Control device, and hydraulic system provided with the control device

Abstract

A control device that controls operation of a valve body of a valve device, includes a flow rate acquisition unit that acquires a flow rate of the valve device, a flow state determination unit that determines whether or not a flow of hydraulic fluid of the valve device is a transient flow state based on an input flow rate target value and a flow rate estimated value estimated by the flow rate acquisition unit, an opening command calculation unit that calculates an opening command based on the flow rate target value and a pressure difference before and after the valve device, and a valve body control unit that controls operation of the valve body, the valve body control unit controlling operation of the valve body based on the opening command when the flow state determination unit determines that it is not a transient flow state, and controlling operation of the valve body based on the flow rate target value when the flow state determination unit determines that it is a transient flow state.

Description

Technical Field

[0001] The present invention relates to a control device for controlling the movement of the valve body of a valve device in a hydraulic system, and a hydraulic system having the control device. Background Technology

[0002] The hydraulic system includes a control device. This control device controls the movement of the valve body of a valve assembly within the hydraulic system, such as the spool of a spool valve. For example, Patent Document 1 is known as such a control device. In the control device of Patent Document 1, position control signals are fed back based on the spool position detected by a sensor circuit.

[0003] Existing technical documents:

[0004] Patent documents:

[0005] Patent document 1: Japanese Patent Application Publication No. 2003-167604. Summary of the Invention

[0006] The problem the invention aims to solve:

[0007] In the control device of Patent Document 1, there is also a control device that controls both the valve core position and the flow rate of the valve device. In such a control device, the valve body opening, i.e., the valve core position command, is calculated based on the target flow rate value and the actual flow rate. For example, the valve core position command is calculated based on the relationship between flow rate and pressure loss. The relationship between flow rate and pressure loss is a relationship that holds true when the flow state of the working fluid in the valve device is a stable flow state or a quasi-stable flow state. Therefore, conventional control devices mainly provide stability in flow control under stable or quasi-stable flow states.

[0008] Therefore, the object of the present invention is to provide a control device that can improve the stability of flow control under transitional flow conditions.

[0009] Solution methods:

[0010] The control device of the present invention controls the operation of the valve body of a valve device, comprising: a flow acquisition unit for acquiring the flow rate of the valve device; a flow state determination unit for determining whether the flow of the working fluid in the valve device is in a transitional flow state based on an input flow target value and a flow estimate value estimated by the flow acquisition unit; an opening command calculation unit for calculating an opening command based on the flow target value and the pressure difference across the valve device; and a valve body control unit for controlling the operation of the valve body; wherein the valve body control unit controls the operation of the valve body based on the opening command when the flow state determination unit determines that the flow state is not in a transitional flow state, and controls the operation of the valve body based on the flow target value when the flow state determination unit determines that the flow state is in a transitional flow state.

[0011] According to the present invention, by dividing the valve body into transitional flow state and non-transitional flow state, i.e., stable flow or quasi-stable flow state, the stability of flow control in transitional flow state can be improved.

[0012] The hydraulic system of the present invention includes the aforementioned control device. The valve device includes at least one electromagnetic proportional valve and a spool valve. The spool valve has a valve core that serves as the valve body. The valve core travels according to a pilot pressure acting on the valve core. The electromagnetic proportional valve outputs a pilot pressure acting on the valve core. When the flow state determination unit determines that the flow state is a non-transitional flow state, the valve body control unit outputs a pilot pressure corresponding to the opening command from the electromagnetic proportional valve to control the operation of the valve body. When the flow state determination unit determines that the flow state is a transitional flow state, the valve body control unit outputs a pilot pressure corresponding to the flow target value from the electromagnetic proportional valve to control the operation of the valve body.

[0013] According to the present invention, a stable hydraulic system with improved flow control under transitional flow conditions can be provided.

[0014] Invention effects:

[0015] According to the present invention, the stability of flow control in transitional flow states can be improved.

[0016] The above-mentioned objects, other objects, features and advantages of the present invention will become clear from the following detailed description of preferred embodiments, in addition to referring to the accompanying drawings. Attached Figure Description

[0017] Figure 1 This is a hydraulic circuit diagram illustrating a hydraulic system according to an embodiment of the present invention;

[0018] Figure 2 yes Figure 1 A block diagram of the control devices of a hydraulic system;

[0019] Figure 3 To show in more detail Figure 2 A block diagram of the opening instruction limit value calculation unit;

[0020] Figure 4 (a) is a graph showing the change of the target flow value and the estimated flow value over time, and (b) is a graph showing the change of the opening command of the prior art and the opening command of the present invention over time;

[0021] Figure 5 This is a graph showing the changes in flow rate over time between the prior art and the present invention. Detailed Implementation

[0022] Hereinafter, a hydraulic system 1 and a control device 17 according to an embodiment of the present invention will be described with reference to the aforementioned accompanying drawings. Furthermore, the directional concepts used in the following description are for ease of explanation and are not intended to limit the orientation of the invention's structure to the described directions. Moreover, the hydraulic system 1 and control device 17 described below are merely one embodiment of the present invention. Therefore, the present invention is not limited to the following embodiment, and additions, deletions, and modifications can be made without departing from the spirit of the invention.

[0023] Construction machinery is equipped with hydraulic actuators and hydraulic systems to enable the movement of its various components. For example, a hydraulic actuator is... Figure 1 The hydraulic cylinder 2 is shown. The hydraulic cylinder 2 is installed correspondingly to various structures of the engineering machinery. The hydraulic cylinder 2 can operate the corresponding structures by extending and retracting. More specifically, the hydraulic cylinder 2 has a rod-side port 2a and a head-side port 2b. The hydraulic cylinder 2 extends and retracts by supplying working fluid to each port 2a and 2b.

[0024] The hydraulic system 1 can supply working fluid to the hydraulic cylinder 2. Moreover, the hydraulic system 1 can extend and retract the hydraulic cylinder 2 by supplying working fluid to the hydraulic cylinder 2. The hydraulic system 1 with such functions includes, for example, a hydraulic pump 11, a valve device 12, three pressure sensors 13-15, an operating device 16, and a control device 17.

[0025] The hydraulic pump 11 discharges working fluid. More specifically, the hydraulic pump 11 is connected to a drive source. The drive source is an engine E and an electric motor. In this embodiment, the drive source is the engine E. The hydraulic pump 11 is driven by the rotation of the engine E to discharge the working fluid. Furthermore, in this embodiment, the hydraulic pump 11 is a swashplate pump or a swashplate pump.

[0026] A valve device 12 is disposed between the hydraulic pump 11 and the hydraulic cylinder 2. Furthermore, the valve device 12 can control the flow direction and flow rate of the working fluid flowing from the hydraulic pump 11 to the hydraulic cylinder 2 according to input action commands. That is, the valve device 12 can switch the flow direction of the working fluid to either of the two ports 2a and 2b of the hydraulic cylinder 2, and can also cut off the flow of working fluid to the two ports 2a and 2b. More specifically, the valve device 12 is an electronically controlled spool valve. The valve device 12 includes a directional control valve 21 and two electromagnetic proportional control valves 22L and 22R.

[0027] The directional control valve 21 is connected to the hydraulic pump 11, the rod-side port 2a and the head-side port 2b of the hydraulic cylinder 2, and the tank 3. Furthermore, the directional control valve 21 can switch the connection status of the hydraulic pump 11, the rod-side port 2a and the head-side port 2b of the hydraulic cylinder 2, and the tank 3 (i.e., connect or disconnect them respectively). This switches the flow from the hydraulic pump 11 to the hydraulic cylinder 2. By changing the flow in this way, the directional control valve 21 can extend and retract the hydraulic cylinder 2. In addition, the directional control valve 21 can adjust the size of the opening when connecting the hydraulic pump 11 and the hydraulic cylinder 2, i.e., the opening degree. This allows adjustment of the flow rate of the working fluid flowing within the hydraulic cylinder 2. In other words, it allows adjustment of the extension and retraction speed of the hydraulic cylinder 2.

[0028] In more detail, the directional control valve 21 has a valve core 21a. The valve core 21a can switch its connection state by changing its position (i.e., stroke). That is, the valve core 21a can connect the hydraulic pump 11 to both the rod-side port 2a and the head-side port 2b, depending on its position. Furthermore, the valve core 21a can adjust its opening degree according to its stroke (or position). This allows for the regulation of the flow rate of the working fluid within the hydraulic cylinder 2. The valve core 21a, having such a function, withstands mutually opposing pilot pressures P1 and P2 and moves to a position corresponding to the pressure difference between the two pilot pressures P1 and P2.

[0029] As examples of electromagnetic proportional valves, the first and second electromagnetic proportional control valves 22L and 22R respectively output a first pilot pressure P1 and a second pilot pressure P2 corresponding to the input signal (current or voltage in this embodiment). The output first pilot pressure P1 and second pilot pressure P2 are introduced into the valve core 21a. More specifically, the first and second electromagnetic proportional control valves 22L and 22R are connected to a pilot pump (not shown). The first and second electromagnetic proportional control valves 22L and 22R adjust the pressure of the working fluid discharged from the pilot pump to the pressure corresponding to the signal and then output it to the valve core 21a.

[0030] Three pressure sensors 13-15 detect the hydraulic pressure before and after the directional control valve 21. More specifically, the first pressure sensor 13 is configured to correspond to the flow path connecting the directional control valve 21 and the hydraulic pump 11. Furthermore, the second pressure sensor 14 is configured to correspond to the flow path connecting the directional control valve 21 and the rod-side port 2a of the hydraulic cylinder 2. Moreover, the third pressure sensor 15 is configured to correspond to the flow path connecting the directional control valve 21 and the head-side port 2b. Each pressure sensor 13-15 detects the hydraulic pressure in its corresponding flow path. Furthermore, each pressure sensor 13-15 outputs the detected hydraulic pressure to the control device 17.

[0031] The operating device 16 outputs an operating command to the control device 17 to operate the hydraulic cylinder 2. The operating device 16 may be, for example, an operating valve or an electric joystick. More specifically, the operating device 16 has an operating lever 16a as an example of an operating tool. The operating lever 16a is configured to be operable by an operator. For example, the operating lever 16a is configured to be swingable. The operating device 16 outputs an operating command corresponding to the amount of operation of the operating lever 16a (the amount of swing in this embodiment) to the control device 17.

[0032] The control device 17 is connected to pressure sensors 13-15, two electromagnetic proportional control valves 22L and 22R, and the operating device 16. The control device 17 controls the operation of the valve core 21a of the valve assembly 12 according to the operating command from the operating device 16. More specifically, the control device 17 calculates the operation command based on the detection results of the pressure sensors 13-15 and the operating command from the operating device 16. The operation command is a pressure command used to control the operation of the valve core 21a of the valve assembly 12. In this embodiment, the operation command is the pressure command described later. The control device 17 outputs a signal corresponding to the pressure command to the electromagnetic proportional control valves 22L and 22R. Then, pilot pressures P1 and P2 corresponding to the pressure command are output from the electromagnetic proportional control valves 22L and 22R. Thus, the operation of the valve core 21a of the valve assembly 12 is controlled according to the operating command.

[0033] In more detail, the control device 17 obtains the target flow rate value and the pressure difference across the valve device 12 for calculating the action command. The target flow rate value is the target flow rate of the working fluid flowing to the hydraulic cylinder 2. In this embodiment, the control device 17 sets the target flow rate value based on the operation command from the operating device 16. On the other hand, the pressure difference across the valve device 12 (i.e., the pressure difference across the directional control valve 21) is the difference in pressure between the upstream and downstream sides of the valve device 12 (more specifically, the directional control valve 21) in the flow path connecting the hydraulic pump 11 and the hydraulic cylinder 2 via the valve device 12. The control device 17 calculates the pressure difference across the directional control valve 21 based on signals from the three pressure sensors 13-15. Furthermore, the control device 17 has an opening command calculation unit 31, a flow rate estimation calculation unit 32, an opening command limit value calculation unit 33, a valve body control unit 34, and an opening estimation calculation unit 35 for calculating the action command.

[0034] The opening command calculation unit 31 calculates the opening command for the directional control valve 21 based on the calculated target flow rate and the pressures before and after the directional control valve 21. The opening command is the degree to which the directional control valve 21 should open. In this embodiment, the opening command calculation unit 31 calculates the opening degree that allows the working fluid at the target flow rate to flow from the directional control valve 21 to the hydraulic cylinder 2.

[0035] As an example of a flow acquisition unit, the flow estimation calculation unit 32 calculates an estimated value, i.e., a flow estimation value, for the flow of the working fluid flowing inside the directional control valve 21 based on the calculated front and rear pressures of the directional control valve 21 and the estimated opening degree described later.

[0036] The opening command limit calculation unit 33 determines the flow state of the working fluid in the directional control valve 21 based on the calculated estimated flow rate and the target flow rate. Furthermore, the determined flow state of the working fluid includes a stable flow state, a quasi-stable flow state, and a transitional flow state. In addition, the opening command limit calculation unit 33 calculates the opening command limit value based on the determined flow state. The opening command limit value is the limit value (upper limit value) set by the valve body control unit 34, which will be described in detail later, when limiting the opening command. Moreover, the opening command limit calculation unit 33 smoothly changes the limit value as the flow transitions from a transitional flow state to a stable flow state or a quasi-stable flow state (hereinafter referred to as "stable flow state, etc.").

[0037] The opening command limit value calculation unit 33 includes a flow state determination unit 36, a limit value selection unit 37, and a rate of change limit unit 38. Furthermore, the flow state determination unit 36 ​​does not necessarily need to be included in the opening command limit value calculation unit 33. That is, the flow state determination unit 36 ​​can be independent of the opening command limit value calculation unit 33.

[0038] The flow state determination unit 36 ​​determines the flow state of the working fluid in the directional control valve 21 based on the calculated estimated flow rate and the target flow rate. In this embodiment, the flow state determination unit 36 ​​determines the flow state based on whether the difference between the calculated estimated flow rate and the target flow rate is within or outside a specified range. More specifically, the flow state determination unit 36 ​​determines whether it is a transitional flow state by whether the absolute value of the difference (hereinafter referred to as "absolute difference value") is less than a specified differential flow rate ΔQ. In this embodiment, the flow state determination unit 36 ​​with such function includes a subtraction calculator 41, an absolute value calculator 42, and a first comparator 43.

[0039] The subtractor 41 calculates the difference between the target flow rate and the estimated flow rate. The absolute value calculator 42 calculates the absolute value of the difference based on the calculated difference. Furthermore, the first comparator 43 determines whether the calculated absolute value of the difference is less than a predetermined differential flow rate ΔQ. Moreover, if the first comparator 43 determines that the absolute value of the difference is less than the differential flow rate ΔQ, the flow state is determined to be a stable flow state or a quasi-stable flow state. Conversely, if the first comparator 43 determines that the absolute value of the difference is greater than or equal to the differential flow rate ΔQ, the flow state is determined to be a transitional flow state. In this way, the flow state determination unit 36 ​​can easily determine the flow state by using the absolute value of the difference.

[0040] The limit value selection unit 37 selects the opening command limit value based on the determination of the flow state determination unit 36. More specifically, the limit value selection unit 37 invalidates the limit value when the flow state is determined to be a stable flow state, etc. In this embodiment, the limit value selection unit 37 invalidates the limit value by setting the limit value to the maximum opening value. On the other hand, when the flow state is determined to be a non-transitional flow state, the limit value selection unit 37 sets a limit value (< the maximum opening value) based on the flow target value. In this embodiment, the limit value selection unit 37 with such functions includes a limit invalidator 45, a limit value calculator 46, and a selector 47.

[0041] The limit invalidator 45 sets the limit values ​​(i.e., the upper and lower limits) to the maximum opening value (invalid limit value). On the other hand, the limit value calculator 46 calculates the limit value based on the calculated flow target value. In this embodiment, the limit value calculator 46 has a pre-set correspondence between the flow target value and the limit value. The limit value calculator 46 calculates the limit value (calculated setting value) based on the aforementioned correspondence. Furthermore, the selector 47 selects either the invalid limit value or the calculated limit value as the selected limit value based on the flow state determined by the flow state determination unit 36. For example, if the selector 47 determines that the flow state is a stable flow state, it selects the invalid limit value as the selected limit value. On the other hand, if the flow state is determined to be a transitional flow state, the selector 47 selects the calculated limit value as the selected limit value.

[0042] The rate of change limiting unit 38 adjusts the limiting value in a way that smooths the change in the opening command as the flow transitions from a transitional flow state to a stable flow state or a quasi-stable flow state (hereinafter referred to as "stable flow state, etc."). In this embodiment, the rate of change limiting unit 38 limits the rate of change of the limiting value to below a predetermined limiting rate of change during a predetermined time Ts after the flow state is switched, as described above. In this embodiment, the rate of change limiting unit 38 with such function includes a timer 51, a second comparator 52, and a rate of change limiting unit 53.

[0043] Timer 51 measures the elapsed time from the point in time when the flow state switching is determined by the flow state determination unit 36. More specifically, timer 51 begins measuring the elapsed time based on the output of the first comparator 43. That is, it begins measuring the elapsed time after the first comparator 43 determines that the differential absolute value is above the differential flow rate ΔQ, or when it determines that the differential flow rate ΔQ is below. The second comparator 52 determines whether the elapsed time measured in timer 51 is less than a predetermined time Ts.

[0044] When the rate of change limiter 53 determines in the second comparator 52 that the elapsed time is less than a predetermined time Ts, it limits the rate of change of the limit value to less than the limit rate of change. The rate of change limiter 53 then sets the limited value as the new limit value (set limit value). On the other hand, when the rate of change limiter 53 determines in the second comparator 52 that the elapsed time is more than the predetermined time Ts, it invalidates the limit related to the rate of change of the limit value. That is, the rate of change limiter 53 sets the selected limit value as the set limit value.

[0045] To elaborate further, the rate of change limiter 53 sets the next set limit value such that the rate of change of the selected limit value relative to the previously set limit value is below the limit rate of change. That is, the rate of change limiter 53 stores at least the previously set limit value. Furthermore, the rate of change limiter 53 calculates the rate of change of the calculated limit value relative to the previously set limit value. When the rate of change is above the limit rate of change, the rate of change limiter 53 sets the value obtained by adding the limit rate of change multiplied by Δt to the previously set limit value as the next set limit value (for example, see below). Figure 4 (b) The solid line from time t0 to t3 and the three-dot dashed line after time t3). In this embodiment, the limit rate of change is the amount of change per unit time, and Δt seconds is the calculation interval for calculating the set limit value. On the other hand, when the rate of change is less than the limit rate of change, the selected limit value is set as the set limit value. In addition, when the elapsed time is more than a predetermined time Ts, as mentioned above, the rate of change limiter 53 sets the selected limit value as the set limit value as is.

[0046] The valve body control unit 34 controls the operation of the valve body based on the flow state determined by the flow state determination unit 36 ​​of the opening command limit value calculation unit 33. That is, when the valve body control unit 34 determines that the flow state is non-transitional, i.e., stable flow, it controls the operation of the valve core 21a based on the opening command calculated by the opening command calculation unit 31. On the other hand, when the flow state is determined to be transitional, the valve body control unit 34 controls the operation of the valve core 21a based on the flow target value. Furthermore, in this embodiment, the valve body control unit 34 limits the opening command according to the flow state, thereby controlling the operation of the valve core 21a based on either the opening command or the flow target value in each state. The valve body control unit 34 with this function in this embodiment includes an opening command limiting unit 55 and a pressure command calculation unit 56.

[0047] The opening command restriction section 55 restricts the opening command based on the setting restriction value set by the opening command restriction value calculation unit 33. That is, when the opening command restriction value calculation unit 33 determines that the flow state is a stable flow state or the elapsed time is more than a predetermined time Ts, it sets the maximum opening value, which is an invalid restriction value, as the setting restriction value. Therefore, since the opening command calculated by the opening command calculation unit 31 is less than or equal to the setting restriction value, the opening command restriction section 55 outputs the opening command as an output command. In addition, the determination condition does not necessarily need to include the elapsed time. On the other hand, in the case of a transitional flow state, the opening command restriction value calculation unit 33 sets the calculated restriction value, which is a selection restriction value, as the setting restriction value. The calculated restriction value calculated based on the flow target value is, for example, less than the opening command. Therefore, the opening command restriction section 55 restricts the opening command to the setting restriction value. That is, the opening command restriction section 55 outputs an output command corresponding to the flow target value. In addition, during the period before the elapsed time reaches the predetermined time Ts, the setting restriction value increases based on the restriction change rate. Therefore, the output command is output from the open command limit section 55 when its rate of change is suppressed below the limit rate of change (see...). Figure 4 (b) at times t2 to t4.

[0048] The pressure command calculation unit 56 calculates the pressure command based on the output command output from the opening command restriction unit 55. An example of an action command is a pressure command used to adjust the opening of the directional control valve 21 to a degree corresponding to the output command. In this embodiment, the pressure command is the command value used to output pilot pressures P1 and P2 from the electromagnetic proportional control valves 22L and 22R for adjusting the opening. That is, the pressure command calculation unit 56 calculates the command values ​​of pilot pressures P1 and P2 according to the output command. Therefore, the operation of the valve core 21a is controlled according to the pressure command.

[0049] In more detail, when the flow state is a stable flow state, the opening command is output as an output command. Therefore, the pressure command calculation unit 56 calculates a first pressure command (first action command) based on the opening command. Furthermore, the pressure command calculation unit 56 outputs a signal corresponding to the first pressure command to the electromagnetic proportional control valves 22L and 22R. Thus, when the flow state is a stable flow state, the operation of the valve core 21a is controlled based on the opening command. On the other hand, when the flow state is a transitional flow state, an output command corresponding to the calculated limit value is output. Therefore, the pressure command calculation unit 56 calculates a second pressure command (second action command) based on the calculated limit value. The calculated limit value is a value set based on the flow target value. Therefore, the pressure command calculation unit 56 calculates the pressure command based on the flow target value. Furthermore, the pressure command calculation unit 56 outputs a signal corresponding to the second pressure command to the electromagnetic proportional control valves 22L and 22R. Therefore, when the flow state is transitional, the operation of the valve core 21a is controlled based on the flow target value.

[0050] Furthermore, when the elapsed time is less than the specified time Ts, the rate of change of the set limit value is below the limit rate of change. Therefore, when the pressure command switches from the first pressure command to the second pressure command, the pressure command can be shifted at a rate of change below the limit rate of change.

[0051] As an example of an opening degree acquisition unit, the opening estimation calculation unit 35 estimates the opening degree of the directional control valve 21, i.e., the estimated opening degree, based on the output value from the opening command restriction unit 55. More specifically, the opening estimation calculation unit 35 estimates the stroke amount of the valve core 21a based on the output command from the opening command restriction unit 55. Furthermore, the opening estimation calculation unit 35 estimates the estimated opening degree from the stroke amount. The estimated opening degree is used by the flow estimation calculation unit 32 when calculating the estimated flow rate value. Alternatively, the opening estimation calculation unit 35 can be an observer.

[0052] When the operating lever 16a of the operating device 16 is operated, the control device 17, configured as described above, performs the following control: The control device 17 calculates the target flow rate value based on the amount of operation of the operating lever 16a. The control device 17 calculates the pressure difference across the directional control valve 21 based on the pressure detected by the three pressure sensors 13-15. Next, the opening command calculation unit 31 in the control device 17 calculates the opening command based on the target flow rate value and the pressure difference across the directional control valve 21. Furthermore, the flow estimation calculation unit 32 calculates the estimated flow rate value based on the estimated opening value and the pressure difference across the directional control valve 21. Then, the opening command limit value calculation unit 33 determines the flow state based on the calculated estimated flow rate value and the target flow rate value. Furthermore, the opening command limit value calculation unit 33 sets a limit value based on the flow state and the elapsed time. The valve body control unit 34 restricts the opening command based on the set limit value. Additionally, the valve body control unit 34 calculates a pressure command based on the restricted opening command, i.e., the output command. Furthermore, the valve body control unit 34 outputs pilot pressures P1 and P2 corresponding to the pressure command from the electromagnetic proportional control valves 22L and 22R. Thus, the control device 17 can control the operation of the valve core 21a according to the pressure command.

[0053] To elaborate further, for example, the operating lever 16a operates as follows: Figure 4 The graph shows the flow rate over time as indicated by the two-point locking line, representing the supply of working fluid from hydraulic pump 11 to hydraulic cylinder 2. That is, control device 17, based on operating commands from operating device 16, is set as follows: Figure 4 The target flow rate is shown by the two-point locking line. The target flow rate increases significantly when the lever 16a is operated from the neutral position (see...). Figure 4 (a) The two points of the line locking time (t0~t1). Therefore, the absolute value of the difference between the estimated flow rate value estimated by the flow rate estimation calculation unit 32 and the target flow rate value exceeds the specified differential flow rate ΔQ. The flow state determination unit 36 ​​of the opening command limit value calculation unit 33 determines that the flow state is a transitional flow state. Then, the limit value selection unit 37 selects the calculated limit value based on the target flow rate value. Furthermore, the rate of change limit unit 38 sets the calculated limit value as the set limit value. The set limit value is a value less than the opening command in the transitional flow state (see Figure 4 (b) The solid line and single-point lock line for times t0 to t3. Therefore, the valve body control unit 34 calculates the pressure command based on the output command that limits the opening command to the set limit value. As mentioned above, when the transition flow state is determined, the set limit value is calculated based on the flow target value, and therefore the pressure command is calculated based on the flow target value. Therefore, the valve body control unit 34 controls the operation of the valve core 21a based on the flow target value (see Figure 4 (b) The solid line from time t0 to t3.

[0054] Subsequently, when the operating lever 16a stops at the desired angle, the target flow rate remains at a constant flow rate (see...). Figure 4 (a) After the time t1 of the two-point locking line. During the period after holding, the absolute value of the difference is above the specified differential flow rate ΔQ (see Figure 4 (a) The two-point locking line after time t1). Therefore, the flow state determination unit 36 ​​continues to determine that the flow state is in a transitional flow state. Thus, the output command is limited to below the set limit value, and the pressure command is set based on the flow target value (see Figure 4 (b) The solid line at time t1 to t2.

[0055] Subsequently, if the absolute value of the difference is less than the specified differential flow rate ΔQ, the flow state determination unit 36 ​​determines that the flow state has switched to a stable flow state, etc. (see [link to relevant documentation]). Figure 4 (a) at time t2). Therefore, the time elapsed is measured starting from timer 51. Furthermore, until the elapsed time reaches the predetermined time Ts, the rate of change of the set limit value is limited to below the limit rate of change, and the set limit value gradually increases. The valve body control unit 34 can smoothly increase the output command according to the limit value, that is, it can smoothly increase the pressure command. Therefore, it can suppress sudden changes in the valve core 21a's opening during decision switching related to the flow state (see...). Figure 4 (b) The solid line at times t2 to t3. That is, it can suppress the sharp changes in flow rate that occur when the decision related to the flow state is switched. As a result, it can suppress the impact on the directional control valve 21 caused by sudden changes in flow rate.

[0056] After the flow state changes, the angle of the operating lever 16a remains constant, thus maintaining the stable flow state. Consequently, the pressure command increases at a predetermined rate of change, resulting in the final opening command being lower than the set limit (see [reference]). Figure 4 (b) at time t3). Therefore, the valve body control unit 34 outputs the opening command as is. That is, the valve body control unit 34 calculates the pressure command based on the opening command. Thus, the valve body control unit 34 controls the operation of the valve core 21a based on the opening command (see...). Figure 4 (b) The solid line after time t3.

[0057] Furthermore, although not described in detail, the control device 17 also performs the same control when the operating lever 16a returns to the neutral position. That is, the control device 17 controls the operation of the valve core 21a based on either the opening command or the target flow rate, according to the determined flow state. Thus, when the flow rate is reduced, the same effect as when the flow rate is increased can be obtained.

[0058] In the control device 17 of the hydraulic system 1 configured in this way, the control method of dividing the valve core 21a into transitional flow states, stable flow states, and non-transitional flow states is employed. This improves stability in flow control during transitional flow states. That is, as... Figure 5As shown, for the target flow value (see...) Figure 5 (Two-point locking), in existing control systems, overshoot occurs in the flow (see...) Figure 5 (Single-point locking). On the other hand, the control device 17 of the present invention can suppress overshoot and other occurrences (see...). Figure 5 (The solid line). That is, the control device 17 can improve the stability of flow control under transitional flow conditions.

[0059] Furthermore, in the control device 17, the estimated flow rate is estimated based on the estimated opening degree obtained by the estimated opening calculation unit 35. Moreover, the control device 17 determines the flow state based on the estimated flow rate value. Therefore, the control device 17 can determine the flow state with high accuracy. As a result, the flow of the working fluid in the transitional flow state can be controlled more stably.

[0060] Furthermore, in the control device 17, the valve body control unit 34 functions as follows: In a stable flow state, the valve body control unit 34 controls the operation of the valve core 21a based on an opening command. The opening command is calculated based on the front and rear pressures and flow target values ​​of the directional control valve 21. In other words, the valve body control unit 34 performs feedback control based on the opening command in relation to the control of the valve core 21a's operation. On the other hand, in a transitional flow state, the valve body control unit 34 controls the operation of the valve core 21a based on a flow target value. The flow target value is calculated based on the operation command from the operating device 16. In other words, in a transitional flow state, the valve body control unit 34 performs open-loop control (feedforward control) based on the flow target value in relation to the control of the valve core 21a's operation. Performing feedback control in a stable flow state improves flow accuracy in such states. On the other hand, performing open-loop control in a transitional flow state improves stability in flow control during transitional flow conditions.

[0061] Furthermore, in the control device 17, the valve body control unit 34's opening command restriction section 55 restricts the opening command. Moreover, the pressure command calculation section 56 controls the operation of the valve core 21a based on the second pressure command. Thus, the control device 17 calculates the second pressure command based on the restricted opening command, thereby enabling control of the valve core 21a's operation based on the target flow rate. This allows for stable control of the working fluid flow even in transitional flow conditions.

[0062] <Other Implementation Methods>

[0063] The hydraulic system 1 of this embodiment is suitable for construction machinery, but it can also be applied to industrial vehicles such as forklifts or industrial machinery such as stamping presses. Furthermore, in the hydraulic system 1 of this embodiment, only one directional control valve 21 is connected relative to the hydraulic pump 11, but multiple directional control valves 21 can also be connected in parallel or in series. Moreover, the hydraulic actuator connected to the directional control valve 21 is not limited to a hydraulic cylinder 2, but can also be a hydraulic motor.

[0064] Furthermore, in the hydraulic system 1 of this embodiment, the hydraulic actuator is exemplified by a hydraulic cylinder 2, but the hydraulic actuator can also be a hydraulic motor. Moreover, the type of hydraulic cylinder 2 is not limited to a single-rod multi-acting cylinder; it can also be a double-rod cylinder or a single-acting cylinder. Furthermore, the structure included in the valve device 12 is not limited to a directional control valve 21, as long as the size of the opening can be adjusted by the valve body. The action command is not limited to a pressure command; it can also be a current command.

[0065] Furthermore, the control device 17 does not necessarily need to have a flow estimation calculation unit 32. The control device 17 may, for example, have a flow acquisition unit. In this case, a flow sensor is provided in the flow path connecting the directional control valve 21 and the hydraulic pump 11 in the hydraulic system 1. The flow acquisition unit obtains the measured flow rate based on the output of the flow sensor. The opening command limit value calculation unit 33 determines the flow state based on the obtained measured flow rate. Similarly, the opening estimation calculation unit 35 may also be an opening acquisition unit. In this case, a stroke sensor is provided on the valve core 21a in the hydraulic system 1. The opening acquisition unit obtains the estimated opening degree based on the output of the stroke sensor.

[0066] Furthermore, the valve body control unit 34 of the control device 17 controls the operation of the valve core 21a based on the flow target value by restricting the opening command in the transitional flow state. However, the control performed by the valve body control unit 34 is not limited to this. For example, the object on which the pressure command calculated by the valve body control unit 34 based on the flow state is based may be switched to either the opening command or the flow target value. In addition, the valve core 21a may also be controlled as follows: The control device 17 calculates the first and second pressure commands based on both the opening command and the flow target value. According to the determined flow state, the valve body control unit 34 outputs either the first or second pressure command to the first and second electromagnetic proportional control valves 22L and 22R. Regardless of the control method, the valve body control unit 34 can control the operation of the valve core 21a based on the opening command in a stable flow state, and control the operation of the valve core 21a based on the flow target value in a transitional flow state.

[0067] Furthermore, in the hydraulic system 1 of this embodiment, the valve core 21a of the directional control valve 21 is actuated by the pilot pressure from the electromagnetic proportional control valves 22L and 22R. However, the driving method of the valve core 21a of the directional control valve 21 is not limited to this method. For example, the valve core 21a of the directional control valve 21 can also be driven by an electric motor via a direct-acting mechanism. In this case, the control device 17 controls the actuation of the valve core 21a via the electric motor.

[0068] Based on the foregoing description, numerous modifications and other embodiments of the present invention will be apparent to those skilled in the art. Therefore, the foregoing description should be interpreted as illustrative only, provided for the purpose of teaching those skilled in the art the optimal mode for implementing the invention. Substantial changes to its specific structure and / or function may be made without departing from the spirit of the invention.

[0069] Symbol explanation:

[0070] 1. Hydraulic System

[0071] 12 Valve Device

[0072] 17. Control device

[0073] 21. Directional control valve (spool valve)

[0074] 21a Valve Core

[0075] 22L First Electromagnetic Proportional Control Valve

[0076] 22R Second Electromagnetic Proportional Control Valve

[0077] 31 Opening Command Calculation Unit

[0078] 32. Flow estimation calculation department (flow acquisition department)

[0079] 34 Valve Body Control Unit

[0080] 35. Opening estimation calculation unit (opening degree acquisition unit)

[0081] 36 Flow State Determination Unit

[0082] 55. Opening command restriction section

[0083] 56 Pressure command calculation section (command calculation section).

Claims

1. A control device, which controls the movement of the valve body of a control valve device, comprising: A flow acquisition unit that obtains the flow rate of the valve device; A flow state determination unit determines whether the flow of the working fluid in the valve device is in a transitional flow state based on the input flow target value and the flow estimate value estimated by the flow acquisition unit. An opening command calculation unit that calculates the opening command based on the target flow rate and the pressure difference before and after the valve device; and A valve body control unit that controls the movement of the valve body; The valve body control unit calculates the action command to control the movement of the valve body, and outputs the action command to the valve device to control the movement of the valve body. When the flow state determination unit determines that the flow is in a non-transitional flow state, the valve body control unit calculates a first action command as the action command based on the opening command; when the flow state determination unit determines that the flow is in a transitional flow state, the valve body control unit calculates a second action command as the action command based on the flow target value. The valve body control unit has an opening command restriction section and a command calculation section. When the flow state determination unit determines that the flow state is a transitional flow state, the opening command restriction section restricts the opening command by setting a restriction value based on the flow target value. The instruction calculation section calculates the second action instruction based on the opening instruction restricted by the opening instruction restriction section.

2. The control device according to claim 1, characterized in that, It also includes an opening degree acquisition unit for acquiring the opening degree of the valve device. The flow acquisition unit estimates the estimated flow rate based on the opening degree obtained by the opening degree acquisition unit and the pressure difference.

3. The control device according to claim 1 or 2, characterized in that, When the flow state determination unit determines that the flow state is a non-transitional flow state, the valve body control unit performs feedback control based on the opening command to control the valve body's operation. When the flow state determination unit determines that the flow state is a transitional flow state, the valve body control unit performs open-loop control based on the flow target value to control the valve body's operation.

4. The control device according to claim 1, characterized in that, When the action command switches from the first action command to the second action command, the valve body control unit pushes the action command at a rate of change below a predetermined limit rate of change.

5. The control device according to claim 1, characterized in that, The flow state determination unit calculates the difference between the target flow rate and the estimated flow rate. If the difference is outside the specified range, it determines that the flow of the working fluid of the valve device is in a transitional flow state.

6. A hydraulic system comprising the control device according to any one of claims 1 to 5, The valve device includes at least one electromagnetic proportional valve and a spool valve. The slide valve has a valve core that serves as the valve body. The valve core travels according to the pilot pressure acting on it. The electromagnetic proportional valve outputs a pilot pressure that acts on the valve core. When the flow state determination unit determines that the flow is in a non-transitional flow state, the valve body control unit outputs a pilot pressure corresponding to the opening command from the electromagnetic proportional valve to control the operation of the valve body. When the flow state determination unit determines that the flow is in a transitional flow state, the valve body control unit outputs a pilot pressure corresponding to the flow target value from the electromagnetic proportional valve to control the operation of the valve body.

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