Work machine

Abstract

A work machine is provided with: a flow control valve that controls a flow rate of working oil supplied to a hydraulic actuator; a central bypass route that guides the working oil from a pump to a tank via a central bypass passage portion of the flow control valve; a bypass switching valve that controls an opening of the central bypass route; an electromagnetic proportional valve that generates a pilot pressure that controls the bypass switching valve; a pilot valve that generates a pilot pressure that controls the flow control valve based on an operation amount of an operation device; and a control device that controls the electromagnetic proportional valve based on the operation amount. The control device controls the electromagnetic proportional valve in such a manner that an opening area of the bypass switching valve becomes smaller as the operation amount increases when the operation amount is smaller than a predetermined operation amount, and controls the electromagnetic proportional valve in such a manner that the opening area of the bypass switching valve becomes an opening area that is larger than a minimum opening area when the operation amount is a maximum operation amount.

Description

Technical Field

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

[0002] A working machine is known, comprising a hydraulic pump, a hydraulic actuator driven by working oil discharged from the hydraulic pump, a control valve for controlling the flow of working oil supplied from the hydraulic pump to the hydraulic actuator, and an operating device for operating the control valve (see Patent Document 1).

[0003] The hydraulic system of the working machine described in Patent Document 1 includes: a central bypass switching valve disposed downstream of a control valve corresponding to a specific hydraulic cylinder in the central bypass route; and a control mechanism that controls the operation of the central bypass switching valve to operate when the operating mechanism is operated to supply working oil to the cylinder chamber on the load holding side of the specific hydraulic cylinder, thereby causing the discharge pressure of the hydraulic pump to be higher than the load pressure of the specific hydraulic cylinder.

[0004] Patent Document 2 discloses a hydraulic circuit for lifting. In this hydraulic circuit that directly drives and controls the lifting of the boom cylinder, a bypass circuit is provided as a device to prevent oil slugging, connecting the bottom oil chamber of the load cylinder to the rod-side oil chamber via an electromagnetic on / off valve and a throttle valve. In the hydraulic circuit for lifting described in Patent Document 2, when the cylinder generating impact pressure starts or stops working, the control unit sends a command to open the bypass circuit to the electromagnetic on / off valve only at a preset time.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2011-85198

[0008] Patent Document 2: Japanese Patent Application Publication No. 2012-229777 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] In the hydraulic system described in Patent Document 1, when a return operation is performed on the control valve corresponding to a specific hydraulic cylinder, the opening of the central bypass switching valve is delayed compared to the return action of that control valve. This situation raises concerns about the generation of impact pressure. The generation of impact pressure leads to a decrease in work efficiency.

[0011] The technology described in Patent Document 2 aims to reduce the generation of impact pressure, but there is a concern that the generation of impact pressure cannot be prevented if the operation of the electromagnetic on / off valve in the bypass circuit is delayed compared to the operation of the hydraulic pilot three-position switching valve.

[0012] The purpose of this invention is to prevent the generation of impact pressure when the hydraulic actuator stops.

[0013] Solution for solving the problem

[0014] One aspect of the present invention comprises a working machine comprising: a pump that discharges working oil drawn from an oil tank; a hydraulic actuator driven by the working oil discharged from the pump; a flow control valve having a central bypass passage that guides the working oil from the pump to the oil tank in a neutral position, and controlling the flow rate of the working oil supplied to the hydraulic actuator based on the displacement from the neutral position; a central bypass route that guides the working oil supplied from the pump to the oil tank via the central bypass passage of the flow control valve; a bypass switching valve disposed downstream of the flow control valve in the central bypass route, controlling the opening of the central bypass route; a solenoid proportional valve that generates a pilot pressure for controlling the bypass switching valve; an operating device for operating the hydraulic actuator; a pilot valve that generates a pilot pressure for controlling the flow control valve based on the operating amount of the operating device; an operating amount detection device that detects the operating amount of the operating device; and a control device that controls the solenoid proportional valve based on the operating amount detected by the operating amount detection device. The control device is configured such that, when the operation amount detected by the operation amount detection device is within the range of a minimum operation amount and less than a predetermined operation amount, the electromagnetic proportional valve is controlled such that the opening area of ​​the bypass switching valve decreases to the minimum opening area as the operation amount increases; and when the operation amount detected by the operation amount detection device is the maximum operation amount, the electromagnetic proportional valve is controlled such that the opening area of ​​the bypass switching valve is an opening area larger than the minimum opening area.

[0015] The effects of the invention are as follows.

[0016] According to the present invention, it is possible to prevent the generation of impact pressure when the hydraulic actuator stops. Attached Figure Description

[0017] Figure 1 This is a side view of the hydraulic excavator according to the first embodiment.

[0018] Figure 2 This is a diagram showing the hydraulic system (hydraulic drive circuit) of the hydraulic excavator according to the first embodiment.

[0019] Figure 3 This is a diagram showing the opening characteristics of the central bypass passage and the inlet throttling passage of the flow control valve.

[0020] Figure 4 This is a diagram showing the opening characteristics of the bypass switching valve.

[0021] Figure 5 This is a block diagram illustrating the calculation and processing of the control current value of the electromagnetic proportional valve performed by the controller of the hydraulic excavator according to the first embodiment.

[0022] Figure 6 This is a diagram showing the target opening characteristics of the bypass switching valve.

[0023] Figure 7 This is a timing diagram showing the time changes in the opening area of ​​each valve and the pressure of the working oil during a boom return operation in a hydraulic excavator of the comparative example of the first embodiment.

[0024] Figure 8 This is a timing diagram showing the time changes in the opening area of ​​each valve and the pressure of the working oil during the boom return operation in the hydraulic excavator of the first embodiment.

[0025] Figure 9 This is a diagram showing the hydraulic system (hydraulic drive circuit) of the hydraulic excavator according to the second embodiment.

[0026] Figure 10 This is a block diagram illustrating the calculation and processing of the control current value of the electromagnetic proportional valve performed by the controller of the hydraulic excavator according to the second embodiment.

[0027] Figure 11 This is a diagram showing the first target opening characteristics and the second target opening characteristics of the bypass switching valve.

[0028] Figure 12 The following is a time-series diagram showing the time changes of the opening area of ​​each valve and the pressure of the working oil during the boom raising operation in the hydraulic excavator of the first embodiment. (a) is a time-series diagram when the temperature T of the working oil is above the threshold T0, and (b) is a time-series diagram when the temperature T of the working oil is below the threshold T0.

[0029] Figure 13 This is a timing diagram showing the time changes in the opening area of ​​each valve and the pressure of the working oil during the boom raising operation in the hydraulic excavator of the second embodiment.

[0030] Figure 14 This is a diagram showing the hydraulic system (hydraulic drive circuit) of the hydraulic excavator according to the third embodiment.

[0031] Figure 15 This is a block diagram illustrating the calculation and processing of the control current value of the electromagnetic proportional valve performed by the controller of the hydraulic excavator according to the third embodiment. Detailed Implementation

[0032] 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. The working machinery performs civil engineering work, construction work, dismantling work, dredging work, and other operations at the work site.

[0033] <First Implementation>

[0034] Figure 1 This is a side view of the hydraulic excavator 100 according to the first embodiment of the present invention. Figure 1 As shown, the hydraulic excavator 100 includes a body 105 and a working device 104 mounted on the body 105. The body 105 has a tracked traveling body 102 and a slewing body 103 rotatably mounted on the traveling body 102. The traveling body 102 travels by a pair of left and right tracks driven by a traveling motor 102A. The slewing body 103 is connected to the traveling body 102 via a slewing device having a slewing motor 103A, and is driven by the slewing motor 103A to rotate (slew) relative to the traveling body 102.

[0035] The slewing body 103 includes a cab 118 for the operator and an engine compartment that houses the engine and hydraulic equipment such as the hydraulic pump driven by the engine. The engine is the power source of the hydraulic excavator 100, and is composed of an internal combustion engine such as a diesel engine.

[0036] The working device 104 is a multi-joint type working device mounted on the slewing body 103, having multiple hydraulic actuators and multiple driven components (front components) driven by the multiple hydraulic actuators. The working device 104 is a structure in which three driven components (boom 111, stick 112, and bucket 113) are connected in series. The base end of the boom 111 is rotatably connected to the front part of the slewing body 103 via a boom pin. The base end of the stick 112 is rotatably connected to the front end of the boom 111 via a stick pin. The bucket 113 is rotatably connected to the front end of the stick 112 via a bucket pin.

[0037] The boom 111 is rotated by the extension and retraction of the boom cylinder 111A, which acts as a hydraulic actuator (hydraulic cylinder). The stick 112 is rotated by the extension and retraction of the stick cylinder 112A, which acts as a hydraulic actuator (hydraulic cylinder). The bucket 113 is rotated by the extension and retraction of the bucket cylinder 113A, which acts as a hydraulic actuator (hydraulic cylinder).

[0038] Figure 2 This is a diagram showing the hydraulic system (hydraulic drive circuit) of the hydraulic excavator 100 according to the first embodiment. Furthermore, for the sake of simplicity, Figure 2 Only the parts related to the drive of boom cylinder 111A are shown, while the parts related to the drive of other hydraulic actuators are omitted.

[0039] like Figure 2 As shown, the hydraulic system includes: an oil tank 4 for storing working oil as the working fluid; a main pump 1 and a pilot pump 9 driven by an engine (not shown) to discharge working oil drawn from the oil tank 4; a boom cylinder 111A driven by the working oil discharged from the main pump 1; a central bypass route 171 connecting the main pump 1 and the oil tank 4; a flow control valve 130 provided in the central bypass route 171; a bypass switching valve 6 provided downstream of the flow control valve 130 in the central bypass route 171; an electromagnetic proportional valve 7 for generating pilot pressure to control the bypass switching valve 6; an operating device 180 for operating the boom cylinder 111A; a controller 150 as a control device for controlling various parts of the hydraulic excavator 100; and pressure sensors 185A and 185B for detecting the pilot pressure acting on the pilot pressure sections 136 and 137 of the flow control valve 130. The central bypass route 171 is an oil passage that guides the working oil supplied from the main pump 1 to the oil tank 4 through the central bypass passage 131 of the flow control valve 130.

[0040] The main pump 1 is a variable-capacity hydraulic pump capable of changing its discharge capacity (displacement), while the pilot pump 9 is a fixed-capacity hydraulic pump with a constant discharge capacity. Alternatively, the main pump 1 can also be a fixed-capacity hydraulic pump.

[0041] The flow control valve (direction control valve) 130 controls the flow direction and flow rate of the working oil supplied from the main pump 1 to the boom cylinder 111A. When the tank pressure acts on the pilot pressure receiving section 136 and the pilot pressure receiving section 137 respectively, the flow control valve 130 is in a neutral position. The flow control valve 130 is a neutral fully open type control valve, having: a central bypass passage 131, which, in the neutral position, guides the working oil from the main pump 1 to the tank 4 via the central bypass route 171; an inlet throttling passage 132, which guides the working oil supplied from the main pump 1 to the boom cylinder 111A; and an outlet throttling passage 133, which guides the working oil (return oil) supplied from the boom cylinder 111A to the tank 4.

[0042] The flow control valve 130 controls the flow rate of working oil supplied to the boom cylinder 111A based on the amount of displacement (spool stroke) from the neutral position. The greater the displacement of the flow control valve 130 from the neutral position, the greater the speed of the boom cylinder 111A. Furthermore, if the flow control valve 130 moves from the neutral position to one side, the boom cylinder 111A extends; if the flow control valve 130 moves from the neutral position to the other side, the boom cylinder 111A retracts. In other words, the flow control valve 130 controls the driving direction and speed of the boom cylinder 111A.

[0043] Operating device 180 is an operating device for operating boom 111 (boom cylinder 111A, flow control valve 130), comprising an operating lever 181 as an operating component, a pilot valve 182 for boom raising that generates pilot pressure (hereinafter also referred to as operating pressure) for controlling flow control valve 130 based on the operating amount of the operating lever 181, and a pilot valve 183 for boom lowering. Operating device 180 is a hydraulically piloted operating device in which pilot valves 182 and 183 generate pilot pressure (operating pressure) corresponding to the operating direction and amount of the operating lever 181, and directly supply the pilot pressure generated by pilot valves 182 and 183 to flow control valve 130. The operating lever 181 is, for example, located on the right side of the driver's seat (see reference). Figure 1 The lever 181 is operated in the forward and backward direction. If the lever 181 is operated backward, the boom 111 moves in the upward direction. If the lever 181 is operated forward, the boom 111 moves in the downward direction.

[0044] The pilot valve 182 for boom raising reduces the pilot primary pressure supplied by the pilot pump 9, generating a pilot pressure (operating pressure) corresponding to the operating amount (rod stroke) in the boom raising direction of the operating lever 181. The operating pressure output from the pilot valve 182 for boom raising is guided via the pilot oil circuit to the pilot pressure receiving part 136 on one side (right side of the figure) of the flow control valve 130, driving the flow control valve 130 to the left in the figure. As a result, the working oil discharged from the main pump 1 is supplied to the bottom oil chamber 111b of the boom cylinder 111A through the inlet throttle passage 132 of the flow control valve 130, and the working oil in the rod side oil chamber 111r is discharged to the oil tank 4 through the outlet throttle passage 133 of the flow control valve 130. As a result, the boom cylinder 111A extends.

[0045] The pilot valve 183 for boom lowering reduces the pilot primary pressure supplied by the pilot pump 9, generating a pilot pressure (operating pressure) corresponding to the operating amount (rod stroke) in the boom lowering direction of the operating lever 181. The operating pressure output from the pilot valve 183 for boom lowering is guided via the pilot oil circuit to the pilot pressure receiving part 137 on the other side (left side of the figure) of the flow control valve 130, driving the flow control valve 130 in the right direction of the figure. As a result, the working oil discharged from the main pump 1 is supplied to the rod-side oil chamber 111r of the boom cylinder 111A through the inlet throttle passage of the flow control valve 130, and the working oil in the bottom-side oil chamber 111b is discharged to the oil tank 4 through the outlet throttle passage of the flow control valve 130. As a result, the boom cylinder 111A retracts.

[0046] Figure 3 This is a diagram showing the opening characteristics A1c of the central bypass passage 131 and the opening characteristics A2c of the inlet throttling passage 132 of the flow control valve 130. Figure 3In the diagram, the horizontal axis shows the operating pressure Po (pilot pressure generated by pilot valve 182) acting on the pilot pressure receiving section 136, and the vertical axis shows the opening area A1 of the central bypass passage section 131 and the opening area A2 of the inlet throttling passage section 132. The operating pressure Po approximately corresponds to the stroke of the flow control valve 130. Furthermore, the pressure in the pilot pressure receiving section 137 is the minimum pressure (tank pressure).

[0047] like Figure 3 As shown, when the flow control valve 130 is in the neutral position, that is, when the operating pressure Po acting on the pilot pressure receiving part 136 is the minimum pressure (tank pressure), the opening area A1 of the central bypass passage 131 becomes the maximum opening area A1max, and the inlet throttling passage 132 is fully closed (that is, the opening area A2 is 0).

[0048] If the operating pressure Po acting on the pilot pressure receiving section 136 increases, the stroke of the flow control valve 130 increases. The higher the operating pressure Po acting on the pilot pressure receiving section 136, the larger the opening area A2 of the inlet throttling passage section 132 and the smaller the opening area A1 of the central bypass passage section 131. If the operating pressure Po becomes a second operating pressure Po2 or higher, the central bypass passage section 131 is fully closed (i.e., the opening area A1 is 0). Furthermore, if the operating pressure Po becomes a predetermined pressure higher than the second operating pressure Po2, the opening area A2 of the inlet throttling passage section 132 becomes the maximum opening area A2max (A2max = A1max). Thus, the change in the opening area A1 of the central bypass passage section 131 relative to the operating pressure Po is inversely related to the change in the opening area A2 of the inlet throttling passage section 132 relative to the operating pressure Po. Furthermore, although not shown, the opening characteristics of the outlet throttling passage section 133 are approximately the same as the opening characteristics A2c of the inlet throttling passage section 132.

[0049] like Figure 2 As shown, the bypass switching valve 6 is a hydraulically pilot-operated control valve capable of controlling the opening of the central bypass route 171. The bypass switching valve 6 has a pilot pressure receiving part 6a that is acted upon by the pilot pressure (secondary pressure) generated by the electromagnetic proportional valve 7, and is controlled by the pilot pressure acting on the pilot pressure receiving part 6a.

[0050] The electromagnetic proportional valve 7 is located in the pilot oil circuit connecting the pilot pump 9 (not shown) driven by the engine to the pilot pressure receiving part 6a of the bypass switching valve 6. The electromagnetic proportional valve 7 reduces the pilot primary pressure supplied from the pilot pump 9, generating a pilot pressure corresponding to the control current from the controller 150. The electromagnetic proportional valve 7 is a pressure reducing valve whose pressure reduction decreases as the input control current increases. Therefore, if the control current input to the electromagnetic proportional valve 7 increases, the secondary pressure (pilot pressure) increases accordingly.

[0051] Figure 4 This is a diagram showing the opening characteristics A3c of the bypass switching valve 6. Figure 4 In the diagram, the horizontal axis shows the pilot pressure acting on the pilot pressure receiving part 6a (the pilot pressure generated by the electromagnetic proportional valve 7), and the vertical axis shows the opening area A3 of the bypass switching valve 6. For example... Figure 4 As shown, when the pilot pressure acting on the pilot pressure receiving part 6a is the minimum pressure (tank pressure), the bypass switching valve 6 is in the fully open position due to the force of the spring. If the pilot pressure acting on the pilot pressure receiving part 6a becomes a predetermined pressure Pp3 or higher, the bypass switching valve 6 is in the closed position. When the bypass switching valve 6 is in the closed position, the central bypass route 171 is cut off (i.e., the opening area A3 becomes 0). The more the pilot pressure Pp acting on the pilot pressure receiving part 6a increases, the smaller the opening area A3 of the bypass switching valve 6 becomes. Furthermore, in this first embodiment, as explained below, during the operation of the hydraulic excavator 100, the opening area A3 of the bypass switching valve 6 is controlled within a range of minimum opening area A3min (A3min > 0) and maximum opening area A3max, depending on the magnitude of the operating pressure Po (see reference). Figure 6 ).

[0052] like Figure 2 As shown, pressure sensor 185A detects the operating pressure Po output from pilot valve 182 for boom raising when boom raising is performed by operating lever 181, and outputs the detection result to controller 150. Pressure sensor 185B detects the operating pressure Po output from pilot valve 183 for boom lowering when boom lowering is performed by operating lever 181, and outputs the detection result to controller 150. The operating pressure Po detected by pressure sensors 185A and 185B is correlated (proportional) with the amount of operation of operating lever 181. Therefore, pressure sensors 185A and 185B function as operating amount detection devices for detecting the amount of operation of operating device 180.

[0053] The controller 150 is a control device that controls the electromagnetic proportional valve 7 based on the operating pressure Po (equivalent to the operating amount of the operating device 180) detected by pressure sensors 185A and 185B. The controller 150 consists of a computer equipped with a processor 151 (such as a CPU, MPU, or DSP), non-volatile memory 152 (such as ROM, flash memory, or hard disk drive), volatile memory 153 (such as RAM), an input interface 154, an output interface 155, and other peripheral circuitry. Furthermore, the controller 150 can be composed of a single computer or multiple computers.

[0054] The non-volatile memory 152 stores programs capable of performing various operations. That is, the non-volatile memory 152 is a storage medium capable of reading programs that implement the functions of this embodiment. The processor 151 is a processing device that expands the program stored in the non-volatile memory 152 into the volatile memory 153 and performs operations, and performs predetermined operations on signals imported from the input interface 154, the non-volatile memory 152, and the volatile memory 153 according to the program.

[0055] The input interface 154 converts the input signal into a value that can be processed by the processor 151. Furthermore, the output interface 155 generates an output signal corresponding to the processing result in the processor 151 and outputs this signal to a device such as the electromagnetic proportional valve 7.

[0056] Figure 5 This is a block diagram showing the calculation and processing of the control current value of the electromagnetic proportional valve 7 performed by the controller 150 of the hydraulic excavator 100 according to the first embodiment, showing the calculation and processing when the boom raising operation is performed. Figure 5 As shown, the controller 150 includes an opening area calculation unit 161, a pilot pressure calculation unit 162, and a current calculation unit 163. The functions of the opening area calculation unit 161, the pilot pressure calculation unit 162, and the current calculation unit 163 are performed by the processor 151 executing a program stored in the non-volatile memory 152.

[0057] The opening area calculation unit 161 refers to the target opening characteristic A3tc pre-stored in the non-volatile memory 152 and calculates the target opening area A3t as the target value of the opening area A3 of the bypass switching valve 6 based on the operating pressure Po detected by the pressure sensor 185A.

[0058] Figure 6 This is a diagram showing the target opening characteristic A3tc of the bypass switching valve 6. Furthermore, Figure 6 In the diagram, the opening characteristic A1c of the central bypass passage 131 of the flow control valve 130 is also shown by a dashed line. For example... Figure 6 As shown, the target opening characteristic A3tc is the characteristic of the target opening area A3t of the bypass switching valve 6 relative to the operating pressure Po acting on the pilot pressure section 136, and is stored in non-volatile memory 152 in tabular form.

[0059] The relationship between the operating pressure Po and the target opening area A3t, determined by the target opening characteristic A3tc, is as follows: Within the range where the operating pressure Po is above the minimum pressure (hereinafter also referred to as the minimum operating pressure) Pon and below the second operating pressure Po2, the target opening area A3t of the bypass switching valve 6 decreases to the minimum opening area A3min as the operating pressure Po increases. Specifically, when the operating pressure Po is the minimum operating pressure Pon (i.e., when the operating lever 181 is in the neutral position and the operating amount is 0), the target opening area A3t is the maximum opening area A3max. Within the range where the operating pressure Po is above the minimum operating pressure Pon and below the first operating pressure Po1, the target opening area A3t of the bypass switching valve 6 continuously decreases as the operating pressure Po increases, and becomes the minimum opening area A3min when the operating pressure Po is the first operating pressure Po1. Furthermore, within the range where the operating pressure Po is above the first operating pressure Po1 and below the second operating pressure Po2, the target opening area A3t of the bypass switching valve 6 is the minimum opening area A3min.

[0060] If the operating pressure Po increases and becomes the second operating pressure Po2, the target opening area A3t of the bypass switching valve 6 increases from the minimum opening area A3min to a predetermined opening area A30. In this first embodiment, within the range where the operating pressure Po is above the second operating pressure Po2 and below the maximum operating pressure Pox, the target opening area A3t of the bypass switching valve 6 is the predetermined opening area A30. The predetermined opening area A30 is a value that is larger than the minimum opening area A3min and less than or equal to the maximum opening area A3max.

[0061] like Figure 5As shown, the pilot pressure calculation unit 162 refers to the target pilot pressure characteristic Cp pre-stored in the non-volatile memory 152, and calculates the target pilot pressure Ppt, which is the target value of the pilot pressure Pp generated by the electromagnetic proportional valve 7, based on the target opening area A3t calculated by the opening area calculation unit 161. The target pilot pressure characteristic Cp is a characteristic that the target pilot pressure Ppt decreases as the target opening area A3t increases, and is stored in the non-volatile memory 152 in tabular form.

[0062] The current calculation unit 163 refers to the control current characteristic Ci pre-stored in the non-volatile memory 152 and calculates the control current value Ic supplied to the solenoid of the electromagnetic proportional valve 7 based on the target pilot pressure Ppt calculated by the pilot pressure calculation unit 162, and outputs the control current corresponding to the calculation result to the electromagnetic proportional valve 7. The control current characteristic Ci is such that the control current value Ic increases as the target pilot pressure Ppt increases.

[0063] The main operations of this first embodiment will be explained. Hereinafter, a lifting operation (hoisting operation) performed by a hydraulic excavator 100 will be used as an example. In the lifting operation, a hook with a metal wire attached to the back of the bucket 113 of the hydraulic excavator 100 is used to lift the load. Furthermore, in the lifting operation, the load is moved vertically by the raising and lowering movements of the boom 111. During the raising movement of the boom 111, the bottom oil chamber 111b of the boom cylinder 111A becomes the load-holding side.

[0064] If the operator operates the control lever 181 towards the boom raising side, the boom cylinder 111A extends, and the boom 111 rotates upward. Subsequently, if the operator performs a return operation to return the control lever 181 to the neutral position, the boom cylinder 111A decelerates and stops.

[0065] In this first embodiment, in the region where the operating pressure Po ranges from the minimum operating pressure Pon to the second operating pressure Po2 where the central bypass passage 131 of the flow control valve 130 is fully closed, the opening area of ​​the central bypass passage 171 becomes the combined opening area (effective area) of the flow control valve 130 and the bypass switching valve 6. This combined opening area is smaller than the opening area A1 of the central bypass passage 131.

[0066] This ensures the discharge pressure of the main pump 1 required for the operation of the boom cylinder 111A, and reduces the flow of working oil returning to the oil tank 4 from the central bypass route 171. As a result, energy loss is reduced, fuel efficiency is improved, and good micro-maneuverability is achieved.

[0067] The controller 150 of this first embodiment controls the electromagnetic proportional valve 7 in such a way that when the operating pressure Po detected by the pressure sensor 185A is the maximum operating pressure Pox, the opening area A3 of the bypass switching valve 6 is made to be a predetermined opening area A30 that is larger than the minimum opening area A3min.

[0068] Therefore, when the operator moves the operating lever 181 to its maximum position on the boom lifting side and then returns the operating lever 181 to the neutral position, no impact is generated, and the boom cylinder 111A can be smoothly decelerated and stopped. Hereinafter, the ability to stop the boom cylinder 111A without impact during the return operation of the operating lever 181 using the structure of this first embodiment will be explained by comparing it with a comparative example of this first embodiment.

[0069] Figure 7 This is a timing diagram showing the time changes in the opening area of ​​each valve and the pressure of the working oil during the boom return operation in the hydraulic excavator of the comparative example of this first embodiment. Figure 8 This is a timing diagram showing the time changes in the opening area of ​​each valve and the pressure of the working oil during the boom return operation in the hydraulic excavator of this first embodiment. Figure 7 and Figure 8 The timing diagram shown is for the case where the operating lever 181 is operated to its maximum operating position on the boom lifting side, and then returned to the neutral position. Furthermore, in the upper timing diagram showing the changes in opening area, the time variations of the opening area A1 of the central bypass passage 131 of the flow control valve 130, the opening area A2 of the inlet throttle passage 132, and the opening area A3 of the bypass switching valve 6 are shown. And in the lower timing diagram showing the changes in pressure, the time variations of the discharge pressure (also referred to as pump pressure) Ppu of the main pump 1, the working oil pressure (also referred to as bottom pressure) Pb of the bottom oil chamber 111b of the boom cylinder 111A, and the working oil pressure (also referred to as rod pressure) Pr of the rod side oil chamber 111r of the boom cylinder 111A are shown.

[0070] exist Figure 7 and Figure 8 In the middle, with time sequence Figure 1 This shows a simplified hydraulic circuit diagram used to illustrate the timing diagram and a target opening characteristic diagram of bypass switching valve 6. (See attached diagram.) Figure 7As shown, the hydraulic excavator of the comparative example of this first embodiment has the same structure as the hydraulic excavator 100 of this first embodiment, but the target opening characteristic A3tcc stored in the non-volatile memory 152 is different from the target opening characteristic A3tc described in this first embodiment. Specifically, the target opening characteristic A3tcc of the comparative example is the characteristic that the target opening area At becomes the minimum opening area A3min within the range where the operating pressure Po is above the second operating pressure Po2 and below the maximum operating pressure Pox.

[0071] like Figure 7 As shown, in the hydraulic excavator of the comparative example of this embodiment, if a return operation is started from the state where the operating lever 181 is operated to the maximum operating amount on the boom raising side (time t11), the flow control valve 130 begins to move towards the neutral position. As a result, from time t11, the opening area A2 of the inlet throttling passage 132 decreases, and the opening area A1 of the central bypass passage 131 increases.

[0072] The bypass switching valve 6 opens after a delay time Δt1 from the moment t11 ​​when the central bypass passage 131 of the flow control valve 130 begins to open. This explains the difference in responsiveness between the flow control valve 130 and the bypass switching valve 6. Due to the return operation of the operating lever 181, the pilot pressure (operating pressure) output from the pilot valve 182 decreases, and the flow control valve 130 begins its return operation.

[0073] In contrast, due to the decrease in pilot pressure output from the electromagnetic proportional valve 7, the bypass switching valve 6 begins its return action. The electromagnetic proportional valve 7 is controlled based on the control current output from the controller 150. After detecting a decrease in the operating pressure Po detected by the pressure sensor 185A, the controller 150 outputs a control current corresponding to the operating pressure Po to the electromagnetic proportional valve 7.

[0074] Thus, the operation of the bypass switching valve 6 is controlled by the controller 150. Therefore, the time required for communication and processing from the time the controller 150 obtains the detection result of the operating pressure Po until it outputs control current to the solenoid proportional valve 7 is cited as one reason for the response delay. Furthermore, the time from the input of control current to the solenoid proportional valve 7 until the change in pilot pressure acting on the pilot pressure receiving part 6a of the bypass switching valve 6 is also cited as one reason for the response delay. In contrast, the flow control valve 130 is not controlled by the controller 150, but is directly controlled by the operating pressure output from the operating device 180 according to the operator's operation. Therefore, the operation of the bypass switching valve 6 is delayed compared to the operation of the flow control valve 130.

[0075] If the action of the bypass switching valve 6 is delayed compared to the return action of the flow control valve 130, the pump pressure Ppu will rise because the opening area A1 of the central bypass passage 131 of the flow control valve 130 increases while the bypass switching valve 6 remains closed. As the pump pressure Ppu rises, the pressure of the working oil in the bottom oil chamber 111b of the boom cylinder 111A, which is connected to the main pump 1 via the inlet throttle passage 132, also increases, i.e., the bottom pressure Pb. If the bottom pressure Pb increases, the braking force (rod pressure Pr × pressure area of ​​rod-side oil chamber 111r - bottom pressure Pb × pressure area of ​​bottom-side oil chamber 111b) that decelerates the boom cylinder 111A weakens. Therefore, in the comparative example, while maintaining a relatively high speed for the boom cylinder 111A, the inlet throttle passage 132 and the outlet throttle passage 133 are closed, generating impact pressure in the rod-side oil chamber 111r (at time t12).

[0076] If impact pressure is generated when the boom cylinder 111A is stopped, impact and vibration will occur in the working device 104, making it difficult to position the working device 104. Furthermore, impact and vibration in the working device 104 will also lead to increased operator fatigue. Therefore, there is a concern that the generation of impact pressure may reduce the operating efficiency of the hydraulic excavator 100.

[0077] In contrast, in this first embodiment, as described above, if the operating pressure becomes a second operating pressure Po2 or higher, the controller 150 controls the electromagnetic proportional valve 7 such that the opening area A3 of the bypass switching valve 6 becomes a predetermined opening area A30. Therefore, in this first embodiment, as... Figure 8 As shown, when the operating lever 181 is operated to the maximum operating amount on the boom lifting side, the opening area A3 of the bypass switching valve 6 becomes the predetermined opening area A30.

[0078] When the operating lever 181 is returned from this state (at time t21), the bypass switching valve 6 is opened, allowing the working oil discharged from the main pump 1 to be released into the oil tank 4. This prevents the pump pressure Ppu and the bottom pressure Pb from rising, and the braking force is applied appropriately to the boom cylinder 111A, so the boom cylinder 111A decelerates and stops smoothly.

[0079] Thus, in this first embodiment, a delay time Δt2 occurs from the moment t21 when the flow control valve 130 begins its return operation until the bypass switching valve 6 begins to open (until the opening area A3 of the bypass switching valve 6 begins to increase). However, by opening the bypass switching valve 6 in advance, impact pressure can be prevented from being generated in the rod-side oil chamber 111r. In other words, in this first embodiment, impacts and vibrations in the working device 104 can be prevented, thus making it easier to position the working device 104. Furthermore, in this first embodiment, impacts and vibrations in the working device 104 can be prevented, thus reducing operator fatigue. As a result, the operating efficiency of the hydraulic excavator 100 can be improved.

[0080] According to the above implementation method, the following effects are achieved.

[0081] (1) The hydraulic excavator (operating machinery) 100 includes: a main pump (pump) 1 that discharges working oil drawn from the oil tank 4; a boom cylinder (hydraulic actuator) 111A that is driven by the working oil discharged from the main pump 1; a flow control valve 130 that has a central bypass passage 131 that guides the working oil from the main pump 1 to the oil tank 4 in a neutral position, and controls the flow rate of the working oil supplied to the boom cylinder 111A according to the displacement from the neutral position; a central bypass route 171 that guides the working oil supplied from the main pump 1 to the oil tank 4 via the central bypass passage 131 of the flow control valve 130; and a bypass switching valve 6 that is provided in the central bypass... Downstream of the flow control valve 130 in the bypass route 171, the opening of the central bypass route 171 is controlled; an electromagnetic proportional valve 7 generates a pilot pressure to control the bypass switching valve 6; an operating device 180 is used to operate the boom cylinder 111A; a pilot valve 182 generates an operating pressure (pilot pressure) to control the flow control valve 130 based on the operating amount of the operating device 180; a pressure sensor (operating amount detection device) 185A detects the operating pressure (operating amount) of the operating device 180; and a controller (control device) 150 controls the electromagnetic proportional valve 7 based on the operating pressure Po detected by the pressure sensor 185A.

[0082] The controller 150 controls the electromagnetic proportional valve 7 such that, within a range where the operating pressure Po detected by the pressure sensor 185A is above the minimum operating pressure Pon and below the second operating pressure Po2, the opening area A3 of the bypass switching valve 6 decreases to the minimum opening area A3min as the operating pressure Po increases. This reduces the energy loss of the main pump 1 and improves fuel efficiency. Furthermore, it provides good micro-operability.

[0083] When the operating pressure Po detected by the pressure sensor 185A is the maximum operating pressure Pox, the controller 150 controls the solenoid proportional valve 7 such that the opening area A3 of the bypass switching valve 6 is larger than the minimum opening area A3min (a predetermined opening area A30). This prevents the generation of impact pressure when the boom cylinder (hydraulic actuator) 111A stops. As a result, the operating efficiency of the hydraulic excavator 100 is improved.

[0084] (2) The central bypass passage 131 of the flow control valve 130 has the following opening characteristic A1c: within the range where the operating pressure Po is less than the second operating pressure Po2, the more the operating pressure Po increases, the smaller the opening area A1 becomes, and it is fully closed at the second operating pressure Po2. When the operating pressure Po detected by the pressure sensor 185A is above the second operating pressure Po2 and below the maximum operating pressure Pox, the controller 150 controls the electromagnetic proportional valve 7 to increase the opening area A3 of the bypass switching valve 6 from the minimum opening area A3min. As a result, energy loss can be reduced compared to the case where the opening area A3 of the bypass switching valve 6 increases from the minimum opening area A3min when the operating pressure Po is less than the second operating pressure Po2. Furthermore, by setting the target opening area A3t of the bypass switching valve 6 when the operating pressure Po is the second operating pressure Po2 to a predetermined opening area A30, the opening delay of the bypass switching valve 6 can be effectively prevented.

[0085] <Second Implementation>

[0086] Reference Figures 9 to 13 The hydraulic excavator 200 of the second embodiment will be described. Furthermore, in the figures, parts that are the same as or equivalent to those in the first embodiment are labeled with the same symbols, mainly illustrating the differences. Figure 9 Is with Figure 2 The same diagram illustrates the hydraulic system (hydraulic drive circuit) of the hydraulic excavator 200 according to the second embodiment. Figure 9 As shown, the hydraulic excavator 200 of the second embodiment has the same structure as the hydraulic excavator 100 of the first embodiment, but also has a temperature sensor 286 for detecting the temperature of the working oil passing through the bypass switching valve 6.

[0087] In this embodiment, temperature sensor 286 detects the temperature of the working oil stored in oil tank 4, which contains the working oil pumped up by main pump 1. Furthermore, the location of temperature sensor 286 is not limited to oil tank 4.

[0088] Figure 10 Is with Figure 5 The same diagram is a block diagram illustrating the calculation and processing of the control current value of the electromagnetic proportional valve 7 performed by the controller 250 of the hydraulic excavator 200 in the second embodiment. Figure 10 As shown, the controller 250 includes a first opening area calculation unit 261A, a second opening area calculation unit 261B, a selection unit 264, a pilot pressure calculation unit 162, and a current calculation unit 163. The first opening area calculation unit 261A has the same function as the opening area calculation unit 161 described in the first embodiment. The first opening area calculation unit 261A calculates the target opening area A3t of the bypass switching valve 6 based on the first target opening characteristic A3ac and the operating pressure Po detected by the pressure sensor 185A.

[0089] The second opening area calculation unit 261B refers to a second target opening characteristic A3bc that is different from the first target opening characteristic A3ac, and calculates the target opening area A3t of the bypass switching valve 6 based on the operating pressure Po detected by the pressure sensor 185A. Figure 11 This is a diagram showing the first target opening characteristic A3ac and the second target opening characteristic A3bc of the bypass switching valve 6. The first target opening characteristic A3ac and the second target opening characteristic A3bc are stored in tabular form in non-volatile memory 152. Figure 11 In the diagram, the first target opening characteristic A3ac is shown by a thin solid line, and the second target opening characteristic A3bc is shown by a thick solid line. Furthermore, Figure 11 In the diagram, the opening characteristic A1c of the central bypass passage 131 of the flow control valve 130 is also shown by dashed lines. The first target opening characteristic A3ac is the same as the target opening characteristic A3tc described in the first embodiment, so its description is omitted.

[0090] The relationship between the operating pressure Po and the target opening area A3t, determined by the second target opening characteristic A3bc, is as follows: When the operating pressure Po is the minimum operating pressure Pon, the target opening area A3t is the maximum opening area A3max. Within the range where the operating pressure Po is above the minimum operating pressure Pon but below the second operating pressure Po2, the target opening area A3t of the bypass switching valve 6 continuously decreases with increasing operating pressure Po until it reaches the minimum opening area A3min2. Furthermore, the minimum opening area A3min2 in the second target opening characteristic A3bc is larger than the minimum opening area A3min in the first target opening characteristic A3ac.

[0091] When the operating pressure Po is above the second operating pressure Po2, the target opening area A3t of the bypass switching valve 6 becomes a predetermined opening area A30 larger than the minimum opening area A3min2. Furthermore, the rate of change (slope) of the target opening area A3t relative to the operating pressure Po within the range where the operating pressure Po is above the minimum operating pressure Pon and below the third operating pressure Po3 is different from the rate of change (slope) of the target opening area A3t relative to the operating pressure Po within the range where the third operating pressure Po3 is above the third operating pressure and below the second operating pressure Po2. Moreover, the magnitudes of the operating pressures are in the order Pon < Po3 < Po1 < Po2 < Pox.

[0092] Within the range where the operating pressure Po is above the third operating pressure Po3 and below the second operating pressure Po2, the target opening area A3t determined by the second target opening characteristic A3bc is larger than the target opening area A3t determined by the first target opening characteristic A3ac.

[0093] like Figure 10 As shown, the selection unit 264 determines whether the temperature T of the working oil detected by the temperature sensor 286 is above or above the threshold T0. The threshold T0 is a threshold used to determine whether the working oil is in a low-temperature state and is pre-stored in the non-volatile memory 152. If the selection unit 264 determines that the temperature T of the working oil is above or above the threshold T0, it selects the target opening area A3t calculated by the first opening area calculation unit 261A and outputs it to the pilot pressure calculation unit 162. If the selection unit 264 determines that the temperature T of the working oil is below the threshold T0, it selects the target opening area A3t calculated by the second opening area calculation unit 261B and outputs it to the pilot pressure calculation unit 162. Furthermore, it is not limited to this; for example, the operating pressure and the working oil temperature can be input, and the target opening area A3t can be selected as a three-dimensional table.

[0094] The pilot pressure calculation unit 162 calculates the target pilot pressure Ppt based on the target opening area A3t selected by the selection unit 264. The current calculation unit 163 calculates the control current value Ic based on the target pilot pressure Ppt calculated by the pilot pressure calculation unit 162, and outputs the control current corresponding to the calculation result to the electromagnetic proportional valve 7.

[0095] The main operations of this second embodiment will be explained. Hereinafter, a lifting operation (hoisting operation) performed by the hydraulic excavator 200 will be used as an example. If the operator operates the control lever 181 towards the boom lifting side, the boom cylinder 111A extends, and the boom 111 rotates upward. The operator gradually increases the amount of operation of the control lever 181 (by performing micro-operations), thereby smoothly lifting the load by the working device 104.

[0096] Here, in the hydraulic excavator 100 of the first embodiment, if the temperature T of the working oil is low, there is a concern that the pressure loss of the working oil passing through the central bypass passage 131 of the flow control valve 130 and the bypass switching valve 6 will increase, and the boom cylinder 111A may not be able to operate smoothly.

[0097] In contrast, in this second embodiment, when the temperature T of the working oil detected by the temperature sensor 286 is low (T < T0), the controller 150 controls the electromagnetic proportional valve 7 in such a way that the opening area A3 of the bypass switching valve 6 is larger than when the temperature T is high (T ≥ T0).

[0098] Therefore, for example, when the operator operates the control lever 181 to the boom raising side, no impact is generated, and the boom cylinder 111A can move smoothly. Hereinafter, the fact that the boom cylinder 111A can be moved without impact during boom raising operation using the structure of this second embodiment will be explained by comparing it with the first embodiment.

[0099] Figure 12 (a) and Figure 12 (b) is a timing diagram showing the time changes in the opening area of ​​each valve and the pressure of the working oil during a boom raising operation in the hydraulic excavator 100 of the first embodiment. Figure 12 (a) is a time series diagram when the working oil temperature T is above the threshold T0. Figure 12 (b) is a time series diagram when the working oil temperature T is less than the threshold T0. Figure 13 This is a timing diagram showing the time changes in the opening area of ​​each valve and the pressure of the working oil during the boom raising operation in the hydraulic excavator 200 of this second embodiment. Figure 12 of (a), Figure 12 (b) and Figure 13 The timing diagram shown illustrates the operation of the control lever 181 from the neutral position towards the boom lifting side. Furthermore, the upper timing diagram, which shows the changes in opening area, illustrates the time variations of the opening area A1 of the central bypass passage 131 of the flow control valve 130, the opening area A2 of the inlet throttle passage 132, and the opening area A3 of the bypass switching valve 6. Additionally, the lower timing diagram, which shows the changes in pressure, illustrates the time variations of the pump pressure Ppu, the bottom pressure Pb of the boom cylinder 111A, and the rod pressure Pr of the boom cylinder 111A.

[0100] like Figure 12As shown in (a), in the first embodiment, when the working oil temperature T is above a predetermined temperature T0, if the operating lever 181 is operated from the neutral position toward the boom lifting side (at time t31), the flow control valve 130 is displaced from the neutral position. Consequently, from time t31, the opening area A1 of the central bypass passage 131 and the opening area A3 of the bypass switching valve 6 gradually decrease. Furthermore, the inlet throttling passage 132 opens from time t32, and the opening area A2 of the inlet throttling passage 132 increases with the increase in the amount of operation.

[0101] When the working oil temperature T is above the predetermined temperature T0, the pump pressure Ppu slowly rises from time t31. The pump pressure Ppu exceeds the bottom pressure Pb just before time t32 when the inlet throttle passage 132 is about to open. In this way, by making the pump pressure pp when the inlet throttle passage 132 opens consistent with the bottom pressure Pb, the operation of the boom cylinder 111A can be started smoothly. Therefore, the boom 111 can be moved slowly to raise the load.

[0102] However, as Figure 12 As shown in (b), if the working oil temperature T is lower than the predetermined temperature T0, the viscosity of the working oil increases, resulting in greater pressure loss when the working oil passes through the central bypass passage 131 of the flow control valve 130 and the bypass switching valve 6. Therefore, from the moment t41 when the operating lever 181 is moved from the neutral position to the boom raising side, the pump pressure Ppu rises sharply. That is, the rate of increase in pump pressure Ppu is greater compared to when the working oil temperature is higher (T≥T0). As a result, when the working oil temperature T is lower than the predetermined temperature T0, the pressure of the working oil flowing into the bottom oil chamber 111b of the boom cylinder 111A (i.e., the bottom pressure Pb) is higher than required when the boom raising operation is performed. Consequently, there is a concern about shock caused by sudden movement of the boom cylinder 111A. Thus, when the working oil temperature T is lower, micro-operability deteriorates, and positioning of the operating device 104 becomes difficult. Furthermore, if the working device 104 suddenly starts operating (if an impact occurs during the start-up operation), it will also lead to increased operator fatigue. Therefore, there is a concern that the sudden operation of the working device 104 may reduce the operating efficiency of the hydraulic excavator 100.

[0103] In contrast, in this second embodiment, as described above, when the working oil temperature T is less than a threshold T0, the controller 250 controls the electromagnetic proportional valve 7 in such a way that the opening area A3 of the bypass switching valve 6 is larger compared to when the working oil temperature T is greater than or equal to the threshold T0. Therefore, in this second embodiment, as... Figure 13As shown, from the moment t51 when the operation of the operating lever 181 is initiated from the neutral position towards the boom raising side, the opening area A1 of the central bypass passage 131 and the opening area A3 of the bypass switching valve 6 decrease, but at moment t52, the rate of decrease of the opening area A3 of the bypass switching valve 6 becomes smaller. Moment t52 is the moment before the moment the inlet throttling passage 132 begins to open. From moment t52 until moment t53 when the central bypass passage 131 is fully closed, the opening area A3 of the bypass switching valve 6 when the working oil temperature T is less than the threshold T0 is larger than the opening area A3 when the working oil temperature T is greater than or equal to the threshold T0. Therefore, the pressure loss of the working oil passing through the central bypass passage 131 of the flow control valve 130 and the bypass switching valve 6 is reduced, thus preventing a sudden increase in pump pressure Ppu. Consequently, a sudden increase in bottom pressure Pb is also prevented.

[0104] As described above, according to this second embodiment, when the working oil temperature is low, the working device 104 can be easily positioned because it can be prevented from suddenly starting to operate. Furthermore, in this second embodiment, when the working oil temperature is low, the operator's fatigue can be reduced because the working device 104 can be prevented from suddenly starting to operate. As a result, the operating efficiency of the hydraulic excavator 200 can be improved.

[0105] <Third Implementation Method>

[0106] Reference Figure 14 and Figure 15 The hydraulic excavator 300 of the third embodiment will be described. Furthermore, in the figures, parts that are the same as or equivalent to those of the second embodiment are marked with the same symbols, mainly illustrating the differences. Figure 14 Is with Figure 2 and Figure 9 The same diagram shows the hydraulic system (hydraulic drive circuit) of the hydraulic excavator 300 according to the third embodiment.

[0107] like Figure 14 As shown, the hydraulic excavator 300 of the third embodiment is equipped with multiple flow control valves 130A and 130B in the central bypass route 171. The flow control valves 130A and 130B, connected in series, have the same structure as the flow control valve 130 described in the first embodiment. Flow control valve 130A controls the flow direction and flow rate of the working oil supplied to the boom cylinder 111A, and flow control valve 130B controls the flow direction and flow rate of the working oil supplied to the stick cylinder 112A.

[0108] The hydraulic excavator 300 is equipped with an operating device 380 for operating the boom cylinder 112A and pressure sensors 385A and 385B for detecting the pilot pressure acting on the pilot pressure sections 136 and 137 of the flow control valve 130B.

[0109] Operating device 380 is an operating device for operating the boom 112 (boom cylinder 112A, flow control valve 130B), comprising an operating lever 381 as an operating component, a boom retraction pilot valve 382 for generating pilot pressure (operating pressure) to control the flow control valve 130B based on the operating amount of the operating lever 381, and a boom release pilot valve 383. Operating device 380 is a hydraulically pilot-operated operating device: pilot valves 382 and 383 generate pilot pressure (operating pressure) corresponding to the operating direction and amount of the operating lever 381, and directly supply the pilot pressure generated by pilot valves 382 and 383 to the flow control valve 130B. The operating lever 381 is, for example, located on the left side of the driver's seat (see reference). Figure 1 The stick 381 is operated in the left and right directions. If the stick 381 is operated to the left, a stick release action is performed. The stick release action is an action that rotates the stick 112 by moving the front end of the stick 112 away from the machine body 105. If the stick 381 is operated to the right, a stick retraction action is performed. The stick retraction action is an action that rotates the stick 112 by moving the front end of the stick 112 towards the machine body 105.

[0110] Pressure sensor 385A detects the operating pressure Po output from the pilot valve 382 for boom retraction when the boom retraction operation is performed by the operating lever 381, and outputs the detection result to the controller 350. Pressure sensor 385B detects the operating pressure Po output from the pilot valve 383 for boom release when the boom release operation is performed by the operating lever 381, and outputs the detection result to the controller 350.

[0111] When multiple flow control valves 130A and 130B are operated in combination by operating levers 181 and 381, the opening area (combined opening area) of the central bypass route 171 is reduced compared to the case of individual operation. Therefore, the supply-side pressure of the boom cylinder 111A, which supplies working oil to the flow control valve 130A upstream of the central bypass route 171 among the multiple flow control valves 130A and 130B connected in series, is higher than required. As a result, similar to the case where the working oil temperature is low as described in the second embodiment, there is a concern about shock occurring when the boom cylinder 111A begins to move.

[0112] Therefore, in this third embodiment, when multiple flow control valves 130A and 130B are operated in combination, the controller 350 controls the electromagnetic proportional valve 7 in such a way that the opening area A3 of the bypass switching valve 6 is larger than when they are operated individually.

[0113] Figure 15 Is with Figure 5 and Figure 10 The same diagram is a block diagram showing the calculation and processing of the control current value of the electromagnetic proportional valve 7 performed by the controller 350 of the hydraulic excavator 300 in the third embodiment. Figure 15 As shown, the controller 350 has a selection unit 364 instead of the selection unit 264 described in the second embodiment. The selection unit 364 determines whether it is in a combined operation state of simultaneously operating the flow control valve 130A and the flow control valve 130B based on the operating pressure Po detected by the pressure sensors 185A, 185B, 385A, and 385B.

[0114] If either the operating pressure Po detected by pressure sensors 185A and 185B is above the threshold Po0, and either the operating pressure detected by pressure sensors 385A and 385B is above the threshold Po0, the selection unit 364 determines that it is a combined operation state; otherwise, it determines that it is not a combined operation state. The threshold Po0 is a threshold used to determine whether the operating devices 180 and 380 are operated, and is predetermined and stored in the non-volatile memory 152. If the selection unit 364 determines that it is not a combined operation state (i.e., a single operation state), it selects the target opening area A3t calculated by the first opening area calculation unit 261A and outputs it to the pilot pressure calculation unit 162. If the selection unit 364 determines that it is a combined operation state, it selects the target opening area A3t calculated by the second opening area calculation unit 261B and outputs it to the pilot pressure calculation unit 162. Furthermore, it is not limited to this. For example, the operating pressure output from the operating device 180 and the operating pressure output from the operating device 380 can be input, and the target opening area A3t can be selected as a three-dimensional table.

[0115] Thus, in the third embodiment, multiple flow control valves 130A and 130B are provided in the central bypass route 171. When the multiple flow control valves 130A and 130B are operated in combination, the controller 350 controls the electromagnetic proportional valve 7 in such a way that the opening area A3 of the bypass switching valve 6 is larger than when they are operated individually.

[0116] Therefore, according to this third embodiment, when multiple flow control valves 130A and 130B are operated in combination, the working device 104 can be easily positioned because it can prevent sudden operation. Furthermore, in this third embodiment, because the working device 104 can be prevented from suddenly starting operation when multiple flow control valves 130A and 130B are operated in combination, operator fatigue can be reduced. As a result, the operating efficiency of the hydraulic excavator 300 can be improved.

[0117] The following variations are also within the scope of the present invention. The structures shown in the variations can be combined with the structures described in the above embodiments, or the structures described in the different embodiments described above can be combined with each other, or the structures described in the different variations below can be combined with each other.

[0118] <Variation Example 1>

[0119] In the first embodiment described above, an example was given in which the controller 150 controls the electromagnetic proportional valve 7 to increase the opening area A3 of the bypass switching valve 6 from the minimum opening area A3min when the operating pressure Po detected by the pressure sensor 185A is the second operating pressure Po2. However, the present invention is not limited thereto.

[0120] <Variation Example 1-1>

[0121] The controller 150 can also control the electromagnetic proportional valve 7 by increasing the opening area A3 of the bypass switching valve 6 from the minimum opening area A3min when the operating pressure Po is greater than the second operating pressure Po2. As described above, when the operating pressure Po is above the second operating pressure Po2 and below the maximum operating pressure Pox, energy loss can be reduced by controlling the electromagnetic proportional valve 7 by increasing the opening area A3 of the bypass switching valve 6 from the minimum opening area A3min.

[0122] <Variations 1-2>

[0123] The controller 150 can also control the electromagnetic proportional valve 7 by increasing the opening area A3 of the bypass switching valve 6 from the minimum opening area A3min when the operating pressure Po is less than the second operating pressure Po2. Furthermore, the lower the operating pressure Po at which the opening area A3 of the bypass switching valve 6 increases from the minimum opening area A3min, the greater the energy loss. Therefore, the operating pressure Po at which the opening area A3 of the bypass switching valve 6 increases from the minimum opening area A3min is preferably higher (i.e., close to the second operating pressure Po2).

[0124] <Variation Example 2>

[0125] In the first embodiment described above, an example of a hydraulically piloted operating device 180 was given, but the present invention is not limited thereto. The operating device 180 may also be an electrical operating device. The operating quantity of the electrical operating device is detected by an operating quantity detection device such as a potentiometer that detects the rotation angle of the operating lever. Based on the operating quantity detected by the operating quantity detection device, the controller 150 outputs a control current to the electromagnetic proportional valve (pilot valve). The electromagnetic proportional valve (pilot valve) reduces the pilot primary pressure supplied from the pilot pump 9 to generate a pilot pressure (operating pressure), and outputs the generated pilot pressure (operating pressure) to the pilot pressure receiving parts 136 and 137 of the flow control valve 130. In this structure, the electromagnetic proportional valve 7 that controls the bypass switching valve 6 and the electromagnetic proportional valve (pilot valve) that controls the flow control valve 130 are controlled by the controller 150 respectively, so it is difficult for the responsiveness to differ. However, due to differences in the length of the pilot oil circuit connecting the pilot pressure receiving part 136 of the flow control valve 130 and the solenoid proportional valve (pilot valve) and the pilot oil circuit connecting the bypass switching valve 6 and the solenoid proportional valve 7, as well as differences in valve characteristics, the action of the bypass switching valve 6 is sometimes delayed compared to the action of the flow control valve 130. Therefore, for hydraulic excavators equipped with electric operating devices, the same effect as described in the above embodiment can also be obtained.

[0126] <Variation Example 3>

[0127] In the first embodiment described above, a structure for preventing the generation of impact pressure in the boom cylinder 111A was explained, but the present invention is not limited thereto. Similarly, the generation of impact pressure in the stick cylinder 112A and the bucket cylinder 113A can also be prevented.

[0128] <Variation Example 4>

[0129] In the above embodiments, the example described is a tracked hydraulic excavator 100, but the present invention is not limited thereto. The present invention can be applied to various types of working machinery such as wheeled hydraulic excavators and wheeled loaders.

[0130] The embodiments of the present invention have been described above. However, the above embodiments only illustrate 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 structure of the above embodiments.

[0131] Symbol Explanation

[0132] 1—Main pump, 4—Oil tank, 6—Bypass switching valve, 7—Solenoid proportional valve, 9—Pilot pump, 100—Hydraulic excavator (operating machinery), 111A—Boom cylinder (hydraulic actuator), 112A—Stick cylinder (hydraulic actuator), 113A—Bucket cylinder (hydraulic actuator), 130—Flow control valve, 130A—Flow control valve, 130B—Flow control valve, 131—Central bypass passage, 132—Inlet section flow Section 133—Exit throttling section; 150—Controller (control device); 161—Opening area calculation unit; 162—Pilot pressure calculation unit; 163—Current calculation unit; 171—Central bypass route; 180—Operating device; 181—Operating lever (operating component); 182, 183—Pilot valves; 185A, 185B—Pressure sensors (operation quantity detection devices); 200—Hydraulic excavator (operating machinery). 250—Controller (control device), 261A—First opening area calculation unit, 261B—Second opening area calculation unit, 264—Selection unit, 286—Temperature sensor, 300—Hydraulic excavator (operating machinery), 350—Controller (control device), 364—Selection unit, 380—Operating device, 381—Operating lever (operating component), 382, ​​383—Pilot valve, 385A, 385B—Pressure sensor (operation quantity detection device), A1—Opening area of ​​central bypass passage, A1c—Opening characteristic of central bypass passage, A2—Opening area of ​​inlet throttling passage, A2c—Opening characteristic of inlet throttling passage, A3—Opening area of ​​bypass switching valve, A3ac—First target opening characteristic of bypass switching valve, A3bc—Second target opening characteristic of bypass switching valve, A3tc—Target opening characteristic of bypass switching valve.

Claims

1. A type of operating machinery, comprising: A pump that discharges working oil drawn from an oil tank; A hydraulic actuator, driven by working oil discharged from the aforementioned pump; A flow control valve having a central bypass passage that guides working oil from the pump to the oil tank in a neutral position, and controls the flow rate of working oil supplied to the hydraulic actuator based on the displacement from the neutral position. The central bypass route guides the working oil supplied from the pump to the oil tank via the central bypass passage of the flow control valve. A bypass switching valve is located downstream of the flow control valve in the central bypass route to control the opening of the central bypass route. An electromagnetic proportional valve generates a pilot pressure that controls the aforementioned bypass switching valve. An operating device for operating the aforementioned hydraulic actuator; A pilot valve that generates a pilot pressure to control the flow control valve based on the amount of operation of the aforementioned operating device; An operation quantity detection device, which detects the operation quantity of the above-mentioned operating device; as well as The control device controls the electromagnetic proportional valve based on the operation quantity detected by the operation quantity detection device. The aforementioned operating machinery is characterized by, The aforementioned control device is configured as follows: When the operation amount detected by the aforementioned operation amount detection device is within the range of above the minimum operation amount but below the predetermined operation amount, the electromagnetic proportional valve is controlled such that the opening area of ​​the bypass switching valve decreases to the minimum opening area as the operation amount increases. When the operation amount detected by the aforementioned operation amount detection device is the maximum operation amount, the electromagnetic proportional valve is controlled such that the opening area of ​​the bypass switching valve is larger than the minimum opening area. The central bypass passage of the aforementioned flow control valve has the following opening characteristics: within the range where the operating amount is less than the predetermined operating amount, the more the operating amount increases, the smaller the opening area becomes, and it is fully closed at the predetermined operating amount. The control device controls the electromagnetic proportional valve by increasing the opening area of ​​the bypass switching valve from the minimum opening area when the operation amount detected by the operation amount detection device is above the predetermined operation amount and below the maximum operation amount.

2. A type of operating machinery, comprising: A pump that discharges working oil drawn from an oil tank; A hydraulic actuator, driven by working oil discharged from the aforementioned pump; A flow control valve having a central bypass passage that guides working oil from the pump to the oil tank in a neutral position, and controls the flow rate of working oil supplied to the hydraulic actuator based on the displacement from the neutral position. The central bypass route guides the working oil supplied from the pump to the oil tank via the central bypass passage of the flow control valve. A bypass switching valve is located downstream of the flow control valve in the central bypass route to control the opening of the central bypass route. An electromagnetic proportional valve generates a pilot pressure that controls the aforementioned bypass switching valve. An operating device for operating the aforementioned hydraulic actuator; A pilot valve that generates a pilot pressure to control the flow control valve based on the amount of operation of the aforementioned operating device; An operation quantity detection device, which detects the operation quantity of the above-mentioned operating device; as well as The control device controls the electromagnetic proportional valve based on the operation quantity detected by the operation quantity detection device. The aforementioned operating machinery is characterized by, The aforementioned control device is configured as follows: When the operation amount detected by the aforementioned operation amount detection device is within the range of above the minimum operation amount but below the predetermined operation amount, the electromagnetic proportional valve is controlled such that the opening area of ​​the bypass switching valve decreases to the minimum opening area as the operation amount increases. When the operation amount detected by the aforementioned operation amount detection device is the maximum operation amount, the electromagnetic proportional valve is controlled such that the opening area of ​​the bypass switching valve is larger than the minimum opening area. It is equipped with a temperature sensor to detect the temperature of the working oil passing through the aforementioned bypass switching valve. When the temperature of the working oil detected by the temperature sensor is low, the control device controls the electromagnetic proportional valve by increasing the opening area of ​​the bypass switching valve compared to when the temperature is high.

3. A type of operating machinery, comprising: A pump that discharges working oil drawn from an oil tank; A hydraulic actuator, driven by working oil discharged from the aforementioned pump; A flow control valve having a central bypass passage that guides working oil from the pump to the oil tank in a neutral position, and controls the flow rate of working oil supplied to the hydraulic actuator based on the displacement from the neutral position. The central bypass route guides the working oil supplied from the pump to the oil tank via the central bypass passage of the flow control valve. A bypass switching valve is located downstream of the flow control valve in the central bypass route to control the opening of the central bypass route. An electromagnetic proportional valve generates a pilot pressure that controls the aforementioned bypass switching valve. An operating device for operating the aforementioned hydraulic actuator; A pilot valve that generates a pilot pressure to control the flow control valve based on the amount of operation of the aforementioned operating device; An operation quantity detection device, which detects the operation quantity of the above-mentioned operating device; as well as The control device controls the electromagnetic proportional valve based on the operation quantity detected by the operation quantity detection device. The aforementioned operating machinery is characterized by, The aforementioned control device is configured as follows: When the operation amount detected by the aforementioned operation amount detection device is within the range of above the minimum operation amount but below the predetermined operation amount, the electromagnetic proportional valve is controlled such that the opening area of ​​the bypass switching valve decreases to the minimum opening area as the operation amount increases. When the operation amount detected by the aforementioned operation amount detection device is the maximum operation amount, the electromagnetic proportional valve is controlled such that the opening area of ​​the bypass switching valve is larger than the minimum opening area. Multiple flow control valves as described above are installed in the aforementioned central bypass route. When the aforementioned multiple flow control valves are operated in combination, the aforementioned control device controls the aforementioned electromagnetic proportional valve in such a way that the opening area of ​​the aforementioned bypass switching valve is increased compared to when they are operated individually.

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