JP2003254156A - Combination of cylinder and piston ring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combination of a cylinder and piston ring having a low friction force upon sliding, less wearing amount both in the cylinder and piston ring, excellent in the scuffing resistance, and emitting less blowby gas. <P>SOLUTION: The cylinder made of aluminum allow is combined with the piston ring using austenite series stainless steel as the parent material whose surface, at least the peripheral sliding surface, is coated with a hard chromium laminated plating film consisting of two or more hard chromium plating layers. In the hard chromium plating layers, micro-cracks are distributed each including a part which opens at the outer surface and has such a depth as remaining in the same chromium plating layer and a part which extends to the other layer situated deeper. This assures excellent oil keeping performance, eliminates substantially any variation of the oil keeping performance, allows showing a low friction force constantly at the time of sliding, and suppressing generation of the blowby gas. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In recent years, from the viewpoint of conservation of the global environment,
Internal combustion engines are required to be lightweight and have improved fuel efficiency. In accordance with such trends, piston rings for internal combustion engines have been made as thin as possible in terms of shape and various improvements have been made in terms of material from cast iron to stainless steel.
In recent piston rings, high hardness martensitic stainless steel is generally used as the piston ring base material to reduce the weight and improve wear resistance and scuff resistance. It is used after being subjected to surface hardening treatment such as plating.

On the other hand, a cylinder, which is a mating material for sliding of a piston ring, has conventionally been made of an iron-based material such as cast iron because of the required mechanical characteristics. However, since a cylinder made of an iron-based material has a heavy weight, it is not possible to satisfy the recent demand for weight reduction of an internal combustion engine, and recently, an engine made of an aluminum alloy is becoming popular. However, since the aluminum alloy cylinder is soft, avoiding direct sliding between the highly hardened piston ring and the inner surface of the soft aluminum alloy cylinder, and usually installing a cylinder liner Abrasion resistance of the inner peripheral surface of the aluminum alloy cylinder is ensured.

Conventionally, as such a cylinder liner, a cast iron cylinder liner has been generally used. But,
Recently, there has been proposed a cylinder liner that uses an aluminum alloy for the purpose of weight reduction and is designed to improve sliding characteristics. For example, Japanese Unexamined Patent Publication (Kokai) No. 9-19757 discloses a hypereutectic aluminum-silicon alloy cylinder liner in which a silicon primary crystal that is hard particles and an intermetallic compound are exposed on a sliding surface.

In Japanese Patent Laid-Open No. 6-322459, a sliding surface portion is compositely reinforced with a reinforcing material which is a mixture of alumina short fibers and non-spherical mullite particles, and aluminum having improved wear resistance and scuff resistance. Alloy cylinder sliding members have been proposed. Further, Japanese Patent Laid-Open No. 5-86964 discloses that
A measure for improving slidability has been proposed in which the inner peripheral surface of an aluminum alloy cylinder is subjected to surface treatment such as Ni-based composite plating treatment.

On the other hand, in an engine in which the heat load increases with the demand for higher engine speed and higher output, the tension of the piston ring has conventionally been set high in order to improve the gas sealability as a measure against blow-by. . JP-A-9-197
The techniques disclosed in Japanese Laid-Open Patent Publication No. 57-322459 and Japanese Laid-Open Patent Publication No. 6-322459 are measures for improving the slidability from the cylinder side in response to such high piston ring tension.

[0007]

However, recently, from the viewpoint of global environment conservation, there has been a strong demand for lower fuel consumption of internal combustion engines. In response to such a trend toward the internal combustion engine, it is required that the piston ring, which is a sliding member of the internal combustion engine, have a low tension in order to obtain a low friction force. However, JP-A-9-19757 and JP-A-6-3
The cylinder manufactured by the technique described in Japanese Patent No. 22459 is supposed to have a high tension in the piston ring when sliding in combination with the piston ring. Therefore, when the low tension piston ring is used in combination with these cylinders, there is a problem that the optimum combination of cylinder and piston ring cannot be obtained.

Furthermore, Japanese Patent Laid-Open Nos. 9-19757 and 6
In the technology described in Japanese Patent No. 322459, there is a problem that the manufacturing process of the cylinder is complicated and the manufacturing cost rises. For this reason, there has been a strong demand for a combination of a cylinder and a piston ring that has a low frictional force during sliding and is inexpensive.

On the other hand, as the piston ring, from the viewpoint of improving wear resistance, scuffing resistance, corrosion resistance, etc., recently, a piston ring made of martensitic stainless steel as a base material is generally used as the first pressure ring. It is used. However, when this martensitic stainless steel piston ring slides with an aluminum alloy cylinder as a mating member, especially when it is used as the first pressure ring, there is a problem that blow-by gas is generated more often. It is considered that this is because the martensitic stainless steel piston ring used as the first pressure ring could not follow the thermal expansion of the aluminum alloy cylinder, the gas sealability was deteriorated, and gas blow-through occurred. .

To solve such a problem, for example, Japanese Patent Laid-Open No. 2000-1
In Japanese Patent No. 45963, a piston ring made of austenitic stainless steel having a coefficient of thermal expansion of 15 × 10 ⁻⁶ / ° C. or higher is proposed for an aluminum alloy cylinder. However, the piston ring described in Japanese Patent Laid-Open No. 2000-145963 is a piston ring that is assumed to be loaded with high tension, and is resistant as a low tension piston ring to obtain low friction force during sliding. There is a problem that the abrasion resistance and the scuff resistance are insufficient. Further, in the technique described in Japanese Patent Application Laid-Open No. 2000-145963, the nitride layer is formed by the nitriding treatment, but there is a problem that the fragile compound layer formed on the surface is easily peeled off.

The present invention advantageously solves the above-mentioned problems of the prior art, has a low frictional force during sliding, a small amount of wear on both the cylinder and the piston ring, and is excellent in scuff resistance. It is an object to provide a combination of a cylinder and a piston ring that generates less gas.

[0012]

[Means for Solving the Problems] In order to achieve the above-mentioned objects, the present inventors diligently studied a piston ring capable of reducing frictional force during sliding. As a result, they have found that by forming a hard chrome laminated plating film on the surface of the base material of the piston ring, the oil retaining property is improved and the frictional resistance during sliding can be significantly reduced. Also, the hardness of the hard chrome laminated plating film is at most Hv900, and its opponent attack is low.The piston ring with such hard chrome laminated plating film formed on the surface can be directly attached without installing a special cylinder liner. It can be used in combination with the inner surface of a soft aluminum alloy cylinder, and has the same or higher wear resistance and durability as the combination of a conventional high hardness piston ring and a cylinder liner containing high hardness particles. It was found that it shows scuffing. Then, the base material of the piston ring for forming such a hard chrome laminated plating film on the surface is made of an aluminum alloy (for example, ADC12, hypereutectic Al) which is a cylinder material.
-Si alloy, etc.) has a coefficient of thermal expansion close to that of austenitic stainless steel, the frictional force during operation can be reduced, and at the same time blow-by gas is not generated while the sealing property does not decrease during operation. I thought that I could prevent it.

The present invention has been completed based on the above findings. The gist of the present invention is as follows. (1) A combination of a cylinder of an internal combustion engine and a piston ring that slides on the inner peripheral surface of the cylinder, wherein the cylinder is an aluminum alloy cylinder, and the piston ring is austenitic stainless steel as a base material. And a piston ring having a hard chrome laminated plating film formed of two or more hard chrome plated layers on at least the outer peripheral sliding surface, the hard chrome laminated plating film comprising:
In each of the two or more hard chrome plating layers, fine cracks opening to the outer surface side are distributed, and the fine cracks remain in each hard chrome plating layer in which their own openings exist in the depth direction, A combination of an aluminum alloy cylinder and a piston ring, which is a plating film including a portion extending into the hard chrome plating layer below each hard chrome plating layer having its own opening. (2) In (1), the fine cracks have an area ratio of 2.0 to 40.0 in a cross section of the hard chromium laminated plating film.
% Within the range of 1.5% to 35.0% of microcracks remaining in each hard chrome plating layer in which the self-opening exists.
%, Micro cracks that extend into the hard chrome plating layer below each hard chrome plating layer that has its own opening
Combination of aluminum alloy cylinder and piston ring, which is 0.5 to 25.0%. (3) In (2), the thickness of each of the hard chromium plating layers is 5.0 to 30.0 μm, and the opening width of the fine cracks is 0.2 μm or less. Combination with a ring. (4) In (2), the thickness of the hard chromium plating layer on the outermost surface side of each of the hard chromium plating layers is set to be thicker than the thickness of other hard chromium plating layers and 50.0 μm or less. A combination of an aluminum alloy cylinder and a piston ring, wherein the thickness of the chrome plating layer is 5.0 to 30.0 μm and the opening width of the fine cracks is 0.2 μm or less. (5) In (2), the hard chrome laminated plating film is composed of three or more hard chrome plating layers, and of the three or more hard chrome plating layers, the thickness of the hard chrome plating layer closest to the base material surface. Thickness is 80.0 μm or less than the thickness of other hard chrome plating layers, and the thickness of the hard chrome plating layer on the outermost surface side is next to the thickness of the hard chrome plating layer closest to the surface of the base material and 50.0 μm. A combination of an aluminum alloy cylinder and a piston ring, wherein the thickness of the other hard chromium plating layer is 5.0 to 30.0 μm, and the opening width of the fine cracks is 0.2 μm or less. (6) In any one of (1) to (5), the austenitic stainless steel is, in mass%, Ni: 3.5 to.
A combination of an aluminum alloy cylinder and a piston ring, which is an austenitic stainless steel having a composition containing 17.0% and Cr: 15.0 to 20.0%. (7) In any one of (1) to (6), the aluminum alloy cylinder is JIS ADC12, J
Cylinder made of die-cast aluminum alloy having a composition specified in either IS ADC10 or JIS ADC14, or JIS AC8A,
A combination of an aluminum alloy cylinder and a piston ring, which is a static casting aluminum alloy cylinder having a composition defined in either JIS AC8B or JIS AC8C.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A combination of a cylinder and a piston ring according to the present invention is a cylinder made of an aluminum alloy, without installing a special cylinder liner in the bore or without strengthening the inner peripheral surface of the cylinder. This is a combination in which the inner circumferential surface of the cylinder is directly used as the sliding surface of the piston ring. In the combination of the present invention, the piston ring base material is austenitic stainless steel, and a hard chromium laminated plating film composed of two or more hard chromium plating layers is formed on at least the outer peripheral sliding surface of the base material surface, Is characterized by.

The piston ring used in the present invention is composed of an austenitic stainless steel material as a base material. Austenitic stainless steel is Ni: 3.5-17.0%,
Cr: 15.0 to 20.0%, preferably C: 0.08% or less, Si: 1.00% or less, Mn: 2.00% or less, or Mo: 6% or less, Cu: 4% or less, Nb: 1%. Below, T
It is preferable that the composition contains one or two or more of i: 0.6% or less and N: 0.3% or less, and the balance Fe and unavoidable impurities. From the viewpoint of ductility, P and S as unavoidable impurities are P: 0.045% or less and S: 0.03% or less.
It is preferably 0% or less.

Next, the reasons for limiting the composition of the austenitic stainless steel material will be explained. Ni: 3.5 to 17.0% Ni has the effect of stabilizing the austenite phase and increasing the coefficient of thermal expansion. The coefficient of thermal expansion of the piston ring,
In order to obtain a value close to the coefficient of thermal expansion of the aluminum alloy that constitutes the cylinder, Ni must be contained at 3.5% or more. Further, when the content exceeds 17.0%, the thermal expansion coefficient decreases, so in the present invention, Ni is preferably limited to the range of 3.5 to 17.0%.

Cr: 15.0 to 20.0% Cr is an element that increases the corrosion resistance and the strength to improve the wear resistance. Further, as an element for forming an austenite structure, Cr of 15% or more is used in the present invention. Requires inclusion. On the other hand, if the content exceeds 20.0%, it is necessary to further increase the content of Ni necessary for forming the austenite structure, which results in an increase in cost, which is not preferable. Therefore, in the present invention, Cr is preferably limited to 15.0 to 20.0%.

The reasons for limiting the components other than Ni and Cr are as follows. C: 0.08% or less C is an element that increases the strength and stabilizes the austenite phase, but if it is contained in a large amount, the strength becomes too high and the workability is lowered, and the thermal expansion coefficient is lowered. Therefore, C is preferably limited to 0.08% or less.

Si: 1.00% or less Si is an element necessary as a deoxidizing agent in the steelmaking process, but it is a ferrite-forming element, and its inclusion in a large amount deteriorates the mechanical properties, so it is desirable to reduce it as much as possible. In the present invention, up to 1.00% is acceptable. Mn: 2.00% or less Mn has a function of forming a solid solution in steel to improve the strength and stabilize the austenite phase, but if it exceeds 2.00%, the strength becomes too high and the machinability deteriorates. Therefore, Mn is 2.00
It is preferably limited to not more than%.

Mo: 6% or less, Cu: 4% or less, Nb: 1% or less, Ti: 0.6% or less, N: 0.3% or less, one or more of Mo, Cu, Nb, Ti and N are It is an element that improves corrosion resistance, strength, and workability, and can be selected as necessary and contained in the above range. As the austenitic stainless steel material having the above composition range, SUS 304, SUS 303, SUS 316
Are exemplified, and any of them can be suitably applied as the piston ring base material used in the present invention. In the present invention, C
There is no problem even if it is a low carbon stainless steel with an amount of 0.03% or less, but it becomes an excessive quality and a high cost.

By using an austenitic stainless steel material having the above composition range as the base material, the coefficient of thermal expansion of the piston ring is close to that of the aluminum alloy that is the cylinder material, that is, 15 × 10 ^-6 / ° C or more. Becomes As a result, the difference in thermal expansion between the cylinder material and the piston ring is small, and the deterioration of the sealability of the piston ring can be prevented.
Generation of blow-by gas can be suppressed.

The piston ring used in the present invention comprises an austenitic stainless steel material having the above composition range as a base material, and a hard chrome laminated layer comprising two or more hard chrome plating layers on at least the outer peripheral sliding surface of the base material surface. Form a plating film. The “hard chrome laminated plating film” in the present invention is a plating film in which two or more hard chrome plated layers are stacked, and each hard chrome plated layer has
Fine cracks that open on the sliding surface side (outer surface of the plating film) are distributed, and these fine cracks remain in each hard chrome plating layer where their own openings exist in the depth direction (fine cracks) and their own openings. Part that extends into the hard chrome plating layer below each hard chrome plating layer where there are (fine cracks)
It means a plating film including and. An example of the "hard chrome laminated plating film" is schematically shown in FIG.

FIG. 1 shows a cross section of a piston ring in which a hard chrome laminated plating film 2 composed of four hard chrome plated layers 2a, 2b, 2c and 2d is formed on the outer peripheral surface of a base material 1. . In each hard chrome plating layer, fine cracks 3 opening on the outer surface side of the plating film are distributed. In each hard chrome plating layer, fine cracks having a substantially V-shaped cross section are formed in a mesh shape and are continuous at least in the opening portion of the surface. Even if there is a single microcrack on the surface of each hard chrome plating layer, the reaching depth of the crack bottom differs depending on the location.

Except for the hard chrome plating layer 2a closest to the surface of the base metal, these fine cracks are divided into a portion 3a remaining in each hard chrome plating layer having its own opening and its own opening in the depth direction. Portion 3 extending from the existing hard chrome plating layers to the lower hard chrome plating layers
b and 3c are included. The fine crack 3b is an example in which the crack extends over two hard chromium plating layers, and 3c is an example in which the crack extends over three layers. The portion of the fine crack extending to the lower layer may be partly combined with the fine crack that opens to the lower layer.

In the hard chrome laminated plating film formed on the piston ring used in the present invention, since two or more hard chrome plated layers having fine cracks are laminated, the outer surface side (sliding surface side) of each hard chrome plated layer is ) Is closed by the upper hard chrome plating layer. Therefore, in the hard chrome laminated plating film formed on the piston ring used in the present invention, stress concentration at the crack bottom during sliding occurs in the outermost hard chrome plated layer, but in the lower hard chrome plated layer, Micro cracks opening in the plating layer are covered by the hard chrome plating layer on the upper layer,
Since the holes are sealed, stress concentration is prevented from occurring at the crack bottom and cracks hardly propagate until the upper plating layer disappears and the microcracks open, and the deterioration of the hard chrome laminated plating film is suppressed.

Since the fine cracks present in each hard chrome plating layer have a substantially V-shaped cross section, the opening area and opening of the fine cracks are increased as the plating film is worn by sliding on the inner peripheral surface of the cylinder. The volume of the cavities gradually decreases. However, in the hard chrome laminated plating film used in the present invention, when the hard chrome plating layer of the upper layer completely disappears due to wear, a large number of fine cracks newly opening in the lower layer appear, and the opening area and opening of the fine cracks are increased. The cavity volume increases again. Furthermore, in the hard chrome laminated plating film used in the present invention, the micro cracks of each hard chrome plating layer are related to the depth direction, and the crack bottom extends to the hard chrome plating layer below the layer in which the self crack opening exists. Since it includes the portion including the cracked portion, a sufficient amount of fine cracks exist even before the hard chrome plating layer as the upper layer disappears. Therefore, the piston ring used in the combination of the present invention has an excellent oil retaining property, and even if the wear of the hard chromium laminated plating film progresses, no periodic reduction of the oil retaining property occurs, or even if it occurs, The fluctuation range is small.
Therefore, with the combination of the cylinder and the piston ring of the present invention, there is little or no periodic decrease in the oil retaining property, and the frictional force can be constantly kept low.

The hard chromium laminated plating film formed on the surface of the base material of the piston ring used in the combination of the present invention has fine cracks within the range of 2.0 to 40.0% in the area ratio in the cross section of the hard chromium laminated plating film. Is preferably present. If the total amount of fine cracks is less than 2.0%, the cavities holding the lubricating oil are insufficient, and the oil retaining property deteriorates. On the other hand, if the amount of fine cracks exceeds 40.0%, the strength of the film becomes insufficient.

Further, in terms of area ratio in the cross section, the portion of the microcracks remaining in each hard chrome plating layer having its own opening is 1.5 to 35.0% in area ratio, and each hard chrome plating layer having its own opening is Also, adjusting the portion extending into the lower hard chrome plating layer to be 0.5 to 25.0% reduces fluctuations in the oil retaining property of the plating film and maintains a low frictional force during sliding. Is preferable.

If the ratio of the portion of the fine cracks that remains in each hard chrome plating layer having its own opening is less than 1.5%, the number of voids in the fine cracks is small and the oil retaining property is deteriorated. on the other hand,
When it exceeds 35.0%, the amount of fine cracks in two or more layers is relatively small, and the oil retention is greatly varied. Of the microcracks, the part that extends into the hard chrome plating layer below each hard chrome plating layer where its own opening exists
If it is less than 0.5%, the fluctuation range of oil retention becomes large. on the other hand,
If it exceeds 25.0%, the influence of stress concentration at the crack bottom during sliding will spread to the lower plating layer, so cracks will easily develop and the plating film will deteriorate.

Various characteristics required for the piston ring are such that the thickness of each hard chrome plating layer constituting the hard chrome laminated plating film is 5.0 to 30.0 μm and the opening width of fine cracks is 0.2 μm or less. Is preferable, and it is preferable from the viewpoint of ensuring the amount and distribution of fine cracks in the cross section of the plating film within the above range. The opening width of the microcracks is 0.2μ.
m or less means that the width of all microcracks is 0.2 μm
It is less than or equal to the amount that does not affect the performance even if a crack having an opening width of more than 0.2 μm is present.

The thickness of each hard chrome plating layer constituting the intermediate layer of the hard chrome laminated plating film is 5.0 to 30.0.
The thickness of the hard chrome plating layer on the outermost surface side is thicker than the thickness of other hard chrome plating layers, and
It is more preferably 0.0 μm or less, preferably 5.0 μm or more. By making the hard chromium plating layer on the outermost surface side thicker than the intermediate layer, the rigidity of the outermost surface can be increased and the breakage resistance of the piston ring is improved. If the thickness of the hard chrome plating layer on the outermost surface side exceeds 50.0 μm, the deformation during sliding is limited to the outermost surface layer, and the deformation absorbability of the entire coating decreases.

When the hard chrome laminated plating film formed on the surface of the base material of the piston ring used in the combination of the present invention is composed of three or more hard chrome plating layers, the hard chrome closest to the base material surface. The thickness of the plating layer is thicker than other hard chromium plating layers and is 80.0 μm or less, and the thickness of the hard chromium plating layer on the outermost surface side is next to the thickness of the hard chromium plating layer closest to the base metal surface. Thick and
50.0 μm or less, and the thickness of other hard chrome plating layers is 5.
The thickness is more preferably 0 to 30.0 μm. Even in this case, it is preferable that the opening width of the microcracks is 0.2 μm or less.

By forming the hard chrome plating layer closest to the surface of the base material thicker than other hard chrome plating layers, it is possible to reduce and thin fine cracks in the hard chrome plating layer. The rigidity of the entire hard chrome laminated plating film can be increased. When the thickness of the hard chrome plating layer closest to the surface of the base material is thinner than the other hard chrome plating layers, the effect of suppressing the displacement amount near the boundary with the piston ring base material is small. When the thickness of the hard chrome plating layer closest to the surface of the base metal exceeds 80.0 μm, the ratio of the bottom layer to the entire plating film increases, and the number of intermediate plating layers decreases, resulting in The advantageous characteristics cannot be effectively exhibited.

A preferred method of manufacturing the piston ring used in the combination of the present invention will be described. In the present invention, preferably, an austenitic stainless steel material having the above-mentioned composition is used as a base material, and after being formed into a predetermined shape of a piston ring, if necessary, subjected to pretreatments such as degreasing, washing, and honing, and then hard chromium lamination Apply plating treatment.

In the hard chrome laminated plating treatment, a hard chrome plating layer forming step of forming a hard chrome plating layer having fine cracks on the surface by immersing the base material in a chrome plating bath and performing a plating step and a reverse electrolysis step, It consists of repeating as many layers as necessary. The chromium plating bath to be used is not particularly limited, but it is a conventionally known acidic chromic acid solution,
It is preferable to use a fluorination bath or the like. From the viewpoint of plating adhesion, it is preferable to immerse the base material in such a chrome plating bath and perform electrolytic polishing to clean the base material surface.

After electropolishing, a plating process is performed to first form a hard chromium plating layer as a lowermost layer having a predetermined thickness on the surface of the base material. In the plating process, the base material is the cathode and the current density is 20 ~
It is preferable to plate as 100 A / dm ² . The plating thickness is preferably adjusted by setting the current application time according to the desired plating thickness. Then, the polarity is reversed with a relatively fast switching time, and the reverse charging process is performed.
When forming the hard chrome plating layer of the bottom layer, it is preferable that the thickness of the bottom layer be 80 μm or less and be the thickest in the plating film, and the depth of fine cracks should be kept within the chrome plating layer of the bottom layer. Since it is necessary, the polarity switching time is preferably 100 μsec or less. In the reverse current step, the base material is used as an anode and the current density is set to 20 to 100 A / dm ² , and the hard chromium plating layer is eluted so that a preset thickness remains.

Since a hard chrome plating layer is further laminated as an intermediate layer on the uppermost hard chrome plating layer,
The second and subsequent plating steps and reverse current steps are performed. After the reverse electrolysis process of the bottom hard chrome plating layer is completed, the polarity is reversed again and the base material is used as the cathode, and the current density is 30 to 120 A /
As dm ² , it is preferable to perform plating and adjust the current application time to form a hard chromium plating layer having a predetermined thickness.
Then, the polarity is reversed at a slow switching time, and a reverse charging process is performed. In the reverse current process, the base material was used as the anode and the current density was 20
The hard chrome plating layer is eluted so that a preset thickness remains at -100 A / dm ² . The thickness of the hard chrome plating layer of the intermediate layer is preferably 5.0 to 30.0 μm, and in this thickness, the polarity switching time from the plating process to the reverse current process is 100 to 2000 μsec. Is preferred. This makes it possible to form a fine crack in which the opening width is 0.2 μm or less and a portion where the fine crack stops in a single layer and a portion that extends to two or more layers are mixed.

By repeating such a plating process and a reverse electrolysis process for the required number of laminated layers, it is possible to form an intermediate layer (hard chrome plated layer) having a desired number of laminated layers. After forming the required number of intermediate layers, the hard chromium plating layer on the outermost surface is formed. After the reverse charge process of the intermediate layer was completed, the polarity was reversed again and the base material was used as the cathode, and the current density was 30
It is preferable that the hard chrome plating layer is formed by plating at 120 A / dm ² and setting the current application time so that a predetermined thickness is obtained. Then, the polarity is reversed at a slow switching time, and a reverse charging process is performed. In the reverse current step, the base material is used as the anode, the current density is set to 20 to 100 A / dm ² , and the current application time is set so that the preset thickness remains, and the hard chromium plating layer is eluted. The thickness of the hard chromium plating layer of the outermost surface layer is preferably 5.0 to 50.0 μm. In this thickness, the polarity switching time from the plating process to the reverse current process is 100 to 2000 μsec. It is preferable. This makes it possible to form a fine crack in which the opening width is 0.2 μm or less and a portion where the fine crack stops in a single layer and a portion that extends to two or more layers are mixed.

By the steps described above, a piston ring having a hard chromium laminated plating film formed on at least the outer peripheral side (sliding surface) of the base material surface can be obtained. The hard chrome laminated plating film has excellent adhesion to the piston ring base material,
The effect is that the durability of the piston ring is improved.
Even if such a piston ring is built into a piston and slid (used) directly in combination with a soft aluminum alloy cylinder bore, it has excellent oil retention, so wear resistance and scuff resistance are combined with the conventional combination. It can be average or higher. According to the combination of the present invention, the cylinder (cylinder) can be directly combined with a soft aluminum alloy cylinder without a special cylinder liner and without special composite reinforcement of the cylinder. (Block) A remarkable effect that the manufacturing process can be simplified and the manufacturing cost can be reduced.

Further, in the present invention, since the austenitic stainless steel is used as the piston ring base material, the difference in thermal expansion between the piston ring and the aluminum alloy cylinder during operation is small, and the gas sealability of the piston ring is deteriorated. Therefore, the effect of preventing the generation of blow-by gas is exhibited. Further, as described above, an aluminum alloy cylinder that can be used in combination with a piston ring having hard chrome laminated plating formed on at least the outer peripheral side (sliding surface side) of the base material is a cast product manufactured by a die casting method, That is, any aluminum alloy die casting specified in JIS H 5302 can be preferably used. Among them, ADC12, ADC10, AD
Aluminum alloy die castings having a composition defined in any of C14 are preferred. Since the aluminum alloy cast product formed by the die casting method has a high cooling rate, the structure becomes finer, the hardness becomes higher, and the tensile strength can be improved.

Further, the aluminum alloy cylinder does not pose any problem as a cast product manufactured by the static casting method.
JIS H 5202 for cast products manufactured by the static casting method
Any of the aluminum alloy castings defined in 1. can be suitably used. Among them, AC8A, AC8B, AC8C
Aluminum alloy castings having compositions defined in any of the above are preferred. Since the stationary casting method is not suitable for the production of large-sized castings such as cylinder blocks, when using the stationary casting method, it is possible to cast it into a thin shape such as a sleeve. .

The method for producing the cylinder used in the combination of the present invention is not particularly limited, and any of the commonly known methods can be applied. For example, a molten aluminum alloy having a predetermined composition is melted, and a mold assembled into a predetermined size and shape is cast by a high-pressure casting method or static casting, or after further forging the melt, the inner peripheral surface is further With a predetermined surface shape (honing)
Is preferably applied.

[0043]

[Example] Austenitic stainless steel (SUS 304:
C: 0.06 mass%, Si: 0.90 mass%, Mn: 1.5 mass%,
P: 0.02 mass%, S: 0.02 mass%, Cr: 18 mass%, Ni:
8% by mass, balance Fe), martensitic stainless steel (S
US 440: C: 0.85 mass%, Si: 0.40 mass%, Mn: 0.30 mass%, Cr: 17.0 mass%, P: 0.03 mass%, S: 0.02 mass%, Mo: 1.0 mass%, V: 0.1 mass% , And the balance Fe) was used as a raw material to produce a piston ring base material of a predetermined size and shape. Degreasing these piston ring base materials as pretreatment,
After washing and liquid honing, it was immersed in a plating bath. The plating bath was a conventionally known fluoride bath.

First, in the plating bath, current density: 60 A /
dm²Electrolytic polishing was performed under the conditions of application time: 20 s. Just
Then, reverse the polarity and use the base material as the cathode, current density: 60A
/ Dm ², Plating time: plating under the condition of 30min
Then, the polarity is switched with the polarity switching time of 750 μs.
Inverted, base material as anode, current density: 60A / dm², Applied
Time: 90 seconds, reverse charge process is applied
A plating layer was formed.

Then, the polarity is reversed again, the base material is used as the cathode, and the plating step is performed under the conditions of current density: 60 A / dm ² and application time: 15 min, followed by the polarity switching time of 750 μs. Reversed, the base material was used as an anode, a reverse current process was performed under conditions of current density: 60 A / dm ² and application time: 90 s to form a hard chrome plating layer (intermediate layer) having a thickness shown in Table 1. The intermediate layer plating step and the reverse current step were repeated 10 times to form a total of 10 intermediate layers.

Next, the polarity was reversed again, the base material was used as the cathode, and the outermost surface layer was formed by the plating step of plating under the conditions of current density: 60 A / dm ² and application time: 20 min. Note that the reverse charge step was omitted in the outermost surface layer. However, since the outermost plating layer is ground by the processing after plating,
The sliding surface becomes a surface having fine cracks. Further, the uncut portion near the upper and lower corners of the piston ring protects the lower plated layer.

When the conditions of the plating process and the reverse current process are changed and the amount of fine cracks is small, the amount of fine cracks is large,
If there is a large amount of cracks remaining in a single layer, form a hard chrome laminated plating film when the amount of cracks extending between two layers is large,
It was used as a comparative example. A piston ring having a hard chrome laminated plating film with different layer thickness and fine crack distribution is combined with an aluminum alloy cylinder bore as shown in Table 1 to measure blow-by gas generation, wear test and scuffing. The test was conducted.

The cylinder as the mating material to be combined with the piston ring is JIS ADC12 or AD.
An aluminum alloy die cast of C10 composition was used, the surface was subjected to polishing, and the surface roughness was set to Rz: 2 μm. Some cylinders were made of aluminum alloy by the static casting method of JIS AC8A composition. The thickness of the plating layer formed on the piston ring surface, the number of layers, the amount of fine cracks in the coating,
Table 1 shows the ratio of fine cracks and the conditions for combining the piston ring and the cylinder.

The same plating process and reverse electrolysis process were performed once using the same plating bath to prepare a piston ring having a single-layer hard chrome plating film formed thereon, which was used as a conventional example. In addition, the gas nitriding layer (nitriding layer thickness: 70μ
m, the hardness of the nitride layer: Hv1100) was formed as one of the comparative examples.

[0050]

[Table 1]

The method for measuring the amount of blow-by gas generated was as follows. (1) Measurement of blow-by gas generation amount Piston rings (No. 1, No. 10) having hard chromium laminated plating film shown in Table 1 formed on the outer peripheral sliding surface were used as test materials for the first pressure ring. . The second pressure ring and oil ring are conventional piston rings (material: FC
250) was used. The gap width of the abutment of the first pressure ring is 0.3 mm, the gap width of the abutment of the second pressure ring is 0.5 mm,
The gap width of the oil ring abutment was set to 0.2 mm.

Using these pressure ring and oil ring, the blow-by gas generation amount was measured with an engine of an aluminum alloy (ACD12) cylinder. The measurement was performed by rotating the engine at each rotation speed and measuring the blow-by gas amount (l / min). From these results, the blow-by gas amount was calculated with Pmax at 6000 rpm-WOT (wide open throttle) set at 65 kg / cm ² .

The obtained results are shown in FIG. The blow-by ratio is shown as a relative ratio to the maximum value of the blow-by gas amount of a piston ring (combination No. 10) having a base material of martensitic stainless steel as a comparative example, which is 100. The test conditions for the wear test and the scuff test were as follows. (2) Abrasion test Using an Amsler type abrasion tester, a fixed piece is cut out from the obtained piston ring, half of the rotating piece (corresponding to the inner peripheral surface of the cylinder), which is the mating material, is immersed in oil and a load is applied. While making contact with the fixed piece, a wear test was performed under the following conditions.

Lubricating oil: Turbine oil (# 100) Oil temperature: 80 ° C Circumferential rotation speed: 478 rpm Load: 80kgf Time: 7h After the test, wear of fixed piece (equivalent to piston ring) and mating material (inner surface of cylinder) The quantity was measured by the step profile with a roughness meter. Using the conventional example as a reference (= 1), evaluation was made with a relative value (wear ratio) to the reference value.

When the wear amount ratio is smaller than 1, it means that the wear amount is smaller than that of the conventional example, and it is desirable that the value is smaller than 1. (3) Scuff test Using an Amsler type abrasion tester, cut out a fixed piece from the obtained piston ring, attach oil to the rotating piece (corresponding to the inner peripheral surface of the cylinder) that is the mating material, and apply a load. Contact the fixed piece and load 10 kg under the conditions shown below.
The load at the time when the scuffing occurred and the load signal was generated was defined as the scuffing limit load, while continuously increasing linearly at the rate of f / min.

Lubricating oil: No. 2 spindle oil Oil temperature: Natural rotation speed: 478 rpm In addition, the conventional example was evaluated as a relative value (scuff limit load ratio) with respect to a reference value with reference (= 1). When the scuff limit load ratio is greater than 1, it indicates that the scuff load is higher than that of the conventional example, and it is desirable that the numerical value is large.

Further, a fatigue strength test and a film impact strength test were carried out on piston rings each having a hard chrome laminated plating film and a hard chrome plating film shown in Table 1 formed on the outer peripheral sliding surface. The test conditions for the fatigue strength test and the film impact strength test are as follows. (4) Fatigue strength test ring Using a physical fatigue tester, while applying a predetermined load to the piston ring, the repetition rate is 2000 cycles /
Repeated 10 ⁷ times as min. After clearing 10 ⁷ times with a predetermined load, the load stage was increased and repeated 10 ⁷ times at the same speed. The maximum load that cleared 10 ⁷ cycles was the fatigue strength (MPa) of the material under test.

The fatigue strength (MPa) of the conventional example was used as a reference (= 1) to evaluate the fatigue strength with a relative value (fatigue strength ratio) to the reference value. When the fatigue strength ratio is greater than 1, it indicates that the fatigue strength is higher than in the conventional example, and the larger the numerical value, the better. (5) Film impact strength test Using an original impact tester of our company, impact with a predetermined load until the plating film peels by hitting the ring corner 45 ° of the material under test (piston ring) with a stalk of 1.5 mm Energy was continuously applied, and the number of hits until the occurrence of peeling was measured.

Incidentally, the film impact strength was evaluated by the relative value (film impact strength ratio) to the reference value, with the number of hits until the occurrence of peeling in the conventional example as a reference (= 1). When the film impact strength ratio is greater than 1, it indicates that the peeling resistance is superior to that of the conventional example. The obtained results are also shown in Table 2.

[0060]

[Table 2]

In all of the examples of the present invention (No. 1 to No. 3), the piston ring wear amount ratio and the cylinder inner peripheral surface wear amount ratio were smaller than 1, and the wear amount was smaller than that of the conventional example. The combination is excellent in sex. Further, in all of the examples of the present invention, the scuff limit load ratio is larger than 1 and the scuff limit load is higher than that of the conventional example, and the combinations are excellent in seizure resistance. Further, in each of the examples of the present invention, the fatigue strength ratio and the film impact strength ratio are higher than those of the conventional example and the comparative example, and the piston ring film is excellent in fatigue resistance and film impact resistance.

In the comparative example (No. 4), since the amount of fine cracks in the piston ring plating film is small, the piston ring wear amount is large and the scuff limit load is low. Comparative example (No.
In 5), the piston ring plating film has a large amount of fine cracks, so the piston ring wear amount is small and the scuffing limit load is high, but the fatigue strength ratio and the film impact strength ratio of the piston ring plating film are low. The comparative example (No. 6) has a large amount of fine cracks accumulated in a single layer in the piston ring plating film, so the piston ring wear amount is small and the scuff limit load is high, but the fatigue strength ratio and film impact strength ratio are low. Has become. In the comparative example (No. 7), the amount of fine cracks extending between the two layers in the piston ring plating film is large, so the piston ring wear amount is small and the scuff limit load is high, but the fatigue strength ratio is low. The comparative example (No. 8) is an example in which a gas nitriding film is formed. Since the film is hard, the amount of piston ring wear is small, but since it is highly aggressive against the aluminum alloy cylinder, the cylinder inner surface Since the amount of wear is large and there is no oil retention, the scuff limit load is low.

In the comparative examples (No. 10 to No. 12), the piston ring base material was martensitic stainless steel SUS 44.
Other than 0, the same hard chrome laminated plating film as in the example of the present invention is formed, and the combination is excellent in wear resistance and seizure resistance, and also in fatigue resistance and film impact resistance. It has an excellent piston ring coating. From FIG. 2, the blow-by ratio of the present invention example (No. 1) is lower than that of the comparative example (No. 10) using martensitic stainless steel as the base material. From this, it is understood that the present invention is less likely to deteriorate the gas sealing property and can suppress the amount of blow-by gas generated.

As described above, according to the combination of the piston ring and the cylinder of the present invention, the cylinder liner is not required and the cylinder made of the aluminum alloy and the piston ring can be directly slid together and the blow-by gas The remarkable effect that the generation can be suppressed is shown.

[0065]

According to the present invention, the frictional force during sliding is low, the amount of wear of both the cylinder and the piston ring is small, and the scuff resistance is excellent. Even if the cylinder is made of aluminum alloy, blow-by gas is generated. It is possible to provide a combination of a cylinder and a piston ring capable of suppressing the above, and it is possible to achieve a marked effect in industry. Further, there is also an effect that the piston ring can be directly combined with the soft inner peripheral surface of the cylinder without requiring a cylinder liner, and the engine manufacturing cost can be remarkably reduced.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing a cross-sectional structure of a hard chrome laminated plating film suitable for the present invention.

FIG. 2 is a graph showing blow-by conversion in Examples and Comparative Examples.

[Explanation of symbols]

1 Piston ring base material 2 Hard chrome laminated plating film 2a, 2b, 2c, 2d Hard chrome plating layer 3a Microcracks that remain in a single layer 3b Fine cracks extending in two layers 3c 3 microcracks extending into 3 layers

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F16J 9/26 F16J 9/26 C 10/00 10/00 A (72) Inventor Kunihiro Iguchi Saitama City, Saitama Prefecture Honmachi Higashi 5-12-12 Japan Piston Ring Co., Ltd. F term (reference) 3G024 AA22 AA23 AA24 FA00 FA06 FA08 FA14 GA02 GA16 GA18 HA01 HA07 3J044 AA02 BA03 BA04 BB15 BB28 BC07 BC13 DA07 4K024 AA02 AB02 BA04 BB04 BC06 CA01 CA06 GA03

Claims (7)

[Claims] 1. A combination of a cylinder of an internal combustion engine and a piston ring which slides on an inner peripheral surface of the cylinder,
A piston in which the cylinder is an aluminum alloy cylinder, the piston ring has a base material of austenitic stainless steel, and a hard chrome laminated plating film having two or more hard chrome plating layers is formed on at least an outer peripheral sliding surface. The hard chrome laminated plating film is a ring, and in each of the two or more hard chrome plated layers, fine cracks that open to the outer surface side are distributed, and the fine cracks have their own openings in the depth direction. An aluminum alloy characterized by being a plating film including a portion remaining in each hard chrome plating layer and a portion extending into the hard chrome plating layer below each hard chrome plating layer having its own opening Combination of cylinder and piston ring. 2. The fine cracks are present in the range of 2.0 to 40.0% in the area ratio of the cross section of the hard chromium laminated plating film, and the fine cracks remain in each hard chromium plating layer in which the self-opening exists. 1.5 to 35.0% of cracks, 0.5 to 2 micro cracks extending into the hard chrome plating layer below each hard chrome plating layer where self-opening exists.
The combination of the aluminum alloy cylinder and the piston ring according to claim 1, which is 5.0%. 3. The thickness of each hard chrome plating layer is 5.
0 to 30.0 μm, and the opening width of the microcracks is 0.2 μm.
The combination of the aluminum alloy cylinder and the piston ring according to claim 2, wherein the combination is m or less. 4. The hard chrome plating layer of each of the hard chrome plating layers, wherein the hard chrome plating layer on the outermost surface side is thicker than the other hard chrome plating layers and has a thickness of 50.0 μm or less. 3. The combination of the aluminum alloy cylinder and the piston ring according to claim 2, wherein the thickness of the aluminum alloy is 5.0 to 30.0 μm, and the opening width of the fine cracks is 0.2 μm or less. 5. The hard chrome laminated plating film is composed of three or more hard chrome plated layers, and among the hard chrome plated layers of three or more hard layers, the thickness of the hard chrome plated layer closest to the surface of the base material is different. Thicker than the thickness of the hard chrome plating layer of 80.0 μm, and the thickness of the hard chrome plating layer on the outermost surface side is next to the thickness of the hard chrome plating layer closest to the surface of the base material and 50.0 μm or less The thickness of the other hard chrome plating layer is 5.0 to 30.0 μm, and the opening width of the fine cracks is 0.2 μm or less. 3. The aluminum alloy cylinder and piston ring according to claim 2, wherein combination. 6. The austenitic stainless steel comprises:
The aluminum alloy cylinder and piston ring according to any one of claims 1 to 5, which is an austenitic stainless steel having a composition containing Ni: 3.5 to 17.0% and Cr: 15.0 to 20.0% by mass. In combination with. 7. The aluminum alloy cylinder is J
IS ADC12, JIS ADC10, JIS AD
Cylinder made of aluminum alloy by die casting having a composition defined in any of C14, or JIS AC8A, JIS AC8B, JIS AC
The combination of the aluminum alloy cylinder and the piston ring according to any one of claims 1 to 6, which is a static casting aluminum alloy cylinder having a composition defined in any of 8C.