Magnetic sensor for distributorless ignition system and position sensing

A magnetic sensor for a distributorless ignition system is useable in an internal combustion engine. A Hall-effect device is spaced intermediate a pair of opposing permanent magnets for concurrently generating dual magnetic flux fields within respective air gap regions formed between each of the magnets and the device. Alternatively a magnet is placed between two Hall-effect devices to define the regions. A toothed disk rotatably connected to the crankshaft of the engine causes different teeth to shunt the fields in each of the regions in a predetermined sequence for generating pulses at the device output indicative of the firing order of the engine. Alternatively, a disk having outer and inner notched rims is used to shunt the fields in each of the regions. Further, an elongated channel shaped member has sides movable in the regions for detecting relative linear motion between two parts.

BACKGROUND OF THE INVENTION 
This invention relates generally to a distributorless and contactless 
ignition system useable in an internal combustion engine and particularly 
to a magnetic sensor employing a Hall-effect device operatively connected 
to an engine crankshaft to enable sensing the rotative position thereof. 
Ignition systems for modern internal combustion engines often employ a 
contactless distributor circuit which produces a predetermined series of 
output pulses suitable for firing the spark plugs of the engine in a 
predetermined firing order sequence. In such circuits passive sensors such 
as variable reluctance magnetic elements are positioned within the 
distributor to threshhold detect or zero crossing detect a waveform 
generated by a passing lobe, notch or tooth formed of appropriate material 
and which is connected to the rotatable distributor shaft. Distributorless 
ignition systems are also known in the prior art wherein a large plurality 
of magnetic responsive elements produce unidirectional pulses from 
magnetic fields. Typically, two or more magnetic sensor elements are 
utilized in applications wherein a first sensor provides a reference pulse 
and a second sensor generates a large plurality of other related timing 
pulses. Alternatively, each of two pickups or transmitters used in 
conjunction with a disc having a large plurality of teeth or gaps are 
applied, respectively, to differing encoding elements utilizing four stage 
binary counting to produce the requisite firing order signals. Such 
ignition systems, when utilizing the distributor concept, incur the 
inherent additional weight, radio frequency interference, mechanical 
complexities, and propensity for misadjustment and tampering involved with 
the incorporation of a distributor in the ignition system. In 
distributorless systems, in addition to the above reasons, the plural 
magnetic sensors increase system costs and complexity. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a sensing 
device responsive to the angular position of a rotating engine shaft such 
as a crankshaft or camshaft and which generates a sequence of output 
pulses indicative of the engine firing order without the use of a 
distributor. Another object is to provide a contactless ignition system. 
Yet another object of the present invention is to provide a magnetic 
sensor for a distributorless ignition system which utilizes a single 
Hall-effect device concurrently responsive to dual opposing magnetic 
fields. Another object is to provide two Hall-effect sensors spaced on 
either side of a magnet and to provide magnetic field shunting members 
which pass through the spaces between the magnet and the sensors as the 
shaft is rotating to provide a two digit binary output to indicate 
predetermined shaft rotational positions. Still another object is to 
provide a magnetic sensor for use in a distributorless ignition system 
which resists tampering and minimizes radio frequency interference (RFI). 
A further object is to provide a sensor for detecting linear position and 
movement between reciprocating members. 
Briefly, these and other objects are accomplished in one embodiment by a 
single Hall-effect device which is spaced equidistantly and intermediately 
of a pair of opposing permanent magnets for concurrently sensing 
variations in dual magnetic flux fields generated within respective 
radially spaced air gap regions formed between each of the magnets and the 
device. A toothed disk having radially spaced teeth is connected to a 
rotatable shaft of the engine and causes teeth of differing radial 
position to rotate through each of the air gap regions in a predetermined 
sequence for generating pulses at the device output indicative of the 
firing order sequence of the engine cylinders. In a second embodiment, a 
magnet is placed between and radially spaced from two Hall-effect sensors 
and a disk having an outer rim and a radially spaced inner rim, with 
notches formed in each rim is rotated by the shaft, with a rim passing 
between the magnet and the sensors, periodically shunting the magnetic 
field between the magnet and the sensors. The output pulses are 
transmitted to a microprocessor which advances or delays the timing of the 
pulses in accordance with engine speed and which provides output pulses to 
coil driving circuits and spark coils for firing of the respective 
cylinders. In another embodiment, a linear channel shaped member has 
notched sides movable, respectively, between a magnet and Hall-effect 
sensor combination, for detecting motion and position relative the 
channel. 
For a better understanding of these and other aspects of the invention, 
references may be made to the following detailed description taken in 
conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIG. 1 there is illustrated a magnetic sensor 10 connected to a spark 
generating circuit 12. Within the magnetic sensor 10 there is positioned a 
Hall-effect device 14 spaced equidistant between a pair of opposing 
permanent magnets 16a, 16b. The Hall-effect device 14 and the magnets 16a, 
16b are all commonly positioned in a linear arrangement on one surface of 
a support member 18. The magnets 16a, 16b are further supported on the 
member 18 by means of "C" shaped support element 20 which extends in back 
of and through the support member 18 so as to provide extension elements 
adjacent each of the magnets 16a, 16b to provide support and bonding 
thereto. The assembly comprising the Hall-effect device 14, magnets 16a, 
16b and support element 20, as positioned on the support member 18, is 
stationary and connected to an appropriate place on the engine block 22. A 
moveable shunt member 24 shown as a rotatable toothed disk is connected to 
a rotatable shaft 26 such as a crankshaft or a camshaft. Positioned on the 
movable member 24 are a pair of teeth 28a, 28b, formed of ferrous 
material. The tooth 28a is positioned on the member 24 so that as the 
member 24 rotates in accordance with the movement of the shaft 26, tooth 
28a is caused to pass in the region between magnet 16a and the Hall-effect 
device 14. Similarly, tooth 28b is positioned on the movable member 24 so 
as to pass in the region between the magnet 16b and the other side of the 
Hall-effect device 14. 
The device 14 provides a pair of output lines to the inputs of a 
microprocessor 30 contained within the spark generating circuit 12. The 
microprocessor 30 provides a pair of output lines, one of which is 
connected to the input of a coil driver 32 which provides an output to a 
spark coil 36 whose outputs are adapted to be connected to the spark plugs 
of cylinders number 1 and 4 of a four cylinder internal combustion engine 
(not shown). Similarly, the other output of the microprocessor 30 is 
connected to the input of a coil driver 34 whose output is connected to a 
spark coil 38 which provides output signals to the spark plugs of 
cylinders number 3 and 2 of the engine. 
Referring now to FIG. 2 there is shown a front elevation view of the 
movable member 24 taken along the lines 2--2 noted in FIG. 1. As now can 
be more clearly seen the member 24 is in the form of a ferrous disk having 
the teeth 28a, 28b positioned thereon at distinctively different radii so 
as to insure passage of the tooth 28a intermediate device 14 and magnet 
16a and passage of the tooth 28b intermediate device 14 and magnet 16b. 
Referring now to FIG. 3, there is shown an elevation view of a portion of 
the support member 18 and the associated Hall-effect device 14, the 
magnets 16a, 16b, and the extended portions of the support element 20. 
More clearly shown are the polarizations of the magnets 16a, 16b, and by 
way of example, the magnets are shown with the south poles thereof facing 
opposite parallel sufaces of the device 14 in opposing fashion. 
Alternatively, the magnets 16a and 16b may also be positioned so that the 
north poles thereof face the opposing surfaces of the device 14. 
FIG. 4 illustrates a schematic block diagram of the circuitry associated 
with the Hall-effect device 14. Such circuitry, though shown as discrete 
elements within the diagram, most preferrably are combined in the 
preferred embodiment in a single monolithic integrated circuit chip 
inclusive of all the elements shown within the dotted lines of the figure. 
As an integrated embodiment the Hall-effect device 14 is essentially a 
four lead device having an input voltage V.sub.1 connection, a ground 
connection, and two output signal leads for carrying output signals which 
will be described in further detail hereinafter. The device 14 includes a 
Hall-effect element 40 having a pair of output lines connected to the 
differential inputs of a first differential amplifier 42. The output of 
amplifier 42 is connected to the input of a first Schmitt trigger 44 which 
drives the base of a first output transistor 46 whose collector forms one 
of the output signal leads of the device 14. Similarly, and connected in 
common with the output leads of the Hall-effect element 40 but in reverse 
polarity, are the inputs of a second differential amplifier 48 whose 
output is connected to a second Schmitt trigger 50 which drives the base 
of second output transistor 52 whose collector forms the second output 
signal lead of the device 14. 
FIG. 5 is a timing diagram of waveforms of output signals A and B produced, 
respectively, at the collector output leads of output transistors 46, 52 
within the device 14. The timing diagram is representative of the firing 
order sequence required in a four cylinder internal combustion engine 
having a waste spark ignition system. 
FIG. 6 is a front elevation view of an alternate form of the movable member 
24 shown in FIGS. 1 and 2. In contrast to the toothed disk form, the 
movable member shown in FIG. 6 is an assembly of interconnected circular 
ferrous disks 56 and 58, each having substantially orthogonal ferrous 
sidewalls or rims 57, 59, respectively, formed around the periphery 
thereof in coaxial relationship with the other. The coaxially aligned 
sidewalls of the disks 56, 58 each have a notch formed therein with a 
notch 60 formed in the sidewall 57 of disk 56 and a notch 62 formed in the 
sidewall 59 of disk 58. 
Referring now to FIG. 7 there is shown a side elevational view taken along 
the line 7--7 shown in FIG. 6. More clearly shown is a portion of the 
sidewall 57 of the disk 56 with associated notch 60 formed therein. Since, 
in this example, the notches are not aligned with one another, a portion 
of the sidewall 59 of disk 58 is viewed through the notch 60. 
Operation of the magnetic sensor as used within the distributorless 
ignition system will now be discussed with reference to FIGS. 1 through 5. 
Referring again to FIG. 1, it will be seen that as the movable member 24 
rotates with the shaft 26, it causes the teeth 28a and 28b to pass, 
respectively, and at predetermined times in the regions between the magnet 
16a and the Hall-effect device 14 and between the magnet 16b and the 
device 14. When either the inner tooth 28a or outer tooth 28b of the 
movable member 24 passes between the respective magnet and the Hall-effect 
device, the field generated by that magnet is shunted and the opposing 
magnetic field overbalances the Hall-effect device and causes a pulse 
output to be generated on one of the respective output lines as noted in 
waveforms A and B of FIG. 5. The Hall-effect element 40 noted in FIG. 4, 
when shunted from the effects of a corresponding magnet 16a, 16b by one or 
the other of the ferrous teeth 28a, 28b, provides a differential output 
signal to the inputs of the differential amplifiers 42, 48. Amplifier 42, 
in the preferred embodiment, is connected to the element 40 such as to 
process positive flux changes experienced by the Hall-effect element 40 
and which changes are converted by the amplifier 42 into a positive 
polarity output signal which is transmitted to the input of the Schmitt 
trigger 44 for pulse shaping and squaring purposes. The shaped positive 
output pulse from trigger 44 is connected to one input of the 
microprocessor 30 by means of the output transistor 46. Similarly, 
differential amplifier 48 responds to negative flux changes experienced by 
the element 40 and converts the negative flux output signal from the 
element into a positive going output pulse which is shaped by Schmitt 
trigger 50 and transmitted to another input of the microprocessor 30 by 
means of driving transistor 52. In this manner, a single Hall-effect 
element concurrently responds to the passage of each of the ferrous teeth 
28a, 28b positioned in the movable member 24 and differentiates between 
the teeth as exhibited by either a positive or negative flux change in the 
field generated by the magnets and varied by the passage of the teeth 
through such fields. 
The width of the respective pulses generated at the outputs A and B of the 
Hall-effect device 14 is predetermined by adjusting the respective lengths 
of the teeth, thus controlling the period of time over which the 
respective flux field is shunted. The main criteria for determination of 
pulse width is related to the desired dwell time in the ignition system 
including time required for retard or advance of the firing signal. In the 
preferred embodiment, a pulse width of approximately 40.degree. arc angle 
from the center of the movable member 24 was found to be most effective. 
In the preferred embodiment, the magnetic sensor and associated circuitry 
are configured for operation with the crankshaft of a four cylinder 
internal combustion engine. In this case and since there are only two 
pairs of cylinders, only two pulses are needed to be generated 180.degree. 
out of phase with respect to each other. Accordingly, the pulse generation 
is implemented by affixing two teeth 28a, 28b on the surface of the 
movable member 24 in diametrically opposite positions 180.degree. out of 
shaft angle position with each other. As the crankshaft rotates, the teeth 
28a and 28b will cause respective signals to be generated by the 
Hall-effect element 40 in a 180.degree. timing relationship and which 
signals are later processed and shaped by the differential amplifiers 42, 
48 and Schmitt triggers 44, 50 to provide output pulses from driving 
transistors 46, 52 to produce output waveform signals as shown in FIG. 5. 
Although shown in the preferred embodiment as a circular disk, it will be 
obvious to those skilled in the art that the member 24 may be fashioned in 
any convenient form such as a simple flat extension designed to support 
the teeth 28a, 28b and to cause the teeth to pass through the respective 
magnetic field regions. 
FIG. 5 illustrates typical waveform output signals A, B formed at the 
collector outputs of transistors 46, 52. The waveforms each illustrate a 
series of pulses wherein each waveform generates a pulse series having a 
180.degree. shaft angle rotation difference with respect to the other. The 
negative-going edge of the pulses indicates the turn-on time for the 
associated spark coil and the positive-going edge indicates the firing 
time of the cylinder. In waveform A and at 0.degree. shaft angle rotation, 
the negative-going pulse edge indicates the energization of spark coil 36. 
At the next succeeding positive edge of the pulse (approximately 
40.degree. shaft rotation later), spark coil 36 simultaneously provides 
firing signals to cylinders 1 and 4. Similarly, and noting waveform B, 
pulses are generated 180.degree. shaft angle rotation later and spark coil 
38 simultaneously turns on and fires cylinders 3 and 2. 
The preferred embodiment illustrated in FIG. 1 illustrates the concurrent 
generation and transmission of firing signals to cylinder numbers 1 and 4 
or to cylinder numbers 3 and 2. The high voltage ignition output pulse 
from each of the spark coils 36, 38 is supplied to a preselected and 
respective pair of cylinders such that each cylinder of a given pair 
simultaneously receives high voltage ignition pulses and each different 
pair of cylinders alternately receives high voltage ignition pulses at 
180.degree. intervals. This type of ignition circuitry is generally known 
as a waste spark ignition system. Ignition timing and selection of 
cylinder pairs are such that for a given pair of cylinders, an ignition 
pulse is supplied when, for example, one cylinder of a given pair is at 
the end of its compression stroke while the other cylinder of the pair is 
at the end of its exhaust stroke. Thus, in a four cylinder engine whose 
firing order sequence is 1-3-4-2, a first pair of cylinders 1 and 4 are 
simultaneously supplied with the high voltage ignition pulse (firing 1) 
and at 180.degree. angle of shaft rotation later, a second pair of 
cylinders 3 and 2 is so supplied (firing 3). The timing and high voltage 
pulse generation process continues firing in sequence the remaining 
cylinders 4 and 2. 
FIGS. 6 and 7 note an alternate embodiment of the toothed disk shown in 
FIGS. 1 and 2. The same sensing effects experienced by the Hall-effect 
element 40 when working in conjunction with a toothed movable shunt member 
24 can be duplicated by the notched disks 56, 58 shown in FIGS. 6 and 7. 
Disk 56 has circular rim 57 with arcuate notch 60 and disk 58 has coaxial 
circular rim 59 with arcuate notch 62, displaced 180.degree. from notch 
60. In this implementation, however, the circuitry of FIG. 4 will operate 
so as to note the presence of the non-shunting notches 60, 62 when the 
respective moveable members are in a rotational position so that the 
notches are in their respective air gap regions, thereby creating an 
imbalance in the opposing magnetic flux fields. 
Referring to FIGS. 8 and 9, in a further embodiment, two Hall-effect 
sensors and one magnet are utilized. Hall-effect sensors 70, 72 are 
radially spaced on the aforementioned non-magnetic bracket 18 and 
supported thereagainst by the aforementioned C-shaped non-magnetic support 
element 20, which is mounted in the manner and as shown in FIG. 1. 
Permanent magnet 74 is supported on bracket 18, as by cementing or other 
suitable means, between sensors 70, 72, with radial regions or gaps 76, 78 
being between magnet 74 and sensors 70, 72 respectively. A magnetic field 
having flux paths 80a, 80b shown diagrammatically, permeates regions 76, 
78 and sensors 70, 72. 
Referring to FIG. 9, sensors 70, 72 each have leads connected to a voltage 
supply terminal 86 and to ground 88. Sensor 70 has output leads 90, 92 and 
sensor 72 has output leads 94, 96. Sensor devices having three leads for 
voltage supply, ground, and output may be utilized, such as manufactured 
by Sprague Electric Company, part no. UGS-3020T. The output across leads 
90, 92 corresponds to the output on lead A for the embodiment of FIGS. 1-5 
and the output across 94, 96 corresponds to the output on lead B of that 
embodiment. Leads 90, 92, 94, and 96 may be connected directly to 
processing circuitry 12, after suitable shaping, as by Schmitt trigger 
circuits, which can be performed by integrated circuitry packaged with the 
Hall-effect sensor 70, 72, or to the circuitry disclosed in copending 
application incorporated herein by reference entitled "Rotational Position 
and Velocity Sensing Apparatus" Ser. No. 06/223,779, filed Jan. 9, 1981 by 
Gary R. Nichols and John J. Kozlowski, Jr. now U.S. Pat. No. 4,373,486. As 
will become apparent, when the field in space 76 is shunted, the output of 
sensor 70 will change and when the field is space 78 is shunted, the 
output of sensor 72 will change. The embodiment of FIGS. 8, 9 may be used 
with disk 24 or disks 56, 58, and will be next described in connection 
with disk 24. 
Referring to FIGS. 2, 5 and 9, tooth 28a is radially positioned from the 
axis 27 of shaft 26 a distance equal to the radial location of gap 78 and 
passes freely through gap 78 upon rotation of shaft 26. Tooth 28b is 
radially positioned from axis 27 a distance equal to the radial location 
of gap 76 and similarly passes through gap 76 upon rotation of shaft 26. 
As tooth 28a passes through gap 78, the output of sensor 72 is changed 
from a high level, or binary "1", to a low level, or binary "0", as shown 
by waveform A in FIG. 5. As tooth 28b passes through gap 76, the output of 
sensor 70 changes from a high level or binary "1", to a low level, or 
binary "0", as shown in waveform B of FIG. 5. Thus, every 360.degree. of 
shaft 26 rotation, a "0" pulse is provided to processor 12 on lead A and, 
at a 180.degree. phase difference, a "0" pulse is provided to processor 12 
on lead B every 360.degree. rotation of shaft 26. Differential amplifiers 
46, 48 in this embodiment are unnecessary to provide the desired pulse 
direction. 
Disks 56, 58 may also be used with the embodiment of FIGS. 8 and 9 and 
operate in a similar manner with the exception that the sensors 70, 72 
have their outputs shunted when rims 57, 59 are in gaps 76, 78, 
respectively, and therefore would have a low, or binary "0", output. When 
notches 60, 62 are in gaps 76, 78 the outputs of sensors 70, 72 will be 
high, or binary "1". The waveforms of FIG. 5 may be obtained by inverting 
the sensor 70, 72 outputs in any manner known to the art. For example, in 
the aforementioned Sprague sensor monolithic circuitry is available in the 
sensor package which inverts the outputs. Further, the waveforms of FIG. 5 
may be inverted to meet the requirements of a particular microprocessor 30 
to provide the desired coil drives. 
By modifying the notch placements in the rims 57, 59 four two digit binary 
outputs 0,0; 0,1; 1,0; and 1,1 may be obtained. In FIGS. 10-13, notches 
60, 62 are positioned in rims 57, 59, respectively, to achieve the 
indicated and desired outputs. In FIG. 10 the field between sensors 70, 72 
and magnet 74 is shunted by rims 57, 59, respectively, and flux paths 80a, 
80b are shunted and pass through rims 57, 59, and disks 56, 58, 
respectively, for a first rotative position of the shaft. Thus no flux 
passes through sensors 70, 72 and their respective outputs are low, or a 
binary "0". As previously mentioned, the high outputs under the no-flux 
condition in the sensors may be achieved in the FIGS. 10-13 examples by 
inverting the sensor outputs, or by conventional circuit methods known to 
the art. 
In FIG. 11, for a second rotative position of the shaft 26, the field 
between magnet 74 and sensor 70 is shunted by rim 57 while the field 
between magnet 74 and sensor 72 is not shunted, since notch 62 is 
positioned therebetween. The binary output of sensors 70, 72 for this 
second rotative position of the shaft is "0,1". 
In FIG. 12, a third rotative position of the shaft positions notch 60 
between magnet 74 and sensor 70 allowing paths 80a and 80b to pass through 
sensor 70, while rim 59 is positioned between magnet 74 and sensor 72 and 
shunts paths 80a and 80b from sensor 72 to provide a binary output of 
"1,0". 
In FIG. 13, a fourth rotative position of the shaft positions notches 60, 
62 at magnet 74 to provide a magnetic field through both sensors 70, 72 
and provide a binary output of "1,1". 
Thus, by proper spacing of the notches 60, 62 in rims 57, 59 respectively, 
binary outputs of 1,1; 0,1; 1,0 and 0,0 are achieved in a relatively 
simple and durable construction to provide indications of corresponding 
shaft rotational positions. These outputs may be used to control engine 
functions, such as those disclosed and described in the aforementioned 
Nichols and Kozlowski, Jr. copending application. 
It should be noted that although the preferred embodiment has been 
illustrated with reference to a four cylinder internal combustion engine 
the magnetic sensor of the present invention may also be implemented for 
use with other combinations of cylinders. For example, in a six cylinder 
engine, implementation would incorporate the positioning of three teeth or 
notches spaced about the movable member in a 120.degree. angular spacing 
relationship. Similarly, an eight cylinder engine would require the 
implementation of four teeth or notches positioned on the movable member 
and spaced 90.degree. apart. With such configurations, including the four 
cylinder configuration of the preferred embodiment, one radius of the 
movable member positions only one tooth or notch which functions as an 
"encoding" shunt to both reference the beginning of the firing sequence 
and to fire a selected pair of cylinders, and the other radius positions 
the remaining teeth or notches which function as "slave" shunts to fire 
the remaining pairs of cylinders. Those skilled in the art will recognize 
that this basic scheme of one encoding shunt and one or more other slave 
shunts may be implemented to operate an odd-cylinder engine or uneven 
firing angles. Because the present invention generates and processes a 
variety of low voltage signals without a conventional distributor, the 
length of the high tension leads may be considerably shortened and the 
spark coils mounted relatively close to the spark plugs to minimize RFI. 
Also, the stationary mounting of the sensor apparatus and electronic 
processing of pulses in non-adjustable and discourages tampering with 
engine emission settings. 
It should be noted that although the sensors shown in FIGS. 3 and 8 have 
been described and illustrated with reference to use in internal 
combustion engines and the like for sensing angular shaft positions, they 
may also be used in sense linear positions of a movable or reciprocating 
member relative to the sensor. One such linear application is the sensing 
of the vertical displacement of a vehicular body relative to the axle of 
the vehicle under various cargo loading conditions of the vehicle to 
adjust the vehicle suspension mechanism to compensate for the load. 
Referring to FIGS. 14-16, apparatus for sensing relative linear motion 
between two parts will be described. As in the embodiments of FIGS. 8-13, 
magnet 74 is affixed to bracket 18 and Hall-effect sensors 70, 72 are 
supported by the arms of C-shaped support 20, defining regions 76, 78, 
respectively, with magnet 74. Support 20 is secured to bracket 18 which is 
mounted to, and movable with, one of the parts, not shown, but which may 
be one of a vehicle body and a wheel axle. The electrical connections to, 
and input and sensing circuitry for, sensors 70, 72 are not shown but may 
be as in the previous embodiment. The sensing circuitry would be modified 
to provide the desired outputs. 
U-shaped in cross section ferrous elongated channel 82 has sides 84, 86. 
Channel 82 is attached to, as with bolts 83, and movable with the other of 
the vehicle body and axle, and is positioned so that sides 84, 86 are 
movable in regions 76, 78, respectively, during relative movement between 
the body and axle. Side 84 has notch 88, defined by edges 88a, 88b and 
side 86 has notch 90, defined by edges 90a, 90b, and notch 92, defined by 
notches 92a, 92b. Thus, as channel 84 moves longitudinally relative 
sensors 70, 72, output waveforms are generated to indicate relative linear 
positions therebetween. 
Referring to FIG. 15, the outputs of sensors 70, 72 when positioned on line 
A would respectively be 0,0, since the magnetic flux in both regions 76, 
78 are shunted; when positioned on line B, the outputs would respectively 
be 0,1, since region 76 is shunted and region 78 is not; when positioned 
on line C, the outputs would be 1,0; and when positioned on line D, the 
outputs would be 1,1. Thus, a two digit binary signal is provided to 
indicate relative linear position between two parts, such as a wheel and 
axle. 
It is also possible to invert each of waveforms A, B by interchanging the 
notches and rim portions. Thus, by placing a rim portion where there is a 
notch, and placing a notch where there is a rim portion, the outputs would 
be inverted. 
Thus, there may be seen that there has been provided a magnetic sensor 
apparatus useable in distributorless and contactless ignition systems as 
well as a linear position detecting apparatus to detect the relative 
position of a wheel and axle. Obviously, many modifications and variations 
of the invention are possible in light of the above teachings. For 
example, the magnetic sensor apparatus may be used for fuel metering 
applications in an internal combustion engine. As illustrated, the 
Hall-effect device may sense the position and speed of the rotating shaft 
as encoded by the placement of shunting teeth or notches thereon and then 
process such information to provide for fuel metering and distribution to 
respective cylinders of an engine in a predetermined sequence suitable for 
fuel injection purposes. 
Various combinations of shunts and gaps may be provided to obtain desired 
outputs. Multiple digit binary codes, including two digit outputs, may be 
provided by utilizing multiple shunting members, such as notched rims or 
channel sides, and a corresponding number of magnets and sensor devices to 
sense the presence and absence of each notch. The magnets and sensors may 
conveniently be supported in a single package in substantial alignment 
along a line transverse to the notched rims or sides. For example, for a 
three digit binary signal, three rims or sides, with associated field 
producing means and sensor means, would be utilized. The invention may 
also be used in a variety of applications wherein it is desired to monitor 
or indicate generally the angular position of a rotating shaft within an 
apparatus or machine. It is therefore to be understood that within the 
scope of the appended claims the invention may be practiced otherwise than 
as specifically described.