JP2010138902A - Method for controlling valve of internal combustion engine and valve cam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve valve control in an internal combustion engine, particularly, a large diesel engine. <P>SOLUTION: In a valve lift curve of drawing an exhaust valve or an intake valve of the internal combustion engine, particularly, the large diesel engine up to the top dead center or the bottom dead center from the bottom dead center or the top dead center, there exists a continuous lift curve having a first or fourth lift part having a first or fourth lift gradient, a second or fifth lift part having a second or fifth lift gradient and a third or sixth lift part having a third or sixth lift gradient. The second lift gradient is smaller than the first lift gradient and the third lift gradient, or the fifth lift gradient is smaller than the fourth lift gradient and the sixth lift gradient. The exhaust valve is controlled so as to be positioned in the second lift part after reaching the top dead center of a piston stroke, or the intake valve is controlled so as to be positioned in the fifth lift part before reaching the top dead center of the piston stroke. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a valve control method for an internal combustion engine, in particular a large diesel engine, and a valve cam for carrying out such a method.

  With respect to internal combustion engines in recent years, demands for emission values are increasing at the same time as improving efficiency, and various attempts have already been known to meet this demand. One possibility is to improve the valve control method of the internal combustion engine.

  In the lift curve of the intake valve of the internal combustion engine known from patent document 1, the process of closing the valve is interrupted for a short time. Control of this valve is variably performed by an electric motor.

  FIG. 10 of Patent Document 2 shows a cam for controlling an exhaust valve of an internal combustion engine, and the cam is provided with two cam peaks at a certain cross section level. The exhaust valve is opened again after being closed by the second cam crest.

NO One effective possibilities for _x emissions is to increase the compression, also increases the same time efficiency. However, increasing compression is limited by the minimum required valve clearance. Although the valve clearance can be increased by the valve pocket, the valve pocket has a disadvantage that it becomes a place for forming a nitrogen compound.

German Patent No. 10311275 German Patent No. 10315783

  The object of the present invention is to improve the valve control of internal combustion engines, in particular large diesel engines.

  This problem is solved by a valve control method for an exhaust valve of an internal combustion engine, particularly a large diesel engine, according to the first aspect of the present invention. The valve lift curve up to a point includes a continuous lift curve portion, a first lift portion having a first lift gradient, a second lift portion having a second lift gradient, and a third lift portion having a third lift gradient. And the second lift gradient is smaller than the first lift gradient and the third lift gradient, and the exhaust valve is positioned at the second lift portion after reaching the top dead center of the piston stroke. Yes.

  According to the second aspect of the present invention, the object is further solved by a valve control method for an intake valve of an internal combustion engine, particularly a large diesel engine. The valve lift curve up to the dead center includes a continuous lift curve portion, a fourth lift portion having a fourth lift gradient, a fifth lift portion having a fifth lift gradient, and a sixth lift having a sixth lift gradient. And the fifth lift gradient is smaller than the fourth lift gradient and the sixth lift gradient, and the intake valve is positioned at the fifth lift portion before reaching the top dead center of the piston stroke. ing.

  Increase the valve overlap period by having the exhaust valve in the lift section with a smaller lift gradient after the piston valve reaches the top dead center of the piston stroke or before the intake valve reaches the top dead center of the piston stroke At the same time, the absolute valve lift in the top dead center region of the piston stroke of the intake valve or the exhaust valve can be reduced. At this time, the overlap time cross section and the intake volume or exhaust volume during the valve overlap are preferably not reduced or significantly reduced compared to the conventional valve lift curve. In other words, if the piston is at its top dead center and approaches the maximum value of the intake valve or the exhaust valve, the valve lift of the intake valve or the exhaust valve becomes flat and the intake volume is anyway if the valve clearance is sufficient. Or, the exhaust volume is sufficient.

  Here, the lift gradient refers to an average value of a quotient obtained from a change in valve lift per change in crankshaft angle. In this connection, the top dead center of the valve lift curve refers to the point at which the valve is maximally closed, in particular fully closed. Similarly, the bottom dead center of the valve lift curve refers to the point at which the valve is fully opened, in particular fully open.

  A continuous lift curve here refers in particular to a lift curve in which the relevant part is only descending or ascending, i.e. monotonic, preferably strictly monotonic, so the valve movement in this part is redirected. Is not seen. The continuous lift curve portion according to the present invention can include delays or interruptions in the lift curve, i.e., regions with lower slope values or regions with neutral slope values.

  Valve overlap particularly refers to the period from the end of the fourth cycle to the beginning of the next first cycle, during which the intake valve is already open before the exhaust valve is completely closed. Thus, fresh air is sucked into the combustion chamber by the accelerated exhaust gas flow, and the remaining exhaust gas remaining in the combustion chamber is reduced. At the end of the fourth cycle, the piston is at its top dead center, at which the piston is closest to the cylinder head. The overlap time section refers to the integral of the valve lift curve over the valve overlap period.

  A particularly effective possibility for increasing the compression occurs when both valves, ie the exhaust valve and the intake valve, are each controlled in the manner described above. If the overlap time cross section is the same, the maximum required valve lift at the top dead center of the piston stroke can be further reduced.

  In a preferred embodiment, at least the second and / or fifth lift part is at least partially linear.

  In a further preferred embodiment, the transition from the first lift part to the second lift part takes place before reaching the top dead center of the piston stroke. In a further preferred embodiment, the transition from the fifth lift to the sixth lift occurs after reaching the top dead center of the piston stroke. This provides additional safety against the collision between the valve and the piston in the top dead center region of the piston stroke.

  In a further preferred embodiment, at least one transition between the two lifts progresses in a concave fashion. In a further preferred embodiment, at least one transition between the two lifts progresses convexly. Due to the convex or concave transition, the valve movement is performed in a harmonic manner and thereby without damaging the components.

  According to a third aspect of the present invention, the present invention further relates to a valve cam for performing valve control of an exhaust valve of an internal combustion engine, particularly a large diesel engine, and a valve lift curve drawn by the valve cam includes A continuous lift curve section from bottom dead center to top dead center, a first lift section having a first lift gradient, a second lift section having a second lift gradient, and a first lift section having a third lift gradient. There are three lift portions, the second lift gradient is smaller than the first lift gradient and the third lift gradient, and the exhaust valve is moved to the third lift portion after reaching the top dead center of the piston stroke. is there.

  According to a fourth aspect of the present invention, the present invention further relates to a valve cam for performing valve control of an intake valve of an internal combustion engine, particularly a large diesel engine, and a valve lift curve drawn by the valve cam includes: A continuous lift curve section from the top dead center to the bottom dead center, a fourth lift section having a fourth lift gradient, a fifth lift section having a fifth lift gradient, and a sixth lift having a sixth lift gradient. The fifth lift gradient is smaller than the fourth lift gradient and the sixth lift gradient, and the intake valve is connected to the fifth lift portion before reaching the top dead center of the piston stroke. is there.

  With such a valve cam, the above method for valve control can be implemented. The advantages already mentioned above are obtained.

  The invention, according to a further aspect, relates to a valve train comprising the valve cam of the invention for valve control of an exhaust valve and the valve cam of the invention for valve control of an intake valve. With such a valve train, intake valves and exhaust valves can also be operated according to the method of the invention for valve control. The aforementioned advantages are obtained.

  The present invention also relates to a valve cam configured to generate a valve lift curve in the preferred embodiment of the method of the present invention for valve control.

It is a figure of the valve lift curve of valve control by a prior art. It is a figure of the valve lift curve of valve control of one example of the present invention. It is a figure of the cam form of the exhaust cam of one Example of this invention. It is a figure of the cam form of the intake cam of one Example of this invention. FIG. 4 is a diagram showing a valve lift curve portion of the valve control of the present invention, in which a) is one concave transition between two lift sections and one transition section showing an abrupt transition for computational reasons. B) is one concave transition and one convex transition between the two lifts, and c) is one transition between the two lifts that shows a sharp transition for computational reasons. FIG. 5 is a diagram illustrating one convex transition portion.

  Further advantages and features are explained in detail in the dependent claims and in the following examples, using partly schematic views.

  FIG. 1 shows a valve lift curve for valve control according to the prior art. In this figure, the valve lift at the crankshaft angle Φ is shown. In this figure, 11 is a valve lift curve of the exhaust valve, and 21 is a valve lift curve of the intake valve.

  At Φ <500 °, the exhaust valve is closed and is located at its top dead center 12. The exhaust valve is opened at Φ = 500 °. The corresponding valve lift curve 11 then shows a continuous rise 13 up to bottom dead center 14 at which the exhaust valve is fully opened. The bottom dead center 14 is reached at Φ = 600 ° and is maintained until Φ = 650 °. The valve lift of the exhaust valve is 25 mm at the bottom dead center. The exhaust valve is then closed again. The corresponding valve lift curve 11 then shows a continuous lowering portion 15 up to the top dead center 12 reached at Φ = 760 °. The transition from the top dead center 12 or the transition to the top dead center 12 forms a concave shape. The transition from the bottom dead center 14 or the transition to the bottom dead center 14 forms a convex shape.

  At Φ <670 °, the intake valve is closed and is located at its top dead center 22. At Φ = 670 °, the intake valve is opened. The corresponding valve lift curve 21 then shows a continuous rise 23 up to the bottom dead center 24, at which the intake valve is fully opened. The bottom dead center 24 is reached at Φ = 775 ° and is maintained until Φ = 800 °. The valve lift of the intake valve at the bottom dead center is 25 mm.

  The intake valve is then closed again. The corresponding valve lift curve 21 then shows a continuous descending part 25 to the top dead center 22 that arrives at Φ = 902 °. The transition from the top dead center 22 or the transition to the top dead center 22 is formed in a concave shape. The transition from the bottom dead center 24 or the transition to the bottom dead center 24 is formed in a convex shape.

  In the crankshaft angle region from Φ = 670 ° to Φ = 760 °, a valve overlap region in which both the exhaust valve and the intake valve are open can be seen. At this time, the valve lift curve 11 of the exhaust valve and the valve lift curve 21 of the intake valve intersect at the crankshaft angle Φ = 720 ° which is the end of the fourth cycle and the beginning of the next first cycle. At this time, the valve lift of these two valves is 15 mm. At this point, the piston is at its top dead center position, that is, the position where the piston is closest to the cylinder head. It can be seen that the top dead center position of the piston is limited by the valve lift of the two valves at the crankshaft angle Φ = 720 °. Increasing compression would mean moving the piston dead center position towards the cylinder head, but this is the minimum required because there is a valve lift for both valves at crankshaft angle Φ = 720 °. This is not possible considering the valve clearance.

  It may also be possible to reduce the valve lift of the two valves at the crankshaft angle Φ = 720 ° by closing the exhaust valve earlier or opening the intake valve later. However, this means a reduction in the overlap time profile during valve overlap, which is undesirable. The overlap time section then corresponds to the area under the valve lift curves 11, 12 in the valve overlap region.

  FIG. 2 shows a valve lift curve for valve control according to the present invention. In this figure, the valve lift h is shown for the crankshaft angle Φ. In this figure, a valve lift curve 31 of the exhaust valve and a valve lift curve 41 of the intake valve are shown.

  At Φ <500 °, the exhaust valve is closed and is located at its top dead center 32. At Φ = 500 °, the exhaust valve is opened. At this time, the corresponding valve lift curve 31 shows a continuously rising portion 33 up to the bottom dead center 34, and the exhaust valve is completely opened at the bottom dead center 34. The bottom dead center 34 is reached at Φ = 600 ° and is maintained until Φ = 630 °. The valve lift of the exhaust valve at the bottom dead center is 25 mm. The exhaust valve is then closed again. The corresponding valve lift curve 31 at this time shows the continuous descending portion 35 up to the top dead center 32 that reaches at Φ = 780 °. The transition from the top dead center 32 or the transition to the top dead center 32 is formed in a concave shape. The transition from the bottom dead center 34 or the transition to the bottom dead center 34 is formed in a convex shape.

Continuous descent portion 35 is three lift portion this time, that is, the first lift unit 36 having a first lift slope S _1, the second lift unit 37 having a second lifting slope S _2, a third lift slope S ₃ It comprises the 3rd lift part 38 which has. It can be seen that the valve lift curve in the second lift part 37 is flatter than the first lift part 36 and the third lift part 38. This second lift slope S ₂ is meant that less than the first lift slope S ₁ and the third lift slope S _3.

  At Φ <650 °, the intake valve is closed and is located at its top dead center 42. The intake valve opens at Φ = 650 °. The corresponding valve lift curve 41 depicts a continuous ascending portion 43 up to the bottom dead center 44, at which the intake valve is fully opened. At this time, the bottom dead center 44 is reached at Φ = 795 °, and is kept only for a short period. The valve lifts of the intake valve and the exhaust valve at the bottom dead center are each 25 mm. The intake valve is then closed again. The corresponding valve lift curve 41 at this time describes a continuous descending portion 45 to the top dead center 32 that reaches at Φ = 902 °. The transition from the top dead center 42 or the transition to the top dead center 42 is formed in a concave shape. The transition from the bottom dead center 44 or the transition to the bottom dead center 44 is formed in a convex shape.

Continuous rise 43 three lift portion this time, that is the fourth lift portion 46 having a fourth lift gradient S _4, the fifth lift portion 47 with the lift slope S ₅ of the fifth, sixth lift slope S ₆ The sixth lift portion 48 having It can be seen that the valve lift curve in the fifth lift portion 47 is flatter than that of the fourth lift portion 46 and the sixth lift portion 48. This is the lift slope S ₅ of the fifth means is smaller than the lift slope S ₆ of the fourth lift gradient S ₄ and the sixth.

From the above values, in the valve control of the present invention, as compared with the valve control according to the prior art of FIG. 1, the process of closing the exhaust valve starts earlier and the crankshaft angle Φ = 720 °. That is, it can be seen that when the piston stroke reaches the top dead center, the exhaust valve is lifted only 7 mm. This provides a lift saving of 8 mm compared to the prior art. After reaching the top dead center of the crankshaft angle [Phi = 720 ° that is the piston stroke, the valve lift curve of the exhaust valve has a rise S ₂ to the smallest second lift unit 37, whereby the exhaust valve is finally closed Is delayed by the duration of the second lift part 47.

Similarly, from the above values, in the valve control of the present invention, the complete opening of the intake valve occurs at a later point in time as compared with the valve control according to the prior art, so when the crankshaft angle Φ = 720 ° is reached. It can be seen that the intake valve is first lifted 7 mm. This provides an 8 mm lift saving at the valve position at Φ = 720 ° compared to the prior art. Crankshaft angle [Phi = 720 ° that is before the arrival top dead center of the piston stroke, the valve lift curve of the intake valve is in the rise S ₅ is the smallest fifth lift portion 47, is thereby final opening of the intake valve , The duration of the fifth lift 47 is delayed. This extends the duration of the valve overlap, so that the overlap time cross section is substantially the same compared to prior art valve control.

  Lift savings allow the piston to be closer to the cylinder head at its top dead center, thereby allowing higher compression.

  The second lift part 37 and the fifth lift part 47 each show a linear course. Since the transition between these lift portions is abrupt for calculation reasons, the valve lift curves 31, 41 have one bent portion at each transition portion. In practice, this transition is not abrupt, but smoother.

FIG. 3 is a view of the cam configuration of the exhaust cam 51 of the present invention. The exhaust cam 51 includes a top dead center contour 52, a rising contour 53, a bottom dead center contour 54, and a descending contour 55. These contours, when the eccentrically arranged exhaust cam 51 about the axis of rotation A ₁ was rotates counterclockwise in cooperation with the exhaust valve, the valve lift curve of the exhaust valve control method according to the invention Configured to be generated. Are variable distance _{R 1} from the axis of rotation _{A 1} in the surface of the contour 52, 53, 54, 55 for this purpose. When this change in distance R ₁ between the cam shaft rotates once, corresponding to the valve lift curve 31 over the crankshaft 2 rotates. At this time, a valve stop is generated at the top dead center 32 or the bottom dead center 34 by the top dead center contour 52 or the bottom dead center contour 54. A rising portion 33 of the valve lift curve 31 is generated by the rising contour 53, and a falling portion 35 of the valve lift curve 31 is generated by the falling contour 55.

The descending contour 55 includes three contour portions, that is, a first contour portion 56, a second contour portion 57, and a third contour portion 58. These contour portions 56, 57, 58 generate lift portions 36, 37, 38 of the valve lift curve 31 of the exhaust valve according to the present invention, respectively. It can be seen that the second contour portion 57 is flatter than the first contour portion 56 and the third contour portion 58. Thus the change in distance R ₁ in the crankshaft rotation, in the second profile part 57, is smaller than when the first contour portion 56 and the third contour portion 58.

FIG. 4 is a view of the cam configuration of the intake cam 61 of the present invention. The intake cam 61 includes a top dead center contour 62, a rising contour 63, a bottom dead center contour 64, and a descending contour 65. These contours, when the intake cam 61 about the eccentrically arranged rotational axis A ₂ is rotated counterclockwise, in cooperation with the intake valve, the valve lift curve of the intake valve control method according to the invention Configured to be generated. A variable distance _{R 2} from the axis of rotation _{A 2} in the surface of the contour 62, 63, 64, 65 for this purpose. When this change in distance R ₂ between the cam shaft rotates once, corresponding to the valve lift curve 41 over the crankshaft 2 rotates. At this time, a valve stop is generated at the top dead center 42 or the bottom dead center 44 by the top dead center outline 62 or the bottom dead center outline 64. A rising portion 43 of the valve lift curve 41 is generated by the rising contour 63, and a falling portion 45 of the valve lift curve 41 is generated by the falling contour 65.

The rising contour 63 includes three contour portions, that is, a fourth contour portion 66, a fifth contour portion 67, and a sixth contour portion 68. These contour portions 66, 67, 68 generate lift portions 46, 47, 48 of the valve lift curve 41 of the intake valve according to the present invention, respectively. It can be seen that the fifth contour portion 67 is flatter than the fourth contour portion 66 and the sixth contour portion 68. Thus the change in distance R ₂ in the crankshaft rotation, in the fifth contour 67, is smaller than if the fourth edge portion 66 and the sixth edge portion 68.

  In FIG. 5, a further example of the valve lift curve of the present invention for an exhaust valve and an intake valve is partially illustrated in the time domain of valve overlap.

  In FIG. 5a), the transition from the first lift part 36 ′ to the second lift part 37 ′ is concave and the transition from the second lift part 37 ′ to the third lift part 38 ′ is compared for computational reasons. It is a sudden abrupt. The transition from the fourth lift portion 46 'to the fifth lift portion 47' is abrupt, and the transition from the fifth lift portion 47 'to the sixth lift portion 48' is concave.

  In FIG. 5b), the transition from the first lift part 36 '' to the second lift part 37 '' is concave and the transition from the second lift part 37 '' to the third lift part 38 '' is convex. is there. The transition from the fourth lift part 46 "to the fifth lift part 47" is a convex type, and the transition from the fifth lift part 47 "to the sixth lift part 48" is a concave type.

  In FIG. 5c) the transition from the first lift part 36 ′ ″ to the second lift part 37 ′ ″ is abrupt and the transition from the second lift part 37 ′ ″ to the third lift part 38 ′ ″. Is convex. The transition from the fourth lift part 46 ′ ″ to the fifth lift part 47 ′ ″ is convex, and the transition from the fifth lift part 47 ′ ″ to the sixth lift part 48 ′ ″ is abrupt. . It can be clearly seen that the transition from the first lift part 36 "" to the second lift part 37 "" occurs at [Phi] <720 [deg.]. Similarly, it can be clearly seen that the transition from the fifth lift part 47 "" to the sixth lift part 48 "" occurs at?> 720 [deg.].

11 Valve lift curve of exhaust valve according to the prior art 12 Top dead center 13 Ascending part 14 Bottom dead center 15 Lowering part 21 Valve lift curve of intake valve according to the prior art 22 Top dead center 23 Ascending part 24 Bottom dead center 25 Lowering part 31 Valve lift curve of exhaust valve according to the invention 32 Top dead center 33 Ascending part 34 Bottom dead center 35 Descent part 36 First lift part 37 Second lift part 38 Third lift part 41 Valve lift curve 42 of intake valve according to the invention 42 Top dead Point 43 Ascending portion 44 Bottom dead center 45 Lowering portion 46 Fourth lift portion 47 Fifth lift portion 48 Sixth lift portion 51 Exhaust cam according to the present invention 52 Top dead center contour 53 Ascent contour 54 Bottom dead center contour 55 Ascent contour 55 1 outline part 57 2nd outline part 58 3rd outline part 61 The intake cam by this invention 62 Top dead center contour 63 Rising contour 64 Bottom dead center contour 65 Lowering contour 66 Fourth contour portion 67 Fifth contour portion 68 Sixth contour portion Φ Crankshaft angle h Valve lift A Rotating shaft S Lift gradient R Distance

Claims (12)

In a valve control method for an exhaust valve of an internal combustion engine, particularly a large diesel engine, a first lift gradient (S ₁ ) is applied to a valve lift curve (31) extending from bottom dead center (34) to top dead center (32). Continuously having a first lift part (36) having, a second lift part (37) having a _second lift gradient (S ₂ ), and a third lift part (38) having a _third lift gradient (S ₃ ) The second lift gradient (S ₂ ) is smaller than the first lift gradient (S ₁ ) and the third lift gradient (S ₃ ), and the exhaust valve has a piston A valve control method characterized by being positioned at the second lift portion (37) after reaching the top dead center of the stroke. In a valve control method for an intake valve of an internal combustion engine, particularly a large diesel engine, a valve lift curve (41) from a top dead center (42) to a bottom dead center (44) has a fourth lift gradient (S ₄ ). the fourth lift portion (46), fifth lift portion having a fifth lift gradient _{(S 5)} (47), continuous with a sixth lift unit with a lifting slope of the 6 _{(S 6)} (48) There is a lift curve, the fifth lift gradient (S ₅ ) is smaller than the fourth lift gradient (S ₄ ) and the sixth lift gradient (S ₆ ), and the intake valve has a piston stroke. A valve control method characterized by being located at the fifth lift section (47) before reaching the top dead center.   A valve control method comprising the exhaust valve control method according to claim 1 and the intake valve control method according to claim 2.   4. The valve control method according to claim 1, wherein the second lift part (37) passes at least partially linearly. 5.   The transition from the first lift part (36 '' ') to the second lift part (37' '') occurs before reaching the top dead center of the piston stroke, 5. The valve control method according to any one of 4 above.   4. The valve control method according to claim 2, wherein the fifth lift part (47) passes at least partially linearly. 5.   The transition from the fifth lift part (47 '' ') to the sixth lift part (48' '') occurs after reaching the top dead center of the piston stroke. The valve control method according to any one of the above.   The valve control method according to any one of claims 1 to 7, characterized in that the transition between the two lift parts changes in a concave shape.   The valve control method according to any one of claims 1 to 8, wherein the transition between the two lift portions transitions in a convex shape. A valve cam (51) for controlling an exhaust valve of an internal combustion engine, particularly a large diesel engine, and a valve lift curve (31) generated by the valve cam (51) is above the bottom dead center (34). By the dead point (32), the first lift part (36) having the first lift gradient (S ₁ ), the second lift part (37) having the second lift gradient (S ₂ ), and the third lift There is a continuous lift curve having a third lift part (38) with a slope (S ₃ ), the second lift slope (S ₂ ) being the first lift slope (S ₁ ) and the third lift slope (S ₁ ). lift gradient (S ₃₎ from the small, also the exhaust valve, after reaching the top dead center of the piston stroke so as to be located on the second lift unit (37), that said valve cam (51) is configured Featuring a bal Bucam (51). A valve cam (61) for controlling a valve of an intake valve of an internal combustion engine, particularly a large diesel engine, and a valve lift curve (41) drawn by the valve cam (61) is bottom dead from the top dead center (42). By the point (44), a fourth lift part (46) having a _fourth lift gradient (S ₄ ), a fifth lift part (47) having a _fifth lift gradient (S ₅ ), and a sixth lift gradient There is a continuous lift curve having a sixth lift portion (48) with (S ₆ ), the fifth lift gradient (S ₅ ) being the fourth lift gradient (S ₄ ) and the sixth lift gradient (S ₄ ). It is smaller than the lift gradient (S ₆ ), and the valve cam (61) is configured so that the intake valve is positioned at the fifth lift portion (47) before reaching the top dead center of the piston stroke. The valve cover (61).   A valve cam comprising a valve cam (51) for controlling an exhaust valve according to claim 10 and a valve cam (61) for controlling the intake valve according to claim 11. Train.

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