JP2007032777A - Piston ring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston ring having an appropriate combination structure of an annular groove of an inner periphery of a ring main body and an expander. <P>SOLUTION: This piston ring comprises the ring main body 2 provided with the annular groove 7 on its inner periphery, and the expander 3 formed by winding a wire rod 3a of the expander into a coil, and mounted in the annular groove 7 to energize the ring main body 2 to an outer peripheral side. The ring main body 2 is provided with a plurality of retracted portions 8a formed by retracting a groove wall 7a of the annular groove 7 to a radial outer peripheral side within a range not reaching a groove bottom 7b of the annular groove 7, at intervals in the circumferential direction of the ring main body 2 with thick portions 9 remaining therebetween, and oil return holes 10 opened in the annular groove 7 in a state of radially penetrating through the ring main body 2 are formed corresponding to the retracted portions 8 in the circumferential position. The expander 3 is fitted to the annular groove 7 in such manner that vertexes 3b at a radial outer peripheral side, of the coil formed by the wire rod 3a of the expander, are respectively corresponded to the thick portion 9 at the circumferential position. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a piston ring provided with a piston ring body and a coiled expander.

  As a piston ring to be mounted on a piston of an internal combustion engine, an annular groove is provided on the inner periphery of the ring body, and a coil-shaped expander is disposed in the annular groove to apply a ring tension toward the outer peripheral side in the radial direction. A so-called two-piece structure combination piston ring is known. In this type of piston ring, the ring body is integrally formed from a steel plate, and slit-shaped notches are provided at predetermined intervals in the circumferential direction on the inner periphery of the ring body to optimize the rigidity of the ring body. A proposed piston ring has been proposed (see, for example, Patent Document 1). In addition, Patent Documents 2 and 3 are other prior art documents disclosing a piston ring having a notch provided on the inner periphery of the ring body.

Japanese Utility Model Publication No. 62-8350 Japanese Utility Model Publication No. 5-8128 JP-A-8-200500

  In the piston ring of Patent Document 1, the inner periphery of the ring body is divided by a notch portion to reach the groove bottom of the annular groove. Therefore, for example, the ring tension acting on the ring body changes discontinuously at the notch, or when the expander is assembled to the ring body, the expander wire fits into the notch and aligns. Various inconveniences such as increased labor of work may occur.

  Then, an object of this invention is to provide the piston ring which optimized the combination structure of the annular groove of the inner periphery of a ring main body, and an expander.

  The piston ring of the present invention includes a ring main body having an annular groove on the inner periphery, and an expander that is formed by winding a wire in a coil shape and is arranged in the annular groove to urge the ring body toward the outer peripheral side. The ring body has a plurality of receding portions in which the groove wall of the annular groove is receded to the outer peripheral side in the radial direction within a range not reaching the groove bottom of the annular groove, and a thick portion remains between them. In this way, an oil return hole that is provided in the circumferential direction of the ring body with a space therebetween and that opens in the annular groove through the ring body in the radial direction is aligned with the position of the receding portion and the circumferential direction. And the expander is fitted into the annular groove so that the vertices on the radially outer peripheral side of the coil formed by the wire are aligned with the thick portion in the circumferential direction. Issues Resolve (claim 1).

  According to the piston ring of the present invention, since the groove bottom and part of the groove wall of the annular groove are left continuously over the entire circumference of the ring main body, various kinds of problems occur when the annular part is divided at the notch. The inconvenience can be avoided. For example, there is no possibility that the tension of the ring body changes discontinuously in the circumferential direction. Furthermore, since the groove bottom is not notched, the expander can be easily placed at an appropriate position with respect to the ring body without the expander being fitted into the notch. In addition, since the expander wire is in contact with the inner surface of the annular groove at the thick part, the expander has a wider range than when the expander wire is fitted into the annular groove at the position of the retracted part. Thus, the tension of the expander can be efficiently transmitted to the ring body. Furthermore, since the oil return hole is provided in alignment with the receding portion, there is an advantage that the oil return hole can be easily processed as compared with the case where the oil return hole is provided in the thick portion where the groove depth is large. . Since there is a relationship between the weight of the piston ring and the oil consumption, the oil consumption decreases as the weight decreases. Therefore, the oil consumption can be reduced by providing a retraction part to reduce the weight of the ring body. You can also.

  In the thick portion, the groove wall may extend to the center side in the radial direction beyond the center of the expander (Claim 2). Since the expander can be sufficiently held by the groove wall of the thick part, the tension of the expander can be efficiently transmitted to the ring body. In particular, when the expander is configured as a variable tension type made of shape memory alloy, the expansion displacement accompanying the temperature rise of the expander in the direction of the axis of the ring body is received by the groove wall of the annular groove, It is possible to reliably reflect the change in the tension, thereby ensuring a large fluctuation range of the ring tension.

  One form of this invention WHEREIN: The adjacent vertex of the said expander may be located in one thick part (Claim 3). According to this aspect, since the wire is fitted into the annular groove over a longer range in each thick portion, the adhesion between the ring body and the expander can be improved. In particular, it is effective when an expander having a thin wire diameter is used, whereby the physique or weight of the entire piston ring can be reduced, and the overall height of the piston of the internal combustion engine can also be reduced. Therefore, it is possible to reduce the piston axial width, reduce the height of the piston, and improve the output of the internal combustion engine by reducing the weight of the piston. In this case, the circumferential width of the receding part may be set so that a part of the wire rod protrudes from the thick part to the receding part in the circumferential direction (Claim 4). While securing sufficient adhesion between the ring body and the expander at each thick part, the width of each thick part can be reduced to reduce the weight of the ring body.

  In a form in which adjacent apexes of the expander are located in one thick portion, a through hole that penetrates the thick portion in the axial direction of the ring body aligns with a gap between the expander wires in the circumferential direction. (Claim 5). While reducing the weight of the ring main body, the rigidity of the thick part can be appropriately reduced, thereby reducing the difference in rigidity between the thick part and the receding part.

  As described above, according to the piston ring of the present invention, the groove bottom of the annular groove of the ring main body and a part of the groove wall remain so as to continue over the entire circumference of the ring main body. Various inconveniences that occur when the annular part is divided at the notch, such that the tension of the ring body does not change discontinuously in the circumferential direction and the expander does not fit into the notch, can be avoided. . In addition, since the wire of the expander is in contact with the inner surface of the annular groove at the thick part, the expander is brought into contact with the ring body in a wider range as compared with the case of contact at the receding part, thereby expanding the expander. Can be transmitted efficiently to the ring body. Furthermore, since the oil return hole is provided in alignment with the receding portion, the oil return hole can be processed more easily than when the oil return hole is provided in a thick portion having a large groove depth. The oil consumption can be reduced by providing the retracting portion to reduce the weight of the ring body.

(First form)
FIG. 1 is a partial cross-sectional view of a piston ring according to the first embodiment of the present invention, and FIG. 2 is a plan view of a part of the piston ring of FIG. 1 viewed from the direction of the ring axis (vertical direction in FIG. 1). The piston ring 1A of this embodiment is mounted in a piston ring groove 102 provided in the piston 101 of the internal combustion engine so as to function as an oil ring that scrapes off the oil adhering to the cylinder wall 100 of the internal combustion engine. Although a compression ring for preventing pressure leakage is disposed above the piston ring 1A, that is, on the combustion chamber side of the internal combustion engine, the illustration thereof is omitted.

  The piston ring 1 </ b> A includes a ring main body 2 and an expander 3 that is disposed on the inner peripheral side of the ring main body 2 and applies a ring tension toward the outer peripheral side in the radial direction to the ring main body 2. The ring body 2 is formed in a C shape having an abutment. On the other hand, the expander 3 is formed by winding a wire 3a having spring properties in a coil shape at a constant pitch. As an example, the ring main body 2 is manufactured by a method in which a steel material as a raw material is processed into a cross-sectional shape shown in the drawing by press molding or the like and cut into a length corresponding to the piston ring groove 102. The expander 3 may be configured as a variable tension coil expander by forming the wire 3a with a shape memory alloy such as Ni—Ti.

  On the outer periphery of the ring main body 2, an upper rail 4 and a lower rail 5 that are in contact with the cylinder wall 100 and scrape off the oil are provided at intervals in the direction of the ring axis. Each of the rails 4 and 5 extends over the entire periphery of the ring body 2, and an annular recess 6 extending over the entire periphery of the ring body 2 is formed between them. On the other hand, an annular groove 7 for receiving the expander 3 is provided on the inner periphery of the ring body 2. The cross-sectional shape of the annular groove 7 is determined so as to curve from the groove wall 7a to the groove bottom 7b while drawing an arc having a radius of curvature equal to or somewhat larger than the radius r of the expander 3. However, the cross-sectional shape of the annular groove 7 only needs to accept the expander 3. For example, the groove wall 7a may be inclined so that the width in the ring axis direction gradually decreases toward the groove bottom 7b. The annular groove 7 also extends over the entire circumference of the ring body 2. The expander 3 is attached to the inner periphery of the ring body 2 so as to extend along the annular groove 7 to the entire periphery of the ring body 2.

  In the inner periphery of the ring body 2, a plurality of receding portions 8, in which the upper and lower groove walls 7 a of the annular groove 7 are retreated to the outer peripheral side in the radial direction within a range not reaching the groove bottom 7 b, are spaced apart in the circumferential direction. Is provided. Between the upper and lower groove walls 7a, the circumferential position of the receding portion 8 is aligned vertically. That is, as is apparent from FIG. 2, the upper and lower receding portions 8 overlap with each other when viewed from the ring axis direction, and the thick portion 9 sandwiched between the receding portions 8 also overlaps with the ring axis direction. As shown in FIG. 1, in the thick portion 9, the upper and lower groove walls 7 a extend slightly beyond the center CP of the expander 3 attached to the annular groove 7 toward the center in the radial direction (left side in FIG. 1). It is provided to extend. In other words, the depth d of the annular groove 7 in the thick portion 9 is somewhat larger than the radius r of the expander 3. In the thick portion 9, the interval in the ring axis direction between the groove walls 7 a extending beyond the center CP of the expander 3 toward the center in the radial direction is equal to or larger than the diameter of the expander 3.

  In each of the upper and lower groove walls 7 a shown in FIG. 1, the circumferential interval of the retreating portion 8 shown in FIG. 2 is equal to the pitch P of the wire 3 a of the expander 3 in the state where the expander 3 is assembled to the annular groove 7. I'm doing it. In FIG. 2, the pitch P is defined with reference to the apex 3 b on the radially outer peripheral side of the coil formed by the wire 3 a of the expander 3. The expander 3 is fitted in the annular groove 7 so that each vertex 3b of the wire 3a is aligned with the thick portion 9 in the circumferential direction. As a result, the wire 3 a of the expander 3 is fitted into the annular groove 7 so as to come into contact with the groove wall 7 a and the groove bottom 7 b at the thick portion 9, while the wire 3 a is inserted from the annular groove 7 at the retracted portion 8. Also retracts toward the center in the radial direction.

  Further, as shown in FIG. 1, the ring body 2 is provided with a plurality of oil return holes 10 so as to penetrate the ring body 2 in the radial direction from the recess 6 to the groove bottom 7 b of the annular groove 7. The oil return hole 10 is provided to guide oil (lubricating oil) scraped off by the rails 4 and 5 and accommodated in the recess 6 to the inner peripheral side of the ring body 2. The oil that has passed through the oil return hole 10 is discharged to a crank chamber (not shown) via a drain passage 103 (see FIG. 1) of the piston 101.

  The oil return hole 10 is provided in alignment with the receding portion 8 in the circumferential direction of the ring body 2. That is, the oil return hole 10 is provided so as to connect the concave portion 6 and the annular groove 7 at the position of the receding portion 8 when viewed from the ring axis direction. In this embodiment, one oil return hole 10 is provided for each receding portion 8, but even if one oil return hole 10 is provided for two or more receding portions 8 in the circumferential direction. Good.

  According to the piston ring 1 </ b> A configured as described above, the wire 3 a of the expander 3 is in contact with the inner surface of the annular groove 7, that is, the groove wall 7 a and the groove bottom 7 b, at the thick portion 9. Compared with the case where the wire rod 3a of the expander 3 is fitted into the annular groove 7 at the position 8, the expander 3 is brought into contact with the ring body 2 in a wider range, and thereby the tension of the expander 3 is applied to the ring body 2. In contrast, it can be transmitted efficiently. Further, since the expander 3 can be sufficiently covered by the thick portion 9, the expander 3 is less likely to protrude from the ring body 2 when the piston ring 1A is mounted in the piston ring groove 102, and the piston ring groove 102 Assembling work of the piston ring 1A with respect to can be easily performed. By providing the retreat part 8, the ring body 2 can be reduced in weight. As shown in FIG. 3, there is a relationship between the weight of the piston ring and the oil consumption that the oil consumption decreases as the weight decreases. Accordingly, the oil consumption can be reduced by providing the retracting portion 8 to reduce the weight of the ring body 2. In addition, the followability with respect to the cylinder wall of a piston ring can be evaluated by the followability coefficient K shown in the following Formula (1).

K = (WD) / (EI) (1)
Here, W is the ring tension, D is the cylinder inner diameter, E is the longitudinal elastic modulus of the ring body, I is the section modulus of the ring body, and the section modulus I is the thickness T in the radial direction of the ring body 2 (see FIG. 1). ) Is smaller the smaller it is. By reducing the thickness T at the position where the retreating portion 8 is formed, the follow-up coefficient K of the piston ring 1A increases as a whole. Therefore, the follow-up ability of the piston ring 1A with respect to the cylinder wall 100 is improved and the oil consumption is reduced. To do.

  In the piston ring 1A of this embodiment, the wire 3a is displaced in the circumferential direction with respect to the oil return hole 10, and the groove depth of the annular groove 7 is small at the position where the oil return hole 10 is formed. The scraped oil can be quickly discharged from the oil return hole 10 to the crank chamber via the drain path 103. Therefore, oil does not stay around the rails 4 and 5, and an increase in oil consumption or an increase in friction due to the oil scraping left by the rails 4 and 5 can be suppressed. Furthermore, since the oil return hole 10 is provided so as to be aligned with the receding portion 8, the oil return hole 10 can be easily processed as compared with the case where the oil return hole is provided in the thick portion 9 having a large groove depth d. There is an advantage that can be done. For example, when the ring main body 2 is manufactured by press molding, the press die for forming the oil return hole 10 can be easily extracted.

  In the piston ring 1A of this embodiment, since the retreating portion 8 is provided in a range not reaching the groove bottom 7b, the groove bottom 7b of the annular groove 7 and a part of the groove wall 7a extend over the entire circumference of the ring body 2. Left to be continuous. For this reason, there is no possibility that the tension of the ring body 2 changes discontinuously in the circumferential direction. Furthermore, since the retracted portion 8 is not cut out to the groove bottom 7b, there is no inconvenience that the expander 3 fits into the notch, and the expander 3 is easily arranged at an appropriate position with respect to the ring body 2. can do.

  Furthermore, in the piston ring 1A of the present embodiment, the groove wall 7a of the annular groove 7 extends beyond the center CP of the expander 3 toward the radial center side in the thick portion 9, so that the tension of the expander 3 is increased. Can be efficiently transmitted to the ring body 2. In particular, when the expander 3 is configured as a variable tension type made of a shape memory alloy, the expansion displacement (refer to the arrow F in FIG. 1) accompanying the temperature rise of the expander 3 in the direction of the ring axis is changed to the annular groove 7. Can be received by the groove wall 7a. For this reason, the outward force in the radial direction applied to the rails 4 and 5 of the ring body 2 by the tension of the expander 3 can be transmitted more greatly. If the center CP of the expander 3 is arranged on the radial center side of the groove wall 7a, the expansion displacement in the direction of the ring axis cannot be received by the groove wall 7a. There is a possibility that the change of the tension of the expander 3 is not correctly transmitted to the ring body 2 due to slipping away from the annular groove 7. On the other hand, according to the piston ring 1A of the present embodiment, the displacement of the expander 3 can be reliably reflected in the change in the tension of the ring main body 2, thereby ensuring a large fluctuation range of the ring tension.

(Second form)
FIG. 4 is a plan view of a part of the piston ring according to the second embodiment of the present invention as seen from the direction of the ring axis. In FIG. 4, parts common to the first embodiment are denoted by the same reference numerals and description thereof is omitted. In the piston ring 1B of the second form, the expander 3 is such that two adjacent vertices 3b on the outer peripheral side in the radial direction of the coil formed by the wire 3a of the expander 3 are located in one thick portion 9. Is different from the first embodiment in that is fitted into the annular groove 7 of the ring body 2. The pitch P of the wire 3a of the expander 3 in a state where the expander 3 is assembled in the annular groove 7 is set to be smaller than the width WT of the thick portion 9 in the circumferential direction of the ring body 2. In FIG. 4, the width WT of the thick portion 9 is defined as the length on the reference line RL in the circumferential direction of the ring body 2 along the groove wall 7 c of the receding portion 8.

  According to the piston ring 1B of the above form, since the wire 3a is fitted in the annular groove 7 over the longer range in each thick part 9, the adhesive force of the ring main body 2 and the expander 3 can be improved. it can. The piston ring 1B of this embodiment is particularly effective when the expander 3 in which the wire diameter of the wire 3a is thin is used. By using the expander 3 in which the wire diameter of the wire 3a is small, the physique or weight of the entire piston ring 1B can be reduced, and the overall height of the piston 101 of the internal combustion engine can also be reduced. For this reason, the output of the internal combustion engine by the weight reduction of the piston 101 can be improved. Three or more vertices 3b of the wire 3a may be arranged in one thick part 9.

(Third form)
FIG. 5 is a plan view of a part of the piston ring according to the third embodiment of the present invention as seen from the direction of the ring axis. In FIG. 5, the same reference numerals are given to portions common to the first form or the second form, and the description thereof is omitted. In the piston ring 1 </ b> C of the third embodiment, the circumferential direction of the ring body 2 of the receding portion 8 is such that a part of the wire 3 a of the expander 3 protrudes from the thick portion 9 to the receding portion 8 in the circumferential direction of the ring body 2. Width WR is set. That is, the width WR of the receding portion 8 is such that a part of the wire 3a of the expander 3 passing through the thick portion 9 with respect to the width WR of the receding portion 8 in the second embodiment is a receding portion from the side surface in the radial direction of the thick portion 9. It has been expanded to a range that protrudes to 8. In FIG. 4 or 5, the width WR of the receding portion 8 is defined as the length on the reference line RL in the circumferential direction of the ring body 2 along the groove wall 7 c of the receding portion 8.

  According to the piston ring 1C of the above form, the ring main body 2 and the expander 3 are formed by fitting the wire 3a into the annular groove 7 over a longer range in each thick part 9 as in the second form. The ring body 2 can be reduced in weight as compared with the second embodiment by reducing the width WR of each thick portion 9 while ensuring sufficient contact strength.

(4th form)
FIG. 6 is a plan view of a part of a piston ring according to the fourth embodiment of the present invention viewed from the direction of the ring axis. In FIG. 6, parts common to the second embodiment are denoted by the same reference numerals and description thereof is omitted. In piston ring 1D of the 4th form, each thick part 9 provided over the perimeter of ring main part 2 is provided with penetration hole 11 which penetrates in the direction of a ring axis. The through hole 11 is provided in the gap between the wire 3 a of the expander 3 passing through the groove wall 7 a of the thick portion 9 so as to be aligned with the receding portion 9 in the circumferential direction. The positions of the through holes 11 in the circumferential direction of the ring body 2 coincide with each other between the upper and lower groove walls 7a. That is, as is clear from FIG. 6, the upper and lower through holes 11 overlap each other when viewed from the ring axis direction.

  According to piston ring 1D of the above form, weight reduction of ring main body 2 can be achieved compared with a 2nd form. Moreover, by providing the through-hole 11, the rigidity of the thick part 9 is moderately reduced as compared with that of the second embodiment, thereby reducing the difference in rigidity between the thick part 9 and the receding part 8. Can be small. Therefore, since the surface pressure distribution with respect to the cylinder wall becomes more uniform over the entire circumference of the ring body 2, good oil scraping performance can be more reliably exhibited over the entire circumference of the ring body 2.

  The present invention is not limited to the form described above, and may be implemented in various forms. For example, the through-hole 11 shown in the fourth form may be provided in the third form, and each form such as the first form and the second form or the first form and the third form may be provided. You may combine.

  The present invention can be applied not only to an internal combustion engine but also to various reciprocating engines as long as a piston ring is used. For example, you may apply this invention with respect to piston rings, such as an external combustion engine, a compressor, and a piston pump.

The fragmentary sectional view of the piston ring which concerns on the 1st form of this invention. The top view which looked at a part of piston ring of FIG. 1 from the direction of the ring axis line. The figure which shows the relationship between the weight of a piston ring, and oil consumption. The top view which looked at a part of piston ring which concerns on the 2nd form of this invention from the direction of the ring axis line. The top view which looked at a part of piston ring which concerns on the 3rd form of this invention from the direction of the ring axis line. The top view which looked at a part of piston ring which concerns on the 4th form of this invention from the direction of the ring axis line.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A, 1B, 1C, 1D Piston ring 2 Ring body 3 Expander 3a Expander wire 3b Apex on the radially outer peripheral side of the coil formed by the wire 7 Annular groove 7a Groove wall 7b Groove bottom 8 Retracted part 9 Thick part 10 Oil return hole

Claims (5)

A ring main body provided with an annular groove on the inner periphery, and an expander formed by winding a wire rod in a coil shape and arranged in the annular groove to urge the ring main body toward the outer periphery,
The ring main body has a plurality of receding parts that are receded radially outward in a range in which the groove wall of the annular groove does not reach the groove bottom of the annular groove so that a thick part remains between them. An oil return hole that is provided in the circumferential direction of the ring body with a space therebetween and that opens in the annular groove through the ring body in the radial direction is provided in alignment with the position of the receding portion and the circumferential direction, The expander is fitted into the annular groove so that each apex on the radially outer peripheral side of the coil formed by the wire is aligned with the thick portion in the circumferential direction. .   2. The piston ring according to claim 1, wherein in the thick portion, the groove wall extends beyond the center of the expander toward the center in the radial direction.   3. The piston ring according to claim 1, wherein the adjacent apexes of the expander are located in one thick portion.   4. The piston ring according to claim 3, wherein a width of the receding portion in the circumferential direction is set so that a part of the wire rod protrudes from the thick portion to the receding portion in the circumferential direction. .   The through-hole which penetrates the said thick part in the axial direction of the said ring main body is provided so that the position between the clearance gap between the wire materials of the said expander may be aligned with the said circumferential direction. Piston ring as described in.

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