Crankshaft position sensor

• US 6,346,808 B1
• Filed: 02/28/2000
• Issued: 02/12/2002
• Est. Priority Date: 02/28/2000
• Status: Expired due to Fees

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Schroeder, Thaddeus
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): Zaveri, Subhash
• Application Number:
  US09/515,077
• Time in Patent Office: 715 Days
• Field of Search: 324/207.21, 324/207.22, 324/207.25, 324/601, 324/691, 324/207-20, 324/207.12, 324/173, 219/121.66, 338/32.R, 123/406.61
• US Class Current: 324/207.21
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01D 5/147 influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other
• CPC Class Codes: G01D 5/2451 Incremental encoders G01D5/2454 takes precedence
• CPC Class Codes: G01P 21/02 of speedometers
• CPC Class Codes: G01P 3/489 Digital circuits therefor

Abstract

A method of accurately emulating any desired tooth/slot format of a desired target wheel from a predetermined tooth/slot arrangement of a rotating actual target wheel used in conjunction with an MR position sensor. The passage of two sequential slots of differing widths or two sequential teeth of differing widths of the actual target wheel determine the rising and falling edge of one tooth of the desired target wheel and define one tooth and one slot of the desired target wheel. The actual target wheel, has, preferably, 2n teeth and 2n slots of two distinct sequential widths whereby the desired target wheel is emulated to have n teeth and n slots. The two MRs of the position sensor are aligned in the circumferential direction of the actual target wheel so as to generate two angularly offset signals (first and second voltages, respectively) from the passage of a single slot of the actual target wheel. The offset signals are input to a signal conditioning circuit. Within the signal conditioning circuit, the two sensor signals (first and second voltages) are differentially amplified to produce a differential signal whereby the width of the slot is used to encode a binary position voltage, high or low. The two distinct sequential slot/tooth widths of the actual target wheel are used to identify a tooth edge of the desired target wheel as rising or falling and, hence, define the teeth and slots of the desired target wheel. Alternatively, the present invention could be implemented with width encoded teeth instead of width encoded slots.

Claims

1. An apparatus for detecting rotational position using a desired target wheel emulated from an actual target wheel, comprising:

a differential sensor comprising a first magnetostatic element and a second magnetostatic element matched to said first magnetostatic element;

magnetic field means for magnetically biasing said differential sensor;

an actual target wheel having 2n slots and 2n teeth arranged circumferentially in a serially repeating pattern of a narrow slot followed by a wide slot each slot being separated by a tooth of the 2n teeth wherein each tooth of the 2n teeth has a mutually equal width, said target wheel being rotatively disposed in relation to said differential sensor, said first and second magnetostatic elements being spaced circumferentially with respect to said target wheel;

current source means connected with said differential sensor for providing first and second voltages respectively from each of said first and second magnetostatic elements responsive to each slot of said 2n slots successively passing said differential sensor; and

signal conditioning circuit means connected with said differential sensor for providing two distinctly different voltage outputs responsive to said first and second voltages, wherein a first distinct voltage output is provided between centers of a wide slot and a next serially adjacent narrow slot, and wherein a second distinct voltage output is provided between centers of the serially adjacent narrow slot and a next serially adjacent wide slot;

wherein said current source means provides matched currents to each of said first and second magnetostatic elements; and

wherein said magnetic field means provides matched biasing magnetic fields to each of said first and second magnetostatic elements; and

wherein a desired target wheel having n slots and n teeth is emulated from said two distinct voltage outputs, wherein each tooth and each slot of the desired target wheel has a mutually equal width, and wherein each tooth of the desired target wheel is assigned to each first distinct voltage output, and each slot of the desired target wheel is assigned to each second distinct voltage output.

2. The apparatus of claim 1, wherein said signal conditioning means comprises:

differential amplifier means for converting said first and second voltages into a differential output signal;

peak detection means for detecting a peak voltage of said differential output signal;

first sampling means for sampling said first and second voltages responsive to said peak detection means detecting said peak voltage to thereby provide a sampled first voltage of said first voltage and a sampled second voltage of said second voltage;

means for determining a midpoint voltage between said sampled first voltage and said sampled second voltage;

zero detection means for detecting a zero voltage of said differential output signal;

second sampling means for sampling at least one of said first and second voltages responsive to said zero detection means detecting said zero voltage to thereby detect a crossover voltage;

comparator means for comparing said midpoint voltage to said crossover voltage, and for providing the two distinctly different voltage outputs, wherein when a narrow slot passes said differential sensor said crossover voltage exceeds said midpoint voltage, and wherein when a wide slot passes said differential sensor said midpoint voltage exceeds said crossover voltage; and

bistable means for providing, responsive to said comparator means, the first distinct voltage output between centers of a wide slot and a next serially adjacent narrow slot, and the second distinct voltage output between centers of the serially adjacent narrow slot and a next serially adjacent wide slot.

3. The apparatus of claim 2, wherein said signal conditioning means further comprises means for selectively enabling said differential amplifier means responsive to passage of each slot with respect to said differential sensor.

4. An apparatus for detecting rotational position using a desired target wheel emulated from an actual target wheel, comprising:

a differential sensor comprising a first magnetostatic element and a second magnetostatic element matched to said first magnetostatic element;

magnetic field means for magnetically biasing said differential sensor;

an actual target wheel having 2n slots and 2n teeth arranged circumferentially in a serially repeating pattern of a narrow tooth followed by a wide tooth each tooth being separated by a slot of the 2n slots wherein each slot of the 2n slots has a mutually equal width, said target wheel being rotatively disposed in relation to said differential sensor, said first and second magnetostatic elements being spaced circumferentially with respect to said target wheel;

current source means connected with said differential sensor for providing first and second voltages respectively from each of said first and second magnetostatic elements responsive to each tooth of said 2n teeth successively passing said differential sensor; and

signal conditioning circuit means connected with said differential sensor for providing two distinctly different voltage outputs responsive to said first and second voltages, wherein a first distinct voltage output is provided between centers of a wide tooth and a next serially adjacent narrow tooth, and wherein a second distinct voltage output is provided between centers of the serially adjacent narrow tooth and a next serially adjacent wide tooth;

wherein said current source means provides matched currents to each of said first and second magnetostatic elements; and

wherein said magnetic field means provides matched biasing magnetic fields to each of said first and second magnetostatic elements; and

wherein a desired target wheel having n slots and n teeth is emulated from said two distinct voltage outputs, wherein each tooth and each slot of the desired target wheel has a mutually equal width, and wherein each tooth of the desired target wheel is assigned to each first distinct voltage output, and each slot of the desired target wheel is assigned to each second distinct voltage output.

5. The apparatus of claim 4, wherein said signal conditioning means comprises:

differential amplifier means for converting said first and second voltages into a differential output signal;

peak detection means for detecting a peak voltage of said differential output signal;

first sampling means for sampling said first and second voltages responsive to said peak detection means detecting said peak voltage to thereby provide a sampled first voltage of said first voltage and a sampled second voltage of said second voltage;

means for determining a midpoint voltage between said sampled first voltage and said sampled second voltage;

zero detection means for detecting a zero voltage of said differential output signal;

second sampling means for sampling at least one of said first and second voltages responsive to said zero detection means detecting said zero voltage to thereby detect a crossover voltage;

comparator means for comparing said midpoint voltage to said crossover voltage, and for providing the two distinctly different voltage outputs, wherein when a narrow tooth passes said differential sensor said crossover voltage exceeds said midpoint voltage, and wherein when a wide tooth passes said differential sensor said midpoint voltage exceeds said crossover voltage; and

bistable means for providing, responsive to said comparator means, the first distinct voltage output between centers of a wide tooth and a next serially adjacent narrow tooth, and the second distinct voltage output between centers of the serially adjacent narrow tooth and a next serially adjacent wide tooth.

6. The apparatus of claim 5, wherein said signal conditioning means further comprises means for selectively enabling said differential amplifier means responsive to passage of each slot with respect to said differential sensor.

7. A method for detecting rotational position using a desired target wheel emulated from an actual target wheel, said method comprising the steps of:

fabricating an actual target wheel having 2n slots and 2n teeth, the 2n teeth being arranged circumferentially in a serially repeating pattern of a wide tooth followed by a narrow tooth, each tooth being separated by a slot of the 2n slots wherein each slot of the 2n slots has a mutually equal width; and

detecting rotation of a desired target wheel emulated from rotation of the actual target wheel, wherein the desired target wheel has n slots and n teeth and wherein each tooth and each slot thereof has a mutually equal width, said step of detecting comprising;

generating a first voltage responsive to passage of a tooth of the actual target wheel across a first predetermined location;

generating a second voltage responsive to passage of the tooth across a second predetermined location;

converting said first and second voltages into a differential output signal;

detecting a peak voltage of said differential output signal;

sampling said first and second voltages responsive to detection of said peak voltage to thereby provide a sampled first voltage of said first voltage and a sampled second voltage of said second voltage and thereby provide a midpoint voltage therebetween;

detecting a zero voltage of the differential output signal;

sampling at least one of the first and second voltages responsive to detection of said zero voltage to thereby detect a crossover voltage;

comparing said midpoint voltage to said crossover voltage; and

generating two distinctly different voltage outputs, responsive to said step of comparing, wherein a first distinct voltage output is provided between centers of a wide tooth and a next serially adjacent narrow tooth, and wherein a second distinct voltage output is provided between centers of the serially adjacent narrow tooth and a next serially adjacent wide tooth;

wherein when a narrow tooth passes said first and second predetermined locations said crossover voltage exceeds said midpoint voltage, and wherein when a wide tooth passes said first and second predetermined locations said midpoint voltage exceeds said crossover voltage.

8. A method for detecting rotational position using a desired target wheel emulated from an actual target wheel, said method comprising the steps of:

fabricating an actual target wheel having 2n slots and 2n teeth, the 2n slots being arranged circumferentially in a serially repeating pattern of a wide slot followed by a narrow slot, each slot being separated by a tooth of the 2n teeth wherein each tooth of the 2n teeth has a mutually equal width; and

detecting rotation of a desired target wheel emulated from rotation of the actual target wheel, wherein the desired target wheel has n slots and n teeth and wherein each tooth and each slot thereof has a mutually equal width, said step of detecting comprising;

generating a first voltage responsive to passage of a slot of the actual target wheel across a first predetermined location;

generating a second voltage responsive to passage of the slot across a second predetermined location;

converting said first and second voltages into a differential output signal;

detecting a peak voltage of said differential output signal;

sampling said first and second voltages responsive to detection of said peak voltage to thereby provide a sampled first voltage of said first voltage and a sampled second voltage of said second voltage and thereby provide a midpoint voltage therebetween;

detecting a zero voltage of the differential output signal;

sampling at least one of the first and second voltages responsive to detection of said zero voltage to thereby detect a crossover voltage;

comparing said midpoint voltage to said crossover voltage; and

generating two distinctly different voltage outputs, responsive to said step of comparing, wherein a first distinct voltage output is provided between centers of a wide slot and a next serially adjacent narrow slot, and wherein a second distinct voltage output is provided between centers of the serially adjacent narrow slot and a next serially adjacent wide slot;

wherein when a narrow slot passes said first and second predetermined locations said crossover voltage exceeds said midpoint voltage, and wherein when a wide slot passes said first and second predetermined locations said midpoint voltage exceeds said crossover voltage.