Charging system and method for charging an electrical energy storage device

Abstract

The invention relates to a charging system and a method for charging the electrical energy storage device of at least one electrically powered motor vehicle equipped with pneumatic tires, comprising a stationary charging device and at least one such motor vehicle, wherein the charging device is connected to an electrical current source and is configured to supply the energy storage device of the at least one motor vehicle with a charging current via a connecting device, characterized in that the charging system further comprises a heating device assigned to the pneumatic tires of the motor vehicle in order to heat the pneumatic tires to a predetermined operating temperature during the charging of the energy storage device.

Description

The invention relates to a charging system for charging the electrical energy store of at least one motor vehicle equipped with pneumatic tires and electrically driven, comprising a stationary charging device and at least one such motor vehicle, wherein the charging device is connected to an electrical power source and is configured to apply a charging current to the energy store of the at least one motor vehicle via a connecting device.The invention also relates to a method for charging the electrical energy store of at least one motor vehicle equipped with tires and electrically driven, in which the energy store of the at least one motor vehicle is charged with a charging current of a stationary charging device via a connecting device.Charging systems of the type mentioned at the beginning are known. They serve to charge the electrical energy store, in particular the rechargeable battery, of the electrically driven motor vehicle with electrical energy during a break in travel. The stationary charging devices used in this case are frequently distinguished in the case of cable-bound systems into so-called wall boxes or fast charging columns as a function of the maximum charging current provided. Inductive charging devices are also known which consist of a transmitting coil embedded in the underlying surface or resting on it and a receiver coil arranged on the vehicle underlying surface.It is also known that the pneumatic tires conventionally used on electric drive motor vehicles have a significantly higher rolling resistance when used at low ambient temperatures. This increased rolling resistance results in a loss in the vehicle range of the electrically driven motor vehicle. Internal investigations show that a loss of the available range of up to 20% can occur in an electrically driven motor vehicle if the pneumatic tires used on the motor vehicle are operated on a test drum far below the legally provided thermal ambient conditions for rolling resistance tests. These legally provided ambient conditions provide a test at room temperature of 25° C.±5° C. and a temperature of about 35° C. to 45° C. achieved after warm-up for 30 min on the inner tire layer.It is an object of the invention to propose a charging system and a method of the type mentioned at the beginning, which overcome the disadvantages of the prior art.To achieve the object set, according to the invention, a charging system according to the features of patent claim 1 is proposed.A method according to the invention for achieving the stated object is the subject matter of claim 6.Advantageous embodiments and developments of the invention are the subject matter of the respective dependent claims.The invention is based on the finding that during the charging process of the electrical energy store of the motor vehicle, in which the electrically driven motor vehicle is usually stationary, a virtually unlimited amount of electrical energy is available by the stationary charging device used for charging.The invention therefore proposes using a small proportion of the available electrical energy during the charging of the energy store to heat or precondition the pneumatic tires of the motor vehicle which is in charge to such a temperature via a suitable heating device which is operated with the small proportion of electrical energy that they can be used in the optimum temperature-dependent rolling resistance range after the charging process has ended. If the charging is ended to this extent and the electrically driven motor vehicle equipped with pre-heated pneumatic tires is put into operation, the rolling resistance is reduced to a minimum by the pneumatic tires and a distinct increase in the range of the electrically driven motor vehicle is achieved.The charging system proposed within the scope of the invention is configured such that the charging system comprises a heating device assigned to the pneumatic tires of the motor vehicle in order to heat the pneumatic tires to a predeterminable operating temperature during the charging of the energy store.According to a proposal of the invention, for this purpose, either in the region of the stationary charging device or the on-board electric system of the motor vehicle of the charging system according to the invention, a tapping device is provided, by means of which a part of the charging current can be tapped off and fed to the heating device, so that the latter can then generate the desired heat.In this case, the tapping device can either be in operation permanently over the entire charging process or else be controlled by the battery management in such a way that, for example, shortly before a predetermined state of charge of the electrical energy store is reached, the heating device for heating the pneumatic tires is put into operation.According to a proposal of the invention, the heating device can be arranged on the motor vehicle, for example in the region of the wheel arch boxes. The heating device according to a further proposal of the invention can also be provided in the region of a vehicle wheel equipped with a pneumatic tire, for example on or in the deep bed of a rim of the vehicle wheel.Alternatively, the heating device of the charging system according to the invention can also be provided stationary, in particular if the stationary charging device comprises a standing surface for the motor vehicle assigned to the charging device and usually also marked. In this case, the heating device can be integrated into the footprint, for example let into the surface on which the pneumatic tires of the motor vehicle to be charged usually come to a standstill at the charging device.According to a further proposal of the invention, the heating device can be, for example, a radiant thermal heater, in particular an electric resistance heater, which emits infrared heat beams onto the pneumatic tires. Such infrared radiation is well absorbed by the pneumatic tires, which are usually black.In addition, it is also possible to use thermal convection within the scope of the heating device of the charging system provided according to the invention for heating the pneumatic tires during the charging of the electrical energy store. A device for generating thermal convection that is possible in this context can be, for example, a steam generator that generates a steam flow from the supplied electrical energy and water as heat transfer medium to the pneumatic vehicle tires.Furthermore, a heating device can also be used within the scope of the invention, which emits electromagnetic radiation, for example microwave radiation. This electromagnetic radiation excites and heats the metallic parts in the pneumatic tire, for example, belts and wire cores. As a result, the rubber components inside the pneumatic tire are also heated by heat conduction from the belts and wire cores to the rubber material.All heating devices explained above can be provided both stationary on the charging device and mobile on the motor vehicle. A heater provided on the automobile may also be integrated with the tire bead of the pneumatic tires used on the automobile, or the pneumatic tires may support a heater on the inside of the pneumatic tire or the tire bead. This heating device can be heated, for example, from the outside and transfers this heat to the tire belts and into the interior of the pneumatic tire because of its good thermal conductivity.The method proposed within the scope of the invention provides that during the charging of the energy store, the pneumatic tires of the motor vehicle are heated to a predeterminable operating temperature.With the charging system and the method described above, the range of a battery-electric motor vehicle can be easily increased, in particular at the low external temperatures which are critical in any case, by a small portion of the electrical energy provided for charging being converted into heat in a suitable heating device which heats the pneumatic tires to a temperature level at which the rolling resistance of the pneumatic tires is configured to be optimally low.A suitable temperature level to which the heating device heats the pneumatic tires during the charging of the energy store is, for example, between 35 and 45° C. However, additional ambient conditions may optionally be included here. For example, a cold tire on a snow-covered roadway achieves better traction values than a warm tire. Also, under very high ambient conditions, such as those occurring in summer, further heating of the pneumatic tire may be unnecessary or even harmful.According to the invention, a regulating device is therefore proposed by means of which the heating power of the heating device is regulated as a function of the measured ambient temperature. A possible control curve of such a control device can operate the heating device at full power, for example at ambient temperatures below 0° C., in order to bring about heating of the pneumatic tires by up to 40 K. Above the ambient temperature of 0° C., the heating power can then be throttled stepwise, in order to bring about, for example, heating of the pneumatic tire of only 5 K to 10 K at temperatures between 20° C. and 30° C., and above an ambient temperature of, for example, 30° C., the heating device could be completely deactivated.

Claims

Charging system for charging the electrical energy store of at least one electrically driven motor vehicle equipped with pneumatic tires, comprising a stationary charging device and at least one such motor vehicle, wherein the charging device is connected to an electrical power source and is configured to apply a charging current to the energy store of the at least one motor vehicle via a connecting device, characterized in that the charging system further comprises a heating device assigned to the pneumatic tires of the motor vehicle in order to heat the pneumatic tires to a predeterminable operating temperature during the charging of the energy store.Charging system according to Claim 1, characterized in that a tapping device is provided, by means of which a part of the charging current can be tapped off and fed to the heating device.Charging system according to Claim 1 or 2, characterized in that the heating device is arranged on the motor vehicle and / or in the region of a vehicle wheel carrying the pneumatic tire.Charging system according to either of Claims 1 and 2, characterized in that the stationary charging device comprises a standing surface for the motor vehicle which is assigned to the charging device, and the heating device is integrated into the standing surface.Charging system according to one of Claims 1 to 4, characterized in that the heating device is formed by an electrical resistance heater, an infrared heat radiator, a steam generator or an electromagnetic radiation source.Charging system according to one of Claims 1 to 5, characterized in that a regulating device is provided, by means of which the heating power of the heating device can be regulated as a function of the ambient temperature.Method for charging the electrical energy store of at least one electrically driven motor vehicle equipped with pneumatic tires, in which the energy store of the at least one motor vehicle is charged with a charging current of a stationary charging device via a connecting device, characterized in that, during the charging of the energy store, the pneumatic tires of the motor vehicle are heated to a predeterminable operating temperature.Method according to Claim 7, characterized in that a part of the charging current is branched off and fed to an electrical heating device for the pneumatic tires.Method according to Claim 7 or 8, characterized in that the heating device is arranged on the motor vehicle.Method according to Claim 7 or 8, characterized in that a footprint for the motor vehicle is provided during charging, and the pneumatic tires are heated by means of a heating device integrated into the footprint of the motor vehicle.Method according to one of Claims 7 to 10, characterized in that the heating device is formed by an electrical resistance heater, an infrared heat radiator, a steam generator or an electromagnetic radiation source.Method according to any one of Claims 7 to 11, characterized in that the heating of the pneumatic tyres is controlled as a function of the ambient temperature.