JPH1184935A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent faulty fixation regardless of the thickness of transfer material by controlling temperature so that the temperature may be 1st fixing temperature when and after the leading edge of transfer material is detected by a fixing entrance sensor and controlling the temperature until the trailing edge of the transfer material is detected by a fixing exit sensor at 2nd fixing temperature obtained by adding a temperature difference between the fixing temperature detected by the fixing exit sensor and the 1st fixing temperature to the fixing temperature. SOLUTION: This device is provided with the fixing entrance sensor 24 on an upstream side in a transfer material carrying direction from a nip part N and the fixing exit sensor 25 on a downstream side in the transfer material carrying direction. As the transfer material P is detected by the sensors 24 and 25, the fixing temperature is detected by a fixing temperature sensor 22c and the fixing temperature is controlled by a control means. Until the leading edge of the transfer material P gets out of a fixing device B from the time just before it enters the fixing device B, the control means detects a heating value taken away by detecting the temperature difference changed from the 1st fixing temperature T1 in the fixing nip part N, and a temperature component insufficient with reference to T1 is added to the fixing temperature and the succeeding fixing temperature is set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or the like, a toner image is formed on an image carrier by an image forming means, and the toner image is transferred onto a transfer material such as paper. And the unfixed toner image on the transfer material is fixed on the transfer material to complete copying (image formation). For the fixing, a so-called heat roller fixing type fixing device in which a pair of heat rollers is heated and a toner is melted and fixed while holding and transferring a transfer material by the pair of heat rollers is widely used.

However, according to the heat roller fixing method,
There is a problem that the rise time is long until the temperature of the heat roller pair reaches a predetermined fixing temperature sufficient to quickly melt and fix the toner image, and if this rise time is to be shortened, preheating is required. This problem is caused by turning on the copy (image formation) switch in the image forming apparatus.
It takes a long time to warm up from the time when copying is possible, so that a quick start cannot be performed.

Accordingly, the applicant of the present invention has proposed a fixing method (hereinafter, referred to as a “surf method”) using a heat-resistant film (hereinafter, referred to as a “fixing film”) in order to reduce a rise time (Japanese Patent Laid-Open Publication No. H11-163873). Sho 63-313182, JP 2-15
No. 7878).

In a surf-type fixing device (hereinafter referred to as a "surf fixing device"), a heating member is formed by providing a resistance heating layer on a substrate formed of a material having high thermal conductivity such as alumina, and further includes a pressure roller. The heat resistant film is pressed against the heating member. Then, the heating member is heated during fixing,
When the pressure roller is rotated and a transfer material carrying an unfixed toner image on its surface is supplied, the toner image on the transfer material is fused and fixed while nipping and transporting the transfer material between the pressure roller and the fixing film. Let it. A thermistor for detecting the temperature of the heating member is adhered on the substrate, and the temperature of the heating member is controlled based on the output.

According to the surf system, in the above-described heat roller system, the entire heat roller is heated. On the other hand, only a pressure contact portion (a portion in contact with the fixing film) between a heating member and a pressure roller required for fixing is used. Is sufficient, the rise time until these portions reach a temperature at which they can be fixed is short, and preheating is not required. This is advantageous in that the image forming apparatus can perform a quick start and consume less power.

[0007]

However, when the transfer material enters the above-described fixing device, the heat of the fixing device is taken away by the transfer material. Therefore, when a thicker transfer material enters the fixing device than a thinner transfer material, more heat is taken by the transfer material.

Therefore, if the fixing is controlled at the same fixing temperature regardless of the thickness of the transfer material, heat is taken away more than the heating by the heater depending on the thickness of the transfer material, so that the fixing temperature gradually decreases, and There is a possibility that defective fixing may occur from the middle to the rear end. If the fixing temperature of the fixing device is increased in order to prevent the above-described fixing failure, the configuration of the fixing device may be unnecessarily large.

The present invention has been made to solve the above problems, and
An object of the present invention is to provide a fixing device that does not cause a fixing defect regardless of the thickness of a transfer material, and an image forming apparatus using the fixing device.

[0010]

In order to achieve the above object, a typical configuration according to the present invention comprises a heating element having a heating element, a film in contact with the heating element, and a nip portion with the film. A fixing device for fixing the image by holding and transferring a transfer material on which an image has been transferred by the film and the pressure rotator, and detecting the transfer material. In the vicinity of the nip portion, a fixing entrance sensor provided on the upstream side of the nip portion in the transfer material transport direction, and in the vicinity of the nip portion to detect the transfer material, A fixing outlet sensor provided on the downstream side in the transfer material transport direction, a fixing temperature sensor for detecting a fixing temperature of the nip portion due to heating of the heating element, and a temperature control unit for controlling a heating temperature of the heating element;
Wherein the temperature control means controls the temperature so that the first fixing temperature T1 is attained from the time when the leading end of the transfer material is detected by the fixing inlet sensor. When the temperature is detected by the sensor, a temperature difference T1-T between the detected fixing temperature T detected by the fixing temperature sensor and the first fixing temperature T1 is obtained, and the fixing exit sensor detects the rear end of the transfer material. Until the detection, the temperature is controlled so that the second fixing temperature T2 = T1 + (T1−T) obtained by adding the temperature difference to the first fixing temperature.

In the above configuration, even if a transfer material having a different thickness is supplied, the correction is performed by the amount corresponding to the decrease in the fixing temperature depending on the thickness, so that the occurrence of a fixing defect can be prevented without increasing the size of the apparatus. Will be able to do it.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the fixing device and the image forming apparatus of the present invention will be described with reference to the drawings.

[First Embodiment] An example of an image forming apparatus provided with a fixing device according to the present invention will be described with reference to FIGS. FIG. 1 is an explanatory view of the configuration of the fixing device, and FIG.
FIG. 3 is an overall schematic explanatory diagram of an image forming apparatus using the fixing device, FIG. 3 is a drive block diagram of the fixing device, and FIG. 4 is a flowchart of an operation procedure mainly on temperature control in the fixing device.

Here, the overall configuration and operation of the image forming apparatus will be briefly described first, and then the configuration of the fixing device will be described.

{Overall Configuration of Image Forming Apparatus} The image forming apparatus A includes a document table 2 on an upper part of an image forming apparatus main body 1 as shown in FIG. The original mounting table 2 is formed of a transparent plate member such as a glass plate, and the original D placed on the upper surface thereof with the image surface facing downward is pressed on the original mounting table 2 by the openable and closable original pressing plate 3. Is done. Then, when the recording start key is pressed, the original image is read by the optical system 4.

In the optical system 4, the scanning mirror 4b moves in the direction of arrow V in FIG. 2 together with the light source 4a, and irradiates the reflected light from the original to the image forming means via the return mirrors 4c1 to 4c6 and the lens 4d. Photoconductor drum 5 as a carrier
Is imagewise exposed on the surface of the substrate.

The photosensitive drum 5 is driven to rotate in a direction indicated by an arrow at a predetermined peripheral speed. In the course of the rotation, the photosensitive drum 5 is subjected to a uniform charging process of a positive or negative polarity by a charging device 6, and the surface of the drum is made uniform. By subjecting the charged surface to the above-described image forming exposure, an electrostatic latent image force corresponding to the document image formed and exposed on the surface is sequentially formed.

The electrostatic latent image is developed (developed) as a toner image by attaching a thermoplastic toner by a developing device 7. The toner image moves toward a transfer section formed between the photosensitive drum 5 and the transfer charger 8 with the rotation of the photosensitive drum 5.

Below the main body of the image forming apparatus, there is provided a feed cassette 9 in which transfer materials P are loaded and stored. The transfer materials P are fed one by one by rotation of a feed roller 10. You. Next, the transfer material P is conveyed by the conveyance rollers 11 and 12, and at a predetermined timing by the registration roller 13, that is, when the front end of the toner image on the photosensitive drum 5 reaches the transfer portion, the front end of the transfer material P is moved. It is supplied to the transfer unit at a timing such that it reaches the transfer unit. In this transfer section, the toner image on the surface of the photosensitive drum 5 is sequentially transferred to the surface of the transfer material P by the transfer charger 8.

The transfer material P after the transfer of the toner image is sequentially separated from the surface of the photosensitive drum 5 by a separating means (not shown), and is conveyed in the direction of the arrow by the conveyance belt 14 with the unfixed toner image carried on the surface. Is supplied to a fixing device B described later via a guide 15. The transfer material P is heated and pressurized by the fixing device B, and the unfixed toner image on the surface is melted and fixed to be fixed.
The sheet is discharged onto the discharge tray 17.

On the other hand, the photosensitive drum 5 after the transfer of the toner image
The cleaning device 18 removes adhered contaminants such as untransferred toner remaining on the surface, and is used for the next image formation starting from charging by the charger 6.

{Configuration of Fixing Device} Next, the fixing device B according to the present invention will be described. As shown in FIG. 1, the fixing device B is a surf fixing device for rotating and fixing a fixing film 19.

The fixing film 19 is an endless belt-like heat-resistant film. The fixing film 19 is held by a driving roller 20, a driven roller 21, which is a supporting rotating body of the film 19, and a heater supporting member provided below the two rollers. The heating element 22 is fixedly supported and suspended between the three members parallel to each other.

The driven roller 21 also serves as a tension roller for the fixing film 19, and the fixing film 19 rotates at a predetermined speed in the clockwise direction in FIG. The unfixed toner image T conveyed from the forming unit side is rotationally driven at the same peripheral speed as the conveying speed of the transfer material P as a member to be heated carrying the unfixed toner image T on the upper surface without wrinkling, meandering, and speed delay.

The pressure roller 23 is a roller having a rubber elastic layer of silicon rubber or the like with good releasability. The pressure roller 23 urges the lower surface of the heating element 22 with the lower film portion of the fixing film 19 therebetween. As a result, for example, the counter pressure contact (the nip portion N is formed) with a contact pressure of a total pressure of 4 to 10 kg, and the transfer material P rotates counterclockwise in the forward direction in the transport direction of the transfer material P.

The above-mentioned fixing film 19 is repeatedly provided for heat-fixing of a toner image, so that it has excellent heat resistance, releasability and durability, and generally has a total thickness of 100 μm or less, preferably, 100 μm or less.
Use a thin material of 40μm or less. For example, a single-layer film of a heat-resistant resin such as polyimide, polyetherimide, PES (polyether sulfide), or PFA (ethylene tetrafluoride verfluoroalkyl vinyl ether copolymer resin) or a composite layer film, for example, at least an image of a 20 μm thick film On the contact surface side, a release coating layer made by adding a conductive material to a fluororesin such as PTFE (tetrafluoroethylene resin) or PFA to a thickness of 10 μm or an elastic layer made of fluororubber, silicon rubber, etc. It was done.

In FIG. 1, the flat substrate 22a of the heating element 22 of the present embodiment is made of a material having a high thermal conductivity and a high electric resistivity such as alumina. Fixing heater 22b composed of a heating element
Is provided. It is, for example, Ag / Pd, Ta2
It is formed by applying an electric resistance material such as N in a linear or band shape by screen printing or the like. Further, the fixing heater
Power supply electrodes (not shown) are formed at both ends of 22b.
By applying a current between the electrodes, the resistance heating element generates heat over the entire length. Further, a fixing temperature sensor 22c constituted by a thermistor is provided on the surface of the substrate 22a opposite to the surface provided with the fixing heater 22b.

The temperature information of the substrate 22a detected by the fixing temperature sensor 22c is sent to a transmission unit (not shown) and control means, and the amount of power supplied to the fixing heater 22b is controlled.
The heating element 22 is controlled to a predetermined temperature as described later.

For controlling the fixing temperature, a fixing inlet sensor 24 is provided near the nip portion N and upstream of the nip portion N in the transfer material transport direction. This sensor
Reference numeral 24 denotes a flag 24a that rotates when the transfer material P passes and a photo interrupter 24b that blocks an optical path when the flag 24a rotates.
The flag 24a rotates and is detected by the photo interrupter 24b when the leading end of the transfer material P passes and when the rear end of the transfer material P passes. Thereby, it is possible to detect whether or not the leading and trailing ends of the transfer material P have passed through the entrance sensor 24. Further, in the vicinity of the nip portion N and downstream of the nip portion N in the transfer material transport direction, the transfer material P is set by the flag 25a and the photo-interrupter 25b in the same configuration as the fixing inlet sensor 24. Is provided with a fixing exit sensor 25 capable of detecting that the front end and the rear end have passed.

The transfer material P by the sensors 24 and 25
The fixing temperature is detected by the fixing temperature sensor 22c in accordance with the detection of, and the fixing temperature is controlled by the control means. Next, regarding the fixing temperature control configuration,
This will be described with reference to FIGS.

As shown in FIG. 3, the control means 26 includes a signal from an operation means 27 for operating the number of recordings and the start of recording by operating a key on an operation panel (not shown) or a fixing entrance sensor.
24, control of fixing temperature and control of image formation are performed according to signals from the fixing exit sensor 25 and the like.

The fixing heater driving means 28 is a fixing heater.
Power is supplied to the heater 22b to cause the heater 22b to generate heat. The temperature is detected by a fixing temperature sensor 22c, and the power supply to the heater 22b is controlled so as to reach a predetermined fixing temperature. In FIG. 3, solid arrows indicate electrical connection, and broken arrows indicate that heat is acting.

By the control means 26, the fixing device B is moved as shown in FIG.
Is controlled as shown in the flowchart of FIG. That is,
When the copy mode and the number of copies are set by the operation means 27 and the start key is pressed, the optical system 4 is initialized, the transfer material P is fed, and the initial temperature control of the fixing temperature of the fixing device B is performed. Start (S1).

Then, a latent image is formed on the photosensitive drum 5, and the transfer timing of the transfer material P is set by the registration roller 13 so that the latent image and the transfer material P are aligned (S2). Transfer formation of a toner image on the material P is performed (S3).

The initial temperature of the fixing device is controlled by the fixing heater driving means 28, the fixing temperature sensor 22c and the fixing heater 22b until the leading end of the transfer material P is detected by the fixing inlet sensor 24. Temperature control is performed so that N becomes the initial fixing temperature T0. The initial fixing temperature T0 may be set to a first fixing temperature T1, which will be described later. However, until the leading end of the transfer material P is detected by the fixing entrance sensor 24,
The temperature may be lower than the temperature T1. That is, since the surf fixing device can quickly raise the fixing temperature,
The temperature may be controlled to a temperature T0 (T1> T0) within a range in which the fixing temperature can be instantaneously raised to the temperature T1.

Next, when the leading end of the transfer material P is detected by the fixing entrance sensor 24 (S4), the temperature is controlled so as to become the first fixing temperature T1 (S5). The first fixing temperature T1 is a temperature suitable for thermally fixing the toner image transferred to the transfer material P having a normal thickness. Then, fixing is started at that temperature, and when the leading end of the transfer material P is detected by the fixing outlet sensor 25, the fixing temperature T is detected by the fixing temperature sensor 22c.

At this time, since the transfer material P loses heat,
Generally, the relationship of the temperature T1> T is satisfied, and the temperature difference T1−T at that time increases as the thickness of the transfer material P increases. If the temperature drop is large, a fixing failure may occur. Therefore, the fixing exit sensor 25
(S6) after detecting the leading end of the transfer material P that has passed through the fixing device B, and adding the temperature difference T1 -T to the first fixing temperature T1 until the trailing end of the transfer material P is detected. Temperature control is performed so that the fixing temperature T2 = T1 + (T1-T) = 2T1-T (2) (S7, S8).

As described above, the temperature difference between the fixing nip N and the temperature T1 is detected between the time immediately before the leading edge of the transfer material P enters the fixing device B and the time the fixing material B exits the fixing device B. The amount of heat taken by the transfer material P is detected,
The subsequent fixing temperatures are set so that the insufficient temperature with respect to the first fixing temperature T1 is added to the fixing temperature. In this manner, even if the thickness of the transfer material P changes for each sheet, the fixing temperature is corrected each time. For example, even when a thick transfer material P is transported, the fixing temperature is insufficient. Defects can be prevented beforehand.

The fixing outlet sensor 25 detects the transfer material P
After detecting the trailing end, since the fixing is not performed until the next transfer material is conveyed to the fixing device, the temperature between the transfer materials is equal to or higher than the first fixing temperature T1. Is controlled so that the fixing temperature T3 is also low (S
9).

The above-described temperature control is performed until the image forming operation for the last sheet is completed (S10). As a result, even if a thick transfer material is conveyed, it is possible to avoid a defective fixing and obtain a good image without expecting the heat capacity of the surf fixing device.

In the above-described embodiment, a copying machine has been exemplified as an image forming apparatus. However, it is obvious that the present invention can be similarly applied to a fixing device used in a facsimile apparatus, a laser beam printer, or the like.

[0042]

The present invention is constructed as described above.
Even if a transfer material having a different thickness is supplied, the correction is performed by the amount corresponding to the decrease in the fixing temperature depending on the thickness, so that it is possible to prevent the occurrence of a fixing defect without increasing the size of the apparatus.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a configuration of a fixing device.

FIG. 2 is an overall schematic explanatory diagram of an image forming apparatus using a fixing device.

FIG. 3 is a drive block diagram of the fixing device.

FIG. 4 is a flowchart of an operation procedure focusing on temperature control in the fixing device.

[Explanation of symbols]

 A: Image forming device B: Fixing device D: Document N: Nip portion P: Transfer material 1: Image forming device main body 2: Document mounting table 3: Document pressing plate 4: Optical system 4a: Light source 4b: Scanning mirror 4c1 to 4c6 … Mirror 4d… Lens 5… Photoconductor drum 6… Charger 7… Developer 8… Transfer charger 9… Supply cassette 10… Supply rollers 11, 12… Cover rollers 13… Register rollers 14… Cover belt 15… Guide 16 ... discharge roller 17 ... discharge tray 18 ... cleaning device 19 ... fixing film 20 ... drive roller 21 ... driven roller 22 ... heating element 22a ... flat substrate 22b ... fixing heater 22c ... fixing temperature sensor 23 ... pressure roller 24 ... fixing inlet Sensor 24a: Flag 24b: Photo interrupter 25: Fixing exit sensor 25a: Flag 25b: Photo interrupter 26: Control means 27: Operating means 28: Fixing heater drive Means

Claims (3)

[Claims] 1. A heating element having a heating element, a film in contact with the heating element, and a pressure rotator forming a nip with the film, wherein an image is formed by the film and the pressure rotator. A fixing device for nipping and transferring the transferred transfer material to fix the image, provided in the vicinity of the nip portion and upstream of the nip portion in the transfer material transfer direction in order to detect the transfer material. A fixing outlet sensor provided in the vicinity of the nip portion and downstream of the nip portion in the transfer material transport direction to detect a transfer material; and A fixing temperature sensor that detects a fixing temperature of the nip portion; and a temperature control unit that controls a heating temperature of the heating element. The temperature control unit detects a leading end of the transfer material by the fixing entrance sensor. Is From the first fixing temperature T1
When the leading end of the transfer material is detected by the fixing outlet sensor, the detected fixing temperature T detected by the fixing temperature sensor and the first fixing temperature T
And a second fixing temperature T2 = T obtained by adding the temperature difference to the first fixing temperature until the fixing exit sensor detects the rear end of the transfer material.
A fixing device, wherein the temperature is controlled so as to be 1+ (T1 -T). 2. The temperature control means controls the temperature so as to return the fixing temperature to the first fixing temperature T1 or lower after the fixing exit sensor detects the rear end of the transfer material. Item 2. The fixing device according to Item 1. 3. An image forming apparatus for transferring and forming an image on a transfer material and fixing the image, an image forming means for forming an image on the transfer material, and the fixing device according to claim 1 or 2. An image forming apparatus comprising: