GB2037888A

GB2037888A - Rocker Shaft Fixing Arrangement for Internal Combustion Engines

Info

Publication number: GB2037888A
Application number: GB7942743A
Authority: GB
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1978-12-21
Filing date: 1979-12-11
Publication date: 1980-07-16
Also published as: AU5367179A; JPS5592005U; GB2037888B

Abstract

Rocker shafts 1 are received in part-cylindrical concave recesses 6 in the cylinder head 4 and firmly fixed thereto by bolts or studs in shaft holes 3. <IMAGE>

Description

SPECIFICATION Rocker Shaft Fixing Arrangement for Internal Combustion Engines This invention relates to a rocker shaft fixing arrangement of a valve operating mechanism for internal combustion engines.

A rocker shaft for supporting rocker arms for internal combustion engines has heretofore been fixed to a cylinder head by arrangements which are different from each other according to the construction of the cylinder head and the kind of valve operating mechanism. Heretofore, it has been the common practice to insert the rocker shaft into a bracket which is then fixed to the cylinder head by means of bolts, or to use a bracket portion having holes adapted to receive the rocker shaft and make it integral with the cylinder head per se.

In such conventional arrangements, the former which makes use of the bracket for the purpose of fixing the rocker shaft to the cylinder head is required to provide a bracket formed with holes into which are inserted the rocker shafts as a separate part and hence has the disadvantage that the number of parts becomes large. While, the latter arrangement having the bracket portion made integral with the cylinder head per se is required to provide small diameter holes adapted to receive the rocker shaft therein in the cylinder head, the holes each having an axis extending lengthwise of the cylinder head. As a result, the latter arrangement is troublesome in assembly and requires a large number of assembly steps.

In order to eliminate the above mentioned drawbacks, it has been proposed to directly fix.a rocker shaft to a cylinder head by means of bolts or the like. In this arrangement, the rocker shaft is provided at its lower surface with a plurality of flat surface portions which are disposed on flat support portions provided on the upper surface of the cylinder head. Such a conventional rocker shaft fixing arrangement requires only a small number of parts and assembly is easy, but has the disadvantage that it is extremely difficult to make all of the flat surface portions of the lower surface of the rocker shaft precisely the same level. The slight difference in level of the flat surface portions of the lower surface of the rocker shaft results in bending of the rocker shaft.In addition, bolt insertion holes provided in the rocker shaft are slightly larger in diameter than the bolt, so that there is a risk of the rocker shaft being misaligned.

An object of the invention, therefore, is to provide a rocker shaft fixing arrangement for internal combustion engines which can eliminate the above mentioned drawbacks encountered with the prior art techniques.

A feature of the invention is the provision of a rocker shaft fixing arrangement for internal combustion engines comprising at least one rocker shaft provided at its upper surface with a flat portion adapted to serve as a seating surface for a bolt or nut and including a hole extending therethrough, and a cylinder head provided at its upper surface portion with a part cylindrical concave surface extending lengthwise of the cylinder head and adapted to be engaged with the lower surface of said rocker shaft, said rocker shaft being firmly fixed to said cylinder head by means of bolts, or studs and nuts.

Further objects and features of the invention will be fully understood from the following detailed description with reference to the accompanying drawings, wherein: Fig. 1A is a fragmentary perspective view of a conventional rocker shaft fixing arrangement for internal combustion engines; Fig. 1 B is a longitudinal cross-sectional view of the conventional rocker shaft fixing arrangement shown in Fig. 1 with a rocker shaft fixed to a cylinder head; Fig. 1 C is a section on the line X-X of Fig. 1 B; Fig. 2 is a fragmentary perspective view of a rocker shaft fixing arrangement for internal combustion engines according to the invention; and Fig. 3 is a transverse cross-sectional view of the rocker shaft fixing arrangement shown in Fig.

2 with a rocker shaft fixed to a cylinder head.

In a conventional rocker shaft fixing arrangement for internal combustion engines shown in Fig. 1 A, a rocker shaft 1 is provided at its upper and lower peripheral surfaces with flat surface portions 2, 2' and a cylinder head 4 is provided at its upper surface portion with a flat support portion 5. The rocker shaft 1 is directly fixed to the cylinder head 4 by means of bolts 8.

The conventional rocker shaft fixing arrangement shown in Fig. 1 has a small number of parts and is not troublesome to assemble, but has the following disadvantages. The rocker shaft 1 must be provided at its lower surface with a plurality of discontinuous flat surface portions 2'.

Since these flat surface portions 2' are discontinuous, it is extremely difficult to make the respective flat surface portions 2' precisely the same in level. A slight difference in level between adjacent flat surface portions 2', 2' results in bending of the rocker shaft 1. In addition, the rocker shaft 1 is provided at its flat surface portion 2 with a bolt hole 3 having a diameter larger than that of the bolt. The use of such bolt hole 3 causes the fixed position of the rocker shaft 1 to be misaligned.

The invention provides a rocker shaft fixing arrangement for internal combustion engines which can obviate the above mentioned drawbacks encountered with the conventional rocker shaft fixing arrangement shown in Fig. 1.

The invention will now be described with reference to Figs. 2 and 3.

Referring to Figs. 2 and 3, a rocker shaft 1 is provided at its desired upper surface portion with a plurality of flat surface portions 2 adapted to serve as a seat for a bolt or nut.

The flat surface portion 2 is provided with a bolt hole 3 adapted to receive a bolt.

A cylinder head 4 is provided at its upper surface 5 with a part-cylindrical concave surface 6 having a tapped hole 7.

The rocker shaft 1 is disposed on the partcylindrical concave surface 6 such that the lower surface portion of the rocker shaft 1 is snugly received in the concave surface 6. Then, a bolt 8 is inserted into the bolt hole 3 and threaded into the tapped hole 7, thereby firmly fixing the rocker shaft 1 to the cylinder head 4 as shown in Fig. 3.

Alternatively, a stud having a lower portion threadedly engaged with the tapped hole 7 may project upwardly to extend through the bolt hole 3 of the rocker shaft 1 and the rocker shaft 1 may be firmly fixed to the cylinder head 4 by means of a nut threadedly engaged with the upper end of the stud.

As stated hereinbefore, the rocker shaft fixing arrangement for internal combustion engines according to the invention has a number of advantages. In the first place, the rocker shaft 1 is not required to have at its lower surface a flat surface portion. Secondly, the rocker shaft 1 is only required to have a flat surface portion at its upper surface. This upper flat surface portion functions as a seat surface for a bolt or nut, and as a result, adjacent upper flat surface portions are not required to be precisely aligned in the same plane. Thus, the upper flat surface portion may be formed by merely cutting the upper surface of the rocker shaft 1 and hence its machining is quite easy. Thirdly, the rocker shaft 1 is snugly received in the concave surface 6 formed in the upper surface of the cylinder head 4 and is firmly fixed to the latter. As a result, even if the bolt hole is larger in diameter than the bolt diameter, it is possible to completely prevent the rocker shaft 1 from being misaligned when it is fixed to the cylinder head 4. Thus, the rocker shaft 1 can be fixed to the cylinder head 4 in a precise and stable manner. Finally,-the arrangement according to the invention only has a small number of constitutional elements and thus contributes greatly to the industry.

Claims

1. A rocker shaft fixing arrangement for internal combustion engines comprising at least one rocker shaft provided at its upper surface with a flat surface portion adapted to serve as a seat surface for a bolt or nut and including a hole extending therethrough, and a cylinder head provided at its upper surface portion with a partcylindrical concave surface extending lengthwise of the cylinder head and adapted to be engaged with the lower surface of said rocker shaft, said rocker shaft being firmly fixed to said cylinder head by means of bolts, or studs and nuts.

2. An arrangement according to claim 1, wherein said part-cylindrical concave surface of said cylinder head is provided with tapped holes and said rocker shaft is firmly fixed to said cylinder head by means of bolts threadedly engaged with said tapped holes.

3. An arrangement accoridng to claim 1, wherein said part-cylindrical concave surface of said cylinder head is provided with tapped holes and said rocker shaft is firmly fixed to said cylinder head by means of nuts threadedly engaged with the upper ends of studs having their lower ends threadedly engaged with said tapped holes and projecting upwardly therefrom.

4. A rocker shaft fixing arrangement substantially as described with reference to, and as illustrated in, Figs. 2 and 3 of the accompanying drawings.