Damping force control apparatus for vehicle

#The present invention relates to a damping force control apparatus for a vehicle which changes and controls damping forces of shock absorbers disposed between the vehicle body and wheels.

#There have actively been proposed apparatuses and methods which change and control damping forces of shock absorbers disposed between the vehicle body and wheels. For example, Japanese Patent Application Laid-Open (kokai) No. 2007-8373 (Patent Document 1) discloses a suspension-characteristic computation method which provides a design index of a suspension in consideration of the correlation between roll and pitch generated in the vehicle body. In this suspension-characteristic computation method, a pitch moment determined by the geometries of suspensions is computed as the sum of a front-wheel-side ascending/descending force and a rear-wheel-side ascending/descending force. The front-wheel-side ascending/descending force is represented by the product of a front-wheel-side geometry proportional coefficient and the square of a tire lateral force. The rear-wheel-side ascending/descending force is represented by the product of a rear-wheel-side geometry proportional coefficient and the square of a tire lateral force. Further, a pitch moment determined by damping forces of the suspensions is computed from the product of a damping force proportional coefficient and a roll rate. A pitch angle is then computed from the sum of the two calculated pitch moments and the product of the gain and phase delay of the pitch angle in relation to the pitch moment, and a phase difference between the pitch angle and the roll angle is computed on the basis of this computed pitch angle.

#In the case where suspensions are designed in accordance with such a suspension-characteristic computation method, the timings of generations of a roll and a pitch can be synchronized through proper setting of an expansion difference and a contraction difference between shock absorbers disposed on the front wheel side and shock absorbers disposed on the rear wheel side. As a result, maneuvering stability can be improved.

#FIG. 1 is a schematic view showing the configuration of a damping force control apparatus for a vehicle common among embodiments of the present invention.

#FIG. 2 is an explanatory view showing connections between a suspension ECU and various sensors and drive circuits in FIG. 1.

#FIG. 3 relates to a first embodiment of the present invention and is a flowchart of a roll control program executed by the suspension ECU of FIG. 1.

#A damping force control apparatus for a vehicle (hereinafter referred to as a “vehicular damping force control apparatus”) according to an embodiment of the present embodiment will now be described in detail with reference to the drawings. FIG. 1 schematically shows the configuration of a vehicular damping force control apparatus 10 common among embodiments of the present invention. This vehicular damping force control apparatus 10 includes shock absorbers 11a, 11b, 11c, and 11d which connect a vehicle body and wheels (left and right front wheels and left and right rear wheels) of the vehicle.

#The shock absorbers 11a, 11b, 11c, and 11d include rotary valves (electrical actuators) 12a, 12b, 12c, and 12d, each of which changes seamlessly, for example, the diameter of a flow path for working fluid (oil, high-pressure gas, etc.). Although detailed description will be omitted, each of the rotary valves 12a, 12b, 12c, and 12d includes an unillustrated electrical drive means (e.g., an electric motor, a solenoid, or the like). A suspension electric control unit 13 (hereinafter simply referred to as an “ECU 13”) electrically controls the rotary valves 12a, 12b, 12c, and 12d so as to change the diameters of the corresponding flow paths for the working fluid, to thereby seamlessly change the damping force characteristics of the shock absorbers 11a, 11b, 11c, and 11d.

#The suspension ECU 13 is a microcomputer which includes a CPU, ROM, RAM, etc., as main components, and which changes the damping forces of the shock absorbers 11a, 11b, 11c, and 11d, when necessary, by executing various programs, including a roll control program to be described later.