Pump system

Abstract

A pump system is provided with a variable displacement hydraulic pump, a regulator, an opening control valve, a first pressure sensor for measuring the upstream pressure of the opening control valve, a second pressure sensor for measuring the downstream pressure of the opening control valve, and a control device for controlling the discharge capacity of the hydraulic pump in accordance with pump characteristics. The control device changes a command signal output to the regulator under a measurement condition in which the opening degree of the opening degree control valve is fixed to a predetermined opening degree, thereby detecting an upstream pressure and a downstream pressure by the first pressure sensor and the second pressure sensor, respectively, under a plurality of command signals different from each other. An actual discharge flow rate discharged from a hydraulic pump is calculated for each command signal on the basis of a differential pressure before and after an opening degree control valve calculated on the basis of an upstream pressure and a downstream pressure, and an opening degree of the opening degree control valve, and a correction table is generated on the basis of a command discharge flow rate and the actual discharge flow rate for each command signal.

Description

Technical Field

[0001] This disclosure relates to a pump system that generates a correction table for correcting the command output flow rate of a variable capacity hydraulic pump. Background Technology

[0002] In a variable-capacity hydraulic pump, a current command value is output according to the pump characteristic (i.e., the so-called IQ characteristic), which represents the relationship between the commanded discharge flow rate and the current command value, thereby discharging the working fluid at the commanded discharge flow rate. On the other hand, in hydraulic pumps, each pump has a deviation regarding the flow rate of the working fluid discharged relative to the current command value. Therefore, in a hydraulic pump, the pump characteristic is corrected in the form of discharging the working fluid at the commanded discharge flow rate relative to the current command value. As a system for correcting pump characteristics, a correction system such as that described in Patent Document 1 is known, for example.

[0003] Existing technical documents: Patent documents: Patent document 1: Japanese Patent Application Publication No. 2019-190443. Summary of the Invention

[0004] The problem the invention aims to solve: The calibration system in Patent Document 1 measures the pump pressure at each current command value while changing the current command value in multiple stages. It then calibrates the pump control table (i.e., pump characteristics) based on the measured pump pressure and the specified pump flow rate in the reference command value. Therefore, the calibration system in Patent Document 1 can calibrate the pump flow rate relative to various current command values. However, because the pump characteristics are calibrated based on the specified pump flow rate in the calibration system of Patent Document 1, a difference may occur between the actual pump flow rate and the commanded discharge flow rate if there are deviations in the pump flow rate for each pump. It is desirable to suppress this difference between the commanded discharge flow rate and the actual pump flow rate.

[0005] Therefore, the purpose of this disclosure is to provide a pump system capable of suppressing the difference between the commanded output flow rate and the actual flow rate of the pump.

[0006] Solution methods: The first disclosed pump system comprises: a variable-capacity hydraulic pump capable of changing its discharge capacity; a regulator for changing the discharge capacity of the hydraulic pump according to an input command signal; an opening control valve connected to the hydraulic pump and capable of changing its opening degree; a first pressure sensor for measuring the upstream pressure of the hydraulic fluid flowing from the hydraulic pump to the opening control valve; a second pressure sensor for measuring the downstream pressure of the hydraulic fluid flowing from the opening control valve; and a control device for controlling the discharge capacity of the hydraulic pump according to pump characteristics indicating the relationship between the commanded discharge flow rate and the command signal, wherein the control device controls the opening degree of the opening control valve by fixing... Under a specified opening measurement condition, the command signal output to the regulator is changed, thereby detecting the upstream pressure and downstream pressure respectively through the first pressure sensor and the second pressure sensor under multiple different command signals. Based on the pressure difference between the upstream and downstream sides of the opening control valve and the opening degree of the opening control valve, the actual discharge flow rate from the hydraulic pump is calculated for each command signal. A correction table for the corrected command discharge flow rate is generated based on the command discharge flow rate and the actual discharge flow rate relative to each command signal. The pressure difference between the upstream and downstream sides of the opening control valve is calculated based on the detected upstream and downstream pressures.

[0007] According to the first disclosure, the actual discharge flow rate calculated based on the pressure difference and opening degree of the control valve is calculated for each command signal. Furthermore, a correction table is generated based on the commanded discharge flow rate and the actual discharge flow rate relative to each command signal. Therefore, the control device, by outputting a command signal based on the commanded discharge flow rate corrected using the correction table, enables the working fluid at a flow rate corresponding to the commanded discharge flow rate to be actually discharged from the hydraulic pump. Thus, the difference between the commanded discharge flow rate and the actual pump flow rate can be suppressed.

[0008] The second disclosed pump system comprises: a variable-capacity hydraulic pump capable of changing its discharge capacity; a regulator that changes the discharge capacity of the hydraulic pump according to an input command signal; an unloading valve disposed between the hydraulic pump and a tank, the opening of which can be changed; a first pressure sensor that measures the hydraulic pressure of the working fluid flowing from the hydraulic pump to the unloading valve; and a control device that controls the discharge capacity of the hydraulic pump according to pump characteristics representing the relationship between the commanded discharge flow rate and the command signal. The control device, by changing the command signal output to the regulator under a measurement condition that fixes the opening of the unloading valve at a predetermined opening, detects the hydraulic pressure using the first pressure sensor under multiple different command signals. Based on the pressure difference between the upstream and downstream sides of the unloading valve and the opening of the unloading valve, it calculates the actual discharge flow rate discharged from the hydraulic pump for each command signal. It generates a correction table for the corrected commanded discharge flow rate based on the commanded discharge flow rate and the actual discharge flow rate relative to each command signal. The pressure difference between the upstream and downstream sides of the unloading valve is calculated based on the detected hydraulic pressure.

[0009] According to the second disclosure, the actual discharge flow rate, calculated based on the pressure difference and opening degree of the unloading valve, is calculated for each command signal. Furthermore, a correction table is generated based on the commanded discharge flow rate and the actual discharge flow rate relative to each signal. Therefore, the control device can actually discharge working fluid from the hydraulic pump at a flow rate corresponding to the commanded discharge flow rate. Thus, the difference between the commanded discharge flow rate and the actual pump flow rate can be suppressed.

[0010] Invention effects: According to the first and second disclosures, it is possible to suppress the difference between the commanded output flow rate and the actual flow rate of the pump.

[0011] The above-mentioned objects, other objects, features and advantages of this disclosure will become clear from the following detailed description of preferred embodiments with reference to the accompanying drawings. Attached Figure Description

[0012] Figure 1 To illustrate the circuit diagram of the hydraulic drive system of the pump system having the first embodiment; Figure 2 To show Figure 1 A flowchart illustrating the sequence of output flow control and correction table generation methods executed by the control device; Figure 3 To show the passage Figure 1 A chart showing the corrected pump characteristics of the pump system; Figure 4 To illustrate the circuit diagram of the hydraulic drive system of the pump system having the second embodiment; Figure 5 To show the passage Figure 4 A chart showing the corrected pump characteristics of the pump system; Figure 6 To illustrate the circuit diagram of the hydraulic drive system of the pump system having the third embodiment; Figure 7 A circuit diagram of the hydraulic drive system of the pump system having the fourth embodiment is shown. Detailed Implementation

[0013] Hereinafter, pump systems 1, 1A to 1C according to the first to fourth embodiments of this disclosure will be described with reference to the aforementioned accompanying drawings. Furthermore, the concept of direction used in the following description is for ease of explanation and is not intended to limit the orientation of the structure of this disclosure to that direction. Also, the pump systems 1, 1A to 1C described below are only one embodiment of this disclosure. Therefore, this disclosure is not limited to any particular embodiment, and additions, deletions, and modifications can be made without departing from the spirit of this disclosure.

[0014] [First Implementation] <Pump System> Figure 1 The pump system 1 shown is, for example, equipped in hydraulic machinery (not shown). Hydraulic machinery includes, for example, engineering vehicles such as hydraulic excavators and hydraulic cranes, and industrial vehicles such as elevators. However, hydraulic machinery is not limited to engineering vehicles; it can also be agricultural machinery, ships, hydrogen-related machinery, and medical machinery. The hydraulic machinery has at least one actuator 2 and a hydraulic drive system 3 including the pump system 1. The actuator 2 is, for example, a hydraulic cylinder and a hydraulic motor. In a hydraulic excavator, the actuator 2 is, for example, a boom cylinder, stick cylinder, bucket cylinder, rotary motor, and travel motor. The hydraulic drive system 3 supplies working fluid (e.g., working oil) to the actuator 2. Thus, the actuator 2 actuates, enabling the hydraulic machinery to perform various operations. The hydraulic drive system 3 with such functions includes a hydraulic pump 11, a regulator 12, a hydraulic circuit 13, an unloading valve 14, two pressure sensors 15 and 16, an operating device 17, and a control device 18. Furthermore, the pump system 1 is configured by at least a hydraulic pump 11, a regulator 12, an unloading valve 14, two pressure sensors 15 and 16, and a control device 18.

[0015] The hydraulic pump 11 is driven by a drive source (e.g., an engine or electric motor) 10. The hydraulic pump 11, by being driven by rotation, discharges working fluid into the pump passage 11a. The hydraulic pump 11 is a variable-capacity pump. In this embodiment, the hydraulic pump 11 is a variable-capacity swashplate pump, and the discharge capacity is changed by tilting the swashplate 11b. Alternatively, the hydraulic pump 11 can also be a variable-capacity swashplate pump, as long as it is a pump capable of changing the discharge capacity and discharging working fluid.

[0016] The regulator 12 changes the output capacity of the hydraulic pump 11 according to the input command signal (more specifically, the signal value of the command signal). In this embodiment, the command signal is a current signal. However, the command signal is not limited to a current signal; it can also be a voltage signal or a CAN signal. The regulator 12 includes, for example, a servo piston 12a and a solenoid proportional valve 12b. The servo piston 12a is connected to the swashplate 11b. The servo piston 12a moves to a position corresponding to the input pilot pressure. Furthermore, by moving, the servo piston 12a tilts the swashplate 11b. As a result, the tilt angle of the swashplate 11b changes, and the output capacity of the hydraulic pump 11 is adjusted to a capacity corresponding to the tilt angle, i.e., a capacity corresponding to the input pilot pressure.

[0017] The electromagnetic proportional valve 12b outputs a pilot pressure corresponding to the command signal. More specifically, the electromagnetic proportional valve 12b is connected, for example, to the pilot pump 20, tank 19, and regulator 12. By adjusting the opening of the passages connected to the pilot pump 20 and tank 19 respectively, the electromagnetic proportional valve 12b outputs a pilot pressure corresponding to the command signal to the servo piston 12a. The servo piston 12a moves to a position corresponding to the pilot pressure. This changes the output capacity of the hydraulic pump 11. That is, the regulator 12 changes the output capacity of the hydraulic pump 11 according to the command signal. Furthermore, the electromagnetic proportional valve 12b is not limited to the aforementioned structure, as long as it can output a pilot pressure corresponding to the command signal.

[0018] Hydraulic circuit 13 is connected to hydraulic pump 11 and at least one actuator 2. More specifically, hydraulic circuit 13 is connected to hydraulic pump 11 via pump passage 11a. Furthermore, hydraulic circuit 13 directs the working fluid discharged from hydraulic pump 11 to actuator 2. Also, hydraulic circuit 13 controls the flow of working fluid from hydraulic pump 11 to actuator 2. Hydraulic circuit 13 may include various valves such as relief valves or control valves, and the flow of working fluid is controlled by operating these valves.

[0019] An unloading valve 14, as an example of an opening control valve, is disposed between the hydraulic pump 11 and the tank 19. The unloading valve 14 can change the opening degree between the hydraulic pump 11 and the tank 19 (hereinafter referred to as "the opening degree of the unloading valve 14"). More specifically, the unloading valve 14 is connected in the pump passage 11a upstream of the hydraulic circuit 13. Alternatively, the unloading valve 14 can be connected in the pump passage 11a downstream of the hydraulic circuit 13. The unloading valve 14 unloads the hydraulic pump 11 by discharging the working fluid discharged from the hydraulic pump 11 into the tank 19. In this embodiment, the unloading valve 14 is a three-position spool valve. That is, the unloading valve 14 has a valve core 14a as the valve body. The valve core 14a moves to any one of the first to third positions A1 to A3 according to the input position signal. The valve core 14a fixes the opening degree of the unloading valve 14 at the first position A1, which is also a neutral position. Furthermore, in the second position, valve core 14a blocks the connection between hydraulic pump 11 and tank 19. Additionally, in the third position A3, valve core 14a changes the opening degree of unloading valve 14 according to the stroke amount. Moreover, unloading valve 14 is not limited to a three-position spool valve; it can be a two-position spool valve or a spool valve with four or more positions.

[0020] The first pressure sensor 15 measures the upstream pressure (e.g., the discharge pressure of the hydraulic pump 11) of the hydraulic fluid flowing from the hydraulic pump 11 to the unloading valve 14. In this embodiment, the first pressure sensor 15 is connected to the pump passage 11a. More specifically, the first pressure sensor 15 is connected in the pump passage 11a upstream of the unloading valve 14. Furthermore, the first pressure sensor 15 measures the pressure of the working fluid flowing in the pump passage 11a as the upstream pressure.

[0021] The second pressure sensor 16 measures the downstream pressure (in this embodiment, tank pressure) of the hydraulic fluid flowing from the unloading valve 14. More specifically, the second pressure sensor 16 is connected to the tank passage 19a. The tank passage 19a is the passage connecting the unloading valve 14 to the tank 19. The second pressure sensor 16 measures the pressure of the working fluid flowing in the tank passage 19a, i.e., the tank pressure, as the downstream pressure.

[0022] The operating device 17 is a device for operating the actuator 2. The operating device 17 includes, for example, at least one operating lever 17a as an operating element. The operating device 17 outputs an operating command corresponding to the tilting amount (i.e., operating amount) of the operating lever 17a. In this embodiment, the operating device 17 is, for example, an electrically operated handle. Alternatively, the operating device 17 may be an operating valve including the operating lever 17a. In this case, the operating device 17 uses a pressure sensor (not shown) to detect the pilot pressure output from the operating valve and outputs a command signal corresponding to the detected pilot pressure. Furthermore, the operating element may also be an operating pedal; the form is not limited as long as it outputs an operating command corresponding to the operating amount.

[0023] The control device 18 obtains the discharge pressure of the hydraulic pump 11 (i.e., the upstream pressure of the unloading valve 14) from the first pressure sensor 15 and the tank pressure (i.e., the downstream pressure of the unloading valve 14) from the second pressure sensor 16. Furthermore, the control device 18 controls the drive source 10, the regulator 12, the hydraulic circuit 13, and the unloading valve 14 according to the command signal from the operating device 17.

[0024] To explain in more detail, control device 18, such as Figure 2 The flowchart for the discharge capacity control is shown, with control regulator 12. That is, when operating device 17 is operated, an operation command is input from operating device 17 to control device 18. Then, control device 18 calculates the flow rate to be discharged from hydraulic pump 11, i.e., the commanded discharge flow rate, based on the operation command. Furthermore, control device 18 calculates a corrected flow rate based on the correction table described later and the commanded discharge flow rate. And, control device 18 corrects the commanded discharge flow rate based on the corrected flow rate. In addition, control device 18... Figure 3 The pump characteristics and the corrected command output flow rate are used to calculate the command signal given to the regulator 12. Furthermore, the control device 18 controls the regulator 12, i.e., controls the output capacity of the hydraulic pump 11, by outputting the command signal to the regulator 12. The pump characteristics are a function (or table) representing the relationship between the command signal and the command output flow rate. In this embodiment, the control device 18 stores pump characteristics obtained through prior measurement, etc., in advance. More specifically, the pump characteristics are set by measuring the hydraulic pump 11 while it is rotating at a predetermined basic speed. The control device 18 also outputs a position signal to the unloading valve 14. This controls the position and stroke of the valve core 14a. This controls the amount of working fluid discharged from the hydraulic pump 11 to the tank 19. The control device 18 also outputs a control command to the hydraulic circuit 13. This controls the flow of working fluid from the hydraulic pump 11 to the actuator 2. In addition, the control device 18 controls the drive source 10. This adjusts the rotational speed of the hydraulic pump 11.

[0025] Furthermore, the control device 18, as previously described, together with the hydraulic pump 11, the regulator 12, the unloading valve 14, and the two pressure sensors 15 and 16, constitutes the pump system 1. The control device 18, together with these structures, can generate a correction table. That is, the control device 18 generates a correction table by implementing the correction table generation method detailed later. The correction table is a table representing the correction flow that should be corrected (e.g., added or subtracted) for each command output flow. In this embodiment, the correction flow is the difference between the command output flow and the actual output flow. The actual output flow is the flow actually output from the hydraulic pump 11 when the command signal is output to the regulator 12 in the hydraulic drive system 3.

[0026] Additionally, the control device 18 includes a memory (not shown) and a processor. The memory stores the detection results of two pressure sensors 15 and 16. Furthermore, the memory stores the aforementioned pump characteristics and correction tables, and stores various programs for controlling the operation of the regulator 12, hydraulic circuit 13, and unloading valve 14, or for implementing the correction table generation method. The processor executes the programs stored in the memory, thereby activating the regulator 12, hydraulic circuit 13, and unloading valve 14, and implementing the correction table generation method.

[0027] <Method for generating correction tables> In pump system 1, control device 18 generates a correction table by executing a correction table generation method. Furthermore, control device 18 corrects the command output flow rate using the correction table generated by the correction table generation method, thereby enabling the hydraulic pump 11 to output the desired flow rate of working fluid. The correction table generation method is described below. When the correction table generation method is executed, control device 18 changes the command signal output to regulator 12 (i.e., changes the signal value of the command signal) under measurement conditions. Thus, control device 18 detects the upstream pressure and downstream pressure respectively using the first pressure sensor 15 and the second pressure sensor 16 under multiple different command signals. Here, the measurement conditions include fixing the opening degree of unloading valve 14 at a first opening degree. In this embodiment, the measurement conditions also include the rotational speed of hydraulic pump 11 being a pre-set correction speed for each command signal. Therefore, control device 18 adjusts the rotational speed of hydraulic pump 11 to a correction speed corresponding to the command signal by controlling drive source 10. Furthermore, the rotational speed used for calibration is set to a smaller value for larger tilt angles and a larger value for smaller tilt angles. This allows the appropriate flow rate of working fluid to be discharged from the hydraulic pump 11 during calibration.

[0028] Next, the control device 18 calculates the pressure difference across the unloading valve 14 based on the upstream and downstream pressures. The pressure difference is the pressure difference between the upstream and downstream sides of the unloading valve 14. Based on the pressure difference and the opening degree of the unloading valve 14, the control device 18 calculates the actual discharge flow rate from the hydraulic pump 11 for each command signal, i.e., the actual discharge flow rate. Furthermore, the control device 18 generates a correction table based on the commanded discharge flow rate and the actual discharge flow rate relative to each command signal. (Refer to the following...) Figure 2 The flowchart further details the method for generating the correction table. In pump system 1, multiple different command signals (hereinafter referred to as "correction command signals") are stored in control device 18 in order to generate the correction table. Furthermore, in pump system 1, multiple correction command signals are output under measurement conditions (for example, referring to...). Figure 3The valve core 14a of the unloading valve 14 is held in the first position A1 during the operation of the unloading valve 14, which receives command signals I1 to I4 and detects the upstream and downstream pressures. Thus, the opening degree of the unloading valve 14 is fixed at the first opening degree.

[0029] Furthermore, in this embodiment, the measurement conditions include: the rotational speed of the hydraulic pump 11 is a preset speed for each command signal. Therefore, the control device 18 stores a calibration tachometer representing the relationship between the calibration command signal and the rotational speed (in this embodiment, the rotational speed) of the hydraulic pump 11. The control device 18 outputs a speed command to the drive source 10 based on the output calibration command signal and the calibration tachometer. As a result, the drive source 10 is controlled, and the rotational speed of the hydraulic pump 11 is adjusted to a speed corresponding to the calibration command signal. In addition, in this embodiment, in order to allow the full flow of the working fluid discharged from the hydraulic pump 11 to pass through the unloading valve 14, the measurement conditions include: each control valve (not shown) of the hydraulic circuit 13 is closed. Therefore, the control device 18 controls each control valve (not shown) of the hydraulic circuit 13 to meet the measurement conditions.

[0030] When all measurement conditions are met, the control device 18 outputs a calibration command signal to the regulator 12 under the measurement conditions. As a result, the discharge capacity of the hydraulic pump 11 is controlled to correspond to the calibration command signal. Working fluid is discharged from the hydraulic pump 11. The control device 18 then calculates the pressure difference across the unloading valve 14 based on the upstream and downstream pressures detected by the two pressure sensors 15 and 16. Furthermore, the control device 18 calculates the flow rate of the working fluid flowing through the unloading valve 14 (i.e., the actual discharge flow rate of the hydraulic pump 11) based on the pressure difference and the first opening degree of the unloading valve 14. In calculating the actual discharge flow rate of the hydraulic pump 11, this embodiment uses a flow coefficient α, and the control device 18 estimates the actual discharge flow rate Q of the hydraulic pump 11 based, for example, on the following equation (1). [Mathematical Expression 1] , Here, Q represents the actual discharge flow rate. A represents the opening area of ​​the unloading valve 14. ΔP represents the pressure difference across the unloading valve 14. The flow coefficient α is set by the control device 18 based on the pressure difference ΔP. More specifically, the control device 18, in addition to the pressure difference ΔP across the unloading valve 14, also stores a flow coefficient table representing the relationship between the flow coefficient α and the opening area of ​​the unloading valve 14. The control device 18 determines the flow coefficient α based on the pressure difference ΔP and the flow coefficient table. Furthermore, the flow coefficient table is a table pre-set by prior measurement (e.g., during manufacturing) and is pre-stored in the control device 18.

[0031] Furthermore, the control device 18 calculates the corrected discharge flow rate by correcting the estimated actual discharge flow rate with rotational speed. Figure 3The corrected discharge flow rates (Q1 to Q4) are calculated. More specifically, the control device 18 calculates the corrected discharge flow rate, converted to the discharge flow rate when the hydraulic pump 11 rotates at its basic speed. Specifically, the control device 18 divides the actual discharge flow rate by the actual speed of the drive source 10 and multiplies it by the basic speed. Furthermore, a speed sensor 10a is provided on the drive source 10. The control device 18 obtains the actual speed through the speed sensor 10a. Also, the basic speed, as mentioned above, is a fixed speed set when measuring specified pump characteristics.

[0032] Furthermore, the control device 18, after calculating the corrected discharge flow rate, calculates the command discharge flow rate relative to the output correction command signal based on the pump characteristics. Figure 3 The command output flow rates q1 to q4). Furthermore, the control device 18 calculates the correction flow rate as the difference between the command output flow rate and the correction output flow rate (see reference). Figure 3 The correction flow rates C1 to C4 are calculated. Furthermore, the control device 18 stores the command output flow rate and the correction flow rate corresponding to each other.

[0033] The control device 18 repeatedly calculates and stores the correction flow for each correction command signal until the correction flow for all correction command signals has been calculated and the corresponding correction output flow has been stored. Furthermore, after the correction flow for all correction command signals has been calculated and stored, the control device 18 generates a correction table based on the stored relationship between the command output flow and the correction flow. More specifically, the control device 18 generates a table representing the correction flow relative to the command output flow (see reference 18). Figure 3 The corrected flow rate for the output flow rate q1~q4 (refer to) Figure 3 The correction table for the corrected flow rates C1 to C4 is used. The control device 18 controls the regulator 12 using the correction table as follows. That is, the control device 18, as... Figure 2 As shown, when an operation command is input from the operating device 17 to the control device 18, the command output flow rate is calculated based on the operation command. Furthermore, the control device 18 corrects the command output flow rate based on a correction table. More specifically, the control device 18 calculates a corrected flow rate based on the command output flow rate and the correction table. Furthermore, the control device 18 corrects the command output flow rate based on the corrected flow rate. For example, the control device 18 subtracts (or adds) the corrected flow rate to the command output flow rate. Then, the control device 18 calculates the command signal to be output to the regulator 12 based on the corrected command output flow rate and the pump characteristics. The control device 18 then outputs the command signal to the regulator 12. Thus, in the pump system 1, the working fluid at a flow rate corresponding to the command output flow rate can be discharged from the hydraulic pump 11.

[0034] In the pump system 1 of this embodiment, the actual discharge flow rate, calculated based on the pressure difference across and the opening degree of the unloading valve 14, is calculated for each command signal. Furthermore, a correction table is generated based on the commanded discharge flow rate and the actual discharge flow rate relative to each command signal. Therefore, the control device 18 outputs a command signal based on the commanded discharge flow rate corrected using the correction table, thereby enabling the working fluid at a flow rate corresponding to the commanded discharge flow rate to be actually discharged from the hydraulic pump 11. Thus, the difference between the commanded discharge flow rate and the actual pump flow rate can be suppressed.

[0035] Furthermore, in the pump system 1 of this embodiment, the flow coefficient α is set in the control device 18 based on the pressure difference across the pump. Therefore, the actual discharge flow rate can be calculated with higher accuracy. Consequently, the difference between the commanded discharge flow rate and the actual pump flow rate can be further suppressed.

[0036] Furthermore, in the pump system 1 of this embodiment, the control device 18 generates a correction table based on the difference between the commanded discharge flow rate and the actual discharge flow rate relative to each command signal. Therefore, the difference between the commanded discharge flow rate and the actual pump flow rate can be further suppressed.

[0037] Furthermore, in the pump system 1 of this embodiment, the measurement conditions include: the rotational speed of the hydraulic pump 11 is a preset speed for each command signal. By maintaining the rotational speed at the preset speed, it is possible to suppress fluctuations in the flow rate of the working fluid discharged from the hydraulic pump 11 due to changes in rotational speed. Therefore, since fluctuations in the discharge pressure of the hydraulic pump 11 can be suppressed, the actual discharge flow rate can be calculated with higher accuracy. Thus, it is possible to further suppress the difference between the commanded discharge flow rate and the actual pump flow rate.

[0038] Furthermore, in the pump system 1 of this embodiment, the control device 18 holds the valve core 14a of the unloading valve 14 at the first position A1 to meet the first measurement condition. Therefore, it is easy to maintain the opening of the unloading valve 14 at the first opening. As a result, the actual discharge flow rate can be calculated with higher accuracy. Therefore, it is possible to further suppress the difference between the commanded discharge flow rate and the actual pump flow rate.

[0039] Furthermore, in the pump system 1 of this embodiment, the unloading valve 14 is connected to the pump passage 11a and is located upstream of the hydraulic circuit 13. Therefore, it is less susceptible to pressure loss caused by the working fluid flowing from the hydraulic pump 11 to the unloading valve 14, allowing for high-precision calculation of the pressure difference across the unloading valve 14. Consequently, the actual discharge flow rate can be calculated with even greater accuracy. Therefore, the difference between the commanded discharge flow rate and the actual pump flow rate can be further suppressed.

[0040] Furthermore, in the pump system 1 of this embodiment, the control device 18 corrects the input command output flow rate based on a correction table, and calculates the command signal to be output based on the corrected command output flow rate and pump characteristics. Therefore, the difference between the command output flow rate and the actual pump flow rate can be suppressed.

[0041] [Second Implementation] <Pump System> The pump system 1A of the second embodiment is as follows: Figure 4 As shown, the structure is similar to that of pump system 1 in the first embodiment. Therefore, regarding the structure of pump system 1A in the second embodiment, the main focus will be on the structures that differ from pump system 1 in the first embodiment, with identical structures marked by the same symbols and their descriptions omitted. Similarly, regarding pump systems 1B and 1C in the third and fourth embodiments, which will be described later, the main focus will also be on the differences from the other embodiments, with identical structures marked by the same symbols and their descriptions omitted.

[0042] The pump system 1A of the second embodiment is equipped with a hydraulic drive system 3A. The hydraulic drive system 3A includes at least one actuator 2, a hydraulic pump 11, a regulator 12, a hydraulic circuit 13, an unloading valve 14A, two pressure sensors 15 and 16, an operating device 17, and a control device 18A. Furthermore, the pump system 1A is configured by at least including the hydraulic pump 11, the regulator 12, the unloading valve 14A, the two pressure sensors 15 and 16, and the control device 18A.

[0043] As an example of an opening control valve, the unloading valve 14A is a four-position spool valve. That is, the valve core 14a moves to any one of the first to fourth positions A1 to A4 according to the input position signal. At the fourth position A4, the valve core 14a fixes the opening of the unloading valve 14 at the second opening degree. In this embodiment, the fourth position A4 is the position after the valve core 14a, which is in the third position A3, has been further stroked. The second opening degree is set to have an opening area larger than the first opening degree.

[0044] Furthermore, the control device 18A, together with the hydraulic pump 11, regulator 12, unloading valve 14A, and two pressure sensors 15 and 16, generates a correction table. That is, the control device 18A generates the correction table by implementing the correction table generation method detailed later.

[0045] <Method for generating correction tables> In pump system 1A, control device 18A generates a first and a second correction table by executing a correction table generation method. Furthermore, the first and second correction tables can be generated starting from either one. Hereinafter, the generation of the first correction table will be described first. Control device 18A generates the first correction table using a method substantially the same as the correction table generation method of the first embodiment (see [reference]). Figure 5The corrected output flow rates Q11 to Q14 and the corrected flow rates C11 to C14). That is, under the first measurement condition which is the aforementioned measurement condition, the control device 18A generates a first correction table based on the upstream and downstream pressures for each of the multiple command signals.

[0046] On the other hand, the correction table generation method executed by the control device 18A for generating the characteristics of the first pump differs from the correction table generation method of the first embodiment in the following aspects. That is, the control device 18A sets the flow coefficient α according to the opening state of the unloading valve 14A, in addition to the pressure difference ΔP. More specifically, the control device 18A stores different flow coefficient tables for each opening of the unloading valve 14 (each of the first opening and the second opening in this embodiment). Furthermore, the control device 18A determines the flow coefficient α based on the first flow coefficient table, which is a flow coefficient table related to the first opening, and the pressure difference ΔP across the unloading valve 14A. Furthermore, the control device 18A estimates the flow rate of the working fluid flowing through the unloading valve 14A (i.e., the actual discharge flow rate of the hydraulic pump 11) based on the aforementioned equation (1). In addition, in equation (1), A is the opening area of ​​the unloading valve 14A when the opening is the first opening.

[0047] Next, the generation of the second correction table will be explained. Under the second measurement conditions, the control device 18A detects the upstream pressure and downstream pressure respectively via the first pressure sensor 15 and the second pressure sensor 16 under multiple different command signals. The second measurement condition includes fixing the opening of the unloading valve 14A at a second opening. Therefore, the control device 18A maintains the opening of the unloading valve 14 at the second opening by moving the valve core 14a to the fourth position A4. Furthermore, in this embodiment, the second measurement condition also includes the rotational speed of the hydraulic pump 11 being the aforementioned correction speed. Therefore, the control device 18A adjusts the rotational speed of the hydraulic pump 11 to the correction speed corresponding to the command signal by controlling the drive source 10. Additionally, the second measurement condition includes the closure of each control valve (not shown) in the hydraulic circuit 13. Therefore, the control device 18A controls each control valve (not shown) in the hydraulic circuit 13 to meet the measurement conditions.

[0048] Next, control device 18A calculates the pressure difference across unloading valve 14A based on the upstream and downstream pressures detected under the second measurement conditions. Control device 18A then calculates the actual discharge flow rate of hydraulic pump 11 for each command signal based on the pressure difference and the second opening degree of unloading valve 14A. Furthermore, control device 18A generates a second correction table based on the commanded discharge flow rate and the actual discharge flow rate relative to each command signal.

[0049] The following describes in detail the method for generating a correction table related to the characteristics of the second pump. However, the method for generating a correction table related to the characteristics of the first pump is similar in process to the method for generating a correction table in the first embodiment. Therefore, regarding the method for generating a correction table related to the characteristics of the second pump, the following mainly describes the differences from the method for generating a correction table in the first embodiment. In pump system 1, in order to output multiple correction command signals and detect upstream and downstream pressures under the second measurement conditions, control device 18A moves the valve core 14a of unloading valve 14A to the fourth position A4. As a result, the opening degree of unloading valve 14A becomes the second opening degree. Furthermore, when estimating the actual discharge flow rate of hydraulic pump 11 based on equation (1), control device 18A determines the flow coefficient α based on the flow coefficient table related to the second opening degree and the pressure difference before and after unloading valve 14. Furthermore, in equation (1), Q is the estimated flow rate of the working fluid flowing through unloading valve 14A (i.e., the estimated discharge flow rate of hydraulic pump 11). Additionally, A is the opening area of ​​the unloading valve 14A when it is at its second opening degree, and ΔP is the pressure difference across the unloading valve 14A. Furthermore, the control device 18A calculates the corrected discharge flow rate based on the actual discharge flow rate, and calculates the supplementary flow rate based on the commanded discharge flow rate and the corrected discharge flow rate (refer to...). Figure 5 The command output flow rates q1 to q4, the correction output flow rates Q21 to Q24, and the correction flow rates C21 to C24 are specified. Then, the control device 18A generates a second correction table based on the relationship between the stored command output flow rates and the correction flow rates after the correction flow rates are calculated and stored accordingly for all correction command signals.

[0050] Control device 18A uses the first and second correction tables to control regulator 12 as follows. That is, control device 18, as... Figure 2 As shown, when an operation command is output from the operating device 17 to the control device 18A, the command output flow rate is calculated based on the operation command. Furthermore, the control device 18A selects which of the first and second correction tables to use to correct the command output flow rate. The control device 18A then corrects the command output flow rate using the selected correction table. For example, if the command output flow rate is less than a specified flow rate, the control device 18A selects the first correction table. The control device 18A then calculates the corrected flow rate based on the command output flow rate and the first correction table. Conversely, if the command output flow rate is greater than a specified flow rate, the control device 18A selects the second correction table. The control device 18A then calculates the corrected flow rate based on the command output flow rate and the second correction table. When the control device 18A calculates the corrected flow rate based on either the first or second correction table, the control device 18A corrects the command output flow rate based on the corrected flow rate. Finally, the control device 18A calculates the command signal to be output to the regulator 12 based on the pump characteristics and the command output flow rate. Thus, in pump system 1, working fluid of a flow rate corresponding to the commanded discharge flow rate can be discharged from hydraulic pump 11.

[0051] In the pump system 1A of this embodiment, the flow coefficient α is set in the control device 18A based on the opening state, in addition to the pressure difference. Therefore, the actual discharge flow rate can be calculated with higher accuracy. Thus, the difference between the commanded discharge flow rate and the actual pump flow rate can be further suppressed.

[0052] Furthermore, in the pump system 1A of this embodiment, the control device 18A maintains the valve core 14a in the fourth position in order to obtain a second correction table under a second measurement condition different from the first measurement condition. Therefore, correction tables can be generated with different opening degrees. This allows for the calculation of the actual discharge flow rate with higher accuracy. Thus, the difference between the commanded discharge flow rate and the actual pump flow rate can be further suppressed. Otherwise, the pump system 1A of the second embodiment achieves the same effects as the pump system 1 of the first embodiment.

[0053] [Third Implementation] <Pump System> The pump system 1B of the third embodiment, such as Figure 6 As shown, a hydraulic drive system 3B is provided. The hydraulic drive system 3B includes actuators 2, a hydraulic pump 11, a regulator 12, a hydraulic circuit 13B, an unloading valve 14, a pressure sensor 15B, an operating device 17, and a control device 18B. In this embodiment, the hydraulic drive system 3B is equipped with a plurality of actuators 2, each actuator 2 being connected to the hydraulic pump 11 in parallel. Furthermore, the plurality of actuators 2 includes actuator 2B. Actuator 2B is, for example, a hydraulic motor, and in this embodiment, a travel hydraulic motor 2B. The travel hydraulic motor 2B drives a travel device (e.g., tracks and tires) provided on the hydraulic machinery. The travel hydraulic motor 2B is connected to the hydraulic pump 11 in parallel with the other actuators 2. That is, the travel hydraulic motor 2B is connected to the pump passage 11a in parallel with the other actuators 2. Furthermore, the hydraulic circuit 13B is configured at least as follows to control the flow rate of the working fluid flowing to the travel hydraulic motor 2B.

[0054] That is, the hydraulic circuit 13B includes at least a priority valve 21, a travel control valve 22, and a travel pressure sensor 16B. As an example of an opening control valve, the priority valve 21 is connected to the pump passage 11a. The priority valve 21 is connected to the travel hydraulic motor 2B via the travel control valve 22. Furthermore, the priority valve 21 causes the working fluid to flow preferentially to other actuators 2 relative to the travel hydraulic motor 2B. More specifically, the priority valve 21 is, for example, an open-end control valve that connects the hydraulic pump 11 to the travel hydraulic motor 2B. Furthermore, the priority valve 21 moves the valve core 21a to a throttling position at a position corresponding to the input opening signal. Thus, the passage between the hydraulic pump 11 and the travel hydraulic motor 2B can be throttled, allowing the working fluid to flow preferentially to other actuators 2 through throttling.

[0055] The travel control valve 22 is connected to the priority valve 21 and the travel hydraulic motor 2B. Furthermore, the travel control valve 22 moves the valve core 22a according to the input travel command signal. Thus, the travel control valve 22 controls the flow of working fluid to the travel hydraulic motor 2B (i.e., the flow direction and flow rate).

[0056] As an example of a second pressure sensor, a driving pressure sensor 16B is disposed downstream of the priority valve 21. More specifically, the driving pressure sensor 16B is connected between the priority valve 21 and the driving control valve 22. Furthermore, the driving pressure sensor 16B detects the hydraulic pressure downstream of the priority valve 21, i.e., the downstream pressure of the priority valve 21.

[0057] In the hydraulic drive system 3B configured as described above, the pump system 1B is configured as follows: The pump system 1B is configured by at least a hydraulic pump 11, a regulator 12, a priority valve 21, two pressure sensors 15B and 16B, and a control device 18B. Furthermore, the first pressure sensor 15B is connected to the pump passage 11a, and the first pressure sensor 15B measures the pressure of the working fluid flowing in the pump passage 11a as the upstream pressure of the priority valve 21. The first pressure sensor 15B does not necessarily need to be connected to the pump passage 11a, as long as it can detect the upstream pressure of the priority valve 21.

[0058] Furthermore, the control device 18B controls the opening degree of the priority valve 21 by outputting an opening signal to the priority valve 21. Moreover, by controlling the opening degree of the priority valve 21, the control device 18B controls which of the hydraulic pump 11's working fluid is directed to the travel hydraulic motor 2B and other actuators 2. Additionally, the control device 18B outputs a travel command signal to the travel control valve 22. Thus, the control device 18B controls the flow of working fluid to the travel hydraulic motor 2B.

[0059] The control device 18B, which has this function, together with the hydraulic pump 11, regulator 12, priority valve 21, and two pressure sensors 15B and 16B, generates a correction table. That is, the control device 18B generates the correction table by implementing the correction table generation method detailed later.

[0060] <Method for generating correction tables> In pump system 1B, control device 18B generates a correction table by executing a correction table generation method. More specifically, control device 18B performs the following detections under measurement conditions: Under multiple different command signals, control device 18B detects the upstream and downstream pressures of priority valve 21 via first pressure sensor 15 and driving pressure sensor 16B, respectively. Measurement conditions include fixing the opening of priority valve 21 at a predetermined opening. Furthermore, in this embodiment, measurement conditions also include the rotational speed of hydraulic pump 11 being a correction speed corresponding to the command signal. Therefore, control device 18B adjusts the rotational speed of hydraulic pump 11 to a correction speed corresponding to the command signal by keeping priority valve 21 in the open position and controlling drive source 10.

[0061] Next, control device 18A calculates the pressure difference across the priority valve 21 based on the upstream and downstream pressures detected under measurement conditions. Control device 18B calculates the actual discharge flow rate of hydraulic pump 11 for each command signal based on the pressure difference and the specified opening degree of priority valve 21. Furthermore, control device 18B generates a correction table based on the commanded discharge flow rate and the actual discharge flow rate relative to each command signal.

[0062] The method for generating the correction table will be described in further detail below, but its process is similar to that of the correction table generation method in the first embodiment. Therefore, regarding the correction table generation method of this embodiment, the following mainly describes the differences from the correction table generation method of the first embodiment. In the pump system 1B, the control device 18B fixes the opening degree of the priority valve 21 to a predetermined opening degree by keeping the priority valve 21 in the open position. In this embodiment, the control device 18B, for example, keeps the priority valve 21 fully open. Furthermore, the control device 18B adjusts the rotational speed of the hydraulic pump 11 to a speed corresponding to the calibration command signal by controlling the drive source 10. In addition, in this embodiment, the measurement conditions include: all control valves (not shown) of the hydraulic circuit 13B other than the travel control valve 22 are closed and the travel control valve 22 is fully open. As a result, the entire flow rate of the working fluid discharged from the hydraulic pump 11 flows through the priority valve 21. The control device 18 controls each control valve (not shown) of the hydraulic circuit 13B in order to allow the entire flow rate to flow through the priority valve 21.

[0063] When the measurement conditions are met, the control device 18B outputs any one of the multiple calibration command signals to the regulator 12. Then, the control device 18B calculates the pressure difference ΔP across the priority valve 21 based on the upstream and downstream pressures detected by the two pressure sensors 15B and 16B. Furthermore, the control device 18B calculates the flow rate (i.e., the actual discharge flow rate of the hydraulic pump 11) Q of the working fluid flowing through the priority valve 21 based on the pressure difference ΔP and the first opening degree of the priority valve 21. The control device 18B estimates the actual discharge flow rate of the hydraulic pump 11, for example, based on the aforementioned equation (1). Additionally, the control device 18B stores a flow coefficient table representing the relationship between the pressure difference ΔP across the priority valve 21 and the flow coefficient α, and determines the flow coefficient α based on the pressure difference ΔP and the flow coefficient table. Furthermore, A is the opening area of ​​the priority valve 21 when the opening degree is a specified opening degree.

[0064] Then, the control device 18B calculates the corrected discharge flow rate by correcting the estimated actual discharge flow rate with the rotational speed. Furthermore, the control device 18B calculates the commanded discharge flow rate based on the correction command signal and pump characteristics, and calculates the corrected flow rate based on the commanded discharge flow rate and the corrected discharge flow rate. The control device 18B then stores the commanded discharge flow rate and the corrected flow rate correspondingly.

[0065] After the correction flow rate is calculated and stored correspondingly for all calibration command signals, the control device 18B generates a correction table based on the relationship between the stored command output flow rate and the correction flow rate. Furthermore, similarly to the control device 18 in the first embodiment, the control device 18B calculates a command signal based on the command output flow rate corrected by the correction table and outputs the command signal. This enables the working fluid with a flow rate corresponding to the command output flow rate to be discharged from the hydraulic pump 11.

[0066] In the pump system 1B of this embodiment, similar to the unloading valves 14 and 14A, the pump characteristics can also be corrected by the priority valve 21. Therefore, in the pump system 1B equipped with the priority valve 21, the difference between the commanded discharge flow rate and the actual pump flow rate can be suppressed.

[0067] Otherwise, the pump system 1B of the third embodiment has the same function as the pump system 1 of the first embodiment.

[0068] [Fourth Implementation] <Pump System> The pump system 1C of the fourth embodiment, such as Figure 7As shown, a hydraulic drive system 3C is provided. The hydraulic drive system 3C includes actuators 2, a hydraulic pump 11, a regulator 12, a hydraulic circuit 13C, an unloading valve 14, a pressure sensor 15C, an operating device 17, and a control device 18C. In this embodiment, the hydraulic drive system 3C is equipped with multiple actuators 2, each actuator 2 connected to the hydraulic pump 11 in parallel. Furthermore, the multiple actuators 2 include an actuator 2C. The actuator 2C is, for example, a hydraulic motor, and in this embodiment, a rotary hydraulic motor 2C. The rotary hydraulic motor 2C, for example, rotates a rotating body equipped on an excavator or crane. The rotary hydraulic motor 2C is connected to the hydraulic pump 11 in parallel with the other actuators 2. That is, the rotary hydraulic motor 2C is connected to the pump passage 11a in parallel with the other actuators 2. Furthermore, the hydraulic circuit 13C is configured at least as follows to control the flow rate of the working fluid flowing to the rotary hydraulic motor 2C.

[0069] That is, the hydraulic circuit 13C includes at least a rotary control valve 22C and a rotary pressure sensor 16C. As an example of an opening control valve, the rotary control valve 22C is connected to the pump passage 11a and the rotary hydraulic motor 2C. Specifically, the hydraulic pump 11 is connected to the rotary hydraulic motor 2C via the rotary control valve 22C. Furthermore, the rotary control valve 22C controls the flow of working fluid to the rotary hydraulic motor 2C. More specifically, the rotary control valve 22C moves the valve core 22Ca according to the input rotary command signal. This switches the connection state between the rotary hydraulic motor 2C and the hydraulic pump 11. Thus, the flow direction of the working fluid to the rotary hydraulic motor 2C is controlled. Also, the rotary control valve 22C is a flow control valve, and its opening can be changed by moving the valve core 22Ca. Thus, the flow rate of the working fluid to the rotary hydraulic motor 2C is controlled. In addition, a position sensor 22Cb is provided on the rotary control valve 22C. The position sensor 22Cb is, for example, a stroke sensor that detects the position (or stroke amount) of the valve core 22Ca.

[0070] As an example of a second pressure sensor, a rotary pressure sensor 16C is disposed downstream of a rotary control valve 22C. More specifically, the rotary pressure sensor 16C is connected between either port of the rotary hydraulic motor 2C and the rotary control valve 22C. Furthermore, the rotary pressure sensor 16C detects the hydraulic pressure downstream of the rotary control valve 22C, i.e., the downstream pressure of the rotary control valve 22C. Alternatively, the rotary pressure sensor 16C may be connected between each port of the rotary hydraulic motor 2C and the rotary control valve 22C.

[0071] In the hydraulic drive system 3C configured as described above, the pump system 1C has the following structure: The pump system 1C is configured by at least a hydraulic pump 11, a regulator 12, a rotary control valve 22C, two pressure sensors 15C and 16C, and a control device 18C. Furthermore, the first pressure sensor 15C is connected to the pump passage 11a. The first pressure sensor 15C measures the pressure of the working fluid flowing towards the rotary control valve 22C, i.e., the upstream pressure of the rotary control valve 22C. Alternatively, the first pressure sensor 15C may not necessarily be connected to the passage connecting the pump passage 11a and the rotary control valve 22C, as long as it can detect the upstream pressure of the rotary control valve 22C.

[0072] The control device 18C outputs a rotation command signal to the rotation control valve 22C. As a result, the control device 18C controls the flow of working fluid to the rotation hydraulic motor 2C. Furthermore, the control device 18C obtains the position of the valve core 22Ca from the position sensor 22Cb.

[0073] Furthermore, the control device 18C can, together with the hydraulic pump 11, the regulator 12, the rotary control valve 22C, and the two pressure sensors 15C and 16C, correct the pump characteristics. That is, the control device 18C generates a correction table by implementing the correction table generation method detailed later.

[0074] <Method for generating correction tables> In pump system 1C, control device 18C generates multiple correction tables by executing a correction table generation method. More specifically, control device 18C generates multiple pump characteristics using a method substantially the same as the correction table generation method of the second embodiment. That is, the following detections are performed under multiple measurement conditions where the opening degree of the rotary control valve 22C differs from each other. Specifically, under multiple command signals that differ from each other, control device 18C detects the upstream pressure and downstream pressure of the rotary control valve 22C respectively using the first pressure sensor 15C and the rotary pressure sensor 16C. Furthermore, each measurement condition also includes: the rotational speed of hydraulic pump 11 being a correction speed corresponding to the command signal. Therefore, control device 18C changes the opening degree of rotary control valve 22C by outputting different rotation command signals, and adjusts the rotational speed of hydraulic pump 11 to a correction speed corresponding to the command signal by controlling drive source 10.

[0075] Next, the control device 18C calculates the pressure difference across the rotary control valve 22C based on the upstream and downstream pressures detected under each measurement condition. Based on the opening degree of the rotary control valve 22C and the pressure difference under the measurement conditions during detection, the control device 18C calculates the actual discharge flow rate of the hydraulic pump 11 for each command signal. Furthermore, for each measurement condition, the control device 18C generates a correction table based on the commanded discharge flow rate and the actual discharge flow rate relative to each command signal; that is, it generates a correction table for each opening degree of the rotary control valve 22C.

[0076] The method for generating the correction table will be described in further detail below, but its process is similar to that of the correction table generation method in the first embodiment. Therefore, regarding the correction table generation method of this embodiment, the following mainly describes the differences from the correction table generation method of the first embodiment. In the pump system 1C, the control device 18C selects any one of a plurality of measurement conditions, and further controls the opening of the rotary control valve 22C to satisfy the selected measurement condition (hereinafter referred to as "selected measurement condition"). At this time, the control device 18C maintains the opening of the rotary control valve 22C at an opening corresponding to the selected measurement condition by referring to the detection result of the position sensor 22Cb. Furthermore, the control device 18C adjusts the speed of the hydraulic pump 11 to a speed corresponding to the correction command signal by controlling the drive source 10. In addition, in this embodiment, the control device 18C closes each control valve (not shown) of the hydraulic circuit 13C other than the rotary control valve 22C.

[0077] When the selected measurement conditions are met, the control device 18C outputs one of multiple calibration command signals to the regulator 12 under the selected measurement conditions. Then, the control device 18C calculates the pressure difference ΔP across the rotary control valve 22C based on the upstream and downstream pressures detected by the two pressure sensors 15C and 16C. Furthermore, the control device 18C calculates the flow rate (i.e., the actual discharge flow rate of the hydraulic pump 11) Q of the working fluid flowing through the rotary control valve 22C based on the pressure difference ΔP and the opening degree of the rotary control valve 22C. More specifically, the control device 18C estimates the actual discharge flow rate of the hydraulic pump 11, for example, based on the aforementioned equation (1). In addition, the control device 18C stores a flow coefficient table showing the relationship between the pressure difference ΔP across the rotary control valve 22C and the flow coefficient α for each opening degree of the rotary control valve 22C. The control device 18C determines the flow coefficient α based on the rotation command signal, the pressure difference ΔP, and the flow coefficient table.

[0078] Then, the control device 18C calculates the corrected discharge flow rate by correcting the estimated actual discharge flow rate with rotational speed. Furthermore, the control device 18C calculates the commanded discharge flow rate based on the correction command signal and pump characteristics, and calculates the corrected flow rate based on the commanded discharge flow rate and the corrected discharge flow rate. The control device 18C stores the commanded discharge flow rate and the corrected discharge flow rate correspondingly. Then, after the corrected flow rate has been calculated and stored correspondingly for all correction command signals, the control device 18C generates a correction table based on the stored relationship between the commanded discharge flow rate and the corrected flow rate.

[0079] Similarly, the control device 18C detects the upstream and downstream pressures under various measurement conditions and generates a correction table based on the detected upstream and downstream pressures. The correction table generation method ends once the correction table is generated under all measurement conditions. Furthermore, the control device 18C selects one of several correction tables based on the commanded discharge flow rate and corrects the commanded discharge flow rate using the selected correction table. The control device 18C then calculates the command signal to be output to the regulator 12 based on the corrected commanded discharge flow rate and the pump characteristics. Thus, in the pump system 1, the working fluid at a flow rate corresponding to the commanded discharge flow rate can be discharged from the hydraulic pump 11.

[0080] In the pump system 1C of this embodiment, similar to the unloading valves 14 and 14A, the pump characteristics can also be corrected by the rotary control valve 22C. Furthermore, in the pump system 1C equipped with the rotary control valve 22C, the difference between the commanded discharge flow rate and the actual pump flow rate can be suppressed.

[0081] Furthermore, in the pump system 1C of this embodiment, the control device 18C generates multiple pump characteristics by correcting the pump characteristics based on the upstream and downstream pressures detected under multiple measurement conditions where the opening degree of the rotary control valve 22C is different from each other. Therefore, the actual discharge flow rate can be calculated with higher accuracy. Thus, the difference between the commanded discharge flow rate and the actual pump flow rate can be suppressed.

[0082] Otherwise, the pump system 1C of the fourth embodiment has the same function as the pump system 1 of the first embodiment.

[0083] <Other Implementation Methods> The pump system 1 of the first embodiment includes a second pressure sensor 16 connected between the unloading valve 14 and the tank 19, but it is not necessary to have a second pressure sensor 16. In this case, the downstream pressure of the unloading valve 14 in the pump system 1 is set to a predetermined tank pressure. As a result, the same effect as the pump system 1 can be achieved, while reducing the number of parts. The pump system 1A of the second embodiment is the same.

[0084] The pump systems 1, 1A to 1C of the first to fourth embodiments generate pump characteristics, but it is not necessary to generate pump characteristics. Furthermore, in the pump systems 1, 1A to 1C of the first to fourth embodiments, the regulator 12 is composed of a servo piston 12a and an electromagnetic proportional valve 12b, but this structure is not limited. For example, it could be a structure where the servo piston 12a is driven by a linear motor or the like. In this case, the output capacity is changed by inputting a command signal to the linear motor. Also, in the pump system 1C of the fourth embodiment, the rotary control valve 22C is composed of a pilot-operated spool valve, but it could also be an electrically operated spool valve where the valve core 22Ca is moved with high precision using a ball screw or the like. In this case, the rotary control valve 22C may not have a position sensor 22Cb.

[0085] Furthermore, in the pump systems 1, 1A to 1C of the first to fourth embodiments, examples of unloading valves 14 and 14A, priority valve 21, and rotation control valve 22C are used as opening control valves. However, the opening control valve is not limited to any valve capable of switching openings. Also, the flow coefficient α is set based on the pressure difference across the flow path, but it can also be a fixed value. Furthermore, the flow coefficient α can be set based on the external air temperature or the working fluid temperature, in addition to the pressure difference and the opening. Furthermore, the measurement conditions include setting the rotational speed of the hydraulic pump 11 to a predetermined speed for each signal, but it is also possible that the rotational speed of the hydraulic pump 11 is fixed. Furthermore, the connection position of the unloading valves 14 and 14A does not necessarily have to be limited to the pump passage 11a, as long as the position where the discharge pressure of the hydraulic pump 11 can be detected or estimated by the first pressure sensor 15 is acceptable.

[0086] <Exemplary Implementation> A pump system of the first aspect comprises: a variable-capacity hydraulic pump capable of changing its discharge capacity; a regulator for changing the discharge capacity of the hydraulic pump according to an input command signal; an opening control valve connected to the hydraulic pump and capable of changing its opening degree; a first pressure sensor for measuring the upstream pressure of the hydraulic fluid flowing from the hydraulic pump to the opening control valve; a second pressure sensor for measuring the downstream pressure of the hydraulic fluid flowing from the opening control valve; and a control device for controlling the discharge capacity of the hydraulic pump according to pump characteristics indicating the relationship between the commanded discharge flow rate and the command signal, wherein the control device controls the opening degree of the opening control valve by fixing... Under a specified opening measurement condition, the command signal output to the regulator is changed, thereby detecting the upstream pressure and downstream pressure respectively through the first pressure sensor and the second pressure sensor under multiple different command signals. Based on the pressure difference between the upstream and downstream sides of the opening control valve and the opening degree of the opening control valve, the actual discharge flow rate from the hydraulic pump is calculated for each command signal. A correction table for the corrected command discharge flow rate is generated based on the command discharge flow rate and the actual discharge flow rate relative to each command signal. The pressure difference between the upstream and downstream sides of the opening control valve is calculated based on the detected upstream and downstream pressures.

[0087] Based on the above, the actual discharge flow rate calculated based on the pressure difference and opening degree of the control valve is calculated for each command signal. Furthermore, a correction table is generated based on the commanded discharge flow rate and the actual discharge flow rate relative to each command signal. Therefore, the control device outputs a command signal based on the commanded discharge flow rate corrected using the correction table, thereby enabling the working fluid at a flow rate corresponding to the commanded discharge flow rate to be actually discharged from the hydraulic pump. Thus, the difference between the commanded discharge flow rate and the actual pump flow rate can be suppressed.

[0088] The second aspect of the pump system is that, in the pump system of the first aspect, the control device uses a flow coefficient when calculating the actual discharge flow rate based on the pressure difference and the opening degree. The flow coefficient is set in the control device according to the state of the pressure difference.

[0089] Based on the above, the flow coefficient is set in the control device according to the pressure differential. Therefore, the actual discharge flow rate can be calculated with higher accuracy. Consequently, the difference between the commanded discharge flow rate and the actual pump flow rate can be further suppressed.

[0090] The third aspect of the pump system is that, in the pump system of the first or second aspect, the control device uses a flow coefficient when calculating the actual discharge flow rate based on the pressure difference and the opening degree, and the flow coefficient is set in the control device according to the opening degree state.

[0091] Based on the above, the flow coefficient in the control device is set according to the opening state, in addition to the pressure difference. Therefore, the actual discharge flow rate can be calculated with higher accuracy. Consequently, the difference between the commanded discharge flow rate and the actual pump flow rate can be further suppressed.

[0092] The fourth aspect of the pump system is that, in any of the first to third aspects of the pump system, the control device generates a correction table for the commanded output flow rate based on the difference between the commanded output flow rate and the actual output flow rate relative to each command signal.

[0093] Based on the above, a correction table is generated based on the difference between the commanded output flow rate and the actual output flow rate relative to each command signal. Therefore, it is possible to further suppress the difference between the commanded output flow rate and the actual pump flow rate.

[0094] The fifth aspect of the pump system is that, in any one of the first to fourth aspects of the pump system, the measurement conditions include: the rotational speed of the hydraulic pump is a preset rotational speed for each command signal.

[0095] Based on the above, the measurement conditions include: the hydraulic pump speed is a predetermined speed for each command signal. By maintaining the speed at the predetermined speed, fluctuations in the flow rate of the working fluid discharged from the hydraulic pump due to changes in speed can be suppressed. Therefore, because fluctuations in the hydraulic pump's discharge pressure can be suppressed, the actual discharge flow rate can be calculated with high accuracy. Thus, the actual discharge flow rate can be calculated with even higher accuracy. Therefore, the difference between the commanded discharge flow rate and the actual pump flow rate can be further suppressed.

[0096] The sixth aspect of the pump system is, in any of the first to fifth aspects of the pump system, the opening control valve having: a valve body capable of moving to a first position fixing the opening at a predetermined opening, a second position blocking the hydraulic pump from the tank, and a third position changing the opening according to the stroke amount, the control device holding the valve body in the first position in order to obtain a first correction table under a first measurement condition.

[0097] Based on the above aspects, the control device maintains the valve body of the opening control valve in a first position, fixing the opening at a predetermined opening, in order to meet the first measurement condition. Therefore, it is easy to maintain the opening of the opening control valve at the predetermined opening. Consequently, the actual discharge flow rate can be calculated with higher accuracy. Therefore, it is possible to further suppress the difference between the commanded discharge flow rate and the actual pump flow rate.

[0098] The seventh aspect of the pump system is that, in the pump system of the sixth aspect, the valve body is movable to a fourth position where the opening is fixed at a second opening greater than a first opening which is a predetermined opening, and the control device holds the valve body in the fourth position in order to obtain a second correction table under a second measurement condition.

[0099] Based on the above aspects, the control device maintains the valve body in the fourth position in order to obtain a second correction table under a second measurement condition different from the first measurement condition. Therefore, correction tables can be generated with different opening degrees. This allows for the calculation of the actual discharge flow rate with higher accuracy. Consequently, the difference between the commanded discharge flow rate and the actual pump flow rate can be further suppressed.

[0100] The eighth aspect of the pump system is, in any of the first to fifth aspects of the pump system, the opening control valve is an unloading valve, the hydraulic pump is connected to the hydraulic circuit supplying the working fluid via a pump passage, and the unloading valve is connected to the pump passage and is upstream of the hydraulic circuit.

[0101] Based on the above, the opening control valve is an unloading valve, connected to the pump passage and positioned upstream of the hydraulic circuit. Therefore, it is less susceptible to pressure losses caused by the working fluid flowing from the hydraulic pump to the unloading valve, allowing for high-precision calculation of the pressure difference across the unloading valve. This, in turn, enables more accurate calculation of the actual discharge flow rate. Consequently, the discrepancy between the commanded discharge flow rate and the actual pump flow rate can be further suppressed.

[0102] The ninth aspect of the pump system is, in any of the first to fifth aspects of the pump system, the opening control valve is a priority valve, the hydraulic pump is connected to a plurality of actuators, and the priority valve preferentially flows to one of the plurality of actuators.

[0103] Based on the above, the opening control valve is a priority valve. The pump characteristics can be corrected through the pressure differential of the priority valve. Therefore, in a pump system equipped with a priority valve, the difference between the commanded discharge flow rate and the actual pump flow rate can be suppressed.

[0104] The pump system of the tenth aspect is, in any of the pump systems of the first to fifth aspects, wherein the opening control valve is a flow control valve, the hydraulic pump is connected to the actuator via the flow control valve, and the flow control valve controls the flow of working fluid to the actuator.

[0105] Based on the above, the opening control valve is a flow control valve. Pump characteristics can be corrected through the pressure difference of the flow control valve. Therefore, in a pump system equipped with a flow control valve, the difference between the commanded output flow rate and the actual pump flow rate can be suppressed.

[0106] The eleventh aspect of the pump system is that, in any of the first to tenth aspects of the pump system, the control device corrects the input command output flow rate based on the generated correction table, and calculates the command signal to be output based on the corrected command output flow rate and pump characteristics.

[0107] Based on the above, the control device corrects the input command output flow rate based on a correction table, and calculates the command signal to be output based on the corrected command output flow rate and pump characteristics. Therefore, it is possible to suppress the difference between the command output flow rate and the actual pump flow rate.

[0108] The pump system of the twelfth aspect comprises: a variable-capacity hydraulic pump capable of changing its discharge capacity; a regulator that changes the discharge capacity of the hydraulic pump according to an input command signal; an unloading valve disposed between the hydraulic pump and a tank, the opening of which can be changed; a first pressure sensor that measures the hydraulic pressure of the working fluid flowing from the hydraulic pump to the unloading valve; and a control device that controls the discharge capacity of the hydraulic pump according to pump characteristics representing the relationship between the command discharge flow rate and the command signal. The control device, by changing the command signal output to the regulator under the measurement condition of fixing the opening of the unloading valve at a predetermined opening, detects the hydraulic pressure using the first pressure sensor under multiple command signals that are different from each other, calculates the actual discharge flow rate discharged from the hydraulic pump for each command signal based on the pressure difference between the upstream and downstream sides of the unloading valve and the opening of the unloading valve, and generates a correction table for correcting the command discharge flow rate based on the command discharge flow rate and the actual discharge flow rate relative to each command signal. The pressure difference between the upstream and downstream sides of the unloading valve is calculated based on the detected hydraulic pressure.

[0109] Based on the above, the actual discharge flow rate, calculated based on the pressure difference and opening degree of the unloading valve, is calculated for each command signal. Furthermore, a correction table is generated based on the commanded discharge flow rate and the actual discharge flow rate relative to each signal value. Therefore, the control device can ensure that the working fluid at a flow rate corresponding to the commanded discharge flow rate is actually discharged from the hydraulic pump. Thus, the difference between the commanded discharge flow rate and the actual pump flow rate can be suppressed.

[0110] Based on the foregoing description, many improvements and other embodiments of this disclosure will be apparent to those skilled in the art. Therefore, the foregoing description should be interpreted as illustrative only and is provided to teach those skilled in the art the best mode of implementation. Details regarding how the construction and / or function can be substantially changed without departing from the spirit of this disclosure are also included.

Claims

1. A pump system, characterized in that, have: A variable-capacity hydraulic pump capable of changing its discharge capacity; A regulator that changes the output capacity of the hydraulic pump according to the input command signal; An opening control valve connected to the hydraulic pump, which can change the opening degree; A first pressure sensor measures the upstream pressure of the hydraulic fluid flowing from the hydraulic pump to the opening control valve; A second pressure sensor measures the downstream pressure of the hydraulic fluid flowing from the opening control valve; and A control device that controls the discharge capacity of a hydraulic pump based on pump characteristics that indicate the relationship between the commanded discharge flow rate and the command signal. The control device, by changing the command signal output to the regulator under the measurement condition of fixing the opening of the opening control valve at a predetermined opening, detects the upstream pressure and downstream pressure respectively through the first pressure sensor and the second pressure sensor under multiple different command signals. Based on the pressure difference between the upstream and downstream sides of the opening control valve and the opening of the opening control valve, it calculates the actual discharge flow rate from the hydraulic pump for each command signal. Based on the command discharge flow rate and the actual discharge flow rate relative to each command signal, it generates a correction table to correct the command discharge flow rate. The pressure difference between the upstream and downstream sides of the opening control valve is calculated based on the detected upstream and downstream pressures.

2. The pump system according to claim 1, characterized in that, The control device uses a flow coefficient when calculating the actual discharge flow rate based on the pressure difference and opening degree. The flow coefficient is set in the control device according to the pressure difference.

3. The pump system according to claim 1, characterized in that, The control device uses a flow coefficient when calculating the actual discharge flow rate based on the pressure difference and opening degree. The flow coefficient is set in the control device according to the opening status.

4. The pump system according to claim 1, characterized in that, The control device generates a correction table for correcting the command output flow rate based on the difference between the command output flow rate and the actual output flow rate relative to each command signal.

5. The pump system according to claim 1, characterized in that, The measurement conditions include: the rotational speed of the hydraulic pump is a preset speed for each command signal.

6. The pump system according to claim 1, characterized in that, The opening control valve has a valve body capable of moving to a first position that fixes the opening at a predetermined opening, a second position that blocks the hydraulic pump from the tank, and a third position that changes the opening according to the stroke amount. The control device holds the valve body in a first position in order to obtain a first correction table under a first measurement condition.

7. The pump system according to claim 6, characterized in that, The valve body is capable of moving to a fourth position, where the opening degree is fixed at a second opening degree that is larger than a first opening degree, which is a predetermined opening degree. The control device holds the valve body in the fourth position in order to obtain a second correction table under the second measurement conditions.

8. The pump system according to claim 1, characterized in that, The opening control valve is an unloading valve. The hydraulic pump is connected to the hydraulic circuit that supplies the working fluid via a pump passage. The unloading valve is connected to the pump passage and is located upstream of the hydraulic circuit.

9. The pump system according to claim 1, characterized in that, The opening control valve is a priority valve. The hydraulic pump is connected to multiple actuators. The priority valve preferentially directs the flow to one of the plurality of actuators.

10. The pump system according to claim 1, characterized in that, The opening control valve is a flow control valve. The hydraulic pump is connected to the actuator via the flow control valve. The flow control valve controls the flow of the working fluid to the actuator.

11. The pump system according to any one of claims 1 to 10, characterized in that, The control device corrects the input command output flow rate based on the generated correction table, and calculates the command signal to be output based on the corrected command output flow rate and pump characteristics.

12. A pump system, characterized in that, have: A variable-capacity hydraulic pump capable of changing its discharge capacity; A regulator that changes the output capacity of the hydraulic pump according to the input command signal; An unloading valve with adjustable opening degree is configured between the hydraulic pump and the tank; A first pressure sensor for measuring the hydraulic pressure of the working fluid flowing from the hydraulic pump to the unloading valve; and A control device that controls the discharge capacity of a hydraulic pump based on pump characteristics that indicate the relationship between the commanded discharge flow rate and the command signal. The control device, by changing the command signal output to the regulator under the measurement condition of fixing the opening of the unloading valve at a predetermined opening, detects hydraulic pressure using the first pressure sensor under multiple different command signals. Based on the pressure difference between the upstream and downstream sides of the unloading valve and the opening of the unloading valve, it calculates the actual discharge flow rate from the hydraulic pump for each command signal. Based on the command discharge flow rate and the actual discharge flow rate relative to each command signal, it generates a correction table to correct the command discharge flow rate. The pressure difference between the upstream and downstream sides of the unloading valve is calculated based on the detected hydraulic pressure.

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