FIELD OF THE INVENTION

The present invention relates to sensing the position of a locking gearset, such as a differential.

BACKGROUND OF THE INVENTION

Locking gearsets can switch between an engaged and disengaged state. One example of such a gearset is a differential, as is frequently found in a vehicle.

Engagement of a locking gearset is effected by an actuator. In a differential, the actuator is powered and signaled by the vehicle through a controller. As is known in the art, the actuator converts electrical current into mechanical force. The flow of electrical current creates a magnetic field that moves a plunger of the actuator, and through downstream mechanical elements, engages the gearset.

It is also beneficial to have a sensor that can relay information regarding the axial position of the actuator back to the controller. Position sensors provide a signal that is indicative of the position of the locking gearset.

Positional sensors are generally of two types: mechanical or magnetic proximity. Prior art mechanical positional sensors can have wear or mounting issues. Magnetic proximity sensors can have accuracy problems based on runout of moving parts and are subject to interfering fields from the adjacent electromagnetic actuator. The proposed solution herein has little or no mechanical contact with moving parts, is less sensitive to runout, and can be made less sensitive to external magnetic fields.

The current design employs the known Hall type sensor. A Hall type sensor is a transducer that varies its output voltage in response to a magnetic field. Hall effect sensors are used extensively for proximity switching, positioning, speed detection, and current sensing applications. Because Hall sensors have hysteresis and temperature effects that affect the magnetic operating point, the magnetic field at the sensor must exhibit a significant change in a small distance. If the slope of the magnetic field is too small, the transition point for the position sensor may drift out of the acceptable range. The embodiments described herein allow for passing a magnet directly over the Hall sensor, giving a large slope to the magnetic field. In certain applications, the axial distance where the position sensor has to transition may be very small, for example, 0.1 to 1.0 mm, 0.2 to 0.8 mm, or 0.3 to 0.5 mm, or about 0.4 mm. This distance is so small that a sensor cannot easily be positioned in production to function optimally. Therefore, the embodiments described herein employ a lever to amplify the movement of the locking system.

Another aspect of the invention addresses the fact that the magnetic field generated by the actuator is large. Almost any orientation of a magnetic proximity sensor will be affected by these fringing fields since the actuator coil generates fields in the surrounding space in both the axial and radial directions, and only the circumferential direction is relatively free from interference. The embodiments herein take advantage of this property by orienting the sensor to read in the circumferential direction.

Advantageously, the current design is largely insensitive to runout of the moving part being sensed. Another advantage of the embodiments described is that the lever arm used to amplify the movement of the locking system contains a magnet. There is no gap between the magnet and the sensor housing. Therefore, the magnet slides along the housing of the sensor assembly as the lever arm rotates without allowing air/oil/debris to collect on the magnet, resulting in prevention of a main cause of failure of prior art position sensors. In addition, the actuator and sensor assembly can be calibrated before it is installed. Also, wires can be routed to allow for a single connector to the sensor and actuator. For all of the reasons, the position sensor described herein is an improvement over the sensors described in the prior art. SUMMARY OF THE INVENTION

The present invention relates to sensing a position of a locking gearset, such as a differential. One aspect of the invention is a method for determining the mode of an actuator by providing an actuator; providing a sensor assembly including a sensor attached to the actuator; providing a lever attached to one of the actuator or the sensor assembly; providing a magnet attached to the lever. The lever is in a first positon when the actuator is in a first mode, and the lever is in a second position when the actuator is in a second mode, and the lever is caused to move between the first and second positions as a result of the actuator changing from the first mode to the second mode. In the first position the magnet is displaced from the sensor and in the second position the magnet is adjacent to the sensor.

Also described herein is an actuator assembly having non-engaged and engaged modes where the actuator assembly includes an actuator comprising a coil and a plate, a sensor assembly attached to the actuator, where the sensor assembly includes a sensor; and a lever. The lever is rotatably coupled to linear movement of the plate and includes a magnet. The lever is fixedly coupled to at least one of the actuator or the sensor assembly. In the non- engaged mode of the actuator assembly, the lever is in a first position where the magnet is not adjacent to the sensor, and wherein in the engaged mode of the actuator assembly, the lever is in a second position where the magnet is adjacent to the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which:

Fig. 1 shows a perspective view of a differential with a sensor assembly of the invention attached.

Figs. 2A and 2B show schematics of the magnetic flux path generated by an actuator and various sensor orientations superimposed thereon.

Fig. 3 shows a perspective view of an uncovered sensor assembly in accordance with a first embodiment of the invention.

Fig. 4 shows a top perspective view of a covered sensor assembly in accordance with the first embodiment of the invention. Fig. 5 shows a side view of the function of the lever arm of a position sensor in accordance with the first embodiment of the invention.

Fig. 6 shows a perspective view of a covered sensor assembly in accordance with a second embodiment of the invention.

Fig. 7 shows a top view of an isolated sensor assembly in accordance with the second embodiment of the invention.

Fig. 8 shows an end view of a sensor assembly in accordance with the second embodiment of the invention.

Fig. 9 shows a side view of the function of the lever arm of a position sensor in accordance with the second embodiment of the invention.

DETAILED DESCRIPTION

It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined herein. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting.

Fig. 1 shows a differential assembly 1. Differential assembly 1 includes a ring gear (not shown) mounted on a ring gear mount 2 and a rotating gearset 3 that rotates around an axis of rotation A. Gearset 3 includes at least two pinion gears, shown here as 4, 5, 6, with a fourth pinion gear not visible in this view. The at least two pinion gears 4, 5, 6 are rotatably supported on at least one cross shaft (shown here as 7 and 8). First and second side gears (only first side gear 9 is shown) are drivingly interconnected to pinion gears 4, 5, 6 and axle shafts (not shown). Differential assembly 1 also includes an actuator 120 and sensor assembly 100 with connector 101 operable to selectively couple first side gear 9 to a dog gear 10 mounted on a clevis assembly 11 that is non-rotatably connected to differential case (not shown), thereby placing differential assembly 1 in a fully locked condition.

The actuator 120 includes a pressure plate 140 that interacts with the dog gear 10 so that the dog gear 10 engages with the first side gear 9 upon activation of the actuator 120. Figs. 2A and 2B show sectional views of the actuator 120 which includes an armature 92 and an electromagnetic coil 95 of copper wires 96 in an actuator housing 97. Upon activation of the actuator 120, current supplied to the copper wires 96 of the electromagnetic coil 95 produce a magnetic flux path 90 that is normal to the plane of the copper wires 96 at that point of the electromagnetic coil 95.

As described above, the magnetic field generated by the actuator 120 is large. Almost any orientation of a magnetic proximity sensor 130 will be affected by these fringing fields since the electromagnetic coil 95 generates fields in the surrounding space in both the axial and radial directions, and only the circumferential direction is relatively free from interference. The

embodiments herein take advantage of this property by orienting the sensor 130 to read in the circumferential direction. Fig. 2A is a schematic of a cross- section of an actuator 120 showing that the magnetic flux path 90 generated by the electromagnetic coil 95 is in the plane normal to the copper wires 96 at that point along the electromagnetic coil 95. Also shown is a first plane of sensing orientation 131 of the sensor 130 superimposed onto the flux path 90. The first plane of sensing orientation 131 in this configuration would orient the sensor 130 so that it senses in the circumferential direction (i.e. in the same plane as the flux path 90). Thus, the first plane of sensing orientation 131 is also a plane normal to the copper wires 96 at that point along the electromagnetic coil 95.

Fig. 2B shows a perspective cross-section schematic of the

electromagnetic coil 95 and flux path 90 with a second plane of sensing orientation 132 of the sensor 130 and a third plane of sensing orientation 133 of the sensor 130 superimposed in varying orientations, illustrating how the second and third planes of sensing orientation 132, 133 in other orientations than the circumferential direction will be sensitive to the flux path 90 generated by the actuator 120. The embodiments herein take advantage of this property by orienting the sensor 130 in the first plane of orientation 131 so that it senses in the circumferential direction.

Figs. 3-5 show various views of the first embodiment of the sensor assembly 100 while Figs. 6-9 show various views of the second embodiment of the sensor assembly 100. Unless specifically stated otherwise, the components and function of the sensor assembly 100 are identical across both embodiments.

As shown in Figs. 3-9, the sensor assembly includes a lever 160 containing a magnet 150. The sensor assembly 100 also includes a sensor 130 in a housing 170. Sensor assembly 100 can have a cover 110, as shown in Figs. 4 and 6-9.

The sensor 130 is usually a Hall element. The sensor 130 may be a discrete component or mounted to a circuit board inside the housing 170. As noted above, the sensor 130 is oriented in the circumferential direction, which is also the magnet pole direction (and thus its front face is perpendicular to the axis of the lever 160).

The housing 170 which is used for attaching the sensor assembly 100 to the actuator 120 can also be used to house pivot mechanism 180 and the sensor 130. The housing 170 can be made of any material known in the art suitable to protect and house the sensor 130. Possible suitable materials include epoxies, resins, or plastics.

Further, the cover 110 can be made of any material known in the art suitable to protect and house the sensor assembly 100 from damage. Being able to protect the magnet 150 from accumulation of debris, as can be found in the oils used to lubricate the locking gearset 3, is a particular advantage of the embodiments described herein.

The magnet 150 is disposed in a pocket (not shown) on the lever 160. The magnet 150 can be on a side of the lever that 160 that faces the housing 170 and sensor 130. The magnet 150 should be flush with the surface of the lever 160 that faces the housing 170 and sensor 130. The magnet 150 is a sense magnet oriented with a pole oriented parallel to the axis of the pivot of the lever 160. The magnet 150 and lever 160 directly contact the housing 170. Therefore, there is no gap between the magnet 150 and either the housing 170 or the sensor 130 to allow debris to collect. The lack of a gap prevents the magnet 150 from collecting debris that results in false reading, which can be a significant contributor to failure mode in these environments. During function of the sensor assembly 100, described in detail below, the magnet 150 slides against the housing 170 as the lever 160 rotates without allowing air/oil/debris to collect on the magnet 150.

Also included in the sensor assembly 100 is a pivot mechanism 180.

Fig. 3 shows an uncovered sensor assembly 100 in accordance with the first embodiment. The lever 160 is shown in three different positions of rotation.

Fig. 4 shows a sensor assembly 100 of the first embodiment with a cover 110.

In the first embodiment, as shown in detail in Fig. 5, the lever 160 has a contact portion 156 that contacts the plate 140. The contact portion 156 can have a first angular face 157 and a second angular face 158. The first and second angular faces 157 and 158 provide points of contact with the plate 140 such that during engagement, the first angular face 157 is in contact with the plate 140 and in disengagement, the second angular face 158 is in contact with the plate 140. The lever 160 also has an effector arm 155 that extends radially outward form the contact portion 156. The effector arm 155 can extend from the contact portion 156 at a right angle. The effector arm 155 is connected to a pivot portion 154. The pivot portion 154 is attached to the pivot mechanism 180. The pivot portion 154 is connected to a long arm 153. The long arm 153 contains an end portion 152 that is distal from the pivot portion 154. The magnet 150 is disposed in the end portion 152.

Fig. 6 shows a sensor assembly 100 of the second embodiment. The cover 110 is represented by the dotted line. Fig. 7 shows a top view of the sensor assembly 100 of the second embodiment. Fig. 8 shows a side view of the sensor assembly 100 of the second embodiment. Fig. 9 shows an end view of an uncovered sensor assembly 100 of the second embodiment.

As shown in Fig. 9, in the second embodiment of the sensor assembly 100, the contact portion 156 of lever 160 does not have a first angular face 157 and a second angular face 158.

As shown in detail in the second embodiment, the pivot mechanism 180 further includes a pivot pin 200, a tortion spring 210, and a bias spring 220. The tortion spring aids in returning the lever 160 to the unengaged, upright position after deactivation of the actuator 120. The bias spring 220 helps to maintain contact between the (i) magnet 150 and lever and (ii) the housing 170. The same pivot mechanism 180 can also be used in the first embodiment.

When the actuator 120 is not activated, the gearset 3 is not locked and side gear 9 is free to rotate independently of the dog gear 10. In this situation, the plate 140 is adjacent to the actuator 120 and the lever 160 is in an upright position. When the actuator 120 is activated, the plate 140 is caused to move away from the actuator 120 in an axial direction, which in turn is responsible for moving the dog gear 10 axially into locking engagement with a side gear 9. In addition, the axial movement of the plate 140 will cause to be moved the magnet 150 via the rotation of a lever 160. The magnet 150 is attached to the lever 160 such that when the plate 140 moves the dog gear 10 into

engagement, the lever 160 is rotated around the pivot mechanism 180 and the magnet 150 passes in front of the sensor 130 and therefore influences the magnetic field near the sensor 130.

The sensor 130 will transition (i.e. turn on or off) at a particular location of the magnet 150 based on the magnetic field level at the sensor 130. The transition point of the sensor 130 in this design is largely insensitive to runout and interfering magnetic fields. In other words, because the lever 160 moves a magnet 150 in close proximity to the sensor 130, it is less sensitive to the runout of the moving parts or the magnetic field produced by the actuator 120.

The magnet 150 passes directly over the sensor 130, giving a large slope to the magnetic field being sensed. In certain applications, the axial distance where the sensor 130 has to transition may be very small, for example, 0.1 to 1.0 mm, 0.2 to 0.8 mm, or 0.3 to 0.5 mm, or about 0.4 mm.

Alternatively, the sensor 130 can provide information regarding the linear position of the plate 140, rather than only providing information about

engaged/disengaged status of the locking gearset 3.

Fig. 5 shows how when the plate 140 is moved in linear direction 141 , the lever 160 will rotate (following path of arrow 151) around a pivot mechanism 180. The lever 160 can be of any shape able to carry out the function of translating movement of the plate 140 into rotational movement for moving the magnet 150 into close proximity of the sensor 130. The mechanical advantage given by the lever 160 can be 3, 2, 1 , or less than 1. In sum the embodiments described herein relate to a sensor device 100 that employs a lever 160 that contacts a moving component in the system, for example, the plate 140 that is pushed by the actuator 120. The lever 160, thus, translates linear motion of the plate 140 into rotary motion. There is a pivot mechanism 180 at a given distance from the contact point and on the opposite end of the lever 160 is a sense magnet 150 oriented with a pole oriented parallel to the axis of the pivot (of the sense arm). As the pressure plate 140 moves the ever 160, the lever 160 rotates and passes the magnet 150 across the front of the sensor 130.

Although the exemplary embodiments refer to a differential assembly 1 , the sensor assembly 100 can be used in other systems, especially those with locking gearsets, where there are small transition zones.

In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiments. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.