# US 7,608,012 B2 · Resolving a non-commanded neutral state in a clutch-to-clutch transmission

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- Number: US 7,608,012 B2
- Document ID: US7608012B2
- Status: Granted
- Kind: B2
- Application number: 11/589,693
- Filed: 2006-10-30
- Published: 2007-10-25
- Granted: 2009-10-27
- Earliest claimed: 2006-04-25
- Assignees: GM Global Technology Operations LLC
- Inventors: Todd J. Thor; David W. Wright; Brian J. Pellerito; Craig A. Brunstetter
- Web page: https://patentgrep.com/patent/US7608012B2

## 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 59/46: dependent on a comparison between speeds
- F16H 2059/465: {Detecting slip, e.g. clutch slip ratio}
- F16H 2061/1224: {Adapting to failures or work around with other constraints, e.g. circumvention by avoiding use of failed parts}
- F16H: GEARING

## Abstract

A method of controlling a clutch-to-clutch transmission. The method includes detecting transmission slip speed that exceeds a predetermined amount for a predetermined time period. Based on the detecting, a shift of a gear ratio of the transmission is forced. When this method is implemented in a vehicle, loss of driver control of the vehicle can be prevented in the event of a non-commanded neutral condition in the transmission.

## Claims

### Claim 1

A vehicle including a transmission having a plurality of clutches for providing a plurality of speed ratios, the vehicle comprising a control module that:
monitors a difference between speed of an input shaft of the transmission and speed of an output shaft of the transmission in a gear state of the transmission for an expected shift time; and
based on the monitoring and a gear ratio of the gear state, forces a shift of the transmission to a different gear state if the difference exceeds a predetermined amount for longer than the expected shift time.

### Claim 2 (depends on 1)

The vehicle of claim 1 wherein the control module forces an upshift or a downshift based on a currently commanded gear.

### Claim 3 (depends on 2)

The vehicle of claim 2 wherein the control module forces an upshift to by one gear state if the currently commanded gear is less than a maximum command gear.

### Claim 4 (depends on 2)

The vehicle of claim 2 wherein the control module forces a downshift to by one gear state if the currently commanded gear equals a maximum command gear.

### Claim 5 (depends on 1)

The vehicle of claim 1 wherein the control module:
monitors a resulting gear ratio in the different gear state; and
issues a diagnostic based on the resulting gear ratio.

### Claim 6

A method of controlling a transmission having a plurality of clutches for providing a plurality of speed ratios, the method comprising:
detecting when a difference between speed of an input shaft of the transmission and a product of speed of an output shaft of the transmission and a gear ratio of the transmission exceeds a predetermined amount for a predetermined time period; and
based on the detecting, forcing a shift of the gear ratio of the transmission.

### Claim 7 (depends on 6)

The method of claim 6 wherein the predetermined time period includes an expected shift time.

### Claim 8 (depends on 6)

The method of claim 6 wherein the predetermined amount includes a commanded difference.

### Claim 9 (depends on 6)

The method of claim 6 wherein forcing a shift of a gear ratio comprises determining whether the gear ratio is a maximum command gear.

### Claim 10 (depends on 9)

The method of claim 9 wherein forcing a shift comprises forcing an upshift or downshift by one gear state.

### Claim 11 (depends on 6)

The method of claim 6 further comprising:
monitoring the shifted gear ratio for a predetermined monitoring time; and
based on the monitoring, issuing a diagnostic.

### Claim 12

A transmission control system for a clutch-to-clutch transmission, the control system comprising a control module configured to:
detect when a difference between speed of an input shaft of the transmission and a product of speed of an output shaft of the transmission and a gear ratio of the transmission exceeds a predetermined amount for a predetermined time period; and
based on the detecting, forcing a shift of the gear ratio of the transmission.

### Claim 13 (depends on 12)

The transmission control system of claim 12 wherein the predetermined time period includes an expected shift time.

### Claim 14 (depends on 12)

The transmission control system of claim 12 wherein the predetermined amount includes a commanded difference.

### Claim 15 (depends on 12)

The transmission control system of claim 12 wherein said control module forces an upshift or downshift of a gear ratio based on whether the gear ratio is a maximum command gear.

### Claim 16 (depends on 12)

The transmission control system of claim 12 wherein said control module forces a shift of a one gear state.

### Claim 17 (depends on 12)

The transmission control system of claim 12 wherein said control module monitors the shifted gear ratio for a predetermined monitoring time, and
based on the monitoring, issues a diagnostic.