Planetary roller screw and electronic mechanical braking system applied by same

Abstract

The planetary roller lead screw comprises a lead screw body, rollers, a retainer, a nut, pistons, an input gear and a thrust bearing, the rollers are provided with multiple sections of outer ring grooves, the nut is provided with multiple sections of inner ring grooves, the rollers are annularly arranged outside the lead screw body through the retainer, the nut is arranged outside the rollers, and the input gear is arranged on the thrust bearing. The roller rotates around the lead screw in the axial direction. According to the invention, the lead screw is used as an input rotating shaft, so that the roller can axially move while rotating and revolving, and the roller drives the nut to rotate through friction, so that the nut axially moves at the same speed, the braking response time of the mechanism can be effectively prolonged, and the boundary dimension and the overall volume of the lead screw can be reduced; the planetary roller lead screw is mainly characterized in that the rollers are stressed through linear contact, the stressed area is large, the bearing capacity of the planetary roller lead screw is effectively improved, and the service life of the planetary roller lead screw is effectively prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle braking systems, and in particular to a planetary roller screw and an electronic mechanical braking system using the same. Background Art

[0002] Electro-mechanical Brake System (EMB) is a braking system that directly drives the brake device through electricity. Unlike traditional hydraulic brake systems, EMB systems do not require hydraulic oil or compressed air as transmission media, but directly control the motor and deceleration mechanism through wires to achieve braking. When the driver steps on the brake pedal or receives a braking command, the electronic control unit (ECU) sends a signal to the motor, which drives the deceleration mechanism to clamp the brake disc or brake pad to generate braking force, which can achieve more efficient and precise braking response.

[0003] The motion conversion mechanism of the electronic mechanical brake system adopts ball screw transmission, which drives the piston to move linearly through the ball screw, and then the piston pushes the brake pad to clamp the brake disc to brake the vehicle. In order to maintain the load-bearing capacity and life of the ball screw currently used in the electronic mechanical brake system, the diameter of the steel ball cannot be less than the set value, resulting in a large lead of the ball screw. In order to ensure sufficient brake clamping force, it is necessary to increase the gear ratio or motor torque, which makes the motor NVH test more risky and increases the size and weight of the motor. For the compact EMB wheel installation environment, it will bring greater installation risks, and at the same time will cause an increase in motion inertia and reduce the response time of the motion conversion mechanism. Summary of the invention

[0004] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a planetary roller screw and an electronic mechanical braking system using the same.

[0006] In order to achieve the above objectives, in a first aspect, the present invention provides a planetary roller screw, comprising:

[0007] Screws, rollers, cages and nuts;

[0008] The roller is provided with multiple sections of outer ring grooves, the nut is provided with multiple sections of inner ring grooves, the roller is arranged outside the screw through the retaining ring, the nut is arranged outside the roller, and the roller rotates around the screw in the axial direction.

[0009] In some of the embodiments, the pitches of the lead screw, the roller, and the nut are equal, and the lead angles of the nut and the roller are equal.

[0010] In some embodiments, the lead screw includes a mounting portion, a first circumferential limiting portion and an external spline portion are respectively provided on both sides of the mounting portion, a threaded portion is provided on one side of the circumferential limiting portion, and a first retaining ring groove is opened in the middle of the external spline portion.

[0011] In some embodiments, the outer ring groove includes a first outer groove, a second outer groove and a third outer groove, the inner ring groove includes a first inner groove and a second inner groove, the first outer groove of the roller is threadedly connected to the threaded portion of the screw, the second outer groove of the roller is threadedly connected to the first inner groove of the nut, and the third outer groove of the roller is threadedly connected to the second inner groove of the nut.

[0012] In some embodiments, the retaining frame is provided with a placement groove, and the roller is fixed on the placement groove through the shaft diameters at both ends.

[0013] In some embodiments, a second retaining ring groove is opened at one end of the nut, and an elastic retaining ring for a hole is arranged in the second retaining ring groove. The elastic retaining ring for the hole is used to axially fix the roller and the retaining frame. A first flat portion is arranged on the outside of the nut, and the first flat portion of the nut and the second flat portion inside the piston abut against each other to limit the circumferential movement of the nut.

[0014] In some embodiments, a second circumferential limit portion is provided on an end face of one side of the outside of the nut, and the height difference between the second circumferential limit portion of the nut and the first circumferential limit portion of the screw is smaller than the lead of the screw. The second circumferential limit portion of the nut and the first circumferential limit portion of the screw cooperate to limit the movement stroke of the roller and the screw.

[0015] In a second aspect, the present invention further provides an electronic mechanical brake system, comprising the planetary roller screw as described in the first aspect, and further comprising:

[0016] A piston, wherein the piston is sleeved outside the nut and is used to transmit a braking torque;

[0017] An input gear, the input gear is rotatably connected to the lead screw and is used to drive the lead screw to rotate;

[0018] A thrust bearing is abutted against the lead screw and is used to bear the axial force of the lead screw.

[0019] In some embodiments, an internal spline portion is provided inside the input gear, and the internal spline portion of the input gear abuts against the external spline portion of the screw, and an inner diameter portion is provided inside the thrust bearing, and the inner diameter portion of the thrust bearing abuts against the mounting portion of the screw.

[0020] In some of the embodiments, a wire retaining ring is further included, wherein the wire retaining ring is installed on the first retaining ring groove of the lead screw and is pressed into the third retaining ring groove of the input gear together with the lead screw.

[0021] The present invention has the following beneficial effects:

[0022] 1. In the planetary roller screw of the present invention, the screw serves as the sun gear, the roller serves as the planet gear, the nut serves as the inner gear ring, the retaining frames on both sides serve as the planet carrier, and the screw serves as the input rotating shaft, so that the roller can perform axial movement while performing rotation and revolution, and the roller drives the nut to rotate through friction, so that the nut performs axial movement at the same speed, which can effectively improve the braking response time of the mechanism and reduce the external dimensions and overall volume of the screw;

[0023] 2. In the present invention, the planetary roller screw is mainly subjected to force through linear contact of the rollers, and the force-bearing area is large, which effectively enhances the bearing capacity and service life of the planetary roller screw. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A cross-sectional view of the planetary roller screw provided by the present invention;

[0025] Figure 2 A cross-sectional view of the planetary roller screw provided by the present invention;

[0026] Figure 3 This is a schematic diagram of the flat position matching of the nut and the piston in the planetary roller screw proposed by the present invention;

[0027] Figure 4 It is a transmission schematic diagram of the planetary roller screw proposed by the present invention;

[0028] Figure 5 Schematic diagram of the explosion of the planetary roller screw proposed by the present invention Figure 1 ;

[0029] Figure 6 Schematic diagram of the explosion of the planetary roller screw proposed by the present invention Figure 2 ;

[0030] Figure 7 Schematic diagram of the explosion of the electromechanical brake system proposed by the present invention Figure 2 ;

[0031] Figure 8 A cross-sectional view of the electromechanical brake system proposed by the present invention.

[0032] Legend:

[0033] 1. Screw; 11. Mounting part; 12. First circumferential limiting part; 13. External spline part; 14. Threaded part; 15. First retaining ring groove; 2. Roller; 21. External ring groove; 211. First external groove; 212. Second external groove; 213. Third external groove; 22. Shaft diameter; 3. Retaining frame; 31. Placement groove; 4. Nut; 41. Internal ring groove; 411. First internal groove; 412. Second internal groove; 42. Second retaining ring groove; 43. First flat part; 44. Second circumferential limiting part; 5. Elastic retaining ring for hole; 6. Piston; 61. Second flat part; 7. Input gear; 71. Internal spline part; 72. Third retaining ring groove; 8. Thrust bearing; 81. Inner diameter part; 9. Wire retaining ring. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Please refer to the following examples for details:

[0036] Reference Figure 1-Figure 6 The present invention provides an embodiment of a planetary roller screw and an electronic mechanical brake system used therein, comprising: a screw 1, a roller 2, a cage 3 and a nut 4. The roller 2 is arranged outside the screw 1 through the cage 3, and the nut 4 is arranged outside the roller 2, so that the roller 2 rotates around the screw 1 in the axial direction and drives the nut 4 to rotate through the friction force.

[0037] Specifically, the pitches of the lead screw 1, the roller 2 and the nut 4 are equal, and the lead angles of the nut 4 and the roller 2 are equal. Exemplarily, the lead angle of the nut 4 and the roller 2 is zero.

[0038] For example, in the planetary roller 2 screw 1, the screw 1 acts as a sun gear, the roller 2 acts as a planetary gear, the nut 4 acts as an inner gear ring, and the cages 3 at both ends act as planet carriers, forming a transmission mechanism similar to a planetary gear. When working, the screw 1 acts as an input rotating shaft, which can make the roller 2 move axially while rotating and revolving, and the roller 2 drives the nut 4 to rotate through friction, so that the nut 4 moves axially at the same speed, which can effectively improve the braking response time of the mechanism and reduce the external dimensions and overall volume of the screw 1.

[0039] It can be understood that in the existing ball screw, the load is mainly borne by the steel balls, and the steel balls and the screw are in point contact, so the meshing area is small, while in the planetary roller screw in the present application, the force is mainly borne by the roller 2, and the roller 2 and the screw 1 are in line contact, so the meshing area is larger, which effectively enhances the load-bearing capacity and service life of the planetary roller 2 and the screw 1.

[0040] Please continue reading Figure 1-Figure 6 The lead screw 1 includes a mounting portion 11, through which the lead screw 1 and other components are assembled; in addition, a first circumferential limiting portion 12 and an external spline portion 13 are respectively provided on both sides of the mounting portion 11, and the first circumferential limiting portion 12 is used to cooperate with the second circumferential limiting portion 44 of the nut 4 to limit the movement stroke of the roller 2 and the nut 4, and when the nut 4 retreats to the limit position, it prevents the outer ring groove 21 of the roller 2 and the threaded portion 14 of the lead screw 1 from biting or yielding in the meshing area, thereby playing a mechanical protection role, and the external spline portion 13 is used to cooperate with the installation of the transmission component; in addition, a threaded portion 14 is provided on one side of the circumferential limiting portion for cooperating with the installation of the roller 2, and a first retaining ring groove 15 is provided in the middle of the external spline portion 13 for installing the limiting component.

[0041] Exemplarily, the roller 2 is provided with multiple sections of outer ring grooves 21, the outer ring grooves 21 include a first outer groove 211, a second outer groove 212 and a third outer groove 213, and the nut 4 is provided with multiple sections of inner ring grooves 41, the inner ring grooves 41 include a first inner groove 411 and a second inner groove 412. Specifically, the first outer groove 211 of the roller 2 is screwed to the threaded portion 14 of the screw 1, the second outer groove 212 of the roller 2 is screwed to the first inner groove 411 of the nut 4, and the third outer groove 213 of the roller 2 is screwed to the second inner groove 412 of the nut 4, so that the roller 2 is subjected to more uniform force during assembly and movement.

[0042] Furthermore, the cage 3 is provided with a U-shaped placement groove 31 , and the roller 2 is fixed on the placement groove 31 of the cage 3 through the shaft diameters 22 at both ends.

[0043] In addition, a second retaining ring groove 42 is opened at one end of the inside of the nut 4, and a hole elastic retaining ring 5 is arranged in the second retaining ring groove 42 for axially fixing the roller 2 and the retaining frame 3. A second circumferential limiting portion 44 is arranged on the end face of one side of the outside of the nut 4. The height difference L between the second circumferential limiting portion 44 of the nut 4 and the first circumferential limiting portion 12 of the screw 1 is less than the lead S of the screw 1. The second circumferential limiting portion 44 of the nut 4 and the first circumferential limiting portion 12 of the screw 1 cooperate with each other to prevent the outer ring groove 21 of the roller 2 and the threaded portion 14 of the screw 1 from biting or yielding when the nut 4 retracts to the end of the stroke, thereby protecting the threaded meshing area of ​​the screw 1 and the roller 2 from damage.

[0044] For example, in order to limit the circumferential rotation of the nut 4, a first flat portion 43 is provided on the outside of the nut 4, so that during installation, the first flat portion 43 of the nut 4 can abut against the second flat portion 61 inside the piston 6, so that the nut 4 maintains axial movement and converts the rotational movement of the screw 1 into linear motion of the nut 4.

[0045] Reference Figure 7-Figure 8 The present invention also provides an embodiment of an electronic mechanical brake system, including the planetary roller screw in the above embodiment, and also including: a piston 6, an input gear 7 and a thrust bearing 8. The piston 6 is sleeved on the outside of the nut 4 for transmitting the braking torque; the input gear 7 is rotatably connected to the screw 1 for driving the screw 1 to rotate; the thrust bearing 8 is in contact with the screw 1 for bearing the axial force of the screw 1.

[0046] Exemplarily, an internal spline portion 71 is provided inside the input gear 7. When installed, the internal spline portion 71 of the input gear 7 abuts against the external spline portion 13 of the screw 1, thereby transmitting torque and power; and an inner diameter portion 81 is provided inside the thrust bearing 8. When installed, the inner diameter portion 81 of the thrust bearing 8 abuts against the mounting portion 11 of the screw 1, thereby bearing the axial force of the screw when the screw moves.

[0047] Furthermore, it also includes a wire retaining ring 9, which is first installed on the first retaining ring groove 15 of the screw 1, and then pressed into the third retaining ring groove 72 of the input gear 7 together with the screw 1, which can limit the axial position of the screw 1 and prevent the screw 1 from axial movement.

[0048] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A planetary roller screw, characterized in that: include: A lead screw (1), a roller (2), a cage (3) and a nut (4); The roller (2) is provided with a plurality of outer ring grooves (21), the nut (4) is provided with a plurality of inner ring grooves (41), the roller (2) is arranged outside the screw (1) through the retaining frame (3), the nut (4) is arranged outside the roller (2), and the roller (2) rotates around the screw (1) in an axial direction.

2. A planetary roller screw according to claim 1, characterized in that: The pitches of the lead screw (1), the roller (2) and the nut (4) are equal, and the lead angles of the nut (4) and the roller (2) are equal.

3. A planetary roller screw according to claim 1, characterized in that: The lead screw (1) comprises a mounting portion (11), a first circumferential limiting portion (12) and an external spline portion (13) are respectively arranged on both sides of the mounting portion (11), a threaded portion (14) is arranged on one side of the circumferential limiting portion, and a first retaining ring groove (15) is opened in the middle of the external spline portion (13).

4. A planetary roller screw according to claim 1, characterized in that: The outer ring groove (21) includes a first outer groove (211), a second outer groove (212) and a third outer groove (213); the inner ring groove (41) includes a first inner groove (411) and a second inner groove (412); the first outer groove (211) of the roller (2) is threadedly connected to the threaded portion (14) of the screw (1); the second outer groove (212) of the roller (2) is threadedly connected to the first inner groove (411) of the nut (4); and the third outer groove (213) of the roller (2) is threadedly connected to the second inner groove (412) of the nut (4).

5. A planetary roller screw according to claim 1, characterized in that: The retaining frame (3) is provided with a placement groove (31), and the roller (2) is fixed on the placement groove (31) via shaft diameters (22) at both ends.

6. A planetary roller screw according to claim 1, characterized in that: A second retaining ring groove (42) is provided at one end of the nut (4), a hole elastic retaining ring (5) is provided in the second retaining ring groove (42), and the hole elastic retaining ring (5) is used to axially fix the roller (2) and the retaining frame (3); a first flat portion (43) is provided on the outside of the nut (4), and the first flat portion (43) of the nut (4) and the second flat portion (61) inside the piston (6) abut against each other to limit the circumferential movement of the nut (4).

7. A planetary roller screw according to claim 1, characterized in that: A second circumferential limiting portion (44) is provided on an end face of one side of the outside of the nut (4); a height difference (12) between the second circumferential limiting portion (44) of the nut (4) and the first circumferential limiting portion (44) of the screw (1) is smaller than the lead of the screw (1); the second circumferential limiting portion (44) of the nut (4) and the first circumferential limiting portion (12) of the screw (1) cooperate to limit the movement stroke of the roller (2) and the screw (1).

8. An electromechanical braking system, characterized in that: The electromechanical brake system comprises a planetary roller screw as claimed in any one of claims 1 to 7, and further comprises: A piston (6), wherein the piston (6) is sleeved on the outside of the nut (4) and is used to transmit a braking torque; An input gear (7), the input gear (7) being rotatably connected to the lead screw (1) and being used to drive the lead screw (1) to rotate; A thrust bearing (8) is in contact with the lead screw (1) and is used to bear the axial force of the lead screw (1).

9. An electromechanical brake system according to claim 8, characterized in that: The input gear (7) is provided with an internal spline portion (71), and the internal spline portion (71) of the input gear (7) abuts against the external spline portion (13) of the screw (1); the thrust bearing (8) is provided with an inner diameter portion (81), and the inner diameter portion (81) of the thrust bearing (8) abuts against the mounting portion (11) of the screw (1).

10. An electromechanical brake system according to claim 8, characterized in that: It also comprises a wire retaining ring (9), which is mounted on the first retaining ring groove (15) of the lead screw (1) and is pressed into the third retaining ring groove (72) of the input gear (7) together with the lead screw (1).

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