Method for diagnosing as to signal plausibility with a speed sensor of a motor vehicle

• US 7,191,041 B2
• Filed: 02/04/2004
• Issued: 03/13/2007
• Est. Priority Date: 02/06/2003
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: von Schwertfuehrer, Gerit, Muehlbauer, Christian
• Primary Examiner(s): Nguyen; Cuong
• Application Number:
  US10/770,439
• Publication Number:
  US 20040158372A1
• Time in Patent Office: 1,133 Days
• Field of Search: 701/110, 701/103, 701/34, 701/31, 340/438, 340/441
• US Class Current: 701/34
• CPC Class Codes: F16H 2061/1208 with diagnostic check cycles; Monitoring of failures
• CPC Class Codes: F16H 2061/1212 Plausibility checks; Counting means for repeated failures
• CPC Class Codes: F16H 2061/1284 the failing part is a sensor
• CPC Class Codes: F16H 61/12 Detecting malfunction or potential malfunction, e.g. fail safe in control of hydrostatic gearing F16H61/4192; Circumventing or fixing failures
• CPC Class Codes: G01P 21/02 of speedometers
• CPC Class Codes: G01P 3/481 of pulse signals
• CPC Class Codes: G01P 3/50 for measuring linear speed G01P3/56 takes precedence

Abstract

A method is for making a diagnosis as to signal plausibility in a speed sensor of a motor vehicle. In the method, the speed sensor outputs a pulse sequence to an evaluation circuit in dependence upon the speed of the vehicle and, in a steady-state operating condition of the motor vehicle, a ratio is formed between the determined speed and an engine rpm and the ratio is averaged over a pregiven time. A plausibility is determined only when the formed mean value lies in a value range permissible for the steady-state operating condition.

Claims

1. A method for making a diagnosis as to signal plausibility in a speed sensor of a motor vehicle, the method comprising the steps of:

causing said speed sensor to output a pulse seguence to an evaluation circuit in dependence upon the speed of the vehicle;

in a steady-state operating condition of said motor vehicle, repeatingly forming a ratio between a determined speed and a motor rpm during a pregiven time and computing the mean value of the ratios formed over said pregiven time; and

,

only determining said signal plausibility when said mean value lies in a value range permissible for the steady-state operating condition.

2. The method of claim 1, comprising the further step of detecting the steady-state operating condition when a constant gear or a constant gear selection is set for said pregiven time.

3. The method of claim 1, comprising the further step of detecting the steady-state operating condition when a gradient of said ratio drops, in magnitude, below a first pregiven threshold value during said pregiven time.

4. The method of claim 1, comprising the further step of detecting the steady-state operating condition when an accelerator pedal value or motor torque drops below a second pregiven threshold value during said pregiven time.

5. The method of claim 1, comprising the further step of detecting the steady-state operating condition when the determined speed exceeds a third pregiven threshold during said pregiven time.

6. The method of claim 1, comprising the further step of detecting the steady-state operating condition when the motor temperature exceeds a fourth pregiven threshold value.

7. A method for making a diagnosis as to signal plausibility in a speed sensor of a motor vehicle, the method comprising the steps of:

causing said speed sensor to output a pulse sequence dependent upon the speed of the vehicle;

supplying said pulse sequence to an evaluation circuit wherein a speed of the vehicle is determined from said pulse sequence to provide a determined speed;

causing an rpm sensor to supply an rpm signal to said evaluation circuit indicative of motor rpm;

repeatingly forming a ratio of said determined speed and said motor rpm during a pregiven time and computing the mean value of the ratios formed over said pregiven time; and

,

only determining said signal plausibility when said mean value lies in a value range permissible for the steady-state operating condition.