Metal working – Method of mechanical manufacture – Prime mover or fluid pump making
Reexamination Certificate
2000-08-03
2001-08-14
Rosenbaum, I Guda (Department: 3726)
Metal working
Method of mechanical manufacture
Prime mover or fluid pump making
C029S559000, C403S013000
Reexamination Certificate
active
06272747
ABSTRACT:
BACKGROUND OF THE INVENTION
Magnetic sensors operate on the principle of detecting magnetic flux density modulation caused by the movement of appropriately configured reluctors (or targets). The magnetic sensor must be affixed very close to the reluctor since its sensitivity decreases very rapidly with the size of the air gap between the reluctor and the magnetic sensor. In most automotive applications, for example, the air gaps are on the order of 0.3 to 1.75 mm. Over such a range of air gaps, the sensor output signal decreases more than ten times. The signal attenuation at large air gaps makes the sensor operation more prone to noise induced failures as well as less accurate in detecting the elements of the reluctor as it spins in relation to the magnetic sensor. Both of these factors are often unacceptable in critical engine control and diagnostic applications.
It may at first glance appear that there would be no problem whatsoever to choose and achieve an appropriate air gap between the magnetic sensor and the reluctor. However, in the majority of production cases, the stack-up of tolerances of the many different components randomly influence the net size of the air gap, which consequently precludes achieving, at each assembly, a precisely predetermined air gap by mere assembly of the parts. As a result, because of the random variations caused by accumulation of tolerances, mere assembly of the parts risks damaging interference between the magnetic sensor and reluctor on the one hand, and inaccurate readings associated with too large an air gap on the other hand. To lessen all the tolerances so that mere assembly assures, at each assembly, the optimum air gap is physically unrealistic and involves inordinate costs associated with manufacturing such precise parts.
The majority of magnetic sensors used in automotive applications involve non-adjustable air gap placement wherein the stack-up of tolerances causes deviation from the optimal air gap. For example, a rigid bracket is affixed to the body of a magnetic sensor. The magnetic sensor is placed into a sensor port in the engine block. and the bracket is bolted, via a bolt hole in the bracket, to a threaded mounting hole in a mounting surface of the engine block. When the bracket is bolted, the length of the sensor body from the bolt hole of the bracket to the sensor tip determines the air gap with respect to the reluctor which air gap is affected by the stack-up of tolerances. Even though subject to tolerance related placement inaccuracy, this structural mounting methodology is used -widely because of the simplicity of the hardware, and ease of assembly and service.
In situations where air gap variation cannot be tolerated, the air gap is preset during magnetic sensor installation by means of an adjustable bracket, often referred to as a “side-mount” bracket. The adjustability of side-mount brackets resides in a bolt slot which allows for the bracket to be adjusted along the slot elongation relative to the threaded mounting hole of the mounting surface.
In one form of operation of the side-mount bracket, the sensor body is placed into the sensor port of the enitine block such that the sensor tip is allowed to touch the surface of the reluctor, and then it is withdrawn a distance equal to the predetermined optimum air gap. This method is more time consuming and is error prone.
In another form of operation of the side-mount bracket, a gauging layer of soft, abradable material is placed onto the sensor tip, wherein the thickness of the gauging layer is equal to the optimum air gap. The gauging layer may be either attached to the sensor body or be a part thereof, such as a protuberance, provided the sensor body is of a soft material. Now, the installer need merely place the sensor body into the sensor port until the gauging layer touches the reluctor, and then tighten the bolt on the mounting surface to thereby hold the sensor body at this position. During initial rotation of the reluctor, a portion of the gauging layer is sacrificial to abrasion due to reluctor runout or differential thermal expansion without damage being incurred to the sensor body or the reluctor. This abrasion can undesirably result in particles being introduced into the engine oil.
In the event the magnetic sensor must be re-installed, an abraded gauging layer cannot again provide position location for the sensor tip, as it was formerly able to do when it was unabraded. Therefore, before dismounting the magnetic sensor, the bracket must be marked to indicate the correct position of the sensor body relative to the bracket so that when the new magnetic sensor is re-installed, its position on the bracket can be alignably sighted—not an exact procedure. Indeed, rather than try to reinstall the old, but still usable, sensor using the sighting method to reset the air gap, a technician would rather install a new sensor having the abradable layer intact, thereby circumventing the error prone sighting step otherwise needed to reinstall the old, but usable, sensor. This results in waste of otherwise good sensors and unnecessary expense for the customer or warranty provider.
Horizontal-mount brackets differ from side-mount brackets, in that a “horizontal” surface, ie., a surface normal to the vertical axis of the sensor port, is used to mount the bracket. The horizontal mount bracket involves convenience in terms of manufacture, installation and space savings as compared to the side-mount bracket. which requires the presence of a vertical surface adjacent the sensor port.
What remains needed in the art, is some way to enable a horizontal-mount bracket to facially interact with a sensor body, wherein the sensor is affixed positionally and wherein a predetermined air gap is set automatically.
SUMMARY OF THE INVENTION
The present invention is a horizontal-mount bracket system for holding sensor position with respect to a horizontal-mount bracket, wherein facial interaction between the bracket and the sensor body provides automatic setting of the air gap which setting may be preserved such that if the sensor is ever reinstalled, the air gap is precisely reset to its original value.
The horizontal-mount bracket system according to the present invention includes a multi-component bracket, having first and second bracket components which lay juxtaposed, one atop the other. The first bracket component has a first sensor opening and a first bolt hole; the second bracket component has a second sensor opening and a second bolt hole. The spacing between the first sensor opening and the first bolt hole is different from the spacing between the second sensor opening and the second bolt hole. Preferably, the distal ends (adjacent the first and second bolt holes) of the multi-component bracket are free. while the near ends (adjacent the first and second sensor openings) are vertically held but horizontally slidable, as for example by a fold-over of the second bracket component with respect to the first bracket component. The first and second sensor openings mutually communicate and the first and second bolt holes mutually communicate wherein initially the first and second sensor openings are mutually communicating and mutually aligned, preferably just sufficiently, so that the sensor body is free to vertically move therein and second bolt holes are mutually misaligned by an offset distance. The first bracket component has at least one cutting tooth at the first sensor opening which is oriented at a predetermined acute pitch angle with respect to a horizontal axis.
Preferably, the sensor body is placed trappingly into the first and second sensor openings of the multi-component bracket as part of the manufacturing process. This not only ensures that the sensor will remain permanently associated with respect to the multi-component bracket, but further ensures the orientation of the sensor with respect to the multi-component bracket will be correct.
Operationally, the sensor body is placed into a sensor port of an engine block so that the tip of the sensor body rests upon a surface of
Schroeder Thaddeus
Stevenson Robin
Delphi Technologies Inc.
Dobrowitsky Margaret A.
Rosenbaum I Guda
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