Measuring and testing – Dynamometers – Responsive to torque
Reexamination Certificate
1999-11-23
2002-04-30
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Dynamometers
Responsive to torque
C073S514220
Reexamination Certificate
active
06378382
ABSTRACT:
TITLE OF THE INVENTION
Device for Measuring Rotation Accuracy and Dynamic Torque for Radial Rolling Bearing
FIELD OF THE INVENTION
The present invention relates to a device for measuring rotation accuracy and dynamic torque for a radial rolling bearing, specifically a device which is used to measure the rotation accuracy and dynamic torque of the radial rolling bearings installed in various kinds of rotation supports in order to make it possible to make a higher performance rotation support unit.
BACKGROUND OF THE INVENTION
In radial rolling bearings such as ball bearings, roller bearings, tapered roller bearings or the like, is known that differences occur in the shapes and dimensions of the rolling bodies such as the balls, roller, tapered rollers, etc., as well as difference in the shapes of the raceways in the inner and outer races, and that non-repetitive minute displacements in the radial direction, called ‘Non-repetitive Run-out’ (NRRO), occur each rotation. In the case of radial bearings that are installed in the rotation supports of high-precision devices such as hard disk drives (HDD), these minute displacements have a large effect on performance.
Therefore, it is very important that rotation accuracy of a radial rolling bearing is measured, and that if it is found that this kind of NRRO exists, measures be taken to remove it in order to improve the performance of the device.
A prior art device, as disclosed in Japanese Patent Publication No. Toku Kai Hei 9-178613, for measuring the rotation accuracy of a radial rolling bearing for this objective has been known.
FIGS. 6
thru
8
show the prior art device that is described in this disclosure.
What is measured by this device is a radial rolling bearing
1
, specifically deep-groove type ball bearing, which comprises an inner race
2
, outer race
3
and multiple rolling bodies, specifically balls
4
provided between the inner race
2
and outer race
3
.
With the device for measuring rotation accuracy for a radial rolling bearing shown in
FIGS. 6
thru
8
, the NRRO of this radial rolling bearing
1
is obtained by measuring the displacement in the radial direction of the outer race
3
of the radial rolling bearing
1
.
This kind of rotation accuracy measurement device for radial rolling bearing includes a frame
8
that comprises a top plate
5
and bottom plate
6
that connected by support posts
7
such that the top plate
5
and bottom plate
6
are parallel with each other. Of these, fastened to and supported by the bottom plate
6
is a drive unit
9
which drives and rotates the inner race
2
in the state where it is predeterminedly positioned in the radial direction.
This drive unit
9
comprises a spindle shaft
10
that is driven and rotated by a motor that is located in the vertical direction (not shown in the drawing), and a precision bearing device
11
such as a hydrostatic gas bearing which supports the spindle shaft
10
with high accuracy such that it can rotate freely and such that there is as little displacement in the radial direction as possible.
The inner race
2
fits without play around the top end of the spindle shaft
10
of this drive device
9
.
On the other hand, fastened to and supported by the top plate
5
is a support device
12
by which the outer race
3
is supported, such that it does not rotate and such that it displaces freely in the radial direction, as well as that an axial load is applied to the outer race
3
. The support device
12
has a cylindrical member
14
that is fastened to the section of retaining hole
13
formed in the center of the top plate
5
. In order to apply this axial load, a through hole
16
is formed in the bottom section
15
of the cylindrical member
14
, and a push rod
17
is inserted through this through hole
16
and has a rimmed section
18
attached on the top end thereof.
Moreover, the support device
12
has a push rod
17
, a receiving plate
19
that is fitted inside the cylindrical member
14
such that it raises and lowers freely, and a compression spring
20
that is located between the top surface of the rimmed section
18
and the bottom surface of the receiving plate
19
, and this spring
20
pushes the push rod
17
downward. Also, the support device
12
has a cover plate
21
that attaches to the opening on the top end of the cylindrical member
14
, and a screw hole (not shown in the figure) is formed in the center of the cover plate
21
, and an adjustment screw
22
is screwed into this screw hole. The axial load that is applied to the push rod
17
by the compression spring
20
can be freely adjusted by adjusting the position of the receiving plate
19
up or down by turning the adjustment screw
22
.
Moreover, the support device
12
has a holder
23
formed on the bottom end thereof, and a circular concave hole
24
is formed on the bottom surface of the holder
23
to hold the outer race
3
, so that it does not move and, so that there is no elastic deformation. On the top surface of the holder
23
, there is a protruding section
25
that is formed such that it extends in a radial direction. Furthermore, the support device
12
has an anchoring plate
26
that is fastened on the bottom end of the push rod
17
, and there is a protruding section
27
that is formed on the bottom surface of the anchoring plate
26
such that it extends in a radial direction.
A porous material
28
, made from a sintered material or the like, is placed and held between the top surface of the holder
23
and the bottom surface of the anchoring plate
26
, and to form a hydrostatic gas bearing
29
that allows displacement in the radial direction.
In other words, on the bottom surface of the porous material
28
there is a concave groove
30
whose width is a little larger than the width of the protruding section
25
on the top surface of the holder
23
, while on the top surface of the porous material
28
, there is a concave groove
31
whose width is a little larger than the width of the protruding section
27
on the bottom surface of the anchoring plate
26
. Both of these grooves
30
,
31
run in a radial direction in the porous material
28
such that they run perpendicular to each other.
There is an air-supply hole
32
formed in a part of the porous material
28
to allow for compressed air to be fed freely inside the porous material
28
. When the rotation accuracy measurement device for radial rolling bearing is operating, the compressed air that is fed to the inside of the porous material
28
from this air-supply hole
32
is blown onto the surfaces of the protruding sections
25
,
27
from the concave grooves
30
,
31
and forms a compressed air layer between the inner surfaces of the concave grooves
30
,
31
and the surfaces of the protruding sections
25
,
27
.
In the same way, the compressed air is blown onto the bottom surface of the anchoring plate
26
from the top of the porous material
28
, and onto the top surface of the holder
23
from the bottom surface of the porous material
28
to form a compressed air layer between these pairs of top and bottom surfaces.
In this state, the holder
23
is supported such that it does not come in contact with the bottom of the anchoring plate
26
, that it does not rotate with respect to the anchoring plate
26
, and that it displaces freely in the radial direction by a very weak force. The axial load due to the compression spring
20
is freely transmitted by way of these compressed air layers.
Furthermore, a non-contact type displacement sensor
33
is located on part of the frame
8
between the bottom surface of the top plate
5
and the top surface of the bottom plate
6
such that it faces the outer surface of the holder
23
that holds the outer race
3
.
A measurement device, such as a laser Doppler vibration meter, which can measure the minute displacement of the outer surface of the holder
23
that holds the measured object, namely the outer race
3
, without coming in contact with it, is used for this displacement sensor
33
. In the example shown in the fig
Endou Ryoma
Noguchi Shoji
Allen Andre
Crowell & Moring LLP
Fuller Benjamin R.
NSK Ltd.
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