EP2646659B1

EP2646659B1 - An arrangement and a method of operating a gas exchange valve of an internal combustion engine, a cylinder head and a method of upgrading an internal combustion engine

Info

Publication number: EP2646659B1
Application number: EP11805067.3A
Authority: EP
Inventors: Ilari Kallio
Original assignee: Wartsila Finland Oy
Current assignee: Wartsila Finland Oy
Priority date: 2010-11-30
Filing date: 2011-11-29
Publication date: 2015-08-05
Anticipated expiration: 2031-11-29
Also published as: KR20130121909A; FI20106256A0; KR101657752B1; EP2646659A1; CN103228878A; WO2012072878A1; CN103228878B

Description

Technical field

The present invention relates to an arrangement and a method of operating a gas exchange valve of an internal combustion engine. The present invention relates also to a novel cylinder head and a new method of upgrading an internal combustion engine.

Background art

Conventionally in internal combustion or piston engines, the gas exchange valves of the cylinders are controlled by a camshaft, which is, on the one hand, connected by means of a gear or chain or belt with the crankshaft of the engine so that it rotates with the crankshaft, and on the other hand, connected mechanically to the valves by means of push rods and rockers, mere rockers, or by direct contact between the camshaft cams and the valve stems. Thus, either all the valves in a cylinder row are controlled by the same camshaft or alternatively, the inlet and outlet valves both have their respective camshafts. In operation, the use of a valve mechanism driven by a camshaft offers only very limited possibilities to change the timing of the valves whereby the timing of the valves is always a compromise.
Due to the increasingly stringent emission regulations the engine manufacturers are obliged to decrease engine emissions. At the same time the aim is to keep the engine performance unchanged or even to improve it. This is possible only through precise real time adjustment and control of the engine. The control of fuel supply has improved considerably along with the introduction of electrically controlled fuel injection. In addition to this, the control of gas exchange valves should be improved in order to make the engine as efficient as possible at all engine rotation speeds and engine loads. Individual control of gas exchange valves improves the efficiency, fuel economy and output of the engine and reduces emissions. This is not possible with a valve mechanism driven by a camshaft. To overcome the above discussed problem, hydraulic actuators have been suggested for operating the engine valves without direct mechanical connection to the crankshaft.
If the gas exchange valve (GEV) is operated with a hydraulic actuator, the actuator needs to be dimensioned against the maximum imaginable opening force of a gas exchange valve in any operating condition. The opening force is the product of the effective surface area of the actuator and the pressure of the hydraulic system connected to the actuator. The hydraulic power consumed in opening a gas exchange valve is the product of the volume flow and the pressure of the hydraulic system. A large effective surface area of the actuator leads to high volume flow and thus high power consumption in the system. In other words, the power consumption of a hydraulic actuator is constant irrespective of the force actually needed to open a gas exchange valve.
EP-B1-1 403 473 discusses a hydraulic valve actuation system. The EP document discloses a hydraulic actuator used for operating a gas exchange valve of an internal combustion engine. The hydraulic actuator has a body provided with an internal cavity housing a piston. The piston is arranged at an axial end thereof in communication with a valve stem. The piston has three coaxial cylindrical sections such that the diameter of the uppermost section (at an end opposite to the end communicating with the valve stem) is the smallest, the centre section having a largest diameter, and the lowermost having a diameter larger than that of the uppermost section but smaller than that of the centre section. The piston sections form together with the internal cavity of the actuator body several coaxial chambers. A first cylindrical chamber above the uppermost piston section, a second annular chamber above the centre section of the piston, and a third annular chamber below the centre section of the piston. The effective cross sectional surface areas of the chambers are varying such that the surface area of the first chamber is the smallest, the surface area of the second annular chamber the largest, and the surface area of the third annular chamber smaller than that of the second annular chamber, but larger than that of the first chamber. The chambers are connected by means of pressure conduits and valve means to a high pressure fluid supply and to a low pressure fluid supply except for the third annular chamber that is in constant flow communication with the high pressure fluid supply. The operation of the hydraulic actuator is controlled by a control valve, which in its first position allows the pressurized fluid flow from the high pressure fluid supply to the second annular chamber. The high pressure fluid acting on the largest surface area affects by opening the valve against the forces originating from the valve spring, from the high pressure fluid acting on the surface area in the third annular chamber, from the gas pressure in the cylinder of the internal combustion engine and the acceleration of the valve. In its second position the control valve allows the communication of the second annular chamber with the low pressure fluid supply so that high pressure prevailing in the third annular chamber acting on the second largest surface area of the piston aids returns the piston up away from the valve. In addition to mere basic operation of the valve, the upper end of the piston i.e. the first chamber is provided with means for dampening the movement of the piston upwards in order to slow down the speed the valve is closing so that the valve plate does not hit the valve seat too strongly when closing. The first chamber is, for the dampening purpose, arranged in flow communication with both the high pressure and the low pressure fluid supply via specific valve arrangements. Thus the first chamber does not participate in the opening of the gas exchange valve, but merely slows down the final closing of the gas exchange valve.
The EP- document discusses also another piston structure for the hydraulic actuator. In a second embodiment the centre section of the piston is formed of two coaxial parts that are slidable in relation to each other. In other words, the outer i.e. the second part of the piston is an annular sleeve arranged around the first part of the piston that is used for operating the valve stem. In a first position (when the gas exchange valve of the internal combustion engine is closed) the annular piston part rests against a shoulder on the first piston part, and in a second position (gas exchange valve open) the annular part rests against a shoulder on the chamber inner wall. The actuator functions such that when the second annular chamber having the largest cross-sectional area i.e. the chamber above the two piston parts is pressurized by the high pressure fluid both piston parts move together i.e. the annular piston part resting on the shoulder on the first piston part aids in moving the piston downwards and in opening or unseating the gas exchange valve. After a certain length of downward travel the annular piston part meets a shoulder on the chamber inner wall and stops whereby the first part of the piston continues to move downwards but now with a significantly smaller force due to a smaller effective area.
In other words, the above discussed prior art hydraulic actuator tries to reduce the energy consumption involved in operating the gas exchange valves. However, the gained saving represents only a small improvement to earlier prior art hydraulic actuator systems. What the hydraulic actuator of the above discussed EP- document in fact does is that it takes into account the pressure reduction in the combustion chamber immediately after the unseating of the gas exchange valve i.e. after lifting the valve plate off the seat surface. In other words, right after unseating the gas exchange valve the pressure in the combustion chamber is released, whereby the cylinder pressure does not resist the opening of the gas exchange valve any more, or at least significantly less, and the opening of the valve may be continued with a smaller force. Thus the EP- document teaches a hydraulic actuator structure that starts opening i.e. unseats a gas exchange valve with a constant force that is the maximum imaginable force required to open the gas exchange valve. After unseating the gas exchange valve the opening force is reduced to a fixed value. The result is that the pressure fluid (and power) consumption is somewhat reduced but only because hydraulic actuator takes into account the two different opening phases of a gas exchange valve i.e. unseating phase and the final opening phase. However, the prior art hydraulic actuator is not capable of taking into account either the varying pressure conditions in the combustion chamber of an internal combustion engine due to varying cylinder load or the varying accelerations of a gas exchange valve due to varying engine speed.
A basis for the present invention is that the force required to operate a gas exchange valve of an internal combustion engine is not constant. The force required to unseat and to open a gas exchange valve depends on several factors. A first factor is the acceleration force i.e. the acceleration of the valve movement, which is proportional to the engine speed and to the masses of the gas exchange valve and the piston of the hydraulic actuator. A second factor is the pressure difference over the valve plate, which has an effect up to the end of the unseating phase. The pressure difference is dependent on the engine operating conditions, i.e. on the engine load and crank angle. A third factor is the force originating from the spring of the gas exchange valve (if such is used). And a fourth factor is fluid pressure (if any) in the actuator acting against the piston movement (third annular chamber in EP-B1-1 403 473 ).

Disclosure of the Invention

A first object of the present invention is to overcome some weaknesses, drawbacks and problems of the prior art hydraulic actuators used for opening gas exchange valve/s of an internal combustion engine.
A second object of the present invention is to reduce the power consumption of a hydraulic actuator by adjusting the force used for opening a gas exchange valve to meet the demands the pressure difference over the valve plate sets for the force required to open a gas exchange valve.
A third object of the present invention is to be able to adjust the operation of a hydraulic actuator and its flow rate to meet the demands the engine speed sets to the valve opening/closing speed.
A fourth object of the invention is to offer a structurally simple hydraulic actuator, i.e. an actuator having minimum number of parts, the parts having very few surfaces to be machined and to be sealed, whereby the resulting actuator for opening gas exchange valve/s of an internal combustion engine is cheap, reliable and extremely adjustable.
A fifth object of the invention is to improve the reliability of the system. When several control valves are used, a failure of one does not make the system unavailable, but only part of the system performance is lost. With intelligent control, the system can identify the failed component and be readjusted to failure mode.
A seventh object of the present invention is to offer simple and energy efficient means for repairing and upgrading/modernizing a state-of-the-art internal combustion engine having a camshaft and mechanical means in communication with the camshaft for operating the gas exchange valves.
An eighth object of the present invention is to offer a novel cylinder head for modernizing an internal combustion engine to meet today's demands for energy efficiency and emission control.
And a ninth object of the invention is to offer a pressure medium actuator for operating a gas exchange valve of an internal combustion engine. In other words, the actuator may be not only hydraulic, but also pneumatic.
At least an object of the invention is met by an arrangement for operating a gas exchange valve of an internal combustion engine, the arrangement comprising:

a pressure medium supply, a pressure medium outlet, a pressure medium actuator, the pressure medium actuator comprising a body having an internal cavity with cylindrical wall portions having different diameters, and a unitary piston arranged movable within the internal cavity, the piston having a shape corresponding to that of the internal cavity, the pressure medium actuator further comprising an opening pressure chamber and the piston comprising an opening effective surface arranged in the chamber, a control means for switching connection of the opening pressure chamber between the pressure medium supply and the pressure, wherein the arrangement further comprises at least one further opening pressure chamber provided in the pressure medium actuator, at least one further effective surface provided on the piston and at least one further control means, the control means being arranged to connect one or more opening pressure chambers to the pressure medium supply for controlling a force opening the gas exchange valve.

At least an object of the invention is achieved by the method of operating a gas exchange valve of an internal combustion engine by means of the above described arrangement so that

the control means of the actuator are operated in relation to one or more engine characteristics by,
- when opening the gas exchange valve,
  - selecting one or more opening pressure chambers to be connected to a pressure medium supply for adjusting a force opening the gas exchange valve, and
- when closing the gas exchange valve,
  - connecting the opening pressure chambers to a pressure outlet.

At least an object of the invention is met by a cylinder head of an internal combustion engine, the cylinder head comprising at least two gas exchange valves and means for operating the gas exchange valves, wherein at least one means for operating a gas exchange valve is the arrangement in accordance with one or more of the apparatus claims.
At least an object of the invention is met by a method of upgrading an internal combustion engine with a cylinder head with at least one gas exchange valve, and mechanical gas exchange valve operating means, wherein mechanical gas exchange valve operating means is replaced with the arrangement in accordance with one or more of the apparatus claims.
The present invention, when solving at least some of the above-mentioned problems, also brings about a number of advantages, of which a few has been listed in the following. The pressure medium actuator of the present invention:

may be used to operate a gas exchange valve of an internal combustion engine. The engine may be a two or four stroke engine
reduces the volume flow in the system, allowing a cost reduction through lower energy consumption
increases the reliability of the valve operating system, since a failure of a single control valve only eliminates part of the force combinations
allows better control of the gas exchange valve speed
makes it possible to control the engine better resulting in reduced emissions
may be used to replace prior art camshaft, push rod, rocker mechanisms so that an old-fashioned cylinder head is easily modernized to meet today's demands
is of simple construction and thus cheap to manufacture, and less prone to malfunctioning or deterioration.

However, it should be understood that the listed advantages are only optional, whereby the number of advantages depends on the way the invention is put into practice.

Brief Description of Drawings

In the following, the present invention is explained in more detail in reference to the accompanying drawings, of which:

Figure 1 illustrates an axial cross sectional view of a pressure medium actuator arrangement together with a gas exchange valve in accordance with an embodiment of the present invention in an opening phase of a gas exchange valve,
Figure 2 illustrates an axial cross-sectional view of the pressure medium actuator arrangement of Figure 1 in the closing phase of a gas exchange valve,
Figure 3 illustrates an axial cross-sectional view of the pressure medium actuator arrangement in another opening phase of a gas exchange valve,
Figure 4 illustrates an axial cross-sectional view of the pressure medium actuator in accordance with another embodiment of the present invention, and
Figure 5 illustrates schematically another exemplary option for the control valve used for controlling the operation of the pressure medium actuator of the present invention.

Detailed Description of Drawings

Figure 1 illustrates an axial cross sectional view of a pressure medium actuator 10. The actuator 10 has a body 12 including an internal cavity extending from the vicinity of an end 14 of the body to the opposite end 16 of the body 10. The end 16 of the body is provided with a cover 18, which is provided with a preferably central opening 20. The internal cavity is formed of several cylindrical wall portions 22, 24 and 26 such that the diameters of the wall portions grow towards the end of the body having the cover 18. The pressure medium actuator 10 has a unitary piston 30, whose shape corresponds substantially to that of the internal cavity of the body 12. In other words, the unitary piston is formed, in this embodiment, of four cylindrical sections 32, 34, 36 and 38, which have been arranged axially one on top of the other. The uppermost section 32 of the piston 30 has a diameter that corresponds to the diameter of the wall portion 22 leaving, however, a sufficient running clearance therebetween. In a similar manner the second section 34 of the piston 30 has a diameter corresponding to that of wall portion 24, and the third section 36 of the piston has a diameter that corresponds to that of the third wall portion 26. The fourth section 38 of the piston 30 has a diameter that corresponds to that of the central opening 20 in the cover 18.
The piston 30 and the internal cavity of the body 12 of the pressure medium actuator form pressure chambers 40, 42, 44 and 46. The chamber 40 is limited by the wall portion 22, the end surface of the internal cavity and the end surface 48 of the first section 32 of the piston 30. The chamber 42 is limited by the wall portion 24, a cylindrical side surface of the first section 32 of the piston 30, the annular end surface 50 of the second section 34 of the piston 30, and the shoulder surface between the first 22 and second wall portions 24 of the internal cavity. The chamber 44 is limited by the wall portion 26, a cylindrical side surface of the second section 34 of the piston 30, the annular end surface 52 of the third section 36 of the piston 30, and the shoulder surface between the second 24 and third wall portions 26 of the internal cavity. The chamber 46 is limited by the wall portion 26, a cylindrical side surface of the fourth section 38 of the piston 30, the lower annular end surface 54 of the third section 34 of the piston 30, and the surface of the cover 18 facing to the internal cavity. Thus the effective surfaces affecting the movement of the piston 30, and the valve stem 100 arranged in communication with the piston 30 are the end surface 48 in pressure chamber 40, the annular end surface 50 in pressure chamber 42, the annular end surface 52 in pressure chamber 44, and the annular end surface 54 in pressure chamber 46. Based on their operation the pressure chambers 40, 42 and 44 may be called opening pressure chambers, and the pressure chamber 46 a closing pressure chamber. In a similar manner the effective surfaces 48, 50 and 52 may be called opening surfaces and surface 54 a closing surface.
A preferred, though not necessary, feature of the present invention is that the areas of the effective surfaces form a geometric series such that the area of surface 48 is A, the area of surface 50 is 2*A and the area of surface 52 is 4*A. The purpose of arranging the areas to form such a geometric series will be explained in more detail later on.
The pressure medium actuator body 12 and piston 30 form a first part of the pressure medium valve operating arrangement. The second part of the operating arrangement is formed of a tank 61 (when it is a question of a hydraulic actuator), a pressure medium supply 70, first control valves 80, 82, 84 and 86, conduits 72, 74, 76 and 78, seconds control valves 90, 92, 94 and 96 with conduits 62, 64, 66 and 68. The conduits 72 - 78 connect the pressure medium supply via the first control valves 80 - 86 to the pressure chambers 40 - 46. The pressure chambers 40 - 46 are connected by means of second control valves 90, 92, 94 and 96 and conduits 62 - 68, and pressure outlet 60 to the tank 61. Thus each pressure chamber has one first control valve and one second control valve for controlling the operation of the chamber. The control valves 80 - 86, and 90 - 96 are preferably solenoid valves or some other electrically operable valves that are connected to a control unit (CU) such that the control unit (CU), based on input from the engine control unit, is able to open and close each valve independently. In other words, a solenoid operated control valve works normally such that it is closed when the control unit (CU) does not allow electric current enter the solenoid. When the electric circuit of the solenoid is closed, i.e. electric current is allowed to enter the solenoid; the solenoid pushes the control valve to open position against a spring. And when the solenoid circuit is opened, the spring pushes the control valve to closed position. Naturally, it is also possible to keep the control valve closed by means of the solenoid and open the control valve by cutting off power from the solenoid circuit. Further, it is also possible to arrange two solenoids in connection with a control valve whereby both opening and closing of the control valve is performed by using solenoids. The first control valves 80 - 86 have been shown here as two-position, two-way valves, i.e. valves that either open or block a flow connection between a pressure chamber 40 - 46 and the pressure medium supply 70. In a similar manner control valves 90 - 96 have been shown as two-position, two-way valves that either open or block a flow connection between a pressure chamber 40 - 46 and the tank 61.
Figure 1 illustrates the pressure connections i.e. positions of the control valves when the counter pressure prevailing in the combustion chamber of a cylinder of an internal combustion engine is at its lowest whereby the force needed to open the gas exchange valve 102 is the lowest possible. To save energy i.e. to create a force that is just enough for opening the gas exchange valve 102 in a desired manner the operation of the pressure medium actuator is adjusted such that control valve 80 connects the pressure chamber 40 to the pressure medium supply 70 via conduit 72, whereas the other three control valves 82, 84 and 86 are closed. The second control valves at the tank 61 side of the actuator are operated such that control valve 90 is kept closed whereby it cuts the connection from pressure chamber 40 along conduits 62 and 60 to the tank 61 and allows the pressure of the pressure medium source affect on the effective piston surface 48. The other control valves 92, 94 and 96 connect their respective pressure chambers 42, 44 and 46 to the tank 61. The high pressure medium acting on the piston surface 48 affects the opening of the gas exchange valve 102, and simultaneously compresses the valve spring 104 and forces the medium in pressure chamber 46 to the tank 61.
Figure 2 illustrates an operating phase of the pressure medium actuator i.e. the positions of the control valves when the gas exchange valve is to be closed. Now the control valve 86 connects the pressure chamber 46 via conduit 78 to the pressure medium supply 70 whereas the rest three control valves 80, 82 and 84 are closed. The second control valves are operated such that three of them, i.e. the control valves 90, 92 and 94 connect their respective pressure chambers 40, 42 and 44 to the tank 61, and the control valve 96 being in communication with the pressure chamber 46 to be pressurized is closed. The high pressure medium acting on effective piston surface 54 moves the piston upwards allowing the gas exchange valve to close and forcing the medium from pressure chambers 40, 42 and 44 to the tank 61.
At this time it should be understood that the pressure medium actuator of the present invention may also be operated such that the piston is stopped at any desired position by using the control valves. For instance the upward movement of the piston, as well as that of the gas exchange valve may be stopped by closing the second valves 90, 92 and 94, and keeping the first valves 80 - 84 closed, too.
Figure 3 illustrates such an operating phase of the pressure medium actuator i.e. the positions of the control valves when the force required to open the gas exchange valve is clearly higher than that in the phase shown in Figure 1. Here, control valves 80 and 84 connect their respective pressure chambers 40 and 44 to the pressure medium supply 70, whereas control valves 82 and 86 are closed. Of the second control valves, valves 90 and 94 are closed allowing the medium pressure act in the pressure chambers 40 and 44 on effective surfaces 48 and 52 (reference numerals shown in Figure 1). Control valves 92 and 96 connect their respective pressure chambers 42 and 46 to the tank 61. In this case the force used for opening the valve is 5-fold compared to the example of Figure 1.
Figure 3 illustrates as a schematical, additional and exemplary arrangement a conduit 98, which has been arranged such that, for instance, when closing the gas exchange valve, the pressure chamber 42 may be emptied via both control valve 92 and control valve 94. By the arrangement the speed of the actuator piston may be adjusted as, if the piston is supposed to move upwards, and only control valves 90 and 94 are open, and control valve 92 closed the medium from both pressure chambers 42 and 44 has to pass control valve 94. Now that the flow rate of a control valve 94 is limited the additional flow (compared to normal situation when each pressure chamber is discharged via its control valve) from pressure chamber 42 increases the total flow and reduces the speed the piston may move. In practice, the conduit 98 may be a valve arrangement with which the outlet flow from chamber 42 may be directed to either control valve 92, to control valve 94 or both, and/or outlet flow from chamber 44 may be directed to either control valve 94, to control valve 92 or both. Naturally, such a conduit, or valve arrangement, may be arranged freely at the outlet side of the actuator body. It would even be possible, in the embodiment of Figure 3, that the medium flow from any pressure chamber 40 - 44 could be directed to one, two or three second control valves 90 - 94, whereby the adjustability of the speed of the piston movement would be maximized. For instance it is possible, in the closing phase of the gas exhaust valve, to first allow the pressure medium from the pressure chambers be discharged via their 'own' control valves i.e. via all three control valves, then close one of the control valves 90 - 94, and allow the pressure medium be discharged via two control valves whereby the valve closing speed is slowed down. In the next stage one more control valve is closed, and the discharge of all pressure chambers 40 - 44 takes place via one control valve, until it is closed, too, stopping the valve, and piston, movement.

In other words, the present invention makes it possible to adjust stepwise the force used for opening a gas exchange valve. The following table lists the various combinations of the positions of the first control valves and the resulting forces when opening the gas exchange valve. Naturally, when opening the gas exchange valve, the control valve 86 is always closed, and control valve 96 is, always connecting chamber 46 to the tank 61 (unless some damping effect is desired). As to the second control valves 90 - 94 their position depends on the positions of the corresponding first control valves 80 - 84, respectively. It means that when a first control valve is in 'open' position, the corresponding (connected to the same pressure chamber) second control valve is in 'closed' position, and vice versa.

Chamber 40 (area A) connected to	Chamber 42 (area 2*A) connected to	Chamber 44 (area 4*A) connected to	Force
Pressure fluid supply/ Valve 80 open	Pressure outlet/Valve 92 open	Pressure outlet/Valve 94 open	F
Pressure outlet/Valve 90 open	Pressure fluid supply/ Valve 82 open	Pressure outlet/Valve 94 open	2*F
Pressure fluid supply/ Valve 80 open	Pressure fluid supply/ Valve 82 open	Pressure outlet/Valve 94 open	3*F
Pressure outlet/Valve 90 open	Pressure outlet/Valve 92 open	Pressure fluid supply/ Valve 84 open	4*F
Pressure fluid supply/ Valve 80 open	Pressure outlet/Valve 92 open	Pressure fluid supply/ Valve 84 open	5*F
Pressure outlet/Valve 90 open	Pressure fluid supply/ Valve 82 open	Pressure fluid supply/ Valve 84 open	6*F
Pressure fluid supply/ Valve 80 open	Pressure fluid supply/ Valve 82 open	Pressure fluid supply/ Valve 84 open	7*F

Thus this exemplary pressure medium actuator is capable of being switched between 7 different force levels in accordance with the requirements of the gas exchange valve. Factors having an influence on the used force i.e. the chosen combination of control valve positions is dependent on the cylinder load, crank angle and engine speed, just to name a few factors.
Naturally, the pressure medium actuator may have more or fewer (however, at least two) pressure chambers active in opening a gas exchange valve than the three pressure chambers 40, 42 and 44 shown in the above embodiment. In other words, if there are only two active pressure chambers, the number of applicable force levels decreases to three, and if there are four active pressure chambers, the number of force levels increases to 15 (1+2+4+8).
Thus, in principle, to be able to meet the objects of the present invention the pressure medium operated gas exchange valve actuator has two or more pressure chambers with effective surface areas A1, A2, ... An, of which one or more can be independently, electronically connected to the pressure medium supply.
A preferred way to select the effective surface areas of the pressure chambers is a geometric series, A, 2*A, 4*A..., but also other modes may be applied.
Figure 4 illustrates yet another preferred embodiment of the present invention. Here, the pressure medium actuator is provided with another pressure medium supply 70' that has been connected via an additional control valve 104 further to the system. The pressure medium supply 70' has a pressure different from that of the pressure medium supply 70. Here, also the first pressure medium supply 70 has been provided with an additional control valve 102 of its own. Both control valves 102 and 104 have been connected to the control unit (CU). Figure 4 shows how, by means of the control valve 102, the pressure medium from supply 70 may be delivered depending in the position of the valves 80 - 86 to pressure chambers 40 - 46, and by means of the control valve 104, the pressure medium from the additional pressure medium supply 70' may be delivered depending in the position of the valves 80 - 86 to pressure chambers 40 - 46. The purpose of adding another pressure medium supply and of arranging separate control valves for the both pressure medium supplies is to be able to control the opening force of the gas exchange valve better. In other words, in accordance with the arrangement shown in Figure 5 it is possible to switch the pressure medium supply having either the lower pressure or the higher pressure to the first control valves 80 - 86 and further to pressure chambers 40 - 46. Naturally, it is also possible to go further by arranging the additional pressure medium supply 70' to be connectable to one or more first control valves 80 - 86, whereby only those valves (and the pressure chambers connected thereto) could utilize the different pressure available in the supply 70'. By adding an another pressure medium supply 70' having a pressure different from that of pressure medium supply 70, the number of different force levels achievable by the pressure medium actuator are doubled. Naturally, it is also possible to add still one or more pressure medium supplies having different pressures to increase the adjustment options of the pressure medium actuator.
In Figure 5 a digital flow control unit 110 that may, optionally, be used to replace one or more of the control valves 80, 82, 84 and 86, as well as one or more of the control valves 90 - 96 has been illustrated. The flow control unit 110 comprises two or more digital valves 112, 114, 116 connected in parallel. Each valve is designed for a certain flow rate at certain pressure differential. The flow rates of different valves can be different. For instance such that the flow rate of the first valve 112 is V, the flow rate of the second valve 114 is 2*V, the flow rate of the third valve 4*V, and the flow rate of n'th valve 2^(n-1)*V. By changing the combination of valves switched on the flow rate of the digital flow control unit 110 may be changed, which leads to a change in the speed the piston 30 (Fig. 1) moves and the gas exchange opens or closes.
As to the more detailed structure and operation of the pressure medium actuator it should be understood that

The actuator body may be formed of several parts, i.e. not only from a single body part and a bottom cover.
The actuator may be provided with additional equipment, like for instance damping means as discussed in connection with the prior art document, EP-B1-1 403 473 .
The actuator piston may be arranged in direct communication with the valve stem as discussed above, but the operation of the gas exchange valve may also be performed by means of, for instance, a rocker arm.
The actuator may be used for merely opening the gas exchange valve as discussed above, but it may as well be arranged to close the gas exchange valve, too, either alone or together with the valve spring. In such a case the actuator piston and the valve stem are attached to each other. Naturally, if the actuator is used for closing the valve, it may be desirable to utilize the present invention in the closing phase, too. In other words, the actuator would have several differently sized pressure chambers for the closing movement, too.
The actuator may be a separate device or it may be integrated to the cylinder head
A single actuator may operate one or more gas exchange valves. The actuator may be arranged to open (and, optionally, close) all inlet, or outlet, valves of the engine cylinder.
The high pressure medium supply may be a specific fluid supply for operating the pressure medium actuators only, but it may also be a part of the engine's pressure medium circuit. For instance, the fluid may be taken from the forced lubrication system of the engine.
The tank mentioned in the above description refers to a hydraulic actuator arrangement, where a preferred, but not necessary, place where the outlet oil from the actuator and the pressure outlet is discharged is an oil tank. If the actuator is pneumatic it is obvious that any tank is not needed but the air may be discharged from the pressure outlet either directly or via some kind of filter or cleaning unit to atmosphere.
The control valves may be actuated not only by means of a solenoid, but also by means of a piezoelectric actuator, or any other applicable electrical actuator that may be driven by the control system of the engine.
By means of the control valves the operating mode discussed in the prior art EP-B1-1 403 473 may be taken into use, i.e. using additional force in the unseating phase of a gas exchange valve, and then reducing the opening force.
The control valves in the above description have been shown as examples only. The control valves may be different from the above discussed ones. For instance, a two-position three-way control valve could be used to combine the first and second control valves of each pressure chamber into one single valve unit so that for instance a single control valve would perform the function of control valves 80 and 90. In a similar manner the rest of the control valve pairs 82 and 92, 84 and 94 and 86 and 96 could be combined.
Each control valve i.e. the first, the second, and the additional control valves are preferably connected independently to the control unit so that the control unit may activate a single control unit independently of any other control unit.

It should be understood that the above is only an exemplary description of a novel and inventive method of and an arrangement for operating a gas exchange valve of an internal combustion engine. The above should not be understood as limiting the invention by any means but the entire scope of the invention is defined by the appended claims only. From the above description it should be understood that separate features of the invention may be used in connection with other separate features even if such a combination has not been specifically shown in the description or in the drawings.

Claims

An arrangement for operating a gas exchange valve of an internal combustion engine, the arrangement comprising:
- a pressure medium supply (70),

- a pressure medium outlet (60),

- a pressure medium actuator (10), the pressure medium actuator (10) comprising a body (12) having an internal cavity with cylindrical wall portions having different diameters, and a unitary piston (30) arranged movable within the internal cavity, the piston (30) having a shape corresponding to that of the internal cavity, the pressure medium actuator (10) further comprising an opening pressure chamber (40) and the piston (30) comprising an opening effective surface (48) arranged in the chamber (40),

- a control means (80, 90) for switching connection of the opening pressure chamber (40) between the pressure medium supply (70) and the pressure medium outlet (60),
characterized in that the arrangement further comprises at least one further opening pressure chamber (42, 44) provided in the pressure medium actuator (10), at least one further effective surface (50, 52) provided on the piston (30) and at least one further control means (82, 84; 92, 94), the control means (80, 82, 84) being arranged to connect one or more opening pressure chambers (40, 42, 44) to the pressure medium supply (70) for controlling a force opening the gas exchange valve (102).
The arrangement as recited in claim 1, characterized in that each effective opening surface (48, 50, 52) of the piston (30) has an area, the areas of the effective opening surfaces (48, 50, 52) being different.
The arrangement as recited in claim 2, characterized in that each effective opening surface (48, 50, 52) of the piston (30) has an area, the areas of the effective opening surfaces (48, 50, 52) being arranged in geometric series.
The arrangement as recited in any one of the preceding claims, characterized in that the pressure medium actuator (10) is arranged to operate more than one gas exchange valve (102).
The arrangement as recited in any one of the preceding claims, characterized in means arranged between at least two pressure chamber (40 - 44) outlets for arranging a flow communication from one of the outlets to another outlet.
The arrangement as recited in any one of the preceding claims, characterized in that one or more of the first and second control valves (80 - 86; 90 - 96) is a digital flow control unit (110) capable of adjusting the flow rate in and/or out of a pressure chamber (40 - 46).
The arrangement as recited in any one of the preceding claims, characterized in that the arrangement is provided with an additional pressure medium supply (70') for connecting by additional control means (104) to at least one pressure chamber (40, 42, 44,46).
A method of operating a gas exchange valve of an internal combustion engine by means of the arrangement of any one of the preceding claims, characterized by
• operating the control means (80, 82, 84; 90, 92, 94) of the actuator (10) in relation to one or more engine characteristics by,
- when opening the gas exchange valve (102),
- selecting one or more opening pressure chambers (40, 42, 44) to be connected to a pressure medium supply (70) for adjusting a force opening the gas exchange valve (102), and

- when closing the gas exchange valve (102),
- connecting the opening pressure chambers (40, 42, 44) to a pressure outlet (60).
The method as recited in claim 8, characterized by
• operating control means (86, 96) located between the pressure medium supply (70) and a closing pressure chamber (46), and between the closing pressure chamber (46) and the pressure outlet (60), respectively, to,
- when opening the gas exchange valve (102),
- open the connection between a closing pressure chamber (46) and the pressure outlet (60), and to close the connection between the pressure medium supply (70) and the closing pressure chamber (46), and

- when closing the gas exchange valve (102),
- close the connection between the closing pressure chamber (46) and the pressure outlet (60), and to open the connection between the pressure medium supply (70) and the closing pressure chamber (46) to allow the pressure medium enter the pressure chamber (46) for lifting the piston (30).
The method as recited in claim 8, characterized by performing the selection of one or more opening pressure chambers (40, 42, 44) based on areas of the effective opening surfaces (48, 50, 52) of the opening pressure chambers (40, 42, 44).
The method as recited in any one of the previous claims 8 - 10, characterized by controlling the opening force of the gas exchange valve (102) by switching one or more opening pressure chambers (40, 42, 44) from the pressure medium supply (70) to additional pressure medium supply (70') having a pressure different from that of the pressure medium supply (70).
A cylinder head of an internal combustion engine, the cylinder head comprising at least one gas exchange valve and means for operating the gas exchange valves, characterized in that at least one means for operating a gas exchange valve is the arrangement in accordance with one or more of claims 1 - 7.
A method of upgrading an internal combustion engine having at least one cylinder with a cylinder head with at least one gas exchange valve, and mechanical gas exchange valve operating means, characterized by replacing mechanical gas exchange valve operating means with the arrangement in accordance with one or more of claims 1 - 7.