阅读说明：本技术 一种飞机应急刹车系统及其设计方法 (Airplane emergency brake system and design method thereof ) 是由 刘忠平 韩亚国 刘辉 于 2019-09-17 设计创作，主要内容包括：一种飞机应急刹车系统及其设计方法。飞机应急刹车系统中的液压电磁阀的刹车油口与机轮的液压缸座的进油口连通。液压减压刹车阀的进油口外接液压源。液压继电器的单刀双置开关的一个接线柱与直流电源连接,另一个接线柱与液压电磁阀的电磁铁通过导线连接。当来自液压减压刹车阀的油液压力达到液压继电器的触点接通压力时,液压继电器的触点导通,并且直流电源与液压电磁阀上的电磁铁导通,使得液压电磁阀卸压,有主动防滑刹车功能的应急刹车系统压力降低。本发明具有主动防滑刹车功能的应急刹车系统能把实际刹车压力与系统设定的刹车压力值进行比较,从而主动调整刹车压力,达到能够主动防滑的目的。(An emergency brake system of an airplane and a design method thereof. And a brake oil port of a hydraulic solenoid valve in the emergency brake system of the airplane is communicated with an oil inlet of a hydraulic cylinder seat of the airplane wheel. An oil inlet of the hydraulic pressure reducing brake valve is externally connected with a hydraulic source. One binding post of the single-pole double-position switch of the hydraulic relay is connected with a direct-current power supply, and the other binding post is connected with an electromagnet of the hydraulic electromagnetic valve through a lead. When the pressure of oil liquid from the hydraulic pressure reducing brake valve reaches the contact connection pressure of the hydraulic relay, the contact of the hydraulic relay is conducted, and the direct-current power supply is conducted with the electromagnet on the hydraulic electromagnetic valve, so that the hydraulic electromagnetic valve is relieved, and the pressure of the emergency brake system with the active anti-skidding brake function is reduced. The emergency brake system with the active anti-skid brake function can compare the actual brake pressure with the brake pressure value set by the system, thereby actively adjusting the brake pressure and achieving the purpose of active anti-skid.)

1. An emergency brake system of an airplane is characterized by comprising a hydraulic electromagnetic valve, a hydraulic relay, a hydraulic pressure-reducing brake valve and a 28V direct-current power supply; wherein: a brake oil port of the hydraulic pressure-reducing brake valve is respectively communicated with an oil inlet of the hydraulic relay and an oil inlet of the hydraulic electromagnetic valve through a pressure oil pipe; an oil return port of the hydraulic pressure-reducing brake valve is communicated with an oil tank through an oil return pipe; a brake oil port of the hydraulic electromagnetic valve is communicated with an oil inlet of a hydraulic cylinder seat of the airplane wheel; an oil return tank of the hydraulic electromagnetic valve is communicated with an oil tank through a pipeline; an oil inlet of the hydraulic pressure-reducing brake valve is connected with a hydraulic source through a pipeline; one binding post of a single-pole double-position switch in the hydraulic relay is connected with a 28V direct-current power supply, and the other binding post of the single-pole double-position switch of the hydraulic relay is connected with an electromagnet in a hydraulic electromagnetic valve through a lead; and oil return ports of the hydraulic pressure-reducing brake valve, the hydraulic relay and the hydraulic electromagnetic valve are communicated with an oil tank through oil return pipes.

2. An aircraft emergency brake system according to claim 1, wherein the 28V dc power supply is in communication with a normally open contact on the positive pole of the hydraulic relay; the contact of the negative pole of the hydraulic relay is connected with the positive pole of the hydraulic electromagnetic valve; the negative electrode of the hydraulic electromagnetic valve is connected to the ground wire of the airplane power supply system; when the oil pressure is equal to or greater than the contact-making pressure of the hydraulic relay, the contact of the hydraulic relay is made, the 28V direct-current power supply is connected with the hydraulic electromagnetic valve, and the pressure of the emergency brake system is reduced.

3. A method for designing an aircraft emergency brake system according to claim 1, wherein the specific process comprises:

step 1, determining emergency brake pressure P of emergency brake system_s：

Axial thrust S through emergency brake device of brake wheel_tAnd the emergency braking pressure P of the braking machine wheel_seDetermining emergency brake pressure P_s；

I axial thrust S for determining emergency braking device of brake wheel_t：

Determining axial thrust S of emergency brake device of brake wheel through formula (1)_t：

In the formula (1), L_sThe braking distance required by the airplane is R is the inner radius of the movable disc, R is the outer radius of the static disc, mu is the dynamic friction coefficient, A_sThe kinetic energy of the aircraft at the moment of landing, N_msNumber of friction surfaces, R_gThe rolling radius of the airplane wheel;

II, determining the emergency braking pressure P of the braking airplane wheel_se：

Determining emergency brake pressure P of brake wheel through formula (2)_se：

In the formula (2), N_hsNumber of pistons, F_hsIs the piston area and Δ P is the pressure loss;

III determining the emergency brake pressure P of the emergency brake system_s：

Determining the emergency braking pressure P of the emergency braking system through the formula (3)_s；

P_s＝P_se+P_i (3)

In formula (3), P_iIs the system pressure safety margin;

emergency brake pressure P of emergency brake system_sWith the emergency braking pressure P of the braking machine wheel_seThe same;

step two, determining the intermediate braking pressure P of the emergency braking system_s1：

Determining the intermediate braking pressure P of the emergency braking system according to the formula (4)_s1；

P_s1＝η×(P_se-△P)+△P (4)

In the formula (4), η is the pressure efficiency of the brake system; Δ P is pressure loss;

step three, determining the slip period T of the emergency brake system with the active anti-slip brake function_s：

Said slip period T_sThe emergency brake pressure of the emergency brake system is increased from the intermediate brake pressure to the contact connection pressure of the hydraulic relay, so that the contact of the hydraulic relay is connected, and the emergency brake pressure of the emergency brake system is released through the hydraulic electromagnetic valve; a process of reducing the braking pressure of the emergency braking system to an intermediate braking pressure;

according to the test data of the brake system, under the test load of 1/2 tire compression amount, the slipping frequency of the normal anti-slip brake system is not more than 3-5 times/second, and the brake system is normal;

determination of slip period T by equation (5)_s：

Step four, determining the maximum braking pressure P of the hydraulic pressure reducing brake valve_mAnd intermediate brake pressure P_z；

The brake pressure of the hydraulic pressure-reducing brake valve comprises a maximum brake pressure P_mAnd intermediate brake pressure P_z；

Determining the maximum braking pressure P of the hydraulic pressure-reducing brake valve through the formula (6)_m：

P_m＝P_s (6)

Determining the intermediate brake pressure P of the hydraulic pressure-reducing brake valve by the formula (7)_z：

P_z＝P_s1 (7)

In formula (6) and formula (7), P_mThe maximum brake pressure is output by the hydraulic pressure-reducing brake valve; p_zThe intermediate brake pressure is output by the hydraulic pressure reducing brake valve;

step five, determining the pressure for switching on and switching off the hydraulic relay:

determination of the switching pressure P of the hydraulic relay by means of the formula (8)₂Determining the opening pressure P of the hydraulic relay by the formula (9)₁；

P₂＝P_se (8)

P₁＝P_s1 (9)

In the formula, P_seFor emergency braking pressure of braking wheels, P_s1The intermediate brake pressure of the emergency brake system with the active anti-skid brake function is provided;

thus, the design of the emergency brake system with the active anti-skid brake function is completed.

4. A method for designing an aircraft emergency brake system according to claim 3, wherein in step five, when the determined closing pressure P of the hydraulic relay is determined₂When the brake pressure is less than the brake pressure output by the hydraulic pressure-reducing brake valve, the contact of the hydraulic relay is switched on; when the off pressure P of the hydraulic relay₁The hydraulic relay contact is disconnected when the brake pressure output by the hydraulic pressure-reducing brake valve is greater than the brake pressure output by the hydraulic pressure-reducing brake valve; the switching-on pressure P of the hydraulic relay₂The maximum brake pressure P output by the hydraulic pressure reducing brake valve_mThe same; the off pressure P of the hydraulic relay₁Intermediate brake pressure P output by hydraulic pressure reducing brake valve_zThe same is true.

5. A method for designing an aircraft emergency brake system according to claim 3, wherein, when applied, the emergency brake system with active anti-skid braking function is divided into three levels:

when the operating force of the first level is less than or equal to 98N, the output minimum brake pressure is less than or equal to 0.98 MPa;

when the operating force of the second level is more than 98N to less than or equal to 280 plus or minus 20N, the output brake pressure is more than 0.98MPa to less than or equal to 4.5 plus or minus 0.5 MPa;

when the operating force of the third level is more than 280 plus or minus 20N to no more than 1080 plus or minus 50N, the output brake pressure is more than 4.5 plus or minus 0.5MPa to no more than 8 plus or minus 0.5 MPa.

6. An aircraft emergency brake system design method according to claim 5, wherein the output 4.5 ± 0.5MPa of brake pressure is an intermediate brake pressure; when the output brake pressure is 0.98 MPa-4.5 +/-0.5 MPa, the wheel of the brake cannot be locked or burst; when the output brake pressure is 4.5 +/-0.5 MPa-8 +/-0.5 MPa, the brake pressure is greater than the connection pressure of the hydraulic relay, the hydraulic electromagnetic valve is electrified, and the brake pressure of the emergency brake system with the active anti-skid brake function is reduced.

Technical Field

The invention relates to the field of airplane brake systems, in particular to an emergency brake system with an active anti-skidding brake function and a method for optimizing parameters of accessories in the emergency brake system.

Background

In order to make the airplane land safely and ensure the ground control safety of the airplane, according to the requirements and regulations of an emergency brake system in the antiskid brake control system general specification (GJB2879A-2008) of the airplane wheel: "in case of failure or malfunction of the normal braking system, the emergency braking system must safely brake the airplane, and the emergency braking system and the normal braking system must be independent from each other".

The emergency brake system of the airplane mostly adopts a manual operation mode to brake and consists of a single hydraulic pressure reducing brake valve or a single air pressure reducing brake valve. The emergency brake system has no antiskid function, and the output emergency brake pressure is in direct proportion to the operating force.

The on-off antiskid control principle is adopted in the Su 27 aircraft brake system, and the accessories of the normal brake system comprise a pressure relief valve, a modulator, an electromagnetic valve and an antiskid automaton; the antiskid control accessories comprise a hydraulic switch, a speed sensor, an electromagnetic valve and an antiskid automat. The brake oil port of the pressure-reducing valve is communicated with the oil inlet of the hydraulic switch, the oil outlet of the hydraulic switch is communicated with the oil inlet of the modulator, the oil outlet of the modulator is communicated with the oil inlet of the electromagnetic valve, and the brake oil port of the electromagnetic valve is communicated with the oil inlet of the anti-skid automatic device; the brake oil port of the antiskid automatic device is communicated with a brake device; one terminal of the hydraulic switch is communicated with a power supply, the other terminal of the hydraulic switch is communicated with one end of the front wheel speed sensor, and the other end of the front wheel speed sensor is communicated with the electromagnet of the electromagnetic valve through a lead; an oil return port of the pressure reducing valve is communicated with the oil tank through an oil return pipe; an oil return port of the electromagnetic valve is communicated with the oil tank through a pipeline; the oil inlet of the pressure reducing valve is externally connected with a hydraulic source through a pipeline. In the braking process, if a certain wheel is stuck or the wheel is decelerated too violently, the anti-skid control system works and consists of an electric part and a mechanical part, after the airplane lands, a front wheel speed sensor switch is switched on, and a wheel speed sensor is switched off, when the rotating speed of the wheel is reduced to a value corresponding to the linear speed, the speed sensor switch on the wheel is switched on, so that an electromagnetic valve works, the oil coming from the brake is cut off, a brake device is communicated with an oil return circuit, and the brake is released. The wheel speed sensor is normally closed, the front wheel speed sensor is normally open, the circuit of an antiskid system is disconnected when the speed of the airplane is low, and antiskid control is completely borne by a mechanical part. The antiskid automaton is a main accessory for mechanical antiskid. When the angular speed deceleration of the airplane wheel reaches a given value, the oil return valve of the anti-skid automatic device is opened, so that the airplane wheel is released to brake. And braking after the tire dragging is released.

The braking system of Su 27 airplane is composed of simple hydraulic and electric accessories, and has complex structure and poor antiskid function, but adopts a double-signal working mode and applies a tyre dragging automatic machine and a hydraulic amplitude limiter, so that the antiskid function is improved, and the braking system has the characteristics of safe system, stable braking and high braking efficiency. However, the su27 aircraft brake system is not an emergency brake system, but a normal anti-skid brake system using an on-off anti-skid control principle.

The invention with application number 201610902426.5 creates an airplane electronic anti-skid braking system for ensuring emergency braking operation, which comprises a normal braking system and an emergency braking system. The normal braking system mainly comprises a brake valve, an electro-hydraulic servo valve, a control box and an airplane wheel speed sensor; the emergency brake system mainly comprises an emergency brake valve, a conversion valve and a switch, and the normal brake system and the emergency brake system are connected and converted through the conversion valve. The normal braking system and the emergency braking system adopt two sets of independent pressure supply source systems. The invention improves the system structure by adding the control device, so that normal braking can be disabled during emergency braking, the switching valve can be completely switched under the action of the emergency braking pressure, and even if the emergency braking and the normal braking are used simultaneously, the switching valve can be switched to an emergency braking system. Thereby ensuring the implementation of emergency braking and fundamentally eliminating the failure of the emergency braking and the accident hidden danger caused by the simultaneous use of the emergency braking and the normal braking. However, the emergency brake system provided by the invention has no antiskid function.

The invention with application number 201610902427.X provides an airplane brake system for preventing improper use of emergency brake, which comprises a normal brake system and an emergency brake system. The normal braking system comprises a braking instruction sensor, an electromagnetic hydraulic lock, an electro-hydraulic servo valve, a control box and an airplane wheel speed sensor. The emergency brake system comprises an emergency brake valve, a conversion valve and a switch. The normal braking system and the emergency braking system are connected and converted through the conversion valve. If normal braking is used during emergency braking, the invention forces the normal braking system to release pressure, so that the normal input port of the conversion valve has no pressure, and the conversion valve is completely converted into the emergency braking system, thereby ensuring the implementation of emergency braking, and fundamentally eliminating the failure of the emergency braking and the accident potential caused by the simultaneous use of the emergency braking and the normal braking. However, the emergency brake system provided by the invention has no antiskid function.

The invention creation 'an aircraft inertia antiskid braking system for ensuring emergency braking' of application number 201610906014.9, the invention creation by normal braking system and emergency braking system, normal braking system and emergency braking system adopt two sets of independent pressure supply source system, and through the conversion valve conversion. The invention improves the system structure by adding the control device, so that normal braking can be disabled during emergency braking, and the switching valve can be completely switched under the action of the emergency braking pressure. However, the emergency brake system provided by the invention has no antiskid function.

The invention with the application number of 201811188978.X creates 'a remote control emergency brake system and a design method thereof', and the invention creates the method that a brake command sensor arranged in a cockpit directly controls an electromagnetic hydraulic lock and an electro-hydraulic pressure servo valve arranged in a main landing gear cabin, thereby realizing the remote control of the emergency brake system. The electromagnetic hydraulic lock and the electro-hydraulic pressure servo valve which are installed in the main landing gear cabin are connected to a hydraulic source nearby, and the hydraulic pipeline of the braking system is arranged in the main landing gear cabin close to the brake wheels, so that the problem that the hydraulic pipeline needs to enter the cockpit is solved, the length of the hydraulic pipeline is reduced, the emergency braking system is simple to maintain, and the complexity and the maintenance difficulty of the emergency braking system are reduced. However, the emergency brake system provided by the invention has no antiskid function.

Through retrieval, the emergency brake system in the prior art has no anti-skid function, and a specific schematic diagram of the emergency brake system without the anti-skid function is shown in an emergency brake system of a certain machine in fig. 1. The brake pressure is lower than that of a normal brake system, the emergency brake system has no antiskid function, and the emergency brake system has no relevant data on the aspect of active antiskid brake control. The emergency brake system controls an emergency brake handle by a pilot to enable an emergency brake valve to output brake pressure to realize emergency brake control for braking and stopping an airplane, but the emergency brake system without an active anti-skid function has no anti-skid function, and if the bonding torque of the ground is sharply reduced under special conditions such as rain, ice, snow, oil tracks and the like, the emergency brake system can not release pressure through active anti-skid, and accidents of tire dragging by a locomotive or tire burst can be caused as long as the brake torque is larger than the bonding torque of the ground.

Disclosure of Invention

The invention provides an airplane emergency brake system and a design method thereof, aiming at overcoming the defect that when the brake torque is larger than the ground combination torque, the airplane wheel drags the tire or the tire burst accident is caused in the emergency brake system without the active anti-skid function in the prior art.

The emergency brake system of the airplane comprises a hydraulic electromagnetic valve, a hydraulic relay, a hydraulic pressure-reducing brake valve and a 28V direct-current power supply; wherein: a brake oil port of the hydraulic pressure-reducing brake valve is respectively communicated with an oil inlet of the hydraulic relay and an oil inlet of the hydraulic electromagnetic valve through a pressure oil pipe; and an oil return port of the hydraulic pressure-reducing brake valve is communicated with an oil tank through an oil return pipe. And a brake oil port of the hydraulic electromagnetic valve is communicated with an oil inlet of a hydraulic cylinder seat of the airplane wheel. An oil return tank of the hydraulic electromagnetic valve is communicated with the oil tank through a pipeline. And an oil inlet of the hydraulic pressure-reducing brake valve is connected with a hydraulic source through a pipeline. One binding post of a single-pole double-position switch in the hydraulic relay is connected with a 28V direct-current power supply, and the other binding post of the single-pole double-position switch of the hydraulic relay is connected with an electromagnet in the hydraulic electromagnetic valve through a lead. And oil return ports of the hydraulic pressure-reducing brake valve, the hydraulic relay and the hydraulic electromagnetic valve are communicated with an oil tank through oil return pipes.

The 28V direct-current power supply is communicated with a normally open contact of the positive electrode of the hydraulic relay; the contact of the negative pole of the hydraulic relay is connected with the positive pole of the hydraulic electromagnetic valve; the negative pole of the hydraulic electromagnetic valve is connected to the ground wire of the airplane power supply system. When the oil pressure is equal to or greater than the contact-making pressure of the hydraulic relay, the contact of the hydraulic relay is made, the 28V direct-current power supply is connected with the hydraulic electromagnetic valve, and the pressure of the emergency brake system is reduced.

The design process of the aircraft emergency brake system provided by the invention is as follows:

step 1, determining emergency brake pressure P of emergency brake system_s：

Axial thrust S through emergency brake device of brake wheel_tAnd the emergency braking pressure P of the braking machine wheel_seDetermining emergency brake pressure P_s；

I axial thrust S for determining emergency braking device of brake wheel_t：

Determining axial thrust S of emergency brake device of brake wheel through formula (1)_t：

In the formula (1), L_sThe braking distance required by the airplane is R is the inner radius of the movable disc, R is the outer radius of the static disc, mu is the dynamic friction coefficient, A_sThe kinetic energy of the aircraft at the moment of landing, N_msNumber of friction surfaces, R_gIs the wheel rolling radius.

II, determining the emergency braking pressure P of the braking airplane wheel_se：

Determining emergency brake pressure P of brake wheel through formula (2)_se：

In the formula (2), N_hsNumber of pistons, F_hsΔ P is the pressure loss in terms of piston area.

III determining the emergency brake pressure P of the emergency brake system_s：

Determining the emergency braking pressure P of the emergency braking system through the formula (3)_s。

P_s＝P_se+P_i (3)

In formula (3), P_iTo be aAnd (4) system pressure safety margin.

Emergency brake pressure P of emergency brake system_sWith the emergency braking pressure P of the braking machine wheel_seThe same is true.

Step two, determining the intermediate braking pressure P of the emergency braking system_s1：

Determining the intermediate braking pressure P of the emergency braking system according to the formula (4)_s1。

P_s1＝η×(P_se-ΔP)+ΔP (4)

In the formula (4), η is the pressure efficiency of the brake system; Δ P is the pressure loss.

Step three, determining the slip period T of the emergency brake system with the active anti-slip brake function_s：

Said slip period T_sThe emergency brake pressure of the emergency brake system is increased from the intermediate brake pressure to the contact connection pressure of the hydraulic relay, so that the contact of the hydraulic relay is connected, and the emergency brake pressure of the emergency brake system is released through the hydraulic electromagnetic valve; and reducing the braking pressure of the emergency braking system to the intermediate braking pressure.

According to the test data of the brake system, the normal anti-skidding brake system has the skid times of not more than 3-5 times/second under the test load of 1/2 tire compression amount, and the brake system is normal.

Determination of slip period T by equation (5)_s：

Step four, determining the maximum braking pressure P of the hydraulic pressure reducing brake valve_mAnd intermediate brake pressure P_z。

The brake pressure of the hydraulic pressure-reducing brake valve comprises a maximum brake pressure P_mAnd intermediate brake pressure P_z。

Determining the maximum braking pressure P of the hydraulic pressure-reducing brake valve through the formula (6)_m：

P_m＝P_s (6)

Determining the intermediate brake pressure P of the hydraulic pressure-reducing brake valve by the formula (7)_z：

P_z＝P_s1 (7)

In formula (6) and formula (7), P_mThe maximum brake pressure is output by the hydraulic pressure-reducing brake valve; p_zThe intermediate brake pressure is output by the hydraulic pressure reducing brake valve.

When the emergency braking system with the active anti-skidding braking function is applied, the emergency braking system with the active anti-skidding braking function is divided into three levels:

when the operating force of the first level is less than or equal to 98N, the output minimum brake pressure is less than or equal to 0.98 MPa;

when the operating force of the second level is more than 98N to less than or equal to 280 plus or minus 20N, the output brake pressure is more than 0.98MPa to less than or equal to 4.5 plus or minus 0.5 MPa; the output 4.5 +/-0.5 MPa of brake pressure is intermediate brake pressure; when the output brake pressure is 0.98 MPa-4.5 +/-0.5 MPa, the wheel of the brake cannot be locked or burst;

when the operating force of the third level is more than 280 plus or minus 20N to no more than 1080 plus or minus 50N, the output brake pressure is more than 4.5 plus or minus 0.5MPa to no more than 8 plus or minus 0.5 MPa; when the output brake pressure is 4.5 +/-0.5 MPa-8 +/-0.5 MPa, the brake pressure is greater than the connection pressure of the hydraulic relay, the hydraulic electromagnetic valve is electrified, and the brake pressure of the emergency brake system with the active anti-skid brake function is reduced.

Step five, determining the pressure for switching on and switching off the hydraulic relay:

determination of the switching pressure P of the hydraulic relay by means of the formula (8)₂Determining the opening pressure P of the hydraulic relay by the formula (9)₁；

P₂＝P_se (8)

P₁＝P_s1 (9)

In the formula, P_seFor emergency braking pressure of braking wheels, P_s1The intermediate brake pressure of the emergency brake system with the active anti-skid brake function is provided.

When the determined closing pressure P of the hydraulic relay₂When the brake pressure is less than the brake pressure output by the hydraulic pressure-reducing brake valve, the contact of the hydraulic relay is switched on; when in useThe off pressure P of the hydraulic relay₁The hydraulic relay contact is disconnected when the brake pressure is greater than the brake pressure output by the hydraulic pressure reducing brake valve. The switching-on pressure P of the hydraulic relay₂The maximum brake pressure P output by the hydraulic pressure reducing brake valve_mThe same; the off pressure P of the hydraulic relay₁Intermediate brake pressure P output by hydraulic pressure reducing brake valve_zThe same is true.

Thus, the design of the emergency brake system with the active anti-skid brake function is completed.

The emergency brake system with the active anti-skidding function is composed of a hydraulic pressure reducing brake valve, a hydraulic relay and a hydraulic electromagnetic valve. The working principle of the emergency brake system with the active anti-skid brake function is as follows:

1) and an emergency brake switch is switched on, a pilot presses an emergency brake handle, the hydraulic pressure reducing brake valve 4 outputs brake pressure smaller than intermediate brake pressure, and an emergency brake system with an active anti-skidding function does not work.

2) The brake pressure output by the hydraulic pressure reducing brake valve 4 is greater than the intermediate brake pressure P of the emergency brake system_s1When the emergency brake system with the active anti-skidding function works; the brake pressure output by the hydraulic pressure reducing brake valve 4 is greater than the maximum brake pressure P of the emergency brake system_sWhen the pressure is higher than the contact connection pressure of the hydraulic relay, the contact of the hydraulic relay 3 is connected, and meanwhile, the hydraulic electromagnetic valve 2 is electrified, so that the emergency brake pressure is reduced; when the brake pressure of the hydraulic pipeline is lower than the contact disconnection pressure of the hydraulic relay 3, the contact of the hydraulic relay 3 is disconnected, the hydraulic electromagnetic valve 2 is powered off, and the emergency brake pressure rises. The pilot presses the emergency brake handle to the end, and the emergency brake system carries out brake control according to the preset control rate until the airplane is braked and stopped.

The brake pressure curve of the emergency brake system with the active anti-skid brake function in working is shown in figure 3.

The invention provides an aircraft emergency brake system and a design method thereof, aiming at overcoming the defect that the emergency brake system without an active anti-skid function can cause tire dragging or tire burst accidents when the brake torque is larger than the ground binding torque in the prior art, and aiming at researching the in-plant test curve of a normal brake system and referring to the standards of the outfield test flight, the test and the use conclusion of the normal brake system. The emergency brake switch is switched off, the emergency brake system with the active anti-skid brake function does not work, a pilot presses the emergency brake handle, and the hydraulic pressure reducing brake valve outputs brake pressure. The force sense difference of the pilot is obvious in the operation process, and safe and reliable braking can be realized by means of the pilot operation. Because the pilot has the difference of strength in the operation process, the emergency brake system with the active anti-skidding brake function is convenient to use and has a good human-computer interface. When the operating force is small, the output brake pressure is lower than the middle brake pressure, and safe and reliable braking can be realized; when the operating force is increased, the force sense is obvious, and the output brake pressure is higher than the intermediate brake pressure, the emergency brake system with the active anti-skid brake function can compare the actual brake pressure with the brake pressure value set by the system, so that the brake pressure is actively adjusted, and the purpose of active anti-skid is achieved. And realizing safe braking.

According to the requirements on braking torque in HB5648 design Specification of airplane wheels and braking devices, the friction coefficient of the airplane wheels and the ground is 0.35-0.55. The moment acted on the airplane wheel when the airplane wheel brakes comprises a braking moment M_sMoment M combined with ground_cThere are three states: m_s＜M_c、M_sApproach to M_cAnd M_s＞M_c。

When M is_s＞M_cWhen in use, the wheel slides without rolling; when M is_s＜M_cWhen in use, the wheel rolls without sliding; when M is_c＝M_sThe wheel will be in unstable equilibrium. In HB5648, M is requested when the wheel is braked_s＜M_cOr M_sApproach to M_c。

During braking, the ground friction coefficient changes continuously, resulting in a binding moment M_cAre constantly changing. Make the airplane wheel brake moment M_sLess than the combined moment M_cThe brake wheel can not be locked or burst, the braking efficiency is high, the braking distance is short, and the landing is safe.

The emergency braking system is added with an active anti-skid braking function, so that the defect that when the braking torque of the braking system is larger than the ground combined torque, the locomotive dragging or tire burst accidents can be caused is overcome, and the conventional method of the technical personnel in the field does not require that a pilot adopts a point braking operation when using the emergency brake or reduces the braking pressure under the condition of meeting the braking distance efficiency of the aircraft. The working strength of pilots is reduced, and the landing safety of the airplane is ensured.

The invention has two points:

1, adding an active anti-skid brake control function in an emergency brake system; the emergency braking system is used for solving the defect that when the braking torque of the braking system is larger than the ground combined torque, the tire dragging of the aircraft wheels or the tire burst accident can be caused, the working strength of a pilot is reduced, the landing safety of the aircraft is ensured, and the tire burst accident can be prevented without adopting the snub operation when the pilot uses the emergency brake.

And 2, performing emergency braking system braking pressure PWM control. According to the invention, the pressure relay is selected, the emergency brake system selects the test and test flight experience of the normal brake system, and the brake pressure PWM control of the emergency brake system is realized by controlling the flow and the pressure of the hydraulic pressure reduction brake valve. In conclusion, the invention aims to solve the practical problems of increasing the anti-skidding function in the emergency brake system, reducing the workload of pilots and avoiding the tire burst accident when the brake system is used. "

Drawings

FIG. 1 is a schematic structural diagram of an emergency braking system of a certain machine;

FIG. 2 is a schematic structural view of the present invention;

fig. 3 is an operating curve of the present invention.

1. A machine wheel; 2. a hydraulic solenoid valve; 3. a hydraulic relay; 4. a hydraulic pressure reducing brake valve; 5. a pressure oil pipe; 6. an oil return pipe; 7. an oil tank; 8.28V DC power supply.

Detailed Description

The embodiment is an emergency brake system with an active anti-skid brake function, and the emergency brake system comprises a hydraulic electromagnetic valve 2, a hydraulic relay 3, a hydraulic pressure-reducing brake valve 4, a 28V direct-current power supply 8 and an oil return pipe 6. Wherein: a brake oil port of the hydraulic pressure-reducing brake valve 4 is respectively communicated with an oil inlet of the hydraulic relay 3 and an oil inlet of the hydraulic electromagnetic valve 2 through a pressure oil pipe 5; the oil return port of the hydraulic pressure-reducing brake valve 4 is communicated with an oil tank 7 through an oil return pipe 6. And a brake oil port of the hydraulic electromagnetic valve 2 is communicated with an oil inlet of a hydraulic cylinder seat of the airplane wheel. An oil return tank of the hydraulic electromagnetic valve 2 is communicated with an oil tank 7 through a pipeline. And an oil inlet of the hydraulic pressure-reducing brake valve 4 is connected with a hydraulic source through a pipeline.

One terminal of a single-pole double-position switch in the hydraulic relay 3 is connected with the 28V direct-current power supply 8, and the other terminal of the single-pole double-position switch of the hydraulic relay 3 is connected with an electromagnet in the hydraulic electromagnetic valve 2 through a lead. When the emergency brake system works, when the brake pressure output by the hydraulic pressure reduction brake valve 4 reaches the contact connection pressure of the hydraulic relay 3, the hydraulic relay is connected, the 28V direct-current power supply is connected with the electromagnet on the hydraulic electromagnetic valve 2, so that the hydraulic electromagnetic valve 2 discharges oil and releases pressure, and the pressure of the emergency brake system with the active anti-skidding brake function is reduced.

In the embodiment, a hydraulic source is connected to an oil inlet of a hydraulic pressure reducing brake valve 4 through a pipe joint of M12 and an oil pipe 5 with the length of 3.6M and the inner diameter of 5.5 mm; a brake oil port of the hydraulic pressure-reducing brake valve 4 is connected with the hydraulic relay 3 through a three-way pipe, a pipe joint of M12 and an oil pipe 5 with the length of 0.2M, and the other connector of the three-way pipe joint is communicated with an oil inlet of the hydraulic electromagnetic valve 2 through the pipe joint of M12 and the oil pipe 5 with the length of 2.1M and the inner diameter of phi 5.5 mm; oil enters the hydraulic cylinder seat of the wheel 1 from the brake working port of the hydraulic electromagnetic valve 2 through a pipe joint of M12 and an oil pipe with the length of 1.5M and the inner diameter of phi 5.5mm to push the hydraulic cylinder to work so as to brake.

The oil return pipe 6 connects return oil of the hydraulic pressure-reducing brake valve 4, the hydraulic relay 3 and the hydraulic solenoid valve 2 and connects the return oil to the oil tank 7, and the return oil is led to the oil tank 7 when the system brake pressure is reduced.

The 28V direct-current power supply 8 of the airplane power supply system is communicated with a normally open contact of the positive pole of the hydraulic relay 3; the contact of the negative pole of the hydraulic relay 3 is connected with the positive pole of the hydraulic electromagnetic valve 2; the negative pole of the hydraulic electromagnetic valve 2 is connected to the ground wire of the airplane power supply system. When the oil pressure is equal to or greater than the contact-making pressure of the hydraulic relay 3, the contact of the hydraulic relay 3 is made, the 28V direct-current power supply is connected with the hydraulic electromagnetic valve 2, and the pressure of the emergency brake system is reduced.

The embodiment further provides a design method of the emergency brake system with the active anti-skid brake function, and the specific process is as follows:

step one, determining the emergency brake pressure P of the emergency brake system with the active anti-skid brake function_s：

Axial thrust S through emergency brake device of brake wheel_tAnd the emergency braking pressure P of the braking machine wheel_seDetermining emergency braking pressure P of emergency braking system with active anti-skid braking function_s. The specific process is as follows:

i axial thrust S for determining emergency braking device of brake wheel_t：

Determining axial thrust S of emergency brake device of brake wheel through formula (1)_t：

In the formula (1), L_sThe braking distance required by the airplane is R is the inner radius of the movable disc, R is the outer radius of the static disc, mu is the dynamic friction coefficient, A_sThe kinetic energy of the aircraft at the moment of landing, N_mcNumber of friction surfaces, R_gIs the wheel rolling radius.

The braking distance required by the airplane in the embodiment is L_s810m, the inner radius R of the movable disc is 0.122m, the outer radius R of the static disc is 0.162m, and R + R is 0.284 m; the coefficient of kinetic friction mu is 0.23; kinetic energy A of landing moment of airplane landing_s12000000J; number of friction surfaces N_mc6; wheel rolling radius R_g＝0.365。

Substituting the data into formula (1) to obtain

II, determining the emergency braking pressure of the braking machine wheelP_se：

Determining emergency brake pressure P of brake wheel through formula (2)_se：

In the formula (2), N_hsNumber of pistons, F_hsΔ P is the pressure loss in terms of piston area.

In this embodiment, the number of pistons N_hs(ii) 5; piston area F_hs＝π×17.5²＝961.625mm²(ii) a Pressure loss Δ P was 1.2 MPa.

Substituting the data into formula (2) to obtain

III determining the emergency brake pressure P of the emergency brake system with the active anti-skid brake function_s：

Determining the emergency brake pressure P by the formula (3)_s。

P_s＝P_se+P_i (3)

In formula (3), P_iIs the system pressure safety margin.

Emergency brake pressure P of emergency brake system with active anti-skid brake function in the embodiment_sWith the emergency braking pressure P of the braking machine wheel_seAnd similarly, from the perspective of safety design, the safety margin of system operation is increased.

In this example, take P_iSubstituted into formula (3) under 1MPa, P_s＝6.9+1＝7.9MPa。

In this embodiment, the emergency braking pressure P of the emergency braking system with the active anti-skid braking function_s＝8±0.5MPa。

Step two, determining the intermediate braking pressure P of the emergency braking system with the active anti-skid braking function_s1：

According to the distance efficiency and pressure efficiency description of a brake system of HB6080 general technical conditions of an antiskid brake control system of airplane wheels, the outfield service efficiency of the brake system is 60-80%.

Intermediate brake pressure P_s1Is the braking pressure at which the brake wheels do not lock in any situation.

Determining the intermediate braking pressure P of the emergency braking system with the active anti-skid braking function according to the formula (4)_s1。

P_s1＝η×(P_se-ΔP)+ΔP (4)

In the formula (4), eta is the pressure efficiency of the brake system, and is obtained by inquiring HB6080 general technical conditions of the antiskid brake control system of the airplane wheels; Δ P is the pressure loss.

In this embodiment, the pressure efficiency η of the braking system is 60%; the pressure loss Δ P was 1.2 MPa. Substituting the data into formula (4) to obtain P_s1＝4.68MPa

In the embodiment, the intermediate brake pressure of the emergency brake system is determined as

Step three, determining the slip period T of the emergency brake system with the active anti-slip brake function_s：

Slip period T_s: said slip period T_sThe emergency brake pressure of the emergency brake system with the active anti-skid brake function is increased from the intermediate brake pressure to the contact connection pressure of the hydraulic relay 3, so that the contact of the hydraulic relay is connected, and the emergency brake pressure of the emergency brake system is relieved through the hydraulic solenoid valve; and reducing the braking pressure of the emergency braking system to the intermediate braking pressure.

According to the test data of the brake system, the normal anti-skidding brake system has the skid times of not more than 3-5 times/second under the test load of 1/2 tire compression amount, and the brake system is normal.

Determination of slip period T by equation (5)_s：

Emergency brake system slip period T with active anti-slip brake function in embodiment_sIs 0.2 to 0.3 s.

And step four, determining the brake pressure of the hydraulic pressure reducing brake valve.

The brake pressure of the hydraulic pressure-reducing brake valve 4 comprises a maximum brake pressure P_mAnd intermediate brake pressure P_z。

When the brake pressure of the hydraulic pressure-reducing brake valve is determined to be less than or equal to the intermediate brake pressure, the handle operating force is small, and the brake is reliable and safe;

when the brake pressure of the hydraulic pressure-reducing brake valve is determined to be the maximum brake pressure, the operating force of the handle is increased, the force sense is obvious, and the safety and the reliability of braking are realized by depending on the operation of a pilot.

When the emergency braking system with the active anti-skid braking function is applied, the emergency braking system with the active anti-skid braking function is divided into three levels on a certain airplane: in the first level, when the brake handle is pressed and the operating force is less than or equal to 98N, the output minimum brake pressure is less than or equal to 0.98 MPa. In the second level, when the operating force is more than 98N to less than or equal to 280 plus or minus 20N, the output brake pressure is more than 0.98MPa to less than or equal to 4.5 plus or minus 0.5 MPa; the output 4.5 +/-0.5 MPa of brake pressure is intermediate brake pressure; under the brake pressure of 0.98 MPa-4.5 +/-0.5 MPa, the brake wheel cannot be locked or burst. In the third level, when the operating force is more than 280 plus or minus 20N to no more than 1080 plus or minus 50N, the output brake pressure is more than 4.5 plus or minus 0.5MPa to no more than 8 plus or minus 0.5 MPa; when the brake pressure is 4.5 +/-0.5 MPa-8 +/-0.5 MPa, the brake pressure is greater than the connection pressure of the hydraulic relay 3, the hydraulic electromagnetic valve 2 is electrified, and the brake pressure of the emergency brake system with the active anti-skid brake function is reduced.

Determining the maximum braking pressure P of a hydraulic pressure reducing brake valve according to the formula (6) according to the use characteristics of an emergency brake system with an active anti-skid brake function_mDetermining the intermediate braking pressure P of the hydraulic pressure-reducing brake valve by the formula (7)_z。

P_m＝P_s (6)

P_z＝P_s1 (7)

P_mThe maximum brake pressure is output by the hydraulic pressure-reducing brake valve; p_zThe intermediate brake pressure is output by the hydraulic pressure reducing brake valve.

In this embodiment, there will be an emergency braking system emergency braking pressure P with an active anti-skid braking function_sIntermediate brake pressure of emergency brake system with active anti-skid brake function of 8 plus or minus 0.5MPaSubstituting the formula (6) to obtain the maximum brake pressure output by the hydraulic pressure-reducing brake valve 4 of 8 +/-0.5 MPa; the hydraulic pressure reducing brake valve 4 outputs the middle brake pressure of 4.5 +/-0.5 MPa.

Step five, determining the pressure for switching on and switching off the hydraulic relay:

when the brake pressure output by the hydraulic pressure reducing brake valve is larger than the connection pressure P of the hydraulic relay₂When the hydraulic relay is in contact connection; when the brake pressure output by the hydraulic pressure reducing brake valve is smaller than the off pressure P of the hydraulic relay₁When the hydraulic relay contacts are open. The switching-on pressure P of the hydraulic relay₂The maximum brake pressure P output by the hydraulic pressure reducing brake valve_mThe same; the off pressure P of the hydraulic relay₁Intermediate brake pressure P output by hydraulic pressure reducing brake valve_zThe same is true.

Determination of the switching pressure P of the hydraulic relay by means of the formula (8)₂Determining the opening pressure P of the hydraulic relay by the formula (9)₁；

P₂＝P_se (8)

P₁＝P_s1 (9)

In the formula, P_seFor emergency braking pressure of braking wheels, P_s1The intermediate brake pressure of the emergency brake system with the active anti-skid brake function is provided.

Will P_se6.9MPa andrespectively substituting into the formula (8) and the formula (9) to obtain the hydraulic relaySwitched-on maximum brake pressure P₂Intermediate brake pressure at 6.9MPa with hydraulic relay off

Thus, the design of the emergency brake system with the active anti-skid brake function is completed.