JP2002132085A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of accurately measuring the surface temperature of a heat roller, regardless of the working circumstances of a fan. SOLUTION: This image forming device is provided with a fixing means for thermally fixing a toner image on paper, a cooling means for cooling the fixing means thermally fixing the toner image, a sensor unit provided with an infrared sensor detecting infrared rays generated by the fixing means and outputting a signal and a temperature sensor measuring the ambient temperature of the infrared sensor and outputting a signal, and an arithmetic calculation means for arithmetically calculating the temperature of the fixing means, based on the output signals from the infrared sensor and the temperature sensor and the working circumstances of the cooling means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a calculating means for calculating the temperature of a fixing means based on an output signal from an infrared sensor for detecting infrared rays emitted by the fixing means and an output signal from a temperature sensor for measuring the temperature of the infrared sensor. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art In electrophotographic copying machines and printers, fixing means such as a fixing roller pair comprising a pair of upper and lower rollers is used to thermally fix a toner image carried on paper. Is done. For a fixing roller pair,
Usually, the upper roller is configured as a heat roller and heats the toner image carried on the sheet. In order to fix the toner image satisfactorily, it is necessary to maintain the surface temperature of the heat roller at an optimum value. For that purpose, it is necessary to accurately and quickly measure the surface temperature of the heat roller. Therefore, there has been proposed an apparatus for measuring the surface temperature of a heat roller in a non-contact manner by detecting infrared rays emitted from the heat roller with an infrared sensor (Japanese Patent Application Laid-Open No. 58-160972).

However, as shown in FIG. 1, there is a problem that the output voltage of the infrared sensor is affected by the ambient temperature even when the amount of infrared rays emitted from the heat roller is constant. Therefore, a technology has been disclosed in which a temperature sensor for detecting the temperature of the infrared sensor itself is installed, and the output voltage of the infrared sensor is corrected by using the output of the temperature sensor (Japanese Patent Laid-Open No. 5-126647). . Further, in order to compensate for the difference in the followability of the infrared sensor and the temperature sensor with respect to the temperature change, at least one of the infrared sensor and the temperature sensor having the better followability with respect to the temperature change may be made of amorphous polyether sulfone or the like. A technique for attaching a member having a large heat capacity (hereinafter referred to as a compensating member) has been disclosed (JP-A-5-126647).

[0004]

However, when the fan for cooling the heat roller is operating, the temperature gradient of the compensating member is increased by the wind, and the temperature of the infrared sensor and the temperature of the infrared sensor detected by the temperature sensor are increased. An error occurs with the ambient temperature. If such an error occurs, the surface temperature of the heat roller cannot be accurately measured.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of accurately measuring the surface temperature of a heat roller regardless of the operating condition of a fan.

[0006]

According to a first aspect of the present invention, there is provided:
A fixing unit that thermally fixes the toner image on the paper, a cooling unit that cools the fixing unit that has performed the heat fixing, an infrared sensor that detects infrared rays emitted by the fixing unit and outputs a signal, and an ambient temperature of the infrared sensor. It has a sensor unit having a temperature sensor that measures and outputs a signal, and a calculation unit that calculates the temperature of the fixing unit based on the output signal of the infrared sensor, the output signal of the temperature sensor, and the operation status of the cooling unit. And

According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the operating state of the cooling means is whether or not the cooling means is operating.

[0008] In a third configuration of the present invention, the arithmetic means includes:
Furthermore, the image forming apparatus according to the first configuration, wherein the temperature of the fixing unit is calculated based on the total number of formed images.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a printer 100 according to an embodiment of the present invention will be described with reference to the drawings.

First, the overall configuration and operation of the printer 100 will be described with reference to FIGS.

The printer 100 includes a control unit, an image forming unit, a paper feeding unit, and a fixing unit.

FIG. 3 is a schematic configuration diagram relating to a temperature control circuit of the heat roller 15 described later. As shown in FIG. 3, the control unit includes a CPU 1, a ROM 2, and a RAM 3. The CPU 1 controls the operation of each unit of the printer 100. The ROM 2 stores a control program for the image forming unit, data for controlling the temperature of the fixing roller pair described later, and the like. The RAM 3 provides a work area for storing an operator's instruction at the time of program execution, an operation state of each unit of the apparatus, and the like.

FIG. 2 is a schematic diagram of the inside of the printer 100. As shown in FIG. 2, a photosensitive drum 4 that rotates at a constant speed in the direction of the arrow is provided in the image forming unit. Around the photosensitive drum 4, a charging charger 5, a writing head 6, a developing device 7, a transfer charger 8, and a cleaner 9 are installed in this order in the direction of the arrow. Photoconductor drum 4
After the surface of the photosensitive drum 4 is charged by the charging charger 5, the writing head 6 irradiates light based on the image information to form an electrostatic latent image on the surface of the photosensitive drum 4. Then, after the electrostatic latent image is developed by the developing device 7 to form a toner image, the toner image is transferred onto the paper P by the transfer charger 8. In this embodiment, the LED head 10 including the LED array is used as the write head 6, but an exposure device that forms an electrostatic latent image by laser scanning may be used.

The paper feeding section includes a paper storage tray 11, a paper feeding roller 12, and a transport belt 13. The paper P stored in the paper storage tray 11 is sequentially pulled out by the paper feed roller 12. The paper P pulled out by the paper feed roller 12 is transported by the transport belt 13 between the photosensitive drum 4 and the transfer charger 8 (hereinafter, referred to as a transfer position) at a predetermined timing. The toner image is transferred onto the sheet P conveyed to the transfer position as described above. The paper P on which the toner image has been transferred is transported by the transport belt 13 to the fixing unit.

The fixing unit includes a pair of fixing rollers including a heat roller 15 and a pressure roller 14, a sensor unit 16, and a fan 17 and a fan 18 for cooling the heated fixing unit under the control of the microcomputer 1. .

The heat roller 15, in which a heater lamp 19 is disposed, is rotated by a pressure roller 14 driven by a motor (not shown). As shown in FIG.
The heater lamp 19 is a switch 2 controlled by the CPU 1.
The heat roller 15 is heated so that the surface temperature of the heat roller 15 becomes a predetermined set temperature by receiving a voltage from the power supply 25 in accordance with the on / off switching of the power supply 2.

FIG. 4 is a schematic sectional view of the sensor unit 16. As shown in FIG. 4, the sensor unit 16 includes a casing 21, a thermistor 22, an infrared sensor 23, and a filler 24.

A casing 24 is filled with a filler 24 made of a material having a large heat capacity, and a thermistor 22 and an infrared sensor 23 are provided therein. The filler 24 compensates for the difference in the followability of the thermistor 22 and the infrared sensor 23 with respect to temperature changes. Note that silicon, ceramic, or the like can be used for the filler 24, and silicon is used in this embodiment.

The infrared sensor 23 is fixed with the light receiving section 25 facing the heat roller 15. In front of the light receiving portion 25, a cylindrical window portion whose diameter increases outward is opened, and infrared rays emitted from the heat roller 15 are transmitted to the light receiving portion 25.
It is configured to be able to reach. Infrared sensor 2
Numeral 3 denotes a light receiving unit 2 for receiving infrared rays emitted from the heat roller 15.
5, the infrared output S according to the amount of infrared light received
G01 is output to CPU1.

The thermistor 22 for measuring the ambient temperature of the infrared sensor 23 is installed near the infrared sensor 23. The thermistor 22 outputs a voltage corresponding to the ambient temperature of the infrared sensor 23 to the CPU 1 as the temperature compensation output SG02.
Output to

In the fixing unit having the above configuration, first, the CPU 1 detects the surface temperature of the heat roller 15 by receiving outputs from the infrared sensor 23 and the thermistor 22. Next, on / off of energization of the heater lamp 19 is switched under the control of the CPU 1 based on the detected surface temperature, and the surface temperature of the heat roller 15 is set to a predetermined set temperature. Then, the paper P on which the toner image has been transferred is transported between the heat roller 15 and the pressure roller 14, and the toner image is fixed on the paper P.

Next, a method for measuring the temperature of the heat roller 15 will be described in detail.

First, the infrared rays emitted from the heat roller 15 reach the light receiving section 25 of the infrared sensor 23. The infrared sensor 23 outputs an infrared output SG01 to the CPU 1 according to the amount of received infrared light.

In order to correct the surface temperature of the heat roller 15 detected by the infrared sensor 23, the thermistor 22 measures the ambient temperature of the infrared sensor 23 and
For 1, the temperature compensation output SG02 is output.

The infrared output SG01 and the temperature compensation output SG0
2 to which the CPU 1 receives the input infrared output SG
01 and the value of the temperature compensation output SG02 are applied to the following equation to obtain the surface temperature TH (SG01, SG01) of the heat roller 15.
SG02). TH (SG01, SG02) = K3 × SG01 + K2 ×
SG02 + K1 However, when the fan 17 or the fan 18 operates, the air blows on the filler 24. Then, since the heat capacity of the filler 24 is large, the heat resistance is reduced due to the wind and the temperature gradient is increased. Infrared sensor 23 and thermistor 2
4. The filler 24 compensating for the follow-up property to the temperature change of 4.
When the temperature gradient becomes large, an error occurs between the temperature of the infrared sensor 23 and the ambient temperature detected by the thermistor 22. Therefore, the calculation formula is corrected by correcting the coefficient K2 of SG02 used in the calculation formula according to ON / OFF of the fan 17 and the fan 18. FIG.
Is a table relating to correction values of the coefficient K2. K21-22
0 is a coefficient calculated based on an experiment, and an error between the temperature of the infrared sensor 23 and the ambient temperature detected by the thermistor 22 is canceled. In this way, by finely correcting the arithmetic expression in accordance with the operating conditions of the fans 17 and 18, the surface temperature TH (SG01, SG02) of the heat roller 15 can be accurately determined regardless of the operating conditions of the fans 17 and 18. Can be detected.

Further, as the number of times the printer 100 is used increases, toner and paper dust floating in the air become light receiving portions 25.
And the amount of infrared rays incident on the light receiving unit 25 decreases. When the amount of infrared rays incident on the light receiving unit 25 decreases, there is a problem that only a temperature lower than the actual surface temperature of the heat roller 15 can be detected.

Here, the number of uses of the printer 100 was determined based on the total number of prints, and the output of the infrared sensor 23 according to the total number of prints when the surface temperature of the heat roller 15 was constant was examined. Then, as shown in FIG. 6, a result was obtained in which the output voltage decreased as the total number of printed sheets increased. Based on such a result, the coefficient K in the above equation is calculated.
3. K1 is finely corrected according to the total number of copies. FIG. 5 is a table relating to correction values of the coefficients K3 and K1. As a result, the error between the actual amount of infrared rays emitted by the heat roller 15 and the amount of infrared rays detected by the infrared sensor 24 is corrected, and the surface temperature TH (SG01, SG0) of the heat roller 15 is accurately determined regardless of the use condition of the printer 100.
2) can be detected.

As described above, since the error between the detected value of each sensor and the actual value is corrected under the control of the CPU 1, accurate temperature detection can be performed at a lower cost than in the case where an error is corrected by installing additional members. Can be.

In the above-described embodiment, the surface temperature of the heat roller 15 is detected by calculation using an arithmetic expression. However, the surface temperature of the heat roller 15 may be detected using a temperature conversion table. For example, FIG. 7 is a temperature conversion table when the total number of copies is 0 to 10000, the fan 17 is off, and the fan 18 is off.
A temperature conversion table as shown in FIG. 7 may be stored in the ROM 2 in advance, and the CPU 1 may sequentially read the surface temperature of the heat roller 15 from this temperature conversion table.

[0030]

According to the present invention, it is possible to provide an image forming apparatus capable of accurately measuring the surface temperature of the heat roller regardless of the operating condition of the fan.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a relationship between an output voltage of an infrared sensor and an ambient temperature when a temperature of a heat roller is constant.

FIG. 2 is a schematic diagram of the inside of the printer 100.

FIG. 3 is a schematic configuration diagram of a temperature control circuit of a heat roller 15;

FIG. 4 is a sectional view of the sensor unit 16;

FIG. 5 is a table relating to correction values of coefficients in a surface temperature calculation formula of the heat roller 15;

FIG. 6 is a characteristic diagram showing the relationship between the output voltage of the infrared sensor 24 and the total number of copies when the temperature of the heat roller 15 is constant.

FIG. 7 is a temperature conversion table relating to the surface temperature of the heat roller 15;

[Explanation of symbols]

1; CPU, 2; ROM, 3; RAM, 4; photoconductor drum, 5; charging charger, 6; writing head, 7; developing device, 8; transfer charger, 9;
ED head, 11; paper storage tray, 12; paper feed roller, 13; transport belt, 14; pressure roller, 15; heat roller, 16; sensor unit, 17 and 18; fan, 19; heater lamp, 20; , 21; casing, 22; thermistor, 23; infrared sensor, 2
4; filler, 25; light receiving section

Continued on front page F term (reference) 2G065 AA04 AB02 BA12 BA14 BA36 BA37 BC33 BC35 CA21 DA01 DA17 2G066 AC07 AC16 BA09 BB11 BC11 BC15 CA15 CB01 2H027 DA12 DA32 DA34 DA45 DE02 DE04 DE07 DE10 EA12 EC06 JA11 JB16 JB23 JC18 BA03 BA03 BA32 BB01 BB18 BB28 CA07 CA09 CA14 CA19 CA27 CA53

Claims (3)

[Claims] A fixing unit configured to thermally fix a toner image on a sheet; a cooling unit configured to cool the fixing unit that has performed the thermal fixing; an infrared sensor configured to detect an infrared ray emitted from the fixing unit and output a signal; A sensor unit having a temperature sensor that measures the ambient temperature of the infrared sensor and outputs a signal, and a calculating unit that calculates the temperature of the fixing unit based on the output signal of the infrared sensor, the output signal of the temperature sensor, and the operating status of the cooling unit An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the operation status of the cooling unit is whether the cooling unit is operating. 3. The image forming apparatus according to claim 1, wherein the calculating unit further calculates a temperature of the fixing unit based on a total number of formed images.