Electricity: motive power systems – Automatic and/or with time-delay means
Reexamination Certificate
2001-06-19
2002-04-02
Ip, Paul (Department: 2837)
Electricity: motive power systems
Automatic and/or with time-delay means
C318S443000, C318SDIG002, C015S250130, C015S250220
Reexamination Certificate
active
06366044
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-202185 filed on Jul. 4, 2000, Japanese Patent Application No. 2000-202186 filed on Jul. 4, 2000, Japanese Patent Application No. 2001-71925 filed on Mar. 14,2001 and Japanese Patent Application No. 2001-135715 filed on May 7, 2001.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotational-position sensing device and a windshield wiper system.
2. Description of Related Art
FIG. 26
shows a rotational-position sensing device for a windshield wiper system disclosed in Japanese Unexamined Utility Model Publication No. 61-35068. A worm
1
and a wheel (acting as a rotator)
2
meshed with the worm
1
constitute a speed reducing gear mechanism. Rotation of an output shaft
3
secured to the wheel
2
is transmitted to a crank mechanism (not shown) acting as a reciprocating swing mechanism. The crank mechanism reciprocally swings wiper blades (not shown) along a windshield.
A cover
4
that covers a gear case opposes the wheel
2
. A follower
5
is rotatably supported by a spindle
4
a
that protrudes from the cover
4
. A switching pattern
6
is arranged in an opposing surface of the follower
5
that opposes the cover
4
. A plurality of contact terminals
7
are arranged in an opposing surface of the cover
4
that opposes the follower
5
. The rotation of the wheel
2
, which generates the swing motion of the wiper blades, is transmitted to the follower
5
through engagement between a protrusion
8
of the wheel
2
and a protrusion
9
of the follower
5
, so that the follower
5
is integrally rotated with the wheel
2
. As the follower
5
rotates, the contact terminals
7
engage and disengage with the switching pattern
6
, so that a rotational position of the wheel
2
or a rotational position of the output shaft
3
is sensed or detected.
The contact terminals
7
are urged against the switching pattern
6
because of their own resilient forces. When the resilient forces of the contact terminals
7
are summed and are applied to the follower
5
to lever the follower
5
about the spindle
4
a
, the follower
5
tilts with respect to the spindle
4
a
. When the follower
5
tilts, the follower
5
cannot rotate freely, causing an increased rotational resistance of the follower
5
. The increase in the rotational resistance of the follower
5
normally results in a decrease in a transmission efficiency of the power transmission system between a wiper drive motor and the follower
5
. Furthermore, the tilt of the follower
5
may cause a contact failure between the contact terminals
7
and the switching pattern
6
. Such a contact failure causes a reduction in a sensing accuracy of the rotational-position sensing device.
To restrain the tilt of the follower
5
, a wave washer
61
is inserted around the spindle
4
a
to urge the follower
5
in an axial direction away from it, and a stationary engaging member
62
, such as a C-ring, is fitted around the spindle
4
a
to hold the follower
5
in place around the spindle
4
a.
However, when an excess force that overcomes the urging force of the wave washer
61
is applied to the follower
5
, the follower
5
is still tilted. Furthermore, both the wave washer
61
and the stationary engaging member
62
are required in the above case, so that a number of assembling steps and a number of components to be assembled are disadvantageously increased.
Furthermore, the wiper blades are controlled to be stopped at a predetermined stop position which is generally one swing end position of the wiper blades. More specifically, when a vehicle driver manually turns off a wiper switch, the following control operation is conducted. That is, the wiper drive motor drives the wiper blades to the predetermined stop position and then stops the wiper blades in the predetermined stop position. This type of automatic stop arrangement for automatically stops the wiper blades in the predetermined stop position is disclosed in Japanese Unexamined Utility Model Publication No. 61-35068. By way of example, it will be assumed that a relatively large amount of snow is present on the windshield. In the windshield wiper system having the automatic stop arrangement, the wiper blades wipe the snow toward the predetermined stop position. When the wiper blades reach the predetermined stop position, the wiper drive motor is turned off, so that the wiper blades lose its driving force. Since the snow has been packed by the wiper blades, the snow exerts a reaction force against the wiper blades to move the wiper blades backward out of the predetermined stop position, and the wiper drive motor is forced to rotate backward. When the follower
5
is rotated backward due to the backward rotation of the wiper drive motor, a state of engagement and disengagement between the switching pattern
6
and the contact terminals
7
is changed to another state different from one that is seen while the wiper blades are held in the stop position. This change in the state of engagement and disengagement causes the wiper drive motor to drive the wiper blades toward the stop position. This results in chattering of the wiper system.
In the previously proposed rotational-position sensing device shown in
FIG. 26
, when the backward rotation of the wiper drive motor or the backward rotation of the wheel
2
occurs, the protrusions
8
and
9
are moved away from each other, so that the backward rotation of the wheel
2
is not transmitted to the follower
5
. The prevention of the transmission of the backward rotation of the wheel
2
to the follower
5
prevents chattering of the wiper system.
However, the contact terminals
7
need to be secured to the cover
4
in manufacturing. Furthermore, the switching pattern
6
and the protrusion
9
need to be provided in the follower
5
. Thus, a number of components to be assembled is increased. Because of this, parts management becomes more complicated, and a number of assembling steps is disadvantageously increased.
SUMMARY OF THE INVENTION
The present invention addresses the above disadvantages. Thus, it is an objective of the present invention to provide a rotational-position sensing device that senses a rotational position of a rotator through engagement and disengagement of contact terminals with a switching pattern based on rotation of a follower and that can be manufactured with a reduced number of assembling steps and a reduced number of components to be assembled while effectively restraining tilt of the follower. It is another objective of the present invention to provide a windshield wiper system having such a rotational-position sensing device. It is a further objective of the present invention to provide a rotational-position sensing device that restrains a change in a state of engagement and disengagement between the switching pattern and the contact terminals when the rotator is forced to rotate in a backward rotational direction and that has a reduced number of components to be assembled while achieving an improved manufacturability of the rotational-position sensing device. It is a further objective of the present invention to provide a windshield wiper system having such a rotational-position sensing device.
To achieve the objectives of the present invention, there is provided a rotational-position sensing device including a stationary body, a rotator and a follower. The stationary body includes a switching pattern. The rotator is rotatably supported by the stationary body. The rotator has a driving-side engaging means. The switching pattern is provided around a rotational axis of the rotator. The follower receives a rotational force to rotate about the rotational axis from the rotator through the driving-side engaging means. The follower is made of an electrically conductive metal plate. The follower has a plurality of contact terminals integrally formed in the electrically conductive metal plate. The follower further includes a driven
Okai Hideo
Uchida Yasuaki
Yamamoto Toshio
Asmo Co. Ltd.
Ip Paul
Law Office of David G. Posz
Leykin Rita
LandOfFree
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