Abstract
A position encoder comprising a cylindrical rotor; first and second magnetic poles having opposite polarity helically disposed about the inner or outer diameter of the rotor; first and second Hall sensors disposed within a distance suitable for the Hall sensors to detect the magnet poles.
Claims
1. A magnetic position encoder system, said encoder system comprising: a rotor, said rotor having a generally cylindrical shape and an exterior; a first magnetic pole helically disposed about the exterior of said rotor; a second magnetic pole, said second magnetic pole helically disposed about the exterior of said rotor and adjacently to said first magnetic pole, said second magnetic pole having a polarity opposite said first magnetic pole; a first Hall sensor, said first Hall sensor disposed within a distance suitable for said first Hall sensor to detect said first and said second magnets; a second Hall sensor, disposed within a distance suitable for said second Hall sensor to detect said first and said second magnets, said second Hall sensor disposed relative to said first Hall sensor such that the output of said first Hall sensor is 90° out of phase from said second Hall sensor.
2. The system of claim 1, wherein the system further comprises an actuating apparatus operatively connected to said rotating shaft, said actuating apparatus selected from the group consisting of an electric motor, a hydraulic motor, a crank, an internal combustion engine, conveyor, gear box, and a bearing system.
3. The system of claim 1, wherein the system further comprises a printed circuit board connected to said Hall sensors.
4. The system of claim 1, wherein said magnetic poles are disposed on a surface selected from the group consisting of the end of said shaft, the outer diameter of said shaft, and the inner diameter of said shaft.
5. The system of claim 1, wherein the system comprises a magnet having at least two magnetic poles adjacently and longitudinally disposed around the exterior of cylinder to create a helical pole pattern relative to a sensor.
6. The magnet of claim 5, wherein said helical magnetic pole pattern comprises slanted magnetic pole stripes.
7. The magnet of claim 5, wherein said helical magnetic pole pattern comprises straight magnetic strips on a magnet tilted at a predetermined pitch.
8. A magnet for use with a magnetic encoder, said magnet comprising at least two magnetic poles adjacently and helically disposed on the face of a cylinder.
9. A magnet for use with a magnetic encoder, said magnet comprising at least two magnetic poles adjacently and longitudinally disposed around the exterior of cylinder to create a helical pole pattern relative to a sensor.
10. The magnet of claim 9, wherein said helical magnetic pole pattern comprises slanted magnetic pole stripes.
11. The magnet of claim 9, wherein said helical magnetic pole pattern comprises straight magnetic strips on a magnet tilted at a predetermined pitch.
12. A magnet for use with a magnetic encoder, said magnet comprising at least two magnetic poles adjacently and helically disposed on the face of a cylinder.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The present invention will be understood more fully from the detailed description given hereinafter and from the accompanying drawings of the preferred embodiment of the present invention, which, however, should not be taken to limit the invention, but are for explanation and understanding only.
[0022] In the drawings:
[0023] FIG. 1 shows a prior art rotary magnetic encoder with magnetic poles disposed on the periphery of a cylinder.
[0024] FIG. 2 shows a diagram of the output of the encoder of FIG. 1.
[0025] FIG. 3 shows a prior art rotary magnetic encoder with magnetic poles disposed on the face of a cylinder.
[0026] FIG. 4 shows a prior art linear magnetic encoder.
[0027] FIG. 5 shows a prior art “end looking” magnetic encoder arrangement.
[0028] FIG. 6 shows a pair of prior art magnetic sensor arrangements having two magnetic poles each where the sensor is “off axis” compared to the “on axis” arrangement of FIG. 5.
[0029] FIG. 7 shows a rotary magnetic encoder according to the present invention with magnetic poles disposed helically around the exterior of a cylinder.
[0030] FIG. 8 shows a diagram of the output of FIG. 7.
[0031] FIG. 9 shows a rotary magnetic encoder according the present invention with magnetic poles disposed helically on an end of a cylinder.
[0032] FIG. 10 shows a linear magnetic encoder according to the present invention.
[0033] FIG. 11 shows an alternative embodiment of the magnetic encoder of FIG. 10.
[0034] FIG. 12 shows a rotary encoder according to the present invention with magnetic poles disposed around the inner diameter of a cylinder.
[0035] FIG. 13 shows an exemplary application of the present invention.
[0036] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplary embodiments set forth herein are not to be construed as limiting the scope of the invention in any manner.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0037] The present invention will be discussed hereinafter in detail in terms of various exemplary embodiments according to the present invention with reference to the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be obvious, however, to those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures are not shown in detail in order to avoid unnecessary obscuring of the present invention.
[0038] Thus, all of the implementations described below are exemplary implementations provided to enable persons skilled in the art to make or use the embodiments of the disclosure and are not intended to limit the scope of the disclosure, which is defined by the claims. As used herein, the word “exemplary” or “illustrative” means “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” or “illustrative” is not necessarily to be construed as preferred or advantageous over other implementations. Moreover, in the present description, the terms “upper”, “lower”, “left”, “rear”, “right”, “front”, “vertical”, “horizontal”, and derivatives thereof Hall relate to the invention as oriented in FIG. 1.
[0039] Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 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 in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.
[0040] Referring first to FIG. 1, there is shown a side view and an end view of a typical prior art rotary magnetic encoder. As illustrated generally in FIG. 1, a typical rotary magnetic encoder comprises a permanent magnet attached to a rotating shaft so that the shaft has a specific number of alternating symmetrical magnetic poles around its periphery. The encoder further comprises a two channel magnetic Hall sensor disposed across an air gap at a functional distance with respect to the position of the magnetic poles so that the two channels of output are in quadrature (i.e. simulating a sine and cosine wave) to each other as depicted in FIG. 2. Persons of ordinary skill in the art will appreciate that a functional distance is a distance within which the Hall sensor is able to detect the magnetic flux of the magnetic poles. Thus, the functional distance will depend on the sensitivity of the Hall sensors as well as the amount of flux generated by the magnetic poles.
[0041] Referring again to FIG. 1, the magnetic poles have a predetermined “field width.” When used with a pitched magnetic sensor, the width of the field produced by each pole of a magnet must be in direct relationship to the pitch of the sensor. For Hall sensors, this magnetic pole width is approximately twice the sensor pitch. This field width constant dictates the final number of magnetic poles and changes with the magnets diameter. Thus, lower pole counts especially two poles (one pole pair) are not practical for use with these types of sensors as illustrated in FIG. 6.
[0042] Referring now to FIG. 2, there is shown a view of the magnetic poles shown in the side view of FIG. 1 where the magnetic poles are displayed along a single line that is analogous to one revolution of the shaft and magnetic pole arrangement shown in FIG. 1. FIG. 2 further shows two exemplary output signals that can be sent directly to a motor controller or similar device for the determination of parameters such as speed and direction of the shaft or be further processed or interpolated into additional positional data.
[0043] Referring next to FIG. 3, there is shown a side view and an end view of a prior art rotary magnetic encoder with magnetic poles disposed on the end of a cylinder. The magnet poles may be provided circumferentially on the magnet face that is mounted on of a rotating shaft or the magnet may be connected using an adaptor or other device disposed at the end of the shaft. As illustrated in FIG. 3, a pitched Hall sensor is disposed vertically above one end of the magnet across an air gap within a functional distance of the magnetic poles at the end of the rotating shaft. Again, persons of ordinary skill in the art will appreciate that a functional distance is a distance within which the Hall sensor detect the magnetic flux of the magnetic poles. Thus, the functional distance will depend on the sensitivity of the Hall sensors as well as the amount of flux generated by the magnetic poles.
[0044] Referring still to FIG. 3, each of the magnetic poles has a predetermined “field width.” When used with a pitched magnetic sensor, the width of the field produced by each pole of a magnet must be in direct relationship to the pitch of the sensor. For Hall sensors, this magnetic pole width is approximately twice the sensor pitch. This field width constant dictates the final number of magnetic poles and changes with the magnets diameter. Lower pole counts especially two poles (one pole pair) are not practical for use with these types of sensors unless the position of the sensor is directly above the axis of the magnet.
[0045] Referring next to FIG. 4, there is shown a linear view of the prior art magnetic encoder of FIG. 3. Specifically, FIG. 4 illustrates a partial side view and a partial top view of a prior art encoder with magnetic poles disposed along the length of a magnet strip. As with FIG. 3, the pitched Hall sensor of FIG. 4 is disposed within a functional distance of the face/end of a cylinder. When used with a pitched magnetic sensor, the width of the field produced by each pole of a magnet must be in direct relationship to the pitch of the sensor. For Hall sensors, this magnetic pole width is approximately twice the sensor pitch. This field width constant dictates the final number of magnetic poles and changes with the magnets length.
[0046] Referring next to FIG. 5, there is shown a prior art “end looking” magnetic encoder. As illustrated in FIG. 5, a non-contacting magnetic sensor (preferably a Hall based sensor) is disposed within a predetermined functional distance from one end of a cylindrical adaptor having a magnet with preferable two magnetic poles. The magnet is disposed on one end of a rotating shaft using an adapter. Together, the shaft, adaptor, and magnet form a magnetic field sensing assembly. An air gap is shown between the magnet and the Hall sensor. The shaft is either intergyral or adapted to be connected to another rotating object such as, for example, a motor shaft, a crankshaft, or a throttle body on a fuel injection system. The shaft rotates about an axis of rotation.
[0047] As further illustrated in FIG. 5, the Hall Effect device is attached to a printed circuit board. The Hall Effect sensor remains stationary in an air gap while the motorized shaft, magnet and adaptor turns around an axis of rotation. The Hall Effect position sensor may be connected to external circuitry via the printed circuit board. The circuit board provides a means for connection of an output signal that the external circuitry receives for processing. Using the output data, the speed or angular position of the shaft can be determined by known means.
[0048] Referring now to FIG. 7, there is shown a side view and an end view of a magnetic encoder 1000 in accordance with the present invention. As illustrated in FIG. 7, magnetic encoder 1000 generally comprises a magnet 120 with a plurality of magnetic poles 120 disposed helically around the exterior of a magnet that is affixed to a rotating cylindrical shaft 130. Encoder 1000 further comprises a Hall sensor 100 disposed radially outside of the magnets magnetic poles 120 on the exterior of shaft 130. An air gap 110 is shown between the magnets magnetic poles 120 and Hall sensor 100. Shaft 130 is either integral or adapted to be connected to another rotating object (not shown) such as, for example, a motor shaft, a crankshaft, or a throttle body on a fuel injection system. Shaft 130 rotates about an axis of rotation 140.
[0049] Similar to FIG. 7, FIG. 12 shows a side view and an end view of a magnetic encoder 1000 in accordance with the present invention. As illustrated in FIG. 12, magnetic encoder 1000 generally comprises a magnet 120 with a plurality of magnetic poles disposed helically around the inner diameter of a magnet 120 mounted to a rotating cylindrical shaft 130. Encoder 1000 further comprises a Hall sensor 100 disposed radially inside of the magnet 120. An air gap 110 is shown between magnet 120 and Hall sensor 100. Shaft 130 is either integral or is adapted to be connected to another rotating object (not shown) such as, for example, a motor shaft, a crankshaft, or a throttle body on a fuel injection system. Shaft 130 rotates about an axis of rotation 140.
[0050] As illustrated in FIG. 10, a linear encoder version may be achieved using slanted magnetic stripes. Alternately, as illustrated in FIG. 11, the same effect can be made using straight magnetic strips but tilting the completed magnet at the correct pitch.
[0051] FIG. 8 depicts the output of magnetic encoder 1000 illustrated in FIG. 7 through FIG. 13. For this example, the spiral pitch is set to simulate a two pole device for an output equal to one side and one cosine output of the sensor per either one mechanical revolution or a fixed linear distance. This type of output is typical for absolute but also incremental positioning devices used in applications such as drive by wire, etc. but are not restrained by magnet diameter but more importantly, the sensor does not have to be facing the centerline of the shaft as typically found providing even more value in an application solution.
[0052] Referring generally to FIG. 7, to FIG. 12, and to FIG. 9, there is shown a pattern which can be described as a double helix (two pole version). This double magnetic helix comprises of stripes of a pair of north and south magnetic poles spiraling around a fixed axis similar to a barber poles red and white stripes. The pole width is also a function of 2× the pitch and type of the sensor used. The spiral pitch is also a function of the sensor pitch and type. For a two pole style, the spiral pitch is equal to 4× the sensor pitch for a Hall device and 8× for the pitch of a magnetoresistor sensor.
[0053] Although one sin and cosine cycle works best for absolute encoding, by using other pitches and increasing the number of helical stripes, other pole counts and resolutions can be simulated using this helix field pattern. This pole pattern technique is easily applied to other types of magnetic sensor targets such but not limited to Hall Effect, all types of magnetoresistors, inductive and eddy current sensors.
[0054] Referring again to FIG. 8, the output signal is a voltage signal substantially proportional to the magnetic field sensed by Hall effect device 100. However, it should be understood that this is not intended as a limitation of the present invention. Depending on the circuitry coupled to Hall effect device 100, the output signal can be either a voltage signal or a current signal and can have any kind of monotonic relation with the magnetic field sensed by Hall effect device 100. The output from Hall effect device 100 is connected to conventional signal processing electronics for amplification, filtering, interpolation algorithms, etc.
[0055] Referring now to FIG. 9, there is shown an alternative embodiment of magnetic encoder 1000 in accordance with the present invention. As illustrated in FIG. 9, magnetic encoder 1000 generally comprises a plurality of magnetic poles 120 disposed helically on the end of magnet 120 mounted on a rotating shaft of a rotating cylindrical shaft 130. Encoder 1000 further comprises a Hall sensor 100 disposed vertically above magnetic poles 120 on the end of shaft 130. Air gap 110 is shown between magnetic poles 120 and Hall sensor 100. Shaft 130 is either integral or adapted to be connected to another rotating object (not shown) such as, for example, a motor shaft, a crankshaft, or a throttle body on a fuel injection system. Shaft 130 rotates about an axis of rotation 140. Shaft 130 may be connected to any actuator capable of initiating rotation of shaft 130 such as an electric motor, combustion engine, gear box, hand crank, conveyor, or bearing system.
[0056] Turning now to FIG. 13, there is shown an embodiment of magnetic system 1000 according to the present invention. As illustrated in FIG. 13, system 1000 of the present invention generally comprises motor 200 having rotating shaft 130 extending vertically therefrom. Shaft 130 is rotatable around longitudinal axis 140.
[0057] Referring again to FIG. 13, system 1000 further comprises a spiral magnet 120 having a plurality of magnetic poles disposed helically or spirally around the external surface of magnet 120. The plurality of magnetic poles is arranged such that each individual pole is adjacent to a pole of opposite polarity. System 1000 further comprises a Hall sensor 100 disposed radially outside of magnetic poles 120 on the exterior of shaft 130. Hall sensor 100 is further connected to a printed circuit board 150. Printed circuit board 150 can be used for communicating output from Hall sensor 100 to conventional signal processing electronics for amplification, filtering, interpolation, etc. The design of FIG. 13 has one advantage over the prior art as shown in FIG. 5. This advantage is the ability of sensor 100 to be positioned “off axis” compared to the “on axis” position required of FIG. 5 and still performs as an absolute encoder using the single cycle sin and cosine output. That advantage gives the design the ability to allow the shaft 130 to extend out pass the encoder system for use with other items such as braking systems, etc.
[0058] There is one other unique ability of the spiral pole magnet that not only allows it to produce a sin and cosine signal with respect to rotation but also produce a sin and cosine signet with respect to any axial movement. Using separate sensors affixed in such a way one sensor to responds to the combination of those two movements and the other responds to just one of those movement direction, a processor can be designed to determined either movement separately giving this type of encoder dual purpose.
[0059] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
