JPH0576841A - Screw turning langevin type ultrasonic vibrator - Google Patents

Abstract

PURPOSE:To obtain the title ultrasonic vibrator taking out high output and having durability by setting the dimensions of the piezoelectric element, first and second metal blocks and fixing nut constituting the vibrator in the thickness direction thereof to predetermined values. CONSTITUTION:Each of the thickness dimensions of piezoelectric elements 1, 2 laminated so that the polarizing directions thereof become mutually reverse is allowed to collide with the 1/4 wavelength of predetermined resonance frequency and the thickness dimension of a first metal block 3 is allowed to collide with the half wave of the predetermined resonance frequency and the thickness dimensions of both of a second metal block 5 and a fixing nut 6 are allowed to collide with the 1/4 wavelength. The total length of a vibrator is set so as to become a wavelength 1.5 times that of the predetermined resonance frequency like a vibration waveform (a) and the diameter of each of the metal blocks is made larger than that of each of the piezoelectric elements to eliminate such a problem that energy loss becomes large in a contact surface. Therefore, a screw turning Langevin type ultrasonic vibrator having high durability and capable of taking out high output can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw tightening Langevin type ultrasonic vibrator used for ultrasonic welding of plastics, ultrasonic bonding of metal wires, high-frequency ultrasonic equipment, and other vibration systems for strong ultrasonic applications. is there.

[0002]

2. Description of the Related Art As an ultrasonic transducer of this type, as shown in FIG. 2, two piezoelectric elements a and a are sandwiched between first and second metal blocks b and c, and they are centered. A screw-tightened Langevin-type vibrator is known which is integrally fastened by a fastening member including a bolt d and a fixing nut e. Further, the total length of this vibrator is equal to a half wavelength of a predetermined resonance frequency, as can be seen from the vibration waveform (b) referenced and shown on one side of FIG.

[0003]

By the way, as an ultrasonic vibrator for a welder of a thermoplastic member such as plastic, the resonance frequency is increased in order to more reliably ultrasonically bond only the welded portion. However, in the above-described vibrator having the conventional structure, if the resonator is designed to operate at a resonance frequency of 100 kHz or higher, the total length is shortened to about 20 mm, and the thickness of the piezoelectric element sandwiched by the metal blocks is 2 mm.
Therefore, the piezoelectric element cannot be firmly tightened and fixed, and the applied electric power is limited to 10 W at most, so that a vibrator with high output and durability cannot be obtained. ..

[0004]

According to the present invention, a first metal abutting against an end face of one of the piezoelectric elements has a thickness dimension of two piezoelectric elements formed by laminating the polarization directions opposite to each other to ¼ wavelength. The thickness dimension of the block is a half wavelength, the thickness dimension of the second metal block abutting on the end surface of the other piezoelectric element is a quarter wavelength, and the thickness dimension of the second metal block is abutting on the outer end surface of the second metal block and the central bolt is The thickness dimensions of the fixing nuts that are screwed to fasten the first and second metal blocks and the piezoelectric element together are made equal to ¼ half wavelength, and the total length of the vibrator is 1 wavelength of the predetermined resonance frequency. The length is set to be 5 times longer.

[0005]

[Function] Since the resonance of the piezoelectric element in the thickness direction is utilized, a thick piezoelectric element can be used.
Not only will it not be damaged even if it is tightly clamped between the metal blocks, but also high input power can be applied, so a vibrator with high output and excellent durability can be obtained.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. Reference numerals 1 and 2 are two ring-shaped piezoelectric elements, and ring-shaped terminal plates (not shown) so that their polarization directions (arrows) are opposite to each other. It is laminated through. Reference numeral 3 denotes a cylindrical first metal block that is in contact with the end surface of the one piezoelectric element 1, and extends in the axial direction from the center of the contact surface.
The male screw part 4a which penetrates 2a in an electrically insulating manner and penetrates an inner hole of a second metal block described later and projects outward.
A central bolt 4 having Reference numeral 5 is a cylindrical second metal block that is in contact with the end face of the other piezoelectric element 2,
As described above, the center bolt 4 is inserted into the inner hole 5a. Reference numeral 6 denotes a fixing nut that abuts on the outer end surface of the second metal block 5 and is screwed with the male screw portion 4a of the central bolt protruding from the inner surface 5a of the metal block 5. Metal block 3 and second
The piezoelectric elements 1 and 2 are firmly and integrally fastened to the metal block 4.

Therefore, in the present invention, in the vibrator having the above laminated structure, in order to utilize the thickness resonance of the piezoelectric elements 1 and 2,
The thickness dimension of each of the elements 1 and 2 is set to a quarter wavelength of a predetermined resonance frequency, the thickness dimension of the first metal block 3 is set to a half wavelength, and the thickness dimension of the second metal block 5 is set to a quarter wavelength. The thickness dimension of the fixed nut 6 is made equal to 1/4 wavelength, and the total length of the vibrator is adjacent to the vibrator of FIG. 1 and is 1.5 times the wavelength of the predetermined resonance frequency as shown in the illustrated vibration waveform (a). It is set to double.

In the above example, if the diameters of the first and second metal blocks 3 and 5 are the same as the diameters of the piezoelectric elements 1 and 2 contacting them, the acoustic impedance ρc (density × sound velocity) of both. However, there is a problem that sound waves are reflected at the contact surface between the metal block and the piezoelectric element, resulting in a large energy loss.However, as shown in the figure, the diameter of the metal block is larger than that of the piezoelectric element, and the wave Dance sρc
This problem can be solved by making (area x density x speed of sound) equal.

Further, the first metal block 3 may be used as an ultrasonic wave radiation side, and a vibrating horn having an integral multiple length of a wavelength of a predetermined resonance frequency may be coupled thereto.

Now, as the piezoelectric elements 1 and 2, a lead zirconate titanate-based piezoelectric ceramic having a ring shape with an outer diameter of 15 mm and an inner diameter of 7 mm and having a thickness dimension of 5.1 mm which is equal to a quarter wavelength of the resonance frequency. The first metal block 3 is made of an aluminum alloy and has a cylindrical shape with an outer diameter of 20 mm and has a thickness dimension of 13.3 mm which is equal to a half wavelength of the resonance frequency, and further extends axially from the center of the inner end face and has a male screw at its tip. A central bolt 4 integrally formed with a diameter of 6 mm and a length of 30.5 mm in which the portion 4a is engraved; the second metal block 5 is made of the same material as the first metal block,
A ring shape with an outer diameter of 20 mm and an inner diameter of 7 mm, the thickness dimension of which is equal to 1/4 wavelength of the resonance frequency; / 4 wavelength, and having an internal thread on the inner surface that engages with the external thread of the central bolt; between the first metal block 3 and the second metal block 5 as shown in FIG. Then, a laminated body formed by sandwiching the piezoelectric elements 1 and 2 was tightened with a central bolt 4 and a fixing nut 6 with a torque of 60 kg · cm to integrally fasten the screw to obtain a Langevin type ultrasonic transducer.

It was confirmed that when this oscillator was driven by applying an alternating voltage, thickness vibration occurred at a resonance frequency of about 200 kHz. Further, the mechanical Q at this time was 185, and the free admittance (mS) was 4.1, which all showed practically satisfactory characteristics.

[0012]

[Effect] As described above, according to the present invention, by simply setting the dimensions in the thickness direction of the piezoelectric element, the first and second metal blocks, and the fixing nut constituting the screw tightened Langevin type ultrasonic vibrator to predetermined values, An ultrasonic transducer exhibiting a desired resonance frequency of 100 kHz or higher can be easily obtained, and since thickness resonance of the piezoelectric element is utilized, the piezoelectric element can be made thicker, which is high. It does not break even if it is tightened with torque or high input power is applied, durability is improved and high output can be taken out, so this type of plastic welding vibrator can be expected to have an outstanding effect. ..

[Brief description of drawings]

FIG. 1 is a quarter sectional view of a screw tightened Langevin type ultrasonic transducer showing an embodiment of the present invention.

FIG. 2 is a quarter sectional view of a conventional screw tightening Langevin type ultrasonic transducer.

[Explanation of symbols]

 1 Piezoelectric Element 2 Piezoelectric Element 3 First Metal Block 4 Center Bolt 5 Second Metal Block 6 Fixing Nut

Claims (2)

[Claims] 1. In a screw tightened Langevin type ultrasonic transducer operating at a resonance frequency of 100 kHz or more, each piezoelectric element formed by laminating two polarization directions opposite to each other has a thickness dimension of ¼ wavelength. The thickness dimension of the first metal block abutting on the end surface of the one piezoelectric element is half wavelength, and the thickness dimension of the second metal block abutting the end surface of the other piezoelectric element is ¼ wavelength. The thickness dimensions of the fixing nuts that come into contact with the outer end surface of the second metal block and are screwed with the central bolts to integrally fasten the first and second metal blocks and the piezoelectric element are made equal to ¼ half wavelength. A screw-fastened Langevin-type ultrasonic vibrator, wherein the total length of the vibrator is set to be 1.5 times the wavelength of a predetermined resonance frequency. 2. The metal block is made larger in diameter than the piezoelectric element so that the wave impedances sρc (surface area × density × sonic velocity) of the contact surfaces of the piezoelectric element and the first and second metal blocks are equal. The screw-fastened Langevin-type ultrasonic transducer according to claim 1, which is characterized in that.