JPH0375992A - Induction heating device for automatic vending machine - Google Patents

Abstract

PURPOSE:To supply a constant heating output without being influenced by an input voltage by controlling a voltage type resonance inverter circuit provided with a heating coil through an oscillation control circuit, based on a result of division of a detection input voltage and a reference voltage. CONSTITUTION:A detection input voltage by an input voltage detecting circuit 21 and a reference voltage by a reference voltage circuit 15 are brought to division by a divider 24. A result of this division and a detection current by an input current detector 11 are processed by a differential amplifier 12 of an oscillation control circuit 18, a power switching transistor 4 of a voltage type resonance inverter circuit 6 provided with a heating coil 1 is controlled through a pulse width variable oscillator 16 and a driving circuit 17, and a constant heating output by a coil 1 is supplied to a commodity irrespective of a fluctuation of an input voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an induction heating device for a vending machine that heats and sells canned beverage products such as coffee (hereinafter referred to as HOT sales) by induction heating.

Prior art As seen in recent Japanese Patent Application Laid-Open No. 64-76398,
A vending machine has been proposed that uses induction heating technology to instantaneously heat canned beverage products for sale at 110 tons.

Since it is difficult to directly detect the temperature of a canned beverage product during induction heating, the heating control method of the induction heating device of these vending machines has mostly been a method of controlling heating for a fixed period of time using a timer or the like.

FIG. 5 shows a configuration diagram of a conventional induction heating device for a vending machine. 1 is a heating coil that inductively heats a canned beverage product 2 that has been refrigerated or stored at room temperature; 3 is a resonant capacitor connected in parallel to the heating coil 1; and 4 is connected in series to the heating coil 1 and the resonant capacitor 3. The power switching semiconductor 5 includes three diodes connected in antiparallel to the power switching semiconductor 4 for reverse conduction operation, and these constitute a voltage type resonant inverter circuit 6. Reactor 7 and capacitor 8 constitute a filter. The voltage-type resonant inverter circuit 6 inputs a commercial power source 10 that has been full-wave rectified by a rectifying bridge diode 9, converts this commercial power source power into high-frequency power, and supplies the high-frequency power to the heating coil 1, so that the heating coil A canned beverage product 2 in 1 is heated by induction.

Reference numeral 11 denotes an input current detection circuit for detecting the input current flowing into the voltage type resonant inverter circuit 6, and is connected to the non-inverting input current (+) of the differential amplifier 12.

A resistor 13 is connected to the inverting input current (-) of the differential amplifier 12.
．． 14, a reference voltage circuit 1 that supplies a constant voltage.
5 is connected. The differential amplifier 12 is configured so that when the voltages of the inverting input current (-) and the non-inverting input current (+) are equal, the output becomes O volts, and the output current is connected to the variable pulse width oscillator 16. has been done. 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 O port. That is, the pulse width for switching the power switching semiconductor 4 is variably controlled. This is the voltage set by the reference voltage circuit 15 and defines the input current to the voltage type resonant inverter circuit 6. This constitutes a so-called current limiter circuit. The output of the variable pulse width oscillator 16 is used in the drive circuit 1 for switching the power switching semiconductor 4.
7 is connected. The differential amplifier 12, variable pulse width oscillator 16, and drive circuit 17 constitute an oscillation control circuit 18. Reference numeral 19 denotes a control circuit for a vending machine (not shown), which receives a sales signal from a product sales switch 20 and operates an oscillation control circuit 1.
18 is operated for a certain period of time.

The operation of the induction heating device for a vending machine configured as above will be explained. First, when the product sales switch 20 is pressed and a sales signal is input to the control circuit 19, the control circuit 19 sends a control signal to the oscillation control circuit 18 for a certain period of time to inductively heat the canned beverage product 2 for a predetermined period of time. Output. The oscillation control circuit 18 receives this control signal, starts the variable pulse width oscillator 16, and switches the power switch 5 and the paging semiconductor 4 via the drive circuit 17. As a result, the voltage type resonant inverter circuit 6 is activated, and induction heating of the canned beverage product 2 is started. When induction heating is started, a current flows through the voltage type resonant inverter circuit 6, and the input current detection circuit 11 outputs a voltage signal proportional to this input current. The differential amplifier 12 outputs the difference between this voltage signal and the reference voltage set by the reference voltage circuit 15. and,
The variable pulse width oscillator 16 varies the pulse width (conduction angle) so that the output signal from the differential amplifier 12 becomes 0 port. That is, the pulse width (conduction angle) is varied so that the output signal from the input current detection circuit 11 is equal to the reference voltage value set by the reference voltage circuit 15, and the input current of the voltage type resonant inverter circuit 6 is It is controlled to a constant value.

Thereby, the canned beverage product 2 is inductively heated for a period of time set by the control circuit 19 with a heating output specified by the input current, and is sold hot.

Problems to be Solved by the Invention However, in the above configuration, when the input voltage of the voltage-type six-page inverter circuit 6 changes, the final temperature of the canned beverage product 2 after induction heating changes. Figure 6 shows the voltage type resonant inverter! ! The heating output characteristics are shown when the input current of 86 is constant and the input current is varied by 200V±15% (the operating voltage range of the vending machine). In the figure, a indicates the input current, and b indicates the heating output characteristic.

Electric power (heating output) is determined by multiplying the power factor (efficiency) by the product of input current and input voltage, so if the input current is constant, the heating output as shown in Figure 6 is naturally proportional to the input voltage. Becomes a characteristic. In conventional vending machine induction heating devices,
For example, as shown in Figure 6, when the rated voltage is 200V, the heating output is 2. If the input current is set to about 12A to obtain OKW, that is, the voltage of the reference voltage circuit wr15 is set so that the input current is about 12A, the input voltage will be ±15%.
When the heating output fluctuates, the heating output fluctuates by about 1.7 kW to 2.3 kW, and since the heating efficiency is almost constant, the temperature rise of the canned beverage product 2 fluctuates by ±15%. For example, 30℃
If the canned beverage product 2 stored at 100° C. is heated for a certain period of time to raise the temperature by 30° C. and sold at 60° C. (HOT sales temperature), a variation of ±4.5° C. will occur. In reality, even the storage temperature of 30℃ has a variation of about ±3.0℃, which results in a variation of ±7.5℃ for the entire vending machine.
There was a problem in that the canned beverage product 2 could not be sold at a constant temperature.

In view of the above problems, the present invention provides an induction heating device for a vending machine that maintains a constant heating output without being affected by input voltage and sells canned beverage products at a stable temperature.

Means for Solving the Problems In order to solve the above problems, the induction heating device for a vending machine of the present invention includes a heating coil for inductively heating canned beverage products, a heating coil, a resonant capacitor, and a power switching semiconductor. A voltage type resonant inverter circuit, an input current detection circuit that detects the input current of the voltage type resonant inverter circuit, an input current detection circuit that detects the input current of the voltage type resonant inverter circuit, and an input current detection circuit that outputs a predetermined constant voltage. A reference voltage circuit, a divider that divides the output of the reference voltage circuit by the output of the input current detection circuit, and controls the oscillation of the voltage-type resonant inverter circuit by receiving output signals from the divider and the input current detection circuit. It is equipped with an oscillation control circuit and a control circuit that operates the oscillation control circuit for a certain period of time in response to a sales signal from a product sales switch.

According to the above-described configuration, the present invention uses a divider to divide the output voltage of the reference voltage circuit that outputs a constant voltage by the output of the input current detection circuit that detects the input current of the voltage type resonant inverter circuit. By controlling the pulse width of the voltage-type resonant inverter circuit using the oscillation control circuit so that the output becomes the voltage determined by the divider, the heating output becomes constant, and without being affected by the input voltage, -window heat output It is possible to heat canned beverage products for a certain period of time.

Example FIG. 1 shows the constituent countries of an embodiment of the present invention.

On page 9, detailed explanations of parts that are the same as those of the conventional example will be omitted. Reference numeral 21 denotes an input current detection circuit for detecting the input current of the voltage type resonant inverter circuit 6, which is composed of a resistor 22 and a resistor 23, and outputs an output proportional to the input voltage of the voltage type resonant inverter circuit 6. 24 is a divider, and the human power is a reference voltage circuit 15 and an input current detection circuit 21, respectively.
The output is connected to the inverting input current (-
)It is connected to the. As shown in FIG. 2, the divider 24 includes a first A/D conversion circuit 25, a second A/D conversion circuit 26, an arithmetic circuit 27, and a D/A conversion circuit 28. The human power of the first A/D conversion circuit 25 is connected to the reference voltage circuit 15, and the human power of the second A/D conversion circuit 26 is connected to the input current detection circuit 21. The outputs of the first A/D conversion circuit 25 and the second A/D conversion circuit 26 are input to the arithmetic circuit 27, and the output of the arithmetic circuit 27 is
The inverting input current (-) of the differential amplifier 12 is supplied via the A conversion circuit #28. Also, the first A/D conversion circuit 2
5 is the reference voltage time! The A/D conversion circuit 26 on the 210th page converts the output of the i'815 into binary code and outputs it to the arithmetic circuit 27. The arithmetic circuit 27 is a binary encoded first A/D conversion circuit 2.
5 is divided by the output of the second A/D conversion circuit 26, and the result is output to the D/A conversion circuit 28 in binary code. The D/A conversion circuit 28 converts the output from the arithmetic circuit 27 into an analog value and outputs it to the inverted input current (-) of the differential amplifier 12.

Further, as the divider 24, an IC such as a commercially available analog arithmetic unit may be used. Generally, an analog calculator IC has input currents X and Z, and an output current of 0 is 10Z/X.The input current X is the output of the reference voltage circuit 15, and the input current Z is the output of the input voltage detection circuit 21. It is sufficient to connect the output current 0 to the inverting input current (-) of the differential amplifier 12.

Next, a method for keeping the heating output constant will be explained with reference to FIGS. 3 and 4. FIG. 3 shows the output characteristics of the input voltage detection circuit 21. The output characteristics of the input current detection circuit 21 change in proportion to the change in the input current.For example, if the output when the input current is 20OV is 1, the output will change if the input current increases by 15%. increases by 15% to 1.15XV1, and the input voltage increases to 15%.
% decrease, the output also decreases by 15% to 0.85XVz. Therefore, if the output of the reference voltage circuit 15 is V REF, the output of the divider 24 is V RE when the input voltage is 200V.
F/V becomes 1, and if the input voltage increases by 15%, the output becomes VREF/(1, 15X Vl), and if the input voltage decreases by 15%, the output becomes VREF/(0.

85XV1). FIG. 4(a) shows the change in input current with the heating output constant at 2.0 kW when the input voltage changes, and FIG. 4(b) shows the output characteristics of the input current detection circuit 11. In FIG. 4(a), if the heating output is constant, the input current is inversely proportional to the input voltage because the efficiency hardly changes. Figure 4(b) is Figure 4(a)
The change in the input current shown in is converted to a low voltage by the input current detection circuit 11. If the output of the input current detection circuit 11 when the input current is 200V is V2, the input voltage is 1.
When the input voltage increases by 5%, the output becomes V2/1.15, and when the input voltage decreases by 15%, the output becomes V210°85.

Therefore, if the input voltage increases by 1.15 times, the input current will be reduced to 1/1.
．． If the input voltage is increased by 0.85 times, the input current is increased by 110.85 times, and a constant heating output can be obtained with high accuracy.

Therefore, when the input voltage of the divider 24 is 200 V, the output V
If RE F / V 1 is 2, then the input voltage is 1.
If the input voltage increases by 15 times, the input current can be controlled by 1/1.15 times, and if the input voltage increases by 0.85 times, the input current can be controlled by 110.85 times.

The operation of the induction heating device for a vending machine configured as above will be explained.

First, the case where the input voltage is 200V will be explained. When the product selection switch 20 is pressed and a sales signal is input to the control circuit 19, the control circuit 19 performs an oscillation control cycle to inductively heat the canned beverage product 2 for a predetermined time! ! A control signal is output to 818. At this time, the input voltage detection circuit 21 outputs an output characteristic shown in FIG. 3 that is proportional to the change in the input voltage of the voltage type resonant inverter circuit 6 (Vl). The output of the reference voltage circuit 13 and page circuit 15 is input to the input current of the first A/D conversion circuit 25. On the other hand, the output of the input voltage detection circuit 1121 is manually input to the second A/D conversion circuit 26. and the first
The A/D conversion circuit 25 and the second A/D conversion circuit 26 encode this human power into binary code and output it to the arithmetic circuit 27. The arithmetic circuit 27 is a binary encoded first A/D conversion circuit 25.
The output is divided by the output of the second A/D conversion circuit 26, and the result is output to the D/A conversion circuit 28. The D/A conversion circuit 28 converts the binary encoded operation result into a differential signal. It is output to the inverting input current (-) of the amplifier 12. Divider 24 at this time
The output is set so that VREF/V1=V2. Next, 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. This allows the voltage type resonant inverter to turn l! 86 is activated, and induction heating of the canned beverage product 2 is started. When induction heating starts, a current flows through the voltage-type resonant inverter circuit 6, and the input current detection circuit 11 outputs a voltage signal proportional to this input current, causing the non-inverting input current (
＋）is human-powered. And the differential amplifier 12 is a divider 24
The variable pulse width oscillator 16 adjusts the pulse width (conduction angle) so that the output signal from the differential amplifier 12 becomes O volts.
Make it variable. Here, since the output of the divider 24 is V2, the pulse width variable oscillator 16 varies the pulse width (conduction angle) until the output of the input current detection circuit 11 becomes V2, and in the end, a heating output of 2.0 kW is obtained. This will happen. Next, when the input voltage changes to 230V, the output of the input current detection circuit 21 becomes 1.15XV1. Further, the output of the reference voltage circuit 15 is VREF, and the output of the divider 24
The output is VREF/(1, 15XVl). In this state, when the product selection switch 20 is pressed and a sales signal is input to the control circuit 19, the control circuit lit')
19 similarly outputs a control signal to the oscillation control circuit 18 for inductively heating the canned beverage product 2 for a predetermined period of time. The output of the divider 24 is VREF/(1,45X Vs
), and the pulse width variable oscillator 16 varies the pulse width (conduction angle) so that the output signal from the differential amplifier 12 becomes 0 port. will be varied by the pulse width (conduction angle) until it becomes VREF/(1,15XV1), and the input voltage will be 1.15
If it is doubled, the input current can be increased to 1/1.15 times, and a heating output of 2°0 kW can be obtained. The same operation also occurs when the input voltage decreases.

According to the configuration of the above embodiment, the heating output remains constant even when the input voltage fluctuates, so the temperature of the canned beverage product 2 after heating for a certain period of time remains constant, and the canned beverage product 2 always maintains a stable temperature. 2 can be sold.

In addition to the effects of the invention, as is clear from the examples, the induction heating device for a vending machine of the present invention uses a voltage-type resonant inverter circuit comprising a heating coil, a resonant capacitor, and a power switching semiconductor for inductively heating canned beverage products. The input current is detected by the input current detection circuit, the output of the reference voltage circuit is divided by the output of the input voltage detection circuit by the divider, the input current is detected by the input current detection circuit, and the output of the input current detection circuit is divided by the output of the input voltage detection circuit by the divider. The heating output is kept constant by controlling the pulse width of the voltage-type resonant inverter circuit by the oscillation control circuit so that the voltage is determined by the voltage, and the control circuit operates the oscillation control circuit for a certain period of time. It is possible to heat a canned beverage product for a certain period of time with a -leg side heat output without being affected by the input voltage, and it is possible to always sell the canned beverage product at a stable temperature.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an induction heating device for a vending machine showing an embodiment of the present invention, Fig. 2 is a block diagram of a divider of this embodiment, and Fig. 3 is a diagram of an input voltage detection circuit of this embodiment. Output characteristic diagram, 4th
Figure (a) is an input current characteristic diagram of the voltage type resonant inverter circuit when the heating output is constant, Figure 4 (b) is an output characteristic diagram of the input current detection circuit of this embodiment, and Figure 5 is the conventional one. FIG. 17, a block diagram of an induction heating device for a vending machine, is a heating output characteristic diagram of a voltage-type resonant inverter circuit when the flow at the input end of the device is constant. 1...Heating coil, 2...Canned beverage products, 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...Sales switch, 21...
- Input voltage detection circuit, 24...divider.

Claims (1)

[Claims] a heating coil for inductively heating a canned beverage product; a voltage-type resonant inverter circuit comprising the heating coil, a resonant capacitor, and a power switching semiconductor; an input current detection circuit for detecting an input current of the voltage-type resonant inverter circuit; an input voltage detection circuit that detects the input voltage of a voltage-type resonant inverter circuit; a reference voltage circuit that outputs a predetermined constant voltage; and an output of the reference voltage circuit that divides the output of the reference voltage circuit by the output of the input voltage detection circuit and outputs the result. a divider; an oscillation control circuit that receives output signals from the divider and the input current detection circuit to control oscillation of the voltage-type resonant inverter circuit; and an oscillation control circuit that receives a sales signal from a product sales switch and controls the oscillation control circuit to a constant level. An induction heating device for a vending machine, characterized by comprising a control circuit that operates over time.