WO2009083041A1

WO2009083041A1 - Engine device and method for operating a reciprocating engine

Info

Publication number: WO2009083041A1
Application number: PCT/EP2008/000072
Authority: WO
Inventors: Günter Pöschl
Original assignee: N-Vent Worldwide Technologies Corporation Limited
Priority date: 2007-12-21
Filing date: 2008-01-08
Publication date: 2009-07-09

Abstract

The invention relates to an engine device (10) comprising a reciprocating engine, particularly a two-cycle internal combustion engine. An injection nozzle (86) of a fuel line opening into the combustion chamber (84) of the engine, an overflow opening opening into the combustion chamber (84), and an exhaust opening (92) to an exhaust line leading away from the combustion chamber (84) are disposed so that they are closed when the piston (80) is present at the upper dead center point, and are exposed when the piston (80) is present at the lower dead center point. When the piston (80) moves from the upper dead center point to the lower dead center point, the injection nozzle (86) is first exposed, and then the overflow opening (88) and exhaust opening (92). When the supercharger (24) is operating, when the piston (80) is present at the top dead center point, a control device unblocks a flow connection between the pressure side (26) of the supercharger (24) and the overflow opening (88) and closes flow connections between the pressure side (26) of the supercharger (24) and the crankcase opening (94) and between the crankcase opening (94) and the overflow opening (88). In a phase wherein the piston (8) moves from the upper dead center point to the lower dead center point, the control device unblocks flow connections between the pressure side (26) of the supercharger (24) and the crankcase opening (94) and between the crankcase opening (94) and the overflow opening (88), and closes a flow connection between the pressure side of the supercharger (24) and the overflow opening (88).

Description

Engine device and method of operating a reciprocating engine

The invention relates to a motor device with a reciprocating engine, in particular a two-stroke internal combustion engine. The invention further relates to a method for operating a reciprocating engine.

It is generally desirable to make better use of fuel. This also applies to internal combustion engines, the outdoor equipment used devices such. B. Power chainsaws. Due to their low weight and easy handling, two-stroke internal combustion engines are preferably used here, but these are generally not very economical.

From a health point of view, it is desirable to keep the combustion exhaust gases from engines pollutant-free and / or at least so low in pollutants that they emit no or no major amounts of carcinogenic substances, which can lead to significant damage to health.

Two-stroke internal combustion engines have the advantage of a high power density with low weight. However, the exhaust gases contain a high proportion of unburned hydrocarbons, as a matter of principle due to the fuel feed from the crankcase by overflow into the combustion chamber of the engine with open exhaust port always unburned fresh gas into the exhaust mixes. In addition to the high pollutant load, a not inconsiderable proportion of fuel is lost unused, which significantly worsens the efficiency of the engine.

Another disadvantage in the operation of two-stroke internal combustion engines is the addition of lubricating oil in the fuel, which remains during atomization (gasification) of the fuel in the crankcase and wets the inner surfaces of the crankcase. Therefore, lubricating oil can also get into the combustion chamber and into the exhaust area, from which it is discharged unburned into the ambient air with the exhaust gas and contributes to a deterioration of the exhaust gas values. The object of the invention is to reduce the exhaust gas load during operation of a reciprocating engine, in particular a two-stroke internal combustion engine.

According to the invention this object is achieved by a motor device having the features of claim 1 and also by a method having the features of claim 17. Advantageous embodiments of the invention form the subject of the dependent claims.

The invention presents a novel concept for operating a two-stroke internal combustion engine. The pollutant content in the exhaust gas is significantly reduced because the combustion chamber of the engine is not flushed with fresh gas, but only with compressed air that is not mixed with fuel. Thus, even strict emission standards can be met.

The invention provides a direct fuel injection, so that can be dispensed with a carburetor with all its disadvantages.

The invention has the advantage that both low-boiling combustible hydrocarbons such as gasoline, methanol or ethanol and gaseous such as butane, propane or methane can be used as a fuel. In principle, fuels from renewable raw materials such as rapeseed oil or biogas, or even diesel oil or kerosene can be used as fuel (without spark ignition). In order to enable operation with these various fuels, the supercharger is provided, which compresses the intake air in the crankcase of the motor housing speed-dependent to a pressure which is higher than the prevailing in the environment of normal air pressure.

A further advantage of the invention is that, in particular in the case of an embodiment as a small engine with a small displacement, a wide power range is covered. This allows a low total weight and volume, which is advantageous when used in gardening equipment or the like.

Further features and advantages of the invention will become apparent from the following description of an embodiment and from the accompanying drawings, to which reference is made. In the drawings show:

- Figure 1 is a motor device according to the invention in plan view; - Figure 2 is a sectional view of a supercharger for the engine device according to the invention;

- Figure 3 shows a supercharger with mounted positive displacement pump; and

FIGS. 4a to 4c schematically show different operating states of the motor device according to the invention.

The structure and operation of a conventional two-stroke internal combustion engine are known in the art, so that in the following mainly the features and deviations of the invention will be described.

FIG. 1 shows an engine device 10 according to the invention with a reciprocating engine, preferably a single-cylinder two-stroke internal combustion engine. The engine has a piston coupled to a crankshaft 12 which is cyclically slidable in the cylinder between a top dead center and a bottom dead center. The engine is accommodated in an engine crankcase 14, which is preferably made of light metal. From the engine crankcase 14 protrudes one end of the crankshaft 12, which is designed to receive a clutch. On the opposite side of the engine crankcase 14, an impeller 16 is coupled to the crankshaft 12. In addition, there is arranged a magnetic signal generator 18 for an electronic ignition system, which also includes a spark plug 20. However, the electronic ignition system, which replaces a conventional magnetic ignition system with ignition coil, is only needed in the case of externally ignited fuels. Further, a muffler 22 designed as a muffler is bolted to the engine crankcase 14.

On the opposite side is a supercharger 24 in the form of a rotary piston pump, which is shown in detail in Figure 2, flanged with its pressure side 26 to the engine crankcase 14. There, a movable membrane 28 is arranged, preferably a steel plate whose control function will be explained later. On its suction side 30, the supercharger 24 has an air inlet 32. The supercharger 24 is driven by the crankshaft 12 via an endless force transmission transmission element 34, preferably a toothed belt. The rotatably coupled to the crankshaft 12 first timing pulley - A -

and the non-rotatably coupled to a drive shaft 36 of the supercharger 24 second timing pulley together with the toothed belt a belt transmission whose transmission ratio can be specified by the choice of the diameter of the toothed belt wheels.

To the supercharger 24 a positive displacement pump 40 shown in more detail in Figure 3 is grown in the form of a high-pressure gear pump. In an advantageous embodiment, the housing of the positive displacement pump 40 is flanged as part of the compressor housing 42. The positive displacement pump 40 delivers fuel from a fuel tank 46 via a suction line 44. The high pressure side 48 of the positive displacement pump 40 is connected to a fuel line. The fuel line comprises a capillary tube 50 with an injection nozzle that leads through the cylinder wall directly into the combustion chamber of the engine (see Figures 4a to 4c).

Figure 2 shows the essential structure of the supercharger 24. Two rotors 52, 54, more precisely a rotor 52 and a counter-rotor 54, are rotatably coupled to the drive shaft 36 and to a parallel shaft 38, both of which are ball-bearing. The profile of the identically shaped rotors 52, 54 corresponds to a lemniscate (lying 8). The rotors 52, 54 are offset in the direction of rotation by 90 ° to each other. Thus, the rotors 52, 54 are in non-contact engagement with each other and the non-driven counter-rotor 54 rotates in the same direction in the reverse direction with the rotor 52, the two rotors 52, 54 frontally a gear in the form of two meshing gears 56, 58 upstream (see FIG ) which are non-rotatably coupled to the shafts 36, 38.

The rotors 52, 54 rotate in a pump chamber 60 adapted to the shape of the rotors 52, 54 and formed in the precompressor housing 42. The supercharger housing 42 is preferably made of plastic and has on the suction side 30 a first opening 62 to the pump chamber 60, which is in communication with the air inlet 32. In that regard, the supercharger 24 is formed like a conventional Roots blower.

At a pressure-side housing opening 64 of the supercharger 24, which produces a flow connection from the pump chamber 60 to the crank chamber of the engine, the membrane 28 is arranged, as already mentioned. The membrane

28 is designed to be the flow connection between the pressure side

26 of the supercharger 24 and the crankcase of the engine in the manner of a return release valve or close, as will be explained later. The membrane 28 is movable and oscillates during operation of the engine device 10 due to the changing pressure differences between the pressure on the pressure side 26 of the supercharger 24 and the dependent on the piston position pressure in the crankcase.

Another special feature of the supercharger 24 is that in the middle of the shafts 36, 38 in each case a bore 66 is provided which is connected to a transverse bore 68 in the respective rotor 52, 54 and at the edge of a wing at a maximum distance from the center of the rotor 52, 54 in the form of a nozzle 70 ends. The two holes 66, 68 are part of a further fuel line, as will be explained below with reference to FIG 3. The nozzle 70 is sealed by the wall of the pump chamber 60 or the other rotor 54, 52 during almost the entire revolution of the rotor 52, 54. This construction ensures that fuel is injected briefly into the air flow conveyed by the supercharger 24 only when the nozzle 70 is in flow connection with the pressure-side housing opening 64.

Figure 3 shows schematically the supercharger 24 with the attached positive displacement pump 40 (tilted in the lower part of the figure by 90 °) with open pump chamber 72. According to a particularly advantageous aspect of the invention, the two meshing in the pump chamber 72 meshing gears 56, 58 of the positive displacement pump 40 the same gears, which also form the gear for the rotors 52, 54. The gears 56, 58 thus fulfill a dual function, which leads to a saving of components and space.

In addition to the air inlet 32 on the suction side 30 of the supercharger 24, the suction line 44 is arranged from a central housing plate 74 to the fuel tank 46. The suction line 44 opposite to the capillary tube 50 and a fuel return line 78 to the fuel tank 46 are mounted on a cover plate 76. The high pressure side 48 of the positive displacement pump 40 is disposed opposite to the suction side 80. Crossing holes lead from the high pressure side 48 through the middle housing plate 74 to the end plate 76 in a distributor space in which meet the crossing holes. The distributor space connects to the longitudinal bores 66 of the shafts 36, 38. Thus, a portion of the funded by the positive displacement pump 40 fuel through the Waves 36, 38 and the rotors 52, 54 are fed into the air flow supplied by the supercharger 24 for the cyclic formation of fresh gas. In the distribution chamber is still a preferably adjustable by a threaded device for fuel quantity regulation arranged (not shown).

The operation of the engine according to the invention using the supercharger 24 and the positive displacement pump 40 will be described below. FIGS. 4a to 4c show the engine device 10 (without positive displacement pump) in certain operating states, from which the control times controlled by the piston 80 of the engine for filling the crank chamber 82 with intake air and the combustion chamber 84 with fresh gas through the supercharger 24 result.

It is also apparent from FIGS. 4a to 4c that above the piston 80 the combustion chamber 84 of the engine and below the piston 80 the crank chamber 82 are formed. The injection nozzle 86 of the capillary tube 50 opens directly into the combustion chamber 84, as well as a further arranged below the overflow 88 of Überströmkanals 90. Furthermore, a likewise disposed below the injection nozzle 86 exhaust port 92 is provided in the form of a slot to the combustion chamber 84 leading away exhaust pipe. In the crank chamber 82 opens a crank chamber opening 94, which is below the bottom dead center of the piston 80 and therefore never covered by the piston 80.

In Figure 4a, the piston 80 is at top dead center. In this position, both the injection nozzle 86, the overflow 88 and the exhaust port 92 are closed by the piston 80, more precisely by the piston skirt.

When starting the engine, the serving as a control device membrane 28 is pressed by the conveyed air from the supercharger 24 in a front position 96 and thus closes the access from the pressure side 26 of the supercharger 24 to the crank chamber 82. In the front position 96, the membrane 28, however clears the way from the pressure side 26 of the supercharger 24 to the overflow channel 90, so that enriched with fuel air (fresh gas) is moved through the overflow 90 in the direction of the combustion chamber 84, which is still sealed by the piston 80. Due to the reduction in volume of the crank chamber 82 during the movement of the piston 80 in the direction of bottom dead center (immersion of the piston 80), the internal pressure in the crank chamber 82 increases so far that the diaphragm 28 is automatically pressed into a rear position 98. In the rear position 98 of the diaphragm 28, the flow connections between the pressure side 26 of the supercharger 24 and the crank chamber opening 94 and between the crank chamber opening 94 and the overflow channel 90 are released, whereas the flow connection between the pressure side 26 of the supercharger 24 and the overflow channel 90 is closed. Thus, air from the supercharger 24 can enter the crank chamber 82. However, this air contains no fuel, since the nozzles of the rotors 52, 54 give fuel only briefly in every second crankshaft revolution (when the gear ratio between the crankshaft 12 and the drive shaft 1: 1) in the region of the housing opening 64. The position of the rotors 52, 54 was accordingly matched to the piston position, as can be seen from FIGS. 4a to 4c.

When the piston 80 passes the position according to FIG. 4b on its way to the bottom dead center, the exhaust gas opening 92 is released by the piston 80 and exhaust gas can escape through the exhaust gas line. As the exhaust port 92 increases in the course of the piston movement and the pressure in the crank chamber 82 increases, the compressed air from the crank chamber 82 containing no unburned fuel is forced into the combustion chamber 84 through the transfer passage 90 and urges the exhaust gas through the exhaust passage Exhaust opening 92 from the combustion chamber 84 (flushing of the combustion chamber).

Upon reaching the bottom dead center (piston position according to Figure 4c), the pressure in the crank chamber 82 has dropped so far that the membrane 28 is pressed back into its front starting position 96. As a result, air enriched with fuel (fresh gas) is again forced through the overflow channel 90 into the combustion chamber 84 by the rotors 52, 54. When the exhaust opening 92 is closed by the movement of the piston 80 upwards, fuel is injected into the combustion space 84 via the capillary tube 50 under high pressure.

The exhaust gas opening 92 in the combustion chamber 84 is arranged so that it remains closed by the piston 80, as long as fresh gas flows through the overflow opening 88 into the combustion chamber 84. Due to the fact that in the crank chamber 82 by means of the Compressor 24 generated overpressure, the filling of the combustion chamber 84 is achieved in a very short time. With a small design of the overflow channel 90, a very fine fuel distribution is achieved by the high resulting flow velocity in the region of the injection nozzle 86 above the spoiler edge, so that a lean, easily flammable air-fuel mixture is formed.

The dynamic pressure peaks solve in the construction of the invention

Engine device 10, the filling of the crank chamber 82 and the fuel injection timing off. By using the supercharger 24 increased internal pressure in the

The crank chamber 82 increases proportionally the compression in the combustion chamber 84, so that it comes with suitable fuels (eg diesel) for auto-ignition.

The injected through the rotors 52, 54 in the intake air fuel is used to enrich the air-fuel mixture at cold start of the engine and to achieve a higher engine performance.

By changing the gear ratio between the driving and driven toothed belt gears, the intake air can be adjusted to the required engine power and the fuel quantity can be assigned to optimal combustion.

Claims

claims

A motor device (10) comprising:

a) a reciprocating engine, in particular a two-stroke internal combustion engine, with

a piston (80) coupled to a crankshaft (12) and cyclically slidable between a top dead center and a bottom dead center;

a combustion chamber (84) formed above the piston (80), and

a crank space (82) formed below the piston (80),

b) a fuel line with an injection nozzle (86) opening into the combustion chamber (84),

c) an overflow opening (88) opening into the combustion chamber (84),

d) an exhaust gas opening (92) to an exhaust pipe leading away from the combustion chamber (84),

e) a crank space opening (94) opening into the crank chamber (82),

f) a supercharger (24) for conveying fresh gas and air, and

g) a control device,

in which

- The injection nozzle (86), the overflow (88) and the exhaust port (92) are arranged so that they are closed when the piston (80) is at top dead center, and are released when the piston (80) is at bottom dead center, and upon movement of the piston (80) from top dead center to bottom dead center first the injector (86) and then the overflow (88) and the exhaust port (92) are released, and

the control device during operation of the supercharger (24),

i) when the piston (80) is at top dead center, a

Fluid communication between the pressure side (26) of the supercharger (24) and the overflow (88) releases and fluid connections between the pressure side (26) of the supercharger (24) and the crank chamber opening (94) and between the crank chamber opening (94) and the overflow opening (88) closes, and

ii) during a phase in which the piston (80) moves from top dead center to bottom dead center, fluid communication between the

Pressure side (26) of the supercharger (24) and the crank chamber opening (94) and between the crank chamber opening (94) and the overflow opening (88) releases and closes a flow connection between the pressure side (26) of the supercharger (24) and the overflow opening (88) ,

2. Motor device according to claim 1, characterized in that the

Precompressor (24) is designed so that it can add fuel to the conveyed air to form fresh gas, but the supercharger (24) does not deliver fuel as long as the flow connection between the pressure side (26) of the supercharger (24) and the crankcase opening ( 94) is released.

3. Motor device according to claim 1 or 2, characterized in that the control device, when the piston (80) has reached the bottom dead center, a flow connection between the pressure side (26) of the supercharger (24) and the overflow (88) releases and fluid connections between the pressure side (26) of the supercharger (24) and the crank chamber opening (94) and between the crank chamber opening (94) and the overflow opening (88) closes.

4. Motor device according to one of the preceding claims, characterized in that the control device comprises a movable diaphragm (28), preferably a steel plate, which is arranged on the crank chamber opening (94).

5. Motor device according to one of the preceding claims, characterized in that the supercharger (24) has a rotary piston pump, in particular a Roots blower, with a pair of rotors (52, 54).

6. Engine device according to claim 5, characterized in that the fuel line to the pressure side (48) of a positive displacement pump (40) is connected, which has two gears (56, 58), one of which is driven by the crankshaft (12), wherein the gears (56, 58) of the positive displacement pump (40) at the same time form a gear for the pair of rotors (52, 54) of the supercharger (24).

7. Motor device according to claim 6, characterized in that the fuel line comprises a capillary tube (50).

8. Motor device according to one of claims 5 to 7, characterized in that the profile of the rotors (52, 54) is designed with two leaves in the manner of a lemniscate.

9. Motor device according to one of claims 5 to 8, characterized in that at least one of the rotors (52, 54) a cyclically variable flow connection between the pressure side (48) of the positive displacement pump (40) and the pressure side (26) of the supercharger ( 24).

10. Motor device according to claim 9, characterized in that at least one further fuel line by a rotationally fixed to the rotor (52, 54) coupled shaft (36, 38) and by a wing of the rotor (52, 54) and extends to an opening ends in the wing.

11. Motor device according to claim 10, characterized in that the opening in the wing as a nozzle (70) is formed.

12. Motor device according to one of claims 6 to 11, characterized in that the pressure side (48) of the positive displacement pump (40) via intersecting holes in a housing cover of the supercharger (24) is connected to a distributor space, which in turn in conjunction with holes ( 66, 68) in the shafts (36, 38) of the rotors (52, 54).

13. Motor device according to claim 12, characterized in that at the intersecting holes, one, preferably by a thread, adjustable means for fuel quantity regulation is arranged.

14. Motor device according to one of claims 6 to 13, characterized in that the housing of the positive displacement pump (40) to the housing (42) of the supercharger (24) is flanged.

15. Motor device according to one of the preceding claims, characterized in that the supercharger (24) from the crankshaft (12) via a endless power transmission element (34), preferably a toothed belt, is driven non-positively.

16. Engine device according to one of the preceding claims, characterized in that between the crankshaft (12) and the supercharger (24) a transmission, preferably a belt transmission, is provided with a specific transmission ratio.

17. A method for operating a reciprocating engine, in particular a two-stroke internal combustion engine, with a combustion chamber (84) and a crank chamber (82) and a cyclically displaceable between a top dead center and a bottom dead center piston (80), the method comprising the steps of:

direct injection of fuel into the combustion chamber (82),

- Upon movement of the piston (80) from top dead center to bottom dead center first releasing an opening into the combustion chamber (84) injection port and then releasing an exhaust port (92) to a combustion chamber (84) leading away the exhaust pipe and into the combustion chamber (84) opening overflow opening (88),

Supplying air without fuel into the crank chamber (82) while the piston (80) is moving from top dead center to bottom dead center, and

Purging the combustion chamber (84) with air from the crank chamber (82) when the

Overflow (88) and the exhaust port (92) are released.

18. The method according to claim 17, characterized in that the exhaust gas outlet (92) remains closed as long as fresh gas is supplied into the combustion chamber (84) through the overflow opening (88).

19. The method according to claim 17 or 18, characterized in that both the air that is supplied into the crank chamber (82), as well as the fresh gas that is supplied into the combustion chamber (84), at least partially by a supercharger (24) provided.

20. The method according to claim 19, characterized in that the supercharger (24) promotes only air, as long as a flow connection between the pressure side (26) of the supercharger (24) and the crank chamber (82) consists, and the fuel is added to the air when there is a flow connection between the pressure side (26) of the supercharger (24) and the combustion chamber (84).