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 in particular 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, one form of which is a planetary roller screw, for converting the rotary motion of a drive motor and a reduction gear into linear motion of a connected part.

[0003] Prior art planetary roller screws are generally classified as follows:

[0004] Standard planetary roller screw: The screw shaft and the nut are engaged by multiple threaded rollers, and this structure places very high requirements on the dimensions and geometric tolerances of the parts. If the precision of the parts does not meet the requirements even slightly, interference may occur and cause malfunction, so 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] Reversing Planetary Roller Screw: The structure and principle are almost the same as for a standard planetary roller screw, but it differs in that the torque and rotational speed are transmitted by the nut, and the axial force is transmitted by the screw shaft.

[0006] Circulating planetary roller screw: The rollers are provided with multiple sets of annular grooves, and the distance between the grooves is adapted to the thread. With each rotation, the rollers leave the thread of the screw shaft and enter the inner groove of the nut, and are then pushed back to their original axial position before rotation by the cams on both ends of the nut. After that, the rollers enter the track of the screw shaft and the nut again. During the process of entering the track, the annular grooves of the rollers are simultaneously aligned with the multiple teeth of the nut before entering the track, which places high requirements on the processing and assembly of the cams and nuts, resulting in very high costs. In addition, it is difficult to properly mesh the multiple teeth of the rollers and the nut under high-speed operating conditions.

[0007] Differential planetary roller screw: The structure is simpler and it can withstand a higher load with the same volume and weight. In addition, it has the advantages of a higher input rotation speed, a smaller lead, and a larger reduction ratio. However, it has the disadvantages of sliding problems occurring in the thread meshing area of ​​the screw shaft, making the transmission ratio unstable, and causing severe wear under heavy loads, resulting in reduced precision and low reliability.

[0008] As described above, the planetary roller screw according to the conventional technology has 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 large loads, making them difficult to apply to automotive safety systems. Summary of the Invention

[0011] In order to solve the above problems, the present invention provides an electrically controlled mechanical dry brake caliper, which includes a motor and a speed reducing 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 reducing mechanism are directly or indirectly connected to the planetary roller screw assembly. The planetary roller screw assembly includes a screw shaft, a nut, and a roller mounted between the screw shaft and the nut, the roller is mounted on a holder located between the screw 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 anti-rotation bosses that match each other, and one side of the anti-rotation boss of the holder is tightly attached to one side of the anti-rotation boss of the nut by the elastic force of the torsion spring. This tightly attached position is the initial position of the roller and the holder. After any working cycle, under no-load conditions, both the roller and the holder are in their initial positions.

[0012] In a further refinement, the rollers are annular groove thread rollers, the rollers being mounted in a holder that limits the circumferential position of the rollers and allows them to rotate within the holder about their own axis. Within a single operating cycle, the initial position of the nut relative to the threaded 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 parts and a connecting part b connecting the two annular parts, and the annular parts 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, the cylindrical ends a and the through holes of the annular parts of the holder are clearance-fitted with the shaft and the hole, the length of the annular groove b is smaller than the shortest distance between the two annular parts of the holder, and a small spring is attached between the end face of the annular groove b and the annular parts of the holder. The small spring is a wave spring.

[0014] As a further refinement, 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 springs is at least one, the torsion spring is a spring that exerts 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 screwing, 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 manner.

[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, the guide portion being a groove or a boss, the guide portion being 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 motion during the actuation process.

[0019] As a further refinement, the nut includes at least a partially cylindrical portion or smooth transition portion that fits within a rubber seal ring of 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 releasing motion of the brake caliper. A normal operating cycle includes a clamping phase, a load phase, and a release phase.

[0022] The clamping step includes the following: Idle stroke stage: In this stage, the planetary roller screw operates and presses the brake pad, so that the gap between the brake pad and the brake disc disappears. The gap between the roller and the nut is smaller than the gap between the roller and the screw shaft, so that in this process, the friction moment between the screw shaft and the roller is smaller than the moment applied by the torsion spring, and the screw shaft slides on the roller without any relative movement between the roller and the nut. The advantage of this configuration is that, under the same load conditions, the operating stroke of the nut is shorter than the rolling motion in the idle stroke, and the cost of the nut can be reduced by shortening the length of the nut. It should be noted that the axial force is zero in this stage, so the friction force is very small, whether it is sliding friction or rolling friction, and the difference is negligible.

[0023] Load stage: After the axial clearance is removed, the brake pad and the caliper body of the caliper begin to deform, and the reaction force caused by this deformation acts on the planetary roller screw, and 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 working principle is the same as that of the circulating planetary roller screw, and it has high transmission efficiency and high load-bearing capacity at the same time. In addition, because the groove and cam on the nut are removed, the motion becomes more continuous, which can adapt to high rotation speeds and meet the response time requirements of the brake system.

[0024] During the load phase, there is a stroke limit in the brake system, 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 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 rapid 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 roller and holder return to their initial positions due to the elastic force of the torsion spring. 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, providing an effect equivalent to that of a sliding screw. Effect 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 the planetary roller screw assembly are lower, which reduces the cost. In a recirculating planetary roller screw, the screw shaft and the nut are fitted with rollers with multiple ring grooves. With each rotation, the rollers leave the threads of the screw shaft and enter the inner grooves of the nut, and the cams on both ends of the nut push the rollers back to their initial axial position before rotation. The rollers then enter the track again. In the process of entering the track, the rollers' ring grooves can be aligned with multiple teeth on the nut at the same time before entering the track. In addition, under a high-speed rotation operating environment, it is difficult for the rollers to enter the track, so the requirements for processing and assembly of the cams and nuts are very high, and the costs are very high. In this embodiment of the present invention, the cams on both ends of the nut and the grooves on the sides of the nut are eliminated, and the rollers can enter the track without simultaneously matching multiple teeth on the nut. Instead, a torsion spring is used to return the rollers to their original position and cooperate with the anti-rotation boss to determine the initial position. The torsion spring and boss have mature manufacturing technology and low cost, which ensures a significant cost reduction.

[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 to reduce the input torque, which reduces the requirements for the strength of the gear mechanism and reduces the volume of the motor and reduction mechanism, thereby reducing the overall volume and cost.

[0030] 2. The system achieves both high load capacity and high transmission efficiency. The present invention has sliding friction during the idle stroke, and theoretically has low transmission efficiency. However, the idle stroke is only used to remove the gap, 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, so the output power can be considered to be infinitesimal. When calculating the overall transmission efficiency, the proportion of this part is small and does not affect the response speed. It is necessary to output a large output power only in the load stage, and at this time, the operating method of the present invention is transmission by rolling elements, and the transmission efficiency is consistent with that of the planetary roller screw, so the adoption of sliding friction during the idle stroke does not affect the overall transmission efficiency, and achieves a high overall transmission efficiency. In addition, the present invention has the same operating method as the circulating planetary roller screw, and has a load-bearing capacity that cannot be exceeded by the ball screw.

[0031] 3. The roller ring groove can automatically adjust to the position according to the track. In the present invention, the roller is composed of an annular groove and cylindrical ends on both sides of the annular groove, the roller is mounted on a holder, the holder is composed of two annular parts and a connecting part connecting the two annular parts, the annular parts have a through hole, and the cylindrical end of the roller and the through hole of the annular part of the holder are fitted with a shaft and a hole. In particular, the length of the annular groove of the roller is smaller than the shortest distance between the two annular parts of the holder, that is, the roller has a space to swing axially in the holder. At the same time, a wave-shaped small spring is installed between the end face of the annular groove of the roller and the annular part of the holder, so that the roller and the holder can be kept in a relatively fixed position when there is no interference of external force. During the assembly of the planetary roller screw, the roller has a certain axial movement distance in the holder, so that the ring groove of the roller can be adjusted to a position that fits with the screw shaft or the screw groove of the nut. [Brief description of the drawings]

[0032] [Figure 1] FIG. 2 is a structural schematic diagram of the electric controlled mechanical dry brake caliper of the present invention. [Diagram 2] FIG. 2 is a structural schematic diagram of the planetary roller screw assembly of the present invention. [Diagram 3] FIG. 2 is an exploded schematic view of the planetary roller screw assembly of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 the purpose of illustrating the present invention 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 in a 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 and torque increase mechanism, to transmit the power output from the motor and the 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, and 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 is engaged 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 is directly engaged with the brake pad of the brake caliper assembly, and the piston design of the conventional hydraulic brake system is not performed. The brake caliper assembly 11, the motor and the reduction gear are manufactured by conventional techniques.

[0035] As shown in FIG. 2 and FIG. 3, FIG. 2 and FIG. 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, so that the frictional force between the screw shaft 1 and the roller 2 under no-load conditions is smaller than the frictional force between the nut 2 and the roller 3. When sliding occurs, the sliding is inevitably between the screw shaft 1 and the roller 3. Both ends of the roller 3 are cylindrical ends 3a, and the cylindrical ends are smooth shafts. In addition, the middle of the roller 3 is an annular groove 3b, which is composed of a plurality of annular closed grooves, and the distance between adjacent annular closed grooves is adapted to the thread pitch of the screw shaft 1 and the nut 2.

[0037] The roller 3 is attached to the holder 5, which is composed of 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, and the holder 5 is formed integrally or assembled from parts. 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, and 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 through holes uniformly distributed. The number of through holes is the same as the number of rollers 3. The cylindrical end 3a of the roller 3 and the through holes of the annular portion of the holder 5 are fitted with a gap between the shaft and the hole, and the roller 3 is freely rotatable around the axis of the roller 3 within the holder 5. The length of the annular groove 3b of the roller 3 is smaller than the shortest distance between the first annular portion 5a and the second annular portion 5c, i.e., the roller 3 has a 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 caused by this wave spring is sufficiently small and does not affect the rotational motion of the roller 3.

[0038] The planetary roller screw assembly 10 includes an anti-rotation mechanism 4, which is comprised of a pair of first and second anti-rotation bosses 4a and 4b that engage with each other. 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 is integrally molded with the nut 2. The second anti-rotation boss 4b is provided on the end surface of the holder 5, and is assembled to and connected to the holder 5 or is integrally molded with the holder 5. The position where the first anti-rotation boss 4a and the second anti-rotation boss 4b come into contact with each other and engage with each other is the initial position of the holder 5 and the roller 3. The nut 2 includes a threaded portion 2a having a female 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 to the one end of the first anti-rotation boss 4a, and the return portion 2b is connected to the base 9 by a thread. The end surface of the base 9 is designed to be 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 bosses are provided at both ends of the torsion spring 8. One boss extends toward the rotation center of the torsion spring 8 and is fixed to the holder 5 by welding, and the other boss extends in a direction away from the rotation center of the torsion spring 8 and is fixed to the nut 2 by welding. The cross section of the torsion spring 8 is cylindrical, and there is one of them. When the holder 5 and the roller 3 are in the initial position, the torsion spring 8 is also in a state of no elastic deformation or a state of slight elastic deformation, that is, the torsion spring 8 is in a state of trying to push the holder 5 back to the 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 a boss, and the guide portion 7 fits into a cylinder hole 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 hole of the brake caliper assembly 11. An anti-rotation screw passes through this threaded hole and enters the guide groove of the nut 2, and the rotation of the nut 2 in the circumferential direction is limited 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 sealing effect. 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 the intrusion of foreign matter.

[0041] Working process: In the process of generating the braking force of the electrically controlled mechanical dry brake caliper, the motor and the reduction mechanism are operated, 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 along the first direction, and the threaded surface of the screw shaft 1 contacts the surface of the annular groove 3b of the roller 3, and the rollers 3 share the load transmitted from the screw shaft 1. Since the gap between the roller 3 and the screw shaft 1 is larger than the gap between the roller 3 and the nut 2, the frictional force between the screw shaft 1 and the roller 3 is smaller than the frictional force between the nut 2 and the roller 3. At this time, the frictional force between the roller 3 and the screw shaft 1 is sufficiently small, and the rotational resistance force applied by the torsion spring 8 to the holder 5 exceeds the frictional force between the screw shaft 1 and the roller 3, so that the position of the roller 3 and the holder 5 does not change relative to the nut 2. The roller 3, the holder 5, and the nut 2 move in the direction of the brake pad as a whole (the gap between the roller 3 and the screw shaft 1 corresponds to a sliding screw pair).

[0042] After the brake pads contact the brake disc, the system starts to generate a braking force, and the reaction force of the braking force is transmitted to the planetary roller screw assembly 10. When the axial force received by the nut 2 starts to increase, the axial force between the screw shaft 1 and the roller 3 increases as well. When a certain axial force is reached, the roller 3 and the holder 5 overcome the rotational resistance force generated by the torsion spring 8, and the roller 3 starts to rotate within the holder 5 while rotating around the axis of the screw shaft 1, and the torsion spring 8 is compressed and elastically deformed. At this time, the torque transmitted by the screw shaft 1 is converted into the vertical movement of the nut 2, the holder 5, and the roller 3 through 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 (performing the action of a planetary roller screw). The nut 2 continues to press the base 9 and the brake pad, thereby clamping the brake disc and obtaining braking force (because it is rolling friction, the friction coefficient is low and the transmission efficiency is high, so that a faster linear drive speed and higher output can be obtained under the same conditions).

[0043] In the braking force release process of the electric control mechanical dry brake caliper, the screw shaft 1 rotates along the second direction. The second direction is 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 of the screw shaft 1 and the nut 2 is generated by the rolling of the roller 3. Since this is rolling friction, the friction coefficient is low, the transmission efficiency is high, and under the same conditions, the clamping force can be released in a shorter time and quick release is possible. The torsion spring 8 is always in a compressed state, and even after the braking force disappears, the torsion spring still has an elastic force to automatically return, and the elastic force of the torsion spring 8 causes the holder 5 and the roller 3 to automatically move in a track until they return to their initial positions, that is, the position where the second anti-rotation boss 4b of the holder 5 and the first anti-rotation boss 4a of the nut 2 contact and engage with each other. Furthermore, when continuing to rotate 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 still slides. This completes one operating cycle and prepares for the next.

[0044] The above example corresponds to the case where torque and rotation speed are input from the screw shaft and pressure is output by the nut. If torque and rotation speed are input from the nut and pressure is output from the screw shaft, the design will operate in the opposite manner 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 realization of the present invention is not limited to the above manner. Any insubstantial improvements made by adopting the methods, concepts and technical means of the present invention, or directly applying the above 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. Roller 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), the planetary roller screw assembly (10) being mounted in a cylinder bore of the brake caliper assembly (11), the motor and the reduction mechanism being 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 a torsion spring (8), this contact position being 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, characterized in that the first anti-rotation boss (4a) is provided on an inner wall of the nut (2), and the second anti-rotation boss (4b) is provided on an end face of the holder (5).

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

4. The electrically controlled mechanical dry brake caliper according to claim 1, characterized in that 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. An electrically controlled mechanical dry brake caliper as claimed in claim 1, characterized in that 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. The electrically controlled mechanical dry brake caliper according to claim 5, characterized in that 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. The electrically controlled mechanical dry brake caliper according to claim 6, characterized in that 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. An electrically controlled mechanical dry brake caliper as claimed in claim 7, characterized in that a small spring (6) is attached between the end face of the annular groove (3b) and the annular part of the holder (5).

9. 2. The electrically controlled mechanical dry brake caliper according to claim 1, characterized in that the nut (2) includes an inner threaded portion (2a) and a bottom end return portion (2b), the torsion spring (8) is mounted in 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 exerts a torsional force.

10. The electrically controlled mechanical dry brake caliper according to claim 9, characterized in that the return portion (2b) of the nut (2) is fixedly connected to a base (9), an 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. An electrically controlled mechanical dry brake caliper as claimed in claim 9, characterized in that the shape of the torsion spring (8) is flat, cylindrical or conical.

12. The electrically controlled mechanical dry brake caliper according to claim 1, characterized in that 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. The electrically controlled mechanical dry brake caliper according to claim 1, characterized in that the nut (2) is provided on its outer wall surface with a guide portion (7), which is a groove or a boss, and the guide portion (7) is 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 the operation process.

14. 2. The electrically controlled mechanical dry brake caliper according to claim 1, characterized in that 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 (11) to form a seal and prevent the ingress of foreign matter.

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

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