JP3797198B2 - Image forming apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an image forming apparatus including a heating type fixing roller and a control unit that controls the temperature of the fixing roller.
[0002]
[Prior art]
2. Description of the Related Art Image forming apparatuses such as digital copying machines and laser beam printers have a fixing unit for fixing a transferred image on a transfer sheet.
[0003]
FIG. 4 is a diagram illustrating the configuration of the fixing unit. The fixing unit 41 includes a fixing roller 42, a pressure roller 43, and a non-contact sensor 44, and a fixing heater 45 is provided at the center of the fixing roller 42.
[0004]
An image is formed with toner on the upper surface 46 a of the transfer paper 46, and the transfer paper 46 is pressed against the fixing roller 42 heated by the fixing heater by the pressure roller 43, so that the toner is fixed to the transfer paper 46.
[0005]
FIG. 5 is a diagram showing the configuration of the non-contact sensor 44. The non-contact sensor 44 includes a detection sensor 44a that detects the temperature of the fixing roller 42 and a compensation sensor 44b that detects the temperature of the detection sensor 44a. Both of these sensors use a thermistor. A control unit (not shown) controls ON / OFF of the fixing heater 45 so that the temperature detected by the non-contact sensor 44 becomes a specific set temperature.
[0006]
With only one detection sensor 44a, the ambient temperature is also detected, and the accurate temperature of the fixing roller cannot be detected. Therefore, the non-contact sensor 44 is provided with a compensation sensor 44b for detecting the ambient temperature of the detection sensor 44a, and the accurate temperature of the fixing roller 42 is determined according to the relationship between the value detected by the detection sensor 44a and the value detected by the compensation sensor 44b. Is to be detected.
[0007]
FIG. 6 is an example of a conversion table for obtaining the temperature of the fixing roller 42 from the values of the detection sensor 44a and the compensation sensor 44b. In FIG. 6, a part of it is omitted for convenience of explanation. The “compensation output (V)” column is a value detected by the compensation sensor 44b, the “roller temperature (° C.)” column is the temperature of the fixing roller 42, and the “detection output (V)” column is a value detected by the detection sensor 44a. Is shown. Since each sensor is a thermistor, it is the voltage that is actually detected. “Compensation temperature (° C.)” indicates the ambient temperature corresponding to the voltage detected by the compensation sensor 44b. When the compensation sensor 44b detects 4.11 V, it can be seen that the compensation temperature is 50 ° C., that is, the ambient temperature of the non-contact sensor 44 is 50 ° C.
[0008]
In the non-contact sensor 44 having such characteristics, when the value detected by the compensation sensor 44b indicates 4.11 (50 ° C.) and the detection sensor 44a indicates 3.89, fixing is performed as follows. The temperature of the roller 42 is known. First, 4.11 is searched from the “compensation output (V)” column in FIG. Looking at the corresponding line to the right, the “roller temperature (° C.)” column of a square with 3.89 is 180. That is, in this case, the temperature of the fixing roller is 180 ° C.
[0009]
Japanese Patent Laid-Open No. 7-77892 uses a conversion table prepared in a memory mounted on a control device to control the temperature of the fixing roller. In the conversion table shown in FIG. 6, the temperature of the fixing roller cannot be obtained unless the roller temperature is in units of 20 ° C. and the compensation temperature is in units of 5 ° C. Control is possible.
[0010]
However, if precise temperature control is attempted, the conversion table becomes large, and the search takes time accordingly. Further, there is a problem that if the detected value is not in the conversion table, the temperature of the fixing roller cannot be known.
[0011]
Japanese Patent Laid-Open No. 10-31390 is a solution to such a problem.
Japanese Patent Laid-Open No. 10-31390 controls the temperature of the fixing roller using an arithmetic expression using T0 and T1, where T0 is a detection output and T1 is a self-temperature output which is a compensation temperature. This arithmetic expression is an expression of a conversion table as shown in FIG. If this arithmetic expression is used, the temperature of the fixing roller can be obtained without using a conversion table, and the burden on temperature control can be reduced.
[0012]
[Problems to be solved by the invention]
However, since the conversion table is expressed by a single arithmetic expression, the arithmetic expression includes power terms of T0 and T1, and the calculation itself is complicated. Therefore, there is a problem that calculation takes time.
[0013]
The present invention, by a temperature compensation sensor detects and only partial use different calculation formula, and to provide an image forming apparatus capable of temperature control with a simple formula.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus of the present invention includes a heating type fixing roller, a detection sensor that detects heat from the fixing roller, and a compensation sensor that detects an ambient temperature of the detection sensor. A contact sensor, and a calculation unit that performs a predetermined calculation using a value obtained from the non-contact sensor, wherein the calculation unit is a coefficient determined in advance according to a value detected by the compensation sensor The temperature of the fixing roller is calculated and controlled from the value detected by the compensation sensor and the value detected by the detection sensor by a primary arithmetic expression including
[0015]
Further, the calculation unit stores an error between the calculated fixing roller temperature and the actual fixing roller temperature in correspondence with the temperature detected by the compensation sensor, and the calculated fixing roller temperature is stored in the calculated fixing roller temperature. It is configured to control the temperature of the fixing roller by adding an error, or in the calculation formula, a value detected by the compensation sensor is used as a compensation voltage, a value detected by the detection sensor is used as a detection voltage, and the detection is performed by the compensation sensor. When the coefficient corresponding to the measured value is a−d, the following arithmetic expression
Temperature = (a × compensation voltage−b) × detection voltage + (c × compensation voltage + d)
Configuration and may be is.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Next, the image forming apparatus of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a system configuration of a fixing unit and a control unit of an image forming apparatus according to the present invention. The fixing unit 11 includes a non-contact sensor 12 and a fixing heater 13. The fixing unit 11 is the same as the fixing unit 41 shown in FIG. 4, and includes a fixing roller and a pressure roller (not shown) in addition to the fixing heater 13 and the non-contact sensor 12. The non-contact sensor 12 includes a detection sensor and a compensation sensor (not shown). These are the same as the detection sensor 44a and the compensation sensor 44b shown in FIG. The voltage detected by each sensor is converted into a digital numerical value from 0 to 1023 by the A / D converter 15 in the control unit 14. The converted digital numerical value is input to the arithmetic expression as a detection temperature and a compensation temperature by the arithmetic unit 16 to calculate the temperature of the fixing roller. The fixing drive circuit 17 is a circuit that controls ON / OFF of the fixing heater 13 according to an instruction from the control unit 14.
[0017]
FIG. 2 is a flowchart showing the temperature control performed by the control unit 14. First, the control unit 14 receives the compensation temperature and the detected temperature from the non-contact sensor 12 (S01, S02). In this case, the voltage detected by the compensation sensor and the detection sensor is converted into a digital numerical value by the A / D converter 15. Next, using this value, the temperature of the fixing roller is calculated (S03). Whether the temperature obtained by the calculation is equal to or lower than the set temperature is checked (S04). If the temperature is equal to or lower than the set temperature, the fixing heater 13 is turned on through the fixing drive circuit 17 (S05). If the temperature of the fixing roller is higher than the set temperature, the fixing heater 13 is turned off (S06). Then, the temperature detected by the non-contact sensor 12 is received again (S01, S02). Temperature control is performed by repeating this process.
[0018]
The calculation formula for calculating the temperature of the fixing roller in S03 is temperature (° C.) = (A compensation voltage−b) detection voltage + (c compensation voltage + d).
[0019]
Among these, “temperature (° C.)” indicates the surface temperature of the fixing roller, and “compensation voltage” and “detection voltage” indicate voltages detected by the compensation sensor and the detection sensor, respectively, by the A / D converter 15. It is the converted digital numerical value. Further, a to d are coefficients, and the values differ depending on the compensation temperature.
[0020]
The calculation formula is obtained by dividing the conversion table in FIG. 6 into a plurality of sections according to the compensation temperature, and the coefficients are determined for each section and stored in the calculation unit 16 in FIG. That is, there are a plurality of arithmetic expressions having different coefficient values. An arithmetic expression to be used is determined based on the compensation temperature detected by the compensation sensor, and the surface temperature of the fixing roller is calculated using the arithmetic expression.
By using the simple arithmetic expression as described above, the calculation of the power of the compensation temperature and the detection temperature is eliminated, and the calculation speed is improved.
[0021]
However, even with the above arithmetic expression, an error of several degrees C. may occur between the actual surface temperature of the fixing roller and the surface temperature calculated by the arithmetic expression. FIG. 3 is a table showing an error between the surface temperature obtained by calculation and the actual surface temperature. Some are omitted for convenience of explanation. A numerical value from 25 to 130 in the “compensation temperature” column indicates the compensation temperature, and a numerical value from 100 to 200 in the “control temperature” column indicates the surface temperature obtained by an arithmetic expression.
[0022]
For example, when the compensation temperature is 25 ° C. and the control temperature is 180 ° C., the actual surface temperature of the fixing roller is 173 ° C. In this case, the set temperature is calculated, but the actual temperature of the fixing roller does not reach the set temperature, so that the toner may not be fixed.
[0023]
In order to prevent such a problem, temperature control may be performed by adding an error between the set temperature and the actual temperature of the fixing roller. In other words, when it is desired to keep the surface temperature of the fixing roller at 180 ° C. when the compensation temperature is 25 ° C., the set temperature is not 180 ° C., but is an error between the calculation result and the actual temperature. Add ℃ to 187 ℃. Further, even when the set temperature is the same 180 ° C., when the compensation temperature is 75 ° C., the control is performed at 179 ° C. which is 1 ° C. lower. The error for each compensation temperature is stored in the arithmetic unit 16 in advance.
[0024]
【The invention's effect】
As described above, according to the image forming apparatus of the present invention, the non-contact method includes the heating type fixing roller, the detection sensor that detects heat from the fixing roller, and the compensation sensor that detects the ambient temperature of the detection sensor. A value detected by the compensation sensor and a value detected by the detection sensor according to a first-order calculation formula having a coefficient determined in advance according to the value detected by the compensation sensor. by having a configuration in which control by calculating the temperature of the fixing roller from the arithmetic speed can eliminate a power of operation is improved.
[0025]
If an error between the calculated temperature of the fixing roller and the actual surface temperature is obtained and added to the calculated temperature of the fixing roller to control the temperature of the fixing roller, more accurate temperature control can be performed.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a system configuration of a fixing unit and a control unit of an image forming apparatus of the present invention.
FIG. 2 is a flowchart showing temperature control performed by a control unit.
FIG. 3 is a table showing an error between a surface temperature obtained by calculation and an actual surface temperature.
FIG. 4 is a configuration diagram of a fixing unit.
FIG. 5 is a configuration diagram of a non-contact sensor.
FIG. 6 is a diagram illustrating a conversion table for obtaining the temperature of the fixing roller from values of a detection sensor and a compensation sensor.
[Explanation of symbols]
16 Calculation units 12 and 44 Non-contact sensor 42 Fixing roller 44a Detection sensor 44b Compensation sensor

Claims (3)

A non-contact sensor comprising a heating type fixing roller, a detection sensor for detecting heat from the fixing roller, a compensation sensor for detecting an ambient temperature of the detection sensor, and a value obtained from the non-contact sensor. A calculation unit that performs a predetermined calculation;
The arithmetic unit calculates a temperature of the fixing roller from a value detected by the compensation sensor and a value detected by the detection sensor by a primary arithmetic expression having a coefficient determined in advance according to the value detected by the compensation sensor. An image forming apparatus characterized by calculating and controlling . The calculation unit stores an error between the calculated temperature of the fixing roller and the actual temperature of the fixing roller in correspondence with the temperature detected by the compensation sensor, and stores the error in the calculated temperature of the fixing roller. 2. The image forming apparatus according to claim 1, wherein the temperature of the fixing roller is controlled by addition . When the arithmetic expression is a value detected by the compensation sensor as a compensation voltage, a value detected by the detection sensor is a detection voltage, and the coefficient corresponding to the value detected by the compensation sensor is a−d, Formula
Temperature = (a × compensation voltage−b) × detection voltage + (c × compensation voltage + d)
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

Images