Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
2000-01-05
2001-06-12
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207250
Reexamination Certificate
active
06246232
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a rotation sensor for generating electric signals corresponding to rotation angle and rotation direction of a steering wheel which is connected to, for example, a steering shaft of an automobile.
2. Description of Related Art
FIG. 42
to
FIG. 46
describe a prior art rotation sensor. The rotation sensor
61
comprises a base
62
fixed at the suitable static position, a rotor
69
which rotates together with a connector
63
with respect to the base
62
, a speed reduction rotor
71
which is engaged rotatably with the rotor
69
, a gear mechanism
73
provided between the rotor
69
and speed reduction rotor
71
, and a composite board
64
supported by the base
62
.
The base
62
is formed of plastic material having a circular shape in the plan view and is provided with a hole
62
a
at the center. The base
62
has a ring-shaped outside peripheral wall
62
b
on the peripheral edge on the under side and a ring-shaped inside peripheral wall
62
d
along the periphery of the hole
62
a.
The connector
63
is formed of plastic material having a cylindrical shape. The connector
63
with a pair of projections
63
a
on the top end and an engagement projection
63
b
on the bottom side of the outside peripheral wall. The connector
63
is inserted into the hole
62
a
of the base
62
and the pair of projections
63
a
are extended beyond the top surface of the base
62
upward. The engaging projection
63
b
is extended beyond the inside peripheral wall
62
d
of the base
62
downward.
The composite board
64
is a circular disc formed of insulating material and has a hole
64
a
at the center, and on the bottom surface is provided with endless ring electrode patterns
65
and
66
, a first resistor pattern
67
positioned inside the electrode pattern
65
, and a second resistor pattern
68
positioned outside the electrode pattern
66
, which are all formed by printing (in
FIG. 43
, slant line bands are drawn on patterns
65
-
68
). The composite board
64
is provided with terminals
65
a
and
66
a
connected to the respective electrode patterns
65
and
66
, with terminals
67
a
and
67
b
connected to both ends of the first resistor pattern
67
, and with terminals
68
a
and
68
b
connected to both ends of the second resistor pattern
68
. The composite board
64
is supported in a recess
62
c
of the base
62
with its bottom surface exposed, wherein the connector
63
and the inside peripheral wall
62
d
are inserted into the hole
64
a.
The rotor
69
, which is provided on the under side of the base, is a ring formed of plastic material having an engagement groove
69
a
on the inside peripheral surface and having an arm
69
b
which supports a first brush
70
on the outside peripheral surface. The connector
63
is inserted into the rotor
69
to engage the engagement projection
63
b
of the connector
63
with the engagement groove
69
a
of the rotor
69
, and the rotor
69
is thereby supported on the base
62
, and thus the rotor
69
is rotatable together with the connector
63
with respect to the base
62
wherein the first brush
70
bridges between the conductive pattern
65
and the first resistor pattern
67
.
The speed reduction rotor
71
is a disk formed of insulating material having a hole
71
a
at the center and having a supporting shaft
71
b
on the top surface. The supporting shaft
71
b
of the speed reduction rotor
71
is positioned in the recess
62
c
of the base
62
so that the bottom end of the rotor
69
is engaged rotatably with the hole
71
a
, and the speed reduction rotor
71
is supported by the base
62
rotatably around the rotor
69
wherein the second brush
72
bridges between the conductive pattern
66
and the second resistor pattern
68
.
The gear mechanism
73
comprises a planetary gear mechanism comprising a sun gear
74
formed on the outside peripheral surface of the rotor
69
, an inside gear
75
formed on the inside peripheral surface of the outside peripheral wall
62
b
of the base
62
, and a planetary gear
76
comprising a double gear supported rotatably by the supporting shaft
71
b
of the speed reduction rotor
71
. A small diameter pinion
76
a
positioned on the upper stage of the planetary gear
76
is engaged with the inside gear and the large diameter pinion
76
b
positioned on the lower stage is engaged with the sun gear
74
so that the rotation of the connector
63
is converted to the revolution of the planetary gear
76
and the revolution is transmitted to the speed reduction rotor
71
. In this system, the speed reduction ratio is set at approximately 1/4, therefore, the speed reduction rotor
71
makes a turn together with the second brush
72
at every four turns of the connector
63
together with the rotor
69
and the first brush
70
.
The rotation sensor
61
structured as described herein above has the first absolute type encoder
77
comprising the first brush
70
, the electrode pattern
65
and the first resistance pattern
67
, and the rotor
69
, and has the second absolute type encoder
78
comprising the second brush
72
, the electrode pattern
66
and the second resistance pattern
68
, and the rotor
69
.
The rotation sensor
61
is used, for example, in an automobile. The base
62
is fixed to a suitable stationary portion such as a steering column, and a steering shaft is inserted into the connector
63
, the pair of projections
63
a
of the connector
63
are engaged with the recess on the steering wheel
79
side as shown in
FIG. 42
so that the connector
63
is rotated together with the steering wheel
79
.
At that time, the first brush
70
bridges between the middle point (C
1
point in
FIG. 43
) of the first resistance pattern
67
and the electrode pattern
65
when the steering wheel
79
is positioned at the neutral position. Therefore, when the steering wheel
79
is positioned at the neutral point, the resistance value between the terminals
65
a
and
67
a
is equal to the resistance value between the terminals
65
a
and
67
b
, however when the steering wheel
79
is turned right or left the above-mentioned resistance values change.
The resistance value increases linearly with a right turn of the steering wheel
79
(a turn in the direction of the arrow D in
FIG. 43
) and decreases linearly with a left turn of the steering wheel. In this case, a constant voltage Vc (the terminal
67
b
is the ground potential) is applied between the terminals
65
a
and
67
b
, and the first voltage signal
80
which varies as shown with a solid line in
FIG. 44
correspondingly to the turn of the steering wheel
79
is generated between the terminals
65
a
and
67
b.
In detail, the first voltage signal
80
varies from 0 to Vc at every turn of the steering wheel
79
, and the turning angle and turning direction of the steering wheel
79
are detected thereby. The no signal area X between adjacent first voltage signals
80
is due to the disconnection between the first resistance pattern
67
and the electrode pattern
65
generated when the first brush
70
is positioned between the terminals
67
a
and
67
b.
On the other hand, when the steering wheel
79
is position at the neutral position, the second brush
72
bridges between the middle point (C
2
point in
FIG. 43
) of the second resistance pattern
68
and the electrode pattern
66
. Therefore, when the steering wheel
79
is positioned at the neutral position, the resistance value between the terminals
66
a
and
68
a
is equal to the resistance value between the terminals
66
a
and
68
b
. The above-mentioned resistance values change correspondingly to a right turn or a left turn of the steering wheel
79
.
As set forth above the resistance value increases linearly with a right turn (turn in the direction of the arrow D in
FIG. 43
) of the steering wheel
79
or decreases linearly with a left turn of the steering wheel
79
. Also in this case, a constant voltage Vc (the terminal
68
b
is the ground potential) is appli
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Patidar Jay
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