Electricity: measuring and testing – Electrical speed measuring – Including speed-related frequency generator
Reexamination Certificate
1998-09-28
2001-04-17
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Electrical speed measuring
Including speed-related frequency generator
C324S173000, C384S448000
Reexamination Certificate
active
06218827
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a rolling bearing unit having a rotating speed detector for rotatably supporting a wheel of an automobile by a suspension, and the rolling bearing unit having a rotating speed detector is used for detecting a rotating speed of the wheel.
A rolling bearing unit having a rotating speed detector is used for rotatably supporting a wheel of an automobile by a suspension and also used for controlling an anti-lock brake system (ABB) or a traction control system (TCS) by detecting a rotating speed of the wheel with the detector. Conventionally, various types of rolling bearing units having rotating speed detectors are well known. Each rotating speed detector incorporated into the rolling bearing unit includes a tone wheel, which is an element to be detected, rotated in conjunction with a wheel, and a sensor to output an output signal, the frequency of which changes in proportion to a rotating speed of the tone wheel. For example, a rolling bearing unit having a rotating speed detector shown in
FIGS. 19 and 20
is described in the Technical Report No. 94-16051 by HATSUMEI KYOKAI, which is referred to as the first conventional example, hereinafter.
A hub
1
includes an inner race assembly. A flange
2
for fixing a wheel is formed on an outer circumferential surface of the outside end portion of the hub
1
. The outside is defined as a side located outside of a vehicle with respect to the width direction of the vehicle when the rolling bearing is assembled into the vehicle. An inner raceway
3
a
and a step portion
4
are formed on an outer circumferential surface of the middle portion of the hub
1
. Further, an inner raceway
3
b
is formed on an outer circumferential surface of the hub
1
. In this way, an inner race
5
composing the inner race assembly in conjunction with the hub
1
is supported while an outer end surface of the inner race
5
is pushed against the step portion
4
. In this connection, instead of directly forming the inner raceway
3
a
on the outer circumferential surface of the hub
1
, another inner race (not shown) different from the hub
1
may be provided, and the inner race and the above inner race
5
may be outwardly engaged with the hub
1
so as to be fixed.
A male screw portion
6
is formed in a portion close to the inside end of the hub
1
. The inside is defined as a side located inside of a vehicle with respect to the width direction of the vehicle when the rolling bearing is assembled into the vehicle. When a nut
7
is fastened to the male screw
6
, the inner race
5
is fixed in a predetermined portion on the outer circumferential surface of the hub
1
, so that the inner race assembly can be composed. An attaching portion
9
for fixing the outer race
8
to the suspension is formed on an outer circumferential surface of an outer race
8
arranged around the hub
1
. Outer raceways
10
a
,
10
b
are formed on an inner circumferential surface of the outer race
8
. The outer raceways
10
a
,
10
b
are respectively opposed to the inner raceways
3
a
,
3
b
. A plurality of rolling elements
11
,
11
are installed between the inner raceways
3
a
,
3
b
and the outer raceways
10
a
,
10
b
. Due to the above arrangement, the hub
1
is capable of rotating inside the outer race
8
. In this connection, in the example shown in
FIGS. 19 and 20
, balls are used for the rolling elements. However, in the case of a rolling bearing unit used for an automobile to which a heavy load is given, tapered rollers are used as the rolling elements in some cases. A seal ring
12
is fitted between the inner circumferential surface of the outside end portion of the outer race
8
and the outer circumferential surface of the hub
1
. Since the seal ring
12
is arranged between the inner circumferential surface of the outer ring
8
and the outer circumferential surface of the hub
1
, an outside and opening of the space in which the plurality of rolling elements are arranged is closed by the seal ring
12
.
A base end portion of the tone wheel
13
, that is, a left end portion of the tone wheel
13
shown in
FIGS. 19
,
20
is engaged with and fixed to and inside end portion of the inner race
5
which is a little distant from the inner raceway
3
b
. The entire tone wheel
13
is formed from a magnetic metal sheet such as a steel sheet into an annular shape (a short cylindrical shape). The tone wheel
13
is composed of a small diameter portion
14
and a large diameter portion
15
which are continuously connected to each other by a step portion
16
, in which the small diameter portion
14
and the large diameter portion
15
are formed concentrically. The large diameter portion
15
of the tone wheel
13
is outwardly engaged with the outer circumferential surface of the end portion of the inner race
5
, and the step portion
15
comes into contact with an end edge of the inner race
5
. Under the above condition, the tone wheel
13
is supported by and fixed to the inner race
5
. Therefore, the small diameter portion
14
is supported concentrically with the inner race
5
. A plurality of through-holes
17
are formed in the small diameter portion
14
of the tone wheel
13
to serve as cutout portions on the rotational side. These through-holes
17
are formed in the circumferential direction at regular intervals. Accordingly, the magnetic characteristic of the tone wheel
13
is alternately changed in the circumferential direction at regular intervals. Shapes of the through-holes
17
are the same. Each through-hole
17
is formed into a rectangle, the long side of which is disposed in the axial direction, that is, the transverse direction in
FIGS. 19 and 20
.
An inside end opening of the outer race
8
is closed by a cover
18
formed into a cylindrical shape having a bottom from a metal sheet such as a stainless steel sheet or an aluminum alloy sheet by means of drawing. An annular synthetic resin member
21
which embeds an annular sensor
20
is fitted on an inner circumferential side of the cylindrical portion
19
composing the cover
18
. The annular sensor
20
includes: a permanent magnet
22
; a stator
23
composed of a magnetic member such as a steel sheet; and a coil
24
. When these members
22
,
23
,
24
are embedded in the above synthetic resin
21
, they are entirely formed into an annular shape.
In the above components of the sensor
20
, the permanent magnet
22
is formed into an annular shape (ring shape) and magnetized in the diametrical direction. An inner circumferential surface of the permanent magnet
22
is opposed to a base end portion of the small diameter portion
14
of the tone wheel
13
while a minute clearance
25
is maintained between them. An outer circumferential surface of the portion of the tone wheel
13
in which the through-hole
17
is not formed is opposed to a base and portion of the small diameter portion
14
of the tone wheel
13
while a minute clearance is maintained between them. The stator
23
is entirely formed into an annular shape, the section of which is a substantial J-shape. An inner circumferential surface of the end portion of the outer diameter side cylindrical portion
26
composing the stator
23
is arranged close to or contacted with an outer circumferential surface of the permanent magnet
22
. An inner circumferential surface of the inner diameter side cylindrical portion
27
composing the stator
23
is opposed to a portion of the tone wheel
13
in which the plurality of through-holes are formed. In the inner diameter side cylindrical portion
27
, a plurality of cutout portions
28
, which are stationary side cutout portions, are formed at regular intervals (central angle pitch), which are the same as those of the through-holes
17
, in the circumferential direction of the inner diameter side cylindrical portion
27
. Accordingly, the inner diameter side cylindrical portion
27
is formed into a comb-shape.
The coil
24
is formed into an annular shape in such a manner that a wire is wound around a bobbin made o
Ohmi Hayato
Ouchi Hideo
NSK Ltd.
Patidar Jay
Sughrue Mion Zinn Macpeak & Seas, PLLC
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