JP4420855B2 - Variable valve mechanism for internal combustion engine - Google Patents

Description

  The present invention relates to a variable valve mechanism that changes a valve lift amount, a working angle, and timing continuously or stepwise in accordance with the operating state of an internal combustion engine.

  As this type of variable valve mechanism, Patent Document 1 discloses a mechanism using a long and complicated link mechanism, but Patent Document 2 discloses a relatively simple configuration that does not use such a long and complex link mechanism. Things have been proposed. As shown in FIG. 7, the latter variable valve mechanism is supported so that it can swing on a camshaft (not shown), a rotating cam (not shown) provided on the camshaft, and a shaft different from the camshaft. And having an input unit 61 (arm) and an output unit 62 (swing cam), and when the input unit 61 is driven by the rotating cam, the output driving unit 63 drives the valve 70 by the output unit 62, and an intermediary. Mediating phase difference varying means for varying the relative phase difference between the input unit 61 and the output unit 62 of the drive mechanism 63 is provided.

The intermediate phase difference varying means includes an input portion spline 61a provided on the inner peripheral surface of the input portion 61, and an output portion spline 62a provided on the inner peripheral surface of the output portion 62 and having an angle different from that of the input portion spline 61a. The intermediate drive mechanism 63 is a shaft body movable in the axial direction, and has an input spline 64a meshing with the input portion spline 61a and an output spline 64b meshing with the output portion spline 62b on the outer peripheral surface of the shaft body. Displacement comprising a slider gear 64 that causes the input portion 61 and the output portion 62 to swing relative to each other in accordance with the movement in the axial direction due to the meshing, a control shaft 67 that adjusts the displacement of the slider gear 64 in the axial direction, and a pin 68. Adjusting means.
JP-A-11-324625 JP 2001-263015 A

In the latter variable valve mechanism of the above-mentioned patent document, the pin 68 protruding from the control shaft 67 is engaged with the pin groove 69, whereby the axial movement of the mediation drive mechanism 63 of the control shaft 67 is controlled. This is transmitted to the shaft body 65 of the slider gear 64 provided on the outer periphery of the support pipe 66 provided on the outer periphery. Further, an input spline 64 is provided in the entire peripheral range of the outer peripheral surface of the portion of the shaft 65 of the slider gear 64 that enters the internal space of the input portion 61, and the outer peripheral surface of the portion of the output gear 62 that enters the internal space. The output spline 64b is provided in the entire circumference range. For this reason, there were the following problems.
(1) The slider gear 64 is large and heavy. In addition, the cost is high.
(2) The pins 68 and the pin grooves 69 need to be processed, which increases the cost.

(3) In order to drive the two valves 70 at the same time, the intermediate drive mechanism 63 has one input portion 61 in the center in the axial direction and two output portions 62 on both sides thereof, and the slider gear 64 has its shaft There may be one input spline 64a in the center of the direction and two output splines 64b on both sides thereof. Further, when a plurality of sets of two valves 70 are arranged, the movement of each mediation drive mechanism 63 in the axial direction is controlled by one control shaft 67. In such a case, the input portion 61 and the output portion 62 and the slider gear 64 are assembled by assembling the support pipe 66 on the outer periphery of the control shaft 67, and then assembling the slider gear 64. After assembling the central input part 61 to the spline 64a for use, the work procedure of assembling the output parts 62 on both sides to the output spline 64b on both sides must be taken, resulting in poor workability.

  Therefore, an object of the present invention is to reduce the size and weight of the slider gear of the intermediate phase difference varying means, and another object is to reduce the number of parts, to reduce the cost, and to improve the assembly workability. .

In order to achieve the above object, a variable valve mechanism for an internal combustion engine of the present invention is a variable valve mechanism for an internal combustion engine having a plurality of cylinders arranged in parallel, the camshaft and the number of cylinders provided on the camshaft. A plurality of rotary cams corresponding to the above, a support shaft different from the camshaft, and supported by the support shaft so as to be swingable. When the input portion is driven by the rotary cam by having an input portion and an output portion, an output is provided. A plurality of mediation drive mechanisms corresponding to the number of cylinders driving the valve in the section, and a plurality of mediation phase difference variable means corresponding to the number of cylinders capable of varying the relative phase difference between the input section and the output section of the mediation drive mechanism ( However, the post-displacement adjusting means of the intermediary phase difference varying means may be singular)
The intermediate phase difference varying means includes an input portion spline provided on the inner peripheral surface of the input portion, an output portion spline provided on the inner peripheral surface of the output portion, and having an angle different from that of the input portion spline, and a shaft of the intermediate drive mechanism. The shaft body is movable in the direction, and has an input spline that meshes with the input spline and an output spline that meshes with the output spline on the outer peripheral surface of the shaft body. In a variable valve mechanism for an internal combustion engine, comprising: a slider gear that relatively swings the input portion and the output portion; and a displacement adjustment means that adjusts the displacement of the slider gear in the axial direction.
The support shaft is divided into a plurality of shaft bodies corresponding to the number of cylinders, the shaft bodies are butted against each other and supported so that they can be displaced in the axial direction and can be rotated independently. It is characterized in that a slider gear is formed by forming an input spline and an output spline on each shaft body.

  In addition to the above means, the variable valve mechanism for an internal combustion engine according to the present invention has a through hole in the axial direction formed in the shaft body of the slider gear, and the same number of slider gears as the number of cylinders are arranged on the axis by a rod passing through the through hole. The rod is coupled to the displacement adjusting means so as to be integrally movable in the direction. According to this means, since the plurality of sliders move together via the rod by the displacement adjusting means, there is an advantage that the axial displacement amount of each slider gear can be adjusted equally. As the displacement adjusting means, a push actuator that pushes the slider gear, a pull actuator that pulls the slider gear, a push-pull actuator that pushes and pulls the slider gear, or the like can be used.

  The variable valve mechanism of the present invention can be applied to either the intake valve or the exhaust valve, but is preferably applied to both.

  According to the present invention, the diameter of the slider gear can be reduced, so that the intermediate phase difference variable means can be reduced in size and weight, and the number of parts can be reduced, so that cost reduction and assembly workability can be achieved. Can also be improved.

  A variable valve mechanism for an internal combustion engine having a plurality of cylinders in parallel, the camshaft (6), a plurality of rotating cams (6a), a support shaft, a plurality of mediating drive mechanisms (20), and a plurality of mediating phase differences The intermediate phase difference varying means is provided on the inner peripheral surface of the input part spline (22b) and the output part (24, 26), and is provided on the inner peripheral surface of the input part (22). An output spline (24b, 26b) having a different angle from the part spline (22b), and a shaft body movable in the axial direction of the mediation drive mechanism, and an input spline (14a) meshing with the input part spline (22b) An output spline (14c, 14e) that meshes with the output portion spline (24b, 26b) is provided on the outer peripheral surface of the shaft body, and the input portion (22) and the output portion ( Comprising 4,26) and a slider gear (14) for relatively swinging and displacement adjustment means for adjusting the displacement in the axial direction of the slider gear (14) and (10). The support shaft is divided into a plurality of shaft bodies (12) corresponding to the number of cylinders, the shaft bodies (12) are butted against each other and supported so that they can be displaced in the axial direction and can be rotated independently. Each shaft body (12) is used as a shaft body (12) of a slider gear (14), and an input spline (14a) and an output spline (14c, 14e) are formed on each shaft body (12) to form a slider. Let it be gear (14).

  1 to 5 show the variable valve mechanism of the first embodiment. Combustion chambers are formed in four parallel cylinders of the internal combustion engine, and two intake valves 2 and two exhaust valves (not shown) are arranged in each combustion chamber in this example. The intake air amount control according to the operation of the accelerator pedal and the engine speed during idle speed control is performed by adjusting the lift amounts of the first intake valve 2a and the second intake valve 2b. The lift amount is adjusted between four intake cams 6a (corresponding to “rotary cams”) corresponding to the number of cylinders provided on the intake camshaft 6, and support shafts 8 and rocker arms 4 different from the intake camshaft 6. The intermediate drive mechanism 20 described later is supported by the support shaft 8 so as to be able to swing between them by the lift amount variable actuator 10 (corresponding to “displacement adjusting means”) being driven. Further, the valve timings of the intake valves 2a and 2b are adjusted according to the operating state of the engine by a known rotational phase difference varying means (not shown, for example, the actuator described in the above-mentioned Patent Document 2). The exhaust valve is opened and closed with a constant lift amount via the rocker arm 4 by the rotation of an exhaust cam (not shown) provided on the exhaust camshaft, but the lift amount can be made variable in the same manner as the intake valve. You can also.

  Now, the variable valve mechanism of the intake valves 2a and 2b will be described in detail. The variable valve mechanism includes four intermediate drive mechanisms 20, one lift amount variable actuator 10 and a rotational phase difference variable means (corresponding to the number of cylinders). (Not shown).

  The intermediate drive mechanism 20 includes an input portion 22 provided at the center, a first swing cam 24 provided on the left (corresponding to an “output portion”), and a second swing cam 26 provided on the right (“output”). Part). The housing 22a of the input portion 22 and the housings 24a and 26a of the swing cams 24 and 26 have a cylindrical shape with the same outer diameter.

  The housing 22a of the input part 22 forms a space in the axial direction inside, and a helical spline 22b ("input part spline") formed in a spiral shape of a right-hand thread in the axial direction on the entire inner peripheral surface of the internal space. Is equivalent to). Further, two arms 22c and 22d are formed to protrude in parallel from the outer peripheral surface. A shaft 22e is stretched between the arms 22c and 22d at the ends of the arms 22c and 22d. The shaft 22e is parallel to the axial direction of the housing 22a, and a roller 22f is rotatably attached thereto.

  The housing 24a of the first swing cam 24 forms a space in the axial direction inside, and a helical spline 24b ("output") is formed in a spiral shape of a left-hand thread in the axial direction on the entire inner peripheral surface of the internal space. Corresponding to the "part spline"). The inner space is covered at the left end with a ring-shaped bearing portion 24c having a center hole with a small diameter. A substantially triangular nose 24d protrudes from the outer peripheral surface. One side of the nose 24d forms a cam surface 24e that curves in a concave shape.

  The housing 26a of the second rocking cam 26 forms a space in the axial direction inside, and a helical spline 26b ("output") is formed in a spiral shape of a left-handed screw in the axial direction on the entire inner peripheral surface of the internal space. Corresponding to the "part spline"). The inner space is covered at the right end with a ring-shaped bearing portion 26c having a center hole with a small diameter. Further, a substantially triangular nose 26d protrudes from the outer peripheral surface. One side of the nose 26d forms a cam surface 26e that curves in a concave shape.

  The first oscillating cam 24 and the second oscillating cam 26 are arranged so that the bearing portions 24c and 26c are outside and the respective end faces are coaxially contacted from both ends of the input portion 22, and are entirely shown in FIGS. As shown in FIG. 2, it has a substantially cylindrical shape having an internal space.

  As shown in FIGS. 1 to 5, the slider gear 14 is disposed in the internal space constituted by the input portion 22 and the two swing cams 24 and 26. The slider gear 14 is formed by dividing the support shaft 8 into four shaft bodies 12 corresponding to the number of cylinders, but each shaft body 12 is abutted against the end faces 13 and can be displaced in the axial direction and can be rotated independently. The shaft bodies 12 supported by the shafts 12 are used as the shaft bodies 12. At the center of the outer peripheral surface of the slider gear 14, an input helical spline 14a formed in a spiral shape of a right-hand thread is formed. A first output helical spline 14c is formed at the left end of the input helical spline 14a. Further, a second output helical spline 14e is formed at the right end of the input helical spline 14a so as to have a left-handed spiral shape with a small diameter portion 14d interposed therebetween. That is, the slider gear 14 is formed over the entire circumference of the outer peripheral surface of the shaft body, with the input helical spline 14a and the first and second output helical splines 14c and 14e.

  The input helical spline 14 a of the slider gear 14 is engaged with a helical spline 22 b inside the input unit 22. The first output helical spline 14 c is meshed with the helical spline 24 b inside the first swing cam 24, and the second output helical spline 14 e is meshed with the helical spline 26 b inside the second swing cam 26.

  Inside the slider gear 14, a small-diameter hole 30 for lubricating oil is formed in the axial direction of the slider gear 14. Two supply holes 31 extend from the small-diameter hole 30 to the internal space sandwiched between the input portion 22, the two swing cams 24 and 26, and the slider gear 14.

  Then, the slider gear 14 is positioned in the axial direction by the end faces 13 of the shaft bodies of the slider gear 14 provided in the adjacent mediating drive mechanism 20 being brought into contact with each other. It is possible to move.

  Each intermediary drive mechanism 20 configured in this manner can swing around an axis by being sandwiched between standing wall portions 33 formed on the cylinder head on the bearing portions 24c and 26c side of the swing cams 24 and 26. However, it is blocked from moving in the axial direction. Each shaft body 12 is supported by the cylinder head but not fixed, so that it can move or rotate in the axial direction.

  As shown in FIG. 4, the shaft body 12 a at one end of the four shaft bodies 12 is connected to the lift amount variable actuator 10 on the one end face 13 a side where the adjacent shaft body 12 and the end face 13 are not abutted. Yes. The axial displacement of the shaft body 12 can be adjusted by the lift amount variable actuator 10. The lift amount variable actuator 10 is configured using, for example, a displacement adjustment cam and a hydraulic cylinder. Further, if necessary, the shaft body 12b at the other end of the four shaft bodies 12 may be provided with a spring as a biasing member 34 on the one end face 13b side where the adjacent shaft body 12 and the end face 13 are not abutted.

  The roller 22f provided in the input part 22 of the mediation drive mechanism 20 is in contact with the intake cam 6a as shown in FIG. For this reason, the input part 22 of each intermediary drive mechanism 20 swings around the axis according to the profile of the cam surface of the intake cam 6a. The arms 22c and 22d that support the roller 22f are provided with a compression spring 22g that urges the roller 22f in the direction of the intake cam 6a. For this reason, the roller 22f is always in contact with the cam surface of the intake cam 6a.

  On the other hand, the swing cams 24 and 26 are respectively in contact with the rollers 4a provided at the center of the two rocker arms 4 at the base circle portion. The rocker arm 4 is supported by the adjuster 4b at the base end 4c with respect to the cylinder head so as to be swingable, and is in contact with the stem ends 2c of the intake valves 2a and 2b at the tip 4d.

  As described above, by adjusting the rotation of the displacement adjusting cam of the lift amount variable actuator 10, the roller 22f of the input unit 22 and the swing cams 24, 26 are connected via the slider gear 14 as shown in FIGS. The phase difference from the noses 24d and 26d can be adjusted, so that the lift amounts of the intake valves 2a and 2b can be made continuously variable.

  In the variable valve mechanism of the present embodiment configured as described above, the slider gear 14 can be reduced in diameter compared to the conventional art, so that the intermediate drive mechanism 20 can be reduced in size and weight. Due to this weight reduction, the driving force required to move the slider gear 14 can be reduced. Further, since the number of parts can be reduced, the cost can be reduced, and the assembly workability can be improved by reducing the number of parts to be assembled. Furthermore, by using the shaft body 12 formed in a divided manner, it is possible to drive corresponding to the variations of the helical splines 14a, 14c, 14e of the input portion 22 and the slider gear 14 for each cylinder.

  Further, the variable valve mechanism of this embodiment operates as follows when assembled. That is, the support shaft 8 is divided and formed as described above, and a single variable valve mechanism can be obtained by assembling one slider gear 14 including the shaft body 12 to one set of intermediate drive mechanism 20. Therefore, it is not bulky when assembled and workability is good. Specifically, the input portion 22 and the swing cams 24, 26 and the slider gear 14 are assembled by engaging the helical spline 14a of the slider gear 14 with the helical spline 22b of the input portion 22, and the slider gear 14 protruding from both ends thereof. The work procedure of meshing the helical splines 24b and 26b of the swing cams 24 and 26 of the swing cams 24 and 26 with the helical splines 14c and 14e can be taken. When the helical spline 14a of the slider gear 14 is engaged with the helical spline 22b of the input unit 22, it is essential that the output helical spline 14c or the output helical spline 14e of the slider gear 14 can be loosely inserted into the input unit 22. Therefore, as described above, the input helical spline 14a has a larger outer diameter than the output helical splines 14c and 14e.

Further, the variable valve mechanism of the present embodiment operates as follows during operation of the internal combustion engine.
First, FIG. 4 (a) and FIG. 5 (a) corresponding thereto show an operating condition where the maximum lift amount is required. Although FIG. 5 shows a mechanism in which the second swing cam 26 drives the first intake valve 2a, the same applies to a mechanism in which the first swing cam 24 drives the second intake valve 2b. At this time, the slider gear 14 is moved in the F direction most by the lift amount variable actuator 10. As a result, the phase difference between the roller 22f of the input unit 22 and the noses 24d and 26d of the swing cams 24 and 26 increases, so that the base circle portion of the intake cam 6a becomes the roller 22f of the input unit 22 in the mediation drive mechanism 20. , The noses 24d and 26d of the swing cams 24 and 26 are not in contact with the roller 4a of the rocker arm 4, and the base circle portions adjacent to the noses 24d and 26d are in contact. Then, when the nose 6b of the intake cam 6a pushes down the roller 22f of the input portion 22, the swing is transmitted from the input portion 22 to the swing cams 24 and 26 via the slider gear 14 in the mediation drive mechanism 20, and the swing is thereby performed. The moving cams 24 and 26 swing so as to push down the noses 24d and 26d. As a result, the curved cam surfaces 24e and 26e provided on the noses 24d and 26d immediately contact the roller 4a of the rocker arm 4, and the roller 4a of the rocker arm 4 is pushed down using the entire range of the cam surfaces 24e and 26e. . As a result, the rocker arm 4 swings around the base end 4c side, and the distal end 4d of the rocker arm 4 largely pushes down the stem end 2c. Thus, the intake valves 2a and 2b open the intake port 3 at the maximum lift amount Lmax.

  Next, FIG. 4B and the corresponding FIG. 5B show the operating conditions in which the lift amount should be reduced. At this time, the slider gear 14 is slightly moved in the R direction from the state of FIG. As a result, the phase difference between the roller 22f of the input unit 22 and the noses 24d and 26d of the swing cams 24 and 26 is reduced, so that the base circle portion of the intake cam 6a becomes the roller 22f of the input unit 22 in the mediation drive mechanism 20. The noses 24d and 26d of the rocking cams 24 and 26 are not in contact with the roller 4a of the rocker arm 4 and are slightly separated from the noses 24d and 26d as compared with the case of FIG. The base circle part is touching. Therefore, even if the nose 6b of the intake cam 6a starts to push down the roller 22f of the input unit 22, the roller 4a of the rocker arm 4 does not contact the curved cam surfaces 24e and 26e provided on the noses 24d and 26d for a while. Continue to touch the circle. Thereafter, since the curved cam surfaces 24e and 26e come into contact with the roller 4a and push down the roller 4a of the rocker arm 4, the rocker arm 4 swings around the base end 4c, but the rocker arm 4 has a small swing angle. Thus, the amount by which the stem end 2c is pushed down, that is, the lift amount L is reduced. Thus, the intake valves 2a and 2b open the intake port 3 with a lift amount smaller than the maximum amount.

  Next, FIG. 4 (c) and FIG. 5 (c) corresponding thereto show an operating condition in which the lift amount should be reduced. At this time, the slider gear 14 is moved most in the R direction by the lift amount variable actuator 10. This minimizes the phase difference between the roller 22f of the input unit 22 and the noses 24d and 26d of the swing cams 24 and 26, so that the base circle portion of the intake cam 6a is the roller of the input unit 22 in the mediation drive mechanism 20. When in contact with 22f, the noses 24d and 26d of the rocking cams 24 and 26 are not in contact with the roller 4a of the rocker arm 4, and a base circle portion that is far away from the noses 24d and 26d is in contact. Therefore, even if the nose 6b of the intake cam 6a pushes down the roller 22f of the input portion 22, the roller 4a of the rocker arm 4 does not contact the curved cam surfaces 24e and 26e provided on the noses 24d and 26d. Continue to touch the. As a result, the rocker arm 4 does not swing around the base end portion 4c, and the amount by which the stem end 2c is pushed down by the distal end portion 4d of the rocker arm 4, that is, the lift amount becomes zero.

  Since the adjustment by the lift amount variable actuator 10 is continuously performed, the lift amounts of the intake valves 2a and 2b can be continuously adjusted. That is, the intermediate phase difference variable means is constituted by the lift amount variable actuator 10, the slider gear 14, the helical spline 22b of the input unit 22, and the helical splines 24b and 26b of the swing cams 24 and 26.

  FIG. 6 shows the variable valve mechanism of the second embodiment. This variable valve mechanism is different from the variable valve mechanism of the first embodiment in that a rod 41 for connecting the four slider gears 14 is provided and a pull actuator 42 is used as the displacement adjusting means. That is, the shaft body 12 of each slider gear 14 is provided with a small diameter hole (through hole) 30 for introducing lubricating oil in the axial direction. A rod 41 is inserted into the small-diameter hole 30 of each shaft body 12, and the base end thereof is coupled to the output portion 43 of the pull type variable lift amount actuator 42. A stopper 44 is provided at the tip of the rod 41 to prevent the slider gear 14 farthest from the actuator 42 from coming off, and the four slider gears 14 can be moved integrally in the axial direction by the rod 41 between the stopper 44 and the actuator 42. It is connected to.

  According to this variable valve mechanism, since the four slider gears 14 are connected by the rod 41, each slider gear 14 moves integrally to the actuator 42 side when the pull actuator 42 is operated. For this reason, there is no possibility that the amount of displacement in the axial direction of the four slider gears 14 will vary, and in the four-cylinder internal combustion engine, the valve lift amounts of the respective cylinders can be made to coincide accurately. In the four intermediary drive mechanisms 20, a gap adjusting shim 45 is interposed between the swing cams 24, 26 and the standing wall portion 33. Other configurations and operational effects are the same as those of the first embodiment.

  In addition, this invention is not limited to the structure of the said Example, It can also change and embody in the range which does not deviate from the meaning of invention.

It is a perspective view which partially fractures and shows the variable valve mechanism based on Example 1 of this invention. It is a perspective view which shows the state which decomposed | disassembled the principal part of the mechanism. It is sectional drawing of the mechanism. (A) is a partially broken perspective view of the main part of the same mechanism when the maximum lift amount is necessary, (b) when the lift amount is decreased, and (c) when the lift amount is zero. . (A) is a side view of the same mechanism when the maximum lift amount is required, (b) when the lift amount is decreased, and (c) when the lift amount is zero. It is sectional drawing which shows the variable valve mechanism based on Example 2 of this invention. It is a perspective view showing a conventional variable valve mechanism partially broken.

Explanation of symbols

4 Rocker arm 8 Support shaft 12 Shaft body 13 End face 14 Slider gear 14a Helical spline for input 14c Helical spline for output 14e Helical spline for output 20 Mediation drive mechanism 22 Input section 22b Input section helical spline 24 First swing cam 24b Output section helical Spline 26 Second swing cam 26b Output section helical spline 41 Rod 42 Pull type actuator

Claims (2)

A variable valve mechanism for an internal combustion engine having a plurality of cylinders in parallel,
A camshaft, a plurality of rotating cams corresponding to the number of cylinders provided on the camshaft, a support shaft different from the camshaft, and a swingable support by the support shaft; an input portion and an output portion; A plurality of intermediate drive mechanisms corresponding to the number of cylinders that drive the valve at the output unit when the input unit is driven by the rotary cam, and the relative relationship between the input unit and the output unit of the intermediate drive mechanism A plurality of intermediate phase difference variable means corresponding to the number of cylinders that make the phase difference variable (however, a single displacement adjusting means of the intermediate phase difference variable means may be singular);
The intermediary phase difference varying means is provided on an inner peripheral surface of the input portion, an input portion spline provided on the inner peripheral surface of the input portion, an output portion spline having a different angle from the input portion spline, and A shaft body that is movable in the axial direction of the intermediate drive mechanism, and has an input spline that meshes with the input portion spline and an output spline that meshes with the output portion spline on the outer peripheral surface of the shaft body. A variable valve mechanism for an internal combustion engine, comprising: a slider gear that relatively swings the input portion and the output portion in accordance with movement in a direction; and a displacement adjusting means that adjusts a displacement of the slider gear in the axial direction. In
The support shaft is divided into a plurality of shaft bodies corresponding to the number of cylinders, the shaft bodies are butted against each other and supported so as to be displaceable in the axial direction and independently rotatable,
A variable valve mechanism for an internal combustion engine, wherein each shaft body is used as a shaft body of the slider gear, and the input spline and the output spline are formed on each shaft body to form the slider gear. .   An axial through-hole is formed in the slider gear shaft, and the same number of cylinders as the number of cylinders are connected by a rod passing through the through-hole so as to be able to move integrally in the axial direction, and the rod is coupled to the displacement adjusting means. The variable valve mechanism for an internal combustion engine according to claim 1.

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