JPS61123747A - Cylinder head structure of siamese upper cam engine - Google Patents

Abstract

PURPOSE:To facilitate fixing of bolts while to reduce the weight by arranging the cylinder head fixing bolts further inside than the axis of respective dynamic valve cam shaft while forming the shaft section of dynamic cam shaft adjoining to the fixing bolts to be thick with short diameter. CONSTITUTION:A cylinder head 3 is fastened through plural fixing bolts 4 to the upper section of cylinder block. Here, respective fixing bolt 4 is arranged with equi-interval around a piston hole 1 while in case of two adjoining piston holes 1, it is provided to the opposite sides of partition wall 1a between both holes 1 to be shared by both holes 1. Consequently, the axes of both dynamic valve cam shafts 5 and the fixing bolt 4 are brought near. In other word, respective fixing bolt 4 is arranged further inside than the axes of both cam shafts 5. The shaft section 5a constituting the dynamic valve cam shaft 5 together with the cam 5b and the journal section 5c is formed thick with short diameter while the central hole 5d is enlarged to reduce the weight.

Description

[Detailed Description of the Invention] [Industrial Applicability] This invention relates to a double overhead cam type engine in which a cylinder head attached to the top of the cylinder is provided with two valve drive camshafts, one for intake and one for exhaust. This relates to the cylinder head structure of.

This type of engine has been widely adopted in recent years as passenger car engines have increased in output, but when trying to bring the distance between the two camshafts closer together, the mounting bolts that fasten the cylinder head to the cylinder and the valve drive The camshafts may interfere with each other, making assembly and disassembly work difficult.

In other words, in a multi-cylinder engine, some of the mounting bolts are shared by adjacent piston holes, so they are provided across the partition between each piston hole, so that the mounting bolts are installed parallel to the crankshaft.
In addition, the two valve drive camshafts, which are offset to one side and the other side from the center of the piston hole, overlap vertically in a plane parallel to the cylinder axis, and the camshafts get in the way when attaching and removing the mounting bolts. It may happen.

[Conventional technology]

Conventionally, in order to solve this problem, the mounting bolt was placed directly under the camshaft, a through hole was provided in the camshaft perpendicular to the shaft center, and tightening was done by approaching the mounting bolt through the hole. , a structure for tightening and loosening a bolt 6 or a nut has been proposed (for example, Japanese Patent Application Laid-Open No. 163141/1983).

[Problem that the invention seeks to solve]

However, in such a structure, the camshaft must have a large diameter to the extent that the presence of the through holes can be ignored for reasons of strength, and the shaft core must be thinned out between adjacent through holes to reduce weight. Furthermore, reducing the outer diameter to avoid interference naturally limits the ability of the camshaft to withstand the large and fluctuating torque of the shaft, resulting in wasted material. It is impossible to avoid problems that increase the weight of the engine.

[Means for solving problems]

The purpose of this invention is to avoid the above-mentioned problems, and the present invention has a cylinder head that is fastened to the cylinder by at least four mounting bolts arranged around the cylinder hole, and has a cylinder head that is fixed to the cylinder by at least four mounting bolts arranged around the cylinder hole. In a double overhead cam engine equipped with a valve camshaft, the four bolts are located slightly inside the axis of each intake and exhaust valve camshaft, and the valve cams adjacent to the mounting bolts are The details of the shaft are made small in diameter and thick.

〔Example〕

The present invention will be explained below with reference to illustrated embodiments. In the figure, reference numeral 1 denotes a plurality of piston holes arranged in the direction of the crankshaft, which are formed in the cylinder block 2 degrees below the reel.

A cylinder head 3 is fastened to the upper part of the cylinder block 20 with mounting bolts 4. 5.5 is a valve drive camshaft consisting of an intake camshaft and an exhaust camshaft; 6 is a peripheral wall of an ignition plug; and 7 is a bearing cap for the camshaft 5.

In this embodiment, the mounting bolts 4 that connect the cylinder head 3 and the cylinder block 2 are of a hexagonal hole type, and are arranged approximately equidistantly around the piston hole 2 and adjacent to each other, as shown in FIG. Because of the two bistoy holes 2, K is
They are provided on both sides across the partition wall 11L between the adjacent piston holes 1, 1 so that they can be shared by both holes. Therefore, the axes of both camshafts 5, 5 and the axis of the mounting bolt 4 naturally become close to each other. 3& is a bearing portion provided on the rounded cylinder head 3 that supports the camshaft 5.

Next, the camshaft 5 is made of sintered metal.
As shown in the figure, a shaft portion 5a made of thin-walled steel pipe with a relatively large diameter, a cam 5b and a journal portion 5c sintered on the outer surface of the shaft portion 5a.
It consists of That is, by making the shaft portion 5a relatively large in diameter and thin, the torsion strength is increased, and the lightening hole 5d in the center portion is made large to reduce the weight. In addition, the lightening hole 5
d is conventionally used as a lubricating oil passage for the through cam 5b.

In this embodiment, the mounting bolts 4 on both sides of the partition wall 1& between the piston holes 1, 1 cannot be installed inside in order to prevent the thickness of the partition wall 2a from increasing any further, so the camshaft Therefore, the outer surface of the shaft portion 5a adjacent to the mounting bolt 4 is set to have a rather small diameter. i.e. the outer surface 5 for engaging a wrench (not shown).
e is a regular hexagon, and the diameter between its vertices is 5
The outer surface 5e has a diameter equal to or smaller than the outer diameter of the shaft portion 5a, and the distance between the facing surfaces is smaller than the outer diameter of the shaft portion 5a.
is formed by cutting the steel pipe that forms the shaft part 5 in the middle, and forming the outer surface member 5f that is interposed between them. A hollow hole 5f is drilled in the outer surface 5e, and the round bar-shaped portions at both ends are press-fitted into the shaft hole of the shaft part 5. cylinder cam sb,
When sb presses the intake valve or exhaust valve and does not open it, that is, it is in the inactive state, if the phase is determined so that the - face of the regular hexagon is parallel to the axis of the mounting bolt 4, then Therefore, interference is reduced, and the distance between the mounting bolt 4 and the camshaft 5 can be made closer. That is, when the camshaft 5 is supported by the bearing part 3m, unless the cam 5b presses the valve springs (not shown) of the intake and exhaust valves to open the valves, one side of the regular hexagon is automatically attached. If the mounting bolt 4 is parallel to the axis of the bolt 4, the gap between the bolt 4 and the mounting bolt 4 will be maximized, making it easier to use the tool. Note that in a cylinder block having three or six cylinders, one of the valves is always in an open state, so this cannot be done. Since the outer diameter of the outer surface 5d of the camshaft 5 is small and the strength of the shaft is reduced, the hollow hole 5e in the shaft core is made small in diameter and the wall thickness is increased to strengthen it. 5g is an end member that supports the timing goo IJ5h provided at the end of the camshaft 5, and is press-fitted into the detail 5m, and a female thread is provided there, and a steel ball is inserted into the center hole as a blind plug. is press-fitted.

Since this embodiment is constructed as described above, in order to attach the cylinder head 3 to the cylinder block 2, the camshaft 5 is supported on the cylinder head 3 in advance, and then placed on the upper surface of the cylinder block 2. Then, as shown in FIG. 2, the mounting bolt 4 can be tilted and inserted into the mounting hole so as not to interfere with the camshaft 5, and then tightened with a tool not shown. Although an example has been shown in which the cross-sectional shape of the outer surface 5d is a regular hexagon and only a part of the outer surface has a small diameter, it goes without saying that this is not limited to this example, and the entire surface may be made into a cylindrical shape with a small diameter.

〔Effect of the invention〕

As described above, in this invention, the four bolts arranged around the piston hole are arranged slightly inside the axes of the intake and exhaust valve drive camshafts, and the The cylinder head structure of the double overhead cam type engine has small diameter and thick camshaft details, so even though the distance between the camshaft and mounting bolts is relatively close, interference with each other is minimized. This makes it easy to tighten and loosen the mounting bolts. In addition, even though this is done, the wall thickness is only increased in the portion where the diameter is reduced, so the increase in weight is minimal and there are effects such as weight reduction.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a plan view of a cylinder head, FIG. 2 is a cross-sectional view along line n-■, and FIG.
The figure is a longitudinal sectional view of the camshaft. 1...piston hole, 1&...fist/bulkhead, 3/foot/
・Cylinder head, 3ILII...11] Receiver, 4. Mounting bolt, 5...Camshaft.

Claims (5)

[Claims] (1) In a double overhead cam type engine in which intake and exhaust valve drive camshafts are installed in the cylinder head which is fastened to the cylinder by at least four mounting bolts arranged around the cylinder hole, The four mounting bolts are arranged slightly inside the axis of the intake and exhaust valve camshafts, and the shaft portion of the valve camshaft adjacent to the mounting bolts is formed to have a small diameter and thick wall. The cylinder head structure of a double overhead cam type engine. (2) A cylinder head structure for a double overhead cam type engine according to claim 1, wherein each valve drive camshaft is formed of sintered metal. (3) A cylinder head structure for a double overhead cam type engine according to claim 1, wherein the four mounting bolts have hexagonal holes. (4) A cylinder head structure for a double overhead cam type engine according to claim 1, wherein the outer surface of the portion of the camshaft adjacent to the mounting bolt has a hexagonal cross section. (5) When the cam is in an inoperative state, one surface of the hexagonal outer surface of the portion of the camshaft adjacent to the mounting bolt is set to be substantially parallel to the axis of the mounting bolt. Cylinder head structure of the double overhead cam type engine described.