JPH07116985B2 - Internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an internal combustion engine having a characteristic structure of a sliding portion between a cylinder bore and a piston ring.

[Prior Art] If aluminum alloy (A390, AC4C, etc.) is used to reduce the weight of the cylinder block, stepped wear at the top dead center of the cylinder bore and scuffing with the piston ring and piston skirt are problems. Becomes So, dry type and thin flake graphite cast iron (F23C etc.)
A method of press-fitting a cylinder liner into a cylinder block is generally used. In this case, it is necessary that the fit between the cylinder block and the cylinder liner be a proper interference fit, and if inappropriate, problems such as fretting wear and scuffing due to heat spots occur.

JP-A-62-29 has been proposed to solve this problem.
The invention of Japanese Patent No. 749, wherein the present invention is a Ni composite plating in which fine particles for strengthening a coating layer are dispersed in a plating coating layer formed on the surface of a cylinder liner and a NiP compound is deposited, the cylinder liner It is a structure of a sliding portion of an internal combustion engine in which a piston ring whose surface is plated with chrome is combined.

The piston ring for an internal combustion engine is composed of a pressure ring for maintaining the airtightness of the combustion chamber and an oil scraping ring for adjusting the lubricating oil film between the piston ring and the cylinder liner. FIG. 1 shows a partial sectional view of a cylinder bore of an internal combustion engine. In FIG. 1, 1 is a cylinder liner, 2 is a cylinder block, 3a, 3b and 3c are pressure rings, 3d is an oil scraping ring, and 4 is a piston. Of these piston rings, the pressure ring is loosely fitted directly below the piston head and is greatly affected by combustion gas.
Wear resistance, scuffing resistance and heat resistance are required.

Regarding piston rings, in recent years, the weight reduction of internal combustion engines,
With the increase in output and rotation, the width of the pressure ring has been actively reduced. The reduction in width of the piston ring reduces the weight of the piston ring, stabilizes the behavior of the piston ring in the piston ring groove, and improves the consumption of lubricating oil by reducing the oil film thickness.

However, when the piston ring is made thinner in this way, the oil film thickness becomes thinner and wear increases and the service life becomes shorter.
Rings made of sili- chrome steel or oil tempered wires have become unusable. That is, it is difficult to manufacture a cast iron ring that is thin in the axial direction, and it is insufficient in terms of breakage strength.Silicone steel rings have a relatively large cross-sectional area because of their low strength at high temperatures. , Inertia is large and fluttering phenomenon is likely to occur.
Therefore, recently, tool steel as a material for piston rings,
Spring steel and stainless steel have been used. Especially, as the stainless steel, 13Cr martensitic stainless steel (0.65C-13.5Cr-0.3Mo-0.1V) is used as a pressure ring and good results have been obtained. There is.

However, these piston rings made of martensitic stainless steel are still insufficient in terms of wear resistance and scuffing resistance when used in an engine with severe friction and wear. Further, the pressure ring gas-nitrided using martensitic stainless steel has a problem that the strength of assembling to the piston is not sufficient, and breakage occurs if the mating opening is unnecessarily widened. In addition, this pressure ring is suitable for internal combustion engines with high requirements for scuff resistance.
There is a problem of scuffing due to insufficient performance.

Therefore, the invention of Japanese Patent Application No. 62-146006 was made to further improve the wear resistance of the conventional martensitic stainless steel piston ring.
By increasing the contents of Cr and C, the carbide of Cr is formed in a larger amount than that of the conventional steel, and the wear resistance is improved. In the invention of Japanese Patent Application No. 62-230446, by further adding Al to the martensitic stainless steel, the wear resistance is improved without substantially reducing the hot workability and the cold workability. Is. In the above invention, by performing a surface treatment such as nitriding treatment,
Further, the wear resistance can be improved.

[Problems to be Solved by the Invention] However, an engine that uses a low-viscosity oil as an engine oil, such as a racing engine, and is operated at a high oil temperature, a high water temperature, and a high rotation speed, has a large amount of fuel dilution and has a lower viscosity. Since lubrication cannot be performed sufficiently, scuffing may occur at the sliding portion with the piston ring.

Also, in the case of a cylinder bore with a Ni-based composite plating film, when combined with a hard chrome plating and a piston ring made of special alloy cast iron, it has the same scuff resistance as that of a cylinder bore with a FC23 cylinder liner.
The required scuff resistance was not obtained. In addition, Ni
In the case of base composite plated cylinder bores, hard particles ensure the wear resistance of the coating, but since these hard particles form protrusions on the sliding surface, they cause wear on the mating piston ring and hard chrome plating. And cast iron piston rings have significantly increased piston ring wear compared to cylinder bores with FC23 cylinder liners,
Engine performance was reduced due to deterioration of oil consumption performance and increase of blow-by gas.

The present invention has been made in view of the above problems in the sliding portion of the cylinder bore of an internal combustion engine, and an object thereof is to provide an internal combustion engine having both wear resistance, scuff resistance, and corrosion resistance.

[Means for Solving the Problems] In order to achieve the above object, the inventors of the present invention have conducted extensive studies on the mechanism of sliding between the cylinder bore and the piston ring. As a result, since the Ni-based composite plating film forming the sliding surface of the cylinder bore has a hard material with high hardness dispersed in the matrix, the friction surface has a convex portion made of the hard material and a concave portion made of the matrix. It was found that, when formed, these recesses became oil pools, and oil shortage was less likely to occur. Therefore, for the mating material piston ring
The present invention has been completed on the idea that a hard material made of Cr carbonitride is crystallized in a matrix and a friction surface is formed by a mechanism similar to that of a cylinder bore.

INDUSTRIAL APPLICABILITY The internal combustion engine of the present invention has a cylinder bore having a surface on which a Ni composite plating layer composed of Ni or a P compound of Ni in which film-reinforced particles are dispersed, and a carbonitride having a particle size of 2 μm or more are crystallized in an area ratio of 3% or more. The gist of the present invention is that it comprises at least a piston ring that is gas-nitrided on the sliding surface with respect to the cylinder bore.

The Ni-based composite plating used in the present invention is prepared by suspending film-reinforcing fine particles, which are dispersed in the film layer to increase the hardness of the film, in a commonly used well-known plating solution, and further depositing a P compound of Ni. An appropriate amount of P compound is added to strengthen the matrix of the plating layer.

In the present invention, for example, SiC, Si ₃ N ₄ , BN, AlN or the like can be used as the film-strengthening fine particles dispersed in the plating layer of the cylinder bore. The average particle size of the film-reinforced particles is 0.5
It is preferably ˜4 μm. This is because if the average particle size of the film-reinforced fine particles is less than 0.5 μm, the depth of the recesses forming the oil pool on the friction surface becomes shallow and the wear resistance deteriorates. On the contrary, if the average particle size of the fine particles exceeds 4 μm, the aggression against the partner material increases, which is not preferable.

The amount of the film-reinforced fine particles to be dispersed is preferably 5 to 30% by volume. The amount of film-reinforced particles dispersed is 5
If it is less than%, sufficient abrasion resistance and scuff resistance cannot be obtained, and if it exceeds 30%, the strength of the plating film layer becomes insufficient and the plating film layer may peel off.

As a material for the piston ring used in the present invention, martensitic stainless steels disclosed in Japanese Patent Application Nos. 62-146006 and 62-230446 are preferable. By the way, when listing the chemical components, C; 0.7-1.1%, Cr; 12
~ 25%, Si; 2% or less, Mn; 2% or less, and further contains Al; 0.05-1.10%, Ni; 0.2-2.0%, Mo; 0.2-2.
0%, V; 0.05 to 0.5%, Nb; 0.05 to 0.5%, Cu; 0.2 to 1.0%
One or more of them are contained, and the balance consists of Fe and impurity elements. If martensitic stainless steel having the above composition is used as the piston ring material, the particle size is 2 μm.
A piston ring in which the above carbonitride crystallizes in an area ratio of 3% or more is obtained.

The carbonitride crystallized in the piston ring material needs to have an area ratio of 3% or more occupied by particles having a particle size of 2 μm or more. If the area ratio of carbonitrides having a particle size of 2 μm or more is less than 3%, the formation of protrusions by carbonitride is low, and the depth of the recesses forming the oil pool on the friction surface is shallow, resulting in wear resistance. This is because the property deteriorates.

[Operation] With the structure of the sliding portion of the internal combustion engine by the combination of the cylinder bore and the piston ring of the present invention, excellent wear resistance far superior to conventional materials, which cannot be obtained by each material alone, is obtained. The reason why such excellent wear resistance is obtained is that, as shown in FIG. 4, both the cylinder bore material 5 and the piston ring material 6 are hard substances having a high hardness in the matrix, that is, film strengthening in the cylinder bore material 5. Since the fine particles 7 and the Cr carbonitride 8 crystallized in the piston ring material 6 exist, the friction surface causes the hard substance to form the convex portions 9 and 10 with respect to the matrix due to abrasion. As a result, the recesses 11 and 12 that function as oil pools are formed between the friction surfaces, which prevents the oil from running out, and the Cr carbonitride 8 and the film-reinforced fine particles 7 that are the substances that form the projections 9 and 10. It is considered that excellent wear resistance and scuffing resistance can be obtained because the friction between the high melting points that do not easily adhere to each other becomes mostly.

[Examples] Next, examples of the present invention will be described in detail to clarify the effects of the present invention.

(Example 1) As shown in FIG. 2, a seizure test piece has an inner diameter of 20 mm and an outer diameter.
25.7mm, 17mm height cylinder bore material 20 FC23 as it is, Ni-3P base on the sliding surface and SiC average particle size 4μm 2
Two types were prepared by applying Ni composite plating in which 0% by volume was dispersed.

0.9C-21Cr stainless steel, 17Cr stainless steel and 13Cr
Using stainless steel, length 30mm, width as shown in Fig. 2
A piston ring material 22 of 30 mm and a height of 5 mm was produced. The piston ring material 22 made of these stainless steels was heated to 530 to 590 ° C. in an ammonia gas stream and subjected to gas nitriding treatment for 5 hours or more. 2 μm of the obtained piston ring material 22
The area ratio of the above carbonitrides and the hardness of the nitride layer of 20 μm from the surface were measured. For comparison, a piston ring material 22 was similarly prepared for a material plated with Cr and a material made of special cast iron.

Using the cylinder bore material 20 and piston ring material 22 obtained as described above, under a severe lubrication condition such as a racing engine, high rotation speed, high oil temperature, low viscosity oil (with fuel dilution), small amount of lubrication A seizure test was conducted assuming the case of use.

For the seizure test, a mechanical testing laboratory type friction and wear tester was used. As shown in FIG. 2, the cylinder bore material 20 and the piston ring material 22
Were brought into contact with each other under a load, and the piston ring member 22 was rotated to slide on the cylinder bore member 20. The test condition is sliding speed 1.
2m / sec, low viscosity engine oil drop lubrication, load increases by 25kg every 2 minutes. For the determination of seizure, the load at which the friction coefficient sharply increased by 0.2 or more was taken as the seizure load. The results obtained are shown in Table 1. Table 2 shows the chemical composition of the stainless steel used for the piston ring material 22, the amount of carbonitride, and the hardness of the nitrided layer.

As is clear from Table 1, in the conventional piston ring and cylinder bore combinations in which the piston ring material is Cr-plated or special cast iron, or the cylinder bore material is FC23, the seizure load is 167.5 kg or less. ,
The combination of the cylinder bore material and the piston ring material of the present invention has a seizure load of 450 kg or more, and the present invention provides excellent seizure resistance as compared with the combination of conventional materials.

(Example 2) As shown in FIG. 3, as a wear test piece, an outer diameter of 35 mm, a width
Two types of 9 mm cylinder bore material 20 were prepared, one with F23C as it was and one with Ni composite plating on the sliding surface of Ni-3P base with 20% by volume of SiC average particle diameter 4 μm dispersed.

0.9C-21Cr stainless steel similar to that used in Example 1, 17
Using Cr stainless steel and 13Cr stainless steel, a piston ring material 22 having a length of 15.75 mm, a width of 6.35 mm and a height of 10.15 mm as shown in FIG. 3 was produced. The piston ring material 22 made of these stainless steels is 530 in an ammonia gas flow.
It was heated to ˜590 ° C. and subjected to gas nitriding treatment for 5 hours or longer.
In addition, for comparison, the piston ring material 22 is also used for those plated with Cr and those made of special cast iron.
Was produced.

Next, a wear test was performed in the case where the obtained cylinder bore material 20 and piston ring material 22 were combined. Wear test is LWF
As shown in FIG. 3, the cylinder bore member 20 and the piston ring member 22 were brought into contact with each other under a load using a -1 abrasion tester, and the cylinder bore member 20 was rotated and slid on the piston ring member 22. The test conditions were a sliding speed of 1.2 m / sec, low-viscosity engine oil dripping, a load of 60 kg, and sliding for 120 minutes, and the amount of wear of the piston ring material 22 was measured. The results obtained are shown in Table 3.

As is clear from Table 3, in the case where the cylinder bore material is Ni-3P base composite plating, compared with the case where the cylinder bore material is FC23, the mating piston ring material is No. 4 13Cr stainless steel / gas nitriding, When Cr-plated or special cast iron, the wear of the piston ring material is about doubled. On the other hand, in the combination of the cylinder bore material and the piston ring material of the present invention, the amount of wear is only slightly increased, and it has been confirmed that the combination of the cylinder bore material and the piston ring material of the present invention can secure excellent wear resistance. It was

[Effects of the Invention] The structure of the cylinder bore of the internal combustion engine of the present invention comprises a cylinder bore having at least a Ni composite plating containing Ni or a P compound of Ni dispersed in the plating film with the plating film reinforcing fine particles formed on the surface thereof. A cylinder bore and a piston are characterized by combining a piston ring in which a carbonitride having a grain size of 2 μm or more crystallized in an area ratio of 3% or more crystallized on the sliding surface with respect to the cylinder bore. On the friction surface of the ring, the film-reinforced fine particles and hard substances such as carbonitrides form protrusions, and the recesses formed in the matrix function as oil reservoirs, making it difficult to run out of oil and Compared to the sliding part of the combination of the conventional cylinder bore and piston ring, the friction between the high melting points where the hard substance that forms is difficult to adhere to becomes the majority. Te, there is excellent effect that markedly excellent wear resistance and scuffing resistance can be obtained.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a cylinder bore, FIG. 2 is a perspective view schematically showing a seizure test, FIG. 3 is a perspective view schematically showing a wear test, and FIG. 4 is a friction surface between a cylinder bore and a piston ring. It is a schematic diagram for microscopically explaining. 1 …… Cylinder liner, 3 …… Piston ring, 20 ……
Cylinder bore material, 22 ... Piston ring material.

Claims (1)

[Claims] 1. A cylinder bore having a Ni composite plating layer composed of Ni or a P compound of Ni in which film-reinforced fine particles are dispersed, and a carbonitride having a particle size of 2 μm or more crystallized in an area ratio of 3% or more. An internal combustion engine comprising a piston ring having a gas nitriding treatment on a sliding surface with respect to a cylinder bore.