Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-11-02
2001-05-29
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C073S862331
Reexamination Certificate
active
06239529
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electrical power-steering device and, in particular, to a fixing structure for a coil assembly for torque detection that is used in an electrical power-steering device.
A device known as an electrical power-steering device for a vehicle takes the rotary output of an electric motor, which is to become an auxiliary steering torque, steps it down by means of a gear train, then transfers it to an output shaft of a steering mechanism to steer the vehicle.
One form of such an electrical power-steering device uses a torsion bar that is connected to both an input shaft that is linked to the steering wheel and an output shaft that is linked to the steering mechanism, with the configuration being such that the steering torque is detected thereby. More specifically, since the torsion bar deforms in accordance with the steering torque applied to the steering wheel, the steering torque can be detected accurately by detecting the magnitude of that deformation. If the steering torque can be detected accurately, it becomes possible to output a suitable auxiliary steering torque.
In known examples of this type of detection device, such as those disclosed in U.S. Pat. No. 5,578,767, U.S. Pat. No. 5,739,616, and U.S. Pat. No. 5,796,014, the impedance of a coil provided within the housing is made to vary in accordance with the applied steering torque, and the steering torque is detected on the basis thereof.
Incidentally, in order to accurately measure the amount of distortion of the torsion bar in such a detection device, it is necessary to fix the coil with respect to the housing in such a manner that it does not move in the axial direction of the output shaft. To overcome that problem, the electrical power-steering device disclosed in Japanese Utility Model Laid-Open Application No. Hei 4-38540, for example, is configured such that a disc spring
34
is disposed between a coil yoke
19
B and a snap ring (or something similar, although hereinafter “snap ring” is used)
33
that is fitted into an inner radial surface of a housing
25
, and the coil yoke
19
B is pre-loaded and fixed by the elastic force of the disc spring
34
, as shown in FIG.
4
.
However, if the configuration is such that this snap ring
33
is disposed between the coil yoke
19
B and a bearing
26
, the coil yoke
19
B and the bearing are inevitably at some distance apart, which has the disadvantage of increasing the length in the axial direction of the device. It is also necessary to provide an installation groove for the snap ring
33
on the inner peripheral surface of the housing
25
, but this has disadvantages in that the number of machining steps is increased and the workability during assembly is bad because the snap ring
33
has to be engaged while the disc spring
34
is being compressed.
In addition, since the snap ring
33
must be compressed diametrically while it is being fitted into the installation groove, part of the circumference thereof has to be cut away. Therefore, the cutaway portion cannot maintain a sealing effect, even when the disc spring is placed into contact with the inner surface of the snap ring
33
. In other words, since this cutaway allows the intrusion of foreign bodies from the bearing side, there is a danger that, if such foreign bodies should adhere to the circuit board disposed on the outer peripheral side of the coil yoke, they could have adverse effects on the circuit board. Therefore, in such an electrical power-steering device of the prior art, some sort of means should be provided to prevent the intrusion of foreign bodies, which will inevitably increase the cost.
SUMMARY OF THE INVENTION
The present invention was designed in the light of the above described problems with prior-art devices, and has as an object thereof the provision of a fixing structure for a coil assembly and an electrical power-steering device that are effectively capable of preventing the intrusion of foreign bodies or the like thereinto.
In order to achieve the above objective, a fixing structure for a coil assembly in accordance with the present invention relates to:
a fixing structure for fixing a coil assembly with respect to a housing, such that the coil assembly comprises a coil bobbin around which a coil is wound and a circular cylindrical coil yoke accommodating the coil bobbin in the interior thereof, and the coil yoke is fitted into a concavity formed in the housing, wherein:
the fixing structure for a coil assembly is provided with a disc-shaped spring that is placed into contact with an outer race of a bearing on one side and with an edge portion of the coil yoke on another side; and
the coil yoke is wedged between edge surfaces of the concavity of the housing by the elastic force of the disc-shaped spring.
Since the fixing structure for a coil assembly in accordance with the present invention is provided with a disc-shaped spring that is placed into contact with an outer race of a bearing on one side and with an edge portion of the coil yoke on another side, and the coil yoke is wedged between edge surfaces of the concavity of the housing by the elastic force of the disc-shaped spring, making it possible to fix the coil yoke within the housing without having to provide extra components such as a snap ring, which facilitates machining and assembly. In addition, the sealing effect can be increased by placing the disc-shaped spring into contact with the entire periphery of the outer race of the bearing, thus efficiently preventing the intrusion of impurities.
If the disc-shaped spring is further provided with a lip portion that is placed into contact with at least one of the bearing and the coil yoke, this would make it possible to further increase the sealing effect.
REFERENCES:
patent: 4996890 (1991-03-01), Taniguchi et al.
patent: 5578767 (1996-11-01), Chikaraishi et al.
patent: 5739616 (1998-04-01), Chikaraishi et al.
patent: 5796014 (1998-08-01), Chikaraishi et al.
patent: 5811903 (1998-09-01), Ueno et al.
patent: 4-38540 (1992-03-01), None
patent: 9-101212 (1997-04-01), None
Dinh Le Dang
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
NSK Ltd.
Ramirez Nestor
LandOfFree
Fixing structure for coil assembly and power-steering device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fixing structure for coil assembly and power-steering device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fixing structure for coil assembly and power-steering device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2465440