Aircraft hydraulic system and method for controlling aircraft hydraulic system

Abstract

An aircraft hydraulic system 100 comprises common hydraulic pressure sources 11 and 12 and pressure reduction valves 21 and 22. The common hydraulic pressure sources 11 and 12 supply a shared hydraulic pressure to a low pressure operation unit 103 that is disposed in an aircraft 101 and that operates by a relatively low operating hydraulic pressure and to a high pressure operation unit 102 that is disposed separately from the low pressure operation unit 103 in the aircraft 101 and that operates by a relatively high operating hydraulic pressure. The pressure reduction valves 21 and 22 reduce the hydraulic pressure that is supplied to the low pressure operation unit 103.

Description

Aircraft hydraulic system and control method for aircraft hydraulic system

[0001] This invention relates to an aircraft hydraulic system and a control method for an aircraft hydraulic system.

[0002] Conventionally, aircraft hydraulic systems are known (see, for example, Patent Document 1).

[0003] Patent Document 1 describes an electro-hydraulic actuator system for raising and lowering the landing gear of an aircraft. The electro-hydraulic actuator system described in Patent Document 1 includes a plurality of hydraulic supply sources provided in parallel with each other on a hydraulic circuit. The plurality of hydraulic supply sources sequentially supply hydraulic oil to a plurality of hydraulic actuators that operate by sequentially receiving the supply of hydraulic oil when the landing gear of the aircraft is stowed and deployed.

[0004] Japanese Unexamined Patent Application Publication No. 2014 - 132189

[0005] Here, although not described in Patent Document 1, there may be cases where a plurality of hydraulic systems that operate with different operating hydraulic pressures are arranged in an aircraft. In that case, for each of the plurality of hydraulic systems with different operating hydraulic pressures, hydraulic supply sources are arranged like the electro-hydraulic actuator system described in Patent Document 1. Therefore, due to the arrangement of separate hydraulic supply sources with different supplied hydraulic pressures, the weight of the hydraulic system in the aircraft increases and the number of parts increases. Therefore, even when a plurality of hydraulic systems (operating parts) that operate with different operating hydraulic pressures are arranged in an aircraft, it is desired to suppress an increase in the weight of the hydraulic system in the aircraft and an increase in the number of parts.

[0006] This invention has been made to solve the above problems, and one object of this invention is to provide an aircraft hydraulic system and a control method for an aircraft hydraulic system that can suppress an increase in weight and an increase in the number of parts in the hydraulic system even when a plurality of operating parts that operate with different operating hydraulic pressures are arranged in an aircraft.

[0007] To achieve the above objective, an aircraft hydraulic system according to the first aspect of this invention comprises a low-pressure operating unit located in the aircraft and operated by a relatively low operating hydraulic pressure, a common hydraulic source that supplies hydraulic pressure to both a high-pressure operating unit located separately in the aircraft and operated by a relatively high operating hydraulic pressure, and a pressure reducing valve that reduces the hydraulic pressure supplied to the low-pressure operating unit.

[0008] The aircraft hydraulic system according to the first aspect of this invention, as described above, includes a common hydraulic source that supplies hydraulic pressure to both a low-pressure operating section, which operates with a relatively low operating hydraulic pressure and is located on the aircraft, and a high-pressure operating section, which operates with a relatively high operating hydraulic pressure and is located separately on the aircraft from the low-pressure operating section, and a pressure reducing valve that reduces the hydraulic pressure supplied to the low-pressure operating section. As a result, hydraulic pressure from the common hydraulic source can be supplied to the high-pressure operating section, and at the same time, hydraulic pressure from the common hydraulic source can also be supplied to the low-pressure operating section via the pressure reducing valve. Therefore, appropriate operating hydraulic pressure can be supplied to both the low-pressure operating section and the high-pressure operating section, which operate with different operating hydraulic pressures, without having to arrange separate hydraulic sources that supply different hydraulic pressures. Therefore, compared to the case where separate hydraulic sources that supply different hydraulic pressures are arranged, it is possible to suppress an increase in the weight of the hydraulic system in the aircraft, as well as an increase in the number of parts in the hydraulic system. As a result, even when multiple operating sections that operate with different operating hydraulic pressures are arranged on the aircraft, it is possible to suppress an increase in the weight and the number of parts in the hydraulic system.

[0009] In the aircraft hydraulic system according to the first aspect described above, preferably, the common hydraulic source includes a hydraulic pump that discharges hydraulic fluid to supply hydraulic pressure to both the low-pressure and high-pressure operating parts, and a motor that serves as the drive source for the hydraulic pump. With this configuration, hydraulic pressure can be supplied by operating the hydraulic pump with the drive of the motor, and the hydraulic pressure supplied from the common hydraulic source can be easily controlled by controlling the operation of the motor. Furthermore, unlike the case where hydraulic pressure is supplied by power from the main engine to obtain the thrust of the aircraft, hydraulic pressure can be supplied to the low-pressure and high-pressure operating parts by the drive of the motor even when the main engine is stopped, thus suppressing energy waste in the main engine. For this reason, when a low-pressure and high-pressure operating parts that operate with different hydraulic pressures are arranged in an aircraft, it is possible to suppress an increase in weight and the number of parts, as well as suppress a decrease in energy efficiency.

[0010] In the aircraft hydraulic system according to the first aspect described above, preferably, the system further includes a pressure gauge for detecting the output pressure of a common hydraulic source, and a control unit for controlling the operation of the common hydraulic source by hydraulic feedback control using the output pressure detected by the pressure gauge. With this configuration, the operation of the common hydraulic source can be controlled by hydraulic feedback control by the control unit so that the output pressure from the common hydraulic source is at an appropriate value. Therefore, the hydraulic pressure supplied to the low-pressure and high-pressure operating parts of an aircraft, which operate with different operating hydraulic pressures, can be more easily adjusted to an appropriate level.

[0011] In the aircraft hydraulic system according to the first aspect described above, preferably, the common hydraulic power source switches between outputting a relatively low operating hydraulic pressure for operating the low-pressure operating section and a relatively high operating hydraulic pressure for operating the high-pressure operating section, depending on the operating state of the low-pressure operating section and the high-pressure operating section. With this configuration, the operation of the common hydraulic power source can be switched to supply appropriate hydraulic pressure according to the operating state of the low-pressure operating section and the high-pressure operating section, thereby suppressing energy waste compared to operating the common hydraulic power source at a constant output at all times. Therefore, by switching the output from the common hydraulic power source according to the operating state of the low-pressure operating section and the high-pressure operating section, it is possible to suppress an increase in weight and the number of parts, as well as suppress a decrease in energy efficiency.

[0012] In this case, preferably, the common hydraulic power source outputs a relatively low operating hydraulic pressure to operate the low-pressure operating section during periods when the high-pressure operating section is not operating, and outputs a relatively high operating hydraulic pressure to operate the high-pressure operating section during periods when the high-pressure operating section is operating. With this configuration, there is no need to supply hydraulic pressure to the high-pressure operating section during periods when it is not operating, and by outputting a relatively low operating hydraulic pressure to operate the low-pressure operating section, energy waste in the common hydraulic power source can be suppressed. As a result, the decrease in energy efficiency in the common hydraulic power source can be further suppressed.

[0013] Furthermore, in this case, preferably, a high-pressure side check valve is provided to suppress the backflow of hydraulic fluid from the high-pressure operating section to the common hydraulic source. With this configuration, by suppressing the backflow of hydraulic fluid from the high-pressure operating section to the common hydraulic source with the high-pressure side check valve, the hydraulic fluid that flowed to the high-pressure operating section during the period when the high-pressure operating section was operating can be retained in the high-pressure operating section even during the period when the high-pressure operating section is not operating. Here, no hydraulic pressure is consumed in the high-pressure operating section during the period when the high-pressure operating section is not operating. Therefore, even during the period when the high-pressure operating section is not operating, a state in which a relatively high operating hydraulic pressure is applied to the high-pressure operating section can be maintained. Consequently, the responsiveness of the high-pressure operating section can be improved when the operation of the high-pressure operating section is started thereafter.

[0014] In the aircraft hydraulic system according to the first aspect described above, preferably, a common hydraulic source supplies hydraulic pressure to both the low-pressure operating section that operates the control surfaces in the aircraft and the high-pressure operating section that operates the landing gear in the aircraft. With this configuration, even when the operating hydraulic pressure differs between the operation of the control surfaces and the operation of the landing gear in the aircraft, the increase in weight and the increase in the number of parts can be effectively suppressed by arranging a common hydraulic source and a pressure reducing valve.

[0015] In the aircraft hydraulic system according to the first aspect described above, preferably, the common hydraulic source stops supplying hydraulic fluid during periods when the operation of both the low-pressure and high-pressure operating parts is stopped. With this configuration, the common hydraulic source can be stopped during periods when it is not necessary to supply hydraulic fluid to either the low-pressure or high-pressure operating parts, thereby further suppressing the decrease in energy efficiency of the common hydraulic source.

[0016] In the aircraft hydraulic system according to the first aspect described above, preferably, the common hydraulic source includes a first common hydraulic source and a second common hydraulic source that supply hydraulic pressure to the low-pressure operating section and the high-pressure operating section independently of each other. With this configuration, hydraulic pressure can be supplied to both the low-pressure operating section and the high-pressure operating section by each of the redundant first common hydraulic source and the second common hydraulic source, thereby improving the stability of the operation of each of the low-pressure operating section and the high-pressure operating section. Furthermore, if separate hydraulic sources are provided to supply hydraulic pressure at different pressures to each of the low-pressure operating section and the high-pressure operating section, which operate with different operating hydraulic pressures, it is necessary to individually make the hydraulic sources with different output pressures redundant in order to make the hydraulic sources redundant. In contrast, in the present invention, since the first common hydraulic source and the second common hydraulic source that supply hydraulic pressure to both the low-pressure operating section and the high-pressure operating section are arranged in a redundant manner, the increase in weight and the increase in the number of parts can be suppressed more effectively compared to the case in which hydraulic sources with different output pressures are individually made redundant.

[0017] In an aircraft hydraulic system where the common hydraulic source includes a first common hydraulic source and a second common hydraulic source, preferably, the pressure reducing valve includes a first pressure reducing valve that reduces the hydraulic pressure supplied to the low-pressure operating section from the first common hydraulic source, and a second pressure reducing valve that is arranged separately from the first pressure reducing valve and reduces the hydraulic pressure supplied to the low-pressure operating section from the second common hydraulic source. With this configuration, the configuration for reducing the hydraulic pressure supplied to the low-pressure operating section can be made redundant by arranging the first and second pressure reducing valves separately, so that the stability of the operation of the aircraft hydraulic system can be further improved compared to the case where the hydraulic pressure from each of the first and second common hydraulic sources is reduced by a common pressure reducing valve.

[0018] In an aircraft hydraulic system where the common hydraulic source includes a first common hydraulic source and a second common hydraulic source, preferably, the system further includes a first check valve that suppresses backflow of hydraulic fluid to the first common hydraulic source, and a second check valve that is disposed separately from the first check valve and suppresses backflow of hydraulic fluid to the second common hydraulic source. With this configuration, by arranging the first check valve and the second check valve separately, the first check valve suppresses backflow to the first common hydraulic source, and the second check valve suppresses backflow to the second common hydraulic source. Therefore, for example, even if either the first common hydraulic source or the second common hydraulic source fails, it is possible to prevent hydraulic fluid from flowing from a normal common hydraulic source to the failed common hydraulic source.

[0019] In an aircraft hydraulic system where the common hydraulic source includes a first common hydraulic source and a second common hydraulic source, preferably, the common hydraulic source supplies hydraulic pressure to both the low-pressure and high-pressure operating parts from both the first and second common hydraulic sources. With this configuration, by operating the first and second common hydraulic sources simultaneously, hydraulic pressure is supplied to both the low-pressure and high-pressure operating parts from both sources, thereby reducing the load on each of the first and second common hydraulic sources. As a result, the lifespan of each of the first and second common hydraulic sources can be extended, and the workload required for maintenance such as replacement of the first and second common hydraulic sources can be reduced. Furthermore, by supplying hydraulic pressure to both the low-pressure and high-pressure operating parts from both the first and second common hydraulic sources, if a malfunction occurs in either the first or second common hydraulic source, the supply of hydraulic pressure can be continued by the other. Therefore, if an abnormality occurs in either the first common hydraulic power source or the second common hydraulic power source, it is possible to prevent interruption of the hydraulic power supply to the low-pressure operating section and the high-pressure operating section.

[0020] In an aircraft hydraulic system where the common hydraulic source includes a first common hydraulic source and a second common hydraulic source, preferably, when the first common hydraulic source is functioning normally, the common hydraulic source supplies hydraulic pressure to both the low-pressure and high-pressure operating parts from the first common hydraulic source while stopping the supply of hydraulic pressure from the second common hydraulic source, and when the first common hydraulic source is malfunctioning, the supply of hydraulic pressure from the first common hydraulic source is stopped while the second common hydraulic source supplies hydraulic pressure to both the low-pressure and high-pressure operating parts. With this configuration, the operating time of each of the first and second common hydraulic sources can be shortened compared to when both are operating continuously. Therefore, when performing maintenance on each of the first and second common hydraulic sources according to their operating time, the opportunities for maintenance can be reduced. As a result, the increase in the workload required for maintenance can be suppressed. Furthermore, if the first common hydraulic power source malfunctions, the second common hydraulic power source can be positioned as a backup hydraulic power source for the first common hydraulic power source by supplying hydraulic pressure to both the low-pressure and high-pressure operating parts from the second common hydraulic power source. Therefore, for example, if the first common hydraulic power source malfunctions due to failure, the second common hydraulic power source can supply hydraulic pressure without interruption.

[0021] In the aircraft hydraulic system according to the first aspect described above, preferably, the pressure reducing valve is configured to reduce the supplied hydraulic pressure by allowing hydraulic fluid to flow from the upstream to the downstream side when the downstream pressure is less than a predetermined pressure, and by blocking the flow of hydraulic fluid from the upstream to the downstream side when the downstream pressure exceeds a predetermined pressure. However, if the pressure reducing valve is configured to reduce the hydraulic pressure by distributing the hydraulic fluid to another flow path, the energy efficiency of the common hydraulic source decreases by the amount of hydraulic pressure that is distributed. Taking this into consideration, in the present invention, the pressure reducing valve is configured to reduce the supplied hydraulic pressure by allowing hydraulic fluid to flow from the upstream to the downstream side when the downstream pressure is less than a predetermined pressure, and by blocking the flow of hydraulic fluid from the upstream to the downstream side when the downstream pressure exceeds a predetermined pressure, thereby suppressing the decrease in energy efficiency of the common hydraulic source.

[0022] In the aircraft hydraulic system according to the first aspect described above, preferably, a low-pressure actuator that operates with a relatively low operating hydraulic pressure in the low-pressure operating section and a high-pressure actuator that operates with a relatively high operating hydraulic pressure in the high-pressure operating section are further included. With this configuration, since the aircraft hydraulic system has both a low-pressure actuator and a high-pressure actuator to which hydraulic pressure is supplied in common, the operation of the common hydraulic source can be set to supply a more appropriate operating hydraulic pressure compared to when hydraulic pressure is supplied to an external actuator.

[0023] In the aircraft hydraulic system according to the first aspect described above, preferably, a check valve is provided to suppress the backflow of hydraulic fluid from the low-pressure operating section and the high-pressure operating section to the common hydraulic source. With this configuration, the check valve can suppress the backflow of hydraulic fluid from the low-pressure operating section and the high-pressure operating section to the common hydraulic source. Furthermore, by suppressing the backflow of hydraulic fluid to the common hydraulic source with the check valve, each of the low-pressure operating section and the high-pressure operating section can maintain its operating hydraulic pressure.

[0024] In an aircraft hydraulic system equipped with the above-described check valves, preferably, multiple check valves are arranged in parallel with respect to a common hydraulic source. This configuration allows for redundancy of check valves that suppress backflow of hydraulic fluid. Therefore, for example, even if one check valve is closed due to sticking and hydraulic pressure is not supplied to the low-pressure and high-pressure operating parts, hydraulic pressure can still be supplied to the low-pressure and high-pressure operating parts via another check valve. Thus, the operational stability of the aircraft hydraulic system can be further improved.

[0025] In an aircraft hydraulic system equipped with the above-described check valve, preferably, the check valve includes a high-pressure side check valve that suppresses the flow of hydraulic fluid from the high-pressure operating section to the common hydraulic source, and a low-pressure side check valve that suppresses the flow of hydraulic fluid from the low-pressure operating section to the common hydraulic source. With this configuration, the high-pressure side check valve suppresses backflow from the high-pressure operating section to the common hydraulic source, and the low-pressure side check valve suppresses backflow from the low-pressure operating section to the common hydraulic source. Here, for example, even if the high-pressure side check valve is closed due to sticking and hydraulic pressure cannot be supplied from the common hydraulic source to the high-pressure operating section, hydraulic pressure can still be supplied from the common hydraulic source to the low-pressure operating section via the low-pressure side check valve. In other words, it is possible to prevent a situation in which hydraulic pressure from the common hydraulic source is not supplied to either the high-pressure operating section or the low-pressure operating section.

[0026] In the aircraft hydraulic system according to the first aspect described above, preferably, a shut-off valve is further provided to block the supply of hydraulic pressure to the high-pressure operating part. With this configuration, it is possible to prevent hydraulic pressure from being supplied to the high-pressure operating part when the high-pressure operating part is stopped. Therefore, it is possible to effectively suppress the supply of hydraulic pressure to the high-pressure operating part when it is not operating, and thus effectively suppress malfunctions of the high-pressure operating part.

[0027] In the aircraft hydraulic system according to the first aspect described above, preferably, a bypass oil passage is further provided to supply hydraulic pressure from a common hydraulic source to a low-pressure operating section while bypassing the pressure reducing valve. With this configuration, the supplied hydraulic pressure is supplied to the low-pressure operating section via the bypass passage, bypassing the pressure reducing valve. The bypass passage forms a flow path that avoids the pressure reducing valve and supplies hydraulic pressure to the low-pressure operating section. Therefore, pressure loss at the pressure reducing valve can be reduced.

[0028] Furthermore, in order to achieve the above objective, a control method for an aircraft hydraulic system according to the second aspect of this invention includes the steps of: acquiring the operating state of a low-pressure operating unit that operates with a relatively low operating hydraulic pressure and a high-pressure operating unit that operates with a relatively high operating hydraulic pressure and is separately arranged in the aircraft from the low-pressure operating unit; and controlling the operation of a common hydraulic source that supplies hydraulic pressure to both the low-pressure operating unit and the high-pressure operating unit. The step of controlling the operation of the common hydraulic source involves switching between two control methods: one that supplies a relatively high operating hydraulic pressure to the high-pressure operating unit by operating the common hydraulic source to output a relatively high operating hydraulic pressure for operating the high-pressure operating unit, while simultaneously supplying a relatively low operating hydraulic pressure to the low-pressure operating unit via a pressure reducing valve that reduces the supplied hydraulic pressure, and another that supplies a relatively low operating hydraulic pressure to the low-pressure operating unit by operating the common hydraulic source to output a relatively low operating hydraulic pressure for operating the low-pressure operating unit, based on the acquired operating state.

[0029] The control method for an aircraft hydraulic system according to the second aspect of this invention includes the step of controlling the operation of a common hydraulic source that supplies hydraulic pressure to both the low-pressure operating section and the high-pressure operating section, as described above. The control method for an aircraft hydraulic system according to the second aspect operates the common hydraulic source to output a relatively high operating hydraulic pressure for operating the high-pressure operating section, thereby supplying a relatively high operating hydraulic pressure to the high-pressure operating section while simultaneously supplying a relatively low operating hydraulic pressure to the low-pressure operating section via a pressure reducing valve that reduces the supplied hydraulic pressure. As a result, hydraulic pressure from the common hydraulic source can be supplied to the high-pressure operating section and the low-pressure operating section via the pressure reducing valve at the same time. Therefore, appropriate operating hydraulic pressure can be supplied to both the low-pressure operating section and the high-pressure operating section, which operate with different operating hydraulic pressures, without having to arrange separate hydraulic sources that supply different hydraulic pressures. Therefore, compared to the case where separate hydraulic sources that supply different hydraulic pressures are arranged, it is possible to suppress an increase in the weight of the hydraulic system in the aircraft and to suppress an increase in the number of parts in the hydraulic system. As a result, it is possible to provide a control method for an aircraft hydraulic system that can suppress increases in weight and the number of parts in the hydraulic system, even when multiple moving parts operating under different hydraulic pressures are arranged in an aircraft.

[0030] Furthermore, in the control method for the aircraft hydraulic system according to the second phase, based on the acquired operating state, the common hydraulic source is operated to output a relatively high operating hydraulic pressure for operating the high-pressure operating part, thereby supplying a relatively high operating hydraulic pressure to the high-pressure operating part while simultaneously supplying a relatively low operating hydraulic pressure to the low-pressure operating part via a pressure reducing valve that reduces the supplied hydraulic pressure. This control method is then switched to operate the common hydraulic source to output a relatively low operating hydraulic pressure for operating the low-pressure operating part, thereby supplying a relatively low operating hydraulic pressure to the low-pressure operating part. As a result, the operation of the common hydraulic source can be switched to supply appropriate hydraulic pressure according to the operating state of the low-pressure and high-pressure operating parts, thus reducing energy waste compared to operating the common hydraulic source at a constant output. Therefore, by switching the output from the common hydraulic source according to the operating state of the low-pressure and high-pressure operating parts, it is possible to provide an aircraft hydraulic system control method that can suppress increases in weight and the number of parts, as well as suppress decreases in energy efficiency.

[0031] According to the present invention, as described above, even when multiple operating parts that operate by different hydraulic pressures are arranged in an aircraft, it is possible to suppress the increase in weight and the number of parts in the hydraulic system.

[0032] This is a schematic diagram illustrating the configuration of an aircraft equipped with a hydraulic system according to the first embodiment of the present invention. This is a block diagram illustrating the configuration of an aircraft equipped with a hydraulic system according to the first embodiment. This is a schematic diagram illustrating the operation of a pressure reducing valve. This is a diagram illustrating the control of the operation of a hydraulic source according to the operating state. This is a flowchart illustrating the control method of a hydraulic system according to the first embodiment of the present invention. This is a block diagram illustrating the configuration of an aircraft equipped with a hydraulic system according to the second embodiment of the present invention. This is a block diagram illustrating the configuration of a hydraulic system according to the first modification of the first and second embodiments of the present invention. This is a block diagram illustrating the configuration of a hydraulic system according to the second modification of the first and second embodiments of the present invention. This is a block diagram illustrating the configuration of a hydraulic system according to the third modification of the first and second embodiments of the present invention. This is a block diagram illustrating the configuration of a hydraulic system according to the fourth modification of the first and second embodiments of the present invention. This is a block diagram illustrating the configuration of a hydraulic system according to the fifth modification of the first and second embodiments of the present invention. This is a block diagram illustrating the configuration of a hydraulic system according to the sixth modification of the first and second embodiments of the present invention. This is a block diagram illustrating the configuration of a hydraulic system according to the seventh modification of the first and second embodiments of the present invention. This is a block diagram illustrating the configuration of a hydraulic system according to the eighth modification of the first and second embodiments of the present invention. This is a block diagram illustrating the configuration of a hydraulic system according to the ninth modification of the first and second embodiments of the present invention. This is a block diagram illustrating the configuration of a hydraulic system according to the tenth modification of the first and second embodiments of the present invention.

[0033] Embodiments of the present invention will be described below with reference to the drawings.

[0034] [First Embodiment] The configuration of the hydraulic system 100 according to the first embodiment of the present invention will be described with reference to Figures 1 to 4. Note that the hydraulic system 100 is an example of an "aircraft hydraulic system" as defined in the claims.

[0035] As shown in Figure 1, the hydraulic system 100 is mounted on the aircraft 101. The hydraulic system 100 includes a landing gear system 102 and a flight control system 103 (hereinafter referred to as FCS 103). The hydraulic system 100 supplies hydraulic pressure to the landing gear system 102 and the FCS 103, which are separately located on the aircraft 101. The landing gear system 102 and the FCS 103 switch their operation based on input operations received by an operating unit 104 located in the cockpit of the aircraft 101. Here, in the aircraft 101, the landing gear system 102 and the FCS 103 are designed to operate with different operating hydraulic pressures. For example, the landing gear system 102 operates with sufficient performance with a relatively high operating hydraulic pressure of 5000 psi or less. The FCS 103 operates with sufficient performance with a relatively low operating hydraulic pressure of 3000 psi or less. The leg lifting system 102 and FCS 103 are examples of the "high-pressure operating unit" and "low-pressure operating unit" as defined in the claims, respectively.

[0036] The landing gear system 102 operates the landing gear 102a that supports the aircraft 101 on the ground. The landing gear 102a comprises wheels and struts to which the wheels are attached, and is configured as the main landing gear and nose gear of the aircraft 101. The landing gear system 102 includes hydraulically operated actuators 102b and 102c. Actuator 102b includes a door actuator that opens and closes the door of the bay that houses the landing gear 102a. Actuator 102c includes a gear actuator that raises and lowers the landing gear 102a. The landing gear system 102 retracts and deploys the landing gear 102a inside and outside the aircraft 101 by operating actuators 102b and 102c. For example, in the landing gear system 102, actuator 102b, which is a door actuator that opens and closes the door, is operated by a relatively high operating hydraulic pressure of 5000 psi or less. The actuator 102c, which is a gear actuator for raising and lowering the leg portion 102a, operates when a relatively high operating hydraulic pressure of 5000 psi or less is supplied in the leg lifting system 102. Actuators 102b and 102c are examples of "high-pressure actuators" as defined in the claims.

[0037] The FCS 103 operates the control surfaces 103a for controlling the flight of the aircraft 101. The control surfaces 103a operate to control the attitude of the aircraft 101 during flight or to increase or decrease lift. The control surfaces 103a include, for example, ailerons, elevators, rudder, and flaps. The FCS 103 is equipped with a hydraulically operated actuator 103b. The actuator 103b changes the orientation of the control surfaces 103a. The actuator 103b is operated by a relatively low operating hydraulic pressure of 3000 psi or less supplied to the FCS 103. The actuators 102b and 102c of the landing gear system 102 and the actuator 103b of the FCS 103 are, for example, hydraulic cylinders operated by the supplied hydraulic pressure. Note that actuator 103b is an example of a "low-pressure actuator" in the claims.

[0038] In each of the leg lifting and lowering systems 102 and FCS 103, a directional control valve (not shown) is provided to control the operation of actuators 102b and 102c and actuator 103b. In each of actuators 102b, 102c, and 103b, the directional control valve switches between connecting either the input or output oil passage to the hydraulic chambers on one side and the other side of the hydraulic cylinder's operating direction, or leaving neither oil passage connected, thereby controlling the extension, retraction, and stopping of the hydraulic cylinder. The drive of the directional control valve is controlled by a control unit located in each of the leg lifting and lowering systems 102 and FCS 103.

[0039] (Configuration of the hydraulic system) As shown in Figure 2, the hydraulic system 100 of the first embodiment includes a hydraulic power source 11, a hydraulic power source 12, a pressure reducing valve 21, and a pressure reducing valve 22. Note that hydraulic power source 11 is an example of the "common hydraulic power source" and "first common hydraulic power source" in the claims. Hydraulic power source 12 is an example of the "common hydraulic power source" and "second common hydraulic power source" in the claims. Pressure reducing valve 21 is an example of the "pressure reducing valve" and "first pressure reducing valve" in the claims. Pressure reducing valve 22 is an example of the "pressure reducing valve" and "second pressure reducing valve" in the claims.

[0040] Hydraulic sources 11 and 12 supply hydraulic pressure to the leg lifting system 102 and the FCS 103, respectively. In the first embodiment, hydraulic sources 11 and 12 supply hydraulic pressure to the leg lifting system 102 and the FCS 103 independently of each other. That is, in the hydraulic system 100, hydraulic sources 11 and 12 are redundant. Hydraulic sources 11 and 12 have a common structure. Hydraulic source 11 includes a hydraulic pump 11a and a motor 11b. Hydraulic source 12 includes a hydraulic pump 12a and a motor 12b. Hydraulic pumps 11a and 12a discharge hydraulic fluid to supply hydraulic pressure to the leg lifting system 102 and the FCS 103, respectively. Motors 11b and 12b are the driving sources for hydraulic pumps 11a and 12a, respectively.

[0041] Each of the hydraulic pumps 11a and 12a is a gear pump that discharges hydraulic fluid by rotating gears driven by, for example, motors 11b and 12b. Motors 11b and 12b are servo motors whose rotational speed is controlled by, for example, a control unit 60, which will be described later. That is, the hydraulic pressure output from each of the hydraulic sources 11 and 12 is controlled by the control unit 60. Each of the motors 11b and 12b has an encoder that detects rotation. Motors 11b and 12b are rotated by electricity from a generator provided in the auxiliary power unit of the aircraft 101, for example. In other words, the hydraulic system 100 of the first embodiment supplies hydraulic pressure by driving the electric pumps, hydraulic pumps 11a and 12a, with the electric motors 11b and 12b. In other words, the hydraulic system 100 constitutes an electro-hydraulic actuator system (EHA system).

[0042] The hydraulic system 100 includes oil passages 41, 42, 43, and 44 through which hydraulic fluid from hydraulic power sources 11 and 12 flows. Hydraulic power source 11 supplies hydraulic fluid by branching into oil passage 41 for supplying hydraulic fluid to the leg lifting system 102 and oil passage 43 for supplying hydraulic fluid to the FCS 103. Hydraulic power source 12 supplies hydraulic fluid by branching into oil passage 42 for supplying hydraulic fluid to the leg lifting system 102 and oil passage 44 for supplying hydraulic fluid to the FCS 103. In other words, the hydraulic fluid output from hydraulic power source 11 is branched and flows through oil passage 41 toward the leg lifting system 102 and oil passage 43 toward the FCS 103. The hydraulic fluid output from hydraulic power source 12 is branched and flows through oil passage 42 toward the leg lifting system 102 and oil passage 44 toward the FCS 103. The oil passage 41 from the hydraulic power source 11 and the oil passage 42 from the hydraulic power source 12 merge before the leg lifting system 102. Similarly, the oil passage 43 from the hydraulic power source 11 and the oil passage 44 from the hydraulic power source 12 merge before the FCS 103.

[0043] In the first embodiment, the hydraulic power sources 11 and 12 are configured to receive hydraulic fluid discharged from the actuator 103b of the FCS 103, the actuator 102b of the leg lifting system 102, and the actuator 102c of the leg lifting system 102 via a return path 90. Specifically, the hydraulic fluid supplied from the hydraulic power sources 11 and 12 to the FCS 103 and the leg lifting system 102 is returned to the reservoir 91 via the return path 90. The reservoir 91 is a tank for storing hydraulic fluid. The reservoir 91 is connected to the respective suction ports of the hydraulic pump 11a of the hydraulic power source 11 and the hydraulic pump 12a of the hydraulic power source 12. The hydraulic power sources 11 and 12 supply hydraulic pressure to the FCS 103 and the leg lifting system 102 by outputting the hydraulic fluid supplied from the reservoir 91 toward the FCS 103 and the leg lifting system 102. Therefore, in the hydraulic system 100 in the first embodiment, a hydraulic circuit, which is a circulating circuit, is formed. In the return path 90, the oil passage from the FCS 103 and the oil passage from the leg lifting system 102 merge and are then connected to the reservoir 91. Upstream of the merging point in the return path 90, a check valve 92 is located on the leg lifting system 102 side and a check valve 93 is located on the FCS 103 side. Check valves 92 and 93 suppress the backflow of hydraulic fluid to the leg lifting system 102 and FCS 103, respectively, in the return path 90. Therefore, it is possible to prevent actuators 102b, 102c, and 103b from moving backward due to the backflow of hydraulic fluid through the return path 90.

[0044] The pressure reducing valves 21 and 22 reduce the hydraulic pressure supplied to the FCS 103. The pressure reducing valves 21 and 22 are arranged separately from each other. The pressure reducing valve 21 reduces the hydraulic pressure supplied from the hydraulic pressure source 11 to the FCS 103. The pressure reducing valve 22 reduces the hydraulic pressure supplied from the hydraulic pressure source 12 to the FCS 103. In the hydraulic system 100, the pressure reducing valve 21 is arranged in the oil passage 43 from the hydraulic pressure source 11 toward the FCS 103. The pressure reducing valve 22 is arranged in the oil passage 44 from the hydraulic pressure source 12 toward the FCS 103. The pressure reducing valves 21 and 22 reduce the hydraulic pressure supplied from the hydraulic pressure sources 11 and 12 to a hydraulic pressure of 3000 psi or less, which is a relatively low operating hydraulic pressure for operating the FCS 103. In the first embodiment, the pressure reducing valves 21 and 22 allow the hydraulic oil to flow from the upstream side to the downstream side when the downstream pressure is less than a predetermined pressure, and block the flow of the hydraulic oil from the upstream side to the downstream side when the downstream pressure exceeds the predetermined pressure, so as to reduce the supplied hydraulic pressure. Note that the pressure reducing valve 20 may be configured to reduce the supplied hydraulic pressure by blocking the flow of the hydraulic oil from the upstream side to the downstream side when the downstream pressure is greater than or equal to a predetermined pressure, for example, when the downstream pressure reaches the predetermined pressure. For example, due to the hysteresis of the valve, the pressure when the pressure reducing valve 20 closes may be different from the pressure when the valve opens. Considering such a case, the criteria for allowing and blocking the flow of the hydraulic oil by the pressure reducing valve 20 may be set as when the pressure exceeds or is less than a predetermined pressure, or as when the pressure is greater than or equal to or less than a predetermined pressure.

[0045] Specifically, as shown in Figure 3, the pressure reducing valve 21 has a spool 21a and a spring 21b. In the pressure reducing valve 21, the flow of hydraulic fluid from upstream to downstream and the blocking of flow are switched by the hydraulic pressure on the downstream side, which moves the valve body, the spool 21a, against the elastic force of the spring 21b. For example, the pressure reducing valve 21 is configured to reduce the pressure supplied up to a predetermined pressure of 3000 psi. As shown in the left figure of Figure 3, when the upstream side is 5000 psi and the downstream side is 1000 psi (less than 3000 psi), the elastic force of the spring 21b moves the spool 21a to a position where hydraulic fluid flows. On the other hand, as shown in the right figure of Figure 3, when the hydraulic pressure on the downstream side becomes 3000 psi, the hydraulic pressure on the downstream side moves the spool 21a to a position where the hydraulic fluid is blocked, against the elastic force of the spring 21b. Furthermore, if the hydraulic pressure downstream falls below 3000 psi again while the hydraulic fluid is shut off, the spool 21a moves back to a position where the hydraulic fluid is circulated again due to the elastic force of the spring 21b. In this way, the pressure reducing valve 21 is configured to reduce the hydraulic pressure from upstream by shutting off the flow of hydraulic fluid so that the hydraulic pressure downstream does not exceed a predetermined pressure of 3000 psi. Note that the pressure reducing valves 21 and 22 have common components. In Figure 3, only the pressure reducing valve 21 is shown, and the explanation of the pressure reducing valve 22 is omitted because its components are the same.

[0046] Furthermore, as shown in Figure 2, the hydraulic system 100, in addition to the above, is equipped with check valves to suppress the backflow of hydraulic fluid from the leg lifting system 102 and FCS 103 to the common hydraulic power sources, hydraulic power sources 11 and 12. In this embodiment, the hydraulic system 100 is equipped with check valves 31, 32, 33, and 34, which are arranged separately from each other. Check valve 31 is located in the oil passage 41 leading from hydraulic power source 11 to leg lifting system 102. Check valve 32 is located in the oil passage 42 leading from hydraulic power source 12 to leg lifting system 102. Check valve 33 is located downstream of the pressure reducing valve 21 in the oil passage 43 leading from hydraulic power source 11 to FCS 103. Check valve 34 is located downstream of the pressure reducing valve 22 in the oil passage 44 leading from hydraulic power source 12 to FCS 103. Note that check valve 31 is an example of the "first check valve" and "high-pressure side check valve" in the claims. Check valve 32 is an example of the "second check valve" and "high-pressure side check valve" in the claims. Check valve 33 is an example of the "first check valve" and "low-pressure side check valve" in the claims. Check valve 34 is an example of the "second check valve" and "low-pressure side check valve" in the claims.

[0047] The check valves 31, 32, 33, and 34 suppress the backflow of the hydraulic oil from the actuator 103b of the FCS 103, the actuator 102b of the leg lifting and lowering system 102, and the actuator 102c to the hydraulic oil sources 11 and 12. The check valves 31 and 33 suppress the backflow of the hydraulic oil to the hydraulic oil source 11. The check valves 32 and 34 suppress the backflow of the hydraulic oil to the hydraulic oil source 12. The check valves 31 and 33 are connected in parallel to the hydraulic oil source 11. The check valves 32 and 34 are connected in parallel to the hydraulic oil source 12. The check valves 31, 32, 33, and 34 allow the hydraulic oil to flow from the upstream side where the hydraulic oil sources 11 and 12 are arranged to the downstream side where the leg lifting and lowering system 102 and the FCS 103 are arranged, and block the flow of the hydraulic oil from the downstream side, which is the opposite direction, to the upstream side. Specifically, the check valves 31, 32, 33, and 34 allow the hydraulic oil to flow from upstream to downstream when the hydraulic pressure on the upstream side is higher than the hydraulic pressure on the downstream side, and block the flow of the hydraulic oil that attempts to flow from downstream to upstream when the hydraulic pressure on the downstream side is higher than the hydraulic pressure on the upstream side. That is, the check valves 31 and 32 each block the flow of the hydraulic oil that attempts to flow from the leg lifting and lowering system 102 side to the hydraulic oil source 11 side and the hydraulic oil source 12 side. The check valves 33 and 34 each block the flow of the hydraulic oil that attempts to flow from the FCS 103 side to the hydraulic oil source 11 side and the hydraulic oil source 12 side.

[0048] The hydraulic system 100 also includes a pressure gauge 51 and a pressure gauge 52, and a control unit 60. The pressure gauge 51 detects the output pressure of the hydraulic oil source 11. The pressure gauge 52 detects the output pressure of the hydraulic oil source 12. Each of the pressure gauge 51 and the pressure gauge 52 outputs a detection result indicating the detected output pressure to the control unit 60. The pressure gauge 51 is connected to a portion before being branched into the oil passages 41 and 43 on the output side of the hydraulic oil source 11. The pressure gauge 52 is connected to a portion before being branched into the oil passages 42 and 44 on the output side of the hydraulic oil source 12.

[0049] The control unit 60 controls the operation of the hydraulic power sources 11 and 12. The control unit 60 is composed of a computer equipped with a processor such as a CPU (Central Processing Unit) and an FPGA (Field-Programmable Gate Array), and a storage device such as volatile or non-volatile memory. The control unit 60 may also include, for example, a personal computer or a circuit. In the first embodiment, the control unit 60 controls the operation of the hydraulic power sources 11 and 12 by hydraulic feedback control using the output pressure detected by the pressure gauges 51 and 52. In this embodiment, the control unit 60 automatically controls the operation of the hydraulic power sources 11 and 12 by hydraulic feedback control. The control unit 60 controls the operation of the hydraulic power source 11 by controlling the rotation of the motor 11b by hydraulic feedback control using the output pressure detection result from the pressure gauge 51. The control unit 60 controls the operation of the hydraulic power source 12 by controlling the rotation of the motor 12b through hydraulic feedback control using the output pressure detection result from the pressure gauge 52. In hydraulic feedback control, the control unit 60 controls the rotation of the motors 11b and 12b so that the output pressure detected by the pressure gauges 51 and 52 follows a set command value, for example, by P control, PI control, or PID control. The control unit 60 controls the electrical signals supplied from the motor driver to the motors 11b and 12b by controlling the gate signals output to the motor driver having an inverter circuit.

[0050] Furthermore, in the first embodiment, hydraulic pressure is supplied to the leg lifting system 102 and the FCS 103 from both the hydraulic power source 11 and the hydraulic power source 12. That is, the control unit 60 is configured to operate the hydraulic power sources 11 and 12 in an active-active redundant configuration by operating them simultaneously. The control unit 60 controls the hydraulic power sources 11 and 12 by hydraulic feedback control so that they output hydraulic pressure of the same magnitude from each other. Specifically, the control unit 60 performs hydraulic feedback control of the hydraulic power source 11 and hydraulic feedback control of the hydraulic power source 12 using a common command value.

[0051] (Output switching control by the control unit) In the aircraft 101, the FCS 103 operates continuously, while the landing gear system 102 operates intermittently. For example, during the operation of the aircraft 101, such as during flight, the FCS 103 is always in operation. On the other hand, the landing gear system 102 operates only temporarily during takeoff and landing. The control unit 60 acquires the operating status of the landing gear system 102 and the FCS 103, and switches the operation of the hydraulic power source 11 and the hydraulic power source 12 according to the operating status of the landing gear system 102 and the FCS 103. In the first embodiment, the control unit 60 is configured to perform control to change the hydraulic pressure output from the hydraulic power source 11 and the hydraulic power source 12 according to the operating status of the landing gear system 102 and the FCS 103.

[0052] As shown in Figure 4, in the first embodiment, the hydraulic power sources 11 and 12 switch between outputting a relatively low operating hydraulic pressure for operating the leg lifting system 102 and a relatively high operating hydraulic pressure for operating the leg lifting system 102, depending on the operating state of the leg lifting system 102 and the FCS 103. Specifically, the hydraulic power sources 11 and 12 output a relatively low operating hydraulic pressure for operating the FCS 103 during periods when the leg lifting system 102 is not operating, and output a relatively high operating hydraulic pressure for operating the leg lifting system 102 during periods when the leg lifting system 102 is operating. That is, when only the FCS 103 is operating, only hydraulic pressure up to 3000 psi is required, so the control unit 60 controls the hydraulic power sources 11 and 12 to output hydraulic pressure of 3000 psi, which is the target of the relatively low operating hydraulic pressure, by setting the command value in the hydraulic feedback control to 3000 psi. On the other hand, when operating the leg lifting system 102, hydraulic pressure up to 5000 psi is required. Therefore, the control unit 60 controls the hydraulic power sources 11 and 12 to output hydraulic pressure of 5000 psi, which is a relatively high target for operating hydraulic pressure, by setting the command value in the hydraulic feedback control to 5000 psi.

[0053] The control unit 60 acquires the operating status of the landing gear system 102 and the FCS 103 based on, for example, input operations to the control unit 104 of the aircraft 101. The operating status here indicates whether or not to operate the landing gear system 102 and the FCS 103. The control unit 60 acquires the operating status of the landing gear system 102 by acquiring a signal from the control unit 104 indicating that an input operation by the pilot to operate the landing gear system 102 has been received. For example, the control unit 104 acquires a position signal indicating the position of the gear handle for operating the landing gear system 102. The control unit 60 acquires the operating status of the landing gear system 102 by acquiring the position signal indicating the position of the gear handle from the control unit 104. If the control unit 60 determines, based on the acquired operating status, that only the FCS 103 should be operated and the landing gear system 102 should not be operated, it controls the operation of the hydraulic power sources 11 and 12 to output 3000 psi of hydraulic pressure to operate the FCS 103. If the control unit 60 determines, based on the acquired operating state, that the leg lifting system 102 should be operated in addition to the FCS 103, it controls the operation of the hydraulic power sources 11 and 12 to output 5000 psi of hydraulic pressure to operate the leg lifting system 102.

[0054] In detail, as shown in Figure 4, the control unit 60 controls the operation of the hydraulic power sources 11 and 12 according to the maximum value of the operating hydraulic pressure required by the leg lifting system 102 and the FCS 103, as an indicator of the operating state of the leg lifting system 102 and the FCS 103. The control unit 60 controls the operation of the hydraulic power sources 11 and 12 to output the maximum required hydraulic pressure according to the operating state of the leg lifting system 102 and the FCS 103.

[0055] Specifically, the FCS 103 constantly requires a relatively low operating hydraulic pressure of 3000 psi or less. On the other hand, the landing gear retraction system 102 requires a relatively high operating hydraulic pressure of 5000 psi or less. That is, when operating the landing gear retraction system 102 during takeoff and landing, the relatively low operating hydraulic pressure of 3000 psi or less is insufficient, and a relatively high operating hydraulic pressure of 5000 psi or less is temporarily required. Therefore, the control unit 60 determines that the operation of the landing gear retraction system 102 has started based on the position signal from the operation unit 104, and determines that the operation of the landing gear retraction system 102 has been completed based on the signal from the landing gear retraction system 102. From the time the operation of the landing gear retraction system 102 is started until the time the operation of the landing gear retraction system 102 is completed, the control unit 60 controls the operation of the hydraulic power sources 11 and 12 to output an operating hydraulic pressure of 5000 psi, which is the target of the relatively high operating hydraulic pressure. For example, the control unit 60 obtains an uplock signal from the leg lifting system 102, which is a signal indicating that the door is locked in the closed position, and thereby obtains timing information indicating the timing when the operation of the leg lifting system 102 is completed, as a signal indicating the operating status of the leg lifting system 102. The control unit 60 controls the hydraulic power sources 11 and 12 to output 5000 psi of hydraulic pressure at the timing when the door is opened and closed, and when the leg portion 102a is raised and lowered.

[0056] For example, Figure 4 shows an example where the leg lifting system 102 retracts the leg 102a during a period when the FCS 103 is continuously operating. In Figure 4, the command value in hydraulic feedback control is represented by a solid line, the hydraulic pressure required by the leg lifting system 102 is represented by a dashed line, and the hydraulic pressure required by the FCS 103 is represented by a dashed line. When the control unit 60 performs the leg 102a retraction operation, it acquires the operating status of the leg lifting system 102 as the start of the door opening operation at timing T1 in Figure 4 based on the position signal from the operation unit 104. In the period before timing T1, the operating hydraulic pressure required by the leg lifting system 102 and the FCS 103 is a relatively low hydraulic pressure of 3000 psi or less, whereas at timing T1, the operating hydraulic pressure required by the leg lifting system 102 becomes a relatively high hydraulic pressure of 5000 psi or less, so the command value in hydraulic feedback control is changed to 5000 psi. Subsequently, at timing T2, the leg lifting system 102 starts the lifting operation of the leg portion 102a. At timing T2, since the operating hydraulic pressure required for the leg lifting system 102 is a relatively high hydraulic pressure of 5000 psi or less, the control unit 60 maintains the command value in the hydraulic feedback control at 5000 psi.

[0057] Then, at timing T3, the lifting operation of the leg portion 102a is completed and the door closing operation begins. At timing T3, the operating hydraulic pressure required for the leg lifting system 102 is a relatively high hydraulic pressure of 5000 psi or less, so the control unit 60 maintains the command value in the hydraulic feedback control at 5000 psi. Then, at timing T4, the control unit 60 receives timing information from the leg lifting system 102 and determines that the door closing operation by the leg lifting system 102 has been completed and the operation of retracting the leg portion 102a has been completed. Therefore, from timing T4 onward, the operating hydraulic pressure required by the hydraulic system 100 becomes a relatively low hydraulic pressure of 3000 psi or less, which is the operating hydraulic pressure required for the FCS 103. Accordingly, at timing T4, the control unit 60 changes the command value in the feedback control back to 3000 psi.

[0058] Furthermore, in the first embodiment, the hydraulic power sources 11 and 12 stop supplying hydraulic pressure during periods when both the landing gear retraction system 102 and the FCS 103 are stopped. That is, the control unit 60 acquires the operating status of the landing gear retraction system 102 and the FCS 103, and if it determines based on the acquired operating status that both the landing gear retraction system 102 and the FCS 103 should be stopped, it stops both the motor 11b of the hydraulic power source 11 and the motor 12b of the hydraulic power source 12, thereby stopping the supply of hydraulic pressure from the hydraulic power sources 11 and 12. For example, when the aircraft 101 is parked on the ground, the operation unit 104 receives an operation to stop the operation of the landing gear retraction system 102 and the FCS 103. If the control unit 60 determines based on the signal from the operation unit 104 that both the landing gear retraction system 102 and the FCS 103 should be stopped, it stops the operation of the hydraulic power sources 11 and 12. When the control unit 60 receives an operation from the operation unit 104 to operate either the leg lifting system 102 or the FCS 103, it restarts the operation of the hydraulic power sources 11 and 12.

[0059] (Control Method for Hydraulic System) Next, with reference to Figure 5, a control method for the hydraulic system 100 in the aircraft 101 will be described. The control processes of steps S1 to S4 in the control method for the hydraulic system 100 are performed by the control unit 60. The control unit 60 performs the control processes of steps S1 to S4 at predetermined control cycles, for example. The control method for the hydraulic system 100 by steps S1 to S4 is an example of a "control method for an aircraft hydraulic system" in the claims.

[0060] First, in step S1, the operating status of the leg lifting system 102 and the FCS 103 is acquired. Based on the signals from the operation unit 104 or the leg lifting system 102, the control unit 60 acquires information on the operating status for setting command values ​​in the hydraulic feedback control of the hydraulic power sources 11 and 12. Signals from the leg lifting system 102 include, for example, a leg uplock signal indicating that the leg 102a is locked in the retracted position, and a door uplock signal indicating that the storage compartment door is locked in the closed position.

[0061] Next, in step S2, it is determined whether the command value for hydraulic feedback control should be set to 3000 psi or 5000 psi. Specifically, based on the operating state acquired in step S1, it is determined whether the command value for hydraulic feedback control should be set to 3000 psi, which is the upper limit of the relatively low operating hydraulic pressure required to operate the FCS 103, or to 5000 psi, which is the upper limit of the relatively high operating hydraulic pressure required to operate the leg lifting system 102. Based on the acquired operating state, the control unit 60 determines that the required hydraulic pressure is a relatively low operating hydraulic pressure of 3000 psi or less, for example, when operating the FCS 103 without operating the leg lifting system 102, and sets the command value to 3000 psi. Alternatively, based on the acquired operating state, the control unit 60 determines that the required hydraulic pressure is a relatively high operating hydraulic pressure of 5000 psi or less, for example, when operating both the leg lifting system 102 and the FCS 103, and sets the command value to 5000 psi. If it is determined that the command value should be set to 3000 psi, proceed to step S3. If it is determined that the command value should be set to 5000 psi, proceed to step S4.

[0062] In step S3, a relatively low operating hydraulic pressure of 3000 psi or less is supplied from the hydraulic power sources 11 and 12. When the command value is set to 3000 psi, the control unit 60 controls the rotation of motors 11b and 12b by hydraulic feedback control using the output pressure detected by pressure gauges 51 and 52, so that the hydraulic pressure output from the hydraulic power sources 11 and 12 follows the command value of 3000 psi.

[0063] In step S4, a relatively high operating hydraulic pressure of 5000 psi or less is supplied from the hydraulic power sources 11 and 12. When the command value is set to 5000 psi, the control unit 60 controls the rotation of motors 11b and 12b by hydraulic feedback control using the output pressure detected by pressure gauges 51 and 52, similar to step S3, so that the hydraulic pressure output from the hydraulic power sources 11 and 12 follows the command value of 5000 psi.

[0064] Steps S2 to S4 control the operation of the hydraulic power sources 11 and 12. Specifically, step S2, which determines which command value to set, step S3, which supplies 3000 psi of hydraulic pressure, and step S4, which supplies 5000 psi of hydraulic pressure, are examples of "steps to control the operation of the common hydraulic power source" in the claims. Steps S2 to S4 switch between two control mechanisms: one that supplies relatively high operating hydraulic pressure to the leg lifting system 102 by operating the hydraulic power sources 11 and 12 to output relatively high operating hydraulic pressure for operating the leg lifting system 102, while simultaneously supplying relatively low operating hydraulic pressure to the FCS 103 via pressure reducing valves 21 and 22 that reduce the supplied hydraulic pressure; and another that supplies relatively low operating hydraulic pressure to the FCS 103 by operating the hydraulic power sources 11 and 12 to output relatively low operating hydraulic pressure for operating the FCS 103.

[0065] As mentioned above, if the control unit 60 determines, based on the acquired operating state, that it should stop the operation of both the leg lifting system 102 and the FCS 103, it stops both the motor 11b of the hydraulic power source 11 and the motor 12b of the hydraulic power source 12, thereby stopping the supply of hydraulic pressure from the hydraulic power sources 11 and 12. Therefore, in this embodiment, as a step of controlling the common hydraulic power source, based on the acquired operating state, control is performed to stop the supply of hydraulic pressure to both the leg lifting system 102 and the FCS 103 by stopping the operation of the hydraulic power sources 11 and 12, thereby stopping the supply of hydraulic pressure to both the leg lifting system 102 and the FCS 103, switching from the control in steps S3 and S4. Specifically, in this case, the operating state of the leg lifting system 102 and the FCS 103 is acquired by obtaining a signal from the operation unit 104 indicating that an input operation to stop the operation of the leg lifting system 102 and the FCS 103 has been received. Then, in order to stop the supply of hydraulic pressure from the hydraulic power sources 11 and 12, the control unit 60 performs control to stop both motor 11b and motor 12b. Note that when the supply of hydraulic pressure from the hydraulic power sources 11 and 12 is stopped, hydraulic feedback control is not performed. Therefore, in this case, the process in step S2 is not performed, and instead, for example, the command value in the hydraulic feedback control may be reset.

[0066] (Effects of the First Embodiment) In the first embodiment, the following effects can be obtained.

[0067] In the first embodiment, as described above, the hydraulic system 100 (aircraft hydraulic system) includes hydraulic sources 11 and 12 (common hydraulic sources) that supply hydraulic pressure in common to both the FCS 103 (low-pressure operating section) which is located on the aircraft 101 and operates with a relatively low operating hydraulic pressure, and the landing gear retraction system 102 (high-pressure operating section) which is located on the aircraft 101 separately from the FCS 103 and operates with a relatively high operating hydraulic pressure, and pressure reducing valves 21 and 22 that reduce the hydraulic pressure supplied to the FCS 103. As a result, hydraulic pressure from the hydraulic sources 11 and 12 can be supplied to the landing gear retraction system 102 at the same time as hydraulic pressure from the hydraulic sources 11 and 12 can be supplied to the FCS 103 via the pressure reducing valves 21 and 22. Therefore, appropriate operating hydraulic pressure can be supplied to both the FCS 103 and the landing gear retraction system 102, which operate with different operating hydraulic pressures, without having to arrange separate hydraulic sources that supply different hydraulic pressures. Therefore, compared to the case where separate hydraulic sources supplying different hydraulic pressures are arranged, it is possible to suppress an increase in the weight of the hydraulic system 100 in the aircraft 101, as well as an increase in the number of parts of the hydraulic system 100. As a result, even when multiple operating parts (landing gear lifting system 102 and FCS 103) that operate with different operating hydraulic pressures are arranged in the aircraft 101, it is possible to suppress an increase in the weight and the number of parts of the hydraulic system 100.

[0068] Furthermore, in the first embodiment, as described above, the hydraulic power sources 11 and 12 (common hydraulic power sources) include hydraulic pumps 11a and 12a that discharge hydraulic fluid to supply hydraulic pressure to the FCS 103 (low-pressure operating section) and the landing gear retraction system 102 (high-pressure operating section), respectively, and motors 11b and 12b that serve as the drive sources for the hydraulic pumps 11a and 12a, respectively. As a result, hydraulic pressure can be supplied by operating the hydraulic pumps 11a and 12a by driving the motors 11b and 12b, and the hydraulic pressure supplied from the hydraulic power sources 11 and 12 can be easily controlled by controlling the operation of the motors 11b and 12b. In addition, unlike the case where hydraulic pressure is supplied by power from the main engine to obtain thrust for the aircraft 101, hydraulic pressure can be supplied to the FCS 103 and the landing gear retraction system 102 by driving the motors 11b and 12b even when the main engine is stopped, thus suppressing energy waste in the main engine. Therefore, when the aircraft 101 has an FCS 103 and a landing gear lifting system 102 that operate under different hydraulic pressures, it is possible to suppress an increase in weight and the number of parts, as well as suppress a decrease in energy efficiency.

[0069] Furthermore, in the first embodiment, as described above, the hydraulic system 100 (aircraft hydraulic system) includes pressure gauges 51 and 52 that detect the output pressure of hydraulic sources 11 and 12 (common hydraulic sources), and a control unit 60 that controls the operation of hydraulic sources 11 and 12 by hydraulic feedback control using the output pressure detected by the pressure gauges 51 and 52. As a result, by controlling the operation of hydraulic sources 11 and 12 by hydraulic feedback control by the control unit 60, the output pressure from hydraulic sources 11 and 12 can be controlled to an appropriate value. Therefore, the hydraulic pressure supplied to the FCS 103 (low-pressure operating section) and the landing gear lifting system 102 (high-pressure operating section), which operate with different operating hydraulic pressures in the aircraft 101, can be more easily set to an appropriate level. In particular, in this embodiment, the operation of each of the hydraulic sources 11 and 12 is automatically controlled by hydraulic feedback control by the control unit 60. Therefore, for example, the operation of hydraulic sources 11 and 12 can be controlled without human intervention, contributing to the prevention of human error.

[0070] Furthermore, in the first embodiment, as described above, the hydraulic power sources 11 and 12 (common hydraulic power sources) switch between outputting either a relatively low operating hydraulic pressure for operating the FCS 103 (low-pressure operating section) and a relatively high operating hydraulic pressure for operating the leg lifting system 102, depending on the operating state of the FCS 103 (low-pressure operating section) and the leg lifting system 102 (high-pressure operating section). This allows the operation of the hydraulic power sources 11 and 12 to be switched to supply appropriate hydraulic pressure according to the operating state of the FCS 103 and the leg lifting system 102, thereby suppressing energy waste compared to operating the hydraulic power sources 11 and 12 at a constant output at all times. Therefore, by switching the output from the hydraulic power sources 11 and 12 according to the operating state of the FCS 103 and the leg lifting system 102, it is possible to suppress an increase in weight and the number of parts, as well as suppress a decrease in energy efficiency.

[0071] Furthermore, in the first embodiment, as described above, the hydraulic power sources 11 and 12 (common hydraulic power source) output a relatively low operating hydraulic pressure to operate the FCS 103 (low-pressure operating part) during periods when the leg lifting system 102 (high-pressure operating part) is not in operation, and output a relatively high operating hydraulic pressure to operate the leg lifting system 102 during periods when the leg lifting system 102 is in operation. As a result, since there is no need to supply hydraulic pressure to the leg lifting system 102 during periods when the leg lifting system 102 is not in operation, energy waste in the hydraulic power sources 11 and 12 can be suppressed by outputting a relatively low operating hydraulic pressure to operate the FCS 103. Consequently, the decrease in energy efficiency in the hydraulic power sources 11 and 12 can be further suppressed.

[0072] Furthermore, in the first embodiment, as described above, the system is equipped with check valves 31 and 32 (high-pressure side check valves) that suppress the backflow of hydraulic fluid from the leg lifting system 102 (high-pressure operating section) to the hydraulic power sources 11 and 12 (common hydraulic power sources). By suppressing the backflow of hydraulic fluid from the leg lifting system 102 to the hydraulic power sources 11 and 12 with check valves 31 and 32, the hydraulic fluid that flowed into the leg lifting system 102 during the period when the leg lifting system 102 is in operation can be retained in the leg lifting system 102 even during the period when the leg lifting system 102 is not in operation. Here, no hydraulic pressure is consumed by the leg lifting system 102 during the period when the leg lifting system 102 is not in operation. Therefore, even during the period when the leg lifting system 102 is not in operation, a relatively high operating hydraulic pressure can be maintained in the leg lifting system 102. Therefore, the responsiveness of the leg lifting system 102 can be improved when the leg lifting system 102 starts operating afterward.

[0073] Furthermore, in the first embodiment, as described above, the hydraulic power sources 11 and 12 (common hydraulic power sources) supply hydraulic pressure in common to the FCS 103 (low-pressure operating section) that operates the control surface 103a in the aircraft 101, and to the landing gear lifting system 102 (high-pressure operating section) that operates the landing gear 102a in the aircraft 101. As a result, even when the operating hydraulic pressure differs between operating the control surface 103a and operating the landing gear 102a in the aircraft 101, the increase in weight and the increase in the number of parts can be effectively suppressed by arranging the hydraulic power sources 11 and 12 and the pressure reducing valves 21 and 22.

[0074] Furthermore, in the first embodiment, as described above, the hydraulic power sources 11 and 12 (common hydraulic power source) stop supplying hydraulic pressure during periods when the operation of both the FCS 103 (low-pressure operating section) and the leg lifting system 102 (high-pressure operating section) is stopped. This allows the operation of the hydraulic power sources 11 and 12 to be stopped during periods when it is not necessary to supply hydraulic pressure to either the FCS 103 or the leg lifting system 102, thereby further suppressing the decrease in energy efficiency in the hydraulic power sources 11 and 12.

[0075] Furthermore, in the first embodiment, as described above, the hydraulic system 100 (aircraft hydraulic system) includes a hydraulic source 11 (first common hydraulic source) and a hydraulic source 12 (second common hydraulic source) that independently supply hydraulic pressure to the FCS 103 (low-pressure operating section) and the landing gear retraction system 102 (high-pressure operating section). As a result, hydraulic pressure can be supplied to the FCS 103 and the landing gear retraction system 102 in common by each of the redundant hydraulic sources 11 and 12, thereby improving the stability of the operation of the FCS 103 and the landing gear retraction system 102. In addition, if separate hydraulic sources are provided to supply hydraulic pressure at different pressures to the FCS 103 and the landing gear retraction system 102, which operate with different operating hydraulic pressures, it is necessary to individually make the hydraulic sources with different output pressures redundant in order to make the hydraulic sources redundant. In contrast, in the first embodiment, since the hydraulic power sources 11 and 12 that supply hydraulic pressure to the FCS 103 and the leg lifting system 102 are arranged redundantly, the increase in weight and the increase in the number of parts can be suppressed more effectively compared to the case where hydraulic power sources with different output pressures are individually made redundant.

[0076] Furthermore, in the first embodiment, as described above, the hydraulic system 100 (aircraft hydraulic system) includes a pressure reducing valve 21 (first pressure reducing valve) that reduces the hydraulic pressure supplied from the hydraulic source 11 (first common hydraulic source) to the FCS 103 (low-pressure operating section), and a pressure reducing valve 22 (second pressure reducing valve) which is arranged separately from the pressure reducing valve 21 and reduces the hydraulic pressure supplied from the hydraulic source 12 (second common hydraulic source) to the FCS 103. By arranging the pressure reducing valve 21 and the pressure reducing valve 22 separately, the configuration for reducing the hydraulic pressure supplied to the FCS 103 can be made redundant, and the stability of the operation of the hydraulic system 100 can be further improved compared to the case where the hydraulic pressure from each of the hydraulic sources 11 and 12 is reduced by a common pressure reducing valve.

[0077] Furthermore, in the first embodiment, as described above, the hydraulic system 100 (aircraft hydraulic system) includes check valves 31 and 33 (first check valves) that suppress backflow of hydraulic fluid to the hydraulic source 11 (first common hydraulic source), and check valves 32 and 34 (second check valves) that are arranged separately from check valves 31 and 33 and suppress backflow of hydraulic fluid to the hydraulic source 12 (second common hydraulic source). By arranging check valves 31 and 33 and check valves 32 and 34 separately, check valves 31 and 33 suppress backflow to the hydraulic source 11, and check valves 32 and 34 suppress backflow to the hydraulic source 12. Therefore, for example, even if either the hydraulic source 11 or the hydraulic source 12 fails, it is possible to prevent hydraulic fluid from flowing from a normal hydraulic source to the failed hydraulic source.

[0078] Furthermore, in the first embodiment, as described above, check valves 31, 32, 33, and 34 (check valves) are provided to suppress the backflow of hydraulic fluid from the FCS 103 (low-pressure operating section) and the leg lifting system 102 (high-pressure operating section) to the hydraulic power sources 11 and 12 (common hydraulic power sources). With this configuration, the backflow of hydraulic fluid from the FCS 103 and the leg lifting system 102 to the hydraulic power sources 11 and 12 can be suppressed by the check valves 31, 32, 33, and 34. In addition, by suppressing the backflow of hydraulic fluid to the hydraulic power sources 11 and 12 with the check valves 31, 32, 33, and 34, the FCS 103 and the leg lifting system 102 can each maintain their operating hydraulic pressure.

[0079] Furthermore, in the first embodiment, as described above, the system includes check valves 31 and 32 (high-pressure side check valves) that suppress the flow of hydraulic fluid from the leg lifting system 102 (high-pressure operating part) to the hydraulic power sources 11 and 12 (common hydraulic power source), and check valves 33 and 34 (low-pressure side check valves) that suppress the flow of hydraulic fluid from the FCS 103 (low-pressure operating part) to the hydraulic power sources 11 and 12. With this configuration, check valves 31 and 32 suppress backflow from the leg lifting system 102 to the hydraulic power sources 11 and 12, and check valves 33 and 34 suppress backflow from the FCS 103 to the hydraulic power sources 11 and 12. Here, for example, even if check valve 31 is closed due to sticking and hydraulic pressure cannot be supplied from the hydraulic power source 11 to the leg lifting system 102, hydraulic pressure can still be supplied from the hydraulic power source 11 to the FCS 103 via check valve 34. Therefore, it is possible to prevent a situation in which hydraulic pressure from the hydraulic power source 11 is not supplied to either the leg lifting system 102 or the FCS 103. Furthermore, since hydraulic pressure can be supplied to the FCS 103 from both the hydraulic power source 11 and the hydraulic power source 12 as before, it is possible to avoid a situation in which the FCS 103 is supplied with hydraulic pressure solely by the hydraulic power source 12. In addition, since the hydraulic power source 12 supplies hydraulic pressure to the leg lifting system 102, it is possible to avoid a situation in which the leg lifting system 102 becomes completely unusable.

[0080] Furthermore, in the first embodiment, as described above, the hydraulic system 100 (aircraft hydraulic system) supplies hydraulic pressure to the FCS 103 (low-pressure operating section) and the landing gear retraction system 102 (high-pressure operating section) from both the hydraulic source 11 (first common hydraulic source) and the hydraulic source 12 (second common hydraulic source). By operating the hydraulic source 11 and the hydraulic source 12 simultaneously, hydraulic pressure is supplied to the FCS 103 and the landing gear retraction system 102 from both the hydraulic source 11 and the hydraulic source 12, thereby reducing the load on each of the hydraulic source 11 and the hydraulic source 12. As a result, the lifespan of each of the hydraulic source 11 and the hydraulic source 12 can be extended, and the workload required for maintenance such as replacement of the hydraulic source 11 and the hydraulic source 12 can be reduced. In addition, by supplying hydraulic pressure to the FCS 103 and the landing gear retraction system 102 from both the hydraulic source 11 and the hydraulic source 12, if a malfunction occurs in either the hydraulic source 11 or the hydraulic source 12, the supply of hydraulic pressure can be continued by the other. Therefore, if an abnormality occurs in either the hydraulic power source 11 or the hydraulic power source 12, it is possible to prevent the supply of hydraulic pressure to the FCS 103 and the leg lifting system 102 from being interrupted.

[0081] Furthermore, in the first embodiment, as described above, the pressure reducing valves 21 and 22 are configured to reduce the supplied hydraulic pressure by allowing hydraulic fluid to flow from the upstream side to the downstream side when the downstream pressure is less than a predetermined pressure, and by blocking the flow of hydraulic fluid from the upstream side to the downstream side when the downstream pressure exceeds a predetermined pressure. However, if the pressure reducing valves 21 and 22 are configured to reduce the hydraulic pressure by distributing the hydraulic fluid to another flow path, the energy efficiency of the hydraulic power sources 11 and 12 (common hydraulic power source) will decrease by the amount of hydraulic pressure that is distributed. Taking this into consideration, in the first embodiment, the pressure reducing valves 21 and 22 are configured to reduce the supplied hydraulic pressure by allowing hydraulic fluid to flow from the upstream side to the downstream side when the downstream pressure is less than a predetermined pressure, and by blocking the flow of hydraulic fluid from the upstream side to the downstream side when the downstream pressure exceeds a predetermined pressure, thereby suppressing the decrease in energy efficiency of the hydraulic power sources 11 and 12.

[0082] Furthermore, in the first embodiment, as described above, the hydraulic system 100 (aircraft hydraulic system) includes an actuator 103b (low-pressure actuator) that operates with a relatively low operating hydraulic pressure in the FCS 103 (low-pressure operating section) and an actuator 102c (high-pressure actuator) that operates with a relatively high operating hydraulic pressure in the landing gear lifting system 102 (high-pressure operating section). As a result, since the hydraulic system 100 includes actuators 102c and 103b to which hydraulic pressure is supplied in common, the operation of the hydraulic sources 11 and 12 (common hydraulic sources) can be set to supply more appropriate operating hydraulic pressure compared to when hydraulic pressure is supplied to external actuators.

[0083] [Second Embodiment] Next, with reference to Figure 6, the configuration of the hydraulic system 200 according to the second embodiment will be described. In the second embodiment, unlike the first embodiment in which the redundant hydraulic power sources 11 and 12 were operated simultaneously, the other is kept in a standby state while one of the redundant hydraulic power sources 11 and 12 is operating. That is, in the second embodiment, the operating parts to which hydraulic pressure is supplied (e.g., high-pressure operating parts and low-pressure operating parts) are the same regardless of whether the hydraulic power source 11 or 12 is operating, and the "control method for an aircraft hydraulic system" in the claims is the same regardless of whether the hydraulic power source 11 or 12 is operating. Components similar to those in the first embodiment are denoted by the same reference numerals and their description is omitted.

[0084] As shown in Figure 6, in the second embodiment, the hydraulic system 200 includes a hydraulic source 11, a hydraulic source 12, a pressure reducing valve 21, and a pressure reducing valve 22, similar to the hydraulic system 100 of the first embodiment. That is, the hydraulic system 200 of the second embodiment includes a hydraulic circuit with the same configuration as the hydraulic system 100 of the first embodiment. In the second embodiment, the hydraulic system 200 includes a control unit 260. The hardware configuration of the control unit 260 is the same as that of the control unit 60 of the first embodiment. Similar to the control unit 60 of the first embodiment, the control unit 260 controls the operation of the hydraulic source 11 and the hydraulic source 12 by hydraulic feedback control using the detection results from the pressure gauge 51 and the pressure gauge 52. Note that the hydraulic system 200 is an example of an "aircraft hydraulic system" as defined in the claims.

[0085] In the second embodiment, the control unit 260 operates one of the redundant hydraulic power sources 11 and 12 to supply hydraulic pressure, while keeping the other in a standby state. If an abnormality occurs in one of the hydraulic power sources 11 or 12, the control unit 260 stops the operation of the other and activates the other, which was in standby state, to supply hydraulic pressure. In the second embodiment, the control unit 260 is configured to operate the hydraulic power sources 11 and 12 in an active-standby redundant configuration.

[0086] For example, in the second embodiment, the control unit 260 determines an abnormality in the hydraulic power source 11 based on the detection result from the pressure gauge 51. If the hydraulic power source 11 is normal, hydraulic power is supplied from the hydraulic power source 11 to both the leg lifting system 102 and the FCS 103, with the supply of hydraulic power from the hydraulic power source 12 stopped. If the hydraulic power source 11 is abnormal, hydraulic power is supplied from the hydraulic power source 12 to both the leg lifting system 102 and the FCS 103, with the supply of hydraulic power from the hydraulic power source 11 stopped.

[0087] The control unit 260 determines that the hydraulic source 11 is functioning normally if the output pressure of the hydraulic source 11 detected by the pressure gauge 51 is greater than a predetermined operating threshold. If the control unit 260 determines that the hydraulic source 11 is functioning normally, it supplies hydraulic pressure from the hydraulic source 11 to the leg lifting system 102 and the FCS 103, and stops the operation of the motor 12b in the hydraulic source 12 to stop the supply of hydraulic pressure. The control unit 260 then determines that the hydraulic source 11 is malfunctioning if the output pressure of the hydraulic source 11 detected by the pressure gauge 51 falls below a predetermined operating threshold. If the control unit 260 determines that the hydraulic source 11 is malfunctioning, it stops the operation of the motor 11b in the hydraulic source 11 to stop the supply of hydraulic pressure, and starts the operation of the motor 12b to activate the hydraulic source 12, which was waiting in standby mode, thereby supplying hydraulic pressure from the hydraulic source 12 to the leg lifting system 102 and the FCS 103. The predetermined operating threshold is set, for example, as a value obtained by multiplying the command value in hydraulic feedback control by a predetermined ratio. Furthermore, the predetermined operating threshold may be a fixed value set in advance. The other configurations of the second embodiment are the same as those of the first embodiment described above.

[0088] By the way, in the second embodiment, for example, if the hydraulic power source 11 is set to operate and the hydraulic power source 12 is set to standby by default, a problem arises in that the usage time of the hydraulic power source 11 increases, and the load on the hydraulic power source 11 becomes heavy. For this reason, for example, the operating hydraulic power source and the standby hydraulic power source may be switched depending on the flight of the aircraft 101, or on odd-numbered or even-numbered days. By switching the operating hydraulic power source and the standby hydraulic power source in this way, the uneven distribution of load on the hydraulic power sources 11 and 12 can be reduced.

[0089] (Effects of the Second Embodiment) In the second embodiment, as described above, when the hydraulic source 11 (first common hydraulic source) is functioning normally, the hydraulic source 11 supplies hydraulic pressure to the FCS 103 (low-pressure operating section) and the leg lifting system 102 (high-pressure operating section) in common. Also, when the hydraulic source 11 is malfunctioning, the hydraulic source 12 supplies hydraulic pressure to the FCS 103 and the leg lifting system 102 in common, while the hydraulic source 11 supplies hydraulic pressure to the FCS 103 and the leg lifting system 102 in common. As a result, the operating time of each of the hydraulic sources 11 and 12 can be shortened compared to when both hydraulic sources 11 and 12 are running continuously. Therefore, when maintenance is performed on each of the hydraulic sources 11 and 12 according to their operating time, the opportunities for maintenance can be reduced. As a result, the increase in the workload required for maintenance work can be suppressed. Furthermore, if the hydraulic power source 11 malfunctions, the hydraulic power source 12 can supply hydraulic pressure to both the FCS 103 and the leg lifting system 102, thereby positioning the hydraulic power source 12 in the second embodiment as a backup hydraulic power source for the hydraulic power source 11. Therefore, for example, if the hydraulic power source 11 malfunctions, the hydraulic power source 12 can supply hydraulic pressure, ensuring an uninterrupted supply of hydraulic pressure. Other effects of the second embodiment are the same as those of the first embodiment.

[0090] (Modifications) It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than the description of the embodiments above, and further includes all modifications (modifications) within the meaning and scope equivalent to the claims.

[0091] For example, in the first and second embodiments described above, examples were shown in which hydraulic pressure is supplied to two types of operating parts, a landing gear lifting system 102 (high-pressure operating part) and an FCS 103 (low-pressure operating part), which operate with different operating hydraulic pressures. However, the present invention is not limited thereto. In the present invention, hydraulic pressure may be supplied to three or more operating parts that operate with different operating hydraulic pressures, such as the hydraulic system 300 (aircraft hydraulic system) according to the first modified example shown in Figure 7. The hydraulic system 300 according to the first modified example shown in Figure 7 includes a common hydraulic power source 311. The common hydraulic power source 311 is configured to supply hydraulic pressure in common to the high-pressure operating part 302, the first low-pressure operating part 303, and the second low-pressure operating part 305, each of which operates with different operating hydraulic pressures. For example, the second low-pressure operating part 305 operates with an even lower operating hydraulic pressure than the first low-pressure operating part 303. Therefore, the hydraulic system 300 includes a pressure reducing valve 321 that reduces the hydraulic pressure to the operating hydraulic pressure required to operate the first low-pressure operating unit 303, and another pressure reducing valve 323 that reduces the hydraulic pressure to the operating hydraulic pressure required to operate the second low-pressure operating unit 305. The hydraulic system 300 directly supplies hydraulic pressure to the high-pressure operating unit 302 by operating the common hydraulic power source 311 to output a relatively high operating hydraulic pressure required to operate the high-pressure operating unit 302, while also supplying hydraulic pressure to the first low-pressure operating unit 303 via the pressure reducing valve 321 and to the second low-pressure operating unit 305 via the other pressure reducing valve 323. As a result, the common hydraulic power source 311 supplies appropriate hydraulic pressure to each of the high-pressure operating unit 302, the first low-pressure operating unit 303, and the second low-pressure operating unit 305, which operate with different operating hydraulic pressures. In addition, when supplying hydraulic pressure to three or more operating units, redundancy may be provided by arranging multiple common hydraulic power sources.

[0092] Furthermore, while the first and second embodiments described above show examples in which the hydraulic power sources 11 and 12 (common hydraulic power sources) include hydraulic pumps 11a and 12a, which are gear pumps, and motors 11b and 12b, the present invention is not limited thereto. In the present invention, the common hydraulic power source may include hydraulic pumps other than gear pumps, such as vane pumps or piston pumps. Also, the common hydraulic power source does not have to include a motor. For example, the common hydraulic power source may not be electric, but may be driven by the main engine of an aircraft or an auxiliary power unit. In addition, when the common hydraulic power source is an electric hydraulic power source including a motor, power may be supplied to the motor from a generator provided in addition to the auxiliary power unit, or power may be supplied to the motor from an energy storage device such as a battery.

[0093] Furthermore, while the first and second embodiments described above show examples in which the control units 60 and 260 control the operation of the hydraulic power sources 11 and 12 (common hydraulic power sources) by performing hydraulic feedback control, the present invention is not limited thereto. In the present invention, the common hydraulic power sources may be operated without performing hydraulic feedback control. For example, the operation of the common hydraulic power sources may be controlled based on a command value without using the output pressure detection result. Moreover, in the first and second embodiments described above, the operation of the hydraulic power sources 11 and 12 was automatically controlled by hydraulic feedback control by the control units 60 and 260. However, the invention is not limited to this, and the operation of the hydraulic power sources 11 and 12 (common hydraulic power sources) may be controlled manually. In this case, for example, the output pressure detected by the pressure gauges 51 and 52 is displayed on a display unit located in the cockpit of the aircraft 101. Then, after the pilot operating the aircraft 101 checks the display unit, the control unit 60 and 260 adjust the operation of the hydraulic power sources 11 and 12 based on the input operation of the control unit 104. In other words, by manually controlling the operation of the hydraulic power sources 11 and 12, the operator's will can be incorporated into the feedback control, increasing the opportunities to reflect human intent in the hydraulic system 100. Furthermore, when there are two redundant common hydraulic power sources, hydraulic power source 11 (first common hydraulic power source) and hydraulic power source 12 (second common hydraulic power source), the operation of the first common hydraulic power source and the operation of the second common hydraulic power source may be controlled by control devices that are arranged separately from each other. That is, the control unit may include a first control unit that controls the operation of the first common hydraulic power source and a second control unit that controls the operation of the second common hydraulic power source. In that case, for example, the first control unit and the second control unit may communicate with each other to control the operation of the first common hydraulic power source and the second common hydraulic power source in the event of an abnormality. Alternatively, for example, the first control unit and the second control unit may each acquire the output pressure of hydraulic power sources that are not under control from a pressure gauge, and use the acquired output pressure to detect abnormalities in the hydraulic power sources that are not under control when the first common hydraulic power source or the second common hydraulic power source becomes abnormal.

[0094] Furthermore, in the first and second embodiments described above, the operating status of the FCS 103 (low-pressure operating unit) and the leg lifting system 102 (high-pressure operating unit) is acquired based on signals from the operation unit 104 and signals from the leg lifting system 102 (high-pressure operating unit), and the operation of the hydraulic power sources 11 and 12 (common hydraulic power sources) is switched according to the acquired operating status. However, the present invention is not limited thereto. In the present invention, the operation of the common hydraulic power source may not be switched according to the operating status of the low-pressure operating unit and the high-pressure operating unit. That is, a constant hydraulic pressure of hydraulic fluid may be output from the common hydraulic power source regardless of the operating status of the low-pressure operating unit and the high-pressure operating unit. In addition, a signal indicating the operating status may be acquired from the low-pressure operating unit, or a signal indicating a different operating status from the high-pressure operating unit may be acquired. In that case, the operation of the hydraulic power source may be switched according to the operating status of the low-pressure operating unit and the operating status of the high-pressure operating unit. In other words, when the operating hydraulic pressure required in the high-pressure and low-pressure operating units changes according to the operating state, the control unit may acquire the operating state and then control the hydraulic pressure output from the common hydraulic source in accordance with the change in the required operating hydraulic pressure. For example, in a landing gear retraction system as a high-pressure operating unit, if the door actuator is a low-pressure actuator that operates with a relatively low operating hydraulic pressure and the gear actuator is a high-pressure actuator that operates with a relatively high operating hydraulic pressure, the control unit may acquire timing information indicating the timing of operation of the door actuator and the gear actuator as information indicating the operating state from the landing gear retraction system, thereby acquiring the operating state including the timing of door opening and closing and the timing of landing gear retraction. In that case, based on the acquired timing information, the control unit controls the common hydraulic source to output a relatively low operating hydraulic pressure at the timing of door opening and closing, and to output a relatively high operating hydraulic pressure at the timing of landing gear retraction. Alternatively, signals indicating the operating state may be acquired from a higher-level control device located in a different aircraft from the low-pressure and high-pressure operating units.

[0095] Furthermore, while the first and second embodiments described above show examples in which the FCS 103 (low-pressure operating unit) operates continuously and the leg lifting system 102 (high-pressure operating unit) operates intermittently, the present invention is not limited thereto. In the present invention, the low-pressure operating unit may operate intermittently, or the high-pressure operating unit may operate continuously. Also, in the present invention, both the high-pressure operating unit and the low-pressure operating unit may operate intermittently or continuously. When both the high-pressure operating unit and the low-pressure operating unit operate intermittently, for example, the timing of operation of the high-pressure operating unit and the timing of operation of the low-pressure operating unit may overlap, or the timing of operation of the high-pressure operating unit and the low-pressure operating unit may differ.

[0096] Furthermore, in the first and second embodiments described above, when switching the operation of the hydraulic power sources 11 and 12 (common hydraulic power sources) according to the operating state of the FCS 103 (low-pressure operating unit) and the leg lifting system 102 (high-pressure operating unit), examples were shown in which the operation of the hydraulic power sources 11 and 12 is switched so that two operating hydraulic pressures are output: a relatively low operating hydraulic pressure of 3000 psi or less for operating the FCS 103 and a relatively high operating hydraulic pressure of 5000 psi or less for operating the leg lifting system 102. However, the present invention is not limited to this. In the present invention, the operation of the common hydraulic power source may be switched so that the output is switched to three or more values ​​according to the operating state of the low-pressure operating unit and the high-pressure operating unit. For example, if there are multiple types of operating hydraulic pressure values ​​required for at least one of the high-pressure operating unit and the low-pressure operating unit, the operation of the common hydraulic power source may be switched in stages according to the required operating hydraulic pressure values.

[0097] Furthermore, while the first and second embodiments described above show examples in which hydraulic pressure is supplied to the FCS 103 (low-pressure operating unit) that operates the control surface 103a in the aircraft 101 and the landing gear retraction system 102 (high-pressure operating unit) that operates the landing gear 102a in the aircraft 101, the present invention is not limited thereto. In the present invention, hydraulic pressure may be supplied to the steering system or the braking system in the aircraft. In that case, the steering system and the braking system may be either low-pressure operating units or high-pressure operating units. Also, the FCS that operates the control surface may be a high-pressure operating unit, and the landing gear retraction system that operates the landing gear may be a low-pressure operating unit. In addition, in the FCS that operates the control surface, some operating units such as hydraulic actuators may be high-pressure operating units, and other operating units such as hydraulic actuators may be low-pressure operating units. Similarly, in the landing gear retraction system that operates the landing gear, some operating units such as hydraulic actuators may be high-pressure operating units, and other operating units such as hydraulic actuators may be low-pressure operating units. In other words, a single device or system may have both a low-pressure operating section and a high-pressure operating section. For example, in a landing gear lifting system, a low-pressure operating section for operating the nose gear and a high-pressure operating section for operating the main gear may be arranged, and different operating hydraulic pressures may be supplied to the landing gear lifting system.

[0098] Furthermore, while the first and second embodiments described above show examples in which the operation of the hydraulic power sources 11 and 12 (common hydraulic power sources) is stopped during periods when the operation of both the FCS 103 (low-pressure operating unit) and the leg lifting system 102 (high-pressure operating unit) is stopped, the present invention is not limited thereto. In the present invention, the supply of hydraulic pressure from the common hydraulic power source may not be stopped when both the low-pressure operating unit and the high-pressure operating unit are stopped.

[0099] Furthermore, while the first and second embodiments described above show examples in which the common hydraulic source is made redundant by hydraulic source 11 (first common hydraulic source) and hydraulic source 12 (second common hydraulic source) having a common structure, the present invention is not limited thereto. In the present invention, the common hydraulic source does not have to be made redundant. Also, the common hydraulic source may be made redundant by three or more hydraulic sources. In addition, when the common hydraulic source is made redundant, the multiple hydraulic sources may have different configurations. For example, when redundancy is achieved by a common hydraulic source for normal operation and a common hydraulic source for standby, the common hydraulic source for standby may be set to have a lower output than the common hydraulic source for normal operation as an emergency supply.

[0100] Furthermore, while the first and second embodiments described above show examples in which the pressure reducing valve 21 (first pressure reducing valve) and pressure reducing valve 22 (second pressure reducing valve) are redundant, and the check valves 31 and 33 (first check valve) and check valves 32 and 34 (second check valve) are redundant, the present invention is not limited thereto. In the present invention, even when the common hydraulic power source is made redundant, the pressure reducing valves may be made common and not redundant. Also, even when the common hydraulic power source is made redundant, the check valves may be made common and not redundant. In addition, a configuration that blocks the flow of hydraulic fluid, such as a solenoid valve, may be provided instead of a check valve. Furthermore, a check valve may not be provided at all.

[0101] Furthermore, while the first and second embodiments described above show examples in which the pressure reducing valves 21 and 22 are configured to reduce the supplied hydraulic pressure by blocking the flow of hydraulic fluid from the upstream side to the downstream side, the present invention is not limited to this. In the present invention, the pressure reducing valve may be configured to reduce the supplied hydraulic pressure by distributing hydraulic fluid from the upstream side. Also, as pressure reducing valves, for example, servo valves and priority valves can be considered.

[0102] Furthermore, while the first and second embodiments described above show examples in which hydraulic pressure is supplied to actuators 102b, 102c (high-pressure actuator), and 103b (low-pressure actuator), which are hydraulic cylinders, the present invention is not limited thereto. In the present invention, hydraulic pressure may also be supplied to a hydraulic motor.

[0103] Furthermore, while the first and second embodiments described above show examples in which the hydraulic systems 100 and 200 (aircraft hydraulic systems) are equipped with actuators 102c (high-pressure actuator) and 103b (low-pressure actuator), the present invention is not limited thereto. In the present invention, the aircraft hydraulic system may be configured to supply hydraulic pressure to external actuators. That is, the aircraft hydraulic system may be an electric hydraulic power pack that does not include actuators.

[0104] Furthermore, while the second embodiment described above shows an example of determining an abnormality in the hydraulic power source 11 (first common hydraulic power source) based on the detection result of the pressure gauge 51, the present invention is not limited thereto. In the present invention, an abnormality in the common hydraulic power source may be determined by detecting an abnormality in the motor based on the current supplied to the motor, the voltage, or the rotation of the motor. Alternatively, an abnormality in the common hydraulic power source may be determined by detecting an abnormality in temperature.

[0105] Furthermore, in the first and second embodiments described above and the first modified example shown in Figure 7, check valves (for example, check valves 31, 32, 33, and 34) were shown to be located in oil passages (for example, oil passages 41, 42, 43, and 44) ​​leading to the high-pressure operating section and the low-pressure operating section, but the present invention is not limited thereto. For example, as in the second modified example shown in Figure 8, when hydraulic pressure is supplied from a common hydraulic source 411 to the high-pressure operating section 402 and to the low-pressure operating section 403 via a pressure reducing valve 421, the check valve 431 may be located in the portion before the oil passages branch off from the common hydraulic source 411 to the high-pressure operating section 402 and the low-pressure operating section 403, respectively. In this case, the check valve 431 suppresses the backflow of hydraulic fluid from both the high-pressure operating section 402 and the low-pressure operating section 403 to the common hydraulic source 411. Therefore, a single check valve 431 can suppress the backflow of hydraulic fluid from the high-pressure operating section 402 and the low-pressure operating section 403 to the common hydraulic power source 411. Consequently, it becomes unnecessary to provide check valves on both the high-pressure operating section 402 and the low-pressure operating section 403 sides, which contributes to suppressing an increase in weight and the number of parts in the hydraulic system.

[0106] Furthermore, in the second modified example shown in Figure 8, the common hydraulic power source 411 is configured to receive hydraulic fluid discharged from the high-pressure operating section 402 and the low-pressure operating section 403 via the return passage 90 and the reservoir 91. Therefore, for example, even if the common hydraulic power source 411 allows backflow of hydraulic fluid into the reservoir 91 or the return passage 90 due to a malfunction, the check valve 431 suppresses the backflow of hydraulic fluid into the common hydraulic power source 411, thereby preventing hydraulic fluid from flowing into the reservoir 91 or the return passage 90.

[0107] Furthermore, as a third modification, as shown in Figure 9, multiple check valves 432a and 432b, which suppress the backflow of hydraulic fluid from both the high-pressure operating section 402 and the low-pressure operating section 403 to the common hydraulic source 411, may be arranged in parallel with the common hydraulic source 411. This makes the check valves 432a and 432b redundant. For example, even if one of the check valves 432a and 432b is closed due to sticking and hydraulic pressure cannot be supplied to the low-pressure operating section 403 and the high-pressure operating section 402, hydraulic pressure can still be supplied to the low-pressure operating section 403 and the high-pressure operating section 402 through the other check valve 432a and 432b. Therefore, the operational stability of the aircraft hydraulic system can be further improved. Note that the redundancy of the check valves is not limited to the case where two check valves 432a and 432b are arranged in parallel, as shown in Figure 9, but three or more check valves may be arranged in parallel. In this way, increasing the number of check valves arranged in parallel can further improve the operational stability of aircraft hydraulic systems.

[0108] Furthermore, as a fourth modification, as shown in Figure 10, the check valve 433 may be located only in the oil passage that supplies hydraulic pressure to the high-pressure operating unit 402. In this case, if the high-pressure operating unit 402 operates intermittently, the check valve 433, acting as a high-pressure side check valve, suppresses the backflow of hydraulic fluid from the high-pressure operating unit 402 to the common hydraulic power source 411, thereby retaining the hydraulic fluid that flowed to the high-pressure operating unit 402 during the period when the high-pressure operating unit 402 is operating, even during the period when the high-pressure operating unit 402 is not operating. Here, during the period when the high-pressure operating unit 402 is not operating, no hydraulic pressure is consumed by the high-pressure operating unit 402. Therefore, even during the period when the high-pressure operating unit 402 is not operating, a relatively high operating hydraulic pressure can be maintained on the high-pressure operating unit 402. Consequently, the responsiveness of the high-pressure operating unit 402 can be improved when it starts operating again. Note that the check valve may also be located only in the oil passage that supplies hydraulic pressure to the low-pressure operating unit 403.

[0109] Furthermore, in the first and second embodiments described above, a relatively low operating hydraulic pressure is output to operate the FCS 103 (low-pressure operating section) during periods when the leg lifting system 102 (high-pressure operating section) is not in operation. Here, for example, when a relatively low operating hydraulic pressure is output to operate the low-pressure operating section, hydraulic pressure may not be supplied to the high-pressure operating section. This effectively prevents hydraulic pressure from being supplied to the high-pressure operating section when it is not in operation, thereby effectively suppressing malfunctions of the high-pressure operating section.

[0110] For example, as shown in the fifth modified example in Figure 11, a shut-off valve 581 may be provided at the confluence of oil passages 41 and 42 before the leg lifting system 102 (high-pressure operating section) to shut off the oil passage when a relatively low operating hydraulic pressure is output to operate the FCS 103 (low-pressure operating section). The shut-off valve 581 shuts off the supply of hydraulic pressure to the leg lifting system 102 by shutting off the oil passage. The flow and shut-off of the hydraulic fluid in the shut-off valve 581 are controlled by the control unit 60. This prevents hydraulic pressure from being supplied to the leg lifting system 102 when it is stopped. Therefore, it is possible to effectively suppress the supply of hydraulic pressure to the leg lifting system 102 when it is not operating, and thus effectively suppress malfunctions of the leg lifting system 102. In addition, the shut-off valves may be made redundant by placing a shut-off valve in each of the branched oil passages 41 and 42. In this case, the shut-off valve may be located upstream or downstream of the check valves 31 and 32. Alternatively, the shut-off valve may be located on the low-pressure operating side. Furthermore, the shut-off valve may be electrically driven, hydraulically driven as shown in Figures 15 and 16, or of any other drive type.

[0111] Furthermore, in the present invention, when the leg lifting system 102 (high-pressure operating section) is configured not to receive hydraulic pressure, as in the fifth modified example, a switching valve may be provided instead of the shut-off valve 581. The switching valve includes, for example, the shut-off valve 581 and a directional control valve. That is, instead of the shut-off valve 581, for example, a switching valve 582, which is a directional control valve, may be arranged as a bypass valve, as in the sixth modified example shown in Figure 12. The switching valve 582 is connected to the leg lifting system 102 (high-pressure operating section) when the leg lifting system 102 is to be operated, and the connection configuration is switched so that it is connected to the oil passage 43 or oil passage 44 before the FCS 103 when only the FCS 103 (low-pressure operating section) is to be operated. In other words, the switching valve 582 also functions as a shut-off valve that blocks the supply of hydraulic pressure from the hydraulic power sources 11 and 12, which serve as a common hydraulic power source, to the leg lifting system 102, which serves as a high-pressure operating unit, and also allows the hydraulic pressure from the hydraulic power sources 11 and 12, which serve as a common hydraulic power source, to be supplied to the FCS 103, which serves as a low-pressure operating unit, via the bypass oil passage 541. The bypass oil passage 541 is an oil passage for supplying hydraulic pressure from the hydraulic power sources 11 and 12, which serve as a common hydraulic power source, to the FCS 103, which serves as a low-pressure operating unit, while bypassing the pressure reducing valves 21 and 22. Therefore, the switching valve 582 in the sixth modified example is an example of a "shut-off valve" in the claims and also functions as a bypass valve that switches the flow of hydraulic fluid to the bypass oil passage 541. This allows the supply of hydraulic pressure to the leg lifting system 102 to be blocked, and the hydraulic pressure supplied to the oil passages 41 and 42 to be supplied (recirculated) to the FCS 103. In this modified configuration, the switching valve 582 is connected to the downstream side of the pressure reducing valves 21 and 22, specifically to the confluence of oil passages 43 and 44 before the FCS 103. As a result, when only the FCS 103 is operated, the hydraulic pressure supplied to oil passages 41 and 43 is supplied (recirculated) to the FCS 103 via the bypass oil passage 541, bypassing the pressure reducing valves 21 and 22. This creates a flow path through which hydraulic pressure is supplied to the FCS 103, bypassing the pressure reducing valves 21 and 22. Therefore, pressure loss in the pressure reducing valves 21 and 22 can be reduced.

[0112] Furthermore, as shown in the seventh modified example in Figure 13, a switching valve 583, which is a shut-off valve, may be provided. That is, the switching valve 583 functions as an example of a "shut-off valve" within the scope of the claims, similar to the shut-off valve 581 in the fifth modification shown in Figure 11. Specifically, when operating the leg lifting system 102 (high-pressure operating part), the switching valve 583 connects the oil passage between the confluence of oil passages 41 and 42 and the leg lifting system 102, and when operating only the FCS 103 (low-pressure operating part), it switches the connection mode to connect the oil passage between the input side of the leg lifting system 102 and the oil passage before the check valve 92 in the return passage 90 on the output side. As a result, when the leg lifting system 102 is not operated, the switching valve 583 shuts off the supply of hydraulic pressure to the leg lifting system 102, and the hydraulic pressure supplied to the leg lifting system 102 and the hydraulic pressure upstream of the leg lifting system 102 can be released into the return passage 90. By releasing the hydraulic pressure in this manner when stopping the operation of the leg lifting system 102 (high-pressure operating part), malfunction of the leg lifting system 102 can be prevented.

[0113] Furthermore, as shown in the eighth modified example in Figure 14, a switching valve 584 may be arranged. Similar to the sixth and seventh modified examples, when operating the leg lifting system 102 (high-pressure operating section), the switching valve 584 connects the oil passage between the confluence of oil passages 41 and 42 and the leg lifting system 102. When operating only the FCS 103 (low-pressure operating section), the switching valve 584 connects the confluence of oil passages 41 and 42 to the confluence of oil passages 43 and 44, as in the switching valve 582 of the sixth modified example, and simultaneously switches the connection mode to connect the oil passage between the input side of the leg lifting system 102 and the oil passage before the check valve 92 on the output side (upstream side), as in the switching valve 583 of the seventh modified example. This makes it possible to both supply (recirculate) the hydraulic pressure supplied to oil passages 41 and 42 to the FCS 103 and prevent malfunction of the leg lifting system 102. In other words, the switching valve 584 in the eighth modification is an example of a "shut-off valve" within the claims, and also serves as a bypass valve that switches the flow of hydraulic fluid to the bypass oil passage 541. Furthermore, the significance of this eighth modification lies in the fact that both of the above can be achieved with a single switching valve 584, thus preventing complexity of the circuit configuration. In addition, in this eighth modification, the pressure reducing valves 21 and 22 are bypassed, similar to the sixth modification, thus reducing pressure loss in the pressure reducing valves 21 and 22. When switching valves 582 to 584 are arranged as in the sixth to eighth modifications, the switching valves 582 to 584 may be made redundant. Also, when switching valves 583 and 584 are arranged as in the seventh and eighth modifications, it is preferable to arrange them downstream of the check valves 31 and 32.

[0114] Furthermore, as shown in the ninth modified example in Figure 15, when the system is configured so that hydraulic pressure is not supplied to the leg lifting system 102 (high-pressure operating section) as in the fifth modified example, a hydraulically driven shut-off valve 585 may be installed instead of the electrically driven shut-off valve 581. In the ninth modified example shown in Figure 15, the shut-off valve 585 is configured to open the passage when the upstream hydraulic pressure is above a predetermined value and to close the passage when it is below the predetermined value. The shut-off valve 585 does not open or close by control processing by the control unit 60, but opens and closes automatically according to the upstream hydraulic pressure. The shut-off valve 585 is a so-called sequence valve. For example, the shut-off valve 585 is configured to open the passage when the upstream hydraulic pressure is a relatively high operating hydraulic pressure for operating the leg lifting system 102, and to close the passage when the upstream hydraulic pressure is a relatively low operating hydraulic pressure for operating the FCS 103 (low-pressure operating section). Even when a sequence valve shut-off valve is installed, the shut-off valves may be made redundant by installing a shut-off valve in each of the branched oil passages 41 and 42.

[0115] Furthermore, as shown in the 10th modified example in Figure 16, when the system is configured so that hydraulic pressure is not supplied to the leg lifting system 102 (high-pressure operating part) as in the 5th modified example, a switching valve 586a may be placed in the oil passage 41 and a switching valve 586b may be placed in the oil passage 42. The switching valves 586a and 586b are directional control valves. The switching valves 586a and 586b are connected to the downstream side of the oil passages 41 and 42 when the hydraulic pressure on the upstream side of the oil passages 41 and 42 is above a predetermined value, and are connected to the low-pressure oil passages 43 and 44 when the hydraulic pressure on the upstream side is below a predetermined value. The switching valves 586a and 586b, like the shut-off valve 585 in the 9th modified example, automatically switch the flow path according to the hydraulic pressure on the upstream side. For example, the switching valves 586a and 586b are connected to the downstream side of oil passages 41 and 42 when the oil pressure on the upstream side of oil passages 41 and 42 is a relatively high operating oil pressure required to operate the leg lifting system 102, and are connected to the low-pressure side oil passages 43 and 44 when the oil pressure on the upstream side is a relatively low operating oil pressure required to operate the FCS 103 (low-pressure operating section).

[0116] In other words, when the hydraulic pressure on the upstream side is less than a predetermined value, the switching valves 586a and 586b shut off the connection between the upstream and downstream sides of the oil passages 41 and 42. Therefore, the switching valves 586a and 586b have the function of shutting off the supply of hydraulic pressure to the high-pressure operating section. Thus, the switching valves 586a and 586b are examples of "shut-off valves" within the scope of the claims. Furthermore, the switching valves 586a and 586b connect the upstream sides of the oil passages 41 and 42 to the low-pressure oil passages 43 and 44, respectively, via bypass oil passages 541a and 541b. Bypass oil passage 541a supplies hydraulic pressure from the hydraulic source 11, which is a common hydraulic pressure source, to the FCS 103, which is a low-pressure operating section, while bypassing the pressure reducing valve 21. The bypass oil passage 541b supplies hydraulic pressure from the hydraulic source 12, which is a common hydraulic power source, to the FCS 103, which acts as a low-pressure operating unit, while bypassing the pressure reducing valve 22. Here, the switching valves 586a and 586b are connected to the downstream side of the oil passages 42 and 43, respectively, from the pressure reducing valves 21 and 22. Therefore, the switching valves 586a and 586b function as bypass valves, supplying hydraulic pressure to the downstream side of the pressure reducing valves 21 and 22 by bypassing them.

[0117] Furthermore, in the sixth, eighth, and tenth modifications described above, examples were shown in which switching valves 582, 584, 586a, and 586b are arranged, which also serve as shut-off valves to block the supply of hydraulic pressure to the leg lifting system 102 (high-pressure operating section) and as bypass valves to supply hydraulic pressure from the hydraulic power source 11 and the hydraulic power source 12 (common hydraulic power source) to the FCS 103 (low-pressure operating section) via bypass oil passages 541, 541a, and 541b. However, the present invention is not limited thereto. In the present invention, a shut-off valve that blocks the supply of hydraulic pressure to the high-pressure operating section and a bypass valve that switches the flow of hydraulic fluid to the bypass oil passage that bypasses the pressure reducing valve may be arranged separately from each other. For example, a bypass valve that opens and closes the flow of hydraulic fluid may be arranged separately from the shut-off valve in a bypass oil passage that is arranged parallel to the pressure reducing valve so as to connect the upstream and downstream sides of the pressure reducing valve. In this case, the bypass valve may be a solenoid valve whose opening and closing is controlled by a control unit, or it may be a sequence valve that opens and closes in accordance with the hydraulic pressure on the upstream side. In other words, the bypass valve switches between supplying hydraulic pressure to the low-pressure operating section via the pressure reducing valve and supplying hydraulic pressure to the low-pressure operating section via the bypass oil passage by opening and closing it. When the bypass valve is open, it supplies hydraulic pressure to the low-pressure operating section via the bypass oil passage, and when it is closed, it shuts off the bypass oil passage and supplies hydraulic pressure to the low-pressure operating section via the pressure reducing valve. Therefore, when supplying hydraulic pressure to the low-pressure operating section, it is possible to switch whether or not to use the pressure reducing valve by switching whether or not to use the bypass oil passage with the bypass valve. Thus, for example, it is possible to switch whether or not to use the pressure reducing valve by considering whether or not the pressure reducing valve becomes a resistive element due to the hydraulic pressure supplied to the low-pressure operating section.

[0118] 11 Hydraulic source (common hydraulic source, first common hydraulic source) 12 Hydraulic source (common hydraulic source, second common hydraulic source) 21 Pressure reducing valve (first pressure reducing valve) 22 Pressure reducing valve (second pressure reducing valve) 31 Check valve (first check valve, high-pressure side check valve) 32 Check valve (second check valve, high-pressure side check valve) 33 Check valve (first check valve, low-pressure side check valve) 34 Check valve (second check valve, low-pressure side check valve) 51, 52 Pressure gauge 60, 260 Control unit 100, 200, 300 Hydraulic system (aircraft hydraulic system) 101 Aircraft 102 Landing gear system (high-pressure operating part) 102a Landing gear 102c Actuator (high-pressure actuator) 103 Flight control system (low-pressure operating part) 103a Control surface 103b Actuators (low-pressure actuators) 302, 402 High-pressure operating section 303 First low-pressure operating section (low-pressure operating section) 305 Second low-pressure operating section (low-pressure operating section) 311, 411 Common hydraulic power source 321, 323, 421 Pressure reducing valve 403 Low-pressure operating section 431, 432a, 432b, 433 Check valves 541, 541a, 541b Bypass oil passages 581, 585 Shut-off valves 582, 583, 584, 586a, 586b Switching valve (shut-off valve)

Claims

1. An aircraft hydraulic system comprising: a low-pressure operating unit located in the aircraft and operated by a relatively low operating hydraulic pressure; a common hydraulic source that supplies hydraulic pressure to both a low-pressure operating unit located separately in the aircraft and operated by a relatively high operating hydraulic pressure; and a pressure reducing valve that reduces the hydraulic pressure supplied to the low-pressure operating unit.

2. The aircraft hydraulic system according to claim 1, wherein the common hydraulic source includes a hydraulic pump that discharges hydraulic fluid to supply hydraulic pressure in common to the low-pressure operating section and the high-pressure operating section, and a motor that serves as a drive source for the hydraulic pump.

3. The aircraft hydraulic system according to claim 1 or 2, further comprising: a pressure gauge for detecting the output pressure of the common hydraulic source; and a control unit for controlling the operation of the common hydraulic source by hydraulic feedback control using the output pressure detected by the pressure gauge.

4. The aircraft hydraulic system according to claim 1 or 2, wherein the common hydraulic power source switches and outputs either a relatively low operating hydraulic pressure for operating the low-pressure operating section or a relatively high operating hydraulic pressure for operating the high-pressure operating section, depending on the operating state of the low-pressure operating section and the high-pressure operating section.

5. The aircraft hydraulic system according to claim 4, wherein the common hydraulic source outputs a relatively low operating hydraulic pressure for operating the low-pressure operating unit during periods when the high-pressure operating unit is not operating, and outputs a relatively high operating hydraulic pressure for operating the high-pressure operating unit during periods when the high-pressure operating unit is operating.

6. The aircraft hydraulic system according to claim 5, further comprising a high-pressure side check valve that suppresses backflow of hydraulic fluid from the high-pressure operating section to the common hydraulic source.

7. The aircraft hydraulic system according to claim 1 or 2, wherein the common hydraulic source supplies hydraulic pressure in common to the low-pressure operating section that operates the control surfaces in the aircraft and the high-pressure operating section that operates the landing gear in the aircraft.

8. The aircraft hydraulic system according to claim 1 or 2, wherein the common hydraulic source stops supplying hydraulic fluid during periods when the operation of both the low-pressure operating unit and the high-pressure operating unit is stopped.

9. The aircraft hydraulic system according to claim 1 or 2, wherein the common hydraulic source includes a first common hydraulic source and a second common hydraulic source that independently supply hydraulic pressure to the low-pressure operating section and the high-pressure operating section.

10. The aircraft hydraulic system according to claim 9, wherein the pressure reducing valve includes a first pressure reducing valve for reducing the hydraulic pressure supplied from the first common hydraulic source to the low-pressure operating unit, and a second pressure reducing valve, which is disposed separately from the first pressure reducing valve and for reducing the hydraulic pressure supplied from the second common hydraulic source to the low-pressure operating unit.

11. The aircraft hydraulic system according to claim 9, further comprising: a first check valve for suppressing backflow of hydraulic fluid to the first common hydraulic source; and a second check valve, disposed separately from the first check valve, for suppressing backflow of hydraulic fluid to the second common hydraulic source.

12. The aircraft hydraulic system according to claim 9, wherein the common hydraulic source supplies hydraulic pressure to both the low-pressure operating section and the high-pressure operating section from both the first common hydraulic source and the second common hydraulic source.

13. The aircraft hydraulic system according to claim 9, wherein the common hydraulic source supplies hydraulic pressure to the low-pressure operating section and the high-pressure operating section from the first common hydraulic source while stopping the supply of hydraulic pressure from the second common hydraulic source when the first common hydraulic source is functioning normally, and supplies hydraulic pressure to the low-pressure operating section and the high-pressure operating section from the second common hydraulic source while stopping the supply of hydraulic pressure from the first common hydraulic source when the first common hydraulic source is malfunctioning.

14. The aircraft hydraulic system according to claim 1 or 2, wherein the pressure reducing valve is configured to reduce the supplied hydraulic pressure by allowing hydraulic fluid to flow from the upstream side to the downstream side when the downstream pressure is less than a predetermined pressure, and by blocking the flow of hydraulic fluid from the upstream side to the downstream side when the downstream pressure exceeds a predetermined pressure.

15. The aircraft hydraulic system according to claim 1 or 2, further comprising: a low-pressure actuator that operates with a relatively low operating hydraulic pressure in the low-pressure operating section; and a high-pressure actuator that operates with a relatively high operating hydraulic pressure in the high-pressure operating section.

16. The aircraft hydraulic system according to claim 1 or 2, further comprising a check valve that suppresses backflow of hydraulic fluid from the low-pressure operating section and the high-pressure operating section to the common hydraulic source.

17. The aircraft hydraulic system according to claim 16, wherein a plurality of check valves are arranged in parallel with respect to the common hydraulic source.

18. The aircraft hydraulic system according to claim 16, comprising, as the check valve, a high-pressure side check valve that suppresses the flow of hydraulic fluid from the high-pressure operating unit to the common hydraulic source, and a low-pressure side check valve that suppresses the flow of hydraulic fluid from the low-pressure operating unit to the common hydraulic source.

19. The aircraft hydraulic system according to claim 1 or 2, further comprising a shut-off valve for cutting off the supply of hydraulic pressure to the high-pressure operating section.

20. The aircraft hydraulic system according to claim 1 or 2, further comprising a bypass oil passage that supplies hydraulic pressure from the common hydraulic source to the low-pressure operating section while bypassing the pressure reducing valve.

21. A control method for an aircraft hydraulic system, comprising: a step of acquiring the operating state of a low-pressure operating unit that operates with a relatively low operating hydraulic pressure and is located on an aircraft, and a high-pressure operating unit that operates with a relatively high operating hydraulic pressure and is located on the aircraft separately from the low-pressure operating unit; and a step of controlling the operation of a common hydraulic source that supplies hydraulic pressure to both the low-pressure operating unit and the high-pressure operating unit, wherein the step of controlling the operation of the common hydraulic source involves switching between and executing the following: a control that supplies a relatively high operating hydraulic pressure to the high-pressure operating unit by operating the common hydraulic source to output a relatively high operating hydraulic pressure for operating the high-pressure operating unit, while simultaneously supplying a relatively low operating hydraulic pressure to the low-pressure operating unit via a pressure reducing valve that reduces the supplied hydraulic pressure, and a control that supplies a relatively low operating hydraulic pressure to the low-pressure operating unit by operating the common hydraulic source to output a relatively low operating hydraulic pressure for operating the low-pressure operating unit.

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