JPH04358189A - Image forming device - Google Patents

Abstract

PURPOSE:To execute excellent fixing by detecting the roughness of a paper by means of a surface properties detecting means disposed on the carrying passage of the paper, and increasing pressure between a fixing roller and a pressure roller when the degree of the roughness is high. CONSTITUTION:A toner image formed on a photosensitive body 1 is transferred on the paper P, carried, and fixed on the paper P by a fixing device 9 as a permanent image, and then, the paper is ejected. A means 10 for detecting the surface properties of the paper P is provided on the carrying passage of the paper P, and the paper P is carried while being interposed between the detecting means 10 and a guiding plate 13 with light pressure. The roughness of the paper P is detected by the surface properties detecting means 10 and the information of the detection is sent to a DC controller, and the pressure between the fixing roller 18 and the pressure roller 22 is adjusted with a control value corresponding to the roughness of the paper P. In other words, when the degree of the detected roughness is high, the pressure between the fixing roller 18 and the pressure roller 22 is enhanced to attain the fixing. Thus, even if the surface roughness of a transfer material is different, an excellent image can be obtained.

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 equipped with a fixing device for fixing a developer image on a transfer material as a permanent image.

0002

2. Description of the Related Art Conventionally, the pressure between a fixing roller and a pressure roller has been set to a predetermined value so that good fixing can be performed at a constant fixing temperature even in a low-temperature environment.

[0003] However, in the past, the thickness, material (for example, pulp paper, Mylar paper, etc.), size, etc. of the transfer material were not taken into consideration, and therefore, depending on the transfer material, good fixing may not be achieved. .

Therefore, before the transfer material enters the fixing device, the thickness, material, and size of the transfer material are detected by a detection means, and the pressure between the fixing roller and the pressure roller is adjusted according to the information. A method has been proposed to ensure good fixing by adjusting the

[0005]

However, according to the above-mentioned conventional example, the surface properties such as the roughness of the transfer material are not taken into account, so that good fixing may not be achieved.

For example, if the surface roughness of the transfer material differs,
Even when the thickness, material, and size of the transfer materials were the same, the fixing properties were different and it was not possible to obtain a good image.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide an image forming apparatus that can obtain good images even when the surface roughness of transfer materials differs.

[0008]

[Means for Solving the Problems] According to the present invention, the above object is achieved by bringing a paper feeding section that supplies a transfer material and a developing section that forms an unfixed developer image on the transfer material into pressure contact with each other. a fixing device including a fixing roller and a pressure roller which are rotatably disposed and fix the unfixed developer image by conveying the transfer material under pressure, and between the fixing roller and the pressure roller; In the image forming apparatus in which the fixing section is provided with a pressure adjusting means that varies the pressure of a detection means for detecting the roughness of the surface; and a pressure adjustment means configured to increase the pressure between the fixing roller and the pressure roller as the roughness of the surface detected by the detection means increases. This is achieved by having a control means for.

[0009]

According to the present invention, when the transfer material is supplied from the paper feed section, the surface roughness of the transfer material is detected by the means for detecting the surface roughness of the transfer material. If the detected degree of roughness is large, the pressure between the fixing roller and the pressure roller is increased by the pressure adjusting means to perform fixing. Therefore, appropriate pressure is applied to the transfer material and good fixing is performed.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS First to third embodiments of the present invention will be explained based on the drawings.

First Embodiment First, a first embodiment of the present invention will be explained based on FIGS. 1 to 3.

FIG. 1 is a schematic sectional view of an electrophotographic apparatus which is a first embodiment of the present invention.

As is well known, the region where a developer image (hereinafter referred to as a toner image) is formed includes a charging device 2, an image exposure device 3, a developing device 4, and a transfer separation charging device around the photoreceptor 1. A toner image is formed on the photoreceptor 1 by an image forming method called the Carlson method.

This toner image is transferred onto a transfer material (hereinafter referred to as "paper") P such as paper supplied from a paper feeding system, is conveyed, and is fixed onto the paper P as a permanent image by a fixing device 9. After that, the paper is ejected.

In the present invention, a means 10 for detecting the surface properties of the paper P is provided on the conveyance system for conveying the paper P.

The detection means 10 is schematically shown in FIG.

The detection means 10 includes a metal conveyance guide 13,
13', it is provided facing the guide 13, and is gently pressurized from the back side by a biasing member 14. Therefore, the paper P is conveyed while being sandwiched between the detection means 10 and the guide plate 13 with light pressure.

When the detection means 10 is viewed from a cross section, it has a structure in which a flexible elastic body 12 like a sponge is wrapped in a conductive film 11, and the film 11 is connected to a capacitance meter 15.
connected to. Further, the opposing guide plate 13 is grounded or grounded via a known impedance element.

Furthermore, a magnetic body 16 is attached to the surface of the detection means 10 facing the guide plate 13', and a gap sensor 17 facing this is attached to the guide plate 13'. (Note that the gap sensor 17 measures the distance between the magnetic body 16 and the sensor using an eddy current measurement method.) In such a configuration, the paper P is connected to the detection means 1.
0 and the guide plate 13, the value detected by the gap sensor 17 changes by the thickness of the paper P that has entered, so the thickness of the paper P passing through can be determined. Further, the capacitance detected by the capacitance meter is detected as a composite capacitance of the capacitance C1 of the paper P itself and the capacitance C2 due to the gaps between the paper P and the guide plate 13 and the paper P and the film 11. Of these, C1 depends on the paper thickness, so C1 can be determined from the thickness of the paper P obtained by the gap sensor. Therefore, the remaining capacity is due to C2 and is proportional to the surface roughness of the paper P, so the rougher the surface, the greater the capacity. Therefore, surface roughness can be approximately detected based on the magnitude of the detected capacitance.

Next, the fixing device 9 will be explained. The fixing device 9 is a heat-pressing type fixing device that fixes the toner image as a permanent image on the paper by heating and pressurizing the paper P carrying the toner image. FIG. 3 shows a heat-pressure fixing device in the apparatus of this embodiment.

The metal roller 19 of the fixing roller 18 has a wall thickness of t.
= 2.5 mm hollow cylindrical aluminum alloy core metal, and the surface layer, which is the release layer 20, is made of PTFE, which is a fluororesin.
(polytetrafluoroethylene) layer is coated. The diameter used was 32 mm. Further, a halogen heater was used as the heater 21 which is a heat source inside the device. The pressure roller 22 has a thickness t=5.0 as an intermediate layer on the core metal.
A silicone rubber layer 23 which is an elastic body with a thickness of 50 μm thick, a tubular fluororesin layer 23 with a thickness of 50 μm made of PFA (copolymer of polytetrafluoroethylene resin and perchloroalkoxyethylene resin) on its surface layer 24, respectively.
The diameter is 30 mm.

The surface temperature of the fixing roller 18 is kept substantially constant by a temperature control element 31. Fixing roller 18
The pressure between the pressure roller 22 and the pressure roller 22 is applied by the arm 26 rotating around the rotating shaft 25 due to the biasing force of the spring 27 and pushing up the metal core end 28 of the pressure roller 22 . A solenoid 29 serving as a driving means for the spring 27 is connected to the spring 27, and adjusts the pressure applied to the spring 27 according to a control value output from a DC controller (not shown).

The operating state of the above-described configuration will be explained.

When a copy button (not shown) is pressed, a toner image formation process progresses on the photoreceptor 1, and in synchronization with this, paper P is fed. Paper P is the conveyance guide 13
, 13', the surface roughness detection means 10 detects the roughness of the paper P as described above, and the information is sent to DC.
sent to a controller (not shown). The toner image on the photoreceptor 1 is transferred onto the paper P by the transfer charger 5, and then conveyed to the fixing device 9. In this fixing process, since information on the roughness of the paper P is sent to the DC controller in advance, a control value corresponding to the roughness of the paper P can be sent to the solenoid 29 from the DC controller. The solenoid 29 applies pressure to the spring 27 according to the control value output from the DC controller, thereby adjusting the pressure between the fixing roller 18 and the pressure roller 22 to a predetermined value according to the roughness of the paper P. For example, when the surface roughness Rz value of the paper P is less than 15 μm, the pressure (total pressure) between the fixing roller 18 and the pressure roller 22 is set to 25 kg, and the surface roughness Rz value of the paper is set to 25 kg. When it is 15 μm or more, the pressure (total pressure) between the fixing roller 18 and the pressure roller 22 is increased by 10 kg to 35 kg.
Set to g weight to increase fixing ability.

As described above, since the pressure between the fixing roller and the pressure roller is set according to the roughness of the paper, defective fixing can be prevented.

<Second Embodiment> Next, a second embodiment of the present invention will be described.

In this embodiment, in order to finely set the pressure between the fixing roller and the pressure roller according to the transfer material, not only the surface properties of the transfer material but also the thickness of the conventional transfer material are used. The pressure between the fixing roller and the pressure roller is set by taking information into consideration. Here, the thickness of the transfer material is measured by the gap sensor 17 in FIG. Below, an example of the pressure setting between the fixing roller and the pressure roller is given. If the thickness of the transfer material is less than 100 μm and the surface roughness Rz value of the transfer material is less than 15 μm, a pressure of 25 kg is applied. Set the thickness of the transfer material to 100
less than μm, and the surface roughness Rz value of the transfer material is 15 μm
m or more, set the pressure to 30 kg force. Table 1 shows pressure settings for other examples.

[0028]

[Table 1] As described above, by taking into consideration not only the surface properties of the transfer material but also the thickness of the transfer material, unnecessary pressure can be avoided, and the pressure can be applied more appropriately depending on the transfer material than in the first embodiment. Can be configured.

<Third Embodiment> Next, a third embodiment of the present invention will be described based on FIG. 4. Note that the same reference numerals are given to the same parts as in the first embodiment, and the explanation thereof will be omitted.

In the above examples, the surface properties of both sides of the paper were detected and controlled, but with ordinary paper, there is usually a difference in the surface properties between the front and back sides of the paper, and the fixing properties are different between the front and back sides of the paper. different. Therefore, it may be sufficient to actually detect and control the surface properties of the surface of the paper on which the toner image is placed. The present embodiment is one of such embodiments, and differs from the first embodiment in that the surface quality of the paper on which the toner is placed is optically detected.

As shown in FIG. 4, a light source (parallel light such as a laser beam is preferable, but a condensed light It is composed of a light receiving element (CCD) 34 that detects reflected light from the paper surface. The light emitted from the light source 33 is reflected by the paper surface, and most of it enters the light receiving element 34. At this time, if the surface of the paper is smooth, the light is reflected in a substantially constant direction, so the light is not received. The spread of light on the element 34 is small. However, if the surface is rough, the light will be diffusely reflected and will be spread onto the light receiving element 34 before entering. The degree of this spread depends on the surface properties of the paper P on the surface irradiated with light. Therefore, from the spread of the reflected light detected by the light receiving element 34, only the surface quality of the paper P on which the toner image is placed can be detected. Note that, in reality, the output from the light receiving element 34 is calculated by the CPU and calculated as the surface property of the paper P, but such a circuit itself is well known, so a description thereof will be omitted.

According to this embodiment, similarly to the first embodiment, by selecting the pressure between the fixing roller and the pressure roller according to the detected paper surface properties, it is possible to avoid fixing defects. can. Further, in this embodiment in particular, since the surface properties of only the surface on which toner is actually placed are detected and controlled, the above-mentioned characteristics can be optimized more than in the first and second embodiments.

In this embodiment, an example of optical detection was shown as a means for detecting the surface properties of the surface on which toner is placed, but the detection method is not limited to such an optical method. Instead, various known methods can be applied, such as a method of tracing the surface of paper with a stylus to directly detect its surface properties.

[0034]

[Effects of the Invention] As explained above, according to the present invention,
Since the pressure between the fixing roller and the pressure roller is increased as the surface roughness of the transfer material increases, good fixing can always be performed even when the surface of the transfer material is rough.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a schematic configuration of a first embodiment of the device of the present invention.

FIG. 2 is a sectional view showing the vicinity of a means for detecting surface roughness of a transfer material in the apparatus of FIG. 1;

FIG. 3 is a sectional view showing a schematic configuration of a fixing device in the apparatus shown in FIG. 1;

FIG. 4 is a sectional view showing the vicinity of means for detecting the surface roughness of a transfer material in a third embodiment of the present invention.

[Explanation of symbols]

9 Fixing device 10 Means for detecting surface roughness (surface roughness detection means)
18 Fixing roller 22 Pressure roller P Transfer material (paper)

Claims (1)

[Claims] Claim 1: A paper feeding section that supplies a transfer material and a developing section that forms an unfixed developer image on the transfer material are rotatably disposed in pressure contact with each other and convey the transfer material under pressure. A fixing device including a fixing roller and a pressure roller for fixing the unfixed developer image, and a pressure adjusting means for varying the pressure between the fixing roller and the pressure roller is provided in the fixing section. In the provided image forming apparatus,
a detection means for detecting surface roughness of the transfer material disposed on a conveyance path until the transfer material reaches the fixing roller and the pressure roller; An image forming apparatus characterized in that the image forming apparatus further comprises a control means for the pressure adjusting means configured to increase the pressure between the fixing roller and the pressure roller as the amount of pressure increases.