GB1584590A

GB1584590A - Internal combustion engine cylinder and piston arrangements

Info

Publication number: GB1584590A
Application number: GB5082077A
Authority: GB
Original assignee: Kawasaki Heavy Industries Ltd; Kawasaki Jukogyo KK
Current assignee: Kawasaki Heavy Industries Ltd; Kawasaki Motors Ltd
Priority date: 1977-12-06
Filing date: 1977-12-06
Publication date: 1981-02-11

Description

(54) INTERNAL COMBUSTION ENGINE CYLINDER AND PISTON ARRANGEMENTS (71) We, KAWASAKI JUKOGYO KABUSHIKI KAISHA of 14, Higashikawasaki-cho 2-chome, Ikuta-ku, Kobe-shi, Hyogo-ken, Japan a Japanese corporation do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to internal combustion engine cylinder and piston arrangements.

Conventionally the pistons of internal combustion engines carry piston rings that are in sliding contact with the inner wall surfaces of the cylinders with which the pistons co-operate. Usually these piston rings are made of graphitized cast iron or steel coated with chromium plating so as to provide wear-resistant characteristics. Such chromium plated piston rings have been found satisfactory when they are used with cast iron cylinders. However, in engines having cylinders of light metal alloy such as aluminum based alloy, it has been usual to provide the cylinders with wear-resistant coatings on the inner surfaces thereof, and there have been problems in utilising chromium plated piston rings with such cylinders.Figure 2 of the accompanying drawings is a microscopic picture of a coated internal combustion engine cylinder surface after operation with a piston carrying conventional chromium plated piston rings. It is to be noted that the coating on the cylinder has become scuffed. This is because both the stationary and the moving surfaces in the piston/cylinder arrangement have high surfaces hardness.

According to the present invention there is provided an internal combustion engine cylinder and piston arrangement in which the cylinder or a liner thereof has its inner surface coated by wire-explosion spray with alternate layers of steel and material having good hard-wearing and sliding characteristics, wherein the piston caries a piston ring, for co-operation with said inner surface, which is of un-plated graphitized cast iron.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to Figures 1 and 3 to 5 of the accompanying drawings, in which: Figure 1 is a-sectional view of a part of an internal combustion engine, Figure 3 is a microscopic picture, similar to Figure 2 discussed above, of a cylinder surface after operation with piston rings as now to be described, Figure 4 is a diagram showing the amount of wear in piston rings, and Figure 5 is a diagram showing the relationship between frictional force and contact pressure as between a piston ring and a cylinder surface.

Referring first to Figure 1, there is shown an internal combustion engine cylinder 1 having an inner coating 2. Within the cylinder 1 there is disposed a piston 3 for reciprocating movement. The piston 3 carries piston rings 4 which are in sliding engagement with the surface of the coating 2. The coating 2 is a metal coating formed in accordance with the process as disclosed by United States Patent No. 4,044,217. More specifically, the coating includes alternate layers formed by wire-explosion spray of steel, and material having good hardwearing and sliding characteristics, this material being selected, for example, from molybdenum, molybdenum-tungsten alloy, tungsten, chromium, nickel and titanium.

The composite layers so formed have excellent surface hardness and are of suitable porosity.

The piston rings 4 are made of graphitized cast iron, preferably of granulous graphite cast iron rather than flaky graphite cast iron.

The piston rings 4 may be nitrided to provide increased surface hardness and wear resistance.

Nitriding also enhances the sliding properties of the rings as there is formed a surface layer of internal compounds comprising nitrides and carbides of iron, such a layer being effective to prevent temperature rise at the sliding surfaces. Alternatively the rings may be coated with a phosphate or polytetrafluoroethylene.

In order to confirm the advantageous effects of the present piston rings, tests have been made using engine cylinders having metal coatings provided in accordance with the aforementioned U.S. Patent using molybdenum. Figure 2, as already mentioned, shows the result after engine running tests with conventional chromium plated piston rings. Figure 3 shows the test result with piston rings made of graphitized cast iron having a nitrided surface. It will be noted from Figures 2 and 3 that whereas the metal coating on the engine cylinder is scuffed, as already mentioned, after operation with the conventional piston rings, no noticeable damage is found in the engine cylinder which has been used with the graphitized cast iron piston rings having a nitrided surface.

Figure 4 shows the amount of wear of the piston rings through the tests. It will be noted that the amount of wear is significantly decreased where the coated engine cylinders are used with graphitized piston rings with nitrided surfaces.

It should of course be noted that the metal coating 2 on the engine cylinder need not necessarily be provided directly on the cylinder but may be provided on a cylinder liner fitted in the cylinder.

Figure 5 shows the frictional force between the piston ring and the cylinder when the piston ring is moved at a velocity of 5 m/sec. under various contact pressures. The test results show that granulous graphite cast iron is significantly better than flaky graphite cast iron in respect of the frictional force. This means that the former shows better sliding properties than the latter.

Further, granulous graphite cast iron has a good property in respect of retention of lubricant oil as compared with flaky graphite cast iron.

WHAT WE CLAIM IS: 1. An internal combustion engine cylinder and piston arrangement in which the cylinder or a liner thereof has its inner surface coated by wire-explosion spray with alternate layers of steel and material having good hard-wearing and sliding characteristics, wherein the piston carries a piston ring, for co-operation with said inner surface, which is of un-plated graphitized cast iron.

2. A cylinder and piston arrangement as claimed in claim 1, wherein said piston ring is of granulous graphite cast iron.

3. A cylinder and piston arrangement as claimed in claim 1 or 2, wherein said piston ring has a nitrided surface.

4. A cylinder and piston arrangement as claimed in claim 1 or 2, wherein said piston ring is coated with a phosphate.

5. A cylinder and piston arrangement as claimed in claim 1 or 2, wherein said piston ring is coated with polytetrafluoroethylene.

6. A cylinder and piston arrangement as claimed in any one of the preceding claims, wherein said material having good hardwearing and sliding characteristics is selected from molybdenum, molybdenumtungsten alloy, tungsten, chromium, nickel or titanium.

7. An internal combustion engine cylinder and piston arrangement substantially as hereinbefore described with reference to Figures 1 and 3 to 5 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The piston rings 4 may be nitrided to provide increased surface hardness and wear resistance. Nitriding also enhances the sliding properties of the rings as there is formed a surface layer of internal compounds comprising nitrides and carbides of iron, such a layer being effective to prevent temperature rise at the sliding surfaces. Alternatively the rings may be coated with a phosphate or polytetrafluoroethylene. In order to confirm the advantageous effects of the present piston rings, tests have been made using engine cylinders having metal coatings provided in accordance with the aforementioned U.S. Patent using molybdenum. Figure 2, as already mentioned, shows the result after engine running tests with conventional chromium plated piston rings. Figure 3 shows the test result with piston rings made of graphitized cast iron having a nitrided surface. It will be noted from Figures 2 and 3 that whereas the metal coating on the engine cylinder is scuffed, as already mentioned, after operation with the conventional piston rings, no noticeable damage is found in the engine cylinder which has been used with the graphitized cast iron piston rings having a nitrided surface. Figure 4 shows the amount of wear of the piston rings through the tests. It will be noted that the amount of wear is significantly decreased where the coated engine cylinders are used with graphitized piston rings with nitrided surfaces. It should of course be noted that the metal coating 2 on the engine cylinder need not necessarily be provided directly on the cylinder but may be provided on a cylinder liner fitted in the cylinder. Figure 5 shows the frictional force between the piston ring and the cylinder when the piston ring is moved at a velocity of 5 m/sec. under various contact pressures. The test results show that granulous graphite cast iron is significantly better than flaky graphite cast iron in respect of the frictional force. This means that the former shows better sliding properties than the latter. Further, granulous graphite cast iron has a good property in respect of retention of lubricant oil as compared with flaky graphite cast iron. WHAT WE CLAIM IS:

1. An internal combustion engine cylinder and piston arrangement in which the cylinder or a liner thereof has its inner surface coated by wire-explosion spray with alternate layers of steel and material having good hard-wearing and sliding characteristics, wherein the piston carries a piston ring, for co-operation with said inner surface, which is of un-plated graphitized cast iron.