JP3993305B2 - Engine valve gear - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a valve operating apparatus for an engine in which intake and exhaust valves arranged radially are driven by an intake cam shaft and an exhaust cam shaft.
[0002]
[Prior art]
Conventionally, as an engine in which a combustion chamber is formed in a hemispherical shape in order to improve combustion efficiency, there is an engine in which, for example, four intake / exhaust valves are radially arranged per cylinder. The valve operating device used for this type of engine has different intake and exhaust valve opening and closing directions one by one as viewed from the direction perpendicular to the axial direction of the camshaft, so that the rotation of the camshaft is transmitted to each valve. It has a complicated structure (for example, see Japanese Patent Application Laid-Open No. 59-29709).
[0003]
In the valve operating device disclosed in this publication, one camshaft is rotatably supported at the center of the cylinder head, and the cam surface of the camshaft is parallel to the axial direction of the camshaft. In this structure, two rocker arms are interposed per intake / exhaust valve between the cam surface and the intake / exhaust valve.
[0004]
One first rocker arm of the two rocker arms is swingably supported by a first support shaft that is supported so as to be parallel to the cam shaft, and has one end in contact with the cam surface. The other end extends to the intake / exhaust valve side. The other second rocker arm is swingably supported by a second support shaft supported in a direction perpendicular to the axial direction of the intake valve or exhaust valve, and the lower surface of the swing end is used as the intake / exhaust valve. I have been attached. The other end portion of the first rocker arm is attached to the swing end portion on the opposite side (upper surface) from the intake / exhaust valve. That is, this valve operating apparatus adopts a structure in which the parallel movement of the cam surface is changed by two rocker arms into a parallel movement parallel to the axial direction of the intake / exhaust valves.
[0005]
[Problems to be solved by the invention]
However, the valve operating apparatus configured as described above has a problem that the manufacturing cost increases and the size increases because the number of rocker arms is large. In order to reduce the cost and size by using one rocker arm per intake / exhaust valve, the cam surface is formed so as to be inclined perpendicular to the axial direction of the intake / exhaust valve so that the cam is a three-dimensional one. It is conceivable to adopt a structure in which the cam surface is in sliding contact with the second rocker arm.
[0006]
However, in order to realize this, lubrication of the 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 contact between the two in a line contact state, and breaks when the contact state between the two becomes a point contact.
[0007]
That is, when a three-dimensional cam is manufactured as an industrial product, the contact state between the cam surface and the sliding contact surface is likely to be point contact due to the manufacturing error of the cam surface, and the oil film is interrupted to cause sliding contact. This is because the part is worn out. In order to form the cam surface of the three-dimensional cam with high accuracy, the grinding operation takes a very long time and the cost is significantly increased.
[0008]
The present invention has been made to solve such problems, and uses a three-dimensional cam while preventing a decrease in lubricity and an increase in cost, and a rocker arm compared to a conventional valve operating device. An object of the present invention is to make it possible to reduce the quantity and reduce cost and size.
[0009]
[Means for Solving the Problems]
A valve operating apparatus for an engine according to the present invention has a base portion in which a plurality of intake valves or exhaust valves are radially arranged in one cylinder and fitted to a rocker pin fixed to a cylinder head. An intake valve or an exhaust valve by an intake cam shaft or an exhaust cam shaft having a rocker arm for each intake / exhaust valve that is rotatably supported by the cylinder head via the rocker pin, and a three-dimensional cam that is in sliding contact with the rocker arm. In the fitting portion between the rocker pin and the base portion of the rocker arm, the gap between the pin hole into which the rocker pin is fitted in the base portion and the rocker pin is from the central portion in the axial direction of the pin hole. A tapered surface is formed so as to gradually become wider toward the opening end side, and the rocker arm is inclined at an angle regulated by the tapered surface. Only in a direction perpendicular to the axial direction of the rocker pin in the rocker pin is what is tiltably connected.
[0010]
According to the present invention, since the rocker arm tilts with respect to the rocker pin so as to follow the cam surface of the three-dimensional cam, the cam surface contacts the sliding contact surface of the rocker arm in a line contact state over the entire circumference. .
[0011]
The valve operating apparatus for an engine according to another aspect of the invention is the valve operating apparatus for the engine according to the above-described invention, wherein the position where the three-dimensional cam contacts the rocker arm is closer to the rocker pin than the position where the rocker arm contacts the intake / exhaust valve. Is positioned.
According to the present invention, the lift amount of the three-dimensional cam can be increased if the opening / closing amount of the intake / exhaust valve is the same as compared with the case where the three-dimensional cam contacts the portion corresponding to the intake / exhaust valve in the rocker arm. It can be set relatively low.
[0012]
The valve operating apparatus for an engine according to another aspect of the invention is the valve operating apparatus for an engine according to the above-described invention, wherein the rocker pin is inclined with respect to the axis of the cam shaft when viewed from the cylinder axial direction.
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 INVENTION
First Embodiment Hereinafter, an embodiment of a valve operating apparatus for an engine according to the present invention will be described in detail with reference to FIGS.
FIG. 1 is a cross-sectional view of an engine that employs a valve gear according to the present invention, FIG. 2 is a plan view of a cylinder head, and in FIG. 2, the fracture position of FIG. 3 is a perspective view showing the configuration of the valve gear according to the present invention, FIG. 4 is a view showing a rocker arm, FIG. 3A is a plan view, FIG. 3B is a side view, and FIG. These are front views which show the state seen from the slipper side. FIG. 5 is a cross-sectional view of the base of the rocker arm, which is a cross-sectional view taken along the line V-V in FIG.
[0014]
In these drawings, what is denoted by reference numeral 1 is the cylinder head of the engine according to this embodiment. This cylinder head 1 is equipped with a water-cooled single-cylinder DOHC type engine. A 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. ing. A spark plug (not shown) is attached between the ports 3 and 4, that is, in the center of the combustion chamber 2.
[0015]
As shown in FIG. 2, the two intake valves 5 and 5 that open and close the intake port 3 and the two exhaust valves 6 and 6 that open and close the exhaust port 4 have a valve shaft 5a, 6 a is arranged to extend radially from the combustion chamber 2. These intake / exhaust valves 5 and 6 are driven by a valve gear 7 described later. The axis of the cylinder is indicated by a one-dot chain line C in FIG.
[0016]
In FIG. 1, the reference numeral 8 through which the valve shafts 5a and 6a of the intake / exhaust valves 5 and 6 pass is a valve spring (not shown) for urging the intake / exhaust valves 5 and 6 to the closed side. A spring holding member for holding. The spring holding member 8 is formed in a bottomed cylindrical shape having a bottom portion (upper portion in FIG. 1) through which the intake / exhaust valves 5 and 6 pass, and is slidably fitted into a holding cylinder 9 fixed to the cylinder head 1. It is combined. The valve spring is elastically mounted between the inner bottom surface of the spring holding member 8 and the cylinder head 1.
[0017]
The valve operating device 7 for driving the intake / exhaust valves 5 and 6 includes a locker for each intake / exhaust valve in which the intake camshaft 11 and the exhaust camshaft 12 are in sliding contact with the three-dimensional cam 13 of the camshafts 11 and 12. It comprises an arm 14.
[0018]
The intake camshaft 11 and the exhaust camshaft 12 are provided with a three-dimensional cam 13 at a portion corresponding to the intake / exhaust valves 5 and 6, and are rotatably supported on the cylinder head 1 by a conventionally known support structure. A cam cap that pivotally supports the cam shafts 11 and 12 together with the cylinder head 1 is denoted by reference numeral 15 in FIGS. The cam shafts 11 and 12 have a timing chain sprocket 16 fixed to one end (the lower end in FIG. 2 ), and the timing when the sprocket 16 is wound between the crankshaft (not shown). A structure is adopted in which the rotation of the crankshaft is transmitted via a chain (not shown).
[0019]
Lubricating oil passages (not shown) formed in the cam shafts 11 and 12 are used to lubricate the bearings that rotatably support the cam shafts 11 and 12 and the sliding contact portions between the three-dimensional cam 13 and the rocker arm 14. It is carried out by supplying lubricating oil to the sliding contact portion.
[0020]
As shown in FIGS. 2 and 3, the three-dimensional cam 13 is formed by inclining the cam surface 13a so that the diameter gradually decreases from one end in the axial direction toward the other end. The inclination angle of the cam surface 13a corresponds to the inclination angle of the valve shafts 5a and 6a of the intake / exhaust valves 5 and 6 with respect to the axis of the cam shafts 11 and 12, and the cam surface 13a slidingly contacting the rocker arm 14 in FIG. -It is set to be parallel to the plane perpendicular to the axis of the exhaust valves 5 and 6 and the contact portion.
[0021]
As shown in FIG. 4, the rocker arm 14 is integrally formed with a cylindrical boss 17 and an arm 18 projecting in one direction from the boss 17, and the three-dimensional cam 13 of the cam shafts 11 and 12. A slipper 19 that is in sliding contact with the arm 18 is fixed. As shown in FIGS. 1 and 2, the rocker arm 14 has a rocker pin 20 made of a cylinder having a constant outer diameter fitted to the boss 17, and is rotated around the cylinder head 1 via the rocker pin 20. It is supported freely. The boss 17 constitutes the base of the rocker arm 14 according to the present invention.
[0022]
The rocker arm 14 and the rocker pin 20 are also inclined so as to correspond to the intake / exhaust valves 5 and 6 that are inclined with respect to the axial direction of the cam shafts 11 and 12. That is, like the cam surface 13a, it is inclined so as to be parallel to a plane orthogonal to the axis of the intake / exhaust valves 5 and 6. More specifically, the rocker pin 20 has an angle α with respect to the axis of the cam shafts 11 and 12 corresponding to the inclination of the intake / exhaust valves 5 and 6 when viewed from the cylinder axial direction as shown in FIG. Just tilted. This angle α is set to about 1 ° in this embodiment. In addition, the rocker pin 20 is inclined with respect to the axis of the cam shafts 11 and 12 even when viewed from the juxtaposed direction of the cam shafts 11 and 12 (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 in the state viewed from the direction in which the cam shafts 11 and 12 are juxtaposed. Inclined to form a letter. By tilting the rocker pin 20 in this manner, the rocker arm 14 swings along the opening / closing direction of the intake / exhaust valves 5, 6 and an excessive bending load is applied to the intake / exhaust valves 5, 6. It can arrange so that it may not occur.
[0023]
The rocker pin 20 is fixed to the cylinder head 1 by fitting one end of the rocker pin 20 on the cylinder axis C side into a central protrusion 21 (see FIG. 2) formed integrally with the cylinder head 1 and the other end. Is adopted to fit into 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 with fixing bolts 23.
[0024]
As shown in FIG. 1, the arm 18 of the rocker arm 14 is integrally formed with a pressing projection 18 a that contacts an end cap 24 provided at the tip of the valve shaft of the intake / exhaust valves 5, 6. The slipper 19 is fixed to the side opposite to the protrusion 18a (upper side in FIG. 1). The slipper 19 is formed in a so-called bowl shape so that the cam shaft side is convex and extends in the axial direction of the cam shafts 11 and 12.
[0025]
In this embodiment, the length and mounting position of the rocker arm 14 and the mounting position of the cam shafts 11 and 12 are rotated from the contact point between the pressing projection 18 a of the rocker arm 14 and the end cap 24. The distance R2 from the contact point between the slipper 19 and the three-dimensional cam 13 to the center of rotation is set shorter than the distance R1 to the center (the axis of the rocker pin 20).
[0026]
As shown in FIG. 5, the pin hole 25 for fitting the rocker pin 20 in the boss 17 of the rocker arm 14 is formed such that the central portion in the axial direction has a constant inner diameter, and the open end extends from the central portion. The inner portion is formed such that the inner diameter gradually increases toward the opening end side. A central portion having a constant inner diameter is indicated by reference numeral 21a in FIG. 5, and a portion that becomes a tapered hole whose inner diameter gradually changes is indicated by reference numeral 21b. The inclination angle θ of the hole wall surface of the tapered hole portion 21b is set to, for example, about 0.5 to 2 °.
[0027]
Thus, by forming the opening side of the pin hole 25 to be a tapered hole, the rocker arm 14 is orthogonal to the axial direction of the rocker pin 20 with the rocker pin 20 fitted in the pin hole 25. Can be tilted.
[0028]
Further, the rocker arm 14 has a plurality of protrusions 26 formed on the end face in the axial direction of the boss 17 as shown in FIG. These protrusions 26 are formed so as to come into contact with the end surface of the central protrusion 21 of the cylinder head 1 and the end surface of the rocker pin holder 22. Thus, by forming the protrusion 26 on the end surface of the boss 17, 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 protrusions 26 are formed on both side portions of the boss 17 (both side portions in a direction orthogonal to both the axis of the cam shafts 11 and 12 and the cylinder axis C). Can be tilted clockwise or counterclockwise in FIG.
[0029]
In the valve operating apparatus 7 configured as described above, the rotation of the intake cam shaft 11 and the exhaust cam shaft 12 is transmitted from the three-dimensional cam 13 to the rocker arm 14, and the rocker arm 14 rotates around the rocker pin 20. As a result, the intake and exhaust valves 5 and 6 are opened and closed. The sliding contact portion between the three-dimensional cam 13 and the slipper 19 of the rocker arm 14 holds the oil film of the lubricating oil when the angle at which the cam surface 13a is inclined coincides with the angle at which the sliding surface of the slipper 19 is inclined. The lubrication is good.
[0030]
When the angle of the cam surface 13a does not coincide with the angle of the sliding contact 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 the gap S is formed between both surfaces, the rocker arm 14 tilts with respect to the rocker pin 20 so that the gap S disappears. 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 surface of the slipper 19 over the entire circumference. Come into contact.
[0031]
Therefore, according to this valve operating device 7, the oil film of the lubricating oil can be reliably held between the cam surface 13a and the sliding surface of the slipper 19 without forming the three-dimensional cam 13 with high accuracy. .
[0032]
Second Embodiment In order to connect the rocker arm 14 to the rocker pin 20 in a tiltable manner, a structure in which a connecting piece is interposed between the boss 17 and the rocker pin 20 as shown in FIG. 6 is adopted. Can do.
[0033]
FIG. 6 is an enlarged cross-sectional view showing a main part of another embodiment of the valve operating apparatus for an engine according to the present invention. These figures are the same as those described in FIGS. Equivalent members are denoted by the same reference numerals, and detailed description thereof is omitted.
[0034]
The rocker arm 14 shown in FIG. 6 is connected to the rocker pin 20 via a cylindrical piece 31. The top 31 is formed so that the inner peripheral surface 31a has a constant inner diameter, and the outer peripheral surface 31b becomes a tapered surface whose outer diameter gradually decreases from the central portion in the axial direction toward the end portion in the axial direction. The rocker pin 20 is fitted to the inner peripheral surface 31 a and the outer peripheral portion is fitted to the pin hole 25 of the rocker arm 14. In this embodiment, a portion having a constant outer diameter is formed in the central portion of the outer peripheral surface 31b of the top 31 in the axial direction.
[0035]
By adopting this embodiment, the manufacture of the valve gear 7 is simplified as compared to the case of adopting the first embodiment described above. This is because the operation of forming the tapered surface on the outer peripheral surface 31 b of the top 31 is simpler than the operation of forming the tapered surface in the pin hole 25 of the rocker arm 14.
[0036]
In each of the above-described embodiments, an example in which all of the intake valves 5 and the exhaust valves 6 are arranged radially has been shown. However, only two intake valves 5, 5 are arranged radially, The exhaust valves 6 and 6 can be arranged so as to be parallel to each other, and conversely, the two exhaust valves 6 and 6 are arranged radially and the two intake valves are parallel to each other. It can also be arranged. The number of intake valves 5 and exhaust valves 6 can be changed as appropriate. For example, the number of intake valves 5 can be three and the number of exhaust valves 6 can be two.
[0037]
【The invention's effect】
As described above, according to the present invention, since the rocker arm tilts 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 surface of the rocker arm over the entire circumference. Contact in the state of.
[0038]
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 accuracy. For this reason, the valve gear for an engine according to the present invention can reduce the number of rocker arms using the three-dimensional cam while improving both the productivity of the three-dimensional cam and the durability of the sliding contact portion. Cost reduction and downsizing can be achieved.
[0039]
According to another invention in which the position where the three-dimensional cam contacts the rocker arm is positioned on the rocker pin side, the part where the three-dimensional cam corresponds to the intake / exhaust valve on the rocker arm, or the opposite of the rocker pin than the intake / exhaust valve Compared to the structure that contacts the side part, if the open / close amount of the intake and exhaust valves is the same, the lift amount of the three-dimensional cam can be set relatively low, and the length of the rocker arm can be shortened. Can be formed.
[0040]
Therefore, since the inertial masses of the three-dimensional cam and the rocker arm can be made relatively small, it is possible to provide a valve gear suitable for a high-speed engine.
[0041]
According to another invention in which the rocker pin is inclined with respect to the camshaft, the rocker arm swings along the opening / closing direction of the intake valve or the exhaust valve, so that an excessive bending load is applied to the intake valve or the exhaust valve. It can arrange | position so that it may not add.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an engine employing a valve gear according to the present invention.
FIG. 2 is a plan view of a cylinder head.
FIG. 3 is a perspective view showing the configuration of the valve gear according to the present invention.
FIG. 4 is a view showing a rocker arm.
FIG. 5 is a cross-sectional view of a base portion of a rocker arm.
FIG. 6 is an enlarged cross-sectional view showing a main part of another embodiment of the valve gear for an engine according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Cylinder head, 5 ... Intake valve, 6 ... Exhaust valve, 11 ... Intake cam shaft, 12 ... Exhaust cam shaft, 13 ... Three-dimensional cam, 13a ... Cam surface, 14 ... Rocker arm, 17 ... Boss, 18 ... Arm , 19 ... slippers, 20 ... rocker pins, 25 ... pin holes.

Claims (3)

A plurality of intake valves or a plurality of exhaust valves are arranged radially in one cylinder, and have a base portion that fits into a rocker pin fixed to the cylinder head, and this base portion is connected to the cylinder head via the rocker pin. and the rocker arm for each intake and exhaust valve is rotatably supported, drive the intake valve or the exhaust valve by the intake camshaft or an exhaust camshaft to form a sliding contact three-dimensional cam to the swing end portion of the rocker arm A valve operating device for the engine,
In the fitting portion between the rocker pin and the base portion of the rocker arm, the gap between the pin hole into which the rocker pin in the base portion fits and the rocker pin is directed from the central portion in the axial direction of the pin hole toward the opening end side. Therefore, a tapered surface is formed so as to gradually become wider,
The engine valve operating apparatus according to claim 1, wherein the rocker arm is connected to the rocker pin by an inclination angle regulated by the tapered surface so as to be tiltable in a direction perpendicular to the axial direction of the rocker pin.   2. The valve operating apparatus for an engine according to claim 1, wherein the position where the three-dimensional cam contacts the rocker arm is positioned closer to the rocker pin than the position where the rocker arm contacts the intake / exhaust valve. apparatus.   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 cam shaft when viewed from the cylinder axial direction.

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