JPH0127729B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heated object detection device suitable for use in a heating device such as a rice cooker, rice cooker, or electric pot, or an electromagnetic range.

Prior Art and Its Problems The most well-known conventional heated object detection device of this type is the center thermo type, but this method detects the presence or absence of a heated object such as a pan, and The circuit was opened and closed by a mechanical switch, and the temperature of the heated object was not continuously detected to control the temperature. As a conventional technology capable of temperature control, there is also a known technology that detects the presence or absence of an object to be heated at the bottom of the pan, and also detects the temperature on the side of the pan to control the temperature. Since there are two detection points, one for detecting the heated object and the other for temperature detection, there is a problem that the number of parts is doubled and the cost is high.

Purpose of the Invention Therefore, the present invention solves the above-mentioned conventional technical problems, and detects the presence or absence of a heated object and its temperature in a heating device such as a rice cooker, rice cooker, or electric pan, or a plate for an electromagnetic range in one place. It is an object of the present invention to provide a heated object detection device that can simplify the configuration and detect the presence or absence of a heated object and its temperature with high accuracy.

Configuration of the Present Invention In order to achieve the above object, a heated object detection device according to the present invention includes a movable body that advances and retreats depending on the presence or absence of a heated body, a case that accommodates the movable body, and a case that moves the movable body forward and backward. A heated object detection device comprising a switch that turns on and off according to , the magnetically responsive switch and the magnet,
The magnetic shield is fixedly provided on either the movable body or the case so as to face each other with a gap, and the magnetic shield is provided on either the case or the movable body to which the magnetic response switch and the magnet are not attached. It is characterized in that it is provided in either one of the magnetically responsive switches so as to go in and out of the gap to turn on and off the magnetically responsive switch.

Embodiment FIG. 1 is a front partial cross-sectional view of a heated object detection device according to the present invention realized for use in a heating device such as a rice cooker, rice cooker, or electric pot, or an electromagnetic range, and FIG. 2 is a front view in the same state of use. FIG. In the figure, 1 is an outer case formed in the shape of a bottomed case. A heater section 2 is arranged on the outside of the outer case 1, and a housing-shaped movable body 3 is arranged inside. The movable body 3 is supported inside the outer case 1 by a coil spring 4 wrapped around the outside thereof.

This movable body 3 is connected to a heated body 5 (a second
It is a part that detects the presence or absence of
When the object to be heated 5 is not placed on the top plate 301, it is lifted upward as shown in the figure by the elastic force of the coil spring 4, but when the object to be heated 5 is placed on the top plate 301 (second In the figure), the coil spring 4 contracts and descends due to its weight. The upper surface plate 301 is made of a metal plate with good thermal conductivity, and its outer surface is formed into a flat shape suitable for placing the object to be heated 5, and the temperature sensing element 6 is mounted on the inner surface. The structure is thermally bonded. As the temperature sensing element 6, an NTC thermistor or a PTC thermistor can be used. Among these, glass-sealed NTC thermistors are particularly preferred. Glass sealed type
This is because NTC thermistors have excellent moisture resistance and stability.

The bottom plate 302 facing the top plate 301 is
For example, it is made of a non-magnetic material with excellent heat resistance, such as a glass epoxy plate, and has a cut-out gap 7 approximately in the center thereof, and magnets 8 on both sides of the gap 7. It has a structure in which a magnetically responsive switch 9 consisting of a reed switch and a reed switch are arranged and fixed facing each other. Numerals 10 and 11 are fixtures for fixing the magnet 8 and the magnetically responsive switch 9.

The magnetic response switch 9 is used as a switch for opening and closing the temperature detection circuit including the temperature sensing element 6. For example, when a normally open type reed switch is used, the magnetic response switch 9 opens and closes the temperature sensing circuit including the temperature sensing element 6. In the case of a normally closed type, they are connected in series to the temperature sensing element 6 as shown in FIG. 3b. In FIG. 3, a and b are signal output terminals.

When fixing the magnetically responsive switch 9, the fourth
As shown enlarged in the figure, the magnetic response switch 9
over an appropriate length of the reed switch main body and its lead wires 91, 92,
A heat-resistant insulating tube 12 is placed over the heat-resistant insulating tube 12 and fixed with a fixture 11 from above.
Such a structure provides advantages such as being able to protect the reed switch body made of a glass tube from tightening force or impact, and also being able to perform insulation treatment on the lead wires 91 and 92. .

The outer case 1 corresponds to the gap 7 formed between the magnet 8 and the magnetically responsive switch 9.
A projection 102 extending toward the gap 7 is provided on the bottom surface 101 of the magnetic head 1, and a magnetic shield 14 made of a ferromagnetic material is provided on the projection 102.

When the heated body 5 is not present on the upper surface 301 of the movable body 3, the movable body 3 is at the upper limit position as shown in FIG. The magnetic response switch 9 responds to the magnetic action from the magnet 8, and when a normally open type reed switch is used as the magnetic response switch 9, as explained in FIG. 3a,
The magnetic response switch 9 is turned on, for example. Therefore, the temperature sensing element 6 is short-circuited by the magnetic response switch 9, current no longer flows through the temperature sensing element 6, and the temperature sensing operation is stopped. In other words, if the object to be heated 5 is not present and therefore the temperature measurement operation is unnecessary, the temperature detection circuit is cut off.

On the other hand, when the object to be heated 5 is placed and a temperature measurement operation becomes necessary, the movable object 3 descends against the coil spring 4, and as shown in FIG.
4 enters the gap 7, the magnetism from the magnet 8 to the magnetically responsive switch 9 is blocked, the magnetically responsive switch 9 is turned off, current flows through the temperature sensing element 6, and temperature is detected from terminals a and b (Figure 3). A signal is extracted.
Temperature control is possible by controlling the heat generation temperature of the heater using this temperature detection signal.

As described above, the heated object detection device according to the present invention detects the presence or absence of the heated object 5 as the movement of the movable body 3 back and forth, and at the same time detects the presence of the heated object by using the temperature sensing element 6 provided on the movable body 3. Since the configuration continuously detects the temperature of the heated object 5, it is possible to detect the presence or absence of the heated object 5 and to detect the temperature in one place.The configuration is simplified, the number of parts is small, and assembly is easy. A low-cost heated object detection device can be obtained.

Further, the magnetic circuit characteristics between the magnet 8 and the magnetic response switch 9 are changed by the forward and backward movement of the movable body 3, and the magnetic response switch 9 is turned on and off. Since it is configured to open and close, the temperature sensing element 6 consisting of an NTC thermistor or PTC thermistor, etc.
Using this, the temperature of the heated object 5 can be continuously detected and the temperature can be controlled with high precision. Moreover, this embodiment uses a magnetically responsive switch 9, which is a reed switch that is less susceptible to the effects of the atmosphere and has an excellent switching function compared to a normal contact switch. such as heating equipment or electromagnetic ranges,
A heated object detection device that operates stably even in a high temperature and humidity atmosphere can be obtained.

Furthermore, by fixing the magnet 8 and the magnetically responsive switch 9 through the gap 7, the relative distance between them is kept constant, and the magnetic shield 14 is moved in and out of the gap 7 to turn the magnetically responsive switch 9 on and off. Since the configuration is configured, turning on the magnetic response switch 9,
The off operation is done by magnet 8 and magnetic response switch 9.
It does not depend on the relative distance relationship between the magnetic shield 14 and the gap 7, but is determined solely by the movement of the magnetic shield 14 into and out of the gap 7. For this reason, a highly reliable heated object detection device is obtained in which there is no possibility of malfunction due to positional deviation between the magnet 8 and the magnetically responsive switch 9.

In addition, since the magnet 8 and the magnetically responsive switch 9 are attached to the bottom plate 302 far from the heated object 5,
It is less susceptible to heat, which improves reliability. Moreover, since the bottom plate 302 is made of a non-magnetic material, even when the magnetic shield 14 is inserted into the gap 7, leakage of magnetic flux is extremely small.
A highly sensitive heated object detection device can be obtained.

In the above embodiment, the structure is shown in which the magnet 8 and the magnetic response switch 9 are moved with respect to the fixed magnetic shield 14, but on the contrary, the magnetic shield 14 is moved with respect to the movable body 3. It is also possible to have a structure in which the magnet 8 and the magnetic response switch 9 are fixed after being attached and moved.

Next, an embodiment will be described in which the heated object detection device according to the present invention is applied to a rice cooker. FIG. 5 is a front partial sectional view thereof, and FIG. 6 is a similar electrical circuit connection diagram. In Figure 5, Figures 1 to 4
The same reference numerals as in the figures indicate identical components. 15 is a heated object detection device according to the present invention;
16 is a rice cooker main body, and 17 is a rice cooker storage section. The heated object detection device 15 has the structure explained in FIGS. 1 to 4, and is attached to the approximate center of the heater section 2 attached to the bottom of the rice bowl storage section 17. 18 is a heater provided in the heater section 2; 19;
is an automatic return type rice cooking switch that is provided outside the rice cooker main body 16 and is turned on manually when cooking rice.

In FIG. 6, 20 is a switch that is turned off when there is a rice bowl 5 as a heated object in the rice bowl storage section 17 and turned on when it is removed, 21 and 22 are comparators, and 23 and 24 are transistors. be. 25
is a relay, and 251 is a contact point of the relay 25. This contact 251 opens and closes a rice cooking circuit including the rice cooking heater 18. 26 is a capacitor, 27 to 36 are resistors, and Vcc is a DC power supply.

In the above rice cooker, water and rice are put into the rice cooker 5, and the rice cooker is set in the rice cooker storage section 17 of the rice cooker main body 16, and the rice cooker switch 19 is turned on by manual operation. When rice cooking switch 19 is turned on, resistor 3
2, the capacitor 26 is charged to the power supply voltage Vcc. The charging voltage Vcc of the capacitor 26 is applied to one input terminal (+) of the comparator 22 and compared with a reference voltage applied to the other input terminal (-). In this case, the reference voltage input to the input terminal (-) side is a value obtained by dividing the power supply voltage Vcc by the resistor 34 and the resistor 35, and is lower than the charging voltage Vcc input from the capacitor 26 to the input terminal (+) side. Therefore, the output of the comparator 22 becomes "H" level,
Base drive is applied to the transistor 24, and the transistor 24 is turned on. transistor 24
The relay 25 is energized by the conduction, and its contact 2
51 is closed, the rice cooking circuit is turned on, and the rice cooking operation is started.

On the other hand, at the same time as the rice cooker 5 is set, the heated object detection device 15 according to the present invention operates and the magnetic response switch 9 is turned off, so that current flows through the temperature sensing element 6 and the temperature measurement operation of the rice cooker 5 starts. be done. However, immediately after setting, the temperature of the rice cooker 5 is low and the resistance value of the temperature sensing element 6 composed of an NTC thermistor etc. is high, so the resistance value of the temperature sensing element 6 and the resistance value of the resistor 27 are divided and compared. The voltage level input to the input terminal (-) of the comparator 21 is higher than the voltage level input to the input terminal (+) of the comparator 21 after being divided by the resistor 28 and the resistor 29. Therefore, the output of comparator 21 is at the "L" level, and transistor 23 is in an off state. Therefore, the charge accumulated in the capacitor 26 is not discharged by turning on the rice cooking switch 19, and the contact 251 of the relay 25 remains on, and the rice cooking operation continues.

If the rice cooking operation is continued in this state, the temperature of the rice cooker 5 will rise and the rice will be cooked. on the other hand,
As the temperature of the rice cooker 5 increases, the resistance value of the temperature sensing element 6 that detects the temperature decreases, and the voltage level input to the input terminal (-) side of the comparator 21 decreases accordingly. When the temperature reaches or exceeds the cooking temperature of the rice, the relationship between the voltage level on the input terminal (-) side of the comparator 21 and the voltage level on the input terminal (+) side is reversed, and the output of the comparator 21 becomes "L". The level is reversed to "H" level. When the output of the comparator 21 becomes "H" level, the transistor 23 becomes conductive, forming a discharge circuit for the capacitor 26, and the charge accumulated in the capacitor 26 is discharged in the circuit loop of the capacitor 26 → resistor 31 → transistor 23. be done. Due to this discharging action, the terminal voltage of the capacitor 26 decreases, and when the voltage level of the input terminal (+) of the comparator 22 decreases below the reference voltage level of the input terminal (-), the output of the comparator 22 goes to "H" level. to "L" level.
This turns off the transistor 24, opens the contact 251 of the relay 25, turns off the rice cooking circuit, and ends the rice cooking operation.

The normal rice cooking operation is as described above, but when the rice cooker 5 is taken out from the rice cooker main body 16 during rice cooking, the magnetically responsive switch 9 constituting the heated object detection device 15 according to the present invention is turned on and the rice is sensed. Since the hot side end of the temperature sensing element 6 is grounded by the magnetic response switch 9, the input terminal (- ) drops to ground potential. Therefore, the output of the comparator 21 becomes "H" level, the transistor 23 becomes conductive, the accumulated charge in the capacitor 26 is discharged, and the rice cooking circuit is turned off by the same circuit action as described above. In other words, it is possible to prevent dry cooking.

In addition, when there is no rice bowl 5, the magnetic response switch 9 is turned on, and the transistor 23 is connected to the comparator 21.
Since it is turned on by the "H" level output from the rice cooker, even if the rice cooker switch 19 is closed, the capacitor 26 will not be charged and the rice cooker circuit will not operate.
That is, in this case as well, the dry cooking prevention function works, and almost complete dry cooking prevention effect can be obtained.

As described above, the heated object detection device 15 according to the present invention detects the presence or absence of a heated object and its temperature at the same position, and at the same time turns on or off the switch composed of a magnet and a magnetically responsive switch. Thus, it is possible to easily obtain a rice cooker that has the same circuit action as when the temperature of the heated object rises, and has an effect of preventing dry cooking. Moreover, since it has a structure that combines a temperature detection section made up of a temperature sensing element and a dry cooking prevention mechanism made up of a magnet and a magnetic response switch, it is small, has a small number of connections, and operates reliably. To provide a rice cooker with dry cooking prevention that requires a small contact capacity, has a simple structure, and is inexpensive.

Effects of the present invention As described above, according to the present invention, the following effects can be obtained.

(a) The switch that is turned on and off by the movement of the movable body is a magnetic response switch, a magnet,
The magnetically responsive switch and the magnet are fixed to either the movable body or the case so as to face each other with a gap in between, and the magnetic shielding includes a magnetically responsive switch and the magnet. Since it is installed in either the case or the movable body to which the magnet is not attached, so as to go in and out of the gap between the magnetically responsive switch and the magnet to turn the magnetically responsive switch on and off. It is possible to provide an inexpensive heated object detection device that can perform presence/absence detection and temperature detection at one location, has a simple configuration, has a small number of parts, and is easy to assemble.

(b) The magnetically responsive switch and magnet are fixed to either the movable body or the case so as to face each other with a gap in between, and the magnetic shield is provided when the magnetically responsive switch or magnet is not attached. Since either the case or the movable body is provided with a switch that goes in and out of the gap between the magnetically responsive switch and the magnet to turn the magnetically responsive switch on and off, the on/off operation of the magnetically responsive switch is controlled by the magnet. It does not depend on the relative distance to the magnetically responsive switch, but is determined solely by the movement of the magnetic shield into and out of the gap. Therefore, it is possible to provide a highly reliable heated object detection device that does not cause malfunctions due to misalignment between the magnet and the magnetically responsive switch or fluctuations in relative distance.

[Brief explanation of drawings]

Fig. 1 is a partial front cross-sectional view of a heated object detection device according to the present invention realized for use in a heating device such as a rice cooker, a rice cooker, or an electric pot, or an electromagnetic range, and Fig. 2 is a partial front cross-sectional view in a state of use. Figures 3a and 3b are electrical circuit connection diagrams of the heated object detection device according to the present invention, Figure 4 is an enlarged partial sectional view showing the mounting structure of the magnetically responsive switch, and Figure 5 is the present invention. FIG. 6 is a front partial cross-sectional view of a rice cooker incorporating the heated object detection device according to the present invention, and FIG. 6 is an electric circuit connection diagram thereof. DESCRIPTION OF SYMBOLS 1... Outer case, 3... Movable body, 5... Heated body, 7... Gap, 8... Magnet, 9... Magnetic response switch.

Claims (1)

[Scope of Claims] 1. A movable body that moves forward and backward depending on the presence or absence of a heated body, a case that houses the movable body, a switch that is turned on and off by the forward and backward movement of the movable body, and a temperature of the heated body that is detected. A heated object detection apparatus includes a temperature sensing element, wherein the switch includes a magnetically responsive switch, a magnet, and a magnetic shield, and the magnetically responsive switch and the magnet include:
The magnetic shield is fixedly provided on either the movable body or the case so as to face each other with a gap, and the magnetic shield is provided on either the case or the movable body to which the magnetic response switch and the magnet are not attached. A device for detecting a heated object, characterized in that it is provided in one of the above-described gaps so as to enter and exit the gap to turn on and off the magnetically responsive switch. 2. The heated object detection device according to claim 1, wherein the switch opens and closes a temperature detection circuit including the temperature sensing element. 3. The heated object detection device according to claim 1 or 2, wherein the temperature sensing element is a thermistor.