# US 2008/0185251 A1 · Clutch to clutch tie-up steady-state diagnostic

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2008/0185251 A1
- Document ID: US20080185251A1
- Status: Published application
- Kind: A1
- Application number: 11/671,979
- Filed: 2007-02-06
- Published: 2008-08-07
- Earliest claimed: 2007-02-06
- Assignees: GM Global Technology Operations LLC
- Inventors: Todd J. Thor
- Web page: https://patentgrep.com/patent/US20080185251A1

## CPC

- F16H 61/12: Detecting malfunction or potential malfunction, e.g. fail safe (in control of hydrostatic gearing F16H61/4192) {; Circumventing or fixing failures}
- F16H 2061/1204: {for malfunction caused by simultaneous engagement of different ratios resulting in transmission lock state or tie-up condition}
- Y10S 477/906: Means detecting or ameliorating the effects of malfunction or potential malfunction
- F16H: GEARING
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A method of regulating operation of an automatic transmission includes identifying a tie-up condition of the automatic transmission, adjusting a pressure of a transmission element in response to the tie-up condition and determining whether a first gear ratio of the automatic transmission holds. The pressure is set to zero if the gear ratio does not hold and a faulty transmission element is identified as one associated with a second gear ratio that is lower than said first gear ratio.

## Claims

### Claim 1

A transmission control system for an automatic transmission, comprising:
a first module that identifies a tie-up condition of the automatic transmission;
a second module that adjusts a pressure of a transmission element in response to said tie-up condition;
a third module that determines whether a first gear ratio of the automatic transmission holds, wherein said second module sets said pressure to zero if said gear ratio does not hold; and
a fourth module that identifies a faulty transmission element as one associated with a second gear ratio that is lower than said first gear ratio.

### Claim 2 (depends on 1)

The transmission control system of claim 1 wherein:
said second module sets said pressure of said transmission element to a value just below a slip pressure of said transmission element if said first gear ratio holds;
said third module again determines whether said first gear ratio of the automatic transmission holds, wherein said second module sets said pressure to zero if said gear ratio does hold; and
said third fourth module identifies a faulty transmission element as one associated with a second gear ratio that is higher than said first gear ratio.

### Claim 3 (depends on 2)

The transmission control system of claim 2 wherein:
said second module sets said pressure to an engagement pressure if said gear ratio does not hold; and
said fourth module indicates a no fault condition of said automatic transmission.

### Claim 4 (depends on 1)

The transmission control system of claim 1 wherein said second module determines a slip pressure of said transmission element, determines an offset pressure and sets said pressure of said transmission element to said slip pressure plus said offset pressure in response to said tie-up condition.

### Claim 5 (depends on 1)

The transmission control system of claim 1 wherein said first module monitors a transmission input shaft speed, monitors a transmission output shaft speed and identifies said tie-up condition based on said transmission input shaft speed and said transmission output shaft speed.

### Claim 6

A method of regulating operation of an automatic transmission, comprising:
identifying a tie-up condition of the automatic transmission;
adjusting a pressure of a transmission element in response to said tie-up condition;
determining whether a first gear ratio of the automatic transmission holds;
setting said pressure to zero if said gear ratio does not hold; and
identifying a faulty transmission element as one associated with a second gear ratio that is lower than said first gear ratio.

### Claim 7 (depends on 6)

The method of claim 6 further comprising:
setting a pressure of said transmission element to a value just below a slip pressure of said transmission element if said first gear ratio holds;
again determining whether said first gear ratio of the automatic transmission holds;
setting said pressure to zero if said gear ratio does hold; and
identifying a faulty transmission element as one associated with a second gear ratio that is higher than said first gear ratio.

### Claim 8 (depends on 7)

The method of claim 7 further comprising:
setting said pressure to an engagement pressure if said gear ratio does not hold; and
indicating a no fault condition of said automatic transmission.

### Claim 9 (depends on 6)

The method of claim 6 wherein said adjusting said pressure includes:
determining a slip pressure of said transmission element;
determining an offset pressure; and
setting said pressure of said transmission element to said slip pressure plus said offset pressure.

### Claim 10 (depends on 6)

The method of claim 6 further comprising:
monitoring a transmission input shaft speed;
monitoring a transmission output shaft speed; and
identifying said tie-up condition based on said transmission input shaft speed and said transmission output shaft speed.

### Claim 11

A method of regulating operation of an automatic transmission, comprising:
identifying a tie-up condition of the automatic transmission;
determining a slip pressure of a transmission element;
adjusting a pressure of said transmission element to a pressure just above said slip pressure in response to said tie-up condition;
determining whether a first gear ratio of the automatic transmission holds;
setting said pressure to zero if said gear ratio does not hold;
identifying a faulty transmission element as one associated with a second gear ratio that is lower than said first gear ratio;
wherein said pressure just above said slip pressure is determined as a sum of said slip pressure and an offset pressure.

### Claim 12 (depends on 11)

The method of claim 11 further comprising:
setting a pressure of said transmission element to a pressure just below said slip pressure of said transmission element if said first gear ratio holds;
again determining whether said first gear ratio of the automatic transmission holds;
setting said pressure to zero if said gear ratio does hold; and
identifying a faulty transmission element as one associated with a second gear ratio that is higher than said first gear ratio.

### Claim 13 (depends on 12)

The method of claim 12 further comprising:
setting said pressure to an engagement pressure if said gear ratio does not hold; and
indicating a no fault condition of said automatic transmission.

### Claim 14 (depends on 11)

The method of claim 11 further comprising determining said offset pressure as a pre-stored value.

### Claim 15 (depends on 11)

The method of claim 11 further comprising:
monitoring a transmission input shaft speed;
monitoring a transmission output shaft speed; and
identifying said tie-up condition based on said transmission input shaft speed and said transmission output shaft speed.