JP2003257591A - Heating device and fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating device having stable luster of an output image and a fixing device applying the heating system above. <P>SOLUTION: A material having thermal conductivity smaller than a casing is inserted into a joining part of the casing of a non-contact temperature sensor and a device body in the heating device to detect the temperature of a detected object being converted to a temperature from a calculated value with an output value of a thermistor device for temperature detection of an infrared absorption material in contact and arranged with the infrared absorption material, and an output value of a thermistor device for temperature compensation to the detect casing temperature, and to control the heater to heat a the material to a given temperature. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device for controlling the temperature of a heating member for heating a material to be heated to a predetermined temperature by using a non-contact temperature sensor, and a fixing device to which the heating device is applied. .

[0002]

2. Description of the Related Art An image forming apparatus using an electrophotographic system is
Normally, a transfer material as a recording material and a toner electrostatically carried on the transfer material, which is composed of resin, magnetic material, colorant, and the like, are pressed against each other and pressed against each other. It has a fixing device that melts and fixes on a transfer material by applying heat and pressure while sandwiching and transporting it with (part).

In such a fixing device, if the temperature detecting means for detecting the temperature of the roller is in contact with the roller, as the number of fixed sheets increases, scratches occur on the surface of the roller and the image quality deteriorates. There is a problem, and as a countermeasure against this, a configuration in which the temperature detecting means is not in contact with the roller is effective.

As the non-contact temperature sensor, a casing having a transparent window for transmitting infrared rays from an object to be detected, an infrared absorbing member which is installed in the casing and absorbs infrared rays transmitted through the transparent window, and the infrared absorbing element. The temperature detecting thermistor element of the infrared absorbing member arranged so as to be in close contact with the member, the temperature compensating thermistor element for detecting the casing temperature, the output voltage from the circuit including the temperature detecting thermistor element and the temperature compensating thermistor. It has been proposed to include an arithmetic processing means for arithmetically operating an output voltage from a circuit including, and to detect the temperature of an object to be detected by converting an arithmetic value of the arithmetic processing means into a temperature in a data table.

[0005]

However, in the non-contact temperature sensor as in the above-mentioned conventional example, when the ambient temperature around the non-contact temperature sensor suddenly changes immediately after the power is turned on, the temperature of the temperature compensating thermistor changes. Does not catch up with the change in ambient temperature, and the temperature of the heating sleeve cannot be detected correctly. Therefore, there is a problem that the gloss of the output image due to the toner formed on the transfer material becomes unstable.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a heating device in which the gloss of an output image is stable and a fixing device to which the heating device is applied. To aim.

[0007]

SUMMARY OF THE INVENTION The present invention is a heating device and a fixing device having the following configurations.

(1) A casing having a transparent window for transmitting infrared rays, an infrared absorbing member for being incorporated in the casing and absorbing infrared rays transmitted through the transparent window, and arranged so as to be in close contact with the infrared absorbing member. A temperature detecting thermistor element for the infrared absorbing member, a temperature compensating thermistor element for detecting the casing temperature, and an arithmetic processing means for calculating an output value of the temperature detecting thermistor element and an output value of the temperature compensating thermistor element. A non-contact temperature sensor for detecting the temperature of an object to be detected by converting the calculated value of the arithmetic processing means into a temperature using a data table,
In a heating device that controls the temperature of a heating member that heats a material to be heated to a predetermined temperature, a member having a lower thermal conductivity than the casing is inserted in a joint portion between the casing of the non-contact temperature sensor and the device body. Heating device.

(2) In the heating device described in (1), a member having a thermal conductivity lower than that of the device frame is inserted into a joint between the casing of the non-contact temperature sensor and the device body.

(3) A fixing device characterized in that the toner image formed on the transfer material is heated and fixed to the transfer material by applying the heating device described in (1) or (2).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows a fixing unit to which the heating device of the present invention is applied and which uses a non-contact type thermistor. In the figure, reference numeral 203 denotes a heater, which heats a heating roller (heating member) 41a. This heating roller 4
A pressure roller 41b is provided in pressure contact with 1a.
Reference numeral 204 is a non-contact type for measuring the temperature of the paper passing portion of the heating roller 41a. Reference numeral 204 is a non-contact type main thermistor for measuring the temperature of the paper passing portion of the heating roller 41a. Reference numeral 205 denotes a contact type sub-thermistor for measuring the temperature of the non-sheet passing portion of the heating roller 41a. The sub thermistor 205 performs error detection for preventing an abnormal temperature rise of the heating roller when the temperature detection abnormality of the main thermistor 204 occurs. Reference numeral 206 denotes a microcomputer (hereinafter, abbreviated as a microcomputer) that controls the fixing unit, and controls the lighting state of the heating heater 203 so as to keep the heating roller 41a at the set temperature based on the temperature detected by the main thermistor 204. To do. Two
Reference numeral 07 is a protection circuit for forcibly turning off the heater 203 when the output of the sub thermistor 205 exceeds a set value, and by turning off the relay 208, even if the control of the microcomputer 206 runs out of control, the heating roller 41a is turned off. It is possible to prevent the temperature from rising abnormally. Similarly, the microcomputer 206 also monitors the temperature detected by the main thermistor 204. When the detected temperature calculated from the output value of the main thermistor 204 exceeds the set value, the relay is turned off and the control program executes error processing. .

FIG. 2 shows a non-contact type main thermistor 204.
It is a figure showing the internal structure of. Reference numerals 301 and 302 are infrared detection thermistors, and 303 is an infrared film.
The film 303 absorbs infrared rays by the infrared rays heated by the heater 203 and emitted from the heating roller 41a,
Warm the thermistor 301. At the same time, the thermistor 301 is also affected by the temperature of the case 304. On the other hand, the thermistor 302 is in the case 304 that is not affected by the infrared rays emitted by the heating roller 41a, and outputs only the effect of the temperature of the case 304.

The thermistors 301 and 302 have a characteristic that the output value becomes small at high temperature. The temperature of the heating roller 41a can be calculated by obtaining only the infrared output value of the heating roller 41a based on these two thermistor outputs. The output of the thermistor 301 is 305, and the output of the thermistor 302 is 0.
It is an amplifier circuit that amplifies to a range of up to 5V. Reference numeral 307 is an amplifier circuit for obtaining two thermistor outputs, that is, a difference between the outputs of the amplifier circuits 305 and 306, and amplifying the output in the range of 0 to 5V.

The thermistor 30 thus obtained
The difference output values of 1 and 302 and the output value of the thermistor 302 (compensation output value) are input to the AD conversion input terminals 308 and 309 of the microcomputer 206, respectively. Can be calculated to.

FIG. 3 shows the internal structure of the microcomputer 206. 401 is a CPU, and 402 and 403 are RO
M and RAM. 404, 405 and 406 are AD converters, 404 is an analog input taken from the input terminal 308, 405 is an analog input taken from the input terminal 309, and 406 is an output value of the sub thermistor taken from the terminal 407, respectively. It has the function of converting to 8-bit digital data. The CPU 401 performs AD conversion by issuing an AD conversion start command to the AD converters 404 and 405. Also, the CPU 401
By reading the digital data stored in the register inside the AD converter, the input values of both terminals can be obtained at arbitrary timing. 408 is the CPU 4
01 indicates an interface when communicating with another CPU.

FIG. 4 shows a ROM 402 and a RAM 403.
Shows the address map of. The ROM 402 stores an area 501 for storing a program and an area 50 for storing a temperature conversion table for obtaining the temperature of the heating roller from the parameters of the difference output value and the compensation output value of the main thermistor.
2. A conversion table for converting the output value of the sub thermistor into a temperature, a data area 503 in which temperature control parameters of the heating roller and the like are stored. RAM
Reference numeral 403 includes a program stack 504, a program variable storage area 505, and a data storage area 506 that stores values calculated by a program.

FIG. 5 is a flow chart for explaining the temperature control routine (601) for the heating roller 41a. First, AD conversion is performed, and terminals 308 (difference output values), 30
AD values from 9 (compensation output value) and 407 (sub-thermistor output value) are read (602). Next, area 502
The temperature detected by the main thermistor is calculated from the input values of the two terminals 308 and 309 according to the temperature conversion table stored in (603). Similarly, the temperature of the sub thermistor is obtained from the sub thermistor temperature conversion table in the area 503 (604).

Next, the temperature of the main thermistor is in the area 50.
3 It is judged whether or not the main thermistor upper limit temperature TL1 stored in the inside is exceeded (605), and if it is exceeded, the relay is turned off and a transition is made to an error state (608, 6).
09). When the detected temperature of the main thermistor does not exceed TL1, it is similarly determined whether the detected temperature of the sub thermistor exceeds the upper limit temperature TL2 (606). When it exceeds, the relay is turned off and the state is changed to the error state as described above (608, 609).

When neither the main thermistor nor the sub-thermistor exceeds the upper limit temperature, the temperature control target temperature TT1 of the heating roller 41a is read from the area 503 (607). The temperature control target temperature TT1 varies depending on the state of the image forming apparatus equipped with the heating roller 41a, such as during paper passing or warming up. If the temperature of the main thermistor does not exceed the temperature control target temperature TT1, the heater heater 203 is turned on (611), and if it exceeds the temperature control target temperature TT1, the heater heater 203 is turned off (612). This subroutine is called by the timer processing at regular time intervals, so that the temperature of the heater 203 can be controlled to be maintained at the temperature control target temperature TT1.

FIG. 6 shows a main thermistor temperature conversion table stored in the area 502. The parameters in this temperature conversion table are two-dimensional arrays calculated in advance from the output characteristics of the thermistor shown in FIG. 2, and the temperature on the temperature conversion table is calculated from the two parameters of the compensation output AD value and the difference output AD value. Parameters can be obtained. Also, due to the structure of the thermistor shown in FIG.
The temperature detected from the top to the bottom in the column direction of the table of FIG. 6 always increases as the differential output AD value increases.

FIG. 7 shows the results of monitoring the temperature of the heating roller 41a and the outputs of the thermistors 301 and 302 in the standby state after the apparatus is activated. The result is that the microcomputer 206 for controlling the heating roller 41a of the fixing unit is driven by an external power source. Since the output value of the thermistor 302 is always larger than the output value of the thermistor 301 when the device is turned on, the amplifier circuit 307 for amplifying the difference between the two thermistor outputs operates without any problem.

In the case of this embodiment, as shown in the sectional view of the fixing device shown in FIG. 8, the casing 304 and the frame are provided between the casing 304 of the non-contact temperature sensor made of aluminum and the fixing device frame 901 made of sheet metal. A heat insulating member 902 (heat conductivity of about 1 W / mK) made of resin having a heat conductivity smaller than that of the body 901 is inserted. The thermal conductivity of this heat insulating member 902 is determined by the casing 3
If it is smaller than 04 or the frame 901, the effect is obtained, but 10 W / mK or less is preferable. Also, the heat capacity should be as small as possible. Due to the effect of the heat insulating member 902, the output value of the thermistor 302 for detecting the temperature of the casing 304 closely follows the rise of the heating roller temperature as shown in FIG. 7, so that the heating roller temperature can be accurately detected. ing. Casing 30 due to rising ambient temperature
This is because the temperature of No. 4 also rises, but it is difficult for heat to escape to the frame body 901 having a large heat capacity due to the heat insulating member 902. Therefore, the temperature of the heating roller 41a can always be controlled by keeping the temperature control target temperature constant, so that the gloss of the output image depending on the heating roller temperature can also be made constant.

The heat insulating member used in this embodiment is made of resin, but rubber, glass, ceramics or the like can be appropriately selected.

For comparison, the temperature of the heating roller 41a and the thermistor 3 which are in a standby state after the apparatus is started in the fixing device in which the non-contact temperature sensor of the conventional example is directly attached to the frame.
FIG. 9 shows the results of monitoring the outputs of 01 and 302, and FIG. 10 shows a sectional view of the fixing device. The output value of the thermistor 302 that detects the temperature of the casing 304 changes as the temperature of the heating roller 41a rises. But casing 3
Since the heat of 04 escapes to the frame 901 of the fixing device, the temperature of the heating roller 41a cannot be accurately detected. As a result, immediately after shifting to the standby state, the heating roller 41
The temperature of a is controlled to be lower than the temperature control target temperature TT1. Therefore, generally, when the temperature of the heating roller 41a is low, the gloss of the output image is also low. Therefore, if the output is made immediately after shifting to the standby state, the gloss is low, and the output of the thermistor 302 becomes stable over time. As the gloss increases. As a result, the gloss of the output image becomes unstable.

In the above embodiments, the case where the heating device of the present invention is used as the heat source of the fixing device has been described. However, the heating device of the present invention removes wrinkles from the material to be heated, polishes the surface, etc. It is also effective to improve the quality of the heating material.

[0027]

As described above, according to the present invention,
A casing having a transparent window for transmitting infrared rays, an infrared absorbing member which is installed in the casing and absorbs infrared rays transmitted through the transparent window, and temperature detection of the infrared absorbing member arranged so as to be in close contact with the infrared absorbing member. Thermistor element, a temperature compensating thermistor element for detecting the casing temperature, an arithmetic processing means for computing the output value of the temperature detecting thermistor element and the output value of the temperature compensating thermistor element, and the arithmetic processing means thereof. A heating device that has a non-contact temperature sensor that detects the temperature of an object to be detected by converting the calculated value into a temperature using a data table, and controls the temperature of a heating member that heats a material to be heated to a predetermined temperature,
Since a member having a lower thermal conductivity than the casing is inserted in the joint between the casing of the non-contact temperature sensor and the main body of the apparatus, the temperature of the heating roller can be accurately controlled at the target temperature, resulting in a glossy output image. It has the effect that it can be kept constant.

According to the present invention, since a member having a lower thermal conductivity than the device frame is inserted in the joint between the casing of the non-contact temperature sensor and the device body, the temperature of the heating roller is accurately controlled at the target temperature. This makes it possible to maintain the gloss of the output image as a result.

According to the present invention, since the above-described heating device is applied as a heat source for heating and fixing the toner image formed on the transfer material to the transfer material, it is possible to accurately fix a large number of sheets. There is an effect.

[Brief description of drawings]

FIG. 1 is a perspective view illustrating an outline of a fixing unit according to an exemplary embodiment of the present invention.

FIG. 2 is a layout configuration diagram of a non-contact thermistor according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of a microcomputer that controls a heating roller of a fixing unit according to an exemplary embodiment of the present invention.

FIG. 4 is an explanatory diagram of a ROM and a RAM inside a microcomputer according to the embodiment of the present invention.

FIG. 5 is a flowchart showing a temperature control subroutine for the heating roller of the fixing unit in the embodiment of the present invention.

FIG. 6 is a temperature conversion table diagram for obtaining the temperature of an object from a non-contact thermistor output in the embodiment of the present invention.

FIG. 7 is a monitor diagram of the output of the thermistor and the temperature change of the heating roller in the standby state from the device startup in the embodiment of the present invention.

FIG. 8 is a cross-sectional compound view of the fixing device according to the exemplary embodiment of the present invention.

FIG. 9 is a monitor diagram of the output of the thermistor and the temperature change of the heating roller in the standby state from the device startup in the conventional example.

FIG. 10 is a cross-sectional compound view of a fixing device in a conventional example.

[Explanation of symbols]

304 casing 901 Fixing device frame 902 heat insulating member 902

Claims (3)

[Claims] 1. A casing having a transparent window for transmitting infrared rays, an infrared absorbing member which is installed in the casing and absorbs infrared rays transmitted through the transparent window, and infrared rays which are arranged so as to be in close contact with the infrared absorbing member. A temperature detecting thermistor element of the absorbing member, a temperature compensating thermistor element for detecting the casing temperature, an arithmetic processing means for calculating an output value of the temperature detecting thermistor element and an output value of the temperature compensating thermistor element, A non-contact temperature sensor for detecting the temperature of an object to be detected by converting the value calculated by the arithmetic processing means into a temperature using a data table, and controlling the temperature of a heating sleeve for heating a material to be heated to a predetermined temperature. In the heating device, a member having a lower thermal conductivity than that of the casing is inserted into the joint between the casing of the non-contact temperature sensor and the device body. And a heating device. 2. The heating device according to claim 1, wherein a member having a thermal conductivity lower than that of the device frame is inserted into a joint between the casing of the non-contact temperature sensor and the device body. 3. A fixing device, characterized in that a toner image formed on a recording material is heated and fixed to the recording material by applying the heating device according to claim 1 or 2.