JP2864482B2 - Fixing roller temperature controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing roller temperature control device for thermally fixing a toner image transferred on a sheet to a sheet in a copying machine or the like.

[Conventional technology]

As a fixing roller used in an electrophotographic printer or a copying machine, for example, there is a fixing roller disclosed in Japanese Utility Model Application Laid-Open No. 61-160644.

The fixing roller is configured by incorporating a heater in a metal pipe such as aluminum, and heats the metal pipe to about 180 ° C. to 200 ° C. by the heat generated by the heater. The toner image is heat-fixed to the paper through the paper on which the image has been transferred.

In such a fixing roller, a rise time of about 5 minutes is required after turning on the power of the heater until the surface temperature of the metal pipe becomes about 180 ° C. to 200 ° C. which can be normally used. There is a disadvantage that power is required.

Therefore, in order to solve this inconvenience, a heating resistor layer is formed on the surface of the roller base material having low thermal conductivity, and Joule heat is generated by applying power to the surface of the heating resistor layer via an electrode. A fixing roller has been developed which thermally fixes the toner image previously transferred onto the sheet by the Joule heat to the sheet.

FIG. 2 is a side sectional view showing a conventional fixing roller having such a heating resistor layer, and FIG. 3 is a perspective view thereof, which is disclosed in Japanese Utility Model Application No. 63-151838.

In the figure, reference numeral 50 denotes a fixing roller. The fixing roller 50 has a heating resistor layer 52 formed on a surface of a roller base material 51 made of a low heat conductor such as glass, enamel or ceramics, and the surface thereof is covered with a fluorine resin layer 53. In this structure, a ring-shaped electrode 54 is attached to both ends of the heating resistor layer 52.

55 is a temperature sensor, and this temperature sensor 55 is a fixing roller 50
Is provided so as to come into contact with the surface.

The manufacturing process of the fixing roller 50 having such a configuration is as follows.

First, the surface of the roller base material 51 is solvent-degreased, then immersed in an aqueous solution of tin chloride and hydrochloric acid for 1 minute, washed with water for 30 seconds, then immersed in an aqueous solution of palladium chloride and hydrochloric acid for 1 minute, and washed for 30 seconds several times. Repeat the pre-processing. After the above pretreatment, the surface of the roller base material 51 is subjected to electroless plating to form the heating resistor layer 52.

Next, the surface of the heating resistor layer 52 is coated with a fluorine resin such as PFA or PTFE and covered with a fluorine resin layer 53, and ring-shaped electrodes 54 are attached to both ends of the heating resistor layer 52.

When used, a voltage is applied between the electrodes 54, while controlling the ON / OFF of the applied voltage using a temperature sensor 55 to keep the surface temperature constant.

[Problems to be solved by the invention]

However, in the conventional technique described above, the temperature sensor 55 rubs the surface of the fixing roller 50 as shown in FIG. 3, so that the surface of the fixing roller 50 is scratched 56, thereby cutting the heating resistor layer 52. Or abnormal heat generation, causing a problem that the device cannot be used immediately.

In addition, since the temperature sensor 55 is provided separately from the fixing roller 50, there is a problem in that manufacturing labor and cost are additionally required.

In order to prevent damage to the surface of the fixing roller 50,
Although a sensor equipped with a sensor 57 utilizing infrared rays which can be used in a non-contact manner as shown in a perspective view in FIG. 4 has been developed, it is very expensive and it is difficult to incorporate it into a general-purpose copying machine. It is impossible, and the problem has not been solved sufficiently.

The present invention can reliably control the temperature of the fixing roller without using a temperature sensor that comes into contact with the surface of the fixing roller, can prevent the damage to the fixing roller, and can reduce the labor and cost of manufacturing. An object of the present invention is to realize a temperature control device for a fusing roller.

[Means for solving the problem]

In order to achieve this object, the present invention relates to a method in which an electroless Ni-P plating film, which is a heating resistor layer on the surface of a roller substrate, has a positive TCR (temperature-resistance gradient) as shown in the graph of FIG. The fact that the value is large and changes linearly between 0 ° C. and 250 ° C. is used, and the change in resistance value itself due to the temperature of the heating resistor is used for roller surface temperature control. And
Temperature determination and temperature adjustment of the heating resistor are performed at the circuit level.

That is, according to the present invention, a heating resistor layer having a first resistance value is formed on the surface of a roller base material, and Joule heat generated by applying a voltage to the heating resistor layer via an electrode causes the heating resistor layer on the paper to be heated. In a fixing roller temperature control device for thermally fixing a toner image on a sheet, a first and second switching unit for switching on and off a voltage applied to the heating resistor layer, and the first switching unit A first current detecting resistor selectively connected in series with the heating resistor layer and having a second resistance lower than the first resistance, or the second current detection resistor;
A second current detecting resistor having a third resistance value lower than the first resistance value, a power supply line selectively connected in series with the heating resistor layer by the second switching means, or a second current detection resistor having a third resistance value lower than the first resistance value. A power supply unit including a first current limiting resistor having a high fourth resistance value, a second limiting resistor having the fourth resistance value, and the same first resistance value as the heating resistor layer; A reproduction resistance connected in series with the second limiting resistance, and a third current detection resistance having the same resistance as the second resistance and connected in series with the reproduction resistance; A reference resistance unit connected in parallel with the unit, a first voltage detection unit for detecting a voltage on the first switching unit side, and a third current detection resistor connected to a side opposite to a power supply connection side; A second detecting means for detecting a voltage generated between both ends of the third current detecting resistor; Pressure detecting means, comparing means for comparing the first and second voltage detection values detected by the first and second voltage detecting means, and first and second voltage detecting means for comparing the first and second voltage detection values according to the result of comparison by the comparing means. Control means for controlling the on / off operation of the switching means.

[Action]

According to the present invention having the above-described configuration, the voltage on the first switching means side is detected by the first voltage detecting means, and the voltage generated across the third current detecting resistor is detected by the first voltage detecting means. , The first and second outputs
Are compared by comparing means.

When the first voltage detection value is lower than the second voltage detection value as a result of the comparison by the comparison means, the control unit connects the first switching means to the second current detection resistor, The second switching means controls the connection to the power supply line so that a voltage is applied to the heating resistor layer so that the heating resistor layer is turned on. When the first voltage detection value is higher than the second voltage detection value, An off state in which the first switching means is connected to a first current detection resistor and the second switching means is connected to the first limiting resistor to stop applying a voltage to the heating resistor layer; Control so that

〔Example〕

 Embodiments will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a control device for a fixing roller according to the present invention.

In the figure, 11 is a commercial power supply (100 VAC), and 12 is a fixing roll having a heating resistor layer formed of an electroless Ni-P plating film on the surface of a roller substrate.

Reference numeral 21 denotes a fixing roll circuit (power supply unit) which includes a resistor (first limiting resistor) R1, a resistor (first current detecting resistor) R5, a resistor (second current detecting resistor) R6, and a changeover switch (second switch). Means) 19 and a changeover switch (first changeover means) 20.

Reference numeral 22 denotes a comparison reference value circuit (reference resistance section), and a resistor R2 (second
, A resistance (reproduction resistance) R3, and a resistance (third current detection resistance) R4, and are connected in parallel to the fixing roll circuit 21.

The resistance value setting of the resistors R ₁ to R ₆ will be described in detail in the description of the action.

13 is a capacitor for AC amplifier, 14 is AC amplifier, 15
Is a diode for rectification, 16 is an integrator, 17 is a voltage comparator (comparator), and 18 is a relay driver.

In the present embodiment, the capacitor 13, the AC amplifier 14, the rectifying diode 15, and the integrator 16 connected to the point X of the changeover switch 20 serve as first voltage detecting means for detecting the voltage at the point X. Capacitor 13 and AC amplifier 1 connected to point Y on the opposite side of the power supply connection side of resistor R4
4. The rectifying diode 15 and the integrator 16 function as second voltage detecting means for detecting the voltage at the point Y.

Further, the voltage comparator 17 is a comparing means for comparing the oil pass force of the two integrators 16, and the relay driver 18 is a voltage comparator.
Turn on switches 19 and 20 according to the comparison result of 17
It serves as control means for controlling the OFF operation.

 Hereinafter, the operation of this embodiment having the above configuration will be described.

First, the heating resistor layer of the fixing roll 12 has a resistance value of about 20Ω at room temperature, and the TCR (temperature coefficient of resistance) of the heating resistor layer is 10,000 PPM / ° C.
At 80 ° C., the resistance value (first resistance value) is obtained by R ₁₈₀ = R ₂₀ × (1 + αt), and is obtained by substituting R ₂₀ = 20, α = 10000/100000, t = 180−20. be able to. This result R ₁₈₀
= 52Ω.

The commercial power supply 11 is directly connected to the heating resistor layer of the fixing roller 12 via the changeover switch 19, or connected to the heating resistor layer via the resistor R1, and the resistor R5 or R6 is connected via the switch 20 to the heating resistor layer. It is connected to the body layer.

Here, the resistance value (second resistance value) of the resistor R5 is set to 1Ω, and the resistance value (third resistance value) of the resistor R6 is 0.001.
Ω is set.

When the switch 19 is connected to the end A and the commercial power supply 11 is connected to the heating resistor layer of the fixing roller 12, the heating resistor layer generates heat. Accordingly, when the resistance value increases and the heating resistor layer reaches 180 ° C., the resistance value becomes 52Ω as described above.

The change in the current flowing in such a circuit is a changeover switch
It can be checked by measuring the voltage across the resistor R6 connected to the A terminal 20 of FIG. The current at this time is il.

Comparison reference circuit 22 connected in parallel with fixing roll circuit 21
Resistor R2, resistor R3 (variable resistor, usually set to 52Ω) and resistor R4 (for current detection) are connected in series. At this time, the current of R2 is set to be 1/1000 of il . Result of the calculation, the resistance value of R ₂ is the resistance value of the resistor R1 (the resistance value of the fourth)
It is the same as 51.948 KΩ.

When the changeover switches 19 and 20 to energize the A-end, the potential Xvolt the X end, the potential Yvolt of Xvolt = i ₁ × 0.001 Similarly Y end becomes _{Yvolt = (i 1/1000)} . That is, Xvolt = Yvolt.

The potentials at the X and Y terminals are AC-amplified by the respective AC amplifiers 14 via the respective capacitors 13 and half-wave rectified by the respective rectifier diodes 15.

After being converted into a DC voltage by each integrator 16, the two voltages are compared by a comparator 17, and a relay driver 18 controls the changeover switches 19 and 20 based on the comparison result.

That is, when the temperature of the heating resistor layer of the fixing roller 12 is lower than the set temperature, the switches 19 and 20 are set to the A end by the output of the relay driver 18. Also,
When the temperature of the heating resistor layer of the fixing roller 12 rises and exceeds 180 ° C., the changeover switches 19 and 20 are switched to the B end.

When the changeover switch 19 is at the end B, the resistor R1 (51.948 KΩ, the same value as R2) is connected in series to the heating resistor layer of the fixing roller 12, so that the heating resistor layer is substantially turned off. And the temperature drops. At this time, a resistor R5 (1Ω) is connected to the B terminal of the changeover switch 20, which is equivalent to the comparison reference circuit 22 composed of the resistors R2, R3, and R4.

When the resistance value falls below 52Ω due to a decrease in the temperature of the heating resistor layer, Xvolt <Yvolt, the comparator 17 is turned on, and the switches 19 and 20 are switched to the A end by the relay driver 18.

In this manner, the resistance of the heating resistor layer of the fixing roller 12 is automatically controlled so as to be equal to the resistance value set by the resistor R3, and the temperature of the heating resistor layer is kept constant.

A feature of this circuit is that even if the power supply is an AC power supply such as a commercial power supply and the power supply has a large voltage fluctuation, control can be performed without any problem. When using DC as a power supply, control is possible simply by removing the capacitor 13 and replacing the AC amplifier 14 with a DC amplifier.

〔The invention's effect〕

As described above, the present invention provides a Joule heat generated by forming a heating resistor layer having a first resistance value on the surface of a roller base material and applying a voltage to the heating resistor layer via an electrode. In the temperature control device of the fixing roller for thermally fixing the toner image on the sheet to the sheet, the first and second switching of the voltage applied to the heating resistor layer is performed.
A first current detection resistor having a second resistance lower than the first resistance and selectively connected in series with the heating resistor layer by the first switching means. Having a third resistance lower than the resistance of the second
A current detection resistor, a power supply line selectively connected in series with the heating resistor layer by the second switching means, or a first current limiting resistor having a fourth resistance higher than the first resistance. , A second limiting resistor having the fourth resistance value, and a reproduction resistor set to the same first resistance value as the heating resistor layer and connected in series with the second limiting resistor. And a third current detection resistor having the same resistance value as the second resistance value and connected in series with the reproduction resistor, and a reference resistance unit connected in parallel with the power supply unit; A first voltage detecting means for detecting a voltage of the first switching means side, and a voltage which is connected to the opposite side of the third current detecting resistor from the power supply connection side and which is generated at both ends of the third current detecting resistor. Second voltage detecting means for detecting, and first and second voltage detecting means Comparing means for comparing the first and second voltage detection values detected by the stage; and as a result of the comparison, if the first voltage detection value is lower than the second voltage detection value, The switching means is connected to the second current detection resistor, and the second switching means is connected to the power supply line to be in an ON state in which a voltage is applied to the heating resistor layer. When the value is higher than the second voltage detection value, the first switching means is connected to the first current detection resistor, and the second switching means is connected to the first limiting resistance, and the heat is generated. And control means for controlling to be in an off state in which application of a voltage to the resistor layer is stopped.

Therefore, according to this, it is possible to reliably control the temperature of the fixing roller without using a temperature sensor that comes into contact with the surface of the fixing roller, to prevent damage to the fixing roller, and to reduce the labor and cost of manufacturing. The effect that it can be achieved is obtained.

Further, by employing the above-described configuration, a low voltage (current) is applied to the heating resistor layer via the limiting resistor even in the off state in which the application of the voltage to the heating resistor layer on the fixing roller surface is stopped. Therefore, the voltage applied to both ends of the current detection resistor is detected by a simple circuit not only in the ON state of the voltage application but also in the OFF state, and it is determined whether the heating resistor layer is at a predetermined temperature or higher. The effect of being able to do so is also obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIG. 2 is a side sectional view showing a conventional example, FIG. 3 is a perspective view of the conventional example, and FIG. 4 is a perspective view of another conventional example. FIG. 5 is a graph showing a temperature resistance straight line of the electroless Ni—P plating film. 12: Fixing roller 13: Capacitor 14: AC amplifier 15: Diode 16: Integrator 17: Voltage comparator 18: Relay driver 21: Fixing roll circuit 22: Comparison reference value circuit

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Takashi Kanamori 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (56) References JP-A-58-192065 (JP, A) JP-A-58-192065 62-157080 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/20 G03G 13/20

Claims (1)

(57) [Claims] 1. A heating resistor layer having a first resistance value is formed on a surface of a roller base material, and Joule heat generated by applying a voltage to the heating resistor layer via an electrode causes the heating resistor layer to have a first resistance value. In a temperature control device of a fixing roller for thermally fixing a toner image on a sheet, a first and second switching unit for switching on / off a voltage applied to the heating resistor layer, and the first switching unit A first resistor having a second resistance lower than the first resistance and selectively connected in series with the heating resistor layer;
Or a second current detection resistor having a third resistance value lower than the second resistance value, and a power supply line selectively connected in series with the heating resistor layer by the second switching means. Alternatively, a power supply unit including a first current limiting resistor having a fourth resistance value higher than the first resistance value; a second limiting resistor having the fourth resistance value; A reproduction resistor set to a resistance value of 1 and connected in series with the second limiting resistor; and a third reproduction resistor having the same resistance value as the second resistance value and connected in series with the reproduction resistor. A reference resistance section comprising a current detection resistor and connected in parallel with the power supply section; a first voltage detection section for detecting a voltage on the first switching section side; and a power supply connection of the third current detection resistor And the other end of the third current detection resistor A second voltage detecting means for detecting a voltage to be viable, first detected by the first, second voltage detecting means,
Comparing means for comparing a second voltage detection value; and as a result of the comparison by the comparison means, when the first voltage detection value is lower than the second voltage detection value, the first switching means outputs the second current. Connected to the detection resistor and the second
The switching means is connected to the power supply line to be in an ON state in which a voltage is applied to the heating resistor layer, and if the first voltage detection value is higher than the second voltage detection value, the first switching is performed. Means is connected to a first current detecting resistor, and said second switching means is connected to said first limiting resistor so as to be in an off state in which application of a voltage to said heating resistor layer is stopped. And a control unit for controlling the temperature of the fixing roller.