JP2003076212A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the fluctuation of subscanning magnification by appropriately judging the temperature rise state of a pressure roller so as to switch the speed of a motor even when plain paper is made to pass after small size paper is made to consecutively pass. SOLUTION: The detected temperature T1 by a thermistor provided at a small size paper passing part is compared with the detected temperature T2 by a thermistor provided at a small size paper non-passing part. When relation T2>T1 is satisfied, it is judged as a situation that the small size paper passes just before. Furthermore, when the size of paper passing next is the plain paper size according to information from a printer driver, the rotating speed of the motor is made low so that the image may not be elongated in size.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A conventional image forming apparatus using electrophotography is constructed, for example, as shown in FIG.

In FIG. 6, 1 is a photosensitive drum, 2 is a charging roller, 3 is a laser exposure device, 4 is a reflection mirror, 5 is a developing sleeve, 6 is toner, 7 is a toner container, 8 is a transfer roller, and 9 is a recording target. Paper as a medium, 10 is a cleaning blade, 11 is a waste toner container, 12 is a fixing device, 13 is a paper cassette, 14 is a paper feed roller, 15 is a separation pad, and 16 is a high-voltage power supply.

The photosensitive drum 1 rotates in the direction of the arrow and is uniformly charged by the charging device 2 fed from the high voltage power source 16. The laser light emitted from the laser exposure device 3 is reflected by the reflection mirror 4 and irradiated on the photosensitive drum, and an electrostatic latent image is formed on the photosensitive drum. Toner 6 is filled in the toner container 7, and an appropriate amount of toner is appropriately charged with the rotation of the developing sleeve 5, and then is supplied onto the photosensitive drum.

The toner on the developing sleeve adheres to the electrostatic latent image on the photosensitive drum, and the latent image is developed and visualized as a toner image. The paper feed roller 14 feeds the recording medium one by one from the paper cassette 13 at a timing. The separation pad 15 is arranged in contact with the paper feed roller, and the friction coefficient, the ground contact angle, and the shape of the surface thereof are adjusted so that only one recording medium is fed for each paper feed. The visualized toner image on the photosensitive drum is transferred onto the recording medium by the transfer roller 8. The transfer residual toner that has not been transferred and remains on the photosensitive drum is stored in the waste toner container by the cleaning blade 10, and the photosensitive drum whose surface has been cleaned repeatedly enters the next image forming process. The recording medium 9 on which the toner image is placed is heated by the fixing device 12,
Upon receiving pressure, the toner image is permanently fixed on the paper.

A conventional fixing device 12 is disclosed in JP-A-63-3.
A film heating method disclosed in Japanese Patent No. 13182 is used in which a pattern of a resistance heating element is provided on a ceramic substrate to form a heating element, and the heating element is heated to heat an object to be heated through a thin film.

However, in such a film heating system, a large twisting force is generated in the endless belt-shaped film. As a countermeasure against this, a method of driving the endless film disclosed in JP-A-04-44057 and JP-A-04-44077 with a margin in a suspended manner to reduce the twisting force of the film and reduce the driving torque is practical. Has been converted.

An example of a sectional view of such a film fixing device is shown in FIG. In the figure, reference numeral 102 denotes a heating element, in which a heating element 108 is formed on a ceramic substrate, and a glass layer 109 as a protective layer is coated thereon. A thermistor 107 is mounted on the back surface of the heating element to detect the temperature of the heating element. The heating element section is powered by a power source (not shown) to generate heat. The triac is driven by the CPU so that the temperature of the thermistor 107 is constant and the amount of power supply is controlled. Fixing film 103
Is a tubular heat-resistant film having a three-layer structure. The innermost layer is the base layer, and the twist strength of the fixing film,
Polyimide, which is a layer responsible for mechanical properties such as smoothness
It is made of resin such as polyamide-imide, PEEK, PES, PPS.

The next layer is a conductive primer layer, in which conductive particles such as carbon black are dispersed,
It also plays the role of an adhesive for joining the third layer and the base layer. The outermost layer is the top layer and is designed to have the optimum resistance value and film thickness so as not to cause various image defects.

Reference numeral 101 denotes a heating member supporting member, which is a heating member 1.
No. 02 support member, which is formed of a heat-resistant resin such as PPS or liquid crystal polymer, and also serves as a guide member for promoting smooth rotation of the fixing film 103.

A fixing stay 106 is made of metal such as iron and aluminum. The fixing stay suppresses the deformation of the heating member supporting member due to creep and plays a role of increasing the rigidity of the heater supporting member.

Reference numeral 104 is a pressure roller, and a cored bar 104a made of aluminum, cast iron or the like is covered with a heat resistant elastic body 104b such as silicon rubber. The surface layer of the pressure roller has releasability from the toner PFA, PTFE, FE
A coating of fluororesin such as P is provided.

The pressure roller 104 is pressed against the heater 102 with the fixing film 103 interposed therebetween, and a fixing nip N is formed at the rear portion thereof. Core metal 10 of pressure roller 104
4a is rotationally driven, and the fixing film 103 is driven to rotate in the fixing nip portion. The recording material P carrying the toner is conveyed by a transfer roller (not shown) and a photosensitive drum, and is guided to the fixing nip portion by the fixing guide 105. The toner T on the recording material is pressed and heated on the recording material at the fixing nip portion, and the toner resin is softened and adheres to the recording material to be permanently fixed.

[0014]

Since a heater having a low heat capacity can be used for such a film heating type fixing device, the weight time can be shortened (quick start) as compared with the conventional heat roller type. While it becomes possible,
Due to the thermal expansion of the pressure member to rotate the pressure member,
There is a problem that the peripheral speed of the pressure member changes and the feeding speed of the recording material changes.

To deal with this problem, Japanese Patent Laid-Open No. 07-2
Japanese Patent No. 61584 discloses a method of detecting the temperature of a pressure member in the paper passing area and changing the driving speed of the pressure member, driving the pressure member by counting the number of sheets of recording material to predict the temperature of the pressure member. A method of changing the speed is disclosed. By these methods, even if the outer diameter of the pressure member changes due to thermal expansion, it is possible to reduce the fluctuation of the feeding speed of the recording material.

However, if continuous feeding of small size paper is continued for a long time, the non-sheet passing portion of the pressure member where the small size sheet does not pass rises in temperature, and the thermal expansion of the non-sheet passing portion of the pressure member causes the sheet passing. It is significantly larger than the area. When a wider plain paper is passed in this state, the transport speed is dominated by the non-sheet-passing portion where the feed speed is high due to thermal expansion, and the feed speed becomes higher than expected. Since the recording material is conveyed at a predetermined speed in the image forming section, which is the processing section on the upstream side of the heating device, for example, the image transfer section, the pressure member pulls the recording material, which causes this effect. Therefore, the toner image is formed on the recording material in the transfer portion in a state in which the toner image extends in the transport direction more than the original size.

It is an object of the present invention to provide an image forming apparatus in which the dimensional variation of an image formed on a recording material is small even when recording materials having various widths are continuously fed.

[0018]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and the above objects are: (1) A recording material carrying an electrostatically formed toner image is pressed against a heating body. In an image forming apparatus having a fixing device for nip-conveying by driving and rotating a pressure member arranged on the recording material and fixing the toner image on the recording material by heating and pressurizing the recording material and the toner image, An image forming apparatus having a plurality of detecting means for detecting, and changing a driving rotation speed of a pressure member according to a temperature detected by the detecting means and a width of a recording material through which a sheet is passed.

(2) An image forming apparatus according to the above (1), characterized in that the drive rotation speed of the pressure member is changed according to the temperature detected by the detection means in the recording material conveyance area.

(3) In the above (2), among the detecting means, the temperature of the detecting means showing the highest temperature is compared with a preset value, and the drive rotation speed of the pressing member is changed. Image forming apparatus. Achieved by

(Function) According to the first invention, the thermal expansion of the pressing member is predicted to reduce the dimensional variation of the image formed on the recording material.

According to the second aspect of the invention, the thermal expansion of the pressure member is predicted, and the dimensional variation of the image formed on the recording material is reduced according to the width of the recording material.

According to the third aspect of the invention, the thermal expansion of the portion of the pressing member that greatly affects the conveyance of the recording material is predicted, and the dimensional variation of the image formed on the recording material is reduced according to the width of the recording material. To do.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION (Embodiment 1) FIG. 2A shows a schematic view of the surface of a heating body according to an embodiment of the present invention.

Reference numeral 130 denotes a substrate having a width of 7 mm and a length of 270.
mm, 1 mm thick alumina, aluminum nitride, silicon carbide,
It is made of ceramics with good thermal conductivity. Reference numeral 131 denotes an electrode pattern, which is formed by screen-printing a paste material containing a conductive material such as silver palladium on a ceramic substrate. Reference numeral 132 is a heating element, and a paste material containing a conductive material such as silver palladium and a resistor is similarly formed on the substrate by screen printing. The total resistance value of the heating element of this embodiment is 25Ω. Reference numeral 133 denotes a glass coat, which is provided to cover and insulate a part of the above-described conductive pattern and the entire heating element. Reference numeral 134 is called a DC pattern, which is formed similarly to the electrode pattern 131 and ensures electrical conduction with the electrode 135 on the back surface through a through hole (not shown).

FIG. 2B is a schematic view of the back surface of the heating element, in which thermistors 136 (a) and 136 (b) are mounted on the conductive pattern 135. Thermistor 135 (b)
Is provided within the width through which the narrowest recording paper of the paper types that can pass through passes, and monitors the temperature T1 of the paper passing portion. Further, the thermistor 136 (a) is provided outside the paper passing area of the recording paper of the minimum width and within the paper passing area of the recording paper of the maximum width, and the temperature T2 of the non-paper passing portion when the small size paper is passed.
Are being monitored.

FIG. 1 shows a control flow chart of the image forming apparatus when this heating element is used in the fixing apparatus shown in FIG. 5 and when the fixing apparatus is used in the image forming apparatus shown in FIG. Here, the paper feeding speed of the fixing device is 50 mm / sec, and the fixing device is 5
The controlled temperature of the first sheet is 190 ° C when the fixing operation is started when the temperature is 0 ° C or lower, and the controlled temperature is when the temperature when the fixing device starts the fixing operation is 50 ° C or higher and 70 ° C or lower. Is controlled to 185 ° C and 180 ° C when the temperature is 70 ° C or higher.

The object of the present invention is to optimize the feeding speed of the recording paper when the large size paper is passed immediately after the small size paper is passed, and first, the small size paper is passed. It is necessary to detect that the paper has been printed.

When a print start command is received from the host computer, the paper size of the recording paper to be passed is first detected. Since it is desired to know the temperature of the hot portion of the pressure roller that governs the conveyance speed within the width of the recording paper passing, if there is information about the width of the paper, information about the length in the paper conveyance direction is not necessary. The paper size is detected by the paper size information from the host computer,
Alternatively, the output is performed by the paper size detection unit of the image forming apparatus. When the paper size is small, the non-sheet passing temperature T2
Does not significantly affect the paper feeding speed of small size paper, so the paper passing portion temperature T1 is detected and the speed of the main motor is changed.

For example, when T1 is 50 ° C. or lower, the main motor is rotated at a normal rotation speed so that T1 is 50 ° C. or higher and 120 ° C.
In the following cases, the main motor is rotated 0.5% slower than the normal speed, and in the case of 120 ° C. or higher, the main motor rotational speed is made 1% slower than the normal speed.

In the image forming apparatus shown in FIG. 6 used in this embodiment, since the image forming speed of the laser image forming section is constant, when the speed of the main motor is changed, the latent image formed on the photosensitive drum is conveyed in the conveying direction. The size can be changed arbitrarily.
That is, the recording material is conveyed faster due to the thermal expansion of the pressure roller and the image extends in the conveying direction at the transfer portion, so that the speed of the main motor is slowed down to reduce the writing of the latent image on the photosensitive drum, thereby forming a toner image on the recording paper. The size in the transport direction is corrected to a predetermined size.

Next, when the paper size is plain paper, T2 and T
1. Detect both temperatures and determine the rotation speed of the main motor by observing the higher temperature value. When the size of the paper passed immediately before is a small size paper such as a postcard, the non-paper-passage portion where the recording paper does not pass does not take heat, so the temperature of the non-paper-passage portion T2.
Is hotter than T1. If plain paper is passed in this state, the transport speed of the plain paper is strongly affected by the peripheral speed of rotation of the portion of the pressure roller where thermal expansion is large. There is.

For example, in the case of T2> T1, the main motor is rotated at the normal rotation speed when T2 is 50 ° C. or lower, and 0.5 times the normal speed when T2 is 50 ° C. or higher and 120 ° C. or lower.
% Rotate the main motor slower than 120 ℃ and 170 ℃
1% below normal when below, 1.5% above 170 ° C
The rotation speed of the main motor is slowed. If about 100 sheets of small size paper such as envelopes are continuously fed, even if T1 is 170 ° C at the end of printing, T2 will rise to 260 ° C. It is necessary to compensate for the increase in transport speed due to thermal expansion.

If this correction is not performed, the length is 355 m.
For the legal paper of m, the printing position of the trailing edge of the paper deviates from the position indicated by the host computer to the trailing edge side by about 1.7 mm to 6 mm, and the outer diameter of the pressure roller protrudes from the trailing edge of the paper under the worst condition of the manufacturing tolerance upper limit. By the control of the present embodiment, what has been settled falls within a deviation of about 0 mm to 4.3 mm, and it does not stick out from the trailing edge of the paper.

(Embodiment 2) In Embodiment 1, the case where there are two temperature detecting elements on the heating element has been described. However, after a small size paper such as a postcard is continuously passed, the second thermistor moves the conveyance width. For example, when B5 size paper that does not enter into the range is passed, the temperature that determines the conveying speed of the pressure roller is between T1 and T2.

In order to know the thermal expansion of the pressure roller in such a case, if there is a temperature detecting element between the first thermistor and the second thermistor, the correction by the main motor speed can be performed more accurately. it can.

As described above, when there are three or more temperature detecting elements of the heating element, the rotation speed of the main motor is adjusted in accordance with the highest temperature among the temperature detecting elements in the width of the paper size to be passed. Should be decided. A flow chart of this control is shown in FIG.

When the print signal is received, the paper size is judged based on the signal from the host computer or the signal from the paper size sensor of the image forming apparatus, and the paper is detected in the temperature detecting element within the width of the paper. The temperature of the element showing the highest temperature is stored in the memory as Tmax.
When Tmax is 50 ° C or lower, the main motor is rotated at the normal rotation speed V1, and when Tmax is 50 ° C or higher and 120 ° C or lower, the main motor is rotated at a speed V2 that is 0.5% slower than the normal speed, and 120 ° C or higher. When the temperature is 170 ° C or lower, the main motor is rotated at a speed V3 which is 1% slower than usual, and when the temperature is 170 ° C or higher, the speed V4 is 1.5% slower than the normal speed.

In the case of having a plurality of temperature detecting elements as described above, if the speed of the main motor is changed by the temperature detected by the temperature detecting element showing the highest temperature in the paper passing width, the image size on the recording paper can be changed regardless of the paper width. It becomes possible to optimize.

Although the present embodiment has been described with respect to the film fixing device, the present invention is not limited to the film fixing device, and the thermal expansion of the heating or pressure member which receives the rotational drive is relatively large and the image is conveyed. It is generally applicable to fixing devices that affect the directional dimension.

For example, as shown in FIG. 4, a fixing device of an electromagnetic induction heating system in which a magnetic force is applied to the magnetic member 38 by an exciting means including a core 36, a coil 37 and the like to generate an induced current in the magnetic member 38 to heat the magnetic member 38. At the magnetic member 3
Even when a plurality of temperature detecting means for detecting the temperature of the magnetic member are provided in the longitudinal direction of 8, the invention of the present application is effective.

[0042]

According to the present invention, it is possible to provide an image forming apparatus in which dimensional variation of an image formed on a recording material is small even when recording materials having various widths are continuously fed.

[Brief description of drawings]

FIG. 1 is a flowchart illustrating control of an image forming apparatus according to a first exemplary embodiment of the present invention.

FIG. 2 is a top view illustrating the heating body according to the first embodiment of the present invention.

FIG. 3 is a flowchart illustrating control of the image forming apparatus according to the second embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating a fixing device according to a second exemplary embodiment of the present invention.

FIG. 5 is a sectional view illustrating a conventional fixing device.

FIG. 6 is a sectional view illustrating a conventional image forming apparatus.

[Explanation of symbols]

101 heating body support member 102 heating body 103 fixing film 104 pressure roller 105 Roller with fixing 106 metal stay 107 Thermistor 108 heating element 109 Heating element protective layer N fixing nip P recording material T toner particles

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H027 DA11 DA12 DC02 DC10 DC19                       ED16 ED25 EE03 EE07 EF06                       FA05 FA35                 2H033 AA14 BA07 BA25 BA59 BB37                       BE03 CA07 CA09 CA17 CA36                       CA40                 3K058 AA41 AA51 BA18 CA12 CA23                       DA05

Claims (3)

[Claims] 1. A recording material carrying an electrostatically formed toner image is nipped and conveyed by drivingly rotating a pressure member arranged so as to be in pressure contact with a heating body, and the recording material and the toner image are conveyed. An image forming apparatus having a fixing device for heating and pressurizing the toner image to fix the toner image on a recording material, comprising a plurality of detecting means for detecting the temperature of the heating body, and detecting temperature of the detecting means and recording material width. An image forming apparatus, characterized in that a drive rotation speed of a pressure member is changed. 2. The image forming apparatus according to claim 1, wherein the drive rotation speed of the pressure member is changed according to the temperature detected by the detection means in the conveyance area of the recording material in the detection means. . 3. The driving rotation speed of the pressurizing member is changed by comparing the temperature of the detection means showing the highest temperature among the detection means with a preset value. The image forming apparatus described.