JP2011174824A - Apparatus for evaluation of bearing rigidity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing rigidity evaluation apparatus, capable of accurately determining the quality of the bearing rigidity of a bearing with an outer ring shape having right-to-left asymmetry and vertical asymmetry. <P>SOLUTION: The bearing rigidity evaluation apparatus for evaluating the bearing rigidity of a bearing such as a double row bearing and a combinational bearing to which a pre-load has been applied includes an outer-ring-fixing device for fixing the outer ring of the bearing, a shaking device for providing vibrations of a prescribed frequency in an axial direction for either the inner ring of the bearing or a shaft fitted in the inner ring, and a vibration detector for detecting vibrations at the position of the axial center of either the inner ring or the shaft fitted in the inner ring. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a bearing stiffness evaluation apparatus that evaluates bearing stiffness for rolling bearings such as double row bearings and combination bearings to which preload is applied, particularly hub unit bearings for supporting wheels.

  Conventionally, in such a rolling bearing, high rigidity is required from the viewpoint of the performance of the machine in which the bearing is incorporated. However, if the amount of preload is increased to increase the rigidity too much, the preload becomes excessive and the bearing performance (increased friction moment, abnormal heat generation, fatigue life, etc.) is reduced. Therefore, it is necessary to control the rigidity value of the bearing within a certain range while associating it with the preload amount.

  Conventionally, as a means for measuring the rigidity value of this bearing in association with the amount of preload, the inner ring is vibrated from the bearing axial direction (hereinafter referred to as the axial direction) in a bearing in which the inner and outer rings are not fixed, There is a known method for evaluating rigidity by detecting axial vibration from a vibration detecting sensor provided on an axial end surface of a shaft body (hereinafter referred to as an inner ring) fitted to an inner ring and an excitation position of an outer ring. ing. This method uses a vibration model having an outer ring and an inner ring as mass points and a bearing having a two-degree-of-freedom system of an inner ring-spring (rolling element) -outer ring, and is schematically shown in FIG. 5B. As shown in this figure, an axial vibration V is applied to the inner ring, and axial vibrations of the outer ring and the inner ring, which are sensitive to the amount of preload applied to the bearing and the bearing rigidity, are detected. The natural frequency of the bearing is obtained from this vibration, and the quality of the rigidity is determined based on the magnitude.

  In recent years, in hub unit bearings for supporting wheels, an outer ring flange portion has an increasing number of asymmetrical shapes in the upper, lower, left, and right sides (hereinafter referred to as upper, lower, left, and right) on a plane perpendicular to the bearing axial direction. When the conventional rigidity evaluation of the bearing is performed by a method of vibrating without fixing the outer ring, the mass distribution of the outer ring flange portion is asymmetrical in the vertical and horizontal directions, and as shown in FIG. The moment M is applied, and the outer ring vibrates in directions other than the axial direction. As a result, it is difficult to detect the axial vibration of the outer ring, it is difficult to detect the natural frequency, and there is a possibility that an accurate erroneous determination of whether the rigidity is good or not may occur. As a technique for solving this problem, Patent Document 1 discloses that the inner ring is vibrated in the axial direction while the inner ring is fixed, and one sensor provided on the inner ring and a plurality of sensors provided on the outer ring are used. A technique for detecting vibration is described. In this method, as shown in FIG. 5D, the phase difference between the vibration of the inner ring and the vibration of each sensor installed at a plurality of locations of the outer ring is obtained. From this phase difference, an axial component and a plurality of other vibration components can be obtained. From this, the natural frequency is obtained by specifying the axial vibration, and the rigidity is evaluated.

JP 2000-74788 A

  However, in the method of Patent Document 1, in order to extract a plurality of vibration components from the vibration signal, at least two sensors for detecting the vibration of the outer ring are required. In addition, complicated calculation is required, and there is a problem that it takes time to evaluate rigidity. In view of the above, the present invention provides a bearing rigidity evaluation apparatus that can accurately determine the quality of bearing rigidity of a bearing provided with preload, particularly a bearing having an asymmetric outer ring shape in the upper, lower, left, and right directions. One purpose. Another object of the present invention is to provide a low-cost bearing rigidity evaluation apparatus that speeds up processing of vibration signals for rigidity evaluation.

The above object of the present invention can be achieved by the following constitution.
(1) In a bearing rigidity evaluation apparatus for evaluating bearing rigidity of a bearing such as a double row bearing or a combination bearing to which preload is applied, an outer ring fixing means for fixing an outer ring of the bearing, an inner ring of the bearing, and an inner ring fitted to the inner ring Vibration at a center position of either the inner ring or the shaft fitted to the inner ring is applied to a vibration device that applies a predetermined frequency vibration in the axial direction to any one of the combined shaft bodies. And a vibration detecting means for detecting the bearing rigidity.
(2) The bearing rigidity evaluation apparatus according to claim 1, wherein the outer ring fixing means is any one of a pneumatic chuck, a hydraulic chuck, a magnet chuck, and a vacuum chuck.
(3) The bearing rigidity evaluation apparatus according to claim 1, wherein the vibration detecting means is any one of a displacement type sensor, a speed type sensor, and an acceleration type sensor.
(4) FFT analysis is performed on the vibration signal output from the vibration detection means, and a frequency peak highly correlated with the bearing preload is extracted from the frequency waveform obtained from the FFT analysis, and the frequency peak is set in advance. The bearing rigidity according to any one of claims 1 to 3, further comprising: a comparison determination unit that determines whether the bearing rigidity is good or bad compared with a frequency range; and a display / recording unit that displays or records a result of the determination. Evaluation device.

  With the configuration as described above, the outer ring is not vibrated by the vibrator because the outer ring is fixed in the bearing rigidity evaluation apparatus according to the present invention. That is, as schematically shown in FIG. 5 (a), an inner ring-spring (rolling element) one-degree-of-freedom system is formed. Therefore, even for bearings with an outer ring shape that is asymmetrical in the vertical and horizontal directions, it is possible to accurately detect the axial vibration of the inner ring without being affected by the shape, so that the natural frequency of the bearing can be accurately calculated. Is possible. As a result, it is possible to accurately determine the quality of the preload and the bearing rigidity even in a bearing having an outer ring shape that is asymmetrical in the vertical and horizontal directions. Further, in the evaluation of the preload amount and the rigidity value, it is only necessary to consider the axial vibration of the inner ring or the shaft body fitted to the inner ring, so that the processing of the vibration signal for determination can be speeded up. Furthermore, since it is only necessary to detect the axial vibration of the inner ring or the shaft fitted to the inner ring, only one vibration sensor is required and the cost is reduced. For this reason, the bearing rigidity evaluation apparatus of the present invention is also effective for a bearing in which the outer ring and other elements do not have an asymmetric shape.

1 is a block diagram showing an overall configuration of a bearing stiffness evaluation apparatus according to a first embodiment of the present invention. It is a frequency spectrum when the outer ring is not fixed. It is a block diagram which shows the whole structure of the bearing rigidity evaluation apparatus which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the whole structure of the bearing rigidity evaluation apparatus which concerns on 3rd Embodiment of this invention. It is a schematic diagram which shows the method of performing this invention and the conventional rigidity evaluation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing the overall configuration of the first embodiment of the bearing stiffness evaluation apparatus of the present invention. As shown in FIG. 1, the bearing stiffness evaluation apparatus 10 according to the present embodiment includes a vibration unit 1 that applies vibration of a predetermined frequency to a bearing to which preload is applied, and vibration for detecting vibration of an inner ring of the bearing. The detecting unit 2, the rigidity of the bearing is obtained from the detected vibration of the inner ring of the bearing, the arithmetic processing unit 3 for calculating the preload applied to the bearing from the obtained bearing rigidity, and the outer ring for fixing The hub unit bearing 4 attached to the wheel of the automobile is attached to the apparatus as a bearing to be measured.

  The hub unit bearing 4 which is a bearing to be measured includes an outer ring 42 having two rows of rolling surfaces formed on the inner periphery, and a hub shaft having a rolling surface facing one of the rolling surfaces of the outer ring 42 formed on the outer periphery. 41, and an inner ring member 45 having a rolling surface facing the other rolling surface of the outer ring 42 formed on the outer periphery. The inner ring member 45 is press-fitted into the hub shaft 41, and the inner ring member 45, the hub shaft 41, Cooperate with each other to form an inner ring for the outer ring 42. Balls 43 and 44 are inserted between the outer ring 42, the hub shaft 41 and the inner ring member 45. A hub flange 41a is integrally formed at one end of the hub shaft 41, and a plurality of holes (not shown) for receiving bolts for fixing the hub unit bearing 4 to a mounting target portion are formed in the flange 41a. Is provided. A shoulder portion is formed at an intermediate portion of the hub shaft 41, and a screw portion 41b into which the nut 46 is screwed is formed at the other end portion. The inner ring member 45 is tightened by a nut 46 that is screwed into the threaded portion 41b while the end portion of the inner ring member 45 is pressed against the shoulder portion of the hub shaft 41. By this tightening, the outer ring 42 is connected to the hub shaft 41 and the inner ring member 45. A preload is applied to the balls 43 and 44. Further, a negative gap is formed between the end faces where the outer ring 42 and the hub shaft 41 face each other. Further, an annular rib is formed at a substantially intermediate position in the axial direction on the outer peripheral surface of the outer ring 42, and the annular rib has a plurality of bolt insertion holes (not shown) and extends radially outward. The outer ring flange 42a is formed at an arbitrary interval in the circumferential direction.

  The outer ring flange 42a is clamped and fixed by the outer ring fixing portion 5. That is, the outer ring fixing portion 5 has a U-shaped groove that sandwiches the outer ring flange 42 a, a chuck portion 51 that is divided into a plurality, and a housing portion that holds the chuck portion 51 and encloses the vibrator 1. 52. As shown in FIG. 1, the housing 52 includes a bottom plate 52 a for installing the vibrator 1, a middle plate 52 b, an upper plate 52 c and a side plate 52 d for holding the chuck 51. Become. An injection hole 52e for injecting at least oil or air is provided in a portion of the side plate 52d facing the chuck portion 51.

  In the outer ring fixing portion 5 having such a configuration, after the outer ring flange 42a is sandwiched between the chuck portions 51, oil or air is injected into the injection hole 52e from a pump or the like installed outside the support box 52, The outer ring flange 42a is supported and fixed by moving the chuck portion 51 in the direction of the center axis (inward in the radial direction) of the hub unit bearing 4, and the outer ring 42 of the hub unit bearing 4 is fixed to the outer ring fixing portion 5. The That is, the chuck portion 51 is a mechanism that becomes a hydraulic chuck or a pneumatic chuck.

  The excitation unit 1 includes an oscillator 1a that generates a voltage waveform that sweeps a sine wave at high speed from the lower limit to the upper limit frequency of the measurement frequency band, and an excitation force that has an amplitude and a frequency that correspond to the voltage waveform generated from the oscillator 1a. , An exciter 1c for transmitting the excitation force generated by the electrodynamic exciter 1b to the hub shaft 41 of the hub unit bearing 4, and the hub unit bearing 4 The inner ring installation base 1d for installing the first inner ring 41 is provided, and the flange portion 41a of the first inner ring 41 is placed on the inner ring installation base 1d. Here, 1 to 5 kHz is set as a measurement frequency band, and a voltage waveform is generated by sweeping a sine wave having a constant amplitude, so that an excitation force having a constant amplitude is generated at 1 to 5 kHz. ing. Therefore, vibration is excited in the hub unit bearing 4 by the excitation force. The vibration applied to the hub shaft 41 from the oscillator is not transmitted to the hub unit bearing 4 from other than the excitation rod 1c, and between the electrodynamic exciter 1b and the inner ring installation table 1d, and the inner ring installation table 1d. A gap is formed between the outer ring fixing portion 5 and the side plate 52d. For the same reason, the electrodynamic exciter 1b and the inner ring mounting base 1d are installed on the bottom plate portion 52a of the outer ring fixing portion 5 via a vibration isolating material 1e such as a vibration isolating rubber.

  The vibration detection unit 2 includes a vibration detection sensor 21 and an amplifier 22. The vibration detection sensor 21 is disposed at the center position of the hub shaft 41, and outputs the detected vibration waveform in the axial direction of the hub shaft 41 as a voltage signal. The vibration detection sensor 21 may be a displacement type, speed type, or acceleration type vibration detection sensor. The voltage signal output from the vibration detection sensor 21 is amplified by the amplifier 22 and then transmitted to the arithmetic processing unit 3.

  The arithmetic processing unit 3 includes an FFT analysis unit 31, a comparison determination unit 32, and a display / recording unit 33. The voltage signal transmitted to the arithmetic processing unit 3 is first input to the FFT analysis unit 31, and the input voltage signal is subjected to fast Fourier transform (FFT) to calculate frequency spectrum data. One frequency peak having a high correlation with the bearing preload, that is, a frequency peak representing the natural frequency is extracted. Next, the frequency peak is transmitted to the comparison / determination unit 32, compared with a preset frequency range, and whether the preload amount and the rigidity are good or not is determined based on whether or not the frequency peak exists within this range. The result obtained by the comparison / determination unit 32 is transmitted to the display / recording unit 33 and displayed and recorded on the screen of a monitor or the like. The arithmetic processing unit 3 may be configured using, for example, an existing operation system and a personal computer in which a rigidity evaluation execution software application is installed, or may be configured by an independent processing circuit or storage circuit for each unit. You may comprise as an arithmetic unit.

  Here, a method of determining the frequency range used for determining the quality of the preload amount and the rigidity will be described. First, a master of an object to be measured for bearing rigidity is installed in the bearing rigidity evaluation apparatus 10. From the frequency spectrum data obtained by exciting the master, the frequency of the first order mode to the second order mode indicating the natural frequency can be obtained. The frequency range of the mode when the appropriate preload range is loaded is obtained using the frequency of the mode showing the highest peak as an index. This is the frequency range used for the determination.

  FIG. 2A is a frequency spectrum of the hub unit bearing 4 measured with the outer ring fixed. FIG. 2B is a frequency spectrum obtained by a method in which the outer ring 42 of the hub unit bearing 4 is not fixed as in the conventional method. The horizontal axis indicates the frequency (Hz), the vertical axis indicates the frequency level, the thick line indicates the case where the preload is large, and the thin line indicates the case where the preload is small.

  When the outer ring 42 is not fixed as in the prior art, a plurality of frequency spectrum peaks are observed in each waveform as shown in FIG. Among them, the peak representing the frequency of the natural frequency of the bearing is only F3 and F4, and the other peaks are peaks related to those other than axial vibration. Thus, when there is a peak equivalent to or higher than the peak representing the frequency of the natural frequency of the bearing, in the process of rigidity evaluation, as a peak representing the frequency of the natural frequency to be compared with the preset frequency range, Such peaks, such as selecting peaks other than F3 and F4, may cause misjudgment.

  On the other hand, when the outer ring 42 is fixed, peaks F1 and F2 of the frequency spectrum can be obtained for each waveform as shown in FIG. These peaks F1 and F2 are peaks representing the frequency of the natural frequency of the bearing. As shown in FIG. 2B, it can be seen that there is no peak that causes erroneous determination. That is, by using the rigidity evaluation apparatus 10 of the present embodiment, it is possible to accurately determine the preload amount, that is, the quality of the bearing rigidity.

  With the configuration as described above, in the bearing stiffness evaluation apparatus 10 according to the present embodiment, the outer ring flange 42a is sandwiched and the outer ring 42 is fixed by the chuck portion 51 provided in the outer ring fixing portion 5, and therefore the vibrator 1 Thus, the outer ring 42 does not vibrate. That is, as schematically shown in FIG. 5A, a one-degree-of-freedom system of hub shaft (inner ring) -spring (rolling element) is provided. For this reason, the axial vibration of the hub shaft 41 can be accurately detected without being affected by the outer ring 42 having an asymmetrical shape in the vertical and horizontal directions, so that the natural frequency of the bearing can be accurately calculated. . As a result, it is possible to accurately determine whether the preload amount and the bearing rigidity are good or bad even with a bearing having an asymmetric outer ring in the vertical and horizontal directions.

  Further, since only the vibration of the hub shaft 41 needs to be considered in the evaluation of the preload amount and the rigidity value, the processing of the vibration signal for determination can be speeded up. Furthermore, since only the vibration of the hub shaft 41 needs to be detected, a single vibration sensor is sufficient and the cost is reduced. For this reason, the bearing rigidity evaluation apparatus of this embodiment is also effective for a bearing in which the outer ring and other elements do not have an asymmetric shape.

(Second Embodiment)
FIG. 3 is a block diagram showing the overall configuration of the second embodiment of the bearing stiffness evaluation apparatus of the present invention. In the bearing rigidity evaluation apparatus 20 according to the present embodiment, as shown in FIG. 3, the outer ring flange 42 a is sandwiched by the magnet chuck 53 and the outer ring 42 is fixed to the outer ring fixing portion 5. With such a configuration, there is no need for an injection hole or a pump for injecting oil or air as shown in FIG. 1, and the cost for rigidity evaluation and device manufacture is reduced. Other configurations and operational effects are the same as those of the first embodiment.

(Third embodiment)
FIG. 4 is a block diagram showing the overall structure of a third embodiment of the bearing stiffness evaluation apparatus of the present invention. In the bearing stiffness evaluation apparatus 30 according to the present embodiment, as shown in FIG. 4, the outer ring flange 42 a is sandwiched by the vacuum chuck 54, and the outer ring 42 is fixed to the outer ring fixing portion 5. That is, the outer ring fixing portion 5 includes a housing portion 52 having a bottom plate portion 52a and a side plate 52d, and a vacuum chuck 54. The vacuum chuck 54 sandwiches the outer ring flange 42a by the sandwiching portion 54a, and the sandwiching portion 54a. The air existing in the minute space S between the outer ring flange 42a is exhausted from the exhaust port 54b, and the outer ring 42 is fixed to the outer ring fixing portion 5 by setting the space S to a negative pressure. Other configurations and operational effects are the same as those of the first embodiment.

  Note that the bearing stiffness evaluation apparatus of the present invention is not limited to the above embodiment, and can be appropriately modified and improved as long as it has a configuration for fixing the outer ring. It can be used as a body. Moreover, in the said embodiment, although it was set as the structure which vibrates a hub shaft and detects the vibration of a hub shaft, it is not limited to this, It is good also as a structure which vibrates an inner ring and detects the vibration of an inner ring. Furthermore, in the above embodiment, the hub unit bearing is the object of rigidity evaluation, but it can be applied to bearings other than the hub unit bearing.

DESCRIPTION OF SYMBOLS 10, 20, 30 Bearing rigidity evaluation apparatus 1 Exciter 2 Vibration detection part 3 Arithmetic processing part 4 Hub unit bearing 5 Outer ring fixing part

Claims (4)

In a bearing rigidity evaluation device for evaluating bearing rigidity for a bearing such as a double row bearing or a combination bearing to which a preload is applied, an outer ring fixing means for fixing an outer ring of the bearing, an inner ring of the bearing, and an inner ring fitted to the inner ring A vibration for detecting vibration at the center position of one of the vibration device for applying a vibration at a predetermined frequency in the axial direction to any one of the shaft bodies and the shaft body fitted to the inner ring and the inner ring. And a bearing rigidity evaluation apparatus. 2. The bearing rigidity evaluation apparatus according to claim 1, wherein the outer ring fixing means is any one of a pneumatic chuck, a hydraulic chuck, a magnet chuck, and a vacuum chuck. The bearing rigidity evaluation apparatus according to claim 1, wherein the vibration detection unit is a displacement type sensor, a speed type sensor, or an acceleration type sensor. FFT analysis of the vibration signal output from the vibration detection means, an FFT analysis unit for extracting a frequency peak highly correlated with bearing preload from the frequency waveform obtained from the FFT analysis, and a frequency range in which the frequency peak is set in advance. The bearing rigidity evaluation apparatus according to claim 1, further comprising a comparison / determination unit that compares and determines whether or not the bearing rigidity is good and a display / recording unit that displays or records a result of the determination.

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