JP5216645B2 - Initial load control method for friction stir welding - Google Patents

Description

  The present invention relates to a friction stir welding in which a tool having a shoulder and a pin is inserted into an object to be joined in a rotated state and then the tool and the object to be joined are relatively moved to join the objects to be joined.

  In a friction stir welding (FSW) method, a rotating tool is generally inserted into an object to be welded and then held for a certain period of time (see Patent Document 1). ). This is to increase the frictional heat generated between the tool and the object to be joined and to promote the softening of the object to be joined necessary for joining. In addition, the holding of the tool is an operation necessary for reducing the load on the tool by softening the objects to be joined and reducing the possibility of breakage of the tool.

JP 2003-080380 A

  In the friction stir welding, a low-hardness material (for example, a material of HRB30 or less) may be used as an object to be joined. When such a low-hardness material is joined by the method of Patent Document 1, the softened material is burrs during the relative movement between the object to be joined and the tool (at the initial movement of the tool) while holding the tool or after holding the tool. May be discharged to the outside. For this reason, a load generated on the tool is insufficient (a material amount necessary for joining cannot be secured), and a defect may occur at the insertion position (starting end portion) of the tool.

  As a countermeasure for suppressing the occurrence of this defect, several methods are conceivable. For example, there is a method of suppressing a decrease in load (initial load) generated in the tool after being held for a certain time by shortening the holding time of the tool, but there is no effect on a specific low hardness material. In addition, there is a method of pressing the burr by enlarging the shoulder diameter of the tool, but there may be a case where a shoulder diameter sufficient for product use cannot be secured. Furthermore, in order to suppress the discharge of the softened material, when a method for sufficiently reducing the speed at the initial movement of the tool is used, the cycle time may increase and the productivity may decrease.

  Then, an object of this invention is to provide the initial load control method of the friction stir welding which can suppress reliably the defect which arises in a start end part, without a cycle time increasing.

  An initial load control method for friction stir welding according to the present invention includes an insertion step of inserting a tool having a shoulder and a pin protruding from the shoulder into a joining object in a rotated state, and the tool inserted into the joining object. A holding step of holding the tool in a rotated state at the insertion position, and a pressing step of moving the tool in the protruding direction of the pin after the predetermined period has elapsed. To solve.

  According to the initial load control method of the friction stir welding of the present invention, since the tool is moved in the protruding direction of the pin in the pressurizing step, the material softened by holding the tool and the material that has not yet been softened together. Stir. Thereby, even if the load generated in the tool falls in the holding step, it can be compensated in the pressurizing step. In other words, the discharge | emission by the softening more than necessary of the joining target object by holding | maintenance of a tool can be suppressed. Therefore, it is not necessary to reduce the speed at the initial movement of the tool, so that the cycle time does not increase. Therefore, it is possible to reliably suppress defects generated at the starting end without increasing the cycle time.

  The movement operation of the tool in the pressing step can be performed by various methods. For example, it is possible to provide a load detection step for detecting a load generated in the tool and move the tool so that the load detected in the load detection step becomes a target load. In this method, it is preferable to control so that the detected load does not increase to the target load in consideration of the softening of the material that occurs during the pressurizing step. As another method, in the pressurizing step, the tool may be moved in a predetermined amount in a protruding direction of the pin. According to this aspect, since the tool may be moved without considering the softening of the material generated during the pressurizing step, the movement control of the tool can be easily performed.

  In one form of the initial load control method of the present invention, the method further comprises a joining step of relatively moving the tool moved in the pressurizing step and the joining object, and the predetermined period is held for the predetermined period. It may be set to a period in which the load generated in the subsequent tool is equal to or less than the load generated in the tool during the joining step. According to this aspect, since the initial load generated in the tool is less than or equal to the load generated in the tool during the joining step, the load generated in the tool in the pressurizing step does not become higher than necessary. This can prevent the tool from being damaged.

  As described above, according to the initial load control method of the friction stir welding of the present invention, since the tool is moved in the protruding direction of the pin in the pressurizing step after the holding step, the material softened after holding the tool and The material that has not yet been softened is stirred together. Thereby, the defect of a start end part can be suppressed reliably, without increasing cycle time.

It is a figure which shows the principal part of the friction stir welding apparatus to which the insertion method which concerns on this invention is applied. It is a figure for demonstrating a holding position and aim insertion position. It is a flowchart which shows an example of the control routine which concerns on this invention. It is the graph which showed the relationship between the load which arises in a tool, and time.

  Hereinafter, an embodiment in which the initial load control method according to the present invention is applied to a friction stir welding apparatus will be described with reference to FIGS.

  First, a friction stir welding apparatus 10 (referred to as a joining apparatus) according to the present embodiment is a pin projecting direction (from a position away from an object to be joined in a state where a tool having a shoulder and a pin projecting from the shoulder is rotated ( The tool is inserted into the joining object by moving it in the thickness direction of the joining object), and after the insertion is completed, the tool is pressed against the joining object and moved relative to the joining object. Do the joining.

  And the joining apparatus 10 of this form has the table 12, the apparatus main body 14, the 1st drive motor 16, the control part 18, and the information input part 20, as shown in FIG.

  A joining object 22 is disposed on the upper surface of the table 12. As the joining object 22, a low hardness material such as an aluminum alloy is used. As the low hardness material, for example, a material having a Rockwell hardness of HRB 30 or less is used.

  The apparatus main body 14 is translated with respect to the upper surface of the table 12 by the first drive motor 16. The apparatus main body 14 includes a head unit 24, a head moving mechanism 26, a second drive motor 28, and a load detection unit 30. The head unit 24 can generate frictional heat between the head unit 24 and the bonding target 22. The head unit 24 is provided with a tool 32 and a spindle motor 34. The tool 32 is rotated by the spindle motor 34 and is inserted into the joining object 22 in a rotated state. The tool 32 includes a shoulder 36 formed in a columnar shape, and a pin 38 protruding from the shoulder 36.

  The head moving mechanism 26 moves the head portion 24 in the protruding direction of the pin 38 by the second drive motor 28. As the head moving mechanism 26, for example, a feed screw mechanism can be used.

  The load detection unit 30 outputs a signal corresponding to the load generated in the spindle motor 34. The load detection unit 30 includes a current sensor 40, a conversion unit 42, and an A / D converter 44. The current sensor 40 detects an analog current flowing through the spindle motor 34. The converter 42 converts the analog current (detected current) detected by the current sensor 40 into an analog voltage (detected voltage). The A / D converter 44 converts the detection voltage converted by the conversion unit 42 into a digital voltage (detection data). Usually, the detection data is proportional to the load generated in the spindle motor 34. Therefore, the load detection unit 30 can estimate the load generated in the spindle motor 34 based on the detection data.

  The control unit 18 controls the first drive motor 16, the second drive motor 28, and the main shaft motor 34.

  The control unit 18 includes a storage unit 46, an insertion control unit 48, and a joining control unit 50.

  The storage unit 46 stores first determination load acquisition map data and second determination load acquisition map data.

  As the first determination load acquisition map data, map data in which the relationship between the first determination load Vm1 and the material of the joining object 22 is described in advance is used. As the first determination load Vm1, data corresponding to the load generated in the tool 32 at the holding position (the position of the tool 32 indicated by the solid line in FIG. 2) is set. The holding position of the tool 32 is set to a position somewhat shallower than the target insertion position of the tool 32 (the position of the tool 32 indicated by a two-dot chain line in FIG. 2). Note that the holding position and the target insertion position of the tool 32 are determined based on the material of the joining object 22. Specifically, the holding position and the target insertion position of the tool 32 are held by performing a bonding test on the bonding target object 22 of a specific material at an arbitrary holding position and the target insertion position, and obtaining a good bonding quality. The position and aim insertion position are selected.

  As the second determination load acquisition map data, map data in which the relationship between the second determination load Vm2 and the material of the joining object 22 is described in advance is used. Since the second determination load Vm2 is also a joining load, data corresponding to a load generated on the tool 32 when the tool 32 inserted to the target insertion position and the joining target object 22 are relatively moved is used. .

  The insertion control unit 48 inserts the rotating tool 32 into the joining target object 22. The insertion control unit 48 includes a first insertion control unit 52, a holding control unit 54, and a second insertion control unit 56.

  The first insertion control unit 52 inserts the tool 32 to the holding position. Whether or not the tool 32 has reached the holding position is determined based on the load (detected load) Va and the first determination load Vm1 acquired with reference to the output signal from the load detection unit 30. Do. Specifically, when the detected load Va reaches the first determination load Vm1, the insertion control unit 48 determines that the tool 32 has been inserted to the holding position, and when the detected load Va has not reached the first determination load Vm1. The insertion control unit 48 determines that the tool 32 has not been inserted to the holding position. The holding control unit 54 holds the tool 32 at the holding position of the tool 32 for a predetermined holding period in a rotated state. The predetermined holding period is determined based on the detected load Va and the second determination load Vm2. Specifically, a period from when the tool 32 reaches the holding position to when the inequality Va ≦ Vm2 is established is determined as the holding period. In the above inequality, Va ≦ 0.8 Vm 2 is preferable. The second insertion control unit 56 inserts the tool 32 from the holding position to the target insertion position. The insertion control unit 48 determines whether or not the tool 32 has reached the target insertion position based on the detected load Va and the second determination load Vm2. Specifically, when the detected load Va reaches the second determination load Vm2, the insertion control unit 48 determines that the tool 32 has been inserted to the target insertion position, and the detected load Va has not reached the second determination load Vm2. Sometimes, the insertion controller 48 determines that the tool 32 has not been inserted to the target insertion position.

  The joining control unit 50 translates the tool 32 inserted to the target insertion position with respect to the upper surface of the table 12.

  The information input unit 20 is an interface for an operator to input information necessary for friction stir welding according to the present invention. Information input to the information input unit 20 is transmitted to the control unit 18. Information input to the information input unit 20 includes material information of the object 22 to be joined.

  Next, an initial load control method in the friction stir welding of this embodiment will be described with reference to the flowchart of the control routine of FIG.

  First, in step S1, the control unit 18 controls the spindle motor 34 so that the tool 32 rotates based on the tool insertion start information input to the information input unit 20 by the operator.

  Thereafter, in step S2, the first insertion control unit 52 controls the second drive motor 28 so that the tool 32 is inserted to the holding position. At this time, the current sensor 40 detects an analog current flowing through the spindle motor 34. Then, the detection load Va is obtained based on the detection current. Whether or not the tool 32 has reached the holding position is determined based on the detected load Va and the first determination load Vm1. The first determination load Vm1 is acquired based on the material information input to the information input unit 20 by the operator and the first determination load acquisition map data.

  Thereafter, in step S3, the holding control unit 54 controls the second drive motor 28 at the holding position so that the tool 32 is held for a predetermined holding period. The predetermined holding period is determined based on the detected load Va and the second determination load Vm2. The second determination load Vm2 is acquired based on the material information input by the operator to the information input unit 20 and the second determination load acquisition map data.

  Thereafter, in step S4, the second insertion control unit 56 controls the second drive motor 28 so that the tool 32 is inserted from the holding position to the target insertion position. Whether or not the tool 32 has reached the target insertion position is determined based on the detected load Va and the second determination load Vm2.

  Thereafter, in step S <b> 5, the joining control unit 50 controls the first drive motor 16 so as to move the tool 32 relative to the joining object 22.

  Thereafter, in step S6, the control unit 18 controls the second drive motor 28 so that the tool 32 is held at the target insertion position.

  Thereafter, in step S <b> 7, the control unit 18 controls the second drive motor 28 so that the tool 32 is extracted from the bonding target 22.

  Thereafter, in step S8, the control unit 18 controls the spindle motor 34 so that the rotation of the tool 32 is stopped. After this process ends, the control routine ends.

  In the above embodiment, the process in step S2 corresponds to the insertion step, the process in step S3 corresponds to the holding step, the process in step S4 corresponds to the pressurizing step, and the processes in steps S5 and S6 correspond to the joining step.

  In the control routine of the present embodiment, the tool 32 is inserted to the insertion position after holding the tool 32 for a predetermined holding period, so that the material softened by holding the tool 32 and the material that has not yet been softened together. Stir. Thereby, even if the load which arises in the tool 32 falls in the holding | maintenance period of the tool 32, it can compensate. In other words, discharge due to unnecessarily softening of the joining object 22 by holding the tool 32 can be suppressed. Therefore, since it is not necessary to reduce the speed at the time of the initial movement of the tool 32, cycle time does not increase. Therefore, it is possible to reliably suppress defects generated at the starting end without increasing the cycle time.

  Further, in this embodiment, the load (initial load) generated in the tool 32 after being held for a predetermined holding period is equal to or less than the load generated when the tool 32 inserted to the target insertion position and the joining object 22 are relatively moved. Therefore, the load generated on the tool 32 when the tool 32 is inserted from the holding position to the target insertion position is not increased more than necessary. Thereby, it is possible to prevent the tool 32 from being damaged.

  It can be understood from FIG. 4 that this embodiment has the effects described above. In FIG. 4, a solid line A indicates a change in load generated in the tool 32 with respect to time, and a one-dot chain line B indicates a change in insertion amount of the tool 32 with respect to time. Further, Vm1 is a load generated on the tool 32 when reaching the holding position, Vm2 is a load generated on the tool 32 when the tool 32 and the joining target object 22 are relatively moved, and Vm0 is 80% of Vm2. The load, the period between T1 and T2, indicates the holding period. When the tool 32 is inserted into the joining object 22, the load Va generated in the tool 32 increases to the load Vm1. Then, after holding the tool 32 until the load Va generated in the tool 32 reaches the load Vm0 (Vm0 = 0.8Vm2), the load Va generated in the tool 32 is joined to the joint load Vm2 by inserting the tool 32 to the target insertion position. It rises to the vicinity. Thereby, since the initial load of the tool 32 does not fall more than necessary, it is possible to prevent the starting end from being defective. Further, the tool 32 can be prevented from being damaged.

(Modification)
Next, a modified example of the above embodiment will be described. In the embodiment described above, when the second insertion control unit 56 inserts the tool 32 from the holding position to the target insertion position, it is determined whether or not the tool 32 has reached the target insertion position by using the detection load Va and the second determination load Vm2. The insertion control unit 48 performs based on the above. On the other hand, in this modification, the second insertion control unit 56 moves the predetermined insertion amount tool 32 determined in advance in the protruding direction of the pin 38. The prescribed insertion amount acquisition map data describing the relationship between the prescribed insertion amount and the material of the joining object 22 is used as the prescribed insertion amount. The specified insertion amount acquisition map data is stored in the storage unit 46.

  According to this modification, the tool 32 needs to be moved by the specified insertion amount without considering the softening of the material that occurs when the tool 32 is inserted from the holding position to the target insertion position. Control can be performed easily.

  The present invention is not limited to the above embodiment, and can be implemented in various forms. The method of detecting the load generated in the tool is not limited to the method of estimating from the analog current flowing through the spindle motor. For example, the load generated in the tool may be estimated based on the deflection amount of the head portion and the spring constant of the head portion. Note that the amount of deflection of the head portion may be detected using a measuring means that measures the amount of movement of the head portion in the protruding direction of the pin. Thereby, it is possible to cope with a case where it is difficult to detect the analog current flowing through the spindle motor.

DESCRIPTION OF SYMBOLS 10 ... Friction stir welding apparatus 14 ... Apparatus main body 16 ... 1st drive motor 18 ... Control part 22 ... Joining object 28 ... 2nd drive motor 32 ... Tool 36 ... Shoulder 38 ... Pin 46 ... Memory | storage part 50 ... Joining control part 52 ... first insertion control unit 54 ... holding control unit 56 ... second insertion control unit

Claims (3)

An insertion step of inserting a tool having a shoulder and a pin protruding from the shoulder into a joining object in a rotated state;
A holding step of holding the tool in a rotated state at the insertion position of the tool inserted into the joining object;
An initial load control method for friction stir welding, comprising: a pressing step for moving the tool in the protruding direction of the pin after the predetermined period has elapsed. In the initial load control method of friction stir welding according to claim 1,
In the pressurizing step, the tool moves in a predetermined amount in a protruding direction of the pin, and the initial load control method for friction stir welding is characterized in that In the initial load control method of friction stir welding according to claim 1 or 2,
Further comprising a joining step of relatively moving the tool and the joining object moved in the pressing step;
The friction stir welding is characterized in that the predetermined period is set such that a load generated in the tool after being held for the predetermined period is equal to or less than a load generated in the tool during the bonding step. Initial load control method.

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