Low-dragging-moment EMB split type brake caliper and brake clearance adjusting method

Abstract

The invention discloses a low-dragging-torque EMB split type brake caliper and a brake clearance adjusting method, and belongs to the field of braking, the low-dragging-torque EMB split type brake caliper comprises a ball screw, a piston and a friction plate set which are arranged on a caliper body, the ball screw comprises a screw shaft connected with the output end of a gear motor through a spline, and an inner threaded hole is formed in the end, facing the screw shaft, of the piston; the inner threaded hole is matched with the lead screw shaft, the end, deviating from the lead screw shaft, of the piston is connected with a brake disc, the brake disc is aligned with an inner friction plate of the friction plate set, and a displacement sensor is arranged at the position, corresponding to the lead screw shaft, of the inner friction plate and used for collecting axial displacement of the lead screw shaft. The clamping force is indirectly collected through the mapping relation of the axial displacement of the lead screw shaft, the deformation of the inner friction plate and the real-time clamping force. By the adoption of the low-dragging-moment EMB split type brake caliper and the brake clearance adjusting method, light weight, low dragging moment and multi-working-condition high-precision brake clearance adjustment of the EMB brake caliper are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of braking, in particular to a low-drag torque EMB split brake caliper and a brake clearance adjustment method. BACKGROUND

[0002] With the development of automobile intelligence and electrification, the electromechanical brake (EMB) system has become the mainstream due to its fast response and high controllability, but the existing technology still has the following key deficiencies: 1. Conflict between brake caliper material and drag torque: the traditional gray cast iron (GCI) brake caliper has a density of 7.2 g / cm 3 , resulting in an increase in the vehicle's unsprung mass and energy consumption; although there have been studies using aluminum matrix composites (Al-MMC) to reduce weight, the transfer film formed by the Al-MMC piston and the NAO friction plate is prone to fall off due to the lack of a fixed containing structure, resulting in fluctuations in the drag torque (traditional structure drag torque > 10%), which affects brake smoothness; 2. High cost and low reliability of clamping force detection: existing EMBs rely on pressure sensors to directly collect clamping force, but the sensors are installed between the ball screw and the reducer, which are prone to failure due to vibration and impact, and increase the system cost and complexity; 3. Poor adaptability of friction coefficient to working conditions: the friction coefficient is significantly affected by temperature (such as long-time braking above 300℃), pressure (1-8MPa), and vehicle speed (>120km / h) during braking, but existing technologies do not dynamically compensate for the friction coefficient for different working conditions, resulting in a clamping force tracking error of more than ±5%, low clearance adjustment accuracy (reset error >0.05mm), and an inability to meet the safety requirements of emergency braking, high-temperature braking, and other scenarios. SUMMARY

[0003] The purpose of the present application is to provide a low-drag torque EMB split brake caliper and a brake clearance adjustment method to solve the above technical problems.

[0004] To achieve the above purpose, the present application provides a low-drag torque EMB split brake caliper, which includes a ball screw, a piston, and a friction plate group arranged on a caliper body. The ball screw includes a screw shaft connected to the output end of a reduction motor through a spline. The piston has an internally threaded hole at one end facing the screw shaft, which is adapted to the screw shaft. The other end of the piston, away from the screw shaft, is connected to an inner friction plate. A displacement sensor is arranged on the inner friction plate at a position corresponding to the screw shaft, which is used to collect the axial displacement of the screw shaft and indirectly collect the clamping force through the mapping relationship between the axial displacement of the screw shaft, the deformation of the inner friction plate, and the real-time clamping force. A contact thermocouple is arranged on the inner friction plate at a position corresponding to the brake disc, which is used to collect the contact temperature between the inner friction plate and the brake disc during braking.

[0005] The brake gap adjusting method of the low-drag torque EMB split brake caliper comprises the following steps: S1, collecting brake working condition parameters, and determining real-time friction coefficient and real-time brake working condition grade in combination with the friction characteristic model of the piston; S2, adopting a segmented control strategy to output a deceleration motor control signal in combination with the real-time friction coefficient and the real-time brake working condition grade.

[0006] Therefore, the low-drag torque EMB split brake caliper and the brake gap adjusting method have the following beneficial effects: 1. Significant lightweight and high wear resistance: the piston is made of Al-MMC material (base Al-Si alloy + 20wt% SiC particles + Ni / Cu / Zr alloy), with a density of only 2.8g / cm 3 , which is more than 50% lighter than the traditional gray cast iron brake caliper, reducing the vehicle's unsprung mass and energy consumption; the SiC particles (hardness 34.4±3.7GPa) and Al3Ni strengthening phase cooperate to improve the piston's wear resistance, forming a stable friction pair with the NAO friction plate, and the piston's service life is extended to more than 80,000 kilometers (the service life of the traditional cast iron piston is about 50,000 kilometers); 2. Effectively reducing the brake drag torque: the annular accommodating groove (diameter 0.5mm, depth 0.1mm, spacing 2mm) on the outer surface of the piston can stably accommodate and transfer the friction debris, forming a protective transfer film with a thickness of 0.05-0.1mm, reducing the invalid contact area between the piston and the brake disc, and reducing the drag torque to less than 50% of the traditional gray cast iron brake caliper (room temperature condition ≤1N·m), improving the energy economy of the vehicle during sliding; at the same time, it avoids the formation of "three-body abrasive wear" of debris on the friction interface, reduces the volume wear of the inner friction plate (more than 40% lower than the traditional structure, the service life of the NAO friction plate is extended to 60,000 kilometers), and reduces the user's maintenance cost; 3. High-precision sensorless clamping force detection: the displacement sensor collects the axial displacement of the lead screw shaft, and the sensorless clamping force estimation is realized by combining the lead screw shaft displacement-inner friction plate deformation-clamping force segmented mapping relationship, the easily failed pressure sensor is cancelled, the system cost is reduced by more than 30%, and the clamping force tracking error is ≤±3%, meeting the high-precision control requirements of EMB; 4. Multi-condition adaptive brake control: based on the contact type thermocouple, pressure sensor and vehicle speed signal, the real-time friction coefficient is calculated according to the working condition, and the segmented control strategy (target speed in the gap elimination stage is adapted to the working condition, PI parameter dynamic switching in the clamping force maintaining stage) is adopted, to ensure that accurate gap adjustment (reset error ≤±0.01mm) can be realized in the normal braking, emergency braking and high-temperature braking scenes, and the brake safety and smoothness are significantly improved.

[0007] The technical solutions of the present application will be further described in detail through the drawings and examples. Attached Figure Description

[0008] Figure 1 This is a half-sectional view of the low drag torque EMB split brake caliper of the present invention.

[0009] Figure Labels 1. Lead screw shaft; 2. Piston; 3. Internal friction plate; 4. Caliper body. Detailed Implementation

[0010] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of the present invention and are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0011] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as a process, method, system, product, or server that includes a series of steps or units, not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or device.

[0012] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0013] like Figure 1 As shown, the low drag torque EMB split brake caliper includes a ball screw, a piston 2, and a friction plate assembly mounted on the caliper body 4. The ball screw includes a screw shaft 1 connected to the output end of a geared motor via a spline. The piston 2 has an internal threaded hole at one end facing the screw shaft 1, which is adapted to the screw shaft 1. The piston 2 is connected to an internal friction plate 3 at the other end facing away from the screw shaft 1. A displacement sensor is installed on the internal friction plate 3 at a position corresponding to the screw shaft 1 to collect the axial displacement of the screw shaft 1. The clamping force is indirectly collected through the mapping relationship between the axial displacement of the screw shaft 1, the deformation of the internal friction plate 3, and the real-time clamping force. A contact thermocouple is installed on the internal friction plate 3 at a position corresponding to the brake disc to collect the contact temperature between the internal friction plate 3 and the brake disc during braking.

[0014] The mapping relationship between the axial displacement of the lead screw shaft, the deformation of the internal friction plate, and the real-time clamping force is expressed as follows: ; In the formula, This indicates the amount of deformation of the internal friction plate, and , This indicates the axial displacement of the leadscrew shaft. This indicates the initial braking clearance.

[0015] The piston's matrix is ​​an Al-Si alloy, with 20wt% SiC particles as the reinforcing phase, and the addition of 3.47wt% Ni, 0.55wt% Cu, and 0.13wt% Zr to form an Al3Ni reinforcing phase and a solid solution reinforced structure. The overall hardness is 145 HV1, and the density is 2.8 g / cm³. 3 The total Si content in the Al-Si alloy is 20.12 wt%, and the 20 wt% SiC particles are a mixture of 30 wt% F360, 40 wt% F400 and 30 wt% F500 particles with an average particle size of 20 μm. The hardness of the SiC particles is 34.4 ± 3.7 GPa.

[0016] The friction plate assembly is made of NAO material. The NAO inner friction plate and the piston form a friction pair with a transfer film. The NAO friction plate contains aramid fiber, phenolic resin binder, and inorganic filler (such as CaCO3).

[0017] The outer surface of the piston has multiple receiving grooves arranged in a ring to accommodate transferred friction debris. The diameter of the receiving grooves is 0.5 mm, the depth is 0.1 mm, and the distance between two adjacent receiving grooves is 2 mm.

[0018] Specifically, the formation mechanism of the transfer film is as follows: During braking, the SiC hard particles (hardness 34.4±3.7GPa) of the Al-MMC piston micro-cut the friction plate, generating debris (containing carbonized resin and fiber fragments) with a particle size of 10μm-50μm. Contact pressure (1MPa-8MPa) and frictional heat (50℃-400℃) cause the resin debris to partially melt. The Al matrix on the surface of the Al-MMC piston softens due to frictional heating (melting point 660℃), and the molten debris embeds into the receiving groove of the Al matrix, forming a mechanical interlock (under pressure, the debris embeds into the receiving groove to form a "barb" structure, increasing the peeling force by 3-5 times (compared to a smooth surface), preventing the film from peeling off). Furthermore, the local pressure at the edge of the receiving groove reaches twice the overall pressure, compacting the debris to form a dense film (density from 1.2g / cm³). 3 →2.0g / cm 3 This reduces porosity and blocks the oxidation of the Al matrix.

[0019] The method for adjusting the brake clearance of a low-drag torque EMB split brake caliper includes the following steps: S1. Collect braking condition parameters and, in conjunction with the piston friction characteristic model, determine the real-time friction coefficient and the real-time braking condition level. The braking parameters mentioned in step S1 include the contact temperature between the internal friction pads and the brake disc. Real-time pressure of brake lines and real-time vehicle speed ; Real-time friction coefficient The expression is as follows: ; Real-time braking conditions are classified into the following three categories: Normal braking conditions: ; Emergency braking condition: ; High-temperature braking conditions: .

[0020] S2. Combining the real-time friction coefficient and the real-time braking condition level, a segmented control strategy is adopted to output the control signal for the geared motor.

[0021] Step S2 specifically includes the following steps: S21, when ,and When the gap elimination phase is entered, a dual closed-loop control of speed and current is used to output the forward rotation PWM signal of the geared motor. The speed loop targets the desired speed and uses a proportional controller, while the output current reference value is... , and then To achieve the target speed, a PI controller outputs a PWM duty cycle signal to control the geared motor to rotate forward at the target speed until... ,and When, execute step S22; where, Indicates pedal displacement; Target speed The expression is as follows: ; In the formula, Indicates the total deceleration of the geared motor; Indicates the second-to-minute conversion factor; Indicates the target elimination time, and under normal braking conditions. Emergency braking conditions High-temperature braking conditions ; This refers to the lead of the ball screw; S22, Clamping force holding stage; S221, Based on the pedal displacement and maximum clamping force Determine the target clamping force : ; In the formula, Indicates the pedal displacement-clamping force conversion coefficient; S222, Correcting the target current based on the real-time friction coefficient: ; In the formula, This indicates the corrected target current for the geared motor; Indicates the reference current; Indicates the reference friction coefficient; S223, Employ current closed-loop control of the geared motor PWM signal until... ,and Execute step S23: Normal braking condition: Set the current loop parameters so that ;in, and These represent the proportional gain and integral gain of the current loop, respectively. Emergency braking condition: Set current loop parameters ,make follow ; High-temperature braking condition: Set current loop parameters and add temperature compensation. At this time, the total current ;in, Indicates the temperature-current conversion factor; S23, gap reset stage control; S231. Estimate the thickness of the transfer film. : ; In the formula, Indicates the stiffness of the brake caliper; S232, Based on the thickness of the transfer film Correct and reset target displacement: when At that time, reset the target displacement At this time, the geared motor rotates in the reverse direction by 0.01mm-0.02mm; when At that time, reset the target displacement At this time, the geared motor reduces its reverse rotation by 0.05mm; when At that time, reset the target displacement ; S233, employs position-current dual closed-loop control to output the reverse PWM signal for the geared motor: Position ring: with Set as the goal and set Output current reference value ;in, and These represent the proportional gain and integral gain of the position loop, respectively. Current loop: Set as the goal and set Output a PWM duty cycle signal to control the geared motor to reverse until... The geared motor stops rotating, completing the gap reset.

[0022] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A low drag torque EMB split-type brake caliper, comprising a ball screw, a piston, and a friction plate assembly mounted on the caliper body, wherein the ball screw includes a screw shaft connected via a spline to the output end of a geared motor, characterized in that: The piston has an internal threaded hole at the end facing the lead screw shaft, which is adapted to the lead screw shaft. The piston is connected to an internal friction plate at the end away from the lead screw shaft. A displacement sensor is set on the internal friction plate at the position corresponding to the lead screw shaft to collect the axial displacement of the lead screw shaft. The clamping force is indirectly collected through the mapping relationship between the axial displacement of the lead screw shaft, the deformation of the internal friction plate, and the real-time clamping force. A contact thermocouple is installed on the inner friction pad at a position corresponding to the brake disc to collect the contact temperature between the inner friction pad and the brake disc during braking.

2. The low drag torque EMB split brake caliper according to claim 1, characterized in that: The mapping relationship between the axial displacement of the lead screw shaft, the deformation of the internal friction plate, and the real-time clamping force is expressed as follows: ； In the formula, This indicates the amount of deformation of the internal friction plate, and , This indicates the axial displacement of the leadscrew shaft. This indicates the initial braking clearance.

3. The low drag torque EMB split brake caliper according to claim 1, characterized in that: The piston's matrix is ​​an Al-Si alloy, with 20wt% SiC particles as the reinforcing phase, and the addition of 3.47wt% Ni, 0.55wt% Cu, and 0.13wt% Zr to form an Al3Ni reinforcing phase and a solid solution reinforced structure. The overall hardness is 145 HV1, and the density is 2.8 g / cm³. 3 ; The total Si content in the Al-Si alloy is 20.12 wt%, and the 20 wt% SiC particles are mixed particles with an average particle size of 20 μm, consisting of 30 wt% F360, 40 wt% F400, and 30 wt% F500; and the hardness of the SiC particles is 34.4 ± 3.7 GPa. The friction plate assembly is made of NAO material, and the NAO material inner friction plate and the piston form a friction pair with a transfer film.

4. The low drag torque EMB split brake caliper according to claim 3, characterized in that: The piston's outer surface has multiple receiving grooves arranged in a ring to accommodate transferred friction debris. The diameter of each groove is 0.5 mm, the depth is 0.1 mm, and the distance between two adjacent grooves is 2 mm.

5. The brake clearance adjustment method for the low drag torque EMB split brake caliper as described in any one of claims 1-4, characterized in that: Includes the following steps: S1. Collect braking condition parameters and, in conjunction with the piston friction characteristic model, determine the real-time friction coefficient and the real-time braking condition level. S2. Combining the real-time friction coefficient and the real-time braking condition level, a segmented control strategy is adopted to output the control signal for the geared motor.

6. The brake clearance adjustment method for the low drag torque EMB split brake caliper according to claim 5, characterized in that: The braking parameters mentioned in step S1 include the contact temperature between the internal friction pads and the brake disc. Real-time pressure of brake lines and real-time vehicle speed ; Real-time friction coefficient The expression is as follows: ； Real-time braking conditions are classified into the following three categories: Normal braking conditions: ; Emergency braking condition: ; High-temperature braking conditions: .

7. The brake clearance adjustment method for the low drag torque EMB split brake caliper according to claim 6, characterized in that: Step S2 specifically includes the following steps: S21, when ,and When the gap elimination phase is entered, a dual closed-loop control of speed and current is used to output the forward rotation PWM signal of the geared motor. The speed loop targets the desired speed and uses a proportional controller, while the output current reference value is... , and then To achieve the target speed, a PI controller outputs a PWM duty cycle signal to control the geared motor to rotate forward at the target speed until... ,and When, execute step S22; where, Indicates pedal displacement; Target speed The expression is as follows: ； In the formula, Indicates the total deceleration of the geared motor; Indicates the second-to-minute conversion factor; Indicates the target elimination time, and under normal braking conditions. Emergency braking conditions High-temperature braking conditions ; This refers to the lead of the ball screw; S22, Clamping force holding stage; S221, Based on the pedal displacement and maximum clamping force Determine the target clamping force : ； In the formula, Indicates the pedal displacement-clamping force conversion coefficient; S222, Correcting the target current based on the real-time friction coefficient: ； In the formula, This indicates the corrected target current for the geared motor; Indicates the reference current; Indicates the reference friction coefficient; S223, Employ current closed-loop control of the geared motor PWM signal until... ,and Execute step S23: Normal braking condition: Set the current loop parameters so that ;in, and These represent the proportional gain and integral gain of the current loop, respectively. Emergency braking condition: Set current loop parameters ,make follow ; High-temperature braking condition: Set current loop parameters and add temperature compensation. At this time, the total current ;in, Indicates the temperature-current conversion factor; S23, gap reset stage control; S231. Estimate the thickness of the transfer film. : ； In the formula, Indicates brake caliper stiffness; S232, Based on the thickness of the transfer film Correct and reset target displacement: when At that time, reset the target displacement At this time, the geared motor rotates in the reverse direction by 0.01mm-0.02mm; when At that time, reset the target displacement At this time, the geared motor reduces its reverse rotation by 0.05mm; when At that time, reset the target displacement ; S233, employs position-current dual closed-loop control to output the reverse PWM signal for the geared motor: Position ring: with Set as the goal and set Output current reference value ;in, and These represent the proportional gain and integral gain of the position loop, respectively. Current loop: Set as the goal and set Output a PWM duty cycle signal to control the geared motor to reverse until... The geared motor stops rotating, completing the gap reset.

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