CN116771872A

CN116771872A - Linear driving mechanism

Info

Publication number: CN116771872A
Application number: CN202210223673.8A
Authority: CN
Inventors: 郭锋亮; 闫光辉; 朱元澄; 李运动; 王玉文
Original assignee: Wuhu Bethel Automotive Safety Systems Co Ltd
Current assignee: Wuhu Bethel Automotive Safety Systems Co Ltd
Priority date: 2022-03-09
Filing date: 2022-03-09
Publication date: 2023-09-19
Also published as: WO2023169413A1

Abstract

The application provides a linear driving mechanism, which belongs to the technical field of automobile transmission, wherein a retainer is of a split type independent structure and consists of a plurality of retainer units, and the manufacturing process of a single retainer is simple; the retainer is divided into a plurality of independent retainers, a single retainer can accommodate 2-15 rolling bodies, small springs are connected between the retainers during assembly, and elastic deformation of the small springs can accommodate screws and nuts adapting to different machining errors, so that clamping is avoided; the screw threads of the screw rod and the nut are zigzag threads, and the side angle of one side tooth is 3-10 degrees, so that high efficiency is ensured; the side angle of one side tooth is 30 degrees, so that high bearing capacity is guaranteed, and meanwhile, the space can be fully used.

Description

Linear driving mechanism

Technical Field

The application relates to the technical field of automobile transmission, in particular to a linear driving mechanism.

Background

In the prior art, there is a large proportion of mechanical transmission, and a linear driving mechanism is required to convert the rotary motion of an input end into the linear motion of an output end. For example, an electromechanical brake system of an automobile, power provided by a motor is generally transmitted to a linear driving mechanism through a speed-reducing and torque-increasing mechanism, and the linear driving mechanism converts rotary motion into linear motion of a connecting piece, and the connecting piece generates thrust on a brake pad and a brake disc, so that braking force is obtained. The linear drive mechanism is typically in the form of a conventional screw, a ball screw and a planetary roller screw.

Patent document CN113883245a proposes a linear driving mechanism, which adopts a cylindrical roller or tapered roller as an object bearing force between a screw and a nut, the screw and the nut have tooth shapes similar to those of a planetary roller screw, the thread teeth are symmetrical, and the tooth side angle is generally 45 degrees, and compared with a common screw, the linear driving mechanism adopts pure rolling instead of sliding in terms of transmission form, and can improve transmission efficiency; compared with a ball screw, in the aspect of a stress form, the linear contact stress is adopted to replace the point contact stress, so that the bearing capacity can be improved, and the transmission efficiency and the bearing capacity are both realized. Meanwhile, the patent proposes a retainer with an integral spiral structure, the retainer is arranged in a spiral space of a screw rod and a nut, the retainer can limit a roller, regular rolling of the roller is guaranteed, and the roller is prevented from excessively tilting, jamming and failure and the like.

Patent document CN113883196a discloses an application of such a roller linear drive mechanism to an electromechanical brake system of a vehicle. Compared with the point stress contact mode of the ball screw in the prior art, the roller linear driving mechanism adopting the cylindrical roller or the tapered roller has the advantages that the load is borne through the contact line, and the roller linear driving mechanism can provide larger bearing capacity for an electromechanical braking system, so that the roller linear driving mechanism can be used for commercial vehicles with severe bearing capacity requirements. Meanwhile, the arrangement mode of the rollers in the structure is that threads are arranged on one side, and in the working direction of the screw rod, the screw rod and the nut are driven by the rollers in the middle of the screw rod and the nut; when the screw rod is stressed in a non-working direction and is stressed in a non-working way, the screw rod is equivalent to a sliding screw rod, the screw rod is in direct contact with the nut and is in transmission, the characteristics of unidirectional stress of the linear driving mechanism when the vehicle brakes are met, and unnecessary functional redundancy is reduced.

The roller linear driving mechanism in the patent document fills the defect that the application in certain fields is difficult due to the insufficient bearing capacity of the ball screw or the high cost of the planetary roller screw in the prior art, and provides a new solution for the development and application of the transmission device.

However, the above patent still has some disadvantages: the cage in CN113883245a is a monolithic helical structure that is difficult to process using existing process technologies; risk of seizing easily occurs; the thread profile of CN113883245a is symmetrical, and the flank angle is typically 45 °, and under the electric braking condition of unidirectional stress, the asymmetrical profile is more advantageous. It is therefore important to solve the above problems.

Disclosure of Invention

In order to solve the problems, the application provides a linear driving mechanism, wherein a retainer is of a split type independent structure and consists of a plurality of retainer units, and the manufacturing process of a single retainer is simple; the retainer is divided into a plurality of independent retainers, a single retainer can accommodate 2-15 rolling bodies, small springs are connected between the retainers during assembly, and elastic deformation of the small springs can accommodate screws and nuts adapting to different machining errors, so that clamping is avoided; the screw threads of the screw rod and the nut are zigzag threads, and the side angle of one side tooth is 3-10 degrees, so that high efficiency is ensured; the side angle of one side tooth is 30 degrees, so that high bearing capacity is guaranteed, meanwhile, the space can be fully used, and the problem in the background technology is solved.

The application aims to provide a linear driving mechanism, wherein a spacing component comprises a retainer, a large spring I, a large spring II and rolling bodies;

the retainer comprises a plurality of retainers which are mutually connected in pairs, the retainer at the head end and the retainer at the tail end are respectively matched and installed with a spiral space formed by the external threads of the screw rod and the internal threads of the nut through a large spring I and a large spring II, and 2-15 rolling bodies are arranged in the retainer.

The further improvement is that: two adjacent retainers are connected through a small spring, and the small spring is fixedly connected or in contact connection with the retainers.

The further improvement is that: the external thread of the screw rod and the internal thread of the nut are zigzag threads; the flank angle of the tooth-shaped thread is 3-10 degrees, and the flank angle of one side is 30 degrees.

The further improvement is that: the retainer is of a fan-shaped annular structure, the rotation center of the retainer is located on the central axis of the screw rod and the nut, the inner diameter boundary of the retainer is matched with the small diameter boundary of the external screw thread of the screw rod, and the outer diameter boundary of the retainer is matched with the large diameter boundary of the internal screw thread of the nut.

The further improvement is that: 2-15 accommodating cavities are arranged in the fan-shaped plane of the retainer, the accommodating cavities accommodate rolling bodies, and the rolling bodies are matched with tooth shapes of zigzag threads; the retaining edges are arranged on two sides of the accommodating cavity, and ensure that the rolling bodies cannot fall off in a normal state, and the rolling bodies can freely rotate in the accommodating cavity.

The further improvement is that: the structure of the retainer along the circumferential direction is a plane or a spiral surface.

The further improvement is that: all the retainers are different or not different so as to be used for matching the spiral space formed by the external threads of the screw rod and the internal threads of the nut.

The further improvement is that: the rolling bodies are drum-type rollers, cylindrical rollers or tapered rollers.

The further improvement is that: the rolling bodies are cylindrical rollers or tapered rollers, and the end surfaces of the rolling bodies are subjected to tangent arc modification, logarithmic curve modification or Johns Gohar curve modification.

The further improvement is that: the number of the spacing components is one or more groups, and the spacing components are arranged on one side or two sides in a spiral space formed by the external threads of the screw rod and the internal threads of the nut.

The further improvement is that: the retainer is formed by injection molding or stamping or cold extrusion; when the rolling element is formed by injection molding, the rolling element can be formed into an imitation-shaped accommodating cavity by injection molding according to the shape of the rolling element; when the flange is formed by stamping or cold extrusion, flanges are stamped and formed on two sides of the accommodating cavity.

The application has the beneficial effects that: 1. the linear driving mechanism has more reliable and stable performance: the independent retainers are designed, the single retainer accommodates 2-15 rolling bodies, the retainers with the rolling bodies and the elastic pieces are sequentially arranged in a threaded space between the screw rod and the nut according to a spiral line, and the independent retainers are combined to form the spacing assembly.

In the prior art, the screw threads of the screw rod and the nut are generally formed through a cold extrusion or grinding process, and certain machining errors are unavoidable, so that the size of the rollaway nest is not completely consistent with the design state. In the application, small springs are arranged between every two retainers, the motion states of different retainer components are slightly inconsistent, and the small springs can be converted into small elastic stroke changes in the working process, so that the condition of clamping is avoided, and the difference of the motion states can enable the spacer components to adapt to screw rods or nuts with different processing errors, thereby improving the reliability of the mechanism.

The rolling body is arranged in a spiral space between the screw rod and the nut, rolls along the circumferential direction around the axis of the screw rod, and moves along a spiral line. The retainer is provided with a containing cavity for containing the rolling bodies, and flanges are arranged on two sides of the containing cavity, so that the rolling bodies can be prevented from falling off in a free state and can freely rotate in the retainer. Under the effect of the retainer, the length direction of the rolling body always points to the axis of the screw rod, and the rolling body always can be kept in a normal working state no matter under normal working conditions, wearing working conditions or high-load deformation working conditions, so that the reliability of the mechanism is improved.

2. The manufacturability of the retainer is improved, and the comprehensive cost can be further reduced: the retainer is of a split type independent structure and is composed of a plurality of retainer units, the retainer is of a fan-shaped annular structure, the structure along the circumferential direction can be a plane, a spiral surface or other shapes, the structure of the retainer is similar to that of a retainer of a thrust needle bearing, the manufacturing process is simple, the prior art can be referred to, and compared with the integral spiral retainer, the machining cost of the independent retainer is lower.

2-15 accommodating cavities are arranged in the fan-shaped plane of the retainer and are used for installing rolling bodies. When the retainer is manufactured through a stamping or cold extrusion process, the retaining sides can be reserved at the two ends of the accommodating cavity while the accommodating cavity is stamped, and the distance between the two corresponding retaining sides is smaller than the rolling diameter of rolling, so that the rolling bodies are prevented from falling off from the two sides of the accommodating cavity; when the retainer is manufactured through an injection molding process, a profiling cavity can be formed by injection molding according to the outline of the rolling body, sharp edges on two sides of the accommodating cavity are removed, and the rolling body is directly extruded into the accommodating cavity during assembly.

The installation of the spacing component can be realized by means of a tool similar to a screw, one end of the tool is detachably connected with the screw, the threads of the tool are matched with the threads of the nut, the nut is firstly fixed, the screw is connected with the tool, then the spacing component is arranged in the threads of the tool, the tool is rotated again, the tool drives the screw to rotate and brings the spacing component into the nut, and finally the connection between the tool and the screw is disconnected, so that the installation of the spacing component is completed.

3. The linear driving mechanism has enough bearing capacity and can further reduce the volume: compared with the tooth shape similar to a planetary roller screw rod selected by the screw rod in the patent CN212407487U, the tooth side angles of the screw rod and the nut are all 45 degrees, the screw rod and the nut in the application adopt zigzag threads, the tooth side angles of both sides of the zigzag threads are smaller than 45 degrees, and the tooth side angle of the non-bearing side is larger than the tooth side angle of the bearing side.

The zigzag thread has the advantages that: the pressure side tooth side angle of the non-bearing roller is 30 degrees generally, the larger the angle is, the larger the supporting capability can be provided for the bearing side, and the higher the structural strength is, but the tooth side angle can be properly reduced because the rolling body screw rod not only considers the structural strength but also needs to consider the contact strength; the spacing component is arranged on one side of the zigzag thread, the flank angle of which is 3-10 degrees, and under the condition of the same axial force, the contact stress is smaller than 45 degrees, so that the space between the screw rod and the nut can be increased, and the larger rolling body can be adapted, thereby increasing the contact area between the rolling body and the thread. Taking a cylindrical roller as an example, when the tooth flank angle of the screw rod is changed from 45 degrees to 10 degrees, and the contact length of the rolling body is increased from 2.5mm to 3mm, the contact stress is reduced by about 23% under the condition that other parameters are unchanged according to the Hertz contact stress formula, and the bearing capacity of the linear driving mechanism can be remarkably improved.

4. In the bearing capacity of the linear driving mechanism, the rolling bodies are cylindrical rollers such as cylindrical rollers, tapered rollers or drum rollers, and the like, and unlike balls, the contact mode of the cylindrical rollers and a screw or a nut in the transmission process is similar to line contact, and compared with the point contact of the ball screw, the line contact can bear larger load; simultaneously, the two end surfaces of the conical roller and the cylindrical roller can be subjected to modification treatment, and after the end surfaces of the cylindrical roller are modified according to tangent circular arcs, logarithmic curves or Johns Gohar curves, the influence of edge effect is further reduced, and the bearing capacity of the cylindrical conical roller can be further increased.

Drawings

Fig. 1 is a schematic structural view of a linear driving mechanism according to an embodiment.

Fig. 2 is a schematic view of a portion of a spacer assembly according to an embodiment.

Fig. 3 is a schematic structural view of a cage assembly of the embodiment.

Fig. 4 is a schematic structural view of the retainer according to the embodiment.

Fig. 5 is a schematic diagram of an electromechanical braking system of an embodiment.

Wherein: the brake caliper comprises a 1-lead screw, a 2-nut, a 3-interval component, a 4-elastic piece, a 4 a-big spring I, a 4b, a big spring II, a 4 c-small spring, a 5-rolling body, a 6-retainer, a 6 a-accommodating cavity, a 6 b-flange, a 7-retainer component, an 8-actuator, a 9-piston and a 10-brake caliper component.

Detailed Description

The present application will be further described in detail with reference to examples, which are provided for the purpose of illustration only and are not intended to limit the scope of the present application.

As shown in fig. 1, the present embodiment provides a linear driving mechanism, which comprises a screw 1, a nut 2 and a spacer assembly 3, wherein the spacer assembly 3 is arranged in a spiral space formed by an external thread of the screw 1 and an internal thread of the nut 2; the spacer 3 is mounted on the thread bearing side of the screw 1 and the nut 2, and inputs torque and rotation speed from the screw 1 and outputs pressure from the nut 2; the screw thread of the screw rod and the screw nut 1 adopts zigzag threads, the bearing roller pressure side tooth side angle of the screw rod 1 and the screw nut 2 is 3-10 degrees, and the non-bearing roller pressure side tooth side angle is 30 degrees.

As shown in fig. 2, the retainers 6 with the rolling bodies 5 are arranged in the spiral space of the screw rod 1 and the nut 2 in sequence by the small springs 4c in pairs to form a spacing assembly; the retainer 6 at the head end and the retainer 6 at the tail end are respectively matched and installed with a spiral space formed by the external thread of the screw rod 1 and the internal thread of the nut 2 through a first large spring 4a and a second large spring 4b, and the lengths of the first large spring 4a and the second large spring 4b can be inconsistent; the rolling bodies 5 are cylindrical rollers, and logarithmic curve modification treatment is carried out on two ends of each cylindrical roller.

As shown in fig. 3-4, the retainer 6 is in a sector annular structure, the rotation center of the retainer 6 is positioned on the central axis of the screw 1 and the nut 2, the inner diameter boundary of the retainer 6 is matched with the small diameter boundary of the external thread of the screw 1, and the outer diameter boundary of the retainer 6 is matched with the large diameter boundary of the internal thread of the nut 2;

the structure of the retainer 6 along the circumferential direction is a plane, the retainer is formed through a stamping process, three pairs of flanges 6b are reserved on two sides of the accommodating cavity 6a while the accommodating cavity 6a is formed, the distance between the corresponding flanges 6b on two sides of the accommodating cavity 6a is smaller than the rolling diameter of the rolling body 5, a single retainer 6 can form three accommodating cavities 6a for accommodating the three rolling bodies 5, the moving body 5 can freely rotate in the accommodating cavities 6a, and the rolling bodies 5 are matched with the tooth shapes of the zigzag threads.

As shown in fig. 5, the present embodiment provides an electromechanical brake system with the above-mentioned linear motion mechanism, wherein the actuator 8 is located at the input end of the linear drive mechanism, and the piston 9 cooperating with the nut 2 is located at the output end of the linear drive mechanism; the actuator 8 is a linear driving mechanism for inputting torque, the linear driving mechanism converts rotary motion into linear motion, and outputs pressure to the piston 9, and the actuator 8 and the brake caliper assembly 10 are both disclosed.

The working principle of the linear driving mechanism in the electromechanical brake of the embodiment is as follows:

the motor drives the reduction gear to rotate under the instruction of the controller, the rolling elements 5 of all cylindrical rollers roll on the threads of the screw 1 and the nut 2 while rotating in the accommodating cavity 6a of the retainer, the working surface matched with the rollers is the flank angle of 3-10 degrees, the included angle between the rollers and the axial force is small, the length is longer than that of the rollers with the flank angle of 45 degrees, and the contact stress is reduced by at least 23% in the working process of converting the rotary motion into the linear motion by the linear driving mechanism, so that the bearing capacity is improved; since the nut 2 is restricted from rotating in the circumferential direction, it does not rotate along with the screw 1, but is converted into linear motion according to a set lead according to the rotation angle of the screw 1, and moves in the working direction, thereby completing the function of the linear driving mechanism.

The motor drives the reduction gear to rotate under the instruction of the controller, the needle roller screw 1 is finally driven by the reduction mechanism to perform release action of the calipers, the output part of the gear transmits torque and rotation speed to the screw, the screw 1 rotates in a second direction opposite to the first direction, in the initial stage, under the condition that axial positive pressure exists, the tooth side angles of the screw 1 and the nut 2 are 3-10 degrees and are matched with rollers to work, the rollers roll, the resistance is small, and rapid release can be achieved; under the condition that the axial positive pressure disappears, the screw 1 and the nut 2 are in sliding motion through the side contact of the thread side angle of about 30 degrees, at the moment, the linear driving mechanism is equivalent to a common sliding screw, the nut moves towards the non-working direction, and the sliding relative rolling resistance is obviously increased; the resistance can cause an increase in current, thereby providing information to the electronic control system, and in addition, the resistance increases the blocking speed, which is beneficial to reducing unnecessary strokes, thereby preventing excessive actions of the electromechanical braking device; after the cylindrical roller is not pressed by the screw rod and the nut, the cylindrical roller returns to the initial state position under the action of the large spring and the small spring, and is ready for the next movement.

The above case is only for the case where the torque and the rotation speed are input from the screw and the pressure is output from the nut, and if the torque and the rotation speed are input from the nut, the design of the flank angle is opposite to the above case.

The application is described above by way of example with reference to the accompanying drawings. It will be clear that the application is not limited to the embodiments described above. As long as various insubstantial improvements are made using the method concepts and technical solutions of the present application; or the application is not improved, and the conception and the technical scheme are directly applied to other occasions and are all within the protection scope of the application.

Claims

1. The linear driving mechanism comprises a screw rod (1), a nut (2) and a spacing component (3), wherein the spacing component (3) is arranged in a spiral space formed by external threads of the screw rod (1) and internal threads of the nut (2);

the method is characterized in that: the spacing component (3) comprises a retainer (6), a first large spring (4 a), a second large spring (4 b) and rolling bodies (5);

the retainer (6) comprises a plurality of retainers which are mutually connected in pairs, the retainer (6) at the head end and the retainer (6) at the tail end are respectively matched and installed with a spiral space formed by the external threads of the screw rod (1) and the internal threads of the nut (2) through a big spring I (4 a) and a big spring II (4 b), and 2-15 rolling bodies (5) are arranged in the retainer (6).

2. A linear drive mechanism as claimed in claim 1, wherein: two adjacent retainers (6) are connected by a small spring (4 c).

3. A linear drive mechanism as claimed in claim 1, wherein: the external thread of the screw rod (1) and the internal thread of the nut (2) are zigzag threads; the flank angle of the tooth-shaped thread is 3-10 degrees, and the flank angle of one side is 30 degrees.

4. A linear drive mechanism as claimed in claim 3, wherein: the retainer (6) is of a fan-shaped annular structure, the rotation center of the retainer (6) is located on the central axis of the screw rod (1) and the nut (2), the inner diameter boundary of the retainer (6) is matched with the small diameter boundary of the external thread of the screw rod (1), and the outer diameter boundary of the retainer (6) is matched with the large diameter boundary of the internal thread of the nut (2).

5. A linear drive mechanism as claimed in claim 4, wherein: 2-15 accommodating cavities (6 a) are arranged in the fan-shaped plane of the retainer (6), the accommodating cavities (6 a) accommodate rolling bodies (5), and the rolling bodies (5) are matched with teeth of zigzag threads; the two sides of the accommodating cavity (6 a) are provided with flanges (6 b), the flanges (6 b) ensure that the rolling bodies cannot fall off in a normal state, and the rolling bodies (5) can freely rotate in the accommodating cavity (6 a).

6. A linear drive mechanism as claimed in claim 4, wherein: the structure of the retainer (6) along the circumferential direction is a plane or a spiral surface.

7. A linear drive mechanism as claimed in claim 1 or claim 5, wherein: the rolling bodies (5) are drum-type rollers, cylindrical rollers or tapered rollers.

8. A linear drive mechanism as claimed in claim 7, wherein: the rolling bodies (5) are cylindrical rollers or tapered rollers, and the end surfaces of the rolling bodies (5) are subjected to tangent arc modification, logarithmic curve modification or Johns Gohar curve modification.

9. A linear drive mechanism as claimed in claim 1, wherein: the number of the spacing components is one or more groups, and the spacing components are arranged on one side or two sides in a spiral space formed by the external threads of the screw rod (1) and the internal threads of the nut (2).