JPS61287612A - Transport device of piezo drive type - Google Patents

Abstract

PURPOSE:To increase the transport speed by changing the voltage to the impressed on a piezo element and its frequency in compliance with the weight change of object transported according to weight detection signal for the object, and thereby driving the piezo element as all times with a voltage having the same frequency as the resonance frequency of the device. CONSTITUTION:The weight detection signal V1 for an object transported 14 is added to the reference value V2, and the weight signal V3 obtained is converted into a frequency signal Sf equivalent to the resonance frequency f0 of an exciting mechanism 19 determined according to the weight sensed by a circuit 24. At the same time, the signal V3 is converted at a circuit 25 into a voltage signal Sv containing the voltage V0 determined according to the sensed weight, while the power supply 21 receives signals Sf, Sv and the output frequency and voltage are controlled into f0 and V0, and then the values are impressed on a sensing element 20. Accordingly the piezo element 16 is driven by an AC voltage having a frequency f0 determined by the spring constant K of a lief spring 12 and the weight applied thereto w and also a voltage V0 determined by the characteristics of said piezo element 16 and maintained in compliance with weight change of the object transported 14 to ensure that the element 16 is always vibrated in max. amplitude.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a piezoelectric drive type vibration device that uses a spring member and a piezoelectric element as a vibration source of a conveying body that conveys relatively small articles such as electrical or mechanical parts by vibration. Regarding.

[Technical Background of the Invention] FIG. 6 shows a conventional piezoelectric driven parts feeder using a piezoelectric element as a vibration source. In this figure 6, 1 is the base, 2
3 is a lower frame, 3 is a vibrating body supported horizontally by two leaf springs 4 that stand up parallel to each other and inclined; 5;
7 is a conveyor, for example, a trough, on which a conveyed article 6 is placed.
is a piezoelectric element attached to each of the leaf springs 4, to which the AC voltage applied between the terminals 8 and 9 is applied to the lead wires 8a and 9a.
It is designed to be applied via the

In this device, when an AC voltage is applied to the piezoelectric element 7 attached to each leaf spring 4 to excite it, each piezoelectric element 7.
Since it extends in the positive half cycle and contracts in the negative half cycle, its cantilevered bimorph structure converts the stretching motion into a bending motion, which is transmitted to the leaf springs 4, and these leaf springs 4 is photographed using the connecting portion with the lower frame 2 as a fulcrum to excite the vibrator 3, thereby causing the trough 5 to vibrate.

[Background technology problem 1] This type of piezoelectric drive parts feeder is
Publication No. 087, Utility Model No. 5. ．． As stated in Publication No. 7-46517, etc., the structure is smaller and simpler than the N11 drive feeder and the electric vibration feeder, so it is easy to handle and repair, and it consumes less power. Although it has many advantages such as being economical and having no concerns about noise, it still has problems in terms of transport efficiency. That is, in the piezoelectric drive parts feeder having the above configuration, when an alternating current voltage is applied to the piezoelectric element 7, the piezoelectric element 7 is integrated with the leaf spring 4 and causes a flexural vibration, causing the trough 5 connected to the movable end of the leaf spring 4 to tilt diagonally. It vibrates in the vertical direction to move the conveyed object 6 along the trough 5 in the direction of the arrow. In this case, the conveyance speed of the conveyed object 6 is proportional to the vibration amplitude of the trough 5.

On the other hand, the vibration amplitude of the trough 5 differs greatly between a resonance point and a non-resonance point determined by the structure of the parts feeder even when excited with the same force. The relationship between this excitation frequency and vibration amplitude is shown in FIG.

As shown in FIG. 4, the resonance points (fL, f2, fa,
It can be seen that the vibration amplitude differs by more than 100 times even with the same excitation force between fa > and the non-resonant point, and that efficiency increases when the frequency of the voltage applied to the piezoelectric element 7 matches the resonant frequency. However, this resonance point, that is, the resonance frequency, is not always constant, and the resonance frequency is fo()12), the spring constant of the leaf spring 4 of the parts feeder is k (Kgf/am), and the weight above the leaf spring 4 of the parts feeder is W (KQf>
, 1 force acceleration is Q (1111/S”),
It is indicated by.

Here, although the spring constant and the gravitational acceleration Q are constant, the weight JiW is the sum of the weight of the trough 5 etc. and the weight of the conveyed object (article 6). Although the weight of the trough 5 and the like is constant, the weight of the transported object 6 always changes.

Therefore, the weight W constantly changes, and the resonant frequency f
o also changes. For this reason, if the frequency of the voltage applied to the piezoelectric element 7 is kept constant, a state in which the object 6 vibrates at a frequency different from the resonance frequency occurs due to a change in the weight of the conveyed object 6, resulting in a decrease in the conveyance speed and therefore a decrease in conveyance efficiency.

On the other hand, FIG. 5 shows the relationship between displacement and force that occurs when the same voltage is applied to the piezoelectric element 7. As shown in FIG. 5, the displacement δ generated when the same voltage is applied to the piezoelectric element 7 and the force F are in a relationship such that as the force F increases, the displacement δ decreases. Therefore, if internal stress is generated in the piezoelectric element 7, a force is required to cancel it, and the displacement that occurs when the same voltage is applied becomes smaller by the amount required to cancel it. Since this internal stress is proportional to the weight applied to the leaf spring 4, the displacement generated in the piezoelectric element 7 becomes smaller as the weight a of the conveyed object 6 increases.

Moreover, since the conveyance speed of the conveyed object is proportional to the displacement of the trough 5, when the displacement of the piezoelectric element 7 becomes small, the displacement of the trough 5 also becomes small, and the conveyance speed decreases. Therefore, there is a problem in that the larger the weight of the conveyed object, the more the conveyance speed decreases even if the object is excited at the resonant frequency.

By the way, as a method for stabilizing the conveyance speed,
There is a method disclosed in Japanese Patent No.-167913. This is a combination of a trough and a leaf spring by inserting a square-shaped auxiliary spring between them. According to this method, the seedling of the trough is absorbed by the deformation of the F-shaped auxiliary spring, which is effective in absorbing the weight of the trough. However, it cannot solve the essential problem of a change in resonance frequency due to a change in the weight ff1W when an object is being moved on a trough.

[Objective of the Invention] Therefore, the object of the present invention is to provide a piezoelectric drive type vibration transfer device that can constantly drive the piezoelectric element with a voltage of approximately the same frequency as the resonant frequency of the device even when the weight changes due to the conveyed object, and that increases the conveyance speed. The goal is to provide equipment.

[Summary of the Invention] A piezoelectric drive type vibration device according to the present invention vibrates a vibrating body that excites a conveyed object by a combination device of a spring member and a piezoelectric element, and detects the weight of the conveyed object by a weight detection means. The voltage applied to the piezoelectric element and its frequency are controlled according to changes in the weight of the conveyed object based on the detection signal, so that the piezoelectric element can always be driven at approximately the resonant frequency point.

[Embodiments of the Invention] A first embodiment of the present invention will be described below with reference to FIG. Reference numeral 10 denotes a fixed part, that is, a fixed base, to which a lower frame 11 is fixed, and two spring members, that is, leaf springs 12, are connected at the lower ends of the fixed base so as to be in an inclined upright state. Between the upper ends of these leaf springs 12, a vibrating body 1 is placed in a horizontal state.
3 are connected to each other, and this vibrating body 13 is attached to a carrier or trough 15 on which a conveyed object 14 is placed and conveyed.

On the other hand, a piezoelectric element 16 is attached to the leaf spring 12 using a conductive adhesive. One lead wire 17 for applying voltage to these piezoelectric elements 16 is connected to the leaf spring 1.
2 and the other lead wire 18 is connected to a portion of the piezoelectric element 16 opposite to the leaf spring 12. Here, the lower frame 11, the leaf spring 12, the vibrating body 13, and the piezoelectric element 16 form a vibrating mechanism 19, and in this vibrating mechanism 19, the weight of the conveyed object 14 on the trough 15 causes displacement or A detection element 20 consisting of a strain gauge, for example, serving as a weight detection means is placed near the free end side of one of the leaf springs 12 to be distorted.
is installed.

Next, the circuit configuration will be explained along with its overall operation.

That is, the variable drive power source 21 outputs a voltage having a frequency between the lead wires 17 and 18, and applies this to the piezoelectric element 16. For this reason, the piezoelectric element 16 vibrates, so the vibrator 13
vibrates diagonally in the vertical direction, and vibrates the trough 15 in the same direction, so that the conveyed object 14 is conveyed in the direction of the arrow.

During this conveyance operation, the weight applied to the vibration mechanism 19 is constantly changing depending on the amount of the conveyed object 14, and this is detected by the weight detection means 22 having the detection element 20, from which a weight detection signal 1 is output. be done. This weight detection signal v1 is added to the reference value ■2 by the adding section 23,
And the weight signal ■3 which is the sum is the conversion rate ε! The frequency conversion circuit 24 converts the detected weight into a frequency signal Sf having a value equal to the resonant frequency fo of the vibration mechanism 19, which is predetermined according to the detected weight. At the same time, the weight signal 3 is converted by a voltage conversion circuit 25 with an amplification factor ε2 into a voltage signal Sv having a predetermined voltage 20 according to the detected weight. The variable drive power supply 21 receives these frequency signals Sr and voltage signals S and its output frequency becomes fO.
and the voltage are respectively controlled to 0, and these values are applied to the detection element 20. As a result, leaf spring 12
The piezoelectric element 16 is driven by an AC voltage having a resonant frequency fo determined by the spring constant and the force ff1W applied to the leaf spring 12, and an applied voltage 0 determined by the characteristics of the piezoelectric element 16, and this relationship is Even if there is a change in weight, the piezoelectric element 16 is maintained by following this change.
is always vibrated with maximum amplitude. As a result, transported object 1
The conveying speed of the conveyed object 14 is increased, the conveying efficiency is improved, and these are stable and are not affected by changes in the weight of the conveyed object 14.

Next, a second embodiment of the present invention will be described with reference to FIGS. 2 and 3. In this embodiment, an eddy current displacement sensor is used as the detection element 26, and this is used as the detection element 26.
Instead, as shown by the two-dot chain line in FIG. 1, a portion that moves up and down depending on the weight of the conveyed object 14 is disposed at a position facing, for example, the lower surface of the vibrating body 13 with a gap in between. The detection output e from the detection element 26 is amplified by the amplifier 27 and then fed to the active filter 28 to extract only its DC component signal E. This is then DC amplified by the preamplifier 29 and fed to the high frequency oscillator 30. The oscillation frequency of the high-frequency oscillator 30 is applied to the piezoelectric element 16 shown in FIG. Here, the active filter 28 includes resistors 31 and 32, capacitors 33 and 34, and an operational amplifier 35. The preamplifier 29 also includes an operational amplifier 36 and resistors 37 and 38.

Now, the output e of the detection element 26 is the standard load, that is, the transported object 14.
When the weight is standard, it is el, and when the weight is heavy, it is el. And these are as shown in Fig. 3, e 1 = E1 + At Sin ω'te
It is expressed as 2 = E2 + A25in ωt. Here, El and E2 are determined by the weight of the transported object 14 in the trough 1.
A1 and A2 are the maximum amplitude values of vibration for each weight (exchange meeting when trough 15 is vibrating). be. Therefore, the DC component signal E1. output from the active filter 28. Ex (shown in FIG. 3) becomes the weight signal of the conveyed object 14, which causes the high frequency oscillator 3
Since the oscillation output of 0 is controlled, the piezoelectric element 16 is driven by a voltage having approximately the same frequency as the resonant frequency that changes depending on the weight of the piezoelectric element 16, as in the case of the first embodiment.

Here, the reason for using the active filter 28 will be explained. The outputs e1 and e2 of the detection element 26 are the gap length displacements E1 and E2 between the detection element 26 and the vibrator 13 due to the weight of the conveyed object 14, and the gap length variation As due to the vibration operation.
, A2 (at sinω), and when the variation due to this vibration At, A2 (sinωt) is removed by an OR circuit, as a result of the smoothing action by the capacitor C, ex = El + o as shown by curve 39 in Figure 3. , 5Al, e2
=E2 +0.5A2 (not shown), and the fluctuation due to vibration (0.5As, 0.5A2) remains as a DC component, which becomes an error with respect to Er and Ex. That is, E
This is because the element that determines s and E2 is the spring constant of the leaf spring 12, whereas At and A2 are determined by factors other than the weight of the transported object 14. Therefore, according to this embodiment, only El and E2 can be extracted by using the active filter 28.

In addition, the present invention is not limited to the above-mentioned sudden collapse, but may also be applied to, for example, a piezoelectric drive parts feeder in which the bowl is vibrated to twist and rotate to convey the conveyed object in a spiral manner. Of course, there is no problem.

[Effects of the Invention] As described above, the present invention moves the conveyed object on the conveyed body by moving the vibrating body that excites the conveyed body using a combination device of a spring member and a pressure element. In things,
The weight of the conveyed object is detected by a detection means, and the voltage applied to the piezoelectric element and its frequency are controlled according to changes in the weight of the conveyed object using the detection signal, so that the piezoelectric element is always kept at approximately resonance. It is possible to provide a piezoelectric drive type conveyance device that can be driven at a frequency point and has a high conveyance speed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention together with its mechanical components, FIG. 2 is a block diagram showing the second embodiment, and FIG. 3 is a diagram for explaining the second embodiment. FIG. 4 is a frequency-displacement characteristic diagram of a typical piezoelectric element, FIG. 5 is a Kerr displacement characteristic diagram of a typical piezoelectric element, and FIG. 6 is a side view for explaining a conventional example. In the figure, 10 is a fixed base, 11 is a lower frame, 12 is a leaf spring, 13
1 is a vibrating body, 14 is a conveyed object, 15 is a trough (transport body), 1
6 is a piezoelectric element, 19 is an excitation mechanism, 20 is a detection element, 21
22 is a weight detection circuit, 24 is a frequency conversion circuit, 25 is a voltage conversion circuit, 26 is a detection element, 27 is an amplifier, 28 is an active filter, 29 is a preamplifier, and 30 is a high frequency oscillator. Applicant: Toshiba Corporation Figure 2 Time + 1) → Figure 3 Closed excitation frequency → Figure 4 Car F (Kgf) Figure 5

Claims (1)

[Claims] 1. A vibrating body that excites a conveying body that carries a conveyed object and conveys it by vibration, a spring member that is provided between this vibrating body and a fixed member and supports this vibrating body, and this spring. a piezoelectric element provided on the member for vibrating the vibrating body in cooperation with the spring member; a weight detection means for obtaining an electrical signal corresponding to the weight of the conveyed object moving on the conveying body; A piezoelectric drive type conveyance device comprising a control means for controlling the voltage and frequency applied to the piezoelectric element based on a signal.