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Paramétrages

Paramétrages

1. WO2005061868 - MOTEUR A COMBUSTION INTERNE

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

Title: A combustion engine

Technical Field

The invention relates to a combustion engine including at least one cylinder with an associated cylinder head, and a reciprocating piston, where the cylinder, the cylinder head and the piston define a combustion chamber, said combustion engine further including at least one inlet valve or inlet port for the feeding of air and/or a mixture of air/fuel to the combustion chamber during the intake period, at least one exhaust valve or exhaust port for the removal of exhaust gas from the combustion chamber during the exhaust period, a further air-supply valve arranged in the cylinder head or an upper portion of the cylinder, as well as a control and operating device for controlling the opening and closing of said air-supply valve in such a manner that compressed air from an associated compressed-air source is fed to the combustion cham-ber during an air-supplying period which overlaps at least partially the exhaust period.

Background Art

US 4,217,866 discloses a four-stroke cycle combustion engine of the above type where the additional air-supply valve is shaped as a conventional combustion engine valve and is mechanically controlled by a camshaft. The up-to-date engines often include two or more both inlet valves and exhaust valves, and it is very difficult to make room for an additional conventional valve and a camshaft for controlling the opening and closing of said valve. In addition, the inclusion of an additional camshaft-controlled valve involves rather extensive structural modifications of the engine. Finally, the camshaft-controlled valve is encumbered with the draw-back that the camshaft continues to open and close said valve in case the supply of compressed air fails, which can have serious consequences for the air-supply system because hot combustion gas or exhaust gas is thereby pressed into said air-supply system.

Disclosure of Invention

The object of the invention is to provide a combustion engine of the above type which eliminates or at least reduces the draw-backs of the above known combustion engines.

The combustion engine according to the invention is characterised in that the air-supply valve is formed by an independent, separate, hydraulically or preferably electrically operated valve unit interchangeably arranged in the cylinder head or in the upper portion of the cylinder, said valve unit including a valve housing with an inlet and an outlet with an outlet opening which opens into the combustion chamber, and where said valve unit further includes a valve seat arranged between the inlet and the outlet as well as a valve member arranged in the housing, said valve member including a valve head displaceably arranged between an open and a closed position rela-tive to the valve seat.

Generally speaking, a supply of air during a phase of the exhaust stroke results in the advantage that most of, if not all the combusted gas or exhaust gas is removed from the combustion chamber before the succeeding intake period is initiated. As a result the mixture of fuel/air is cleaner than hitherto known during said intake period. Consequently, the combustion is cleaner than hitherto known, and accordingly the pollution and the fuel consumption are reduced, the engine performance is increased and the engine torque is improved.

By providing the air-supply valve in form of an independent, separate valve unit which is hydraulically or preferably electrically operated, a simple, reliable and space-saving solution is obtained because an electrically or hydraulically operated valve unit can be formed so as to require less space and fewer modifications of the engine than hitherto known camshaft-controlled valves. In addition, an electrically or hydraulically operated valve unit renders it possible in a simple manner to prevent an opening of the valve and thereby to allow a normal operation of the engine. In other words, the engine can run without the supply of additional air which has not been possible in connection with the conventional camshaft-controlled valves. Finally, it is possible in a relatively simple manner to retrofit the hydraulically or electrically operated valve units on existing engines, as well as thereby to obtain the op-erational advantages mentioned above in connection with the supply of additional air.

According to the invention, the valve head may be preloaded to adopt its closing position with the effect that an opening and consequently a supply of compressed air to the combustion chamber is only obtained when the valve unit is activated by means of the control and operating device. Consequently, an opening of the valve is avoided in case the control and operating device fails.

Moreover, the inlet, the valve member, the valve seat and the outlet of the valve may according to the invention be coaxially arranged with the advantageous result that a particularly compact and space-saving embodiment of the valve unit is obtained.

Furthermore according to the invention, the valve unit may according to a preferred embodiment be an electromagnetically operated valve unit including a coil arranged in the valve housing and surrounding an inlet member serving as a core, and an armature connected to the valve member.

Such electromagnetic valves are known per se because they are today used for injection of fuel into the inlet port of the engine or directly into the combustion chamber. Therefore, at present it is preferred to use the principles known from the fuel injection valves for the valve unit for injection of air into the combustion chamber. Such fuel injection valves appear inter alia from EP 0 602 001 Bl, EP 0 201 190 Bl and US 4,423,842, and as far as the fundamental structures of an air-supply valve are concerned, reference is made to these publications.

Moreover, the valve member and the valve seat of the valve unit may according to the invention be arranged upstream the outlet opening of the valve when seen in the outflow direction of the air. This preferred embodiment of the valve unit renders it possible to obtain an optimum displacement or scavenging of the combustion gases from the combustion chamber by means of the shape of the valve outlet and the valve outlet opening.

Furthermore, at least one outlet opening of the valve unit may according to the invention be shaped in such a manner that an air jet leaving said outlet opening is substantially conical with the peak thereof being at said outlet opening. Such an em-bodiment of the invention renders it possible to position the outlet opening of the valve unit in such a manner in the combustion chamber that the air jet entering said outlet opening forces the combustion gas or the exhaust gas out through the exhaust valve or the port in an optimum manner.

In addition, a detecting means connected to the control and operating device may according to the invention be provided for detecting the pressure of the supplied compressed air, and the control and operating device may include means for preventing an activation of the valve so as to enter its open position when the air pressure is below a predetermined value. In this manner it is advantageously avoided that exhaust gas is pressed into the air-supply system in case the pressure provided by the pressure source is not sufficiently high for suppressing the pressure inside the combustion chamber. Such a situation can be caused by a failure in the compressed-air source, said compressed-air source preferably being formed by a compressor.

Furthermore, a compressed-air tank can be arranged between the compressed-air source and the valve, said compressed-air tank ensuring the desired pressure in the compressed air fed to the combustion chamber.

In the latter connection, the detecting means can be connected to the compressed-air tank.

Finally, when the engine is a four-stroke cycle engine the control and operating device may according to the invention be adapted to activate the valve unit so as to enter its open position and thereby allow a supply of compressed air during the last phase, preferably the last third or less of the exhaust stroke, where the supply of air is preferably interrupted before the exhaust valve is efficiently closed, hi order to minimize the supplied quantity of compressed air and the pressure thereof and consequently the power necessary for providing said compressed air, it is preferred to supply the compressed air to the combustion chamber at a relatively late phase during the exhaust stroke and while the exhaust valve is relatively open. Accordingly, the primaiy object of the invention is not to carry out a pressure charging of the suction stroke.

In connection with a two-stroke cycle engine it is preferred that the control and operating device is adapted to activate the valve unit so as to enter its open position and thereby to supply compressed air during the period from the initial opening of the inlet port and until said inlet port is two thirds open. It should be understood that the valve unit is not necessarily open during the entire period.

It is preferred to supply the compressed air to the combustion chamber at a pressure below 5 bar, preferably below or equal to 3 bar.

Brief Description of the Drawings

The invention is explained in detail below with reference to the accompanying draw-ings, in which

Fig. 1 is a diagrammatic view of a four-stroke cycle combustion engine according to the invention with four cylinders,

Fig. 2 is a diagrammatic, vertical, sectional view through a cylinder of the engine of Fig. 1 and including a preferred embodiment of an air-supply valve unit, Fig. 3 illustrates on a larger scale a sectional view through the air-supply valve unit of Fig. 2 in form of an electromagnetic valve unit, and

Fig. 4 is a diagrammatic, sectional view tlirough a further air-supply valve unit in form of a hydraulically operated valve unit.

Best Mode for Carrying out the Invention

Figs 1 and 2 show an embodiment of a combustion engine 1 according to the invention with four cylinders 2 with associated cylinder heads 3. Each cylinder 2 houses a reciprocating piston 4, and the cylinder head 3 defines together with the cylinder 2 and the piston 4 a combustion chamber 5. The cylinder head 3 is provided with an intake port 6 and an exhaust port 7. The intake port 6 is open into the combustion chamber 5 tlirough an intake opening 8, and the exhaust port 7 is open into the combustion chamber 5 through an exhaust opening 9. In a manner known per se, the cylinder head 3 further includes an intake valve 10 with a valve head 11 displaceable between an open and a closed position relative to the intake opening 8. The cylinder head 3 is further provided with an exhaust valve 12 with a valve head 13 displace-able between an open and a closed position relative to the exhaust opening 9. The inlet valve 10 is shown in the closed position whereas the exhaust valve 12 is shown in the open position.

The piston 4 is shown during its upward movement during the exhaust stroke where the exhaust valve 12 is open.

An air- supply unit 15 is furthermore arranged in a bore 14 in the cylinder head 3. This air-supply unit 15 includes an outlet opening 16 opening into the combustion chamber 5, and it is adapted to supply compressed air to the combustion chamber 5. The air- supply valve unit 15 is an elecfromagnetic valve described in greater detail below.

As illustrated in Fig. 1, an air-supply valve unit 15 is arranged in each cylinder head 3. Through an air- supply line 17 connection to a compressed-air tank 18, the air-supply valve units 15 are connected to a compressed-air source 19 in form of a com-pressor. In addition, each air-supply valve unit 15 is connected to a control and operating device 21 through a line 20. The control and operating device 21 controls the opening and closing of the air-supply valve units 15 in such a manner that the combustion chamber 5 is supplied with compressed air for a predetermined period of time during the power stroke of the pistons 4 inside the cylinders 2 in question with the associated cylinder heads 3.

The above period of time corresponds to at least the last phase, viz. the last half of the exhaust stroke, and preferably the last third of said exhaust stroke where the exhaust valve 12 is efficiently open, the object of injecting compressed air into the combustion chamber being to expel the mixed gas or the exhaust gas from said combustion chamber 15 tlirough the exhaust port 7. In this connection it should be noted that the position shown in Fig. 2 of the air-supply valve unit 15 and of the outlet opening 16 thereof is included for the sake of illustration. In practice, the outlet opening 16 is directed such that in an efficient manner the supplied compressed air presses the exhaust gas out of the combustion chamber 5 and into the exhaust port 7. Accordingly, in practice the outlet opening 16 of the air-supply valve unit 15 is rather directed as shown in Fig. 1 , i.e. in a direction away from the opening 9 of the exhaust port and towards the opening 8 of the intake port duct 6 in such a manner that the supplied compressed air circulates inside the combustion chamber 5. In or-der to minimize the quantity of supplied compressed air, said air is preferably only supplied during the last phase of the exhaust stroke and preferably at a relatively low pressure of below 5 bar and preferably below 3 bar.

Referring again to Fig. 1, the compressed-air tank 18 is provided with a pressure sensor 22 detecting the pressure of the compressed air inside said compressed-air tank 18. The pressure sensor 22 is connected to the control and operating device 21 tlirough a line 23, said control and operating device monitoring the pressure inside the compressed-air tank 18 detected by the sensor 22. The control and operating device only activates the air-supply valve unit 15 so as to open in case the detected pressure exceeds a predetermined value. The predetermined value must with abso-lute certainty exceed the pressure provided during the exhaust stroke inside the combustion chamber 5, and accordingly combustion gas is prevented from being pressed into the air-supply valve unit 15 and the associated air-supply system during the exhaust stroke.

Fig. 3 is a diagrammatic, vertical, sectional view tlirough the elecfromagnetic air-supply valve unit 15. The air-supply valve unit 15 includes a housing 30 shown in form of a single part, but in practice it can include several parts. A coil 31 is arranged inside the housing 30 in a conventionally known manner, said coil being connected to the control and operating device 21 through a plug connection 33 and the line 20. The coil 31 surrounds an inlet member 34 serving as a core and being fixedly connected to the housing 30. The inlet member 34 is tubular with a hollow interior representing an inlet duct 35 for compressed air. A bushing 36 fixedly connected to the inlet member 34 is arranged in the inlet duct of said inlet member 34, and a preloading spring 37 abuts the lower end of said bushing 36. The lower end of the preloading spring 37 abuts a tube 38 of a valve member 47, and a tubular armature 39 is secured to the outer side of the upper end of said tube 38. The armature 39 is guided in a bore 40 in the lower portion 41 of the housing 30. A valve head 42 is secured at the lower end of the tube 38, said valve head 42 sealingly engaging a valve seat 43 in the non-activated position of the valve unit 15 due to the preloading of the spring 37. The housing 30 is provided with an outlet or ejection opening 44 downstream the valve seat 43.

Thus the compressed air supplied to the valve unit 15 through the supply pipe 17 is present in the inlet duct 35 of the inlet member 34, in the interior of the tube 38 as well as in the area between said tube 38 and the bore 40 in the lower portion 41 of the housing and forwards to the sealing area between the valve head 42 and the valve seat 43, said tube 38 being provided with radial openings 45. When the valve unit 15 is activated, i.e. when the coil 31 is fed with current from the control and operating device 21 through the line 20, the armature 39 of the tube 38 is pulled towards the inlet member 34 serving as a core. As a result, the valve head 42 fixedly connected to the lower end of the tube 38 is raised from the valve seat 43, and accordingly compressed air exits through the outlet opening 16 of the valve unit and enters the combustion chamber 5. The opening or upward movement of the valve unit is determined by the distance 46 between the lower end of the inlet member 34 and the upper end of the tubular armature 39 in the closed position of the valve member 47. The valve member 47 is formed by the valve head 42, the tube 38 and the armature 39 secured to said pipe. Finally, it should be noted that the lower portion 41 of the valve housing 30 is provided with an external thread 48 allowing the valve unit to be releasably mounted in the mounting bore 14 of the cylinder head 3, cf. Fig. 2.

Fig. 4 is a diagrammatic, sectional view tlirough a further embodiment of an air-supply valve unit 55 in form of a hydraulically operated valve unit. This valve unit includes a valve housing 56 which is divided into an upper hydraulic chamber 57 with an inlet 58 and a lower compressed- air chamber 60 with a compressed-air inlet 61 by means of partition 65. At its lower end, the compressed-air chamber 60 con-tinues tlirough a valve seat 62 into a conically pointed outlet 63 ending in an outlet opening 65. The lower portion of the housing is provided with an external thread 66 allowing the valve unit 65 to be mounted in a mounting bore in the cylinder head 3, cf. the above explanation associated with Figs. 1 to 3.

A valve member 67 is displaceably arranged inside the housing 55. This valve member 67 includes a valve stem 68 which is provided with a disc-shaped valve head 69 at its lower end. The valve head 69 is preloaded by means of a spring 70 towards its closed position in which it sealingly engages the valve seat 62. The valve stem 68 extends in a sealed manner through an opening 71 in the partition 65 and upwards into the hydraulic chamber 57. At its upper end, the valve stem 68 is provided with a piston 72 sealingly engaging the inner surface of the housing 56. A scavenged chamber 73 is defined between the piston 62 and the housing above said piston 62. Thus the hydraulic chamber 57 with the inlet 58 is per se defined between the lower face of the piston, the upper face of the partition 65 and the inner surface of the housing 56.

The compressed-air chamber 60 is continuously fed with compressed air presenting a pressure determined by the pressure supplied by the associated compressed-air source, cf. the arrow 74. In order to open the valve unit 55, compressive pulses are supplied to the hydraulic chamber 57 by a pressure-supplying source, cf. the arrow 75. The feeding of a compressive pulse has the result that the pressure inside the hydraulic chamber 57 is increased so as to exceed the preloading of the spring 70. As a result, the valve member 67 is moved upwards and the valve head 69 is raised from its engagement with the valve seat 62. As a result, compressed air exits the compressed-air chamber 60 through the outlet 63 and further through the outlet opening 64 into the combustion chamber 5. A removal of the compressive pulse has the effect that the spring 70 forces the valve member 69 into engagement with the valve seat 62 whereby the discharging of compressed air is interrupted. The pressure-supplying source supplying the compressive pulse can for instance be a piston pump or a cylinder/piston unit with the result that the compressive pulse is generated during the forward movement of the piston, and that said compressive pulse is interrupted by the returning movement of said piston.

The invention has been described above with reference to a four stroke cycle engine, which, of course, can be a gasoline engine, a gas engine as well as a diesel engine. However, it should be understood that the invention can also be used in connection with two stroke cycle engines. When it is a question of a two stroke cycle engine, the injection of compressed air is, however, carried out while the inlet port is open and preferably at a time between the initiation of the opening thereof and the moment the port is two third open during the downward movement of the piston.