Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Patent
1994-05-25
1998-02-03
Silverberg, Sam
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
4284723, C23C 2600, B23F 324, F16H 5500
Patent
active
057140162
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a gear for wheel speed detection (hereinafter referred to as a sensor ring) which can be used in an electronically controlled anti-locking brake system (hereinafter referred to as ABS) for an automobile and a method of manufacturing the same.
BACKGROUND ART
In recent years, developments have been made toward the improved safety and the high reliability of a disc brake system for an automobile, due to the increasing social requirements for the improved stability of an automobile. Due to the rapid development and cost reduction of microelectronics, in particular, it is now becoming prevalent to provide an ABS for preventing the wheels of an automobile from slipping during abrupt braking on frozen or wet pavement for preventing an accident. However, the components of the ABS must be cost economical in addition to having a high performance and reliability, and there still remain a number of problems to be solved.
As to a wheel speed detecting component that is the core of the ABS, an electromagnetic system having excellent environmental resistance is now being used. A sensor ring of a magnetic material having a gear shaped surface of high gear tooth pitch accuracy is employed for this detecting system. FIG. 1A is a front elevational view of a sensor ring, FIG. 1B is a sectional view taken along the line B--B in FIG. 1A, and FIG. 1C is an enlarged view showing a portion C in FIG. 1A. FIG. 2 is a diagram showing an operation principle of electromagnetic wheel speed detection utilizing the sensor ring shown in FIG. 1A.
As shown in FIG. 2, the sensor ring 1 is mounted on a wheel to have a constant clearance between a pole piece 3 of a sensor coil 2 and each tip of the sensor ring 1. The electromagnetic coil 2 receives the magnetic flux change which is caused in the changing clearance between the coil 2 and the successive tips and grooves of the gear teeth during rotation of the wheel. The coil 2 correspondingly generates an excited output voltage 5 which can be detected to correctly read the speed of each wheel. The ABS correctly operates on the basis of the measured speed of each wheel to control the brake on that wheel so that the wheel does not become locked and will not slip.
The material for this sensor ring must have excellent corrosion resistance in addition to excellent magnetic properties as output characteristics and high pitch accuracy of the gear teeth. A drive shaft direct mounting system for the sensor ring is preferred. The drive shaft direct mounting type is so simple in structure that the sensor ring can be mounted and maintained easily and at a low cost. In such a drive shaft direct mounting type sensor ring, however, the surface of the sensor ring is exposed to the exterior environment Therefore, the requirement of corrosion resistance for the sensor ring is so high that a sensor ring having a suitable corrosion resistance has not yet been obtained. Namely, a sensor ring material cannot be used in practice unless it can withstand salt water corrosion caused by salt that is spread.
In response to the aforementioned requirement for corrosion resistance, ingot metallurgical stainless steel was first regarded as a possible material for the sensor ring. However, because a high dimensional accuracy is required for the sensor ring, a substantial material loss results from machining work if ingot metallurgical stainless steel is employed, which increase the working cost. Therefore, it is rather advantageous to employ a ferrous sintered material which can be formed to reduce the material loss, and thereby ensure dimensional accuracy at a low cost.
As to the sintered material, sintered stainless steel itself having corrosion resistance has been employed, or a ferrous sintered material provided with corrosion resistance by a surface treatment or sintered stainless steel subjected to surface corrosion resistance treatment has been studied. However, pores are present in any sintered material. When a surface treatment such as plating treatment is per
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JIS Z 2371-1988 Japanese Industrial Standard Methods of Neutral Salt Spracy Testing, pp. 1-25.
Inui Naoki
Takeda Yoshinobu
Ueda Hiroshi
Fasse W. F.
Fasse W. G.
Silverberg Sam
Sumitomo Electric Industries Ltd.
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