JPH01194287A - High-frequency heating device - Google Patents

Abstract

PURPOSE:To reduce the heating time and to guarantee the reliability and the safety by increasing the electromagnetic output larger than the value of the normal time at the operation starting time of the device, and reducing the electromagnetic output to control at the normal time value when the temperature of the heating parts is presumed or detected to be higher than a specific value. CONSTITUTION:A heating control unit 40 gives a heating instruction of a specific heating time to a drive control unit 41. As a result, the control unit 41 gives a starting instruction to a control unit 34 and operates a magnetron 32 at the output larger than the rating output in the normal time. When a specific time passes, or when the temperature of the heating parts rises higher than a specific value, the electromagnetic output is reduced to control to the value at the normal time. The heating time is reduced and the reliability and the stability are guaranteed, consequently.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a high-frequency heating device for heating foods, fluids, etc. More specifically, the present invention relates to a high-frequency heating device for heating foods, fluids, etc. This invention relates to a heating device.

2. Description of the Related Art Power supply circuits for high-frequency heating devices such as household microwave ovens often have a configuration as shown in FIG.

In FIG. 6, when the operation switch 1 is turned on, the commercial power source 2 is connected to the high voltage transformer 3. High voltage transformer 3-2
The output of the next winding 4 is rectified by a capacitor 6 and a diode 6 and is supplied to a magnetron 7. The heater winding 1IA8 of the high voltage transformer 3 is connected to the magneton A 70 cand and heats the cand. Therefore, the magnetron 7 loses power, outputs high-frequency electromagnetic waves (radio waves), and dielectric heating becomes possible.

FIG. 7(&) is a diagram showing the time course of the radio wave output Po of the magnetron 7 after the switch 1 is turned on at time 1=0. When switch 1 is turned on with 1=0, cathode heater power and high voltage power are simultaneously applied to magnetron 7. After about 1 to 2 seconds, at j=t1, the temperature of the cand rises sufficiently, and the radio wave output Po rises and thereafter remains almost constant as shown in the figure. Of course magnetron 7
The radio wave output may decrease slightly over time due to the temperature characteristics of the high voltage transformer 3, etc., but basically the radio wave output P is determined as the rated output of the device.
a (for example, 500 W).

FIG. 7 (bl is a diagram showing the temperature rise of components inside the device when the high-frequency heating device is operated as described above).

For example, the temperature TM of the magnetron 7 and the temperature Ta of the air around the high voltage transformer 3 rise as shown in the figure.

FIG. 8 is a sectional view of the high frequency heating device. Inside the housing 9 is an oven 10. Magnetron 71 high voltage transformer 3
etc. are arranged as shown in the figure, and are forcibly cooled by a cooling fan 11.

The efficiency of the magnetron 7 is approximately 60%, and the efficiency of the high voltage transformer 3 is approximately 90%, so in the case of a device with an actual radio wave output rating of soow, the magnetron 7 is approximately 60% efficient, and the high voltage transformer 7 is approximately 100W. loss will occur. Therefore, the temperature of these parts gradually rises during operation as shown in Fig. 7(b), and the time t= determined by the thermal time constant of each part
The temperature rises at a relatively fast rate until t2 (for example, 16° minutes), and then at t=t3 (for example, 60 to 120 minutes), the temperature of the entire apparatus reaches the maximum temperature and is saturated.

In this way, the high-frequency heating device has many components with relatively low conversion efficiency, such as the magnetron 7 and the high-voltage transformer 3, and therefore the heat loss is large, so the temperature rise during operation is relatively large.
Moreover, it takes a long time to reach a stable temperature.

In order to guarantee the rated output Po of the device, it is necessary to use insulating materials and constituent materials that can maintain sufficient safety even when such heat loss occurs, so the configuration of the cooling conditions and specifications of each component must be carefully determined. Designed to meet such warranty conditions
ing. That is, at 1=15 in FIG. 7(b), the constituent materials, component specifications, and cooling configuration are determined with due consideration given to the temperature rise that has occurred.

Therefore, when the rated output is 500W, eo.

The cooling conditions and parts specifications are significantly different from the case of W. For example, the magnetron 7 has a different generation loss, so in the case of the EOOW, its cooling structure becomes larger, making it larger and more expensive, and the high voltage transformer 3 also has to be larger and more expensive.

Problems to be Solved by the Invention As described above, conventional high-frequency heating devices have specifications for each component that can guarantee the safety and reliability of the device under the temperature conditions when the temperature rise due to heat loss of the device is saturated. Establish this.
It was configured using n.

However, because high-frequency heating equipment uses a unique heating method called dielectric heating, the heating time is relatively short, and it is extremely difficult to use the heating time for reheating, which is often used in general households, for less than 6 minutes. many. That is, in FIG. 7(b), there are many uses where the use is finished in a time of t=tOa degrees, and cooking that reaches t=ts is rarely performed. Therefore, in most cases, a high-frequency heating device with a guaranteed temperature rise at t=t3, which does not need to be guaranteed at all under many conditions of use, can be used in most cases with 1=1. This means that the product is being used for an amount of time, and in this respect, the quality is excessive. However, since there may be usage conditions where t=t5 is possible for man, until now the quality has been essentially excessive.

Means for Solving the Problems The present invention has been made to solve the problems of such conventional high-frequency heating devices, and has the configuration described below.

In other words, a power supply unit obtained from a commercial power supply or the like.

A power converter having a semiconductor element and converting power from the power supply unit into high-frequency power, a control unit controlling the semiconductor element, and a radio wave radiating unit radiating the output of the power converter as electromagnetic waves, start operation. an activation control unit that controls the energy of the electromagnetic wave to be larger than that of a steady state by giving a rising signal at times; and a heating unit that receives the signal or a signal substantially equivalent thereto and adjusts the operating time of the power converter in accordance with this signal. It has a different configuration with the control section.

Effects The high frequency heating device according to the present invention with the above structure has the following effects.

At the start of operation of the high-frequency heating device, a rising signal is applied to the start-up control section and the control section, so that the control section controls the operation of the semiconductor element of the power converter to make its electromagnetic wave output larger than during normal operation. Therefore, at the beginning of use of the high-frequency heating device, it is possible to obtain a higher radio wave output than during normal operation, making it possible to shorten the heating time, and to improve the cooling configuration, heat resistance specifications, and quality performance of each component. It can be made appropriate without being excessive.

In addition, it was detected that the temperature of the heat-generating component rose above a predetermined value due to long heating time or repeated operation9.
Alternatively, if the estimated value is n, the electromagnetic wave output is lowered and controlled to the steady state value, so the amount of electricity handled by each heat generating component is reduced, the amount of heat generated is reduced, and reliability and safety are guaranteed. It can operate within the temperature range that it is capable of.

Then, the heating control section detects the magnitude of the electromagnetic wave output changing in this way using the rising signal of the startup control section or a signal equivalent to it, changes the operating time of the power converter according to this signal, and as a result, , the total heating amount is controlled to be kept substantially constant even if the magnitude of the electromagnetic wave output changes. In other words, when cooking a predetermined amount of the object to be heated, when the electromagnetic wave output is larger than the steady state, the heating time is controlled to be short, and when the electromagnetic wave output is at the steady state, the heating time is controlled to be longer than in the former case. It's about controlling. Therefore, due to the operation of the heating control section, the user can simply perform the same operation for cooking the same heated object without worrying about the magnitude of the electromagnetic wave output that changes automatically. It's good.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a high frequency heating device showing an embodiment of the present invention. In the figure, a filter circuit consisting of a commercial power supply 20° diode bridge 21, an inductor 22, and a capacitor 23 constitutes a power supply section 24, and a capacitor 26. Step-up transformer 271 Transistor 28. Diode 29° Capacitor 30. Diode 31. Power is supplied to a power converter 33 consisting of a magnetron 32 and a magnetron 32 . The power converter 33 includes a capacitor 26. Step-up transformer27. Transistor 28. an inverter comprising a diode 29; a high voltage rectifier circuit comprising a diode 31 and a capacitor 3o that rectifies the output of the step-up transformer 27;
a magnetron 32 that generates high frequency power;
This magnetron 32 also functions as a radio wave radiating section that radiates this high frequency power as electromagnetic wave energy. Of course, the power converter 33 may be configured with a semiconductor oscillator that completely loses at 900 MHz or 2450 Mmz, and an antenna or the like may be provided as a radio wave radiating section.

The transistor 28 receives, for example, a frequency of 20 KHz from the control unit 34.
A switching control signal of ~200KH2 is applied to perform a switching operation. Therefore, a high-frequency voltage is generated in the primary winding 35 of the step-up transformer 27, and this high-frequency voltage is stepped up, rectified, and supplied to the magnetron 32, causing a total loss of the magnetron 32.

A signal proportional to the input current is sent to the control unit 34 from the input current detector 36. This input current detection signal is
As shown in the figure, n
, and the signal from the reference signal generator 38, and the error signal thereof is sent to the pulse width control circuit 39. Therefore, the conduction time of transistor 28 is controlled,
The input current is controlled to a predetermined value by so-called pulse width control. As a result, the electromagnetic wave (radio wave) output po of the magnetron 32 is a predetermined value n (
For example, it is controlled to a constant value of 500 W).

In such a configuration, when operating the high-frequency heating device, a heating start command is sent from the heating control section 40 to the activation control section 4.
Sent to 1. When the startup control unit 41 receives a heating start command, it outputs an output (for example, eooW) larger than the rated output (for example, soow) during a steady state for a predetermined time at the start of operation.
) A rising signal is given to the control section 34 so that the control section 34 operates as shown in FIG.

FIG. 3 (al is a time change diagram of the radio wave output Pa showing this state. When the transistor 28 starts operating at 1 = 0, the magnetron 32 starts to operate 1 to 2 seconds later at 1 = 1. The output Po is controlled to be 600 W, which is larger than the steady state (that is, the rated value).Then, after 1 s, the time t
When it becomes 4, the output Pa becomes 5 at steady state (i.e. rated).
It is controlled so that it becomes 00W. Such radio wave output Po
The control of can be achieved in various ways, but
For example, as shown in FIG. 2, this can be easily realized by controlling the signal generated by the input current reference signal generator 38 by the activation control section 41. That is, Fig. 3(a)
This can be realized by changing the reference signal of the input current after time 1a so that a change in the output Po occurs.

The time period 1 s in FIG. 3 (IL) is a time period during which a higher output than in a steady state is generated while the temperature of the device and each component is sufficiently low. Therefore, FIG. 7(b) of the explanatory diagram of the prior art
As is clearer, the period during which the internal temperature of the device or the temperature of each component is lower than a predetermined temperature may be set to 1°. Based on this idea, the 1s is, for example, as shown in FIG. The activation control unit 41 configured to compare the signal from the signal generator 43 with the comparator 44 can be configured to determine the temperature control center. Further, as shown in FIG. 5, a stop time counter 46 is provided to count the time during which the equipment is stopped operating (that is, the time during which devices and parts are cooled).
Determine the time 1s using the signal of 1. Count 1a
This 18 may be determined by detecting the operating state of the device by providing a starting modulation counter 46 that later changes the reference signal 38 of the input current.

Of course, the activation control section 41 may be configured with a simple timer device, with the time period 18 limited to a short period of, for example, about 6 minutes and fixed.

In order to notify the user that the radio wave output Po is being controlled to be greater than the normal state, a display section 47 is provided as shown in FIG. 2, and is activated by a signal from the activation control section 41. By doing so, the user can either be in a powered up state (i.e. eoow) or in a steady state (5o
It is extremely easy to use and can perform high-speed cooking because it can recognize whether it is oW or not and start cooking.

Next, the heating control section 4o will be explained in more detail.

As shown in FIG.
1, it is configured to give a heating command to heat the object for a predetermined heating time, and at the same time receive a start-up signal from the startup control section 41. This is a configuration for the heating control unit 4o to detect the current magnitude of the electromagnetic wave output (for example, 600W or soow), and the heating control unit 4o detects the object to be heated in accordance with this signal. Adjust heating time. For example, in FIG. 3 (&), when the heating time is completed within ts, it is assumed that the heating time is 100 seconds. However, due to repeated use,
In fact, when heating occurs when t8 is zero, the heating control section 4o automatically adjusts the heating time to 100 seconds x 6 degrees. The time is adjusted to 1=120 seconds. Of course, there may be an intermediate state, but even in that case, the heating time is adjusted depending on the magnitude of the electromagnetic wave output po. Therefore, even when performing heating such as ta=O, which occurs rarely, the user does not have to worry about changes in the magnitude of the output Po, and the output Po is always 600! It is possible to use a high-frequency heating device that is extremely easy to use and is not of excessive quality.

As described above, the heating control section 4o, the startup control section 41, or the display section 47 are components that include many logical operations and time control elements, so some or all of these components can be implemented using logical operation means such as a microcomputer. By configuring the apparatus with the provided control means, the entire apparatus can be made extremely simple and inexpensive.

Further, it is clear that the rising signal to the heating control unit 40 does not necessarily have to be supplied from the startup control unit 41, and may be supplied from the control unit 34 or the like as a signal corresponding to the electromagnetic wave output Po. .

Furthermore, although the heating time control of the heating control unit 40 in the embodiment is shown only when the output of the high-frequency heating device is maximum, for example, the average value of the output can be controlled to be equivalent to about 200 W by well-known intermittent control. Similarly, the heating time can be adjusted in the same way when defrosting and cooking, and the same effect can be obtained.

Effects of the Invention (1) As described above, according to the present invention, there is provided a startup control section that includes a power supply section, a power converter, and a radio wave radiating section, and that controls electromagnetic wave energy to a greater extent than during normal operation at the start of operation; Since it is equipped with a heating control section that adjusts the heating time in response to the start-up signal from the start-up control section or an equivalent signal, it is extremely rational and economical and prevents excessive quality, while also ensuring safety and reliability. A guaranteed high frequency heating device can be realized.

(2) Furthermore, even if the electromagnetic wave output changes depending on the state of the device, the user will not be bothered by it at all due to the action of the heating control unit, and the output will continue to function as if the output had not changed. Therefore, it is possible to provide a high-frequency heating device that is extremely easy to use.

(3) By providing a logic operation means or a temperature detection means in the heating control section, the power supply section at the start of operation.

The temperature of the power converter and radio wave emitting part can be detected and the optimum output can be determined, allowing for the most efficient heating.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a high-frequency heating device showing an embodiment of the present invention, Fig. 2 is a block diagram of the control section of the circuit, and Fig. 3 (I
L), (b) is a time chart of the radio wave output of the same device,
Fig. 4 is a circuit diagram of the startup control section of the same device, Fig. 5 is a block diagram showing another embodiment of the same circuit, Fig. 6 is a circuit diagram of a conventional high frequency heating device, Fig. 7 (&), Φ) is a time chart of the radio wave output and component temperature of the device, and FIG. 8 is a sectional view showing the configuration of the device. 24... Power source section, 32... Radio wave radiation section, 33... Power converter, 4o... Heating control section, 41... Start-up control section. Name of agent: Patent attorney Toshio Nakao and 1 other person 2 Do-Kakuo, Shu 32-・-t, Seifou t'TfIS Figure 1 33-J7+Nenjawei 40・-False accusation Shu No. 3 Figure 6 Figure 7

Claims (3)

[Claims] (1) A power supply unit obtained from a commercial power source, a power converter having a semiconductor element that converts the power of the power supply unit into high-frequency power, a control unit that controls the semiconductor element, and an output of the power converter. a radio wave emitting part that emits as an electromagnetic wave, a startup control part that gives a rising signal at the start of operation and controls the energy of the electromagnetic wave to be greater than in a steady state, and receives the signal or a signal substantially equivalent to the signal; A high-frequency heating device comprising: a heating control section that adjusts the operating time of the power converter according to this signal. (2) The heating control section is equipped with logical calculation means such as a microcomputer, and is configured to process the rising signal of the startup control section or a signal substantially equivalent thereto to adjust the operating time of the power converter. The high frequency heating device according to claim 1. (3) The startup control unit is configured to include temperature detection means for detecting the temperature of heat-generating components such as semiconductor elements or radio wave emitting parts, or the ambient temperature thereof, and generates a rising signal in response to a signal from the temperature detection means. The high frequency heating device according to claim 1 or 2.