JP4501527B2 - Toroidal continuously variable transmission - Google Patents

Description

  The present invention relates to an improvement of a toroidal continuously variable transmission that is used as an automatic transmission for a vehicle (automobile) or as a transmission for adjusting the operating speed of various industrial machines such as a pump.

  The use of a toroidal continuously variable transmission as an automatic transmission for automobiles has been studied and implemented in part. In addition, it is described in Patent Documents 1 to 4 and the like that a continuously variable transmission is configured by combining a toroidal type continuously variable transmission and a planetary gear type transmission. Furthermore, Patent Document 5 describes a specific structure of a continuously variable transmission that is a coaxial combination of a toroidal continuously variable transmission and a planetary gear transmission. 4 to 5 show the continuously variable transmission described in Patent Document 5 as described above. This continuously variable transmission is a combination of a toroidal continuously variable transmission 1 and first to third planetary gear type transmissions 2 to 4, and is supported concentrically and freely in relative rotation. , An input shaft 5, a transmission shaft 6, and an output shaft 7. The third planetary gear type transmission 4 is connected to the transmission shaft 6 in a state where the first and second planetary gear type transmissions 2 and 3 are spanned between the input shaft 5 and the transmission shaft 6. And the output shaft 7 are provided in a state of being spanned.

  Of these, the toroidal-type continuously variable transmission 1 includes a pair of input-side disks 8 a and 8 b, an integrated output-side disk 9, and a plurality of power rollers 10 and 10. One of the pair of input side disks 8a and 8b (right side in FIG. 4) corresponds to the first disk described in the claims. These two input-side disks 8a and 8b are positioned at two positions separated from each other in the axial direction in the input shaft 5 in a state in which one axial side surfaces, which are toroidal curved surfaces each having an arcuate cross section, are opposed to each other. Rotation that is concentric with each other and synchronized with the input shaft 5 is supported freely. Further, the output side disk 9 has both axial side surfaces, each of which is a toroidal curved surface having a circular arc cross section, at a position between the input side disks 8a and 8b around the intermediate portion of the input shaft 5. In a state of being opposed to one side surface in the axial direction of the input side discs 8a and 8b, the input side discs 8a and 8b are concentrically supported and freely supported for relative rotation with respect to the both input side discs 8a and 8b. .

  Further, a plurality of each of the power rollers 10 and 10 is sandwiched between both side surfaces in the axial direction of the output side disk 9 and one side surface in the axial direction of the both input side disks 8a and 8b. Each of the power rollers 10 and 10 has a spherical convex surface, and both the input side and output side discs 8a are sandwiched between the input side discs 8a and 8b and the output side disc 9. , 8b and 10 can freely transmit power. The power rollers 10 and 10 are rotatably supported on the inner surfaces of the trunnions 11 and 11. The trunnions 11 and 11 support the pivot shafts 12 and 12 provided at both ends of the trunnions 11 and 13b on support plates 13a and 13b installed in the casing 14 so as to be swingable and axially displaceable. . These two support plates 13a and 13b are respectively supported by both ends of support columns 17 and 17 supported and fixed in the casing 14 via a connecting plate 15 and an actuator body 16.

  Further, the output side disk 9 is rotatably supported by a pair of thrust angular ball bearings 18 and 18 between the intermediate portions of the respective pillars 17 and 17 formed in an annular shape. Further, the base end portion (the left end portion in FIG. 4) of the hollow rotary shaft 19 is spline engaged with the output side disk 9. The hollow rotary shaft 19 is inserted inside the input side disk 8a on the side far from the engine (right side in FIG. 4) so that power transmitted to the output side disk 9 can be taken out. Further, a first sun gear for constituting the first planetary gear type transmission 2 at a portion protruding from the outer surface of the input side disk 8a at the tip end portion (the right end portion in FIG. 4) of the hollow rotary shaft 19. The gear 20 is fixed.

On the other hand, between the portion protruding from the hollow rotary shaft 19 at the tip end portion (the right end portion in FIG. 4) of the input shaft 5 inserted inside the hollow rotary shaft 19 and the input side disk 8a, there is a claim. The input side disk 8a and the input shaft 5 rotate in synchronization with each other by providing a first carrier 21 corresponding to the carrier described in the above-mentioned range. Then, the first and second planetary gear type shifts each having a double pinion type at circumferentially equidistant positions (generally 3 to 4 positions) on both side surfaces in the axial direction of the first carrier 21. Planetary gears 22 to 24 for constituting the machines 2 and 3 are rotatably supported. Further, a first ring gear 25 is rotatably supported around one half of the first carrier 21 (the right half of FIG. 4).

  Among the planetary gears 22 to 24, the planetary gear 22 provided inside the radial direction of the first carrier 21 near the toroidal type continuously variable transmission 1 (leftward in FIG. 4) is the first sun gear 20. Is engaged. Further, the planetary gear 23 provided on the inner side with respect to the radial direction of the first carrier 21 on the side far from the toroidal-type continuously variable transmission 1 (the right side in FIG. 4) is a base end portion of the transmission shaft 6 (see FIG. 4). It meshes with the second sun gear 26 fixed at the left end). Further, the remaining planetary gears 24 provided on the outer side in the radial direction of the first carrier 21 have axial dimensions larger than those of the planetary gears 22 and 23 provided on the inner side. The first ring gear 25 is meshed with the first ring gear 25.

  On the other hand, a second carrier 27 for constituting the third planetary gear type transmission 4 is coupled and fixed to a base end portion (left end portion in FIG. 4) of the output shaft 7. The second carrier 27 and the first ring gear 25 are coupled through a low speed clutch 28. Further, a third sun gear 29 is fixedly provided near the tip of the transmission shaft 6 (near the right end in FIG. 4). A second ring gear 30 is disposed around the third sun gear 29, and a high speed clutch 31 is provided between the second ring gear 30 and a fixed portion such as the casing 14. Further, a plurality of planetary gears 32 and 33 arranged between the second ring gear 30 and the third sun gear 29 are rotatably supported on the second carrier 27. The planetary gears 32 and 33 mesh with each other, and the planetary gear 32 provided on the inner side with respect to the radial direction of the second carrier 27 is provided on the third sun gear 29 and the planetary gear 33 provided on the outer side is provided on the first side. The two ring gears 30 mesh with each other.

  In the case of the continuously variable transmission configured as described above, the power transmitted from the input shaft 5 to the integrated output disk 9 via the pair of input disks 8a and 8b and the power rollers 10 and 10 is It is taken out through the hollow rotating shaft 19. In the low speed mode in which the low speed clutch 28 is connected and the high speed clutch 31 is disconnected, the rotational speed of the input shaft 5 is kept constant by changing the gear ratio of the toroidal continuously variable transmission 1. In this state, the rotational speed of the output shaft 7 can be converted into forward rotation and reverse rotation with the stop state interposed therebetween. That is, in this state, the differential component between the first carrier 21 that rotates in the forward direction together with the input shaft 5 and the first sun gear 20 that rotates in the reverse direction together with the hollow rotation shaft 19 is converted into the first ring. The gear 25 is transmitted to the output shaft 7 through the low speed clutch 28 and the second carrier 27. In this state, the output shaft 7 is stopped by setting the gear ratio of the toroidal continuously variable transmission 1 to a predetermined value, and the speed ratio of the toroidal continuously variable transmission 1 is increased from the predetermined value. By changing to the side, the output shaft 7 is rotated in the direction in which the vehicle moves backward. On the other hand, the output shaft 7 is rotated in the direction in which the vehicle moves forward by changing the gear ratio of the toroidal type continuously variable transmission 1 from the predetermined value to the deceleration side.

  Further, in the high speed mode in which the low speed clutch 28 is disconnected and the high speed clutch 31 is connected, the output shaft 7 is rotated in a direction to advance the vehicle. That is, in this state, the first carrier 21 that rotates in the forward direction together with the input shaft 5 and the first sun gear 20 that rotates in the reverse direction together with the hollow rotary shaft 19 rotate according to the differential component. The rotation of the planetary gear 22 of the first planetary gear type transmission 2 is transmitted to the planetary gear 23 of the second planetary gear type transmission 3 via another planetary gear 24 to cause the second sun gear 26 to move. Then, the transmission shaft 6 is rotated. And the 3rd sun gear 29 provided in the front-end | tip part of this transmission shaft 6, the 2nd ring gear 30 and the planetary gears 32 and 33 which comprise the said 3rd planetary gear type transmission 4 with this 3rd sun gear 29, The second carrier 27 and the output shaft 7 coupled to the second carrier 27 are rotated in the forward direction. In this state, the rotational speed of the output shaft 7 can be increased as the gear ratio of the toroidal type continuously variable transmission 1 is changed to the speed increasing side.

  By the way, in the case of the conventional structure as shown in FIGS. 4 to 5 described above, a rotational force and a force are applied to one input side disk 8a via the first carrier 21 coupled to the input shaft 5 (right side in FIG. 4). The pressing force generated by the pressing device 36 can be transmitted. The first carrier 21 has a plurality of first and second planetary shafts 41 and 42 between the intermediate support plate 39 and the first and second connecting plates 37 and 40, respectively. A plurality of third planetary shafts 43 are spanned between the first and second connecting plates 37 and 40, respectively. Further, the planetary gears 22, 23, 24 are rotatably supported around the planetary shafts 41-43 through radial needle bearings 44a, 44b, 44c, respectively. A cylindrical portion 45 provided at the center of the intermediate support plate 39 is spline-engaged with a portion near the tip of the intermediate portion of the input shaft 5 and is held down by a loading nut 46. The annular portion 47 of the intermediate support plate 39 and the first and second connection plates 37 and 40 are connected to the planetary gears 22, 23, and 21 at positions dislocated in the circumferential direction. The intermediate support plate 39 and the first and second connection plates 37 and 40 are formed integrally with each other through the connection portions (not shown).

  Each of the protrusions 34 is formed at a plurality of locations on the outer side surface (right side surface in FIG. 4) of the one input side disk 8a and the outer peripheral edge of the first connecting plate 37 constituting the first carrier 21. Rotational force can be transmitted between the one input side disk 8a and the first carrier 21 by engaging the notch 35 formed at the position aligned with the portion 34 in an uneven manner. At the same time, the pressing device 36 is generated by bringing the outer surface of the one input side disk 8a into contact with one side surface (left side surface in FIG. 4) of the first connecting plate 37 in the axial direction. The pressing force can be transmitted to the one input side disk 8a through the input shaft 5 and the first carrier 21. Accordingly, during operation, the one input side disk 8a is in rolling contact with the axial side surface of the one input side disk 8a based on the pressing force generated by the pressing device 36 for securing the surface pressure of the traction portion. The power rollers 10 and 10 are pressed in the axial direction.

  In this way, the one input side disk 8a pressed toward the power rollers 10 and 10 overlaps with the power rollers 10 and 10 in the axial direction based on the reaction force received from the power rollers 10 and 10. The portion is elastically deformed so as to bend toward the first carrier 21 side. Therefore, of the contact portion between the outer side surface of the one input side disk 8a and one side surface of the first carrier 21, the portion overlapping the power rollers 10 and 10 in the axial direction is applied with a large surface pressure. In addition, the power rollers 10 and 10 are in contact with the power rollers 10 and 10 in the circumferential direction with a small surface pressure (or no contact). Moreover, during operation, as the first carrier 21 and the one input side disk 8a rotate, the relative positions of the one input side disk 8a and the first carrier 21 and the power rollers 10 and 10 in the circumferential direction. Is constantly changing.

  For this reason, the surface pressure of the contact portion between the outer side surface of the one input side disk 8a and one side surface of the first carrier 21 determines the rotational speed of the one input side disk 8a and the one input side disk 8a. The value is increased or decreased in a period multiplied by the number (for example, 2) of the power rollers 10 and 10 that are in rolling contact with each other. Such a periodic change in the surface pressure of the contact portion between the outer side surface of the one input side disk 8a and one side surface of the first carrier 21 causes these side surfaces to slide minutely (rubbing). There is a possibility of fretting wear on both sides. And when abrasion powder generate | occur | produces based on such fretting abrasion, this abrasion powder may mix in lubricating oil (traction oil). Such mixing of wear powder into the lubricating oil makes the lubrication state of each rolling contact part including the traction part defective, and the life of the input side and output side disks 8a and 8b and the power rollers 10 and 10 etc. Is not preferable because of the possibility of shortening.

Japanese Patent No. 3407319 JP 2000-220719 A US Pat. No. 6,358,178 JP 2002-139124 A Japanese Patent Laid-Open No. 2004-084712

  The toroidal-type continuously variable transmission of the present invention has been invented to realize a structure having excellent durability by preventing lubrication failure due to wear powder based on fretting wear in view of the above-described circumstances.

The toroidal-type continuously variable transmission of the present invention is similar to the conventional toroidal-type continuously variable transmission shown in FIGS. 4 to 5 described above, and is first and second arranged concentrically and relatively rotatably. The disc includes a plurality of power rollers that are sandwiched between the axial side surfaces of the first and second discs facing each other and transmit power between the first and second discs.
Then, a planetary gear type transmission provided in a state adjacent to the first disk is configured, and a carrier whose one side is in contact with the outer surface of the first disk is connected to the first disk . Combined with a state that rotates in sync with the disc.
In particular, in the toroidal type continuously variable transmission according to the present invention, between the one side surface of these carriers facing each other and the outer side surface of the first disk, the inner diameter side and the outer side of the contact portion between these both side surfaces are provided. In a state of surrounding the diameter side , a pair of seal members having different diameters are provided to close a gap existing between the both side surfaces.

According to the toroidal-type continuously variable transmission of the present invention configured as described above, it is possible to prevent the lubricating oil from being contaminated by wear powder generated based on fretting wear. That is, even if abrasion powder based on rubbing (fretting) of the one side of the carrier which abuts the outer surface of the first disc and to the first disk is generated, is provided between the adjacent these sides, from each other The pair of seal members having different diameters can prevent the wear powder from being mixed into the lubricating oil. For this reason, the lubrication state of each rolling contact portion including the traction portion can be kept good, and the durability of the input side, output side discs, power rollers, etc. can be ensured.
That is, the lubrication state of the toroidal continuously variable transmission and the planetary gear type transmission provided adjacent to the toroidal type continuously variable transmission is kept in good condition. Ensuring durability.

In carrying out the present invention, preferably, as described in claim 2, a flexible sealing member (made of an elastic material such as an elastomer such as rubber) is attached to one side surface of the carrier . by clamped axially between the outer surface of one disc, regardless of the axial displacement of these carriers and the first disc, on either side faces facing each other of these carriers and the first disc The inner diameter side and outer diameter side of the gap existing between them are kept closed.
With this configuration, the inner diameter side and the outer diameter side of the gap existing between the both side surfaces can always be closed with a simple structure regardless of the operating state, and wear generated based on fretting wear. It is possible to reliably prevent the powder from being mixed into the lubricating oil.

Preferably, as described in claim 3 , a groove is provided on the side surface of the carrier so as to be recessed from the side surface, and a seal member is provided in the groove.
If comprised in this way, the support rigidity of a sealing member is securable, without reducing the intensity | strength of the 1st disk to which high stress is added. That is, when the seal groove for supporting the seal member is provided in this manner, stress tends to concentrate on the seal groove portion, but the seal groove is not directly applied to the carrier as compared with the first disk. By providing the above, it is possible to secure the support rigidity of the seal member while ensuring the durability. Further, it is possible to prevent the pressing force from being applied to the seal member and to ensure the durability of the seal member.
Preferably, as described in claim 4 , the one side surface of the carrier and the outer side surface of the first disk are brought into contact with each other around the entire circumference in a ring shape. An annular seal member {for example, an O-ring ( Claim 5 ), a seal ring ( Claim 6 ), an oil seal ( Claim 7 ), etc. }, The inner and outer peripheral edges of the contact portion between the both side surfaces are surrounded over the entire circumference.
If comprised in this way, the said contact part can be efficiently enclosed by a pair of sealing members, ensuring the contact area of a carrier and a 1st disk.

FIG. 1 shows a first embodiment of the present invention corresponding to claims 1 to 5 . The feature of this embodiment is that the outer side surface (the right side surface in FIG. 1) of one input side disk 8a and one side surface (the left side surface in FIG. 1) of the first connecting plate 37 constituting the first carrier 21a. By providing a pair of seal members 38, 38 concentrically with each other in between, wear powder based on fretting wear generated at the abutting portions of both side surfaces that abut each other is mixed into the lubricating oil. It is in the point to prevent. Since the structure and operation of the other parts are the same as those of the conventional structure shown in FIGS. 4 to 5 described above, the illustration and explanation of the equivalent parts are omitted or simplified, and the following description will focus on the characteristic parts of the present invention. To do.

  In the case of the present embodiment, the inner diameter side and the outer diameter side of the abutting portion between these both side surfaces are arranged between one side surface of the first connecting plate 37 facing each other and the outer side surface of the one input side disk 8a. In a surrounding state, a pair of seal members 38, 38 are provided for closing a gap existing between the both side surfaces. That is, one side surface of the first connecting plate 37 and the outer side surface of the one input side disk 8a are in contact with each other around the entire circumference, and the outer peripheral edge and the inner peripheral edge of the contacted part in the annular shape. The ring-shaped sealing members 38, 38 are provided respectively. Each of the sealing members 38, 38 is an O-ring (annular sealing packing having a circular cross section) made of a flexible elastic material such as an elastomer such as rubber. It is installed in a pair of concave grooves 48, 48 provided over the entire circumference in a state of being recessed from one side surface on the side surface.

  Then, each of the sealing members 38, 38 is clamped in the axial direction between the bottom surface of each of the concave grooves 48, 48 and the outer surface of the one input side disk 8a. Regardless of the axial displacement between the first input disk 8a and the first input disk 8a, the inner diameter side and outer diameter of the gaps between the opposite side surfaces of the first connecting plate 37 and the first input disk 8a. The side is left closed. When assembling the first connecting plate 37 and the one input side disk 8a, grease or lubricating oil is applied to one side surface of the first connecting plate 37 and the outer side surface of the one input side disk 8a that are in contact with each other. It is also preferable to reduce the fretting wear that occurs at the abutting portions between these two side surfaces by applying. The grease and lubricating oil are prevented from being mixed into the traction oil by the sealing materials 38 and 38 described above.

  In the case of the present embodiment configured as described above, it is possible to prevent the lubricating oil from being contaminated by wear powder generated based on fretting wear. That is, even if abrasion powder is generated due to friction (fretting) between one side surface of the first connecting plate 37 and the outer side surface of one input side disk 8a, the both side surfaces are in contact with each other. The pair of seal members 38, 38 provided so as to surround the contact portion can prevent the wear powder from being mixed into the lubricating oil. Therefore, the lubrication state of the rolling contact portions and the meshing portions of the gears 20, 22, 24, and 25 is kept good, and the toroidal continuously variable transmission 1 and the planetary gear transmissions 2 and 3 (see FIG. 4). The durability of the can be ensured.

FIG. 2 shows Embodiment 2 of the present invention corresponding to claims 1 to 4 and 6. In the case of the present embodiment, the pair of seal members 38a, 38a is made of a ring-shaped seal made of a soft metal having a self-lubricating property such as brass (a metal softer than the one input side disk 8a). It is a ring. Then, by installing such seal members 38a, 38a in a pair of concave grooves 48, 48 provided on one side (the left side in FIG. 2) of the first connecting plate 37 over the entire circumference, A gap that exists between the side surfaces of the one connecting plate 37 and the one input side disk 8a facing each other is closed. Other configurations and operations are the same as those in the first embodiment described above, and thus redundant description is omitted.
In addition, although illustration is abbreviate | omitted, the annular | circular shaped spacer made from a copper alloy can also be clamped between the one side surface of the 1st connection plate which comprises a 1st carrier, and the outer surface of one input side disk. When such a spacer is sandwiched, the spacer is formed between the one side surface of the first connection plate and the outer side surface of one input side disk, and the carbon constituting the first connection plate and the input side disk. It is in contact with iron-based alloys of steel and bearing steel and exhibits excellent self-lubricating properties. For this reason, it is possible to suppress the occurrence of fretting wear between the first connecting plate and the one input side disk. In this case, the seal member can be omitted.

FIG. 3 shows Embodiment 3 of the present invention corresponding to claims 1 to 4 and 7 . In the case of the present embodiment, the pair of seal members 38b, 38b are made of a flexible elastic material such as an elastomer such as rubber, or a soft metal having self-lubricating properties such as brass (on one input side). The oil seal is made of a metal that is sufficiently softer than the disk 8a and has a seal lip that can be brought into contact with the entire outer surface of the one input side disk 8a (the right side surface in FIG. 3). Such seal members 38b and 38b are respectively installed in a pair of concave grooves 48 and 48 provided on one side (the left side in FIG. 3) of the first connecting plate 37 over the entire circumference, and the seal By bringing the tip edge of the lip into contact with the outer surface of the one input side disk 8a over the entire circumference, the side surfaces of the first connecting plate 37 and the one input side disk 8a that face each other are opposed to each other. It closes an existing gap. Other configurations and operations are the same as those of the first embodiment described above, and thus redundant description is omitted.

  The above description has been made when the present invention is applied to a double cavity type half toroidal continuously variable transmission. However, the present invention is not limited to such a structure, and can be applied to a toroidal continuously variable transmission of a single cavity type or a full toroidal type. In addition, the O-ring, the seal ring, and the oil seal have been described as examples of the seal members 38, 38a, and 38b. However, the seal members 38, 38a, and 38b are not limited to such seal members 38, 38a, and 38b. , 38a, 38b can be used in combination.

The expanded sectional view equivalent to the A section of FIG. 4 which shows Example 1 of this invention. Sectional drawing similar to FIG. Sectional drawing similar to FIG. Sectional drawing which shows an example of the continuously variable transmission incorporating the toroidal type continuously variable transmission conventionally known. BB sectional drawing of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Toroidal type continuously variable transmission 2 1st planetary gear type transmission 3 2nd planetary gear type transmission 4 3rd planetary gear type transmission 5 Input shaft 6 Transmission shaft 7 Output shaft 8a, 8b Input side disk 9 Output side disk DESCRIPTION OF SYMBOLS 10 Power roller 11 Trunnion 12 Pivot shafts 13a and 13b Support plate 14 Casing 15 Connection plate 16 Actuator body 17 Strut 18 Thrust angular ball bearing 19 Hollow rotating shaft 20 First sun gears 21 and 21a First carrier 22 Planetary gear 23 Planetary gear 24 Planetary gear Gear 25 first ring gear 26 second sun gear 27 second carrier 28 low speed clutch 29 third sun gear 30 second ring gear 31 high speed clutch 32 planetary gear 33 planetary gear 34 convex portion 35 notch 36 pressing device 37 first One connecting portion 38, 38a, 38b Seal member 39 Intermediate support plate 40 Second connecting plate 1 the first planetary shaft 42 the second planetary shaft 43 third planetary shaft 44a, 44b, 44c the radial needle bearing 45 cylindrical section 46 loading nut 47 circular ring portion 48 groove

Claims (7)

The first and second disks arranged concentrically and relatively rotatably, and the first and second disks sandwiched between the axial side surfaces of the first and second disks facing each other. A plurality of power rollers that transmit power between the disks, and a planetary gear type transmission that is provided adjacent to the first disk is configured on the outer surface of the first disk. In a toroidal-type continuously variable transmission in which the carrier with one side abutting is combined to rotate in synchronization with the first disk, the one side of the carrier and the first disk facing each other A pair of seal members having different diameters that close the gap between the two side surfaces in a state of surrounding the inner diameter side and the outer diameter side of the abutting portion between the two side surfaces between the outer side surfaces. Toroidal stepless provided Speed machine. By holding a pair of flexible sealing members in the axial direction between one side surface of the carrier and the outer side surface of the first disk, regardless of the axial displacement of the carrier and the first disk, The toroidal continuously variable transmission according to claim 1, wherein the inner diameter side and the outer diameter side of a gap existing between the opposite side surfaces of the carrier and the first disk are kept closed. In a state of recessed from the side surface side of the carrier, it provided a pair of recessed groove diameters different, each of these two grooves is installed a sealing member, toroidal described in any one of claims 1-2 Continuously variable transmission. One side surface of the carrier and the outer side surface of the first disk are in contact with each other around the entire circumference, and annular seal members are respectively provided on the outer peripheral edge and the inner peripheral edge of the portion in contact with the annular shape. The toroidal type continuously variable transmission according to any one of claims 1 to 3 , wherein the inner and outer peripheral edges of the abutting portion between both side surfaces are surrounded by the entire circumference. The toroidal continuously variable transmission according to any one of claims 1 to 4 , wherein the seal member is an O-ring. The toroidal type continuously variable transmission according to any one of claims 1 to 4 , wherein the seal member is a seal ring. The toroidal type continuously variable transmission according to any one of claims 1 to 4 , wherein the seal member is an oil seal.

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