JPH0344963B2 - - Google Patents

Description

[Detailed description of the invention]

[Object of the Invention] (Industrial Application Field) The present invention relates to a system for conveying relatively small parts such as electronic parts or small mechanical parts by vibration.
In particular, the present invention relates to a piezoelectrically driven conveyance device using a piezoelectric element as its vibration source. (Prior Art) This type of conveyance device, for example, a parts feeder, generally employs a bimorph, which is formed by pasting piezoelectric elements on both sides of an elastic plate such as a leaf spring, as a vibrating body. When an AC voltage is applied to the piezoelectric elements on both sides of this bimorph so that their polarization directions are opposite, for example, one piezoelectric element expands and the other piezoelectric element contracts in the positive half cycle, and one piezoelectric element contracts in the negative half cycle. By repeating the stretching motion in which one piezoelectric element contracts and the other piezoelectric element extends, the bimorph is excited and flexibly vibrates. By this,
A conveying body connected to this bimorph is vibrated diagonally in the vertical direction to sequentially convey the articles on the conveying body. By the way, in order to carry out vibration conveyance most efficiently,
It is necessary to cause the entire parts feeder to vibrate resonantly as one spring system, and for this to occur, it is necessary to match the frequency of the bimorph with the natural frequency of the mechanical system of the entire parts feeder. In the conventional configuration, the frequency of the AC voltage applied to the bimorph remains constant at the frequency of the commercial power supply, so the frequency of the bimorph remains constant and the natural vibration of the entire mechanical system. The number was adjusted to match the frequency of the bimorph (50 or 60Hz). The natural frequency of such a mechanical system can be adjusted by, for example, changing the type of connecting fittings that connect the elastic plate of the bimorph and the carrier, or adjusting the height position of the carrier. Ta. However, it is difficult for even a highly skilled person to accurately perform adjustment work on such a mechanical system at once, and there have been problems with the adjustment workability. Therefore, in order to eliminate the need for such troublesome adjustment work of the mechanical system, as shown in Japanese Utility Model Publication No. 52-48554, the frequency of the power supply voltage is configured to be adjustable.
It is considered that by adjusting the frequency, the frequency of the bimorph can be adjusted to match the natural frequency of the entire mechanical system. However, in this case, the output waveform is a rectangular wave. When such a rectangular wave voltage is applied to the piezoelectric element, the vibration waveform of the piezoelectric element, and thus the vibration waveform of the carrier, will contain many harmonic components, as shown by b in FIG. 4. For this reason, the vibration state of the conveyor becomes unstable, which not only causes a decrease in conveyance efficiency, but also has the drawback that a large amount of noise is generated due to its harmonic components. (Problems to be Solved by the Invention) As mentioned above, in the case of adjusting the natural frequency of the entire mechanical system, the adjustment work is extremely troublesome, whereas in the case of adjusting the frequency of the power supply voltage, the adjustment work is extremely troublesome. Since the voltage waveform was a rectangular wave, there were drawbacks such as a decrease in conveying efficiency and an increase in noise due to the instability of the vibration state. The present invention is intended to solve the above-mentioned drawbacks, and its purpose is to simplify the adjustment work to bring the whole into a resonant state, improve transport efficiency by stabilizing the vibration of the transport body, and reduce noise. The object of the present invention is to provide a piezoelectrically driven conveying device that obtains the desired results. [Structure of the Invention] (Means for Solving the Problems) The present invention provides an AC power supply device that applies an AC voltage to a piezoelectric element of a vibrating body that vibrates a conveyance body, in which the output frequency is variable and the output waveform is variable. It is configured to have a sine wave shape. (Function) When adjusting to obtain a resonant state, the frequency of the piezoelectric element of the vibrating body is adjusted to match the natural frequency of the entire mechanical system by adjusting the output frequency of the AC power supply. do. Furthermore, by making the waveform of the AC voltage applied from this AC power supply device to the piezoelectric element sinusoidal, harmonic components are prevented from being generated in the vibration waveform of the piezoelectric element and, ultimately, the vibration waveform of the carrier. This is what I did. (Example) Hereinafter, an example in which the present invention is applied to a bowl-shaped parts feeder will be described based on the drawings. Reference numeral 1 denotes a disc-shaped base, and a mounting base 2 is protruded from the upper surface of this base. Reference numeral 3 denotes a plurality of bimorphs (only two are shown for convenience in FIG. 1) as vibrating bodies, and each bimorph 3 has piezoelectric elements on both sides of a band-shaped elastic plate 4, as shown in FIGS. 2 and 3. 5a and 5b are attached by, for example, adhesion. In this case, the piezoelectric elements 5a and 5b are made of, for example, lead zirconate titanate ceramics. The lower end of the elastic plate 4 of the bimorph 3 is screwed and fixed to the circumferential side of the mounting base 2, so that each bimorph 3 is tilted at a predetermined angle on the same circumference on the base 1. They are arranged at equal intervals. 6 is a carrier connected to the upper end of the elastic plate 4 of each bimorph 3 via a connector 7 made of an elastic material;
This has a dish-like shape as a whole, and a spiral conveyance path (not shown) is formed on the inner circumference thereof. On the other hand, 8
is commercial power supply 9 (100V or 200V, 50Hz or 60Hz)
An AC power supply device connected to A voltage regulation circuit is provided. The output terminals of this AC power supply device 8 are connected to the piezoelectric elements 5a, 5b of the bimorph 3 via lead wires 10a, 10b so that their polarization directions are opposite. Next, the operation of the above configuration will be explained. When making adjustments to bring the entire parts feeder into a resonant state, first set the output voltage of the AC power supply 8 to, for example,
The voltage is adjusted to 150V and applied to the piezoelectric elements 5a and 5b. Then, for example, in a positive half cycle, one piezoelectric element 5a extends and the other piezoelectric element 5b contracts, and in a negative half cycle, one piezoelectric element 5a contracts and the other piezoelectric element 5b extends, and so on. By repeating this, the bimorph 3 is excited and flexibly vibrates, causing the carrier 6 to vibrate diagonally up and down in the circumferential direction. Then, an operation knob (not shown) of the AC power supply device 8 is operated to change the output frequency of the AC power supply device 8 (the frequency of the AC voltage applied to the piezoelectric elements 5a and 5b of the bimorph 3). Since the frequency of the bimorph 3 at this time is equal to the frequency of the applied voltage, the frequency of the bimorph 3 changes as the frequency of the applied voltage changes, and as a result, the frequency of the bimorph 3 changes, and as a result, the frequency of the bimorph 3 changes as the frequency of the applied voltage changes.
The frequency of vibration changes. Then, when the frequency of the bimorph 3 matches the natural frequency of the mechanical system of the entire parts feeder, the whole becomes in a resonant state, and the vibration amplitude of the bimorph 3 and, in turn, the vibration amplitude of the carrier 6 suddenly increases and reaches its maximum. The conveyance speed of the conveyed items is maximized. Therefore, the operator changes the output frequency of the AC power supply device 8 while checking the conveyance speed of the conveyed product, the vibration amplitude of the conveyor 6, or the vibration amplitude of the bimorph 3, and sets the output frequency to the maximum conveyance speed. You can adjust it accordingly. For this reason, the adjustment work to obtain a resonant state is much easier than adjusting the conventional mechanical system, and therefore, it is possible to change the transport body 6 to another transport body depending on the type of goods to be transported, for example. Even in the case of replacement, the adjustment work does not require much effort, improving productivity. Furthermore, in this embodiment, since the waveform of the AC voltage applied from the AC power supply device 8 to the piezoelectric elements 5a and 5b is sinusoidal, the voltage waveform almost matches the basic vibration waveform of the bimorph 3. Therefore, generation of high frequency components in the vibration waveform of the bimorph 3 and, ultimately, in the vibration waveform of the carrier 6 is prevented. The inventor actually measured the vibration waveform of the carrier 6 at this time, and the results are shown in FIG. 4 by a. As is clear from this, since the vibration waveform of the carrier 6 becomes a sine wave with no harmonic components, the vibration state of the carrier 6 is stabilized and the transport efficiency is improved compared to when the waveform of the applied voltage is a rectangular wave. is improved, and noise is significantly reduced. By the way, the diameter of the conveyor 6 is
Table 1 shows the measurement results of the noise generated when Bimorph 3 was driven with a 200Hz sine wave voltage and a square wave voltage in a 150mm model. As is clear from Table 1, the noise of the sine wave is 5 dB lower than that of the rectangular wave, and it can be seen that the noise reduction effect is greater.

【table】

Table 2 also compares the maximum current during driving in the piezoelectric parts feeder of this embodiment and the electromagnetic parts feeder in which the carrier is vibrated by an electromagnet. In this case, both have a resonant frequency of 50
Hz, and compared multiple types of carriers with diameters from 100 mm to 300 mm.As is clear from Table 2, the piezoelectric type has a significantly higher current value than the electromagnetic type. It can be seen that the power consumption is extremely small. Note that the present invention can be applied not only to bowl-shaped parts feeders but also to linear parts feeders, and as the vibrator, not only bimorphs but also elastic plates with piezoelectric elements affixed to only one side can be used. Various changes can be made without departing from the gist. [Effects of the Invention] As is clear from the above description, the present invention is configured to make the output frequency of the AC power supply variable. Therefore, the adjustment work to bring the whole into a resonant state can be done by adjusting the output frequency. The adjustment work can be simplified. Moreover, since the output waveform of the AC power supply is made into a sine wave, it is possible to prevent harmonic components from being generated in the vibration waveform of the piezoelectric element and ultimately the vibration waveform of the carrier, thereby stabilizing the vibration of the carrier. This has the excellent effect of improving conveyance efficiency and reducing noise.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention.
2 is a side view of the bimorph, FIG. 3 is a front view thereof, and FIG. 4 is a photograph showing an oscilloscope waveform of the vibration of the carrier. In the drawings, 3 is a bimorph, 4 is an elastic plate, 5a and 5b are piezoelectric elements, 6 is a carrier, and 8 is an AC power supply device.

Claims (1)

[Claims] 1. A carrier is connected to a vibrating body comprising a piezoelectric element attached to an elastic plate, and the carrier is vibrated by applying an alternating current voltage to the piezoelectric element to excite it, in which the piezoelectric 1. A piezoelectric drive type conveyance device, characterized in that an AC power supply device that applies an AC voltage to an element is configured so that the output frequency is variable and the output waveform is sinusoidal.