Measuring and testing – Speed – velocity – or acceleration – Structural installation or mounting means
Reexamination Certificate
2001-03-22
2003-04-01
Kwok, Helen (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Structural installation or mounting means
C029S525010, C188S073340
Reexamination Certificate
active
06539800
ABSTRACT:
TECHNICAL FIELD
This invention relates to a wheel speed sensor-mounting structure for a drum brake.
BACKGROUND OF THE INVENTION
One known type of a conventional wheel speed sensor-mounting structure is illustrated in FIG.
7
. The wheel speed sensor is utilized for an antilock brake system. The structure used in a publicly known duo two leading drum brake will now be described with reference to
FIGS. 5-7
.
A dust cover
11
closes a bell-house shaped opening of a brake drum (not shown) and is secured to a torque plate
10
on the reverse side thereof by means of shoe-holding pins
20
,
21
. Each of a number of bolts
30
are force fit through an attachment member, such as the torque plate
10
and/or the dust cover
11
, to fix the attachment member to a non-rotatable vehicular portion. Each of the bolts
30
are received by a respective engagement hole
10
a
of the torque plate
10
at a central portion thereof. Threaded portions of the bolts
30
engage with the non-rotatable vehicular portion, such as an axle casing (not shown), to secure the attachment member thereto in generally coaxial alignment with one another.
In
FIG. 5
, a pair of wheel cylinders
40
,
41
rigidly bolted to the torque plate
10
and dust cover
11
are opened at both ends thereof and also function as anchors for supporting brake shoes
50
,
51
, positioned between the wheel cylinders
40
,
41
, at both ends thereof.
The wheel cylinder
40
includes pistons
40
a
,
40
b
, while the wheel cylinder
41
includes pistons
41
a
,
41
b
. The pistons
40
a
,
41
a
are provided with respective manually-operated shoe clearance adjusting mechanisms. In addition, automatically-operated shoe clearance adjusting mechanisms are respectively disposed between the pistons
40
a
and
40
b
and between the pistons
41
a
and
41
b
. The structure and operation of these two types of the shoe clearance adjusting mechanisms, as well as brake actuation associated therewith, are described in details in published Japanese Utility Model Application Laid-Open No. 1-178242 filed by the present Applicant; therefore, further descriptions related thereto will be omitted.
The brake shoes
50
,
51
are comprised of shoe rims
50
a
,
51
a
and shoe webs
50
b
,
51
b
fixed to form a T-shape in cross-section. The brake shoes
50
,
51
also include linings
50
c
,
51
c
attached to the shoe rims
50
a
,
51
a
on outer peripheral surfaces thereof, respectively. The shoe webs
50
b
,
51
b
have respective elongated holes pierced at central portions thereof; and, the shoe-holding pins
20
,
21
, which extend upward from the torque plate
10
, are loosely inserted through the elongated holes. Pairs of slotted nuts
22
screw onto the respective shoe-holding pins
20
,
21
, thereby permitting respective outer peripheral surfaces of the linings
50
c
,
51
c
to be aligned with an inner peripheral surface of the brake drum (not shown), and further holding the brake shoes
50
,
51
between the pairs of nuts
22
so as to permit the brake shoes
50
,
51
to be slidable in a brake-applying/brake-releasing direction.
The shoe-holding pins
20
,
21
are adjusted in the manner described below. Since the upper and lower shoe-holding pins
20
,
21
in
FIG. 5
are adjusted in the same manner, only the upper shoe-holding pin
20
will be described with reference to FIG.
6
. Initially, the slotted nut
22
closer to the torque plate
10
is set on the shoe-holding pin
20
to have a predetermined height from an attached surface of the dust cover
11
mounted to the non-rotatable vehicular portion. Then, the nut
22
is fixed in position by means of a cotter pin
23
. Next, the brake shoe
50
is temporally placed on the nut
22
fixed on the shoe-holding pin
20
. A second slotted nut
22
disposed on the opposite side of the shoe web
50
b
from the first slotted nut
22
is fully screwed in, and is then screwed out by a predetermined degree of rotation. In this state, the second nut
22
is fixed in position by means of a respective cotter pin
23
, completing the manual operation. Shoe return springs
24
,
24
are extended between the brake shoes
50
,
51
.
A wheel speed sensor
60
(
FIGS. 6 and 7
) for an antilock brake system (hereafter “ABS wheel speed sensor”) includes a sensor body
61
, a lead wire
62
extending from the sensor body
61
and a bracket
63
for retaining the sensor body
61
in position. As is well known, the ABS wheel speed sensor
60
senses a wheel velocity to control directional stability and steerability of a vehicle, and further to avoid full wheel locking, thereby providing shorter braking distance.
The lead wire
62
extends outside of the drum brake through the torque plate
10
and dust cover
11
and is connected to, e.g., an electronic control unit. The typically cast-molded bracket
63
disposed on the torque plate
10
has a small hole
63
a
for engaging with a projection
10
b
of the torque plate
10
. In addition, a mounting bolt
64
is screwed into an internal thread
10
c
of the torque plate
10
through a mounting hole
63
b
of the bracket
63
from the inside of the drum brake. The bolt
64
fastens the bracket
63
to the torque plate
10
through a spring washer
65
. In this state, a top end of the sensor body
61
is positioned to face an outer peripheral surface of a sensor wheel (not shown) with a predetermined gap. The sensor wheel (not shown) is able to rotate together with a rotating axle shaft (not shown).
However, there are problems associated with the above-described prior art wheel speed sensor-mounting structure.
In a drum brake assembly line, when the wheel speed sensor is assembled on the torque plate at either an initial or intermediate process of the assembling, there is a likelihood that the sensor body and lead wire will be damaged when the torque plate having the wheel speed sensor disposed thereon is transferred to subsequent processes, and/or when other components are assembled onto the torque plate.
Accordingly, it is desirable to mount the wheel speed sensor onto the torque plate at the final process of the assembling line. However, space availability for sensor installation is usually limited because of both an inner diameter of the brake drum and the engagement hole of the torque plate at the central portion thereof. In addition, the brake shoes stand in the way. As a result, the assembling sequence as mentioned above is difficult to realize.
For this reason, the brake shoes adjusted in position by means of the shoe-holding pins and the slotted nuts as previously described must be disassembled in order to mount the wheel speed sensor onto the torque plate. The brake shoes are then reassembled after the wheel speed sensor is mounted on the torque plate. Such a laborious operation is inefficient and involves a great deal of effort.
In view of the above, an object of the present invention is to provide a wheel speed sensor-mounting structure for a drum brake, designed to be assembled with significantly less effort, without detracting from qualities of the wheel speed sensor.
SUMMARY OF THE INVENTION
In a first aspect, a wheel speed sensor-mounting structure for a drum brake comprises: a wheel speed sensor disposed inside the drum brake on an attachment member fixed to a non-rotatable vehicular portion, the attachment member constituting part of the drum brake, the wheel speed sensor being mounted on the attachment member from outside of the drum brake.
In a second aspect of a wheel speed sensor-mounting structure, the wheel speed sensor bracket has an internal thread defined therein and the attachment member has a mounting hole. A mounting bolt is inserted into the wheel speed sensor through the mounting hole of the attachment member to secure the wheel speed sensor by threading engagement with the internal thread.
In a third aspect of a wheel speed sensor-mounting structure, the wheel speed sensor is formed integrally with a stem extending through the attachment member, and the stem is defined with an external thread. A mounting nut is secured to t
Nisshinbo Industries Inc.
Seed IP Law Group PLLC
LandOfFree
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