JP2003343353A - Cylinder and piston-ring combination of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston causing little seizure to a cylinder of an internal combustion engine made of an aluminum alloy. <P>SOLUTION: The aluminum alloy of the cylinder contains 9-18% Si and a PVD film composed chiefly of Cr and N is formed on the surface of the piston ring, so that the piston ring causing no wear by the primary-crystal Si of the aluminum alloy and causing little seizure, by virtue of the excellent wettability of the PVD film even under conditions that oil films easily run out. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combination of a cylinder and a piston ring for an internal combustion engine, and more particularly to a combination of a cylinder and a piston ring made of an aluminum alloy.

[0002]

2. Description of the Related Art As the weight of a cylinder block of an automobile engine is being reduced, material replacement is being promoted as one of the measures. In particular, material replacement from iron-based materials to light metals such as aluminum alloys is being carried out ("friendly car materials for design engineers" Nikkei BP, 199.
Issued on Sep. 6, 3rd, pp. 46-47) Although aluminum alloy cylinder blocks and liners can be made lighter, their wear resistance and seizure resistance are insufficient compared to iron-based materials. The combination with the mating piston ring sliding surface is important. Therefore, JP-A-62
No. 282150, a piston ring, which is a counterpart material of a hypereutectic Al-Si alloy cylinder having a structure in which primary Si particles are dispersed, has Ni-P and Ni-C on its sliding surface.
It has a so-called Ni, Ni—Co based composite dispersed plating film in which silicon nitride particles are dispersed in an o-P matrix. This Ni, Ni-Co-based composite dispersion plating film contains 1 to 10% by weight of P in the film and has a hardness of 800 to 900 HV by heat treatment to improve mutual wear resistance.

[0003]

In the combination of the cast iron liner material and the hard chrome plated piston ring used from the 1970s to the 1980s, the hardness of the former is Hv2.
The hardness of the latter is Hv800-900. With this combination, the aggressiveness of the mating material is low for all of the structural constituents of the cast iron liner material, ferrite, graphite, and cementite.

On the other hand, since the Al matrix of the hypoeutectic / hypereutectic Al-Si alloy of the Al-Si cylinder material has low wear resistance and the primary Si particles are hard (about 1300 HV),
The opponent material of the primary crystal Si has high aggression. In such a sliding condition, the hardness is 8
The place where relatively remarkable wear occurs when the pressure is increased to 00 to 900 HV is the alloy matrix of the Al—Si cylinder material and the entire plating film of the piston ring. That is, since the former is soft, it is locally worn in the aluminum alloy by the composite dispersion plating, and the latter is entirely worn by the primary crystal Si. As a result, Si particles protrude from the Al-Si alloy matrix and rub against the mating material, which further promotes the above tendency.

That is, the primary crystal Si particles in the Al-Si cylinder material are projected from the matrix surface to accelerate the wear of the composite dispersion plating. Since this abrasion powder promotes abrasion of the composite dispersed plating film and the Al-Si cylinder material,
The wear amount of the piston ring material and the liner material is larger than that of the combination with the commonly used cast iron liner material. Further, if the dispersed particles are not uniformly dispersed in the plating film, in addition to the abrasion resistance being partially reduced, there is a problem that seizure is likely to occur because the sliding surfaces are in contact with each other. there were.

[0006]

The present invention for solving these problems is a combination of an aluminum alloy cylinder and a piston ring material as a mating sliding member,
The aluminum alloy contains 9-18 wt% Si
The piston ring is an Al-Si alloy and is characterized in that a PVD film containing chromium and nitrogen as main components is formed on the outer peripheral sliding surface.

In the present invention, the aluminum alloy is S
i9-18 wt%, Cu 1.0-5.0 wt%, Mg, Zn, Fe, Mn, Ni, Ti, Pb, S
It is preferable that the aluminum alloy contains at least one of n, Cr, and P in a total amount of 10% by weight or less and the balance is Al. The additive elements such as Cu and Mg enhance the wear resistance by strengthening the aluminum alloy.

Further, the PVD coating formed on the outer peripheral sliding surface of the piston ring and containing chromium and nitrogen as the main components preferably has a coating hardness in the range of HV1000-2000.

The combination of the present invention can be applied to a mechanism that makes relative movement under the same use conditions as the combination of the piston ring of the internal combustion engine and the liner material and the cylinder block material.

[0010]

The present invention is a combination of a liner material or a cylinder (1) block material made of an aluminum alloy and a piston ring 2 that slides with this as shown in FIG. A film containing chromium and nitrogen as the main components on the base material of the piston ring, which is
To improve wear resistance and seizure resistance. In order to obtain this result, the Si content in the aluminum alloy is important. If the Si content is less than 9% by weight, the proportion of Si in the aluminum alloy crystallized as eutectic Si is high, resulting in insufficient wear resistance. Si content is 18% by weight
Beyond the above, the primary crystal Si grains in the aluminum alloy become coarse, the attacking power of the opponent increases, and the self-abrasion is promoted by the abrasion powder of the Si grains. Since the workability is reduced, it also leads to an increase in cost.

In order to achieve both wear resistance and seizure resistance, it is important that the film formed on the outer peripheral sliding surface of the piston ring is a PVD film containing chromium and nitrogen as main components. The hardness of this film is as high as 1000 HV or more,
Therefore, the hardness of the primary crystal Si of the Al-Si cylinder alloy is equal to or higher than the hardness (about 1300 HV), and is less likely to be worn by the primary crystal Si. More specifically, the hard coating mainly composed of chromium and nitrogen has a greater tendency to wear the alloy matrix (structure other than primary crystal Si) of the Al-Si cylinder material, which is the counterpart material, than the composite plating coating, Since the coating containing chromium and nitrogen as the main components has excellent wear resistance,
There is little tendency for the primary crystal Si of the Al-Si cylinder material to wear. Therefore, the primary-crystal Si particles of the Al-Si alloy do not protrude from the aluminum alloy matrix and become "files", and there is little tendency to wear the mating material.

By the way, since the Cr-N film has excellent wettability with molten aluminum as used for a molten aluminum jig, it is a combination with excellent seizure resistance with an aluminum alloy under cylinder operating conditions. It is said that conventional cast iron materials have the effect of improving the sliding characteristics due to the lubricating effect of graphite in the structure and the oil retaining effect due to the oil pool in the graphite part. Since it does not exist, seizure resistance is said to be low. In such an aluminum alloy with an oil film that easily breaks, seizure resistance is achieved by utilizing its excellent wettability with the aluminum alloy even in a sliding state where the speed becomes zero at the folded part during reciprocation and the oil film is easily broken Is secured.

[0013]

EXAMPLES Next, specific examples of the present invention will be described by referring to the results of evaluation of sliding characteristics by a unit test simulating sliding between a cylinder and a piston ring of an internal combustion engine, and consideration of the above experimental results Will be explained.

A flat plate of an aluminum alloy material corresponding to the dimensions of the cylinder of the internal combustion engine was prepared by casting. As an example of a cylinder material having a low Si content, JIS ADC12
An aluminum alloy corresponding to the alloy, and as an example having a large Si content, an aluminum alloy corresponding to the AA standard A390 alloy. From aluminum alloy cast flat plate 7
A test piece having a size of 0 × 17 × 14 mm was cut out and used as a test piece for a single wear test and a seizure test. The roughness of the sliding surface was adjusted by polishing so as to correspond to cylinder honing.

The material equivalent to the piston ring was a sliding surface of a SUS440B wire having a curved surface in the contact sliding direction. 1 on this surface
A film containing chrome and nitrogen as main components with a thickness of -30 μm was formed by the arc ion plating method. Table 1 shows the structure of the test piston ring material. The composition of the film was changed by changing the film forming conditions, specifically, the nitrogen partial pressure. Although the notation of Cr (N) in Table 1 of Example 1 is confirmed only by the Cr component in the measurement by X-ray diffraction,
The film is a film that can be detected by elemental analysis by EPMA, in which N is solid-dissolved in Cr.

[0016]

[Table 1] * Droplets were confirmed on the surfaces of Examples 1 to 5.

A schematic diagram of the reciprocating motion tester used for the abrasion test and the seizure test is shown in FIG. The cylinder-corresponding test piece 4 is fixed by a movable holder and reciprocates. The piston ring-equivalent test piece 5 is fixed and pressed downward from above with a constant load.

In the wear test, a base oil was used as a lubricating oil and a constant load of 500 N was applied, and a frequency of 600 cycl was applied.
A stroke of 50 mm was reciprocated at a speed of es / min. The reciprocating motion holding time was set to 1 hour, and after the test, the amount of wear of the folded portion of the aluminum alloy cylinder material corresponding to the vertical dead center of the internal combustion engine cylinder was measured. The wear amount of the cylinder material was measured at right angles to the sliding direction, and the wear cross-sectional area was calculated. The wear amount of the piston ring material was calculated by calculating the height of wear from the wear width.

FIG. 3 shows the results of the abrasion test. In the example of the present invention, the wear amount of both the piston ring material and the cylinder material was much smaller than that of the comparative example. Comparative Example 1 corresponds to a hard chrome plated piston ring which is a mass production technology in the 1970s to 1980s. Although the gas nitriding of Comparative Example 2 was harder than the composite dispersion plating of Example 3, the wear amount was large. This is 10 μm in the nitrided diffusion layer.
It is considered that the wear was promoted because the chromium carbonitrides before and after existed and were separated from the diffusion layer. Example 1
In Nos. 5 to 5, the hardness is higher than in Comparative Examples 1 to 3. Further, in these examples, none of Cr (N), Cr ₂ N, and CrN is a particle that is scraped off by the primary crystal silicon particles in the aluminum alloy from the viewpoint of hardness, and causes wear.
Although these particles are hard, the behavior of scraping Si particles in the aluminum alloy is prevented.

The same test piece combination used in the abrasion test to evaluate the seizure resistance was used. As the lubricating oil, the same oil as in the abrasion test was used, and the reciprocating motion test was started only by the initial oil application. Apply an initial load of 100N,
It was reciprocated at a rotation speed of 600 rpm. The pressure was increased stepwise and stopped when the torque suddenly increased, and the load at that time was taken as the seizure generation load.

FIG. 4 shows the result of the baking test. It can be seen that the examples of the present invention have higher seizure resistance than the comparative examples. Like the combination of the cast iron cylinder of the prior art and the hard chrome plated piston ring, the seizure load is low when metal contact occurs, but in Examples 1 to 5, only ceramics in which metal adhesion or transfer does not easily occur It is considered that the seizure resistance is remarkably improved because it is a film formed of

[0022]

As described above, the cylinder of the internal combustion engine is
A cylinder made of an aluminum alloy of the present invention, which is made of an aluminum alloy containing 9 to 18% by weight of Si, and the piston ring has a PVD coating containing chromium and nitrogen as main components on the outer peripheral sliding surface. In the case of a combination of a piston ring and a piston ring, the speed is zero at the folded part during reciprocation, and even in a sliding state that causes oil film breakage, seizure resistance is good while ensuring wear resistance. An advantageous effect is acquired.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic diagram of a reciprocating motion test.

FIG. 3 is a graph showing test results of a wear test.

FIG. 4 is a graph showing the test results of a baking test.

Claims (5)

[Claims] 1. A cylinder in which an inner peripheral surface of a cylinder on which a piston ring of an internal combustion engine slides is made of an aluminum alloy,
In the combination of this and the sliding piston ring,
The aluminum alloy contains 9-18 wt% Si,
A combination of a cylinder and a piston ring of an internal combustion engine, wherein the piston ring has a PVD film containing chromium and nitrogen as main components on the outer peripheral sliding surface. 2. The aluminum alloy is Si9-18
%, Cu 1.0 to 5.0% by weight, and further M
g, Zn, Fe, Mn, Ni, Ti, Pb, Sn and C
The combination of a cylinder and a piston ring of an internal combustion engine according to claim 1, characterized in that it contains at least 10% by weight in total of one or more kinds selected from the group consisting of r, and the balance is Al. 3. The hardness of the PVD coating formed on the outer peripheral sliding surface of the piston ring and containing chromium and nitrogen as the main components is in the range of HV850 to 2000. Combining cylinder and piston ring of internal combustion engine. 4. The combination of a cylinder and a piston ring of an internal combustion engine according to claim 1, wherein the cylinder is a cylinder block. 5. The combination of a cylinder and a piston ring of an internal combustion engine according to claim 1, wherein the cylinder is a cylinder liner.