Ultrasonic welding method

Abstract

To provide an ultrasonic welding method capable of suppressing generation of burrs and obtaining excellent welding strength and sealing performance with small welding energy.SOLUTION: The method comprises: a preparation step of preparing a first member 1 comprising a welding groove 10 having an angle θ1 formed by left and right first inclined sides 13, 13, and a second member 2 comprising a welding rib 20 having a base portion 20a with a width L2 between left and right second vertical sides 22, 22 that is narrower than a width L1 of the welding groove 10, a tip portion 20b having an angle θ2 formed by left and right second inclined sides 23, 23 that is larger than θ1, and side surface corner portions 24; a first step of inserting the welding rib 20 into the welding groove 10, first bringing the side surface corner portions into contact with the first inclined sides, and applying load and ultrasonic vibration in an insertion direction of the welding rib; a second step of forming a V-shaped cross-sectional space 30 between the welding groove and the welding rib, and accommodating, compressing, and melting welding burrs in the V-shaped cross-sectional space; and a third step of forming a V-shaped cross-sectional welded portion 40 between the welding groove and the welding rib.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an ultrasonic welding method for welding resin members using ultrasonic vibrations. [Background technology]

[0002] One ultrasonic welding method involves overlapping two resin components, applying pressure in the overlapping direction, and applying ultrasonic vibrations to weld them together. For example, as shown in Figure 11A, a first component is placed on a receiving tool, and a second component is attached to a horn and placed above it. Typically, a welding rib that protrudes downward is formed on the second component, and ultrasonic vibrations are applied as the horn moves downward, causing the welding rib to sink into the first component, thereby welding the first and second components together. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4509370 [Patent Document 2] Japanese Patent Publication No. 62-221526 Summary of the Invention [Problem to be solved by the invention]

[0004] When the first and second members are welded using such conventional ultrasonic welding methods, the molten resin may overflow from the gap between the first and second members, forming burrs (welding burrs) X, as shown in FIG. 11B. Furthermore, if a large amount of sinking is required in the welded portion, a relatively large amount of welding energy is required. Applying a large amount of welding energy can also result in burrs (hammer burrs) Y forming not only between the first and second members but also at the contact point between the second member and the horn. When the welded parts are used in precision equipment, such burrs may cause malfunctions in the equipment.

[0005] Various structures have been proposed for the welded portions of the first and second members. For example, Patent Document 1 discloses a sealed connection structure for a resin structure in which two welds are formed on the inner and outer peripheries, and the inner and outer peripheries are welded at different times, thereby providing an airtight seal. Patent Document 2 discloses an ultrasonic welding method in which a holding groove is provided in the first member and an annular wall and a welding protrusion are provided in the second member, and molten resin is collected in the gap between the wall of the holding groove and the annular wall to prevent burrs from leaking out.

[0006] However, ultrasonic welding methods such as those disclosed in Patent Documents 1 and 2 require a sufficient welding area to achieve the required welding strength. To achieve this, the welding rib must be deeply recessed. However, using large welding energy for this purpose can easily result in burrs. Furthermore, in structures where the contact area between two components remains small during the welding process, as in Patent Documents 1 and 2, the welding energy is concentrated in that small contact area, causing a rapid rise in the resin temperature, generating gas and, in the worst case, even rupture, which can potentially compromise strength and airtightness. Patent Documents 1 and 2 also disclose a groove in the receiving component into which the welding rib fits, allowing the molten resin (weld burr) to accumulate in the groove. However, simply providing a groove increases the distance between the horn and the welded portion and increases vibration resistance, requiring large welding energy and making burrs more likely to occur.

[0007] The present disclosure has been made in consideration of these points, and its object is to provide an ultrasonic welding method that can suppress the generation of burrs and obtain excellent welding strength and sealing properties with small welding energy. [Means for solving the problem]

[0008] In order to achieve the above object, the first invention is: An ultrasonic welding method for welding a first member and a second member made of resin, comprising: a preparation process for preparing a first member having a welding groove whose cross section includes left and right first inclined sides concave in a V shape and whose angle formed by the left and right first inclined sides is a first angle; a base portion whose cross section includes left and right second vertical sides extending toward the first member and whose width between the left and right second vertical sides is narrower than the width of the welding groove; a tip portion which includes left and right second inclined sides that extend toward each other from the tip of the second vertical sides and protrude in a V shape toward the welding groove and whose angle formed by the left and right second inclined sides is a second angle that is larger than the first angle; and a second member having a welding rib having a side corner portion formed by the second vertical sides and the second inclined sides; a first step of inserting the welding rib into the welding groove, first abutting the side corner portion against the first inclined edge, and applying a load and ultrasonic vibration in the insertion direction of the welding rib; a second step of forming a V-shaped cross-sectional space between the welding groove and the welding rib during the process of welding the welding rib while sinking it into the welding groove, and accommodating, compressing, and melting the welding flash in the V-shaped cross-sectional space; and a third step of forming a welding portion having a V-shaped cross section between the welding groove and the welding rib.

[0009] With this configuration, a V-shaped weld is formed by the first inclined left and right sides recessed in a V shape and the second inclined left and right sides protruding in a V shape, ensuring a longer weld length than a flat weld. This significantly improves the weld strength of the weld and also improves sealing performance. Furthermore, while achieving these effects, space savings are also possible.

[0010] Since a V-shaped weld is formed by the left and right first inclined edges that are concave in a V shape and the left and right second inclined edges that protrude in a V shape, the weld length can be secured in the overlapping direction of the first and second members, i.e., in the pressure-resistant direction, and therefore the weld strength in the pressure-resistant direction can also be improved.

[0011] By making the angle formed by the second inclined side larger than the angle formed by the first inclined side, a V-shaped space is formed between the first inclined side and the second inclined side during the welding process, and welding burrs can be trapped in this V-shaped space and compressed and melted. This not only suppresses the occurrence of welding burrs, but also increases the resin density of the welded part, greatly improving the sealing performance at the welded part and increasing the weld strength.

[0012] Furthermore, the required welding length can be secured even with a small sinking amount, meaning that welding is possible with less welding energy, which can greatly contribute to reducing hammering burrs and also enables space saving.

[0013] Furthermore, by first abutting the side corner against the first inclined edge, the resin begins to melt at the line contact area between the first inclined edge and the side corner. As the side corner subsequently melts, the first inclined edge and the second inclined edge enter a molten state due to surface contact. By gradually transitioning from line contact to broader surface contact, the concentration of welding energy can be prevented. In this way, it is possible to prevent the resin from becoming too hot and generating gas due to the concentration of welding energy, and it is also possible to improve sealing performance.

[0014] The second invention is the first invention, In the first step, the left and right side surface corner portions are brought into contact with the left and right first inclined sides at different times.

[0015] With this configuration, the left and right side corners abut one by one against the left and right first inclined sides, and melting begins at different times, allowing welding with less energy than when they abut simultaneously. This contributes even more to reducing hammer burrs. In addition, by melting the left and right side corners one by one at different times, air can easily escape from the V-shaped cross-section space, making it less likely for bubbles to form in the welded area, further improving sealing performance.

[0016] The third invention is the first invention, the first member has a welding burr accommodating groove that is further recessed at a tip end portion of the V-shaped welding groove, and the capacity of the welding burr accommodating groove is smaller than the capacity of the welding burr accommodated in the cross-sectional V-shaped space; In the second step, the welding burr is accommodated in the welding burr accommodating groove, compressed, and melted.

[0017] With this configuration, the welding burr containing groove also becomes a welded part, which allows for further improvement in welding strength. The welding burr containing groove does not need to be deep; even a shallow groove can be effective, which contributes to space savings. In addition, because the first and second components do not come into contact in the welding burr containing groove, the area to which the load is directly applied can be reduced. This means that welding is possible with less welding energy, further reducing hammer burrs.

[0018] The fourth invention is the first invention, The welding groove has first vertical sides on the left and right that extend further in the opening direction of the welding groove than the first inclined sides and that face the second vertical sides with a gap of 0.1 mm to 0.2 mm between them, In the second step, the welding burr is accommodated in the gap between the first vertical side and the second vertical side.

[0019] With this configuration, by narrowing the gap between the second vertical side and the first vertical side to 0.1 mm to 0.2 mm, the resin that would normally become a burr is contained in a molten state in the gap between the first vertical side and the second vertical side, and a weld is formed in that area as well.As a result, the weld is longer and the weld strength can be further improved, and the sealing performance can also be further improved.

[0020] The fifth invention is the first invention, The first angle is equal to or greater than 70° and equal to or less than 120°, and the second angle is equal to or greater than 10° and equal to or less than 30° larger than the first angle.

[0021] This configuration makes it possible to reduce the required welding energy as much as possible while ensuring the welding strength, and also makes it possible to suppress the occurrence of burrs and hammer burrs in the welded portion.

[0022] If the first angle is less than 70°, the amount of sinking required to form the V-shaped weld increases, which increases the required welding energy and makes it more likely that defects such as hammer burrs will occur. Furthermore, the weld groove in the first component may deform and widen, or crack. If the first angle is greater than 120°, the V-shaped weld becomes flattened. The cross-sectional length of the weld is shortened, reducing the effect of improving weld strength. Furthermore, the left-right positioning effect achieved by the engagement between the V-shaped weld groove and the weld rib is lost.

[0023] Furthermore, if the difference between the second angle and the first angle is less than 10°, the contact area between the side corner and the first inclined edge changes from an initial line contact to a surface contact over a wide area during the welding process, which increases the required welding energy and makes defects such as tapping burrs more likely to occur.If the difference between the second angle and the first angle is greater than 30°, the amount of sinking required to form a V-shaped weld becomes larger.This increases the required welding energy and makes defects such as tapping burrs more likely to occur. [Effects of the Invention]

[0024] As explained above, the angle of the end of the welding rib and the angle of the welding groove that accommodates the welding rib are set to a predetermined angle, and a V-shaped space is formed during the welding process, which suppresses the generation of burrs and makes it possible to obtain excellent welding strength and sealing performance with small welding energy. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a longitudinal sectional view showing an example of a welding structure used in an ultrasonic welding method according to an embodiment of the present invention. [Figure 2] 2 is a longitudinal sectional view corresponding to part A in FIG. 1 and showing the ultrasonic welding method of the first embodiment. [Figure 3A] 1 is a vertical cross-sectional view showing a first step of the ultrasonic welding method of the first embodiment. FIG. [Figure 3B]FIG. 3 is a vertical cross-sectional view showing a second step of the ultrasonic welding method of the first embodiment. [Figure 3C] FIG. 4 is a vertical cross-sectional view showing a third step of the ultrasonic welding method of the first embodiment. [Figure 4A] FIG. 10 is a vertical cross-sectional view showing a first step of an ultrasonic welding method according to a second embodiment. [Figure 4B] FIG. 10 is a vertical cross-sectional view showing a second step of the ultrasonic welding method of the second embodiment. [Figure 4C] FIG. 10 is a vertical cross-sectional view showing a third step of the ultrasonic welding method of the second embodiment. [Figure 5A] FIG. 10 is a vertical cross-sectional view showing a first step of an ultrasonic welding method according to a third embodiment. [Figure 5B] FIG. 10 is a vertical cross-sectional view showing a second step of the ultrasonic welding method of the third embodiment. [Figure 5C] FIG. 10 is a vertical cross-sectional view showing a third step of the ultrasonic welding method of the third embodiment. [Figure 6] FIG. 10 is a vertical cross-sectional view showing an ultrasonic welding method according to a fourth embodiment. [Figure 7A] FIG. 10 is a vertical cross-sectional view showing a first step of an ultrasonic welding method according to a fourth embodiment. [Figure 7B] FIG. 10 is a vertical cross-sectional view showing a second step of the ultrasonic welding method of the fourth embodiment. [Figure 7C] FIG. 10 is a vertical cross-sectional view showing a third step of the ultrasonic welding method of the fourth embodiment. [Figure 8] FIG. 10 is a vertical cross-sectional view showing an ultrasonic welding method according to a fifth embodiment. [Figure 9A] FIG. 10 is a vertical cross-sectional view showing a first step of an ultrasonic welding method according to a fifth embodiment. [Figure 9B] FIG. 10 is a vertical cross-sectional view showing a second step of the ultrasonic welding method of the fifth embodiment. [Figure 9C] FIG. 11 is a vertical cross-sectional view showing a third step of the ultrasonic welding method of the fifth embodiment. [Figure 10A] FIG. 10 is a vertical cross-sectional view showing a first step of an ultrasonic welding method according to a sixth embodiment. [Figure 10B] FIG. 13 is a vertical cross-sectional view showing a third step of the ultrasonic welding method of the sixth embodiment. [Figure 11A]FIG. 1 is a longitudinal sectional view showing an example of a welding structure used in a conventional ultrasonic welding method. [Figure 11B] FIG. 1 is a longitudinal cross-sectional view showing an example of a welding structure used in a conventional ultrasonic welding method in a state after welding. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses.

[0027] 1 is a longitudinal cross-sectional view showing an example of a welding structure used in the ultrasonic welding method according to this embodiment. The ultrasonic welding method according to this embodiment involves placing a downwardly opening concave second member on top of an upwardly opening concave first member 1, and welding their peripheral edges together. More specifically, a first flange portion 1a formed on the peripheral edge of the first member 1 and a second flange portion 2a formed on the peripheral edge of the second member 2 are placed on top of each other, and a load and ultrasonic vibrations are applied in the overlapping direction to airtightly weld the first member 1 and the second member 2 together.

[0028] The first flange portion 1a is provided with a welding groove 10 having a V-shaped recess in cross section, and the second flange portion 2a is provided with a welding rib 20 having a V-shaped protrusion in cross section. The first member 1 is placed on top of a receiving tool 101, and the second member 2 is placed on top of the first member 1 with the welding rib 20 of the second member 2 inserted into the welding groove 10 of the first member 1. The horn 100 is lowered, pressing the second member 2 against the first member 1, and vibrating the horn 100 in this state, generating frictional heat between the welding groove 10 and the welding rib 20. The frictional heat melts the welding groove 10 and the welding rib 20, which then solidifies, thereby hermetically welding the first member 1 and the second member 2 together.

[0029] The first member 1 and the second member 2 are obtained by injection molding nylon resin such as PA6 or PA66, but the resin material constituting the first member 1 and the second member 2 is not limited to nylon resin and can be any material that can be heat-welded. This ultrasonic welding method can be applied to the formation of various resin products such as automobile oil strainers, water tanks, air tanks, actuators, manifolds, and piping, but its uses are not particularly limited.

[0030] (First embodiment) FIG. 2 is a longitudinal cross-sectional view corresponding to part A in FIG. 1 and illustrating the ultrasonic welding method of the first embodiment. The first member 1 of the first embodiment has a welding groove 10 that opens upward on the upper surface 11 of the first flange portion 1a. When viewed in cross section as in FIG. 2, the welding groove 10 includes two first inclined sides 13, 13 on the left and right that extend downward from the upper surface 11, which is a substantially horizontal plane, so as to approach each other. The welding groove 10 is recessed in a V shape by the left and right first inclined sides 13, 13. The angle formed by the left and right first inclined sides 13, 13 is a first angle θ1.

[0031] The second member 2 of the first embodiment has a welding rib 20 that protrudes downward from the underside 21 of the second flange portion 2a. The welding rib 20 is formed opposite the welding groove 10. When viewed in cross section as in FIG. 2, the welding rib 20 has a base portion 20a extending from the underside 21, a tip portion 20b extending downward from the base portion 20a, and a side corner portion 24 formed between the base portion 20a and the tip portion 20b. More specifically, the base portion 20a includes left and right second vertical sides 22, 22 that extend substantially vertically from the underside 21, which is a substantially horizontal plane, toward the first member 1. A width L2 between the left and right second vertical sides 22, 22 is narrower than a width L1 of the welding groove 10. The width L2 is, for example, 0.5 mm to 5.0 mm. Two second inclined sides 23 extend downward from the tips of the left and right second vertical sides 22, 22, approaching each other. The tip portion 20b includes the left and right second inclined sides 23, 23. The tip portion 20b protrudes in a V-shape toward the welding groove 10 by the left and right second inclined sides 23, 23. Side corners 24 are formed on the left and right sides by the left and right second vertical sides 22 and the left and right second inclined sides 23, 23, respectively. The angle formed by the left and right second inclined sides 23, 23 is a second angle θ2. The second angle θ2 is greater than the first angle θ1.

[0032] In the first embodiment, the welding groove 10 and the welding rib 20 are formed symmetrically about the center lines C1 and C2, respectively. The first angle θ1 is preferably 70° or more and 120° or less, and the second angle θ2 is preferably 10° or more and 30° or less greater than the first angle θ1.

[0033] (Ultrasonic welding method) Next, a method for ultrasonically welding the first member 1 and the second member 2 configured as described above will be described in detail. First, the first member 1 and the second member 2 configured as described above are prepared. The first member 1 is placed on the receiving tool 101, and the second member 2 is placed on the first member 1 by inserting the welding ribs 20 of the second member 2 into the welding grooves 10 of the first member 1. At this time, the first member 1 and the second member 2 are arranged so that the center lines C1 of the welding grooves 10 and C2 of the welding ribs 20 are aligned. Note that the welding grooves 10 and the welding ribs 20 are in a convex-concave relationship that allows them to fit together, so they can be easily aligned so that the center lines C1 of the welding grooves 10 and C2 of the welding ribs 20 are aligned. Next, a horn 100 is placed in a position facing the top surface of the second flange portion 2a of the second member 2. This completes the preparation process.

[0034] Next, the horn 100 is lowered to contact the upper surface of the second flange portion 2a of the second member 2. FIG. 3A is a longitudinal cross-sectional view showing a first step of the ultrasonic welding method according to the first embodiment. As shown in FIG. 3A, the first step involves first contacting the side corner 24 with the first inclined edge 13 and applying a load and ultrasonic vibration in the insertion direction of the welding rib 20. The contact of the side corner 24 with the first inclined edge 13 at this time is linear contact. By setting the angle θ1 between the first inclined edge 13 and the angle θ2 between the second inclined edge 23 to θ1<θ2, a V-shaped space 30 is formed between the welding groove 10 and the welding rib 20. The ultrasonic vibration applied by the horn 100 has a frequency of 15 to 40 kHz and an amplitude of 30 to 80 μm, for example. The pressing force applied by the horn 100 is 0.5 to 20 MPa, for example.

[0035] 3B is a vertical cross-sectional view showing a second step of the ultrasonic welding method of the first embodiment. In the second step, the horn 100 is further lowered, continuing from the first step, to weld the welding rib 20 into the welding groove 10 while sinking it. The side corners 24 and the first inclined edges 13 at their contact points gradually melt due to frictional heat. The line contact in the first step becomes surface contact between the second inclined edges 23 and the first inclined edges 13 in the second step, gradually expanding the melting area. In the second step, the side corners 24, the second inclined edges 23, and the first inclined edges 13 melt to form the initial weld 40a. The welding burrs 50 generated in the second step flow along the first inclined edges 13 into the V-shaped cross-sectional space 30 between the welding groove 10 and the welding rib 20. The V-shaped cross-section space 30 accommodates the welding burrs 50 generated in the process of sinking the welding rib 20 into the welding groove 10, and as the welding rib 20 further sinks, the welding burrs 50 are compressed and melted.

[0036] 3C is a vertical cross-sectional view showing a third step of the ultrasonic welding method of the first embodiment. In the third step, the molten resin is hardened at the final sinking position of the welding rib 20 to form a welded portion 40 having a V-shaped cross section between the welding groove 10 and the welding rib 20. Welding burrs 50 generated during the process of sinking the welding rib 20 into the welding groove 10 are integrated with the surrounding resin and become part of the V-shaped cross-sectional welded portion 40. Welding burrs 50 protruding upward from the V-shaped cross-sectional welded portion 40 can also be accommodated between the second vertical edge 22 and the first inclined edge 13.

[0037] When the length between the upper surface 11 of the first flange portion 1a and the lower surface 21 of the second flange portion 2a when the side corner portion 24 first abuts against the first inclined edge 13 in the first step is defined as L3, and the length between the upper surface 11 of the first flange portion 1a and the lower surface 21 of the second flange portion 2a when the welding rib 20 is finally sunk in the third step is defined as L4, the amount of sinking of the welding rib 20 is L3-L4. For example, when the width L1 of the welding groove 10 is 1.5 mm to 3.0 mm and the width L2 between the left and right second vertical edges 22, 22 is 1.0 mm to 2.0 mm, the amount of sinking (L3-L4) is approximately 0.3 mm.

[0038] (Operation and effect of the first embodiment) According to the ultrasonic welding method of the first embodiment configured as described above, the V-shaped weld 40 is formed by the V-shaped recessed left and right first inclined edges 13, 13 and the V-shaped protruding left and right second inclined edges 23, 23, thereby ensuring a longer weld length than a flat weld. This significantly improves the weld strength of the weld and also improves sealing performance. Furthermore, while achieving these effects, space savings are also possible.

[0039] The V-shaped welded portion 40 is formed by the left and right first inclined edges 13, 13 that are concave in a V shape and the left and right second inclined edges 23, 23 that protrude in a V shape, so that the weld length can be secured in the overlapping direction of the first member 1 and the second member 2, i.e., in the pressure-resistant direction, and therefore the weld strength in the pressure-resistant direction can also be improved.

[0040] By making the angle θ1 between the first inclined sides 13, 13 and the angle θ2 between the second inclined sides 23, 23 satisfy θ2>θ1, a V-shaped space 30 is formed during the welding process (first step and second step), and the weld burr 50 can be confined, compressed, and melted in this V-shaped space 30. This not only prevents the occurrence of weld burrs, but also increases the resin density of the welded portion 40, greatly improving the sealing performance at the welded portion 40 and increasing the weld strength.

[0041] Furthermore, the required welding length can be secured even with a small sinking amount, meaning that welding is possible with less welding energy, which can greatly contribute to reducing hammering burrs and also enables space saving.

[0042] Furthermore, in the first step, by first abutting the side corner 24 against the first inclined edge 13, the line contact between the first inclined edge 13 and the side corner 24 is gradually transitioned to surface contact between the first inclined edge 13 and the second inclined edge 23, and the melting area is gradually expanded, which prevents the resin from becoming too hot due to the concentration of welding energy and the generation of gas, and also improves sealing properties.

[0043] If the first angle θ1 is less than 70°, the sinking amount (L3-L4) required to form the V-shaped welded portion 40 becomes large, which increases the required welding energy and makes it more likely that defects such as hammer burrs will occur. Furthermore, the weld groove 10 of the first member 1 may deform and widen, or crack. If the first angle θ1 is greater than 120°, the V-shaped welded portion 40 becomes flattened. The cross-sectional length of the welded portion 40 becomes shorter, reducing the effect of improving the weld strength. Furthermore, the left-right positioning effect achieved by the engagement between the V-shaped welded groove 10 and the welded rib 20 is lost.

[0044] Furthermore, if the difference between the second angle θ2 and the first angle θ1 is less than 10°, the contact area between the side corner 24 and the first inclined edge 13 changes rapidly from an initial line contact to a surface contact over a wider area during the welding process, increasing the required welding energy and making defects such as tapping burrs more likely to occur. If the difference between the second angle θ2 and the first angle θ1 is greater than 30°, the amount of sinking required to form the V-shaped weld 40 becomes larger. This increases the required welding energy and makes defects such as tapping burrs more likely to occur.

[0045] (Second embodiment) Next, an ultrasonic welding method according to a second embodiment will be described. In the following description, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 4A is a longitudinal cross-sectional view showing a first step of the ultrasonic welding method according to the second embodiment, corresponding to FIG. 3A of the first embodiment. The configurations of the first member 1 and the second member 2 in the second embodiment are the same as those in the first embodiment, except that the left and right side corners 24 are brought into contact with the left and right first inclined edges 13 at different times. As shown in FIG. 4A, the first member 1 and the second member 2 are placed so that the center line C1 of the welding groove 10 and the center line C2 of the welding rib 20 are not aligned but are offset to the left or right. As long as the center lines C1 and C2 are not aligned, they may be offset to the left or right. However, in the second embodiment, the center line C1 is offset to the left of the center line C2. When horn 100 is lowered in this state, side corner 24 on the right side abuts against first inclined side 13 before the left side, as shown in FIG. 4A.

[0046] 4B is a longitudinal cross-sectional view showing a second step of the ultrasonic welding method of the second embodiment, corresponding to FIG. 3B of the first embodiment. Melting gradually occurs due to frictional heat, starting from the right-side corner 24 and the first inclined edge 13 at the abutment portion. In the second step, the right-side corner 24, the right-side second inclined edge 23, and the right-side first inclined edge 13 melt to form the initial weld 40a. The welding burr 50 generated during this process flows along the first inclined edge 13 into the V-shaped cross-sectional space 30 between the welding groove 10 and the welding rib 20. As shown in FIG. 4B, the upper left side of the V-shaped cross-sectional space 30 is open until the left-side corner 24 and the left-side second inclined edge abut.

[0047] 4C is a vertical cross-sectional view showing a third step of the ultrasonic welding method of the second embodiment, corresponding to FIG. 3C of the first embodiment. The first inclined right edge 13 and the second inclined right edge 23, which start to melt first, and the first inclined left edge 13 and the second inclined left edge 23, which start to melt later, ultimately form a weld 40 with a V-shaped cross section. Weld burrs 50, which are generated during the process of sinking the weld rib 20 into the weld groove 10, are integrated with the surrounding resin and become part of the weld 40 with a V-shaped cross section.

[0048] (Third embodiment) Next, an ultrasonic welding method according to a third embodiment will be described. In the following description, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 5A is a longitudinal cross-sectional view showing a first step of the ultrasonic welding method according to the third embodiment, corresponding to FIG. 3A of the first embodiment. The configuration of the first member 1 according to the third embodiment is the same as that of the first embodiment, but differs in that, as shown in FIG. 5A, the welding ribs 20 are formed asymmetrically, so that the left and right side corners 24 abut against the left and right first inclined edges 13 at different times. More specifically, in the second member 2 according to the third embodiment, the inclination angles of the second inclined edges 23 are different on the left and right, and the perpendicular line C3 passing through the tip of each second inclined edge 23 is shifted leftward from the center of the welding ribs 20. When the second member 2 having such a configuration is placed so that the center line C1 of the welding groove 10 and the perpendicular line C3 passing through the tip of the welding rib 20 are aligned, and the horn 100 is lowered, the right side corner 24 abuts against the first inclined edge 13 before the left side, as shown in Figure 5A.

[0049] 5B is a vertical cross-sectional view showing a second step of the ultrasonic welding method of the third embodiment, and corresponds to FIG. 3B of the first embodiment. Melting gradually occurs from the right side corner 24 and the first inclined edge 13 at the abutting portion thereof due to frictional heat, and the upper left side of the V-shaped cross-section space 30 is open until the left side corner 24 and the left second inclined edge abut, as in the second embodiment.

[0050] 5C is a longitudinal cross-sectional view showing a third step of the ultrasonic welding method of the third embodiment, corresponding to FIG. 3C of the first embodiment. As in the second embodiment, the first inclined edge 13 and the second inclined edge 23 on the right side, which start to melt first, and the first inclined edge 13 and the second inclined edge 23 on the left side, which start to melt later, ultimately form a weld 40 with a V-shaped cross section. Weld burrs 50 generated during the process of sinking the weld rib 20 into the weld groove 10 are integrated with the surrounding resin and become part of the weld 40 with a V-shaped cross section.

[0051] (Effects of the second and third embodiments) According to the ultrasonic welding methods of the second and third embodiments configured as described above, in addition to the effects obtained in the first embodiment, the left and right side corners 24 abut against the first inclined edge 13 and begin to melt at different times, allowing welding with less energy than when both sides abut simultaneously. This further contributes to reducing hammer burrs. Furthermore, one side corner 24 abuts against the first inclined edge 13 first, and the upper part of the other side of the V-shaped cross-section space 30 is open until the other side corner 24 abuts against the first inclined edge 13. This allows air to escape easily, making it less likely for bubbles to form in the welded area, further improving sealing performance.

[0052] (Fourth embodiment) Next, an ultrasonic welding method according to a fourth embodiment will be described. In the following description, the same components as those in the first embodiment will be designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 6 is a longitudinal cross-sectional view showing the ultrasonic welding method according to the fourth embodiment. The second member 2 has the same configuration as that of the first embodiment. However, the first member 1 of the fourth embodiment differs in that it includes a welding burr storage groove 15 that is recessed further into the V-shaped tip of the welding groove 10, as shown in FIG. 6. More specifically, the first member 1 has welding burr storage vertical edges 14 extending downward from the lower ends of the left and right first inclined edges 13, respectively. The welding burr storage vertical edges 14 form the welding burr storage groove 15. In this embodiment, the welding burr storage groove 15 is formed as a recess by the vertically extending welding burr storage vertical edges 14 and the bottom surface. However, the shape of the welding burr storage groove 15 is not limited and may be, for example, U-shaped. The capacity of the welding burr accommodating groove 15 is smaller than the capacity of the welding burr accommodated in the V-shaped cross-section space 30 .

[0053] 7A is a vertical cross-sectional view showing a first step of the ultrasonic welding method of the fourth embodiment, and corresponds to FIG. 3A of the first embodiment. Note that the center line C1 of the welding groove 10 and the center line C2 of the welding rib 20 are aligned. When the side corner 24 is brought into contact with the first inclined edge 13, a V-shaped space 30 is formed above the welding flash receiving groove 15.

[0054] FIG. 7B is a vertical cross-sectional view showing a second step of the ultrasonic welding method of the fourth embodiment, corresponding to FIG. 3B of the first embodiment. In the second step, the left and right side corners 24, the left and right second inclined edges 23, and the left and right first inclined edges 13 melt to form the initial weld 40a. The tip of the second inclined edge 23 is inserted into the welding burr receiving groove 15, so it does not abut against the first inclined edge 13 and is not subjected to the load from the horn 100. The welding burr 50 generated when the initial weld 40a is formed flows into the welding burr receiving groove 15. The welding burr 50 generated during the welding process is received in the welding burr receiving groove 15, compressed, and melted.

[0055] 7C is a longitudinal cross-sectional view showing a third step of the ultrasonic welding method of the fourth embodiment, corresponding to FIG. 3C of the first embodiment. As shown in FIG. 7C, when the molten resin is cured at the final sinking position of the welding rib 20, a weld 40 having a substantially V-shaped cross section is formed between the welding groove 10 and the welding rib 20. This substantially V-shaped weld 40 consists of left and right first welds 41 formed by fusing the left and right side corners 24, the left and right second inclined edges 23, and the left and right first inclined edges 13, and a second weld 42 formed by fusing and integrating the tips of the second inclined edges 23 with the welding burr 50 accommodated in the welding burr accommodation groove 15.

[0056] (Operation and effect of the fourth embodiment) The ultrasonic welding method of the fourth embodiment configured as described above achieves the same effects as the first embodiment, but further improves weld strength because the welding burr containing groove 15 becomes the second weld portion 42, which is part of the substantially V-shaped weld portion 40. The welding burr containing groove 15 does not need to be deep; even a shallow groove can be effective, contributing to space savings. Furthermore, in the welding burr containing groove 15, the tip of the second inclined edge 23 does not abut the first inclined edge 13, creating a portion where the first member 1 and the second member 2 do not abut. This reduces the area to which a direct load is applied. This allows welding with less welding energy and further reduces hammer burrs.

[0057] (Fifth embodiment) Next, an ultrasonic welding method according to a fifth embodiment will be described. In the following description, the same components as those in the first embodiment will be designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 8 is a longitudinal cross-sectional view showing the ultrasonic welding method according to the fifth embodiment. The second member 2 has the same configuration as that of the first embodiment, but the first member 1 of the fifth embodiment differs in that it has a first vertical side 12 extending from the first inclined side 13 toward the opening of the welding groove 10, as shown in FIG. 8. More specifically, the first member 1 has first vertical sides 12, 12 extending upward from the upper ends of the left and right first inclined sides 13, respectively, and the first vertical sides 12, 12 form part of the welding groove 10. The center line C1 of the welding groove 10 and the center line C2 of the welding rib 20 are aligned in a straight line.

[0058] 9A is a vertical cross-sectional view showing a first step of the ultrasonic welding method of the fifth embodiment, and corresponds to FIG. 3A of the first embodiment. It is preferable that the length L6 of the first vertical side 12 is 1 mm or less, and the distance L5 between the first vertical side 12 and the second vertical side 22 of the second member 2 is 0.1 mm to 0.2 mm. When the side corner 24 is brought into contact with the first inclined side 13, a V-shaped space 30 is formed above the welding burr receiving groove 15.

[0059] FIG. 9B is a vertical cross-sectional view showing a second step of the ultrasonic welding method of the fifth embodiment, corresponding to FIG. 3B of the first embodiment. In the second step, the left and right side corners 24, the left and right second inclined edges 23, and the left and right first inclined edges 13 fuse to form the initial weld 40a. A welding burr 50 generated when the initial weld 40a is formed flows into the welding burr receiving groove 15. The welding burr 50 generated during the welding process flows along the first inclined edges 13 into the V-shaped cross-sectional space 30 between the welding groove 10 and the welding rib 20, and is received in the gap between the first vertical edge 12 and the second vertical edge 22. The V-shaped cross-sectional space 30 receives the welding burr 50 generated during the process of sinking the welding rib 20 into the welding groove 10, and as the welding rib 20 further sinks, the welding burr 50 is compressed and melted.

[0060] 9C is a vertical cross-sectional view showing a third step of the ultrasonic welding method of the fifth embodiment, corresponding to FIG. 3C of the first embodiment. At the final sinking position of the welding rib 20, the molten resin is hardened to form a weld 40 with a V-shaped cross section between the welding groove 10 and the welding rib 20, and the welding flash 50 that has spilled upward is accommodated in the gap between the first vertical side 12 and the second vertical side 22 and integrated with the surrounding resin, forming a third weld 43.

[0061] (Operation and effect of the fifth embodiment) According to the ultrasonic welding method of the fifth embodiment configured as described above, in addition to the effects obtained in the first embodiment, by narrowing the distance L5 between the second vertical side 22 and the first vertical side 12 to 0.1 mm to 0.2 mm, resin that would normally become burrs is contained in a molten state in the gap between the first vertical side 12 and the second vertical side 22, and a welded portion (third welded portion 43) is formed in that portion as well, which makes it possible to further greatly improve the weld strength and the sealing performance. Furthermore, because the length L6 of the first vertical side 12 that forms the gap with the second vertical side 22 is 1 mm or less, this reduces the increase in required welding energy and can also result in space savings.

[0062] (Sixth embodiment) Next, an ultrasonic welding method according to a sixth embodiment will be described. In the following description, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 10A is a longitudinal cross-sectional view showing a first step of the ultrasonic welding method according to the sixth embodiment, corresponding to FIG. 3A of the first embodiment. The second member 2 has the same configuration as that of the first embodiment, but the first member 1 of the sixth embodiment is a combination of the configurations of the first member 1 of the first, fourth, and fifth embodiments. More specifically, as shown in FIG. 10A , the first member 1 has first vertical sides 12, 12 extending upward from the upper ends of the left and right first inclined sides 13, respectively. The first vertical sides 12, 12 form part of the welding groove 10. It is preferable that the length L6 of the first vertical side 12 is 1 mm or less, and the distance L5 between the first vertical side 12 and the second vertical side 22 of the second member 2 is 0.1 mm to 0.2 mm. Furthermore, the first member 1 has weld burr accommodating vertical sides 14, 14 extending downward from the lower ends of the left and right first inclined sides 13, respectively, and the weld burr accommodating vertical sides 14, 14 form a weld burr accommodating groove 15.

[0063] FIG. 10B is a vertical cross-sectional view showing a third step of the ultrasonic welding method of the fifth embodiment, corresponding to FIG. 3C of the first embodiment. At the final sinking position of the welding rib 20, a weld 40 with a substantially V-shaped cross section is formed between the welding groove 10 and the welding rib 20. This substantially V-shaped weld 40 consists of left and right first welds 41 formed by fusing the left and right side corners 24 and the left and right second inclined edges 23 with the left and right first inclined edges 13, and a second weld 42 formed by fusing and integrating the tip of the second inclined edge 23 with the welding burr 50 accommodated in the welding burr accommodation groove 15. Furthermore, the welding burr 50 that spills upward is accommodated in the gap between the first vertical edge 12 and the second vertical edge 22 and integrated with the surrounding resin, forming a third weld 43.

[0064] (Operation and effect of the sixth embodiment) The ultrasonic welding method of the sixth embodiment configured as described above achieves the advantages of the first embodiment. Furthermore, the welding burr containing groove 15 functions as the second welding portion 42, which is part of the substantially V-shaped welding portion 40. The welding burr containing groove 15 does not need to be deep; even a shallow groove can be effective, contributing to space savings. Furthermore, in the welding burr containing groove 15, the tip of the second inclined edge 23 does not abut the first inclined edge 13, creating a portion where the first member 1 and the second member 2 do not abut. This reduces the area to which a direct load is applied. This reduces welding energy and further reduces burrs. Furthermore, because the resin that would normally become a burr is contained in the gap between the first vertical edge 12 and the second vertical edge 22 in a molten state, a welding portion (third welding portion 43) is formed in that portion as well. This further improves welding strength and sealing performance. Furthermore, since the length L6 of the first vertical side 12 that forms a gap with the second vertical side 22 is 1 mm or less, the increase in welding energy required is small, and space can also be saved.

[0065] The configuration of the first member 1 in the sixth embodiment is a combination of the configurations of the first member 1 in the first, fourth, and fifth embodiments, but is not limited to such a combination and can be implemented by any combination of the configurations of the first to fifth embodiments.

[0066] The above-described embodiments are merely examples in all respects and should not be construed as limiting. Furthermore, all modifications and variations within the scope of the claims are within the scope of the present invention. [Explanation of symbols]

[0067] 1 First member 2 Second member 10 Welding groove 12 First vertical side 13 First inclined edge 14 Welding burr accommodation vertical side 15 Welding burr accommodation groove 20 Welded rib 20a base part 20b Tip 22 Second vertical side 23 Second inclined edge 24 Side corner 30 V-shaped space 40 Welded area 40a Initial weld area 50 Welding burrs θ1 First angle θ2 Second angle L1 Welding groove width L2 Welding rib width

Claims

1. An ultrasonic welding method for welding a first member (1) and a second member (2) made of resin, comprising: a preparation step of preparing a first member (1) having a welding groove (10) whose cross section includes left and right first inclined sides (13) recessed in a V-shape, the angle formed by the left and right first inclined sides (13) being a first angle (θ1); a second member (2) having a base portion (20a) whose cross section includes left and right second vertical sides (22) extending toward the first member (1), the width between the left and right second vertical sides (22) being narrower than the width of the welding groove (10); a tip portion (20b) having left and right second inclined sides (23) extending toward each other from the tip of the second vertical side (22) and protruding in a V-shape toward the welding groove (10), the angle formed by the left and right second inclined sides (23) being a second angle (θ2) larger than the first angle (θ1); and a second member (2) having a welding rib (20) having a side corner portion (24) formed by the second vertical side (22) and the second inclined side (23). a first step of inserting the welding rib (20) into the welding groove (10), first abutting the side corner portion (24) against the first inclined edge (13), and applying a load and ultrasonic vibration in the insertion direction of the welding rib (20); a second step of forming a V-shaped cross-sectional space (30) between the welding groove (10) and the welding rib (20) during the process of welding the welding rib (20) while sinking it into the welding groove (10), and accommodating, compressing, and melting the welding flash (50) in the V-shaped cross-sectional space (30); and a third step of forming a welded portion (40) having a V-shaped cross section between the welding groove (10) and the welding rib (20).

2. 2. The ultrasonic welding method according to claim 1, wherein in the first step, the left and right side corner portions (24) are brought into contact with the left and right first inclined sides (13) at different times.

3. The first member (1) is provided with a welding burr accommodating groove (15) that is further recessed into the V-shaped tip of the welding groove (10), and the capacity of the welding burr accommodating groove (15) is smaller than the capacity of the welding burr (50) accommodated in the V-shaped cross-section space (30); 2. The ultrasonic welding method according to claim 1, wherein in the second step, the welding burr (50) is accommodated in the welding burr accommodation groove (15), compressed, and melted.

4. The welding groove (10) has first vertical sides (12) on the left and right, which extend further in the opening direction of the welding groove (10) than the first inclined side (13) and face the second vertical side (22) with a gap of 0.1 mm to 0.2 mm therebetween; 2. The ultrasonic welding method according to claim 1, wherein in the second step, a welding burr (50) is accommodated in a gap between the first vertical side (12) and the second vertical side (22).

5. 2. The ultrasonic welding method according to claim 1, wherein the first angle (θ1) is equal to or greater than 70° and equal to or less than 120°, and the second angle (θ2) is equal to or greater than 10° and equal to or less than 30° greater than the first angle (θ1).

Images