Work machine

Abstract

A working machine includes: a cylinder control valve that controls the flow of working oil from a hydraulic pump to a hydraulic cylinder; a first pressure reducing valve that reduces the pressure of the working oil injected from the hydraulic pump to generate a pilot primary pressure; a second pressure reducing valve that generates a secondary pressure acting on the pressure-receiving part of the cylinder control valve; a bypass shut-off valve; a third pressure reducing valve that generates a secondary pressure acting on the pressure-receiving part of the bypass shut-off valve; a regeneration passage connecting an inlet throttling passage and an outlet throttling passage; an outlet throttling section; and a control device. When the pressure of the hydraulic pump detected by a pressure sensor decreases, the control device controls the third pressure reducing valve to reduce the opening area of ​​the bypass shut-off valve. The greater the amount of operation that causes the working machine to work in the direction of gravity, the more the control device reduces the opening area of ​​the outlet throttling section.

Description

Technical Field

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

[0002] A known working machine includes: a main circuit that uses a cylinder control valve to control the supply of working oil injected from a hydraulic pump to a hydraulic cylinder; and a pilot circuit that uses a pilot pressure reducing valve to reduce the pressure of a portion of the working oil injected from the hydraulic pump, supplying it as pilot primary pressure to an electromagnetic proportional pressure reducing valve, and guiding the secondary pressure generated by the electromagnetic proportional pressure reducing valve to the cylinder control valve (see Patent Document 1). In the working machine described in Patent Document 1, a bypass sequence valve is provided in the bypass passage connecting the hydraulic pump and the oil tank. The bypass sequence valve is controlled to be in an open state when there is no manual operation signal from the operating device, and when there is a manual operation signal from the operating device, it is controlled so that the pressure at the inlet of the bypass sequence valve (i.e., the injection pressure of the hydraulic pump) becomes a pressure greater than or equal to the pilot primary pressure.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2001-263304 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] The working device includes a boom, stick, and bucket. In working machinery equipped with the aforementioned working device, when the working device is moved in the direction of gravity (hereinafter, the direction of gravity) during operations such as boom lowering when the bucket is in the air, or stick loading operations that pull the working device closer to the front when it is extended, the hydraulic pump's ejection pressure decreases. In the technology described in Patent Document 1, as described above, the bypass sequence valve is controlled so that the hydraulic pump's ejection pressure becomes a pressure greater than or equal to the pilot primary pressure.

[0008] However, when the weight and center of gravity of the working device change due to changes such as replacing the bucket installed at the front of the working device with a heavier bucket, and the inertial torque of the working device increases, the hydraulic pump's injection pressure may be lower than the pilot primary pressure when the working device is operated in the direction of gravity, even with the control of the bypass sequence valve alone. That is, in the technology described in Patent Document 1, it is sometimes difficult to ensure a stable pilot primary pressure when the specifications of the working device are changed.

[0009] The purpose of this invention is to provide a working machine that can ensure a stable pilot primary pressure when the working device is operated in the direction of gravity.

[0010] Methods for solving problems

[0011] An embodiment of the present invention provides a working machine comprising: a working device having a plurality of hydraulic cylinders and a plurality of drive components driven by the plurality of hydraulic cylinders; an operating device for operating the hydraulic cylinders; a main circuit for supplying working oil injected from a hydraulic pump to the hydraulic cylinders; a cylinder control valve disposed in the main circuit and controlling the flow of working oil supplied from the hydraulic pump to the hydraulic cylinders; a pilot circuit for guiding a portion of the working oil injected from the hydraulic pump to a pilot pressure-receiving portion of the cylinder control valve; and a first pressure-reducing valve disposed in the pilot circuit. A pilot primary pressure is generated by reducing the pressure of the working oil injected from the hydraulic pump; a second pressure reducing valve, located in the pilot circuit, reduces the pilot primary pressure to generate a pilot secondary pressure acting on the pilot pressure receiving part of the cylinder control valve; a central bypass passage connects the hydraulic pump and the oil tank and is equipped with the cylinder control valve; a bypass shut-off valve is located in the central bypass passage; and a third pressure reducing valve, located in the pilot circuit, reduces the pilot primary pressure to generate a pilot secondary pressure acting on the pilot pressure receiving part of the bypass shut-off valve. The system comprises: a regeneration passage connecting an inlet throttling passage and an outlet throttling passage, wherein the inlet throttling passage guides the working oil ejected from the hydraulic pump to the hydraulic cylinder, and the outlet throttling passage guides the return oil from the hydraulic cylinder to the oil tank; a check valve located in the regeneration passage, allowing the working oil to flow from the outlet throttling passage to the inlet throttling passage and prohibiting the flow of working oil from the inlet throttling passage to the outlet throttling passage; an outlet throttling section located in the outlet throttling passage; a pressure sensor detecting the pressure of the working oil on the ejection side of the hydraulic pump; and a control device controlling a second pressure reducing valve based on the operation amount of the operating device, wherein the control device controls a third pressure reducing valve based on the pressure detected by the pressure sensor. When the pressure detected by the pressure sensor decreases, the control device controls the third pressure reducing valve to reduce the opening area of ​​the bypass shut-off valve. The greater the operation amount performed by the operating device to make the working device work in the direction of gravity, the greater the reduction in the opening area of ​​the outlet throttling section by the control device.

[0012] Invention Effects

[0013] According to the present invention, when the working device is operated in the direction of gravity, a stable pilot primary pressure can be ensured. Attached Figure Description

[0014] Figure 1 This is a side view of a hydraulic excavator according to the first embodiment of the present invention.

[0015] Figure 2 This is a diagram showing the hydraulic system of a hydraulic excavator equipped with the first embodiment of the present invention.

[0016] Figure 3 This is a flowchart illustrating an example of a valve control process executed by the main controller according to the first embodiment of the present invention.

[0017] Figure 4 It is a graph showing the time series changes of the operating position of the door lock lever device, the boom lowering operation amount of the boom operating device, the injection pressure of the hydraulic pump, the injection capacity of the hydraulic pump, the opening area of ​​the bypass shut-off valve, and the opening area of ​​the outlet throttling section of the CT opening control valve.

[0018] Figure 5 This is a functional block diagram of the main controller according to the second embodiment of the present invention, showing the functions related to the control of the bypass shut-off valve.

[0019] Figure 6 This is a diagram illustrating a modified example of a hydraulic system according to an embodiment of the present invention. Detailed Implementation

[0020] Referring to the accompanying drawings, the working machinery according to an embodiment of the present invention will be described. In this embodiment, an example of a tracked hydraulic excavator will be described.

[0021] <First Embodiment>

[0022] Figure 1 This is a side view of the hydraulic excavator 1 according to the first embodiment of the present invention. For ease of explanation, as shown... Figure 1 The diagram shows the front-to-back and up-to-down directions of the hydraulic excavator 1. In this embodiment, unless otherwise specified, the area in front of the driver's seat (left-hand direction in this diagram) is defined as the front of the hydraulic excavator 1.

[0023] The hydraulic excavator 1 includes: a body (frame) 20 and a working device 10 mounted on the body 20. The body 20 includes: a traveling body 2 and a slewing body 3 rotatably mounted on the traveling body 2. The traveling body 2 includes: a pair of left and right tracks and a traveling hydraulic motor 2a as an actuator. The traveling body 2 travels by driving the tracks with the traveling hydraulic motor 2a. The slewing body 3 includes: a slewing frame 30, a slewing hydraulic motor 3a as an actuator, and a reduction mechanism that reduces the rotation of the slewing hydraulic motor 3a and transmits it to the slewing frame 30. The slewing body 3 rotates relative to the traveling body 2 by the slewing hydraulic motor 3a.

[0024] The slewing body 3 includes: a driver's cab 31 located on the front left side of the slewing frame 30; a counterweight 32 located at the rear of the slewing frame 30; and an engine compartment 33 located behind the driver's cab 31 within the slewing frame 30. The engine compartment 33 houses an engine serving as a prime mover, as well as hydraulic equipment such as hydraulic pumps, valves, and accumulators. The working device 10 is rotatably connected to the center of the front of the slewing frame 30.

[0025] The working device 10 is a multi-joint type working device, which includes: multiple drive components rotatably connected, and multiple hydraulic cylinders for driving the drive components. In this embodiment, the three drive components—boom 11, stick 12, and bucket 13—are connected in series. The base end of the boom 11 is rotatably connected to the front of the slewing frame 30. The base end of the stick 12 is rotatably connected to the front end of the boom 11. The bucket 13 is rotatably connected to the front end of the stick 12.

[0026] The boom 11 is driven by a hydraulic cylinder (hereinafter also referred to as boom cylinder 11a) acting as an actuator, and rotates relative to the slewing frame 30. The stick 12 is driven by a hydraulic cylinder (hereinafter also referred to as stick cylinder 12a) acting as an actuator, and rotates relative to the boom 11. The bucket 13 is driven by a hydraulic cylinder (hereinafter also referred to as bucket cylinder 13a) acting as an actuator, and rotates relative to the stick 12.

[0027] Figure 2 This diagram shows the hydraulic system 90 mounted on a hydraulic excavator 1. Furthermore, the hydraulic system 90 includes hydraulic devices for driving multiple hydraulic actuators (2a, 3a, 11a, 12a, 13a), but... Figure 2 The diagram only shows the hydraulic equipment used to drive the boom cylinder 11a and the stick cylinder 12a, while the diagrams of the hydraulic equipment used to drive other hydraulic actuators (2a, 3a, 13a) are omitted. Furthermore, while multiple hydraulic pumps 81 are usually used in driving the actuators, the following description will use a case where only one hydraulic pump 81 is used in driving the actuators as an example.

[0028] exist Figure 2 The diagram also shows the main controller 100, which serves as the control device for the hydraulic system 90, and a device that outputs signals to the main controller 100. Figure 2 As shown, the hydraulic excavator 1 includes: an engine control dial 21 for setting the target speed of the engine 80; an operating device (also referred to as a boom operating device) 23 for operating the boom cylinder 11a (boom 11); an operating device (also referred to as a stick operating device) 24 for operating the stick cylinder 12a (stick 12); and a door lock lever device 22. These devices (21-24) are located inside the cab 31.

[0029] The boom operating device 23 includes: an operating lever 23a, which can be tilted from a neutral position towards the boom raising side and the boom lowering side; and an operating sensor that detects the operating direction and amount of the operating lever 23a and outputs an operating signal indicating the operating direction and amount of the operating lever 23a to the main controller 100. The stick operating device 24 includes: an operating lever 24a, which can be tilted from a neutral position towards the stick loading side and the stick unloading side; and an operating sensor that detects the operating direction and amount of the operating lever 24a and outputs an operating signal indicating the operating direction and amount of the operating lever 24a to the main controller 100. The operating amount (operating angle) of the operating levers 23a and 24a detected by the operating sensors of the operating devices 23 and 24 is 0% (0°) in the neutral position, and its absolute value increases as the tilting distance from the neutral position increases.

[0030] The door lock lever device 22 includes a lever 22a, which is selectively operated to a locked position (raised position) that allows entry and exit of the driver's cab 31 and prohibits the operation of the actuators (11a, 12a, 13a), and an unlocked position (lowered position) that prohibits entry and exit of the driver's cab 31 and allows the operation of the actuators (11a, 12a, 13a). Additionally, the door lock lever device 22 includes an operation position sensor that detects the operation position of the lever 22a and outputs a door lock lever signal indicating the operation position of the lever 22a to the main controller 100.

[0031] The engine control dial 21 is an operating device used to set the target speed of the engine 80, and outputs an operating signal to the main controller 100. The main controller 100 determines the target speed based on the operating signal from the engine control dial 21, and outputs the determined target speed signal to the engine controller 105. The engine 80 is equipped with a speed sensor 80a that detects the actual speed of the engine 80, and a fuel injection device 80b that adjusts the amount of fuel injected into the cylinders of the engine 80. The engine controller 105 controls the fuel injection device 80b so that the actual speed of the engine 80 detected by the speed sensor 80a becomes the target speed output from the main controller 100.

[0032] The hydraulic system 90 includes: a hydraulic pump 81; a main circuit HC1 that supplies working oil, which is the working fluid ejected from the hydraulic pump 81, to the boom cylinder 11a and the stick cylinder 12a; a pilot circuit HC2 connected to the main circuit HC1; and a center bypass passage Lb that connects the hydraulic pump 81 to a tank 19 for storing working oil. The pilot circuit HC2 is a circuit that guides a portion of the working oil ejected from the hydraulic pump 81 to the following parts: the pilot pressure receiving parts 45a, 45b, 46a, and 46b of the cylinder control valves 45 and 46 (described later), the pilot pressure receiving part 17a of the bypass shut-off valve 17 (described later), and the pilot pressure receiving parts of the CT opening control valves 26A and 26B (described later).

[0033] Hydraulic pump 81 is connected to and driven by engine 80, drawing in and injecting working oil from oil tank 19. Hydraulic pump 81 is a variable-capacity piston-type hydraulic pump; the injection capacity (displacement) changes by adjusting the tilt angle of the swashplate via regulator 81a. Regulator 81a includes: a tilt actuator that controls the tilt angle of the swashplate of hydraulic pump 81; and an electromagnetic proportional valve that generates the control pressure of the tilt actuator using the injection pressure of hydraulic pump 81 as the initial pressure. Engine 80 is the power source of the hydraulic excavator 1, and is composed of an internal combustion engine such as a diesel engine.

[0034] The main circuit HC1 is equipped with: a cylinder control valve (hereinafter also referred to as boom control valve) 45, which controls the flow (flow rate and direction) of the working oil supplied from the hydraulic pump 81 to the boom cylinder 11a, and a cylinder control valve (hereinafter also referred to as stick control valve) 46, which controls the flow (flow rate and direction) of the working oil supplied from the hydraulic pump 81 to the stick cylinder 12a.

[0035] An overflow valve 47 is installed in the main circuit HC1. If the injection pressure (circuit pressure) of the hydraulic pump 81 exceeds the preset set pressure, the overflow valve 47 will spray the working oil injected from the hydraulic pump 81 into the oil tank 19, thereby specifying the maximum pressure of the injection pressure of the hydraulic pump 81.

[0036] The main circuit HC1 has: a pump discharge passage Ld connected to the outlet of the hydraulic pump 81, and a parallel passage Lp connected to the pump discharge passage Ld.

[0037] The parallel passage Lp is a passage that guides the working oil from the pump injection passage Ld to the pump ports of the boom control valve 45 and the stick control valve 46. That is, the parallel passage Lp constitutes part of the inlet throttling passage that guides the working oil injected from the hydraulic pump 81 to the hydraulic cylinder. A check valve 41 is provided in the parallel passage Lp connected to the pump port of the boom control valve 45 to maintain the load pressure of the boom cylinder 11a. The check valve 41 is fully closed when the pump injection pressure is lower than the cylinder pressure. A check valve 42 is provided in the parallel passage Lp connected to the pump port of the stick control valve 46 to maintain the load pressure of the stick cylinder 12a. The check valve 42 is fully closed when the pump injection pressure is lower than the cylinder pressure.

[0038] The oil tank port of the boom control valve 45 is connected to the oil tank 19 via the return oil passage 45r. The return oil passage 45r forms part of the outlet throttling passage that guides the return oil from the automatic boom cylinder 11a to the oil tank 19. A CT opening control valve (outlet throttling control valve) 26A is provided in the return oil passage 45r. The CT opening control valve 26A has an outlet throttling section 28A that applies resistance to the flow of the passing working oil, and the return oil from the automatic boom cylinder 11a is discharged to the oil tank 19 through the outlet throttling section 28A. The CT opening control valve 26A operates according to the pilot secondary pressure output from the solenoid valve 35A (described later), and the opening area (opening degree) of the outlet throttling section 28A changes. The return oil passage (outlet throttling passage) 45r of the boom control valve 45 is connected to the parallel passage (inlet throttling passage) Lp via a regeneration passage equipped with a regeneration check valve 27A. Check valve 27A is a non-return valve that allows working oil to flow from the return oil line 45r to the parallel passage Lp and prohibits the flow of working oil from the parallel passage Lp to the return oil line 45r.

[0039] For example, when the bucket 13 is not in contact with the ground and the working device 10 is held in the air, during a boom lowering operation that lowers the working device 10, the boom cylinder 11a retracts, causing the rod pressure to decrease and the bottom pressure to increase. The regeneration check valve 27A opens when the bottom pressure exceeds the rod pressure. As a result, a portion of the return oil from the bottom chamber is regenerated and supplied to the boom chamber through the check valve 27A, and the remainder returns to the oil tank 19 through the outlet throttle section 28A of the CT opening control valve 26A. Furthermore, when the boom lowering operation is performed with the bucket 13 on the ground, or when the boom pressure exceeds the bottom pressure due to a lifting action such as the lifting action of the machine body 20 performed by the working device 10, the regeneration check valve 27A closes completely.

[0040] A similar regeneration passage is also provided in the stick control valve 46. The oil tank port of the stick control valve 46 is connected to the oil tank 19 via the return oil passage 46r. The return oil passage 46r forms part of the outlet throttling passage that guides the return oil from the stick cylinder 12a to the oil tank 19. A CT opening control valve (outlet throttling control valve) 26B is provided in the return oil passage 46r. The CT opening control valve 26B has an outlet throttling section 28B that applies resistance to the flow of the working oil, through which the return oil from the stick cylinder 12a is discharged to the oil tank 19. The CT opening control valve 26B operates according to the pilot secondary pressure output from the solenoid valve 35B (described later), and the opening area (opening degree) of the outlet throttling section 28B changes.

[0041] The return oil passage (outlet throttle passage) 46r of the boom control valve 46 and the parallel passage (inlet throttle passage) Lp are connected via a regeneration passage equipped with a regeneration check valve 27B. The check valve 27B is a non-return valve that allows working oil to flow from the return oil passage 46r to the parallel passage Lp and prevents working oil from flowing from the parallel passage Lp back to the return oil passage 46r. The regeneration check valve 27B opens when the bottom pressure exceeds the boom pressure due to the contraction of the boom cylinder 12a. As a result, a portion of the return oil from the bottom chamber is regenerated and supplied to the boom chamber through the check valve 27B, and the remaining portion returns to the oil tank 19 through the outlet throttle portion 28B of the CT open control valve 26B. Furthermore, when the boom pressure exceeds the bottom pressure, the regeneration check valve 27B closes completely.

[0042] The central bypass passage Lb branches off from the pump discharge passage Ld and connects to the oil tank 19. A boom control valve 45, a stick control valve 46, and a bypass shut-off valve 17 are sequentially connected in series from upstream to downstream along the central bypass passage Lb. The bypass shut-off valve 17 has a throttling section that resists the flow of the working oil, through which the working oil ejected from the hydraulic pump 81 is discharged to the oil tank 19. By changing the opening area (opening degree) of the throttling section, the bypass shut-off valve 17 can adjust the pump discharge pressure.

[0043] The pilot circuit HC2 includes: a pilot pressure reducing valve (first pressure reducing valve) 71, which reduces the pressure of the working oil injected from the hydraulic pump 81 (i.e., the pump injection pressure) to generate a pilot primary pressure; a check valve 72, which maintains the pilot primary pressure; an accumulator 73, which smooths the pilot primary pressure; and a locking valve 74, which blocks the pilot primary pressure. Additionally, the pilot circuit HC2 includes: solenoid valves (second pressure reducing valves) 61A and 61B, which reduce the pilot primary pressure to generate a pilot secondary pressure acting on the pilot pressure receiving parts 45a and 45b of the boom control valve 45; and solenoid valves (second pressure reducing valves) 62A and 62B, which reduce the pilot primary pressure to generate a pilot secondary pressure acting on the pilot pressure receiving parts 46a and 46b of the stick control valve 46. In addition, a solenoid valve (third pressure reducing valve) 63 is provided in the pilot circuit HC2, which reduces the pilot primary pressure and generates a pilot secondary pressure that acts on the pilot pressure receiving part 17a of the bypass shut-off valve 17.

[0044] Furthermore, the pilot circuit HC2 is equipped with: a solenoid valve (fourth pressure reducing valve) 35A, which reduces the pilot primary pressure to generate a pilot secondary pressure acting on the pilot pressure-receiving part of the CT opening control valve 26A; and a solenoid valve (fourth pressure reducing valve) 35B, which reduces the pilot primary pressure to generate a pilot secondary pressure acting on the pilot pressure-receiving part of the CT opening control valve 26B. Solenoid valves 35A, 35B, 61A, 61B, 62A, 62B, and 63 are electromagnetic proportional valves driven by solenoid thrust, which is generated based on the control current supplied to the solenoid.

[0045] Solenoid valves 61A and 61B use the pilot primary pressure generated by the pilot pressure reducing valve 71 as the initial pressure to generate a pilot secondary pressure that is output to the pilot pressure receiving parts 45a and 45b of the boom control valve 45. Solenoid valves 61A and 61B are controlled according to the signal (control current) output from the main controller 100. The main controller 100 controls solenoid valves 61A and 61B according to the operating signal output from the slave boom operating device 23.

[0046] If the pilot secondary pressure generated by the solenoid valve 61A acts on the pilot pressure-receiving part 45a of the boom control valve 45, the boom control valve 45 switches to the extended position. As a result, the working oil injected from the hydraulic pump 81 is guided to the bottom chamber of the boom cylinder 11a, and the working oil is discharged from the boom chamber to the oil tank 19, causing the boom cylinder 11a to extend. Consequently, the boom 11 rotates upward (i.e., the boom 11 is raised).

[0047] If the pilot secondary pressure generated by the solenoid valve 61B acts on the pilot pressure-receiving part 45b of the boom control valve 45, the boom control valve 45 switches to the retracted position. This directs the working oil injected from the hydraulic pump 81 towards the rod chamber of the boom cylinder 11a, and discharges the working oil from the bottom chamber to the oil tank 19, causing the boom cylinder 11a to retract. As a result, the boom 11 rotates downwards (i.e., the boom 11 tilts).

[0048] Solenoid valves 62A and 62B use the pilot primary pressure generated by the pilot pressure reducing valve 71 as the initial pressure to generate a pilot secondary pressure that is output to the pilot pressure receiving parts 46a and 46b of the boom control valve 46. Solenoid valves 62A and 62B are controlled according to signals (control current) output from the main controller 100. The main controller 100 controls solenoid valves 62A and 62B according to operating signals output from the boom operating device 24.

[0049] If the pilot secondary pressure generated by the solenoid valve 62A acts on the pilot pressure-receiving part 46a of the stick control valve 46, the stick control valve 46 switches to the extended position. As a result, the working oil injected from the hydraulic pump 81 is guided to the bottom chamber of the stick cylinder 12a, and the working oil is discharged from the stick chamber to the oil tank 19, causing the stick cylinder 12a to extend. Consequently, the stick 12 rotates downwards (i.e., the stick 12 performs a shoveling action).

[0050] If the pilot secondary pressure generated by the solenoid valve 62B acts on the pilot pressure-receiving part 46b of the stick control valve 46, the stick control valve 46 switches to the retracted position. As a result, the working oil injected from the hydraulic pump 81 is guided to the stick chamber of the stick cylinder 12a, and the working oil is discharged from the bottom chamber to the oil tank 19, causing the stick cylinder 12a to retract. Consequently, the stick 12 rotates upwards (i.e., the stick 12 performs a tipping action).

[0051] Solenoid valve 63 uses the pilot primary pressure generated by pilot pressure reducing valve 71 as the initial pressure to generate a pilot secondary pressure output to the pilot pressure receiving section 17a of bypass shut-off valve 17. Solenoid valve 63 is controlled according to the signal (control current) output from main controller 100. Main controller 100 controls solenoid valve 63 according to the door lock lever signal output from door lock lever device 22, the operation signals output from operating devices 23 and 24, and the pressure detected by pressure sensor 25 (described later).

[0052] The bypass shut-off valve 17 controls the position of the valve core based on the pilot secondary pressure acting on the pilot pressure receiving part 17a. When the pilot secondary pressure is equivalent to the tank pressure, the valve core is held in the neutral position by the spring force of the return spring. At this time, the opening area of ​​the throttling part becomes the maximum opening area Abmax.

[0053] If the pilot secondary pressure acting on the pilot pressure receiving part 17a increases, the valve core moves against the spring force of the return spring, and the opening area of ​​the throttling part decreases. If the pilot secondary pressure acting on the pilot pressure receiving part 17a increases further, the valve core moves to the blocking position, and the connection between the hydraulic pump 81 and the oil tank 19 is blocked through the bypass shut-off valve 17. At this time, the opening area of ​​the throttling part becomes the minimum opening area Abmin (e.g., 0).

[0054] A locking valve 74 is provided between the pilot pressure reducing valve 71 and the solenoid valves 35A, 35B, 61A, 61B, 62A, 62B, and 63. The locking valve 74 is an electromagnetic switching valve that is switched to a blocking position or a connecting position by a control signal, wherein the control signal is output from the main controller 100 according to the operating position of the door lock lever device 22.

[0055] When the door lock lever device 22 is operated to the locked position, the locking valve 74 is switched to the blocking position. This blocks the pilot pressure to solenoid valves 61A, 61B, 62A, and 62B, and disables the operation of levers 23a and 24a. Furthermore, the pilot pressure to solenoid valve 63 is also blocked; therefore, regardless of the operation of devices 23 and 24, the bypass shut-off valve 17 is held in the neutral position.

[0056] When the door lock lever device 22 is operated to the unlocked position, the locking valve 74 is switched to the connected position. Therefore, when the door lock lever device 22 is operated to the unlocked position, the solenoid valves 61A, 61B, 62A, and 62B generate pilot secondary pressures corresponding to the operating direction and amount of the operating levers 23a and 24a, and the actuators (11a and 12a) corresponding to the operated levers 23a and 24a are activated.

[0057] Furthermore, as described above, a check valve 72 and an accumulator 73 are provided in the pilot circuit HC2, so that the pilot primary pressure can be maintained even when the injection pressure of the hydraulic pump 81 is temporarily lower than the set pressure of the pilot pressure reducing valve 71.

[0058] The main controller 100 is composed of a microcomputer having a CPU (Central Processing Unit) 101 as the operating circuit, a ROM (Read Only Memory) 102 as the storage device, a RAM (Random Access Memory) 103 as the storage device, an input / output interface 104, and other peripheral circuits. The main controller 100 can be composed of one microcomputer or multiple microcomputers. The engine controller 105 also has the same structure as the main controller 100 and is connected to the main controller 100 to exchange information (data).

[0059] ROM 102 is a non-volatile memory such as EEPROM, which stores programs capable of performing various operations. In other words, ROM 102 is a storage medium capable of reading programs that implement the functions of this embodiment. RAM 103 is a volatile memory, a working memory that directly inputs and outputs data with the CPU 101. RAM 103 temporarily stores necessary data during the execution of the program by the CPU 101. Furthermore, the main controller 100 may also include storage devices such as flash memory or hard disk drives.

[0060] CPU 101 is a processing device that expands and executes the program stored in ROM 102 in RAM 103. It performs prescribed processing on signals received from input / output interface 104, ROM 102, and RAM 103 according to the program. Signals from engine control dial 21, door lock lever device 22, operating devices 23 and 24, pressure sensor 25, engine controller 105, etc., are input to input / output interface 104. The input section of input / output interface 104 converts the input signals into signals that can be processed by CPU 101. Furthermore, the output section of input / output interface 104 generates an output signal corresponding to the processing result in CPU 101 and outputs this signal to locking valve 74, solenoid valves 35A, 35B, 61A, 61B, 62A, 62B, 63, and regulator 81a, etc.

[0061] Pressure sensor 25 detects the pressure of the working oil on the injection side of hydraulic pump 81. In this embodiment, pressure sensor 25 detects the injection pressure of hydraulic pump 81 (the circuit pressure of main circuit HC1) and outputs a signal indicating the detection result (pump injection pressure) to main controller 100. Main controller 100 controls the injection capacity of hydraulic pump 81 via regulator 81a based on the pump injection pressure detected by sensors 25 and 80a, the actual engine speed, and the operation signals from operating devices 23 and 24.

[0062] The hydraulic system 90 of this embodiment includes: a control valve block 4, which has a boom control valve 45, a stick control valve 46, a bypass shut-off valve 17, CT opening control valves 26A and 26B, check valves 27A, 27B, 41, and 42, and an overflow valve 47; a first solenoid valve block 5, which has solenoid valves 61A and 62A; a second solenoid valve block 6, which has solenoid valves 61B, 62B, and 63; a third solenoid valve block 8, which has solenoid valves 35A and 35B; and a pilot primary pressure generating block 7, which has a pilot pressure reducing valve 71, a check valve 72, and a locking valve 74.

[0063] Control valve block 4 distributes the working oil injected from hydraulic pump 81 to hydraulic cylinders such as boom cylinder 11a and stick cylinder 12a. Pilot primary pressure generating block 7 uses pilot pressure reducing valve 71 to reduce the working oil injected from hydraulic pump 81 to an appropriate set pressure (e.g., 4 MPa). When locking valve 74 is switched to the open position, the pilot primary pressure generated by pilot pressure reducing valve 71 is guided to the first to third solenoid valve blocks 5, 6, and 8. When locking valve 74 is switched to the closed position, the pilot primary pressure circuit of the first to third solenoid valve blocks 5, 6, and 8 is connected to oil tank 19. As a result, the primary pressure of solenoid valves 35A, 35B, 61A, 61B, 62A, 62B, and 63 is opened to near 0 (zero), and therefore, valves 17, 26A, 26B, 45, and 46 are held in the neutral position. Furthermore, the pilot primary pressure generating block 7 has a check valve 72 and an accumulator 73, so that even if the pump discharge pressure is lower than the set pressure of the pilot pressure reducing valve 71, the pilot primary pressure is temporarily maintained.

[0064] If operations such as lowering the boom while the bucket 13 is in the air, or loading the stick 12 in a vertical direction relative to the ground are performed, causing the working device 10 to work in the direction of gravity, the pump discharge pressure will decrease. When the pump discharge pressure decreases, the main controller 100 increases the pump discharge pressure by reducing the opening area of ​​the throttling section of the bypass shut-off valve 17, ensuring the pilot pressure. However, if the working device 10 becomes a different specification than the standard due to changes such as replacing the bucket 13, the weight of the working device 10 may increase, or the center of gravity of the working device 10 may be further away from the rotation center. In this case, the moment of inertia of the working device 10 increases. With the moment of inertia increased compared to the standard specification, when operations are performed that cause the working device 10 to work in the direction of gravity, the pump discharge pressure may be lower than the pilot pressure maintained by the check valve 72, even with the control of the bypass shut-off valve 17 alone.

[0065] Therefore, in this embodiment, when the working device 10 is operated in the direction of gravity, in addition to controlling the bypass shut-off valve 17, the CT opening control valves 26A and 26B are also controlled to reduce the opening of the outlet throttling sections 28A and 28B, thereby increasing the regeneration flow to the hydraulic cylinders 11a and 12a. This minimizes the consumption of pump ejection flow, allowing the hydraulic cylinders 11a and 12a to be driven at a speed corresponding to the operating amount, preventing the ejection pressure of the hydraulic pump 81 from falling below the set pressure of the pilot pressure reducing valve 71, and maintaining the pilot primary pressure.

[0066] Reference Figure 3 An example of the valve control process executed by the main controller 100 will be described. Figure 3 The process shown in the flowchart begins by turning on the ignition switch (not shown) and is repeated repeatedly in a prescribed control cycle.

[0067] like Figure 3 As shown, in step S100, the main controller 100 obtains the door lock bar signal from the door lock bar device 22, the operation signal from the operation devices 23 and 24, and the pressure signal from the pressure sensor 25, so that the processing proceeds to step S105.

[0068] In step S105, the main controller 100 determines whether the door lock lever device 22 has been operated to the unlocked position (lowered position) based on the door lock lever signal obtained in step S100. If it is determined in step S105 that the door lock lever device 22 has been operated to the unlocked position (i.e., a state where the actuator can move), the process proceeds to step S110. If it is determined in step S105 that the door lock lever device 22 has been operated to the locked position (raised position) (i.e., a state where the actuator cannot move), the process proceeds to step S115.

[0069] In step S115, the main controller 100 sets the target opening area Abt of the bypass shut-off valve 17 to the maximum opening area Abmax, and sets the target opening area Act of the CT opening control valves 26A and 26B to the maximum opening area Acmax, so that the process proceeds to step S180.

[0070] In step S110, the main controller 100 determines whether at least one of the operating devices 23 and 24 has been operated based on the operation signal obtained in step S100. If the operation amount of the operating devices 23 and 24 is above a predetermined value, the main controller 100 determines that the operating devices 23 and 24 have been operated. If the operation amount of the operating devices 23 and 24 is less than the predetermined value, the main controller 100 determines that the operating devices 23 and 24 have not been operated. If, in step S110, it is determined that at least one of the operating devices 23 and 24 has been operated, the process proceeds to step S120. If, in step S110, it is determined that neither of the operating devices 23 nor 24 has been operated, the process proceeds to step S125.

[0071] In step S125, the main controller 100 sets the non-operational opening area Abn to the target opening area Abt of the bypass shut-off valve 17, and sets the maximum opening area Acmax to the target opening area Act of the CT opening control valves 26A and 26B. Here, the non-operational opening area Abn is a value that is larger than the minimum opening area Abmin and smaller than the maximum opening area Abmax (Abmin < Abn < Abmax). The non-operational opening area Abn is set such that even if a slight pressure drop occurs, a pilot primary pressure sufficient to displace the valve core of control valves 45 and 46 to their maximum stroke can be generated. For example, if the pilot primary pressure sufficient to displace the valve core to its maximum stroke is 3.0 [MPa], the non-operational opening area Abn is an opening area sufficient to generate a pilot primary pressure of 3.3 [MPa], which is the lower limit pressure Pimin of the pilot primary pressure.

[0072] The opening area Abn used during non-operation is only required to generate a pilot primary pressure that allows the valve core to be displaced within a certain range of its maximum stroke (above the lower limit pressure Pimin and below the upper limit pressure Pimax). In this embodiment, when the door lock lever device 22 is operated to the unlocked position and the operating devices 23 and 24 are not operated (standby state), the opening area Abn used during non-operation is set so that the pump discharge pressure Pp becomes the upper limit pressure Pimax of the pilot primary pressure (for example, about 4 MPa).

[0073] In addition, the main controller 100 can also detect the pump injection flow rate that varies according to the temperature of the working oil and the engine speed, and calculate the opening area Abn used during non-operation, so that the injection pressure of the hydraulic pump 81 detected by the pressure sensor 25 converges within a certain range (above the lower limit pressure Pimin and below the upper limit pressure Pimax).

[0074] In step S120, the main controller 100 determines, based on the pressure signal obtained in step S100, whether the pump injection pressure Pp converges within a certain range (above the lower limit pressure Pimin and below the upper limit pressure Pimax). If, in step S120, the pump injection pressure Pp is determined to converge within a certain range, the process proceeds to step S130. If, in step S120, the pump injection pressure Pp is determined not to converge within a certain range, the process proceeds to step S135.

[0075] In step S130, the main controller 100 sets the target opening area Abt (previous value) set one control cycle ago to the target opening area Abt of the bypass shut-off valve 17, and sets the target opening area Act (previous value) set one control cycle ago to the target opening area Act of the CT opening control valves 26A and 26B, so that the process proceeds to step S180.

[0076] In step S135, the main controller 100 determines whether the pump discharge pressure Pp is higher than the upper limit pressure Pimax based on the pressure signal obtained in step S100. If the pump discharge pressure Pp is determined to be higher than the upper limit pressure Pimax in step S135, the process proceeds to step S140. If the pump discharge pressure Pp is determined to be lower than the upper limit pressure Pimax in step S135, the process proceeds to step S150.

[0077] In step S140, the main controller 100 determines whether the target opening area Abt of the bypass shut-off valve 17 is greater than or equal to the maximum opening area Abmax. If, in step S140, the target opening area Abt of the bypass shut-off valve 17 is determined to be greater than or equal to the maximum opening area Abmax, the process proceeds to step S130. If, in step S140, the target opening area Abt of the bypass shut-off valve 17 is determined to be less than the maximum opening area Abmax, the process proceeds to step S145.

[0078] In step S145, the main controller 100 sets the target opening area Abt (previous value) of the bypass shut-off valve 17 by adding a predetermined value ΔAb as the new target opening area Abt (current value). Additionally, the main controller 100 sets the target opening area Act (previous value) set one control cycle ago as the target opening area Act of the CT opening control valves 26A and 26B, causing the process to proceed to step S180.

[0079] In step S150, the main controller 100 determines whether the pump injection pressure Pp is lower than the lower limit pressure Pimin based on the pressure signal obtained in step S100. If, in step S150, the pump injection pressure Pp is determined to be lower than the lower limit pressure Pimin, the process proceeds to step S160. If, in step S150, the pump injection pressure Pp is determined to be higher than the lower limit pressure Pimin, the process returns to step S120.

[0080] In step S160, the main controller 100 determines whether the target opening area Abt of the bypass shut-off valve 17 is less than or equal to the minimum opening area Abmin. If, in step S160, the target opening area Abt of the bypass shut-off valve 17 is determined to be less than or equal to the minimum opening area Abmin, the process proceeds to step S170. If, in step S160, the target opening area Abt of the bypass shut-off valve 17 is determined to be greater than or equal to the minimum opening area Abmin, the process proceeds to step S175.

[0081] In S170, the main controller 100 sets the minimum opening area (e.g., 0) Acmin to the target opening area Act of the CT opening control valves 26A and 26B. Additionally, the main controller 100 sets the target opening area Abt (previous value) set one control cycle ago to the target opening area Abt of the bypass shut-off valve 17, causing the process to proceed to step S180.

[0082] In step S175, the main controller 100 sets the value obtained by subtracting a predetermined value ΔAb from the target opening area Abt (previous value) of the bypass shut-off valve 17 as the new target opening area Abt (current value). Additionally, the main controller 100 sets the target opening area Act (previous value) set one control cycle ago as the target opening area Act of the CT opening control valves 26A and 26B, causing the process to proceed to step S180.

[0083] In step S180, the main controller 100 outputs a control current to the solenoid valve 63 corresponding to the target opening area Abt of the bypass shut-off valve 17, causing the process to proceed to step S190. In step S190, the main controller 100 outputs a control current to the solenoid valves 61A and 61B corresponding to the target opening area Act of the CT opening control valves 26A and 26B, ending the process. Figure 3 The process is shown in the flowchart.

[0084] Reference Figure 4 The main actions of the hydraulic system 90 during the boom lowering operation are explained. Figure 4 This is a graph showing the time-series changes of the operating position Pg of the door lock lever device 22, the boom lowering operation amount L of the boom operating device 23, the injection pressure Pp of the hydraulic pump 81, the injection capacity (tilt angle of the ramp) q of the hydraulic pump 81, the opening area Ab of the bypass shut-off valve 17, and the opening area Ac of the outlet throttling section 28A of the CT opening control valve 26A. Figure 4In the diagram, the horizontal axis represents time (elapsed time). At time t0, the door lock lever device 22 is in the locked position, and the bucket 13 is fully away from the ground. At time t1, the operator moves the door lock lever device 22 to the unlocked position. This results in a state where the working device 10, based on the operating devices 23 and 24, can be operated (standby state). The opening area of ​​the bypass shut-off valve 17 decreases from the maximum opening area Abmax to the opening area Abn used during non-operation (refer to...). Figure 3 (Step S125). As the opening area of ​​the bypass shut-off valve 17 decreases, the discharge pressure Pp of the hydraulic pump 81 increases to the upper limit pressure Pimax. This ensures that the required pilot primary pressure, when the operating devices 23 and 24 are operated, becomes such that the pilot secondary pressure corresponding to the operating amount can be appropriately generated by the solenoid valves 61A, 61B, 62A, and 62B.

[0085] Starting at time t2, the operator performs a boom lowering operation via boom operating device 23. From time t2 to time t3, the operating amount L of boom operating device 23 gradually increases. From time t3 to time t4, the operating amount L is maintained at a micro-operation amount L1. As the operating amount L increases from time t2, the injection capacity q of hydraulic pump 81 increases. The valve core of boom control valve 45 shifts to the position corresponding to the operating amount L, and boom 11 lowers. As the operating amount L of the boom lowering operation increases, the injection pressure Pp of hydraulic pump 81 decreases.

[0086] If the injection pressure Pp of hydraulic pump 81 decreases to the lower limit pressure Pimin at time t3, the opening area Ab of bypass shut-off valve 17 decreases by a specified value ΔAb (refer to...). Figure 3 (Step S175). As a result, the ejection pressure Pp of the hydraulic pump 81 rises to the upper limit pressure Pimax.

[0087] From time t4 to time t5, the operating amount L of the boom operating device 23 gradually increases. From time t5 to time t6, the operating amount L is maintained at a half-operational operating amount L2. As the operating amount L increases from time t4, the injection capacity q of the hydraulic pump 81 increases. The valve core of the boom control valve 45 is displaced to the position corresponding to the operating amount L, and the lowering speed of the boom 11 increases. As the operating amount L of the boom lowering operation increases, the injection pressure Pp of the hydraulic pump 81 decreases.

[0088] If the injection pressure Pp of hydraulic pump 81 decreases to the lower limit pressure Pimin at time t5, the opening area Ab of bypass shut-off valve 17 decreases by a specified value ΔAb (refer to...). Figure 3 (Step S175). As a result, the ejection pressure Pp of the hydraulic pump 81 rises to the upper limit pressure Pimax.

[0089] From time t6 to time t7, the operating amount L of the boom operating device 23 gradually increases. From time t7 to time t8, the operating amount L is maintained at an operating amount L3 between half-operation and full operation. As the operating amount L increases from time t6, the injection capacity q of the hydraulic pump 81 increases. The valve core of the boom control valve 45 is displaced to the position corresponding to the operating amount L, and the lowering speed of the boom 11 increases. As the operating amount L of the boom lowering operation increases, the injection pressure Pp of the hydraulic pump 81 decreases.

[0090] If the injection pressure Pp of hydraulic pump 81 decreases to the lower limit pressure Pimin at time t7, the opening area Ab of bypass shut-off valve 17 decreases to the minimum opening area Abmin (e.g., 0) (refer to...). Figure 3 (Step S175). As a result, the ejection pressure Pp of the hydraulic pump 81 rises to the upper limit pressure Pimax.

[0091] From time t8 to time t9, the operating amount L of the boom operating device 23 gradually increases. From time t9 to time t10, the operating amount L is maintained at the maximum operating amount Lmax for full operation. As the operating amount L increases to the maximum operating amount Lmax from time t8, the injection capacity q of the hydraulic pump 81 increases to the maximum injection capacity (maximum tilt angle) qmax. The valve core of the boom control valve 45 is displaced to the maximum stroke position, and the descent speed of the boom 11 increases. As the operating amount L of the boom descent operation increases, the injection pressure Pp of the hydraulic pump 81 decreases.

[0092] If the injection pressure Pp of hydraulic pump 81 decreases to the lower limit pressure Pimin at time t9, then the opening area Ac of CT opening control valve 26A decreases from the maximum opening area Acmax to the minimum opening area Acmin (e.g., 0) (refer to...) Figure 3 (Step S170). As a result, the ejection pressure Pp of the hydraulic pump 81 rises to the upper limit pressure Pimax.

[0093] As described above, in this embodiment, when the bucket 13 is sufficiently far from the ground, during a boom lowering operation, for example, when the operating amount L is lower than the operating amount L3, the opening area of ​​the bypass shut-off valve 17 decreases, thereby increasing the discharge pressure Pp of the hydraulic pump 81 and preventing the discharge pressure Pp from being lower than the lower limit pressure Pimin of the set pressure of the pilot pressure reducing valve 71. Furthermore, during a boom lowering operation, for example, when the operating amount L is the maximum operating amount Lmax, in addition to the bypass shut-off valve 17, the opening area of ​​the outlet throttling section 28A of the CT opening control valve 26A also decreases. This increases the flow rate (regeneration flow rate) of the working oil discharged from the bottom chamber of the boom cylinder 11a and regenerated in the boom chamber. That is, sufficient flow is ensured on the inlet throttling side with minimal consumption of the hydraulic pump 81's discharge flow rate. As a result, the discharge pressure (circuit pressure on the inlet throttling side) Pp of the hydraulic pump 81 increases, preventing the discharge pressure Pp from being lower than the set pressure of the pilot pressure reducing valve 71. That is, according to this embodiment, when the bucket 13 is away from the ground, a stable pilot pressure can be ensured during the boom lowering operation, thereby preventing the cylinder speed from decreasing.

[0094] In addition, the operation of the bypass shut-off valve 17 and the CT opening control valve 26A during boom lowering operation is explained, but the operation of the bypass shut-off valve 17 and the CT opening control valve 26B during stick loading operation is the same.

[0095] According to the first embodiment described above, the following effects are achieved.

[0096] (1) When the pressure (ejection pressure Pp) detected by the pressure sensor 25 is lower than the lower limit pressure (first pressure) Pimin, and the opening area Ab of the bypass shut-off valve 17 is greater than the minimum opening area (first area) Abmin, the main controller (control device) 100 controls the solenoid valve (third pressure reducing valve) 63 to reduce the opening area Ab of the bypass shut-off valve 17 (refer to...). Figure 3Steps S150, S160, S175, and S180. Specifically, when the pressure Pp detected by pressure sensor 25 decreases, the main controller 100 controls the solenoid valve (third pressure reducing valve) 63, causing the opening area Ab of the bypass shut-off valve 17 to decrease. Consequently, when the working device 10 moves towards gravity due to boom lowering and stick loading operations, resulting in a decrease in the ejection pressure of the hydraulic pump 81, the bypass shut-off valve 17 is controlled to close, and the ejection pressure of the hydraulic pump 81 increases. Furthermore, when the pressure Pp detected by pressure sensor 25 is higher than the upper limit pressure (second pressure) Pimax (which is higher than the lower limit pressure Pimin), and the opening area Ab of the bypass shut-off valve 17 is less than the maximum opening area (second area) Abmax (which is larger than the minimum opening area Abmin), the main controller 100 controls the solenoid valve 63, causing the opening area Ab of the bypass shut-off valve 17 to increase (see reference). Figure 3 (Steps S135, S140, S145, S180). Therefore, when the ejection pressure of the hydraulic pump 81 increases, the bypass shut-off valve 17 is controlled to open, and the ejection pressure of the hydraulic pump 81 decreases. Thus, in this embodiment, because feedback control based on the ejection pressure Pp of the hydraulic pump 81 is performed, the ejection pressure Pp of the hydraulic pump 81 can be maintained within a certain range (above the lower limit pressure Pimin and below the upper limit pressure Pimax) regardless of the flow rate or temperature of the working oil.

[0097] Here, as described above, when the weight and center of gravity of the working device 10 are changed by replacing the bucket 13 installed at the front end of the working device 10 with a heavier bucket, etc., when the working device 10 is operated in the direction of gravity, the injection pressure of the hydraulic pump 81 may be lower than the pilot primary pressure by controlling the opening of the bypass shut-off valve 17 alone.

[0098] When the pressure Pp detected by pressure sensor 25 is lower than the lower limit pressure Pimin, and the opening area Ab of bypass shut-off valve 17 is below the minimum opening area, the main controller 100 of this embodiment controls solenoid valves (fourth pressure reducing valves) 35A and 35B to reduce the opening area of ​​outlet throttling sections 28A and 28B (see reference). Figure 3 (Steps S150, S160, S170, S190). That is, the hydraulic system 90 of this embodiment is configured such that the greater the amount of operation performed by the operating devices 23 and 24 to make the working device 10 work in the direction of gravity (boom lowering operation, stick loading operation), the smaller the opening area of ​​the outlet throttling sections 28A and 28B.

[0099] According to this structure, when the specifications of the working device 10 are changed, resulting in an increase in the inertial torque of the working device 10, and an operation is performed that causes the working device 10 to operate in the direction of gravity, in addition to the opening area of ​​the bypass shut-off valve 17, the opening areas of the outlet throttling sections 28A and 28B also decrease. The working oil required to maintain the speed of the hydraulic cylinders 11a and 12a is regenerated and supplied to the hydraulic cylinders through the regeneration passage. Therefore, according to this embodiment, when an operation is performed that causes the working device 10 to operate in the direction of gravity, a stable pilot primary pressure can be ensured, and as a result, a decrease in cylinder speed can be prevented.

[0100] (2) Under the condition that the pressure Pp detected by the pressure sensor 25 is lower than the lower limit pressure Pimin, and the opening area Ab of the bypass shut-off valve 17 is larger than the minimum opening area Abmin (in Figure 3 In step S150 (yes), and in step S160 (no), the main controller 100 controls the solenoid valve 63 so that the opening area Ab of the bypass shut-off valve 17 becomes the opening area of ​​the minimum specified value ΔAb (refer to...). Figure 3 Steps S175 and S180). Whenever the above conditions are met, the main controller 100 controls the solenoid valve 63, thereby periodically reducing the opening area Ab of the bypass shut-off valve 17 (refer to...). Figure 4 Therefore, it is possible to suppress rapid pressure changes in the main circuit HC1.

[0101] <Second Implementation>

[0102] Reference Figure 5 The main controller 100 controlling the hydraulic excavator 1 according to the second embodiment of the present invention will be described. Furthermore, for structures that are identical or equivalent to those described in the first embodiment, the differences will be explained primarily. Figure 5 This is a functional block diagram of the main controller 100 according to the second embodiment of the present invention, showing the functions related to the control of the bypass shut-off valve 17.

[0103] In the first embodiment, an example of feedback control based on the injection pressure Pp of the hydraulic pump 81 performed by the main controller 100 is described. In the first embodiment, when the injection pressure Pp is lower than the lower limit pressure Pimin, the main controller 100 increases the injection pressure Pp by decreasing the opening area of ​​the bypass shut-off valve 17; when the injection pressure Pp is higher than the upper limit pressure Pimax, it decreases the injection pressure Pp by increasing the opening area of ​​the bypass shut-off valve 17.

[0104] The main controller 100 of the second embodiment has the functions described in the first embodiment, and also has the function of controlling the opening area of ​​the bypass shut-off valve 17 according to the rotational speed of the hydraulic pump 81 and the temperature of the working oil so that the injection pressure Pp converges within a certain range (above the lower limit pressure Pimin and below the upper limit pressure Pimax). The control method (control mode) of the bypass shut-off valve 17 described in the first embodiment and the control method (control mode) of the bypass shut-off valve 17 to be described in this second embodiment can be switched, for example, by the operator performing a mode switching operation on the input device in the cab 31.

[0105] The main controller 100 in the second embodiment considers the effects of flow rate changes caused by changes in the rotational speed of the hydraulic pump 81 and viscosity changes caused by changes in the temperature of the working oil to control the opening area of ​​the bypass shut-off valve 17. For example, if the rotational speed of the hydraulic pump 81 increases while the opening area of ​​the bypass shut-off valve 17 is maintained at a predetermined area, the flow rate of the working oil through the bypass shut-off valve 17 increases, and the injection pressure of the hydraulic pump 81 increases. Therefore, while maintaining the opening area of ​​the bypass shut-off valve 17 at a predetermined area, when the rotational speed of the hydraulic pump 81 is at a predetermined speed and the injection pressure reaches the target pressure (e.g., 4 [MPa]), the opening area of ​​the bypass shut-off valve 17 needs to be larger than the predetermined area when the rotational speed of the hydraulic pump 81 is greater than the predetermined area. Similarly, while maintaining the opening area of ​​the bypass shut-off valve 17 at a predetermined area and the temperature of the working oil is at a predetermined temperature, when the injection pressure reaches the target pressure (e.g., 4 [MPa]), the opening area of ​​the bypass shut-off valve 17 needs to be larger than the predetermined area when the temperature of the working oil is lower than the predetermined temperature.

[0106] Therefore, it is preferable to store in advance, in tabular or functional form, the characteristics of the opening area of ​​the bypass shut-off valve 17 relative to the rotational speed of the hydraulic pump 81 such that the injection pressure becomes the target pressure, and the characteristics of the opening area of ​​the bypass shut-off valve 17 relative to the temperature of the working oil, in a non-volatile memory, and use these characteristics to control the opening area of ​​the bypass shut-off valve 17.

[0107] like Figure 5 As shown, the main controller 100 of this second embodiment includes: a first target area setting unit 111, a second target area setting unit 112, a minimum value selection unit 113, a proportional valve pressure setting unit 114, and a control current setting unit 118.

[0108] The hydraulic pump 81 is mechanically connected to the engine 80. Therefore, the speed sensor 80a functions as a sensor to detect the speed of the hydraulic pump 81. Alternatively, the sensor for detecting the speed of the hydraulic pump 81 can be installed separately from the speed sensor 80a of the engine 80. The temperature sensor 19a is installed in the oil tank 19, etc. (see reference). Figure 2The system detects the temperature of the working oil and outputs a signal indicating the detection result to the main controller 100.

[0109] The first target area setting unit 111 refers to a speed-opening table and sets the first target area Ab1 of the bypass shut-off valve 17 based on the rotational speed N of the hydraulic pump 81 detected by the speed sensor 80a. The speed-opening table is a data table that defines the relationship between the rotational speed N of the hydraulic pump 81 and the first target area Ab1, and is stored in non-volatile memory. The speed-opening table defines the characteristic that as the rotational speed N of the hydraulic pump 81 increases, the first target area Ab1 increases from the minimum opening area Abmin to the opening area Abn used during non-operation. Therefore, the larger the rotational speed N detected by the speed sensor 80a, the larger the first target area setting unit 111 sets the first target area Ab1 of the bypass shut-off valve 17 to. The rotational speed value of the speed-opening table uses a preset rotational speed value to obtain a pressure that "ensures a stable pilot primary pressure."

[0110] The second target area setting unit 112 refers to a temperature-opening table and sets the second target area Ab2 of the bypass shut-off valve 17 based on the working oil temperature To detected by the temperature sensor 19a. The temperature-opening table is a data table that defines the relationship between the working oil temperature To and the second target area Ab2, and is stored in non-volatile memory. The temperature-opening table defines the characteristic that as the working oil temperature To rises, the second target area Ab2 decreases from the non-operating opening area Abn to the minimum opening area Abmin. Therefore, the higher the temperature To detected by the temperature sensor 19a, the smaller the second target area setting unit 112 sets the second target area Ab2 of the bypass shut-off valve 17. The temperature value of the temperature-opening table uses a preset temperature value to obtain a pressure that "ensures a stable pilot primary pressure."

[0111] The minimum value selection unit 113 selects the smaller of the first target area Ab1 set by the first target area setting unit 111 and the second target area Ab2 set by the second target area setting unit 112, and sets it as the target opening area Abt of the bypass shut-off valve 17. In this way, the first target area setting unit 111, the second target area setting unit 112 and the minimum value selection unit 113 function as the target opening area setting unit for setting the target opening area of ​​the bypass shut-off valve 17.

[0112] The proportional valve pressure setting unit 114, referring to the open-proportional valve pressure gauge, sets the pilot secondary pressure generated by the solenoid valve 63, i.e., the proportional valve pressure po, based on the target open area Abt set by the minimum value selection unit 113. The open-proportional valve pressure gauge is a data table specifying the relationship between the target open area Abt and the proportional valve pressure po, and is stored in non-volatile memory. The open-proportional valve pressure gauge specifies that as the target open area Abt increases, the proportional valve pressure po decreases. Therefore, the larger the target open area Abt, the smaller the proportional valve pressure po is set to by the proportional valve pressure setting unit 114.

[0113] The control current setting unit 118 sets the control current I output to the solenoid valve 63 based on the proportional valve pressure po set by the proportional valve pressure setting unit 114. A data table specifying the relationship between these set proportional valve pressures po and the control current I is stored in non-volatile memory as a proportional valve pressure-control current table. The proportional valve pressure-control current table specifies that the control current I increases as the proportional valve pressure po increases. Therefore, the larger the proportional valve pressure po, the larger the control current setting unit 118 sets the control current I to. The control current setting unit 118 outputs the set control current I to the solenoid valve 63.

[0114] Thus, the higher the rotational speed N of the hydraulic pump 81 detected by the speed sensor 80a, the larger the first target area Ab1 of the bypass shut-off valve 17 will be set by the main controller 100 in this second embodiment. Conversely, the higher the temperature To of the working oil detected by the temperature sensor 19a, the smaller the second target area Ab2 of the bypass shut-off valve 17 will be set by the main controller 100 in this second embodiment. The main controller 100 selects the smaller of the first target area Ab1 and the second target area Ab2 as the target opening area Abt. The main controller 100 sets the control current I based on the set target opening area Abt, and controls the solenoid valve (third pressure reducing valve) 63 through the set control current I.

[0115] According to this structure, it achieves the same effect as the first embodiment. Furthermore, according to this second embodiment, the fluctuation risk based on feedback control can be avoided. Additionally, the bypass shut-off valve 17 can be appropriately controlled based on the rotational speed N of the hydraulic pump 81 and the temperature To of the working oil. Therefore, according to this second embodiment, when the working device 10 is operated in the direction of gravity, the pump ejection pressure Pp can be appropriately maintained at the target value Ppt.

[0116] The following variations are also within the scope of the present invention. The structures shown in the variations may be combined with the structures described in the above embodiments, or the structures described in the different embodiments described above may be combined with each other, or the structures described in the different variations below may be combined with each other.

[0117] <Variation Example 1>

[0118] In the above embodiments, an example is provided with a regeneration passage outside the cylinder control valves 45 and 46 and CT opening control valves 26A and 26B having outlet throttling sections 28A and 28B (see example). Figure 2 The invention has been described in detail, but is not limited thereto. For example... Figure 6 As shown, the regeneration passage and outlet throttling sections 28A and 28B can also be assembled inside the cylinder control valves 45 and 46. The outlet throttling sections 28A and 28B are configured such that, as the valve cores of the cylinder control valves 45 and 46 move from the neutral position, their opening areas increase, and then gradually decrease in proportion to the valve core displacement. Furthermore, the hydraulic system 90 of this modified example does not have the CT opening control valves 26A and 26B and the solenoid valves 35A and 35B described in the above embodiments.

[0119] According to this modified example, the opening areas of the outlet throttling sections 28A and 28B are adjusted by the displacement of the valve cores of the cylinder control valves 45 and 46, thus achieving the same effect as in the above-described embodiment. However, in this case, the opening areas of the outlet throttling sections 28A and 28B change with the displacement of the valve cores of the cylinder control valves 45 and 46, thus affecting the speed of the hydraulic cylinder during micro-operation and semi-operation. Furthermore, the outlet throttling sections 28A and 28B need to be defined according to the shape of the valve core and the orifice accommodating the valve core, therefore, the formation of the cylinder control valves 45 and 46 requires considerable effort. Therefore, it is preferable that, as in the above-described embodiment, the CT opening control valves 26A and 26B and the cylinder control valves 45 and 46 are configured to be independently controllable.

[0120] <Variation Example 2>

[0121] In the above embodiment, an example was described in which a pressure sensor 25, which detects the ejection pressure of the hydraulic pump 81, is used as the pressure sensor for detecting the pressure of the working oil on the ejection side of the hydraulic pump 81, and the main controller 100 controls the solenoid valve 63 based on the detection result of the pressure sensor 25. However, the present invention is not limited to this. The main controller 100 may also replace the detection result of the pressure sensor 25 with a pressure sensor 75 (see reference 75) that detects the pressure of the working oil on the ejection side of the hydraulic pump 81. Figure 2 and Figure 6The solenoid valve 63 is controlled based on the detection results of the pressure sensor 25, which is located upstream of the pilot pressure reducing valve 71 and is a pump pressure sensor that detects the discharge pressure of the hydraulic pump 81. Conversely, the pressure sensor 75, located downstream of the pilot pressure reducing valve 71, is an accumulator pressure sensor that detects the pressure of the accumulator 73. By configuring the solenoid valve 63 to be controlled based on the detection results of the pressure sensor 75 (which detects the pressure of the accumulator 73), the frequency of throttling of the bypass shut-off valve 17 can be reduced compared to a configuration that controls the solenoid valve 63 based on the detection results of the pressure sensor 25 (which detects the discharge pressure of the hydraulic pump 81).

[0122] <Variation Example 3>

[0123] In the first embodiment, the following example is illustrated: when the boom lowering operation is performed and the bypass shut-off valve 17 is fully closed, the CT opening control valve 26A is controlled to be fully closed to prevent a decrease in the ejection pressure Pp of the hydraulic pump 81; when the stick loading operation is performed and the bypass shut-off valve 17 is fully closed, the CT opening control valve 26B is controlled to prevent a decrease in the ejection pressure Pp of the hydraulic pump 81. However, the present invention is not limited thereto. The control of the CT opening control valve described in the first embodiment may also be applied to only one of the CT opening control valves 26A and 26B.

[0124] <Variation Example 4>

[0125] In the above embodiment, the structure in which working oil injected from a single hydraulic pump 81 is supplied to the boom cylinder 11a through the boom control valve 45 has been described as an example, but the present invention is not limited thereto. The present invention can also be applied, for example, to a structure in which working oil injected from two or more hydraulic pumps 81 is supplied to the boom cylinder 11a through multiple boom control valves 45. In this case, for one of the multiple boom control valves 45, the outlet throttle portion 28A is assembled as in the second embodiment, so that the boom control valve 45 with the outlet throttle portion 28A operates in the same way as the CT opening control valve 26A described in the first embodiment, thereby obtaining the same effect as in the first embodiment described above.

[0126] <Variation Example 5>

[0127] In the second embodiment, an example is described in which the main controller 100 selects the smaller of a first target area Ab1 set according to the rotational speed N of the hydraulic pump 81 and a second target area Ab2 set according to the temperature To of the working oil as the target opening area Abt of the bypass shut-off valve 17. That is, the main controller 100 of the second embodiment has a structure that takes into account both the rotational speed N of the hydraulic pump 81 and the temperature To of the working oil when setting the target opening area Abt. However, the method for setting the target opening area Abt is not limited to this method.

[0128] <Variation Example 5-1>

[0129] For example, the larger the rotational speed N detected by the speed sensor 80a, the larger the target opening area Abt of the bypass shut-off valve 17 can be set by the main controller 100, thus controlling the solenoid valve 63. In this configuration, the bypass shut-off valve 17 can be appropriately controlled according to the rotational speed N of the hydraulic pump 81.

[0130] <Variation Example 5-2>

[0131] For example, the higher the temperature To detected by the temperature sensor 19a, the smaller the target opening area Abt of the bypass shut-off valve 17 is set by the main controller 100, controlling the solenoid valve 63. In this configuration, the bypass shut-off valve 17 can be appropriately controlled according to the temperature To of the working oil.

[0132] <Variation Example 6>

[0133] In the above embodiment, an example was described where the bypass shut-off valve 17 is located downstream of the cylinder control valves 45 and 46 in the central bypass passage Lb, but the present invention is not limited thereto. The bypass shut-off valve 17 may also be located upstream of the cylinder control valves 45 and 46 in the central bypass passage Lb.

[0134] The embodiments of the present invention have been described above. However, the above embodiments only represent a part of the application examples of the present invention and are not intended to limit the technical scope of the present invention to the specific structures of the above embodiments.

[0135] Symbol Explanation

[0136] 1…Hydraulic excavator (operating machinery), 10…Working device, 11…Boom (driving object component), 11a…Boom cylinder (hydraulic cylinder), 12…Stick (driving object component), 12a…Stick cylinder (hydraulic cylinder), 13…Bucket (driving object component), 13a…Bucket cylinder (hydraulic cylinder), 17…Bypass shut-off valve, 17a…Pilot pressure receiving part, 19…Oil tank, 19a…Temperature sensor, 20…Body (body), 22…Door lock lever device, 23…Boom operating device (operating device), 24…Stick operating device (operating device), 25…Pressure sensor, 26A, 26B…CT open control valve (outlet throttle control valve), 27A, 27B…Check valve, 2 8A, 28B…Outlet throttling section, 35A, 35B…Solenoid valves (fourth pressure reducing valve), 45…Boom control valve (cylinder control valve), 45a, 45b…Pilot pressure receiving section, 45r…Return oil circuit (outlet throttling circuit), 46…Stick control valve (cylinder control valve), 46a, 46b…Pilot pressure receiving section, 46r…Return oil circuit (outlet throttling circuit), 61A, 61B, 62A, 62B…Solenoid valves (second pressure reducing valve), 63…Solenoid valve (third pressure reducing valve), 71…Pilot pressure reducing valve (first pressure reducing valve), 73…Accumulator, 74…Lock-in valve, 75…Pressure sensor, 80…Engine, 80a…Speed ​​sensor, 81…Hydraulic pump, 81a…Regulator, 90…Hydraulic system, 100…Main controller (control device), 111…First target area setting unit, 112…Second target area setting unit, 113…Minimum value selection unit, 114…Proportional valve pressure setting unit, 118…Control current setting unit, Ab…Opening area of ​​bypass shut-off valve, Ab1…First target area, Ab2…Second target area, Abmax…Maximum opening area (second area), Abmin…Minimum opening area (first area), Abn…Opening area used during non-operation, Abt…Target opening area of ​​bypass shut-off valve, Ac…Opening area of ​​CT opening control valve, Acmax…Maximum opening area, Acmin…Minimum opening area, A ct…Target opening area of ​​CT open control valve, HC1…Main circuit, HC2…Pilot circuit, I…Control current, L…Operating amount, Lb…Center bypass passage, Ld…Pump ejection passage, Lp…Parallel passage (inlet throttling passage), N…Speed ​​of hydraulic pump, Pimax…Upper limit pressure (second pressure), Pimin…Lower limit pressure (first pressure), po…Proportional valve pressure, po'…Corrected proportional valve pressure, Pp…Ejection pressure of hydraulic pump (measured value), Ppt…Target pressure value of working oil on the ejection side of hydraulic pump, q…Ejection capacity of hydraulic pump, To…Temperature of working oil, ΔAb…Specified value, Δpo…Corrected value, ΔPp…Pressure deviation (deviation).

Claims

1. A type of operating machinery, comprising: The working device has multiple hydraulic cylinders and multiple drive object components driven by the multiple hydraulic cylinders; An operating device for operating the hydraulic cylinder; The main circuit supplies the working oil injected from the hydraulic pump to the hydraulic cylinder; A cylinder control valve is provided in the main circuit and controls the flow of working oil supplied from the hydraulic pump to the hydraulic cylinder; A pilot circuit that guides a portion of the working oil injected from the hydraulic pump to the pilot pressure section of the cylinder control valve; A first pressure reducing valve is provided in the pilot circuit and reduces the pressure of the working oil injected from the hydraulic pump to generate a pilot primary pressure. The second pressure reducing valve is provided in the pilot circuit and reduces the pilot primary pressure to generate a pilot secondary pressure that acts on the pilot pressure receiving part of the cylinder control valve. A central bypass passage connects the hydraulic pump and the oil tank, and is equipped with the cylinder control valve; A bypass shut-off valve is provided in the central bypass passage; The third pressure reducing valve is installed in the pilot circuit and reduces the pilot primary pressure to generate a pilot secondary pressure that acts on the pilot pressure receiving part of the bypass shut-off valve. A regeneration passage connects an inlet throttle passage and an outlet throttle passage, wherein the inlet throttle passage guides the working oil injected from the hydraulic pump to the hydraulic cylinder, and the outlet throttle passage guides the return oil from the hydraulic cylinder to the oil tank; A check valve is provided in the regeneration passage and allows working oil to flow from the outlet throttle passage to the inlet throttle passage, while prohibiting the flow of working oil from the inlet throttle passage to the outlet throttle passage. An outlet throttling section is provided in the outlet throttling path; A pressure sensor detects the pressure of the working oil on the ejector side of the hydraulic pump; and A control device that controls the second pressure-reducing valve based on the amount of operation of the operating device. Its features are, The control device controls the third pressure-reducing valve based on the pressure detected by the pressure sensor. When the pressure detected by the pressure sensor decreases, the control device controls the third pressure reducing valve to reduce the opening area of ​​the bypass shut-off valve. The greater the amount of the operation performed by the operating device to make the working device work in the direction of gravity, the more the control device reduces the opening area of ​​the outlet throttling section.

2. The operating machinery according to claim 1, characterized in that, The operating machinery has: An outlet throttling control valve having the outlet throttling section; and The fourth pressure reducing valve is installed in the pilot circuit and reduces the pilot primary pressure to generate a pilot secondary pressure that acts on the pilot pressure receiving part of the outlet throttling control valve. If the pressure detected by the pressure sensor is lower than the first pressure, and the opening area of ​​the bypass shut-off valve is larger than the first area, the control device controls the third pressure reducing valve to reduce the opening area of ​​the bypass shut-off valve. When the pressure detected by the pressure sensor is higher than a second pressure (which is higher than the first pressure), and the opening area of ​​the bypass shut-off valve is smaller than a second area (which is larger than the first area), the control device controls the third pressure reducing valve to increase the opening area of ​​the bypass shut-off valve. When the pressure detected by the pressure sensor is lower than the first pressure and the opening area of ​​the bypass shut-off valve is lower than the first area, the control device controls the fourth pressure reducing valve to reduce the opening area of ​​the outlet throttling section.

3. The operating machinery according to claim 2, characterized in that, If the pressure detected by the pressure sensor is lower than the first pressure and the opening area of ​​the bypass shut-off valve is greater than the first area, the control device controls the third pressure reducing valve to make the opening area of ​​the bypass shut-off valve smaller than a predetermined value. The control device controls the third pressure reducing valve whenever the condition is met, thereby reducing the opening area of ​​the bypass shut-off valve in stages.

4. The operating machinery according to claim 1, characterized in that, The operating machinery has: A speed sensor that detects the speed of the hydraulic pump; and The temperature sensor detects the temperature of the working oil. The higher the rotational speed detected by the speed sensor, the larger the first target area of ​​the bypass shut-off valve will be set by the control device. The higher the temperature detected by the temperature sensor, the smaller the second target area of ​​the bypass shut-off valve will be set by the control device. The control device selects the smaller of the first target area and the second target area and sets it as the target opening area of ​​the bypass shut-off valve. The control device controls the third pressure reducing valve.

5. The operating machinery according to claim 1, characterized in that, The operating machinery includes: a speed sensor that detects the speed of the hydraulic pump. The higher the rotational speed detected by the speed sensor, the larger the target opening area of ​​the bypass shut-off valve will be set by the control device. The control device controls the third pressure reducing valve.

6. The operating machinery according to claim 1, characterized in that, The operating machinery includes: a temperature sensor that detects the temperature of the working oil. The higher the temperature detected by the temperature sensor, the smaller the target opening area of ​​the bypass shut-off valve will be set by the control device. The control device controls the third pressure reducing valve.

7. The operating machinery according to claim 1, characterized in that, The pressure sensor is located downstream of the first pressure reducing valve.

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