JPH0129964B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a camshaft support device for an overhead camshaft engine, and its purpose is to support the bolts and camshafts that attach a cylinder head to a lower structure such as a cylinder or crankcase. The objective is to eliminate interference with the bearings that are used, and to simplify their configuration.

In general, the position of the mounting bolt for attaching the cylinder head and the position of the bearing bolt for attaching the valve train camshaft to the cylinder head are located between two adjacent cylinder holes, so they tend to interfere with each other. The tendency is for the so-called double overhead cam type (hereinafter referred to as
This is particularly noticeable in the DOHC type engine, where the angle between the intake valve and exhaust valve is narrowed to improve engine performance, and many difficulties are involved in the design to avoid this interference.

This invention actively arranges the mounting bolts of the cylinder head and the bearing bolts of the bearing that supports the valve camshaft on the same axis, so that the mounting bolts also serve as bearing bolts, and the arrangement of the valve cam bearings is improved. It is something that can be done easily.

The present invention will be described below based on illustrated embodiments. The overhead camshaft engine 1 has a crankcase 2.
The cylinder head 4 is attached to the upper part of the cylinder via the cylinder 3, and has two valve drive camshafts, an intake camshaft 5 and an exhaust camshaft 6, which is the so-called DOHC type. These valve drive camshafts are mounted on semicircular bearings 7 formed on the upper surface of the cylinder head 4 and arranged on both sides of the cylinder hole, and held by covering them with bearing caps 8. A valve cam 9 is integrally provided on each valve camshaft, and as is conventionally known, the intake valve 12 or the exhaust valve 13 is moved in the axial direction via a tappet 11, thereby opening the intake passage 1.
4 or the exhaust passage 15 is intermittently communicated with the combustion chamber 16.

Reference numeral 17 denotes stud bolts as mounting bolts, four of which are arranged around the cylinder hole 3a, and their lower ends are tightly screwed into the crankcase 2, which is the lower structure, to prevent them from coming off. The stud bolt 17 passes through the cylinder 3 and the cylinder head 4 and protrudes from the upper surface, and the bolt hole of the bearing cap 8 is fitted into the protrusion and tightened with a nut 18. 19
is a hexagonal bolt that fixes the other end of the bearing cap 8 to the cylinder head 4. That is,
Of the bolts that attach the bearing cap 8 to the cylinder head 4, the bolts located closer to the inner cylinder hole are the stud bolts 17 that tighten and attach the bearing cap 8 and the cylinder head 4 to the lower structure together. The bolt is a hexagonal bolt 19 that attaches only the bearing cap 8 to the cylinder head 4, and this hexagonal bolt 1
The bolt 9 is made sufficiently shorter than the stud bolt 17 within a range where the tightening force of the bearing cap 8 can be obtained.

In addition, in this embodiment, four stud bolts 17 are used as mounting bolts around the cylinder hole 3a,
Two bolts 20 are mounted upward, and six bolts are arranged, but the number of bolts corresponding to the stud bolts 17 may be five or six.
Therefore, cylinder 3 and cylinder head 4
The bolts for attaching the bearing cap to the crankcase 2 and the bolts for attaching the bearing cap 8 can be shared.

As described above, this invention places the mounting bolts of the cylinder head on the immediate outside of the bearing of the valve train camshaft, thereby tightening the cylinder head and bearing cap together, which is different from the conventional one shown in Fig. 3. There is no need for a complicated structure such as screwing together a mounting bolt and a nut on the lower surface of the bearing, and the concentricity of the bearing can be maintained with high accuracy. In addition, since the bolts inside the bearing cap are used as mounting bolts to tighten the cylinder bed together, the mounting bolt can be used to tighten the part of the cylinder head that is close to the cylinder hole, improving the sealing performance of the combustion chamber. be able to. moreover,
Since the outer bolts are short, there is no need to provide holes in the cylinder and cylinder head through which long bolts are inserted, and the cylinder and cylinder head can be made smaller.

[Brief explanation of drawings]

FIG. 1 is a partial plan view of a cylinder head showing an example of an embodiment of the present invention, FIG. 2 is a sectional view thereof, and FIG. 3 is a sectional view corresponding to the above-mentioned cross section showing a conventional configuration. 4... Cylinder head, 7... Bearing, 8... Bearing cap, 17... Stud bolt that is the mounting bolt.

Claims (1)

[Claims] 1. The cylinder head 4 is attached to the lower structure with a mounting bolt, and the semicircular bearings 7, 7 formed in the cylinder head 4 and arranged on both sides of the cylinder hole, and the bearing cap 8 attached to cover the upper surface thereof. In an overhead camshaft type engine that supports two valve drive camshafts 5, 6 which drive intake and exhaust valves with . The bearing caps 8, 8 and the cylinder head 4 are jointly attached to the lower structure by using the bolts closer to the cylinder holes as mounting bolts 17, 17, and the outer bolts 19, 19 are made shorter than the inner bolts to attach the bearing cap. This is a camshaft support device for an overhead camshaft engine, which is made up of 8, 8 attached to a cylinder head 4.