HANDHELD WORK APPARATUS HAVING A CONTROL UNIT FOR AN ELECTRIC HEATING ELEMENT

摘要

The invention relates to a portable, handheld work apparatus such as a chain saw having at least one combustion engine (8) for driving a work tool, wherein handles (3, 4) are arranged for guiding the work apparatus (1). For the operation of the combustion engine (8), an air/fuel mixture is supplied to the latter via a carburetor (10), wherein the carburetor (10) is provided with an electrical heating element (13) for heating to a given temperature. The heating element (13) is connected to a switch (LS) via which electrical energy, which is provided by a generator (23) driven by the combustion engine (8), is supplied. When a given temperature is exceeded, the switch (LS) interrupts the energy supply. In order to achieve an exact temperature control, the ohmic resistance value of the heating element in dependence on the temperature is stored in a memory (48). The current (I) flowing through the heating element (13) and the voltage drop (U H) at the heating element are measured and the instantaneous resistance of the heating element (13) is calculated from these values. The calculated, instantaneous ohmic resistance value is compared to the value stored in the memory (48) in order to open or close the switch (LS) in dependence on the result of the comparison.