A method for detecting the roundness of a bearing groove

Abstract

The present invention belongs to the field of testing for measuring bearing profiles, and in particular relates to a method for detecting the roundness of a bearing groove. In order to eliminate the influence of the parallelism difference between the section to be measured and the end face of the bearing ring, the method for detecting the roundness of the bearing groove of the present invention is as follows: the first step is to select multiple detection positions at intervals in the circumferential direction of the groove of the ring to be measured, and measure the coordinates of the center of the circle corresponding to the actual curvature of the groove at each detection position; the second step is to use the coordinates of the center of the circle corresponding to all detection positions as the calculation data of the least squares method, and use the least squares method to fit a reference circle; the third step is to use the plane where the reference circle is located as the reference plane and the direction perpendicular to the reference plane as the z-axis to establish a measurement coordinate system; the fourth step is to measure the coordinates of the intersecting loop line between the plane where the reference circle is located and the groove of the ring to be measured in the measurement coordinate system, and use the intersecting loop line as the actual loop line to evaluate the groove roundness of the ring to be measured, thereby avoiding the introduction of the parallelism difference between the section to be measured and the end face of the bearing ring.

Description

Technical Field

[0001] The invention belongs to the field of testing for measuring bearing profiles, and in particular relates to a method for detecting the roundness of a bearing groove. Background Art

[0002] The roundness of a bearing's groove refers to the degree of deviation between the actual shape of the grooves on the inner and outer rings of the bearing and the theoretical circle. In the bearing industry, the least squares method is commonly used to calculate groove roundness. This method is used as an example to illustrate how to calculate groove roundness: When measuring groove roundness, the coordinates of each point on the actual groove must be measured. Using the coordinates of each point and the least squares method, an auxiliary circle and its center are determined. The maximum inscribed circle and minimum circumscribed circle of the actual groove are then drawn with the center of the auxiliary circle as the center. The difference between the minimum circumscribed circle radius and the maximum inscribed circle radius is calculated; this difference is the groove roundness.

[0003] Of course, the minimum area method can also be used to calculate channel roundness. After measuring the coordinates of each point on the actual channel, two concentric circles are drawn. All actual channels are located within the ring formed by these two concentric circles. When the absolute value of the difference between the radii of the two concentric circles is the smallest, this difference is the channel roundness. It should be noted that no matter which method is used to calculate channel roundness, the coordinates of each point on the actual channel must be measured first.

[0004] The smaller the groove roundness deviation, the closer the groove shape is to the theoretical circle, the better the bearing's rotational accuracy and smoothness, and the longer the bearing's service life. Conversely, the larger the groove roundness deviation, the greater the vibration, noise, and wear generated during bearing operation, which in turn affects the performance and life of the entire mechanical system. Therefore, during the bearing manufacturing process, it is necessary to test and evaluate the groove roundness of the bearing ring to determine whether the bearing is qualified.

[0005] At present, the groove roundness of small and medium-sized bearing rings (bearing rings with a diameter of less than 400mm) is mainly tested with high precision by roundness meters. The groove roundness of extra-large bearing rings used in medical equipment such as CT machines is mainly measured by three-coordinate measuring machines. Specifically, Figure 1 As shown, the upper end face 1 (or lower end face) of the bearing ring is first used as the reference surface, and a coordinate system is established with the projection of the center of the bearing ring inner circumference onto the reference surface as the coordinate origin, where the z-axis is perpendicular to the upper end face 1 (or lower end face) of the bearing ring. The actual loop of the bearing ring's groove is then measured when z = c, and this actual loop is used to evaluate the groove roundness of the oversized bearing ring. When the height of the bearing ring is h, c is -h / 2.

[0006] In the above detection method, Figure 2As shown in the figure, ideally, the upper end face 1 and the middle section 2 of the bearing ring are parallel. When z = -h / 2, the actual measured loop is the intersection of the middle section 2 and the bearing ring groove. In this case, the evaluation of the groove roundness of extra-large bearing rings is more accurate. When the reference plane is the lower end face, z = h / 2.

[0007] However, in the actual measurement process, due to the errors in the processing of the bearing ring, it is impossible to ensure that the upper end face 1 (or lower end face) of the bearing ring and the middle section 2 (i.e., the actual section to be measured) are parallel. Figure 3 There is a large deviation between the middle section 2 (actually measured section) and the theoretical section 2' ( Figure 3 The dimensions do not represent actual dimensions and are provided for ease of understanding only). At this time, when z = -h / 2 (or h / 2), the actual measured loop line is different from the above-mentioned intersecting loop line. When actually evaluating the groove roundness of the bearing ring, the parallelism difference between the middle section 2 and the upper end face 1 (or lower end face) is mistakenly introduced, resulting in inaccurate evaluation of the groove roundness of the bearing ring by the above-mentioned detection method. Summary of the Invention

[0008] The object of the present invention is to provide a method for detecting the roundness of a bearing groove, so as to solve the technical problem in the prior art that, due to errors in the processing of the bearing ring, the end face of the bearing ring cannot be guaranteed to be parallel to the cross section to be measured, and when actually evaluating the groove roundness of the bearing ring, the parallelism difference between the cross section to be measured and the end face of the bearing ring is erroneously introduced, resulting in inaccurate evaluation of the groove roundness of the bearing ring by the above-mentioned detection method.

[0009] To achieve the above-mentioned purpose, the technical solution of the bearing groove roundness detection method provided by the present invention is:

[0010] A method for detecting the roundness of a bearing groove comprises the following steps: first, after establishing an original coordinate system, selecting multiple detection positions at intervals in the circumferential direction of the groove of a ring to be measured, and measuring the coordinates of the center of the circle corresponding to the actual curvature of the groove at each detection position in the original coordinate system; second, using the coordinates of the center of the circle corresponding to all detection positions as calculation data for the least squares method, and using the least squares method to fit a reference circle; third, using the plane where the reference circle is located as a reference plane and the direction perpendicular to the reference plane as the z-axis to establish a measurement coordinate system; fourth, measuring the coordinates of the intersecting loop line between the plane where the reference circle is located and the groove of the ring to be measured in the measurement coordinate system, and using the intersecting loop line as the actual loop line to evaluate the groove roundness of the ring to be measured.

[0011] Furthermore, in the first step, the detection positions are evenly spaced along the circumference of the channel.

[0012] Furthermore, in the first step, the number of detection bits is 8-32.

[0013] Furthermore, in the first step, when the coordinate measuring machine is used to measure the coordinates of the center of the circle corresponding to the actual curvature of the groove at each detection position, the stylus is located in the plane where the theoretical groove center diameter is located when it is horizontal, and the rotation measurement radius of the stylus is the theoretical curvature radius of the groove.

[0014] Furthermore, when establishing the original coordinate system, the upper end face of the ring to be measured is used to establish the original reference plane, and the coordinates of multiple points on the inner ring of the ring to be measured at a set distance from the original reference plane are measured. Based on the coordinates of these points, the auxiliary circle different from the reference circle and the center of the auxiliary circle are determined, and the projection of the center of the auxiliary circle on the original reference plane is used as the coordinate origin, and the original coordinate system is established with the direction perpendicular to the original reference plane as the z-axis.

[0015] Furthermore, when establishing the original coordinate system, the original reference plane is established using the lower end face of the ring to be measured, and the coordinates of multiple points on the inner ring of the ring to be measured at a set distance from the original reference plane are measured. Based on the coordinates of these points, the auxiliary circle different from the reference circle and the center of the auxiliary circle are determined, and the projection of the center of the auxiliary circle on the original reference plane is used as the coordinate origin, and the original coordinate system is established with the direction perpendicular to the original reference plane as the z-axis.

[0016] The beneficial effects of the bearing groove roundness detection method of the present invention are as follows: the present invention is a pioneering invention. The coordinates of the circle centers corresponding to all detection positions are used as calculation data for the least squares method. A reference circle is fitted using the least squares method, and the intersection line between the plane containing the reference circle and the groove is used to evaluate the groove roundness of the ring to be tested. This avoids the introduction of parallelism errors between the measured section and the end face of the bearing ring, thereby improving the accuracy of the bearing ring groove roundness evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the bearing ring and coordinate system in the existing detection method;

[0018] Figure 2 This is the main view of the bearing ring in the existing detection method;

[0019] Figure 3 This is a schematic diagram showing errors in the machining of bearing rings in existing detection methods (does not represent actual dimensions);

[0020] Figure 4 Schematic diagram of the bearing ring and the original coordinate system in the method for detecting the roundness of the bearing groove of the present invention;

[0021] Figure 5 Schematic diagram of the reference circle of the bearing ring and the arc to be measured in the method for detecting the roundness of the bearing groove of the present invention;

[0022] Figure 6Schematic diagram of the bearing ring and the second coordinate system in the method for detecting the roundness of the bearing groove of the present invention.

[0023] Description of reference numerals:

[0024] 1. Upper end face; 2. Middle section; 2', actual section; 3. Reference circle; 4. Arc to be measured. DETAILED DESCRIPTION

[0025] With the development of the times, new generation coordinate measuring machines such as four-axis coordinate measuring machines, five-axis coordinate measuring machines, and six-axis coordinate measuring machines with better performance than three-axis coordinate measuring machines continue to emerge. With the upgrading of coordinate measuring machines, it has become possible to measure the roundness of bearing grooves by other methods. Therefore, it is urgent to develop a new bearing groove roundness detection method that is compatible with the new generation of coordinate measuring machines to improve the accuracy of bearing ring groove roundness evaluation.

[0026] In order to solve the problems in the background technology, the core inventive concept of the present invention is: using the coordinates of the center of the circle corresponding to all detection positions as the calculation data of the least squares method, using the least squares method to fit a reference circle, and using the intersecting ring line of the plane where the reference circle is located and the channel to evaluate the channel roundness of the ring to be tested, thereby avoiding the introduction of parallelism difference between the measured section and the end face of the bearing ring, and improving the accuracy of the evaluation of the channel roundness of the bearing ring.

[0027] The present invention is described in further detail below with reference to the examples.

[0028] Specific embodiments of the bearing groove roundness detection method provided by the present invention:

[0029] like Figure 4-6 As shown, the method for detecting the roundness of a bearing groove of the present invention comprises the following steps:

[0030] The first step is to establish the original coordinate system, select multiple (ie at least three) detection positions at intervals along the circumference of the groove of the ring to be tested, and measure the coordinates of the center of the circle corresponding to the actual curvature of the groove at each detection position in the original coordinate system (ie Figure 5 The coordinates of the center point of the arc 4 to be measured corresponding to the actual curvature thereof);

[0031] In the second step, the coordinates of the circle centers corresponding to all detection positions are used as calculation data for the least squares method, and the reference circle 3 is fitted using the least squares method;

[0032] The third step is to establish a measurement coordinate system with the plane where the reference circle 3 is located as the reference plane and the direction perpendicular to the reference plane as the z-axis;

[0033] The fourth step is to measure the coordinates of the intersecting line between the plane where the reference circle 3 is located and the groove of the ring to be measured in the measurement coordinate system, and use the intersecting line as the actual line to evaluate the groove roundness of the ring to be measured.

[0034] In the present invention, the reason for using the plane containing reference circle 3 as the reference plane in the third step is that during the manufacturing process of bearing rings, it is impossible to ensure that all bearing rings have the same shape. Therefore, for any two bearing rings, the angle between the plane containing reference circle 3 and the upper end surface 1 of the shaft sleeve ring may be different. It is impossible to use a fixed function to represent the plane containing reference circle 3 for different bearing rings. Therefore, it is impossible to input the function of the plane containing reference circle 3 into the coordinate measuring machine. As a result, the coordinate measuring machine cannot measure the coordinates of the intersection loop between the plane containing reference circle 3 and the groove of the ring to be measured. After establishing a measurement coordinate system using the plane containing reference circle 3 as the reference plane, for a single bearing ring, only the measurement parameter z = 0 needs to be input, and the coordinate measuring machine can automatically measure the coordinates of the intersection loop between the plane containing reference circle 3 and the groove of the ring to be measured.

[0035] Specifically, if Figure 5 As shown, in the first step, there are eight detection positions. However, in other specific embodiments, there may be three, four, five, or more detection positions. The more detection positions there are, the more accurate the evaluation of the bearing ring groove roundness is, but the detection time is also longer. Preferably, the number of detection positions is 8-32, thereby shortening the detection time while ensuring accuracy.

[0036] In the second step, the least squares method is used to fit the reference circle 3. Specifically, the reference circle 3 is determined by calculating the square of the shortest distance between each coordinate of the center of the circle measured in the first step and a certain circle. When the sum of all the calculated data is the smallest, the circle is the reference circle 3.

[0037] The coordinates of the circle centers corresponding to all detection positions are used as the calculation data for the least squares method. The reference circle 3 is fitted using the least squares method, and the intersecting ring line between the reference circle 3 and the groove is used to evaluate the groove roundness of the ring to be tested, thereby avoiding the introduction of parallelism difference between the measured section and the end face of the bearing ring, and improving the accuracy of the evaluation of the bearing ring groove roundness.

[0038] In order to facilitate calculation, as a specific implementation method, Figure 4As shown, when establishing the original coordinate system, the upper end face 1 of the ring to be measured is used to establish the original reference plane, and the coordinates of multiple points of the inner ring of the ring to be measured at a set distance from the original reference plane are measured, and the auxiliary circle and the center of the auxiliary circle are determined according to the coordinates of these points (it should be noted that the auxiliary circle is different from the reference circle 3. The auxiliary circle is a circle on the inner ring of the ring to be measured. The diameter of the auxiliary circle is ideally equal to the inner diameter of the inner ring of the ring to be measured). The projection of the center of the auxiliary circle on the original reference plane is used as the coordinate origin, and the original coordinate system is established with the direction perpendicular to the original reference plane as the z-axis. When measuring the arc 4 to be measured, the measured coordinates are relatively simple, which is convenient for measuring the coordinates of the center of the circle corresponding to the arc 4 to be measured (that is, the coordinates of the center of the circle corresponding to the actual curvature of the channel at each detection position).

[0039] However, in other specific embodiments, the lower end surface of the ferrule to be measured can also be used to establish the original reference surface. In this case, the ferrule to be measured needs to be supported on a bracket, otherwise it is difficult to measure the lower end surface of the ferrule to be measured. Alternatively, the surface of the measuring table used to place the ferrule to be measured can be used as the original reference surface. In this embodiment, the original coordinate system can be any coordinate system. After measuring the coordinates of the center point corresponding to the arc 4 to be measured using any coordinate system, the final calculated reference circle 3 will not be changed when calculating the reference circle 3, but will only affect the difficulty of the calculation.

[0040] In order to further improve the accuracy of the evaluation of the roundness of the bearing ring groove, as a specific implementation method, Figure 5 As shown, in the first step, the detection positions are evenly spaced along the circumference of the groove, so that the distribution of the detection positions is more uniform, thereby improving the accuracy of the evaluation of the roundness of the bearing ring groove.

[0041] However, in other specific embodiments, when there are eight detection positions, the distance between two of the detection positions can be closer (that is, the central angle corresponding to the line connecting the two detection positions is less than 45°), and the distance between the other two detection positions can be farther (that is, the central angle corresponding to the line connecting the two detection positions is greater than 45°). In this case, more detection positions need to be set to ensure the accuracy of the evaluation of the roundness of the bearing ring groove.

[0042] In order to conveniently measure the coordinates of the center of the circle corresponding to the actual curvature of the channel at each detection position, as a specific implementation method, refer to Figure 5 As shown, in the first step, when the coordinate measuring machine is used to measure the coordinates of the center of the circle corresponding to the actual curvature of the groove at each detection position, the stylus is located in the plane where the theoretical groove center diameter is located when it is horizontal, and the rotation measurement radius of the stylus is the theoretical curvature radius of the groove.

[0043] When designing the bearing ring, the plane where the theoretical groove center diameter of the measured ring is located, the diameter of the theoretical groove center diameter (i.e., the theoretical circle) and the theoretical curvature radius of the groove are already known. In the process of manufacturing the bearing ring, although there is a certain processing error, the processing error is relatively small. When the diameter of the bearing ring is 1000mm, the roundness deviation of the bearing ring groove is generally within 0.1mm. Of course, the standards of different countries and different manufacturers are different, but the same point in these standards is that the roundness deviation value of the bearing ring is much smaller than the diameter of the bearing ring.

[0044] Since the ball head of the stylus has a certain diameter and can be deformed, the stylus is positioned in the plane of the theoretical groove center diameter when horizontal, and the rotation measurement radius is equal to the theoretical curvature radius of the groove. This makes it easy to measure the coordinates of the center of the circle corresponding to the actual curvature of the groove at each detection position, and avoids interference between the non-ball head part of the stylus and the bearing ring, making measurement easier.

[0045] However, in other specific embodiments, the stylus can also be set at a distance from the plane of the theoretical groove center diameter when horizontal. The stylus has a certain length. According to the actual situation of the stylus, it is sufficient to ensure that the non-ball head part of the stylus does not interfere with the bearing ring.

[0046] It should be noted that when measuring the roundness of the bearing groove, for small and medium-sized bearing rings (bearing rings with a diameter of less than 400 mm), the existing roundness meter can be used for high-precision detection, or the bearing groove roundness detection method of the present invention can be used for high-precision detection; for large bearing rings (bearing rings with a diameter of not less than 400 mm), only the bearing groove roundness detection method of the present invention can be used for high-precision detection.

[0047] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments without inventive effort, or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for detecting the roundness of a bearing groove, characterized in that: The first step is to establish the original coordinate system, select multiple detection positions at intervals in the circumferential direction of the groove of the ring to be measured, and measure the coordinates of the center of the circle corresponding to the actual curvature of the groove at each detection position in the original coordinate system; the second step is to use the coordinates of the center of the circle corresponding to all detection positions as the calculation data of the least squares method, and use the least squares method to fit the reference circle; the third step is to use the plane where the reference circle is located as the reference plane and the direction perpendicular to the reference plane as the z-axis to establish a measurement coordinate system; the fourth step is to measure the coordinates of the intersecting ring line between the plane where the reference circle is located and the groove of the ring to be measured in the measurement coordinate system, and use the intersecting ring line as the actual ring line to evaluate the groove roundness of the ring to be measured.

2. The method for detecting the roundness of a bearing groove according to claim 1, wherein: In the first step, the detection positions are evenly spaced along the circumference of the channel.

3. The method for detecting the roundness of a bearing groove according to claim 1, wherein: In the first step, the number of bits is detected to be 8-32.

4. The method for detecting the roundness of a bearing groove according to claim 2, wherein: In the first step, the number of bits is detected to be 8-32.

5. The method for detecting the roundness of a bearing groove according to claim 1, wherein: In the first step, when using a coordinate measuring machine to measure the coordinates of the center of the circle corresponding to the actual curvature of the groove at each detection position, the stylus is located in the plane of the theoretical groove center diameter when it is horizontal, and the rotation measurement radius of the stylus is the theoretical curvature radius of the groove.

6. The method for detecting the roundness of a bearing groove according to claim 2, wherein: In the first step, when using a coordinate measuring machine to measure the coordinates of the center of the circle corresponding to the actual curvature of the groove at each detection position, the stylus is located in the plane of the theoretical groove center diameter when it is horizontal, and the rotation measurement radius of the stylus is the theoretical curvature radius of the groove.

7. The method for detecting the roundness of a bearing groove according to any one of claims 1 to 6, characterized in that: When establishing the original coordinate system, the upper end face of the ring to be measured is used to establish the original reference plane, and the coordinates of multiple points on the inner ring of the ring to be measured at a set distance from the original reference plane are measured. Based on the coordinates of these points, the auxiliary circle different from the reference circle and the center of the auxiliary circle are determined, and the projection of the center of the auxiliary circle on the original reference plane is used as the coordinate origin, and the original coordinate system is established with the direction perpendicular to the original reference plane as the z-axis.

8. The method for detecting the roundness of a bearing groove according to any one of claims 1 to 6, characterized in that: When establishing the original coordinate system, the lower end face of the ring to be measured is used to establish the original reference plane, and the coordinates of multiple points on the inner ring of the ring to be measured at a set distance from the original reference plane are measured. Based on the coordinates of these points, the auxiliary circle different from the reference circle and the center of the auxiliary circle are determined, and the projection of the center of the auxiliary circle on the original reference plane is used as the coordinate origin, and the original coordinate system is established with the direction perpendicular to the original reference plane as the z-axis.

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