A vehicle may be equipped with an accelerator pedal for translating a driver torque request into a powertrain torque request. The powertrain torque request may be provided via an engine or an engine cooperating with a motor to propel the vehicle. By applying or depressing the accelerator pedal, a driver may request additional torque from the vehicle. Vehicle torque may be reduced via releasing or partially releasing the accelerator pedal, thereby allowing the accelerator pedal to return to an initial or base position.
An accelerator pedal or accelerator pedal sensor may degrade over a vehicle's life cycle. The accelerator pedal and/or accelerator pedal sensor may output a signal having a value higher or lower than is expected when the accelerator pedal or accelerator pedal sensor is degraded. Alternatively, or in addition, the accelerator pedal may not travel as freely as is desired during some conditions. Consequently, it may be possible for the accelerator pedal and/or accelerator pedal sensor output to be a substantially constant value representing an accelerator pedal position other than base accelerator pedal position during a condition where it is expected that the accelerator pedal is in its base position. Whether or not the accelerator pedal and/or accelerator pedal position sensor is degraded, it may be desirable to be able to stop the vehicle during conditions of accelerator pedal degradation while a driver is applying vehicle brakes.
If a driver applies vehicle brakes during periods of accelerator pedal degradation, brake performance may be reduced over time. Further, vehicle braking system components may degrade during such conditions. Therefore, it may be desirable to provide sufficient braking power to stop a vehicle when an accelerator pedal demand is requested without significantly increasing braking system degradation.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for operating a vehicle, comprising: reducing powertrain torque in response to a speed of a vehicle being greater than a speed at which vehicle brakes have capacity to fully stop the vehicle at a present temperature of vehicle brakes.
By reducing powertrain torque in response to speed of a vehicle being greater than a speed at which vehicle brakes have capacity to fully stop the vehicle at a present temperature of vehicle brakes, it may be possible to provide a desired level of vehicle braking without causing significant brake component degradation. Further, in some examples, a transmission of the vehicle may be shifted from a forward gear into neutral so as to further reduce an amount of braking force to stop a moving vehicle. In these ways, powertrain power may be reduced to lower the possibility of brake system component degradation while providing braking power sufficient to stop the vehicle.
The present description may provide several advantages. In particular, the approach may reduce the possibility of brake system component degradation. Additionally, the approach may provide a desired amount of braking power to stop a vehicle during conditions of accelerator pedal and/or accelerator pedal sensor degradation. Further, the approach compensates for driving conditions in an effort to provide more consistent vehicle braking during conditions of accelerator pedal and/or accelerator pedal sensor degradation.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.