JPH03172511A - Valve system for sohc engine - Google Patents

Abstract

PURPOSE:To promote the sphering of a combustion chamber shape provided with at least three intake valves per one cylinder by making the axis of the central intake valve and the axes of both side intake valves cross each other above the upper end of each valve shaft to lessen the cross angles of these intake valves. CONSTITUTION:In an engine 10 where three intake valve openings 17-19 putting a plug threaded hole of a wall surface 13a of a combustion chamber in a cylinder head 13 therebetween are formed on one side periphery to be opened and closed by intake valves 34-36 driven through swing arms 51, 52 respectively with the rotation of a cam shaft 42, the respective intake valves 34-36 are disposed nearly at a right angle to the cam shaft 42 as viewed axially of a cylinder. The axis A of the central intake valve 35 is made more upright than the axes B of both left and right side intake valves 34, 36 and constituted to cross the axes B of the both side intake valves 34, 36 above the upper ends of the intake valves 34-36. Thus, the cross angle between the intake valves 34-36 is lessened, the irregularities of the wall surface of the combustion chamber are reduced and the sphering of the combustion chamber shape can be promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to 5o) a valve operating system for an IC engine having three or more intake valves, and in particular to a valve train for an IC engine that has three or more intake valves, and in particular, to reduce irregularities on the wall surface of a combustion chamber and to create a spherical shape of the combustion chamber. This invention relates to an improvement in the arrangement structure of intake valves that can promote the improvement of intake valves.

[Conventional technology]

Recently, multi-valve engines equipped with three or more intake valves have been attracting attention in order to further increase the opening area of the intake valves while ensuring the rigidity of the cylinder head.

Furthermore, it is known that it is advantageous to make the combustion chamber wall shape spherical in order to improve the combustion efficiency of the engine. When a large number of intake valves are provided as described above, it is sufficient to arrange the multi-valve valve plate along the wall surface of the spherical combustion chamber, but if this is done, each valve stem will extend radially, The valve train becomes extremely complex. In order to avoid this complication, a structure is generally adopted in which each valve stem is arranged perpendicular to the camshaft when viewed in the cylinder axis direction (plan view).

As such a valve train, there is a conventional valve train described in, for example, Japanese Patent Application Publication No. 1983-502681.

In this conventional device, three intake valve openings are formed along the periphery of the combustion chamber, and each intake valve that opens and closes each opening is perpendicular to the camshaft when viewed in the cylinder axis direction, and externally when viewed in the camshaft direction. It is placed tilted towards the side. In this case, make the central intake valve more upright and left.

It intersects with the right intake valve at a predetermined angle, and the intersection of the two is located below the upper end of the center intake valve rod.

[Problem that the invention seeks to solve]

By the way, when each intake valve is arranged perpendicular to the camshaft in plan view, as in the valve train described in the above publication, the valve train becomes simple, but especially the central intake valve opening on the wall of the combustion chamber and the left,
Irregularities tend to occur at the boundary with the right intake valve opening, and if both intake valves are simply inclined, the above-mentioned requirement for making the combustion chamber wall surface spherical cannot be met.

The present invention has been made in view of the above-mentioned conventional demands, and it is possible to reduce unevenness at the boundary between the central intake valve opening and the left and right intake valve openings on the wall surface of the combustion chamber, thereby further promoting sphericity.
The purpose is to provide a valve train for an HC engine.

[Means for solving problems]

The present invention provides three or more intake valves on one side of one camshaft,
In the valve operating system for a 5OIIC engine, an exhaust valve is disposed on the other side, and the exhaust valve is driven by the camshaft via a rocker arm pivotally supported by a rocker shaft disposed parallel to the camshaft. Each intake valve is arranged perpendicular to the camshaft when viewed in the direction of the cylinder axis, and is divided into a central intake valve group and both side intake valve groups located on both sides of the central intake valve group.The axis of the central intake valve group when viewed in the camshaft direction stands up from the axis of both intake valve groups, and the axis of the center intake valve group and the axis of both side intake valve groups intersect above the upper end of either intake valve.

[Effect]

According to the engine valve train according to the present invention, since the axis of the central intake valve group and the axis of both side intake valve groups intersect above the upper end of either valve shaft when viewed in the camshaft direction, the center The intersecting angle of the two intake valves on both sides in the center is smaller than that described in the above publication, in which the intake valves intersect below the upper end of the intake valves, and in other words, the two intake valves become more parallel to each other. The unevenness that occurs at the boundary between the openings on both sides is reduced, and as a result, the shape of the combustion chamber wall becomes more spherical.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 to 7 are 5ooc according to an embodiment of the present invention.
1 and 2 are cross-sectional views taken along the line II in FIG. 3; FIG.

3 is a plan view of the device, 4 is a sectional plan view of the vicinity of the intake and exhaust passages, 5 is a bottom view of the cylinder head, and 6 is a view of the upper end of the intake valve. The rear view and FIG. 7 are right side views of the motorcycle equipped with the engine of this embodiment. In addition, in the plan view and side view, the right side in the figure is the front of the vehicle, and hereinafter, unless otherwise specified, the description will be made assuming that the front is viewed from the rear side of the vehicle.

In the figure, 1 is a motorcycle on which the engine of this embodiment is mounted, and the body frame 2 of the motorcycle 1 has one main pipe 2b at the top and bottom of a head pipe 2a,
This is a so-called diamond-shaped structure in which the front end of the down tube 2C is welded and the upper end of the seat pillar 2d is welded to the rear end of the main pipe 2b. Note that 2g is an under guard that protects the crankcase, 2e is a support pipe for suspending the engine with a frame extending between the main pipe 2b and the down tube 2C, and 2f is a seat rail.

A front fork 3 that pivotally supports a front wheel at its lower end is pivotally supported on the head pipe 2a so as to be steerable left and right, and a rear arm 5 that pivotally supports a rear wheel 4 at its rear end is pivoted on the rear pipe 2d. It is pivoted for free movement. Also this rear arm 5
is connected to the vicinity of the rear end of the main pipe 2b via a link mechanism (not shown) and one shock absorber 8.

In addition, 6 is a fuel tank, 7 is a seat, 9a is an air scoop that covers the side of the tank, 9b is a side cover that covers the lower part of the seat, and 9C is a rear cover that covers the rear part of the vehicle.

An engine unit 10 is suspended and supported within the vehicle body frame 2. This engine unit IO is a water-cooled 4-stroke single-cylinder 5-valve engine, and has a cylinder body 12. It has a structure in which the cylinder head 13 and the hand cover 14 are stacked with the cylinder head 13 and the hand cover 14 tilted slightly forward. One combustion chamber wall surface 13a is recessed approximately in the center of the lower surface of the cylinder head 13. The wall surface 13a is a piston (not shown) slidably inserted into the cylinder liner 12a of the cylinder body 12.
A combustion chamber 15 is constituted by the head of the cylinder.

A plug screw hole 13b is located approximately in the middle of the combustion chamber wall surface 13a.
is formed, and the plug screw hole 13b is connected to the cylinder by the rad 13. The plugs are led out through plug insertion holes 13c and 14a formed in the head cover 14 so as to be inclined toward the exhaust side (front side) with respect to the cylinder axis. Further, a spark plug 16 is screwed into the plug screw hole 13b.

On the peripheral edge of the combustion chamber wall surface 13a of the cylinder head 13 on one side sandwiching the plug hole 13b, there are left, center, and right intake valve openings 17, 18, 19, and on the other side, the left, A right exhaust valve opening 20.21 is formed, and the plug insertion hole 13c extends upwardly between the left and right exhaust valve openings 20.21. The left intake valve opening 17 is led out to the rear wall of the cylinder head by a left intake passage 22 that extends toward the rear of the vehicle so as to be substantially perpendicular to the axis of a camshaft 42 (described later) in plan view, and is connected to the center and right intake valves. The openings 18 and 19 form a middle intake passage 23a extending to the right in the vehicle width direction with respect to the camshaft 42.
The merging passage 23 of both intake passages 23a and 23b extends to the right in the vehicle width direction as a whole. Above left intake passage 22. Left and right carburetors 26 and 27 are connected to the rear end opening of the merging passage 23 via left and right cab joints 24 and 25, respectively.

In addition, the left and right exhaust valve openings 20.21 are connected to left and right exhaust passages 28 and 29 that extend toward the front of the vehicle while expanding in a V-shape.
The left and right exhaust pipes 31 and 32 of the exhaust system 30 are connected to the front end of each road. These exhaust pipes 31 and 32 pass through the left and right sides of the down tube 2C, are bent to the right, merge here, and then extend toward the rear of the vehicle. 33 are connected.

The left, center, and right intake valve openings 17.18°19 have left, center, and right intake valves 34°35.36 that open and close them.
The left and right exhaust valve openings 20.21 have left and right exhaust valves 37.3 which open and close the valve plates 34a, 35a and 36a, respectively.
Eight valve plates 37a and 38a are arranged, respectively. The valve rods 34b to 38b of the answers 34 to 38 are each of the above-mentioned intake air,
The exhaust passages 22.23a, 23b, and 28.29 penetrate through the ceiling walls and protrude upward from the base surface of the cylinder head 13.

Here, the valve rods 37b and 38b of the exhaust valves 37 and 38 are perpendicular to the camshaft 42, that is, parallel to each other, when viewed from above, and are inclined forward at the same angle when viewed in the direction of the camshaft 42. overlap each other. and the right exhaust valve 37.
38 is adapted to close the openings 20° 21 by a biasing spring 41 interposed between an upper stopper 39 fixed to the upper end thereof and a lower stopper 40 disposed on a spring seat of the cylinder body 13. Forced.

Further, the valve stems 34b to 36b of each of the intake valves 34 to 36 are also perpendicular to the camshaft 42 in plan view, and when viewed in the camshaft direction, the left and right intake valves 34 and 36 are similar to the exhaust valves 37 and 38. Roads - slope backwards at an angle and overlap each other. Also, the valve stem 35b of the central intake valve 35 is the left and right intake valve 34.36.
It is placed in a more upright position than the And above left.

The upper ends of the valve stems 34b, 36b of the right intake valve 34, 36 are located below the upper end of the valve stem 35b of the middle intake valve 35,
And the intersection point C of these axes A and H is located at a high place on the left,
It is located further above the upper ends of the right valve stems 34b, 36b. Furthermore, when viewed in the cylinder axial direction, the upper end of the valve rod 35b of the central intake valve 35 is located rearward than the upper ends of the left and right valve rods 34b and 36b. In addition, each of the above intake valves 34 to 3G
is the biasing spring 4 interposed between the upper and lower stoppers 39 and 40.
1, it is biased in the closing direction. In addition, each of the above 3'T.

Intake valves 34-36. The exhaust z'f'i' a does not need to be perfectly perpendicular to the camshaft 42, and may be arranged obliquely within a range that does not interfere with rocking by the rocker arm.

Further, the above-mentioned camshaft 42 is disposed between the intake and exhaust valves so as to cross a position substantially above the center of the combustion chamber 15.

This camshaft 42 is supported by cam bearings at its left, right end and center, and the left and right cam bearings are connected to the cylinder end 1.
The left and right lower bearings 13d and 13f formed on the mating surface of head cover 14 and the left and right upper bearings formed on the mating surface of head cover 14 (
(not shown). The central cam bearing is composed of a lower center bearing 13e formed at the center of the cylinder head 13 and an upper center bearing 14b formed at the center of the head cover 14.

Note that 43 is a drive sprocket fixed to the left end of the camshaft 42, and 44 is a decompression device for reducing the starting torque by slightly releasing compression pressure from the left exhaust valve 37 when the engine is started.

Here, the left, right, and center cam bearings are of a two-piece type, and are constructed by fixing the head cover 14 to the cylinder head 13, and the head cover 14 and the cylinder head 13 are The peripheral edge of the opening (mating surface), each of the above cam bearings, and the above plug insertion port 13
Both edges of c are fixed with fixing bolts (shown with hunting in FIG. 3). On the exhaust side of this opening periphery, a flange 14g formed on the outside between camps 56 and 56, which will be described later, is fixed with fixing bolts 50a, while on the intake side, between the above-mentioned intake valves. Flange portions 14h formed on the inside at two locations are fixed with fixing bolts 50b. In addition, this fixing bolt 5
0b faces outward when the camp 57 is removed. Further, 50 of the fixing bolts are used for fixing the cylinder head and the head cover and for preventing rotation of the rocker shaft, which will be described later. However, 50C is a dedicated bolt for preventing rotation.

Between the camshaft 42 and the left and right exhaust valves 37 and 38, left and right exhaust rocker shafts 46a and 46b are arranged parallel to the camshaft 42, and are integral with the inner surface of the spatula 12 door cover 14. It is supported by the formed bearing portion 14e, and is prevented from rotating by a head cover fixing bolt 50. Left and right exhaust rocker arms 47 and 48 are swingably supported by the left and right exhaust rocker shafts 36a and 36b. Sliding parts 47a, 48a formed at the rear ends of each rocker arm 47, 48 are in sliding contact with the left and right exhaust cams 42a, 42d of the camshaft 42, and adjusters 47a, 48a are screwed into the front ends 47b, 48b. screw 49
The lower end of the valve is in contact with the upper end of the left and right exhaust valve rods 37b and 38b.

Further, between the camshaft 42 and the intake valves 34 to 36, an intake rocker shaft 45 having a length spanning the left and right cam bearings is disposed parallel to the camshaft 42, and the rocker shaft 45 has both ends thereof. and the center portion are supported by a bearing portion 14f integrally formed with the head cover 14, and are prevented from rotating by a head cover fixing bolt 50. A left intake rocker arm 51 is located on the left side of the central cam bearing of the rocker shaft 45.
However, a right intake rocker arm 52 is pivotably supported on the right side portion. A sliding portion 51a formed at the front end of the left intake rocker arm 51 is in sliding contact with a left intake cam 42b formed on the left side of the central cam bearing of the camshaft 42,
The lower end of the adjustment screw 53 screwed into the rear end 51b is in contact with the upper end of the left intake valve rod 34b. Further, a sliding portion 52c formed at the front end of the right intake rocker arm 52 is in sliding contact with a right intake cam 42C formed on the right side of the central cam bearing of the camshaft 42. The rear half of the right intake rocker arm 52 is branched into a center arm 52a and a right arm 52b, each with a rear end 52d.
, Adjustment screw 54.53 screwed into 52e
are in contact with the upper ends of the center and right intake valve rods 35b and 36b. Here, as described above, when viewed in the camshaft direction, the upper end of the central intake valve rod 35b is located above the upper ends of the left and right intake valve rods 34b and 36b, and when viewed in the cylinder axial direction, it is located at the rear. There is. Therefore, the plane projected distance from the rocker shaft 45 to the upper end of the adjusting screw 54 for the central intake valve 35! 2' is longer than the plane projected distance 111i7!1' to the adjustment screw 53 for the left and right intake valves 34 and 36. As a result, the arm length (vertical distance from the rocker axis to the axis A) 12 of the central intake valve 35 is also longer than the arm length 7!1 of the left and right intake valves 34, 36.

Furthermore, two adjustment ports 14C are formed on the exhaust valve side of the head cover 14 for adjusting the adjustment screws 49 of the left and right exhaust valves 37 and 38, and these can be opened and closed using separate caps 56. ing. Also on the intake valve side are the above left and center.

Right intake valve 34-36 adjustment screw 53°54
One adjustment port 14d is formed for adjusting this, and this is opened and closed by one cap 57.

Next, the effects of this embodiment will be explained.

When the three intake valves are arranged perpendicular to the camshaft in plan view as described above, a step is likely to occur at the boundary between the central intake valve opening and the left and right intake valve openings on the wall of the combustion chamber. A problem arises in that it is difficult to make the chamber wall surface spherical. In this embodiment, the axis &IA of the central intake valve rod 35b and the left and right intake valve rods 34b, 3
Since the intersection C with the axis B of the central intake valve rod 35b is located above the upper end of the central intake valve rod 35b located at a high place, the above-mentioned two-wheel line The angle formed by A and B becomes smaller, that is, both intake valves become closer to parallel, and this occurs at the boundary part a of the combustion chamber wall surface 13a between the middle intake valve opening 18 and the left and right intake valve openings 17.19. The level difference becomes smaller, and the combustion chamber wall surface 13a
The unevenness is reduced, making it more spherical. Moreover, the volume of the combustion chamber can be reduced by the amount of spheroidization achieved in this way, and the compression ratio can also be increased.

In the above embodiment, the upper end of the central intake valve rod 35b and the upper ends of the left and right intake valve rods 34b and 36b are located at different heights. As shown, the present invention can of course be applied to the case where the upper ends of the center, left, and right intake valve rods are located at the same height. In addition, in the figure,
The same reference numerals as in FIG. 1 indicate the same or equivalent parts.

Furthermore, in the above embodiment, the case where there are three intake valves is explained5 6 , but the present invention can also be applied when there are four or more intake valves.For example, in the case of four intake valves, the central two (center intake valve group) ) and the two axes A on the left and right thereof, the intersection point C may be located above the upper end of either valve shaft.

Furthermore, although the present invention relates to the intersection angle between intake valves, the technical idea of the present invention can also be applied to exhaust valves in the case of an engine equipped with three or more exhaust valves.

Furthermore, although a single cylinder engine has been described in the above embodiment, the present invention can of course be applied to a multi-cylinder engine.

[Effects of the Invention] As described above, according to the valve operating system for an SOHC engine according to the present invention, the axis of the central intake valve and the axis of the intake valves on both sides intersect above the upper end of either valve axis. Therefore, the intersection angle of these intake valves becomes smaller, that is, they become more parallel to each other, and the unevenness of the combustion chamber wall surface is reduced, which has the effect of promoting the spherical shape of the combustion chamber.

[Brief explanation of the drawing]

FIGS. 1 to 7 show a SOHC according to an embodiment of the present invention.
1 and 2 are sectional views taken along line 1-1 and nn of FIG. 3, respectively, and FIG. 3 is a plan view of the device; FIG. , Fig. 4 is a sectional plan view showing the intake and exhaust passages, Fig. 5 is a bottom view of the cylinder head, Fig. 6 is a rear view of the upper end of the intake valve shaft, and Fig. 7 is a cross-sectional plan view showing the intake and exhaust passages. right side view of a motorcycle,
FIG. 8 is a cross-sectional side view showing a modification of the above embodiment. In the figure, 10 is the engine, 15 is the combustion chamber, 34.3
6 is the left and right intake valves, 35 is the middle intake valve, 37.38 is the exhaust valve, 42 is the camshaft, 45 is the intake rocker shaft, 51.52 is the left and right rocker arm, A. B is the left and right intake valve axes, middle intake valve axis, and C is the intersection of both axes.

Claims (1)

[Claims] (1) Three or more intake valves are arranged on one side of one camshaft, and an exhaust valve is arranged on the other side, and each valve is shafted by a rocker shaft arranged parallel to the camshaft. In a valve operating system for an SOHC engine that is driven via a supported rocker arm, each of the above-mentioned intake valves is arranged substantially perpendicular to the camshaft when viewed in the direction of the cylinder axis, and a central intake valve group and a central intake valve on both sides thereof are arranged. The axis of the center intake valve group is made to stand up from the axis of the intake valve groups on both sides when viewed in the camshaft direction, and the axis of the center intake valve group and the axis of the intake valve groups on both sides are A valve train for a SOHC engine, characterized in that the intake valves intersect above the upper end.