JPH0580605A - Image heating device - Google Patents

Abstract

PURPOSE:To prevent defective traveling by providing a 2nd temperature detecting member at a different position from a 1st temperature detecting member in the longitudinal direction of a heating body and stopping image heating processing based on the detection output of the 2nd detecting member. CONSTITUTION:A heating layer 3 which is energized to generate heat is formed on a line along the longitudinal direction of a substrate 2 nearly in the center part of the rear surface of the substrate 2. Energizing electrodes(input terminals) 3a and 3b made of good electrically conductive material such as silver are provided at the left and the right ends of the heating layer 3. Then, the 2nd temperature detecting element 5B is provided at the different position from the 1st temperature detecting element 5A in the longitudinal direction of the heating body. Furthermore, an MPU 13 controls a heater driving circuit 14 at the time of fixing so that the detection output of the thermistor 5A may be a specified fixed value and controls energizing of the heating layer 3. When the detected temperature by the 2nd thermistor 5B exceeds a specified temperature, the image heating processing is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image heating apparatus for heating an image on a recording material, and more particularly to an image heating apparatus suitable for an apparatus for heating and fixing an unfixed image on a recording material.

[0002]

2. Description of the Related Art As an image heating apparatus that heat-fixes an unfixed image and modifies the surface property of the image, a heat roller system in which a recording material supporting an image is sandwiched and conveyed by a heating roller and a pressure roller is widely used. The

In such a heat roller system, the thickness of the core metal of the heat roller is becoming thinner in order to increase the temperature rising rate of the heat roller.

Further, Japanese Patent Laid-Open No. 63-313182,
Japanese Patent Application Laid-Open No. 2-157878 proposes a heat fixing device using a thermal head having a low heat capacity and a film sliding on the thermal head.

This heat fixing device has an energization heat generating layer along a direction orthogonal to the moving direction of the recording material, and current is applied to the entire energization heat generating layer regardless of the size of the recording material.

[0006]

In the image heating apparatus using a heating roller or a thermal head having a very thin cored bar, the temperature rise in the non-sheet passing portion occurs outside the width of the recording material.

Particularly, when a recording material having a width smaller than the maximum size is continuously fed, the temperature rise in the non-sheet passing portion is large.

When the temperature rise in the non-sheet passing portion becomes large, the image heating apparatus becomes abnormal, deteriorates, or is seriously damaged.

Further, in the image heating apparatus using the above-mentioned film, wrinkles and meanders are generated in the film due to a large temperature difference between the paper passing portion and the non-paper passing portion.

[0010]

SUMMARY OF THE INVENTION The present invention which solves the above problems includes a heating body provided along a direction intersecting a moving direction of a recording material for heating an image on a moving recording material,
An image heating apparatus having a first temperature detecting member that detects the temperature of the heating body, and an energization control unit that controls energization to the heating body so that the detection temperature of the first temperature detecting member is constant. In the above, in the longitudinal direction of the heating element, a second temperature detecting member provided at a position different from the first temperature detecting member,
And a pausing means for pausing the image heating process based on the temperature detected by the second temperature detecting member.

[0011]

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

FIG. 2 shows a schematic structure of an example of an image forming apparatus using the fixing device 60 of the embodiment of the present invention.

The image forming apparatus of this embodiment is a fixed original-moving optical system type, a rotating drum type, and a transfer type electrophotographic copying apparatus.

When the original 19 is placed on the fixed original glass 20 and the required copying conditions are set and the copy start key is pressed, the photosensitive drum 39 is rotated by a predetermined amount in the clockwise direction indicated by the arrow. It is driven to rotate at speed.

Further, the light source 21 (22 is a reflection shade) and the first mirror 23 move forward along the lower surface of the original table glass 20 from the home position on the left side of the glass to the right side of the glass at a predetermined speed V, and the second mirror. When the third mirrors 24 and 25 move forward in the same direction at a speed of V / 2, the downward image surface of the document 19 placed on the document glass 20 is illuminated and scanned from the left side to the right side, and the illumination scanning is performed. The light reflected from the document surface is formed by the imaging lens 2
9. Imaging exposure (slit exposure) is performed on the surface of the rotating photosensitive drum 39 through the fixed fourth to sixth mirrors 26, 27, and 28.

Prior to this exposure, the surface of the rotating photosensitive drum 39 is uniformly charged to a predetermined positive or negative potential by the primary charger 30, and the charged surface is subjected to the above-mentioned exposure. Then, an electrostatic latent image having a pattern corresponding to the original image is sequentially formed on the surface of the drum 39. Photosensitive drum 3
The electrostatic latent image formed on the 9th surface is visualized as a toner image by the developing roller 32 of the developing device 31.

On the other hand, the transfer material sheet P as a recording material is fed by the paper feed roller 61 and is introduced into the transfer portion between the drum 39 and the transfer charger 34 at a predetermined timing through the guide 33 and transferred. Drum 39 by receiving corona
The toner visible image on the side of the drum 39 is sequentially transferred to the surface of the sheet P.

The sheet P that has passed through the image transfer portion has a charge eliminating needle 35.
While being discharged by the rear surface charges by the drum 39, they are sequentially separated from the surface of the drum 39, are introduced into the fixing device 60 by the transport unit 38 and the entrance guide 10, and are subjected to toner image fixing as described later, and are discharged as an image-formed product as a discharge guide. 12, discharge roller pair 4
0 is discharged outside the machine.

The surface of the drum 39 after the transfer is the cleaning device 3
A cleaning blade 37 of No. 6 removes stains such as residual toner to form a clean surface, and is repeatedly used for image formation.

When the movable optical members 21 to 25 that have reciprocally moved reach a predetermined forward movement end point, they are returned to the initial home position and return to the initial home position, and wait until the start of the next copy cycle (back stroke of the optical system). ).

If a plurality of (for example, 100) copies are designated before the copy start key is pressed,
After the back stroke of the optical system is completed, the microcomputer MPU shown in FIG. 3 repeats the above steps at predetermined intervals to continuously form an image.

Next, the fixing device 60 which is the image heating device of the embodiment of the present invention will be described.

FIG. 1 is a side sectional view of the fixing device 60.

Reference numeral 6 denotes a fixing film in the form of an endless belt, which includes a driving roller 7 for rotating and driving the fixing film on the left side of the figure, a driven roller 8 which is driven and rotated by the fixing film on the right side, and between these rollers 7, 8. It was fixedly arranged below. The low heat capacity linear heater 1 is suspended and stretched between the three members 7, 8 and 1.

The driven roller 8 also serves as a tension roller for applying tension in the direction in which the fixing film 6 is stretched outward.

The fixing film 6 has a surface thereof covered with a rubber layer such as silicon rubber to rotate in a clockwise direction of the driving roller 7 having a higher friction coefficient, and thus, the fixing film 6 has a predetermined peripheral speed in a clockwise direction to wrinkle or meander. It is driven to rotate without any speed delay.

Reference numeral 9 denotes a heater, a fixing film, a pressure roller for applying pressure between the recording materials, and a pressure roller having an elastic layer such as silicone rubber having a good releasability,
The endless belt-shaped fixing film 6 is sandwiched between the heater 1 and the lower surface of the heater 1 is pressed against the lower surface of the heater 1 by a biasing means such as a spring with a contact pressure of 5 to 10 kg. , And rotates in the counterclockwise direction in the drawing, which is the forward direction of the sheet P conveyance direction.

Since the endless fixing film 6 which is rotationally driven is repeatedly subjected to heat fixing of the toner image, it is excellent in heat resistance, releasability and durability, and is generally 100.
A thin wall having a thickness of less than or equal to μm, preferably less than or equal to 40 μm is used. As an example, a highly heat-resistant resin such as polyimide, polyetherimide, polyethersulfone, or polyetheretherketone having a thickness of 20 μm, or a thin-walled enterless belt made of metal such as nickel or SUS may be coated with PTFE.
(Tetrafluoroethylene resin), PFA (Tetrafluoroethylene / Perfluoroalkyl vinyl ether copolymer resin)
Or a resin having a low surface energy, or a conductive material such as carbon black was added to these resins. An endless belt having a total thickness of 30 μm, in which a releasable coat layer is applied to a thickness of 10 μm.

The heater 1 having a low heat capacity has, for example, a thickness of 1.
A resistive material such as silver palladium ruthenium oxide having a thickness of 10 μm and a width of 1.0 mm is applied to an alumina substrate 2 having a good thermal conductivity of 0 mm, a width of 10 mm, and a longitudinal length of 340 mm to form a heating layer 3, and 10μm thick film 6 on top
A protective layer 4 made of glass or the like is formed in consideration of sliding with respect to, and is fixedly supported by being attached and held to the heater support 11.

The heater support 11 has a heat insulating property, a high heat resistance, and a rigidity for adiabatically supporting the heater 1 with respect to the fixing device 60 and the image forming apparatus. For example, PPS (polyphenylene sulfide), PEEK (polyether). (Ether kettle), a liquid crystal polymer or other high heat resistant resin, or a composite material of these resins and ceramics, metal or the like.

The heating layer 3 of the heater is energized from both ends in the longitudinal direction.

The power supply is 100 V AC, and the back surface of the substrate 2 is adhered, pressure-bonded or integrally formed with a heat conductive silicon adhesive or the like. Energization is controlled by the microcomputer MPU13 (FIG. 3) so that the temperature detected by the temperature detecting element 5 such as an NTC thermistor is maintained at a predetermined constant temperature.

FIG. 3 is a side view of the heater 1 as seen from the paper feed side. The heat generating layer 3 that generates heat when energized is formed in a straight line along the length of the substrate in the substantially central portion of the lower surface of the substrate 2.
Reference numerals 3a and 3b denote current-carrying electrodes (input terminals) made of a good conductive material such as silver provided at the left and right ends of the heat generating layer 3.

E is the effective total length area of the heat generating layer 3 between the electrodes 3a and 3d. In the case of this example, the maximum size transfer material sheet that can be supplied to the apparatus and used is a length corresponding to A3 size (width 297 mm). It is set to the size.

In the image forming apparatus shown in FIG. 2, the base line a on the left end side of the heat generating layer 3 is used as a reference. Transfer material sheets of various sizes are supplied on a so-called one-sided basis.

The paper passing area C of the A6 size (width 105 mm) is shown in FIG.
It is a sheet passing area of the smallest size recording material that can be used in the image forming apparatus shown in FIG.

Reference numeral 5A is a thermistor which is a temperature detecting element provided in the minimum sheet passing area.

At the time of fixing, the MPU 13 controls the heater driving circuit 14 so that the detection output of the thermistor 5A becomes a predetermined constant value, and controls the power supply to the heat generating layer 3.

Reference numeral 5B denotes a thermistor which is a temperature detecting element provided outside the minimum paper passing area, and is arranged in the maximum paper passing area e in the present embodiment and further outside the paper passing area d of the B4 plate (width 257 mm). is there.

Next, the fixing operation of the first sheet will be described.

After the image forming apparatus starts the image forming operation by the image forming start signal, the fixing film 6 is rotated and the heater 1 is energized at a predetermined timing.

The transfer material sheet P having an unfixed toner image T on its upper surface, which is a recording material, is conveyed from the transfer section 34 to the fixing device 60. The sheet P is guided by the inlet guide 10 and enters into the pressure contact portion N between the heater 1 that has rapidly heated to a predetermined fixing temperature and the pressure roller 9 with the unfixed toner on the heater side in close contact with the fixing film 6. To do.

The sheet P is overlapped with the moving and fixing film 6 without causing surface deviation or wrinkling, and the heater 1
And passing through the fixing nip portion N between the pressure roller 9 and the pressure roller 9.

The toner image bearing surface of the sheet P receives the heat of the heating element 3 through the fixing film 6 while passing through the fixing nip portion N in a pressure fixing state on the fixing film surface, and the toner image is melted at a high temperature. To soften and adhere to the sheet 6 surface.

In the apparatus of this embodiment, the recording material sheet P and the fixing film 6 are separated from each other when the sheet P passes through the fixing nip portion N and comes out.

At the time of this separation, the temperature of the molten toner Ta is still higher than the glass transition point of the toner.

Since the toner Ta at a temperature higher than the glass transition point at this separation point has appropriate rubber characteristics, the toner image surface at the time of separation does not follow the surface of the fixing film and has an appropriate uneven surface property. Since the surface property is maintained and the toner image is cooled and solidified, an excessive image gloss is not generated on the fixed toner image surface, and a high quality image is obtained.

The sheet P separated from the fixing film 6 is guided by the sheet discharge guide 12 and, while reaching the sheet discharge roller pair (40), the temperature of the toner Ta higher than the glass transition point is naturally lowered (natural cooling). Then, the temperature reaches a temperature below the glass transition point, solidification Tb is reached, and the image-fixed sheet P is output.

Next, the operation sequence during continuous image formation will be described.

FIG. 4 shows the timing when the image formation start signal is on and the sheet P passes through the fixing nip portion N when a plurality of copies (for example, 100 copies) is set before the copy start key is pressed. Timing (“Yes”)
(When the sheet P is passing, when nothing is passing)
2 is a diagram in which the two timing cute, the temperature T ₁ detected by the first thermistor 5A, and the temperature T ₂ detected by the second thermistor 5B are plotted along the same time axis.

The image forming start signal of the present embodiment is a signal from the microcomputer MPU 19 for starting the operation of the clutches (not shown) for controlling the operation of the sheet feeding roller 61 and the light sources 21 and 22, and the first image forming operation. This is a signal for making it take place.

In this example, B4 size (width 257 m
m), a sheet weighing 80 g / m ² and a speed of 100 m
Paper is passed at m / sec. In this example, the heater 1 is supplied with a predetermined power corresponding to the value of T ₁ so that the detection temperature T ₁ of the first thermistor 5B is maintained at a fixed fixing temperature T ₁ ′ (for example, 190 ° C.). It Copy key is time τ ₀
An image formation start signal is transmitted from the MPU 19 to each part of the image forming apparatus in the same manner as when the sheet P is pressed, and, for example, the sheet feeding roller 61 starts rotating and the sheet P is conveyed toward the transfer charger 34. At the same time τ ₀ , rotation of the film 6 of the fixing device and energization of the heater 3 are started.

At time τ ₁ , the sheet P of width B4 reaches the fixing P, but by that time, the thermistor detection temperatures T ₁ and T ₂ have reached from room temperature to T ₁ ′ at substantially the same speed. While the sheet P is passing through the nip N, T ₁ = T ₁ ′.
₂ rises above T ₁ ′ due to the so-called non-sheet passing portion temperature rise.

After staying in the nip N for a time t _c (= τ ₂ −τ ₁ ), the sheet exits the fixing nip N.

The image forming signal for the second sheet is generated from the MPU 19 after the time t ₀ (for example, 5 sec) from the copy key start, and the sheet P is fed. Then, the second sheet plunges into the nip N at time τ ₃ at a predetermined time t _i after the first sheet exits the nip N. After that, the above operation is repeated for a while.

The second thermistor detection temperature T ₂ rises during the sheet passing period t _{c and} falls during the interval period t _i .
In the macro, it gradually rises.

Then, after the image forming signal corresponding to the 53rd sheet is issued at the time τ ₄ , and at the time τ ₅ during the passage of the 52nd sheet P through the fixing nip N, the second thermistor 5B.
Detection temperature T ₂ is a predetermined temperature T ₂ ′ (240 ° C. in this example)
Reach

In this way, the temperature of the non-sheet passing portion rises, and the temperature detected by the second thermistor 5B in the non-sheet passing area is 50 from the fixing temperature T _1.
Microcomputer MPU when the temperature is higher than T ₂ ′
13 suspends the fixing operation.

That is, the image forming signal is not issued even when the time t ₀ has elapsed from the time τ ₄ . At time τ ₆ when a sensor (not shown) detects that the 53rd sheet P has undergone the fixing process at the speed Vp and passed through the nip, the heater 3 is deenergized,
A little later (about 0.3 to 10 seconds) time τ ₇
Then, the rotation of the drive roller 7 is stopped, so that the fixing film 6
Also stops running. In this example, if the fixing film 6 is stopped at the same time as the energization of the heater 3 is stopped (at time τ ₆ ), the fixing film 6 may thermally stick to the pressure roller 9, so that from time τ ₆ to time τ ₇ Until the fixing film 6 and the pressure roller 9 are idled without heating for a while, they are stopped. If there is no risk of clinging between the fixing film 6 and the pressure roller because the temperature of T ₂ ′ is sufficiently low, τ ₇
May be done simultaneously with τ ₆ .

Further, the microcomputer MPU13
When the temperature detected by the second thermistor becomes equal to or higher than T ₂ ′ and the fixing process of the sheet P which is being fixed at that time is completed,
A display indicating "waiting" is displayed on a display panel (not shown), and no key input by the operator is accepted during this display.

Also, during this period, the state of "waiting" is held in the MPU 13 even when the main body power is turned off.

If the detected temperature T ₂ > T ₂ ″ of the second thermistor (50 ° C. in this example) when the power is turned on again, the wait operation is continued.

After the fixing operation is stopped, at time τ ₈ , T ₂ drops to T ₂ ″.

At this time, the temperature T ₂ of the non-sheet passing portion and the temperature T ₁ of the sheet passing portion are substantially equal to each other due to heat dissipation and heat conduction in the longitudinal direction of the heater.

When T ₂ ≤T ₂ ″ at time τ ₈ , the microprocessor MPU 13 cancels the pause of the display and fixing operation indicating the wait state, and the MPU 19 automatically sends the 54th image formation start signal from the MPU 19. The image forming operation is restarted. After that, image formation and fixing processing for 100 sheets in total are performed.

[0066] However, when the T ₂ again 54 and subsequent sheets has exceeded the T ₂ 'is, go into hibernation process again in the manner described above, again T ₂ ≦
After cooling to T ₂ ″, the subsequent operation is restarted.

(Comparative Example) The fixing process was continued even when the detected temperature T ₂ of the second thermistor 5B became T ₂ ′ or higher.

T ₂ = 260 ° C. was obtained on the 100th sheet.

Then, the film is displaced to the higher temperature side,
The edge of the film was damaged.

Further, when 100 copies were repeated 20 times (a total of 2000 copies), the coating of the fixing film was damaged.

(Embodiment 2) In the first embodiment described above, the wait release temperature T ₂ ″ for releasing the suspension of the fixing operation is made variable.

In one continuous copy, T ₂ ≧ T ₂ ′ is satisfied a plurality of times, and when the idle process is performed a plurality of times, the wait release temperature T ₂ ″ is changed each time. That is, the wait release temperature for the second time is set lower than that for the first time.

Since the area around the heater is warmer during the second pause than during the first pause during continuous copying, the temperature at T ₂ is again T ₂ ≧ T ₂ ≧ at the same wait release temperature.
It takes a short time to reach T ₂ ′.

Therefore, the number of pauses can be reduced by lowering the wait release temperature for the second time than that for the first time.

Further, the wait release temperature may be changed according to the number of remaining copies at the time when T ₂ ≧ T ₂ ′. That is, if the number of remaining sheets is less than the predetermined number, the wait release temperature is raised.

[0076] Further, according to the rate of temperature increase T _2, varying the weights cancel the temperature T ₂ ''. Specifically, assuming that T ₂ ≧ T ₂ ′ at the time of copying the nth sheet, the wait release temperature is increased as the value of n is increased.

The pause time can be shortened without damaging the device or increasing the number of pause steps.

(Embodiment 3) It is preferable that the heat radiation of the heater is large during the time τ _{6 to} τ ₈ which is the rest period of the fixing operation.

Therefore, in this embodiment, the pressure contact force of the pressure roller 9 with respect to the heater 3 is reduced or released by a pressure release means (not shown) such as a solenoid at a predetermined time between times τ _{6 and} τ ₇ .

Then, the time τ _{8 at} which the suspension of the fixing operation is released
Then, the original pressurized state is restored again.

Heat dissipation from the heater is promoted, and the rest period can be shortened.

(Embodiment 4) FIG. 5 shows a timing chart of the fourth embodiment.

At time τ ₅ , the detected temperature T ₂ ≧ T ₂ ′ of the second thermistor 5B is reached, and at time τ ₆ , the energization of the heater 3 is stopped and the weight display is performed to suspend the image forming operation including the fixing process.

During this rest period, the drive roller 7 continues to rotate, so that the fixing film 6 also continues to run.

The pressure roller 9 also follows the fixing film 6 and continues to rotate.

At time τ ₉ , T ₂ ≦ T ₂ ″ and the image forming operation is restarted.

The convection heat radiation increases due to the rotation of the fixing film 6 and the pressure roller 9, and the temperature of the heater lowers quickly. Therefore, the down time can be shortened. Further, since the fixing film 6 and the pressure roller 9 are not brought into pressure contact with each other at a high temperature, sticking due to a heat factor of the fixing film 6 and the pressure roller 9 does not occur and the life of parts is extended.

(Embodiment 5) FIG. 6 shows a timing chart of the fifth embodiment of the present invention.

At time τ _10, which is a predetermined time after the time τ ₆ when the 53rd sheet has passed through the fixing nip, the pressure roller is separated from the fixing film by a pressure control means such as a solenoid (not shown). At time τ ₁₁ where T ₂ = T ₂ ″, the pressure of the pressure roller against the heater is restored and the image forming operation is restarted.

Since an air layer is interposed between the fixing film and the pressure roller, convective heat radiation from the fixing film increases. Therefore, the heat dissipation rate from the heater through the fixing film increases. Therefore, T ₂ can be lowered and the rest time can be shortened. Further, problems such as clinging between the fixing film and the pressure roller are eliminated. Further, since the sliding frictional force between the fixing film and the heater is reduced, it is possible to prevent the inner peripheral surface of the fixing film from being abraded due to the rotation during rest.

(Embodiment 6) Times τ _{10 to} τ ₁₁ in the fifth embodiment.
During the period, the rotation direction of the drive roller may be reversed by a drive transmission unit (not shown) including a clutch and the like. that time,
At time τ ₁₁ , the pressure may be restored after the rotation direction is restored again.

Regarding the longitudinal direction, a heater, a fixing film,
If there is a temperature difference in the drive roller, the fixing film tends to be displaced to the high temperature side in the configuration of this example. However, when the fixing film is rotated in the opposite direction, the tendency of displacement is reversed, so
The displacement of the fixing film can be adjusted by the method of this embodiment.

(Embodiment 7) FIG. 7 shows a sectional view of a seventh embodiment of the present invention.

In this embodiment, a fan 70 (in this embodiment, a clofa flow fan having blades arranged over substantially the entire area of the fixing film in the longitudinal direction) is arranged at the sheet discharge side position, and the fan 70 is provided over the entire area of the fixing film of the drive roller portion. I am trying to hit the cooling air.

FIG. 8 shows a timing chart of this embodiment.

At time τ ₁₀ , the fan is turned on almost simultaneously with the release of the pressure, and the temperature T ₂ detected by the second thermistor becomes T ₂ ″ or less. At time τ ₁₁ , the rotation of the fan is stopped at about the same time as the return of pressure.

Since the heat radiation of the heater through the fixing film which is running during the rest is promoted, the rest time can be further shortened.

In this embodiment, the fan is blown to the position of the drive roller, but the discharge side of the nip between the heater and the pressure roller may be cooled.

The cooling effect is further enhanced.

(Embodiment 8) FIG. 9 shows an eighth embodiment of the present invention.

In this embodiment, a plurality of fans are provided in the longitudinal direction of the heater, and at least one fan is provided in the non-sheet passing portion. The fan 70A is provided in the B4 paper passing area, and the fan 70B is provided in the B4 non-paper passing area including the second thermistor position.

Then, the temperature T ₂ ′ at which the fixing process is stopped is set to 2
It is set as low as 20 ℃.

FIG. 10 shows a timing chart of this embodiment.

During continuous copying, since the fan 70B cools the non-sheet passing portion in the longitudinal direction, the rising speed of T ₂ is small.

T ₂ ≧ T ₂ ′ (220 ° C.) is reached on the 52nd sheet.

An example in which T ₂ = T ₂ ′ is reached on the 52nd sheet will be shown.
At τ ₆ , stop energization, start rest, then at τ ₁₀ , fan 7 in the paper passage area
0A also turns on.

The fan 70A is turned off at τ ₁₁ where T ₂ ≤T ₂ ″.

The fan 70B is always on from the copy start to the end of the final copy.

Since the temperature rising rate of T ₂ is slow, T ₂ ′ may be lowered. Therefore, even if the large size paper is copied immediately after the temperature is raised from T ₂ to T ₂ ′, the toner offset does not occur in the range of | large size width−small size width |. Further, if the same T ₂ ′, the number of copies until T ₂ ≧ T ₂ ′ can be increased.

(Ninth Embodiment) FIGS. 11 and 12 are sectional views of an image forming apparatus according to a ninth embodiment of the present invention.

In this embodiment, the charging device 3 is provided above the fixing device 60.
A fan 72 for exhausting ozone generated at 0 and 34 is provided.

Reference numeral 71 is an ozone filter.

The fan 72 has the runner 72A fixed, and the casing 72B can be set to two positions in the rotational direction about the central axis of the runner 72A by a driving means (not shown). The casing 72B position in FIG. 11 is a position during image formation (hereinafter referred to as position A), and
The position of the second casing 72B is moved from the position of the rest period (hereinafter referred to as the position B) to the position A → the position B by rotating the casing about 120 ° counterclockwise in the figure and locking the position.

FIG. 13 is a timing chart of this embodiment.

The fan always rotates from copy-on. From time τ _{0 to} τ _10, the position of the casing is A ', and the fixing device is not exposed to the wind. At times τ _{0 to} τ ₁₁ , the casing position is B, and the rotating fixing film is blown with air, and cooling of the heater is promoted through the film.

According to this embodiment, it is not necessary to provide a special fan for cooling the fixing film.

(Embodiment 10) FIG. 14 shows a tenth embodiment of the present invention.

In this embodiment, a single fan 7C and wind shields 74A and 74B corresponding to the paper width provided between the fan opening and the fixing film are provided.

The wind shields 74A and 74B are retracted by the wind shield drive means including a stepping motor or a latching solenoid to obtain the same blowing condition as in the eighth embodiment.

It is also possible to provide a large number of wind shields in a form corresponding to the paper size, detect the paper passing size, and drive the wind shield at a position corresponding to the paper passing size.

(Embodiment 11) FIG. 15 is a side view of a heater showing an eleventh embodiment of the present invention.

In this embodiment, the thermistor 5A for constant temperature control is used.
Besides, a plurality of thermistors 5B, 5C, 5D and 5E are provided.

In particular, they are provided corresponding to each recording material size.

Then, the detected temperatures of the thermistors 5B to 5E are set to T _{2 to} T _5, and when any of T _{2 to} T ₅ becomes equal to or higher than T ₂ ′, the rest process is started.

In addition, a predetermined temperature detecting element is selected by a relay according to the paper passing size (for example, the thermistor in the non-paper passing area closest to the paper passing edge), and the temperature of the selected thermistor is set to T ₂ ′ or higher. When that happens, the rest process begins.

Further, in this embodiment, one thermistor is provided corresponding to each recording material size, but a plurality of thermistors may be provided.

(Embodiment 12) The degree of temperature rise in the non-sheet-passing portion varies depending on the sheet-passing size, particularly the distance from the sheet-passing edge.

Therefore, in this embodiment, the size of the recording material is detected by the size detecting means (not shown), and the value of the temperature T ₂ ′ at which the fixing operation is stopped is switched according to the detected size of the recording material.

In accordance with the above, the value of the temperature T ₂ ′ for changing the sheet passing interval during continuous image formation is switched.

That is, when B4 is fed, T ₂ ′ = 240 ° C., A ₄
T ₂ ′ = 235 ° C. when passing paper, T ₂ ′ = 225 when passing A6
The temperature at which the fixing operation is stopped is lowered when the distance between the paper feed edge and the second thermistor becomes large as the temperature rises.

Therefore, the maximum temperature on the heater surface is 255 ° C. when T ₂ = 240 ° C. when A6, which is the minimum size, is fed.
However, the maximum temperature on the heater surface can be kept low by switching the temperature at which the fixing process is stopped depending on the recording material size.

In the embodiments described so far, the temperature detected by the temperature detecting element outside the paper passing area of the smallest size recording material is compared with a predetermined temperature, and the heating process is stopped. An example will be described in which the heating process is stopped based on the difference between the temperature detected by the temperature detecting element and the temperature detected by the temperature detecting element outside the sheet passing area.

(Thirteenth Embodiment) FIG. 16 is a timing chart of a thirteenth embodiment of the present invention, in which a plurality of (for example, 100) copies are set before the copy start key is pressed, and B4 size (width 257 mm). At the time of continuous copying using a sheet with a weight of 80 g / m ² at 1) a graph of time change of the first thermistor detection temperature T ₁ and the second thermistor detection temperature T ₂ 2) rotation timing of the driving roller 7 3) microcomputer Timing of turning on a signal (hereinafter, referred to as an image formation start signal) for starting an operation of an optical system including a clutch (not shown) for controlling the operation of the paper feed roller 61 and the light source 21 from the MPU 4) P
Is passing (when "Yes" is passing,
"When nothing" has passed) is shown.

In this example, at least during the fixing process, the detected temperature T ₁ of the first thermistor 5B has a constant value T ₁ ′ (for example, 1).
90 ° C.), a predetermined electric power according to the value of T ₁ is supplied by the power source and the heater driving circuit.

At the same time when the copy key is pressed at time τ ₀ , an image formation start signal is transmitted from the MPU 19 to the paper feed roller, high voltage power supply, main motor drive circuit, optical system motor drive circuit and the like. Then, the engaging paper roller 61 starts to rotate,
The sheet P is conveyed toward the transfer charger 34. At the same time τ ₀ , in the fixing device 60, the energization of the heater 3 is started, the driving roller 7 is rotated, and the fixing film 6 starts running.

At time τ ₁ , the sheet P of B4 width reaches the fixing nip portion N. By then, the thermistor detection temperatures T ₁ and T ₂ have risen from room temperature to T ₁ ′ at substantially the same rate. While the sheet P passes through the nip N, T ₁ is kept at T ₁ ′, but T ₂ is T ₁ ′ due to so-called non-sheet passing portion temperature rise.
The sheet P exits the nip N after being further raised and staying in the nip N for a time Tc.

The image forming signal for the second sheet is issued from the MPU 19 after the time t ₀ (for example, 5 sec) from the copy key on, and the sheet P is fed. Then, after the first sheet has passed through the nip N, it enters the nip N at time τ ₃ at an interval of a predetermined time t _i . After that, the above operation is repeated for a while.

The second thermistor detection temperature T ₂ rises during the sheet passing period t _{c and} falls during the interval period t _i .
In the macro, it gradually rises. Therefore, the temperature difference T
_2- T ₁ also rises. Then, after the image forming signal corresponding to the 53rd sheet is issued at time τ ₄ , and while the 52nd sheet P is passing through the fixing nip N, time τ ₅
In addition, T ₂ −T ₁ (hereinafter referred to as Δ) reaches a predetermined value (50 deg in this embodiment).

Then, the image forming signal is not issued even when the time t ₀ has passed from the time τ ₄ and the 53rd sheet P has undergone the fixing process at the speed Vp and passed through the nip by a sensor (not shown). At the detected time τ ₆ , the energization of the heater 3 is stopped, and with a slight delay (about 0.3 to 10 seconds), the rotation of the drive roller 7 is stopped at the time τ _7, and the running of the fixing film 6 is also stopped. ..

Then, "Waiting" is displayed on the display panel, and the pause process is started.

Time τ ₈ when time T has passed from τ ₇ and temperature T ₂
Falls to T ₂ ″, at which point the difference Δ between the temperatures T ₂ and T ₁ (due to the longitudinal heat conduction and heat dissipation of the heater)
It is a sufficiently small value Δ ″ (for example, 10 deg). At time τ ₈ , the display of “waiting” is released, the image forming start signal for the 54th sheet is automatically issued from the MPU 19, and the image forming operation is restarted. After that, a total of 100 sheets of images are formed and fixed.
When Δ exceeds Δ ′, the resting process of time T is started again as described above, and then the operation is restarted.

[0142] A large difference and without comparing the predetermined value T ₂ also monitors the T ₂ -T ₁ for temperature T ₁ is always in continuous copying constant in this embodiment, then T ₂ An example in which it is effective to stop the heat treatment at the value of −T ₁ will be described.

(Embodiment 14) FIG. 17 is a timing chart showing the present embodiment.

[0144] When the 5 th sheets detected by the sheet discharge sensor (not shown) to time tau ₄ that has passed through the fixing nip portion, the target temperature T ₁ of the _{T 1 '(225 ℃) T} 1 from''( 190 ° C)
Can be lowered to. Since the heat capacity of the heater 1 is sufficiently small, the temperature T ₁ is quickly lowered to T ₁ ″ by reducing the electric power supplied to the heater 1. Along with that, the temperature of T ₂ also drops. Therefore, the value of Δ = T ₂ −T ₁ remains almost unchanged. The detected temperature T ₂ of the second thermistor gradually rises in macro view. On the other hand, since the temperature of T ₁ is accurately maintained, the value of T ₂ −T ₁ will increase. After the 53rd image forming signal is issued at time τ ₄ and while the 52nd sheet P is passing through the fixing nip portion N, at time τ ₅ , the value of Δ is a predetermined value Δ ′.
(Here 50 ° C.) is reached. Then, the 54th image forming signal is not issued even when the time t ₀ has elapsed from the time τ ₄ .

When the temperature of T ₁ changes in this way, T ₂ −T
It is effective to suspend the fixing process based on the value of ₁ .

Incidentally, when switching the temperature control of constant temperature control,
T ₂ T ₂ compared to -T ₁ rather than T ₂ '' may be changed according to the switching of the temperature adjustment temperature.

(Fifteenth Embodiment) FIG. 18 is a timing chart of the fifteenth embodiment of the present invention.

The second thermistor detection temperature T ₂ rises during the sheet passing period t _{c and} falls during the interval period t _i .
In the macro, it gradually rises. After the image forming signal corresponding to the 53rd sheet is issued at time τ ₄ , and while the 52nd sheet P is passing through the fixing nip N, at time τ ₅ , T ₂ is a predetermined temperature. T ₂ ′ (here 24
0 ° C) is reached.

Then, the image forming signal is not issued even when the time t ₀ has elapsed from the time τ ₄ . At time τ ₆ when a sensor (not shown) detects that the 53rd sheet P has undergone the fixing process at the speed Vp and has exited the nip, the heater 3 is de-energized and slightly delayed (0.3-). The rotation of the driving roller 7 is stopped at time τ ₇ and the running of the fixing film 6 is also stopped at the time τ ₇ to start the resting step.

A predetermined time T from τ ₇ (3 m in this embodiment)
in), "waiting" on the display panel (not shown)
Is displayed and during that time, no key input by the operator is accepted. Even if the power supply of the main body is turned off during that time, τ ₇ is generated by the clock (not shown) built in the MPU 19.
When the main switch is turned on again during the time T, the display and operation are continued. At time τ ₈ after lapse of time T from τ ₇ , the temperature T ₂ drops to T ₂ ″, but at this time, the difference between the temperatures T ₂ and T ₁ is almost isothermal (due to heat conduction and heat dissipation in the longitudinal direction of the heater). It has become. At time τ ₈ , the display of “waiting” is canceled and the 54th image formation start signal is automatically sent to MPU3.
Is emitted, and the image forming operation is restarted. 100 after that
The image formation and fixing process of the sheet are performed, but when T ₂ again exceeds T ₂ ′ after the 54th sheet, the resting step of time T is resumed as described above, and the operation is restarted after a predetermined time.

In this way, the heater and the film can be prevented from being damaged by restarting the operation after a predetermined time has passed from the start of the resting step.

Further, the start of the resting step may be performed by the value of T ₂ -T ₁ .

(Embodiment 16) When a pause process occurs a plurality of times during one continuous copy, the pause time generated after the pause process is lengthened.

In this embodiment, the first pause time is 3 minutes,
The rest time after the second time is 5 minutes.

[0155] Since than the first is better the second time has warmed up the peripheral heater, temperature it is of T ₂ again that's the same dwell time second time is the time until the T ₂ ≧ T ₂ 'short .. Therefore, the number of pause steps can be reduced by extending the pause time.

It is also preferable to shorten the rest time if the number of remaining sheets at the start of the rest step is small.

Further, depending on the temperature rise temperature of T ₂ , the rest time T
It is also preferable to change Specifically, assuming that T ₂ ≧ T ₂ ′ at the time of copying the nth sheet, the larger the value of n, the smaller the value of T.

Although the embodiments of the present invention have been described above, these embodiments may be appropriately combined.

[0159]

According to the present invention, it is possible to prevent the damage of the apparatus due to the temperature rise of the non-sheet passing portion and the defective running of the film due to the temperature difference in the longitudinal direction.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a fixing device that is an image heating device according to an exemplary embodiment of the present invention.

FIG. 2 is a schematic sectional view of an image forming apparatus using the apparatus of FIG.

FIG. 3 is a side view of the heater of the embodiment shown in FIG.

FIG. 4 is a timing chart of an example of the present invention.

FIG. 5 is a timing chart of another embodiment of the present invention.

FIG. 6 is a timing chart of another embodiment of the present invention.

FIG. 7 is a sectional view of an image heating apparatus according to another embodiment of the present invention.

FIG. 8 is a timing chart of another embodiment of the present invention.

FIG. 9 is a side view of another embodiment of the present invention.

FIG. 10 is a timing chart of another embodiment of the present invention.

FIG. 11 is a sectional view of an image forming apparatus according to another embodiment of the present invention.

12 is a cross-sectional view showing the rotation of the fan of the embodiment shown in FIG.

FIG. 13 is a timing chart of another embodiment of the present invention.

FIG. 14 is a side view of another embodiment of the present invention.

FIG. 15 is a side view of a heater according to another embodiment of the present invention.

FIG. 16 is a timing chart of another embodiment of the present invention.

FIG. 17 is a timing chart of another embodiment of the present invention.

FIG. 18 is a timing chart of another embodiment of the present invention.

[Explanation of symbols]

 1 Heater 5A First Temperature Detection Element 5B Second Temperature Detection Element 6 Fixing Film 7 Drive Roller 8 Driven Roller 9 Pressure Roller 60 Fixing Device

Claims (7)

[Claims] 1. A heating body provided along a direction intersecting a moving direction of a recording material for heating an image on a moving recording material, and a first temperature detecting member for detecting a temperature of the heating body. And an energization control unit that controls energization to the heating body so that the temperature detected by the first temperature detection member becomes constant. An image heating apparatus comprising: a second temperature detecting member provided at a position different from that of; and a suspending unit that suspends the image heating process based on the temperature detected by the second temperature detecting member. 2. The image heating apparatus according to claim 1, wherein the suspending means suspends the image heating process when the temperature detected by the second temperature detecting member exceeds a predetermined temperature. 3. The image heating apparatus according to claim 1, wherein the suspending means suspends the image heating process when the difference between the temperatures detected by the second and first temperature detecting members exceeds a predetermined value. 4. The image heating apparatus according to claim 2, wherein the pause means releases the pause of the image heating process when the temperature detected by the second temperature detecting member falls below a predetermined value. 5. The image heating apparatus according to claim 3, wherein the pause means releases the pause of the image heating process when the difference between the temperatures detected by the second and first temperature detecting members falls below a predetermined temperature. .. 6. The image heating apparatus according to claim 1, wherein the first temperature detecting member is arranged inside the minimum recording material passage area and the second temperature detecting member is arranged outside the minimum recording material passage area. .. 7. The apparatus further comprises a film which moves in contact with the recording material, and the image on the recording material is heated by the heat from the heating body through the film. 1 to 6 image heating device.