JP3143835B2 - Combination of piston rings - 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 ring used for an internal combustion engine, and more specifically, to a first ring made of a steel material suitable for a large diesel engine.
And a second pressure ring.

[0002]

2. Description of the Related Art Conventionally, as a first pressure ring of a large-size diesel engine, a cast iron ring having a chrome plating on its outer periphery has been used.
If the R (exhaust gas recycling) method is adopted, the wear resistance is insufficient with chrome plating. Therefore, the first pressure ring must be made of martensitic stainless steel and the surface must be subjected to nitriding treatment to improve wear resistance. is there.

[0003] The environment in the cylinder of the second pressure ring is not as severe as that of the first pressure ring. However, in the case where the outer periphery chrome is applied to the ring made of cast iron, if the EGR method is adopted, there is still a problem in wear resistance. Occurs. Further, when the second pressure ring is made thinner to improve fuel efficiency, the strength of the cast iron ring is insufficient. Therefore, it is desirable that the second pressure ring be a steel ring. The pressure ring made of steel is Japanese Patent Publication 58
No. 25863 and JP-B-61-54103 propose that both the first and second pressure rings be made of the same steel.

[0004]

The pressure ring used for a diesel engine, particularly the first pressure ring, is required to have a high degree of wear resistance, and is therefore made of a relatively expensive high Cr steel material. When the second pressure ring is also manufactured, there is a problem that the cost of the pressure ring becomes expensive. Also, if the first and second pressure rings are formed from the same steel material and plated with chrome of the same hardness, the difference between the first and second pressure ring openings becomes abnormally large in the case of long-term use. In addition, there is a problem that the sealing performance of the pressure ring is reduced and the blow-by amount is increased.

The present invention has been made in order to solve these problems, and an object of the present invention is to consider the strict use conditions of the first pressure ring and the second pressure ring, and consider the second oil. An object of the present invention is to downgrade the steel material and surface treatment of the ring, thereby reducing the cost of combining the first and second pressure rings and maintaining the sealing property for a long period of time.

[0006]

Means for Solving the Problems To achieve the above object, the present invention adopts a means in which the first pressure ring is formed such that the weight ratio of C is 0.16 to 1.4% and Cr is 11.0 to 19.
0%, is formed from a steel material in which Cr carbide is mainly precipitated in the base structure, and is subjected to a surface treatment so that the hardness of the hardened layer becomes Hv1050 or more. 0.4-0.8%, Si 0.3-1.0%, Mn
Surface hardening containing 0.5 to 1.0%, Cr 2.0 to 10.0%, formed from a steel material with Cr carbide precipitated in the base structure, and the hardness of the hardened layer becomes less than Hv1050 The processing has been performed.

Here, the surface hardening treatment is a nitriding treatment including gas nitriding, gas nitrocarburizing, oxynitriding, salt bath nitriding, ion nitriding and the like, and the steel material of the first pressure ring is Mo, Ni, V , Co,
It is preferable to include one or more types of W wear-resistant elements.
Also, PVD or composite plating may be applied on the cured layers of the first and second pressure rings.

[0008]

The first and second pressure rings are both formed by subjecting a martensitic stainless steel material to nitriding treatment to provide a hardened layer on the surface. The reasons for limiting the components of the steel material forming the first pressure ring are as follows. It is as follows. When C is less than 0.16%, the amount of carbide that contributes to wear resistance is small.
If excellent wear resistance is not obtained and the content exceeds 1.4%, carbides become coarse and the strength required for the ring is reduced and the ring is embrittled, so C is in the range of 0.16 to 1.4%. Limited to.

When the content of Cr is less than 11.0%, it is related to the amount of C. However, the amount of carbide having high hardness and excellent wear resistance is small, and the corrosion resistance and the like are also reduced. Although it is related to the amount, the amount of Cr carbide dissolved in the matrix increases, and the strength, particularly toughness, of the material decreases.
Is limited to the range of 11.0 to 19.0%. When Mo, Ni, V , Co, and W are added as components, wear resistance, corrosion resistance, and heat resistance can be further improved.

The first pressure ring formed from the above steel material is subjected to a surface treatment such as nitriding, nitrocarburizing, or ion nitriding to provide a hard nitrided layer of Hv1050 or more on the surface. Due to this nitrided layer, the first pressure ring can exhibit excellent wear resistance even under severe use conditions of a diesel engine employing the EGR system. Although it is possible to use the first pressure ring as the second pressure ring,
Since the pressure ring is less severe in wear and thermal conditions than the first pressure ring, it is formed from a relatively expensive steel with a low Cr content to reduce the overall cost. The reasons for limiting the composition of the steel material are as follows.

C is an important element that gives the pressure ring material the necessary hardness and strength, and contributes to the improvement of wear resistance by forming fine hard Cr carbides. To obtain these effects, at least 0.4% or more is required. However, if it exceeds 0.8%, the toughness and workability in forming a ring are impaired, so this was made the upper limit. S
i is an element that imparts heat-resistant settling at high temperatures, similar to Cr added as a deoxidizing agent. For this purpose, it is necessary to add 0.3% or more. But 1.0%
If it exceeds, the workability is impaired and the toughness is reduced, so the upper limit was made 1.0%.

Mn is added as a deoxidizing agent like Si,
It is also an element that increases strength. Usually 0.3 as deoxidizer
The content is about 0.45%, but the lower limit is set to 0.5% from the viewpoint of improving the strength. If the content is more than 1.0%, the hot workability and the cold workability during ring forming are impaired, so the upper limit is set. 1.0%. Cr forms a solid solution to impart heat resistance and heat set resistance, and also improves corrosion resistance. Some are important elements that form carbides and impart seizure resistance and wear resistance. In order to exert these effects, at least 2.0% or more is necessary from the balance with C. Also,
If it exceeds 10.0%, the workability during ring molding is reduced, so that the upper limit is set to 2.0 to 10.0%.
And

The second pressure ring formed from the above steel material is also subjected to a treatment such as nitriding, soft nitriding, ion nitriding, etc.
Provide less than 1050 hard nitrided layers. This nitride layer has a lower hardness than that of the first pressure ring, but the conditions of the second pressure ring are not as severe as those of the first pressure ring. Excellent wear resistance can be exhibited. The second pressure ring does not need to have the same cross-sectional shape as the first pressure ring, and may have a shape such as a taper, a taper undercut, or a taper inner cut in order to exhibit its function. Abrasion resistance is further improved by applying PVD or composite plating on the nitrided layers of the first and second pressure rings. .

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pressure ring according to the present invention will be described with reference to an embodiment shown in the drawings. FIG. 1 is a sectional view of a main part of a diesel engine equipped with a combination of pressure rings according to the present invention.
The pressure ring 1, the second pressure ring 2, and the oil ring 3 with the spacer expander 4 are mounted in respective piston ring grooves 6, 7, 8 of the piston 5, and their outer peripheral surfaces are in contact with the inner peripheral surface of the cylinder liner 9. . The first pressure ring 1 contains 0.16 to 1.4% of C and 11.0 to 1 of Cr.
It is a barrel-shaped cross-section piston ring made of 9.0% martensitic stainless steel. As shown in FIG. 2, the first pressure ring 1 is subjected to a nitriding treatment, and the surface thereof is covered with a hard nitride layer 11 of Hv1050 or more. The second pressure ring 2 of FIG.
0.8%, Si 0.3-1.0%, Mn 0.5-
It is a cross-section tapered pistring formed of a martensitic stainless steel material of 1.0% and Cr 2.0 to 10.0%. As shown in FIG. 3, the second pressure ring 2
Is subjected to a nitriding treatment, and its surface is covered with a hard nitrided layer 22 having a Hv of less than 1050.

As Comparative Example 1, first and second pressure rings having the same shape and dimensions were formed from the respective steel materials formed in the above-described embodiment, and each was subjected to chrome plating, and the surface thereof was made of chromium having the same hardness as that of the embodiment. A plating layer was provided. Example 1 and Comparative Example 1 were subjected to an actual machine test using the same diesel engine, and their wear properties were measured. The result was as shown in FIG.

As can be seen from FIG. 4, the embodiment subjected to the nitriding treatment is much more excellent in abrasion resistance than the conventional chrome-plated comparative example 1. Further, a combination of the first pressure ring of the example and the second pressure ring of the comparative example 1 is referred to as a comparative example 2, and long-term tests of the example, comparative example 1, and comparative example 2 are performed on the same diesel engine, Was measured. FIG. 5 illustrates the measurement result with respect to the estimated traveling distance. As can be seen from FIG. 5, there is no difference in the blow-by amount between the example and the comparative example 2 up to a running distance of about 700,000 km, and only the comparative example 1 slightly increases compared to the others. However, when the traveling distance exceeds 1.1 million km, the blow-by amount of the example increases only slightly, but the blow-by amount of the comparative example 1 and the comparative example 2 increases significantly.
The blow-by amount of Comparative Example 2, which was smaller than Comparative Example 1 up to 10,000 km, is larger than Comparative Example 1. This indicates that the embodiment in which the first and second pressure rings are subjected to the nitriding treatment suitable for each retains good sealing properties even after long-term use.

[0017]

As described above, the first and second pressure rings of the present invention are made of a martensitic stainless steel containing Cr, but unlike the conventional chrome-plated surface, Has a hard nitrided layer, so that it exhibits good wear resistance even in a diesel engine employing an EGR system. In addition, the present invention reduces the grade of the steel material and reduces the hardness of the nitrided layer correspondingly to the second pressure ring, which is less severe in terms of use than the first pressure ring. In addition to reducing the cost, the wear of the first and second pressure rings is balanced and the amount of change in the abutment gap is always the same, so that good sealing performance is maintained even after long-term use. It has a special effect.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of a diesel engine provided with a pressure ring combination according to an embodiment of the present invention;

FIG. 2 is an enlarged cross-sectional view of the first pressure ring of FIG. 1;

FIG. 3 is an enlarged cross-sectional view of the second pressure ring of FIG. 1;

FIG. 4 is a graph showing test results on wear resistance;

FIG. 5 is a graph showing test results on sealing properties;

[Explanation of symbols]

1: first pressure ring, 2: second pressure ring, 11, 12
2: Nitride layer

────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C23C 8/50 C23C 8/50 14/06 14/06 Z F02F 5/00 F02F 5/00 F (56) References JP 60-108550 (JP, A) JP-A-60-155647 (JP, A) JP-A-4-8861 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16J 9/26 C22C 38/00 301 C22C 38/00 302 C23C 8/26 C23C 8/38 C23C 8/50 C23C 14/06 F02F 5/00

Claims (5)

(57) [Claims] 1. The first pressure ring has a weight ratio of C 0.16.
~ 1.4%, Cr 11.0 ~ 19.0%, formed from a steel material in which Cr carbide is mainly precipitated in the base structure, and subjected to a surface hardening treatment to obtain a hardness of Hv1050 or more. The second pressure ring has a weight ratio of C 0.4 to 0.8%, Si 0.3 to 1.0%, and Mn.
It is formed from a steel material containing 0.5 to 1.0% and 2.0 to 10.0% of Cr and mainly having Cr carbide precipitated in a matrix structure, and is subjected to surface hardening to have a hardness of Hv1050. Combination of piston rings characterized by having less than less hardened layer. 2. The piston ring combination according to claim 1, wherein the surface hardening treatment is a nitriding treatment. 3. The piston ring combination according to claim 2, wherein the nitriding treatment includes gas nitriding, gas nitrocarburizing, oxynitriding, salt solution nitriding, and ion nitriding. 4. The piston ring combination according to claim 1, wherein the surface hardening is further performed by PVD or composite plating on the nitriding treatment. 5. The combination according to claim 1, wherein the first pressure ring contains one or more wear resistance improving elements.