JPH0895421A - Fixing device - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a fixing device which improves temperature control of a heat roller and prevents melting of the heat roller. A fixing device 80 of the present invention includes a heat roller heated by a heat source to fix a toner image on an image forming medium, a press roller for pressing the image forming medium to the heat roller, and an image forming medium of the heat roller. Temperature detecting means 91 for detecting the temperature of the center and both sides of the passage area,
The width detection means 93 for detecting the width of the image forming medium, and the preset temperature of the heat roller lower than the normal value by a predetermined temperature based on the detection result of the narrow width image forming medium by the width detection means 93, and When the temperature detection result of the temperature detection means 91 on both sides of the heat roller reaches an allowable value, the fixing drive means 90 restarts the fixing operation by the heat roller and the press roller after stopping for a predetermined time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device in an image forming apparatus such as an electronic copying machine.

[0002]

2. Description of the Related Art A fixing device in an electronic copying machine or the like is equipped with a heat roller (fuser roller) using aluminum as a core metal material and a press roller, and heat from a heat source provided in the heat roller is transferred to the heat roller. Via the heat roller and the press roller while allowing the paper to pass while contacting the heat roller and the press roller under pressure, and the unfixed toner image transferred onto the paper is pressed by the heat roller and the press roller. It is designed to be fixed on this sheet by utilizing the heating effect.

[0003]

By the way, when fixing a toner image to a sheet (copy sheet), the peripheral temperature of the heat roller is about 180.degree.
00 ° C is required.

However, in the case of a conventional fixing device in which a heat roller made of aluminum is incorporated in a core metal material, the outer peripheral temperature of the heat roller is usually detected at the center thereof and the set temperature of the heat roller is maintained. Because
For example, when fixing a large number of B5 size or A4-R size sheets, heat is not taken by the sheets in the areas on both sides of the heat roller through which the sheets do not pass, and as a result,
There is a problem that the material of the heat roller is melted because the temperature rises excessively in both areas of the heat roller.

In addition, a warm-up time is required until the temperature of the heat roller reaches a required temperature before the electronic copy machine is turned on and ready for copying (ready). It depends on the diameter of the heat roller and the thickness of the core metal of the heat roller. In conventional electronic copying machines, this warm-up time is
In the case of 30 sheets / minute), it takes about 60 seconds, and there is a problem that the serviceability is poor such that the user has to wait a long time. For example, in the case of a heat roller using an aluminum core metal (t = 2 mm), it has been confirmed that the warm-up time takes 60 seconds.

Therefore, the present invention improves the temperature control of the heat roller, prevents the heat roller from melting, changes the material of the core metal of the heat roller, and reaches a ready (ready) state in which copying is possible after the power is turned on. It is an object of the present invention to provide a fixing device capable of reducing the warm-up time of the fixing device.

[0007]

According to another aspect of the present invention, there is provided a fixing device including: a heat roller which is heated by a heat source to fix a toner image on an image forming medium; and a press roller which presses the image forming medium against the heat roller. Temperature detecting means for detecting the temperature of the center and both sides of the image forming medium passing area of the heat roller, width detecting means for detecting the width of the image forming medium, and the detection result of the narrow image forming medium by the width detecting means. Based on the above, the set temperature of the heat roller is lowered by a predetermined temperature from the normal value, and when the temperature detection result on both sides of the heat roller by the temperature detection means reaches the allowable value, the fixing operation by the heat roller and the press roller is performed. And a fixing drive unit for restarting after stopping for a predetermined time.

According to a second aspect of the present invention, there is provided a fixing device including a heat roller which is heated by a heat source to fix a toner image on an image forming medium, a press roller which presses the image forming medium against the heat roller, and an image forming by the heat roller. Temperature detecting means for detecting the temperature of the center and both sides of the medium passage area,
Based on the width detection means for detecting the width of the image forming medium and the detection result of the narrow width image forming medium by the width detection means, the preset temperature of the heat roller is lowered by 10 ° C. from the normal value and the temperature detection is performed. When the temperature detection result of both sides of the heat roller by the means reaches 250 ° C., the fixing operation means restarts the fixing operation by the heat roller and the press roller after stopping for a predetermined time.

According to a third aspect of the present invention, there is provided a fixing device including a heat roller including iron as a core metal which is heated by a heat source to fix a toner image on the image forming medium, and a press roller which presses the image forming medium against the heat roller. Temperature detecting means for detecting the temperature of the center and both sides of the image forming medium passing area of the heat roller, width detecting means for detecting the width of the image forming medium, and the detection result of the narrow image forming medium by the width detecting means. Based on the above, the set temperature of the heat roller is lowered by 10 ° C. from the normal value, and when the temperature detection result of both sides of the heat roller by the temperature detection means reaches 250 ° C., the fixing operation by the heat roller and the press roller is performed. And a fixing drive unit for restarting after stopping for a predetermined time.

[0010]

According to the present invention, the toner image is fixed on the image forming medium by the heat roller and the press roller which presses the image forming medium against the heat roller in the fixing device. The means detects the temperature at the center and both sides of the image forming medium passage area of the heat roller. In addition, the width detecting means detects the width of the image forming medium.

The fixing drive means lowers the set temperature of the heat roller by a predetermined temperature below a normal value based on the detection result of the narrow width image forming medium by the width detection means, and both sides of the heat roller by the temperature detection means. When the temperature detection result reaches the allowable value, the fixing operation by the heat roller and the press roller is stopped for a predetermined time and then restarted.

This makes it possible to prevent melting of both sides of the image forming medium passing region of the heat roller.

The toner image is fixed on the image forming medium by the heat roller and the press roller for bringing the image forming medium into pressure contact with the heat roller in the fixing device according to the second aspect. At this time, the temperature detection is accompanied by the fixing operation. The means detects the temperature at the center and both sides of the image forming medium passage area of the heat roller. In addition, the width detecting means detects the width of the image forming medium.

The fixing drive means lowers the set temperature of the heat roller by 10 ° C. below the normal value based on the detection result of the narrow width image forming medium by the width detection means, and the both sides of the heat roller by the temperature detection means. When the temperature detection result of (2) reaches 250 ° C., the fixing operation by the heat roller and the press roller is stopped for a predetermined time and then restarted.

As a result, the temperature of both sides of the image forming medium passage area of the heat roller does not rise beyond the allowable value exceeding 250 ° C., and its melting can be prevented.

According to the fixing device of the third aspect, the same function as that of the fixing device of the second aspect is exhibited, and since the core metal material of the heat roller is iron, the core metal material is aluminum. Compared with the conventional device, the warm-up time after power-on can be shortened due to the difference in specific heat between iron and aluminum.

[0017]

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

FIG. 1 shows an outline of an image forming apparatus 2 which constitutes the digital electronic copying machine of this embodiment.

The image forming apparatus 2 has a configuration in which an image reading section 4 and an image forming section 6 are mounted in a box-shaped apparatus body 3.

The image reading section 4 is provided with a document table 10 on which a document D having a document image is placed, and a size plate which is arranged at one end of the document table 10 and indicates a position where the document D should be placed. 10a, and a document pressing plate 12 that is formed so as to be openable and closable with respect to the document table 10 and that allows the document D placed on the document table 10 to come into close contact with the document table 10. In addition, in FIG.
Reference numeral 10a is a document stopper.

Inside the document table 10 (below), an illumination lamp 22 for illuminating a document D placed on the document table 10,
A reflector 24 that collects the illumination light emitted from the illumination lamp 22 on the original D, and a first mirror 26 that reflects the reflected light from the original D toward a second carriage 30 described later.
The first carriage 20 including is arranged.

The first carriage 20 is arranged so as to be movable in parallel with the document table 10 and is driven by a pulse motor (not shown) via a toothed belt (not shown) or the like.
It is designed to be driven in parallel along 0.

The second carriage arranged on the side of the first carriage 20.
The carriage 30 is provided with a second mirror 32 and a third mirror 34 that sequentially bend the reflected light from the document D that is bent via the first mirror 26 of the first carriage 20, with their anti-slope surfaces facing each other. There is. The second carriage 30 is
The first carriage 20 is driven by a toothed belt or the like (not shown) that drives the first carriage 20, and is driven parallel to the first carriage 20 along the document table 10 at a speed of 1/2. It is supposed to be done.

Below the first carriage 20,
A region including the optical axis of the reflected light that has returned through the second carriage 30 is configured to be movable via a drive mechanism (not shown), and provides the reflected light from the second carriage 30 with focusing and reflection. An image forming lens 36 for forming an image of light at a desired magnification, and the reflected light focused through the image forming lens 36 are photoelectrically converted to an image memory 78, which will be described later, according to an original image of an original D. A CCD sensor 38 that outputs a signal is arranged.

The image forming section 6 includes a light source, that is, a semiconductor laser oscillator 42, and the semiconductor laser oscillator 42 corresponds to the image information of the document D read by the image reading section 4.
It has an exposure device 40 that changes the intensity of the laser beam LB from the device and performs exposure scanning with respect to a photosensitive drum 50 as an image carrier described later.

This exposure apparatus 40 gives a focusing property to the laser beam LB generated from the semiconductor laser oscillator 42 and converts it into a laser beam LB having a substantially circular cross-sectional shape, and this first lens. A polygon mirror 44 driven by a polygon motor 44A as a light deflecting means for deflecting the light converted into the laser beam LB having a circular cross-sectional shape through the lens along the axial direction of the photosensitive drum 50 described later. In order to sequentially scan the deflected laser beam LB to a desired position on the photoconductor drum 50, the deflection angle of the laser beam LB and the optical axis on the photoconductor drum 50 to the position where the beam is to be imaged. The second lens 46 and the second lens 4 that match the distance
The mirror 48 that reflects the laser beam LB having passed through 6 toward the photoconductor drum 50 is included.

Further, a photosensitive drum 50 as an image carrier having a conductive support, a photoconductive layer and an insulating layer as a basic structure is arranged substantially at the center of the image forming section 6.

Around the photosensitive drum 50, a pre-exposure device 51 as residual charge removing means for irradiating the photosensitive drum 50 with light along the rotation direction (arrow direction) to remove residual charges, A charging device 52 as a charging means for uniformly charging the surface of the photosensitive drum 50, and the exposure device 40.
A developing device including a developing roller 54a as a developing unit that develops the electrostatic latent image formed on the surface of the photoconductor drum 50 by irradiating the laser beam LB with a two-component developer including toner and carrier. 54, a corona discharge device as a transfer means for transferring the toner image formed on the photosensitive drum 50 onto a sheet (plain paper, OHP sheet, etc.) P as an image forming medium fed from the sheet cassette 55. Transfer charger 56, a peeling charger 57 using a corona discharge device as a peeling means for peeling the sheet P on which the toner image is transferred from the photosensitive drum 50, and a cleaning means for scraping off the toner remaining on the photosensitive drum 50. Cleaners 58 are arranged in order.

On the inlet side of the transfer charger 56,
A transfer guide 75 as a guide member is provided, and a peeling supporter 76, which is a guide means, is provided at the upper opening of the shield case 57b of the peeling charger 57. It is guided so that it can be in close contact.

Further, in the apparatus main body 3, a paper cassette 5
The paper P fed from the paper 5 through the paper feed roller 59 or the paper P fed by the manual paper feed tray 60 through the paper feed roller 61 is fed to the photosensitive drum 50 and the transfer charger 56. A sheet conveying path 64 is formed on the left side surface of the apparatus main body 3 through an image transfer point 62 formed between the sheet conveying path 64 and the sheet conveying path 64.

The image transfer point 6 on the sheet conveying path 64
On the upstream side of 2, the sheet P is aligned and the sheet P is aligned with the image forming timing of the photoconductor drum 50.
A registration roller pair 65 for feeding the sheet to the image transfer point 62 and a registration roller pre-switch 66 provided near the upstream position of the registration roller pair 65 for detecting the fed paper P are provided.

Further, on the downstream side of the image transfer point 62 of the paper transport path 64, a transport device 67 for transporting the paper P separated from the photosensitive drum 50 by the separation charger 57, and electrostatic transferred to the paper P. Fixing device 80 for fixing the toner image on the paper P by heating the toner image in a state where the toner image is adhered, and a pair of discharge rollers 69 for discharging the paper P on which the toner image is fixed onto the discharge tray 63. Is provided.

Then, the registration roller pair 65, the transfer guide 75, the peeling supporter 76, the conveying device 67, etc. constitute a conveying means for conveying the paper P so as to pass the image transfer point 62.

The fixing device 80 is made of iron Fe (heat conductivity: 80 w / mk; aluminum: 237 w / mk) which is heated by a heater lamp 81 as a heat source and fixes the toner image on the paper P. Heat roller 8 with gold
2 and a press roller 83 for pressing the paper P against the heat roller 82.

Further, the heat roller 82 is made of thin iron t =
It is processed into a cylindrical shape with a core metal of 0.5 to 0.9 mm.

FIG. 2 shows the arrangement positions P0, P1 and P2 of the temperature detecting means 91 with respect to the heat roller 82. That is, a thermistor for detecting the center temperature is arranged at the arrangement position P0, a thermistor for detecting the front temperature is arranged at the arrangement position P1, and a thermistor for detecting the rear temperature is arranged at the arrangement position P2. Are configured.

The end gear 8 of the heat roller 82
The rotational force from the drive source 92 is transmitted to 2a.

Further, the width of the paper P of various sizes (wide size such as B4 and A3, small size such as B5 and A4-R) passing through the paper passage area AR of the heat roller 82 is the width shown in FIG. It is adapted to be detected by the detection means 93.

FIG. 3 shows a control system of the fixing device 80, and a fixing drive means 90 for controlling the entire drive.
Further, the temperature detection means 91 and the width detection means 93 are connected, and the fixing drive means 90 controls the drive of the drive source 92 and the energization control of the heater lamp 81.

Next, the operation of the fixing device 80 will be described mainly with respect to the temperature control of each of the center, front and rear parts of the heat roller 82 and with reference to FIGS. 4 to 6.

The heat roller 8 in this fixing device 80
The toner image is fixed on the paper P by the heat roller 82 and the press roller 83 that presses the paper P against the heat roller 82.
At this time, with the fixing operation, the thermistors of the temperature detecting means detect the temperatures of the center, front and rear parts of the paper passage area AR of the heat roller 82. Further, the width detecting means 93 detects the width of the paper P.

The fixing drive means 90 heats the fixing paper 90 when the fixing operation of, for example, 50 sheets is carried out based on the detection result of the narrow width paper P by the width detecting means 93, for example, the small width paper P such as A4-R. As shown in FIG. 4, the set temperature of the center of the roller 82 is lowered to 190 ° C., which is 10 ° C. lower than the normal value of 200 ° C.

At the same time, the fixing driving means 90 performs the fixing operation by the heat roller 82 and the press roller 83 for a predetermined time (for example, 10 when the temperature detection result of the temperature detection means 91 on both sides of the heat roller 82 reaches 250 ° C.).
After 20 seconds), the fixing operation is restarted, and
The operation of fixing the 50 sheets is repeated.

As a result, the temperature of both sides of the paper passage area AR of the heat roller 82 does not rise outside the allowable value exceeding 250 ° C., and its melting can be prevented.

The heat roller 82 is made of iron and has a thin wall thickness t = 0.5 to 0.9 mm and is formed into a cylindrical shape. Since the specific heat of the heat roller 82 is larger than that of aluminum, the warm-up time after the power is turned on. Can be shortened. In this embodiment, the warm-up time is 16 seconds from the conventional 60 seconds.
It was confirmed that the time could be shortened to about 40 seconds.

FIG. 5 shows the fixing device 80 of the present embodiment
4 shows changes over time in the temperatures of the center, front, and rear of the heat roller 82 when the fixing operation of 4, A3 size paper P is performed. In this case, the center,
It can be seen that the temperatures of the front and rear parts have converged to 200 ° C.

FIG. 6 shows the center of the heat roller 82 when the fixing operation of the A4-R size paper P is performed without any control by the fixing device 80 of this embodiment,
This figure shows the changes over time in the front and rear temperatures. In this case, the temperature of the center converges to 200 ° C., but it is understood that the temperatures of the front and rear parts may exceed 250 ° C. and the front and rear parts may melt.

From the above, it is understood that the control of this embodiment as described above is appropriate.

[0049]

According to the first aspect of the present invention, the fixing device capable of preventing melting of both sides of the image forming medium passing region of the heat roller by the operations of the temperature detecting means, the width detecting means and the fixing driving means. Can be provided.

According to the second aspect of the present invention, the temperature detection means, the width detection means, and the fixing drive means operate to raise the temperature of both sides of the image forming medium passage area of the heat roller beyond the allowable value exceeding 250 ° C. Therefore, it is possible to provide a fixing device capable of preventing its melting.

According to the invention of claim 3, in addition to the effect of the invention of claim 2, since the core metal material of the heat roller is iron, a fixing device capable of shortening the warm-up time after power-on is provided. Can be provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an image forming apparatus including an apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a temperature detection position of the device according to the embodiment of the present invention.

FIG. 3 is a block diagram showing a control system of the apparatus according to the embodiment of the present invention.

FIG. 4 is a graph showing temperature control for a narrow width sheet of the apparatus according to the embodiment of the present invention.

FIG. 5 is a graph showing a temperature change at the time of fixing on a wide size sheet of the apparatus of the embodiment of the present invention.

FIG. 6 is a graph showing a temperature change when temperature control is not performed on a narrow-width sheet of the apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 2 image forming apparatus 80 fixing device 81 heater lamp 82 heat roller 90 fixing driving means 91 temperature detecting means 92 driving source 93 width detecting means

Claims (3)

[Claims] 1. A heat roller heated by a heat source for fixing a toner image on an image forming medium, a press roller for pressing the image forming medium against the heat roller, and a center and both sides of an image forming medium passing region of the heat roller. Temperature detecting means for detecting the temperature of, the width detecting means for detecting the width of the image forming medium, the set temperature of the heat roller from the normal value based on the detection result of the narrow width image forming medium by the width detecting means. And a fixing drive unit that lowers the predetermined temperature and restarts the fixing operation by the heat roller and the press roller after stopping for a predetermined time when the temperature detection result of both sides of the heat roller by the temperature detection unit reaches an allowable value. A fixing device characterized by the above. 2. A heat roller heated by a heating source to fix a toner image on an image forming medium, a press roller for pressing the image forming medium against the heat roller, and a center and both sides of an image forming medium passing region of the heat roller. Temperature detecting means for detecting the temperature of, the width detecting means for detecting the width of the image forming medium, the set temperature of the heat roller from the normal value based on the detection result of the narrow width image forming medium by the width detecting means. And 10% lowering temperature, and when the temperature detection result of both sides of the heat roller by the temperature detecting means reaches 250 ° C., the fixing operation means restarts the fixing operation by the heat roller and the press roller after stopping for a predetermined time. A fixing device characterized by the above. 3. A heat roller having an iron core as a core metal which is heated by a heat source to fix a toner image on the image forming medium, a press roller which presses the image forming medium against the heat roller, and an image forming medium of the heat roller. Temperature detecting means for detecting the temperature of the center and both sides of the passage area, width detecting means for detecting the width of the image forming medium, and the heat roller of the heat roller based on the detection result of the narrow image forming medium by the width detecting means. The set temperature is lowered by 10 ° C. from the normal value, and when the temperature detection result of both sides of the heat roller by the temperature detection means reaches 250 ° C., the fixing operation by the heat roller and the press roller is stopped for a predetermined time and then restarted. A fixing device comprising: a fixing driving unit.