Spot welding machine

Abstract

The present invention provides a spot welding machine that can insulate the ultrasonic vibration device from the electrode while suppressing vibration damping caused by the insulating material. [Solution] The spot welding machine of the present invention is a spot welding machine that clamps a workpiece with a pair of spot welding electrodes and applies pressure and current, and is equipped with an ultrasonic vibration device that vibrates at least one of the spot welding electrodes. Furthermore, since the horn of the ultrasonic vibration device grips the spot welding electrode via an insulating member, and the spot welding electrode vibrates in a direction perpendicular to the direction of pressure, it is possible to provide a spot welding machine that can insulate the ultrasonic vibration device and the electrode while preventing vibration attenuation.

Description

Technical Field

[0001] The present invention relates to a spot welding machine, and more particularly to a spot welding machine that performs welding by vibrating spot welding electrodes.

Background Art

[0002] Spot welding is a metal joining method in which the metals to be welded are overlapped, the welding portion is sandwiched between a pair of spot welding electrodes, pressurized and energized, and melted and adhered by Joule heat generated by the contact resistance at the welding site.

[0003] An oxide film often exists on the surface of metals. Even if this oxide film is removed, it will be reformed again by oxygen in the air.

[0004] When there is a film resistance due to an oxide film or the like at the welding site, generally the film resistance is larger than the contact resistance, so the heat generation becomes rapid. Also, the film resistance tends to decrease as the temperature rises, and as the temperature rises, the current easily flows rapidly, resulting in an overheated state and causing problems such as splashing and poor welding.

[0005] Patent Document 1 discloses that a vibrator that vibrates by an ultrasonic oscillator is attached to a shank that supports an upper electrode, and the spot welding electrode is vibrated to remove the film on the surface of the metal material to be welded.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Between the ultrasonic vibrator and the electrode of the ultrasonic vibration device, it is necessary to insulate in order to prevent the shunting and leakage of the welding current.

[0008] However, the boosters and horns of ultrasonic vibration devices are made of metal materials such as aluminum alloys and titanium alloys, from the standpoint of acoustic and structural properties.

[0009] If these boosters or horns were made from other insulating materials such as resin, or if insulating materials were added, for example, between the transducer and the booster, it would not only require modifications to the existing equipment, but the number of contact points between the components would increase, causing vibration attenuation. Furthermore, it is difficult to provide insulating materials to the spot welding electrodes themselves.

[0010] This invention has been made in view of the problems of the prior art, and its objective is to provide a spot welding machine that can insulate the ultrasonic vibration device and the electrode while preventing vibration damping. [Means for solving the problem]

[0011] The inventors of the present invention conducted extensive research to achieve the above objectives and discovered that these objectives can be achieved by gripping the spot welding electrode via an insulating member and performing fixing and insulation at the same location, thus completing the present invention.

[0012] In other words, the spot welding machine of the present invention is a spot welding machine that clamps a workpiece between a pair of spot welding electrodes and applies pressure and current, and is equipped with an ultrasonic vibration device that vibrates at least one of the spot welding electrodes. Furthermore, the horn of the ultrasonic vibration device grips the spot welding electrode via an insulating member, and the spot welding electrode vibrates in a direction perpendicular to the direction of pressure. [Effects of the Invention]

[0013] According to the present invention, since the spot welding electrode is gripped by the horn via an insulating member, it is possible to provide a spot welding machine that can insulate the ultrasonic vibration device and the electrode while preventing vibration damping. [Brief explanation of the drawing]

[0014] [Figure 1] It is a schematic diagram of a main part showing an example of the spot welding machine of the present invention. [Figure 2] It is a diagram for explaining a state in which a spot welding electrode is gripped by an insulating member having a hollow cylindrical shape. [Figure 3] It is a diagram for explaining a state in which a spot welding electrode is gripped by a hollow cylindrical shape having a cut. [Figure 4] It is a diagram for explaining a state in which a spot welding electrode is gripped by an insulating member having a hollow truncated cone shape. [Figure 5] It is a graph showing the vibration characteristics of the spot welding electrode of the spot welding machine of the present invention.

Embodiments for Carrying Out the Invention

[0015] The spot welding machine of the present invention will be described in detail. As shown in FIG. 1, the spot welding machine of the present invention sandwiches a workpiece in which metal materials are stacked with a pair of spot welding electrodes, and melts and joins the metal materials by the heat generated by energization while applying pressure, and includes an ultrasonic vibration device that vibrates at least one of the spot welding electrodes.

[0016] The ultrasonic vibration device includes an ultrasonic vibrator in which a piezoelectric element expands and contracts and vibrates by on / off of voltage application, a booster, and a horn.

[0017] The vibration of the ultrasonic vibrator is adjusted to an appropriate amplitude by the booster, and further adjusted to resonate correctly at the frequency used in the horn and transmitted to the spot welding electrode.

[0018] The spot welding electrode is composed of an electrode tip and a shank that supports the electrode tip, and the vibration from the ultrasonic vibration device is transmitted and vibrates in a direction orthogonal to the pressing direction, removing a film such as an oxide film on the surface of the metal material, and flowing a large current to generate Joule heat at the welding site.

[0019] In the spot welder of the present invention, since the spot welding electrode is held by the horn of the ultrasonic vibration device via an insulating member, welding current does not flow to the ultrasonic vibration device side, preventing shunting and leakage of the welding current.

[0020] In addition, the horn holds the spot welding electrode via an insulating member, and since the fixing portion of the spot welding electrode and the portion insulating it are the same location, the number of contact locations between members due to providing the insulating member does not increase, suppressing vibration attenuation, and enabling the spot welding electrode to vibrate at a desired frequency.

[0021] As the above-mentioned insulating member, one with high insulation and low vibration attenuation can be used, such as ceramic or resin.

[0022] Examples of the above-mentioned ceramic include silicon nitride, etc., and examples of the above-mentioned resin include phenol resin, PEEK (thermoplastic resin), etc.

[0023] From the viewpoints of insulation and vibration transmission, it is preferable that the shank side surface of the above-mentioned spot welding electrode is covered with an insulating member over the entire circumference.

[0024] Specifically, as shown in FIG. 2, it is preferable that the spot welding electrode is held by the horn in a state of being inserted into a hollow cylindrical insulating member.

[0025] Thereby, a reliable insulation effect is obtained, and vibration is transmitted from the entire circumference of the side surface of the spot welding electrode, improving vibration transmission efficiency. At this time, when the height of the hollow cylindrical insulating member is higher than the height of the gripping portion of the horn, insulation and vibration transmission are further improved.

[0026] Also, as shown in FIG. 3, the above-mentioned hollow cylindrical insulating member can be in a hollow cylindrical shape formed by combining two half-split tubes, or in a hollow cylindrical shape having a slit in the height direction. The hollow cylindrical shape of the insulating member allows for diameter reduction, which increases the contact area between the insulating member and the shank, thereby improving the efficiency of vibration transmission from the insulating member to the shank.

[0027] As the gripping portion of the horn, one can be used that contacts and grips the entire circumference of the side surface of the insulating member. For example, a circular clamp with a circular inner circumference or one with a frustoconical inner surface can be used.

[0028] By ensuring that the entire inner surface of the horn's gripping portion contacts the side surface of the insulating material, the efficiency of vibration transmission from the horn to the insulating material is improved.

[0029] If the gripping portion is a circular clamp, it is preferable that the fastened portion, i.e., the divisible portion, be a single location. In the fastened portion, vibration damping is unavoidable because the mating surfaces are not continuous even if they are in firm contact, and vibration damping can be suppressed by limiting the fastened portion to a single location.

[0030] Furthermore, if the gripping portion has a frustoconical shape on its inner surface, as shown in Figure 4, the insulating member can be made into a hollow frustoconical shape and press-fitted into the gripping portion to grip the spot welding electrode.

[0031] Such a gripping portion with a frustoconical inner surface has no fastening portion like the circular clamp described above, so in addition to having high vibration transmission efficiency of the horn itself, there are no gaps in the insulating material, so vibration damping due to gaps does not occur, resulting in high vibration transmission efficiency, and therefore it can be used in a preferred manner.

[0032] As described above, the spot welding machine of the present invention is equipped with an ultrasonic vibration device and can remove coatings from the workpiece surface, making it suitable for welding aluminum and aluminum-containing alloys, which are prone to oxide film formation. [Examples]

[0033] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

[0034] [Example 1] In the spot welding machine with the structure shown in Figure 4, the spot welding electrode was inserted into the hollow part of the insulating member and held in place. Vibrations from an ultrasonic vibration device were transmitted to the spot welding electrode, and the vibration characteristics were measured. The measurement results are shown in Figure 5.

[0035] From the left side of Figure 5, it can be seen that a vibration with a constant displacement is transmitted to the spot welding electrode, and from the right side, it can be seen that a single vibration with a constant frequency and amplitude is transmitted. [Explanation of symbols]

[0036] 1. Ultrasonic vibration device 11. Oscillator 12 Boosters 13 Horns 131 Gripping part 132 Part to be fastened 133 mating surface 134 Fastening components (screws) 2. Insulating material 3 Spot welding electrodes 31 Shank 32 electrode tips 4. Workpiece (aluminum alloy base material) 41 Oxide film

Claims

1. A spot welding machine that clamps a workpiece between a pair of spot welding electrodes and applies pressure and current to it, It is equipped with an ultrasonic vibrator that vibrates at least one of the spot welding electrodes, The horn of the ultrasonic vibration device grips the spot welding electrode via an insulating member, A spot welding machine characterized in that the spot welding electrode described above vibrates in a direction perpendicular to the direction of pressure.

2. The above insulating member has a hollow cylindrical shape, The spot welding machine according to claim 1, characterized in that the spot welding electrode is inserted into the hollow portion of the insulating member and gripped.

3. The above insulating member is a hollow cylindrical shape having two split tubes or slits, The spot welding machine according to claim 1, characterized in that the horn has a fastening portion, and the insulating member is tightened and gripped with the fastening portion.

4. The above insulating member is hollow and has a truncated cone shape. The spot welding machine according to claim 1, characterized in that the insulating member is press-fitted into the horn to grip the spot welding electrode.

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