JP2001228746A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the surface temperature of a fixing roller with good precision, and to simultaneously detect the fault of a non-contacting infrared temperature sensor and coiling round of a transfer material to the fixing roller. SOLUTION: Processing is applied to the output signals of the infrared temperature sensor by using low-pass filters whose time constants differ, respectively. Filtering by a large time constant is applied to temperature controls, filtering by a small time constant is applied to the malfunction and coiling round detection. The detection of the coiling round of the transfer material and the fault of the sensor are simultaneously performed with a highly accurate temperature detection based on the processed signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copier or a printer, and has a fixing device.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a toner image is transferred from a photosensitive drum to a transfer material, and then heated or heated and pressed by a contact type temperature detecting means such as a thermistor. Image formation is performed by performing heat treatment or heat and pressure treatment with a certain fixing heat roller (fixing roller). At that time, the thermistor is brought into contact with the fixing heat roller to measure the temperature of the heat roller. The temperature detecting means by the thermistor is provided in a region of the fixing heat roller through which the transfer material does not pass so as not to affect an image to be fixed because it is a contact type. In addition, because of the contact type, winding of the transfer material,
An error in the measured temperature occurs due to a decrease in contact pressure or poor contact, so that the thermistor unit is periodically replaced or a plurality of thermistors are attached for compensation.

[0003]

However, in the above-mentioned prior art, since the mounting position of the thermistor is at a position where the transfer material does not pass, the fixing heat is set to an appropriate temperature for fixing the toner image on the transfer material. There is a drawback that it is difficult to accurately adjust the temperature of the roller. In addition, such a defect is present not only in the fixing heat roller but also in a fixing device having a fixing heating unit.

Accordingly, a main object of the present invention is to provide an image forming apparatus capable of accurately adjusting the temperature of a heating or heating / pressing unit of a heating or heating / pressing fixing device.

Another object of the present invention is to provide an image forming apparatus capable of easily detecting a failure of a temperature detecting means of a heating or heating and pressurizing fixing device or a stagnation and wrapping of a transfer material around the heating or heating and pressurizing means. That is.

[0006]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
In an image forming apparatus provided with a heating or heating / pressing fixing device having a heating or heating / pressing means for applying heat or heating / pressing to an unfixed image to fix the unfixed image to a transfer material, and a heating element, The surface temperature of the pressure means, by measuring the amount of infrared rays emitted from the heating or heating and pressurizing means, non-contact surface temperature detection means, a time constant to the surface temperature signal from the surface temperature detection means Filtering means for performing two kinds of filtering processes different from each other, temperature adjusting means for driving the heating element to adjust the temperature of the heating or heating / pressing means to a specified temperature, and the surface temperature detecting means Detecting means for detecting a failure of the transfer material or stagnation and wrapping of the transfer material around the heating or heating / pressing means; The temperature adjustment is performed based on the surface temperature signal that has been subjected to the low frequency pass filtering processing with a large time constant among the means, and the detection means causes a failure of the surface temperature detection means or a transfer material to the heating or heating / pressing means. The image forming apparatus is characterized in that the detection of stagnation and wrapping is performed based on the surface temperature signal that has been subjected to low-frequency pass filtering processing with a small time constant among the filtering means.

[0007] The surface temperature detecting means has an infrared detector for detecting an amount of infrared radiation emitted from the heating or heating / pressurizing means, and a thermistor for compensating the temperature of the infrared detector.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 FIG. 1 shows an embodiment of an image forming apparatus as a digital copying machine according to the present invention. First, the configuration and operation will be described with reference to FIG.

The image forming apparatus of the present embodiment has a reader unit 1 at the top of the apparatus main body and a printer unit 2 at the bottom.

A reader unit 1 includes a document table 1 on which a document is placed.
1. a document pressure plate 12 for pressing a placed document from above,
A light source 13 for irradiating the image surface of the document, a plurality of mirrors 14 and lenses 15 for guiding the reflected light from the image surface, and the reflected light are subjected to photoelectric conversion by a CCD, and various image processing is performed on the obtained electric signal. The image processing unit 16 that performs the above operation is a main component.

The image processing unit 16 includes a CCD (not shown)
It has image processing functions such as / D conversion, S / H, shading correction, masking correction, scaling, and LOG conversion.

The operation of the reader unit 1 having the above configuration is as follows.

A document is placed on a document table 11 such that the image surface faces downward, and is pressed from above by a document pressure plate 12. The light source 13 moves in the direction of arrow K1 while irradiating light, and scans the image surface of the document. The reflected light image from the image plane is transmitted through a plurality of mirrors 14 and lenses 15 to the CC.
An image is formed on D, where it is photoelectrically converted into an electric signal. The image signal, which has been converted into an electric signal,
After being subjected to various image processing, it is sent to the next printer unit 2.

As shown in FIG. 1, the printer unit 2 converts the electric signal transmitted from the reader unit 1 into a laser element 18.
An image control unit 17 that converts the surface of the photosensitive drum 30 with a laser beam L to form an electrostatic latent image; an image forming unit 3 including the photosensitive drum 30; A fixing unit (fixing device) 39 disposed on the most downstream side is a main component.

The image forming section 3 includes a photosensitive drum 30 rotatably supported in a direction indicated by an arrow, and a photosensitive drum 30 disposed around the photosensitive drum 30 substantially in the rotation direction.
Primary charger 31 and photosensitive drum 30 for uniformly charging the surface
A developing unit 20 for developing the electrostatic latent image formed thereon as a toner image, a transfer charger 35 for transferring the toner image on the photosensitive drum 30 to the transfer material P, and a cleaner 34 for removing transfer residual toner on the photosensitive drum 30 , An auxiliary charger 33 for removing electricity,
And a pre-exposure lamp 32 for removing residual charges.

The developing device 20 has a developing roller 20a disposed opposite to the photosensitive drum 30. When the developing roller 20a rotates in a direction opposite to the photosensitive drum 30, the electrostatic latent image on the photosensitive drum 30 is converted into a toner image. And develop.

The toner image on the photosensitive drum 30 is transferred to a transfer material P by a transfer charger 35, and the transfer material P on which the toner image has been transferred is conveyed to a fixing unit 39 by a pre-fixing belt 37. In the fixing unit 39, the fixing roller 39a, 39b as a heating / pressing unit rotates and conveys the transfer material P to be pressed, and receives the heat and pressure to fix the toner image on the surface. The transfer material P after fixing is discharged onto a tray 41 outside the apparatus main body.

The feeding section for feeding and transferring the transfer material P has a transfer path for the transfer material P, and a feed cassette 36 and a feed roller 36 are provided at the most upstream side in the transfer direction of the transfer material P.
a, a paper feeder having a transport roller 36b and the like.

In addition to the paper feeder, a multi paper feeder 38 is provided. Since the paper feed path is straight from the multi paper feeder 38, various transfer materials P having different properties such as material and size can be supplied to the image forming unit 3.

Next, image formation in the above-described image forming apparatus will be described with reference to FIG.

The system controller 71 performs various controls of the image forming apparatus, and has an internal CPU 71a.
The control is performed comprehensively. For example, it controls the image input unit 72, the image processing unit 16, and the fixing unit 39 that constitute a part of the reader unit 1. The semiconductor laser 18 is modulated and driven by the laser drive circuit 17 based on the image data obtained by the image processing unit.

An electrostatic latent image is formed on the surface of the photosensitive drum 30 by the output light of the semiconductor laser 18. The electrostatic latent image is developed as a toner image by the developing device 20, and then transferred to the transfer material P by the transfer charger 35.

The fixing unit 39 is composed of fixing rollers 39a and 39b and fixing roller temperature sensors 39c and 39d as surface temperature measuring means. The fixing unit 39 transfers the toner image transferred to the transfer material P by heating and pressing. Fix to material P.

Next, the temperature control of the fixing rollers 39a and 39b in the fixing unit 39 will be described with reference to FIG.

In the present apparatus, in order to measure the temperatures of the fixing rollers 39a and 39b, infrared temperature sensors 39c and 39d which measure infrared rays emitted from the fixing rollers 39a and 39b, convert the amount of infrared rays into temperature, and measure the temperature. Is used at the center of the fixing rollers 39a and 39b, that is, at the center in the transport direction of the transfer material.

As described above, in order to measure the temperature of such a fixing roller, a means for measuring the temperature by bringing a temperature sensor such as a thermistor into contact with the fixing roller or disposing the temperature sensor very close to the fixing roller is usually employed. I was However, in this case, since the temperature sensor is brought into contact with or close to the fixing roller, problems such as wear of the fixing roller have occurred. Therefore, the present device employs a non-contact type temperature sensor.

For heating the fixing rollers 39a and 39b, halogen heaters 208 and 209 are used as heating elements. On / off control of the halogen heaters 208 and 209 is performed through a heater control unit 210 according to a control command from the system controller 71. Since the halogen heaters 208 and 209 are driven by AC, the heater control unit 210 has a built-in SSR (Solid State Relay) inside, and based on a control command from the system controller 71, controls the AC power supply for heater supply. ON / OFF
Are doing.

Next, the infrared temperature sensors 39c and 39d
Will be described with reference to FIG. 4 in addition to FIG.

Only the infrared rays corresponding to the radiant heat from the fixing rollers 39a and 39d are radiated to the inside of the temperature sensors 39c and 39d. Detector 20
3, 204. This infrared detector 203, 2
04 is formed by a thermopile, and thermopile 20
3, 204, it is possible to output a voltage corresponding to the amount of infrared light incident on the light. Before the thermopiles 203 and 204, for the purpose of monitoring only a predetermined wavelength range (infrared ray), an infrared pass filter and condenser lenses LE1 and LE are used.
2 is installed. In addition, thermopile 203, 2
04 is constituted by a thermocouple, so that the side that generates heat by irradiating infrared rays is a hot junction and the side that does not generate heat is a cold junction, and the temperature difference is output as a voltage. Therefore, it is necessary to monitor the temperature on the cold junction side, that is, the temperature of the sensor itself.
6 is also equipped. Here, the relationship between the measurement medium temperature and the temperature of the sensor itself with respect to the thermopile output voltage is as follows: E = A (Tx ⁴ −Ta ⁴ ) (1) E: Output voltage Tx: Measurement medium temperature (K) Ta: Sensor Temperature (K) A: Defined as a constant.

FIG. 5 shows the relationship between E and A (Tx ⁴ -Ta ⁴ ) in the present apparatus, that is, the basic static characteristics when Tx is obtained from Ta and E. Based on this static characteristic,
The temperature of the measurement medium, that is, the temperature of the fixing roller can be calculated by measuring E and Ta by calculating backward from the above equation (1). However, in order to actually perform the above operation, a large analog operation circuit or CP
A digital operation circuit using U or the like is required, and it is considered that problems such as cost and operation speed occur. Therefore, in the present apparatus, the arithmetic processing units 201 and 202 can obtain output signals corresponding to the temperature of the device under test in the actual use area as linearly as possible without performing the above arithmetic operation.
Is used. Hereinafter, using FIG. 6, the arithmetic processing unit 201,
The configuration of 202 will be described.

The outputs of the infrared detectors 203 and 204 inside the temperature sensors 39c and 39d are extremely low (8 mV / 20
0 ° C.), it is necessary to amplify to the A / D conversion level. Therefore, in the present apparatus, the gain of the thermopiles 203 and 204 is multiplied by about 1000 times by the amplifier 250.

The thermistors 205 and 206 for monitoring the temperatures of the temperature sensors 39c and 39d themselves only change their resistance values depending on the temperature. (10
Similarly, the signal is input to the amplifier 251 via the same kΩ) to apply a gain of about twice.

The amplified thermopile 203, 2
04 and the thermistors 205 and 206 are input to the adder 252, and the thermopiles 203 and 20
4 and the difference between the signal levels of the thermistors 205 and 206 are output. The signals α201 and α202 are A / D conversion level signals, that is, the relationship between the output voltage and the measured temperature is obtained.

Here, FIG. 6B shows the operation processing unit 201,
4 is a graph showing the relationship between output voltages α201 and α202 at 202 and measured temperatures. As shown in FIG. 6B, the amplifiers 250 inside the arithmetic processing units 201 and 202,
By adjusting the amplification factor of 251, it is possible to make the characteristic of the actual use area close to linear, and in the case of this device, it is adjusted so as to obtain the characteristic that is linearly approximated in the area from about 60 ° C. to 190 ° C. Have been.

Signals α201 and α202 which have been processed
Are filtering / A / D converters 211 and 212
, A low-frequency pass filtering process for controlling the temperature of the fixing rollers 39a and 39b is performed, and at the same time, the failure of the temperature sensors 39c and 39d or the winding and stay of the transfer material P around the fixing rollers 39a and 39b are detected. After each of the low frequency pass filtering processes of
Bit A / D conversion processing is performed.

A / D-converted temperature control signals α205 and α206 and failure or transfer material P winding detection signals α203 and α204 are transmitted to the system controller 7.
1 and based on the temperature control signals α205 and α206, the system controller 71 controls the heater control unit 21 so that each of the fixing rollers 39a and 39b has a specified temperature.
ON / OF of heaters 208 and 209 collectively through
F is performed to control the temperature.

Further, the system controller 71 as a detecting means analyzes the failure or the wrapping detection signals α203 and α204 of the transfer material to detect the failure of the temperature sensors 39c and 39d or the fixing roller 39 of the transfer material P.
a, wrapping around 39b is detected.

Here, the internal details of the filtering / A / D converters 211 and 212 will be described with reference to FIG.

As described above, the filtering process A
Although the / D converters 211 and 212 perform two types of low-frequency pass filtering processing, the arithmetic processing output signal α
201 and α202 are passed through Butterworth type low frequency cut filters 221 and 222 having two time constants with cutoff frequencies of 1 Hz and 1 kHz, respectively, for temperature control and detection of failure or winding of the transfer material. α205 and α206, and a signal α203 and α204 for detecting a failure or transfer material wrapping.

Next, the change level of the arithmetic processing capability signal when each filter is passed and not passed will be described with reference to FIG. FIG. 8A shows a waveform that has not been subjected to the filtering process. The horizontal axis indicates the elapsed time, and the vertical axis indicates the detected temperature, and indicates the temperature change in each of the periods when the fixing roller rotates, when the transfer material passes, and when the transfer material is wound.

Since the temperature sensor of the present apparatus detects the surface temperature of the object to be measured in a non-contact manner, its temperature responsiveness is extremely higher than that of the contact type. For this reason, when the fixing roller rotates, it detects temperature unevenness in the rotation direction of the fixing roller, detects the temperature drop with the passage of the transfer material when passing the transfer material, and further detects the temperature drop effect by the transfer material when winding the transfer material. It is possible to detect an extremely large temperature drop. When a sensor fails, its output value becomes almost zero.

FIG. 8B shows a waveform when filtering processing for detecting a failure or winding of the transfer material is performed. Compared to FIG. 8A, the filtering constant is such that the noise component overlapping the signal is cut and the detection accuracy of other signal components such as the passage or wrapping of the transfer material is not reduced.

FIG. 8C shows a waveform when a filtering process for temperature control is performed. In order to perform temperature control, such as temperature unevenness in the rotation direction of the fixing roller, the filtering constant is used to smooth signal components that easily cause hunting.

Next, a method of controlling the temperatures of the fixing rollers 39a and 39b, winding the transfer material P around the fixing rollers 39a and 39b, and detecting a failure of the temperature sensors 39c and 39d will be described with reference to the algorithm of FIG.

Each sequence is arithmetically processed by the CPU 71, and controls the entire system.

First, when the temperature control during the image forming sequence is started (S20), the rotation of the fixing rollers 39a and 39b is started, and the surface temperatures of the fixing rollers 39a and 39b are measured for controlling the fixing roller temperature. (S21). Here, the upper fixing roller (hereinafter referred to as “upper fixing roller”)
TU is the surface temperature for controlling the fixing roller temperature at 39a, and the lower fixing roller (hereinafter, referred to as “lower fixing roller”) 39b is the lower fixing roller.
Is defined as TL. At the same time, the surface temperatures of the upper and lower fixing rollers 39a and 39b are measured to detect the winding of the transfer material and the failure of the temperature sensors 39c and 39d (S2).
2). Similarly, the measured temperature of the upper fixing roller 39a is TU ′,
The measured temperature of the lower fixing roller 39b is TL '. Here, when the transfer material P is wound around one of the upper and lower fixing rollers 39a and 39b, or when the temperature sensor 39c
When 39d breaks down, each fixing roller surface temperature TU ',
Since TL 'indicates a value as shown in FIG. 8B, it is determined whether or not the level of this change has fallen below the specified value Ts (S2).
3). If the value falls below the specified value Ts, it is determined that the transfer material P is wrapped around each of the fixing rollers 39a and 39b, or that the temperature sensors 39c and 39d are malfunctioning. The set fixing heaters 208 and 209 are turned off by the system controller 71 via the heater control unit 210 (S24).
Further, the winding (jam) of the transfer material P around each fixing roller is displayed on the operation unit 4 (see FIG. 1) (S25), and the entire image sequence is terminated in addition to the temperature control (26).

Further, each fixing roller temperature TU 'or T
If L ′ does not exceed Ts, it is determined that the winding of the transfer material P has not occurred, and a normal temperature adjustment sequence is performed.

Normal temperature adjustment is performed by measuring the temperature TU or T
If L has decreased to the temperature T _ON at which each fixing heater needs to be turned on (S27), the fixing heater of the fixing roller of each of the fixing heaters 208 and 209 which has decreased to T _ON or less is turned on (S28). The process returns to the measurement of the surface temperature of each fixing roller (S21).

The measured temperature TU or TL is determined by each fixing heater 2.
If the temperature is higher than the temperature T _ON at which it is necessary to turn on 08 and 209 and is equal to or higher than the temperature T _OFF at which each of the fixing heaters 208 and 209 must be _{turned off} (S29).
Of the fixing heaters 208 and 209, the fixing heater of the fixing roller which has risen to T _OFF or more is turned off, and the process returns to the measurement of the surface temperature of each fixing roller (S21).

Further, if the measured temperature TU or TL is To
If the temperature is between n and Toff, in order to avoid excessive ON / OFF of the fixing heater for adjusting the fixing temperature,
The process returns to the measurement of the surface temperature of each fixing roller without switching ON / OFF of each fixing heater (S21). That is, it is a dead zone region for temperature adjustment.

As described above, according to the present apparatus, the temperature of the fixing rollers 39a and 39b can be accurately adjusted, and at the same time, the transfer material P is wound around each fixing roller or the temperature sensors 39c and 39d are controlled. Failures can also be detected.

Embodiment 2 In the first embodiment, the surface temperature signal is subjected to a filtering circuit process with a different time constant by an analog circuit. At the same time as performing the processing and adjusting the temperature of the fixing roller, it is also possible to detect the failure of the temperature sensor by winding the transfer material around each fixing roller.

The integration coefficient at that time is, for example, when the sampling rate is set to 10 mS, (+ 1 + 1... +1 +1 +2 +1 +1... +1 +1) / 12 d-10 d-9 ... d-2 d-1 d d + 1 Calculation is performed using d + 2... d + 9 d + 10. d is the data to be integrated, d + 1,
d-1 represents the immediately preceding and succeeding data, respectively. The coefficient and the number of data can be arbitrarily adjusted to calculate integrated data for each detection.

In the first embodiment, the temperature of the fixing roller in the digital copying machine is adjusted, and at the same time, the transfer material is wound around each fixing roller and the failure of the temperature sensor is detected. The present invention is also applicable to all electrophotographic printers, copiers, and the like, including analog copiers using.

In the above embodiment, the case where the present invention is applied to a fixing device provided with a heating and pressing means has been described. However, the present invention is also applied to a fixing device provided with a heating means acting as a fixing means. Applicable.

[0057]

As is apparent from the above description, according to the image forming apparatus of the present invention, the surface temperature of the heating or heating / pressing unit is measured by measuring the amount of infrared rays emitted from the heating or heating / pressing unit. Surface temperature detecting means for performing non-contact detection, a filtering means for performing two kinds of filtering processes having different time constants on the surface temperature signal from the surface temperature detecting means, and a heating or heating and pressing fixing device. Temperature control means for controlling the temperature of the heating or heating / pressing means to a specified temperature by driving the heating element, and a failure of the surface temperature detecting means or transfer to the heating or heating / pressing means. Detecting means for detecting stagnation and wrapping of the material, wherein the temperature adjusting means includes a low-frequency pass filter having a large time constant among the filtering means. The temperature adjustment is performed based on the processed surface temperature signal, and the detection of the failure of the surface temperature detection unit or the stagnation and wrapping of the transfer material in the heating or heating / pressing unit by the detection unit is performed by the filtering unit. The temperature of the heating or heating / pressing means can be accurately adjusted by performing the processing based on the surface temperature signal subjected to the low frequency pass filtering processing having a small time constant, so that the fixing processing can be performed satisfactorily. And high quality images can be obtained. Further, the stagnation and wrapping of the transfer material around the heating or heating / pressing means can be easily detected.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a diagram illustrating details of an image forming unit.

FIG. 3 is a diagram for explaining details of a configuration for performing temperature adjustment control of a fixing roller using a non-contact surface temperature sensor;

FIG. 4 is a diagram illustrating a configuration of a non-contact surface temperature sensor unit.

FIG. 5 is a diagram showing static characteristics of a non-contact surface temperature sensor unit.

6A is a circuit block diagram of an arithmetic processing unit, and FIG. 6B is a diagram showing static characteristics of the non-contact surface temperature sensor after the arithmetic processing.

FIG. 7 is a circuit diagram for explaining details of a filtering processing unit;

8A and 8B are diagrams showing a signal of a non-contact surface temperature sensor related to a filtering process, (a) a waveform diagram without filtering process, (b) a waveform diagram after filtering process for detecting failure or winding of a transfer material, FIG. 4C is a waveform diagram when a filtering process for temperature control is performed.

FIG. 9 is a flowchart illustrating a procedure of temperature adjustment control, a failure of a surface temperature sensor, and detection of winding of a transfer material around a fixing roller.

[Explanation of symbols]

39a, 39b Fixing roller (heating / pressing unit) 39c, 39d Temperature sensor (surface temperature detecting unit) 71 System controller (detecting unit) 208, 209 Heater (heating element) 210 Heater control unit (temperature adjusting unit) 211 Filtering process A / D converter (filtering means) 203, 204 Thermopile (infrared detector) 205, 206 Thermistor

Claims (2)

[Claims] An image forming apparatus provided with a heating or heating and pressing fixing device having a heating or heating and pressing means for applying heating or heating and pressing to an unfixed image and fixing the unfixed image to a transfer material, and a heating element, The surface temperature of the heating or heating and pressurizing means, by measuring the amount of infrared rays emitted from the heating or heating and pressurizing means, a surface temperature detecting means for detecting in a non-contact manner, the surface from the surface temperature detecting means Filtering means for performing two kinds of filtering processes having different time constants on the temperature signal; temperature adjusting means for driving the heating element and adjusting the temperature so that the temperature of the heating or heating / pressing means becomes a specified temperature; Detecting means for detecting failure of the surface temperature detecting means or stagnation and wrapping of the transfer material around the heating or heating / pressing means; and The temperature adjustment is performed based on the surface temperature signal that has been subjected to the low-frequency-pass filtering processing with a large time constant among the filtering means, and the failure of the surface temperature detection means by the detection means or the heating or heating / pressing means is performed. The image forming apparatus according to claim 1, wherein the detection of the stagnation and wrapping of the transfer material is performed based on the surface temperature signal that has been subjected to the low-frequency pass filtering processing with a small time constant among the filtering means. 2. The apparatus according to claim 1, wherein the surface temperature detecting means includes an infrared detector for detecting an amount of infrared light emitted from the heating or heating / pressing means, and a thermistor for performing temperature compensation of the infrared detector. 2. The method according to claim 1, wherein
Image forming apparatus.