Heating of engine and vehicle components increases engine efficiency by reducing the viscosity of various lubricating fluids, thus reducing the energy needed to pump the fluids among the vehicle components. Further, a heated engine converts fuel to shaft work more efficiently than does a cold engine because of lowered heat losses to the combustion chamber. While the engine may be heated relatively rapidly via the heat produced during combustion, transferring the heat to downstream driveline components may take a longer duration, thus delaying when the driveline components reach operating temperature and extending the period that the vehicle operates with reduced efficiency. Further, heating the driveline components via energy sourced from fuel or other stored potential energy reduces fuel economy.
The inventors have recognized the above issues and provide a method to at least partly address them. In one embodiment, a method for a vehicle comprises heating a fluid with kinetic vehicle energy in response to a vehicle braking request, and directing the fluid to a driveline component.
The kinetic vehicle energy produced in response to a vehicle braking request may be used to heat a fluid, and this heated fluid may in turn heat a driveline component. To heat a fluid via kinetic vehicle energy, a viscous brake may be engaged responsive to the vehicle braking request. The viscous brake may decelerate the vehicle as requested by the vehicle braking request, while simultaneously heating the fluid used to lubricate the viscous brake. The heated fluid is then used to heat the driveline components, via a heat exchanger for example. In this way, the driveline components may be heated without relying solely on combustion heat, improving engine efficiency and fuel economy.
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.