The invention relates to a cylinder head device for an internal combustion engine with at least one cylinder. For each cylinder in the engine a combustion chamber is defined by the cylinder head together with the cylinder wall and the end surface of a piston in the cylinder. The cylinder head for each cylinder comprises, firstly, at least one inlet channel with an inlet valve for regulating the communication between the inlet channel and the combustion chamber, secondly, at least one outlet chamber with an outlet valve for regulating the communication between the combustion chamber and the outlet channel and, thirdly, at least one spark plug.

Cylinder heads ofthe above mentioned types are used in almost all internal com¬ bustion engines which are manufactured for use in motor vehicles and the like, for example. The valves are usually in the form of poppet or disc valves, which are very effective for regulating gas exchange in the engine.

In designing internal combustion engines, it is a general goal to increase the effici¬ ency of the engine. With increased efficiency it is possible to reduce fuel consump¬ tion and reduce the percentage of harmful emissions in the engine exhaust. For engines working under varying operating conditions, e.g. in motor vehicles, it is a goal to make the engines more adaptable to prevailing operating conditions. In order to achieve this, it has been proposed to change the compression ratio in the engine cylinders, to change the fuel supply and ignition system and to change the valve opening and closing times. These steps can be taken separately or in various combi- nations.

Changing the compression ratio in the engine cylinders is an effective measure for adapting the engine to various operating conditions, and thereby achieve an increase in efficiency. Various devices for achieving a change in the engine compression ratio during operation are previously known, but certain of these known devices are of complicated design and are therefore expensive to manufacture and mamtain, while other known designs do not provide satisfactory results in practice. There is

therefore a need for a simple device for changing the compression ratio in an inter¬ nal combustion engine during operation for adaptation to various operating condi¬ tions.

The present invention is therefore intended to achieve a cylinder head device for an internal combustion engine, said device making it possible to change the compres¬ sion ratio in the engine cylinders during operation in a simple and reliable manner. This is achieved according to the invention by means of a device which is provided with those features which are disclosed in the characterizing clause of claim 1.

Advantageous embodiments ofthe device according to the invention are defined in the subclaims.

The invention will be described in more detail below with reference to the accom- panying drawings, which show schematic, partially cut away views ofthe upper portion of an internal combustion engine with certain components left out. Figs. 1-5 show corresponding sectional views of the various components in the cylinder head and the upper portion ofthe engine in various positions, and Figs. 6a-i show, in extremely simplified form, various conceivable variants of a cylinder head in accordance with the invention as seen from the combustion chamber.

Figs. 1-5 show a portion of an internal combustion engine with an engine block 1 and a cylinder head 2. There is also shown a portion of a piston 3, which can reci¬ procate in a cylinder 4. The walls ofthe cylinder 4 define, together with the surface ofthe cylinder head 2 facing the cylinder 4 and the end surface ofthe piston 3, a combustion chamber 5. The cylinder head 2 is also made with an inlet channel 6, in which there is an inlet valve 7 for regulating the communication between the inlet channel 6 and the combustion chamber 5. There is also in the cylinder head 2 an exhaust channel 8 with an exhaust valve 9 for regulating the communication between the combustion chamber 5 and the exhaust channel 8. Furthermore, there is a spark

plug 10 mounted in the cylinder head 2 in such a manner that its electrode end at least partially protrudes into the combustion chamber 5.

As can be seen in the drawings, the spark plug 10 is screwed into a sleeve 11, which functions as a valve means, as will be described in more detail below. Fig. 1 shows the sleeve 11 in a first position, in which a sealing element 12, disposed at the sleeve 11 and located closest to the combustion chamber 5, with a contact surface 13 abuts against a seat 14 in the cylinder head 2. This provides a seal between the combustion chamber 5 and a chamber 15, which is formed in the cylinder head 2 and through which the sleeve 11 extends in the position shown in Fig. 1.

Fig. 2 shows the sleeve 11 in a second position, in which the sealing element 12 abuts with a second contact surface 16 against a second seat 17 in the cylinder head 2 at the end ofthe chamber 15 remote from the combustion chamber 5. This means that the chamber 15 has in this position free communication with the combustion chamber 5 and in practice is a part thereof. By moving the sleeve 11 between the first position shown in Fig. 1 and the second position shown in Fig. 2, it is therefore possible to provide two different compression ratios in the engine to adapt the engine to different operating conditions.

In order to move the valve means or sleeve 11 between the two positions, an opera¬ ting cylinder 18 is disposed in the cylinder head 2 coaxial to the sleeve 11. On the sleeve 11 an operating piston 19 is is fixed. The operating piston 19 is displaceable in the operating cylinder 18 and is sealed against the cylinder wall. The operating cylinder 18 is also provided with an intermediate wall, which is fixed and is intended for a purpose which will be described in more detail below. The sleeve 11 extends through the intermediate wall 20.

Two pressure medium channels 21 and 22 open into the operating cylinder 18 on either side ofthe operating piston 19. By supplying pressure medium to the opera¬ ting cylinder 18 through one or the other of the pressure medium channels 21 or 22, the operating piston 19, and thereby also the sleeve 11 with it, is displaced between its two positions. The pressure medium channels 21 and 22 are coupled in a manner,

not shown in more detail here, to a pressure medium system (not shown) with a pres¬ sure medium source and the required valves for regulating the pressure medium flow to and from the pressure medium channels 21 and 22.

Figs. 1 and 2 show the inlet valve 7 closed against the valve seat 23 in the cylinder head 2. The valve seat 23 is located at the end of a second chamber 24 remote from the combustion chamber 5. The second chamber constitutes in this position a portion ofthe combustion chamber 5. The valve 7 is operated in a conventional manner by means of a cam shaft 25 and a cam lobe 26 which actuates the valve 7 by means of a tappet 27. A valve spring 28 biases the valve 7 towards a closed position against the seat 23. Fig. 3 shows the valve 7 in the open position actuated by the lobe 26 of the cam shaft 25. It is also evident that the second chamber 24 here constitutes an expanded portion ofthe inlet channel 6, so that the flow about the inlet valve 7 is not affected negatively.

In Figs. 4 and 5 the inlet valve 7 is shown in another position, in which it abuts with a contact surface 29 against a seat 30 in the cylinder head 2 at the connection between the combustion chamber 5 and the second chamber 24. For moving the valve 7 to the position in contact with the seat 30, a rocker 31 is pivotally mounted on a shaft 32, which is mounted in the cylinder head 2 in a manner not shown in more detail here. One arm 33 of the rocker 31 actuates the tappet 27, while the other arm 34 is actuated by a second operating piston 35, which is displaceably arranged in the operating cylinder 18 on the opposite side ofthe intermediate valve 20 with respect to the first operating piston 19. The second operating piston 35 is thus in the foπn of a ring piston, and the sleeve 11 extends through at least a portion ofthe second operating piston 35. At its end remote from the intermediate wall 20, the operating cylinder 18 is sealed by means of an end wall 36 with an opening through which the second operating piston 35 extends.

Two pressure medium channels 37 and 38 open into the operating cylinder 18 on either side ofthe second operating piston 35 in the space between the intermediate wall 20 and the end wall 36. By supplying pressure medium to the pressure medium channel 37 or 38, respectively, the second operating piston 37 can be displaced in

the operating cylinder 18 between the position shown in Figs. 1-3, where the rocker 31 does not act on the tappet 27, and the position shown in Figs. 4 and 5 in which the arm 33 ofthe rocker 31, via the tappet 27, presses the inlet valve 7 into contact with the seat 30. The pressure medium channels 37 and 38 are connected to a pressure medium system (not shown) with a pressure medium source and required valves for regulating a pressure medium flow to or from, respectively, the pressure medium channels 37 and 38, respectively.

By either allowing the inlet valve 7 to work as a normal inlet valve against the valve seat 23 or keeping the inlet valve 7 closed against the seat 30, it is possible to achieve two different compression ratios in the cylinder 4 ofthe engine. When the inlet valve 7 is held closed against the seat 30, there must, of course, be at least one other inlet valve for the cylinder 4. It is also, of course, conceivable to use, instead of or in addition to the inlet valve 7, an exhaust valve for corresponding purposes, i.e. allowing an exhaust valve to work in a chamber in the manner described above for the inlet valve 7.

By using a conjoin/isolatable chamber with a valve means or a valve sleeve, such as the chamber 15 and the sleeve 11, and at least one other chamber with a valve, such as the chamber 24 with the valve 7, it is possible by suitable dimensioning ofthe chambers to change the compression ratio of the engine incrementally to adapt to various operating conditions. In order to illustrate a number of possible embodi¬ ments, Fig. 6 shows nine different embodiments in very schematic form. I designates inlet and exhaust valves of conventional type, while II designates valve means in the form of a sleeve with spark plug, corresponding to the sleeve 11 with the spark plug 10, and UI designates valves with chambers corresponding to the valve 7 and the chamber 24. It should, however, be observed that the valves HI can, of course, be either inlet or exhaust valves. It should also be observed that the embodiments shown in Fig. 6 are only examples and are not intended to provide a complete picture of all conceivable variants.

The invention is not limited to the above described examples. Rather, changes can be made within the scope ofthe following patent claims.