JP2016205493A - Fluid pressure circuit and work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluid pressure circuit capable of ensuring a necessary pump flow rate even when working fluid is accumulated in an accumulator with a simple structure, and to provide a work machine.SOLUTION: A fluid pressure circuit includes: an accumulation circuit A in which pressure oil from the head side of a cylinder 7c1 is accumulated in an accumulator 46 through a control valve 61 capable of changing a communication amount between the head side of the cylinder 7c1 and the accumulator 46 according to an operation amount of a lever; a regeneration circuit B in which pressure oil from the head side of a cylinder 7c2 is regenerated to the boom cylinders 7c1, 7c2 through a main control valve 62 capable of disconnecting communication between the head sides of cylinders 7c1, 7c2 and communicating between the head side of the cylinder 7c2 and the respective rod sides of the cylinders 7c1, 7c2 in a case where the pressure oil is accumulated in the accumulator 46; and an auxiliary regeneration circuit C in which part of working fluid accumulated in the accumulator 46 is regenerated on the rod side of the cylinder 7c1 through a regeneration control valve 63 capable of changing a communication amount between the control valve 61 and the rod side of the cylinder 7c1 according to the operation amount of the lever.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fluid pressure circuit including an accumulator and a work machine equipped with the fluid pressure circuit.

  In the work machine, the pressure oil discharged from the boom hydraulic cylinder when the boom is lowered is stored in the accumulator, and the pressure oil that is relieved from the swing hydraulic motor when the swing is accelerated or decelerated is also stored in the accumulator ( For example, see Patent Document 1).

JP 2010-84888 A

  While the pressure oil discharged from the boom hydraulic cylinder is accumulated in the accumulator, the pressure oil discharged from the boom hydraulic cylinder cannot be regenerated into the boom hydraulic cylinder, so the necessary pump flow rate can be secured. Therefore, the operating speed of the boom hydraulic cylinder may be slow. Therefore, it is desired to regenerate the pressure oil discharged from the boom hydraulic cylinder with a simpler configuration to ensure the necessary pump flow rate.

  The present invention has been made in view of these points, and an object of the present invention is to provide a fluid pressure circuit and a work machine that can secure a necessary pump flow rate even when a working fluid is accumulated in an accumulator with a simpler configuration. And

  According to the first aspect of the present invention, there are provided a plurality of fluid pressure cylinders that simultaneously operate the same operation by a working fluid pressurized and supplied from a pump according to an operation of an operating body, an accumulator that accumulates pressure by the working fluid, A first valve that changes the communication amount between the head side of the fluid pressure cylinder and the accumulator in accordance with the operation amount of the operating body, and is pushed out from the head side of one fluid pressure cylinder through the first valve. A pressure accumulator for accumulating the accumulated working fluid in the accumulator, and when the accumulator accumulates pressure in the accumulator, the communication between the head sides of the plurality of fluid pressure cylinders is interrupted and the other fluid pressure cylinder of the plurality of fluid pressure cylinders A second valve that communicates between the head side and the rod side of each of the one and other fluid pressure cylinders. The amount of communication between the regeneration circuit that regenerates the working fluid pushed out from the head side of the pressure cylinder to one and other fluid pressure cylinders, and the first valve and the rod side of the one fluid pressure cylinder is the operation amount of the operating body. And an auxiliary regeneration circuit that regenerates a part of the working fluid accumulated in the accumulator by the accumulator circuit through the third valve to the rod side of one fluid pressure cylinder. Is a fluid pressure circuit.

  According to a second aspect of the present invention, the first valve in the fluid pressure circuit according to the first aspect is configured such that the accumulator communicates with the head side of one fluid pressure cylinder in accordance with the operation amount of the operating body and the accumulator pressure. The amount is changed, and the third valve is a fluid pressure circuit that changes the amount of communication between the first valve and the rod side of one fluid pressure cylinder in accordance with the amount of operation of the operating body and the accumulator pressure.

  According to a third aspect of the present invention, there is provided an airframe, a work device mounted on the airframe, and a fluid pressure circuit according to claim 1 or 2 provided for a plurality of fluid pressure cylinders that move up and down the work device. Is a working machine.

  According to the first aspect of the present invention, the accumulator circuit and the regeneration circuit are separated from each other, and a part of the working fluid pushed out from the head side of one fluid pressure cylinder is accumulated in the accumulator by the first valve. The other part is regenerated to the rod side of one fluid pressure cylinder by the third valve of the auxiliary regeneration circuit, and the working fluid pushed out from the head side of the other fluid pressure cylinder is simultaneously regenerated by the second valve. Since the regeneration is performed on the rod side of the fluid pressure cylinder, the regeneration flow rate of the pump when accumulator is accumulating can be suppressed, and the necessary pump flow rate can be easily secured with a simple configuration using the first to third valves.

  According to the invention described in claim 2, the first valve changes the communication amount between the head side of one fluid pressure cylinder and the accumulator according to the operation amount of the operating body and the accumulator pressure, and the third valve The valve changes the amount of communication between the first valve and the rod side of one fluid pressure cylinder in accordance with the operation amount of the operating body and the accumulator pressure, thereby accumulating pressure in the accumulator more appropriately. The working fluid is effectively regenerated to the rod side of the pressure cylinder, the flow rate of the working fluid discharged from the pump to the rod side of one fluid pressure cylinder can be reduced, and the necessary pump flow rate can be secured more easily.

  According to the third aspect of the present invention, it is possible to suppress the regeneration flow rate of the pump when the accumulator is accumulating when the working device of the work machine is lowered, and the necessary pump flow rate can be easily secured.

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 explanatory drawing which shows typically the control algorithm of the 1st valve | bulb of a circuit same as the above. It is explanatory drawing which shows typically the control algorithm of the 2nd valve | bulb of a circuit same as the above. It is explanatory drawing which shows typically the control algorithm of the 3rd valve | bulb of a circuit same as the above. It is explanatory drawing which shows typically a part of flow control algorithm of the pump of a circuit same as the above. It is explanatory drawing which shows typically a part of flow control algorithm of the pump of a circuit same as the above. It is explanatory drawing which shows typically the control algorithm of the engine power assist function of a circuit same as the above. It is a perspective 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. 9, 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 a stick is attached to the tip of the boom 7. A stick 8 rotated in the front-rear direction is pivotally supported by a cylinder 8c, and a bucket 9 rotated by a bucket cylinder 9c 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.

  In FIG. 1, the potential energy of the working device 6 is stored in the accumulator via the boom cylinder 7c1, and the kinetic energy of the upper swing body 3 is stored in the accumulator via the swing motor 3m and used for assisting the engine power. An engine power assist system is shown.

  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 the pilot-type control valves for directional control and flow control connected to the main pumps 12 and 13, one output passage 27 drawn from the boom control valve 26 which is the main valve for controlling the boom cylinders 7c1 and 7c2, and the sub An output passage 29 drawn from the boom control valve 28 is connected to a boom energy recovery valve 31 as a composite valve by a passage 30.

  This boom energy recovery valve 31 is a hydraulic oil supplied with pressure from the main pumps 12 and 13 during the boom raising operation shown in FIG. 2 and the pressure accumulating circuit A, the regeneration circuit B and the auxiliary regeneration circuit C shown in FIG. This is a composite valve in which a plurality of circuit functions for switching the circuit for guiding the two to the head side of the two boom cylinders 7c1, 7c2 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).

  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 check valve 57 with a spring and further via an oil cooler 58 or a check valve 59 with a spring. 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 60.

  The boom energy recovery valve 31 is a control valve 61 as a first valve constituting a part of the accumulator circuit A and a boom circuit switching valve as a second valve constituting a part of the regeneration circuit B. A control valve 62 and a regeneration control valve 63 as a third valve constituting a part of the auxiliary regeneration circuit C are provided. These valves 61 to 63 control the supply and discharge of pilot pressure by an electromagnetic switching valve operated by operating a lever (not shown) operated by an operator such as in the cab 5 (FIG. 9), for example. A pilot-operated type that switches is used, but is shown as an electromagnetic proportional directional control valve in the drawings for the sake of clarity.

  The control valve 61 switches the communication between the passage 68 connected to the first accumulator 46 (accumulator block 60) 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. This control valve 61 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.

  The main control valve 62 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, when the main control valve 62 accumulates pressure in the first accumulator 46 by switching the control valve 61, the main control valve 62 cuts off the communication between the head sides of the boom cylinders 7c1 and 7c2, and the boom cylinder 7c2 head side 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 regeneration control valve 63 includes a passage 82 branched from the upstream side of the check valve 67 with respect to the control valve 61, that is, the passage 68, and a passage 84 connected to the passage 39, that is, the rod side of the boom cylinder 7c1 via the check valve 83. By switching between communication and shut-off, a part (approximately half) of the hydraulic oil discharged from the head side of the boom cylinder 7c1 to the first accumulator 46 via the control valve 61 is transferred to the rod side of the boom cylinder 7c1. This is a regenerative flow control valve. The regeneration control valve 63 is linked to the control valve 61, and communicates between the control valve 61 and the head side of the boom cylinder 7c1 when accumulating pressure in the first accumulator 46 by switching the control valve 61. When the communication between the head side of the boom cylinder 7c1 and the first accumulator 46 is cut off by switching 61, the control valve 61 and the head side of the boom cylinder 7c1 are cut off.

  As shown in FIG. 1, the pressure accumulating circuit A is connected to a control valve 61 in the boom energy recovery valve 31 through a drift reduction valve 33 and a passage 34 from a passage 32 drawn from the head side end of one boom cylinder 7c1. And a circuit extending from the passage 68 to the first accumulator 46 via the check valve 67, and a part (substantially half) of the hydraulic oil pushed out from the head side of the boom cylinder 7c1 is accumulated in the first accumulator 46. It has a function.

  Further, the regeneration circuit B passes through the passage 35 drawn out from the head side end of the other boom cylinder 7c2 through the drift reduction valve 36 and the passage 37, to the passage 73 in the boom energy recovery valve 31, the main control valve 62, the passage 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 side end of one boom cylinder 7c1 through the control valve 62, passage 74, check valve 80, passage 76, main control valve 62, passage 75 and passage 39, and is pushed out from the head side of the boom cylinder 7c2. Has a function of regenerating the hydraulic oil to the rod side of each of the boom cylinders 7c1 and 7c2.

  The auxiliary regeneration circuit C is branched from the pressure accumulating circuit A and passes through the passage 32 drawn out from the head side end of one boom cylinder 7c1 via the drift reduction valve 33 and the passage 34, and the inside of the boom energy recovery valve 31. This circuit extends from the passage 39 to the rod side end of one boom cylinder 7c1 through the control valve 61, passage 82, regeneration control valve 63, check valve 83 and passage 84, and is pushed out from the head side of the boom cylinder 7c1. The hydraulic oil has a function of regenerating the other part of the hydraulic oil excluding a part accumulated in the first accumulator 46 to the rod side of the boom cylinder 7c1.

  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 makeup passage 99 having a makeup function capable of replenishing hydraulic oil is connected to the second accumulator 100. The makeup passage 99 is connected to a second accumulator 100 that supplies pressure oil. Then, hydraulic fluid is passed from the makeup passage 99 to the side of the passages 92 and 93 where there is a risk of vacuum generation via the check valves 97 and 98 at a pressure not exceeding the spring biasing pressure of the check valve 57 with spring. refill.

  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 swash plate angle sensor 16φ, 17φ, 18φ, pressure sensor 24, 25, 55 inputs the detected swash plate angle signal and pressure signal to an in-vehicle controller (not shown), The valves 42 and 51 are switched by an on / off operation or a proportional operation in accordance with the drive signal according to a drive signal output from an in-vehicle controller (not shown). 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. 9). A pilot operation is performed by a so-called remote control valve, which is a manually operated valve 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.

  Below, the content controlled by the said vehicle-mounted controller is demonstrated functionally.

  FIG. 1 shows a circuit state during a boom lowering operation for lowering the boom 7 (FIG. 9). The hydraulic oil pushed out from the head side of one boom cylinder 7c1 by the load of the working device 6 (FIG. 9) A control valve 61 that 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 is communicated with the passage 68 and the passage 82 via the check valve 67. The accumulator 46 accumulates pressure and is regenerated to the rod side of the boom cylinder 7c1 via the check valve 83, the passage 84 and the passage 39 via the regeneration control valve 63 switched from the passage 82 to the communication position.

  At this time, the control valve 61 controls the head of one boom cylinder 7c1 in accordance with 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. Is an output for operating the control valve 61. More specifically, in the present embodiment, as shown in FIG. 3, in the table T1, when the pilot pressure set by the lever operation amount is relatively small, the output pressure is increased with respect to the increase amount of the input pressure. In the region where the pilot pressure set by the lever operation amount exceeds the predetermined threshold TH1, the increase in the output pressure relative to the increase in the input pressure is suppressed more than when it is less than the threshold TH1. Further, the output pressure is set to be constant in a region that exceeds a predetermined threshold value TH2 that is greater than the predetermined threshold value 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.

  In addition, the regeneration control valve 63 includes a control valve 61 and one boom according to the lever operation amount, that is, the pilot pressure set by the operation amount and the accumulator pressure of the first accumulator 46 detected by the pressure sensor 55. Switches the amount of communication with the rod side of cylinder 7c1. Specifically, the pilot pressure set by the lever operation amount is corrected by a predetermined table (converter) T3, and the accumulator pressure is corrected by a predetermined table (converter) T4. Is an output for operating the regeneration control valve 63. More specifically, in the present embodiment, as shown in FIG. 5, in the table T3, when the pilot pressure set by the lever operation amount is relatively small, the output pressure is proportional to the increase in the input pressure. Increases and the output pressure is set constant in a region where the pilot pressure set by the lever operation amount exceeds a predetermined threshold TH4. In the table T4, the gain is set constant with respect to the increase amount of the accumulator pressure.

  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 62 of the boom energy recovery valve 31. The control oil is further 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 into the passage 76 through the check valve 80 is returned to the check valve in the main control valve 62. 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 62 changes according to the operation amount of the lever, that is, the pilot pressure set by the operation amount. Specifically, the pilot pressure set by the amount of lever operation is corrected by a predetermined table (converter) T5 to obtain an output for operating the main control valve 62. More specifically, in this embodiment, as shown in FIG. 4, the input pressure and the output pressure of the pilot pressure set by the lever operation amount are set by the table T5 similar to the table T1 of FIG. Basically, when a boom lowering operation is detected, the operation is switched immediately. 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. 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. 9) based on the head pressure of the boom cylinders 7c1 and 7c2, a predetermined set value is set. Accordingly, the separation of the pressure accumulating cylinder and the self-regenerating cylinder of the boom cylinders 7c1 and 7c2 is released.

  In this way, the boom energy recovery valve 31 has the control valve 61, the regeneration control valve 63, and the main control valve 62 to accumulate pressure on the first accumulator 46 when the boom is lowered and to the rod side of the boom cylinders 7c1 and 7c2. Playback to 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 during a predetermined time at the initial operation of the boom lowering operation and supplies hydraulic oil to the rod side of the boom cylinder 7c1 via the output passage 38 and the passage 39, and the boom 7 When the descent starts, hydraulic fluid 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.

  Further, the pump flow rate from the main pump 12 to the boom cylinder 7c1 controlled by the boom control valve 26 is the operation amount of the lever, that is, the pilot pressure set by this operation amount, the accumulator pressure of the first accumulator 46, Is set according to Specifically, in the present embodiment, as shown in FIG. 6, the pump flow rate is the same as the flow rate set by a predetermined table (converter) T6 according to the pilot pressure set by the lever operation amount. A minimum value of a flow rate set by a predetermined table (converter) T7 according to a predetermined short time at the start of the boom lowering operation counted by the timer counter TC, for example, an elapsed time of 10 ms, and a timer It is set by a predetermined short time at the start of the boom lowering operation counted by the counter TC, for example, an acceleration flow rate set by a predetermined table (converter) T8 and an operation amount of the lever according to an elapsed time of 10 ms. The larger one of the integrated value with the gain set by a predetermined table (converter) T9 is set as the base flow rate according to the pilot pressure. In the table T6, the flow rate is set constant in the region where the pilot pressure set by the lever operation amount is equal to or less than the predetermined threshold value TH5, and the pilot pressure exceeds the predetermined threshold value TH5 and exceeds the predetermined threshold value TH5. In the following region, the flow rate decreases in proportion to the increase, and in the region exceeding the predetermined threshold TH6, the flow rate is set constant. In the table T7, the flow rate increases in proportion to the elapse of the time counted by the timer counter TC, and the flow rate is set constant during a time exceeding a predetermined threshold value TH7. In table T8, the flow rate increases in proportion to the passage of time counted by the timer counter TC, and the flow rate is set constant for a time that exceeds the predetermined threshold TH8 and is less than or equal to the predetermined threshold TH9. In the time exceeding the predetermined threshold TH9, the flow rate decreases in proportion to the passage of time. In the table T9, when the pilot pressure set by the lever operation amount is relatively small, the gain increases in proportion to the increase, and is set constant (for example, 1) in the region exceeding the predetermined threshold TH10.

  Then, as shown in FIG. 7, the above-described pump at the time of the boom lowering single operation is obtained by integrating the base flow rate with the gain set by the predetermined table (converter) T10 according to the accumulator pressure. When the lever operation for stick-in, stick-out, bucket-in and bucket-out is performed simultaneously with the boom lowering operation, a predetermined table (in accordance with the pilot pressure set by these operations is set. Converter) Add the flow rate set by T11 to T14. In the table T10, when the accumulator pressure is equal to or lower than a predetermined threshold TH11, the gain is set to be constant (for example, 1). In the region exceeding the predetermined threshold TH11, when the accumulator pressure is relatively small, the gain is increased with respect to the increase amount. In the region where the accumulator pressure exceeds the predetermined threshold TH11 and is greater than the predetermined threshold TH11, the gain increase relative to the accumulator pressure increase is less than the threshold TH11. Further, the gain is set to be constant (greater than 1) in a region exceeding a predetermined threshold TH13 that is larger than the predetermined threshold TH12. Further, in the tables T11 to T14, in the region where the pilot pressure set by the lever operation amount is equal to or less than the predetermined threshold TH14, the increase amount of the flow rate is relatively large with respect to the increase amount, and the pilot pressure is the predetermined threshold value. In a region that exceeds TH14 and is below a predetermined threshold TH15 that is greater than this predetermined threshold TH14, the increase in flow rate relative to the increase in pilot pressure is suppressed more than when it is less than or equal to threshold TH14, and in a region that exceeds the predetermined threshold TH15 The flow rate is set constant. These tables T11 to T14 may be the same table, or may be tables having different values for the threshold values TH14 and TH15.

  2 shows a circuit state at the time of a boom raising operation for raising the boom 7 (FIG. 9). The boom energy recovery valve 31 at the time of the boom raising operation shuts off the control valve 61 and the regeneration control valve 63. And the main control valve 62 are 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. The hydraulic oil supplied to passage 30 via 28 is led from passage 79 to passage 37, drift reduction valve 36 and passage 35 to the head side of the other boom cylinder 7c2, and from check valve 78 to passage 34, drift reduction. It is guided to the head side of one boom cylinder 7c1 through the valve 33 and the passage 32. 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 62 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 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, at the time of 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 61 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. During this engine power assist, the electromagnetic switching valve 51 is switched to the communication position, the assist motor 15 is rotated by the energy accumulated in the first accumulator 46, and the hydraulic output of the main pumps 12, 13 is assisted. Reduce the engine load. Note that when the airframe 1 is lifted, engine power assist by the assist motor 15 is not performed.

  Specifically, as shown in FIG. 8, it is set to 0 and 1 according to the boom lowering single operation (boom lowering single state) and the operation other than the boom lowering operation (state other than the boom lowering). And a predetermined table (converter) corresponding to the accumulator pressure by a predetermined table (converter) T15 corresponding to an operation other than the boom lowering operation and a predetermined table (converter) corresponding to the boom lowering operation A logical sum with a flag set according to the accumulator pressure is output as an assist flag by T16. When this assist flag is on, ie, 1 the electromagnetic switching valve 51 is in the communication position, and when it is off, ie, 0, the electromagnetic type The switching valve 51 is in the cutoff position. In the table T15, a predetermined threshold TH16 and a predetermined threshold TH17 larger than the predetermined threshold TH16 are set, and when the accumulator pressure increases, the flag is switched from 0 to 1 when the threshold TH17 or more is reached, and the accumulator pressure is When the value decreases, the flag is switched from 1 to 0 when the threshold value becomes less than TH16. In the table T16, a predetermined threshold TH18 larger than the predetermined threshold TH17 and a predetermined threshold TH19 larger than the predetermined threshold TH18 are set, and when the accumulator pressure increases, the flag is set to 0 when the threshold TH19 or higher is reached. When the accumulator pressure decreases, the flag is switched from 1 to 0 when the threshold value TH18 or less is reached. Therefore, these tables T15 and T16 are set with a so-called hysteresis in which the thresholds differ with respect to the increase or decrease of the accumulator pressure.

  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.

  As a result, for example, during the boom lowering operation, the control valve 61 is switched to the communication position, the main control valve 62 is disconnected from the head side of the boom cylinders 7c1, 7c2, and the boom cylinder 7c2, the boom cylinders 7c1, 7c2 The first sequence in which the pressure accumulating circuit A and the regeneration circuit B are formed by switching to the positions where the respective rod sides are connected to each other, and following this first sequence, accumulating pressure from the control valve 61 to the first accumulator 46 and regeneration By switching the control valve 63 to the communication position, a part of the hydraulic oil accumulated in the first accumulator 46 is regenerated to the rod side of the boom cylinder 7c1, and from the main pump 12 via the boom control valve 26 The second sequence in which the supply of hydraulic oil to the rod side of 7c1 is increased for a short time and then throttled, and following this second sequence, the first accumulator 46 is stored. And while a third sequence to rotate the assist motor 15 by utilizing the surplus of the accumulator is energy by switching the electromagnetic switch valve 51 to the communicating position is set.

  Then, as described above, 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, a part of the hydraulic oil pushed out from the head side of the boom cylinder 7c1 (approximately half) ) Is accumulated in the first accumulator 46 by the control valve 61, and the other part of the hydraulic fluid (substantially the other half) is regenerated to the rod side of the boom cylinder 7c1 by the regeneration control valve 63 of the auxiliary regeneration circuit C. Since the hydraulic oil pushed out from the head side of 7c2 is regenerated to the rod side of the boom cylinders 7c1 and 7c2 by the main control valve 62, the regenerative flow rate of the main pumps 12 and 13 when the first accumulator 46 is accumulating. The main pump can easily secure the required pump flow rate including the main pump flow rate required by other hydraulic actuators with a simple configuration using the control valves 61, 62, 63. 12 and 13 can be downsized.

  Moreover, the hydraulic oil pushed out from the head side of the boom cylinder 7c1 by the auxiliary regeneration circuit C even when the boom cylinders 7c1, 7c2 and other hydraulic actuators (swing motor 3m, stick cylinder 8c, bucket cylinder 9c, etc.) are operated in conjunction. Is regenerated to the rod side of the boom cylinder 7c1, and 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. The pumps 12 and 13 can be turned to other hydraulic actuators to prevent a decrease in speed during linked operation, improve linked operability, and boom cylinders 7c1 and 7c2 at the stroke end of other hydraulic actuators It is also possible to effectively prevent the boom 7 from rapidly dropping due to a sudden increase in the regeneration flow rate to the rod side.

  Also, at the initial operation of the boom lowering operation, hydraulic oil is supplied from the main pump 12 to the rod side of the boom cylinder 7c1 by the boom control valve 26. Therefore, the initial operation speed during the boom lowering operation (when the boom cylinders 7c1, 7c2 contract) Can be improved.

  Further, a part of the oil on the head side of the boom cylinder 7c1 on one side is turned to accumulate 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. By concentrating on one boom cylinder 7c1, the energy density can be increased, and the pressure generated from the boom cylinder 7c1 can be increased to increase the accumulated energy in the first accumulator 46, in other words, Components such as the first accumulator 46 and the assist motor 15 can be downsized, the cost can be reduced, and the layout can be facilitated.

  The control valve 61 changes the communication amount between the head side of the boom cylinder 7c1 and the first accumulator 46 in accordance with the lever operation amount and the accumulator pressure of the first accumulator 46, and the regeneration control valve 63. However, since the communication amount between the control valve 61 and the rod side of the boom cylinder 7c1 is changed according to the lever operation amount and the accumulator pressure, the first operation can be performed more appropriately without sacrificing the operability of the boom lowering operation. Accumulator 46 can be accumulated to satisfy both operability and energy accumulator at the same time, and can effectively regenerate the hydraulic oil to the rod side of boom cylinder 7c1, and the main pump 12 to the rod side of boom cylinder 7c1. The flow rate of hydraulic oil discharged from 13 can be reduced, and the necessary pump flow rate can be secured more easily.

  Furthermore, 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.

  In addition, by concentrating the load on one boom cylinder 7c1, the accumulated energy of the first accumulator 46 can be increased, and a large accumulator can provide great assistance, thus reducing costs and making the aircraft layout compact. Can do.

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

A Accumulation circuit B Regeneration circuit C Auxiliary regeneration circuit
HE Excavator as work machine 1 Airframe 6 Work device
7c1, 7c2 Boom cylinder as fluid pressure cylinder
12, 13 Main pump as a pump
46 The first accumulator that is an accumulator
61 Control valve as first valve
62 Main control valve as second valve
63 Regeneration control valve as third valve

Claims (3)

A plurality of fluid pressure cylinders that simultaneously operate the same operation by a working fluid pressurized and supplied from a pump according to the operation of the operating body;
An accumulator that accumulates pressure with the working fluid;
There is provided a first valve that changes the communication amount between the head side of one fluid pressure cylinder and the accumulator in accordance with the operation amount of the operating body, and from the head side of one fluid pressure cylinder via this first valve. An accumulator circuit for accumulating the pushed working fluid in an accumulator;
When accumulator accumulates pressure by the accumulator circuit, the communication between the head sides of the plurality of fluid pressure cylinders is cut off, and the head side of the other fluid pressure cylinder among the plurality of fluid pressure cylinders and each of the one and other fluid pressure cylinders A regeneration circuit that includes a second valve that communicates with the rod side, and that regenerates the working fluid pushed out from the head side of another fluid pressure cylinder to the one and other fluid pressure cylinders via the second valve; ,
A third valve is provided for changing the amount of communication between the first valve and the rod side of one fluid pressure cylinder in accordance with the operation amount of the operating body, and the accumulator is connected to the accumulator via the third valve. A fluid pressure circuit comprising: an auxiliary regeneration circuit for regenerating a part of the accumulated working fluid to the rod side of one fluid pressure cylinder. The first valve changes the communication amount between the head side of one fluid pressure cylinder and the accumulator according to the operation amount of the operating body and the accumulator pressure,
The fluid pressure according to claim 1, wherein the third valve changes a communication amount between the first valve and a rod side of one fluid pressure cylinder according to an operation amount of the operating body and an accumulator pressure. circuit. The aircraft,
Working equipment mounted on the aircraft,
A working machine comprising: the fluid pressure circuit according to claim 1 or 2 provided for a plurality of fluid pressure cylinders that move up and down the work device.

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