JP4772737B2 - piston ring - Google Patents

Description

  The present invention relates to a piston ring used in an internal combustion engine, and more particularly to a piston ring that can effectively prevent an aluminum adhesion (welding) phenomenon to the piston ring.

  In general, a reciprocating piston is provided with a pressure ring and an oil ring as a piston ring. This pressure ring has a function of preventing a phenomenon (blow-by) that high-pressure combustion gas flows out from the combustion chamber side to the crank chamber side. On the other hand, the oil ring mainly has a function of suppressing a phenomenon (oil up) in which excess lubricating oil on the inner wall of the cylinder enters the combustion chamber side from the crank chamber side and is consumed. As a conventional standard piston ring combination, a total of three piston ring combinations of two pressure rings including a top ring and a second ring and one oil ring are known.

  In recent years, the quality required for piston rings has been increasing more and more with the reduction in weight and output of internal combustion engines. Conventionally, piston rings for internal combustion engines have been subjected to wear resistant surface treatment such as nitriding treatment, ion plating treatment or hard chrome plating treatment on the sliding surface as means for improving the durability.

  Among these surface treatments, the nitriding treatment is particularly noticeable and widely used as a surface treatment for piston rings used under severe operating conditions because it exhibits excellent wear resistance.

  However, although the piston ring formed with the nitriding layer is excellent in wear resistance, when it is mounted on an aluminum alloy piston, there is a tendency that the ring groove wear of the piston increases. Further, as shown in FIGS. 1A to 1C, aluminum agglomeration in which aluminum on the groove lower surface 11 of the aluminum alloy piston 10 adheres to the lower surface 3 of the piston ring 1 due to wear of the piston ring groove. Wearing occurs (FIG. 1 (c)).

  FIGS. 2A to 2C are charts obtained by a stylus type surface roughness tester showing changes in the surface state of the upper surface 2 and the lower surface 3 of the ring groove of the piston. As shown in FIG. 2, the surface state of the upper surface 2 and the lower surface 3 of the ring groove of the piston is changed from a normal state (FIG. 2 (a)) to a rough piston groove state (FIG. 2 (b)), an aluminum adhesion state ( It changes to FIG.2 (c)).

  2A to 2C, the horizontal axis indicates the position of the piston, and the vertical axis indicates the undulation of the piston groove. In the figure, (F) indicates the front direction, (AT) indicates the anti-thrust direction, (R) indicates the rear direction, and (T) indicates the thrust direction.

  3A to 3C show an aluminum adhesion mechanism, in which an oxide film 8 in which a lower surface 3 of a piston ring 1 and a groove lower surface 11 of an aluminum alloy piston 10 are formed on both surfaces, respectively. (Fig. 3 (a)), the stress of the oxide film 8 at the contact portion is locally increased and the oxide film 8 is destroyed, and the lower surface 3 of the piston ring 1 is broken. Fe and Al on the groove lower surface 11 of the piston 10 made of aluminum alloy are joined (FIG. 3B), and the aluminum alloy 20 is welded to the lower surface 3 of the piston ring 1 (FIG. 3C). An enlarged view of the aluminum adhesion part is shown in FIG. In FIG. 4, 20 indicates the adhered aluminum, and 21 indicates the joint between Al and Fe.

  As described above, when local wear (also referred to as piston groove roughening) due to this welding phenomenon occurs in a certain portion of the piston groove as the piston ring moves up and down, the internal combustion engine is sealed by blow-by gas blow-through. The output decreases. Since this phenomenon occurs in a short time under the ring groove of the piston and has a great influence on the durability of the internal combustion engine, many countermeasures for wear of the piston groove have been proposed.

  For example, to prevent direct contact between the piston and the piston ring as a measure against piston groove wear, the piston is treated with an anodized film, plating or matrix strengthening (in the piston), and to the piston ring. As countermeasures, phosphate coating treatment, plating treatment is performed, or, as shown in FIGS. 5A and 5B, the surfaces of the piston 10 and the piston ring 1 are coated with resin coating 8 (for example, deflick (( (Coating process manufactured by Kawamata Laboratories Co., Ltd.).

  In order to solve the above problem, a wear-resistant treatment layer such as a nitrided layer or a chrome plating layer is formed only on the upper and lower surfaces of the piston ring, or the lower surface, and a solid is formed on the surface of the wear-resistant treatment layer. A piston ring formed with a polybenzimidazole resin film containing a lubricant has been developed (see Patent Document 1).

Furthermore, piston rings whose surfaces are coated with a heat-resistant resin containing a solid lubricant have been developed even by those other than the applicant of the present application (see, for example, Patent Documents 2 and 3).
Japanese Patent Application Laid-Open No. 07-063266 JP-A-10-246149 JP 11-246823 A

  However, although the above-described conventional measures against piston groove wear have the effect of preventing aluminum adhesion at the initial stage when the piston is used, the medium-to-long life is insufficient, and further improvement in durability is desired. Yes.

More specifically, for example, Patent Document 1 discloses a surface film made of a polybenzimidazole resin and a solid lubricant (graphite or MoS ₂ ). The liquid resin is easy to oxidize and deteriorates with time. In addition, it may be difficult to stabilize the quality over a long period of time.

Further, Patent Document 2 discloses a surface coating made of polyamideimide resin or polyimide resin and a solid lubricant (graphite, MoS _2, WS ₂ , polytetrafluoroethylene). Then, aluminum adhesion cannot be prevented sufficiently, and the high cost becomes a problem.

Further, Patent Document 3 discloses a surface coating composed of polyamideimide resin or polyimide resin and MoS ₂ as a solid lubricant and antimony oxide. It cannot be prevented and antimony oxide is harmful to the environment and is not preferred for use.

  This invention is made | formed in view of such a condition, and makes it a main subject to provide the piston ring which can prevent the aluminum adhesion phenomenon to a piston ring effectively.

  The present invention for solving the above-described problems is a piston comprising a piston ring body and a surface coating formed on either the upper surface or the lower surface of the piston ring body, or on both the upper and lower surfaces of the piston ring body. The surface coating is composed of a heat-resistant resin and a substantially spherical copper-based powder contained in the heat-resistant resin, and the content of the copper-based powder with respect to the entire surface coating is 20 It is ˜80% by mass.

  In the piston ring, the copper-based powder may be any powder of pure copper, copper oxide, or copper alloy.

  Moreover, in the piston ring, the average particle diameter of the copper-based powder may be smaller than the film thickness of the surface film.

  Moreover, in the said piston ring, 1.0-10.0 micrometers may be sufficient as the average particle diameter of the said copper-type powder.

  In the piston ring, the heat-resistant resin may be a polyamideimide resin.

  In the piston ring, the surface of the piston ring body on which the surface film is formed may be subjected to a chemical conversion treatment as a base treatment.

  In the piston ring, the heat-resistant resin may further contain a solid lubricant, and the content of the solid lubricant with respect to the entire surface film may be 2 to 10% by mass.

  In the piston ring, the solid lubricant may be one or more selected from the group consisting of molybdenum disulfide, tungsten disulfide, and graphite.

  According to the present invention, since a surface film made of a heat-resistant resin and a substantially spherical copper-based powder is formed on one or both of the upper surface and the lower surface of the piston ring, a part of the ring groove of the aluminum alloy piston is peeled off. Thus, adhesion to the piston ring can be prevented.

  In the above-described measures against piston ring groove wear, in other words, aluminum adhesion prevention measures (see the column of the prior art), a surface film containing a solid lubricant is formed for the purpose of imparting lubricity to the surface of the piston ring body. On the other hand, the present invention is characterized in that a surface film containing a substantially spherical copper-based powder is formed instead of a solid lubricant.

  Conventionally, attention has been paid to improving the lubricity of the surface of the piston ring as a measure for reducing the wear of the piston ring groove as much as possible. If this improves the lubricity of the surface of the piston ring, the aggressiveness of the piston ring against the piston ring groove can be reduced accordingly, and as a result, wear of the piston ring groove will be prevented. .

  However, this measure does not cause a problem at the initial stage where the surface film that contributes to lubricity is sufficiently present, but after a long period of time, the surface film itself may be worn away and peeled off. High, after wear and peeling, the lubricity is lost and the exposed piston ring body causes wear of the piston ring groove.

  The present inventor pays attention to this problem, and in order to solve the problem, in order to secure lubricity by the heat-resistant resin constituting the surface film and to maintain the lubricity by the heat-resistant resin for a longer time, the surface film It was conceived that a substantially spherical copper-based powder was dispersed and blended therein to impart wear resistance to the surface film. In other words, the present invention has a different concept from the conventional one, and the copper-based powder in the present invention has a main role of imparting heat resistance and wear resistance in order to protect the surface film.

  According to the present invention, lubricity can be imparted to the surface of the piston ring by the heat-resistant resin constituting the surface coating, and the surface coating formed on the surface of the piston ring by the substantially spherical copper-based powder is resistant to the surface coating. Since wearability can be imparted, the lubricity by the heat-resistant resin can be functioned for a long time. In the present invention, the shape of the copper-based powder is substantially spherical in order to reduce the partner (piston ring groove) aggression, and this purpose can be achieved by selecting the shape.

  Further, by uniformly dispersing the copper-based powder in the surface film, it is possible to improve the thermal conductivity of the surface of the piston ring, thereby efficiently releasing the heat of the entire piston ring to the outside.

  Further, by uniformly dispersing the solid lubricant, it is possible to further improve the initial compatibility with the piston material and the wear resistance.

  The piston ring of the present invention will be specifically described below with reference to the drawings.

  FIG. 6 is a cross-sectional view of the piston ring of the present invention.

  FIG. 7 is an enlarged cross-sectional view of the vicinity of the upper surface of the piston ring shown in FIG.

  As shown in FIG. 6, the piston ring 60 of the present invention is composed of a piston ring main body 61 and a surface coating 62 formed on one or both of the upper surface and the lower surface (both in FIG. 6). Has been.

  The material of the piston ring body 61 of the present invention is not particularly limited, and any material can be used. For example, steel (steel material) can be mainly used as the material, and SUS440, SUS410, SUS304, or 8Cr steel, 10Cr steel, SWOSC-V, SWRH material, or the like can be used as stainless steel. it can. Further, as a kind of piston ring, not only a top ring that functions as a so-called pressure ring but also a second ring that is the same pressure ring can be used, and further, the present invention can be applied to an oil ring.

  As shown in FIGS. 6 and 7, the surface of the piston ring main body 61 of the present invention has a surface film composed of a heat-resistant resin 63 and a substantially spherical copper-based powder 64 contained in the heat-resistant resin 63. Is formed.

  The heat-resistant resin 63 is mainly intended to impart lubricity to the piston ring surface, while the substantially spherical copper-based powder 64 imparts abrasion resistance to the surface film 62 contained therein, thereby The object is to maintain the lubricity by the heat-resistant resin for a long time.

  The heat-resistant resin 63 constituting the surface film 62 of the present invention can withstand the environment (temperature) in which the piston ring is used and has lubricity. The resin is not particularly limited as long as it can be held and fixed. Specifically, polyamide imide (PAI) resin, polyimide (PI) resin, and the like can be given.

  On the other hand, in the copper-based powder 64 constituting the surface film 62 of the present invention, in addition to pure copper powder, various copper-based powders such as copper oxide powder and various copper alloys (for example, brass alloys) are used. Can be used. However, in the present invention, the copper-based powder has a role of preventing the above-mentioned heat-resistant resin from being worn, but it must avoid attacking the piston ring groove which is the counterpart material and has a very high hardness. Don't pass too much. From this point of view, the copper-based powder is preferably pure copper or copper oxide.

  Here, the present invention is characterized in that the shape of the copper-based powder 64 is limited to a substantially spherical shape. By making the shape substantially spherical, the attacking ability to the piston ring groove which is the counterpart material can be lowered. Here, “substantially spherical” means that the whole has a substantially spherical shape, and does not necessarily mean that the cross section is a perfect circle.

  Further, the average particle diameter of the copper-based powder 64 is not particularly limited. However, in view of the function of the copper-based powder 64 described above, it is preferably smaller than the film thickness of the surface coating 62, specifically Is preferably 1.0 to 10.0 μm. If the average particle size is less than 1.0 μm, the cost required for refining the copper-based powder is increased. On the other hand, if the average particle size is greater than 10.0 μm, the film thickness of the surface coating 62 may be larger. This is because there is a risk of attacking the piston ring groove.

  In the surface film 62 constituting the piston ring of the present invention, regarding the content of the copper-based powder 64 with respect to the heat-resistant resin 63, the heat-resistant resin 63 exhibits sufficient lubrication performance, and the copper-based powder 64 is friction resistant. It can be appropriately set with a balance that can sufficiently exhibit the performance. Specifically, the content of the copper-based powder 64 with respect to the entire surface film 62 is preferably 20 to 80% by mass, and particularly preferably 40 to 60% by mass. When the content of the powder 64 is less than 20% by mass, reduction or disappearance due to friction of the surface film cannot be effectively prevented, and aluminum adhesion cannot be sufficiently prevented. On the other hand, when the content of the powder 64 exceeds 80% by mass, the flexibility of the entire surface film is lowered, and it is difficult to fix the powder with a heat-resistant resin, and the powder may be detached. .

  The heat resistant resin 63 preferably contains a solid lubricant 65 (see FIG. 7), and is preferably dispersed uniformly. The solid lubricant is preferably one or more selected from molybdenum disulfide, tungsten disulfide, and graphite. Thus, by adding a solid lubricant, it is possible to improve the initial familiarity of aluminum adhesion. Specifically, the content of the solid lubricant 65 with respect to the entire surface film 62 is preferably 2 to 10% by mass (in this case, the content of the substantially spherical copper-based powder 64 is 20 to 80% by mass). %, The remainder becomes the heat resistant resin 63). Improve initial wearability and wear resistance with piston material made of aluminum material by forming a surface film containing solid lubricant in addition to substantially spherical copper-based powder on the upper and lower surfaces of the piston ring As a result, the occurrence of aluminum adhesion can be prevented, and a piston ring excellent in durability can be provided.

  The method for forming the surface film 62 in the present invention is not particularly limited. For example, the above-described copper-based powder 64 is contained in a polyamide-imide resin as a heat-resistant resin, and this is spray coated, dip coated, electrostatic painted, or the like. May be applied to the surface of the piston ring main body 61. In addition, the surface film 62 may be subjected to post-treatment such as heating and baking as necessary.

  About the thickness of the surface film in this invention formed by such a method, it is preferable to set it as about 3-20 micrometers, for example.

  In addition, before the surface coating 62 is formed, the surface of the piston ring body 61 on which the surface coating 62 is formed may be subjected to chemical conversion treatment as a base treatment. Examples of the chemical conversion treatment include phosphate treatment, more specifically, manganese-based phosphate coating treatment. By performing the phosphate treatment, the adhesion between the surface of the piston ring main body 61 and the surface coating 62 can be improved.

  The piston ring of the present invention will be described more specifically with reference to examples.

(Examples 1-39, Comparative Examples 1-33)
A member corresponding to the piston ring main body was prepared using JIS SWOSC-V equivalent material. The dimensions of the piston ring were as follows: outer diameter: 71 mm, ring thickness (a ₁ dimension): 2.55 mm, and ring width (h ₁ dimension): 1.2 mm. The composition of the JIS SWOSC-V equivalent material is as follows: C: 0.55% by mass, Si: 1.4% by mass, Mn: 0.6% by mass, P: 0.02% by mass, S: 0.02 % By mass, Cr: 0.65% by mass, Cu: 0.08% by mass, the balance being Fe and inevitable impurities.

  A surface film having a thickness of 10 μm was formed on both the upper surface and the lower surface of the member made of the above materials by using a polyamide-imide resin as a heat-resistant resin and using a substantially spherical copper-based powder by a spray method. The shape of the copper-based powder used (substantially spherical or non-spherical), the average particle diameter, and the amount of the powder added to the entire surface coating are as shown in Table 1, respectively.

  In some of the examples and comparative examples, molybdenum disulfide having an average particle size of 3 μm or less is added as a solid lubricant, and the amounts of these additions are as shown in Table 1, respectively.

  Moreover, in each Example and a part of comparative example, the manganese-type phosphate membrane | film | coat process which is a kind of chemical conversion treatment was performed as a surface treatment on the surface which forms a surface membrane | film | coat (refer Table 1). , "Chemical conversion treatment").

  The piston ring test pieces formed in this way are referred to as Examples 1 to 39 and Comparative Examples 1 to 33 (see Table 1).

  An aluminum adhesion evaluation test, a peeling evaluation test, and a sliding test were performed on the test pieces of the above Examples and Comparative Examples.

<Aluminum adhesion evaluation test>
This test was performed using the aluminum adhesion simple substance evaluation apparatus 80 shown in FIG. Test conditions are: eccentricity cycle: 50 Hz, gas pressure: 0.5 MPa, groove bottom temperature: 200 ° C., eccentricity 0.03 mm, oil supply: supply of mist oil for 8 seconds every 10 minutes, operation time: 25 Time (finished when blow-by becomes excessive).

  The evaluation device 80 includes a piston member (Al material) 83 provided with a groove 87 for mounting test pieces (Test-rings) 81 and 82, and a liner member provided at a position facing the piston member 83. 88.

  As shown in FIG. 8, when the test pieces 81 and 82 are mounted in the groove 87 and an evaluation test is performed, a predetermined amount of gas is discharged from the gas discharge hole 85 provided in the liner member 88. The upper test piece 81 discharged to the piston member 83 side and thus mounted in the groove 87 is pressed against the upper surface of the groove 87, while the lower test piece 82 is pressed against the lower surface of the groove 87. Become. Further, the evaluation device 80 is configured to drive a motor (not shown) under the above test conditions, and the piston member 83 can be rotated while being eccentric in the radial direction in the above state. As 83 continues to rotate, the groove 87 functions as a piston ring groove in the internal combustion engine, the test pieces 81 and 82 function as a piston ring, and the wall surface 84 functions as an inner peripheral wall surface of the cylinder liner. Can be reproduced.

  The evaluation in the evaluation device 80 is performed by measuring the gas flow rate of the portion by the gas sensor 86 provided on the upper side of the groove in which the test piece 81 is mounted. This means that adhesion or damage to the coating occurred and the adhesion between the test pieces 81 and 82 and the wall surface 84 was lost, and it was evaluated that blow-by gas was generated when the gas flow rate increased. It was decided to. “None” in Table 1 indicates that the gas flow rate was constant during the operation time (25 hours), that is, blow-by gas was not generated, and “Yes” increased the gas flow rate during the operation time. That is, it shows that blow-by gas was generated.

<Peeling evaluation test>
In this test, a cross-cut test based on JIS K 5400 was performed.

  Specifically, as shown in FIG. 9, incisions having a depth penetrating the surface film are put at an arbitrary position of each test piece with a cutter at an interval of about 1 mm, and a commercially available adhesive tape is affixed. The tape was peeled off and the tape was observed. In Table 1, the case where there was no adhesion of the surface film to the tape was defined as “none”, and the case where it was adhered even a little was defined as “present”.

<Slip test>
This test was performed using a high-temperature valve seat wear tester 101 shown in FIG. The test conditions were: stroke: 4 mm, repetition rate: 500 times / min, ring rotation speed: 3 rpm, test time: 7 hours, piston temperature: about 250 ° C., piston material: aluminum alloy (AC8A).

  In the sliding tapping test, the piston material 103 is fixed to the testing machine 101 so as not to move in the axial direction, the piston ring test piece 102 is mounted on the piston material 103 concentrically, and the internal phase of the piston ring test piece 102 is determined. This test is performed by reciprocating the cast iron circular bar 105 provided on the side in the axial direction, and is a test method in which an operation mode is given in which the piston material 103 is struck while rotating the piston ring test piece 102. The testing machine 101 has a heater 104 for heating the test material, and can reproduce the high temperature state during combustion in the engine without actually burning the fuel, and simulates the state change of the piston material. Can do.

  The wear amount on the piston side and the wear amount on the piston ring side were evaluated by the test. In addition, the amount of wear measured the level | step difference with the surface roughness meter, and calculated each amount of wear when the amount of wear of the comparative example 1 was set to 100.

  Table 1 below shows the evaluation results of the aluminum adhesion evaluation test, the peeling evaluation test, and the sliding tapping test, and the comprehensive evaluation.

  In the case of aluminum adhesion “existing” in the aluminum adhesion evaluation test, or “existing” in the peeling evaluation test, the overall evaluation was “x”. “No” when aluminum adhesion and peeling is “None” and either of the piston material wear amount ratio or the piston ring material wear amount ratio exceeds 100 in the sliding test, “A”, aluminum adhesion and peeling Is “None”, and the case where the piston material wear amount ratio and the piston ring material wear amount ratio are slightly lower than 100 in the sliding test was evaluated as “◯”. Aluminum adhesion and peeling is “None”, and in the sliding test, the piston material wear rate ratio and the piston ring material wear rate ratio are less than 100, and the piston wear rate ratio and the piston ring material wear rate ratio The case where either one was less than 90 was designated as “◎”.

表１に示す各試験の結果を比較すれば明らかなように、本発明の実施例のピストンリング試験片にはアルミ凝着および剥離がみられず、耐摩耗性も良好であり、本発明のピストンリングの効果を確認することができる。

As is clear from the comparison of the results of the tests shown in Table 1, the piston ring specimens of the examples of the present invention did not show aluminum adhesion and peeling, and had good wear resistance. The effect of the piston ring can be confirmed.

  Moreover, the effect of the addition amount (20-80 mass%) of the powder consisting of the predetermined material used in the present invention and the effect of the addition amount (2-10 mass%) of the solid lubricant can be confirmed.

It is explanatory drawing of an aluminum adhesion phenomenon, (a) is a perspective view of a piston, (b) is an enlarged perspective view of a ring groove and a piston ring of a piston, (c) is an enlarged perspective view showing aluminum adhesion to a piston ring. FIG. (A)-(c) is a figure which shows the mode of the change of the surface state of the shape surface of a ring groove of a piston, and a lower surface. (A)-(c) is sectional drawing which shows an aluminum adhesion mechanism. It is an enlarged view of an aluminum adhesion part. It is sectional drawing which shows the conventional resin coating process. It is sectional drawing of the piston ring of this invention. It is an expanded sectional view of the upper surface vicinity of the piston ring shown in FIG. It is a schematic explanatory drawing of the aluminum adhesion single-piece evaluation apparatus. It is explanatory drawing of a peeling evaluation test. It is a figure which shows a high temperature valve seat abrasion tester.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 60 ... Piston ring 2 ... Piston groove upper surface 3 ... Piston groove lower surface 10 ... Piston 61 ... Piston ring main body 62 ... Surface coating 63 ... Heat-resistant resin 64 ... Substantially spherical copper-type powder

Claims (3)

A piston ring comprising a piston ring body and a surface coating formed on either the upper surface or the lower surface of the piston ring body, or both the upper surface and the lower surface of the piston ring body,
The surface film is composed of a heat-resistant resin and a substantially spherical copper-based powder contained in the heat-resistant resin,
And the content rate of the said copper-type powder with respect to the said whole surface film is 20-80 mass% ,
The copper-based powder is a powder of pure copper, copper oxide, or copper alloy,
The average particle diameter of the copper-based powder is smaller than the film thickness of the surface coating,
The heat-resistant resin is a polyamide-imide resin;
The heat-resistant resin further contains molybdenum disulfide as a solid lubricant,
The piston ring, wherein a content ratio of the solid lubricant with respect to the entire surface film is 2 to 10% by mass . 2. The piston ring according to claim 1, wherein an average particle diameter of the copper-based powder is 1.0 to 10.0 μm . The piston ring according to claim 1 or 2, wherein a surface of the piston ring body on which the surface film is formed is subjected to a chemical conversion treatment as a base treatment .

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