IGNITION DEVICE FOR RECIPROCATING INTERNAL COMBUSTION ENGINE

Abstract: Reciprocating internal combustion engine (1) comprising at least one combustion chamber (4) with a screwthreaded hole (6) in a wall thereof, normally provided for mounting a spark plug. In the screwthreaded hole (6) a pre-chamber member (8) is mounted, said member enclosing a pre-combustion chamber (10) and comprising a wall section (12) provided with at least one orifice with a smaller cross-section than the pre-chamber and forming a communication opening between the combustion chamber (4) and the pre-chamber (10), said spark plug being connected with the pre-chamber member, for example by screwthread engagement or by forming an integral unit therewith, such that the spark plug electrodes (9) are exposed in the pre-chamber.

Description: Ignition device for reciprocating internal combustion engine. The invention relates to a reciprocating internal com¬ bustion engine comprising at least one combustion chamber and an ignition device, including a spark plug mounted in a screw¬ threaded hole in a wall of the combustion chamber such that electrodes of the spark plug are in communication with the in¬ terior of the combustion chamber. In such an engine a combustable gas mixture is com¬ pressed and after compression ignited by a spark at the elec¬ trodes of the spark plug, which spark is generated by means of a high tension ignition coil of the ignition device. The ignition causes combustion of the gas mixture and the occur¬ ring high pressures are converted in mechanical power in a way known per se. To obtain a good ignition with a sufficient intensity at the right moment of the working cycle of the engine, the ignition device are made high demands upon. If this device is not working optimally, the combustion is not complete with as a consequence a reduced efficiency and an increased emission of harmful waste products. The invention has for its object to provide an engine of the kind set forth above, in which with strongly differ¬ ring circumstances for the ignition device an optimal overall performance of the engine is obtained. With an internal combustion engine according to the invention this is achieved in that in the screwthreaded hole a pre-chamber member is mounted, said member enclosing a pre- combustion chamber and comprising a wall section provided with at least one orifice with a smaller cross-section than the pre-chamber and forming a communication opening between the combustion chamber and the pre-chamber, said spark plug being connected with the pre-chamber member such that said elec¬ trodes are exposed in the pre-chamber. In the pre-combustion chamber a pre-ignition takes place which produces a fire jet out of the orifice into the combustion chamber, which fire jet ignites the main combustion in the combustion chamber. Even if the ignition device is not working optimally, with as a consequence a not fully optimal combustion in the pre- chamber, nevertheless an optimal main combustion will take place through the fire jet, which is very strong in relation to an ignition spark, even with a not fully optimal pre-com¬ bustion. It is found that the engine according to the inven- tion emits clearly fewer harmful waste products. Also it is found that fuel with a relatively low volatility such as kerosene or diesel oil, can also successfully be used in an engine according to the invention. Further it is found that the engine according to the invention is less sensitive for detonation, probably because the glowing spark plug electrodes are not directly exposed in the combustion chamber, such that fuels with lower octane numbers can be used. An existing internal combustion engine can be easily converted to an engine according to the invention, when the pre-chamber member is a substantially tube-formed member, at one end comprising the wall section with at least one orifice and at the opposite end a screwthreaded hole in which the spark plug is mounted, said member externally at the one end being provided with screwthread engaging in the , screwthreaded hole in the combustion chamber wall. The spark plug engaged in the pre-chamber member can be of a smaller type than origi¬ nally used for the respective engine. The invention relates to and provides furthermore a pre-chamber member to be used in an internal combustion engine according to the invention. According to a further development of the invention the wall section is formed by an annular member being enclosed in a body of the pre-chamber member and dimensioned in such a way that with substantially equal temperatures of the annular member and the body, the former has a sliding fit in the latter. With low operation temperatures, that is shortly after starting the engine equipped with a pre-chamber member of this kind, the annular member is swiftly at a higher tempera¬ ture, as the heat transfer towards the body of the pre-chamber member is low. Therefore, in the pre-chamber member swiftly favourable operation conditions are established. Overheating of the annular member is prevented as with rising temperature, the contact of the annular member with the body becomes stronger with increasing heat transfer. . , According to a preffered embodiment of the invention the pre-chamber member is formed integral with the spark plug. The existing spark plugs of a motor, therefore, can - easily be replaces by a spark plug having a. pre-chamber mem¬ ber according to the invention. According to a further development the wall section comprises a number of orifices, the axes of which diverge in¬ to the combustion chamber. In this way a number of fire jets are produced by the pre-combustion. The invention will be further illustrated in the following description of examplary embodiments, in conjunc- tion with the accompanying Figures. Fig. 1 shows a partial cross-section of an internal combustion engine according to the invention. Fig. 2 is a cross-section showing a second embodiment of a pre-chamber member. Fig. 3 shows a third embodiment. Fig. 4 shows a fourth embodiment. Fi . 5 shows a cross-section according to V-V in Fig. 4. In Fig. 1 the reference numeral 1 designates reci- procating internal combustion engine. This engine 1 comprises a cylinder 2 in which a piston 3 reciprocates in a known manner by means of a crank mechanism. In the upper part of the cylinder 2 a combustion chamber 4 is defined. In the wall 5 of this combustion chamber 4 a screwthreaded hole 6 is pro¬ vided. This screwthreaded hole can be the hole in which nor¬ mally a spark plug is engaged. According to the invention in the screwthreaded hole 6 a pre-chamber member 8 is mounted. This member 8 encloses a pre-combustion chamber 10 and a wall section 12 in which a orifice 11 is provided with a smaller cross-section than the cross-section of the pre-chamber 10. As is clear from the Figure the pre-chamber member 8 is substantially tube-formed and has at the end opposite to the orifice 11 a screwthreaded hole 13 in which a spark plug 7 is engaged. This spark plug 7 can be of a smaller type than normally used for an engine of the present kind, so that the pre-chamber member 8 together with the spark plug 7 can be replaced for an existing spark plug of a bigger type. The spark plug 7 is mounted in such a way in the pre- - chamber member 8, that its electrodes 9 are exposed in the pre-combustion chamber 10. In Fig. 1 the piston 3 is shown at the end of the com- pression stroke, in which combustable gas mixture is com¬ pressed in the combustion chamber 4. By this compression also some of the gas mixture is flown through the orifice 11 in the pre-chamber 10. At the right timing, a spark is produced at the electrodes 9, which spark ignites the gas mixture in the pre-chamber 10 and, therefore, causes combustion thereof. Because of this combustion the pressure in the pre-chamber 10 rises rapidly, causing a part of the burning gasses to be ex¬ pelled.through the orifice 11 into the combustion chamber 4. This fire jet, which is much more powerful than a normal spark of a spark plug very thoroughly and reliably ignites the compressed gasses in the combustion chamber 4. As a con¬ sequence, the combustion of these gasses takes also place very thoroughly. Fig. 2 shows a second embodiment of a pre-chamber mem- ber 15. This pre-chamber member 15 also comprises a pre- chamber 16. The wall section of the pre-chamber member 15 is formed by an annular member 17 which is enclosed in the body of the member 15. With substantially equal temperatures of the body and the annular member, this annular member has a sliding fit in the body. After the initial starting up of the engine, the pre-combustion caused by the spark plug 19 in the pre-combustion chamber 16 and the fire jet through the ori- fice 18 very rapidly heats up the annular member 17, as the heat transfer from the annular member 17 to the surrounding body of the pre-chamber member 15 is poor, as a consequence of the sliding fit. Therefore, in the pre-chamber 16 very rapidly favourable operating conditions are formed. In the embodiment 20 of the invention shown in Fig. 3, the spark plug and pre-chamber member are formed integral¬ ly. The pre-chamber 26 is formed in a lower part of the spark plug 20. The central electrode which is surrounded by isola¬ tion material 25 in a way known as such, does not extend out of the spark plug but ends inside the plug. In this embodi¬ ment the mass electrodes are formed by side electrodes 22. The wall section 23 is formed as an annular member, which is mounted to the body of the spark plug 20 by means of a cir- clip 24. The pre-chamber member 30 of Fig. 4 mainly corresponds to the pre-chamber member 8 of Fig. 1. The member 30, however, comprises a wall section 31 which has nine orifices 32 having axes which diverge outwardly. With this embodiment a number of fire jets is formed.

Claims: C l a i m s 1. Reciprocating internal combustion engine compris¬ ing at least one combustion chamber and an ignition device, including a spark plug mounted in a screwthreaded hole in a wall of the combustion chamber such that electrodes of the spark plug are in communication with the interior of the com¬ bustion chamber c h a r a c t e r i z e d in that in the screwthreaded hole a pre-chamber member is mounted, said member ' enclosing a pre-combustion chamber and comprising a wall section provided with at least one orifice with a smaller cross-section than the pre-chamber and forming a communication opening between the combustion chamber and the pre-chamber, said spark plug being connected with the pre-chamber member such that said electrodes are exposed in the pre-chamber. 2. Internal combustion engine according to claim 1, c h a r a c t e r i z e d in that the pre-chamber member is a substantially tube-formed member, at one end comprising the wall section with at least one orifice and at the opposite end a screwthreaded hole in which the spark plug is mounted, said member externally at the one end being provided with screwthread engaging in the screwthreaded hole in the combus¬ tion chamber wall. 3. Pre-chamber member to be used in an internal com¬ bustion engine according to claim 1 or 2. 4. Pre-chamber member according to claim 3 c h a r a c t e r i z e d in that the wall section is formed by an annular member being enclosed in a body of the pre- chamber member and dimensioned in such a way that with sub¬ stantially equal temperatures of the annular member and the body, the former has a sliding fit in the latter. 5. Pre-chamber member according to one of the claims 3 and 4, c h a r a c t e r i z e d in that it is formed integral with the spark plug. 6. Pre-chamber member according to one of the claims 3 to 5, c h a r a c t e r i z e d in that the wall section comprises a number of orifices, the axes of which diverge into the combustion chamber.

Inventors: BAKKER ALBERT, BAKKER, ALBERT
Applicants: BAKKER ALBERT, BAKKER, ALBERT
Application year: 1984
Main classification: H01T13
IPC codes: F02P13, H01T13