Transmission system for vehicle electromechanical brakes and method for distributing loads uniformly

Abstract

A planetary roller drive system for an electromechanical braking module. The planetary roller drive system includes a roller screw having a screw thread formed on its outer surface. The system also includes a plurality of rollers, each having a roller thread formed on its outer surface, the roller thread threading into the screw thread, wherein, in an unloaded state, at least one of the screw thread and the roller thread has a non-uniform pitch. The system further includes a nut having a cylindrical body with an inner wall defining a nut thread formed thereon, the nut thread threading into the screw thread.

Description

Technical Field

[0001] This disclosure relates to vehicle braking systems, and more particularly to a transmission system for electromechanical brakes and a method for uniformly distributing loads within the transmission system. Background Technology

[0002] Electromechanical brakes (EMB) are an advanced automotive braking technology that combines electronic and mechanical technologies to provide a more efficient and environmentally friendly braking solution. EMB eliminates the hydraulic system found in electro-hydraulic braking systems, replacing it with a motor-driven brake actuator that acts directly on the brake disc or brake pad. Each brake on each wheel is equipped with an electric motor, and the motor's action is controlled by an electrical signal sent from a control unit, thus achieving braking. This method avoids the influence of the PV characteristics of hydraulic systems on response speed, improving response speed. It features a simple structure, flexible control, and high efficiency, achieving complete decoupling between the driver and the vehicle, making it a brake-by-wire system.

[0003] Electromechanical brakes may require a transmission system to transfer motion from the input actuator to the braking mechanism. For example, commercially available transmission devices may include planetary roller screw assemblies. In such assemblies, multiple rollers surround a portion of a roller screw to transmit motion to a nut. The threaded pair relationship between the rollers and the roller screw typically utilizes components with equal pitch. However, during actual use, differences in axial deformation occur due to variations in the stiffness of the components. This causes a difference between the actual contact of the thread teeth and the simultaneous contact considered during design. In areas of high axial deformation within the screw section, the contact stress of the thread teeth is high and wears rapidly, shortening the service life of the threaded pair and associated components. Summary of the Invention

[0004] According to one aspect of this disclosure, a planetary roller drive system for an electromechanical braking module is provided. The planetary roller drive system includes a roller screw having a screw thread formed on its outer surface. The planetary roller drive system also includes a plurality of rollers, each having a roller thread formed on its outer surface, the roller thread threading into the screw thread, wherein, in the unloaded state of the planetary roller drive system, at least one of the threads and the roller threads has a non-uniform pitch. The planetary roller drive system also includes a nut having a columnar body with an inner wall defining a nut thread formed thereon, the nut thread threading into the screw thread.

[0005] According to another aspect of this disclosure, a vehicle electromechanical braking system includes a brake pedal unit and an electric drive motor electrically connected to the brake pedal unit. The braking system also includes a braking module operatively coupled to the electric drive motor. The braking module includes a roller screw having a screw thread formed on its outer surface. The braking module also includes a plurality of rollers, each having a roller thread formed on its outer surface, the roller thread threading into the screw thread, wherein, in the unloaded state of the planetary roller drive system, at least one of the threads and the roller thread has a non-uniform pitch. The braking module also includes a nut having a columnar body with an inner wall defining a nut thread formed thereon, the nut thread threading into the screw thread.

[0006] According to another aspect of this disclosure, a method for manufacturing a planetary roller drive system for an electromechanical braking module is provided. The method includes manufacturing a roller screw having a screw thread formed on the outer surface of a lead screw, wherein the screw thread has an original lead screw thread profile. The method also includes manufacturing rollers having roller threads formed on the outer surface of rollers, wherein the roller threads have an original roller thread profile. The method further includes shaping at least one of the original lead screw thread profile and the original roller thread profile to form a non-uniform pitch.

[0007] These and other advantages and features will become more apparent from the following description taken in conjunction with the accompanying drawings. Attached Figure Description

[0008] The subject matter considered to be in this invention is specifically pointed out and explicitly claimed in the appended claims. The foregoing and other features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings: Figure 1 The illustration shows a vehicle equipped with an electromechanical braking system.

[0009] Figure 2 It is an exploded 3D view of the transmission system of the electromechanical braking system.

[0010] Figure 3 This is a cross-sectional view of a part of the transmission system.

[0011] Figure 4A It is a cross-sectional view of the threaded pair of the transmission system, showing the formed teeth in the unloaded state of the transmission system.

[0012] Figure 4B It is a cross-sectional view of the threaded pair of the transmission system, showing the formed teeth under load in the transmission system.

[0013] Figure 5This is a flowchart illustrating a method for manufacturing a planetary roller screw assembly for a transmission system. Detailed Implementation

[0014] The following discussion pertains to various embodiments of this disclosure. While one or more of these embodiments may be described in more detail than others, the disclosed embodiments should not be construed as or otherwise used to limit the scope of this disclosure (including the claims). Furthermore, those skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is merely an example of that embodiment and is not intended to imply that the scope of this disclosure (including the claims) is limited to that embodiment.

[0015] Reference Figure 1 The diagram schematically illustrates an electromechanical braking (EMB) system, generally indicated by reference numeral 10. The EMB system 10 is part of a wheeled vehicle 12. A battery 14, an EMB pedal 16 with an ECU, an EMB module 18, and one or more sensors 19 are in electrical communication with the signal.

[0016] Each wheel configured to have a braking effect applied thereto includes a corresponding EMB module 18. The EMB module 18 includes a drive motor 20. Figure 2 The drive motor 20 is equipped with a deceleration and torque amplification device (not shown) and a transmission system 30. The EMB controller 32 controls the rotation of the drive motor 20, while the transmission system 30 converts the rotational motion into translational motion, thereby converting the torque through the deceleration and torque amplification device into a squeezing braking force that pushes the brake disc pads to achieve a braking effect.

[0017] During operation, when the driver presses the EMB pedal 16, sensor 19 activates. Sensor 19 monitors parameters such as vehicle speed, acceleration, steering angle, and wheel speed. This data is transmitted to the ECU in real time to provide the ECU with precise information about the vehicle's current state. The ECU receives data from sensor 19 and calculates the required braking force based on this data and other factors such as vehicle weight, road conditions, and driving mode. The ECU is also responsible for adjusting the braking force distribution to ensure vehicle stability during braking, especially during emergency braking or cornering. Once the ECU has calculated the required braking force, it instructs the EMB module 30 to provide appropriate assistance. The EMB module responds quickly to provide precise assistance to help the driver achieve the desired braking effect. Based on the ECU's instructions, the EMB module mechanically controls the opening and closing of the brakes to apply braking force directly to the brakes, eliminating the need for a hydraulic system and reducing issues related to leaks and maintenance.

[0018] Now refer to Figure 2 and Figure 3 The transmission system 30 of the EMB module 18 is shown in detail. Figure 2 The transmission system 30 is shown in a disassembled state, and Figure 3 A transmission system 30 in an assembled state is shown. The transmission system 30 includes a planetary roller screw assembly. Specifically, the transmission system 30 includes a screw 40, a plurality of rollers 42, a retaining frame 44, and a nut 46. The screw 40 rotates based on the rotation of the output shaft (not shown) of a drive motor 20. The screw 40 has a threaded pattern 50 on a portion of its outer surface, which threadedly engages with a corresponding threaded pattern 52 of each roller 42. The rollers 42 surround a portion of the outer surface of the screw 40. The threaded patterns 52 of the rollers 42 also threadedly engage with threaded patterns 54 on the inner surface of the nut 46.

[0019] The lead screw 40 is axially constrained to rotate only and remain axially fixed. Rotation of the lead screw 40 causes axial movement of the nut 46 via an intermediate roller 42. Axial movement of the nut 46 provides braking force to the brake disc pad directly by means of a piston 58 formed on the end of the nut 46 or by pressing against an intermediate component disposed between the nut 46 and the brake disc pad. The piston 58 may be integrally formed with the nut 46 or may be operably coupled to it as a separate structural component.

[0020] The number of rollers 42 can vary depending on the application, but in some embodiments of the EMB module 18, five (5) to eight (8) rollers can be provided. The rollers 42 are fitted into the openings of the retaining frame 44. The retaining frame 44 is a single, integrally molded structure, which can improve the positioning accuracy of the rollers 42, reduce the deflection of the rollers 42, and improve the motion stability of the rollers 42. In some embodiments, the retaining frame 44 can be made by powder metallurgy or metal injection molding processes, which can effectively reduce mass production costs.

[0021] Now refer to Figure 4A and Figure 4B The diagram illustrates the threaded relationship of components that are part of the transmission system 30. In particular, the threaded area of ​​the lead screw 40 and one of the rollers 42 are shown. Figure 4A The threaded pair in an unloaded state of engagement of the lead screw 40 is shown. Figure 4B The diagram illustrates a threaded pair in engagement under load of the leadscrew 40. Under load of the leadscrew 40, an axial force is applied to the assembly, as indicated by arrow F. The force F, representing the force along the axial direction of the leadscrew 40, causes different axial deformations on the individual teeth within the engagement region between the leadscrew 40 and the roller 42. Therefore, while existing threaded regions are manufactured and assembled with teeth of equal pitch to meet design requirements, the axial force F under load causes the aforementioned different axial deformations on the teeth.

[0022] In the embodiments disclosed herein, the lead screw 40 has teeth 60 that engage with the teeth 62 of the roller 42. One or two sets of teeth 60, 62 are shaped to compensate for axial deformation that occurs under load on the lead screw 40. Thus, after the manufacturing forming process, the teeth 60 and / or teeth 62 do not have uniform equal pitch. Specifically, the teeth 60 have relatively non-uniform pitch, the teeth 62 have non-uniform pitch, or both teeth 60 and teeth 62 have non-uniform pitch. Figure 4A The unloaded state shows at least some clearance between teeth 60 and 62. Once in Figure 4B When an axial force F is applied under load, teeth 60 and 62 engage to meet design standards for performance and service life. The embodiments disclosed herein ensure that the planetary roller screw 40 achieves the desired load distribution (e.g., uniform distribution) and is also easily achievable in actual machining.

[0023] The final forming of teeth 60 and / or 62 is based on calculated values ​​of the actual segment stiffness of the leadscrew 40, the amount of axial deformation (or tensile deformation) of each segment under load, and a functional expression for controlling the pitch of teeth 60 and / or 62. Under different actual operating conditions, the leadscrew 40 can be modified on one side, the roller 42 can be modified on one side, or the roller 42 can be modified on both sides. By controlling the amount of deformation, the threaded pair of the leadscrew 40 and roller 42 can have a uniform load condition under actual operating conditions. The forming of teeth 60 and / or 62 compensates for the deformation of the axial segment of the leadscrew 40 by changing the threaded pair, thereby providing a uniformly distributed thread load model under actual load conditions.

[0024] Figure 5 The method for manufacturing a planetary roller screw assembly for the transmission system 30 disclosed herein is generally illustrated. Specifically, boxes at reference numeral 100 denote steps for manufacturing the screw 40 and roller 42. Initial manufacturing includes manufacturing the original tooth profiles of teeth 60 and 62 of the screw 40 and roller 42, respectively. However, tooth profiles with equal pitch cause the problems described herein. Box 102 denotes the step of calculating the segment stiffness values ​​of the screw 40, and box 104 denotes the calculation of the amount of axial deformation (or tensile deformation) of each segment. Functional expressions based on these values ​​are used to control the pitch of teeth 60 and / or 62. Box 106 denotes the formed teeth of the screw 40 and / or roller 42 based on the aforementioned functional expressions.

[0025] By utilizing the method of forming thread pairs as described above to provide teeth 60 and / or 62 with uneven pitch, a more efficient and reliable use of the planetary roller screw assembly is achieved, while extending the service life of components within the transmission system 30.

[0026] Although the invention has been described in detail with reference to only a limited number of embodiments, it is readily understood that the invention is not limited to these disclosed embodiments. Rather, the invention can be modified to include any number of variations, alterations, substitutions, or equivalent arrangements not previously described but commensurate with the spirit and scope of the invention. Furthermore, while various embodiments of the invention have been described, it should be understood that aspects of the invention may include only some of the embodiments described. Therefore, the invention should not be considered as limited to the foregoing description.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that data used in this manner can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those described or illustrated herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatuses.

Claims

1. A planetary roller transmission system for an electromechanical braking module, the transmission system comprising: A roller screw has a screw thread formed on the outer surface of the screw; A plurality of rollers, each having a roller thread formed on its outer surface, the roller thread engaging with a leadscrew thread, wherein, in the unloaded state of the planetary roller drive system, at least one of the leadscrew thread and the roller thread has a non-uniform pitch; and A nut having a columnar body having an inner wall defining a nut thread formed thereon, the nut thread engaging with a lead screw thread, wherein the nut and the plurality of rollers are axially fixed relative to each other.

2. The planetary roller transmission system according to claim 1, wherein, The lead screw thread has an uneven pitch.

3. The planetary roller transmission system according to claim 1, wherein, The roller thread has an uneven pitch.

4. The planetary roller transmission system according to claim 1, wherein, The lead screw thread and the roller thread each have uneven pitch.

5. The planetary roller transmission system according to claim 1, wherein, The nut has a piston that is integrally formed to the end of the column.

6. The planetary roller transmission system according to claim 1, wherein, The nut has a piston that is operatively coupled to the end of the column.

7. An electromechanical braking system for a vehicle, comprising: Brake pedal unit; An electric drive motor is electrically connected to the brake pedal unit; as well as A braking module, operably coupled to the electric drive motor, the braking module comprising: A roller screw has a screw thread formed on the outer surface of the screw; A plurality of rollers, each having a roller thread formed on its outer surface, the roller thread engaging with a leadscrew thread, wherein, in the unloaded state of the planetary roller drive system, at least one of the leadscrew thread and the roller thread has a non-uniform pitch; and A nut having a columnar body having an inner wall defining a nut thread formed thereon, the nut thread engaging with a lead screw thread.

8. The vehicle electromechanical braking system according to claim 7, wherein, The lead screw thread has an uneven pitch.

9. The vehicle electromechanical braking system according to claim 7, wherein, The roller thread has an uneven pitch.

10. The vehicle electromechanical braking system according to claim 7, wherein, The lead screw thread and the roller thread each have uneven pitch.

11. The vehicle electromechanical braking system according to claim 7, wherein, The nut has a piston that is integrally formed to the end of the column.

12. The vehicle electromechanical braking system according to claim 7, wherein, The nut has a piston that is operatively coupled to the end of the column.

13. A method for manufacturing a planetary roller drive system for an electromechanical braking module, the method comprising: Manufacturing a roller screw having a screw thread formed on the outer surface of the screw, wherein the screw thread has an original screw thread profile; Manufacturing a roller having a roller thread formed on the outer surface of the roller, wherein the roller thread has an original roller thread profile; and The teeth of at least one of the original lead screw thread profile and the original roller thread profile are shaped to form an uneven pitch.

14. The method according to claim 13, wherein, The lead screw thread has an uneven pitch.

15. The method according to claim 13, wherein, The roller thread has an uneven pitch.

16. The method according to claim 13, wherein, The lead screw thread and the roller thread each have uneven pitch.

17. The method of claim 13, further comprising: Calculate the stiffness of the section of the lead screw; as well as Calculate the deformation of the lead screw under load; Specifically, the teeth of at least one of the original lead screw thread profile and the original roller thread profile are shaped to form a non-uniform pitch based on the calculated stiffness and the amount of deformation.

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