JP3253016B2 - Piston with improved wear resistance of the contact surface with piston ring and combination of piston and cylinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston having improved wear resistance at a contact surface with a piston ring. Further, the present invention relates to a combination of the piston and the cylinder used for an internal combustion engine or the like.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for lighter motors and the like to save energy. To meet such demands, the use of light metals such as aluminum-containing metals is increasing. In internal combustion engines, the use of aluminum-containing metals has been promoted for the purpose of reducing fuel consumption by weight reduction.

[0003] However, aluminum-containing metals generally require further improvement in heat resistance, rigidity and mechanical strength. In particular, when used as a sliding member such as a piston or a cylinder for an internal combustion engine, there is a drawback that durability such as seizure resistance and wear resistance is lacking. Therefore, it has been proposed to subject the aluminum-containing metal to various surface treatments for the purpose of improving such durability. In the case of a general-purpose engine, a combination of a piston made of an aluminum alloy casting and a cylinder made of an aluminum alloy die-cast in which a sliding surface is subjected to hard chrome plating is known. However, this combination is expensive and
In addition, there is a problem that the image sticks easily.

[0004]

In a practical combination of a piston and a cylinder for an internal combustion engine, the piston is made of an aluminum-containing metal, and the cylinder is made of an aluminum alloy or cast iron. Further, the piston has a groove for fitting the piston ring, and the piston ring (O-ring) is fitted. The piston is coated with iron plating on the sliding surface with the cylinder to prevent seizure, and the inner surface of the groove for fitting the piston ring (the contact surface with the piston ring) is coated with hard anodized aluminum. It has been subjected. The hard alumite coating is provided for the purpose of preventing wear due to contact with the piston ring.

[0005] With the reciprocation of the piston, the piston ring reciprocates in the groove for a very short distance, but contacts the inner surface of the groove each time. The contact surface of the groove with the piston ring is worn by being hit by the piston ring. Due to such “hitting wear”, the width of the groove is widened, and as a result, airtightness cannot be maintained, so that blow-by gas increases, oil consumption increases, noise increases, and the like. Cause. The contact surface of the groove of the piston with the piston ring is required to have excellent wear resistance against the above-mentioned "hitting wear",
The hard alumite coating is used.

However, when manufacturing the above piston,
The iron plating on the sliding surface and the hard alumite coating of the groove for fitting the piston ring need to be provided in separate steps, and there is a problem in that it is complicated. Specifically, the sliding surface is iron-plated by masking the piston ring fitting groove,
Then, it was necessary to form a hard alumite coating on the groove for fitting the piston ring by masking iron plating.

As a sliding member of an aluminum-containing metal,
For the purpose of improving abrasion resistance and seizure resistance, there has been proposed one having a composite plating film in which hard particles such as boron carbide are dispersed in a Ni-P alloy matrix on a substrate made of an aluminum-containing metal ( For example, JP-A-9-
42447). With this composite plating film, the film can be applied to the sliding surface and the groove for fitting the piston ring at a time. However, this member has a problem that the boron carbide particles contained in the composite plating film are too hard, so that the mating material (cylinder) is easily damaged and causes seizure. Also, a plating film made of a Ni-P alloy containing no boron carbide particles is being studied. The plating film made of a Ni-P alloy has a problem that it has a good resistance to abrasion but has poor slidability and poor seizure resistance.

Therefore, an object of the present invention is to provide a piston ring which can be formed by a single surface treatment, is made of the same material, has physical properties such as seizure resistance required for a sliding surface, and a piston ring required for a piston ring fitting groove. It is an object of the present invention to provide a piston having a coating that satisfies both the resistance to abrasion and the abrasion. It is a further object of the invention to provide a combination with a cylinder, in particular for an internal combustion engine, using this piston.

[0009]

According to the present invention, there is provided a piston having at least one groove for fitting a piston ring on an outer peripheral surface thereof, wherein at least a surface of the inner surface of the groove which is in contact with the piston ring is nickel-nickel. The present invention relates to a piston having a phosphorus-boron-based coating. Further, the present invention relates to a combination of the piston and the cylinder according to the present invention.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A piston according to the present invention has at least one groove for fitting a piston ring on an outer peripheral surface. Pistons having such a structure are known, and examples thereof include those shown in FIG. The piston shown in FIG. 1 has an outer diameter land portion (top land 1, second land 3, and third land 5) and a ring groove portion (second groove 4, oil groove 6) including a top groove 2 which is a groove for fitting a piston ring. ) And an outer diameter skirt portion 8, and a pin hole 7 is formed between the outer diameter skirt portion 8 and the outer diameter land portion.

The groove for fitting the piston ring has three inner surfaces, of which a nickel-phosphorus-boron coating is provided on at least the surface that comes into contact with the piston ring. Preferably, all three inner surfaces in the groove for fitting the piston ring have nickel-
A phosphorus-boron based film is formed. The nickel-phosphorus-boron coating contains 0.5 to 3% by weight of phosphorus and 0.1% of boron.
Suitably, it is a nickel coating containing 0.5 to 2% by weight. The balance of phosphorus and boron is nickel.
When the phosphorus content is less than 0.5% by weight, there is a problem that it is difficult to form a plating film, and when the phosphorus content exceeds 3% by weight, the hardness of the film tends to decrease. If the content of boron is less than 0.05% by weight, the hardness of the film tends to decrease, and if the content of boron exceeds 2% by weight, a film having sufficient hardness tends not to be obtained. The nickel-phosphorus-boron-based coating preferably has phosphorus of 1 to 1.
It is a nickel coating containing 2% by weight and 0.05 to 1% by weight of boron.

The piston of the present invention suitably has a nickel-phosphorus-boron coating on at least the sliding surface in addition to the groove for fitting the piston ring.
The sliding surface is, for example, an outer diameter land portion or an outer diameter skirt portion shown in FIG.

The thickness of the nickel-phosphorus-boron coating is as follows:
For example, the thickness is suitably 2 to 50 μm. The thickness of the nickel-phosphorus-boron coating is preferably 5 to 30.
It is in the range of μm.

In the piston of the present invention, the base material can be made of an aluminum-containing metal. The aluminum-containing metal is selected from the group consisting of, for example, wrought aluminum and aluminum alloy, cast aluminum alloy, and die-cast aluminum alloy.

[0015] The nickel-phosphorus-boron coating is prepared, for example, by the method described in JP-A-8-158008.
It can be formed using an electroless plating bath containing a phosphorus compound and a boron compound as a reducing agent in a nickel salt.
The method using the electroless plating bath has an advantage that a uniform film can be formed at high speed regardless of the shape and surface condition of the piston to be plated. Further, it is preferable that the plating film is subjected to a heat treatment to improve the adhesion to the piston base material and the film hardness. The heat treatment conditions can be appropriately determined in consideration of the hardness required for the film, the heat resistance of the base material, and the like. For example, 30 to 1 at 200 to 350 ° C.
Heat treatment can be performed for 20 minutes. Since the film hardness can be improved by such a heat treatment at a relatively low temperature, it can be formed even on a piston made of a heat-treated aluminum-based alloy as a base material.

The present invention also includes the piston according to the present invention, wherein a piston ring is fitted into at least one of the grooves of the piston. Examples of the piston ring include an iron piston ring.

The present invention includes the combination of the piston and the cylinder of the present invention. The cylinder can be made of, for example, an aluminum alloy or cast iron. These cylinders can be appropriately selected from known ones. Further, the combination of piston and cylinder of the present invention can be, for example, an engine component for an internal combustion engine.

[0018]

The present invention will be described in more detail with reference to the following examples. Example 1 An AC8A material (JIS H5202) was cast into a predetermined piston shape, and a Ni-P-B alloy plating film was formed on the entire surface thereof. Table 1 shows the plating bath, plating conditions, film thickness, and heat treatment conditions used. The sliding surface with the cylinder is machined to have a pitch of 0.1 to 0.3 µm and a roughness of 6
It was finished to a surface state of μm.

[0019]

[Table 1]

The cylinder as the mating material is an ADC12.
The material (JIS H5302) was finished into a predetermined cylinder block shape by casting. The sliding surface between the piston and piston ring is machined to have a pitch of 3 μm and a roughness of 3 μm
Finished surface condition. The piston ring was made of gray cast iron.

Comparative Example 1 A piston, a cylinder, and a piston ring were manufactured in the same manner as in Example 1. However, the piston was manufactured from AC8A material, and iron plating and a hard alumite film were applied to the surface of the piston as described below. That is, after masking the ring groove and the pin hole, an outer peripheral portion such as a skirt and a land was coated with an iron plating film. Table 2 shows the iron plating bath and plating conditions.

[0022]

[Table 2]

Next, the mask in the ring groove portion was peeled off, and a mask was formed on the outer peripheral portion of the skirt land portion. Then, a hard alumite film was applied to the ring groove portion. Table 3 shows the hard alumite bath and oxidation conditions.

[0024]

[Table 3]

Comparative Example 2 A piston, a cylinder and a piston ring were manufactured in the same manner as in Example 1. However, the piston was made of AC8A material, but the Ni-P-B film was not applied and the piston was left untreated.

Test Example 1: Sliding Characteristics A seizure test was conducted using the combination of the materials of Example 1 and Comparative Examples 1 and 2 assuming a sliding member of an internal combustion engine, which is a main application of the present invention. Test method-Reciprocating motion wear test-Table 4 shows the test piece combinations.

[0027]

[Table 4]

Test method Load 2.5 kgf / cm ² to 2.5 kgf every 6 seconds
/ Cm ² Step-up speed 2.5 m / sec Lubrication Dry state During the test, the frictional force was measured, and the point where the frictional force increased sharply was defined as the seizure limit surface pressure. -Test results are shown in Table 5.

[0029]

[Table 5]

Test Example 2: Durability test of actual machine The piston, cylinder, and piston ring obtained in the steps of Example 1 and Comparative Examples 1 and 2 were assembled into a two-cycle air-cooled two-cylinder engine, and an actual machine test was performed. The actual machine test was performed under the conditions of a rotation speed of 5,200 rpm, a full load, and a test time of 100 HR. Table 6 shows the results.

[0031]

[Table 6]

As shown in Table 6, the piston of the present invention of Example 1 is superior to the pistons of Comparative Examples 1 and 2 in slidability, abrasion resistance, and seizure resistance. Improvements were seen. Furthermore, in the piston of Example 1, the piston clearance hardly changed even under a severe actual machine durability test. Therefore, in the piston of the first embodiment,
Loss such as an increase in the amount of probe gas and an increase in noise due to an increase in the piston clearance, and an increase in the consumption of lubricant can be prevented. As a result, fuel efficiency is improved.

[0033]

According to the present invention, the piston ring can be formed by a single surface treatment, is made of the same material, has physical properties such as seizure resistance required for the sliding surface, and the piston ring required for the piston ring fitting groove. It is possible to provide a piston having a coating that satisfies both the resistance to contact and wear. Further, according to the present invention, it is possible to provide a combination with a cylinder, particularly a combination for an internal combustion engine, using the piston of the present invention.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a piston of the present invention.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toru Asano 1620 Kamagabuchi, Kawaji-shi, Saitama Prefecture Honda Metal Technology Co., Ltd. Inside Japan Kanigen Co., Ltd. (72) Inventor Yukinori Saiki 3-11-10 Edagawa, Koto-ku, Tokyo Inside Japan Kanigen Co., Ltd. (56) References JP-A-3-267553 (JP, A) JP-A-8- 158058 (JP, A)

Claims (8)

(57) [Claims] 1. A piston for an internal combustion engine having at least one groove for fitting an iron piston ring on an outer peripheral surface, wherein at least one of the inner surfaces of the groove contacts a nickel piston ring that reciprocates. A phosphorous-boron-based coating, and the nickel-phosphorus-boron-based coating contains 0.5 to 3% by weight of phosphorus and 0.05 to
A piston comprising a nickel coating containing 2% by weight. 2. The sliding surface of the piston is also nickel-phosphorous.
The piston according to claim 1 having a boron-based coating. 3. The piston according to claim 1, wherein the nickel-phosphorus-boron coating has a thickness of 2 to 50 μm. 4. The piston according to claim 1, wherein the base material is made of an aluminum-containing metal. 5. The piston according to claim 4, wherein the aluminum-containing metal is selected from the group consisting of wrought aluminum and aluminum alloys, cast aluminum alloys, and die-cast aluminum alloys. 6. A piston according to claim 1, wherein an iron piston ring is fitted in at least one of said grooves. 7. A combination of a piston and a cylinder according to claim 6. 8. The combination according to claim 7, wherein the cylinder comprises an aluminum alloy or cast iron.