Ball screw assembly and electronic mechanical braking system

Abstract

The invention relates to the technical field of vehicle chassis, in particular to a ball screw assembly and an electronic mechanical braking system, the circumferential inner wall of a nut is provided with a first threaded raceway, the circumferential outer wall of a screw is provided with a second threaded raceway, and a plurality of balls are arranged in the first threaded raceway and the second threaded raceway in a rolling manner; a plurality of commutators are uniformly and fixedly arranged on the circumferential inner wall of the nut; a through hole is formed in the inner side of the lead screw, an inner convex ring is fixedly arranged on the inner wall of the through hole, a center hole is formed in the inner side of the inner convex ring, and one end of the driving shaft is fixedly connected with the inner wall of the center hole; a piston end cover is fixedly arranged at one end of the nut, an anti-collision pin is fixedly arranged on the side face, facing the piston end cover, of the inner protruding ring, and a stop block matched with the anti-collision pin is fixedly arranged on the inner side face of the piston end cover. The anti-collision device plays a role in rotating and stopping, when the nut axially returns, the nut drives the piston end cover to return until the anti-collision pin collides with the stop block and then stops, and the lead screw or the driving shaft is prevented from axially impacting the piston end cover.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle chassis, and in particular to a ball screw assembly and an electronic mechanical braking system. Background Art

[0002] EMB, as a brake actuator directly arranged at the wheel end, integrates service brakes and parking brakes with high integration, greatly reducing the number of vehicle parts and making it more convenient to integrate and control with other functional components of the chassis. In addition, EMB is directly driven by a brushless motor, reducing the intermediate hydraulic transmission link, and responding faster, which is more conducive to supporting the AEB rapid response of high-order ADAS. Therefore, EMB is the main trend in the development of the current braking system. The existing EMB transmission system is mostly composed of a gear reduction structure + ball screw or a wedge force enhancement structure + ball screw combination. However, EMB is an unsprung component at the wheel end, and the heating, vibration, and impact conditions are complex. Therefore, the stability and reliability of the transmission system are extremely high. The existing technology lacks fundamental solutions to these problems, and there are common problems such as loud noise, looseness, and bottoming out.

[0003] There are three mainstream forms of existing EMB transmission mechanisms: one is the swash plate structure, the second is the roller screw drive, and the third is the ball screw drive. The swash plate form requires a large space, has a complex structure, is difficult to arrange, and has poor accuracy; the roller screw has low efficiency and high noise; and the existing ball screw structure transmission generally has problems such as poor connection reliability, easy loosening, bottoming, and high noise. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a ball screw assembly and an electronic mechanical brake system with the advantages of reliable transmission, high efficiency, anti-loosening, anti-bottoming and low noise.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: a ball screw assembly, comprising a nut, a ball, a screw, a drive shaft and a commutator, the circumferential inner wall of the nut is provided with a first threaded raceway, the circumferential outer wall of the screw is provided with a second threaded raceway corresponding to the first threaded raceway, the first threaded raceway and the second threaded raceway are connected and configured as a path for ball rolling, and a plurality of the balls are arranged in the first threaded raceway and the second threaded raceway for rolling; a plurality of commutators are evenly fixed on the circumferential inner wall of the nut; a through hole is provided on the inner side of the screw, an inner convex ring is fixed on the inner wall of the through hole, the inner side of the inner convex ring is a center hole, the center hole is coaxial with the screw, and one end of the drive shaft is fixedly connected to the inner wall of the center hole; a piston end cover is fixed on one end of the nut, an anti-collision pin is fixed on the side of the inner convex ring facing the piston end cover, and a stop block matching the anti-collision pin is fixed on the inner side surface of the piston end cover.

[0006] The beneficial effect of the present invention is that the present invention plays a role of rotation stop by arranging an anti-collision pin and a stop block. When the nut returns axially, the nut drives the piston end cover to return until the anti-collision pin collides with the stop block and stops, thereby preventing the screw or drive shaft from axially colliding with the piston end cover.

[0007] Based on the above technical solution, the present invention can also be improved as follows.

[0008] Furthermore, a blind hole is provided on the side of the inner convex ring facing the piston end cover, and one end of the anti-collision pin is fixedly inserted in the blind hole.

[0009] The beneficial effect of adopting the above further scheme is: the anti-collision pin is installed and limited by the blind hole, which reduces the processing difficulty and processing time of the screw through hole, and the bottom of the blind hole is used as an assembly limit to avoid the problems of overpressure and out of position.

[0010] Furthermore, at least one anti-rotation surface is provided in the center hole, the anti-rotation surface is arranged parallel to the axis of the center hole, the end of the drive shaft matches the shape of the center hole, and the drive shaft is interference fit with the center hole.

[0011] The beneficial effect of adopting the above further scheme is: since the EMB braking force is large, when the interference surface between the drive shaft and the center hole is not sufficient to resist the torsional force, the anti-rotation surface can reliably transmit the torque to prevent the drive shaft and the screw from slipping during forward braking or loosening during rapid retraction.

[0012] Furthermore, a transition chamfer is provided at one end of the center hole away from the piston end cover.

[0013] The beneficial effect of adopting the above further solution is to prevent the drive shaft from loosening due to the high hardness material of the lead screw cutting the drive shaft to produce debris during the press-fitting process.

[0014] Furthermore, a limiting convex ring is fixedly provided on the outer peripheral wall of the driving shaft, and the side surface of the limiting convex ring abuts against the side surface of the inner convex ring.

[0015] The beneficial effect of adopting the above further solution is that the setting of the limiting convex ring can position the drive shaft and the lead screw for installation, and prevent the drive shaft from extending too much from the center hole.

[0016] Furthermore, at least one anti-rotation rib is fixedly provided on the outer peripheral wall of the nut.

[0017] The beneficial effect of adopting the above further solution is that the provision of the anti-rotation rib can prevent the nut from rotating, thereby ensuring that the nut moves linearly in the axial direction.

[0018] Furthermore, the anti-rotation rib is a boss structure whose surfaces of both side surfaces pass through the axis of the nut.

[0019] The beneficial effect of adopting the above further scheme is that the anti-rotation rib of the nut contacts the inner wall of the guide hole in the caliper body during sliding, avoiding line contact sliding and the occurrence of high-frequency sharp noise. Another benefit is that surface contact enhances torsional strength and avoids stress concentration.

[0020] Furthermore, a concave-convex pattern is provided on the outer side surface of the piston end cover.

[0021] The beneficial effect of adopting the above further solution is that it can reduce the impact sound with the brake pad and is also conducive to air cooling and heat dissipation.

[0022] Furthermore, the shoulders of the first thread raceway and the second thread raceway are rounded and smoothly transitioned.

[0023] The beneficial effect of adopting the above further solution is: ensuring the smooth running of the ball and reducing sharp noise.

[0024] Furthermore, an edge is provided on the outer periphery of the side of the piston end cover facing the nut, a first step-shaped structure is provided at the end of the edge away from the piston end cover, and a second step-shaped structure matching the first step-shaped structure is provided at the end of the nut facing the piston end cover, and the first step-shaped structure is interference-engaged in the second step-shaped structure.

[0025] The beneficial effect of adopting the above further solution is: ensuring the stability of the connection between the piston end cover and the nut.

[0026] The present invention solves the above technical problem and further provides an electronic mechanical brake system, comprising the above-mentioned ball screw assembly.

[0027] The beneficial effect of adopting the above scheme is that the present invention plays a role of rotation stop by arranging an anti-collision pin and a stop block. When the nut returns axially, the nut drives the piston end cover to return until the anti-collision pin collides with the stop block and stops, thereby preventing the screw or drive shaft from axially colliding with the piston end cover. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the present invention;

[0029] Figure 2 It is a schematic diagram of the installation of the lead screw and the drive shaft in the present invention;

[0030] Figure 3 It is a left side view of the installation of the lead screw and the drive shaft in the present invention;

[0031] Figure 4 It is a schematic diagram of the installation of the commutator and the nut in the present invention;

[0032] Figure 5 It is a left side view of the present invention;

[0033] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0034] 1. Nut; 11. First thread raceway; 12. Anti-rotation rib; 2. Ball; 3. Lead screw; 31. Second thread raceway; 32. Through hole; 33. Inner convex ring; 34. Center hole; 35. Blind hole; 36. Anti-rotation surface; 37. Transition chamfer; 4. Drive shaft; 41. Limiting convex ring; 5. Piston end cover; 51. Stop block; 52. Concave and convex pattern; 53. Edge; 54. First step-like structure; 55. Second step-like structure; 6. Anti-collision pin; 7. Commutator; 71. Hole edge; 8. Shoulder. DETAILED DESCRIPTION

[0035] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0036] Embodiment 1

[0037] like Figure 1 As shown, an embodiment of the present invention includes a nut 1, a ball 2, a lead screw 3, a drive shaft 4 and a commutator 7. The circumferential inner wall of the nut 1 is provided with a first thread raceway 11, and the circumferential outer wall of the lead screw 3 is provided with a second thread raceway 31 corresponding to the first thread raceway 11. The first thread raceway 11 and the second thread raceway 31 are connected and configured as a path for the ball 2 to roll. A plurality of the balls 2 are arranged to roll in the first thread raceway 11 and the second thread raceway 31. The circumferential inner wall of the nut 1 is evenly fixed with a plurality of balls 2. A plurality of commutators 7 are provided; a through hole 32 is provided on the inner side of the lead screw 3, an inner convex ring 33 is fixedly provided on the inner wall of the through hole 32, the inner side of the inner convex ring 33 is a center hole 34, the center hole 34 is coaxial with the lead screw 3, and one end of the drive shaft 4 is fixedly connected to the inner wall of the center hole 34; a piston end cover 5 is fixedly provided on one end of the nut 1, an anti-collision pin 6 is fixedly provided on the side of the inner convex ring 33 facing the piston end cover 5, and a stop block 51 matching the anti-collision pin 6 is fixedly provided on the inner side surface of the piston end cover 5.

[0038] Specifically, Figure 4As shown, the nut 1 is mainly made by machining, grinding and heat treatment processes. The processing quality of the first thread raceway 11 will seriously affect the operating efficiency and noise of the screw 3 assembly. Therefore, it is not only required to have high stroke accuracy and raceway finish, but also requires smooth transition between the shoulder 8 at each part of the first thread raceway 11, the hole edge 71 of the commutator 7 and the raceway of the commutator 7, which is conducive to the smooth rolling of the ball 2, reducing sharp noise and improving the service life. No step feeling, large gaps, sharp edges or burrs are allowed. The outer cylindrical surface of the nut 1 slides with the caliper body hole; the outer cylindrical surface of the nut 1 is evenly opened, Used to install the commutator 7; at least one anti-rotation rib 12 is arranged on the outer circumference of the nut 1, preferably, the number of the anti-rotation ribs 12 is two, and the two anti-rotation ribs 12 are symmetrically arranged, and the anti-rotation rib 12 only allows the nut 1 to move horizontally and prevents the nut 1 from rotating. Preferably, the anti-rotation rib 12 is a boss structure in which the surfaces of the two side surfaces pass through the axis of the nut 1, so that the nut 1 is in surface contact during the sliding process, thereby avoiding line contact sliding and avoiding the occurrence of high-frequency sharp noise. Another advantage is that the surface contact enhances the torsional strength and avoids stress concentration.

[0039] The ball 2 is usually polished and installed in the first thread raceway 11 and the second thread raceway 31 between the screw 3 and the nut 1. It is a transition body for the transmission of kinetic energy between the screw 3 and the nut 1. The size of the ball 2 affects the dynamic and static loads of the ball screw assembly. Preferably, standard steel balls can be selected according to load verification. Due to the low friction characteristics of the steel balls, they have the advantages of low operating noise and high efficiency.

[0040] like Figure 2 , Figure 3As shown, the screw 3 is similar to the nut 1 and is mainly made by machining, grinding and heat treatment processes. A through hole 32 is arranged inside the screw 3, which is a hollow structure, which greatly reduces the weight of the assembly. The remaining parts can be placed inside the hollow structure, which is conducive to reducing the axial space. Similarly, the processing quality of the second thread raceway 31 will seriously affect the operating efficiency and noise of the screw 3 assembly. Therefore, it is also necessary to have high stroke accuracy and raceway finish. It is also required that the transition area of ​​the shoulder 8 at each location of the second thread raceway 31 has a smooth transition fillet; the end of the center hole 34 away from the piston end cover 5 is provided with a transition chamfer 37 to prevent the drive shaft 4 from loosening due to the hard cutting of the drive shaft 4 by the screw 3 during the press-fitting process; the center hole 34 is connected to the drive shaft 4; at least one anti-rotation surface 36 is arranged in the center hole 34, preferably There are two anti-rotation surfaces 36, which are arranged opposite to each other and connected by a cylindrical surface. The shape of the drive shaft 4 matches the shape of the center hole 34, and the drive shaft 4 and the cylindrical surface are interference fit, and the drive shaft 4 and the anti-rotation surface 36 are small clearance fit. Since the EMB braking force is large, when the interference surface is not enough to resist the torsional force, the anti-rotation surface 36 can also reliably transmit the torsional force, so as not to slip during forward braking or loosen from the drive shaft 4 screw 3 during rapid retreat; a blind hole 35 is provided on the side of the inner convex ring 33 facing the piston end cover 5, and one end of the anti-collision pin 6 is fixedly inserted in the blind hole 35 to resist torsion and prevent the retreat shaft surface from hitting the bottom, so as to avoid impact damage to components, and the step at the bottom of the blind hole 35 serves as an assembly limit.

[0041] The drive shaft 4 is a high-strength metal component that transmits the torque of the power source to the screw 3 .

[0042] like Figure 5 As shown, the piston end cover 5 is a closed structure, and an edge 53 is provided on the outer periphery of one side of the piston end cover 5 facing the nut 1, and a first step-shaped structure 54 is provided on the end of the edge 53 away from the piston end cover 5, and a second step-shaped structure 55 matching the first step-shaped structure 54 is provided on the end of the nut 1 facing the piston end cover 5, and the first step-shaped structure 54 is interference-engaged on the second step-shaped structure 55, and the first step-shaped structure 54 is interference-pressed on the inner side of the second step-shaped structure 55 and limited, and the second step-shaped structure 55 is installed with a dust cover, which has dust-proof and waterproof effects, and a stop block 51 matching the anti-collision pin 6 is fixedly provided on the inner side surface of the piston end cover 5 to prevent the screw 3 from retreating out of control and hitting the bottom, especially, in the initial zero position, a gap is provided between the end face of the stop block 51 and the end face of the screw 3, so as to avoid premature locking with the end face of the screw 3 during the retreat process, and a concave-convex pattern 52 is processed on the end face of the other side of the piston end cover 5, which can reduce the sound of collision with the brake pad and is also conducive to air cooling and heat dissipation.

[0043] The anti-collision pin 6 is interference-pressed onto the inner convex ring 33 of the screw 3 to act as a rotation stop. In particular, at the initial zero position, there is a gap between the end face of the anti-collision pin 6 and the piston end cover 5, thereby preventing the pin face and the piston end cover 5 from locking prematurely during the retraction process. On the other hand, using a separate anti-collision pin 6 reduces the difficulty of processing the screw 3.

[0044] The commutator 7 (conventional technology in this field, the specific structure is not described) is installed on the nut 1 and is evenly distributed to avoid load imbalance. The commutator 7 is provided with a groove. After the commutator 7 is installed, the groove of the commutator 7 and the groove of the nut 1 have a smooth transition. Excessive gaps and steps have a great impact on the assembly noise.

[0045] In one embodiment of the present invention, the parameters of the ball screw assembly are designed as follows: lead 4 mm, ball 2 diameter 3.175 mm, and effective number of turns 4 turns; Advantages: Reasonable parameter design ensures efficiency and noise level while meeting stroke and load requirements, while shortening the axial space.

[0046] Working principle:

[0047] The screw 3 is fixedly connected to the driving shaft 4. When moving forward, the driving shaft 4 rotates counterclockwise to drive the screw 3 to rotate. The rotation of the screw 3 drives the ball 2 to roll in the first threaded raceway 11 and the second threaded raceway 31. The movement trajectory of the ball 2 advances in a spiral manner along the screw 3. The movement direction has a circumferential direction and an axial direction, driving the nut 1 to move. Since the freedom of the nut 1 in the circumferential direction is limited by the anti-rotation rib 12, it can only move axially forward; when retreating, the driving shaft 4 rotates clockwise to drive the screw 3 to rotate. The rotation of the screw 3 drives the ball 2 to roll in the first threaded raceway 11 and the second threaded raceway 31. The forward movement limit is limited by the friction plate. The movement trajectory of the ball 2 advances in a spiral manner along the axis of the screw 3. The movement direction has a circumferential direction and an axial direction, driving the nut 1 to move. Since the freedom of the nut 1 in the circumferential direction is limited by the anti-rotation rib 12, it can only move axially backward. The retreat limit is until the anti-collision pin 6 collides with the stop block 51 on the piston end cover 5.

[0048] At the same time, the torque of the driving shaft 4 is transmitted to the screw 3, the raceway of the screw 3 pushes the ball 2, the ball 2 pushes the nut 1, and the nut 1 pushes the piston end cover 5, finally realizing the conversion of the torque into the axial force of the piston end cover 5.

[0049] The ball screw assembly of the present invention realizes conversion of EMB driving torque into piston end axial force; realizes reliable connection between the screw 3 and the driving shaft 4 without loosening and torque transmission; realizes anti-rotation of the nut 1, improves sliding noise, and enhances structural strength; realizes smooth operation of the ball 2, improves rolling noise; and realizes prevention of the screw rod and nut 1 from bottoming out and locking.

[0050] Embodiment 2

[0051] This embodiment discloses an electronic mechanical brake system, including the ball screw assembly described above. By providing an anti-collision pin 6 and a stop block 51, a rotation stop function is performed. When the nut 1 returns axially, the nut 1 drives the piston end cover 5 to return until the anti-collision pin 6 collides with the stop block 51 and stops, thereby preventing the screw 3 or the drive shaft 4 from axially impacting the piston end cover 5.

[0052] In the description of the present invention, it is necessary to understand that the terms "center", "length", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "inside", "outside", "peripheral", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred system or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0053] In the description of the present invention, “plurality” means at least two, for example, two, three, etc., unless otherwise clearly and specifically defined.

[0054] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0055] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A ball screw assembly, characterized in that: The invention comprises a nut (1), a ball (2), a lead screw (3), a drive shaft (4) and a commutator (7); the nut (1) is provided with a first thread raceway (11) on its circumferential inner wall; the lead screw (3) is provided with a second thread raceway (31) corresponding to the first thread raceway (11) on its circumferential outer wall; the first thread raceway (11) and the second thread raceway (31) are connected and configured as a path for the ball (2) to roll; a plurality of the ball (2) are arranged to roll in the first thread raceway (11) and the second thread raceway (31); a plurality of commutators are evenly fixed on the circumferential inner wall of the nut (1); (7); A through hole (32) is provided on the inner side of the lead screw (3), an inner convex ring (33) is fixedly provided on the inner wall of the through hole (32), the inner side of the inner convex ring (33) is a center hole (34), the center hole (34) is coaxial with the lead screw (3), and one end of the drive shaft (4) is fixedly connected to the inner wall of the center hole (34); a piston end cover (5) is fixedly provided on one end of the nut (1), an anti-collision pin (6) is fixedly provided on the side of the inner convex ring (33) facing the piston end cover (5), and a stop block (51) matching the anti-collision pin (6) is fixedly provided on the inner side surface of the piston end cover (5).

2. A ball screw assembly according to claim 1, characterized in that: A blind hole (35) is provided on the side of the inner convex ring (33) facing the piston end cover (5), and one end of the anti-collision pin (6) is fixedly inserted in the blind hole (35).

3. A ball screw assembly according to claim 1, characterized in that: At least one anti-rotation surface (36) is provided in the center hole (34), and the anti-rotation surface (36) is arranged parallel to the axis of the center hole (34). The end of the drive shaft (4) matches the shape of the center hole (34), and the drive shaft (4) and the center hole (34) are interference fit.

4. A ball screw assembly according to claim 1, characterized in that: A transition chamfer (37) is provided at one end of the center hole (34) away from the piston end cover (5).

5. A ball screw assembly according to claim 1, characterized in that: A limiting convex ring (41) is fixedly provided on the outer peripheral wall of the driving shaft (4), and the side surface of the limiting convex ring (41) abuts against the side surface of the inner convex ring (33).

6. A ball screw assembly according to claim 1, characterized in that: At least one anti-rotation rib (12) is fixedly provided on the outer peripheral wall of the nut (1).

7. A ball screw assembly according to claim 6, characterized in that: The anti-rotation rib (12) is a boss structure whose two side surfaces both pass through the axis of the nut (1).

8. A ball screw assembly according to any one of claims 1 to 7, characterized in that: The outer side surface of the piston end cover (5) is provided with a concave-convex pattern (52).

9. A ball screw assembly according to any one of claims 1 to 7, characterized in that: An edge (53) is provided on the outer periphery of one side of the piston end cover (5) facing the nut (1); a first step-shaped structure (54) is provided at one end of the edge (53) away from the piston end cover (5); a second step-shaped structure (55) matching the first step-shaped structure (54) is provided at one end of the nut (1) facing the piston end cover (5); the first step-shaped structure (54) is interference-engaged with the second step-shaped structure (55).

10. An electromechanical braking system, characterized in that: Comprising a ball screw assembly as described in any one of claims 1 to 9.

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