Calibration system and calibration method for hydraulic systems

Abstract

To accurately and easily perform a calibration for calibrating a correspondence relationship between a pump control current value and a pump flow rate of a hydraulic pump, in a hydraulic system having the variable-capacity hydraulic pump whose capacity is variably controlled according to the pump control current value, a flow rate control valve whose opening area is variably controlled according to a valve control current value, and a pressure compensation valve for constantly holding a fore-and-aft pressure difference of the flow rate control valve.SOLUTION: A pump control current value is sweep-raised in a state that a spool valve 8 is held in an opening area corresponding to a spool valve output flow rate being an arbitrary target flow rate, and a peak of a change of pump pressure during the sweep-rise is calibrated as a pump control current value of a pump flow rate being a target flow rate.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to the technical field of a calibration system and a calibration method in a hydraulic system of a working machine such as a hydraulic excavator.

Background Art

[0002] Generally, in a hydraulic system of a working machine such as a hydraulic excavator, a variable displacement hydraulic pump whose capacity is variably controlled according to a control current value output from a controller is widely used as a hydraulic supply source for various hydraulic actuators. In this case, data indicating the correspondence between the pump flow rate and the control current value of the hydraulic pump is stored in the controller, and a control current value obtained using this data is output from the controller. The data indicating the correspondence between the pump flow rate and the control current value is the specification data created in advance and stored in the controller, and the control current value is output using this specification data. However, due to manufacturing variations, aging changes, etc., a deviation may occur between the value of the pump flow rate in the specification data for the control current value and the actual pump flow rate value. Therefore, conventionally, as calibration for matching the value of the specification data to the actual value, while monitoring the pressure value acting on the actuator piston that variably adjusts the swash plate tilt angle of the hydraulic pump, the control current value is changed to obtain the current value at at least one of the actual minimum swash plate position and the maximum swash plate position corresponding to the change point of the captured pressure value. A technique for correcting the control current value using the difference between this actual control current value and the control current value in the specification as a correction value (see, for example, Patent Document 1), or a technique for updating the control parameter (specification table) related to the control current value based on the control current value and the pump pressure when the discharge flow rate of the hydraulic pump is the maximum flow rate and the minimum flow rate is known (see, for example, Patent Document 2). The techniques of these Patent Documents 1 and 2 do not require a swash plate tilt angle sensor or a flow meter for calibration and can perform calibration with a simple configuration at low cost.

Prior Art Documents

[0003] [Patent Document 1] Japanese Patent Publication No. 2008-303813 [Patent Document 2] Japanese Patent Publication No. 2014-177969 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The aforementioned Patent Documents 1 and 2 both perform calibration of the pump flow rate (pump capacity) with respect to the control current value of a hydraulic pump. They determine the calibration value of the control current value for the minimum flow rate (minimum swash plate position) and the maximum flow rate (maximum swash plate position) based on the pressure change when the pump flow rate is at the minimum flow rate and the maximum flow rate (maximum swash plate position), and then use this calibration value to calibrate the control current value for the entire range of flow rates between the minimum and maximum flow rates. However, when the hydraulic pump is at the minimum flow rate, the pressure is too low to find the exact pressure displacement point, and when the hydraulic pump is at the maximum flow rate, there is a risk of a decrease in engine output, making it difficult to find the exact pressure displacement point. For this reason, it is difficult to accurately determine the calibration value of the control current value for the minimum and maximum flow rates. In other words, Patent Documents 1 and 2 perform calibration at the minimum and maximum flow rates, where it is difficult to accurately determine the calibration value, and for this reason, there is a problem of inferior calibration accuracy, which is the problem that the present invention aims to solve. [Means for solving the problem]

[0005] The present invention was created in view of the above circumstances and with the aim of solving these problems, and the invention of claim 1 is a hydraulic system for a work machine comprising: a variable displacement hydraulic pump whose capacity is variably controlled according to a pump control current value; a flow control valve disposed in the hydraulic oil supply passage from the hydraulic pump to a hydraulic actuator, the opening area of ​​the supply opening is variably controlled according to a valve control current value; a pressure compensation valve disposed upstream of the flow control valve and operating to maintain a constant differential pressure across the flow control valve; and a controller that outputs the pump control current and the valve control current, wherein, in order to perform calibration to calibrate the correspondence between the pump control current value and the pump flow rate of the hydraulic pump, a pressure detection means is provided to detect the pump pressure of the hydraulic pump, and the output of the flow control valve This hydraulic system calibration system is characterized by connecting a relief oil passage to the force side to deliver the output flow rate to the oil tank in a low back pressure state, while the controller is provided with a valve control means that determines a valve control current value corresponding to the flow control valve output flow rate of an arbitrarily set target flow rate based on calibrated correspondence data between the valve control current value and the flow control valve output flow rate, and outputs the valve control current value as the calibrated valve control current value; a pump control means that sweeps up and outputs the pump control current value while the calibrated valve control current value is being output; and a calibration control means that determines the pump control current value when the change in pump pressure during the sweep rise reaches its peak, and calibrates the pump control current value as the pump control current value corresponding to the arbitrarily set target flow rate. The invention of claim 2 is a hydraulic system for a work machine comprising: a variable displacement hydraulic pump whose capacity is variably controlled according to a pump control current value; a flow control valve disposed in a pressurized oil supply passage from the hydraulic pump to a hydraulic actuator, the opening area of ​​the supply opening being variably controlled according to a valve control current value; a pressure compensation valve disposed upstream of the flow control valve, which operates to maintain a constant differential pressure across the flow control valve; and a controller that outputs the pump control current and the valve control current, wherein, in order to perform calibration to calibrate the correspondence between the pump control current value and the pump flow rate of the hydraulic pump, a pressure detection means is provided to detect the pump pressure of the hydraulic pump, and a relief oil passage is provided on the output side of the flow control valve to supply the output flow rate to the oil tank in a low back pressure state. The calibration method for a hydraulic system is characterized by the following steps: connecting the valves, and the calibration is performed by determining a valve control current value corresponding to the flow control valve output flow rate of an arbitrarily set target flow rate based on calibrated correspondence data between the valve control current value and the flow control valve output flow rate, and outputting the valve control current value from the controller as the calibrated valve control current value; sweeping up the pump control current value while the calibrated valve control current value is being output and outputting it from the controller; determining the pump control current value when the change in pump pressure during the sweep rise reaches its peak, and calibrating the pump control current value as the pump control current value corresponding to the pump flow rate of the arbitrarily set target flow rate. [Effects of the Invention]

[0006] By adopting the inventions of claims 1 and 2, high-precision calibration can be performed efficiently and easily. [Brief explanation of the drawing]

[0007] [Figure 1] This is a hydraulic circuit diagram showing a part of the hydraulic system of a work machine. [Figure 2] This is a flowchart illustrating the calibration procedure. [Figure 3]This figure shows the relationship between the pump control current value, pump pressure, and the time derivative of the pump pressure during calibration. [Modes for carrying out the invention]

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 shows a part of a hydraulic system installed in a hydraulic excavator, which is an example of a work machine. In Figure 1, 1 is an on-board controller (control device), 2 is a variable displacement hydraulic pump, 2a is a variable displacement means for the hydraulic pump 2, 3 is a solenoid proportional valve for the pump, 4 is an oil tank, 5 is a hydraulic actuator that uses the hydraulic pump 2 as a hydraulic power source, and 6 is a control valve located in the pressurized oil supply path from the hydraulic pump 2 to the hydraulic actuator 5, which controls the supply and discharge of hydraulic oil to the hydraulic actuator 5. In the case of a hydraulic excavator, the excavator is equipped with various hydraulic actuators such as a boom cylinder, stick cylinder, bucket cylinder, travel motor, swing motor, and hydraulic actuators for optional attachments, as well as one or more hydraulic pumps that serve as the hydraulic power source for these hydraulic actuators. However, Figure 1 only shows the hydraulic pump 2 on which the calibration of this embodiment is performed, and the circuit used for the calibration of the hydraulic pump 2.

[0009] The aforementioned electromagnetic proportional valve 3 for the pump outputs a pump control signal pressure corresponding to the pump control current value input from the controller 1 to the variable capacity means 2a of the hydraulic pump 2. The variable capacity means 2a then operates in accordance with the input pump control signal pressure to control the flow rate of the hydraulic pump 2, and the pump flow rate of the hydraulic pump 2 is variably controlled according to the pump control current value output from the controller 1 to the electromagnetic proportional valve 3 for the pump.

[0010] Furthermore, the control valve 6 is configured to include a pilot-operated spool valve (corresponding to the flow control valve of the present invention) 8, which will be described later, a pressure compensation valve 9 arranged upstream of the spool valve 8, and first and second solenoid proportional valves 10A and 10B that output pilot pressure to the spool valve 8. The spool valve 8 is a directional control valve that controls the supply and discharge flow rates to the hydraulic actuator 5 and switches the direction of supply and discharge. It comprises first and second pilot ports 8a and 8b connected to first and second solenoid proportional valves 10A and 10B, respectively; a pump port 8p connected to the hydraulic pump 2 via a pressure compensation valve 9; a tank port 8t connected to the oil tank 4; a first actuator port 8c connected to the first input / output port 5a of the hydraulic actuator 5; a second actuator port 8d connected to the second input / output port 5b of the hydraulic actuator 5; and a load pressure output port 8e connected to the second pilot port 9b of the pressure compensation valve 9, which will be described later, via a load pressure introduction oil passage 11. Furthermore, when no pilot pressure is input to the first and second pilot ports 8a and 8b, the spool valve 8 is in a neutral position N, which does not perform supply and discharge control to the hydraulic actuator 5 and closes the load pressure output port 8e. However, when pilot pressure is input to the first pilot port 8a, it switches to the first operating position X, opening the supply opening 8f from the pump port 8p to the first actuator port 8c, the discharge opening 8g from the second actuator port 8d to the tank port 8t, and the load pressure opening 8h from the downstream side of the supply opening 8f to the load pressure output port 8e. Additionally, when pilot pressure is input to the second pilot port 8b, it switches to the second operating position Y, opening the supply opening 8f from the pump port 8p to the second actuator port 8d, the discharge opening 8g from the first actuator port 8c to the tank port 8t, and the load pressure opening 8h from the downstream side of the supply opening 8f to the load pressure output port 8e. Furthermore, the opening area of ​​the supply opening 8f is determined according to the movement stroke of the spool valve 8, which is moved by the pilot pressure output from the first and second electromagnetic proportional valves 10A and 10B, and the output flow rate from the spool valve 8 to the hydraulic actuator 5 is controlled by the opening area of ​​the supply opening 8f. In addition, when the spool valve 8 is in the first and second operating positions X and Y, the load pressure opening 8h opens, allowing the outlet pressure of the spool valve 8 (the load pressure of the hydraulic actuator 5) to be introduced into the load pressure introduction oil passage 11.

[0011] Furthermore, the pressure compensation valve 9 includes a first pilot port 9a into which the inlet pressure of the spool valve 8 is input, a second pilot port 9b into which the outlet pressure of the spool valve 8 is input via the load pressure introduction oil passage 11, and a spring 9c. The inlet pressure of the spool valve 8 input to the first pilot port 9a presses the valve body of the pressure compensation valve 9 to the closed side, and the outlet pressure of the spool valve 8 input to the second pilot port 9b and the pressing force of the spring 9c press the valve body of the pressure compensation valve 9 to the open side. The opening area of ​​the pressure compensation valve 9 is controlled so that the differential pressure (front-to-back differential pressure) between the inlet pressure and the outlet pressure of the spool valve 8 remains constant. In other words, when the differential pressure across the spool valve 8 increases, the valve body of the pressure compensation valve 9 moves to the closed position, reducing the opening area and increasing the pressure loss through which the spool valve 8 passes. This causes the inlet pressure of the spool valve 8 to decrease. Conversely, when the differential pressure across the spool valve 8 decreases, the valve body of the pressure compensation valve 9 moves to the open position, increasing the opening area and reducing the pressure loss through which the spool valve 8 passes. This causes the inlet pressure of the spool valve 8 to increase. Through this operation of the pressure compensation valve 9, the differential pressure across the spool valve 8 is maintained at a constant level.

[0012] Here, the output flow rate from the spool valve 8 to the hydraulic actuator 5 is determined by the following orifice equation (1), using the opening area of ​​the supply opening 8f of the spool valve 8, the differential pressure across the spool valve 8, and the flow coefficient. Q = C × A × √ΔP ···(1) In equation (1) above, Q is the output flow rate from the spool valve 8, C is the flow coefficient, A is the opening area of ​​the supply opening 8f of the spool valve 8, and ΔP is the differential pressure across the spool valve 8. As mentioned above, the differential pressure ΔP across the spool valve 8 is kept constant by the pressure compensation valve 9, and the opening area A of the supply opening 8f is determined according to the pilot pressure output from the first and second solenoid proportional valves 10A and 10B. Therefore, assuming the flow coefficient C is constant, the output flow rate from the spool valve 8 to the hydraulic actuator 5 will be determined according to the pilot pressure output from the first and second solenoid proportional valves 10A and 10B, even if the pump pressure of the hydraulic pump 2 or the load of the hydraulic actuator 5 fluctuates.

[0013] The first and second electromagnetic proportional valves 10A and 10B output pilot pressure corresponding to the valve control current value input from the controller 1 to the first and second pilot ports 8a and 8b of the spool valve 8, respectively. The spool valve 8 opens the supply opening 8f and the discharge opening 8g with an opening area corresponding to the input pilot pressure to control the supply flow rate and discharge flow rate to the hydraulic actuator 5. The differential pressure across the spool valve 8 is kept constant by the pressure compensation valve 9. The output flow rate from the spool valve 8 is variably controlled according to the valve control current value output from the controller 1 to the first and second electromagnetic proportional valves 10A and 10B.

[0014] Furthermore, in Figure 1, 12 is a relief oil passage that branches off from the actuator oil passage 13 connecting the control valve 6 and the hydraulic actuator 5 and leads to the oil tank 4. The relief oil passage 12 is equipped with a variable relief valve 14 that can change the relief pressure based on a control signal from the controller 1. For example, if the hydraulic actuator 5 is a hydraulic actuator such as a breaker that requires back pressure reduction, the set pressure of the variable relief valve 14 can be set to a low pressure, allowing the discharged oil from the hydraulic actuator 5 to flow through the relief oil passage 12 to the oil tank 4 in a low back pressure state.

[0015] Furthermore, in Figure 1, 18 is a monitor device 18 that is freely connected to the controller 1 for input and output. This monitor device 18 is located, for example, in the operator's cab of a hydraulic excavator and is equipped with a display screen (not shown), a keyboard, a touch panel, a dial, and other operating means. It is used to display the machine status and perform various settings. In this embodiment, however, the start, operation, and completion of calibration, which will be described later, can be performed based on the operation of the operating means of the monitor device 18.

[0016] On the other hand, the controller 1 has an operation detection means 16 for detecting the operating direction and amount of the operating tool 15 for the hydraulic actuator 5, and a pressure sensor (corresponding to the pressure detection means of the present invention) 17 for detecting the pump pressure of the hydraulic pump 2 connected to its input side, while the pump electromagnetic proportional valve 3, the first and second electromagnetic proportional valves 10A and 10B, and the variable relief valve 14 connected to its output side. When the calibration described later is not performed, the controller 1 determines the target pump flow rate based on the operating direction and amount of the operating tool 15 input from the operation detection means 16 and the pump pressure input from the pressure sensor 17, and outputs a pump control current value to the pump electromagnetic proportional valve 3 so that the pump flow rate of the hydraulic pump 2 becomes the target pump flow rate. In this case, the controller 1 stores pump correspondence data PD that shows the correspondence between the pump control current value and the pump flow rate, and is configured to output a pump control current value corresponding to the target pump flow rate to the pump electromagnetic proportional valve 3 based on the pump correspondence data PD. As described above, the electromagnetic proportional valve 3 for the pump outputs a pump control signal pressure corresponding to the pump control current value to the variable capacity means 2a of the hydraulic pump 2, thereby controlling the discharge flow rate of the hydraulic pump 2 to the target pump flow rate. During the calibration described later, the controller 1 outputs a pump control current to the electromagnetic proportional valve 3 for the pump even when the operating tool 15 is not being operated.

[0017] Furthermore, during normal operation when calibration is not being performed, the controller 1 determines the required flow rate of the actuator based on the operation direction and operation amount of the operating tool 15 input from the operation detection means 16, and outputs a valve control current to the first and second electromagnetic proportional valves 10A and 10B so that the output flow rate from the spool valve 8 to the hydraulic actuator 5 becomes the required flow rate of the actuator. In this case, valve correspondence data VD showing the correspondence relationship between the output flow rate of the spool valve 8 and the valve control current value is stored in the controller 1, and based on the valve correspondence data VD, the valve control current value corresponding to the required flow rate of the actuator is output to the first and second electromagnetic proportional valves 10A and 10B. And, as described above, the first and second electromagnetic proportional valves 10A and 10B output a pilot pressure corresponding to the valve control current value input from the controller 1 to the spool valve 8, whereby the output flow rate from the spool valve 8 to the hydraulic actuator 5 is controlled to be the required flow rate of the actuator. Incidentally, during the execution of calibration described later, a valve control current is output from the controller 1 to the second electromagnetic proportional valve 10B in a state where the operating tool 15 is not being operated.

[0018] Here, the valve correspondence data VD indicating the correspondence between the output flow rate of the spool valve 8 and the valve control current value is used for calibration of the correspondence between the pump control current value and the pump flow rate as will be described later. The valve correspondence data VD used for this calibration is not based on specifications, but calibrated valve correspondence data VD obtained by calibrating the correspondence between the output flow rate of the spool valve 8 and the valve control current value based on measured data is used. The calibrated valve correspondence data VD is created, for example, on the supplier side of the control valve 6 based on the measured data obtained during the pre-shipment inspection of the control valve 6, and is input and stored in the controller 1 using the monitor device 18 or via other input means or communication means. Also, with the control valve 6 mounted on the hydraulic excavator, the correspondence between the output flow rate of the spool valve 8 and the valve control current value is measured, and the valve correspondence data VD according to the specifications is calibrated based on the measured data to obtain the calibrated valve correspondence data VD. And this calibrated valve correspondence data VD is not only used for calibration of the correspondence between the pump control current value and the pump flow rate, but of course is also used during the normal operation described above.

[0019] Furthermore, the controller 1 is provided with a calibration control unit 20 for controlling the calibration of the correspondence between the pump control current value and the pump flow rate. As will be described later, the calibration control unit 20 includes a valve control unit 21 (corresponding to the valve control means of the present invention) that outputs a valve control current to the second electromagnetic proportional valve 10B during calibration execution, a pump control unit 22 (corresponding to the pump control means of the present invention) that outputs a pump control current value by sweeping it upward, a calibration control unit 23 (corresponding to the calibration control means of the present invention) that calibrates the pump correspondence data PD, etc.

[0020] Next, the calibration control performed by the calibration control unit 20 will be described based on the flowchart in FIG. 2. When performing calibration, as a preliminary step, the oil passages connecting the first and second actuator ports 8c and 8d of the spool valve 8 to the first and second input / output ports 5a and 5b of the hydraulic actuator 5 are closed, and the output flow rate from the second actuator port 8d of the spool valve 8 is set to flow to the oil tank 4 via the variable relief valve 14 of the relief oil passage 12 mentioned above. In this case, by setting the set pressure of the variable relief valve 14 to a low pressure, the output flow rate from the spool valve 8 flows to the oil tank 4 under low back pressure.

[0021] First, when the calibration control unit 20 receives an operation signal from the monitoring device 18 to start the calibration process, it sets an arbitrary target flow rate to be used as the calibration point (step S1). This target flow rate can be arbitrarily set and changed by the monitoring device 18. Next, based on the corresponding data VD for the calibrated valve, the valve control current value corresponding to the output flow rate of the spool valve 8 at the target flow rate is determined, and this valve control current value is set as the calibration valve control current value (step S2). Then, the valve control unit 21 outputs this calibration valve control current value to the second electromagnetic proportional valve 10B (step S3). This output of the calibration valve control current value continues until the calibration is completed. As a result, the spool valve 8 switches to the second operating position Y, and the opening area of ​​the supply opening 8f at the second operating position Y is fixed and held at the opening area corresponding to the calibration valve control current value. Next, while the valve control current value during calibration is being output, the pump control unit 22 outputs a pump control current value to the solenoid proportional valve 3 for the pump at a predetermined constant speed suitable for sweeping, while sweeping it upwards (step S4). Furthermore, during the sweep-up of the pump control current value in step S4, the pressure sensor 17 detects the pump pressure of the hydraulic pump 2 (step S5). Then, the time derivative of the detected pump pressure is calculated, and based on this time derivative, the peak of the change in pump pressure during the sweep-up is detected (step S6). In other words, when the pump control current is swept up while the opening area of ​​the supply opening 8f of the spool valve 8 is fixed and held to the opening area corresponding to the calibration valve control current value (the valve control current value corresponding to the output flow rate of the spool valve 8 for an arbitrary target flow rate), the discharged oil from the hydraulic pump 2 flows to the oil tank 4 via the pressure compensation valve 9, the spool valve 8, and the variable relief valve 14 of the relief oil passage 12. In this case, if the pump flow rate, which increases with the sweep of the pump control current, is less than the target flow rate, the output flow rate from the spool valve 8, which passes through the supply opening 8f without resistance, flows to the oil tank 4 in a low back pressure state, and the pump pressure is maintained at a low pressure. If the pump control current is further swept up from this state and the pump flow rate exceeds the target flow rate, the resistance when the pump flow rate passes through the supply opening 8f of the spool valve 8 increases, and the inlet pressure of the spool valve 8 increases. As a result, the differential pressure across the spool valve 8 increases, and the pressure compensation valve 9 closes. Then, when the pressure compensation valve 9 closes, the pump pressure rises sharply, and this sharp rise in pump pressure is detected based on the peak of the time derivative of the pump pressure. Furthermore, the calibration control unit 23 determines the pump control current value when the change in pump pressure reaches its peak, and uses this pump control current value as the pump control current value corresponding to the target flow rate of the pump to calibrate the corresponding pump data PD stored in the controller 1 (step S7). In this case, if there is only one target flow rate setting for calibration, the calibration control unit 23 further uses the difference between the calibrated pump control current value and the pump control current value corresponding to the target flow rate in the pump data PD stored in the controller 1 as the calibration amount, and calibrates the correspondence between the pump flow rate and the pump control current value in the pump data PD over the entire range of pump flow rates, thereby completing the calibration. In this case, even if there is only one target flow rate setting, by using the target flow rate as the flow rate in the intermediate region of the pump flow rate and calibrating the flow rate in the intermediate region, high-precision flow rate control can be performed over the entire range of pump flow rates. Furthermore, if there are multiple target flow rate settings, although not shown in the flowchart in Figure 2, after performing steps S1 to S7 for each target flow rate, the correspondence between the pump flow rate and the pump control current value in the corresponding pump data PD is calibrated across the entire range of pump flow rates using multiple calibrated pump control current values, and the calibration is completed. In this way, when there are multiple target flow rate settings, more precise flow rate control of the pump flow rate can be achieved. Figure 3 shows an example of the relationship between the pump control current value output from controller 1 during calibration, the pump pressure of hydraulic pump 2, and the time derivative of the pump pressure. As shown in Figure 3, the peak of the change in pump pressure is detected by the spike-like peak of the time derivative.

[0022] In this embodiment configured as described above, the hydraulic system of the work machine includes a variable displacement hydraulic pump 2 whose capacity is variably controlled according to the pump control current value, a spool valve 8 located in the pressurized oil supply path from the hydraulic pump 2 to the hydraulic actuator 5, the opening area of ​​the supply opening 8f being variably controlled according to the valve control current value, a pressure compensation valve 9 located upstream of the spool valve 8, which operates to maintain a constant differential pressure across the spool valve 8, and a controller 1 that outputs the pump control current and the valve control current. In this system, when performing calibration to adjust the correspondence between the pump control current value and the pump flow rate of the hydraulic pump 2, a pressure sensor 17 is provided to detect the pump pressure of the hydraulic pump 2, and a relief oil passage 12 is connected to the output side of the spool valve 8 to supply the output flow rate of the spool valve 8 to the oil tank 4 in a low back pressure state. Furthermore, the controller 1 is provided with a valve control means 21 that determines a valve control current value corresponding to the spool 8 output flow rate of an arbitrarily set target flow rate based on the calibrated valve corresponding data VD of the valve control current value and the spool valve 8 output flow rate, and outputs the valve control current value as the calibrated valve control current value; a pump control means 22 that sweeps up and outputs the pump control current value while the calibrated valve control current value is being output; and a calibration control means 23 that determines the pump control current value when the change in pump pressure during the sweep rise reaches its peak, and calibrates the pump control current value as the pump control current value corresponding to the pump flow rate of the arbitrarily set target flow rate.

[0023] In this embodiment, during calibration, the controller 1 outputs a calibration valve control current value to maintain the opening area of ​​the supply opening 8f of the spool valve 8 at an opening area corresponding to the spool 8 output flow rate of an arbitrary target flow rate determined based on the corresponding data VD for the calibrated valve. In this state, the pump control current value is swept up to increase the pump flow rate of the hydraulic pump 2. When the pump flow rate supplied to the supply opening 8f of the spool valve 8 exceeds the target flow rate, the pressure compensation valve 9 closes to maintain a constant differential pressure across the spool valve 8. However, the closing of the pressure compensation valve 9 causes a sharp increase in pump pressure, which is detected as the peak of the pump pressure change. The pump control current value at this peak of the pump pressure change is then calibrated as the pump control current value corresponding to the pump flow rate of the target flow rate.

[0024] As a result, when performing calibration to adjust the correspondence between the pump control current value and the hydraulic pump's flow rate, the pump control current value can be calibrated for an arbitrarily set target flow rate based on the peak of the pump pressure change. This allows for highly accurate and reliable calibration without the inferior calibration accuracy that can occur when calibrating at the minimum or maximum pump flow rate, where it is difficult to find the pump pressure displacement point. Furthermore, by calibrating the pump flow rate in the intermediate region, with the arbitrarily set target flow rate as the intermediate region of the pump flow rate, highly accurate flow rate control can be performed across the entire discharge flow rate range of the hydraulic pump 2. Moreover, this calibration can be performed simply by outputting valve control current values ​​and pump control current values ​​from the controller 1 and detecting the pump pressure in the output. Therefore, no special calibration equipment is required, and efficient calibration can be performed with a simple configuration.

[0025] It should be noted that the present invention is not limited to the above embodiments. For example, in the above embodiment, a relief oil passage 12 is used as the relief oil passage connected to the output side of the flow control valve (spool valve 8) during calibration. This relief oil passage is provided to allow the discharged oil from the hydraulic actuator 5 to flow into the oil tank 4 in a low back pressure state when the hydraulic actuator 5 is a hydraulic actuator such as a breaker that requires back pressure reduction. However, if such a relief oil passage 12 is not provided, calibration can also be performed by connecting a relief oil passage from another section (not shown in Figure 1) of the hydraulic system to the flow control valve via piping. Furthermore, in the above embodiment, the flow control valve (spool valve 8) is a pilot-operated type in which the spool moves due to the pilot pressure output from the first and second solenoid proportional valves 10A and 10B to which the valve control current value is input. However, the invention is not limited to this, and the flow control valve may be a solenoid valve, with the valve control current value being directly input to the flow control valve. [Industrial applicability]

[0026] This invention can be used to calibrate the correspondence between the pump control current value output from the controller and the pump flow rate of the hydraulic pump in a hydraulic system of a work machine such as a hydraulic excavator. [Explanation of Symbols]

[0027] 1 Controller 2. Hydraulic pump 4 Oil tanks 5. Hydraulic Actuator 8 Spool valve 9. Pressure Compensation Valve 12 Relief oil channels 17. Pressure Sensor 20 Calibration Control Unit 21 Valve control unit 22 Pump Control Unit 23 Calibration Control Unit

Claims

1. In a hydraulic system for a work machine comprising a variable displacement hydraulic pump whose capacity is variably controlled according to the pump control current value, a flow control valve disposed in the hydraulic oil supply path from the hydraulic pump to the hydraulic actuator and whose opening area of ​​the supply opening is variably controlled according to the valve control current value, a pressure compensation valve disposed upstream of the flow control valve and operating to maintain a constant differential pressure across the flow control valve, and a controller that outputs the pump control current and the valve control current, when performing calibration to calibrate the correspondence between the pump control current value and the pump flow rate of the hydraulic pump, A pressure detection means is provided to detect the pump pressure of the hydraulic pump, A relief oil passage is connected to the output side of the flow control valve to allow the output flow rate to flow to the oil tank in a low back pressure state, The aforementioned controller, A valve control means that, based on calibrated correspondence data between the valve control current value and the flow control valve output flow rate, determines a valve control current value corresponding to the flow control valve output flow rate of an arbitrarily set target flow rate, and outputs the valve control current value as the calibrated valve control current value. A pump control means that, while the aforementioned calibration valve control current value is being output, sweeps up and outputs the pump control current value, A calibration system for a hydraulic system, characterized by comprising a calibration control means that determines the pump control current value when the change in pump pressure during sweep rise reaches its peak, and calibrates the pump control current value as a pump control current value corresponding to the pump flow rate of the arbitrarily set target flow rate.

2. In a hydraulic system for a work machine comprising a variable displacement hydraulic pump whose capacity is variably controlled according to the pump control current value, a flow control valve disposed in the hydraulic oil supply path from the hydraulic pump to the hydraulic actuator and whose opening area of ​​the supply opening is variably controlled according to the valve control current value, a pressure compensation valve disposed upstream of the flow control valve and operating to maintain a constant differential pressure across the flow control valve, and a controller that outputs the pump control current and the valve control current, when performing calibration to calibrate the correspondence between the pump control current value and the pump flow rate of the hydraulic pump, A pressure detection means is provided to detect the pump pressure of the hydraulic pump, A relief oil passage is connected to the output side of the flow control valve to allow the output flow rate to flow to the oil tank in a low back pressure state, The aforementioned calibration is Based on the calibrated correspondence data between the valve control current value and the flow control valve output flow rate, the valve control current value corresponding to the flow control valve output flow rate of an arbitrarily set target flow rate is determined, and this valve control current value is output from the controller as the calibrated valve control current value. The steps include: sweeping up the pump control current value and outputting it from the controller while the valve control current value during calibration is being output; A calibration method for a hydraulic system, characterized by including the steps of: determining the pump control current value when the change in pump pressure during sweep rise reaches its peak; and calibrating the pump control current value as the pump control current value corresponding to the pump flow rate of the arbitrarily set target flow rate.

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