JPH04214921A - Dohc multiple cylinder engine for motorcycle - Google Patents

Abstract

PURPOSE:To obtain a DOHC multiple engine for a motorcycle with which the cooling effect by a blow hole can be improved by setting the blow hole while securing a length of a cam cap tightening bolt sufficently. CONSTITUTION:Four cylinders 6 are disposed in order, two intake valves 7 for each cylinder are disposed in a cam shaft direction, and a intake port 7a to guide an aperture for both valves to a cylinder head outer wall is formed in a cylinder head 1. Two intake cam noses 11d for driving the intake valves 7 are formed for each cylinder in a intake cam shaft 10b, and a intake cam bearing 12b is disposed between the intake cam noses 11d, 11d. A blow hole 15b connected with a cylinder head back wall is formed from a center recess 3a in the cylinder head 1 at a part between the intake ports 7a, 7a in the cylinder head 1.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a DOHC for motorcycles.
The present invention relates to a multi-cylinder engine, and particularly to a cooling structure that can improve the cooling performance of the cylinder head portion.

0002

[Prior Art] As a DOHC multi-cylinder engine for a motorcycle, for example, four cylinders are arranged in parallel in the vehicle width direction, and each cylinder is provided with two intake valves and one exhaust valve for a total of three. There is one in which the intake and exhaust valves are driven by independent intake and exhaust camshafts. When an air-cooling system is used to cool the engine from the outside using running wind, conventionally, an air hole is formed in the cylinder head that communicates with the rear surface of the cylinder wall from the central concave part of the cylinder head. Some head covers are designed to improve cooling performance by introducing running air from above the head cover into the central recess and exhausting it rearward through the air holes.

0003

[Problem to be Solved by the Invention] However, the above-mentioned DOHC has two intake valves per cylinder, and each intake valve is driven to open and close by an independent intake camshaft.
When the above-mentioned air hole is formed in the engine, there is a problem that it is difficult to make the air hole large depending on the arrangement position of the bearing of the camshaft, and sufficient cooling performance cannot be ensured. One reason for this is, for example, when the bearing of the camshaft is placed between the cylinders, the boss of the tightening bolt of the cam cap that makes up the bearing protrudes into the area where the air hole is provided. . Particularly in the case of a direct-acting engine in which each valve is directly opened and closed by the camshaft via a tappet (valve lifter), force acts in the direction of pushing up the camshaft, so the above-mentioned boss is used to more reliably support the camshaft. It is necessary to form the part deeper, and as a result, there is a problem that the air hole becomes even smaller. The present invention was made to solve the above-mentioned conventional problems, and it is possible to set a large air hole while ensuring a sufficient length of the cam cap tightening bolt, and as a result, the cooling effect of the air hole can be further improved. DOH for motorcycles
The purpose is to provide a C multi-cylinder engine.

0004

[Means for Solving the Problems] The present invention arranges a plurality of cylinders in parallel, arranges two valves of the same type for each cylinder in the camshaft direction, and provides openings for both valves in the cylinder head. A port leading to the outer wall is formed, two cam noses for each cylinder are formed on the camshaft to drive the respective valves, a cam bearing is arranged between the two cam noses, and a portion of the cylinder head between the ports for each cylinder is provided with a cam bearing. A DO for a motorcycle characterized by forming an air hole communicating from the cylinder head central recess to the cylinder head outer wall.
It is an HC multi-cylinder engine. Here, the present invention is applicable to a 3-valve engine in which each cylinder has two intake valves and one exhaust valve, for a total of three valves, and a four-valve engine in which each cylinder has two intake valves and two exhaust valves in total, for a total of four. It can be applied to anything. The air holes of the present invention are formed on the intake side in the case of the 3-valve engine, and on either or both of the intake and exhaust sides in the case of the 4-valve engine.

[0005]

[Operation] According to the DOHC multi-cylinder engine for motorcycles according to the present invention, the cam bearing is arranged between the two cam noses provided per cylinder, and the air hole is formed between the ports for each cylinder, so that the cam cap can be tightened. This means that the bolt boss and the air hole are offset in the camshaft direction. Therefore, even if the boss portion is formed large and deep, the air hole can be set large regardless of this, and as a result, the amount of running air introduced can be increased while reliably supporting the camshaft.
The cooling performance of the upper part of the cylinder can be greatly improved.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 3 are diagrams for explaining a DOHC four-cylinder engine for a motorcycle according to an embodiment of the present invention, and FIG. 1 is a plan view showing only the left half of the engine of the embodiment with the head cover removed. , FIG. 2 is a front view of the above engine partially cut away and seen from the exhaust side, and FIG. 3 is a left side view showing a motorcycle equipped with the above engine with a rider M riding on it.

In FIG. 3, reference numeral 50 denotes an air-cooled DOHC four-cylinder engine, which is mounted so that each cylinder is aligned in the width direction of the vehicle, that is, parallel to the body. This engine 50 is constructed by stacking a cylinder block 50b, a cylinder head 1, and a head cover 5 on top of a crankcase 50a, and fixing each with bolts. Further, 60 is a front wheel, and 70 is a rear wheel.

In FIGS. 1 and 2, the cylinder head 1 is fixed to the cylinder block 50b by head bolts 2a to 2c. Furthermore, exhaust and intake cam chambers 3a and 3b are formed in the front and rear parts of the upper part of the cylinder head 1, respectively, and the part between the exhaust and intake cam chambers 3a and 3b has a central recess 3c that is open to the outside.
The head bolts 2a to 2c tighten the bottom portion of the central recess 3c. A chain chamber 4 is formed in the upper widthwise center of the cylinder head 1, and the chain chamber 4 communicates with the cam chambers 3a and 3b. These cam chambers 3a, 3b and chain chamber 4 are removably covered with the head cover 5,
This head cover 5 has a substantially H shape.

A total of four cylinders 6 are provided in parallel in the lower part of the central recess 3c of the cylinder block 50b, two on each side with the chain chamber 4 in between. In addition, in the upper part of each cylinder 6 of the cylinder head 1, there are two intake valves 7 per cylinder on the rear side of the machine body.
, 7, one exhaust valve 8 per cylinder is provided on the front side of the fuselage, biased toward the chain chamber 4 side, and one spark plug 9 is provided biased toward the opposite side of the exhaust valve 8. It is being The cylinder head 1 also has one exhaust port 8a for each cylinder, which leads an exhaust valve opening opened and closed by the exhaust valve 8 to the front surface of the cylinder wall, and an intake valve opening opened and closed by the intake valve 8, which leads to the rear surface of the cylinder wall. One intake port 7a is formed for each cylinder. When viewed from above the engine, the exhaust port 8a extends substantially straight in the longitudinal direction of the vehicle, while the intake port 7a extends obliquely toward the chain chamber 4 side.

Exhaust and intake camshafts 10a and 10b are disposed in the exhaust and intake cam chambers 3a and 3b, respectively. Sprocket 13 placed and fixed on the part
is driven by the crankshaft via. In addition, the above exhaust,
The exhaust valve 8 is located below the intake camshafts 10a and 10b.
, exhaust and intake tappets (valve lifters) 11a and 11b attached to the upper end of the intake valve 7 are located. The exhaust camshaft 10a is formed with one exhaust cam nose 11c for each cylinder, which presses the exhaust tappet 11a, and the exhaust camshaft 10a is located between the exhaust cam noses 11c on the left side of the chain chamber 4. A thrust stop portion 14a is integrally formed. This thrust stop 14
Axial movement of a is restricted by a thrust receiving portion 14c formed in the exhaust cam chamber 3a. And the above exhaust camshaft 1
0a is pivotally supported by an exhaust bearing 12a arranged to sandwich the exhaust cam noses 11c, 11c therebetween, and this bearing 12a is positioned to sandwich the exhaust ports 8a, 8a.

Further, the intake camshaft 10b is formed with two intake cam noses 11d for each cylinder, which press the intake tappet 11b.
is an intake cam nose 11d provided for each cylinder,
It is pivotally supported by an intake bearing 12b arranged between 11d and 11d. A cam cap constituting the upper half of this intake bearing 12b is bolted and fixed to the cylinder head side with tightening bolts 12c and 12d. Here, the rear tightening bolt 12d is disposed outside the intake port 7a and in a position overhanging the rear, whereas the front tightening bolt 12c is located above the intake port 7a. . Therefore, there is a possibility that the front tightening bolt 12c cannot be made very long, but the front part of the intake port 7a is located near the mating surface of the cylinder head 1, and there is a sufficient distance between it and the bottom of the intake cam chamber 3b. Since there is a gap, there is no problem in increasing the length of the tightening bolt 12c. Further, a thrust stop portion 14b is formed in the inter-cylinder portion of the intake camshaft 10b, and this is engaged with a thrust receiving portion 14d formed in the inter-cylinder portion of the cylinder head 1. This prevents the intake camshaft 10b from moving in the axial direction.

Exhaust side air holes 15a are provided below the exhaust cam chamber 3a of the cylinder head 1, in a portion between adjacent exhaust ports 8a, and in a portion between the exhaust port 8a and the chain chamber 4. This exhaust side air hole 15a is shown in Figure 1.
As shown by the broken line in FIG. 2, the through hole is provided as a through hole that extends close to the exhaust valve 8, which has the highest temperature in the engine, and communicates the front wall surface of the cylinder head 1 with the central recess 3c. Adjacent intake ports 7a, 7a below the intake cam chamber 3b of the cylinder head 1
An intake side air hole 15b is provided in the intermediate portion. This intake side air hole 15b communicates the rear wall surface of the cylinder head 1 with the central recess 3c, as shown by the broken line in FIG.

Next, the effects of this embodiment will be explained. In the engine 50 of this embodiment, a part of the running air flows from the front of the engine through the exhaust side air hole 15a or over the exhaust side portion of the head cover 5, and is introduced into the central recess 3c of the cylinder head 1, and is introduced into the central recess 3c of the cylinder head 1, and is introduced into the central recess 3c of the cylinder head 1. It is discharged to the rear of the engine through the side air hole 15b.

As described above, in this embodiment, the cooling performance can be improved by causing the running air to flow through the central recess 3c of the cylinder head 1, but the air holes 15a and 15b functioning as described above are , for the following reasons, can be set larger, so that the amount of traveling air passing through the center recess 3c can be increased, and the cooling performance of the upper part of the engine can be greatly improved. By improving the cooling performance by the air holes 15a and 15b, it is possible to prevent blow-through of the cylinder head gasket due to thermal deformation.

First, regarding the exhaust side air hole 15a, the exhaust bearing 12a that pivotally supports the exhaust camshaft 10a is connected to the exhaust port 8.
a, 8a, and exhaust side air hole 1.
5a is arranged between the exhaust ports 8a, 8a, there is no interference, and therefore the exhaust side air hole 15a can be set large without any problem.

Regarding the intake side air hole 15b, there are two intake bearings 12b for each cylinder that pivotally support the intake camshaft 10b.
Since the intake cam nose 15b is arranged between the two intake cam noses 11d and 11d, that is, above the intake port 7a, and the intake side air hole 15b is arranged between the intake ports 7a and 7a, the intake side air hole 1
5b are the tightening bolts 12c and 12d of the intake bearing 12b.
Therefore, this intake side air hole 15b
can be set larger without any problem.

Furthermore, in this embodiment, the intake bearing 12b
The tightening bolts 12c and 12d are connected to the intake side air hole 15.
Since the rear tightening bolt 12d is located outside the intake port 7a, the front tightening bolt 12c is located near the mating surface of the intake port 7a as described above. Since the intake cam shaft 10b is located at a large distance from the intake cam chamber 3b, the length of each tightening bolt can be increased, and the intake cam shaft 10b can be reliably supported. The fact that the intake camshaft 10b can be supported reliably in this manner is particularly effective when a direct-acting valve mechanism is employed in which the intake tappet 11b is directly pressed by the intake cam nose 11d as in this embodiment. That is, in the case of a direct-acting type, a force acts in a direction that pushes the camshaft upward, so it is necessary to support the camshaft more firmly, but this embodiment can meet this requirement.

FIG. 4 is a diagram for explaining another embodiment of the present invention. In this embodiment, the uneven distribution relationship between the exhaust valve 8 of the cylinder 6 located on the side of the chain chamber 4 and the spark plug 9 is opposite to that of the above embodiment. That is, the uneven distribution relationship between the exhaust valve 8 and the spark plug 9 is that the cylinder 6 is located on the chain chamber 4 side, and the cylinder 6' is located on the outer wall side.
In the former cylinder 6, the spark plug 9 is located on the chain chamber 4 side and the exhaust valve 8 is located on the opposite side, and in the latter cylinder 6', the exhaust valve 8 is located in the adjacent cylinder. On the 6 side, a spark plug 9 is located so as to be unevenly distributed on the outer wall side. Since the exhaust valve 8 of the cylinder 6 on the side of the chain chamber 4 is arranged away from the chain chamber 4, the gap between the exhaust port 8a on the side of the chain chamber 4 and the chain chamber 4 is widened, and a The exhaust side air hole 15a' can be set wider.

[0019]

As described above, according to the DOHC multi-cylinder engine for motorcycles according to the present invention, two camshafts are provided for each cylinder, and the portion between the cam noses is pivotally supported, and the camshaft is provided between the ports of each cylinder. Since the air hole is formed, the air hole can be set large while reliably supporting the camshaft, which has the effect of greatly improving the cooling performance of the upper part of the engine.

[Brief explanation of the drawing]

FIG. 1: DOHC for motorcycles according to an embodiment of the present invention
FIG. 2 is a plan view of a cylinder head of a four-cylinder engine with a head cover removed.

FIG. 2 is a partially sectional front view of the engine of the above embodiment.

FIG. 3 is a left side view of a motorcycle equipped with the engine of the above embodiment.

FIG. 4 is a plan view of a cylinder head showing another embodiment of the present invention.

[Explanation of symbols]

1 Cylinder head 3c Center recess 6 Cylinder (cylinder) 7 Intake valve (same type of valve) 7a　Intake port 10b Intake camshaft 11d Intake cam nose 12b Intake bearing 15b Wind hole 50 engine

Claims (1)

[Claims] Claim 1: A plurality of cylinders are arranged in parallel, two valves of the same type are arranged in the camshaft direction for each cylinder, and a port is formed in the cylinder head to lead out the openings for the two valves to the outer wall of the cylinder head. , two cam noses for each cylinder are formed on the camshaft to drive the respective valves, a cam bearing is arranged between the two cam noses, and a portion of the cylinder head between the ports for each cylinder is connected from the cylinder head center recess to the cylinder head outer wall. A DOHC multi-cylinder engine for a motorcycle, characterized by forming an air hole that communicates with the