An internal combustion engine including variable compression ratio and a method of operating the engine

Abstract

 An internal combustion engine (1) including variable compression ratio comprises a crankcase (2) and a crankshaft (3) including a crankshaft axis (4). The crankshaft (3) has at least a central main portion (5), a crankpin (6) and a crankshaft web (7) located between the central main portion (5) and the crankpin (6). The crankshaft (3) is supported by the crankcase (2) and rotatable with respect thereto about the crankshaft axis (4). The engine (1) comprises at least a connecting rod (11) including a big end (10) and a small end (12), a piston (13) which is rotatably connected to the small end (12) and a crank member (8) that is rotatably mounted on the crankpin (6), and comprises at least a bearing portion (9) which is eccentrically disposed with respect to the crankpin (6). The bearing portion (9) has an outer circumferential wall which bears the big end (10) of the connecting rod (11) such that the connecting rod (11) is rotatably mounted on the bearing portion (9) of the crank member (8) via the big end (10). The engine (1) comprises a driving mechanism for driving the crank member (8) at half speed of the crankshaft (3) as seen from the crankcase (2). The driving mechanism comprises a control member (17) for varying the compression ratio, which is rotatable with respect to the crankcase (2) and drivably coupled to the crank member (8), but has a fixed position with respect to the crankcase (2) under operating conditions at fixed compression ratio. The rotational position of the control member (17) with respect to the crankcase (2) is adjustable by means of a hydraulic actuator (18), which comprises a hydraulic piston (20) that is drivably connected to the control member (17), a working chamber (21), a pump (23) and an oil supply line (25) through which the pump (23) and the working chamber (21) communicate.

Description

[0001] The present invention pertains to an internal combustion engine including variable compression ratio.

[0002] An engine with variable compression ratio is well-known in the field of spark-ignition engines. It provides the opportunity to operate the engine at high efficiency, particularly under part-load conditions. Increasing the compression ratio leads to decreasing fuel consumption. At high-load or full-load the compression ratio must be lowered in order to avoid knocking. Several earlier applications of the applicant disclose internal combustion engines with variable compression ratio, for example WO 2013/110700.

[0003] An object of the invention is to provide a low-noise engine with variable compression ratio.

[0004] This is achieved by the internal combustion engine according to claim 1.

[0005] The engine according to the invention provides the opportunity to change the compression ratio by adjusting the rotational position of the control member upon switching-on the pump. The rising pressure in the working chamber causes the hydraulic piston to adjust the crank member position with respect to the crankcase at a virtual standstill of the crankshaft.

[0006] The advantage of the hydraulic actuator is that vibrations generated by the control member are dampened since repetitive combustion forces that are transferred from the piston to the control member are absorbed by the hydraulic actuator. Consequently, noise generation by the engine according to the invention is lower than in case of adjusting the control member by means of a worm gear transmission, for example. Furthermore, a hydraulic actuator provides the opportunity to achieve a high transmission ratio in terms of rotational speed of the pump and speed of the hydraulic piston.

[0007] The combustion forces are transferred from the piston to the crank member through the connecting rod. Due to the eccentricity of the bearing portion of the crank member the combustion forces exert a torque onto the crank member gear which is transferred to the control member since the control member is drivably coupled to the crank member. The combustion forces as well as the positions of the crank member and the crankshaft with respect to each other and with respect to the crankcase vary over time causing vibrations on the control member which are transferred to the hydraulic piston as mentioned above. The repetitive combustion forces provide an average continuous force on the hydraulic piston in one direction thereof. This means that without sufficient back force on the hydraulic piston the control member will be rotated in one direction automatically.

[0008] This provides the opportunity to operate the engine by a method according to the invention, wherein the control member is turned in one direction with respect to the crankcase over a certain angle by means of increasing the pressure in the working chamber, for example by pumping oil to the working chamber, and wherein the control member is turned over a certain angle in opposite direction by means of reducing the pressure in the working chamber, for example by pumping oil out of the working chamber so as to allow the combustion forces on the control member to rotate the control member in the opposite direction. At fixed compression ratio the hydraulic piston may be balanced between average oil pressure in the working chamber, on the one hand, and average combustion force, on the other hand. In such a situation the pump may be switched-off. It is also possible to apply an additional locking element which locks the control member with respect to the crankcase in case of operating at fixed compression ratio.

[0009] In a specific embodiment the control member comprises a control shaft which extends concentrically through the central main portion and which is drivably coupled to the crank member via a transmission at a side of the crankshaft web where the crankpin is located, and the hydraulic piston is drivably connected to the control shaft at an opposite side of the crankshaft web.

[0010] The transmission may be adapted such that under operating conditions the crank member rotates in the same direction as the crankshaft as seen from the crankcase. This means that friction between the crank member and the crankpin is relatively low.

[0011] In a practical embodiment the transmission comprises an external crank member gear which is fixed to the crank member, an external intermediate gear that is rotatably mounted to the crankshaft and an external control shaft gear which is fixed to the control shaft, wherein the intermediate gear meshes with both the crank member gear and the control shaft gear. In this configuration the centre line of the crankpin and the centre line of the intermediate gear extend parallel to the crankshaft axis and rotate thereabout under operating conditions.

[0012] In a particular embodiment the hydraulic actuator comprises a relief valve for depressurizing the working chamber. This provides the opportunity to move the hydraulic piston without building-up a significant back-force from the working chamber onto the hydraulic piston. This allows the engine to change the compression ratio very rapidly by means of the combustion forces, since the oil can be forced out from the working chamber rapidly. This may be desired in case of switching from low engine load to high engine load for achieving a rapid change to a lower compression ratio.

[0013] The working chamber may be a first working chamber which communicates with a high-pressure side of the pump via the oil supply line and the hydraulic actuator may have a second working chamber, wherein opposite sides of the hydraulic piston contact the first and second working chambers, respectively, and wherein the second working chamber communicates with a low-pressure side of the pump via an oil discharge line. This provides the opportunity to apply a closed hydraulic circuit, which requires minimum maintenance. If the pump is switched-on oil is transferred from the high-pressure side of the pump to the first working chamber, whereas oil is also transported from the second working chamber to the low-pressure side of the pump. It is also conceivable to reverse the oil flow to and from the working chambers such that the high-pressure side communicates with the second working chamber and the low-pressure side communicates with the first working chamber in order to be able to adjust the position of the hydraulic piston in opposite direction when the pump is switched-on. It is also conceivable to apply a pump which operates in opposite directions. It is noted that in case of two working chambers the oil pressure as well as the combustion forces exert a force on the hydraulic piston in one direction.

[0014] If a relief valve is present, it may be located between the first and second oil chamber. If the relief valve is open and the pump is switched-off the oil may freely flow between the first and second working chambers.

[0015] Preferably, the relief valve comprises an electronically controlled valve, since this allows to switch rapidly. The relief valve may be a solenoid valve.

[0016] The hydraulic piston may be directly fixed to the control member. This means that the hydraulic piston follows a circular path. This provides the opportunity to configure a compact engine without any transmission between the hydraulic piston and the control member. This also means that opposite walls of the working chamber may extend concentrically about the crankshaft axis along which the piston slides.

[0017] The hydraulic actuator may be provided with a pressure sensor for measuring actual pressure in the working chamber. This pressure is directly related to the combustion forces.

[0018] In an advantageous embodiment, wherein the control shaft extends concentrically through the main portion, the engine comprises a pulley for driving auxiliary devices of the engine, wherein the pulley is fixed to the central main portion and wherein the hydraulic actuator is at least partly accommodated within the circumference of the pulley, since this provides a compact configuration.

[0019] The control member may be provided with a rotational position sensor, such as a potmeter, which is connected to a controller for adjusting the rotational position of the control member. This allows to monitor the actual compression ratio.

[0020] The oil in the hydraulic actuator may be hydraulic oil.

[0021] The invention will hereafter be elucidated with reference to the schematic drawings showing an embodiment of the invention by way of example.

Fig. 1 is a perspective view of a part of an embodiment of an internal combustion engine according to the invention.

Fig. 2 is a perspective view of an interior part of the embodiment as shown in Fig. 1.

Fig. 3 is a similar view as Fig. 2, showing a part thereof on a larger scale and seen from a different side.

Fig. 4 is a perspective view of a part of a hydraulic actuator, which is part of the engine as shown in Fig. 1, but shown on a larger scale.

Fig. 5 is a perspective view of the interior of the hydraulic actuator as partly shown in Fig. 4.

Fig. 6 is a similar view as Fig. 1 without the hydraulic actuator.

Fig. 7 is a perspective broken-away view of a part of the embodiment as shown in Fig. 1.

Fig. 8 is an illustrative view of an engine including a crank member with an eccentrical bearing portion.

[0022] Fig. 1 shows a part of an embodiment of an internal combustion engine 1 according to the invention. Figs. 2 and 3 show details of the interior of the engine 1. The engine 1 is a four-stroke engine and has a variable compression ratio which provides the opportunity to operate the engine at high compression ratio under part-load conditions resulting in improved efficiency. Under high-load conditions the compression ratio can be lowered in order to avoid knocking. The engine 1 comprises a crankcase 2, which supports a crankshaft 3 by crankshaft bearings. The crankshaft 3 has a crankshaft axis 4 and is rotatable with respect to the crankcase 2 about the crankshaft axis 4.

[0023] The crankshaft 3 comprises a central main portion 5, a crankpin 6 and a crankshaft web 7. The crankshaft web 7 is located between the central main portion 5 and the crankpin 6. It is noted that in Figs. 2 and 3 a front side of the engine 1 is located at the right side in the drawings. Thus, the central main portion 5 projects from the crankcase 2 at the front side of the engine 1. At the opposite rear side of the engine 1 a flywheel (not shown) is fixed to the crankshaft 3. Fig. 1 is a view of the front side of the engine 1.

[0024] The engine 1 comprises a crank member 8 which is rotatably mounted on the crankpin 6. The crank member 8 is provided with a bearing portion 9 which is disposed eccentrically with respect to the crankpin 6. The bearing portion 9 has an outer circumferential wall which bears a big end 10 of a connecting rod 11. Thus, the connecting rod 11 is rotatably mounted on the crank member 8 via its big end 10. The connecting rod 11 also includes a small end 12 to which a piston 13 is rotatably connected.

[0025] The crank member 8 is provided with an external crank member gear 14 which meshes with two external intermediate gears 15. The intermediate gears 15 are rotatably mounted to the crankshaft 3 and their axes of rotation extend parallel to the crankshaft axis 4. Each of the intermediate gears 15 also meshes with an external control shaft gear 16, which is fixed to a control shaft 17. The control shaft 17 extends concentrically through the central main portion 5 of the crankshaft 5 and projects from the central main portion 5 as seen from the crankpin 6. The control shaft 17 is rotatable with respect to the crankshaft 3 about the crankshaft axis 4. Thus, the control shaft 17 is rotatable about a control shaft axis which coincides with the crankshaft axis 4. Similarly, the centre line of the control shaft gear 16 also coincides with the crankshaft axis 4.

[0026] The crank member gear 14, the intermediate gears 15 and the control shaft gear 16 together form a transmission between the control shaft 17 and the crank member 8 at a side of the crankshaft web 7 where the crankpin 6 is located. The mentioned gears 14 - 16 are dimensioned such that under operating conditions the crank member 8 rotates at half speed of the crankshaft 3 and in the same direction thereof, as seen from the crankcase 2, when the control shaft 17 has a fixed rotational position with respect to the crankcase 2.

[0027] It is noted that Fig. 2 only shows one piston 13 and corresponding crankpin 6 and crank member 8, but the engine 1 may be a multi-cylinder engine including a plurality of crankpins and associated crank members, in which the crank members are mutually coupled in order to achieve similar rotational movements of the respective crank members with respect to the crankcase 2.

[0028] In order to be able to change the compression ratio of the engine 1 under operating conditions the crank member 8 can be rotated with respect to the crankpin 6 at a virtual standstill of the crankshaft 3 by means of adjusting the rotational position of the control shaft 17 with respect to the crankcase 2.

[0029] The rotational position of the control shaft 17 with respect to the crankcase 2 is adjustable by means of a hydraulic actuator 18. A part of the hydraulic actuator 18 of the embodiment of the engine 1 as shown in the drawings is depicted as a separate part in Fig. 4. Fig. 5 shows the interior of the hydraulic actuator 18 and Figs. 6 and 7 illustrate the position of the hydraulic actuator 18 with respect to the crankcase 2 in more detail.

[0030] The hydraulic actuator 18 comprises a housing 19 which is fixed to the crankcase 2. A hydraulic piston 20 is fixed to the control shaft 17 and movable within the housing 19 about the crankshaft axis 4, i.e. the free end of the hydraulic piston 20 is slidable along an inner ring portion of the housing 19. Fig. 7 shows that the piston 20 is mounted on a splined portion of the control shaft 17 and fixed in axial direction thereof by means of a nut 37 which presses the hydraulic piston 20 against a collar of the control shaft 17. The hydraulic piston 20 divides an interior space of the housing 19 into a first working chamber 21 and a second working chamber 22, such that the opposite sides of the piston 20 contact the first and second working chambers 21, 22. Both working chambers 21, 22 have opposite walls extending in circumferential direction of the control shaft 17, i.e. the opposite walls are concentrical with respect to the crankshaft axis 4.

[0031] The hydraulic actuator 18 is also provided with a pump 23 which is driven by an electric motor 24. A high-pressure side of the pump 23 communicates with the first working chamber 21 via an oil supply line 25. The second working chamber 22 communicates with a low-pressure side of the pump 23 via an oil discharge line 26. Fig. 5 shows that the piston 20 and the housing 19 have cooperating recesses, as indicated by reference number 27 in the first working chamber 21, which recesses 27 form a small chamber at the end of the oil supply line 25 if a radially extending contact surface of the piston 20 abuts against the housing 19 in clockwise direction in Fig. 5. This allows the hydraulic piston 20 to be moved anti-clockwise when it abuts against the housing 19 upon pumping oil to the first working chamber 21.

[0032] The part as shown in Fig. 4 partly forms a cover 28 in order to close the first and second working chambers 21, 22. This means that opposite walls of the first and second working chambers 21, 22 in longitudinal direction of the control shaft 17 are formed by a rear wall of the housing 19 and the cover 28.

[0033] When under practical conditions the control shaft 17 should be turned anti-clockwise over a certain angle in the embodiment as shown in Fig. 1, the electric motor 24 is switched-on and oil pressure in the first working chamber 21 will be increased. At the same time oil will flow from the second working chamber 22 to a low-pressure side of the pump 23 via the oil discharge line 26.

[0034] In order to turn the control shaft 17 clockwise over a certain angle the first working chamber 21 is depressurized rapidly by means of opening an electronically controlled relief valve 29, for example a solenoid valve. This allows the piston 20 to be rotated clockwise without back-pressure of the first working chamber 21. The pump 24 may remain switched-off in this case. The relief valve 29 is located in a bypass between the oil supply line 25 and the oil discharge line 26. Fig. 4 shows that the oil supply line 25, the oil discharge line 26 and the bypass are integrated in the cover 28.

[0035] In order to turn the control shaft 17 clockwise rapidly the engine uses its combustion forces. The combustion force on the piston 13 is exerted via the big end 10 onto the bearing portion 9 of the crank member 8. Due to the eccentrical position of the bearing portion 9 with respect to the crankpin 6, a natural average torque is exerted on the crank member 8 such that the crank member 8 tends to rotate about the crankpin 6. In the embodiment as shown the mentioned torque on the control shaft 17 is directed clockwise. It is noted that a higher number of pistons 13 will increase the average torque on the control shaft 17.

[0036] A torque that is generated by combustion forces can be further illustrated with reference to Fig. 3. Assuming that the crankshaft 3 rotates clockwise when looking from the front side to the rear side of the engine 1, the crank member 8 also rotates clockwise with respect to the crankcase 2 at half crankshaft speed. Furthermore, a condition of maximum compression ratio is selected such that at the end of the compression stroke in top dead centre of the piston 13 a centre line of the bearing portion 8, a centre line of the crankpin 6 and the crankshaft axis 4 lie in a common plane, whereas the centre line of the crank pin 6 lies between the crankshaft axis 4 and the centre line of the bearing portion 8. The rotational position of the crank member 8 at maximum compression ratio at the end of the compression stroke in top dead centre of the piston 13 may be different, for example the crank member 8 may be turned 10° clockwise with respect to the crankcase 2 at the end of the compression stroke in top dead centre relative to the above-mentioned position. In order to decrease compression ratio the crank member 8 is rotated clockwise at a virtual standstill of the crankshaft 3. The combustion forces also create a torque on the crank member 8 clockwise due to the eccentricity of the bearing portion 9. Due to the presence of the intermediate gears 15 this results in a torque on the control shaft 17 which is also directed clockwise. This implies that there is a natural torque on the control shaft 17 to rotate the crank member 8 in a direction of lower compression ratio in this case.

[0037] In the embodiment as shown the compression ratio is increased by switching-on the pump 23 at closed relief valve 29 such that the oil pressure in the first working chamber 21 rises and the pressure in the second working chamber 22 decreases to a condition that the hydraulic force on the hydraulic piston 20 exceeds the average combustion forces in opposite direction. When the relief valve 29 is opened and the pump 23 is switched-off the combustion forces will adjust the rotational position of the control shaft 17 to a condition of lower compression ratio. The angle of rotation can be controlled by the duration of the open position of the relief valve 29.

[0038] In practice a fast change to reduced compression ratio is typically desired in case of switching from low to high engine load in order to avoid the risk of knocking. For this reason, the embodiment of the engine 1 as shown is configured such that upon rotating the control shaft 17 clockwise with respect to the crankcase 2 the compression ratio is reduced. Turning the control shaft 17 anti-clockwise results in a higher compression ratio. This may be performed less rapidly such that the pump 23 can have limited power. Hence, the electric motor 24 for driving the pump 23 may be relatively small and low-cost.

[0039] Fig. 1 shows that the engine 1 is provided with a pulley 31 for driving auxiliary devices such as an alternator 32 via an endless belt. The pulley 31 is fixed to the central main portion 5 of the crankshaft 3. Figs. 6 and 7 show that inside the pulley 31 a space is available in which the hydraulic actuator 18 is partly accommodated. In order to facilitate replacement of the endless belt a bridge 33 between the crankcase 2 and the cover 28 of the hydraulic actuator 18 is releasably mounted over the endless belt. Furthermore, Fig. 7 illustrates that the pulley 31 is attached to the central main portion 5 by means of a ring 36 which is clamped against a collar on the central main portion 5 by a nut 35 through which the control shaft 17 extends.

[0040] Fig. 1 shows that the hydraulic actuator 18 is also provided with a potmeter 34 for measuring the rotational position of the control shaft 17. The signal from the potmeter 34 can be used for a closed loop control of the hydraulic actuator 18.

[0041] The hydraulic actuator 18 is provided with a pressure sensor 30 for measuring actual pressure in the first working chamber 21. The sensor 30 provides a signal which corresponds to the actual cylinder pressure.

[0042] The actual combustion pressure can be derived from the oil pressure according to the following relationship with reference to Fig. 8:

wherein

p_comb = actual combustion pressure on the piston 13

p_oil = oil pressure as measured in the first working chamber 21

A = effective surface of the hydraulic piston 20

a = distance from the centre of the surface of the hydraulic piston 20 to the centre line of the control shaft 17

tr-rat = transmission ratio between the crank member 8 and the control shaft 17

E = maximum eccentricity of the bearing portion 9; Fig. 8 shows that E is the distance between the centre lines of the bearing portion 9 and the crankpin 6

α₁ = angle between the connecting rod 11 and a plane through the piston pin and the crankshaft axis 4

α₂ = angle between the connecting rod 11 and a plane through the centre lines of the bearing portion 9 and the crankpin 6

A_piston = upper surface of the piston 13

in the embodiment as shown in the figures:

wherein

N_cmg = number of teeth of crank member gear

N_dsg = number of teeth of drive shaft gear

[0043] The calculated combustion pressure may provide an indication of the quality of combustion. In a multi-cylinder engine it provides the opportunity to monitor the combustion in different cylinders, for example detecting misfiring. An aspect of the invention is a method for deriving combustion pressure of the engine according to one of the claims, wherein the above-mentioned relationship is used.

[0044] From the foregoing, it will be clear that the invention provides an improved internal combustion engine including variable compression ratio and low noise emission.

[0045] The invention is not limited to the embodiment shown in the drawings and described hereinbefore, which may be varied in different manners within the scope of the claims and their technical equivalents. The transmission may be configured differently, for example by means of sprocket wheels and a chain. Furthermore, the crank member may be driven through an alternative driving mechanism which has a control member that is different and is located at a different location than the control shaft, but which is also rotatable with respect to the crankcase and drivable coupled to the crank member, which has also a fixed position with respect to the crankcase under operating conditions at fixed compression ratio. For example, the control member may comprise the internal ring gear of the planetary mechanism of the internal combustion engine as disclosed in EP14154720.8 of the same applicant and filed on the same date as the present application. At fixed compression ratio the rotational position of the internal ring gear with respect to the crankcase is fixed.

Claims

1. An internal combustion engine (1) including variable compression ratio, comprising

a crankcase (2);

a crankshaft (3) including a crankshaft axis (4), said crankshaft (3) having at least a central main portion (5), a crankpin (6) and a crankshaft web (7) located between the central main portion (5) and the crankpin (6), said crankshaft (3) being supported by the crankcase (2) and rotatable with respect thereto about the crankshaft axis (4);

at least a connecting rod (11) including a big end (10) and a small end (12);

a piston (13) being rotatably connected to the small end (12);

a crank member (8) being rotatably mounted on the crankpin (6), and comprising at least a bearing portion (9) which is eccentrically disposed with respect to the crankpin (6), and having an outer circumferential wall which bears the big end (10) of the connecting rod (11) such that the connecting rod (11) is rotatably mounted on the bearing portion (9) of the crank member (8) via the big end (10);

a driving mechanism for driving the crank member (8) at half speed of the crankshaft (3) as seen from the crankcase (2), which driving mechanism comprises a control member (17) for varying the compression ratio, which is rotatable with respect to the crankcase (2) and drivably coupled to the crank member (8), but which has a fixed position with respect to the crankcase (2) under operating conditions at fixed compression ratio;

wherein the rotational position of the control member (17) with respect to the crankcase (2) is adjustable by means of a hydraulic actuator (18), which comprises a hydraulic piston (20) that is drivably connected to the control member (17), a working chamber (21), a pump (23) and an oil supply line (25) through which the pump (23) and the working chamber (21) communicate.

2. An internal combustion engine (1) according to claim 1, wherein the control member comprises a control shaft (17) extending concentrically through the central main portion (5) and being drivably coupled to the crank member (8) via a transmission (14-16) at a side of the crankshaft web (7) where the crankpin (6) is located, wherein the hydraulic piston (20) is drivably connected to the control shaft (17) at an opposite side of the crankshaft web (7).

3. An internal combustion engine (1) according to claim 2, wherein the transmission (14-16) is adapted such that under operating conditions the crank member (8) rotates in the same direction as the crankshaft (3) as seen from the crankcase (2).

4. An internal combustion engine (1) according to claim 3, wherein the transmission comprises an external crank member gear (14) which is fixed to the crank member (8), an external intermediate gear (15) that is rotatably mounted to the crankshaft and an external control shaft gear (16) which is fixed to the control shaft (17), wherein the intermediate gear (15) meshes with both the crank member gear (14) and the control shaft gear (16).

5. An internal combustion engine (1) according to one of the preceding claims, wherein the hydraulic actuator (18) comprises a relief valve (29) for depressurizing the working chamber (21).

6. An internal combustion engine (1) according to one of the preceding claims, wherein the working chamber is a first working chamber (21) which communicates with a high-pressure side of the pump (23) via the oil supply line (25) and the hydraulic actuator (18) has a second working chamber (22), wherein opposite sides of the hydraulic piston (20) contact the first and second working chambers (21, 22), respectively, wherein the second working (2) chamber communicates with a low-pressure side of the pump (23) via an oil discharge line (26).

7. An internal combustion engine (1) according to claim 5 and 6, wherein the relief valve (29) is located between the first and second oil chamber (21, 22).

8. An internal combustion engine (1) according to one of the preceding claims and claim 5, wherein the relief valve (29) comprises an electronically controlled valve.

9. An internal combustion engine (1) according to one of the preceding claims, wherein the hydraulic piston (20) is directly fixed to the control member (17).

10. An internal combustion engine (1) according to one of the preceding claims, wherein the hydraulic actuator (18) is provided with a pressure sensor (30) for measuring actual pressure in the working chamber (21).

11. An internal combustion engine (1) according to one of the preceding claims and claim 2, wherein a pulley (31) for driving auxiliary devices (32) of the engine (1) is fixed to the central main portion (5) and the hydraulic actuator (18) is at least partly accommodated within the circumference of the pulley (31).

12. An internal combustion engine (1) according to one of the preceding claims, wherein the control member (17) is provided with a rotational position sensor, such as a potmeter (34), which is connected to a controller for adjusting the rotational position of the control member (17).

13. A method of operating the internal combustion engine (1) according to one of the preceding claims, wherein the control member (17) is turned in one direction with respect to the crankcase (2) over a certain angle by means of increasing the pressure in the working chamber (21), and wherein the control member (17) is turned over a certain angle in opposite direction by means of reducing the pressure in the working chamber (21) so as to allow the combustion forces on the control member (17) to rotate the control member (17) in the opposite direction.

Drawing