JP2000008813A - Valve system of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cost of a valve system, and to miniaturize the valve system by using a three-dimensional cam while preventing degradation of the lubricity or increase in the cost. SOLUTION: A plurality of intake valve and exhaust valve 5, 6 are arranged in one cylinder in a radial direction. A rocker arm 14 for each intake valve and exhaust valve is turnably supported by a cylinder head 1 through a rocker pin 20. The intake valve and the exhaust valve 5, 6 are driven by an intake cam shaft 11 and an exhaust cam shaft 12 having a three-dimensional cam 13 which is brought into slidable contact with the rocker arm 14. A boss 17 of the rocker arm 14 is connected to the rocker pin 20 tiltably in the direction orthogonal to the axial direction of the rocker pin 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve train for an engine in which intake and exhaust valves arranged radially are driven by an intake camshaft and an exhaust camshaft.

[0002]

2. Description of the Related Art Conventionally, as an engine having a hemispherical combustion chamber for improving combustion efficiency, there is an engine in which, for example, four intake / exhaust valves are arranged radially per cylinder. In the valve gear used for this type of engine, the opening and closing directions of the intake and exhaust valves are different from each other one by one when viewed from a direction orthogonal to the axial direction of the camshaft, so that the rotation of the camshaft is transmitted to each valve. It adopts a complicated structure (for example,
29709).

In the valve train disclosed in this publication, one cam shaft is rotatably supported at the center of a cylinder head, and the cam surface of the cam of the cam shaft is parallel to the axial direction of the cam shaft. And a structure in which two rocker arms are interposed for each intake / exhaust valve between the cam surface and the intake / exhaust valve.

A first rocker arm of the two rocker arms is swingably supported by a first support shaft suspended in parallel with the cam shaft, and one end of the first rocker arm is connected to the cam surface. In addition to contact, the other end extends toward the intake / exhaust valve side. The other second rocker arm is swingably supported by a second support shaft suspended in a direction orthogonal to the axial direction of the intake valve or the exhaust valve, and sucks and holds the lower surface of the swing end.
It is attached to the exhaust valve. The other end of the first rocker arm is attached to the opposite side (upper surface) of the swing end from the intake / exhaust valve. That is, this valve train is
The parallel movement of the cam surface is absorbed by two rocker arms.
The structure is changed to parallel movement parallel to the axial direction of the exhaust valve.

[0005]

However, the valve train configured as described above has a problem that the manufacturing cost is increased and the size is increased due to the large number of rocker arms. 1 rocker arm per intake / exhaust valve
In order to reduce the cost and size as a book, the cam surface is formed so as to be inclined so as to be orthogonal to the axial direction of the intake / exhaust valve so that the cam is a so-called three-dimensional cam, and the cam surface is the second surface. It is conceivable to adopt a structure that slides on the rocker arm.

However, in order to realize this, lubrication of a contact portion between the three-dimensional cam and the rocker arm becomes a problem. The contact portion is lubricated by forming a lubricating oil film between the cam surface of the three-dimensional cam and the sliding contact surface of the rocker arm. It is known that the oil film is held by the two contacting in a line contact state, and is broken when the contact state of the two becomes a point contact.

That is, when the three-dimensional cam is manufactured as an industrial product, the contact state between the cam surface and the sliding contact surface tends to be point contact due to a manufacturing error of the cam surface, and the oil film is interrupted. This causes the sliding contact portion to wear. In order to form the cam surface of the three-dimensional cam with high accuracy, the time for the grinding operation becomes extremely long, and the cost is significantly increased.

The present invention has been made to solve such a problem, and uses a three-dimensional cam while preventing a decrease in lubricity and an increase in cost. It is an object of the present invention to reduce the number of rocker arms to achieve cost reduction and downsizing.

[0009]

According to the present invention, a plurality of intake valves or exhaust valves are radially arranged in one cylinder, and the cylinder head is rotatably mounted on a cylinder head via a rocker pin. The intake / exhaust valve is driven by a rocker arm for each of the supported intake / exhaust valves, and an intake camshaft and an exhaust camshaft having a three-dimensional cam slidably contacting the rocker arm, and the base of the rocker arm is The rocker pin is connected to the rocker pin so as to be tiltable in a direction orthogonal to the axial direction of the rocker pin.

According to the present invention, since the rocker arm is tilted with respect to the rocker pin so as to follow the cam surface of the three-dimensional cam, the cam surface is in line contact with the sliding contact surface of the rocker arm over the entire circumference. Touch with.

According to another aspect of the present invention, there is provided an engine valve gear according to the above-described invention, wherein the position at which the three-dimensional cam contacts the rocker arm is determined by comparing the position at which the rocker arm contacts the intake / exhaust valve. It is located on the rocker pin side. According to the present invention, the lift amount of the three-dimensional cam is reduced if the opening and closing amounts of the intake and exhaust valves are the same, as compared with the case where the three-dimensional cam contacts the portion corresponding to the intake and exhaust valves in the rocker arm. It can be set relatively low.

According to another aspect of the present invention, there is provided a valve train for an engine according to the above-described engine, wherein the rocker pin is inclined with respect to the axis of the cam shaft as viewed from the cylinder axis. According to the present invention, the rocker arm swings along the opening / closing direction of the intake valve or the exhaust valve.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Hereinafter, an embodiment of an engine valve gear according to the present invention will be described in detail with reference to FIGS. FIG. 1 is a cross-sectional view of an engine employing a valve train according to the present invention, and FIG. 2 is a plan view of a cylinder head. In FIG. 2, a broken position in FIG. 3 is a perspective view showing the configuration of the valve train according to the present invention, FIG. 4 is a view showing a rocker arm, FIG. 3 (a) is a plan view, FIG.
FIG. 3C is a front view showing a state viewed from the slipper side. FIG. 5 is a sectional view of the base of the rocker arm, and FIG. 5 is a sectional view taken along line VV in FIG. 4B.

In these figures, the reference numeral 1 denotes an engine cylinder head according to this embodiment. This cylinder head 1 is a water-cooled single cylinder DOHC
The combustion chamber 2 is formed in a substantially hemispherical shape, and two intake ports 3 and two exhaust ports 4 communicating with the combustion chamber 2 are formed. A spark plug (not shown) is attached between these ports 3 and 4, that is, in the center of the combustion chamber 2.

Two intake valves 5 for opening and closing the intake port 3
5, and two exhaust valves 6, 6 for opening and closing the exhaust port 4,
As shown in FIG. 2, the valve shaft 5 is viewed from the axial direction of the cylinder.
a, 6a are arranged to extend radially from the combustion chamber 2. These intake and exhaust valves 5 and 6 are driven by a valve operating device 7 described later. The axis of the cylinder is indicated by a dashed line C in FIG.

In FIG. 1, a valve spring 8 (shown in FIG. 1) for urging the intake and exhaust valves 5 and 6 to the closing side is indicated by reference numeral 8 through which the valve shafts 5a and 6a of the intake and exhaust valves 5 and 6 pass. ) Is a spring holding member for holding the spring. The spring holding member 8 is formed in a bottomed cylindrical shape having a bottom portion (an upper portion in FIG. 1) through which the intake and exhaust valves 5 and 6 penetrate, and is slidably fitted to a holding cylinder 9 fixed to the cylinder head 1. Have been combined. The valve spring is elastically mounted between the inner bottom surface of the spring holding member 8 and the cylinder head 1.

A valve operating device 7 for driving the intake / exhaust valves 5 and 6 includes an intake / exhaust valve in which an intake camshaft 11 and an exhaust camshaft 12 and a three-dimensional cam 13 of the camshafts 11 and 12 slide. And each rocker arm 14.

The intake camshaft 11 and the exhaust camshaft 12 are
A three-dimensional cam 13 is provided at a position corresponding to the intake / exhaust valves 5 and 6, and is rotatably supported on the cylinder head 1 by a conventionally known support structure. A cam cap for supporting these cam shafts 11 and 12 together with the cylinder head 1 is shown in FIG.
And 15 in FIG. These camshafts 11 and 12 have a timing chain sprocket 16 fixed at one end (lower end in the figure) and a timing chain wound around the sprocket 16 and a crankshaft (not shown). A structure is employed in which rotation of the crankshaft is transmitted via (not shown).

The lubrication of the bearings for rotatably supporting the camshafts 11 and 12 and the sliding contact between the three-dimensional cam 13 and the rocker arm 14 is performed by lubricating oil passages formed in the camshafts 11 and 12 (see FIG. (Not shown) to supply the lubricating oil to the sliding contact portion.

As shown in FIGS. 2 and 3, the three-dimensional cam 13 is formed by inclining a cam surface 13a such that the diameter gradually decreases from one end in the axial direction to the other end. The inclination angle of the cam surface 13a corresponds to the inclination angle of the valve shafts 5a, 6a of the intake and exhaust valves 5, 6 with respect to the axis of the cam shafts 11, 12, and the cam surface 13a slidingly contacting the rocker arm 14 in FIG. -It is set so as to be parallel to the plane perpendicular to the axis of the exhaust valves 5 and 6 and the contact portion.

As shown in FIG. 4, the rocker arm 14 is formed integrally with a cylindrical boss 17 and an arm 18 projecting in one direction from the boss 17. The slipper 19 to which the original cam 13 slides is fixed to the arm 18. As shown in FIGS. 1 and 2, the rocker arm 14 is fitted with a rocker pin 20 made of a column having a constant outer diameter on the boss 17, and
0 to the cylinder head 1 so as to be rotatable. The boss 17 forms the base of the rocker arm 14 according to the present invention.

The rocker arm 14 and the rocker pin 20 are also inclined so as to correspond to the intake and exhaust valves 5 and 6 which are inclined with respect to the axial direction of the camshafts 11 and 12. That is, similarly to the cam surface 13a, the intake and exhaust valves 5 and 6 are inclined so as to be parallel to a plane orthogonal to the axis thereof. More specifically, the rocker pin 20 has an angle α with respect to the axes of the camshafts 11 and 12 corresponding to the inclination of the intake and exhaust valves 5 and 6 when viewed from the cylinder axis direction as shown in FIG. Only inclined. This angle α
Is set to about 1 ° in this embodiment. The rocker pin 20 is also inclined with respect to the axis of the camshafts 11 and 12 in the state where the camshafts 11 and 12 are viewed from the side by side direction (see FIG. 3). In FIG. 3, the rocker pin 20 for the intake valve 5 and the rocker pin 20 for the exhaust valve 6 on the left side, and the other two rocker pins 20 are substantially c when viewed from the direction in which the camshafts 11 and 12 are arranged side by side. It is inclined to form a letter. By inclining the rocker pin 20 in this manner, the rocker arm 14 swings along the opening and closing directions of the intake / exhaust valves 5 and 6, and the intake / exhaust valves 5 and 6 are opened and closed.
The exhaust valves 5 and 6 can be arranged so as not to apply an excessive bending load.

The cylinder head 1 of the rocker pin 20
The one end on the cylinder axis C side of the rocker pin 20 is fixed to the central protruding portion 2 formed integrally with the cylinder head 1.
1 (see FIG. 2) and the other end is fitted to the rocker pin holder 22. The rocker pin holder 22 is formed separately from the cylinder head 1, and is fixed to the cylinder head 1 by fixing bolts 23.

The arm 18 of the rocker arm 14 is shown in FIG.
As shown in FIG. 1, a pressing projection 18a that contacts the end cap 24 provided at the tip of the valve shaft of the intake / exhaust valves 5 and 6 is integrally formed at the tip, and is opposite to the pressing projection 18a (FIG. 1).
, The upper side) is fixed to the slipper 19. The slipper 19 is formed in a so-called semi-cylindrical shape so that the camshaft side is convex and extends in the axial direction of the camshafts 11 and 12.

In this embodiment, the length and mounting position of the rocker arm 14 and the camshafts 11, 12
The mounting position of the rocker arm 14 is
The distance R2 from the contact point between the slipper 19 and the three-dimensional cam 13 to the center of rotation is smaller than the distance R1 from the point of contact of the end cap 24 to the center of rotation (the axis of the rocker pin 20). Is set to be shorter.

As shown in FIG. 5, a pin hole 25 for fitting the rocker pin 20 in the boss 17 of the rocker arm 14 is formed so that the central portion in the axial direction has a constant inner diameter. Is formed so that the inner diameter gradually increases toward the opening end. A central portion having a constant inner diameter is denoted by reference numeral 21a in FIG. 5, and a portion which becomes a tapered hole whose inner diameter gradually changes is denoted by reference numeral 21b. This tapered hole portion 21
The inclination angle θ of the hole wall surface of b is set to, for example, about 0.5 to 2 °.

By forming the opening side of the pin hole 25 to be a tapered hole in this manner, the rocker arm 14 can be moved in the axial direction of the rocker pin 20 with the rocker pin 20 fitted in the pin hole 25. It can be tilted in the direction perpendicular to the direction.

The rocker arm 14 has a plurality of projections 26 formed on the axial end surface of the boss 17 as shown in FIG. These protrusions 26 are formed so as to contact the end face of the central protrusion 21 of the cylinder head 1 and the end face of the rocker pin holder 22.
By forming the protrusion 26 on the end surface of the boss 17 in this manner, the direction in which the rocker arm 14 tilts with respect to the rocker pin 20 can be regulated. That is, as shown in FIG. 4, the rocker arm 14 is formed by forming the protrusions 26 on both sides of the boss 17 (both sides in a direction orthogonal to both the axis of the camshafts 11 and 12 and the cylinder axis C). Can be tilted clockwise or counterclockwise in FIG. 4 (c).

In the valve gear 7 constructed as described above, the rotations of the intake camshaft 11 and the exhaust camshaft 12 are transmitted from the three-dimensional cam 13 to the rocker arm 14, and the rocker arm 14 is centered on the rocker pin 20. The intake / exhaust valves 5 and 6 are opened and closed by the rotation. 3D cam 1
When the angle of inclination of the cam surface 13a and the angle of inclination of the sliding surface of the slipper 19 coincide with each other, the lubricating oil film is held in the sliding contact portion of the rocker arm 14 with the slipper 19 so that lubrication is maintained. Good done.

When the angle of the cam surface 13a does not coincide with the angle of the sliding surface due to a manufacturing error of the three-dimensional cam 13, that is, as shown by a two-dot chain line in FIG. When a gap S is formed between both surfaces due to point contact, the rocker arm 14 is tilted with respect to the rocker pin 20 so that the gap S is eliminated. In other words, the rocker arm 14 tilts with respect to the rocker pin 20 so as to follow the cam surface 13a of the three-dimensional cam 13, and the cam surface 13a is in line contact with the sliding contact surface of the slipper 19 over the entire circumference. Come into contact.

Therefore, according to the valve gear 7, even if the three-dimensional cam 13 is not formed with high precision, the oil film of the lubricating oil is reliably held between the cam surface 13a and the sliding contact surface of the slipper 19. be able to.

Second Embodiment In order to connect the rocker arm 14 to the rocker pin 20 so as to be tiltable, a structure in which a connecting piece is interposed between the boss 17 and the rocker pin 20 as shown in FIG. Can be adopted.

FIG. 6 is an enlarged sectional view showing a main part of another embodiment of the engine valve gear according to the present invention, which is illustrated in FIGS. 1 to 5 in these figures. The same reference numerals are given to the same or equivalent members, and the detailed description is omitted.

The rocker arm 14 shown in FIG. 6 is connected to the rocker pin 20 via a cylindrical top 31.
In the top 31, the inner peripheral surface 31a is formed so as to have a constant inner diameter, and the outer peripheral surface 31b is formed into a tapered surface in which the outer diameter gradually decreases from the central portion in the axial direction to the end in the axial direction. The rocker pin 20 is fitted to the inner peripheral surface 31 a, and the outer peripheral part is fitted to the pin hole 25 of the rocker arm 14. In this embodiment, a portion having a constant outer diameter is formed at the axial center of the outer peripheral surface 31b of the top 31.

By adopting this embodiment, the manufacture of the valve train 7 is simplified as compared with the case of employing the above-described first embodiment. This is because the operation of forming a tapered surface on the outer peripheral surface 31b of the top 31 is simpler than the operation of forming a tapered surface in the pin hole 25 of the rocker arm 14.

In each of the embodiments described above, an example is shown in which all of the intake valve 5 and the exhaust valve 6 are radially arranged.
It is also possible to arrange only the two intake valves 5 and 5 radially and to arrange the two exhaust valves 6 and 6 so as to be parallel to each other. , 6 are arranged radially, and the two intake valves are arranged so as to be parallel to each other. Further, the number of intake valves 5 and exhaust valves 6 can be appropriately changed. For example, three intake valves 5 and two exhaust valves 6 can be used.

[0037]

As described above, according to the present invention, since the rocker arm is tilted with respect to the rocker pin so as to follow the cam surface of the three-dimensional cam, the cam surface contacts the sliding surface of the rocker arm. Contact is made in line contact over the entire circumference.

Therefore, the oil film of the lubricating oil can be reliably held between the cam surface and the sliding surface of the rocker arm without forming the three-dimensional cam with high precision. For this reason, the valve train of the engine according to the present invention can reduce the number of rocker arms by using the three-dimensional cam while increasing both the productivity of the three-dimensional cam and the durability of the sliding contact portion. , Cost and size can be reduced.

According to another invention in which the position where the three-dimensional cam comes into contact with the rocker arm is positioned on the rocker pin side, the three-dimensional cam is located on the rocker arm at a position corresponding to the intake / exhaust valve, or at the position where the rocker is located at the rocker arm. If the opening and closing of the intake and exhaust valves are the same, the lift of the three-dimensional cam can be set relatively low and the length of the rocker arm can be set shorter than when a structure is used that contacts the part opposite to the pin. The length can be shortened.

Accordingly, since the inertial mass of the three-dimensional cam and the rocker arm can be made relatively small, a valve train suitable for a high-speed engine can be provided.

According to another invention in which the rocker pin is inclined with respect to the camshaft, the rocker arm swings in the opening and closing direction of the intake valve or the exhaust valve. It can be arranged so that no bending load is applied.

[Brief description of the drawings]

FIG. 1 is a sectional view of an engine employing a valve train according to the present invention.

FIG. 2 is a plan view of a cylinder head.

FIG. 3 is a perspective view showing a configuration of a valve train according to the present invention.

FIG. 4 is a view showing a rocker arm.

FIG. 5 is a sectional view of a base of the rocker arm.

FIG. 6 is an enlarged sectional view showing a main part of another embodiment of the engine valve train according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cylinder head, 5 ... Intake valve, 6 ... Exhaust valve, 11 ...
Intake camshaft, 12 ... exhaust camshaft, 13 ... three-dimensional cam, 1
3a: cam surface, 14: rocker arm, 17: boss, 1
8 ... arm, 19 ... slipper, 20 ... rocker pin, 2
5 ... Pin hole.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01L 13/00 301 F01L 13/00 301A F02F 1/24 F02F 1/24 F (72) Inventor Matsunori Narita 2500 Shinkai, Iwata City, Shizuoka Prefecture Yamaha Motor Co., Ltd.F-term (reference)

Claims (3)

[Claims] A rocker arm for each intake / exhaust valve in which a plurality of intake valves or a plurality of exhaust valves are radially arranged in one cylinder, and a base is rotatably supported on a cylinder head via a rocker pin. And an intake camshaft and an exhaust camshaft, each of which forms a three-dimensional cam that is in sliding contact with the rocking ends of the rocker arms, and a valve train for the engine that drives the intake and exhaust valves. An engine valve operating device, wherein a base portion is connected to the rocker pin so as to be tiltable in a direction orthogonal to an axial direction of the rocker pin. 2. The valve train of an engine according to claim 1, wherein a position at which the three-dimensional cam contacts the rocker arm is positioned closer to the rocker pin than a position at which the rocker arm contacts the intake / exhaust valve. Engine valve gear. 3. The valve operating apparatus for an engine according to claim 1, wherein the rocker pin is inclined with respect to the axis of the camshaft as viewed from the cylinder axis direction. .