Fluid sealing structure

Abstract

To provide a fluid sealing structure capable of suppressing the fly of a sealing agent peeled from a plug when fixing the plug to which the sealing agent is applied, into a communication hole of a housing.SOLUTION: A plug 10 has a male screw formation part 11 in which a pipe tapered male screw is formed with a rear end 10B having a larger diameter than a front end 10A and to which a sealing agent 12 is applied. A housing 2 has: a female screw formation part 21 which constitutes an inner peripheral face of a communication hole 20 and in which a female screw is formed; and a peripheral wall part 23 which constitutes an inner peripheral face of an entrance of the communication hole 20 to form a storage hole 22 having a larger diameter than the female screw formation part 21. The peripheral wall part 23 encircles the periphery of the rear end 10B of the plug 10 in a state that the male screw formation part 11 of the plug 10 is fixed to the female screw formation part 21 of the communication hole 20 with screw joint. A female screw formed on the female screw formation part 21 is a pipe parallel female screw.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a fluid sealing structure. [Background technology]

[0002] The drain plug interference prevention structure described in Patent Document 1 prevents obstacles from interfering with the drain plug and suppresses oil leakage by integrally mounting a cover body on the bottom wall of a case for a vehicle drive mechanism, the cover body consisting of a hanging part that surrounds the outer periphery of the head of the drain plug and a horizontal part that extends in the fore-and-aft direction from the lower end of the hanging part in front of the drain plug. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Jpn. Jpn. Published No. 63-2694 Summary of the Invention [Problem to be solved by the invention]

[0004] In transmissions, differential devices, and the like, a sealant is applied to the surface of the male thread of the drain plug to prevent oil leakage from communication holes such as drain holes. When the drain plug is screwed into the communication hole, the excess sealant falls off and scatters around, resulting in extra cleaning work to remove the scattered sealant.

[0005] However, the technique described in Patent Document 1 does not assume that a sealant will be applied to the drain plug, and therefore has the problem that it is not possible to prevent the sealant from scattering.

[0006] Therefore, an object of the present invention is to provide a fluid sealing structure that can prevent sealing agent from peeling off from a plug and scattering when the plug to which the sealing agent has been applied is screwed and fixed into a communicating hole in a housing. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a fluid sealing structure comprising: a communication hole formed in a housing having a fluid therein, the communication hole communicating with the inside and outside of the housing; and a plug fixed to the communication hole by a screw connection and sealing the communication hole, wherein the plug has a male thread forming portion having a tapered male thread for pipes with a larger diameter at its rear end than at its front end and to which a sealant is applied, and the housing has a female thread forming portion which forms the inner surface of the communication hole and has a female thread formed therein, and a surrounding wall portion which forms the inner surface of the entrance of the communication hole and forms a receiving hole with a larger diameter than the female thread forming portion, and wherein when the male thread forming portion of the plug is fixed to the female thread forming portion of the communication hole by a screw connection, the surrounding wall portion surrounds the periphery of the rear end of the plug. Effect of the Invention

[0008] In this way, according to the present invention, a fluid sealing structure can be provided that can prevent sealing agent from peeling off from the plug and scattering when the plug to which the sealing agent has been applied is fixed to the communicating hole of the housing. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a communication hole of a power transmission device having a fluid sealing structure according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view of a plug of a power transmission device having a fluid sealing structure according to one embodiment of the present invention. [Diagram 3] FIG. 3 is a cross-sectional view of a power transmission device equipped with a fluid sealing structure according to one embodiment of the present invention, showing a state in which a plug is screwed and fixed into a communication hole of a housing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A fluid sealing structure according to an embodiment of the present invention is a fluid sealing structure including a communication hole formed in a housing having a fluid therein and communicating between the inside and the outside of the housing, and a plug that is fixed to the communication hole by screw engagement and seals the communication hole, the plug having a male thread forming portion having a tapered male thread for pipes with a larger diameter at its rear end than at its front end and coated with a sealant, the housing having a female thread forming portion forming an inner circumferential surface of the communication hole and having a female thread formed therein, and a peripheral wall portion forming an inner circumferential surface of an inlet of the communication hole and forming a receiving hole with a larger diameter than the female thread forming portion, the peripheral wall portion surrounding the periphery of the rear end of the plug when the male thread forming portion of the plug is fixed to the female thread forming portion of the communication hole by screw engagement. As a result, the fluid sealing structure according to an embodiment of the present invention can suppress scattering of sealant peeled off from the plug when the plug coated with sealant is fixed to the communication hole of the housing. EXAMPLES

[0011] A fluid sealing structure according to an embodiment of the present invention will be described below with reference to the drawings. Figures 1 to 3 are diagrams illustrating a fluid sealing structure according to an embodiment of the present invention.

[0012] As shown in Fig. 1, the power transmission device 1 includes a housing 2. The power transmission device 1 is, for example, a manual transmission, an automatic transmission, or a differential device. The housing 2 has a fluid in its interior 2A. The fluid in the interior 2A of the housing 2 is oil when the power transmission device 1 is a manual transmission or a differential device, and is ATF (Automatic Transmission Fluid) when the power transmission device 1 is an automatic transmission.

[0013] 1 and 3, a cylindrical communication hole 20 is formed in the housing 2. The communication hole 20 communicates between the interior 2A and the exterior 2B of the housing 2. The communication hole 20 is a filler hole that fills a fluid such as oil from the exterior 2B into the interior 2A of the housing 2, or a drain hole that discharges a fluid such as oil from the interior 2A of the housing 2 to the exterior 2B. The communication hole 20 is disposed horizontally on a side surface of the housing 2.

[0014] 3, the communication hole 20 is sealed by a cylindrical plug 10. The plug 10 is fixed to the communication hole 20 by screw connection.

[0015] Here, there are two types of threaded connections: one whose main purpose is mechanical connection, and one whose main purpose is tightness. The threaded connection between the plug 10 and the communication hole 20 is mainly intended to provide tightness. In a threaded connection whose main purpose is tightness, when a tapered male pipe thread (denoted as R in the JIS standard) is used as the male thread, the female thread that can be combined with this tapered male pipe thread is a parallel female pipe thread (denoted as Rp in the JIS standard) or a tapered female pipe thread (denoted as Rc in the JIS standard). These combinations are possible by applying a sealant to the tapered male pipe thread.

[0016] As shown in Fig. 2, the plug 10 has a truncated cone shape, with one bottom surface having a smaller diameter than the other bottom surface, and a side surface forming an external thread forming portion 11. An external thread forming portion 11 is formed with a tapered external pipe thread in which a rear end portion 10B (larger diameter bottom surface side) has a larger diameter than a front end portion 10A (smaller diameter bottom surface side). The external thread forming portion 11 constitutes the entire side surface of the plug 10, and the entire side surface of the plug 10 is formed with a tapered external pipe thread.

[0017] As shown in FIG. 3, a sealant 12 is applied to the male thread forming portion 11 to ensure hermeticity. In the figure, the sealant 12 is represented by hatching with diagonal lines slanting upward to the right. The sealant 12 fills the gap between the male thread shape and the female thread shape in the screw connection to improve the sealing performance. The sealant 12 used in the present invention is also called a pre-coat agent, and is applied to the plug 10 in advance. This sealant 12 is modified by being screwed into the screw hole to fill the gap of the thread. A recess 10C is formed at the rear end 10B of the plug 10 to engage with a fastening tool such as a hexagonal wrench.

[0018] 1 and 3, the communication hole 20 of the housing 2 has an internal thread forming portion 21 and a surrounding wall portion 23. The internal thread forming portion 21 constitutes the inner circumferential surface on the rear side (interior 2A side) of the communication hole 20. The surrounding wall portion 23 constitutes the inner circumferential surface on the inlet side (outer 2B side) of the communication hole 20.

[0019] An internal thread is formed in the internal thread forming portion 21, and the external thread forming portion 11 of the plug 10 is screwed into the internal thread forming portion 21. The surrounding wall portion 23 is disposed coaxially with the internal thread forming portion 21, and is formed so that its internal space forms an accommodating hole 22 having a larger diameter than the internal thread forming portion 21. Note that although the upper surface portion of the surrounding wall portion 23 in FIG. 1 (the portion that forms the outer surface of the housing 2) protrudes in a cylindrical shape, this does not necessarily have to be the case. The surrounding wall portion 23 does not represent the portion that protrudes in a cylindrical shape, but represents the portion where the accommodating hole 22 having a larger diameter than the internal thread forming portion 21 is formed (the portion at the inlet of the communication hole 20).

[0020] In this manner, in this embodiment, the surrounding wall portion 23 (accommodating hole 22) is provided at the entrance portion of the communicating hole 20, and the female thread forming portion 21 is provided at the remaining portion of the communicating hole 20. In other words, instead of forming a female thread over the entire communicating hole 20 including the entrance portion, the large-diameter accommodating hole 22 is formed at the entrance portion of the communicating hole 20 by countersinking or the like.

[0021] With the male thread forming portion 11 of the plug 10 fixed to the female thread forming portion 21 of the communicating hole 20 by screw connection, the peripheral wall portion 23 surrounds the periphery of the rear end portion 10B of the plug 10. In other words, at the inlet portion of the communicating hole 20, a space 24 is present between the rear end portion 10B of the plug 10 and the peripheral wall portion 23 so as to surround the plug 10. Since the male thread formed in the plug 10 is a tapered male thread for pipes, the protruding end side of the plug 10 is the large-diameter bottom side, which becomes the large-diameter rear end portion 10B, and the space 24 becomes closer to the peripheral wall portion 23 as it approaches the protruding end. In other words, the gap between the plug 10 and the peripheral wall portion 23 becomes narrower as it approaches the protruding end of the plug 10, and the opening of the space 24 becomes narrower.

[0022] In this embodiment, the female thread formed in the female thread forming portion 21 is a parallel female thread for pipes. Note that the female thread formed in the female thread forming portion 21 may be a tapered female thread for pipes.

[0023] As described above, in this embodiment, the plug 10 has a male thread forming portion 11 in which a tapered male thread for pipes having a larger diameter is formed at the rear end portion 10B than at the front end portion 10A, and to which a sealant 12 is applied. The housing 2 has a female thread forming portion 21 in which a female thread is formed and which forms the inner circumferential surface of the communicating hole 20, and a surrounding wall portion 23 in which a receiving hole 22 having a larger diameter than the female thread forming portion 21 is formed and which forms the inner circumferential surface of the inlet of the communicating hole 20. In the surrounding wall portion 23, when the male thread forming portion 11 of the plug 10 is fixed to the female thread forming portion 21 of the communicating hole 20 by screw engagement, a space 24 with a narrowed opening to the outside surrounds the periphery of the rear end portion 10B of the plug 10.

[0024] As a result, when the plug 10 to which the sealing agent 12 is applied is rotated and screwed into the communication hole 20 of the housing 2 for assembly, the excess sealing agent 12 that cannot enter the female thread and is scraped off is pushed by the other excess sealing agent 12 and moves along the inner wall surface of the peripheral wall portion 23, rotating together with the plug 10. However, as the plug 10 moves to the far side, it is likely to remain inside the receiving hole 22, and since the gap between the plug 10 and the peripheral wall portion 23 becomes narrower toward the protruding end of the plug 10 and the opening of the space 24 becomes narrower, as shown in Fig. 3, the sealing agent 12A peeled off from the plug 10 is held in the space 24 inside the receiving hole 22. Therefore, when the plug 10 to which the sealing agent 12 is applied is fixed to the communication hole 20 of the housing 2, scattering of the sealing agent 12A peeled off from the plug 10 can be suppressed. Furthermore, since the male thread formed on the plug 10 is a tapered male thread for pipes, the space 24 inside the receiving hole 22 becomes narrower toward the upper part and is less susceptible to external influences, so that the sealant 12A peeled off from the plug 10 can be stably held.

[0025] In this embodiment, the female thread formed in the female thread forming portion 21 is a parallel female thread for pipes.

[0026] As a result, parallel female pipe threads are easier to machine than tapered female pipe threads, and manufacturing costs can be reduced.

[0027] Although an embodiment of the present invention has been disclosed, it is obvious that modifications can be made by those skilled in the art without departing from the scope of the present invention. It is intended that all such modifications and equivalents are included in the following claims. For example, in the embodiment shown in FIG. 3, the plug 10 protrudes from the receiving hole 22 (the surrounding wall 23), but the plug 10 does not have to protrude from the surrounding wall 23. If the plug 10 does not protrude from the surrounding wall 23, the surrounding wall 23 can protect the plug 10. Also, if the plug 10 does not protrude from the surrounding wall 23, the maximum diameter portion of the plug 10 is located inside the receiving hole 22, so that the gap between the plug 10 and the surrounding wall 23 can be set to a value intended to suppress scattering. [Explanation of symbols]

[0028] 2. Housing 2A internal 2B External 10 Plug 10A Tip 10B Rear end 11 Male thread forming part 12 Sealant 20 Communication hole 21 Female thread forming section 22 Receiving hole 23 Surrounding wall

Claims

1. a communication hole formed in a housing having a fluid therein and communicating between the inside and the outside of the housing; a plug fixed to the communication hole by screw connection and sealing the communication hole, The plug is A tapered male thread for pipes is formed at a rear end portion thereof, the rear end portion being larger in diameter than the front end portion thereof, and the male thread forming portion is coated with a sealant, The housing includes: a female thread forming portion that constitutes an inner circumferential surface of the communication hole and has a female thread formed thereon; a surrounding wall portion that constitutes an inner circumferential surface of the inlet of the communication hole and forms a receiving hole having a diameter larger than that of the female thread forming portion, a peripheral wall portion surrounding a rear end portion of the plug when the male thread portion of the plug is fixed to the female thread portion of the communication hole by a screw connection.

2. 2. The fluid sealing structure according to claim 1, wherein the female thread formed in the female thread forming portion is a parallel female thread for pipes.

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