Automatic transmission with fail-safe function

• US 4,918,606 A
• Filed: 08/21/1989
• Issued: 04/17/1990
• Est. Priority Date: 08/11/1986
• Status: Expired due to Term

• Current Assignee: Aisin-Warner K.K.
• Original Assignee: Aisin-Warner K.K.
• Inventors: Yamamoto, Masanari, Ito, Yasunobu
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): Makay, Christopher L.
• Application Number:
  US07/396,793
• Time in Patent Office: 239 Days
• Field of Search: 364/424.1, 364/426, 74/866
• US Class Current: 701/63
• CPC Class Codes: F16H 2061/1208 with diagnostic check cycles; Monitoring of failures
• CPC Class Codes: F16H 2061/1232 Bringing the control into a predefined state, e.g. giving priority to particular actuators or gear ratios
• CPC Class Codes: F16H 2061/1244 Keeping the current state
• CPC Class Codes: F16H 2061/1284 the failing part is a sensor
• CPC Class Codes: F16H 2306/00 Shifting
• CPC Class Codes: F16H 59/24 dependent on the throttle opening
• CPC Class Codes: F16H 59/44 dependent on machine speed of the machine, e.g. the vehicle
• 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: F16H 61/686 with orbital gears
• CPC Class Codes: Y10S 477/906 Means detecting or ameliorating the effects of malfunction or potential malfunction

Abstract

A rate of change in vehicle velocity is calculated by comparing a present vehicle velocity signal and an immediately preceding vehicle velocity signal. If the rate of change in vehicle velocity is greater than a rate of change capable of being produced by actual traveling of the vehicle, a decision is rendered to the effect that the vehicle velocity sensor is faulty, fail-safe mode processing is executed and the automatic transmission is controlled in such a manner that traveling of the vehicle will not be impaired. Thus, if the vehicle velocity sensor malfunctions, the automatic transmission can be controlled so as not to impair traveling of the vehicle, thereby allowing the vehicle to travel safely and stably. The fail-safe function can be performed satisfactorily even if only a single vehicle velocity sensor is provided.

Claims

1. An automatic transmission having shift solenoids controlled by a microcomputer in response to a vehicle velocity signal and a throttle opening signal, comprising:

computing means for computing a speed changing rate in the vehicle velocity by comparing a vehicle velocity signal indicating the present vehicle velocity with a vehicle velocity signal indicating an immediately preceding vehicle velocity; and

fail-safe means for controlling said shift solenoids so that said automatic transmission is immediately and permanently set at a gear corresponding to said immediately preceding vehicle velocity until said vehicle is stopped when said speed changing rate computed by said computing means exceeds a predetermined value indicating at least a partial malfunctioning of said vehicle velocity sensor.

2. The automatic transmission according to claim 1, wherein said computing means includes means for continuously computing said speed changing rate;

and when said speed changing rate exceeds said predetermined value, said gear is set by said fail-safe means.

3. The automatic transmission according to claim 1, wherein the fail-safe means sets said automatic transmission at a gear independent of shift lever position.

4. An automatic transmission having shift solenoids controlled by a microcomputer in response to a vehicle velocity signal and a throttle opening signal, comprising:

computing means for computing a speed changing rate in the vehicle velocity by comparing a vehicle velocity indicating the present vehicle velocity with a vehicle velocity signal indicating an immediately preceding vehicle velocity; and

fail-safe means for controlling said shift solenoids so that said automatic transmission is immediately and permanently set at the highest-speed gear of the range presently selected by a shift lever of said transmission until said vehicle is stopped when said speed changing rate computed by said computing means exceeds a predetermined value indicating at least a partial malfunctioning of said vehicle velocity sensor.

5. The automatic transmission according to claim 4, wherein said computing means includes means for continuously computing said speed changing rate;

and when said speed changing rate exceeds said predetermined value, said gear is set by said fail-safe means.

6. An automatic transmission comprising:

a vehicle velocity sensor,

shift solenoids for selecting a gear of said transmission,

microcomputer means for controlling said shift solenoids based in part on a vehicle velocity signal received from said vehicle velocity sensor, and

fail-safe means for controlling aid shift solenoids based upon partial malfunctioning of said vehicle velocity sensor, said fail-safe means including computing means for computing a rate of change in vehicle velocity by comparing a vehicle velocity signal indicating present vehicle velocity with a vehicle velocity signal indicating an immediately preceding vehicle velocity, and means for setting a gear of said transmission corresponding to said immediately preceding vehicle velocity until said vehicle is stopped when said rate of change in vehicle velocity computed by said computing means exceeds a predetermined value indicating a partial malfunctioning of said vehicle velocity sensor.