Special-shaped piston structure, brake caliper and EMB brake

Abstract

The invention discloses a special-shaped piston structure, brake calipers and an EMB brake, and belongs to the field of EMB.The special-shaped piston structure comprises a special-shaped piston head, the special-shaped piston head is of a double-cambered-surface structure extending in the length direction of an inner friction plate, the outer diameter of the special-shaped piston head is not smaller than the size of a back plate of the inner friction plate, and it is ensured that a ballast surface completely covers a stress area of the back plate of the friction plate; therefore, the purpose of enlarging the ballast surface is achieved. By the adoption of the special-shaped piston structure, the brake caliper and the EMB brake, through special-shaped expansion of the piston head, precise size adaptation and double-ring pattern optimization, multiple breakthrough of clamping force improvement, friction plate stress homogenization and attachment stability is achieved on the premise that the cost is hardly increased and the system size is not increased.

Description

Technical Field

[0001] This invention relates to the field of EMB braking technology, and more particularly to irregular piston structures, brake calipers, and EMB brakes. Background Technology

[0002] The braking process of an electromechanical brake (EMB) must follow the core logic of "precise signal control - efficient power transmission - bidirectional clamping braking": When the driver presses the brake pedal, the pedal position sensor collects the braking intention and generates a signal, which is transmitted to the vehicle's electronic control unit (ECU). The ECU combines data from multiple sensors, such as vehicle speed and load, to accurately calculate the required braking force and then sends a drive command to the EMB motor. The rotational power output by the motor after starting is reduced and amplified by the gear train in the reduction gearbox, and then transmitted to the lead screw shaft of the lead screw mechanism through the output shaft spline. With the meshing of the lead screw roller and the raceway of the lead screw piston, the rotational motion is converted into the axial linear forward motion of the lead screw piston. The lead screw piston then pushes the piston head fixed to it, applying pressure to the inner friction pad and causing it to slide along the T-slot of the caliper bracket, pressing against the brake disc; at the same time, based on the reaction force, the lead screw mechanism drives the caliper body to slide along the guide pin, and the caliper jaws simultaneously push the outer friction pad towards the brake disc, realizing bidirectional clamping of the inner and outer friction pads against the brake disc, generating a deceleration effect through friction until the vehicle comes to a smooth stop.

[0003] It is known that the contact pressure effect between the piston head and the friction pad directly determines the magnitude, uniformity, and stability of the clamping force acting on the brake disc, and is one of the core factors affecting the EMB braking performance and safety.

[0004] In current EMB systems, pistons generally adopt a cylindrical structure, and their pressure head contact area is usually directly determined by the caliper cylinder diameter. When the axial length of the friction pad is large, the pressure head contact area of ​​a single cylindrical piston is limited, which easily leads to force concentration on the friction pad and uneven wear, affecting braking stability and shortening the service life of the friction pad. To solve this problem, conventional designs often use a dual-piston structure to achieve uniform pressure on the friction pad, but this solution has significant limitations: on the one hand, it greatly increases the structural complexity of the caliper, and the addition of pistons and matching transmission components not only increases manufacturing costs but also requires increasing the overall size of the caliper; on the other hand, it occupies more of the limited space in the wheel hub, which contradicts the design trend of lightweight and compact automotive parts, and also affects the adaptability of the overall wheel hub layout. Summary of the Invention

[0005] The purpose of this invention is to provide an irregularly shaped piston structure, a brake caliper, and an EMB brake to solve the aforementioned technical problems.

[0006] To achieve the above objectives, the present invention provides an irregular piston structure, including an irregular piston head. The irregular piston head is a double-arc surface structure extending along the length direction of the inner friction plate. The outer diameter of the irregular piston head is not less than the size of the inner friction plate backing plate, ensuring that the ballast surface completely covers the stress area of ​​the friction plate backing plate, thereby expanding the ballast surface.

[0007] Preferably, the contact arc of the irregular piston head is a non-circular arc that matches the curvature of the inner friction plate backing plate.

[0008] Preferably, the contact surface of the irregular piston head is provided with a double-ring pattern. The double-ring pattern is a double-ring groove structure arranged symmetrically about the center line of the piston body. The ring width of the pattern is uniform and matches the contour of the irregular piston head. It is used to increase the friction coefficient between the piston head and the friction plate, so as to achieve anti-slip, anti-rotation and firm fit.

[0009] Preferably, the piston body diameter Effective width of the internal friction plate The following compatibility relationships exist: ; in, ; In the formula, Indicates the fit coefficient; This indicates the clamping force required for the EMB brake; Indicates the working pressure of the EMB brake; Maximum outer diameter of irregular piston head Length of the back plate of the internal friction plate The following relationship exists between them: ; In the formula, This indicates the single-sided coverage allowance of the irregularly shaped piston head extending beyond the end of the inner friction plate backing plate; Indicates unilateral manufacturing and assembly tolerances; Radius of curvature of irregular piston head Curvature of the back plate of the internal friction plate The following relationship exists between them: ; In the formula, Indicates fit tolerance; Double ring pattern spacing Length of the back plate of the internal friction plate The following relationship exists between them: .

[0010] The brake caliper includes a caliper body, a lead screw shaft disposed within the caliper body, a lead screw roller that cooperates with the lead screw shaft, and a lead screw nut piston that cooperates with the lead screw roller. The output end of the lead screw nut piston is fixedly connected to a shaped piston structure. The contact surface of the shaped piston structure is aligned with the inner friction plate, and the center of the shaped piston structure is coaxial with the center of the inner friction plate.

[0011] EMB brake, including EMB motor and reducer connected to the output of EMB motor, the output of reducer being connected via spline to the input of the lead screw shaft of brake caliper.

[0012] Therefore, the present invention, employing the aforementioned irregular piston structure, brake caliper, and EMB brake, has the following beneficial effects: 1. Significantly solves the problem of uneven wear of friction plates: The contact area of ​​the irregular piston head is nearly twice that of the traditional round piston. Combined with the force-equalizing design of the double-ring structure, the clamping force is evenly distributed on the entire force-bearing surface of the long strip friction plate, avoiding local pressure concentration, greatly reducing the wear difference in different areas of the friction plate, and extending the service life of the friction plate. 2. Improved braking clamping force and effectiveness: The piston body diameter is increased to better fit the pressure head and friction plate backing, effectively expanding the piston's pressure area and improving force transmission efficiency, significantly enhancing braking clamping force output and ensuring that braking distance and deceleration meet design targets. 3. Simplified system structure and optimized space occupation: It replaces the traditional dual-piston solution, only optimizes the piston head structure, without adding pistons, pipelines and other components, without increasing the caliper size, adapts to the original wheel hub space layout, avoids component interference, and conforms to the trend of compact and lightweight automotive parts. 4. Controllable cost and outstanding economic efficiency: No new parts or complex processing technology are required. Only the piston head forming parameters are adjusted. The amount of modification is small and the manufacturing cost is almost not increased. At the same time, the frequency of friction pad replacement is reduced, which reduces the total life cycle cost of the vehicle braking system. 5. Strong adaptability and high compatibility: By quantifying the dimensional relationship (piston diameter, maximum outer diameter of the pressure head, etc., and matching the friction plate parameters), it can match friction plates of different specifications without changing the core transmission and assembly logic of the EMB actuator and caliper assembly, making it easy to directly upgrade and replace existing production lines. 6. Improved braking stability and reliability: The double-ring pattern design increases the friction coefficient between the piston head and the friction pad, achieving anti-slip and anti-rotation effects and preventing relative slippage or rotation between the two during braking; at the same time, the uniformity of force transmission is optimized, reducing the risk of braking vibration and deviation, and improving the overall vehicle braking safety.

[0013] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0014] Figure 1 This is a perspective view of the irregular piston structure described in this invention; Figure 2 This is an axial sectional view of the brake caliper described in this invention; Figure 3 This is a perspective view of the brake caliper described in this invention; Figure 4 This is a perspective view of the EMB brake described in this invention.

[0015] Figure Labels 1. Irregularly shaped piston head; 111. Double-ring pattern; 2. Inner friction plate; 3. Brake disc; 4. Outer friction plate; 5. Bracket; 6. Lead screw nut piston; 7. Lead screw washer; 8. Thrust bearing; 9. Bearing washer; 10. Caliper body; 11. Lead screw roller; 12. Lead screw shaft; 13. Reducer; 14. EMB motor. Detailed Implementation

[0016] 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.

[0017] 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.

[0018] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0019] like Figure 1As shown, the irregular piston structure includes an irregular piston head 1, which is a double-arc surface structure extending along the length of the inner friction plate 2. The outer diameter of the irregular piston head 1 is not smaller than the size of the back plate of the inner friction plate 2, ensuring that the ballast surface completely covers the stress area of ​​the friction plate back plate, thereby expanding the ballast surface. That is, the aforementioned irregular structure is not limited to the size of a circle, extending the contact range along the extension direction of the elongated inner friction plate 2, while maintaining a radial width comparable to that of a traditional piston, avoiding the occupation of additional hub space. Simultaneously, the irregular contour perfectly fits the arc-shaped back plate of the friction plate, expanding the contact area from the localized point contact of a traditional circle to a long annular surface contact, achieving an effect where the ballast surface is nearly twice that of a traditional piston.

[0020] The contact arc of the irregular piston head 1 is a non-circular arc that matches the curvature of the back plate of the inner friction plate 2.

[0021] The contact surface of the irregularly shaped piston head 1 is provided with a double-ring pattern 111. The double-ring pattern 111 is a double-ring groove structure arranged symmetrically about the center line of the piston body 11. The ring width of the pattern is uniform and matches the contour of the irregularly shaped piston head 1. It is used to increase the friction coefficient between the piston head and the friction plate, so as to achieve anti-slip, anti-rotation and firm fit. That is, the double-ring pattern 111 forms a bidirectional friction constraint by increasing the roughness and friction coefficient of the contact surface. Compared with smooth plane contact, the double-ring pattern 111 can form multi-point ring support, avoiding relative slippage or rotation between the piston and the friction plate due to uneven force during braking, ensuring the firmness of the fit and the stability of pressure transmission.

[0022] Piston body diameter 11 With the effective width of the internal friction plate 2 The following fitting relationship exists between the internal friction pads 2 and the effective load-bearing width of the brake disc 3: ; in, ; In the formula, Indicates the fit coefficient; This indicates the clamping force required for the EMB brake; Indicates the working pressure of the EMB brake; The maximum outer diameter of the irregular piston head 1 (The maximum outline dimension of the irregular piston head 1 along the length of the inner friction plate 2) and the length of the back plate of the inner friction plate 2 The following relationship exists between the actual effective lengths of the internal friction pad 2 metal backing plate along the circumference of the brake disc 3: ; In the formula, This indicates the single-sided coverage allowance of the irregular piston head 1 beyond the end of the back plate of the inner friction plate 2; Indicates unilateral manufacturing and assembly tolerances; The radius of curvature of the irregular piston head 1 arc Curvature of the back plate of the internal friction plate 2 The following relationship exists between them: ; In the formula, Indicates fit tolerance; Double ring pattern spacing Length of the back plate of the internal friction plate 2 The following relationship exists between them: .

[0023] like Figure 2 and 3 As shown, the brake caliper includes a caliper body 10, a lead screw shaft 12 disposed within the caliper body 10, a lead screw roller 11 cooperating with the lead screw shaft, and a lead screw nut piston 6 cooperating with the lead screw roller 11. The output end of the lead screw nut piston 6 is fixedly connected to a shaped piston structure. The contact surface of the shaped piston structure is aligned with the inner friction plate 2, and the center of the shaped piston structure is coaxial with the center of the inner friction plate 2.

[0024] like Figure 4 As shown, the EMB brake includes an EMB motor 14 and a reducer 13 connected to the output end of the EMB motor 14. The output end of the reducer 13 is connected to the input end of the lead screw shaft 12 of the brake caliper via a spline.

[0025] The braking principle of the EMB brake is as follows: When the driver presses the brake pedal, the pedal position sensor collects the braking intention signal in real time and transmits it to the vehicle's electronic control unit (ECU). The ECU combines parameters such as vehicle speed, load, and road adhesion coefficient to calculate the required braking torque and then sends a drive command to the EMB motor 14. After the EMB motor 14 starts, it outputs rotational power, which is reduced and amplified by the reducer 13. The torque is transmitted to the lead screw shaft 12 of the brake caliper through the spline at the output end. When the lead screw shaft 12 is driven to rotate, the lead screw roller 11 on its surface meshes with the raceway of the lead screw piston 6, converting the rotational motion into linear forward motion of the lead screw piston 6 along the axial direction of the caliper body 10. Since the output end of the lead screw piston 6 is fixedly connected to the irregular piston structure, and the center of the irregular piston structure is coaxial with the center of the inner friction plate 2, the lead screw piston 6 synchronously drives the irregular piston head 1 to apply force to the inner friction plate. The inner friction pad 2 slides along the T-slot of the brake caliper bracket 5 and presses against the brake disc 3. At the same time, based on the principle of force reaction, the lead screw shaft 12 is subjected to a reverse force, which sequentially drives the lead screw washer 7, thrust bearing 8 and bearing washer 9 of the brake caliper to press against the bottom annular surface of the caliper body 10, causing the caliper body 10 to slide outward along the guide pin. The outer claw of the caliper body 10 simultaneously pushes the outer friction pad 4 towards the brake disc 3. At this time, the irregular piston head 1, with its double arc surface structure and high fit with the back plate of the inner friction pad 2, evenly transmits the clamping force to the inner friction pad 2 through a long annular ballast surface that is nearly twice the length of a traditional piston. Combined with the bidirectional friction constraint formed by the double annular pattern 111, it prevents the friction pad and the pressure head from slipping relative to each other. Finally, it achieves a stable and efficient bidirectional clamping of the inner and outer friction pads 4 against the brake disc 3. The friction force consumes the kinetic energy of the brake disc 3, achieving the braking effect of vehicle deceleration or stopping.

[0026] When the brake is released, the ECU issues a reset command, the EMB motor 14 reverses, driving the lead screw shaft 12, the lead screw piston 6 and the irregular piston structure to reset in the opposite direction, the inner and outer friction plates 4 disengage from the brake disc 3, and the braking process ends.

[0027] 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. An irregularly shaped piston structure, characterized in that: It includes an irregularly shaped piston head, which is a double-arc structure extending along the length of the inner friction plate. The outer diameter of the irregularly shaped piston head is not less than the size of the inner friction plate backing plate, ensuring that the ballast surface completely covers the stress area of ​​the friction plate backing plate, so as to expand the ballast surface.

2. The irregular piston structure according to claim 1, characterized in that: The contact arc of the irregularly shaped piston head is a non-circular arc that matches the curvature of the inner friction plate backing plate.

3. The irregular piston structure according to claim 2, characterized in that: The contact surface of the irregular piston head is provided with a double-ring pattern. The double-ring pattern is a double-ring groove structure that is symmetrically arranged about the center line of the piston body. The ring width of the pattern is uniform and matches the contour of the irregular piston head. It is used to increase the friction coefficient between the piston head and the friction plate, so as to achieve anti-slip, anti-rotation and firm fit.

4. The irregular piston structure according to claim 3, characterized in that: Piston body diameter Effective width of the internal friction plate The following compatibility relationships exist: ； in, ； In the formula, Indicates the fit coefficient; This indicates the clamping force required for the EMB brake; Indicates the working pressure of the EMB brake; Maximum outer diameter of irregular piston head Length of the back plate of the internal friction plate The following relationship exists between them: ； In the formula, This indicates the single-sided coverage allowance of the irregularly shaped piston head extending beyond the end of the inner friction plate backing plate; Indicates unilateral manufacturing and assembly tolerances; Radius of curvature of irregular piston head Curvature of the back plate of the internal friction plate The following relationship exists between them: ； In the formula, Indicates fit tolerance; Double ring pattern spacing Length of the back plate of the internal friction plate The following relationship exists between them: 。 5. A brake caliper, comprising a caliper body, a lead screw shaft disposed within the caliper body, a lead screw roller cooperating with the lead screw shaft, and a lead screw nut piston cooperating with the lead screw roller, characterized in that: The output end of the screw piston is fixedly connected to the irregular piston structure described in any one of claims 1-4, the contact surface of the irregular piston structure is aligned with the inner friction plate, and the center of the irregular piston structure is coaxial with the center of the inner friction plate.

6. An EMB brake, comprising an EMB motor and a reducer connected to the output terminal of the EMB motor, characterized in that: The output end of the reducer is connected via a spline to the input end of the lead screw shaft of the brake caliper as described in claim 5.

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