US 7,803,081 B2 · System and method of controlling automatic transmission

Abstract

In system and method of controlling an automatic transmission that includes a lowest gear-stage friction element and has a lowest gear stage having a largest gear ratio and a gear stage other than the lowest gear stage, the lowest gear stage being established through engagement of the lowest gear-stage friction element, the gear stage other than the lowest gear stage being established while the lowest gear-stage friction element is kept in disengagement, a temperature of working oil in the automatic transmission is sensed, and use of the lowest gear stage is inhibited and use of the gear stage other than the lowest gear stage is allowed when the sensed temperature of the working oil is lower than a first predetermined temperature as a predetermined extremely low temperature at which an engagement failure of the lowest gear-stage friction element is caused.

Claims20

Dependent claims

A system for controlling an automatic transmission, the automatic transmission comprising a plurality of friction elements which come into engagement upon being supplied with a working oil and include a lowest gear-stage friction element, the automatic transmission having a lowest gear stage that has a largest gear ratio and a gear stage other than the lowest gear stage, the lowest gear stage being established through engagement of the lowest gear-stage friction element, the gear stage other than the lowest gear stage being established while the lowest gear-stage friction element is kept in disengagement, the system comprising:

a sensor that senses a temperature of the working oil in the automatic transmission;
and
an electronic control unit operative depending on the sensed temperature, the electronic control unit being programmed to:
inhibit use of the lowest gear stage and allow use of the gear stage other than the lowest gear stage when the sensed temperature of the working oil is lower than a first predetermined temperature as a predetermined extremely low temperature at which an engagement failure of the lowest gear-stage friction element is caused.

1 more element

An automatic transmission having a lowest gear stage that has a largest gear ratio and a gear stage other than the lowest gear stage, the automatic transmission comprising:

a plurality of friction elements which come into engagement upon being supplied with a working oil, the plurality of friction elements including a lowest gear-stage friction element that is in engagement when the lowest gear stage is established, the lowest gear-stage friction element being kept in disengagement when the gear stage other than the lowest gear stage is established;
a sensor that senses a temperature of the working oil in the automatic transmission;
and
an electronic control unit operative depending on the sensed temperature, the electronic control unit being programmed to:
inhibit use of the lowest gear stage and allow use of the gear stage other than the lowest gear stage when the sensed temperature of the working oil is lower than a first predetermined temperature as a predetermined extremely low temperature at which an engagement failure of the lowest gear-stage friction element is caused.

2 more elements

A method of controlling an automatic transmission, the automatic transmission comprising a plurality of friction elements which come into engagement upon being supplied with a working oil and include a lowest gear-stage friction element, the automatic transmission having a lowest gear stage that has a largest gear ratio and a gear stage other than the lowest gear stage, the lowest gear stage being established through engagement of the lowest gear-stage friction element, the gear stage other than the lowest gear stage being established while the lowest gear-stage friction element is kept in disengagement, the method comprising the steps of:

sensing a temperature of the working oil in the automatic transmission;
and
inhibiting use of the lowest gear stage and allowing use of the gear stage other than the lowest gear stage when the sensed temperature of the working oil is lower than a first predetermined temperature as a predetermined extremely low temperature at which an engagement failure of the lowest gear-stage friction element is caused.

Dependencies are inferred from the claim text.

System and method of controlling automatic transmission

Life of this patent

System and method of controlling automatic transmission

Life of this patent

Abstract

Claims20