JP2009180573A - Method and apparatus for measuring groove curvature of ball bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for measuring a groove curvature of a ball bearing, which is easily applied to a site for grooving an orbital plane of the bearing and the like, and precisely measures the groove curvature of the orbital plane at a low cost, without being dependent on the measurement technique of an operator, and to provide an apparatus for measuring the groove curvature which is used for the measuring method. <P>SOLUTION: In the method for measuring the groove curvature of the ball bearing, a spherical-surface electrode 3 made of a conductive body 4 being coated by an insulating film 5 and having a spherical surface simulated to a ball of the ball bearing, is set such that the spherical surface is in pressed contact with the orbital plane 2 of the ball bearing, and in this state, a capacitance between the spherical-surface electrode 3 and the orbital plane 2 is measured, and then the groove curvature of the orbital plane 2 is measured based on a value of the capacitance. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a groove curvature measuring method for measuring the groove curvature of a raceway surface of a ball bearing and a groove curvature measuring apparatus used for the measuring method.

  A ball bearing has a groove curvature ratio of a bearing raceway surface as one factor affecting the life and friction torque. The groove curvature ratio is defined as groove radius of curvature / ball radius and is a value larger than 1. That is, for example, in a radial ball bearing, if the groove curvature ratio of the raceway surface of the inner ring or the outer ring is large, the contact stress with the ball becomes high and the fatigue life of the bearing is shortened. Conversely, when the groove curvature ratio of the raceway surface is small, the slip component increases and the friction torque of the bearing increases. For this reason, on the bearing raceway surface of the ball bearing, a groove curvature ratio that optimizes the relationship between the life and the torque is selected according to the application.

As described above, in the ball bearing, the groove curvature radius that determines the groove curvature ratio of the bearing raceway surface is an important management value for the bearing performance, and should be constantly monitored even at the groove machining site. Since the grooving in this case is grinding, regular grindstone dressing is required to maintain sharpness. Since the dressing of the grindstone is to cut the grindstone by putting the diamond on the grindstone, the diamond gradually wears. When diamond wears out, it is impossible to make an accurate shape on the grindstone. For this reason, after grinding the bearing raceway surface, it is necessary to periodically measure the groove curvature and correct the diamond dresser.
As described above, when the groove curvature is measured periodically, a high-grade measuring instrument such as a shape measuring instrument can be used if the measurement interval is long, but if the measurement frequency is high, the processing machine Use of a shape measuring instrument is not practical.

There has been no published example of the technique for measuring the groove curvature of the raceway surface in the ball bearing, but a technique for measuring the spherical curvature radius of the hydrodynamic bearing has been proposed (for example, Patent Document 1).
JP 58-193408 A

  The technique disclosed in Patent Document 1 measures the spherical radius of curvature of a hydrodynamic bearing using a laser interferometer, and can measure with high accuracy because of the high resolution of the wavelength level of laser light. However, even if this measurement method is used to measure the groove curvature of the raceway surface of a ball bearing, a laser interferometer cannot be used at a groove processing site where the environment is bad, so a laser interferometer must be installed in a dedicated place. It must be impractical.

  An object of the present invention is a ball bearing groove that can be easily applied at a groove processing site of a bearing raceway surface and can measure the groove curvature of the raceway surface with high accuracy at a low cost without being influenced by an operator's measurement technique. It is providing the curvature measuring method and the groove curvature measuring apparatus used for the measuring method.

The method of measuring the groove curvature of a ball bearing according to the present invention is to push the spherical surface of a spherical electrode made of a conductor having a spherical surface imitating a ball of a ball bearing, the surface of which is coated with an insulating film, onto the raceway surface of the raceway of the ball bearing. In the applied state, the capacitance between the spherical electrode and the raceway surface is measured, and the groove curvature of the raceway surface is measured from the capacitance value. The spherical surface imitating the ball of the above-mentioned ball bearing is a spherical surface having substantially the same radius of curvature as the ball bearing ball to be measured. It may be a partial spherical surface that becomes the surface of the part.
According to this measurement method, the capacitance between the spherical electrode and the bearing raceway surface is measured, and the groove curvature of the raceway surface is measured from the measured capacitance value. It can be easily applied and the groove curvature can be measured at low cost. Moreover, it can measure with high precision, without being influenced by the operator's measurement technique. In particular, since the spherical electrode uses a conductor having a spherical surface imitating the ball of a ball bearing and presses the spherical surface against the raceway surface, the contact state between the raceway surface of the ball bearing and the ball is measured. Therefore, accurate measurement can be performed.

  In the present invention, the spherical electrode may be formed by coating the surface of a steel ball imitating a ball of a ball bearing with an insulating film.

In this invention, the spherical electrode may be a facing surface that faces the raceway surface of the ball bearing, and has a partial spherical surface imitating the ball of the ball bearing, and the spherical surface is covered with an insulating film. good. That is, the spherical surface is a surface that becomes a part of the surface of the sphere, and the shape of the spherical electrode other than the spherical surface is an arbitrary shape. In this case, the width of the spherical electrode corresponding to the axial direction of the raceway surface of the ball bearing may be a width facing a surface area narrower than the width excluding the chamfered portion on the raceway surface of the ball bearing.
In a ball bearing race, the raceway surface and the outer diameter surface portion are connected by a chamfered portion. Therefore, if there are variations in the dimensions of the chamfered portion, the dimensions of the chamfered portion are the same even if the groove curvature of the raceway surface is the same. Accordingly, the measured capacitance changes, and an error is given to the groove curvature measurement. Therefore, when the width of the spherical surface of the spherical electrode is a width facing a surface area narrower than the surface area excluding the chamfered portion on the raceway surface of the ball bearing, the dimensional variation of the chamfered portion affects the measured capacitance. The influence can be eliminated, the measurement error can be reduced, and the groove curvature can be measured with high accuracy.

  In the present invention, the raceway surface may be a raceway surface of an inner ring or an outer ring of a radial ball bearing, or may be a raceway surface of a thrust ball bearing.

The groove curvature measuring device for a ball bearing according to the present invention is a measuring device used in any one of the above-described ball curvature measuring methods for a ball bearing according to the present invention, and the surface is insulated from the measuring table for supporting the bearing ring of the ball bearing. A spherical electrode made of a conductor having a spherical surface coated with a film and imitating a ball of a ball bearing; pressing means for pressing the spherical surface of the spherical electrode against the raceway surface of the raceway ring; the conductor of the spherical electrode and the raceway surface AC voltage applying means for applying an AC voltage between them, voltage generating means corresponding to the capacitance between the conductor of the spherical electrode and the raceway surface by these means, and calculating this voltage as the groove curvature radius of the raceway ring Output means.
According to this configuration, using the method of the present invention, the groove curvature of the raceway surface can be measured with high accuracy at low cost without being affected by the operator's measurement technique as described above. Further, the present invention can be applied to a groove processing site of a bearing raceway surface.

The method of measuring the groove curvature of a ball bearing according to the present invention is to push the spherical surface of a spherical electrode made of a conductor having a spherical surface imitating a ball of a ball bearing, the surface of which is coated with an insulating film, onto the raceway surface of the raceway of the ball bearing. In the contact state, the capacitance between the spherical electrode and the raceway surface is measured, and the groove curvature of the raceway surface is measured from the capacitance value. However, it can be easily applied, and the groove curvature of the raceway surface can be measured with high accuracy at low cost without being affected by the operator's measurement technique.
The groove curvature measuring apparatus for a ball bearing according to the present invention is a measuring apparatus used in the groove curvature measuring method for a ball bearing according to the present invention, the measuring table for supporting the bearing ring of the ball bearing, and the surface thereof being covered with an insulating film. A spherical electrode made of a conductor having a spherical surface imitating a ball of a ball bearing, a pressing means for pressing the spherical surface of the spherical electrode against the raceway surface of the raceway ring, and an AC voltage between the conductor of the spherical electrode and the raceway surface And means for calculating and outputting a voltage corresponding to the electrostatic capacity of the conductor of the spherical electrode and the raceway surface to the groove radius of curvature, and so on. However, it can be used without any problem, and the groove curvature of the raceway surface can be measured with high accuracy at low cost without being affected by the operator's measurement technique.

  An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a principle diagram of a method for measuring the groove curvature of a ball bearing according to this embodiment. In the figure, a spherical electrode 3 is obtained by coating the surface of a spherical conductor (here, a steel ball) 4 imitating a ball of a ball bearing to be measured with an insulating film 5. The radius of curvature Rb of the conductor 4 of the spherical electrode 3 is made smaller than the groove radius of curvature Ra of the raceway surface 2 in the raceway (in this case, the inner race) 1 of the ball bearing. When the spherical electrode 3 is pressed against the raceway surface 2 of the raceway ring 1, a capacitor is formed between the spherical electrode 3 and the raceway ring 1. When the groove curvature of the raceway surface 2 is large (that is, the radius of curvature Ra is short) and the gap between the spherical electrode 3 and the raceway ring 1 is small, the capacitance of the capacitor increases. Conversely, when the groove curvature of the raceway surface 2 is small (that is, the radius of curvature Ra is long) and the gap between the spherical electrode 3 and the raceway ring 1 is large, the capacitance of the capacitor is small. The groove curvature measuring method of this ball bearing measures the groove curvature of the raceway surface 2 from the electrostatic capacity by using the principle described above. In FIG. 1, Ob represents the center of curvature of the sphere 4, Or represents the center of curvature of the raceway surface 2, and δ represents the film thickness of the insulating film 5. Needless to say, there is a relationship of Ra> Rb + δ, and if the largest steel ball is used within a range satisfying this relationship, the detection sensitivity becomes high.

  As the material of the insulating film 5 of the spherical electrode 3, for example, ceramic having wear resistance can be used. However, in this case, there is a defect that the shape after coating is disturbed. Therefore, as the material of the insulating film 5, a PAI (polyamide-imide) resin which is an example of a resin excellent in wear resistance and chemical resistance, or a material in which a ceramic such as alumina is added to the PAI resin as wear-resistant powder. It is desirable to use If the insulating film 5 has a film thickness δ that is too thick, it cannot be applied to the raceway surface 2 having a large groove curvature (short curvature radius Ra). Therefore, the film thickness δ is set to 25 μm here.

  FIG. 1 shows a configuration example of a circuit for detecting the capacitance of the capacitor. The capacitance detection circuit 6 includes an AC voltage application means 14, a reference capacitor 15, and a capacitance output means that constitute a part of a groove curvature measuring device 11 described later used in the groove curvature measuring method of the ball bearing. 16.

  The AC voltage application means 14 is a means that is electrically connected to the conductor 4 of the spherical electrode 3 and applies an AC voltage between the conductor 4 and the raceway ring 1. It has been confirmed by experiments that the waveform of the AC voltage to be applied may be rectangular or sinusoidal. Moreover, it has been confirmed by experiments that the frequency of the AC voltage is preferably higher in order to enable stable measurement. Specifically, stable measurement is possible when the frequency is 1 MHz rather than 100 kHz.

  The reference capacitor 15 is connected in series with the capacitor formed between the spherical electrode 3 and the race 1 by electrically connecting one end to the race 1 and grounding the other end. As the reference capacitor 15, it is desirable to use a capacitor of the same order as the measured capacitance, in other words, having the same order of capacitance.

  The capacitance output means 16 is a signal processing circuit that is electrically connected to the race 1 and outputs the capacitance between the spherical electrode 3 and the race 1 as a partial pressure of the reference capacitor 15. The capacitance output means 16 includes a rectifier circuit unit 17 that rectifies the divided voltage to process the signal using the capacitance as a voltage, a linear circuit (not shown), a zero point moving circuit, an amplifier 18, and a display 19. For example, it is constituted by various circuit units added to a general measuring instrument. The rectifier circuit unit 17 includes diodes 17a and 17b, a capacitor 17c, and the like. Since the groove curvature of the raceway surface 2 and the capacitance are in a non-linear relationship, the linear circuit corrects the relationship to a linear relationship. As another circuit unit constituting the capacitance output means 16, an output unit for recording measured data may be provided.

  FIG. 2 shows an example of a groove curvature measuring device 11 used in the above-described method for measuring the groove curvature of a ball bearing. This groove curvature measuring device 11 presses a measuring table 12 for supporting a ball bearing race 1, the spherical electrode 3 shown in FIG. 1, and the spherical surface of the spherical electrode 3 against the raceway 2 of the race 1. The pressing means 13, the AC voltage applying means 14 for applying an AC voltage between the conductors 4 of the spherical electrode 3, the reference capacitor 15 connected to the raceway 1 of the ball bearing, and the spherical electrode 3 and the raceway surface 2 And a capacitance output means 16 for outputting the capacitance between them as a partial pressure with the reference capacitor 15. The AC voltage applying means 14, the reference capacitor 15, and the capacitance output means 16 are combined into one circuit device housing 17 as the capacitance detection circuit 6, as in the case of the principle diagram shown in FIG. 1. Yes.

  FIG. 2 shows a case where the raceway 1 of the ball bearing to be measured is an inner ring of a radial ball bearing. The measurement table 12 is made of a substantially U-shaped member, and two lower electrodes 7 and 8 projecting upward are provided on the lower side portion 12a. The two lower electrodes 7 and 8 are also responsible for the alignment function of the raceway ring 1. The raceway ring 1 is placed on the lower electrodes 7 and 8 and supported in a predetermined posture. The reference capacitor 15 and the capacitance output means 16 are connected to one of the two lower electrodes 7 and 8 by a wiring 18 such as a coaxial line.

  A cylindrical pressing means 13 is provided on the upper side 12b of the measuring table 12 so as to be movable up and down, and the spherical electrode 3 is fixed to the lower end thereof. A spherical surface is formed on the groove bottom of the raceway surface 2 of the raceway ring 1 supported by the measurement table 12 by adjusting the pressing means 13 by raising and lowering the pressing means 13 as indicated by an arrow A with respect to the upper side portion 12b of the measurement table 12. The electrode 3 is pressed. The AC voltage applying means 14 is connected to the conductor 4 of the spherical electrode 3 by a wiring 19 such as a coaxial line passing through the inside of the pressing means 13. The outer conductors 18 a and 19 a of the wirings 18 and 19 are grounded together with the circuit device housing 17. By grounding in this way, the signal system of this measuring apparatus can be protected from incoming noise, and stable measurement can be performed.

  According to the groove curvature measuring method of this ball bearing, the spherical surface of the spherical electrode 3 formed by coating the surface of the conductor 4 having a spherical surface imitating the ball of the ball bearing with an insulating film 5 is used as the raceway surface of the raceway 1 of the ball bearing. 2, the capacitance between the spherical electrode 3 and the raceway surface 2 is measured, and the groove curvature of the raceway surface 2 is measured from the measured capacitance value. It can be easily applied at the groove processing site, and the groove curvature can be measured at low cost. Moreover, it can measure with high precision, without being influenced by the operator's measurement technique. In particular, the spherical electrode 3 is made of a conductor having a spherical surface imitating a ball of a ball bearing, and the spherical surface is pressed against the raceway surface 2. Therefore, the contact state between the raceway surface 2 of the ball bearing and the ball is measured. Therefore, accurate measurement can be performed.

  In the implementation of this measuring method, when the groove curvature measuring device 11 having the configuration shown in FIG. 2 is used, the bearing ring 1 of the ball bearing to be measured can be stably supported, and the groove of the raceway surface 2 can be supported. Since the spherical electrode 3 can be reliably pressed against the bottom, the groove curvature of the raceway surface 2 can be measured with high accuracy at low cost without being influenced by the operator's measurement technique.

By the way, in the bearing ring 1 of the ball bearing to which the above measuring method is applied, as shown in FIG. 3, the raceway surface 2 and the outer diameter surface portion 1a are connected by a chamfered portion 1b. For this reason, if the dimension of the chamfered portion 1b varies, the area of the raceway surface 2 facing the spherical electrode 3 changes. Since the electrostatic capacitance between the spherical electrode 3 corresponding to both electrodes of the capacitor and the raceway surface 2 is determined by the gap, the opposing area, and the dielectric constant between the electrodes, even if the groove curvature of the raceway surface 2 is the same, The capacitance changes in accordance with the size of the chamfered portion 1b, which gives an error in groove curvature measurement.
As an example of a measure for avoiding such a measurement error, prior to the groove curvature measurement, the groove depth (indicated by d in FIG. 3) of the raceway surface 2 is measured in advance, and the groove depth is determined according to the groove depth. What is necessary is just to correct | amend the measured electrostatic capacitance value. Thereby, the influence of the chamfered portion 1b on the groove curvature measurement can be eliminated.

  FIG. 4 shows another example of measures for avoiding the above-described measurement error. In this countermeasure example, a partial spherical surface 4a imitating a ball of a ball bearing is formed on the conductor 4 as an opposing surface of the raceway surface 2, and the spherical surface 4a is covered with an insulating film 5 to form an aspherical spherical electrode 3. It is composed. In this case, the width A of the spherical surface 4a covered with the insulating film 5 is a width facing a surface area narrower than the width B of the surface area excluding the chamfered portion 1b on the raceway surface 2. Thereby, the influence which the dispersion | variation in the dimension of the chamfer part 1b has on the measured electrostatic capacitance can be eliminated. In addition, since the detection sensitivity is so high that the difference between A and B is small, A / B is preferably 0.8 or more.

  When a steel ball is used as the conductor 4 of the spherical electrode 3 as shown in FIGS. 1 and 2, since the ball of the ball bearing can be used as it is, it is easy to obtain and the manufacturing cost of the spherical electrode 3 can be reduced. Thus, by using the spherical electrode 3 having a special shape other than the spherical shape, the groove curvature can be measured with high accuracy by reducing the measurement error.

  In the above embodiment, the reference capacitor 15 is connected to the raceway surface 2 of the ball bearing, and an AC voltage is applied to the conductor 4 of the spherical electrode 3 to measure the capacitance between the spherical electrode 3 and the raceway surface 2. Although the case has been described, conversely, even if the reference capacitor 15 is connected to the conductor 4 of the spherical electrode 3 and an AC voltage is applied to the raceway surface 2 of the ball bearing, The groove curvature can be accurately measured.

  Further, in the above embodiment, the case where the raceway surface of the inner ring of the radial ball bearing is set as the measurement object has been described as an example. Similarly, the groove curvature can be accurately measured.

It is a principle figure of the groove curvature measuring method of the ball bearing concerning one Embodiment of this invention. It is a block diagram which shows the groove curvature measuring apparatus used for the measuring method. It is explanatory drawing which shows the relationship between the track surface and chamfering part in the bearing ring to which the same measuring method is applied. It is sectional drawing which shows the other structural example of the spherical electrode in a groove curvature measuring apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ball bearing ring 1b ... Chamfer 2 ... Raceway surface 3 ... Spherical electrode 4 ... Conductor 5 ... Insulating film 6 ... Capacitance detection circuit 11 ... Groove curvature measuring device 12 ... Measuring stand 13 ... Pushing means 14 ... AC voltage application means 15 ... reference capacitor 16 ... capacitance output means

Claims (3)

  In a state where the spherical surface of the spherical electrode made of a conductor having a spherical surface coated with an insulating film and partially or partially imitating a ball of a ball bearing is pressed against the raceway of the raceway of the ball bearing, A groove curvature measuring method for a ball bearing, wherein a capacitance between a spherical electrode and the raceway surface is measured, and a groove curvature of the raceway surface is measured from the capacitance value.   2. The chamfered portion in the raceway surface of the ball bearing according to claim 1, wherein a width corresponding to the axial direction of the raceway surface of the ball bearing of the spherical electrode, a part of which is a conductor having a spherical surface imitating a ball of the ball bearing. A groove curvature measuring method of a ball bearing having a width opposite to a surface area narrower than a width excluding.   A measuring device used in the groove curvature measuring method of the ball bearing according to claim 1 or 2, wherein the measuring table for supporting the bearing ring of the ball bearing, and the ball of the ball bearing whose surface is coated with an insulating film. A spherical electrode made of a conductor having a simulated spherical surface, pressing means for pressing the spherical surface of the spherical electrode against the raceway surface of the raceway ring, and an AC voltage for applying an AC voltage between the conductor of the spherical electrode and the raceway surface A device for measuring the groove curvature of a ball bearing, comprising means for converting the capacitance between the spherical electrode and the raceway surface into an electrical signal by an applying means and calculating the signal as a groove radius of curvature of the raceway ring.

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