WO2009117692A2

WO2009117692A2 - Position sensor and method

Info

Publication number: WO2009117692A2
Application number: PCT/US2009/037861
Authority: WO
Inventors: David P. Wilcox; Howard Warren Kuhlman
Original assignee: Strattec Power Access Llc
Priority date: 2008-03-20
Filing date: 2009-03-20
Publication date: 2009-09-24
Also published as: WO2009117692A3

Abstract

A sensor assembly includes a magnetic element operable to generate a magnetic field, a position sensor having a first sensor element operable to detect the magnetic field and a second sensor element placed at an angle with respect to the first sensor element and operable to detect the magnetic field, the first sensor element and the second sensor element each operable to generate a signal related to the magnetic field, and a processor operable to receive the signals from the first sensor element and the second sensor element to determine an angular position relating the magnetic element and the position based on the signals generated by the first sensor element and the second sensor element.

Description

POSITION SENSOR AND METHOD

RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 61/070,257 filed on March 20, 2008, the contents of which are incorporated herein by reference.

BACKGROUND

[0002] Position sensors are commonly used in automotive systems to determine the position of a moveable object, such as a powered sliding door or liftgate. Obstacle detection is also used to lessen the likelihood of injury from the powered doors or liftgate if unsafe conditions are sensed. One example of this is a door closing on an obstacle or closing too quickly due to street grade.

[0003] An Electronic Control Unit (ECU) is typically used to calculate the position and speed of the door or liftgate so that door or liftgate speed can be controlled and obstacles may be detected. Current power liftgate and sliding door systems use optical encoders or Hall effect sensors to incrementally update gate or door position and speed during operation. As the door or gate moves, changes in magnetic field orientation (Hall effect) or in light transmission levels (optical) cause the sensor to output a digital signal (0 or 1) which the ECU uses to determine door or gate opening/closing direction, speed and location.

[0004] At least one and typically two "known" positions are used to give the ECU a reference position from which to count. This technique prevents errors from accumulating over time, and increases reliability of the system. Common reference points used are the latched position and limit switches at maximum door or liftgate travel.

[0005] Unfortunately, using an incremental position technique requires the ECU to be active at all times to maintain the door or liftgate position count, whether the door or liftgate is in use manually or in powered mode. This increases the load on the vehicle electrical system. If the ECU is powered down, door or liftgate control is typically compromised until a known door or liftgate position is reached again. As an example, the ECU would not know the door or liftgate should be slowed down because it is near the latch. [0006] Previous systems typically require as many as nine wires to operate the motor driving the door or liftgate, provide power to the sensor, and return data to the ECU. Automotive systems demand that the number of pieces, connections and wires be reduced to a minimum to improve reliability, packaging and ease of manufacture.

SUMMARY

[0007] Some embodiments of the present invention provide a position sensor in conjunction with a gear train (which in some embodiments is a rotation-reducing gear train).

[0008] Some embodiments of the present invention also provide for a position sensor used in conjunction with a rotation-reducing gear train or other gear train to allow an ECU to obtain the location of a moveable object (e.g., sliding door, lift gate, powered hood, and any other vehicular panel, hereinafter individually and collectively referred to herein and in the appended claims simply as a "door'p at any point of the door's travel. This device can provide accurate door information to the ECU immediately after a power interruption. Since accurate door position is available at all times, the ECU and the sensor can be powered down to save electrical load without compromising the speed and obstacle detection functions upon activation. Furthermore, in some embodiments, this device will require no more than two data lines to communicate position data to the ECU.

[0009] Some embodiments of present invention also provide a drive unit for actuating a door or other moveable object of a vehicle, the drive unit comprising: a motor having an output shaft; a position sensing device including a cam connected to the shaft, an inner sun gear driven by the cam, an outer ring gear in cooperation with sun gear, a single pole magnet connected to or defined by the sun gear, and at least two sensors spaced apart from each other to detect the magnetic field of the magnet; and an ECU module cooperating with the position sensors to determine the position of the moveable object based upon the change in magnetic field angle produced by the magnet in proximal relationship with the at least two sensors.

[0010] In some embodiments, a sensor assembly is provided, and comprises a magnetic element operable to generate a magnetic field; a position sensor including a first sensor operable to detect the magnetic field, and a second sensor placed at an angle with respect to the first sensor and operable to detect the magnetic field, the first sensor and the second sensor each operable to generate a signal related to the magnetic field; and a processor operable to receive the signals from the first sensor and the second sensor to determine an angular position relating the magnetic element and the position sensor based on the signals generated by the first sensor and the second sensor.

[0011] Some embodiments of the present invention provide a method of operating a sensor assembly including a magnetic element operable to generate a magnetic field, a position sensor having a first sensor for detecting the magnetic field, and a second sensor displaced from the first sensor and operable to detecting the magnetic field, and a processor connected to the first sensor and the second sensor, the method comprising: the first sensor generating a first signal related to the magnetic field; the second sensor generating a second signal related to the magnetic field; sending the first signal and the second signal to the processor; and the processor determining an angular position relating the magnetic element and the position sensor based on the first signal and the second signal.

[0012] Other aspects of the present invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0013] Fig. 1 is a schematic representation of an exemplary drive unit according to an embodiment of the present invention.

[0014] Fig. 2 is an exploded side view of a sensor assembly according to an embodiment of the present invention.

[0015] Fig. 3 is a front view of the sensor assembly of Fig. 2, taken along line 3-3 of Fig. 2.

[0016] Fig. 4 is an exploded side view of a sensor assembly according to another embodiment of the present invention.

[0017] Fig. 5 is a front view of the sensor assembly of Fig. 4.

[0018] Fig. 6 is an exploded side view of a sensor assembly according to another embodiment of the present invention.

[0019] Fig. 7 is a front view of the sensor assembly of Fig. 6, taken along line 7-7 of Fig. 6. [0020] Fig. 8 is a exploded side view of a sensor assembly according to yet another embodiment of the present invention.

[0021] Fig. 9 is a front view of the sensor assembly of Fig. 8.

[0022] Fig. 10 is a chart illustrating signal levels as a function of rotation angle related to a sensor assembly according to an embodiment of the present invention.

[0023] Fig. 11 is a schematic representation of an exemplary position sensor assembly according an embodiment of the present invention.

DETAILED DESCRIPTION OF INVENTION

[0024] Before any embodiments of the present invention are explained in detail, it is to be understood that the present invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description and illustrated in the following drawings. The present invention is capable of other embodiments and of being practiced or of being carried out in various ways.

[0025] Figs. 1-3 illustrate an exemplary drive unit 10 according to an embodiment of the present invention. The illustrated drive unit 10 includes a motor 15 for driving a shaft 20, a gearing system 25 associated with the motor 15 and a door 30' or 30" of a vehicle 35, and a sensor assembly 40 mounted on the shaft 20 and connected to an ECU 45 of the vehicle 35. Optionally, the drive unit 10 can include a clutch system 50 associated with the gearing system 25. During operation of the drive unit 10, the motor 15 is operable to transfer a force to, thus causing movement of, the door 30 via the gearing system 25. Concurrently, the sensor assembly 40 generates one or more signals indicative of the state of the door 30.

[0026] The sensor assembly 40 of the illustrated embodiment is operable to generate at least one signal indicative of the position of the door 30 between, and including, opened and closed positions. In the illustrated embodiment of Figs. 1-3, the signal or signals are sent to the ECU 45 of the vehicle 35.

[0027] The position sensor assembly 40 in Fig. 1 is located between the geared motor output and the actuating mechanism operating the door 30', or if a clutch 50 is used, between the clutch 50 and the actuating mechanism operating the door 30' as shown in Fig. 1. It is to be understood that the sensor assembly 40 can also be placed at other stages or positions with respect to the shaft 20 and the motor/gear systems of the drive unit 10. Further, one of ordinary skill in the art will understand that the sensor assembly 40 can be mounted on a structure other than the shaft 20, and thus the particular embodiments described herein are not limiting to the scope of the present invention.

[0028] Figs. 2 and 3 illustrate the sensor assembly 40 in greater detail. The sensor assembly 40 of Figs. 2 and 3 includes an outer ring 55 static with respect to movement of the shaft 20, an inner sun gear 60 coupled to the shaft 20 for rotational movement therewith, a single pole disk magnet 65, and a PC board 70 having sensors 105 for generating one or more signals indicative of the position of the door 30', as further explained below. The sun gear 60 is mounted on a cam 75 of the shaft 20 such that, during operation of the drive unit 10, the sun gear 60 rotates eccentrically with respect to an axis 80 of the shaft 20, and outer teeth 85 of the sun gear 60 engage inner teeth 90 of the ring 55.

[0029] As further explained below, the number of teeth 85 and 90 of the sun gear 60 and ring 55 can be used to calculate a ratio relating the number of revolutions of the shaft of the number of revolutions of the sun gear 60. Harmonic drives consisting of the outer ring 55 and inner sun gear 60 are mounted on the eccentric cam 75 to perform in such manner in a minimum of space. In the illustrated construction of Figs. 2 and 3, the ring 55 and sun gear 60 are sized such that, during operation of the drive unit 10, movement of the door between a fully opened position and a fully closed position causes the sun gear 60 to rotate 360 degrees or less.

[0030] The magnet 65 is coupled to the shaft 20 for rotation therewith. In some embodiments, this connection is facilitated by mounting the magnet 65 to the sun gear 60. In the illustrated embodiment by way of example only, the sun gear 60 includes an aperture 95 for receiving a pin 100 (or other projection). In other words, the magnet 65 also engages the sun gear 60 for rotation therewith. The single pole disk magnet 65 used by the sensor assembly 40 is pinned to the sun 60 and placed between the sun gear 60 and the PC board 70 with at least one sensor, as further explained below. In other embodiments, the magnet 65 can have other shapes and sizes, and can be connected to the sun gear 60 and/or directly to the shaft 20 in any other suitable manner

[0031] The PC board 70, similar to the ring 55, is static with respect to movement of the shaft 20. Among other things, the PC board 70 includes a position sensor 105 mounted thereon and operable to generate signals indicative of the position of the sun gear 60 (based upon the rotational position of the magnet 65), and thus the position of the door of the vehicle 35, as further explained below. For the purposes of this application, the position sensor 105 can be one or more discrete sensors or an absolute sensor. In other words, the term "position sensor" is inclusive of one or more discrete elements utilized to generate signals sent to the ECU 45, or a single element (e.g., a microcontroller) including sensing elements, processing elements, memory, interphase mechanisms and other suitable components readily clear to one of ordinary skill in the art.

[0032] In the illustrated embodiment of Figs. 2 and 3, the position sensor 105 is described as a single element. As illustrated in Fig. 11, the position sensor 105 can include, among other things, an input interface 110, an output interface 115, a processing unit 125, a memory 130 and two Hall effect sensors 135. Although a single line is connected to each of the input interface 110 and output interface 115, it is to be understood that each one of the interfaces 110, 115 can include mechanisms to send and/or receive analog and/or digital signals. Further, the interfaces 110, 115 can include wireless devices to exchange information with the ECU 45 or other devices of the vehicle 35.

[0033] The processing unit 125 is operable to control the interfaces 110, 115, receive signals from the two Hall effect sensors 135 and to process such signals based on instructions recorded in the memory 130. Other embodiments and capabilities of the exemplary position sensor 105 fall within the spirit and scope of the present invention. During operation of the drive unit 10, each of the two Hall effect sensors 135 detect the magnet 65, and each generates a signal indicative of the position of the Hall effect sensor 135 with respect to the magnet 65. Because the magnet 65 rotates with the sun gear 60, the processing unit 125 can determine the angular position of the sun gear 60, and thus the position of the door of the vehicle 35, based on the signals of the Hall effect sensors 135. The position sensor 105 can send the position information to the ECU 45 via the output interface 115. In some embodiments, the processing unit 125 relays the signals generated by the Hall effect sensors 135 to the ECU 45 for determining the position of the door of the vehicle 35.

[0034] In the illustrated embodiment of Figs. 2 and 3, the position sensor 105 in conjunction with a geartrain (ring 55 and sun gear 60) allow the ECU 45 to obtain the location of the mechanism (e.g., sliding door) at any point in its travel. This sensor assembly 40 can provide accurate information related to the position of the door to the ECU 45 immediately after a power interruption. Since accurate door position is available at all times, the ECU 45 and the position sensor 105 can be powered down to save electrical load without compromising the speed and obstacle detection functions upon activation. Further, in some embodiments, the sensor assembly 40 requires no more than two data lines to communicate the position data to the ECU 45.

[0035] The sensor assembly 40, as illustrated in Figs. 1 -3, can be broken into, or viewed as including, two functional areas: the first functional area being the gearing mechanism encompassing the ring 55 and the sun gear 60, and the second functional area being the sensing mechanisms encompassing the magnet 65 and PC board 70 for generating position information. With respect to the gearing mechanism, rotation of the geared motor output in the illustrated embodiment is reduced to 360 degrees rotation per door actuation, hi other words, if the output (shaft 20) rotates 20 revolutions during an entire open or close cycle and the sun gear rotates a single revolution, a ratio of at least 20: 1 is used.

[0036] By way of example only, the ring 55 can include an outer gear with 22 teeth and the sun gear 60 can include an inner gear with 21 teeth. Using this example, one rotation of the shaft/eccentric will rotate the sun gear by (22-21)/22= 1/22 of one rotation. In other words, 22 rotations of the shaft 20 are approximately equivalent to one rotation of the sun gear 60. This rotation is measured by the Hall effect sensors 135, and the information generated by the position sensor 105 is sent to the ECU as an analog, PWM or digital signal. The sun gear 60 in some embodiments is sized such that one rotation of the sun gear 60 is equivalent to movement of the door between fully opened and fully closed positions. The sun gear 60 and ring 55 can be sized differently based on the application (e.g., lift gates, powered hood, etc.).

[0037] Fig. 10 is a graph illustrating the relative signal level of signals generated by the Hall effect sensors 135 as a function of rotation angle of the sun gear 60. With respect to the second functions area of the sensor assembly 40, the two Hall effect sensors 135 with linear output, for example, are mounted at approximately a 90 degree angle with respect to one another. The relative signal levels of the two channels (each channel corresponding to the signal of one Hall effect sensor 135) allow the processing unit 125 and/or the ECU 45 to calculate the position of the door 30 of the vehicle 35. More specifically, the magnet 65 of the sensor assembly 40 is detected by the two Hall effect sensors 135. The angle between the Hall effect sensors 135 causes the output of each Hall effect sensor 135 to differ from one another as the magnetic field (of the magnet 65) angle changes.

[0038] In the illustrated embodiment, the angle of the magnetic field is calculated using an arctangent function, since the right angle between the two Hall effect sensors 135 and the angles the magnetic field makes with respect to each of the Hall effect sensors 135 can be used to describe a right triangle. In is to be understood that, in other embodiments, the processing unit 125 and/or the ECU 45 can process the signals generated by the Hall effect sensors 135 differently based upon, for example, if the signals are analog or digital. Further, in other embodiments, the Hall effect sensors 135 may be positioned at a different orientation, thus also affecting how the signals generated therefrom are processed.

[0039] The present invention encompasses the use of linear output sensors or a digital representation of linear outputs, allowing significant reductions in the number of wires needed to transmit position information to the ECU 45. Discrete Hall devices, as indicated above, often require two data lines, while integration of the two Hall effect sensors with a signal processor would only require one data line (as with the Melexis MLX90316 or similar device).

[0040] Figs. 4-5 illustrate an alternative construction of a sensor assembly according to an additional embodiment of the present invention. This embodiment employs much of the same structure and have many of the same properties as the embodiment of the sensor assembly described above in connection with Figs. 1-3. Accordingly, the following description focuses primarily upon the structure and features that are different than the embodiment described above in connection with Figs. 1-3. Reference should be made to the description above in connection with Figs. 1-3 for additional information regarding the structure and features, and possible alternatives to the structure and features of the sensor assembly illustrated in Figs. 4-5 and described below. Structure and features of the embodiments shown in Figs. 4-5 that correspond to structure and features of the embodiment of Figs. 1-3 are designated hereinafter in respective two and three hundred series of reference numbers.

[0041] Figs. 4-5 illustrate a sensor assembly 240 having an outer ring 255 static with respect to movement of a shaft 220, a magnetized inner sun gear 260 coupled to the shaft 220 for rotational movement therewith, and a PC board 270 with a position sensor 305 for generating one or more signals indicative of the position of a door of a vehicle (for example). The magnetized sun gear 260 is mounted on a cam 275 of the shaft 220 such that, during operation of a drive unit (e.g., drive unit 10 in Fig. 1), the magnetized sun gear 260 rotates eccentrically with respect to an axis 280 of the shaft 220, and outer teeth 285 of the magnetized sun gear 260 engage inner teeth 290 of the ring 255. Note that, unlike the embodiment illustrated in Figs. 1-3, the sensor assembly 240 does not include a disk magnet. The position sensor 305 is operable to generate a signal related to the position of the sun gear 260 by detecting the magnetic field of the magnetized sun gear 260 itself.

[0042] Figs. 6-7 illustrate an alternative construction of a sensor assembly according to an additional embodiment of the present invention. This embodiment employs much of the same structure and have many of the same properties as the embodiments of the sensor assembly described above in connection with Figs. 1-5. Accordingly, the following description focuses primarily upon the structure and features that are different than the embodiments described above in connection with Figs. 1-5. Reference should be made to the description above in connection with Figs. 1-5 for additional information regarding the structure and features, and possible alternatives to the structure and features of the sensor assembly illustrated in Figs. 6-7 and described below. Structure and features of the embodiments shown in Figs. 6-7 that correspond to structure and features of the embodiments of Figs. 1-5 are designated hereinafter in respective four and five hundred series of reference numbers.

[0043] The sensor assembly 440 shown in Figs. 6-7 includes an outer friction-type ring 455 static with respect to movement of a shaft 420, a friction-type inner sun gear 460 coupled to the shaft 420 for rotational movement therewith, a single pole disk magnet 465 and a PC board 470 with a position sensor 505 for generating one or more signals indicative of the position of a door of a vehicle (for example). The friction-type sun gear 460 is mounted on a cam 475 of the shaft 420 such that, during operation of a drive unit (e.g., drive unit 10 in Fig. 1), the friction-type sun gear 460 rotates eccentrically with respect to an axis 480 of the shaft 420, and an outer surface 486 of the sun gear 460 engages an inner surface 491 of the friction-type ring 455. In the illustrated embodiment of Figs. 6-7, the friction-type sun gear 460 includes an aperture 495 for receiving a pin 500 (or other projection). In other words, the magnet 465 also engages the sun gear 460 for rotation therewith. Note that, unlike the embodiment illustrated in Figs. 1-3, the sensor assembly 440 includes friction-type ring 455 and friction-type sun gear 460. It is to be understood that the invention encompasses other types of rings and sun gears.

[0044] Figs. 8-9 illustrate an alternative construction of a sensor assembly according to an additional embodiment of the present invention. This embodiment employs much of the same structure and have many of the same properties as the embodiments of the sensor assembly described above in connection with Figs. 1-7. Accordingly, the following description focuses primarily upon the structure and features that are different than the embodiments described above in connection with Figs. 1-7. Reference should be made to the description above in connection with Figs. 1-7 for additional information regarding the structure and features, and possible alternatives to the structure and features of the sensor assembly illustrated in Figs. 8-9 and described below. Structure and features of the embodiments shown in Figs. 8-9 that correspond to structure and features of the embodiments of Figs. 1-7 are designated hereinafter in respective six and seven hundred series of reference numbers.

[0045] Figs. 8-9 illustrate a sensor assembly 640 including a friction-type outer ring 655 static with respect to movement of a shaft 620, a magnetized friction-type inner sun gear 660 coupled to the shaft 620 for rotational movement therewith, and a PC board 670 with a position sensor 705 for generating one or more signals indicative of the position of a door of a vehicle (for example). The magnetized friction-type sun gear 660 is mounted on a cam 675 of the shaft 620 such that, during operation of a drive unit (e.g., drive unit 10 in Fig. 1), the magnetized friction-type sun gear 660 rotates eccentrically with respect to an axis 680 of the shaft 620, and an outer surface 686 of the magnetized friction-type sun gear 660 engages an inner surface 491 of the friction-type ring 655. Note that, unlike the embodiments illustrated in Figs. 1-3 and 6-7, the sensor assembly 640 does not include a disk magnet. The position sensor 705 is operable to generate a signal related to the position of the friction-type sun gear 660 by detecting the magnetic field of the magnetized friction-type sun gear 660 itself. Also note that, unlike the embodiments illustrated in Figs. 1-5, the sensor assembly 640 includes friction-type ring 655 and friction-type sun gear 660. It is to be understood that the invention encompasses other types of rings and sun gears.

[0046] Various features and advantages of the invention are set forth in the following claims.

Claims

CLAIMSWhat is claimed is:

1. A drive unit for actuating a moveable object, the drive unit comprising: a motor having an output shaft; a position sensor engaged to the output shaft, the position sensor including a cam connected to the shaft, an inner sun gear driven by the cam, an outer ring gear in cooperation with sun gear, a single pole magnet connected to or defined by the sun gear, and at least two sensors spaced apart from each other to detect the magnet, the magnet; and an ECU module cooperating with the position sensor to determine the position of the moveable object based upon the change in magnetic field angle produced by the magnet in proximal relationship with the at least two sensors.

2. A drive unit for actuating a moveable object of claim 1 , wherein the magnet is defined by the sun gear.

3. A drive unit for actuating a moveable object of claim 1 , wherein the magnet is coupled to the sun gear.

4. A sensor assembly comprising: a magnetic element operable to generate a magnetic field; a position sensor including a first sensor operable to detect the magnetic field, and a second sensor placed at an angle with respect to the first sensor and operable to detect the magnetic field, the first sensor and the second sensor each operable to generate a signal related to the magnetic field; and a processor operable to receive the signals from the first sensor and the second sensor to determine an angular position relating the magnetic element and the position sensor based on the signals generated by the first sensor and the second sensor.

5. The sensor assembly of claim 4, wherein a portion of the sensor assembly is mounted on a rotatable shaft, the sensor assembly further comprising a gear mounted on the shaft such that the magnetic element is connected to the gear for rotation therewith.

6. The sensor assembly of claim 5, wherein the shaft includes a cam such that the gear is mounted onto the cam for eccentric rotation with respect to the shaft.

7. The sensor assembly of claim 5, further comprising a ring at least partially enclosing the gear, the ring being static with respect to the shaft and supporting rotation of the gear therein.

8. The sensor assembly of claim 4, wherein the magnetic element is gear mounted onto a shaft for relative rotation therewith.

9. The sensor assembly of claim 8, wherein the shaft includes a cam such that the magnetic element is mounted onto the cam for eccentric rotation with respect to the shaft.

10. The sensor assembly of claim 5, further comprising a ring at least partially enclosing the magnetic element, the ring being static with respect to the shaft and supporting rotation of the gear therein.

11. The sensor assembly of claim 4, wherein the position sensor incorporates the processor and includes an output interface to send at least one signal related to the angular position to an ECU placed remotely from the sensor assembly.

12. The sensor assembly of claim 4, wherein the position sensor further includes a processing unit operable to relay processor at least one signal related to the signals from the first sensor and the second sensor.

13. The sensor assemble of claim 12, wherein the processor is an ECU of a vehicle.

14. A method of operating a sensor assembly including a magnetic element operable to generate a magnetic field, a position sensor having a first sensor for detecting the magnetic field, and a second sensor displaced from the first sensor and operable to detecting the magnetic field, and a processor connected to the first sensor and the second sensor, the method comprising: the first sensor generating a first signal related to the magnetic field; the second sensor generating a second signal related to the magnetic field; sending the first signal and the second signal to the processor; and the processor determining an angular position relating the magnetic element and the position sensor based on the first signal and the second signal.

15. The method of claim 14, wherein the sensor assembly is partially mounted onto a shaft, the method further comprising eccentrically rotating the magnetic element with respect to an axis substantially parallel to the shaft such that one rotation of the magnetic element corresponds to a number of rotations of the shaft.

16. The method of claim 14, wherein the position sensor incorporates the processor, the method further comprising the processor sending at least one signal related to the angular position to an ECU placed remotely from the sensor assembly.

17. The method of claim 14, wherein the position sensor further includes a processing unit, the method further comprising the processing unit relaying to the processor at least one signal related to the first signal and the second signal.