Electric transmission type helicopter rotor brake hydraulic system and aircraft

Abstract

The invention belongs to the technical field of hydraulic pressure, and particularly relates to a telex helicopter rotor brake hydraulic system and an aircraft, the telex helicopter rotor brake hydraulic system comprises an oil tank, an electric pump, a brake pressure oil filter, a stop valve, a brake accumulator, a rotor brake control switch, a rotor brake device, a brake pressure electric regulating valve, a pressure relief valve, an oil return filter and a control box; the electric pump sucks oil from the oil tank, the oil is filtered by the brake pressure oil filter and then pressurizes the pressure accumulator, the pressure accumulator is connected with a pressure supply port of the brake pressure electric regulating valve, a load port of the brake pressure electric regulating valve is connected with the rotor brake device, and an oil return port of the brake pressure electric regulating valve is connected with the oil tank through the oil return filter; the rotor brake control switch is used for adjusting the brake pressure electric adjusting valve to be in different working positions, so that the oil supply pressure of the rotor brake device is adjusted; the stop valve is arranged between the brake pressure oil filter and the brake pressure accumulator, and the pressure relief valve is arranged between the brake pressure accumulator and the oil return filter; the control box is used for controlling on-off of the stop valve and the pressure relief valve.

Description

Technical Field

[0001] The invention belongs to the field of hydraulic technology, and in particular relates to an electric-by-wire helicopter rotor brake hydraulic system and an aircraft. Background Art

[0002] In addition to achieving rapid rotor stop, the helicopter rotor brake system can also assist the helicopter in resisting crosswinds during parking. In addition, the rotor brake is also required during the engine start-up process in strong winds. For medium or large helicopters, the rotor brake is often hydraulically assisted, that is, the rotor brake hydraulic system is used for assisted braking.

[0003] Traditional domestic helicopter rotor brake hydraulic systems mainly include manually pressurized closed hydraulic systems and powered hydraulic systems using the main hydraulic source on board. These two hydraulic systems have the following problems: 1. For manually pressurized closed hydraulic systems, there are rotor brake ducts in the cockpit, and the "leakage" of the system connection will cause contamination in the cockpit and even threaten the safety of the driver; 2. For manually pressurized closed hydraulic systems, the pilot needs to manually depress the manual assistance, and it needs to be installed in a position and space that is convenient for operation, otherwise it will be inconvenient for the driver to operate; 3. For manually pressurized closed hydraulic systems, due to the limited installation space and the limited size of the control device, The ergonomics of the pilot's operation is poor. Taking a certain model as an example, the maximum operating force of the pilot with one hand is as high as 280N; 4. For the power test hydraulic system using the main hydraulic source on the aircraft, there are long-span steel cables in the cockpit, and the cable path needs to be strictly planned to avoid the problem of long-path steel cables being stuck due to the small bending radius during installation; 5. The installation inspection of the duct or steel cable increases the maintenance workload of the maintenance personnel; 6. The steel cable or duct needs to be arranged from the cockpit, front fuselage and mid-fuselage to the rotor brake control device located on the main reducer, resulting in a heavy weight of the rotor brake hydraulic system; 7. The rotor brake control device or control handle in the cockpit requires a larger installation and motion envelope space. Summary of the invention

[0004] Purpose of the invention: In order to solve the above problems of the existing helicopter rotor brake hydraulic system, a distributed installed electric-by-wire rotor brake hydraulic system and aircraft are designed, which have the characteristics of high ergonomics, good maintainability, small size and light weight.

[0005] Technical solution:

[0006] An electric-by-wire helicopter rotor brake hydraulic system comprises: an oil tank 1, an electric pump 2, a brake pressure oil filter 6, a cut-off valve 7, a brake accumulator 8, a rotor brake control switch 11, a rotor brake device 12, a brake pressure electric regulating valve 13, a pressure relief valve 14, a return oil filter 17, and a control box 19;

[0007] The electric pump draws oil from the oil tank, and after filtering through the brake pressure oil filter, pressurizes the accumulator, the accumulator is connected to the pressure supply port of the brake pressure electric regulating valve, the load port of the brake pressure electric regulating valve is connected to the rotor brake device 12, and the return port of the brake pressure electric regulating valve is connected to the oil tank through the return oil filter;

[0008] The rotor brake control switch is used to adjust the brake pressure electric regulating valve to different working positions, thereby adjusting the oil supply pressure to the rotor brake device;

[0009] The cut-off valve is arranged between the brake pressure oil filter and the brake accumulator, and the pressure relief valve is arranged between the brake accumulator and the return oil filter;

[0010] The control box is used to control the on and off of the cut-off valve and the pressure relief valve.

[0011] The rotor brake control switch 11 is preferably partially or fully integrated through an internal flow channel, and the valve element may preferably be in the form of a combination valve.

[0012] The inlet of the rotor brake device 12 is connected to the load port of the brake pressure electric regulating valve through a hydraulic hose 9, and one end of the hydraulic hose 9 is connected to the hydraulic conduit through a quick-release self-sealing joint, which facilitates the disconnection of the oil circuit between the rotor brake device and the hydraulic source to exhaust the system or maintain the rotor brake device;

[0013] Preferably, the system further comprises: a hand pump;

[0014] The hand pump draws oil from the oil tank and is used to charge the brake accumulator when the electric pump cannot be started.

[0015] Preferably, the system further comprises: a first one-way valve, a second one-way valve;

[0016] The first one-way valve is arranged at the outlet of the hand pump, and the second one-way valve is arranged at the outlet of the electric pump;

[0017] A check valve is used to prevent oil from flowing back to the hand pump or electric pump.

[0018] Preferably, the system further comprises: an accumulator pressure gauge, the accumulator pressure gauge being connected to the brake accumulator for displaying the brake accumulator pressure in real time;

[0019] The system further comprises: a pressure signal device, which is used to monitor the pressure of the brake accumulator in real time and feed back the pressure signal to the control box;

[0020] The control box controls the electric pump to start charging the brake accumulator when the pressure of the brake accumulator is lower than a set value.

[0021] Preferably, the system further comprises: a safety valve, which is arranged between the inlet of the rotor brake device and the return oil filter; and is used to relieve pressure for the rotor brake device in the event of overpressure.

[0022] Preferably, the rotor brake control switch 11 has three gears, namely static brake, dynamic brake and release brake;

[0023] The rotor brake device 12 has three working positions I, II and III, which correspond to the three gear positions of the rotor brake control switch respectively;

[0024] When the rotor brake control device is turned to the static brake position, the brake pressure electric regulating valve is controlled to work in position I, the pressure supply port and the load port of the brake pressure electric regulating valve are connected, and the oil return port is disconnected from the pressure supply port and the load port. The brake pressure electric regulating valve reduces the oil pressure provided by the brake accumulator to the static brake pressure and then transmits it to the rotor brake device;

[0025] When the rotor brake control device is turned to the dynamic brake position, the brake pressure electric regulating valve is controlled to work in the II position, the pressure supply port and the load port of the brake pressure electric regulating valve are connected, and the oil return port is disconnected from the pressure supply port and the load port. The brake pressure electric regulating valve reduces the oil pressure provided by the brake accumulator to the dynamic brake pressure and then transmits it to the rotor brake device;

[0026] When the rotor brake control device is turned to the release position, the brake pressure electric regulating valve is controlled to work in position III, the pressure supply port and the load port of the brake pressure electric regulating valve are disconnected, and the load port is connected to the return port to release the pressure in the rotor brake device;

[0027] The static brake pressure is greater than the dynamic brake pressure. The charging pressure value P0 of the brake accumulator 8 is equal to the static brake pressure value P 静 Close, but the maximum working pressure of the accumulator should be greater than the rotor static brake pressure value P 静 .

[0028] Preferably, the system further comprises: a bypass valve 16;

[0029] The bypass valve is arranged in parallel with the return oil filter, and is used to open when the return oil filter is blocked, so that the return oil flows back to the oil tank directly without passing through the return oil filter, thereby avoiding the rotor brake device from being blocked due to poor return oil.

[0030] Preferably, the oil tank is an open hydraulic oil tank or a closed hydraulic oil tank. The oil tank 1 is provided with an oil level observation window and oil level scale lines and marks for observing the oil level when the rotor is parked for a long time.

[0031] Preferably, when the oil tank is a closed oil tank, a return oil check valve is provided at the front end of the return oil filter to prevent the oil from flowing back to the rotor brake device.

[0032] Preferably, the control box is also used to detect the flight status of the helicopter. When the helicopter is in the air, the output signal of the pressure signal device is shielded, and the cut-off valve is controlled to be disconnected and the unloading valve is connected;

[0033] When the helicopter is on the ground, the shielding of the output signal of the pressure signal device is released, and at the same time, the cut-off valve is controlled to be connected and the unloading valve is disconnected.

[0034] The aircraft status signal can be replaced by the engine power control switch status signal, "wheel-load signal" or "air-to-ground" signal. For a helicopter, the engine power control switch signal is not in the flight position, which is equivalent to the wheels landing, which is equivalent to the helicopter being in the ground state; similarly, the engine power control switch signal is in the flight position, which is equivalent to the wheels leaving the ground, which is equivalent to the helicopter being in the air.

[0035] When all engine power control switches are not in the flight position, the control box 19 outputs a control signal to control the pressure signal device 9 to work, that is, when the pressure of the brake accumulator 8 is low, the pressure signal device 9 senses the low pressure signal of the brake accumulator 8, and controls the electric pump 2 to automatically work to charge the brake accumulator 8; and when any engine power control switch is placed in the flight position, the control box 19 outputs a control signal to inhibit the pressure signal device 9, that is, when the pressure of the brake accumulator 8 is low, the pressure signal device 9 senses the low pressure signal of the brake accumulator 8, and cannot control the electric pump 2 to automatically work to charge the brake accumulator 8. When any engine power control switch is placed in the flight position, the control box 19 outputs a signal to control the cut-off valve 7 to be in the disconnected position and the pressure relief valve 14 to be in the connected position, thereby releasing the brake accumulator 8 and failing to replenish pressure.

[0036] An aircraft comprises the fly-by-wire helicopter rotor brake hydraulic system.

[0037] Beneficial Effects

[0038] The present invention relates to a helicopter electric-by-wire rotor brake hydraulic system. Compared with a conventional helicopter rotor brake hydraulic system, the hydraulic conduit or steel cable arranged from the cockpit to the main reducer platform is eliminated, and the rotor brake control device or control handle in the cockpit is eliminated, thereby solving the problem that the rotor brake control device or control handle requires a large installation and motion envelope space. Only one electrical control switch is required to realize rotor brake control, which greatly improves the intelligent control level of the cockpit, greatly improves the ergonomics of the human machine, reduces the weight of the system, reduces the maintenance work of the hydraulic conduit or steel cable in the cockpit, and completely avoids the maintenance, The hydraulic oil pollution problem in the cockpit during disassembly or assembly or failure improves the system reliability; the rotor brake pressure supply system is automatically depressurized and interlocked in combination with the helicopter flight status, which has double insurance and can effectively prevent the hydraulic pressure from entering the rotor brake device in the air to cause non-command rotor braking, effectively improving the system safety; the system components can be highly integrated and installed at the rotor brake device position, which can effectively reduce the layout of hydraulic ducts, thereby reducing the system weight and maintenance work; when the helicopter is parked for a long time, the static brake pressure of the helicopter rotor can be maintained manually, which has good security. In short, the present invention relates to a helicopter electric rotor brake hydraulic system that can be distributedly installed, has good ergonomics, high reliability and safety, high maintainability and security, small size, light weight and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of the working of the rotor brake hydraulic system when the helicopter is in flight;

[0040] Figure 2 This is a schematic diagram of the working of the rotor brake hydraulic system when the helicopter is on the ground. DETAILED DESCRIPTION

[0041] A helicopter electric rotor brake hydraulic system: the hydraulic conduit or steel cable from the cockpit to the main reducer platform is eliminated, the rotor brake control device or control handle in the cockpit is eliminated, and only one electrical control switch is needed in the cockpit to realize rotor brake control; the rotor brake pressure supply system is automatically depressurized and interlocked in combination with the engine power state to avoid hydraulic pressure entering the rotor brake device in the air to cause non-command rotor braking; the main accessories are integrated and installed at the rotor brake device position, which can effectively reduce the layout of hydraulic conduits and reduce the weight of the system; when the helicopter is parked for a long time, the static brake pressure of the helicopter rotor can be maintained manually.

[0042] Technical solution: The present invention relates to a helicopter fly-by-wire rotor brake hydraulic system, which consists of a hydraulic power source subsystem, a control unit, a rotor brake device 12, and a rotor brake control switch 11; the hydraulic power source subsystem outputs high-pressure hydraulic energy, controls the pressure state through the control unit, and transmits it to the rotor brake device.

[0043] The hydraulic power source subsystem includes an oil tank 1, a return oil filter 17, a bypass valve 16, a return oil check valve 15, a brake accumulator 8, an accumulator pressure signal device 9, an accumulator pressure gauge 18, a brake pressure oil filter 6, a first check valve 4, a hand pump 3, a second check valve 5, and an electric pump 2; the electric pump 2 draws oil from the oil tank 1, and the oil passes through the second check valve 5 and is filtered by the brake pressure oil filter 26, which can be used to charge the brake accumulator 8. When the brake pressure is released, the return oil flows back to the oil tank 1 through the return oil check valve 15 and the return oil filter 17. In addition, when the electric pump cannot be started after being parked on the ground for a long time, the hand pump 3 can also be used to draw oil from the oil tank 1 to supplement the pressure of the brake accumulator 8. The first check valve 4 and the second check valve 5 can prevent the oil from entering the hand pump 3 or the electric pump 2 in reverse, so as to avoid damaging the pump body; when the flow resistance of the return oil filter 17 increases to a certain value, the bypass valve 16 is connected to prevent the oil from being unable to return.

[0044] The control unit includes a cut-off valve 7, a pressure relief valve 14, a brake pressure electric regulating valve 13, a pressure signal device 9, a control box 19, and a safety valve 20. The control box 19 receives the engine power control switch status information and outputs a control signal to control the cut-off valve 7, the pressure relief valve 14, and the working status of the pressure signal device 9. When any engine power control switch is in the flight position, the control box 19 sends a control signal to put the cut-off valve 7 in the cut-off position to prevent the power source system from charging the brake accumulator 8; at the same time, the pressure relief valve 14 is connected, so that the hydraulic cavity of the brake accumulator 8 is connected to the oil return line of the oil tank to ensure the release of the accumulator pressure, thereby ensuring that the action of the brake pressure electric regulating valve 13 will not cause substantial braking when the control switch 11 is braked or the signal is interfered; when all engine power control switches are not in the flight position, the control box 19 sends a control signal to put the cut-off valve 7 in the connection position, so that the power source system can automatically charge the brake accumulator 8; at the same time, the pressure relief valve 14 remains disconnected, so that the high-pressure cavity of the brake accumulator 8 stores energy, and the rotor brake control switch 11 is turned to the brake position, and the brake pressure electric regulating valve 13 responds to perform rotor braking;

[0045] Specifically, the rotor brake control switch 11 is an electrical switch having three working positions, namely, release brake, dynamic brake, and static brake, and can be maintained in position at each working position; the brake pressure electric regulating valve 13 has three working positions, I, II, and III, and each working position has a P port, an A port, and an R port, wherein the P port is a pressure supply port, the A port is a load port, and the R port is an oil return port; when the rotor brake control switch 11 is turned to the release brake position, the brake pressure electric regulating valve 13 is controlled to work in the III position; when the rotor brake control switch 11 is turned to the dynamic brake position, the brake pressure electric regulating valve 13 is controlled to work in the II position; when the rotor brake control switch 11 is turned to the static brake position, the brake pressure electric regulating valve 13 is controlled to work in the I position;

[0046] Specifically, when the brake pressure electric regulating valve 13 is in the working position I, the pressure port P and the port A of the brake pressure electric regulating valve 13 are connected, the port P and the port A are disconnected from the port R, and the SS static brake pressure is reduced from the port P to the port A, and the pressure reaches the rotor brake device 12 to perform static braking; when the brake pressure electric regulating valve 13 is in the working position II, the pressure port P and the port A of the brake pressure electric regulating valve 13 are connected, the port P and the port A are disconnected from the port R, and the dynamic brake pressure is reduced from the port P to the port A, and the pressure reaches the rotor brake device 12 to perform dynamic braking; when the brake pressure electric regulating valve 13 is in the working position III, the pressure port P and the port A and the port R of the brake pressure electric regulating valve 13 are disconnected, and the port A is connected to the port R, the pressure in the rotor brake device 12 is released, and the brake is released;

[0047] Among them: the oil port S1 of the oil tank 1 is connected to the oil suction port of the hand pump 3, the oil port S2 of the oil tank 1 is connected to the oil suction port of the hydraulic pump 2, and the oil port R of the oil tank 1 is the system oil return port. The working state of the cut-off valve 7 and the pressure relief valve 14 is automatically controlled by the engine power control switch state; when the pressure of the brake accumulator 8 is low, after the pressure signal of the brake accumulator 8 is sensed by the pressure signal device 9, the electric pump 2 is controlled to automatically work to charge the brake accumulator 8, and the pressure signal device 9 is also controlled by the engine power control switch state; the pressure supply port of the accumulator is connected to the pressure supply port P of the brake pressure electric regulating valve 13;

[0048] Specifically, during flight, the engine power control switch is in the flight position, and the control box 19 sends a control signal to put the cut-off valve 7 in the cut-off position, so as to prevent the power source system from charging the brake accumulator 8; at the same time, the pressure relief valve 14 remains connected, so that the hydraulic chamber of the brake accumulator 8 is connected to the oil tank through the return oil circuit, ensuring the release of the accumulator pressure; at the same time, the low-pressure signal of the brake accumulator 8 sensed by the pressure signal device 9 will be suppressed, and the electric pump 2 cannot be controlled to work to charge the brake accumulator 8; the rotor brake control switch 11 is in the release position, the brake pressure electric regulating valve 13 pressure supply port P and the load port A are disconnected, and the brake pressure electric regulating valve 13 return oil port R is connected to the load port A, so that there is no hydraulic pressure in the rotor brake device 12;

[0049] Specifically, during flight, if the rotor brake control switch 11 is mistakenly turned to the dynamic brake position, the brake pressure electric regulating valve 13 works in the II position, the pressure supply port P is connected to the load port A, and the dynamic brake pressure can be reduced. However, if the engine power control switch is in the flight position, the control box 19 sends a control signal to put the cut-off valve 7 in the cut-off position to prevent the power source system from charging the brake accumulator 8; at the same time, the pressure relief valve 14 remains connected, so that the hydraulic cavity of the brake accumulator 8 is connected to the oil tank through the return oil circuit to ensure the release of the accumulator pressure; at the same time, the low-pressure signal of the brake accumulator 8 sensed by the pressure signal device 9 will be suppressed, and the electric pump 2 cannot be controlled to work to charge the brake accumulator 8; therefore, due to the absence of a hydraulic source, mis-braking can be effectively avoided;

[0050] Specifically, the rotor braking sequence should be to first perform the rotor dynamic braking, and then perform the rotor static braking after the rotor stops completely;

[0051] Specifically, when the rotor is in dynamic braking, that is, when the rotor stops quickly, the transmitter power control switch should not be in the flight position, then the control box 19 sends a control signal to control the pressure signal device 9, the shut-off valve 7, and the pressure relief valve 14 to switch the working state; after the pressure signal device 9 senses the low-pressure signal of the brake accumulator 8, it controls the electric pump 2 to work automatically; the shut-off valve 7 is automatically adjusted to the connected position, so that the power source system can automatically charge the brake accumulator 8; at the same time, the pressure relief valve 14 is automatically adjusted to the disconnected position, so that the high-pressure chamber of the brake accumulator 8 stores energy; the driver in the cockpit turns the rotor brake control switch 11 from the release brake working position to the dynamic brake working position, and controls the brake pressure electric regulating valve 13 in the II position, the pressure of the brake pressure electric regulating valve 13 is connected to the P port and the A port, the P port and the A port are disconnected from the R port, and the dynamic brake pressure is reduced from the P port to the A port, and the pressure reaches the rotor brake device 12 to perform dynamic braking;

[0052] Specifically, when the rotor dynamic braking is completed and the helicopter needs to be parked for a long time, the rotor brake hydraulic system needs to be operated to the static braking position. After the rotor stops completely, the transmitter power control switch should not be in the flight position, then the control box 19 sends a control signal to continuously control the pressure signal device 9, the cut-off valve 7, and the pressure relief valve 14 to maintain the working state during the previous dynamic brake; after the pressure signal device 9 senses the low-pressure signal of the brake accumulator 8, it controls the electric pump 2 to work automatically to ensure that the pressure of the brake accumulator 8 is within the normal working range; the cut-off valve 7 remains in the connected position, so that the power source system can automatically charge the brake accumulator 8; at the same time, the pressure relief valve 14 remains in the disconnected position, so that the high-pressure chamber of the brake accumulator 8 stores energy; the driver in the cockpit turns the rotor brake control switch 11 from the release brake working position to the static brake working position, and controls the brake pressure electric regulating valve 13 in the I position, the pressure of the brake pressure electric regulating valve 13 is connected to the P port and the A port, the P port and the A port are disconnected from the R port, and the static brake pressure is reduced from the P port to the A port, and the pressure reaches the rotor brake device 12 to perform static braking;

[0053] Specifically, after the helicopter is parked for a long time under static braking, if there is power supply on board, since hydraulic accessories such as the brake pressure electric regulating valve 13 inevitably have internal leakage, the internal leakage will cause the pressure of the rotor brake device 13 to decrease, and the pressure of the brake accumulator 8 to decrease. After the pressure signal device 9 senses the low-pressure signal of the brake accumulator 8, it controls the electric pump 2 to automatically work, automatically charge the brake accumulator 8, and ensure that the pressure of the brake accumulator 8 is within the normal working range, and the static brake pressure in the rotor brake device 13 is never maintained;

[0054] Specifically, after the helicopter is parked for a long time with static braking, if there is no electricity on board, the hydraulic accessories such as the brake pressure electric regulating valve 13 will inevitably have internal leakage, which will cause the pressure of the rotor brake device 13 to decrease, and the pressure of the brake accumulator 8 to decrease. The pressure state can be judged by observing the pressure value of the accumulator pressure gauge 18. If the pressure of the brake accumulator 8 is lower than the set value, since the electric pump starting conditions are not met, the brake accumulator 8 can be manually pressurized by the hand pump 3. While replenishing the pressure, check the value of the accumulator pressure gauge 18. The pressure replenishment pressure shall not exceed the maximum working pressure of the brake accumulator 8.

[0055] Specifically, when the helicopter rotor is in static braking state, the increase in ambient temperature will cause the pressure of the rotor brake device 13 to increase. After the pressure rises to the safety valve setting value, the brake pressure safety valve 20 will open to release the pressure to protect the rotor brake device and other accessories.

Claims

1. A fly-by-wire helicopter rotor brake hydraulic system, characterized in that: The system comprises: an oil tank (1), an electric pump (2), a brake pressure oil filter (6), a cut-off valve (7), a brake accumulator (8), a rotor brake control switch (11), a rotor brake device (12), a brake pressure electric regulating valve (13), a pressure relief valve (14), a return oil filter (17), and a control box (19); The electric pump draws oil from the oil tank, and after filtering through the brake pressure oil filter, pressurizes the pressure accumulator, the pressure accumulator is connected to the pressure supply port of the brake pressure electric regulating valve, the load port of the brake pressure electric regulating valve is connected to the rotor brake device (12), and the return port of the brake pressure electric regulating valve is connected to the oil tank through the return oil filter; The rotor brake control switch is used to adjust the brake pressure electric regulating valve to different working positions, thereby adjusting the oil supply pressure to the rotor brake device; The cut-off valve is arranged between the brake pressure oil filter and the brake accumulator, and the pressure relief valve is arranged between the brake accumulator and the return oil filter; The control box is used to control the on and off of the cut-off valve and the pressure relief valve.

2. The system according to claim 1, characterized in that The system also includes: a hand pump; The hand pump draws oil from the oil tank and is used to charge the brake accumulator when the electric pump cannot be started.

3. The system according to claim 2, characterized in that The system further comprises: a first one-way valve and a second one-way valve; The first one-way valve is arranged at the outlet of the hand pump, and the second one-way valve is arranged at the outlet of the electric pump; A check valve is used to prevent oil from flowing back to the hand pump or electric pump.

4. The system according to claim 3, characterized in that The system further comprises: an accumulator pressure gauge, the accumulator pressure gauge being connected to the brake accumulator for displaying the brake accumulator pressure in real time; The system further comprises: a pressure signal device, which is used to monitor the pressure of the brake accumulator in real time and feed back the pressure signal to the control box; The control box controls the electric pump to start charging the brake accumulator when the pressure of the brake accumulator is lower than a set value.

5. The system according to claim 4, characterized in that The system further comprises a safety valve, which is arranged between the inlet of the rotor brake device and the return oil filter and is used for relieving pressure of the rotor brake device in the event of overpressure.

6. The system according to claim 5, characterized in that: The rotor brake control switch (11) has three gear positions, namely static brake, dynamic brake and release brake; The rotor brake device (12) has three working positions, I, II and III, which respectively correspond to the three gear positions of the rotor brake control switch; When the rotor brake control device is turned to the static brake position, the brake pressure electric regulating valve is controlled to work in position I, the pressure supply port and the load port of the brake pressure electric regulating valve are connected, and the oil return port is disconnected from the pressure supply port and the load port. The brake pressure electric regulating valve reduces the oil pressure provided by the brake accumulator to the static brake pressure and then transmits it to the rotor brake device; When the rotor brake control device is turned to the dynamic brake position, the brake pressure electric regulating valve is controlled to work in the II position, the pressure supply port and the load port of the brake pressure electric regulating valve are connected, and the oil return port is disconnected from the pressure supply port and the load port. The brake pressure electric regulating valve reduces the oil pressure provided by the brake accumulator to the dynamic brake pressure and then transmits it to the rotor brake device; When the rotor brake control device is turned to the release position, the brake pressure electric regulating valve is controlled to work in position III, the pressure supply port and the load port of the brake pressure electric regulating valve are disconnected, and the load port is connected to the return port to release the pressure in the rotor brake device; Static brake pressure is greater than dynamic brake pressure.

7. The system according to claim 6, characterized in that: The system further comprises: a bypass valve (16); The bypass valve is arranged in parallel with the return oil filter and is used to open when the return oil filter is blocked, so that the return oil flows back to the oil tank directly without passing through the return oil filter.

8. The system according to claim 1, characterized in that: The oil tank is an open hydraulic oil tank or a closed hydraulic oil tank; when the oil tank is a closed oil tank, a return oil check valve is arranged at the front end of the return oil filter to prevent the oil from flowing back to the rotor brake device.

9. The system according to claim 8, characterized in that: The control box is also used to detect the flight status of the helicopter. When the helicopter is in the air, the output signal of the pressure signal device is shielded, and the cut-off valve is controlled to be disconnected and the unloading valve is connected; When the helicopter is on the ground, the shielding of the output signal of the pressure signal device is released, and at the same time, the cut-off valve is controlled to be connected and the unloading valve is disconnected.

10. An aircraft, characterized in that: The aircraft includes the fly-by-wire helicopter rotor brake hydraulic system according to any one of claims 1-9.

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