JPH0230910A - Four-cycle engine - Google Patents

Abstract

PURPOSE:To secure a compact space for installing a cylinder head bolt by providing three intake or discharge valves per a cylinder while arranging both side valves closer to a center of the cylinder in a direction perpendicular to a cam shaft than the intermediate one. CONSTITUTION:In an engine wherein three intake valves 5 are arranged per a cylinder, one end of a rocker arm 14 is abutted against an upper end of each intake valve 5, the other end of the rocker arm 14 is journalled by a cylinder head (b), and a can 9a of a cam shaft 9 is abutted against the upper surface of the rocker arm 14. Both side intake valves 5 are sot closer to a center of the cylinder in a direction perpendicular to the cam shaft 9 than the intermediate one. When alpha1, not shown, denotes an inclination angle of the intermediate intake valve 5 and those of both side valves 5 alpha2, alpha2 are larger than alpha1. Space for installing a cylinder bead bolt 17 is secured on outer side of both side rocker arms 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a four-stroke engine having three intake valves or three intake valves per cylinder.

[Prior Art] Cylinder head bolts for properly attaching the cylinder head to the cylinder are usually provided on both sides of the valve for each outer cylinder (see Utility Model Publication No. 53-643).

(See German Patent Publication No. 2342530, etc.).

[Problems to be Solved by the Invention] In order to improve the output performance of a four-cycle engine in its high-speed operating range, the number of exhaust valves and exhaust valves per engine has been increased.

By the way, when three intake valves or three exhaust valves are provided per cylinder, if the above-mentioned conventional technology is adopted as is, the cylinder head bolts will be installed at wider intervals, resulting in the engine crankshaft There is a problem that the dimension in the direction becomes long.

The present invention has been made in view of the problems of the prior art, and its purpose is to provide a compact engine with excellent sealing performance by narrowing the spacing between the cylinder head bolts. This is what we are trying to provide.

[Means for Solving the Problems] In order to achieve the above object, the four-stroke engine of the present invention opens and closes the valves by a cam of a camshaft via a rocker arm, and the valves on both sides are compared with the intermediate valve. The cylinder head bolt is arranged close to the center of the cylinder in a direction perpendicular to the camshaft, and on the outer side of the rocker arm that opens and closes the valves on both sides and close to the rocker arm.

[Function] Since the valves on both sides are closer to the center of the cylinder in the direction perpendicular to the camshaft than the valve in the middle, the cylinder is placed close to the rocker arm on the outside of the rocker arm that opens and closes the valves on both sides. A roller is created to secure a space for installing the head bolt, and by arranging the cylinder head bolt here, the distance between the cylinder head bolts can be narrowed.

[Example] Embodiments of the invention will be described below with reference to the drawings.

The drawing shows one cylinder of a 4-cycle engine, where a is the cylinder, b is the cylinder head, 1 is the intake passage, and 2 is the cylinder head.
is the exhaust passage.

3 is the combustion vE formed on the lower surface of the cylinder spatula l''b.
It is a chamber, and an intake passage 1 and an exhaust passage 2 are open.

Reference numeral 4 denotes a screw hole for attaching a spark plug, which opens at the center of the upper surface of the combustion chamber 3.

5 is an intake valve that opens and closes the intake passage 1, and 6 is an exhaust valve that opens and closes the exhaust passage 2.

These intake valves 5 and exhaust valves 6 have umbrella portions at their lower ends facing the combustion chamber 3 and corresponding to the opening ends of the intake passage 1 and exhaust passage 2, respectively, and the middle portions are closed. - Supported via 5a and 6a on the wall surface of cylinder head b for free IH movement.

7.8 is a spring that urges the valves 5 and 6 in the valve-closing direction.

9 and 1O are camshafts for driving the valves 5 and 6, which are rotatably held between the upper end of the cylinder head b and the cam caps 11 and 12, respectively.

13 is the front 5d camshaft 9, 10 and cam cap 11.1
2, and is connected to the upper end of the cylinder head b.

This four-stroke engine is provided with three intake valves 5 and two exhaust valves 6 per cylinder in order to improve its output performance.

In addition, the arrangement structure of the three intake valves 5 is such that the middle intake valve is closer to the axis of cylinder a than the intake valves on both sides.
The combustion chamber 3 is faced to the combustion chamber 3 with a small inclination relative to the combustion chamber 1.

That is, if the inclination angle of the middle intake valve 5 is α1, and the inclination angle of the intake valves 5 on both sides is α2, then α1<α2.

Further, the three intake valves 5 are arranged such that their upper ends are located on substantially the same straight line 13 parallel to the axis 12 of the camshaft 9.

Therefore, as shown in FIG. 2, the intake valve 5 is arranged along the center line 14 that separates the intake side from the iJl: electric control in the combustion chamber 3, with the middle valve being deviated outward from the valves on both sides. Therefore, the valves 5 do not interfere with each other.

Further, each of the intake valves 5 is connected to a camshaft 9, and a rocker arm 14 is used as the connection means.

Each end of the three arms 14a of this rocker arm 14 is in contact with the upper end of each intake valve 5, and is extended downwardly outside the engine while the other end is attached to the cylinder head b. The cam 9a of the camshaft 9 is in contact with the upper surface of the intermediate portion of the cam shaft 9.

If the structure is such that one rocker arm 14 drives three intake valves 5, the cam 9a provided on the camshaft 9 can be eliminated, and the operation of each intake valve 5 can be reliably synchronized. can.

Note that as a means for connecting the intake valves 5 to the camshaft 9, an independent rocker arm 15 may be used for each valve 5 as shown in FIGS. 5 and 6.

In this case, each rocker arm 15 has a substantially equal distance from the camshaft 9h) to the upper end of each intake valve 5, so it is possible to use the same shape. The cams 9a can also have the same shape.

On the other hand, as the intake valve 5 is arranged as described above, the middle one of the intake passage 1 has a smaller inclination with respect to the axis 11 of the cylinder a than that of the Ql+ one, so that the combustion chamber 3 and the cylinder a It comes within.

If such a structure is adopted, as shown in FIG. 7, within the cylinder a, the intermediate intake path "#
The intake air flow s3 from J1 flows in, which pushes down the former intake air flows S+, S2 and collides with the piston C, and thereafter the flow in the cylinder a is maintained, so that the intake air flows S l, S i! , S3 does not stagnate on the way, and the intake air flow sl, S2. This allows the flow of S3 to be maintained smoothly.

When arranging the cylinder heads 17.17 on the outside of the intake valves 5 on both sides, the intake valves 5 on both sides are placed in the center of the cylinder a in the direction perpendicular to the camshaft 9 compared to the intake valve 5 in the middle. Since the cylinder head bolts are arranged close to each other, a space for installing the cylinder head bolt is secured on the outer side of the rocker arm 14 or 15 that opens and closes the intake valves 5 on both sides and close to the rocker arm.

1, when the cylinder head bolts 17 are disposed in the space, the distance between the cylinder head bolts 17 and 17 will be considerably narrower.

On the other hand, two exhaust valves 6 are provided, and are arranged on a straight line 15 parallel to the center line 14 in the combustion chamber 3.

The 11L air valves 6 are set to have the same inclination angle α3 with respect to the axis 11 of the cylinder a, and their upper ends are connected to the camshaft 1o via rocker arms 16, respectively.

Although there are two exhaust valves 6, they will not interfere with each other even if they are arranged in series within the combustion chamber 3.

In the above embodiment, two exhaust valves 6 are provided, but the exhaust valve 6 also has the intake valve 5.
Three cylinder head bolts can be provided if the arrangement is similar to the above, and in this case, the distance between the two cylinder head bolts on the exhaust valve 6 side can be narrowed.

[Effects of the Invention] In this invention, when three intake or exhaust valves are provided, the valves on both sides are closer to the center of the cylinder in the direction perpendicular to the camshaft than the valve in the middle. A space for installing cylinder head bolts is secured on the outside of the rocker arm that opens and closes, close to the rocker arm, and the cylinder head bolts can be installed in this space. Since it is considerably narrower, a compact engine with excellent sealing performance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of an engine according to the present invention;
Figure 2 is a sectional view taken along the line n-II in Figure 1, Figure 3 is a sectional view taken along the line rn-m in Figure 2, Figure 4 is a sectional view taken along the line IV-rV in Figure 3, and Figure 5 is a sectional view taken along the line A vertical cross-sectional view showing a modified example of the arm,
FIG. 6 is a sectional view taken along the line Vl--Vl in FIG. 5, and FIG. 7 is a schematic diagram showing the flow of intake air within the cylinder. a...Cylinder, b...Cylinder head, l...
Intake passage, 2... Exhaust passage, 3... Combustion chamber, 5...
- Intake valve, 6... Exhaust valve, 9.10... Camshaft, 9a, 10a - Cam, 14, . 15.16...
Rocker arm, 17... Cylinder head bolt, 1 Bi... Cylinder axis, α Bi... Inclination angle of middle intake valve, α2... Inclination angle of intake valves on both sides. Patent applicant Yamaha Motor Co., Ltd. agent Patent attorney Art supplies Mikio

Claims (1)

[Claims] In a four-stroke engine having three intake valves or three exhaust valves per cylinder, the valves are opened and closed by a cam on a camshaft via a rocker arm, and the valves on both sides are closer to the camshaft than the middle valve. A four-stroke engine characterized in that a cylinder head bolt is disposed close to the center of the cylinder in the right angle direction and close to the rocker arm on the outside of the rocker arm that opens and closes valves on both sides.