JP2012255373A - Drain plug installing structure of synthetic resin cover - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent oozing and leakage of oil, by enhancing sealability of a drain plug 2 detachably installed in a synthetic resin oil pan 1.SOLUTION: A metallic nut 11 has a cylindrical part 14 and a hexagonal nut part 15, the cylindrical part 14 is fitted via a very small clearance d1 to a through-hole 3 of the oil pan 1, and the nut part 15 is fitted via a very small clearance d2 to a nut fitting part 5 of a hexagonal shape. An O ring storage part 16 is formed of a step part 7, and a nut 11 is sealed in the radial direction by an O ring 12 stored in the O ring storage part 16. A gasket 25 is interposed between an end surface 14b of the cylindrical part 14 and the drain plug 2, and is sealed in the axial direction by axial force of the drain plug 2. Even in an installed state of deforming the gasket 25 by a predetermined quantity, a bottom wall of the oil pan 1 is not compressed in the axial direction. Thus, the nut 11 is self-centered, and excellent sealability is provided by the O ring 12.

Description

  The present invention relates to a drain plug mounting structure for a synthetic resin cover suitable as an oil pan for an internal combustion engine or an automatic transmission.

  For example, an oil pan for an internal combustion engine is generally made of a steel plate, but recently, attempts have been made to use a synthetic resin oil pan such as FRP. An oil pan of an internal combustion engine needs a screw-type drain plug that is detachable in order to discharge oil from the inside. Patent Document 1 discloses a metal insert member having a female screw portion in a synthetic resin oil pan. A configuration is disclosed in which the drain plug is screwed onto the insert member from the outside of the oil pan.

  In Patent Document 1, the insert member has a cylindrical shape having a hexagonal collar, and the hexagonal recess formed on the synthetic resin oil pan side is fitted with the collar and penetrated through the oil pan. By extending the front end edge of the cylindrical portion outward, it is configured to be fixed to the bottom wall of the oil pan.

JP 2000-34916 A

  In the configuration in which the metal insert member is attached to the synthetic resin oil pan as described above and the drain plug is screwed to the insert member, the synthetic resin oil pan and the metal insert member are used as a seal against the internal oil. Two seals are necessary: a seal between the two and a seal of a drain plug screwed into the insert member. However, in the said patent document 1, only the insert member is hold | maintained at the oil pan by expanding the front-end edge of an insert member outside, and the positive seal between both is not made | formed. Therefore, there is a concern that oil bleeding or leakage may occur between the oil pan and the insert member due to a difference in coefficient of thermal expansion between the synthetic resin oil pan and the insert member.

  Further, if the drain plug is configured to be in contact with the synthetic resin oil pan on the outer peripheral side of the tip end edge (the portion bent outward) of the insert member and seal between the oil pan, the synthetic resin Since the material is less rigid than the metal material, sufficient axial force necessary for sealing the drain plug cannot be secured, and oil bleeding and leakage are likely to occur.

  And in the structure of the said patent document 1, in order to fix an insert member to a synthetic resin oil pan, the caulking process with respect to an insert member front-end | tip edge is required.

This invention is a synthetic resin cover drain plug mounting structure in which a metal nut is held in a synthetic resin cover, and a drain plug is screwed into the female thread portion of the nut,
The metal nut includes a cylindrical portion that is concentric with the female screw portion, and a non-circular nut portion that is connected to one end of the cylindrical portion and projects from the outer peripheral surface of the cylindrical portion to the outer peripheral side,
The synthetic resin cover is provided with a through hole in which the cylindrical portion is fitted through a minute gap and an inner surface of the cover so as to surround the periphery of the through hole, and the nut portion has a minute gap. A nut fitting portion that is fitted through, and a cylindrical step portion provided concentrically with the through hole on the bottom surface of the nut fitting portion,
An O-ring that radially seals the space between the inner peripheral surface of the step portion and the outer peripheral surface of the cylindrical portion is disposed in a space generated by the step portion between the synthetic resin cover and the metal nut.
The drain plug has a flange surface that extends to the outer peripheral side from the opening edge of the through hole, and includes a gasket between the tip surface of the cylindrical portion and the flange surface,
In a state where a predetermined load is applied to the gasket by fastening the drain plug, the synthetic nut cover is not compressed in the axial direction between the flange surface and the nut portion, and the metal nut is attached to the O-ring. The axial dimension of each part is set so as to be self-centering.

  That is, in the above configuration, the drain plug and the metal nut are sealed in the axial direction via a gasket interposed therebetween. As this gasket, for example, a metal packing made of a relatively soft metal such as plastically deformable copper is used. The gasket is narrowed between a metal drain plug and a metal nut that are screwed together. Therefore, a reliable sealing property can be obtained in the same manner as a general metal oil pan or the like. On the other hand, the gap between the synthetic resin cover and the metal nut is radially sealed by an O-ring between the inner peripheral surface of the step portion on the synthetic resin cover side and the outer peripheral surface of the cylindrical portion on the metal nut side. Here, the tightening of the drain plug does not affect the O-ring. That is, when the drain plug is tightened with a standard torque, that is, when a predetermined load is applied to the gasket, the axial force of the drain plug does not act on the synthetic resin cover, and the metal nut has a radius together with the drain plug. It is movable in the direction (within a minute gap with respect to the through hole and the nut fitting portion). Therefore, the self-centering action for the through hole is obtained by the elasticity of the O-ring, and the metal nut is always concentric with the through hole together with the drain plug. Therefore, good sealing performance can be obtained over the entire circumference of the O-ring, and even if there is a relative thermal expansion between the synthetic resin cover and the metal nut, oil bleeding or leakage may occur. Absent.

  In one specific aspect, in a state where the gasket is deformed by a predetermined amount due to the predetermined load, the distance between the flange surface and the nut portion is the same as that of the synthetic resin cover in the nut fitting portion. Slightly larger than the wall thickness, a minute gap remains in the axial direction.

  In the present invention, since the synthetic resin cover does not have to be compressed in the axial direction, the minute interval may be 0, that is, the minute gap may not substantially exist.

  Moreover, in one preferable aspect, the engagement protrusion which prevents the said nut part from coming off is provided in the opening edge of the said nut fitting part. In such a configuration, even when the drain plug is removed, the metal nut is held by the nut fitting portion, so that the drain plug can be easily attached and detached.

  According to the present invention, since the metal nut is not completely fixed to the synthetic resin cover, the step of caulking the metal nut to the synthetic resin cover becomes unnecessary. And by combining the axial seal by fastening the metal members of the metal nut and the metal drain plug with the self-centered radial seal that is not affected by the axial force of the drain plug, it is high. Sealability is obtained, and oil bleeding from the inside can be reliably prevented over a long period of time.

Sectional drawing of one Example which applied this invention to the drain plug of the oil pan. The perspective view which shows the principal part by the side of an oil pan. The perspective view shown in the state which turned upside down the metal nut with the O-ring. The perspective view which shows the modification of metal nuts. Sectional drawing of the 2nd Example provided with the engagement protrusion which prevents a metal nut from falling out. The perspective view which shows the principal part by the side of the oil pan of this 2nd Example. The perspective view of the principal part by the side of the oil pan which shows the modification which provided the engagement protrusion in the perimeter. Sectional drawing of the principal part which shows an example of the cross-sectional shape of an engaging protrusion. Sectional drawing of the principal part which shows the example from which the cross-sectional shape of an engaging protrusion differs. Sectional drawing of the principal part which shows the example from which the cross-sectional shape of an engaging protrusion further differs.

  Hereinafter, an embodiment in which the present invention is applied to an oil pan provided at the bottom of an automobile internal combustion engine will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a mounting structure of a drain plug 2 that is detachably attached to the bottom of a synthetic resin oil pan 1 for oil discharge. The oil pan 1 is, for example, a polyamide-based fiber reinforced It is integrally injection-molded with a resin material having high strength and rigidity such as a synthetic resin.

  A circular through hole 3 is formed at an appropriate position on the bottom wall of the oil pan 1, generally at the lowest position in the vehicle-mounted state, and the oil pan 1 is surrounded so as to surround the through hole 3. As shown also in FIG. 2, the nut fitting part 5 which consists of the hexagonal wall part 4 is formed in the inner surface (in other words, the upper surface of a bottom wall). In the nut fitting portion 5, the distance between two opposite sides of the hexagon is larger than the diameter of the through hole 3. A cylindrical step 7 that is concentric with the through hole 3 is further formed on the bottom surface 5 a of the nut fitting portion 5 that is inside the wall portion 4. In other words, by expanding the diameter of the upper end portion of the through-hole 3, the stepped portion 7 that is open to the bottom surface 5a is formed. The step portion 7 has a step portion bottom surface 7a parallel to the bottom surface 5a of the nut fitting portion 5 and an inner peripheral surface 7b forming a cylindrical surface. In the illustrated example, the diameter of the stepped portion 7 is slightly smaller than the interval between two opposite sides of the hexagonal shape of the nut fitting portion 5, but the diameter is substantially equal to the interval between the two sides. Is also possible.

  The nut fitting portion 5 may be a recess recessed in a hexagonal shape when the thickness of the bottom wall of the oil pan 1 is large, or a part of the height may be a bottom of the oil pan 1. It can also be set as the structure which was depressed in the wall and the remaining part of height was enclosed by the wall part.

  A metal nut 11 is disposed together with the O-ring 12 in the through hole 3 and the nut fitting portion 5. As shown in FIG. 3, the metal nut 11 has a female screw portion 13 formed through the center thereof, and has a cylindrical portion 14 concentric with the female screw portion 13, and one end of the cylindrical portion 14. In addition, a hexagonal nut portion 15 is provided. A step surface 15 a (in other words, one end surface of the nut portion 15) between the cylindrical portion 14 and the nut portion 15 forms a plane orthogonal to the center line of the female screw portion 13. In the assembled state in which the nut 11 is assembled to the oil pan 1, the cylindrical portion 14 is fitted into the through hole 3 on the oil pan 1 side, but the diameter of the through hole 3 is larger than the diameter of the cylindrical portion 14. Slightly large, therefore, they are fitted together with a minute gap d1 left in the radial direction. Similarly, the nut part 15 is fitted to the nut fitting part 5 on the oil pan 1 side, but the radial dimension of the nut fitting part 5 is slightly larger than the radial dimension of the nut part 15, Therefore, they are fitted together with a minute gap d2 left in the radial direction. That is, the nut 11 does not fit closely to the through-hole 3 or the nut fitting portion 5 but fits in a state that can be displaced by a minute amount in the radial direction. Note that the two minute gaps d1 and d2 may be equal to each other or slightly different sizes.

  Further, when the nut 11 is fitted to the nut fitting portion 5, the step surface 15a covers the step portion 7, so that the annularly continuous space, that is, the O-ring housing portion 16 is formed in the oil pan. 1 and the nut 11. The O-ring accommodating portion 16 has a rectangular cross section, and is provided on four surfaces including a step bottom surface 7a and an inner peripheral surface 7b of the step portion 7, a step surface 15a of the nut 11, and an outer peripheral surface 14a of the cylindrical portion 14. being surrounded. The O-ring 12 accommodated in the O-ring accommodating portion 16 is a general O-ring made of silicone rubber or the like, and in an assembled state, the outer peripheral surface of the inner peripheral surface 7b of the stepped portion 7 and the cylindrical portion 14 It is sandwiched between the surface 14a in a compressed state. That is, the O-ring 12 seals the space between the inner peripheral surface 7b of the stepped portion 7 and the outer peripheral surface 14a of the cylindrical portion 14 in the radial direction.

  The metal drain plug 2 combined with the nut 11 has a male screw portion 21 screwed into the female screw portion 13, a hexagonal head portion 22, and a circular shape at the base portion of the head portion 22. A flange portion 23 is provided. The end surface of the flange portion 23, that is, the flange surface 23 a is larger in diameter than the through hole 3 and extends to the outer peripheral side from the opening edge of the through hole 3. The drain plug 2 is fastened to the nut 11 with an annular gasket 25 attached to the outer periphery of the male screw portion 21. As the gasket 25, for example, a flat metal packing made of a relatively soft metal such as plastically deformable copper is used, but other types of gaskets such as a non-metallic gasket may be used. Here, the gasket 25 has an outer diameter corresponding to the end surface 14b of the cylindrical portion 14 of the metal nut 11, and the cylindrical portion 14 end surface 14b of the metal nut 11 and the metal drain plug 2 having high rigidity. The flange surface 23a is narrowly pressed. In other words, the gasket 25 is configured so as to be smaller than the diameter of the through hole 3 and not to protrude from the resin material surface outside the through hole 3, that is, the oil pan 1 outer surface 1a.

  On the other hand, regarding the dimensional relationship between the respective parts in the axial direction, if the stepped surface 15a of the nut 11 is in contact with the bottom surface 5a of the nut fitting portion 5, the end surface 14b of the cylindrical portion 14 is located near the lower end of the through hole 3. When the axial thickness of the gasket 25 is added, the bottom surface of the gasket 25 slightly protrudes downward from the through hole 3. More specifically, when the drain plug 2 is fastened to the nut 11 with a reference tightening torque and a predetermined load is applied to the gasket 25 (that is, the gasket 25 is deformed by a predetermined amount in the axial direction), the nut 11 The distance between the step surface 15a and the flange surface 23a of the drain plug 2 is the thickness of the oil pan 1 in the nut fitting portion 5, that is, between the bottom surface 5a of the nut fitting portion 5 and the outer surface 1a of the oil pan 1. The axial length of the cylindrical portion 14 and the dimensions of the gasket 25 are set so that the distance from the distance does not fall and therefore the bottom wall of the oil pan 1 is not subjected to a compressive load.

  In the illustrated example, in consideration of the tolerance of each part, the stepped surface 15a of the nut 11 and the flange of the drain plug 2 in a state where a predetermined load is applied to the gasket 25 (that is, the gasket 25 is deformed by a predetermined amount in the axial direction). Each part so that the distance between the surface 23a is slightly larger than the thickness of the oil pan 1 in the nut fitting part 5, that is, the distance between the bottom face 5a of the nut fitting part 5 and the outer surface 1a of the oil pan 1. Are set between the step surface 15a of the nut 11 and the bottom surface 5a of the nut fitting portion 5, or between the oil pan 1 outer surface 1a and the flange surface 23a of the drain plug 2 in the axial direction. The minute gap remains. In the actual fastening operation, the O-ring 12 exists between the nut 11 and the oil pan 1, and the nut portion 15 is slightly lifted from the bottom surface 5a of the nut fitting portion 5 in the initial state. As the drain plug 2 is tightened, the flange surface 23a first comes into contact with the outer surface 1a of the oil pan 1, and finally, a minute gap is formed between the step surface 15a of the nut 11 and the bottom surface 5a of the nut fitting portion 5. d3 remains. Since the minute gap d3 is extremely small, it is not drawn in FIG.

  Thus, in the above configuration, the gap between the metal drain plug 2 and the metal nut 11 is sealed in the axial direction by the gasket 25 that is narrowly pressed between the end face 14b of the cylindrical portion 14 and the flange face 23a. Since both the metal drain plug 2 and the nut 11 have high rigidity, the axial force necessary for the sealing can be surely given, and the sealing performance is as high as that of the drain plug in a general metal oil pan. can get.

  On the other hand, the gap between the synthetic resin oil pan 1 and the metal nut 11 is sealed in the radial direction by the O-ring 12 accommodated in the O-ring accommodating portion 16 as described above. Here, the tightening of the drain plug 2 does not affect the O-ring 12. That is, in the state where the drain plug 2 is tightened with the reference tightening torque, the axial force of the drain plug 2 does not act on the synthetic resin oil pan 1 as described above. Therefore, even in the tightened state, the metal nut 11 can move together with the drain plug 2 in the radial direction within the range of the minute gaps d1 and d2. Therefore, the metal nut 11 can be moved by the elasticity of the O-ring 12. Eleven self-centering operations are performed. In other words, the metal nut 11 is always concentric with the drain plug 2 with respect to the inner peripheral surface 7 b (and thus the through hole 3) of the step portion 7, and the inner peripheral surface 7 b of the step portion 7 and the outer peripheral surface 14 a of the cylindrical portion 14. The spacing in the radial direction between them is always constant over the entire circumference. Therefore, a good sealing property can be obtained over the entire circumference of the O-ring 12. For example, even if there is a relative thermal expansion between the synthetic resin oil pan 1 and the metal nut 11, There is no leakage.

  If the axial force of the drain plug 2 acts on the bottom wall of the oil pan 1 around the through hole 3, the nut 11 is fixed at a position that is eccentric with respect to the center of the through hole 3. As a result, the axial force of the drain plug 2 is reduced due to the plastic deformation (so-called “sagging”) of the bottom wall of the oil pan 1 over time.

  In the above embodiment, the hexagonal nut portion 15 of the metal nut 11 is shown. However, the nut portion 15 may be any shape as long as the nut 11 can be held so as not to rotate with respect to the oil pan 1. Such a shape may be used. For example, FIG. 4 shows an example of a square nut portion 15, but a spline-like uneven shape can also be used. In the example of FIG. 1, the depth of the nut fitting portion 5 (the height of the wall portion 4) is equal to the height of the nut portion 15, but the present invention is not necessarily limited to this and is held so as not to rotate. If possible, the depth of the nut fitting portion 5 is arbitrary. For example, the nut fitting portion 5 can be formed deeper so that the nut 11 does not jump out of the nut fitting portion 5 when the drain plug 2 is removed.

  Next, FIGS. 5 and 6 show a second embodiment in which the metal nut 11 is prevented from coming out into the nut fitting portion 5 in consideration of workability when the drain plug 2 is attached / detached. ing. That is, the wall portion 4 constituting the hexagonal nut fitting portion 5 is extended to a height that exceeds the upper end of the nut portion 15 and protrudes inward from the upper end edge of the wall portion 4. A mating protrusion 31 is provided.

  As shown in FIG. 6, the engaging protrusions 31 are provided along two opposing sides of the hexagonal wall portion 4, and the nut 11 is press-fitted into the nut fitting portion 5 to synthesize the engaging protrusion 31. The engaging protrusions 31 facing each other are expanded by elastic deformation of the resin material, and the nut 11 can be inserted. And in the state inserted in the predetermined position, the engagement protrusion 31 engages with the upper end edge of the nut part 15, and it retains retaining.

  The engaging protrusion 31 may be provided only on a part of each side of the hexagonal wall portion 4 or, conversely, may be provided over the entire circumference of the hexagonal wall portion 4. FIG. 7 shows an embodiment in which engagement protrusions 31 are provided on all six sides. In this embodiment, the wall portion 4 is axially arranged on the upper portion of the wall portion 4 so as to be divided into each side. Along each slit 32 is provided. Accordingly, the wall portions 4 of each side having the engaging projections 31 at the upper end are individually expanded and deformed, and even if the engaging projections 31 are provided on all of the six sides, the nut portion 15 is relatively pressed. Easy.

  FIG. 8 shows an example of the cross-sectional shape of the engaging protrusion 31. In this example, the tapered surface 33 serving as a guide surface is provided on the inner side of the tip so that the engaging protrusion 31 is easily expanded when the nut 11 is press-fitted. And the engagement surface 34 bent in an L-shape forms a horizontal surface (a surface parallel to the bottom surface 5a of the nut fitting portion 5) bent by 90 ° with respect to the wall portion 4, and the engagement surface 34 is a nut. Engage with the end face of the part 15. Therefore, basically, once the metal nut 11 is assembled, the nut 11 cannot be removed.

  FIG. 9 shows a modified example of the engaging protrusion 31. In this example, the engaging protrusion 31 bulges in a substantially semicircular cross section toward the inside of the wall portion 4. That is, the arcuate inlet side guide surface 35 and the arcuate engagement surface 36 are continuous, and the wall 4 is expanded outward by the action of the inlet side guide surface 35 when the nut 11 is press-fitted. After opening and press-fitting, the engaging surface 36 engages with the end edge of the nut portion 15. Since the engaging surface 36 has an arc shape as described above, if the nut 11 is pressed upward from the assembled position, the engaging protrusion 31 is expanded and the nut 11 can be removed. is there. In particular, in this embodiment, a tapered surface 15b having a relatively large chamfer is provided on the end edge of the nut portion 15, and the engagement protrusion 31 (engagement surface 36) is engaged with the tapered surface 15b. Therefore, the nut 11 can be taken out more smoothly.

  FIG. 10 shows still another modification of the engagement protrusion 31. In this example, the engagement projection 31 has a tapered surface 37 serving as a guide surface so that the engagement projection 31 can be easily expanded when the nut 11 is press-fitted, and the engagement with the end edge of the nut portion 15. The mating surface 38 is a reverse tapered surface. Further, a chamfered tapered surface 15 b is formed at the edge of the nut portion 15. Therefore, as in the embodiment of FIG. 9, the nut 11 can be removed relatively easily.

  As described above, according to the configuration in which the engagement protrusion 31 is provided in the nut fitting portion 5 and the metal nut 11 is held, the metal nut 11 is not prepared when the drain plug 2 is attached or detached. Further, it is avoided that the nut fitting portion 5 is separated from the nut fitting portion 5, and the workability is improved. In addition, when the nut 11 is assembled, there is no need to bend and squeeze the metal part, and the nut 11 can be attached to the oil pan 1 simply by pushing it in. Even when the engagement protrusion 31 prevents the seal from being removed, the same effect as that of the above-described embodiment can be obtained for the seal.

  As mentioned above, although the Example which applied this invention to the oil pan of the internal combustion engine was described in detail, the synthetic resin cover of this invention is not limited to an oil pan, but is widely applied to various covers which require a drain plug. Is possible.

DESCRIPTION OF SYMBOLS 1 ... Synthetic resin oil pan 2 ... Drain plug 3 ... Through-hole 5 ... Nut fitting part 7 ... Step part 11 ... Metal nut 12 ... O-ring 14 ... Cylindrical part 15 ... Nut part 16 ... O-ring accommodating part 25 ... Gasket 31 ... engagement protrusion

Claims (3)

A drain plug mounting structure for a synthetic resin cover in which a metal nut is held by a synthetic resin cover and a drain plug is screwed into the female thread portion of the nut,
The metal nut includes a cylindrical portion that is concentric with the female screw portion, and a non-circular nut portion that is connected to one end of the cylindrical portion and projects from the outer peripheral surface of the cylindrical portion to the outer peripheral side,
The synthetic resin cover is provided with a through hole in which the cylindrical portion is fitted through a minute gap and an inner surface of the cover so as to surround the periphery of the through hole, and the nut portion has a minute gap. A nut fitting portion that is fitted through, and a cylindrical step portion provided concentrically with the through hole on the bottom surface of the nut fitting portion,
An O-ring that radially seals the space between the inner peripheral surface of the step portion and the outer peripheral surface of the cylindrical portion is disposed in a space generated by the step portion between the synthetic resin cover and the metal nut.
The drain plug has a flange surface that extends to the outer peripheral side from the opening edge of the through hole, and includes a gasket between the tip surface of the cylindrical portion and the flange surface,
In a state where a predetermined load is applied to the gasket by fastening the drain plug, the synthetic nut cover is not compressed in the axial direction between the flange surface and the nut portion, and the metal nut is attached to the O-ring. A drain plug mounting structure for a synthetic resin cover, characterized in that the axial dimension of each part is set so as to be self-centering.   In a state where the gasket is deformed by a predetermined amount due to the predetermined load, the distance between the flange surface and the nut portion is slightly larger than the thickness of the synthetic resin cover in the nut fitting portion, The drain plug mounting structure for a synthetic resin cover according to claim 1, wherein a minute gap remains in the axial direction.   The drain plug mounting structure for a synthetic resin cover according to claim 1 or 2, wherein an engaging projection for preventing the nut portion from coming off is provided at an opening edge of the nut fitting portion.

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