Helical Spring Forming Cooling Channel Around Liquid-Cooled Cylinder

1. Field of the Invention

This invention concerns a liquid-cooled cylinder pipe of an internal combustion engine, especially a diesel engine.

2. The Prior Art

It is known from German Published Application No. DE-OS 28 25 870 to provide a helical dividing wall on the side of the housing of the internal combustion engine facing the cylinder pipe, which essentially extends to the cylinder pipe. In this manner, a helical cooling channel surrounding the cylinder pipe is formed, which assures a high degree of heat discharge from the cylinder pipe. However, the construction of the dividing wall in the cooling gap between the housing and the cylinder pipe is difficult to manufacture and thus expensive.

The object of the present invention is to provide a helical cooling agent pathway around the cylinder pipe of an internal combustion engine which is inexpensive to construct and which uses simple means.

According to the present invention a helical spring is inserted into the cooling gap between the housing and the cylinder pipe, such that it sits firmly in the cooling gap by radial tension, thus forming a helical cooling channel. Such a helical spring can be inserted into any internal combustion engine, whereby the slope of the windings as well as the number of windings of the helical spring can easily be adapted to the respective cooling requirement. The helical spring is constructed according to the desired heat transfer value.

The helical spring for the most part rests tightly against one wall of the cooling gap and at a slight distance from the other wall. In this manner it is assured that, apart from the helical flow, it is also possible to obtain a partial axial flow along the cylinder, which provides for an additional increase in the heat transfer value.

Preferably, the outer diameter of the helical spring is larger than the inside diameter of the location hole in the housing, so that the helical spring rests under radial tension against the housing wall. As the helical spring also has a gap towards the cylinder pipe, the cylinder pipe can be inserted without obstruction after the helical spring is installed.

The cross section of the helical spring wire is preferably rectangular, particularly square, whereby one lateral wall of the cross section sits against one wall of the cooling gap, thus providing for a relatively large contact surface.

Further features and advantages of the invention will become apparent by reference to the attached drawings taken in conjunction with the following discussion.

FIG. 1 shows a cross sectional view of a part of the housing of an internal combustion engine and the associated cylinder pipe, the cooling gap therebetween containing a helical spring according to one embodiment of the present invention for providing a helical cooling channel, and

FIG. 2 shows a similar cross sectional view, the cooling gap containing a helical spring according to another embodiment of the present invention.

In FIGS. 1 and 2 only the cylindrical part of the housing 1 of the internal combustion engine which holds the cylinder pipe 2 is shown. This cylindrical housing part has, at its upper edge, a surrounding indentation 6 to accept a ring flange 4 of the cylinder pipe 2, pointing radially towards the outside. The flange 4 has a radial extension in such a manner that a cooling gap 5 is formed between the cylindrical inside wall 8 of the housing 1 and the cylindrical outside wall 7 of the cylinder pipe 2.

A helical spring 3 is inserted into the cooling gap 5, the spring wire of which has a rectangular cross section, preferably square as shown in the embodiment. In FIG. 1 the helical spring 3 rests, under radial tension, with its windings mostly tightly against the cylindrical inside wall 8 of the housing 1. In this manner the sides of the cross section are arranged parallel or at right angle to the side wall 8. Towards the cylindrical outside wall of the cylinder pipe, the inside surface of the helical spring or its winding have a gap s, which provides for a partial axial flow along the cylinder pipe. This partial axial flow accumulates next to the helical flow in the cooling channel between the individual windings of the helical spring 3, which have a distance d between each other, that determines the height of the cooling channel. The convection, forced in this manner, provides for the increase heat transfer from the cylinder pipe to the cooling agent flowing through. This increase in heat transfer is particularly advantageous in cooling liquids which have a lower heat transfer property than water.

The embodiment according to FIG. 2 agrees with the one according to FIG. 1 in its basic construction, whereby the same reference numbers are used. The helical spring inserted in FIG. 2 rests against the cylinder pipe 2 under radial tension and has a distance (s) from the cylindrical inside wall 8 of the housing 1.

In the embodiment according to FIG. 1, the helical spring in the unstressed state has an outside diameter which is larger than the inside diameter of the cylindrical wall 8 of the housing part 1. In the embodiment according to FIG. 2, the inside diameter of the helical spring in the unstressed state is smaller than the outside diameter of the cylinder pipe 2.

It may be suitable to variably design the distance d of adjoining windings of the helical spring 3. Thus, it would be possible, e.g., to have a smaller distance d in the upper area of the cylinder pipe (in the area of the combustion chamber) than in the lower area. This is the progression, e.g., of a helical spring with progressive slope. Through this construction, the higher incident of heat from the combustion chamber is taken into account. It thus provides for a stronger heat discharge at the end of the cylinder pipe 2 facing towards the combustion chamber.