Vehicle braking-force control device

• US 20080208427A1
• Filed: 02/25/2008
• Published: 08/28/2008
• Est. Priority Date: 02/26/2007
• Status: Active Grant

• Current Assignee: Subaru Corp.
• Original Assignee: Fuji Heavy Industries Limited (Subaru Corp.)
• Inventors: Yoneda, Takeshi, Matsuno, Koji, Igarashi, Masato, Morokuma, Yosuke
• Granted Patent: US 8,958,967 B2
• Time in Patent Office: Days
• US Class Current: 701/80
• CPC Class Codes: B60T 8/1755 Brake regulation specially adapted to control the stability of the vehicle, e.g. taking into account yaw rate or transverse acceleration in a curve road vehicle drive control systems for control of driving stability otherwise than by controlling a particular sub-unit B60W30/02
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/184 with wheel brakes
• CPC Class Codes: B60W 30/18109 Braking

Abstract

A braking-force control device has a brake control function for performing brake control on a front outside wheel when a vehicle is detected to be in an oversteer condition during a turning operation and for performing brake control on a rear inside wheel when the vehicle is detected to be in an understeer condition during a turning operation. For preventing the oversteer condition, a command for reducing the engine torque is output. On the other hand, for preventing the understeer condition, the engine torque is limited in accordance with a permissible engine torque value that is calculated on the basis of a road-surface friction coefficient, and ground loads and lateral tire forces of individual wheels. If it is detected that engine braking is in operation, the engine torque is adjusted to substantially zero.

Claims

1. A vehicle braking-force control device comprising:

road-surface friction coefficient estimator configured to estimate a road-surface friction coefficient;

ground-load estimator configured to estimate ground loads acting on individual wheels;

lateral-tire-force estimator configured to estimate lateral tire forces acting on the individual wheels;

permissible-engine-torque calculator configured to calculate a permissible engine torque on the basis of the road-surface friction coefficient, the ground loads of the individual wheels, and the lateral tire forces of the individual wheels,;

vehicle-behavior detector configured to at least detect whether a vehicle is running in an understeer condition;

brake controller configured to perform brake control on an inside turning wheel when the understeer condition is detected; and

engine-torque controller configured to limit an engine torque in accordance with the permissible engine torque when the understeer condition is detected.

2. The vehicle braking-force control device according to claim 1, wherein if a operation of engine braking is detected when the brake controller performs the brake control, the engine-torque controller maintains the engine torque at substantially zero.

3. The vehicle braking-force control device according to claim 1, wherein the vehicle-behavior detector detects the vehicle is in an oversteer condition, and the engine-torque controller reduces an engine torque to an amount lower than that of a current engine torque when the oversteer condition is detected.

4. The vehicle braking-force control device according to claim 1, further comprising brake controller configured to perform brake control on an rear inside turning wheel when the understeer condition is detected.

5. The vehicle braking-force control device according to claim 1, further comprising brake controller configured to perform brake control on an front outside turning wheel when the oversteer condition is detected.

6. A vehicle braking-force control device comprising:

road-surface friction coefficient estimator configured to estimate a road-surface friction coefficient;

ground-load estimator configured to estimate ground loads acting on individual wheels;

lateral-tire-force estimator configured to estimate lateral tire forces acting on the individual wheels;

permissible-engine-torque calculator configured to calculate a permissible engine torque on the basis of the road-surface friction coefficient, the ground loads of the individual wheels, and the lateral tire forces of the individual wheels;

vehicle-behavior detector configured to at least detect whether a vehicle is running in an oversteer condition or an understeer condition;

brake controller configured to perform brake control on an outside turning wheel when the oversteer condition is detected, and to perform brake control on an inside turning wheel when the understeer condition is detected; and

engine-torque controller configured to reduce an engine torque to an amount lower than that of a current engine torque when the oversteer condition is detected, and to limit an engine torque in accordance with the permissible engine torque when the understeer condition is detected.

7. The vehicle braking-force control device according to claim 6, wherein if a operation of engine braking is detected when the brake controller performs the brake control, the engine-torque controller maintains the engine torque at substantially zero.

8. The vehicle braking-force control device according to claim 6, wherein the brake controller performs brake control on an front outside turning wheel when the oversteer condition is detected.

9. The vehicle braking-force control device according to claim 6, wherein the brake controller performs brake control on an rear inside turning wheel when the understeer condition is detected.