Hydraulic drive device

Abstract

To provide a hydraulic drive device capable of improving energy efficiency of an entire work machine by efficiently regenerating hydraulic energy of return oil from a hydraulic actuator by using an accumulator.SOLUTION: A hydraulic drive device 200 includes: a second pressure accumulation device 11; a third pipeline 26 that connects a portion connecting a first hydraulic actuator 4 and a first pressure accumulation regulation device 10 in a second pipeline 25 and the second pressure accumulation device 11; a second pressure accumulation regulation device 12 that is installed in the third pipeline 26 and regulates a flow of work oil from the first hydraulic actuator 4 to the second pressure accumulation device 11; and first pressure detectors 48, 49 that detect pressure of the first hydraulic actuator 4. A control device 100 controls at least one of a first flow control valve 13 and the second pressure accumulation regulation device 12 in accordance with an operation amount detected by a first operation amount detector 29, pressures detected by the first pressure detectors 48, 49 and pressure of the second pressure accumulation device 11.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a hydraulic drive system mounted on a work machine such as a hydraulic excavator. [Background technology]

[0002] There is a hydraulic drive system that can store potential energy of a working implement in an accumulator via a boom cylinder and store kinetic energy of an upper rotating body in an accumulator via a swing motor and use the energy to assist engine power. For example, Patent Document 1 is a prior art document that discloses such a hydraulic drive system.

[0003] According to the above-mentioned conventional technology, the potential energy of the working implement and the kinetic energy of the upper rotating body are regenerated as hydraulic energy, making it possible to reduce energy conversion loss compared to when the energy is regenerated as electrical energy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-90194 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the case of conventional hydraulic drive systems, in order to efficiently regenerate regenerative energy from the hydraulic actuator in the accumulator, it is necessary to set the set pressure of the accumulator to a high value close to the pressure of the hydraulic actuator and reduce the pressure loss between the hydraulic actuator and the accumulator.

[0006] However, when a pressure equal to or lower than the set pressure of the accumulator is generated by the hydraulic actuator, the energy of the pressurized oil from the hydraulic actuator cannot be regenerated by the accumulator. Therefore, if the set pressure of the accumulator is increased to reduce pressure loss, there is a problem that in a work machine that is driven by various operations, the number of situations in which energy can be regenerated by the accumulator decreases.

[0007] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a hydraulic drive system that can improve the energy efficiency of the entire work machine by efficiently regenerating the hydraulic energy of the return oil from the hydraulic actuator in an accumulator. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a hydraulic oil tank that stores hydraulic oil, a hydraulic pump that draws in and discharges hydraulic oil from the hydraulic oil tank, a first hydraulic actuator, a first flow control valve that is installed in a first pipe that connects the hydraulic pump and the first hydraulic actuator and that controls a flow rate of hydraulic oil supplied from the hydraulic pump to the first hydraulic actuator and a flow rate of hydraulic oil discharged from the first hydraulic actuator to the hydraulic oil tank, a first pressure accumulator, a second pipe that connects the first hydraulic actuator and the first pressure accumulator, a first pressure accumulator adjustment device that is installed in the second pipe and that adjusts the flow of hydraulic oil from the first hydraulic actuator to the first pressure accumulator, a first operating device that instructs an operation of the first hydraulic actuator, and a control device that controls the first operating device. a second accumulator; a third conduit connecting a portion of the second conduit that connects the first hydraulic actuator and the first accumulator regulation device to the second accumulator; a second accumulator regulation device installed in the third conduit and regulating a flow of hydraulic oil from the first hydraulic actuator to the second accumulator; and a first pressure detection device that detects the pressure of the first hydraulic actuator, and the control device controls at least one of the first flow control valve and the second accumulator regulation device in accordance with the amount of operation detected by the first operation amount detection device, the pressure detected by the first pressure detection device, and the pressure of the second accumulator. Effect of the Invention

[0009] According to the present invention, the hydraulic energy of the return oil from the hydraulic actuator can be efficiently regenerated in the accumulator, so that it is possible to improve the energy efficiency of the entire work machine. [Brief description of the drawings]

[0010] [Figure 1] 1 is a perspective view showing a hydraulic excavator equipped with a hydraulic drive system according to an embodiment of the present invention. [Diagram 2]1 is a schematic configuration diagram of a hydraulic drive system according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram showing details of a portion of the hydraulic drive system according to the embodiment of the present invention that is involved in driving a swing motor and a boom cylinder. [Figure 4] 4 is a diagram showing changes in a swing operation amount, a swing speed, a pressure of a swing motor, a pressure of a first accumulator, and a pressure of a second accumulator 11 during a swing operation in the embodiment of the present invention. FIG. [Diagram 5] FIG. 2 is a functional block diagram of a control device related to driving of a swing motor in the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same reference numerals are used to denote the same components, and duplicated explanations will be omitted as appropriate.

[0012] FIG. 1 is a perspective view showing a hydraulic excavator equipped with a hydraulic drive system according to this embodiment. The hydraulic drive system according to the present invention is not limited to hydraulic excavators, and can also be applied to other work machines such as crawlers and wheel loaders. In FIG. 1, the hydraulic excavator 1 includes a multi-joint type working device 1A having a boom 1a, an arm 1b, and a bucket 1c, and a vehicle body 1B having an upper rotating body 1d and a lower traveling body 1e. The upper rotating body 1d is provided rotatably on the lower traveling body 1e, and is driven by a swing motor 4 (shown in FIG. 2). The boom 1a is rotatably supported by the upper rotating body 1d, and is driven by a boom cylinder 3a (second hydraulic actuator). The arm 1b is rotatably supported by the boom 1a, and is driven by an arm cylinder 3b (second hydraulic actuator). The bucket 1c is rotatably supported by the arm 1b, and is driven by a bucket cylinder 3c (second hydraulic actuator).

[0013] Fig. 2 is a schematic diagram of a hydraulic drive system according to this embodiment. In Fig. 2, a hydraulic drive system 200 includes a first hydraulic pump 6 and a second hydraulic pump 7 that are mechanically connected to an engine 5 and driven by the power of the engine 5, a boom cylinder 3a, an arm cylinder 3b, a bucket cylinder 3c, and a swing motor 4 (first hydraulic actuator) that are actuators driven by pressure oil discharged from the hydraulic pumps 6 and 7, and a first accumulator 9 (first pressure accumulator) and a second accumulator 11 (second pressure accumulator) that accumulate pressure oil discharged from the swing motor 4.

[0014] The first hydraulic pump 6 and the second hydraulic pump 7 are connected to each actuator through a pipeline. Pipes 60, 61 connecting the first hydraulic pump 6 and the boom cylinder 3a are provided with a flow control valve 14 that controls the flow rate of pressure oil supplied from the first hydraulic pump 6 to the boom cylinder 3a, and pipes 62, 63 connecting the second hydraulic pump 7 and the boom cylinder 3a are provided with a flow control valve 15 that controls the flow rate of pressure oil supplied from the second hydraulic pump 7 to the boom cylinder 3a.

[0015] Similarly, a flow control valve 16 is provided in the pipelines 64, 65 connecting the first hydraulic pump 6 and the arm cylinder 3b to control the flow rate of pressurized oil supplied from the first hydraulic pump 6 to the arm cylinder 3b, and a flow control valve 17 is provided in the pipelines 66, 67 connecting the second hydraulic pump 7 and the arm cylinder 3b to control the flow rate of pressurized oil supplied from the second hydraulic pump 7 to the arm cylinder 3b.

[0016] In addition, a flow control valve 18 is provided in the pipelines 68, 69 connecting the first hydraulic pump 6 and the bucket cylinder 3c, which controls the flow rate of pressurized oil supplied from the first hydraulic pump 6 to the bucket cylinder 3c, and a flow control valve 13 (first flow control valve) is provided in the pipelines 51, 52 (first pipelines) connecting the second hydraulic pump 7 and the swing motor 4, which controls the flow rate of pressurized oil supplied from the second hydraulic pump 7 to the swing motor 4.

[0017] The above-mentioned flow rate control valves 13 to 18 are center bypass type control valves that discharge pressure oil from the hydraulic pumps 6, 7 via center bypass pipes 70, 71 to the hydraulic oil tank 35 when in the neutral position.

[0018] Mutually opposite check valves 44, 45 and relief valves 46, 47 are provided between a pipe 51 connecting the flow control valve 13 and the right swing port of the swing motor 4, and a pipe 52 connecting the flow control valve 13 and the left swing port of the swing motor 4, and these check valves 44, 45 and relief valves 46, 47 are connected to the hydraulic oil tank 35 by a pipe 50. The pipe 50 has a tank passage function that returns hydraulic oil discharged from the swing motor 4 to the hydraulic oil tank 35, and a make-up function that can replenish hydraulic oil to the swing motor 4.

[0019] Further, a high pressure selection valve 8 is provided between the pipes 51 and 52, and the high pressure selection valve 8 selects the high pressure side of the pipes 51, 52 when the swing motor 4 is braking for left or right swing, and discharges pressure oil downstream. The high pressure selection valve 8 is connected to the first accumulator 9 and the second accumulator 11 by pipes 25 and 26, respectively. The pipe 25 (second pipe) connecting the high pressure selection valve 8 and the first accumulator 9 is provided with a pressure control valve 10 (first accumulation regulator) that adjusts the flow of pressure oil from the swing motor 4 to the second accumulator 11.

[0020] Furthermore, in the pipeline 25, a pipeline 26 (third pipeline) branches off between the high pressure selection valve 8 and the first pressure accumulation regulator 10 and connects to the second accumulator 11. The pipeline 26 (third pipeline) is provided with a flow control valve 12 (second pressure accumulation regulator) that adjusts the flow of pressurized oil from the swing motor 4 to the second accumulator 11 and is controlled by a control device 100 described later.

[0021] The first accumulator 9 and the second accumulator 11 are connected to each actuator via a respective pipeline, and the energy regenerated by the first accumulator 9 and the second accumulator 11 is used to drive each actuator. A flow control valve 19 (first control valve) that controls the flow rate of pressure oil supplied from the first accumulator 9 to the boom cylinder 3a is provided in pipeline 38 (fourth pipeline) connecting the first accumulator 9 and the boom cylinder 3a, and a flow control valve 20 (second control valve) that controls the flow rate of pressure oil supplied from the second accumulator 11 to the boom cylinder 3a is provided in pipeline 39 (fifth pipeline) connecting the second accumulator 11 and the boom cylinder 3a.

[0022] Similarly, a flow control valve 21 (first control valve) that controls the flow rate of pressurized oil supplied from the first accumulator 9 to the arm cylinder 3b is provided in a pipeline 40 (fourth pipeline) connecting the first accumulator 9 and the arm cylinder 3b, and a flow control valve 22 (second control valve) that controls the flow rate of pressurized oil supplied from the second accumulator 11 to the arm cylinder 3b is provided in a pipeline 41 (fifth pipeline) connecting the second accumulator 11 and the arm cylinder 3b.

[0023] Furthermore, a flow control valve 23 (first control valve) that controls the flow rate of pressurized oil supplied from the first accumulator 9 to the bucket cylinder 3c is provided in a pipe 42 (fourth pipe) connecting the first accumulator 9 and the bucket cylinder 3c, and a flow control valve 24 (second control valve) that controls the flow rate of pressurized oil supplied from the second accumulator 11 to the bucket cylinder 3c is provided in a pipe 43 (fifth pipe) connecting the second accumulator 11 and the bucket cylinder 3c.

[0024] Each of the above-mentioned control valves 19 to 24 is driven by a command signal from a control device 100, which will be described later, and controls the flow rate by changing the position of the internal spool.

[0025] Next, the control for changing the connection according to the lever operation amount will be described with reference to Figs.

[0026] Fig. 3 is a diagram showing details of the parts of the hydraulic drive system 200 according to this embodiment that are involved in driving the swing motor 4 and the boom cylinder 3a. In Fig. 3, a pressure control valve 10 adjusts the inlet pressure to a preset set pressure and adjusts the flow of pressure oil from the swing motor 4 to the second accumulator 11. In addition, a flow control valve 12 adjusts the flow rate of pressure oil from the swing motor 4 to the second accumulator 11 in response to a command signal from a control device 100, which will be described later.

[0027] A pressure sensor 49 is installed on a pipe 51 connected to the swing motor 4, and a pressure sensor 48 is installed on a pipe 52 connected to the swing motor 4, and the pressure sensors 48 and 49 each input the detected pressure to the control device 100 described later.

[0028] In addition, the second accumulator 11 is preset to a pressure lower than that of the first accumulator 9, the set pressure of the first accumulator 9 is set lower than the set pressures of the relief valves 46, 47, and the set pressure of the pressure control valve 10 is set lower than the set pressures of the relief valves 46, 47 and higher than the set pressure of the first accumulator 9 (for example, the pressure of the first accumulator 9: 25 MPa, the pressure of the second accumulator 11: 14 MPa, the set pressures of the relief valves 46 and 47: 32 MPa, and the set pressure of the pressure control valve 10: 31.5 MPa).

[0029] In addition, a rotation speed sensor 33 (rotation speed detection device) that detects the rotation speed, a pressure sensor 34 (second pressure detection device) that detects the pressure of the second accumulator 11, and a pressure sensor 53 that detects the pressure of the second accumulator 11 are provided, and the rotation speed detected by the rotation speed sensor 33, the pressure of the second accumulator 11 detected by the pressure sensor 34, and the pressure of the first accumulator 9 detected by the pressure sensor 53 are input to the control device 100.

[0030] A pressure sensor 27 that detects the bottom side pressure of the boom cylinder 3a and a pressure sensor 32 that detects the rod side pressure of the boom cylinder 3a are installed, and the boom cylinder bottom pressure detected by pressure sensor 27 and the boom cylinder rod pressure detected by pressure sensor 32 are input as detected pressures to the control device 100.

[0031] In this embodiment, the configuration is characterized by comprising a flow control valve 13 that controls the flow rate from the second hydraulic pump 7 to the swing motor 4 and the flow rate from the swing motor 4 to the hydraulic oil tank 35, a first accumulator 9, a second accumulator 11 that is installed separately from the first accumulator 9 and is set in advance to a lower pressure than the first accumulator 9, a pressure control valve 10 installed in a pipeline that sends energy discharged from the swing motor 4 to the first accumulator 9, and a flow control valve 12 that branches off from the pipeline connecting the swing motor 4 and the pressure control valve 10 and is installed in a pipeline connected to the second accumulator 11, and the flow control valve 12 and the flow control valve 13 are adjustable by a control device 100.

[0032] In addition, in this embodiment, the control features are that the excess pressurized oil discharged from the second hydraulic pump 7 and sent to the swing motor 4 during swing acceleration is regenerated in the first accumulator 9, and when medium-pressure return oil (return oil whose pressure is higher than the pressure of the second accumulator 11 and lower than the set pressure of the pressure control valve 10) is discharged from the swing motor 4 during swing deceleration, this medium-pressure return oil is regenerated in the second accumulator 11, and when high-pressure return oil (return oil whose pressure is higher than the set pressure of the pressure control valve 10) is discharged from the swing motor 4 during swing deceleration, this high-pressure return oil is regenerated in the first accumulator 9.

[0033] The control device 100 outputs electromagnetic commands to each valve according to the operation amount of each operation device 28, 30 detected by each operation amount detection device 29, 31. The flow control valve 14 and the flow control valve 15 are provided with operation terminals 14a, 14b, 15a, 15b at both ends that receive electromagnetic commands from the control device 100. The flow control valve 14 and the flow control valve 15 switch spool positions in response to electromagnetic commands from the control device 100 to their operation terminals, and supply pressure oil from the first hydraulic pump 6 and the second hydraulic pump 7 to the boom cylinder 3a to drive the boom 1a. The flow control valve 13 is provided with operation terminals 13a, 13b at both ends that receive electromagnetic commands from the control device 100. The flow control valve 13 switches spool positions in response to electromagnetic commands from the control device 100 to their operation terminals, and supply pressure oil from the second hydraulic pump 7 to the swing motor 4 to swing the upper swing body 1d.

[0034] Additionally, the flow control valves 19 and 20 are three-position closed center directional control valves, and are provided at both ends with operation terminals 19a, 19b, 20a, and 20b which receive electromagnetic commands from the control device 100. The flow control valves 19 and 20 switch their spool positions in response to electromagnetic commands from the control device 100 to their operation terminals, and supply pressure oil from the first accumulator 9 and the second accumulator 11 to the boom cylinder 3a to drive the boom 1a.

[0035] The operation amount of the operation device 30 (second operation device) is detected by a boom operation amount detection device 31 (second operation amount detection device), and this is input to the control device 100. In response to this, the control device 100 outputs an electromagnetic command to drive at least one of the flow control valves 14, 15, 19, and 20.

[0036] Next, the operation will be described. When the operating device 30 is operated, the control device 100 sends an electromagnetic command corresponding to the amount of operation to the flow control valves 14 and 15, and operates the flow control valves 14 and 15. As a result, the pressure oil discharged from the first hydraulic pump 6 and the second hydraulic pump 7 is sent to the boom cylinder 3a, and the boom cylinder 3a operates.

[0037] Furthermore, when the operating device 28 (first operating device) is operated, the control device 100 sends an electromagnetic command corresponding to the amount of operation to the flow control valve 13, and operates the flow control valve 13. As a result, the pressure oil discharged from the second hydraulic pump 7 is sent to the swing motor 4, and the swing motor 4 operates.

[0038] Although omitted in FIG. 3, the driving of the arm cylinder 3b by the first hydraulic pump 6 and the second hydraulic pump 7 and the driving of the bucket cylinder 3c by the first hydraulic pump 6 are similar to the driving of the boom cylinder 3a described above.

[0039] The amount of operation of the operation device 28 is detected by a swing operation amount detection device 29 (first operation amount detection device), and this is input to the control device 100. In response to this, the control device 100 outputs an electromagnetic command to at least one of the flow control valve 12 and the flow control valve 13, and controls the opening of the flow control valve 12 and the flow control valve 13.

[0040] Next, an overview of the control that changes the connection according to the lever operation amount will be explained with reference to FIG.

[0041] 4 is a diagram showing changes in the amount of swing operation, the swing speed, the pressure of the swing motor 4, the pressure of the first accumulator 9, and the pressure of the second accumulator 11 during a swing operation. It is a diagram showing changes in the swing speed, the pressure on both sides of the swing motor 4, the pressure of the first accumulator 9, and the pressure of the second accumulator 11 when a swing operation amount is input by the operating device 28. The operation of the flow control valve 12 and the flow control valve 13 in each process is also shown.

[0042] First, in step S1, since no turning operation is performed, the flow control valves 12 and 13 are closed and the turning speed is also zero.

[0043] Next, when a rotation operation is input, the process moves to step S2, and the flow control valve 13 opens through the control described below, so that pressurized oil from the second hydraulic pump is sent to the right rotation port of the rotation motor 4, the right rotation port pressure rises, and the rotation speed accelerates.

[0044] Next, in step S3, when the right rotation port pressure of the swing motor 4 reaches the set pressure of the pressure control valve 10, the flow control valve 12 is closed, so that the surplus oil discharged from the second hydraulic pump 7 and sent to the swing motor 4 is sent to the first accumulator 9 via the pressure control valve 10. This allows the first accumulator 9 to regenerate the surplus pressure oil discharged from the second hydraulic pump 7.

[0045] Next, in step S4, as the amount of rotation operation decreases, the opening of the flow control valve 13 becomes smaller through control described below, so that the flow rate sent to the right rotation port of the rotation motor 4 decreases and the right rotation port pressure decreases.

[0046] When the swing operation amount further decreases, the process proceeds to step S5. In step S5, as the opening of the flow control valve 13 decreases, the flow rate discharged to the hydraulic oil tank 35 via the flow control valve 13 decreases, so the left swing port pressure of the swing motor 4 rises and the swing speed decelerates. At this time, the flow control valve 12 is opened by the control described later, but since the pressure of the left swing port is lower than the pressure of the second accumulator 11, no oil flows to the second accumulator 11.

[0047] Furthermore, when the left swing port pressure of the swing motor 4 increases and becomes higher than the pressure of the second accumulator 11, the process proceeds to step S6. In step S6, the flow control valve 13 is closed by the control described later, while the flow control valve 12 is open, so that all the oil discharged from the left swing port of the swing motor 4 is sent to the second accumulator 11 via the flow control valve 12. This allows the second accumulator 11 to regenerate the medium-pressure oil discharged from the swing motor 4.

[0048] The left swing port pressure of the swing motor 4 further increases, and when the left swing port pressure of the swing motor 4 becomes higher than the set pressure of the pressure control valve 10, the process proceeds to step S7. In step S7, the flow control valves 12 and 13 are closed by control described later, so that the oil discharged from the left swing port of the swing motor 4 is sent to the first accumulator 9 via the pressure control valve 10. This allows the first accumulator 9 to regenerate the high-pressure oil discharged from the swing motor 4.

[0049] Next, a specific control method for the flow control valves 12 and 13 will be described with reference to FIG.

[0050] Fig. 5 is a functional block diagram of the control device 100 related to the drive of the swing motor 4. In Fig. 5, the control device 100 includes a first subtraction calculation unit 101, a first switching calculation unit 102, a second switching calculation unit 103, an output conversion unit 104, a swing acceleration / deceleration determination unit 105, a first function generation unit 106, a second function generation unit 107, a first multiplication calculation unit 108, a maximum value calculation unit 109, a second subtraction calculation unit 110, a third function generation unit 111, a fourth function generation unit 112, a second multiplication calculation unit 113, a third subtraction calculation unit 114, a third switching calculation unit 115, and a third multiplication calculation unit 116. The control device 100 includes a calculation unit such as a CPU, a storage device such as a ROM and a RAM, and an input / output interface for inputting and outputting signals between the control device 100 and an external device, and realizes the functions of each unit by executing a program stored in the ROM or the like.

[0051] 5, maximum value calculation unit 109 inputs the left turning port side pressure detected by pressure sensor 48 to one input end, and inputs the right turning port side pressure detected by pressure sensor 49 to a second input end. These maximum values ​​are output as turning high pressure side pressure 109A to one input end of first subtraction calculation unit 101 and one input end of third subtraction calculation unit 114.

[0052] The first subtraction calculation unit 101 inputs the swing high pressure side pressure 109A to one input terminal, and inputs the pressure of the second accumulator 11 detected by the pressure sensor 34 to a second input terminal. The first subtraction calculation unit 101 calculates the difference between the swing high pressure side pressure 109A and the pressure of the second accumulator 11, and outputs this as a differential pressure 101A between the swing pressure and the second accumulator 11 to the second input terminal of the first switching calculation unit 102 and to the third function generation unit 111.

[0053] A pilot pressure corresponding to the operation amount of the operating device 28 is output from the pilot valve 28A, and this is detected by a swing operation amount detection device 29. The swing operation pilot pressure of the pilot valve 28A of the operating device 28 detected by the swing operation amount detection device 29 is output to the third input terminal of the first switching calculation unit 102 and to the first function generation unit 106 as a swing lever operation signal 29A.

[0054] The first switching calculation unit 102 inputs 0 to one input terminal, inputs the pressure difference 101A between the swing pressure and the second accumulator 11 to a second input terminal, and inputs the swing lever operation signal 29A to a third input terminal. When the pressure difference 101A between the swing pressure and the second accumulator 11 is greater than 0, the first switching calculation unit 102 outputs the 0 input to the first input terminal as the output 102A of the first switching calculation unit 102 to the third input terminal of the second switching calculation unit 103. When the pressure difference 101A between the swing pressure and the second accumulator 11 is equal to or less than 0, the first switching calculation unit 102 outputs the swing lever operation signal 29A input to the third input terminal as the output 102A of the first switching calculation unit 102 to the third input terminal of the second switching calculation unit 103.

[0055] A turning acceleration / deceleration determination unit 105 inputs the turning speed detected by the turning speed sensor 33 to one input end, the left turning port side pressure detected by the pressure sensor 48 to a second input end, and the right turning port side pressure detected by the pressure sensor 49 to a third input end. The turning acceleration / deceleration determination unit 105 determines whether the turning is accelerating or decelerating based on the sign of the turning speed and the magnitude of the left and right turning port pressures.

[0056] For example, if the sign of the swing speed becomes positive when the flow control valve 13 is opened from a state in which the swing motor 4 is stopped and the discharge flow rate of the second hydraulic pump 7 is supplied to the right swing port side, the swing acceleration / deceleration determination unit 105 determines that the swing is accelerating if the sign of the swing speed is positive and the pressure on the right swing port side is higher than the pressure on the left swing port side, and outputs 0 to the second input terminal of the second switching calculation unit 103 and the first input terminal of the third multiplication calculation unit 116. Conversely, if the sign of the swing speed is positive and the pressure on the right swing port side is lower than the pressure on the left swing port side, the swing acceleration / deceleration determination unit 105 determines that the swing is decelerating and outputs 1 to the second input terminal of the second switching calculation unit 103 and the first input terminal of the third multiplication calculation unit 116. The above is also the same as when the sign of the swing speed is negative.

[0057] The second switching calculation unit 103 inputs 0 to one input terminal, inputs the output of the turning acceleration / deceleration determination unit 105 to a second input terminal, and inputs the output 102A of the first switching calculation unit 102 to a third input terminal. When the output of the turning acceleration / deceleration determination unit 105 is greater than 0.5 (when turning is decelerating), the second switching calculation unit 103 outputs 0 input to the first input terminal to the output conversion unit 104 as the operation signal 103A of the flow control valve 13. When the output of the turning acceleration / deceleration determination unit 105 is less than 0.5 (when turning is accelerating), the second switching calculation unit 103 outputs the output 102A of the first switching calculation unit 102 input to the third input terminal to the output conversion unit 104 as the operation signal 103A of the flow control valve 13.

[0058] The output conversion unit 104 receives an operation signal 103A of the flow control valve 13, and outputs a control command for the flow control valve 13 calculated according to this value to either the operation end 13a or the operation end 13b of the flow control valve 13.

[0059] By controlling the flow control valve 13 as described above, if the pressure of the return oil during deceleration of a swing is higher than that of the second accumulator 11 and the return oil during deceleration of a swing can be regenerated in the second accumulator 11 or the first accumulator 9, the flow control valve 13 can be closed to send the return oil to the accumulator without being discarded into the hydraulic oil tank 35.

[0060] A first function generating section 106 receives a turning lever operation signal 29A, calculates a target passing flow rate of the flow control valve 12 in response to the signal, and outputs the calculated target passing flow rate to a second function generating section 107 as a target passing flow rate 106A of the flow control valve 12.

[0061] The first function generating unit 106 stores the characteristics of a hydraulic drive unit that does not perform turning regeneration.

[0062] Here, a hydraulic drive system that does not perform swing regeneration is a hydraulic drive system in which the high pressure selection valve 8, the pipeline 25, the pipeline 26, the pressure control valve 10, the flow control valve 12, the first accumulator 9, and the second accumulator 11 have been removed from the hydraulic drive system 200 according to this embodiment, and when the pressure of the pressurized oil discharged from the swing motor 4 during swing deceleration is lower than the set pressure of the relief valves 46, 47, the pressurized oil discharged from the swing motor 4 is discharged to the hydraulic oil tank 35 via the flow control valve 13, and when the pressure of the pressurized oil discharged from the swing motor 4 during swing deceleration is higher than the set pressure of the relief valves 46, 47, the pressurized oil discharged from the swing motor 4 is discharged to the hydraulic oil tank 35 via the relief valves 46, 47.

[0063] The first function generating unit 106 pre-stores the characteristics of the flow rate discharged from the swing motor 4 through the flow control valve 13 to the hydraulic oil tank 35 when a hydraulic drive unit that does not perform swing regeneration is decelerating, and the characteristics are set as a two-dimensional table such that the target passing flow rate 106A of the flow control valve 12 increases as the swing lever operation signal 29A increases.

[0064] The second function generating section 107 receives a target passing flow rate 106A of the flow control valve 12, calculates an opening 107A of the flow control valve 12 based on this, and outputs this to one input terminal of a first multiplication calculation section .

[0065] The second function generating unit 107 pre-stores the opening characteristics of the flow control valve 12, and sets the characteristics of the passing flow rate when the pressure difference across the flow control valve 12 is kept at a constant value (pressure difference across the flow control valve 12 ΔP1) and the opening of the flow control valve 12 is changed.

[0066] The third function generating unit 111 receives the rotation pressure and the pressure difference 101A of the second accumulator 11, and outputs a value calculated in response to this to the second input terminal of the first multiplication calculation unit 108 as a correction coefficient 111A.

[0067] In the third function generating unit 111, characteristics for correcting the opening 107A of the flow control valve 12 are set as a two-dimensional table in order to match the target passing flow rate 106A of the flow control valve 12 with the flow rate actually passing through the flow control valve 12, even when the differential pressure before and after the flow control valve 12 is changed from ΔP1.

[0068] The first multiplication calculation unit 108 inputs the opening 107A of the flow control valve 12 to one input terminal and the correction coefficient 111A to the second input terminal, and outputs the multiplied value of these as the target opening 108A of the flow control valve 12 to the fourth function generation unit 112.

[0069] By calculating the target opening of the flow control valve 12 as described above, the flow rate discharged from the swing motor 4 to the hydraulic oil tank 35 via the flow control valve 13 when a hydraulic drive device that does not perform swing regeneration is decelerating can be made to match the flow rate passing through the flow control valve 12 in this embodiment, and the return oil during swing deceleration can be regenerated in the second accumulator 11 while decelerating at a swing speed equivalent to that of a hydraulic drive device that does not perform swing regeneration.

[0070] Next, the fourth function generating unit 112 receives the target opening 108A of the flow control valve 12 and calculates an operation signal for the flow control valve 12. This is output to one input terminal of the second multiplication calculation unit 113 as an operation signal 112A for the flow control valve 12.

[0071] The third subtraction calculation unit 114 inputs the swing high pressure side pressure 109A to one input terminal and inputs the preset set pressure of the pressure control valve 10 to a second input terminal. The difference between these is output to the second input terminal of the third switching calculation unit 115 as differential pressure 114A between the swing high pressure side pressure and the set pressure of the pressure control valve 10.

[0072] The third switching calculation unit 115 inputs 0 to one input end, inputs pressure difference 114A between the swing high-pressure side pressure and the set pressure of pressure control valve 10 to a second input end, and inputs 1 to a third input end. When the value of pressure difference 114A between the swing high-pressure side pressure and the set pressure of pressure control valve 10 is greater than 0, the third switching calculation unit 115 outputs the 0 input to the first input end to the second input end of the second multiplication calculation unit 113 as a first accumulator 9 regeneration flag 115A, and when the value of pressure difference 114A between the swing high-pressure side pressure and the set pressure of pressure control valve 10 is equal to or less than 0, the third switching calculation unit 115 outputs the 1 input to the third input end to the second input end of the second multiplication calculation unit 113 as a first accumulator 9 regeneration flag 115A.

[0073] The second multiplication calculation unit 113 receives the operation signal 112A of the flow control valve 12 at one input terminal and the first accumulator 9 regeneration flag 115A at a second input terminal. The multiplied value is output to the second input terminal of the third multiplication calculation unit 116.

[0074] The third multiplication calculation unit 116 receives the output of the turning acceleration / deceleration determination unit 105 at one input terminal and receives the output of the second multiplication calculation unit 113 at a second input terminal. These multiplied values ​​are output to the flow control valve 12 as a control command 116A for the flow control valve 12.

[0075] By doing as described above, the high-pressure oil discharged from the second hydraulic pump 7 during turning acceleration can be regenerated in the first accumulator 9 without being sent to the second accumulator 11. Therefore, compared to the case of regeneration in the second accumulator 11, the pressure difference between the discharge port of the second hydraulic pump 7 and the accumulator can be made smaller, and excess oil from the second hydraulic pump 7 can be regenerated efficiently.

[0076] In addition, during slewing deceleration, when the slewing high-pressure side pressure is higher than the set pressure of the pressure control valve 10, the flow control valve 12 is closed, so that high-pressure slewing return oil can be regenerated in the first accumulator 9. Compared to the case of regeneration in the second accumulator 11, the pressure difference between the discharge port of the slewing motor 4 and the accumulator can be made smaller, and slewing return oil can be regenerated efficiently.

[0077] Returning to Fig. 3, when the boom cylinder 3a is operated, a boom operation signal is output by operating the boom with the operation device 30, and this is detected by the boom operation amount detection device 31. The boom operation amount detected by the boom operation amount detection device 31 is input to the control device 100.

[0078] The control device 100 outputs a control signal calculated based on the boom operation amount, the pressure of the second accumulator 11 detected by the pressure sensor 34, the pressure of the first accumulator 9 detected by the pressure sensor 53, the boom cylinder bottom pressure detected by the pressure sensor 27, and the boom cylinder rod pressure detected by the pressure sensor 32 to at least one of the flow control valves 14, 15, 19, and 20.

[0079] Although omitted in FIG. 3, the drive of the arm cylinder 3b and the drive of the bucket cylinder 3c are similar to the drive of the boom cylinder 3a described above.

[0080] According to the hydraulic drive system 200 according to the present embodiment described above, the following operational effects can be obtained. (1) The hydraulic drive unit 200 includes a flow control valve 13 that controls the flow rate from the second hydraulic pump 7 to the swing motor 4 and the flow rate from the swing motor 4 to the hydraulic oil tank 35, a first accumulator 9, a second accumulator 11 that is installed separately from the first accumulator 9 and is set to a lower pressure than the first accumulator 9, a pressure control valve 10 that is installed in a pipe that sends energy discharged from the swing motor 4 to the first accumulator 9, and a pressure control valve 10 that is separated from a pipe that connects the swing motor 4 and the pressure control valve 10. The control device 100 has a means for determining whether or not the swing motor 4 is in a swing deceleration state (swing acceleration / deceleration determination unit 105), and is capable of recovering in the second accumulator 9 the medium-pressure return oil discharged from the swing motor 4 during swing deceleration, and is capable of recovering in the first accumulator 9 the high-pressure return oil discharged from the swing motor 4 during swing deceleration. (2) When the pressure of the return oil discharged from the swing motor 4 during deceleration of swing is higher than that of the second accumulator 11, the control device 100 can close the flow control valve 13. In this way, the return oil discharged from the swing motor 4 can be regenerated in the second accumulator 11 or the first accumulator 9 without being discharged into the hydraulic oil tank 35. (3) When the control device 100 regenerates in the second accumulator 11 the medium-pressure return oil discharged from the swing motor 4 during swing deceleration, it can match the flow rate when the swing motor of a hydraulic drive device that does not perform swing regeneration discharges medium-pressure return oil to the hydraulic oil tank with the flow rate passing through the flow control valve 12 in this embodiment. In this way, it is possible to decelerate at a swing speed equivalent to that of a hydraulic drive device that does not perform swing regeneration, while regenerating medium-pressure return oil in the second accumulator 11 during swing deceleration. (4) The control device 100 has a means for determining whether or not a turning acceleration state is occurring (turning acceleration / deceleration determination unit 105), and during turning acceleration, the excess pressurized oil discharged from the second hydraulic pump 7 and sent to the turning motor 4 can be regenerated in the first accumulator 9. (5) The hydraulic drive system 200 includes pipes 38, 40, 42 connecting the first accumulator 9 and the second hydraulic actuators (boom cylinder 3a, arm cylinder 3b, bucket cylinder 3c), first control valves (flow control valves 19, 21, 23) installed in the pipes 38, 40, 42 and controlled by the control device 100, pipes 39, 41, 43 connecting the second accumulator 11 and the second hydraulic actuators 3a, 3b, 3c, and second control valves (flow control valves 20, 22, 24) installed in the pipes 39, 41, 43 and controlled by the control device 100, and the control device 100 can control the first control valve or the second control valve according to the operation amount of the second hydraulic actuators 3a, 3b, 3c. In this way, it becomes possible to assist the drive of the second hydraulic actuators 3a, 3b, 3c by the energy regenerated by the first accumulator 9 and the second accumulator 11.

[0081] The following modifications are also within the scope of the present invention, and one or more of the modifications may be combined with the above-described embodiment.

[0082] (Variation 1) In the above-described embodiment, the pressure control valve 10 is a valve that adjusts the pressure on the inlet side to a preset pressure. Instead, a pressure control valve that adjusts the differential pressure before and after the pressure control valve 10 to a preset value may be used. In that case, in order to regenerate high-pressure regenerative oil in the first accumulator 9, the pressure on the inlet side of the pressure control valve 10 needs to be lower than the set pressures of the relief valves 46 and 47 (for example, the set pressures of the relief valves 46 and 47: 32 MPa, the target pressure on the inlet side of the pressure control valve 10: 31.5 MPa), so that the differential pressure before and after the pressure control valve 10 needs to be controlled by the control device 100. Specifically, the value obtained by subtracting the pressure of the first accumulator 9 from the target pressure on the inlet side of the pressure control valve 10 is output to the pressure control valve as the target differential pressure before and after the pressure control valve 10, so that the high-pressure regenerative oil is sent to the first accumulator 9 via the pressure control valve 10.

[0083] Alternatively, by using as the first accumulator 9 an accumulator that is sufficiently large relative to the amount of oil flowing in and has almost no pressure fluctuation, it is possible to preset a value obtained by subtracting the preset set pressure of the first accumulator 9 from the target pressure on the inlet side of the pressure control valve 10 as the target differential pressure across the pressure control valve 10, eliminating the need to control the pressure control valve 10 with the control device 100 (for example, when the target pressure on the inlet side of the pressure control valve 10 is 31.5 MPa and the set pressure of the first accumulator 9 is 25 MPa, the target differential pressure across the pressure control valve 10 is 6.5 MPa).

[0084] (Variation 2) Accumulators whose pressure is sufficiently large relative to the amount of oil flowing in and whose pressure hardly fluctuates may be used as the first accumulator 9 and the second accumulator 11. In this case, by storing the set pressures of the first accumulator 9 and the second accumulator 11 in advance in the control device 100, the pressure sensor 34 that detects the pressure of the second accumulator 11 and the pressure sensor 53 that detects the pressure of the first accumulator 9 become unnecessary.

[0085] (Variation 3) In the above embodiment, the turning speed sensor 33, the pressure sensor 48 detecting the left turning port side pressure, and the pressure sensor 49 detecting the right turning port side pressure are used to determine whether the turning speed sensor 33 is accelerating or decelerating, but instead, a sensor detecting the turning acceleration may be used to determine whether the turning speed sensor 33 is accelerating or decelerating. In this case, however, the turning speed sensor 33 and the pressure sensor 48 and the pressure sensor 49 are not required. In this case, however, it is necessary to detect the pressures before and after the flow control valve 12 in order to calculate the target opening of the flow control valve 12, so a pressure sensor is required on the pipe connecting the high pressure selection valve 8 and the flow control valve 12.

[0086] (summary) In this embodiment, there are a hydraulic oil tank 35 that stores hydraulic oil, hydraulic pumps 6, 7 that suck in and discharge hydraulic oil from the hydraulic oil tank 35, a first hydraulic actuator 4, a first flow control valve 13 that is installed in a first pipe connecting the hydraulic pumps 6, 7 and the first hydraulic actuator 4 and that controls the flow rate of hydraulic oil supplied from the hydraulic pumps 6, 7 to the first hydraulic actuator 4 and the flow rate of hydraulic oil discharged from the first hydraulic actuator 4 to the hydraulic oil tank 35, a first accumulator 9, a second pipe 25 that connects the first hydraulic actuator 4 and the first accumulator 9, a first accumulator regulating device 10 that is installed in the second pipe 25 and adjusts the flow of hydraulic oil from the first hydraulic actuator 4 to the first accumulator 9, a first operating device 28 that instructs the operation of the first hydraulic actuator 4, and a control valve 13 that controls the operation amount of the first operating device 28. The hydraulic drive system 200 includes a first operation amount detection device 29 that detects a pressure of the first hydraulic actuator 4 and a control device 100 to which the operation amount detected by the first operation amount detection device 29 is input, a second accumulator 11, a third line 26 that connects the second accumulator 11 to a portion of the second line 25 that connects the first hydraulic actuator 4 and the first accumulator regulating device 10, a second accumulator regulating device 12 that is installed in the third line 26 and adjusts the flow of hydraulic oil from the first hydraulic actuator 4 to the second accumulator 11, and first pressure detection devices 48, 49 that detect the pressure of the first hydraulic actuator 4, and the control device 100 controls at least one of the first flow control valve 13 and the second accumulator regulating device 12 in accordance with the operation amount detected by the first operation amount detection device 29, the pressures detected by the first pressure detection devices 48, 49, and the pressure of the second accumulator 11.

[0087] According to the present embodiment configured as described above, it is possible to reduce the pressure difference between the first hydraulic actuator 4 and the first accumulator 9 or the second accumulator 11 when regenerating return oil from the first hydraulic actuator 4. This allows the regenerative energy generated from the first hydraulic actuator 4 to be efficiently regenerated by the first accumulator 9 and the second accumulator 11, making it possible to improve the energy efficiency of the entire work machine 1.

[0088] Furthermore, in this embodiment, the set pressure of the second accumulator 11 is lower than the set pressure of the first accumulator 9, the first accumulator regulation device 10 is a pressure control valve 10 that regulates the inlet pressure to a preset pressure, and the second accumulator regulation device 12 is a second flow control valve 12 that controls the flow rate of pressure oil supplied from the first hydraulic actuator 4 to the second accumulator 11. This makes it possible to regenerate high-pressure return oil from the first hydraulic actuator 4 in the first accumulator 9, and regenerate medium-pressure return oil from the first hydraulic actuator 4 in the second accumulator 11.

[0089] In this embodiment, the first hydraulic actuator 4 is a swing motor 4, and the hydraulic drive system 200 further includes a high-pressure selection valve 8 that connects the high-pressure sides of the left and right swing ports of the swing motor 4 to a portion of the second pipe 25 where the third pipe 26 branches off. This makes it possible to regenerate return oil from the swing motor 4 in the first accumulator 9 or the second accumulator 11.

[0090] In this embodiment, the control device 100 further includes a swing speed detection device 33 that detects the speed of the swing motor 4. The control device 100 determines whether the swing motor 4 is decelerating based on the detection value of the swing speed detection device 33 and the detection values ​​of the first pressure detection devices 48, 49. When it is determined that the swing motor 4 is decelerating and the discharge side pressure of the swing motor 4 is lower than the pressure of the second pressure accumulator 11, the control device 100 controls the opening of the first flow control valve 13 in accordance with the operation amount of the first operation device 28 ... When the discharge side pressure of the swing motor 4 is higher than the pressure in the second accumulator 11 and lower than the preset pressure of the first accumulator adjustment device 10, the first flow control valve 13 is closed and the opening of the second flow control valve 12 is controlled according to the operation amount of the first operating device 28, the discharge side pressure of the swing motor 4, and the pressure of the second accumulator 11, and when it is determined that the swing motor 4 is decelerating and the discharge side pressure of the swing motor 4 is higher than the set pressure of the first accumulator adjustment device 10, the first flow control valve 13 and the second flow control valve 12 are closed. This makes it possible to efficiently regenerate return oil from the swing motor 4 in the first accumulator 9 or the second accumulator 11 during swing deceleration.

[0091] Furthermore, in this embodiment, a swing speed detection device 33 that detects the speed of the swing motor 4 is further provided, and the control device 100 determines whether or not the swing motor 4 is accelerating based on the detection value of the swing speed detection device 33 and the detection values ​​of the first pressure detection devices 48, 49, and when it is determined that the swing motor 4 is accelerating, closes the second flow control valve 12. This makes it possible to regenerate in the first accumulator 9 the surplus of pressure oil discharged from the second hydraulic pump 7 and sent to the swing motor 4 during swing acceleration.

[0092] Furthermore, in this embodiment, the hydraulic drive system 200 includes the second hydraulic actuators 3a, 3b, 3c, a second operating device 30 that instructs the operation of the second hydraulic actuators 3a, 3b, 3c, a second operation amount detection device 31 that detects the operation amount of the second operating device 30, fourth pipelines 38, 40, 42 that connect a portion of the second pipeline 25 that connects the first accumulator 9 and the first accumulator regulation device 10 to the second hydraulic actuators 3a, 3b, 3c, and first control valves 19, 21, 23 that are installed in the fourth pipelines 38, 40, 42 and adjust the flow of pressure oil from the first accumulator 9 to the second hydraulic actuators 3a, 3b, 3c. The control device 100 further includes fifth pipelines 39, 41, 43 that connect a portion of the third pipeline 26 that connects the second accumulator 11 and the second accumulator adjustment device 12 to the second hydraulic actuators 3a, 3b, 3c, and second control valves 20, 22, 24 that are installed in the fifth pipelines 39, 41, 43 and adjust the flow of pressure oil from the second accumulator 11 to the second hydraulic actuators 3a, 3b, 3c, and the control device 100 controls at least one of the first control valves 19, 21, 23 and the second control valves 20, 22, 24 in accordance with the operation amount detected by the second operation amount detection device 31, the pressure of the first accumulator 9, and the pressure of the second accumulator 11. This makes it possible to assist the drive of the second hydraulic actuators 3a, 3b, 3c by the energy regenerated by the first accumulator 9 and the second accumulator 11.

[0093] Although the embodiment of the present invention has been described above in detail, the present invention is not limited to the above-mentioned embodiment and includes various modified examples. For example, the above-mentioned embodiment has been described in detail to easily explain the present invention, and the present invention is not necessarily limited to an embodiment having all of the described configurations. [Explanation of symbols]

[0094] 1...hydraulic excavator (working machine), 1a...boom, 1A...working device, 1b...arm, 1B...vehicle body, 1c...bucket, 1d...upper rotating body, 1e...lower traveling body, 3a...boom cylinder (second hydraulic actuator), 3b...arm cylinder (second hydraulic actuator), 3c...bucket cylinder (second hydraulic actuator), 4...swing motor (first hydraulic actuator), 5...engine, 6...first hydraulic pump, 7...second hydraulic pump, 8...high pressure selection valve, 9...first accumulator (first Accumulator), 10...pressure control valve (first accumulator regulator), 11...second accumulator (second accumulator), 12...flow rate control valve (second flow rate control valve, second accumulator regulator), 13...flow rate control valve (first flow rate control valve), 13a, 13b...operation end portion, 14...flow rate control valve, 14a, 14b...operation end portion, 15...flow rate control valve, 15a, 15b...operation end portion, 16 to 18...flow rate control valve, 19...flow rate control valve (first control valve), 19a, 19b...operation end portion, 20...flow rate control valve (second control valve), 20a, 20b... Operation end portion, 21...flow control valve (first control valve), 22...flow control valve (second control valve), 23...flow control valve (first control valve), 24...flow control valve (second control valve), 25...pipe (second pipe), 26...pipe (third pipe), 27...pressure sensor, 28...operation device (first operation device), 28A...pilot valve, 29...swing operation amount detection device (first operation amount detection device), 29A...swing lever operation signal, 30...operation device (second operation device), 31...boom operation amount detection device (second operation amount detection device), 32...pressure Force sensor, 33... Swing speed sensor (swing speed detection device), 34... Pressure sensor (second pressure detection device), 35... Hydraulic oil tank, 38... Pipe (fourth pipe), 39... Pipe (fifth pipe), 40... Pipe (fourth pipe), 41... Pipe (fifth pipe), 42... Pipe (fourth pipe), 43... Pipe (fifth pipe), 44, 45... Check valve, 46, 47... Relief valve, 48, 49... Pressure sensor (first pressure detection device), 50... Pipe, 51, 52... Pipe (first pipe), 53... Pressure sensor, 60 to 69... Pipe, 70,71...center bypass pipe, 100...control device, 101...first subtraction calculation unit, 101A...differential pressure, 102...first switching calculation unit, 102A...output, 103...second switching calculation unit, 103A...operation signal, 104...output conversion unit, 105...swing acceleration / deceleration determination unit, 106...first function generation unit, 106A...target passing flow rate, 107...second function generation unit, 107A...opening, 108...first multiplication calculation unit, 108A...eye Target opening, 109... maximum value calculation unit, 109A... high pressure side pressure for turning, 110... second subtraction calculation unit, 111... third function generation unit, 111A... correction coefficient, 112... fourth function generation unit, 112A... operation signal, 113... second multiplication calculation unit, 114... third subtraction calculation unit, 114A... differential pressure, 115... third switching calculation unit, 115A... regeneration flag, 116... third multiplication calculation unit, 116A... control command, 200... hydraulic drive unit.

Claims

1. A hydraulic oil tank for storing hydraulic oil; a hydraulic pump that draws in and discharges hydraulic oil from the hydraulic oil tank; A first hydraulic actuator; a first flow control valve that is installed in a first pipeline that connects the hydraulic pump and the first hydraulic actuator and controls a flow rate of hydraulic oil supplied from the hydraulic pump to the first hydraulic actuator and a flow rate of hydraulic oil discharged from the first hydraulic actuator to the hydraulic oil tank; A first pressure accumulator; a second pipeline connecting the first hydraulic actuator and the first pressure accumulator; a first pressure accumulator adjustment device that is installed in the second pipeline and adjusts the flow of hydraulic oil from the first hydraulic actuator to the first pressure accumulator; A first operating device that instructs an operation of the first hydraulic actuator; a first operation amount detection device that detects an operation amount of the first operation device; a control device to which an operation amount detected by the first operation amount detection device is input, A second pressure accumulator; a third pipe connecting a portion of the second pipe that connects the first hydraulic actuator and the first pressure accumulation regulator to the second pressure accumulation device; and a second pressure accumulator adjustment device that is installed in the third pipeline and adjusts the flow of hydraulic oil from the first hydraulic actuator to the second pressure accumulator; a first pressure detection device that detects a pressure of the first hydraulic actuator, The control device controls at least one of the first flow control valve and the second pressure accumulation regulation device in response to the operation amount detected by the first operation amount detection device, the pressure detected by the first pressure detection device, and the pressure of the second pressure accumulation device. A hydraulic drive system comprising:

2. 2. The hydraulic drive system according to claim 1, The set pressure of the second pressure accumulator is lower than the set pressure of the first pressure accumulator, The first pressure regulating device is a pressure control valve that regulates the pressure on the inlet side to a preset pressure, The second pressure accumulator regulation device is a second flow control valve that controls the flow rate of pressure oil supplied from the first hydraulic actuator to the second pressure accumulator. A hydraulic drive system comprising:

3. The hydraulic drive system according to claim 2, the first hydraulic actuator is a swing motor; The hydraulic drive device further includes a high-pressure selection valve that connects the high-pressure sides of the left and right rotation ports of the rotation motor to a portion of the second pipeline where the third pipeline branches off. A hydraulic drive system comprising:

4. The hydraulic drive system according to claim 3, A rotation speed detection device for detecting the speed of the rotation motor is further provided, The control device includes: determining whether the rotation motor is decelerating based on the detection value of the rotation speed detection device and the detection value of the first pressure detection device; when it is determined that the swing motor is decelerating and the discharge side pressure of the swing motor is lower than the pressure of the second pressure accumulator, controlling the opening of the first flow control valve in accordance with the operation amount of the first operation device; when it is determined that the swing motor is decelerating and the discharge side pressure of the swing motor is higher than the pressure of the second pressure accumulator and lower than a preset pressure of the first pressure accumulator, closing the first flow control valve and controlling the opening of the second flow control valve in accordance with the operation amount of the first operation device, the discharge side pressure of the swing motor, and the pressure of the second pressure accumulator; When it is determined that the swing motor is decelerating and the discharge side pressure of the swing motor is higher than the set pressure of the first pressure accumulation regulator, the first flow control valve and the second flow control valve are closed. A hydraulic drive system comprising:

5. The hydraulic drive system according to claim 3, A rotation speed detection device for detecting the speed of the rotation motor is further provided, The control device includes: determining whether the rotation motor is accelerating or not based on the detection value of the rotation speed detection device and the detection value of the first pressure detection device; When it is determined that the rotation motor is accelerating, the second flow control valve is closed. A hydraulic drive system comprising:

6. 2. The hydraulic drive system according to claim 1, A second hydraulic actuator; A second operating device that instructs an operation of the second hydraulic actuator; a second operation amount detection device that detects an operation amount of the second operation device; a fourth line connecting a portion of the second line that connects the first pressure accumulator and the first pressure accumulation regulator to the second hydraulic actuator; a first control valve that is installed in the fourth pipeline and adjusts the flow of pressure oil from the first pressure accumulator to the second hydraulic actuator; a fifth line connecting a portion of the third line that connects the second pressure accumulator and the second pressure accumulation regulator to the second hydraulic actuator; a second control valve that is installed in the fifth pipeline and adjusts the flow of pressure oil from the second accumulator to the second hydraulic actuator; The control device controls at least one of the first control valve and the second control valve in response to the operation amount detected by the second operation amount detection device, the pressure of the first accumulator, and the pressure of the second accumulator. A hydraulic drive system comprising:

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