JP3591005B2 - Temperature sensor - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a temperature sensor in a cooking device such as a table stove.
[0002]
[Prior art]
Conventionally, with a temperature sensor equipped with a temperature-sensitive ferrite and a magnet, the heat-sensitive part is brought into close contact with the bottom of the pot of the cooking vessel, and when the temperature reaches a predetermined temperature, the magnetism of the temperature-sensitive ferrite changes from ferromagnetic to paramagnetic. There is a technique in which a magnet is detached from a temperature-sensitive ferrite by a return spring force that is urged in a magnet detaching direction to operate a switch, thereby stopping supply of fuel gas to extinguish a fire.
As shown in FIG. 5, for example, such a temperature-sensitive sensor has a disc-shaped temperature-sensitive ferrite 2 at the upper end, a magnet 3 in contact with the temperature-sensitive ferrite 2 from below, and a magnet 3 that receives the magnet 3 and is integrated with the movement of the magnet 3. Connecting rod 22 for transmitting the movement to the micro switch 21, a dish-shaped spring receiver 5 fixed vertically at an intermediate position of the connecting rod 22, and a cover 47 that contacts the temperature-sensitive ferrite 2 and covers these components from above. A holder 8 fitted to the cover 47 to guide the movement of the spring receiver 5 inside and extend to the microswitch 21; a return spring 6 for urging the upper surface of the holder 8 and the spring receiver 5 in the direction in which the magnet 3 is detached; It comprises a microswitch 21 fixed to the lower part of the holder 8 and the like.
Thus, when the temperature-sensitive ferrite 2 that has come into contact with the cooking vessel 30 via the cover 47 reaches a predetermined temperature due to heat conduction from the bottom of the pot, the magnetism is lost. As a result, the magnet 3 cannot withstand the force of the return spring 6 and is separated from the temperature-sensitive ferrite 2. The movement of the magnet 3 causes the connecting rod 22 to turn on the microswitch 21.
[0003]
[Problems to be solved by the invention]
However, since the thickness L of the portion of the cover 47 in contact with the cooking vessel 30 is as thin as 0.5 to 0.8 mm, a considerable amount of the magnetic flux of the magnet 3 passes through the temperature-sensitive ferrite 2 and leaks to the outside of the cover 47. . If there is a leakage magnetic flux, even if the amount is small, the leakage magnetic flux reaches the bottom of the pan, so that when the cooking container 30 is a ferromagnetic (for example, iron) pan, an attractive force is generated between the cooking container 30 and the magnet 3. As a result, the suction force increases as compared with a non-magnetic (for example, aluminum) pot. That is, when an iron pot is used for the cooking container 30, the temperature-sensitive sensor 40 has a higher operating temperature than that of an aluminum pot. Then, the attraction force between the magnet 3 and the iron pot also increases or decreases according to the magnitude of the leaked magnetic flux, and when the attraction force is large, even if the magnetism of the temperature-sensitive ferrite 2 is lost, the force between the iron pot and the magnet 3 is reduced. Since the attraction force is superior to the force of the return spring 6, the magnet 3 does not separate from the pot bottom with the temperature-sensitive ferrite 2 sandwiched therebetween. That is, the temperature-sensitive ferrite 2 and the magnet 3 remain in close contact with each other, so that the temperature-sensitive sensor does not operate.
Also, if there is iron powder or the like around, it adheres to the surface of the cover 47. For this reason, the cover 47 to which the iron powder or the like adheres also varies the heat conduction from the bottom of the pot, which causes a variation in the temperature response performance of the temperature sensor 40.
[0004]
The above is described in detail with reference to FIG.
FIG. 6 is a graph showing how the attraction force of the magnet 3 changes depending on the temperature of the temperature-sensitive ferrite 2 when a ferromagnetic (eg, iron) pan and a non-magnetic (eg, aluminum) pan are used. is there. The solid line is a graph showing the temperature sensor 40 when an aluminum pan is used, and the broken line is a graph showing the temperature sensor 40 when an iron pan is used. The two-dot chain line indicates that the thickness L of the cover 47 is small and the leakage magnetic flux is large. This is when a pot is used.
In the case of an aluminum pan, the adsorption force (g) between the magnet 3 and the temperature-sensitive ferrite 2 gradually decreases from normal temperature to a high temperature, and sharply decreases at a certain temperature (the so-called Curie point of the temperature-sensitive ferrite 2). I do. Accordingly, by adjusting the load of the return spring 6, the operating temperature a1 (° C.) can be set when the suction force is A (g). Under these conditions, when the change in the attraction force due to the temperature when changing from an aluminum pot to an iron pot is measured, the apparent attraction force between the magnet 3 and the temperature-sensitive ferrite 2 is as follows. Is slightly positively displaced as shown by the broken line. Accordingly, the operating temperature (° C.) at the time of the adsorption force A (g) changes from a1 to a2. On the other hand, in the case of a temperature sensor in which the leakage magnetic flux has increased as a result of the cover L having a thin thickness L of 0.5 mm (normally 0.8 mm), the adsorption force is as shown by a two-dot chain line. Large positive displacement. In other words, even if the temperature of the temperature-sensitive ferrite 2 reaches the Curie point and the attraction force between the magnet 3 and the temperature-sensitive ferrite 2 rapidly decreases, the magnet 3 strongly adsorbs the iron pot (see FIG. Bg). In addition, since the attraction force (Bg) has exceeded the load (Ag) of the return spring 6, the magnet 3 remains attracted to the iron pot with the temperature-sensitive ferrite 2 sandwiched therebetween. That is, as described above, regardless of the temperature of the temperature-sensitive ferrite 2, the magnet 3 does not separate from the temperature-sensitive ferrite 2 while being in contact with the temperature-sensitive ferrite 2, so that the temperature-sensitive sensor does not operate even when the temperature rises. It will be.
An object of the temperature sensor of the present invention is to solve the above-mentioned problems and reduce the magnetic flux leakage to stabilize the operating temperature.
[0005]
[Means for Solving the Problems]
The first temperature sensor of the present invention, which solves the above-mentioned problems, contacts a temperature measuring object via a nonmagnetic material cover and is thermally conducted from the temperature measuring object. When the temperature rises, the magnetic sensor changes from a ferromagnetic material to a paramagnetic material. Temperature-sensitive ferrite that changes and returns to a ferromagnetic material at room temperature, a magnet that adsorbs to and desorbs from the temperature-sensitive ferrite according to a change in magnetism due to the temperature of the temperature-sensitive ferrite, and releases the magnet from the temperature-sensitive ferrite In a temperature sensor having a return spring biased in a direction, and a switch for turning on and off in a relative positional relationship between the temperature-sensitive ferrite and the magnet, the cover has a thickness in a portion in contact with the temperature-measuring object. The gist of the present invention is that the thickness is such that the magnetic flux leaking from the magnet to the temperature measuring object does not attract the surrounding iron powder or the ferromagnetic pot of the temperature measuring object.
[0006]
Further, the second temperature sensor is characterized in that in the first temperature sensor, a spacer of a nonmagnetic material and a good heat conductor is provided between the cover and the temperature sensitive ferrite.
[0007]
Further, the third temperature-sensitive sensor is characterized in that in the first and second temperature-sensitive sensors, the magnet has an outer peripheral portion covered with a ferromagnetic material except for a surface adsorbed to the temperature-sensitive ferrite.
[0008]
[Action]
The first temperature-sensitive sensor of the present invention having the above-described configuration is configured such that, in a cover that contacts the temperature-measuring object and conducts heat of the temperature-measuring object to the temperature-sensitive ferrite, the thickness of the portion that comes into contact with the temperature-measuring object is determined by the magnet The thickness is set so that it does not adsorb the surrounding iron powder or the ferromagnetic pot of the thermometer due to the magnetic flux leaking to the thermometer. This utilizes the fact that the magnetic force generated between the magnet and the temperature-sensitive ferrite becomes weaker as the distance from the magnet increases. That is, since the thickness of the cover is made thick so that the magnetic flux does not leak, even the magnetic field lines passing through the temperature-sensitive ferrite and reaching the cover are extremely weak outside the cover. Therefore, since the magnetic force leaking to the outside of the cover is weak, even if the temperature measuring object to be contacted is an iron pot or the like, it is unlikely to be magnetized or attracted by the influence of the magnetic force from the temperature sensor. In addition, iron powder and the like hardly adhere to the cover surface.
[0009]
Since the second temperature sensor further includes a spacer between the cover and the temperature-sensitive ferrite, the second temperature sensor has the same operation and effect as increasing the thickness of the cover. This also utilizes the fact that the magnetic force generated between the magnet and the temperature-sensitive ferrite becomes weaker as the distance from the magnet increases. In other words, if a non-magnetic spacer is created and assembled, and the distance to the cover is increased, the magnetic field lines passing through the temperature-sensitive ferrite and the spacer and reaching the cover will be extremely weak outside the cover. It is.
Since the spacer uses a good heat conductor, even if the spacer is incorporated, the heat conduction from the temperature measuring object to the temperature-sensitive ferrite does not become so bad.
[0010]
In the third temperature-sensitive sensor, since the outer periphery is covered with a ferromagnetic material except for the surface where the magnet is attracted to the temperature-sensitive ferrite, the lines of magnetic force from the magnet penetrate the ferromagnetic material to the outside. Does not leak. That is, only the lines of magnetic force in the direction of the temperature-sensitive ferrite generated from the magnet surface not covered with the ferromagnetic material are diffused from the magnet. In addition, when the magnetic field lines are provided with the ferromagnetic material, the lines of magnetic force easily pass through the inside of the ferromagnetic material, avoiding other portions. Therefore, even such lines of magnetic force that are about to diffuse from the magnet, near the ferromagnetic material, pass through the inside of the ferromagnetic material that covers the magnet, and cannot diffuse extremely far from the ferromagnetic material. Absent.
Therefore, the magnetic force that leaks out of the cover is weaker, so iron powder etc. are less likely to adhere to the surface of the cover. Or less.
[0011]
【Example】
In order to further clarify the configuration and operation of the present invention described above, a preferred embodiment of the temperature-sensitive sensor of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a temperature sensor 10 for a table stove as a first embodiment. The temperature-sensitive sensor 10 includes a disk-shaped temperature-sensitive ferrite 2 at the upper end, a magnet 3 in contact with the temperature-sensitive ferrite 2 from below, a ferromagnetic yoke 4 covering the periphery of the magnet 3, and a magnet 3 receiving the yoke 4. A connecting rod 22 for transmitting the movement to the micro switch 21 integrally with the movement of the micro switch 21, a dish-shaped spring receiver 5 fixed vertically to an intermediate position of the connecting rod 22, and these parts which are in contact with the temperature-sensitive ferrite 2. , A holder 8 fitted to the cover 7 to guide the movement of the spring receiver 5 inside and extend to the microswitch 21, and a return spring 6 urged between the upper surface of the holder 8 and the spring receiver 5. And a micro switch 21 fixed to the lower portion of the holder 8.
The magnet 3 has a cylindrical shape, and magnetic poles (N and S) are provided on the upper surface 3a and the bottom surface 3b, and the yoke 4 covers the entire circumference and the bottom surface except for the upper surface 3a. In addition, the cover 7 has a special thickness of 2 mm between the cooking container 30 and the temperature-sensitive ferrite 2, that is, a portion (L in the figure) of a portion that comes into contact with the cooking container is thicker than its surroundings. (Conventionally, the thickness is 0.5 to 0.8 mm.) A non-magnetic material is selected so that the material is not magnetic, and the heat conduction from the cooking vessel 30 does not decrease even if the thickness increases. As described above, a good heat conductor such as a copper alloy is used.
[0012]
The temperature sensor 10 is often used in a state where the temperature sensor 10 is in close contact with the bottom of the pot of the cooking container 30. In this state, the temperature-sensitive ferrite 2 to which the heat of the pot bottom is transmitted via the cover 7 changes its magnetism when it reaches a predetermined temperature, and becomes a paramagnetic material rather than a ferromagnetic material. For this reason, the magnet 3 that has attracted the temperature-sensitive ferrite 2 decreases in the attraction force between the magnet 3 and the temperature-sensitive ferrite 2, cannot withstand the force of the return spring 6, and separates from the temperature-sensitive ferrite 2. At the same time, the connecting rod 22 interlocked with the magnet 3 via the yoke 4 pushes the movable contact 21a of the microswitch 21 to operate.
Further, when the temperature of the temperature-sensitive ferrite 2 returns to normal temperature due to the removal of the cooking vessel 30 or the like, the paramagnetic material returns to the ferromagnetic material with the temperature, so the attraction force between the magnet 3 and the temperature-sensitive ferrite 2 again increases. As they increase, they both adsorb. In conjunction with the movement, the connecting rod 22 leaves the movable contact 21a of the micro switch 21, so that the micro switch 21 returns to its original state.
[0013]
When the magnetic flux density leaking to the surface of the cover 7 is measured in a state where the temperature-sensitive ferrite 2 and the magnet 3 are adsorbed, and compared with the conventional temperature-sensitive sensor 40, there is a large difference as shown in FIG. FIG. 4 shows a measurement using a columnar rare earth magnet having a diameter of 8 mm and a thickness of 6 mm. The horizontal axis represents the cover thickness L (mm), and the vertical axis represents the leakage magnetic flux density (G) on the cover surface. Is represented. The case of the temperature sensor 10 of the first embodiment is indicated by a solid line, and the case of the conventional temperature sensor 40 is indicated by a mark.
In the first embodiment, the leakage magnetic flux density (G) on the surface of the cover 7 is reduced as compared with the conventional example. For example, since the cover 7 has a thickness L of 2 mm, the leakage magnetic flux density is about 200 gauss. In the conventional example, the cover has a thickness of 0.8 mm and the leakage magnetic flux density is about 800 gauss or more.
Moreover, as the thickness L (mm) of the cover 7 increases, the leakage magnetic flux density (G) measured in inverse proportion decreases. For example, when the thickness L increases from 2 mm to 4 mm, the leakage magnetic flux density is halved from about 200 Gauss to about 100 Gauss.
[0014]
This is because, in the temperature sensor 10, the magnetic field lines of the magnet 3 rarely leak through the temperature-sensitive ferrite 2 and outside the cover 7. That is, since the thickness L (mm) of the cover 7 is large, even lines of magnetic force that pass through the temperature-sensitive ferrite 2 and reach the cover 7 become extremely weak when reaching the outside beyond the thickness L (mm) of the cover 7. It is.
Moreover, since the outer peripheral portion of the magnet 3 is covered with the yoke 4, the magnetic field lines from the magnet 3 do not leak to the outside from the yoke 4, and most of the magnetic lines diffusing far from the magnet are covered with the yoke 4. This is generated from the upper surface 3a of the non-existing magnet 3.
Further, the line of magnetic force has a property of easily passing through the inside of the ferromagnetic material when there is a ferromagnetic material, avoiding other parts. For this reason, even if such lines of magnetic force tend to diffuse far from the upper surface 3a of the magnet 3, they return to the bottom surface 3b through the inside of the yoke 4 near the yoke 4, which is a ferromagnetic material. It does not spread more than 4. Of course, the magnetic field lines passing through the temperature-sensitive ferrite 2 and reaching the cover 7 are extremely weak outside the cover 7 because the thickness L of the cover 7 is increased.
As a result, unlike the related art, the temperature sensor 10 is less affected by the magnetic force on the iron pot or the like that comes into contact. That is, since the magnet 3 hardly generates an attraction force except for the temperature-sensitive ferrite 2, the magnet 3 does not attract the iron pot, and the temperature operation performance is stabilized.
Further, since the iron powder or the like hardly adheres to the surface of the cover 7 of the temperature sensor 10, even when the temperature sensor 10 is used in close contact with the bottom of the pot of the cooking container 30, the heat conduction from the bottom of the pot is hardly varied.
[0015]
Next, a second embodiment will be described. This is different from the temperature sensor 10 of the first embodiment described above in that the yoke 4 is not provided in the configuration as shown in FIG. The thickness L of the cover 27 is 4 mm. This is because, as described above, the surface of the cover 27 not only attracts iron powder and the like when the leakage magnetic flux increases, but also attracts an iron pot or the like of a temperature measurement object. The reason is that it is desirable to set the thickness so that the leakage magnetic flux on the surface of the cover 7 is, for example, 500 gauss or less. That is, in the second embodiment, it is appropriate that the thickness L of the cover 7 is at least 2.5 mm or more, which will be described below with reference to FIG.
Similarly to the first embodiment, the magnetic flux density leaking to the cover surface is measured in a state where the temperature-sensitive ferrite 2 and the magnet 3 are attracted to each other. So there is a big difference. FIG. 4 illustrates the case where the thickness L (mm) of the cover is plotted on the abscissa and the leakage magnetic flux density (G) of the cover surface is measured on the ordinate. Is represented by a symbol.
In the second embodiment, as in the first embodiment, the leakage magnetic flux density (G) on the surface of the cover 27 is reduced as compared with the conventional example. Also, as the thickness L (mm) of the cover 27 increases, the measured leakage magnetic flux density (G) decreases in inverse proportion.
However, the magnitude of the leakage magnetic flux density (G) is smaller than that of the conventional example, but slightly larger than that of the first embodiment. That is, for example, since the thickness L is 4 mm in the second embodiment, the leakage magnetic flux density is about 380 gauss, but in the first embodiment, the thickness L is about 200 gauss at 2 mm, and the thickness L is increased to the same thickness L = 4 mm. And about 100 Gauss. On the other hand, in the conventional example, the cover thickness was 0.8 mm, which was as large as about 800 gauss or more.
Also, from this graph, it can be seen that the thickness L of the cover 27 must be at least 2.5 mm or more in order to reduce the leakage magnetic flux to, for example, 500 Gauss or less.
[0016]
The difference in the leakage magnetic flux density (G) between the first embodiment and the second embodiment is apparent from the difference between the two configurations, that is, the yoke 4 covering the magnet 3, as shown in FIGS. The degree of diffusion of the lines of magnetic force generated by the magnet 3 differs depending on the presence or absence of the magnetic field lines.
In the case of the first embodiment, the magnetic lines of force from the magnet 3 are not leaked from the yoke 4 to the outside, and even if the magnetic lines of force are to diffuse far from the upper surface 3a of the magnet 3, the yoke 4 made of a ferromagnetic material is used. Is returned to the bottom surface 3b through the inside of the yoke 4, so that it does not diffuse more than the yoke 4. Of course, the magnetic lines of force that pass through the temperature-sensitive ferrite 2 and reach the cover 7 are extremely weak outside the cover 7 due to the thickness L of the cover 7.
On the other hand, in the case of the second embodiment, since the yoke 4 is not provided in the configuration, the magnetic lines of force generated from the upper surface 3a of the magnet 3 do not take a short cut through the yoke 4 and are diffused while the bottom surface of the magnet 3 is diffused. Return to 3b. Accordingly, the number of lines of magnetic force that pass through the temperature-sensitive ferrite 2 and reach the cover 27 increases, and the leakage flux to the outside of the cover 27 increases accordingly.
Of course, since the cover 27 still has the thickness L, it goes without saying that the leakage magnetic flux density (G) on the surface of the cover 27 is much smaller than that of the conventional example.
[0017]
As a result, similarly, unlike the related art, the temperature sensor 20 is unlikely to adsorb the iron pot or the like that comes into contact with the temperature sensor 20, and the temperature operation performance is stabilized.
In addition, since iron powder and the like hardly adhere to the surface of the cover 7, heat conduction from the bottom of the pot does not vary.
[0018]
Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments at all, and it goes without saying that the present invention can be implemented in various modes without departing from the gist of the present invention.
For example, the covers 7 and 27 in the first and second embodiments have a large thickness L at a portion which is in contact with the cooking container 30 which is a temperature measuring object, but as shown in FIG. The thickness L may be secured by adding a new spacer 37 and adding the thicknesses of both. However, the spacer 37 must be made of a non-magnetic material similar to the covers 7 and 27 and a good heat conductor, for example, a copper alloy, so that the heat conduction from the cooking container 30 does not decrease or the magnetic force does not change. is there. The spacer 37 also needs to be in close contact with the temperature-sensitive ferrite 2 and the cover 47.
Such a temperature sensor can be easily implemented simply by adding the spacer 37 to the conventional cover 47, and has the same operation and effect as the first and second embodiments. It is easy to manufacture and does not cost much.
[0019]
【The invention's effect】
As described above in detail, according to the first temperature sensor of the present invention, in the cover that is in contact with the temperature measuring object and covers the temperature-sensitive ferrite, the magnetic field lines that pass through the temperature-sensitive ferrite and leak to the outside of the cover are weakened. Also, since the thickness of the cover is increased, even if the temperature measuring object to be contacted is an iron pot or the like, the cover is less likely to be magnetized or adsorbed. Thus, no extra suction force is generated between the temperature sensor and the temperature measuring object.
In addition, iron powder and the like hardly adhere to the cover surface. Therefore, for example, when the cover surface is used in close contact with the pot bottom of the cooking vessel, the heat conduction from the pot bottom does not vary, so that the temperature of the pot bottom can be reliably detected.
As a result, since the magnet turns on and off the switch by reliably detecting the change in magnetism due to the temperature of the temperature-sensitive ferrite, the temperature of the temperature-measuring object is accurately detected, and the temperature-sensitive sensor is less affected by the material of the temperature-measuring object Can be realized.
[0020]
Further, since the second temperature sensor has a spacer between the cover and the temperature-sensitive ferrite, the same operation and effect as increasing the thickness of the cover can be achieved without increasing the thickness of the cover. There is. In other words, even lines of magnetic force that pass through the temperature-sensitive ferrite and the spacer and reach the cover are extremely weak outside the cover.Therefore, the magnetic force that leaks outside the cover is small, and iron powder or the like is adsorbed on the cover or the temperature is measured. It does not affect the magnetic force on the object. Further, since the spacer uses a good heat conductor, heat conduction from the temperature measuring object to the temperature-sensitive ferrite does not deteriorate. As compared with the cover of the first temperature sensor, a spacer is added as a component, but the manufacturing method is simpler and the cost is lower.
[0021]
The third temperature-sensitive sensor further covers the outer periphery of the magnet with a ferromagnetic material except for a surface to be adsorbed to the temperature-sensitive ferrite. Since it does not diffuse to the outside, the amount of lines of magnetic force leaking to the outside of the cover is further reduced. As a result, it is possible to provide a temperature-sensitive sensor with less influence of the material of the temperature measuring object and improved accuracy. In addition, there is an advantage that the temperature-sensitive portion can be made compact because the magnetic field lines are not widened.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a first embodiment.
FIG. 2 is a schematic configuration diagram of a second embodiment.
FIG. 3 is a schematic configuration diagram to which the first embodiment is applied.
FIG. 4 is a graph showing a relationship between a cover thickness and a leakage magnetic flux density.
FIG. 5 is a schematic configuration diagram of a conventional example.
FIG. 6 is a graph showing a relationship between an adsorption force and an operating temperature.
[Explanation of symbols]
10, 20, 40 Temperature sensor 2 Temperature sensitive ferrite 3 Magnet 4 Yoke 5 Spring receiver 6 Return spring 7, 27, 47 Cover 8 Holder 21 Micro switch 22 Connecting rod 30 Cooking vessel 37 Spacer

Claims (3)

A temperature-sensitive ferrite that contacts a temperature measuring object through a non-magnetic material cover, is thermally conducted from the temperature measuring object, changes in magnetism from a ferromagnetic material to a paramagnetic material when the temperature rises, and returns to a ferromagnetic material at room temperature;
A magnet that adsorbs to and desorbs from the temperature-sensitive ferrite according to a change in magnetism due to the temperature of the temperature-sensitive ferrite;
A return spring that biases the magnet in a direction away from the temperature-sensitive ferrite,
A temperature sensor comprising a switch that turns on and off based on a relative positional relationship between the temperature-sensitive ferrite and the magnet,
The above-mentioned cover is characterized in that the thickness of the portion in contact with the above-mentioned temperature measuring object is such that the magnetic flux leaking from the magnet to the above-mentioned temperature measuring object does not attract the surrounding iron powder or the ferromagnetic pot of the temperature measuring object. Temperature sensor. The temperature sensor according to claim 1,
A temperature-sensitive sensor, wherein a spacer made of a nonmagnetic material and a good heat conductor is provided between the cover and the temperature-sensitive ferrite. The temperature sensor according to claim 1 or 2,
A temperature-sensitive sensor, wherein the magnet has an outer peripheral portion covered with a ferromagnetic material except for a surface to be attracted to the temperature-sensitive ferrite.

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