Patent Description:
Non-contact sensors are useful for monitoring the position of moving components since they have few moving parts and thus generally exhibit high durability. An example of such a non-contact sensor is a Hall effect sensor, which can measure the magnitude of a magnetic field. A typical Hall effect sensor arrangement is illustrated in <FIG>, and <FIG>. Such an arrangement includes a single magnet <NUM> carried by a magnet carrier <NUM>, the magnet <NUM> being polarized through the width of the magnet and a Hall effect sensor <NUM> that is spaced apart from the magnet <NUM> in a direction that is substantially perpendicular to the direction of the magnetic field of the magnet. The effectiveness of this kind of sensor arrangement relies on the magnet <NUM> producing a magnetic field with sufficient rough gain to ensure sensor functionality.

In some configurations, however, such as where the sensor magnet <NUM> and the Hall effect sensor <NUM> are separated by a field of a magnetically-responsive medium <NUM>, the magnetic flux at the Hall effect sensor <NUM> is reduced. This reduction is illustrated in one exemplary configuration illustrated in <FIG>. Alternatively or in addition, in some configurations, the magnet carrier <NUM> or other structure surrounding the magnet <NUM> includes other magnetically-responsive materials such as steel, which likewise acts to concentrate the magnetic flux, resulting in a reduction in the magnetic flux experienced at the Hall effect sensor <NUM>, such as is illustrated in <FIG>. In any of these arrangements, a reduction in magnetic flux reduces the rough gain and thus the sensor magnetic performance. In addition, design limitations imposed by using magnetically-responsive material can further limit the performance of standard magnets provided or recommended by sensor manufacturers. Prior art disclosures are referenced in <CIT>, <CIT> and <CIT>. <CIT> discloses a rotary shaft position sensor including pole pieces and a Hall effect device. <CIT> discloses a magnetic position transducer with an integrated Hall effect switch.

In accordance with this disclosure, there is provided a sensor system and method in accordance with the appended claims.

Although some of the aspects of the subject matter disclosed herein have been stated hereinabove, and which are achieved in whole or in part by the presently disclosed subject matter, other aspects will become evident as the description proceeds when taken in connection with the accompanying drawings as best described hereinbelow.

The features and advantages of the present subject matter will be more readily understood from the following detailed description which should be read in conjunction with the accompanying drawings that are given merely by way of explanatory and non-limiting example, and in which:.

The present subject matter provides configurations for a Hall effect sensor system in which a plurality of magnets are arranged to create a more directed magnetic field having a stronger flux concentration axially in the direction of the Hall effect sensor. In some embodiments, an arrangement of multiple magnets that exhibits polarization across the length of the magnet arrangement is used in place of a single magnet that is polarized across its width. In some embodiments, this magnet arrangement includes two permanent magnets placed side by side with reversed polarity to complete the magnetic circuit.

In one exemplary arrangement illustrated in <FIG>, a sensor system, generally designated <NUM>, includes a first magnet <NUM> and a second magnet <NUM> arranged next to the first magnet <NUM>. The first magnet <NUM> is arranged with a first pole <NUM> oriented at least generally in a first direction D1 and a second pole <NUM> oriented at least generally in a second direction D2 substantially opposite from the first direction D1. A second magnet <NUM> has a first pole <NUM> oriented at least generally in the second direction D2, wherein the first pole <NUM> of the second magnet <NUM> has a polarity that matches a polarity of the first pole <NUM> of the first magnet <NUM>. The second magnet <NUM> further has a second pole <NUM> that is oriented at least generally in the first direction D1, wherein the second pole <NUM> of the second magnet <NUM> has a polarity that matches a polarity of the second pole <NUM> of the first magnet <NUM>. This configuration of the first magnet <NUM> and the second magnet <NUM> in a side-by-side arrangement with reversed polarities creates an aggregate magnetic field that has a shape that is somewhat similar to that of a typical sensor magnet, but the magnetic field is more concentrated in the first direction D1 and the second direction D2.

In some embodiments, the sensor system <NUM> provides improved performance of a sensor configuration similar to the conventional sensor arrangement discussed above. In the configuration illustrated in <FIG>, the first magnet <NUM> and the second magnet <NUM> are carried together by a magnet carrier <NUM>, and a Hall effect sensor <NUM> is spaced apart from the first magnet <NUM> and the second magnet <NUM> in the first direction D1. The magnet carrier <NUM> is movable with respect to the Hall effect sensor <NUM> to at least a sensing position at which the first magnet <NUM> and the second magnet <NUM> are proximal to the Hall effect sensor <NUM>. In some embodiments, such a sensing position is a position at which the magnet carrier <NUM> having the first magnet <NUM> and the second magnet <NUM> is proximal to the Hall effect sensor <NUM> within a threshold at which the Hall effect sensor <NUM> can be used to identify the relative position of the magnet carrier <NUM>. In some embodiments, the first magnet and the second magnet <NUM> are positioned side-by-side in the magnet carrier <NUM> such that the magnets are substantially equidistant from the Hall effect sensor <NUM> when in this proximal sensing position.

The directional concentration of the magnetic field that results from the arrangement of the first magnet <NUM> and the second magnet <NUM> discussed above helps to ensure that the magnetic field at the Hall effect sensor <NUM> has sufficient rough gain to ensure sensor functionality. This directional concentration of the magnetic field compensates for configurations that tend to cause deterioration of sensor functionality in conventional sensor systems. In some embodiments where a magnetically-responsive medium <NUM> is provided between the Hall effect sensor <NUM> and the first and second magnets <NUM> and <NUM>, because a directed magnetic field is produced by the arrangement of the first magnet <NUM> and the second magnet <NUM>, the magnetically-responsive medium <NUM> does not significantly diminish the magnetic field directed toward the Hall effect sensor <NUM>, such as is illustrated in <FIG>. In some embodiments, the presence of other magnetically-responsive materials on a side of the sensor system <NUM> opposing the Hall effect sensor <NUM> shorts the lower poles, resulting in a higher flux concentration in the direction of the Hall effect sensor <NUM>, such as is illustrated in <FIG>. In some embodiments, this other magnetically-responsive material includes the magnet carrier <NUM> or one or more elements thereof being composed of steel.

In some embodiments, the present subject matter provides particular utility for devices in which the sensor system <NUM> is associated with a rotating member that moves within a field of a magnetically-responsive medium. In one embodiment illustrated in <FIG> and <FIG>, a magnetically-responsive device generally designated <NUM> includes a shaft <NUM> to which a rotor <NUM> and the magnet carrier <NUM> are interconnected to restrain relative rotation therebetween. In some embodiments, a housing <NUM> is positioned substantially about the shaft <NUM>, the rotor <NUM>, and the magnet carrier <NUM>. The Hall effect sensor <NUM> is attached to or integrated within the housing <NUM>. In addition, one or more pole <NUM> is attached to or integrated within the housing <NUM>, and a magnetic field generator <NUM> associated with the pole <NUM> is spaced from the rotor <NUM> by a void <NUM>. A magnetically responsive medium <NUM>, comprising a magnetically-responsive powder such as iron powder, is contained within and at least partially fills the void <NUM>, including within a space separating the magnet carrier <NUM> from the housing <NUM> and the Hall effect sensor <NUM>. The magnetic field generator <NUM> is controllable to cause the magnetically-responsive medium <NUM> to align along the flux path within the void <NUM> and thereby cause a change in torsional resistance of the rotor <NUM> (and the shaft <NUM>).

In a rotating system of this kind, the first magnet <NUM> and the second magnet <NUM> are rotatable in a plane, wherein the first direction D1 with which the magnetic field of the first magnet <NUM> and the second magnet <NUM> is aligned is substantially orthogonal to the plane of rotation. In this arrangement, the magnets are moved relative to the Hall effect sensor <NUM> such that changes in the flux concentration directed toward the Hall effect sensor <NUM> is recognized as a change in relative position between the elements. In some embodiments, this change in position includes a change in proximity between the magnets and the Hall effect sensor <NUM>, wherein the magnets are rotated to a sensing position once per rotation at which the magnets are proximal to the hall effect sensor <NUM>. Alternatively or in addition, in some embodiments, the Hall effect sensor <NUM> detects a change in the angular orientation of the magnetic field produced by the magnets, and this angular orientation is correlated to the angular position of the magnets relative to the Hall effect sensor <NUM>. By using the sensor system <NUM> in any such configuration, the improved directionality of the magnetic field compensates for a reduced field strength at the Hall effect sensor <NUM> caused by the magnetically-responsive medium shorting the magnetic flux path. In some embodiments, one or more of the shaft <NUM> or elements of the magnet carrier <NUM> comprise magnetically-responsive materials, such as steel, such that the poles opposing the Hall effect sensor <NUM> are shorted, resulting in a further enhanced concentration in the direction of the Hall effect sensor <NUM>.

In some embodiments, the sensor system <NUM> includes multiple Hall effect sensors <NUM>. Because the present subject matter provides improved sensor functionality by increasing the directionality of the magnetic field rather than by simply increasing the strength of the magnets, the sensor system <NUM> is configured so as to not saturate the Hall effect sensor <NUM> that is proximal to the first magnet <NUM> and the second magnet <NUM>. In some embodiments, this directional flux concentration further allows for better differentiation among the magnetic fields experienced at different relative positions of the first magnet <NUM> and the second magnet <NUM>, which allows multiple Hall effect sensors <NUM> to more precisely discern the relative position of the rotating elements. In some embodiments, a first Hall effect sensor 120a and a second Hall effect sensor 120b are positioned at different relative distances with respect to first magnet <NUM> and second magnet <NUM>. As illustrated in <FIG>, in some embodiments, first Hall effect sensor 120a is positioned on a side of a printed circuit board <NUM> that faces towards first magnet <NUM> and second magnet <NUM>, whereas second Hall effect sensor 120b is positioned on an opposing side of printed circuit board <NUM> that faces away from first magnet <NUM> and second magnet <NUM>.

Claim 1:
A position sensor system (<NUM>) comprising:
a Hall effect sensor (<NUM>) coupled to a fixed housing (<NUM>) having a void (<NUM>) defined therein;
a plurality of magnets (<NUM>,<NUM>) coupled to a movable component (<NUM>) that is rotatable relative to the fixed housing (<NUM>);
wherein the movable component (<NUM>) positions the plurality of magnets (<NUM>, <NUM>) in a sensing position, at which the plurality of magnets (<NUM>, <NUM>) is proximal to the Hall effect sensor (<NUM>);
characterised in that:
a magnetically-responsive powder (<NUM>) is contained within and at least partially fills the void (<NUM>), including within a space separating the plurality of magnets (<NUM>,<NUM>) from the fixed housing (<NUM>) and the Hall effect sensor (<NUM>);
wherein the plurality of magnets (<NUM>, <NUM>) is arranged to produce an aggregate magnetic field having a flux concentration directed across the space toward the Hall effect sensor (<NUM>) when the plurality of magnets (<NUM>, <NUM>) is in the sensing position.