Combined oil control ring

Abstract

To provide a combined oil control ring comprising a pair of upper and lower side rails and an axially corrugated spacer expander having upper and lower portions for automobile engines, which is capable of keeping an excellent oil-controlling function without sticking between a spacer expander and side rails even in a long period of engine operation, the upper and lower portions of the spacer expander have tabs pushing inner peripheral surfaces of the side rails, projections supporting the side rails, and intermediate portions between the tabs and the projections; each intermediate portion opposing the side rail has at least one groove extending in a substantially circumferential direction is recessed when viewed along a radial direction.

Claims

1. A combined oil control ring comprising: a pair of side rails, the pair of side rails including an upper side rail and a lower side rail; and an axially corrugated spacer expander having upper and lower portions; said upper and lower portions of said spacer expander comprising tabs pushing inner peripheral surfaces of said side rails, projections supporting said side rails, intermediate portions between said tabs and said projections, and two circumferential ends; each of said intermediate portions opposing one of said side rails and having at least one groove with a curved or angled bottom; and each groove primarily extending in a substantially circumferential direction and being recessed when viewed along a circumferential direction such that each groove connects the respective circumferential ends, and an oil on the intermediate portion can mainly flow in the substantially circumferential direction and downwardly from the respective circumferential ends of the groove.

2. The combined oil control ring according to claim 1, wherein a depth, d, of each groove is 0.5-20% of a combined width, h1, and the combined width, h1, is a distance from an upper surface of the upper side rail to a lower surface of the lower side rail.

3. A combined oil control ring comprising: a pair of side rails, the pair of side rails including an upper side rail and a lower side rail; and an axially corrugated spacer expander having upper and lower portions; said upper and lower portions of said spacer expander comprising tabs pushing inner peripheral surfaces of said side rails, projections supporting said side rails, intermediate portions between said tabs and said projections, and two circumferential ends; each of said intermediate portions opposing one of said side rails and having at least one groove with an angled bottom; each groove primarily extending in a substantially circumferential direction and being recessed when viewed along a circumferential direction such that each groove connects the respective circumferential ends, and wherein each groove has a raised bottom when viewed along a substantially radial direction such that it has a reversed V-shape.

4. The combined oil control ring according to claim 3, wherein a depth, d, of said groove having the raised bottom at a top of the raised bottom is 0.5-20% of a combined width, h1, and the combined width, h1, is a distance from an upper surface of the upper side rail to a lower surface of the lower side rail.

5. The combined oil control ring according to claim 1, wherein each groove is constituted by pluralities of planar portions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1(a) is a perspective view partially showing an example of spacer expanders constituting the oil ring of the present invention.

(2) FIG. 1(b) is a cross-sectional view showing the oil ring of the present invention, in which the spacer expander of FIG. 1(a) is combined with side rails.

(3) FIG. 2 is a perspective view partially showing another example of spacer expanders constituting the oil ring of the present invention.

(4) FIG. 3(a) is a perspective view partially showing a further example of spacer expanders constituting the oil ring of the present invention.

(5) FIG. 3(b) is a cross-sectional view showing the oil ring of the present invention, in which the spacer expander of FIG. 3(a) is combined with side rails.

(6) FIG. 4(a) is a perspective view partially showing a conventional spacer expander.

(7) FIG. 4(b) is a cross-sectional view showing a conventional oil ring.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) The examples of the oil ring of the present invention will be explained below referring to the drawings.

(9) FIGS. 1(a) and 1(b) show an example of spacer expanders constituting the oil ring of the present invention. Like a conventional spacer expander, the spacer expander 11 comprises upper and lower portions each having a tab 12a, 12b, a projection 13a, 13b and an intermediate portions 14a, 14b. Each intermediate portion opposing a side rail has a substantially circumferentially extending groove, which is arcuately recessed when viewed in a radial direction. In this structure, the grooves have curved surfaces. This shape provides large spaces 15a, 15b between the intermediate portions of the spacer expander and the side rails. The depth d of each groove, an index indicating the size of the space, is preferably 0.5-20% of the combined nominal width h1. Specifically, the depth d is preferably 0.05 mm or more, and its upper limit is preferably not more than 0.5 mm.

(10) FIG. 2 shows a spacer expander 21 having pluralities of grooves in its intermediate portion in another embodiment.

(11) FIGS. 3(a) and 3(b) show a further example of spacer expanders 31, which comprises intermediate portions 34a, 34b having grooves defined by pluralities of planar portions. Each groove bottom is raised in a reverse V shape when viewed along a substantially radial direction, and recessed in a V shape when viewed along a circumferential direction. The basically V-shaped recess when viewed along a circumferential direction provides a large space 35a, 35b between each intermediate portion of the spacer expander and the side rail, and the raised bottom when viewed along a substantially radial direction makes it easy to flow oil from the intermediate portion to both circumferential sides. The depth d of each groove at a top of the raised bottom is preferably 0.5-20% of the combined width h1. Specifically, the depth d is preferably 0.05 mm or more, and its upper limit is preferably not more than 0.5 mm.

(12) The above spacer expander can be formed by plastically working a wire.

Example 1

(13) A SUS440 wire of 0.35 mm1.72 mm was formed into side rails, and a SUS304 wire of 0.25 mm1.9 mm was formed into a spacer expander, to produce a combined oil ring having a nominal diameter d1 of 71 mm, a nominal combined width h1 of 2.0 mm, and a combined thickness a1 of 2.3 mm. The spacer expander had a pitch of 2.7 mm from an upper portion (lower portion) to an upper portion (lower portion), and each groove in the intermediate portion had a curved surface shape with a depth d of 0.1 mm as shown in FIGS. 1(a) and 1(b). There were spaces 15a, 15b of 0.2 mm between the deepest points of grooves in the intermediate portions of the spacer expander and the side rails.

Example 2

(14) As shown in FIGS. 3(a) and 3(b), a combined oil ring was produced in the same manner as in Example 1, except for changing each groove in the intermediate portion of the spacer expander to a groove constituted by four planar portions such that it was raised in a reverse V shape when viewed along a radial direction. The depth d of each groove at a top of the raised bottom was 0.1 mm. Spaces 15a, 15b between the deepest points of the intermediate portions of the spacer expander and the side rails were as wide as 0.2 mm.

Comparative Example 1

(15) As shown in FIGS. 4(a) and 4(b), a combined oil ring was produced in the same manner as in Example 1, except for using a conventional spacer expander having flat intermediate portions with no grooves. The distance between a side-rail-supporting surface of each projection and each intermediate portion was 0.1 mm.

Example 3

(16) A SUS304 wire for a spacer expander used in Example 1 was provided with a Ni plating comprising a half-luster Ni plating layer and a bright Ni plating layer using a sulfamate solution, and subjected to a softening heat treatment at 600 C. for 30 seconds. The resultant Ni plating had a thickness of 5 m and hardness of 214 HV0.01. A combined oil ring was produced in the same manner as in Example 1 except for using this Ni-plated wire.

Example 4

(17) A combined oil ring was produced in the same manner as in Example 2 except for using a Ni-plated wire in Example 3.

(18) [1] Actual Engine Test

(19) Each combined oil ring of Examples 1 and 2 and Comparative Example 1 was mounted to each of first to third cylinders in a one-liter, three-cylinder engine. This engine was repeatedly subjected to a predetermined operation pattern for an actual engine test. According to the following evaluation methods after 250 hours, the gaps of side rails and the amount of oil sludge deposited were measured. Each measurement was conducted three times in each Example and Comparative Example. Top and second rings used had the following specifications.

(20) (1) Top Ring

(21) Material: SWOSC-V,

(22) Outer peripheral surface: ion-plated with chromium nitride, and

(23) Size: d1=71 mm, h1=1.0 mm, and a1=2.3 mm.

(24) (2) second Ring

(25) Material: SWOSC-V,

(26) Entire surface: treated with zinc phosphate, and

(27) Size: d1=71 mm, h1=1.0 mm, and a1=2.3 mm.

(28) Using the above one-liter, three-cylinder engine, the combined oil rings of Examples 3 and 4 and Comparative Example 1 were subjected to the actual engine test in the same manner as in Examples 1 and 2 and Comparative Example 1.

(29) [2] Evaluation Method

(30) The following evaluations were conducted after the actual engine test.

(31) (1) Measurement of Side Rail Gap

(32) After the actual engine test, a piston was withdrawn from each cylinder to measure gaps (S.sub.2) of upper and lower side rails in each oil ring. Before the actual engine test, gaps (S.sub.1) of upper and lower side rails when the oil ring was assembled to the piston, which were equal to gaps in a free state, were also measured to determine a ratio S.sub.2/S.sub.1. S.sub.2/S.sub.1 was determined in both upper and lower side rails, and averaged in three actual engine tests (six actual engine tests in Comparative Example 1).

(33) (2) Measurement of Amount of Oil Sludge Deposited

(34) After the actual engine test, the oil ring was detached from the piston, dried at 200 C. for 1 hour in an electric furnace, cooled to room temperature in a desiccator, and then measured with respect to its mass. Difference between the masses of the oil ring measured before and after the actual engine test was calculated, and averaged in three actual engine tests (six actual engine tests in Comparative Example 1) to determine the amount of oil sludge deposited.

(35) The actual engine test results of Examples 1-4 and Comparative Example 1 are shown in Table 1. The gap is expressed by a relative value, assuming that S.sub.2/S.sub.1 in Comparative Example 1 is 100, and the amount of oil sludge deposited is expressed by a relative value, assuming that the amount of carbon sludge deposited in Comparative Example 1 is 100.

(36) TABLE-US-00001 TABLE 1 Amount of Oil No. S.sub.2/S.sub.1 Sludge Deposited Example 1 220 78 Example 2 300 49 Example 3 255 54 Example 4 320 43 Com. Ex. 1 100 100

(37) Table 1 indicates that as compared with the gap and the amount of oil sludge deposited after the actual engine test in Comparative Example 1, the gaps were as large as about 2.2-3.0 times in Examples 1 and 2 and about 2.55-3.2 times in Examples 3 and 4, and the amounts of oil sludge deposited were as small as 49-78% in Examples 1 and 2 and 43-54% in Examples 3 and 4. In Comparative Example 1, the accumulated oil sludge constrained the side rails, so that the gap did not easily return to an original one, even when the piston was withdrawn from the cylinder. On the other hand, in Examples 1-4, the attachment and accumulation of oil sludge were so reduced that constraint to the oil ring was lowered, closer to a state before the operation than in Comparative Example 1. With each groove having a raised bottom in Examples 2 and 4 when viewed along a substantially circumferential direction, it was observed that the amount of oil sludge deposited was extremely reduced when combined with a sticking-preventing Ni coating as in Examples 3 and 4.

DESCRIPTION OF REFERENCE NUMERALS

(38) 11, 21, 31: Spacer expander 12a, 12b, 32a, 32b, 105a, 105b: Tab 13a, 13b, 33a, 33b, 106a, 106b: Projection 14a, 14b, 34a, 34b, 107a, 107b: Intermediate portion 15a, 15b, 35a, 35b, 108a, 108b: Space 102: Upper portion 103: Lower portion 104: Leg portion 120a, 120b: Side rail