CN114951987A

CN114951987A - Joining device and joining method

Info

Publication number: CN114951987A
Application number: CN202210001440.3A
Authority: CN
Inventors: 河合泰宏; 高桥昭彦; 田中真实; 瓦井健太
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2021-02-24
Filing date: 2022-01-04
Publication date: 2022-08-30
Also published as: JP2022128734A

Abstract

The invention aims to inhibit poor joint caused by a gap generated between parts to be jointed of workpieces and improve the joint quality. In order to solve the above problem, the present invention provides a joining device including: a pressing force applying unit that presses at least one of a first workpiece having a first portion to be engaged and a second workpiece having a second portion to be engaged toward the other, thereby causing the first portion to be engaged and the second portion to be engaged to approach each other; a laser beam irradiation unit that irradiates a portion of the first portion to be joined close to the second portion to be joined with a laser beam, thereby melting the first portion to be joined and the second portion to be joined; a distance measuring unit that measures a distance between the first portion to be joined and the second portion to be joined on the approach portion; and a control unit for controlling the pressing force applying unit and the laser beam irradiating unit. When the distance measured by the distance measuring unit exceeds the standard distance, the control section performs at least any one of control of the pressing force applying unit to increase the pressing force and control of the laser beam irradiating unit to bring the focal point of the laser beam close to the approach portion.

Description

Joining device and joining method

Technical Field

The present invention relates to a joining apparatus and a joining method.

Background

Conventionally, a joining method is known in which portions to be joined, which extend linearly on two workpieces respectively, are irradiated with a laser beam to join the portions to be joined to each other. As such a joining method, there is also known a method in which a galvanized layer coated on the surface of a portion to be joined is removed by a laser beam, the portion to be joined is melted, and pressed by a pair of rollers, thereby joining the portions to be joined to each other (for example, refer to patent document 1).

[ Prior art documents ]

(patent document)

Patent document 1: japanese patent laid-open publication No. 2018-75596

Disclosure of Invention

[ problems to be solved by the invention ]

When joining two workpieces, the portions to be joined are arranged close to each other, and a laser beam is irradiated in a manner focused on each of the portions to be joined on the close portion thereof. However, if the pressing force of the workpiece is insufficient, or the zinc plating layer that is not completely removed is deposited on the portions to be joined, there is a possibility that a gap may be generated between the portions to be joined. If a gap is generated between the portions to be joined, there is a problem in that: the laser beam is not properly focused on the portion to be joined, resulting in insufficient melting of the portion to be joined to cause poor joining, and the joining quality is degraded.

Therefore, an object of the present invention is to provide a joining apparatus and a joining method capable of suppressing poor joining due to a gap generated between portions to be joined of two workpieces and capable of improving joining quality.

[ means for solving problems ]

(1) A joining apparatus (for example, a joining apparatus 1 described later) that joins a first workpiece (for example, a workpiece W1 described later) having a first portion to be joined (for example, a portion to be joined Wa described later) that extends linearly with a second workpiece (for example, a workpiece W2 described later) having a second portion to be joined (for example, a portion to be joined Wb described later) that extends linearly, the joining apparatus comprising: a pressing force applying unit (for example, a pressing force applying unit 2 described later) that presses at least one of the first workpiece and the second workpiece toward the other to thereby bring the first portion to be joined and the second portion to be joined close to each other; a laser beam irradiation unit (for example, a laser beam irradiation unit 4 described later) that irradiates a portion to be approached by the first portion to be joined and the second portion to be joined (for example, a portion to be approached Ap described later) with a laser beam, thereby melting the first portion to be joined and the second portion to be joined; a distance measuring unit (e.g., a distance measuring unit 5 described later) that measures a distance between the first portion to be engaged and the second portion to be engaged at the approach portion; and a control unit (for example, a control unit 6 described later) for controlling the pressing force applying unit and the laser beam irradiating unit; and, when the distance measured by the distance measuring unit exceeds a preset standard distance, the control section performs at least any one of control of the pressing force applying unit to increase the pressing force and control of the laser beam irradiating unit to bring the focal point of the laser beam closer to the approaching portion.

(2) The joining apparatus described in the above (1) is provided with a nugget diameter measuring unit (e.g., a nugget diameter measuring unit 7 described later) that measures a nugget diameter (e.g., a nugget diameter d described later) of a joining portion of the first portion to be joined and the second portion to be joined; and the control portion controls the laser beam irradiation unit to increase the amount of melting of the first portion to be joined and the second portion to be joined when the nugget diameter is larger than a preset standard diameter.

(3) In the engaging device described in the above (2), when the distance between the first portion to be engaged and the second portion to be engaged exceeds the standard distance, the control portion controls the pressing force applying unit so that the pressing force does not increase.

(4) A joining method in which at least one of a first workpiece (for example, a workpiece W1 described later) having a first portion to be joined (for example, a portion to be joined Wa described later) extending in a linear shape and a second workpiece (for example, a workpiece W2 described later) having a second portion to be joined (for example, a portion to be joined Wb described later) extending in a linear shape is pressed toward the other, thereby, the first part to be joined and the second part to be joined are brought close to each other, and a laser beam is irradiated to a close portion (for example, an approach portion Ap described later) to join the first workpiece and the second workpiece, wherein the distance between the first portion to be joined and the second portion to be joined at the approach portion is measured, when the measured distance exceeds a preset standard distance, at least any one of increasing the pressing force and bringing the focal point of the laser beam closer to the approach portion is performed.

(5) In the joining method described in the above (4), a nugget diameter (for example, a nugget diameter d described later) of a joining portion between the first portion to be joined and the second portion to be joined is measured, and an amount of melting by the laser beam is increased for the first portion to be joined and the second portion to be joined when the nugget diameter is larger than a preset standard diameter.

(6) In the joining method described in the above (5), the pressing force is not increased when the distance between the first portion to be joined and the second portion to be joined exceeds the standard distance.

(Effect of the invention)

According to the joining apparatus described in the above (1), when a gap is generated between the first part to be joined and the second part to be joined, at least either one of the pressing force that presses the workpiece and the focal position of the laser beam is adjusted, whereby the laser beam can be focused on the portion of the first part to be joined that is close to the second part to be joined and appropriately melted. Therefore, the occurrence of poor bonding can be suppressed, and the bonding quality can be improved.

According to the joining apparatus described in the above (2), when the nugget diameter of the joining portion is longer than the standard diameter, the amount of melting by the laser beam irradiation for the first portion to be joined and the second portion to be joined is increased, and therefore, it is possible to ensure appropriate joining strength of the workpieces.

According to the joining apparatus described in the above (3), even in the case where the nugget diameter of the joining portion is longer than the standard diameter, when the distance between the first portion to be joined and the second portion to be joined exceeds the standard distance, the amount of melting can be increased without increasing the pressing force, and therefore, the reduction of the penetration width due to the excessive pressing can be suppressed, and more appropriate joining strength of the workpieces can be ensured.

According to the joining method described in the above (4), in the case where a gap is generated between the first part to be joined and the second part to be joined, at least either one of the pressing force to press the workpiece and the focal position of the laser beam is adjusted, whereby the laser beam can be focused on the portion of the first part to be joined close to the second part to be joined and melted. Therefore, the occurrence of poor bonding can be suppressed, and the bonding quality can be improved.

According to the joining method described in the above (5), when the nugget diameter of the joining portion is longer than the standard diameter, the amount of melting by the laser beam is increased for the first portion to be joined and the second portion to be joined, and therefore, it is possible to ensure appropriate joining strength of the workpieces.

According to the joining method described in the above (6), even in the case where the nugget diameter of the joining site is longer than the standard diameter, when the distance between the first portion to be joined and the second portion to be joined exceeds the standard distance, the amount of melting can be increased without increasing the pressing force, and therefore, the reduction of the penetration width due to the excessive pressing can be suppressed, and more appropriate joining strength of the workpieces can be ensured.

Drawings

Fig. 1 is a schematic view illustrating a bonding apparatus according to an embodiment of the present invention.

Fig. 2 is a perspective view showing a state where a laser is irradiated to an approaching portion of a portion to be joined in a joining apparatus according to an embodiment of the present invention.

Fig. 3 is a schematic view showing a state where laser light is focused on a proximity portion of a portion to be bonded in a bonding apparatus according to an embodiment of the present invention.

Fig. 4 is a schematic view showing a state where a laser is not focused on an approaching portion of a portion to be joined in the joining apparatus according to an embodiment of the present invention.

Fig. 5 is a schematic view showing a state where a pressing force is increased in the bonding apparatus according to the embodiment of the present invention.

Fig. 6 is a schematic view showing a state where a focal position of a laser beam is adjusted in the bonding apparatus according to the embodiment of the present invention.

Fig. 7 is a sectional view taken along line a-a in fig. 1.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Fig. 1 is a schematic view illustrating a bonding apparatus according to an embodiment of the present invention. Fig. 2 is a perspective view showing a state where a laser is irradiated to an approaching portion of a portion to be joined in a joining apparatus according to an embodiment of the present invention.

The joining apparatus 1 laser-welds to-be-joined portions Wa, Wb linearly extending in the longitudinal direction of the respective works W1, W2 to each other while conveying the two works W1, W2 in the X direction. In the present embodiment, the workpiece W1 is a first workpiece, and the workpiece W2 is a second workpiece. The to-be-engaged portion Wa is a first to-be-engaged portion, and the to-be-engaged portion Wb is a second to-be-engaged portion. The workpieces W1 and W2 of the present embodiment are made of long strip-shaped galvanized steel sheets, the surfaces of which are galvanized.

The joining device 1 includes a pair of

press rollers

2a,2b and a pair of

delivery rollers

3a,3b that are respectively rotationally driven by a motor, not shown. The workpieces W1, W2 are respectively fed out from winding rollers, not shown, arranged at a distance from each other and introduced between the

pressing rollers

2a,2 b.

The

pressing rollers

2a,2b press at least one of the two works W1, W2 toward the other, thereby bringing the portions to be joined Wa, Wb close to each other so that a laser beam to be described later can be focused. The workpieces W1, W2 are conveyed in the X direction by the rotation of the

press rolls

2a,2b while being pressed through the gap G between the

press rolls

2a,2 b. The workpieces W1, W2 having passed through the

pressing rollers

2a,2b are further nipped between the

delivery rollers

3a,3b disposed on the downstream side in the conveying direction, and are delivered from the joining apparatus 1 by the rotation of the

delivery rollers

3a,3 b.

One pressing roller 2b of the pair of

pressing rollers

2a,2b is connected to a pressing force adjusting portion 2 c. The pressing force adjusting portion 2c is constituted by a moving mechanism that moves one pressing roller 2b in the approaching direction and the separating direction with respect to the other pressing roller 2 a. Thereby, the size of the gap G between the

pressing rollers

2a and 2b is adjusted, and the pressing force applied to the workpieces W1 and W2 when passing through the gap G is adjusted. Specifically, the pressing force adjusting portion 2c moves one of the pressing rollers 2b in the approaching direction with respect to the other pressing roller 2a, thereby reducing the gap G between the

pressing rollers

2a and 2b and increasing the pressing force for pressing the workpiece W2 toward the workpiece W1 when passing through the gap G. In the joining apparatus 1 of the present embodiment, the pressing force applying unit 2 that brings the portions to be joined Wa, Wb close to each other is constituted by the

pressing rollers

2a,2b and the pressing force adjusting portion 2 c.

In the joining apparatus 1, the laser irradiation section 4a is disposed closer to the workpiece W1 than the

pressing rollers

2a and 2b and on the upstream side in the conveying direction of the W2. The laser irradiation section 4a is disposed between the workpieces W1, W2 conveyed toward the gap G between the

press rollers

2a,2b, and irradiates a laser beam so as to be focused on an approaching portion Ap of the portions to be joined Wa, Wb pressed and brought close to each other by the

press rollers

2a,2 b. The approach portion Ap is a portion slightly on the upstream side in the transport direction of a portion (a portion of the gap G) of the workpieces W1, W2 where the distance between the portions Wa, Wb to be joined that are brought close to each other by the

press rolls

2a,2b is the smallest, and is a target portion to be melted by the laser beam.

The laser irradiation portion 4a irradiates a laser beam in a manner focused on the approach portion Ap of the portions to be joined Wa, Wb, thereby removing the galvanized layer on the surfaces of the portions to be joined Wa, Wb arranged on the approach portion Ap and melting the portions to be joined Wa, Wb in the areas where the galvanized layer is removed. The workpieces W1, W2 whose portions Wa, Wb to be joined have been melted are pressed and closely contacted and joined by pressing the gap G between the

rollers

2a,2 b.

The laser irradiation unit 4a is connected to the focal position adjustment unit 4 b. The focal point position adjustment unit 4b is configured by a moving mechanism that moves the laser irradiation unit 4a in the approaching direction and the separating direction with respect to the approaching portion Ap. The focal distance of the laser irradiation unit 4a of the present embodiment is fixed, and the focal position of the laser beam is adjusted by moving the laser irradiation unit by the focal position adjusting unit 4 b. In the joining apparatus 1 of the present embodiment, the laser beam irradiation unit 4 for melting the portions to be joined Wa, Wb is constituted by the laser irradiation portion 4a and the focal position adjustment portion 4 b.

In the bonding apparatus 1, a camera 5a is disposed in the vicinity of the laser irradiation portion 4 a. The camera 5a is disposed between the workpieces W1, W2 conveyed toward the gap G between the

press rollers

2a,2b, and photographs a specific area around the gap G between the

press rollers

2a,2b including the approach portion Ap of the to-be-joined portions Wa, Wb.

The camera 5a is connected to the distance measuring section 5 b. The distance measuring section 5b reads the image data captured by the camera 5a and performs image analysis, thereby measuring the distance between the portions to be joined Wa, Wb on the approach portion Ap. Further, since the thickness of the workpieces W1, W2 is known and the workpieces W1, W2 are conveyed on a specified path, the distance measuring section 5b can also measure the size of the gap G between the

press rollers

2a,2b from the image data captured by the camera 5a, thereby calculating the distance between the portions to be joined Wa, Wb. In the joining device 1 of the present embodiment, the distance measuring unit 5 that measures the distance between the portions to be joined Wa, Wb at the approach portion Ap is configured by the camera 5a and the distance measuring portion 5 b.

The joining device 1 includes a control unit 6, and the control unit 6 is connected to the pressing force adjusting unit 2c, the focal position adjusting unit 4b, and the distance measuring unit 5 b. The control section 6 inputs the distance between the to-be-joined portions Wa, Wb measured by the distance measuring section 5b, and controls at least one of the pressing force adjusting section 2c and the focus position adjusting section 4b based on the distance.

Specifically, the control section 6 compares the distance between the to-be-joined sections Wa, Wb measured by the distance measuring section 5b with a preset standard distance, and determines whether or not the measured distance exceeds the standard distance, thereby determining whether or not at least one of the pressing force adjusting section 2c and the focus position adjusting section 4b needs to be controlled. The pressing force adjusting portion 2c is controlled to move the pressing roller 2b, thereby adjusting the pressing force applied to the workpieces W1, W2. The focal position adjusting section 4b is controlled to move the laser irradiation section 4a, thereby adjusting the focal position of the laser beam.

Next, a specific joining method of the workpieces W1, W2 in the joining apparatus 1 will be described with reference to fig. 3 to 6. Fig. 3 shows a state where the laser beam irradiated by the laser irradiation section 4a is properly focused on the approach portion Ap of the to-be-joined portion Wa, Wb of the workpiece W1, W2. At this time, the distance between the portions to be joined Wa, Wb measured by the distance measuring portion 5b is appropriately maintained. Therefore, the approach portion Ap of the to-be-joined portions Wa, Wb is pressed through the gap G between the

pressing rollers

2a,2b after being sufficiently melted by the laser beam having high energy density. Since the pressed workpieces W1, W2 are sufficiently closely fitted and joined, and therefore, have high joining quality.

Fig. 4 shows a state where a gap is generated between the portions to be joined Wa, Wb of the workpieces W1, W2. If the pressing force is insufficient when the workpieces W1, W2 pass through the gap G between the

pressing rollers

2a,2b, and the galvanized layer that is not completely removed by the laser beam is deposited between the portions to be joined Wa, Wb, the portions to be joined Wa, Wb are not in close contact with each other, and a gap is formed between the portions to be joined Wa, Wb. If the gap between the portions to be joined Wa, Wb is increased, the approach portion Ap to be melted by the laser beam is disposed on the downstream side in the conveyance direction from the focal position of the laser beam, and therefore, a non-focused state is formed even if the laser beam is irradiated. Therefore, the energy density of the laser beam irradiated on the approach portion Ap is reduced, and the melting of the portions to be joined Wa, Wb is insufficient. In this case, since the workpieces W1, W2 do not properly come into close contact with each other and the joining quality is degraded, the gap between the parts to be joined Wa, Wb to be continuously welded thereafter further increases.

If it is judged from the measurement result of the distance measuring section 5b that the distance between the portions to be joined Wa, Wb in the approach portion Ap exceeds the standard distance, the control section 6 controls at least one of the pressing force adjusting section 2c and the focal position adjusting section 4b to adjust the pressing force generated by the

pressing rollers

2a,2b and the focal position of the laser beam irradiated from the laser irradiating section 4 a.

Fig. 5 shows a case where the pressing force generated by the

pressing rollers

2a,2b is adjusted. If the gap between the portions to be joined Wa, Wb is increased, the approach portion Ap that should be melted by the laser beam is arranged on the conveyance direction downstream side than the focal position of the laser beam. The controller 6 controls the pressing force adjusting portion 2c to move the pressing roller 2b toward the pressing roller 2a in accordance with the distance measured by the distance measuring portion 5b, thereby increasing the pressing force with which the workpiece W2 presses the workpiece W1. Thereby, the gap between the portions to be joined Wa, Wb is reduced, and the approach portion Ap is adjusted in a direction closer to the focal position of the laser beam.

FIG. 6 is a diagram illustrating the adjustment of the focal position of the laser beam. If the gap between the portions to be joined Wa, Wb is increased, an approach portion Ap that should be melted by the laser beam is arranged on the conveyance direction downstream side of the focal position of the laser beam. The controller 6 controls the focal position adjuster 4b to move the laser irradiator 4a toward the approach portion Ap in accordance with the distance measured by the distance measuring unit 5 b. Thereby, the focal position of the laser beam is adjusted in a direction to approach the approach portion Ap.

It is also possible that when it is judged that the distance between the to-be-joined portions Wa, Wb exceeds the standard distance, the control section 6 controls the pressing force applying unit 2 and the laser beam irradiating unit 4 based on the distance measured by the distance measuring section 5b, thereby adjusting both the pressing force generated by the

pressing rollers

2a,2b and the focal position of the laser beam.

In this way, when the distance between the portions to be joined Wa, Wb in the approach portion Ap of the workpieces W1, W2 exceeds the preset standard distance, the joining device 1 performs at least either of controlling the pressing force applying unit 2 to increase the pressing force of the

pressing rollers

2a,2b and controlling the laser beam irradiating unit 4 to bring the focal point of the laser beam closer to the approach portion Ap. Thereby, it is possible to focus the laser beam on the approach portion Ap of the parts to be joined Wa, Wb and appropriately melt the parts to be joined Wa, Wb. Therefore, the occurrence of poor joining of the workpieces W1, W2 can be suppressed, and the joining quality can be improved.

As shown in fig. 1, the bonding apparatus 1 of the present embodiment includes an ultrasonic sensor 7a and an ultrasonic measuring unit 7 b. The ultrasonic sensor 7a is disposed on the downstream side in the conveyance direction of the

press rollers

2a and 2b and on the upstream side in the conveyance direction of the

delivery rollers

3a and 3b, and performs ultrasonic inspection of the joint of the workpieces W1 and W2 that have passed through the gap G between the

press rollers

2a and 2b and have been joined. The inspection data of the bonding portion detected by the ultrasonic sensor 7a is transmitted to the ultrasonic measurement unit 7 b. The ultrasonic measuring section 7b measures a diameter (nugget diameter) d of a nugget N formed on the joining site (refer to fig. 7) by the portions to be joined Wa, Wb being melted and pressed against each other, based on the inspection data of the ultrasonic sensor 7 a. The nugget diameter d is the length of the nugget N in the direction orthogonal to the extending direction (X) of the portions to be joined Wa, Wb. In the joining device 1 of the present embodiment, the nugget diameter measurement unit 7 is configured by the ultrasonic sensor 7a and the ultrasonic measurement unit 7 b.

The nugget diameter d indicates the joining state of the to-be-joined portions Wa, Wb of the workpieces W1, W2. In the case where the pressing force by the

pressing rollers

2a,2b against the workpieces W1, W2 is insufficient and the amount of melting by the laser beam against the portions to be joined Wa, Wb is insufficient, the nugget diameter d is shortened. A shorter nugget diameter may result in poor bonding. In addition, when the melting amount of the laser beam to the portions Wa, Wb to be joined is insufficient and the pressing force of the workpieces W1, W2 is excessively large, the penetration width W is reduced although the nugget diameter d is sufficient, resulting in poor joining. The penetration width W is the width of the nugget N in the plate thickness direction of the workpieces W1, W2 bounded by the portions to be joined Wa, Wb. The control unit 6 inputs the nugget diameter d measured by the ultrasonic measuring unit 7b, and controls the pressing force applying unit 2 or the laser beam irradiating unit 4 based on the nugget diameter d.

Specifically, the control unit 6 compares the nugget diameter d of the joining portion measured by the ultrasonic measuring unit 7b with a preset standard diameter. In the case where the distance between the portions to be joined Wa, Wb does not exceed the standard distance, and the measured nugget diameter d is shorter than the standard diameter, the control section 6 controls the pressing force adjustment section 2c and moves the pressing roller 2b toward the pressing roller 2a in accordance with the nugget diameter d. In this case, since there is no gap, the heating by the laser beam is appropriately performed, the melting amount of the portions to be joined Wa, Wb is sufficient, and the pressing force with which the workpiece W2 presses the workpiece W1 is increased, so that the portions to be joined Wa, Wb of the workpieces W1, W2 that have passed through the gap G between the

pressing rollers

2a,2b are brought into closer contact with each other. As a result, the nugget diameter d increases, and a suitable joining strength of the workpieces W1, W2 is ensured. In the case where the distance between the portions to be joined Wa, Wb does not exceed the standard distance, and the measured nugget diameter d is longer than the standard diameter, the pressing force may be reduced.

Next, when it is determined that the distance between the portions to be joined Wa, Wb exceeds the standard distance and the nugget diameter d of the joined portion is longer than the standard diameter, the control section 6 controls the focal position adjusting section 4b so as to adjust the focal position of the laser beam or the output of the laser beam so as to increase the amount of melting of the portions to be joined Wa, Wb at the approach portion Ap without increasing the pressing force of the

pressing rollers

2a,2 b. Since the pressing force is not increased, a decrease in the penetration width W due to excessive pressing is suppressed, and a suitable joining strength of the workpieces W1, W2 is ensured.

Further, when it is judged that the distance between the portions to be joined Wa, Wb exceeds the standard distance and the nugget diameter d of the joined portion is shorter than the standard diameter, the control section 6 increases the pressing force of the

pressing rollers

2a,2b and controls the focal position adjusting section 4b to adjust the focal position of the laser beam or the output of the laser beam so as to increase the amount of melting of the portions to be joined Wa, Wb at the approach portion Ap.

The joining device 1 is not limited to the above embodiment. For example, the pressing force adjusting portion 2c may adjust the pressing force by moving both of the pair of

pressing rollers

2a and 2 b. When the laser irradiation unit 4a has a focusing lens capable of adjusting the focal position, the focal position adjustment unit 4b may adjust the focal position of the laser beam by moving the focusing lens of the laser irradiation unit 4 a. Instead of the camera 5a, a contact sensor or a distance sensor may be used to measure the distance between the portions to be joined Wa, Wb.

Reference numerals

1 bonding device

2 pressing force applying unit

4 laser beam irradiation unit

5 distance measuring unit

6 control part

7 nugget diameter measuring unit

Ap proximal site

W1, W2 workpiece

Wa, Wb to-be-joined part

d nugget diameter

Claims

1. An engagement device that engages a first workpiece having a first portion to be engaged that extends linearly with a second workpiece having a second portion to be engaged that extends linearly, the engagement device comprising:

a pressing force applying unit that presses at least one of the first workpiece and the second workpiece toward the other workpiece, thereby causing the first portion to be joined and the second portion to be joined to approach each other;

a laser beam irradiation unit that irradiates a portion of the first portion to be joined and a portion of the second portion to be joined that are close to each other with a laser beam, thereby melting the first portion to be joined and the second portion to be joined;

a distance measuring unit that measures a distance between the first portion to be engaged and the second portion to be engaged at the approach portion; and a process for the preparation of a coating,

a control unit for controlling the pressing force applying unit and the laser beam irradiating unit;

and, when the distance measured by the distance measuring unit exceeds a preset standard distance, the control section performs at least any one of control of the pressing force applying unit to increase the pressing force and control of the laser beam irradiating unit to bring the focal point of the laser beam closer to the approaching portion.

2. The joining apparatus according to claim 1, wherein a nugget diameter measuring unit is provided that measures a nugget diameter of a joining portion of the first portion to be joined and the second portion to be joined; and the number of the first and second electrodes,

the control portion controls the laser beam irradiation unit to increase the amount of melting of the first portion to be joined and the second portion to be joined when the nugget diameter is larger than a preset standard diameter.

3. The joining apparatus according to claim 2, wherein the control portion controls the pressing force applying unit so that the pressing force does not increase when a distance between the first portion to be joined and the second portion to be joined exceeds the criterion distance.

4. A joining method of pressing at least one of a first workpiece having a first portion to be joined which linearly extends and a second workpiece having a second portion to be joined which linearly extends toward the other, thereby bringing the first portion to be joined and the second portion to be joined close to each other, and irradiating a laser beam to the close portion to join the first workpiece and the second workpiece, the joining method characterized by:

measuring a distance between the first portion to be joined and the second portion to be joined at the approach portion,

when the measured distance exceeds a preset standard distance, at least any one of increasing the pressing force and bringing the focal point of the laser beam closer to the approach portion is performed.

5. The joining method according to claim 4, wherein a nugget diameter of a joining portion between the first portion-to-be-joined and the second portion-to-be-joined is measured,

and increasing the amount of melting of the first portion to be joined and the second portion to be joined by the laser beam when the nugget diameter is larger than a preset standard diameter.

6. The joining method according to claim 5, wherein the pressing force is not increased when a distance between the first portion to be joined and the second portion to be joined exceeds the criterion distance.