# US 8,788,159 B1 · Transmission gear shift control

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- Number: US 8,788,159 B1
- Document ID: US8788159B1
- Status: Granted
- Kind: B1
- Application number: 13/766,829
- Filed: 2013-02-14
- Published: 2014-08-14
- Granted: 2014-07-22
- Earliest claimed: 2013-02-14
- Assignees: Ford Global Technologies, LLC
- Applicants: Ford Global Technology Operations, LLC
- Inventors: Gregory Michael Peitron; Sarah M. Thornton; Diana Yanakiev; James William Loch McCallum; Anuradha Annaswamy
- Web page: https://patentgrep.com/patent/US8788159B1

## CPC

- F16H 61/061: {using electric control means}
- F16D 48/06: Control by electric or electronic means, e.g. of fluid pressure
- F16H 63/3026: {comprising friction clutches or brakes (band brake actuating mechanisms F16H63/3003)}
- F16D 2500/3026: Stroke
- F16D 2500/30814: Torque of the input shaft
- F16D 2500/30822: Torque of the output shaft
- F16D 2500/5012: Accurate determination of the clutch positions, e.g. treating the signal from the position sensor, or by using two position sensors for determination
- F16D 2500/50236: Adaptations of the clutch characteristics, e.g. curve clutch capacity torque - clutch actuator displacement
- F16D 2500/50653: Gearing shifting without the interruption of drive
- F16D 2500/70406: Pressure
- F16D 2500/7044: Output shaft torque
- F16D 2500/70605: Adaptive correction; Modifying control system parameters, e.g. gains, constants, look-up tables
- F16D 2500/7061: Feed-back
- F16H 2061/064: {for calibration of pressure levels for friction members, e.g. by monitoring the speed change of transmission shafts}
- F16H: GEARING
- F16D: COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES

## Abstract

A method for controlling pressure applied to a displaceable piston in a cylinder, piston displacement actuating a control element of an automatic transmission during a gearshift, includes determining whether piston displacement exceeds a free length of an isolation spring located between the piston and a friction plate of the control element; calculating the pressure using A the cross-sectional area of the piston; K a coefficient of a return spring extending between the piston and a reference position in the cylinder; x the piston displacement; F0 a pre-load of the return spring; xfree the free length of the isolation spring; and Kis a coefficient of the isolation spring; and applying the calculated pressure to the piston.

## Claims

### Claim 1

A method for controlling pressure applied to a displaceable piston in a cylinder, piston displacement actuating a control element of an automatic transmission during a gearshift, comprising the steps of:
(a) determining whether piston displacement exceeds a free length of an isolation spring located between the piston and a friction plate of the control element;
(b) calculating said pressure using A, a cross-sectional area of the piston; K, a coefficient of a return spring extending between the piston and a reference position in the cylinder; x, the piston displacement; F0 a pre-load of the return spring; xfree the free length of the isolation spring; and Kis a coefficient of the isolation spring;
(c) applying said calculated pressure to the piston.

### Claim 2 (depends on 1)

The method of claim 1, wherein step (a) further comprises:
comparing the piston displacement to the free length of the isolation spring.

### Claim 3 (depends on 1)

The method of claim 1, wherein step (b) further comprises:
setting xcontact equal to 0 provided that the free length of the isolation spring is equal to or greater than the piston displacement;
setting xcontact equal to 1 provided that that the free length of the isolation spring is not equal to or greater than the piston displacement; and
calculating said pressure from the following equation
P=1/A(F0−Kx+xcontact(xfree−x)Kis).

### Claim 4 (depends on 1)

The method of claim 1, further comprising:
(d) determining a difference between said calculated pressure and a commanded pressure;
(e) calculating Q a flow rate of fluid in the cylinder using K1 a laminar flow coefficient; K2 a turbulent flow coefficient; and said difference;
(f) updating displacement of the piston using the flow rate of fluid in the cylinder, a cross sectional area of the piston, and the length of a period between executing steps (a) and (f).

### Claim 5 (depends on 4)

The method of claim 4, wherein step (d) further comprises determining the commanded pressure to be applied to the piston.

### Claim 6 (depends on 4)

The method of claim 4, wherein step (e) further comprises calculating Q the flow rate of fluid in the cylinder using the following equation:
Q=K1ΔP+K2(ΔP)1/2
wherein ΔP is the a difference between said calculated pressure and the commanded pressure.

### Claim 7 (depends on 4)

The method of claim 4, wherein step (f) further comprises updating displacement of the piston using the following equation:
x(t+1)=x(t)+1/A*Q*Δt
wherein x (t+1) is the updated displacement of the piston, x(t) is an immediately previous displacement of the piston, A is the cross-sectional area of the piston, Q is the flow rate of fluid in the cylinder, and Δt is the length of said period.

### Claim 8 (depends on 1)

The method of claim 1, wherein step (b) further comprises calculating said pressure from the following equation provided that piston displacement is greater than xfree: P=1/A (F0−Kx).

### Claim 9 (depends on 1)

The method of claim 1, wherein step (b) further comprises calculating said pressure from the following equation provided that piston displacement is between xfree and zero:
P=1/A(F0−Kx+(xfree−x)Kis)

### Claim 10

A method for controlling pressure applied to a displaceable piston in a cylinder, piston displacement actuating a control element of an automatic transmission during a gearshift, comprising the steps of:
(a) determining the displacement of the piston, and controlling the pressure based at least in part on a calculated piston displacement;
(b) determining whether piston displacement exceeds at least one of: a free length of an isolation spring located between the piston and a friction plate of the control element, and a free length of a return spring located between the piston and a non-axial moving member;
(c) calculating estimated pressure using A, a cross-sectional area of the piston; K, a coefficient of a return spring extending between the piston and a reference position in the cylinder; x, the piston displacement; F0 a pre-load of the return spring; xfree the length of the isolation spring; xmax, this maximum displacement of the piston, and Kis a coefficient of the isolation spring;
(d) applying the estimated pressure to the piston.

### Claim 11 (depends on 10)

The method of claim 10, wherein step (a) further comprises:
comparing the piston displacement to the free length of the isolation spring.

### Claim 12 (depends on 10)

The method of claim 10, wherein step (b) further comprises:
setting xcontact equal to 0 provided that the free length of the isolation spring is equal to or greater than the piston displacement;
setting xcontact equal to 1 provided that that the free length of the isolation spring is not equal to or greater than the piston displacement; and
calculating said pressure from the following equation
P=1/A(F0−Kx+xcontact(xfree−x)Kis).

### Claim 13 (depends on 10)

The method of claim 10, further comprising:
(d) determining a difference between said calculated pressure and a commanded pressure;
(e) calculating Q a flow rate of fluid in the cylinder using K1 a laminar flow coefficient; K2 a turbulent flow coefficient; and said difference;
(f) updating displacement of the piston using the flow rate of fluid in the cylinder, a cross sectional area of the piston, and the length of a period between executing steps (a) and (f).

### Claim 14 (depends on 13)

The method of claim 13, wherein step (e) further comprises calculating Q the flow rate of fluid in the cylinder using the following equation:
Q=K1ΔP+K2(ΔP)1/2
wherein ΔP is the a difference between said calculated pressure and the commanded pressure.

### Claim 15 (depends on 13)

The method of claim 13, wherein step (f) further comprises updating displacement of the piston using the following equation:
x(t+1)=x(t)+1/A*Q*Δt
wherein x (t+1) is the updated displacement of the piston, x(t) is an immediately previous displacement of the piston, A is the cross-sectional area of the piston, Q is the flow rate of fluid in the cylinder, and Δt is the length of said period.

### Claim 16 (depends on 10)

The method of claim 10, wherein step (b) further comprises calculating said pressure from the following equation provided that piston displacement is greater than xfree: P=1/A (F0−Kx).

### Claim 17 (depends on 10)

The method of claim 10, wherein step (b) further comprises calculating said pressure from the following equation provided that piston displacement between xfree and zero:
P=1/A(F0−Kx+(xfree−x)Kis).