Work machine

Abstract

A work machine has a prime mover, a hydraulic pump, a hydraulic actuator, a pressure accumulator, an auxiliary flow control valve that controls a flow rate of working oil supplied from the pressure accumulator to the hydraulic actuator, an operating device, an operating amount sensor, a pressure accumulator sensor, and a control device. The control device performs the following actions: calculates a target flow rate of working oil supplied to the hydraulic actuator in accordance with an operating amount; calculates an auxiliary flow rate of working oil supplied from the pressure accumulator to the hydraulic actuator through the auxiliary flow control valve in accordance with a change amount per unit time of pressure detected by the pressure accumulator sensor; calculates a target discharge flow rate of the hydraulic pump by subtracting the auxiliary flow rate from the target flow rate; and controls at least one of a rotational speed of the prime mover and a displacement of the hydraulic pump so that a flow rate of working oil discharged from the hydraulic pump is equal to the target discharge flow rate.

Description

Technical Field

[0001] This invention relates to work machinery. Background Technology

[0002] In hydraulic excavators and other operating machinery, there is a known system that utilizes energy stored in an accumulator to drive a hydraulic actuator. In this system, an auxiliary flow control valve is installed between the accumulator and the hydraulic actuator. Opening the auxiliary flow control valve delivers pressurized oil from the accumulator to the hydraulic actuator, thereby correspondingly reducing the pump's output flow rate. If the pump's output flow rate is reduced, the pump output decreases, thus contributing to energy savings.

[0003] In the above system, the working oil flow rate supplied to the hydraulic actuator is the sum of the working oil flow rate supplied from the hydraulic pump to the hydraulic actuator (pump supply flow rate) and the working oil flow rate supplied from the accumulator to the hydraulic actuator through the auxiliary flow control valve (auxiliary flow rate). Therefore, if the pump supply flow rate is not changed accordingly when the auxiliary flow rate changes, the working oil flow rate supplied to the hydraulic actuator will change. Therefore, in order to maintain the operability of the hydraulic actuator, it is necessary to estimate the auxiliary flow rate (the flow rate through the auxiliary flow control valve) and use the estimated result to control the pump supply flow rate.

[0004] As a technique for estimating the flow rate of a valve, the following techniques are known: measuring the differential pressure across the valve and estimating the flow rate based on the orifice plate formula (throttling formula). Patent Document 1 describes deriving the estimated flow rate of the working oil through the control valve based on the flow coefficient, the opening area of ​​the control valve, the density of the working oil, and the differential pressure across the control valve.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-159210 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, when calculating the flow rate of a valve using the orifice plate formula, the flow coefficient varies depending on the flow state of the working oil (temperature, viscosity, etc.), or the orifice area varies depending on the fluid forces. Consequently, parameters (valve orifice area, working oil density, differential pressure across the valve) change accordingly. Furthermore, even with pressure sensors installed before and after the valve, the calculated flow rate will vary due to pressure losses in the valve's internal oil passages and in the connectors used to link the pressure sensors. Therefore, to improve the accuracy of the flow rate calculated using the orifice plate formula, it is necessary to investigate the characteristics of each varying parameter under various conditions, which requires significant development time and costs. Therefore, a low-cost technique for estimating the flow rate of an auxiliary flow control valve is desired.

[0010] The purpose of this invention is to provide a working machine that can supply energy stored in an accumulator to a hydraulic actuator and can estimate the flow rate of an auxiliary flow control valve at low cost and high accuracy. This auxiliary flow control valve is used to control the flow rate of working oil supplied from the accumulator to the hydraulic actuator.

[0011] Methods for solving problems

[0012] An operating machine according to one aspect of the present invention comprises: a prime mover; a hydraulic pump driven by the prime mover; a hydraulic actuator driven by working oil ejected from the hydraulic pump; a accumulator for storing working oil; a pump flow control valve for controlling the flow rate of working oil supplied from the hydraulic pump to the hydraulic actuator; an auxiliary flow control valve for controlling the flow rate of working oil supplied from the accumulator to the hydraulic actuator; an operating device for operating the hydraulic actuator; an operation quantity sensor for detecting the operation quantity of the operating device; an accumulator sensor for detecting the pressure of the working oil in the accumulator; and a control device for controlling the prime mover and the hydraulic actuator based on the operation quantity detected by the operation quantity sensor and the pressure detected by the accumulator sensor. In at least one of the pumps, the control device performs the following actions: calculates a target flow rate based on the operation amount detected by the operation amount sensor, the target flow rate being a target value for the flow rate of working oil supplied to the hydraulic actuator; calculates an auxiliary flow rate based on the pressure change per unit time detected by the accumulator sensor, the auxiliary flow rate being the flow rate of working oil supplied from the accumulator to the hydraulic actuator through the auxiliary flow control valve; calculates a target ejection flow rate by subtracting the auxiliary flow rate from the target flow rate, the target ejection flow rate being a target value for the ejection flow rate of the hydraulic pump; and controls at least one of the rotational speed of the prime mover and the volume of the hydraulic pump such that the flow rate of working oil ejected from the hydraulic pump is equal to the target ejection flow rate.

[0013] Invention Effects

[0014] According to the present invention, a working machine is provided that can supply energy stored in an accumulator to a hydraulic actuator and can estimate the flow rate of an auxiliary flow control valve at low cost and high accuracy, the auxiliary flow control valve being used to control the flow rate of working oil supplied from the accumulator to the hydraulic actuator. Attached Figure Description

[0015] Figure 1 This is a perspective view of a hydraulic excavator, shown as an example of a work machine according to an embodiment of the present invention.

[0016] Figure 2 This is a schematic diagram of the hydraulic drive unit mounted on a hydraulic excavator.

[0017] Figure 3 This is a diagram showing the drive control system installed on a hydraulic excavator.

[0018] Figure 4 It is a block diagram representing the function of the control device. Detailed Implementation

[0019] The working machinery according to embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a perspective view of a hydraulic excavator 1, shown as an example of a work machine according to an embodiment of the present invention. Figure 1 As shown, the hydraulic excavator 1 has a body 52 and a multi-joint type working device 51 mounted on the body 52. ​​The working device 51 includes: a boom 1a, a stick 1b, and a bucket 1c. Additionally, the working device 51 includes: a boom cylinder 3a for driving the boom 1a, a stick cylinder 3b for driving the stick 1b, and a bucket cylinder 3c for driving the bucket 1c. The body 52 has a lower traveling body 1e and an upper slewing body 1d mounted on the lower traveling body 1e. The upper slewing body 1d is connected by a slewing motor 4 (see reference 4). Figure 2 It rotates relative to the lower traveling body 1e. The lower traveling body 1e moves via the left and right traveling motors 3e.

[0020] The boom 1a is rotatably mounted on the upper slewing body 1d and is driven by the boom cylinder 3a. The stick 1b is rotatably mounted on the boom 1a and is driven by the stick cylinder 3b. The bucket 1c is rotatably mounted on the stick 1b and is driven by the bucket cylinder 3c. The bucket 1c is a work tool used in excavation operations and in loading excavated objects such as sand and soil into dump trucks.

[0021] Figure 2 This is a schematic diagram of the hydraulic drive unit mounted on a hydraulic excavator 1. (See diagram for example.) Figure 2As shown, the hydraulic drive unit of the hydraulic excavator 1 includes: an engine 5, a first hydraulic pump 6, a second hydraulic pump 7, multiple hydraulic actuators (3a, 3b, 3c, 4), multiple flow control valves (8, 13-22), and an accumulator 9. The multiple hydraulic actuators include: a boom cylinder 3a, a stick cylinder 3b, a bucket cylinder 3c, and a swing motor 4. The boom cylinder 3a, stick cylinder 3b, and bucket cylinder 3c are hydraulic cylinders, each having a cylinder barrel, a circular plate-shaped piston dividing the cylindrical cylinder barrel into a bottom chamber 301 and a rod chamber 302, and a piston rod connected to the piston. The swing motor 4 is a hydraulic motor. The multiple flow control valves (8, 13-22) are controlled by a control device 100 (described later) (see reference). Figure 3 Driven by instructions from the valve core, the flow control valves (8, 13~22) adjust the opening area by changing the position of the internal valve core, thereby controlling the flow rate of the working oil through the opening.

[0022] The engine 5, which serves as the prime mover, is, for example, an internal combustion engine such as a diesel engine. The engine 5 is equipped with a fuel injection device 5a that injects fuel into the combustion chamber.

[0023] The first hydraulic pump 6 and the second hydraulic pump 7 are mechanically connected to the engine 5, driven by the engine 5, and inject working oil (pressurized oil). The first hydraulic pump 6 and the second hydraulic pump 7 are variable-capacity hydraulic pumps capable of changing the injection capacity (discharge volume). The first hydraulic pump 6 and the second hydraulic pump 7 are, for example, known swashplate or inclined-shaft hydraulic pumps, and the injection capacity (volume) is adjusted by changing the tilt angle. The volume (tilt angle) of the first hydraulic pump 6 is controlled by an adjuster 23 attached to the first hydraulic pump 6. The volume (tilt angle) of the second hydraulic pump 7 is controlled by an adjuster 24 attached to the second hydraulic pump 7.

[0024] The first hydraulic pump 6 and the second hydraulic pump 7 are respectively connected to multiple hydraulic actuators via pipelines. The multiple hydraulic actuators are driven by pressurized oil ejected from the first hydraulic pump 6 and the second hydraulic pump 7. The accumulator 9 is a pressure storage device that stores pressurized oil supplied from the bottom chamber 301 of the boom cylinder 3a, which contracts due to the weight of the working device 51, during boom lowering operations. The accumulator 9 has a liquid chamber and a gas chamber divided by a diaphragm. Nitrogen gas is sealed in the gas chamber. Working oil is stored in the liquid chamber.

[0025] In the pipeline connecting the first hydraulic pump 6 and the boom cylinder 3a, a flow control valve (pump flow control valve), namely the first boom control valve 14, is installed to control the flow rate of working oil supplied from the first hydraulic pump 6 to the boom cylinder 3a. The first boom control valve 14 also controls the flow rate of working oil discharged from the boom cylinder 3a to the oil tank 12. In the pipeline connecting the second hydraulic pump 7 and the boom cylinder 3a, a flow control valve (pump flow control valve), namely the second boom control valve 15, is installed to control the flow rate of working oil supplied from the second hydraulic pump 7 to the boom cylinder 3a. The second boom control valve 15 also controls the flow rate of working oil discharged from the boom cylinder 3a to the oil tank 12.

[0026] In the pipeline connecting the first hydraulic pump 6 and the boom cylinder 3b, a flow control valve (pump flow control valve), namely the first boom control valve 16, is installed to control the flow rate of working oil supplied from the first hydraulic pump 6 to the boom cylinder 3b. The first boom control valve 16 also controls the flow rate of working oil discharged from the boom cylinder 3b to the oil tank 12. In the pipeline connecting the second hydraulic pump 7 and the boom cylinder 3b, a flow control valve (pump flow control valve), namely the second boom control valve 17, is installed to control the flow rate of working oil supplied from the second hydraulic pump 7 to the boom cylinder 3b. The second boom control valve 17 also controls the flow rate of working oil discharged from the boom cylinder 3b to the oil tank 12.

[0027] In the pipeline connecting the first hydraulic pump 6 and the bucket cylinder 3c, a flow control valve (pump flow control valve), namely the bucket control valve 18, is installed to control the flow rate of working oil supplied from the first hydraulic pump 6 to the bucket cylinder 3c. The bucket control valve 18 also controls the flow rate of working oil discharged from the bucket cylinder 3c to the oil tank 12. In the pipeline connecting the second hydraulic pump 7 and the swing motor 4, a flow control valve (pump flow control valve), namely the swing control valve 13, is installed to control the flow rate of working oil supplied from the second hydraulic pump 7 to the swing motor 4. The swing control valve 13 also controls the flow rate of working oil discharged from the swing motor 4 to the oil tank 12.

[0028] The flow control valves (13-18) described above are central bypass type control valves. Flow control valves (14, 16, 18) have a central bypass passage that connects the first hydraulic pump 6 to the oil tank 12 in the neutral position, and in the neutral position, the working oil injected from the first hydraulic pump 6 is discharged to the oil tank 12 through the central bypass passage. Flow control valves (13, 15, 17) have a central bypass passage that connects the second hydraulic pump 7 to the oil tank 12 in the neutral position, and in the neutral position, the working oil injected from the second hydraulic pump 7 is discharged to the oil tank 12 through the central bypass passage.

[0029] A replenishment device is provided between the pipe 10 connecting the right-hand rotation port of the rotary control valve 13 and the rotary motor 4, and the pipe 11 connecting the left-hand rotation port of the rotary control valve 13 and the rotary motor 4. The replenishment device includes check valves 25 and 26 and relief valves 27 and 28, which are arranged in opposite directions. Between these check valves 25 and 26 and relief valves 27 and 28, a pipe 29 is provided to return oil discharged from the rotary motor 4 to the oil tank 12. Pipe 29 functions as a replenishment line capable of replenishing working oil to the rotary motor 4.

[0030] The accumulator 9 is connected to pipe 38, through which pressurized oil ejected from the accumulator 9 is supplied to each hydraulic actuator. The bottom chamber 301 of the boom cylinder 3a is connected to pipe 38 via pipe (hereinafter also referred to as the bottom side pipe) 32. A regeneration valve 8 is installed in the bottom side pipe 32 to regenerate the pressurized oil in the bottom chamber 301 of the boom cylinder 3a to the accumulator 9 during boom descent. The regeneration valve 8 is a regeneration flow control valve (flow control valve) that controls the flow rate of the working oil flowing from the bottom chamber 301 side of the boom cylinder 3a to the accumulator 9, i.e., the regeneration flow rate, by adjusting the opening area.

[0031] Multiple branch pipes 39, 40, 41, and 42 are connected to pipe 38. Branch pipe 39 is connected to boom cylinder 3a. Branch pipe 40 is connected to stick cylinder 3b. Branch pipe 41 is connected to bucket cylinder 3c. Branch pipe 42 is connected to swing motor 4.

[0032] A flow control valve (auxiliary flow control valve), namely boom auxiliary valve 19, is installed on branch line 39 to control the flow rate of working oil supplied from accumulator 9 to boom cylinder 3a. A flow control valve (auxiliary flow control valve), namely stick auxiliary valve 20, is installed on branch line 40 to control the flow rate of working oil supplied from accumulator 9 to stick cylinder 3b. A flow control valve (auxiliary flow control valve), namely bucket auxiliary valve 21, is installed on branch line 41 to control the flow rate of working oil supplied from accumulator 9 to bucket cylinder 3c. A flow control valve (auxiliary flow control valve), namely swing auxiliary valve 22, is installed on branch line 42 to control the flow rate of working oil supplied from accumulator 9 to swing motor 4.

[0033] In this way, the accumulator 9 is connected to each hydraulic actuator through pipelines. The energy stored in the accumulator 9 is used to drive each hydraulic actuator.

[0034] Figure 3 This diagram illustrates the drive control system mounted on the hydraulic excavator 1. Furthermore, an actuator operating device for operating each hydraulic actuator is installed in the cab of the hydraulic excavator 1, but... Figure 3The diagram shows the boom operating lever (cylinder operating device) 30 for operating boom cylinder 3a and the bucket operating lever (cylinder operating device) 44 for operating a hydraulic actuator different from boom cylinder 3a, namely bucket cylinder 3c. Other actuator operating devices and the operation quantity sensors for detecting the operation amounts of other actuator operating devices are omitted. Additionally, in... Figure 3 The diagrams of the boom cylinder 3b, the rotary motor 4, and the flow control valves (13, 16, 17, 20, 22) used to control these hydraulic actuators are also omitted.

[0035] like Figure 3 As shown, the drive control system includes: multiple sensors for detecting the state of the hydraulic drive unit; and a control device 100 for controlling the flow control valve of the hydraulic drive unit, the engine 5, and the hydraulic pumps (6, 7) based on the detection results of the multiple sensors. The multiple sensors include: a rotational speed sensor 5b for the engine 5, a pressure accumulator sensor 43, and multiple operation quantity sensors. The rotational speed sensor 5b detects the rotational speed of the engine 5 and outputs a signal indicating the detected rotational speed (actual rotational speed) to the control device 100. The pressure accumulator sensor 43 is installed in the pipeline 38 and detects the working oil pressure (hereinafter also referred to as accumulator pressure) in the accumulator 9. As a pressure sensor, the pressure accumulator sensor 43 outputs a signal indicating the detected pressure to the control device 100. The multiple operation quantity sensors include a boom operation quantity sensor 31 and a bucket operation quantity sensor 45.

[0036] The boom operation amount sensor 31 is an operation amount sensor that detects the operation amount of the boom operating lever 30 (hereinafter also referred to as boom operation amount) and outputs a signal indicating the detected operation amount to the control device 100. The bucket operation amount sensor 45 is an operation amount sensor that detects the operation amount of the bucket operating lever 44 (hereinafter also referred to as bucket operation amount) and outputs a signal indicating the detected operation amount to the control device 100. In addition, as the boom operation amount detected by the boom operation amount sensor 31, there are boom lifting operation amounts that operate the boom 1a in the lifting direction and boom lowering operation amounts that operate the boom 1a in the lowering direction. In addition, as the bucket operation amount detected by the bucket operation amount sensor 45, there are bucket loading operation amounts that operate the bucket 1c in the loading direction and bucket unloading operation amounts that operate the bucket 1c in the unloading direction.

[0037] The first boom control valve 14 is a three-position, neutral-position closed directional control valve with operating ends 14a and 14b at both ends that receive electromagnetic commands from the control device 100. The first boom control valve 14 switches the valve spool position via electromagnetic commands from the control device 100 to its operating ends. During boom raising operations, an electromagnetic command is sent to operating end 14b to supply pressurized oil from the first hydraulic pump 6 to the bottom chamber 301 of the boom cylinder 3a through the first boom control valve 14, and to discharge working oil from the rod chamber 302 of the boom cylinder 3a to the oil tank 12 through the first boom control valve 14. During boom lowering operations, an electromagnetic command is sent to operating end 14a, connecting the first hydraulic pump 6 to the rod chamber 302 of the boom cylinder 3a via the first boom control valve 14. Furthermore, during boom raising operations, the boom cylinder 3a's rod chamber 302 is connected to the oil tank 12 via the first boom control valve 14. Conversely, during boom lowering operations, the boom cylinder 3a's bottom chamber 301 is not connected to the oil tank 12 via the first boom control valve 14. Therefore, during boom lowering operations, the working oil is not discharged from the boom cylinder 3a's bottom chamber 301 to the oil tank 12 through the first boom control valve 14.

[0038] The second boom control valve 15 is a three-position, neutral-closed directional control valve with operating ends 15a and 15b at both ends that receive electromagnetic commands from the control device 100. The second boom control valve 15 switches the valve spool position according to the electromagnetic commands from the control device 100 to its operating ends. During boom raising operations, an electromagnetic command is sent to operating end 15b to supply pressurized oil from the second hydraulic pump 7 to the bottom chamber 301 of the boom cylinder 3a through the second boom control valve 15, and to discharge working oil from the rod chamber 302 of the boom cylinder 3a to the oil tank 12 through the second boom control valve 15. During boom lowering operations, an electromagnetic command is sent to operating end 15a. Thus, the second hydraulic pump 7 is connected to the rod chamber 302 of the boom cylinder 3a via the second boom control valve 15, and the bottom chamber 301 of the boom cylinder 3a is connected to the oil tank 12 via the second boom control valve 15.

[0039] The bucket control valve 18 is a three-position, neutral-closed directional control valve with operating ends 18a and 18b at both ends that receive electromagnetic commands from the control device 100. The bucket control valve 18 switches the valve core position according to the electromagnetic commands from the control device 100 to its operating ends. During a bucket dumping operation, an electromagnetic command is sent to operating end 18a to supply pressurized oil from the first hydraulic pump 6 to the rod chamber 302 of the bucket cylinder 3c through the bucket control valve 18, and to discharge working oil from the bottom chamber 301 of the bucket cylinder 3c to the oil tank 12 through the bucket control valve 18. During a bucket loading operation, an electromagnetic command is sent to operating end 18b to supply pressurized oil from the first hydraulic pump 6 to the bottom chamber 301 of the bucket cylinder 3c through the bucket control valve 18, and to discharge working oil from the rod chamber 302 of the bucket cylinder 3c to the oil tank 12 through the bucket control valve 18.

[0040] In addition, although Figure 3 The details are omitted, but the drive of the boom cylinder 3b based on the first hydraulic pump 6 and the second hydraulic pump 7, as well as the drive of the slewing motor 4 based on the second hydraulic pump 7, are the same as the drive of the bucket cylinder 3c mentioned above.

[0041] The hydraulic drive unit of the hydraulic excavator 1 in this embodiment includes an auxiliary system capable of using the energy of the accumulator 9 to drive the hydraulic actuator. In such a hydraulic drive unit, the working oil flow rate supplied from the accumulator 9 to the hydraulic actuator via the auxiliary flow control valve, i.e., the auxiliary flow rate, is estimated with high precision. Therefore, even if the auxiliary flow rate fluctuates, the operability of the hydraulic actuator can be maintained. Thus, the control device 100 of this embodiment can estimate the auxiliary flow rate based on the change in pressure of the accumulator 9 per unit time. A detailed description will follow.

[0042] The control device 100 comprises a computer having the following components: a processing unit 100a such as a CPU (Central Processing Unit), MPU (Micro Processing Unit), and DSP (Digital Signal Processor); a non-volatile memory 100b such as ROM (Read Only Memory), flash memory, or hard disk drive; a volatile memory 100c called RAM (Random Access Memory); input / output interfaces; and other peripheral circuitry. This hardware works together to enable software operation, thereby achieving multiple functions. Furthermore, the control device 100 can be composed of a single computer or multiple computers.

[0043] The non-volatile memory 100b stores programs capable of performing various operations. That is, the non-volatile memory 100b is a storage medium (storage device) capable of reading programs that implement the functions of this embodiment. The volatile memory 100c is a storage medium (storage device) that temporarily stores the operation results of the processing device 100a and signals input from the input / output interface. The processing device 100a is an apparatus that expands and executes the program stored in the non-volatile memory 100b in the volatile memory 100c, and performs prescribed operations on data retrieved from the input / output interface, the non-volatile memory 100b, and the volatile memory 100c according to the program.

[0044] The input section of the input / output interface converts signals input from various devices (sensors, etc.) into data that can be processed by the processing device 100a. Furthermore, the output section of the input / output interface generates an output signal corresponding to the processing result in the processing device 100a and outputs this signal to various devices (flow control valves, regulators 23, 24, fuel injection device 5a, etc.).

[0045] In this embodiment, the control device 100 outputs a pump control command to the regulator 23, and controls the discharge volume of the first hydraulic pump 6 through the regulator 23. Additionally, the control device 100 outputs a pump control command to the regulator 24, and controls the discharge volume of the second hydraulic pump 7 through the regulator 24.

[0046] Based on the operating amount detected by the boom operation amount sensor 31, the control device 100 outputs an electromagnetic command to the operating end of the flow control valve of the driven object to drive at least one of the first boom control valve 14, the second boom control valve 15, the regeneration valve 8, and the boom auxiliary valve 19. For example, if a boom lifting operation is performed when the pressure of the accumulator 9 is above a threshold, the control device 100 controls each of the first boom control valve 14, the second boom control valve 15, and the boom auxiliary valve 19 to have an opening area corresponding to the boom lifting operation amount. This supplies working oil injected from the first hydraulic pump 6 and the second hydraulic pump 7, as well as working oil injected from the accumulator 9, to the bottom chamber 301 of the boom cylinder 3c, driving the boom cylinder 3a in the extension direction. As another example, if a boom lowering operation is performed when the pressure of the accumulator 9 is below a threshold, the control device 100 controls each of the first boom control valve 14, the second boom control valve 15, and the regeneration valve 8 to have an opening area corresponding to the boom lowering operation amount. As a result, working oil from the bottom chamber 301 of the boom cylinder 3c, which contracts due to the weight of the working device 51, is supplied to the accumulator 9, and the accumulator 9 is pressurized.

[0047] Based on the operating amount detected by the bucket operating amount sensor 45, the control device 100 outputs an electromagnetic command to the operating end of the flow control valve of the driven object, which is used to drive at least one of the bucket control valve 18 and the bucket auxiliary valve 21. For example, if the bucket loading operation is performed when the pressure of the accumulator 9 is above a threshold, the control device 100 controls each of the bucket control valve 18 and the bucket auxiliary valve 21 to have an opening area corresponding to the bucket loading operation amount. As a result, working oil injected from the first hydraulic pump 6 and working oil injected from the accumulator 9 are supplied to the bottom chamber 301 of the bucket cylinder 3c, driving the bucket cylinder 3c in the extension direction.

[0048] The control device 100 controls the engine rotation speed by adjusting the fuel injection quantity through the fuel injection device 5a. The control device 100 calculates the target rotation speed of the engine 5 and controls the fuel injection device 5a so that the rotation speed (actual rotation speed) of the engine 5 detected by the rotation speed sensor 5b is the target rotation speed.

[0049] Figure 4 This is a block diagram illustrating the functions of the control device 100. (Usage) Figure 4 The processing of the control device 100 is described in detail. The control device 100 controls the ejection flow rates of the first hydraulic pump 6 and the second hydraulic pump 7 based on the operating amount of the hydraulic actuator and the pressure of the accumulator 9. Figure 4 The diagram shows that when operating the bucket cylinder 3c, working oil is supplied to the bucket cylinder 3c from the first hydraulic pump 6 through the bucket control valve 18, and also from the accumulator 9 through the bucket auxiliary valve 21. This represents the various calculations performed when driving the bucket cylinder 3c. Furthermore, although not shown, the diagram also shows the various calculations performed when assisting the boom cylinder 3a, stick cylinder 3b, and swing motor 4. Figure 4 The various calculations performed by the bucket cylinder 3c shown are the same when it is driven by auxiliary means, so the explanation is omitted.

[0050] like Figure 4 As shown, the control device 100 includes: a target flow rate calculation unit 101, an ejection flow rate calculation unit 102, a first filter 103, a volume calculation unit 104, a differential calculator 105, a second filter 106, an ejection flow rate control unit 107, an engine command unit 108, a pump command unit 109, a sign conversion unit 110, and an auxiliary flow rate determination unit 111. The control device 100 implements these functions by executing a program stored in the non-volatile memory 100b.

[0051] The target flow calculation unit 101 receives the bucket operation amount Lb detected by the bucket operation amount sensor 45. Referring to the target flow table, the target flow calculation unit 101 calculates the target flow rate Qb of the working oil supplied to the bucket cylinder 3c based on the bucket operation amount Lb. The target flow table is a data table (characteristic data) used to define the relationship between the target flow rate Qb of the bucket cylinder 3c and the bucket operation amount Lb. The target flow table specifies that the larger the bucket operation amount Lb, the larger the target flow rate Qb. The target flow table is determined in advance through experiments, etc., and stored in the non-volatile memory 100b. Furthermore, the characteristic data of the target flow rate Qb corresponding to the bucket operation amount Lb is not limited to table form and can also be defined by function form (mathematical formula). The target flow rate Qb calculated by the target flow calculation unit 101 is output to the ejection flow calculation unit 102.

[0052] The first filter 103 is input with the accumulator voltage p detected by the accumulator sensor 43. A The first filter 103 performs filtering processing to attenuate the amplitude of noise contained in the detection result (pressure signal) of the accumulator sensor 43, and then filters the accumulator pressure p. A Output to the volume calculation unit 104.

[0053] The volume calculation unit 104 inputs the filtered accumulator voltage p A The volume calculation unit 104 calculates the accumulator voltage p after filtering. A The volume of pressurized oil in the accumulator 9 is calculated. The volume calculation unit 104 uses the following formulas (1) to (3) to calculate the volume of pressurized oil in the accumulator 9.

[0054] Assuming that the pressure and volume of nitrogen in accumulator 9 change due to reversible adiabatic change, the following basic equation (1) for accumulator 9 holds.

[0055] [Mathematical Expression 1]

[0056]

[0057] In equation (1) of the thermodynamic adiabatic change, p A0 This is the pressure of the nitrogen gas being sealed into the accumulator 9. That is, p A0 This is the nitrogen pressure before the oil enters the accumulator 9, and it will also be referred to as the reference pressure below. V A0 This is the volume of nitrogen gas sealed into the accumulator 9. That is, V A0 This is the volume of nitrogen gas before the oil enters the accumulator 9, and it will also be referred to as the reference volume below. A This is the nitrogen pressure when oil enters the accumulator 9. Additionally, V... A The nitrogen pressure is p AThe nitrogen volume at that time. Here, the nitrogen pressure in accumulator 9 is approximately equal to the oil pressure in accumulator 9; therefore, the value of the accumulator pressure after filtering corresponds to p. A That is, p A This is the pressure of the accumulator 9 at the current moment. κ is the adiabatic index (polygonal index). The adiabatic index κ is a value that varies depending on the pressure inside the accumulator 9 and the inflow and outflow time of the accumulator 9. Furthermore, the accumulator 9 used for the hydraulic actuator of the auxiliary hydraulic excavator 1 has a short operating time (e.g., even if long, it is about 6 to 7 seconds). Therefore, the effect of the inflow and outflow time can be ignored.

[0058] The volume of nitrogen V when pressurized oil flows into accumulator 9 A It can be calculated using the following formula (2).

[0059] [Mathematical Expression 2]

[0060]

[0061] In equation (2), Q A This refers to the flow rate of pressurized oil flowing into accumulator 9. If at time t, for Q... A Integrating, this becomes the volume of pressurized oil flowing into accumulator 9. As mentioned above, the reference volume V A0 This is the volume of nitrogen gas before the oil enters the accumulator 9. As shown in equation (2), the nitrogen gas volume V A Become from the reference volume V A0 The value is obtained by subtracting the volume of pressurized oil flowing into accumulator 9.

[0062] Substituting equation (2) into equation (1) and transforming it, we obtain the following equation (3). The value of equation (3) is the volume of pressurized oil in the accumulator 9 at the current moment.

[0063] [Mathematical Expression 3]

[0064]

[0065] Volume calculation unit 104 calculates based on accumulator pressure p A Reference volume V A0 Reference pressure p A0 And the adiabatic index κ, using equation (3) derived from equation (1) of thermodynamic adiabatic change, calculates the volume of pressurized oil flowing into accumulator 9, ∫Q. A dt (the value on the left side of equation (3)). As mentioned above, the accumulator pressure p A The data is input to the volume calculation unit 104. Reference volume V A0 and reference pressure p A0 It is determined in advance through experiments, etc., and stored in non-volatile memory 100b.

[0066] Additionally, the non-volatile memory 100b stores information on the relationship between the adiabatic index κ and the accumulator voltage p. A The data table relating these factors is called the index table. The index table contains characteristic data for the adiabatic index κ. The index table specifies the accumulator pressure p. A The larger the value, the greater the adiabatic index κ. Furthermore, it relates to the accumulator pressure p. A The characteristic data of the corresponding adiabatic index κ is not limited to tabular form, but can also be specified by function form (mathematical formula). Before calculating the volume, the volume calculation unit 104 refers to the index table and calculates the volume based on the accumulator pressure p. A To calculate the adiabatic index κ.

[0067] The volume calculation unit 104 outputs the calculated pressure oil volume in the accumulator 9 to the differential calculation unit 105.

[0068] The differential arithmetic unit 105 performs time differentiation on the value of the pressure oil volume in the accumulator 9 to calculate the change in volume per unit time. When performing time differentiation on the value of the pressure oil volume in the accumulator 9, the following equation (4) is obtained. Q is calculated using equation (4). A The inflow rate of working oil to the accumulator 9 is output to the second filter 106. For example, the differential operator 105 subtracts the working oil volume calculated by equation (3) in the previous control cycle from the working oil volume calculated by equation (3) in this control cycle, and divides the result by the time of the control cycle to obtain the inflow rate Q of working oil to the accumulator 9. A .

[0069] [Mathematical Expression 4]

[0070]

[0071] Furthermore, the adiabatic index κ varies depending on the operating conditions of the accumulator 9, but it can be easily obtained through experiments if the operating conditions are known in advance. Regarding methods for obtaining the characteristics of κ, one method is to measure the inflow flow rate when the accumulator 9 is pressurized using a flow meter or similar device, and adjust κ based on this measurement result. Another method for obtaining the characteristics of κ is to measure the flow rate ejected from the accumulator 9 using a flow meter or similar device, and adjust κ based on this measurement result. By selecting Q calculated from equation (4)... AThe characteristic of κ can be obtained by having a value equal to the flow rate measurement value of accumulator 9. For example, in an actual machine, working oil is supplied from the first hydraulic pump 6 and accumulator 9 to the bucket cylinder 3c. The difference between the measured flow rate of the working oil supplied to the bucket cylinder 3c and the measured flow rate of the working oil ejected from the first hydraulic pump 6 is used to determine the adiabatic index κ, such that the difference is consistent with the flow rate Q1 calculated using formula (4). The experimental conditions for obtaining the characteristic of κ can be matched with the pressure conditions and inflow / outflow time of accumulator 9 when the hydraulic drive device of this embodiment is actually driven. In addition, as mentioned above, the accumulator 9 used for the hydraulic actuator of the auxiliary hydraulic excavator 1 has a short service life. Therefore, the influence of the inflow / outflow time can be ignored. That is, the adiabatic index κ that varies only with the pressure of accumulator 9 can be determined.

[0072] The second filter 106 is input with the inflow rate Q to the energy storage unit 9, calculated by the differentiator 105. A The second filter 106 performs filtering processing to attenuate the noise amplitude contained in the calculation result of the differentiator 105, and the filtered inflow flow Q A Output to the symbol conversion unit 110.

[0073] The symbol conversion unit 110 inputs the filtered inflow flow Q A The sign conversion unit 110 will process the filtered inflow flow Q A The value obtained by multiplying by -1 is the discharge flow rate of accumulator 9, i.e., the auxiliary flow rate Q. AS Output to the auxiliary flow determination unit 111.

[0074] Auxiliary flow determination unit 111 inputs auxiliary flow Q AS The auxiliary flow determination unit 111 determines the auxiliary flow Q. AS Is it a value greater than or equal to 0? The auxiliary flow determination unit 111 determines the auxiliary flow Q. AS When the value is above 0, the input auxiliary flow Q will be... AS The output is directly sent to the ejection flow calculation unit 102. The auxiliary flow determination unit 111 determines the auxiliary flow rate Q. AS When it is less than 0, the auxiliary flow Q will be... AS The output of the injection flow calculation unit 102 is set to 0. Therefore, when the working oil flows into the accumulator 9, the auxiliary flow rate Q... AS It was output as 0.

[0075] The first filter 103, volume calculation unit 104, differential calculation unit 105, second filter 106, symbol conversion unit 110, and auxiliary flow determination unit 111 serve as the auxiliary flow rate Q for calculation. AS The auxiliary flow calculation unit 112 performs its function. As described above, the auxiliary flow calculation unit 112 calculates the accumulator pressure p detected by the accumulator sensor 43.A To calculate the volume of working oil in accumulator 9, ∫Q A dt (first filter 103 and volume calculation unit 104). Auxiliary flow calculation unit 112 calculates the working oil volume ∫Q in accumulator 9. A The auxiliary flow rate Q is calculated from the change in dt per unit time. AS (Differential operator 105, second filter 106, symbol conversion unit 110, auxiliary flow determination unit 111). Furthermore, volume ∫Q A The change in dt per unit time includes the accumulator pressure p A The effect of the change in flow rate per unit time. That is, the auxiliary flow calculation unit 112 calculates the flow rate based on the accumulator pressure p. A The auxiliary flow rate Q is calculated from the change per unit time. AS .

[0076] The ejection flow calculation unit 102 inputs the target flow rate Qb and auxiliary flow rate Q of the bucket cylinder 3c. AS The ejection flow calculation unit 102 calculates the auxiliary flow rate Q by subtracting the target flow rate Qb from the auxiliary flow rate Q. AS To calculate the target value of the ejection flow rate of the first hydraulic pump 6, i.e., the target ejection flow rate Qp (Qp = Qb - Q AS The target ejection flow rate Qp calculated by the ejection flow rate calculation unit 102 is output to the ejection flow rate control unit 107.

[0077] The ejection flow control unit 107 inputs the target ejection flow rate Qp. The ejection flow control unit 107 calculates the target rotational speed (target engine speed value) Nt of the engine 5 and the target volume (target displacement value) qt of the first hydraulic pump 6 to achieve the target ejection flow rate Qp. The calculated target rotational speed Nt of the engine 5 is output to the engine command unit 108. Additionally, the calculated target volume qt of the first hydraulic pump 6 is output to the pump command unit 109.

[0078] The engine command unit 108 receives the target rotational speed Nt of the engine 5. The engine command unit 108 calculates the control command value for the fuel injection device 5a corresponding to the target rotational speed Nt. The engine command unit 108 outputs an engine control command (electrical signal) corresponding to the calculated control command value to the fuel injection device 5a of the engine 5. Thus, the engine 5 is controlled so that its actual rotational speed equals the target rotational speed Nt.

[0079] The pump command unit 109 receives the target volume qt of the first hydraulic pump 6. The pump command unit 109 calculates the control command value corresponding to the target volume qt and sends it to the regulator 23. The pump command unit 109 outputs a pump control command (electrical signal) corresponding to the calculated control command value to the regulator 23 of the first hydraulic pump 6. Thus, the first hydraulic pump 6 is controlled so that its actual displacement equals the target volume qt.

[0080] The hydraulic pump's ejection flow rate is determined by multiplying the engine 5's rotational speed, the hydraulic pump's displacement (equivalent to the flow rate ejected per revolution), and the pump's volumetric efficiency. In this embodiment, the ejection flow rate control unit 107 controls the hydraulic pump's ejection flow rate by adjusting the target volume qt to a constant value for the engine 5's target rotational speed Nt. However, the ejection flow rate control method is not limited to this. It could also be a method of adjusting the engine 5's target rotational speed Nt to a constant value for the target volume qt. Furthermore, it could be a method of adjusting both the target volume qt and the target rotational speed Nt. That is, the engine command unit 108 and the pump command unit 109 can be structured such that at least one of the engine 5's rotational speed and the first hydraulic pump 6's volume is controlled, such that the flow rate of working oil ejected from the first hydraulic pump 6 is equal to the target ejection flow rate Qp. Additionally, the ejection flow rate control unit 107 can also change the ejection flow rate control method according to the operating conditions of the hydraulic excavator 1.

[0081] As described above, in this embodiment, when driving the hydraulic actuator, the flow rate (auxiliary flow rate) of the working oil supplied from the accumulator 9 to the hydraulic actuator (e.g., bucket cylinder 3c) can be estimated based on the pressure of the accumulator 9. By reducing the ejection flow rate of the hydraulic pump (e.g., the first hydraulic pump 6) by the estimated auxiliary flow rate, the output of the hydraulic pump can be reduced while maintaining operability. Reducing the output of the hydraulic pump can improve energy efficiency and help reduce fuel consumption.

[0082] As with existing technologies, the flow rate of a valve is estimated based on the differential pressure across the valve and an orifice plate formula. However, in this case, multiple parameters (valve opening area, working oil density, and differential pressure across the valve) vary under various conditions, requiring extensive prior testing to investigate the characteristics of each varying parameter. In contrast, the adiabatic index κ used in the flow rate estimation method of this embodiment is determined solely by the pressure p of the accumulator 9. A Confirmed. In other words, according to the flow estimation method of this embodiment, the only variable parameter is the pressure p of the accumulator 9. A Furthermore, by simply operating the accumulator 9 under actual usage conditions, it is possible to obtain the pressure p of the accumulator 9. A The corresponding adiabatic index κ has characteristics that allow for a reduction in the number of prior tests.

[0083] According to the above implementation method, the following effects are achieved.

[0084] (1) A hydraulic excavator (operating machinery) 1, comprising: an engine (prime mover) 5; a hydraulic pump (first hydraulic pump 6 and second hydraulic pump 7) driven by the engine 5; a bucket cylinder (hydraulic actuator) 3c driven by working oil sprayed from the first hydraulic pump 6; an accumulator (pressure storage device) 9 for storing working oil; a bucket control valve (pump flow control valve) 18 for controlling the flow rate of working oil supplied from the first hydraulic pump 6 to the bucket cylinder 3c; a bucket auxiliary valve (auxiliary flow control valve) 21 for controlling the flow rate of working oil supplied from the accumulator 9 to the bucket cylinder 3c; a bucket operating lever (operating device) 44 for operating the bucket cylinder 3c; a bucket operating amount sensor (operating amount sensor) 45 for detecting the operating amount of the bucket operating lever 44; a pressure accumulator sensor 43 for detecting the pressure of the working oil in the accumulator 9; and a control device 100 that controls at least one of the engine 5 and the first hydraulic pump 6 based on the operating amount detected by the bucket operating amount sensor 45 and the pressure detected by the pressure accumulator sensor 43.

[0085] The control device 100 calculates the target flow rate Qb based on the operating amount detected by the bucket operating amount sensor 45. This target flow rate Qb is the target value of the flow rate of the working oil supplied to the bucket cylinder 3c. The control device 100 also calculates the pressure (accumulator pressure) detected by the accumulator sensor 43. A The auxiliary flow rate Q is calculated from the change in the value of the auxiliary flow rate Q per unit time. AS The auxiliary flow Q AS This refers to the flow rate of working oil supplied from the accumulator 9 to the bucket cylinder 3c via the bucket auxiliary valve 21. The control device 100 controls this by subtracting the auxiliary flow rate Q from the target flow rate Qb. AS To calculate the target ejection flow rate Qp (Qp = Qb - Q AS The target ejection flow rate Qp is the target ejection flow rate value of the first hydraulic pump 6. The control device 100 controls at least one of the rotational speed of the engine 5 and the volume of the first hydraulic pump 6, such that the flow rate of the working oil ejected from the first hydraulic pump 6 is equal to the target ejection flow rate Qp.

[0086] In this structure, based on the state quantity (pressure p) of the accumulator 9 A The auxiliary flow rate Q is calculated from the change in the value of the auxiliary flow rate Q per unit time. AS Therefore, it is possible to calculate the auxiliary flow Q. AS It is unaffected by the piping connected to the accumulator 9, the structure of the bucket auxiliary valve 21, etc. Therefore, according to this embodiment, the auxiliary flow rate Q is estimated using the orifice plate formula based on the differential pressure before and after the bucket auxiliary valve 21. AS Compared to the previous situation, it can estimate the auxiliary flow rate Q with high accuracy.AS As a result, the ejection flow rate of the hydraulic pump can be properly controlled, thus maintaining the operability of the hydraulic actuator even when the auxiliary flow rate changes.

[0087] (2) The control device 100 uses the pressure (accumulator pressure) p detected by the pressure sensor 43 to control the accumulator pressure. A To calculate the volume of working oil (pressure oil) in accumulator 9, ∫Q A The control device 100 calculates the auxiliary flow rate Q based on the change in the volume of the working oil in the accumulator 9 per unit time. AS Furthermore, the change in working oil pressure per unit time within accumulator 9 (the pressure difference between the pressure at a certain point in time and the pressure after a specified time) is used to calculate the change in working oil volume per unit time within accumulator 9. In this way, by calculating the change in working oil volume per unit time within accumulator 9, the flow rate of working oil ejected from accumulator 9, i.e., the auxiliary flow rate Q, can be estimated with high accuracy. AS .

[0088] (3) The control device 100 calculates the adiabatic index κ based on the pressure detected by the accumulator sensor 43. In this embodiment, the control device 100 refers to the index table stored in the non-volatile memory 100b and calculates the adiabatic index κ based on the accumulator pressure p. A The adiabatic index κ is calculated. The control device 100 calculates the adiabatic index κ and the accumulator pressure p detected by the accumulator sensor 43. A The volume of working oil in accumulator 9, ∫Q, is calculated using the thermodynamic adiabatic change formula (refer to formula (1)). A Specifically, the volume V of the gas (nitrogen) sealed in the accumulator 9 is calculated using equation (1). A And based on the calculated volume V A and reference volume V A0 The volume of the working oil in the accumulator 9 is calculated as ∫Q. A dt. Thus, considering that the storage characteristic of accumulator 9 is an adiabatic change, the adiabatic change formula (Poisson's formula: p) is used. A V A κ =constant), thus enabling the high-precision estimation of the auxiliary flow rate Q. AS .

[0089] Furthermore, as mentioned above, the adiabatic index κ can be easily obtained, thus reducing development time and costs compared to using the orifice plate formula. Additionally, the flow coefficient c used in the orifice plate formula varies depending on the valve structure, the valve-related circuit structure (bends and lengths of the piping connected to the valve), and environmental conditions. Therefore, it is difficult to use the same flow coefficient c across various models of hydraulic excavators 1. In contrast, in this embodiment, even with different machine models, as long as the same accumulator 9 is installed, the same index table can be used even with differences in valve structure, circuit structure, and operating conditions, thus demonstrating high versatility.

[0090] (4) The hydraulic excavator 1 includes: a boom cylinder (second hydraulic actuator) 3a, which is a different hydraulic actuator from the bucket cylinder (first hydraulic actuator) 3c described above; and a regeneration valve 8, which controls the flow rate of working oil flowing from the boom cylinder 3a to the accumulator 9. According to this structure, during the lowering action of the boom cylinder 3a, the pressure oil from the bottom chamber 301 of the boom cylinder 3a, which contracts due to the weight of the working device 51, can be used to pressurize the accumulator 9, wherein the working device 51 includes the boom 1a. Therefore, it is possible to improve energy efficiency without the need for a dedicated hydraulic pump or the like to supply working oil to the accumulator 9. As a result, fuel economy can be improved.

[0091] (5) The hydraulic excavator 1 has a boom auxiliary valve (second auxiliary flow control valve) 19, which is different from the bucket auxiliary valve (first auxiliary flow control valve) 21 described above. It is an auxiliary control valve that controls the flow rate of working oil supplied from the accumulator 9 to the boom cylinder 3a. According to this structure, the regenerative energy generated when the boom is lowered can be stored in the accumulator 9 and utilized when the boom is raised.

[0092] As described above, according to this embodiment, a hydraulic excavator 1 can be provided, which can supply energy stored in an accumulator 9 to a hydraulic actuator, and can estimate the flow rate of an auxiliary flow control valve at low cost and high accuracy, the auxiliary flow control valve being used to control the flow rate of working oil supplied from the accumulator 9 to the hydraulic actuator.

[0093] The following modifications are also within the scope of this invention, and one or more of the modifications can be combined with the above embodiments.

[0094] (Variation Example 1)

[0095] In the above embodiment, an example of regenerating the return oil of the boom cylinder 3a through the accumulator 9 was described, but the return oil from other hydraulic actuators can also be regenerated through the accumulator 9.

[0096] (Variation Example 2)

[0097] The working machinery is not limited to tracked hydraulic excavators 1. This invention can also be applied to wheeled hydraulic excavators. In addition, the working tool can also be a grab bucket, a crusher, an electromagnetic chuck, etc., instead of a bucket.

[0098] (Variation Example 3)

[0099] There can be two or more accumulators. The hydraulic pump that supplies working oil to the hydraulic actuator can be a single unit or three or more units.

[0100] (Variation Example 4)

[0101] The prime mover driving the hydraulic pumps (6, 7) is not limited to engine 5. The prime mover can also be an electric motor.

[0102] The embodiments of the present invention have been described above, but the above embodiments only represent a part of the application examples of the present invention, and the technical scope of the present invention is not limited to the specific structure of the above embodiments.

[0103] Symbol Explanation

[0104] 1…Hydraulic excavator (operating machinery), 1a…Boom, 1b…Stick, 1c…Bucket, 1d…Upper slewing body, 1e…Lower traveling body, 3a…Boom cylinder (hydraulic actuator, an example of a second hydraulic actuator), 3b…Stick cylinder (hydraulic actuator), 3c…Bucket cylinder (hydraulic actuator, an example of a first hydraulic actuator), 3e…Travel motor (hydraulic actuator), 4…Slewing motor (hydraulic actuator), 5…Engine (prime mover), 5a…Fuel injection device, 5b…Rotation speed sensor, 6…First hydraulic pump (hydraulic pump) 7…Second hydraulic pump (hydraulic pump), 8…Regeneration valve (flow control valve), 9…Accumulator (accumulator device), 12…Oil tank, 13…Swing control valve (flow control valve), 14…First boom control valve (flow control valve), 15…Second boom control valve (flow control valve), 16…First stick control valve (flow control valve), 17…Second stick control valve (flow control valve), 18…Bucket control valve (an example of a flow control valve, pump flow control valve), 19…Boom auxiliary valve (an example of a flow control valve, second auxiliary flow control valve), 2 0… boom auxiliary valve (auxiliary flow control valve), 21… bucket auxiliary valve (auxiliary flow control valve, an example of the first auxiliary flow control valve), 22… swing auxiliary valve (auxiliary flow control valve), 23, 24… regulator, 30… boom control lever, boom operation sensor, 43… accumulator sensor (pressure sensor), 44… bucket control lever (operating device), 45… bucket operation sensor (operation sensor), 51… working device, 52… vehicle body, 100… control device, 100a… processing device, 100b… non-volatile storage Storage device, 100c…Volatile memory, 101…Target flow calculation unit, 102…Ejection flow calculation unit, 103…First filter, 104…Volume calculation unit, 105…Differential calculator, 106…Second filter, 107…Ejection flow control unit, 108…Engine command unit, 109…Pump command unit, 110…Sign conversion unit, 111…Auxiliary flow determination unit, 112…Auxiliary flow calculation unit, Lb…Bucket operating amount, Nt…Target rotational speed (target value of engine speed), p A …accumulator pressure (pressure of the working oil inside the accumulator, pressure of the nitrogen gas sealed in the accumulator), p A0 …the reference pressure of the nitrogen gas sealed in the accumulator, Q A …Inflow rate (flow rate of working oil into the accumulator), Q AS …Auxiliary flow rate (flow rate of working oil supplied from the accumulator to the bucket cylinder), Qb…Target flow rate (target value of working oil flow rate supplied to the bucket cylinder), Qp…Target ejection flow rate (target value of ejection flow rate of the first hydraulic pump), qt…Target volume (target value of displacement of the first hydraulic pump), V A…the volume of gas sealed in the accumulator, V A0 …the reference volume of the gas sealed in the accumulator, κ…the adiabatic index.

Claims

1. A type of operating machinery, characterized in that, have: prime mover; A hydraulic pump, driven by the prime mover; A hydraulic actuator, driven by working oil ejected from the hydraulic pump; Accumulators, which store working oil; A pump flow control valve controls the flow rate of working oil supplied from the hydraulic pump to the hydraulic actuator; An auxiliary flow control valve controls the flow rate of working oil supplied from the accumulator to the hydraulic actuator; An operating device that operates the hydraulic actuator; An operation quantity sensor that detects the operation quantity of the operating device; A pressure accumulator sensor that detects the pressure of the working oil in the pressure accumulator device; as well as A control device that controls at least one of the prime mover and the hydraulic pump based on the operation amount detected by the operation amount sensor and the pressure detected by the accumulator sensor. The control device performs the following actions: The target flow rate is calculated based on the operation amount detected by the operation amount sensor. The target flow rate is the target value of the flow rate of the working oil supplied to the hydraulic actuator. The auxiliary flow rate is calculated based on the change in pressure per unit time detected by the accumulator sensor. This auxiliary flow rate is the flow rate of working oil supplied from the accumulator to the hydraulic actuator through the auxiliary flow control valve. The target ejection flow rate is calculated by subtracting the auxiliary flow rate from the target flow rate. This target ejection flow rate is the target value of the ejection flow rate of the hydraulic pump. Control at least one of the rotational speed of the prime mover and the volume of the hydraulic pump such that the flow rate of the working oil ejected from the hydraulic pump is equal to the target ejection flow rate.

2. The operating machinery according to claim 1, characterized in that, The control device performs the following actions: The volume of working oil in the accumulator is calculated based on the pressure detected by the accumulator sensor; The auxiliary flow rate is calculated based on the change in the volume of the working oil in the accumulator per unit time.

3. The operating machinery according to claim 2, characterized in that, The control device performs the following actions: The adiabatic index is calculated based on the pressure detected by the pressure sensor. The volume of working oil in the accumulator is calculated using the adiabatic change formula of thermodynamics based on the adiabatic index and the pressure detected by the accumulator sensor.

4. The operating machinery according to claim 1, characterized in that, The operating machinery has: A second hydraulic actuator, different from the first hydraulic actuator that is said to be a hydraulic actuator; and A regeneration valve controls the flow rate of working oil from the second hydraulic actuator to the accumulator.

5. The operating machinery according to claim 4, characterized in that, The working machine has a second auxiliary flow control valve, which is different from the first auxiliary flow control valve that serves as the auxiliary flow control valve, and the second auxiliary flow control valve controls the flow rate of working oil supplied from the accumulator to the second hydraulic actuator.

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