watermarking operation in which the working device is moved upward during the excavation by the working device of the working machine to release the load.

It is a circuit diagram which shows the switching state of one Embodiment of the fluid pressure circuit which concerns on this invention. It is a circuit diagram which shows the other switching state of a circuit same as the above. It is a circuit diagram which shows the other switching state of a circuit same as the above. (A) is explanatory drawing which shows typically the control algorithm of one valve | bulb of the same circuit, (b) is explanatory drawing which shows typically the control algorithm of the other valve | bulb of the same circuit. It is explanatory drawing which shows typically the outline of the control algorithm by each block of the controller of a circuit same as the above. It is explanatory drawing which shows typically the control algorithm of the control valve and bypass valve by a controller same as the above. It is explanatory drawing which shows typically the control algorithm of the pump flow rate by a controller same as the above. It is a side view which shows the working machine provided with the fluid pressure circuit same as the above.

  Hereinafter, the present invention will be described in detail based on one embodiment shown in FIGS.

  As shown in FIG. 8, a hydraulic excavator HE as a working machine is formed by a lower traveling body 2 and an upper revolving body 3 provided on the upper traveling body 3 so as to be turnable by a turning motor 3m. A machine room 4 in which an engine, a pump, and the like are mounted on the body 3, a cab 5 that protects an operator, and a work device 6 are mounted.

  In this working device 6, the base end of the boom 7 that is pivoted up and down by two boom cylinders 7 c 1 and 7 c 2 as fluid pressure cylinders arranged in parallel is pivotally supported on the upper swing body 3, and fluid is applied to the tip of the boom 7. A stick 8 rotated in the front-rear direction is pivotally supported by a stick cylinder 8c as a pressure cylinder, and a bucket 9 pivoted by a bucket cylinder 9c as a fluid pressure cylinder is pivotally supported at the tip of the stick 8. The two boom cylinders 7c1 and 7c2 are arranged side by side with respect to the common boom 7 and operate simultaneously in the same operation.

  FIGS. 1 to 3 show the engine power assist by storing the potential energy of the working device 6 in the accumulator through the boom cylinder 7c1 and storing the kinetic energy of the upper swing body 3 in the accumulator through the swing motor 3m. Shows the engine power assist system used.

  Next, the circuit configuration of this system will be described.

  An assist motor 15 is connected to the main pump shaft 14 of the main pumps 12 and 13 as pumps driven by the mounted engine 11 in the machine room 4 directly or via a gear, and the main pumps 12 and 13 and the assist motor 15 are , Equipped with a swash plate that can variably adjust the pump / motor capacity (piston stroke) according to the angle, and its swash plate angle (tilt angle) is controlled by regulators 16, 17, 18 and swash plate angle sensor 16φ, Detection is performed by 17φ and 18φ, and regulators 16, 17 and 18 are controlled by electromagnetic valves. For example, the regulators 16 and 17 of the main pumps 12 and 13 can be automatically controlled by the negative flow control pressure (so-called negative control pressure) guided by the negative flow control passage 19nc, and the electromagnetic type of the negative flow control valve 19 It is possible to control with signals other than the negative control pressure by the switching valves 19a and 19b.

  The main pumps 12 and 13 discharge the working oil as the working fluid sucked up from the tank 21 to the passages 22 and 23, and the pump discharge pressures are detected by the pressure sensors 24 and 25. Of pilot control valves for directional control and flow control connected to the main pumps 12 and 13, one of the pilot control valves for the boom cylinders 7c1 and 7c2 is drawn from the main boom control valve 26 which is an electromagnetic proportional control valve. An output passage 29 drawn from the output passage 27 and the sub boom control valve 28 which is an electromagnetic proportional control valve is connected to a boom energy recovery valve 31 as a composite valve by a passage 30.

  The boom energy recovery valve 31 includes two accumulator circuits A and a regeneration circuit B shown in FIG. 2 and hydraulic oil supplied from the main pumps 12 and 13 during boom raising operation shown in FIG. 7c1, 7c2 head side circuit, bleed-off circuit C that bypasses return oil from the rod side of boom cylinders 7c1, 7c2 to tank 21, and tank 21 head side of boom cylinders 7c1, 7c2 This is a composite valve in which a plurality of circuit functions for switching between a makeup circuit M for replenishing makeup hydraulic oil are incorporated in a single block.

  A passage 32 drawn from the head side end of one boom cylinder 7c1 is connected to the boom energy recovery valve 31 by a passage 34 via a drift reduction valve 33, and a passage 35 drawn from the head side end of the other boom cylinder 7c2 is connected. Connection is made by a passage 37 through a drift reduction valve 36. The other output passage 38 drawn from the main boom control valve 26 is connected to the regeneration circuit B of the boom energy recovery valve 31. Each rod side of the boom cylinders 7c1 and 7c2 is connected to the boom energy recovery valve 31 through passages 39 and 40. The drift reduction valves 33 and 36 control the opening and closing and the opening degree between the ports by controlling the pilot pressure in the spring chamber by a pilot valve (not shown). The passage 34 is connected with a pressure sensor 41 that detects the head pressure acting on the head side of the boom cylinder 7c1.

  One output passage 27 drawn out from the main boom control valve 26 can communicate with the other output passage 38 via the electromagnetic switching valve 42 and the check valve 43.

  Further, the discharge side of the assist motor 15 is connected to the tank 21 via the discharge passage 44. Furthermore, on the suction side of the assist motor 15, an accumulator passage 47 provided with a plurality of first accumulators 46, a tank passage 50 and an electromagnetic switching valve 51 via a relief valve 48 and a check valve 49 are provided. Then, the suction side passage 52 is connected. A pressure sensor 55 that detects the pressure accumulated in the first accumulator 46 is connected to the accumulator passage 47. The tank passage 50 is connected to the tank 21 from the tank passage 56 via a spring check valve 57 which is a back pressure check valve, and further via an oil cooler 58 or a spring check valve 59. Further, a first makeup passage 60 which is a makeup passage branched from the tank passage 56 is, for example, boom energy / passage through a check valve (check valve) 61 and a passage 62 in the first makeup passage 60. Connect to recovery valve 31. The first accumulator 46, accumulator passage 47, relief valve 48, electromagnetic switching valve 51, and pressure sensor 55 are incorporated in a single block to constitute an accumulator block 63.

  The boom energy recovery valve 31 is a main control valve which is a control valve 64 as one valve constituting a part of the pressure accumulating circuit A and a boom circuit switching valve as another valve constituting a part of the regeneration circuit B. 65 and a bleed-off valve 66 as a bypass valve. The control valve 64, the main control valve 65, and the bleed-off valve 66 are piloted by an electromagnetic switching valve that is operated by operation of a lever (not shown) that is operated by an operator such as in the cab 5 (FIG. 8). A pilot-operated type that is switched by controlling supply and discharge of pressure is used. However, in order to clarify the explanation, it is illustrated as an electromagnetic proportional directional control valve.

  The control valve 64 switches the communication between the passage 68 connected to the first accumulator 46 (accumulator block 63) via the check valve 67 and the passage 34, thereby switching the first accumulator 46 from the boom cylinder 7c1. This is a flow control valve that allows the accumulation of pressure. The control valve 64 is a valve that allows a larger amount of hydraulic oil to flow than returning from a normal cylinder (boom cylinders 7c1, 7c2, etc.) to the tank 21, and priority is given to storing pressure oil in the first accumulator 46. It has become. Further, the head side of the boom cylinder 7c1 is connected to the opposite side (upstream side) of the control valve 64 with respect to the check valve 67 via the passage 34.

  The main control valve 65 accumulates the boom cylinder 7c1 and the boom cylinder 7c2 by switching the relationship between the passage 71 and the passage 72, the relationship between the passage 73 and the passage 74, and the relationship between the passage 75 and the passage 76, respectively. The cylinder is separated into a self-reproducing cylinder and a self-reproducing cylinder. That is, the main control valve 65 cuts off the communication between the head sides of the boom cylinders 7c1 and 7c2 when accumulating pressure in the first accumulator 46 by switching the control valve 64, and the head side of the boom cylinder 7c2 and the boom cylinder. 7c1 and 7c2 are configured to communicate with each rod side.

  The passage 30 is connected to the passage 71 via the check valve 78, the passage 72 is connected to the passage 37 and the passage 79 branched from the passage 30, the passage 73 is branched from the passage 72, and the passage 74 is reversed. The passage 40 is connected to the passage 40 through the stop valve 80, the passage 75 is connected to the output passage 38 and the passage 39, and the passage 76 is branched from the passage 40.

  The bleed-off valve 66 is operated during a watermark operation during excavation work, which will be described later. The bleed-off valve 66 is connected to the passages 39 and 75 through the passage 82 and is connected to the tank 21 through the passage 83.

  As shown in FIGS. 1 to 3, the pressure accumulating circuit A is provided in the boom energy recovery valve 31 from the passage 32 drawn from the head side end of one boom cylinder 7c1 through the drift reducing valve 33 and the passage 34. The circuit extends from the passage 68 to the first accumulator 46 through the control valve 64 and the check valve 67, and has a function of accumulating oil pushed out from the head side of the boom cylinder 7c1 in the first accumulator 46.

  In addition, the regeneration circuit B is connected to the passage 73 in the boom energy recovery valve 31, the main control valve 65, the passage from the passage 35 drawn from the head side end of the other boom cylinder 7c2 through the drift reduction valve 36 and the passage 37. 74, through the check valve 80 and the passage 40 to the rod side end of the other boom cylinder 7c2, and from the passage 35 through the drift reduction valve 36 and the passage 37, the passage 73 in the boom energy recovery valve 31, the main This circuit reaches the rod end of one boom cylinder 7c1 through the control valve 65, passage 74, check valve 80, passage 76, main control valve 65, passage 75 and passage 39, and is pushed out from the head side of the boom cylinder 7c2. Has a function of regenerating the recovered oil on the rod side of each of the boom cylinders 7c1 and 7c2.

  The bleed-off circuit C extends from the rod side of one boom cylinder 7c1 to the tank 21 through the passage 39, passage 82, bleed-off valve 66 and passage 83, and from the rod side of the other boom cylinder 7c2 to the passage 40. This is a circuit that reaches the tank 21 through the passage 76, the main control valve 65, the passage 75, the passage 82, the bleed-off valve 66, and the passage 83, and at least part of the return oil from the rod side of the boom cylinders 7c1 and 7c2 is supplied to the tank 21. It has a function to bypass.

  The make-up circuit M also passes from the tank 21 through the oil cooler 58, the spring check valve 57, the tank passage 56 and the first make-up passage 60 to the passage 62, check valve via the check valve 61. Passing through the passage 34, the drift reduction valve 33 and the passage 32 to the head side of the boom cylinder 7c1 through 78, and passing through the check valve 78 to the passage 71, main control valve 65, passage 72, passage 37, drift reduction This circuit reaches the head side of the boom cylinder 7c2 via the valve 36 and the passage 35, and has a function of replenishing hydraulic oil from the tank 21 to the head side of the boom cylinders 7c1 and 7c2. That is, the makeup circuit M includes passages communicating with the head sides of the boom cylinders 7c1 and 7c2 from the tank 21 via the check valves 61 and 78, respectively.

  Relief valves 94, 95 opposite to each other are provided between the passages 92, 93 of the motor drive circuit D for connecting the turning control valve 91 for controlling the turning direction and speed of the turning motor 3m and the turning motor 3m. A check valve 97, 98 is provided, a tank passage function for returning oil discharged from the motor drive circuit D to the tank 21 between the relief valves 94, 95 and between the check valves 97, 98, and a motor drive circuit D A second makeup passage 99 having a makeup function capable of replenishing hydraulic oil is connected to the second accumulator 100. The second makeup passage 99 is connected to a second accumulator 100 for supplying pressure oil. . Then, from the second makeup passage 99 to the side where there is a risk of vacuum generation in the passages 92 and 93 through the check valves 97 and 98 at a pressure not exceeding the spring biasing pressure of the check valve 57 with spring. Top up with hydraulic fluid.

  Further, the passages 92 and 93 of the motor drive circuit D are communicated with the turning energy recovery passage 104 via the check valves 102 and 103, and the original pressure on the inlet side is changed by the back pressure on the outlet side. The passage 106 is connected to the first accumulator 46 and the passage 68 through the difficult sequence valve 105.

  In the circuit configuration as described above, each of the swash plate angle sensors 16φ, 17φ, 18φ, and the pressure sensors 24, 25, 55 sends the detected swash plate angle signal and pressure signal to the in-vehicle controller CR (FIG. 8) as a controller. Further, the valves 42 and 51 are switched by an on / off operation or a proportional operation corresponding to the drive signal according to the drive signal output from the in-vehicle controller CR (FIG. 8). The boom control valves 26 and 28, the turning control valve 91, and other hydraulic actuator control valves (not shown) (for travel motors, stick cylinders, bucket cylinders, etc.) are provided in the cab 5 (FIG. 8). A pilot operation is performed by a manually operated valve so-called a remote control valve or the like that is operated by a lever or a pedal by an operator, and pilot valves (not shown) of the drift reduction valves 33 and 36 are also pilot operated in conjunction.

  The contents controlled by the on-vehicle controller CR (FIG. 8) will be functionally described below.

  FIG. 2 shows a circuit state during a boom lowering operation for lowering the boom 7 (FIG. 8). The hydraulic oil pushed out from the head side of one boom cylinder 7c1 by the load of the working device 6 (FIG. 8) A control valve 64 which is switched from the passage 34 to the communication position of the boom energy recovery valve 31 via the passage 32 and the drift reduction valve 33 communicates with the passage 68 via the check valve 67, and from this passage 68 to the first accumulator 46. Accumulate pressure.

  At this time, the control valve 64 controls the head of one boom cylinder 7c1 according to the lever operation amount, that is, the pilot pressure set by this operation amount and the accumulator pressure of the first accumulator 46 detected by the pressure sensor 55. The communication amount between the first accumulator 46 side and the first accumulator 46 side is switched. Specifically, the pilot pressure set by the lever operating amount is corrected by a predetermined table (converter) T1, and the accumulator pressure is corrected by a predetermined table (converter) T2. The result of integrating is used as an output for operating the control valve 64. More specifically, in the present embodiment, as shown in FIG. 4A, in the table T1, when the pilot pressure set by the lever operation amount is relatively small, the input pressure increases. When the output pressure increase is relatively large and the pilot pressure set by the lever operation amount exceeds the predetermined threshold TH1, the output pressure increase relative to the input pressure increase is less than the threshold TH1. The output pressure is set to be constant in a region that is more suppressed and exceeds a predetermined threshold TH2 that is greater than the predetermined threshold TH1. Further, in the table T2, the gain increases with respect to the increase amount of the accumulator pressure in the region where the accumulator pressure is equal to or less than the predetermined threshold TH3, and the gain is constant (for example, 1) in the region where the accumulator pressure exceeds the predetermined threshold TH3. Set to At this time, the hydraulic oil does not return to the boom control valve 26 side by the check valve 78.

  At the same time, the hydraulic oil pushed out from the head side of the other boom cylinder 7c2 passes from the passage 37 to the passage 74 through the passage 35 and the drift reduction valve 36 and from the passage 37 to the main control valve 65 of the boom energy recovery valve 31. The control oil is regenerated to the rod side of the other boom cylinder 7c2 through the check valve 80 and the passage 40, and the hydraulic oil branched to the passage 76 through the check valve 80 is returned to the check valve in the main control valve 65. Then, the direction is controlled to the passage 75 and is also regenerated to the rod side of one boom cylinder 7c1 via the passage 39.

  At this time, the operation amount of the main control valve 65 changes according to the operation amount of the lever, that is, the pilot pressure set by this operation amount. Specifically, the pilot pressure set by the amount of lever operation is corrected by a predetermined table (converter) T3 to obtain an output for operating the main control valve 65. More specifically, in the present embodiment, as shown in FIG. 4B, the input pressure of the pilot pressure set by the amount of operation of the lever by the table T3 similar to the table T2 of FIG. The output pressure is set, and basically it switches immediately when a boom lowering operation is detected. The surplus flow rate of the hydraulic oil pushed out from the head side of the other boom cylinder 7c2 is returned from the boom control valve 26 to the tank 21 through the passage 37, the passage 79 and the passage 30. Further, for example, when it is detected that the body 1 is lifted by lowering the boom by detecting the grounding of the working device 6 (FIG. 8) based on the head pressure of the boom cylinders 7c1 and 7c2 (when the body lifting flag is on). Releases the separation of the accumulator cylinder and the self-regenerating cylinder of the boom cylinders 7c1 and 7c2 according to a predetermined set value.

  In this way, the boom energy recovery valve 31 uses the control valve 64 and the main control valve 65 to accumulate pressure on the first accumulator 46 when the boom is lowered and to regenerate the boom cylinders 7c1 and 7c2 to the rod side. Do it at the same time.

  Part of the hydraulic oil discharged from the main pump 12 during the boom lowering operation is supplied from the output passage 38 to the rod side of the boom cylinder 7c1 through the passage 39 through the boom control valve 26. At this time, the boom control valve 26 maximizes the flow rate only at the start of the boom lowering operation and supplies hydraulic oil to the rod side of the boom cylinder 7c1. When the valve 65 is used, the hydraulic oil is regenerated from the head side of the boom cylinder 7c2 to the rod side of the boom cylinders 7c1 and 7c2, so the flow rate is reduced.

  FIG. 3 shows a circuit state at the time of a boom raising operation for raising the boom 7 (FIG. 8). The boom energy recovery valve 31 at the time of the boom raising operation switches the control valve 64 to the shut-off position and the main state. The control valve 65 is switched to stop the pressure accumulation in the first accumulator 46 and the regeneration of the boom cylinders 7c1 and 7c2 to the rod side, and the passage 30 from the main pumps 12 and 13 through the boom control valves 26 and 28. Is supplied from the passage 79 to the head side of the other boom cylinder 7c2 through the passage 37, the drift reduction valve 36 and the passage 35, and from the check valve 78 to the passage 34, the drift reduction valve 33 and the passage 32. Then, it is guided to the head side of one boom cylinder 7c1. The hydraulic oil pushed out from the rod side of the boom cylinder 7c1 returns to the tank 21 via the boom control valve 26 from the passage 39 and the output passage 38, and the hydraulic oil pushed out from the rod side of the boom cylinder 7c2 The direction is controlled to the passage 75 by the main control valve 65 through the passage 40 and the passage 76, and is returned from the output passage 38 to the tank 21 through the boom control valve 26.

  Further, at the time of the boom lowering operation and the boom raising operation described above, the assist motor 15 having a motor function directly connected to the main pump shaft 14 or connected via a gear functions as a hydraulic motor as shown in FIG. Thus, engine power assist can be performed to reduce the engine load. For example, during a boom lowering operation, engine power assist is performed when the pressure sensor 55 detects that the accumulator pressure of the first accumulator 46 accumulated via the control valve 64 is equal to or higher than a predetermined first threshold pressure, When a boom raising operation is not performed, for example, during a boom raising operation, the pressure sensor 55 indicates that the accumulator pressure of the first accumulator 46 is equal to or higher than a predetermined second threshold pressure different from the predetermined first threshold pressure. If it is detected, engine power assist is performed. In this engine power assist, the electromagnetic switching valve 51 is switched to the communication position according to the flag, the assist motor 15 is rotated by the energy accumulated in the first accumulator 46, and the hydraulic pressure of the main pumps 12 and 13 is increased. Assists output to reduce engine load. Note that when the airframe 1 is lifted, engine power assist by the assist motor 15 is not performed.

  As described above, the engine power assist function rotates the assist motor 15 by the energy accumulated in the first accumulator 46 from the head side of one boom cylinder 7c1, and this assist motor 15 causes the main pump shaft 14 to pass through. To reduce the load on the mounted engine 11 connected.

  Further, in excavation work by the working device 6 as shown in FIG. 8, the above-described boom lowering and boom raising operations and stick-in / out and bucket-in / out operations are arbitrarily combined. For example, when the bucket 9 is inserted too deep into the earth or sand, or when the earth or sand to be excavated is hard and heavy, the reaction force applied to the bucket 9 due to the earth and sand is large, and a load that lifts the boom 7 is generated. Occasionally, the stick 8 or the bucket 9 may not be pulled. In such a case, the operator may perform a so-called watermarking operation (represented by an imaginary line) in which the working device 6 (boom 7) is rotated upward to release the load. Therefore, in the case of this watermarking operation, the pump pressure that has become high due to the load flows into the head side of the boom cylinders 7c1 and 7c2, resulting in energy loss.

  Therefore, as shown in FIG. 5, the in-vehicle controller CR generally includes an operation detection unit 107 that detects an operation state of the work device 6 (FIG. 8), a valve control unit 108 that is an opening area control unit, A pump flow rate control unit 109, and an output and bleed-off valve for operating the boom control valves 26 and 28 by the valve control unit 108 when the operation detection unit 107 detects that the work device 6 is in the excavation state. When the output for operating 66 is set and the required pump flow rate is set by the pump flow rate control unit 109 and the operation detection unit 107 does not detect that the work device 6 is in the excavation state, in other words, the operation detection unit 107 When the operation state of the work device 6 detected by the above is not the excavation state, the output for operating the boom control valves 26 and 28, the output for operating the bleed-off valve 66, and the pump required flow rate are set to 0, respectively. By setting, to reduce the pressure loss.

  Specifically, the motion detection unit 107 includes a stick-in operation amount by a lever, that is, a pilot pressure set according to the operation amount, a bucket-in operation amount, that is, a pilot pressure set according to the operation amount, Based on the pump pressure of the main pumps 12 and 13, the head pressure of the boom cylinders 7c1 and 7c2, and the boom raising operation amount, that is, the pilot pressure set according to this operation amount, the working device 6 (FIG. 8) Detect the operating state. More specifically, the motion detection unit 107 has a pilot pressure set according to the stick-in operation amount greater than a predetermined pressure (for example, 1.8 MPa), and the pilot pressure set according to the bucket-in operation amount is a predetermined pressure. (For example, 1.3 MPa), the pump pressure is greater than a predetermined pressure (for example, 15 MPa), the head pressures of the boom cylinders 7c1, 7c2 are greater than the predetermined pressure (for example, 5 MPa), and the boom raising operation amount is set. When the pilot pressure is less than a predetermined pressure (for example, 1.5 MPa), it is determined that the working device 6 (FIG. 8) is performing excavation work, and otherwise, it is determined that no excavation work is being performed. To do.

  Further, the valve control unit 108 is based on the boom raising operation amount by the lever, that is, the pilot pressure set according to the operation amount, the pump pressure of the main pumps 12 and 13, and the rod pressure of the boom cylinders 7c1 and 7c2. Thus, the output for operating the boom control valves 26 and 28 and the bleed-off valve 66 is set. More specifically, the valve control unit 108 includes a gain set by a predetermined table (converter) T4 according to the pump pressure, and rod pressures of the boom cylinders 7c1 and 7c2 detected by a pressure sensor (not shown). Is set by the predetermined table (converter) T6 according to the integrated value of the gain set by the predetermined table (converter) T5 according to the pilot pressure set by the lever operation amount of the boom raising operation. The pilot that is set by the amount of lever operation for boom raising operation is set as an output that operates the bleed-off valve 66 by further converting the area pressure to the value obtained by integrating the opening area Depending on the pressure, the difference between the opening area set by the table T6 and the smaller opening area is further converted to area pressure to limit the operation of the boom control valves 26 and 28. To set up as. In the table T4, the gain is set to be constant in the region where the pump pressure is equal to or lower than the predetermined threshold TH4, and in proportion to the increase in the region where the pump pressure exceeds the predetermined threshold TH4 and is higher than the predetermined threshold TH4. Thus, the gain decreases, and the gain is set to be constant in a region exceeding a predetermined threshold value TH4. In the table T5, in the area where the head pressure is equal to or less than the predetermined threshold value TH9, the gain increase amount is relatively large with respect to the increase amount, and the head pressure exceeds the predetermined threshold value TH6 and exceeds a predetermined threshold value TH6. In the area below the threshold TH7, the amount of gain increase relative to the amount of increase in the head pressure is suppressed more than when the threshold TH6 or less, and the head is exceeded in the area below the predetermined threshold TH8 that exceeds the predetermined threshold TH7 and is greater than the predetermined threshold TH7. The gain is set to be constant in a region where the amount of increase in gain relative to the amount of increase in pressure is suppressed more than when the threshold TH7 or less, and exceeds a predetermined threshold TH8. In the table T6, when the pilot pressure set by the lever operation amount is relatively small below the predetermined threshold TH9, the opening area increases in proportion to the increase, and exceeds the predetermined threshold TH9 and exceeds the predetermined threshold TH9. In the region below the large predetermined threshold TH10, the amount of increase in the opening area relative to the amount of increase in the pilot pressure is increased compared to when it is below the predetermined threshold TH9, and in the region exceeding the predetermined threshold TH10, the opening area is set constant. The

  Returning to FIG. 5, the pump flow rate control unit 109 includes a boom raising operation amount by the lever, that is, a pilot pressure set according to this operation amount, and the boom control valve 26 output from the valve control unit 108, The required pump flow rate is set based on each of the output for operating 28 and the predetermined flow rate distribution. More specifically, as shown in FIG. 7, the pump flow rate control unit 109 is set by a predetermined table (converter) T7 in accordance with the pilot pressure set by the operation amount of the lever for boom raising operation. For the value obtained by dividing the opening area by the output that restricts the operation of the boom control valves 26 and 28 output from the valve control unit 108 and the value obtained by integrating the difference between 1 and a predetermined base flow coefficient, A base flow coefficient is added, and a value obtained by integrating the added value and a value obtained by integrating a predetermined flow rate distribution with the maximum flow rate is output as a pump required flow rate. In the table T7, as in the table T6, when the pilot pressure set by the lever operation amount is relatively small below the predetermined threshold TH9, the opening area increases in proportion to the increase and exceeds the predetermined threshold TH9. In the region below the predetermined threshold TH10 greater than the predetermined threshold TH9, the amount of increase in the opening area relative to the amount of increase in the pilot pressure is increased than when the predetermined threshold TH9 or less, and in the region exceeding the predetermined threshold TH10, the opening is increased. The area is set constant.

  Therefore, during the above watermark operation, as shown in FIG. 1, the hydraulic oil (at least part of the hydraulic oil) flows from the rod side of the boom cylinders 7c1 and 7c2 through the bleed-off valve 66 of the bleed-off circuit C. The boom, in which the supply of hydraulic fluid from the main pumps 12 and 13 to the rod side of the boom cylinders 7c1 and 7c2 is cut off (reduced) by the boom control valves 26 and 28, and instead a vacuum may occur. On the head side of the cylinders 7c1 and 7c2, a back pressure set by the spring force of the spring check valve 57 is generated in the tank passage 56 of the make-up circuit M, so that the spring of the spring check valve 57 The hydraulic oil in the tank 21 is replenished to the head side of the boom cylinders 7c1 and 7c2 through the makeup circuit M at a pressure that does not exceed the urging pressure, thereby preventing vacuum generation. Further, the main pumps 12 and 13 do not require or have little hydraulic oil to be supplied to the head side of the boom cylinders 7c1 and 7c2, and the pump flow rate discharged is suppressed.

  In this way, when it is detected that the working device 6 is in the excavation state, at least the working device 6 is moved upward, that is, the main pumps are connected to the boom cylinders 7c1 and 7c2 according to the operation amount of the lever for boom raising operation. The hydraulic oil supplied from 12 and 13 is reduced (shut off), and high pressure oil (at least a part of the return oil) from the rod side of the boom cylinders 7c1 and 7c2 is bypassed to the tank 21, and from the main pumps 12 and 13 During excavation, the pump flow rate is reduced to limit the operation of the electromagnetic proportional boom control valves 26 and 28, and the hydraulic oil is supplied from the tank 21 to the head side of the boom cylinders 7c1 and 7c2. In addition, it is possible to reduce energy loss and pressure loss during the watermark operation in which the working device 6 is operated upward to release the load.

  Further, in the above configuration, since the watermarking operation can be performed by the operator's own operation when the operator desires without performing the watermarking operation of the work device 6, floor digging that is not easy to excavate by the automatic watermarking operation, etc. It is possible to efficiently perform the excavation work.

  Furthermore, since the vehicle-mounted controller CR (motion detector 107) detects the operating state of the work device 6 based on the pilot pressure, pump pressure of the boom cylinders 7c1 and 7c2, and the head pressure of the boom cylinders 7c1 and 7c2, the work device 6 excavates. The state can be easily detected with a simple configuration.

  Further, when the pressure accumulating circuit A and the regeneration circuit B are separated and the working device 6 of the hydraulic excavator HE is lowered, the hydraulic oil pushed out from the head side of the boom cylinder 7c1 is transferred to the first accumulator 46 by the control valve 64. At the same time as accumulating pressure, the hydraulic oil pushed out from the head side of the boom cylinder 7c2 is regenerated to the rod side of the boom cylinders 7c1 and 7c2 by the main control valve 65, so that the regenerative flow rate even when the first accumulator 46 is accumulating. The pump flow can be saved, and the required pump flow including the main pump flow required by other hydraulic actuators can be easily secured with a simple configuration using control valves 64 and 65, and the main pumps 12 and 13 can be downsized. it can.

  Further, by turning the head side oil of the boom cylinder 7c1 on one side for accumulating the pressure on the first accumulator 46, that is, the load of the working device 6 is not distributed to the two boom cylinders 7c1 and 7c2, but one By concentrating on the boom cylinder 7c1, the energy density can be increased, the pressure generated from the boom cylinder 7c1 can be increased, and the accumulated energy in the first accumulator 46 can be increased, in other words, the first accumulator. Components such as 46 and assist motor 15 can be miniaturized, cost can be reduced, and layout can be facilitated.

  The control valve 64 changes the communication amount between the head side of the boom cylinder 7c1 and the first accumulator 46 according to the lever operation amount and the accumulator pressure of the first accumulator 46. Thus, the first accumulator 46 can be more appropriately pressure-accumulated without sacrificing the operability, and the operability and the energy pressure-accumulation can be satisfied simultaneously.

  Further, when the boom cylinders 7c1 and 7c2 and other hydraulic actuators (such as the swing motor 3m, the stick cylinder 8c, and the bucket cylinder 9c) are operated in conjunction, the hydraulic oil pushed out from the head side of the boom cylinder 7c2 on one side is supplied to the boom cylinder 7c1. , Because it regenerates to the rod side of 7c2, the amount of oil for that regeneration can be turned from the main pumps 12 and 13 to other hydraulic actuators, speed reduction during linked operation can be prevented, and linked operability can be improved Can do.

  In addition, the boom energy recovery valve 31 that integrates a plurality of circuit functions into a single block facilitates layout and enables cost reduction by reducing the number of assembly steps.

  Furthermore, by concentrating the load on one boom cylinder 7c1, the accumulated energy of the first accumulator 46 can be increased, and the small accumulator can provide a large assist, thereby reducing costs and making the aircraft layout compact. Can do.

  Moreover, since the pressure accumulating hydraulic oil discharged from the first accumulator 46 is supplied to the assist motor 15 to assist the operation of the pumps 12 and 13, the pumps 12 and 13 are operated by effectively using the pressure accumulating hydraulic oil. The load on the installed engine 11 can be further reduced.

  The present invention has industrial applicability to operators who manufacture and sell fluid pressure circuits or work machines.

In-vehicle controller that is a CR controller
HE Excavator as work machine M Make-up circuit 1 Airframe 6 Work device 7 Boom
7c1, 7c2 Boom cylinder as a hydraulic cylinder 8 Stick 9 Bucket
12, 13 Main pump as a pump
21 tanks
26, 28 Boom control valve
61, 78 Check valve
66 Bleed-off valve as bypass valve

Claims (3)

A fluid pressure cylinder that moves up and down the work device by operating with a working fluid pressurized and supplied from a pump according to the operation of the operating body;
An electromagnetic proportional control valve for controlling the working fluid supplied from the pump to the fluid pressure cylinder;
A bypass valve that controls the amount of communication between the rod side of the fluid pressure cylinder and the tank;
When the operation state of the work device is detected, and when it is detected that the work device is in the excavation state, the operation of each of the control valve and the bypass valve is performed at least according to the operation amount of the operation body that moves the work device upward. By controlling, the working fluid supplied from the pump to the fluid pressure cylinder is reduced, and at least part of the return fluid from the rod side of the fluid pressure cylinder is bypassed to the tank, and the pump flow rate discharged from the pump is reduced. And a controller to
A passage that connects the head side of the fluid pressure cylinder and the tank via a check valve is provided, and at least part of the return fluid from the rod side to the pump is bypassed to the tank by the bypass valve, and the fluid pressure cylinder head side is bypassed. A fluid pressure circuit comprising a makeup circuit for replenishing a working fluid from a tank. Controller, the pilot pressure is set in accordance with the operation amount of the operation member, the fluid pressure circuit according to claim 1, wherein the detecting the operating state of the working device based on the head pressure of the pump pressure and the fluid pressure cylinder . The aircraft,
Boom provided to be rotatable in the vertical direction with respect to the machine body, a stick provided to be rotatable inward and outward with respect to the boom, and a working device provided with a bucket provided to be rotatable inward and outward with respect to the stick. When,
A working machine comprising: a fluid pressure circuit according to claim 1, wherein at least a boom cylinder that rotates the boom is provided as a fluid pressure cylinder to the fluid pressure cylinder.

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