Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
2000-02-04
2001-09-25
Williams, Hezron (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
C073S865800
Reexamination Certificate
active
06293151
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a ball bearing inspection apparatus for inspecting a ball bearing for surface defects of rolling elements (balls), or the like, interposed between inner and outer races of the ball bearing by detecting vibration generated when rotating the inner and outer races relatively to each other.
2. Description of the Related Art
In a ball bearing incorporated in a precision machine such as a hard disk driving device, or the like, there is a possibility that vibration may be caused by rotation even in the case where a surface of any one of races or balls has a little defect. Therefore, the ball bearing to be incorporated in such a precision machine must be individually inspected for defects of ball surfaces, or the like, by a ball bearing inspection apparatus.
As this type ball bearing inspection apparatus, there is known a conventional apparatus for inspecting a ball bearing for defects by detecting vibration (sound) caused by rotation when relatively rotating inner and outer races of the ball bearing to each other. For example, the conventional ball bearing inspection apparatus is formed so that an outer race is rotated by a rotation shaft in the condition that an inner race is fixed to a stationary shaft. On this occasion, the stationary shaft is pressed with a predetermined load in an axial direction by a cylinder. In this manner, the stationary shaft press the inner race to thereby apply a pre-load to balls. The magnitude of the pre-load is set to be equal to that in use of the ball bearing. In this condition, vibration (sound) caused by rotation is detected by a vibrometer (mircophone), and a judgment is made on the basis of a result of the detection as to whether any one of ball surfaces has a defect or not.
The aforementioned conventional ball bearing inspection apparatus is, however, able to inspect no area but a constant contact area (running trace) of ball surfaces because the balls are loaded with a predetermined constant load (pre-load) in the inspecting operation (even though there is a clearance in the ball bearing itself), so that there is no large change in balls' own rotation axes. There is a possibility that a large part of the ball surfaces except the range of the running trace is unable to be inspected.
On the other hand, changing the load to be applied in the axial direction might be thought of. The balls' own rotation axes are, however, unable to be changed greatly by such a simple means of changing the load. There is still a possibility that a lot of portions which have not been inspected yet might be left.
In addition, applying a pre-loading the balls in a reverse direction to change the balls' own rotation axes by inverting an installing posture of the ball bearing as an object into the ball bearing inspection apparatus might be thought of. Installing operation (that is, an operation in which the ball bearing is installed into the ball bearing inspection apparatus), however, has to be repeated by a plurality of times. There is an expected problem that a long time is required for the inspection.
SUMMARY OF THE INVENTION
The present invention is designed in consideration of the aforementioned circumstances and it is an object thereof to provide a ball bearing inspection apparatus in which a large area of ball surfaces can be inspected in a short time at one installing try.
In order to achieve the above object, according to an aspect of the present invention, there is provided a ball bearing inspection apparatus for inspecting a ball surface state of a ball bearing by measuring vibration generated while relatively rotating inner and outer races of the ball bearing, comprising: a rotation shaft fitted to one of the inner and outer races for rotating the one race while limiting the movement of the one race in an axial direction of the rotation shaft; a press plate disposed on an opposite side of the rotation shaft with respect to the ball bearing for pressing the other race in the axial direction of the rotation shaft while limiting the rotation of the other race; and a press-back plate provided so as be movable in the axial direction of the rotation shaft for pressing back the other race in a direction reverse to the pressing direction of the press plate.
In this ball bearing inspection apparatus, when the rotation shaft is rotated, either one of inner and outer races fitted to the rotation shaft is rotated. Hence, the inner and outer races rotate relatively to each other. When the other one of the inner and outer races is pressed by the press plate in this condition, the inner and outer races are displaced relatively to each other in an axial direction of the rotation shaft. When the other one of the races is contrariwise pressed back by the press-back plate in a direction reverse to the pressing direction of the press plate, the inner and outer races are displaced in an axial direction reverse to the aforementioned direction of the displacement thereof. Hence, the pressing direction applied to the other one of the inner and outer races is changed over to the one or the other one of the axial directions, by which rotation axes of the balls interposed between the inner and outer races change. As a result, contact surfaces of the balls change. Hence, a larger area of the contact surfaces can contribute to the measurement at an installing try or a small number of installing tries, so that the whole area of the contact surfaces of the balls can be measured in a short time.
A ball bearing inspection method using the ball bearing inspection apparatus according to the present invention is a ball bearing inspection method for inspecting a ball surface state of a ball bearing by measuring vibration generated while relatively rotating inner and outer races of the ball bearing. The method comprises the steps of: rotating one of the inner and outer races of the ball bearing by a rotation shaft; pressing the other of the inner and outer races in an axial direction of the rotation shaft while limiting the rotation of the other race by use of a press plate disposed on an opposite side of the rotation shaft with respect to the ball bearing; pressing back the other race in a direction reverse to the pressing direction of the press plate by use of a press-back plate provided movably in the axial direction of the rotation shaft; and pressing the other race in the axial direction of the rotation shaft again by use of the press plate after removing the pressure based on the press-back plate; wherein the pressing step, the pressing-back step and the re-pressing step are repeated successively by a predetermined number of times to thereby inspect the ball surface state of the ball bearing on the basis of vibration measured in the pressing step.
In this ball bearing inspection method, the other one of the relatively rotating inner and outer races is pressed by the press plate and then pressed back in a reverse direction by the press-back plate and then pressed in the axial direction again by the press plate. Hence, whenever the pressing direction is changed over, the rotation axes of the balls interposed between the inner and outer races change and the contact surfaces of the balls change. Hence, when the pressing step, the pressing-back step and the re-pressing step are repeated by a predetermined number of times to thereby inspect the ball surface state of the ball bearing on the basis of vibration measured in the pressing step, new surfaces of ball come into contact successively to make it possible to inspect a wider range of the ball surfaces as the number of changing-over tries increases.
Further, the ball bearing inspection method using the ball bearing inspection apparatus according to the present invention may be of the type for inspecting a ball surface state of a ball bearing by measuring vibration generated in a vibrometer attached to a press plate while relatively rotating inner and outer races of the ball bearing in the condition that a rotation shaft is removably attached t
Kawamata Takeo
Maeda Takashi
Shibazaki Hiroshi
NSK Ltd.
Saint-Surin Jacques
Sughrue Mion Zinn Macpeak & Seas, PLLC
Williams Hezron
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