Combustion engine, vehicle comprising the combustion engine and method for controlling the combustion engine

Abstract

A method to control a four-stroke combustion engine, comprising at least one cylinder; a piston arranged in each cylinder; at least one inlet valve arranged in each cylinder which is connected with an inlet system; at least one first camshaft which controls each inlet valve; at least one exhaust valve arranged in each cylinder which is connected with an exhaust system; at least one second camshaft which controls each exhaust valve; and a crankshaft which controls each camshaft. At least one phase-shifting device is arranged between the crankshaft and the second camshaft, to phase-shift the second camshaft in relation to the crankshaft to a state, where the exhaust valve is controlled in such a way, that it is opened during the expansion stroke of the engine and closed during the exhaust stroke of the engine, to achieve engine braking through compression in the cylinders during the exhaust stroke.

Claims

1. A four-stroke combustion engine comprising: at least one cylinder; a piston arranged in the at least one cylinder, wherein said piston is connected via a connecting rod to a crankshaft; at least one inlet valve arranged in the at least one cylinder, wherein the at least one inlet valve is connected with an inlet system; at least one first camshaft, wherein said at least one first camshaft is in operable contact with the at least one inlet valve; at least one exhaust valve arranged in the at least one cylinder, wherein the at least one exhaust valve is connected with an exhaust system; at least one second camshaft in operable contact with the at least one exhaust valve, such that the at least one second camshaft controls the at least one exhaust valve using a valve lift profile designed to open the at least one exhaust valve during an exhaust stoke of the engine to release exhaust gas from the at least one cylinder; wherein the crankshaft is in operable contact with and is configured to control each of said at least one first camshaft and at least one second camshaft; at least one cam phase-shifting device arranged between the crankshaft and the at least one second camshaft, such that the at least one cam phase-shifting device is configured to phase-shift the at least one second camshaft in relation to the crankshaft, to a state where the valve lift profile for the at least one exhaust valve is altered such that the at least one exhaust valve is opened during an expansion stroke of the engine and closed during the exhaust stroke of the engine, in order to achieve engine-braking via compression in the at least one cylinder during the exhaust stroke of the engine; and a decompression device positioned between the at least one second camshaft and the at least one exhaust valve, such that after phase-shifting the at least one second camshaft, the decompression device is arranged to contact the at least one exhaust valve and further alter the valve lift profile for the at least one exhaust valve, such that the at least one exhaust valve is controlled to open and close in a transition area between the exhaust stroke of the engine and an inlet stroke of the engine, when the piston is at a top dead center in the at least one cylinder.

2. The combustion engine according to claim 1, wherein the phase-shift of the at least one second camshaft is controlled, to thereby control the compression in the at least one cylinder during the exhaust stroke of the engine, for achieving stepless control of a size of an amount of braking torque during engine braking.

3. The combustion engine according to claim 1, wherein the phase-shift of the at least one second camshaft takes place between 60 and 120 crankshaft degrees.

4. The combustion engine according to claim 1, wherein the at least one cam phase-shifting device is also arranged between the crankshaft and the at least one first camshaft, to phase-shift the at least one first camshaft in relation to the crankshaft to a state, where the at least one inlet valve is controlled in such a way, that said at least one inlet valve is opened at a crankshaft angle where the at least one exhaust valve is closed with the decompression device.

5. The combustion engine according to claim 1, wherein the decompression device is adapted to open and close the at least one exhaust valve in another transition area between the inlet stroke of the engine and the exhaust stroke of the engine, when the piston is at the top dead center in the at least one cylinder.

6. The combustion engine according to claim 1, wherein the combustion engine further comprises two inlet valves and two exhaust valves arranged in the at least one cylinder.

7. The combustion engine according to claim 1, wherein the combustion engine further comprises two first camshafts and two second camshafts arranged in the combustion engine.

8. The combustion engine according to claim 1, wherein the at least one phase-shifting device comprises first and second cam phase-shifting devices that are arranged for each of the at least one first camshaft and the at least one second camshaft, respectively.

9. A vehicle, comprising a four-stoke combustion engine, said combustion engine comprising: at least one cylinder; a piston arranged in the at least one cylinder, wherein said piston is connected via a connecting rod to a crankshaft; at least one inlet valve arranged in the at least one cylinder, wherein the at least one inlet valve is connected with an inlet system; at least one first camshaft, wherein said at least one first camshaft is in operable contact with the at least one inlet valve; at least one exhaust valve arranged in the at least one cylinder, wherein the at least one exhaust valve is connected with an exhaust system; at least one second camshaft in operable contact with the at least one exhaust valve, such that the at least one second camshaft controls the at least one exhaust valve using a valve lift profile designed to open the at least one exhaust valve during an exhaust stroke of the engine to release exhaust gas from the at least one cylinder; wherein the crankshaft is in operable contact with and is configured to control each of said at least one first camshaft and at least one second camshaft; at least one cam phase-shifting device arranged between the crankshaft and the at least one second camshaft, such that the at least one cam phase-shifting device is configured to phase-shift the at least one second camshaft in relation to the crankshaft, to a state where the valve lift profile for the at least one exhaust valve is altered such that the at least one exhaust valve is opened during an expansion stroke of the engine and closed during the exhaust stroke of the engine, in order to achieve engine-braking via compression in the at least one cylinder during the exhaust stroke of the engine; and a decompression device positioned between the at least one second camshaft and the at least one exhaust valve, such that after phase-shifting the at least one second camshaft, the decompression device is arranged to contact the at least one exhaust valve and further alter the valve lift profile for the at least one exhaust valve, such that the at least one exhaust valve is controlled to open and close in a transition area between the exhaust stroke of the engine and an inlet stroke of the engine, when the piston is at a top dead center in the at least one cylinder.

10. A method to control a four-stroke combustion engine, wherein the combustion engine comprises: at least one cylinder; a piston arranged in the at least one cylinder, wherein said piston is connected via a connecting rod to a crankshaft; at least one inlet valve arranged in the at least one cylinder, wherein the at least one inlet valve is connected with an inlet system; at least one first camshaft, wherein said at least one first camshaft is in operable contact with the at least one inlet valve; at least one exhaust valve arranged in the at least one cylinder, wherein the at least one exhaust valve is connected with an exhaust system; at least one second camshaft in operable contact with the at least one exhaust valve, such that the at least one second camshaft controls the at least one exhaust valve using a valve lift profile designed to open the at least one exhaust valve during an exhaust stroke of the engine to release exhaust gas from the at least one cylinder; wherein the crankshaft is in operable contact with and is configured to control each of said at least one first camshaft and at least one second camshaft, wherein the method comprises: a) phase-shifting the at least one second camshaft in relation to the crankshaft, such that the at least one second camshaft is phase-shifted to a state, where the valve lift profile for the at least one exhaust valve is altered such that the at least one exhaust valve is opened during an expansion stroke of the engine and closed during the exhaust stroke of the engine, in order to achieve engine-braking via compression in the at least one cylinders during the exhaust stroke of the engine; and b) further altering the valve lift profile for the at least one exhaust valve with a decompression device, said decompression device positioned between the at least one second camshaft and the at least one exhaust valve, such that the at least one exhaust valve is controlled to open and close in a transition area between the exhaust stroke of the engine and an inlet stroke of the engine, when the piston is at a top dead center in the at least one cylinder.

11. The method according to claim 10, wherein the phase-shifting of the at least one second camshaft is controlled, to thereby control the compression in the at least one cylinder during the exhaust stroke of the engine, for achieving stepless control of a size of an amount of braking torque during engine braking.

12. The method according to claim 10, wherein the phase-shifting of the at least one second camshaft takes place between 60 and 120 crankshaft degrees.

13. The method according to claim 10, wherein the opening of the at least one exhaust valve with the decompression device takes place between 40 and 80 crankshaft degrees, before the top dead center between the exhaust stroke of the engine and the inlet stroke of the engine; and the closing of the at least one exhaust valve with the decompression device takes place between the exhaust stroke of the engine and the inlet stroke of the engine.

14. The method according to claim 13, further comprising: c) phase-shifting the at least one first camshaft in relation to the crankshaft, such that the at least one first camshaft is phase-shifted to a state, where the at least one inlet valve is controlled in such a way, that said at least one inlet valve is opened at a crankshaft angle where the at least one exhaust valve is closed with the decompression device.

15. The method according to claim 14, wherein the at least one inlet valve is opened between 20 and 80 crankshaft degrees, after the top dead center between the exhaust stroke of the engine and the inlet stroke of the engine.

16. The method according to claim 10, wherein in step a), there are two exhaust valves per cylinder that are controlled with the at least one second camshaft.

17. The method according to claim 10, wherein in step a), the at least one exhaust valve is controlled with two second camshafts.

18. The method according to claim 10, further comprising: stopping or reducing an amount of fuel being supplied to the at least one cylinder via control of a fuel injection device.

19. The method according to claim 10, further comprising: opening and closing the at least one exhaust valve with the decompression device in another transition area between the inlet stroke of the engine and the exhaust stroke of the engine, when the piston is at the top dead center in the at least one cylinder.

20. The combustion engine according to claim 1, wherein said decompression device is located on said at least one second camshaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Below is a description, as an example, of preferred embodiments of the invention with reference to the enclosed drawings, in which:

(2) FIG. 1 is a side view of a schematically displayed vehicle, with a combustion engine according to the present invention,

(3) FIG. 2 is a cross-sectional view of a schematically displayed combustion engine according to the present invention,

(4) FIG. 3 shows a diagram of a phase shift of inlet and exhaust valves in a combustion engine according to the present invention, and

(5) FIG. 4 shows a flow chart of a method to control a combustion engine according to the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

(6) FIG. 1 shows a schematic side view of a vehicle 1, which vehicle 1 is equipped with a four-stroke combustion engine 2 according to the present invention. The combustion engine 2 is preferably a diesel engine. The vehicle 1 is also equipped with a gearbox 4 connected to a combustion engine 2, driving the driving wheels 6 of the vehicle 1 via the gearbox 4, and a propeller shaft 8.

(7) FIG. 2 shows a cross-sectional view of a combustion engine 2 according to the present invention. The combustion engine 2 comprises at least one cylinder 10, with a piston 12 arranged in each cylinder 10. The piston 12 is connected via a connecting rod 14 to a crankshaft 16, which at rotation moves the piston 12 forwards and backwards in the cylinder 10. At least one inlet valve 18 is arranged in each cylinder 10, which inlet valve 18 is connected with an inlet system 20. At least one first camshaft 22 controls each inlet valve 18. At least one exhaust valve 24 is arranged in each cylinder 10, which exhaust valve 24 is connected with an exhaust system 26. Preferably, two inlet valves 18 and two exhaust valves 24 are arranged in each cylinder 10. At least one second camshaft 28 controls at least one exhaust valve 24. Depending on the type of combustion engine 2, two first and two second camshafts 22, 28 may be arranged in the combustion engine 2. This is advantageous if the engine 2 is of V-type. Preferably, the combustion engine has several cylinders.

(8) A camshaft control 30 is arranged in the combustion engine 2 according to the present invention. The crankshaft 16 controls each camshaft 22, 28 via a camshaft transmission 32. At least one phase-shifting device 34 is arranged between the crankshaft 16 and each camshaft 22, 28, so that each camshaft 22, 28 may be phase-shifted to a desired angular position in relation to the angular position of the crankshaft. Preferably, a phase-shifting device 34 is arranged for each camshaft 22, 28. A control device 36 receives signals from a number of different sensors (not shown), such as absolute pressure in the inlet manifold, charge air temperature, mass airflow, throttle position, engine speed, engine load. The control device 36 operates the phase-shifting devices 34, which adjust the angle position of the camshafts 22, 28 in relation to the crankshaft 16. A decompression device 37 is connected to the exhaust valves 24, decompression device 37 is adapted to open and close the exhaust valves 24 in the transition area between an exhaust stroke and an inlet stroke, when the piston 12 is at top dead center in the cylinder 10. By opening the exhaust valves 24 in the transition area between an exhaust stroke and an inlet stroke, the pressure in the cylinders 10 is reduced when the inlet valves 18 are opened. The risk of engine failure is therefore reduced when engine braking is carried out by using compression during the exhaust stroke. The decompression device 37 is connected to the control device 36.

(9) FIG. 3 shows a graph representing a phase shift of inlet and exhaust valves 18, 24 in a combustion engine 2 according to the present invention. The Y-axis represents the distance that the inlet and exhaust valves 18, 24 move. The X-axis represents the angular movement of the crankshaft 16. The piston 12 moves between a top dead center, TDC, and a bottom dead center, BDC, in the cylinder 10. At e.g. 0, the piston 12 is at the top dead center, TDC, and at 180 the piston 12 is at the bottom dead center, BDC. The graph in FIG. 3 represents a combustion engine 2 of four-stroke type, which entails that the crankshaft 16 and therefore the piston 12 will have moved 720 when all four strokes have been completed.

(10) The curve A1 represents the movement of the exhaust valve 24 in relation to the piston movement at normal load. The curve 11 represents the movement of the inlet valve 18 in relation to the piston movement at normal load. FIG. 3 thus shows, through the curve A1, that the exhaust valve 24 at normal load opens at the end of the expansion stroke, i.e. at 120, in order to release the exhausts to the exhaust and after-treatment system 38 during the exhaust stroke. The exhaust valve 24 then closes at the start of the inlet stroke, which occurs at 360. Roughly at the same time, the inlet valve 18 opens, shown by the curve 11, in order to let air into the cylinder 10. The inlet valve 18 then closes at 590, at which point the compression stroke is initiated. At 720, corresponding to 0, the expansion stroke is started.

(11) The curve A2 illustrates a situation where the engine 2, and therefore the vehicle 1, are decelerated through engine braking according to the present invention, wherein the phase-shifting device 34 for the second camshaft 28 has been adjusted, so that the exhaust valves 24 open and close earlier than what would be the case with normal load. At the same time, the fuel supply to one or several of the cylinders 10 of the engine 2 is closed or restricted, so that no fuel, or a limited volume of fuel is injected into one or several of the cylinders 10. By phase-shifting the second camshaft 28 in relation to the crankshaft 16, so that every second camshaft 28 is phase-shifted to a state, where the exhaust valves 24 are controlled in such a way that they are opened during the expansion stroke of the engine and closed during the exhaust stroke of the engine, engine braking is achieved through compression in the cylinders 10 during the exhaust stroke. Preferably, the second camshaft 22 is phase-shifted between 60 and 120 crankshaft degrees, preferably 90 crankshaft degrees. Engine braking is thus obtained, since compression arises in the cylinders 10 during both the compression stroke and the exhaust stroke.

(12) In order to utilize the braking energy at engine braking, the pressure of the air compressed in the cylinders 10 must be reduced at the end of each compression. The exhaust valves 24 are therefore opened and closed with the decompression device 37 in the transition area between an exhaust stroke and an inlet stroke, when the piston 12 is at a top dead center in the cylinder 10. The air compressed in the cylinders 10 will therefore leave the cylinders 10 through the exhaust channels and further along through the exhaust system. The decompression device 37 subsequently closes the exhaust valves 24, so that air may be sucked in through the inlet valves 18, and an overpressure may be built up in the cylinders 10 at the next compression. With the decompression device the exhaust valves 24 are opened 40-80 crank-shaft degrees, preferably 60 crankshaft degrees, before the top dead center between the exhaust stroke and the inlet stroke, and the exhaust valves 24 are closed with the decompression device 40-80, preferably 60, after the top dead center between the exhaust stroke and the inlet stroke. The opening and closing of the exhaust valves 24 with the decompression device 37 is shown by the curves D1 in FIG. 3.

(13) FIG. 3 and the curves D1 thus show that the decompression device 37 may also open and close the exhaust valves 24 in the transition area between an inlet stroke and an exhaust stroke when the piston 12 is at a top dead center in the cylinder 10. The air compressed in the cylinders 10 will therefore leave the cylinders 10 through the exhaust channels and further along through the exhaust system. With the decompression device, the exhaust valves 24 are opened 50-90 crankshaft degrees, preferably 70 crankshaft degrees, before the top dead center between the inlet stroke and the exhaust stroke, and the exhaust valves 24 are closed with the decompression device 20-60, preferably 40, after the top dead center between the inlet stroke and the exhaust stroke.

(14) By opening the exhaust valves 24 in the transition area between an exhaust stroke and an inlet stroke, the pressure in the cylinders 10 is reduced when the inlet valves 18 are opened. Thus, the risk of engine failure reduced when engine braking is carried out by using compression during the exhaust stroke. In order to further reduce the risk of the inlet valves 18 opening at too high a pressure in the cylinders 10, the first camshaft 22 is phase-shifted in relation to the crankshaft 16, so that the first camshaft 22 is phase-shifted to a state, where the inlet valves 18 are controlled in such a way, that they are opened at a crankshaft degree where the exhaust valves 24 are closed with the decompression device. The first camshaft 22 is phase-shifted to a state where the inlet valves are opened 20-80 crankshaft degrees, preferably 50 crankshaft degrees, after the top dead center between the exhaust stroke and the inlet stroke, as shown by the curve 12 in FIG. 3. Phase-shifting of the inlet lifting during the engine braking entails, that the pressure in the cylinders 10 is reduced to a level where the risk of the inlet valves 18 and their drivetrain failing is reduced. At the same time, pressure pulses in the inlet pipe are avoided when the inlet valves 18 open, which reduces the risk of noise arising in the combustion engine 2.

(15) The method to control the combustion engine 2 according to the present invention will be described below jointly with the flow chart in FIG. 4, which method comprises the steps:

(16) a) to phase-shift every second camshaft 28 in relation to the crankshaft 16, so that every second camshaft 28 is phase-shifted to a state, where the exhaust valves 24 are controlled in such a way, that they are opened during the expansion stroke of the engine and closed during the exhaust stroke of the engine, to achieve engine-braking through compression in the cylinders 10 during the exhaust stroke.

(17) According to one embodiment of the invention, the at least one second camshaft 22 is phase-shifted in step a), representing 60 to 120 crankshaft degrees, preferably 90 crankshaft degrees.

(18) The method also comprises the additional step:

(19) b) to open and close the exhaust valves with the decompression device in the transition area between an exhaust stroke and an inlet stroke, where the piston 12 is at a top dead center in the cylinder 10.

(20) According to one embodiment of the invention, the phase shift of every second camshaft may be controlled in order to thus control the second compression during the exhaust stroke, for achieving stepless control of the size of the braking torque during engine braking.

(21) According to one embodiment of the invention, in step b) the exhaust valves are opened with the decompression device 40-80 crankshaft degrees, preferably 60 crankshaft degrees, before the top dead center between the exhaust stroke and the inlet stroke, and the exhaust valves are closed with the decompression device 40-80, preferably 60, after the top dead center between the exhaust stroke and the inlet stroke.

(22) The method also comprises the additional step:

(23) c) to phase-shift each first camshaft 22 in relation to the crankshaft 16, so that each first camshaft 22 is phase-shifted to a state, where the inlet valves 18 are controlled in such a way, that they are opened at a crankshaft angle where the exhaust valves are closed with the decompression device.

(24) According to one embodiment of the invention, in step c) the inlet valves are opened 20-80 crankshaft degrees, preferably 50 crankshaft degrees, after the top dead center between the exhaust stroke and the inlet stroke.

(25) According to one embodiment of the invention, in step a) two exhaust valves 24 per cylinder are controlled

(26) with the at least one second camshaft 28.

(27) According to one embodiment of the invention, in step a) each exhaust valve 24 is controlled with two second camshafts 28.

(28) According to one embodiment of the invention, every second camshaft 28 is phase-shifted in step a) with a phase-shifting device 34, arranged for every second camshaft 28.

(29) According to one embodiment of the invention, the method before step a) comprises the additional step:

(30) d) to close or reduce the fuel supply to at least one of the cylinders 10.

(31) According to one embodiment of the invention, the combustion engine 2 is powered with diesel fuel.

(32) According to one embodiment of the invention, the method comprises the additional step:

(33) e) to open and close the at least one exhaust valve 24 with a decompression device in the transition area between an inlet stroke and an exhaust stroke, when the piston 12 is at a top dead center in the cylinder 10.

(34) The components and features specified above may, within the framework of the invention, be combined between different embodiments specified.