JP2003106216A - Combination of cylinder and piston ring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the combination of a cylinder and a piston ring capable of reducing frictional force in sliding and the abrasion of both of the cylinder and the piston ring, and improving its scuff-proof characteristic. SOLUTION: The combination is composed of the aluminium alloy cylinder and the piston ring provided with hard chrome laminated plating film composed of at least two hard chrome plating layers at least on an outer peripheral sliding face of a base material surface. The hard chrome plating layers forming the hard chrome laminated plating film are provided with fine cracks including a part opened to an outer face side and stayed in each hard chrome plating layer having the self-opening with respect to its depth direction, and a part extended to the hard chrome plating layer lower than the hard chrome plating layer having the self-opening, in a distributed state. Whereby the oil-holding property can be improved, the change of the oil-holding property is hardly found, and the low frictional force can be constantly kept in sliding.

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 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. According to such a trend, the piston ring for an internal combustion engine has 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 required mechanical characteristics. However, since a cylinder made of an iron-based material is heavy, it is not possible to satisfy the recent demand for weight reduction of an internal combustion engine.
Aluminum alloy engines are becoming popular. However, since the aluminum alloy cylinder is soft, avoiding direct sliding between the highly hardened piston ring and the inner peripheral surface of the aluminum alloy cylinder, it is usually necessary to install a cylinder liner to mount the aluminum alloy cylinder. Wear resistance of the inner surface of the alloy cylinder is ensured.

As such a cylinder liner,
Conventionally, cast iron cylinder liners have been commonly used.
However, recently, there has been proposed a cylinder liner that uses an aluminum alloy for the purpose of weight reduction and considers the improvement of sliding characteristics. For example, Japanese Unexamined Patent Publication No. 9-19757 discloses a hypereutectic aluminum-silicon alloy cylinder liner in which hard particles of silicon primary crystals and intermetallic compounds are exposed on a sliding surface.

Further, Japanese Unexamined Patent Publication No. 6-322459 proposes that a sliding surface of an aluminum alloy cylinder is compositely reinforced with a reinforcing material which is a mixture of alumina short fibers and non-spherical mullite particles. Further, in Japanese Patent Laid-Open No. 5-86964, Ni is attached to the inner peripheral surface of an aluminum alloy cylinder.
A measure for improving slidability by applying a surface treatment such as a base composite plating treatment has been proposed.

On the other hand, in an engine in which the heat load increases due to 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 sealability as a measure against blow-by. The techniques disclosed in Japanese Patent Laid-Open Nos. 9-19757 and 6-322459 are measures for improving slidability from the cylinder side in response to such high tension of the piston ring.

[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 movements of the internal combustion engine, the piston ring, which is a sliding member of the internal combustion engine, is required to have a low tension in order to obtain a low frictional force. However, JP-A-9-19757 and JP-A-6-3
The cylinder manufactured by the technology described in Japanese Patent No. 22459 is assumed to have a high tension in the piston ring when it is slid in combination with the piston ring. No consideration was given to the optimum combination.

Furthermore, Japanese Patent Laid-Open Nos. 9-19757 and 6
The cylinder manufactured by the technique described in Japanese Patent No. 322459 has a problem that the manufacturing process of the cylinder is complicated and the manufacturing cost rises. From the above, there has been a strong demand for an inexpensive combination of a cylinder and a piston ring that has low frictional force during sliding.

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 intended to provide a combination with a piston ring.

[0010]

[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. Further, the piston ring having a hard chrome laminated plating film formed on such a surface can be used directly in combination with a soft aluminum alloy cylinder inner peripheral surface without mounting a special cylinder liner, and, A wear resistance equivalent to that of a combination of a conventional high hardness piston ring and a cylinder liner in which silicon primary crystals and intermetallic compounds, which are high hardness particles, are exposed on the inner peripheral surface,
It has been found that it exhibits scuff resistance.

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 an inner peripheral surface of the cylinder, wherein the cylinder is an aluminum alloy cylinder, and the piston ring is at least an outer peripheral sliding surface of a base material surface. A piston ring formed by forming a hard chrome laminated plating film composed of two or more hard chrome plated layers on the outer surface side of each of the two or more hard chrome plated layers. Open microcracks are distributed, and the microcracks remain in the respective hard chrome plating layers where their own openings exist in the depth direction, and the hard chrome underlying each hard chrome plating layer where their own openings exist. A cylinder and a piston ring made of an aluminum alloy, which is a plating film including a portion extending into the plating layer Combination. (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 the area in the cross section, which is the portion below each hard chrome plating layer having its own opening. A combination of an aluminum alloy cylinder and a piston ring, wherein the area extending into the hard chrome plating layer has an area ratio of 0.5 to 25.0% in cross section. (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 made thicker than the thickness of other hard chromium plating layers and is 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 surface of the base material. The thickness of the hard chrome plating layer is thicker than other hard chrome plating layers and 80.0 μm or less, 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 aluminum alloy cylinder is JIS ADC12,
A combination of an aluminum alloy cylinder and a piston ring, which is a die cast aluminum alloy cylinder having a composition defined in either JIS ADC10 or JIS ADC14. (7) In any one of (1) to (5), the aluminum alloy cylinder is JIS AC8A, J
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 IS AC8B or JIS AC8C.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The combination of a cylinder and a piston ring of the present invention is a cylinder made of an aluminum alloy, without attaching a special cylinder liner to the bore or without strengthening the inner peripheral surface of the cylinder. It is a combination with a piston ring that directly uses the inner circumferential surface of the cylinder as the sliding surface of the piston ring. In the combination of the present invention, the greatest feature is that the piston ring is a piston ring formed by forming a hard chromium laminated plating film composed of two or more hard chromium plating layers on at least the outer peripheral sliding surface of the base material surface. is there.

The "hard chrome laminated plating film" referred to 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 is a cross section of a piston ring in which a hard chrome laminated plating film 2 composed of four hard chrome plating layers (2a, 2b, 2c, 2d) is formed on the outer peripheral surface of a base material (1). Is shown. 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 remain in each hard chrome plating layer where self crack openings exist in the depth direction and the self crack. And portions 3b and 3c extending into the hard chrome plating layer below each hard chrome plating layer having openings. 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 laminated. ) 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 at the crack bottom is prevented from occurring and cracks hardly propagate until the upper plating layer disappears and the microcracks open, and deterioration of the hard chrome laminated plating film is suppressed.

Since the microcracks existing in each hard chrome plating layer have a substantially V-shaped cross section, as the plating film is worn by sliding on the inner peripheral surface of the cylinder, the opening area and the opening of the microcracks are formed. 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 a fine crack 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. 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 chromium plating layer having its own opening is less than 1.5%, the number of voids of 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 of oil retaining property becomes large. On the other hand, if it exceeds 25.0%, the effect 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 the fine crack 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 comprises 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 to be thicker than the 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, any conventionally known material is suitable for the material used as the piston ring base material, but among them, martensitic stainless steel is preferred from the viewpoint of strength and corrosion resistance.

Preferably, the above-mentioned material is molded into a predetermined shape of the piston ring, and if necessary, pretreatments such as degreasing, washing and honing are performed, and then a hard chrome laminated plating treatment is performed. Hard chrome laminated plating treatment in the present invention, a piston ring base material is immersed in a chrome plating bath, a hard chrome plating layer forming step of forming a hard chrome plating layer having fine cracks by performing a plating step and a reverse electrolysis step, It consists of repeating as many layers as necessary.

The chromium plating bath used is not particularly limited, but it is preferable to use a conventionally known acidic chromic acid solution, a fluoride 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 first perform electrolytic polishing to clean the base material surface. After electrolytic polishing, a plating step is performed to first form a lowermost hard chromium plating layer having a predetermined thickness on the surface of the base material. In the plating process, the base material is used as a cathode and the current density is 20 to 100 A / dm ²
It is preferable to plate as. 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 bottom hard chrome plating layer, the thickness of the bottom layer is 80μ
It is preferable to make the thickness thickest in the plating film at m or less, and it is necessary to stop the depth of fine cracks in the chromium plating layer at the bottom, so the polarity switching time is 100 μsec.
The following is preferable. 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. It is preferable that the width of the opening is 0.2 μm or less, and a fine crack in which a portion where the fine crack stops in a single layer and a portion where the fine crack extends to two or more layers are mixed can be formed.

By repeating such a plating process and a reverse current process as many times as necessary, an intermediate layer (hard chrome plating layer) having a desired number of stacks can be formed. 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 that the width of the opening is 0.2 μm or less, and it is possible to form a fine crack in which a portion in which the fine crack stops in a single layer and a portion extending in two or more layers are mixed.

Through the above steps, 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. Even if such a piston ring is built into the piston and slid (used) in direct combination with the aluminum alloy cylinder bore, it has excellent oil retention, so wear resistance and scuff resistance are as good as those of conventional combinations. It can be more. According to the combination of the present invention, the cylinder (cylinder block) can be directly combined with an aluminum alloy cylinder without a special cylinder liner and without special composite reinforcement of the cylinder. The remarkable effect is that the manufacturing process can be simplified and the manufacturing cost can be reduced.

As described above, the aluminum alloy cylinder which can be used in combination with the piston ring having the hard chrome laminated plating film formed on at least the outer peripheral side (sliding surface side) of the base material surface is manufactured by the die casting method. As the product, any of aluminum alloy die castings specified in JIS H 5302 can be preferably used. Among them, an aluminum alloy die casting having a composition defined by any one of ADC12, ADC10, ADC14 is preferable. In addition, since the aluminum alloy 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.

The aluminum alloy cylinder is
There is no problem even as a cast product manufactured by the stationary casting method. JIS H 52 for castings produced by the static casting method
Any of the aluminum alloy castings specified in 02 can be suitably used. Among them, JIS AC8A, JIS
An aluminum alloy casting having a composition defined in either AC8B or JIS AC8C is preferable.
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 make a thin shape like a sleeve and cast it as a sleeve. It is possible.

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 then cast in a mold assembled in a predetermined size and shape by a high-pressure casting method, or a stationary casting method, or after further molten metal casting,
Further, processing (honing processing) is performed so that the inner peripheral surface has a predetermined surface shape.

[0034]

[Example] Martensitic stainless steel (C: 0.85% by mass, Si: 0.40% by mass, Mn: 0.30% by mass, Cr: 17.5% by mass, P: 0.04% by mass or less, S: 0.04% by mass or less, balance F
Using e) as a material, a piston ring base material having a predetermined size and shape was produced. The piston ring base material was subjected to degreasing, cleaning, and liquid honing as pretreatments, and then 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 process is performed under the conditions of current density: 60 A / dm ² and application time: 15 min, followed by a 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.

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: 20 min, and then the polarity is reversed with the polarity switching time of 750 μs. Then, the base material was used as an anode, and a reverse current process was performed under the conditions of current density: 60 A / dm ² and application time: 60 s to form a hard chromium plating layer on the outermost surface side. In addition,
Hard chrome lamination when the conditions of plating process and reverse electrolysis process are changed and the amount of microcracks is small, the amount of microcracks is large, the amount of cracks remaining in a single layer is large, and the amount of cracks extending between two layers is large. A plating film was formed as a comparative example.

Piston rings having hard chrome laminated plating films having different layer thicknesses and distributions of fine cracks formed as described above were combined with aluminum alloy cylinder bores as shown in Table 1, and a wear test and a scuff test were carried out. . The cylinder to be combined with the piston ring is JIS ADC12 or ADC1.
The aluminum alloy was die-cast with 0 composition, the surface was polished, and the surface roughness was Rz: 2 μm. Some cylinders were made of aluminum alloy by the static casting method of JIS AC8A composition.

Table 1 shows the thickness of the plating layer formed on the surface of the piston ring, the number of laminated layers, the amount of fine cracks in the coating, the ratio of fine cracks, and the combination conditions of the piston ring and the cylinder. In addition, the same plating process and the reverse electrolysis process were performed once using the same plating bath, and a piston ring having a single-layer hard chrome plating film formed thereon was produced, which was used as a conventional example. In addition, a gas nitriding layer (nitriding layer thickness:
A piston ring having a thickness of 150 μm and a nitride layer hardness of Hv1100) was used as one of the comparative examples.

Next, the test conditions for the wear test and the scuff test will be described. (1) Abrasion test Using an Amsler type abrasion tester, a fixed piece is cut out from the obtained piston ring, and 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, the fixed piece (equivalent to the piston ring) and the mating material (inner surface of the cylinder) wear 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.

A wear amount ratio of less than 1 indicates that the wear amount is smaller than that of the conventional example, and a value smaller than 1 is desirable. (2) 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), which 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 The conventional example was evaluated as a relative value (scuff limit load ratio) with respect to a reference value (= 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.

The results obtained are shown in Table 2. 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 gas nitrided layer shown in Table 1 on the outer peripheral sliding surface. Next, the test conditions for the fatigue strength test and the film impact strength test will be described. (3) Fatigue strength test ring Using a physical fatigue tester, load a predetermined load on the piston ring and repeat at a speed of 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. (4) Film impact strength test Using our own original impact tester, 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.

[0047]

[Table 1]

[0048]

[Table 2]

In all of the examples of the present invention, 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 the conventional example, and the combination was excellent in wear resistance. . Further, all of the examples of the present invention
The scuff limit load ratio is larger than 1 and shows a higher scuff limit load than the conventional example, and the combination has excellent 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 also 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.

From the above, it is possible to adjust the piston ring plating film to the amount of fine cracks within the scope of the present invention, the amount of fine cracks accumulated in a single layer, and the amount of fine cracks extending between two layers. Improve
It is also found that it is effective in improving the fatigue resistance and film impact resistance of the piston ring.

[0052]

According to the present invention, there is provided a combination of a cylinder and a piston ring, which has a low frictional force during sliding, a small amount of wear on both the cylinder and the piston ring, and excellent scuff resistance. It is possible,
It has a great effect on 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.

[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) C25D 7/00 C25D 7/00 C F02F 1/00 F02F 1/00 D F16J 9/26 F16J 9/26 C 10/04 10/04 F Term (reference) 3G024 AA21 GA01 GA06 HA07 3J044 AA02 BA01 BA04 BB15 BB28 BC07 DA09 4K024 AA02 AB02 AB03 AB04 AB19 BA06 BB04 CA08 GA03

Claims (7)

[Claims] 1. A combination of a cylinder of an internal combustion engine and a piston ring that slides on an inner peripheral surface of the cylinder, wherein the cylinder is an aluminum alloy cylinder, and the piston ring is at least an outer peripheral sliding surface of a base material surface. A piston ring formed by forming a hard chrome laminated plating film composed of two or more hard chrome plated layers on the moving surface, wherein the hard chrome laminated plating film has an outer surface on each of the two or more hard chrome plated layers. The microcracks that open to the side are distributed, and the microcracks remain in each hard chrome plating layer where their own openings are present 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. 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, which is less than or equal to m. 4. The hard chrome plating layer on the outermost surface side of each of the hard chrome plating layers is thicker than the thickness of the other hard chrome plating layers and is 50.0 μm or less. The combination of an aluminum alloy cylinder and a piston ring according to claim 2, wherein the thickness 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. The aluminum alloy cylinder and the piston ring according to claim 2, wherein combination. 6. The aluminum alloy cylinder comprises:
JIS ADC12, JIS ADC10, JIS A
A combination of an aluminum alloy cylinder and a piston ring according to any one of claims 1 to 5, which is a die-cast aluminum alloy cylinder having a composition defined in any one of DC14. 7. The aluminum alloy cylinder comprises:
JIS AC8A, JIS AC8B, JIS AC8
A combination of the aluminum alloy cylinder and the piston ring according to any one of claims 1 to 5, which is a static casting aluminum alloy cylinder having a composition defined in any of C.