JPH05106737A - Piston ring - Google Patents

Abstract

PURPOSE:To restrict abrasion due to sticking of a piston to a piston ring even in the case of an aluminum-made piston, by forming a coat of organic resin including solid lubricant on the surface of a titanium-alloy piston ring body which is in contact with a ring groove of a piston, and setting the thickness of the coat to a specific value. CONSTITUTION:A coat of organic resin including solid lubricant is formed on the surface of a titanium-alloy piston ring body 1 which is in contact with a ring groove of a piston, and the thickness of the coat is set to 0.001-0.02mm. The piston ring, compared with a steel-made piston ring, can better acquire a required rigidity even if it is made thin, can restrict flattering and therefore is effective for preventing the generation of blowby gas, and can restrict abrasion due to sticking of the piston to the piston ring groove even in case the piston is made of aluminum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston ring mounted on a piston of an internal combustion engine.

[0002]

2. Description of the Related Art In recent years, there has been a problem that blow-by gas rapidly increases due to fluttering of a piston as the engine speed increases. As is well known, it is considered that the fluttering phenomenon of the piston occurs when the piston ring starts to lift when the piston is in a state before the compression top dead center. It is considered that the lifting of the piston occurs because the force obtained by subtracting the frictional force from the inertial force of the piston ring is larger than the force pressed against the lower surface side due to the difference in gas pressure acting on the upper and lower surfaces of the piston. By the way, the inertial force of the piston ring is proportional to the square of the engine speed and the piston ring weight. From this relationship, it is necessary to reduce the weight of the piston ring in order to raise the engine speed to the limit immediately before fluttering occurs. Therefore, it is generally considered effective to reduce the width dimension (B) of the piston ring and lower it. However, when the width dimension is reduced to, for example, 0.8 mm or less to reduce the thickness, the rigidity in the width dimension direction is reduced and it becomes difficult to maintain a stable posture in the piston groove. As a result, the function of the gas sealing property is deteriorated and the adverse effect of increasing the blow-by gas is brought about.
As described above, there is a limit in reducing the width of the piston ring as a measure for increasing the engine speed, and the required rigidity must be ensured. It is effective to use a low specific gravity material as the piston ring material as one of the solutions to these conflicting problems. Titanium alloy, for example, is known as a low specific gravity material, and it has a light weight of about 60% of the specific gravity of steel material, and has the advantage of maintaining the required mechanical properties even under high temperature conditions where the temperature rises to about 300 ° C during engine operation. is there.

[0003]

Utilizing the characteristics of titanium alloy, the surface of the ring body made of titanium alloy that slides on the cylinder is hard surface treated (chrome plating, ion plating method, molybdenum spraying, and A method for obtaining the required sliding characteristics by applying nitriding or the like has been studied. However, the titanium alloy has a thermal conductivity of about 1/10 that of steel, and is a very activating metal. for that reason,
When the pistons are made of aluminum alloy, adhesion occurs between the aluminum pistons and wears the piston ring groove. Due to such inconvenience, it has been said that it is almost impossible to use a titanium alloy as it is as a piston ring material. Therefore, the object of the present invention is to pay attention to the characteristics of the titanium alloy effective for the blow-by gas generation prevention measure,
An object of the present invention is to provide a piston ring capable of suppressing wear due to adhesion with the piston ring groove even when the histone is made of aluminum.

[0004]

In the piston ring according to the present invention, a film made of an organic resin containing a solid lubricant is formed on the surface of the piston ring body made of a titanium alloy that contacts the ring groove of the piston. In this case, it is effective that the organic resin film has a thickness of 0.001 to 0.02 mm.

[0005]

[Function] Suitable for suppressing fluttering and suppressing generation of blow-by gas by forming a film made of an organic resin containing a solid lubricant on the upper and lower side surfaces of the titanium ring main body which comes into contact with the ring groove of the piston. Therefore, aluminum adhesion is less likely to occur and it can be used in actual equipment. When the surface treatment by hard chrome plating is performed on the outer peripheral sliding surface with the cylinder, the reason why the aluminum piston is violated is that there is a problem of surface roughness and a problem that can be solved by performing side surface polishing finish. However, in this case, it is necessary to increase the thickness of the plating, and this is not always a good idea because of the inconvenience of increasing the number of steps. For this reason, according to the present invention, a solid lubricant-containing organic resin film is simply formed without performing hard surface treatment on the outer peripheral sliding surface with the cylinder and requiring no additional steps.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a piston ring according to the present invention will be described below with reference to the drawings. As titanium alloys, α-type alloys, β-type alloys and α-β-type alloys are known. The α-type alloy has excellent high temperature strength and high high temperature stability. The β-type alloy has a good hot workability and a heat treatment property (age hardenability). Therefore, the α + β type alloy has characteristics of α type and β type, respectively, and has good workability and plastic working on a wire rod, and can be used equivalent to steel. In the examples, the typical Ti-6Al-4V in α + β type alloy is used. This alloy has mechanical and physical properties necessary and sufficient for a piston ring.

The manufacturing procedure is as follows: Ti-6Al-4V material is hot-worked or cold-worked to have a sectional size of 1.25 mm ×
It is processed into a wire rod of 3 mm, and then cold plastically processed to coil into the shape of a piston ring. After cutting to provide a ring abutment, heat treatment (strain relief) is performed, and the side surface and outer periphery are processed. The outer peripheral surface of the piston ring, which is a sliding surface with respect to the cylinder, is subjected to surface treatment by hard chrome plating, and then further finishing is performed.

An organic resin containing a solid lubricant is sprayed onto the upper and lower side surfaces of the piston ring processed up to this point, that is, the upper and lower surfaces in contact with the ring groove on the piston side, and the resin is hardened by baking to form a film. To form.
The titanium alloy piston ring thus completed has an outer diameter of 85 mm, a width of 1.2 mm, and a thickness of 3.1 m.
m, thickness of hard chrome plating on outer periphery is 0.1 mm, thickness of organic resin film containing side solid lubricant is 0.005 mm
m. Compared to conventional steel piston rings of the same size, the weight can be reduced by about 40%.

Next, using the piston ring of the embodiment manufactured by the above procedure as sample A, hard chrome plating (thickness: 0.02 m) applied to the outer peripheral surface sliding on the cylinder surface.
m) was also applied to the upper and lower side surfaces (contact surface with the piston ring groove), and sample C with no surface treatment applied to the upper and lower side surfaces was subjected to an aluminum adhesion test by the adhesion test apparatus shown in FIG. It carried out 3 times on the conditions shown in Table 1.

Here, in the adhesion test apparatus of FIG. 1, a disk-shaped holder 12 is connected to a rod of an air cylinder 10 via a floating joint 11, and the holder 12 has the above-mentioned 3
The piston ring 1, which is one of the test samples A to C, is held. The holder 12 holding the piston ring 1 can move up and down in the figure by the operation of the air cylinder 10. Immediately below the holder 12, a disk-shaped stator 13 that faces the piston ring 1 is arranged. This stator 13 is manufactured by assuming a piston material, and is supported on a turntable 16 which is rotatable on a device frame 14 via a bearing 15. The turntable 16 is connected to a rotary shaft 18 of a motor 17 and receives the rotation of the motor 17. Further, a heater 19 is arranged on the back surface of the stator 13 so as to be buried in the turntable 16, and the stator 13 can be heated by energizing the heater 19 from the lead wire 20. Further, a thermocouple 21 is embedded in the stator 13, and a temperature controller 22 that adjusts the temperature of the stator 13 heated by the heater 19.
Has been deployed.

Table 1 Test conditions Stator (piston material) temperature 250 ° C. ± 5 ° C. Ring beating surface pressure 5 kg / cm ² Holder stroke 10 mm Number of beating 4 times / sec Test time 1 hour , Each sample A to C of the piston ring after the test, and the stator 13 (piston material)
The struck surface was observed and evaluated according to the grade shown in the following "Table 2". That is, the grades 0 to 3 were evaluated as acceptable for use in the actual machine, and the grades 4 and 5 were evaluated as rejected because they could not withstand the use of the actual machine and the possibility of aluminum adhesion was large. In FIG. 2, the test was performed three times (test No. 1 to No.
3) is performed and these evaluations are graphed.

As shown in FIG. 2, in terms of piston ring adhesion grade, sample A of the embodiment in which coatings are formed on the upper and lower sides with an organic resin containing a solid lubricant, and a hard chrome plating treatment are applied to a cylinder. Both of the samples B applied to the contacting outer peripheral surface are evaluated as acceptable. However, regarding the adhesion grade in the stator 13 made of aluminum, the sample B having the outer peripheral surface subjected to the hard chrome plating has not been evaluated as acceptable, and only the sample A of the example in which the organic resin film containing the solid lubricant is formed. It is evaluated as acceptable by the judgment that it can withstand the actual use.

However, in the case of the sample B which was surface-treated by hard chrome plating, the stator 1 made of aluminum was used.
As a reason for violating No. 3, there is a problem of surface roughness, which is solved by side surface polishing finish. However, in this case, it is necessary to increase the thickness of the plating, and this is not always a good idea because of the inconvenience of increasing the number of steps. For this reason, in the present invention, a solid lubricant-containing organic resin film is simply formed without performing a hard surface treatment like the sample B on the outer peripheral sliding surface with the cylinder and without requiring additional steps. ing.

[0015]

As described above, the piston ring according to the present invention uses the titanium alloy for the ring body, and the required rigidity can be obtained even if the ring is made thinner than the conventional one made of steel. It is effective in preventing blow-by gas generation by suppressing the ring, and by forming a film of organic resin containing solid lubricant on the upper and lower sides that contact the piston ring groove of the ring body, the piston is especially made of aluminum. Even in this case, there is an advantage that abrasion due to adhesion with the piston ring groove can be suppressed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an apparatus for performing an aluminum adhesion test by mounting a sample piston ring.

FIG. 2 is a graph of test results of samples.

[Explanation of symbols]

1. ． Sample piston ring, 12. ． Holder, 1
3. ． 15. A stator that assumes an aluminum piston. ．
Turntable, 19. ． heater

Claims (2)

[Claims] 1. A piston ring comprising a piston ring body made of a titanium alloy, and a film made of an organic resin containing a solid lubricant formed on a surface of the piston ring body in contact with the ring groove of the piston. 2. The organic resin film has a thickness of 0.001 to
The piston ring according to claim 1, which has a diameter of 0.02 mm.