Hydraulic drive device

Abstract

A hydraulic drive device (1) is provided with a pump (21), an actuator (25), and a controller (40). The pump (21) discharges oil by being rotationally driven by the power source (17). The capacity of the pump (21) can be changed. The actuator (25) is operated by being supplied with oil discharged from the pump (21). The controller (40) controls the capacity of the pump (21) according to the operation content of the actuator (25). The controller (40) changes the upper limit value (R) of the magnitude of the pump capacity change amount ([delta] q), which is the change amount per unit time of the capacity of the pump (21), in accordance with the rotational speed (N) of the pump (21).

Description

Technical Field

[0001] The present invention relates to a hydraulic drive device including an actuator and a pump for supplying oil to the actuator. Background Art

[0002] For example, Patent Document 1 describes a conventional pump-related technology. In the technology described in the document, when an actuator (a hydraulic cylinder in the document) is started, the increase ratio of the flow rate of oil supplied from the pump to the actuator gradually increases. This reduces the shock when the actuator is started and achieves good acceleration (see the abstract of the document).

[0003] The flow rate of oil supplied from the pump to the actuator changes according to the rotation speed of the pump. However, the invention described in the document does not take the rotation speed of the pump into consideration. Therefore, depending on the rotation speed of the pump, it is possible that the effect of reducing the impact when the actuator is started and the effect of obtaining the acceleration of the actuator cannot be properly obtained. In addition, sometimes, in addition to the impact when the actuator is started, there may be problems caused by the sudden change in the flow rate of oil supplied from the pump to the actuator.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Publication No. 2005-139658 Summary of the invention

[0007] Therefore, an object of the present invention is to provide a hydraulic drive device capable of setting the flow rate of oil supplied from a pump to an actuator to an appropriate amount according to the rotation speed of the pump.

[0008] The hydraulic drive device includes a pump, an actuator and a controller. The pump is driven by a power source to rotate and discharge oil. The pump is capable of changing its capacity. The actuator is operated by being supplied with the oil discharged by the pump. The controller controls the capacity of the pump according to the operation content of the actuator. The controller changes the change amount of the pump capacity per unit time, i.e., the upper limit value of the size of the change amount of the pump capacity, according to the rotation speed of the pump.

[0009] According to the above configuration, the flow rate of oil supplied from the pump to the actuator can be set to an appropriate amount according to the rotation speed of the pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a diagram showing construction machinery viewed from the side.

[0011] Figure 2 This is a circuit diagram of a hydraulic drive device according to an embodiment.

[0012] Figure 3 Yes means Figure 2 FIG. 2 is a graph showing the relationship between the operation amount of the operating unit and the target pump capacity of the pump.

[0013] Figure 4 It is a graph showing the time change of the operation amount of the operating part and the time change of the pump capacity of the pump.

[0014] Figure 5 The graph shows the time change of the operation amount of the operation unit and the time change of the pump discharge flow rate of the pump, and is a graph in the case where the upper limit value is constant.

[0015] Figure 6 It is a graph showing the relationship between the upper limit value and the pump rotation speed of the pump, and the relationship between the pump discharge flow rate change amount and the pump rotation speed of the pump.

[0016] Figure 7 The graph shows the time change of the operation amount of the operation unit and the time change of the pump discharge flow rate of the pump, and is a graph in the case where the upper limit value is changed according to the pump rotation speed of the pump.

[0017] Figure 8 It means by Figure 2 A flowchart of an example of a calculation process performed by the controller shown. DETAILED DESCRIPTION

[0018] Reference Figures 1 to 8 A hydraulic drive device 1 according to the embodiment will be described.

[0019] The hydraulic drive device 1 is a device for setting the flow rate of oil supplied from a pump to an actuator to an appropriate amount corresponding to the rotation speed of the pump. The hydraulic drive device 1 includes Figure 1 The engineering machinery 10 shown, Figure 2 The operating unit 31, the operating amount detection unit 33 and the controller 40 are shown.

[0020] like Figure 1 As shown, the construction machine 10 is a machine for performing work, such as a construction machine for performing construction work, and may be, for example, an excavator or a crane. The following mainly describes the case where the construction machine 10 is an excavator. The construction machine 10 may be operated by an operator in the cab 13a, or may be remotely operated by an operator outside the construction machine 10 (e.g., an operator who is far away from the construction machine 10), or may be operated by automatic driving. The construction machine 10 includes a lower traveling body 11, an upper slewing body 13, an attachment 15, a power source 17, and a hydraulic circuit 20 (see Figure 2 ).

[0021] The lower traveling body 11 can travel on a traveling surface (the ground, etc.). The lower traveling body 11 may include crawlers or wheels.

[0022] The upper revolving body 13 is mounted on the lower traveling body 11 so as to be rotatable. Specifically, the upper revolving body 13 is mounted on the lower traveling body 11 so as to be rotatable about a rotation axis extending in the vertical direction. The upper revolving body 13 includes a cab 13a. The cab 13a is a part (operating room) in which an operator can operate the construction machine 10.

[0023] The attachment 15 is a part for performing work, and includes, for example, a boom 15a, an arm 15b, and a distal attachment 15c. The boom 15a is mounted on the upper slewing body 13 so as to be able to rise and fall (rotate in the up and down direction). The arm 15b is rotatably mounted on the boom 15a. The distal attachment 15c is provided at the distal end of the attachment 15 and is rotatably mounted on the arm 15b. The distal attachment 15c may be, for example, a bucket for digging up or excavating an object to be worked, a device for clamping an object to be worked (a grab, a shear, etc.), or a device for crushing an object to be worked (a breaker, etc.).

[0024] The power source 17 drives the pump 21. The power source 17 is mounted on the construction machine 10, specifically, on the upper swing body 13. The power source 17 may be an internal combustion engine (engine) or an electric motor. Figure 2 The power source 17 shown can change the rotation speed (rotation speed), and more specifically, can change the rotation speed of the output shaft 17a. The rotation speed of the power source 17 can be changed according to the operation of the operator, and can also be controlled according to the command from the controller 40. The power source 17 has an output shaft 17a. The output shaft 17a is a shaft member that rotates by the drive of the power source 17.

[0025] The hydraulic circuit 20 is a circuit for controlling the actuator 25. The hydraulic circuit 20 is mounted on the construction machine 10 and is mounted on the upper swing structure 13. The hydraulic circuit 20 includes a pump 21, a pump capacity control unit 23, an actuator 25, and a control valve 27.

[0026] The pump 21 is a hydraulic pump that ejects oil (working oil) by being driven to rotate by the power source 17. The pump 21 sucks oil from the oil tank and ejects the oil by being driven to rotate by the power source 17. The hydraulic circuit 20 may have only one pump 21 or may have a plurality of pumps 21. The pump 21 is connected to the output shaft 17a of the power source 17. Specifically, for example, the input shaft of the pump 21 is connected to the output shaft 17a of the power source 17. The pump 21 may also be directly connected to the output shaft 17a. The rotation speed of the pump 21, i.e., the pump rotation speed N, may also be equal to the rotation speed of the output shaft 17a of the power source 17. The pump 21 may also be connected to the output shaft 17a via a transmission (reducer or speed increaser). When the speed ratio (reduction ratio or speed increase ratio) of the transmission is constant, the pump rotation speed N may also be proportional to the rotation speed of the power source 17.

[0027] The capacity of the pump 21, namely, the pump capacity q, can be changed. That is, the pump 21 is a variable capacity hydraulic pump. The pump capacity q can be, for example, Figure 4 However, the pump capacity q is not limited to being changed by Figure 4 The curve shown in FIG. 1 is a specific example. The pump capacity q is equal to the flow rate of oil ejected by the pump 21 when the input shaft of the pump 21 rotates one circle. Specifically, the pump capacity q (tilting capacity) is changed by, for example, changing the tilting angle of the swash plate (not shown) relative to the input shaft of the pump 21.

[0028] The pump capacity control unit 23 (regulator) controls the pump capacity q. The pump capacity control unit 23 controls the pump capacity q according to the instruction input to the pump capacity control unit 23, namely the pump capacity instruction. The pump capacity instruction may be, for example, an electrical signal output by the controller 40, and more specifically, may be, for example, an electric current value. Hereinafter, this electric current value is sometimes referred to as the pump capacity instruction current (tilt angle instruction current). The pump capacity control unit 23 may also change the pump capacity q based on the pump capacity instruction of the electrical signal. That is, the pump capacity control unit 23 may change the pump capacity q without converting the electrical signal. In addition, it may be that the pump capacity control unit 23 converts the pump capacity instruction from the electrical signal into a pilot pressure (hydraulic pressure) and changes the pump capacity q based on the pilot pressure. A specific example of the case where the pump capacity control unit 23 converts the electrical signal into a pilot pressure is described below. In this case, the pump capacity control unit 23 includes a pump capacity changing valve 23a and a pump capacity changing device 23b.

[0029] The pump capacity varying valve 23a is a valve that converts an input electric signal into a pilot pressure (hydraulic pressure). The pump capacity varying valve 23a may be an electromagnetic proportional valve or another valve different from the electromagnetic proportional valve.

[0030] The pump capacity varying device 23b varies the pump capacity q (eg, the tilting angle of the pump 21) based on the pilot pressure outputted from the pump capacity varying valve 23a.

[0031] The actuator 25 is a hydraulic actuator that is operated by being supplied with oil (working oil) ejected from the pump 21. The actuator 25 operates the construction machine 10. The actuator 25 is connected to the pump 21 via an oil path through which oil flows. The hydraulic circuit 20 includes at least one actuator 25. In the present embodiment, the hydraulic circuit 20 includes a plurality of actuators 25. For example, Figure 1 As shown, the plurality of actuators 25 include a boom cylinder 25a, an arm cylinder 25b, a remote attachment cylinder 25c, a travel motor 25d, and a slewing motor 25e. The boom cylinder 25a causes the boom 15a to rise and fall relative to the upper slewing body 13. The boom cylinder 25a is a telescopic cylinder (hydraulic cylinder) that is extended and retracted by being supplied with oil. The arm cylinder 25b and the remote attachment cylinder 25c are each hydraulic cylinders that are the same as the boom cylinder 25a. The arm cylinder 25b causes the arm 15b to rotate relative to the boom 15a. The remote attachment cylinder 25c causes the remote attachment 15c to rotate relative to the arm 15b. In the case where the remote attachment 15c is a device for clamping a work object, the plurality of actuators 25 may also include a cylinder or a motor for driving the following opening and closing member, which is used to clamp the work object. In addition, when the remote attachment 15c is a device for crushing the work object, the plurality of actuators 25 may also include a cylinder or a motor for driving a component that crushes the work object. The travel motor 25d causes the lower travel body 11 to travel. Specifically, for example, the travel motor 25d may also drive the crawler tracks of the lower travel body 11. The travel motor 25d and the slewing motor 25e are each hydraulic motors that rotate by being supplied with oil. The slewing motor 25e causes the upper slewing body 13 to slew relative to the lower travel body 11. In addition, in Figure 2 In FIG. 1 , only two hydraulic cylinders among the components of the actuator 25 are shown, and the other actuators 25 are omitted from the illustration.

[0032] The control valve 27 is a valve for controlling the operation of the plurality of actuators 25. The control valve 27 is disposed in an oil path connecting at least one pump 21 and the plurality of actuators 25. Figure 2 In the specific example shown, the control valve 27 is arranged between the two pumps 21 and the plurality of actuators 25. The control valve 27 is a direction switching valve that switches the flow direction (oil path) of the oil, switches the actuator 25 to be operated, and switches the operating direction (e.g., extension direction or rotation direction) of the actuator 25. The control valve 27 can also change the flow rate of the oil supplied to the actuator 25 and change the operating speed of the actuator 25.

[0033] The operation unit 31 is a part for operating the actuator 25. When the operator operates the construction machine 10, the operation unit 31 may be arranged in the cab 13a (see Figure 1) and may also be included in a device for remote operation (remote operation device). The operating unit 31 may have an operating lever or an operating pedal. The operating unit 31 outputs an operating instruction, which is an instruction for operating the actuator 25. The operating unit 31 outputs the operating instruction to the control valve 27 to control (operate) the control valve 27, thereby operating the actuator 25. The operating instruction output by the operating unit 31 may also be a pilot pressure. In this case, the operating unit 31 may also be a hydraulic rod device having a hydraulic remote control valve. The operating instruction output by the operating unit 31 may also be an electrical signal. In this case, the operating unit 31 may also be an electric joystick.

[0034] The operation amount detection unit 33 detects the operation amount of the operating unit 31. Hereinafter, the operation amount of the operating unit 31 will also be referred to as simply "operation amount". When the operator operates the construction machinery 10, the operation amount detection unit 33 may also detect the operation angle of the operating unit 31 as the operation amount. In this case, the operation angle of the operating unit 31 may be the angle of the operating lever or the angle of the operating pedal. For example, in the case where the operating unit 31 outputs a pilot pressure (secondary pressure of the hydraulic remote control valve) corresponding to the operation amount, the operation amount detection unit 33 may also be a pressure sensor that detects the pilot pressure. For example, in the case where the operating unit 31 outputs an electrical signal corresponding to the operation amount, the operation amount detection unit 33 may also detect the electrical signal. In this case, the operation amount detection unit 33 may also be a part of the controller 40.

[0035] Furthermore, when the construction machine 10 is operated by automatic driving, the function of at least one of the operation unit 31 and the operation amount detection unit 33 may be part of the function of the controller 40. In this case, the controller 40 may also have a function of controlling the automatic driving of the construction machine 10, and the operation content of the actuator 25 is determined by the part of the controller 40 corresponding to the operation unit 31, and the operation content of the actuator 25 is obtained by the part of the controller 40 corresponding to the operation amount detection unit 33.

[0036] The controller 40 is a computer that performs signal input and output, calculation (processing), information storage, etc., and the computer has a calculation processing device and a memory (storage unit). For example, the calculation processing device executes the program stored in the storage unit of the controller 40, thereby realizing various functions of the controller 40. For example, the controller 40 may also have a function of automatically driving the construction machine 10. The controller 40 may also operate the actuator 25 by outputting a command to the control valve 27.

[0037] The controller 40 performs various controls. For example, the controller 40 performs the following control, that is, changes the upper limit value R of the change amount of the pump capacity q per unit time, that is, the size of the pump capacity change amount Δq, according to the pump speed N. The above-mentioned unit time can be a control cycle of the controller 40, or seconds, or minutes. This also applies to the "unit time" in the following description.

[0038] The controller 40 may be entirely or partially mounted on the construction machine 10 or may be disposed outside the construction machine 10. The controller 40 includes an operation content acquisition unit 41, a pump speed acquisition unit 43, a pump capacity calculation unit 45, and a pump capacity instruction unit 47.

[0039] The operation content acquisition unit 41 acquires the operation content of the actuator 25. The operation content of the actuator is the content of the operation for operating the actuator 25. Specifically, when the operator operates the construction machine 10, the operation content of the actuator 25 may also be the content of the operation applied by the operator to the operating lever or the operating pedal of the operating unit 31. In this case, the operation content may include information on the amount of operation, information on the direction of operation, or information on both the amount of operation and the direction of operation. In addition, when the construction machine 10 is operated by automatic driving, the operation content of the actuator 25 may also be the content of the instruction output by the controller 40 to the control valve 27 in order to operate the actuator 25.

[0040] If the case where the operator operates the construction machine 10 is taken as an example and described specifically, it is as follows. The operation content acquisition unit 41 can also obtain the operation content of the operation unit 31 as the operation content of the actuator 25. The "operation content" obtained by the operation content acquisition unit 41 can also include information on the existence or non-existence of the operation of the operation unit 31. The "operation content" obtained by the operation content acquisition unit 41 can also include information on the operation direction and operation amount of one or more actuators 25 that are the operation objects of the operation unit 31. The operation content acquisition unit 41 can also obtain the detection result (for example, an electrical signal) of the operation amount detection unit 33. That is, the operation content acquisition unit 41 can also obtain the operation amount of the operation unit 31 detected by the operation amount detection unit 33. In addition, when the construction machine 10 is automatically driven, the operation content acquisition unit 41 can also obtain the content (operation content) of the instruction set by the part (automatic driving control unit) corresponding to the operation unit 31 contained in the controller 40.

[0041] The pump speed acquisition unit 43 acquires the pump speed N. The pump speed acquisition unit 43 may also acquire the detected value of the pump speed N of the input shaft of the pump 21. The pump speed acquisition unit 43 may also acquire the pump speed N by acquiring the speed (e.g., engine speed) of the power source 17. In this case, for example, the pump speed acquisition unit 43 may acquire the detected value of the speed of the power source 17, or may acquire the speed command sent from the controller 40 to the power source 17. When the speed of the power source 17 and the pump speed N are different from each other, the pump speed acquisition unit 43 may also calculate the pump speed N based on the speed of the power source 17.

[0042] The pump capacity calculation unit 45 calculates the pump capacity q instructed by the controller 40 to the pump capacity control unit 23. The pump capacity calculation unit 45 calculates (determines) the pump capacity q based on the operation content of the operation unit 31 obtained by the operation content acquisition unit 41 and the pump speed N obtained by the pump speed acquisition unit 43. The details of the calculation of the pump capacity q will be described below.

[0043] The pump capacity instruction unit 47 instructs the pump capacity q. More specifically, the pump capacity instruction unit 47 outputs a pump capacity instruction, which is an instruction of the pump capacity q calculated by the pump capacity calculation unit 45, to the pump capacity control unit 23. The pump capacity instruction output by the pump capacity instruction unit 47 may be, for example, an electrical signal (e.g., a current value).

[0044] The hydraulic drive device 1 is configured to operate as follows. Hereinafter, the calculation process performed by the pump capacity calculation unit 45 of the controller 40 will be mainly described.

[0045] (Calculation of target pump capacity qr corresponding to operation content)

[0046] The controller 40 may also perform positive control. The controller 40 calculates a target pump capacity qr, which is a target value of the pump capacity q, based on the operation content of the operation unit 31 (e.g., the operation amount of the operation unit 31). Specifically, for example, the relationship between the operation content of the operation unit 31 and the information on the target pump capacity qr is preset in the controller 40. This relationship may be, for example, a map such as a positive control map.

[0047] The above-mentioned “information about the target pump capacity qr” may be the target pump capacity qr, or may be information substantially indicating the target pump capacity qr, i.e., information related to the target pump capacity qr. The “information about the target pump capacity qr” may also be a target value of a pump capacity instruction, i.e., a target value of an instruction input from the controller 40 to the pump capacity control unit 23. Specifically, for example, the “information about the target pump capacity qr” may also be a daily value of a current value, i.e., a target pump capacity instruction current Ir.

[0048] Figure 3 3 is a graph showing an example of the relationship between the operation amount of the operation unit 31 and the target pump capacity qr. Figure 3The graph shows the relationship between the operation amount (e.g., pilot pressure) and the target pump capacity qr (e.g., target pump capacity command current Ir) when a specific actuator 25 is operated in a specific direction. The specific actuator 25 is any one of the multiple actuators 25. The specific direction is the direction of movement (extension direction or rotation direction) of the specific actuator. Figure 3 In FIG. 1 , the target pump capacity command current Ir is simply described as “current Ir”. Figure 3 The graph of FIG. 4 shows the following relationship, which includes a curve portion in which the target pump capacity qr increases as the operation amount increases, and a straight line portion in which the target pump capacity qr becomes a constant value when the operation amount is greater than a specific value. However, the shape of the curve portion can be set in various ways. In addition, the straight line portion of the graph can be omitted. A part or all of the curve portion can also be a straight line. In addition, the controller 40 can also be based on the following Figure 3 For example, the controller 40 may calculate the target pump capacity qr based on a mathematical formula according to the operation content of the operation unit 31.

[0049] (Limitation of pump capacity change Δq)

[0050] Next, the control when the operation amount in the prescribed operation content changes is described. Specifically, the control when the operation amount of the operation to move the specific actuator 25 in a specific direction changes is described. The situation where the operation amount in the prescribed operation content changes may also include, for example, a situation where the angle of the operating lever or the operating pedal is changed.

[0051] The controller 40 changes the target pump capacity qr according to the change of the operation amount (refer to Figure 3 ) Next, the controller 40 changes the actual pump capacity q based on the target pump capacity qr.

[0052] The controller 40 may limit the pump capacity change amount Δq. The pump capacity change amount Δq is the magnitude (absolute value) of the change in the pump capacity q per unit time. Figure 4 The slope of the curve showing the relationship between pump capacity q and time is shown.

[0053] (Problems caused by sudden changes in the pump discharge flow rate Q)

[0054] The flow rate of oil discharged per unit time by the pump 21 is defined as the pump discharge flow rate Q (see Figure 5 ). If the pump capacity change Δq is not limited, there may be a problem caused by a sudden change (sudden increase or decrease) in the pump discharge flow rate Q. More specifically, if the operation amount changes suddenly, the target pump capacity qr determined by the controller 40 will change suddenly (see Figure 3). When the pump capacity change Δq is not limited, if the target pump capacity qr changes suddenly, the pump capacity q changes suddenly, the pump discharge flow rate Q changes suddenly, and the flow rate of oil supplied to the actuator 25 changes suddenly. As a result, for example, the actuator 25 may perform undesirable operations and cavitation may occur in the hydraulic circuit 20. The following describes a specific example of a problem caused by a sudden change in the pump discharge flow rate Q. The problem when the pump discharge flow rate Q increases suddenly ([Problem A]) and the problem when the pump discharge flow rate Q decreases suddenly ([Problem B]) are described.

[0055] [Problem A] If the operation amount suddenly increases and the pump discharge flow rate Q suddenly increases, the following problems may occur.

[0056] [Question A1] If the pump discharge flow rate Q increases suddenly, the construction machine 10 may be impacted. More specifically, if the pump discharge flow rate Q increases suddenly, the flow rate supplied to the actuator 25 increases suddenly, the actuator 25 accelerates suddenly, and the construction machine 10 may be impacted, shaken, blown down, etc. For example, when the actuator 25 accelerates suddenly from a stopped state, the construction machine 10 may be impacted by the actuator 25 starting up, i.e., a start-up shock.

[0057] [Question A2] If the pump discharge flow rate Q increases suddenly, there may be a problem in which the output of the pump 21 exceeds the output of the power source 17. In more detail, the output of the pump 21 is proportional to the product of the discharge pressure (P) of the pump 21 and the pump discharge flow rate Q. Therefore, if the pump discharge flow rate Q increases suddenly, the output of the pump 21 will increase suddenly. If the output of the pump 21 increases suddenly, the PQ control performed by the controller 40 may not be timely. PQ control is a control that adjusts the output of the pump 21 in a manner that does not allow the output of the pump 21 to exceed the output of the power source 17. If the PQ control is not timely, the output of the pump 21 exceeds the output of the power source 17, and the rotational speed of the power source 17 (output shaft 17a) may decrease, or the power source 17 may stop (engine shutdown, etc.).

[0058] [Question A2-1] If PQ control is not timely and the rotation speed of the power source 17 decreases, the pump rotation speed N may decrease, the pump discharge flow rate Q may decrease, and the speed of the actuator 25 may decrease. In addition, if the power source 17 stops, the actuator 25 may stop.

[0059] [Question A2-2] It is expected that the PQ control is not timely, and after the rotation speed of the power source 17 temporarily decreases, the PQ control is performed, and the rotation speed of the power source 17 increases (recovers). In this case, the flow rate of oil supplied to the actuator 25 will increase after temporarily decreasing. In this way, the actuator 25 may not operate smoothly (for example, perform two-stage operation).

[0060] [Question A3] If the pump discharge flow rate Q increases suddenly, the hydraulic equipment (actuator 25, control valve 27, piping, etc.) will be supplied with excess oil, causing a sudden influx of oil into the hydraulic equipment. As a result, the hydraulic equipment may be subjected to a sudden pressure fluctuation (shock pressure) and damaged (damaged).

[0061] [Problem A4] If the pump discharge flow rate Q increases suddenly, the pump 21 may supply an excessive amount of oil. In this case, the fuel efficiency of the construction machine 10 deteriorates.

[0062] [Problem B] If the operation amount suddenly decreases and the pump discharge flow rate Q suddenly decreases, the following problem may occur.

[0063] [Question B1] If the pump discharge flow rate Q decreases suddenly, cavitation may occur in the hydraulic circuit 20. For example, the operation amount suddenly changes from a value greater than zero (the operation amount that causes the actuator 25 to operate) to zero (the operation amount that does not cause the actuator 25 to operate). In this way, the flow rate of oil supplied to the actuator 25 decreases suddenly. On the other hand, even if the operation amount becomes zero, the object driven by the actuator 25 will continue to move while slowing down due to the inertia of the object. Specifically, for example, even if the motor 25e (see Figure 1 ) becomes zero, and the object driven by the rotary motor 25e, that is, the upper rotary body 13, continues to rotate (overrunning). In this way, there is a possibility that the oil supplied to the actuator 25 (for example, the rotary motor 25e) is insufficient, and the pressure of the oil circuit, that is, the supply pipeline, that supplies oil to the actuator 25 drops, causing cavitation in the actuator 25, the supply pipeline, etc. Cavitation is likely to occur in the actuator 25 that operates an object with a large inertial force in the object driven by the actuator 25. Specifically, for example, cavitation is likely to occur in the rotary motor 25e that operates the upper rotary body 13, the boom cylinder 25b that operates the boom 15b, etc.

[0064] [Question B1-1] If Figure 2 If cavitation occurs in the actuator 25 or the supply line, the flow rate of oil supplied to the actuator 25 fluctuates, and the speed of the actuator 25 fluctuates. As a result, for example, the actuator 25 may perform undesirable operations and hunting may occur.

[0065] [Problem B1-2] If cavitation occurs in the actuator 25, the supply line, etc., the hydraulic equipment may be damaged by the cavitation.

[0066] [Question B1-3] The hydraulic circuit 20 may have a compensation circuit for preventing cavitation. For example, the actuator 25 may have a compensation port connected to the compensation circuit. The compensation circuit prevents cavitation by supplying oil from an oil circuit (tank line) connected to an oil tank to a supply line of the actuator 25. In this case, in order for the compensation circuit to function, it is necessary to supply oil to the tank line and ensure the pressure of the tank line.

[0067] (When the change of pump discharge flow rate Q is stable)

[0068] When the change in the operation amount is stable, specifically, when the pump capacity change Δq is less than the upper limit R described later, the above-mentioned problem caused by the sudden change in the pump discharge flow rate Q is unlikely to occur. Therefore, when the change in the operation amount is stable, the controller 40 may not limit the pump capacity change Δq. In this case, the controller 40 may also control the actual pump capacity q to the target pump capacity qr corresponding to the operation amount. That is, the controller 40 may also use, for example, Figure 3 The target pump capacity qr corresponding to the operation amount is determined by the map shown in FIG. 1 , and the actual pump capacity q is controlled to be the target pump capacity qr. The case where the change in the operation amount is stable corresponds to, for example, the Figure 8 The case where the step S31 is "No", and the case where the step S41 is "No". (Regarding the upper limit value R)

[0069] The controller 40 sometimes limits the pump capacity change Δq to suppress the occurrence of problems caused by the sudden change of the pump discharge flow rate Q. The following mainly describes the case where the controller 40 limits the pump capacity change Δq. The controller 40 limits the pump capacity change Δq in such a way that the size (absolute value) of the pump capacity change Δq is less than the upper limit value R. The upper limit value R is the upper limit (limitation amount) of the size (absolute value) of the pump capacity change Δq. The controller 40 may also set the upper limit value R (upper limit value R on the increase side) of the size of the pump capacity change Δq when the pump capacity q increases, and the upper limit value R (upper limit value R on the decrease side) of the size of the pump capacity change Δq when the pump capacity q decreases. The controller 40 may also limit the pump capacity change Δq when the pump capacity q increases and decreases. The upper limit value R on the increase side and the upper limit value R on the decrease side may be different sizes from each other, or may be the same size as each other. In addition, the controller 40 may also limit the pump capacity change Δq only in either case when the pump capacity q increases or decreases. Hereinafter, the case where the controller 40 limits the pump capacity change amount Δq when the pump capacity q increases or decreases will be mainly described.

[0070] Specifically, the upper limit value R is, for example, the upper limit of the amount of change per unit time of the pump capacity command output from the controller 40 to the pump capacity control unit 23. When the pump capacity command is a current value (pump capacity command current), the upper limit value R is the upper limit of the amount of change per unit time (gain) of the current value. The unit of the upper limit value R in this case may be "mA / control cycle", "mA / second", or "mA / minute".

[0071] Figure 4 The relationship between time and pump capacity q is shown for the case where the pump capacity change Δq is not limited (curve G1) and the case where it is limited (curve G2). Figure 4 The relationship between time and the operation amount is also shown. The operation amount increases from time t0 to time t1, and after time t1, it is fixed at a predetermined operation amount.

[0072] When the pump capacity change amount Δq is not limited (curve G1), the operation amount increases from time t0 to time t1, and the pump capacity q increases. The operation amount is fixed at the specified operation amount, and the pump capacity q reaches the pump capacity q corresponding to the specified operation amount, that is, the target pump capacity qr, at the same time or substantially at the same time (at time t1), and then is fixed at the capacity.

[0073] When the pump capacity change Δq is limited (curve G2), the pump capacity q increases as the operation amount increases from time t0 to time t2. Time t2 is a time later than time t1. When the pump capacity change Δq is limited, the pump capacity change Δq (i.e., the slope of the curve) is smaller than when the pump capacity change Δq is not limited, and the increase rate of the pump capacity q is slower. From time t1 to time t2 after the operation amount is fixed at the specified operation amount, the pump capacity q continues to increase until it reaches the pump capacity q corresponding to the specified operation amount, i.e., the target pump capacity qr. After time t2, the pump capacity q is fixed at the target pump capacity qr.

[0074] (Size of upper limit value R)

[0075] The upper limit value R can also be calculated based on Figure 2 The upper limit value R is set in a different manner depending on the operation content of the operation unit 31 shown in the figure. The appropriate upper limit value R varies depending on the operation direction and operation amount of the actuator 25 as the operation object. Therefore, the upper limit value R may also be changed according to the type of the actuator 25. The controller 40 sets the upper limit value R to an appropriate size corresponding to the operation content. For example, the relationship (mapping, etc.) between the operation content and the upper limit value R may also be pre-set in the controller 40. In addition, for example, the controller 40 may also calculate the upper limit value R based on a pre-set mathematical formula according to the operation content.

[0076] If the upper limit value R is too large, the magnitude (absolute value) of the pump capacity change Δq will increase, and there is a possibility that a problem caused by a sudden change in the pump discharge flow rate Q as described above will occur.

[0077] (The problem of slow change in pump discharge flow rate Q)

[0078] On the other hand, if the upper limit value R is too small, the magnitude (absolute value) of the pump capacity change amount Δq becomes small, and there arises a problem that the change in the pump discharge flow rate Q becomes slow.

[0079] [Question C] In more detail, if the pump capacity change Δq is too small relative to the change in the operation amount, the change in the pump discharge flow rate Q will be slow, and the change in the flow rate of oil supplied to the actuator 25 will be slow. In this way, the responsiveness of the speed change of the actuator 25 relative to the change in the operation amount may be deteriorated. When the construction machine 10 is operated by the operator, the operability of the actuator 25 will be deteriorated due to the slow change in the pump discharge flow rate Q.

[0080] [Question C-1] Specifically, if the pump capacity change Δq is too small relative to the increase in the operation amount, the increase in the flow rate of oil supplied to the actuator 25 will become slow, and the flow rate required for the operation of the actuator 25 cannot be ensured, and the acceleration of the actuator 25 will slow down.

[0081] [Problem C-2] If the magnitude (absolute value) of the pump displacement change Δq is too small relative to the decrease in the operation amount, the deceleration of the actuator 25 will become slow.

[0082] (About the change in pump discharge flow rate ΔQ)

[0083] As described above, when the operation amount changes, the pump capacity q changes, and the pump discharge flow rate Q changes. The pump discharge flow rate Q is proportional to the product of the pump rotation speed N and the pump capacity q. Specifically, for example, the pump discharge flow rate Q is expressed by the following formula.

[0084] Pump discharge flow rate Q (L / min) = pump capacity q (cm 3 )×Pump speed N (times / min) / 1000

[0085] Here, the change in the pump discharge flow rate Q per unit time is defined as the pump discharge flow rate change ΔQ. The pump discharge flow rate change ΔQ may also be referred to as a flow rate change gain, a flow rate increase gain, or a flow rate decrease gain. The pump discharge flow rate change ΔQ is Figure 5 The slope of the curve showing the relationship between the pump discharge flow rate Q and time is shown.

[0086] (Problems when the upper limit value R does not change according to the pump rotation speed N)

[0087] As mentioned above, the pump discharge flow rate Q is proportional to the product of the pump speed N and the pump capacity q. Therefore, the pump discharge flow rate change ΔQ is proportional to the pump speed N. Therefore, Figure 5 As shown in the curves G3 and G4 of FIG. 1 , even if the upper limit value R of the pump capacity change Δq is the same, the pump discharge flow change ΔQ will be different if the pump rotation speed N is different. The higher the pump rotation speed N, the larger the pump discharge flow change ΔQ becomes. The larger the pump discharge flow change ΔQ, the easier it is to cause the above-mentioned "problem caused by the sudden change of the pump discharge flow Q". If the upper limit value R is set in such a way that the "problem caused by the sudden change of the pump discharge flow Q" does not occur when the pump rotation speed N is a specific "low pump rotation speed N", then when the pump rotation speed N is a pump rotation speed N higher than the above-mentioned "low pump rotation speed N", the problem caused by the sudden change of the pump discharge flow Q may occur. On the other hand, if the upper limit value R is set in such a way that the "problem caused by the sudden change of the pump discharge flow Q" does not occur when the pump rotation speed N is a specific "high pump rotation speed N", then when the pump rotation speed N is a pump rotation speed N lower than the above-mentioned "high pump rotation speed N", the above-mentioned "problem of slow change of the pump discharge flow Q" may occur.

[0088] Figure 5 Graphs showing time changes in the amount of operation of the operating unit 31 and time changes in the pump discharge flow rate of the pump 21 are graphs when the upper limit value R is constant. Specifically, Figure 5 When the upper limit value R is set to a constant value (α), the relationship between time and the pump discharge flow rate Q is shown for the case where the pump speed N is β (curve G3) and the case where the pump speed N is (β / 2) (curve G4). Figure 5 It also expresses the relationship between time and operation amount (with Figure 4 same).

[0089] In the case where the pump speed N is β (curve G3) and the case where the pump speed N is (β / 2) (curve G4), the operation amount increases from time t0 to time t2, and the pump discharge flow rate Q increases. The pump discharge flow rate change amount ΔQ (the slope of curve G4) when the pump speed N is (β / 2) is 1 / 2 of the pump discharge flow rate change amount ΔQ (the slope of curve G3) when the pump speed N is β.

[0090] After time t2, the pump capacity q reaches a constant value (target pump capacity qr) in both the curve G3 and the curve G4. In this example, after time t2, the pump discharge flow rate Q of the curve G4 becomes 1 / 2 of the pump discharge flow rate Q of the curve G3. The pump discharge flow rate change amount ΔQ (the slope of the curve) when the pump capacity q increases from time t0 to time t2 is different between the curve G3 and the curve G4.

[0091] (Specific example using numerical values)

[0092] The difference in the pump discharge flow rate change amount ΔQ when the upper limit value R is the same and the pump rotation speed N is different will be further described using specific numerical values. Figure 2 The minimum capacity of the pump 21 shown (the minimum value of the pump capacity q) is set to 10 cm 3 / rev, and set the maximum capacity (maximum value of the pump capacity q) to 200cm 3 Assume that the controller 40 sets the upper limit value R of the pump displacement change amount Δq to 10 cc per 0.1 second.

[0093] When the pump speed N is 1000 times / min, for example, the pump discharge flow rate Q at time t=0 (sec) reaches 10 L / min, the pump discharge flow rate Q at time t=0.5 (sec) reaches 60 L / min, and the pump discharge flow rate Q at time t=1 (sec) reaches 110 L / min. In this case, the pump discharge flow rate change ΔQ per second is 100 L / min.

[0094] When the pump speed N is 2000 times / min, for example, the pump discharge flow rate Q at time t=0 (sec) reaches 20 L / min, the pump discharge flow rate Q at time t=0.5 (sec) reaches 120 L / min, and the pump discharge flow rate Q at time t=1 (sec) reaches 220 L / min. In this case, the pump discharge flow rate change ΔQ per second is 200 L / min.

[0095] The following example is used for explanation. This example refers to the threshold value of the pump discharge flow rate change ΔQ, which is 120 L / min, where the startup shock of the actuator 25 (an example of a problem caused by a sudden change in the pump discharge flow rate Q) becomes a problem. In this example, when the pump speed N is 1000 times / min, the pump discharge flow rate change ΔQ per second is 100 L / min, which is less than the threshold value (120 L / min), so the startup shock will not become a problem. On the other hand, when the pump speed N is 2000 times / min, the pump discharge flow rate change ΔQ per second is 200 L / min, which exceeds the threshold value (120 L / min), so the startup shock will become a problem.

[0096] Next, the following example is used to explain that the threshold value of the pump discharge flow rate change ΔQ, which is 220 L / min, is a case where the startup shock of the actuator 25 becomes a problem. In this example, even when the pump rotation speed N is 2000 times / min, the startup shock will not become a problem. However, when the pump rotation speed N is 1000 times / min, the problem of slow change of the above-mentioned pump discharge flow rate Q may occur.

[0097] (Upper limit value R corresponding to pump speed N)

[0098] In the present embodiment, the controller 40 changes the upper limit value R of the magnitude (absolute value) of the pump capacity change amount Δq, which is the amount of change in the pump capacity per unit time, according to the pump rotation speed N.

[0099] Specifically, the controller 40 may set the upper limit value R as described in [Condition 1], [Condition 2], and [Condition 3], for example. In addition, the following conditions are conditions when an operation (specified operation content) is performed to move a specific actuator 25 in a specific direction. In the case where the actuator 25 to be operated is changed, or in the case where the operation direction is changed, the following conditions do not necessarily have to be satisfied. In addition, the following conditions are conditions when the pump speed N is within a specified range. In the case where the pump speed N is outside the specified range, the following conditions do not need to be satisfied. A specific example of the specified range will be described below.

[0100] [Condition 1] If Figure 6 As shown, the controller 40 sets the upper limit value R to the first upper limit value R1 when the pump rotation speed N is the first rotation speed N1. The controller 40 preferably sets the upper limit value R to the second upper limit value R2 which is smaller than the first upper limit value R1 when the pump rotation speed N is the second rotation speed N2 which is larger than the first rotation speed N1. In this case, the magnitude of the pump capacity change amount Δq1 when the pump rotation speed N is the first rotation speed N1 is limited by the first upper limit value R1, and the magnitude of the pump capacity change amount Δq2 when the pump rotation speed N is the second rotation speed N2 is limited by the second upper limit value R2.

[0101] The controller 40 preferably sets the upper limit value R so that the magnitude (absolute value) of the pump capacity change Δq at the second rotation speed N2 is smaller than the magnitude (absolute value) of the pump capacity change Δq1 at the first rotation speed N1. By setting the upper limit value R in the above manner, the hydraulic drive device 1 can suppress the problem caused by the sudden change of the pump discharge flow rate Q regardless of the pump rotation speed N, and can suppress the problem of the slow change of the pump discharge flow rate Q.

[0102] [Condition 1a] For example, the controller 40 may be pre-set with a threshold value related to the pump rotation speed N. The threshold value may be set before setting the upper limit value R. The controller 40 may set the upper limit value R to a first upper limit value R1 when the pump rotation speed N is less than the threshold value, and may set the upper limit value R to a second upper limit value R2 when the pump rotation speed N is greater than the threshold value. In this case, the first rotation speed N1 is a value included in a range less than the threshold value, and the second rotation speed N2 is a value included in a range greater than the threshold value.

[0103] [Condition 2] The controller 40 preferably sets the upper limit value R so that the upper limit value R decreases as the pump rotation speed N increases. In this case, the magnitude (absolute value) of the pump capacity change Δq is limited by the upper limit value R that decreases as the pump rotation speed N increases. The controller 40 preferably sets the upper limit value R so that the magnitude (absolute value) of the pump capacity change Δq decreases as the pump rotation speed N increases.

[0104] [Condition 2a] For example, the controller 40 may also reduce the upper limit value R in stages as the pump speed N increases. [Condition 2b] For example, the controller 40 may also reduce the upper limit value R continuously as the pump speed N increases. In this case, the curve representing the relationship between the pump speed N and the upper limit value R (the curve satisfying [Condition 2b]) may be a straight line or a curve. [Condition 2b1] For example, the controller 40 preferably sets the upper limit value R in a manner that makes the upper limit value R proportional to the pump speed N (for example, refer to the following formula 1). The controller 40 preferably sets the upper limit value R in a manner that makes the size of the pump capacity change Δq limited by the upper limit value R proportional to the pump speed N.

[0105] [Condition 3] The controller 40 preferably sets the upper limit value R in such a manner that the pump discharge flow rate change amount ΔQ is constant when the pump rotation speed N is any rotation speed within a predetermined range. The controller 40 preferably sets the upper limit value R in such a manner that the pump discharge flow rate change amount ΔQ becomes constant regardless of the pump rotation speed N. The "prescribed range" of the pump rotation speed N may be, for example, a range of the pump rotation speed N used when the construction machine 10 is operating (e.g., a use area), or a range narrower than the use area.

[0106] Figure 6 The graph shown is a graph showing the relationship between the pump rotation speed N and the upper limit value R, and the relationship between the pump rotation speed N and the pump discharge flow rate change amount ΔQ. Figure 6 The upper limit value R in the graph of may be the size (absolute value) of the pump capacity change Δq limited by the upper limit value R. The controller 40 may also set the size of the pump capacity change Δq to the upper limit value R set according to the pump speed N. This graph is a graph when the above-mentioned [Condition 1], [Condition 2], [Condition 2b1] and [Condition 3] are satisfied.

[0107] (Calculation of upper limit value R)

[0108] Specifically, for example, the controller 40 may calculate the upper limit value R in the following manner.

[0109] First, the controller 40 determines a reference upper limit value Rs, which is an upper limit value R of a reference speed Ns serving as a reference for the pump speed N. The reference speed Ns may be, for example, a maximum value (high idle) of the use range of the pump speed N, or a value other than high idle. For example, the relationship (mapping) between the operation content and the reference upper limit value Rs may also be pre-set in the controller 40. For example, the controller 40 may also calculate the reference upper limit value Rs according to a condition specified by a mathematical formula or the like. In addition, the controller 40 calculates the ratio of the reference speed Ns to the current pump speed N (use speed Nc), that is, the speed ratio. The speed ratio is represented, for example, by (Ns / Nc). Next, the controller 40 calculates the upper limit value R of the use speed Nc based on the reference upper limit value Rs and the speed ratio (Ns / Nc). The upper limit value R of the current use speed Nc is calculated based on the reference upper limit value Rs of the reference speed Ns, in other words, the reference upper limit value Rs of the reference speed Ns is corrected to the upper limit value R of the current use speed Nc.

[0110] Specifically, for example, the controller 40 may calculate the magnitude α of the upper limit value R according to the following formula 1.

[0111] α = reference upper limit value Rs × (reference rotation speed Ns / operating rotation speed Nc) (Formula 1)

[0112] In this case, if Figure 6 As shown, the pump discharge flow rate change amount ΔQ is constant at any pump rotation speed N within a predetermined range (usage area).

[0113] (Specific example using numerical values)

[0114] The relationship between the pump speed N and the upper limit value R is further described using specific numerical values. Assuming that when the operation content of the actuator is the specified operation content, the threshold value of the magnitude of the change amount ΔQ of the pump discharge flow rate per second that can suppress the problem caused by the sudden change of the pump discharge flow rate Q is 200L / mmin. Below, the upper limit value R that makes the magnitude of the change amount ΔQ of the pump discharge flow rate per second reach 200L / min is calculated when the pump speed N is 1000 times / min and 2000 times / mmin respectively. Here, the case where the pump capacity instruction is a current value (pump capacity instruction current) and the upper limit value R is the upper limit of the change amount of the current value per unit time is described.

[0115] [Calculation 1] When the pump rotation speed N is 2000 (times / min), the pump capacity change Δq required to adjust the pump discharge flow rate change ΔQ per second to the above threshold value, i.e., 200 (L / min), is calculated using the following formula.

[0116] 200(L / min / sec)÷2000(times / min)×1000=100(cm 3 / sec)

[0117] If the control cycle of the controller 40 is set to 10 (msec), the pump displacement change amount Δq obtained by converting the "unit time" into one control cycle is calculated using the following equation.

[0118] 100(cm 3 / sec)×10(msec)÷1000(msec)=1(cm 3 / Control cycle)

[0119] will be used to change the pump capacity q by 1 cm 3 The change in pump capacity command current is set to 20 (mA / cm 3 ). In this way, the pump capacity change Δq is adjusted to 1 (cm 3 The amount of change in the pump capacity command current per control cycle ( / control cycle) is calculated using the following equation.

[0120] 20(mA / cm 3 )×1(cm 3 / control cycle) = 20 (mA / control cycle)

[0121] Therefore, by setting the change in the pump capacity command current per control cycle (upper limit value R) to 20 (mA / control cycle), the pump discharge flow rate change ΔQ per second can be adjusted to 200 (L / min), which is the above threshold.

[0122] [Calculation 2] When the pump rotation speed N is 1000 (times / min), the pump capacity change Δq required to adjust the pump discharge flow rate change ΔQ per second to the above threshold value, i.e., 200 (L / min), is calculated using the following formula.

[0123] 200(L / min / sec)÷1000(times / min)×1000=200(cm 3 / sec)

[0124] In this example, the control cycle of the controller 40 is set to 10 (msec), and therefore the pump displacement change amount Δq obtained by converting the "unit time" into one control cycle is calculated using the following equation.

[0125] 200(cm 3 / sec)×10(msec)÷1000(msec)=2(cm 3 / Control cycle)

[0126] In this example, the pump capacity q is changed by 1 (cm 3 ) of the pump capacity command current is 20 (mA / cm 3). In this way, the pump capacity change Δq is adjusted to 2 (cm 3 The amount of change in the pump capacity command current per control cycle ( / control cycle) is calculated using the following equation.

[0127] 20(mA / cm 3 )×2(cm 3 / control cycle) = 40 (mA / control cycle)

[0128] Therefore, by setting the change in pump capacity command current per control cycle (upper limit value R) to 40 (mA / control cycle), the pump discharge flow rate change ΔQ per second can be adjusted to 200 (L / min), which is the above threshold.

[0129] The validity of the above formula 1 is studied. Based on the state of the above [Calculation 1], the reference speed Ns is set to 2000 (times / min), and the reference upper limit Rs is set to 20 (mA / control cycle). The upper limit R when the speed Nc is 1000 (times / min) is calculated as follows using the above formula 1.

[0130] 20(mA / control cycle)×2000 / 1000=40(mA / control cycle)

[0131] This calculation result agrees with the upper limit value R obtained by the above-mentioned [Calculation 2]. Similarly, even when the pump rotation speed N is varied, the upper limit value R that makes the pump discharge flow rate change amount ΔQ reach the above-mentioned threshold value can be calculated according to Formula 1.

[0132] Figure 7 It is a graph showing the time change of the operation amount of the operation part 31 and the time change of the pump discharge flow rate of the pump 21. Figure 7 This is a graph showing the relationship between time and pump discharge flow rate Q when the upper limit value R is changed according to the pump speed N, for the case where the pump speed N is β (curve G3) and the case where the pump speed N is (β / 2) (curve G5). In addition, Figure 7 It also expresses the relationship between time and operation volume. Figure 4 and Figure 5 The curve G3 when the pump speed N is β is the same as Figure 5The same curve as the curve G3 shown. In this example, β is the reference speed Ns. The size of the upper limit value R (i.e., the reference upper limit value Rs) when the pump speed N is β is set to α. When the pump speed N is (β / 2) (curve G5), the size of the upper limit value R is different from α, specifically, 2α. As a result, between time t1 and time t1a, the slopes (pump discharge flow rate change ΔQ) of the curves when the pump speed N is β (curve G3) and when the pump speed N is (B / 2) (curve G5) are equal.

[0133] (flow chart)

[0134] Reference Figure 8 The flowchart shown in the figure shows the Figure 2 The controller 40 shown in the figure calculates the pump capacity q. Figure 8 Steps S11 to S51 of the flowchart will be described. In this example, a specific actuator 25 (eg Figure 2 In the embodiment of the present invention, an operation (predetermined operation content) of causing one of the actuators 25 shown in the figure to move in a specific direction is performed. In addition, the pump capacity instruction is a current value (pump capacity instruction current), and the upper limit value R is the upper limit of the amount of change per unit time of the current value.

[0135] In step S11, the controller 40 (operation content acquisition unit 41) acquires (acquires) the operation content of the operation unit 31. The acquired operation content may be, for example, the operation amount of the operation performed by the operator on the operation unit 31. In addition, the controller 40 (pump speed acquisition unit 43) acquires (acquires) the pump speed N.

[0136] In step S12, the controller 40 determines the target pump capacity qr (specifically, the target pump capacity command current Ir) based on the acquired operation content. For example, the controller 40 determines the target pump capacity qr based on the relationship between the preset operation content and the target pump capacity qr. Figure 3 Such a map calculates the target pump capacity qr corresponding to the operation content. Figure 8 , the target pump displacement instruction current Ir is simply described as “current Ir”.

[0137] In step S13, Figure 2The controller 40 shown determines the upper limit value R (reference upper limit value Rs) of the reference rotation speed Ns based on the acquired operation content. For example, the controller 40 reads the reference upper limit value Rs corresponding to the operation content based on the relationship (mapping) between the operation content and the reference upper limit value Rs that is set in advance. The controller 40 may also determine the reference upper limit value Rs on the increase side of the pump capacity q (specifically, the reference current upper limit value Id1 on the increase side) and the reference upper limit value Rs on the decrease side of the pump capacity q (specifically, the reference current upper limit value Id2 on the decrease side). The reference current upper limit value Id1 on the increase side and the reference current upper limit value Id2 on the decrease side are each the values ​​of the upper limits of the reference of the change amount of the current value of the pump capacity instruction.

[0138] In step S14, the controller 40 calculates the upper limit value R of the operating rotation speed Nc. The controller 40 calculates the upper limit value R on the increase side of the pump capacity q (specifically, the correction current upper limit value Id3 on the increase side), and the upper limit value R on the decrease side of the pump capacity q (specifically, the correction current upper limit value Id4 on the decrease side). Specifically, the controller 40 calculates the correction current upper limit value Id3 on the increase side and the correction current upper limit value Id4 on the decrease side according to the following formula.

[0139] Correction current upper limit value Id3 on the increasing side = reference current upper limit value Id1 on the increasing side × (reference speed Ns / operating speed Nc)

[0140] Correction current upper limit value Id4 on the decreasing side = reference current upper limit value Id2 on the decreasing side × (reference speed Ns / operating speed Nc)

[0141] In step S21, Figure 2 The controller 40 shown determines whether the obtained operation content is an operation content that increases the pump capacity q or an operation content that does not change the pump capacity q. Specifically, the controller 40 determines whether the value obtained by subtracting the pump capacity q indicated one control cycle ago (the last indicated pump capacity q) from the current target pump capacity qr is greater than 0. The value obtained by subtracting the pump capacity q indicated one control cycle ago (last time) from the current target pump capacity qr is also called the "target value of the pump capacity change Δq". More specifically, the controller 40 determines whether the target pump capacity command current Ir (refer to step S12) is subtracted from the last indicated pump capacity command current (last value I n-1 ) is greater than 0 (Ir - previous value I n-1 ≥≥0”). When the operation content is an operation to increase the pump capacity q or an operation not to change the pump capacity q (when the answer is “Yes” in step S21), the controller 40 performs the processing of step S31. When the operation content is an operation to reduce the pump capacity q (when the answer is “No” in step S21), the controller 40 performs the processing of step S41.

[0142] In step S31, the controller 40 determines whether the target value of the pump capacity change amount Δq is greater than the upper limit R (the upper limit R on the increase side). Specifically, the controller 40 determines whether the value obtained by subtracting the last indicated pump capacity command current from the target pump capacity command current Ir is greater than the corrected current upper limit Id3 on the increase side (Ir-last value Id3). n-1 ≥Id3).

[0143] When the target value of the pump capacity change amount Δq is greater than the upper limit value R on the increasing side (if "yes" in step S31), the controller 40 sets the sum of the pump capacity q instructed last time and the upper limit value R as the pump capacity q instructed this time (step S32). Specifically, the controller 40 sets the pump capacity instruction current instructed last time (the previous value I n-1 ) and the correction current upper limit value Id3 on the increase side are set as the pump capacity instruction current (this time value In) (I n =Last value I n-1 +Id3).

[0144] When the target value of the pump capacity change Δq is smaller than the upper limit R of the increase side (in the case of "No" in step S31), the controller 40 sets the pump capacity q instructed this time as the target pump capacity qr (step S33). In this case, the controller 40 does not limit the pump capacity change Δq by the upper limit R. Specifically, the controller 40 sets the pump capacity instruction current instructed this time (this value I n ) is set as the target pump capacity command current Ir(I n =Ir). After step S32 or step S33, the controller 40 performs the process of step S51.

[0145] In step S41, the controller 40 determines whether the magnitude (absolute value) of the target value of the pump displacement change Δq is greater than the upper limit R (the upper limit R on the decreasing side). Specifically, the controller 40 determines whether the pump displacement command current (the last value I n-1 ) minus the target pump capacity command current Ir is greater than or equal to the correction current upper limit value Id4 on the decreasing side (is it “the previous value I n-1 -Ir≥Id4”). In addition, the controller 40 can also determine the target pump capacity command current Ir minus the previous value I n-1 Is the absolute value of the obtained value greater than or equal to the correction current upper limit value Id4 on the decreasing side (Is it "|Ir-previous value Id4"? n-1 |≥Id4”).

[0146] When the target value of the pump capacity change Δq is greater than the upper limit R (if "yes" in step S41), the controller 40 sets the value obtained by subtracting the upper limit R from the last instructed pump capacity q as the currently instructed pump capacity q (step S42). Specifically, the controller 40 sets the last instructed pump capacity command current (last value I n-1 ) minus the corrected current upper limit value Id4 is set as the pump capacity command current indicated this time (this value I n )(I n =Last value I n-1 -Id4).

[0147] If the target value of the pump capacity change Δq is not greater than the upper limit R (if step S41 is "No"), the controller 40 sets the pump capacity q instructed this time as the target pump capacity qr (step S43). In this case, the controller 40 does not limit the pump capacity change Δq by using the upper limit R. Specifically, the controller 40 sets the pump capacity instruction current instructed this time (this value I n ) is set as the target pump capacity command current Ir(I n =Ir).

[0148] The controller 40 may also set the pump capacity q (specifically, the current value I) determined in step S32, S33, S42 or S43 to be the pump capacity q of this instruction. n ) is indicated to (output to) the pump capacity control unit 23. The controller 40 may also return to the process of step S11 after step S32, S33, S42 or S43. In this case, step S51 may also be omitted.

[0149] The controller 40 may also perform the processing of step S51 following step S42 or step S43. In step S51, the controller 40 may perform other controls related to the pump capacity q, and may also correct the pump capacity q. Specifically, for example, the controller 40 may also perform control to limit the output of the pump 21 (such as PQ control, etc.). In addition, the above-mentioned "pump capacity q indicated last time" and "pump capacity q indicated this time" are values ​​determined in steps S32, S33, S42 or S43 before step S51 is performed, and are not the pump capacity q corrected in step S51. Specifically, the "this time value I n " and "Last value I n-1 " is a value determined in step S32, S33, S42 or S43 before step S51 is performed, and is not a current value corrected in step S51. After step S51, the controller 40 returns to the process of step S11. The controller 40 repeatedly performs the processes from step S11 to step S51.

[0150] (Effect of the First Invention)

[0151] Depend on Figure 2 The effects produced by the hydraulic drive device 1 shown are as follows. The hydraulic drive device 1 includes a pump 21, an actuator 25, and a controller 40. The pump 21 is driven to rotate by the power source 17 to eject oil. The pump 21 can change its capacity. The actuator 25 is operated by being supplied with the oil ejected by the pump 21. The controller 40 controls the capacity of the pump 21 according to the operation content of the actuator 25.

[0152] [Structure 1] The controller 40 changes the upper limit value R (refer to the upper limit value R) of the change amount per unit time of the capacity of the pump 21, that is, the pump capacity change amount Δq, according to the rotation speed (pump rotation speed N) of the pump 21. Figure 6 ).

[0153] In the above-mentioned [Structure 1], the controller 40 sets the upper limit value R of the size of the pump capacity change amount Δq in consideration of the pump speed N. Thus, for example, compared with the case where the upper limit value R is set without considering the pump speed N, the hydraulic drive device 1 can set the pump capacity change amount Δq to an appropriate size corresponding to the pump speed N. Therefore, the hydraulic drive device 1 can set the flow rate of oil supplied from the pump 21 to the actuator 25 to an appropriate amount corresponding to the pump speed N. As a result, the hydraulic drive device 1 can set the upper limit value R that can suppress a sudden change in the pump discharge flow rate Q, and can also set the upper limit value R that can suppress the pump discharge flow rate Q from changing too slowly with respect to the change in the operation content (for example, the operation amount).

[0154] (Effect of the Second Invention)

[0155] [Structure 2] The controller 40 sets the upper limit value R when the pump rotation speed N is the first rotation speed N1 to the first upper limit value R1, and sets the upper limit value R when the pump rotation speed N is the second rotation speed N2 greater than the first rotation speed N1 to the second upper limit value R2 smaller than the first upper limit value R1. Specifically, the controller 40 sets the size of the pump capacity change Δq (the size of the pump capacity change Δq limited by the upper limit value R) to the first pump capacity change Δq1 when the pump rotation speed N is the first rotation speed N1. In addition, the controller 40 sets the size of the pump capacity change Δq (the size of the pump capacity change Δq limited by the upper limit value R) to the second pump capacity change Δq2 when the pump rotation speed N is the second rotation speed N2 greater than the first rotation speed N1. The controller 40 sets the upper limit value R so that the second pump capacity change Δq2 becomes smaller than the first pump capacity change Δq1.

[0156] According to the above-mentioned [Structure 2], the following effects can be obtained. If the pump capacity change Δq is the same, the larger the pump speed N, the larger the pump discharge flow rate change ΔQ (refer to Figure 5), the pump discharge flow rate Q is prone to sudden changes. Therefore, according to the above-mentioned [Structure 2], when the pump speed N is the second speed N2 which is greater than the first speed N1, the second pump capacity change amount Δq2 can be made smaller than the first pump capacity change amount Δq1 (refer to Figure 6 ). Thus, the hydraulic drive device 1 can suppress the pump speed N from becoming the second speed which is large.

[0157] The sudden change of the pump discharge flow rate Q at N2. As a result, for example, the hydraulic drive device 1 can suppress undesirable operation (shock, etc.) of the actuator 25 and cavitation of the actuator 25 and its periphery.

[0158] In addition, if the pump capacity change Δq is the same, the smaller the pump speed N is, the smaller the pump discharge flow rate change ΔQ is, and the change in the pump discharge flow rate Q is likely to be slower than the change in the operation content (such as the operation amount) (see Figure 5 ). Therefore, according to the above-mentioned [Configuration 2], when the pump speed N is the first speed N1 which is smaller than the second speed N2, the first pump capacity change amount Δq1 can be made larger than the second pump capacity change amount Δq2 (refer to Figure 6 ). Thus, the hydraulic drive device 1 can suppress the change of the pump discharge flow rate Q too slowly with respect to the change of the operation content (e.g., the operation amount) when the pump rotation speed N is a small first rotation speed N1. As a result, for example, the hydraulic drive device 1 can ensure the responsiveness of the operation of the actuator 25 with respect to the change of the operation content (e.g., the operation amount). Therefore, according to the above-mentioned [Structure 2], the hydraulic drive device 1 can set the flow rate of oil supplied from the pump 21 to the actuator 25 to a more appropriate amount corresponding to the pump rotation speed N.

[0159] (Effect of the Third Invention)

[0160] [Configuration 3] The controller 40 sets the upper limit value R so that the upper limit value R decreases as the pump rotation speed N increases.

[0161] According to the above-mentioned [Structure 3], the effect produced by the above-mentioned [Structure 2] can be obtained more reliably.

[0162] (Effect of the Fourth Invention)

[0163] [Configuration 4] The controller 40 sets the upper limit value R so that the amount of change per unit time in the discharge flow rate of the pump 21 (pump discharge flow rate change amount ΔQ) is constant when the pump rotation speed N is within a predetermined range.

[0164] In the above-mentioned [Configuration 4], the pump discharge flow rate change amount ΔQ can be made constant regardless of the pump rotation speed N (refer to Figure 6). As a result, it is possible to more reliably suppress a sudden change in the pump discharge flow rate Q, and thus it is possible to more reliably suppress an excessively slow change in the pump discharge flow rate Q relative to a change in the operation content (e.g., the operation amount). Therefore, the hydraulic drive device 1 can set a more appropriate pump capacity change amount Δq corresponding to the pump rotation speed N. As a result, the hydraulic drive device 1 can set the flow rate of oil supplied from the pump 21 to the actuator 25 to a more appropriate amount corresponding to the pump rotation speed N.

[0165] (Effect of the Fifth Invention)

[0166] [Structure 5] The power source 17 and the pump 21 are mounted on the construction machine 10. The actuator 25 operates the construction machine 10.

[0167] In the above-described [Configuration 5], the construction machine 10 including the power source 17 , the pump 21 , and the actuator 25 can achieve the effect of setting the flow rate of oil supplied from the pump 21 to the actuator 25 to an appropriate amount corresponding to the pump rotation speed N.

[0168] (Variation Example)

[0169] The above-mentioned embodiments may be modified in various ways. For example, the number of components (including modified examples) of the above-mentioned embodiments may be changed, or some of the components may not be provided. For example, the modified examples of the above-mentioned embodiments may be combined in various ways. For example, the fixing or connection between the components may be direct or indirect. For example, the number of components (including modified examples) of the above-mentioned embodiments may be changed, or some of the components may not be provided. Figure 2 The connection of each component shown. For example, the inclusion relationship of the components may be changed in various ways. For example, a component described as a subordinate component contained in a certain upper component may not be included in the upper component, and may be included in other components. For example, a component described as multiple components or parts different from each other may be set as one component or part. For example, a component described as one component or part (such as the controller 40) may be divided into multiple components or parts different from each other and set. For example, various parameters (set values, thresholds, ranges, etc.) may be pre-set to the controller 40, or may be directly set by manual operation of the operator. Various parameters may be calculated by the controller 40 based on information set by manual operation of the operator, or may be calculated by the controller 40 based on information detected by the sensor. For example, various parameters may not be changed, may be changed by manual operation, or may be automatically changed by the controller 40 according to certain conditions. For example, it is possible to change Figure 8 The order of the steps in the flowchart shown may not be performed in part. For example, each component may have only a part of each feature (function, arrangement, shape, operation, etc.).

[0170] Explanation of symbols

[0171] 1 Hydraulic drive unit

[0172] 10 Construction Machinery

[0173] 17 Power Source

[0174] 21 Pump

[0175] 25 Actuator

[0176] 40 Controller

[0177] N Pump speed (speed of pump 21)

[0178] N1 1st speed

[0179] N2 2nd speed

[0180] R Upper limit

[0181] Δq Pump capacity change

[0182] Δq1 Change in the capacity of the first pump

[0183] Δq2 Change in the capacity of the second pump

Claims

1. A hydraulic drive device, characterized in that include: A pump that ejects oil by being rotationally driven by a power source and can change its capacity; an actuator operated by being supplied with oil ejected by the pump; as well as A controller controls the capacity of the pump according to the operation content of the actuator, wherein: The controller changes an upper limit value of a change in the capacity of the pump per unit time, ie, a pump capacity change amount, according to a rotation speed of the pump.

2. The hydraulic drive device according to claim 1, characterized in that: the controller, The upper limit value when the rotation speed of the pump is the first rotation speed is set as the first upper limit value, The upper limit value when the rotation speed of the pump is a second rotation speed greater than the first rotation speed is set to a second upper limit value smaller than the first upper limit value.

3. The hydraulic drive device according to claim 2, characterized in that: The controller sets the upper limit value so that the upper limit value decreases as the rotation speed of the pump increases.

4. The hydraulic drive device according to claim 3, characterized in that: The controller sets the upper limit value so that a change per unit time in a discharge flow rate of the pump is constant when a rotation speed of the pump is within a predetermined range.

5. The hydraulic drive device according to any one of claims 1 to 4, characterized in that: The power source and the pump are mounted on a construction machine. The actuator causes the construction machine to operate.

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