JPH1031390A - Electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic device capable of exactly detecting the temp. of a heating roller for a fixing device adopting a non-contact temp. detecting sensor instead of depending on the change of ambient temp. inside the electrophotographic device. SOLUTION: In the electrophotographic device controlling the temp. of the heating roller 9 based on detection output by a non contact temp. sensor 14, the non contact temp. censor 14 is provided with self temp. detecting means, the detection output of the non contact temp. sensor 14 is detected and outputted corresponding to the temp. difference between the self temp. and the heating roller temp. to be detected, and the temp. of the heating roller is controlled based on the value T while recognizing the heating roller temp. as T, which satisfies the next multiple degree equation of T0, T=C(T1)+f(T1)×T0+g(T 1)×TO<2> +h(T1)×TO<3> +... and the next functional equation of T1, C(T1), f(T1), g(T1), h(T1),... (example: f(T1) = constant A + α×T1 + β×T1<2> + γ×T1<3> + ...), when assuming the detection output as T0 and self temp. output as T1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus using an electrophotographic process, such as a copying machine, a printer, and a facsimile, and more particularly to an electrophotographic apparatus having a fixing device using a heating roller.

[0002]

2. Description of the Related Art Conventionally, there has been a demand for energy saving in electrophotographic apparatuses such as copiers, printers, and facsimile machines using an electrophotographic process. In order to save energy, many systems have been studied in which a heater of a heating roller is energized only when paper is passed for fixing, and preheating is not performed at other times. In this method, since no preheating is performed, it is necessary to start up the apparatus immediately when the user wants to use the apparatus, and the method is characterized in that the rise time is shortened as much as possible. However, the temperature detection method used in this fixing device is a contact-type thermistor that is often used in conventional fixing devices, and the response speed of the temperature is slow, and furthermore, the release is caused by friction with the release layer on the surface of the heating roller. May wear the layer. For this reason, when a contact-type thermistor is used, there is a problem in that durability is reduced due to deterioration of the release layer on the surface of the heating roller. Therefore, as a countermeasure, a fixing device using a non-contact type temperature sensor (hereinafter, referred to as a non-contact temperature sensor) capable of detecting the temperature without contacting the surface of the subject such as a heating roller has been proposed. (See JP-A-60-51872). As the non-contact temperature sensor, there is a non-contact thermoelectric type infrared temperature sensor described in the above publication, but this non-contact temperature sensor also has a feature that its response speed is fast. It was a match.

However, the output of the non-contact temperature sensor is not linear with respect to the temperature of the subject, and has a characteristic that the output curve itself changes due to a temperature change (change in environmental temperature) of the sensor itself.

Conventionally, a non-contact temperature sensor has been put to practical use by detecting the room temperature of an air conditioner as a typical example. However, the change in the ambient temperature of the sensor and the change in the room temperature are almost the same. Level (10 ° C. to 30 ° C.) and changes in the temperature inside the electrophotographic apparatus such as a copying machine (1
0 ° C. to 80 ° C.) and the temperature change of the heating roller (10 ° C. to 200 ° C.), which is very small. Therefore, the output curve of the non-contact temperature sensor, the temperature of the sensor itself, and the temperature of the subject There was almost no problem even if the relationship with the temperature difference was uniquely determined. However, since the change in the internal temperature of the electrophotographic apparatus is as large as 10 ° C. to 80 ° C., when the non-contact temperature sensor is used for detecting the temperature of the heating roller of the fixing device, the non-contact temperature sensor may be affected by the temperature change of the sensor itself (self temperature change). The change of the output curve of the contact temperature sensor became large and was not practical.

In the technique described in Japanese Patent Application Laid-Open No. 60-51872, it is not noticed that the output curve of the non-contact temperature sensor greatly changes due to the temperature change of the sensor itself. Rough settings were made such that the correction was made and the insufficient correction was made higher than the correction level. Further, the technique described in Japanese Patent Application Laid-Open No. 5-159790 has adopted a very complicated method of performing a calculation for correcting a temperature error by a combination of a non-contact temperature sensor and a contact temperature sensor.

FIG. 3 is a graph showing how much temperature error occurs in the conventional method. This graph uses an output conversion table whose output corresponds exactly to the temperature of the heating roller, which is almost the subject, when the environmental temperature of a certain non-contact temperature sensor is 30 ° C.
Environmental temperature 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃,
The temperature of the heating roller is 2
The difference (temperature error) between the actual temperature of the subject and the temperature detected by the non-contact temperature sensor when the output is converted to a temperature by changing the temperature to 00 ° C. is plotted. As is clear from the graph of FIG. 3, it is understood that the conventional method has a large temperature error due to the influence of the environmental temperature change.

As described above, in the conventional electrophotographic apparatus,
When a non-contact temperature sensor is used to detect the temperature of the heating roller of the fixing device, the temperature error between the detected temperature and the actual temperature is large due to the influence of the environmental temperature change, and the temperature of the heating roller cannot be accurately detected. The problem had arisen.

Therefore, the applicant of the present invention first measures the temperature of the fixing device by receiving infrared rays radiated from the fixing device by the non-contact temperature measuring means, and measures the temperature of the non-contact temperature measuring means by the self-temperature measuring means. Measuring the temperature of the fixing device based on the temperature measurement result of the self-temperature measuring device and the temperature measurement result of the non-contact temperature measuring device. The temperature measurement results of the self-temperature measuring means are converted into digital values, and converted into temperature data corresponding to these two digital values in a conversion table, and the temperature of the fixing device is controlled in accordance with the measured values based on the conversion results. A proposed temperature control method has been proposed (Japanese Patent Application Laid-Open No. 7-77892).

[0009]

SUMMARY OF THE INVENTION Japanese Patent Application Laid-Open No. 7-77892
In the temperature control method described in Japanese Patent Application Laid-Open No. H11-157, a non-contact type temperature measuring means (non-contact temperature sensor) is used when measuring the temperature of the fixing device. Since the corrected temperature needs to be corrected, the self-temperature (value) by the self-temperature measuring means provided in the non-contact temperature sensor and the detection result (value) are converted (corrected) by a conversion table, and the correction is performed. The temperature of the fixing device is controlled based on the value.

However, in order to create a conversion table, it is necessary to create data one by one. In order to increase the accuracy, the table must be made finer, and the work required for creating the table increases. This causes an increase in the memory for storing the table data. Further, when the detected temperature exceeds the range of the created table, no measure can be taken. In this regard, the range of the table to be created may be increased, but in this case, as described above, an increase in the amount of work for creating the table and an increase in the memory for storing the data of the table are inevitable. . In particular, when the temperature changes greatly during heating as in the case of a fixing device, these disadvantages appear remarkably.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a problem to be solved is to use a non-contact temperature sensor and a self-temperature detection output (value) without using the above conversion table. By performing control to correct the detection output (value) with a function related to the temperature, the temperature of the heating roller of the fixing device can be accurately detected using the non-contact temperature sensor regardless of the environmental temperature change in the electrophotographic apparatus. An object of the present invention is to provide an electrophotographic apparatus provided with means.

[0012]

According to another aspect of the present invention, there is provided an electrophotographic apparatus having a fixing device using a heating roller, wherein the fixing device includes a heating roller. In an electrophotographic apparatus having a non-contact temperature sensor for detecting a temperature and controlling the temperature of the heating roller by a detection output of the non-contact temperature sensor, the non-contact temperature sensor has a self-temperature detecting means, The detection output of the temperature sensor is detected and output according to the temperature difference between the self-temperature and the temperature of the heating roller as the subject. When the detection output is T0 and the self-temperature output is T1, the heating roller temperature (Or substitute characteristic of heating roller temperature) T
Is expressed by the following equation: T = C (T1) + f (T1) × T0 + g (T1) × T0 ＾ 2 + h (T
1) × T0 ＾ 3 +... And a functional expression of T1, C (T1), f (T1), g (T1), h (T1), etc. (Example: f (T1) = constant A + α × T1 + β × T1 ＾ 2 + γ ×
T1 ＾ 3 +... (Constants A, α, β, and γ are real numbers not including 0), and the temperature of the heating roller is controlled based on the value of T. As a result, the temperature of the heating roller can be accurately detected irrespective of the environmental temperature change in the electrophotographic apparatus, and the temperature of the heating roller can be controlled stably.

Further, according to the invention described in claim 2, according to claim 1,
In the electrophotographic apparatus described above, the polynomial expression of T0 is less than the cubic expression and the functional expression of T1 is the cubic expression or less. The heating roller temperature can be accurately detected regardless of the change, and the heating roller temperature can be stably controlled.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of a printer (or an image forming section of a copying machine or a facsimile) showing an example of the configuration of an electrophotographic apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes a drum-shaped photoconductor serving as an image carrier. Around the photoconductor 1, a charging device 2, a writing unit 3, a developing device 4, Members such as a transfer / transport device 5, a cleaning device 6, and a static eliminator 7 are provided. When the image forming operation is started, the surface of the photoreceptor 1 is sequentially charged by the charging device 2, and the electrostatic latent image is written in dot units or line units by the irradiation light from the writing unit 3. As the writing unit 3, a unit that performs writing by scanning a laser beam, a unit that performs writing by using an LED array, or the like is used. The electrostatic latent image formed on the photoreceptor 1 is visualized by the toner of the developing device 4, then fed from a paper feed unit 11 by a paper feed roller 12, and is fed through a registration roller 13 at a predetermined timing. Is transferred to the transfer paper conveyed to the transfer section between the photoreceptor 1 and the transfer conveyance device 5. The transfer paper on which the toner image has been transferred is conveyed to the fixing device 8 by the transfer conveyance device 5, subjected to a fixing process by the heating roller 9 and the pressure roller 10 of the fixing device 8, and then transferred to the paper discharge tray by the conveyance roller. Is discharged. The photosensitive member 1 after the transfer of the toner image is cleaned by a cleaning device 7.
, The residual toner is removed, and the charge is removed by the charge removing device 7.

In the printer having the above configuration and operation, a non-contact temperature sensor is provided in a space between the fixing device 8 and the photosensitive member 1 in order to detect the temperature (surface temperature) of the heating roller 9 of the fixing device 8. (For example, an infrared temperature sensor) 14 is disposed, and the heating roller 9 is viewed through the opening provided on the side surface of the cover of the fixing device 8.

FIG. 2 is a diagram showing an outline around the fixing device of the printer shown in FIG. Here, an example in which a self-heating type heating roller with a fast rise is used as the heating roller 9 is shown, but a type incorporating a heater such as a halogen lamp may be used. The power supply brush 15 is in sliding contact with the electrode portions 16 provided at both ends of the heating roller 9.
An AC power supply 17 and a triac 18 are connected via the control unit 5, and the triac 18 controls energization to the heating roller 9 by a signal from a control circuit 19. Output of non-contact temperature sensor 14 (both detection output T0 and self-temperature output T1)
Is input to the control circuit 19, and the control circuit 19 detects the temperature of the heating roller from the output of the non-contact temperature sensor 14,
The triac 18 is controlled according to the temperature of the heating roller 9 with respect to the set temperature, and the heat generation of the heating roller 9 is controlled.

More specifically, the control circuit 19
Is a known microcomputer or memory (RAM, R
OM), an input / output circuit, various control signal generation circuits, and the like. The non-contact temperature sensor 14 has a self-temperature detecting means (for example, a thermistor or the like for detecting the self-temperature is provided in the case of the sensor). Is detected and output in accordance with the temperature difference between the temperature of the subject and the temperature of the heating roller (roller surface temperature).
Then, the self-temperature output T1 is input to the control circuit 19. Then, the control circuit 19 detects the detection output T0 and the self-temperature output T1.
Is input, the heating roller temperature (or the substitute property of the heating roller temperature) T is calculated by a polynomial expression of T0 (second or higher order), T = C (T1) + f (T1) × T0 + g (T1) × T0 ＾ 2 + h (T
1) × T0 ＾ 3 +... And a functional expression of T1, C (T1), f (T1), g (T1), h (T1), etc. (Example: f (T1) = constant A + α × T1 + β × T1 ＾ 2 + γ ×
T1 ＾ 3 +... (Constants A, α, β, and γ are real numbers not including 0), control the triac 18 based on the value of T, and control the temperature of the heating roller 9.

FIG. 4 is a graph showing the effect when the present invention is carried out. The heating roller temperature (or the substitute property of the heating roller temperature) T obtained by the non-contact temperature sensor 14 is shown in FIG.
The cubic expression of T0, T = C (T1) + f (T1) × T0 + g (T1) × T0 ＾ 2 + h (T
1) × T0 ＾ 3 and a functional expression of T1, C (T1), f (T1), g (T1), h (T1) (Example: f (T1) = constant A + α × T1 + β × T1 ＾ 2 + γ ×
T1 ＾ 3 + δT1 ＾ 4) The difference between the actual temperature of the heating roller 9 and the difference between the actual temperature and the actual temperature of the heating roller 9 is shown in FIG. As is clear from the graph of FIG. 4, the temperature error is about ± 1 especially at 180 ° C. to 200 ° C. which is the control temperature of the heating roller.
This is a very small error of deg, and the temperature of the heating roller can be accurately detected regardless of the environmental temperature change.

FIG. 5 shows the function formulas C (T1), f (T1), g (T1) and h (T1) from which the graph of FIG. 4 is obtained, and its graph. In each graph, the vertical axis y corresponds to a value obtained from each function formula, and the horizontal axis x corresponds to T1.

Next, FIGS. 6 and 7 are diagrams showing the effect of the second embodiment of the present invention, and FIG.
FIG. 7 corresponds to FIG. In this example, the heating roller temperature T (or the substitute property of the heating roller temperature) T obtained by the non-contact temperature sensor 14 is represented by a cubic expression of T0, T = C (T1) + f (T1) × T0 + g (T1) × T0 ＾ 2 + h (T
1) × T0 ＾ 3 and a functional expression of T1, C (T1), f (T1), g (T1), h (T1) (Example: f (T1) = constant A + α × T1 + β × T1 ＾ 2 + γ ×
T1 ＾ 3) (Each cubic expression of T1). Even if the polynomial expression of T0 and the function expression of T1 are less than the cubic expression, as shown in FIG. 180 which is the temperature
The temperature error is about ± 3 deg. C. or less in a temperature range of from about ° C. to about 200 ° C., which is an acceptable level of temperature control for an electrophotographic fixing device.

As described above, in the present invention, the control for correcting the detection output (value) of the self-temperature and the detection output (value) of the non-contact temperature sensor by using a related function without using the conversion table. It is. This is because, in the conventional control method using a conversion table, it is necessary to create a conversion table in advance, and to create a conversion table, it is necessary to create data one by one. If this is done, the table must be made finer accordingly, resulting in an increase in the amount of work for creating the table, an increase in the memory for storing the data of the table, and the range of the table created by the detected temperature. It is not possible to cope with the case where the number exceeds the limit (for this point, the range of the table to be created may be expanded, but also in this case, the amount of work for creating the table is increased, and the data of the table is stored. It is unavoidable that the increase in memory is unavoidable). Particularly, when the temperature changes greatly during heating as in a fixing device, these problems are remarkably exhibited. It is obtained based on the.

That is, the present inventors have attempted to determine whether or not the heating roller temperature T cannot be represented by a polynomial expression of the detected output T0, and the coefficient of each T0 term can be represented by a function expression of the self-temperature output T1. This is the result of the present invention described above by performing a checking operation in an actual fixing device. Hereinafter, a specific procedure of the confirmation work will be described.

[1] The surface temperature T of the heating roller is separately measured by a thermistor, a thermocouple or the like. The output value of the non-contact temperature sensor is measured. The self-temperature of the non-contact temperature sensor is measured. Table 1 shows an example of these measurement results. In actual measurement, the temperature T of the heating roller is changed between 180 and 30 (° C.), for example, 180, 150, 120, 90, 60,
A large number of measurements are performed at 30 (° C.), and measurements are also performed when the sensor self-temperature T 1 is 40, 60, and 70 (° C.), but is omitted in Table 1.

[0025]

[Table 1]

[2] Next, it is determined (assumed) that the correction formula for T should be what order. Here, it was calculated as a cubic equation. That is, the heating roller temperature T is expressed by the cubic expression of T0, T = C (T1) + f (T1) × T0 + g (T1) × T0 ＾ 2 + h (T
1) × T0 ＾ 3 and a functional expression of T1, C (T1), f (T1), g (T1), h (T1) (Example: f (T1) = constant A + α × T1 + β × T1 ＾ 2 + γ ×
T1 ＾ 3) (Each cubic expression of T1).

[3] The measured coefficients T1 and T0 are substituted into the above equation to convert the coefficients into functions. That is, a certain sensor self temperature T
1, for example, each coefficient C (30), f (30), g at T1 = 30 ° C.
(30) and h (30) are obtained. Specifically, T1 is fixed at 30 ° C., and the following simultaneous equations are solved using the data at T1 = 30 ° C. (Table 1). 180 (° C) = C (30) + f (30) × 1.8 + g (30) × 1.8 ² + h (30) × 1.8 ³ 150 (° C) = C (30) + f (30) × 1.6 + g (30) × 1.6 ² + h (30) × 1.6 ³ : 150 (° C.) = C (30) + f (30) × 0.3 + g (30) × 0.3 ² + h (30) × 0.3 ³

Among the above equations (formulas can be formed by the number of heating roller surface temperatures T), coefficients C, f, g, h are obtained by combining the equations of the numbers of coefficients C, f, g, h. Can be obtained, and by changing the combination, each coefficient C, f,
The average value of g and h is determined as a coefficient value. Also, changing the sensor self-temperature T1 to another temperature (T1 = 40 ° C., 50 ° C.
80 ° C.), and obtain the respective coefficient values C, f, g, and h. The plot points of the graphs shown in FIGS. 5 and 7 are obtained in this manner. Then, from the plot points of the coefficients obtained above, the function formulas C (T1), f (T1), and g of T1 are obtained.
An approximate expression of (T1), h (T1) is obtained (an approximate expression written on the graphs of FIGS. 5 and 7).

[4] Next, the heating roller temperature (calculated value) T 'obtained from the function formula obtained above and the actual heating roller temperature (actual measurement value) T are compared and confirmed. First, the self temperature T1 of the sensor is measured by an actual machine (T1 = YY (YY: measured temperature)). Then, the non-contact temperature sensor output T0 at the actual heating roller surface temperature T is measured. Next, the sensor self-temperature T1 = YY is input to the approximate expression of the functional expression obtained in the procedure of [3], and the values of the coefficients C (YY), f (YY), g (YY) and h (YY) are obtained. Ask for. The obtained coefficient is expressed by a polynomial expression (for example, a cubic expression) of the detection output T0 of the heating roller temperature T. T '= C (T1) + f (T1) × T0 + g (T1) × T0 ＾ 2 + h
(T1) × T0 ＾ 3, and the heating roller surface temperature T 'is calculated from the detection output T0 of the non-contact temperature sensor. That, T '= C (YY) + f (YY) × T0 + g (YY) × T0 2 + h (YY) ×
T0 is ^3, for example, T1 = 30 ° C., when T0 = 1.8V, T '= C (30) + f (30) × 1.8 + g (30) × 1.8 2 + h (30) ×
1.8 ³ ≒ 179.5 (° C.). This is plotted by obtaining T 'at various actual heating roller surface temperatures T and sensor self-temperatures T1, taking TT' (temperature error) on the vertical axis and the roller temperature T on the horizontal axis. 7 is a graph shown in FIGS.

From the results of the above-described checking work (FIGS. 4 and 6), it was confirmed that the error could be set within a range that would cause substantially no problem even when employed in an actual fixing device.

[0031]

As described above, in the electrophotographic apparatus according to the first aspect, the non-contact temperature sensor has the self-temperature detecting means, and the detection outputs of the non-contact temperature sensor are the self-temperature and the subject. When the detected output is T0 and the self-temperature output is T1, the temperature of the heated roller (or a substitute characteristic of the temperature of the heated roller) T is represented by T0. Polynomial (second order or higher), T = C (T1) + f (T1) × T0 + g (T1) × T0 ＾ 2 + h (T
1) × T0 ＾ 3 +... And a functional expression of T1, C (T1), f (T1), g (T1), h (T1), etc. (Example: f (T1) = constant A + α × T1 + β × T1 ＾ 2 + γ ×
T1 ＾ 3 + ...) (constants A, α, β, and γ are real numbers not including 0), and the temperature of the heating roller is controlled based on the value of T.
The temperature of the heating roller can be accurately detected irrespective of the environmental temperature change in the electrophotographic apparatus, and the temperature of the heating roller can be controlled stably. Further, since the control for correcting the detection output (value) of the self-temperature and the detection output (value) of the non-contact temperature sensor using a related function is performed without using the conversion table, the load on the control can be reduced. it can.

In the electrophotographic apparatus according to the second aspect, in the electrophotographic apparatus according to the first aspect, the polynomial of T0 is less than a cubic and the functional equation of T1 is less than a cubic. Further, the heating roller temperature can be accurately detected irrespective of the environmental temperature change in the electrophotographic apparatus, and the heating roller temperature can be controlled stably, while reducing the burden on the control.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing one configuration example of an electrophotographic apparatus in which the present invention is implemented.

FIG. 2 is a diagram showing a schematic configuration around a fixing device of the electrophotographic apparatus shown in FIG.

FIG. 3 is a graph mainly showing a detection error of a non-contact temperature sensor according to the related art, and is a graph showing a change in a detection temperature error of the non-contact temperature sensor with respect to a heating roller temperature when an environmental temperature is changed.

FIG. 4 is a graph mainly showing the operation and effect of the embodiment of the present invention, and is a graph showing a change in a detection temperature error of a non-contact temperature sensor with respect to a heating roller temperature when an environmental temperature is changed.

FIG. 5 is a functional equation C (T1), which is a basis for obtaining the graph of FIG.
It is a figure which shows f (T1), g (T1), h (T1), and its graph.

FIG. 6 is a graph mainly showing an operation and effect according to another embodiment of the present invention, and is a graph showing a change in a detection temperature error of a non-contact temperature sensor with respect to a heating roller temperature when an environmental temperature is changed.

FIG. 7 is a functional equation C (T1), which is a basis for obtaining the graph of FIG.
It is a figure which shows f (T1), g (T1), h (T1), and its graph.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoreceptor (image carrier) 2 Charging device 3 Writing unit 4 Developing device 4 Transfer transport device 6 Cleaning device 7 Static elimination device 8 Fixing device 9 Heating roller 10 Pressure roller 11 Paper supply unit 12 Paper supply roller 13 Registration roller 14 Non-contact temperature sensor 15 Power supply brush 16 Electrode unit 17 AC power supply 18 Triac 19 Control circuit

Claims (2)

[Claims] 1. An electrophotographic apparatus comprising a fixing device using a heating roller, comprising: a non-contact temperature sensor for detecting a temperature of the heating roller in a non-contact manner; In the electrophotographic apparatus that controls the temperature of the heating roller, the non-contact temperature sensor has a self-temperature detecting unit, and a detection output of the non-contact temperature sensor is based on a temperature difference between the self-temperature and the temperature of the heating roller that is a subject. When the detection output is T0 and the self-temperature output is T1, the heating roller temperature (or a substitute characteristic of the heating roller temperature) T is expressed by a polynomial (second or higher order) of T0. , T = C (T1) + f (T1) × T0 + g (T1) × T0 ＾ 2 + h (T
1) × T0 ＾ 3 +... And a functional expression of T1, C (T1), f (T1), g (T1), h (T1), etc. (Example: f (T1) = constant A + α × T1 + β × T1 ＾ 2 + γ ×
An electrophotographic apparatus characterized by recognizing T1 ＾ 3 + (constants A, α, β, and γ are real numbers not including 0) and controlling the temperature of the heating roller based on the value of T. 2. The electrophotographic apparatus according to claim 1, wherein T
An electrophotographic apparatus, wherein a polynomial of 0 is less than a cubic, and a functional formula of T1 is less than a cubic.