JPH10159513A - Valve driving mechanism of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately drive a valve by forcibly opening and closing the valve by means of a cam and eliminating a spring. SOLUTION: In this valve driving mechanism, a center side came face 14a is made match to the outer peripheral face in an existing cam, and a cam groove 14 whose outer peripheral side cam face 14b is similar to the cam face 14a is formed in the side face. A driven member 15 with roller, which is provided in side of the end section of a stem 8a in a valve 8 is fitted in the cam groove 14, and the driven member 15 is incorporated so as to be movable along the cam groove 14 in relation to the cam groove 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-stroke engine, which is driven directly or by a cam which is rotated in conjunction with the rotation of a crankshaft at a speed reduction ratio of one half of the rotation speed of the crankshaft. The present invention relates to a valve drive mechanism of an engine that opens and closes a valve via a rod and / or a rocker arm.

[0002]

2. Description of the Related Art A four-stroke engine is operated by repeating four steps of suction, compression, explosion, and exhaust during two revolutions of a crankshaft, and is repeatedly operated. It is necessary to open and close each intake / exhaust valve. A cam is effectively used for the opening and closing operation means of the valve, and in the case of a recent automobile engine, a valve urged in a closing direction by a spring is pushed by a cam arranged near a crankshaft. A rocker arm system that pushes and opens indirectly via a rocker arm, etc., an overhead cam (OHC) system in which a camshaft is arranged on a cylinder head and pushes a valve through or not through a rocker arm, and intake and exhaust valves A double overhead cam (DOHC) system is known in which an independent camshaft is provided and a valve is pushed directly on the cam surface. In gasoline engines for automobiles, OHC,
Alternatively, the DOHC method is predominantly used. In addition, the adoption of the OHC method for diesel engines is progressing, and for industrial machines and large ships that do not require high-speed rotation,
The rocker arm system is still the mainstream, and both systems are active.

[0003]

The valve is pushed and opened by the cam surface. However, since the closing operation is 100% dependent on the spring force, energy loss for forcibly pushing and opening the valve against the spring force is caused. This energy loss causes a decrease in output, affects the fuel consumption, and if the spring breaks, control of the valve becomes impossible.
Also, in high-speed operation, the valve retraction speed by the spring cannot follow the rotation of the crankshaft, and the valve timing cannot be accurately executed.

[0004]

SUMMARY OF THE INVENTION The present invention is to provide a valve mechanism which pursues a reduction in energy loss and a reliable valve operation. In a valve drive mechanism of an engine that directly opens and closes a valve by a cam that is rotated in conjunction with the rotation of the crankshaft at a ratio, an engaging portion protrudes from an end of the valve stem of the valve. On the other hand, the cam has a cam surface that pulls the engaging portion in the valve closing direction and a cam surface that presses the engaging portion or the valve stem in the valve opening direction. The valve is opened and closed via a rocker arm by a cam which is rotated in conjunction with the rotation of the crankshaft at a speed reduction ratio of one half of the rotation speed of the crankshaft. In the valve drive mechanism of the engine, while an engaging portion protrudes from the end of the rocker arm, a cam surface that pulls the engaging portion in the valve closing direction on the cam surface, The engaging portion or the rocker arm is formed with a cam surface which presses and operates in the opening direction of the valve, and interlocks with the rotation of the crankshaft at a speed reduction ratio of one half with respect to the rotation speed of the crankshaft. In a valve drive mechanism of an engine that opens and closes a valve via a push rod and a rocker arm by a cam that is rotated by a cam, an engaging portion protrudes from an end side of the rocker arm, while the cam has A cam surface that operates to pull the engaging portion in the valve closing direction and a cam surface that presses the engaging portion or the end of the rocker arm in the valve opening direction. Lies in that it has.

[0005] Only one of the engaging portions is protruded, and the engaging portion is fitted along the cam groove in a state in which the engaging portion is fitted into the cam groove formed in the side surface of the cam. The cam groove of the cam has a width such that both inner walls are always in contact with the engaging portion, and the cam groove of the cam is a positive-acting type in which both inner walls of the cam groove are used as a cam surface. Two joints are juxtaposed in the operating direction, and the engaging portions can be moved relative to the cam wall protruding from the side of the cam along the cam wall with the cam wall interposed therebetween. Or the engaging portion is a follower with a rotatable roller, or the engaging portion is a rotatable pinion gear, and one of the cam surfaces is formed with a rack that meshes with the pinion gear. Or the cam is set so that the center side wall of both inner walls in the cam groove is , A pressing cam surface is formed on the extending portion, and the pressing cam surface is brought into contact with the valve stem, the rocker arm, the end of the connecting rod or the back surface of the rocker arm, and the pressing cam surface is used for the valve. Supporting or executing the pushing-down operation, making the engaging portion detachable from the existing valve, rocker arm, connecting rod, and forming the engaging portion on both the left and right sides and disposing the cams on the left and right can do.

[0006]

According to the constructions of claims 1 to 3, any one of the push rod, the rocker arm and the valve stem is pressed on the cam surface so as to move in the opening direction of the valve with the rotation of the cam. One of the push rod, the rocker arm and the valve stem is forcibly pulled to move in the direction to close the valve, whereby the valve is reliably opened and closed. According to the configuration of the fourth aspect, the engaging portion is not fitted into and disengaged from the cam groove. In particular, in the positive type of the fifth aspect, the follower is sandwiched between both inner walls of the cam groove, It does not bounce in the axial direction, and the movement is faithful to the cam curve. Also, according to the configuration of claim 6, the cam wall is sandwiched between the engagement portions so that the cam wall does not come off. According to the configuration of claim 7, the frictional resistance is reduced by the rotation, and the configuration of claim 8 provides For example, the engagement increases the reliability of the operation. Further, according to the configuration of claim 9, the valve stem, the rocker arm, and the connecting rod itself can be effectively used. According to the configuration of claim 10, the existing valve can be used, and according to the configuration of claim 11, In this case, since the strength is doubled by the two engaging portions, the reliability is high. The performance of the engine can be further improved by selecting the configuration of each of the claims so as to have an optimal form for the engine to be implemented and improving the followability of the valve.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a valve mechanism according to the present invention will be described with reference to the drawings. First, a description will be given of an example of a DOHC type engine in which a valve is directly opened and closed by a cam. In FIG. 1, reference numeral 1 denotes a vertically open cylinder formed in a cylinder block 2, and a piston 3 is provided in the cylinder 1. By closing the upper end surface of the cylinder with a cylinder head 4 having a roof-shaped recess, which is reciprocally movable, the piston 3 moves between the upper surface of the piston 3 and the cylinder head 4 at the top dead center position. Combustion chamber 5
Is formed. An intake port 6 and an exhaust port 7 are formed in the cylinder head 4 and open to the combustion chamber 5. Valve seats 6 a and 7 a are provided around openings of the intake and exhaust ports 6 and 7. . Further, the intake valve 8 and the exhaust valve 9 are incorporated in the cylinder head 4 so that the stems 8a, 9a are respectively orthogonal to the opening surfaces of the intake and exhaust ports 6, 7, and the stems 8a, 9a are extended. The camshafts 10 and 11 are arranged respectively, and the valves 8 and 9 are moved forward and backward by cams 12 and 13 provided on the camshafts 10 and 11, respectively, and the umbrella portions 8b and 9b of the valves 8 and 9 are arranged. To the valve seats 6a, 7a respectively, or the valve seats 6a, 7a
The ports 6 and 7 can be opened and closed by moving them apart from each other.

Since the basic structures of the drive mechanisms of the intake valve 8 and the exhaust valve 9 are common, only the intake valve 8 side will be described below. In FIG.
Is a front groove cam provided so as to be able to rotate integrally with the camshaft 10, and the cam groove 14 formed on the side surface matches the cam surface 14a, which is the inner wall on the center side, with the outer peripheral surface of the existing cam, Cam surface 14b which is the inner wall on the outer peripheral side
Is similar to the cam surface of the inner wall 14a,
This is a positive acting type that secures a certain groove width. on the other hand,
At the base end of the stem 8 a of the intake valve 8, as an engaging portion engageable with the cam groove 14, a follower with a roller having a diameter which is always in contact with both inner side walls of the cam groove 14 when engaged. The follower 15 is rotatably mounted on the cam groove 14 of the cam 12, and both the wall surfaces of the follower 1
5 while being constantly in contact with the cam groove 14.

In the valve driving mechanism configured as described above, the cam surfaces 14 are rotated with the rotation of the camshaft 10.
Since the follower 15 sandwiched between a and b is guided by the cam groove 14 and moves forward and backward in the axial direction of the stem 8a, the intake valve 8 forcibly and surely opens and closes the intake port 6 (FIG. 3). A, b). Since this valve drive mechanism does not require a spring for urging the valve in the closing operation direction, one factor of energy loss is reduced, and the rotation of the camshaft can be performed without resistance. It goes without saying that the same applies to the exhaust valve.

In the above-described embodiment, the positive type in which the cam groove of the front groove cam is formed over the entire circumference has been described, but the cam groove is provided at least on the inner wall on the center side with respect to the follower. It is sufficient if the cam surface for pressing the valve in the direction of pushing down, that is, the opening operation direction, and the cam surface for pressing the valve with respect to the follower, that is, the cam surface for pushing in the closing operation direction, are formed on the inner wall on the outer peripheral side. Although not shown, the diameter of the follower is made smaller than the groove width of the cam groove, and the follower is pressed in the direction in which the valve opens by only the center inner wall surface, while only the outer circumferential inner wall surface is pressed. An unnecessary cam surface for pressing the intake valve 8 in the opening operation direction on the cam surface 14b which is the inner wall on the outer peripheral side by omitting the follower from the valve in the closing operation direction or omitting an unnecessary cam surface in FIG. ) And (b) As described above, by partially opening the outer peripheral side of the cam groove 14, when the opening operation is performed, the follower 15 is changed so as to be pressed only by the cam surface 14a which is the inner side wall on the center side, and the size of the cam is reduced. Can be. In addition, the side surface of the cam is not limited to the symmetrical egg shape, but is appropriately changed to an asymmetric shape in order to change the valve timing and reduce the sliding resistance, and the width of the cam groove is not always constant, The cam surface can also be tapered to increase the degree of engagement.

It is desirable that the engaging portion is a follower with a roller as shown in the embodiment to reduce frictional resistance against the cam surface. However, the engaging portion is formed integrally with the stem to be rollerless. The joint portion can be rotatably assembled around the stem axis so that the valve can be rotated during the opening and closing operation. As shown in FIG.
In the axial direction, the followers 15 ′ and 15 ′ having a small diameter are provided specifically for each inner wall surface of the cam groove 14, and the followers 15 ′ and 15 ′ are mutually connected as illustrated in FIG. It is also possible to interpose a spring 16 for urging to separate.

As shown in FIG. 7, in addition to a follower 15 to be engaged in the cam groove 14, a sub follower 17 for tracing the outer peripheral surface of the cam 12 is provided side by side in the operation direction. As shown in FIG. 8, the auxiliary follower 17 is assembled so as to sandwich the thickness between the outer peripheral side surface of the cam groove 14 and the outer periphery of the cam.
As shown in (1), the follower 15 and the sub follower 17 are assembled so as to sandwich a cam wall 18 formed on the side surface of the disc-shaped cam 12 so as to be relatively movable along the cam wall 18. As shown in FIGS. 9A and 9B, the cam surface 14a of the inner side wall of the cam groove 14 has a stepped shape extending in the axial direction, and While the follower 15 is pulled up by the cam surface 14b on the inner side wall, the tip of the stem 8a is directly pressed by the cam surface 14c formed on the extended portion. And the cam surface 14c formed on the extension portion can support the pressing operation. In the latter case, if the tip of the stem and the outer periphery of the follower are not at the same level, the cam surface formed on the extended portion is formed so as to be shifted from the extension of the central inner wall toward the central side. And in that case, FIG.
As shown in FIG. 0, the engagement portion is a rotatable pinion tooth 19, a rack 20 is provided on the outer inner side wall of the cam groove 14, and the pinion tooth 19 and the rack 20 are engaged with each other, so that the valve operation of the valve operation is performed. Certainty can be increased.

In these embodiments, the shape of the cam surface,
The number, size, form, and the like of the cam grooves and followers may be appropriately changed within the range in which the object of the present invention is achieved. In the above embodiment, the DOHC engine has been described. However, as illustrated in FIG. 11, a side-valve engine in which both valves 8, 9 can be directly driven by cams 12, 13 provided on a single camshaft, As illustrated in FIG. 12, the cams 12, 13 are arranged above the cylinder,
A 0HC engine in which rocker arms 21 and 21 are interposed between the cams 12 and 13 and the valves 8 and 9 or, as illustrated in FIG. Arranged and its cam 12, (13)
Thus, the present invention can also be applied to a push rod type engine that opens and closes the valves 8 and 9 via the push rod 22 and the rocker arm 21. In the case of the OHC type engine, FIGS. ), The cams 12 and (13) can be arranged above the rocker arm 21 or the back surface of the rocker arm 21 can be directly pushed down by the cam surface 14c.

If the engaging portion is made detachable from the existing valve, rocker arm, and push rod, the existing member can be used. The detachable member is not limited to the engaging portion. , A rocker arm, and a member integrated with a contact portion of the push rod with the cam. Further, as exemplified in FIG.
And a pair of cams 12 are arranged so as to sandwich
The followers 15, 15 are attached to both sides of the stem 8a, respectively.
The followers 15, 15 are engaged with cam grooves 14, 14 provided on the facing surfaces of the cams 12, 12, respectively, and one cam is driven by two cams, and FIG. As shown in FIG. 2, cam grooves are provided on both side surfaces of the cam 12, and two valves are individually driven by one cam, or in an engine having a plurality of intake valves, two valves may be simultaneously driven. It is possible, in these cases, to combine with the various variations shown in the above embodiments. Further, the cam surface and the engaging portion in contact with the cam surface may be provided with a taper so that the engaging portion and the cam surface do not shift in the axial direction.

The present invention does not deny the use of a spring, and may add an urging means for urging the valve in the closing direction. The urging means may be a coil spring or a leaf spring. , Torsion springs and the like.
In the method using a rocker arm or a push rod, when the urging means is omitted, a pivoting or locking means is provided between the valve stem and the rocker arm or between the bush rod and the rocker arm, and the valve is provided. In the DOHC method, it is desirable that the urging means be omitted and a springless structure be adopted.

[0016]

As described above, according to the present invention, since the opening and closing operation of the valve can be forcibly performed only by the cam, it is possible to eliminate the spring which is a factor of energy loss from the driving mechanism, and the valve can be reliably mounted. Operate. In addition, if a positive-acting front groove cam is used, the dancing phenomenon in which the valve bounces even at a high rotation can be suppressed. Further, by selecting a structure suitable for the application from the various variations shown in the above embodiment, the valve operation can be improved and the reliability can be increased. The valve drive mechanism of the present invention can cope with a partial design change of the cylinder head in an existing engine, and the drive system of the camshaft can be used as it is.

[Brief description of the drawings]

FIG. 1 is a partial explanatory view of an engine provided with a valve mechanism according to the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a cam and a valve.

FIGS. 3A and 3B are explanatory diagrams of a valve operation.

FIGS. 4A and 4B are explanatory views showing a modified example of a cam.

FIG. 5 is an explanatory view of a modification in which two small diameter followers are provided.

FIG. 6 is an explanatory view of a modified example in which a spring is interposed between two followers.

FIG. 7 is an explanatory view of a modified example in which a sub follower is added and the follower and the sub follower are assembled so as to sandwich a thickness portion between an outer side surface of a cam groove and an outer periphery of a cam.

FIG. 8 is an explanatory view of a modified example in which a sub follower is added and the follower and the sub follower are assembled so as to sandwich a cam wall.

FIGS. 9A and 9B are explanatory views of a modified example in which the inner wall on the center side of the cam groove is extended in the axial direction.

FIG. 10 is an explanatory view of a modified example in which the engaging portions are formed as pinion teeth.

FIG. 11 is an explanatory diagram implemented for a side-valve engine.

FIG. 12 is an explanatory diagram illustrating an operation of the OHC engine.

FIG. 13 is an explanatory diagram implemented for a push rod engine.

FIG. 14 is an explanatory view of an OHC engine in which a cam is arranged above a rocker arm.

15A is an explanatory diagram showing a modified example in which one cam drives two valves, and FIG. 15B is an explanatory diagram showing a modified example in which one cam drives two valves.

[Explanation of symbols]

1, cylinder, 2 cylinder block, 3 piston, 4 cylinder head, 5 combustion chamber, 6 intake port, 7 exhaust port, 8 intake valve, 8a
..Stem, 8b ·· Umbrella part, 9 ·· Exhaust valve, 9a ·
· Stem, 9b ··· Umbrella part, 10, 11 ··· Camshaft, 12, 13 ·· Cam, 14 ·· Cam groove, 14a, 1
4b, 14c ... cam surface, 15 ... follower, 15 '...
Small diameter followers, 16 springs, 17 followers, 18 cam walls, 19 pinion teeth, 20 racks, 21 rocker arms, 22 push rods.

Claims (11)

[Claims] 1. A valve drive mechanism for an engine which directly opens and closes a valve by a cam rotated in conjunction with the rotation of the crankshaft at a speed reduction ratio of one half of the rotation speed of the crankshaft, An engaging portion protrudes from the end of the valve stem of the valve, and the cam has a cam surface that pulls the engaging portion in the valve closing direction and the engaging portion or the valve stem. An engine valve drive mechanism having a cam surface that presses and operates in the valve opening direction. 2. A valve driving mechanism for an engine that opens and closes a valve via a rocker arm by a cam rotated in conjunction with the rotation of the crankshaft at a reduction ratio of one-half the rotation speed of the crankshaft. In the meantime, while an engaging portion is protruded on the side of the end of the rocker arm,
The valve drive of an engine having a cam surface formed with a cam surface that pulls the engagement portion in the valve closing direction and a cam surface that presses the engagement portion or rocker arm in the valve opening direction. mechanism. 3. An engine which opens and closes a valve via a push rod and a rocker arm by means of a cam which is rotated in conjunction with the rotation of the crankshaft at a reduction ratio of one half of the rotation speed of the crankshaft. In the valve drive mechanism, an engaging portion is provided to project from an end of the rocker arm, and the cam has a cam surface that pulls the engaging portion in a valve closing direction and the engaging surface. A valve drive mechanism for an engine having a cam surface that presses an end portion of a rocker arm or a rocker arm in a valve opening direction. 4. The method according to claim 1, wherein only one of said engaging portions protrudes, and said engaging portion is inserted into said cam groove in a cam groove recessed in a side surface of the cam. The engine valve mechanism according to any one of claims 1 to 3, wherein the valve mechanism is mounted so as to be relatively movable along the engine. 5. The engine according to claim 4, wherein the cam is a positive-acting type in which a cam groove has a width such that both inner walls are always in contact with the engagement portion, and both inner walls of the cam groove are used as cam surfaces. Cam drive mechanism. 6. A cam wall in which two engaging portions are arranged and protruded in the operation direction, and the engaging portions are sandwiched by a cam wall protruding from a side surface of a cam. The valve mechanism for an engine according to any one of claims 1 to 3, wherein the valve mechanism is mounted so as to be relatively movable along the axis. 7. A valve mechanism for an engine according to claim 1, wherein said engaging portion is a follower with a rotatable roller. 8. The engine according to claim 1, wherein said engaging portion is a rotatable pinion gear, and a rack meshing with said pinion gear is formed on one of the cam surfaces. Valve mechanism. 9. The cam extends in the axial direction from a center wall of both inner walls of the cam groove, and forms a pressing cam surface on the extending portion. The pressing cam surface is formed by a valve stem and a rocker. The valve mechanism of an engine according to any one of claims 1 to 7, wherein said valve cam is abutted against an end of an arm, a connecting rod or a back surface of a rocker arm to support or execute a valve pressing operation by said pressing cam surface. 10. The valve drive mechanism for an engine according to claim 1, wherein said engagement portion is detachable from an existing valve, rocker arm, and connecting rod. 11. The valve drive mechanism for an engine according to claim 1, wherein the engagement portions are formed on both left and right sides, and cams are arranged on left and right sides.