Patent Application
20210021177
The present invention relates to an alternator assembly.
Internal combustion engines of the type generally used for powering lawn mowers, pumps, generators, outboard motors, automotive engines and the like can utilize an alternator assembly that generates electrical current. The alternator may have a rotor that can be coupled with a flywheel. The flywheel/rotor are rotatably coupled with a crankshaft. Electrical current may be generated by the rotation of the flywheel/rotor in close proximity to a stator. The electrical current may be used to charge a battery and/or supply electrical energy for various electronics that are connected with the combustion engine.
For example, in some instances, an electronically-controlled fuel injection system which is adapted for use in small-sized engines may not be equipped with a battery, and thus, may utilize power generated from the alternator assembly to power various electrical components. The electrically powered components may include a control unit for controlling a time period over which fuel injection valves are opened in accordance with operating conditions of the engine. However, such systems regularly fail to inject fuel at proper times, thereby producing excessive emissions. Moreover, as the revolutions per minute (RPM) of the crankshaft is increased, the accuracy at which commercially available crankshaft position measuring sensor assemblies degrades dramatically.
In addition, various sensors can be mounted within a stator pole of the stator. However, as more power is pulled from stator windings disposed around the poles of the stator, the flux density available for the sensor will diminish until unreliable switching occurs. Therefore, what is needed is an alternator assembly that is configured to detect a position of the crankshaft that may be used with various small engines, possibly with higher degrees of precision.
In some aspects, an alternator assembly includes a crankshaft that is rotatable about an axis. A rotor is coupled with the crankshaft and is rotatable about the axis in conjunction with the crankshaft. The rotor defines a hub and a cylindrical shell extending outwardly from one end of the hub. A plurality of magnetic segments is disposed circumferentially about an interior surface of the shell. Each of the plurality of magnetic segments includes one or more portions having one of a north or south polarity and at least one of the portions on one of the plurality of magnetic segments configured as a datum section. The datum section has a varied characteristic from the remaining one or more portions of the plurality of magnetic segments. A stator is separated from the rotor by a gap and includes a plurality of stator poles. The plurality of stator poles includes first and second groups of poles each having respective windings on each pole within the first and second group. The first and second groups are separated by a pair of blank poles. A Hall Effect sensor extends between and is supported by the blank poles. The Hall Effect sensor is configured to generate signals based on the magnitude and polarity of magnetic flux generated by each portion of the plurality of magnetic segments.
In some aspects, an alternator assembly includes a rotor rotatably coupled with a crankshaft about a common axis. A first magnetic segment is positioned on the rotor and includes at least a first portion and a datum section separated from the first portion. The first portion has one of a north or south polarity, and the datum section has at least one varied characteristic from the first portion. A stator is separated from the rotor by a gap and includes a plurality of stator poles. The plurality of stator poles include first and second poles each having respective windings thereabout. The first and second stator poles separated by a pair blank stator poles. A Hall Effect sensor extends between and is supported by the blank poles. The Hall Effect sensor is configured to generate signals based on the polarity of magnetic flux generated by at least one of the first portion and the datum section.
In some aspects, a method of manufacturing an alternator assembly includes forming a rotor having a hub and a shell. The method also includes assembling one or more non-magnetized segments to the rotor. The method further includes determining a plurality of magnetization orientation directions of the non-magnetized magnet portions and a varied characteristic for a datum section. In addition, the method includes positioning the rotor within a magnetizing fixture and aligning magnetization directions of the magnet portions with the calculated direction of flux from the magnetizing fixture. The datum section is aligned with a datum portion of the magnetizing fixture. Lastly, the method includes energizing the magnetizing coils using a power source.
The following discussion is presented to enable a person skilled in the art to make and use embodiments of the invention. Various modifications to the illustrated embodiments will be readily apparent to those skilled in the art, and the generic principles herein can be applied to other embodiments and applications without departing from embodiments of the invention. Thus, embodiments of the invention are not intended to be limited to the embodiments shown, but are to be accorded the widest scope consistent with the principles and features disclosed herein. The following detailed description is to be read with reference to the figures, in which like elements in different figures have like reference numerals. The figures, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of embodiments of the invention. Skilled artisans will recognize the examples provided herein have many useful alternatives and fall within the scope of embodiments of the invention.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the attached drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. For example, the use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” “coupled,” and the like are used broadly and encompass both direct and indirect mountings, connections, supports, couplings, and so on. Further, “connected” and “coupled” and the like are not restricted to physical or mechanical connections or couplings.
Referring to
Referring to
The rotor 18 is configured to be fixedly coupled with the crankshaft 20 and is magnetically coupled with the stator 12. The stator 12 includes one or more windings 16 or coils of wire for magnetic flux coupling with the rotor 18 as the rotor 18 rotates with the crankshaft 20. The windings 16 of wire are electrically connected to a regulator 42 for rectifying, smoothing and stabilizing output voltage or current from the stator 12. In other embodiments, other orientations of the stator 12 and rotor 18 are possible. For example, the rotor 18 may rotate within the stator 12, or the rotor 18 may be adjacent to the stator 12.
A fuel pump 50 is arranged above the cylinder 24 for pressurizing fuel to be supplied to the fuel injection valve 40. A cam 48 also may be included for driving the fuel pump 50. The fuel pump 50 is connected to a fuel tank 54 via a conduit 52, and also to the fuel injection valve 40 and a pressure regulator 60 via a conduit 58. Connected to the regulator are the conduit 58 and a conduit 62 connected to the fuel tank 54. A fuel filter 56 is disposed in the fuel tank 54 such that it covers an open end of the conduit 52 which opens into the fuel tank 54. Fuel in the fuel tank 54 is supplied to the fuel pump 50 via the fuel filter 56 and the conduit 52. Pressurized fuel from the fuel pump 50 then is supplied via the conduit 58 to the fuel injection valve 40.
A sensor, such as a Hall Effect sensor 44, is positioned on the stator 12 and is in magnetic communication with the rotor 18. The Hall Effect sensor 44 may also be electrically coupled with the regulator 42. The regulator 42 can further be electrically coupled with a controller 46 that includes an oscillator. As the crankshaft 20 is connected to the rotor 18, the controller 46 is configured to determine a crankshaft position by receiving signals from the Hall Effect sensor 44 and to generate inputs to operate one or more components of the engine 22 based on a computed crankshaft position. Computation is provided by an integrated circuit of the controller 46 which accepts the oscillator's output and determines the crankshaft position by reading the outputs of the Hall Effect sensor 44, decodes these signals, and provides appropriate logic input to operate various components of the engine 22. For example, in response to receiving the crankshaft position, the controller 46 controls the timing for opening the fuel injection valve 40 and the duration over which the fuel injection valve 40 is opened by generating a signal for driving the fuel injection valve 40 to open, thereby allowing fuel to be injected into the intake pipe 34. The injection timing may be based on the piston location, which is fixedly attached to the crankshaft 20. By utilizing a sensor, such as the one described herein, the engine 22 can be provided with a rich fuel and air mixture that is injected into each combustion chamber of the engine 22 thereby improving combustion within each combustion chamber. In addition, by utilizing the positional data provided by the Hall Effect sensor 44, precisely controlled injection of fuel into each chamber can reduce fuel consumption, reduce exhaust emissions, create a simple adjustment of fuel injection timing, improve injection timing to reduce introduction of fuel into cylinder exhaust scavenge gas, which utilizes crankcase air flow controlled by a main throttle valve 38 to provide a source of inducted air for combustion in the combustion chamber, be adapted to various existing engine designs with minimal modifications, or improve run quality and starting of the engine 22.
Referring to
The magnetic segments 70 are fixed to the inside surface of the sidewall 69 of the rotor 18 at substantially equally spaced angular intervals about the rotor 18. Each magnetic segment 70 is magnetized in a circumferential direction with periodic polarities. In the embodiment illustrated in
In some instances, one or more of the magnetic segments 70 may include a datum section 74 that has varied characteristics from the remaining portions 72 of the respective magnetic segment 70 or surrounding magnetic segments 70. The magnetic flux generated by the rotation of the rotor 18 relative the stator 12 generates an altered pulse as measured by the Hall Effect sensor 44 when the datum section 74 passes the Hall Effect sensor 44 compared to each remaining portion 72 of the plurality of magnetic segments 70. For example, the varied characteristic may be that the datum section 74 has a thickness (in any direction, including a circumferential or a radial direction) that is different from that of the remaining portions 72 of the plurality of magnetic segments 70 thereby altering the magnetic characteristics of the datum section 74 relative the remaining portions 72. Additionally or alternatively, the datum section 74 may be formed from a material having different or varied magnetic properties including different elemental compositions. Additionally or alternatively, the datum section 74 may have reduced or increased magnetic flux density (or other detectable property) when compared to one or more of the remaining portions 72. In some embodiments, the polarity of each adjacent portion 72 to the datum section 74 may be of a common polarity. For example, as illustrated in
As the datum section 74 has varied magnetic characteristics, the output current of the alternator assembly 10 may be altered as compared to each portion 72 having a common characteristic as measured by the sensor, which can be a Hall Effect sensor 44. Accordingly, in embodiments using six magnetic segments 70 each having three portions 72, the altering of the characteristics for one portion 72 may minimize this effect by altering the characteristics of just 1/18 or 5.6% of the magnetic portions 72. As more magnetic segments 70 or portions 72 are disposed about the rotor 18, this percentage may be even further decreased leading to less alteration from the original output of the alternator assembly 10 while still producing a detectable datum point. In such instances, a pulse rate may be adjusted to account for and provide accurate data as to the position of the crankshaft 20.
In some embodiments, the magnetic materials used to form the magnetic segments 70 may include magnetic composites, such as neodymium-iron-boron (NdFeB), ceramic, neodymium, samarium-cobalt, alnico, a combination thereof, or any other practicable material. As used herein, the term “magnetic composite” may be defined as nay ferrous powder metal material that can be molded into a component. In some cases, the magnetic composite may be formed into the component using a high-pressure compaction process. In accordance with some embodiments, the magnetic composite may include a ferromagnetic material and a polymer coating. In still other embodiments, the magnetic composite may include an insulating material disposed over a ferromagnetic material or serving as a matrix within which a ferromagnetic material is disposed.
In various embodiments, in order to provide materials having varying magnetic properties, the datum section 74 and the remaining portions 72 may comprise different magnetic materials including different elemental compositions. For example, the datum section 74 may include a ferromagnetic material and a first type of insulating material, while the remaining portions 72 may include the ferromagnetic material and a second type of insulating material. Alternatively, in some embodiments, the datum may include a first type of ferromagnetic material and a first insulating material, and the remaining portions 72 may include a second type of ferromagnetic material and the first insulating material or a second insulating material. In other embodiments, the first and second magnetic materials respectively forming the datum section 74 and the remaining portions 72 may comprise substantially identical elemental compositions; however, the constituents of the compositions may be present at different weight percentages. For example, the first magnetic material may include, by volume, about 6.0% to about 6.5% of the insulating material, while the second magnetic material may include, by volume, about 4.0% to about 5.0% of the insulating material. In other embodiments, percentage ranges may be more or less than the aforementioned ranges. In still other embodiments, the first magnetic material and the second magnetic material may each comprise ferromagnetic materials that are coated with an insulating material, and a thickness of the insulating material may differ for each of the first and second magnetic materials.
With further reference to
With further reference to
Some sensors may function with increased accuracy when isolated. Accordingly, in some embodiments, the Hall Effect sensor 44 is disposed on or extends between a set 88 having one or more blank poles 78, as illustrated in
As illustrated in
The Hall Effect sensor 44 is configured to generate an output signal to the controller 46, which assumes a first state, such as a high state when the magnetic field is greater than a predetermined positive threshold UT. Conversely, the logic output of the Hall Effect generates a second state, such as a low state, if the magnetic field falls below a predetermined negative threshold LT. During rotation of the rotor 18, the amplitude of the magnetic field, which acts on the Hall Effect sensor 44, varies sinusoidally at a frequency dependent on the RPM of the rotor 18 (and consequently, the crankshaft 20), the characteristics and properties of the magnetic segments 70, and the distance the Hall Effect sensor 44 is placed from the rotor 18.
Due to the magnetization process, there is a degree of blurring as the magnetic polarity changes from North to South (and vice versa), so the change waveforms 90, 92 can be more sinusoidal, rather than square. This means the switching point moves to the right (delayed) on the illustrated graph as the thresholds increase in amplitude (i.e., from line 90 to line 92). Additionally, flux density from one magnetic segment 70 can also vary from that of adjacent segments 70, as will the effects of temperature and the width of the gap 84 (
Referring to
Referring to
In various embodiments, the rotor may be integrally formed with a flywheel or later attached thereto. In embodiments in which the flywheel is later attached to the rotor, any practicable attachment assembly may be used for coupling the components with one another. For example, the rotor and the flywheel may be coupled to one another through fasteners, weldment, and so on.
The rotor and flywheel may be made of a variety of materials, which may be generally non-magnetized. In various embodiments, the rotor may be made of any castable metal, such as, for example, iron, aluminum, zinc, magnesium, etc. Other materials may also be used depending on the desired use for the rotor.
At step 102, non-magnetized segments are coupled to the rotor with an adhesive and/or are mechanically secured in place. In one instance, for example, the segments may be coupled using an epoxy, particularly a high temperature-resistant epoxy, such as the one sold under the trademark 9340 HYSOL, by Loctite. The segments may also be coupled to the rotor by welding, staking, through use of a retaining ring, or the like. The non-magnetized permanent magnetic segments are arranged around the rotor shell, as provided herein, to form an annular array. In some embodiments, the permanent magnetic segments of the rotor can form a Halbach array (i.e. obtained by Halbach magnetization) to produce an essentially sinusoidal shaped flux distribution with low harmonic content within an electrical machine. This reduces alternating current (AC) harmonic losses, torque ripple, vibration, and acoustic noise.
At step 104, a magnetizing fixture is utilized for magnetization of multiple non-magnetized permanent magnetic segments of the rotor. The magnetization fixture can include multiple magnetization coils wound around a magnetizing yoke. Generally, the number of magnetizing coils chosen is equal to the number of magnetic segments of the rotor. Accordingly, in some embodiments, the magnetization fixture can include seventeen magnetizing coils and a non-magnetized segment that aligns with the datum section, such as the datum section 74 illustrated in one example in
In operation, the rotor is positioned within a magnetizing fixture of a magnetizer system and magnetization directions of the permanent magnetic segments are aligned with the calculated direction of flux from the magnetizing fixture. The magnetizing coils are then energized by the power source. This power source may be tuned to the magnetizing fixture so that the internal impedance of the source under load approximately matches the impedance of the magnetizing fixture. This allows for the maximum utilization of the energy transfer capability of the power source. Once the permanent magnetic segments are magnetized, the rotor is removed from the magnetizing fixture and is assembled within the stator, such as the stator 12 illustrated in
At step 106, a sensor is operably coupled to a stator and the stator is positioned within the rotor. The sensor is configured to detect a datum section as the datum section of the magnetic segments passes the sensor. In some embodiments, the sensor is configured as a Hall Effect sensor that is supported on two opposing sides by blank stator poles that are free of windings. By placing the Hall Effect sensor between two blank stator poles, the Hall Effect sensor may be further isolated from any proximately disposed windings thereby allowing for a better measurement of the magnetic flux of the various portions of the magnetic segments as well as the datum section. The Hall Effect sensor can be configured to generate signals based on the magnitude and polarity of magnetic flux generated by each portion of the plurality of magnetic segments. Other types of sensors, which may be wound about a single pole, and/or formed from a coil of wire about a pole may not be capable of generating all of the data with similar accuracy as the sensor provided herein. For example, other types of examples may be less effective at detecting a polarity and/or the magnetic flux generated based on the proximity to other stator poles. Moreover, other types of sensors may be less effective at differentiating between the polarities of the various segments than the Hall Effect sensor of the alternator assembly described herein.
The system of the present disclosure provides many advantages over currently available electronic systems. For example, the use of the Hall Effect sensor between two blank poles of the stator may allow for the removal of locating teeth on the rotor. The removal of the teeth reduces the manufacturing cost of the alternator assembly. Moreover, the electronic system provided herein may alter a single portion of a magnetic segment thereby forming a datum section. The datum section may be a minimal disturbance in the flux of the system thereby reducing the effect of adding the datum section to the rotor. The system of the present disclosure can also be manufactured in a compact, relatively inexpensive assembly, of relatively simple design and economical manufacture that can be readily adaptable to a wide range of engine applications, while maintaining durability requiring little maintenance, and having a long useful life.
It will be appreciated by those skilled in the art that while the invention has been described above in connection with particular embodiments and examples, the invention is not necessarily so limited, and that numerous other embodiments, examples, uses, modifications, and departures from the embodiments, examples, and uses are intended to be encompassed by the present disclosure and claims. The entire disclosure of each patent and publication cited herein is incorporated by reference, as if each such patent or publication were individually incorporated by reference herein.
