Electrically controlled mechanical dry brake caliper

Abstract

The present invention provides an electrically controlled mechanical dry brake caliper. A planetary roller screw assembly (10) is mounted in a cylinder bore of a brake caliper assembly (11), and a motor and a speed reducing mechanism are directly or indirectly connected to the planetary roller screw assembly (10). The planetary roller screw assembly (10) includes a screw shaft (1), a nut (2), and a roller (3) mounted between the screw shaft (1) and the nut (2). The roller (3) is mounted in a holder (5) located between the screw shaft (1) and the nut (2), and a torsion spring (8) is mounted between the holder (5) and the nut (2), and the nut (2) and the holder (5) are respectively provided with anti-rotation bosses (4a, 4b) that match each other. The elastic force of the torsion spring (8) causes one side of the second anti-rotation boss (4b) of the holder (5) to be in intimate contact with one side of the first anti-rotation boss (4a) of the nut (2). This contact position is the initial position of the roller (3) and holder (5).

Description

[Technical Field]

[0001] The present invention relates to the technical field of braking systems, and more particularly to electrically controlled mechanical dry brake calipers. [Background technology]

[0002] In the prior art, electrically controlled mechanical dry brake calipers generally include a linear drive mechanism for converting the rotational motion of a drive motor and a reduction mechanism into linear motion of a connected part, one form of which is a planetary roller screw.

[0003] Planetary roller screws in the prior art are generally classified as follows:

[0004] Standard planetary roller screws: The screw shaft and nut are fitted together by multiple threaded rollers, and this structure places extremely high demands on the dimensional and geometric tolerances of the parts. If the precision of the parts does not meet the requirements even slightly, interference may occur, resulting in malfunction. Therefore, the processing and assembly requirements are very high, and the production manufacturing process is very precise. As a result, the cost of planetary roller screws is very high.

[0005] Reverse Planetary Roller Screw: The structure and principle are almost the same as standard planetary roller screws, but the difference is that torque and rotational speed are transmitted by the nut, and axial force is transmitted by the screw shaft.

[0006] Circulating planetary roller screws: The rollers are provided with multiple sets of annular grooves, the distance between which matches the thread. With each rotation, the rollers disengage from the threads of the screw shaft and enter the inner groove of the nut, whereupon the cams on both ends of the nut push the rollers back to their original axial position before rotation. The rollers then re-enter the raceways of the screw shaft and nut. During the raceway entry process, the roller annular grooves must simultaneously align with multiple teeth on the nut before entering the raceway. This places significant demands on the machining and assembly of the cams and nuts, resulting in very high costs. Furthermore, it is difficult to ensure proper engagement of the rollers with the multiple teeth on the nut under high-speed operating conditions.

[0007] Differential planetary roller screws: They have a simpler structure and can withstand higher loads with the same volume and weight. They also have the advantages of higher input rotation speeds, smaller leads, and larger reduction ratios. However, they have the disadvantages of sliding problems occurring in the thread engagement area of ​​the screw shaft, making the transmission ratio unstable, causing severe wear under heavy loads, and reducing precision and reliability.

[0008] As described above, the planetary roller screws of the prior art have the following two problems.

[0009] (1) Standard planetary roller screws, reversing planetary roller screws, and circulating planetary roller screws are difficult to widely use in the automotive industry due to their high cost and limited production capacity.

[0010] (2) Differential planetary roller screws have problems with durability and reliability under heavy loads, making them difficult to apply to automotive safety systems. Summary of the Invention

[0011] To solve the above-mentioned problems, the present invention provides an electrically controlled mechanical dry brake caliper. The device includes a motor and a speed reduction mechanism, a planetary roller screw assembly, and a brake caliper assembly. The planetary roller screw assembly is mounted in a cylinder bore of the brake caliper assembly, and the motor and the speed reduction mechanism are directly or indirectly connected to the planetary roller screw assembly. The planetary roller screw assembly includes a threaded shaft, a nut, and a roller mounted between the threaded shaft and the nut. The roller is mounted in a holder located between the threaded shaft and the nut, and a torsion spring is mounted between the holder and the nut. The nut and the holder are respectively provided with matching anti-rotation bosses, and one side of the holder's anti-rotation boss is tightly fitted to one side of the nut's anti-rotation boss by the elastic force of the torsion spring. This tight fitting position is the initial position of the roller and holder. After any operating cycle, under no-load conditions, both the roller and holder are in their initial positions.

[0012] In a further refinement, the rollers are annular groove thread rollers, and the rollers are mounted in a holder that limits the circumferential position of the rollers and allows the rollers to rotate about their own axis within the holder. Within a single operating cycle, the initial position of the nut relative to the screw shaft and the initial position of the holder relative to the nut both move after a predetermined time.

[0013] As a further improvement, the holder is composed of two annular portions and a connecting portion b connecting the two annular portions, and the annular portions have uniformly distributed through-holes. The roller is composed of an annular groove b and cylindrical ends a on both sides of the annular groove b, and the cylindrical ends a and the through-holes of the annular portions of the holder are clearance-fitted with the shaft and the hole, the length of the annular groove b is shorter than the shortest distance between the two annular portions of the holder, and a small spring is attached between the end face of the annular groove b and the annular portions of the holder. This small spring is a wave spring.

[0014] As a further improvement, the nut includes an inner thread portion a and a bottom end return portion b, the torsion spring is attached to the inner space of the return portion b of the nut, the number of the torsion spring is at least one, the torsion spring is a spring that applies a torsional force, and the shape of the torsion spring is flat, cylindrical, or conical.

[0015] As a further improvement, the return portion b of the nut is fixedly connected to a base, and an end surface of the base is circular or elliptical. The return portion b and the base are connected by threading, welding, or riveting. The base abuts against an end surface of a brake pad of a brake caliper assembly.

[0016] As a further improvement, the number of the anti-rotation bosses is at least one pair, and each pair having two anti-rotation bosses is fixed to the inner walls of the end of the holder and the end of the nut by an assembly or integral molding method.

[0017] As a further improvement, the gap between the roller and the nut is smaller than the gap between the roller and the screw shaft, so that under no load conditions, the friction force between the screw shaft and the roller is smaller than the friction force between the nut and the roller.

[0018] As a further improvement, a guide portion is provided on the outer wall surface of the nut, which is a groove or a boss, and the guide portion is fitted into the cylinder hole of the brake caliper assembly, and the nut is restricted in the circumferential direction by the guide portion, thereby ensuring that the movement of the nut is restricted to linear movement during the operation process.

[0019] As a further refinement, the nut includes at least a cylindrical portion or smooth transition portion that fits over a rubber seal ring on the brake caliper assembly to provide a seal and prevent the ingress of foreign matter.

[0020] As a further improvement, a seal cover is attached between the cylinder hole end face of the brake caliper assembly and the nut.

[0021] The forward and reverse motion of the motor and reduction mechanism is converted from rotational motion to translational motion of the brake pads by the planetary roller screw assembly to achieve the clamping and release action of the brake caliper. A typical operating cycle includes a clamping phase, a load phase, and a release phase.

[0022] The clamping step includes the following: Idle stroke phase: During this phase, the planetary roller screw operates and presses the brake pads, eliminating the gap between the brake pads and the brake disc. Because the gap between the rollers and the nut is smaller than the gap between the rollers and the screw shaft, the friction moment between the screw shaft and the rollers is smaller than the moment applied by the torsion spring. This results in no relative movement between the rollers and the nut, and the screw shaft slides on the rollers. The advantage of this configuration is that, under the same load conditions, the operating stroke of the nut is shorter than the rolling motion during the idle stroke. This shortens the nut length, thereby reducing the cost of the nut. It should be noted that, because the axial force is zero during this phase, the frictional force is very small, whether it is sliding or rolling friction, and the difference is negligible.

[0023] Load stage: After the axial clearance is removed, the brake pads and caliper body begin to deform, and the reaction force from this deformation acts on the planetary roller screw. The friction moment between the screw and the roller gradually exceeds the elastic force of the torsion spring. At this time, the roller performs a rolling motion between the screw shaft and the nut. The operating principle is the same as that of a recirculating planetary roller screw, and it simultaneously has high transmission efficiency and high load-bearing capacity. Furthermore, by eliminating the groove and cam on the nut, the motion becomes more continuous, adapting to high rotational speeds and meeting the response time requirements of the brake system.

[0024] In the load stage, the brake system has a stroke limit, and the stroke at which the torsion spring is compressed is greater than the stroke of the brake system to meet the requirement.

[0025] The release step includes the following: Unloading stage: The roller and screw shaft are subjected to an axial load, and the friction moment is greater than the moment caused by the torsion spring. The planetary roller screw has rolling friction, so the reverse efficiency is high and quick unloading is possible.

[0026] When the axial load is released, the friction moment becomes smaller than the moment caused by the torsion spring, and the elastic force of the torsion spring returns the roller and holder to their initial positions. As the screw shaft continues to rotate in the release direction, the friction moment becomes much smaller than the moment caused by the anti-rotation mechanism, and sliding friction continues, resulting in an effect equivalent to that of a sliding screw. [Effects of the Invention]

[0027] Advantageous effects of the present invention: the electrically controlled mechanical dry brake caliper has the following features:

[0028] 1. The machining requirements for planetary roller screw assemblies are lower, which reduces costs. In a recirculating planetary roller screw, the screw shaft and nut are fitted together by rollers with ring grooves. With each rotation, the rollers disengage from the threads of the screw shaft and enter the inner grooves of the nut, whereupon the cams on both ends of the nut push the rollers back to their original axial position before rotation. The rollers then re-enter the raceway. During this process, the rollers must simultaneously align with the ring grooves of the rollers and multiple teeth on the nut before entering the raceway. Furthermore, because the rollers have difficulty entering the raceway under high-speed operating conditions, the processing and assembly requirements for the cams and nuts are very high, resulting in very high costs. In one embodiment of the present invention, the cams on both ends of the nut and the grooves on the sides of the nut are eliminated, allowing the rollers to enter the track without simultaneously engaging multiple teeth on the nut. Instead, a torsion spring is used to return the rollers to their original position, and the anti-rotation boss cooperates with the torsion spring to establish the initial position. The torsion spring and boss are manufactured using mature technology and are inexpensive, ensuring significant cost savings.

[0029] Next, the planetary roller screw of the present invention also inherits the advantages of the recirculating planetary roller screw, and the lead can be reduced to, for example, 1 mm, thereby reducing the input torque, thereby reducing the requirements for strength of the gear mechanism and reducing the volume of the motor and reduction mechanism, thereby reducing the overall volume and cost.

[0030] 2. The system can achieve both high load capacity and high transmission efficiency. The present invention has sliding friction during the idle stroke, which theoretically results in low transmission efficiency. However, since the idle stroke is used only to remove clearance or the output axial force is small, and the output power is equal to the product of the output axial force and the axial movement distance, the output power can be considered infinitesimal. This portion accounts for a small proportion when calculating the overall transmission efficiency and does not affect the response speed. Large output power is required only during the load phase, and since the operating method of the present invention uses rolling elements for transmission, its transmission efficiency is consistent with that of a planetary roller screw, adopting sliding friction during the idle stroke does not affect the overall transmission efficiency, thereby achieving high overall transmission efficiency. Furthermore, the present invention has the same operating method as a recirculating planetary roller screw and has a load-bearing capacity that cannot be exceeded by a ball screw.

[0031] 3. The roller ring groove can automatically adjust to the position according to the track. In this invention, the roller is composed of an annular groove and cylindrical ends on both sides of the annular groove. The roller is mounted in a holder. The holder is composed of two annular sections and a connecting section connecting the two annular sections. The annular sections have through holes, and the cylindrical ends of the roller and the through holes of the annular sections of the holder are loosely fitted with the shaft. In particular, the length of the annular groove of the roller is shorter than the shortest distance between the two annular sections of the holder, meaning that the roller has space to swing axially within the holder. At the same time, a small wave-shaped spring is installed between the end faces of the annular groove of the roller and the annular sections of the holder, so that the roller and the holder can be kept in a fixed position relative to each other in the absence of external force interference. During assembly of the planetary roller screw, the roller has a certain axial movement distance within the holder, allowing the annular groove of the roller to be adjusted to fit into the thread groove of the screw shaft or nut. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a structural schematic diagram of an electrically controlled mechanical dry brake caliper according to the present invention; [Figure 2] FIG. 2 is a structural schematic diagram of the planetary roller screw assembly of the present invention. [Figure 3] FIG. 1 is an exploded schematic view of a planetary roller screw assembly of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] In order to provide a better understanding of the present invention, the present invention will be described in more detail with reference to the following examples, which are merely for illustrative purposes and are not intended to limit the scope of the present invention.

[0034] As shown in FIG. 1 , this embodiment provides an electrically controlled mechanical dry brake caliper including a motor and a reduction mechanism, a planetary roller screw assembly 10, and a brake caliper assembly 11. The planetary roller screw module 10 is mounted within the cylinder bore of the brake caliper assembly 11. The output end of the motor is directly connected to the input end of the planetary roller screw assembly 10 or indirectly connected via a reduction / torque increase mechanism to transmit power output from the motor and reduction mechanism to the planetary roller screw assembly 10. The input end of the planetary roller screw assembly 10 may be a screw shaft or a nut. In this embodiment, the screw shaft is the input end and the nut is the output end. The nut 2 of the planetary roller screw assembly 10 engages with the output member of the brake caliper assembly 11. The output member is a brake pad. That is, the nut 2 of the planetary roller screw assembly 10 directly engages with the brake pad of the brake caliper assembly, eliminating the piston design of a conventional hydraulic brake system. The brake caliper assembly 11, motor and reduction gear are manufactured by conventional techniques.

[0035] As shown in FIGS. 2 and 3, FIGS. 2 and 3 are structural schematic diagrams of the planetary roller screw assembly in this embodiment.

[0036] The planetary roller screw assembly includes a screw shaft 1, a nut 2, and a roller 3 mounted between the screw shaft 1 and the threaded portion 2a of the nut 2. The gap between the annular groove 3b of the roller 3 and the threaded portion 2a of the nut 2 is smaller than the gap between the annular groove 3b of the roller 3 and the thread of the screw shaft 1. Therefore, under no-load conditions, the frictional force between the screw shaft 1 and the roller 2 is smaller than the frictional force between the nut 2 and the roller 3. If sliding occurs, it will inevitably be sliding between the screw shaft 1 and the roller 3. Both ends of the roller 3 are cylindrical ends 3a, which are smooth shafts. The middle of the roller 3 is an annular groove 3b, which is composed of multiple annular closed grooves, and the distance between adjacent annular closed grooves matches the thread pitch of the screw shaft 1 and the nut 2.

[0037] The roller 3 is attached to a holder 5. The holder 5 comprises a first annular portion 5a, a second annular portion 5c, and a connecting portion 5b connecting the first annular portion 5a and the second annular portion 5c. The holder 5 may be integrally formed or assembled from components. In this embodiment, ring grooves are provided on the outer wall surfaces of the first annular portion 5a and the second annular portion 5c of the holder 5. The connecting portion 5b is wrapped around the ring grooves on the outer wall surfaces of the first annular portion 5a and the second annular portion 5c and can be fixed by laser welding. The first annular portion 5a and the second annular portion 5c have a plurality of uniformly distributed through holes. The number of through holes corresponds to the number of rollers 3. The cylindrical end 3a of the roller 3 and the through holes in the annular portion of the holder 5 are loosely fitted to each other, allowing the roller 3 to rotate freely around its axis within the holder 5. The length of the annular groove 3b of the roller 3 is shorter than the shortest distance between the first annular portion 5a and the second annular portion 5c, i.e., the roller 3 has space to swing axially within the holder 5, and a small spring 6 is attached between the end face of the annular groove 3b of the roller 3 and the annular portion of the holder 5. This small spring 6 may be a wave spring, and is intended to maintain the relative position of the roller 3 and the holder 5. The damping effect produced by this wave spring is sufficiently small so as not to affect the rotational movement of the roller 3.

[0038] The planetary roller screw assembly 10 includes an anti-rotation mechanism 4, which is comprised of a pair of interlocking anti-rotation bosses: a first anti-rotation boss 4a and a second anti-rotation boss 4b. The first anti-rotation boss 4a is provided on the inner wall surface of the nut 2 and is assembled to the nut 2 or molded integrally therewith. The second anti-rotation boss 4b is provided on the end surface of the holder 5 and is assembled and connected to the holder 5 or molded integrally therewith. The position where the first anti-rotation boss 4a and the second anti-rotation boss 4b come into contact and engage with each other is the initial position of the holder 5 and the roller 3. The nut 2 is comprised of a threaded portion 2a having an internal thread and a return portion 2b having an internal space. The return portion 2b is located at the other end of the nut 2 opposite the one end of the first anti-rotation boss 4a, and is connected to the base 9 by threads. The end surface of the base 9 is designed circular, and the base 9 engages with the brake pad as the output end of the planetary roller screw assembly 10. A torsion spring 8 is provided in the internal space of the return portion 2b, and a boss is provided at each end of the torsion spring 8. One boss extends toward the center of rotation of the torsion spring 8 and is fixed to the holder 5 by welding, while the other boss extends away from the center of rotation of the torsion spring 8 and is fixed to the nut 2 by welding. The torsion spring 8 has a cylindrical cross section, and there is only one of them. When the holder 5 and roller 3 are in their initial positions, the torsion spring 8 is in a state of no elastic deformation or a state of slight elastic deformation; that is, the torsion spring 8 tries to push the holder 5 back to its initial position with the nut 2.

[0039] A guide portion 7 is provided on the outer wall of the nut 2. The guide portion 7 is a groove or boss that fits into a cylinder bore of a brake caliper assembly 11. In this example, the guide portion 7 is a groove on the outside of the nut 2, and at the same time, a threaded hole is provided on the inner wall of the cylinder bore of the brake caliper assembly 11. An anti-rotation screw passes through this threaded hole and enters the guide groove of the nut 2. Circumferential rotation of the nut 2 is restricted by the anti-rotation screw, and only linear movement is possible.

[0040] The nut 2 includes at least a cylindrical portion or a smooth transition portion, which fits into a rubber seal ring 13 of the brake caliper assembly to provide a seal. A seal cover 14 is provided between the end of the cylinder hole of the brake caliper assembly 11 and the nut 2 to prevent foreign matter from entering.

[0041] Working process: During the braking force generation process of the electrically controlled mechanical dry brake caliper, the motor and the reduction mechanism are operating, and the rotational motion of the motor and the reduction mechanism is transmitted to the planetary roller screw assembly 10. Then, the screw shaft 1 rotates in a first direction, and the threaded surface of the screw shaft 1 contacts the surface of the annular groove 3b of the rollers 3, causing the rollers 3 to share the load transmitted from the screw shaft 1. Because the gap between the rollers 3 and the screw shaft 1 is larger than the gap between the rollers 3 and the nut 2, the frictional force between the screw shaft 1 and the rollers 3 is smaller than the frictional force between the nut 2 and the rollers 3. At this time, the frictional force between the rollers 3 and the screw shaft 1 is sufficiently small that the rotational resistance force applied to the holder 5 by the torsion spring 8 exceeds the frictional force between the screw shaft 1 and the rollers 3. Therefore, the rollers 3 and the holder 5 do not change position relative to the nut 2. The rollers 3, the holder 5, and the nut 2 move as a whole toward the brake pad (the relationship between the rollers 3 and the screw shaft 1 corresponds to a sliding screw pair).

[0042] After the brake pads contact the brake disc, the system begins to generate a braking force, and the reaction force of the braking force is transmitted to the planetary roller screw assembly 10. As the axial force received by the nut 2 begins to increase, the axial force between the screw shaft 1 and the roller 3 similarly increases. When a certain axial force is reached, the roller 3 and holder 5 overcome the rotational resistance generated by the torsion spring 8, and the roller 3 begins to rotate within the holder 5 while rotating around the axis of the screw shaft 1. The torsion spring 8 is compressed and elastically deformed. At this time, the torque transmitted by the screw shaft 1 is converted into vertical movement of the nut 2, holder 5, and roller 3 via the threads of the screw shaft 1 and the annular groove 3b of the roller 3, and the annular groove 3b of the roller 3 and the threads of the nut 2 (achieving the function of a planetary roller screw). The nut 2 continues to press the base 9 and the brake pad, thereby clamping the brake disc and generating braking force (due to rolling friction, the friction coefficient is low and the transmission efficiency is high, allowing for a faster linear drive speed and higher output under the same conditions).

[0043] During the braking force release process of an electrically controlled mechanical dry brake caliper, the screw shaft 1 rotates in a second direction, opposite to the first direction. At the beginning of the release process, the roller 3 is still pressed by the screw shaft 1 and the nut 2. The relative motion between the screw shaft 1 and the nut 2 is generated by the rolling of the roller 3. This rolling friction results in a low friction coefficient and high transmission efficiency, enabling the clamping force to be released in a shorter time under the same conditions and faster release. The torsion spring 8 is always compressed, and even after the braking force is released, the torsion spring still has the elastic force to automatically return to its original position, where the second anti-rotation boss 4b of the screw shaft 5 and the first anti-rotation boss 4a of the nut 2 are in contact and engaged with each other. Furthermore, when rotation continues in the release direction, the friction moment between the screw 2 and the roller 3 is smaller than the moment generated by the engagement of the two bosses, and they still slide. This completes one operating cycle and prepares for the next.

[0044] The above example corresponds to the case where torque and rotational speed are input from the screw shaft and pressure is output by the nut. If torque and rotational speed are input from the nut and pressure is output from the screw shaft, the design will operate inversely to the above example.

[0045] The present invention has been described above by way of example with reference to the drawings. It is clear that the specific implementation of the present invention is not limited to the above-mentioned manner. Various insubstantial improvements made by adopting the methods, concepts and technical means of the present invention, or direct application of the above-mentioned concepts and technical means of the present invention to other situations without any improvements, are all within the scope of protection of the present invention. [Explanation of symbols]

[0046] 1 Screw shaft 2 nuts 2a Threaded part 2b Return section 3 Rollers 3a Cylinder end 3b Annular groove 4 Anti-rotation mechanism 4a First anti-rotation boss 4b Second anti-rotation boss 5 Holder 5a First annular section 5b Connection 5c Second annular section 6 Small springs 7 Guide section 8 Torsion spring 9. Base 10 Planetary Roller Screw Assembly 11 Brake caliper assembly 12 Guide screw 13 Seal ring 14 Seal cover

Claims

1. An electrically controlled mechanical dry brake caliper comprising: a motor and a reduction mechanism, a planetary roller screw assembly (10), and a brake caliper assembly (11), wherein the planetary roller screw assembly (10) is mounted in a cylinder bore of the brake caliper assembly (11), and the motor and the reduction mechanism are directly or indirectly connected to the planetary roller screw assembly (10), The planetary roller screw assembly (10) includes a screw shaft (1), a nut (2), and a roller (3) attached between the screw shaft (1) and the nut (2), the roller (3) is attached to a holder (5) located between the screw shaft (1) and the nut (2), and a torsion spring (8) is attached between the holder (5) and the nut (2); The nut (2) is provided with a first anti-rotation boss (4a), the holder (5) is provided with a second anti-rotation boss (4b) that fits the first anti-rotation boss (4a), and one side edge of the second anti-rotation boss (4b) of the holder (5) is brought into close contact with one side edge of the first anti-rotation boss (4a) of the nut (2) by the elastic force of the torsion spring (8), and this contact position is the initial position of the roller (3) and the holder (5); An electrically controlled mechanical dry brake caliper, characterized in that after any operating cycle, under no-load conditions, the roller (3) and the holder (5) are both in their initial positions.

2. 2. The electrically controlled mechanical dry brake caliper according to claim 1, wherein the first anti-rotation boss (4a) is provided on the inner wall of the nut (2), and the second anti-rotation boss (4b) is provided on the end face of the holder (5).

3. 3. The electrically controlled mechanical dry brake caliper according to claim 2, wherein the first anti-rotation boss (4a) is integrally formed with the nut (2), and the second anti-rotation boss (4b) is integrally formed with the holder (5).

4. 2. The electrically controlled mechanical dry brake caliper according to claim 1, wherein, within a single operating cycle, the initial position of the nut (2) relative to the screw shaft (1) and the initial position of the holder (5) relative to the nut (2) both move after a predetermined time.

5. 2. The electrically controlled mechanical dry brake caliper according to claim 1, wherein the holder (5) limits the circumferential position of the roller (3) and allows the roller (3) to rotate about its own axis within the holder (5).

6. 6. The electrically controlled mechanical dry brake caliper according to claim 5, wherein the holder (5) is composed of two annular portions and a connecting portion (5b) connecting the two annular portions, and the annular portions have uniformly distributed through holes.

7. 7. The electrically controlled mechanical dry brake caliper according to claim 6, wherein the roller (3) is an annular groove thread roller, the roller (3) is composed of an annular groove (3b) and cylindrical ends (3a) on both sides of the annular groove (3b), the cylindrical ends (3a) and the through holes of the annular parts of the holder (5) are clearance-fitted with the shaft and the hole, and the length of the annular groove (3b) is shorter than the shortest distance between the two annular parts of the holder (5).

8. 8. The electrically controlled mechanical dry brake caliper according to claim 7, wherein a small spring (6) is attached between the end face of the annular groove (3b) and the annular portion of the holder (5).

9. 2. The electrically controlled mechanical dry brake caliper according to claim 1, wherein the nut (2) includes an inner thread portion (2a) and a bottom end return portion (2b), the torsion spring (8) is attached to the internal space of the nut return portion (2b), the number of the torsion springs is at least one, and the torsion spring (8) is a spring that applies a torsional force.

10. 10. The electrically controlled mechanical dry brake caliper according to claim 9, wherein the return portion (2b) of the nut (2) is fixedly connected to a base (9), the end surface of the base (9) is circular or elliptical, the return portion (2b) and the base (9) are connected by screwing, welding or riveting, and the base (9) abuts against an end surface of a brake pad of a brake caliper assembly (11).

11. 10. The electrically controlled mechanical dry brake caliper according to claim 9, wherein the shape of the torsion spring (8) is flat, cylindrical or conical.

12. 2. The electrically controlled mechanical dry brake caliper according to claim 1, wherein the gap between the roller (3) and the nut (2) is smaller than the gap between the roller (3) and the threaded shaft (1), so that under no-load conditions, the friction force between the threaded shaft (1) and the roller (3) is smaller than the friction force between the nut (2) and the roller (3).

13. 2. The electrically controlled mechanical dry brake caliper according to claim 1, characterized in that the nut (2) has a guide portion (7) on its outer wall surface, the guide portion (7) being a groove or a boss, the guide portion (7) being fitted into a cylinder hole of the brake caliper assembly (11), and the nut (2) is restricted in the circumferential direction by the guide portion (7), thereby ensuring that the movement of the nut (2) is restricted to linear movement during operation.

14. 2. The electrically controlled mechanical dry brake caliper according to claim 1, wherein the nut (2) includes at least a cylindrical portion or a smooth transition portion that fits into a rubber seal ring (13) of the brake caliper assembly (11) to form a seal and prevent the intrusion of foreign matter.

15. 2. The electrically controlled mechanical dry brake caliper according to claim 1, wherein a seal cover (14) is attached between the cylinder hole end face of the brake caliper assembly (11) and the nut.

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