U.S. patent number 3,855,983 [Application Number 05/345,152] was granted by the patent office on 1974-12-24 for magnetic sensor device for ignition systems.
This patent grant is currently assigned to Motorola, Inc.. Invention is credited to Robert J. Valek.
United States Patent |
3,855,983 |
Valek |
December 24, 1974 |
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."
Inventors: |
Valek; Robert J. (Wheaton,
IL) |
Assignee: |
Motorola, Inc. (Franklin Park,
IL)
|
Family
ID: |
23353761 |
Appl.
No.: |
05/345,152 |
Filed: |
March 26, 1973 |
Current U.S.
Class: |
123/146.5A;
123/146.5R; 123/617 |
Current CPC
Class: |
F02P
7/0675 (20130101) |
Current International
Class: |
F02P
7/00 (20060101); F02P 7/067 (20060101); F02p
007/06 () |
Field of
Search: |
;123/146.5,146.5A,148R,148AC,148E,146.5R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Antonakas; Manuel A.
Assistant Examiner: Argenbright; Tony
Attorney, Agent or Firm: Lisa; Donald J. Rauner; Vincent
J.
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.
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.
* * * * *