A design method for a drum brake with both temperature regulation and pressure compensation

Abstract

The present invention relates to the technical field of drum brakes, and specifically to a method for designing a drum brake that has both temperature regulation and pressure compensation. By designing a brake shoe system consisting of a NiTi alloy compensation pin, a brake shoe, and a NiTi alloy friction lining, and utilizing the characteristics of the material's martensitic phase transformation, heat absorption and heat release, and volume contraction and expansion, the heat generation and heat dissipation properties of the drum brake are improved. Based on experimental data and related calculation formulas, the structure of the brake shoe system is improved to achieve alternating pressure between the friction plate and the brake drum, thereby improving steering control performance and reducing the possibility of safety accidents caused by failure of heavy machinery brakes. The present invention has a reasonable design, can reduce brake failure caused by high temperature due to brake friction and control failure caused by emergency braking, and has great practical application value.

Description

Technical Field

[0001] The present invention relates to the technical field of drum brakes, in particular to a design method of a drum brake with both temperature regulation and pressure compensation. Background Art

[0002] Drum brakes are mechanical devices that use a brake transmission mechanism to force the brake shoe to press the brake friction pad against the inner side of the brake drum, thereby generating braking force. This allows the wheel to slow down or stop within the shortest distance as needed to ensure safe and reliable parking of the equipment. Drum brakes are mainly composed of brake drum 1, friction pad 2, brake shoe adjuster 3, brake wheel cylinder 4, positioning pin 5, friction lining 6, brake shoe 7, return spring 8 and other components (such as Figure 1-2 (as shown). During braking, when the wheel cylinder receives hydraulic pressure from the master cylinder, the pistons at each end of the wheel cylinder push against the upper and lower brake shoes, causing them to expand outward. The attached friction pads then rub against the inside of the brake drum, achieving the desired braking effect. Drum brakes offer advantages such as low cost, reliable operation, and simple structure, making them widely used in many heavy-duty vehicles and rotating machinery.

[0003] Due to the high-pressure friction between the friction pads and brake drums during prolonged or emergency braking on heavy vehicles and rotating machinery, brake pad temperatures can reach as high as 700-800°C, or even over 1000°C. According to national standard GB5763-2008, brake pads should maintain normal performance at operating temperatures around 500°C to ensure safe driving. Therefore, considering the heat generated during braking on heavy vehicles and rotating machinery, ensuring good heat dissipation and thermal stability are key attributes in evaluating brake performance. Summary of the Invention

[0004] In view of the technical problems existing in the prior art, the present invention provides a design method for a drum brake with both temperature regulation and pressure compensation.

[0005] According to one aspect of the present invention, the present invention provides the following technical solutions:

[0006] A method for designing a drum brake with both temperature regulation and pressure compensation comprises the following steps:

[0007] S1. Design a brake shoe system including a NiTi alloy compensating pin, a brake shoe, and a NiTi alloy friction lining;

[0008] S2. performing long-term braking or emergency braking on a drum brake including the brake shoe system, and determining the pressure and heat generated between the friction pad and the brake drum during braking under corresponding conditions;

[0009] S3. Calculate the stress distribution on the NiTi alloy friction lining based on the pressure between the friction pad and the brake drum during braking, and determine the stress and strain state of the NiTi alloy friction lining and the NiTi alloy compensation pin;

[0010] S4. Calculate the required weight of NiTi alloy in the brake shoe system based on the heat generated between the friction pad and the brake drum during braking;

[0011] S5. Design the thickness and shape of the NiTi alloy friction lining according to the drum brake structure and the alloy weight and density, and determine the number, length, and cross-sectional area of the NiTi alloy compensation pins;

[0012] S6. Based on the above design results, analyze the stress-strain relationship and phase change characteristics of NiTi alloy friction linings and NiTi alloy compensation pins under long-term braking or emergency braking to verify the braking effect.

[0013] As a preferred embodiment of the present invention's method for designing a drum brake with both temperature regulation and pressure compensation, in step S1, a NiTi alloy friction lining is positioned between the brake shoe and the friction pad; a cavity is provided within the brake shoe to accommodate a NiTi alloy compensating pin, and the NiTi alloy friction lining is provided with a through-hole corresponding to the cavity. The NiTi alloy compensating pin is positioned and connected to the brake shoe and the NiTi alloy friction lining through the cavity within the brake shoe and the through-hole corresponding to the cavity provided on the NiTi alloy friction lining, and the NiTi alloy compensating pin contacts the friction pad through the through-hole provided on the NiTi alloy friction lining. The NiTi alloy compensating pin ensures precise positioning through positioning holes in the alloy friction pad and the brake shoe, and the phase change properties of the NiTi alloy, combined with the alloy friction pad, achieve sinusoidal braking pressure, enhancing braking effectiveness.

[0014] As a preferred solution of the method for designing a drum brake with both temperature regulation and pressure compensation according to the present invention, in step S1, the NiTi alloy comprises, in atomic percentage, 48-52 at % Ni and 48-52 at % Ti.

[0015] As a preferred solution of the method for designing a drum brake with both temperature regulation and pressure compensation according to the present invention, in step S2, the friction plate material is a composite material formed by hot pressing of basalt fiber reinforced phenolic resin.

[0016] As a preferred embodiment of the design method of a drum brake with both temperature regulation and pressure compensation according to the present invention, in step S2, the heat generated between the friction pad and the brake drum during braking is Q1, part of which is transferred to the air and part is transferred to the friction lining; and the friction lining generates heat Q' due to phase change expansion, and the proportion of heat retained in the brake shoe system after dissipation is ξ; the weight of the NiTi alloy in the brake shoe system is W , then the NiTi alloy phase transition endothermic heat is , where Δ H is the phase change enthalpy of NiTi alloy, then the heat of brake shoe system Q(t)=(Q1(t)+Q'(t))×ξ- W Δ H .

[0017] As a preferred solution of the design method of a drum brake with both temperature regulation and pressure compensation according to the present invention, wherein: in the step S4, the weight of the NiTi alloy is W for:

[0018] .

[0019] As a preferred solution of the design method of a drum brake with both temperature regulation and pressure compensation according to the present invention, wherein: in the step S5, according to the brake shoe system structure, the weight of the NiTi alloy W for:

[0020]

[0021] in, ρ is the density of NiTi alloy, 6.5 g / cm 3 ; S is the area of NiTi alloy friction lining, h is the thickness of NiTi alloy friction lining; N is the number of NiTi alloy compensation pins, d For diameter, l is the length.

[0022] As a preferred solution of the design method of a drum brake with both temperature regulation and pressure compensation described in the present invention, in step S5, in order to increase the heat transfer effect between the NiTi alloy compensation pin and the brake shoe, a copper sleeve is wrapped around the outer layer of the NiTi alloy compensation pin.

[0023] The beneficial effects of the present invention are as follows:

[0024] The present invention provides a design method for a drum brake that combines temperature regulation and pressure compensation. By designing a brake shoe system consisting of a NiTi alloy compensating pin, a brake shoe, and a NiTi alloy friction lining, the heat generation and heat dissipation properties of the drum brake are improved by utilizing the heat absorption and heat release characteristics of the martensitic phase transformation and the volumetric contraction and expansion characteristics of the material. Based on experimental data and relevant calculation formulas, the structure of the brake shoe including the NiTi alloy compensating pin and the NiTi alloy friction lining is improved to achieve alternating pressure between the friction plate and the brake drum, thereby improving steering control performance and reducing the possibility of safety accidents caused by brake failure of heavy machinery. The present invention has a reasonable design and can reduce brake failure caused by high temperature due to brake friction and control failure caused by emergency braking, and has excellent practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0026] Figure 1 This is an exploded view of an existing drum brake.

[0027] Figure 2 It is the front view of the existing drum brake.

[0028] Figure 3 This is a schematic diagram of the overall structure of the brake shoe, compensation pin, and friction lining of the present invention.

[0029] Figure 4 This is a separate schematic diagram of the brake shoe, compensation pin, and friction lining structure of the present invention.

[0030] Figure 5 Schematic diagram of phase transformation and stress-strain relationship of NiTi alloy.

[0031] Figure 6 It is a cyclic process of increase and decrease of system pressure due to volume expansion and contraction of NiTi alloy.

[0032] Figure 7 This is a schematic diagram of a compensating pin with an outer copper sleeve wrapped therein according to the present invention.

[0033] Among them, 1-brake drum; 2-friction plate; 3-brake shoe adjuster; 4-brake wheel cylinder; 5-locating pin; 6-friction lining; 7-brake shoe; 8-return spring; 9-NiTi alloy compensation pin; 10-NiTi alloy friction lining; 11-copper sleeve.

[0034] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0035] The following will be a clear and complete description of the technical solutions in the embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0036] Existing drum brakes generate significant heat during prolonged or emergency braking due to high-pressure friction between the friction pads and the brake drum. However, heat conduction is insufficient to reduce the temperature of the friction pads, which can lead to degradation of the friction pads' friction performance at high temperatures and potentially cause safety accidents. Furthermore, emergency braking can easily cause loss of vehicle steering control. Alternating the pressure between the friction pads and the brake drum can effectively address steering control issues. Based on these considerations, the present invention proposes a design method for a drum brake that combines temperature regulation and pressure compensation. This approach addresses these issues by modifying the drum brake's structure and materials to improve the brake's heat generation and heat dissipation properties, while also achieving alternating pressure between the friction pads and the brake drum, thereby reducing safety accidents caused by brake failure in heavy machinery.

[0037] According to one aspect of the present invention, the present invention provides the following technical solutions:

[0038] A method for designing a drum brake with both temperature regulation and pressure compensation comprises the following steps:

[0039] S1. Considering the heat absorption and heat release characteristics of shape memory alloy phase transition, a brake shoe system including NiTi alloy compensation pin 9, brake shoe 7 and NiTi alloy friction lining 10 is designed. In order to increase the heat conduction property of brake shoe 7, the design is as follows: Figure 3-4 The structure shown is as follows: the NiTi alloy friction lining 10 is located between the brake shoe 7 and the friction plate 2; a cavity for accommodating the NiTi alloy compensation pin 9 is provided inside the brake shoe 7, and a through hole corresponding to the cavity is provided on the NiTi alloy friction lining 10. The NiTi alloy compensation pin 9 is positioned and connected to the brake shoe 7 and the NiTi alloy friction lining 10 through the cavity provided inside the brake shoe 7 and the through hole corresponding to the cavity provided on the NiTi alloy friction lining 10, and the NiTi alloy compensation pin 9 contacts the friction plate 2 through the through hole provided on the NiTi alloy friction lining 10.

[0040] S2. Performing long-term braking or emergency braking on a drum brake including the brake shoe system to determine the pressure and heat generated between the friction pad 2 and the brake drum 1 during braking under corresponding conditions;

[0041] S3. Calculate the stress distribution on the NiTi alloy friction lining 10 based on the pressure between the friction plate 2 and the brake drum 1 during braking, and determine the stress and strain state of the NiTi alloy friction lining 10 and the NiTi alloy compensation pin 9;

[0042] S4. Calculate the required weight of NiTi alloy in the brake shoe system based on the heat generated between the friction pad 2 and the brake drum 1 during braking;

[0043] S5. Design the thickness and shape of the NiTi alloy friction lining 10 according to the drum brake structure and the alloy weight and density, and determine the number, length, and cross-sectional area of the NiTi alloy compensation pins 9;

[0044] S6. Based on the above design results, analyze the stress-strain relationship and phase change characteristics of the NiTi alloy friction lining 10 and the NiTi alloy compensation pin 10 under long-term braking or emergency braking to verify the braking effect.

[0045] Preferably, in step S1, the NiTi alloy comprises, in atomic percentage, 48-52 at % Ni and 48-52 at % Ti.

[0046] Preferably, in step S2, the material of the friction plate 2 is a composite material formed by hot pressing of basalt fiber reinforced phenolic resin.

[0047] Preferably, in step S2, the heat generated between the friction plate 2 and the brake drum 1 during braking is Q1, part of the heat Q1 is transferred to the air, and part is transferred to the NiTi alloy friction lining 10; and the NiTi alloy friction lining 10 generates heat Q' due to phase change expansion, and the proportion of heat retained in the brake shoe system after the heat is dissipated is ξ; the weight of the NiTi alloy in the brake shoe system is W , then the NiTi alloy phase transition endothermic heat is , where Δ H is the phase change enthalpy of NiTi alloy, then the heat of brake shoe system Q(t)=(Q1(t)+Q'(t))×ξ- W Δ H .

[0048] Preferably, in step S4, the weight of the NiTi alloy is W for:

[0049] .

[0050] Preferably, in step S5, according to the brake shoe system structure, the weight of the NiTi alloy W for:

[0051]

[0052] in, ρ is the density of NiTi alloy, 6.5 g / cm 3 ; S is the area of NiTi alloy friction lining, h is the thickness of NiTi alloy friction lining; N is the number of NiTi alloy compensation pins, d For diameter, l is the length.

[0053] Preferably, in step S5, in order to increase the heat transfer effect between the NiTi alloy compensation pin 9 and the brake shoe 7, the outer layer of the NiTi alloy compensation pin 9 is wrapped with a copper sleeve 11, such as Figure 7 shown.

[0054] Specifically, the present invention first performs a long-term or emergency braking test on a heavy machinery brake, and a portion of the generated heat is transferred to the air, and a portion is transferred to the friction lining.

[0055] NiTi alloys with nearly equal atomic ratios have excellent shape memory effect and superelastic properties, high mechanical properties and corrosion resistance. The alloy parent phase is usually a high-temperature austenite phase with a B2 cubic structure. Both stress and temperature can induce martensitic transformation in NiTi alloys, such as Figure 5 As shown in the figure, the stress-strain relationship at room temperature can be divided into four stages: the elastic deformation stage of austenite A, the stress-induced martensite M phase transformation stage, the elastic deformation stage of martensite M, and the plastic deformation stage of martensite M. Considering that the pressure generated between the friction plate and the brake drum is usually not higher than the yield stress of martensite, the stress-strain relationship can be approximated as the first three stages. The total strain of the three stages is

[0056] (1)

[0057] in, is the elastic strain, is the phase transition strain. According to the generalized Hooke's law, the total stress can be expressed as

[0058] (2)

[0059] in, is the equivalent elastic modulus, which can be calculated by Ruess's mixing rule and expressed as:

[0060] (3)

[0061] in, and are the elastic moduli of austenite A and martensite M, ηis the volume fraction of martensite. According to the generalized plasticity theory, the phase transformation strain rate can be expressed as follows without considering the phase transformation direction:

[0062] (4)

[0063] in, is the maximum phase transformation strain.

[0064] Based on the above calculations and the NiTi alloy material parameters given in Table 1, the stress and strain of the NiTi alloy compensation pins can be determined as needed, and the diameter, length, and number of the compensation pins can be designed as needed.

[0065] Table 1 NiTi alloy material parameters

[0066]

[0067] When braking begins, pressure builds up between the friction pad and the brake drum, causing the NiTi alloy to deform. This first causes elastic deformation of the alloy's austenite parent phase A (cubic B2 phase). Subsequently, stress-induced phase transformation of A into martensite M (monoclinic B19' phase) occurs. If the NiTi alloy is hot-rolled, the B2→B19' phase transformation occurs; if the NiTi alloy has been aged, the B2→R (rhombohedral R intermediate phase)→B19' transformation occurs. This process is exothermic, and because the atoms are relatively sparsely arranged in the body-centered cubic martensite lattice, the volume expands by approximately 4%, increasing the pressure and friction between the friction pad and the brake drum, thereby improving braking effectiveness.

[0068] As the pressure between the friction pad and brake drum increases, the NiTi alloy enters the elastic deformation phase of the martensite phase, and the heat generated by friction increases. At this point, the temperature induces a phase transformation of the martensite in the alloy, from B19' to B2. This process involves volumetric contraction and heat absorption, thus helping to reduce pressure between the friction pad and brake drum and lower system heat.

[0069] If the phase transition characteristics of NiTi alloy are not considered, the heat generated by the system is Q1; the heat generated by the system due to its phase transition expansion is Q' (the pressure between the friction plate and the brake drum increases due to the B2→B19' phase transition, which increases the friction heat). If the proportion of this heat retained in the brake shoe system after dissipation is ξ, the system heat is

[0070] Q(t)=(Q1(t)+Q'(t))×ξ (5)

[0071] If the weight of NiTi alloy in the brake shoe system is W , then the phase change endotherm is

[0072] (6)

[0073] where Δ H is the phase change enthalpy of NiTi alloy. Heat of brake shoe system It is reduced to

[0074] (7)

[0075] The weight of NiTi alloy in the brake shoe system is

[0076] (8)

[0077] Considering that Q1 and Q' can be obtained through experimental calculation, the phase change enthalpy of NiTi alloy in different processing states is shown in Table 2. The weight of NiTi alloy can be determined according to formula (8): W , further design the diameter, length and quantity of the compensation pins.

[0078] (9)

[0079] in, ρ is the density of NiTi alloy, 6.5 g / cm 3 , S is the area of NiTi alloy friction lining, h is the thickness of NiTi alloy friction lining; N is the number of NiTi alloy compensation pins, d is the diameter, l is the length.

[0080] Table 2 NiTi alloy phase change enthalpy

[0081]

[0082] If the braking process is completed at this time, the deformation process of the NiTi alloy ends. If the system has not completed the braking process, the NiTi alloy will repeat the above phase change process under the pressure between the friction plate and the brake drum, thereby realizing the system pressure reciprocating cycle, such as Figure 6 As shown, this is a cyclic process of phase change absorbing and releasing heat, material volume expansion and contraction, and system pressure increase and decrease.

[0083] Through the above-mentioned temperature regulation and pressure compensation cycle, the thermal properties of the brake are improved, the pressure between the friction plate and the brake drum is alternating between loose and tight, the steering control performance is improved, and the possibility of safety accidents caused by failure of heavy mechanical brakes is reduced.

[0084] The present invention utilizes a brake shoe system consisting of a NiTi alloy compensating pin, a brake shoe, and a NiTi alloy friction lining, utilizing the heat absorption and release characteristics of the martensitic phase transformation and the volumetric expansion and contraction characteristics of the material to improve the heat generation and heat dissipation properties of the drum brake. Based on experimental data and relevant calculation formulas, the structure of the brake shoe, including the NiTi alloy compensating pin, and the NiTi alloy friction lining is improved to achieve alternating pressure between the friction lining and the brake drum, thereby improving steering control performance and reducing the possibility of safety accidents caused by brake failure in heavy machinery. The present invention has a rational design and can reduce brake failure caused by high brake friction temperature and control failure caused by emergency braking, thus having excellent practical application value.

[0085] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention specification under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A design method for a drum brake with both temperature regulation and pressure compensation, characterized in that: The steps include: S1. Design a brake shoe system including a NiTi alloy compensating pin, a brake shoe, and a NiTi alloy friction lining; S2. performing long-term braking or emergency braking on a drum brake including the brake shoe system, and determining the pressure and heat generated between the friction pad and the brake drum during braking under corresponding conditions; S3. Calculate the stress distribution on the NiTi alloy friction lining based on the pressure between the friction pad and the brake drum during braking, and determine the stress and strain state of the NiTi alloy friction lining and the NiTi alloy compensation pin; S4. Calculate the required weight of NiTi alloy in the brake shoe system based on the heat generated between the friction pad and the brake drum during braking; S5. Design the thickness and shape of the NiTi alloy friction lining according to the drum brake structure and the alloy weight and density, and determine the number, length, and cross-sectional area of the NiTi alloy compensation pins; S6. Based on the above design results, analyze the stress-strain relationship and phase change characteristics of NiTi alloy friction linings and NiTi alloy compensation pins under long-term braking or emergency braking to verify the braking effect.

2. The design method of a drum brake with both temperature regulation and pressure compensation according to claim 1, characterized in that: In step S1, the NiTi alloy friction lining is located between the brake shoe and the friction plate; a cavity for accommodating the NiTi alloy compensation pin is provided inside the brake shoe, and a through hole corresponding to the cavity is provided on the NiTi alloy friction lining. The NiTi alloy compensation pin is positioned and connected to the brake shoe and the NiTi alloy friction lining through the cavity provided inside the brake shoe and the through hole provided on the NiTi alloy friction lining corresponding to the cavity, and the NiTi alloy compensation pin contacts the friction plate through the through hole provided on the NiTi alloy friction lining.

3. The design method of a drum brake with both temperature regulation and pressure compensation according to claim 1, characterized in that: In step S1, the NiTi alloy comprises, in atomic percentage, 48-52 at % Ni and 48-52 at % Ti.

4. The design method of a drum brake with both temperature regulation and pressure compensation according to claim 1, characterized in that: In step S2, the friction plate material is a composite material formed by hot pressing of basalt fiber reinforced phenolic resin.

5. The design method of a drum brake with both temperature regulation and pressure compensation according to claim 1, characterized in that: In step S2, the heat generated between the friction pad and the brake drum during braking is Q1. Part of the heat Q1 is transferred to the air, and part is transferred to the friction lining. The friction lining generates heat Q' due to phase change expansion. The proportion of heat retained in the brake shoe system after dissipation is ξ. The weight of the NiTi alloy in the brake shoe system is W , then the NiTi alloy phase transition endothermic heat is , where Δ H is the phase change enthalpy of NiTi alloy, then the heat of brake shoe system Q(t)=(Q1(t)+Q'(t))×ξ- W Δ H .

6. The design method of a drum brake with both temperature regulation and pressure compensation according to claim 1, characterized in that: In the step S4, the weight of the NiTi alloy W for: 。 7. The design method of a drum brake with both temperature regulation and pressure compensation according to claim 1, characterized in that: In step S5, according to the brake shoe system structure, the weight of the NiTi alloy W for: in, ρ is the density of NiTi alloy, 6.5 g / cm 3 ; S is the area of NiTi alloy friction lining, h is the thickness of NiTi alloy friction lining; N is the number of NiTi alloy compensation pins, d For diameter, l is the length.

8. The design method of a drum brake with both temperature regulation and pressure compensation according to claim 1, characterized in that: In the step S5, a copper sleeve is wrapped around the outer layer of the NiTi alloy compensation pin.

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