Brake Assisted Vehicle Engine Restart on a Road Grade

• US 20110065548A1
• Filed: 09/17/2009
• Published: 03/17/2011
• Est. Priority Date: 09/17/2009
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Soliman, Ihab S., Yu, Hai, McGee, Ryan A., Boesch, Mathew A.
• Granted Patent: US 9,457,811 B2
• Time in Patent Office: Days
• US Class Current: 477/203
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/11 Stepped gearings
• CPC Class Codes: B60W 10/115 with planetary gears
• CPC Class Codes: B60W 10/184 with wheel brakes
• CPC Class Codes: B60W 2510/0657 Engine torque
• CPC Class Codes: B60W 2510/105 Output torque
• CPC Class Codes: B60W 2520/30 Wheel torque
• CPC Class Codes: B60W 2552/15 Road slope, i.e. the inclination of a road segment in the longitudinal direction
• CPC Class Codes: B60W 2710/1005 Transmission ratio engaged
• CPC Class Codes: B60W 2710/182 Brake pressure, e.g. of fluid or between pad and disc
• CPC Class Codes: B60W 30/18027 Drive off, accelerating from standstill
• CPC Class Codes: B60W 30/18054 at stand still, e.g. engine in idling state hill holding B60W30/18118
• CPC Class Codes: B60W 30/18118 Hill holding

Abstract

A method for restarting an engine of a vehicle stopped on a grade, comprising the steps of engaging a gear of a transmission through which the engine and wheels of the vehicle are driveably connected mutually, using brake pressure to engage wheel brakes and produce a road gradient wheel torque that holds the vehicle stationary on the grade, initiating an engine restart, operating the engine to produce wheel torque equal to or greater than the road gradient wheel torque, and releasing the brake pressure.

Claims

1. A method for assisting vehicle launch on a grade that accompanies an automatic engine restart, comprising:

(a) engaging a gear of a transmission through which the engine and wheels of the vehicle are driveably connected mutually;

(b) applying brake pressure to produce wheel brake torque capacity sufficient to hold the vehicle stationary on the grade and mitigate combustion torque when the engine restarts;

(c) initiating an engine restart;

(d) maintaining brake pressure until a peak in engine speed occurs and the engine produces wheel torque equal to or greater than a road gradient wheel torque for a predetermine period.

2. The method of claim 1 further comprising releasing the brake pressure.

3. The method of claim 2 wherein releasing the brake pressure further comprises releasing a brake pedal.

4. The method of claim 1 wherein step (a) further comprises engaging a forward drive gear.

5. The method of claim 1 wherein step (b) further comprises determining the road gradient wheel torque using the relationship T_RL=mg sin e*Rw, wherein T_RL is the gradient wheel torque, (m) is vehicle mass and θ

is the angle of the road gradient with respect to a horizontal plane and Rw is the effective tire radius

6. The method of claim 1 wherein step (c) further comprises using a starter motor to crank the engine during the engine restart.

7. The method of claim 1 wherein step (d) further comprises:

if an engine speed peak occurs during a first period, performing steps (d) and (e) provided either a second period following the first period has expired or the engine is producing wheel torque that is equal to or greater than the road gradient wheel torque.

8. The method of claim 1 wherein step (d) further comprises:

if an engine speed peak does not occur during said period and the engine is not running, maintaining brake pressure during an allowable actuation period until another engine restart occurs.

9. A system for restarting an engine of a vehicle stopped on a grade, comprising:

wheels for propelling the vehicle;

wheel brakes for alternately holding and releasing rotation of the wheels;

a brake system for pressurizing the wheel brakes;

an engine;

a starter motor connectable to the engine;

a transmission engaged in a gear through which the engine is driveably connected to the wheels; and

a controller configured to use brake pressure to engage the wheel brakes and to produce a counteractive road gradient wheel torque that holds the vehicle stationary on the grade, use the starter motor to crank the engine initiating an engine restart, operate the engine to produce wheel torque equal to or greater than the road gradient wheel torque, and use the brake system to release the pressure in the wheel brakes.

10. The system of claim 9 wherein the controller is further configured to use the engine to accelerate the vehicle.

11. The system of claim 9 wherein the controller is further configured to determine the road gradient wheel torque using the relationship TRL=mg sin e*Rw, wherein T_RL is the gradient wheel torque, m is vehicle mass, θ

is the angle of the road gradient with respect to a horizontal plane, positive for uphill slope and negative for downhill slope, and Rw is the effective tire radius.

12. The system of claim 9 wherein the controller is further configured to determine that an engine speed peak occurs during a first period, and operate the engine to produce wheel torque equal to or greater than the road gradient wheel torque, and use the brake system to release the pressure in the wheel brakes, provided either a second period following the first period has expired or the engine is producing wheel torque that is equal to or greater than the road gradient wheel torque.

13. The system of claim 9 wherein the controller is further configured to initiate another engine restart, if an engine speed peak does not occur during a first period and the engine is not running.

14. The system of claim 9 wherein the controller is further configured to adaptively determine HSBA brake pressure or torque with reference to road gradient information and initial combustion torque surge magnitude, and to hold the vehicle in standstill on the grade.

15. The system of claim 9 wherein the controller is further configured to determine HSBA torque for an uphill vehicle launch from the relationship T_HSBA=max(T_RL, T_TSM)+T_sm, wherein T_TSM is the torque for initial combustion torque mitigation, T_RL is a gradient wheel torque, and T_SM is a torque safety margin.

16. The system of claim 9 wherein the controller is further configured to determine HSBA torque for a downhill vehicle launch from the relationship T_HSBA=|T_RL|+T_TSM+T_SM, wherein T_TSM is the torque for initial combustion torque mitigation, T_RL is a gradient wheel torque, and T_SM is a torque safety margin.