JP3305435B2 - Side rail of combined steel oil ring and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a side rail of a steel combined oil ring used for an internal combustion engine and a method of manufacturing the same.

[0002]

2. Description of the Related Art A steel oil ring is composed of a spacer expander and a pair of side rails. The pair of side rails is pressed radially outward by the spacer expander to be pressed against the inner wall surface of the cylinder. To remove excess oil from the cylinder inner wall. Also on the side rail of this steel combination oil ring,
2. Description of the Related Art In recent years, a nitriding treatment has been performed with an increase in the load on an internal combustion engine (see Japanese Patent Publication No. 57-61888 or Japanese Patent Application Laid-Open No. 58-136771).

[0003]

When the surface treatment of the side rail is nitriding, the nitriding is performed by a gas nitriding method or a molten salt method. According to this method, the side rails are nitrided not only on the outer peripheral surface but also on the upper and lower surfaces and the inner peripheral surface,
The nitride layer is formed with substantially the same thickness on all surfaces. Since the thin side rails whose entire surface is nitrided become brittle,
The breaking strength is remarkably reduced, and it is not possible to meet the demand for thinner side rails and high wear resistance.

In order not to provide a nitrided layer on the upper and lower surfaces of the side rails, it is necessary to remove unnecessary nitrided parts by machining after the nitriding treatment or to perform a nitridation prevention treatment. Demerits are large in terms of aspect.

On the other hand, Japanese Patent Application Laid-Open Nos. 4-18067, 4-362373, and 5-448
No. 40 describes a combined oil ring side rail or a single compression ring in which a nitride layer is formed only on the outer peripheral surface and no nitride layer is formed on the other surface.

However, an oil ring in which the thickness of the nitrided layer is changed according to the required wear resistance required for each surface has not been known.

An object of the present invention is to provide a side rail of a steel combined oil ring which is thin and has good wear resistance, fatigue strength and breakage resistance, and a method of manufacturing the same.

[0008]

The side rail of the steel combined oil ring according to the present invention is a side rail of a steel combined oil ring comprising a spacer expander and a pair of side rails. The nitride layer is formed only on the inner peripheral surface, and the thickness of the nitride layer formed on the outer peripheral surface of the side rail is 30 to 10
0 μm, and the thickness of the nitride layer formed on the inner peripheral surface of the side rail is 5 to 20 μm.

The method for manufacturing a side rail of a combined oil ring made of steel according to the present invention comprises the steps of winding a side rail material into a coil to manufacture a coil, and simultaneously ion-nitriding the outer and inner peripheral surfaces of the coil. And a step of ion-nitriding the outer peripheral surface of the coil before or after the ion nitriding step, a step of cutting the coil after the two ion nitriding steps to obtain a side rail with an abutment, And performing a finishing process.

[0010] The step of simultaneously ion-nitriding the outer peripheral surface and the inner peripheral surface of the coil is performed by bringing the adjacent surfaces in the axial direction of the coil into close contact with each other and partially closing the openings at both ends of the coil. May be ion-nitrided. In the step of ion-nitriding the outer peripheral surface of the coil, the surfaces adjacent to each other in the axial direction of the coil may be adhered to each other, and the openings at both ends of the coil may be closed while ion-nitriding.

The nitriding may not be performed at the coil stage but at the side rail stage. That is,
A step of manufacturing a coil by winding the side rail material into a coil shape, a step of cutting the coil to obtain a side rail having a joint, and a step of simultaneously ion-nitriding the outer peripheral surface and the inner peripheral surface of the side rail. Before or after the ion nitriding step, there is provided a step of ion nitriding the outer peripheral surface of the side rail, and a step of subjecting the side rail to finishing.

In the step of simultaneously ion-nitriding the outer peripheral surface and the inner peripheral surface of the side rail, the ion nitriding may be performed with the openings at both ends of the stacked side rails partially closed. In this case, the abutment of the side rail is preferably closed. Further, the step of ion-nitriding the outer peripheral surface of the side rail is performed by closing each joint of the plurality of stacked side rails and closing each opening at both ends of the stacked side rails. I just need.

[0013]

The thick nitride layer formed on the outer peripheral surface of the side rail exhibits abrasion resistance when sliding against the inner wall of the cylinder. The thin nitride layer formed on the inner peripheral surface of the side rail exhibits wear resistance in sliding with the spacer expander. Since the inner peripheral surface is not required to be as wear resistant as the outer peripheral surface, the nitride layer on the inner peripheral surface may be thin. By reducing the thickness of the nitride layer on the inner peripheral surface, both breakage resistance and wear resistance can be achieved. Since the abrasion resistance of the upper and lower surfaces is sufficient for the abrasion resistance of the side rail base material, it is not necessary to form nitrided layers on the upper and lower surfaces. Wear of the oil ring groove of the piston can also be prevented.

The thickness of the nitrided layer on the outer peripheral surface is required to be 30 μm or more in view of the wear life due to sliding with the cylinder, and is preferably 100 μm or less in view of breakage resistance. The thickness of the nitride layer on the inner peripheral surface is 5 μm from the wear life due to sliding with the spacer expander.
This is necessary, and is preferably 20 μm or less from the viewpoint of breakage resistance.

According to the method for manufacturing a side rail of the present invention, there are provided a step of ion-nitriding the outer peripheral surface and the inner peripheral surface of the coil or the side rail simultaneously, and a step of ion-nitriding the outer peripheral surface of the coil or the side rail. As a result, it is possible to obtain a side rail in which the nitride layer is thick on the outer peripheral surface and thin on the inner peripheral surface.

According to the method for manufacturing a side rail according to the seventh or tenth aspect, the surfaces adjacent to each other in the axial direction are brought into close contact with each other and ion-nitrided, whereby the upper and lower surfaces are not nitrided. Can be obtained. In addition, most of the nitrogen ions generated by the discharge generated in the ion nitriding furnace are used for nitriding the outer peripheral surface of the coil or the side rail, and partially block the openings at both ends of the coil or the laminated side rail. The inner surface of the coil or the side rail is nitrided by moving to the inner peripheral surface side through a portion that is not formed. Therefore, the outer peripheral surface and the inner peripheral surface of the coil or the side rail are nitrided, and the nitride layer is formed thicker on the outer peripheral surface and thinner on the inner peripheral surface.

According to the method for manufacturing a side rail according to the eighth or twelfth aspect, since the openings at both ends of the coil or the laminated side rail are closed, the side rail is formed in the ion nitriding furnace. Nitrogen ions generated by the discharge are used for nitriding the outer peripheral surface of the coil or the side rail. As a result, only the outer peripheral surface of the coil or the side rail is nitrided.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a steel combined oil ring assembled in an oil ring groove of a piston inserted into a cylinder. The steel combined oil ring 1 mounted in the oil ring groove 21 of the piston 20 is composed of a pair of upper and lower steel side rails 2 and 3 (see FIG. 2) having an annular joint and a steel joint rail having an annular joint. And a spacer expander 4.

The spacer expander 4 has a substantially U-shaped cross section, and the upper and lower pieces 6 and 7 connected by the upright pieces 5.
The upper and lower pieces 6 and 7 are provided with side rail pressing pieces 8 and 9 that extend obliquely inward in the radial direction.

The spacer expander 4 is formed as follows. As shown in FIG.
A large number of tortoise-shaped holes 11 serving as oil holes are provided in the longitudinal direction of 0, and a substantially V-shaped slit 12 is provided on both sides of the thin steel strip between these holes 11. Then, both sides in the width direction of the thin steel strip 10 are bent in a substantially U-shape in the same direction along the bending line A-A, and the front end portion of the bent portion is slanted outward along the bending line BB. To bend. Next, the piece cut into a predetermined length is formed into an annular shape with the side rail pressing pieces 8 and 9 on the inner peripheral side.

The combined oil ring 1 made of steel is
Is mounted in the oil ring groove 21, the pair of side rails 2 and 3 are axially separated and held by the upper and lower pieces 6 and 7 of the spacer expander 4. Further, since the spacer expander 4 is mounted in a compressed state, the pair of side rails 2 and 3 are pressed radially outward by the side rail pressing pieces 8 and 9. Therefore, the pair of side rails 2 and 3 have their outer sliding surfaces uniformly pressed and contacted with the inner wall 31 of the cylinder 30 to scrape off excess oil on the inner wall 31 of the cylinder. Also, a pair of side rails 2,
Reference numeral 3 denotes upper and lower surfaces 22 of an oil ring groove
23, the upper and lower surfaces 22, 23 are sealed.

As shown in FIG. 1, the side rails 2 and 3 have the ion nitride layers 13 and 13 only on the outer peripheral surface and the inner peripheral surface.
14 are formed, and the upper and lower surfaces 15, 16 form a base material surface.

Accordingly, since the side rails 2 and 3 have the ion nitride layer 13 formed on the outer peripheral surface, the cylinder 3
0 has good abrasion resistance against sliding with the inner wall 31 and the ion nitride layer 14 is formed on the inner circumferential surface, so that the spacer expander 4 slides against the side rail pressing pieces 8 and 9. And have excellent wear resistance. In addition, since the upper and lower surfaces 15 and 16 form a base material surface, the oil ring groove 21 is unlikely to be abnormally worn due to the base material having a soft contact surface with the aluminum alloy piston 20.

As shown in FIG. 3, the corners between the end face 17 of the abutment and the upper and lower surfaces 15, 16 are not sharp edges, but are chamfered over the entire length of the corners, so that the radius of curvature is increased. A chamfered portion 18 of 0.03 mm to 0.3 mm is formed. FIG. 3 shows one side rail 2
However, the other side rail 3 is similarly formed with a chamfer. As described above, since the side rails 2 and 3 have smooth chamfers, the occurrence of abnormal wear on the upper and lower surfaces 22 and 23 of the oil ring groove 21 is reduced.

The inner peripheral surfaces of both side rails 2 and 3 are:
Before or after ion nitriding, blast processing is performed to prevent side rails 2 and 3 from rotating independently.
Surface roughness.

An example of a method for manufacturing the side rails 2 and 3 will be described below with reference to FIGS. A coil 40 is manufactured by winding a martensitic stainless steel wire containing 17% by weight of Cr into a coil shape.
0 is inserted into the jig cylindrical body 41 (see FIG. 5).
Next, clamp disks 42 and 43 are provided at both ends of the coil 40 inserted into the cylindrical body 41, and the shaft portions of the bolt members 44 are inserted into the central holes formed in the clamp disks 42 and 43, respectively. Insert 45. Then, while the head 46 of the bolt member 44 is in contact with the one clamp disk 43, a nut 47 is screwed into a screw portion of the shaft portion 45 that is inserted through the center hole of the other clamp disk 42 and tightened. The coil 40 has a bolt member 44 and a nut 4 between the clamp disks 42 and 43.
When the coil 40 is fastened in the axial direction, the surfaces adjacent to each other in the axial direction of the coil 40 are in close contact with each other. Next, a work 48 including the coil 40 fixed between the pair of clamp disks 42 and 43 is moved to the cylindrical body 41.
Remove from (Fig. 6).

The bolt member 44 is provided with a shaft portion 49 having a threaded portion, and a pair of clamp disks 42,
It protrudes from the head 46 on the side opposite to the shaft 45 inserted through 43.

Further, the pair of clamp disks 42, 43
In order to nitride the inner peripheral surface of the coil 40, a plurality of arc-shaped nitriding holes 50, 5 are equally spaced on the same circle.
1 are formed respectively.

Next, nitriding treatment was performed on the outer and inner peripheral surfaces of the coil 40 in an ion nitriding furnace. Conditions for ion nitriding are, for example, atmosphere gas composition, nitrogen: hydrogen = 7: 3, work temperature 580 ° C., processing time 3 hours.

In the above ion nitriding process, the coil 40
The surfaces adjacent to each other in the axial direction are closely adhered to each other, so that the surface in the axial direction of the coil 40 is not ion-nitrided. The outer peripheral surface and the inner peripheral surface of the coil 40 are ion-nitrided.
In this case, most of the nitrogen ions generated by the discharge generated in the ion nitriding furnace are used for nitriding the outer peripheral surface of the coil 40, and a part of the nitrogen ions is formed in the clamp disks 42 and 43. It moves to the inner peripheral surface side of the coil 40 through 51, and the inner peripheral surface of the coil 40 is nitrided. Therefore, the nitride layer is formed thick on the outer peripheral surface of the coil 40 and thinner on the inner peripheral surface. As a result, an ion nitride layer having a Vickers hardness H _{V of} 700 or more, a thickness of 10 μm on the inner peripheral surface, and a thickness of 40 μm on the outer peripheral surface was obtained. The balance of the thickness of the nitride layer formed on the outer peripheral surface and the inner peripheral surface can be adjusted by the size, distribution, and the like of the holes for nitridation formed in the clamp disks 42 and 43.

Next, as shown in FIGS. 7 and 8, disk-shaped nitriding hole closing members 52, 53 are respectively disposed on a pair of clamping disks 42, 43, and the clamping disks 4
The 2, 43 nitriding holes 50, 51 are closed. One of the nitriding hole closing members 52 is provided with a shaft portion 45 of the bolt member 44 at the center.
Is provided with a through hole 54 through which a nut 47 to be attached to the shaft portion 45 is inserted at the center of the bottom surface. This nitriding hole closing member 5
2 has substantially the same outer diameter as the clamp disks 42 and 43, and the clearance recess 55 of the nut 47 is
The inner diameter is formed so as to be disposed inside the nitriding hole 50.

The other hole closing member 53 for nitriding is similarly formed. In other words, the nitriding hole closing member 53 has a through hole 56 through which the shaft 49 of the bolt member 44 is inserted at the center.
And a clamp disc 43 at the center of the bottom surface.
And a circular relief recess 57 into which the head 46 of the bolt member 44 that is in contact with is inserted. Further, the hole closing member 53 for nitriding has substantially the same outer diameter as the clamp disks 42 and 43, and the escape recess 5 of the head 46 of the bolt member 44 is formed.
7 has an inner diameter formed so as to be disposed inside the nitriding hole 51 of the clamp disk 43.

The respective nitriding hole closing members 52 and 53 are arranged outside the pair of clamping disks 42 and 43 by inserting the respective through holes 54 and 56 into the respective shaft portions 45 and 49 of the bolt member 44, respectively. Nuts 58 and 59 are screwed and fixed to the threaded portions of the shaft portions 45 and 49 protruding from the respective nitriding hole closing members 52 and 53. Thus, a pair of clamp disks 4
The work 60 in which the holes 43 for nitriding 50 and 51 are closed by the hole closing members 52 and 53, respectively, is completed.

Next, the outer peripheral surface of the coil 40 was subjected to a nitriding treatment in an ion nitriding furnace. Conditions for ion nitriding are, for example, atmosphere gas composition, nitrogen: hydrogen = 7: 3, work temperature 580 ° C., processing time 3 hours.

In the above-mentioned ion nitriding process, the nitriding holes 50 formed in the pair of clamp disks 42 and 43 are formed.
Since 51 is closed by the nitriding hole closing members 52 and 53, nitrogen ions generated by the discharge generated in the ion nitriding furnace do not enter the inner peripheral side of the coil 40. As a result, only the outer peripheral surface of the coil 40 is nitrided.
As a result, an ion nitride layer having a Vickers hardness H _{V of} 700 or more, a thickness of 10 μm on the inner peripheral surface, and a thickness of 70 μm on the outer peripheral surface was obtained. By the ion nitriding treatment for nitriding only the outer peripheral surface, the thickness of the nitrided layer does not change on the inner peripheral surface, but is 30 μm on the outer peripheral surface.
m increased.

FIG. 9 shows an example of the hardness distribution of the ion nitride layer in the depth direction.

After the nitriding treatment, the nitriding hole closing members 52, 53
The clamp disks 42 and 43 were removed, and the coil 40 was cut to obtain a plurality of side rails having an abutment. Then, the normal grinding process (polishing of the upper and lower surfaces,
Wrapping of the outer peripheral surface).

In the above embodiment, the coil was nitrided. However, after cutting the coil to obtain a plurality of side rails, these side rails may be subjected to a nitriding treatment.

In this case, a plurality of side rails are closed at each abutment to perform the nitriding process. Therefore, instead of the cylindrical body 41 used at the time of the nitriding process of the coil 40, a joint closing jig shown in FIG. The tool 61 is used. This jig for closing a mouth 6
Except for using No. 1, the same process as in the nitriding process of the coil 40 is performed. The abutment closing jig 61 has a pair of half members 63 and 64 rotatably attached to the shaft portion 62. Each of the pair of half members 63 and 64 has an arc-shaped cross section. When closed, it forms a cylinder. The pair of half members 63 and 64 have flanges 65 and 66, respectively, protruding from the tips, and bolt holes are formed in the flanges 65 and 66, respectively. Therefore, after a plurality of side rails are inserted and stacked in the pair of half members 63 and 64, the outer peripheral surfaces are pressed inward by the air cylinder. As a result, each side rail is tightened by the pair of half members 63 and 64, and the abutment of each side rail is closed. In this state, a pair of half members 63,
The bolt 67 is inserted through the bolt holes of the 64 flanges 65 and 66, and the nut 68 is attached to the bolt 67. afterwards,
The pressing of the air cylinder is released.

Next, after a pair of clamp disks 42 and 43 are fixed to both ends of the stacked side rails by the bolt members 44 and the nuts 47, the abutment closing jig 61 is removed.

Next, the laminated side rails are subjected to ion nitriding under the same ion nitriding conditions as in the case of nitriding the coil 40, and the outer and inner peripheral surfaces of the side rails are nitrided. After that, the nitriding holes 50 and 51 of the clamp disks 42 and 43 are closed with the hole closing members 52 and 53 fixed to the pair of clamp disks 42 and 43, respectively. Under the same ion nitriding conditions as in the case, the outer peripheral surface of the side rail is further nitrided.

As described above, a thick nitride layer is formed on the outer peripheral surface of the side rail, and a thin nitride layer is formed on the inner peripheral surface.

In the above embodiment, an example in which the outer peripheral surface and the inner peripheral surface are nitrided, and then the outer peripheral surface is further nitrided. However, first, the outer peripheral surface is nitrided, and then the outer peripheral surface and the inner peripheral surface are nitrided. Further, nitriding may be performed.

In this case, when the nitriding jig is used, the outer peripheral surfaces are nitrided with the pair of clamp disks 42, 43 having the nitriding hole closing members 52, 53 mounted thereon, respectively. The outer peripheral surface and the inner peripheral surface may be further nitrided in a state where the closing members 52 and 53 are removed and the pair of clamp disks 42 and 43 are mounted.

[0045]

As described above, according to the present invention, it is possible to obtain a side rail of a steel combined oil ring which is thin and has good wear resistance, fatigue strength, and breakage resistance.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention and showing a steel combined oil ring mounted in an oil ring groove of a piston inserted into a cylinder.

FIG. 2 is a plan view of a side rail.

FIG. 3 is a front view of one end of a side rail.

FIG. 4 is a plan view showing a spacer expander material.

FIG. 5 is a longitudinal sectional view showing a state where the coil is mounted on a nitriding jig.

FIG. 6 is a perspective view showing a workpiece in a state where a cylindrical body has been removed from the state of FIG. 5;

7 is a longitudinal sectional view showing a state in which a hole closing member for nitriding is attached to the work of FIG. 6;

8 is a perspective view showing a state in which a hole closing member for nitriding is attached to the work of FIG. 6;

FIG. 9 is a graph showing an example of a hardness distribution in a depth direction of the ion nitride layer.

FIG. 10 shows a jig for closing a mouth, (a) is a plan view,
(B) is a front view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combined oil ring made of steel 2, 3 Side rail 4 Spacer expander 5 Upright piece 6 Upper piece 7 Lower piece 8, 9 Side rail pressing piece 10 Thin steel strip 11 Drilled hole 12 Substantially V-shaped slit 13, 14 Ion-nitrided layer 15 Side rail upper surface 16 Side rail lower surface 17 Abutment end face 18 Chamfered portion 20 Piston 21 Oil ring groove 22 Ring groove upper surface 23 Ring groove lower surface 30 Cylinder 31 Cylinder inner wall 40 Coil 41 Cylindrical body 42, 43 Clamp disk 44 Bolt Member 45, 49 Shaft 46 Head 47, 58, 59 Nut 48, 60 Work 50, 51 Nitriding hole 52, 53 Nitriding hole closing member 54, 56 Through hole 55, 57 Relief recess 61 Joint closing jig 62 Shaft part 63, 64 Half-piece member 65, 66 Flange 67 Bolt 68 Nut

Continuation of front page (56) References JP-A-4-181067 (JP, A) JP-A-5-33866 (JP, A) JP-A-53-147309 (JP, U) JP-A-61-140259 (JP, A) , U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02F 5/00 F16J 9/06 F16J 9/26

Claims (12)

(57) [Claims] 1. A side rail of a steel combined oil ring comprising a spacer expander and a pair of side rails, wherein a nitride layer is formed only on an outer peripheral surface and an inner peripheral surface of the side rail. A thickness of a nitride layer formed on an outer peripheral surface of the side rail is 30 to 100 μm, and a thickness of a nitride layer formed on an inner peripheral surface of the side rail is 5 to 20 μm. Combination oil ring side rail. 2. The side rail of the steel combined oil ring according to claim 1, wherein upper and lower surfaces of the side rail are base metal surfaces. 3. The side rail of a steel combined oil ring according to claim 1, wherein the material of the side rail is martensitic stainless steel containing 10% by weight or more of Cr. 4. A smooth chamfered portion is provided on at least a corner of a corner between an end surface of an abutment portion of the side rail and upper and lower surfaces, which is in contact with a wall surface of an oil ring groove of a piston. The side rail of the steel combined oil ring according to 2 or 3. 5. The side rail has an inner peripheral surface of 5 to 20 μm.
The side rail of a steel combined oil ring according to any one of claims 1, 2, 3, and 4, wherein the side rail is formed to have a surface roughness of m. 6. A step of manufacturing a coil by winding a side rail material into a coil, a step of ion-nitriding an outer peripheral surface and an inner peripheral surface of the coil at the same time, and an outer periphery of the coil before or after the ion nitriding step. Steel, comprising: a step of ion-nitriding a surface; a step of cutting a coil after the two ion-nitriding steps to obtain a side rail having an abutment; and a step of finishing the side rail. Method of manufacturing side rails for combined oil rings. 7. The step of simultaneously ion-nitriding an outer peripheral surface and an inner peripheral surface of the coil includes bringing surfaces adjacent to each other in the axial direction of the coil into close contact with each other and partially closing each opening at both ends of the coil. 7. The method for producing a side rail of a steel combined oil ring according to claim 6, wherein ion nitriding is performed in a state where the ring is formed. 8. The step of ion-nitriding the outer peripheral surface of the coil is characterized in that surfaces adjacent to each other in the axial direction of the coil are brought into close contact with each other, and each opening at both ends of the coil is closed. The method for producing a side rail of a steel combined oil ring according to claim 6, wherein 9. A step of manufacturing a coil by winding a side rail material into a coil, a step of cutting the coil to obtain a side rail having an abutment, and simultaneously forming an outer peripheral surface and an inner peripheral surface of the side rail. A combination oil ring made of steel, comprising: a step of ion nitriding; a step of ion nitriding the outer peripheral surface of the side rail before or after the ion nitriding step; and a step of finishing the side rail. Side rail manufacturing method. 10. The step of simultaneously ion-nitriding the outer peripheral surface and the inner peripheral surface of the side rail includes performing ion-nitriding while each opening at both ends of the stacked side rails is partially closed. The method for manufacturing a side rail of a steel combined oil ring according to claim 9, characterized in that: 11. The method according to claim 10, wherein an abutment of the side rail is closed. 12. The step of ion-nitriding the outer peripheral surface of the side rail includes closing each abutment of the plurality of stacked side rails and closing each opening at both ends of the stacked side rails. The method for manufacturing a side rail of a steel combined oil ring according to claim 9, wherein ion nitriding is performed.