JPH08314321A - Image recorder provided with temperature controller for thermal roller type fixing unit - Google Patents

Abstract

PURPOSE: To execute temperature control not for generating a failure such as a hot offset and underfixing, in a thermal roller type fixing unit. CONSTITUTION: The set temp. of a heater H is previously set to be a normal control temp. T1. A control part 20 turns on the heater H and the surface temperature of a fixing roller 12 rises and reaches the control temp. T1. When a copying start button 22 is depressed, the surface temperature of the fixing roller 12 is controlled at the control temp. T1. When the detection temp. of the fixing roller 12 temporarily drops to a control temp. T2 lower than the control temp. T1 or below and then, rises to the control temp. T2 again because of room in a heat supply, as copying is advanced, the control temp. is switched from the control temp. T1 to a control temp. T3 lower than the control temp. T2. Thus, when the copying is continued and completed in a state where the control temp. is switched to the control temp. T3, the control temp. is switched to return to the first set control temp. T1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat roller type fixing device having an image recording apparatus provided with a temperature controller which does not cause problems such as hot offset and fixing under.

[0002]

2. Description of the Related Art Conventionally, in heat roller fixing, a heater 1 for heating a portion corresponding to a small-sized sheet passing portion of a fixing roller.
There is a method of making the temperature distribution of the fixing roller as uniform as possible by using two heaters (the electric power W1) and the heater 2 (the electric power W2) that heats a portion of the fixing roller corresponding to the small-size non-sheet passing portion (the electric power W2). The value of W1 + W2 is limited to a certain value or less).

That is, the two heaters are controlled by detecting the roller temperatures at the positions corresponding to the respective heat generating portions, and the temperatures for controlling the two heaters are usually the same. When passing a small size sheet, the heater 1 keeps ON because the roller temperature drops, but the heater 2 turns ON / OFF because the roller temperature at the non-sheet passing portion does not drop.
State. Therefore, it cannot be said that the power of W2 is effectively used during copying. However, if the heater 2 is kept on like the heater 1, the temperature drop in the paper passing portion is reduced, but the meaning of using two heaters is meaningless, and the roller temperature in the non-paper passing portion becomes abnormally high, and the parts deteriorate. Or, in a large size copy after a small size copy, a so-called hot offset phenomenon occurs in which minute toner adheres to the surface of the heat roller.

Further, in the fixing device using the non-contact type temperature sensor for detecting the temperature of the fixing roller, there are a case where the heater is turned on and warming up from a state where the fixing device is cold, and a case where the fixing device is warm. Since the difference TR-TS = ΔT between the roller surface temperature TR and the sensor detected temperature TS is different, the roller surface temperature becomes as shown in FIG. 1 when the temperature is controlled at the same set temperature (the sensor ambient temperature is sufficient immediately after warming up. Since it is not warm, ΔT is large). That is, the roller temperature immediately after warming up becomes extremely high, and the roller life may be shortened and hot offset may occur. Whether or not the roller rotates because the surroundings of the sensor warm up differently when the copy is performed (when the roller rotates) and during standby (when the roller is stopped). It is difficult to control the target roller temperature without considering such factors.

Further, in the heat roller fixing, when the temperature is not switched during the continuous copying of the paper having the width shorter than the heater heat generating portion, as shown in FIG. The temperature rises, causing problems such as hot offset and reduced roller life. The following has been proposed as a means for suppressing the temperature rise of the heater heat generating portion of the fixing roller and the non-sheet passing portion. JP Sho 60-247
In No. 277, the set temperature of the fixing roller is sequentially switched to the lower one after a certain number of copies are made from the start of copying. In Japanese Utility Model Laid-Open No. 63-105169, the set temperature of the fixing roller is switched to a low temperature after a certain time has passed from the start of copying. However, the proposal of Japanese Patent Laid-Open No. 60-247277 is a prospective control when the heat supply amount is assumed to be a constant value, and hot offset and fixing under can not occur, but for example, when the power supply voltage is low, As shown in FIG. 2 (b), there may be a fixing undershoot.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a first object of the present invention is to provide a position corresponding to a small-sized sheet passing portion and a non-sheet passing portion of a recording sheet. In a heat roller type fixing device in which each heater is incorporated in the fixing roller, the roller temperature of the non-paper passing portion becomes abnormally high, the hot offset phenomenon does not occur, and the fixing underpass does not occur in the paper passing portion, and It is an object of the present invention to provide an image recording apparatus capable of controlling temperature by effectively using electric power of two heaters.

A second object of the present invention is to provide an image recording apparatus capable of accurately controlling the surface temperature of the fixing roller in a heat roller type fixing device using a non-contact temperature sensor for detecting the temperature of the fixing roller.

A third object of the present invention is to detect the temperature of the fixing roller in a heat roller type fixing device using a temperature sensor, when the power supply voltage is still higher or lower after a certain time from the start of copying or after a certain number of sheets. However, it is an object of the present invention to provide an image recording apparatus capable of temperature control without causing hot offset of a non-sheet passing portion or fixing underfix of a sheet passing portion.

[0009]

The above object can be achieved by any one of the following means.

(1) Two heaters, a heater having a heat generating portion in a small-size sheet passing portion and a heater having a heat generating portion in a small-size non-sheet passing portion, are installed in the fixing roller, and the heat generating portion of each heater is provided. On the outer surface of the fixing roller.
Alternatively, in a heat roller type fixing device that is provided a little distance from the outer peripheral surface to detect the temperature and has a pressure roller that comes into pressure contact with this fixing roller and rotates in cooperation with each other, to control the temperature An image recording apparatus equipped with a temperature controller, which sets a control temperature of a paper section higher than a control temperature of a sheet passing section and lower than a temperature at which a problem such as hot offset occurs.

(2) A fixing roller having a built-in heater, a pressure roller that is in pressure contact with the fixing roller and rotates in cooperation with each other, and a temperature sensor that is in close proximity and does not contact to detect the temperature of the outer peripheral surface of the fixing roller are used. In the heat roller type fixing device, the temperature detected before the heater is turned ON by the main switch ON, the elapsed time from the completion of warm-up, the fixing roller rotation time (the number of copies), etc. are detected, and the heater is turned ON based on the detection result. An image recording apparatus equipped with a temperature controller that changes a control set temperature to be turned on / off in a plurality of ways.

(3) A fixing roller having a built-in heater, and a pressure contact roller that is in pressure contact with the fixing roller and rotates in cooperation with each other, and a temperature sensor is provided on the outer peripheral surface of the fixing roller or at a slight distance from the outer peripheral surface. In the heat roller type fixing device for detecting, the normal setting temperature of the fixing roller is T1, the second setting temperature is T2, and the third setting temperature is T3.
(T1> T2 ≧ T3), the image recording apparatus having a temperature controller that switches the control temperature from T1 to T3 when the fixing roller temperature reaches T2 from a temperature lower than T2 during copying. An image recording apparatus equipped with a controller for performing this switching control a plurality of times.

[0013]

According to the image recording apparatus of the first aspect, the control temperature of the non-sheet passing portion is set to be higher than the control temperature of the sheet passing portion and lower than the temperature at which a problem such as hot offset occurs when passing a small size sheet. An image recording apparatus equipped with a temperature controller, in which the non-sheet passing portion of the fixing roller is controlled to a temperature at which hot offset does not occur, and the sheet passing portion of the fixing roller is controlled to a temperature at which fixing under does not occur. Has been done.

According to the image recording apparatus of claim 2,
The temperature detected before the heater is turned on by the main switch being turned on, the elapsed time from the completion of warm-up, the fixing roller rotation time (the number of copies), etc. are detected, and based on the detection results,
An image recording apparatus equipped with a temperature controller that changes a control set temperature for turning on / off a heater in a plurality of ways, depending on an elapsed time after warm-up and a fixing roller surface temperature detected by a temperature sensor at that time. The setting temperature of the fixing roller is appropriately switched, and the temperature is controlled so as not to cause hot offset or fixing under.

According to the image recording apparatus of claim 3,
During copying, if the fixing roller temperature is lower than T2,
When the temperature reaches 2, the control temperature is switched from T1 to T3 (T1> T2 ≧ T3), and the image recording apparatus is equipped with a temperature controller. By switching the set temperature, fixing in the non-sheet passing portion and the sheet passing portion is performed. The temperature of the roller is controlled appropriately to prevent hot offset and fixing under. Further, even if the power supply voltage of the apparatus is low, even if the roller temperature during copying set to the normal control temperature T1 gradually decreases, the
Since the temperature does not rise again to T2 after the temperature drops from 2, the temperature under which the normal control temperature T1 is not switched to a low temperature is controlled to prevent the occurrence of fixing under.

[0016]

Embodiment 1 FIG. 3 shows Embodiment 1 of the image recording apparatus according to the present invention.
Through FIG. 7.

FIG. 3 shows a main part of the image recording apparatus according to the present invention. The photoconductor drum 1 is rotated in the direction of the arrow while a potential is applied to the outer circumference of the photoconductor by the charger 2 and the exposure part is further exposed. A latent image is formed by the projection of the document image in 3.

The latent image is visualized by the developing device 4 to form a toner image.
It is fed from the recording sheet and is transferred onto the recording sheet by the timing roller 7 so as to match the toner image. The recording paper on which the toner image has been transferred is separated from the peripheral surface of the photoconductor 1 by the separator 8 and is conveyed to the heat roller fixing device 10 to be described later through the conveyor belt 9 to heat and fix the toner image. It is received and output as an image formed product.

After the transfer of the toner image onto the recording paper, the photoreceptor is cleaned by a cleaning device (not shown) to remove residual toner, and is repeatedly subjected to image formation.

In the image recording apparatus of this embodiment, the recording paper is fed and conveyed in the apparatus on the basis of one-sided conveyance reference.

FIG. 4 is an enlarged view of the heat roller fixing device 10 shown in FIG. 12 in the fixing device 10 is
The heater A14 and the heater B15 are built-in, and the surface of the roller is coated with a layer of a releasable material such as fluororesin or silicon rubber, which is a heating roller for melting and fixing the toner image on the recording paper as the transfer material. Rollers 13 are pressure contact rollers that cover the surface of the roller with no built-in heating means with silicone rubber or the like and rotate in cooperation with the fixing roller 12 while pressure contact. Further, as shown in FIG. 5, the heater A is a heater having a heat generating portion in a small-sized sheet passing portion such as a halogen lamp provided in the fixing roller in parallel with the roller axis, and the heater B is also a heater in the fixing roller. A heater that is provided together with A and includes a halogen lamp or the like having a heat generating portion in a small-size non-sheet passing portion. Reference numeral 18 is a separation claw that prevents the recording paper from being wound around the peripheral surface of the fixing roller, and 20 is a control unit provided in the main body of the image recording apparatus. 21A and 2
Reference numeral 1B denotes a temperature sensor, which is a temperature detecting means such as a thermistor for detecting the surface temperature of the fixing roller 12 corresponding to the positions of the heater A and the heater B, on the outer peripheral surface or the outer peripheral surface of the fixing roller 12. It is provided a little away from. Reference numeral 22 is a copy button, 23 is an input key such as a numeric keypad for inputting the recording paper size, the number of copies, etc., 24 and 25 are power supply to the heater A and the heater B, respectively, and power is supplied by the control of the control unit 20. It is a heater power supply that turns on and off.

Next, the temperature control sequence of the first embodiment will be described based on the flowchart of FIG. 6 and the diagram showing the control state of the roller surface temperature shown in FIG.

First, the control temperatures T of the heaters A and B respectively.
a and Tb are preset to the same specified temperature T1 (step 1). When a main switch (not shown) is turned on and the power is turned on, the controller turns on the heaters A and B via the heater power supplies 24 and 25 to heat the fixing roller 12 from the inside to raise the outer peripheral surface temperature of the fixing roller and copy. When the temperature reaches the specified temperature T1 lower than the control temperature at the time, the temperature sensor 21A,
The control unit 20 turns on the heaters A and B by the temperature signal of 21B.
The FF is performed, the warm-up is completed, and thereafter, the copy temperature is controlled at the specified temperature until the copy start. After the warm-up is completed, the copy start button is pressed (step 2), the recording paper size width to be used is judged (step 3), and A4 is selected.
If it is less than the width (step 4), the control temperature T of the heater A
a is set to the specified temperature T2, and the control temperature Tb of the heater B is set to a specified temperature T3 (T2 <T3) higher than the specified temperature T2 (step 4), and copying is performed. When the copying is completed (step 5), the control temperatures Ta and Tb of the heater A and the heater B are reset to the specified temperature T1 during warm-up (step 6).
On the other hand, when the recording paper size width to be used is A4 width or more (step 7), both the control temperatures Ta and Tb of the heater A and the heater B are reset to the specified temperature T2 (step 4), and copying is performed. When the copying is completed (step 8), the control temperatures Ta and Tb of the heater A and the heater B are reset to the specified temperature T1 for warming up as described above. In addition, the heater A and the heater B
The ON / OFF control is controlled independently so that when the temperature detected by the temperature sensors 21A and 21B is lower than the control temperature, the heater is turned on, and when it is higher than the control temperature, the heater is turned off.

According to the first embodiment, it is possible to reduce the temperature decrease of the sheet passing portion as much as possible while preventing problems such as hot offset due to the abnormal temperature rise of the non-sheet passing portion.

In the present embodiment, the case of one-sided standard paper feeding has been described. However, also in the case of center-standard paper feeding, only the heater for heating the small-size sheet passing portion and the heater for heating only the small-size non-sheet passing portion are heated. A similar effect can be obtained by the above control method using a heater that operates.

Next, a second embodiment of the image recording apparatus according to the present invention will be described with reference to FIGS.

FIG. 8 is an enlarged view of the second embodiment of the heat roller fixing device 10 used in the image recording apparatus shown in FIG.
The inside of the fixing device 10 is composed of a fixing roller 12 having at least one heater H including a halogen lamp and the like, and a pressure contact roller 13 which is in pressure contact with the fixing roller from directly below. The toner image is melted and fixed while the recording paper is conveyed by the pressure contact portion.

A temperature sensor S for detecting the temperature of the peripheral surface of the fixing roller 12 is arranged on the fixing roller 12 in a non-contact state with the peripheral surface.

The temperature detected by the non-contact type temperature sensor S is fed back to the control unit of the recording apparatus main body, and the control unit operates the heater power source via the drive system according to the temperature data, The electric current is intermittently supplied to the heater H to control the temperature of the fixing roller. Based on the detection result of the temperature detected by the temperature sensor S before the heater H is turned on, the elapsed time from the completion of warm-up, the rotation time of the fixing roller 12 corresponding to the number of copies, etc. The control (setting) temperature for turning ON / OFF is changed in multiple ways. The temperature control sequence will be described below with reference to the flowchart shown in FIG. 9 and the diagram showing the state of the roller temperature control shown in FIG.

When the main switch MSW of the recording apparatus is on and the fixing detection temperature is below the normal set temperature T1 (step 1), the control temperature is changed to T20 higher than T1 (step 2), and the fixing detection temperature is changed. Is the normal set temperature T
If it is 1 or more, the control temperature is changed to the highest control temperature T2n (step 3). Then, if a predetermined time A minutes or more has elapsed from the completion of warm-up or if the rotation of the fixing roller has elapsed A'minutes or more (step 4), The control temperature T21 higher than T20 is changed (step 5). The control temperature T20 is not changed when a predetermined time A minutes or less has elapsed after the warm-up is completed or when the rotation of the fixing roller is A'minutes or less. Further, when the time has elapsed and the predetermined time B or more has elapsed from the completion of warm-up or the rotation of the fixing roller has elapsed B'or more minutes (step 6), the control temperature T22 higher than T21 is changed (step 7). ). The control temperature T21 is not changed when the predetermined time B or less has passed or the rotation of the fixing roller has passed B'or less than the completion of warm-up. In this manner, the control temperature T23, which is higher than T22, when the time further elapses and a predetermined time longer than the completion of warm-up or a rotation of the fixing roller elapses a predetermined time T23, T24, T
25 ... T2n, the control temperatures are successively switched and changed (step 8).

According to the second embodiment, the surface temperature of the fixing roller can be accurately controlled even by the non-contact type sensor.

Next, a third embodiment of the image recording apparatus according to the present invention will be described with reference to FIGS.

The heat roller fixing device 10 of the third embodiment is
The heat roller fixing device 10 used in the second embodiment described above.
The configuration is basically the same. The fixing roller 12 has a temperature sensor S for detecting the temperature of the peripheral surface of the fixing roller 12.
However, they are arranged on the outer peripheral surface or in a state of being slightly separated from the outer peripheral surface.

The temperature sensor S controls the energization of the heater H so that it can always detect a predetermined control temperature in the sheet passing portion, and thereby the peripheral surface of the fixing roller 12 is maintained at a temperature suitable for fixing.

Below, the flowchart shown in FIG. 11 and FIGS. 12A and 12 showing the state of the roller temperature control.
The temperature control sequence will be described based on FIG.

In the heat roller fixing device 10 of the third embodiment, the normal control temperature of the fixing roller is T1, the second control temperature is T2, and the third control temperature is T3 (T1> T2).
≧ T3).

First, the preset temperature of the heater H is preset to the normal control temperature T1 (step 1). When a main switch (not shown) is turned on and the power is turned on, the controller turns on the heater via the heater power supplies 24 and 25 to heat the fixing roller 12 from the inside to raise the surface temperature of the fixing roller and reach the control temperature T1. Then, the temperature signal of the temperature sensor 21 causes the control unit 20 to turn off the heater H and complete the warm-up. After the warm-up is completed, when the copy start button is pressed (step 2), the surface temperature of the fixing roller is controlled by the control temperature T1 (step 3). As copying progresses, heat is taken by the recording paper passing through the fixing roller, and the surface temperature of the fixing roller in the paper passing portion gradually decreases.
However, if the temperature detected by the fixing roller once drops below T2, which is lower than T1, and then rises to T2 again due to the margin of heat supply (step 4), the control temperature is changed from T1 to T2. The temperature is switched to T3, which is a lower temperature (step 5). The operation of switching the control temperature from T1 to T3 may be repeated. In this manner, when the control temperature is switched to T3 and the copying is continued (step 6), the control temperature is switched back to the initially set control temperature T1 (step 7). However, if there is no margin in the amount of heat supply and the temperature does not rise to T2 again in step 4, the control temperature is kept at T1 and is not switched.

FIG. 12A shows the fixing roller temperature control state when the power supply voltage of the image recording apparatus of the present invention is low. That is, the roller temperature during copying, which is set to the normal control temperature T1, gradually decreases, and after temporarily decreasing from T2,
Since the temperature does not rise again to T2, it is considered that the temperature rise of the non-sheet passing portion is not a problem, so the temperature is not switched from the normal control temperature T1. However, since the temperature is not switched to a low temperature, the temperature does not drop such that the fixing becomes under-fixed.

FIG. 12B shows the case where the power supply voltage is high.
The state of the fixing roller temperature control is shown. That is, the roller temperature during copying, which is set to the normal control temperature T1, gradually decreases, but once decreases from T2, the temperature again increases to T2. Therefore, if the copying is continued as it is, the temperature rise of the non-sheet passing portion may occur. Therefore, the control temperature is switched from T1 to T3. However, since the power supply voltage is high, even if the control temperature is switched to the lower one and set, the temperature does not drop to cause fixing undershoot.

[0040]

The following effects can be obtained by the configuration of the above embodiment.

(1) It is possible to reduce the temperature drop of the paper passing portion as much as possible while preventing the hot offset phenomenon due to the abnormal temperature rise of the non-paper passing portion.

(2) Even with a non-contact sensor, the surface temperature of the fixing roller can be accurately controlled while preventing overshoot.

(3) When the power supply voltage is low, it is considered that the temperature rise of the non-sheet passing portion is small, so the control temperature is not switched to a low temperature. Since the temperature is not switched, the temperature of the sheet passing portion does not drop until the fixing under reaches. Further, when the power supply voltage is high, even if the control temperature is switched, the temperature of the sheet passing portion does not decrease until the fixing under reaches.

[Brief description of drawings]

FIG. 1 is a diagram showing a temperature control situation in a conventional fixing device using a non-contact type temperature sensor.

FIG. 2A and FIG. 2B are views showing a situation in which the temperature of the upper roller changes when the set temperature of the fixing roller is not switched or when the power supply voltage is low in the conventional example.

FIG. 3 is a diagram showing a main part of an image recording apparatus according to the present invention.

FIG. 4 is an enlarged view of the heat roller fixing device shown in FIG.

FIG. 5 is a diagram showing a positional relationship between a heater and a temperature sensor used in the first embodiment.

FIG. 6 is a flowchart showing a temperature control sequence according to the first embodiment.

FIG. 7 is a diagram showing a state of temperature control of a sheet passing portion and a non-sheet passing portion according to the first embodiment of the present invention in comparison with a conventional example.

FIG. 8 is an enlarged view of a fixing device according to a second embodiment of the present invention, which uses a non-contact temperature sensor.

FIG. 9 is a diagram showing a flowchart of temperature control according to the second embodiment of the present invention.

FIG. 10 is a diagram showing a situation of temperature control.

FIG. 11 shows a flowchart of temperature control according to the third embodiment of the present invention.

FIG. 12 is a diagram showing the situation of the upper roller temperature change when the power supply voltage is low in the third embodiment of the present invention.
FIG. 12A shows the situation of the upper roller temperature change when the power supply voltage is high.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 2 Charging device 3 Exposure part 4 Developing device 5 Transfer device 6 Paper cassette 7 Timing roller 8 Separator 9 Conveying belt 10 Heat roller fixing device 12 Fixing roller 13 Pressing roller 14, 15 Heater A, B H Heater S Temperature sensor

Front Page Continuation (72) Inventor Kazumi Ishii 2970 Ishikawacho, Hachioji City, Tokyo Konica Stock Company

Claims (3)

[Claims] 1. A heater having a heat generating portion in a small size sheet passing portion and a heater having a heat generating portion in a small size sheet non-passing portion are installed in a fixing roller, and each heater has a heat generating portion. A corresponding pressure sensor is provided on the outer peripheral surface of the fixing roller or at a distance from the outer peripheral surface to detect the temperature, and a pressure contact roller that is in pressure contact with the fixing roller and rotates in cooperation with the fixing roller.
In a heat roller type fixing device that has temperature control, the control temperature of the non-sheet-passing part is higher than the control temperature of the paper-passing part and lower than the temperature at which problems such as hot offset occur when passing small size paper. An image recording device equipped with a temperature controller for setting. 2. A heat using a fixing roller having a built-in heater, a pressure contact roller which is in pressure contact with the fixing roller and rotates in cooperation with the fixing roller, and a temperature sensor which is in close proximity and does not contact to detect the temperature of the outer peripheral surface of the fixing roller. In the roller type fixing device,
The temperature detected before the heater is turned on by the main switch being turned on, the elapsed time from the completion of warm-up, the fixing roller rotation time (the number of copies), etc. are detected, and based on the detection results,
An image recording apparatus equipped with a temperature controller that changes a control set temperature for turning on / off a heater in a plurality of ways. 3. A fixing roller having a built-in heater, and a pressure contact roller which is in pressure contact with the fixing roller and rotates in cooperation therewith, and a temperature sensor is provided on the outer peripheral surface of the fixing roller or at a slight distance from the outer peripheral surface of the fixing roller. In a heat roller type fixing device that performs detection, the normal set temperature of the fixing roller is set to T
When the first and second set temperatures are T2 and the third set temperature is T3 (T1> T2 ≧ T3), when the fixing roller temperature reaches T2 from a temperature lower than T2 during copying, the control temperature is set to An image recording apparatus equipped with a temperature controller for switching from T1 to T3. Further, an image recording apparatus equipped with a controller that performs this switching control a plurality of times.