Hydraulic system for aircraft and inscription gear pump for aircraft
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- SUMITOMO PRECISION PRODUCTS CO LTD
- Filing Date
- 2023-06-23
- Publication Date
- 2026-06-24
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
[Technical field]
[0001] The present disclosure relates to an aircraft hydraulic system and an aircraft internal gear pump. [Background technology]
[0002] Patent Document 1 describes a conventional hydraulic system for an aircraft. The conventional hydraulic system includes a hydraulic cylinder that retracts and deploys the landing gear of the aircraft from the fuselage, a hydraulic motor that drives the wheels attached to the landing gear, and an electric hydraulic pump that supplies hydraulic pressure to the hydraulic cylinder and the hydraulic motor. The electric hydraulic pump is, for example, a piston pump. [Prior art documents] [Patent documents]
[0003] [Patent Document 1] JP 2014-132189 A Summary of the Invention [Problem to be solved by the invention]
[0004] Conventional aircraft hydraulic systems are equipped with piston pumps, as described above. This is because hydraulic pumps in aircraft hydraulic systems are required to have the following performance characteristics: (1) the ability to supply high-pressure hydraulic oil to hydraulic equipment, and (2) the ability to be used over a wide range of flow rates from low to high. In particular, in hydraulic systems for flight control actuators such as aileron actuators, elevator actuators, or rudder actuators, the hydraulic pumps are strongly required to satisfy the performance requirements (1) and (2) above. Piston pumps have relatively high volumetric efficiency and can employ a variable volume structure, so they can satisfy the performance requirements (1) and (2) above.
[0005] However, piston pumps are expensive due to their complex structure, and they also have the disadvantage that their sliding parts are prone to wear and are relatively susceptible to contamination.
[0006] Hydraulic pumps of types other than piston pumps have not been adopted in aircraft hydraulic systems so far. This is because it is difficult for hydraulic pumps of types other than piston pumps to meet the performance requirements (1) and (2) above. For example, internal gear pumps have a simple structure and are therefore low cost. In addition, internal gear pumps have the advantages that the material of the sliding parts is resistant to wear, and the structure of the internal gear pump provides forced lubrication, making them less susceptible to wear and moreover resistant to contamination. However, it is difficult for conventional internal gear pumps to meet the performance requirements (1) and (2) above.
[0007] The technology disclosed herein provides an aircraft hydraulic system using an internal gear pump, and an internal gear pump suitable for aircraft hydraulic systems. [Means for solving the problem]
[0008] The present disclosure relates to an aircraft hydraulic system. a hydraulic pump connected to at least one hydraulic device of an aircraft via a supply line and configured to supply hydraulic fluid to the hydraulic device through the supply line; a prime mover connected to the hydraulic pump and configured to drive the hydraulic pump; a controller electrically connected to the prime mover and controlling the prime mover to change the rotation speed of the hydraulic pump in accordance with the required flow rate of the hydraulic equipment; The hydraulic pump is a multi-stage internal gear pump having multiple gear sets, each including a pinion gear and a ring gear that mesh with each other, and in which the discharge portion of each stage is connected in series with the suction portion of the next stage.
[0009] The hydraulic system uses a hydraulic pump to supply hydraulic fluid to hydraulic equipment of an aircraft. The hydraulic equipment may be a hydraulic actuator, a hydraulic motor, or both a hydraulic actuator and a hydraulic motor. The hydraulic pump is driven by a prime mover. The prime mover may be an engine or an electric motor. The hydraulic pump, driven by the prime mover, supplies hydraulic fluid to the hydraulic equipment through a supply line.
[0010] The hydraulic pump is an internal gear pump. More specifically, the internal gear pump is a multi-stage internal gear pump having a plurality of gear sets, with ports of the plurality of gear sets connected in series.
[0011] Multi-stage internal gear pumps can supply high-pressure hydraulic oil to hydraulic equipment. Generally, internal gear pumps are less efficient at high pressures than piston pumps, and are more likely to seize at high pressures. However, multi-stage internal gear pumps use multiple gear sets to increase pressure, which reduces the load on the gear sets. Multi-stage internal gear pumps can suppress the occurrence of seizure.
[0012] A multi-stage inscribing gear pump with variable rotation speed can be used in a wide range of flow rates, from low to high. The multi-stage inscribing gear pump itself cannot change its discharge flow rate. However, if the rotation speed of the pump is changed, the discharge flow rate of the multi-stage inscribing gear pump changes. The rotation speed of the inscribing gear pump is changed by a controller. Through control of the prime mover, the controller changes the rotation speed of the multi-stage inscribing gear pump according to the flow rate required by the hydraulic equipment.
[0013] An aircraft hydraulic system equipped with a multi-stage internal gear pump (1) can supply high-pressure hydraulic oil to hydraulic equipment and (2) can be used over a wide range of flow rates, from low to high.
[0014] The aircraft hydraulic system comprises: a bypass passage directly or indirectly connected to the internal gear pump, which returns at least a portion of the hydraulic oil from the internal gear pump to a tank while bypassing the hydraulic device; The system may further include a valve located on the bypass passage, the valve opening the bypass passage when the required flow rate is low and closing the bypass passage when the required flow rate is high.
[0015] If the hydraulic device is a flight control actuator, the hydraulic system may be required to maintain high hydraulic fluid pressure while providing zero or near zero flow to the hydraulic device, and the high pressure and substantially zero flow conditions may continue for long periods of time.
[0016] When the valve opens the bypass passage when flow demand is low, at least a portion of the hydraulic fluid from the internal gear pump driven by the prime mover is returned to the tank through the bypass passage. The driven internal gear pump can maintain a high hydraulic fluid pressure in the supply passage. Meanwhile, the hydraulic fluid flow rate to the hydraulic equipment is reduced because at least a portion of the hydraulic fluid bypasses the hydraulic equipment. The hydraulic system can maintain a high hydraulic fluid pressure while reducing or eliminating the supply flow rate to the hydraulic equipment.
[0017] Furthermore, under conditions of high pressure and substantially zero flow rate, hydraulic oil passes through the driven internal gear pump and circulates through the hydraulic system. The hydraulic oil that has received heat inside the internal gear pump can transport the received heat to the outside of the internal gear pump. In other words, even if the flow rate supplied to the hydraulic equipment is zero or nearly zero, the internal gear pump is cooled by the hydraulic oil circulating through the hydraulic system. When the conditions of high pressure and substantially zero flow rate continue for a long period of time, seizure of the internal gear pump is prevented.
[0018] On the other hand, when the required flow rate of the hydraulic system is high, the valve closes the bypass passage. The hydraulic oil discharged by the internal gear pump is supplied to the hydraulic equipment through the supply passage. The hydraulic system can satisfy the required flow rate. The hydraulic system can achieve a wide range of flow rates, from low to high.
[0019] the internal gear pump has a drain port for discharging hydraulic oil leaked from within the internal gear pump to the outside of the internal gear pump, The bypass passage may be connected to the drain port.
[0020] An internal gear pump having a drain port can increase the amount of hydraulic oil discharged through the drain port, thereby reducing the flow rate of hydraulic oil discharged from the internal gear pump. A hydraulic system having an internal gear pump having a drain port can achieve a wide range of flow rates, from low to high. In addition, a hydraulic system having an internal gear pump having a drain port can reduce the flow rate of hydraulic oil supplied to hydraulic equipment while maintaining the pressure of the hydraulic oil at a high pressure.
[0021] The bypass passage may branch off from the supply passage connected to the hydraulic pump.
[0022] When the valve opens the bypass passage when the required flow rate is low, at least a portion of the hydraulic oil discharged from the internal gear pump to the supply passage returns to the tank through the bypass passage. The driven internal gear pump can maintain the pressure of the hydraulic oil in the supply passage at high pressure. Meanwhile, because at least a portion of the hydraulic oil bypasses the hydraulic equipment, the flow rate of the hydraulic oil supplied to the hydraulic equipment is reduced. The hydraulic system can reduce the supply flow rate to the hydraulic equipment to zero or nearly zero while maintaining a high pressure of the hydraulic oil. Also, when a state of high pressure and substantially zero flow rate continues for a long period of time, the internal gear pump is prevented from seizing.
[0023] The aircraft hydraulic system may further include a bypass path branching off from the supply path connected to the inscribed gear pump, the bypass path returning at least a portion of the hydraulic oil from the inscribed gear pump to a tank, bypassing the hydraulic equipment.
[0024] The valve in the bypass path can be omitted. Even if there is no valve in the bypass path, it is possible to achieve a wide range of flow rates from low to high, and to achieve a state of high pressure and substantially zero flow rate, by changing the rotation speed of the internal gear pump and combining it with a bypass path connected to the internal gear pump.
[0025] the internal gear pump has a drain port for discharging hydraulic oil leaked from within the internal gear pump to the outside of the internal gear pump, The aircraft hydraulic system may further include a bypass path connected to the drain port, the bypass path returning hydraulic oil discharged from the drain port to a tank, bypassing the hydraulic equipment.
[0026] This aircraft hydraulic system does not have a valve on the bypass passage. If the drain passage of the internal gear pump is designed so that the flow rate of the hydraulic oil discharged from the drain port is an appropriate flow rate, the hydraulic system can simultaneously achieve a wide range of flow rates from low to high, and a state of high pressure and substantially zero supply flow rate, by changing the rotation speed of the internal gear pump.
[0027] The internal gear pump comprises: a shaft supporting the gear set; a housing that supports the shaft and accommodates the rotating gear set; The compressor may have a drain passage extending from a high pressure portion of the housing, through a gap between the gear set and the housing, and around the shaft, to the drain port opening into the housing.
[0028] As described above, in an aircraft hydraulic system, a multi-stage internal gear pump having a drain passage and a drain port can satisfy the following requirements: (1) supplying high-pressure hydraulic oil to hydraulic equipment; and (2) use over a wide range of flow rates, from low to high, by combining changing the rotational speed of the internal gear pump with connecting a bypass passage to the drain port.
[0029] The hydraulic equipment may include flight control actuators and take-off and landing actuators.
[0030] The flight control actuators include at least one of an aileron actuator, an elevator actuator, and a rudder actuator. The flow rate of hydraulic fluid required to operate the flight control actuators is relatively low. The flight control actuators may require the hydraulic system to maintain a high pressure and substantially zero flow rate for a long period of time. For example, when an aircraft is flying stably with the angles of the ailerons, elevators, and rudder maintained constant, the hydraulic system is required to maintain a high pressure and substantially zero flow rate to the flight control actuators for a long period of time. The aileron actuator, elevator actuator, and rudder actuator are primary flight control actuators.
[0031] The flight control actuators may include secondary flight control actuators, such as flap actuators, slat actuators, or both flap actuators and slat actuators. The secondary flight control actuators require a moderate flow rate of hydraulic fluid to operate and have a relatively short duration of operation.
[0032] The takeoff and landing actuators include at least one of a gear actuator for raising and lowering the landing gear, a door actuator for opening and closing the door of the hangar, and a down-lock release actuator for releasing a down-lock mechanism for fixing the landing gear in a lowered state. The takeoff and landing actuators have a large stroke, and therefore require a relatively high flow rate of hydraulic oil for operation. In addition, the operation duration of the takeoff and landing actuators is relatively short.
[0033] The hydraulic system described above can change the discharge flow rate of the internal gear pump over a wide range from a low flow rate range to a high flow rate range, and can maintain a high pressure and substantially zero supply flow rate to the flight control actuators for a long period of time. The hydraulic system is suitable for use in aircraft hydraulic systems including flight control actuators and takeoff and landing actuators.
[0034] The technology disclosed herein relates to an internal gear pump for aircraft that supplies hydraulic oil to hydraulic equipment of an aircraft. a shaft to which the prime mover is connected; a gear set including a pinion gear supported by the shaft and a ring gear meshing with the pinion gear, the gear sets including a plurality of gear sets having hydraulic oil ports connected in series; a housing that supports the shaft and accommodates the rotating gear set; a drain port that opens into the housing and that drains hydraulic oil leaking from within the pump to the outside of the pump; A drain passage extends from a high pressure portion of the housing, through a gap between the gear set and the housing, and around the shaft, to the drain port.
[0035] A multi-stage internal gear pump having a drain passage and a drain port has a relatively low volumetric efficiency. However, as described above, a multi-stage internal gear pump having a relatively low volumetric efficiency is suitable as a hydraulic pump for an aircraft hydraulic system that is required to at least (1) supply high-pressure hydraulic oil to hydraulic equipment and (2) be used over a wide range of flow rates from low to high. Effect of the Invention
[0036] As described above, the aircraft hydraulic system disclosed herein can supply high-pressure hydraulic oil to hydraulic equipment and can be used over a wide range of flow rates from low to high. Furthermore, the aircraft internal gear pump disclosed herein is suitable for aircraft hydraulic systems. [Brief description of the drawings]
[0037] [Figure 1] FIG. 1 shows an aircraft hydraulic system. [Diagram 2] FIG. 2 illustrates the arrangement of hydraulic actuators on an aircraft. [Diagram 3] FIG. 3 is a cross-sectional view of an internal gear pump. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 5 is an enlarged view of the inside of the internal gear pump. [Figure 6] FIG. 6 shows a modification of an aircraft hydraulic system. [Figure 7] FIG. 7 shows a modified example of an aircraft hydraulic system. [Figure 8] FIG. 8 shows a modified example of an aircraft hydraulic system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0038] Hereinafter, an embodiment of an aircraft hydraulic system and an aircraft internal gear pump will be described with reference to the drawings. The aircraft hydraulic system and the aircraft internal gear pump described here are merely examples.
[0039] (Hydraulic system configuration) Fig. 1 shows a hydraulic system 1. The hydraulic system 1 is a hydraulic system for an aircraft. Fig. 2 shows an aircraft equipped with the hydraulic system 1. The hydraulic system 1 is a system for supplying hydraulic oil to each of a plurality of hydraulic devices. The hydraulic system 1 includes a hydraulic circuit 10 including the plurality of hydraulic devices.
[0040] The hydraulic equipment includes, for example, the following hydraulic actuators 21-26. That is, as shown in Fig. 1 or 2, the hydraulic equipment includes an aileron actuator 21, an elevator actuator 22, a rudder actuator 23, a flap actuator 24, a slat actuator 25, and a landing gear extension actuator 26. The landing gear extension actuator 26 includes, for example, at least one actuator selected from a gear actuator, a door actuator, and a down lock release actuator. The gear actuator is an actuator that raises and lowers the landing gear strut. The door actuator is an actuator that opens and closes the door of the hangar that houses the landing gear. The down lock release actuator is an actuator that releases a down lock mechanism that fixes the landing gear strut in a lowered state.
[0041] 2, the aircraft 2 has multiple hydraulic actuators for each of the aileron actuator 21, elevator actuator 22, rudder actuator 23, flap actuator 24, slat actuator 25, and landing gear extension / retraction actuator 26. In the following description, each of the aileron actuator 21, elevator actuator 22, rudder actuator 23, flap actuator 24, slat actuator 25, and landing gear extension / retraction actuator 26 includes multiple hydraulic actuators.
[0042] The hydraulic system 1 may supply hydraulic oil to some of the hydraulic actuators 21-26. The hydraulic system 1 may supply hydraulic oil to hydraulic devices other than the hydraulic actuators 21-26.
[0043] The hydraulic actuators 21-26 are telescopic actuators having, for example, a cylinder and a piston. The aileron actuator 21, the elevator actuator 22, and the rudder actuator 23 are flight control actuators that operate during cruising flight of the aircraft 2 and during takeoff and landing. The flight control actuators have a relatively short stroke and operate continuously for long periods of time while the aircraft 2 is in flight. The pressure required to operate the flight control actuators is relatively high. In addition, the flow rate of hydraulic oil required to operate the flight control actuators is relatively low.
[0044] The flight control actuators may require the hydraulic system 1 to maintain a high pressure while the flow rate is zero or substantially zero. For example, while the aircraft 2 is flying stably, the angles of the ailerons, elevators, and rudder are maintained at constant angles, that is, the flow rate supplied to the flight control actuators is zero or substantially zero. Meanwhile, by maintaining the pressure of the hydraulic oil in the hydraulic circuit 10 at high pressure, the responsiveness of the flight control actuators to operation commands is improved. The state in which the hydraulic circuit 10 is in a high pressure state and the flow rate is zero or substantially zero may continue for a long period of time.
[0045] The flap actuator 24 and the slat actuator 25 are also included in the flight control actuators. The flap actuator 24 and the slat actuator 25 are secondary flight control actuators. The flap actuator 24 and the slat actuator 25 have a medium stroke and operate temporarily when the aircraft 2 takes off and lands. The aileron actuator 21, the elevator actuator 22, and the rudder actuator 23 are primary flight control actuators. Hereinafter, the aileron actuator 21, the elevator actuator 22, the rudder actuator 23, the flap actuator 24, and the slat actuator 25 may be collectively referred to as the flight control actuators 21-25.
[0046] The landing gear retraction / extension actuator 26 is an example of a takeoff / landing actuator that operates during takeoff and landing of the aircraft 2. The landing gear retraction / extension actuator 26 has a relatively long stroke, and operates temporarily during takeoff and landing of the aircraft 2. The pressure required for operation of the landing gear retraction / extension actuator 26 is relatively high. In addition, the flow rate of hydraulic oil required for operation of the landing gear retraction / extension actuator 26 is relatively high.
[0047] The hydraulic system 1 for an aircraft is required to have the following performance: (1) the ability to supply high-pressure hydraulic oil to the hydraulic actuators 21-26, (2) the ability to be used over a wide range of flow rates from low to high, and (3) the ability to maintain the hydraulic circuit 10 in a high-pressure state with a zero or near-zero flow rate for an extended period of time.
[0048] The hydraulic system 1 includes a hydraulic pump 7. The structure of the hydraulic pump 7 will be described later. A discharge port 85 of the hydraulic pump 7 is connected to a supply path 41. The supply path 41 is connected to each of the hydraulic actuators 21-26. Each of the hydraulic actuators 21-26 is connected in parallel to the hydraulic pump 7. The hydraulic pump 7 supplies hydraulic oil via the supply path 41 individually to each of the aileron actuator 21, elevator actuator 22, rudder actuator 23, flap actuator 24, slat actuator 25, and landing gear extension / retraction actuator 26.
[0049] The suction port 84 of the hydraulic pump 7 is connected to a return path 42. The return path 42 connects the hydraulic pump 7 to each of the hydraulic actuators 21-26. A tank 43 is connected to the return path 42. The tank 43 is a reservoir that stores hydraulic oil. The return path 42 includes a first return path 42a from each of the hydraulic actuators 21-26 to the tank 43, and a second return path 42b from the tank 43 to the hydraulic pump 7.
[0050] The hydraulic circuit 10 is a circulation circuit made up of the hydraulic actuators 21-26, the hydraulic pump 7, a supply path 41, a return path 42, and a tank 43. As shown by solid arrows in Fig. 1, the hydraulic oil flows from the tank 43 through the second return path 42b, the hydraulic pump 7, the supply path 41, the hydraulic actuators 21-26, and the first return path 42a, and returns to the tank 43.
[0051] The hydraulic circuit 10 has a bypass path 44. Note that the bypass path 44 is not an essential element of the hydraulic system disclosed herein. The bypass path 44 is connected to a drain port 86 (described later) of the hydraulic pump 7. The bypass path 44 bypasses each of the hydraulic actuators 21-26 and is connected to the first return path 42a.
[0052] The hydraulic circuit 10 has a valve 45. The valve 45 is not an essential element of the hydraulic system disclosed herein. The valve 45 is located in the middle of the bypass passage 44. The valve 45 is an open / close valve that switches the bypass passage 44 between an open state and a closed state. The valve 45 is normally open. A pilot line 48 of the valve 45, shown by a dashed line in FIG. 1, is connected to the front and rear of a throttle 47 located in the supply passage 41. When the pressure difference between the front and rear of the throttle 47 is small, the valve 45 opens the bypass passage 44. When the bypass passage 44 is open, the hydraulic oil discharged from the drain port 86 returns to the tank 43 without being supplied to each hydraulic actuator 21-26, as shown by the two-dot chain arrow in FIG. 1. When the pressure difference between the front and rear of the throttle 47 is large, the valve 45 closes the bypass passage 44. When the bypass passage 44 is closed, the discharge of the hydraulic oil from the drain port 86 stops.
[0053] A prime mover is connected to the hydraulic pump 7. The prime mover drives the hydraulic pump 7. The prime mover may be, for example, an electric motor 5. The electric motor 5 may be, for example, a servo motor. The prime mover may be an engine.
[0054] A controller 6 is electrically connected to the electric motor 5. A pressure sensor 61 is also electrically connected to the controller 6. Note that the pressure sensor 61 is not an essential element of the hydraulic system disclosed herein. The pressure sensor 61 is connected to the supply path 41. The pressure sensor 61 outputs a measurement signal corresponding to the pressure of the hydraulic oil in the supply path 41 to the controller 6. The pressure of the hydraulic oil in the supply path 41 is related to the supply flow rate to the hydraulic actuators 21-26 and the required flow rate of the hydraulic actuators 21-26.
[0055] The controller 6 is connected to a host controller. The host controller is, for example, a flight controller. The controller 6 receives a signal related to a required flow rate, which is a signal output from the host controller. The required flow rate is a flow rate of hydraulic oil required for the flight control actuators 21-25, the landing gear retraction actuator 26, or both the flight control actuators 21-25 and the landing gear retraction actuator 26 to operate. The host controller transmits the signal related to the required flow rate to the controller 6 in response to an operation by the pilot of the aircraft 2, in response to the flight status of the aircraft 2, or in response to both the operation and the flight status.
[0056] The controller 6 outputs a control signal to the electric motor 5 in response to the measurement signal of the pressure sensor 61 and a signal related to the required flow rate from a higher-level controller. The rotational speed of the electric motor 5 changes in response to the control signal from the controller 6. As the rotational speed of the electric motor 5 changes, the rotational speed of the hydraulic pump 7 changes, and the discharge flow rate of the hydraulic pump 7 changes. The flight control actuators 21-25 and the landing gear retraction / extension actuator 26, or the flight control actuators 21-25 and the landing gear retraction / extension actuator 26, are operated by the supply of hydraulic oil from the hydraulic pump 7. The control of the hydraulic system 1 will be described in detail later.
[0057] The sensor of the hydraulic system 1 is not limited to the pressure sensor 61. Furthermore, the hydraulic system 1 may include a plurality of hydraulic pumps 7 and electric motors 5 for redundancy.
[0058] (Pump structure) FIG. 3 illustrates a cross section of the hydraulic pump 7. FIG. 4 is a cross section taken along line IV-IV in FIG. 3. FIG. 5 shows an enlarged view of a portion of the cross section of the hydraulic pump 7. The hydraulic pump in a conventional aircraft hydraulic system is a piston pump. The piston pump has a relatively high volumetric efficiency and is efficient at high pressure. In addition, a variable displacement piston pump can change the supply flow rate to the hydraulic actuators 21-26. In contrast, the hydraulic pump 7 in the aircraft hydraulic system 1 disclosed herein is a multi-stage internal gear pump 70.
[0059] The inscribed gear pump 70 includes a plurality of gear sets. The illustrated inscribed gear pump 70 includes two gear sets 71, a first gear set 71a and a second gear set 71b. The number of gear sets 71 is determined according to the discharge pressure required for the inscribed gear pump 70. The number of gear sets 71 is not limited to two, and may be three or more. In the following description, the first and second gear sets 71a, 71b will be collectively referred to simply as the gear set 71.
[0060] The first gear set 71a and the second gear set 71b are arranged at a distance from each other along the shaft 76 of the inscribed gear pump 70. The shaft 76 extends in the left-right direction of the paper in Fig. 3. The shaft 76 is a rotating shaft that rotates around its central axis. The electric motor 5 is connected to a first end of the shaft 76, i.e., the left end in Fig. 3. In the following description, the direction in which the shaft 76 extends may be referred to as the axial direction of the inscribed gear pump 70.
[0061] The gear set 71 has a pinion gear 72 and a ring gear 74. The pinion gear 72 is fixed to a shaft 76. The pinion gear 72 and the shaft 76 are coaxial. When the shaft 76 rotates, the pinion gear 72 rotates together with the shaft 76. The pinion gears 72 of the first and second gear sets 71a, 71b rotate in the same direction. The pinion gear 72 has external teeth 721 as shown in FIG. 4.
[0062] The ring gear 74 meshes with the pinion gear 72. The ring gear 74 has internal teeth 741 on its inner circumferential surface. In the region on the left side of the page in FIG. 4, a portion of the external teeth 721 of the pinion gear 72 meshes with a portion of the internal teeth 741 of the ring gear 74. The ring gear 74 is eccentric with respect to the shaft 76. In FIG. 4, C1 is the center of rotation of the pinion gear 72, and C2 is the center of rotation of the ring gear 74.
[0063] The internal gear pump 70 includes a housing 80. The housing 80 includes a gear housing 77, a front cover 81, and a back cover 82. Note that the structure of the housing 80 described below is an example. Various structures can be used for the housing structure of the multi-stage internal gear pump 70.
[0064] The gear housing 77 accommodates the gear set 71. The internal gear pump 70 has two gear housings 77, a first gear housing 77a and a second gear housing 77b, corresponding to the first and second gear sets 71a and 71b. The first and second gear housings 77a and 77b are aligned along the shaft 76. The first and second gear housings 77a and 77b are fixed to each other to form an integrated unit. In the following description, the first and second gear housings 77a and 77b will be collectively referred to simply as the gear housing 77.
[0065] The gear housing 77 has a recess 78. The gear set 71 is accommodated in the recess 78. As also shown in FIG. 5, the recess 78 opens to a first side surface of the gear housing 77 and is recessed from the first side surface in the axial direction of the internal gear pump 70. In FIG. 3 or FIG. 5, the first side surface is the left side surface of the gear housing 77. As shown in FIG. 4, the recess 78 has a circular shape when viewed along the axis of the internal gear pump 70. The pinion gear 72 and the ring gear 74 can rotate within the recess 78.
[0066] The gear housing 77 has a crescent 79. The crescent 79 is located in a portion of the recess 78 where the pinion gear 72 and the ring gear 74 are no longer meshed with each other. Specifically, the crescent 79 is located in a region of the recess 78 on the right side of the paper in Fig. 4. The crescent 79 has a crescent shape when viewed along the axis of the internal gear pump 70.
[0067] The tips of the external teeth 721 of the pinion gear 72 abut against a first arc-shaped wall 791 of the crescent 79. The tips of the internal teeth 741 of the ring gear 74 abut against a second arc-shaped wall 792 of the crescent 79. The first arc-shaped wall 791 and the second arc-shaped wall 792 are both fixed walls that do not move toward the external teeth 721 and the internal teeth 741. The internal gear pump 70 is a fixed displacement pump with a constant pump capacity.
[0068] The gear housing 77 has a through hole 710. The through hole 710 penetrates the gear housing 77 in the axial direction of the internal gear pump 70. The shaft 76 is located within the through hole 710. The shaft 76 extends across the entirety of the integrated first and second gear housings 77a, 77b.
[0069] The gear housing 77 has a first port 73 and a second port 75. The first port 73 faces a port for sucking hydraulic oil into the recess 78. The first port 73 communicates with the recess 78 as shown by a dashed line in FIG. 4. The opening of the first port 73 extends in the circumferential direction near a first end of the crescent 79. The second port 75 is a port for discharging hydraulic oil from the recess 78. The second port 75 communicates with the recess 78 as shown by a dashed line in FIG. 4. The opening of the second port 75 extends in the circumferential direction near a second end of the crescent 79. The opening of the first port 73 and the opening of the second port 75 are located on opposite sides across the shaft 76. As shown in FIG. 3, the positions of the first port 73 and the second port 75 of the first gear housing 77a and the positions of the first port 73 and the second port 75 of the second gear housing 77b are reversed with respect to the shaft 76.
[0070] The first gear housing 77a has a first communication passage 711. The first communication passage 711 communicates between the second port 75 of the first gear housing 77a and the first port 73 of the second gear housing 77b. The second port 75 corresponds to a discharge portion of the first stage, and the first port 73 corresponds to a suction portion of a second stage next to the first stage. The second gear housing 77b has a second communication passage 712. The second communication passage 712 communicates between the second port 75 of the second gear housing 77b and a discharge port 85, which will be described later.
[0071] The front cover 81 is located axially adjacent to the first gear housing 77a and the internal gear pump 70. The front cover 81 is fixed to the first gear housing 77a.
[0072] The front cover 81 has a support hole 83. The support hole 83 penetrates the front cover 81 in the axial direction of the internal gear pump 70. The shaft 76 penetrates the support hole 83. The shaft 76 is supported by a bearing 831 fixed in the support hole 83.
[0073] The front cover 81 has a suction port 84. An inlet of the suction port 84 opens at a side surface of the front cover 81 and is connected to the return path 42 of the hydraulic circuit 10. An outlet of the suction port 84 opens at a rear surface of the front cover 81. With the front cover 81 fixed to the first gear housing 77a, the outlet of the suction port 84 faces the first port 73 of the first gear housing 77a and communicates with the recess 78.
[0074] The back cover 82 is located axially adjacent to the internal gear pump 70 with respect to the second gear housing 77b. The back cover 82 is fixed to the second gear housing 77b.
[0075] The back cover 82 has a discharge port 85. An inlet of the discharge port 85 opens to the front surface of the back cover 82. With the back cover 82 fixed to the second gear housing 77b, the inlet of the discharge port 85 communicates with the second port 75 of the second gear housing 77b via a second communication passage 712. An outlet of the suction port 84 opens to a side surface of the back cover 82, and is connected to the supply passage 41 of the hydraulic circuit 10.
[0076] Next, a brief description will be given of the operation of the internal gear pump 70. When the shaft 76 is rotated in the counterclockwise direction in Figure 4 by the electric motor 5, the pinion gear 72 and the ring gear 74 of each of the first and second gear sets 71a, 71b rotate.
[0077] In the recess 78 of the first gear housing 77a, as the meshed external teeth 721 of the pinion gear 72 and the internal teeth 741 of the ring gear 74 separate, hydraulic oil is sucked into between the external teeth 721 and the internal teeth 741 from the suction port 84. The sucked hydraulic oil is carried toward the second port 75 as the pinion gear 72 and the ring gear 74 rotate.
[0078] In the recess 78 of the first gear housing 77a, the external teeth 721 and the internal teeth 741, which were separated from each other, gradually approach each other and mesh with each other. As the external teeth 721 and the internal teeth 741 mesh with each other, the hydraulic oil is discharged from between the external teeth 721 and the internal teeth 741 to the second port 75 of the first gear housing 77a.
[0079] The hydraulic oil discharged to the second port 75 of the first gear housing 77a reaches the recess 78 of the second gear housing 77b through the first communication passage 711. Similarly, in the recess 78 of the second gear housing 77b, the rotation of the pinion gear 72 and the ring gear 74 causes the hydraulic oil sucked between the external teeth 721 and the internal teeth 741 from the first communication passage 711 and the first port 73 to be discharged to the second port 75 of the second gear housing 77b. The hydraulic oil discharged to the second port 75 of the second gear housing 77b is sent to the supply passage 41 through the second communication passage 712 and the discharge port 85. Since the pressure of the hydraulic oil increases in each of the first gear set 71a and the second gear set 71b, whose discharge and suction parts are connected in series, the multi-stage internal gear pump 70 can discharge high-pressure hydraulic oil.
[0080] (Characteristic structure of internal gear pump) The inscribed gear pump 70 shown in Fig. 3 or 4 is characterized in that it is a multi-stage high-pressure pump, and in addition, has an external drain. In more detail, the inscribed gear pump 70 has a drain port 86. The drain port 86 is a port that discharges hydraulic oil leaked inside the inscribed gear pump 70 to the outside of the inscribed gear pump 70. The inscribed gear pump 70 has a first drain port 86a and a second drain port 86b. The first drain port 86 is attached to the front cover 81. The second drain port 86 is attached to the back cover 82. The number of drain ports can be set to any number.
[0081] The inscribed gear pump 70 has a drain passage 88. Specifically, in the inscribed gear pump 70 disclosed herein, the drain passage 88 includes a first gap 871, a second gap 872, a third gap 873, a first passage 881, and a second passage 882, as shown in Figures 3 and 5. The structure of the drain passage 88 disclosed herein is just one example.
[0082] The first gap 871 is a gap between the gear set 71 and the inner wall of the housing 80. The second gap 872 is a gap between the shaft 76 and the inner circumferential surface of the through hole 710 of the gear housing 77. The third gap 873 is a gap between the shaft 76 and the inner circumferential surface of the support hole 83 of the front cover 81. The first passage 881 is a passage formed in the front cover 81, and is a passage connecting the support hole 83 and the first drain port 86a. The second passage 882 is a passage formed in the back cover 82, and is a passage connecting the through hole 710 of the second gear housing 77b and the second drain port 86b.
[0083] During operation of the internal gear pump 70, a part of the hydraulic oil pressurized in the recess 78 flows from the high-pressure second port 75 and its surroundings, i.e., the high-pressure portion of the housing 80, through the first gap 871 to the second gap 872 due to the pressure difference in the drain passage 88, as shown by the two-dot chain arrow in Fig. 3, 4 or 5. In the second gap 872, the hydraulic oil flows along the shaft 76 toward the first end (i.e., the left end in Fig. 3) or the second end (i.e., the right end in Fig. 3) of the shaft 76. The hydraulic oil that has flowed toward the first end of the shaft 76 passes through the third gap 873, the bearing 831, reaches the first passage 881, and is discharged to the outside of the internal gear pump 70 from the first drain port 86a. The hydraulic oil that flows toward the second end of the shaft 76 reaches the second passage 882 and is discharged to the outside of the internal gear pump 70 from the second drain port 86b.
[0084] Here, the gaps 871, 872, 873 that form the drain passage 88 are set to an appropriate size. The size of the gaps 871, 872, 873 may be set to be larger so that more leakage occurs inside compared to a typical inscribed gear pump. The multi-stage inscribed gear pump 70, which has a relatively large leakage, in other words, a relatively low volumetric efficiency, is suitable for the hydraulic pump 7 of the aircraft hydraulic system 1, as will be described later.
[0085] The drain passage 88 is also located at the sliding point between the gear set 71 and the housing 80, the sliding point between the shaft 76 and the housing 80, and at the bearing 831, and therefore contributes to lubrication, cooling, or both lubrication and cooling of the internal gear pump 70.
[0086] (Hydraulic system control) The controller 6 changes the discharge flow rate of the internal gear pump 70 through control of the electric motor 5. Specifically, the controller 6 outputs a control signal to the electric motor 5 to increase the rotation speed of the electric motor 5 when the supply flow rate to the hydraulic actuators 21-26 falls below the flow rate required by the hydraulic actuators 21-26 based on the required flow rate from the upper controller and the measurement signal of the pressure sensor 61. The controller 6 also outputs a control signal to the electric motor 5 to decrease the rotation speed of the electric motor 5 when the supply flow rate to the hydraulic actuators 21-26 exceeds the flow rate required by the hydraulic actuators 21-26.
[0087] During cruising flight of the aircraft 2, the primary flight control actuators, i.e., the aileron actuator 21, the elevator actuator 22, and the rudder actuator 23, operate. The secondary flight control actuators, i.e., the flap actuator 24, the slat actuator 25, and the landing gear retraction actuator 26, do not operate during cruising flight of the aircraft 2. The primary flight control actuators 21-23 require a relatively low flow rate. During cruising flight of the aircraft 2, the hydraulic actuators 21-26 require a low flow rate.
[0088] When the aircraft 2 is in cruising flight and the required flow rate of the hydraulic actuators 21-26 is low, the flow rate in the supply passage 41 is low, so the pressure difference across the restrictor 47 is small. The valve 45 opens the bypass passage 44. When the bypass passage 44 is open, the amount of hydraulic oil discharged from the drain port 86 of the inscribed gear pump 70 increases. The flow rate of hydraulic oil discharged from the discharge port 85 of the inscribed gear pump 70 decreases. The hydraulic system 1 is able to meet the required flow rate, which is a low flow rate, to the primary flight control actuators 21-23 during cruising flight.
[0089] As described above, when the aircraft 2 is flying stably and the hydraulic system 1 is required to maintain a high pressure while the flow rate is zero or substantially zero, the inscribed gear pump 70 is driven with the bypass passage 44 open. Driving the inscribed gear pump 70 maintains the pressure of the hydraulic circuit 10 at high pressure. The driven inscribed gear pump 70 discharges hydraulic oil to the outside of the inscribed gear pump 70 through the drain port 86. The hydraulic oil discharged through the drain port 86 returns to the tank 43 through the bypass passage 44 and the first return passage 42a. The hydraulic system 1 can maintain the pressure of the hydraulic circuit 10 at high pressure while the supply flow rate to the hydraulic actuators 21-26 is zero or substantially zero.
[0090] Although the inscribed gear pump 70 is driven, the discharge of hydraulic oil from the discharge port 85 is restricted, and so there is a risk of the inscribed gear pump 70 burning out. However, the inscribed gear pump 70 can discharge hydraulic oil through the drain port 86. The hydraulic oil discharged through the drain port 86 receives heat inside the inscribed gear pump 70. Even if the flow rate of the supply passage 41 remains low or zero for a long period of time, a rise in temperature of the inscribed gear pump 70 is suppressed. The inscribed gear pump 70, which has a drain port 86, has a self-cooling function.
[0091] The hydraulic system 1, which combines a multi-stage internal gear pump 70 equipped with an external drain, a bypass path 44, and a valve 45, can maintain a high pressure state in the hydraulic circuit 10 and a zero or nearly zero flow rate state for a long period of time. The hydraulic system 1 is suitable as a system for supplying hydraulic oil to the primary flight control actuators 21-23 of an aircraft 2.
[0092] When the aircraft 2 takes off or lands, in addition to the primary flight control actuators 21-23, the secondary flight control actuators 24-25 and the landing gear retraction / extension actuator 26 also operate. The secondary flight control actuators 24-25 and the landing gear retraction / extension actuator 26 require a relatively high flow rate. The bypass path 44 being open is disadvantageous in terms of satisfying the required flow rate of the hydraulic actuators 21-26.
[0093] When the aircraft 2 takes off or lands and the hydraulic actuators 21-26 require a large flow rate, the flow rate in the supply path 41 is high, and therefore the pressure difference between the front and rear of the restrictor 47 is large. The valve 45 closes the bypass path 44. All of the hydraulic oil discharged by the internal gear pump 70 is supplied to the hydraulic actuators 21-26. During takeoff or landing, the hydraulic system 1 can satisfy the flow rates required for the operation of the primary flight control actuators 21-23, secondary flight control actuators 24-25, and takeoff and landing actuator 26. The controller 6 increases the rotational speed of the electric motor 5 as necessary.
[0094] Therefore, the hydraulic system 1 can be used over a wide range from low flow rate to high flow rate. The primary flight control actuators 21-23, the secondary flight control actuators 24-25, and the landing gear retraction actuator 26 can each operate appropriately. The pressure difference across the throttle 47 at which the valve 45 switches between opening and closing can be set to an appropriate pressure difference. Taking into consideration the performance of the internal gear pump 70, a pressure difference across the throttle 47 at which the valve 45 opens and closes, i.e., a threshold value related to the required flow rate of the hydraulic actuators 21-26, is set so that the hydraulic system 1 can satisfy the requirements (1), (2), and (3) described above. The valve 45 opens the bypass path 44 when the required flow rate of the hydraulic actuators 21-26 exceeds the set threshold, and closes the bypass path 44 when the required flow rate is equal to or lower than the threshold.
[0095] A typical single-stage inscribed gear pump has low pump efficiency at high pressure and is prone to seizure at high pressure. The aforementioned inscribed gear pump 70 is a multi-stage inscribed gear pump 70 in which the ports of multiple gear sets 71a, 71b are connected in series. The multi-stage inscribed gear pump 70 can increase the pressure of the hydraulic oil in each of the multiple gear sets 71a, 71b. The load on each of the gear sets 71a, 71b is low. The multi-stage inscribed gear pump 70 can discharge high-pressure hydraulic oil. The multi-stage inscribed gear pump 70 is suitable for the hydraulic pump 7 of an aircraft hydraulic system 1 that is required to supply high-pressure hydraulic oil to hydraulic actuators 21-26.
[0096] The inscribed gear pump 70 is not a variable displacement pump but a fixed displacement pump. The inscribed gear pump 70 itself cannot change the discharge flow rate. However, the controller 6 changes the rotation speed of the inscribed gear pump 70 through the control of the electric motor 5, so that the inscribed gear pump 70 can be used in a wide range of flow rates from low to high.
[0097] The aircraft internal gear pump 70 does not have a structure for suppressing internal leakage by, for example, reducing the gap between the sliding parts between the gear set and the housing. The aircraft internal gear pump 70 has a relatively large amount of internal leakage, and has a drain port 86 for discharging hydraulic oil leaked inside to the outside of the inscribed gear pump 70. This inscribed gear pump 70 is suitable for the hydraulic pump 7 of the aircraft hydraulic system 1 because it makes it possible to reduce the flow rate of hydraulic oil discharged from the discharge port 85 to zero or substantially zero while maintaining the pressure of the hydraulic circuit 10 at high pressure by driving.
[0098] (Modification) 6 shows a hydraulic system 11 according to a modified example. The hydraulic system 11 has a solenoid valve 46 instead of the valve 45 that opens and closes according to a pressure difference. The solenoid valve 46 is electrically connected to the controller 6. The solenoid valve 46 opens and closes the bypass passage 44 upon receiving a control signal from the controller 6.
[0099] Specifically, when the aircraft 2 is in cruising flight and the required flow rate of the hydraulic actuators 21-26 is low, the controller 6 outputs a control signal to the solenoid valve 46 to open the bypass passage 44. During cruising flight, the hydraulic system 11 can maintain the hydraulic circuit 10 in a high-pressure state while satisfying the required flow rate to the primary flight control actuators 21-23. In addition, a temperature rise in the internal gear pump 70 is suppressed.
[0100] When the aircraft 2 is taking off or landing and the required flow rate of the hydraulic actuators 21-26 is high, the controller 6 outputs a control signal to the solenoid valve 46 to close the bypass path 44. The hydraulic system 11 can satisfy the flow rate required for the operation of the primary flight control actuators 21-23, the secondary flight control actuators 24-25, and the takeoff and landing actuator 26 during takeoff and landing.
[0101] 7 shows a hydraulic system 12 according to another modified example. The hydraulic system 12 omits the valve 45 and the solenoid valve 46. The valve 45 and the solenoid valve 46 are not essential elements of the aircraft hydraulic system disclosed herein. If the performance required for an aircraft hydraulic system, such as (1) the ability to supply high-pressure hydraulic oil to the hydraulic actuators 21-26, (2) the ability to use a wide range of flow rates from low to high, and (3) the ability to maintain the hydraulic circuit 10 in a high-pressure state and a zero or nearly zero flow rate state for a long period of time, can be achieved by changing the rotation speed of the internal gear pump 70, the hydraulic system 12 can omit the valve 45 and the solenoid valve 46.
[0102] In other words, by appropriately setting the shape, structure, or both the shape and structure of the drain passage 88 of the inscribed gear pump 70, it is possible to realize the following without opening or closing the bypass path 44: (a) hydraulic oil can be supplied to the hydraulic actuators 21-26 over a wide flow rate range from low to high by controlling the rotational speed of the inscribed gear pump 70 based on a control signal from the controller 6, and (b) when the hydraulic circuit 10 is in a high-pressure state and the required flow rate is zero or nearly zero, the hydraulic oil can be discharged from the inscribed gear pump 70 through the drain port 86.
[0103] FIG. 8 shows a hydraulic system 13 according to yet another modified example. The inscribed gear pump 700 of the hydraulic system 13 does not have a drain port 86. The bypass passage 44 is connected to the supply passage 41 upstream of the throttle 47. The bypass passage 44 is indirectly connected to the inscribed gear pump 700. When the bypass passage 44 is open, at least a part of the hydraulic oil discharged from the discharge port 85 of the inscribed gear pump 70 returns to the tank 43 through the bypass passage 44. The hydraulic system 13 can satisfy the required flow rate to the hydraulic actuators 21-26 during cruising flight of the aircraft 2. Similarly to the hydraulic system 1 described above, the hydraulic system 13 can suppress the temperature rise of the inscribed gear pump 700 when the required flow rate of the hydraulic actuators 21-26 is zero or almost zero.
[0104] If the bypass passage 44 is closed, all of the hydraulic oil discharged from the discharge port 85 is supplied to the hydraulic actuators 21-26. The hydraulic system 13 can satisfy the required flow rate to the hydraulic actuators 21-26 when the aircraft 2 takes off or lands.
[0105] It should be noted that the aircraft hydraulic system disclosed herein is not limited to the hydraulic system for controlling the primary flight control actuators 21-23, the secondary flight control actuators 24-25, and the landing gear retraction / extension actuator 26 described above. The aircraft hydraulic system may be a hydraulic system for controlling only the primary flight control actuators 21-23, only the secondary flight control actuators 24-25, or the primary flight control actuators 21-23 and the secondary flight control actuators 24-25. The aircraft hydraulic system may be a hydraulic system for controlling the landing gear retraction / extension actuator 26. The aircraft hydraulic system may be a hydraulic system for controlling other actuators.
[0106] Moreover, the hydraulic equipment to which the hydraulic system supplies hydraulic oil includes hydraulic motors in addition to hydraulic actuators.
[0107] The above-mentioned configurations of the hydraulic systems may be combined with each other to the extent possible. For example, the hydraulic system 13 shown in Fig. 8 may include the electromagnetic valve 46 shown in Fig. 6 instead of the valve 45.
[0108] Also, for example, in the hydraulic system 13 shown in FIG. 8, the valve 45 and the throttle 47 may be omitted. [Explanation of symbols]
[0109] 1 Hydraulic system 11 Hydraulic system 12 Hydraulic system 13 Hydraulic system 2 aircraft 21 Aileron actuator (hydraulic equipment, flight control actuator) 22 Elevator actuators (hydraulic equipment, flight control actuators) 23 Rudder actuator (hydraulic equipment, flight control actuator) 24 Flap actuators (hydraulic equipment, flight control actuators) 25 Slat actuators (hydraulic equipment, flight control actuators) 26 Landing gear extension actuator (hydraulic equipment, takeoff and landing actuator) 41 Supply route 43 Tank 44 Bypass Road 45 Valve 5 Electric motor (prime mover) 6 Controller 7 Hydraulic Pump 70 Internal gear pump 700 Internal Gear Pump 71 Gear Set 71a 1st gear set 71b 2nd gear set 72 Pinion gear 73 First Port 74 Ring gear 75 2nd Port 76 Shaft 80 Housing 85 Discharge port 86 Drain port 86a No. 1 drain port 86b 2nd drain port 88 Drain passage
Claims
1. A hydraulic pump connected to the hydraulic equipment of at least one aircraft via a supply line and supplying hydraulic fluid to the hydraulic equipment via the supply line, A prime mover connected to the hydraulic pump and driving the hydraulic pump, The system includes a controller that is electrically connected to the prime mover and, through the control of the prime mover, changes the rotational speed of the hydraulic pump according to the required flow rate of the hydraulic equipment, The hydraulic pump is a multi-stage internal gear pump having multiple gear sets, each including a pinion gear and a ring gear that mesh with each other, wherein the discharge section of each stage and the suction section of the next stage are connected in series. A bypass path directly or indirectly connected to the internal gear pump, which returns at least a portion of the hydraulic fluid from the internal gear pump to the tank, bypassing the hydraulic equipment, An aircraft hydraulic system further comprising a valve located on the bypass path, which opens the bypass path when the required flow rate is low and closes the bypass path when the required flow rate is high.
2. In the aircraft hydraulic system according to claim 1, The internal gear pump has a drain port for discharging the hydraulic fluid that has leaked inside the internal gear pump to the outside of the internal gear pump. The bypass is connected to the drain port and is part of an aircraft hydraulic system.
3. In the aircraft hydraulic system according to claim 1, The aforementioned bypass path branches off from the supply path connected to the hydraulic pump, and is part of an aircraft hydraulic system.
4. A hydraulic pump connected to the hydraulic equipment of at least one aircraft via a supply line and supplying hydraulic fluid to the hydraulic equipment via the supply line, A prime mover connected to the hydraulic pump and driving the hydraulic pump, The system includes a controller that is electrically connected to the prime mover and, through the control of the prime mover, changes the rotational speed of the hydraulic pump according to the required flow rate of the hydraulic equipment, The hydraulic pump is a multi-stage internal gear pump having multiple gear sets, each including a pinion gear and a ring gear that mesh with each other, wherein the discharge section of each stage and the suction section of the next stage are connected in series. The internal gear pump has a drain port for discharging the hydraulic fluid that has leaked inside the internal gear pump to the outside of the internal gear pump. A bypass path connected to the drain port, further comprising a bypass path that returns the hydraulic fluid discharged from the drain port to the tank, bypassing the hydraulic equipment, The aforementioned internal gear pump is A shaft supporting the gear set, A housing that supports the shaft and houses the rotating gear set, The housing has a high-pressure area, a drain passage that extends through the gap between the gear set and the housing, and around the shaft, to the drain port that opens into the housing, An aircraft hydraulic system wherein, when the required flow rate is high, the internal gear pump supplies hydraulic fluid to the hydraulic equipment through the supply passage, and when the pressure of the hydraulic fluid is high and the required flow rate is zero or nearly zero, the internal gear pump is configured such that the clearance between the gear set and the housing, and the circumference of the shaft, allows the internal gear pump to discharge the hydraulic fluid through the drain passage and the drain port by its operation.
5. In the aircraft hydraulic system according to claim 4, The hydraulic system for an aircraft includes a flight control actuator and an actuator for takeoff and landing.
6. In the aircraft hydraulic system according to claim 5, If the required flow rate is high, it will occur during the takeoff and landing of the aircraft. When the required flow rate is zero or nearly zero, the aircraft hydraulic system occurs during the flight of the aircraft while maintaining the angle of the flight control actuator at a constant angle.
7. In the aircraft hydraulic system according to claim 6, The flight control actuator comprises a primary flight control actuator and a secondary flight control actuator. During the takeoff and landing of the aircraft, the flight control actuator and the takeoff and landing actuator operate. An aircraft hydraulic system in which the primary flight control actuator operates at any time while the aircraft is in flight.
8. An aircraft internal gear pump that supplies hydraulic fluid to the hydraulic equipment of an aircraft, The shaft to which the prime mover is connected, A gear set including a pinion gear supported on the shaft and a ring gear that meshes with the pinion gear, wherein a plurality of gear sets are provided, the hydraulic fluid ports of which are connected in series. A housing that supports the shaft and houses the rotating gear set, the housing having a discharge port for discharging hydraulic fluid, A drain port opening in the housing, which discharges the hydraulic fluid leaked inside the pump to the outside of the pump, The housing comprises a drain passage extending from the high-pressure portion of the housing through the gap between the gear set and the housing, and around the shaft, to the drain port. An aircraft internal gear pump, wherein the clearance between the gear set and the housing, and the size of the circumference of the shaft are set so that when the gear set is rotating and the flow rate of the hydraulic fluid discharged from the discharge port is zero or nearly zero, the hydraulic fluid can be discharged from the drain port through the drain passage.