Patent Grant
9784369
This is a U.S. national stage of application No. PCT/JP2015/059962, filed on Mar. 30, 2015. Priority under 35 U.S.C. §119(a) and 35 U.S.C. §365(b) is claimed from Japanese Patent Applications No. 2014-185940 filed on Sep. 12, 2014, the disclosure of which is also incorporated herein by reference.
The present invention relates to a combination oil ring installed in an oil ring groove of a piston.
In a piston ring groove provided in the outer periphery of a piston of an internal combustion engine, a piston ring is installed. A configuration of the piston ring in the ordinary gasoline internal combustion engine is composed of two compression rings (a top ring and a second ring) and a combination oil ring. The combination oil ring has an oil control function to suppress the consumption of an engine oil.
As a prior art literatures relating to such an oil ring, the followings are exemplified. PTL 1 discloses, in two discs (side rails) of the oil ring having running surfaces in an asymmetrical convex shape, an oil scraping ring whose vertex lines of the outer peripheral surfaces of the discs being directed in opposite directions toward the middle of the ring groove, and an oil scraping ring whose vertex lines of the outer peripheral surfaces of the discs being directed in the same direction toward the side surface in the opposite direction to the piston top of the ring groove. Further, it is also disclosed that the transverse section of the running surface of the disc is in an asymmetrical shape of a quadratic polynomial expressed by h(x)=ax+bx2 in a first section, and in an asymmetrical shape of a function of h(x)=cx2 in a third section, after a supporting vertex (II)h(x=0) configured as an edge.
Further, PTL 2 discloses a two-piece type combination oil ring having upper and lower rails and an expander. PTL 2 discloses that each of outer peripheral surfaces of the upper and lower rails is formed by an asymmetric barrel curve with a position closer to the lower part in the axial direction from the center of the width in the rail axial direction as a vertex, and the drop in the radial direction on the upper side of the asymmetric barrel curve is preferably 25 to 75 μm and the drop in the radial direction on the lower side of the asymmetric barrel curve is preferably 1 to 20 μm.
Further, NPL 1 discloses a configuration that the outer peripheral surface shape of the segment (side rail) is provided in a symmetrical convex shape in actual operation of a 2-liter 4-cycle gasoline engine. NPL 1 states an oil film thickness on a contour curve of the segment (side rail) when supplying to a test a 3-piece oil ring having a drop from the outer peripheral vertex of a measurement width of 0.15 mm in a slide direction of the segment (side rail) on the order of about 4 μm. It is studied and reported (
Further, in NPL 2, it is studied and reported (
In recent years, to realize reduction of fuel consumption of an engine, the internal combustion is increasingly reduced in tension of an oil ring for the purpose of reducing the friction and is required to have an abrasion resistant coating film with low friction formed at an outer peripheral surface of a segment (side rail). However, the reduction in tension of the oil ring causes a problem of the oil film becoming thicker and the oil consumption increasing, in particular, in a high-speed region where the engine becomes high revolution. Therefore, it is a problem to enable the reduction in oil consumption in the high-speed region even if the oil ring is low in tension.
The present invention has been made based on the above circumstance, and its object is to provide a combination oil ring capable of reducing an oil consumption in a high-speed region where the engine becomes high revolution even if an oil ring tension is low.
In order to solve the above problem, according to a first aspect of the present invention, there is provided a combination oil ring installed in an oil ring groove of a piston for an internal combustion engine and including: a pair of segments having outer peripheral surfaces sliding on an inner wall of a cylinder; and an expander spacer arranged between the pair of segments and pressing the outer peripheral surfaces of the pair of segments against the inner wall of the cylinder, wherein:
a shape of the outer peripheral surface in an arbitrary longitudinal section of the segment has, in a radial direction from both end faces forming a segment width toward the inner wall of the cylinder, curved shapes symmetric while forming a pair on an engine combustion chamber side and on a side distant from an engine combustion chamber of the segment width, and the shape of the outer peripheral surface on a side of an outer peripheral vertex in contact with the inner wall when inserted into the cylinder has an asymmetrical shape in the segment width direction across a portion of the outer peripheral vertex, which is a shape continuous to the curved shapes;
the asymmetrical shape takes a first intermediate line passing through a center of the segment width;
at an outer peripheral tip end part where a contour curve of the outer peripheral surface in the segment longitudinal section is traced, among two positions on the contour curve corresponding to a position at a distance of 3 μm from the outer peripheral vertex toward the inner peripheral side in the segment radial direction, a position on the engine combustion chamber side is a position a1 and a position on the side distant from the engine combustion chamber is a position b1;
when a length of a line segment between the position a1 and the position b1 is L and an intermediate line of the line segment of the length L is a second intermediate line, the second intermediate line is located on the side more distant from the engine combustion chamber than the first intermediate line, and the outer periphery vertex of the segment is located on the second intermediate line or on the side more distant from the engine combustion chamber than the second intermediate line; and
the pair of segments are installed in the oil ring groove so that the respective outer periphery vertexes are located on the side distant from the engine combustion chamber.
Further, in another aspect of the present invention, it is preferable in the above-described invention that: the contour curve of the outer peripheral surface in the segment longitudinal section is traced from the outer peripheral vertex of the segment to at least 0.025 mm toward the inner peripheral side in the segment radial direction so that a symmetrical shape taking both end sides in an axial direction as a pair exists on inner peripheral side positions in the segment radial direction;
when the contour curve of the asymmetrical shape at the segment outer peripheral tip end part is sectioned into a curved portion sandwiched between the outer peripheral vertex and a distance of 1.5 μm from the outer peripheral vertex toward the inner peripheral side in the segment radial direction and a contour portion sandwiched between the distance of 1.5 μm and a distance of 3.0 μm from the outer peripheral vertex toward the inner peripheral side in the segment radial direction, a first contour section, a second contour section, and a third contour section are set from the engine combustion chamber side of the cylinder;
the first contour section is provided at a part of a linear shape or a part of a quadratic curve shape starting from a first end portion on the engine combustion chamber side of the second contour section;
the second contour section has the outer peripheral vertex at a intermediate thereof and is provided in an arc shape;
the third contour section is provided to be a part of a quadratic curve shape starting from a second end portion on the side distant from the engine combustion chamber of the second contour section;
a surface roughness of the asymmetrical portion of the segment outer peripheral surface is 0.6 μmRp or less;
a length on the position a1 side and a length on the position b1 side of the line segment L divided by a line in the radial direction orthogonal to a line segment between the position a1 and the position b1 of the outer peripheral tip end part in the contour curve and passing through the outer peripheral vertex, are L1 and L2 respectively;
further, when at two positions on the contour curve at the distance of 1.5 μm toward the inner peripheral side in the segment radial direction, a position on the engine combustion chamber side is a position a2 and a position on the side distant from the engine combustion chamber is a position b2, and a length of a line segment between the position a2 and the position b2 is L3, conditions of 0.05 mm≦L≦0.15 mm, L1/L≧0.5, and L3/L≦0.74 are satisfied;
when an angle formed between a first straight line passing through the position a1 and through the position a2 and the axial direction of the cylinder is an angle θ1, a condition of 2 degrees ≦θ1≦7 degrees is satisfied; and
when an angle formed between a second straight line passing through the position b1 and through the position b2 and the axial direction of the cylinder is an angle θ2, a condition of 9 degrees ≦θ2 is satisfied.
Further, in another aspect of the present invention, it is preferable in the above-described invention that regarding the angle θ1, a condition of 3 degrees ≦θ1≦6 degrees is satisfied.
Further, in another aspect of the present invention, it is preferable in the above-described invention that: the contour curve of the outer peripheral surface in the segment longitudinal section is traced from the outer peripheral vertex of the segment to at least 0.025 mm toward the inner peripheral side in the segment radial direction so that a symmetrical shape taking both end sides in an axial direction as a pair exists on inner peripheral side positions in the segment radial direction;
when the contour curve of the asymmetrical shape at the segment outer peripheral tip end part is sectioned into a curved portion sandwiched between the outer peripheral vertex and a distance of 1.5 μm from the outer peripheral vertex toward the inner peripheral side in the segment radial direction and a contour portion sandwiched between the distance of 1.5 μm and a distance of 3.0 μm from the outer peripheral vertex toward the inner peripheral side in the segment radial direction, a first contour section, a second contour section, and a third contour section are set from the engine combustion chamber side of the cylinder;
the first contour section is provided at a part of a linear shape or a part of a quadratic curve shape starting from a first end portion on the engine combustion chamber side of the second contour section;
the second contour section has a flat part at a intermediate thereof, and is provided in a shape composed of a part of a linear shape or a part of a quadratic curve shape from an end portion on the engine combustion chamber side in the axial direction of the flat part and continuous to the first contour section, and composed of a part of a quadratic curve shape from an end portion on the side distant from the engine combustion chamber in the axial direction of the flat part and continuous to the third contour section;
the third contour section is provided to be a part of a quadratic curve shape continuous to the second end portion;
a surface roughness of the asymmetrical portion of the segment outer peripheral surface is 0.6 μmRp or less;
a length on the position a1 side and a length on the position b1 side of the line segment L divided by a line in the radial direction orthogonal to a line segment between the position a1 and the position b1 of the outer peripheral tip end part in the contour curve of the segment outer peripheral surface and passing through the outer peripheral vertex, are L1 and L2 respectively;
further, when at two positions on the contour curve at the distance of 1.5 μm toward the inner peripheral side in the segment radial direction, a position on the engine combustion chamber side is a position a2 and a position on the side distant from the engine combustion chamber is a position b2, a length of a line segment between the position a2 and the position b2 is L3, and a length in the axial direction of the flat part in the second contour section is L4, conditions of 0.05 mm≦L≦0.15 mm, L1/L≧0.5, L3/L≦0.76, and 0<L4≦0.05 mm are satisfied;
when an angle formed between a first straight line passing through the position a1 and through the position a2 and the axial direction of the cylinder is an angle θ1, a condition of 3 degrees ≦θ1≦6 degrees is satisfied; and
when an angle formed between a second straight line passing through the position b1 and through the position b2 and the axial direction of the cylinder is an angle θ2, a condition of 9 degrees ≦θ2 is satisfied.
Further, in another aspect of the present invention, it is preferable in the above-described invention that: the outer peripheral surface of the segment has one of coating films:
(1) a coating film by an ion plating method, composed of a nitride of one kind or two kinds selected from among chromium and titanium;
(2) a coating film by an ion plating method, composed of a nitride of one kind or two kinds selected from among chromium and titanium, and containing aluminum;
(3) the coating film by the ion plating method of (1) further solid-dissolving at least one element selected from among oxygen, carbon and boron;
(4) a coating film by an ion plating method in which metal chromium solid-dissolving nitrogen and Cr2N mixedly exist;
(5) a DLC (amorphous carbon) coating film by an ion plating method using only carbon;
(6) a DLC (amorphous carbon) coating film by an ion plating method containing one kind or two or more kinds of elements among silicon, oxygen, hydrogen, tungsten, and titanium in addition to carbon; and
(7) a coating film constituted by covering any of the DLC coating film of the (5) and the DLC coating film of the (6) on any of the coating films of the (1), the (2), the (3), and the (4):
a surface hardness of each of the coating films from the coating film of the (1) to the (7) is HV 1000 or more: and
a thickness of each of the coating films of the coating film of (1) to the (6) is 3 μm or more, and a thickness of a plurality of layers of the (7) is 3 μm or more.
In a combination oil ring according to the present invention, it becomes possible to reduce the oil consumption in a high-speed region where the engine becomes high revolution even if the oil ring tension is low.
Hereinafter, a combination oil ring 10 according to one embodiment of the present invention will be described based on the drawings.
<1. Regarding the Configuration of the Combination Oil Ring 10>
In
As illustrated in
Hereinafter, a portion of the expander spacer 13 located on the engine combustion chamber side than a center line M in the axial direction of the cylinder 1 is regarded as an upper projecting part 14, and a portion thereof located on the side more distant from the engine combustion chamber than the center line M is regarded as a lower projecting part 15. The upper projecting part 14 and the lower projecting part 15 are repeatedly and periodically consecutive in the circumferential direction of the expander spacer 13, whereby the expander spacer 13 is formed to have many wave-form portions.
The upper projecting part 14 and the lower projecting part 15 are formed into a wave form by performing plastic forming on the expander spacer 13. In addition, the upper projecting part 14 has an upper piece part 14a, an ear part 14b, and an outer peripheral support part 14c. The upper piece part 14a is a portion facing the segment 11 and substantially horizontally provided, but, not limited to this, may be provided with, for example, a recessed groove in a direction from a middle position in the circumferential direction of the outer peripheral support part 14c toward a middle position in the circumferential direction of the ear part 14b.
Further, the ear part 14b is located on the inner peripheral side than the upper piece part 14a, and additionally provided to project further to the engine combustion chamber side (in a direction distant from the center line M) than the upper piece part 14a. On the outer peripheral side of the ear part 14b, an inclined surface 14b1 inclined with respect to the axial direction of the cylinder 1 is provided, and the inclined surface 14b1 is inclined toward the outer peripheral side as it goes to the center line M. Against the inclined surface 14b1, a region on the inner peripheral side of the segment 11 comes into abutment. Besides, not limited to this, the inclined surface 14b1 does not have to be inclined toward the outer peripheral side as it goes to the center line M, also in which case the region on the inner peripheral side of the segment 11 comes into abutment against it. In a state that the piston 2 with the combination oil ring 10 installed therein is inserted into the cylinder 1, the segment 11 is pressed toward the inner wall side of the cylinder 1 (the outer peripheral side). Note that at a boundary portion between the ear part 14b and the upper piece part 14a, a communication hole 14d through which the engine oil can flow is provided, but a configuration without the communication hole 14d may be employed.
Further, the outer peripheral support part 14c is located on the outer peripheral side than the upper piece part 14a. The outer peripheral support part 14c is provided to project further to the engine combustion chamber side (in the direction distant from the center line M) than the upper piece part 14a. In addition, the outer peripheral support part 14c is a portion that supports, on its upper surface side, the segment 11. Therefore, the outer peripheral support part 14c projects less than the ear part 14b, and its upper surface is also substantially horizontally provided.
Further, the lower projecting part 15 is provided in a symmetrical shape across the center line M to the upper projecting part 14, and is provided adjacent to the upper projecting part 14. Therefore, the lower projecting part 15 also has a lower piece part 15a in a symmetrical shape to the upper piece part 14a, an ear part 15b in a symmetrical shape to the ear part 14b, and an outer peripheral support part 15c in a symmetrical shape to the outer peripheral support part 14c. Further, the ear part 15b is provided with an inclined surface 15b1 against which a region on the inner peripheral side of the segment 12 comes into abutment, and the inclined surface 15b1 is inclined toward the outer peripheral side as it goes to the center line M. Against the inclined surface 15b1, the region on the inner peripheral side of the segment 12 comes into abutment. Besides, not limited to this, the inclined surface 15b1 does not have to be inclined toward the outer peripheral side as it goes to the center line M, also in which case, in a state that the piston 2 with the combination oil ring 10 against which the region on the inner peripheral side of the segment 12 comes into abutment installed therein is inserted into the cylinder 1, the segment 12 is pressed toward the inner wall side of the cylinder 1 (the outer peripheral side). Further, at a boundary portion between the ear part 15b and the upper piece part 15a, a communication hole 15d through which the engine oil can flow is provided, but a configuration without the communication hole 15d may be employed.
Note that the outer peripheral support part 15c supports, on its lower surface side (a surface on a crankshaft side), the segment 12. Therefore, the segment 11 and the segment 12 are held in a state of being separated in the axial direction of the cylinder 1. Further, the segment 11 and the segment 12 are pressed by the inclined surfaces 14b1, 15b1 respectively, whereby the tip end parts SA on the outer peripheral surfaces S of the segments 11, 12 press the inner peripheral surface of the cylinder 1. This makes it possible to form an oil film so that the engine oil existing on the inner wall of the cylinder 1 becomes an appropriate thickness.
<2. Regarding the Shape of the Outer Peripheral Surface S of the Segment 11, 12>
Subsequently, the shape of the outer peripheral surface S of the segment 11, 12 will be described.
As illustrated in
In this embodiment, the outer peripheral surface S of the segment 11, 12 has the symmetrical region R1on the engine combustion chamber side, the asymmetrical region R2, and the symmetrical region R1 on the side distant from the engine combustion chamber.
Further, the asymmetrical region R2 is located between the two symmetrical regions R1. A contour curve of the asymmetrical region R2 is an asymmetrical shape with respect to a center axis of a line symmetry of the contour curve found from the two symmetrical regions R1. The center axis of this line symmetry is referred to as a first intermediate line W1.
Here, in the above-described
Further, in
Here, as illustrated in
Note that a display for identifying the direction on the engine combustion chamber side is applied on the segment 11, 12 having a predetermined asymmetrical shape. Further, each of the pair of segments 11, 12 is installed in the oil ring groove 4 such that its vertex part SP is located on the side distant from the engine combustion chamber.
<3. A First Shape of the Tip End Part SA of the Outer Peripheral Surface S of the Segment 11, 12>
Subsequently, the first shape of the tip end part SA of the outer peripheral surface S of the segment 11, 12 will be described.
Further, in this Description, the tip end part SA of the outer peripheral surface S of the segment 11, 12 refers to the asymmetrical region R2 in the axial direction (the Y-direction) of the cylinder 1 in a range in which the contour curve from the outer peripheral vertex of the segment 11, 12 to at least 0.025 mm toward the radial direction (the X-direction) of the segment 11, 12 is traced in the contour curve when measuring the outer peripheral surface S of the segment 11, 12.
The segment 11, 12 in this embodiment is provided not in a symmetrical shape but in an asymmetrical shape, across the vertex part SP, in the axial direction (the Y-direction) of the cylinder 1 of the tip end part SA, at the tip end part SA of the outer peripheral surface S. Specifically, a continuous contour curve of the cross-section at the tip end part SA of the outer peripheral surface S existing in a region from the vertex part SP of the tip end part SA to a distance of 3 μm toward the inner peripheral side in the radial direction (the X-direction) is sectioned into three sections such as a first contour section S1, a second contour section S2, and a third contour section S3 from the engine combustion chamber side.
(1) First Aspect of the First Contour Section S1, the Second Contour Section S2, and the Third Contour Section S3
The first contour section S1 is provided, as illustrated in
Further, at a intermediate portion in the second contour section S2 , the vertex part SP exists. The end portion on the engine combustion chamber side of the second contour section S2 continues to the above-described first contour section S1. Further, an end portion on the side distant from the engine combustion chamber of the second contour section S2 continues to the third contour section S3. The second contour section S2 is provided in an arc shape. As the arc shape, for example, a curved shape approximating the quadratic curve can be exemplified. Further, the third contour section S3 exists on the side more distant from the engine combustion chamber than the vertex part SP. The third contour section S3 is provided to become a part of the quadratic curve starting from the end portion on the side distant from the engine combustion chamber of the contour section S2.
The surface roughness of the first contour section S1, the second contour section S2, and the third contour section S3 is 0.6 μmRp or less. Note that Rp is a kind of the parameter of roughness, and is the maximum peak height in ISO4287 (JIS B0601: '01).
Further, in the contour curve formed of the first contour section S1, the second contour section S2, and the third contour section S3 of the outer peripheral tip end part of the segment longitudinal section, two positions on the contour curve corresponding to a position at a distance of 3 μm from the outer peripheral vertex toward the inner peripheral side in the segment radial direction are a1, b1, and two positions on the contour curve corresponding to a position at a distance of 1.5 μm from the outer peripheral vertex toward the inner peripheral side in the segment radial direction are a2, b2.
Further, the distance between the position a1 and the position b1 (the length of the line segment W4) is L. Note that the line W2 passing through the vertex part SP is orthogonal to the line segment W4. Further, in the length L, a length on the position a1 side from the line W2 is L1, and a length on the position b1 side from the line W2 is L2. Furthermore, the distance in the axial direction (the Y-direction) of the cylinder 1 between the position a2 and the position b2 is L3. Then, the relationship of the following expression is satisfied.
0.05 mm≦L≦0.15 mm [Expression 1]
L1/L≧0.5 [Expression 2]
L3/L≦0.74 [Expression 3]
Further, the straight line passing through the position a1 and the position a2 is a straight line N1. An angle formed between the straight line N1 and the line W3 passing through the vertex part SP and along the axial direction (the Y-direction) of the cylinder 1 (namely, orthogonal to the radial direction (the X-direction)) is an angle θ1 (an upper angle θ1). Further, a straight line passing through the position b1 and the position b2 is a straight line N2. An angle formed between the straight line N2 and the line W3 is an angle θ2 (a lower angle θ2). Then, the angle θ1 and the angle θ2 satisfy the relationship of the following expression.
2 degrees ≦θ1≦7 degrees [Expression 4]
9 degrees≦θ2 [Expression 5]
Note that the predetermined shapes of the first contour section S1 and the second contour section S2 of the outer peripheral surface S may be formed by machining or formed in shapes similar to a segment wire rod being the base material of the segment 11, 12. On the other hand, the third contour section S3 is formed in a shape similar to the base material of the segment 11, 12.
(2) Second Aspect of the First Contour Section S1, the Second Contour Section S2, and the Third Contour Section S3
Next, the second aspect of the first contour section S1, the second contour section S2, and the third contour section S3 will be described. In this second aspect, the above-describe angle θ1 satisfies the relationship of the following expression.
3 degrees ≦θ1≦6 degrees [Expression 6]
Note that the contour curve of the outer peripheral surface S when the segment 11 as illustrated in
<4. Regarding a Second Shape of the Tip End Part SA of the Outer Peripheral Surface S of the Segment 11, 12>
Next, the second shape of tip end part SA of the outer peripheral surface S of the segment 11, 12 different from that in
At the tip end part SA of the outer peripheral surface S of the segment 11, 12 illustrated in
L3/L≦0.76 [Expression 7]
Further, in the outer peripheral surface S illustrated in
0<L4≦0.05 mm [Expression 8]
Note that also in the outer peripheral surface S as illustrated in
Here,
<5. Regarding a Forming Method of the Outer Peripheral Surface S of the Segment 11, 12>
Subsequently, the forming method of the outer peripheral surface S of the segment 11, 12 will be described. The outer peripheral surface S is formed into a predetermined shape by using, for example, a belt grinding apparatus and elastically pressing a rotating belt with abrasive particles of the belt grinding apparatus against the outer peripheral surface of one horizontally fixed segment using an elastic body. This shape may be formed in a state of the segment wire rod being the base material of the segment 11, 12. Further, the shape may be formed after molding into an annular shape, and may be formed by any of the methods.
<6. Regarding a Film-Forming Method of the Hard Coating Film 11a, 12a on the Outer Peripheral Surface S of the Segment 11, 12>
Next, the method of forming the hard coating film 11a, 12a on the outer peripheral surface S of the segment 11, 12 will be described. Note that as the hard coating film 11a, 12a, the one formed by any one of the following methods is selected.
(6-1) A Film-Forming Method of a Nitride Coating Film (PVD Coating Film)
First, the method of forming the nitride coating film being the hard coating film 11a, 12a on the outer peripheral surface S of the segment 11, 12 will be described. Examples of the film-forming method include a method of forming a film using an arc ion plating apparatus for performing an arc ion plating method being one kind of a physical vapor deposition (PVD) method. When forming the nitride coating film by the arc ion plating method, a metal target of Cr according to the composition of the hard coating film to be formed is used and the base material for the segment 11, 12 is set in the arc ion plating apparatus. Thereafter, the inside of the arc ion plating apparatus is reduced in pressure by evacuation and the base material is heated.
Thereafter, a bias voltage is applied to the base material to perform ion bombardment using the metal target. The bias voltage to be applied can be, for example, −500 to −1000 V. Next, another bias voltage is applied, and a process gas is introduced into the arc ion plating apparatus to form the hard coating film 11a, 12a with a predetermined thickness on an outer peripheral slide surface of the segment 11, 12. The another bias voltage can be, for example, 0 to −200 V. As the process gas, only a N2 gas was used. Besides, as the process gas, an O2 gas, a CH4 gas or the like may be used. As the metal target, other than the above Cr, Ti may be used or Ti and Al may be used in combination.
(6-2) A Film-Forming Method of a Nitride Coating Film (PVD Coating Film) (a Partially Different Film-Forming Method)
In the film-formation of the nitride coating film (PVD coating film) in the above-described (6-1), a coating film using a nitride of one kind or two kinds selected from among Cr, Ti and containing Al as the metal target may be formed. In this case, the film-formation can be performed using a material made by mixing Cr and Al as the metal target, and using a mixed gas made by mixing a N2 gas and a CH4 gas, a N2 gas and an O2 gas, a N2 gas and an Ar gas or the like as the process gas.
(6-3) A Film-Forming Method of a Nitride Coating Film (PVD Coating Film) (a Partially Different Film-Forming Method)
Further, a coating film composed of a nitride of one kind or two kinds selected from among Cr, Ti solid-dissolving at least one element selected from among O, C may be formed. In this case, a material made by mixing a N2 gas and an O2 gas or a N2 gas and a CH4 gas may be used as the process gas. Further, a coating film composed of a nitride of one kind or two kinds selected from among Cr, Ti solid-dissolving a B element may be formed. In this case, a material made by mixing Cr and B may be used as the metal target.
(6-4) A Film-Forming Method of a Nitride Coating Film (PVD Coating Film) (a Partially Different Film-Forming Method)
Further, a coating film in which metal chromium solid-dissolving nitrogen and Cr2N mixedly exist may be formed. In this case, a mixed gas made by mixing a N2 gas and an Ar gas may be used as the process gas.
(6-5) A Film-Forming Method of an Amorphous Carbon Coating Film (DLC Coating Film)
Next, a method of film-forming an amorphous carbon coating film (DLC (diamond like carbon) coating film) as the hard coating film 11a, 12a on the outer peripheral surface S of the segment 11, 12 will be described. The method of forming the DLC coating film can use the arc ion plating apparatus for performing the arc ion plating method. In the arc ion plating apparatus, the base material of the segment 11, 12 is set. Thereafter, the inside of the arc ion plating apparatus is reduced in pressure by evacuation and the base material is heated. Thereafter, a bias voltage is applied to the segment base material to perform ion bombardment using argon ions. The bias voltage to be applied can be, for example, −50 to −300 V.
Then, after a predetermined bias voltage is applied, a Ti coating film is formed as an adhesive layer. The predetermined bias voltage can be, for example, −50 to −300 V. Then, a DLC coating film (an a-C layer) composed of an amorphous carbon structure is formed on the Ti coating film by sputtering using argon ions. In this event, the bias voltage is set to, for example, −50 to −300 V. Furthermore, a DLC coating film (a ta-C layer) composed of a tetrahedral carbon structure is formed on the a-C layer by filtered arc ion plating. In this event, the bias voltage is set to, for example, −100 to −300 V. These two layers are alternately and repeatedly stacked to form the hard coating film 11a, 12a with a predetermined thickness on an outer peripheral slide surface of the segment base material.
(6-6) A Film-Forming Method of an Amorphous Carbon Coating Film (DLC Coating Film) (a Partially Different Film-Forming Method)
In the film-formation of the DLC coating film in the above-described (6-5), a DLC coating film containing one kind or two or more kinds of elements such as Si, O, H, W, Ti in addition to carbon may be formed. Further, as the film-forming method of the DLC coating film, a chemical vapor deposition (CVD) method may be used.
(6-7) Regarding a Composite Coating Film
Further, on the outer periphery of one of the nitride coating films of the above-described (6-1) to (6-4), the DLC coating film of one of the DLC coating film of (6-5) and the coating film of (6-6) may be formed to form the hard coating film 11a, 12a.
<7. Regarding a Method of an Oil Consumption Measurement Test>
Subsequently, the oil consumption measurement test performed using the combination oil ring 10 in this embodiment will be described. In the oil consumption measurement test, an engine having a 2 L class displacement and a 80 mm class bore diameter was used. After break-in of the engine, an engine oil of 5W-20 (viscosity classification SAE J300) was used with a cooling water temperature set to 100° C. and an engine oil temperature set to 125° C., under a load condition WOT (wide open throttle; full load).
Then, the oil consumption was evaluated under the condition that a mean piston speed of the engine was in a high-speed region at two levels of 20.2 m/s and 18.9 m/s. The mean piston speed is a mean speed of the piston 2 found from the engine revolution speed and the stroke of the engine. As the oil consumption measurement, the oil consumption per hour was measured by a continuous gravimetric method. Note that the operating time after the break-in until the end of the oil consumption measurement test was about 70 hours.
As a top ring of piston rings used in the test, the one having a width (the dimension in the axial direction of the cylinder 1) of 1.2 mm and having a hard coating film by the PVD method applied on its outer peripheral surface was used. Further, as a second ring, the one having a width (the dimension in the axial direction of the cylinder 1) of 1.2 mm and having a hard Cr plating applied on its outer peripheral surface was used. As the combination oil ring 10, the one having a combination width h0 of 2.0 mm and a segment width h1 of the segment 11, 12 of 0.4 mm was used. Further, the oil ling tension was set to 0.24 (N/mm) in bore diameter ratio, which is equal to or less than 0.3 (N/mm) that is called a low tension.
As the base material of the segment 11, 12, the one using a material corresponding to JIS SUS440B and having a CrN coating film (a film thickness of 20 μm, a Vickers hardness HV of 1100) being a hard coating film by the arc ion plating method applied on the outer peripheral surface of the segment 11, 12 was used. Regarding the shape of the outer peripheral surface S of the segment 11, 12, the outer peripheral surface S was variously formed into asymmetrical convex shapes based on the shape having a measured width of 0.15 mm and having a drop (a distance in the radial direction) from the vertex part SP of the outer peripheral surface S of 0.008 to 0.015 mm that is a conventionally employed symmetrical convex shape, and supplied for the test.
The side clearance SC between the combination oil ring 10 and the oil ring groove 4 of the piston 2 is generally in a range of 0.07 mm to 0.15 mm, but the side clearance SC was set to 0.11 mm in this test.
Note that regarding measurement of the above Vickers hardness, after a measurement sample was polished into a mirror surface, and then the Vickers hardness was measured by a micro Vickers hardness tester under conditions of a test force of 0.9807 N and a test force retention time of 15 s in conformity to “Vickers hardness test-test method” of JIS Z 2244 (this also applies to the other Vickers hardness).
Further, regarding the measurement of the above second misalignment amount P2, when the contour curve from the vertex part SP of the outer peripheral surface S of the segment 11, 12 to at least a distance of 0.025 mm toward the inner peripheral side in the radial direction (the X-direction) is measured, the magnification in the radial direction (the X-direction) of the segment 11, 12 is 2000 times, and the magnification in the axial direction (the Y-direction) of the cylinder 1 is 200 times. Further, the measurement position is set at three positions of 90 degrees, 180 degrees, and 270 degrees in the circumferential direction from the gap of the segment 11, 12, and as the measured value in Table 1, the average value at the three positions is used.
Further, for the measurement of the outer peripheral shape (contour curve) of the outer peripheral surface S of the segment 11, 12, a stylus-type surface roughness measuring instrument (Surf Coder SE-30C) manufactured by Kosaka Laboratory Ltd. was used, and as a detector, PU-DJ2S (a radius of a tip spherical surface of 2 μm, a tapered angle of a cone of 60 degrees) was used. Further, the feeding speed of the lateral magnification was 0.1 mm/s when the magnification in the axial direction (the Y-direction) of the cylinder 1 was 200 times, and the feeding speed of the lateral magnification was 0.05 mm/s when the magnification in the axial direction (the Y-direction) of the cylinder 1 was 1000 times, but the speed may be lower than them.
The result when the oil consumption measurement was performed under such conditions was listed in Table 1. In Table 1, the length L of the line segment W4 between the position a1 and the position b1 (L=L1+L2), L1/L relating to [Expression 2], L3/L relating to [Expression 3], the length L4 of the flat part SF, and the second misalignment amount P2 are also listed in addition to the type of the shape of the outer peripheral surface S (outer peripheral shape), the upper angle θ1, and the lower angle θ2.
Note that in Table 1, Examples 1 to 7 indicate the case of using the segments 11, 12 of the outer peripheral surfaces S in the first shape as illustrated in
Further, regarding Comparative Example 2, the angle θ1 being the upper angle does not satisfy [Expression 4], the angle θ2 being the lower angle does not satisfy [Expression 5], the length L of the line segment W4 does not satisfy [Expression 1], and the L3/L being the ratio of the length L3 between the position a1 and the position b1 with respect to the length L does not satisfy [Expression 3].
Note that regarding the oil consumption ratio in Table 1, the oil consumption in the case of using the segments in the conventional shape in a symmetrical shape in which the angle θ1 being the upper angle is 7.5 degrees and the angle θ2 being the lower angle is 7.5 degrees as indicated in Comparative Example 1 (conventional shape) and the mean piston speed when using the segment of 20.2 m/s, is regarded as 100, other oil consumptions are indicated in ratio.
<8. Review of the Result of the Shape of the Outer Peripheral Surface S and the Oil Consumption Measurement Test>
Among the above, the angle θ1 in the case of 2 degrees or more and 7 degrees or less as expressed in [Expression 4], is considered to be an angle at which the engine oil forming the oil film on the inner wall surface is easy to flow in from the engine combustion chamber side of the outer peripheral surface S of the segment 11, 12 in an oil ring rising process, and to be able to suppress the action of the segment 11, 12 scraping up the engine oil on the inner wall surface of the cylinder 1. Therefore, there appears an effect in reduction of the oil consumption in a high-speed region that is said that the oil film becomes thicker. Here, the engine oil scraping action by the segment 11, 12 is said to promote disappearance of the engine oil by its combustion during engine combustion and the discharge of the engine oil in an engine exhaust process, whereby the oil consumption increases.
In contrast, when the angle θ1 being the upper angle of the segment 11, 12 becomes less than 2 degrees, the engine oil forming the oil film on the inner wall surface of the cylinder 1 becomes difficult to flow in from the engine combustion chamber side of the outer peripheral surface S of the segment 11, 12 when the combination oil ring 10 rises up. For this reason, the engine oil is considered to stay in the gap formed between the inner wall surface of the cylinder 1 and the outer peripheral surface S of the segment 11, 12 on the engine combustion chamber side and the engine oil is conveyed to the raised end of the of the segment 11, 12, so that the reduction of the oil consumption cannot be expected.
On the other hand, when the angle θ1 being the upper angle of the segment 11, 12 is more than 7 degrees, the action of the segment 11, 12 of scraping up the engine oil on the inner wall surface of the cylinder 1 increases to increase the oil consumption.
Further, setting the angle θ2 being the lower angle of the segment 11, 12 to 9 degrees or more as expressed in [Expression 5] is preferable in forming the outer peripheral shape of the segment 11, 12 forming the angle θ1 being the upper angle to 2 degrees or more and 7 degrees or less as expressed in [Expression 4] into an asymmetrical shape.
Here, the angle θ2 being the lower angle of the segment 11, 12 in the case of less than 9 degrees, corresponds to the lower angle θ2 when the contour curve of the conventional segment is symmetric as in Comparative Example 1 in the above Table 1. As in found from Table 1, the lower angle θ2 in the case of less than 9 degrees is not preferable because the reduction of the oil consumption in a high-speed region of the engine cannot be expected.
Further, the surface roughness in the asymmetrical region R2 in the axial direction (the Y-direction) of the cylinder 1 in the case of 0.6 μmRp or less on the outer peripheral surface S of the segment 11, 12, is preferable in reducing the friction between the outer peripheral surface S of the segment 11, 12 and the inner wall surface of the cylinder 1. However, the surface roughness in the asymmetrical portion in the case of more than 0.6 μmRp, is not preferable because it becomes more likely to induce generation of scuff in the inner wall surface of the cylinder 1 and abrasion of the cylinder 1.
Further, as in the result of Table 1, when the angle θ1 satisfies the above-described [Expression 6], the oil consumption ratio is further reduced, resulting in a preferable state.
Further, in the case where the segment 11, 12 is the outer peripheral surface S in the second shape as illustrated in
<9. Effect and Operation>
According to the combination oil ring 10 in the above configuration, L is set to be 0.05 mm≦L≦0.15 mm as a range that is the prerequisite at the tip end part SA of the outer peripheral surface S in this embodiment, and additionally the asymmetrical region R2 exists in a range from the vertex part SP of the segment 11, 12 to at least 0.025 mm toward the inner peripheral side in the radial direction (the X-direction). In addition, under the condition that the surface roughness of the asymmetrical portion is 0.6 μmRp or less, when [Expression 1] of 0.05 mm≦L 0.15 mm, [Expression 2] of L1/L≧0.5, [Expression 3] of L3/L≦0.74, [Expression 4] of 2 degrees ≦θ1≦7 degrees, and [Expression 5] of 9 degrees ≦θ2 (in the case of the configuration as illustrated in
This appearance is illustrated in
Note that
Further,
Here, in
Incidentally, at the present circumstances, to reduce the fuel consumption of the engine, reduction in tension of the oil ring is under progression for the purpose of reducing the friction. By the reduction in tension, the oil film thickness increases particularly in the high-speed region where the engine becomes high revolution, along with which the oil consumption increases particularly in the high-speed region. However, as is clear from Table 1 and
Note that in the conventional segment, the shape of the outer peripheral surface S is grasped in a range in which the dimension in the radial direction is larger such that it is 15 μm toward the center of the radial direction. For example, FIG. 1, FIG. 2 in PTL 1 also illustrates the locus of the outer peripheral surface seemed to be measured in such a range. However, in this embodiment, the tip end part SA of the outer peripheral surface S in the shape finely defined in a narrower range such as 3 μm from the vertex part SP is provided as is clear from
Further, as is clear from the disclosure of NPL 1, it is indicated that the oil film thickness when the oil ring is supplied to the test ranges from about 1 μm to 6 μm in four cycles on the thrust side under a full-load operation condition of 2000 rpm by the LIF (Laser-Induced-Fluorescence) method. In addition, the fact that the oil film thickness increases with an increase in the number of revolutions of the engine is described. Thus, in the high revolution region (the high-speed region) of the engine, when the fine shape of the outer peripheral surface S is defined in the range of 3 μm from the vertex part SP as in the segment 11, 12 in this embodiment, the improvement in performance of the oil consumption is considered to be greatly affected. Conversely, even if the shape of the outer peripheral surface S in a region of 10 μm or 15 μm toward the inner peripheral wall in the radial direction from the vertex part SP being a range exceeding the oil film thickness is finely defined, it cannot be expected to improve performance of the oil consumption, as compared with the case of defining the fine shape of the outer peripheral surface S in the range of 3 μm from the vertex part SP.
However, though there is mention about the oil film thickness in NPL 1 as described above, an effective outer peripheral surface S created by actually variously studying that what kind of shape of the outer peripheral surface S is actually effective to reduce the oil consumption in a range close to the oil film thickness, is not found at filing.
In contrast, in this embodiment, the contour shape of the outer peripheral surface S is finely defined in the range of 3 μm from the vertex part SP for the outer peripheral surface S, and the reduction of the oil consumption in the high-speed region is further actually verified. In this regard, this embodiment can be said to have an inventive step even if compared with any documents.
Further, in this embodiment, the angle θ1 of the outer peripheral surface S in the first shape as illustrated in
Further, in this embodiment, the flat part SF as illustrated in
Further, in this embodiment, the hard coating films 11a, 12a are formed on the outer peripheral surfaces S of the segments 11, 12, and the hard coating films 11a, 12a are one of the followings.
Further, regarding the above-described hard coating films 11a, 12a, the surface hardness of each of (6-1) to (6-7) is HV 1000 or more, and the thickness of each of the coating films of (6-1) to (6-6) is 3 μm, and the thickness of a plurality of layers of (6-7) is 3 μm or more.
When the hard coating films 11a, 12a are provided, it becomes possible to improve the abrasion resistance.
<10. Modified Example>
The embodiments of the present invention have been described above, but the present invention is variously modified in addition to them. Hereinafter, they will be described.
In the above embodiments, regarding the shape of the outer peripheral surface S, the contours of the first contour section S1 to the third contour section S3 have the curved shapes. However, linear portions may partially exist in the curved shapes.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-185940 | Sep 2014 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2015/059962 | 3/30/2015 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2016/038916 | 3/17/2016 | WO | A |
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