JP2001158992A - Piston engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston engine which can sufficiently increase the durability of a cylinder block and a piston ring. SOLUTION: An Ni-Cu alloy plating film 4 is formed on an inner surface 3a of a cylinder of the aluminum alloy cylinder block 2, and a CrN film 8d is formed on at least a top ring 8a of the piston ring 8 reciprocating along the plating film 4. The wear resistance of the cylinder inner surface 3a and the piston ring 8 can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston engine in which a plating film is formed on an inner surface of a cylinder of an aluminum alloy cylinder block, and a piston ring reciprocates along the plating film.

[0002]

2. Description of the Related Art Some cylinder blocks for internal combustion engines used in piston engines for automobiles have a cylinder block and a cylinder inner surface that are integrally formed by die casting. This cylinder block for an internal combustion engine has a nickel (Ni) plating film formed on the inner surface of the cylinder in order to maintain the hardness, slidability and abrasion of the inner surface of the cylinder.

[0003]

The fuel (gasoline) contains a trace amount of sulfur as an impurity. If sulfuric acid is generated from the sulfur in the cylinder, a Ni plating film on the inner surface of the cylinder is required. May be corroded by sulfuric acid. For this reason, it is difficult to further increase the durability of the cylinder block for an internal combustion engine.

Further, the piston and the piston ring incorporated in the cylinder block for an internal combustion engine may be corroded by sulfuric acid, similarly to the cylinder block for an internal combustion engine. In particular,
If the piston ring is corroded by sulfuric acid, the wear of the piston ring proceeds, and the gap between the inner surface of the cylinder and the piston ring becomes large. For this reason, there is a possibility that air-fuel mixture or exhaust gas in the cylinder may leak from a gap between the inner surface of the cylinder and the piston ring, and it is difficult to increase the durability of the piston engine.

Accordingly, an object of the present invention is to provide a piston engine capable of further increasing the durability of a cylinder block and a piston ring.

[0006]

The present inventors proceeded with an experiment on corrosion resistance to sulfuric acid, and found that nickel (Ni) contained copper (Cu) having excellent corrosion resistance, so that a plating film formed on the inner surface of the cylinder was formed. It has been found that the corrosion resistance can be increased. Here, since the piston ring reciprocates along the plating film on the inner surface of the cylinder, the plating film and the piston ring need to have excellent wear resistance.
As a result of examination from these viewpoints, it was obtained that the wear resistance of the inner surface of the cylinder and the piston ring can be secured by forming a chromium nitride film (CrN film) on the piston ring.

Specifically, a first aspect of the present invention is to form a Ni-Cu alloy plating film on the inner surface of a cylinder of an aluminum alloy cylinder block, and to provide at least a top ring of piston rings reciprocating along the plating film. CrN
A film is formed.

[0008] By forming a plating film of a Ni-Cu alloy on the inner surface of the cylinder, the wear resistance of the inner surface of the cylinder can be improved. In addition, by including the Cu component in the metal matrix of the plating film, the corrosion resistance of the plating film to sulfuric acid can be increased. Also, a CrN coating was formed on at least the top ring of the piston rings. Since the CrN coating is relatively hard and has excellent corrosion resistance, the wear resistance of the piston ring can be enhanced.

A second aspect of the present invention is characterized in that the Ni component of the Ni-Cu alloy is 50 to 90 wt%, and the balance is the Cu component.

[0010] The Ni component of the Ni-Cu alloy is 50 to 90 watts.
t%, and the balance being Cu component, Ni-C
The Cu component in the u matrix can be set to 10 to 50 wt%. If the Cu component is less than 10 wt%, the Cu component is too small, and the corrosion resistance of the plating film decreases. Therefore, the corrosion resistance of the plating film is ensured by setting the Cu component to 10 wt% or more. Also,
If the Cu component exceeds 50% by weight, the Cu component is too large, so that the wear resistance cannot be secured. Therefore, the wear resistance of the plating film is ensured by setting the Cu component to 50 wt% or less.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals. FIG. 1 is a perspective view of a piston engine according to the present invention. The piston engine 1 is made of aluminum alloy 4
The cylinder block 2 for a cylinder is provided with a hollow portion 3, and the hollow portion 3 is provided.
A plating film (composite plating film) 4 is formed on the cylinder inner surface 3a (shown in FIG. 2), and the piston 7 slides in the hollow portion 3.

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1 and shows a state in which a piston 7 is incorporated in the hollow portion 3 of the cylinder block 2. The composite plating film 4 is coated with Ni on the inner surface 3a of the cylinder.
A ceramic matrix (SiC) 6 is deposited on the Ni-Cu matrix 5 (e.g.,... Indicates a plurality).

The Ni-Cu matrix 5 has a Ni component of 50 to 90% by weight (% by weight) and a balance of Cu component. For this reason, the Ni-Cu matrix 5 contains 10 to 50 wt% of the Cu component. The reason why the composite plating film 4 is the Ni-Cu matrix 5 and the Cu component is set to 10 to 50 wt% will be described later.

The piston 7 has a ring groove (not shown) formed on the outer circumference, and a piston ring 8 (a top ring 8a for compression, a second ring 8b for compression, and an oil ring 8c) are attached to the ring groove. . The compression top ring 8a is formed by forming a CrN coating 8d on the outer peripheral surface (the surface of the cylinder inner surface 3a in contact with the plating coating 4). The reason why the CrN film 8d is formed on the top ring 8a is that the top ring 8a is arranged at a position where the top ring 8a is most likely to contact exhaust gas in the cylinder. In addition,
The reason why the coating is the CrN coating 8d will be described later.

Hereinafter, a composite plating apparatus for forming the composite plating film 4 on the cylinder block 2 will be described with reference to FIGS. FIG. 3 is an overall view of a composite plating apparatus for forming a composite plating film on a cylinder block of a piston engine according to the present invention. The composite plating apparatus 10 includes a work mounting table 12 mounted on a main body 11 for mounting a cylinder block 2 made of an aluminum alloy, and a cylindrical electrode disposed in a hollow portion 3 of the cylinder block 2 mounted on the work mounting table 12. 15 and an axis 15 a of the cylindrical electrode 15.
, A composite plating solution circulating mechanism 30 for supplying the composite plating solution 9 to the inner hole 16 of the cylindrical electrode 15, an energizing mechanism 45 for energizing the cylinder block 2 and the cylindrical electrode 15. Consists of The cylindrical electrode 15 will be described in detail with reference to FIGS. 2a is a water jacket serving as a cooling water passage, 2b is a crankcase,
Reference numeral 13 denotes an annular passage of a gap S1 formed by the cylinder inner surface 3a and the cylindrical electrode 15.

The work mounting table 12 has a work receiving surface 12a.
And a recovery hole 12 for the composite plating solution.
b. The insulating member 14 is a plate material formed of, for example, ceramic or synthetic resin. Insulation member 14
Is because the cylinder block 2 is mounted on the work table 1
This is because a composite plating film 4 (shown in FIG. 2) is efficiently formed on the cylinder inner surface 3a of the cylinder block 2 by insulating only the cylinder block 2 while being insulated from the cylinder block 2.

The reason why the work mounting table 12 is provided with the recovery hole 12b is that the composite plating solution 9 hitting the cylinder inner surface 3a of the cylinder block 2 is recovered from the recovery hole 12b and the composite plating solution 9 is smoothly circulated. Thereby, the composite plating film 4 (shown in FIG. 2) is efficiently formed on the cylinder inner surface 3a of the cylinder block 2.

Next, the rotation mechanism 20 will be described. The rotating mechanism 20 is a mechanism that is applied to a cylinder block for a four-cylinder engine and rotates four cylindrical electrodes 15... Here, the content of rotating one cylindrical electrode 15 will be described. . The rotation mechanism 20 includes a motor 21 mounted on the main body 11, a drive shaft 22 connected to the motor 21, and a drive gear 2 mounted on the drive shaft 22.
3, a gear 24 meshed with the drive gear 23, and a rotary shaft 25 having the gear 24 mounted substantially at the center and the upper end to which the screw portion 19a of the cylindrical electrode 15 is mounted. The mechanism for rotating the four cylindrical electrodes 15 will be described in detail with reference to FIG.

The composite plating solution circulating mechanism 30 includes a tank 31 for storing the composite plating solution 9, a first supply path 33 extending from the tank 31 to a supply port 32, and a pump provided in the middle of the first supply path 33. 34, a chamber 35 formed on the outlet side of the supply port 32, a second supply path 36 opened on the rotating shaft 25 so that an inlet side 36 a communicates with the chamber 35, and a chamber 35 formed on the outlet side of the second supply path 36. Connected cylindrical electrode 1
5, an annular passage 13 communicating with the inner hole 16 by a through hole 18, a collecting port 37 communicating with the annular passage 13 by a collecting hole 12 b of the work mounting table 12, and a collecting port Recovery path 38 extending from 37 to tank 31
And a control valve 39 provided in the middle of the recovery path 38, and a stirrer 40 attached to the tank 31.

The control valve 39 is connected to the crank chamber 2
This is a valve for adjusting the liquid level 9a of the composite plating solution 9 in b. The stirrer 40 stirs the composite plating solution 9 in the tank 31 with the wing 41. The energizing mechanism 45 has a rotary connector 46 for energization attached to the lower end of the rotating shaft 25, an anode 47 connected to the rotary connector 46, and a cathode 48 connected to the cylinder block 2.

FIG. 4 is a sectional view taken along line 4-4 of FIG. The drive gear 23 of the rotating mechanism 20 meshes with the inner gears 24, 24, and the inner gears 24, 24 mesh with the first and second transmission gears 26, 27, respectively, and the first and second transmission gears 26, 27 respectively.
27 meshes with the outer gears 24,24. Therefore, the rotational force of the motor 21 is first transmitted from the drive gear 23 to the inner gears 24, 24 as shown by arrows, and then from the inner gears 24, 24 to the first and second transmission gears 26, 24 as shown by arrows. 27, and then the first and second transmission gears 2
The gears are transmitted from the gears 6 and 27 to the outer gears 24 and 24 as indicated by arrows.

As a result, the rotating shafts 25... To which the gears 24... Are respectively rotated as indicated by white arrows, and the cylindrical electrodes 15. ) Rotate in the same manner as the rotation shafts 25.

FIGS. 5A and 5B are explanatory views of a cylindrical electrode for forming a composite plating film on a cylinder block of a piston engine according to the present invention, wherein FIG. 5A is a sectional view, and FIG.
FIG. 3 is a view as viewed from an arrow b in FIG. In (a), a cylindrical electrode 15 is, for example, an electrode in which platinum (Pt) is clad coated on a titanium (Ti) base or iridium oxide (Ir) is coated on a Ti base.
O ₂ ) is an electrode clad and covered with an inner hole 16 formed along an axis 15 a and a cylindrical peripheral wall 1 facing a cylinder inner surface 3 a (shown in FIG. 3) of a cylinder block 2.
7 and a plurality of through holes 1 spirally arranged in the peripheral wall 17.
.., A lid 19b formed at the upper end, and a screw 19a formed at the lower end.

In (b), the cylindrical electrode 15 is attached to the peripheral wall 1.
7 is set to the height H (see (a)) and the circumference L, and the peripheral wall 17 is set.
Are arranged at a fixed angle θ (24 °). The arrangement of the through holes 18 will be described in detail with reference to FIG.

FIG. 6 is a development view of a cylindrical electrode for forming a composite plating film on a cylinder block of a piston engine according to the present invention. The through holes 18 are arranged in the peripheral wall 17 in a staggered manner at a pitch P along a spiral with an inclination angle θ1. The reason why the through holes 18 are spirally arranged is that the inner surface 3 of the cylinder block 2 facing the peripheral wall 17
This is because the composite plating solution 9 is applied more uniformly to a (shown in FIG. 3). Also, the reason why the through holes 18 are arranged in a staggered manner is that the through holes 18 and the through holes 1
8 are arranged to be densely arranged on the peripheral wall 17.

Next, a composite plating method for forming the composite plating film 4 on the cylinder inner surface 3a of the piston engine 1 will be described with reference to FIGS. FIG. 7 is an explanatory view of a first composite plating method for a cylinder block of a piston engine according to the present invention, showing a principle diagram of the composite plating method. First,
The cylinder block 2 is connected to the insulating member 14 of the work table 12.
To cover the cylindrical electrode 15 with a gap S1 opened. Next, the motor 21 is driven, and the rotational force of the motor 21 is transmitted to the driving gear 23 → the gear 24 → the rotating shaft 25 so that the cylindrical electrode 15
Is rotated about the axis 15a.

Next, the blade 41 of the stirrer 40 is rotated to stir the composite plating solution 9 in the tank 31. In this state,
By driving the pump 34, the composite plating solution 9 in the tank 31 is supplied from the first supply path 33 to the supply port 3 as shown by arrows a1 to a3.
2 → chamber 35 → cylindrical electrode 1 through second supply path 36
5 to the inner hole 16.

The composite plating solution 9 in the inner hole 16 is
.. Are injected to the outside of the cylindrical electrode 15 as shown by an arrow b and strikes the cylinder inner surface 3a of the cylinder block 2 at right angles. Then, the composite plating solution 9 hitting the cylinder inner surface 3a
To the annular passage 13 as shown by arrows c1 and c2 → the recovery port 37
→ Recover in the tank 31 through the recovery path 38. With the composite plating solution 9 circulated, the energizing mechanism 45 is operated to energize the cylindrical electrode 15 and the cylinder block 2.

FIG. 8 is an explanatory view of a second composite plating method for a cylinder block according to the present invention, and shows a state in which a composite plating solution 9 is sprayed from the through holes 18 of the cylindrical electrode 15.
The composite plating solution 9 is sprayed from the through holes 18 and arrows b ...
As described above, the composite plating solution 9 hitting the cylinder inner surface 3a becomes turbulent by hitting the cylinder inner surface 3a of the cylinder block 2 at a substantially right angle. In addition, by making the injection speed of the composite plating solution 9 from the through holes 18... Substantially the same, the collision conditions of the composite plating solution 9 on the cylinder inner surface 3a are averaged.

Therefore, metal ions (Ni ions, Cu ions)
And the ceramic particles (SiC) 6... Can be uniformly dispersed in the composite plating solution 9. As a result, the metal ion (Ni ion, Cu ion) concentration of the composite plating solution 9 can be maintained at a specified concentration in the vicinity of the cylinder inner surface 3a.
The matrix 5 can be deposited to a defined thickness T. In addition, since the ceramic particles 6 of the composite plating solution 9 can be uniformly dispersed in the vicinity of the cylinder inner surface 3a, the ceramic particles 6 can be co-deposited uniformly in the Ni-Cu matrix 5. .

Further, by rotating the cylindrical electrode 15, the composite plating solution 9 sprayed from the through holes 18 can be uniformly applied to the entire area of the cylinder inner surface 3a of the cylinder block 2. Therefore, N is applied to the entire area of the cylinder inner surface 3a.
The i-Cu matrix 5 can be deposited to a uniform thickness.
Can be uniformly eutectoid.

FIG. 9 is an explanatory view of a third composite plating method for a cylinder block according to the present invention, and shows a state in which a cylindrical electrode 15 is developed on the right side of a sectional view of the cylinder block 2. It is to be noted that, for convenience, the through holes 18 are described by adding a to j.
The cylindrical electrode 15 (see FIG. 5) is rotated while spraying the composite plating solution 9 from the through holes 18a to 13j. As a result, first, the composite plating solution 9 jetted from the through hole 18a is applied to the position P1 on the cylinder inner surface 3a of the cylinder block 2 as shown by the arrow, and the composite plating solution 9 jetted from the through hole 18b is shifted slightly above the position P1. Guess.

The composite plating solution 9 sprayed from the through hole 18c is applied to the position P2 as shown by the arrow, and the composite plating solution 9 sprayed from the through hole 18d is applied slightly above the position P2, and the composite solution sprayed from the through hole 18e. The plating solution 9 is applied to the position P3 as shown by the arrow. Further, the composite plating solution 9 sprayed from the through hole 18f is applied to the position P4 on the cylinder inner surface 3a of the cylinder block 2 as shown by the arrow, and
g, 13h, the composite plating solution 9 sprayed from position P4
Slightly above and touch it. Then, the composite plating solution 9 sprayed from the through hole 18j is applied to the position P5 as indicated by an arrow.

Therefore, the composite plating solution 9 can be uniformly applied to the area E at the positions P1 to P5 on the cylinder inner surface 3a of the cylinder block 2. As a result, with the metal ion (Ni ion, Cu ion) concentration in the composite plating solution 9 kept at the specified concentration, the Ni-Cu matrix 5 was removed.
Can be deposited on the cylinder inner surface 3a to a specified thickness, and the ceramic particles 6...
Can be kept uniform and the ceramic particles 6... Can be co-deposited uniformly in the Ni-Cu matrix 5. Hereinafter, the adhesion, corrosion resistance, and abrasion resistance of the composite plating film 4 will be described.

FIG. 10 is a graph showing the relationship between the thickness of the composite plating film according to the present invention and the rate of occurrence of peeling. The horizontal axis represents the thickness of the composite plating film, and the vertical axis represents the occurrence of peeling of the composite plating film. Indicates the rate. This graph shows that the piston 7 is slid in the hollow portion 3 of the cylinder block 2 shown in FIG. 1 and the friction distance ((piston stroke) × (number of reciprocating motions of the piston)) is 1 km. It shows a peeled state.

The composite plating film of the Ni—Cu alloy causes peeling when the composite plating thickness is less than 20 μm, but when the composite plating thickness exceeds 20 μm, the peeling rate can be suppressed to 0%. As a result, in the composite plating film of the Ni—Cu alloy, the composite plating thickness was set to at least 20.
It is understood that a composite plating film having high adhesion can be obtained by setting the thickness to μm. The maximum thickness of the composite plating film was set to about 70 μm in consideration of engine durability and composite plating processing time.

FIGS. 11 (a) and 11 (b) are graphs showing the relationship between the sulfuric acid concentration and the amount of corrosive wear of the composite plating film according to the present invention, wherein the abscissa indicates the sulfuric acid concentration and the ordinate indicates the corrosive wear. Indicates the amount. (A) shows a comparative example, and (b) shows an example.

This graph shows the result of measurement by the electrochemical measurement method, and the measurement conditions are as follows.
Using the composite plating film as the anode, set the temperature of the sulfuric acid aqueous solution to 80 ° C.
After dipping the composite plating film in this aqueous sulfuric acid solution for 10 minutes, electrolysis is performed in a sulfuric acid aqueous solution at a sweep rate of 50 mV / min, and the amount of corrosion and wear of the composite plating film is measured.

The term "corrosive wear" as used herein means that the friction surface undergoes a chemical change and changes in quality, and the deteriorated portion is removed by mutual movement to progress the wear. Oxidation and the like also fall into this category.

In (a), when the concentration of sulfuric acid exceeds 30%, the amount of corrosive wear of the composite plating film of Ni-9 wt% Cu alloy increases, and when the concentration of sulfuric acid is 50%, the amount of corrosive wear increases to 5 μm. Therefore, if the Cu content is as low as 9 wt%, corrosion resistance cannot be ensured.

In (b), the composite plating film of Ni-10 wt% Cu alloy (shown by a solid line) can suppress the amount of corrosion and wear to less than 2 μm even when the sulfuric acid concentration increases. Therefore, when the content of Cu is 10 wt%, corrosion resistance can be ensured. Further, the composite plating film of Ni-50 wt% Cu alloy (indicated by a broken line) can suppress the amount of corrosion and wear to less than 2 μm even when the sulfuric acid concentration increases. Therefore, C
When the content of u is 50 wt%, corrosion resistance can be ensured. As a result, it can be seen that in the case of a Ni—Cu alloy composite plating film, if the Cu content is 10 wt% or more, a composite plating film having excellent corrosion resistance can be obtained.

FIGS. 12 (a) and 12 (b) are graphs showing the relationship between the friction distance and the amount of adhesive wear of the composite plating film according to the present invention. The horizontal axis represents the friction distance, and the vertical axis represents the friction distance. Shows the amount of wear. (A) shows a comparative example, and (b) shows an example.

The term "adhesive wear" as used herein refers to abrasion that occurs when metal adheres to each other on a friction surface and the softer metal is pulled and transferred to the harder metal. Say.

In (a), the composite plating film of the Ni-51 wt% Cu alloy has a frictional distance of about 20 km and an adhesive wear amount of 1.5 μm, and a friction distance of about 50 km and an adhesive wear amount of 1.8 μm. And the friction distance is 1
When the distance exceeds 00 km, the adhesive wear amount becomes 2.0 μm.
Therefore, when the content of Cu is as large as 51 wt%, it is not possible to secure wear resistance.

In (b), the composite plating film of Ni-50 wt% Cu alloy (shown by a broken line) has a friction distance of about 5
At 0 km, the amount of adhesive wear is as small as about 0.25 μm, and even when the friction distance exceeds 100 km, the amount of adhesive wear can be suppressed to less than 0.5 μm. Therefore, the content of Cu is 50 wt.
%, The wear resistance can be ensured.

Further, the composite plating film of Ni-10 wt% Cu alloy (shown by a solid line) has an adhesive wear amount of almost 0 and a friction distance of 180 km until the friction distance exceeds 100 km.
, The adhesive wear amount can be suppressed to less than 0.1 μm. Therefore, when the content of Cu is 10 wt%, wear resistance can be ensured. As a result, it can be seen that in the case of a Ni—Cu alloy composite plating film, if the Cu content is 50 wt% or less, a composite plating film having excellent wear resistance can be obtained.

[0047]

EXAMPLES Examples of the present invention will be described below with reference to Tables 1 and 2 and FIGS. However, the present invention is not limited to these experimental examples. First, the surface treatment states of Comparative Examples 1, 2 and Examples will be described with reference to Table 1.

[0048]

[Table 1]

Comparative Example 1 The cylinder block was made of an aluminum alloy, and a composite plating film was formed on the inner surface of the cylinder. This composite plating film was obtained by including ceramic particles (SiC) in a Ni-Cu matrix, and the thickness of the plating film was 56.5 μm. As a result of measuring the surface hardness of the plating film with a Vickers hardness meter, Vickers hardness (hereinafter, referred to as Vickers hardness)
"Hv") 578. Further, the piston ring was made of stainless steel, and the surface of the piston ring was subjected to gas nitriding. As a result of measuring this surface hardness with a Vickers hardness tester, it was Hv1013.

Comparative Example 2: The same composite plating film as in Comparative Example 1 was formed on the inner surface of the cylinder. The piston ring was made of stainless steel, and a 3 μm-thick TiN film was formed on the surface of the piston ring by an ion plating method. Ti
The surface hardness of the N coating was Hv2260.

Example: The same composite plating film as in Comparative Example 1 was formed on the inner surface of the cylinder. The piston ring was made of stainless steel, and a CrN film having a coating thickness of 30 μm was formed on the surface of the piston ring by an ion plating method. Cr
The surface hardness of the N coating was Hv 1864. Here, the ion plating method refers to a film formation method in which an electric field is applied to metal ions to give a large energy, thereby increasing the adhesion to the piston ring.

Next, the wear test method will be described with reference to Table 2 and FIG.

[0053]

[Table 2]

FIG. 13 is a diagram illustrating a method for testing wear of a piston engine according to the present invention. As a wear test method, first, a “run-in test” is performed, and then, a “main test” is performed. In the test, the outer surface of the piston ring (top ring 8a) was applied to the composite plating film 4 on the inner surface 3a of the cylinder, a load of 2 kgf was applied to the top ring 8a, and the top ring 8a was supplied at a moving speed of 100 cm / min and a stroke of 50 mm. The top ring 8a was moved along the composite plating film 4 for 5 minutes while dropping 2.5% sulfuric acid at a rate of 40 cm ³ per hour from the tube 60.

In this test, the top ring 8a was moved along the composite plating film 4 for 120 minutes while changing the load of the top ring 8a to 3 kgf and changing the moving speed of the top ring 8a to 200 cm / min. The results of this wear test will be described with reference to the following figures.

FIGS. 14A and 14B are graphs showing the wear resistance of the piston engine according to the present invention, wherein FIG. 14A shows a comparative example and FIG. 14B shows an example. In (a), the horizontal axis shows Comparative Examples 1 and 2, and the vertical axis shows the amount of wear. In (b), the abscissa indicates the example and the ordinate indicates the wear amount. In these graphs, the wear amount of the composite plating film is indicated by a broken-line rectangular frame, and the wear amount of the piston ring (top ring) is indicated by a solid-line rectangular frame.

In (a), in Comparative Example 1, the maximum wear amount of the composite plating film was 3 μm, and the maximum wear amount of the top ring was 28 μm. The surface hardness of the gas nitriding treatment is Hv1013, which is softer than the surface hardness of the TiN film or CrN film. Therefore, the amount of wear of the top ring increased.

On the other hand, in Comparative Example 2, the maximum wear amount of the composite plating film was 2.5 μm, and the maximum wear amount of the top ring was 23 μm. Since the TiN coating has relatively poor corrosion resistance as compared with the CrN coating, corrosion wear is likely to progress and it is difficult to keep the surface flat. Therefore, suspicious wear on the plating film is promoted. For this reason, the amount of wear of the composite plating film increased, and the amount of wear of the top ring also increased.

In (b), in the example, the maximum wear amount of the composite plating film was as small as 1 μm, and the maximum wear amount of the top ring was as small as 10 μm. Since the CrN film has better corrosion resistance than the TiN film,
The surface can be kept flat by suppressing the amount of corrosion and wear of the N film. Therefore, suspicious wear on the plating film can be suppressed. Therefore, the amount of wear of the composite plating film can be reduced, and the amount of wear of the top ring can also be reduced.

As a result, the abrasion resistance of the composite plating film is improved and the CrN film is formed on the top ring by using the Ni—Cu matrix as the composite plating film on the inner surface of the cylinder as in the embodiment. This indicates that the wear resistance of the top ring can be improved.

In the above embodiment, an example was described in which the CrN film was formed only on the top ring of the piston rings. However, the CrN film may be formed on both the top ring and the second ring.

[0062]

According to the present invention, the following effects are exhibited by the above configuration. According to the first aspect, the wear resistance of the cylinder inner surface can be enhanced by forming the Ni—Cu alloy plating film on the cylinder inner surface. In addition, by including the Cu component in the metal matrix of the plating film, the corrosion resistance of the plating film to sulfuric acid can be increased.

A CrN coating was formed on at least the top ring of the piston rings. Since the CrN coating is relatively hard and has excellent corrosion resistance, the wear resistance of the piston ring can be enhanced. As a result, the wear resistance of both the inner surface of the cylinder and the piston ring can be increased, so that the durability of the piston engine can be further increased.

According to a second aspect of the present invention, the Ni component of the Ni—Cu alloy is 50 to 90 wt%, and the balance is the Cu component. Therefore, the Cu component in the Ni-Cu matrix is reduced to 10 wt%.
With the above settings, the corrosion resistance of the plating film is ensured, and Cu
By setting the component to 50 wt% or less, the wear resistance of the plating film can be ensured. As a result, the corrosion resistance and wear resistance of the plating film can be secured, and a cylinder block for an internal combustion engine with higher durability can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a piston engine according to the present invention.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is an overall view of a composite plating apparatus for forming a composite plating film on a cylinder block of a piston engine according to the present invention.

FIG. 4 is a sectional view taken along line 4-4 in FIG. 3;

FIG. 5 is an explanatory view of a cylindrical electrode for forming a composite plating film on a cylinder block of a piston engine according to the present invention.

FIG. 6 is a developed view of a cylindrical electrode for forming a composite plating film on a cylinder block of a piston engine according to the present invention.

FIG. 7 is an explanatory view of a first composite plating method for a cylinder block of a piston engine according to the present invention.

FIG. 8 is an explanatory view of a second composite plating method for a cylinder block of a piston engine according to the present invention.

FIG. 9 is an explanatory view of a third composite plating method for a cylinder block of a piston engine according to the present invention.

FIG. 10 is a graph showing the relationship between the thickness of the composite plating film according to the present invention and the rate of occurrence of peeling.

FIG. 11 is a graph showing the relationship between the sulfuric acid concentration and the amount of corrosion and wear of the composite plating film according to the present invention.

FIG. 12 is a graph showing the relationship between the friction distance and the amount of adhesive wear of the composite plating film according to the present invention.

FIG. 13 is a view for explaining a wear test method for a piston engine according to the present invention.

FIG. 14 is a graph showing the wear resistance of the piston engine according to the present invention.

[Explanation of symbols]

1 ... piston engine, 2 ... cylinder block, 3a ...
Inner surface of cylinder, 4 ... Plating film (composite plating film), 5
... Ni-Cu matrix, 6 ... ceramic particles, 7
... Piston, 8 ... Piston ring, 8a ... Top ring, 9 ... Composite plating solution, 10 ... Composite plating apparatus, 15 ...
Cylindrical electrode, 20: rotating mechanism, 30: plating solution circulation device.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02F 1/00 F02F 1/00 G 5/00 5/00 F F16J 9/26 F16J 9/26 C (72 ) Inventor Nobuhiko Yoshimoto 1-10-1 Shinsayama, Sayama City, Saitama Prefecture, Honda Engineering Co., Ltd. (72) Inventor Tadashi Kobayashi 1-10-1, Shinsayama, Sayama City, Saitama Prefecture Honda Engineering Co., Ltd. 3G024 AA22 FA06 GA18 HA07 3J044 AA02 BB06 BB16 BB28 BB29 BC13 DA09 4K023 AB21 AB38 4K024 AA15 AB01 BA06 BB04 BC04 CA10 CB13 CB15 FA02 GA03 GA04 4K029 AA02 BA58 BC01 BD04 FA07

Claims (2)

[Claims] An aluminum alloy cylinder block has a Ni—Cu alloy plating film formed on the inner surface of a cylinder, and a CrN film is formed on at least a top ring of a piston ring reciprocating along the plating film. Features piston engine. 2. The method according to claim 1, wherein the Ni component of the Ni—Cu alloy is 50 to 50%.
2. The piston engine according to claim 1, wherein the content is 90 wt%, and the balance is a Cu component.