Hydraulic system and control method of hydraulic system

Abstract

To provide an electrically driven hydraulic system which has a wide control range of a flow rate.SOLUTION: A hydraulic system 1 includes a variable capacity pump 3 which supplies hydraulic oil to hydraulic devices (21 to 26), an electric motor 5 which drives the variable capacity pump, a controller 6 which controls operation of the variable capacity pump and a sensor (pressure sensor 61) which outputs a measurement signal related to a supply flow rate of the hydraulic oil to be supplied to the hydraulic devices to the controller. The variable capacity pump has a mechanical compensator 31 which changes a pump capacity by receiving a pressure of the hydraulic oil in a supply path. The controller outputs a control signal which increases a rotational speed of the electric motor when the supply flow rate is lower than a necessary flow rate of the hydraulic devices, and outputs a control signal which decreases a rotational speed of the electric motor when the supply flow rate exceeds the necessary flow rate of the hydraulic devices.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a hydraulic system and a method for controlling a hydraulic system. [Background technology]

[0002] Patent Document 1 describes a hydraulic system used in the technical field of industrial machinery, such as injection molding machines. This conventional hydraulic system includes a variable displacement swash plate pump that supplies hydraulic oil to an actuator. The control device of the system controls both the rotation speed of a servo motor that drives the pump and changes the pump displacement by adjusting the angle of the swash plate of the swash plate pump.

[0003] The control device switches between first, second, and third modes. In the first mode, the control device fixes the pump displacement of the swash plate pump to a small displacement and changes the rotation speed of the servo motor in accordance with the command flow rate. In the second mode, the control device fixes the rotation speed of the servo motor to a low speed and changes the pump displacement of the swash plate pump in accordance with the command flow rate. In the third mode, the control device fixes the pump displacement of the swash plate pump to a maximum displacement and changes the rotation speed of the servo motor in accordance with the command flow rate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5143619 Summary of the Invention [Problem to be solved by the invention]

[0005] Meanwhile, an aircraft is equipped with various hydraulic actuators such as an aileron actuator, a flap actuator, a gear actuator, etc. A centralized hydraulic source in the hydraulic system of the aircraft supplies hydraulic oil to each of these hydraulic actuators.

[0006] In recent years, the electrification of aircraft has been progressing. Conventional hydraulic systems use engine power, but instead of engines, the use of a constant-speed electric motor and a variable displacement pump as the hydraulic source of the hydraulic system is being considered. The variable displacement pump changes the discharge flow rate according to the flow rate of hydraulic oil required to operate each hydraulic actuator. If the variable displacement pump is a pump having a mechanical compensator that automatically changes the pump displacement according to the discharge pressure, for example, the hydraulic system can be simplified.

[0007] However, a hydraulic system using a constant speed electric motor and a variable displacement pump has a problem in that once the pump displacement reaches its maximum displacement, the discharge flow rate of the variable displacement pump cannot be increased any further, meaning that the hydraulic system has a narrow range of flow rate control.

[0008] The technology disclosed herein realizes an electrically powered hydraulic system with a wide range of flow rate control. [Means for solving the problem]

[0009] The present disclosure relates to a hydraulic system. a variable displacement pump connected to at least one hydraulic device via a supply passage and supplying hydraulic oil to the hydraulic device through the supply passage; an electric motor coupled to the variable displacement pump and configured to drive the variable displacement pump; a controller electrically connected to the electric motor and configured to control operation of the variable displacement pump through output of a control signal to the electric motor; a sensor that outputs a measurement signal related to a supply flow rate of the hydraulic oil supplied to the hydraulic device to the controller; The variable displacement pump has a mechanical compensator that changes the pump displacement by receiving the pressure of the hydraulic oil in the supply passage, Based on the measurement signal of the sensor, the controller outputs a control signal to increase the rotational speed of the electric motor when the supply flow rate falls below the flow rate required by the hydraulic equipment, and outputs a control signal to decrease the rotational speed of the electric motor when the supply flow rate exceeds the flow rate required by the hydraulic equipment.

[0010] A hydraulic system is a system that supplies hydraulic fluid to hydraulic devices, such as hydraulic actuators and / or hydraulic motors.

[0011] The hydraulic system includes a variable displacement pump and an electric motor. The variable displacement pump may be, for example, a variable displacement swash plate pump. The variable displacement pump may be, for example, a variable displacement bent axis pump. The variable displacement pump may be, for example, a variable displacement vane pump.

[0012] The variable displacement pump has a mechanical compensator that changes the pump displacement according to the pressure of the hydraulic oil in the supply passage. The pump displacement of the variable displacement pump is automatically changed by the compensator, and the controller does not change the pump displacement of the variable displacement pump, so the hydraulic system can be simplified.

[0013] The electric motor may be, for example, a servo motor, and the controller may be a servo controller, which controls the operation of the variable displacement pump, more specifically, the rotational speed, through control of the electric motor.

[0014] The sensor outputs a measurement signal related to the supply flow rate of hydraulic oil supplied to the hydraulic equipment. The sensor may be, for example, a pressure sensor that is installed in a supply line and measures the pressure of the hydraulic oil in the supply line. The pressure of the hydraulic oil in the supply line is related to the supply flow rate of the hydraulic oil supplied to the hydraulic equipment. When the supply flow rate to the hydraulic equipment falls below the flow rate required by the hydraulic equipment, the pressure of the hydraulic oil in the supply line decreases. The controller can determine whether the supply flow rate to the hydraulic equipment is below the flow rate required by the hydraulic equipment based on the measurement signal of the sensor. However, the sensor is not limited to a pressure sensor.

[0015] The compensator varies the pump displacement in response to the pressure of the hydraulic fluid in the supply passage, and the variable displacement pump is capable of delivering hydraulic fluid to meet the flow requirements of the hydraulic equipment without the need for a controller to control the speed of the variable displacement pump.

[0016] When the pump capacity of the variable displacement pump is at its maximum capacity due to the compensator, and the supply flow rate to the hydraulic equipment is lower than the flow rate required by the hydraulic equipment, the variable displacement pump cannot satisfy the required flow rate as it is. Therefore, the controller outputs a control signal to increase the rotation speed of the electric motor. The rotation speed of the variable displacement pump increases, and the discharge flow rate of the variable displacement pump increases. As a result, the variable displacement pump can satisfy the required flow rate. Furthermore, when the supply flow rate exceeds the flow rate required by the hydraulic equipment, the controller outputs a control signal to decrease the rotation speed of the electric motor.

[0017] Therefore, the above-mentioned hydraulic system is an electrically operated hydraulic system having a simple configuration equipped with a variable displacement pump having a mechanical compensator, yet is capable of widening the flow rate control range.

[0018] the controller sets the rotation speed of the electric motor to a low first speed in a low flow rate region where the discharge flow rate of the variable displacement pump is low, and sets the rotation speed of the electric motor to a speed higher than the first speed and to a higher speed as the required flow rate increases in a high flow rate region where the discharge flow rate is higher than the low flow rate region; The pump displacement of the variable displacement pump may be increased by the compensator as the required flow rate increases in the low flow rate range, and may be maximum in the high flow rate range.

[0019] In the low flow rate range, the rotational speed of the electric motor is a low first speed, so that the hydraulic system can reduce power consumption. For example, if the first speed is adjusted to a rotational speed at which the electric motor and / or the variable displacement pump are highly efficient, the hydraulic system can achieve further power savings. The first speed may or may not be constant. In the low flow rate range, the compensator adjusts the pump displacement, so that the variable displacement pump can meet the required flow rate even if the rotational speeds of the electric motor and the variable displacement pump are constant.

[0020] In addition, since the rotation speeds of the electric motor and the variable displacement pump are low in the low flow rate range, the variable displacement pump is prevented from continuing to operate at high speed, which reduces wear on the variable displacement pump and extends the life of the variable displacement pump.

[0021] In the high flow rate range, the pump displacement of the variable displacement pump is maximum. In other words, the pump displacement is constant. Meanwhile, the controller increases the rotation speed of the electric motor as the required flow rate increases. Since the rotation speed of the variable displacement pump is higher than the first speed, the variable displacement pump can meet the required flow rate.

[0022] The controller may continuously increase the discharge flow rate of the variable displacement pump over an entire range from the low flow rate range to the high flow rate range.

[0023] This hydraulic system is capable of continuously changing the discharge flow rate of the variable displacement pump over a wide flow rate range by combining changing the pump displacement of the variable displacement pump with changing the rotational speed of the electric motor.

[0024] The hydraulic equipment may include flight control actuators and take-off and landing actuators in an aircraft.

[0025] Flight control actuators, which may include, for example, aileron actuators, elevator actuators, and / or rudder actuators, require a relatively low flow rate of hydraulic fluid to operate.

[0026] The takeoff and landing actuators include, for example, a gear actuator that raises and lowers the landing gear, a door actuator that opens and closes the door of the hangar, and / or a down lock release actuator that releases a down lock mechanism that fixes the landing gear in a lowered state. The takeoff and landing actuators may also include a flap actuator and / or a slat actuator. Since these takeoff and landing actuators have a large stroke, they require a relatively high flow rate of hydraulic oil for their operation.

[0027] The hydraulic system described above is suitable for electric hydraulic systems for aircraft, including flight control actuators and takeoff and landing actuators, because the discharge flow rate of the variable displacement pump can be changed over a wide range from low flow rate to high flow rate.

[0028] The controller, while the flight of the aircraft is in flight with the flight control actuator moving and the takeoff and landing actuator not moving, the rotational speed of the electric motor is set to a low first speed; When the aircraft is taking off or landing and the flight control actuator and the takeoff and landing actuator are moving, the rotational speed of the electric motor may be made higher than the first speed and increased as the required flow rate increases.

[0029] While the aircraft is flying, the flight control actuators operate and the takeoff and landing actuators do not operate. As described above, the flow rate required by the flight control actuators is low. Furthermore, the flight control actuators operate for long periods of time while the aircraft is flying. While the aircraft is flying, the controller sets the rotational speed of the electric motor to a low first speed. By changing the pump displacement, the variable displacement pump can satisfy the flow rate required by the flight control actuators during flight. Furthermore, since the rotational speed of the electric motor is low for a long period of time, this is advantageous in terms of saving power in the hydraulic system.

[0030] When an aircraft takes off or lands, the takeoff and landing actuators operate in addition to the flight control actuators. As described above, the required flow rate of the takeoff and landing actuators is high. In addition, the takeoff and landing actuators operate temporarily during takeoff and landing. When the aircraft takes off or lands, the controller increases the rotation speed of the electric motor as the required flow rate increases. By making the rotation speed of the variable displacement pump higher than the first speed, the variable displacement pump can meet the flow rate required for the operation of the flight control actuators and / or the takeoff and landing actuators. Although the rotation speed of the electric motor increases, the operation of the takeoff and landing actuators is temporary, so that the power consumption of the hydraulic system is suppressed. In addition, the high-speed operation of the variable displacement pump does not continue for a long time, which is advantageous for extending the life of the variable displacement pump.

[0031] Therefore, the aircraft hydraulic system can appropriately operate each of the flight control actuators and the takeoff and landing actuators while simultaneously reducing power consumption and extending the life of the system.

[0032] The present disclosure relates to a method for controlling a hydraulic system, comprising: a variable displacement pump connected to at least one hydraulic device via a supply passage and supplying hydraulic oil to the hydraulic device through the supply passage, the variable displacement pump having a mechanical compensator that changes a pump displacement by receiving a pressure of the hydraulic oil in the supply passage; an electric motor coupled to the variable displacement pump and configured to drive the variable displacement pump; a controller electrically connected to the electric motor and configured to control operation of the variable displacement pump through output of a control signal to the electric motor; The hydraulic device further includes a sensor that outputs a measurement signal related to the flow rate of the hydraulic oil supplied to the hydraulic device to the controller.

[0033] The method for controlling a hydraulic system includes: In a low flow rate region where the discharge flow rate of the variable displacement pump is low, the controller sets the rotational speed of the electric motor to a low first speed, and the variable displacement pump increases the pump displacement by the compensator as the required flow rate of the hydraulic device increases; In a high flow rate range where the discharge flow rate is higher than the low flow rate range, the variable displacement pump maximizes the pump displacement using the compensator, and the controller increases the rotational speed of the electric motor faster than the first speed and as the required flow rate increases based on the measurement signal of the sensor.

[0034] According to this control method, it is possible to widen the flow rate control range in an electrically operated hydraulic system of a simple configuration that includes a variable displacement pump having a mechanical compensator. Effect of the Invention

[0035] According to the above-described hydraulic system and control method for the hydraulic system, the flow rate control range can be widened by using an electrically operated hydraulic system having a simple configuration equipped with a variable displacement pump having a mechanical compensator. [Brief description of the drawings]

[0036] [Figure 1] FIG. 1 shows a hydraulic system. [Diagram 2] FIG. 2 illustrates the arrangement of hydraulic actuators on an aircraft. [Diagram 3] FIG. 3 shows changes in the discharge flow rate of the variable displacement pump, changes in the rotational speed of the variable displacement pump, and changes in the pump displacement of the variable displacement pump relative to the required flow rate of the hydraulic actuator. [Figure 4] Figure 4 shows the electric motor control procedure executed by the controller. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Hereinafter, an embodiment of a hydraulic system and a control method for the hydraulic system will be described with reference to the drawings. The hydraulic system and the control method for the hydraulic system described here are merely examples.

[0038] (Hydraulic system configuration) FIG. 1 shows a hydraulic system 1. The hydraulic system 1 is a system mounted on an aircraft 2 shown in FIG. 2. The hydraulic system 1 is a system for supplying hydraulic oil to each of a plurality of hydraulic devices. As shown in FIG. 2, the hydraulic devices to which the hydraulic system 1 disclosed herein supplies hydraulic oil include an aileron actuator 21, an elevator actuator 22, a rudder actuator 23, a flap actuator 24, a slat actuator 25, and a landing gear extension actuator 26. The landing gear extension actuator 26 includes, for example, a gear actuator, a door actuator, and / or a down lock release actuator. The gear actuator is an actuator that raises and lowers the landing gear strut. The door actuator is an actuator that opens and closes the door of a hangar that houses the landing gear. The down lock release actuator is an actuator that releases a down lock mechanism that fixes the landing gear strut in a lowered state.

[0039] 2, the aircraft 2 has a plurality of hydraulic actuators for each of the aileron actuator 21, elevator actuator 22, rudder actuator 23, flap actuator 24, slat actuator 25, and landing gear retraction / extension actuator 26. In the following description, each of the aileron actuator 21, elevator actuator 22, rudder actuator 23, flap actuator 24, slat actuator 25, and landing gear retraction / extension actuator 26 includes a plurality of these hydraulic actuators.

[0040] Furthermore, the hydraulic system 1 may supply hydraulic oil to some of these hydraulic actuators 21 to 26. The hydraulic system 1 may supply hydraulic oil to hydraulic devices other than these hydraulic actuators 21 to 26.

[0041] The hydraulic actuators 21-26 are, for example, telescopic actuators having a cylinder and a piston. The aileron actuator 21, the elevator actuator 22, and the rudder actuator 23 are flight control actuators 21-23 that operate while the aircraft 2 is flying and during takeoff and landing. While the strokes of the flight control actuators 21-23 are relatively short, they operate continuously for long periods of time while the aircraft 2 is flying. The flow rate of hydraulic oil required to operate the flight control actuators 21-23 is relatively low.

[0042] The flap actuator 24, the slat actuator 25, and the landing gear retraction / extension actuator 26 are actuators that operate when the aircraft 2 takes off and lands. The flap actuator 24 and the slat actuator 25 have a medium stroke, and operate temporarily when the aircraft 2 takes off and lands. The landing gear retraction / extension actuator 26 has a relatively long stroke, and operates temporarily when the aircraft 2 takes off and lands. Hereinafter, the flap actuator 24, the slat actuator 25, and the landing gear retraction / extension actuator 26 may be collectively referred to as the takeoff and landing actuators 24-26. The flow rate of hydraulic oil required for the operation of the takeoff and landing actuators 24-26 is relatively high.

[0043] The hydraulic system 1 includes a pump 3. The pump 3 is a variable displacement pump. The pump 3 may be, for example, a swash plate type pump as shown in FIG. 1. The pump 3 may also be a bent axis type pump. The pump 3 may also be a vane pump. A known variable displacement pump may be appropriately adopted as the pump 3 of the hydraulic system 1.

[0044] The discharge port of the pump 3 is connected to a supply path 41. The supply path 41 is connected to each of the hydraulic actuators 21-26. Each of the hydraulic actuators 21-26 is connected in parallel to the pump 3. The pump 3 supplies hydraulic oil via the supply path 41 individually to each of the aileron actuator 21, elevator actuator 22, rudder actuator 23, flap actuator 24, slat actuator 25, and landing gear extension / retraction actuator 26.

[0045] The suction port of the pump 3 is connected to a return path 42. The return path 42 connects the pump 3 to each of the hydraulic actuators 21 to 26. A tank 43 is connected to the return path 42. The tank 43 is a reservoir that stores hydraulic oil.

[0046] The hydraulic actuators 21 to 26, the pump 3, the supply path 41, the return path 42, and the tank 43 form a hydraulic circuit 10 of the hydraulic system 1 (see the arrows in FIG. 1).

[0047] The pump 3 has a mechanical compensator 31. A control path 44 is connected to the compensator 31. The control path 44 is connected to the supply path 41. The compensator 31 receives the pressure of the hydraulic oil discharged by the pump 3 through the control path 44 and changes the angle of the swash plate. The mechanical compensator 31 automatically changes the pump capacity of the pump 3 in accordance with the discharge pressure of the pump 3. More specifically, if the supply flow rate to the hydraulic actuators 21-26 falls below the required flow rate of the hydraulic actuators 21-26, thereby reducing the pressure of the hydraulic oil in the supply path 41, the compensator 31 changes the angle of the swash plate so that the pump capacity of the pump 3 increases. This increases the discharge flow rate of the pump 3, and the supply flow rate to the hydraulic actuators 21-26 is satisfied.

[0048] An electric motor 5 is connected to the pump 3. The electric motor 5 drives the pump 3. The electric motor 5 may be, for example, a servo motor.

[0049] A controller 6 is electrically connected to the electric motor 5. A pressure sensor 61 is also electrically connected to the controller 6. The pressure sensor 61 is provided in the supply path 41. The pressure sensor 61 outputs a measurement signal corresponding to the pressure of the hydraulic oil in the supply path 41 to the controller 6. As described above, the pressure of the hydraulic oil in the supply path 41 is related to the supply flow rate to the hydraulic actuators 21-26 and the required flow rate of the hydraulic actuators 21-26.

[0050] The controller 6 is further connected to a higher-level controller. The higher-level controller is, for example, a flight controller. The controller 6 receives a signal related to the required flow rate output by the higher-level controller. The required flow rate is the flow rate of hydraulic oil required for the flight control actuators 21-23 and / or the takeoff and landing actuators 24-26 to operate. The higher-level controller transmits the signal related to the required flow rate to the controller 6 so that the flight control actuators 21-23 and / or the takeoff and landing actuators 24-26 operate in response to the operation by the pilot of the aircraft 2 and / or in response to the flight conditions of the aircraft 2.

[0051] The controller 6 outputs a control signal to the electric motor 5 according to the measurement signal of the pressure sensor 61 and a signal related to the required flow rate from the upper controller. The rotation speed of the electric motor 5 changes according to the control signal from the controller 6. The change in the rotation speed of the electric motor 5 changes the rotation speed of the pump 3, and as a result, the discharge flow rate of the pump 3 changes.

[0052] The sensor of the hydraulic system 1 is not limited to the pressure sensor 61. Furthermore, the hydraulic system 1 may include a plurality of pumps 3 and electric motors 5 for redundancy.

[0053] (Hydraulic system control) The hydraulic system 1 is configured by a combination of a variable displacement pump 3 having a mechanical compensator 31 and an electric motor 5 that changes its rotation speed in response to a control signal from a controller 6 .

[0054] The controller 6 outputs a control signal to the electric motor 5 to increase the rotation speed of the electric motor 5 when the supply flow rate to the hydraulic actuators 21-26 falls below the required flow rate of the hydraulic actuators 21-26 based on the required flow rate from the host controller and the measurement signal of the pressure sensor 61. The controller 6 also outputs a control signal to the electric motor 5 to decrease the rotation speed of the electric motor 5 when the supply flow rate to the hydraulic actuators 21-26 exceeds the required flow rate of the hydraulic actuators 21-26.

[0055] More specifically, as shown in the upper diagram of Fig. 3, the controller 6 controls the electric motor 5 so that the discharge flow rate of the pump 3 changes continuously from a low flow rate to a high flow rate. As shown in the middle diagram of Fig. 3, in a low flow rate range where the discharge flow rate of the pump 3 is low, the controller 6 keeps the rotation speed of the electric motor 5 constant at a low first speed. The low speed here means a speed that is lower than the maximum speed of the electric motor 5. As will be described later, the first low speed may be set to a speed at which the electric motor 5 and / or the pump 3 are highly efficient.

[0056] The controller 6 also increases the rotation speed of the electric motor 5 faster than the first speed in a high flow rate range where the discharge flow rate of the pump 3 is higher than in a low flow rate range, as the required flow rate increases.

[0057] 3, in the low flow rate range where the rotation speed of the electric motor 5 is constant, the compensator 31 of the pump 3 increases the pump capacity of the pump 3 as the required flow rate increases. In the high flow rate range, the compensator 31 also keeps the pump capacity of the pump 3 constant at the maximum capacity.

[0058] As a result, the discharge flow rate of the pump 3 changes continuously from a low flow rate to a high flow rate, as shown in the upper diagram of FIG.

[0059] The low flow rate region described above corresponds to the time when the aircraft 2 is in flight. When the aircraft 2 is in flight, the flight control actuators, that is, the aileron actuator 21, the elevator actuator 22, and the rudder actuator 23, operate. On the other hand, the takeoff and landing actuators, that is, the flap actuator 24, the slat actuator 25, and the landing gear extension / retraction actuator 26, do not operate when the aircraft 2 is in flight.

[0060] The flight control actuators 21-23 have a relatively low required flow rate. By keeping the rotational speed of the electric motor 5 constant at a low first speed, and thereby changing the pump capacity of the pump 3 while the rotational speed of the pump 3 is kept constant at a low first speed, the pump 3 can meet the required flow rate of the flight control actuators 21-23 during flight.

[0061] Since the rotation speed of the electric motor 5 is maintained at a constant low speed for a long period of time while the aircraft 2 is in flight, this is advantageous for saving power in the hydraulic system 1. If the first speed of the electric motor 5 is set so that the electric motor 5 and / or the pump 3 operate with high efficiency, it is possible to further reduce the power consumption of the hydraulic system 1. As shown by the dashed arrow in the center diagram of FIG. 3, the discharge flow rate of the pump 3 when the pump capacity is maximum changes as the first speed of the electric motor 5 changes, and therefore the boundary between the low flow rate region and the high flow rate region changes. The boundary between the low flow rate region and the high flow rate region is the limit at which the pump 3 can meet the required flow rate when the rotation speed of the electric motor 5 is at the first speed and the pump 3 is at its maximum capacity.

[0062] The above-mentioned high flow rate region corresponds to the takeoff and landing of the aircraft 2. When the aircraft 2 takes off and lands, in addition to the flight control actuators 21-23, the takeoff and landing actuators 24-26 are operated.

[0063] The takeoff and landing actuators 24-26 require a relatively high flow rate. Therefore, even if the pump capacity is at its maximum capacity, if the rotation speed of the electric motor 5 is the first speed, which is a low speed, the pump 3 cannot meet the required flow rate. Therefore, the controller 6 makes the rotation speed of the electric motor 5 higher than the first speed as the required flow rate increases. The pump 3 can meet the flow rate required for the operation of the flight control actuators 21-23 and the takeoff and landing actuators 24-26. In this case, although the rotation speed of the electric motor 5 increases, the operation of the takeoff and landing actuators 24-26 is temporary, so that the power consumption of the hydraulic system 1 is suppressed.

[0064] Therefore, by continuously changing the discharge flow rate of the pump 3 over a wide range from low flow rate to high flow rate, the hydraulic system 1 allows the flight control actuators 21-23 and the takeoff and landing actuators 24-26 to operate properly while also achieving power savings in the hydraulic system 1.

[0065] Furthermore, in the hydraulic system 1, high-speed operation of the electric motor 5 and the pump 3 is temporary, and the pump 3 is prevented from operating continuously for long periods at maximum capacity and high speed. Since wear of the pump 3, which is a positive displacement pump, is suppressed, the life of the pump 3 is extended.

[0066] 4 shows a control procedure for the hydraulic system 1 executed by the controller 6. In step S41 after start, the controller 6 reads a signal from the host controller and a measurement signal from the pressure sensor 61. In the following step S42, the controller 6 determines whether the discharge flow rate of the pump 3 is in the low flow rate range. Note that instead of the determination in step S42, the controller 6 may determine whether the aircraft 2 is in flight or not (whether it is not taking off or landing or not).

[0067] If the determination in step S42 is Yes, that is, if the discharge flow rate is in the low flow rate range (or if the aircraft 2 is in flight), the controller 6 keeps the rotational speed of the electric motor 5 constant at the first speed in step S43.

[0068] If the determination in step S42 is No, that is, if the discharge flow rate is in the high flow rate range (or if the aircraft 2 is taking off or landing), in step S44, the controller 6 changes the rotation speed of the electric motor 5 according to the required flow rate.

[0069] In the above-described hydraulic system 1, the first speed is constant, but the first speed does not necessarily have to be constant.

[0070] Furthermore, the hydraulic system disclosed herein is not limited to the hydraulic system of an aircraft for controlling the above-mentioned flight control actuators 21-23 and the takeoff and landing actuators 24-26. The hydraulic system disclosed herein can also be applied to hydraulic systems for various industrial machines.

[0071] Moreover, the hydraulic equipment to which the hydraulic system supplies hydraulic oil includes hydraulic motors in addition to hydraulic actuators. [Explanation of symbols]

[0072] 1 Hydraulic system 21 Aileron actuator (hydraulic equipment) 22 Elevator actuators (hydraulic equipment) 23 Rudder actuator (hydraulic equipment) 24 Flap actuator (hydraulic equipment) 25 Slat actuator (hydraulic equipment) 26 Landing gear retraction actuator (hydraulic equipment) 3 Pump (variable displacement pump) 31 Compensator 41 Supply route 5 Electric motor 6 Controller 61 Sensor (pressure sensor)

Claims

1. A variable displacement pump connected to at least one hydraulic device via a supply line and supplying hydraulic fluid to the hydraulic device via the supply line, An electric motor connected to the variable displacement pump and driving the variable displacement pump, A controller electrically connected to the electric motor and controlling the operation of the variable displacement pump through the output of a control signal to the electric motor, The system includes a sensor that outputs a measurement signal related to the supply flow rate of the hydraulic fluid supplied to the hydraulic equipment to the controller, The variable displacement pump has a mechanical compensator that changes the pump capacity by receiving the pressure of the hydraulic fluid in the supply line. The controller outputs a control signal to increase the rotational speed of the electric motor when the supply flow rate falls below the required flow rate for the hydraulic equipment, and outputs a control signal to decrease the rotational speed of the electric motor when the supply flow rate exceeds the required flow rate for the hydraulic equipment. The controller maintains the rotational speed of the electric motor at a low first speed in the low flow rate range where the discharge flow rate of the variable displacement pump is low, and increases the rotational speed of the electric motor to a speed higher than the first speed and as the required flow rate increases in the high flow rate range where the discharge flow rate is higher than in the low flow rate range. A hydraulic system in which the pump capacity of the variable displacement pump increases in the low flow rate range as the required flow rate increases due to the compensator, and is at its maximum in the high flow rate range.

2. In the hydraulic system according to claim 1, The controller is a hydraulic system that continuously increases the discharge flow rate of the variable displacement pump across the entire range from the low flow rate range to the high flow rate range.

3. In the hydraulic system according to claim 1 or 2, The hydraulic equipment is a hydraulic system in an aircraft that includes a flight control actuator and a takeoff and landing actuator.

4. In the hydraulic system according to claim 3, The aforementioned controller, During the flight of the aircraft, when the flight control actuator is operating and the takeoff and landing actuator is not operating, the rotational speed of the electric motor is kept constant at a low first speed. A hydraulic system that, when the aircraft takes off or lands, the rotational speed of the electric motor is increased to a speed higher than the first speed and to an increased speed as the required flow rate increases.

5. A method for controlling a hydraulic system, The hydraulic system is, A variable displacement pump connected to at least one hydraulic device via a supply line and supplying hydraulic fluid to the hydraulic device via the supply line, the variable displacement pump having a mechanical compensator that changes the pump capacity by receiving the pressure of the hydraulic fluid in the supply line, An electric motor connected to the variable displacement pump and driving the variable displacement pump, A controller electrically connected to the electric motor and controlling the operation of the variable displacement pump through the output of a control signal to the electric motor, The system includes a sensor that outputs a measurement signal related to the supply flow rate of the hydraulic fluid supplied to the hydraulic equipment to the controller, In the low flow rate range where the discharge flow rate of the variable displacement pump is low, the controller keeps the rotational speed of the electric motor constant at a low first speed, and the variable displacement pump increases its capacity as the required flow rate of the hydraulic equipment increases, as controlled by the compensator. A control method for a hydraulic system, wherein in a high flow rate range where the discharge flow rate is higher than the low flow rate range, the variable displacement pump maximizes the pump capacity using the compensator, and the controller increases the rotational speed of the electric motor to a speed higher than the first speed and to an increased speed as the required flow rate increases, based on the measurement signal from the sensor.

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