Clutch position sensor for vehicle transmission

A transmission clutch position sensor includes two Hall sensors located at opposite ends of a flux concentrator outside the casing of the transmission to sense a magnetic field generated by a magnet attached to the clutch piston. To reduce sensitivity to magnet-to-sensor gap tolerances, a ratio of the voltage of one Hall sensor to the sum of the voltages from both Hall sensors is used to correlate to the piston and, hence, clutch position.

I. FIELD OF THE INVENTION

The present invention relates generally to clutch position sensors for automotive vehicle transmissions.

II. BACKGROUND OF THE INVENTION

Modern automotive vehicles employ an engine transmission system having gears of different sizes to transfer power produced by the vehicle's engine to the vehicle's wheels based on the speed at which the vehicle is traveling. The engine transmission system typically includes a clutch mechanism which may engage and disengage these gears. The clutch mechanism may be operated manually by the vehicle's driver, or automatically by the vehicle itself based on the speed at which the driver wishes to operate the vehicle.

In automatic transmission vehicles, a need arises for the vehicle to sense the position of the clutch for smooth, effective shifts between gears in the transmission and for overall effective transmission control. Therefore, a clutch-position sensing component for sensing the linear position of the clutch must be used by automatic transmission vehicles to facilitate gear shifting and transmission control.

Current clutch-position sensing components utilize magnetic sensors. One advantage to using magnetic sensors is that the sensor need not be in physical contact with the object being sensed, thereby avoiding mechanical wear between the sensor and the object. However, actual linear clutch measurement accuracy may be compromised when the sensor is not in physical contact with the sensed object because of a necessary gap or tolerance that exists between the sensor and the object. Moreover, current sensing systems addressing this problem use coils and certain application-specific integrated circuits which are relatively expensive.

SUMMARY OF THE INVENTION

Accordingly, an apparatus has a magnet disposable inside an engine transmission casing and movable by an engine clutch mechanism in the casing as the engine clutch mechanism moves. A flux concentrator is disposable outside the engine transmission casing to concentrate magnetic flux from the magnet, and a first Hall sensor is juxtaposed with the flux concentrator for generating a first signal in response to a magnetic field. Additionally, a second Hall sensor is juxtaposed with the flux concentrator for generating a second signal in response to a magnetic field. A position determination circuit receives the first and second signals and based thereon outputs a signal representative of a linear position of the engine clutch mechanism.

In some embodiments the flux concentrator is elongated and defines first and second ends, with the first Hall sensor being juxtaposed with the first end and the second Hall sensor being juxtaposed with the second end. If desired, a first magnetic booster and a second magnetic booster can be provided. The first Hall sensor may be disposed between the first end of the flux concentrator and the first magnetic booster, and the second Hall sensor may be disposed between the second end of the flux concentrator and the second magnetic booster.

The flux concentrator can be made of a soft magnetic material. The magnet is disposed inside the transmission casing and is coupled to the engine clutch mechanism. On the other hand, the flux concentrator and Hall sensors typically are disposed outside the casing. In non-limiting implementations the flux concentrator tapers inwardly to the first and second ends as do the boosters.

In another aspect, an apparatus has a position sensor disposed outside a transmission casing and bearing a distance within a tolerance from a moving part in the transmission whose position is sought to be measured with a desired degree of accuracy regardless of where in the tolerance the sensor is located relative to the part. The position sensor includes plural sensing elements whose individual outputs representing position of the part are affected by the location of the sensor within the tolerance. The sensor also includes a position determination member receiving the signals from the sensing elements and combining the signals in a way that produces a signal representative of the position of the part that is less affected by the location of the sensor within the tolerance than are the signals from the sensing elements.

In another aspect, a method includes receiving first and second signals from first and second Hall sensors, respectively. The signals represent a position of a moving part. The method includes determining a ratio in which a numerator is derived from only one of the signals, or from a difference between the signals, and the denominator is a sum derived from both of the signals. Position of the moving part is indicated using the ratio.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is intended for application in automotive transmission systems and will be described in that context. It is to be understood, however, that the present invention may also be applied to other applications and contexts requiring non-contact linear position sensors.

Beginning initially withFIG. 1, a schematic view of an automotive vehicle is shown. The automotive vehicle10has an engine12and an engine transmission14. It is to be understood that the engine transmission14has a clutch capable of engaging transmission gears by means known within the art. Further, the engine transmission14is understood to employ a clutch position sensor described further below. The vehicle10also has plural wheels16so that the vehicle10may be mobile.

Now referencingFIG. 2, a schematic view of an engine transmission is shown. The engine transmission14is surrounded by an engine transmission casing16, the casing16being made of a metal such as aluminum (or any non-magnetic material) in non-limiting embodiments. Additionally, the engine transmission14includes a clutch mechanism18.

A magnet20is also shown inFIG. 2. The magnet20is disposed inside the casing16and is coupled to the engine clutch mechanism18. The magnet20can be particularly coupled to a moving part22of the clutch mechanism18. The moving part22may be a transmission clutch component such as a piston that moves a transmission clutch in non-limiting embodiments. Moreover, the clutch component may have a movement range in excess of 25 millimeters in non-limiting embodiments. However, it is to be understood herein that the magnet20may be placed on any acceptable moving part of the clutch mechanism18as determined by those skilled in the art.

Continuing withFIG. 2, a transmission clutch position sensor24is disposed outside the casing16and is capable of sensing a magnetic field generated by the magnet20. It is to be understood that the sensor24is relatively inexpensive and preferably does not include a coil, including any type of electro-magnetic coil. The sensor24will be described in greater detail inFIGS. 3 and 4.

The position sensor24disposed outside a transmission casing16bears a gap distance26within a tolerance from the moving part22. In non-limiting embodiments, the normal gap26may be anywhere from 5 millimeters up to 30 millimeters. After the sensor being calibrated at the normal gap, the sensor24may still output relatively constant measurements of the relatively large linear position of the moving part22at particular times based on the magnetic field generated by the magnet20regardless of where in the few millimeters tolerance of the gap the sensor is disposed. Further, the position sensor24may include plural sensing elements that will be functionally described in greater detail inFIGS. 3 and 4.

Still in reference toFIG. 2, the position sensor24is electrically connected at least one position determining circuit28. The circuit28receives signals from the position sensor24and outputs a signal to an engine control module30indicating the linear position of the engine clutch mechanism18. The method of calculation for the linear position of the mechanism18will be described in greater detail below. The engine control module30is understood to be electronically connected to the circuit28and may use the linear position information in conjunction with vehicle operation in non-limiting embodiments to establish demanded clutch positions.

Now referencingFIG. 3, a schematic view of an example embodiment of a position sensor is shown. It is to be understood that a sensor32may be disposable outside an engine transmission casing37and is substantially similar in function and configuration to the sensor24described above. Thus,FIG. 3shows particular elements of a sensor32for the current embodiment.

The sensor32has at least one elongated flux concentrator34which may concentrate magnetic flux generated by a magnet36coupled to a moving part inside the transmission casing37, the magnet36being substantially similar in function and configuration to the magnet20described inFIG. 2. Moreover, the flux concentrator34may be made of a soft magnetic material such as ferrite ceramic, magnet annealed NiFe, etc.

FIG. 3also shows plural sensing elements38, for example a first Hall sensor38A and a second Hall sensor38B, which are closely juxtaposed with respective ends40of the flux concentrator34. It is to be understood that the sensing elements may be, without limitation, Hall sensors. It is to be further understood that each of the sensing elements38is capable of generating a signal or output in response to a magnetic field generated by the magnet36and concentrated onto the sensors by the flux concentrator.

Thus, the plural sensing elements38, which may be Hall sensors in non-limiting embodiments, may each yield a signal or output representing the linear position a moving part, similar to the moving part22described inFIG. 2, which is measured based on the magnetic field created by movement of the magnet36. Accordingly, the individual outputs are received by the position determination circuit, which combines the signals in a way (described below) that produces a signal representative of the actual position of a moving part that is relatively unaffected by the location of the sensor32within a gap or tolerance.

Still describingFIG. 3, the sensor32may also have plural magnetic boosters42which have respective ends44facing each booster's respective sensing element38in non-limiting embodiments. Accordingly, each of the sensing elements38may be disposed between a respective end40of the flux concentrator34and a respective end44of a magnetic booster42. The relative position of the sensing elements38between ends40and44will be described further inFIG. 4.

Now referencingFIG. 4, a perspective view of an example embodiment of the sensor32also described inFIG. 3is shown. From the perspective view shown inFIG. 4, it may be appreciated that the flux concentrator34tapers inwardly toward the ends40. It may be further appreciated that the magnetic boosters42taper inwardly toward their respective ends44that face their respective sensing elements38. These inward tapers may increase the ability of the sensing elements38to sense a magnetic field strength.

Continuing now in reference toFIG. 5, a graph showing magnetic field intensity ratios versus clutch positions is shown. The graph46shows magnetic field intensity ratios which are based on the magnetic field intensity from one position sensor divided by the sum of the magnetic field intensity from both sensors. Also, the ratio could be that the magnetic field intensity difference between the two sensors over the sum of the magnetic field intensity of both sensors.

In other words, the ratios used in the graph46are determined by a numerator which is derived from only one of the signals of a position sensor or the difference between both sensors and a denominator which is the sum derived from both signal of the position sensors. This ratio may then be used to indicate the position of a moving part to within a certain degree of accuracy (preferably 3-5% of the actual position of the moving part) such as the piston of a clutch mechanism inside a vehicle transmission in non-limiting embodiments. The ratio thus allows an accurate measurement of the position of the moving part irrespective of where in the tolerance a position sensor may be, such as sensor24referenced inFIG. 1(i.e. despite a gap such as the gap26inFIG. 1).

The position indicated by the ratio may then be used by a vehicle, particularly by an engine control module in a vehicle, to control a subsequent position of the moving part in non-limiting embodiments. Thus, the graph shows voltage ratios ranging from 0 to 1.2 in the vertical column48and magnet positions ranging within a 50 millimeter range in the horizontal column50. The graph line52represents the sensor output when the Hall sensors are 26 mm from the magnet, whereas graph line54, which is nearly coterminous with graph line52, shows sensor output when the Hall sensors are 29 mm from the magnet.

While the particular CLUTCH POSITION SENSOR FOR VEHICLE TRANSMISSION is herein shown and described in detail, it is to be understood that the subject matter which is encompassed by the present invention is limited only by the claims.