JP2004117626A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an offset phenomenon, caused by a rise in the temperature of a non-paper passing part, regardless of the size of each recording paper even where a fixing roller with a thin wall is used and to ensure an appropriate fixing capability without exceeding the heat resistant temperatures of surrounding members. <P>SOLUTION: When sheets of recording paper are consecutively passed, a time interval between the sheet of recording paper passed previously and the sheet of recording paper to be passed subsequently is controlled based upon the temperature of a fixing roller 2. The timing of paper feed is controlled based upon the size of the sheet of recording paper to be passed or the temperature of the fixing roller 2. Thereby, regardless of the size of the recording paper P, the effect of a rise in the temperature of the end thereof is reduced. Accordingly, temperature control is correctly exerted and the rise in the temperature of the end is restricted. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a printer, a copier, and a facsimile, and more particularly, to a fixing device that appropriately detects the temperature of a fixing roller and controls the temperature.
[0002]
[Prior art]
In recent years, so-called electrophotographic image forming apparatuses have been used as image forming apparatuses because of their good print quality.
[0003]
In such an electrophotographic image forming apparatus, an electrostatic latent image is formed on a photoconductor by light modulated based on image data, and toner is attached to the photoconductor on which the electrostatic latent image is formed. develop. The toner adhered to the photoreceptor is transferred to a recording paper, and the recording paper having the toner adhered thereto is transported to a fixing roller, and the toner is fixed on the recording paper by the fixing roller. The fixing roller is heated by a fixing heater, is controlled to a predetermined fixing temperature, and performs a process of preventing overheating.
[0004]
To control the fixing temperature in a conventional fixing device, only one temperature detector such as a thermistor is provided at a predetermined fixed position, and the minimum temperature of the fixing roller is detected by the one temperature detector. A control circuit controls on / off of a fixing heater to control the fixing roller to a fixing temperature so as to be within a preset on / off temperature range centered on the center.
The overheating prevention in the conventional fixing device is provided in the event of an abnormality such as runaway of a control circuit, and is provided with a thermal fuse or a thermoswitch (SW) to protect the fixing heater from overheating, or to use an analog comparator for the fixing heater. Overheat protection. Further, two temperature detectors such as thermistors are provided at predetermined fixed positions, one of the temperature detectors is used for temperature control, and the other temperature detector is used for detecting abnormal temperatures. Has been proposed to protect the fixing heater from overheating to prepare for occurrence of abnormalities such as runaway of the control circuit.
However, the fixing devices that have been proposed in the past have a common configuration in that there is only one temperature detector that controls the temperature of the fixing roller. Normally, when a small-size recording sheet is passed, the temperature difference between the sheet passing area and the non-sheet passing area becomes large. In the configuration in which the control is performed, since the temperature of the paper passing area cannot be accurately detected, the fixing is performed without rising to a predetermined fixing temperature in a part of the fixing roller in the longitudinal direction. May occur.
Also, when the temperature detecting element constituting the temperature detector is a safety device such as a thermoswitch, the temperature rise at the end is too large, and the safety device may be disconnected erroneously, or the runaway control circuit may be activated to connect the heater to the heater. In some cases, there is a problem that the power supply is stopped, or a problem occurs in that the temperature of the peripheral members exceeds the heat-resistant temperature and the durability is reduced.
[0005]
As described above, the conventional fixing device has a problem that the minimum temperature of the fixing roller cannot be appropriately detected and managed.
[0006]
[Problems to be solved by the invention]
According to the above-described conventional example, when the light distribution (heat distribution) of the heater is set so as to secure the fixing property of the recording paper having the maximum width, the small-sized recording paper has a paper-passing side and a non-paper-passing side. That is, the amount of heat taken out differs greatly between the center of the fixing roller and the left and right. At this time, there is a possibility that a so-called offset may occur due to a remarkable temperature rise of the non-sheet passing portion or the fixing device may be damaged. In order to avoid this, the thermal conductivity of the fixing roller in the lateral direction must be improved, and for that purpose, the thickness of the core metal of the fixing roller must be increased. Since the heat capacity of the thick fixing roller increases, inconveniences such as a longer warm-up time and an increase in cost arise.
[0007]
On the other hand, if a thin fixing roller is used to shorten the warm-up time, the heat conductivity in the lateral direction is deteriorated due to the thinning. Therefore, when starting up the apparatus in the room temperature state, the temperature rise at the end of the fixing roller is slower than that near the center of the sheet passing portion, so that there is a problem that the fixability at the end is deteriorated. On the other hand, if the heater light distribution at both ends is increased to secure the fixing property of the end portion at the time of startup, the heat supply balance is lost during printing, and the temperature of the end portion is maintained even when the maximum width recording paper is passed. Is higher than the center. As a result, the temperature of the non-sheet passing portion rises above the heat-resistant temperature of the peripheral members, the temperature rise of the end portion is too large, the safety device is erroneously disconnected, or the runaway control circuit operates and the heater power supply is stopped. Inconvenience occurs.
[0008]
Further, unless the amount of heat generated by the heater is increased as the sheet passing speed is increased, the amount of heat taken out by the recording paper (the amount of heat required for fixing) cannot be compensated. If the heating value of the heater is increased when a thin fixing roller is used, the temperature of the non-sheet passing portion rises significantly.
[0009]
As a countermeasure, there is a method of using two heaters. The first heater has a higher heat distribution at both ends with respect to the center, and the second heater has a lower heat distribution at both ends with respect to the center. As a result, the amount of heat required for fixing is secured by using the first and second heaters for large-size recording paper. On the other hand, for a recording sheet such as a small-sized recording sheet which takes a small amount of heat, only the second heater is used to prevent the temperature from rising at the end. However, disadvantages arise in that complicated control is required to turn on the heater, power consumption is increased by using two heaters, and cost is increased due to an increase in the number of parts.
[0010]
In addition, in order to suppress the temperature rise at the end in the configuration of one heater, a roller made of an Al material or a SUS material is installed on the pressure roller, and heat is radiated by the AL or SUS roller through the pressure roller to fix the fixing roller and the heating roller. There is also a method of making the heat in the lateral direction of the pressure roller uniform. However, since this method is equivalent to increasing the heat capacity of the pressure roller, the warm-up time is somewhat longer, which is contrary to the shortening of the warm-up time, and the cost is increased by additional members. And the like.
[0011]
Therefore, the present invention solves the above-mentioned problems, and prevents the offset phenomenon due to the temperature rise of the non-sheet passing portion regardless of the paper size of each recording paper even with a thin fixing roller, and without exceeding the heat resistance temperature of the peripheral member, It is an object of the present invention to provide an image forming apparatus provided with a fixing device having a relatively inexpensive configuration capable of ensuring excellent fixing performance.
[0012]
[Means for Solving the Problems]
According to the present invention, when recording paper is continuously passed, the time (inter-sheet time) between the recording paper that has passed last time and the recording paper that passes next is controlled based on the temperature of the fixing roller. Control the paper feed timing based on the size of the recording paper to be passed and the temperature of the fixing roller, thereby reducing the effect of the temperature rise at the edges regardless of the size of the recording paper, and achieving accurate temperature control. Suppress the temperature rise at the end.
[0013]
A first aspect of the present invention is an aspect for controlling a paper interval time during continuous paper passing, in which a recording paper carrying an unfixed toner image on its surface is sandwiched between a pair of rollers including a fixing roller and a pressure roller. In an image forming apparatus provided with a fixing device for fixing an unfixed toner image on recording paper by inserting the same while applying heat and pressure, temperature detection is performed to detect at least two temperatures along the longitudinal direction of the fixing roller. Means, power supply control means for controlling power supply to the fixing heater based on the temperature detected by each temperature detection means, and temperature detection means based on a paper interval time table which defines the relationship between the temperature of the fixing roller and the paper interval time. An inter-sheet time control means for controlling an inter-sheet time during continuous sheet feeding by obtaining an inter-sheet time for at least one detected temperature to be detected.
[0014]
The inter-paper time control means obtains the inter-paper time according to the temperature of the fixing roller using the inter-paper time table, and performs control to extend the inter-paper time to prevent the temperature of the end from rising. Heat resistance of roller bearings, heater elements, etc., and erroneous disconnection of safety devices are avoided.
[0015]
A second aspect of the present invention is an aspect for controlling the paper feed timing, and includes a temperature detecting means and an energization control means as well as the first aspect, and defines a relationship between a recording paper size and a paper feed start temperature. Paper feed start temperature for the recording paper size based on the obtained paper feed start temperature table, and compares the obtained paper feed start temperature with all the detected temperatures to control paper feed timing. A configuration is provided.
[0016]
The paper feed timing control means starts the paper feed immediately based on the detected temperature of the fixing roller based on the paper feed start temperature determined according to the recording paper size, or waits until the paper feed start temperature decreases. By performing such control, the influence of the temperature rise at the end is suppressed.
[0017]
Further, a third aspect of the present invention is an aspect for controlling a sheet interval time and a paper feed timing, and includes a temperature detecting means and an energization control means as in the first and second aspects, and a first aspect. And a sheet feed timing control unit according to the second embodiment.
[0018]
In the above aspect, the paper feed timing control means stores the recording paper size that has been passed last time in order to obtain a paper feed start temperature corresponding to the recording paper size, and stores the stored paper size and paper feeding size. And a comparing unit for comparing the recording paper size with the recording paper size. The paper feed timing control means determines a paper feed start temperature based on the comparison result of the recording paper size by the comparison means, and performs control according to the detected temperature of the fixing roller based on the paper feed start temperature.
[0019]
The control by the paper feed timing control means, for example, starts the paper feed when the recording paper size to be passed is smaller than or the same size as the previously passed recording paper, and the recording paper size to be passed last time When the paper size is larger than the recording paper size, the paper supply start temperature determined by the recording paper size is compared with the maximum temperature among the detected temperatures based on the paper supply start temperature table, and based on the comparison result, Start paper feeding or wait until the paper feeding start temperature is reached.
[0020]
In the above aspect, the sheet interval time control means obtains the sheet interval time table based on the sheet interval time with respect to the maximum temperature of the end position of the non-sheet passing area of the maximum size of the recording sheet of the fixing roller. The inter-sheet time table defines the relationship between the maximum temperature for setting the inter-sheet time and the time width for extending the inter-sheet time. The higher the temperature, the longer the extension time is set. By waiting for paper feeding for this extended time, the temperature of the fixing roller is lowered, and the temperature rise at the end is suppressed.
[0021]
Further, according to the present invention, one heater is disposed inside the fixing roller, and this heater is provided with a light distribution peak only in the vicinity of both side edges of the paper passing area of the maximum size of the recording paper. At least the lower limit is made higher than the central light distribution level, and the light distribution levels in the other paper passing areas are all provided with a flat light distribution in the high light distribution area. The light distribution level of the peak is, for example, in a range of 110 ± 10% (that is, more than 100% and 120% or less) when the central light distribution level is 100%. With this light distribution, fixing can be performed with a relatively low heat capacity even when the fixing roller is thin or when the recording paper having the maximum width is passed.
[0022]
For example, if only the end temperature detecting means is set extremely high, the inter-sheet time will be prolonged due to the high temperature due to the light distribution, and the temperature of the other parts will be insufficient, and the fixability will be poor. Also, if only the non-end temperature detecting means is set high, the end temperature of the non-end detecting means becomes excessively high, and when printing a large-size recording paper after printing a small-size recording paper. However, there is a problem of durability such that an offset phenomenon occurs at an end portion and wear is accelerated due to thermal deterioration of a bearing or the like.
[0023]
On the other hand, according to the present invention, accurate temperature control and suppression of temperature rise at the end can be performed even when the end detection temperature means detects at least one side.
[0024]
In the above aspect, the temperature detecting means detects the temperature of the end position of the non-sheet passing area on at least one side and the sheet passing area position including at least the center position among the both ends of the recording paper maximum size. Further, the paper passing area position where the temperature is detected may be a plurality of positions corresponding to the end of the size of the recording paper to be passed. Further, the paper passing area position for performing the temperature detection may be on both sides or only one side with respect to the center position.
[0025]
The temperature detecting means is disposed at the end position and the center position of the non-sheet passing area on at least one side of both ends of the recording paper maximum size, so that the excessive temperature rise at the end regardless of the recording paper size. Can be detected. By adjusting the fixing temperature based on the temperature detected by the temperature detector installed at the center position, even when recording paper of various widths is passed, it is not affected by the temperature rise at the edge. It is possible to control the temperature and suppress the temperature rise at the end.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the embodiments described below are preferred embodiments of the present invention, and thus various technically preferable limitations are added. However, the scope of the present invention is not limited to the embodiments described below. The embodiments are not limited to these embodiments unless otherwise specified.
[0027]
First, a first embodiment of the present invention will be described. FIGS. 1 to 7 are diagrams showing a first embodiment of a fixing device provided in the image forming apparatus of the present invention. In this embodiment, two temperature detectors are fixed in the longitudinal direction of the fixing roller. The example shown in FIG.
[0028]
FIG. 1 is a view showing a side portion of a fixing device 1 to which the first embodiment of the image forming apparatus of the present invention is applied, and FIG. 2 is a diagram showing the first embodiment of the image forming apparatus of the present invention. FIG. 3 is a diagram illustrating a front part of the fixing device 1 to which the fixing device 1 is applied and a light distribution of a heater.
[0029]
In FIG. 1, a fixing device 1 has a pressure roller 3 pressed by a pressure spring 4 against a fixing roller 2, and a fixing roller 2 is provided in the fixing roller 2 as shown in FIG. A heater (fixing heater) 5 is provided over the entire width in the longitudinal direction (the horizontal direction in FIG. 2). Further, the fixing roller 2 and the pressure roller 3 are provided with static elimination needles 12 and 13 in contact with the roller to stabilize the potential on the roller surface so that the toner does not adhere electrostatically, and are connected to GND. And grounded.
[0030]
As shown in FIG. 2, the light distribution characteristic of the heater (fixing heater) 5 has a light distribution peak only in the vicinity of both side ends of the paper passing area having the maximum size of the recording paper, and the light distribution in the central portion is 100%. In this case, the light distribution peak near both ends is 110 ± 10%. The light distribution in the vicinity of both end portions is at least larger than the light distribution in the central portion and is within a range of 20% of the light distribution in the central portion.
[0031]
The fixing roller 2 is provided with two thermistors (temperature detecting means) 6a and 6b for detecting the surface temperature thereof, which are arranged side by side along the longitudinal direction of the fixing roller 2 as shown in FIG. The thermistor 6 a is disposed at a non-sheet passing portion located outside the maximum size of the recording paper in the longitudinal direction of the fixing roller 2, and the thermistor 6 b is disposed at the center of the fixing roller 2.
[0032]
As shown in FIG. 1, the fixing roller 2 is provided with a thermo SW (safety device) 7 that shuts off the power supply to the heater 5 when the surface temperature of the fixing roller 2 becomes equal to or higher than a predetermined temperature. The thermo SW 7 is provided in the non-sheet passing portion having the maximum size of the recording paper, and is provided with the fixing roller 2 on the circumference at the same position as the non-sheet passing portion having the maximum size of the recording paper in which the thermistor 6a is provided. It is arranged in contact. FIG. 2 does not show the thermo SW (safety device) 7.
[0033]
In FIG. 1, a plurality of separation claws 10 are disposed on the left side of the fixing roller 2. The separation claw 10 separates the recording paper on which the toner has been fixed from the fixing roller 2. The recording paper separated by the separation claw 10 is guided by a paper discharge guide plate 9 to a pair of paper discharge rollers 11a and 11b. The discharge roller pairs 11a and 11b discharge the recording paper on which the toner is fixed by the fixing roller 2 to a recording paper tray (not shown). That is, the recording paper onto which the toner has been transferred is conveyed to the fixing device 1 from the right side in FIG. 1 and guided by the entrance guide 8 to enter the fixing device 1. The pressure roller 3 presses the recording paper against the fixing roller 2 heated by the heater 5, and fixes the toner on the recording paper by the heat of the fixing roller 2. The recording paper on which the toner has been fixed is separated from the fixing roller 2 by the separation claw 10, and is guided to the paper ejection guide plate 9 and sent to the paper ejection roller pairs 11a and 11b. The recording paper is discharged to a recording paper tray (not shown).
[0034]
As shown in FIG. 2, the thermistors 6a and 6b are connected to a CPU (Central Processing Unit) 15 constituting a print engine unit (control means) provided in the image forming apparatus to which the fixing device 1 is applied, and the detected fixing is performed. The surface temperature of the roller 2 is output to the CPU 15.
[0035]
Hereinafter, a description will be given of a startup process in which the image forming apparatus is driven from a room temperature. The start-up process is generally performed at the beginning of the morning or the like, and the rollers are at room temperature.
[0036]
FIG. 3 is a flowchart for explaining the start-up process. In the start-up process, since the fixing roller and the pressure roller start up from a cold state, the thinner the fixing roller is, the slower the temperature rise at the end portion than in the vicinity of the center portion. After the power of the main body is turned on (step S1a), when the heater 5 is turned on (step S1b), the temperature detection signal of the central thermistor 6b is monitored while each roller is stationary. When the temperature of the thermistor 6b reaches a predetermined temperature (hereinafter, referred to as a pre-rotation start temperature) (step S1c), the fixing roller 2 is rotated, and the pressure roller 3 is rotated and heated to secure the fixing property (step S2a). .
[0037]
The CPU 15 compares the temperature detection signal input from the central thermistor 6b with a lower limit set as a temperature suitable for starting printing (hereinafter referred to as a READY set lower limit), and detects the lowest detected temperature of the thermistor 6b. It is checked whether the temperature is equal to or higher than the READY set lower limit (for example, set temperature = 145 ° C.) (step S2b).
[0038]
Next, the CPU 15 compares the temperature detection signal input from the thermistor 6a at the end with a lower limit set as a temperature at the end suitable for starting printing (hereinafter referred to as an end READY setting lower limit). Then, it is checked whether or not the minimum detected temperature of the thermistor 6a is equal to or higher than the lower limit of the end READY setting (for example, set temperature = 110 ° C.) (step S2c).
[0039]
If the detected temperature does not exceed the set lower limit in steps S2b and 2c, the rotation and heating of the roller are continued.
[0040]
The heater driver 14 supplies / stops power to the heater 5 according to a drive signal from the CPU 15. In Steps S2b and 2c, when the detected temperatures at the center and the end exceed the set lower limit (the lower limit of the READY setting and the lower limit of the READY set at the end), the power supply to the heater 5 is stopped. Is also stopped (step S2d), and a standby (standby) control is started (step S2e).
[0041]
That is, the CPU 15 inputs a temperature detection signal of the central thermistor 6b, and when the detected temperature indicated by the temperature detection signal reaches the pre-rotation start temperature, drives and rotates each roller to perform heating (step S1). While the temperature detection signals input from the end and center thermistors 6a and 6b are compared with the READY set lower limit and the end READY set lower limit to reach the set temperature, the drive signal of the heater driver 14 is stopped. Then, a stop of the power supply to the heater 5 is output, and the rotation of each roller is also stopped, READY is completed (printable state), and standby (standby) control is started (step S2).
[0042]
When there is no print signal, the standby (standby) control is maintained. FIG. 4 is a flowchart for explaining the standby (standby) control.
[0043]
In the standby (standby) control, as shown in the flowchart of FIG. 4, when a print signal is input from the image processing unit 16 to the CPU 15 (steps S3a and 3e), a print mode is started (steps S3f and 3g). Until a print signal is input, the temperature of the fixing roller is maintained at a predetermined temperature suitable for fixing by the processes of steps S3b to 3d.
[0044]
In the step S3b, the CPU 15 compares the lower limit value of the temperature suitable for fixing (hereinafter referred to as the standby temperature lower limit value) with the temperature detection signal from the thermistor 6b disposed at the center, and determines the lowest detected temperature. It is checked whether or not (hereinafter, referred to as a minimum detection temperature) is higher or lower than a standby temperature lower limit value (for example, set temperature = 150 ° C.), and a drive signal is output to the heater driver 14. The heater driver 14 controls the energization by supplying / stopping power to the heater 5 in accordance with the drive signal from the CPU 15 (steps S3c and 3d). The standby temperature lower limit is set at a temperature lower than the temperature suitable for fixing during printing in order to save power.
[0045]
Next, the operation of the present embodiment will be described. FIG. 5 is a flowchart for explaining sheet feed control according to the present invention.
[0046]
In the standby control state (step S2e), a print signal is transmitted from the image processing unit 16 (step S4a), and when the print signal is input to the CPU 15, the print mode starts. At this time, the CPU 15 also inputs the recording paper size (step S4b) and starts the rotation of each roller (step S4c).
[0047]
The CPU 15 compares the temperature detection signal from the thermistor 6b disposed in the center with a lower limit value (hereinafter referred to as a set lower limit value) set as a temperature suitable for fixing in advance, and determines the lowest detected temperature (hereinafter referred to as a set lower limit value). , The minimum detected temperature) is equal to or lower than a set lower limit (for example, set temperature = 175 ° C.), and a drive signal is output to the heater driver 14 (steps S5a and 4c). The heater driver 14 supplies / stops power to the heater 5 in accordance with a drive signal from the CPU 15 and controls energization (steps S4c and 5b).
[0048]
At this time, when the print signal is input to the CPU 15, the recording paper size is also input, and the temperature detection signal of the thermistor 6a arranged in the non-sheet passing portion having the maximum size of the recording paper is also input. The CPU 15 records the recording paper size of the previous print, and compares the input recording paper size with the recorded previous recording paper size (step S5c). If the current recording paper size is smaller than the previous recording paper size or the same size, paper feeding is started.
[0049]
On the other hand, when the current recording paper size is larger than the previous recording paper size, the paper feed timing is controlled depending on the recording paper size. This paper feed timing control is to start paper feed when the detected temperature of the non-sheet passing portion is equal to or lower than the paper feed start temperature. It is determined based on a table (shown in FIG. 6) between the starting temperature. If the maximum temperature of the temperature detection signal of the thermistor 6a in the non-sheet passing portion (hereinafter, referred to as the maximum detection temperature of paper feed start) is higher than the set temperature obtained from this table, the heater is stopped and the roller is rotated to fix. The temperature of the roller is lowered (step S5d).
[0050]
On the other hand, if the maximum feed start detection temperature is equal to or lower than the set temperature, the lowest temperature detected by the thermistor 6b at the center is set in advance as a temperature suitable for fixing by the same process as step S5a. By comparing with the lower limit (set lower limit), it is confirmed that the minimum detected temperature (minimum detected temperature) is equal to or higher than the set lower limit (step S5e), and the sheet feeding is started (step S5f). If the minimum detected temperature is equal to or lower than the set lower limit, heating is performed in step S4c.
[0051]
FIG. 6 is a table that determines the relationship between the recording paper size and the paper supply start temperature. The offset phenomenon does not occur when a large-sized recording paper is passed after printing a small-sized recording paper. Is set to The recording paper size and the paper feed start temperature table can be determined based on, for example, experimental data shown in FIG.
[0052]
FIG. 8 shows the temperature distribution from the center to the end of the fixing roller 2 when the A5 size recording paper is continuously passed while controlling the temperature to the set lower limit by the central thermistor 6b. In FIG. 8, the solid thick line G2 indicates the temperature distribution when the temperature detected by the end thermistor 6a reaches 215 ° C. The dashed thick lines G3 and G4 indicate that the temperature detection signals of the thermistor 6a disposed in the non-sheet passing portion outside the maximum width of the recording paper are 195 ° C and 190 ° C, respectively, in a state where the rollers are rotated and in a standby state. It is a temperature distribution when it becomes.
[0053]
From this graph, 190 ° C. is set as the offset prevention temperature so that the end temperature of each recording paper size is not printed at the offset temperature of 195 ° C., and the maximum detected temperature of the end thermistor 6 a is determined by the offset prevention temperature (190 ° C.). The paper feed start maximum detected temperature at which paper feed is started when C) is reached is set.
[0054]
Further, the temperature distribution when the detection temperature of the end thermistor 6a reaches 215 ° C. when the recording paper of B6 size which is equal to or smaller than A5 size is continuously passed is indicated by a solid thin line G1. Since the end of the A5 size is equal to or lower than the offset prevention temperature, the maximum feed start detection temperature is not set.
[0055]
That is, when the print signal and the recording paper size are input to the CPU 15, each roller starts rotating, and the temperature detection signal from the thermistor 6b disposed at the center is compared with the set lower limit value. It is checked whether it is equal to or less than the set lower limit value, and a drive signal is output to the heater driver 14. The heater driver 14 supplies / stops power to the heater 5 and controls energization (step S4).
[0056]
If the recording paper size to be passed this time is smaller than the previous recording paper size or the same size, paper feeding is started.If the recording paper size is larger than the previous printing paper size, the recording paper size and The set temperature obtained based on the sheet feed start temperature table is compared with the detected temperature at the end. If the set temperature is lower than the set temperature, sheet feeding is started, and if the set temperature is higher than the set temperature, the process stands by (step S5).
[0057]
When the paper feeding is started (step S5f), the recording paper on which the toner is transferred is conveyed to the fixing device 1 from the right side in FIG. 1, and the printing process is executed (step S6).
[0058]
In the printing process, the fixing device 1 compares the temperature detection signal from the thermistor 6b disposed at the center of the fixing roller with a set lower limit (step S6a), and when the lowest detected temperature among the detected temperatures is equal to or higher than the set lower limit. It is checked whether or not there is, power is supplied / stopped to the heater 5, and the print temperature is controlled (steps S6b, 6c).
[0059]
After the printing process for one page is completed (step S6d), it is determined whether or not the entire job corresponding to one print signal is completed (step S6e). When the job has not been completed (continuous paper passing), paper time control for adjusting the extension of the time between paper feeds according to the temperature state is performed, and the temperature rise at the end is suppressed.
[0060]
In this sheet interval control, the temperature detection signal from the thermistor 6b disposed at the center of the fixing roller is compared with a set lower limit value in the same manner as in the steps shown in steps S6a to 6c, and the lowest detected temperature is set. By checking whether the detected temperature is equal to or lower than the set lower limit and supplying / stopping power to the heater 5 to control the fixing roller temperature during printing, based on the sheet interval table shown in FIG. Until the next sheet feeding, the interval between sheets set by the maximum temperature of the temperature detection signal of the thermistor 6a disposed in the non-sheet passing portion of the recording sheet having the maximum size of the fixing roller (hereinafter, referred to as the end print maximum detection temperature). Is controlled (step S8).
[0061]
FIG. 7 shows an example of the sheet interval time table. For example, when the set maximum detected temperature is 207 ° C. or less, sheet feeding is started immediately without extending the sheet interval time. When the temperature is between 1 ° C. and 208 ° C., the sheet feeding is started after the inter-sheet time is extended by 2 seconds. In addition, in the sheet interval time table, in addition to setting the extension time, the apparatus waits until the set maximum detected temperature becomes 210 ° C., as in the case where the set maximum detected temperature is between 216.1 ° C. and 218 ° C. If the temperature is higher, the heater may be forcibly stopped when it is determined that the temperature is abnormal.
[0062]
According to the sheet interval time table, the sheet interval is extended based on the maximum detected temperature at the end of the thermistor 6a disposed in the non-sheet passing portion of the fixing roller having the maximum size of the recording sheet to prevent the temperature rise at the end. When the recording paper of a small size is passed, the heat of the roller bearings and the heater element due to the temperature rise at the roller end and the temperature rise at the end of the thermo SW7 which is a safety device are large. It is possible to avoid such a problem that an inconvenience such as erroneous disconnection occurs. According to the setting example of FIG. 7, the recording paper is fed at an average temperature of 210 ° C. detected by the end thermistor 6a on average.
[0063]
After the paper is fed as described above, the fixing device 1 presses the recording paper against the fixing roller 2 heated by the heater 5 by the pressure roller 3, and fixes the toner of the recording paper to the recording paper by the heat of the fixing roller 2. Let it. The fixing device 1 separates the recording paper on which the toner has been fixed from the fixing roller 2 by the separation claw 9, and sends the recording paper to the pair of paper discharge rollers 11a and 11b while being guided by the guide plate 10. The fixing device 1 discharges the fixed recording paper to a recording paper tray (not shown) by the discharge roller pair 11a and 11b. After the entire job is completed (step S6e), the CPU 15 stores the size of the printed recording paper (step S7).
[0064]
When there is a print signal, when the recording paper size of the continuous paper passing is different (when a plurality of continuous JOBs are processed), the size of the printed recording paper is recorded in the CPU 15 after the printing is completed. At the time of the next print signal, the temperature detection signal from the thermistor 6b arranged at the center is adjusted to the set lower limit (steps S4c and 5a), and the size of the recording paper to be printed this time is compared with the size of the previous print. In step S5c, when the sheet passing width is small or when the sheet size is the same, sheet feeding is started regardless of the sheet feeding start detection temperature of the thermistor 6a arranged in the non-sheet passing portion having the maximum recording sheet width. (Steps S5e and 5f). Also, when the paper passing width is larger than the previously printed recording size, the paper feed start maximum temperature is detected based on the recording paper size and the paper feed start temperature table shown in FIG. When the temperature is equal to or higher than the set temperature, a standby control is performed (step S5d) (step S9).
[0065]
According to the present embodiment, the light distribution of the heater 5 is set to 110% ± 10%, and two temperature detectors are arranged in the longitudinal direction of the fixing roller 2. The fixing temperature is controlled by the detection temperature detected by the thermistor 6b disposed in the recording sheet, and the timing of sheet feeding start is controlled by the detection temperature detected by the thermistor 6a disposed in the non-sheet passing section having the maximum recording paper width. To prevent offset, and by controlling the sheet interval time, the temperature rise at the end is suppressed. In the paper feed timing control, only when the recording paper size to be printed this time is larger than the previous recording paper size, the paper feeding start timing is controlled based on the recording paper size and the paper feeding start temperature table, so that various types of paper feeding can be performed. Even when recording paper of a wide paper width is passed, accurate temperature control and suppression of end temperature rise can be achieved by an inexpensive fixing device having a relatively simple configuration without being affected by end temperature rise. .
[0066]
Next, a second embodiment of the present invention will be described.
[0067]
FIGS. 9 to 12 are a diagram showing a front part for explaining a fixing device to which the second embodiment of the image forming apparatus of the present invention is applied, and a flowchart for explaining the operation. This embodiment is an example of a configuration in which a plurality of temperature detectors are arranged at positions corresponding to both ends of the recording paper size in the longitudinal direction of the fixing roller.
[0068]
This embodiment is applied to a fixing device similar to that of the first embodiment. In the description of this embodiment, the same components as those of the first embodiment will be described. , The same reference numerals are given, and the detailed description is omitted.
[0069]
9, the fixing device 20 has a plurality of thermistors 21a to 21e arranged in the longitudinal direction of the fixing roller 2. The thermistor 21a is provided at a central position of the fixing roller 2 (a position indicated by a broken line in FIG. 9). Further, the thermistors 21b (1), 21b (2), to 21d (1) are located at the respective end positions of the recording paper size (in FIG. 9, each broken line position of A5 to A3 corresponds to the recording paper size A5, B5). / B4, A4 / A3 indicating the end positions of the recording paper).
[0070]
The thermistors 21e (1) and 21e (2) are provided in the non-sheet passing portion having the maximum width of the recording paper, and are disposed on the circumference at the same position as the thermo SW 7 shown in FIG. 1 (see FIG. 9). The thermo SW7 is not shown in the drawing). 9, the thermistors 21b (1), 21b (2),..., 21d (1), 21d (2) are located at both ends of each recording paper size distributed to both sides with respect to the center position of the fixing roller 2. It is located at the location.
[0071]
Hereinafter, a description will be given of a startup process when the image forming apparatus is driven from a cold state.
[0072]
FIG. 10 is a flowchart for explaining the start-up process. Steps similar to those in the flowchart shown in FIG. 3 are denoted by the same step numbers, and different steps (steps S1c ', 2b', 2c ') are described. The symbol “′” is attached.
[0073]
In the start-up process, since the fixing roller and the pressure roller start up from a cold state, the temperature rise of the thinner fixing roller is slower at the end than in the vicinity of the center. After the power of the main body is turned on (Step S1a), when the heater 5 is turned on (Step S1b), the temperature detection signal of the central thermistor 21a and the thermistors 21b (1), 21b (2),. When the temperature detection signal of the thermistor corresponding to the maximum width of the recording paper selected from 21d (1) and 21d (2) reaches a predetermined temperature (hereinafter referred to as pre-rotation start temperature) (step S1c '), the fixing roller Is rotated, and the pressure roller is turned to warm up in order to secure the fixing property (step S2a).
[0074]
That is, temperature detection signals of the central thermistor 21a and the thermistors (for example, 21b (1), 21b (2)) corresponding to the maximum width of the recording paper are input to the CPU 15, and the thermistors 21a, 21b (1), 21b < When the detected temperature indicated by the temperature detection signal input from 2 ▼ reaches the pre-rotation start temperature, each roller is rotated (step S1).
[0075]
The CPU 15 compares the temperature detection signal of the thermistor 21a disposed at the center with a lower limit value (hereinafter, referred to as a READY setting lower limit value) set as a temperature suitable for starting printing, and determines the minimum detection temperature of the thermistor detection temperature as the READY setting. It is checked whether the temperature is equal to or higher than a lower limit (for example, set temperature = 145 ° C.) (step S2b ′).
[0076]
Next, the CPU 15 determines the thermistor corresponding to the maximum width of the recording paper selected from the thermistors 21b (1), 21b (2), 21d (1), and 21d (2) (for example, thermistors 21b (1), 21b). {Circle around (2)}, a temperature detection signal input from the thermistor will be described below as an example, and a lower limit value set as an end temperature suitable for starting printing (hereinafter referred to as an end READY set lower limit value). Then, it is checked whether the lowest detected temperature of the selected thermistors 21b (1) and 21b (2) is equal to or higher than the end READY setting lower limit (set temperature = 110 ° C.) (step S2c ′). .
[0077]
If the detected temperature does not exceed the set lower limit in steps S2b 'and 2c', the rotation and heating of the roller are continued (step S2a).
[0078]
The heater driver 14 supplies / stops power to the heater 5 according to a drive signal from the CPU 15. In steps S2b 'and 2c', after the detected temperatures at the center and the end have reached their set lower limits (the READY set lower limit and the value end READY set lower limit), the power supply to the heater 5 is stopped, and the roller 5 is turned off. Also stops (step S2d), and enters a standby (standby) control (step S2e).
[0079]
That is, the CPU 15 inputs a temperature detection signal of the central thermistor 21a, and when the detected temperature indicated by the temperature detection signal reaches the pre-rotation start temperature, drives and rotates each roller to perform heating (step S1). The temperature detection signal input from the selected end thermistor (for example, 21b {1}, 21b <2>) and the center thermistor 21a is set by comparing with the end READY setting lower limit and the READY setting lower limit. After reaching the temperature, the drive signal of the heater driver 14 is stopped to output the stop of the power supply to the heater 5, and the rotation of each roller is also stopped, and READY is completed (printable state). ) Enter control (step S2).
[0080]
When there is no print signal, the standby (standby) control is maintained. FIG. 11 is a flowchart for explaining the standby (standby) control, which is almost the same as the flowchart of FIG. 4 described above. Here, the same steps as those in the flowchart shown in FIG. 4 are denoted by the same step numbers, and similar steps (step S3b ′) are denoted by “′”.
[0081]
In the standby (standby) control, as shown in the flowchart of FIG. 11, when a print signal is input from the image processing unit 16 to the CPU 15 (steps S3a and 3e), a print mode is started (steps S3f and 3g). Until a print signal is input, the temperature of the fixing roller is maintained at a predetermined temperature suitable for fixing by the processes of steps S3b to 3d.
[0082]
In the step S3b ', the CPU 15 compares the lower limit value of the temperature suitable for fixing (hereinafter referred to as a standby lower limit value) with the temperature detection signal from the thermistor 21a arranged at the center, and determines the lowest detected temperature. It checks whether the temperature (hereinafter, referred to as the minimum detection temperature) is higher or lower than a standby set lower limit (for example, set temperature = 150 ° C.), and outputs a drive signal to the heater driver 14. The heater driver 14 controls the energization by supplying / stopping power to the heater 5 in accordance with the drive signal from the CPU 15 (steps S3c and 3d). The lower limit of the standby setting is set at a temperature lower than a temperature setting suitable for fixing during printing in order to save power.
[0083]
Next, the operation of the present embodiment will be described. FIG. 12 is a flowchart for explaining sheet feed control according to the second embodiment of the present invention.
[0084]
In the standby (standby) control state, when a print signal is input from the image processing unit 16 to the CPU 15, the recording paper size is input (steps S4a and 4b), and the thermistors 21b (1), 21b (2) to 21d (21). A thermistor for detecting the temperature at a position corresponding to the recording paper size is selected from 1) and 21d (2).
[0085]
In the fixing device 1, when the heater is turned on, each roller starts rotating (step S4c), and the detected temperature of the thermistor 21a disposed at the center is compared with a set lower limit value. , Set temperature = 175 ° C.) or less, and outputs a drive signal to the heater driver 14 (step S5a ′). The heater driver 14 supplies / stops power to the heater 5 according to a drive signal from the CPU 15 and controls energization (step S5b).
[0086]
At this time, the CPU 15 compares the recording paper size input by the print signal with the stored recording paper size of the previous print (step S5c), and determines that the current recording paper size is smaller than the previous recording paper size. Alternatively, in the case of the same size, in step S5e ', the detected temperature of the thermistor 21a arranged at the center is compared with the set lower limit value, and if the temperature is equal to or larger than the set lower limit value, the sheet feeding is started. In step S5c, paper feeding is also started when there is no record of the previous print size (when the power is turned off).
[0087]
On the other hand, when the recording size is larger than that of the previous print, the temperature detection signal of the thermistor selected in accordance with the recording paper size position from the thermistors 21b (1), 21b (2) to 21d (1), 21d (2). (Hereinafter referred to as a maximum detected temperature at the start of feeding, for example, 195 ° C.) or the temperature detection signals of all thermistors and the set temperature. The set temperature is determined according to the recording paper size based on the recording paper size and the paper feed start temperature table shown in FIG. Thus, paper feed timing control according to the recording paper size is performed (step S5d '). In the feed timing control in step S5d ', if the temperature is equal to or lower than the set temperature, the detected temperature of the thermistor 21a disposed in the center is compared with the set lower limit in step S5e', and then the feed is started. In the case described above, control to wait while rotating the roller is performed. Note that the maximum feed start detection temperature is set so that an offset phenomenon does not occur when a large-size recording sheet is passed after a small-size recording sheet.
[0088]
That is, when the print signal is input to the CPU 15, the recording paper size is input, and as shown in the flowchart of FIG. 12, each roller starts rotating, and the thermistor corresponding to the recording paper size position from the input recording paper size. (21b-1), 21b-2 to 21d-1 and 21d-2) are selected. The temperature detection signal of the thermistor 21a is compared with a set lower limit, and it is checked whether the lowest detected temperature is equal to or lower than the set lower limit. The heater driver 14 supplies / stops power to the heater 5 according to a drive signal from the CPU 15 and controls energization (step S4).
[0089]
If the size of the recording paper fed this time is smaller than the size of the recording paper of the previous print, if the size is the same, and if there is no recording of the previous print size (when the power is turned off), paper feeding is started. On the other hand, when the recording paper size fed this time is larger than the recording paper size of the previous print, the thermistors (21b (1), 21b (2) to 21d (1), 21d) selected according to the recording paper size. The control unit compares the maximum detected sheet feed start temperature of the temperature detection signal of 2)) with the set temperature. If the temperature is equal to or lower than the set temperature, sheet feeding is started, and if the temperature is equal to or higher than the set temperature, control is performed to wait (step S5).
[0090]
When the sheet feeding is started, the temperature detection signals from the thermistor 21a arranged in the center and the selected thermistors (21b (1), 21b (2) to 21d (1), 21d (2)) are set to the lower limit. Then, it is checked whether the lowest detected temperature is equal to or lower than the set lower limit, and a drive signal is output to the heater driver 14. The heater driver 14 supplies / stops power to the heater 5 in response to a drive signal from the CPU 15 and controls energization (step S6).
[0091]
In the case where the paper is continuously passed, the paper interval time is controlled. The temperature detection signals from the thermistor 21a disposed at the center of the fixing roller and the selected thermistors (21b (1), 21b (2) to 21d (1), 21d (2)) are compared with a set lower limit. It is checked whether the minimum detected temperature is equal to or lower than the set lower limit value (set temperature, for example, 175 ° C.), and the power supply to the heater 5 is supplied / stopped to control the temperature of the fixing roller during printing.
[0092]
Further, in the temperature detection by the selected thermistors (21b (1), 21b (2) to 21d (1), 21d (2)), there is a problem of heat resistance of bearings and heater elements of each roller corresponding to a peripheral member, and a safety device. Since the problem of the thermo SW 7 being erroneously broken due to a large temperature rise at the end cannot be avoided, the thermistor disposed on the circumference at the same position as the thermo SW 7 in the non-sheet passing portion having the maximum width of the recording paper. The maximum detected temperature of the non-sheet passing portion is detected by 21e (1) and (2), and the interval between sheets to be fed next is controlled based on the set interval time table (step S8).
[0093]
As described above, the fixing device 20 presses the recording paper against the fixing roller 2 heated by the heater 5 by the pressure roller 3, and fixes the toner of the recording paper to the recording paper by the heat of the fixing roller 2. After the end of the job, the size of the printed recording paper is stored in the CPU 15 (step S6).
[0094]
Further, when the recording paper size of the continuous paper passing is different (when a plurality of continuous JOBs are processed), the CPU 15 records the size of the recording paper that has been printed. At the time of the print signal, the thermistor corresponding to the recording paper size end and the corresponding thermistor are selected from the thermistors 21b (1), 21b (2) to 21d (1), 21d (2), and the highest detected temperature during printing is detected. Compare the print size with the current print size.If the print size is smaller than the previous print size, and if the print size is the same, immediately start feeding the paper, and the paper passing width is larger than the previous print size. At this time, when the temperature is equal to or lower than the set temperature of the maximum detected feed start temperature, the sheet feeding is started, and when the detected temperature is equal to or higher than the set temperature, standby control is performed (step S9).
[0095]
Therefore, according to the present embodiment, the thermistor 21a disposed at the center of the fixing roller 2 is used, and the thermistors 21b disposed at positions corresponding to both ends of each recording paper size in the longitudinal direction of the fixing roller 2. Since the thermistor corresponding to the recording paper size can be selected from (1), 21b (2) to 21e (1), 21e (2) to perform temperature control, the temperature can be further increased in the longitudinal direction of the recording paper. Fixability can be secured at a small temperature.
[0096]
The recording paper size to be printed is stored, and only when the recording paper size to be printed is larger than the previous recording paper size, the thermistor (21b (1), 21b (2)) selected according to the recording paper size. -21d-1) and 21d-2) to control the paper feed start timing, so that even when recording paper of various widths is passed, it is not affected by the temperature rise at the edge. Accurate temperature control and suppression of end temperature rise can be performed.
[0097]
Regarding the temperature rise of the non-sheet passing portion, thermistors 21e (1) and 21e (2) are disposed at the non-sheet passing portions at both ends, and the inter-sheet time is controlled based on the detected temperature, so that the peripheral members can be heated. The heat resistance temperature can be suppressed. Further, since the thermistor is disposed at the end of each recording sheet, the heat distribution of the heater is not so much taken into consideration, so that an inexpensive fixing device having a relatively simple configuration is provided.
[0098]
Next, a third embodiment of the present invention will be described. FIG. 13 is a diagram showing a third embodiment of the fixing device provided in the image forming apparatus of the present invention. In this embodiment, a plurality of temperature detectors are arranged at positions corresponding to only one end of the recording paper size in the longitudinal direction of the fixing roller. In this embodiment, the heater light distribution may use a heater having a peak value of 110% ± 10% at both ends of the maximum size of the recording paper with respect to the central portion of 100%.
[0099]
This embodiment is applied to the same fixing device as the second embodiment. In the embodiment shown in FIG. 13, a plurality of thermistors 31 a to 31 e are provided in the longitudinal direction of the fixing roller 2 in a configuration substantially similar to the above-described second embodiment. The thermistor 31a is provided at the center position of the fixing roller 2 (the position indicated by the dashed line in FIG. 13), and the thermistors 31b to 31d are located at the end positions of the recording paper size (indicated by A5 to A3 in FIG. 13). The broken line position indicates the end position of the recording paper of the recording paper size A5, B5 / B4, A4 / A3). The thermistor 31e is provided in the non-sheet passing portion outside the maximum width of the recording paper, and is disposed on the circumference at the same position as the thermo SW7 (not shown). In FIG. 13, the thermistors 31b to 31e are the same as those in FIG. 9 described above except that the thermistors 31b to 31e are arranged on both sides with respect to the center of the fixing roller 2 and disposed at the end positions of the respective recording paper sizes. Therefore, the detailed description is omitted.
[0100]
In the above embodiments, the temperature of the fixing roller 2 is detected by the thermistors 6a to 6b, 21a, 21b (1), 21b (2) to 21e (1), 21e (2), and 31a to 31e. However, the temperature detecting means is not limited to the thermistor.
[0101]
Further, according to each of the above embodiments, the on / off control of the heater 5 is determined based on whether the minimum temperature detected by the thermistors 6a to 6c, 21a to 21e, and 31a to 31e is equal to or lower than a preset lower limit. However, the on / off control of the heater 5 is not limited to this.
[0102]
【The invention's effect】
As described above, according to the present invention, a plurality of temperature detecting units are disposed on the fixing roller, and the detected temperature of at least one temperature detecting unit and the sheet interval are controlled by the sheet interval time table. By storing the paper size, comparing the previous recording paper size with the recording paper size to be passed, and performing paper feed start timing control based on the detected temperatures of all temperature detecting means only when the paper size is large, The temperature rise of the non-sheet passing area for the recording paper of the size can be kept within the heat-resistant temperature of the peripheral members of the fixing roller. The offset phenomenon due to temperature can be suppressed.
[0103]
Further, according to the present invention, the size of the passed recording paper is stored, the previous recording paper size is compared with the recording paper size to be passed, and only when the size is large, the detected temperature of at least one temperature detecting means is detected. By controlling the paper feed timing based on the recording paper size and the paper feed start temperature table based on the recording paper size, it is possible to keep the temperature rise in the non-sheet passing area for the small size paper within the heat resistance temperature of the peripheral members of the fixing roller. It is possible to suppress an offset phenomenon caused by a rise in temperature at the end portion which occurs when a large-size sheet is subsequently passed.
[0104]
In addition, regarding the temperature rise at the end of the non-sheet passing portion, which is notable due to the use of a thin fixing roller, and the problem of securing the end fixability at startup, the lowest Can be overcome by detecting the temperature and controlling the temperature, so that a relatively inexpensive fixing device can be configured.
[0105]
Further, according to the present invention, the light distribution of the heater is regulated, and two or more temperature detecting means are provided. The temperature detecting means is provided at the end position and the center position of the recording paper maximum size non-sheet passing area on at least one side. In addition, the temperature during printing is controlled at the center position, and the sheet interval time can be controlled by detecting the temperature by the temperature detecting means disposed at the end of the recording paper maximum size non-sheet passing area on one side.
[0106]
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a side portion of a fixing device to which an image forming apparatus according to a first embodiment of the present invention is applied.
FIG. 2 is a diagram illustrating a front part of a fixing device to which the first embodiment of the image forming apparatus according to the invention is applied, and a diagram illustrating a light distribution of a heater.
FIG. 3 is a flowchart illustrating a start-up process performed by the fixing device of the image forming apparatus according to the present invention.
FIG. 4 is a flowchart for explaining standby (standby) control by the fixing device of the image forming apparatus of the present invention.
FIG. 5 is a flowchart for explaining sheet feed control by a fixing device of the image forming apparatus of the present invention.
FIG. 6 is a diagram illustrating a table between a recording sheet size and a sheet feeding start temperature used in a fixing device of the image forming apparatus of the present invention.
FIG. 7 is a diagram illustrating a sheet interval time extension table used in the fixing device of the image forming apparatus according to the present invention.
FIG. 8 is a graph showing experimental data showing a relationship between a recording paper size and a paper feeding start temperature.
FIG. 9 is a diagram showing a front part for explaining a fixing device to which a second embodiment of the image forming apparatus of the present invention is applied.
FIG. 10 is a flowchart illustrating a start-up process according to a second embodiment of the present invention.
FIG. 11 is a flowchart illustrating standby (standby) control according to a second embodiment of the present invention.
FIG. 12 is a flowchart illustrating a sheet feed control according to a second embodiment of the present invention.
FIG. 13 is a view showing a third embodiment of the fixing device provided in the image forming apparatus of the present invention.
[Explanation of symbols]
1,20,30 Fixing device
2 Fixing roller
3 Pressure roller
4 Pressure spring
5 heating means (heater)
6a Central thermistor
6b Non-sheet passing part thermistor
7 Thermo SW (safety device)
8 entrance guide
9 Paper ejection guide
10 Separating claws
11a, 11b discharge roller
12, 13 static elimination needle
14 Heater driver
15 CPU
16 Image processing unit
21a, 31a Central thermistor
21b (1), (2), 31b A3 recording paper end thermistor
21c (1), (2), 31c B4 recording paper end thermistor
21d (1), (2), 31d A5 recording paper edge thermistor
21e (1), (2), 31e Non-sheet passing portion thermistor outside the maximum width of recording paper

Claims (10)

The unfixed toner image is fixed on the recording paper by sandwiching the recording paper carrying the unfixed toner image on the surface with a pair of rollers including a fixing roller and a pressure roller, and inserting the unfixed toner image while applying heat and pressure. An image forming apparatus having a fixing device for causing
Temperature detecting means for detecting at least two temperatures along the longitudinal direction of the fixing roller;
Energization control means for controlling energization to the fixing heater based on the detected temperatures of the temperature detection means,
By obtaining a paper interval determined for at least one detected temperature detected by the temperature detecting means based on a paper interval table that determines a relationship between the temperature of the fixing roller and the paper interval, the paper interval during continuous paper passing is determined. An image forming apparatus, comprising: a sheet interval time control unit that controls an interval time. The unfixed toner image is fixed on the recording paper by sandwiching the recording paper carrying the unfixed toner image on the surface with a pair of rollers including a fixing roller and a pressure roller, and inserting the unfixed toner image while applying heat and pressure. An image forming apparatus having a fixing device for causing
Temperature detecting means for detecting at least two temperatures along the longitudinal direction of the fixing roller;
Energization control means for controlling energization to the fixing heater based on the detected temperatures of the temperature detection means,
A paper feed start temperature determined for the recording paper size is determined based on a paper feed start temperature table that determines the relationship between the recording paper size and the paper feed start temperature, and a comparison is made between the paper feed start temperature and all the detected temperatures. An image forming apparatus comprising: a sheet feed timing control unit for controlling sheet feed timing. The unfixed toner image is fixed on the recording paper by sandwiching the recording paper carrying the unfixed toner image on the surface with a pair of rollers including a fixing roller and a pressure roller, and inserting the unfixed toner image while applying heat and pressure. An image forming apparatus having a fixing device for causing
Temperature detecting means for detecting at least two temperatures along the longitudinal direction of the fixing roller;
Energization control means for controlling energization to the fixing heater based on the detected temperatures of the temperature detection means,
By obtaining a paper interval determined for at least one detected temperature detected by the temperature detecting means based on a paper interval table that determines a relationship between the temperature of the fixing roller and the paper interval, the paper interval during continuous paper passing is determined. Paper interval time control means for controlling the interval time,
A paper feed start temperature determined for the recording paper size is determined based on a paper feed start temperature table that determines the relationship between the recording paper size and the paper feed start temperature, and a comparison is made between the paper feed start temperature and all the detected temperatures. An image forming apparatus comprising: a sheet feed timing control unit for controlling sheet feed timing. Comparing means for storing the recording paper size that has been passed last time and comparing the recording paper size with the recording paper size to be passed,
4. The image forming apparatus according to claim 2, wherein the paper feed timing control unit determines a paper feed start temperature based on a comparison result of the recording paper size by the comparison unit. 5. The paper feed timing control means,
If the size of the recording paper to be passed is smaller than or the same as the size of the recording paper last passed, paper feeding is started,
When the size of the recording paper to be passed is larger than the size of the recording paper that has passed the previous time, the maximum paper temperature between the paper supply start temperature and the detected temperature determined in the paper supply start temperature table is determined. The image forming apparatus according to any one of claims 2 to 4, wherein the start of the sheet feeding or the standby is based on the comparison. The paper interval time control means,
4. The image forming apparatus according to claim 1, wherein an inter-sheet time with respect to a maximum temperature at an end position of a non-sheet-passing area of a maximum size of the recording sheet of the fixing roller is obtained based on the inter-sheet time table. One heater is disposed inside the fixing roller, and the heater has a light distribution peak only in the vicinity of both side edges of the paper passing area of the maximum size of the recording paper, and the light distribution level of the peak is at least the lower limit at the center. The image forming apparatus according to any one of claims 1 to 6, wherein the light distribution level is higher than the light distribution level, and all the light distribution levels in the other paper passing areas have a flat light distribution in a high light distribution area. The temperature detecting means detects a temperature of an end position of a non-sheet passing area on at least one side and a temperature of a sheet passing area including at least a center position among both ends of the recording paper maximum size. The image forming apparatus according to any one of claims 1 to 7. 9. The image forming apparatus according to claim 8, wherein the sheet passing area position at which the temperature is detected includes a plurality of positions corresponding to ends of a recording sheet size to be passed. The image forming apparatus according to claim 9, wherein the paper passing area position is on both sides or only one of the center position.

Images