JPH04214911A - Dohc parallel multiple cylinder engine - Google Patents

Abstract

PURPOSE:To provide a DOHC parallel multiple cylinder engine in which a valve hold angle can be set small while restricting enlargement of an engine width. CONSTITUTION:Two cylinders 6 are disposed in parallel on each of a right side and a left side of cam chains for driving a camshaft, and intake and exhaust camshafts 10b, 10a are disposed in parallel having a line connecting the centers of the cylinders 6 between them. Two intake valves 7 are disposed for each cylinder in parallel to the intake camshaft 10b, while two intake cam noses 11d for driving the two intake valve 7 are formed for each cylinder, and an intake cam bearing 12b is disposed between the cam noses 11d, 11d. Head bolts 2b, 2a, 2c for tightening a cylinder head to a cylinder block are disposed at deflected positions toward the camshafts 10b, 10a between the cylinders, on the outer side of the outer end cylinder, and between a cam chain chamber 4 and the adjacent cylinder. A thrust stop part 14b is formed between the cylinders 6, 6 on the left side of the intake camshaft 10b, and a thrust bearing part 14d to be stopped at the thrust stop part 14b is disposed between the cylinders 6, 6.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a DOHC parallel multi-cylinder engine suitable for use in motorcycles, for example, and in particular, when a center cam chain system is adopted, the engine width (length in the cam axis direction) can be made compact, and the valve This invention relates to a cam bearing that can reduce the included angle of the cam bearing, and to an improvement in the arrangement position of the thrust stop.

0002

[Prior Art] As a DOHC parallel multi-cylinder engine, for example, four cylinders are arranged in parallel, and each cylinder is provided with two intake and two exhaust valves, for a total of four.
Some engines have separate intake and exhaust camshafts that open and close the exhaust valves, and a cam chain that drives both camshafts is located in the center of the engine.
(See Publication No. 81). Furthermore, in the engine described in this publication, the portions of the camshafts between the cylinders are supported by bearings, and the thrust load is supported in the portions of the camshafts between the cam chain chambers and the adjacent cylinders. A thrust stop is formed in the cylinder head, and a thrust receiving part is formed in the cylinder head to be engaged with the thrust stop.

0003

[Problems to be Solved by the Invention] However, in the case of the engine described in the above publication, since the thrust stop part and the thrust receiving part are formed adjacent to the cam chain chamber in the center of the engine, the cylinder adjacent to the cam chain chamber A space is required to form the above-mentioned thrust stop and the thrust receiving part that supports it, and space for the head bolt must be secured while avoiding interference with this thrust receiving part. Therefore, there is a concern that the engine width will increase accordingly. Such an increase in engine width is particularly disadvantageous in the case of engines for motorcycles. In order to avoid expanding the engine width and secure space for the head bolts, etc., it is possible to move the camshaft outward in the direction perpendicular to the axis, but this increases the angle between the valves and improves engine performance. It is disadvantageous in terms of improving. The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a DOHC parallel multi-cylinder engine that can reduce the valve angle while suppressing the expansion of the engine width.

0004

[Means for Solving the Problems] The present invention arranges a plurality of cylinders in parallel on one side and the other side of a cam chain for driving a camshaft, and arranges a pair of cylinders in parallel across a line connecting the centers of each cylinder. The camshafts are arranged in parallel, two intake valves or two exhaust valves are arranged in each cylinder substantially parallel to the camshafts, and two cam noses are formed per cylinder for driving the two valves. , a cam bearing is arranged between both cam noses, and a head bolt for tightening the cylinder head to the cylinder block is installed between each cylinder, on the outside of the outer end cylinder, and between the cam chain chamber and the adjacent cylinder, and on the camshaft. A thrust stop portion is formed in a portion between the cylinders on either the one side or the other side of the camshaft, and a thrust receiving portion that is engaged with the thrust stop portion is disposed at a position offset to the side. This is a DOHC parallel multi-cylinder engine characterized by being located in the middle part. Here, the present invention provides a three-valve engine with two intake valves and one exhaust valve per cylinder, a total of three valves, and an intake valve per cylinder.
It can be applied to any four-valve engine that has two exhaust valves each, for a total of four exhaust valves.

[0005]

[Operation] According to the DOHC parallel multi-cylinder engine according to the present invention, since the cam bearing is arranged between the two cam noses provided per cylinder, the thrust stop portion and the thrust receiving portion are located between the cylinders where there is sufficient space. can be provided. Therefore, in order to secure space for a thrust stop between the cam chain chamber and the adjacent cylinder, the width of the engine must be expanded, or the camshaft must be moved in a direction perpendicular to the axis. There is no need to do this, and as a result, it is possible to make the engine width more compact and to narrow the valve angle. In addition, thrust stops etc. were provided between the cylinders, so
The widths on one side and the other side of the cam chain are approximately the same, resulting in good left-right balance of the engine. Incidentally, if a thrust stop or the like is provided adjacent to the cam chain chamber, the width on the side where the thrust stop is provided becomes larger, and there is a concern that the left-right balance may be lost. Furthermore, since the cam bearings are arranged between the two cam noses provided per cylinder, that is, each cylinder is pivotally supported, the intervals between the bearings are approximately equal, and the cam bearings can be more reliably supported.

[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 parallel four-cylinder engine for a motorcycle according to an embodiment of the present invention, and FIG. 1 shows only the left half of the embodiment engine with the head cover removed. 2 is a partially sectional front view of the engine as seen from the exhaust side, and FIG. 3 is a left side view showing a motorcycle equipped with the engine with a rider M riding on it.

In FIG. 3, reference numeral 50 denotes an air-cooled DOHC parallel 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. Further, 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.
It becomes. 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. The cam chambers 3a, 3b and the chain chamber 4 are removably covered by the head cover 5, which 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.

Further, 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 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.

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 pivotally supported by an intake bearing 12b disposed between the intake cam noses 11d, 11d. The cam cap constituting the upper half of this intake bearing 12b has a tightening bolt 12c.
, 12d are bolted and fixed to the cylinder head side. Here, the rear tightening bolt 12d is disposed outside the intake port 7a and at 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, tighten bolt 1
There is no problem in making 2c longer.

A thrust stop 14b is formed in the center between the cylinders 6 and 6 on the left side of the chain chamber 4 of the intake camshaft 10b, and this thrust stop 14b surrounds the entire circumference of the intake camshaft 10b. It is circular. Further, a thrust receiving portion 14d is formed in the intake cam chamber 3b portion of the cylinder head 1, and this thrust receiving portion 14d supports approximately a semicircumference below the thrust stop portion 14b. This prevents the intake camshaft 10b from moving in the axial direction.

Here, the head bolts 2a to 2a for fixing the cylinder head 1 to the cylinder block 50b are
2c tightens the bottom surface of the central recess 3c of the cylinder head 1, the head bolt 2b is attached between the cylinders 6, 6, the head bolt 2a is attached to the outside of the cylinder 6 at the outer end, and the head bolt 2c is attached to the inner cylinder. 6 and the chain chamber 4, and are located offset toward the intake camshaft 10b and exhaust camshaft 10a sides, respectively.

Next, the effects of this embodiment will be explained. In the engine 50 of this embodiment, one exhaust valve 8 is provided per cylinder, whereas two intake valves 7 are provided per cylinder. Therefore, the engine width and valve angle are influenced by the shaft support structure and thrust bearing structure of the intake camshaft 10b. In this embodiment, the intake camshaft 10
Two intake cam noses 11d are formed for each cylinder in b, and an intake bearing 12 is formed between the two cam noses 11d.
b is arranged, there is ample space between the cylinders. Therefore, the thrust stop portion 14b and the thrust receiving portion 14d can be disposed in the above-mentioned extra space without interference with the head bolt 2b. Therefore, the engine width can be made more compact, and since there is no need to move the camshaft outward, the angle between the valves can be narrowed. Incidentally, when a thrust stop part and a receiving part are formed between the inner cylinder 6 and the chain chamber 4, in order to avoid interference with the head bolt 2c located in the part, the inner cylinder 6 and the chain chamber 4 are or move the intake camshaft 10b outward in the direction perpendicular to the axis (see Fig. 1).
This results in an increase in the engine width or valve angle.

Furthermore, in this embodiment, since the thrust stop portion 14b and the thrust receiving portion 14d are formed in the spare space between the cylinders, the lengths of the left and right portions with respect to the chain chamber 4 are the same, and the engine Good left and right balance. Furthermore, two cam noses 11d are formed for each cylinder,
Since the intake bearings 12b are arranged between the intake bearings 11d, the intervals between the intake bearings 12b are approximately the same, and the camshaft can be supported symmetrically, so that there is no difference in the deformation of the camshaft between the left and right sides. , it can be supported more reliably.

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.
There is a difference between In the cylinder 6 on the chain chamber 4 side, the spark plug 9 is located on the chain chamber 4 side, and the exhaust valve 8 is located on the opposite side, so that the exhaust cam nose 11c is also located on the outer wall side. Also, the latter cylinder 6
', the exhaust valve 8 is located on the adjacent cylinder 6 side, and the spark plug 9 is located unevenly on the outer wall side. In addition,
The intake camshaft 10b side is the same as the embodiment shown in FIGS. 1 to 3 above. In addition, in the above embodiment, the thrust receiving part 14
d is formed integrally with the cylinder head 1, but it may be formed separately.

[0018]

As described above, according to the DOHC parallel multi-cylinder engine according to the present invention, two camshafts are provided for each cylinder, and the portion between the cam noses is pivotally supported, and a thrust stop portion is provided between each cylinder. and a thrust receiver, there is no need to widen the gap between the chain chamber and the adjacent cylinder or move the camshaft outward in the direction perpendicular to the axis, making the engine width more compact while narrowing the valve clamping angle. It has the effect of making it more effective.

[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 parallel four-cylinder engine with a head cover removed.

FIG. 2 is a partially sectional front view of the engine of the 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 2a Head bolt 2b on the outside of the outer end cylinder Head bolt 2c between the cylinders Head bolt between the chain chamber and the adjacent cylinder 6 Cylinder (cylinder) 7, 8 Intake and exhaust valves 10a and 10b Intake and exhaust cams Shaft 11d Intake cam nose 12b Intake cam bearing 14b Thrust stop part 14d Thrust receiving part 50 DOHC parallel four-cylinder engine 50b Cylinder block

Claims (1)

[Claims] Claim 1: A plurality of cylinders are arranged in parallel on one side and the other side of a cam chain for driving a camshaft, and a pair of camshafts are arranged in parallel so as to sandwich a line connecting the centers of the cylinders, Two intake valves or two exhaust valves are arranged in each cylinder substantially parallel to the camshaft, two cam noses are formed per cylinder for driving the two valves, and a cam bearing is installed between the two cam noses. The head bolts for tightening the cylinder head to the cylinder block are located between each cylinder, on the outside of the outer end cylinder, between the cam chain chamber and the adjacent cylinder, and at a position offset toward the camshaft. , forming a thrust stop in a portion between the cylinders on either the one side or the other side of the camshaft;
A DOHC parallel multi-cylinder engine, characterized in that a thrust receiver that engages with the thrust stop is located in the inter-cylinder section.