Electric power steering system ball screw pair fatigue test tool and method

Abstract

The application discloses a kind of electric power steering system ball screw pair fatigue test tooling, comprising: drive device is used to drive the ball nut assembly of ball screw pair to rotate;Fixing device is used to fix ball nut assembly;Anti-rotation device is used to fix and compress rack screw rod of ball screw pair, and has limit function;Fixed device and anti-rotation device are all arranged on base device;Connecting device is used to connect the both ends of rack screw rod of ball screw pair, and connecting device has swing angle function;Loading device is connected with the end of connecting device away from ball screw pair, and is used to apply both ends load to ball screw pair.The electric power steering system ball screw pair fatigue test tooling of the application ensures the installation accuracy of ball screw pair fatigue test, and eliminates the lateral force received during the operation of ball screw pair fatigue test.The application also discloses a kind of electric power steering system ball screw pair fatigue test method.

Description

Technical Field

[0001] This invention belongs to the technical field of vehicle steering systems. Specifically, this invention relates to a fatigue testing fixture and method for ball screw pairs in electric power steering systems. Background Technology

[0002] As a core transmission component in electric power steering systems, the ball screw assembly's fatigue life directly determines the reliability of the system and the overall vehicle safety. Therefore, it requires durability verification using specialized fatigue testing fixtures to simulate actual operating conditions. Currently, mainstream ball screw assembly fatigue testing fixtures in the industry generally adopt a basic "fixed-drive-load" structure. This involves fixing the axial position of the ball nut assembly, driving it to rotate to cause the ball screw to perform linear reciprocating motion, and applying a passive load to both ends of the ball screw to achieve fatigue testing loading.

[0003] However, existing tooling has many shortcomings in structural design and experimental applications that urgently need to be addressed:

[0004] Firstly, during the installation and fixing process, the tooling adopts a "three-point fixing" mode, which involves fixing the axial position of the ball nut assembly and the load connection points at both ends of the ball screw pair separately. Under this mode, if one point is fixed before the loads at both ends are connected, the single installation reference and imbalanced force can easily lead to height deviations at both ends of the ball screw. This not only increases the difficulty of subsequent assembly and adjustment but may also subject the screw to additional initial stress at the initial stage of the test, affecting the accuracy of the test data.

[0005] Secondly, regarding the load connection method, the existing tooling often uses rigid, fixed structures to connect the ball screw pairs at both ends to the load. In actual testing, the linear motion of the ball screw cannot guarantee absolute axial consistency, and rigid connections cannot compensate for minor misalignments during movement. This results in the ball screw being subjected to additional lateral forces in the vertical and horizontal directions, in addition to the designed axial load. These lateral forces not only exacerbate wear on the ball screw pair and shorten its test life, but also interfere with the stress loading accuracy of fatigue tests, causing deviations between the test results and the actual fatigue characteristics of the component, thus reducing the effectiveness of the test.

[0006] Thirdly, in terms of anti-rotation design, existing solutions mostly rely on the rigid connection of the load at both ends and an additional set of linear guides to achieve the anti-rotation function, without directly designing an effective anti-rotation structure for the rack and pinion itself in the ball screw pair. This indirect anti-rotation method has low reliability. When the linear guides wear or have positioning deviations, the anti-rotation effect will decrease significantly, causing the rack and pinion to rotate unexpectedly during the test, compromising the stability of the test load, and possibly even causing collision damage between the tooling and the test components, affecting the smooth progress of the test.

[0007] In summary, how to solve the defects of existing ball screw fatigue testing fixtures in terms of installation and fixation, lateral force elimination, and anti-rotation reliability, and improve the reliability and efficiency of test operation, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a fatigue testing fixture for ball screw pairs in electric power steering systems. The purpose is to ensure the accurate installation and fixing of the ball screw pair during fatigue testing, while simultaneously eliminating the lateral forces experienced by the ball screw pair during fatigue testing, thereby improving the reliability of the ball screw pair fatigue testing operation.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is: a fatigue testing fixture for ball screw pairs in an electric power steering system, comprising:

[0010] A drive unit for driving the ball nut assembly of the ball screw pair to rotate;

[0011] A fixing device is used to fix the ball nut assembly;

[0012] An anti-rotation device is used to fix and press the rack and pinion of the ball screw pair, and also has a limiting function;

[0013] The base device includes a fixing device and an anti-rotation device, both of which are mounted on the base device. The base device is adjustable in the installation positions of the fixing device and the anti-rotation device.

[0014] A connecting device for connecting the two ends of the rack and pinion of the ball screw assembly, and the connecting device having a swing angle function; and

[0015] A loading device is connected to the end of the connecting device away from the ball screw assembly and is used to apply a load to both ends of the ball screw assembly.

[0016] The driving device includes a drive motor and a transmission mechanism, and the transmission mechanism is connected to the drive motor and the ball nut assembly.

[0017] The fixing device includes a base plate, a mounting plate, and a limiting flange; the base plate and the base device are adjustablely connected, the mounting plate is fixed above the base plate, the limiting flange is fixed to the end face of the mounting plate, and the limiting flange is fixedly connected to the ball nut assembly.

[0018] The base device includes a base, an adjustment plate, a second slider, and a third slider;

[0019] The base is provided with a third sliding groove, the third slider is slidably disposed in the third sliding groove of the base, and the adjusting plate is fixedly connected to the third slider;

[0020] The adjusting plate is provided with a second sliding groove, and the second slider is slidably disposed in the second sliding groove of the adjusting plate. The base plate of the fixing device is fixedly connected to the second slider, and the length direction of the second sliding groove is perpendicular to the length direction of the third sliding groove.

[0021] The anti-rotation device includes a linear guide rail, a first slider, a connecting plate, a support base, a support block, a locking block, and two sets of travel locking blocks;

[0022] The linear guide rail is fixed to the base plate of the fixing device, the first slider is slidably disposed on the linear guide rail, and the connecting plate is fixed on the first slider;

[0023] The support base is fixed to the connecting plate, the support block is fixed to the support base, and the support block is provided with a semi-circular groove that mates with the back of the rack screw.

[0024] The locking block is located above the support block and engages with the tooth profile of the rack screw end face. Both the locking block and the support block are fixedly connected to the support base, and the connection surface between the locking block and the support block has a gap of 0.5mm.

[0025] The two sets of travel locking blocks are fixed to the base plate and are located at both ends of the linear guide rail, respectively.

[0026] The connecting device includes a first adapter, a second adapter, a third adapter, an inner pull rod, a first locking nut, a tension / compression sensor, and an outer pull rod;

[0027] One end of the external tie rod is connected to the first adapter, and the other end is connected to the loading device;

[0028] One end of the tension / compression sensor is connected to the second adapter, and the other end is connected to the first adapter;

[0029] The third adapter is configured to be threaded to the end of the rack and pinion of the ball screw assembly. One end of the inner pull rod is threaded to the third adapter, and the other end is locked to the second adapter through the first locking nut.

[0030] The loading device includes an electric loading system, a tapered flange, and a second locking nut;

[0031] The tapered sleeve flange is fixed to the end rotating component of the electric loading system, and the tapered hole of the tapered sleeve flange is taperedly engaged with the end of the outer tie rod away from the first adapter.

[0032] The second locking nut is threaded to the ball pin of the outer pull rod and locks the outer pull rod to the tapered sleeve flange. There is a set distance between the tapered sleeve flange and the axis of the end rotating component.

[0033] This invention also provides a fatigue testing method for ball screw pairs in electric power steering systems, using the aforementioned fatigue testing fixture for ball screw pairs in electric power steering systems, comprising the following steps:

[0034] S1: The slider assembly is pre-installed on the base device. After the fixing device and anti-rotation device are initially assembled, they are placed on the base device without being locked.

[0035] S2: Install the ball screw assembly on the limiting flange of the fixed device, and fix and press the rack and screw of the ball screw assembly by the support block and locking block of the anti-rotation device;

[0036] S3: Assemble the drive unit to make the drive unit and the ball nut assembly of the ball screw pair drive each other.

[0037] S4: Install connecting devices at both ends of the rack and screw of the ball screw pair to connect the loading device to the end of the rack and screw away from the ball screw pair.

[0038] S5: Adjust the position of the drive device and the adjustable structure of the base device to center and tension the transmission components of the drive device, and lock the slider assembly of the base device and the drive device.

[0039] S6: Fatigue test run of ball screw pair. The ball nut assembly rotates, driving the rack and pinion screw to move.

[0040] Step S1 specifically includes:

[0041] Place the third slider into the third groove of the base, place the adjusting plate on the base and connect it to the third slider with bolts, but do not lock it;

[0042] Place the second slider into the second groove of the adjusting plate, assemble the mounting plate, support plate and limiting flange onto the base plate to form a fixed device, place it on the adjusting plate and connect it to the second slider with bolts, but do not lock it;

[0043] Assemble the linear guide rail, the first slider, the connecting plate, the support base, and the travel locking block onto the base plate to complete the initial assembly of the anti-rotation device.

[0044] In step S6, while the rack screw is moving linearly, it drives the locking block, support block, support base, connecting plate and first slider to move linearly on the linear guide rail. At the same time, the rack screw drives the loading devices at both ends to move through the third adapter, inner pull rod, first locking nut, second adapter, tension and pressure sensor, and outer pull rod, and collects the loading force in real time through the tension and pressure sensor.

[0045] The electric power steering system ball screw pair fatigue testing fixture of the present invention, through the cooperation of a fixing device, an anti-rotation device, a base device, a connecting device, and a loading device, etc., adds an anti-rotation device that can prevent rotation while also serving as an installation fixing point, ensuring the accuracy of the ball screw pair fatigue test installation and fixing, and eliminating the lateral force experienced by the ball screw pair during fatigue test operation, thereby improving the reliability and efficiency of the ball screw pair fatigue test operation. Attached Figure Description

[0046] This manual includes the following figures, which illustrate the following:

[0047] Figure 1 This is a schematic diagram of the fatigue testing fixture for the ball screw pair of the electric power steering system of the present invention.

[0048] Figure 2 This is a schematic diagram of the explosion of the drive device;

[0049] Figure 3 This is a schematic diagram of an explosion of a fixed device;

[0050] Figure 4 This is a schematic diagram of an anti-rotation device exploding;

[0051] Figure 5 This is a schematic diagram of the base device in an explosion.

[0052] Figure 6 This is a schematic diagram of the explosion of the connecting device;

[0053] Figure 7 This is a schematic diagram of the loading device exploding.

[0054] Figure 8 This is a partial structural diagram of a ball screw assembly;

[0055] Figure 9 This is a schematic diagram of the connection structure between the external tie rod and the tapered flange.

[0056] The diagram is marked as follows:

[0057] 1. Drive motor; 2. Large connecting flange; 3. Large synchronous pulley; 4. Small synchronous pulley; 5. Small connecting flange; 6. Synchronous belt; 7. Ball screw pair; 8. Support plate; 9. Mounting plate; 10. Limit flange; 11. Base plate; 12. Support base; 13. Support block; 14. Locking block; 15. Stroke locking block; 16. Connecting plate; 17. First slider; 18. Linear guide rail; 19. Adjusting plate; 20. Second slider; 21. Base; 22. Third slider; 23. Third adapter; 24. Inner tie rod; 25. First locking nut; 26. Tension / compression sensor; 27. First adapter; 28. Outer tie rod; 29. ​​Second adapter; 30. Tapered sleeve flange; 31. Electric loading system; 32. Second locking nut; 33. Flange plate; 34. Nut body; 35. Rack and pinion screw; 36. Ball head; 37. Outer conical surface. Detailed Implementation

[0058] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solutions of the present invention, and to facilitate its implementation.

[0059] It should be noted that in the following embodiments, the terms "first," "second," and "third" do not represent an absolute distinction in structure and / or function, nor do they represent the order of execution; they are merely for the convenience of description.

[0060] Firstly, such as Figures 1 to 7 As shown, this embodiment of the invention provides a fatigue testing fixture for a ball screw pair in an electric power steering system, comprising:

[0061] A drive unit for driving the ball nut assembly of the ball screw pair to rotate;

[0062] A fixing device is used to fix the ball nut assembly;

[0063] An anti-rotation device is used to fix and press the rack and pinion of the ball screw pair, and also has a limiting function;

[0064] The base device includes a fixing device and an anti-rotation device, both of which are mounted on the base device. The base device is adjustable in the installation positions of the fixing device and the anti-rotation device.

[0065] A connecting device for connecting the two ends of the rack and pinion of the ball screw assembly, and the connecting device having a swing angle function; and

[0066] A loading device is connected to the end of the connecting device away from the ball screw assembly and is used to apply a load to both ends of the ball screw assembly.

[0067] The driving device includes a drive motor and a transmission mechanism, and the transmission mechanism is connected to the drive motor and the ball nut assembly.

[0068] The fixing device includes a base plate, a support plate, a mounting plate, and a limiting flange; the base plate and the base device are adjustablely connected, the mounting plate is fixed above the base plate, the limiting flange is fixed to the end face of the mounting plate, and the limiting flange is fixedly connected to the ball nut assembly.

[0069] The base device includes a base, an adjustment plate, a second slider, and a third slider;

[0070] The base is provided with a third sliding groove, the third slider is slidably disposed in the third sliding groove of the base, and the adjusting plate is fixedly connected to the third slider;

[0071] The adjusting plate is provided with a second sliding groove, and the second slider is slidably disposed in the second sliding groove of the adjusting plate. The base plate of the fixing device is fixedly connected to the second slider, and the length direction of the second sliding groove is perpendicular to the length direction of the third sliding groove.

[0072] The anti-rotation device includes a linear guide rail, a first slider, a connecting plate, a support base, a support block, a locking block, and two sets of travel locking blocks;

[0073] The linear guide rail is fixed to the base plate of the fixing device, the first slider is slidably disposed on the linear guide rail, and the connecting plate is fixed on the first slider;

[0074] The support base is fixed to the connecting plate, the support block is fixed to the support base, and the support block is provided with a semi-circular groove that mates with the back of the rack screw.

[0075] The locking block is located above the support block and engages with the tooth profile of the rack screw end face. Both the locking block and the support block are fixedly connected to the support base, and the connection surface between the locking block and the support block has a gap of 0.5mm.

[0076] The two sets of travel locking blocks are fixed to the base plate and are located at both ends of the linear guide rail, respectively.

[0077] The connecting device includes a first adapter, a second adapter, a third adapter, an inner pull rod, a first locking nut, a tension / compression sensor, and an outer pull rod;

[0078] One end of the external tie rod is connected to the first adapter, and the other end is connected to the loading device;

[0079] One end of the tension / compression sensor is connected to the second adapter, and the other end is connected to the first adapter;

[0080] The third adapter is configured to be threaded to the end of the rack and pinion of the ball screw assembly. One end of the inner pull rod is threaded to the third adapter, and the other end is locked to the second adapter through the first locking nut.

[0081] The loading device includes an electric loading system, a tapered flange, and a second locking nut;

[0082] The tapered sleeve flange is fixed to the end rotating component of the electric loading system, and the tapered hole of the tapered sleeve flange is taperedly engaged with the end of the outer tie rod away from the first adapter.

[0083] The second locking nut is threaded to the ball pin of the outer pull rod and locks the outer pull rod to the tapered sleeve flange. There is a set distance between the tapered sleeve flange and the axis of the end rotating component.

[0084] Specifically, such as Figures 1 to 7 As shown, the ball screw pair fatigue testing fixture of this invention includes a driving device for driving the ball nut assembly in the ball screw pair, a fixing device for fixing the ball nut assembly in the ball screw pair, an anti-rotation device for fixing and pressing the rack screw in the ball screw pair and having a limiting function, a base device for installing the fixing device and the anti-rotation device, a connecting device for connecting the two ends of the ball screw pair and having a swing angle function, and a loading device for applying loads at both ends.

[0085] like Figure 1 As shown, the ball screw assembly for the electric power steering system includes a rack and pinion screw and a ball nut assembly. The ball nut assembly includes a nut body and a bearing mounted on the nut body. The nut body and the rack and pinion screw cooperate to form a helical drive. A flange plate is provided on the outer ring of the bearing, which is used to connect to a limiting flange. The bearing is located at one end of the nut body, and the other end of the nut body is used to connect to the drive device.

[0086] like Figure 2As shown, the drive unit includes a drive motor 1 and a transmission mechanism. The drive motor 1 is a servo motor. The transmission mechanism is connected to the drive motor 1 and the ball nut assembly. The transmission mechanism includes a large synchronous pulley 3, a large connecting flange 2, a small synchronous pulley 4, a small connecting flange 5, and a timing belt 6. The diameter of the small synchronous pulley 4 is smaller than the diameter of the large synchronous pulley 3. The large connecting flange 2 is located on the end face of the drive motor 1 and is fixed to the drive motor 1 by six M6 bolts. The center hole in the large synchronous pulley 3 mates with the center shaft on the large connecting flange 2, and the two are fixedly connected by four M8 bolts. Thus, the large synchronous pulley 3 is connected to the output end of the drive motor 1 through the large connecting flange 2. The small connecting flange 4 is connected to the end face of the nut body of the ball nut assembly by four M5 bolts. The center hole on the small synchronous pulley 4 mates with the center shaft of the small connecting flange 5, and the two are connected by four M6 bolts. Finally, the large synchronous pulley 3 and the small synchronous pulley 4 are connected by the timing belt 6. Once the drive motor 1 rotates, the drive motor 1 drives the large connecting flange 2 to rotate, the large connecting flange 2 drives the large synchronous pulley 3 to rotate, and then transmits the rotation to the small synchronous pulley 4 through the synchronous belt 6. Since the small synchronous pulley 4 is fixed to the ball nut assembly through the small connecting flange 5, the rotation of the ball nut assembly in the ball screw pair 7 is realized.

[0087] like Figure 3 As shown, the fixing device includes a base plate 11, a mounting plate 9, two sets of support plates 8, and a limiting flange 10. The base plate 11 is fixed to the second slider 20 located in the second groove on the adjusting plate 19 by 10 M10 bolts. The mounting plate 9 is located above the base plate 11 and is fixedly connected to the base plate 11 by 4 M10 bolts. The support plates 8 are located on both sides of the mounting plate 9 and are fixed to the base plate 11 and the mounting plate 9 by 5 M10 bolts respectively. The limiting flange 10 is located on the end face of the mounting plate 9 and is fixedly connected to the mounting plate 9 by 8 M8 bolts. During installation, the flange plate of the ball nut assembly in the ball screw pair 7 is fixedly connected to the limiting flange 10 by 5 M6 bolts, and the flange plate fits against the limiting flange 10.

[0088] like Figure 4As shown, the anti-rotation device is used to circumferentially limit the rack screw and prevent it from rotating. The anti-rotation device includes a linear guide rail 18, a first slider 17, a connecting plate 16, a support base 12, a support block 13, a locking block 14, and two sets of stroke locking blocks 15. Two linear guide rails 18 are provided. The length direction of the linear guide rails 18 is parallel to the first direction, and the two linear guide rails 18 are on the same straight line parallel to the second direction. Both the first and second directions are horizontal and perpendicular. The axial direction of the rack screw is parallel to the first direction. The two linear guide rails 18 are located on the base plate 11, and each linear guide rail 18 is fixedly connected to the base plate 11 by nine M5 bolts. Each linear guide rail 18 is provided with a first slider 17, which acts as a linear actuator. The connecting plate 16 is located on the first slider 17 and is fixedly connected to the first slider 17 by eight M5 bolts. The support base 12 is located on the connecting plate 16, and the two are fixedly connected by two M10 bolts. The support block 13 is located on the support base 12 and has a semi-circular groove on its top surface. The axis of the semi-circular groove is parallel to the first direction. During installation, the rack screw is embedded in the semi-circular groove, and the smooth semi-circular groove engages with the smooth rod (the surface without protruding teeth) on the back of the rack screw, thus supporting the rack screw. The locking block 14 is located above the support block 13. The locking block 14 and the support block 13 are fixedly connected to the support base 12 by bolts. The support block 13 is located between the locking block 14 and the support base 12. Both the support block 13 and the locking block 14 have through holes for the bolts to pass through. The locking block 14 engages with the teeth on the surface of the rack screw, and is fixed to the support base 12 by two M8 bolts passing through the locking block 14 and the support block 13 respectively. The locking block 14 and the support block 13 cooperate to clamp the rack screw. At the same time, there is a 0.5mm gap at the connection between the locking block 14 and the support block 13 to further improve the reliability of the tooth end face clamping.

[0089] When the test drive device drives the ball nut assembly to rotate, the ball nut assembly drives the rack screw to move linearly along the axial direction. During the linear movement, the rack screw is locked onto the support base 12 by the locking block 14 pressing against the tooth end face and the support block 13. The connecting plate is also fixed to the support base 12 and slides linearly on the linear guide rail 18 together with the first slider 17. This solves the problem of preventing rotation during the operation of the ball screw pair 7 and ensures the reliability of the test. To prevent the first slider 17 from falling off due to overtravel during the test of the ball screw pair 7, two sets of travel locking blocks 15 are added above the base plate 11. Each set of travel locking blocks 15 is fixedly connected to the base plate 11 by two M8 bolts. The first slider 17 is located between the two sets of travel locking blocks 15. In the event of overtravel, the travel locking blocks 15 contact the connecting plate 16 to prevent the test from continuing to move forward or backward.

[0090] like Figure 5 As shown, the base device includes a base 21, an adjusting plate 19, a second slider 20, and a third slider 22. The adjusting plate 19 is located above the base 21. A third slide groove is provided on the base 21, and the third slider 22 is disposed in the third slide groove. The length direction of the third slide groove is parallel to the second direction. The adjusting plate 19 is fixedly connected to the third slider 22 located in the third slide groove of the base 21 by four M20 bolts. When adjusting the forward and backward displacement (i.e., adjusting the position of the adjusting plate 19 along the second direction, and simultaneously adjusting the position of the base plate 11 along the second direction), the four M20 bolts can be loosened to loosen the third slider 22. Then, the third slider 22 can be moved in the third slide groove to adjust the position of the adjusting plate 19. Finally, the bolts are tightened to fix the third slider 22, thus completing the position adjustment of the adjusting plate 19. A second slide groove is provided on the adjusting plate 19, and a second slider 20 is installed in the second slide groove. The second slider 20, located in the slide groove of the adjusting plate 19, is fixedly connected to the base plate 11 by 10 M10 bolts. When adjusting the displacement in the left and right directions (i.e., adjusting the position of the base plate 11 along the first direction), the 10 M10 bolts can be loosened to loosen the second slider 20. Then, the second slider 20 can be moved in the second slide groove to adjust the position of the base plate 11. Finally, the bolts are tightened to fix the second slider 20, completing the position adjustment of the base plate 11. By setting slide grooves in two directions, the slide grooves provide adjustment freedom. For rack and pinion screws of different lengths / diameters, the spacing of the support blocks and the position of the locking blocks can be adjusted through the two-dimensional slide grooves, so that the same base can be adapted to various specifications of rack and pinion screws. For parts with slightly lower machining precision, fine-tuning compensation can be achieved through the slide grooves, without rework or replacement of parts, thus improving the versatility and economy of the device.

[0091] like Figure 1 and Figure 6As shown, two connecting devices are provided, each connecting to both ends of the rack screw of the ball screw axis 7. The connecting devices include a third adapter 23, an inner pull rod 24, a first locking nut 25, a second adapter 29, a tension / compression sensor 26, a first adapter 27, and an outer pull rod 28. The rack screw has an internal threaded hole at one end, and the third adapter 23 has an external thread at one end, connected to the internal threaded hole of the rack screw. The other end of the third adapter 23 is connected to the end of the inner pull rod 24 via a ball joint. The tension / compression sensor 26 is connected to the other end of the inner pull rod 24, and is locked and fixed to the inner pull rod 24 by the first locking nut 25. The two ends of the first adapter 27 are fixedly connected to the tension / compression sensor 26 and the outer pull rod 28 respectively. The first adapter 27 is located between the tension / compression sensor 26 and the outer pull rod 28, and the tension / compression sensor collects the loading force of the loading device in real time.

[0092] like Figure 1 and Figure 7 As shown, two loading devices are provided, each connected to one of two connecting devices. The loading devices include an electric loading system 31, a tapered flange 30, and a second locking nut 32. The electric loading system 31 is used to apply load during the test. An end-rotating component is provided at the end of the electric loading system 31. The electric loading system 31 includes a motor that provides driving force. The motor is connected to the end-rotating component via a power transmission mechanism. After the motor operates, it drives the end-rotating component to rotate through the power transmission mechanism. The second locking nut 32 is threaded to the rod portion 38 of the ball pin of the outer pull rod 28, and locks the outer pull rod 28 onto the tapered flange 30. A set distance exists between the tapered flange 30 and the axis of the end-rotating component; that is, the tapered flange 30 is eccentrically positioned relative to the rotation center line of the end-rotating component (i.e., the axis of the end-rotating component, which is perpendicular to the first and second directions).

[0093] The tapered flange 30 is installed on the end rotating component of the electric loading system 31. After the flange face is flattened, it is fixed with eight M6 bolts and tapers the outer tie rod 28 to match the actual vehicle assembly effect. Figure 9As shown, a ball pin is provided at the end of the outer tie rod 28. The ball pin includes a rod portion 38 and a ball head 36. The ball head 36 is fixedly connected to one end of the rod portion 38 and is installed in a ball socket provided on the outer tie rod 28. The other end of the ball pin rod portion 38 is provided with an external thread. The second locking nut 32 is located below the tapered sleeve flange 30. A central hole is provided at the center of the tapered sleeve flange 30 for the ball pin rod portion 38 to pass through. An outer conical surface 37 is provided on the rod portion 38. An inner conical surface that fits with the outer conical surface 37 is provided in the central hole of the tapered sleeve flange 30. The outer conical surface 37 and the inner conical surface are coaxial conical surfaces, forming a tapered fit. The axes of the outer conical surface 37 and the inner conical surface are parallel to the axis of the end rotating component. The distance between the large diameter end of the outer conical surface 37 and the upper ball head is less than the distance between the small diameter end of the outer conical surface 37 and the upper ball head. The large diameter end and the small diameter end are opposite ends of the outer conical surface 37 in the axial direction, and the diameter of the large diameter end is greater than the diameter of the small diameter end.

[0094] The second locking nut 32 is threadedly connected to the external thread of the ball pin rod 38. Tightening the second locking nut 32 to make it contact the tapered sleeve flange 30 achieves the connection between the ball pin and the tapered sleeve flange 30. In this way, by installing the connecting device and the loading device together, the adjustable loading force required for the fatigue test of the ball screw assembly 7 can be achieved.

[0095] This design, with the inner tie rod 24 and outer tie rod 28 having a swing angle function, avoids a direct rigid connection to both ends of the ball screw assembly 7. This eliminates the lateral forces (up, down, left, and right) experienced by the ball screw assembly 7 during fatigue testing.

[0096] In fatigue testing, the lateral force on the ball screw pair is not the target force of the test load (the target force is usually the axial fatigue load along the screw axis), but rather an additional force caused by misalignment of the force transmission path. The inner tie rod 24 and the outer tie rod 28 are connected to adjacent components via ball joints. The inner tie rod 24 and the outer tie rod 28 inherently possess a swing angle characteristic, essentially meaning they have a small degree of freedom of rotation within the connection structure. This degree of freedom can directly solve the problem of misalignment in force transmission. The specific process is as follows:

[0097] 1. Actively adapt to axis deviation: When there is a deviation between the axis of the connecting device and the rack and screw, the tie rod with the swing angle can rotate slightly (swing angle) around its own fulcrum or connection point to automatically adjust its own axis direction, so that the force direction of the tie rod is as consistent as possible with the axis of the rack and screw.

[0098] 2. Cut off the transmission link of lateral force: If the tie rod is rigid and has no swing angle, the deviation between its own axis and the lead screw axis will be directly converted into a lateral component force and transmitted to the rack and pinion screw; while the tie rod with a swing angle cancels out the deviation through its own rotation, so that the loading force mainly acts on the rack and pinion screw in the form of axial force, and hardly generates a lateral component force.

[0099] 3. Dynamic compensation for offset during operation: During long-term reciprocating operation in fatigue testing, the vibration and slight deformation of components will cause dynamic changes in deviation. The swing angle characteristic can adjust the attitude of the tie rod in real time and dynamically, continuously maintain the axial alignment of the force, and thus eliminate lateral force in the long term.

[0100] The failure modes (fatigue, wear) of ball screw pairs are directly related to lateral forces. Lateral forces exacerbate local stress concentration between the balls and raceways, increase friction and wear, leading to shortened fatigue life and even jamming. Therefore, by setting up a connecting device, the swing angle characteristics of the inner / outer tie rods eliminate lateral forces, thus avoiding premature failure of the ball screw pair due to additional loads and ensuring that all test loads act in the target direction (axial direction). Ultimately, this achieves the technical effects of protecting the ball screw pair and eliminating lateral forces, ensuring the accuracy of fatigue test data.

[0101] Secondly, embodiments of the present invention also provide a fatigue testing method for a ball screw pair in an electric power steering system, using the above-described fatigue testing fixture for a ball screw pair in an electric power steering system, comprising the following steps:

[0102] S1: The slider assembly is pre-installed on the base device. After the fixing device and anti-rotation device are initially assembled, they are placed on the base device without being locked.

[0103] S2: Install the ball screw assembly on the limiting flange of the fixed device, and fix and press the rack and screw of the ball screw assembly by the support block and locking block of the anti-rotation device;

[0104] S3: Assemble the drive unit to make the drive unit and the ball nut assembly of the ball screw pair drive each other.

[0105] S4: Install connecting devices at both ends of the rack and screw of the ball screw pair to connect the loading device to the end of the rack and screw away from the ball screw pair.

[0106] S5: Adjust the position of the drive device and the adjustable structure of the base device to center and tension the transmission components of the drive device, and lock the slider assembly of the base device and the drive device.

[0107] S6: Fatigue test run of ball screw pair. The ball nut assembly rotates, driving the rack and pinion screw to move.

[0108] In this embodiment of the invention, step S1 specifically includes:

[0109] Place the third slider 22 into the third slide groove of the base 21, place the adjusting plate 19 on the base 21 and connect it to the third slider 22 with bolts, but do not tighten the bolts, that is, the third slider 22 can still move in the third slide groove.

[0110] Place the second slider 20 into the second slide groove of the adjusting plate 19, and assemble the mounting plate 9, support plate 8 and limiting flange 10 onto the base plate 11 to form a fixed device. Place it on the adjusting plate 19 and connect it to the second slider 20 with bolts. Do not tighten the bolts, that is, the second slider 20 can still move in the second slide groove.

[0111] Assemble the linear guide rail 18, the first slider 17, the connecting plate 16, the support base 12, and the travel locking block 15 onto the base plate 11 to complete the initial assembly of the anti-rotation device.

[0112] Specifically, in step S1 above, the third slider 22 is first placed into the groove of the base 21, then the adjusting plate 19 is placed on the base 21 and connected to the third slider 22 with four M20 bolts, but not locked. Finally, the second slider 20 is placed into the groove of the adjusting plate 19. The mounting plate 9 is fixed to the base plate 11 with four M10 bolts. The support plates 8 on both sides of the mounting plate 9 are respectively connected and fixed to the base plate 11 with two M10 bolts and to the mounting plate 9 with three M10 bolts. Then, the limiting flange 10 is flush with the mounting plate 9 through its end face and fixed with six M8 bolts. Finally, the whole assembly is placed on the adjusting plate 19 and connected to the second slider 20 in the groove of the adjusting plate 19 with ten M10 bolts, but not locked. Each linear guide rail 18 is fixed to the base plate 11 with 9 M5 bolts. Then, the first slider 17 is installed on the linear guide rail 18. The connecting plate 16 is placed on the first slider 17 and fixed with 8 M5 bolts. The support base 12 is then installed on the connecting plate 16 with 2 M10 bolts. Finally, stroke locking blocks 15 are installed at the ends of the linear guide rail 18 and fixed to the base plate 11 with 2 M8 bolts.

[0113] In step S2 above, the support block 13 is placed on the support base 12. The ball screw assembly 7 slowly passes through the center hole of the limiting flange 10 and the mounting plate 9 from one side of the limiting flange 10 until the end face of the ball nut assembly of the ball screw assembly 7 is flush with the limiting flange 10. Then, the smooth rod on the back of the rack screw of the ball screw assembly 7 is placed on the support block 13. The locking block 14 is flush with the rack screw tooth profile of the ball screw assembly 7 and the locking block 14, the support block 13 and the support base 12 are connected by two M8 bolts but not locked. Finally, the ball nut assembly of the ball screw assembly 7 is connected and fixed to the end face of the limiting flange 10 with five M6 bolts, and the two M8 bolts connecting the locking block 14, the support block 13 and the support base 12 are locked and fixed at the same time.

[0114] In step S3 above, the other end face of the small connecting flange 5 and the ball nut assembly in the ball screw pair 7 is connected and fixed by 4 M5 bolts. Then, the center hole in the small synchronous pulley 4 is slowly passed through the center shaft of the small connecting flange 5 until the end face contacts and flattens, and then it is locked and fixed by 4 M6 bolts. In this way, the small synchronous pulley 4 is connected to the ball nut assembly in the ball screw pair 7.

[0115] In step S4 above, after the third adapter 23 is connected and locked to the internal threads of both ends of the ball screw assembly 7, the two sets of inner pull rods 24 are connected and locked to the third adapter 23. Then, the second adapter 29 is connected to the inner pull rod 24 and the tension / compression sensor 26 respectively and locked by the first locking nut 25 on the inner pull rod 24. The first adapter 27 is threaded and locked to the other end of the tension / compression sensor 26. Finally, the outer pull rod 28 is threaded and locked to the other side of the first adapter 27.

[0116] In step S5 above, the small synchronous pulley 4 is manually rotated so that the ball nut assembly in the ball screw pair 7 is in the middle of the effective stroke. The synchronous belt 6 is slowly passed from the end near the ball nut assembly in the ball screw pair 7 through the outer tie rod 28, the tension / compression sensor 26, and the inner tie rod 24, and then connected to the small synchronous pulley 4 fixed on the small connecting flange 5. After that, it is connected to the large synchronous pulley 3 fixed on the large connecting flange 2. The position of the drive motor 1, the adjusting plate 19, and the base plate 11 are finely adjusted so that the synchronous belt 6, the large synchronous pulley 3, and the small synchronous pulley 4 are on the same straight line and are taut. Finally, the drive motor 1 is fixed, and the second slider 20 in the second groove on the adjusting plate 19 and the third slider 22 in the third groove on the base 21 are locked.

[0117] The tapered sleeve flange 30 is flush with the end rotating component of the electric loading system 31 through the flange face and locked and fixed to the end rotating component by 8 M6 bolts. The two outer tie rods 28 at both ends are connected to the tapered holes in the fixed tapered sleeve flange 30 respectively. Finally, the second locking nut 32 is locked to the threaded connection on the ball pin and fixed below the tapered sleeve flange 30. At this point, the entire ball screw pair 7 fatigue test fixture has been connected.

[0118] In step S6 above, the ball screw pair fatigue test is performed. The drive device drives the ball nut assembly to rotate, and the ball nut assembly drives the rack screw to move linearly along the axial direction. The rotation of the drive motor 1 drives the large connecting flange 2 connected to it, which in turn causes the large synchronous pulley 3 to rotate. The large synchronous pulley 3 is transmitted to the small synchronous pulley 4 through the synchronous belt 6. The small synchronous pulley 4 is fixed to the ball nut assembly in the ball screw pair 7 through the small connecting flange 5. Since the ball nut assembly in the ball screw pair 7 is fixedly connected to the mounting plate 9 by the limiting flange 10, the ball nut assembly only rotates without axial movement. The rack screw is driven to move by the ball pressing raceway inside.

[0119] Since the first slider 17 is installed on the linear guide rail 18 and connected to the support block 13 and locking block 14 through the connecting plate 16, support base 12, and locking plate 14, the rack screw can drive the locking block 14, support block 13, support base 12, connecting plate 16 and the first slider 17 locked to the tooth end face to run linearly on the linear guide rail 18 while performing linear motion. This eliminates sway and rotation and directly adds a fixed point on the ball screw pair 7 to ensure the stability of operation.

[0120] While the rack and pinion screw is moving linearly, it drives the locking block 14, support block 13, support base 12, connecting plate 16 and first slider 17 to move linearly on the linear guide rail 18. At the same time, the rack and pinion screw drives the loading devices at both ends to move through the third adapter 23, inner pull rod 24, first locking nut 25, second adapter 29, tension and pressure sensor 26, first adapter 27 and outer pull rod 28. The tension and pressure sensor 26 collects the loading force in real time and transmits the collected loading force to the control system.

[0121] Because the tapered flange 30 is connected and fixed to the electric loading system 31, and through the tapered fit with the ball pin of the outer tie rod 28, and with the addition of the second locking nut 32 to fix the external thread on the ball pin, the outer tie rods 28 at both ends are connected to the electric loading system 31 at both ends to achieve loading at both ends. At the same time, because the inner tie rod 24 and the outer tie rod 28 in the connecting device have their own swing angle characteristics, the lateral force on the ball screw pair 7 during fatigue test operation is further eliminated.

[0122] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A fatigue testing fixture for ball screw pairs in an electric power steering system, characterized in that, include: A drive unit for driving the ball nut assembly of the ball screw pair to rotate; A fixing device is used to fix the ball nut assembly; An anti-rotation device is used to fix and press the rack and pinion of the ball screw pair, and also has a limiting function; The base device includes a fixing device and an anti-rotation device, both of which are mounted on the base device. The base device is adjustable in the installation positions of the fixing device and the anti-rotation device. A connecting device for connecting the two ends of the rack and pinion of the ball screw assembly, and the connecting device having a swing angle function; and A loading device is connected to the end of the connecting device away from the ball screw assembly and is used to apply a load to both ends of the ball screw assembly.

2. The fatigue testing fixture for the ball screw pair of the electric power steering system according to claim 1, characterized in that, The driving device includes a drive motor and a transmission mechanism, and the transmission mechanism is connected to the drive motor and the ball nut assembly.

3. The fatigue testing fixture for the ball screw pair of the electric power steering system according to claim 1, characterized in that, The fixing device includes a base plate, a mounting plate, and a limiting flange; the base plate and the base device are adjustablely connected, the mounting plate is fixed above the base plate, the limiting flange is fixed to the end face of the mounting plate, and the limiting flange is fixedly connected to the ball nut assembly.

4. The fatigue testing fixture for the ball screw pair of the electric power steering system according to claim 3, characterized in that, The base device includes a base, an adjustment plate, a second slider, and a third slider; The base is provided with a third sliding groove, the third slider is slidably disposed in the third sliding groove of the base, and the adjusting plate is fixedly connected to the third slider; The adjusting plate is provided with a second sliding groove, and the second slider is slidably disposed in the second sliding groove of the adjusting plate. The base plate of the fixing device is fixedly connected to the second slider, and the length direction of the second sliding groove is perpendicular to the length direction of the third sliding groove.

5. The fatigue testing fixture for the ball screw pair of the electric power steering system according to any one of claims 1 to 4, characterized in that, The anti-rotation device includes a linear guide rail, a first slider, a connecting plate, a support base, a support block, a locking block, and two sets of travel locking blocks; The linear guide rail is fixed to the base plate of the fixing device, the first slider is slidably disposed on the linear guide rail, and the connecting plate is fixed on the first slider; The support base is fixed to the connecting plate, the support block is fixed to the support base, and the support block is provided with a semi-circular groove that mates with the back of the rack screw. The locking block is located above the support block and engages with the tooth profile of the rack screw end face. Both the locking block and the support block are fixedly connected to the support base, and the connection surface between the locking block and the support block has a gap of 0.5mm. The two sets of travel locking blocks are fixed to the base plate and are located at both ends of the linear guide rail, respectively.

6. The fatigue testing fixture for the ball screw pair of the electric power steering system according to any one of claims 1 to 4, characterized in that, The connecting device includes a first adapter, a second adapter, a third adapter, an inner pull rod, a first locking nut, a tension / compression sensor, and an outer pull rod; One end of the external tie rod is connected to the first adapter, and the other end is connected to the loading device; One end of the tension / compression sensor is connected to the second adapter, and the other end is connected to the first adapter; The third adapter is configured to be threaded to the end of the rack and pinion of the ball screw assembly. One end of the inner pull rod is threaded to the third adapter, and the other end is locked to the second adapter through the first locking nut.

7. The fatigue testing fixture for the ball screw pair of the electric power steering system according to claim 6, characterized in that, The loading device includes an electric loading system, a tapered flange, and a second locking nut; The tapered sleeve flange is fixed to the end rotating component of the electric loading system, and the tapered hole of the tapered sleeve flange is taperedly engaged with the end of the outer tie rod away from the first adapter. The second locking nut is threaded to the ball pin of the outer pull rod and locks the outer pull rod to the tapered sleeve flange. There is a set distance between the tapered sleeve flange and the axis of the end rotating component.

8. A fatigue test method for a ball screw pair in an electric power steering system, using the fatigue test fixture for a ball screw pair in an electric power steering system as described in any one of claims 1-7, characterized in that, Includes the following steps: S1: The slider assembly is pre-installed on the base device. After the fixing device and anti-rotation device are initially assembled, they are placed on the base device without being locked. S2: Install the ball screw assembly on the limiting flange of the fixed device, and fix and press the rack and screw of the ball screw assembly by the support block and locking block of the anti-rotation device; S3: Assemble the drive unit to make the drive unit and the ball nut assembly of the ball screw pair drive each other. S4: Install connecting devices at both ends of the rack and screw of the ball screw pair to connect the loading device to the end of the rack and screw away from the ball screw pair. S5: Adjust the position of the drive device and the adjustable structure of the base device to center and tension the transmission components of the drive device, and lock the slider assembly of the base device and the drive device. S6: Fatigue test run of ball screw pair. The ball nut assembly rotates, driving the rack and pinion screw to move.

9. The fatigue test method for ball screw pairs in an electric power steering system according to claim 8, characterized in that, Step S1 specifically includes: Place the third slider into the third groove of the base, place the adjusting plate on the base and connect it to the third slider with bolts, but do not lock it; Place the second slider into the second groove of the adjusting plate, assemble the mounting plate, support plate and limiting flange onto the base plate to form a fixed device, place it on the adjusting plate and connect it to the second slider with bolts, but do not lock it; Assemble the linear guide rail, the first slider, the connecting plate, the support base, and the travel locking block onto the base plate to complete the initial assembly of the anti-rotation device.

10. The fatigue test method for ball screw pairs according to claim 8, characterized in that, In step S6, while the rack screw is moving linearly, it drives the locking block, support block, support base, connecting plate and first slider to move linearly on the linear guide rail. At the same time, the rack screw drives the loading devices at both ends to move through the third adapter, inner pull rod, first locking nut, second adapter, tension and pressure sensor, and outer pull rod, and collects the loading force in real time through the tension and pressure sensor.

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