JP2000045719A - Valve mechanism of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a valve mechanism of an internal combustion engine where a linear contact between suction and exhaust cams and a locker arm is realized without a highly accurate processing to restrain the wear and heating of a sliding face between them. SOLUTION: In this valve mechanism of an internal combustion engine where suction and exhaust valves are radially arranged, and the rotation of the suction and exhaust valves is converted through a rocker arm 25 into the sliding motion of the suction and exhaust valves to open and close the valves, a slipper 29 of the rocker arm 25 is formed in different body and slidably supported. Thus, the slipper 29 oscillates on the rocker arm 25 on account of processing accuracy and assembly error to stably maintain a contact between the slipper 29 and the suction cam 15a in a linear contact state, and the linear contact between the slipper 29 and the suction cam 15a can be realized without requiring highly accurate processing to restrain the wear and heating of both sliding faces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a valve operating mechanism for an internal combustion engine employing a rocker arm system.

[0002]

2. Description of the Related Art In a four-stroke engine, an intake port and an exhaust port that open to a combustion chamber are opened and closed at appropriate timing by an intake valve and an exhaust valve, respectively, to perform necessary gas exchange. As one of the driven valve mechanisms, a rocker arm system is known in which the rotation of the intake / exhaust cam shaft is converted into sliding movement of the intake / exhaust valve via a rocker arm to open / close the intake / exhaust valve. I have.

[0003] In a valve operating mechanism employing a system in which a rocker arm is rotatably supported by a rocker shaft, a configuration in which a cam shaft and a rocker shaft are arranged in parallel is generally adopted.

On the other hand, in a valve operating mechanism of an internal combustion engine in which intake and exhaust valves are three-dimensionally arranged radially, it is impossible to arrange a cam shaft and a rocker shaft in parallel, and a rocker arm on the intake and exhaust sides. Is driven by one intake / exhaust camshaft, three cams are formed on the intake / exhaust camshaft.
I have to adopt a dimension cam.

[0005]

However, when a three-dimensional cam is used as described above, a special grinding machine is used to always keep the three-dimensional cam and the slipper of the rocker arm in linear contact. There is a problem that it is necessary to precisely process the contact portion between the two with high precision, which requires a great amount of processing time and processing cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object thereof is to realize a line contact between the intake / exhaust cam and the rocker arm without requiring high-precision processing, thereby allowing the two to slide. It is an object of the present invention to provide a valve train for an internal combustion engine that can suppress surface wear and heat generation.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, an intake / exhaust valve is radially arranged, and rotation of an intake / exhaust cam shaft is controlled via a rocker arm. In a valve operating mechanism for an internal combustion engine that opens and closes the intake / exhaust valve by converting the sliding movement of the exhaust valve, the slipper of the rocker arm is separately supported and swingably supported.

According to a second aspect of the present invention, in the first aspect of the present invention, a separate holder is attached to the cylinder head, and the rocker arm is supported by the holder.

According to a third aspect of the present invention, in the first or second aspect, the intake / exhaust cam formed on the intake / exhaust cam shaft is a three-dimensional cam.

According to a fourth aspect of the present invention, in the third aspect, a rocker shaft rotatably supporting the rocker arm is inclined with respect to the intake / exhaust cam shaft in a side view. I do.

According to a fifth aspect of the present invention, in the first to third or fourth aspects of the present invention, a bearing for supporting the intake / exhaust cam shaft is disposed between a plurality of adjacent intake / exhaust valves. Features.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of an upper portion (cylinder head portion) of an internal combustion engine provided with a valve mechanism according to the present invention, FIG. 2 is a plan view showing a state where a head cover of the internal combustion engine is removed, and FIG. FIG. 4 is a side view showing a sliding contact state of the rocker arm, FIG. 4 is a front view thereof (a view in the direction of arrow A in FIG. 3), and FIG. 5 is a perspective view thereof.

The internal combustion engine 1 according to the present embodiment is a four-cycle four-valve engine, and as shown in FIG.
An aluminum alloy cylinder head 2 has two intake valves 3 and two exhaust valves 4 (only one is shown in FIG. 1).
Is provided.

The cylinder head 2 is mounted on an upper portion of a cylinder block (not shown), and a head cover 5 made of an aluminum alloy is mounted on the upper portion. A piston (not shown) is vertically slidably fitted in a cylinder formed in the cylinder block, and the piston is connected to a crankshaft (not shown) via a connecting rod (not shown).

Also, as shown in FIG.
Are formed with two intake passages 6 and two exhaust passages 7 (only one is shown in FIG. 1). The port 7a is opened and closed at an appropriate timing by the intake valve 3 and the exhaust valve 4, respectively, to perform a required gas exchange.

Here, the configuration of the valve operating mechanism according to the present invention for opening and closing the intake valve 3 and the exhaust valve 4 will be described.

As shown in FIG. 1, each of the intake valves 3 and each of the exhaust valves 4 are slidably inserted and held by valve guides 8 and 9 press-fitted into the cylinder head 2, and are closed by an air spring. Has been energized. That is, the valve lifters 10 and 11 attached to the upper ends of the intake valves 3 and the exhaust valves 4 respectively slidably fit into the recesses of the housings 13 and 14 attached to the cylinder head 2 by a plurality of bolts 12. A pressure chamber (not shown) is formed therein, and compressed air supplied to each pressure chamber from a compressor (not shown) constitutes an air spring to close the intake valve 3 and the exhaust valve 4 as described above. Biased to the side.

By the way, in the internal combustion engine 1 according to the present embodiment, as shown in FIG. 1, the intake valve 3 and the exhaust valve 4 are arranged so as to be inclined upward so as to open three-dimensionally and radially. And therefore the valve lifter 10,
11 and housings 13, 14 are likewise mounted radially.

On the other hand, as shown in FIG. 2, bearing bosses 2a and 2b on the intake and exhaust sides are provided on both longitudinal sides of the intake valve 3 and the exhaust valve 4 of each cylinder of the cylinder head 2.
Are formed facing each other, and semi-cylindrical bearings (not shown) are formed on the upper surfaces of these bearing bosses 2a and 2b, respectively. Each bearing has an intake camshaft 1
5 and an exhaust camshaft 16 are rotatably supported and arranged in parallel with each other.
7, 18 are respectively attached. Here, an endless timing belt 19 is wound between the sprockets 17 and 18 and a sprocket (not shown) attached to the end of the crankshaft. The rotation of the crankshaft may be transmitted to the intake / exhaust camshafts 15 and 16 via multiple gears.

The intake cam shaft 15 and the exhaust cam shaft 16
Are supported by bearing caps 20 and 21, respectively.
Thus, it is mounted on the upper surface of the bearing bosses 2a, 2b of the cylinder head 2.

Two intake cams 15a are integrally connected to a portion of the intake camshaft 15 opposed to the two intake valves 3. Similarly, two intake cams 15a are connected to the two exhaust valves 4 of the exhaust camshaft 16. Two exhaust cams 16 are provided at opposing portions.
a are integrally connected, these intake cams 15a
And the exhaust cam 16a constitute a three-dimensional cam, and their sliding surfaces (outer peripheral surfaces) form a tapered surface.

The valve operating mechanism according to the present invention employs a rocker arm system. As shown in FIGS. 1 and 2, a total of four rocker arms oscillating about rocker shafts 23 and 24 are provided. 25, 26 to the intake camshaft 15
Between the intake camshaft 15 and the exhaust camshaft 16 and converts the rotation of the intake camshaft 15 and the exhaust camshaft 16 into sliding motion of the intake valve 3 and the exhaust valve 4 via the rocker arms 25 and 26, thereby And the exhaust valve 4 are opened and closed at appropriate timing to perform a required gas exchange.

In this embodiment, as shown in FIG. 1, a space is provided between the intake and exhaust cam shafts 15, 16 below the upper surface of the cylinder head 2 (the mounting surface of the head cover 5). Is formed, and a separate holder 27 is attached to this space by a bolt 28, and the four rocker arms 25 and 26 are swingably supported by the four rocker shafts 23 and 24 on the holder 27. ing. The holder 27 is made of an iron-based material having higher strength and rigidity than an aluminum alloy. As shown in FIG. 2, a plug hole 27a is formed in the center of the holder 27.

The upper surface of the distal end of each of the rocker arms 25, 26 extending laterally from the holder 27 is in contact with the suction / exhaust cams 15a, 16a via the slippers 29, 30, and the lower surface is suction / exhaust. It contacts the upper ends of the exhaust valves 3 and 4. In the valve operating mechanism according to the present embodiment,
As shown in FIG. 1, the centers of the intake and exhaust camshafts 15 and 16 are located on the axial center lines of the intake and exhaust valves 3 and 4.

By the way, in the internal combustion engine 1 according to the present embodiment, since the intake and exhaust valves 3 and 4 are three-dimensionally radially arranged as described above, the intake and exhaust cams 1 are provided.
Although three-dimensional cams are used as 5a and 16a, the taper angles of the sliding surfaces of the intake / exhaust cams 15a and 16a are different from each other.
The angles are set such that the axes of the exhaust valves 3 and 4 intersect perpendicularly with the sliding surface.

The rocker shafts 23, 24 for supporting the respective rocker arms 25, 26 on the holder 27 are substantially parallel to the intake / exhaust cam shafts 15, 16 in plan view as shown in FIG. Is within 1 °),
In side view, the intake and exhaust camshafts 15 and 16 are arranged to be inclined by an inclination angle in the longitudinal direction (crankshaft direction) of the intake and exhaust valves 3 and 4.

In the valve train according to the present embodiment, the slipper 2 of each rocker arm 25, 26 is provided.
The rocker arms 9 and 30 are formed separately from the rocker arms 25 and 26 and have a vertical surface parallel to the axis of the rocker shafts 23 and 24 (FIG. 4).
In a plane parallel to the plane of the drawing).

Here, the configurations of the rocker arm 25 and the slipper 29 on the intake side will be described with reference to FIGS.
Since the configurations of the rocker arm 26 and the slipper 30 on the exhaust side are the same, illustration and description thereof are omitted.

As shown in FIG. 3, the upper surface (sliding contact surface) 29a of the slipper 29 forms a convex surface having an arcuate curved surface in a plane perpendicular to the axis of the rocker shaft 23, and its lower surface (supported surface). ) 29b is the rocker shaft 2 as shown in FIG.
A convex surface having an arcuate curved surface is formed in a vertical plane parallel to the axis of No. 3.

On the other hand, the slipper 29 of the rocker arm 25
As shown in FIG. 4, the support surface 25 a that forms the concave surface having an arcuate curved shape corresponding to the convex shape of the lower surface 29 b of the slipper 29.

The slipper 29 has its convex lower surface 29b fitted to and received by the concave support surface 25a of the rocker arm 25, as described above, so that the slipper 29 is perpendicular to the axis of the rocker shaft 23. The slipper 29 is swingably supported in the plane, and the slipper 29 is in line contact with the sliding surface of the intake cam 15a at a point a shown in FIG. Similarly, the slipper 30 of the rocker arm 26 is also swingably supported in a vertical plane parallel to the axis of the rocker shaft 24, and the slipper 30 is in line contact with the exhaust cam 16a.

Next, the operation of the valve train according to the present invention will be described.

When the internal combustion engine 1 is started and the crankshaft (not shown) is driven to rotate, the rotation of the crankshaft is rotated by a sprocket (not shown), a timing belt 19, and sprockets 17 and 18 (see FIG. 2) and the intake / exhaust camshaft 15,
The intake / exhaust cam shafts 15, 16 and the intake / exhaust cams 15a, 16a are rotationally driven at a predetermined speed (a half speed of the crankshaft).

Thus, as described above, the intake / exhaust cam 15
When each of the rocker arms 2a and 16a is driven to rotate,
The suction / exhaust cams 15a, 16 abut via slippers 29, 30 swingably supported at their distal ends.
Since the intake / exhaust valves 3 and 4 are pushed down against the urging force of the air spring, they are opened for a predetermined time to perform required gas exchange.

In the above, in the present embodiment, since the slippers 29 and 30 of the rocker arms 25 and 26 are separately supported so as to be swingable, the slippers 29 and 30 may be displaced due to machining accuracy and assembly error. 25,26
Swinging up, the slippers 29, 30 and the intake / exhaust cam 15
a and 16a are stably maintained in a line contact state.
Therefore, the slippers 29, 30 and the intake / exhaust cams 15a, 1
The line contact can be realized without requiring high-precision processing of 6a, and wear and heat generation of the sliding surfaces of both can be suppressed.

In this embodiment, the intake / exhaust camshaft 1
Since the bearings for supporting the intake and exhaust camshafts 15 and 16 are arranged between the two intake valves 3 and the exhaust valves 4 respectively.
The supporting stiffness of the support members 16 is increased, and their bending deformation is suppressed to a small value.

Further, in the present embodiment, since the centers of the intake and exhaust camshafts 15 and 16 are located on the axial center lines of the intake and exhaust valves 3 and 4, the load acting on each rocker shaft 23 and 24 is reduced. Thus, the durability of the rocker shafts 23, 24 can be improved.

The above description is based on the assumption that the present invention uses two intake and exhaust valves.
Although the case where the present invention is applied to a four-valve engine provided one by one has been described, it is needless to say that the present invention can be similarly applied to any other internal combustion engine employing a rocker arm system as a valve operating mechanism.

[0040]

As is apparent from the above description, according to the present invention, since the rocker arm slippers are separately supported as these are swingably supported, the slippers may be displaced due to machining accuracy and assembly errors. By swinging above, the contact between the slipper and the suction / exhaust cam can be stably maintained in a line contact state, realizing the line contact without requiring high precision processing of the slipper and the suction / exhaust cam. Thus, the effect of suppressing wear and heat generation on the sliding surfaces of the two can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an upper portion (cylinder head portion) of an internal combustion engine provided with a valve mechanism according to the present invention.

FIG. 2 is a plan view showing a state where a head cover of an internal combustion engine including the valve train according to the present invention is removed.

FIG. 3 is a side view showing a sliding contact state between a cam and a rocker arm of the valve mechanism according to the present invention.

4 is a front view (a view in the direction of arrow A in FIG. 3) showing a sliding contact state between a cam and a rocker arm of the valve train according to the present invention.

FIG. 5 is a perspective view showing a sliding contact state between a cam and a rocker arm of the valve train according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder head 3 Intake valve 4 Exhaust valve 15 Intake camshaft 15a Intake cam 16 Exhaust camshaft 16a Exhaust cam 23,24 Rocker shaft 25,26 Rocker arm 27 Holder 29,30 Slipper

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) F02F 1/24 F02F 1/24 RF Term (Reference) 3G016 AA02 AA08 AA19 BA03 BA06 BA21 BA22 BB14 CA13 CA22 CA40 CA43 CA44 CA45 CA46 CA57 DA01 EA02 FA27 GA00 GA02 3G024 AA16 AA18 DA03 DA10 EA01 FA00 FA06 GA26

Claims (5)

[Claims] An intake / exhaust valve is arranged radially, and the rotation of an intake / exhaust cam shaft is converted into a sliding motion of the intake / exhaust valve via a rocker arm to open / close the intake / exhaust valve. An engine valve operating mechanism for an internal combustion engine, characterized in that the slipper of the rocker arm is separately supported and swingably supported. 2. The valve train of an internal combustion engine according to claim 1, wherein a separate holder is attached to the cylinder head, and the rocker arm is supported by the holder. 3. The valve operating mechanism for an internal combustion engine according to claim 1, wherein the intake / exhaust cam formed on the intake / exhaust cam shaft is a three-dimensional cam. 4. The valve train according to claim 3, wherein a rocker shaft rotatably supporting the rocker arm is inclined with respect to the intake / exhaust cam shaft in a side view. 5. A valve mechanism for an internal combustion engine according to claim 1, wherein a bearing for supporting said intake / exhaust camshaft is arranged between a plurality of adjacent intake / exhaust valves. .