JPH03189360A - Dohc engine - Google Patents

Abstract

PURPOSE:To reduce protrusion of a head cover and to improve maintainability of a head bolt by mounting cams to the end parts of suction and exhaust shafts and positioning the head bolt in the vicinity of a line for interconnecting suction and exhaust cam covers. CONSTITUTION:Suction and exhaust cams 13a' and 13b' are mounted to the end parts of suction and exhaust cam shafts 14a and 14b. The walls on the cylinder side of suction and exhaust chambers 5a and 5b and suction and exhaust cam covers 7a and 7b are formed in the shape of an uneven surface. A head bolt 12 by means of which a cylinder head 4 is securely fastened against the cylinder block side is arranged outside the suction and exhaust cam covers 7a and 7b and in a recessed part on the cam shafts 14a and 14b side. A head bolt 12' at the end part in an axial direction of the cam shaft is positioned in the vicinity of a line for interconnecting the end surfaces of the suction end exhaust cam covers 7a and 7b. This constitution reduces protrusion of a head cover through prevention of extension of the cam shaft and improves maintainability.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a DOHC engine in which an intake camshaft and an exhaust camshaft are arranged in parallel above a plurality of cylinders arranged in parallel, and in particular, axial dimension) and improve maintainability of head bolts.

[Conventional technology]

Recently, DOHC engines have been commercially available in which intake valves and exhaust pulp are driven by independent intake camshafts and exhaust camshafts, respectively. This DOHC engine takes air into the upper part of the combustion chamber in the cylinder head.

An exhaust cam chamber is formed, which is covered with an intake and exhaust cam cover, and an intake cam shaft and an exhaust cam shaft are arranged parallel to each other in each cam chamber, and the cam formed on each cam shaft controls the intake and exhaust air of each cylinder. Configured to drive pulp.

[Problem to be solved by the invention]

However, in the DOHC engine, the camshaft becomes longer depending on the bearing position of each camshaft and the formation position of the cam, which causes the head force bar to become wider and the engine width to increase. Depending on the arrangement position of the head bolt fixed to the block side, a problem arises in that maintainability such as retightening of the head bolt is deteriorated.

The present invention has been made to solve the above conventional problems, and provides a DOHC engine that avoids the extension of the camshaft, reduces the protrusion of the head cover, and improves the maintainability of the head bolts. The purpose is to

[Means to solve the problem]

In the present invention, intake and exhaust cam chambers are formed above a plurality of cylinders arranged in parallel, and air is taken into each of the cam chambers.

A direct-acting DOHC in which the exhaust camshafts are arranged in parallel, each cam chamber is covered with an intake and exhaust cam cover, and each cam formed on the intake and exhaust camshafts directly drives the intake and exhaust valves. In the engine, a cam for the cylinder at the end is provided at the end of each of the camshafts, and the intake air,
Exhaust cam chamber and intake.

The cylinder side wall of the exhaust cam cover is formed into an uneven shape, and the head bolts for tightening and fixing the cylinder head to the cylinder block side are arranged in a concave part outside the intake and exhaust cam cover and on the camshaft side, and It is characterized in that the head bolt at the end is located near the line connecting the end surfaces of the intake and exhaust cam covers.

[Effect]

According to the DOHC engine according to the present invention, since the cam for the cylinder at the end of the camshaft is provided, that is, each camshaft is supported so that the cam at the end overhangs, the cam There is no need to provide a cam bearing at the end of the shaft, so the length of the camshaft can be shortened accordingly, the overhang of the head cover can be suppressed, and the engine width can be narrowed.

In addition, the head bolts are placed outside the intake and exhaust cam covers in a concave area, allowing the camshaft to move closer to the center of the cylinder, making the engine more compact, and also allowing the head bolts to be placed in an ideal position, equidistant from the center of the cylinder. .

In addition, since the head bolts are placed in the concave portion, the head bolts at the ends in the camshaft direction can be placed near the line connecting the end faces of each cam cover, that is, closer to the inside of the engine, which also helps reduce the engine width. can.

Furthermore, since the head bolts are placed outside the cam cover, the head bolts can be retightened with the cam cover attached, which improves maintainability accordingly.

〔Example〕

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

FIGS. 1 to 4 show a DOHC according to an embodiment of the present invention.
FIG. 1 is a plan view of the engine with the head cover removed, and FIG. 2 is a plan view of the engine with the head cover removed.
3 and 4 are a left side view and a front view of a motorcycle equipped with the engine of this embodiment. Note that FIGS. 1 and 2 show only the right half when viewed in the traveling direction (direction A), and the left half has a symmetrical structure with respect to the right side.

In the figure, reference numeral 20 denotes a motorcycle equipped with the engine of this embodiment, in which a body frame 21 supports a front fork 22 that pivots the front wheel 2 so as to be steerable left and right, and also supports the rear wheel 3 pivotably. A supporting rear arm 23 is pivotably supported vertically, the engine unit 1 is suspended and supported at the center of the vehicle body frame 21, and a fuel tank 24 is mounted above the engine and a seat 25 is mounted behind it. It has become.

The engine unit 1 includes a cylinder block 28. This is an air-cooled 4-cycle parallel 4-cylinder DOHC engine in which cylinder heads 4 are stacked and fastened with head bolts 12, and the upper surfaces of the cylinder heads 4 are covered with a head cover 7.

In the cylinder block 28, four cylinders (cylinder bores) 8 are formed in parallel with a central chain chamber in between. A combustion recess 4a that forms a combustion chamber with a piston disposed within the cylinder 8 is provided.

In each combustion recess 4a, two intake valves 9, 9 and two exhaust valves 10, 10 are arranged for each cylinder.
Further, a spark plug 11 is inserted into the center thereof.

and the above-mentioned intake valve 9. The valve stems of the exhaust valve 10 extend into an intake cam chamber 5a and an exhaust cam chamber 5b, which are formed in the upper part of the cylinder head 4, respectively.

The intake cam chamber 5a and the exhaust cam chamber 5b each extend in the vehicle width direction to approximately the same width as the cylinder head 4, and communicate with each other through a chain chamber 6 formed in the center. Further, the intake cam chamber 5a and the exhaust cam chamber 5b are arranged such that both the cam chambers 5a,
Each cylinder 8 is formed in such a size that it faces upward from between Sb. Also, the cylinder side wall (inner wall) of each cam chamber 5a, 5b
A recessed portion consisting of an inclined wall 5C inclined toward each of the camshafts 14a and 14b is formed in the camshaft.

An intake cam shaft 14a and an exhaust cam shaft 14b are arranged in parallel in the intake cam chamber 5a and exhaust cam chamber 5b, respectively. A driving sprocket 16 is formed at the center of the intake camshaft 14a and the exhaust camshaft 14b, and two intake cams 13a and two exhaust cams 13b are formed for each cylinder.

Intake cams 13a' and exhaust cams 13b at both left and right ends
' are located at the outermost left and right ends of the intake camshaft 14a and the exhaust camshaft 14b, respectively.

The intake camshaft 14a and the exhaust camshaft 14b are connected to a cam bearing 15 disposed between the two cams of each cylinder.
It is supported by a shaft. The cam bearing 15 is composed of a head-side bearing part 15a integrally formed with the cylinder head 4, and a bearing cap 15b detachably attached to the bearing part 15a with bolts 15C. Valve lifters 2 are disposed on both sides of the portion 15a.
A recess 15d is formed to avoid interference with 9. This valve lifter 29 is attached to the upper end of each valve 9.10, and thereby each cam 13a, 13b
A direct-acting valve mechanism is constructed that transmits the rotation of the valves 9 and 10 to each valve 9 and 10 via the valve lifter 29, and raises and lowers these to open and close the intake and exhaust ports.

Further, a stepped portion 17 is protruded in the shape of a flange between the two cylinders 8.8 on the right side of the intake camshaft 14a and the exhaust camshaft 14b. This stepped portion 17 corresponds to the cylinder head 4.
The camshafts 14a and 14a are slidably positioned in a sliding groove 30a of a thrust receiving portion 30 integrally formed with the camshafts 14a and 14a, respectively.
Axial movement of 14b is prevented.

Further, the head cover 7 is H-shaped, which is formed by connecting an intake cam cover 7a that covers the intake cam chamber 5a and an exhaust cam chamber 5b, and an exhaust cam cover 7b with a chain chamber cover 70 that covers the chain chamber 6, Both base surfaces are formed to match. In this way, the portion of the cylinder head 4 between the intake and exhaust cam covers 7a and 7b forms an outwardly open space C that is open to the outside. The head cover 7 has a damper 31 attached thereto.
Insert the mounting bolt 31 into the above bearing cap 15b.
It is fixed on the cylinder head 4 by screwing into the cylinder head 4.

Now, turn the cylinder 4. The head bolt 12 for fastening the cylinder block 28 is located outside the head cover 7, that is, between the intake cam cover 7a and the exhaust cam cover 7b, and at a position corresponding to each of the inclined walls 5c.
Alternatively, it is located in a concave portion formed by the inclined wall 5c.

As a result, each head bolt 12 is connected to each camshaft 14a.
, 14b, and are arranged in a staggered manner with the cam bearing 15. Furthermore, among the head bolts 12,
The head bolts 12' located at both ends in the camshaft direction are located on the left and right end surfaces of the intake and exhaust cam covers 7a and 7b, that is, on the left side of the intake and exhaust cam chambers 5a and 5b.

It is located on the line connecting the right end faces.

Next, the effects of this embodiment will be explained.

In the engine 1 of this embodiment, the intake and exhaust camshafts 14a, 1
Intake and exhaust cams 13a'13b' are provided at both ends of 4b,
Since the inner cam bearing 15 supports the cam in an overhanging manner, there is no need to provide a bearing located further outside of each of the cams 13a' and 13b', such as the cam bearing 15'. By avoiding extension of the camshaft, the protrusion of the head cover 7 can be reduced compared to the conventional head cover 7'. Therefore, interference of the rider M's feet with the head cover 7 can be avoided, and the degree of freedom in riding posture can be increased.

In addition, an inclined wall 5C is formed on the inner wall of the intake and exhaust cam chambers 5a and 5b.
, and the head bolt 12 was placed in that part.
Even if the valve angle is narrowed, a wide interval between the cam chambers 5a and 5b can be ensured, that is, the outward open space C can be expanded, and cooling performance can be ensured.

Further, the degree of freedom in the arrangement position of the head bolt 12 is expanded, so that, for example, the head bolt 12 can be arranged closer to the center of the cylinder 8, and the engine head becomes more compact. Further, the distance d' from the center of the cylinder to the head bolt 12' at the end and the distance d from the center head bolt 12 can be set to be the same, and sealing performance can be improved.

Furthermore, since the head bolt 12' at the end is placed on the inclined wall 5C, it can be positioned on the line connecting the end faces of the intake and exhaust cam chambers 5a and 5b, that is, on the inner side. Also, it is possible to avoid expanding the engine width.

In the above embodiment, a 4-valve engine has been described, but the present invention can also be applied to a 2-pulp or 5-valve engine.

[Effects of the Invention] As described above, according to the 001 (C engine) according to the present invention, the cams are provided at the ends of the intake and exhaust camshafts and are supported by overhanging them. Since the head bolts at the end can be placed near the end face of the head cover, this has the effect of avoiding expansion of the engine width, and also allows the head bolts to be placed near the end of the head cover.
Since it is placed in the concave part formed by the outer sloped wall of the exhaust cam cover, the valve included angle can be narrowed, and the position of the head bolt can be freely set while ensuring maintainability of the head bolt.

[Brief explanation of drawings]

FIGS. 1 to 4 show a DOHC according to an embodiment of the present invention.
FIG. 1 is a plan view with the head cover removed, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIGS. 3 and 4 are views of the present embodiment. Left side view of a motorcycle equipped with an engine. It is a front view. In the figure, 1 is a DOHC engine, 4 is a cylinder head, 5C is an inclined wall (concave part), 7a and 7b are intake and exhaust cam covers, 8 is a cylinder, 9 and 10 are intake and exhaust valves, 12 is a head bolt, 12 ' is the head bolt at the end in the cam axis direction, 13a, 13b are the cams, 13a', 13b'
Intake and exhaust cams for the left and right cylinders, 14a and 14b are intake and exhaust cam shafts, 28 is a cylinder block, and D is a line connecting the ends of both force bars. Figure 1

Claims (1)

[Claims] (1) Intake and exhaust cam chambers are formed above multiple cylinders arranged in parallel, intake and exhaust cam shafts are arranged in parallel within each cam chamber, and each cam chamber is covered with an intake and exhaust cam cover. , in a direct-acting DOHC engine in which the intake and exhaust valves are directly driven by each cam formed on the intake and exhaust camshafts, a cam for the cylinder at the end is provided at the end of each of the camshafts, The cylinder side walls of the intake and exhaust cam chambers and the intake and exhaust cam covers are formed in an uneven shape, and the head bolts for tightening and fixing the cylinder head to the cylinder block side are formed in a concave shape on the outside of the intake and exhaust cam covers and on the camshaft side. The DOHC is characterized in that the head bolt at the end in the camshaft direction is located near a line connecting the end surfaces of the intake and exhaust cam covers.
engine.