Hydraulic system

Abstract

The present application aims to provide a hydraulic system capable of making a control pressure output from a solenoid valve rapidly follow a control required value at the start of driving of the solenoid valve. To this end, the hydraulic system is provided with: a solenoid valve generating a control pressure for making a control valve act; an operating device performing an operation for inputting a control required value as a required value of the control pressure; and a controller setting a control target value as a target value of the control pressure according to the control required value, and driving the solenoid valve according to the control target value, wherein the controller sets the control target value in such a manner that a driving start time point of the solenoid valve becomes a maximum output pressure within a use range of the solenoid valve, and gradually approaches the control required value with the passage of time after becoming the maximum output pressure.

Description

Technical Field

[0001] This invention relates to a control device for a solenoid valve used in a hydraulic circuit of engineering machinery, and more particularly to a control device using a driving method in which an excitation current flows through the solenoid valve's solenoid at the start of actuation of the solenoid valve, followed by a current for maintaining the required operation of the solenoid valve. Background Technology

[0002] In recent years, the demand for automated operation of construction machinery such as hydraulic excavators has increased, and the electronic control of construction machinery has continued to develop. One method for electronic control of construction machinery is the use of solenoid valves. For example, it is known to use hydraulic pressure controlled by solenoid valves to operate control valves used to control the main actuators of construction machinery such as hydraulic cylinders and hydraulic motors.

[0003] On the other hand, when implementing electronic control of construction machinery, the operational precision of the machinery is paramount. In the solenoid valves used in such electronic control methods, the hydraulic pressure needs to rapidly follow the control requirements to ensure the machinery operates with the specified precision. However, the wasted time of the hydraulic response at the start of the solenoid valve's actuation delays the control valve's operation, resulting in a deviation from the target action at the start of the machinery's movement, thus deteriorating operational precision. Therefore, reducing the wasted time of hydraulic rise at the start of the solenoid valve's actuation becomes a crucial issue in the electronic control of construction machinery.

[0004] As a method for reducing the useless time at the start of actuation of a solenoid valve, the following method is known: at the start of actuation of the solenoid valve, the solenoid valve is opened at high speed by flowing an excitation current in the solenoid, and after the valve is opened, a holding current flows in order to maintain the required hydraulic pressure.

[0005] For example, in Patent Document 1, a method is proposed to store in advance the overexcitation current value and holding current value flowing through the solenoid and the supply time of the overexcitation current as a function of the temperature information measured by the temperature sensor installed in the solenoid valve unit, and to store them in the solenoid valve drive control device.

[0006] The viscosity of the working fluid in a solenoid valve, represented by the working oil, is temperature-dependent. Therefore, the response of the solenoid valve during actuation also depends on the temperature of the working fluid. That is, at low temperatures, the viscosity of the working fluid increases, and its viscous resistance hinders the movement of the valve core at the start of the solenoid valve actuation, thus increasing the idle time.

[0007] According to Patent Document 1, a function that sets the overexcitation current value at low temperature and the overexcitation current supply time to be larger than that at high temperature is pre-stored in the solenoid valve drive control device, thereby controlling the supply current of the solenoid. As a result, the solenoid can output a force that can counteract the adhesion of the working fluid at low temperature, and can reduce the useless time of hydraulic response throughout the temperature range.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent No. 6646740 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] However, among the solenoid valves commonly used in construction machinery, there are electromagnetic proportional pressure control valves. These valves control the output pressure proportionally to the current supplied to the solenoid, achieving pressure control by supplying a current corresponding to the required control pressure. Furthermore, electromagnetic proportional pressure control valves are not always driven at the same required control pressure at the start of operation; the gradient of the required control pressure at the start of operation varies depending on the required operating speed of the construction machinery. That is, the gradient of the required control current at the start of operation also varies depending on the specific circumstances.

[0013] When the current control method shown in Patent Document 1 is applied to the control of the aforementioned electromagnetic proportional pressure control valve, the target control current value of the solenoid of the solenoid valve is set to become an overexcitation current value within a specified time corresponding to the temperature at the start of the solenoid valve actuation, and then decrease to a control requirement current value corresponding to the control requirement pressure, and the supply current is controlled according to this target control current value. However, if the supply time of the overexcitation current is determined independently of the change gradient of the control requirement pressure value (control requirement current value), then at the start of the actuation of the electromagnetic proportional pressure control valve, a useless time reduction effect is achieved for a specific time change gradient of the control requirement pressure value (control requirement current value), but for a different time change gradient of the control requirement pressure value (control requirement current value), the following problems arise: if the overexcitation time is too long, the valve core of the electromagnetic proportional pressure control valve is excessively displaced, and the output pressure greatly exceeds the control requirement pressure value; or if the overexcitation time is too short, the valve core of the electromagnetic proportional pressure control valve is not sufficiently displaced, and the useless time reduction effect cannot be obtained.

[0014] The present invention was made in view of the above-mentioned problems, and its object is to provide a hydraulic system that enables the control pressure output from the solenoid valve to quickly follow the control requirement value when the actuation of the solenoid valve begins.

[0015] Methods for solving problems

[0016] To achieve the above objectives, the hydraulic system of the present invention comprises: a hydraulic pump; a hydraulic actuator driven by hydraulic oil discharged from the hydraulic pump; a control valve that controls the supply and discharge of hydraulic oil discharged from the hydraulic pump to the hydraulic actuator; a solenoid valve that generates a control pressure for actuating the control valve; an operating device that performs an operation for inputting a required value of the control pressure, i.e., a control requirement value; and a controller that sets a target value of the control pressure, i.e., a control target value, according to the control requirement value, and drives the solenoid valve according to the control target value, wherein the controller sets the control target value in such a way that it becomes the maximum output pressure within the operating range of the solenoid valve at the start time of actuation of the solenoid valve, and gradually approaches the control requirement value over time after reaching the maximum output pressure.

[0017] According to the present invention configured as described above, the control target value at the start time of solenoid valve actuation is set independently of the control requirement value as the maximum output pressure within the operating range of the solenoid valve. Therefore, the delay time from the start time of solenoid valve actuation to the rise of control pressure is shortened. Furthermore, as time passes from the start time of solenoid valve actuation, the control target value gradually approaches the control requirement value; therefore, after the control pressure rises, the control pressure gradually approaches the control requirement value. Thus, at the start of solenoid valve actuation, the control pressure output from the solenoid valve can quickly follow the control requirement value.

[0018] Invention Effects

[0019] According to the present invention, when the actuation of the solenoid valve begins, the control pressure output from the solenoid valve can quickly follow the control requirement value. Attached Figure Description

[0020] Figure 1 This is a circuit diagram of the solenoid valve control device according to the first embodiment of the present invention.

[0021] Figure 2 This is a partial cross-sectional view of the electromagnetic proportional pressure reducing valve according to the first embodiment of the present invention.

[0022] Figure 3 This is a functional block diagram of the hydraulic system according to the first embodiment of the present invention.

[0023] Figure 4 This is the time-historical waveform of the control requirement value and control target value according to the first embodiment of the present invention.

[0024] Figure 5 This is a flowchart illustrating the processing in the control target value determination unit of the first embodiment of the present invention.

[0025] Figure 6 This is a graph showing the time history waveforms of the control requirement value, control target value, and control pressure output from the electromagnetic proportional pressure reducing valve according to the first embodiment of the present invention.

[0026] Figure 7 This is a graph showing the time history waveforms of the control requirement value and the control target value according to the second embodiment of the present invention.

[0027] Figure 8 This is the time-historical waveform of the control requirement value and control target value according to the third embodiment of the present invention. Detailed Implementation

[0028] The following description, using the example of mounting the hydraulic system of the present invention on a hydraulic excavator, will be provided in detail with reference to the accompanying drawings. Furthermore, in the drawings, the same reference numerals are used to label the same elements, and redundant descriptions are omitted where appropriate.

[0029] Example 1

[0030] Figure 1 This is a circuit diagram of the hydraulic system 100 according to the first embodiment of the present invention. Figure 1 In this configuration, hydraulic pump 1 and oil tank 2 together constitute the main hydraulic power source. Hydraulic pump 1 is driven by the prime mover (not shown) of a large hydraulic excavator, for example, to rotate and discharge the working oil drawn from oil tank 2 as high-pressure hydraulic oil.

[0031] The hydraulic cylinder 3 used for operation represents a typical example of a hydraulic actuator. This hydraulic cylinder 3, for example, constitutes the boom cylinder, stick cylinder, or bucket cylinder (none shown) of the working device installed on a hydraulic excavator. The hydraulic cylinder 3 is composed of a pipe 3A, a piston 3B, and a rod 3C.

[0032] The pipe 3A of the hydraulic cylinder 3 is divided into two oil chambers 3D and 3E by the piston 3B, and the base end of the rod 3C is fixed to the piston 3B. The front end of the rod 3C protrudes outward from the pipe 3A and extends and contracts due to the hydraulic oil supplied and discharged from the hydraulic pump 1 to the oil chambers 3D and 3E in the pipe 3A. Furthermore, the hydraulic actuator is not limited to the hydraulic cylinder 3; for example, it could be a hydraulic motor for rotation or travel in a hydraulic excavator.

[0033] The directional control valve 4 is a control valve for the hydraulic cylinder 3, and is located between the hydraulic pump 1, the oil tank 2, and the hydraulic cylinder 3. This directional control valve 4 is, for example, a hydraulically piloted directional control valve with 6 ports at position 3, and hydraulic pilot sections 4A and 4B are provided on the left and right sides. The hydraulic pilot sections 4A and 4B of the directional control valve 4 are connected to the electromagnetic proportional pressure reducing valves 11A and 11B (described later) via control pressure lines 5A and 5B.

[0034] The directional control valve 4 switches from the neutral position (N) to one of the switching positions (L) or (R) by supplying control pressures pA and pB from the electromagnetic proportional pressure reducing valves 11A and 11B to the hydraulic pilot sections 4A and 4B. As a result, hydraulic oil from the hydraulic pump 1 is supplied to the oil chambers 3D and 3E of the hydraulic cylinder 3 via a pair of main pipes 6A and 6B, and the rod 3C of the hydraulic cylinder 3 extends (is driven) from pipe 3A. At this time, the flow rate of hydraulic oil supplied to the oil chambers 3D and 3E of the hydraulic cylinder 3 is variablely controlled in correspondence with the displacement of the directional control valve 4 (i.e., the operating signal based on the tilting operation of the operating lever 10A described later, or the design information of the hydraulic excavator's working face pre-stored in the controller 30 described later).

[0035] The pilot pump 7, together with the oil tank 2, constitutes the pilot hydraulic power source. The pilot pump 7 is driven by the prime mover along with the main hydraulic pump 1. A low-pressure relief valve 8 is provided on the discharge side of the pilot pump 7, between it and the oil tank 2. This low-pressure relief valve 8 suppresses the discharge pressure of the pilot pump 7 below a predetermined relief set pressure. The pilot pressure generated by the pilot pump 7 is supplied via the primary pressure line 16 (described later) to the pump port 14a of the electromagnetic proportional pressure reducing valve 11A and the pump port 14b of the electromagnetic proportional pressure reducing valve 11B, respectively.

[0036] In the main hydraulic pump 1, a high-pressure relief valve 9 is installed between the discharge line 1A and the oil tank 2. This high-pressure relief valve 9 suppresses the discharge pressure of the hydraulic pump 1 below a predetermined relief set pressure to prevent excessive pressure from being generated in the hydraulic pump 1. This relief set pressure is set to a pressure sufficiently higher than that of the low-pressure relief valve 8.

[0037] The control lever device 10 is an electrical control device configured to remotely operate the hydraulic cylinder 3. The control lever device 10 includes a control lever 10A that is manually tilted by the operator of the hydraulic excavator. The control lever device 10 outputs operation signals corresponding to the operating direction and amount of the control lever 10A to the electromagnetic proportional pressure reducing valves 11A and 11B via the controller 30.

[0038] Here, the control lever device 10 is located inside the cab (not shown) that constitutes the operating compartment of the hydraulic excavator. On the other hand, the electromagnetic proportional pressure reducing valves 11A and 11B are positioned significantly separated from the cab (e.g., near the directional control valve 4). That is, since the control lever device 10 is an electrically operated device, it can be connected to the electromagnetic proportional pressure reducing valves 11A and 11B using only electrical wiring (signal lines), and the distance between them can be extended to several meters or more as needed. Furthermore, in the case of using pilot hydraulic piping (i.e., using a pressure reducing valve type pilot operating valve instead of an electric lever device), the piping length is typically limited to, for example, less than 1 meter.

[0039] Electromagnetic proportional pressure reducing valves 11A and 11B supply control pressure proportional to the current controlled by the controller 30 to control pressure lines 5A and 5B based on the operation signal from the operating lever device 10 or the design information of the construction surface pre-stored in the controller 30. The directional control valve 4 switches from the neutral position (N) to one of the switching positions (L) or (R) by supplying the control pressure at this time to the hydraulic pilot sections 4A and 4B. Therefore, hydraulic oil from the hydraulic pump 1 is supplied to the oil chambers 3D and 3E of the hydraulic cylinder 3 via a pair of main lines 6A and 6B, causing the rod 3C of the hydraulic cylinder 3 to extend and retract (drive). Thus, the extension and retraction of the hydraulic cylinder 3 is remotely operated via the electromagnetic proportional pressure reducing valves 11A and 11B and the directional control valve 4, based on the operation signal from the operating lever device 10 or the design information of the construction surface pre-stored in the controller 30.

[0040] The base end of the primary pressure line 16 is connected to the discharge side of the pilot pump 7, and the front end is connected to the pump port 14 of the electromagnetic proportional pressure reducing valves 11A and 11B. Thus, the pilot pressure discharged from the pilot pump 7 is supplied to the pump port 14 as the primary pressure for the electromagnetic proportional pressure reducing valves 11A and 11B. The discharge line 17 keeps the discharge ports 15 of the electromagnetic proportional pressure reducing valves 11A and 11B always connected to the oil tank 2.

[0041] In controller 30, the current flowing in electromagnetic proportional pressure reducing valves 11A and 11B is controlled by pulse width modulation of the voltage applied to them. Details will be described later.

[0042] Next, refer to Figure 2 The specific structures of electromagnetic proportional pressure reducing valves 11A and 11B will be described. Furthermore, electromagnetic proportional pressure reducing valves 11A and 11B have substantially the same structure; therefore, in the following description, electromagnetic proportional pressure reducing valve 11A will be used as an example, and the description of electromagnetic proportional pressure reducing valve 11B will be omitted.

[0043] The electromagnetic proportional pressure reducing valve 11A is configured to include, for example, an electromagnetic actuator 20 composed of an electromagnetic proportional solenoid, and an electromagnetically operated pressure control valve 21 controlled by switching the electromagnetic actuator 20 via a push rod 20C. The electromagnetic actuator 20 is configured to include: an actuator housing 20A constituting its outer casing; and a connecting portion 20B integrally disposed within the actuator housing 20A, which is connected to a controller 30 (see reference 11A) via a signal line, etc. Figure 1 The actuator housing 20A is connected to the actuator housing 20A; a push rod 20C is disposed within the actuator housing 20A in a displaceable manner; and a solenoid (not shown) is disposed within the actuator housing 20A and extends axially ( Figure 2 Drive push rod 20C in the direction of arrow A or arrow B.

[0044] like Figure 2 As shown, a control current from the controller 30 is input to the electromagnetic actuator 20 via the connection 20B, and the push rod 20C moves from the actuator housing 20A to the control unit 20 in proportion to the current value at that time. Figure 2 The push rod 20C is driven to extend in the direction of arrow A. The push rod 20C is structured such that when the pilot slide valve 24 is subjected to a load exceeding the electromagnetic force of the solenoid (force in the direction of arrow B), it can be displaced in the opposite direction to arrow A (i.e., arrow B).

[0045] That is, the push rod 20C of the electromagnetic actuator 20 applies force to the pilot slide valve 24 (in the direction of arrow A) with a force less than that of the return spring 26 described later, via a spring (not shown) on the solenoid side provided in the actuator housing 20A. Therefore, through the elastic flexural deformation of the solenoid side spring, the push rod 20C can be displaced in the direction of arrow B under the aforementioned load. Furthermore, when the supply current from the controller 30 becomes zero, the push rod 20C of the electromagnetic actuator 20 returns to its original position. Figure 2 The smallest position shown.

[0046] The pressure control valve 21 of the electromagnetic proportional pressure reducing valve 11A is configured to include: a sleeve 22, which is fitted into the solenoid valve box insertion hole 13 of the housing 12 that constitutes its outer shell, and is configured to be coaxial with the push rod 20C of the electromagnetic actuator 20; and a pilot slide valve 24, which is inserted into the stepped hole 23 formed on the inner circumferential side of the sleeve 22.

[0047] The sleeve 22 of the pressure control valve 21 has an opening on the other side of the actuator housing 20A of the electromagnetic actuator 20 screwed onto its outer periphery on one axial side. Thus, the electromagnetic proportional pressure reducing valve 11A becomes a cartridge structure pre-assembled in a sub-component state, containing the electromagnetic actuator 20, the sleeve 22 of the pressure control valve 21, the pilot spool valve 24, and the return spring 26. In this state, the sleeve 22 is pressed into the solenoid valve housing insertion hole 13 of the housing 12 from one axial side to the other, together with the pilot spool valve 24 and the return spring 26. Thus, the end face of the sleeve 22 on the other axial side abuts against the bottom side of the solenoid valve housing insertion hole 13 via the partition plate 27 and the spring member 28 (described later). In other words, the actuator housing 20A of the electromagnetic actuator 20 is fixedly disposed in the housing 12 such that it closes the solenoid valve housing insertion hole 13 and the spring receiving hole 23A of the sleeve 22 from one axial side.

[0048] On the sleeve 22, radial oil holes 22A, 22B, and 22C are provided, axially separated, and communicating with the stepped bore 23. Specifically, oil hole 22A, located on the axial side of the sleeve 22, is always connected to the pump port 14 of the housing 12. Oil hole 22B, located axially in the middle, is always connected to the control pressure line 5A. Oil hole 22C, located on the opposite axial side of the sleeve 22, is always connected to the discharge port 15. These oil holes 22A, 22B, and 22C are mutually sealed on the outer periphery of the sleeve 22 by O-rings or the like.

[0049] The stepped hole 23 formed on the inner circumferential side of the sleeve 22 includes a spring receiving hole portion 23A located on its axial side (open end side) and sliding hole portions 23B to 23E formed with a diameter smaller than that of the spring receiving hole portion 23A. The spring receiving hole portion 23A of the stepped hole 23 is formed as an enlarged diameter hole having an inner diameter larger than that of the sliding hole portions 23B to 23E of the stepped hole 23 located on the axial side. The end of the spring receiving hole portion 23A (the end on the axial side) becomes an open end that communicates (opens) with the opening on one side of the housing 12 and the other side of the actuator housing 20A.

[0050] The stepped hole 23 is a sliding valve hole formed on the inner circumference of the sleeve 22, having multiple sliding hole portions 23B, 23C, 23D, and 23E into which the pilot valve 24 is inserted. These sliding hole portions 23B, 23C, 23D, and 23E are formed such that their inner diameter decreases progressively from one side of the sleeve 22's axial direction towards the other. Sliding hole portions 23B and 23C can be formed with the same diameter as each other, as long as they are larger than the diameters of sliding hole portions 23D and 23E. Sliding hole portions 23D and 23E can also be formed with the same diameter as each other, as long as they are smaller than the diameters of sliding hole portions 23B and 23C.

[0051] The pilot valve 24 is axially inserted into the stepped hole 23 of the sleeve 22. In this state, the pilot valve 24 is installed such that the boss 24A, which forms the closed end on the axial side, always abuts against the push rod 20C of the electromagnetic actuator 20. As the push rod 20C moves from the actuator housing 20A towards... Figure 2 If the pilot slide valve 24 extends in the direction of arrow A or shrinks in the direction of arrow B, it moves axially (sliding displacement) within the stepped orifice 23.

[0052] On the outer periphery of the pilot valve 24, four pads 24B, 24C, 24D, and 24E are axially separated. The pad 24B located on the boss side (the side closest to the axial direction) has a larger diameter than the pad 24E located on the front end side (the other side closest to the axial direction). The intermediate pads 24C and 24D between the pads 24B and 24E on one side are formed as annular flanges, with the outer diameter of one intermediate pad 24C larger than that of the other intermediate pad 24D. The pads 24B and 24C on the larger diameter side can also be formed with the same diameter. Similarly, the intermediate pad 24D on the smaller diameter side and 24E on the other side can also be formed with the same diameter.

[0053] With the pilot slide valve 24 inserted into the sleeve 22 (stepped hole 23), one side pad 24B is configured to slide axially within the sliding hole portion 23B, and the other side pad 24E is configured to slide within the sliding hole portion 23E. The intermediate pad 24C on the larger diameter side of the intermediate pads 24C and 24D is configured to slide within the sliding hole portion 23C. On the other hand, the intermediate pad 24D on the smaller diameter side is positioned to connect the oil hole 22B with the sliding hole portion 23D. When the intermediate pad 24C on the larger diameter side moves (enters) from the sliding hole portion 23C to the position of the oil hole 22B, the sliding hole portion 23C (pump port 14) is connected to the control pressure line 5A via the oil hole 22B. At this time, the intermediate pad 24D on the small diameter side is slidably inserted into the sliding hole 23D, so that the oil hole 22B (control pressure line 5A) is cut off relative to the discharge port 15 (sliding hole 23D).

[0054] Thus, the intermediate pad 24C on the large-diameter side is a pad provided on the pilot slide valve 24 to disconnect or connect the pump port 14 and the control pressure line 5A. On the other hand, the intermediate pad 24D on the small-diameter side is a pad provided on the pilot slide valve 24 to connect or disconnect the control pressure line 5A and the discharge port 15.

[0055] That is, with the pilot slide valve 24 in a state where the intermediate pad 24C on the large-diameter side is positioned (sliding contact) within the sliding hole 23C of the sleeve 22, it cuts off the connection between oil holes 22A and 22B (between pump port 14 and control pressure line 5A). However, when the pilot slide valve 24 moves axially to the other side ( Figure 2 When the intermediate pad 24C on the large-diameter side moves from the sliding hole 23C into the oil hole 22B, the oil holes 22A and 22B (between pump port 14 and control pressure line 5A) are connected. Therefore, from Figure 1The working oil supplied by the primary pressure line 16 (pump port 14) flows in the space between the sleeve 22 and the pilot slide valve 24, and is introduced from the oil hole 22B through the control pressure line 5A to the hydraulic pilot part 4A of the directional control valve 4.

[0056] At this time, the intermediate pad 24D on the small diameter side inserts (sliding contact) into the sliding hole 23D of the sleeve 22, cutting off the connection between oil holes 22B and 22C (between the control pressure line 5A and the discharge port 15). Therefore, working oil will not flow from the control pressure line 5A towards the discharge port 15. However, when the pilot slide valve 24 returns to the axial side ( Figure 2 (In the direction of arrow B), when the intermediate pad 24D on the small diameter side reaches the position of the oil hole 22B from the sliding hole portion 23D (i.e., Figure 2 As shown in the diagram, oil holes 22B and 22C are connected (between control pressure line 5A and discharge port 15). Therefore, the working oil supplied to the hydraulic pilot section 4A of the directional control valve 4 flows through control pressure line 5A to oil hole 22B, flows in the space between sleeve 22 and pilot slide valve 24, and flows from discharge port 15 to discharge line 43 (see reference). Figure 1 )return.

[0057] Here, the pressure-bearing area of ​​one axial end face of the intermediate pad 24C on the large-diameter side is equal to the pressure-bearing area of ​​the other axial end face of the intermediate pad 24B on the small-diameter side. Therefore, hydraulic pressure in the direction of arrow B is generated at the intermediate pad 24C on the large-diameter side. On the other hand, the pressure-bearing area of ​​the other axial end face of the intermediate pad 24D on the small-diameter side is equal to the pressure-bearing area of ​​one axial end face of the intermediate pad 24E on the small-diameter side. Therefore, hydraulic pressure in the direction of arrow A is generated at the intermediate pad 24C on the small-diameter side. Therefore, a pressure-bearing area difference is generated between the intermediate pads 24C and 24D when they are subjected to pressure in the control pressure line 5A via the oil hole 22B. That is, a pressure-bearing area difference relative to the control pressure in the sleeve 22 is generated between the intermediate pads 24C and 24D. Therefore, the pilot slide valve 24 bears the hydraulic pressure (pressing pressure) of the pressure difference between the intermediate pad 24C on the large diameter side and the intermediate pad 24D on the small diameter side as a load in the direction opposite to the push rod 20C (arrow B direction).

[0058] Furthermore, the pilot slide valve 24 is provided with a bottomed shaft hole 24F extending axially from its axial end face toward the boss portion 24A. A cylindrical throttling orifice 25 is provided on the open end of the shaft hole 24F (the end on the damping chamber 29 side described later), and the shaft hole 24F is always in communication with the damping chamber 29 via the throttling orifice 25. Moreover, oil passages 24G and 24H are formed in the pilot slide valve 24, extending radially outward toward the shaft hole 24F. These oil passages 24G and 24H ensure that the shaft hole 24F is always in communication with the spring receiving hole portion 23A and the oil hole 22C of the sleeve 22.

[0059] Low-pressure working oil is guided from the discharge port 15 through oil passage 24H, shaft hole 24F, and oil passage 24G into the spring receiving hole 23A of the sleeve 22. This working oil has the following functions: it is guided from the outer periphery of the boss portion 24A of the pilot slide valve 24 along the periphery of the push rod 20C into the actuator housing 20A of the electromagnetic actuator 20, keeping the interior of the actuator housing 20A in a lubricated state, and cooling the solenoid and the like.

[0060] The return spring 26 is a force-applying component that always applies force to the pilot slide valve 24 towards the axial side. The return spring 26 is disposed in a retracted state between the spring receiving hole 23A of the sleeve 22 (stepped hole 23) and the boss 24A of the pilot slide valve 24. Figure 2 As shown, the pilot slide valve 24 is housed in the sleeve 22 (spring receiving hole 23A) while being constantly pressed against the push rod 20C side of the electromagnetic actuator 20 by the force of the return spring 26. Furthermore, the push rod 20C of the electromagnetic actuator 20 applies a force to the pilot slide valve 24 with a smaller force than the return spring 26 via the aforementioned spring (not shown) provided in the actuator housing 20A.

[0061] The partition plate 27 closes the axial end face of the sleeve 22 on the bottom side of the solenoid valve box insertion hole 13. A spring member 28, such as a wave washer, is provided between the bottom of the solenoid valve box insertion hole 13 and the partition plate 27. This spring member 28 is kept in a state that presses the partition plate 27 against the other end face of the sleeve 22. A damping chamber 29 is formed on the axial side of the pilot slide valve 24 by the partition plate 27.

[0062] The damping chamber 29, located on the opposite side of the electromagnetic actuator 20 across the pilot slide valve 24, is a circular space surrounded by the inner wall of the sleeve 22 (sliding hole 23E) and the partition plate 27. The damping chamber 29 is always in communication with the shaft hole 24F of the pilot slide valve 24 via the throttle hole 25. Therefore, when the pilot slide valve 24 is axially inclined towards the other side within the sleeve 22 (… Figure 2 When the pilot valve 24 moves (in the direction of arrow A), the working oil in the damping chamber 29 is discharged into the shaft hole 24F through the throttle orifice 25. The throttle orifice 25 slows down the movement of the pilot valve 24 by throttling the flow of the discharged oil. That is, the movement (speed) of the pilot valve 24 is adjusted according to the throttling diameter of the throttle orifice 25.

[0063] Next, refer to Figure 3 The specific structure of the controller 30 will be described. Furthermore, in the following description, the case of controlling the current supply to the electromagnetic proportional pressure reducing valve 11A will be used as an example. Regarding the electromagnetic proportional pressure reducing valve 11B, the current can also be controlled within the controller 30 through the same process as the control of the electromagnetic proportional pressure reducing valve 11A.

[0064] The controller 30 is a control device according to the first embodiment of the present invention, and is configured to include a control requirement value calculation unit 31, a control target value determination unit 32, a control target value conversion unit 33, a construction surface design information storage area 34, and a current feedback control unit 35.

[0065] In the control requirement value calculation unit 31, based on the operation signal of the operating lever device 10 and the design information of the construction surface stored in the construction surface design information storage area 34 (described later), the control quantity of the electromagnetic proportional pressure reducing valve 11A, namely the control requirement value pR of the control pressure, is calculated and output.

[0066] Alternatively, the calculation content of the control requirement value pR in the control requirement value calculation unit 31 can be selected according to the operation method of the hydraulic excavator. For example, when the hydraulic excavator is manually operated via the control lever device 10, a control requirement value pR proportional to the operation amount of the control lever 10A can be output. In addition, when the hydraulic excavator is operated automatically, the track of the hydraulic excavator's working device during construction can be calculated based on the design information of the construction surface (width, height, slope, etc.), and the control pressure of the directional control valve 4, which outputs the extension and retraction amount of the boom cylinder, stick cylinder, or bucket cylinder, can be calculated in a way that follows the track, and output as the control requirement value pR.

[0067] In the control target value determination unit 32, the control requirement value pR output from the control requirement value calculation unit 31 is corrected, and the control target value pT of the control pressure of the electromagnetic proportional pressure reducing valve 11A is output. The detailed processing flow in the control target value determination unit 32 will be described later.

[0068] In the control target value conversion unit 33, the input control target value pT is converted into the control target current value IT of the electromagnetic proportional pressure reducing valve 11A and output. The relationship between the input current to the electromagnetic proportional pressure reducing valve 11A and the control pressure output to it is obtained in advance, for example, stored in the controller 30 as a numerical table. The conversion from the control target value pT to the control target current value IT is performed in the control target value conversion unit 33 with reference to this current-control pressure relationship. Furthermore, in this embodiment, if the control target value pT exceeds the maximum output pressure pmax within the operating range of the electromagnetic proportional pressure reducing valve 11A and is input to the control target value conversion unit 33, the control target value conversion unit 33 replaces the control target value pT with pmax and outputs the maximum drive current value Imax corresponding to pmax. Additionally, if the control target value pT is less than the non-drive equivalent value p0 of the electromagnetic proportional pressure reducing valve 11A, the control target value pT is replaced with p0 and the non-drive equivalent current value I0 corresponding to p0 is output. Here, the non-driving equivalent current value I0 is set to the current value where the electromagnetic force of the electromagnetic actuator 20 does not exceed the force of the return spring 26.

[0069] The construction surface design information storage area 34 stores pre-stored construction surface design information (width, height, slope, etc.), which is referenced when calculating the control requirement value pR in the control requirement value calculation unit 31. Writing information to the construction surface design information storage area 34 can be configured, for example, via a control panel (not shown) installed in the cab (not shown) constituting the hydraulic excavator's operating room. Alternatively, it can be configured to use an external communication device (not shown) installed in the hydraulic excavator to retrieve the construction surface design information from an external server via wired or wireless communication for writing.

[0070] In the current feedback control unit 35, the actual current (actual current) IA flowing in the electromagnetic actuator 20 of the electromagnetic proportional pressure reducing valve 11A is obtained in the current detector 35C, and an A / D conversion of the actual current IA is performed, converting the actual current from an analog value IA to a digital value IAF. During the A / D conversion, a digital filter may be applied to the converted value to smooth it out as needed to remove noise, and this smoothed value may be set as the digital value IAF of the actual current. Then, the deviation (IT-IAf) between the target control current value IT and the actual current IAF is calculated, and the calculation result is input to the PID compensator 35A.

[0071] In the PID compensator 35A, compensation is achieved by reducing the deviation (IT﹣IAf) between the target current value IT and the actual current value IAf, which is then used as the duty cycle output.

[0072] In the PWM drive device 35B, the pulse width modulation of the drive voltage VC applied to the electromagnetic actuator 20 is performed according to the duty cycle output from the PID compensator 35A. Furthermore, an actual current IA corresponding to the drive voltage VC, resistor, and inductor flows in the electromagnetic actuator 20.

[0073] That is, in the current feedback control unit 35, feedback control is performed with the actual current IA as the control quantity, the target current value IT as the target value, and the duty cycle in the pulse width modulation of the drive voltage VC as the operating quantity.

[0074] Here, the content and detailed processing flow of the correction calculation for the control requirement value pR in the control target value determination unit 32 will be explained.

[0075] First, refer to Figure 4 The content of the correction calculation in the control target value determination unit 32 will be explained. Figure 4 The time history waveforms of the control requirement value pR (represented by solid lines) and the control target value pT (represented by dashed lines) output by the control target value determination unit 32 are schematically shown respectively.

[0076] In the control target value determination unit 32, it determines whether the control requirement value pR has switched from the non-drive equivalent value p0 (e.g., pR = p0 = 0 MPa) of the electromagnetic proportional pressure reducing valve 11A to the drive equivalent value (e.g., pR > p0 = 0 MPa). From the point when the control requirement value pR switches from the non-drive equivalent value to the drive equivalent value, the control requirement value pR is corrected, and the control target value pT of the control pressure of the electromagnetic proportional pressure reducing valve 11A is output. Figure 4 In this process, the control requirement value pR starts to rise from the non-drive equivalent value p0 at time t0, and the control target value determination unit 32 starts to correct the control requirement value pR from this time point. Time t0 is taken as the drive start time, and the elapsed time from this drive start time is set as τ (i.e., τ = t - t0). In this embodiment of the present invention, the calculation formula for correction is, for example, formula (1).

[0077] [Formula 1]

[0078] p T =(p max -p R )exp(-K·τ)+p R …Formula (1)

[0079] In equation (1), pmax is the maximum output pressure within the operating range of the electromagnetic proportional pressure reducing valve 11A, and K is a positive specified value. Furthermore, the function exp(x) represents an exponential function with the Napier constant as the base and x as the exponent.

[0080] The first term on the right-hand side of equation (1) contains the exponential function exp(-K·τ), which is represented by the product of the elapsed time τ from the start of the drive and a constant value. Therefore, at time t0 (i.e., τ = 0), which is the start of the drive, if the control target value pT is calculated using equation (1), the output value of the exponential function is 1, calculated as pT = pmax. That is, at time t0 (the start of the drive), if... Figure 4 As shown, the control target value pT is set to the maximum output pressure pmax within the operating range of the electromagnetic proportional pressure reducing valve 11A.

[0081] On the other hand, the base of the exponential function exp(-K·τ) is exp(-K), and the exponent is τ. Furthermore, since K is a positive number, exp(-K) is a value less than 1. Therefore, as the elapsed time τ from the start of the drive increases, the exponential function exp(-K·τ) gradually approaches zero. That is, the first and second terms on the right-hand side of equation (1) gradually approach zero as time passes from the start of the drive, thus the control target value pT... Figure 4 The value pR gradually approaches the control requirement value shown.

[0082] The degree to which the target control value pT asymptotically approaches the required control value pR can be adjusted by a predetermined value K. For example, the predetermined value K can be pre-adjusted for several gradients in the control required value pR, taking into account the reduction effect of the control pressure's idle time in the controller 30 (described later). Alternatively, the predetermined value K can be adjusted for several working oil temperatures before implementation and stored as a function of temperature in the controller 30, so that the predetermined value K varies according to the measurement values ​​of the working oil thermometers (not shown) located near the electromagnetic proportional pressure reducing valves 11A and 11B.

[0083] Based on the above, in the control target value determination unit 32, the control target value pT is corrected relative to the control requirement value pR in such a way that it becomes the maximum output pressure pmax within the operating range of the electromagnetic proportional pressure reducing valve 11A at the start of the drive. After that, as time passes, the control target value pT is corrected in such a way that it gradually approaches the control requirement value pR.

[0084] Next, refer to Figure 5 The processing flow in the control target value determination unit 32 is explained. In the control target value determination unit 32, in... Figure 5 In step S1, the control requirement value pR is obtained. Then, in step S2, it is determined whether the control requirement value pR is below the non-drive equivalent value p0 of the electromagnetic proportional pressure reducing valve 11A. If the determination in step S2 is "yes", the process branches to step S3; if the determination is "no", the process branches to step S5.

[0085] If the determination in step S2 is "yes," that is, if the control requirement value pR is the requirement value for setting the electromagnetic proportional pressure reducing valve 11A to non-drive, then in step S3, the control target value pT is set to the non-drive equivalent value p0. Then, in step S4, the duration of the state where the control requirement value pR is below the non-drive equivalent value p0, i.e., the duration TI of the drive stop requirement, is incremented. Finally, in step S5, the elapsed time τ from the start of drive is incremented, and the control target value pT (=p0) is output from the control target value determination unit 32.

[0086] On the other hand, if the determination in step S2 is "no," that is, if the control requirement value pR is the required value for driving the electromagnetic proportional pressure reducing valve 11A, then in step S6 it is determined whether the duration TI of the drive stop requirement is greater than or equal to a predetermined time TC. The predetermined time TC is a predetermined value greater than zero. For example, when the maximum drive current Imax is supplied to the electromagnetic proportional pressure reducing valve 11A (i.e., the control pressure is pmax), it is set to be the time from the instant the drive voltage drops to zero until the control pressure drops from pmax to zero.

[0087] If the determination in step S6 is "yes", τ is set to zero in step S7. Conversely, if the determination in step S6 is "no", the process in step S7 is skipped and proceeds to step S8. In step S8, the control target value pT is calculated using equation (1), and in step S9, the duration TI required for the drive to stop is set to zero. Finally, in step S5, the elapsed time τ since the start of the drive is incremented, and the control target value pT is output from the control target value determination unit 32.

[0088] The above processing is written as a program into controller 30, including Figure 3 The processing, including that from the control requirement value calculation unit 31 to the current feedback control unit 35, is performed according to a fixed control sampling time set in the controller 30.

[0089] The control device of this embodiment has the above-described structure. Therefore, the operation of the controller 30 when applied to the current control of the electromagnetic proportional pressure reducing valves 11A and 11B in the hydraulic system 100 of the hydraulic excavator will be described next. Furthermore, the electromagnetic proportional pressure reducing valves 11A and 11B have substantially the same structure, and they operate identically as long as the supplied current value is the same. Therefore, the operation when controlling the electromagnetic proportional pressure reducing valve 11A will be described as an example.

[0090] The following section will first explain the operation of the electromagnetic proportional pressure reducing valve 11A when supplying control current and when stopping the supply.

[0091] First of all, Figure 1 When the operating lever 10A is in the neutral position and the operating signal from the operating lever device 10 is zero, thus no current is supplied from the controller 30 to the electromagnetic actuator 20, the pilot slide valve 24 applies force to the push rod 20C side of the electromagnetic actuator 20 via the return spring 26. Therefore, the intermediate pad 24C of the pilot slide valve 24 disconnects the pump port 14 from the control pressure line 5A, and the control pressure line 5A (i.e., the hydraulic pilot section 4A of the directional control valve 4) is in a state of communication with the discharge port 15.

[0092] Next, when the operator tilts the operating lever 10A and sends an operation signal from the operating lever device 10, a control current is supplied from the controller 30 to the electromagnetic actuator 20 via the connection part 20B. The solenoid within the actuator housing 20A of the electromagnetic actuator 20 is energized, and the movable iron core receives an electromagnetic force corresponding to the current flowing in the solenoid coil (not shown). This electromagnetic force is transmitted as a force that presses the pilot slide valve 24 in the direction of arrow A from the movable iron core via the push rod 20C. When this pressing force (electromagnetic force) exceeds the force of the return spring 26, the pilot slide valve 24 moves towards the damping chamber 29 (sliding displacement).

[0093] Therefore, the intermediate pad 24C on the large-diameter side of the pilot slide valve 24 enters the position of the oil hole 22B from the sliding hole 23C, connecting the oil holes 22A and 22B (between the pump port 14 and the control pressure line 5A). At this time, the intermediate pad 24D on the small-diameter side slides (enters) into the sliding hole 23D of the sleeve 22, cutting off the connection between the oil holes 22B and 22C (between the control pressure line 5A and the discharge port 15).

[0094] Therefore, the working oil supplied from the primary pressure line 16 to the pump port 14 flows through the oil hole 22A into the space between the sleeve 22 and the pilot spool valve 24, and is introduced from the oil hole 22B through the control pressure line 5A into the hydraulic pilot section 4A of the directional control valve 4. As a result, working oil is supplied from the electromagnetic proportional pressure reducing valve 11A through the control pressure line 5A to the hydraulic pilot section 4A of the directional control valve 4, and the control pressure PA in the hydraulic pilot section 4A rises.

[0095] Here, the intermediate pad 24C of the pilot slide valve 24 is formed with a diameter larger than that of the intermediate pad 24D, thus creating a pressure-bearing area difference between the intermediate pads 24C and 24D within the sleeve 22 for the control pressure. As a result, as described above, the pilot slide valve 24 bears the hydraulic pressure (pressing pressure) of the pressure-bearing area difference between the intermediate pad 24C on the large-diameter side and the intermediate pad 24D on the small-diameter side as a load in the direction opposite to the push rod 20C (arrow B direction).

[0096] At this time, while the sum of the load (hydraulic force) in the direction of arrow B generated by the aforementioned difference in pressure area and the force of the return spring 26 is less than the pressing force (electromagnetic force) in the direction of arrow A generated by the push rod 20C, the pilot slide valve 24 moves further towards the damping chamber 29 in the direction of arrow A. As a result, the opening between the pump port 14 and the control pressure line 5A increases, further supplying working oil from the pump port 14 to the control pressure line 5A, and the control pressure rises.

[0097] On the other hand, when the sum of the load in the direction of arrow B generated by the difference in the pressure area and the force of the return spring 26 is greater than the pressing force in the direction of arrow A generated by the push rod 20C, the pilot slide valve 24 is pushed back towards the electromagnetic actuator 20 in the direction of arrow B. As a result, the intermediate pad 24C on the large-diameter side of the pilot slide valve 24 slides into the sliding hole 23C, disconnecting the pump port 14 from the control pressure line 5A. The intermediate pad 24D on the small-diameter side returns from the sliding hole 23D of the sleeve 22 to the position of the oil hole 22B, connecting the control pressure line 5A to the discharge port 15. Therefore, the working oil in the hydraulic pilot section 4A of the directional control valve 4 is discharged to the discharge port 15 via the control pressure line 5A, reducing the control pressure.

[0098] In this way, the pilot valve 24 repeatedly reciprocates within the sleeve 22 along the axial direction (arrows A and B), repeatedly causing the working oil to flow in and out of the hydraulic pilot section 4A of the directional control valve 4. As a result, the control pressure within the hydraulic pilot section 4A of the directional control valve 4 is adjusted to balance the pressing force (electromagnetic force) applied to the push rod 20C of the pilot valve 24, the force of the return spring 26, and the load (hydraulic) in the direction of arrow B caused by the difference in the pressure area. In other words, the pressing force of the push rod 20C in the direction of arrow A is adjusted by the value of the current supplied to the electromagnetic actuator 20, and therefore, the control pressure within the hydraulic pilot section 4A of the directional control valve 4 can be variably controlled by the value of the current supplied to the electromagnetic actuator 20.

[0099] Furthermore, during the adjustment of the control pressure within the hydraulic pilot section 4A of the directional control valve 4, a volume change occurs in the damping chamber 29 due to the movement (axial displacement) of the pilot spool valve 24. Simultaneously, along with this volume change in the damping chamber 29, the working oil flows within the throttle orifice 25, thus generating flow resistance in the throttle orifice 25 to exert a damping effect by suppressing rapid volume changes. In this way, by providing the throttle orifice 25 and the damping chamber 29, rapid axial displacement of the pilot spool valve 24 can be suppressed, vibration can be mitigated, and therefore the control pressure can be stabilized.

[0100] On the other hand, when the operator moves the operating lever 10A (refer to...) Figure 1When the supply of control current from controller 30 to electromagnetic actuator 20 stops, such as when the controller returns to the neutral position, the solenoid of electromagnetic actuator 20 is demagnetized, and push rod 20C returns to its initial state (standby position) in the direction of arrow B. Therefore, pilot valve 24 is pushed back towards electromagnetic actuator 20 by the force of return spring 26. As a result, pump port 14 is disconnected from control pressure line 5A, and control pressure line 5A becomes connected to discharge port 15. Therefore, the working oil in the hydraulic pilot section 4A of directional control valve 4 is discharged to discharge port 15 via control pressure line 5A, and the control pressure decreases to tank pressure as the control current stops.

[0101] Next, the operation of the controller 30 will be explained. In the controller 30, an operation signal from the operating lever device 10 is first input to the control requirement value calculation unit 31. The control requirement value calculation unit 31 calculates and outputs the control requirement value pR based on the operation signal and the design information of the construction surface pre-stored in the construction surface design information storage area 34.

[0102] The control requirement value pR output from the control requirement value calculation unit 31 is input to the control target value determination unit 32 and corrected. Then, the control target value determination unit 32 outputs its correction result as the control target value pT. Details of this correction process will be described later.

[0103] The control target value pT output from the control target value determination unit 32 is converted into the control target current value IT in the control target value conversion unit 33 according to the relationship between the current and control pressure of the electromagnetic proportional pressure reducing valve 11A stored in the controller 30 as a numerical table in advance, and then output.

[0104] Then, in the current feedback control unit 35, feedback control is performed with the target current value IT as the target value, the actual current IA flowing through the electromagnetic actuator 20 as the control quantity, and the duty cycle in the pulse width modulation of the drive voltage VC as the operating quantity. The electromagnetic actuator 20 drives the pressure control valve 21 by means of the electromagnetic force Fact corresponding to the actual current IA.

[0105] The following is based on Figure 6 Taking the input of the control requirement value pR (indicated by the dashed line) as an example, the detailed processing flow and operation of the control target value determination unit 32 up to the output control target value pT (indicated by the dotted line) will be explained, as well as the operation of the electromagnetic proportional pressure reducing valve 11A controlled by the controller 30, which includes the processing in the control target value determination unit 32.

[0106] First of all, Figure 6In the context of the control target value determination unit 32, if we focus on the interval SEC1 divided between time t0 and t1, the control requirement value pR is the non-drive equivalent value p0 (0 MPa). Therefore, in the control target value determination unit 32, Figure 5 In step S2, if "Yes" is selected in the decision, then in interval SEC1, Figure 5 The processes S1, S2, S3, S4, and S5 are executed sequentially and repeatedly at each control sampling time. Therefore, in interval SEC1, the non-drive equivalent value p0 is continuously output from the control target value determination unit 32 as the control target value pT. Therefore, the non-drive equivalent current value I0 (e.g., I0 = 0A) corresponding to the non-drive equivalent value p0 is continuously output from the control target value conversion unit 33.

[0107] Then, through the current control of the current feedback control unit 35, the actual current IA is controlled to maintain the non-drive equivalent current value I0. The non-drive equivalent current value I0 is set to the current value at which the electromagnetic force Fact of the electromagnetic actuator 20 does not exceed the force of the return spring 26. Therefore, by continuously maintaining the actual current IA at the non-drive equivalent current value I0, the intermediate pad 24C of the pilot slide valve 24 disconnects the pump port 14 from the control pressure line 5A, and the control pressure line 5A (i.e., the hydraulic pilot section 4A of the directional control valve 4) remains connected to the discharge port 15. Therefore, the control pressure pA of the electromagnetic proportional pressure reducing valve 11A is as follows: Figure 6 As shown by the solid line, the output non-driven equivalent value is p0 (0 MPa).

[0108] Additionally, within interval SEC1, through repeated... Figure 5 In step S4, the control requirement value pR is converted into a stop requirement duration TI that is below the non-drive equivalent value p0, which is accumulated as TI1. Here, for ease of explanation later, TI1 satisfies TI1≥TC with respect to the specified time TC.

[0109] Next, in Figure 6 In the context of the control target value determination unit 32, when considering the interval SEC2 divided between times t1 and t2, the control requirement value pR exceeds the non-drive equivalent value p0 from time t1 onwards. Therefore, in the control target value determination unit 32, Figure 5 In step S2, if "No" is selected, the process proceeds to step S6. Furthermore, in step S6, the relationship between the duration TI and the predetermined time TC is determined.

[0110] At time t1, TI = TI1, and as mentioned above, TI1 ≥ TC, therefore at Figure 5In step S6, select "Yes" and proceed to step S7. In step S7, the elapsed time τ from the start of the drive is set to zero. Therefore, time t1 becomes the start of the drive. In step S8, the control target value pT is calculated using equation (1). At time t1, the elapsed time τ from the start of the drive is zero, so pT = pmax is calculated in equation (1). Then, in step S9, the stop requirement duration TI is set to zero, and finally, in step S5, the control sampling time is increased by the elapsed time τ from the start of the drive t1.

[0111] After the control sampling time has elapsed and at time t1, "No" is selected again in step S2, and the process proceeds to step S6. Here, in the process of step S9 at time t1, the stop requirement duration TI is set to zero. Therefore, at times after t1, "No" is selected in step S6, and the process of step S7 is not executed, but proceeds to step S8. Then, the processes of steps S8, S9, and S5 are executed sequentially, just as they were at time t1.

[0112] That is, in Figure 6 In the interval SEC2, at time t1, Figure 5 The processes of steps S1, S2, S6, S7, S8, S9, and S5 are executed in a series. After time t1, the processes of steps S1, S2, S6, S8, S9, and S5 are repeated in a series according to each control sampling time.

[0113] Through this action, pT = pmax is output at time t1, and therefore the maximum drive current value Imax is output from the control target value conversion unit 33 as the control target current value IT. The current feedback unit uses this as the target value to control the actual current IA of the electromagnetic actuator 20. That is, at the start of the drive at time t1, the electromagnetic actuator 20 is controlled to press the pilot slide valve 24 of the pressure control valve 21 with the maximum electromagnetic force that can be output within the operating range.

[0114] Furthermore, after time t1, the elapsed time τ from the start of the drive gradually increases. Based on the calculation of equation (1), the control target value pT gradually approaches the control requirement value pR. Therefore, after time t1, the control target current value IT gradually approaches the current value corresponding to the control requirement value pR from the maximum drive current value Imax.

[0115] Therefore, according to the control device of this embodiment, when the drive based on the electromagnetic actuator 20 starts, the pilot slide valve 24 is displaced towards the damping chamber 29 with the maximum drive acceleration within the operating range. As a result, the intermediate pad 24C on the large diameter side enters the position of the oil hole 22B from the sliding hole portion 23C, so that the oil holes 22A and 22B (between the pump port 14 and the control pressure line 5A) are connected, and the intermediate pad 24D on the small diameter side slides (enters) into the sliding hole portion 23D of the sleeve 22, shortening the time until the oil holes 22B and 22C (between the control pressure line 5A and the discharge port 15) are cut off, and reducing the useless time when the control pressure rises.

[0116] Furthermore, according to the hydraulic system 100 of this embodiment, the target current value IT gradually approaches the current value corresponding to the control requirement value pR, thus suppressing excessive displacement of the pilot spool valve 24 (suppressing excessive opening between the pump port 14 and the control pressure line 5A). After the control pressure is generated, the control pressure pA can follow the control requirement value pR without significantly exceeding the control requirement value pR.

[0117] Next, in Figure 6 In this context, focusing on the interval SEC3 divided between times t2 and t3, the control requirement value pR is the non-drive equivalent value p0. Therefore, the control target value determination unit 32 continuously outputs the non-drive equivalent value p0 as the control target value pT through the same operation as in interval SEC1. Furthermore, the duration TI of the stop requirement when the control requirement value pR is below the non-drive equivalent value p0 is accumulated as TI2. Here, for ease of explanation later, before the control pressure pA in interval SEC2 completely decreases to the non-drive equivalent value p0 in interval SEC3, the next interval SEC4 begins, and TI2 satisfies TI2 < TC relative to the specified time TC.

[0118] exist Figure 6 If we focus on the interval SEC4, which is divided between times t3 and t4, then from time t3 onwards, the control requirement value pR again exceeds the non-drive equivalent value p0. Therefore, similar to interval SEC2, in the control target value determination unit 32, in Figure 5 In step S2, if "No" is selected, the process proceeds to step S6. Then, in step S6, the relationship between the duration TI and the specified time TC is determined.

[0119] However, at time t3, TI = TI2, and as mentioned above, TI2 < TC. Therefore, in step S6, unlike the case of interval SEC2, "No" is selected, and the processing of step S7 is not performed, but the process is transferred to step S8. Steps S8, S9, and S5 are then executed sequentially. That is, time t3 is not reset to the drive start time, but the drive start time is processed in the state of the previously set time t1, and the elapsed time τ from the drive start time is also incremented in the state starting from time t1. Therefore, at time t3, in the calculation of the control target value pT based on equation (1) in step S8, the exponential function exp(-K·τ) is maintained in a state that gradually approaches zero. Figure 6 As shown, at time t3, the control target value pT is not pT = pmax, but is output as a value that gradually approaches the control requirement value pR. Moreover, after the control sampling time, even at times after time t3, TI = 0 < TC, so the same processing as at time t3 is performed, and the control target value pT is output as a value that gradually approaches the control requirement value pR.

[0120] That is, when the control requirement value pR in the interval SEC2 decreases to the start of drive in the interval SEC4, and the stop requirement duration TI2 in the interval SEC3 is less than the specified time TC, the control target value determination unit 32 does not perform correction, and the control requirement value pR is set as the control target value pT.

[0121] However, in the electromagnetic proportional pressure reducing valve 11A, as described above, pressure control is achieved through the reciprocating motion of the pilot slide valve 24, causing the intermediate pad 24C on the large-diameter side and the intermediate pad 24D on the small-diameter side of the pilot slide valve 24 to connect and close the pump port 14 with the control pressure line 5A, and the control pressure line 5A with the discharge port 15, respectively. That is, during pressure control, the pilot slide valve 24 repeatedly reciprocates near the positions where this connection and closure occur. Furthermore, the pilot slide valve 24 exhibits a displacement delay relative to the output of the control requirement value pR in the controller 30, in terms of its motion characteristics.

[0122] Therefore, even when the control requirement value pR drops completely to the non-drive equivalent value p0, the pilot spool valve 24 remains in the open / closed position due to the movement delay of the pilot spool valve 24, and the electromagnetic proportional pressure reducing valve 11A sometimes continues to perform pressure control operations.

[0123] When the control requirement value pR is increased again from this state, similar to the start of the drive in interval SEC1, if the control target value pT is set to pmax, the pilot slide valve 24 experiences the maximum electromagnetic force from the electromagnetic actuator 20 near the opening / closing position. Therefore, the pilot slide valve 24 is excessively displaced towards the damping chamber 29, causing excessive opening between the pump port 14 and the control pressure line 5A. As a result, the control pressure pA significantly exceeds the control requirement value pR.

[0124] In contrast, in the control device of this embodiment, as in the operation at time t3 in interval SEC4, the control pressure pA does not fully decrease during the time when it has not fully returned to the position near the opening and closing position of the pilot slide valve 24. Figure 2 During the non-drive period, when the control requirement value pR becomes the equivalent value of the drive, the control target value determination unit 32 does not set the control target value pT to pmax, but directly outputs the control requirement value pR. Therefore, it can prevent the control pressure pA of the electromagnetic proportional pressure reducing valve 11A from deviating significantly from the control requirement value pR.

[0125] <Summary>

[0126] In this embodiment, the hydraulic system 100 includes: a hydraulic pump 1; a hydraulic actuator 3 driven by hydraulic oil discharged from the hydraulic pump 1; a control valve 4 that controls the supply and discharge of hydraulic oil discharged from the hydraulic pump 1 to the hydraulic actuator 3; a solenoid valve 11A (11B) that generates a control pressure pA (pB) for actuating the control valve 4; an operating device 10 that performs an operation to input a required value of the control pressure pA (pB), i.e., a control requirement value pR; and a controller 30 that sets a target value of the control pressure pA (pB), i.e., a control target value pT, based on the control requirement value pR, and drives the solenoid valve 11A (11B) based on the control target value pT. The controller 30 sets the control target value pT in such a way that it becomes the maximum output pressure pmax within the operating range of the solenoid valve 11A (11B) at the start time of actuation of the solenoid valve 11A (11B), and gradually approaches the control requirement value pR over time after becoming the maximum output pressure pmax.

[0127] According to this embodiment configured as described above, the control target value pT at the start time of actuation of solenoid valve 11A (11B) is set to the maximum output pressure pmax within the operating range of solenoid valve 11A (11B), independent of the control requirement value pR. Therefore, immediately after the start of actuation of solenoid valve 11A (11B), the valve core of solenoid valve 11A (11B) rapidly moves to the open position, thus shortening the delay time from the start of actuation of solenoid valve 11A (11B) to the start of rise in control pressure pA (pB). Furthermore, after the control pressure pA (pB) begins to rise, as time passes from the start of actuation of solenoid valve 11A (11B), the control target value pT gradually approaches the control requirement value pR, thus preventing the control pressure pA (pB) from significantly exceeding the control requirement value pR. Therefore, when the solenoid valve 11A (11B) is actuated, the control pressure pA (pB) output from the solenoid valve 11A (11B) can quickly follow the control requirement value pR. Furthermore, in this embodiment, an exponential function is used to make the control target value pT gradually approach the control requirement value pR, but other functions (e.g., hyperbolic functions) can also be used.

[0128] Furthermore, the controller 30 calculates the control target value pT by recognizing that the difference between the control target value pT and the control requirement value pR decreases exponentially with increasing time τ. Therefore, the calculation formula for the control target value pT installed on the controller 30 can be defined using a simple exponential function. Moreover, the degree to which the control target value pT gradually approaches the control requirement value pR can be determined simply by changing the base of the exponential function.

[0129] Furthermore, if the time from the start of the drive of solenoid valve 11A (11B) to the next start of the drive is less than a predetermined time TC, the controller 30 measures the elapsed time τ starting from the previous start of the drive of solenoid valve 11A (11B). If the time from the start of the drive of solenoid valve 11A (11B) to the next start of the drive is greater than or equal to the predetermined time TC, the controller 30 measures the elapsed time τ starting from the next start of the drive of solenoid valve 11A (11B). Therefore, the controller measures the elapsed time τ from the time when the control pressure pA (pB) has not fully decreased, i.e., when it has not fully returned to the position near the opening / closing position of the pilot spool valve 24. Figure 2 During the non-drive position time shown, when the control requirement value pR becomes the drive equivalent value, the control target value pT is not set to pmax in the control target value determination unit 32, but the control requirement value pR is directly output. Therefore, it is possible to prevent the control pressure pA (pB) of the solenoid valve 11A (11B) from deviating significantly from the control requirement value pR.

[0130] Furthermore, the solenoid valve 11A (11B) has an electromagnetic actuator 20 controlled by a voltage output from the controller 30, and a pressure control valve 21 driven by the electromagnetic actuator 20. The controller 30 calculates the target value IT of the current IA (IB) flowing through the electromagnetic actuator 20 based on the control target value pT. By using feedback control with at least one of proportional compensation, derivative compensation, and integral compensation, the current IA (IB) flowing through the electromagnetic actuator 20 follows the target value IT. This improves the driving accuracy of the electromagnetic actuator 20.

[0131] Example 2

[0132] Reference Figure 7 The second embodiment 100 of the present invention will be described. Figure 7 This is a functional block diagram of the hydraulic system 100 in this embodiment. Hereinafter, it will be compared with the first embodiment (see reference...). Figure 3 The explanation will focus on the differences between them.

[0133] exist Figure 7 In the middle, the controller 30 omits the control target value conversion unit 33 (see reference). Figure 3 ), replacing the current detector 35C (refer to) that detects the current IA (IB) flowing in the electromagnetic actuator 20. Figure 3 The controller 30 of the first embodiment (see reference 35D) is equipped with a detector 35D that detects the control pressure pA (pB) output from the pressure control valve 21. Figure 3 The current IA flowing through the electromagnetic actuator 20 is controlled by feedback using at least one of proportional compensation, derivative compensation, and integral compensation. In contrast, the controller in this embodiment (refer to...) Figure 7 Feedback control is performed on the control pressure pA (pB) output from solenoid valve 11A (11B).

[0134] <Summary>

[0135] The controller 30 of the hydraulic system 100 in this embodiment uses feedback control of at least one of proportional compensation, derivative compensation and integral compensation to make the control pressure pA (pB) output from the solenoid valve 11A (11B) follow the control target value pT.

[0136] According to this embodiment configured as described above, the control pressure pA (pB) output from the solenoid valve 11A (11B) is subjected to feedback control, thereby improving the control accuracy of the control pressure pA (pB).

[0137] Example 3

[0138] The third embodiment of the present invention will be described focusing on its differences from the first embodiment. In this embodiment, only the differences from the first embodiment are described. Figure 5 The calculation of the control target value pT in step S8 is different.

[0139] In this embodiment, Figure 5 In step S8 shown, the control target value pT is calculated using the following formula (2).

[0140] [Formula 2]

[0141] p T =(p max -p C -p R )exp(-K A ·τ)+p C exp(-K B ·τ)+p R …Formula (2)

[0142] In equation (2), pc is a specified value that is smaller than the maximum output pressure pmax and greater than zero, and KA and KB are positive specified values. In addition, KA represents the speed at which the first term on the right side of equation (2) gradually approaches zero, and KB represents the speed at which the second term on the right side of equation (2) gradually approaches zero. KA is set to a value greater than KB. That is, the second term on the right side of equation (2) gradually approaches zero more smoothly than the first term on the right side of equation (2).

[0143] exist Figure 7 The table shows the time history waveforms of the control requirement value pR (represented by solid lines) and the control target value pT (represented by dashed lines) calculated by equation (2). The first and second terms on the right-hand side of equation (2) contain exponential functions (exp(-KA·τ) and exp(-KB·τ)), where the exponent is the product of the elapsed time τ from the start of the drive and a constant value. Therefore, at time t0 (i.e., τ = 0), which is the start of the drive, if the control target value pT is calculated using equation (2), the output value of the exponential function is 1, calculated as pT = pmax. That is, at time t0 (the start of the drive), if... Figure 7 As shown, the control target value pT is set to the maximum output pressure pmax within the operating range of the electromagnetic proportional pressure reducing valve 11A.

[0144] On the other hand, the exponential functions (exp(-KA·τ) and exp(-KB·τ)) contained in the first and second terms on the right-hand side of equation (2) have bases of exp(-KA) and exp(-KB), respectively, and exponents of τ. Furthermore, KA and KB are positive numbers, so the bases exp(-KA) and exp(-KB) are both less than 1. Therefore, as the elapsed time τ from the start of the drive increases, the exponential functions exp(-KA·τ) and exp(-KB·τ) gradually approach zero. That is, the first and second terms on the right-hand side of equation (2) gradually approach zero as time passes from the start of the drive, therefore... Figure 7 As shown, the control target value pT (represented by the dashed line) gradually approaches the control requirement value pR (represented by the solid line).

[0145] As described above, the target control value pT gradually approaches the required control value pR. However, if we change the way we observe equation (2), the first term on the right-hand side gradually approaches zero, thus... Figure 7 As shown, the control target value pT gradually approaches the sum of the second term on the right and the control requirement value pR (represented by a single-dotted line), while the second term on the right gradually approaches zero, thus the control target value pT gradually approaches the control requirement value pR. Therefore, by using the calculation based on equation (2), the control target value pT can gradually approach the control requirement value pR, and in the process of gradually approaching, the control target value pT is set to a larger value than that in equation (1).

[0146] Therefore, in this embodiment, for example, when the working oil of the pilot slide valve 24 has a large viscosity resistance due to low temperature environment, when the electromagnetic proportional pressure reducing valves 11A and 11B are used continuously, and when the throttling diameter of the throttling orifice 25 is set to be small in order to ensure the stability of the pressure control of the electromagnetic proportional pressure reducing valves 11A and 11B, the movement of the pilot slide valve 24 slows down, etc., a better effect of reducing the useless time can be obtained compared with the first embodiment.

[0147] In addition, by setting the specified value pc to zero, Equation (2) becomes the same calculation as Equation (1), and can also be processed as the first implementation method.

[0148] <Summary>

[0149] The controller 30 of the hydraulic system 100 in this embodiment sets the value obtained by adding the first value (the first term on the right side of equation (2)), the second value (the second term on the right side of equation (2)), and the control requirement value pR as the control target value pT. The first value is a value that gradually approaches zero as time τ increases, obtained by subtracting the control requirement value pR and a predetermined value pc smaller than the maximum output pressure pmax from the maximum output pressure pmax. The second value is a value that slowly approaches zero compared to the first value as time τ increases.

[0150] According to this embodiment configured as described above, the sum of the first value (the first term on the right side of equation (2)) and the second value (the second term on the right side of equation (2)) of the actuation start time of solenoid valve 11A (11B) is the value obtained by subtracting the control requirement value pR of the actuation start time from the maximum output pressure pmax. The control target value pT of solenoid valve 11A (11B) is the sum of the first value, the second value, and the control requirement value pR of the actuation start time. Therefore, the control target value pT of the actuation start time of solenoid valve 11A (11B) is set to the maximum output pressure pmax of solenoid valve 11A (11B) regardless of the control requirement value pR, just like in the first embodiment.

[0151] Furthermore, both the first and second values ​​gradually approach zero as the elapsed time τ from the start of actuation of solenoid valve 11A (11B) increases. Therefore, the control target value pT of solenoid valve 11A (11B) gradually approaches the control requirement value pR as the elapsed time τ increases, similar to the first embodiment. Here, the second value approaches zero at a slower rate than the first value. Therefore, a predetermined value pc is appropriately set according to the response characteristics of solenoid valve 11A (11B), thereby adjusting the rate at which the control target value pT gradually approaches the control requirement value pR. Thus, for example, in situations where solenoid valve 11A (11B) is continuously used under conditions of high viscous resistance of the working fluid acting on the valve core, such as in low-temperature environments, or when the displacement of the valve core of solenoid valve 11A (11B) is slow, increasing the predetermined value pc suppresses the rate at which the control target value pT gradually approaches the control requirement value pR, thereby achieving a better reduction in wasted time than in the first embodiment.

[0152] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments and includes various modifications. For example, the above embodiments are described in detail for the purpose of easily understanding the present invention and are not limited to having all the structures described. In addition, a part of the structure of another embodiment may be added to the structure of a certain embodiment, a part of the structure of a certain embodiment may be deleted, or a part of the structure of another embodiment may be replaced.

[0153] Symbol Explanation

[0154] 1. Hydraulic pump; 1A Discharge line; 2. Oil tank; 3. Hydraulic cylinder (hydraulic actuator); 3A pipe; 3B piston; 3C rod; 3D, 3E oil chambers; 4. Directional control valve; 4A, 4B hydraulic pilot sections; 5A, 5B control pressure lines; 6A, 6B main lines; 7. Pilot pump; 8. Low-pressure relief valve; 9. High-pressure relief valve; 10. Operating lever device (operating device); 11A, 11B electromagnetic proportional pressure reducing valves (solenoid valves); 12. Housing; 13. Solenoid valve box insertion hole; 14. Pump port; 15. Discharge port; 16. Primary pressure line; 17. Discharge line; 20. Electromagnetic actuator; 21. Pressure control valve ; 22 Sleeve; 22A, 22B, 22C Oil Holes; 23 Stepped Hole; 23A Spring Receiving Hole; 23B, 23C, 23D, 23E Sliding Hole; 24 Pilot Slide Valve; 24A Boss; 24B Pad; 24C, 24D Intermediate Pad; 24E Pad; 24F Shaft Hole; 24G, 24H Oil Circuit; 25 Throttling Orifice; 27 Partition Plate; 28 Component; 29 Damping Chamber; 30 Controller; 31 Control Requirement Value Calculation Unit; 32 Control Target Value Determination Unit; 33 Control Target Value Conversion Unit; 34 Construction Surface Design Information Storage Area; 35 Current Feedback Control Unit; 35A PID Compensator; 35B PWM Drive Device; 35C Current Detector; 43 Discharge Pipeline; 100 Hydraulic System.

Claims

1. A hydraulic system comprising: Hydraulic pump; A hydraulic actuator driven by hydraulic oil discharged from the hydraulic pump; A control valve that controls the supply and discharge of hydraulic oil from the hydraulic pump to the hydraulic actuator; A solenoid valve that generates a control pressure to actuate the control valve; Operating device, which performs the operation of inputting the required value of the control pressure, i.e., the control requirement value; and The controller sets the target value of the control pressure, i.e., the control target value, based on the control requirement value, and drives the solenoid valve according to the control target value. Its features are, The controller sets the control target value as follows: at the start time of the solenoid valve's actuation, it becomes the maximum output pressure within the solenoid valve's operating range; after reaching this maximum output pressure, it gradually approaches the control requirement value over time. The controller sets the value obtained by adding the first value, the second value, and the control requirement value as the control target value. The first value is a value that gradually approaches zero as time increases, obtained by subtracting the control requirement value and a predetermined value smaller than the maximum output pressure from the maximum output pressure. The second value is a value that slowly approaches zero compared to the first value as time increases.

2. The hydraulic system according to claim 1, characterized in that, The controller calculates the control target value in such a way that the difference between the control target value and the control requirement value decreases exponentially as time increases.

3. The hydraulic system according to claim 1, characterized in that, If the time from the start of the drive of the solenoid valve to the next start of the drive is less than a predetermined time, the controller measures the elapsed time starting from the previous start of the drive of the solenoid valve. If the time from the start of the drive of the solenoid valve to the next start of the drive is greater than or equal to the predetermined time, the controller measures the elapsed time starting from the next start of the drive of the solenoid valve.

4. The hydraulic system according to claim 1, characterized in that, The solenoid valve includes: an electromagnetic actuator controlled by a voltage output from the controller; and a pressure control valve driven by the electromagnetic actuator. The controller calculates the target value of the current flowing through the electromagnetic actuator, i.e., the target current value, based on the control target value. By using feedback control with at least one of proportional compensation, derivative compensation, and integral compensation, the current flowing through the electromagnetic actuator follows the target current value.

5. The hydraulic system according to claim 1, characterized in that, The controller uses feedback control employing at least one of proportional compensation, derivative compensation, and integral compensation to ensure that the control pressure output from the solenoid valve follows the target control value.

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