Bung hole formation method

Abstract

To provide a bung hole formation method that can reduce occurrence of poor welding, reduce a load to process control and quality control, and manufacture a bung hole at an inexpensive price.SOLUTION: A formation method for a bung hole 2, which is formed in a housing cover 12 of an accelerator housing 1, with which a drain bolt 3 engages, and which is sealed tightly, comprises a plug insertion process in which a cylindrical part 22 of a plug 20 having the cylindrical part 22 and a flange part 21 is inserted in an opening 14 which is formed in the housing cover 12 and has a container side cylindrical part 15 projecting to an inner side; a plug joining process in which the flange part 21 and the housing cover 12 are welded and joined to the whole circumference of the flange part 21; and a screw part formation process in which after the plug joining process, a screw part 24 is formed on an inside surface of the cylindrical part 22.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for forming a filler port formed in a metal container into which a liquid is poured and which is sealed by a screwed lid. [Background technology]

[0002] 7, for example, an injection section 200 for injecting gear oil (liquid) into a cover 120 of a metal axle housing 100 has an opening 140 drilled in the cover 120, a through-hole 150 having a generally T-shaped cross section drilled around the central axis of the opening 140, a plug 210 having a threaded circumferential surface of the through-hole 150 fitted into the opening 140, and the plug 210 is welded to the cover 120 at a welded portion X at the outer periphery of the opening 140. A technology has also been disclosed (for example, Patent Document 1) in which a lid 300 is detachably screwed into the through-hole 150. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 126934 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology of Patent Document 1, when welding plug 210 to cover 120 at the outer peripheral edge of opening 140, this is generally done by arc welding, but arc welding is prone to welding defects such as pinholes due to variations in precision of parts and misalignment that occurs when setting the welding jig. Also, to prevent unnecessary welding, the worker needs to be highly skilled.

[0005] Furthermore, the occurrence of defects increases costs, and the burden on process control and quality control for reducing defects increases, resulting in increased costs.

[0006] Furthermore, the plug 210 needs to be thick to ensure the length of the screw groove, and expensive materials such as cold-forged products are used, which increases costs.

[0007] The present invention provides a method for forming a pouring port that reduces the occurrence of welding defects, reduces the burden on process control and quality control, and allows the pouring port to be manufactured inexpensively. [Means for solving the problem]

[0008] A method for forming an injection port according to a first aspect of the present invention is a method for forming an injection port that is formed in a metal container into which a liquid is injected and that is sealed by a lid that is screwed onto it, and is characterized by comprising: a plug insertion process for inserting the cylindrical portion of a plug, which has a cylindrical portion and a flange portion, into an opening formed in the container and has a container-side cylindrical portion that protrudes toward the inside; a plug joining process for welding the flange portion to the container around the entire circumference of the flange to join them; and a thread forming process for forming a thread portion on the inner surface of the cylindrical portion of the plug after the plug joining process.

[0009] A method for forming a filler port according to a first aspect of the present invention includes a plug insertion step of inserting the tubular portion of a plug, which has a tubular portion and a flange portion, into an opening formed in a container and has a container-side tubular portion protruding inward, a plug joining step of joining the flange portion to the container by welding the entire circumference of the flange, and a thread forming step of forming a thread portion on the inner surface of the tubular portion of the plug after the plug joining step.Since the thread portion is not affected by heat during welding, it is possible to process and form the thread portion with high precision.Furthermore, the plug, in particular, can be formed from a thin metal material.

[0010] A second aspect of the present invention relates to a method for forming an injection port according to the first aspect, wherein in the plug insertion step, the inner container-side surface of the container-side cylindrical portion and the outer container-side surface of the plug cylindrical portion abut against each other.

[0011] In the method for forming an injection port according to the second aspect of the present invention, in the plug insertion step, the container-side inner surface of the container-side tubular portion and the outer surface of the plug tubular portion come into contact, and therefore, in the thread forming step for forming a thread on the inner surface of the plug tubular portion, the container-side tubular portion pushes back the force that spreads the plug tubular portion outward, preventing the plug tubular portion from deforming toward the container-side tubular portion, and as a result, the thread can be processed and formed with high precision.

[0012] A method of forming a filler port according to a third aspect of the present invention is a method of forming a filler port according to the first or second aspect, in which the plug is produced by pressing a flat plate. In the method of forming a filler port according to the third aspect of the present invention, the plug is produced by pressing a flat plate, which makes it possible to produce the plug inexpensively. Here, "press processing" refers to a processing method in which a member is clamped between dies and pressure is applied, and includes shearing, bending, drawing, and the like.

[0013] A fourth aspect of the present invention is a method for forming an injection port according to any one of the first to third aspects, wherein a conductive protrusion is formed circumferentially on the cylindrical portion side of the flange, and the plug joining step is performed by ring projection welding.

[0014] In the method for forming a filler port according to the fourth aspect of the present invention, a conductive protrusion is formed circumferentially on the cylindrical portion of the flange, and the plug joining step is performed by ring projection welding, which makes it easy to automate the welding step and enables efficient welding in a short time, resulting in low-cost processing.

[0015] Furthermore, since there is no effect of deformation or the like due to heat during welding, the surface precision of the plug flange can be maintained, and a stable sealing surface against the lid can be ensured. [Effects of the Invention]

[0016] This method for forming a filling port is formed in a metal container into which a liquid is poured and which is sealed by a screw-on lid, and includes the following steps: a plug insertion step for inserting the cylindrical portion of a plug, which has a cylindrical portion and a flange portion, into an opening formed in the container and has a container-side cylindrical portion protruding toward the interior; a plug joining step for joining the flange portion to the container by welding the entire circumference of the flange; and a thread forming step for forming a thread portion on the inner surface of the cylindrical portion of the plug after the plug joining step. Therefore, the thread portion is not affected by the heat of welding, and the thread portion can be precisely machined and formed. Furthermore, the plug, in particular, can be formed from a thin metal plate. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 2 is a rear perspective view of an axle housing showing an embodiment of the present invention. [Figure 2] 2 is a cross-sectional view taken along the line AA in FIG. 1 after the metal gasket and the drain bolt have been attached. [Figure 3] 1A and 1B are front and BB cross-sectional views of a plug used in an embodiment; [Figure 4] FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1 for explaining a plug insertion step. [Figure 5] FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1 for explaining a plug joining step. [Figure 6] FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1, illustrating a thread forming step. [Figure 7] FIG. 1 is a partially enlarged cross-sectional view of an oil injection portion of a conventional axle housing (Patent Document 1). DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment of the present invention will be described with reference to Figures 1 to 6. In this embodiment, the metal container is an automobile axle housing (a storage case for gears that perform a type of gear conversion when transmitting rotation of a propeller shaft to an axle). The materials of the housing cover 12 and the plug 20, the shape and dimensions of the plug 20, etc., described below are examples and may be changed as appropriate depending on the type of container, lid, etc.

[0019] As shown in Figure 1, the axle housing 1 includes a housing center section 10 and a pair of left and right axle tube sections 11 connected to the left and right sides of the housing center section 10. The housing center section 10 houses a differential gear (not shown), and a case that supports a propeller shaft is attached to its front side, and a housing cover 12 is attached to its rear side. In addition, upper brackets 13 to which upper control arms (not shown) are respectively connected are provided on the outer surface.

[0020] The hollow interior of the housing center part 10, which is a metal container, is filled with gear oil (liquid) to approximately 1 / 3 capacity. A housing cover 12 of the housing center part 10 is fitted with a filler port 2 for pouring gear oil.

[0021] 2 is a cross-sectional view taken along line AA in FIG. 1 after the metal gasket 4 and drain bolt 3 have been attached, with the metal gasket 4 inserted between the housing cover 12 and the drain bolt 3. The drain bolt 3 is removed from the filler port 2 when pouring oil into the hollow interior of the housing center section 10 and when setting the oil level immediately after this operation, but is left attached to the filler port 2 at other times.

[0022] A container-side cylindrical portion 15 that protrudes inward is formed by burring at the opening 14 of the housing cover 12. A plug 20 is joined by welding to the opening 14. A threaded portion 24 is formed on the inner surface 25 (FIG. 3(b)) of the cylindrical portion 22 of the plug 20.

[0023] The housing cover 12 is made of hot-rolled steel sheet for automobile structures. The thickness (t1) of the housing cover 12 is 3.5 mm, the inner diameter (φ1) of the container-side cylindrical portion 15 is 21 mm, the depth (h1) of the container-side cylindrical portion 15 from the top surface of the housing cover 12 is 10 mm, and the bending radius (R1) between the top surface of the housing cover 12 and the container-side cylindrical portion 15 is 5 mm.

[0024] 3 shows a plug 20 used in an embodiment, where (a) is a front view and (b) is a B-B cross-sectional view of (a). The plug 20 is made of a general structural rolled steel plate by pressing a flat plate. The plug 20 has a flange portion 21 and a tubular portion 22. A bend R is formed at the connecting portion between the flange portion 21 and the tubular portion 22. A conductive protrusion 23 is formed circumferentially on the flange portion 21 facing the tubular portion 22.

[0025] In plug 20, the plate thickness (t2) is 2.6 mm, the outer diameter (φ2) of flange portion 21 is 30 mm, the inner diameter (φ3) of tubular portion 22 is 16 mm, the outer diameter (φ4) of tubular portion 22 is 21.2 mm, the bend R (R2) between flange portion 21 and tubular portion 22 is 4 mm, and the depth (h2) of tubular portion 22 from the upper surface of flange portion 21 is 10 mm. In addition, the height of conductive protrusion 23 from the lower surface of flange portion 21 is 1 mm.

[0026] Here, with regard to the housing cover 12 and the plug 20, the relationship between the inner diameter (φ1) of the container-side cylindrical portion 15 of the housing cover 12 and the outer diameter (φ4) of the cylindrical portion 22 of the plug 20 is set to φ4≧φ1 so that the outer surface 26 of the cylindrical portion 22 of the plug 20 can be inserted while abutting against the container-side inner surface 16 (Figures 1 and 4) of the container-side cylindrical portion 15 of the housing cover 12.

[0027] In addition, the depth (h1) of the container side cylindrical portion 15 from the top surface of the housing cover 12 is set so that when the threaded portion 24 is formed on the inner surface 25 of the cylindrical portion 22, the container side cylindrical portion 15 is at the same position as the tip portion of the cylindrical portion 22 or lower than the tip portion of the cylindrical portion 22.

[0028] A method for forming the injection port 2 will be described with reference to Figures 4 to 6. Figure 4 is a cross-sectional view taken along line AA in Figure 1, illustrating the plug insertion step.

[0029] The inside (the lower side in the drawing) of the opening 14 of the housing cover 12 is set on the lower press-fitting jig 30. Next, the plug 20 is placed in the opening 14 of the housing cover 12 with the cylindrical portion 22 facing downward.

[0030] Next, an upper press-fitting jig 31 having a portion that penetrates the cylindrical portion 22 of the plug 20 is set above the flange portion 21 of the plug 20 and pressed in the direction of the arrow to insert the cylindrical portion 22 of the plug 20 into the container-side cylindrical portion 15 of the opening 14 of the housing cover 12, and the conductive protrusion 23 of the flange portion 21 is brought into contact with the housing cover 12.

[0031] Thereafter, the upper press-fitting jig 31 is removed from the plug 20 , and the housing cover 12 is removed from the lower press-fitting jig 30 .

[0032] 1. First, the inside of housing cover 12 with plug 20 inserted therein is set on lower welding jig 32. Next, upper welding jig 33 is placed on flange portion 21 of plug 20, and upper welding jig 33 is pressed downward.

[0033] Next, current is passed between the upper welding jig 33 and the lower welding jig 32 to heat and melt the contact surfaces of the current-carrying protrusion 23 of the plug 20 and the housing cover 12, joining the plug 20 and the housing cover 12 around their entire circumference by ring projection welding.

[0034] Thereafter, the upper welding jig 33 is pulled upward, and the housing cover 12 is removed from the lower welding jig 32.

[0035] Fig. 6 is a cross-sectional view taken along the line AA in Fig. 1, illustrating the thread forming process. For example, a thread cutting tool 34, such as a tap, is rotated and moved downward to form the threaded portion 24 (Fig. 2) having a thread shape on the inner surface 25 of the cylindrical portion 22 of the plug 20.

[0036] At this time, a force in the direction of the dashed arrow is applied to the inner surface 25 of the tubular portion 22 by the thread cutting tool 34, but because the tubular portion 22 of the plug 20 is press-fitted into and abuts against the container-side tubular portion 15 of the housing cover 12, it is pushed back in the direction of the solid arrow from the container-side tubular portion 15. Therefore, the tubular portion 22 of the plug 20 is not deformed in the thread forming process, and the desired thread portion 24 is formed.

[0037] As described above in detail, according to this embodiment, the following effects can be obtained. (1) The above embodiment includes a plug insertion step of inserting the tubular portion 22 of the plug 20, which has a tubular portion 22 and a flange portion 21, into the opening 14 formed in the housing cover 12 of the axle housing 1 and has a container-side tubular portion 15 protruding inward, a plug joining step of joining the flange portion 21 to the housing cover 12 by welding the entire circumference of the flange portion 21, and a thread forming step of forming the thread portion 24 on the inner surface 25 of the tubular portion 22 of the plug 20 after the plug joining step. Therefore, the thread portion 24 is not affected by heat during welding, and the thread portion 24 can be processed and formed with high precision. Furthermore, the plug 20 can be formed from a metal material with a thin plate thickness.

[0038] (2) In the above embodiment, in the plug insertion step, the container-side inner surface 16 of the container-side tubular portion 15 comes into contact with the outer surface 26 of the tubular portion 22 of the plug 20. Therefore, in the thread forming step of forming the thread portion 24 on the inner surface 25 of the tubular portion 22 of the plug 20, the container-side tubular portion 15 pushes back the force that spreads the tubular portion 22 outward, thereby preventing the tubular portion 22 of the plug 20 from deforming toward the container-side tubular portion 15. As a result, the thread portion 24 can be processed and formed with high precision.

[0039] (3) In the above embodiment, the plug 20 is manufactured by pressing a flat plate of a general structural rolled steel plate. Therefore, the plug 20 can be manufactured at lower cost than when a forged product is used.

[0040] (4) In the above embodiment, the conductive protrusion 23 is formed circumferentially on the cylindrical portion 22 side of the flange portion 21, and the plug joining process is performed by ring projection welding. This makes it easy to automate the welding process and enables efficient welding in a short time, resulting in low-cost processing. Furthermore, since there is no effect of deformation or the like due to heat during welding, the surface precision of the flange portion 21 of the plug 20 on the drain bolt 3 side can be maintained, and a stable sealing surface against the drain bolt 3 can be ensured.

[0041] Claim 4 of the claims further includes the following configuration. 4. The method for forming a filler port according to claim 3, wherein a conductive protrusion is formed circumferentially on the cylindrical portion side of the flange portion, and the plug joining step is performed by ring projection welding.

[0042] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the object of the present invention.

[0043] For example, in the above embodiment, the inlet 2 for injecting differential gear oil into the axle housing 1 was described, but the present invention can also be applied to other cases in which the inlet is formed in a metal container into which liquid is injected and is sealed by a screw-on lid, and in which a separate member is joined to the container by welding. [Explanation of symbols]

[0044] 1 axle housing 2 Inlet 10 Housing Center 12 Housing cover 14 Openings 15 Container side cylindrical part 16 Inner surface of container 20 plugs 21 Flange 22 Cylindrical part 23 Current-carrying protrusion 24 Threaded part 25 Inner side 26. Outer surface

Claims

1. A method for forming an injection port formed in a metal container into which a liquid is injected and sealed by a screw-on lid, comprising: a plug insertion step of inserting a cylindrical portion of a plug having a cylindrical portion and a flange portion into an opening formed in the container and having a container-side cylindrical portion protruding toward the interior of the container; a plug joining step of joining the flange portion and the container by welding the entire periphery of the flange portion; a thread forming step of forming a thread on the inner surface of the cylindrical portion of the plug after the plug joining step.

2. 2. The method for forming an injection port according to claim 1, wherein in the plug inserting step, an inner surface of the container-side cylindrical portion and an outer surface of the cylindrical portion of the plug abut against each other.

3. 3. The method for forming an injection port according to claim 1, wherein the plug is manufactured by press-molding a flat plate.

4. 3. The method for forming a filler port according to claim 1, wherein a conductive protrusion is formed circumferentially on the cylindrical portion side of the flange portion, and the plug joining step is performed by ring projection welding.

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