Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
2002-03-22
2004-03-30
Snow, Walter E. (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207200, C324S207250
Reexamination Certificate
active
06714005
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is based on and claims priority under 35 U.S.C. §119 with respect to a Japanese Patent Application
2001-084262
, filed on Mar. 23, 2001, the entire content of which is incorporated herein by reference.
FIELD OF THE INVENTION
This invention generally relates to a displacement sensor or a displacement sensor structure. More particularly, this invention pertains to a non-contact type displacement sensor structure or an angle displacement sensor structure. Further, this invention relates to a displacement sensor preferably applied to an accelerator pedal sensor.
BACKGROUND OF THE INVENTION
Various sensor structures have been known already. A non-contact type displacement sensor for detecting a displacement of angle by using a hall element or a magnetic resistor is disclosed, for example, Japanese Patent Laid-Open Publications No. 8 (1996)-68606 and 2 (1990)-122205.
Referring to
FIG. 9
, a sensor body
22
disclosed in the former Japanese Patent Laid-Open Publication No. 8 (1996)-68606 is formed of a housing
21
having an IC containing portion
241
containing a hall element and a casing
13
for supporting an input shaft
14
. The input shaft
14
is connected to a rotational member
15
for supporting magnets
171
,
172
and a yoke
16
. The magnets
171
,
172
form a magnetic field interacting with the hall element. The input shaft
14
and the rotational member
15
are completely independent members from each other. The rotational member
15
is connected to the input shaft
14
as an external connecting member. Therefore, the magnets
171
,
172
and the yoke
16
supported by the rotational member
15
are also completely independent members which are present outside the input shaft
14
. The yoke
16
to which the magnets
171
,
172
are attached is secured to the rotational member
15
by means of a screw.
A peninsular portion
211
including the IC containing portion
241
is formed in the housing
21
so as to intersect with the parallel magnetic field produced by the magnets
171
,
172
. In such a case, the hall element (the magnetic sensing element) is required to be accurately located at a position in which the distortion of the magnetic field can be reduced as much as possible, i.e., at a position on a central axis of the input shaft
14
, so as to detect the magnetic field with a high level of accuracy.
Referring to
FIG. 10
, according to the sensor disclosed in the latter Japanese Patent Laid-Open Publication No. 2(1990)-122205, a rotational shaft
2
having a small diameter is provided with a large diameter portion having a diameter nearly twice as large as the rotational shaft
2
at a tip end portion thereof. The large diameter portion is employed as a magnetic holder
22
in which permanent magnets
3
A,
3
B are disposed. A hall element
5
(a magnetic sensing element) is disposed in a cylindrical space which is enclosed by the permanent magnets
3
A,
3
B and has approximately the same diameter as the diameter of the rotational shaft
2
. The space in the rotational shaft
2
is in a filled structure (i.e., a solid structure) except for the space where the hall element
5
is disposed.
However, according to the former described sensor in which the yoke
16
is secured to the rotational member
15
by the screw, the rotational member
15
and the yoke
16
are required to be large-sized in order to assure a space for fixing them to each other. The size of the sensor main body
22
itself is hence increased, as well. This may lead to an increase of cost expended on each component. Further, the yoke
16
and the magnets
171
,
172
are externally connected to an end portion of the input shaft
14
via the rotational member
15
. Therefore, those components may be required to be large-sized in each width direction. The sensor main body
22
is hence required to be large-sized, as well.
As described above, the hall element (the magnetic sensing element) is required to be positioned on the central axis of the input shaft
14
and on a central position of the magnetic field having small distortion so as to detect the magnetic field with a high level of accuracy. However, the input shaft
14
, the rotational member
15
, the yoke
16
and the magnets
171
,
172
exist and are assembled as members independent from one another. Therefore, position detecting of each component with a high level of accuracy may be difficult due to size fluctuation of each component or dimensional errors for assembly each component.
On the other hand, according to the latter described sensor, the housing
1
for supporting the rotational shaft
2
is required to include a complicated inner structure due to the small diameter of the rotational shaft
2
. When the sensor is applied to an automotive vehicle or the like, vibration may occur affecting the accuracy of detection of a rotational angle of the magnetic field.
Further, the rotational shaft
2
is required to be light in weight and have a large surface area so as to perform a delicate control of the rotation of the rotational shaft
2
under a simple structure. However, the rotational shaft disclosed in the latter publication is the solid structure, which is not a hollow structure, and has the small diameter. Therefore, a mechanism for controlling the rotational shaft
2
may be required to be complicated. As illustrated in
FIG. 10
, there is a large unnecessary space in the sensor. The entire size of the housing of the sensor may become unnecessarily large.
Accordingly, the above disclosed sensors are still subject to certain improvements with respect to accurately determining a position of a magnetic sensing element in a magnetic field, a downsizing of the sensor, and providing a displacement sensor for performing a delicate control of a rotational shaft of the sensor under a simple structure.
SUMMARY OF THE INVENTION
According to the present invention, a non-contact type displacement sensor is provided with a housing, a rotational shaft being in an approximately cylindrical hollow shape, a magnetic circuit forming member disposed in an inner space of the rotational shaft, and a magnetic sensing element supported by a housing so as to be positioned on a central axis of the rotational shaft in a space enclosed by the magnetic circuit forming member, wherein the magnetic sensing element is not displaced.
REFERENCES:
patent: 5252919 (1993-10-01), Uemura
patent: 5789917 (1998-08-01), Oudet et al.
patent: 2001/0015642 (2001-08-01), Fischer et al.
patent: 43 17 259 (1993-05-01), None
patent: 100 07 968 (2000-02-01), None
patent: 2-12205 (1988-11-01), None
patent: 8-68606 (1994-08-01), None
patent: 2001-264110 (2001-02-01), None
Office Action dated Apr. 11, 2003, from the German Patent Office with English translation.
Fukaya Kiyohiro
Kimura Masahiro
Yasuda Keiji
A. Marquez, Esq. Juan Carlos
Aisin Seiki Kabushiki Kaisha
Fisher Esq. Stanley P.
Smith LLP Reed
Snow Walter E.
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