JP2709680B2 - Composite positive temperature coefficient thermistor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite positive temperature coefficient thermistor device used for a demagnetizing circuit of a shadow mask type color cathode ray tube (CRT).

[0002]

2. Description of the Related Art Positive characteristics (PTC: Positive Tempe) are used in portions where the current value needs to be gradually reduced, such as a demagnetizing circuit of a shadow mask type CRT, a relay circuit for starting a compressor motor of a refrigerator or an air conditioner, or a protector circuit of a communication device.
(rature Coefficient) thermistor.

A demagnetizing circuit of a shadow mask type color CRT, which is a typical example of using the positive temperature coefficient thermistor, will be described. A shadow mask, which is a main component of the shadow mask type color CRT, is provided immediately before the phosphor screen of the color CRT, and collides electron beams emitted from three electron guns with the corresponding phosphors.

[0004] As a material used for the shadow mask, a thin steel plate is usually used in view of workability and cost. For this reason, the shadow mask may be magnetized by an external magnetic field or the like, and the magnetization may cause the path of the electron beam to be bent. As a result, color shift, color unevenness, or screen distortion may occur.

In order to prevent such a color shift caused by the magnetization of the shadow mask, a degaussing coil is provided on the outer periphery of a face plate which is a front glass of the shadow mask type color CRT. To demagnetize the shadow mask.

A PTC thermistor is used to generate the gradually decreasing demagnetizing current. The PTC thermistor is an oxide semiconductor ceramic containing barium titanate (BaTiO ₃ ) as a main component. Since a resistance sudden change temperature, that is, a switching temperature can be arbitrarily set by controlling a material composition, a temperature sensor, a current limiting element, or a constant temperature. Used as a heating element.

FIGS. 3A and 3B show the structure of the PTC thermistor, and FIG. 3C shows the resistance-temperature characteristics of the PTC thermistor. As the shape of the PTC thermistor, there are a case type shown in (a) and a lead type shown in (b).
In the case type shown in (a), the PTC thermistor element 10 is housed in a case 13 sandwiched between spring terminals 11 and 12. The lead type shown in (b) has the same structure as the case type.
The TC thermistor element and the electrode are molded.

(C) shows a PTC thermistor resistance-temperature characteristic curve in which the temperature T is plotted on the horizontal axis and the resistance R is plotted on the vertical axis, and the resistance value of the PTC thermistor changes as the temperature rises. While the temperature is extremely low, the temperature gradually decreases, reaches the minimum resistance value _Rmin before the temperature reaches the switching temperature, and rapidly increases when the temperature exceeds the switching temperature. Normally, the temperature at which the resistance value becomes twice as large as R _min is defined as the switching temperature T _{S in the} circuit operation.

The internal resistance and the surface temperature of the PTC thermistor become constant when the self-heating amount and the heat radiation amount of the PTC thermistor are balanced. Therefore, by making the internal resistance at the time of equilibrium larger and performing equilibrium in a short time, the equilibrium point current becomes smaller and a more excellent demagnetizing effect can be obtained.

FIG. 4 shows an example of a degaussing circuit using this PTC thermistor. A PTC thermistor 21 and a degaussing coil 23 attached around the face plate of a CRT 22 are connected in series to an AC power supply 20. Further, a switch 24 for turning on / off the degaussing circuit is added.

In this degaussing circuit, when a driving voltage is applied to the CRT 22, an AC current is supplied from an AC power supply 20 via a PTC thermistor 21 to start degaussing. The PTC thermistor 21 is self-heated and heated by the supplied AC current, and when the temperature reaches around a predetermined switching temperature, the resistance value of the PTC thermistor 21 sharply increases and the AC current sharply decreases. The degaussing operation ends when the alternating current decreases and equilibrates.

If the resistance value of the degaussing PTC thermistor at the time of equilibrium is increased and reaches the resistance value in a short time, complete demagnetization can be performed by lowering the final equilibrium point current. As a result, it is possible to reduce the total power consumption. For this purpose, a composite PTC thermistor composed of two PTC thermistors is used.

FIG. 5A shows the structure of the composite PTC thermistor, and FIG. 5B shows the operation of the composite PTC thermistor.
The composite PTC thermistor shown in FIG.
A C thermistor element 30 and a PTC thermistor element 31 for current control are arranged with a common terminal 32 interposed therebetween, and spring terminals 33 and 34 are in contact with each other.

In (b), A is a characteristic curve showing the resistance-temperature characteristic of the heating PTC thermistor 30, and B is a characteristic curve showing the resistance-temperature characteristic of the PTC thermistor 31 for current control. When an alternating current is applied in the circuit of FIG. 6, the PTC thermistors 30 and 31 generate heat by themselves and the temperature rises. The heat of the heating PTC thermistor 30 having a high heat generation temperature is transferred to the common terminal
, The current control PTC thermistor 31 is further heated and its temperature rises. Therefore, the balanced state R ₂ having a higher resistance value than the balanced state R ₁ when operated alone.
, The current becomes difficult to flow and the equilibrium point current decreases.

The switching temperature of the heating PTC thermistor 30 and the resistance value at equilibrium are set higher than the switching temperature of the current control PTC thermistor 31 for the purpose of supplying heat. Therefore, the respective switching temperatures T _S and R _S are set to different values, for example, the switching temperature T ₂ of the heating PTC thermistor 30.
Is set to 130 ° C., and the switching temperature T ₁ of the current control PTC thermistor 31 is set to 50 ° C.

FIG. 6 shows a configuration of a degaussing circuit using a composite type PTC thermistor.
, A current control PTC thermistor 41 and a demagnetizing coil 42 are connected in series.
A heating PTC thermistor 43 is connected in parallel with the serial connection of the coil and the degaussing coil 42, and a switch 44 for turning on / off the degaussing circuit is added.

In this degaussing circuit, the degaussing coil 42
When a drive voltage is applied to the AC power supply, an AC current is supplied to demagnetize the shadow mask, and the heating PTC thermistor 43 generates heat, thereby heating the current control PTC thermistor 41 to a higher temperature. When the switching temperature is exceeded, the AC current flowing through the current control PTC thermistor 41 gradually decreases, and when the AC current reaches the equilibrium point current, the degaussing operation ends.

The common terminal 32, the spring terminal 33,
In some cases, electrodes are formed on both surfaces of the PTC element in order to improve the electrical contact between the PTC element 34 and the PTC thermistor elements 30 and 31. (A) shows an electroless plating method.
A metal layer 2 made of Ni or the like is formed on both surfaces of the PTC thermistor element, and a metal layer 7 made of Ag or the like is further formed on the electrode layer by screen printing. Also,
(B) shows an electrode layer formed by a thermal spraying method. A metal layer 8 such as Al or brass is formed on both surfaces of the PTC thermistor element 1.

The surface of the electrode layer formed in this way cannot be prevented from being uneven. Therefore, the adhesion between the heating PTC thermistor 30 and the common terminal 32 and the adhesion between the common terminal 32 and the current control PTC thermistor 31 are poor, and the heat conduction via the common terminal 32 becomes insufficient, and the final equilibrium point current becomes a predetermined value. And the demagnetization may be insufficient.

In order to reduce the final current of the current control PTC thermistor 31 to a predetermined equilibrium point current, the heating PTC
Although there is a method of increasing the switching temperature of the TC thermistor 30, there is a limit in terms of heat resistance because the case 35 is usually made of plastic.

[0021]

SUMMARY OF THE INVENTION The present invention relates to a composite PTC thermistor in which electrodes are formed on the surface of a PTC thermistor element, wherein a heat is applied between a heating PTC thermistor and a common terminal and between a current controlling PTC thermistor and a common terminal. It is an object to reduce the equilibrium point current and the power consumption during operation by improving conduction.

[0022]

In order to solve the above-mentioned problems, in the present application, the surface of an electrode formed on a PTC thermistor used for a composite type PTC thermistor, particularly a surface in contact with a common terminal, is polished flat. Yes, that is, `` a positive temperature coefficient thermistor for heating and a current control positive temperature coefficient thermistor having an electrode layer formed on the surface, and an electrode surface disposed between the heating positive temperature coefficient thermistor and the current control positive temperature coefficient thermistor. In a combined type positive temperature coefficient thermistor device comprising one common terminal that contacts and two spring terminals that contact one electrode surface of the positive temperature coefficient thermistor for heating and one of the current control positive temperature coefficient thermistors, The invention provides a composite positive temperature coefficient thermistor device characterized in that the electrode layer of the characteristic thermistor has an unevenness of 10 μm or less.

[0023]

In the present invention having such a structure, the heat generated from the PTC thermistor for heating is efficiently transmitted to the PTC thermistor for current control via the common terminal in contact with the electrode having high smoothness. Is done.

[0024]

An embodiment will be described. FIG. 1 shows an embodiment of the present invention. As shown in FIG. 5, (a) shows an example in which an electrode layer is formed by electroless plating and then screen printing in the same manner as in the prior art shown in FIG. () Shows an electrode layer formed by a thermal spraying method. By the electroless plating method shown in (a), Ni is applied to both sides of the PTC thermistor element.
A metal layer 2 made of Ag or the like is further formed on the electrode layer by a screen printing method. Has been removed by

In the case where the electrode layer shown in FIG. 2B is formed by the thermal spraying method, the PTC thermistor element 1 is provided with A
1 or a metal layer 5 of brass or the like is formed, and this metal layer 5 is also removed by polishing the metal layer 6 that was originally present.

In the embodiment shown in FIG. 1, the electrodes on both surfaces of the PTC thermistor element are polished on a flat surface. If only the surface is polished, the processing cost can be reduced.

Experimental data comparing the product of the embodiment of the present invention with the conventional product are shown. In the experiment, a composite PTC thermistor was constructed using PTC thermistor elements with electrodes having the same shape and the same characteristics. In the degaussing circuit shown in FIG. 6, an equilibrium current was measured by connecting an AC power supply having an effective voltage of 100 V and a degaussing coil having an AC resistance of 7.5Ω.

In the experiment, φ = 11.0 mm, t = 2.5 mm, Ts = 120 ° C., φ = 10.5 mm, t = 2.3 mm, Ts = 130 ° C., φ = 11.0 mm as a heating PTC thermistor , T = 2.3 mm, Ts = 140 ° C., and as a PTC thermistor for current control φ = 13.3 mm, t = 2.2 mm, Ts = 50 ° C., φ = 14.0 mm, t = 1. 8 mm, Ts = 50 ° C. was used, and the equilibrium point current was measured for various types.

The results are shown in Table 1, the rate of change of the equilibrium point current calculated from Table 1 is shown in Table 2, and the unevenness of the electrode surface is shown in Table 3.

[Table 1]

[Table 2]

[Table 3]

As is apparent from Table 1, the equilibrium point current is P
It is reduced by polishing the surface of the TC thermistor element, especially the PTC thermistor element for heating and the PT for current control.
Polishing both of the C thermistor elements reduced the maximum by 31.8%. Further, when one of the electrode surfaces of the heating PTC thermistor element and the current control PTC thermistor element is polished, the reduction rate is greater when only the heating PTC thermistor element is polished.

From this fact, the surface of the PTC thermistor element is subjected to plane polishing to reduce the unevenness, so that the heat conduction efficiency of the heating PTC thermistor and the current control PTC thermistor is increased, and the balance of the current control PTC thermistor element is improved. It is clear that the point resistance increases and the equilibrium point current can be reduced.

[0032]

As described above, the plane-point polishing increases the equilibrium point resistance of the composite PTC thermistor.
The equilibrium point current can be reduced. The decrease in the equilibrium point current value means that the residual magnetic charge of the shadow mask of the CRT can be reduced, thereby improving the image quality (color shift and the like) of the CRT. Further, by reducing the large current in a short time, the image output of the cathode ray tube is stabilized in a very short time.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a PTC thermistor element used in the present invention.

FIG. 2 is a structural view of a conventional PTC thermistor element.

FIG. 3 is a structural diagram and an operation explanatory diagram of a PTC thermistor.

FIG. 4 is a degaussing circuit diagram using a PTC thermistor.

FIG. 5 is a structural diagram and an operation explanatory diagram of a composite PTC thermistor.

FIG. 6 is a degaussing circuit diagram using a composite PTC thermistor.

[Explanation of symbols]

 1,10,21 PTC thermistor element 2,3,4,5,6,7,8 Metal layer 21 PTC thermistor 11,12,33,34 Spring terminal 13,35 Case 20,40 AC power supply 22 CRT 23,42 Demagnetization Coil 24,44 Switch 30,43 PTC thermistor for heating 31,41 PTC thermistor for current control 32 Common electrode

Claims (3)

(57) [Claims] 1. A positive temperature coefficient thermistor for heating and a current control positive temperature coefficient thermistor having an electrode layer formed on its surface, and an electrode disposed between said heating positive temperature coefficient thermistor and said current control positive temperature coefficient thermistor. A composite positive temperature coefficient thermistor device comprising: one common terminal that contacts a surface; and two spring terminals that contact one electrode surface of the heating positive temperature coefficient thermistor and the current control positive temperature coefficient thermistor. 3. The composite positive temperature coefficient thermistor device according to claim 1, wherein the unevenness of the electrode layer of the positive temperature coefficient thermistor is 10 μm or less. 2. The composite positive temperature coefficient thermistor device according to claim 1, wherein at least the electrode layer surface of the electrode layer of the positive temperature coefficient thermistor that is in contact with the common terminal is polished. 3. The composite positive temperature coefficient thermistor device according to claim 1, wherein only the electrode layer of the positive temperature coefficient thermistor for heating is subjected to planar polishing.