Vibration conversion apparatus with flexural resonator portions

To provide a vibration conversion apparatus capable of reducing occurrence of cracks although using a longitudinal vibration converter for obtaining a torsional vibration. The vibration conversion apparatus comprises: a first longitudinal vibration converter and a longitudinal-torsional transducer having a one-wavelength torsional vibrator portion and a first flexural resonator portion. The first flexural resonator portion is interposed between the first longitudinal vibration converter and the one-wavelength torsional vibrator portion. The first flexural resonator portion is configured such that when a longitudinal vibration generated by at least the first longitudinal vibration converter is received from one end of the first flexural resonator portion, the first flexural resonator portion is bent and imparts a rotational force from the other end of the first flexural resonator portion to the one-wavelength torsional vibrator portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase Application under 35 U.S.C. 371 of International Application No. PCT/US2019/067638, filed on Dec. 19, 2019, which claims priority to Japanese Patent Application No. 2018-236996, filed on Dec. 19, 2018. The entire disclosures of the above applications are expressly incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a vibration conversion apparatus that converts a longitudinal vibration to a torsional vibration.

BACKGROUND ART

Application techniques using strong ultrasonic waves are widely accepted in an industry such as welding, cleaning, and pulverizing. One of the techniques is ultrasonic welding technology. From the point of view of the welding device, the objects to be welded can be broadly classified into plastics and metals.

Further, from the point of view of the vibration mode, the vibration can be broadly classified into a longitudinal vibration, a transverse vibration, and a torsional vibration. As used herein, the longitudinal vibration is a designation that the pressurizing direction is the same as the vibration direction, and the transverse vibration is a designation that the pressurizing direction is orthogonal to the vibration direction. The same converter serving as the vibration source can be adopted for both the longitudinal vibration and the transverse vibration, and in general, the transverse vibration is applied to metal welding.

Meanwhile, the torsional vibration is a designation that the vibration direction follows an arc about a predetermined axis. The method of generating a torsional vibration is classified into a first mode in which a torsional vibration is generated directly by a torsional converter, and a second mode in which a torsional vibration is generated from a longitudinal vibration converter. However, the first mode using the torsional converter has a tendency that a high output power cannot be obtained. Meanwhile, as the second mode, there is a configuration disclosed in European Patent Application No. EP 0962261 A, Specification.

As described in the configuration disclosed in European Patent Application No. EP 0962261 A, Specification, when a longitudinal vibration is converted to a torsional vibration, linear motion needs to be mechanically coupled to arc vibration. Therefore, this configuration involves a problem that excessive concentrated stress is repeatedly generated at a portion connecting a longitudinal vibration converter and a torsional vibrator portion mutually connected by brazing or welding, resulting in that cracks are likely to occur in a member of the connected portion.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In view of the above problem, the present invention has been made, and an object of the present invention is to provide a vibration conversion apparatus capable of reducing occurrence of cracks although using a longitudinal vibration converter for obtaining a torsional vibration.

Solution to Problem

A vibration conversion apparatus of the present invention for achieving the above object comprises: a first longitudinal vibration converter; and a longitudinal-torsional transducer having a one-wavelength torsional vibrator portion and a first flexural resonator portion, wherein the first flexural resonator portion is interposed between the first longitudinal vibration converter and the one-wavelength torsional vibrator portion, and the first flexural resonator portion is configured such that when a longitudinal vibration generated by at least the first longitudinal vibration converter is received from one end of the first flexural resonator portion, the first flexural resonator portion is bent and imparts a rotational force from the other end of the first flexural resonator portion to the one-wavelength torsional vibrator portion.

Advantageous Effects of Invention

The present invention can reduce the occurrence of cracks although using a longitudinal vibration converter for obtaining a torsional vibration.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments in which the vibration conversion apparatus of the present invention is implemented as an ultrasonic welding device will be described with reference to the accompanying drawings. It should be noted that in the drawings, the same reference numerals or characters denote the same or corresponding portions.

First Embodiment

FIG.1is a perspective view illustrating an outline of an ultrasonic welding device according to a first embodiment of the present invention.FIG.2is a perspective view illustrating the ultrasonic welding device ofFIG.1as viewed from a direction different from that ofFIG.1.FIG.3is a perspective view illustrating an entire longitudinal-torsional transducer of the ultrasonic welding device according to the first embodiment. Note that the description uses three axes of XYZ orthogonal to each other, assuming that in the drawings, the X direction is the left-right direction, the Y direction is the height direction, and the Z direction is the front-back direction.

An ultrasonic welding device1comprises a vibration conversion apparatus3, a working torsional horn5, and a torsional support horn7. Hereinafter, the detail of the vibration conversion apparatus3will be described.

As illustrated inFIGS.1and2, the vibration conversion apparatus3comprises a first longitudinal vibration converter11a; and a longitudinal-torsional transducer14having a one-wavelength torsional vibrator portion13and a first flexural resonator portion15a. Although the present invention is not necessarily limited to this example, in the present embodiment, the vibration conversion apparatus3further comprises a first longitudinal vibration horn17aand a second longitudinal vibration horn17b. As the entire configuration is illustrated inFIG.3, the longitudinal-torsional transducer14includes the one-wavelength torsional vibrator portion13and the first flexural resonator portion15a. The one-wavelength torsional vibrator portion13and the first flexural resonator portion15aare a one-piece component that can be manufactured by cutting out from an integral metal body as an example. Further, another example may include a molding method by pouring into a mold or a molding method by powder metallurgy.

The support horn7and the working torsional horn5are threadedly connected to an upper end and a lower end of the longitudinal-torsional transducer14, respectively. A flange portion of the support horn7plays a role of supporting and pressurizing the entire vibration conversion apparatus including the longitudinal vibration converter. The one-wavelength torsional vibrator portion13is torsionally rotated so as to substantially prevent the rotating shaft from moving while being pressurized toward the object to be welded. The one-wavelength torsional vibrator portion13is a rod-shaped member (a columnar member), and as an example, in the present embodiment, is a prismatic member whose cross section perpendicular to the axial direction has a substantially regular octagonal outer shape, extending in the vertical direction. Note that any member having a circular cross section, a square section other than the octagonal cross section, a star-shaped cross section, or an asymmetrical cross section can be used, but a columnar member having an octagonal cross section is easily machined.

The first flexural resonator portion15ais interposed between the first longitudinal vibration converter11aand the one-wavelength torsional vibrator portion13. The first longitudinal vibration horn17ais located on a vibration transmission path between the first longitudinal vibration converter11aand one end21of the first flexural resonator portion15a. Further, the other end23of the first flexural resonator portion15ais connected to the longitudinal-torsional transducer13.

The vibration conversion apparatus3of the first embodiment further comprises the second longitudinal vibration horn17b. The one end21of the first flexural resonator portion15ais interposed between the first longitudinal vibration horn17aand the second longitudinal vibration horn17bin a longitudinal vibration direction (X direction).

Then, an operation of the ultrasonic welding device, namely, the vibration conversion apparatus of the thus configured first embodiment will be described with reference toFIGS.4to6.FIG.4is a view illustrating an operation of the vibration conversion apparatus of the present invention.FIG.5is a view illustrating another operation of the vibration conversion apparatus.FIG.6is a view illustrating still another operation of the vibration conversion apparatus.

First, a longitudinal vibration generated by the first longitudinal vibration converter11ais transmitted to the first longitudinal vibration horn17a. This longitudinal vibration causes the state ofFIG.5and the state ofFIG.6to be alternately repeated.FIG.5illustrates the state in which when the first longitudinal vibration horn17acauses a stretching vibration, the second longitudinal vibration horn17bcauses a shrinking vibration; andFIG.6illustrates the state in which when the first longitudinal vibration horn17acauses a shrinking vibration, the second longitudinal vibration horn17bcauses a stretching vibration. More specifically, the state changes from the state ofFIG.4to the state ofFIG.5, then, passing through the neutral state ofFIG.4, enters the state ofFIG.6, and then passing through the neutral state ofFIG.4, returns to the state ofFIG.5. Such state changes are repeated.

Further, in the neutral state ofFIG.4, there is a distance L is a distance in plan view between the annular outer shape (for example, a circular circumference or a square-shaped outer periphery, in the present embodiment, the square-shaped outer periphery) of the one-wavelength torsional vibrator portion13and the outer periphery line of the longitudinal vibration horn. In other words, the annular outer shape of the one-wavelength torsional vibrator portion13does not directly contact the outer periphery of the longitudinal vibration horn. Still another way of saying this is that the first flexural resonator portion15ais disposed to cause the annular outer shape of the one-wavelength torsional vibrator portion13to be separated from the outer periphery of the longitudinal vibration horn in the Z direction (direction orthogonal to the longitudinal vibration direction). Therefore, the one-wavelength torsional vibrator portion13rotationally vibrates through bending of the first flexural resonator portion15a(note that the annular one end21of the first flexural resonator portion15ais not bent). More specifically, in the state ofFIG.5in which the first longitudinal vibration horn17astretches and the second longitudinal vibration horn17bshrinks, the one-wavelength torsional vibrator portion13rotates clockwise; and in the state ofFIG.6in which the first longitudinal vibration horn17ashrinks, and the second longitudinal vibration horn17bstretches, the one-wavelength torsional vibrator portion13rotates counterclockwise.

The first flexural resonator portion15ais configured such that when a longitudinal vibration generated by at least the first longitudinal vibration converter11ais received from the one end21of the first flexural resonator portion15a, the first flexural resonator portion15ais bent, and imparts a rotational force from the other end23of the first flexural resonator portion15ato the one-wavelength torsional vibrator portion13.

By the longitudinal vibration generated by the first longitudinal vibration converter11aas described above, the one-wavelength torsional vibrator portion13performs a torsional vibration. In other words, the longitudinal vibration is converted to the torsional vibration. When ultrasonic welding is performed, an object to be welded is brought into pressurized contact with the working torsional horn5, and then welding is performed. More specifically, a driving force is inputted to the annular peripheral surface of the one-wavelength torsional vibrator portion13and is outputted from an end surface in the axial direction of the one-wavelength torsional vibrator portion13, thereby to work on a workpiece.

Further, the mechanism of vibration will be described. The present invention greatly reduces the occurrence of stress concentration not by directly converting from a longitudinal vibration to a torsional vibration, but by passing through the flexural resonator portion in the middle. First, as illustrated in a half-wavelength torsional vibration ofFIG.7, a half-wavelength longitudinal vibration horn is coupled to a longitudinal vibration converter; and further as illustrated in a one-wavelength torsional vibration ofFIG.8, a transducer generating a flexural vibration half-wavelength is sandwiched between half-wavelength horns, thereby to impart a stable driving force to a flexural plate. The flexural resonator portion for use as the flexural plate is designed with the same resonant frequency as the longitudinal vibration horn and thus stress concentration does not occur. Further, as illustrated inFIG.8, the flexural plate is coupled at an intermediate position of the one-wavelength torsional horn having the same resonant frequency, and the flexural vibration of the plate is converted to the torsional vibration.

The longitudinal vibration and the flexural vibration are coupled to each other not by using nuts and the like but by sandwiching the transducer between the half-wavelength horns having high rigidity. The reason for this is to prevent loss from occurring during conversion of the flexural vibration, which might otherwise be caused by deformation of the sandwiched portion in the mode using the nuts.

A resonance equation for a general beam can be applied to the resonance of the flexural vibration plate.

where I is the cross sectional secondary moment, B is the width direction of the cross direction, and H is the thickness direction.

Further, assume that the relation to the frequency f is
2πf=(1.875/L){circumflex over ( )}2×√(EI/ρA),
where E is the Young's modulus of the material, ρ is the density, A is the cross sectional area, and L is the length.

At this time, 1.875 is a first-order constant when one end is fixed, and L is ¼ wavelength. A length of about 2×L is required as a coupling between resonators.

As an example, in the case of 20 kHz and an iron material, the length is about 29 mm to 45 mm with a width of 5 mm to 12 mm; and in the case of one-wavelength, the length is 58 mm to 90 mm with a width of 5 mm to 12 mm.

Note that for obtaining an exact solution, finally, a numerical analysis (finite element method) can be used to obtain the length corresponding to the current shape.

The above described present embodiment can greatly reduce the occurrence of cracks although using a longitudinal vibration converter for obtaining a torsional vibration.

Second Embodiment

With reference toFIG.9, a second embodiment of the present invention will be described. The present invention is not limited to the embodiment having only one longitudinal vibration converter, but may include a mode in which one end of the flexural resonator receives a longitudinal vibration generated by another longitudinal vibration converter. The second embodiment is one example of this.

As illustrated inFIG.9, the vibration conversion apparatus of the second embodiment comprises a second longitudinal vibration converter11b. The second longitudinal vibration horn17bis located on a vibration transmission path between the second longitudinal vibration converter11band the one end21of the first flexural resonator portion15a.

This mode not only has the advantages of the above described first embodiment but also can achieve high power using a plurality of converters and driving the converters by one oscillator. Note that this mode illustrates an example of incorporating an even number of converters, but another mode incorporating an odd number of converters can also be implemented by controlling the phase on the oscillator side.

Third Embodiment

With reference toFIG.10, a third embodiment of the present invention will be described. The present invention is not limited to the embodiment having only one flexural resonator portion, but may include a mode in which the longitudinal-torsional transducer has a plurality of flexural resonator portions, and the one-wavelength torsional vibrator portion is vibrated by the plurality of flexural resonator portions. The third embodiment is one example of this.

As illustrated inFIG.10, the vibration conversion apparatus of the third embodiment comprises a longitudinal-torsional transducer16; a third longitudinal vibration converter11cand a fourth longitudinal vibration converter11d; and a third longitudinal vibration horn17cand a fourth longitudinal vibration horn17d. The longitudinal-torsional transducer16comprises the one-wavelength torsional vibrator portion13, and the first flexural resonator portion15aand a second flexural resonator portion15b. The wavelength torsional vibrator portion13, the first flexural resonator portion15a, and the second flexural resonator portion15bare also configured as a one-piece component in the same manner as the above described first embodiment.

As viewed in the axial direction (Z direction) of the first flexural resonator portion15a, the second flexural resonator portion15bis disposed on the opposite side of the first flexural resonator portion15awith the one-wavelength torsional vibrator portion13interposed therebetween. The third longitudinal vibration horn17cis located on a vibration transmission path between the third longitudinal vibration converter11cand the one end25of the second flexural resonator portion15b.

The other end27of the second flexural resonator portion15bis connected to the one-wavelength torsional vibrator portion13. The one end25of the second flexural resonator portion15bis interposed between the third longitudinal vibration horn17cand the fourth longitudinal vibration horn17din the longitudinal vibration direction (X direction). The fourth longitudinal vibration horn17dis located on a vibration transmission path between the fourth longitudinal vibration converter11dand the one end25of the second flexural resonator portion15b. Although the present invention is not limited to this configuration, the configuration illustrated inFIG.10is front-rear symmetric and left-right symmetric about the one-wavelength torsional vibrator portion13.

OTHER EMBODIMENTS

The present invention is not limited to the embodiment requiring a longitudinal vibration horn, but may omit the longitudinal vibration horn (longitudinal vibration booster) and the one end of the flexural resonator portion may be sandwiched directly between the converters as long as the material of a front drive of the converters can sufficiently withstand the high power. A fourth embodiment illustrated inFIG.11and a fifth embodiment illustrated inFIG.12are the specific examples. The fourth embodiment illustrated inFIG.11illustrates a mode omitting the longitudinal vibration horns in the configuration ofFIG.9. The fifth embodiment illustrated inFIG.12illustrates a mode omitting the longitudinal vibration horns in the configuration ofFIG.10.

REFERENCE SIGNS LIST