Design method of drum brake with temperature regulation and pressure compensation functions

Abstract

The invention relates to the technical field of drum brakes, in particular to a design method of a drum brake with temperature regulation and pressure compensation, which comprises the following steps of: 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 heat absorption and heat release and volume shrinkage and expansion of martensite phase change of a material; the heat generation and heat dissipation properties of the drum brake are improved. According to experimental data and related calculation formulas, the structure of the brake shoe system is improved, the pressure between the friction plate and the brake drum is loosened and loosened, the steering control performance is improved, and the possibility of safety accidents caused by failure of a heavy mechanical brake is reduced. The device is reasonable in design, braking failure caused by friction and high temperature of the brake and control failure caused by emergency braking can be reduced, and the device has good practical application value.

Description

Technical Field

[0001] The present invention relates to the technical field of drum brakes, and specifically to a design method for a drum brake that combines temperature regulation and pressure compensation. Background Art

[0002] A drum brake is a mechanical device that uses a brake transmission mechanism to press brake friction linings against the inner side of a brake drum to generate braking force, and decelerates the wheels or stops the vehicle within the shortest distance as needed to ensure the safe and reliable parking of the equipment. The drum brake mainly consists of structures such as a brake drum 1, a friction lining 2, a brake shoe adjuster 3, a brake wheel cylinder 4, a positioning pin 5, a friction lining 6, a brake shoe 7, a return spring 8, etc. (as shown in Figure 1-2 ). When the brake wheel cylinder is subjected to the master cylinder hydraulic pressure during braking, the pistons at both ends of the wheel cylinder will push against the ends of the upper and lower brake shoes, and the brake shoes will expand outwards, and then the attached friction linings will rub against the inner side of the brake drum to achieve the purpose of braking. The drum brake has the advantages of low cost, reliable operation, and simple structure, and is widely used in many heavy vehicles and rotating machinery.

[0003] Due to the high-pressure friction between the friction linings and the brake drum during long-term or emergency braking of the brakes of heavy vehicles and rotating machinery, the temperature of the brake pads may reach as high as 700 - 800 °C or even over 1000 °C. According to the national standard GB5763-2008, the brake pads should maintain normal performance at a working temperature of about 500 °C to ensure the safety of driving without worry. Therefore, considering the heat generated during the braking of heavy vehicles and rotating machinery, ensuring that the brake has good heat dissipation and thermal stability is the main attribute for evaluating its braking performance. Summary of the Invention

[0004] Aiming at the technical problems existing in the prior art, the present invention provides a design method for a drum brake that combines temperature regulation and pressure compensation.

[0005] According to one aspect of the present invention, the following technical solution is provided: A design method for a drum brake that combines temperature regulation and pressure compensation, comprising the following steps: S1. Design a brake shoe system including a NiTi alloy compensation pin, a brake shoe, and a NiTi alloy friction lining; S2. Conduct long-term braking or emergency braking on the drum brake including the brake shoe system, and determine the pressure and heat generated between the friction lining and the brake drum during braking under corresponding conditions; S3. Based on the pressure between the friction lining and the brake drum during braking, calculate the stress distribution on the NiTi alloy friction lining, and determine the stress-strain state of the NiTi alloy friction lining and the NiTi alloy compensation pin; S4. Calculate the weight of the NiTi alloy required in the brake shoe system based on the heat generated between the friction lining and the brake drum during braking. S5. Design the thickness and shape dimensions of the NiTi alloy friction lining according to the structure of the drum brake, the alloy weight, and the density, and determine the number, length, and cross-sectional area of the NiTi alloy compensating pins. S6. Analyze the stress-strain relationship and phase change characteristics of the NiTi alloy friction lining and the NiTi alloy compensating pins under long-term braking or emergency braking conditions according to the above design results, and verify the braking effect.

[0006] 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 S1, the NiTi alloy friction lining is located between the brake shoe and the friction lining; a cavity for accommodating the NiTi alloy compensating pin is provided inside the brake shoe, through holes corresponding to the cavity are provided on the NiTi alloy friction lining, and the NiTi alloy compensating pin is positioned through the cavity provided inside the brake shoe and the through holes corresponding to the cavity on the NiTi alloy friction lining to realize the connection between the brake shoe and the NiTi alloy friction lining, and the NiTi alloy compensating pin contacts the friction lining through the through holes provided on the NiTi alloy friction lining. The NiTi alloy compensating pin can ensure its precise positioning through the positioning holes on the alloy friction plate and the brake shoe, and the phase change characteristics of the NiTi alloy are combined with the alloy friction plate to achieve a sinusoidal braking pressure and improve the braking effect.

[0007] 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 S1, the NiTi alloy, in atomic percentage, includes 48-52 at% of Ni and 48-52 at% of Ti.

[0008] 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 S2, the friction lining material is a composite material formed by hot pressing basalt fiber-reinforced phenolic resin.

[0009] 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 S2, the heat generated between the friction lining and the brake drum during braking is Q1, a part of the heat Q1 is conducted to the air, and a part is conducted to the friction lining; and due to the phase change expansion of the friction lining, heat Q' is generated, and the proportion 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 endothermic heat of the NiTi alloy phase change is , where Δ HLet ΔH be the phase change enthalpy of the NiTi alloy, then the heat Q(t) of the brake shoe system is (Q1(t) + Q’(t)) × ξ - W Δ H .

[0010] As a preferred embodiment of the design method of the 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 W is: .

[0011] As a preferred embodiment of the design method of the drum brake with both temperature regulation and pressure compensation according to the present invention, wherein: in the step S5, according to the structure of the brake shoe system, the weight of the NiTi alloy W is: Wherein, ρ is the density of the NiTi alloy, 6.5 g / cm 3 ; S is the area of the NiTi alloy friction lining, h is the thickness of the NiTi alloy friction lining; N is the number of NiTi alloy compensating pins, d is the diameter, l is the length.

[0012] As a preferred embodiment of the design method of the drum brake with both temperature regulation and pressure compensation according to the present invention, wherein: in the step S5, to increase the heat transfer effect between the NiTi alloy compensating pin and the brake shoe, a copper sleeve is wrapped around the outer layer of the NiTi alloy compensating pin.

[0013] The beneficial effects of the present invention are as follows: The present invention provides a design method of a drum brake with both temperature regulation and pressure compensation. By designing a brake shoe system composed of NiTi alloy compensating pins, brake shoes and NiTi alloy friction linings, and utilizing the characteristics of heat absorption and heat release and volume shrinkage and expansion of the martensitic phase transformation of the material, the heat generation and heat dissipation properties of the drum brake are improved. According to the experimental data and relevant calculation formulas, the structures of the brake shoes and NiTi alloy friction linings including NiTi alloy compensating pins are improved to realize the alternating tightness of the pressure between the friction plate and the brake drum, enhance the steering control performance, and reduce the possibility of safety accidents caused by the failure of heavy machinery brakes. The design of the present invention is reasonable, which can reduce the brake failure caused by the high temperature of the brake friction and the control failure caused by the emergency braking, and has good practical application value. Brief Description of the Drawings

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0015] Figure 1 It is an exploded view of an existing drum brake.

[0016] Figure 2 It is a front view of an existing drum brake.

[0017] Figure 3 It is a schematic diagram of the overall structure of the brake shoe, compensating pin, and friction lining of the present invention.

[0018] Figure 4 It is a split schematic diagram of the structure of the brake shoe, compensating pin, and friction lining of the present invention.

[0019] Figure 5 It is a schematic diagram of the phase transformation and stress-strain relationship of NiTi alloy.

[0020] Figure 6 It is a cyclic process of the increase and decrease of the system pressure caused by the volume expansion and contraction of NiTi alloy.

[0021] Figure 7 It is a schematic diagram of the compensating pin with a copper sleeve wrapped on the outer layer of the present invention.

[0022] Among them, 1 - brake drum; 2 - friction plate; 3 - brake shoe adjuster; 4 - brake wheel cylinder; 5 - positioning pin; 6 - friction lining; 7 - brake shoe; 8 - return spring; 9 - NiTi alloy compensating pin; 10 - NiTi alloy friction lining; 11 - copper sleeve.

[0023] The realization of the object, functional features, and advantages of the present invention will be further described with reference to the embodiments and the accompanying drawings. Specific Embodiments

[0024] The following will clearly and completely describe the technical solutions in the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0025] In existing drum brakes, high-pressure friction between the friction lining and the brake drum during long-term or emergency braking generates a large amount of heat, and heat conduction is not sufficient to reduce the temperature of the friction lining. This may lead to the degradation of the friction performance of the friction lining at high temperatures, triggering safety accidents. At the same time, emergency braking is likely to cause the vehicle to lose steering control. If the pressure between the friction lining and the brake drum can be alternately tightened and relaxed, the steering control problem can be effectively solved. Based on the above considerations, the present invention proposes a design method for a drum brake with both temperature regulation and pressure compensation, and changes the structure and materials of the drum brake to address this problem, so as to improve the heat generation and heat dissipation properties of the brake, and achieve alternate tightening and relaxation of the pressure between the friction lining and the brake drum, reducing safety accidents caused by the failure of heavy machinery brakes.

[0026] According to one aspect of the present invention, the present invention provides the following technical solution: A design method for a drum brake with both temperature regulation and pressure compensation, comprising the following steps: S1. Considering the characteristics of heat absorption and heat release during the phase change of shape memory alloy, design a brake shoe system including a NiTi alloy compensating pin 9, a brake shoe 7, and a NiTi alloy friction lining 10. To increase the heat conduction property of the brake shoe 7, design the structure as shown in Figure 3-4 Figure; the NiTi alloy friction lining 10 is located between the brake shoe 7 and the friction lining 2; a cavity for accommodating the NiTi alloy compensating pin 9 is provided inside the brake shoe 7, through holes corresponding to the cavity are provided on the NiTi alloy friction lining 10, and the NiTi alloy compensating pin 9 is positioned and connected to the NiTi alloy friction lining 10 through the cavity provided inside the brake shoe 7 and the through holes corresponding to the cavity provided on the NiTi alloy friction lining 10, and the NiTi alloy compensating pin 9 contacts the friction lining 2 through the through holes provided on the NiTi alloy friction lining 10.

[0027] S2. Perform long-term braking or emergency braking on the drum brake including the brake shoe system, and determine the pressure and heat generated during braking under corresponding conditions between the friction lining 2 and the brake drum 1; S3. Based on the pressure between the friction lining 2 and the brake drum 1 during braking, calculate the stress distribution on the NiTi alloy friction lining 10, and determine the stress-strain state of the NiTi alloy friction lining 10 and the NiTi alloy compensating pin 9; S4. Based on the heat generated between the friction lining 2 and the brake drum 1 during braking, calculate the weight of NiTi alloy required in the brake shoe system; S5. According to the structure of the drum brake, the weight and density of the alloy, design the thickness and shape dimensions of the NiTi alloy friction lining 10, and determine the number, length, and cross-sectional area of the NiTi alloy compensating pins 9; S6. According to the above design results, analyze the stress-strain relationship and phase transformation characteristics of the NiTi alloy friction lining 10 and the NiTi alloy compensating pin 10 under long-term braking or emergency braking conditions, and verify the braking effect.

[0028] Preferably, in the step S1, the NiTi alloy, in atomic percentage, comprises Ni 48-52 at%, and Ti 48-52 at%.

[0029] Preferably, in the step S2, the material of the friction plate 2 is a composite material formed by hot pressing basalt fiber reinforced phenolic resin.

[0030] Preferably, in the step S2, when braking, the heat generated between the friction plate 2 and the brake drum 1 is Q1. A part of the heat Q1 is conducted to the air, and a part is conducted to the NiTi alloy friction lining 10; and due to the phase transformation expansion of the NiTi alloy friction lining 10, heat Q' is generated. The proportion of the heat retained in the brake shoe system after heat dissipation is ξ; the weight of the NiTi alloy in the brake shoe system is W , then the heat absorption of the NiTi alloy phase transformation is , where Δ H is the phase transformation enthalpy of the NiTi alloy. Then the heat Q(t) of the brake shoe system = (Q1(t) + Q'(t))×ξ - W Δ H .

[0031] Preferably, in the step S4, the weight W of the NiTi alloy is: .

[0032] Preferably, in the step S5, according to the structure of the brake shoe system, the weight W of the NiTi alloy is: where, ρ is the density of the NiTi alloy, 6.5 g / cm 3 ; S is the area of the NiTi alloy friction lining, h is the thickness of the NiTi alloy friction lining; N is the number of NiTi alloy compensating pins, d is the diameter, l is the length.

[0033] Preferably, in the step S5, to increase the heat transfer effect between the NiTi alloy compensating pin 9 and the brake shoe 7, a copper sleeve 11 is wrapped around the outer layer of the NiTi alloy compensating pin 9, as Figure 7 shown.

[0034] Specifically, the present invention first conducts long-term or emergency braking experiments on heavy machinery brakes. Part of the generated heat is conducted to the air, and part is conducted to the friction lining.

[0035] NiTi near-equiatomic ratio alloys have excellent shape memory effect and superelastic properties, higher 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. As Figure 5 shown, at room temperature, its stress-strain relationship can be divided into four stages: the elastic deformation stage of austenite A, the stress-induced martensitic M 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 usually does not exceed the martensitic yield stress, its stress-strain relationship can be approximately regarded as the first three stages. The total strain of the three stages (1) Among them, is the elastic strain, is the transformation strain. According to Hooke's law of elasticity, the total stress can be expressed as (2) Among them, is the equivalent elastic modulus, which can be calculated by the Ruess mixing rule and is expressed as: (3) Among them, and are the elastic moduli of austenite A and martensite M respectively, η is the martensite volume fraction. According to the generalized plasticity theory, when the phase transformation direction is not considered, the phase transformation strain rate can be expressed as: (4) Among them, is the maximum phase transformation strain.

[0036] Based on the above calculations and the NiTi alloy material parameters given in Table 1, the stress and strain of the NiTi alloy compensating pin can be determined as needed, and at the same time, the diameter, length and number of the compensating pin can be designed as needed.

[0037] Table 1 NiTi alloy material parameters After the braking starts, pressure is generated between the friction plate and the brake drum, causing the NiTi alloy to deform. First, the elastic deformation of the austenite parent phase A (cubic structure B2 phase) of the alloy is induced. Subsequently, due to stress-induced martensite M (monoclinic structure B19’ phase) phase transformation occurs in A. If the NiTi alloy is in the hot-rolled state, the B2→B19’ phase transformation occurs; if the NiTi alloy has undergone aging treatment, the B2→R (rhombohedral structure R intermediate phase)→B19’ transformation occurs. This process is a heat-generating process, and since the atoms are relatively sparsely arranged in the body-centered cubic lattice of martensite, the volume will expand by about 4%, thereby increasing the pressure and frictional force between the friction plate and the brake drum and enhancing the braking effect.

[0038] As the pressure between the friction plate and the brake drum increases, the NiTi alloy will enter the elastic deformation stage of the martensite phase, and the heat generated by friction increases. At this time, the temperature will induce the martensite in the alloy to undergo a phase transformation, that is, B19’→B2. This process is a process of material volume shrinkage and heat absorption, so it helps to reduce the pressure between the friction plate and the brake drum and lower the heat of the system.

[0039] If the phase transformation characteristics of the NiTi alloy are not considered, the heat generated by the system is Q1; considering the heat generated by the system due to its phase transformation expansion is Q’ (the increase in frictional heat caused by the increase in pressure between the friction plate and the brake drum due to the B2→B19’ phase transformation). If the proportion of these heats remaining in the brake shoe system after dissipation is ξ, then the system heat is Q(t)=(Q1(t)+Q’(t))×ξ (5) If the weight of the NiTi alloy in the brake shoe system is W , then the heat absorption during phase transformation is (6) where Δ H is the phase transformation enthalpy of the NiTi alloy. The heat of the brake shoe system then decreases to (7) Then the weight of the NiTi alloy in the brake shoe system is (8) Considering that Q1 and Q’ can be obtained through experimental calculations, the phase transformation enthalpies of NiTi alloys in different processing states are shown in Table 2. Furthermore, the weight of the NiTi alloy can be determined according to formula (8) W , and further design the diameter, length, and quantity of the compensation pins.

[0040] (9) where, ρ is the density of the NiTi alloy, 6.5g / cm 3 , Sis the area of the NiTi alloy friction lining, h is the thickness of the NiTi alloy friction lining; N is the number of NiTi alloy compensating pins, d is the diameter, l is the length.

[0041] Table 2 Phase change enthalpy of NiTi alloy 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 reciprocating cycle of the system pressure, as Figure 6 shown, that is, the cycle process of phase change heat absorption and heat release, material volume expansion and contraction, and system pressure increase and decrease.

[0042] Through the above 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 loosened and tightened alternately, the steering control performance is improved, and the possibility of safety accidents caused by the failure of heavy machinery brakes is reduced.

[0043] The brake shoe system of the present invention is composed of NiTi alloy compensating pins, brake shoes and NiTi alloy friction linings. By utilizing the characteristics of martensitic phase change heat absorption and heat release and volume shrinkage and expansion of the material, the heat generation and heat dissipation properties of the drum brake are improved. According to the experimental data and relevant calculation formulas, the structures of the brake shoes including NiTi alloy compensating pins and NiTi alloy friction linings are improved to realize the alternate loosening and tightening of the pressure between the friction plate and the brake drum, improve the steering control performance, and reduce the possibility of safety accidents caused by the failure of heavy machinery brakes. The design of the present invention is reasonable, which can reduce the brake failure caused by high friction temperature of the brake and the control failure caused by emergency braking, and has good practical application value.

[0044] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made using the content of the specification of the present invention under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields, is 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, It includes the following steps: S1. Design a brake shoe system including a NiTi alloy compensating pin, a brake shoe, and a NiTi alloy friction lining; S2. Conduct long-term braking or emergency braking on a drum brake including the brake shoe system, and determine the pressure and generated heat between the friction lining and the brake drum under corresponding conditions during braking; S3. Calculate the stress distribution on the NiTi alloy friction lining based on the pressure between the friction lining and the brake drum during braking, and determine the stress-strain states of the NiTi alloy friction lining and the NiTi alloy compensating pin; S4. Calculate the weight of NiTi alloy required in the brake shoe system based on the heat generated between the friction lining and the brake drum during braking; S5. Design the thickness and shape dimensions of the NiTi alloy friction lining according to the structure of the drum brake, the alloy weight, and the density, and determine the number, length, and cross-sectional area of the NiTi alloy compensating pins; S6. Analyze the stress-strain relationship and phase change characteristics of the NiTi alloy friction lining and the NiTi alloy compensating pin under long-term braking or emergency braking conditions according to the above design results, and verify the braking effect.

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

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

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

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

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

8. The design method of the 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 compensating pin.

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