JPH10103519A - Piston ring and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston ring subjected to composite plating by which the initial fitting is improved. SOLUTION: Composite Cr plating 2 is formed on the outer peripheral sliding surface of a piston ring 1. The composite Cr plating 2 includes cracks and composite particles of aluminum or silicon nitride, etc., are included in the cracks. In the composite Cr plating 2, Cr plating layer 2A of more than 0 volumetric % and less than 1.5 volumetric % of small composite rate, and a Cr plating layer 2B of more than 1.5 volumetric % and not more than 12 volumetric % of large composite rate are plurally and alternately laminated to be formed, and the Cr plating layer 2A of small composite rate and the Cr plating layer 2B of large composite rate are axially and alternately exposed on the sliding surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piston ring for an internal combustion engine.

[0002]

2. Description of the Related Art In recent years, the operating environment of a piston ring has become extremely harsh in response to higher engine output, lower fuel consumption and compliance with exhaust gas regulations.
Performance cannot be maintained by plating or nitriding.

On the other hand, as described in JP-A-62-56600, there is an attempt to improve the wear resistance and seizure resistance of Cr plating by dispersing hard particles in Cr plating. . In this method, first, a positive electroplating is performed to precipitate a Cr plating having a network-like crack,
Next, a crack is expanded and developed by performing a reverse voltage treatment, and the crack contains hard particles.

[0004]

However, this composite Cr plating is excellent in wear resistance and seizure resistance, but is inferior in initial conformability.

[0005] It is an object of the present invention to provide a composite-plated piston ring having improved initial conformability.

[0006]

According to the piston ring of the present invention, a plating layer having a low composite ratio of 0% by volume or more and less than 1.5% by volume, a composite layer having a composite ratio of 1.5% by volume or more and 12% by volume or less. A composite plating in which a plurality of plating layers having a high composite ratio of not more than volume% are alternately laminated is formed on the outer peripheral sliding surface, and a plating layer having a low composite ratio of the composite plating and a plating layer having a high composite ratio are provided. Are exposed on the sliding surface.

[0007] In the above, good wear resistance and seizure resistance are obtained by a plating layer having a large composite ratio, and initial conformability is secured by a plating layer having a small composite ratio. As a result, the piston ring of the present invention has excellent wear resistance and seizure resistance, and also has excellent initial conformability.

[0008] The plating layer having a large composite ratio exposed on the sliding surface has an axial pitch along the sliding surface of 0.05 to 0.05 mm.
An arrangement of 0.2 mm is desirable from the viewpoint of initial conformability.

As the composite plating, for example, composite Cr
Plating is used.

The features of the method for manufacturing a piston ring according to the present invention are as follows.

(1) By repeatedly performing positive electroplating and reverse electrolysis on the outer peripheral sliding surface of the piston ring using a plating bath containing composite particles, the composite ratio is 0% by volume or more.
Peripheral sliding of composite plating in which a plurality of plating layers having a low composite ratio of less than 1.5% by volume and a plurality of plating layers having a high composite ratio of 1.5% by volume or more and 12% by volume or less are alternately laminated. Form on the surface.

As shown in FIG. 2, meshes are formed in the plating deposited by the positive electroplating, and these cracks are enlarged by the reverse voltage treatment. The composite particles 4 are fixed. Furthermore, when the positive electroplating → reverse electric treatment is repeatedly performed, the first 1
The composite plating 40 is further laminated on the composite plating 30 formed in the cycle process. Therefore, the composite particles 4 in the crack 3 of the first composite plating 30 are confined in the layer. The second-layer composite plating 40 has cracks 3 extending in a mesh shape on the surface, and the composite particles 4 are fixed to the cracks 3. Hereinafter, when the positive electroplating → reverse electric treatment is repeatedly performed a predetermined number of times, composite plating is formed with a predetermined thickness on the outer peripheral sliding surface of the piston ring.

In the above description, since the crack 3 has a substantially V-shaped cross section, the amount of the composite particles 4 contained in the crack 3 increases toward the surface. As a result, composite plating formed by one cycle of positive electroplating →
The composite particles 4 are almost uniformly dispersed along the surface, and the composite ratio is uniform along the surface and has constant sliding characteristics. However, it cannot be said that the composite particles 4 are uniformly dispersed in the thickness direction. The composite ratio differs in the thickness direction. In addition, as shown in FIG. 2, if the crack 3 is prevented from penetrating in the thickness direction, a portion where the crack 3 does not enter is formed in the lower layer portion, and the composite ratio can be set to zero.

The composite ratio of the composite particles is governed by the ratio of the composite particles in the plating bath composition, the conditions of the positive electroplating and the reverse electrolysis. That is, the amount of composite particles entering the crack depends on the ratio of the composite particles in the plating bath composition, the electroplating conditions determine the crack density, and the reverse electrolysis conditions determine the crack width to be enlarged.

Therefore, when the positive electroplating → reverse electroplating is repeatedly performed, as described above, a composite plating is formed on the outer peripheral sliding surface of the piston ring with a predetermined thickness. % And less than 1.5% by volume of the plating layer having a small composite ratio, and a composite ratio of 1.5% by volume or more and 12
It can be formed by alternately laminating plating layers having a large composite ratio of not more than volume%.

(2) By processing the surface of the composite plating, a plating layer having a low composite ratio and a plating layer having a high composite ratio are exposed on the sliding surface.

An example of processing the surface of the composite plating is shown below. The shape of the outer peripheral sliding surface before plating is a flat surface parallel to the axial direction, and the plated surface is processed into a barrel shape. The shape of the outer peripheral sliding surface before plating is a barrel shape, and the plating surface is processed into a barrel shape with a curvature different from the barrel shape before the plating. The shape of the outer peripheral sliding surface before plating is a barrel shape, and the plated surface is processed into a flat surface parallel to the axial direction. The shape of the outer peripheral sliding surface before plating is a tapered surface, and the plated surface is processed into a flat surface parallel to the axial direction.

By the above-mentioned processing, the plating layers having a low composite ratio and the plating layers having a high composite ratio can alternately appear on the sliding surface in the axial direction.

[0019]

FIG. 1 is a longitudinal sectional view showing a part of a piston ring according to an embodiment of the present invention. A composite Cr plating 2 is formed on the outer peripheral sliding surface of the piston ring 1. When viewed from a direction perpendicular to the plating surface, the composite Cr plating 2 has a network of cracks 3 on its surface and inside.
And the composite particles 4 such as alumina or silicon nitride are contained in the cracks 3 and fixed.

The composite Cr plating 2 has a composite ratio of 0% by volume or more and less than 1.5% by volume and has a small composite ratio.
And a plurality of Cr plating layers 2B having a high composite ratio of 1.5% by volume or more and 12% by volume or less are alternately laminated and formed, and the Cr plating layer 2A having a low composite ratio is formed. And the Cr plating layer 2B having a large composite ratio are alternately exposed on the sliding surface in the axial direction.

Hereinafter, a method for manufacturing the piston ring 1 will be described.

First, the plating process of the composite Cr plating 2 will be described. The composite Cr plating is formed by repeatedly performing positive electroplating and then reverse electroplating on the outer peripheral sliding surface of the piston ring.

Examples of the plating bath composition of the composite Cr plating and the respective conditions of positive electroplating and reverse electrolysis are shown below. Plating bath composition CrO ₃ 250 g / l H ₂ SO ₄ 1.0 g / l H ₂ SiF ₆ 5 g / l composite particles (alumina or silicon nitride) 20 g / l Positive electroplating Current density 60 A / dm ² Plating bath temperature 55 ° C. Plating Time 10 minutes Reverse voltage treatment Current density 50A / dm ² Plating bath temperature 55 ° C Plating time 1 minute

Under the above conditions, when the positive electroplating → reverse electric treatment is repeatedly performed a predetermined number of times, a flat outer periphery parallel to the axial direction of the piston ring 1 is obtained as shown in FIG. A composite C in which a plurality of Cr plating layers 2A having a low composite rate and a plurality of Cr plating layers 2B having a high composite rate are alternately laminated on the sliding surface.
r plating 2 is formed.

Next, as shown in FIG.
By processing the surface of the composite Cr plating 2 into a barrel shape, the sliding surface of the piston ring 1 has a small composite rate C
The r-plated layer 2A and the Cr-plated layer 2B having a large composite ratio are alternately exposed in the axial direction.

The positive electroplating → reverse electroplating is performed by repeating the number of cycles according to the thickness of the composite Cr plating. Under the above conditions, one cycle of positive electroplating → reverse electrolysis is performed.
Since a plating thickness of about μm can be obtained, for example, 12 cycles are repeated.

The results of a wear test performed using a reciprocating friction tester will be described below.

FIG. 4 shows an outline of a reciprocating friction tester used for the test. Pin-shaped upper test piece 10 is fixed block 1
1, a downward load is applied from above by a hydraulic cylinder 12 and pressed against a lower test piece 13.
On the other hand, the flat plate-shaped lower test piece 13 is held by a movable block 14 and reciprocated by a crank mechanism 15. Reference numeral 16 denotes a load cell.

The test conditions are as follows. Load: 98N Speed: 600 cpm Stroke: 50 mm Time: 1 hour Lubricating oil: Bearing oil with viscosity equivalent to light oil

(1) Wear test Specimen Upper specimen: The surface of an upper specimen made of steel for a piston ring was subjected to composite Cr plating and surface processing of composite Cr plating. Lower specimen: Cast iron material for cylinder liner

Composite Cr Plating and Surface Shape Processing of Composite Cr Plating Same as the piston ring 1 described in the embodiment of the present invention. However, five kinds of test pieces having different composite ratios were prepared by changing the reverse voltage treatment conditions (see Table 1).

[0032]

Test Method A wear test was performed using the reciprocating friction tester described above.

Results The results of the amount of wear of the upper test piece are shown in FIG. In addition, the test was also performed on the case where ordinary hard Cr plating was formed on the upper test piece, and the wear ratio in FIG. As shown in FIG. 5, it was confirmed that the test piece having the composite Cr plating of the present invention had better wear resistance than the test piece having the ordinary hard Cr plating.

Next, the results of a seizure test performed using a high surface pressure seizure tester will be described.

FIG. 6 shows an outline of a high surface pressure seizure tester used for the test. The test piece 20 is held by the rotor 21 and is rotated by the rotation of the rotor 21. on the other hand,
The mating test piece 22 is held by the stator 23 and is pressed against the rotor 21 with a predetermined load P by a hydraulic device.

In such an apparatus, the test piece 20 is rotated while supplying a predetermined amount of oil to the sliding surface from the oil hole 24 formed in the stator 23. The load applied to the test piece 20 is increased stepwise at regular intervals, and the test piece 2
The torque generated by the sliding between 0 and the counterpart test piece 22 is measured with a torque meter and recorded on a recorder. When the burn-in phenomenon occurs, the torque rises sharply. Therefore,
The load acting on the test piece 20 when the torque sharply increases is defined as a seizure load, and the quality of the seizure characteristics is determined based on the magnitude of the seizure load.

The test conditions are as follows. Rotation speed 8m / s Constant load Start from 20kgf Increase stepwise at a rate of 10kgf / min Lubricant Light oil Oil temperature 80 ℃

(1) Seizure test test piece Test piece: Composite C was applied to the surface of a steel test piece for piston rings.
The surface shape processing of r plating and composite Cr plating was performed. Mating specimen: Cast iron material for cylinder liner

Surface treatment of composite Cr plating and composite Cr plating Same as in the wear test.

Test Method A seizure test was performed using the above-described high surface pressure seizure tester.

Results The results of the seizure load of each test piece obtained in the seizure test are shown in FIG. In addition, the test was also performed on the case where ordinary hard Cr plating was formed on the test piece, and the seizure load ratio in the figure is 1 with the seizure load when the hard Cr plating was formed on the test piece. As shown in FIG. 7, it was confirmed that the test piece having the composite Cr plating of the present invention had better seizure resistance than the test piece having the ordinary hard Cr plating.

Next, the result of an actual machine test for testing the initial conformability will be described.

(1) Actual machine test Piston ring to be tested Piston ring 1 described in one embodiment of the present invention
And φ95mm, axial width 3mm, radial thickness 3.8
mm. In addition, by changing the curvature of the barrel shape in the surface shape processing of the composite Cr plating, five types of test pieces having different axial pitches along the sliding surface of the Cr plating layer having a large composite ratio were prepared (see Table 2). .

[0045]

Test method Engine: φ95 mm x in-line 4-cylinder diesel engine Operating conditions: Full load durability 300 hours Test method: Oil consumption was measured 1 hour after starting operation under the above conditions.

Results FIG. 8 shows the results of the initial oil consumption of each test piston ring obtained in the actual machine test. In addition, the test was also performed on the case where the conventional composite Cr plating was formed on the piston ring, and the oil consumption ratio in FIG. 8 was set assuming that the oil consumption when the conventional composite Cr plating was formed on the piston ring was 1. I have. As shown in FIG. 8, the piston ring having the composite Cr plating of the present invention is the same as the conventional composite C plating.
It can be seen that the initial oil consumption is lower than that of the piston ring having r plating, and the initial conformability is improved.

In the above embodiment, the shape of the outer peripheral sliding surface of the piston ring before plating is axially changed in order to expose the low-composite-rate Cr plating layer and the high-composite-rate Cr plating layer on the sliding surface. Although a processing example in which a parallel flat surface is formed and the surface of the composite Cr plating is formed in a barrel shape has been described, the present invention is not limited to this. Below, other examples are shown.

Although FIGS. 9 to 11 show an example in which two cycles of positive electroplating and reverse electroplating are performed for the sake of explanation, actually, a cycle corresponding to the thickness of the composite Cr plating is performed.

FIG. 9 shows a working example in which the outer sliding surface of the piston ring has a barrel shape before plating and the surface of the composite Cr plating has a barrel shape having a curvature different from the barrel shape before plating.

FIG. 10 shows a working example in which the outer peripheral sliding surface of the piston ring has a barrel shape before plating and the surface of the composite Cr plating has a flat surface parallel to the axial direction.

FIG. 11 shows a working example in which the shape of the outer peripheral sliding surface of the piston ring before plating is a tapered surface, and the surface of the composite Cr plating is a flat surface parallel to the axial direction.

[0053]

As described above, the piston ring of the present invention is excellent not only in wear resistance and seizure resistance, but also in initial conformability.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, in which (a) is a longitudinal sectional view showing a part of a piston ring, and (b) is an enlarged view of a composite Cr plated portion of the piston ring.

FIGS. 2A and 2B are perspective views illustrating a manufacturing process of a composite Cr plating, wherein FIG. 2A shows one cycle after positive-electrode plating → reverse-electrode treatment, and FIG. 2B shows two cycles after the same process.

FIG. 3 is a vertical cross-sectional view for explaining a processing step of a surface of a composite Cr plating, where (a) shows a state after the composite Cr plating;
(B) shows the surface of the composite Cr plating after processing.

FIG. 4 is a front view showing the outline of a reciprocating friction tester.

FIG. 5 is a graph showing the results of a wear test.

FIG. 6 is a longitudinal sectional view showing an outline of a high surface pressure seizure tester.

FIG. 7 is a graph showing the results of a burn-in test.

FIG. 8 is a graph showing the results of an actual machine test.

FIG. 9 is a longitudinal sectional view showing another example of processing the surface of the composite Cr plating, where (a) shows a state after the composite Cr plating and (b)
Shows the surface of the composite Cr plating after processing.

FIGS. 10A and 10B are longitudinal sectional views showing still another processing example of the surface of the composite Cr plating, wherein FIG. 10A shows a state after the composite Cr plating and FIG. 10B shows a state after the composite Cr plating surface is processed.

11A and 11B are longitudinal sectional views showing still another processing example of the surface of the composite Cr plating, wherein FIG. 11A shows a state after the composite Cr plating and FIG. 11B shows a state after the composite Cr plating surface is processed.

[Explanation of symbols]

 Reference Signs List 1 piston ring 2 composite Cr plating 2A plating layer with low composite rate 2B plating layer with high composite rate 3 crack 4 composite particle 10 upper test piece 11 fixed block 12 hydraulic cylinder 13 lower test piece 14 movable block 15 crank mechanism 16 load cell 20 test Piece 21 rotor 22 mating test piece 23 stator 24 lubrication hole

Claims (8)

[Claims] 1. A plating layer having a low composite ratio of not less than 0% by volume and less than 1.5% by volume, and a plating layer having a high composite ratio of not less than 1.5% by volume and not more than 12% by volume. A plurality of composite platings alternately laminated are formed on the outer peripheral sliding surface, and the plating layer having a low composite ratio and the plating layer having a high composite ratio of the composite plating are exposed on the sliding surface. A piston ring. 2. A plating layer having a large composite ratio exposed on the sliding surface has an axial pitch along the sliding surface of 0.05 to 0.05.
2. The piston ring according to claim 1, wherein the piston rings are arranged at 0.2 mm. 3. The piston ring according to claim 1, wherein the composite plating is a composite Cr plating. 4. A composite rate of 0 vol% or more is obtained by repeatedly performing positive electroplating and reverse electroplating on the outer peripheral sliding surface of the piston ring using a plating bath containing composite particles.
A plating ratio of less than 5% by volume and a composite ratio of 1.5
Forming a composite plating on the outer peripheral sliding surface by alternately laminating a plurality of plating layers having a large composite ratio of not less than 12% by volume and not more than 12% by volume, and processing the surface of the composite plating to reduce the composite ratio. Exposing the plating layer of (1) and the plating layer having a high composite ratio to the sliding surface. 5. The method according to claim 1, wherein the shape of the outer peripheral sliding surface before plating is a flat surface parallel to the axial direction, and the processing of the surface of the composite plating is processing of forming a plating surface into a barrel shape. Item 5. A method for manufacturing a piston ring according to Item 4. 6. A shape of the outer peripheral sliding surface before plating is a barrel shape, and a process of a surface of the composite plating is a process of forming a plating surface into a barrel shape having a curvature different from the barrel shape before the plating. The method for producing a piston ring according to claim 4, wherein: 7. The method according to claim 1, wherein a shape of the outer peripheral sliding surface before plating is a barrel shape, and a process of the surface of the composite plating is a process of making a plating surface a flat surface parallel to an axial direction. Item 5. A method for manufacturing a piston ring according to Item 4. 8. The method according to claim 1, wherein a shape of the outer peripheral sliding surface before plating is a tapered surface, and the processing of the surface of the composite plating is a processing of making the plating surface a flat surface parallel to an axial direction. Item 5. A method for manufacturing a piston ring according to Item 4.