JP2002169413A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming device using a film heating type thermal fixing device in which high temperature offset and fixing slip or the like are prevented from occurring while preventing the excessive temperature rise of a paper non-passing part and maximizing the throughput of small-size recording material. SOLUTION: The thermal fixing device is provided with a temperature detection means 15 on the inside from maximum paper passing width and on the outside from minimum paper passing width, and the throughput is successively lowered such as P1, P2,...Pn (P1>P2>...>Pn) every time detected temperature by the detection means 15 exceeds thresholds T1, T2,...Tn (T1<T2<...<Tn). Furthermore, the throughput is successively increased such as P1, P2,...Pn (P1<P2<...<Pn) every time the detected temperature by the detection means 15 is lower than the thresholds T1, T2,...Tn (T1>T2>...>Tn). A temperature rise rate is detected by the detection means 15 and fixing temperature is made different in accordance with the detected result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a printer, a copying machine, a facsimile, and the like.

More specifically, the present invention relates to an improvement in an image forming apparatus using a film-heating type heat fixing device (fixing device) as a device for fixing an unfixed image formed and carried on a recording material.

[0003]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic system or an electrostatic recording system, as a heat fixing device for heating and fixing an unfixed image formed and carried on a recording material, a heat roller system or a film heating system is used. Is widely used.

In particular, a heat fixing device of a film heating type is disclosed in Japanese Patent Application Laid-Open No. 63-313182 and Japanese Patent Application Laid-Open No.
No. 7878, Japanese Patent Application Laid-Open No. 4-44075, Japanese Patent Application Laid-Open No. 4-204980, and the like, which does not supply power during standby and can minimize power consumption. It is effective as a device.

Basically, a fixing member having a heater (heating member, heating member) fixedly supported on a support, a heat-resistant thin-walled film (fixing film) sliding on the heater, and a fixing member And a pressure roller as a pressure member that forms a fixing nip by being in pressure contact with the heater through the fixing nip, and conveys the recording material on which the unfixed image is formed between the film of the fixing nip and the pressure roller. That is, the unfixed image is heated and fixed as a permanent image by the heat from the heater via the film.

Generally, a ceramic heater is used as the heater. For example, a ceramic substrate such as alumina (Al ₂ O ₃ ) / aluminum nitride (AlN) having electrical insulation, good thermal conductivity, and low heat capacity is used as a heater substrate, and silver palladium (Ag / Pd) · Ta ₂ N is provided on the surface thereof. Is formed by screen printing or the like, and the surface on which the current-generating resistance layer is formed is covered with a thin glass protective layer. In this ceramic heater, when current is applied to the current-carrying heat-generating resistor layer, the current-carrying heat-generating resistor layer generates heat, and the entire heater including the ceramic substrate and the glass protective layer rapidly rises in temperature. The temperature rise of the heater is detected by temperature detecting means arranged on the back of the heater, and is fed back to the power supply control unit. The energization control unit controls energization to the energization heating resistance layer such that the heater temperature detected by the temperature detection unit is maintained at a predetermined substantially constant temperature (fixing temperature). That is, the heater is heated and adjusted to a predetermined fixing temperature.

[0007]

When recording materials (hereinafter, referred to as paper) having different sizes (paper widths) are passed through the heat fixing device, the amount of heat taken from the heater is reduced in the paper passing portion and the non-paper passing portion. Therefore, the temperature of the non-sheet passing portion where the heat is not deprived by the paper is gradually increased as the sheet is passed. Excessive temperature rise in the non-sheet-passing section causes adverse effects such as uneven fixing and high-temperature offset of toner, which causes heat loss of the components of the heat fixing device and shortens the life of the device.

[0008] For this reason, a measure has been taken by reducing the throughput. Further, since the temperature rise of the non-sheet passing portion varies depending on the thickness of the paper, a method of reducing the throughput with the number of sheets that does not cause a problem even under the worst condition (small size thick paper, etc.) Attempts have been made to provide a member and reduce the throughput or the like when the temperature reaches a predetermined temperature.

However, as described above, the temperature rise in the non-sheet passing portion differs depending on the thickness of the paper. In other words, thick paper must be passed at a low throughput, and thin paper can be passed at a relatively high throughput. There has been a problem that the temperature of the paper portion is excessively increased, and the throughput of thin paper is unnecessarily reduced.

In particular, in the on-demand fixing device of the film heating type, the fixing film and the pressure roller are constituted by members having a small heat capacity in order to enable quick start, so that the temperature rise phenomenon of the non-paper passing portion appears remarkably. . Therefore, when a recording material having a width smaller than the maximum width that can be passed through the fixing device is passed, the following problem occurs.

For example, in a fixing device in which the maximum paper width is such that the A4 size recording material is passed vertically,
When the recording material of the size is passed in the vertical direction, in the non-paper passing area where the recording material is not passed in the fixing nip portion,
The balance between the amount of heat generated by the heater and the amount of heat taken by the recording material is lost, so that the temperature of the end portion of the non-sheet passing portion is increased in the fixing film or the pressure roller formed of a member having a small heat capacity.

Immediately after such an edge temperature rise, when a recording material (A4 size in this case) having the maximum sheet passing width is passed, the fixing nip where the edge temperature rise of the non-sheet passing portion occurs. In the section, the excessive supply of heat to the recording material causes the toner image on the recording material in the fixing nip to separate from the fixing film without separating from the fixing film and to remain on the fixing film surface. In other words, a high-temperature offset appears as an offset image on the recording material after one rotation of the fixing film, or a large amount of water vapor is generated from the recording material present in the fixing nip. , The recording material is not conveyed at a predetermined conveyance speed, that is, a so-called fixing slip occurs. This phenomenon is remarkable in a recording material left in a high-temperature environment or a high-humidity environment.

The present invention has been proposed in view of the above,
The above-mentioned problems in the image forming apparatus using the heat fixing device of the film heating type are solved, that is, the excessive non-paper-passing portion temperature is prevented, while maximizing the throughput of the small-size recording material, An object is to prevent occurrence of offset, fixing slip, and the like.

[0014]

SUMMARY OF THE INVENTION The present invention is an image forming apparatus having the following configuration.

(1) A fixing member having a heater, a film which slides on the heater, and a pressing member which presses the heater through the film to form a fixing nip. An image forming apparatus having a heat fixing device for nipping and conveying a recording material having an unfixed image formed between pressure members and fixing the unfixed image as a permanent image on the recording material by heat from a heater via a film , The heat fixing device has temperature detecting means inside the maximum paper passing width and outside the minimum paper passing width, and the temperature detected by the temperature detecting means is equal to threshold values T1, T2,... Tn (T1 <T2). <
... <Tn) every time the throughput exceeds P1, P
2,... Pn (P1> P2 >>...> Pn).

With the above-mentioned characteristic configuration, it is possible to converge to the final throughput corresponding to the paper thickness (thickness of the recording material), to prevent an excessive temperature rise in the non-paper passing portion, and to adjust to the paper thickness. Throughput can be maximized.

(2) A fixing member having a heater, a film which slides on the heater, and a pressing member which presses the heater through the film to form a fixing nip. An image forming apparatus having a heat fixing device for nipping and conveying a recording material having an unfixed image formed between pressure members and fixing the unfixed image as a permanent image on the recording material by heat from a heater via a film , The heat fixing device has temperature detecting means inside the maximum paper passing width and outside the minimum paper passing width, and the temperature detected by the temperature detecting means is equal to threshold values T1, T2,... Tn (T1> T2). >
...> Tn), the throughput is reduced to P1, P
2,... Pn (P1 <P2 <... <Pn).

According to the above-mentioned characteristic configuration, it is possible to further maximize the throughput and to prevent an excessive rise in the temperature of the non-sheet passing portion.

(3) The image forming apparatus according to (1) or (2), wherein a temperature rise rate is detected by the temperature detecting means, and the fixing temperature is changed according to the detection result.
It is.

With the above-mentioned characteristic configuration, the throughput of thin paper can be further improved.

(4) A fixing member having a heater, a film that slides on the heater, and a pressing member that presses the heater through the film to form a fixing nip. An image forming apparatus having a heat fixing device for nipping and conveying a recording material having an unfixed image formed between pressure members and fixing the unfixed image as a permanent image on the recording material by heat from a heater via a film Wherein the heat fixing device has a fixing temperature detecting means inside the maximum paper passing width and outside the minimum paper passing width, and has an outside air temperature detecting means for detecting an ambient temperature in which the image forming apparatus is installed; An image forming apparatus characterized in that a conveyance interval between recording materials is switched in a plurality of stages in accordance with detection temperatures of a temperature detection unit and an outside air temperature detection unit.

With the above-described characteristic configuration, in order to suppress the temperature rise at the end of the non-sheet passing portion which occurs when a recording material having a width smaller than the recording material having the maximum sheet passing width in the image forming apparatus is passed, If the temperature detected by the outside air temperature detecting means is high, the time when the recording material is not present in the fixing nip is extended by increasing the conveyance interval between the recording materials, and during that time, As well as stopping the power supply to the heater and moving the heat in the longitudinal direction between the fixing member and the pressing member, it is possible to suppress the temperature rise at the end of the non-sheet passing portion to be small. In this case, it is possible to prevent the recording material from being conveyed at a predetermined speed, which may be caused by the rise in the temperature of the end portion of the recording medium.

(5) A plurality of fixing temperature detecting means are provided in the longitudinal direction of the heater, and one of them is provided inside the maximum paper passing width and outside the minimum paper passing width, and the detected temperature is the threshold temperature. The image forming apparatus according to (4), wherein the transport interval between the recording materials is switched to a plurality of stages each time T1, T2,..., Tn is reached.
It is.

(6) The heater has a current-carrying resistance layer,
The image forming apparatus according to any one of (1) to (5), wherein the image forming apparatus generates heat by energizing the energizing heat generating resistance layer.
It is.

(7) The image according to any one of (1) to (5), wherein the heater is an electromagnetic induction heating member, and generates heat by a magnetic field generated by a magnetic field generating means that generates a magnetic field when energized. Forming device.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment (1) Example of Image Forming Apparatus FIG. 1 is a schematic structural model of an example of an image forming apparatus according to the present invention. The image forming apparatus of this example is a laser beam printer using a transfer type electrophotographic process, and has a process speed of 151 mm / s and a throughput of 24 ppm (A
4).

Reference numeral 1 denotes a photosensitive drum serving as an image carrier;
A photosensitive material such as C, amorphous Se, amorphous Si or the like is formed on a cylindrical base such as aluminum or nickel.

The photosensitive drum 1 is driven to rotate in the clockwise direction of the arrow at a predetermined peripheral speed, and its surface is uniformly charged by a charging roller 2 as a charging device.

Next, an image exposure L by a laser scanner 3 as an image exposure device is received. Laser scanner 3
Outputs a laser beam that is ON / OFF modulated and controlled in accordance with a time-series electric digital pixel signal of image information, and performs scanning exposure L on the charged surface of the rotating photosensitive drum 1. This scanning exposure forms an electrostatic latent image of image information on the photosensitive drum 1.

The electrostatic latent image is developed as a toner image by the developing device 4 and is visualized. As a development method, a jumping development method or the like is used, and in many cases, a combination of image exposure and reversal development is used.

On the other hand, a recording material (transfer material) P is fed one by one from a paper feed mechanism (not shown), and a predetermined amount is transferred to a transfer nip portion which is a press contact portion between the photosensitive drum 1 and a transfer roller 5 as a transfer device. Is supplied at the control timing of. In the transfer nip portion, the toner image on the photosensitive drum 1 is transferred to the recording material P by the action of a transfer bias from a power supply (not shown).

The recording material P that has passed through the transfer nip is separated from the surface of the photosensitive drum 1 and transported to the fixing device 6 while holding the toner image. The image is fixed on the recording material P to become a permanent image, and is discharged outside the apparatus.

On the other hand, the transfer residual toner remaining on the surface of the rotary photosensitive drum 1 after the recording material is separated is removed by a cleaning device (cleaner) 7 and is repeatedly used for image formation.

(2) Fixing Device 6 FIG. 2 is an enlarged schematic cross-sectional view of the fixing device 6. The fixing device 6 of the present example is disclosed in Japanese Patent Application Laid-Open Nos. 4-44075-44083,
JP-A-204980-204984 discloses a fixing device of a film heating type and a rotary driving type driving device (tensionless type) using a cylindrical (endless belt-shaped) fixing film.

Reference numeral 10 denotes a fixing member (fixing unit), and reference numeral 20 denotes a pressing roller as a pressing member.

The fixing member 10 is a member having a longitudinal direction perpendicular to the drawing, and is a heat-insulating stay holder (film holder) 12 having a heat resistance and rigidity having a substantially semicircular trough cross section.
On the lower surface of the heat insulating stay holder 12, a heater (heating body) 11, which is fitted and fixed in a concave groove provided along the length of the member and which generates heat by energization, and a heater 11 are attached. It is composed of a cylindrical heat-resistant fixing film 13 loosely fitted to the heat-insulating stay holder 12 or the like.

The pressure roller 20 includes a core 21 and an elastic layer 22 formed concentrically and integrally on the core with heat resistant rubber such as silicone rubber or fluorine rubber or foamed silicone rubber. It is a rotating body composed of an elastic layer. A heat-resistant release layer 23 made of a fluororesin such as PFA, PTFE, or FEP may be formed on the elastic layer 22.

The pressure roller 20 is disposed such that both ends of a core 21 are rotatably supported between front and rear side plates of an apparatus chassis (not shown) via a bearing member.

The fixing member 10 is disposed above the pressure roller 20 in parallel with the pressure roller 20 with the heater 11 facing downward, and both ends of the heat insulating stay holder 12 are pressed by a spring or the like (not shown). By urging the pressing roller 20 in the axial direction with the urging member, the downward surface of the heater 11 is fixed to the elastic layer 22 of the pressing roller 20 via the fixing film 13 against the elasticity of the elastic layer. To form a fixing nip portion N having a predetermined width. It is also possible to adopt a configuration in which the pressure roller 20 side is pushed up and pressed against the lower surface of the fixing member 10 by a pressure urging member to form a fixing nip portion N having a predetermined width.

The pressing roller 20 is driven to rotate at a predetermined peripheral speed in a counterclockwise direction indicated by an arrow by a driving means M. The rotational force acts on the cylindrical fixing film 13 by the frictional contact between the outer surface of the pressing roller 20 and the fixing film 13 at the fixing nip portion N due to the rotational driving of the pressing roller 20, and the fixing film 13 is removed. While the inner surface side is in close contact with the downward surface of the heater 11 and slides, the outer periphery of the heat insulating stay holder 12 is driven to rotate in a clockwise direction indicated by an arrow.

The pressure roller 20 is driven to rotate, and accordingly, the cylindrical fixing film 13 is driven to rotate.
When the heater 11 is energized and the temperature of the heater 11 rises to a predetermined temperature and the temperature is controlled, an unfixed toner image t is formed between the fixing film 13 and the pressure roller 20 in the fixing nip N. The carried recording material P is introduced, and the toner image carrying surface side of the recording material P in the fixing nip portion N comes into close contact with the outer surface of the fixing film 13, and the fixing nip portion N is conveyed together with the film 13. In this nipping and conveying process, the heat of the heater 11 is applied to the recording material P via the fixing film 13, and the unfixed toner image t on the recording material P is heated and pressed onto the paper P to be fused and fixed. The recording material P that has passed through the fixing nip N is separated from the fixing film 13 by a curvature.

A) Heater 11 FIG. 3 is an enlarged cross-sectional model diagram of the fixing nip portion N, and FIG. 4 is a partially cutaway model diagram of the heater 11. The heater 11 of this example is a backside heating type ceramic heater.

11 ₁ is Al ₂ O ₃ or Al having high thermal conductivity
This is a heater substrate using N, and is a horizontally long and thin plate member whose longitudinal direction is the paper passing direction.

Reference numerals 11 ₂ , 11 _3, and 11 ₄ are formed on the back side of the heater substrate 11 ₁ in parallel along the longitudinal direction of the substrate.
The second and third three heat-generating resistance layers (hereinafter, referred to as heating elements). Each of the heating elements 11 ₂ , 11 ₃ , 11 ₄ is provided with a pattern formed by screen printing or the like using a current-generating heating resistor paste such as silver palladium (Ag / Pd) · Ta ₂ N and baking.

[0045] 11 _5, 11 _6, 11 _7, 11 ₈ heater substrate 11 ₁ of the rear side first, second, third, fourth power supply that both ends surfaces is divided into form comprising two each of It is an electrode pattern. First, third, and fourth power supply electrode patterns 11
₅ 11 ₇ 11 ₈ are electrically connected to one end side of the first, second and third heating elements 11 ₂ 11 ₃ 11 ₄ via an extended electric path, respectively. The second power supply electrode pattern 11 ₆ first, second, third heating element 11 _2, 11 _3, 11 ₄
Is electrically connected to the other end through an extension circuit. Each power supply electrode pattern 11 ₅・ 11 ₆・ 11 ₇・ 11 ₈
Further, the extension electric circuit is provided by forming a pattern by screen printing or the like using a conductive paste such as silver (Ag) and baking.

[0046] 11 ₉ is a glass coating layer for ensuring the protection and insulation of the heating element 11 _2, 11 _3, 11 _4.

14 and 15 are glass coating layers 11 ₉
And temperature detecting elements such as first and second thermistors provided in contact with the surfaces of the first and second thermistors.

[0048] The above heater 11 as a heater surface side surface opposite to the heating element forming surface of the heater substrate 11 _1, and arranged to fix the heater surface to the lower surface of the outer film holder 12 The inner surface of the fixing film 13 slides in close contact with the heater surface.

Reference numerals 16 and 17 denote first and second power supply connectors fitted to both ends of the heater 11, respectively. First
The first and third power supply electrode patterns 11 ₅ and 11 ₇ of the heater 11 and the AC driver 18 are electrically connected by the power supply connector 16. In addition, the second and fourth power supply electrode patterns 1 of the heater 11 are provided by the second power supply connector 17.
And one _{6-11 8} and the AC driver 18 is in electrical communication.

Reference numeral 19 denotes a commercial AC power supply, and reference numeral 30 denotes a control circuit. The AC driver 18 is controlled by the control circuit 30. Electrical temperature detection information of the first and second temperature detection elements 14 and 15 is input to the control circuit 30 via A / D converters 31 and 32, respectively. Reference numeral 33 denotes an outside air temperature detection unit (outside air temperature detection sensor) provided at an appropriate position in the image forming apparatus main body. The detection information of the sensor 33 is also input to the control circuit 30 via the A / D converter 34.

The control circuit 30 includes first, second and third heating elements 11 _2, 11 ₃ of the heater 11 controls the AC driver 18
· 11 ₄ to be selectively energized to generate heat.

The first and third heating elements 11 ₂ and 11 ₄ are A4,
It is a heating element for a wide recording material such as an LTR and has a length of 222 mm. The second heating element 11 ₃ com1
This is a heating element for envelopes (a recording material having a narrow width) such as 0 and DL, and has a length of 116 mm.

The control circuit 30 detects the size of the recording material passed by a paper width sensor (not shown) in the recording material conveyance path, and uses the information to detect the first and third heating elements 11 ₂ and 11 _4.
When switches the second heating element 11 _3. However, if the size of the recording material, such as B5 and A5 size, subjected to heat fixing using the first-third heating element 11 _2, 11 _4, in this case, the non-sheet passing B5 and A5 size The second temperature detecting element (end thermistor) 15 provided in the area detects the temperature rise in the non-sheet passing portion and controls the throughput.

As described above, since the first, second, and third heating elements 11 ₂ , 11 _3, and 11 ₄ of the heater 11 are selectively energized, the heater 11 is quickly heated by the heat generated by the heating elements. Raise the temperature. The temperature information of the heater is input from the first and second temperature detecting elements 14 and 15 to the control circuit 30 via the A / D converters 31 and 32.

The control circuit 30 controls the AC driver 18 to control the temperature of the paper passing area of the heater 11 to a predetermined constant temperature based on the input temperature information. That is, the heater temperature is controlled to the target temperature (print temperature) by supplying an AC current whose power is controlled to the heating element of the heater 11.

B) Heat-insulating stay holder 12 The heat-insulating stay holder 12 functions as a guide member for promoting smooth rotation of the fixing film 13, holds the heater 1, and radiates heat in the direction opposite to the fixing nip portion N. The fixing film 13 is also loosely fitted with a margin to the outside, and is formed of a liquid crystal polymer, a phenol resin, PPS, PEEK, or the like. Further, since the inner surface of the fixing film 13 rotates while sliding on the heater 11 and the heat insulating stay holder 12, it is necessary to reduce the frictional resistance between the heater 11 and the heat insulating stay holder 12 and the fixing film 13. Therefore, a small amount of lubricant such as heat-resistant grease is interposed between the surfaces of the heater 11 and the heat insulating stay holder 12. Thus, the fixing film 13 can rotate smoothly.

C) Fixing Film 13 The fixing film 13 is a film having a small heat capacity, has a thickness of 100 μm or less, and has heat resistance and thermoplasticity, such as polyimide, polyamideimide, PEEK, PES, and PPS, in order to enable quick start. , PFA, PTF
E, FEP and other films. In addition, a film having sufficient strength to form a long-life heat fixing device and having excellent durability must have a thickness of 20 μm or more. Therefore, the thickness of the fixing film 13 is optimally 20 μm or more and 100 μm or less. Further, in order to prevent offset and ensure the separation of the recording material, PFA, P
A heat-resistant resin such as TFE or FEP having good release properties is mixed or coated alone.

(3) Throughput Control In this embodiment, the temperature rise of non-sheet passing is detected by the end thermistor 15 provided in the non-sheet passing area as described above, and the control circuit 3
0 controls the throughput.

As a method for controlling the throughput of small-size paper, the temperature of the non-paper passing portion exceeds the heat-resistant temperature of the fixing device even under the worst conditions (thick paper of small size paper) without providing the temperature detecting means in the non-paper passing portion. In many cases, a method of reducing the throughput by a predetermined number of sheets so as not to cause the problem or a method of providing a temperature detecting member in the non-sheet passing portion and reducing the throughput when the non-sheet passing portion reaches a temperature near the heat-resistant temperature of the fixing device are often adopted. However, in either method, if the throughput is unnecessarily reduced with thin paper or the throughput is increased with thin paper, the non-sheet passing portion may be excessively heated during thick paper.

Therefore, in the present embodiment, the control circuit 30 controls the throughput of the small-sized paper based on the temperature of the non-sheet passing portion detected by the end thermistor 15 as in the control shown in FIG. The control of this embodiment will be described with reference to the flowchart of FIG.

Step 1: First, monitor whether the temperature of the non-sheet passing portion does not exceed the threshold temperature T1 (240 ° C.) during the passage of the small size paper. To P1 (15 ppm).

Steps 2-4: Similarly, threshold value T
2 (260 ° C), T3 (265 ° C), T4 (270 ° C)
Is monitored, and if it is exceeded, the throughput is respectively P2 (12 ppm), P3 (9 ppm),
P4 (6 ppm).

At this time, the determination of the magnitude relationship with the threshold temperature is made at the highest temperature during the sheet passing. Further, the threshold value T4 (2
The temperature (70 ° C.) is set to a temperature that allows for a sufficient safety with respect to the melting temperature of the heat insulating stay holder 12 that holds the heater 11.

Incidentally, when the temperature reaches the threshold temperature, the paper is already fed, and the printing operation is performed on the paper being passed to the end.

According to this control, the thickness of the sheet where the temperature rise in the non-sheet passing portion is severe is finally reduced to a low throughput, and the thin paper whose temperature rise is relatively small is finally settled in the high throughput.

Table 1 shows the relationship of the final throughput when B5 size paper having a different thickness is passed by this control.

[0067]

[Table 1]

As can be seen from the example shown in Table 1, the sequence of this embodiment indicates that thin paper is passed at a high final throughput and thick paper is passed at a low final throughput.

Incidentally, the threshold value of the end portion temperature at which the throughput is reduced and the amount of the throughput reduction can be variously set depending on the process speed and the fixing device configuration.

As described above, a plurality of non-sheet passing portion temperature thresholds T1, T2,..., Tn (T1 <T2 <.
n), and the throughput is increased by P each time each threshold value is exceeded.
1, P2,..., Pn (P1>P2>...> Pn)
Step-by-step, it is possible to converge to the final throughput according to the paper thickness without excessively increasing the temperature of the non-sheet passing portion, and it is possible to maximize the throughput according to the paper thickness .

<Second Embodiment> In this embodiment, the first
In addition to the control of the embodiment, when the temperature of the non-sheet passing portion falls below a predetermined threshold value, a control for increasing the throughput is performed.

The other conditions are the same as those in the first embodiment, and the description will not be repeated.

In the on-demand fixing device, since the fixing temperature is controlled to decrease stepwise as the fixing device warms up, when the printing is started from a state in which the fixing device is not so warmed, the fixing temperature is high, so that the fixing temperature is temporarily high. In some cases, the threshold value of the above embodiment is exceeded, and the throughput may be reduced more than necessary.

Therefore, in this embodiment, control for increasing the throughput is performed as shown in FIG. The control of this embodiment will be described with reference to the flowchart of FIG.

First, after the temperature of the non-sheet passing portion during the passing of the small size sheet temporarily exceeds T2 (260 ° C.), the threshold value t1 (2
(50 ° C.), the throughput is reduced to P1 (15p).
pm) (step 1 ').

Similarly, the threshold value T2 (255 ° C.)
If the temperature falls below T3 (260 ° C.), the throughput becomes P
2 (12 ppm) and P3 (9 ppm) are sequentially increased (steps 2 ′ to 3 ′). The determination of the magnitude relationship with the threshold temperature is performed so that abnormal throughput reduction or increase due to temperature ripple due to paper passing does not occur. First, the maximum value during the passing of each page is used.

By the above control, it is possible to converge to the maximum throughput according to the paper thickness regardless of the printing conditions such as cold start.

As described above, a plurality of non-sheet passing portion temperature thresholds T1, T2,..., Tn (T1 <T2 <.
n) and the throughput is reduced by P
1, P2,..., Pn (P1>P2>...> Pn)
In this way, the throughput can be further finely maximized according to the paper thickness.

<Third Embodiment> In this embodiment, in addition to the above-described embodiment, control is performed to detect the sheet thickness and change the fixing temperature by the temperature rise rate α of the non-sheet passing portion.

The other conditions are the same as those in the above embodiment, and the description will not be repeated.

As described in the above embodiment, in the on-demand fixing device, the fixing temperature is lowered stepwise. At this time, the lower limit temperature of the fixing temperature is determined so that the fixing property can be ensured even for a thick paper or an envelope having a strict fixing property. Therefore, for thin paper or the like, the fixing property tends to be excessive, and the temperature rise in the non-paper passing portion becomes severe.

Therefore, in the present embodiment, control is performed to detect the sheet thickness based on the temperature rise rate of the non-sheet passing portion and change the fixing temperature. The control of this embodiment will be described with reference to the flowchart of FIG.

Step 1 ″: First, the temperature rise rate α (° C./sheet) is measured from the temperature of the non-sheet passing portion during sheet passing.

The temperature rise rate α is measured in a high-temperature region where the amount of heat radiation is large and in a low-temperature region where the amount of heat radiation is small even if the paper is passed under the same conditions. Perform the measurement in the state.

Step 2 ″: Next, the temperature rise rate α is 5
The fixing temperature table is switched between table A and table B shown in FIG. 8 when the temperature is not less than 5 ° C./sheet and when the temperature is less than 5 ° C./sheet (Table 2 shows the relationship between the sheet thickness and the temperature rise rate).

By this control and the control of the first and second embodiments, the final throughput is converged to the final throughput corresponding to the paper thickness.

[0087]

[Table 2]

By the above control, the tab shown in FIG.
Since the fixing temperature for thin paper is applied as in leB and the fixing temperature is lowered, an optimal fixing state is achieved, and the throughput is improved.

As described above, by changing the fixing temperature in accordance with the temperature rise rate of the non-sheet passing portion, excessive temperature rise in the non-sheet passing portion is suppressed irrespective of the sheet thickness, and the throughput is maximized. Becomes possible.

<Fourth Embodiment> A fourth embodiment of the present invention will be described below with reference to FIGS. Note that, in the configuration of the image forming apparatus and the fixing device in the present embodiment, description of the same portions as those in the conventional example and the first embodiment will be omitted. The description of a widely known electrophotographic image forming apparatus is also omitted.

This embodiment is characterized in that the detection temperature of the outside air temperature detection sensor 33 (FIG. 4) for detecting the ambient temperature where the image forming apparatus is placed and the temperature detection for controlling the fixing temperature provided in the fixing film. In accordance with the temperature detected by the thermistor 15, which is an element, the conveyance interval between recording materials (hereinafter, the throughput is expressed as ppm
Is switched to a plurality of stages. Actually, when the temperature detected by the outside air temperature detection sensor 33 is detected as high and the temperature at the end of the non-sheet passing portion at the thermistor 15 is detected as high, the throughput is reduced to reduce the end temperature. The point is to prevent the recording material existing in the fixing nip from being conveyed at a predetermined conveyance speed while keeping the temperature at a lower level.

Hereinafter, this embodiment will be described in detail.

The image forming apparatus used in this embodiment also has a process speed of 151 mm / sec and uses an A4 size recording material of 24 mm, as in the first and second embodiments.
It can output with a throughput of ppm, and the recording material having the maximum paper width is the LTR size.

As in the first and second embodiments, the fixing device used in this embodiment is also small, such as A5 size and B5 size, in which the temperature rises in the non-sheet passing portion. For the size paper, the throughput is changed as shown in Table 3 depending on the magnitude relationship between the detected temperature of the end thermistor 15 and a preset threshold temperature for raising the non-sheet passing portion.

[0095]

[Table 3]

In a normal use range, the above-described device for suppressing the temperature rise at the edge portion may exert a detrimental effect due to the temperature rise at the edge portion while maximizing the performance as the image forming apparatus. High temperature offset and recording material slip can be prevented.

The high-temperature offset and the recording material slip described above will be described. The high-temperature offset causes the toner on the recording material in the fixing nip to separate in the toner without separating from the fixing film surface and the toner surface. This is an offset phenomenon that occurs when the toner separated in the toner remains on the surface of the fixing film and is transferred to the recording material again after one round of the fixing film to be embodied. This occurs when the amount of heat in is excessively supplied.

Further, the recording material slip is caused by the water vapor generated from the recording material existing in the fixing nip, whereby the frictional force between the recording material and the pressing roller as the recording material conveying means is reduced, and the recording material is conveyed in a predetermined manner. This is a phenomenon in which the sheet is not conveyed at a high speed, and also occurs when the amount of heat in the fixing nip becomes excessive.

These phenomena are caused by a situation in which a large amount of small-size paper is passed, and the temperature of the end portion rises in the non-paper passing portion. (LTR size, A4 size) in the image forming apparatus, and it is likely to occur when the recording material is left in a high-temperature environment where the temperature of the recording material is higher or the amount of water vapor contained in the recording material may increase. In a high-temperature, high-humidity environment, the occurrence becomes remarkable.

Therefore, in this embodiment, the throughput is changed according to the temperature detected by the end thermistor 15 when small-size paper is passed and the environmental temperature detected by the outside air temperature sensor 33 at that time. In an environment in which the above-described problem is likely to occur, the above-described high-temperature offset and fixing slip are prevented from being generated by controlling the temperature rise of the end portion to be further reduced.

In this embodiment, the outside air temperature detected by the outside air temperature detection sensor 33 is classified into a low temperature environment below 17 ° C., a normal temperature environment between 17 ° C. and 30 ° C., and a high temperature environment above 30 ° C. Distinguished. The relationship between the detected temperature of the end thermistor 15 and the throughput when a narrow recording material is passed under each environment is classified as shown in Table 4 below.

[0102]

[Table 4]

The description in the table shows that the end thermistor 1 was used in each environment detected by the outside air temperature detection sensor 33.
What is the throughput when the detection temperature of 5 becomes
It shows how many ppm from pm.

As an example, in an environment of 30 ° C. or more, when the detection temperature of the end thermistor 33 reaches 220 ° C., the throughput is changed from 19 ppm to 15 ppm, and
15 ° C to 12ppm throughput at 5 ° C
And similar changes will be made below.

As described above, by changing the throughput in accordance with the temperature detected by the end thermistor 33, the temperature rise at the end of the non-sheet passing portion can be suppressed. By changing the throughput more aggressively in an environment where the temperature is more likely to occur, it is possible to prevent the occurrence of a high-temperature offset or a fixing slip which is an adverse effect due to the temperature rise at the end.

Next, the case where the throughput is changed only by the detected temperature of the end thermistor 33 without depending on the conventional environment, and the control by the detected temperature of the end thermistor 33 under each environment in this embodiment are performed. Table 5 shows the results of a comparative study of the high-temperature offset and the fixing slip in the case of the above.

The conditions for the comparative study were as follows. After continuously passing 100 sheets of A5 size recording material having a basis weight of 64 g / m ² as a narrow recording material at which the temperature of the end portion was raised, immediately, By passing 10 sheets of A4 size recording material having an amount of 64 g / m ² , occurrence of high-temperature offset and fixing slip was confirmed.

The recording material of A4 size was one immediately after opening in each environment and one that was left for about 48 hours.
At each level, each examination was performed three times, and if no problem occurred in all three times, it was confirmed as ○, if it occurred only once, as △, and if it occurred 2-3 times, ×.

[0109]

[Table 5]

As shown in the table, no problem occurred in the conventional example in a low-temperature environment of less than 17 ° C.
In a normal temperature environment of 17 ° C. or higher and lower than 30 ° C., a fixing slip occurs on the abandoned paper, and under the environment of 30 ° C. or higher, any problem has been confirmed in all cases.
In this example, it can be seen that no problem occurs in all cases.

As described above, the end-portion temperature rise in the non-sheet-passing portion is detected by the end-portion thermistor 15, and in accordance with the outside temperature detection temperature of the outside temperature detection sensor 33, By changing to a throughput that does not cause problems,
It is possible to prevent the occurrence of the high-temperature offset and the fixing slip which have conventionally occurred.

In an environment in which no problem occurs (in a low-temperature environment of 17 ° C. or less in this embodiment), the threshold temperature of the end thermistor whose throughput is difficult to change is set, so that the image forming apparatus can be used. It has also achieved maximum performance.

In this embodiment, as described in the second embodiment, the throughput can be increased stepwise.

<Others> 1) The configuration of the ceramic heater 11 is not limited to the embodiment.

2) A film fixing heating fixing device is
Although the embodiment is a pressing rotary member driving system, a driving roller may be provided on the inner peripheral surface of the endless fixing film, and a device of driving while applying tension to the film may be used, or the film may be rolled. An apparatus of a type in which a wound end-shaped web is formed, and the running is driven.

3) The film heating type heat fixing device may be of an electromagnetic induction heating type using an electromagnetic induction heating member such as an iron plate as a heater.

FIG. 12 is a schematic structural diagram of an example of a heating and fixing device of a film heating system, an electromagnetic induction heating system, and a driving system for a rotating rotating body for pressurization. 11A is an electromagnetic induction heating member such as an iron plate as a heater. Reference numeral 40 denotes a magnetic field generator including an exciting coil 41 and a magnetic core 42. The heater 11A generates electromagnetic induction heat by a high-frequency magnetic field generated when a high-frequency current is supplied from the excitation circuit 43 to the excitation coil 41.
The recording material P nipped and conveyed through the fixing nip n is heated by the heat of the heater 11A. The chip thermistor 14 serving as a heater temperature detecting means detects the temperature information of the heater 11A.
15 is taken into the control circuit 30 via the A / D converters 31 and 32. The control circuit 30 controls the excitation circuit 43 to control the temperature of the heater 11A to a predetermined constant temperature based on the input temperature information. That is, by controlling the high-frequency current to the exciting coil 41 that causes the heater 11A to generate heat by electromagnetic induction, the heater temperature is set to the target temperature (print temperature).
Temperature control.

The other constitutions and controls of the heat fixing device are the first.
To the third embodiment.

[0119]

As described above, according to the present invention, in an image forming apparatus using a heat fixing device of a film heating type, it is possible to prevent an excessive temperature rise in a non-sheet passing portion, Throughput can be maximized depending on the thickness.

Further, in a case where the temperature rises at the end portion in the non-sheet passing portion, and in an environment where problems such as high-temperature offset and fixing slip are likely to occur, the environmental temperature and the fixing temperature detected by the outside air temperature detecting means are detected. By changing the throughput according to the temperature rise of the end portion by means, the occurrence of high-temperature offset and fixing slip can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration model diagram of an image forming apparatus according to an embodiment.

FIG. 2 is a schematic diagram illustrating the configuration of a heat fixing device according to an embodiment.

FIG. 3 is an enlarged cross-sectional model diagram of a fixing nip portion.

FIG. 4 is a partially cutaway plan model diagram of a rear side of a heater and a block circuit diagram of a power supply / temperature control system.

FIG. 5 is a flowchart of a control sequence according to the first embodiment.

FIG. 6 is a flowchart of a control sequence in the second embodiment.

FIG. 7 is a flowchart of a control sequence in a third embodiment.

FIG. 8 is a diagram illustrating a fixing temperature table according to a sheet thickness.

FIG. 9 is a flowchart for explaining a fourth embodiment (part 1);

FIG. 10 is a flowchart for explaining a fourth embodiment (part 2);

FIG. 11 is a flowchart illustrating a fourth embodiment.
(Part 3)

FIG. 12 is a schematic configuration diagram of an example of a heat fixing device of an electromagnetic induction heating system.

[Explanation of symbols]

11 Heater 11 ₁ Ceramic substrate 11 _{2 to} 11 ₄ Electric heating resistance layer 11 ₉ Thin glass protective layer 12 Stay holder 13 Thin film (fixing film) 14 First temperature Detecting element 15 ‥‥ Second temperature detecting element (end thermistor) 20 ‥‥ Pressure roller 21 ‥‥ Core of pressure roller 22 弾 性 Elastic layer of pressure roller

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshio Miyamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Eiji Uekawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Within non-corporation (72) Inventor Kenji Kanari 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. F-term (reference) 2H033 AA03 AA23 AA32 AA42 BA11 BA12 BA25 BA31 BA32 BE03 BE06 CA06 CA08 CA37 CA46 3K058 AA86 BA18 CA12 CA22 CA31 CA92 DA01 3K059 AB19 AC33 AD05 BD15 CD14

Claims (7)

[Claims] A fixing member having a heater, a film which slides on the heater, and a pressing member which presses the heater through the film to form a fixing nip. An image forming apparatus having a heat fixing device for nipping and conveying a recording material on which an unfixed image is formed between pressure members and fixing the unfixed image as a permanent image on the recording material by heat from a heater via a film. The heat fixing device has a temperature detecting unit inside the maximum sheet passing width and outside the minimum sheet passing width, and the temperature detected by the temperature detecting unit is equal to threshold values T1 and T1.
.. Tn (T1 <T2 <... <Tn), the throughput is increased by P1, P2,.
P2>...> Pn). 2. A fixing member having a heater, a film sliding on the heater, and a pressure member pressing the heater through the film to form a fixing nip. An image forming apparatus having a heat fixing device for nipping and conveying a recording material on which an unfixed image is formed between pressure members and fixing the unfixed image as a permanent image on the recording material by heat from a heater via a film. The heat fixing device has a temperature detecting unit inside the maximum sheet passing width and outside the minimum sheet passing width, and the temperature detected by the temperature detecting unit is equal to threshold values T1 and T1.
, Tn (T1> T2 >>...> Tn), the throughput is reduced to P1, P2,.
P2 <... <Pn). 3. The image forming apparatus according to claim 1, wherein a temperature rise rate is detected by the temperature detection unit, and the fixing temperature is changed according to the detection result. 4. A fixing member having a heater, a film sliding with the heater, and a pressing member pressing the heater through the film to form a fixing nip. An image forming apparatus having a heat fixing device for nipping and conveying a recording material on which an unfixed image is formed between pressure members and fixing the unfixed image as a permanent image on the recording material by heat from a heater via a film. The heat fixing device has a fixing temperature detecting unit inside the maximum sheet passing width and outside the minimum sheet passing width, and has an outside air temperature detecting unit for detecting an ambient temperature in which the image forming apparatus is installed; An image forming apparatus characterized in that a conveyance interval between recording materials is switched in a plurality of stages according to the detection temperatures of the detection means and the outside air temperature detection means. 5. A plurality of fixing temperature detecting means are provided in the longitudinal direction of the heater, one of which is provided inside the maximum paper passing width and outside the minimum paper passing width, and the detected temperature is set to the threshold temperature T1. 5. The image forming apparatus according to claim 4, wherein the transport interval between the recording materials is switched in a plurality of stages each time the recording material reaches Tn,..., Tn. 6. The image forming apparatus according to claim 1, wherein the heater includes an energizing heat generating resistive layer, and generates heat by energizing the energizing heat generating resistive layer. 7. The image forming apparatus according to claim 1, wherein the heater is an electromagnetic induction heating member, and generates heat by a magnetic field generated by a magnetic field generating unit that generates a magnetic field when energized.