JP3243155B2 - Overcurrent protection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overcurrent prevention device for preventing overcurrent at an initial stage of energization in a heater such as a hot plate for cooking for home use or business use.

[0002]

2. Description of the Related Art A conventional hot plate for cooking is shown in FIG.
As shown in FIG. 1, a sheathed heater 2 such as a nichrome heating element having a small resistance change rate is provided on the hot plate body 1 side, and a cooking plate 3 is placed on the sheathed heater 2 to cook food on the cooking plate 3. The temperature of the cooking plate 3 is detected by a temperature sensor such as a thermostat or a thermistor, and the temperature of the cooking plate 3 is adjusted by controlling the energization of the sheath heater 2 based on the detected temperature.

However, in this type of cooking hot plate, the cooking plate is heated mainly by the radiant heat of the sheathed heater, so that the heat distribution on the surface of the cooking plate is uneven and the heat efficiency is poor. Since the sheathed heater was provided, the sheathed heater was exposed when the cooking plate was removed, and the appearance was poor, and the cleanability of the hot plate body was also poor.

Therefore, in recent years, a cooking hot plate has been proposed in which a heating element is integrally attached to the back side of the cooking plate to generate heat, thereby improving the thermal efficiency, improving the appearance by eliminating the sheathed heater, and improving the cleanability. Have been.
In particular, when a planar heating element having a negative characteristic (NTC characteristic) or a positive characteristic (PTC characteristic) is used as the heating element, the resistance value increases when the temperature of the cooking plate decreases due to the load condition, that is, the food placed on the cooking plate. The self-sensor function to detect the temperature of the cooking plate, the local heating function,
Furthermore, a safety function for self-control of abnormal heat generation can be added, and a hot plate having more excellent functionality than a hot plate using a conventional sheathed heater can be provided.

[0005]

However, when a planar heating element having PTC characteristics is used as the heating element, the resistance value is low when the temperature is low (for example, room temperature). Since the resistance value is low and overcurrent flows, the nominal power may be exceeded, the control circuit,
It is necessary to set the allowable current of the electric circuit and the like to be high, which is a problem in use.

In view of the above, an object of the present invention is to provide an overcurrent prevention device for preventing an overcurrent at an initial stage of energization in a heater in which a heating element having a PTC characteristic is integrally provided in a heating vessel.

[0007]

Means for Solving the Problems According to the present invention, there is provided a heating device in which a plurality of heating elements having positive characteristics are electrically connected in parallel and provided integrally with a heating vessel, There are provided a current shifting means for temporally shifting the current supply to each heating element, and a control means for operating the current shifting means at the beginning of the current supply to each heating element.

The current shifting means is a diode which is electrically connected in series by changing the polarity of each heating element, or a switching element which is electrically connected in series to each heating element.

In addition, an auxiliary resistor electrically connected in series to the heating element and a control means for supplying electricity to the auxiliary resistor at the initial stage of energizing the heating element are provided, or an auxiliary resistor having a negative characteristic is provided. I have.

Thus, in the initial stage of energization of each heating element, the energization of each heating element is shifted in time by the half-wave rectifying action of each diode, or each switching element is sequentially turned on to energize each heating element. Or if the auxiliary resistor has a negative characteristic, the change in the resistance of the heating element and the change in the resistance of the auxiliary resistor may occur if the auxiliary resistor has a negative characteristic. By canceling each other, the current flowing through each heating element is suppressed, and an overcurrent is prevented. After the overcurrent is prevented, the heating vessel is returned to the normal energized state by short-circuiting each diode, keeping each switch element turned on, short-circuiting the auxiliary resistor, etc. Start up quickly to the prescribed temperature.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described as applied to a cooking hot plate. As shown in FIGS. 2 and 3, the cooking hot plate is a cooking plate 10 which is a heating vessel for placing and heating the food, and a hot plate main body 11 to which the cooking plate 10 is detachably mounted.
, A lid 12 for covering the cooking plate 10, and the hot plate body 1
A power plug cord 14 that can be attached to and detached from one connector 13 is provided. 2 and 3, reference numeral 15 denotes an operation panel provided on the hot plate main body 11, and 16 denotes legs for supporting the hot plate main body 11. And operation panel 1
The side with 5 is the front side.

As shown in FIG. 2, the cooking plate 10 has a rectangular bottom portion 20 and peripheral walls 20a and 20b rising from the outer peripheral edge of the bottom portion 20 integrally formed of an insulating material such as crystallized glass. It becomes. The peripheral wall 2 before and after this cooking plate 10
A flange 21 engaged with the hot plate main body 11 is provided at 0a so as to protrude in the left-right direction.

The surface and the peripheral wall 2 of the bottom 20 of the cooking plate 10
A protective layer coated with a fluororesin or the like is formed on the surfaces (plate surfaces) of 0a and 20b so as to prevent the food and the like from burning and sticking, thereby improving the releasability of the food.

On the back surface of the bottom portion 20 of the cooking plate 10,
As shown in FIG. 4, for example, a TCR (temperature coefficient of resistance) 0.68 mainly composed of nickel flakes and inorganic frit is used.
The two heating elements 22 having the PTC characteristics described above are formed as films. These heating elements 22 are arranged in parallel in the left-right direction,
Electrode portions 23 are formed in a strip shape on the left and right ends of each heating element 22 by spraying a metal such as aluminum.
Each of the heating elements 2 is arranged by continuously arranging the electrode portions 23 on one side so as to connect the ends of the two heating elements 22.
2 are electrically connected in parallel, and the front end of each electrode portion 23 is extended to the front end of the cooking plate 10. Except for the front end of each electrode part 23, the back surface of the bottom part 20 of the cooking plate 10 is coated with an insulating material such as non-conductive ceramics to provide safety considerations such as prevention of electric leakage and electric shock. I have.

Here, in a general hot plate, the power consumption is 1.2 kW to 1.3 kW (current: 100 VAC) in consideration of the power required for cooking and the rated power capacity of a household power outlet. Those having a value of 12A to 13A) are mainstream. Heating element 2 having PTC characteristics
As shown in FIG. 5, No. 2 has a characteristic that the resistance value increases with an increase in temperature, and conversely, the current value decreases with an increase in temperature. Therefore, in order to keep the plate surface at about 280 ° C. suitable for cooking within the range of 1.2 KW to 1.3 KW, the combined resistance value of the heating element 22 at normal temperature (for example, room temperature 25 ° C.) at the beginning of energization is about It is set to be 5Ω. In this case, at the initial stage of energization of each heating element 22, an overcurrent of 20 A flows at a power consumption of 2.0 kW because the combined resistance value is about 5Ω at AC 100V. Therefore, the hot plate is provided with an overcurrent prevention device for preventing an overcurrent at the initial stage of energization of each heating element 22. The details of the overcurrent prevention device will be described later.

The hot plate body 11 is shown in FIGS.
The first main body 25 and the second main body 27 are formed in a rectangular box shape, and include a first main body 25 that supports the cooking plate 10 and a second main body 27 in which the electrical components 26 are concentrated. Is detachably divided into two.

The first main body 25 includes the hot plate main body 11.
And a vertical wall 25a, 25b on three sides except the front side.
The cooking plate 10 is mounted in a space surrounded by the vertical walls 25a and 25b. In the rear vertical wall 25a, a concave portion 28 in which the flange 21 of the cooking plate 10 is fitted is formed in the left-right direction.

The second main body 27 has a front upper surface slightly inclined toward the front lower side, and the operation panel 15 for operating the electric equipment 26 is disposed on the inclined portion. Further, a concave portion 29 into which the flange 21 of the cooking plate 10 is fitted is formed in the rear end face of the second main body 27 in the left-right direction.

The electric part 26 projects an electrode portion coming into contact with the electrode part 23 on the cooking plate 10 side from the inside of the hot plate main body 11 only when the cooking plate 10 is mounted on the hot plate main body 11, so that the electricity can be supplied. Power supply control mechanism 30
And an overcurrent prevention device 40 for preventing an overcurrent at an initial stage of energization of each heating element 22.

The energization control mechanism 30 is provided at the front end of each of the electrode portions 23 on the cooking plate 10 side, and is attached to the lower surface of the second main body 27 via an insulator as shown in FIG. The fixed electrode 31, which protrudes from the second main body 27 and comes into contact with the electrode portion 23 on the cooking plate 10 and the fixed electrode 31, fits in the second main body 27, and comes into non-contact with the electrode portion 23 and the fixed electrode 31. The movable electrode 32 which can be switched between the storage positions, and the flange 2 of the cooking plate 10
1 is fitted into the concave portion 29 of the second main body 27 (when the cooking plate 10 is mounted), and comes into contact with the cooking plate 10 to move the movable electrode 32.
And an operating body 33 that switches from the storage posture to the protruding posture.

Each movable electrode 32 passes through a fan-shaped first rotary rib 35 disposed in the second main body 27, and the first rotary rib 3
5 is arranged along the front and back surfaces of the cooking plate 10 in a protruding position, such that an end on the front surface contacts the front end of the electrode portion 23 of the cooking plate 10 and an end on the back surface contacts the fixed electrode 31. I have.

The first rotating rib 35 is fixed to a longitudinal axis 37 rotatably supported by upper and lower bearings 36 in the second main body 27 so as to be horizontally rotatable. A return spring 39 for urging the first rotary rib 35 in the direction in which the movable electrode 32 is stored is interposed between the first and second ribs. In the concave portion 29 of the second main body 27, an opening through which each of the first rotating ribs 35 can be inserted, that is, an opening / recess opening 29a of the movable electrode 32 is formed.

The operating body 33 comprises a fan-shaped second rotating rib fixed to the longitudinal axis 37 above the first rotating rib 35 and rotatable horizontally. An upper / lower opening 29b of the operating body 33 is formed above the upper / lower opening 29a of the movable electrode 32. The operating body 33 is held in a state of protruding from the opening / retreat opening 29b by the urging force of the return spring 39.

When the cooking plate 10 is mounted on the hot plate main body 11 by the power supply control mechanism 30 as described above, the cooking plate 10 comes into contact with the operating body 33, and the movable electrode 32 is switched from the retracted position to the projected position. The electrode 32 and the electrode portion 23 on the cooking plate 10 are brought into contact with each other to be in an energizable state. When the cooking plate 10 is removed from the hot plate main body 11, the operating body 33 returns to the original state, the movable electrode 32 switches from the protruding posture to the storage posture, and does not protrude from the hot plate main body 11, and hands and objects are movable. The electrode 32 is not touched.

As shown in FIG. 1, the overcurrent prevention device 40 includes an energization shifting unit 41 for temporally shifting energization to each heating element 22 and an energization shifting unit 41 at the beginning of energization to each heating element 22. And a control means 42 for operating.

The current shifting means 41 is provided on the operation panel 1.
5 comprises diodes 44a and 44b arranged on a control board 43 connected to the fixed electrode 31 and electrically connected in series to the respective heating elements 22 by changing the polarity. When an alternating current flows through the diodes 44a and 44b, the heating elements 22 are alternately energized by half-wave rectification, and as a result, the heating elements 2
2 will be staggered in time.

The control means 42 comprises relays 45a, 45b arranged on a control board 43 and electrically connected in parallel to the respective diodes 44a, 44b, and a control circuit 46 for controlling ON / OFF of the relays 45a, 45b. The control circuit 46 turns off the relays 45a and 45b at the same time as the energization of the heating elements 22 is started, and turns off the diodes 44a and 4b.
4b, when the temperature of the heating element 22 rises and the combined resistance value of the heating element 22 rises to about 8Ω after the energization (when the current value when both heating elements 22 are
A), the relays 45a and 45b are turned on and the diodes 44a and 44b are short-circuited to return to a normal energized state. It is to be noted that, using a timer, approximately two minutes after the start of energization when the combined resistance value of each heating element 22 becomes about 8Ω (when the current value when both heating elements 22 are energized becomes about 12 A or less), each diode is turned off. 4
4a and 44b may be short-circuited, or the diodes 44a and 44b may be short-circuited by electronic control.

In the above configuration, the hot plate body 1
When the power plug cord 14 attached to the connector 13 is connected to a power outlet and the cooking plate 10 is mounted on the hot plate main body 11, the power supply control mechanism 30 controls the electrode portion 23 on the cooking plate 10 side and the hot plate main body 11 side. Is connected to the electrical unit 26 to be in an energizable state.

When energization is started, each relay 45a, 45
b is turned off, and the heating elements 22 are alternately energized by the half-wave rectification of the diodes 44a and 44b. At this time, the combined resistance value of each heating element 22 at normal temperature is set to about 5Ω, and since each heating element 22 is electrically connected in parallel, the resistance value of one heating element 22 is about 10Ω. At the start of energization (at room temperature), a current of about 12 A or less in the current capacity flows, and overcurrent can be prevented.

Then, as shown in FIG. 6, when the temperature of each heating element 22 rises from the start of energization and the combined resistance value of each heating element 22 becomes about 8Ω, that is, both heating elements 22 are energized. When the current value becomes about 12A or less,
The relays 45a and 45b are turned on, and the diodes 44 are turned on.
The overcurrent protection is released by short-circuiting a and 44b to return to a normal energized state in which both heating elements 22 are energized. Thereafter, the cooking plate 10 continues to rise in temperature and stabilizes at about 280 ° C. suitable for cooking, and the current value stabilizes at 6 to 7 A.
Thus, overcurrent can be prevented and the cooking plate 10 can be quickly raised to a predetermined temperature. In addition,
When a timer is used, the diodes 44a and 44b may be short-circuited about 2 minutes after the start of energization when the combined resistance value of each heating element 22 becomes about 8Ω.

As described above, the diodes 44a and 44b are electrically connected in series to the respective heating elements 22 which are electrically connected in parallel while changing the polarity. Each heating element 2 by half-wave rectification
2 to prevent overcurrent by alternately energizing, and to return to a normal energized state in which both heating elements 22 are energized after preventing overcurrent, thereby quickly raising the cooking plate 10 to a predetermined temperature. Can be.

Next, a second embodiment will be described.
In the second embodiment, as shown in FIG.
The three heating elements 22 having characteristics are provided on the bottom 20 of the cooking plate 10.
A film is formed on the back surface of. These heating elements 22 are arranged in parallel in the left-right direction, and electrode sections 23 are formed in a band shape at the left and right ends of each heating element 22. Then, the electrode portions 23 on one side are continuously arranged so as to connect the ends of the three heating elements 22, so that the heating elements 22 are electrically connected in parallel, and the front end of each electrode section 23 is The cooking plate 10 is extended to the front end. Each heating element 22 is set so that the combined resistance at room temperature in the initial stage of energization is about 5Ω.

As shown in FIG. 8, timer contact portions T1 and T2, which are switch elements arranged on the control board 43 and electrically connected in series to the respective heating elements 22, are used as a current shifting means in the overcurrent prevention device. , T3, and the timer having the timer contact portions T1, T2, T3 functions as control means. Each timer sequentially turns on each timer contact portion T1, T2, T3 until approximately two minutes have elapsed from the start of energization (ON start time of T1 <T
2 <ON start time <T3 ON start time <2 minutes).

In the above configuration, when the energization is started, each of the timer contact portions T1, T2, T3 is turned on sequentially until about two minutes have elapsed from the start of the energization.
2 can be staggered in time. At this time,
The combined resistance value of each heating element 22 at normal temperature is set to about 5Ω, and since each heating element 22 is electrically connected in parallel, the resistance value of the heating element 22 in one circuit is about 15Ω, A current of about 6.7 A flows, and at the start of energization (at normal temperature), the current in the current capacity flows, and overcurrent can be prevented.

Then, about two minutes after the start of energization,
Since the temperature of the heating element 22 rises and the combined resistance value also rises, the overcurrent protection is released by turning on all the timer contact portions T1, T2, and T3, so that all the heating elements 22 are energized. Return to the energized state. Other configurations and operations are the same as those of the first embodiment, and members having the same functions as those of the first embodiment are denoted by the same reference numerals.

As described above, the timer contacts T1, T2, and T3 are electrically connected in series to each of the heating elements 22 electrically connected in parallel, and each of the timer contact sections T1 is initially connected to each of the heating elements 22 in the initial stage. , T2, and T3 are sequentially turned on to stagger the energization of each heating element 22 in time to prevent an overcurrent, and after preventing the overcurrent, return to a normal energization state in which all the heating elements 22 are energized. Thus, the cooking plate 10 can be quickly raised to a predetermined temperature.

Next, a third embodiment will be described.
In the third embodiment, as shown in FIG.
The two heating elements 22 having characteristics are provided on the bottom 20 of the cooking plate 10.
A film is formed on the back surface of. These heating elements 22 are arranged in parallel in the left-right direction, and electrode sections 23 are formed in a band shape at the left and right ends of each heating element 22. Then, since the electrode portions 23 on both sides are continuously arranged so as to connect the ends of the two heating elements 22, the heating elements 22 are electrically connected in parallel, and the front end of each electrode section 23 is cooked. It is extended to the front end of the plate 10.

Further, a U-shaped auxiliary resistor 50 is provided on the back surface of the bottom portion 20 of the cooking plate 10 so as to surround each heating element 22.
Are printed or formed in a belt shape. The auxiliary resistor 50 has a resistance value set to about 3Ω, and both front ends thereof are extended to the front end of the cooking plate 10.

Then, as shown in FIG.
2 and the auxiliary resistor 50 are electrically connected in series on the control board 43. Further, a control means for energizing the auxiliary resistor 50 at an initial stage of energizing each heating element 22, comprising a relay 51 electrically connected in parallel to the auxiliary resistor 50, and a control circuit 52 for controlling ON / OFF of the relay 51. 53 is provided, and the auxiliary resistor 50 and the control means 53 constitute an overcurrent prevention device.

The control circuit 52 has a function of turning off the relay 51 and energizing the auxiliary resistor 50 at the start of energization of each heating element 22, and a function of increasing the temperature of the heating element 22 and increasing the combined resistance of the heating element 22 after energization. When the value rises to about 8 Ω (when the current value when both heating elements 22 are energized becomes about 12 A or less), the relay 51 is turned on and the auxiliary resistor 50 is short-circuited to return to a normal energized state. It has a return function.

It should be noted that approximately two minutes after the start of energization when the combined resistance value of each heating element 22 becomes about 8Ω using a timer (when the current value when both heating elements 22 are energized becomes about 12 A or less) The auxiliary resistor 50 may be short-circuited, or the auxiliary resistor 50 may be short-circuited by electronic control.

In the above configuration, when the energization is started, the relay 51 is turned off and the auxiliary resistor 50 is energized together with the energization of each heating element 22. Here, since each heating element 22 and the auxiliary resistor 50 are electrically connected in series, the combined resistance value of each heating element 22 and the auxiliary resistor 50 becomes about 8Ω, and when the energization starts (at room temperature). , A current of about 12 A or less within the current capacity flows, and overcurrent can be prevented.

Then, when the temperature of each heating element 22 rises from the start of energization and the combined resistance value of each heating element 22 becomes about 8Ω, that is, when the current value when only both heating elements 22 are energized, the current value becomes about When the current becomes 12 A or less, the overcurrent protection is released by turning on the relay 51 and short-circuiting the auxiliary resistor 50 to return to the normal energized state in which only both heating elements 22 are energized. In the case where a timer is used, the heating resistance is about 2Ω from the start of energization when the combined resistance value of each heating element 22 becomes about 8Ω.
After a lapse of minutes, the auxiliary resistor 50 may be short-circuited. Other configurations and operations are the same as those of the first embodiment, and members having the same functions as those of the first embodiment are denoted by the same reference numerals.

As described above, the auxiliary resistors 50 are electrically connected in series to the heating elements 22 electrically connected in parallel, and the auxiliary resistors 50 are also energized in the initial stage of energizing the respective heating elements 22. Then, the combined resistance value is increased to prevent overcurrent, and after preventing overcurrent, the cooking plate 10 is quickly raised to a predetermined temperature by returning to the normal energized state in which only both heating elements 22 are energized. be able to.

Next, a fourth embodiment will be described.
In the fourth embodiment, an auxiliary resistor having NTC characteristics is used, and a third embodiment is provided except that a relay, a control circuit, or a timer for short-circuiting the auxiliary resistor is eliminated. Is the same as

The auxiliary resistor having the NTC characteristic has a characteristic opposite to that of the heating element 22 having the PTC characteristic, that is, a characteristic that the resistance value decreases as the temperature rises. Therefore, when energization is started, each heating element 22 and the auxiliary resistor are electrically connected in series, so that the combined resistance value of each heating element 22 and the auxiliary resistor becomes about 8Ω, and the resistance increases with the temperature rise. Since the resistance value of the heating element 22 increases and the resistance value of the auxiliary resistance element decreases, the changes in the resistance values of each other cancel each other out, so that at the start of energization (at normal temperature), about 12 A in the current capacity is reached.
Since the following current flows, overcurrent can be prevented, and the cooking plate 10 can be quickly raised to a predetermined temperature.

Japanese Patent Laid-Open No. 49-77767 discloses a control circuit in which a heater, an NTC thermistor and a PTC thermistor are electrically connected in series. There is no technical idea of forming an auxiliary resistor having NTC characteristics integrally with a cooking plate to prevent overcurrent and to function as a heater in order to prevent overcurrent. The purpose is to perform temperature adjustment such that a change in the heat retention temperature by the heater is reduced.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that many modifications and changes can be made to the above-described embodiment within the scope of the present invention. For example, in the above-described embodiment, the overcurrent prevention device is applied to a cooking hot plate. However, any heating device having PTC characteristics that is electrically connected in parallel and that is integrally provided in a heating container may be used. , And can be applied to any of them. In the first and second embodiments, any number of heating elements may be used as long as a plurality of heating elements are electrically connected in parallel. Furthermore, in the third and fourth embodiments, the number of heating elements may be one or three or more.

[0049]

As is apparent from the above description, according to the present invention, a plurality of heating elements having a positive characteristic and electrically connected in parallel are electrically connected in series by changing the polarity of a diode. In the initial stage of energization of the body, half-wave rectifying action of each diode alternately energizes each heating element, or electrically connects a switch element to each heating element in series, and switches each switching element in the initial stage of energization of each heating element. By sequentially turning on the heating elements, the energization of each heating element is shifted in time to prevent overcurrent at the beginning of energization, which was a problem when using a heating element having a positive characteristic, that is, a heating element having a low resistance value at room temperature. can do.

Further, an auxiliary resistor is electrically connected in series to a heating element having a positive characteristic, and the auxiliary resistor is also energized at the beginning of energization of the heating element, so that the resistance value is increased to increase the resistance at the beginning of energization. Current can be prevented.

Further, when an auxiliary resistor having a negative characteristic is used, the change in the resistance value of the heating element having a positive characteristic and the change in the resistance value of the auxiliary resistor cancel each other at the initial stage of energization.
Overcurrent at the beginning of energization can be prevented. Moreover, a structure for energizing the auxiliary resistor only at the beginning of energization, that is, a member for short-circuiting the auxiliary resistor, such as a relay, a control circuit, or a timer, can be eliminated, and the structure can be simplified.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of an overcurrent prevention device according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of a cooking hot plate.

3A and 3B are diagrams showing a state in which a movable electrode is in a protruding posture in a cooking hot plate, wherein FIG. 3A is a plan sectional view of an electrode portion, and FIG. 3B is a side sectional view of the cooking hot plate.

FIG. 4 is a bottom view of the cooking plate.

FIG. 5 is a diagram showing a change in a resistance value and a current value with respect to a cooking plate temperature in a heating element having PTC characteristics.

FIG. 6 is a diagram showing changes in a cooking plate temperature and a current value with respect to an elapsed time from the start of energization.

FIG. 7 is a bottom view of a cooking plate according to the second embodiment.

FIG. 8 is an electric circuit diagram of the overcurrent prevention device.

FIG. 9 is a bottom view of a cooking plate according to the third embodiment.

FIG. 10 is an electric circuit diagram of the overcurrent prevention device.

FIG. 11 is a side sectional view of a conventional cooking hot plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Cooking plate 22 Heating element 41 Electricity shifting means 42 Control means 44a, 44b Diode 50 Auxiliary resistor T1-T3 Timer contact part

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI // H02H 9/02 H02H 9/02 B (56) References JP-A-2-301983 (JP, A) JP-A-2- 189884 (JP, A) JP-A-3-102409 (JP, A) JP-A-4-259780 (JP, A) JP-A-56-24087 (JP, U) JP-A-2-37030 (JP, U) (58) Field surveyed (Int.Cl. ⁷ , DB name) A47J 37/06 321 G05D 23/19 H02J 1/00 309 H05B 3/00 H05B 3/14 H02H 9/02

Claims (3)

(57) [Claims] 1. A heating element having a positive characteristic is provided on one side of a heating vessel.
Used for heaters provided integrally with
Is provided on one side of the heating vessel and electrically connected directly to the heating element.
Auxiliary resistor connected in a row and auxiliary at the beginning of energization of heating element
Control means for energizing the resistor, wherein the auxiliary resistor is
Is printed in a strip shape around the heating element.
Overcurrent protection device. 2. A heating element having a positive characteristic is used for a heater integrally provided on one surface of a heating container, and is provided on one surface of the heating container and electrically connected in series to the heating element. includes an auxiliary resistor which is, and control means for energizing the auxiliary resistor to the initial energizing of the heating element, said auxiliary resistor
Indicates that a film was formed in a band around the heating element.
Overcurrent protection device. 3. The auxiliary resistor has a negative characteristic.
The overcurrent prevention device according to claim 1 or 2, wherein