Ultrasonic welding apparatus, ultrasonic welding method, and control program

Abstract

To provide an ultrasonic welding apparatus, an ultrasonic welding method, and a control program which are capable of properly determining the stop timing of an ultrasonic vibration.SOLUTION: An ultrasonic welding apparatus melts a pin by transmitting an ultrasonic vibration to the pin. The ultrasonic welding apparatus includes an ultrasonic wave electric power generation part, an oscillator, and a control circuit. The ultrasonic wave electric power generation part generates an ultrasonic wave electric power. The oscillator generates an ultrasonic vibration based on an ultrasonic wave electric power generated by the ultrasonic wave electric power generation part. The control circuit determines the stop timing of the oscillator in accordance with changes in the resonant frequency of the oscillator or a parameter having a correlation with the resonant frequency.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ultrasonic welding apparatus, an ultrasonic welding method, and a control program. [Background technology]

[0002] Japanese Patent No. 4412901 (Patent Document 1) discloses an implantation device used to implant an implant. This implantation device includes an oscillator and an oscillation unit. The oscillation unit holds the implant. The oscillation unit oscillates by being excited based on energy generated by the oscillator. The implant is welded by oscillating the oscillation unit (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4412901 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, when the embedding device disclosed in the above-mentioned Patent Document 1 is used and ultrasonic vibration is transmitted to the pin, the pin melts. This melting of the pin is utilized to perform welding. The pull-out strength of the pin after welding is affected by the degree of melting of the pin. For example, when the pin is not melted sufficiently, and when the pin is melted too much, there is a risk that sufficient pull-out strength will not be achieved. Therefore, in order to achieve sufficient pull-out strength, it is necessary to stop the propagation of ultrasonic vibration to the pin at an appropriate timing. However, it is not necessarily easy to determine the appropriate timing to stop the ultrasonic vibration.

[0005] The present invention has been made to solve such problems, and its purpose is to provide an ultrasonic welding device, an ultrasonic welding method, and a control program that can appropriately determine the timing to stop ultrasonic vibration. [Means for solving the problem]

[0006] An ultrasonic welding device according to an aspect of the present invention melts a pin by propagating ultrasonic vibrations to the pin. The ultrasonic welding device includes an ultrasonic power generation unit, a transducer, and a control circuit. The ultrasonic power generation unit generates ultrasonic power. The transducer generates ultrasonic vibrations based on the ultrasonic power generated by the ultrasonic power generation unit. The control circuit determines the timing to stop the transducer in response to a change in the resonant frequency of the transducer or a parameter correlated with the resonant frequency.

[0007] The inventor(s) discovered that the resonant frequency of the vibrator or a parameter correlated with the resonant frequency changes depending on the melting state of the pin. In this ultrasonic welding device, the timing to stop the vibrator is determined depending on the change in the resonant frequency of the vibrator or a parameter correlated with the resonant frequency. Therefore, with this ultrasonic welding device, the timing to stop the vibrator can be appropriately determined taking into account the melting state of the pin.

[0008] In the ultrasonic welding apparatus, the parameter may be a phase difference between a voltage applied to the transducer and a current generated in the transducer.

[0009] The inventor(s) discovered that when the frequency of ultrasonic vibration is substantially constant, the phase difference between the voltage applied to the vibrator and the current generated in the vibrator changes depending on the melting state of the pin. In this ultrasonic welding device, the timing to stop the vibrator is determined depending on the change in the phase difference between the voltage applied to the vibrator and the current generated in the vibrator. Therefore, with this ultrasonic welding device, the timing to stop the vibrator can be appropriately determined taking into account the melting state of the pin.

[0010] In the ultrasonic welding apparatus, the control circuit may detect a peak of the resonance frequency or the parameter, and determine the stop timing in response to detection of a peak that satisfies a predetermined condition.

[0011] The inventor(s) discovered that when the melting of the pin has progressed to a suitable degree, a peak appears in the resonant frequency of the transducer or in a parameter correlated with the resonant frequency. In this ultrasonic welding device, the stop timing is determined in response to the detection of a peak that satisfies a predetermined condition. Therefore, this ultrasonic welding device can appropriately determine the stop timing of the transducer, taking into account the melting state of the pin.

[0012] The ultrasonic welding apparatus may further include a notification unit that notifies a user of the ultrasonic welding apparatus, and the control circuit may control the notification unit to notify the user of the stop timing based on the result of the stop timing determination.

[0013] In this ultrasonic welding device, the stop timing is notified to the user based on the result of the determination of the stop timing, so that the ultrasonic welding device can make the user aware of the stop timing.

[0014] In the ultrasonic welding device, the control circuit may perform control to stop the ultrasonic vibration based on the result of determining the stop timing.

[0015] In this ultrasonic welding device, the ultrasonic vibration is stopped based on the result of the determination of the stop timing, so that the ultrasonic vibration can be automatically stopped at an appropriate timing.

[0016] In the ultrasonic welding device, the control circuit may start determining the timing to stop the ultrasonic vibrations after a predetermined time has elapsed since the ultrasonic vibrations were started.

[0017] The inventor(s) found that immediately after the pin starts to melt, the resonant frequency of the vibrator or the change in a parameter correlated with the resonant frequency of the vibrator is unstable, and that erroneous judgment is likely to occur if the timing to stop the vibrator is judged immediately after the pin starts to melt. Also, the pin does not melt sufficiently immediately after it starts to melt. In this ultrasonic welding device, judgment of the timing to stop the vibrator is started a predetermined time after the start of ultrasonic vibration. Therefore, with this ultrasonic welding device, erroneous judgment of the timing to stop the vibrator is suppressed, and the timing to stop the vibrator can be judged appropriately.

[0018] An ultrasonic welding method according to another aspect of the present invention is an ultrasonic welding method for melting a pin by propagating ultrasonic vibrations to the pin, comprising the steps of generating ultrasonic power, causing a transducer to generate ultrasonic vibrations based on the ultrasonic power, and determining the timing to stop the transducer in response to a change in the resonant frequency of the transducer or a parameter correlated with the resonant frequency.

[0019] In this ultrasonic welding method, the timing to stop the transducer is determined according to the change in the resonant frequency of the transducer or a parameter correlated with the resonant frequency, and therefore, according to this ultrasonic welding method, the timing to stop the transducer can be appropriately determined while taking into account the melting state of the pin.

[0020] A control program according to another aspect of the present invention is a control program for an ultrasonic welding device that melts pins by propagating ultrasonic vibrations to the pins. The ultrasonic welding device includes an ultrasonic power generating unit that generates ultrasonic power, and a transducer that generates ultrasonic vibrations based on the ultrasonic power generated by the ultrasonic power generating unit. The control program causes a computer to execute a step of determining the timing to stop the transducer in response to a change in the resonant frequency of the transducer or a parameter correlated with the resonant frequency.

[0021] When this control program is executed by a computer, the timing to stop the oscillator is determined according to the change in the resonant frequency of the oscillator or a parameter correlated with the resonant frequency, and therefore, according to this control program, the timing to stop the oscillator can be appropriately determined while taking into account the melting state of the pin. Effect of the Invention

[0022] According to the present invention, it is possible to provide an ultrasonic welding device, an ultrasonic welding method, and a control program that are capable of appropriately determining the timing to stop ultrasonic vibration. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of an ultrasonic welding device. [Diagram 2] FIG. 13 is a diagram showing a schematic view of how pins are attached to protrusions of a chip. [Diagram 3] FIG. 13 is a diagram for explaining how welding of a pin by a tip proceeds. [Figure 4] 4 is a diagram showing an example of a transition of a phase difference when a pin is welded according to the procedure shown in FIG. 3. FIG. [Diagram 5] 5 is a diagram showing a portion of the transition of the phase difference shown in FIG. 4 after a first predetermined period has elapsed. FIG. [Figure 6] FIG. 6 is a diagram showing a transition of the gradient of the phase difference shown in FIG. 5. [Figure 7] FIG. 7 is a diagram showing the transition of the gradient of the phase difference shown in FIG. 6 after trend removal processing. [Figure 8] FIG. 11 is a diagram showing another example of a transition of the gradient of the phase difference subjected to trend removal processing. [Figure 9] 10 is a flowchart showing a procedure for notifying the timing of stopping ultrasonic vibration. [Figure 10] 13 is a flowchart showing a procedure for forcibly stopping ultrasonic vibration in the first alternative embodiment. [Figure 11]13 is a flowchart showing a procedure for forcibly stopping ultrasonic vibration in a second alternative embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment according to one aspect of the present invention (hereinafter also referred to as "the present embodiment") will be described in detail with reference to the drawings. Note that the same or corresponding parts in the drawings are given the same reference numerals and their description will not be repeated. Also, each drawing is drawn in a schematic manner with objects appropriately omitted or exaggerated for ease of understanding.

[0025] [1. Overview of ultrasonic welding equipment] <1-1. Configuration of ultrasonic welding device> 1 is a schematic diagram showing the configuration of an ultrasonic welding apparatus 10 according to the present embodiment. The ultrasonic welding apparatus 10 is configured to melt the pins by propagating ultrasonic vibrations to the pins, for example, and weld the pins. The pins are made of, for example, a bioabsorbable material, and are welded to human bones.

[0026] Examples of bioabsorbable materials include synthetic polymers such as polyglycolide, polylactide, poly-ε-caprolactone, lactide-glycolic acid copolymer, glycolide-ε-caprolactone copolymer, lactide-ε-caprolactone copolymer, polycitric acid, polymalic acid, poly-α-cyanoacrylate, poly-β-hydroxy acid, polytrimethylene oxalate, polytetramethylene oxalate, polyorthoester, polyorthocarbonate, polyethylene carbonate, poly-γ-benzyl-L-glutamate, poly-γ-methyl-L-glutamate, poly-L-alanine, etc., polysaccharides such as starch, alginic acid, hyaluronic acid, chitin, pectinic acid and derivatives thereof, and natural polymers such as proteins such as gelatin, collagen, albumin, fibrin, etc. These bioabsorbable materials may be used alone or in combination of two or more kinds.

[0027] For example, a bone fracture is treated by fixing a plate placed at a position spanning the fracture site to the bone. The plate has a plurality of through holes for inserting pins. Holes are formed in the bone at positions corresponding to the through holes in the plate. The pins inserted into both the holes in the plate and the holes formed in the bone are welded to the bone by the ultrasonic welding device 10, thereby fixing the plate placed at a position spanning the fracture site to the bone. The ultrasonic welding device 10 is used, for example, for such applications.

[0028] 1, the ultrasonic welding apparatus 10 includes an oscillator 100 and a handpiece 200. The oscillator 100 and the handpiece 200 are connected via a cable 150.

[0029] The oscillator 100 is configured to convert power supplied from a commercial power source into ultrasonic power and supply the ultrasonic power to the handpiece 200 via the cable 150. For example, the frequency of the ultrasonic power supplied by the oscillator 100 is approximately constant. Also, for example, the magnitude of the ultrasonic power supplied by the oscillator 100 (the product of a voltage value and a current value) is approximately constant. The oscillator 100 includes, for example, an ultrasonic power generating circuit 110, a voltage sensor V1, a current sensor A1, and a control circuit 120.

[0030] The ultrasonic power generating circuit 110 is configured to generate ultrasonic power by using power supplied from a commercial power source. The generation of ultrasonic power in the ultrasonic power generating circuit 110 is realized by using, for example, various known techniques. The voltage sensor V1 is configured to detect a voltage applied to a BL (bolt-clamped Langevin type transducer) transducer 210 (described later) of the handpiece 200, and the current sensor A1 is configured to detect a current generated in the BL transducer 210.

[0031] The control circuit 120 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like, and is configured to control each component in response to information processing. The control circuit 120 is an example of the "computer" of the present invention. The control circuit 120 controls the notification unit 700 based on the detection results of the voltage sensor V1 and the current sensor A1, for example. The control contents by the control circuit 120 will be described in detail later.

[0032] The notification unit 700 is configured to notify the user of the ultrasonic welding apparatus 10. The notification unit 700 is configured, for example, by a light-emitting element such as an LED (Light Emitting Diode) or a speaker. The notification unit 700 may be included in the handpiece 200, may be included in the oscillator 100, or may be configured as a device separate from the handpiece 200 and the oscillator 100.

[0033] The handpiece 200 includes a BL transducer 210, a case 220, a horn 225, and a tip 230. The BL transducer 210 is configured to generate ultrasonic vibrations based on ultrasonic power supplied from the oscillator 100. The case 220 has, for example, a hollow cylindrical shape, and is configured to accommodate the BL transducer 210 therein. The horn 225 is attached to the tip of the BL transducer 210, and is configured to amplify the ultrasonic vibrations generated by the BL transducer 210.

[0034] The tip 230 is connected to the tip of the horn 225 and configured to propagate the ultrasonic vibration amplified by the horn 225 to the welding object. The tip 230 may be configured to be detachable from the horn 225, or may be configured integrally with the horn 225. The tip 230 is made of, for example, stainless steel, aluminum, iron, titanium, or ceramics, and includes a base 235 and a protrusion 231. The base 235 has, for example, a substantially cylindrical shape. The protrusion 231 is formed on the tip surface of the base 235 and has a substantially cylindrical shape. The length of the protrusion 231 in the width direction is shorter than the length of the base 235 in the width direction. The protrusion 231 is configured to hold a pin 300 that is the welding object. Next, an example of a procedure for using the ultrasonic welding device 10 will be described.

[0035] <1-2. Example of how to use ultrasonic welding equipment> Fig. 2 is a schematic diagram showing how pin 300 is attached to protrusion 231 of chip 230. Referring to Fig. 2, pin 300 is attached to protrusion 231, for example, in a state in which pin 300 is placed on fixed base 400. Fixed base 400 has a plurality of holes H1 formed therein, and each hole H1 houses a pin 300.

[0036] As described above, the pin 300 is made of, for example, a bioabsorbable material. The pin 300 includes a shaft portion 310 and a head portion 320. In a plan view, the shaft portion 310 has a circular shape.

[0037] Head 320 is formed at one end of shaft 310. In plan view, head 320 has a circular shape. In plan view, the diameter of head 320 is longer than the diameter of shaft 310. Head 320 is formed with recess 322 recessed in the direction in which shaft 310 extends. Recess 322 forms a substantially cylindrical space. Protrusion 231 of tip 230 is inserted into recess 322.

[0038] By inserting protrusion 231 into recess 322, pin 300 is held by frictional force on tip 230. When handpiece 200 is lifted up with tip 230 holding pin 300, pin 300 is removed from fixed base 400. In this manner, pin 300 is attached to protrusion 231 of tip 230.

[0039] 3 is a diagram for explaining how welding of the pin 300 by the tip 230 proceeds. Referring to FIG. 3, the horizontal axis indicates time. In this example, welding of the pin 300 is performed in a state in which the pin 300 is inserted into both a hole formed in the plate 500 and a hole formed in the bone 600. The plate 500 is fixed to the bone 600 by welding the pin 300.

[0040] At time t0, the pin 300 is pressed downward by the tip 230, and the pin 300 is gradually pushed into the hole of the bone 600. In this state, ultrasonic vibration is propagated from the tip 230 to the pin 300. When the pin 300 receives the ultrasonic vibration, frictional heat is generated between the pin 300 and each of the plate 500 and the bone 600, and the side of the pin 300 begins to melt. At time t1, the pin 300 is further pushed into the hole of the bone 600, and the melting of the pin 300 progresses further. At time t3, the shaft portion 310 is completely melted, and the resin enters the gap of the hole of the bone 600. As a result, the pin 300 is firmly attached to the bone 600. In this way, the plate 500 is fixed to the bone 600 by welding the pin 300. For example, the ultrasonic welding device 10 is used in such a procedure.

[0041] [2.Timing for stopping ultrasonic vibration] For example, the pull-out strength of the pin 300 welded in the procedure shown in Fig. 3 is affected by the degree of melting of the pin 300. For example, when the pin 300 is not melted sufficiently, and when the pin 300 is melted too much, there is a risk that sufficient pull-out strength will not be achieved. Therefore, in order to achieve sufficient pull-out strength, it is necessary to stop the propagation of ultrasonic vibration to the pin 300 at an appropriate timing. However, for example, there are cases where it is difficult to visually confirm the position where the pin 300 is fixed. In such cases, since the melting state of the pin 300 cannot be sufficiently confirmed visually, it is difficult for the user to determine the appropriate timing to stop the ultrasonic vibration.

[0042] The inventor(s) discovered that when the frequency of ultrasonic vibration propagating to pin 300 is substantially constant, the phase difference (hereinafter also simply referred to as "phase difference") between the voltage applied to BL vibrator 210 and the current generated in BL vibrator 210 changes according to the melted state of pin 300. In other words, the inventor(s) discovered that it is possible to detect the timing at which pin 300 has adequately melted (timing at which ultrasonic vibration is stopped) based on the change in phase difference. Note that the phase difference changes according to the resonant frequency of BL vibrator 210, and therefore can be said to be a parameter correlated with the resonant frequency of BL vibrator 210.

[0043] In ultrasonic welding apparatus 10 according to the present embodiment, the timing to stop BL vibrator 210 is determined according to a change in the phase difference. Therefore, ultrasonic welding apparatus 10 can appropriately determine the timing to stop BL vibrator 210 in consideration of the melted state of pin 300. This will be described in detail below.

[0044] FIG. 4 is a diagram showing an example of the transition of the phase difference when the welding of the pin 300 is performed according to the procedure shown in FIG. 3. Referring to FIG. 4, the horizontal axis indicates time (seconds) and the vertical axis indicates the phase difference (°). The phase difference indicates how much the phase of the current generated in the BL transducer 210 leads, coincides, or lags with the phase of the voltage applied to the BL transducer 210 as a reference. The unit of the phase difference is indicated in degrees (°). Specifically, the phase difference is derived by subtracting the phase of the current generated in the BL transducer 210 from the phase of the voltage applied to the BL transducer 210. In this example, the frequency of the ultrasonic power supplied from the oscillator 100 to the BL transducer 210 was approximately constant. Also, the magnitude (the product of the voltage value and the current value) of the ultrasonic power supplied from the oscillator 100 to the BL transducer 210 was approximately constant.

[0045] In the period W1, the pin 300 is gradually pushed into the hole of the bone 600 while melting. In the period W1, the phase difference is decreasing. In the period W2, the lower surface of the head 320 of the pin 300 contacts the plate 500, and thereafter, the melting of the head 320 accelerates. In the period W2, the phase difference is increasing. In the period W3, the melting of the head 320 of the pin 300 accelerates, and thereafter, the tip 230 approaches the plate 500. In the period W3, the phase difference is decreasing again. In the period W4, the tip 230 approaches the plate 500, and then the head 320 of the pin 300 melts sufficiently. In the period W4, the phase difference is increasing again. For example, it is preferable that the ultrasonic vibration is stopped at the time point (time t4) when the period W4 has elapsed.

[0046] Immediately after the pin 300 starts to melt, the change in the phase difference is unstable, and if the timing to stop the ultrasonic vibration is determined based on the phase difference immediately after the pin 300 starts to melt, an erroneous determination is likely to occur. In the ultrasonic welding apparatus 10 according to the present embodiment, the determination of the timing to stop the ultrasonic vibration starts after the first predetermined time has elapsed since the start of the ultrasonic vibration. The "first predetermined period" is, for example, around 2 seconds, and may or may not coincide with the period W1.

[0047] FIG. 5 is a diagram showing a portion of the transition of the phase difference shown in FIG. 4 after the lapse of a first predetermined period. FIG. 6 is a diagram showing the transition of the gradient of the phase difference shown in FIG. 5. FIG. 7 is a diagram showing the transition of the gradient of the phase difference shown in FIG. 6 after trend removal processing. Various known techniques can be used for the trend removal processing. Referring to FIG. 7, a minimum point clearly appears at time t3. The point (time t4) at which the period W4 (see FIG. 4) has elapsed arrives after the lapse of a second predetermined time from the appearance of the minimum point of the phase difference.

[0048] In the ultrasonic welding apparatus 10 according to the present embodiment, the minimum point of the phase difference (negative peak: time t3) is detected, and the timing to stop the ultrasonic vibration (for example, time t4) is determined based on the minimum point of the phase difference. Therefore, the ultrasonic welding apparatus 10 can appropriately determine the timing to stop the BL vibrator 210 while taking into consideration the melted state of the pin 300. Note that the time t4 is, for example, the time after the second predetermined period has elapsed from the time t3. The "second predetermined period" is, for example, about 0.5 seconds, and may or may not coincide with the period W4. Similar trends were also confirmed in examples other than those shown in FIGS. 4 to 7.

[0049] FIG. 8 is a diagram showing another example of the transition of the gradient of the phase difference subjected to trend removal processing. In this example, the force of the tip 230 pressing the pin 300 is smaller than that in the examples shown in FIGS. 4 to 7. Referring to FIG. 8, a minimum point appears clearly at time t5 in this example as well. The timing to stop the ultrasonic vibration arrives, for example, after a second predetermined time has elapsed since the minimum point of the phase difference appears. In the ultrasonic welding apparatus 10, the minimum point of the phase difference (negative peak: time t5) is detected, and the timing to stop the ultrasonic vibration (for example, time t6) is determined based on the minimum point of the phase difference. Therefore, according to the ultrasonic welding apparatus 10, the timing to stop the BL vibrator 210 can be appropriately determined in various cases while taking into account the melting state of the pin 300.

[0050] More specifically, in the ultrasonic welding apparatus 10 according to the present embodiment, when the timing to stop the ultrasonic vibration is determined, a notification is given to the user to make the user aware of the timing to stop the ultrasonic vibration. The procedure for notifying the user of the timing to stop the ultrasonic vibration will be described below.

[0051] [3. Notification of timing to stop ultrasonic vibration] Fig. 9 is a flowchart showing a procedure for notifying the timing of stopping ultrasonic vibration. The process shown in this flowchart is executed by the control circuit 120 after the supply of ultrasonic power from the oscillator 100 to the handpiece 200 is started. In parallel with the process shown in the flowchart in Fig. 9, a process for calculating a phase difference by subtracting the phase of the current generated in the BL transducer 210 from the phase of the voltage applied to the BL transducer 210 (for example, a process for deriving a transition of the phase difference as shown in Fig. 5), a process for calculating a gradient of the phase difference (for example, a process for deriving a transition of the gradient of the phase difference as shown in Fig. 6), and a process for removing a trend from the transition of the gradient of the phase difference (for example, a process for deriving a transition of the gradient of the phase difference as shown in Fig. 7) are executed.

[0052] 9, the control circuit 120 determines whether or not a first predetermined time has elapsed since the start of ultrasonic vibration (step S100). If it is determined that the first predetermined time has not elapsed (NO in step S100), the control circuit 120 executes the process of step S100 again.

[0053] On the other hand, when it is determined that the first predetermined time has elapsed (YES in step S100), the control circuit 120 starts to determine the timing to stop the ultrasonic vibration, and determines whether the phase difference has updated to a minimum value (step S110). Specifically, the determination in step S110 is made based on the transition of the slope of the phase difference that has been subjected to trend processing. When it is determined that the phase difference has updated to a minimum value (YES in step S110), the control circuit 120 resets the count of the second predetermined time and starts counting the second predetermined time (step S120). Thereafter, the control circuit 120 determines whether the second predetermined time has elapsed (step S130).

[0054] On the other hand, if it is determined that the phase difference has not updated to the minimum value (NO in step S110), the control circuit 120 determines whether or not the second predetermined time has elapsed without resetting the count of the second predetermined time (step S130). If it is determined that the second predetermined time has not elapsed (NO in step S130), the control circuit 120 executes the process of step S110 again.

[0055] On the other hand, when it is determined that the second predetermined time has elapsed (YES in step S130), the control circuit 120 controls the notification unit 700 to notify the user (step S140). For example, if the notification unit 700 is configured with a speaker, the control circuit 120 controls the notification unit 700 to output sound. Also, for example, if the notification unit 700 is configured with a light-emitting element, the control circuit 120 controls the notification unit 700 to emit light. In this way, in the oscillator 100, the stop timing is notified to the user based on the determination result of the stop timing of the ultrasonic vibration. Therefore, the ultrasonic welding apparatus 10 can make the user aware of the stop timing.

[0056] [4. Features] As described above, in ultrasonic welding apparatus 10 according to the present embodiment, the timing to stop BL vibrator 210 is determined according to a change in a parameter (phase difference) that has a correlation with the resonance frequency of BL vibrator 210. Therefore, ultrasonic welding apparatus 10 can appropriately determine the timing to stop BL vibrator 210 while taking into consideration the melted state of pin 300.

[0057] 5. Other embodiments The concept of the above embodiment is not limited to the embodiment described above. Hereinafter, an example of another embodiment to which the concept of the above embodiment can be applied will be described.

[0058] <5-1> In the above embodiment, the user is notified in response to the determination of the timing to stop the ultrasonic vibration. However, when the timing to stop the ultrasonic vibration is determined, the user does not necessarily need to be notified. For example, in response to the determination of the timing to stop the ultrasonic vibration, a process for stopping the ultrasonic vibration may be executed.

[0059] Fig. 10 is a flow chart showing the procedure for forcibly stopping ultrasonic vibration in another embodiment 1. Steps S200, S210, S220, and S230 in Fig. 10 are the same as steps S100, S110, S120, and S130, respectively, in Fig. 9. The following mainly describes the points that are different from the above embodiment.

[0060] 10, when it is determined in step S230 that the second predetermined time has elapsed (YES in step S230), control circuit 120 executes a process for stopping the ultrasonic vibration of BL vibrator 210 (step S240). Control circuit 120 controls ultrasonic power generating circuit 110 to stop the supply of ultrasonic power from oscillator 100 to handpiece 200, for example. In this manner, in ultrasonic welding apparatus 10 according to the first alternative embodiment, ultrasonic vibration is stopped based on the determination result of the stop timing. Therefore, ultrasonic welding apparatus 10 according to the first alternative embodiment can automatically stop ultrasonic vibration at an appropriate timing.

[0061] <5-2> In the above embodiment, the user was not notified until the negative peak of the phase difference was detected. Also, in the above first other embodiment, the ultrasonic vibration was not forcibly stopped until the negative peak of the phase difference was detected. However, for example, when the negative peak of the phase difference is not detected for a predetermined time or more, the user may be notified or the ultrasonic vibration may be forcibly stopped.

[0062] Fig. 11 is a flow chart showing the procedure for forcibly stopping ultrasonic vibration in another embodiment 2. Steps S300, S310, S320, and S330 in Fig. 11 are the same as steps S100, S110, S120, and S130, respectively, in Fig. 9. The following mainly describes the points that are different from the above embodiment.

[0063] Referring to FIG. 11, when it is determined in step S330 that the second predetermined time has elapsed (YES in step S330), control circuit 120 executes a process for stopping the ultrasonic vibration of BL transducer 210 (step S350).

[0064] On the other hand, if it is determined in step S330 that the second predetermined time has not elapsed (NO in step S330), the control circuit 120 determines whether or not a third predetermined time has elapsed since the start of ultrasonic vibration (step S340). The "third predetermined time" is a time longer than the first predetermined time, and is, for example, a time during which melting of the pin 300 is considered to have progressed sufficiently. The third predetermined time is set in advance, for example, through experiments.

[0065] If it is determined that the third predetermined time has not elapsed (NO in step S340), control circuit 120 executes the process of step S310 again. On the other hand, if it is determined that the third predetermined time has elapsed (YES in step S340), control circuit 120 executes a process for stopping the ultrasonic vibration of BL vibrator 210 (step S350). Note that a notification may be given to the user in step S350. In this way, in ultrasonic welding apparatus 10 according to the second alternative embodiment, when a negative peak of the phase difference is not detected for the third predetermined time or longer, ultrasonic vibration is forcibly stopped or a notification is given to the user. Therefore, ultrasonic welding apparatus 10 according to the second alternative embodiment can prevent melting of pin 300 from continuing for an excessively long time.

[0066] <5-3> In the above embodiment, the frequency of the ultrasonic power supplied by the oscillator 100 is assumed to be substantially constant. However, the frequency of the ultrasonic power supplied by the oscillator 100 does not necessarily need to be substantially constant. For example, the frequency of the ultrasonic power supplied by the oscillator 100 may follow the resonance frequency of the BL transducer 210. That is, the oscillator 100 may be configured to adjust the frequency of the ultrasonic power so that the frequency of the ultrasonic power follows the resonance frequency of the BL transducer 210. In this case, the control circuit 120 may detect the resonance frequency of the BL transducer 210 and determine the stop timing of the BL transducer 210 according to the detected resonance frequency. More specifically, the control circuit 120 may detect the peak of the temporal change of the resonance frequency of the BL transducer 210 and determine the stop timing of the BL transducer 210 based on the detected peak of the temporal change of the resonance frequency.

[0067] <5-4> In the above embodiment, the voltage sensor V1, the current sensor A1, and the control circuit 120 are provided in the oscillator 100. However, each of the voltage sensor V1, the current sensor A1, and the control circuit 120 does not necessarily have to be provided in the oscillator 100. Each of the voltage sensor V1, the current sensor A1, and the control circuit 120 may be provided in the handpiece 200, for example.

[0068] <5-5> In the above embodiment, the phase difference is the phase of the voltage applied to BL vibrator 210 minus the phase of the current generated in BL vibrator 210. However, the phase difference is not limited to this. The phase difference may be, for example, the phase of the current generated in BL vibrator 210 minus the phase of the voltage applied to BL vibrator 210. In this case, for example, a positive peak (maximum point) of the phase difference is detected, and a notice is given to the user or the ultrasonic vibration is forcibly stopped after a second predetermined time has elapsed since the detection of the maximum point.

[0069] The above describes the embodiments of the present invention by way of example. That is, the detailed description and the accompanying drawings are disclosed for the purpose of illustrative description. Therefore, some components described in the detailed description and the accompanying drawings may be non-essential components for solving the problem. Therefore, just because the non-essential components are described in the detailed description and the accompanying drawings, it should not be immediately determined that the non-essential components are essential.

[0070] Moreover, the above-described embodiments are merely examples of the present invention in every respect. Various improvements and modifications of the above-described embodiments are possible within the scope of the present invention. For example, at least a part of the configuration of any of the embodiments may be combined with at least a part of the configuration of any of the other embodiments. In other words, in implementing the present invention, specific configurations can be appropriately adopted according to the embodiment. [Explanation of symbols]

[0071] 10 ultrasonic welding device, 100 oscillator, 110 ultrasonic power generating circuit, 120 control circuit, 150 cable, 200 handpiece, 210 BL vibrator, 220 case, 225 horn, 230 tip, 231 protrusion, 235 base, 300 pin, 310 shaft, 320 head, 322 recess, 400 fixing base, 500 plate, 600 bone, 700 notification part, A1 current sensor, H1 hole, V1 voltage sensor, W1, W2, W3, W4, W5 period.

Claims

1. An ultrasonic welding device that melts a pin by propagating ultrasonic vibration to the pin, an ultrasonic power generating unit that generates ultrasonic power; a transducer that generates the ultrasonic vibration based on the ultrasonic power generated by the ultrasonic power generation unit; a control circuit that determines a timing to stop the transducer in response to a change in a resonant frequency of the transducer or a parameter correlated with the resonant frequency.

2. The ultrasonic welding apparatus according to claim 1 , wherein the parameter is a phase difference between a voltage applied to the transducer and a current generated in the transducer.

3. 3. The ultrasonic welding apparatus according to claim 1, wherein the control circuit detects a peak of the resonance frequency or the parameter, and determines the stop timing in response to detection of the peak that satisfies a predetermined condition.

4. A notification unit that notifies a user of the ultrasonic welding device, The ultrasonic welding apparatus according to claim 1 or 2, wherein the control circuit controls the notification unit to notify the user of the stop timing based on a result of the determination of the stop timing.

5. 3. The ultrasonic welding apparatus according to claim 1, wherein the control circuit performs control for stopping the ultrasonic vibration based on a result of the determination of the stop timing.

6. 3. The ultrasonic welding device according to claim 1, wherein the control circuit starts determining the timing to stop the ultrasonic vibration after a predetermined time has elapsed since the ultrasonic vibration was started.

7. 1. An ultrasonic welding method for melting a pin by propagating ultrasonic vibrations to the pin, comprising: generating ultrasonic power; A transducer generating the ultrasonic vibration based on the ultrasonic power; determining a timing to stop the transducer in response to a change in a resonant frequency of the transducer or a parameter correlated with the resonant frequency.

8. A control program for an ultrasonic welding device that melts a pin by propagating ultrasonic vibration to the pin, The ultrasonic welding apparatus includes: an ultrasonic power generating unit that generates ultrasonic power; a transducer that generates the ultrasonic vibration based on the ultrasonic power generated by the ultrasonic power generation unit, The control program causes a computer to execute a step of determining a timing to stop the vibrator in accordance with a change in a resonant frequency of the vibrator or a parameter correlated with the resonant frequency.

Images