Work machine

Abstract

A work machine has a regeneration valve that controls a flow rate of working oil flowing from a bottom chamber of a hydraulic cylinder to a pressure accumulating device, a pressure increasing valve that controls a flow rate of working oil flowing from the bottom chamber to a rod chamber, a discharge valve that controls a flow rate of working oil flowing from the bottom chamber to a tank, and a control device. The control device performs the following actions: calculates a target bottom outflow rate and a target pressure increasing rate in accordance with an operation amount detected by a cylinder operation amount sensor; controls the pressure increasing valve so that the pressure increasing rate gradually increases with the passage of time to be equal to the target pressure increasing rate, and controls the regeneration valve, or the regeneration valve and the discharge valve, so that the sum of the regeneration rate, the pressure increasing rate, and a return rate is equal to the target bottom outflow 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 type of operating machinery with an engine power assistance system, in which the engine power assistance system stores the pressurized oil flowing out of the boom cylinder during boom descent into an accumulator and uses it to assist the engine power.

[0003] Patent Document 1 describes the following: When the pressure oil from the boom head side is stored in the accumulator via the accumulator circuit, the working oil from the boom head side is regenerated in the boom cylinder via the main control valve of the regeneration circuit. Furthermore, Patent Document 1 also describes the following: When the boom head side is connected to the oil tank via the vent valve of the vent circuit, working oil pressurized from the main pump is supplied to the boom cylinder rod side, thereby increasing the initial movement speed during boom retraction.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-205494 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, in the working machinery described in Patent Document 1, if the main control valve connecting the bottom (head) side and the boom side of the boom cylinder is opened significantly after an emergency large boom descent operation, an impact may occur in the boom cylinder due to the pressure difference between the bottom and boom sides. This impact deteriorates the operability during boom descent.

[0009] The purpose of this invention is to ensure the speed of the hydraulic cylinder corresponding to the operating amount and to prevent the generation of hydraulic cylinder shock in a working machine that can supply working oil flowing from the bottom chamber of the hydraulic cylinder to the rod chamber and the accumulator.

[0010] Methods for solving problems

[0011] An operational machine according to one aspect of the present invention comprises: a prime mover; a hydraulic pump driven by the prime mover; a hydraulic cylinder having a base chamber and a rod chamber, driven by working oil injected from the hydraulic pump; an accumulator for storing working oil supplied from the base chamber; a regeneration valve for controlling the flow rate of working oil flowing from the base chamber to the accumulator; a booster valve for controlling the flow rate of working oil flowing from the base chamber to the rod chamber; a discharge valve for controlling the flow rate of working oil flowing from the base chamber to an oil tank; a cylinder operating device for operating the hydraulic cylinder; a cylinder operating quantity sensor for detecting the operating quantity of the cylinder operating device; and a control device for controlling at least the regeneration valve and the booster valve based on the operating quantity detected by the cylinder operating quantity sensor, wherein the control device performs the following action: calculating a target bottom outflow rate and a target booster flow rate based on the operating quantity detected by the cylinder operating quantity sensor, wherein the target bottom outflow rate is from the base of the hydraulic cylinder. The target flow rate of the working oil flowing out of the chamber is defined as follows: the target boost flow rate is the target flow rate of the working oil supplied from the bottom chamber to the rod chamber through the boost valve; the boost valve is controlled such that the boost flow rate gradually increases with time at a predetermined rate of change until it equals the target boost flow rate, wherein the boost flow rate is the flow rate of the working oil supplied from the bottom chamber to the rod chamber through the boost valve; in the transition state before the boost flow rate reaches the target boost flow rate and in the stable state after the boost flow rate reaches the target boost flow rate, the regeneration valve, or the regeneration valve and the discharge valve, are controlled such that the sum of the regeneration flow rate, the boost flow rate, and the return flow rate equals the target bottom outflow flow rate, wherein the regeneration flow rate is the flow rate of the working oil supplied from the bottom chamber to the accumulator through the regeneration valve, and the return flow rate is the flow rate of the working oil discharged from the bottom chamber to the oil tank through the discharge valve.

[0012] Invention Effects

[0013] According to the present invention, in a working machine capable of supplying working oil flowing from the bottom chamber of the hydraulic cylinder to the rod chamber and the accumulator, it is possible to ensure the speed of the hydraulic cylinder corresponding to the operating amount and to prevent the generation of hydraulic cylinder impact. Attached Figure Description

[0014] Figure 1 This is a perspective view of a hydraulic excavator, shown as an example of a working machine according to an embodiment of the present invention.

[0015] Figure 2 This is a schematic diagram of the hydraulic drive unit mounted on a hydraulic excavator.

[0016] Figure 3 This diagram shows the drive control system installed on a hydraulic excavator.

[0017] Figure 4 This is a graph showing the time-varying flow rate of the working oil through the flow control valve during an emergency maximum boom descent operation.

[0018] Figure 5 This is a schematic diagram representing the distribution of the target bottom outflow rate Qst under steady-state conditions.

[0019] Figure 6 This is a schematic diagram representing the allocation of the target bottom outflow rate Qst under transition conditions.

[0020] Figure 7 It is a block diagram representing the function of the control device. Detailed Implementation

[0021] 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.

[0022] 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 loading excavated objects such as sand and soil into dump trucks.

[0023] 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, 34), 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 having: a cylinder barrel, a circular plate-shaped piston dividing the interior of 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, 34) are controlled by a control device 100 (described later) (see reference). Figure 3 Driven by instructions, the flow control valves (8, 13~22, 34) adjust the opening area by changing the position of the internal valve core, thereby controlling the flow rate of working oil through the opening.

[0024] The engine 5, serving as the prime mover, is composed of an internal combustion engine such as a diesel engine. The first hydraulic pump 6 and the second hydraulic pump 7 are mechanically connected to the engine 5 and driven by the engine 5 to spray working oil (pressurized oil). The first hydraulic pump 6 and the second hydraulic pump 7 are variable-capacity hydraulic pumps capable of changing their capacity (discharge volume). 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 the pressurized oil sprayed from the first hydraulic pump 6 and the second hydraulic pump 7. The accumulator 9 is a pressure accumulator device that stores the pressurized oil supplied from the bottom chamber 301 of the boom cylinder 3a, which retracts due to the weight of the working device 51, during boom lowering operations.

[0025] A first boom control valve 14, serving as a flow control valve, is installed in the pipeline connecting the first hydraulic pump 6 and the boom cylinder 3a. This first boom control valve 14 controls the flow rate of working oil supplied from the first hydraulic pump 6 to the boom cylinder 3a and the flow rate of working oil discharged from the boom cylinder 3a to the oil tank 12. A second boom control valve 15, also serving as a flow control valve, is installed in the pipeline connecting the second hydraulic pump 7 and the boom cylinder 3a. This second boom control valve 15 controls the flow rate of working oil supplied from the second hydraulic pump 7 to the boom cylinder 3a and the flow rate of working oil discharged from the boom cylinder 3a to the oil tank 12.

[0026] The second boom control valve 15 is installed on the pipeline 35 connecting the bottom chamber 301 of the boom cylinder 3a and the oil tank 12. The second boom control valve 15 functions as a discharge valve, which controls the flow rate of working oil from the bottom chamber 301 side of the boom cylinder 3a to the oil tank 12 side by adjusting the opening area.

[0027] A first boom control valve 16, serving as a flow control valve, is installed in the pipeline connecting the first hydraulic pump 6 and the boom cylinder 3b. This first boom control valve 16 controls the flow rate of working oil supplied from the first hydraulic pump 6 to the boom cylinder 3b and the flow rate of working oil discharged from the boom cylinder 3b to the oil tank 12. A second boom control valve 17, also serving as a flow control valve, is installed in the pipeline connecting the second hydraulic pump 7 and the boom cylinder 3b. This second boom control valve 17 controls the flow rate of working oil supplied from the second hydraulic pump 7 to the boom cylinder 3b and the flow rate of working oil discharged from the boom cylinder 3b to the oil tank 12.

[0028] A bucket control valve 18, serving as a flow control valve, is installed in the pipeline connecting the first hydraulic pump 6 and the bucket cylinder 3c. This bucket control valve 18 controls the flow rate of working oil supplied from the first hydraulic pump 6 to the bucket cylinder 3c and the flow rate of working oil discharged from the bucket cylinder 3c to the oil tank 12. A swing control valve 13, also serving as a flow control valve, is installed in the pipeline connecting the second hydraulic pump 7 and the swing motor 4. This swing control valve 13 controls the flow rate of working oil supplied from the second hydraulic pump 7 to the swing motor 4 and the flow rate of working oil discharged from the swing motor 4 to the oil tank 12.

[0029] 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.

[0030] An oil replenishment device is installed between pipes 10 and 11. Pipe 10 connects the rotary control valve 13 to the right-hand rotation port of the rotary motor 4, and pipe 11 connects the rotary control valve 13 to the left-hand rotation port of the rotary motor 4. The oil replenishment device has check valves 25 and 26 and safety valves 27 and 28 that operate in opposite directions. A pipe 29 is installed between these check valves 25 and 26 and safety valves 27 and 28 to return oil discharged from the rotary motor 4 to the oil tank 12. Pipe 29 functions as an oil replenishment line capable of replenishing working oil to the rotary motor 4.

[0031] Accumulator 9 is connected to pipeline 38, and pressurized oil ejected from accumulator 9 is supplied to each hydraulic actuator through pipeline 38. The bottom chamber 301 of boom cylinder 3a is connected to pipeline 38 via pipeline (hereinafter also referred to as bottom side pipeline) 32. A regeneration valve 8 is installed in bottom side pipeline 32 to regenerate the pressurized oil in the bottom chamber 301 of boom cylinder 3a to accumulator 9 during boom descent. Regeneration valve 8 is a flow control valve that controls the flow rate of working oil from the bottom chamber 301 side of boom cylinder 3a to the accumulator 9 by adjusting the opening area.

[0032] A pipe (hereinafter also referred to as the rod-side pipe) 33 is provided between the bottom chamber 301 of the boom cylinder 3a and the regeneration valve 8 in the bottom-side pipe 32, branching off from the bottom-side pipe 32 and connecting to the rod chamber 302 of the boom cylinder 3a. A pressure boosting valve 34 is provided in the rod-side pipe 33. The pressure boosting valve 34 pressurizes the working oil in the bottom chamber 301 of the boom cylinder 3a by connecting the bottom chamber 301 and the rod chamber 302 when the boom is lowered. The pressure boosting valve 34 is a flow control valve that controls the flow rate of working oil from the bottom chamber 301 side to the rod chamber 302 side of the boom cylinder 3a by adjusting the opening area.

[0033] Pipeline 38 is connected to multiple branch pipelines 39, 40, 41, and 42. Branch pipeline 39 is connected between the bottom chamber 301 of the boom cylinder 3a and the regeneration valve 8 in the bottom pipeline 32. A boom auxiliary valve 19, which acts as a flow control valve, is provided in branch pipeline 39 to control the flow rate of working oil supplied from the accumulator 9 to the boom cylinder 3a.

[0034] A boom auxiliary valve 20, acting as a flow control valve, is installed on branch line 40. This boom auxiliary valve 20 controls the flow rate of working oil supplied from accumulator 9 to boom cylinder 3b. A bucket auxiliary valve 21, also acting as a flow control valve, is installed on branch line 41. This bucket auxiliary valve 21 controls the flow rate of working oil supplied from accumulator 9 to bucket cylinder 3c. A swing auxiliary valve 22, acting as a flow control valve, is installed on branch line 42. This swing auxiliary valve 22 controls the flow rate of working oil supplied from accumulator 9 to swing motor 4.

[0035] 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.

[0036] 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 actuator operating amount sensors for detecting the operating 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.

[0037] 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 at least one of multiple flow control valves of the hydraulic drive unit based on the detection results of the multiple sensors. The multiple sensors include multiple pressure sensors and multiple actuator operation sensors. The multiple pressure sensors include: a bottom pressure sensor 23, a lever pressure sensor 24, and an accumulator sensor 43. The multiple actuator operation sensors include a boom operation sensor 31 and a bucket operation sensor 45.

[0038] Bottom pressure sensor 23 detects the pressure of the working oil in the bottom chamber 301 of the boom cylinder 3a (hereinafter also referred to as bottom pressure). Rod pressure sensor 24 detects the pressure of the working oil in the rod chamber 302 of the boom cylinder 3a (hereinafter, rod pressure). Accumulator sensor 43 is installed in pipeline 38 and detects the pressure of the working oil in accumulator 9 (hereinafter also referred to as accumulator pressure). Each pressure sensor (23, 24, 43) outputs a signal indicating the detected pressure to the control device 100.

[0039] The boom operation sensor 31 is a cylinder operation 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 sensor 45 is an actuator operation 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. Furthermore, the boom operation amount detected by the boom operation sensor 31 includes a boom lifting operation amount (operating the boom 1a in the lifting direction) and a boom lowering operation amount (operating the boom 1a in the lowering direction). Additionally, the bucket operation amount detected by the bucket operation sensor 45 includes a bucket loading operation amount (operating the bucket 1c in the loading direction) and a bucket dumping operation amount (operating the bucket 1c in the dumping direction).

[0040] The first boom control valve 14 is a three-position, neutral-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, an electromagnetic command is sent to operating end 14b, supplying 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 discharging 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, 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 will not be discharged from the boom cylinder 3a's bottom chamber 301 to the oil tank 12 through the first boom control valve 14.

[0041] 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 via electromagnetic commands from the control device 100 to its operating ends. During boom raising, an electromagnetic command is sent to operating end 15b, supplying 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 discharging 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, an electromagnetic command is sent to operating end 15a, connecting the second hydraulic pump 7 to the rod chamber 302 of the boom cylinder 3a via the second boom control valve 15. Furthermore, when the boom lowering operation is performed, and the specified conditions are met, in response to the electromagnetic command from the control device 100 described later, the working oil in the bottom chamber 301 of the boom cylinder 3a is discharged to the oil tank 12 through the second boom control valve 15.

[0042] 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 via 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, supplying 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 discharging 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, supplying 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 discharging working oil from the rod chamber 302 of the bucket cylinder 3c to the oil tank 12 through the bucket control valve 18.

[0043] In addition, although Figure 3 The details are omitted, but the drive of the boom cylinder 3b by the first hydraulic pump 6 and the second hydraulic pump 7, as well as the drive of the slewing motor 4 by the second hydraulic pump 7, are the same as those for the bucket cylinder 3c described above.

[0044] The hydraulic drive unit of the hydraulic excavator 1 in this embodiment has a pressure-boosting regeneration circuit including a regeneration valve 8 and a pressure-boosting valve 34. By performing regeneration while connecting the bottom chamber 301 of the boom cylinder 3a to the rod chamber 302, the pressure of the accumulator 9 can be efficiently increased, thus increasing the availability of auxiliary hydraulic actuators and auxiliary equipment.

[0045] However, for example, in the event of an emergency operation where the boom control lever 30 is moved from the neutral operating position to the maximum boom lowering operating position, if the pressure boosting valve 34 is opened immediately in response to this operation, an impact may occur in the boom cylinder 3a due to the pressure difference between the bottom chamber 301 and the boom chamber 302. This impact deteriorates the operability during boom lowering, leading to reduced work efficiency. Therefore, in this embodiment, when an emergency maximum boom lowering operation is performed, the control device 100 controls the pressure boosting valve 34 to gradually open over time. By gradually opening the pressure boosting valve 34, the aforementioned impact can be prevented.

[0046] However, if the pressure boosting valve 34 is opened slowly, the supply of working oil from the bottom chamber 301 of the boom cylinder 3a to the rod chamber 302 is suppressed. Therefore, the retraction speed of the boom cylinder 3a (i.e., the boom descent speed) decreases, and operating efficiency may decrease. Therefore, in this embodiment, the control device 100 adjusts the opening area of ​​the second boom control valve 15 and the opening area of ​​the regeneration valve 8 accordingly to the change in the opening area of ​​the pressure boosting valve 34, so that the boom cylinder 3a operates at a speed corresponding to the boom descent operation amount. A detailed description will follow.

[0047] 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); non-volatile memory 100b such as ROM (Read Only Memory), flash memory, and hard disk actuator; volatile memory 100c, also known as RAM (Random Access Memory); input / output interfaces; and other peripheral circuitry. This hardware works together to enable software operation, thereby implementing multiple functions. Furthermore, the control device 100 can be composed of a single computer or multiple computers.

[0048] 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.

[0049] 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, etc.).

[0050] Reference Figure 4 The flow control during boom lowering operation performed by the control device 100 of this embodiment will be described in general. Figure 4 This is a graph showing the time-varying flow rate of the working oil through the flow control valve during an emergency maximum boom descent operation. Figure 4 The horizontal axis represents the elapsed time. Figure 4 The vertical axis of (a) represents the boom lowering operation amount. Figure 4 The vertical axis of (b) represents the flow rate of the working oil through the flow control valves (8, 15, 34). Furthermore, the flow rate through each flow control valve is indicated by different shading lines marked on each valve.

[0051] The control device 100 controls the boost valve 34 and the regeneration valve 8 or the second boom control valve 15 based on the boom lowering operation amount Lb detected by the boom operation amount sensor 31. Furthermore, in this embodiment, the control of each flow control valve will be described when only the boom cylinder 3a of the multiple hydraulic actuators is operated (when performing a single boom lowering operation). In the case of a single boom lowering operation, the flow rates of the first hydraulic pump 6 and the second hydraulic pump 7 are controlled to 0. That is, when a boom lowering operation is performed, the boom 1a moves in the lowering direction due to the weight of the working device 51. The speed of the boom 1a's movement in the lowering direction is determined by the flow rate of the working oil flowing out of the boom cylinder 3a.

[0052] The control device 100 calculates the target flow rate of the working oil flowing out of the bottom chamber 301 of the boom cylinder 3a, i.e., the target bottom outflow flow rate Qst, based on the boom lowering operation amount Lb detected by the boom operation amount sensor 31. The target bottom outflow flow rate Qst is determined accordingly with the boom lowering operation amount Lb, and is equivalent to the standard flow rate of the working oil discharged from the bottom chamber 301 of the boom cylinder 3a to the oil tank 12 through the second boom control valve 15 in a standard hydraulic drive device without a boost regeneration circuit, that is, a hydraulic drive device with a structure in which the return oil of the boom cylinder 3a is only delivered to the oil tank 12.

[0053] The control device 100 calculates the target flow rate, i.e., the target boosting flow rate Qbrt, of the working oil supplied from the bottom chamber 301 of the boom cylinder 3a to the rod chamber 302 through the boosting valve 34, based on the target bottom outflow rate Qst and the pressure-bearing area ratio Ar / Ab of the bottom chamber 301 and the rod chamber 302 of the boom cylinder 3a. As mentioned above, the target bottom outflow rate Qst is determined by the boom lowering operation amount Lb; therefore, the target boosting flow rate Qbrt is also determined by the boom lowering operation amount Lb.

[0054] The control device 100 controls the boosting valve 34 so that the working oil flow rate, i.e. the boosting flow rate Qbr, supplied from the bottom chamber 301 of the driven boom cylinder 3a to the rod chamber 302 through the boosting valve 34 gradually increases with time t at a specified rate of change, thereby becoming equal to the target boosting flow rate Qbrt.

[0055] The control device 100 controls the booster valve 34, the regeneration valve 8, and the second boom control valve 15, such that the target bottom outflow Qst is equivalent to the sum of the booster flow Qbr, the regeneration flow Qba, and the return flow Qbt. The regeneration flow Qba ​​is the flow rate of working oil supplied (regenerated) from the bottom chamber 301 of the boom cylinder 3a to the accumulator 9 through the regeneration valve 8. The return flow Qbt is the flow rate of working oil discharged from the bottom chamber 301 of the boom cylinder 3a to the oil tank 12 through the second boom control valve 15.

[0056] like Figure 4As shown, during boom lowering, the boost flow rate Qbr increases with time t until it reaches the target boost flow rate Qbrt corresponding to the boom lowering operation amount Lb. Here, the state where the boost flow rate Qbr reaches the target boost flow rate Qbrt is defined as the steady state, and the state from the start time t0 of the boom lowering operation to the time point t1 when the steady state is reached is defined as the transition state.

[0057] In the transition state, the boost flow rate Qbr is smaller compared to the steady state. To ensure sufficient boom descent speed even in the transition state, the control device 100 compensates for the insufficient flow rate with regenerative flow rate Qba and return flow rate Qbt. Furthermore, the insufficient flow rate is equivalent to the remaining portion of the bottom outflow flow rate required for the boom cylinder 3a to operate at the target speed corresponding to the boom descent operation amount Lb; therefore, for convenience, it is denoted as the residual flow rate Qr. The residual flow rate Qr is equivalent to the value obtained by subtracting the boost flow rate from the target bottom outflow flow rate (Qr = Qst - Qbr). Thus, the regenerative flow rate Qba is greater in the transition state than in the steady state. Similarly, the return flow rate Qbt is greater in the transition state than in the steady state.

[0058] When the accumulator pressure is sufficiently low, it is preferable to use only the regeneration flow rate Qba to ensure the insufficient flow (i.e., the remaining flow rate Qr). Therefore, when the accumulator pressure Pa is less than the predetermined value Pa0, the control device 100 controls the regeneration valve 8 so that the regeneration flow rate Qba is equal to the remaining flow rate Qr. On the other hand, when the accumulator pressure Pa is above the predetermined value Pa0, the control device 100 controls the regeneration valve 8 and the second boom control valve 15 so that the sum of the regeneration flow rate Qba and the return flow rate Qbt is equal to the remaining flow rate Qr.

[0059] Figure 5 This is a schematic diagram illustrating the distribution of the target bottom outflow rate Qst under steady-state conditions. Figure 6 This is a schematic diagram illustrating the distribution of the target bottom outflow rate Qst during the transition state. The control device 100 controls the regeneration valve 8, or the regeneration valve 8 and the second boom control valve 15, respectively, during the transition state before the boosted flow rate Qbr reaches the target boosted flow rate Qbrt, and during the stable state after the boosted flow rate Qbrt reaches the target boosted flow rate Qbrt, so that the sum of the regeneration flow rate Qba, the boosted flow rate Qbr, and the return flow rate Qbt is equal to the target bottom outflow rate Qst.

[0060] like Figure 5 and Figure 6As shown, in both the steady state and the transient state, when the accumulator pressure Pa is less than the specified value Pa0, the insufficient flow (residual flow Qr) is ensured by the regeneration flow rate Qba. When the accumulator pressure Pa is less than the specified value Pa0, the differential pressure ΔPba across the regeneration valve 8 is large, therefore, the opening of the regeneration valve 8 is reduced.

[0061] When the accumulator pressure Pa is above the specified value Pa0, the differential pressure ΔPba across the regeneration valve 8 decreases. Even if the regeneration valve 8 is fully open, the remaining flow rate Qr cannot be ensured solely by the regeneration flow rate Qba. When the accumulator pressure Pa is above the specified value Pa0, the insufficient flow rate (remaining flow rate Qr) is ensured by the regeneration flow rate Qba and the return flow rate Qbt.

[0062] Thus, the control device 100 of this embodiment increases the regeneration flow rate Qba to the accumulator 9 as much as possible during boom descent. As a result, the regeneration efficiency of the accumulator 9 during boom descent can be improved.

[0063] Figure 7 This is a block diagram illustrating the functions of the control device 100. (Usage) Figure 7 The processing procedures of the control device 100 are described in detail. For example... Figure 7 As shown, the control device 100 includes: a target bottom outflow calculation unit 101, a boost flow calculation unit 102, a slope limiting unit 103, a first differential pressure calculation unit 104, a boost valve opening calculation unit 105, a residual flow calculation unit 106, a second differential pressure calculation unit 107, a provisional opening calculation unit 108, a regeneration valve opening calculation unit 109, a regeneration flow calculation unit 110, a return flow calculation unit 111, a second boom control valve opening calculation unit 112, a boost valve command unit 113, a regeneration valve command unit 114, and a second boom control valve command unit 115. The control device 100 implements these functions by executing a program stored in the non-volatile memory 100b.

[0064] like Figure 7As shown, the target bottom outflow rate calculation unit 101 receives the boom lowering operation amount Lb detected by the boom operation amount sensor 31. Referring to the outflow rate table, the target bottom outflow rate calculation unit 101 calculates the target bottom outflow rate Qst based on the boom lowering operation amount Lb. The outflow rate table is a data table (characteristic data) that defines the relationship between the target bottom outflow rate Qst and the boom lowering operation amount Lb. The outflow rate table is determined in advance through experiments, etc., and stored in the non-volatile memory 100b. Furthermore, the outflow rate table is equivalent to the return flow table of the second boom control valve 15 in a standard hydraulic drive device without a boost regeneration circuit. Additionally, the characteristic data of the target bottom outflow rate Qst corresponding to the boom lowering operation amount Lb is not limited to a table format and can also be defined by a function format (mathematical formula). The target bottom outflow rate Qst calculated by the target bottom outflow rate calculation unit 101 is output to the boost flow rate calculation unit 102 and the residual flow rate calculation unit 106.

[0065] The boost flow calculation unit 102 inputs the target bottom outflow flow rate Qst, multiplies the target bottom outflow flow rate Qst by the pressure-bearing area ratio Ar / Ab of the boom cylinder 3a, and calculates the target boost flow rate (hereinafter also referred to as the target boost flow rate) Qbrt (Qbrt = Qst × (Ar / Ab)). Here, Ar is the pressure-bearing area of ​​the rod chamber 302 of the boom cylinder 3a, and Ab is the pressure-bearing area of ​​the bottom chamber 301 of the boom cylinder 3a. The target boost flow rate Qbrt calculated by the boost flow calculation unit 102 is output to the slope limiting unit 103.

[0066] The slope limiting unit 103 takes the target boost flow rate Qbrt as input and calculates the value obtained by limiting the time change rate of the boost flow rate Qbrt. For example, the slope limiting unit 103 multiplies the target boost flow rate Qbrt by a correction coefficient c corresponding to the elapsed time t from the start time t0 of the boom descent operation, and calculates the corrected target boost flow rate Qbr* (Qbr* = c × Qbrt) corresponding to the elapsed time t. The time change rate (slope) of the correction coefficient c is pre-stored in the non-volatile memory 100b. The correction coefficient c is 0 at the start time t0 of the boom descent operation and increases to 1 at a predetermined time change rate as time t elapses. The time change rate of the correction coefficient c, that is, the time change rate of the increased corrected target boost flow rate Qbr*, is determined to be a value that will not cause an impact due to the connection between the bottom chamber 301 and the boom chamber 302. The corrected target boost flow rate Qbr* calculated by the slope limiting unit 103 is output to the boost valve opening calculation unit 105 and the residual flow calculation unit 106.

[0067] The first differential pressure calculation unit 104 takes into account the base pressure Pb detected by the base pressure sensor 23 and the rod pressure Pr detected by the rod pressure sensor 24. The first differential pressure calculation unit 104 calculates the differential pressure ΔPbr (ΔPbr = Pb - Pr) across the booster valve 34 by subtracting the rod pressure Pr from the base pressure Pb. The differential pressure ΔPbr across the booster valve 34 calculated by the first differential pressure calculation unit 104 is output to the booster valve opening calculation unit 105.

[0068] The pressure booster valve opening calculation unit 105 inputs the target flow rate through the pressure booster valve 34, i.e., the corrected target pressure boosting flow rate Qbr*, and the differential pressure ΔPbr across the pressure booster valve 34. Referring to the pressure booster valve opening table corresponding to the differential pressure ΔPbr, the pressure booster valve opening calculation unit 105 calculates the target opening area Abr of the pressure booster valve 34 based on the corrected target pressure boosting flow rate Qbr*. The pressure booster valve opening table is a data table (characteristic data) specifying the relationship between the corrected target pressure boosting flow rate Qbr* and the target opening area Abr of the pressure booster valve 34. Multiple pressure booster valve opening tables are stored in the non-volatile memory 100b, corresponding to the differential pressure ΔPbr across the pressure booster valve 34. Furthermore, the characteristic data of the target opening area Abr of the pressure booster valve 34 corresponding to the corrected target pressure boosting flow rate Qbr* and the differential pressure ΔPbr is not limited to a table format and can also be specified in a functional format (e.g., an orifice plate formula). The target opening area Abr of the pressure booster valve 34 calculated by the pressure booster valve opening calculation unit 105 is output to the pressure booster valve command unit 113.

[0069] The pressure boosting valve command unit 113 receives the target opening area Abr of the pressure boosting valve 34, calculates the control command value (e.g., the solenoid current value) corresponding to the target opening area Abr, and outputs the electromagnetic command corresponding to the calculated control command value to the pressure boosting valve 34. Thus, the pressure boosting valve 34 is controlled so that its actual opening area is equal to the target opening area Abr.

[0070] The residual flow calculation unit 106 takes into input the corrected target boost flow rate Qbr* and the target bottom outflow flow rate Qst. The residual flow calculation unit 106 subtracts the corrected target boost flow rate Qbr* from the target bottom outflow flow rate Qst to calculate the residual flow rate Qr (Qr = Qst - Qbr*). The residual flow rate Qr calculated by the residual flow calculation unit 106 is output to the provisional opening calculation unit 108 and the return flow calculation unit 111. The residual flow rate Qr is the flow rate (the remaining flow rate other than the boost flow rate) required to ensure the boom speed corresponding to the boom descent operation amount Lb, and is provided only by the regeneration flow rate Qba, or by the regeneration flow rate Qba and the return flow rate Qbt.

[0071] The second differential pressure calculation unit 107 takes into account the base pressure Pb detected by the base pressure sensor 23 and the accumulator pressure Pa detected by the accumulator sensor 43. The second differential pressure calculation unit 107 subtracts the accumulator pressure Pa from the base pressure Pb to calculate the differential pressure ΔPba (ΔPba = Pb - Pa) across the regeneration valve 8. The differential pressure ΔPba calculated by the second differential pressure calculation unit 107 across the regeneration valve 8 is output to the provisional opening calculation unit 108 and the regeneration flow calculation unit 110.

[0072] The provisional opening calculation unit 108 inputs the remaining flow rate (the sum of the flow rate through the regeneration valve 8 and the flow rate through the second boom control valve 15) Qr and the differential pressure ΔPba across the regeneration valve 8. The provisional opening calculation unit 108 calculates the opening area when the working oil flow rate through the regeneration valve 8 equals the remaining flow rate Qr, as the provisional target opening area. Referring to the valve opening table corresponding to the differential pressure ΔPba, the provisional opening calculation unit 108 calculates the provisional target opening area aba0 of the regeneration valve 8 based on the remaining flow rate Qr. The valve opening table is a data table (characteristic data) that specifies the relationship between the remaining flow rate Qr and the provisional target opening area aba0 of the regeneration valve 8. Multiple valve opening tables are stored in the non-volatile memory 100b, corresponding to the differential pressure ΔPba across the regeneration valve 8. Furthermore, the characteristic data of the provisional target opening area aba0 of the regeneration valve 8 corresponding to the regeneration flow rate Qba and the differential pressure ΔPba is not limited to a table format; it can also be specified in a functional format (e.g., an orifice plate formula). The provisional target opening area aba0 of the regeneration valve 8, calculated by the provisional opening calculation unit 108, is output to the regeneration valve opening calculation unit 109.

[0073] The provisional target opening area Aba0 of the regeneration valve 8 calculated by the provisional opening calculation unit 108 sometimes exceeds the maximum opening area Abamax of the regeneration valve 8. In other words, the characteristic data of the provisional target opening area Aba0 used in the calculation of the provisional target opening area Aba0 is determined to be data that is capable of being calculated to a value that is sufficiently large than the maximum opening area Abamax of the regeneration valve 8, assuming that the opening area of ​​the regeneration valve 8 has no upper limit.

[0074] The regeneration valve opening calculation unit 109 inputs the provisional target opening area Aba0 of the regeneration valve 8, and calculates the target opening area Aba of the regeneration valve 8 based on the provisional target opening area Aba0 and the maximum opening area Abamax of the regeneration valve 8. Specifically, first, the regeneration valve opening calculation unit 109 compares the maximum opening area Abamax of the regeneration valve 8 with the provisional target opening area Aba0. The maximum opening area Abamax of the regeneration valve 8 is stored in the non-volatile memory 100b. If the provisional target opening area Aba0 is less than or equal to the maximum opening area Abamax, the regeneration valve opening calculation unit 109 calculates the provisional target opening area Aba0 as the target opening area Aba of the regeneration valve 8 (Aba = Aba0, Aba0 ≤ Abamax). If the provisional target opening area Aba0 is greater than the maximum opening area Abamax, the regeneration valve opening calculation unit 109 calculates the maximum opening area Abamax as the target opening area Aba of the regeneration valve 8 (Aba = Abamax, Aba0 > Abamax). The target opening area Aba of the regeneration valve 8, calculated by the regeneration valve opening calculation unit 109, is output to the regeneration valve command unit 114 and the regeneration flow calculation unit 110.

[0075] The regeneration valve command unit 114 receives the target opening area Aba of the regeneration valve 8, calculates the control command value (e.g., the current value of the solenoid) corresponding to the target opening area Aba, and outputs the electromagnetic command corresponding to the calculated control command value to the regeneration valve 8. Thus, the regeneration valve 8 is controlled so that its actual opening area is equal to its target opening area Aba.

[0076] The regeneration flow calculation unit 110 receives the target opening area Aba of the regeneration valve 8 and the differential pressure ΔPba across the regeneration valve 8. Referring to the regeneration flow table corresponding to the differential pressure ΔPba, the regeneration flow calculation unit 110 calculates the estimated regeneration flow rate, i.e., the estimated regeneration flow rate Qba*, based on the target opening area Aba of the regeneration valve 8. The regeneration flow table is a data table (characteristic data) that defines the relationship between the target opening area Aba of the regeneration valve 8 and the estimated regeneration flow rate Qba*. Multiple regeneration flow tables are stored in the non-volatile memory 100b, corresponding to the differential pressure ΔPba across the regeneration valve 8. Furthermore, the characteristic data of the estimated regeneration flow rate Qba* corresponding to the target opening area Aba and differential pressure ΔPba of the regeneration valve 8 is not limited to a table format; it can also be defined by a function (e.g., an orifice plate formula). The estimated regeneration flow rate Qba* calculated by the regeneration flow calculation unit 110 is output to the return flow calculation unit 111.

[0077] The return flow calculation unit 111 receives the estimated regeneration flow rate (estimated value of regeneration flow rate) Qba* and the remaining flow rate (target value of the sum of regeneration flow rate and return flow rate) Qr. The return flow calculation unit 111 subtracts the estimated regeneration flow rate Qba* from the remaining flow rate Qr to calculate the target return flow rate (target value of return flow rate) Qbt* (Qbt* = Qr - Qba*). The target return flow rate Qbt* calculated by the return flow calculation unit 111 is then output to the second boom control valve opening calculation unit 112.

[0078] The second boom control valve opening calculation unit 112 inputs the target return flow rate Qbt* and the bottom pressure Pb detected by the bottom pressure sensor 23. The bottom pressure Pb is gauge pressure, equivalent to the differential pressure between the bottom pressure (absolute pressure) and the tank pressure (absolute pressure), i.e., the front-to-back differential pressure ΔPbt of the second boom control valve 15 (ΔPbt = Pb). The second boom control valve opening calculation unit 112 refers to the second boom control valve opening table corresponding to the front-to-back differential pressure ΔPbt (bottom pressure Pb) and calculates the target opening area Abt of the second boom control valve 15 based on the target return flow rate Qbt*. The second boom control valve opening table is a data table (characteristic data) that defines the relationship between the target return flow rate Qbt* and the target opening area Abt of the second boom control valve 15. In the non-volatile memory 100b, multiple second boom control valve opening tables are stored corresponding to the front-to-back differential pressure ΔPbt (bottom pressure Pb) of the second boom control valve 15. Furthermore, the characteristic data of the target opening area Abt of the second boom control valve 15, corresponding to the target return flow rate Qbt* and the differential pressure ΔPbt, is not limited to tabular form, but can also be specified in functional form (e.g., orifice plate formula). The target opening area Abt of the second boom control valve 15 calculated by the second boom control valve opening calculation unit 112 is output to the second boom control valve command unit 115.

[0079] The second boom control valve command unit 115 receives the target opening area Abt of the second boom control valve 15, calculates the control command value (e.g., the solenoid current value) corresponding to the target opening area Abt, and outputs the electromagnetic command corresponding to the calculated control command value to the second boom control valve 15. Thus, the second boom control valve 15 is controlled so that its actual opening area is equal to its target opening area Abt.

[0080] Through the above, the pressure boosting valve 34 is controlled so that the pressure boosting flow rate Qbr (the actual flow rate through the pressure boosting valve 34) is equal to the corrected target pressure boosting flow rate Qbr*, the regeneration valve 8 is controlled so that the regeneration flow rate Qba (the actual flow rate through the regeneration valve 8) is equal to the estimated regeneration flow rate Qba*, and the second boom control valve 15 is controlled so that the return flow rate (the actual flow rate through the second boom control valve 15) is equal to the target return flow rate Qbt*.

[0081] According to the above implementation method, the following effects are achieved.

[0082] (1) The hydraulic excavator (operating machinery) 1 has a body 52 and an operating device 51 mounted on the body 52. ​​The operating device 51 has: a boom 1a mounted on the body 52, a stick 1b mounted on the boom 1a, and a bucket (operating tool) 1c mounted on the stick 1b. In addition, the hydraulic excavator 1 has: an engine (prime mover) 5, hydraulic pumps (a first hydraulic pump 6 and a second hydraulic pump 7) driven by the engine 5, and a plurality of hydraulic cylinders driven by working oil injected from the hydraulic pumps (6, 7). The plurality of hydraulic cylinders are hydraulic actuators for driving the operating device 51, and have a base chamber 301 and a rod chamber 302. The plurality of hydraulic cylinders include a boom cylinder 3a for driving the boom 1a. The hydraulic excavator 1 includes: an accumulator (accumulator device) 9 for storing working oil supplied from the bottom chamber 301 of the boom cylinder 3a; a regeneration valve 8 for controlling the flow rate of working oil from the bottom chamber 301 to the accumulator 9; a booster valve 34 for controlling the flow rate of working oil from the bottom chamber 301 to the boom chamber 302; a second boom control valve (discharge valve) 15 for controlling the flow rate of working oil from the bottom chamber 301 to the oil tank 12; a boom operating lever (cylinder operating device) 30 for operating the boom cylinder 3a; a boom operating amount sensor (cylinder operating amount sensor) 31 for detecting the operating amount of the boom operating lever 30; and a control device 100 for controlling at least the regeneration valve 8 and the booster valve 34 based on the operating amount detected by the boom operating amount sensor 31. The operating amount detected by the boom operating amount sensor 31 includes a boom lowering operating amount Lb for operating the boom 1a in the lowering direction.

[0083] In this structure, during boom lowering operation, the control device 100 opens the regeneration valve 8, thereby accumulating pressure in the accumulator 9 using pressurized oil from the bottom chamber 301 of the boom cylinder 3a, which contracts due to the weight of the working device 51. Additionally, during boom lowering operation, the control device 100 opens the pressure boosting valve 34, thereby increasing the pressure in the rod chamber 302 using pressurized oil from the bottom chamber 301 of the boom cylinder 3a, which contracts due to the weight of the working device 51. As a result, the bottom chamber 301 is further pressed in by the piston, and the pressure in the bottom chamber 301 increases. Thus, in this embodiment, during boom lowering, regeneration can be performed using the accumulator 9 while simultaneously increasing the pressure in the bottom chamber 301. Consequently, the accumulator 9 can be pressurized to a higher pressure. Therefore, according to this embodiment, the opportunities for the accumulator 9 to assist in various hydraulic actuators such as boom lifting, stick tipping, bucket tipping, and slewing can be increased.

[0084] (2) The control device 100 calculates the target bottom outflow rate Qst and the target boost flow rate Qbrt based on the boom lowering operation amount Lb detected by the boom operation amount sensor 31. The target bottom outflow rate Qst is the target flow rate of the working oil flowing out of the bottom chamber 301 of the boom cylinder 3a, and the target boost flow rate Qbrt is the target flow rate of the working oil supplied from the bottom chamber 301 to the rod chamber 302 through the boost valve 34. The control device 100 controls the boost valve 34 so that the flow rate of the working oil supplied from the bottom chamber 301 to the rod chamber 302 through the boost valve 34, i.e., the boost flow rate Qbrt, gradually increases with time t and becomes equal to the target boost flow rate Qbrt. The control device 100 increases the boost flow rate Qbrt at a predetermined time variation rate (time variation characteristic). The control device 100 controls the regeneration valve 8, or the regeneration valve 8 and the second boom control valve 15, respectively, in the transition state before the boosted flow rate Qbr reaches the target boosted flow rate Qbrt and in the stable state after the boosted flow rate Qbrt reaches the target boosted flow rate Qbrt, so that the sum of the regeneration flow rate Qba, the boosted flow rate Qbr, and the return flow rate Qbt is equal to the target bottom outflow flow rate Qst. Among them, the regeneration flow rate Qba is the flow rate of working oil supplied from the bottom chamber 301 to the accumulator 9 through the regeneration valve 8, the boosted flow rate Qbr is the flow rate of working oil supplied from the bottom chamber 301 to the rod chamber 302 through the boosted valve 34, and the return flow rate Qbt is the flow rate of working oil discharged from the bottom chamber 301 to the oil tank 12 through the second boom control valve 15.

[0085] In this structure, the control device 100 gradually opens the pressure boosting valve 34, thus preventing impact on the boom cylinder 3a when the bottom side of the boom cylinder 3a is connected to the rod side. Furthermore, insufficient flow during the gradual opening of the pressure boosting valve 34 can be compensated by the regeneration flow rate Qba or the combination of the regeneration flow rate Qba and the return flow rate Qbt. Therefore, according to this embodiment, the boom cylinder 3a can be driven at the same operating speed as a hydraulic drive unit without a pressure boosting regeneration circuit, wherein the hydraulic drive unit only supplies boom return oil to the oil tank 12 without performing boom regeneration. That is, the speed of the boom cylinder 3a corresponding to the boom descent operation amount Lb can be appropriately ensured. Thus, according to this embodiment, the operability of the boom cylinder 3a can be maintained, and the accumulator 9 is pressurized to a high pressure by the return oil from the boom cylinder 3a, thereby improving the overall efficiency of the hydraulic excavator.

[0086] (3) When the accumulator pressure (pressure of accumulator 9) Pa is less than the specified value Pa0, the control device 100 controls the regeneration valve 8 so that the sum of the regeneration flow rate Qba and the boost flow rate Qbr is equal to the target bottom outflow rate Qst. When the accumulator pressure Pa is greater than or equal to the specified value Pa0, the control device 100 controls the regeneration valve 8 and the second boom control valve 15 so that the sum of the regeneration flow rate Qba, the boost flow rate Qbr, and the return flow rate Qbt is equal to the target bottom outflow rate Qst.

[0087] In this structure, the regeneration valve 8 in the regeneration valve 8 and the second boom control valve 15 can be preferentially controlled to increase the regeneration flow rate Qba. By compensating the remaining flow rate (residual flow rate Qr) obtained by subtracting the boost flow rate Qbr from the flow rate Qst flowing out of the target bottom with the regeneration flow rate Qba as much as possible, the flow rate (return flow rate Qbt) discharged from the bottom chamber 301 to the oil tank 12 through the second boom control valve 15 can be minimized. Therefore, according to this embodiment, the regeneration efficiency of the accumulator 9 can be maximized.

[0088] (4) The control device 100 calculates the target boost flow rate Qbrt based on the target bottom outflow rate Qst and the pressure-bearing area ratio (Ar / Ab) of the bottom chamber 301 and the rod chamber 302 of the boom cylinder 3a. The control device 100 calculates the corrected target boost flow rate Qbr* corresponding to the elapsed time t by multiplying the correction coefficient c by the target boost flow rate Qbrt, wherein the correction coefficient c is a coefficient that increases from 0 to 1 corresponding to the elapsed time t from the start time point t0 of operating the boom operating lever 30. Thus, the corrected target boost flow rate Qbr*, which increases at a predetermined rate of change over time, is calculated. Furthermore, in this embodiment, after the corrected target boost flow rate Qbr* equals the target boost flow rate Qbrt, the correction process of multiplying the correction coefficient c = 1 by the target boost flow rate Qbrt is also performed, but the correction process can also be omitted after the corrected target boost flow rate Qbr* equals the target boost flow rate Qbrt. In this case, the target boost flow rate Qbrt is directly input into the boost valve opening calculation unit 105 to calculate the target opening area Abr of the boost valve 34.

[0089] Control device 100 calculates the remaining flow rate Qr by subtracting the corrected target boost flow rate Qbr from the target bottom outflow rate Qst. Control device 100 calculates the opening area when the working oil flow rate through regeneration valve 8 equals the remaining flow rate Qr, and uses this as the provisional target opening area Aba0. Control device 100 compares the provisional target opening area Aba0 with the maximum opening area Abamax of regeneration valve 8. When the provisional target opening area Aba0 is less than the maximum opening area Abamax of regeneration valve 8, control device 100 calculates the provisional target opening area Aba0 as the target opening area Aba of regeneration valve 8. When the provisional target opening area Aba0 is greater than the maximum opening area Abamax of regeneration valve 8, control device 100 calculates the maximum opening area Abamax as the target opening area Aba of regeneration valve 8.

[0090] The control device 100 calculates the estimated value of the regeneration flow rate Qba, i.e., the estimated regeneration flow rate Qba*, based on the target opening area Aba of the regeneration valve 8. The control device 100 subtracts the estimated regeneration flow rate Qba* from the remaining flow rate Qr to calculate the target return flow rate Qbt*. The control device 100 controls the booster valve 34 to make the booster flow rate Qbr equal to the corrected target booster flow rate Qbr*. The control device 100 controls the regeneration valve 8 to make its opening area equal to the target opening area Aba. The control device 100 controls the second boom control valve 15 to make the return flow rate Qbt equal to the target return flow rate Qbt*.

[0091] In this structure, the accumulator pressure Pa is compared with a predetermined value Pa0, without needing to change the calculation method according to the magnitude relationship between the accumulator pressure Pa and the predetermined value Pa0. When the accumulator pressure Pa is above the predetermined value Pa0 and the remaining flow rate Qr cannot be ensured by the regeneration flow rate Qba alone, the target return flow rate Qbt* is calculated as a value greater than 0. Thus, by opening the second boom control valve 15, the remaining flow rate Qr can be ensured by the regeneration flow rate Qba and the return flow rate Qbt.

[0092] (5) The hydraulic excavator 1 has: an accumulator pressure sensor 43 for detecting accumulator pressure (pressure of accumulator 9) Pa, a bottom pressure sensor 23 for detecting bottom pressure of boom cylinder 3a (pressure of bottom chamber 301) Pb, and a rod pressure sensor 24 for detecting rod pressure of boom cylinder 3a (pressure of rod chamber 302) Pr.

[0093] The control device 100 calculates the target opening area Abr of the booster valve 34 based on the bottom pressure Pb detected by the bottom pressure sensor 23, the rod pressure Pr detected by the rod pressure sensor 24, and the corrected target booster flow rate Qbr*. The control device 100 controls the booster valve 34 so that the opening area of ​​the booster valve 34 is equal to the target opening area Abr of the booster valve 34.

[0094] The control device 100 calculates a provisional target opening area Aba0 based on the accumulator pressure Pa detected by the accumulator sensor 43, the bottom pressure Pb detected by the bottom pressure sensor 23, and the remaining flow rate Qr. The control device 100 then calculates the target opening area Aba of the regeneration valve 8 based on the provisional target opening area Aba0 and the maximum opening area Abamax of the regeneration valve 8. The control device 100 controls the regeneration valve 8 such that its opening area is equal to the target opening area Aba.

[0095] The control device 100 calculates the estimated regeneration flow rate Qba* based on the accumulator pressure Pa detected by the accumulator pressure sensor 43, the bottom pressure Pb detected by the bottom pressure sensor 23, and the target opening area Aba of the regeneration valve 8. The control device 100 calculates the target opening area Abt of the second boom control valve 15 based on the bottom pressure Pb detected by the bottom pressure sensor 23 and the target return flow rate Qbt*. The control device 100 controls the second boom control valve 15 such that the opening area of ​​the second boom control valve 15 is equal to the target opening area Abt of the second boom control valve 15.

[0096] In this structure, the target opening area of ​​each flow control valve can be appropriately calculated based on the differential pressure across each flow control valve (pressure booster valve 34, regeneration valve 8, and second boom control valve 15). That is, according to this embodiment, each flow control valve can be controlled with high precision.

[0097] (6) The hydraulic excavator 1 has a boom cylinder 3b, a bucket cylinder 3c, and a swing motor 4 as hydraulic actuators different from the boom cylinder 3a. The hydraulic excavator 1 has: an actuator operating device (e.g., a bucket operating lever 44) that operates these hydraulic actuators, an actuator operating amount sensor (e.g., a bucket operating amount sensor 45) that detects the operating amount of the actuator operating device, and a supply valve (e.g., a bucket auxiliary valve 21) that controls the flow rate of working oil supplied from the accumulator 9 to the hydraulic actuators. The control device 100 controls the supply valve (e.g., the bucket auxiliary valve 21) based at least on the operating amount detected by the actuator operating amount sensor (e.g., the bucket operating amount sensor 45). In addition, the control device 100 considers not only the operating amount (e.g., the bucket operating amount) but also the accumulator pressure Pa detected by the accumulator sensor 43 when controlling the supply valve (e.g., the bucket auxiliary valve 21). For example, when the bucket operation amount is less than a specified value or the accumulator pressure Pa is less than a specified value, the control device 100 maintains the bucket auxiliary valve 21 in a closed state, and opens the bucket auxiliary valve 21 when the bucket operation amount is above the specified value and the accumulator pressure Pa is above the specified value.

[0098] According to this structure, the energy stored in the return oil of the boom cylinder 3a can be used to drive other hydraulic actuators, thereby improving energy efficiency (i.e., improving fuel efficiency).

[0099] The following modifications are also within the scope of the present invention, and one or more of the modifications may be combined with the above embodiments.

[0100] (Variation Example 1)

[0101] For example, in the above embodiment, the flow rate of the regeneration valve 8 is estimated based on the differential pressure ΔPba across the regeneration valve 8 and the target opening area Aba of the regeneration valve 8. However, a flow meter for measuring the flow rate of the regeneration valve 8 can also be provided. That is, the estimated regeneration flow rate Qba* in the above embodiment can be replaced with the value measured by the flow meter to perform various calculations. In this case, the regeneration valve 8 and the second boom control valve 15 can be controlled with higher precision.

[0102] (Variation Example 2)

[0103] 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 be a grab bucket, a crusher, a lifting magnet, etc., instead of a shovel bucket.

[0104] (Variation Example 3)

[0105] Two or more accumulators can be installed. The hydraulic pump that supplies working oil to the hydraulic actuator can be configured as a single unit or as three or more units.

[0106] (Variation Example 4)

[0107] The prime mover driving the hydraulic pumps (6, 7) is not limited to engine 5. The prime mover can also be an electric motor.

[0108] 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.

[0109] Symbol Explanation

[0110] 1…Hydraulic excavator (operating machinery), 1a…Boom, 1b…Stick, 1c…Bucket, 1d…Upper slewing body, 1e…Lower traveling body, 3a…Boom cylinder (hydraulic cylinder), 3b…Stick cylinder (hydraulic actuator), 3c…Bucket cylinder (hydraulic actuator), 3e…Travel motor (hydraulic actuator), 4…Slewing motor (hydraulic actuator), 5…Engine (prime mover), 6…First hydraulic pump (hydraulic pump), 7…Second hydraulic pump (hydraulic pump), 8…Regenerator valve (flow control valve), 9…Accumulator (pressure accumulator), 12…Oil tank, 13…Slewing control valve (flow control valve), 14…First boom control valve (flow control valve), 15…Second boom control valve (discharge valve, flow control valve), 16…First bucket 17… Second boom control valve (flow control valve), 18… Bucket control valve (flow control valve), 19… Boom auxiliary valve (supply valve, flow control valve), 20… Stick auxiliary valve (supply valve, flow control valve), 21… Bucket auxiliary valve (supply valve, flow control valve), 22… Swing auxiliary valve (supply valve, flow control valve), 23… Bottom pressure sensor (pressure sensor), 24… Boom pressure sensor (pressure sensor), 30… Boom operating lever (cylinder operating device), 31… Boom operating amount sensor (cylinder operating amount sensor), 34… Pressure boosting valve (flow control valve), 43… Accumulator sensor (pressure sensor), 44… Bucket operating lever (actuator operating device), 45… Bucket operating… 51…Actuator operation quantity sensor, 52…Working device, 100…Control device, 100a…Processing device, 100b…Non-volatile memory (storage device), 100c…Volatile memory (storage device), 101…Target bottom outflow calculation unit, 102…Boost flow calculation unit, 103…Slope limiting unit, 104…First differential pressure calculation unit, 105…Boost valve opening calculation unit, 106…Residual flow calculation unit, 107…Second differential pressure calculation unit, 108…Opening calculation unit, 109…Regeneration valve opening calculation unit, 110…Regeneration flow calculation unit, 111…Return flow calculation unit, 112…Second boom control valve opening calculation unit, 113…Boost valve command unit, 1 14…Regeneration valve command section, 115…Second boom control valve command section, 301…Bottom chamber, 302…Rod chamber, Aba…Target opening area of ​​regeneration valve, Aba0…Provisional target opening area of ​​regeneration valve, Abr…Target opening area of ​​booster valve, Abt…Target opening area of ​​second boom control valve (discharge valve), c…Correction coefficient, Lb…Operating amount, Pa…Accumulator pressure, Pa0…Specified value, Pb…Bottom pressure, Pr…Rod pressure, Qba…Regeneration flow rate, Qba*…Estimated regeneration flow rate, Qbr…Booster flow rate, Qbr*…Corrected target booster flow rate, Qbrt…Target booster flow rate, Qbt…Return flow rate, Qbt*…Target return flow rate, Qr…Residual flow rate, Qst…Target bottom outflow flow rate,ΔPba… Differential pressure across the regeneration valve, ΔPbr… Differential pressure across the booster valve, ΔPbt… Differential pressure across the second boom control valve (discharge valve).

Claims

1. A type of operating machinery, characterized in that, have: prime mover; A hydraulic pump, driven by the prime mover; A hydraulic cylinder having a base chamber and a rod chamber, driven by working oil ejected from the hydraulic pump; An accumulator that stores working oil supplied from the bottom chamber; A regeneration valve controls the flow rate of working oil flowing from the bottom chamber to the accumulator; A pressure boosting valve controls the flow rate of the working oil flowing from the bottom chamber to the rod chamber; A discharge valve controls the flow rate of the working oil flowing from the bottom chamber to the oil tank; A cylinder operating device that operates the hydraulic cylinder; A cylinder operation quantity sensor that detects the operation quantity of the cylinder operating device; and The control device controls at least the regeneration valve and the pressure boosting valve based on the operating amount detected by the cylinder operating amount sensor. The control device performs the following actions: The target bottom outflow rate and the target boost flow rate are calculated based on the operation amount detected by the cylinder operation amount sensor, wherein the target bottom outflow rate is the target value of the flow rate of the working oil flowing out of the bottom chamber of the hydraulic cylinder, and the target boost flow rate is the target value of the flow rate of the working oil supplied from the bottom chamber to the rod chamber through the boost valve. The pressure boosting valve is controlled such that the pressure boosting flow rate gradually increases with time at a predetermined rate of change until it becomes equal to the target pressure boosting flow rate, wherein the pressure boosting flow rate is the flow rate of working oil supplied from the bottom chamber to the rod chamber through the pressure boosting valve; In the transition state before the boosted flow rate reaches the target boosted flow rate and in the stable state after the boosted flow rate reaches the target boosted flow rate, the regeneration valve, or the regeneration valve and the discharge valve, are controlled such that the sum of the regeneration flow rate, the boosted flow rate, and the return flow rate is equal to the target bottom outflow rate. The regeneration flow rate is the flow rate of working oil supplied from the bottom chamber to the accumulator through the regeneration valve, and the return flow rate is the flow rate of working oil discharged from the bottom chamber to the oil tank through the discharge valve.

2. The operating machinery according to claim 1, characterized in that, The control device performs the following actions: When the pressure in the accumulator is less than a specified value, the regeneration valve is controlled so that the sum of the regeneration flow rate and the boost flow rate is equal to the target bottom outflow flow rate. When the pressure in the accumulator is above the specified value, the regeneration valve and the discharge valve are controlled so that the sum of the regeneration flow rate, the boost flow rate, and the return flow rate is equal to the target bottom outflow rate.

3. The operating machinery according to claim 1, characterized in that, The control device performs the following actions: The target pressure boosting flow rate is calculated based on the target bottom outflow rate and the ratio of the pressure-bearing area of ​​the bottom chamber to the rod chamber of the hydraulic cylinder. The corrected target boost flow rate is calculated based on the target boost flow rate and the elapsed time from the start time of operating the cylinder operating device; The remaining flow rate is calculated by subtracting the corrected target boost flow rate from the target bottom outflow rate. The opening area when the flow rate of the working oil through the regeneration valve is equal to the remaining flow rate is calculated and used as a provisional target opening area; Compare the provisional target opening area with the maximum opening area of ​​the regeneration valve; If the provisional target opening area is below the maximum opening area of ​​the regeneration valve, the provisional target opening area is calculated as the target opening area of ​​the regeneration valve. If the provisional target opening area is greater than the maximum opening area of ​​the regeneration valve, the maximum opening area is calculated as the target opening area of ​​the regeneration valve. The estimated value of the regeneration flow rate is calculated based on the target opening area of ​​the regeneration valve. The target return flow is calculated by subtracting the estimated regeneration flow from the remaining flow. Control the pressure boosting valve so that the pressure boosting flow rate is equal to the corrected target pressure boosting flow rate; Control the regeneration valve so that the opening area of ​​the regeneration valve is equal to the target opening area of ​​the regeneration valve; Control the discharge valve so that the return flow rate is equal to the target return flow rate.

4. The operating machinery according to claim 3, characterized in that, The operating machinery has: A pressure accumulator sensor that detects the pressure of the pressure accumulator device; A bottom pressure sensor that detects the pressure in the bottom chamber of the hydraulic cylinder; and A rod pressure sensor detects the pressure in the rod chamber of the hydraulic cylinder. The control device performs the following actions: The target opening area of ​​the booster valve is calculated based on the pressure in the bottom chamber detected by the bottom pressure sensor, the pressure in the rod chamber detected by the rod pressure sensor, and the corrected target booster flow rate. Control the pressure boosting valve so that the opening area of ​​the pressure boosting valve is equal to the target opening area of ​​the pressure boosting valve; The provisional target opening area is calculated based on the pressure of the accumulator device detected by the accumulator sensor, the pressure of the bottom chamber detected by the bottom pressure sensor, and the remaining flow rate; Calculate the target opening area of ​​the regeneration valve based on the provisional target opening area and the maximum opening area of ​​the regeneration valve; Control the regeneration valve so that the opening area of ​​the regeneration valve is equal to the target opening area of ​​the regeneration valve; The estimated regeneration flow rate is calculated based on the pressure of the accumulator device detected by the accumulator sensor, the pressure of the bottom chamber detected by the bottom pressure sensor, and the target opening area of ​​the regeneration valve; The target opening area of ​​the discharge valve is calculated based on the pressure in the bottom chamber detected by the bottom pressure sensor and the target return flow rate. Control the discharge valve so that the opening area of ​​the discharge valve is equal to the target opening area of ​​the discharge valve.

5. The operating machinery according to claim 1, characterized in that, The operating machinery includes: a vehicle body; and an operating device mounted on the vehicle body. The working device includes: a boom mounted on the vehicle body; a stick mounted on the boom; and a working tool mounted on the stick. The hydraulic cylinder is a boom cylinder that drives the boom. The operation amount detected by the cylinder operation amount sensor is the operation amount of operating the boom in the lowering direction.

6. The operating machinery according to claim 1, characterized in that, The operating machinery has: A hydraulic actuator, which is different from the hydraulic cylinder; An actuator operating device that operates the hydraulic actuator; Actuator operation quantity sensor, which detects the operation quantity of the actuator operating device; and A supply valve controls the flow rate of working oil supplied from the accumulator to the hydraulic actuator. The control device controls the supply valve based at least on the amount of operation detected by the actuator operation sensor.

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