JP2733289B2 - Vending machine induction heating device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating apparatus of a vending machine for heating and selling (hereinafter, referred to as HOT sale) a canned beverage product such as coffee by induction heating. .

2. Description of the Related Art In recent years, there has been proposed a vending machine that applies an induction heating technique and instantly heats a canned beverage product at the time of sale to sell HOT. Most of the heating control methods of the induction heating devices of these vending machines are fixed time control methods using a timer or the like because it is difficult to directly detect the temperature of a canned beverage product during induction heating.

FIG. 6 shows a configuration diagram of a conventional induction heating device of a vending machine. 1 is a heating coil for inductively heating a canned beverage product 2 stored at refrigeration or room temperature, 3 is a resonance capacitor connected in parallel to the heating coil 1, and 4 is connected in series to the heating coil 1 and the resonance capacitor 3. The power switching semiconductors 5 are diodes connected in antiparallel to the power switching semiconductors 4 for reverse conduction, and these constitute a voltage-type resonant inverter circuit 6. Reactor 7
And the capacitor 8 constitutes a filter. The voltage-type resonance inverter circuit 6 receives a commercial power supply 10 that has been full-wave rectified by the rectifier bridge diode 9 as input, converts the commercial power supply into high-frequency power, and supplies high-frequency power to the heating coil 1 to thereby supply the heating coil. The canned beverage product 2 in 1 is induction-heated. An input current detection circuit 11 detects an input current flowing through the voltage-type resonance inverter circuit 6 and is connected to the inverting input terminal of the differential amplifier 12. A non-inverting input terminal of the differential amplifier 12 is connected to a reference voltage circuit 15, which includes resistors 13 and 14 and supplies a constant voltage. Differential amplifier 12
Is configured such that when the voltages at the inverting input terminal and the non-inverting input terminal are equal, the output is 0 volt, and the output terminal is connected to the variable pulse width oscillator 16. The variable pulse width oscillator 16 controls the conduction angle of the power switching semiconductor 4 so that the output signal from the differential amplifier 12 becomes 0 volt. That is, the pulse width for switching the power switching semiconductor 4 is variably controlled. This constitutes a so-called current limiter circuit which regulates the input current to the voltage-type resonance inverter circuit 6 with the voltage set by the reference voltage circuit 15. The output of the variable pulse width oscillator 16 is connected to a drive circuit 17 for switching the power switching semiconductor 4. The differential amplifier 12, the variable pulse width oscillator 16, and the drive circuit 17 form an oscillation control circuit 18. Reference numeral 19 denotes a control circuit of a vending machine (not shown), which receives a sales signal from a product sales switch 20 and operates the oscillation control circuit 18 for a predetermined time.

The operation of the induction heating device of the vending machine configured as described above will be described. First, when the product sale switch 20 is pressed and a sale signal is input to the control circuit 19, the control circuit 19 sends a control signal to the oscillation control circuit 18 for a predetermined time to inductively heat the canned beverage product 2 for a predetermined time. Output. The oscillation control circuit 18 receives the control signal, starts the variable pulse width oscillator 16, and switches the power switching semiconductor 4 via the drive circuit 17. Thereby, the voltage-type resonance inverter circuit 6 is activated, and the induction heating of the canned beverage product 2 is started. When the induction heating is started, a current flows through the voltage-type resonance inverter circuit 6, and the input current detection circuit 11 outputs a voltage signal proportional to the input current. The differential amplifier 12 outputs a difference between the voltage signal and a reference voltage set by the reference voltage circuit 15. And a variable pulse width oscillator
Numeral 16 varies the pulse width (conduction angle) so that the output signal from the differential amplifier 12 becomes 0 volt. That is, the pulse width (conduction angle) is varied so that the output signal from the input current detection circuit 11 becomes equal to the reference voltage value set by the reference voltage circuit 15. It is controlled to be a constant value. Thus, the beverage product 2 in a can is induction-heated with the heating output specified by the input current for the time set by the control circuit 19, and is sold by HOT.

However, in the above configuration, when the input voltage of the voltage-type resonant inverter circuit 6 fluctuates, the final temperature of the canned beverage product 2 after the induction heating fluctuates. FIG. 7 shows the characteristics of the heating output when the input current of the voltage-type resonance inverter circuit 6 is constant and the input voltage is varied by 200 V ± 15% (operating voltage range of the vending machine). In the figure, a shows the characteristics of the input current and b shows the characteristics of the heating output. Electric power (heating output)
Is obtained by multiplying the power factor (efficiency) by the product of the input current and the input voltage. If the input current is kept constant, the heating output as shown in FIG. 7 naturally has a characteristic proportional to the input voltage. In a conventional induction heating device of a vending machine, for example, as shown in FIG. 7, the input current is set to about 12 A so that a heating output of 2.0 kW can be obtained at a rated voltage of 200 V.
When the voltage of the reference voltage circuit 15 is set to be 2 A, when the input voltage fluctuates ± 15%, the heating output fluctuates by about 1.7 KW to 2.3 KW, and the heating efficiency is almost constant.
Will fluctuate ± 15%. For example, 30 ° C
When the beverage product 2 in a can stored in the above is heated for a certain period of time, raised by 30 ° C., and sold at 60 ° C. (HOT selling temperature), a variation of ± 4.5 ° C. occurs. Actually, the storage temperature at 30 ° C also fluctuates by about ± 3.0 ° C, and the entire vending machine has ± 7.5 ° C.
And there was a problem that the canned beverage product 2 could not always be sold at a stable temperature.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an induction heating device for a vending machine that reduces a change in heating output due to an influence of a change in input voltage and reduces a variation in temperature of a canned beverage at the time of sale.

Means for Solving the Problems In order to solve the above problems, an induction heating device for a vending machine of the present invention comprises a heating coil for inductively heating a canned beverage product, and a voltage comprising a heating coil, a resonance capacitor, and a power switching semiconductor. -Type resonance inverter circuit, an input current detection circuit for detecting an input current of the voltage-type resonance inverter circuit, an input voltage detection circuit for detecting an input voltage of the voltage-type resonance inverter circuit, and a correction for correcting an output of the input voltage detection circuit Circuit, an adder for adding the outputs of the input current detection circuit and the correction circuit, a reference voltage circuit for defining the heating output, and an output circuit for receiving the output signals from the adder and the reference voltage circuit. An oscillation control circuit that controls oscillation, and a control circuit that operates the oscillation control circuit for a predetermined time in response to a sale signal from a product sale switch. It is provided with.

Effect of the Invention According to the above configuration, the input voltage of the voltage-type resonant inverter circuit detected by the input voltage detection circuit is increased by the correction circuit when the input voltage is high, and the output of the correction circuit is increased when the input voltage is low. Low input voltage characteristics are corrected, the corrected output and the output of the input current detection circuit are added by an adder, and the input current is adjusted by the oscillation control circuit so that the output of the adder becomes the same as the output of the reference voltage circuit. By controlling the input current, the input current can be controlled to be low when the input voltage is high, and the input current can be controlled to be high when the input voltage is low. And the variation in the temperature of the canned beverage at the time of sale can be reduced.

Embodiment FIG. 1 is a block diagram showing an embodiment of the present invention. still,
Detailed description of the same parts as those in the conventional example will be omitted. An input voltage detection circuit 21 detects an input voltage of the voltage-type resonance inverter circuit 6, and its output is connected to a correction circuit 22. Reference numeral 23 denotes an adder, the input of which is connected to the correction circuit 22 and the input current detection circuit 11, and the output of which is input to the oscillation control circuit 18.

Next, a method for reducing the change in the heating output will be described with reference to FIG. 2. FIG. 2 shows the change in the input current with respect to the change in the input voltage when the heating output is fixed at 2.0 kW in the voltage-type resonant inverter circuit 6. (A). As shown in the drawing, the input current has a characteristic inversely proportional to the input voltage when the heating output is constant. The input current should change in the voltage fluctuation range as shown in FIG. 2 (a) if the heating output is constant. Therefore, if the input current is controlled so as to have the characteristic shown in FIG. 2 (a), The heating output is constant. Here, when the input current characteristics in FIG. 2A are approximated by a straight line (b) and the input voltage 170v to 230v in the voltage fluctuation range (normally a vending machine ± 15% of the rating) is considered, the input voltage 170v and the input voltage Voltage 23
At 0v, the heating output is 2.0kw. In addition, when the input voltage is 200 V, the heating output increases because the input current becomes larger than the input current that makes the heating output constant. However, the increase in the heating output is about 2%, and when the temperature of the canned beverage at the time of sale is 0.7 ° C., the change in the temperature of the canned beverage at the time of sale is reduced.

FIG. 3 shows an example of a specific circuit of a main part. The input current detection circuit 11 includes a current transformer 24 for extracting a current flowing through the voltage-type resonance inverter circuit 6 as a voltage value;
Current transformer connected in parallel with the current transformer 24
The output is composed of a load resistor 25 for determining the output voltage of 24, a rectifying bridge diode 26, a resistor 27, and a capacitor 28, and the output is connected to the adder 23. The output characteristic of the input current detection circuit 11 is such that the output increases in proportion to the input current. The input voltage detection circuit 21 is a voltage-type resonance inverter circuit 6.
A resistor 29 and a resistor 30 for dividing the input voltage of the
A transistor for inputting the divided voltage to the base of the transistor 31 and holding the peak value of the input voltage
An emitter-follower type peak hold circuit 34 including a resistor 31, a resistor 32 and a capacitor 33 is provided. The output of the peak hold circuit 34 is connected to the correction circuit 22. The correction circuit 22 is an in-phase amplifier including an operational amplifier 35 and resistors 36 and 37, and the output is connected to the adder 23. The adder 23 is an in-phase addition circuit including an operational amplifier 38 and resistors 39, 40, 41, and 42. The adder 23 adds the outputs of the correction circuit 22 and the input current detection circuit 11 and outputs the result. The output of the adder 23 is the oscillation control circuit 18
Are connected to the inverting input terminal of the differential amplifier 12 inside. The control circuit 19 includes a microcomputer 43 and peripheral circuits. The microcomputer 43 shown here is a CP
It has U, ROM, RAM and input / output unit. It is a so-called one-chip microcomputer. The merchandise sales switch 20 is input to the microcomputer 34 so as to determine whether or not it has been pressed. The microcomputer 43 is a product sales switch.
An output for causing the variable pulse width oscillator 16 to oscillate for a fixed time in response to the sales signal from 20 is connected to a variable pulse width generator (16) in the oscillation control circuit 18.

The operation of the induction heating device of the vending machine configured as described above will be described.

When any one of the product selection switches 20 is pressed and a sales signal is input to the microcomputer 43, the microcomputer 43 performs induction heating of the canned beverage product 2 for a predetermined time stored in the internal ROM. Oscillation control circuit 18
To output a control signal. The oscillation control circuit 18 receives the control signal, starts the variable pulse width oscillator 16, and switches the power switching semiconductor 4 via the drive circuit 17. Thereby, the voltage type resonance inverter circuit 6 is started. The induction heating of the canned beverage product 2 is started. When the induction heating is started, a current flows through the voltage-type resonance inverter circuit 6, and a voltage signal proportional to the input current is output from the input current detection circuit 11 which is composed of the current transformer 24 and holds the peak value of the input current. You. On the other hand, the input electron detection circuit 21 constituting the emitter-follower type peak hold circuit 34 outputs a voltage characteristic shown in FIG. 4 which is proportional to the change of the input voltage of the voltage type resonance inverter circuit 6. The correction circuit 22 corrects this voltage characteristic and outputs it to the adder 23. This output is input to the inverting input terminal of the differential amplifier 12 in the oscillation control circuit 18. The variable pulse width oscillator 16 has a pulse width (conduction angle) such that the output signal from the differential amplifier 12 becomes 0 volt.
Variable. That is, the pulse width (conduction angle) is varied so that the output signal from the input current detection circuit 11 becomes equal to the output voltage of the adder 23. Here, if the input current characteristic for making the heating output shown in FIG. 2 (b) constant (2.0 kW) is replaced by the output of the input current detection circuit 11, as shown in FIG. Since the output characteristic is such that the output increases in proportion to the input current, the output characteristic is low when the input voltage is high, and is high when the input voltage is low. The detection voltage to keep the heating output constant when the input voltage is 170 V is V170, and the detection voltage to keep the heating output constant when the input voltage is 230 V is V230.For example, when the input voltage is 170 V, the input current is detected. If the output of the circuit 11 becomes V170, the heating output will be 2.0 kw. Also, the output voltage of the reference voltage circuit 15 is set to V1
Then, the variable pulse width oscillator 16 changes the pulse width (conduction angle) of the output of the adder 23 to the output voltage of the reference voltage circuit 15 to the same value as V1. Here, the adder 23 is a correction circuit
22 and the sum of the outputs of the input current detection circuit 11 and the correction circuit 22
Is Vh, the output of the input current detection circuit 11 is V1−Vh
Becomes Therefore, when the input voltage is 170 V, V1−Vh = V17
0, when the input voltage is 230v, if Vh is determined so that V1-Vh = V230, the heating output becomes 2.0kw. Therefore, the input current of the voltage-type resonant inverter circuit 6 keeps the heating output constant (2.
0KW) and the current characteristics approximate the input current when
Almost constant heating output (2.0Kw) against fluctuations in input voltage
Becomes In this way, the canned beverage product 2 is induction-heated at a constant heating output for a fixed time set by the microcomputer 43, and is sold by HOT.

According to the configuration of the above embodiment, the variation in the heating output with respect to the variation in the input voltage can be reduced, and the variation in the temperature of the canned beverage product 2 after heating for a certain time can be reduced,
The canned beverage product 2 can always be sold at a stable temperature.

As described above, as apparent from the embodiments, the induction heating device of the vending machine of the present invention comprises a heating coil for induction heating of a canned beverage product, a resonance capacitor, and a voltage-type resonance inverter circuit comprising a power switching semiconductor. The input voltage is detected by an input voltage detection circuit, and the input voltage characteristic of the voltage-type resonant inverter circuit is corrected by a correction circuit. When the input voltage is high, the output of the correction circuit is high. When the input voltage is low, the output of the correction circuit is low. , And the corrected output and the output of the input current detection circuit are added by an adder, and the oscillation control circuit controls the input current so that the output of the adder becomes the same as the output of the reference voltage circuit. As a result, the input current is reduced when the input voltage is high, and the input current is increased when the input voltage is low. Since the configuration is such that the heating output change is small, the change in the heating output due to the effect of the input voltage change is small, the temperature variation of the canned beverage at the time of sale is reduced, and it is always stable It can sell beverage products in cans at a temperature.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an induction heating device of a vending machine showing one embodiment of the present invention, FIG. 2 is an input current characteristic diagram of a voltage-type resonance inverter circuit when a heating output is fixed, and FIG. FIG. 4 is a circuit diagram of a main part of the present embodiment, FIG. 4 is a detection voltage characteristic diagram of the input voltage detection circuit of the embodiment, FIG. 5 is a characteristic diagram of the input current detection circuit when the heating output is approximated to be constant, FIG. 6 is a configuration diagram of a conventional induction heating device of a vending machine, and FIG. 7 is a heating output characteristic diagram of a voltage-type resonance inverter circuit when an input current is fixed. 1 ... heating coil, 2 ... beverage product in can, 3 ... resonance capacitor, 4 ... power switching semiconductor, 6 ...
Voltage-type resonant inverter circuit, 11 ... input current detection circuit,
18 …… Oscillation control circuit, 19 …… Control circuit, 20 …… Sale switch, 21 …… Input voltage detection circuit, 22 …… Correction circuit, 23…
... adders.

Claims (1)

(57) [Claims] 1. A heating coil for inductively heating a canned beverage product, a voltage-type resonance inverter circuit comprising the heating coil, a resonance capacitor, and a power switching semiconductor;
An input current detection circuit that detects an input current of the voltage-type resonance inverter circuit, an input voltage detection circuit that detects an input voltage of the voltage-type resonance inverter circuit, and a correction circuit that corrects an output of the input voltage detection circuit; An adder for adding the outputs of the input current detection circuit and the correction circuit; a reference voltage circuit for defining a heating output; and the voltage-type resonance inverter circuit receiving an output signal from the adder and the reference voltage circuit. An induction heating apparatus for a vending machine, comprising: an oscillation control circuit for controlling the oscillation of a vending machine; and a control circuit for receiving the sales signal from a product sales switch and operating the oscillation control circuit for a predetermined time.