Magnetic Sensor Device For Ignition Systems

Abstract

A magnetic sensor device in the ignition system for an internal combustion engine includes a reluctor plate of magnetizable material mounted on a shaft of magnetizable material driven rotatably in synchronism with the rotation of the engine drive shaft. The reluctor plate includes a plurality of radial arms preferably equal in number to the cylinders of the engine. A circular cylindrical permanent magnet structure having alternately poled permanent magnet sections, equal in number to twice the cylinders of the engine, is mounted at one end thereof on a collector plate of magnetizable material. The reluctor plate is positioned adjacent the opposite end of the permanent magnet structure with the rotatably driven shaft extending centrally through the collector plate and permanent magnet structure. A coil assembly is mounted within the permanent magnet structure so that rotation of the reluctor plate with respect to the permanent magnet structure produces flux lines through the coil assembly varying between a predetermined positive and negative amplitude, to in turn, produce a corresponding output voltage at the coil assembly. Alteration of the position and/or relative dimensions of the magnet sections of the permanent magnet structure may be used to change "dwell."

Description

BACKGROUND

This invention relates generally to magnetic sensor devices and more particularly to such devices used in conjunction with ignition systems for internal combustion engines.

Many conventional magnetic sensor devices which are mounted in the distributor of a vehicle ignition system as a substitute for mechanical ignition points, include only a permanent magnet mounted on the distributor shaft and rotatable in synchronism with the operation of the engine, and a stationary coil, past which the permanent magnet rotates for passing lines of flux through the coil thereby producing an output voltage proportional to the rate of change of the lines of flux through the coil. With the conventional sensor, the flux varies from a maximum positive value to some fraction of the maximum positive value and thus a relatively small output voltage is produced. This output voltage must thereafter be amplified for use in actuating circuitry in the ignition system which controls the operation of the ignition coil and the spark to the engine spark plugs.

SUMMARY

Accordingly, it is a primary object of the present invention to provide a new and improved magnetic sensor device for use with the ignition system of an internal combustion engine in place of standard ignition points.

It is another object of the present invention to provide a magnetic sensor device of the above described type which produces a greater output voltage than conventionally used magnetic sensor devices of the type described.

It is yet another object of the present invention to provide a new and improved magnetic sensor device of the above described type which is relatively simple in construction, which can be used in the standard distributor assembly of an ignition system with a minimum of modification thereof and which is efficient in operation.

Briefly, a preferred embodiment of a magnetic sensor device according to the invention includes a reluctor plate of magnetizable material mounted on the shaft of the distributor for rotation therewith and having a plurality of vanes or arms extending radially therefrom and spaced at a predetermined number of degrees with respect to each other; preferably, the number of vanes being equal to the number of cylinders in the internal combustion engine with which the sensor is used. A circular cylindrical permanent magnet structure having alternately poled permanent magnet segments, is mounted with one end positioned on a magnetizable collector plate. The opposite end of the cylindrical permanent magnet structure is positioned adjacent the rotatable reluctor plate. The number of magnetic poles on the magnet device is twice the number of vanes on the reluctor plate. A cylindrically shaped coil assembly is placed inside the permanent magnet structure and is also mounted on the collector plate. A non-magnetizable support is provided upon which the collector plate is mounted.

As the engine drive shaft rotates, the distributor shaft rotates in synchronism therewith to in turn rotate the reluctor plate with respect to the permanent magnet structure, passing the alternate magnetic poles spaced about the cylinder, producing magnetic flux paths in a first direction from first magnetic poles through the corresponding reluctor vanes, and the plate through the rotor shaft, collector plate and back to the opposite magnetic poles. Thereafter, upon further rotation of the reluctor plate to position the vanes with respect to the next alternate set of poles, the paths are reversed. The movement between alternate poles sets up lines of flux through the coil which extends circumferentially about the coil assembly to produce an alternating polarity output voltage therefrom. The arrangement provides a change of flux through the coil ranging between a maximum positive value to a maximum negative value thereby producing a relatively large output voltage which is used to operate circuitry in an ignition system which in turn controls the operation of the ignition coil.

The collector plate is rotatable by the standard vacuum advance mechanism in the distributor to provide an ignition advance when required.

In alternative embodiments of the sensor device, the alternately poled magnetic segments of the permanent magnet structure are arranged to provide an unsymmetrical output voltage waveform to change the "dwell" being controlled by the sensor. In a first embodiment, equal dimensioned poles are provided which are oriented in an unsymmetrical fashion, and in another embodiment, unequal dimensioned poles are used.

DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a side, partially sectioned view of a distributor assembly including a magnetic sensor device according to the invention;

FIG. 2 is an exploded, perspective view of the distributor of FIG. 1;

FIGS. 3 and 4 are alternative embodiments of permanent magnet structures used in the magnetic sensor device according to the invention; and

Fig. 5 is a diagrammatical representation of a typical electronic ignition system in which the magnetic sensor device according to the invention may be used.

DETAILED DESCRIPTION

Referring now to the drawings wherein like numerals have been employed throughout the various views to designate similar components, there is shown in FIGS. 1 and 2 a standard distributor 10 as would be found in an automobile or the like vehicle, which has been modified to include a preferred embodiment of a magnetic sensor device 12 (FIG. 2) according to the invention.

The distributor 10 includes the usual base portion 14 on which the magnetic sensor device 12, which replaces conventional "points," is mounted and a distributor cap 16 including female connector portions 18 into which male connector portions attached to spark plug wires of an internal combustion engine, are received. A central female connector portion 20 is also provided for receiving the male connector portion provided at the end of the lead from the ignition coil 22 (See FIG. 5).

Looking at FIGS. 1 and 2 in particular, a conventional rotor assembly 24 is mounted for rotation on the rotatable shaft 26 of the distributor,, driven in synchronism with the engine of the vehicle. The rotor assembly includes a standard rotor contactor 27 which distributes, between the various spark plugs of the ignition system, current from the ignition coil to fire the spark plugs in corresponding engine cylinders. A rotatable electrical contact is made with the ignition coil 22 at bearing ball 25.

The magnetic sensor device 12 according to the invention, is mounted beneath the rotor assembly 24 and includes a reluctor plate 28, seen best in FIG. 2, fabricated of a magnetizable material, such as iron or the like substance. The reluctor plate is mounted at the center opening 30 thereof on the rotatable distributor shaft 26, which is also fabricated of a magnetizable material. The reluctor plate may be press fitted on the shaft end 32 beneath rotor contactor 27. The reluctor plate includes a plurality of vanes or arms 34 extending radially outwardly therefrom, in the particular embodiment shown, the vanes are fan-shaped. The shaping of the vanes and the effect on voltage output of the sensor device will be described hereinafter. The number of vanes provided is directly proportional to the number of cylinders in the internal combustion engine with which the ignition system is to be used. Herein, as shown, the magnetic sensor device is for use with a four cylinder engine.

Directly beneath the reluctor plate, spaced therefrom slightly by a small air gap d (See FIG. 1) is a cylindrically shaped permanent magnet structure including a plurality of arcuate permanent magnet sections or segments, such as, 38, separated by non-magnetic insulators 40. The number of permanent magnet segments in the magnet structure is equal to twice the number of vanes on the reluctor plate.

Each of the magnet segments has a north and south magnetic pole at opposite ends thereof with alternate ones of the segments having opposite poles positioned adjacent the reluctor plate (See FIG. 2).

Mounted concentrically with the cylindrical permanent magnet structure 36 is a wound coil assembly 42. The coil assembly includes a plastic or the like insulative bobbin or spool 44 about which a coil of wire 46 is wound circumferentially.

Both the permanent magnet structure 36 and coil assembly 42 are mounted on a circular collector plate 48 of magnetizable material, such as, for example, iron. The collector plate, as will be described in greater detail hereinafter, completes the magnetic path about coil assembly 46 to produce a current flow therein for proper activation of the ignition coil of the ignition system. The collector plate includes a central hub 50 which is received in the central opening 52 of the bobbin 44 of the coil assembly to retain the relative positions of the collector plate and coil assembly.

A lower base or mounting plate 54 of a non-magnetizable material, such as, for example, brass, is provided to support the magnetic sensor device elements described heretofore. The brass plate is circular,, having a diameter similar to that of the collector plate, and is press fitted onto a bushing 56 also of magnetizable material. The bushing 56 is received in a central opening 58 in the neck 15 of base portion 14 of the distributor housing. The central rotatable distributor shaft 26 passes through the bushing as well.

Attached also to the base portion 14 of the distributor housing is a vacuum advance assembly, designated generally by the numeral 62, having the standard diaphragm mechanism, etc., to which there is connected a rod 64. The vacuum assembly likewise includes an engine vacuum hose connection 63. The vacuum advance assembly is mounted on a platform portion 66 included in the base portion 14 of the distributor, by screws, such as, 68, extending through a mounting plate 70 of the assembly and into threaded apertures,, such as, 72 in the base portion. The end 74 of the vacuum advance assembly rod 64 is received in an aperture 76 in a tab 78 extending downwardly from the collector plate through a slotted opening 80 in the brass mounting plate 54. Ignition advance provided by the vacuum assembly 62 is produced by rotation of the permanent magnet structure with respect to reluctor plate 28. Other types of advance mechanisms, such as, for example, centrifugal weight and the like variety may be employed as well with the magnetic sensor device of the invention.

The collector plate 48 and permanent magnet structure 36 are fastened together by screws such as 82 received in apertures such as 84 in plate 48 and in threaded apertures such as 86 in the ends of certain ones of the magnets of the permanent magnet structure. The screws are countersunk to permit smooth rotation of the collector plate with respect to the brass mounting plate 54. The wire leads 88 from coil 46 pass through an aperture 90 in the collector plate, a slot 92 in the brass mounting plate and out of the base portion 14 of the distributor housing through a grommet 92 fitted into an aperture 94 in the lower wall 96 of the base portion. The distributor cap 16 is snapped on to the distributor base portion 16 in the conventional manner with the upper edge 98 of the base portion being received in the interior rim 100 of the cap. A pair of snap-on retainer clips 102, 104, holds the cap and base portions together.

In operation, the central shaft 26 of the distributor is driven rotatably in synchronism with the engine drive shaft (not shown). Rotation of the distributor shaft rotates both the reluctor plate 28 and the rotor assembly 24.

The rotation of the reluctor plate arms 34 past the oppositely poled arcuate magnet sections, sets up alternately poled flux lines through the coil 46.

As the reluctor rotates, it passes both north and south poles of the permanent magnet structure. Upon being adjacent the north magnetic poles of the permanent magnet structure, magnetic paths are set up from the north poles through respective reluctor plate arms, through the central drive shaft, through the collector plate and to the opposite poles of the magnetic sections. The path is reversed as the reluctor plate moves to alternate adjacent poles. A typical waveform of the flux through the coil is a sine wave. It has been found that the vane angle a; i.e., the angular dimension of the sector of the circular plate which comprises the vane extending outwardly from the central portion of the reluctor plate (See FIG. 2), can alter the waveform. In the particular embodiment shown, the waveform remains sinusoidal with vane angles of approximately 25.degree.-45.degree.. However, when a vane angle of less than 25.degree. is attempted, the sinusoid is noticeably distorted. The voltage output of the device, it has been found, is increased when using vanes having smaller vane angles. This is due, it would appear, to the considerable decrease in flux leakage between the vanes and adjacent poles. The output voltage waveform is established by the rate of change of the flux lines and is thus the time differential of the waveform of the flux lines set up by the rotating reluctor plate.

Dimensional changes of the various components of the device will affect the output voltage and waveform thereof provided. Selection of dimensions for the reluctor plate vanes, thickness, size of and strength of the permanent magnet sections, etc., of the device will be easily made, however, by one skilled in the art in accordance with the results desired from the magnetic sensor. In the embodiments of the permanent magnet structure of the magnetic sensor according to the invention, the magnetic strength of the material used for the various magnet segments is similar.

As seen in FIG. 5, the output voltage from the coil assembly is provided at leads 88. The leads are connected to an electronic ignition circuit 106 of a conventional design, and, just as in the case of ignition points or a conventional magnetic sensor device, the output "pulses" are used to actuate circuitry in the ignition circuit which "make" and "break" connections to the ignition coil 22 via leads 108 for providing an output voltage from the ignition coil at lead 110 to the distributor rotor assembly. The current provided is distributed by the rotor assembly in a conventional manner over leads such as 112 to the various spark plugs such as, 114 of the internal combustion engine.

As explained heretofore, a change in engine speed operates the advance mechanism, which in the case of the embodiment shown, is of the vacuum type. The operation of the advance mechanism rotates the collector plate 48 and permanent magnet structure with respect to the reluctor plate, to in turn advance the spark to the spark plugs of the engine.

To change the "dwell" i.e., in the case of the magnetic sensor of the invention, the relative time duration of the positive and negative portions of the output voltage waveform with respect to a zero crossing, the permanent magnet structure of the magnetic sensor device is modified. Two ways to accomplish the latter are illustrated in FIGS. 3 and 4. In the case of the permanent magnet structure of FIG. 3, dimensionally equal arcuate magnet sections 38a are used. North and south pole pairs thereof are spaced from the other pairs by a fixed arcuate non-magnetic segment 116. In the case of the permanent magnet structure in FIG. 4, the dimensions of predetermined ones of the arcuate segments is increased, (see segments 118 and 38b). A similar result is achieved with this arrangement as in the case of the permanent magnet structure embodiment of FIG. 3.

With the magnetic sensor device according to the invention the lines of flux passing through the sensor coil varies from a maximum positive value to a maximum negative value. Since the output voltage of the coil is established by the rate of change of the lines of flux, the magnetic sensor of the invention produces two to four times greater voltage output than with conventional magnetic sensors of the type described heretofore.

While a particular embodiment of the invention has been shown and described, it should be understood that the invention is not limited thereto since many modifications may be made. It is therefore contemplated to cover by the present application any and all such modifications as fall within the true spirit and scope of the appended claims.

Claims

I claim:

1. A magnetic sensor device in the ignition system for an internal combustion engine including in combination: rotatable shaft means of magnetizable material driven in synchronism with the rotation of the engine drive shaft, a first plate of magnetizable material, said plate having a plurality of radially extending arms, a permanent magnet structure having a cylindrical shape and comprising a plurality of permanent magnet sections, said magnet sections having north and south magnetic poles on opposite ends thereof, with alternate sections having opposite poles located adjacent each other, the number of said magnet sections being equal to twice the number of cylinders of the internal combustion engine and the number of said arms of said plate equaling one-half the number of said magnetic sections, a first end of said permanent magnet structure being mounted adjacent said first plate, a second plate of magnetizable material mounted in spaced relation with respect to said first plate adjacent the oppoosite end of said permanent magnet structure, and sensor coil assembly means mounted concentrically with respect to said permanent magnet structure within the confines thereof, said rotatable shaft means extending through the centers of said second plate, coil assembly and permanent magnet structure, said first plate being coupled to and rotatable with said shaft means with respect to said permanent magnet structure in response to the operation of said engine for providing magnetic flux lines through said coil assembly varying between a predetermined positive amplitude and a predetermined negative amplitude, whereby an alternately poled output voltage is provided at said coil assembly for regulating the operation of said ignition system in accordance with the speed of said engine.

2. A magnetic sensor device as claimed in claim 1 wherein each of said radially extending arms of said first plate are fan shaped and each said fan shaped arm comprises a predetermined sector of a circle having a predetermined radius.

3. A magnetic sensor device as claimed in claim 1 wherein the arcuate dimension of each said fan shaped sector falls in the range of 25.degree.-45.degree..

4. A magnetic sensor device as claimed in claim 1 wherein the dimensions of said magnet sections of said permanent magnet structure are equal and wherein pairs thereof are spaced predeterminedly from other pairs thereof about said structure.

5. A magnetic sensor device as claimed in claim 1 wherein the dimensions of said magnet sections are unequal, predetermined ones of predetermined pairs thereof being sufficiently greater in arcuate dimension than the remaining pairs of said magnet sections to effect a predetermined change in dwell.

6. In the distributor assembly of an ignition system for an internal combustion engine having an output drive shaft, including a distributor housing and a central shaft member of magnetizable material driven rotatably in synchronism with the rotation of the engine drive shaft, a magnetic sensor device including in combination; a reluctor plate of magnetizable material mounted on the free end of said rotatably drive shaft, said reluctor plate having a plurality of radially, outwardly extending arms equal in number to the cylinders of said internal combustion engine, a permanent magnet structure having a cylindrical shape and comprising a plurality of arcuate permanent magnet segments placed thereabout, said magnet segments being separated by non-magnetic separators and having north and south magnetic poles on opposite ends thereof, with alternate sections having opposite poles located adjacent each other, the number of said magnet segments being equal to twice the number of arms of said reluctor plate, a first end of said permanent magnet structure being mounted adjacent said reluctor plate, a generally circular collector plate of magnetizable material mounted in spaced relation with respect to said reluctor plate within the housing of said distributor assembly, adjacent the opposite end of said permanent magnet structure, and sensor coil means mounted concentrically with respect to said permanent magnet structure within the confines thereof, the rotatable drive shaft of said distributor extending through the centers of said collector plate, coil means and permanent magnet structure, said reluctor plate being rotated on said drive shaft with respect to said first end of said permanent magnet structure in response to the operation of said engine for providing magnetic flux lines through said coil varying between a predetermined positive amplitude and predetermined negative amplitude, whereby an alternately poled output voltage is produced at said coil.

7. A distributor assembly as claimed in claim 6 further including a rotor assembly for distributing current between the various sprak plugs of said engine, said rotor assembly being mounted on said rotatable drive shaft for rotation with said reluctor plate.

8. A distributor assembly as claimed in claim 6 further including engine advance means coupled to said collector plate and permanent magnet structure for changing the position thereof with respect to a predetermined position in response to a predetermined change in engine speed, the latter being rotated within the housing of said distributor assembly about said rotatable shaft.