JPS627084B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a resonant electromagnetic vibrator.

Various types of resonant electromagnetic vibrators are known, and in the case of an electromagnetic feeder, for example, a drive section is coupled to a trough as a vibrated body via a leaf spring. The drive unit includes an electromagnet, and when an alternating current is applied to this coil, an excitation force is generated, and the trough vibrates at the frequency of this alternating current. Such an electromagnetic feeder constitutes a two-mass vibration system consisting of the mass of the driving part, the mass of the trough, the spring constant of the leaf spring, etc., and the natural frequency or resonance frequency is determined by these. The trough is normally excited with an excitation force at or near this natural frequency. That is, although a commercial power source is generally used as a driving power source, the electromagnetic feeder is designed so that its natural frequency matches or is close to the frequency of the commercial power source. Thereby, the magnitude of the excitation force for obtaining a predetermined swing width in the trough can be minimized or close to this. Therefore, the magnitude of the current flowing through the electromagnetic coil of the drive unit can be reduced, and power consumption can be reduced.

However, the trough is not supplied with any transfer material;
That is, there is no problem when there is no load or when the load is very small, but when the load increases to a certain extent, the amplitude of the trough becomes small even though the excitation force is constant. This is due to the synergistic effect of the increase in the weight of the vibrated body including the transferred material and the resulting fluctuation in the natural frequency. The natural frequency under no load was determined by taking into account the amount of time required.
However, if the load is constant, the objective is almost achieved, but if the load changes, the natural frequency and amplitude will change accordingly. Therefore, not only is the advantage of vibrating the trough at the natural frequency lost, but the desired effect cannot be obtained.

In addition, at the design stage of the electromagnetic feeder, it is necessary to match its natural frequency with the frequency of the AC power source used and to set the amplitude to a predetermined value.
Various design constraints are added, making the design that much more difficult.

On the other hand, it has been theoretically and experimentally proven that the material transport speed of an electromagnetic feeder is approximately proportional to the amplitude of the trough multiplied by the frequency of the excitation force.

The present invention has been made in view of the above points, and is a control for a resonant electromagnetic vibrator that can manufacture a resonant electromagnetic vibrator with a simple design and that can always obtain a constant transport speed with minimum power consumption. The purpose is to provide equipment. According to the invention, this purpose is
AC power supply; AC to DC converter connected to the AC power supply; DC to AC converter connected to the converter;
A resonant electromagnetic vibrator having a drive unit that receives the AC output of the DC to AC converter; a phase difference between the detected vibration of the vibrated body of the resonant electromagnetic vibrator and the excitation force based on the AC output; a phase difference π/2 or a value close to this between the vibration and the excitation force at the natural frequency of the resonant electromagnetic oscillator or a frequency close thereto; and the output of the phase detection means. and a multiplication means for multiplying the amplitude of the detected vibration of the vibrated body by the frequency of the excitation force; the output of the multiplication means and a predetermined transport speed. and a second comparing means for comparing the frequency of the excitation force to the natural frequency or the frequency of the excitation force by controlling the frequency of the AC output of the DC/AC converter based on the output of the first comparison means. The magnitude of the excitation force is controlled so that the vibration frequency is uniformly close to that of the excitation force, and the level of the DC output of the AC to DC converter is controlled based on the output of the second comparison means. This is achieved by a control device for a resonant electromagnetic vibrator, which controls the transport speed of the body to match the predetermined transport speed.

Practical examples to which the present invention is applied will be described below with reference to the drawings.

FIG. 1 shows a block circuit diagram of a control device for a resonant electromagnetic vibrator according to an embodiment. As schematically shown in the figure, the resonant electromagnetic vibrator controlled in this embodiment is an electromagnetic feeder 1. , which consists of a trough 2 as an excitation force and an electromagnetic drive section 3 as an exciter, which are coupled via a stacked leaf spring as is known. This drive section 3
A controlled alternating current is supplied to the electromagnetic coil as described below, and the control device according to this embodiment mainly uses an AC-DC converter 5 connected to the commercial AC power supply 4 and a synchronization with the commercial AC power supply 4. a gate circuit 6 that operates as a gate circuit and generates a pulse that controls the DC output level of the AC-DC converter 5; and a DC-AC converter 7 that converts the DC output of the AC-DC exchanger 5 into AC. , trough 2 of electromagnetic feeder 1
An amplitude detector 8 for detecting the vibration, that is, the amplitude of A comparator 10 for comparing the output of the phase detector 9 with a set phase, and a PI (Proportional
Integral) controller 11, a V-F converter 12 that receives the output of this PI controller 11 and generates a pulse with a frequency according to the magnitude, and outputs the output pulse of this V-F converter 12. A pulse distributor 13 for distributing to the four transistors in the DC to AC converter 7, which will be described in detail, and a multiplier 30 that receives the output of the amplitude detector and the output of the PI controller 11 and multiplies them. , a comparator 14 for comparing this output with a set transport speed, and a PI controller 15 that performs PI control in response to the output of this comparator 14 and generates a voltage according to this magnitude. It consists of

The output of the PI control section 15 is supplied to the gate circuit 6, which controls the phase of the gate pulse to the AC to DC converter 5. Therefore, an alternating current whose magnitude and frequency are controlled according to the output of the multiplier 30 and the output of the phase detector 9 is obtained from the DC to AC converter 7, and this is used to drive the drive unit 3 of the electromagnetic feeder 1. Supplied to the electromagnetic coil. The drive unit 3 generates an excitation force at the frequency of the alternating current applied to the electromagnetic coil and having a magnitude corresponding to the magnitude of the alternating current.

Next, the above-mentioned AC → DC converter 5 and DC AC →
Details of the converter 7 will be explained with reference to FIG.

In the AC to DC converter 5, the diode
D ₁ , D ₂ and thyristors SCR ₁ , SCR ₂ constitute a bridge circuit, to which a commercial AC power supply 4 is connected. The gate pulse of the gate circuit 6 shown in FIG. 1 is supplied to the gate electrodes of the thyristors SCR ₁ and SCR ₂ from the gate signal supply terminal G via the diodes D ₃ and D ₄ . A rectified output in which the conduction angles of the thyristors SCR ₁ and SCR ₂ are controlled by this gate pulse is obtained from the bridge circuit, and the diodes D ₉ and
The DC output is smoothed by a smoothing circuit consisting of a reactor L and a capacitor _C1 , and is supplied to the DC to AC converter 7 via a protection circuit 20 (not shown in FIG. 1).

In the DC to AC converter 7, a transistor
TR ₂ and TR ₅ form one pair, and the transistor
TR ₃ and TR ₄ form the other pair. Further, overvoltage absorbing diodes _D5 to _D8 are connected in parallel with each of the transistors _TR2 to _TR5 , respectively. The connection point between the transistors TR ₂ and TR ₄ and the connection point between the diodes D ₅ and D ₇ are connected to one terminal 21 of the electromagnetic coil 23 of the drive unit 3 of the electromagnetic feeder 1, and the connection point between the transistors TR ₃ and TR ₅ is Connection points and diodes D ₆ and D ₈
The connection point is the other terminal 22 of the electromagnetic coil 23
connected to. The electromagnetic coil 23 is wound around the core 24 in a known manner. Transistor TR ₂ ~
A rectangular wave pulse is supplied as a base signal from the pulse distributor 13 in FIG. 1 to the base electrodes B ₂ to _{B 5} of TR ₅ , but one transistor TR ₂ ,
Base electrodes B ₂ and B ₅ of TR ₅ and the other transistor
Base signals are alternately supplied to base electrodes B ₃ and B ₄ of TR ₃ and TR ₄ . Therefore, when one pair of transistors TR ₂ and TR ₅ is in a conducting state, the other pair of transistors TR ₃ and TR ₄ are in a non-conducting state, and one pair of transistors TR ₂ and TR ₅ is in a non-conducting state. When in the non-conducting state, the transistors of the other pair
TR ₃ and TR ₄ are in a conductive state.

The protection circuit 20 includes a detection coil 2 wound around the track.
5. Consists of a series circuit of a resistor R and a transistor TR ₁ , and when an overcurrent is detected by the detection coil 25, a cutoff circuit (not shown) shuts down the gate to the gate signal supply terminal G in the AC to DC converter 5. The pulse is interrupted and the base electrodes B ₂ - B ₅ of the transistors TR ₂ - _{TR 5} in the DC to AC converter 7
The base signal to is cut off. At the same time, a base signal is supplied to the base electrode _B1 of the transistor _TR1 , and the transistor _TR1 becomes conductive, and the capacitor in the AC to DC converter 5 is turned on.
The charge stored in _C1 is discharged through the resistor R. This protects each of the above-mentioned circuit elements from overcurrent. Note that the voltage between both electrodes of the capacitor _C1 may be detected, and when an overvoltage is detected, the above-mentioned protective action may be performed.

The gate circuit 6 of this embodiment is also configured as follows. That is, although not shown, when the start button of this device is pressed, a start command signal is given to the gate circuit 6, whereby the gate circuit 6 generates a gate pulse as shown in FIG. 3B. ing. In FIGS. 3A to 3D, temporal changes in the signals of each part immediately after recording are shown. The pulse phase θ is configured to change as θ=180°−k ₁ t (where t is time and k ₁ is a constant).
That _{is ,} as shown in _{FIG .}
θ changes as _{+ 1} > . This predetermined value α is determined by the transport speed value set in the comparator 14. Although not shown, when the stop button of this device is pressed, a stop command is given to the gate circuit 6, which causes the gate circuit 6 to change as θ=α+k ₁ t until the phase of the gate pulse reaches 180°. configured.

The above-mentioned constant k ₁ is determined in consideration of the following points. In other words, in general, when an excitation force of a certain frequency is applied to a vibrator, the 4th frequency is applied at startup and stop depending on the viscous resistance coefficient and the height of the natural frequency of the vibration system.
It vibrates in a transient state as shown in Figure A. Therefore, the amplitude is very large immediately after starting and immediately after stopping, and eventually reaches a steady value or zero, but such a transient state may adversely affect the desired action of the vibrator. In this embodiment, in view of this point, FIG.
The constant k ₁ is determined so that the vibrator starts and stops smoothly as shown in . That is, when the viscous drag coefficient is small, the time required for θ to reach a predetermined value α, that is, the rise time of the amplitude, is controlled to be long, and when the viscous drag coefficient is large, the rise time is controlled to be shortened. . The same applies to the falling time when stopping.

Due to the gate pulse shown in FIG. 3B, a rectified output as shown in FIG. 3C is obtained from the bridge circuit in the AC to DC converter 5, and this is smoothed by the smoothing circuit to complete the AC to DC conversion. A DC voltage as shown in FIG. 3D is obtained from the device 5.
This DC voltage reaches a steady value E as the phase θ of the gate pulse becomes α, but E≒k ₂ α(k ₂
is a constant), and since the excitation force to the trough 2 is uniquely determined by the height of E, the transportation speed of the trough 2 is ultimately determined by α.

Next, the phase value set in the comparator 10 will be explained.

Excitation force generated by the drive unit 3 of the electromagnetic vibrator 1;
The phase difference δ between the amplitude of the trough 2 that vibrates in response to this is generally expressed by the following relational expression in terms of vibration engineering.

tanδ=2γλ/1−λ ² In the above equation, γ is the viscous drag coefficient of the vibration system, and λ=f/fo=frequency of excitation force/resonance frequency of the vibration system.

Therefore, when f=fo, that is, when λ=1, there is a resonance state, and in this case, from the above equation, δ=π/2. Also, at λ→0, δ→0, and at λ→∞, δ
→π/2. Therefore, δ increases from 0 to π/ as f increases.
2 → π/2, but the manner of this change differs depending on the viscous drag coefficient γ. When γ=0, f=fo and δ changes stepwise from 0 to π/2. However, in reality, the viscous drag coefficient γ cannot be zero, so δ=π/2 in the resonance state. However, in this embodiment, a value slightly smaller than π/2 is set in the comparator 10 for stability of control.

Note that when the AC output of the DC to AC converter 7 is energized to the electromagnetic coil 23 of the drive unit 3,
An attractive force is generated, which becomes an excitation force, but the phases of the AC output and the excitation force are the same. Note that although these phases are not strictly the same, they can be made to match by increasing or decreasing a slight fixed phase difference, so the following description will be made assuming that they are the same.

The electromagnetic vibrator control device according to the embodiment of the present invention is constructed as described above, and its operation will be explained next.

Now, when a start button (not shown) is pressed, a start command signal is supplied to the gate circuit 6, and a gate signal as shown in FIG. 3B is supplied to the gate electrodes of the thyristors SCR ₁ and SCR ₂ of the AC to DC converter 5. be done. As a result, a rectified output as shown in FIG. 3C is obtained from the bridge circuit, which is smoothed by the smoothing circuit, and an output as shown in FIG. 3D is obtained from the AC to DC converter 5, which is It is supplied to the DC→AC converter 7.

On the other hand, a pulse with a frequency that varies depending on the difference between the output of the phase detector 9 and the set phase value at this time is transmitted from the pulse distributor 13 to the base electrodes B 2 of the transistors TR ₂ and TR ₅ in the DC to AC converter _7. , B ₅ and
The base electrodes B ₃ and B ₄ of TR ₃ and TR ₄ are alternately supplied. Now, this pulse is applied to one pair of transistors.
If supplied to the base electrodes B ₂ and B ₅ of TR ₂ and TR ₅ , these transistors TR ₂ and TR ₅ become conductive, and the current flows through the transistor TR ₂ → terminal 21 →
The current flows from the coil 23 to the terminal 22 to the transistor _TR5 , and the coil 23 is excited. Next, when a pulse is supplied to the base electrodes B ₃ and B ₄ of the other pair of transistors TR ₃ and TR ₄ , these transistors TR ₃ and TR ₄
becomes conductive, and the current flows through the transistor TR ₃ → terminal 22 → coil 23 → terminal 21 → transistor
The current flows through TR ₄ and excites the coil 23. In this way, an alternating current of a magnitude corresponding to the level of the direct current output of the alternating current-direct current converter 5 flows through the coil 23. This alternating current generates an alternating current attraction force in the electromagnet 24, which excites the trough 2.

At startup, a DC output with a rising characteristic as shown in FIG. 3D is supplied to the DC to AC converter 7, so that the trough 2 is started extremely stably as shown in FIG. 4B. The DC output of the AC to DC converter 5 eventually reaches a level E corresponding to the set transport speed, but if DC at this level is supplied to the DC to AC converter 7 at the same time as startup, the trough 2
begins to vibrate in a transient state as shown in FIG. 4A, which adversely affects its operation.

The phase detector 9 generates an output that detects the phase difference between the AC output of the DC to AC converter 7 and the output of the amplitude detector 8. ₂ ), and the PI control unit 11 adjusts the difference so that the difference becomes zero.
The pulses with a frequency controlled by the pulse distributor 13
is supplied to the DC to AC converter 7. Therefore,
The trough 2 is controlled to vibrate at a frequency very close to the resonant frequency.

On the other hand, the multiplication value of the output of the amplitude detector 8 and the output of the PI controller 11 representing the instantaneous value of the frequency of the excitation force is compared with the set transport speed by a comparator 14, and the difference between them is reduced to zero. A gate signal whose phase is controlled by the PI controller 15 is supplied to the AC to DC converter 5, whereby a DC output at a level corresponding to the set transport speed is obtained from the converter 5. The trough 2 will therefore vibrate with an amplitude value that provides the desired transport speed.

As described above, in the steady state, the trough 2 is vibrating at a frequency approximately equal to the resonant frequency and at an amplitude that provides the desired transport speed. It is assumed that the water is supplied from a hopper (not shown) provided above the left end. The sand is transferred to the right in the figure by the transfer force caused by the vibration of the trough 2, and is discharged from the right end of the trough, but when subjected to such a load, the width of the trough 2 becomes smaller and the sand is transferred. The resonant frequency of the vibration system containing the material decreases. However, according to this embodiment, the amplitude of the trough 2 x the frequency of the excitation force is detected and compared with the set transport speed by the comparator 14, and the AC →
Since the DC converter 5 generates a DC output, it vibrates at an amplitude value that provides a desired transport speed even in a loaded state. Also, the resonant frequency decreases with the load,
The phase difference between the excitation force and the amplitude at this time is immediately detected, this is compared with the set phase value in the comparator 10, and the DC to AC converter 7 is adjusted to match this phase value.
Since the frequency of the AC output is controlled, the frequency decreases compared to when there is no load, but the resonance state is still maintained.

When a stop button (not shown) is pressed to stop the vibration of the trough 2, a stop command signal is supplied to the gate circuit 6. As a result, the phase θ of the gate signal is forced to change according to the equation θ=α+k ₁ t (where α is a value in a steady state with no load) until it reaches 180°. Therefore, the gate signal changes in the opposite direction to the change shown in FIG. 3B, and the AC to DC converter 5
The rectified output of the bridge circuit also changes in the opposite direction to the change shown in FIG. 3C. This allows exchange →
The DC output of the DC converter 5 changes in the opposite direction to the change shown in FIG. 3D and approaches zero, thus coming to a quiet stop as shown in FIG. 4B. If the DC output level is set to E without providing such a falling characteristic,
If it is brought directly to zero, the trough 2 will undergo transient oscillations as shown in FIG. 4A.

If an excessive current flows for some reason during operation of the trough 2 or at startup, this will be detected by the detection coil 25 in the protection circuit 20 and a base signal will be supplied to the base electrode B ₁ of the transistor TR ₁ . The transistor _TR1 becomes conductive. As a result, the charge in the capacitor _C1 is discharged through the resistor R, and the thyristor
Gate signals to the gate electrodes of SCR ₁ and SCR ₂ are cut off, and the base electrodes B ₂ - of transistors TR ₂ - _{TR 5}
The base signal to _B5 is blocked. This results in
Each circuit element is protected.

Although the embodiments of the present invention have been described above, the present invention is of course not limited to these and can be modified in various ways based on the technical idea of the present invention.

For example, in the above embodiments, an electromagnetic feeder was shown as the electromagnetic vibrator, but the present invention is applicable to various electromagnetic vibrators such as parts feeders, truck cars, and spiral elevators.

Particularly when applied to a parts feeder, as an embodiment, the rise time and fall time of the excitation force, that is, the output of the AC to DC converter 5, at startup and stop are as shown in FIG. 3D (however, regarding the fall time (in the opposite direction) When configured to control according to the viscous drag coefficient of the vibration system, the large amplitude of the vibration transient state conventionally seen at startup and stop
This eliminates the possibility that the parts inside the ball would jump up and disrupt its posture. Therefore, the feeding or aligning action of the parts feeder is not disturbed when starting or stopping.

Further, the circuit configuration is not limited to the illustrated embodiment; for example, in FIG. 2, the DC to AC converter 7 has four transistors for switching.
Although TR ₂ to TR ₅ were used, it is also possible to use only two.

Further, in the above embodiment, the phase detector 9 compares the phase of the amplitude of the trough 2 and the phase of the output of the DC to AC converter 7, but the present invention is not limited to this, and for example, the phase of the magnetic flux of the electromagnet 24 is compared. and the phase of the amplitude of the trough 2 may be compared.

In addition, in the above embodiment, the phase value to be set is π/2. I set it to a slightly smaller value, but of course you could also set it to π/2. stomach.

As described above, according to the control device for a resonant electromagnetic vibrator of the present invention, it is possible to design an electromagnetic vibrator more easily than before, and the size of the leaf spring that connects the driving part and the vibrated body can be increased. There is no need to adjust the sheath, number of sheaths, tightening force, etc., and the body to be vibrated by the electromagnetic vibrator can always be vibrated in a resonant state or in a state close to this so as to obtain a predetermined transport speed.
Therefore, the magnitude of the excitation force can be minimized, and power consumption can be reduced accordingly.

[Brief explanation of the drawing]

Fig. 1 is a block circuit diagram of a control device for a resonant electromagnetic vibrator according to an embodiment of the present invention, and Fig. 2 shows details of the AC to DC converter, DC to AC converter, and related parts in Fig. 1. FIG. 3 is a graph for explaining the operation of the gate circuit in FIG. 1, and FIG. 4 is a graph for explaining the operation of the embodiment. In the figure, 1...electromagnetic feeder, 2...
... Trough, 3 ... Drive section, 5 ... AC to DC converter, 6 ... Gate circuit, 7 ... DC to AC converter, 8 ... Amplitude detector, 9 ... Phase detector, 1
0, 14... Comparator, 11, 15... PI controller,
12... V-F converter, 30... Multiplier.

Claims (1)

[Scope of Claims] 1 AC power source; an AC to DC converter connected to the AC power source; a DC to AC converter connected to the converter; a drive unit that receives the AC output of the DC to AC converter; a resonant electromagnetic vibrator; a phase detection means for detecting a phase difference between the detected vibration of the vibrated body of the resonant electromagnetic vibrator and the excitation force based on the AC output; and the resonant electromagnetic vibrator. a first comparing means for comparing the output of the phase detecting means with a phase difference π/2 between the vibration and the excitation force at the natural frequency or a frequency close to this, or a value close to this; and a multiplication means for multiplying the amplitude of the detected vibration of the body by the frequency of the excitation force; a second comparison means for comparing the output of the multiplication means with a predetermined transport speed; 1. Controlling the frequency of the AC output of the DC/AC converter based on the output of the comparison means so that the frequency of the excitation force matches the natural frequency or a frequency close to this, and 2
The level of the DC output of the AC to DC converter is controlled based on the output of the comparison means to adjust the magnitude of the excitation force such that the transport speed of the vibrated body matches the predetermined transport speed. A control device for a resonant electromagnetic vibrator. 2. When starting up the resonant electromagnetic vibrator, the alternating current →
gradually increasing the level of DC output of the DC converter from zero to a level corresponding to the predetermined amplitude;
2. The control device according to claim 1, wherein the control device gradually decreases from the level to zero when stopping.