JPH06288294A - Combination of cylinder liner and piston ring for diesel engine - Google Patents

Abstract

PURPOSE:To improve a life resistance of a diesel engine by providing a hardening part hardened scatteredly on the inner circumferential sliding surface of a cylinder liner by laser hardening method, and providing a chrome nitride layer made of columnar crystal texture formed vertically on the outer circumferential sliding surface of a piston ring. CONSTITUTION:A surface treatment range 2 in which multiple hardening treatment parts formed by local laser hardening treatment are distributed is formed on the inner circumferential surface of a cylinder liner 1. A piston ring formed of a chrome nitride layer made of fine columnar crystal texture grown up vertically on an outer circumferential surface is mounted as the piston ring which uses the inner circumferential surface of the cylinder liner 1 as the other sliding surface. It is thus possible to improve the life resistance of a diesel engine extra or dinarity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combination of a cylinder liner and a piston ring effective for improving the durability of a diesel engine.

[0002]

2. Description of the Related Art Recent technical trends of internal combustion engines have been highlighted as a challenge to achieve high output and dramatic improvement in durability, and development efforts are being continued to meet these technical requirements. In order to improve the performance of the internal combustion engine, especially the durable life, it is essential to improve the durability of the cylinder liner and piston ring, which are the functional parts of the internal combustion engine,
Various proposals have been made in the past. The piston ring is installed in the ring groove of the piston that is reciprocally arranged in the cylinder liner of the engine so that its outer peripheral surface is in sliding contact with the inner peripheral surface of the cylinder liner. Although it is used under severe sliding conditions, it is essential to improve the wear resistance of the piston ring. It is necessary to improve the wear resistance of the sliding surface. However, the sliding characteristics such as wear resistance of a member depend on the sliding surface structure of the sliding partner member, and even if the wear resistance of one member is excellent, Depending on the dynamic surface structure, the expected wear resistance cannot be obtained, and when both members are evaluated independently, even if each has excellent wear resistance, use them in combination as a sliding pair. In this case, the expected characteristics are not always obtained, and therefore, when developing a sliding member, selection of compatibility between the two members that slide in contact with each other is a major development issue. Conventionally, as a surface treatment for improving the wear resistance of the piston ring, a chromium plating treatment is applied to the outer peripheral sliding surface of the piston ring, a nitriding treatment is applied, or a thermal spray treatment of molybdenum, ceramics or the like is performed, Etc. have been proposed and implemented. Further, as means for improving the wear resistance of the inner peripheral sliding surface of the cylinder liner, chrome plating treatment, thermal spray treatment of wear resistant material, laser hardening treatment and the like have been proposed and implemented.

Particularly, in a diesel engine, a cylinder having a quench-hardened portion formed in spots on the inner peripheral sliding surface by laser quenching in order to withstand harsh operating conditions and to prolong the service life, and the outer layer sliding. A combination with a piston ring having a wear-resistant sprayed layer formed on the surface is used, and good results have been obtained.

[0004]

As described above, various wear-resistant surface treatments for piston rings and cylinder liners have been proposed as measures for improving the durability of internal combustion engines.
In recent years, in particular, there is an increasing demand for further improving the durability of diesel engines, and further improvement is desired. Accordingly, it is an object of the present invention to provide a combination of a cylinder liner and a piston ring in a sliding surface pair arrangement which allows further improvement of the durability of a diesel engine.

[0005]

SUMMARY OF THE INVENTION In view of the above problems, the present inventor has found that a cylinder liner having a quench-hardened portion, which is hardened by a laser hardening method, scattered on an inner peripheral sliding surface, and an outer periphery. By using in combination with a piston ring having a chromium nitride layer formed of a columnar crystal structure formed on the sliding surface substantially perpendicular to the sliding surface, excellent wear resistance of the cylinder liner and the piston ring The present invention has been completed by finding a combination of a piston ring and a cylinder liner having a sliding layer surface pair configuration having good compatibility that is exhibited together with excellent wear resistance and durability.

In the present invention, the cylinder liner is formed with spots of quench-hardened portion dispersed in a spot shape by laser quenching treatment on the inner peripheral sliding surface thereof. Here, each quench-hardened portion having a spot shape is about 1 in the circumferential direction of the cylinder liner.
It has a width of 5 mm, a width of about 4 mm in the lengthwise direction, and is formed in spots at intervals of about 15 mm in the circumferential direction and about 2 mm in the lengthwise direction. It is dispersed at 750. The quenching treatment area extends at least over the sliding area of the pressure piston ring. On the other hand, in the piston ring, a chromium nitride layer is preferably formed by an ion plating method on the outer circumferential surface side of the ring that slides in contact with the inner circumferential sliding surface of the cylinder liner. Here, the chromium nitride layer has a columnar crystal structure,
The chromium nitride layer has a structure in which pores formed along the columnar crystal structure in a substantially vertical direction are scattered, and the presence of the pores causes the density of the chromium nitride layer to be a true density of 80 to 98.
It is set to 5% (porosity 1.5 to 20 vol%). A good effect is obtained when the columnar crystals of the columnar crystal structure of the chromium nitride layer are oriented so that their (111) faces are almost parallel to the ring surface.
This is remarkable in the chromium nitride layer having a composition of rN. The thickness of the chromium nitride layer is in the range of 1 to 80 μm. The thickness of the chromium nitride layer needs to be 1 μm or more in order to avoid disappearing at least during the initial familiarization period. Further, if the thickness of the chromium nitride layer is excessively increased, the manufacturing cost will increase and there is a risk that the chromium nitride layer will peel off. Therefore, in the present invention, the thickness of the chromium nitride layer is set to 80 μm or less. A particularly preferred thickness of the chromium nitride layer is 10-60 .mu.m.

In the present invention, the cylinder liner is manufactured by a conventional laser hardening method. That is, by locally heating and cooling the inner peripheral surface of the cylinder liner with a laser beam, a quench-hardened portion is locally formed on the inner peripheral surface of the cylinder liner, and the cured portion is distributed in spots. The method is adopted.

The chromium nitride layer on the outer peripheral surface of the piston ring of the present invention is preferably formed by an ion plating method. The ion plating method is a kind of PVD method (physical vapor deposition method). Among them, in particular, a reactive ion plating method capable of reacting a vapor of chromium with nitrogen to form chromium nitride on the outer peripheral surface of a piston ring. It is desirable to adopt the Ting method. The chromium vapor is obtained by irradiating a chromium target with a high energy beam such as an electron beam to vaporize the chromium. Chromium is an element that easily forms a nitride, and when plasma is generated in a gas phase in which chromium gas is mixed with nitrogen gas,
Chromium ionizes and combines with each nitrogen ion to form chromium nitride. Here, chromium nitride is formed as CrN when the supply amount of nitrogen gas is large, and as Cr ₂ N when the supply amount of nitrogen gas is small, depending on the amount of supply of nitrogen gas.
When the nitrogen gas is less, unreacted Cr is also formed.

The chromium nitride layer is formed on the outer peripheral surface of the piston ring by the following method. Clean the piston ring base material,
After thoroughly cleaning and holding it at a predetermined position in the vacuum chamber of the ion plating device, the chamber pressure is 1.
Evacuation is performed until the pressure reaches 3 × 10 ^{−3 to} 5 × 10 ⁻³ Pa. Then, the heater built into the ion plating device is used to heat the piston ring base material to release the gas contained therein. The heating temperature is preferably 300 to 500 ° C. Then, it cools to 100-400 degreeC.
When the chamber internal pressure becomes 4.0 × 10 ⁻³ Pa or less, a chromium target is used as a cathode and arc discharge is generated on the surface of the target to release chromium ions. At that time, a bias voltage is applied to the piston ring base material, and chromium ions emitted from the cathode are made to collide with the base material surface at high energy, that is, a so-called bombard cleaning method for removing oxides on the base material surface. Perform activation processing. The bias voltage at this time is -700 to -90.
It is preferably in the range of 0V. Then, the bias voltage is lowered to deposit chromium ions on the outer peripheral surface of the piston ring to form a thin layer of Cr on the outer peripheral surface, and then nitrogen gas is introduced into the chamber. 1.3 x 10 ^{-1 to} 13.3 P
By setting the nitrogen partial pressure in the range of a and using the bias voltage in the range of 0 to −100 V, the ion plating film made of the chromium nitride layer is formed on the outer peripheral surface of the piston ring. Also, by selecting the operating pressure, a chromium nitride film having a predetermined porosity can be obtained. After forming the coating, the piston ring is taken out after cooling in the chamber to 200 ° C. or lower.

[0010]

According to the present invention, the cylinder liner has the hardened portions locally hardened by the laser hardening treatment on the inner peripheral sliding surface of the cylinder liner scattered on the base surface. In this type of cylinder liner, the wear of the relatively soft base surface portion progresses earlier than that of the hard portion during sliding with the piston ring during use. Therefore, the inner peripheral sliding surface of the cylinder liner is a surface in which a slight convex portion formed by a hard portion having good wear resistance and a small concave portion formed by abrasion of the base surface portion are densely distributed. Due to the structure, the presence of the hard portion ensures good wear resistance characteristics, and the presence of slight recesses provides a good distribution of lubricating oil on the sliding surface, thus providing good durability and sliding characteristics. Show. Therefore, this kind of cylinder liner is suitable as a cylinder liner for a diesel engine used under particularly severe operating conditions. However, on the other hand, for the piston ring, which is the sliding partner, it is extremely harsh to use the sliding surface having a non-uniform surface structure with the soft and hard parts distributed. It becomes a condition.
Conventionally, a means for forming a surface treatment layer on the sliding surface of the piston ring has been adopted in order to impart wear resistance characteristics to the piston ring, but the surface treatment layer intended for wear resistance becomes a high hardness, It is fragile. The piston ring is
External tension is applied by closing the abutment portion of the ring and reducing the diameter, and the ring outer peripheral sliding surface is used in pressure contact with the inner peripheral sliding surface of the cylinder liner. Therefore, the piston ring in use is in a state where tensile stress is generated in the circumferential direction on the outer peripheral surface side and compressive stress is generated on the inner peripheral side. It will slide on the sliding surface. A piston ring having a high hardness and fragile surface treatment layer formed on the sliding surface has a distribution of hard and soft portions such as the inner peripheral surface of the cylinder liner described above, even though the piston ring itself has good wear resistance. When a sliding surface having a non-uniform sliding surface structure is used as a sliding partner and is used under severe operating conditions for a diesel engine, the surface treatment layer may be fragile. As a result, the surface treatment layer may be peeled or dropped during use, which is not practical. Further, peeling / falling off of the hard surface treatment layer of the piston ring not only impairs the life and function of the piston ring, but also causes other sliding parts to malfunction during the process in which the falling piece mixes with the lubricating oil and circulates in the engine. There is a risk of wear.

In the present invention, a piston using the inner peripheral surface of a cylinder liner for a diesel engine as a mating sliding surface, the inner peripheral sliding surface having scattered quench-hardened portions hardened by a laser hardening method. As the ring, a piston ring having a chromium nitride layer formed on its outer peripheral sliding surface and having a fine columnar crystal structure grown in a direction substantially perpendicular to the sliding surface is adopted. When the outer peripheral surface treatment layer of the piston ring is formed as described above, cracks generated by circumferential tensile stress acting on the surface layer located on the outer periphery of the piston ring do not occur in the circumferential direction. It tends to be finely dispersed vertically along the columnar structure, so that the stress in the surface layer is alleviated uniformly, and the inter-layer delamination and detachment found in the conventionally proposed chromium nitride layer are caused. Is effectively prevented. Therefore, even when used under severe operating conditions in combination with the cylinder liner for a diesel engine described above, the chromium nitride layer does not peel or fall off, and the chromium nitride layer has good material properties that are good resistance. The wear characteristics can be utilized to improve the wear resistance and durability of the piston ring. Further, in the surface-treated layer of the piston ring of the present invention, fine holes are finely dispersed along the columnar crystal structure in the chromium nitride layer having a fine columnar crystal structure. The dispersed pores serve to disperse the generation of cracks and promote the fine dispersion of cracks, so that the stress relaxation of the surface treatment layer is made more uniform, and the effect of preventing the peeling and falling of the surface layer is further enhanced. Further, the surface treatment layer of the piston ring of the present invention is also effective in that a thin layer made of metallic chromium is formed as an underlayer between the chromium nitride layer formed of a fine columnar crystal structure and the piston ring base material. Is. The presence of this thin layer of chromium metal enhances the bonding strength of the chromium nitride layer to the piston ring base material, and also makes it possible to use fine pores in the chromium nitride layer when used in a corrosive environment, especially when used in diesel engines. It shows corrosion resistance to corrosive fluids that enter through microcracks and peels off the chromium nitride layer due to corrosion.
It works effectively to prevent falling off.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a cylinder liner 1 used in the present invention.
FIG. On the inner peripheral surface of the cylinder liner 1,
A surface treatment area 2 is formed in which a large number of hardening treatment portions formed by local laser hardening treatment are distributed. Figure 2 shows the surface treatment area 2 on the inner surface of the cylinder liner 1.
A part of is shown enlarged. The hardening portion 3 is 5 to 5 in the circumferential direction.
It has a width W of 30 mm and a width H of 2 to 8 mm in the longitudinal direction, and the width w between the circumferential directions of the adjacent curing treatment parts is 5 to 40 m
m, and the vertical interval h is 1 to 8 mm, which are dispersed and formed on the base surface. Here, the hardness of the hardened part 3 is Hv4.
90 to 750, hardness of base surface 4 (untreated portion) is HB1
80 to 269. FIG. 3 shows a piston ring 5 used in the present invention. The piston ring has a chromium nitride layer 6 formed on the outer peripheral surface thereof. FIG. 4 is a micrograph showing the structure of the chromium nitride layer 5 formed on the outer peripheral surface of the piston ring.

Embodiment 1 In this embodiment, a piston ring used in the present invention has a nominal diameter × width × thickness of φ95 mm × 2.5 mm × 3.4 mm and is made of SUS440 material on the outer peripheral surface of the piston ring. A chromium nitride layer was formed using a cathodic arc plasma type ion plating apparatus. First, after cleaning the piston ring base material with CFC and holding it in the vacuum chamber of the ion plating device, the pressure inside the chamber is 1.3 × 10 ^-3 P
Evacuate until it reaches a, energize the heater built into the ion plating device, and set the piston ring to 30
The internal gas of the piston ring base material was released by heating to 0 to 500 ° C, and then cooled to 20 ° C. Then, when the chamber internal pressure became 4.0 × 10 ⁻³ Pa or less, an arc discharge was generated on the chromium target surface with a bias voltage of −700 to −900 V applied to the piston ring to generate chromium ions. After popping out and cleaning the piston ring surface by bombarding, nitrogen gas is introduced into the chamber to set the nitrogen partial pressure to 1.3 × 10 ^-1 ~
Set the bias voltage to 0 to -100V by setting it to about 13.3 Pa.
By applying, an ion plating film was formed on the outer peripheral sliding surface of the piston ring. After forming the film, the piston ring was taken out of the chamber after cooling to 200 ° C. or lower in the vacuum chamber.

According to the above-mentioned method, the fracture surface of the coating on the outer peripheral surface of the piston ring has a columnar crystal structure having a columnar shape from the base material surface toward the coating surface, and the pores along the columnar structure are A 40 μm thick coating layer having a CrN composition of 3 to 5% was formed. (Ring sample-1) The columnar crystals were composed of crystals oriented in the (111) direction toward the outer peripheral sliding surface, which was confirmed by X-ray diffraction. In addition, the hardness of the obtained coating made of CrN composition is Hv 600 to 10 when measured from the surface side.
00, the hardness when measured from the cross section side is Hv1000
It was ~ 1200, and the hardness showed directionality.

In the same manner as in Example 1, the fracture surface of the coating on the outer peripheral surface of the piston ring had a columnar crystal structure having a columnar shape from the surface of the base material to the surface of the coating, and along the columnar structure. C with 8-10% volume ratio of voids
A 40 μm-thick coating layer composed of a mixture of rN and Cr ₂ N was formed. (Ring sample-2)

As a comparative piston ring, a piston ring having a hard chromium plating layer having a thickness of 100 μm formed on the outer peripheral sliding surface (Comparative Example 1) and CrN having no columnar crystal structure having a thickness of 40 μm on the outer peripheral sliding surface were used. A piston ring (Comparative Example 2) on which a film having the composition was formed was prepared.

Each piston ring (ring sample 1,
2 and Comparative Samples 1 and 2) were a 4-cylinder 4-cycle diesel engine having a cylinder liner that had not been subjected to a surface treatment such as speckled laser quench hardening treatment, and a speckled laser quench hardening treatment. Four-cylinder four with cylinder liner used in the present invention
Each of them was installed as a first pressure seal in a cycle diesel engine, and an actual machine operation test was carried out. The test conditions are as follows. Rotation speed: 4,000 rpm Test time: 100 hours Oil temperature: 120 ° C Water temperature: 100 ° C

The results of the test are shown in Tables 1 and 2, and when a piston ring (Comparative Example 1) having a hard chromium plating layer having a thickness of 100 μm formed on the outer peripheral sliding surface was mounted, the piston was The ring is heavily worn, and therefore
It is impossible to extend the durability and life of the engine. Also, when a piston ring (Comparative Example 2) having a CrN composition coating without columnar crystal structure was installed, the piston ring coating had peeled and fell off, causing abnormal wear on the cylinder surface. Has been generated. Peeling off of this film
It is particularly remarkable when used in an engine having a cylinder liner that has been subjected to speckled laser quench hardening treatment, and therefore cannot be put to practical use. On the other hand, a piston ring having a columnar crystal structure having a columnar shape toward the coating surface on the outer peripheral surface of the piston ring, and forming a chromium nitride layer containing pores along the columnar structure (ring sample 1 and 2), even when used in an engine equipped with a spot line laser quench hardening treated cylinder liner, the surface treatment layer does not peel or fall off, and Very few occurrences, and no abnormal wear was found on the mating sliding surface.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

As is clear from the above description, the nitriding which has a columnar crystal structure having a columnar shape on the outer peripheral surface toward the film surface and which has pores along the columnar structure is incorporated. Piston rings with a chrome layer have good resistance to peeling and dislodging of the chrome nitride layer, so wear resistance that has hardened parts hardened by laser hardening on the inner peripheral sliding surface is scattered. Even when used in a diesel engine in combination with a highly durable cylinder liner, it does not peel or drop even under severe operating conditions, and the excellent wear resistance of the chromium nitride layer can be effectively utilized. Therefore, in combination with the excellent durability of the cylinder liner, it is possible to dramatically improve the durable life of the diesel engine.

The piston ring having a chromium nitride layer on the outer peripheral surface used in the present invention can be used in combination with a cylinder liner having a laser hardening treatment on the inner peripheral surface in a speckled manner to improve the durability life of a diesel engine. Although it is a drastic improvement, the sliding surface structure is not severe for the piston ring as compared with that of the cylinder liner, for example, a cylinder liner or the like obtained by subjecting the inner peripheral surface to a helical laser hardening treatment. It is needless to say that the same effect can be obtained even when the combination is used.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a cylinder liner used in the present invention.

FIG. 2 is an explanatory diagram illustrating a laser-quenched surface of a cylinder liner used in the present invention.

FIG. 3 is a sectional view of a piston ring used in the present invention.

FIG. 4 is a micrograph of a metal structure of a chromium nitride layer formed on an outer peripheral surface of a piston ring used in the present invention.

5 is a micrograph of a metal structure of a non-columnar chromium nitride layer formed on the outer peripheral surface of the piston ring used in Comparative Example 2. FIG.

[Explanation of symbols]

 1 Cylinder Liner 2 Laser Quenched Area 3 Quench Hardened Area by Laser Quenching 4 Base of Inner Circumferential Surface of Cylinder Liner 5 Piston Ring 6 Chromium Nitride Layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical indication location F16J 10/04 7366-3J (72) Inventor Hidetsugu Yamamoto 5-3-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (72) Inventor Toshiharu Matsui 5-3-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (72) Inventor Satoshi Hinata 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Industry Co., Ltd.

Claims (5)

[Claims] 1. A combination of a cylinder liner for a diesel engine and a piston ring that is in contact with and slides on the inner peripheral surface of the cylinder liner, wherein the cylinder liner is a quench hardened on the inner peripheral sliding surface by a laser hardening method. Diesel having scattered hardening and hardening portions, and the piston ring having a chromium nitride layer having a columnar crystal structure formed on the outer peripheral sliding surface substantially perpendicular to the sliding surface. Combination of cylinder liner and piston ring for engine. 2. The combination of a cylinder liner and a piston ring according to claim 1, wherein the cylinder liner has a hardness Hv 490 to 75 on the inner peripheral surface of a base hardness HB 180 to 269.
It is a cylinder liner in which quench hardening parts hardened by the laser hardening method of No. 0 are scattered, and the Vickers hardness of the piston ring measured from the surface direction is HmV 600 to
A combination of a cylinder liner and a piston ring for a diesel engine, which has a columnar crystal structure chromium nitride layer of 1000. 3. The combination of a cylinder liner and a piston ring according to claim 1, wherein the chromium nitride layer formed on the outer peripheral surface of the piston ring is CrN or Cr ₂ N formed by an ion plating method. Cylinder liner and piston ring combination for diesel engines with composition or mixed composition of CrN and Cr ₂ N. 4. A combination of a cylinder liner and a piston ring according to claim 1, wherein a chromium nitride layer formed of a columnar crystal structure formed on an outer peripheral surface of the piston ring is along the columnar structure. A combination of a cylinder liner and a piston ring for a diesel engine, which has pores of 1.5 to 20 vol% finely dispersed. 5. The combination of the cylinder liner and the piston ring according to claim 1 or 4, wherein the columnar crystal structure of the chromium nitride layer formed on the outer peripheral surface of the piston ring is (111) on the sliding surface. A cylinder liner and piston ring combination for a diesel engine characterized by being oriented face-to-face.