JP2733306B2 - Valve system for 4-cycle engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve train of a five-valve engine provided with, for example, three intake valves and two exhaust valves, and particularly to a case where each valve is radially arranged. In addition, the present invention relates to an improvement in a cam shape in which only one kind of valve is required on the intake side or the exhaust side, and the grinding property of the cam surface of the cam shaft can be improved.

[Conventional technology]

In order to achieve high output in a 4-cycle engine,
There are cases where a plurality of intake valves and exhaust valves are provided. For example, there is a five-valve engine provided with three intake valves and two exhaust valves. Conventionally, as an arrangement structure of the intake valve and the exhaust valve in such an engine, there is, for example, a structure shown in FIG. In this figure, the valve arrangement is shown as viewed from the inside of the combustion chamber, and the intake valves 43a to 43c and the exhaust valves 44a and 44b are arranged in parallel with each other. In addition, 45 is a spark plug.

However, in the case of the above-mentioned conventional arrangement structure, particularly, the intake valves 43a, 43
Since the distance between b and 43c is likely to be narrow, there is a limit in increasing the diameter of the lifter mounted on the upper end of each intake valve, and there is a problem that the lift amount of each valve cannot be sufficiently secured.

In order to solve the above problem, there is a structure in which the valves are radially arranged as shown in FIGS. In this structure, as shown in FIG. 10, the outer intake valves 43b and 43c
By tilting the exhaust valves 44a, 44b outward in the axial direction of the camshaft 46, all the valves are radially arranged around the ignition plug 45. Also, as shown in FIG.
The above-mentioned inclined valve driving cam 46a is formed such that its outer surface is tapered so as to be perpendicular to the axis E of the inclined valve. Thus, the obliquely arranged valves can be driven to open and close without any trouble, the interval between the intake valves is widened, and the lifter diameter can be increased to secure the lift amount.

[Problems to be solved by the invention]

However, in the case of the above-described conventional valve arrangement and the valve gear adopting the cam shape, if the top surface of the combustion chamber is formed flat in order to increase the compression ratio, the outer intake valves 43b and 43c and the central intake valve 43a are not provided with the same valve. In addition to the difference in the distance from the lower end to the axis of the camshaft, it is necessary to increase the valve shaft length by the amount that the outer intake valves 43b and 43c are also inclined in the camshaft direction. Two types of valves are required.

Further, in the grinding of the inclined valve cam 46a, since the grindstone 47 is also inclined, the end 47a of the grindstone 47 is formed.
May interfere with the journal portion 46b of the cam shaft 46,
If the clearance groove 46c is increased to avoid this, a problem occurs in that the journal width is reduced.

The present invention has been made in order to solve the above-mentioned conventional problems. When the valves are arranged radially and the top surface of the combustion chamber is substantially flat, the inner valve and the outer valve have the same dimensions. The invention provides a valve device for a four-stroke engine that requires only one kind of valve on the intake side or the exhaust side, has excellent grinding properties on the tapered cam surface, and does not sacrifice the journal width. The purpose is.

[Means for solving the problem]

According to the present invention, a plurality of intake valves and exhaust valves are arranged, each of which is opened and closed by an intake camshaft and an exhaust camshaft. In the valve train of a four-stroke engine arranged in a radially inclined manner, an outer cam for driving the outer valves is formed in a tapered shape so that a cam surface thereof is perpendicular to an axis of the outer valve. The base circle of the outer cam is larger in diameter than the base circle of the straight inner cam that drives the inner valve located inside the outer valve.

Here, the base circle diameter of the cam in the present invention refers to the diameter at a portion where the lift amount is zero, and the base circle of the tapered outer cam is the base circle at the point where the cam intersects the axis of the outer valve. It is. Further, regarding the specific size of the base circle diameter of the outer cam, the distance from the lower end surface of the outer valve to the axis of the camshaft is reduced by tilting the outer valve also in the cam axis direction. The length is set to such an extent that a portion longer than the distance from to the axis of the camshaft can be absorbed.

Further, the outer cam in the present invention is a cam for driving valves located on both outer sides of three or more intake valves or exhaust valves arranged in the cam axis direction. And the exhaust valve driving cam.

[Action]

According to the valve train of the four-stroke engine according to the present invention, the base circle of the tapered outer cam is made larger than the base circle of the straight inner cam. By doing so, the extension of the distance from the lower end surface of the outer valve to the axis of the camshaft can be absorbed, so that the inner valve and the outer valve can be set to the same size, and, for example, three intake valves can be used as one type. .

Further, as described above, since the base circle of the tapered cam is made larger in diameter than the base circle of the straight cam, the base circle of the tapered cam can be compared with a journal having a smaller diameter than the base circle of the straight cam. It has a larger diameter. Therefore, it is possible to prevent the grinding wheel from interfering with the journal during the grinding of the tapered cam, thereby improving the grinding process, and the clearance groove may have the same width as before, and the journal width is not reduced.

〔Example〕

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

1 to 7 are views for explaining a four-stroke engine according to one embodiment of the present invention. FIG. 7A is a bottom view of the valve arrangement viewed from the inside of the combustion chamber, and FIG.
7 (b) and 7 (c) are a sectional view taken along line VIIb-VIIb and a sectional view taken along line VIIc-VIIc in FIG. 7 (a).

In the drawing, reference numeral 1 denotes a water-cooled type 4 employing the structure of the present embodiment.
This is a cycle single-cylinder 5-valve engine, in which a two-part cylinder head 3 composed of a lower head 5 and an upper head 6 is mounted on a cylinder body 2, and the upper surface of the upper head 6 is covered with a head cover 4. It has a structure.

On the mating surface 5a of the lower head 5 with the cylinder body 2, a combustion recess 7 constituting a combustion chamber A with a piston (not shown) inserted into a bore 2a of the cylinder body 2 is provided. The combustion recess 7 constitutes a ceiling wall of the combustion chamber A. An intake port 8 and an exhaust port 9 are formed in the lower head 5. The intake port 8 is branched into three passages, and the exhaust port 9 is branched into two passages, each of which is open to the combustion recess 7. Each opening 9a, 9b of the exhaust port 9 on the combustion chamber A side can be opened and closed by exhaust valves 10a, 10b, and a central opening 8a of the intake port 8 is a central intake valve 11a, and outer openings 8b on both outer sides thereof. , 8c can be opened and closed by outer intake valves 11b, 11c, respectively. Note that 2
Reference numeral 3 denotes a fuel injection device, which connects an intake pipe 23b provided with a slide type throttle valve 23a to an outside opening of the intake port 8.
8d, a fuel injection valve 23c is attached to the intake pipe 23b,
This injection nozzle has a structure in which it is directed downstream from the throttle valve 23a.

Here, the surface shape of the combustion recess 7 will be described in detail.
Line B connecting the centers C1 of the openings 8a and 8b of the intake port 8
1, and the height of the opening edges 7a, 7b from the mating surface 5a on the line B1 connecting the centers C1 of the openings 8a, 8c is the same.
The height of the opening edge from the mating surface 5a is the same for the opening edges 7c and 7d on the line B2 connecting the centers C2 of the openings 9a and 9b of the exhaust port 9, and furthermore, the center C1 The same applies to the opening edges 7e and 7f on the line B3 connecting C2 and C2.

The intake and exhaust valves are arranged radially about the center of the combustion recess 7, that is, the ignition plug 12 inserted into the center of the bore 2a. That is, the exhaust valves 10a and 10b are inclined so that the axis E intersects with the axis F of the exhaust cam shaft 15 when viewed from the side in the camshaft direction, and further, when viewed from a plane, in the direction of the exhaust camshaft 15. It is inclined left and right outside.
When the intake valves 11a to 11c are viewed from the side in the camshaft direction,
The axis E is inclined so as to intersect with the axis F of the intake camshaft 16, and when viewed from a plane, the central intake valve 11a is orthogonal to the intake camshaft 16, and the outer intake valves 11b and 11c are similar to the exhaust valves. It is inclined left and right outward in the cam axis direction.

Above each of the valves 11a to 11c, 10a and 10b, a two-part cotter 12 is provided.
a, a retainer 12b is mounted via the
b and the spring seat 12c of the lower head 5 have a valve spring 12
d and 12e are interposed, whereby each valve is biased in the closing direction. In addition, an inner pad is provided at the upper end of each valve.
Exhaust lifters 13, 13 and intake lifters 14a to 14c are mounted via 12f, and each lifter is slidably supported by a guide hole 6a formed in the upper head 6.

An exhaust camshaft 15 and an intake camshaft 16 are arranged above the exhaust lifters 13, 13 and the intake lifters 14a to 14c, respectively. The exhaust cam 15 has a pair of exhaust cams 15a, 15b, and a journal 15c formed between and substantially at the center of the two cams, and the intake cam shaft 16 has a central intake cam 16a, a pair of It has outer intake cams 16b and 16c, and journals 16d formed between the respective cams and at substantially the center, and the journals 15c and 16d are mounted on the bearings 6 of the upper head 6.
b and the bearing 17a of the cap 17 are pivotally supported. One end of each of the exhaust camshaft 15 and the intake camshaft 16 is supported by a ball bearing 18. This is to bear the thrust load generated by the tapered cam surface, as described later.

A transmission gear 19 that meshes with the other ends of the exhaust camshaft 15 and the intake camshaft 16 is mounted.
A connecting flange 19a formed at one end thereof is connected to the camshafts 15 and 16 by a key 21.
By connecting the pin 20a to the connecting plate 20 which is fastened and fixed by the above, the shaft is connected to each of the camshafts 15, 16. Although not shown, the rotation of the crankshaft is transmitted to any one of the transmission gears 19 via a gear, whereby the camshafts 15 and 16 are driven.

The cam surfaces of the exhaust cams 15a and 15b and the intake cams 16b and 16c have the exhaust valves 10a and 10 arranged radially as described above.
b, the outside is formed in a high tapered shape so as to be perpendicular to the axis E of the intake valves 11b and 11c. Also, the above outer intake cam
Base circles D1 of 16b and 16c are larger in diameter than base circle D2 of central intake cam 16a. Here, the base circle in each of the cams having a tapered shape means a base circle at a point E 'where the axis E of the intake and exhaust valves intersects with the intake and exhaust cam surfaces. The base circles D1 and D2 are half of the difference between the two diameters.
Is substantially equal to the difference between the distance from the lower end surfaces of the outer intake valves 11b and 11c to the axis F of the intake camshaft 16 and the distance from the lower end surface of the central intake valve 11a to the axis F of the intake camshaft 16. Is set to The intersection E 'is connected to the intake cams 16b, 16c.
Are located on the smaller diameter side than the center in the axial direction, but they may be located on the center in the axial direction of each cam or on the larger diameter side.

The exhaust cams 15a and 15b are in sliding contact with the exhaust lifter 13, and the intake cams 16a to 16c are in sliding contact with the intake lifters 14a to 14c. By rotating the exhaust cam shaft 15 and the intake cam shaft 16, the exhaust valve 10a, 10b and intake valves 11a to 11c are driven to open and close.

 Next, the operation and effect of this embodiment will be described.

When the three intake valves are arranged radially and the top surface of the combustion chamber is substantially flat as in the valve gear of this embodiment, the outer intake valves 11b and 11c are also inclined in the cam axis direction. Since the distance from the lower end surface of the intake valve to the axis of the camshaft becomes longer, the outer valve needs to be longer than the inner valve depending on the design, resulting in two types of intake valves. In the present embodiment, the outer valve driving cam 16c is formed in a tapered shape, and its base circle D1 is made larger in diameter than the inner circle D2 of the inner valve driving cam by an amount corresponding to the increase in the distance. Therefore, the outer intake valve and the inner intake valve may have the same size, and only one type of intake valve is required.

Further, since the base circle D1 of the outer intake cam 16c is made larger in diameter than the base circle D2 of the inner intake cam 16a, the grindability of the outer intake cam 16c is improved. That is, in the grinding of the cam surface, as shown in FIG.
The end 47a is moved along the cam surface so that a predetermined amount of the end 47a protrudes outward from the end of the cam. Therefore, in grinding the tapered cam surface, depending on the diameter of the base circle, the end of the grindstone may interfere with the journal 16d, and in order to avoid this, it is conceivable to increase the clearance groove 16e. In this case, the journal width is reduced. In the present embodiment, the base circle D1 is
Since the diameter is set to be larger than the base circle D2 of the inner cam 16a set to be larger, the diameter difference from the journal 16d becomes considerably large, and the above-mentioned problem of the interference of the grinding wheel does not occur, and therefore, the journal width is reduced. Does not become narrow.

In this embodiment, the height of the opening edge 7a of the central opening 8a of the intake port 8 and the height of the outer opening 8b or the opening edge 7b of the opening 8c in the cylinder axis direction substantially coincide with each other. The heights are also almost the same. Therefore, the step formed between the valves on the inner surface of the combustion recessed portion 7, that is, the top surface (ceiling wall) of the combustion chamber is made small, and the ceiling wall surface of the combustion chamber can be entirely flattened.

Further, since the outer intake valves 11b and 11c and the exhaust valves 10a and 10c are arranged radially, the masking 7g and 7f in the outer peripheral portion of the combustion chamber of each valve is reduced, and the flow of intake or exhaust can be smoothed accordingly. .

In the above embodiment, five intake valves and two exhaust valves are used.
The valve engine has been described.
The present invention can be applied to a case where there are more than three valves or a case where there are more than three exhaust valves, provided that the respective valves are arranged radially.

〔The invention's effect〕

As described above, according to the valve train of the four-stroke engine according to the present invention, since the base circle of the outer valve cam is set to be larger than the base circle of the inner valve cam, the inner and outer valves have the same length. In this case, only one type of the valve is required, and the effect of improving the grinding workability of the tapered outer valve cam is obtained.

[Brief description of the drawings]

1 to 7 are views for explaining a valve train of a four-stroke engine according to one embodiment of the present invention.
FIG. 2 is a front view of the camshaft, FIG. 2 is a side view thereof, FIG. 3 is a front view around the camshaft, FIGS. 4 and 5 are cross-sectional side views of the engine of the embodiment, and FIG. FIG. 7 (a) is a bottom view of the valve arrangement viewed from the inside of the combustion chamber, and FIGS. 7 (b) and 7 (c) are VIIs in FIG. 7 (a), respectively. Fig. 7 (d) is a side view showing a valve arrangement state, Figs. 8 to 10 are views showing a conventional example, and Figs. FIG. 10 is a bottom view of the valve arrangement as viewed from the inside of the combustion chamber, and FIG. 9 is a front view of the camshaft. In the figure, 1 is an engine, 10a and 10b are exhaust valves, 11a is an inner intake valve, 11b and 11c are outer intake valves, 15 is an exhaust cam shaft, 16 is an intake cam shaft, 16a is an inner intake cam, 16b and 16c are The outer intake cam, D1 is the base circle of the outer intake cam, D2 is the base circle of the inner intake cam, and E is the axis of the outer intake valve.

Claims (1)

(57) [Claims] A plurality of intake valves and exhaust valves are arranged, and each of them is opened and closed by an intake camshaft and an exhaust camshaft, respectively.
In a valve train for a four-stroke engine in which outer valves located on both outer sides as viewed in the camshaft direction are tilted outward in the camshaft direction and radially arranged, an outer cam for driving the outer valve has a cam surface. A taper is formed at right angles to the axis of the outer valve, and the base circle of the outer cam is
A valve train for a four-stroke engine, wherein the diameter is larger than a base circle of a straight inner cam for driving an inner valve located inside the outer valve.