Oil Temperature Prediction and Vehicle Protection

• US 20080201036A1
• Filed: 02/15/2007
• Published: 08/21/2008
• Est. Priority Date: 02/15/2007
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Karlsson, Rolf B.
• Granted Patent: US 7,747,366 B2
• Time in Patent Office: Days
• US Class Current: 701/35
• CPC Class Codes: G01M 13/021 Gearings

Abstract

A vehicle having an oil temperature prediction algorithm that allows for protection of the vehicle is disclosed. The algorithm may predict an oil sump temperature for a manual transmission and, upon reaching a first transmission heat threshold, enter a transmission protection mode.

Claims

1. A method for determining an estimated oil sump temperature of a component of a vehicle, the method comprising the steps of:

(a) obtaining an initial oil sump temperature;

(b) determining a heat input to the component based on vehicle operating parameters;

(c) determining a heat loss from the component based on the vehicle operating parameters;

(d) adding the heat input to and subtracting the heat loss from the initial oil sump temperature to obtain the estimated oil sump temperature; and

(e) storing the estimated oil sump temperature in an electronic control module of the vehicle.

2. The method of claim 1 wherein step (a) is further defined by the initial oil sump temperature being set to an engine coolant temperature.

3. The method of claim 1 wherein step (a) is further defined by:

monitoring an engine off time;

comparing the engine off time to a predetermined time period; and

calculating the initial oil sump temperature by solving the equation Ts=Tao+(Tso−

Tao)*e<sup>(−

EOT/3304)</sup>, where Ts is the initial oil sump temperature, Tao is an ambient air temperature at a time an engine was last turned off, Tso is an oil sump temperature at the time the engine was last turned off, and EOT is the engine off time in seconds, if the engine off time is less than the predetermined time period.

4. The method of claim 1 wherein the component is a transmission and step (b) is further defined by:

determining in which one of a plurality of gears the transmission is operating;

calculating a mechanical inefficiency value for the one gear by solving the equation IEFF=(C1+C2*|ENGTRQACT|+C3*ENGSPD* e<sup>(−

C4*Ts)</sup>)/|ENGTRQACT|, where IEFF is the mechanical inefficiency value, |ENGTRQACT| is an absolute value of a torque being produced by an engine, ENGSPD is a rotational speed of the engine, Ts is a current value of the estimated oil sump temperature, and C1, C2, C3 and C4 are constants that are based in part on the one gear in which the transmission is operating; and

using the mechanical inefficiency value as a factor when determining the heat input to the transmission.

5. The method of claim 4 wherein step (b) is further defined by the heat input to the transmission being determined by (|ENGTRQACT|*ENGSPD*(2π

/60)*IEFF.

6. The method of claim 4 wherein step (c) is further defined by:

determining a vehicle speed;

calculating a heat transfer coefficient by solving the equation HA=C5*(VEHSPD)²+C6*VEHSPD+C7, where HA is the heat transfer coefficient, VEHSPD is the vehicle speed, and C5, C6 and C7 are constants; and

using the heat transfer coefficient as a factor when determining the heat loss from the transmission.

7. The method of claim 1 wherein step (c) is further defined by:

determining a vehicle speed;

calculating a heat transfer coefficient by solving the equation HA=C5*(VEHSPD)²+C6*VEHSPD+C7, where HA is the heat transfer coefficient, VEHSPD is the vehicle speed, and C5, C6 and C7 are constants; and

using the heat transfer coefficient as a factor when determining the heat loss from the component.

8. The method of claim 1 wherein step (d) is further defined by the heat input being |ENGTRQACT|*ENGSPD*(2π

/60)*IEFF/C_THM and the heat loss being HA*(Ts−

Ta))/C_THM, where |ENGTRQACT| is an absolute value of a torque being produced by an engine, ENGSPD is a rotational speed of the engine, Ts is a current value of the estimated oil sump temperature, Ta is a current ambient air temperature, IEFF is a mechanical inefficiency value of the component, HA is a convective heat transfer coefficient, and C_THM is a thermal mass of the component.

9. The method of claim 1 wherein the component is a manual transmission.

10. A method for protecting a manual transmission of a vehicle, the method comprising the steps of:

(a) obtaining an initial estimated transmission oil sump temperature;

(b) estimating a heat input to the manual transmission based on vehicle operating parameters;

(c) estimating a heat loss from the manual transmission based on the vehicle operating parameters;

(d) adding the heat input to and subtracting the heat loss from the initial estimated transmission oil sump temperature to obtain an incremental estimated oil sump temperature;

(e) determining if the incremental estimated oil sump temperature is greater than a first transmission heat threshold; and

(f) entering a transmission protection mode if the incremental estimated oil sump temperature is greater than the first transmission heat threshold.

11. The method of claim 10 further including the steps of:

(g) estimating a second heat input to the manual transmission based on the vehicle operating parameters;

(h) estimating a second heat loss from the manual transmission based on the vehicle operating parameters;

(i) adding the second heat input to and subtracting the second heat loss from the incremental estimated oil sump temperature to obtain a second incremental estimated oil sump temperature;

(j) determining if the second incremental estimated oil sump temperature is less than a second transmission heat threshold; and

(i) exiting the transmission protection mode if the transmission protection mode was entered and the second incremental estimated oil sump temperature is less than the second transmission heat threshold.

12. The method of claim 11 wherein the second transmission heat threshold is at least three degrees Celsius lower than the first transmission heat threshold.

13. The method of claim 10 wherein step (f) is further defined by reducing a maximum allowable engine torque output when the transmission protection mode is entered such that a new estimated heat input to the manual transmission is less than or equal to a new estimated heat loss from the manual transmission.

14. The method of claim 13 wherein step (f) is further defined by the maximum allowable engine torque output being reduced by ramping down the maximum allowable engine torque output over a predetermined time interval.

15. The method of claim 10 wherein step (b) is further defined by the vehicle operating parameters including which one of a plurality of gears the manual transmission is operating in, determining the one gear the transmission is operating in, determining a mechanical inefficiency factor for the one gear the transmission is operating in, and using the mechanical inefficiency factor as a factor in estimating the heat input to the manual transmission.

16. The method of claim 10 wherein step (c) is further defined by the vehicle operating parameters including a vehicle speed and an ambient air temperature, determining the vehicle speed, determining an ambient air temperature, and using the vehicle speed and the ambient air temperature as factors in estimating the heat loss from the manual transmission.

17. A vehicle comprising:

an engine;

a manual transmission including a gear set and an oil sump; and

an electronic control module operatively engaging the engine and the manual transmission and including an initial oil sump temperature estimator, a transmission heat input estimator, a transmission heat loss estimator, and an incremental oil sump temperature estimator that adds a first value from the heat input estimator to, and subtracts a second value from the heat loss estimator from, a third value from the initial oil sump temperature estimator to calculate an incremental estimated oil sump temperature.

18. The vehicle of claim 17 wherein the electronic control module further includes a transmission protector that determines if the incremental estimated oil sump temperature is greater than a first transmission heat threshold, and operatively engages the engine to reduce a maximum available engine torque if the incremental estimated oil sump temperature is greater than the first transmission heat threshold.

19. The vehicle of claim 17 including a cooling system temperature sensor operatively engaging the electronic control module, whereby the initial oil sump temperature estimator sets the third value for an initial oil sump temperature equal to a temperature sensed by the cooling system temperature sensor if the engine has been off longer than a predetermined time interval.

20. The vehicle of claim 17 wherein the electronic control module includes a transmission mechanical inefficiency determiner that creates a heat input factor for the transmission heat input estimator based on which one of a plurality of gears in the gear set the transmission is operating in.