JP3283898B2 - PTC heating 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 PTC heating device used for fixing toner of an electronic copying machine, a facsimile or the like, or for sealing vinyl.

[0002]

2. Description of the Related Art A heater using a PTC thermistor rapidly increases its resistance at the Curie point.
It has many advantages such as high safety, fast rising temperature, and no need for a temperature control device, and is used in various fields. When utilizing the advantage that the rising temperature is fast among these characteristics, there is a disadvantage that the rush current becomes too large.

In order to solve this drawback, Japanese Patent Laid-Open No.
JP 97143 describes that a PTC thermistor is connected in series with a negative characteristic thermistor. JP 5
Japanese Patent Application Laid-Open No. 4-115445 describes joining an ohmic electrode and a non-ohmic electrode. JP-A-49-
Japanese Patent No. 27932 describes that positive temperature coefficient thermistors having different Curie points are combined. Japanese Patent Laid-Open Publication No. Sho 63-218184 describes the use of a phase temperature control device.

[0004] However, such a conventional technique has a problem that a circuit is complicated and a man-hour is required. In particular, in the case of Japanese Patent Application Laid-Open No. 49-27932, there is a disadvantage that a portion having a low surface temperature is formed, and is not suitable for use in a fixing device or the like which requires a uniform surface temperature. In addition, a method has been considered in which a plurality of rod-shaped PTC thermistor elements are input with time intervals, or set based on the output and the room temperature resistance value.

[0005]

However, even with these methods, in order to shorten the rise time and to obtain a relatively large amount of heat and a predetermined surface temperature, it is necessary to avoid an inrush current corresponding to the number of wires used. There is a drawback that you can not. Further, as described above, the method of providing additional time with a time interval after only one power is input has a disadvantage that the configuration is complicated.

The problem to be solved by the present invention is to provide a heat generating device which has a fast rise time and a large heat capacity while suppressing an inrush current by a PTC thermistor itself without using an additional circuit or element. .

[0007]

In order to solve this problem, the present invention provides a rod-shaped heater using a PTC element (n).
+1) In a PTC heating device formed in parallel and formed, the total resistance value required for preventing inrush current and required for quick rise is xΩ, and one of the resistance values is (x + z) Ω, and the remaining n resistance values are yΩ
(However, when it exceeds xΩ ), y = nx (x / z
+1) Ω (where 0 <z <x)... In a PTC heating device in which each resistance value is set so as to satisfy the expression (1),
The heater is thermally insulated from each other around the heater by one of silicon resin, epoxy resin and fluorine resin. The above resistance value is a nominal resistance value of the PTC element, that is, a resistance value at 20 ° C. In the present invention, xΩ and (x + z) Ω of the total resistance value are determined, and yΩ is determined so as to satisfy the expression (1).

Further, a portion other than the heat radiating plate portion is fixed around the plurality of heaters with a silicone resin, an epoxy resin, a fluororesin or the like.

Equation (1) can be obtained by the resistance circuit shown in FIG. Assuming that the resistance value of one resistor is x + z, the resistance value of the remaining n resistors is y, and the resistance value of the entire parallel connection circuit is x, the following equation is established. 1 / x = 1 / (x + z) + n × (1 / y) By transposing, 1 / x−1 / (x + z) = n / y, z / x (x + z) = n / y Equation (1) is obtained as y = nx (x + z) / z = nx (x / z + 1).

The above description regulates the relationship between the resistance values, but the condition of the proviso of the equation (1) is given in consideration of the rising characteristic. That is, the reason that z is smaller than x is that when x and z have the same value, for example, when the total is two, y = 1.x. (1 + 1) = 2x, and each heater Is 2x, which is the same value.
When the two heaters having such resistance values are energized, the same current flows in both at the same time, so that the rate of temperature rise is significantly reduced. Therefore, it is necessary that z has a value smaller than x, and when it is desired to raise the temperature more quickly, z is preferably a value closer to 0.

[0011]

In the present invention, as long as the resistance value of the heater of a plurality of electrically connected heating devices satisfies the equation (1), the current value of any equipment used does not exceed the allowable current value. . Therefore, even if a plurality of heaters are turned on at the same time, a large current flows through the heater with the lowest resistance,
At the same time as the temperature reaches the predetermined temperature, the current also flows to other heaters with a high resistance value. Also, it is possible to obtain a heat generating device having large characteristics.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. [Embodiment] As shown in FIG.
The opposite surface of the PTC element 1 made of barium titanate of 5 mm width × 10 mm length × 2.5 mm thickness at 0 ° C.
After the electrode films 2 and 2 are formed by plating, as shown in FIG.
By bonding five C elements 1 in parallel, a PTC heater 4 was obtained,
When the resistance value was measured, it was 80Ω. In order to further increase the heat capacity, similarly, a PTC element having a large resistance value is used so that the total resistance value becomes 90Ω or less.
The calculation was performed by adding 3 to z in the equation, and two PTC heaters 5 were obtained. These resistance values were 5.5 KΩ and 5.6 KΩ. These PTC heaters 4 and 5 are connected as shown in FIG.
This parallel connection was performed, and a heat insulating material was interposed between the heaters, and the heaters were fixed with a silicone resin 6 as shown in FIG. When 100 V was applied to the heating element thus obtained, the surface temperature reached 210 ° C. within 8 seconds, and the maximum inrush current was 3.5 A.

Comparative Example 1 By the same operation as in the embodiment,
The resistance value of each of the three PTC heaters 4, 5, and 5 is 27
Assemble the heat generator with 0Ω, 260Ω, 275Ω,
When a voltage of 100 V was applied, the maximum inrush current was 3.6 A, which was not different from that of the embodiment, but it took about 20 seconds until the surface temperature reached 210 ° C. This is because the current flowing through the heater flowed uniformly into three lines.

Comparative Example 2 By the same operation as in the example,
The resistance values of the three PTC heaters 4, 5, and 5 were set to 93, respectively.
Ω, 90Ω, 91Ω and assemble the heating device,
When V was applied, the surface temperature was 210 ° C within 10 seconds.
, But the maximum inrush current was 10.1A. This is because the resistance value of the entire heater has decreased.

Comparative Example 3 By the same operation as in the example,
The resistance value of each of the three PTC heaters 4, 5, and 5 is set to 18
When the heating device was assembled with 0 Ω, 362 Ω, and 360 Ω (x = z) and 100 V was applied, the maximum inrush current was 3.7 A, but it took nearly 17 seconds for the surface temperature to reach 210 ° C. Was. This is because the current flowing through the heater was dispersed into three.

Comparative Example 4 By the same operation as in the example,
The resistance value of each of the three PTC heaters 4, 5, and 5 is set to 80
Ω, 5.6 KΩ, 5.9 KΩ, the heaters were assembled close to each other without any space between heaters, and 100 V was applied. As a result, the maximum inrush current was 3.6 A, but the surface temperature was 210 A. It took nearly 25 seconds to reach ° C.
This is because the heat of the heater that started up quickly diffused into the other two heaters.

As can be seen by comparing the above embodiment and the comparative example, the PTC having the resistance value defined by the equation (1)
By connecting the heaters in parallel with each other while being thermally insulated from each other, a rush current can be suppressed, and a heat generating device with a fast rise can be obtained.

[0018]

As described above, according to the present invention, the following effects can be obtained. With a simple configuration in which heaters having resistance values satisfying the expression (1) are simply connected in parallel, it is possible to obtain a heat generation device that suppresses inrush current, has a fast rise, and has a large heat capacity. By changing the value of z in the equation (1), it is possible to arbitrarily suppress the rush current during the time until the rise.

[Brief description of the drawings]

FIG. 1 is a perspective view of a heat generating device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a parallel circuit for deriving equation (1).

FIG. 3 is an explanatory diagram illustrating a configuration of a heater according to the embodiment of the present invention.

FIG. 4 is a connection circuit diagram of PTC heaters of an example and a comparative example.

[Explanation of symbols]

1 PTC element, 2 electrode film, 3 electrode plate, 4,5P
TC heater, 6 silicone resin

Claims (1)

(57) [Claims] A bar-shaped heater using a PTC element is provided as (n +
1) This, in the PTC heating device formed by parallel connection, and xΩ the total resistance value required for and fast rise necessary for preventing inrush current, of which one the resistance value (x + z) Ω, and the remaining n resistance values are yΩ
(However, it exceeds xΩ), y = nx (x / z +
1) In a PTC heating device in which each resistance value is set so as to satisfy the expression of Ω (where 0 <z <x), the heaters are thermally connected to each other around the heater by using one of silicon resin, epoxy resin and fluororesin. An insulated PTC heating device.