Design method of piston assembly for aviation brake airplane wheel

Abstract

The invention discloses a design method of a piston assembly for an aviation brake airplane wheel, and belongs to the field of airplane wheel brake systems. The method comprises the steps of determining the piston total area according to brake torque requirements; the piston stroke is determined according to the reserved abrasion thickness of the brake disc and the axial deformation amount of the brake device; designing a gap adjusting mechanism; the gap adjusting mechanism comprises a return spring, a spring seat, an expansion pipe and a pull rod; determining the piston diameter and the number of pistons according to the total area of the pistons; the brake clearance is determined according to the designed clearance adjusting clearance and the brake deformation amount; performing sealing ring type selection according to the sealing performance of the piston; the material surface treatment mode is determined according to the natural environment and the mechanical environment. According to the method, the design input requirement of the piston assembly and the specific steps of the design process are limited, the piston assembly for the brake airplane wheel meeting the requirement of an airplane can be designed, and the method has high application value.

Description

Technical Field

[0001] The invention belongs to the field of aircraft wheel brake systems, and in particular relates to a design method for a piston assembly for an aircraft brake wheel. Background Art

[0002] Hydraulic brakes are the mainstream technology in the field of aircraft brakes. The brake piston assembly is a key component in the brake device and plays a decisive role in the reliable operation of the brake device. The piston assembly design technology is the most critical technology in the structural design of the brake device. The hydraulic brake piston assembly has developed from a separate structure to an integrated structure, from a wet piston to a dry piston, and from a friction-type clearance adjustment mechanism to an expansion tube-type clearance adjustment mechanism. The most common failure mode of the existing brake wheel piston assembly is that the piston does not return. The so-called piston does not return means that the brake clearance between the piston and the brake disc is less than the design value, or even there is no brake clearance. The piston does not return to its position will cause slow brake response, aggravated brake disc wear and shortened life, uneven brake torque transmission affecting brake performance and other problems. The piston assembly is mainly composed of a piston bushing, a piston, a clearance adjustment mechanism, a heat insulation pad, a sealing ring, and a protective ring.

[0003] Therefore, the present invention proposes a design method for an aircraft brake wheel piston assembly. Summary of the invention

[0004] Technical issues to be solved:

[0005] In order to avoid the shortcomings of the prior art, the present invention provides a design method for an aircraft brake wheel piston assembly. First, the total area of ​​the piston is determined according to the braking torque requirement, and then the piston stroke, clearance adjustment mechanism, piston diameter and the number of pistons are designed. Finally, the brake clearance, sealing performance, and material surface treatment are determined. The method limits the design input requirements and specific steps of the design process of the piston assembly, and can design a brake wheel piston assembly that meets the requirements of the aircraft, which has great application value.

[0006] The technical solution of the present invention is: a design method for a piston assembly for an aircraft brake wheel, wherein the piston assembly comprises a pull rod, an expansion tube, a spring seat, a return spring, an isolation cylinder, and a piston coaxially arranged in a bushing, and force transmission plates and heat insulation pad assemblies are respectively encapsulated at both ends of the bushing; the specific steps are as follows:

[0007] Step 1: Determine the total piston area according to the braking torque requirement;

[0008] Step 2: Determine the piston stroke according to the reserved wear thickness of the brake disc and the axial deformation of the brake device;

[0009] Step 3, designing a gap adjustment mechanism; the gap adjustment mechanism includes a return spring, a spring seat, an expansion tube, and a pull rod;

[0010] Step 4, determine the piston diameter and the number of pistons according to the total area of ​​the pistons;

[0011] Step 5, determining the brake clearance according to the designed clearance adjustment gap and the brake deformation;

[0012] Step 6: Select the sealing ring according to the sealing performance of the piston;

[0013] Step 7: Determine the material surface treatment method based on the natural environment and mechanical environment.

[0014] A further technical solution of the present invention is: the calculation formula of the total area of ​​the piston is as follows:

[0015]

[0016] Where: F n Represents the total piston area, μ d represents the friction coefficient; P represents the normal braking pressure, ΔP represents the pressure loss, n T Represents the number of friction pairs, R m It represents the middle diameter of the brake disc, and Ms represents the braking torque.

[0017] A further technical solution of the present invention is that the piston stroke is greater than or equal to the sum of the reserved wear thickness of the brake disc and the axial deformation of the brake device.

[0018] A further technical solution of the present invention is: the design process of the return spring is as follows:

[0019] Step 3.1.1 Determine the elastic force of the return spring installation height based on the piston area and return oil pressure:

[0020] The elastic force of the total installation height of the return spring ≥ F n ×F 回 ;

[0021] The elastic force of a single return spring at the installation height Ph≥F n / n×F 回 ≥Minimum spring force of a single return spring;

[0022] Among them, F n represents the total area of ​​the piston, n represents the number of return springs, F 回 Indicates the oil return pressure;

[0023] Step 3.1.2 Determine the installation height and inner and outer diameters of the spring based on the installation space in the piston and the return spring force:

[0024] The outer diameter of the return spring is smaller than the inner diameter of the piston, and the inner diameter thereof is larger than the spring installation position diameter of the spring seat;

[0025] Step 3.1.3 Calculate whether the spring is coiled:

[0026] The coil height of the spring = the number of coils × the diameter of the spring wire;

[0027] When the height of the spring after compression is greater than the coil height of the spring, coiling will not occur; the height of the spring after compression = the free height of the spring - the compressed height of the spring under the maximum elastic force.

[0028] A further technical solution of the present invention is: the design process of the expansion tube is as follows:

[0029] Step 3.2.1 Design of the outline dimensions of the expansion tube:

[0030] The outer diameter range of the expansion tube is determined according to the installation space limitation of the spring seat; the inner diameter range of the expansion tube is determined according to the diameter of the pull rod; and the length range of the expansion tube is determined according to the working stroke of the piston;

[0031] Step 3.2.2 Design of expansion force of expansion tube:

[0032] The expansion force of the expansion tube is greater than or equal to 1.5 times the maximum spring force of the return spring, that is, the expansion force is ≥ 1.5 times the maximum spring force of the return spring;

[0033] The maximum expansion force is less than or equal to the single piston thrust S corresponding to 1 / 2 normal working pressure of the piston T , that is, the maximum expansion force ≤ S T ,

[0034]

[0035] The expansion force calculation formula is as follows:

[0036]

[0037] Among them, σ represents the expansion stress, R represents the outer radius of the expansion tube before expansion, r represents the inner radius of the expansion tube before expansion, μ represents the friction coefficient of the expansion tube, λ1 represents the material property change coefficient, λ2 represents the friction property change coefficient, α represents the expansion angle, R 球 Indicates the radius of the ball head;

[0038] The range of expansion force is calculated. When S T >F>Minimum expansion force, meeting design requirements.

[0039] A further technical solution of the present invention is: the design requirement of the pull rod is: the maximum load borne by the pull rod is equal to the expansion force of the expansion tube.

[0040] A further technical solution of the present invention is: the design requirements of the spring seat are: setting the gap between the spring seat and the inner cavity of the piston to 0.2mm~0.3mm; setting the gap between the spring seat and the inner diameter of the spring to 0.5mm~0.7mm, so as to reduce the radial swing of the pull rod and the expansion tube and ensure the stable operation of the spring.

[0041] A further technical solution of the present invention is: the method for determining the piston diameter and the number of pistons is:

[0042]

[0043] Where: n represents the number of pistons, that is, the number of springs, D represents the piston diameter, and d represents the tie rod diameter;

[0044] The pistons are evenly distributed at the friction middle diameter position of the brake disc, and the number is greater than or equal to 4.

[0045] A further technical solution of the present invention is: the method for determining the brake clearance is that the sum of the brake clearance and the axial deformation of the brake device is less than the adjustment clearance, that is, C D >H+D B ;

[0046] C D = k × D B +C I ,

[0047] Among them, C D is the gap adjustment clearance, C I is the minimum guaranteed clearance, K is the coefficient considering the influence of temperature on axial deformation, D B is the axial deformation of the brake structure under maximum brake pressure, and H is the brake clearance.

[0048] A further technical solution of the present invention is: the method for selecting the sealing ring according to the sealing performance of the piston is:

[0049] The rated compression rate of the static seal of the piston bushing is 30%-35%, and the sum of the volumes of the sealing ring and the protection ring should not be greater than 80% of the volume of the sealing groove to prevent the expansion of the sealing ring from affecting the sealing performance;

[0050] The rated compression rate of the dynamic seal in the piston is 19% to 25%, and the minimum compression is not less than 15%; the sum of the volume of the sealing ring and the protection ring should not be greater than 75% of the volume of the sealing groove to prevent the expansion of the sealing ring from affecting the sealing performance;

[0051] The rated compression rate of the tie rod seal in the piston is 18% to 22%, and the minimum compression is not less than 13%; when using double protection rings, the sum of the volumes of the sealing ring and the protection ring should not be greater than 80% of the volume of the sealing groove.

[0052] Beneficial Effects

[0053] The beneficial effects of the present invention are as follows: the present invention proposes a design method for a piston assembly, adopts a forward design, uses a new expansion tube type clearance adjustment mechanism, comprehensively considers the design factors affecting the brake clearance at the beginning of the design, and provides a design method. By applying the piston assembly design method of the present invention, a piston assembly with higher stability, reliability, and sensitivity can be designed, and the failure mode of the piston not returning to its position can be avoided, and the problems of slow brake response, aggravated wear of the brake disc and shortened life, and uneven transmission of the brake torque affecting the brake performance caused by the piston not returning to its position can be solved.

[0054] 1. The piston assembly designed based on the method of the present invention can realize that the return spring is compressed under the action of brake pressure, the piston moves forward, and the brake force is transmitted to the brake disc to brake the wheel. When the brake is released, the piston retreats under the action of the return spring to release the friction between the brake discs. The method is universal and applicable to the design of piston assemblies under various brake performance requirements.

[0055] 2. The method of the present invention can improve the sensitivity of the brake. After multiple braking, the thickness of the brake disc decreases due to wear, and the distance of the piston moving forward becomes larger. At this time, the piston needs to drive the spring seat to overcome the expansion force between the expansion tube and the ball head and move forward more than the distance caused by the wear of the brake disc. After releasing the brake, the return spring returns to its initial state, and the piston extends more than before braking due to the wear of the brake disc. In this way, the brake clearance reserved by the design is always maintained between the piston and the brake disc, thereby improving the sensitivity of the brake. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 The structure of the piston assembly designed in the embodiment of the present invention is schematically shown in FIG. Figure 1 ;

[0057] Figure 2 The structure of the piston assembly designed in the embodiment of the present invention is schematically shown in FIG. Figure 2 ;

[0058] Figure 3 Schematic diagram of an expansion tube according to an embodiment of the present invention;

[0059] Attached Figure 1 Marking description: 1- force transmission plate, 2- bushing, 3- piston, 4- expansion tube, 5- pull rod, 6- return spring, 7- isolation tube, 8- spring seat, 9- spring seat clamp, 10- hexagonal slotted nut, 11- thermal insulation pad clamp, 12, 13, 20, 21- sealing ring, 14- pull rod protection ring, 15- piston protection ring, 16- bushing protection ring, 17- oil scraper ring, 18- ball head, 19- thermal insulation pad assembly, 22, stainless steel wire. DETAILED DESCRIPTION

[0060] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0061] This embodiment provides a design method for an aircraft brake wheel piston assembly, and the designed aircraft brake wheel piston assembly is disclosed in ZL202111206633.4, including a force transmission plate 1, 2 bushings, a piston 3, an expansion tube 4, a pull rod 5, a return spring 6, an isolation tube 7, a spring seat 8, a spring seat clamp 9, a hexagonal slotted nut 10, a heat insulation pad clamp 11, sealing rings 12, 13, 20, 21, a pull rod protection ring 14, a piston protection ring 15, a bushing protection ring 16, an oil scraper ring 17, a ball head 18, a heat insulation pad assembly 19, and a stainless steel wire 22. The specific steps of the design method are as follows:

[0062] Step 1: Determine the total piston area according to the braking torque requirement;

[0063]

[0064] Where: μ d —friction coefficient is 0.2; P—normal brake pressure is 21MPa, ΔP—pressure loss (the initial pressure loss should not be designed to be too small, which will lead to slow brake release or incomplete brake release. Excessive pressure loss will cause waste of braking force and reduce braking efficiency. Generally, ΔP is within the range of (10-20)% of the normal brake pressure, and this embodiment takes 12% or 2.5MPa), n T —Number of friction pairs (8), R m —The middle diameter of the brake disc is 183mm,

[0065] The braking torque requirement is Ms = 47668 N m, and the total piston area is F n =8800mm 2

[0066] Step 2, determining the piston stroke according to the reserved wear thickness of the brake disc and the axial deformation of the brake device, wherein the piston stroke is greater than or equal to the sum of the reserved wear thickness of the brake disc and the axial deformation of the brake device;

[0067] In this embodiment, the reserved wear thickness of the brake disc is 34 mm, and the axial deformation of the brake device is 1.5 mm, so the stroke of the piston is designed to be 36 mm.

[0068] Step 3: Design of gap adjustment mechanism;

[0069] The gap adjustment mechanism is mainly composed of a return spring, a spring seat, an expansion tube and a pull rod.

[0070] The design sequence of the gap adjustment mechanism is: first design the return spring, then design the expansion tube, and finally design the pull rod.

[0071] 1) Spring design

[0072] The spring is designed according to the standard HB3-51~3. The following requirements must be met during the design process:

[0073] a. Determine the elastic force of the return spring installation height based on the piston area and return oil pressure. The elastic force of the return spring installation height ≥ piston area × return oil pressure;

[0074] The elastic force of a single return spring at the installation height Ph≥(8800 / 5)mm 2 ×1.3Mpa≥2288N.

[0075] b. Determine the installation height and inner and outer diameters of the spring based on the installation space inside the piston and the spring force.

[0076] Steel wire diameter: Try to choose a smaller diameter. The spring steel wire diameter in this embodiment is 7.5 mm.

[0077] Working turns: If space permits, choose more turns. The minimum should not be less than 4 turns. This embodiment takes 4.5 turns.

[0078] In this embodiment, the free height of the space for installing the spring in the piston is M = 52mm. According to the installation space, the outer diameter of the spring is smaller than the inner diameter of the piston, and the outer diameter of the spring is 34.5mm. The inner diameter of the spring is larger than the diameter of the spring seat, and the inner diameter of the spring is 19.6mm.

[0079] c. Calculate whether the springs are coiled.

[0080] The spring coil height is the number of coils (4.5 coils) multiplied by the spring wire diameter (7.5 mm). The result is 4.5 × 7.5 = 33.75 mm.

[0081] The free height of the spring in this embodiment is 58.2mm, and the compression height under the maximum elastic force of the spring is 11.2mm. When the free height of the spring minus the compression height under the maximum elastic force of the spring 11.2mm is greater than the coil height, the coil phenomenon will not occur. That is, 58.2-11.2=47mm>33.75mm, so the coil phenomenon will not occur.

[0082] 2) Expansion tube design

[0083] The outer diameter range of the expansion tube is determined according to the installation space limitation of the spring seat, the inner diameter range of the expansion tube is determined according to the diameter of the pull rod, and the length range of the expansion tube is determined according to the working stroke of the piston.

[0084] The maximum elastic force of the return spring is the basis for the design of the expansion tube. The expansion force of the expansion tube should be greater than the maximum elastic force of the return spring. Generally, to ensure reliable operation: the expansion force of the expansion tube should not be less than 1.5 times the maximum spring force of the return spring;

[0085] Minimum expansion force = 4053 × 1.5 = 6079.5N

[0086] The maximum pull-through load (expansion force) should not be greater than the single piston thrust S corresponding to 1 / 2 normal working pressure. T .

[0087] The braking torque corresponding to 1 / 2 normal working pressure is 20613N·m (Ms=μ d F n (P-ΔP)n T R m )

[0088]

[0089] =14080N

[0090] Maximum expansion force ≤S T

[0091] Expansion force (pull-through load) design:

[0092] If the expansion rate of the expansion tube is newly designed at about 15%, the expansion force F (pull-through load) of the expansion tube can be estimated according to the following formula:

[0093]

[0094] Among them, σ-expansion stress (230-290) MPa, R-external radius of the expansion tube before expansion (13mm), r-inner radius of the expansion tube before expansion (11mm), μ-friction coefficient of the expansion tube (0.1), λ1-material property change coefficient is 1.2, λ2-friction property change coefficient is 1.1, α-expansion angle R 球 -Ball head radius (6mm).

[0095] Calculate the expansion force F = 7748 ~ 9769N

[0096] 14080N>F>6079.5N, meeting the design requirements.

[0097] 3) Tie rod design

[0098] The maximum load borne by the pull rod is the expansion force of the expansion tube.

[0099] 4) Spring seat design

[0100] When designing the spring seat, the gap between the spring seat and the inner cavity of the piston should be controlled (0.2mm-0.3mm) to reduce the radial swing of the pull rod and the expansion tube. At the same time, the gap between the spring seat and the inner diameter of the spring should be controlled (0.5mm-0.7mm) to ensure stable operation of the spring.

[0101] Step 4, determine the piston diameter and the number of pistons according to the total area of ​​the pistons;

[0102]

[0103] Where: n-number of pistons, D-piston diameter, d-tie rod diameter (the greater the expansion force of the expansion tube, the thicker the tie rod should be, the tie rod diameter is generally Ф6-Ф8mm, and the tie rod diameter of this embodiment is Ф8mm). Pistons are generally evenly distributed at the friction center diameter of the brake disc. The uniformity of the braking force is considered during design, and generally more than 4 pistons are selected. Too many pistons will reduce reliability, and the pistons of this embodiment are designed to be 5. Calculated D = 50mm

[0104] Step 5: Determine the brake clearance based on the designed adjustment clearance and brake deformation;

[0105] The sum of the brake clearance and the axial deformation of the brake device must be smaller than the adjustment clearance.

[0106] C D = k × D B +C I , C D >H+D B

[0107] C D To design the gap adjustment clearance.

[0108] C I To ensure the minimum clearance, take 2 to 4 mm.

[0109] K is the coefficient considering the influence of temperature on axial deformation, which is generally taken as 2.

[0110] D B It is the axial deformation of the brake structure under the maximum brake pressure, in mm.

[0111] H is the brake clearance.

[0112] Design gap adjustment gap C D Generally, it is 4mm to 8mm. The larger the brake device specification, the larger the clearance adjustment gap is designed to be. In this embodiment, it is 5.5mm. B is the axial deformation of the brake structure under the maximum brake pressure, which is 1.5 mm in this embodiment, and the brake clearance is determined to be 3.5 mm.

[0113] Step 6: Select the sealing ring according to the sealing performance of the piston;

[0114] The static seal of the bushing is designed as an external fixed seal type with a rated compression rate of 30% to 35%. The sum of the volume of the sealing ring and the protective ring should not be greater than 80% of the volume of the sealing groove to prevent the expansion of the sealing ring from affecting the sealing performance.

[0115] The piston dynamic seal is designed as an external active seal type, with a rated compression rate of 19% to 25% and a minimum compression of no less than 15%. Standard seal rings can be selected according to HB4-56. The sum of the volume of the seal ring and the protection ring should not be greater than 75% of the volume of the seal groove to prevent the expansion of the seal ring from affecting the sealing performance.

[0116] The tie rod seal is designed as an external active seal type, with a rated compression rate of 18% to 22% and a minimum compression of no less than 13%. Use double protection rings. The sum of the volume of the sealing ring and the protection ring should not be greater than 80% of the volume of the sealing groove.

[0117] Step 7: Determine the surface treatment of the material based on the natural environment and mechanical environment.

[0118] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A design method for a piston assembly for an aircraft brake wheel, the piston assembly comprising a pull rod, an expansion tube, a spring seat, a return spring, a spacer tube, and a piston coaxially arranged in a bushing, and a force transmission plate and a heat insulation pad assembly are respectively encapsulated at both ends of the bushing; characterized in that The specific steps are as follows: Step 1: Determine the total piston area according to the braking torque requirement; Step 2: Determine the piston stroke according to the reserved wear thickness of the brake disc and the axial deformation of the brake device; Step 3, designing a gap adjustment mechanism; the gap adjustment mechanism includes a return spring, a spring seat, an expansion tube, and a pull rod; Step 4: Determine the piston diameter and the number of pistons according to the total area of ​​the pistons; Step 5, determining the brake clearance according to the designed adjustment clearance and brake deformation; Step 6: Select the sealing ring according to the sealing performance of the piston; Step 7: Determine the material surface treatment method based on the natural environment and mechanical environment.

2. The design method of an aircraft brake wheel piston assembly according to claim 1, characterized in that: The calculation formula of the total piston area is as follows: Where: F n Represents the total piston area, μ d represents the friction coefficient; P represents the normal brake pressure, ΔP represents the pressure loss, n T Represents the number of friction pairs, R m It represents the middle diameter of the brake disc, and Ms represents the braking torque.

3. The design method of a piston assembly for an aircraft brake wheel according to claim 2, characterized in that: The piston stroke is greater than or equal to the sum of the reserved wear thickness of the brake disc and the axial deformation of the brake device.

4. The design method of a piston assembly for an aircraft brake wheel according to claim 3, characterized in that: The design process of the return spring is as follows: Step 3.1.1 Determine the elastic force of the return spring installation height based on the piston area and return oil pressure: The elastic force of the return spring installation height ≥ F n ×F 回 ; The elastic force of a single return spring at the installation height Ph≥F n / n×F 回 ≥Minimum spring force of a single return spring; Among them, F n represents the total area of ​​the piston, n represents the number of return springs, F 回 Indicates the oil return pressure; Step 3.1.2 Determine the installation height and inner and outer diameters of the spring based on the installation space in the piston and the return spring force: The outer diameter of the return spring is smaller than the inner diameter of the piston, and the inner diameter thereof is larger than the spring installation position diameter of the spring seat; Step 3.1.3 Calculate whether the spring is coiled: The coil height of the spring = the number of coils × the diameter of the spring wire; When the height of the spring after compression is greater than the coil height of the spring, coiling will not occur; the height of the spring after compression = the free height of the spring - the compressed height of the spring under the maximum elastic force.

5. The design method of an aircraft brake wheel piston assembly according to claim 4, characterized in that: The design process of the expansion tube is as follows: Step 3.2.1 Design of the outline dimensions of the expansion tube: The outer diameter range of the expansion tube is determined according to the installation space limitation of the spring seat; the inner diameter range of the expansion tube is determined according to the diameter of the pull rod; and the length range of the expansion tube is determined according to the working stroke of the piston; Step 3.2.2 Design of expansion force of expansion tube: The expansion force of the expansion tube is greater than or equal to 1.5 times the maximum spring force of the return spring, that is, the expansion force is ≥ 1.5 times the maximum spring force of the return spring; The maximum expansion force is less than or equal to the single piston thrust S corresponding to 1 / 2 normal working pressure of the piston T , that is, the maximum expansion force ≤ S T , the formula is as follows: The expansion force calculation formula is as follows: Among them, σ represents the expansion stress, R represents the outer radius of the expansion tube before expansion, r represents the inner radius of the expansion tube before expansion, μ represents the friction coefficient of the expansion tube, λ1 represents the material property change coefficient, λ2 represents the friction property change coefficient, α represents the expansion angle, R 球 Indicates the radius of the ball head; The range of expansion force is calculated. When S T >F>Minimum expansion force, meeting design requirements.

6. The design method of an aircraft brake wheel piston assembly according to claim 5, characterized in that: The design requirement of the pull rod is that the maximum load borne by the pull rod is equal to the expansion force of the expansion tube.

7. The design method of a piston assembly for an aircraft brake wheel according to claim 6, characterized in that: The design requirements of the spring seat are: setting the gap between the spring seat and the piston cavity to 0.2mm~0.3mm; setting the gap between the spring seat and the inner diameter of the spring to 0.5mm~0.7mm, so as to reduce the radial swing of the pull rod and the expansion tube and ensure stable operation of the spring.

8. The design method of an aircraft brake wheel piston assembly according to claim 7, characterized in that: The method for determining the piston diameter and the number of pistons is: Where: n represents the number of pistons, that is, the number of springs, D represents the piston diameter, and d represents the tie rod diameter; The pistons are evenly distributed at the friction middle diameter position of the brake disc, and the number is greater than or equal to 4.

9. The design method of an aircraft brake wheel piston assembly according to claim 8, characterized in that: The method for determining the brake clearance is that the sum of the brake clearance and the axial deformation of the brake device is less than the adjustment clearance, that is, C D >H+D B ; C D =k×D B +C I , Among them, C D is the gap adjustment clearance, C I is the minimum guaranteed clearance, K is the coefficient considering the influence of temperature on axial deformation, D B is the axial deformation of the brake structure under maximum brake pressure, and H is the brake clearance.

10. The design method of an aircraft brake wheel piston assembly according to claim 9, characterized in that: The method for selecting the sealing ring according to the sealing performance of the piston is: The rated compression rate of the static seal of the piston bushing is 30% to 35%, and the sum of the volumes of the sealing ring and the protection ring should not be greater than 80% of the volume of the sealing groove to prevent the expansion of the sealing ring from affecting the sealing performance; The rated compression rate of the dynamic seal in the piston is 19% to 25%, and the minimum compression is not less than 15%; the sum of the volume of the sealing ring and the protection ring should not be greater than 75% of the volume of the sealing groove to prevent the expansion of the sealing ring from affecting the sealing performance; The rated compression rate of the tie rod seal in the piston is 18% to 22%, and the minimum compression is not less than 13%; when using double protection rings, the sum of the volumes of the sealing ring and the protection ring should not be greater than 80% of the volume of the sealing groove.

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