Browse Prior Art Database

Automotive Engine Acceleration Measurement Interface

IP.com Disclosure Number: IPCOM000035863D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 54K

Publishing Venue

IBM

Related People

Landry, JA: AUTHOR [+4]

Abstract

This article describes an attachment card interface to conditioned output signals from an autmotive vehicle for measuring the acceleration of the vehicle engine to allow for diagnostic analysis of operating parameters.

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Automotive Engine Acceleration Measurement Interface

This article describes an attachment card interface to conditioned output signals from an autmotive vehicle for measuring the acceleration of the vehicle engine to allow for diagnostic analysis of operating parameters.

Fig. 1 shows the hardware arrangement in block diagram. An engine under test is attached to an automotive vehicle circuitry which includes sensors and circuits to digitize analog signals from the sensors. The outputs of the circuits go to a personal system attachment card, as disclosed herein. This attachment card will take the data from the engine and send it to the personal system which will run diagnostic and analysis routines to measure engine performance. As one example, the attachment card must meet the following requirements concerning the interface to the circuits:

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1. The time between every ring gear tooth-to-tooth transition must be counted as a 16-bit count. 2. The counter value must be at least 347 counts between teeth for the maximum engine speed of 6000 rpm for a ring gear with 144 teeth. This requires a count rate of at least 5 MHz. 3. The attachment card must note when top dead center (TDC) occurred in relation to the ring gear teeth.

Fig. 2 shows the hardware arrangement in detail. The engine flywheel with its ring gear will turn as the engine moves. One sensor is used to detect TDC, which occurs every engine revolution. The other sensor produces a signal whenever a ring gear tooth (RGT) passes it. This signal is know as RGT. There are typically 144 ring gear teeth in one engine revolution.

The automotive vehicle provides circuitry to convert the TDC and RGT signals to digital levels. The signals then go to the personal system attachment card. The signals go through conditioning circuits to provide sharp digital transitions, and protection circuits to ensure that the attachment card is protected from damage if either signal is shorted to battery voltage (+14 V).

The time between RGT signals is required to be counted with a counter. Requirements state that the counter value must be at least 347 counts for the maximum engine speed of 6000 revolutions per minute (RPM) for a ring gear which has 144 teeth. This requires a counter clock of 5 MHz. The calculation is shown below. 1 min/6000 rev X 60 sec/min X 1 rev/144 teeth X 5,000,000 counts/sec = 347 counts/tooth

Internal counters (not shown) of the microcontroller may not count pulses faster than 1/25 of its oscillator frequency. The microcontroller is running at
14.31818 MHz, so its counter will count pulses no faster than 596 KHz. Since requirements dictate a count rate of at least 5 MHz, the internal counters are not adequate by themselves. External coun...