Cylinder Liner for Reciprocating-Type Internal Combustion Engines

1. Field of the Invention

The present invention relates to a cylinder liner for reciprocating-piston-type internal combustion engines, with the liner of a given cylinder having a ring-shaped or annular insert that narrows the cylinder in a zone opposite the fire land (top land) of the pertaining piston when the latter is in its top dead center position.

2. Description of the Prior Art

The ring-shaped insert, which narrows the top end of the cylinder, is intended to prevent carbon from depositing on the fire land of the piston, since as the fire land slides over those parts of the cylinder (the cylinder liner) that are swept or passed over by the piston rings, such deposits tend to cause local polishing of these cylinder areas. As a result of this "bore polishing", the hydrodynamic lubrication film is disturbed due to insufficient oil adhesion; this means that the risk of ring and piston seizures and/or scoring increases as the area of these polished surfaces increases.

Ring-shaped inserts serving such a function were disclosed by the German Pat. No. 30 38 235 and the German preliminary Pat. No. 19 00 922 corresponding to U.S. Pat. No. 3,489,130--Polidan et al dated Jan. 13, 1970. However, these disclosures fail to provide simple and, at the same time, secure fastening, i.e., among other things, easy installation in, or removal from, the cylinder liner. The press fit or shrink fit of the insert described in the prior art in a recess of the liner on the one hand makes removal of the insert difficult, and, moreover, involves the danger of the insert loosening under thermal stress due to upsetting.

The latter applies also where, for instance, the insert is made of a material having a coefficient of expansion that is somewhat greater than that of the material of the cylinder liner (see German preliminary Pat. No. 19 00 922 corresponding to U.S. Pat. No. 3,489,130--Polidan et al dated Jan. 13, 1970). Furthermore, the recess provided in the liner area weakens the upper cross-sectional area of the liner. Where the insert is fitted by straight overlapping (form-locking closure), which is also described in the German preliminary Pat. No. 19 00 922, corresponding to U.S. Pat. No. 3,489,130--Polidan et al dated Jan. 13, 1970, via a lip on the cylinder head, an oscillating movement of the insert in the micro range is inevitable; where forced-locking fitting is adopted, the load is applied to the insert, and failure or separation of the liner flange or breaking away thereof can occur.

Therefore, the object of the present invention is to simplify and improve the attachment of the insert in a cylinder liner of the aforementioned general type in such a way that, in addition to easy installation and removal of the insert, no weakening of components (i.e. no weakening of the upper liner area) results and no loosening of the insert develops during operation.

This object, and other objects and advantages of the present invention, will appear more clearly from the following specification in conjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view through the upper part of a cylinder/piston unit of a first exemplary inventive embodiment;

FIG. 2 is a cross-sectional view similar to that of FIG. 1 of a second exemplary inventive embodiment; and

FIG. 3 is a cross-sectional view of a third exemplary inventive embodiment.

The cylinder liner of the present invention is characterized primarily in that the ring-shaped insert, which is freely placed in the cylinder in the upper region of the liner, is provided at its upper end with a flange that extends over the entire cross-sectional area of the liner, including a liner flange, if present.

Due to the freely installed insert, there is no weakening of the upper liner cross-sectional area and, apart from that, easy installation and removal are ensured. The inventive flange on the insert on the one hand ensures secure seating of the insert and, on the other hand, permits a defined force-locking effect, i.e. a force-locking effect where the force application is at the liner flange and not at the insert.

As a result, micro movements, i.e. loosening of the insert, are prevented. At the same time, there is no risk of the liner flange failing or being torn off. An added advantage is in the fact that such an insert can be readily retrofitted in production engines without any major expense, and with the design conditions being maintained.

The insert may be produced as a deep-drawn part or as a turned part. In the former case, the flange of the insert is either provided with a bead in the region of the liner flange, or in that region has a recess to accommodate the cylinder head gasket, with the recessed portion of the insert flange registering, or being accommodated, in a corresponding recess in the liner flange. Where a turned part is used, the recess in the liner flange could possibly be omitted.

Further specific features of the present invention will be described in detail subsequently.

Referring now to the drawings in detail, the reference numeral 1 in the figures denotes a cylinder liner. At the head end of the liner 1, and specifically in the region where the top or fire land 3 of the piston 2 that moves in the cylinder is situated when the piston is in the top dead center position, a ring-shaped insert 4 is inserted. The inner diameter .phi. d of the insert 4 is less than the bore diameter .phi. D of the cylinder liner 1, and the axial height 4a of the insert 4 extends approximately from the uppermost piston ring groove 5 to slightly above the piston crown 2a (corresponding to the fire land 3 of the piston 2). For better protection of the first piston ring, there is a small ridge or shoulder (not denoted by a reference numeral) between the insert 4 (4a) and the piston ring groove 5. The piston ring could also be "exposed". In order to assure the load capacity of the upper groove side (groove 5) in such a case, it may be useful to reduce the thickness of the insert 4 (4a) somewhat in this area. This may be done by chamfering or turning it down. The annular or ring-shaped insert 4 extends freely into the upper region of the cylinder; in other words, it is not accommodated in an addtional (inner) recess of the cylinder liner 1. The insert 4 is secured by providing a flange 4b at the upper end of the insert 4. This flange extends over the entire cross-sectional area of the liner 1, including a liner flange 1a provided at its top (by means of which the liner is supported at the top of the crankcase). In the region of the liner flange 1a, the insert flange 4b has a recess 4c in which the cylinder head gasket 6 acts on the insert 4 or, more specifically, the flange 4b of the insert. Due to the recess 4c, the cylinder head gasket 6 is protected from the direct exposure to the flame. If the insert 4 is constructed as a deep-drawn part, the recess 4c in the flange registers in a corresponding recess 1b in the flange 1a of the liner.

The embodiment of FIG. 2 differs from that of FIG. 1 in that a bead 4d is provided instead of the recess 4c in the flange, with this bead serving as a seal against the combustion chamber. To obtain a defined force application at the liner flange 1a, a ring 7 might be useful.

FIG. 3 shows the insert 4 constructed as a turned part. This embodiment differs from that of FIG. 1 only in that, with a suitable thickness of the insert flange 4b, there is no recess provided in the liner flange 1a corresponding to the recess 4c of the flange 4b.

The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.