摘要:
The invention is directed to a tensioning arrangement for adjusting the tension in the saw chain of a chain saw. The cutter bar for the saw chain has an elongated opening for engaging the guiding means upon which the cutter bar is displaceably mounted and guided in the housing of the chain saw. The tensioning arrangement includes a bolt-like drive member which extends through the elongated opening of the cutter bar and acts upon an output member via a transmission. The output member is configured as a slider which entrains the cutter bar for displacing the latter to tension the saw chain. The drive member extends through the elongated opening and beyond the housing as well as the cover of the sprocket wheel to the outside so that it can be adjusted conveniently and simply from outside of the housing for tensioning the saw chain.
摘要:
The invention is directed to an ignition circuit for an internal combustion engine in a portable handheld work apparatus wherein a work tool is driven via a clutch. The ignition circuit includes an ignition time point control which connects a spark plug via a switch to a voltage source in order to trigger an ignition spark. The spark plug is mounted in the combustion chamber of the engine. This connection takes place in dependence upon the crankshaft angle and the rpm of the engine. In order to prevent damage to the clutch because of a blocked work tool, a test value counter driven via a rpm gate circuit is provided. The test value counter increments its value in the pregiven rpm window of the gate circuit with each rotation of the crankshaft and the content of the test value counter is compared to a pregiven limit value by a comparator. The output of the comparator activates a rpm-reducing protective circuit and the output of the comparator indicates reaching or exceeding the limit value.
摘要:
The invention is directed to an ignition arrangement for an internal combustion engine of a handheld portable tool such as a chain saw or the like. The engine has a crankshaft and a fan wheel is seated on the crankshaft for rotation therewith. The ignition arrangement includes a permanent magnet. The magnet has two pole shoes and an exciter coil is mounted on the permanent magnet. The permanent magnet equipped in this way is fixedly mounted on the tool to save weight. A relatively light self-supporting annular member with projections is mounted in the fan wheel. The projections of the annular member and the permanent magnet with its pole shoes conjointly define a magnetic circuit. As the projections pass the pole shoes at a minimal spacing therefrom during operation of the engine, the projections alternately open and close the magnetic circuit thereby causing changes in the flux of this circuit. The flux changes cause a voltage to be inducted in the exciter coil which serves to generate the igniting spark via an appropriate electronic circuit.
摘要:
An automatic starting arrangement for a hand-started internal combustion engine is disclosed. Internal combustion engines of this type have a choke flap and a throttle flap positioned one behind the other in the air-intake channel. In order to ensure a reliable starting of the engine independently of manual positioning activities, the invention provides that in the start position the choke flap is coupled with the throttle flap in a position-dependent manner and the choke flap holds the throttle flap in a position between the full-throttle position and the idle position. The choke flap is brought into an at-rest position via an actuating device which is actuable in dependence upon the operating condition of the engine. The choke flap is decoupled from the throttle flap in the at-rest position.
摘要:
The invention is directed to a pump for pumping a viscous fluid. The pump includes a stator body and a rotor body rotatably mounted in the stator body so as to be coaxial therewith. The stator body has a wall structure having a spiral slot formed therein which communicates with a suction connection formed in the stator body for conducting the viscous fluid to be pumped into the slot. A pressure connection is formed in the stator body for conducting the viscous fluid out of the slot. The suction connection and the pressure connection open into respective peripheral annular slots which are formed between a total of at least three sealing rings on the outer surface of the stator body. The channels for liquids provided in a housing can be disposed in any rotational position relative to the stator. This affords the advantage that the pump stator can be seated with any rotational position in a receiving cylinder of the housing. The sealing rings are injection molded on the stator body to define a tight seat in the receiving cylinder of the housing without additional seals. By a simple insertion of the pump rotor, a connection between the connections of the pump and the channels in the housing is provided which is tight with respect to the medium under pressure.
摘要:
The invention is directed to a fuel injection pump for a two-stroke engine which is especially for portable handheld tools such as motor-driven chain saws or the like. A pneumatic drive chamber is provided in the pump housing which is partitioned by a membrane into a pulse chamber charged by the crankcase pressure and a return chamber. A membrane plate holds the membrane and charges a pump piston which plunges into a pump cylinder for injecting fuel when a pulse is present in the pulse chamber. The pump piston draws fuel in by suction during a return stroke of the membrane plate into a start position determined by a stop. The stop is configured so as to be displaceable in the direction of the stroke of the piston in dependence upon temperature in order to obtain an adaptation of the injected quantity of fuel to the operating temperature of the engine. In this way, the stroke of the pump piston can be varied and therefore also the quantity of fuel supplied by the pump.
摘要:
The invention is directed to a fuel-injection arrangement for a two-stroke engine in a portable handheld work apparatus such as a motor-driven chain saw or the like. Fuel is drawn by suction from a fuel tank by a fuel-feed pump and is made available at the suction connection of an injection pump. The injection pump has a pressure connection which is connected to an injection line through which the engine is supplied with fuel. A rapid start of a two-stroke engine provided with this fuel-injection arrangement is achieved by providing a bypass line which conducts fuel and bypasses the injection pump. A switchable flow valve is mounted in the bypass line. The bypass line opens directly into the intake channel conducting combustion air to the engine so that even without the pump action of the injection pump, adequate fuel is made available to the engine for starting the same.
摘要:
The invention relates to an operating-mode position selector arrangement for an internal combustion engine in a portable handheld tool such as a motor-driven chain saw. The engine includes an electrical ignition system and is supplied with a fuel mixture by a carburetor. In a start position of the operating-mode position selector, the position selector holds the choke flap and the throttle flap of the carburetor in pregiven start positions. In an operating position of the operating-mode position selector, the throttle flap is released for actuation via a throttle lever and the choke flap is fully opened. In a stop position of the operating-mode position selector, an electric contact is closed between a terminal of the electric ignition system and ground. The different positions of the operating-mode position selector are detected electrically. This is achieved in that for the operating position of the operating-mode position selector, the terminal of the electric ignition system is connected to ground via a further electric contact and a resistor. In this way, the operating position of the operating-mode position selector can be distinguished from the stop position and the start position because of the different voltages which adjust in each position.
摘要:
The invention is directed to a fuel injection arrangement for two-stroke engines for portable tools such as motor-driven saws. In known fuel-injecting arrangements, the injection pump is driven by the pressure of the crankcase. The crankcase pressure increases up to a maximum value which remains constant starting with a predetermined rotational speed up to and including the maximum rotational speed. When the peak pressure of the crankcase is constant, the stroke of the pump piston of the injection pump is also constant and so is the quantity of fuel which is pumped. However, at higher speeds where the speed is increasing because of throttling in the air intake channel, the air charge of the cylinder reduces and an overrich mixture is formed. The fuel injection arrangement of the invention provides for an automatic reduction in the quantity of fuel injected at high and at the highest speeds. For adapting the required quantity of fuel at high speeds, a counterpressure is developed in the return chamber of the injection pump in dependence upon speed whereby the stroke of the pump piston is reduced. In this way, a corresponding reduction of the pumped quantity of fuel is achieved.
摘要:
The invention is directed to a method of fuel injection for two-stroke engines, especially for hand-operated tools such as motor-driven saws and the like. The fuel-injection pump is charged with pressure present in the crankcase thereby causing fuel to be pumped for injection and combustion in the engine. The injection operation is triggered and the onset of injection into the combustion chamber is effected when the crankcase pressure rises. The pressure conducted from the crankcase to the injection pump can be automatically regulated as a function of the rotational speed and/or load conditions of the engine.