EP3660284A1 - Four-stroke engine lubricated with pre-mix, hand-held work device with a four-stroke engine and method for operating a four-stroke engine lubricated with a compound - Google Patents
Four-stroke engine lubricated with pre-mix, hand-held work device with a four-stroke engine and method for operating a four-stroke engine lubricated with a compound Download PDFInfo
- Publication number
- EP3660284A1 EP3660284A1 EP18209488.8A EP18209488A EP3660284A1 EP 3660284 A1 EP3660284 A1 EP 3660284A1 EP 18209488 A EP18209488 A EP 18209488A EP 3660284 A1 EP3660284 A1 EP 3660284A1
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- EP
- European Patent Office
- Prior art keywords
- valve
- stroke engine
- fuel
- stroke
- opening
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01M—LUBRICATING OF MACHINES OR ENGINES IN GENERAL; LUBRICATING INTERNAL COMBUSTION ENGINES; CRANKCASE VENTILATING
- F01M9/00—Lubrication means having pertinent characteristics not provided for in, or of interest apart from, groups F01M1/00 - F01M7/00
- F01M9/04—Use of fuel as lubricant
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B75/00—Other engines
- F02B75/02—Engines characterised by their cycles, e.g. six-stroke
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01M—LUBRICATING OF MACHINES OR ENGINES IN GENERAL; LUBRICATING INTERNAL COMBUSTION ENGINES; CRANKCASE VENTILATING
- F01M1/00—Pressure lubrication
- F01M1/04—Pressure lubrication using pressure in working cylinder or crankcase to operate lubricant feeding devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01M—LUBRICATING OF MACHINES OR ENGINES IN GENERAL; LUBRICATING INTERNAL COMBUSTION ENGINES; CRANKCASE VENTILATING
- F01M3/00—Lubrication specially adapted for engines with crankcase compression of fuel-air mixture or for other engines in which lubricant is contained in fuel, combustion air, or fuel-air mixture
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B33/00—Engines characterised by provision of pumps for charging or scavenging
- F02B33/02—Engines with reciprocating-piston pumps; Engines with crankcase pumps
- F02B33/04—Engines with reciprocating-piston pumps; Engines with crankcase pumps with simple crankcase pumps, i.e. with the rear face of a non-stepped working piston acting as sole pumping member in co-operation with the crankcase
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B33/00—Engines characterised by provision of pumps for charging or scavenging
- F02B33/02—Engines with reciprocating-piston pumps; Engines with crankcase pumps
- F02B33/26—Four-stroke engines characterised by having crankcase pumps
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B63/00—Adaptations of engines for driving pumps, hand-held tools or electric generators; Portable combinations of engines with engine-driven devices
- F02B63/02—Adaptations of engines for driving pumps, hand-held tools or electric generators; Portable combinations of engines with engine-driven devices for hand-held tools
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B75/00—Other engines
- F02B75/16—Engines characterised by number of cylinders, e.g. single-cylinder engines
- F02B75/18—Multi-cylinder engines
- F02B75/24—Multi-cylinder engines with cylinders arranged oppositely relative to main shaft and of "flat" type
- F02B75/243—Multi-cylinder engines with cylinders arranged oppositely relative to main shaft and of "flat" type with only one crankshaft of the "boxer" type, e.g. all connecting rods attached to separate crankshaft bearings
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D41/003—Adding fuel vapours, e.g. drawn from engine fuel reservoir
- F02D41/0032—Controlling the purging of the canister as a function of the engine operating conditions
- F02D41/0035—Controlling the purging of the canister as a function of the engine operating conditions to achieve a special effect, e.g. to warm up the catalyst
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M17/00—Carburettors having pertinent characteristics not provided for in, or of interest apart from, the apparatus of preceding main groups F02M1/00 - F02M15/00
- F02M17/38—Controlling of carburettors, not otherwise provided for
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M37/00—Apparatus or systems for feeding liquid fuel from storage containers to carburettors or fuel-injection apparatus; Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines
- F02M37/0011—Constructional details; Manufacturing or assembly of elements of fuel systems; Materials therefor
- F02M37/0023—Valves in the fuel supply and return system
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M7/00—Carburettors with means for influencing, e.g. enriching or keeping constant, fuel/air ratio of charge under varying conditions
- F02M7/12—Other installations, with moving parts, for influencing fuel/air ratio, e.g. having valves
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B75/00—Other engines
- F02B75/02—Engines characterised by their cycles, e.g. six-stroke
- F02B2075/022—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle
- F02B2075/027—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle four
Definitions
- the invention relates to a mixed-lubricated four-stroke engine of the type specified in the preamble of claim 1, a hand-held implement with a mixed-lubricated four-stroke engine and a method for operating a mixed-lubricated four-stroke engine of the type specified in the preamble of claim 13.
- a generic mixed-lubricated four-stroke engine is known.
- a flow connection is provided for lubricating the crankcase, which connects the intake duct to the crankcase.
- a mixture preparation device is provided for supplying fuel to the intake duct.
- Mixture preparation devices of this type are usually carburettors in which the amount of fuel supplied to the intake duct depends on the negative pressure prevailing in the intake duct.
- the invention has for its object to provide a four-stroke engine of the generic type, which enables improved control of the amount of fuel supplied with good lubrication of the crankcase. Another object of the invention is to provide a hand-held implement with a four-stroke engine. Another object of the invention is to provide a method for operating a mixed-lubricated four-stroke engine.
- this object is achieved by a four-stroke engine with the features of claim 1.
- the object is achieved by an implement having the features of claim 12.
- the object is achieved by a method for operating a mixed-lubricated four-stroke engine with the features of claim 13.
- the invention provides that the fuel quantity supplied to the fuel opening is controlled by a fuel valve.
- the amount of fuel supplied to the internal combustion engine can be controlled more precisely than, for example, in the case of a fuel supply in which the amount of fuel drawn is solely dependent on the negative pressure in the intake duct. This is the case, for example, with carburettors that work without a controlled fuel valve.
- the control of the four-stroke engine is designed to control the fuel valve depending on the position of the crankshaft.
- the opening time and the closing time of the fuel valve are therefore not only selected as a function of the quantity of fuel to be supplied, but also as a function of the position of the crankshaft, that is to say as a function of the crankshaft angle. It is provided that the fuel valve is open at least during part of the compression stroke of the four-stroke engine. During the compression stroke, the pressure in the combustion chamber rises and the inlet valve closes shortly after the compression stroke begins. It has now been shown that the fact that the fuel valve is open at least also during part of the compression stroke of the four-stroke engine enables improved suction of fuel into the crankcase interior via the flow connection.
- the fuel valve is only opened before and / or during the intake stroke, as in the prior art, the fuel fed into the intake duct largely, in particular almost completely, gets into the combustion chamber, so that adequate lubrication of the crankcase cannot be ensured.
- the fuel valve is opened regardless of the position of the crankshaft and closed, there are strong fluctuations in the mixture composition in the combustion chamber, which lead to a restless run of the four-stroke engine.
- the intake stroke of the four-stroke engine is the stroke in which the piston increases the volume of the combustion chamber and the intake valve is opened at least temporarily, in particular over the entire stroke.
- the compression stroke is the stroke in which the piston reduces the volume of the combustion chamber and in which the exhaust valve is closed.
- the intake valve is also at least temporarily closed in the compression cycle.
- the work cycle is the cycle in which the piston increases the volume of the combustion chamber and the inlet valve is closed. At the end of the compression stroke or at the beginning of the work stroke, combustion takes place in the combustion chamber.
- the exhaust stroke is the stroke in which the exhaust valve is opened and the piston reduces the volume of the combustion chamber, whereby exhaust gases are expelled through the exhaust.
- the intake stroke, compression stroke, work stroke and extension stroke follow each other in this order.
- the fuel valve is advantageously opened in each engine cycle both during part of the intake stroke and during at least part of the compression stroke.
- the fuel valve opens during the compression stroke and is opened during the working stroke, the push-out stroke and at least part of the intake stroke.
- the fuel valve can also be closed during the work cycle and the push-out cycle.
- the fuel valve is advantageously opened at least once during each opening period of the inlet valve. This ensures an adequate supply of fuel to the combustion chamber.
- at least 20% of the opening period of the fuel valve is advantageously in the compression cycle. It has been shown that good lubrication of the moving parts in the interior of the crankcase can be achieved as a result.
- the mixture formation device is a carburetor.
- the carburetor has at least one fuel opening which is fed by a fuel channel.
- the fuel quantity flowing through the fuel channel is advantageously controlled by the fuel valve.
- the fuel opening is preferably arranged in the region of a venturi section of the carburetor, and the fuel is sucked into the suction channel due to the negative pressure prevailing in the intake duct when the fuel valve is open. Accordingly, there is no fuel injection into the intake duct, but an intake.
- the fuel valve is preferably an electromagnetic valve.
- the fuel valve is open when de-energized. In an alternative advantageous embodiment it can also be provided that the fuel valve is closed in the de-energized state.
- the inlet valve and the outlet valve are advantageously controlled via a valve train depending on the position of the crankshaft.
- the valve train can comprise push rods in a known manner, which act on rocker arms for actuating the inlet valve and the outlet valve.
- the valve train can comprise a drive wheel and a driven wheel, which are coupled to one another via a transmission means such as a chain, a belt or the like, the driven wheel driving a camshaft which actuates the inlet valve and the outlet valve.
- the valve train can be designed as a gear transmission.
- Other known designs for the valve train can also be advantageous.
- the valve train is advantageously arranged in a valve train chamber, at least part of the valve train chamber forming at least part of the flow connection.
- the valve train is lubricated by the mixture flowing out of the intake duct into the interior of the crankcase and back.
- the valve train is designed as a rocker arm drive, and the valve drive chamber comprises a rocker arm chamber and at least one connecting channel, which form parts of the flow connection.
- the rocker arm space is advantageous via at least one connection opening with the intake duct connected.
- a connection opening can be provided which connects the intake duct to the connection duct or a cam chamber of the four-stroke engine.
- the connection opening to the intake duct can be permanently opened or controlled, for example, as a function of the speed.
- the four-stroke engine rotates at full speed at a speed of 5,000 to 11,000 revolutions per minute. It has been shown that, in particular in a speed range of 5,000 to 11,000 revolutions per minute, the intended opening of the fuel valve can ensure sufficient lubrication of the interior of the crankcase even during part of the compression stroke, even at full load.
- the four-stroke engine preferably rotates at full speed at a speed of 5,000 to 9,000 revolutions per minute. If the opening and closing times of the fuel valve are not adapted to the engine cycle at such comparatively low full-load speeds, an inadequate fuel supply and thus an uneven running of the internal combustion engine and inadequate lubrication of the crankcase interior can result.
- the combustion chamber being delimited by a piston movably mounted in the cylinder, the piston rotatingly driving a crankshaft rotatably mounted in a crankcase interior
- the four-stroke engine having an intake duct which opens into the combustion chamber via an inlet opening controlled by an inlet valve, an outlet duct controlled by an outlet valve leading from the combustion chamber, with a mixture formation device, the mixture formation device comprising at least one fuel opening which opens into the intake duct
- the four-stroke engine for lubrication of the crankcase interior has a flow connection that connects the intake duct to the crankcase interior with a connection opening that opens into the intake duct downstream of the mixture formation device the fuel quantity supplied to the fuel opening is controlled by a fuel valve, and the fuel valve is controlled depending on the position of the crankshaft in such a way that the fuel valve is open at least also during part of the compression stroke of the four-stroke engine.
- Fig. 1 shows schematically a four-stroke engine 1, which can be used to drive the tool in a hand-held implement.
- the hand-held implement can be, for example, a chain saw, a grinder, a brush cutter or the like.
- a hand-held blower 50 is shown as an exemplary embodiment of a working device.
- the tool of a blower 50 is a fan wheel, not shown, which promotes a flow of working air through a blow pipe 52.
- the blower 50 has a handle 51 with which the blower 50 can be guided.
- the blower 50 also has a housing 53 in which the in Fig. 1 schematically illustrated four-stroke engine 1 is arranged.
- a starter device (not shown in detail), in particular a cable starter, whose starter handle 54 protrudes from the housing 53, serves to start the four-stroke engine 1.
- the four-stroke engine should preferably be started manually by an operator.
- the four-stroke engine 1 has a cylinder 2, in which a combustion chamber 3 is formed.
- the combustion chamber 3 is delimited by a piston 4, which is mounted such that it can move back and forth in a cylinder bore 43 of the cylinder 2.
- Fig. 1 shows the four-stroke engine 1 during the downward stroke of the piston 4, in which the piston 4 moves in the direction of an arrow 32.
- the volume of the combustion chamber 3 increases.
- the volume of the combustion chamber 3 decreases.
- the piston 4 drives a crankshaft 7 rotatably mounted in a crankcase 5 via a connecting rod 8.
- the crankshaft 7 is rotatably supported about an axis of rotation 44.
- the crankshaft 7 rotates in the direction of an arrow 31 during operation.
- the rotational position of the crankshaft 7 is indicated as the crankshaft angle ⁇ .
- the crankshaft angle ⁇ is 4 0 ° at the top dead center of the piston and 4 180 ° at the bottom dead center of the piston.
- a crankcase interior 6 is formed in the crankcase 5.
- the four-stroke engine 1 has an intake duct 21 for supplying a fuel / air mixture.
- a section of the intake duct 21 is formed in a mixture formation device 17.
- the mixture formation device 17 is advantageously a carburetor.
- the mixture formation device 17 has a venturi section 29, in which a fuel opening 18 opens into the intake duct 21.
- the fuel opening 18 is connected via a fuel channel 33 to a fuel valve 19, to which fuel is supplied from a fuel tank (not shown).
- the fuel valve 19 controls the amount of fuel supplied to the fuel opening 18.
- the fuel valve 19 is advantageously an electromagnetic valve.
- the fuel valve 19 is controlled by a controller 20.
- the fuel valve 19 is activated as a function of the rotational position of the crankshaft 7, ie as a function of the crankshaft angle ⁇ .
- the controller 20 is designed in such a way that the fuel valve 19 in the corresponding manner, which is coordinated with the engine cycle can be controlled.
- the controller 20 is equipped with a rotational position detection 47 for detecting the rotational position of the crankshaft 7, that is to say for detecting the crankshaft angle ⁇ .
- the rotational position detection 47 can have, for example, at least one sensor for detecting the rotational position of the crankshaft 7.
- the rotational position detection 47 can also determine the rotational position of the crankshaft 7, that is to say the crankshaft angle ⁇ , from other signals, for example the voltage induced in an ignition device of the four-stroke engine 1 or the voltage induced in a generator of the four-stroke engine 1 or a combination of several signals. Detection of the rotational position of the crankshaft 7 from other signals, for example with the aid of the pressure prevailing in the interior of the crankcase 6, can also be provided.
- the fuel valve 19 is a normally open valve.
- the fuel valve 19 can also be a fuel valve that is closed in the de-energized state.
- a throttle element 16 in the exemplary embodiment a throttle valve, is pivotably mounted downstream of the fuel opening 18. Via the throttle element 16, an operator can adjust the amount of fuel / air mixture sucked in through the intake duct 21.
- the intake duct 21 opens with an inlet opening 22 on the combustion chamber.
- the inlet opening 22 is controlled by an inlet valve 24.
- the inlet valve 24 is movable in the direction of a double arrow 45.
- the inlet valve 24 has a valve plate 27, which opens or closes the inlet opening 22 depending on the position of the inlet valve 24.
- An outlet opening 23 leads out of the combustion chamber 3 and is opened or closed by a valve plate 28 of an exhaust valve 25.
- An outlet duct 26 adjoins the outlet opening 23, via which exhaust gases flow out of the combustion chamber 3.
- An exhaust silencer, not shown, is advantageously connected to the outlet duct 26.
- valve train 34 is provided, which is shown in FIG Fig. 1 schematically indicated and closed Fig. 2 is described in detail.
- the valve train 34 is arranged in a valve train chamber 30.
- the intake duct 21 is connected to the crankcase interior 6 via a flow connection.
- the flow connection comprises the valve drive chamber 30 and a connection opening 11 Fig. 1 shows, the connection opening 11 opens into the intake duct 21 with an opening 42.
- the opening 42 is arranged downstream of the throttle element 16.
- the valve drive chamber 30 comprises a rocker arm chamber 10 and at least one connection channel 9, which in the exemplary embodiment is connected to the crankcase interior 6 via a further connection opening 48.
- Fig. 2 schematically shows a possible embodiment variant for the design of the valve train 34.
- a drive wheel 35 is connected to the crankshaft 7 in a rotationally fixed manner, which meshes with an output wheel 36.
- the diameter of the driven wheel 36 is significantly larger than that of the drive wheel 35, so that the drive wheel 35 and the driven wheel 36 form a reduction gear.
- a cam 37 is fixed to the driven gear 36, against which two rocker arms 38 rest.
- the driven gear 36 and the cam 37 advantageously rotate at half the speed of the crankshaft 7.
- a support 41 is formed on each rocker arm 38, on which a push rod 39 rests.
- the push rods 39 each actuate a rocker arm 40.
- the rocker arms 40 are arranged in the rocker arm space 10 and in turn actuate the push rods of the inlet valve 24 and the outlet valve 25.
- the valves 24 and 25 ( Fig. 1 ) are spring-loaded in the direction of their closed position and are moved by the rocker arms 40 in the direction of their open position when the push rods 39 move further away from the crankcase 5 into the rocker arm space 10.
- the push rods 39 run through the connecting channels 9.
- the driven wheel 36, the cam 37 and the rocker arm 38 are arranged in a cam chamber 46.
- the cam chamber 46 is over the in Fig. 1 schematically shown connection opening 48 connected to the crankcase interior 6.
- Fig. 3 shows schematically the course of the pressure p in the combustion chamber 3, the opening period A of the exhaust valve, the opening period E of the intake valve and the opening period T of the fuel valve 19 over the crankshaft angle ⁇ .
- Fig. 3 shows the course over two engine cycles. Each engine cycle comprises an operating cycle 14, an extension cycle 15, an intake cycle 12 and a compression cycle 13, which follow one another in this order.
- the inlet valve 24 and the outlet valve 25 are closed.
- the pressure p in the combustion chamber 3 reaches its maximum at the beginning of the work cycle 14 and then drops sharply.
- the pressure maximum results from the combustion of the fuel / air mixture in the combustion chamber 3.
- the piston 4 moves in the direction from the combustion chamber 3 to the crankcase interior 6, ie in the direction of the arrow 32 in Fig. 1 .
- the piston 4 executes a downward stroke, the volume of the combustion chamber 3 increasing. Due to the increasing volume in the combustion chamber 3, the pressure drops.
- crankshaft angle ⁇ 180 °
- crankshaft angle ⁇ 180 ° to 360 ° in the diagram in Fig. 3
- the extension stroke 15 extends.
- the piston 4 moves in the upward stroke from the crankcase interior 6 towards the combustion chamber 3.
- the piston 4 increases the volume of the crankcase interior 6 and decreases the volume of the combustion chamber 3.
- the opening period A of the exhaust valve is in Fig. 3 represented by a block that begins at an opening time a 1 and ends at a closing time a 2 .
- the opening period E of the intake valve 24 is in Fig. 3 represented by a block that begins at an opening time e 1 and ends at a closing time e 2 .
- the outlet valve 25 opens at the opening time a 1 , which is in the second half of the work cycle 14. As a result, exhaust gases flow out of the combustion chamber 3 through the opened outlet opening 23 into the outlet channel 26. During the extension stroke 15, the piston 4 pushes the exhaust gases through the outlet opening 23. During the extension stroke 15, the outlet valve 25 is fully opened.
- the exhaust valve 25 closes at a closing time a 2 , which is in the intake stroke 12 following the push-out stroke 15.
- the piston 4 moves in a downward stroke from the combustion chamber 3 in the direction of the crankcase interior space 6.
- the pressure p in the combustion chamber 3 is low, so that fuel / air mixture from the intake duct 21 into the combustion chamber 3 through the opened inlet opening 22 is sucked in.
- the inlet valve 24 opens at the time of opening e 1 , which in the exemplary embodiment lies in the second half of the extension stroke 15.
- the inlet valve 24 is fully open.
- the inlet valve 24 closes at a closing time e 2 , which is in the compression stroke 13.
- the compression stroke 13 connects to the intake stroke 12.
- the piston 4 moves from the crankcase interior 6 towards the combustion chamber 3 and thereby compresses the fuel / air mixture arranged in the combustion chamber 3.
- the inlet valve 24 is closed, the pressure in the combustion chamber 3 rises sharply, such as Fig. 2 shows.
- the mixture is then ignited at the end of the compression stroke 13 and the piston is accelerated in the direction of the crankcase interior 6, as already described for the first engine cycle.
- the fuel valve 19 opens at an opening time t 1 and closes at a closing time t 2 .
- this is shown schematically by the energy supply to the de-energized open fuel valve 19.
- Energy is supplied to the fuel valve 19 while the fuel valve 19 is closed, in the exemplary embodiment over a closing period S which extends from the closing time t 2 to the subsequent opening time t 1 .
- the fuel valve 19 is a fuel valve 19 that is closed when de-energized.
- the opening time t 1 lies in the compression stroke 13.
- the fuel valve 19 opens at an opening time t 1 , which is simultaneously at the closing time e 2 , at which the inlet opening 22 closes.
- the piston 4 is in the upward stroke. This increases the volume of the crankcase interior 6. Since the inlet valve 24 is closed, the fuel / air mixture is drawn from the intake duct 21 into the crankcase interior 6 via the valve drive chamber 30. Effective lubrication of the moving parts in the crankcase interior 6 is thereby achieved.
- At least 20%, in particular at least 30%, preferably at least 40% of the opening period T of the fuel valve 19 is advantageously in the compression cycle 13 in each engine cycle.
- the fuel valve 19 is advantageously over at least 20%, in particular at least 30%, preferably at least 40% of the compression cycle 13 open. In the exemplary embodiment, the fuel valve 19 is opened over more than half of the compression stroke 13.
- the fuel valve 19 remains open until a time t 2 , which is in the intake stroke 12.
- the fuel valve 19 is therefore advantageously opened over the entire working cycle 14 and the entire push-out cycle 15. Due to the pulsation of the mixture in the intake duct 21, fuel / air mixture can also be conveyed into the crankcase interior 6 in the valve drive chamber 30 during this time.
- the pulsation in the intake duct 21 arises, for example, from the change in volume of the crankcase interior 6 when the piston 4 is moving.
- the closing point in time t 2 is at the end of the intake stroke 12.
- the position of the closing point in time t 2 during the intake stroke 12 makes it possible to set the richness of the fuel / air mixture flowing into the combustion chamber.
- the fuel valve 19 is closed.
- the inlet valve 24 is open.
- the opening period E of the inlet valve 24 and the closing period S, during which the fuel valve 19 is closed, therefore overlap a period D. Both the inlet valve 24 and the fuel valve 19 are open over a period B.
- Fig. 3 schematically shows a further, alternative closing time t 2 'for the fuel valve 19, which is earlier than the closing time t 2 .
- the alternative closing time t 2 ' is shortly after the closing time a 2 of the exhaust valve 25.
- the period B' during which both the inlet valve 24 and the fuel valve 19 are open is shorter than the period B in an operating state of the four-stroke engine 1 , in which the fuel valve 19 does not close until the closing time t 2 . Due to the position of the closing time t 2 , t 2 ', the amount of fuel supplied can be adapted to the operating state of the four-stroke engine 1.
- the fuel valve 19 is open at least also during part of the compression stroke 13 of the four-stroke engine 1 ensures adequate lubrication of the crankcase interior 6.
- the fuel valve 19 is advantageously opened both during part of the intake stroke 12 to ensure sufficient fuel supply to the combustion chamber 3 and during at least part of the compression stroke 13 to ensure fuel supply into the crankcase interior 6. Due to the fact that the fuel valve 19 is controlled as a function of the engine cycle, adequate lubrication of the four-stroke engine 1 and a smooth running of the four-stroke engine 1 can be ensured.
- the fuel valve 19 is opened at least once during each opening period E of the intake valve 24.
- At least 20%, in particular at least 30%, preferably at least 40% of the opening period T of the fuel valve 19 is advantageously in the compression cycle 13.
- the fuel valve 19 is advantageously over at least 20%, in particular at least 30%, preferably at least 40% of the compression cycle 13 open.
- the four-stroke engine 1 of the blower 50 turns at full load preferably at a speed of about 5,000 to about 11,000 revolutions per minute, in particular from about 5,000 to about 9,000 revolutions per minute. It has been shown that, in particular at such rather low speeds at full load, the specified matching of the opening time t 1 and the closing time t 2 to the engine cycle and in particular also to the opening period E of the intake valve 24 ( Fig. 3 ) is advantageous to ensure that a sufficient amount of fuel in the combustion chamber 3 ( Fig. 1 ) is present so that combustion can take place. By the specified adjustment of the opening period T of the fuel valve 19 to the crankshaft angle ⁇ ( Fig. 3 ) is also sufficient lubrication of the crankcase interior 6 ( Fig. 1 ) reached.
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- Combustion & Propulsion (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Lubrication Of Internal Combustion Engines (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
- Output Control And Ontrol Of Special Type Engine (AREA)
Abstract
Ein gemischgeschmierter Viertaktmotor (1) besitzt einen Zylinder (2), in dem ein Brennraum (3) ausgebildet ist. Der Brennraum (3) ist von einem im Zylinder (2) beweglich gelagerten Kolben (4) begrenzt. Der Viertaktmotor (1) weist einen Ansaugkanal (21) auf, der über eine von einem Einlassventil (24) gesteuerte Einlassöffnung (22) in den Brennraum (3) mündet. Der Viertaktmotor (1) weist eine Gemischbildungseinrichtung (17) auf, die mindestens eine Kraftstofföffnung (18) umfasst, die in den Ansaugkanal (21) mündet. Zur Schmierung des Kurbelgehäuseinnenraums (6) weist der Viertaktmotor (1) eine Strömungsverbindung auf, die den Ansaugkanal (21) mit einer stromab der Gemischbildungseinrichtung (17) in den Ansaugkanal (21) mündenden Verbindungsöffnung (11) mit dem Kurbelgehäuseinnenraum (6) verbindet. Die der Kraftstofföffnung (18) zugeführte Kraftstoffmenge ist von einem Kraftstoffventil (19) gesteuert. Der Viertaktmotor (1) weist eine Steuerung (20) auf, die dazu ausgebildet ist, das Kraftstoffventil (19) in Abhängigkeit der Stellung der Kurbelwelle (7) derart anzusteuern, dass das Kraftstoffventil (19) zumindest auch während eines Teils des Kompressionstakts (13) des Viertaktmotors (1) geöffnet ist. Ein Verfahren zum Betrieb des Viertaktmotors (1) sieht vor, dass das Kraftstoffventil (19) in Abhängigkeit der Stellung der Kurbelwelle (7) derart angesteuert wird, dass das Kraftstoffventil (19) zumindest auch während eines Teils eines Kompressionstakts (13) des Viertaktmotors (1) geöffnet ist.A mixed-lubricated four-stroke engine (1) has a cylinder (2) in which a combustion chamber (3) is formed. The combustion chamber (3) is delimited by a piston (4) movably mounted in the cylinder (2). The four-stroke engine (1) has an intake duct (21) which opens into the combustion chamber (3) via an inlet opening (22) controlled by an inlet valve (24). The four-stroke engine (1) has a mixture formation device (17) which comprises at least one fuel opening (18) which opens into the intake duct (21). To lubricate the crankcase interior (6), the four-stroke engine (1) has a flow connection that connects the intake duct (21) to the crankcase interior (6) with a connection opening (11) that opens into the intake duct (21) downstream of the mixture-forming device (17). The fuel quantity supplied to the fuel opening (18) is controlled by a fuel valve (19). The four-stroke engine (1) has a controller (20) which is designed to control the fuel valve (19) depending on the position of the crankshaft (7) in such a way that the fuel valve (19) at least also during part of the compression stroke (13 ) of the four-stroke engine (1) is open. A method for operating the four-stroke engine (1) provides that the fuel valve (19) is actuated as a function of the position of the crankshaft (7) in such a way that the fuel valve (19) also at least during part of a compression stroke (13) of the four-stroke engine ( 1) is open.
Description
Die Erfindung betrifft einen gemischgeschmierten Viertaktmotor der im Oberbegriff des Anspruchs 1 angegebenen Gattung, ein handgeführtes Arbeitsgerät mit einem gemischgeschmierten Viertaktmotor und ein Verfahren zum Betrieb eines gemischgeschmierten Viertaktmotors der im Oberbegriff des Anspruchs 13 angegebenen Gattung.The invention relates to a mixed-lubricated four-stroke engine of the type specified in the preamble of
Aus der
Der Erfindung liegt die Aufgabe zugrunde, einen Viertaktmotor der gattungsgemäßen Art zu schaffen, der eine verbesserte Steuerung der zugeführten Kraftstoffmenge bei guter Schmierung des Kurbelgehäuses ermöglicht. Eine weitere Aufgabe der Erfindung besteht darin, ein handgeführtes Arbeitsgerät mit einem Viertaktmotor anzugeben. Eine weitere Aufgabe der Erfindung besteht darin, ein Verfahren zum Betrieb eines gemischgeschmierten Viertaktmotors anzugeben.The invention has for its object to provide a four-stroke engine of the generic type, which enables improved control of the amount of fuel supplied with good lubrication of the crankcase. Another object of the invention is to provide a hand-held implement with a four-stroke engine. Another object of the invention is to provide a method for operating a mixed-lubricated four-stroke engine.
Diese Aufgabe wird bezüglich des gemischgeschmierten Viertaktmotors durch einen Viertaktmotor mit den Merkmalen des Anspruchs 1 gelöst. Bezüglich des Arbeitsgeräts wird die Aufgabe durch ein Arbeitsgerät mit den Merkmalen des Anspruchs 12 gelöst. Bezüglich des Verfahrens wird die Aufgabe durch ein Verfahren zum Betrieb eines gemischgeschmierten Viertaktmotors mit den Merkmalen des Anspruchs 13 gelöst.With regard to the mixed-lubricated four-stroke engine, this object is achieved by a four-stroke engine with the features of
Die Erfindung sieht vor, dass die der Kraftstofföffnung zugeführte Kraftstoffmenge von einem Kraftstoffventil gesteuert ist. Dadurch kann die dem Verbrennungsmotor zugeführte Kraftstoffmenge präzisier gesteuert werden als beispielsweise bei einer Kraftstoffzufuhr, bei der die angesaugte Kraftstoffmenge allein abhängig von dem Unterdruck im Ansaugkanal ist. Dies ist beispielsweise bei Vergasern, die ohne ein gesteuertes Kraftstoffventil arbeiten, der Fall. Um eine ausreichende Schmierung des Kurbelgehäuses zu gewährleisten, ist vorgesehen, dass die Steuerung des Viertaktmotors dazu ausgebildet ist, das Kraftstoffventil in Abhängigkeit der Stellung der Kurbelwelle anzusteuern. Der Öffnungszeitpunkt und der Schließzeitpunkt des Kraftstoffventils werden demnach nicht nur in Abhängigkeit der zuzuführenden Kraftstoffmenge gewählt, sondern auch in Abhängigkeit der Stellung der Kurbelwelle, also in Abhängigkeit des Kurbelwellenwinkels bestimmt. Dabei ist vorgesehen, dass das Kraftstoffventil zumindest auch während eines Teils des Kompressionstakts des Viertaktmotors geöffnet ist. Während des Kompressionstakts steigt der Druck im Brennraum, und das Einlassventil schließt kurz nach Beginn des Kompressionstakts. Es hat sich nun gezeigt, dass dadurch, dass das Kraftstoffventil zumindest auch während eines Teils des Kompressionstakts des Viertaktmotors geöffnet ist, eine verbesserte Ansaugung von Kraftstoff in den Kurbelgehäuseinnenraum über die Strömungsverbindung erreicht werden kann. Wird das Kraftstoffventil dagegen wie im Stand der Technik nur vor und/oder während des Ansaugtakts geöffnet, so gelangt der in den Ansaugkanal zugeführte Kraftstoff weitgehend, insbesondere nahezu vollständig in den Brennraum, so dass eine ausreichende Schmierung des Kurbelgehäuses nicht sichergestellt werden kann. Wird das Kraftstoffventil unabhängig von der Stellung der Kurbelwelle geöffnet und geschlossen, so ergeben sich starke Schwankungen der Gemischzusammensetzung im Brennraum, die zu einem unruhigen Lauf des Viertaktmotors führen.The invention provides that the fuel quantity supplied to the fuel opening is controlled by a fuel valve. As a result, the amount of fuel supplied to the internal combustion engine can be controlled more precisely than, for example, in the case of a fuel supply in which the amount of fuel drawn is solely dependent on the negative pressure in the intake duct. This is the case, for example, with carburettors that work without a controlled fuel valve. In order to ensure adequate lubrication of the crankcase, it is provided that the control of the four-stroke engine is designed to control the fuel valve depending on the position of the crankshaft. The opening time and the closing time of the fuel valve are therefore not only selected as a function of the quantity of fuel to be supplied, but also as a function of the position of the crankshaft, that is to say as a function of the crankshaft angle. It is provided that the fuel valve is open at least during part of the compression stroke of the four-stroke engine. During the compression stroke, the pressure in the combustion chamber rises and the inlet valve closes shortly after the compression stroke begins. It has now been shown that the fact that the fuel valve is open at least also during part of the compression stroke of the four-stroke engine enables improved suction of fuel into the crankcase interior via the flow connection. If, on the other hand, the fuel valve is only opened before and / or during the intake stroke, as in the prior art, the fuel fed into the intake duct largely, in particular almost completely, gets into the combustion chamber, so that adequate lubrication of the crankcase cannot be ensured. The fuel valve is opened regardless of the position of the crankshaft and closed, there are strong fluctuations in the mixture composition in the combustion chamber, which lead to a restless run of the four-stroke engine.
Der Ansaugtakt des Viertaktmotors ist der Takt, in dem der Kolben das Volumen des Brennraums vergrößert und das Einlassventil zumindest zeitweise, insbesondere über den gesamten Takt geöffnet ist. Der Kompressionstakt ist der Takt, in dem der Kolben das Volumen des Brennraums verringert und in dem das Auslassventil geschlossen ist. Auch das Einlassventil ist im Kompressionstakt zumindest zeitweise geschlossen. Der Arbeitstakt ist der Takt, in dem der Kolben das Volumen des Brennraums vergrößert und das Einlassventil geschlossen ist. Am Ende des Kompressionstakts oder zu Beginn des Arbeitstakts erfolgt eine Verbrennung im Brennraum. Der Ausschiebetakt ist der Takt, in dem das Auslassventil geöffnet ist und der Kolben das Volumen des Brennraums verringert, wodurch Abgase durch den Auslass ausgeschoben werden. Ansaugtakt, Kompressionstakt, Arbeitstakt und Ausschiebetakt folgen in dieser Reihenfolge aufeinander.The intake stroke of the four-stroke engine is the stroke in which the piston increases the volume of the combustion chamber and the intake valve is opened at least temporarily, in particular over the entire stroke. The compression stroke is the stroke in which the piston reduces the volume of the combustion chamber and in which the exhaust valve is closed. The intake valve is also at least temporarily closed in the compression cycle. The work cycle is the cycle in which the piston increases the volume of the combustion chamber and the inlet valve is closed. At the end of the compression stroke or at the beginning of the work stroke, combustion takes place in the combustion chamber. The exhaust stroke is the stroke in which the exhaust valve is opened and the piston reduces the volume of the combustion chamber, whereby exhaust gases are expelled through the exhaust. The intake stroke, compression stroke, work stroke and extension stroke follow each other in this order.
Vorteilhaft ist das Kraftstoffventil in jedem Motorzyklus sowohl während eines Teils des Ansaugtakts als auch während zumindest eines Teils des Kompressionstakts geöffnet. In besonders bevorzugter Gestaltung öffnet das Kraftstoffventil während des Kompressionstakts und ist während des Arbeitstakts, des Ausschiebetakts und zumindest eines Teils des Ansaugtakts geöffnet. Je nach zuzuführender Kraftstoffmenge kann das Kraftstoffventil während des Arbeitstakts und des Ausschiebetakts jedoch auch geschlossen sein. Vorteilhaft ist das Kraftstoffventil mindestens einmal während jedes Öffhungszeitraums des Einlassventils geöffnet. Dadurch wird eine ausreichende Kraftstoffzufuhr in den Brennraum sichergestellt. Vorteilhaft liegt in jedem Motorzyklus mindestens 20% des Öffnungszeitraums des Kraftstoffventils im Kompressionstakt. Es hat sich gezeigt, dass sich dadurch eine gute Schmierung der bewegten Teile im Kurbelgehäuseinnenraum erreichen lässt.The fuel valve is advantageously opened in each engine cycle both during part of the intake stroke and during at least part of the compression stroke. In a particularly preferred embodiment, the fuel valve opens during the compression stroke and is opened during the working stroke, the push-out stroke and at least part of the intake stroke. Depending on the amount of fuel to be supplied, the fuel valve can also be closed during the work cycle and the push-out cycle. The fuel valve is advantageously opened at least once during each opening period of the inlet valve. This ensures an adequate supply of fuel to the combustion chamber. In each engine cycle, at least 20% of the opening period of the fuel valve is advantageously in the compression cycle. It has been shown that good lubrication of the moving parts in the interior of the crankcase can be achieved as a result.
In vorteilhafter Gestaltung ist die Gemischbildungseinrichtung ein Vergaser. Der Vergaser besitzt mindestens eine Kraftstofföffnung, die von einem Kraftstoffkanal gespeist ist. Die durch den Kraftstoffkanal strömende Kraftstoffmenge ist vorteilhaft von dem Kraftstoffventil gesteuert. Die Kraftstofföffnung ist bevorzugt im Bereich eines Venturiabschnitts des Vergasers angeordnet, und der Kraftstoff wird aufgrund des im Ansaugkanal herrschenden Unterdrucks in den Ansaugkanal angesaugt, wenn das Kraftstoffventil geöffnet ist. Es findet demnach keine Kraftstoffeinspritzung in den Ansaugkanal statt, sondern eine Ansaugung. Das Kraftstoffventil ist bevorzugt ein elektromagnetisches Ventil. In vorteilhafter Gestaltung ist das Kraftstoffventil in stromlosem Zustand offen. In alternativer vorteilhafter Gestaltung kann auch vorgesehen sein, dass das Kraftstoffventil in stromlosem Zustand geschlossen ist.In an advantageous embodiment, the mixture formation device is a carburetor. The carburetor has at least one fuel opening which is fed by a fuel channel. The fuel quantity flowing through the fuel channel is advantageously controlled by the fuel valve. The fuel opening is preferably arranged in the region of a venturi section of the carburetor, and the fuel is sucked into the suction channel due to the negative pressure prevailing in the intake duct when the fuel valve is open. Accordingly, there is no fuel injection into the intake duct, but an intake. The fuel valve is preferably an electromagnetic valve. In an advantageous embodiment, the fuel valve is open when de-energized. In an alternative advantageous embodiment it can also be provided that the fuel valve is closed in the de-energized state.
Das Einlassventil und das Auslassventil sind vorteilhaft über einen Ventiltrieb in Abhängigkeit der Stellung der Kurbelwelle angesteuert. Der Ventiltrieb kann in bekannter Weise Stößelstangen umfassen, die auf Kipphebel zur Betätigung von Einlassventil und Auslassventil wirken. In vorteilhafter alternativer Gestaltung kann der Ventiltrieb ein Antriebsrad und ein Abtriebsrad umfassen, die über ein Übertragungsmittel wie beispielsweise eine Kette, einen Riemen oder dgl. miteinander gekoppelt sind, wobei das Abtriebsrad eine Nockenwelle antreibt, die Einlassventil und Auslassventil betätigt. In weiterer alternativer Gestaltung kann der Ventiltrieb als Zahnradgetriebe ausgebildet sein. Auch andere bekannte Gestaltungen für den Ventiltrieb können vorteilhaft sein. Der Ventiltrieb ist vorteilhaft in einem Ventiltriebraum angeordnet, wobei zumindest ein Teil des Ventiltriebraums zumindest einen Teil der Strömungsverbindung bildet. Dadurch wird der Ventiltrieb von dem aus dem Ansaugkanal in den Kurbelgehäuseinnenraum und zurückströmenden Gemisch geschmiert. Eine separate Schmierung für den Ventiltrieb kann dadurch entfallen. In vorteilhafter Gestaltung ist der Ventiltrieb als Kipphebeltrieb ausgebildet, und der Ventiltriebraum umfasst einen Kipphebelraum und mindestens einen Verbindungkanal, die Teile der Strömungsverbindung bilden. Der Kipphebelraum ist vorteilhaft über mindestens eine Verbindungsöffnung mit dem Ansaugkanal verbunden. In alternativer Gestaltung kann eine Verbindungsöffnung vorgesehen sein, die den Ansaugkanal mit dem Verbindungskanal oder einem Nockenraum des Viertaktmotors verbindet. Die Verbindungsöffnung zum Ansaugkanal kann dabei permanent geöffnet oder beispielsweise in Abhängigkeit der Drehzahl gesteuert sein.The inlet valve and the outlet valve are advantageously controlled via a valve train depending on the position of the crankshaft. The valve train can comprise push rods in a known manner, which act on rocker arms for actuating the inlet valve and the outlet valve. In an advantageous alternative embodiment, the valve train can comprise a drive wheel and a driven wheel, which are coupled to one another via a transmission means such as a chain, a belt or the like, the driven wheel driving a camshaft which actuates the inlet valve and the outlet valve. In a further alternative design, the valve train can be designed as a gear transmission. Other known designs for the valve train can also be advantageous. The valve train is advantageously arranged in a valve train chamber, at least part of the valve train chamber forming at least part of the flow connection. As a result, the valve train is lubricated by the mixture flowing out of the intake duct into the interior of the crankcase and back. This eliminates the need for separate lubrication for the valve train. In an advantageous embodiment, the valve train is designed as a rocker arm drive, and the valve drive chamber comprises a rocker arm chamber and at least one connecting channel, which form parts of the flow connection. The rocker arm space is advantageous via at least one connection opening with the intake duct connected. In an alternative design, a connection opening can be provided which connects the intake duct to the connection duct or a cam chamber of the four-stroke engine. The connection opening to the intake duct can be permanently opened or controlled, for example, as a function of the speed.
Für ein handgeführtes Arbeitsgerät mit einem Viertaktmotor ist vorteilhaft vorgesehen, dass der Viertaktmotor bei Volllast mit einer Drehzahl von 5.000 bis 11.000 Umdrehungen pro Minute dreht. Es hat sich gezeigt, dass insbesondere in einem Drehzahlband von 5.000 bis 11.000 Umdrehungen pro Minute durch die vorgesehene Öffnung des Kraftstoffventils auch während eines Teils des Kompressionstakts auch bei Volllast eine ausreichende Schmierung des Kurbelgehäuseinnenraums gewährleistet werden kann. Bevorzugt dreht der Viertaktmotor bei Volllast mit einer Drehzahl von 5.000 bis 9.000 Umdrehungen pro Minute. Wird der Öffnungs- und Schließzeitpunkt des Kraftstoffventils bei derartigen vergleichsweise geringen Vollastdrehzahlen nicht auf den Motortakt angepasst, so können sich eine unzureichende Kraftstoffversorgung und damit ein unruhiger Lauf des Verbrennungsmotors und eine unzureichende Schmierung des Kurbelgehäuseinnenraums ergeben.For a hand-held implement with a four-stroke engine, it is advantageously provided that the four-stroke engine rotates at full speed at a speed of 5,000 to 11,000 revolutions per minute. It has been shown that, in particular in a speed range of 5,000 to 11,000 revolutions per minute, the intended opening of the fuel valve can ensure sufficient lubrication of the interior of the crankcase even during part of the compression stroke, even at full load. The four-stroke engine preferably rotates at full speed at a speed of 5,000 to 9,000 revolutions per minute. If the opening and closing times of the fuel valve are not adapted to the engine cycle at such comparatively low full-load speeds, an inadequate fuel supply and thus an uneven running of the internal combustion engine and inadequate lubrication of the crankcase interior can result.
Für ein Verfahren zum Betrieb eines gemischgeschmierten Viertaktmotors mit einem Zylinder, in dem ein Brennraum ausgebildet ist, wobei der Brennraum von einem im Zylinder beweglich gelagerten Kolben begrenzt ist, wobei der Kolben eine in einem Kurbelgehäuseinnenraum drehbar gelagerte Kurbelwelle rotierend antreibt, wobei der Viertaktmotor einen Ansaugkanal aufweist, der über eine von einem Einlassventil gesteuerte Einlassöffnung in den Brennraum mündet, wobei aus dem Brennraum ein von einem Auslassventil gesteuerter Auslasskanal führt, mit einer Gemischbildungseinrichtung, wobei die Gemischbildungseinrichtung mindestens eine Kraftstofföffnung umfasst, die in den Ansaugkanal mündet, wobei der Viertaktmotor zur Schmierung des Kurbelgehäuseinnenraums eine Strömungsverbindung aufweist, die den Ansaugkanal mit einer stromab der Gemischbildungseinrichtung in den Ansaugkanal mündenden Verbindungsöffnung mit dem Kurbelgehäuseinnenraum verbindet, ist vorgesehen, dass die der Kraftstofföffnung zugeführte Kraftstoffmenge von einem Kraftstoffventil gesteuert wird, und dass das Kraftstoffventil in Abhängigkeit der Stellung der Kurbelwelle derart angesteuert wird, dass das Kraftstoffventil zumindest auch während eines Teils des Kompressionstakts des Viertaktmotors geöffnet ist.For a method for operating a mixed-lubricated four-stroke engine with a cylinder, in which a combustion chamber is formed, the combustion chamber being delimited by a piston movably mounted in the cylinder, the piston rotatingly driving a crankshaft rotatably mounted in a crankcase interior, the four-stroke engine having an intake duct which opens into the combustion chamber via an inlet opening controlled by an inlet valve, an outlet duct controlled by an outlet valve leading from the combustion chamber, with a mixture formation device, the mixture formation device comprising at least one fuel opening which opens into the intake duct, the four-stroke engine for lubrication of the crankcase interior has a flow connection that connects the intake duct to the crankcase interior with a connection opening that opens into the intake duct downstream of the mixture formation device the fuel quantity supplied to the fuel opening is controlled by a fuel valve, and the fuel valve is controlled depending on the position of the crankshaft in such a way that the fuel valve is open at least also during part of the compression stroke of the four-stroke engine.
Ein Ausführungsbeispiel der Erfindung wird im Folgenden anhand der Zeichnung erläutert. Es zeigen:
- Fig. 1 und Fig. 2
- schematische Schnittdarstellungen eines Zweitaktmotors,
- Fig. 3
- eine schematische Darstellung des Drucks im Brennraum, der Öffnungs- und Schließzeit des Kraftstoffventils sowie der Öffnungs- und Schließzeiten von Einlassventil und Auslassventil über dem Kurbelwellenwinkel,
- Fig. 4
- eine Seitenansicht eines Blasgeräts.
- 1 and 2
- schematic sectional views of a two-stroke engine,
- Fig. 3
- a schematic representation of the pressure in the combustion chamber, the opening and closing times of the fuel valve and the opening and closing times of the intake valve and exhaust valve over the crankshaft angle,
- Fig. 4
- a side view of a blower.
Wie
Der Kolben 4 treibt über ein Pleuel 8 eine in einem Kurbelgehäuse 5 drehbar gelagerte Kurbelwelle 7 an. Die Kurbelwelle 7 ist um eine Drehachse 44 drehbar gelagert. Die Kurbelwelle 7 dreht sich im Betrieb in Richtung eines Pfeils 31. Die Drehlage der Kurbelwelle 7 ist als Kurbelwellenwinkel α angegeben. Der Kurbelwellenwinkel α beträgt im oberen Totpunkt des Kolbens 4 0° und im unteren Totpunkt des Kolbens 4 180°. Im Kurbelgehäuse 5 ist ein Kurbelgehäuseinnenraum 6 ausgebildet. Zur Zufuhr von Kraftstoff/Luft-Gemisch weist der Viertaktmotor 1 einen Ansaugkanal 21 auf.The piston 4 drives a
Ein Abschnitt des Ansaugkanals 21 ist im Ausführungsbeispiel in einer Gemischbildungseinrichtung 17 ausgebildet. Die Gemischbildungseinrichtung 17 ist vorteilhaft ein Vergaser. Die Gemischbildungseinrichtung 17 weist einen Venturiabschnitt 29 auf, in dem eine Kraftstofföffnung 18 in den Ansaugkanal 21 mündet. Die Kraftstofföffnung 18 ist über einen Kraftstoffkanal 33 mit einem Kraftstoffventil 19 verbunden, dem Kraftstoff aus einem nicht dargestellten Kraftstofftank zugeführt wird. Das Kraftstoffventil 19 steuert die der Kraftstofföffnung 18 zugeführte Kraftstoffmenge. Das Kraftstoffventil 19 ist vorteilhaft ein elektromagnetisches Ventil.In the exemplary embodiment, a section of the
Das Kraftstoffventil 19 ist von einer Steuerung 20 angesteuert. Die Ansteuerung des Kraftstoffventils 19 erfolgt in Abhängigkeit der Drehlage der Kurbelwelle 7, also in Abhängigkeit des Kurbelwellenwinkels α. Die Steuerung 20 ist so ausgebildet, dass das Kraftstoffventil 19 in der entsprechenden, auf den Motorzyklus abgestimmten Weise angesteuert werden kann. Hierzu ist die Steuerung 20 mit einer Drehlagenerfassung 47 zur Erfassung der Drehlage der Kurbelwelle 7, also zur Erfassung des Kurbelwellenwinkels α, ausgestattet. Die Drehlagenerfassung 47 kann beispielsweise mindestens einen Sensor zur Erfassung der Drehlage der Kurbelwelle 7 aufweisen. Die Drehlagenerfassung 47 kann jedoch auch aus anderen Signalen, beispielsweise der in einer Zündeinrichtung des Viertaktmotors 1 induzierten Spannung oder der in einem Generator des Viertaktmotors 1 induzierten Spannung oder einer Kombination mehrerer Signale die Drehlage der Kurbelwelle 7, also den Kurbelwellenwinkel α, ermitteln. Auch eine Erfassung der Drehlage der Kurbelwelle 7 aus anderen Signalen, beispielsweise unter Zuhilfenahme des im Kurbelgehäuseinnenraum 6 herrschenden Drucks, kann vorgesehen sein. Das Kraftstoffventil 19 ist in vorteilhafter Gestaltung ein stromlos offenes Ventil. In alternativer Gestaltung kann das Kraftstoffventil 19 auch ein in stromlosem Zustand geschlossenes Kraftstoffventil sein.The
Stromab der Kraftstofföffnung 18 ist im Ansaugkanal ein Drosselelement 16, im Ausführungsbeispiel eine Drosselklappe schwenkbar gelagert. Über das Drosselelement 16 kann ein Bediener die durch den Ansaugkanal 21 angesaugte Menge von Kraftstoff/Luft-Gemisch einstellen.A
Der Ansaugkanal 21 mündet mit einer Einlassöffnung 22 am Brennraum. Die Einlassöffnung 22 ist von einem Einlassventil 24 gesteuert. Das Einlassventil 24 ist hierzu in Richtung eines Doppelpfeils 45 beweglich. Das Einlassventil 24 besitzt einen Ventilteller 27, der die Einlassöffnung 22 in Abhängigkeit der Position des Einlassventils 24 frei gibt oder verschließt. Aus dem Brennraum 3 führt eine Auslassöffnung 23, die von einem Ventilteller 28 eines Auslassventils 25 geöffnet oder geschlossen ist. An die Auslassöffnung 23 schließt ein Auslasskanal 26 an, über den Abgase aus dem Brennraum 3 ausströmen. An den Auslasskanal 26 ist vorteilhaft ein nicht dargestellter Abgasschalldämpfer angeschlossen.The
Zur Steuerung der Öffnungs- und Schließzeiten von Einlassventil 24 und Auslassventil 25 ist ein Ventiltrieb 34 vorgesehen, der in
Zu Beginn des Arbeitstakts 14 sind Einlassventil 24 und Auslassventil 25 geschlossen. Der Druck p im Brennraum 3 erreicht im Ausführungsbeispiel zu Beginn des Arbeitstakts 14 sein Maximum und fällt daraufhin stark ab. Das Druckmaximum ergibt sich aufgrund der zuvor erfolgten Verbrennung von Kraftstoff/Luft-Gemisch im Brennraum 3. Während des Arbeitstakts 14 bewegt sich der Kolben 4 in Richtung vom Brennraum 3 zum Kurbelgehäuseinnenraum 6, also in Richtung des Pfeils 32 in
Bei einem Kurbelwellenwinkel von 180° ist der untere Totpunkt des Kolbens 4 erreicht. In einem Bereich des Kurbelwellenwinkels α von 180° bis 360° im Diagramm in
Der Öffnungszeitraum A des Auslassventils ist in
Das Auslassventil 25 öffnet zum Öffnungszeitpunkt a1, der in der zweiten Hälfte des Arbeitstakts 14 liegt. Dadurch strömen Abgase aus dem Brennraum 3 durch die geöffnete Auslassöffnung 23 in den Auslasskanal 26 aus. Während des Ausschiebetakts 15 schiebt der Kolben 4 die Abgase durch die Auslassöffnung 23. Während des Ausschiebetakts 15 ist das Auslassventil 25 vollständig geöffnet.The
Das Auslassventil 25 schließt zu einem Schließzeitpunkt a2, der in dem auf den Ausschiebetakt 15 folgenden Ansaugtakt 12 liegt. Während des Ansaugtakts 12 bewegt sich der Kolben 4 im Abwärtshub vom Brennraum 3 in Richtung auf den Kurbelgehäuseinnenraum 6. Der Druck p im Brennraum 3 ist gering, so dass durch die geöffnete Einlassöffnung 22 Kraftstoff/Luft-Gemisch aus dem Ansaugkanal 21 in den Brennraum 3 angesaugt wird. Das Einlassventil 24 öffnet zum Öffnungszeitpunkt e1, der im Ausführungsbeispiel in der zweiten Hälfte des Ausschiebetakts 15 liegt. Während des Ansaugtakts 12 ist das Einlassventil 24 vollständig geöffnet. Das Einlassventil 24 schließt zu einem Schließzeitpunkt e2, der im Kompressionstakt 13 liegt. Der Kompressionstakt 13 schließt an den Ansaugtakt 12 an. Im Kompressionstakt 13 bewegt sich der Kolben 4 vom Kurbelgehäuseinnenraum 6 in Richtung auf den Brennraum 3 und komprimiert dadurch das im Brennraum 3 angeordnete Kraftstoff/Luft-Gemisch. Sobald das Einlassventil 24 geschlossen ist, steigt der Druck im Brennraum 3 stark an, wie
Das Kraftstoffventil 19 öffnet im Ausführungsbeispiel zu einem Öffnungszeitpunkt t1 und schließt zu einem Schließzeitpunkt t2. In
Der Öffnungszeitpunkt t1 liegt im Ausführungsbeispiel im Kompressionstakt 13. Im Ausführungsbeispiel öffnet das Kraftstoffventil 19 zu einem Öffnungszeitpunkt t1, der gleichzeitig zum Schließzeitpunkt e2, zu dem die Einlassöffnung 22 schließt, liegt. Im Kompressionstakt 13 befindet sich der Kolben 4 im Aufwärtshub. Dadurch vergrößert sich das Volumen des Kurbelgehäuseinnenraums 6. Da das Einlassventil 24 geschlossen ist, wird Kraftstoff/Luft-Gemisch aus dem Ansaugkanal 21 über den Ventiltriebraum 30 in den Kurbelgehäuseinnenraum 6 angesaugt. Dadurch wird eine effektive Schmierung der bewegten Teile im Kurbelgehäuseinnenraum 6 erreicht. Vorteilhaft liegt in jedem Motorzyklus mindestens 20%, insbesondere mindestens 30%, bevorzugt mindestens 40% des Öffhungszeitraums T des Kraftstoffventils 19 im Kompressionstakt 13. Vorteilhaft ist das Kraftstoffventil 19 über mindestens 20%, insbesondere mindestens 30%, bevorzugt mindestens 40% des Kompressionstakts 13 geöffnet. Im Ausführungsbeispiel ist das Kraftstoffventil 19 über mehr als die Hälfte des Kompressionstakts 13 geöffnet.In the exemplary embodiment, the opening time t 1 lies in the
Im Ausführungsbeispiel bleibt das Kraftstoffventil 19 bis zu einem Zeitpunkt t2 geöffnet, der im Ansaugtakt 12 liegt. Über den gesamten Arbeitstakt 14 und den gesamten Ausschiebetakt 15 ist das Kraftstoffventil 19 demnach vorteilhaftgeöffnet. Aufgrund der Pulsation des Gemisches im Ansaugkanal 21 kann auch während dieser Zeit im Ventiltriebraum 30 Kraftstoff/Luft-Gemisch in den Kurbelgehäuseinnenraum 6 gefördert werden. Die Pulsation im Ansaugkanal 21 entsteht beispielweise durch die Volumenveränderung des Kurbelgehäuseinnenraums 6 beim sich bewegenden Kolben 4.In the exemplary embodiment, the
Der Schließzeitpunkt t2 liegt im Ausführungsbeispiel gegen Ende des Ansaugtakts 12. Durch die Lage des Schließzeitpunkts t2 während des Ansaugtakts 12 kann die Fettigkeit des in den Brennraum einströmenden Kraftstoff/Luft-Gemischs eingestellt werden. Während des Endes des Ansaugtakts 12 und des Beginns des Kompressionstakts 13 ist das Kraftstoffventil 19 geschlossen. Während dieses Zeitraums ist das Einlassventil 24 geöffnet. Der Öffnungszeitraum E des Einlassventils 24 und der Schließzeitraum S, während dem das Kraftstoffventil 19 geschlossen ist, überschneiden sich demnach über einen Zeitraum D. Über einen Zeitraum B sind sowohl das Einlassventil 24 als auch das Kraftstoffventil 19 geöffnet.In the exemplary embodiment, the closing point in time t 2 is at the end of the
In
Dadurch, dass das Kraftstoffventil 19 zumindest auch während eines Teils des Kompressionstakts 13 des Viertaktmotors 1 geöffnet ist, wird eine ausreichende Schmierung des Kurbelgehäuseinnenraums 6 sichergestellt. Das Kraftstoffventil 19 ist dabei in jedem Motorzyklus vorteilhaft sowohl während eines Teils des Ansaugtakts 12 geöffnet, um eine ausreichende Kraftstoffzufuhr in den Brennraum 3 zu gewährleisten, als auch während zumindest eines Teils des Kompressionstakts 13, um eine Kraftstoffzufuhr in den Kurbelgehäuseinnenraum 6 zu gewährleisten. Dadurch, dass das Kraftstoffventil 19 in Abhängigkeit des Motorzyklus angesteuert wird, können eine ausreichende Schmierung des Viertaktmotors 1 sowie ein gleichmäßiger Lauf des Viertaktmotors 1 gewährleistet werden. Das Kraftstoffventil 19 ist während jedes Öffnungszeitraums E des Einlassventils 24 zumindest einmal geöffnet. Vorteilhaft liegt in jedem Motorzyklus mindestens 20%, insbesondere mindestens 30%, bevorzugt mindestens 40% des Öffhungszeitraums T des Kraftstoffventils 19 im Kompressionstakt 13. Vorteilhaft ist das Kraftstoffventil 19 über mindestens 20%, insbesondere mindestens 30%, bevorzugt mindestens 40% des Kompressionstakts 13 geöffnet.The fact that the
Der Viertaktmotor 1 des Blasgeräts 50 (
Claims (13)
dadurch gekennzeichnet, dass das Kraftstoffventil (19) in jedem Motorzyklus sowohl während zumindest eines Teils des Ansaugtakts (12) als auch während zumindest eines Teils des Kompressionstakts (13) geöffnet ist.Four-stroke engine according to claim 1,
characterized in that the fuel valve (19) is open in each engine cycle both during at least part of the intake stroke (12) and during at least part of the compression stroke (13).
dadurch gekennzeichnet, dass das Kraftstoffventil (19) mindestens einmal während jedes Öffnungszeitraums (E) des Einlassventils (24) geöffnet ist.Four-stroke engine according to one of claims 1 or 2,
characterized in that the fuel valve (19) is opened at least once during each opening period (E) of the inlet valve (24).
dadurch gekennzeichnet, dass in jedem Motorzyklus mindestens 20% des Öffnungszeitraums (T) des Kraftstoffventils (19) im Kompressionstakt (13) liegt.Four-stroke engine according to one of claims 1 to 3,
characterized in that at least 20% of the opening period (T) of the fuel valve (19) lies in the compression stroke (13) in each engine cycle.
dadurch gekennzeichnet, dass die Gemischbildungseinrichtung (17) ein Vergaser ist.Four-stroke engine according to one of claims 1 to 4,
characterized in that the mixture formation device (17) is a carburetor.
dadurch gekennzeichnet, dass die Kraftstofföffnung (18) im Bereich eines Venturiabschnitts (29) des Vergasers angeordnet ist und dass der Kraftstoff aufgrund des im Ansaugkanal (21) herrschenden Unterdrucks in den Ansaugkanal (21) angesaugt wird.Four-stroke engine according to claim 5,
characterized in that the fuel opening (18) is arranged in the region of a venturi section (29) of the carburetor and that the fuel is sucked into the suction channel (21) due to the negative pressure prevailing in the suction channel (21).
dadurch gekennzeichnet, dass das Kraftstoffventil (19) ein elektromagnetisches Ventil ist.Four-stroke engine according to one of claims 1 to 6,
characterized in that the fuel valve (19) is an electromagnetic valve.
dadurch gekennzeichnet, dass das Kraftstoffventil (19) in stromlosem Zustand offen ist.Four-stroke engine according to claim 7,
characterized in that the fuel valve (19) is open when de-energized.
dadurch gekennzeichnet, dass das Kraftstoffventil (19) in stromlosem Zustand geschlossen ist.Four-stroke engine according to claim 7,
characterized in that the fuel valve (19) is closed when de-energized.
dadurch gekennzeichnet, dass das Einlassventil (24) und das Auslassventil (25) über einen Ventiltrieb (34) in Abhängigkeit der Stellung der Kurbelwelle (7) angesteuert sind, wobei der Ventiltrieb (34) in einem Ventiltriebraum (30) angeordnet ist, und dass der Ventiltriebraum (30) einen Teil der Strömungsverbindung bildet.Four-stroke engine according to one of claims 1 to 9,
characterized in that the inlet valve (24) and the outlet valve (25) are controlled via a valve train (34) depending on the position of the crankshaft (7), the valve train (34) being arranged in a valve train chamber (30), and in that the valve train chamber (30) forms part of the flow connection.
dadurch gekennzeichnet, dass der Ventiltrieb (34) als Kipphebeltrieb ausgebildet ist und der Ventiltriebraum (30) einen Kipphebelraum (10) und mindestens einen Verbindungskanal (9) umfasst, die Teile der Strömungsverbindung bilden.Four-stroke engine according to claim 10,
characterized in that the valve train (34) is designed as a rocker arm drive and the valve drive chamber (30) comprises a rocker arm chamber (10) and at least one connecting channel (9) which form parts of the flow connection.
dadurch gekennzeichnet, dass die der Kraftstofföffnung (18) zugeführte Kraftstoffmenge von einem Kraftstoffventil (19) gesteuert wird, und dass das Kraftstoffventil (19) in Abhängigkeit der Stellung der Kurbelwelle (7) derart angesteuert wird, dass das Kraftstoffventil (19) zumindest auch während eines Teils eines Kompressionstakts (13) des Viertaktmotors (1) geöffnet ist.Method for operating a mixed-lubricated four-stroke engine (1) with a cylinder (2) in which a combustion chamber (3) is formed, the combustion chamber (3) being delimited by a piston (4) movably mounted in the cylinder (2), the piston Piston (4) drives a crankshaft (7) rotatably mounted in a crankcase interior (6), the four-stroke engine (1) having an intake duct (21) which opens into the combustion chamber (3) via an inlet opening (22) controlled by an inlet valve (24), an outlet channel (21) controlled by an outlet valve (25) leading from the combustion chamber (3) with a Mixture formation device (17), the mixture formation device (17) comprising at least one fuel opening (18) which opens into the intake duct (21), the four-stroke engine (1) for lubricating the crankcase interior (6) having a flow connection which connects the intake duct (21 ) connects to the crankcase interior (6) with a connection opening (11) opening downstream of the mixture formation device (17) into the intake duct (21),
characterized in that the fuel quantity supplied to the fuel opening (18) is controlled by a fuel valve (19), and in that the fuel valve (19) is controlled as a function of the position of the crankshaft (7) such that the fuel valve (19) at least also during part of a compression stroke (13) of the four-stroke engine (1) is open.
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP18209488.8A EP3660284A1 (en) | 2018-11-30 | 2018-11-30 | Four-stroke engine lubricated with pre-mix, hand-held work device with a four-stroke engine and method for operating a four-stroke engine lubricated with a compound |
US16/672,166 US11168593B2 (en) | 2018-11-30 | 2019-11-01 | Four stroke engine, handheld work apparatus having a four stroke engine, and method for operating a four stroke engine |
EP19207081.1A EP3660285B1 (en) | 2018-11-30 | 2019-11-05 | Four-stroke engine lubricated with pre-mix, hand-held work device with a four-stroke engine and method for operating a four-stroke engine lubricated with pre-mix |
CN201911200271.0A CN111255563B (en) | 2018-11-30 | 2019-11-29 | Four-stroke motor, manually guided working device comprising a four-stroke motor, and method for operating a four-stroke motor |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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EP18209488.8A EP3660284A1 (en) | 2018-11-30 | 2018-11-30 | Four-stroke engine lubricated with pre-mix, hand-held work device with a four-stroke engine and method for operating a four-stroke engine lubricated with a compound |
Publications (1)
Publication Number | Publication Date |
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EP3660284A1 true EP3660284A1 (en) | 2020-06-03 |
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EP18209488.8A Withdrawn EP3660284A1 (en) | 2018-11-30 | 2018-11-30 | Four-stroke engine lubricated with pre-mix, hand-held work device with a four-stroke engine and method for operating a four-stroke engine lubricated with a compound |
EP19207081.1A Active EP3660285B1 (en) | 2018-11-30 | 2019-11-05 | Four-stroke engine lubricated with pre-mix, hand-held work device with a four-stroke engine and method for operating a four-stroke engine lubricated with pre-mix |
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EP19207081.1A Active EP3660285B1 (en) | 2018-11-30 | 2019-11-05 | Four-stroke engine lubricated with pre-mix, hand-held work device with a four-stroke engine and method for operating a four-stroke engine lubricated with pre-mix |
Country Status (3)
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US (1) | US11168593B2 (en) |
EP (2) | EP3660284A1 (en) |
CN (1) | CN111255563B (en) |
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CN113352907A (en) * | 2021-06-15 | 2021-09-07 | 武汉理工大学 | Range-extending type alcohol mixed fuel electric motor coach system |
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Also Published As
Publication number | Publication date |
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EP3660285A1 (en) | 2020-06-03 |
US11168593B2 (en) | 2021-11-09 |
EP3660285B1 (en) | 2022-04-06 |
CN111255563A (en) | 2020-06-09 |
US20200173319A1 (en) | 2020-06-04 |
CN111255563B (en) | 2023-07-14 |
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