Rotational speed detector for an internal combustion engine comprising a waveform processor for eliminating unwanted pulses

• US 5,066,910 A
• Filed: 12/19/1990
• Issued: 11/19/1991
• Est. Priority Date: 08/31/1987
• Status: Expired due to Fees

• Current Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.)
• Original Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.)
• Inventors: Sugiyama, Naoki
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): EDMONDS, WARREN
• Application Number:
  US07/629,030
• Time in Patent Office: 335 Days
• Field of Search: 324/160, 324/161, 324/166, 324/163, 324/168, 324/169, 324/170, 324/173, 324/174, 324/175, 324/178, 324/179, 324/180, 324/205.15, 324/207.25, 324/225
• US Class Current: 324/166
• CPC Class Codes: F02D 41/0097 using means for generating speed signals
• CPC Class Codes: G01P 3/4807 by using circuits for the detection of the pulses delivered by the ignition system of an internal combustion engine

Abstract

A rotational speed detector for an internal combustion engine comprises a waveform processor for eliminating pulses generated within a predetermined period of time after a certain pulse appears and a measuring circuit for measuring a rotational speed based on outputs from the waveform processor. The waveform processor of the rotational speed detector thus eliminates the effects of such an unexpected pulse generated, for example, by the vibration of the ignition coil for the engine. Consequently, the measuring means detects the rotational speed accurately without measuring the unexpected pulse.

Claims

1. A rotational speed detector for an internal combustion engine comprising:

a waveform processor for processing an input ignition waveform and for eliminating unwanted pulses therefrom;

the unwanted pulses being generated within a predetermined period of time after a desired ignition signal pulse in the input ignition waveform appears;

the waveform processor particularly comprising a square wave waveform shaper responsive to the input ignition waveform for providing a square wave output, a monostable multi-vibrator responsive to the square wave output of the waveform shaper, a logic circuit responsive to the monostable multi-vibrator and the square wave output of the waveform shaper to provide an output signal with unwanted pulses eliminated therefrom; and

measuring means responsive to the output signal of the logic circuit of the waveform processor for measuring a rotational speed.

2. A rotational speed detector for an internal combustion engine according to claim 1, wherein said waveform processor further includes means for blocking high frequency components of an input ignition waveform.

3. A rotational speed detector for an internal combustion engine according to claim 1, wherein said waveform processor further includes means for clipping excessively high voltages of an input ignition waveform.

4. A rotational speed detector for an internal combustion engine according to claim 2, the high frequency signal component blocking means comprising a low pass filter.

5. A rotational speed detector for an internal combustion engine according to claim 3, the high voltage clipping means particularly comprising a zener diode.

6. A rotational speed detector for an internal combustion engine according to claim 1, the waveform shaper of the waveform processor particularly comprising a transistor switching circuit, the transistor switching circuit being connected to the monostable multi-vibrator and the logic circuit.

11. A rotational speed detector for an internal combustion engine according to claim 4, the high voltage clipping means particularly comprising a zener diode.

7. A rotational speed detector for an internal combustion engine comprising:

a waveform processor for processing an input ignition waveform and for eliminating unwanted pulses therefrom;

the unwanted pulses being generated within a predetermined period of time after a desired ignition signal pulse in the input ignition waveform appears;

the waveform processor particularly comprising a square wave waveform shaper responsive to the input ignition waveform for providing a square wave output, a monostable multi-vibrator responsive to the square wave output of the waveform shaper, a logic circuit responsive to the monostable multi-vibrator and the square wave output of the waveform shaper to provide an output signal with unwanted pulses eliminated therefrom; and

measuring means responsive to the output of the signal of the logic circuit of the waveform processor for measuring a rotational speed;

the measuring means comprising means responsive to the waveform processor for determining an amount of time passage between two separate input ignition pulses, and

means for calculating a rotational speed based on the determined amount of time between the two separate input ignition pulses and the number of cylinders of the engine.

8. A rotational speed detector for an internal combustion engine according to claim 7, wherein said waveform processor further includes means for blocking high frequency components of an input ignition waveform.

9. A rotational speed detector for an internal combustion engine according to claim 7, wherein said waveform processor further includes means for clipping excessively high voltages of an input ignition waveform.

10. A rotational speed detector for an internal combustion engine according to claim 8, the high frequency signal component blocking means comprising a low pass filter.

12. A rotational speed detector for an internal combustion engine according to claim 7, the waveform shaper of the waveform processor particularly comprising a transistor switching circuit, the transistor switching circuit being connected to the monostable multi-vibrator and the logic circuit.