Wear test device and method for simulating actual contact state of single ball and raceway in ball screw pair

Abstract

The invention provides an abrasion test device and method for simulating the actual contact state of a single ball and a raceway in a ball screw pair. The test device comprises a device body, a sample piece driving module, a loading module and a solution box. The measuring method comprises the following steps: designing a to-be-measured sample piece according to a ball screw pair to be subjected to simulation test, selecting a grinding accompanying ball, designing a grinding accompanying piece, processing and manufacturing the grinding accompanying piece, cleaning the grinding accompanying piece, airing the grinding accompanying piece, and measuring the quality of the to-be-measured sample piece; mounting and testing, finally stopping, cleaning and airing the to-be-tested sample piece, and accurately measuring the quality of the to-be-tested sample piece again; and calculating mass wear before and after the test and carrying out surface observation. By adopting the technical scheme of the invention, the elliptical contact state of the ball screw pair can be accurately reproduced in a laboratory environment, a real fatigue crack initiation and propagation path of the ball screw pair under complex stress coupling can be reproduced, and accurate boundary conditions are provided for a life prediction model.

Description

Technical Field

[0001] The present invention belongs to the field of wear test of the raceway surface of ball screw pairs, and particularly relates to a wear test device and method for simulating the actual contact state between a single ball and the raceway in a ball screw pair. Background Art

[0002] As a core component of a precision transmission system, the wear behavior of a ball screw pair is directly related to the performance and reliability of the equipment. It is very necessary to carry out wear tests on ball screw pairs at the design stage. The results of wear tests can provide important references for the design of ball screw pairs. By analyzing the types and causes of wear, the design can be optimized to improve its wear resistance and reliability.

[0003] Traditional wear tests are generally carried out based on wear testing machines. The specimens of the wear testing machines on the market are generally flat disc specimens, and their contact area is a ball-plane contact mode (circular contact area). However, the contact area of a ball screw pair is an elliptical contact area in a ball-curved surface contact mode, and there is an essential difference between the two. Under the actual contact state, the stress distribution, slip trajectory and subsurface stress field characteristics in the elliptical contact area directly affect the fretting wear mechanism. Precise reproduction of the elliptical contact can reveal more real failure modes such as material spalling and plastic deformation.

[0004] In order to solve this problem, Patent CN118883337A, on the basis of a flat disc, processes an arc ring groove with the same radius as the raceway radius of the ball screw pair on the disc plane. So that its contact area is in a ball-curved surface contact mode, and to a certain extent, it simulates the contact state at the raceway in the ball screw pair. However, from the perspective of Hertz contact theory, the four principal curvatures of the contact area between the raceway and the ball of the ball screw pair are:

[0005]

[0006] Wherein, d b is the ball diameter, f s is the conformity ratio, d0 is the pitch diameter, α is the contact angle, and λ is the lead angle. And the four principal curvatures of the contact area simulated by the solution of Patent CN118883337A are:

[0007]

[0008] It can be seen that the first three principal curvatures of the two are the same. In the actual state, ρ 22 Although very small, it is not zero, and the solution of Patent CN118883337A can only approximately simulate. Obviously, this problem cannot be solved in the existing wear testing machines. Therefore, in order to solve this problem, the present invention provides a wear test device and method that can simulate the actual contact state between a single ball and the raceway in a ball screw pair. Summary of the Invention

[0009] The object of the present invention is to provide a wear test device and method for simulating the actual contact state between a single ball and a raceway in a ball screw pair, which can completely and accurately reproduce the ball-curved surface contact mode between the ball and the raceway in the ball screw pair, so as to accurately simulate the wear behavior of the ball screw pair under actual working conditions in a laboratory environment, and reveal more real failure modes such as material spalling and plastic deformation in the ball screw pair.

[0010] The technical solution for achieving the object of the present invention is as follows:

[0011] A wear test device for simulating the actual contact state between a single ball and a raceway in a ball screw pair, comprising:

[0012] A device main body for installing a sample driving module and a loading module;

[0013] A sample driving module for installing a sample to be tested, providing a driving force for the rotation of the sample to be tested, and controlling the number of working turns of the sample to be tested;

[0014] The sample to be tested and the accompanying grinding ball are made of the same material as the ball screw pair to be simulated and tested; the sample to be tested is provided with an annular raceway for simulating the raceway of the ball screw pair;

[0015] A solution tank for containing a lubricating substance;

[0016] An accompanying grinding part is arranged in the solution tank and is provided with an arc-shaped inner raceway for supporting the accompanying grinding ball;

[0017] A loading module for applying a load to the sample to be tested to simulate the actual load of the ball in the ball screw pair to be simulated in the test.

[0018] A wear test device for simulating the actual contact state between a single ball and a raceway in a ball screw pair, and its test method includes:

[0019] Start the loading module to make the sample to be tested, the accompanying grinding ball and the accompanying grinding part in direct contact;

[0020] Make the force application points of the sample to be tested, the accompanying grinding ball and the accompanying grinding part all on the loading axis of the loading module, and then rigidly connect the sample driving module to the device main body;

[0021] The loading module applies the required load F m , and the driving module drives the sample to be tested to rotate to the required number of turns N m ;

[0022] Stop the machine, remove the sample to be tested, clean and dry it, and accurately measure its mass again; calculate the mass wear before and after the test and conduct a surface observation.

[0023] Compared with the prior art, the remarkable advantages of the present invention are as follows:

[0024] The present invention can more accurately simulate the elliptical contact area of the ball screw pair, ensuring that the four principal curvatures of the contact area of the sample to be tested are exactly the same as those of the contact area of the ball screw pair to be simulated and tested. This can reveal the real failure modes such as material spalling and plastic deformation of the ball screw pair under actual working conditions in a laboratory environment; reproduce the real fatigue crack initiation and propagation paths of the ball screw pair under complex stress coupling, providing accurate boundary conditions for the life prediction model. Description of the Drawings

[0025] Figure 1 Isometric view of the wear test device for simulating the actual contact state between a single ball and the raceway in the simulated ball screw pair.

[0026] Figure 2 Front view of the wear test device for simulating the actual contact state between a single ball and the raceway in the simulated ball screw pair.

[0027] Figure 3 Isometric view of the contact area between the sample to be tested and the lapping ball.

[0028] Figure 4 Key dimension drawing of the sample to be tested.

[0029] Figure 5 Key dimension drawing of the part.

[0030] Symbol Description:

[0031] 1. Device main body; 2. Sample driving module; 201. Driving motor; 202. Driving motor mounting seat; 203. Magnetic isolation device; 204. Sample mounting rod; 3. Loading module; 301. Loading motor; 302. Loading motor mounting seat; 303. Transmission module; 304. Nut mounting seat; 305. Ball screw pair; 306. Force sensor; 4. Solution tank; 5. Lapping part; 6. Lapping ball; 7. Sample to be tested. Detailed Embodiment

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] As Figure 1 And Figure 2As shown in the figure, the present invention provides a wear test device for simulating the actual contact state between a single ball and a raceway in a ball screw pair, which consists of 7 modules: a device main body 1, a sample driving module 2, a loading module 3, a solution tank 4, a counter sample 5, a counter ball 6, and a sample to be tested 7. The device main body 1 is similar to the bed of a machine tool and is used to install other components. The function of the sample driving module 2 is to drive the sample to be tested 7 to rotate during the test, generating a wear behavior with the counter ball 6. The sample driving module 2 is composed of a driving motor 201, a driving motor mounting seat 202, a magnetic isolation device 203, and a sample mounting rod 204. The sample module 2 has no degrees of freedom relative to the device main body 1 during the test and is firmly adsorbed on the device main body 1. Only considering the machining error of the sample to be tested 7, resulting in Figure 3 In the contact area shown, the counter sample 5, the counter ball 6, and the sample to be tested 7 are offset in the Y direction, and the contact point is not on the central axis of the ball screw pair 305 in the loading module 3. The Y direction is the direction parallel to the central axis of the sample mounting rod 204. Therefore, when installing the sample to be tested 7, the sample driving module 2 and the device main body 1 have degrees of freedom in the Y direction. At this time, the sample driving module 2 can be finely adjusted adaptively in the Y direction to ensure that the contact point of the counter sample 5, the grinding ball 6, and the sample to be tested 7 is on the central axis of the ball screw pair 305, reaching an ideal state. In this specific embodiment, a magnetic adsorption scheme is adopted between the sample driving module 2 and the device main body 1. When a positive current is applied, there is an attractive force between the driving module 2 and the device main body 1, and a repulsive force when a reverse current is applied, thereby allowing the driving module 2 to displace in the Y direction. To prevent magnetic interference, a magnetic isolation device 203 is provided for magnetic shielding. The driving motor 201 provides the driving force and is installed in the driving motor mounting seat 202. The driving motor mounting seat 202 is directly in contact with the device main body 1, and the magnetic isolation device 203 is installed in the driving motor mounting seat 202 to shield the leaked magnetic force. The sample mounting rod 204 is directly fixed to the motor and is used to quickly install the sample to be tested 7.

[0034] The loading module 3 consists of a loading motor 301, a loading motor mounting base 302, a transmission module 303, a nut mounting base 304, a ball screw pair 305, and a force sensor 306. The loading module applies a load to the contact area to simulate the load on the balls during the operation of the ball screw pair. The loading motor 301 is installed in the loading motor mounting base 302, and the loading motor mounting base 302 is installed on the device main body 1. The loading motor 301 transmits torque to the ball screw pair 305 through the transmission module 303. The nut of the ball screw pair 305 is installed in the nut mounting base 304, and the nut mounting base 304 is connected to the device main body 1. In this embodiment, the transmission module 303 is composed of a synchronous belt and synchronous belt pulleys. When the loading motor 301 rotates, it drives the nut of the ball screw pair 305 to rotate in place through the transmission module 303, thereby driving the screw to move up and down. A force sensor 306 is installed on the screw of the ball screw pair 305. The force sensor 306 is used to measure the value of the applied load.

[0035] A solution tank 4 is installed on the force sensor 306. The solution tank 4 is used to hold the lubricant in the ball screw pair under the required simulated working conditions. The amount of lubricant should be sufficient to ensure that at least the entire contact area is in the lubricant. The counter grinding part 5 is installed in the solution tank 4. The counter grinding part 5 is connected to the solution tank 4 by a shaft-hole connection, and the diameter accuracy grade of the connection part is not lower than m6.

[0036] The counter grinding balls 6 are the same as the balls of the ball screw pair to be simulated in the test. The counter grinding balls 6 are naturally placed in the arc grooves of the counter grinding part 5, as Figure 3 shown. When the screw in the loading module 3 is jacked up, the counter grinding balls 6 are squeezed tightly against the test sample 7 to be measured. After the sample driving module 2 adapts in the Y direction, the corresponding load can be applied to the Figure 3 contact area shown.

[0037] On this basis, the present invention also provides a wear test method for simulating the actual contact state between a single ball and the raceway in a ball screw pair, including the following steps:

[0038] S1: Design the test sample 7 to be measured and select the counter grinding balls 6 according to the ball screw pair to be simulated in the test. The materials of the test sample 7 to be measured and the counter grinding balls 6 should be the same as those of the ball screw pair to be simulated in the test. The structure of the test sample 7 to be measured is similar to the inner ring of a ball bearing. Assume that the ball diameter of the ball screw pair to be simulated in the test is d b , the adaptation ratio is f s , the pitch circle diameter is d0, the contact angle is α, and the lead angle is λ. According to the Hertz contact theory, the main curvature and ∑ρ of the screw s are calculated by the following formula:

[0039]

[0040] The principal curvature sum ∑ρ of the nut n is calculated by the following formula:

[0041]

[0042] Therefore, the principal curvature sum ∑ρ of the lead screw s is greater than the principal curvature sum ∑ρ of the nut n .

[0043] The greater the principal curvature sum, the greater the elastic contact stress σ max . Therefore, when conducting the wear test verification, the wear test at the contact area points between the lead screw and the ball bearings shall prevail. So the diameter of the accompanying wear ball bearing 6 in the test is d b . As Figure 4 shown, the value of the raceway radius r1 of the annular raceway is: r1 = f s d b . The value of the bottom groove circle diameter d4 is the diameter d of the pitch circle formed by the centers of the accompanying wear ball bearings 6 a which is Then the outer circle diameter d2 of the sample 7 needs to satisfy d4 < d2 < d a . The diameter d3 formed by the centers of the raceway circles of the annular raceway is

[0044] S2: Design the accompanying wear part 5 based on the sample 7 to be measured and the accompanying wear ball bearing 6. As Figure 5 shown, the main part of the accompanying wear part 5 is an arc-shaped inner raceway. The top circle radius r5 of the inner raceway needs to satisfy the following conditions: The raceway radius r6 of the inner raceway needs to satisfy r6 > f s d b . The bottom groove circle radius r7 of the inner raceway needs to satisfy the following conditions:

[0045] S3: Manufacture the sample 7 to be measured and the accompanying wear part 5, clean and dry them, and accurately measure the mass of the sample 7 to be measured.

[0046] S4: Install the sample 7 to be measured on the sample installation rod 204, and install the accompanying wear part 5 in the solution tank 4. Place the accompanying wear ball bearing 6 naturally in the accompanying wear part 5. Then drive the loading motor to make the sample 7 to be measured, the accompanying wear ball bearing 6 and the accompanying wear part 5 in direct contact.

[0047] S5: The sample drive module 2 adapts to make the force application points of the sample 7 to be measured, the accompanying wear ball bearing 6 and the accompanying wear part 5 all on the central axis of the ball screw pair 305 of the loading module 3. Then reverse the power supply to make the drive module suck firmly on the device main body 1.

[0048] S6: Add the same lubricant in the ball screw pair to be simulated and tested into the solution tank, ensuring that the lubricant completely covers the contact area between the wear-matching ball 6 and the test sample 7.

[0049] S7: The loading module applies the required load F m , and the driving module drives the test sample 7 to rotate to the required number of turns N m .

[0050] S701: The loading module 3 drives the ball screw pair 305 to descend, so that the wear-matching ball 6 is separated from the test sample 7. Then the force sensor 306 measures the load under no load, denoted as G.

[0051] S702: Calculate the load Q1 required for a single ball in the ball screw pair to be simulated and tested. The calculation formula is:

[0052]

[0053] where F a is the axial load on the ball screw pair to be simulated and tested, z is the number of working balls, α is the contact angle, and λ is the lead angle.

[0054] Then the load F m applied by the loading module is: F m = G + Q1

[0055] The loading module drives the motor to rotate, causing the ball screw pair 305 to rise. When the load measured by the force sensor 306 is F m , stop loading. During the test, if the test sample 7, the ball 6, and the wear-matching part 5 are worn, resulting in the applied load being less than F m , the loading module automatically starts, so that the applied load is always F m during the test.

[0056] S703: Calculate the number of working turns N m of the test sample 7 as follows:

[0057]

[0058] where N A is the predicted life of the ball screw pair to be simulated and tested in terms of the number of turns. It can be calculated from the total working stroke L and the lead P h of the ball screw pair to be simulated and tested:

[0059] The contact stress stroke L of the balls in a single ball chain in the ball screw pair to be simulated and tested d0 is calculated as follows:

[0060] L d0=(z1 + z u ) × z1 × d b

[0061] where z1 is the number of working balls in a single ball chain, and z u is the number of non-working balls in a single ball chain, which is the number of balls in the reverser.

[0062] S8: Stop the machine, remove the test sample 7, clean and dry it, and then accurately measure its mass again. Calculate the mass wear before and after the test and conduct surface observation. Judge the wear condition by measuring the mass and surface state of the test sample before and after the wear test.

Claims

1. A wear test device for simulating the actual contact state between a single ball and a raceway in a ball screw pair, characterized in that: include: The device body is used to install the sample drive module and loading module; The sample drive module is used to install the sample to be tested, provide driving force for the rotation of the sample to be tested, and control the number of working circles of the rotation of the sample to be tested; The material of the sample to be tested and the accompanying grinding ball is consistent with the material of the ball screw pair to be simulated and tested; the sample to be tested is provided with an annular raceway for simulating the raceway of the ball screw pair; a solution tank, used to contain lubricating substances; The accompanying grinding part is arranged in the solution tank and is provided with an arc-shaped inner raceway for supporting the accompanying grinding balls; The loading module applies load to the sample to be tested, simulating the actual load of the ball in the ball screw pair to be simulated.

2. The wear test device for simulating the actual contact state between a single ball and a raceway in a ball screw pair according to claim 1, characterized in that: The value of the roller radius r1 of the annular roller of the sample to be tested is: r1 = f s d b ; The value of the bottom groove circle diameter d4 is: The outer diameter d2 of the sample to be tested satisfies d4<d2<d a , The diameter d3 formed by the center of the annular raceway is: where f s is the adaptability ratio of the ball screw pair to be simulated and tested, d b is the ball diameter of the ball screw pair to be simulated and tested, d0 is the pitch diameter, α is the contact angle, λ is the lead angle, d a It is the diameter of the pitch circle formed by the centers of the grinding balls.

3. The wear test device for simulating the actual contact state between a single ball and a raceway in a ball screw pair according to claim 2, characterized in that: The top circle radius r5 of the arc-shaped inner raceway of the wear-accompanying part satisfies: The inner raceway radius r6 satisfies r6>f s d b ; The radius of the inner raceway bottom groove circle r7 satisfies:

4. The wear test device for simulating the actual contact state between a single ball and a raceway in a ball screw pair according to claim 1, characterized in that: The device body and the sample drive module are connected with controllable degrees of freedom; when the sample to be tested is installed, the sample drive module can have a displacement parallel to the central axis direction of the sample to be tested relative to the device body.

5. The wear test device for simulating the actual contact state between a single ball and a raceway in a ball screw pair according to claim 1, characterized in that: The controllable degree of freedom connection method is a magnetic coupling locking device.

6. The wear test device for simulating the actual contact state between a single ball and a raceway in a ball screw pair according to claim 5, characterized in that: The sample driving module includes: a driving motor, a driving motor mounting seat, a magnetic isolation device and a sample mounting rod; the driving motor is connected to the device body through the driving motor mounting seat; the sample mounting rod is connected to the driving motor and is used to install the sample to be tested; the magnetic isolation device is used to isolate the leakage magnetic force of the magnetic coupling locking device.

7. The wear test device for simulating the actual contact state between a single ball and a raceway in a ball screw pair according to claim 1, characterized in that: The loading module includes: a loading motor, a loading motor mounting seat, a transmission module, a nut mounting seat, a ball screw pair and a force sensor; the loading motor is connected to the device body through the loading motor mounting seat; the nut of the ball screw pair is connected to the loading motor mounting seat; the loading motor drives the ball screw pair to rotate through the transmission module; the force sensor is arranged on the ball screw pair to measure the applied load value.

8. The wear test device for simulating the actual contact state between a single ball and a raceway in a ball screw pair according to claim 1, characterized in that: The testing methods include: Start the loading module to make the sample to be tested, the grinding ball and the grinding part directly contact; Make sure that the force points of the sample to be tested, the grinding balls and the grinding parts are all on the loading center axis of the loading module, and then rigidly connect the sample driving module to the device body; The loading module applies the required load F m The driving module drives the sample to be tested to rotate to the required number of circles N m ; Stop the machine, remove the sample to be tested, clean it and dry it, and accurately measure its mass again; calculate the mass wear before and after the test and observe the surface.

9. The wear test device for simulating the actual contact state between a single ball and a raceway in a ball screw pair according to claim 8, characterized in that: Load F m The calculation method is: F m =G+Q1 Among them, G is the load measured when the loading module is unloaded, and Q1 is the load required for a single ball in the ball screw pair to be simulated and tested; Among them, F a , z, α and λ are the axial load, number of working balls, contact angle and lead angle of the ball screw pair to be simulated and tested respectively; Number of circles N m The calculation method is: L d0 =(z1+z u )×z1×d b Among them, N A is the expected life of the ball screw pair to be tested in terms of the number of turns, based on the total working stroke L and lead P of the ball screw pair to be tested h Calculated; L d0 is the contact stress stroke of the ball in a single ball chain in the ball screw pair to be simulated and tested, z1 is the number of working balls in a single ball chain, and z u is the number of inactive balls in a single ball chain, is the number of balls in the return device, d b is the ball diameter of the ball screw pair to be simulated and tested.

10. The wear test device for simulating the actual contact state between a single ball and a raceway in a ball screw pair according to claim 8, characterized in that: The loading module continuously detects the applied load during the wear test. If the load is less than F m , then it is corrected to F m .

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