The invention is classified in the International Patent Classification as F, Machines or Engines in General ; FOIL, Cyclically Operating Valves for Machines or Engines, which includes piston-engine valve mechanisms.

2. TECHNICAL PROBLEM Internal combustion engines, in order to facilitate the medium exchange, have intake and exhaust valves in each cylinder head. The valves are operated by cams on camshaft. The valve opening and closing moments are determined by the cam position and shape.

Regardless of the engine working conditions (change of the number of revolutions, load, etc.), the valve opening and closing moments with the present engines are always the same. At changing of the engine working conditions, there appears need of changing the cam position against the camshaft and changing of cam shape, i. e. of controlling the cam shaft motion.

3. STATE OF THE ART In internal combustion engines, the crankshaft drives camshaft by means of a chain, belt or gears. The intake and exhaust valves opening and closing moments are always the same, regardless of the engine working conditions.

4. DISCLOSURE OF THE INVENTION The valve opening and closing mechanism enables changing of the intake and exhaust valves opening and closing moments as required, i. e. in accordance with the engine working conditions. To facilitate this, the valve opening and closing mechanism has a gear transmission for controlling the camshaft, and a camshaft with adjustable cams. The camshaft consists of a hollow shaft through which passes a solid shaft. Cams are situated on both the hollow and the solid shafts, the solid-shaft cam passing through a slot in the hollow-shaft cam. The crankshaft drives the camshaft control mechanism, changing thereby the cam shape and position, which in turn changes the valve opening and closing moments in accordance with changes of the engine working conditions.

5. ILLUSTRATION DESCRIPTIONS Figure 1 shows a partial section through the valve opening and closing mechanism.

Figure 2 shows camshaft with adjustable cams positioned as when the hollow shaft is turned against the solid shaft by an angle a.

Figure 3 shows camshaft with cams positioned as when the solid shaft is turned against the hollow shaft by an angle p.

Figure 4 shows position and shape of cams on the camshaft when the engine works in normal working conditions.

Figure 5 shows the adjusted position and shape of cams on the camshaft when the engine works in changed working conditions.

As evident in Figure 1, the valve opening and closing mechanism consists of a gear transmission that drives the camshaft A, and of the camshaft with adjustable cams B. The gear transmission for driving the camshaft consists of gear belt 1, cylinder gears with outer and inner gears 2, planetary gears for hollow shaft 3, lever 4 for moving the planetary gears 3, cylinder gears on the hollow shaft 5, planetary gears for the solid shaft 6, lever 7 for moving the gears 6, cylinder gears on the solid shaft 8, and bearings 14,15 and 16. The camshaft with adjustable cams B consists of hollow shaft 9, cams 10 on the hollow shaft 9, solid shaft 12, cams 13 on the solid shaft 12 and bearings 17.

6. DETAILED DESCRIPTION OF THE INVENTION EMBODIMENT The crankshaft (not presented in the illustration), by means of a gear belt 1 or by a chain or gears (not presented in the illustration), drives the gear transmission that operates the camshaft A by means of operating the cylinder gears with outer and inner gears 2. The cylinder gears 2, by means of the planetary gears 3 and the planetary gears 6, drives the cylinder gears 5 on the hollow shaft 9, and the cylinder gears 8 on the solid shaft 12. The planetary gears 3 rotate around the lever 4 in the axis y, whereas the planetary gears 6 rotate around the lever 7 in the axis z.

The planetary gears 3 can be moved by the lever 4 along the cylinder gears 5 circumference by a certain angle a, whereas the planetary gears 6 can be moved by the lever 7 along the cylinder gears 8 circumference by a certain angle 3. Levers 4 and 7 have bearings for turning and controlling in the axis x.

The cylinder gears 2, cylinder gears 5 and 8, and the hollow and the solid shafts 9 and 12 have the common rotation axis x.

The cylinder gears 5 are fixed to the hollow shaft 9. On the hollow shaft 9, there are cams 10 with slots 11. The cylinder gears 8 are fixed to the solid shaft 12. On the solid shaft 12, there are cams 13 that pass through the slots 11 in the cams 10 on the hollow shaft 9. The solid shaft 12 passes through the hollow shaft 9, both of them rotating in the same direction and simultaneously. The solid and the hollow shafts may turn by a certain angle, independently from each other, both when inactive and active. The turning is achieved by moving of the planetary gears 3 and 6 by means of the levers 4 and 7.

When the engine is normally loaded, cams 10 on the hollow shaft 9, and cams 13 on the solid shaft 12, are positioned as shown in Fig. 4. However, when the engine working conditions change, the camshaft operating mechanism enables adjustment of the cam position and shape. By moving the planetary gears 3 and/or 6, by a certain angle a or ß (Figs. 2 and 3), position and shape of the cams 10 and 13 are being adjusted as shown in the Fig. 5, effecting thereby the intake and exhaust valves opening and closing moments. In that case, while the engine works, the intake and exhaust valves open and close at given angles, depending on the piston position. At changing the engine working regime (number of revolutions, load, etc.), there appears need for changing the valve opening and closing angle. Turning of the axis y around the axis x during the work of the engine, causes relative turning of the gears 5 against the gears 8, which means turning of the cam 10 against the cam 13. The same can be achieved by turning the axis z around the axis x, that is of the gears 8 against the gears 5, which means that cam 13 is turned against the cam 10.

The cams 10 and 13 can be turned simultaneously, if so required.

The above described procedure can be fully automatic, so that the cam position and shape on the camshaft are being adjusted automatically in accordance with the engine working conditions.

Component parts of the mechanism are shown partly in cross-section in Fig. 1.

7. INVENTION APPLICATION The valve opening and closing control mechanism can be applied with all piston engines where the intake and exhaust valve operation is to be adjusted in accordance with changes of the engine working conditions, such as internal combustion engines, piston compressors, etc.