JP2001154531A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of reducing the frequency of the fluctuation of power voltage. SOLUTION: At the time of idling, when a first halogen heater lamp 210 is driven when the detected result of a first temperature detection means 330 becomes T1on or lower, the drive of the first halogen heater lamp 210 is stopped when it becomes T1off or higher which is a temperature higher than T1on, a second halogen heater lamp 220 is driven when the detected result of a second temperature detection means 340 becomes T2on or lower and the drive of the second halogen heater lamp 220 is stopped when it becomes T2off or higher which is the temperature higher than T2on, (T1off-T1on)>;(T2off-T2on) is defined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a heating roller and a pressure roller which presses against the heating roller, and allows a transfer material on which a toner image has been transferred to pass between the heating roller and the pressure roller. The present invention relates to a fixing device that thermally fixes the toner image on the transfer material.

[0002]

2. Description of the Related Art At present, a fixing device of a heat roller type used in an image forming apparatus such as a copying machine or a laser beam printer has a halogen heater lamp as a heating means inside, and a surface of the fixing device is separated from toner. It is composed of a heating roller provided with a coat layer for improving moldability, and a pressure roller having a surface made of a rubber layer.

[0003]

In the fixing device having such a configuration, since the power consumption of the heating means is large, when the heating means is turned on, an inrush current several times the steady-state current flows, and the current is supplied to the apparatus. There is a problem in that the voltage of the power supply drops.

When such a power supply voltage fluctuation occurs,
The fluorescent lamp in the room where the device is installed may flicker. In order to reduce such a phenomenon, it is effective to reduce the inrush current, and means for inserting a resistor in series when the heating means is turned on has been proposed.

[0005] However, such means has another problem that the cost is increased. The present invention has been made in view of the above problems, and an object of the present invention is to provide a fixing device in which the frequency of a power supply voltage fluctuates less.

[0006]

According to a first aspect of the present invention, there is provided an image forming apparatus comprising: a heating roller; and a pressure roller which is in pressure contact with the heating roller. A fixing device for passing a transfer material onto which an image has been transferred and thermally fixing the toner image to the transfer material, wherein the fixing device is provided in the heating roller, and mainly heats both end portions of the heating roller in a rotation axis direction. First heating means,
A second heating unit provided in the heating roller and mainly heating a central portion of the heating roller in a rotation axis direction, and a first temperature detection unit that detects a temperature of at least one end portion of the heating roller. Means, a second temperature detecting means for detecting the temperature of the central portion of the heating roller, and, when idling, drive the first heating means when the detection result of the first temperature detecting means becomes T1on or less. When the temperature becomes equal to or higher than T1off which is a temperature higher than T1on, the driving of the first heating unit is stopped, and the detection result of the second temperature detection unit is T2on.
When the following, the second heating means is driven, and the T2on
Control means for stopping the driving of the second heating means when the temperature becomes equal to or higher than the higher temperature T2off, (T1off-T1o
n)> (T2off−T2on).

At the time of idling, the control unit controls the first
When the detection result of the temperature detecting means of T
T1o which is a temperature higher than T1on by driving the heating means 1
When ff or more, stop driving the first heating means,
When the detection result of the second temperature detecting means is equal to or lower than T2on, the second heating means is driven, and when the detection result is equal to or higher than T2off which is a temperature higher than T2on, the driving of the second heating means is stopped. That is, the first and second heating means are driven by hysteresis control (on / off control) having an operation gap.

On the other hand, the amount of heat per unit time radiated from the heating roller to the outside air is larger at both ends than at the center in the rotation axis direction of the heating roller.
If the operation gap of the hysteresis control of the first heating means and the operation gap of the hysteresis control of the second heating means are the same, the ON / OFF cycle of the first heating means is shorter than that of the second heating means, and the power supply The frequency of the change of the voltage increases.

However, in the present invention, (T1off-T1on)> (T2of
f-T2on), that is, by setting the operation gap of the hysteresis control of the first heating means larger than the operation gap of the hysteresis control of the second heating means,
The on / off cycle of the heating means becomes longer, and the frequency of fluctuation of the power supply decreases.

According to a second aspect of the present invention, in the cross section of the heating roller according to the first aspect of the present invention, the first heating means and the first heating means are provided on one side with the rotation axis of the heating roller interposed therebetween. A fixing device provided with a temperature detecting means, and the second heating means and the second temperature detecting means provided on the other side.

Since the respective heating means and the temperature detecting means can be provided close to each other, the temperature controllability of the respective heating means is improved, and the operating gap for the hysteresis control of the respective heating means can be set large. The on / off cycle of the first and second heating means becomes longer, and the frequency of the voltage of the power supply decreases.

According to a third aspect of the present invention, in the first aspect of the present invention, there is provided a cleaning mechanism for cleaning the surface of the heating roller which has been pressed against the pressure roller, and the cleaning mechanism cleans the surface of the heating roller. The first and second temperature detecting means are provided so as to detect the surface of the heating roller before being pressed against the pressure roller, and further, in a cross section of the heating roller, the rotation axis of the heating roller is sandwiched. A fixing device provided with the first heating means on the side where the first and second temperature detecting means are provided, and the second heating means on the other side.

The cleaning mechanism cleans the
By providing the first and second temperature detection means to detect the surface of the heating roller before pressing against the pressure roller, the first and second temperature detection means on the surface of the heating roller Even in the case of a contact type in which contact is made, dirt on the detection section of the detection means can be reduced, and temperature controllability can be maintained for a long time.

Further, since the first heating means and the first temperature detecting means can be provided close to each other, the temperature controllability of the first heating means is improved, and the hysteresis control of the first heating means is improved. Since the operation gap can be set large, the ON / OFF cycle of the first heating means is lengthened, and the frequency of fluctuation of the power supply is reduced.

According to a fourth aspect of the present invention, in the pressure roller according to any one of the first to third aspects, the nip width between the heating roller and the heating roller is larger at both ends in the rotation axis direction.
A fixing device having an inverted crown shape wider than a central portion.

At the time of idling, since the ON / OFF cycle of the first heating means is set to be long, the contact width of the temperature at both ends in the rotation axis direction of the heating roller becomes large, and the fixing rate may be poor.

However, since the pressure roller has an inverted crown shape in which the nip width with the heating roller is wider at both ends in the rotation axis direction than at the center portion, both ends of the heating roller in the rotation axis direction are formed. Of the fixing temperature is widened to prevent the fixing rate at both ends from deteriorating.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to the drawings. (Overall Configuration) First, the overall configuration of the image forming apparatus provided with the fixing device of the present embodiment will be described with reference to FIG.

In FIG. 1, an image forming apparatus 1 includes an automatic document feeder (ADF) A and a document image reading unit B for reading an image of a document conveyed by the automatic document feeder A.
An image control unit C for processing the read document image; a writing unit D including a writing unit 12 for writing on an image carrier 10 formed of a photosensitive drum in accordance with the data after the image processing; Around the charging electrode 14,
An image forming section E including image forming means such as a developing means 16 composed of a magnetic brush type developing device, a transfer electrode 18, a separation electrode 20, and a cleaning means 21, and a tray for storing a transfer material (hereinafter, referred to as recording paper) P Paper storage means (hereinafter, referred to as
Storage section for 22, 24 (referred to as a paper feed tray or tray)
F etc.

The automatic document feeder A includes a document table 26,
The main components are a roller group including the roller R1 and a document transport processing unit 28 including a switching unit for appropriately switching the movement path of the document.

The original image reading section B is located below the original glass G and can move back and forth while maintaining the optical path length, and a fixed imaging lens (hereinafter, referred to as a lens).
33, a line-shaped image sensor (hereinafter referred to as CCD) 35, etc., and a writing unit D is a laser light source 40, a polygon mirror.
(Polarizer) 42 and the like.

The automatic document feeder A has a difference in configuration from the conventional automatic document feeder, but the principle is well known. The original image reading unit B, the writing unit D, and the image processing means (image carrying means) An image forming apparatus and an image forming process including a unit that forms a toner image on the body 10 and transfers the toner image onto a sheet) are well known.
The description is briefly given.

In addition, R10 shown on the front side of the transfer electrode 18 is a registration roller, H shown on the downstream side of the separation electrode is a fixing device (details will be described later), and the heating roller 91 is pressed against the heating roller 91. The recording paper P on which the toner image has been transferred is fixed between the heating roller 91 and the pressure roller 92, so that the toner image is thermally fixed on the recording paper P. You.

In the above configuration, a process for forming a toner image on the image carrier 10, transferring the toner image on a sheet, and then discharging the toner image to a paper discharge tray is as follows. In this specification, a transfer area where a transfer electrode is located may be referred to as an image recording unit.

A document (not shown) placed on the document table 26 is transported in the document transport processor 28, and slit exposure is performed by the exposure means L while passing under the roller R1. It is.

In this embodiment, the original table 26
The original placed on top is based on the center. The reflected light from the original is transmitted to the mirror units 30 and 3 at the fixed position.
Via 1 and lens 33, it is combined on the CCD and read.

The image information read by the document image reading section B is processed by the image processing means, encoded, and stored in a memory on the image control board C. Image data is
Called in accordance with the image formation, the laser light source 40 in the writing section D is driven in accordance with the image data, and the image carrier 10 is exposed.

Prior to this exposure, the direction of the arrow (counterclockwise)
The rotating image carrier 10 is provided with a predetermined surface potential by corona discharge of the charging electrode 14, but the exposure reduces the potential of the exposed portion in accordance with the exposure amount, and as a result, the static potential corresponding to the image data. An electrostatic latent image is formed on the image carrier 10.

The electrostatic latent image is reversely developed by the developing means 16 to be a visible image (toner image). On the other hand, the image carrier 10
Before the top end of the upper toner image reaches the transfer area, for example, one sheet P in the feed tray 22 is fed and conveyed, reaches the registration roller R10, and is regulated.

The sheet P has a toner image, that is, the image carrier 10.
The sheet is conveyed toward the transfer area by a registration roller R10 that starts rotating in synchronization so as to overlap the upper image area.

In the transfer area, the toner image on the image carrier 10 is transferred onto the sheet P by the bias of the transfer electrode, and the sheet P is separated from the image carrier 10 by the bias of the separation electrode 20. You.

Thereafter, the toner powder for forming the toner image is melted and fixed on the sheet P by heating and pressing of the fixing device H, and the sheet P is discharged via the paper discharge path 78 and the paper discharge roller 79 to the paper discharge tray T. The paper is ejected on top.

(Fixing Device) The configuration of the fixing device H will be described in detail with reference to FIGS. FIG. 1 is a side view of the fixing device H, and FIG. 2 is a configuration diagram viewed from the X direction in FIG.

In FIG. 1, reference numeral 191 denotes a cylindrical core (roller base) of the heating roller 91 having both open end faces.
A release layer 194 is formed on the outer peripheral surface of the metal core 191.

In this embodiment, the material of the core metal 191 is either aluminum or iron, and the material of the release layer 194 is PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), A resin having good releasability such as ethylene fluoride was used.

Further, the core metal 191 had a thickness of 2.0 mm or less, and the release layer 194 had a thickness of about 20 μm, thereby forming a thin structure.
Inside the heating roller 91, in cross section, a first halogen heater lamp 210 as a first heating unit is provided on one side of the rotation axis O, and a second heating unit is provided on the other side. The second halogen heater lamp 220 is provided.

The heating roller 91 and the pressing roller 92
Thus, the sheet P is nipped and conveyed in the direction of the arrow R. As shown in FIG. 2, the first halogen heater lamp 210 mainly heats both end portions (L1) in the rotation axis direction of the heating roller 91, and the second halogen heater lamp 220 In the direction, the central portion (L2) is mainly heated.

The pressure roller 92 has a structure in which a PFA tube is covered on the circumferential surface of foamed silicone rubber, and has a surface hardness (Asker C hardness) of 35 to 75. The pressing roller 92 applies the urging force of the spring 90 to apply a total load of 49 to the heating roller 91.
By pressing at 245245 N, the nip pressure between the pressure roller 92 and the heating roller 91 is 19600 Pa to 196000 Pa, and the nip passage time is 20 to 40 msec.

Further, the pressure roller 92 of the present embodiment
Has an inverted crown shape in which the nip width with the heating roller 91 is wider at both end portions (L1) in the rotation axis direction than at the center portion.

In the fixing device H of the present embodiment, as shown in FIG. 1, a first halogen heater lamp 210 is provided on the cross section of the heating roller 91 with the rotation axis of the heating roller 91 interposed therebetween. The heating roller 91 in the area L1
A first temperature detecting means 330 for detecting the temperature of the second halogen heater lamp 220 is provided on the side where the second halogen heater lamp 220 is provided.
A second temperature detecting means 340 for detecting the temperature of the heating roller 91 is provided.

In this embodiment, a thermistor is used as the temperature detecting means. In FIG. 2, 350 is an area
This is a fan as a cooling means for cooling the end of L2.

Returning to FIG. 1, the cleaning mechanism 100 for cleaning the surface of the heating roller 91 which has been pressed against the pressing roller 92 is a web 1 made of an aromatic polyamide nonwoven fabric.
01, a winding roller 105 for winding the web 101, and a web backup roller 10 for pressing the web 101 against the heating roller 91.
It consists of seven.

The take-up roller 105 is driven to rotate by a predetermined amount when an image is formed on a predetermined number of recording sheets P, so that an unused portion of the web 101 is pressed against the heating roller 91.

Next, the electrical configuration of the fixing device according to the present embodiment will be described with reference to FIG. FIG. 3 is a block diagram illustrating an electrical configuration of the fixing device shown in FIG. In the figure, reference numeral 310 denotes a first heating driving unit including a circuit for driving the first halogen heater lamp 210, and reference numeral 320 denotes a second driving heating unit including a circuit for driving the halogen heater lamp 220.

Reference numeral 500 denotes a control unit, which is a first temperature detecting means 3
30 and the second temperature detecting means 340.
When the power switch of the image forming apparatus main body is turned on, a start command sent from the image forming apparatus main body, and when the copy button of the image forming apparatus main body is turned on, the temperature information (t2) from the image forming apparatus main body is turned on. , The recording paper size information (W), and the set copy number information (I), and the first and second halogen heaters via the first and second heating driving means 310 and 320. The fan 350 is driven via the lamps 210 and 220 and the cooling driving means 360 and has a counter 501.

Next, the operation of the fixing device having the above configuration will be described with reference to FIGS.
This will be described with reference to FIG. First, the overall operation of the image forming apparatus will be described with reference to FIG. 4, which is a state transition diagram illustrating the overall operation of the image forming apparatus. When the power switch is turned on, a warm-up operation (state 1) is performed. When the warm-up is completed, an end flag is turned on, and an idling operation (state 2) is performed.

If there is a copy command during the idling operation, a copy operation (state 3) is performed.
The operation returns to the idling operation (state 2). Next, a warm-up operation, an idling operation, and a copy operation will be described.

(Warm-Up Operation) The warm-up operation of the fixing device shown in FIG. 1 will be described with reference to FIGS.

FIG. 5A is a flowchart showing the warm-up operation of the first halogen heater lamp, and FIG.
FIG. 6 is a flowchart showing a warm-up operation of the second halogen heater lamp, and FIG. 6 is a flowchart showing an end judgment operation of the warm-up operation.

As a warm-up operation, the control section 500 performs the three flows shown in FIGS. 5A, 5B and 6 every 200 msec. In the flow shown in FIG. 5A, the temperature information (t1) from the first temperature detecting means 330 is fetched,
The temperature (t1) of the region L1 of the heating roller 91 is compared with a predetermined temperature (T1) (Step 1).

The temperature (t1) of the heating roller 91 becomes a predetermined temperature (T1)
If lower, the first halogen heater lamp 210 is driven (step 2). If the temperature (t1) of the heating roller 91 is equal to or higher than the predetermined temperature (T1), the first halogen heater lamp 21
0 drive is stopped (step 3) and warm-up (W
U) The end flag 1 is turned on (step 4).

Similarly, in the routine shown in FIG. 5B, the temperature information (t2) from the second temperature detecting means 340 is fetched, and the temperature (t2) of the region L2 of the heating roller 91 and the predetermined temperature (T2 ) (Step 1).

The temperature (t2) of the heating roller 91 reaches a predetermined temperature (T2)
If lower, the second halogen heater lamp 220 is driven (step 2). If the temperature (t2) of the heating roller 91 is equal to or higher than the predetermined temperature (T2), the second halogen heater lamp 22
0 drive is stopped (step 3) and warm-up (W
U) The end flag 2 is turned on (step 4).

In the flow shown in FIG. 6, the WU end flag
It is checked whether both 1 and WU end flag 2 are on (step 1). If both are on, the WU end flag is turned on (step 2).

(Idling Operation) The idling operation of the fixing device shown in FIG. 1 will be described with reference to FIG. 7 which is a flowchart for explaining the idling operation.

When both the WU end flag 1 and the WU end flag 2 are turned on, the control section 500 checks whether or not the first halogen heater lamp 210 is being driven (step 1). If present, the first temperature detecting means 3
The temperature information (t1) from the first halogen heater lamp 210 is taken, and if the temperature is lower than the set temperature (T1off), the driving of the first halogen heater lamp 210 is continued. Stop (steps 2 and 3).

In step 1, if the driving of the first halogen heater lamp 210 is stopped, the temperature information (t1) from the first temperature detecting means 330 is fetched, and if the temperature is equal to or higher than the set temperature (T1on). If the first halogen heater lamp 210
Is stopped, and if the temperature is lower than the third set temperature (T1off), the first halogen heater lamp 210 is driven.
(Steps 4 and 5).

Note that (T1off)> (T1on). Next, the controller 500 checks whether or not the second halogen heater lamp 220 is being driven (step 6). If the second halogen heater lamp 220 is being driven, the temperature information (t2) from the second temperature detecting means 340 is obtained.
If the temperature is lower than the set temperature (T2off), the driving of the second halogen heater lamp 220 is continued, and the second set temperature (T2off) is continued.
2on) or more, the driving of the second halogen heater lamp 220 is stopped (steps 7, 8).

In step 6, if the driving of the second halogen heater lamp 220 is stopped, the temperature information (t2) from the second temperature detecting means 340 is fetched, and if the temperature is equal to or higher than the set temperature (T2on). If the first halogen heater lamp 210
Is stopped, and if the temperature is lower than the third set temperature (T2off), the second halogen heater lamp 220 is driven.
(Steps 9 and 10).

Note that the set temperature (T2off)> (T2on). That is, at the time of idling, the control unit 500 drives the first halogen heater lamp 210 when the detection result of the first temperature detecting means 330 becomes equal to or lower than the set temperature (T1on), and sets the set temperature higher than the set temperature (T1on). (T1off) or more, the driving of the first halogen heater lamp 210 is stopped, and the detection result of the second temperature detecting means 340 indicates that the temperature is equal to the set temperature (T2off).
on), the second halogen heater lamp 220 is driven, and the set temperature is higher than the set temperature (T2on) (T2of
f) When the above is reached, the driving of the second halogen heater lamp 220 is stopped. That is, the first and second halogen heater lamps 210 and 220 are driven by hysteresis control (on / off control) having an operation gap.

Then, (T1off-T1on)> (T2off-T2on). That is, the operating gap for the hysteresis control of the first halogen heater lamp 210 is set to be larger than the operating gap for the hysteresis control of the second halogen heater lamp 220.

Therefore, when T1off = T2off, T2on> T1on, the temperature change on the surface of the heating roller 91 during idling is as shown in FIG. In the figure, a solid line at the time of idling indicates a temperature change at a central portion of the heating roller 91 in the rotation axis direction, and a broken line indicates a temperature change at an end portion.

(Copying Operation) The copying operation of the fixing device shown in FIG. 1 will be described with reference to FIGS. 8 and 9, which are flowcharts for explaining the copying operation.

In FIG. 8, (a) is a flowchart showing the copying operation of the first halogen heater lamp, and (b) is a flowchart showing the copying operation of the second halogen heater lamp. 9A is a flowchart showing a driving operation of the fan, and FIG. 9B is a flowchart showing a stopping operation of the fan.

The control unit 500 performs the copying operation as shown in FIG.
The two flows shown in (a) and (b) are performed every 200 msec.
In the flow shown in FIG. 8A, the first temperature detecting means 33
The temperature information (t1) from 0 is taken in, and the temperature (t1) of the area L1 of the heating roller 91 is compared with a predetermined temperature (T1 ″) (step 1).

The temperature (t1) of the heating roller 91 reaches a predetermined temperature (T
1 ″), the first halogen heater lamp 210
(Step 2). If the temperature (t1) of the heating roller 91 is equal to or higher than the predetermined temperature (T1 ″), the driving of the first halogen heater lamp 210 is stopped (step 3).

Similarly, in the flow shown in FIG.
The temperature information (t2) from the second temperature detecting means 340 is fetched, and the temperature (t2) of the region L2 of the heating roller 91 and the predetermined temperature (T2) are taken.
2 ″) (step 1).

The temperature (t2) of the heating roller 91 reaches a predetermined temperature (T
2 ″), the second halogen heater lamp 220
(Step 2). If the temperature (t2) of the heating roller 91 is equal to or higher than the predetermined temperature (T2 ″), the driving of the second halogen heater lamp 220 is stopped (step 3).

Further, when there is a copy command, the control unit 500
Executes the flow of FIG. 9A once. In the flow shown in FIG. 9A, when a copy command is issued, the control unit 500 reads the size information (w) of the recording paper P (step 1), and determines the size (w) of the recording paper P to be passed. Predetermined size
(W: for example, B5 portrait) (step 2), and when the size (w) of the recording paper P to be passed is equal to or smaller than a predetermined size (W), the fan 350 is driven. (Step 3).

When there is a copy end command, the control unit 5
00 executes the flow of FIG. 9B once. In the flow shown in FIG. 9B, if there is a copy end command, the control unit 500 determines that the fan 350 is being driven (step
1), driving of the fan 350 is stopped (step 2).

According to the above configuration, the following effects can be obtained. (1) At the time of idling, at the time of idling, the control unit 500 drives the first halogen heater lamp 210 when the detection result of the first temperature detecting means 330 becomes equal to or lower than the set temperature (T1on), and sets the set temperature (T1on). When the temperature becomes higher than the set temperature (T1off), the first halogen heater lamp 2
10 is stopped, and when the detection result of the second temperature detecting means 340 becomes lower than the set temperature (T2on), the second halogen heater lamp 220 is driven, and the set temperature is higher than the set temperature (T2on) ( When T2off) or more, the driving of the second halogen heater lamp 220 is stopped. That is, the first and second halogen heater lamps 210 and 220 are driven by hysteresis control with an operation gap.

On the other hand, the amount of heat radiated from the heating roller 91 to the outside air per unit time is larger at the both end portions (L1) than at the center portion (L2) in the direction of the rotation axis of the heating roller 91. If the operation gap of the hysteresis control of the halogen heater lamp 210 is the same as the operation gap of the hysteresis control of the second halogen heater lamp 220, the first halogen heater lamp 210 is turned on and off more than the second halogen heater lamp 220. The period becomes shorter, and the frequency of the voltage of the power supply increases.

However, in this embodiment, (T1off-T1o
n)> (T2off-T2on), that is, by setting the operation gap of the hysteresis control of the first halogen heater lamp 210 to be larger than the operation gap of the hysteresis control of the second halogen heater lamp 220, The on / off cycle of one halogen heater lamp 210 is lengthened, and the frequency with which the voltage of the power supply fluctuates can be reduced.

(2) In the cross section of the heating roller 91, the first halogen heater lamp 210 and the first temperature detecting means 330 are provided on one side with the rotation axis O of the heating roller 91 interposed therebetween.
And a second halogen heater lamp 220 on the other side.
And the provision of the second temperature detecting means 340, the first halogen heater lamp 210 and the first temperature detecting means 33 are provided.
0, since the second halogen heater lamp 220 and the second temperature detecting means 340 can be provided close to each other, the temperature controllability of each of the halogen heater lamps 210 and 220 is improved, and each of the halogen heater lamps 21 and 220 is improved.
Since the operating gap of the hysteresis control of 0,220 can be set large, the first and second halogen heater lamps 21
The on / off cycle of 0,220 becomes longer, and the frequency of fluctuation of the power supply voltage can be reduced.

(3) Since the on / off cycle of the first halogen heater lamp 210 is set to be long during idling, the contact width of the temperature at both ends (L1) of the heating roller 91 in the rotation axis direction becomes large, and The rate may be bad.

However, the pressing roller 92 is
The nip width with respect to the both ends (L1) of the heating roller 91 in the direction of the rotation axis of the heating roller 91 is formed by an inverted crown shape in which both ends (L1) in the direction of the rotation axis are wider than the center part (L2).
The tolerance range for the fluctuation of the fixing temperature is widened, and it is possible to prevent the fixing rate at both ends (L1) from deteriorating.

The present invention is not limited to the above embodiment. For example, a fixing device having a configuration as shown in FIG. 11 may be used. In the figure, a cleaning mechanism 100 is shown.
The first and second temperature detecting means 330 and 340 are provided so as to detect the surface of the heating roller 91 which is cleaned by the heating roller 91 before being pressed against the pressing roller 92.

Then, in the cross section of the heating roller 91,
A first halogen heater lamp 210 is provided on the side where the first and second temperature detecting means 330 and 340 are provided, and a second halogen heater lamp is provided on the other side with the rotation axis O of the heating roller 91 interposed therebetween. 220 are provided.

According to such a configuration, the first and second sensors are cleaned so as to detect the surface of the heating roller 91 before being pressed against the pressure roller 92 by the cleaning mechanism 100.
By providing the temperature detection means 330 and 340 of
And the second temperature detecting means 330 and 340
Even if it is a contact type that comes into contact with the surface, the contamination of the detection unit of the detection means can be reduced, and the temperature controllability can be maintained for a long time.

Since the first halogen heater lamp 210 and the first temperature detecting means 330 can be provided close to each other, the temperature controllability of the first halogen heater lamp 210 is improved, and the first halogen heater lamp 210 is improved. Since the operation gap of the hysteresis control of the heater lamp 210 can be set large,
The on / off cycle of the first halogen heater lamp 210 is lengthened, and the frequency of power supply voltage fluctuation can be reduced.

[0081]

EXAMPLES The present inventor conducted the following experiments to confirm the effects of the present invention.

(Fixing device) Heating roller 91: outer diameter 27.5 mm, core metal wall thickness 0.8 mm, material is aluminum alloy, surface layer material is fluororesin, reverse crown 80μ Pressure roller 92: outer diameter 26.0 mm, material is Silicone sponge rubber, PFA tube coating, hardness 48 ° (AscerC, 4900mN load), reverse crown 100μm First halogen heater lamp 210: 425W (rated) Second halogen heater lamp 220: 475W (rated) L2 width about 200mm Nip load: 127.4 N Nip width: 4 mm at center, 4.5 mm at end Fixing linear velocity: 140 mm / sec (First experiment) As shown in FIG.
The operation gap of the hysteresis control between the halogen heater lamp 210 and the second halogen heater lamp 220 was set to 15 ° C.

In the experiment of No. 2, the operation gap for the hysteresis control of the first halogen heater lamp 210 was set to 20 ° C.
The operation gap for the hysteresis control of the second halogen heater lamp 220 was set to 15 ° C.

The flicker (short-time flicker value: Pst) of the flicker (short-time flicker value: Pst) weighted by reflecting the characteristics of the human eye (most sensitive to a change of about 10 Hz) is used to determine the degree of flickering of the illumination due to the fluctuation of the power supply voltage. The value was determined.

The voltage of the power supply fluctuates when the experiment of No. 2 is performed, that is, when the operation gap of the hysteresis control of the first halogen heater lamp 210 is set to be larger than the operation gap of the hysteresis control of the second halogen heater lamp 220. It was confirmed that the frequency decreased.

(Second Experiment) The relationship between the surface temperature of the heating roller 91 and the fixing rate in a fixing device using the heating roller 91 and the pressure roller 92 having an inverted crown shape was examined, and the results are shown in FIG. Show.

Since the nip width is wider at both ends in the direction of the rotation axis, the fixing rate is higher. Therefore, it was confirmed that even when the operation gap of the hysteresis control was set to be lower by 5 ° C., the fixing rate at both ends was substantially the same as the fixing rate at the center.

The fixing rate was determined by exposing a place having a reflection density of 1.0 on the sheet P on which the sample image was fixed, rubbing the sheet P left and right a predetermined number of times with a weight wound with cloth, and measuring the reflection density after rubbing.
It was determined as follows. Fixing rate (%) = ((reflection density after rubbing) /
(Reflection density before rubbing)) × 100

[0089]

As described above, according to the first aspect of the present invention, at the time of idling, the control unit sets the first temperature detection means to the first temperature detection means when the detection result becomes T1on or less.
T1of which is a temperature higher than the T1on
Stop the drive of the first heating means when f or more, drive the second heating means when the detection result of the second temperature detection means is T2on or less, the temperature is higher than T2on When T2off or more, the driving of the second heating means is stopped. That is, the first and second heating means are driven by hysteresis control (on / off control) having an operation gap.

On the other hand, the amount of heat radiated from the heating roller to the outside air per unit time is larger at both ends than in the center in the rotation axis direction of the heating roller.
If the operation gap of the hysteresis control of the first heating means and the operation gap of the hysteresis control of the second heating means are the same, the ON / OFF cycle of the first heating means is shorter than that of the second heating means, and the power supply The frequency of the change of the voltage increases.

However, in the present invention, (T1off-T1on)> (T2of
f-T2on), that is, by setting the operation gap of the hysteresis control of the first heating means larger than the operation gap of the hysteresis control of the second heating means,
The on / off cycle of the heating means becomes longer, and the frequency of fluctuation of the power supply decreases.

According to the second aspect of the present invention, since the respective heating means and the temperature detecting means can be provided close to each other, the temperature controllability of the respective heating means is improved.
Since the operation gap of the hysteresis control of each heating means can be set large, the ON / OFF cycle of the first and second heating means is lengthened, and the frequency of the voltage of the power supply is reduced.

According to the third aspect of the present invention, the first cleaning unit is configured to detect the surface of the heating roller before being pressed against the pressure roller by the cleaning mechanism.
And the provision of the second temperature detecting means,
Even if the second temperature detecting means is a contact type in which the temperature detecting means comes into contact with the surface of the heating roller, the contamination of the detecting portion of the detecting means can be reduced, and the temperature controllability can be maintained for a long time.

Further, since the first heating means and the first temperature detecting means can be provided close to each other, the temperature controllability of the first heating means is improved, and the hysteresis control of the first heating means is improved. Since the operation gap can be set large, the ON / OFF cycle of the first heating means is lengthened, and the frequency of fluctuation of the power supply is reduced.

According to the fourth aspect of the invention, since the on / off cycle of the first heating means is set to be long during idling, the contact width of the temperature at both ends in the rotation axis direction of the heating roller also becomes large, Fixing rate may be poor.

However, since the pressure roller has an inverted crown shape in which the nip width with the heating roller is wider at both ends in the rotation axis direction than at the center portion, the pressure roller has both ends in the rotation axis direction of the heating roller. Of the fixing temperature is widened to prevent the fixing rate at both ends from deteriorating.

[Brief description of the drawings]

FIG. 1 is a side view of a fixing device.

FIG. 2 is a configuration diagram viewed from an X direction in FIG. 1;

FIG. 3 is a block diagram illustrating an electrical configuration of the fixing device illustrated in FIG.

FIG. 4 is a state transition diagram illustrating the overall operation of the image forming apparatus provided with the fixing device according to the embodiment.

5 is a flowchart illustrating a warm-up operation of the fixing device illustrated in FIG. 1, wherein FIG. 5 (a) is a flowchart illustrating a warm-up operation of a first halogen heater lamp, and FIG. FIG. 5 is a flowchart showing a warm-up operation of the halogen heater lamp of FIG.

FIG. 6 is a flowchart illustrating an idling operation of the fixing device shown in FIG. 1 in the fixing device shown in FIG. 1;

FIG. 7 is a flowchart illustrating an idling operation of the fixing device illustrated in FIG. 1;

FIGS. 8A and 8B are flow charts illustrating a copy operation of the fixing device shown in FIG. 2, wherein FIG. 8A is a flow chart illustrating a copy operation of a first halogen heater lamp, and FIG. It is a flowchart which shows the copying operation | movement of a heater lamp.

9A and 9B are flowcharts illustrating a copy operation of the fixing device illustrated in FIG. 2, wherein FIG. 9A is a flowchart illustrating a fan driving operation, and FIG. 9B is a flowchart illustrating a fan stopping operation; is there.

FIG. 10 is a diagram illustrating an overall configuration of an image forming apparatus provided with a fixing device according to the present embodiment.

FIG. 11 is a configuration diagram of a fixing device illustrating another embodiment.

FIG. 12 is a diagram illustrating a temperature change on the surface of a heating roller during idling.

FIG. 13 is a diagram showing the results of a first experiment of the example.

FIG. 14 is a diagram showing the results of a second experiment of the example.

[Explanation of symbols]

 Reference Signs List 91 heating roller 92 pressure roller 191 core metal 210 first halogen heater lamp (heating means) 220 second halogen heater lamp (heating means) 330 first temperature detecting means 340 second temperature detecting means 500 control unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H033 BA31 BA48 BB18 BB30 CA02 CA48 5G065 BA00 BA04 GA04 JA07 KA02 KA05 LA07

Claims (4)

[Claims] An image forming apparatus comprising: a heating roller; and a pressure roller which is in pressure contact with the heating roller. A transfer material on which a toner image has been transferred passes between the heating roller and the pressure roller, and the toner image is transferred. A fixing device that thermally fixes to a material, provided in the heating roller, a first heating unit that mainly heats both end portions of the heating roller in a rotation axis direction, and provided in the heating roller, A second heating unit that mainly heats a central portion of the heating roller in the rotation axis direction; a first temperature detection unit that detects a temperature of at least one end portion of the heating roller; and a central portion of the heating roller. A second temperature detecting means for detecting the temperature of the first temperature detecting means, when idling, when the detection result of the first temperature detecting means is T1on or less, the first heating means is driven, T1off which is a temperature higher than the T1on When it is over, 1
The driving of the heating means is stopped, and the second heating means is driven when the detection result of the second temperature detection means is T2on or less, and the second heating means is driven when the temperature becomes higher than T2off which is higher than T2on. And a control unit for stopping the driving of the heating unit, wherein (T1off-T1on)> (T2off-T2on). 2. In the cross section of the heating roller, the first heating means and the first temperature detecting means are provided on one side with the rotation axis of the heating roller interposed therebetween, and the second side is provided on the other side. 2. The fixing device according to claim 1, further comprising a heating unit and the second temperature detecting unit. 3. A cleaning mechanism for cleaning the surface of the heating roller which has been pressed against the pressure roller, wherein the cleaning mechanism cleans the surface of the heating roller and presses the surface of the heating roller before being pressed against the pressure roller. The first and second temperature detecting means are provided so as to detect, and further, in a cross section of the heating roller, the first and second temperature detecting means are provided across a rotation axis of the heating roller. 2. The fixing device according to claim 1, wherein the first heating unit is provided on one side, and the second heating unit is provided on the other side. 3. 4. The pressure roller according to claim 1, wherein a nip width between the pressure roller and the heating roller is an inverted crown shape in which both end portions in the rotation axis direction are wider than a center portion.
The fixing device according to any one of the above.