Disc brake with cooling mechanism and cooling control method

Abstract

The application relates to a disc brake with a cooling mechanism and a cooling control method, and belongs to the technical field of brakes. The disc brake comprises a brake disc mechanism and a shaft, the brake disc mechanism comprises a pair of friction discs, a pair of mounting discs and a middle cooling disc; the improvement lies in that a radial inner cooling channel, a gas discharge channel and a spiral channel are uniformly arranged on the cooling disc to form a cooling channel; a pair of mounting discs are uniformly arranged with semiconductor refrigerating sheets respectively; an axial air inlet through hole and a uniformly arranged radial air inlet channel are arranged on the shaft to form an air inlet channel. During work, refrigerating gas enters the air inlet channel and the cooling channel to cool the hot end face of the semiconductor refrigerating sheet on the mounting disc adjacent to the cooling disc, and a pair of friction discs are cooled. The cooling control operation based on the disc brake comprises the following steps: a formula for accurately calculating a real-time friction coefficient when a vehicle is in a thermal decay stage or a non-thermal decay stage is obtained; the thermal decay condition is judged according to the calculated real-time friction coefficient; and it is determined whether to perform the cooling work.

Description

Technical Field

[0001] This invention belongs to the field of brake technology and relates to a cooling device and cooling control method for a disc brake that resists heat fade. Background Technology

[0002] With the continuous development of society, the automotive industry has undoubtedly become an important pillar industry of the national economy. As the main actuator in the vehicle's braking system, the stability of the automotive brake is crucial to the overall safety of the vehicle. During vehicle operation, prolonged continuous braking and frequent braking can cause the brake temperature to rise excessively, leading to thermal fade of braking performance, a decrease in the coefficient of friction, reduced braking performance, and a shortened brake disc lifespan. This can easily result in brake failure, potentially causing serious traffic accidents, resulting in personal injury and economic losses. Therefore, it is particularly important to be able to monitor the braking performance of disc brakes in real time, provide early warnings when the coefficient of friction is too low and the brakes cannot operate normally, and force cooling of the brake pads to ensure braking performance.

[0003] Automotive disc brakes are cooled in two ways: air-cooled and liquid-cooled. Ventilated brake discs have stringent manufacturing requirements and are more expensive. Liquid-cooled brake discs have cooling chambers for circulating water or other liquid coolants, absorbing braking heat even when the coolant is not boiling excessively. However, in high-speed applications, the sealing requirements at the connection between the hydraulic lines and the brake disc cooling chamber are very high, and coolant leakage is possible, increasing system complexity. Furthermore, neither method can accurately identify brake fade in real time or provide precise cooling. Existing methods for identifying vehicle brake fade only consider the impact of temperature on braking performance, ignoring the influence of other factors such as particulate matter. Preset temperatures are also based on empirical data, failing to accurately identify braking performance states. Brake fade compensation methods often only provide general approaches without specific friction coefficient curves or fade compensation algorithms. Summary of the Invention

[0004] To achieve rapid forced cooling of the brake pairs of a disc brake, this invention provides a disc brake with a cooling mechanism; simultaneously, it provides a cooling control method based on the disc brake with the cooling mechanism.

[0005] A disc brake with a cooling mechanism includes a brake caliper mechanism, a brake disc mechanism, and a shaft 6. The brake disc mechanism includes a left friction disc 101, a pair of heat-absorbing discs 102, a pair of mounting discs 114, a cooling disc 106 located between the pair of mounting discs 114, and a right friction disc 115, all connected axially. The improvements are as follows:

[0006] The cooling plate 106 is provided with more than ten radial inner cooling channels 108 that penetrate the inner circumference and more than ten venting channels 109 that penetrate the outer circumference. Corresponding to the radial inner cooling channels 108, the cooling plate 106 is provided with more than two spiral channels 107 along the circumference of the cooling plate 106 from the inside to the outside. The more than two spiral channels 107 penetrate the radial inner cooling channels 108 along the circumference.

[0007] The pair of mounting plates 114 are each provided with more than ten cooling plate holes 105 that pass through the mounting plate 114 along the circumference. The pair of mounting plates 114 adjacent to the pair of heat absorption plates 102 are each provided with more than ten cold grooves 104 that are each provided with more than ten cold grooves 104 along the circumference. The number of cold grooves 104 is the same as the number of cooling plate holes 105 and they correspond one-to-one. One end of each cold groove 104 is connected to the cooling plate hole 105, and the other end of each cold groove 104 is connected to the inner circumference of the mounting plate 114.

[0008] Each of the cooling chip holes 105 of the pair of mounting plates 114 is provided with a semiconductor cooling chip 103, and more than ten semiconductor cooling chips 103 correspond to more than ten radial inner cooling channels 108 on the cooling plate 106 respectively;

[0009] The shaft 6 has a through axial air inlet hole 110 on its axis; and four or more radial air inlets 111 are evenly distributed on the circumference of the convex ring in the middle of the shaft 6, which have through axial air inlet holes 110.

[0010] The axial air intake hole 110 and the evenly distributed radial air intake passages 111 on the shaft 6 constitute an air intake channel, and the evenly distributed radial inner cooling passages 108 and the spiral passages 107 with two or more turns on the cooling plate 106 constitute a cooling channel.

[0011] During cooling operation, the semiconductor cooling chips 103 evenly distributed on the mounting plate 114 transfer heat from the left friction plate 101 and the right friction plate 115 to the hot end face of the semiconductor cooling chip 103 adjacent to the cooling plate 106 through a pair of heat absorption plates 102. Cooling gas enters through the air inlet channel, passes through the cooling channel, and cools the hot end face of the semiconductor cooling chip 103 evenly distributed on the mounting plate 114 adjacent to the cooling plate 106, ultimately achieving the cooling of the left friction plate 101 and the right friction plate 115. The cooling gas that has exchanged heat is discharged through the air outlet 109.

[0012] The further defined technical solution is as follows:

[0013] The cooling plate 106 is provided with twenty radial inner cooling channels 108 that penetrate the inner circumference and twenty venting channels 109 that penetrate the outer circumference; the pair of mounting plates 114 are provided with twenty cooling plate holes 105 that penetrate the mounting plate 114 and are provided with twenty venting channels 109 that penetrate the mounting plate 114.

[0014] The material of the semiconductor cooling chip 103 is silicon.

[0015] The radial inner cooling channel 108 is a tapered channel with a smaller inner diameter and a larger outer diameter, and the venting channel 109 is a rectangular channel, with the width of the venting channel 109 being smaller than the width of the radial inner cooling channel 108.

[0016] The circumference of the convex ring in the middle of the shaft 6 is provided with eight radial air intake channels 111 that pass through the axial air intake hole 110. The radial air intake channels 111 are rectangular channels, and the width of the radial air intake channels 111 is greater than 1 / 16 of the circumference of the axial air intake hole 110 and less than 1 / 8 of the circumference of the axial air intake hole 110.

[0017] The cooling plate 106 corresponding to the radial inner cooling channel 108 has three spiral channels 107 arranged from the inside to the outside along the circumference of the cooling plate 106.

[0018] The cooling control operation steps for the disc brake with the cooling mechanism are as follows:

[0019] (1) Establish a friction coefficient calculation model

[0020] The friction coefficient calculation model formula (1) is as follows:

[0021]

[0022] In equation (1), F is the first-order differential function of the friction coefficient; n Normal pressure, unit is N; V r The relative velocity is expressed in m / s; μ is the coefficient of friction; T is a function of the brake disc surface temperature, expressed in °C; ρ is the particle density, expressed in particles / m³. 2 r is the particle radius in meters; η is the density of rough peaks in cubic meters per cubic meter. 2 R is the radius of the rough peak, in meters; Z is the height of the rough peak, in meters; α = a1, an undetermined coefficient; β = a2 / (a1a3), an undetermined coefficient; δ = a6 / a1, an undetermined coefficient; λ = a4 / a1, an undetermined coefficient; γ = a5 / a1, an undetermined coefficient; a1, a2, a3, a4, a5, a6 are undetermined coefficients.

[0023] (2) Establish a calculation model for the surface temperature of the brake disc considering particles between the brake pairs of the disc brake.

[0024] The formula (2) for calculating the surface temperature of the brake disc is as follows:

[0025]

[0026] In equation (2), Let be the first differential function of the brake disc surface temperature; T be a function of the brake disc surface temperature, in °C; T0 be the initial surface temperature of the brake disc, in °C; k = a9, which are undetermined coefficients; m = a4a7 / (a9A) p ), where n = a8 / a9 are undetermined coefficients; A p The nominal contact area of ​​the brake pad, in meters. 2 a7, a8, and a9 are undetermined coefficients.

[0027] (3) Establish a transient friction model of the friction coefficient and temperature of the disc brake.

[0028] The friction model formula is as follows:

[0029]

[0030] In equations (3), (4), and (5), T s This refers to the real-time temperature of the brake disc, in °C; μ s1 The transient real-time friction coefficient of the brake pair in the pre-heat fade stage of the disc brake; μ s2 t represents the real-time friction coefficient of the transient braking pair during the thermal fade phase of the disc brake; t is the braking time in seconds. p T is the critical time for a disc brake to enter the heat fade stage, measured in seconds. p C1, C2, and C3 are the critical temperatures at which disc brakes enter the heat fade stage, expressed in °C; C1, C2, and C3 are undetermined coefficients.

[0031] α′, β′, and δ′ are undetermined coefficients;

[0032] (4) Determine the control target and calculate the real-time friction coefficient.

[0033] Taking the upper limit value of equation (3) at t→+∞, and substituting it into equations (4) and (5) respectively, and then taking the upper limit values ​​of equations (4) and (5) at t→+∞, we obtain the steady-state real-time friction coefficient μ of the disc brake pair. s Steady-state real-time friction coefficient μ s The calculation formula (6) is as follows:

[0034]

[0035] Real-time temperature parameter T is collected while the car is in motion. s The real-time temperature parameter T s Substituting into the friction model formula (6), the steady-state real-time friction coefficient μ is obtained. s value;

[0036] (5) Determine the thermal decay situation and control the switching on and off of the cooling mechanism.

[0037] The calculated steady-state real-time friction coefficient μ s Compared with the critical friction coefficient that meets the operating conditions, when the steady-state real-time friction coefficient μ s When the coefficient of friction is less than the critical coefficient of friction, the semiconductor cooling chip 103 in the brake disc mechanism and the air conditioner in the car are activated to provide forced cooling for the left friction disc 101 and the right friction disc 115 in the brake disc mechanism; when the steady-state real-time coefficient of friction μ s When the value is greater than the critical friction coefficient, the semiconductor cooling chip 103 in the brake disc mechanism and the air conditioner in the car will not be turned on for cooling.

[0038] The further defined cooling control method is as follows:

[0039] In step (1), the specific operations are as follows:

[0040] (1.1) First, a first-order differential equation is established to study the dynamic characteristics of the friction of the brake pair. The influence of pressure, relative speed, actual contact area, and the radius and density of particles between the brake pairs of the disc brake on the friction coefficient is considered. The first-order differential function g (7) to reduce the friction coefficient is as follows:

[0041]

[0042] In equation (7), g is the first-order differential function of the friction coefficient considering pressure, relative velocity, particle radius, and particle density; F f This refers to tangential friction, measured in N; V r A1 is the relative velocity, in m / s; A2 is the actual contact area of ​​the friction block, in m². 2 A p The nominal contact area of ​​the friction block, in meters. 2 a1, a2, and a4 are undetermined coefficients; ρ is the particle density, in particles / m³. 2 r is the particle radius, in meters (m).

[0043] Considering the effects of friction, pressure, and contact area on the coefficient of friction, the formula for the coefficient of friction μ is as follows (8):

[0044]

[0045] In equation (8), F n denoted as normal pressure, in N; a3 is a coefficient to be determined.

[0046] Substituting equation (8) into equation (7), we obtain the following formula (9) for the first-order differential function g that reduces the friction coefficient with respect to the friction coefficient μ:

[0047]

[0048] (1.2) Considering the influence of temperature and surface morphology of the braking pair on the friction coefficient of the three-body braking pair, the first-order differential function f of the friction coefficient is increased as follows (10):

[0049] f = a5ηRZ + a6T (10)

[0050] In equation (10), η is the density of rough peaks, in units of peaks / m³. 2 R is the radius of the rough peak, in meters; Z is the height of the rough peak, in meters; T is a function of the brake disc surface temperature, in degrees Celsius; a5 and a6 are undetermined coefficients.

[0051] (1.3) Subtract formula (9) from formula (10) to obtain the friction coefficient calculation model formula (1) which comprehensively considers temperature, the radius and density of particles between the brake pairs of the disc brake and the surface morphology parameters.

[0052] In step (3), the specific operations are as follows:

[0053] (3.1) Combining equations (1) and (2) yields and Solving the system of equations by differentiation yields the real-time temperature T of the brake disc during the non-heat fade stage of the disc brake. s and transient real-time friction coefficient μ s1 The formula for calculating the temperature and transient real-time friction coefficient of a disc brake before heat fade is as follows:

[0054]

[0055] In equations (3) and (4), T s This refers to the real-time temperature of the brake disc, in °C; μ s1 t represents the transient real-time friction coefficient of the brake pair in the pre-heat fade stage of the disc brake; t is the braking time in seconds; C1 and C2 are undetermined coefficients.

[0056] (3.2) When the critical temperature for the disc brake to enter the thermal fade stage is reached, the coefficient of friction will decrease as the temperature rises. At this time, temperature acts as a factor in reducing the coefficient of friction. Let the coefficient of friction change after t... p The temperature at which the temperature begins to decrease is T. p The coefficient of friction at this time is μ. p At this point, temperature is the primary factor affecting the coefficient of friction, and t = t p Substituting into equation (4), the peak value of the friction coefficient of the disc brake is calculated. Subtracting equation (4) from the peak value of the friction coefficient of the disc brake, the transient real-time friction formula (5) for the thermal fade stage is obtained as follows:

[0057]

[0058] In equation (5), μ s2 t represents the transient real-time friction coefficient of the brake pair during the heat fade phase of a disc brake. p T is the critical time for a disc brake to enter the heat fade stage, measured in seconds. p C3 represents the critical temperature at which a disc brake enters the heat fade stage, in °C; C3 is an undetermined coefficient; α′, β′, and δ′ are undetermined coefficients.

[0059] (3.3) By combining equations (3), (4) and (5), we obtain the transient friction model formula for the friction coefficient of disc brakes in relation to temperature.

[0060] The beneficial technical effects of this invention are reflected in the following aspects:

[0061] 1. The present invention provides a disc brake with a cooling mechanism, wherein the brake disc mechanism 1 includes a left friction disc 101, a pair of heat-absorbing discs 102, a pair of mounting discs 114, a cooling disc 106 and a right friction disc 115;

[0062] The cooling channel inside the cooling plate 106 consists of twenty radial inner cooling channels 108 that run through the inner circumference, twenty venting channels 109 that run through the outer circumference, and two or more spiral channels 107. The number of radial inner cooling channels 108 and the number of semiconductor cooling chips 103 are the same and correspond one-to-one. The radial inner cooling channels 108 are smaller inside and larger outside, so that the area of ​​the position of the radial inner cooling channel 108 corresponding to the semiconductor cooling chip 103 is large enough. While ensuring the strength of the cooling plate 106, the number and area of ​​the radial inner cooling channels 108 are increased as much as possible. Each radial inner cooling channel 108 is connected to the circumference by the spiral channel 107, which increases the volume of the cooling channel and allows the cooling gas to fill the cooling channel fully and evenly. The contact area between the cooling gas and the hot end face of the semiconductor cooling chip 103 is larger, and the heat exchange is faster, thereby improving the cooling effect on the left friction plate 101 and the right friction plate 115.

[0063] The cooling plate 106 uses refrigerant gas instead of coolant as the medium, which avoids leakage problems. The airtightness requirement of the cooling plate 106 is lower than that of the coolant. The cooling gas has a low density and can quickly and evenly fill the cooling plate. It will not generate centrifugal force due to the rotation of the brake disc, which would make the cooling medium in the cooling plate insufficient. Therefore, the cooling effect on the left friction disc 101 and the right friction disc 115 is better.

[0064] The semiconductor cooling chip 103 is made of silicon material. Silicon-based semiconductor materials have advantages such as high thermal conductivity, high electrical conductivity, and ease of processing. They have excellent semiconductor properties and can quickly transfer the heat of the left friction disk 101 and the right friction disk 115 from the cold end face to the hot end face of the semiconductor cooling chip 103, thereby rapidly cooling the left friction disk 101 and the right friction disk 115.

[0065] The width of the eight radial air intake channels 111 evenly distributed on the circumference of the convex ring in the middle of shaft 6 is greater than 1 / 16 of the circumference of the axial air intake through hole 110 and less than 1 / 8 of the circumference of the axial air intake through hole 110. While ensuring the strength of the shaft, the number and area of ​​the radial air intake channels 111 are increased as much as possible. The axial air intake through hole 110, which is connected to the air outlet of the air conditioner in the car, has a larger diameter, which can increase the speed and efficiency of transporting the refrigerant gas, thereby increasing the speed at which the refrigerant gas enters the cooling channel.

[0066] The vent 109 is connected to the radial inner cooling channel 108, which allows the cooled gas that has exchanged heat to be released into the air, thus avoiding the problem of excessive air pressure inside the brake disc. In addition, the width of the vent 109 is smaller than the width of the radial inner cooling channel 108, preventing the cooled gas entering the radial inner cooling channel 108 from being dissipated into the air through the vent 109 before exchanging heat. When the cooling mechanism is not working, external air can enter the cooling passage in the cooling disc 106 through the vent 109, thereby dissipating heat from inside the brake disc through air cooling.

[0067] 2. This invention provides a cooling control method. A grating temperature sensor monitors temperature parameters in real time, calculates the real-time friction coefficient using a provided real-time friction coefficient formula, compares the friction coefficient with the critical friction coefficient, and controls whether the cooling mechanism operates based on the result. When the real-time friction coefficient is less than the critical friction coefficient, the semiconductor refrigeration chip 103 in the cooling mechanism and the air conditioner in the car activate cooling operation to force cooling of the left friction disc 101 and the right friction disc 115. When the steady-state real-time friction coefficient is greater than the critical friction coefficient, the semiconductor refrigeration chip 103 in the cooling mechanism and the air conditioner in the car do not activate cooling operation. This allows for real-time and precise control of whether the cooling mechanism operates, avoiding energy waste and increased operating costs caused by continuous operation of the cooling mechanism.

[0068] See Figure 16 Disc brakes enter the heat fade stage after 60 seconds of braking. Disc brakes without the cooling device of this invention have a friction coefficient lower than the critical friction coefficient after 111 seconds of braking. Disc brakes with the cooling device of this invention can maintain a friction coefficient up to the critical friction coefficient after 111 seconds of braking, meeting the requirements for vehicle operation. It can be seen that the cooling mechanism and cooling control method of this invention have a significant anti-heat fade effect.

[0069] 3. This invention provides a cooling control method, which provides a formula for accurately calculating the real-time friction coefficient of a vehicle during or before the heat fade stage. Based on the calculated real-time friction coefficient, the heat fade situation is judged, and it is decided whether to perform cooling. The cooling control method of this invention not only considers the influence of temperature, load, relative speed, and actual contact area on the friction coefficient, but also considers the influence of particles between the brake pairs of disc brakes and the rough peaks on the surface of the friction pairs on the friction coefficient. The parameters of the particles themselves between the brake pairs and the surface morphology parameters of the brake pairs both affect the braking process and the friction coefficient. Therefore, the formula for calculating the real-time friction coefficient is more accurate. Attached Figure Description

[0070] Figure 1 This is a schematic diagram of the structure of the present invention;

[0071] Figure 2 for Figure 1 The front view;

[0072] Figure 3 for Figure 2 AA section view;

[0073] Figure 4 for Figure 2 Side view;

[0074] Figure 5 for Figure 4 BB cross-sectional view;

[0075] Figure 6 This is a schematic diagram of the brake disc structure;

[0076] Figure 7 This is an exploded view of the brake disc;

[0077] Figure 8 This is a radial sectional view of the cooling plate;

[0078] Figure 9 This is a front view of the brake disc;

[0079] Figure 10 for Figure 9 EE sectional view;

[0080] Figure 11 This is a side view of the brake disc;

[0081] Figure 12 for Figure 11 CC section view;

[0082] Figure 13 This is a schematic diagram of the shaft structure;

[0083] Figure 14 This is an axial sectional view of the shaft;

[0084] Figure 15 for Figure 14 DD sectional view;

[0085] Figure 16 The curves showing the changes in temperature and friction coefficient over time with and without the application of a brake disc are shown.

[0086] Figure 17 This is a graph showing the relationship between the friction coefficient and temperature in the friction model provided by this invention.

[0087] Figure 18 The curves showing the change of speed and braking distance over time in the friction model provided by this invention;

[0088] Figure 19 This is the curve showing the speed change over time with and without brake discs when a vehicle is descending a long slope, according to the present invention.

[0089] Figure 1-15 Serial number: Brake disc mechanism 1, left friction disc 101, heat absorption disc 102, semiconductor cooling chip 103, cold groove 104, cooling chip hole 105, cooling disc 106, spiral channel 107, radial inner cooling channel 108, venting channel 109, axial air inlet hole 110, radial air inlet channel 111, positioning hole 112, mounting hole 113, mounting disc 114, right friction disc 115, brake caliper body 2, brake caliper 3, grating temperature sensor 4, brake block 5, shaft 6. Detailed Implementation

[0090] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0091] Example

[0092] See Figure 1 and Figure 2 A disc brake with a cooling mechanism includes a brake caliper mechanism, a brake disc mechanism, and a shaft 6.

[0093] See Figure 3 and Figure 4 The brake caliper mechanism includes a brake caliper body 2, a brake caliper 3, a grating temperature sensor 4, and a brake block 5.

[0094] See Figure 6 , Figure 7 , Figure 9 and Figure 10 The brake disc mechanism includes an axially connected left friction disc 101, a pair of heat-absorbing discs 102, a pair of mounting discs 114, a cooling disc 106 located between the pair of mounting discs 114, and a right friction disc 115.

[0095] See Figure 5 and Figure 8The cooling plate 106 has twenty radially distributed inner cooling channels 108 penetrating the inner circumference and twenty venting channels 109 penetrating the outer circumference; see also Figure 11 and Figure 12 The cooling plate 106 corresponding to the radial inner cooling channel 108 has three spiral channels 107 arranged from the inside to the outside along the circumference of the cooling plate 106. Two or more spiral channels 107 penetrate the radial inner cooling channel 108 along the circumference.

[0096] See Figure 8 The radial internal cooling channel 108 is a tapered channel with a smaller inner diameter and a larger outer diameter, and the venting channel 109 is a rectangular channel, with the width of the venting channel 109 being smaller than the width of the radial internal cooling channel 108.

[0097] See Figure 7 and Figure 10 Twenty cooling plate holes 105 are evenly distributed along the circumference of each of the two mounting plates 114. Twenty cold grooves 104 are evenly distributed along the circumference of each of the two mounting plates 114 adjacent to the pair of heat absorption plates 102. The number of cold grooves 104 is the same as the number of cooling plate holes 105, and they correspond one-to-one. One end of each cold groove 104 is connected to the cooling plate hole 105, and the other end of each cold groove 104 is connected to the inner circumference of the mounting plate 114.

[0098] See Figure 10 Each of the two mounting plates 114 has a thermoelectric cooler 103 installed in each cooler hole 105, and the twenty thermoelectric coolers 103 correspond to the twenty radial internal cooling channels 108 on the cooling plate 106. The thermoelectric cooler 103 is made of silicon.

[0099] See Figure 13 and Figure 15 A through axial air intake hole 110 is provided along the axis of shaft 6; eight radial air intake passages 111, passing through the axial air intake hole 110, are evenly distributed on the circumference of the convex ring in the middle of shaft 6. See also Figure 13 and Figure 14 The radial air intake duct 111 is a rectangular channel, and the width of the radial air intake duct 111 is greater than 1 / 16 of the circumference of the axial air intake through hole 110 and less than 1 / 8 of the circumference of the axial air intake through hole 110.

[0100] The axial air intake hole 110 and the evenly distributed radial air intake passages 111 on the shaft 6 constitute the air intake channel, and the evenly distributed radial inner cooling passages 108 and the spiral passages 107 with two or more turns on the cooling plate 106 constitute the cooling channel.

[0101] Using a certain type of sedan as a prototype, its main parameters are as follows: vehicle weight M = 1335 kg, and both front and rear wheels are as described above. Figure 1-15The disc brake shown has vehicle dimensions of 4635×1780×1455mm and a maximum speed of V. max =180km / h; The correlation coefficients of the disc brake friction pair are as follows: Braking pressure F n =1500N, relative velocity V r =7.5m / s, initial temperature T0=0℃, rough peak density, rough peak radius R=0.00005m, rough peak height Z=0.00001m, particle density ρ=100000 particles / m³ 2 Particle radius r = 0.00003 m, critical temperature T p =230℃, the coefficients in the friction coefficient formula of the above friction model are respectively δ=43.91, δ′=72.51, γ=100000, λ=1, m=0.1, n=1, k=0.0125, α=α′=1, β′=β=30.

[0102] According to the Chinese national standard GB 5763-2018 "Automotive Brake Liners" regarding the friction performance requirements of disc brake linings, disc brakes belong to category 4. The required coefficient of friction is 0.25–0.65 at 100℃, and 0.25–0.70 at temperatures of 150–350℃ and above. Therefore, in this embodiment, the critical value for the coefficient of friction is set to μ. 临界 =[μ min临界 ,μ max临界 ]=[0.25,0.70], the minimum requirement for the coefficient of friction under normal operating conditions is μ min临界 =0.25.

[0103] The cooling control operation steps for the disc brake with the aforementioned cooling mechanism are as follows:

[0104] (1) Establish a friction coefficient calculation model

[0105] The friction coefficient calculation model formula (1) is as follows:

[0106]

[0107] In equation (1), is the first-order differential function of the friction coefficient; μ is the friction coefficient; T is a function of the brake disc surface temperature, in °C.

[0108] The specific steps for step (1) are as follows:

[0109] (1.1) First, a first-order differential equation is established to study the dynamic characteristics of the friction of the brake pair. The influence of pressure, relative speed, actual contact area, and the radius and density of particles between the brake pairs of the disc brake on the friction coefficient is considered. The first-order differential function g (7) to reduce the friction coefficient is as follows:

[0110]

[0111] In equation (7), g is the first-order differential function of the friction coefficient considering pressure, relative velocity, particle radius, and particle density; F f A1 is the tangential friction force, in N; A1 is the actual contact area of ​​the friction block, in m². 2 A p The nominal contact area of ​​the friction block, in meters. 2 a1, a2, and a4 are undetermined coefficients.

[0112] Considering the effects of friction, pressure, and contact area on the coefficient of friction, the formula for the coefficient of friction μ is as follows (8):

[0113]

[0114] In equation (8), μ is the friction coefficient; a3 is an undetermined coefficient.

[0115] Substituting equation (8) into equation (7), we obtain the following formula (9) for the first-order differential function g that reduces the friction coefficient with respect to the friction coefficient μ:

[0116]

[0117] (1.2) Considering the influence of temperature and surface morphology of the braking pair on the friction coefficient of the three-body braking pair, the first-order differential function f of the friction coefficient is increased as follows (10):

[0118] f=a5×100000×0.00005×0.00001+a6T (10)

[0119] In equation (10), f is the first-order differential function of the friction coefficient considering temperature and surface morphology parameters; T is a function of the surface temperature of the brake disc, in °C; a5 and a6 are undetermined coefficients.

[0120] (1.3) Subtract formula (9) from formula (10) to obtain the friction coefficient calculation model formula (1) which comprehensively considers temperature, the radius and density of particles between the brake pairs of the disc brake and the surface morphology parameters.

[0121] (2) Establish a calculation model for the surface temperature of the brake disc considering particles between the brake pairs of the disc brake.

[0122] The formula (2) for calculating the surface temperature of the brake disc is as follows:

[0123]

[0124] In equation (2), It is the first-order differential function of the brake disc surface temperature.

[0125] (3) Establish a transient friction model of the friction coefficient and temperature of the disc brake.

[0126] The friction model formula is as follows:

[0127]

[0128] In equations (3), (4), and (5), T s This refers to the real-time temperature of the brake disc, in °C; μ s1 The transient real-time friction coefficient of the brake pair in the pre-heat fade stage of the disc brake; μ s2 t represents the real-time friction coefficient of the transient braking pair during the thermal fade phase of the disc brake; t is the braking time in seconds. p C1, C2, and C3 are the critical time for a disc brake to enter the thermal fade stage, measured in seconds; C1, C2, and C3 are undetermined coefficients.

[0129] The specific steps for step (3) are as follows:

[0130] (3.1) Combining equations (1) and (2) yields and Solving the system of equations by differentiation yields the real-time temperature T of the brake disc during the non-heat fade stage of the disc brake. s and transient real-time friction coefficient μ s1 The formula for calculating the temperature and transient real-time friction coefficient of a disc brake before heat fade is as follows:

[0131]

[0132] (3.2) When the critical temperature for the disc brake to enter the thermal fade stage is reached, the coefficient of friction will decrease as the temperature rises. At this time, temperature acts as a factor in reducing the coefficient of friction. Let the coefficient of friction change after t... p The temperature at which the temperature begins to decrease is T. p The coefficient of friction at this time is μ. p At this point, temperature is the primary factor affecting the coefficient of friction, and t = t p Substituting into equation (4), the peak value of the friction coefficient of the disc brake is calculated. Subtracting equation (4) from the peak value of the friction coefficient of the disc brake, the transient real-time friction formula (5) for the thermal fade stage is obtained as follows:

[0133]

[0134] (3.3) By combining equations (3), (4) and (5), we obtain the transient friction model formula for the friction coefficient of disc brakes in relation to temperature.

[0135] like Figure 16The figure shows the curves of temperature and friction coefficient changing with time when there is no brake disc. The formulas used are formulas (3), (4) and (5). When the brake starts to brake, the temperature increases with time, but the rate of increase gradually slows down. p The critical temperature T is reached at 60s. p =230℃, at which point the coefficient of friction reaches its maximum value, and then begins to gradually decrease, t p The formulas for the coefficient of friction are different before and after, due to Figure 16 It can be seen that the rates of increase and decrease are different. During the stage of decreasing friction coefficient, the slope of the curve gradually decreases, and eventually both friction coefficient and temperature tend to a stable value, but this stable value is less than μ. min临界 =0.25, from Figure 16 It is known that at t=111s, the friction coefficient is too low, and the braking performance suffers severe thermal decay, failing to meet the usage requirements. The method of the present invention to resist thermal decay is to reduce the temperature of the friction pair by forcibly cooling the cooling plate when the friction coefficient is too low, keeping it at the critical value, so that the friction coefficient is maintained at least at the minimum usage requirements. Therefore, at 111s, the curves of temperature and friction coefficient change with time with and without the cooling mechanism begin to separate. When the cooling mechanism is in effect, the temperature will maintain a certain value after 111s and will not continue to rise. Correspondingly, the friction coefficient will not continue to decrease and can be maintained at the minimum required friction coefficient value. Obviously, the cooling mechanism is beneficial to improving the braking performance of the brake.

[0136] (4) Determine the control target and calculate the real-time friction coefficient.

[0137] Taking the upper limit value of equation (3) at t→+∞, and substituting it into equations (4) and (5) respectively, and then taking the upper limit values ​​of equations (4) and (5) at t→+∞, we obtain the steady-state real-time friction coefficient μ of the disc brake pair. s Steady-state real-time friction coefficient μ s The calculation formula (6) is as follows:

[0138]

[0139] like Figure 17 The figure shows the curve of friction coefficient as a function of temperature. This curve corresponds one-to-one with real-time temperature and real-time friction coefficient, measured by the grating temperature sensor at temperature T. s Then, by substituting into formula (6), the corresponding real-time friction coefficient can be obtained.

[0140] When the temperature sensor measures a real-time temperature parameter value of T s When the temperature is 110℃, substituting into equation (6) yields the following result:

[0141]

[0142] When the temperature sensor measures a real-time temperature parameter value of T s When the temperature is 340℃, substituting into equation (6) yields the following result:

[0143]

[0144] (5) Determine the thermal decay situation and control the switching on and off of the cooling mechanism.

[0145] The calculated steady-state real-time friction coefficient μ s The value is compared with the critical friction coefficient that meets the requirements of the working conditions.

[0146] When the temperature sensor measures a real-time temperature parameter value of T s At 340℃, substituting into equation (6) yields the real-time friction coefficient μ. s (340℃) = 0.1884, which is less than the critical friction coefficient μ. min临界 =0.25, indicating severe brake fade. The semiconductor cooling chip 103 in the brake disc mechanism and the air conditioner in the car are activated to provide forced cooling to the left friction disc 101 and right friction disc 115 in the brake disc mechanism.

[0147] During cooling operation, the thermoelectric cooling chips 103 evenly distributed on the mounting plate 114 transfer the heat from the left friction plate 101 and the right friction plate 115 to the hot end face of the thermoelectric cooling chip 103 adjacent to the cooling plate 106 through a pair of heat absorption plates 102. The cooling gas enters through the air inlet channel, passes through the cooling channel, and cools the hot end face of the thermoelectric cooling chip 103 evenly distributed on the mounting plate 114 adjacent to the cooling plate 106, thus achieving the cooling of the left friction plate 101 and the right friction plate 115. The cooling gas that has exchanged heat is discharged through the air outlet 109.

[0148] When the temperature sensor measures a real-time temperature parameter value of T s At 110℃, substituting into equation (6) yields the real-time friction coefficient μ. s (110℃)=0.4284, at which point the real-time friction coefficient is greater than the critical friction coefficient μ. min临界 =0.25 indicates that the braking performance is good at this time, meeting the current driving needs of the vehicle. The semiconductor cooling chip 103 in the brake disc mechanism and the air conditioner in the vehicle are not turned on for cooling.

[0149] When vehicles travel in mountainous areas, they often need to descend long slopes. Under these conditions, vehicles require prolonged and continuous braking to maintain a stable speed. According to the Chinese industry standard JTGD20-2017 "Specifications for Highway Route Design," the gradient of highways and secondary roads should generally not exceed 10%. Therefore, using a 10% gradient as the critical value, the force analysis of the vehicle during downhill driving yields the following results:

[0150] ma = F f -Mg sinθ=μF n -Mg sinθ=μMg cosθ-Mg sinθ=Mg cosθ(μ-tanθ)≥0 (11)

[0151] In equation (11), θ is the slope angle of the long slope where the car is located, in °.

[0152] According to Newton's second law, the braking deceleration a = μ s ×F n The braking deceleration of the vehicle during braking can be obtained from / M:

[0153]

[0154] The braking speed v is:

[0155]

[0156] In equation (13), v0 is the initial speed of the vehicle when it begins to brake, in m / s, and is taken as 20 m / s.

[0157] Braking distance s is:

[0158]

[0159] In equation (14), v1 represents the vehicle's speed from 0 to t. p The real-time braking speed at time t, in m / s; v2 is the vehicle's braking speed at time t. p Real-time braking speed after the specified time, in m / s.

[0160] like Figure 18 The figure shows the curves of speed and braking distance changing with time in the friction model provided by this invention. The formulas used are formula (12), formula (13), and formula (14). Figure 18 Taking a vehicle with an initial braking speed of v0 = 20 m / s as an example, the curves of speed and braking distance changing with time are obtained. At t = 17.2 s, the vehicle brakes to zero speed, and the braking distance is 227.8 m. Therefore, the braking time and braking distance can be calculated based on the initial braking speed value of the vehicle measured by the wheel speed sensor. This can be used as a reference for the driver to judge whether the braking distance is sufficient, ensure vehicle braking safety, and avoid traffic accidents.

[0161] like Figure 19This invention relates to the velocity-time curve of a vehicle descending a long slope with and without brake disc action. To maintain a constant speed while descending a long slope, μ - tanθ ≥ 0, i.e., μ ≥ tanθ. According to the definition of slope, the slope value is equal to the value of tanθ. Therefore, the critical slope value for descending a long slope is 10%, and the minimum requirement for the brake friction coefficient is μ. min =tanθ 临界 =10% =0.1.

[0162] Depend on Figure 19 As can be seen, taking an initial vehicle braking velocity of v0 = 20 m / s as an example, in the initial stage of braking, the coefficient of friction increases with increasing temperature. Since the temperature is very low, the coefficient of friction is also very low at this time, so the velocity gradually increases until the coefficient of friction is greater than μ. min At that moment, the braking deceleration is greater than zero, and the speed begins to decrease. When the speed drops to the initial speed v0 = 20 m / s, the coefficient of friction is still greater than μ. min The vehicle maintained a constant speed until, after t = 201 s, the coefficient of friction decreased to μ. min Without the forced cooling effect of the cooling disc, the brakes will experience severe heat fade, the temperature will continue to rise, the speed will increase, and the acceleration will also continue to increase. The vehicle speed will become uncontrollable, making it easy to rear-end other vehicles and other accidents. Excessive speed on long downhill slopes can also easily lead to rollover accidents. Therefore, the algorithm and cooling mechanism constructed in this invention have a good anti-heat fade effect on disc brakes when going downhill on long slopes. This helps the vehicle to travel at a constant speed on long downhill slopes, maintain safety and driving stability, and avoid traffic accidents.

Claims

1. A disc brake with a cooling mechanism, comprising a brake caliper mechanism, a brake disc mechanism, and a shaft (6), wherein the brake disc mechanism comprises a left friction disc (101), a pair of heat-absorbing discs (102), a pair of mounting discs (114), a cooling disc (106) located between the pair of mounting discs (114), and a right friction disc (115) connected axially; characterized in that: The cooling plate (106) is provided with more than ten radial inner cooling channels (108) that penetrate the inner circumference and more than ten venting channels (109) that penetrate the outer circumference. The cooling plate (106) corresponding to the radial inner cooling channels (108) is provided with more than two spiral channels (107) from the inside to the outside along the circumference of the cooling plate (106), and the more than two spiral channels (107) penetrate the radial inner cooling channels (108) along the circumference. The pair of mounting plates (114) are provided with more than ten cooling plate holes (105) that pass through the mounting plate (114) evenly distributed along the circumference. The pair of mounting plates (114) adjacent to the pair of heat absorption plates (102) are provided with more than ten cold grooves (104) evenly distributed along the circumference on the side. The number of cold grooves (104) is the same as the number of cooling plate holes (105) and they correspond one-to-one. One end of each cold groove (104) is connected to the cooling plate hole (105), and the other end of each cold groove (104) is connected to the inner circumference of the mounting plate (114). Each cooling chip hole (105) of the pair of mounting plates (114) is provided with a semiconductor cooling chip (103), and more than ten semiconductor cooling chips (103) correspond to more than ten radial internal cooling channels (108) on the cooling plate (106); The shaft (6) has a through axial air inlet hole (110) on its axis; and four or more radial air inlets (111) are evenly distributed on the circumference of the convex ring in the middle of the shaft (6) through the axial air inlet hole (110). The axial air intake hole (110) and the evenly distributed radial air intake channel (111) on the shaft (6) constitute the air intake channel, and the evenly distributed radial inner cooling channel (108) and the spiral channel (107) with two or more turns on the cooling plate (106) constitute the cooling channel. During cooling operation, the semiconductor cooling chips (103) evenly distributed on the mounting plate (114) transfer the heat from the left friction plate (101) and the right friction plate (115) to the hot end face of the semiconductor cooling chip (103) adjacent to the cooling plate (106) through a pair of heat absorption plates (102). The cooling gas enters through the air inlet channel, passes through the cooling channel, and cools the hot end face of the semiconductor cooling chip (103) evenly distributed on the mounting plate (114) adjacent to the cooling plate (106), thus achieving the cooling of the left friction plate (101) and the right friction plate (115). The cooling gas that has exchanged heat is discharged through the air outlet channel (109).

2. A disc brake with a cooling mechanism according to claim 1, characterized in that: The cooling plate (106) is provided with twenty radial inner cooling channels (108) that penetrate the inner circumference and twenty venting channels (109) that penetrate the outer circumference; the pair of mounting plates (114) are provided with twenty cooling plate holes (105) that penetrate the mounting plate (114) respectively.

3. A disc brake with a cooling mechanism according to claim 1, characterized in that: The material of the semiconductor cooling chip (103) is silicon.

4. A disc brake with a cooling mechanism according to claim 1, characterized in that: The radial inner cooling channel (108) is a tapered channel with a smaller inner diameter and a larger outer diameter, and the venting channel (109) is a rectangular channel, with the width of the venting channel (109) being smaller than the width of the radial inner cooling channel (108).

5. A disc brake with a cooling mechanism according to claim 1, characterized in that: The circumference of the convex ring in the middle of the shaft (6) is provided with eight radial air intake channels (111) that pass through the axial air intake hole (110). The radial air intake channels (111) are rectangular channels, and the width of the radial air intake channels (111) is greater than 1 / 16 of the circumference of the axial air intake hole (110) and less than 1 / 8 of the circumference of the axial air intake hole (110).

6. A disc brake with a cooling mechanism according to claim 1, characterized in that: The cooling plate (106) corresponding to the radial inner cooling channel (108) has three spiral channels (107) arranged from the inside to the outside along the circumference of the cooling plate (106).

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