Brake-by-wire actuator for vehicles

Abstract

The present invention discloses a brake-by-wire actuator for a vehicle, comprising an actuator and a screw drive mechanism, wherein the screw drive mechanism comprises a screw, a nut, a roller, and a retaining frame, wherein a spiral space is formed between the external thread of the screw and the internal thread of the nut, and the roller is disposed on the retaining frame, and the retaining frame and the roller are located within the spiral space. The brake-by-wire actuator for a vehicle of the present invention incorporates a retaining frame and a roller combination between the screw and the nut of the screw drive mechanism, so that multiple rollers perform rolling motion when the screw drive mechanism is in operation. The structure is easy to implement, has low production and assembly difficulty, and is low in cost. The retaining frame enables the rollers to roll regularly, ensuring that the screw drive mechanism can operate continuously during operation, avoiding jamming and failure, and meeting the requirement of providing large braking thrust.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle braking systems, and in particular, relates to a brake-by-wire actuator for a vehicle. Background Art

[0002] Brake-by-wire technology enhances vehicle automation and safety, gaining popularity in hybrid and all-electric vehicles and becoming a growing trend in the automotive industry. The main forms of brake-by-wire technology currently include electric boosters (Eboosters), electronic hydraulic brakes (EHBs), and electromechanical brakes (EMBs).

[0003] The actuator is a key challenge in brake-by-wire technology. It typically takes the form of power provided by an electric motor, which is transmitted to a screw drive mechanism via a torque-reduction mechanism. The screw drive mechanism converts the rotational motion into linear motion of the connecting member, which then generates thrust on the brake pads and disc, thereby generating braking force. The brake-by-wire actuator must meet the following characteristics:

[0004] 1. Short reaction time: The reaction time here refers to the time it takes for the braking system to receive a command and reach maximum braking force. At the same vehicle speed, the shorter the reaction time, the shorter the braking distance;

[0005] 2. Large thrust: Under the condition that the road adhesion coefficient is satisfied, the greater the thrust of the braking device, the greater the deceleration that can be achieved;

[0006] The brake-by-wire actuator needs to meet the requirements of short reaction time and high thrust at the same time, which is equivalent to meeting the requirement of high output power. However, in the existing widely used vehicle battery technology, the voltage is generally 12V to 14V. Due to the influence of low-voltage power supply, the maximum power of the motor is limited, resulting in low motor power. Smaller input power and larger output power require the transmission mechanism to have high transmission efficiency as a whole. The above-mentioned transmission mechanism at least includes a screw transmission mechanism. As a motion conversion mechanism, the transmission efficiency and load-bearing capacity of the screw transmission mechanism directly affect the overall performance of the actuator. The screw transmission mechanism may become the key to solving this problem.

[0007] In the prior art, the screw transmission mechanisms that can meet high transmission efficiency include "ball screw transmission mechanism" and "planetary roller screw transmission mechanism", but both of these screw transmission mechanisms have the following deficiencies:

[0008] 1. Insufficient load-bearing capacity of the ball screw transmission mechanism: The ball screw mechanism is mainly composed of a screw, a nut, and balls. Its basic principle is to install balls in the spiral space formed by the screw and the nut, and the screw and the nut are transmitted through multiple rolling balls. The ball screw has the characteristics of low friction and high transmission efficiency, but the problem is that the power-transmitting balls are in point contact with the screw or nut, resulting in high contact stress, which leads to insufficient load-bearing capacity. This problem is very serious for EMB. In the existing technology, the ball screw transmission mechanism can only meet the needs of rear wheel braking. For the front wheel, which requires greater braking force, the ball screw transmission mechanism cannot meet the EMB requirements.

[0009] 2. Although planetary roller screw transmission mechanisms can meet functional requirements, they are too expensive and difficult to industrialize: Patent document CN108583543A proposes a wire-controlled brake actuator using a planetary roller screw. Compared to ball screw solutions, the brake device in this invention has a higher load-bearing capacity and can provide greater thrust. However, patent document CN108583543A does not consider the cost of planetary roller screw transmission mechanisms. Planetary roller screw transmission mechanisms have very high requirements for the dimensional and geometric tolerances of components. In addition, the transmission mechanism's components, in principle, are very prone to interference, resulting in high processing and overall assembly requirements, and very precise manufacturing. As a result, the planetary roller screw and the brake device used are very expensive, making it difficult to promote and apply them in the automotive industry. Summary of the Invention

[0010] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a brake-by-wire actuator for a vehicle, the purpose of which is to reduce costs while meeting the requirement of providing high braking thrust.

[0011] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a wire control brake actuator for a vehicle, including an actuator and a screw transmission mechanism connected to the actuator and used to convert the rotational motion from the actuator into linear motion for driving the functional part forward, the screw transmission mechanism includes a screw, a nut, a roller and a retaining frame, a spiral space is formed between the external thread of the screw and the internal thread of the nut, the roller is arranged on the retaining frame, and the retaining frame and the roller are located in the spiral space.

[0012] The rollers are cylindrical rollers or tapered rollers.

[0013] The retaining frame is configured to control the tilt angle of the roller to be within a set range during movement.

[0014] The retaining frame has an accommodating cavity for accommodating the roller, and the roller can rotate freely in the retaining frame.

[0015] The thickness of the retaining frame is smaller than the minimum diameter of the roller, and the outer circumferential surface of the roller contacts the threaded surface of the lead screw and / or the nut.

[0016] The retaining frame has a first avoidance hole and a second avoidance hole, the accommodating cavity is located between the first avoidance hole and the second avoidance hole, and the inner side surface of the accommodating cavity is in gap contact with the side surface and two end faces of the roller; at least one set of bosses is provided on both sides of the first avoidance hole and the second avoidance hole, and the bosses are used to prevent the roller from escaping from the accommodating cavity, and the roller passes through the first avoidance hole and the second avoidance hole respectively and contacts the lead screw and the nut.

[0017] There are multiple rollers, and all the rollers are arranged in sequence along the spiral direction in the spiral space. The cross section of the spiral space is rectangular or trapezoidal.

[0018] The retaining frame is made of elastic steel material.

[0019] The screw transmission mechanism also includes a first limit member, a second limit member, a first elastic member and a second elastic member arranged in the spiral space, the retaining frame is located between the first elastic member and the second elastic member, the first elastic member is located between the retaining frame and the first limit member, and the second elastic member is located between the retaining frame and the second limit member.

[0020] The first elastic member and the second elastic member are both coil springs, and the side surfaces of the envelope of the first elastic member and the second elastic member match the shape of the coil space.

[0021] The present invention is used for a wire-controlled brake actuator for a vehicle. By adding a combination of a retaining frame and a roller between the screw and the nut of the screw transmission mechanism, multiple rollers perform rolling motion when the screw transmission mechanism is in operation. The structure is easy to implement, has low production and assembly difficulty, and is low in cost. The retaining frame enables the rollers to roll regularly, ensuring that the screw transmission mechanism can work continuously during operation, avoiding jamming and failure, and meeting the requirement of providing large braking thrust. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] This manual includes the following drawings, which show the following contents:

[0023] Figure 1 It is a structural diagram of the braking device;

[0024] Figure 2 It is a cross-sectional view of the screw drive mechanism;

[0025] Figure 3 It is a schematic diagram of the combined structure of the cage, roller, elastic part and limit part of the screw transmission mechanism;

[0026] Figure 4This is a schematic diagram of the cage and rollers of the screw transmission mechanism;

[0027] The markings in the figure are: 1. Screw; 2. Nut; 3. Roller; 4. Cage; 5. First elastic member; 6. First limit member; 7. Second elastic member; 8. Second limit member; 9. Brake caliper bracket; 10. Brake inner pad; 11. Brake disc; 12. Brake outer pad; 13. Actuator; 14. Brake caliper body. DETAILED DESCRIPTION

[0028] The following is a further detailed description of the specific implementation methods of the present invention through the description of embodiments with reference to the accompanying drawings, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention and to facilitate its implementation.

[0029] like Figures 1 to 3 As shown, the present invention provides a brake-by-wire actuator for a vehicle, comprising an actuator 13 and a screw drive mechanism connected to the actuator 13 and configured to convert the rotational motion of the actuator 13 into linear motion that drives the functional components of the braking device forward. When the functional components of the braking device advance, they can push the inner brake pad 10 of the braking device to move, so that the inner brake pad 10 and the outer brake pad 12 clamp the brake disc 11, thereby generating braking force and achieving wheel braking. The screw drive mechanism comprises a screw 1, a nut 2, rollers 3, and a retainer 4. A spiral space is formed between the external thread of the screw 1 and the internal thread of the nut 2. The rollers 3 are disposed on the retainer 4, and the retainer 4 and the rollers 3 are located within the spiral space. The screw 1 and the nut 2 achieve relative motion through the rolling of the multiple rollers 3 on the threaded surface.

[0030] In response to the shortcomings of ball screws and planetary roller screws in wire-controlled brake actuators, the present invention analyzes the movement of existing wire-controlled brake actuators: when the actuator is operating, the screw mechanism is generally required to perform reciprocating motion, and the range of nut movement is limited, so the use of a non-circulating screw can also meet the requirements.

[0031] The force characteristics of the functional parts are that the thrust will increase from 0 to the required value and then decrease to 0. At this time, the force is 0, and then the thrust changes back and forth continuously; at the same time, the force direction is unidirectional, and the force gradually decreases in the opposite direction, and the load-bearing capacity requirements are not high.

[0032] The transmission efficiency of the screw transmission mechanism used in the present invention is consistent with that of a ball screw, but the load-bearing capacity is improved. The screw transmission mechanism of this structure uses cylindrical or tapered rollers instead of balls, but the working principle of the screw and nut is still rolling. The transmission efficiency is basically the same as that of a ball screw, but it is still significantly improved compared to an ordinary screw. In addition, both the screw transmission mechanism and the ball screw transmission mechanism in the prior art are applicable to Hertz's law. The ball screw in the prior art is loaded by the sphere between the screw and the nut, and the sphere and the thread surface are in point contact. In the present invention, the load is loaded by the cylindrical or tapered roller between the screw and the nut, and the roller and the thread surface are in line contact. According to Hertz's formula, the roller screw with line contact has a higher load-bearing capacity.

[0033] The screw transmission mechanism used in the present invention can achieve regular rolling of the rollers. Patent document No. CN108561523A proposes a tapered roller screw pair with a reversing device at each end of the nut, forming a circulation channel between the screw and the nut, and multiple tapered rollers arranged in the channel to form a circulation chain. To meet the requirements of its circulation motion, the structure of the nut is relatively complex, and reversing devices need to be installed at both ends of the nut, which increases the difficulty of processing and assembly. Multiple tapered rollers are arranged in the channel. The closer the points of contact between the rollers and the working surface are to the axis of the screw, the lower the linear velocity. This difference in linear velocity can cause the rollers to tilt during movement. Although the inconsistency in linear velocity can be compensated by varying the diameter of the tapered rollers, due to manufacturing deviations and problems such as eccentricity of the screw, the rollers are still prone to tilting during rolling. The tilt of the rollers can cause the actual rolling direction of the rollers to deviate from the designed direction of motion. When the angle of deviation is too large, the circulation chain will become stuck, leading to transmission failure.

[0034] In the screw transmission mechanism used in the present invention, several rollers are restricted on a spiral retaining frame. When the mechanism is in operation, the retaining frame moves together with the rollers. Under the restriction of the retaining frame, the rollers will not tilt excessively, thereby achieving regular rolling of the rollers and eliminating the possibility of the structure getting stuck.

[0035] The screw transmission mechanism adopted in the present invention has a simple structure and reduced production and manufacturing costs: the screw transmission mechanism in the prior art is usually designed as a circulating structure, but in the actuator, the screw or nut generally performs reciprocating motion when performing relative motion, and the range of its relative motion is limited; and the force characteristic of the screw structure is that the positive pressure will increase from 0 to the required value and then decrease to 0, continuously reciprocating. When the positive pressure is 0, the roller can be returned to the initial position through the return device and begin to prepare for the next working cycle, which can also meet the requirements of mechanical transmission, so it is not necessary to design it into a complex circulating structure.

[0036] Specifically, if Figures 1 to 3As shown, nut 2 is sleeved onto screw 1, which has an external thread and an internal thread. The helical space is a cavity formed with a certain lead between the external thread of screw 1 and the internal thread of nut 2. Retainer 4, located within the helical space, has a helical structure. The lead of retainer 4 is consistent with the lead of screw 1 or nut 2. Retainer 4 extends in the helical direction within the helical space. Roller 3, along with retainer 4, is installed in the helical space. Retainer 4 is used to limit roller 3 within the helical space, and roller 3 within retainer 4 can rotate freely about its axis.

[0037] The retainer 4 is constructed to control the inclination angle of the roller 3 during movement (the inclination angle is the angle between the axis of the roller 3 and the width direction of the retainer 4) to be within a set range. The setting range of the inclination angle is 0 to 5°, so as to prevent the roller 3 from excessively tilting during the operation of the screw transmission mechanism, so that the actual movement direction of the screw transmission mechanism and the theoretical design movement direction will not deviate significantly, ensuring that the screw transmission mechanism can work continuously during operation and the circulating chain will not become stuck and fail. Moreover, the structure of this screw transmission mechanism is similar to that of a non-circulating ball screw, with a relatively simple structure, low difficulty from manufacturing and processing to assembly, low cost, and an easier-to-implement structure.

[0038] The closer the points where roller 3 contacts the threaded surface are to the axis of screw 1, the smaller the linear velocity is, resulting in inconsistent axial speeds at both ends of roller 3, which easily causes tilting. Therefore, a retainer 4 is provided. The function of retainer 4 is to ensure that the tilt angle of roller 3 is within a reasonable range, so that the actual movement direction of roller 3 does not deviate significantly from the designed movement direction.

[0039] Roller 3 can be a cylindrical roller or a tapered roller. Cylindrical rollers are cylindrical structures with a constant diameter, while tapered rollers are conical structures. The outer surface of roller 3 forms a line contact with the threaded surfaces of screw 1 and nut 2. Compared to the point force contact of spherical balls used in the prior art, the advantage of using cylindrical rollers or tapered rollers is that the load is supported by the contact line. Therefore, compared to the ball screw transmission mechanism of the prior art, the load-bearing capacity of the screw transmission mechanism used in the present invention is improved, thereby improving the load-bearing capacity of the wire control brake actuator, so that the load-bearing capacity of the wire control brake actuator can meet the EMB requirements of the vehicle's front wheels. Moreover, by adding a combination of retainer 4 and roller 3 between screw 1 and nut 2, multiple rollers 3 perform rolling motion when the screw transmission mechanism is in operation, which can improve transmission efficiency.

[0040] like Figures 1 to 3As shown, the cage 4 has a cavity for accommodating the roller 3. The cage 4 encloses the two end faces and side faces of the roller 3. In the free state, the roller 3 will not fall out and can rotate freely within the cage 4. The thickness of the cage 4 is less than the minimum diameter of the roller 3. The outer circumference of the roller 3 extends toward opposite sides of the cage 4 in the thickness direction and contacts the threaded surface of the screw 1 and / or nut 2.

[0041] like Figures 1 to 3 As shown, the retainer 4 has a first avoidance hole and a second avoidance hole, with the accommodating cavity located between the first avoidance hole and the second avoidance hole. The roller 3 passes through the first avoidance hole and the second avoidance hole, respectively, to contact the screw 1 and the nut 2. The first avoidance hole is a hole set on the first outer wall surface of the retainer 4, and the second avoidance hole is a hole set on the second outer wall surface of the retainer 4. The first outer wall surface and the second outer wall surface are two outer wall surfaces facing each other in the thickness direction of the retainer 4. The thickness direction of the retainer 4 is perpendicular to the threaded surface of the screw 1. The width direction of the first avoidance hole and the second avoidance hole is perpendicular to the axis of the roller 3 and perpendicular to the thickness direction of the retainer 4. A set of bosses is provided on either side of the first avoidance hole on the first outer wall surface, and two sets of bosses are provided on either side of the second avoidance hole on the second outer wall surface. The distance between the bosses on the first outer wall surface on opposite sides of the first avoidance hole is less than the diameter of roller 3 or less than the width of the accommodating cavity. The distance between the bosses on the second outer wall surface on opposite sides of the second avoidance hole is also less than the diameter of roller 3 or less than the width of the accommodating cavity. The first and second avoidance holes are connected to the accommodating cavity. The width of the accommodating cavity is approximately equal to the diameter of roller 3, and the length of the accommodating cavity is approximately equal to the length of roller 3. There is clearance contact between the inner side surface of the accommodating cavity and the two end faces and side faces of the roller. Roller 3 is located between two opposing inner wall surfaces along the length of the accommodating cavity, allowing roller 3 to rotate freely within the accommodating cavity. Roller 3 is retained in the accommodating cavity of retainer 4 by the bosses on opposite sides of the first and second avoidance holes, preventing it from falling out.

[0042] like Figures 1 to 3 As shown, multiple rollers 3 are provided, and all rollers 3 are arranged sequentially along the spiral direction within the spiral space. The cross-sectional shape of the spiral space matches the shape of the rollers 3. The spiral space can be modified by changing the thread profile or thread angle. When rollers 3 are cylindrical rollers, the cross-sectional shape of the spiral space is rectangular; when rollers 3 are tapered rollers, the cross-sectional shape of the spiral space is trapezoidal.

[0043] like Figures 1 to 3As shown, the screw drive mechanism also includes a first stopper 6, a second stopper 8, a first elastic member 5, and a second elastic member 7 disposed within the spiral space. The retainer 4 is located between the first elastic member 5 and the second elastic member 7. The first elastic member 5 is located between the retainer 4 and the first stopper 6, and the second elastic member 7 is located between the retainer 4 and the second stopper 8. One end of the first elastic member 5 is connected to the first stopper 6, and the other end of the first elastic member 5 is connected to one end of the retainer 4. One end of the second elastic member 7 is connected to the second stopper 8, and the other end of the second elastic member 7 is connected to the other end of the retainer 4. The first elastic member 5 and the second elastic member 7 in the spiral space have a spiral structure and extend in a spiral direction within the spiral space. The first elastic member 5 applies an elastic force to the retainer 4 to move it toward a position away from the first stopper pin, and the second elastic member 7 applies an elastic force to the retainer 4 to move it toward a position away from the second stopper pin. The first elastic member 5 and the second elastic member 7 are used to push the retainer 4 to reset.

[0044] During the operation of the screw drive mechanism, after one working cycle, roller 3 is no longer squeezed by screw 1 and nut 2, and the assembly formed by retainer 4 and roller 3 is free. Then, under the action of first elastic member 5 or second elastic member 7, retainer 4 can return to its initial position, driving roller 3 synchronously back to its initial position, preparing for the next working cycle. This non-circulating screw drive mechanism can meet the transmission requirements of wire control actuators. Moreover, compared with circulating ball screw structures or planetary roller screws, this structure is simpler, has lower component size requirements, and is easily implemented using existing technology, thereby reducing manufacturing costs.

[0045] like Figures 1 to 3 As shown, a through hole is provided on each of the axial ends of the nut 2. The first stopper 6 passes through the through hole provided on the side of one end of the nut 2 and extends into the thread groove of the screw 1. The second stopper 8 passes through the through hole provided on the side of the other end of the nut 2 and extends into the thread groove of the screw 1. The retainer 4, the roller 3, and the first elastic member 5 and the second elastic member 7 move between the first stopper 6 and the second stopper 8 in the spiral space. The first stopper 6 and the second stopper 8 are fixedly provided on the nut 2. After the first stopper 6 and the second stopper 8 are inserted into the thread groove of the screw 1, they will not affect the normal movement of the screw 1 and the nut 2. The retainer 4 with the roller 3 and the first elastic member 5 and the second elastic member 7 have limited movement in the space formed by the first stopper 6 and the second stopper 8, the screw 1, and the nut 2.

[0046] like Figure 2 and Figure 3As shown, the first elastic member 5 and the second elastic member 7 are preferably coil springs, and the side surfaces of the envelope of the first elastic member 5 and the second elastic member 7 match the shape of the spiral space.

[0047] In order to meet the strength of the screw 1 or nut 2, the screw 1 and nut 2 are preferably made of alloy steel or carbon steel. The thread profile of the screw or nut can be triangular, trapezoidal or rectangular, and the thread angle varies according to requirements.

[0048] The retainer 4 is made of metal material, preferably elastic steel material. The retainer 4 has elastic properties and can produce a certain amount of elastic deformation to ensure that the retainer 4 can return to its original state after being deformed by force.

[0049] The first limiting member 6 and the second limiting member 8 are made of metal material, and the first limiting member 6 and the second limiting member 8 are preferably made of material.

[0050] like Figure 1 and Figure 2 As shown, the spiral space is formed by the first and second thread surfaces of the screw 1 and the first and second thread surfaces of the nut 2. The first and second thread surfaces of the screw 1 are surfaces located on both sides of the tooth profile of the external thread of the screw 1 (the angle between the first and second thread surfaces of the screw 1 is the tooth profile angle), and the roller 3 and the retainer 4 are located between the first and second thread surfaces of the screw 1. The first and second thread surfaces of the nut 2 are surfaces located on both sides of the tooth profile of the internal thread of the nut 2 (the angle between the first and second thread surfaces of the nut 2 is the tooth profile angle), and the roller 3 and the retainer 4 are located between the first and second thread surfaces of the nut 2. The first threaded surface of the screw 1 and the first threaded surface of the nut 2 are arranged opposite to each other, the second threaded surface of the screw 1 and the second threaded surface of the nut 2 are arranged opposite to each other, and the second threaded surface of the screw 1 and the second threaded surface of the nut 2 are parallel to each other, the axis of the roller 3 is perpendicular to the second threaded surface of the screw 1 and the second threaded surface of the nut 2, the first threaded surface of the screw 1 and the first threaded surface of the nut 2 are located on opposite sides of the thickness direction of the retaining frame 4, the second threaded surface of the screw 1 and the second threaded surface of the nut 2 are located on opposite sides of the width direction of the retaining frame 4, and the width direction of the retaining frame 4 is perpendicular to the thickness direction of the retaining frame 4.

[0051] like Figure 1 and Figure 2As shown, in this embodiment, the rollers 3 are cylindrical rollers. The outer circumference of the rollers 3 is in line contact with the first threaded surfaces of the screw 1 and the nut 2. The cross-section of the spiral space is rectangular. The screw 1 and the nut 2 achieve relative motion by the rolling of the multiple rollers 3 on the first threaded surfaces of the screw 1 and the nut 2. The two opposing outer wall surfaces of the cage 4 in the width direction are in contact with the second threaded surfaces of the screw 1 and the nut 2, respectively.

[0052] like Figure 1 and Figure 2 As shown, in this embodiment, the combination of the retainer 4 and the roller 3 is arranged at the lower end of the external thread of the screw and the upper end of the internal thread of the nut 2, and the upper end of the external thread of the screw is in direct contact with the lower end of the internal thread of the nut 2.

[0053] Figure 2 The working angle α demonstrated in the figure is 45 degrees, but the working angle can be changed according to requirements. The minimum working angle can be designed to be 0, at which time the thread becomes a rectangular thread.

[0054] like Figure 1 and Figure 2 As shown, during the operation of the screw transmission mechanism, the screw 1 serves as a power input component, the nut 2 serves as a power output component, and the screw 1 rotates around its axis.

[0055] Actuator 13 includes a motor. The end of screw 1 is connected to the power output of actuator 13, and nut 2 is connected to the functional component. The functional component is movable and its movement direction is parallel to the axis of screw 1. The functional component receives the axial thrust applied by nut 2. Therefore, the screw transmission mechanism converts the rotational motion of actuator 13 into linear motion of the functional component. The functional component generates thrust on the brake inner pad 10 and brake disc 11 of the brake device, thereby generating braking force.

[0056] The brake device includes a brake caliper body 14, and a brake inner pad 10 and a brake outer pad 12 mounted on the brake caliper body 14. The brake inner pad 10 and the brake outer pad 12 are located on opposite sides of a brake disc 11, which is mounted on a vehicle wheel. The functional component is movably mounted within the brake caliper body 14. When the functional component moves forward, it pushes the brake inner pad 10 to move, causing the brake inner pad 10 and the brake outer pad 12 to clamp against the brake disc 11, thereby generating braking force and achieving braking.

[0057] The working principle of the screw drive mechanism is as follows:

[0058] After the actuator 13 is running, the screw transmission mechanism converts the rotational motion from the actuator 13 into linear motion. The screw 1 rotates in the first direction, and all the rollers 3 fixed on the retaining frame 4 roll on the threaded surfaces of the screw 1 and the nut 2. The assembly formed by the retaining frame 4 and the rollers 3 moves toward one end of the spiral space in the spiral space. The first elastic member 5 or the second elastic member 7 is squeezed, and the rollers 3 share the load transmitted from the screw 1 and transmit the power to the nut 2 through the contact line. Since the nut 2 is limited in the radial and circumferential directions, the nut 2 will be converted into linear motion according to the corresponding lead as the screw 1 rotates at an angle, and can eventually push the functional part to perform linear motion and drive the functional part forward.

[0059] After the motion conversion is completed, the screw 1 rotates in the second direction. When the external pressure of the screw transmission mechanism has not disappeared, the roller 3 is squeezed by the screw 1 and the nut 2. At this time, the relative motion between the screw 1 and the nut 2 is generated by the rolling of the roller 3. After the external pressure of the screw transmission mechanism disappears, the squeezing force of the roller 3 by the screw 1 and the nut 2 disappears. At this time, the second thread surface of the screw 1 contacts the second thread surface of the nut 2. The relative motion is completed by sliding through the direct contact between the thread surfaces of the screw 1 and the nut 2. At this time, the screw transmission mechanism can be regarded as an ordinary screw-nut transmission mechanism, and the transmission efficiency is significantly reduced. However, since the screw 1 in this case is only used for unilateral force, the screw 1 is in a non-working state when it is reversed, and the pressure load it carries is very small or almost non-existent, so even if the efficiency is reduced here, it will not consume much energy.

[0060] The first and second directions are opposite directions. For example, if the first direction is clockwise, the second direction is counterclockwise. Therefore, roller 3 is used to transfer the load between screw 1 and nut 2 when screw 1 rotates in the first direction, enabling the screw drive mechanism to convert rotational motion to linear motion. When screw 1 rotates in the second direction, the screw drive mechanism converts rotational motion to linear motion through sliding friction between the threaded surfaces of screw 1 and nut 2.

[0061] During the operation of the screw transmission mechanism, when multiple rollers 3 roll, the screw 1 and the nut 2 produce relative motion, and the positive pressure increases from 0 to the required value, and the assembly formed by the retaining frame 4 and the rollers 3 moves to one side in the spiral space; when the positive pressure decreases from the required value to 0, the rollers 3 are no longer squeezed by the screw 1 and the nut 2, and the assembly is in a free state. Under the action of the elastic member, it returns to the initial position, thus completing a working cycle and preparing for the next working cycle.

[0062] The brake-by-wire actuator of the present invention has the following characteristics:

[0063] 1. The transmission efficiency is consistent with that of the ball screw mechanism, but the load capacity can meet the requirements of the front wheel EMB: The screw transmission mechanism adopted in the present invention uses cylindrical or tapered rollers instead of balls. Its working principle is still rolling, and its efficiency is consistent with that of the ball screw. Compared with the point force contact of the balls, the cylindrical or tapered rollers support the load through the contact line during movement, which improves the load capacity of the brake device.

[0064] 2. Compared to the planetary roller screw mechanism, the screw drive mechanism used in the present invention has a simpler structure, is less difficult to manufacture and assemble, is low-cost, and is easy to promote: the structure of the planetary roller screw places very high demands on the dimensional and geometric tolerances of the components; and, in principle, the components of this structure are very prone to interference, resulting in very high processing and overall assembly requirements, and extremely precise manufacturing. This leads to high costs for the planetary roller screw and the brake device used for it, making it difficult to promote and apply in the automotive industry. The screw drive mechanism used in the present invention, on the other hand, has a structure consistent with that of a non-circulating ball screw, is simple in structure, has low requirements on the dimensional dimensions of the components, is less difficult to manufacture, and is low-cost, making it easy to promote.

[0065] Example

[0066] There are many types of brake devices, such as Figure 1 As shown, in this embodiment, an electric brake caliper assembly is used as an example. The electric brake caliper assembly includes an actuator 13, a brake caliper assembly, and a screw drive mechanism. Actuator 13 includes a motor and a reduction gear. Actuator 13 integrates the reduction gear and the motor, which reduce speed and increase torque. The reduction gear is connected to the motor and the screw drive mechanism. The power input of the reduction gear is connected to the motor, and the power output of the reduction gear is connected to the screw 1. During braking or release, the rotational motion of the motor is transmitted to the screw drive mechanism through the reduction gear. The structure of actuator 13 is well known to those skilled in the art and will not be described in detail here.

[0067] The brake caliper assembly primarily comprises a caliper body 14, and inner and outer brake pads 10, 12 mounted on the caliper body. These inner and outer brake pads 10, 12 are positioned on opposite sides of a brake disc 11, which is mounted on a vehicle wheel. The functional component is removably mounted within the caliper body 14. When the functional component advances, it pushes the inner brake pad 10, causing it to clamp against the disc 11, generating braking force and achieving braking. The actuator 13 is mounted on the caliper body 14.

[0068] The screw transmission mechanism is connected to the functional parts arranged on the outside through the nut 2. The functional parts are installed in the cavity of the brake caliper body 14 together with the screw transmission mechanism. The end of the functional part away from the actuator 13 is in contact with the brake inner plate 10. The screw 1 is movably connected to the brake caliper body 14 through a thrust bearing. The bearing is used to limit the axial movement of the screw 1. The rotational motion of the motor is transmitted to the screw 1 through the reduction mechanism, so that the screw 1 rotates, and the rotational motion is converted into linear motion of the functional part through the screw transmission mechanism. The nut 2 pushes the functional part in the axial direction toward the brake inner plate 10. The brake inner plate 10 and the brake outer plate 12 clamp the brake disc 11 to obtain braking force.

[0069] In this embodiment, the screw transmission mechanism adopts a unilateral arrangement, that is, the roller 3, retaining frame 4, first elastic member 5 and second elastic member 7 of the screw transmission mechanism are arranged on one side of the two sides of the thread, which can also be considered as a solution for the screw transmission mechanism of this embodiment to be used for a unidirectional force transmission structure.

[0070] The braking force generation process of the electric brake caliper assembly is as follows: actuator 13 operates, transmitting the motor's rotational motion to the screw drive mechanism. Screw 1 rotates in a first direction, and roller 3 rolls in the spiral space formed between screw 1 and nut 2. The assembly formed by retainer 4 and roller 3 moves inward toward one end of the spiral space, compressing first elastic member 5. Roller 3 shares the load transmitted from screw 1 and transmits power to nut 2 via several contact lines. Nut 2 drives the functional components forward, and the thrust of the functional components increases from 0 to the required value. Because the nut is limited in the radial and circumferential directions, nut 2 converts the rotation angle of screw 1 into linear motion according to the corresponding lead, pushing the connected functional components into axial linear motion, which in turn pushes the inner brake pad 10. The inner brake pad 10 and the outer brake pad 12 clamp the brake disc 11 to generate braking force.

[0071] The braking force release process of the electric brake caliper assembly is as follows: Screw 1 rotates in the second direction. While the braking force persists, roller 3 is still squeezed by screw 1 and nut 2, and the relative motion between screw 1 and nut 2 is generated by the rolling of roller 3. After the braking force disappears, the squeezing force on roller 3 by screw 1 and nut 2 disappears. At this time, the second threaded surface of screw 1 contacts the second threaded surface of nut 2, and the relative motion is achieved through sliding caused by the direct contact between the threaded surfaces of screw 1 and nut 2. At this point, the screw transmission mechanism can be regarded as a conventional screw-nut transmission mechanism, and the transmission efficiency is significantly reduced. At this time, the functional component thrust is reduced from the required value to 0, and roller 3 is no longer squeezed by screw 1 and nut 2. The cage and roller combination is in a free state and returns to its initial position under the action of the first elastic member, thus completing one working cycle and preparing for the next working cycle.

[0072] If the screw continues to rotate in the second direction, it is in a non-braking state and the pressure load it carries is very small, so even if the efficiency decreases here, it will not consume much energy; and the transmission mode of the screw transmission mechanism changes from rolling to sliding. The phase change of this transmission mode can help the electronic control device determine whether the braking device has returned to its position and whether there is braking force on the vehicle.

[0073] The first and second directions are opposite directions. For example, if the first direction is clockwise, the second direction is counterclockwise. Therefore, roller 3 is used to transfer the load between screw 1 and nut 2 when screw 1 rotates in the first direction, enabling the screw drive mechanism to convert rotational motion to linear motion. When screw 1 rotates in the second direction, the screw drive mechanism converts rotational motion to linear motion through sliding friction between the threaded surfaces of screw 1 and nut 2.

[0074] To sum up, the braking device of this embodiment adopts a roller screw transmission mechanism, and the screw and the nut transmit the load through a number of cylindrical or tapered rollers, changing the contact mode from point contact to line contact. Compared with the braking device using a ball screw, it can withstand a larger load; and compared with the braking device using a planetary roller screw, the structure of the screw transmission mechanism is relatively simple, and the production cost and assembly difficulty are reduced; when braking occurs, the screw transmission mechanism acts as a cylindrical or tapered roller screw mechanism, which improves the load-bearing capacity. When the brake is released, the phase change of its transmission mode can determine whether there is braking force in the system and whether the functional parts have returned to their position.

[0075] The present invention has been described above with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described method. Any non-substantial improvements made using the method concepts and technical solutions of the present invention, or any direct application of the above-described concepts and technical solutions to other situations without modification, fall within the scope of protection of the present invention.

Claims

1. A brake-by-wire actuator for a vehicle, comprising an actuator and a screw drive mechanism connected to the actuator and configured to convert rotational motion from the actuator into linear motion for driving a functional component forward. The screw drive mechanism comprises a screw, a nut, and a roller, wherein a spiral space is formed between the external threads of the screw and the internal threads of the nut. The invention is characterized in that: The screw transmission mechanism further includes a retaining frame, the roller is arranged on the retaining frame, and the retaining frame and the roller are located in the spiral space; The spiral space is formed by the first and second thread surfaces of the screw and the first and second thread surfaces of the nut, the first and second thread surfaces of the screw being surfaces on both sides of the tooth profile of the external thread of the screw, and the roller and the retainer being located between the first and second thread surfaces of the screw; the first and second thread surfaces of the nut are surfaces on both sides of the tooth profile of the internal thread of the nut, and the roller and the retainer are located between the first and second thread surfaces of the nut; the first thread surface of the screw and the first thread surface of the nut are arranged relative to each other, the second thread surface of the screw and the second thread surface of the nut are arranged relative to each other, and the second thread surface of the screw and the second thread surface of the nut are parallel to each other, the axis of the roller is perpendicular to the second thread surface of the screw and the second thread surface of the nut, the first thread surface of the screw and the first thread surface of the nut are located on opposite sides in the thickness direction of the retainer, the second thread surface of the screw and the second thread surface of the nut are located on opposite sides in the width direction of the retainer, and the width direction of the retainer is perpendicular to the thickness direction of the retainer; The rollers are cylindrical rollers, the outer circumference of which is in contact with the first thread surface of the screw and the first thread surface of the nut, forming a line contact. The cross-sectional shape of the spiral space is rectangular. The screw and the nut complete relative motion by the rolling of the multiple rollers on the first thread surfaces of the screw and the nut. Two opposite outer wall surfaces of the retainer in the width direction are in contact with the second thread surface of the screw and the second thread surface of the nut respectively; The cage in the spiral space has a spiral structure. The lead of the cage is consistent with the lead of the screw or nut. The cage extends in the spiral direction in the spiral space. The cage is used to limit the roller in the spiral space, and the roller in the cage can rotate freely around its axis. After the actuator is running, the screw transmission mechanism converts the rotational motion from the actuator into linear motion. The screw rotates in the first direction, and the nut will convert it into linear motion according to the corresponding lead as the screw rotates at an angle, and finally it can push the functional part to move in a linear direction and drive the functional part forward. After the motion conversion is completed, the screw rotates in the second direction. After the external pressure of the screw transmission mechanism disappears, the extrusion force of the roller by the screw and the nut disappears, and the second threaded surface of the screw contacts the second threaded surface of the nut. The relative motion is completed by sliding due to the direct contact between the threaded surfaces of the screw and the nut.

2. The brake-by-wire actuator for a vehicle according to claim 1, characterized in that: The combination of the retainer and the roller is arranged at the lower end of the external thread of the screw and the upper end of the internal thread of the nut, and the upper end of the external thread of the screw is in direct contact with the lower end of the internal thread of the nut.

3. The brake-by-wire actuator for a vehicle according to claim 1, characterized in that: The retaining frame is configured to control the tilt angle of the roller to be within a set range during movement.

4. The brake-by-wire actuator for a vehicle according to claim 3, characterized in that: The retaining frame has an accommodating cavity for accommodating the roller, and the roller can rotate freely in the retaining frame.

5. The brake-by-wire actuator for a vehicle according to claim 4, characterized in that: The thickness of the retaining frame is smaller than the minimum diameter of the roller.

6. The brake-by-wire actuator for a vehicle according to claim 4, characterized in that: The retaining frame has a first avoidance hole and a second avoidance hole, the accommodating cavity is located between the first avoidance hole and the second avoidance hole, and the inner side surface of the accommodating cavity is in gap contact with the side surface and two end faces of the roller; at least one set of bosses is provided on both sides of the first avoidance hole and the second avoidance hole, and the bosses are used to prevent the roller from escaping from the accommodating cavity, and the roller passes through the first avoidance hole and the second avoidance hole respectively and contacts the lead screw and the nut.

7. The brake-by-wire actuator for a vehicle according to claim 3, characterized in that: There are multiple rollers, and all the rollers are arranged in sequence along the spiral direction in the spiral space. The cross section of the spiral space is rectangular or trapezoidal.

8. The brake-by-wire actuator for a vehicle according to claim 1 or 2, characterized in that: The retaining frame is made of elastic steel material.

9. The brake-by-wire actuator for a vehicle according to claim 1 or 2, characterized in that: The screw transmission mechanism also includes a first limit member, a second limit member, a first elastic member and a second elastic member arranged in the spiral space, the retaining frame is located between the first elastic member and the second elastic member, the first elastic member is located between the retaining frame and the first limit member, and the second elastic member is located between the retaining frame and the second limit member.

10. The brake-by-wire actuator for a vehicle according to claim 9, characterized in that: The first elastic member and the second elastic member are both coil springs, and the side surfaces of the envelope of the first elastic member and the second elastic member match the shape of the coil space.

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