METHOD FOR PROVIDING VARIABLE COMPRESSION RATIO IN AN INTERNAL COMBUSTION ENGINE AND ACTUATOR FOR SAID METHOD

Abstract

In a combustion chamber of a piston combustion engine there is a displaceable piston that can be moved progressively up or down between an upper and a lower turning position. The displacement takes place via an electrically controlled step motor which is connected to the piston via a hydraulic link, including a hydraulic lock. The lock is deactivated during the displacement a certain number of steps up or down ordered by a motor control system, and when the displacement is ended, the lock is activated by said engine control system and the moving piston is locked in a certain position ordered by the motor control system.

Claims

1. A method to control the size of a combustion chamber by an actuator in the cylinder head of a piston combustion engine comprising: A vertically displaceable piston; A first chamber with a piston: associated shaft having a flange and a spring in the chamber acting between the flange and a chamber floor to reposition the piston in an upward direction; Wherein the actuator further comprises a second chamber and a third chamber filled with hydraulic fluid and separated by a valve with an opening, wherein the valve is horizontally repositionable via an electromagnet; Wherein the actuator further comprises a step motor and a shaft vertically displaceable by said step motor in the second chamber, the method comprising: Changing the size of the combustion chamber by displacing the valve with the electromagnet so that the opening connects the second and third chambers.

2. The method of claim 1, comprising downwardly displacing the shaft by the step motor, thereby forcing hydraulic fluid from the second chamber to the third chamber and downwardly displacing the piston-associated shaft to compress the spring while reducing the size of the combustion chamber until a repositioning of the shaft is ended.

3. The method of claim 1, comprising ending a repositioning of the shaft by displacing the valve so that the opening no longer connects the second chamber and the third chamber, whereby the piston is no longer displaceable.

4. The method of claim 1, comprising moving the shaft upwards by the step motor, thereby forcing the hydraulic fluid from the third chamber to the second chamber by action of the spring on the flange of the shaft, wherein the piston is moved upward at a same time as the spring expands such that a size of the combustion chamber increases until displacement of the shaft has come to an end.

5. The method of claim 1, comprising ending displacement of the shaft by displacing the valve so that the opening no longer connects the second chamber and the third chamber, whereby the piston is no longer displaceable.

6. An actuator comprising: a combustion chamber; a vertically displaceable piston; a chamber with a piston associated shaft with a flange; a spring between the flange and a chamber floor; two hydraulic fluid chambers; a valve with an opening; an electromagnet; a step motor; and a shaft displaceable in one of the hydraulic fluid chambers; wherein a size of the combustion chamber is changeable when the valve is displaced so that the opening connects the two hydraulic fluid chambers.

7. The method of claim 2, comprising ending a repositioning of the shaft by displacing the valve so that the opening no longer connects the second chamber and the third chamber, whereby the piston is no longer displaceable.

8. The method of claim 4, comprising ending the displacement of the shaft by displacing the valve so that the opening no longer connects the second chamber and the third chamber, whereby the piston is no longer displaceable.

Description

SUMMARY OF FIGURES

[0010] FIG. 1 shows schematically a section through the upper part of a diesel engine cylinder with cylinder head where the combustion chamber volume is adapted to small engine load and with the engine piston in its upper turning position after a compression stroke.

[0011] FIG. 2 shows schematically a section through the upper part of a diesel engine cylinder with cylinder head where the combustion chamber volume is adapted for maximum engine load and with the motor piston in its upper turning position after a compression stroke.

[0012] FIG. 3 shows schematically a section through the upper part of a diesel engine cylinder with cylinder head where the combustion chamber volume is adapted to medium-sized engine load and with the engine's piston in its upper turning position after a compression stroke

[0013] FIGS. 4-10 show schematically how an actuator 4 is deplacing a piston in a combustion chamber, ex.g. in a cylinder head of a diesel engine, shown in FIG. 1-3, and makes the piston to take different positions in dependent of the motor load. It is stressed that the invention can be used with all types of piston combustion engines.

[0014] FIG. 1 shows a schematic view of a cylinder of a diesel engine with a cylinder head 1 and with a piston 2 mounted on a crank shaft 3. An actuator 4 with a principal function according to the present invention is shown in FIGS. 4-10. A piston 5 can by an input from a motor control system, not shown, be controlled to take different positions in the combustion chamber 7 and thereby vary the volume on the portion under the piston, whereby an essential part of the combustion takes place when fuel is sprayed by the injector 9.

[0015] Said different positions are locked in a hydraulic circuit 6. An outlet valve 8 controlled by a cam shaft or by an actuator according to ex.g. patent (SE535886 C2, SE1100435A1) are schematically shown as well as an inlet valve 10, which preferably, but not necessary is opened and closed by an actuator on input from the control system of the engine, with a function according ex.g. any of said mentioned patents. An air mass meter 11 to measure the amount of air being introduced during the intake stroke through the inlet valve 10. The piston 2 is shown in upper turning position where it is prohibited to mechanically contact the cylinder head including the poppet valves 8, 10.

[0016] FIG. 2 shows the piston 5 in its upper position where the combustion chamber is at its maximum in size, and the engine can, but must not, be maximally loaded. Still can, as today more or less engine load be taken out depending how much fuel being injected, in such a case with the exhaust emission valid today. It may be advantageously having a little bowl in the piston where the bowl of today is situated, that is directly under the combustion chamber.

[0017] FIG. 3 shows a schematic view of the upper part of the cylinder of the engine with cylinder head where the volume of the combustion chamber is adapted to a middle big engine load and with the piston of the engine in its upper turning position after a compression stroke. In princip all air from the intake stroke is pressed into said volume. At the end of the compression stroke a suitable amount of fuel is injected to minimize NOx. Said activities are controllably performed by the control system of the engine.

[0018] FIG. 4 display part of the cylinder 1 with an actuator 4 according to the invention having a step motor 12 with a vertical, upward or downward displaceable shaft 13 running in a chamber 14 filled with hydraulic fluid. Further, there is shown a hydraulic lock 6 consisting of a valve with an opening where the valve is horizontal, left or right, displaceable in chamber 14 or between chamber 14 and below chamber 17 via an electromagnet 16 or other type of electrical element, for opening and closing flow of hydraulic fluid between chamber 14 and a chamber 17 also filled with hydraulic fluid. Further, the piston 5 running in the combustion chamber 7 is shown, which in itself is shown in more detail in FIGS. 1-3. The piston has a shaft 18 the upper part of which is present in the chamber 17 and displaceable disposed therein. A chamber 20 with a mechanical spring 19 which makes the piston 5 slidable upwardly by acting between the floor of the chamber and a flange 21 existing on the shaft 18. The valve with its aperture 15 can be displaced in both directions by a double acting electromagnet or in a direction via an electromagnet and in the other direction via a mechanical spring, not shown.

[0019] FIG. 5 shows the step motor 12 with the shaft 13 maximally displaced upwards and the piston 5 with the shaft 18 likewise is maximally displaced upwardly. The hydraulic lock with the valve 6 shifted to the right has shut the connection between the chambers 14 and 17. The step motor can not affect the piston 5 in this position.

[0020] FIG. 6 shows the hydraulic lock deactivated by the electromagnet repositioning the valve 6 to the left so that its opening 15 creates connection between the hydraulic fluid filled chambers 14 and 17.

[0021] FIG. 7 shows that the step motor 12 repositioned the shaft 13 downwardly, thereby pushing hydraulic fluid from the chamber 14 through the opening 15 in the valve 6 to the chamber 17 and thereby pushing the piston shaft 18 with the piston 5 downwardly under compression of the spring 19. Thus the combustion chamber, not directly illustrated, decreases.

[0022] FIG. 8 shows the electromagnet 16 with the valve 6 in a position where the connection between the chambers 14 and 16 is switched of and hence the hydraulic lock is activated. The piston 5 can neither move upwards nor downwards.

[0023] FIG. 9 shows the hydraulic lock deactivated.

[0024] FIG. 10 shows a position where the step motor 12 has moved the shaft 13 upwards, whereby, by action of the spring 19, hydraulic fluid is pressed from the chamber 17 to 14 and the piston shaft 18 with its piston 5 has been moved upwards.

[0025] Actions undertaken by a man skilled in the art have not been described, as the hydraulic fluid is suitably engine oil, how the volume of hydraulic fluid is substantially kept constant, selection and placement of the engine control system, deciding the combustion chamber size, etc. An engine control system is obvious today and therefore it is not mentioned in the claims that the action of the electromagnet and step motor is controlled by the engine control system.