Piston assembly for electronic mechanical braking system
By using a planetary roller screw structure with the piston and nut integrally formed, the problems of complex structure, high cost and heat transfer of piston components in electromechanical braking systems are solved, achieving low cost, simple structure and efficient heat dissipation.
Patent Information
- Application Number
- CN202520003943.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-02
- Publication Date
- 2025-10-28
- Estimated Expiration
- 2035-01-02
AI Technical Summary
Existing electromechanical braking systems have complex piston assembly structures, numerous components, high costs, and many processing steps, and also suffer from heat transfer problems.
The planetary roller screw structure, which integrates the piston and nut, eliminates the welding process. It features ventilation slots and limiting bosses to improve heat dissipation and reduces friction by using gaps to achieve relative movement between the piston and the screw.
It simplifies the processing steps, reduces costs, decreases component size, improves heat dissipation and stability, ensures pure rolling of the piston and lead screw, and avoids seizing damage.
Smart Images
Figure CN223483240U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to a piston assembly, and more particularly to a piston assembly for an electromechanical braking system. Background Technology
[0002] With the continuous development of motor, battery, and electric drive technologies, more and more drive-by-wire technologies have emerged to replace traditional mechanical control technologies. Electromechanical Brake (EMB) systems, due to their advantages such as intelligence, lightweight design, and high safety, are gradually becoming the preferred braking technology for the next generation of electric vehicles.
[0003] Compared to traditional hydraulic braking, the EMB system adopts an electromechanical integrated design, eliminating complex hydraulic lines and resulting in a simpler structure. It is also clean and environmentally friendly. Since it does not rely on brake fluid, the EMB system avoids the braking delay caused by it and has a faster response speed. In addition, the EMB system can precisely control the required braking force, significantly improving the safety and reliability of the vehicle.
[0004] Currently, most piston assemblies in electromechanical braking systems are composed of ball screws or standard planetary roller screws welded together with the piston. This technology has the following problems: 1. Due to its structural characteristics, the ball screw is relatively large when high load-bearing capacity is required; 2. The standard planetary roller screw has an internal gear ring designed in the nut that meshes with the gears at both ends of the roller, resulting in higher processing costs; 3. The piston and nut need to be fixed together by welding, and the weld seam needs to be ground after welding. This not only increases the processing steps, but also requires protection of the screw assembly during weld seam grinding, thus increasing processing costs. Summary of the Invention
[0005] This utility model provides a piston assembly for an electromechanical braking system that is low in cost, simple in structure, has good heat dissipation, and has fewer processing steps; it solves the technical problems of complex structure, many parts, high cost, and many processing steps in the piston assembly of the existing electromechanical braking system.
[0006] The above-mentioned technical problem of this utility model is solved by the following technical solution: A piston assembly for an electromechanical braking system includes a piston, a planetary roller screw structure inside the piston, the planetary roller screw including a nut, rollers and a lead screw located inside the nut, the piston and nut being integrally formed, a receiving cavity being formed at one end of the piston, a lead screw being installed in the receiving cavity, a common thread being formed on the inner wall surface of the receiving cavity, rollers being installed between the receiving cavity and the lead screw, a ventilation groove being provided on the end face of the piston, and a gap being provided between the bottom surface of the receiving cavity and the end face of the lead screw. Replacing the nut with a piston eliminates the traditional welding process, reducing processing costs. Furthermore, integrally forming the piston and bolt also reduces the overall volume of the piston assembly. The ventilation groove on the end face of the piston effectively reduces the heat generated during braking from being transferred to the piston assembly, improving product stability. The gap facilitates the relative movement of the piston and lead screw, improving heat dissipation. It also ensures that the two do not move excessively, causing the piston and lead screw to seize and become damaged.
[0007] Preferably, one end of the lead screw is provided with a countersunk hole, and a limiting boss is installed in the countersunk hole. One end of the limiting boss protrudes above the countersunk hole, and the protruding end of the limiting boss is connected to the bottom surface of the receiving cavity. The limiting boss forms the gap between the lead screw and the piston, resulting in a simple structure that is easy to adjust.
[0008] Preferably, the end face of the limiting boss that connects with the bottom surface of the receiving cavity is an arc surface. Designing it as an arc surface allows the limiting boss to make point contact with the piston, reducing friction and thus enabling more precise positioning.
[0009] Preferably, the limiting boss and the countersunk hole are interference fit.
[0010] Preferably, the lead screw has a stepped, hollow shaft structure. The outer circumferential surface of the section with a larger diameter is provided with threads that mate with rollers, and the section with a smaller diameter is a smooth shaft with an internal spline at the end.
[0011] Preferably, the inner wall surface of the receiving cavity is a stepped surface, one section of which is a roller mating surface, and a continuous inner annular groove is provided at each end of the roller mating surface, and the roller is provided with a corresponding inner annular groove at both ends.
[0012] Preferably, the roller comprises five annular surfaces, with the middle section being a threaded section that mates with the lead screw, both ends of the middle section being inner annular groove sections, and the outer side of the inner annular groove being a smooth shaft section. Different annular surfaces on the roller achieve different fits and installations. The threaded section is threadedly connected to the piston and lead screw, and the inner annular groove section mates with the inner annular groove on the piston to prevent torsion and ensure pure rolling between the roller and the piston. The smooth shaft section is used to mount the cage.
[0013] Preferably, the outer circumferential surface of the piston is provided with a positioning plane, which serves to prevent rotation.
[0014] Preferably, the piston has a weight-reducing groove on its end face, thereby reducing costs.
[0015] Therefore, the piston assembly for an electromechanical braking system of this utility model has the following advantages: 1. The piston and nut are designed as an integral structure, which can eliminate the traditional welding process; 2. The piston inner hole and the roller surface are machined with matching inner ring grooves, which can replace the internal gear ring of the standard planetary roller screw, so that the roller will not twist during the movement and ensure that the helical motion between the roller and the nut is a pure rolling state; 3. Several ventilation grooves are designed on the piston end face near the friction plate, which can effectively reduce the heat generated during the braking process and transfer it to the piston assembly; 4. The contact surface between the limiting boss and the nut is designed as a spherical surface, which can achieve more precise positioning. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of a piston assembly used in an electromechanical braking system.
[0017] Figure 2 yes Figure 1 A 3D view of the internal piston.
[0018] Figure 3 yes Figure 1 A cross-sectional view of the piston.
[0019] Figure 4 yes Figure 1 A schematic diagram of the middle roller.
[0020] Figure 5 yes Figure 1 A schematic diagram of the lead screw.
[0021] Figure 6 yes Figure 1 A schematic diagram of the middle limiting boss. Detailed Implementation
[0022] The technical solution of the utility model will be further described in detail below through embodiments and in conjunction with the accompanying drawings.
[0023] Example:
[0024] like Figure 1As shown, a piston assembly for an electromechanical braking system includes a cylindrical piston 1 with a receiving cavity 14 inside. A roller screw structure is installed within the receiving cavity 14. The roller screw structure includes a nut, a plurality of evenly distributed rollers 3, and a lead screw 5 located within the nut. The nut is integrally formed with the piston 1, and the piston 1 performs the function of the nut. Cages 2 are installed at both ends of the rollers 3, and snap rings 6 are installed at the ends of the rollers 3. A limiting boss 4 is installed between the lead screw 5 and the piston 1.
[0025] like Figure 2 and 3 As shown, the piston 1 has ventilation grooves 11 formed on its end face, and three evenly distributed weight-reducing grooves 11-1 are inserted in the middle of the ventilation grooves 11. Two symmetrically arranged positioning planes 12 are formed on the outer circumferential surface of the piston 1. The inner wall of the piston's receiving cavity 14 is a three-section stepped surface with increasing diameter. The middle stepped surface is a roller mating surface 14, with threads machined on it for mating with the rollers. At each end of the roller mating surface 14, a continuous inner annular groove 13-1 is formed for mating with the inner annular grooves at both ends of the rollers, preventing the rollers from twisting during movement and ensuring that the helical motion between the rollers and the nut is purely rolling. A retaining ring groove 13-2 is also formed on the outer side of the inner annular groove 13-1 for installing a retaining ring 6.
[0026] like Figure 4 As shown, the roller forming has a 5-segment structure. The middle segment is a threaded segment 33, with threads formed on it for mating with the piston 1 and the lead screw 5. Each end of the threaded segment 33 has an inner annular groove segment 32, with a roller inner annular groove formed on it for mating with the inner annular groove on the piston's inner wall. The outer side of the inner annular groove segment 32 is a smooth shaft segment 31, on which the cage 2 is mounted.
[0027] like Figure 5 As shown, the lead screw 5 is a stepped shaft. To reduce cost and weight, the lead screw 5 has a hollow structure. The outer circumferential surface of the large-diameter section 54 of the lead screw is threaded for mating with rollers. The small-diameter section of the lead screw is a smooth shaft. A countersunk hole 53 is formed at one end of the lead screw, and a limiting boss 4 is interference-fitted inside the countersunk hole 53. An internal spline 55 is formed at the other end of the lead screw.
[0028] like Figure 6 As shown, one end of the limiting boss is located inside the countersunk hole, and the end of the limiting boss extending out of the countersunk hole is formed with a spherical surface 42, so that the contact surface between the lead screw and the bottom surface of the piston's receiving cavity is a spherical surface, achieving precise positioning. Weight reduction holes 41 are provided on both sides of the spherical surface of the limiting boss to reduce costs and weight.
[0029] The specific embodiments described herein are merely illustrative of the concept of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.
Claims
1. A piston assembly for an electromechanical braking system, comprising a piston, wherein a planetary roller screw structure is provided within the piston, the planetary roller screw comprising a nut, rollers and a lead screw located within the nut, characterized in that: The piston and nut are integrally formed. A receiving cavity is provided at one end of the piston. A lead screw is installed in the receiving cavity. A common thread is formed on the inner wall surface of the receiving cavity. A roller is installed between the receiving cavity and the lead screw. A ventilation groove is provided on the end face of the piston. A gap is provided between the bottom surface of the receiving cavity and the end face of the lead screw.
2. The piston assembly for an electromechanical braking system according to claim 1, characterized in that: One end of the lead screw is provided with a countersunk hole, and a limiting boss is installed in the countersunk hole. One end of the limiting boss protrudes above the countersunk hole, and the protruding end of the limiting boss is connected to the bottom surface of the receiving cavity.
3. A piston assembly for an electromechanical braking system according to claim 2, characterized in that: The end face of the limiting boss that connects with the bottom surface of the receiving cavity is an arc surface.
4. A piston assembly for an electromechanical braking system according to claim 2, characterized in that: The aforementioned limiting boss and countersunk hole are interference-fitted.
5. A piston assembly for an electromechanical braking system according to any one of claims 1 to 4, characterized in that: The lead screw has a stepped, hollow shaft structure. The outer circumferential surface of the section with a larger diameter is provided with threads that mate with rollers, while the section with a smaller diameter is a smooth shaft with an internal spline at the end.
6. A piston assembly for an electromechanical braking system according to any one of claims 1 to 4, characterized in that: The inner wall of the cavity is a stepped surface, one section of which is a roller mating surface. A continuous inner annular groove is provided at each end of the roller mating surface, and the roller is provided with a corresponding inner annular groove at both ends.
7. A piston assembly for an electromechanical braking system according to any one of claims 1 to 4, characterized in that: The roller comprises 5 annular surfaces, with the middle section being a threaded section that mates with the lead screw, the two ends of the middle section being inner annular groove sections, and the outer side of the inner annular groove being a smooth shaft section.
8. A piston assembly for an electromechanical braking system according to any one of claims 1 to 4, characterized in that: The outer circumferential surface of the piston is provided with a positioning plane.
9. A piston assembly for an electromechanical braking system according to any one of claims 1 to 4, characterized in that: The piston has a weight-reducing groove on its end face.