Driving device for a motor scythe

Details Driving device for a motor scythe Driving device for a motor scythe

1999-06-11

2001-03-20

Moulis, Thomas N. (Department: 3747)

Internal-combustion engines

Combustion chamber means having fuel injection only

Having a particular relationship between injection and...

C123S185100

Reexamination Certificate

active

06202625

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a driving device for a motor driven vegetation cutter, or the like, such as a lawn mower, grass or weed trimmer, hedge clipper or leaf blower, with a two cycle engine having a fuel injection valve, an output coupling placed in a coupling box, cooling air intake and discharge devices, a fuel pump, and a starter housing, as well as possible other additional components.
PRIOR ART
For motor driven vegetation cutters, it has been proved to be advantageous to use a combustion engine as the driving gear. Hereby an improvement, i.e. a reduction of the pollutant emission is obtained, while maintaining or neutralizing the power. Simultaneously, the use of fuel injection results in a compact construction and a reduction of weight. However, the use of fuel injection also leads to quite special problems.
For driving devices for motor driven vegetation cutters known by the prior art, the driving gear is so adjusted that the axis of the crankshaft is placed linearly to the main shaft or the main pipe, and thus to the power take-off. The fan wheel and the output coupling are driven directly by a crankshaft and lie on the power take-off side of the motor unit. The cooling air is sucked generally from below the crankcase which is placed under the motor unit and is discharged in a plane above the axis of the crankshaft where it flows over the motor unit which has bulkheads serving for the air conduction.
Motor driven vegetation cutters should, as hand-held equipment, have a compact construction especially in the area of the driving device and their weight should be as low as possible. This is partially contrary to an optimal cooling which is still significant for the motor life, even if not necessary for operation. An optimal combustion through adequate air-fuel conduction and an optimal ignition are equally desirable.
SUMMARY OF THE INVENTION
Thus, it is an object of this invention to improve the above stated driving device with regard to compact construction and to configure it so as to obtain optimal motive functions, whereby an optimal cooling of the temperature sensitive parts of the driving device can simultaneously be maintained.
The aim of the invention is reached by way of a driving device having a cylinder with a fuel injection valve, an output coupling in a coupling box, cooling air intake and discharge devices, a fuel pump and a starter box, wherein the output coupling box and the starter box are placed on opposite sides of the cylinder longitudinal axis and the injection valve is set with its jet directed onto the cylinder head. An arrangement of the fuel injection valve above the starter box fully exploits the relatively big existing space. Since the injection valve is not placed parallel to the ignition plug longitudinal axis with regard to its longitudinal axis orientation, the overall height of the whole driving device can still be minimized. Furthermore, the fuel is directed in the direction of the ignition plug by the jet direction, whereby the combustion can be optimalized.
The nozzle opening of the fuel injection valve is preferably placed above or in the upper area of a transfer port (of the two cycle engine).
The coupling box and a cooling air fan wheel are placed the one near the other directly on the crankshaft on the power take-off side of the cylinder, while the starter box is placed on a tail shaft on the opposite side of the cylinder, and the fuel pump, which is also directly driven by the crankshaft, is placed between the starter box and the crankcase placed below the engine unit. The arrangement of the fuel pump provides the advantage that the cooling air which flows along under the crankcase also flows around the pump case, which is getting warmer when in operation, and cools this pump case. Moreover, by means of the arrangement of the fuel pump on the same side of the cylinder as the injection valve, a short fuel supply line to the injection valve can be provided.
For the function control, according to another embodiment of the invention, the fuel injection valve is connected to an electronic control unit which is preferably placed above or in the upper area of the driving device, near a combustion air intake casing which has the advantage of short connecting lines to the sensors for the temperature and operating status registration. There is another cooling effect by the flowing combustion intake air if the control device is located in the corresponding intake area of the intake casing.


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