JP2001265159A - Fixing machine and image forming device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing machine for avoiding the temperature reduction of a fixing body and the temperature difference between the fixing body and a pressure body at the time of continuously performing a fixing processing, and capable of suppressing curling of a recording medium after the fixation processing, while shortening a warm-up time without damaging the fixation stability and the productivity, and to provide an image forming device equipped with the fixing machine. SOLUTION: A fixing roller 4 and a pressure roller 5 are controlled to start rotation, when the temperature detected by a thermistor 8 reaches 195 deg.C at the start of the heating operation of a main heater 6 and a sub heater 7 and so as to rotate preliminarily, before a transfer material P reaches a nip part. The rollers are set to continue the preliminary rotation, until one minute elapses even after the detection temperature reaches 200 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium carrying an unfixed image, which is nipped and conveyed by a nip formed by a fixing member and a pressure member, and is heated and pressed to transfer the unfixed image to the recording medium. More specifically, the present invention relates to a fixing device for fixing an image to an image forming apparatus and an image forming apparatus including the fixing device.

[0002]

2. Description of the Related Art Image forming apparatuses such as copiers and printers
A fixing device is provided for fixing a toner image, which is an unfixed image electrostatically formed on a transfer material as a recording medium such as paper, to the transfer material.

[0003] Many such fixing devices have been proposed in the past, and in general, fixing devices are known in which a toner image on a transfer material is heated and melted and fixed on the transfer material. In particular, a roller pair as a fixing body and a pressure body which press against each other and rotate (a fixing roller and a pressure roller)
And a heating source heater serving as a heating element for heating the fixing roller. The toner image on the transfer material is heated and pressed by nipping and transporting the transfer material in a nip formed by the fixing roller and the pressure roller. Fixing devices for fixing are widely used in practice.

In the above-described image forming apparatus, in order to maintain good fixing performance, when the apparatus is started up in the morning (when the heating source heater is started up), a temperature detecting means for detecting the temperature of the fixing roller is used. The copying is enabled after the surface temperature of the fixing roller detected by the temperature element reaches a predetermined temperature (copyable temperature).

When the temperature at which copying can be started is set low, the time from the start of the apparatus to when copying can be started (warm-up time) is shortened. However, if the power of the heating source heater is not sufficiently large, continuous copying is performed. There is a possibility that the temperature of the fixing roller decreases, and fixing failure occurs.

As a means for preventing such a defective fixing, a sequence (copy speed down sequence) for reducing the copy speed when the temperature of the fixing roller is lowered to a predetermined temperature (fixing limit temperature or a temperature higher than the fixing limit temperature) is set. However, the productivity at the time of performing a large amount of continuous copying is low, so that the copy startable temperature is usually set relatively higher than the fixing limit temperature.

[0007]

However, in the conventional image forming apparatus, if the temperature at which copying can be started is set to an unnecessarily high temperature, not only the warm-up time becomes long, but also the transfer paper is fixed to the fixing device. There is a possibility that a stacking failure may occur due to an increase in the amount of curl after passing through.

This is because one of the causes of the curl is a difference in the evaporation amount of water on the front and back surfaces of the transfer paper due to the temperature difference between the fixing roller and the pressure roller.
As a result, curling occurs after passing through the fixing device, and the temperature difference between the fixing roller and the pressure roller is particularly large immediately after the warm-up in the morning, so that the curling amount increases, which may cause a stacking failure at the paper discharge unit. There is.

Accordingly, the present invention prevents a decrease in the temperature of the fixing body during a continuous fixing process and a temperature difference between the fixing body and the pressure body, thereby shortening the warm-up time without impairing the fixing stability and productivity. It is an object of the present invention to provide a fixing device capable of suppressing the occurrence of curling of a recording medium after a fixing process, and an image forming apparatus including the fixing device.

[0010]

According to the present invention, the object is to provide a fixing member and a pressurizing member which rotate in pressure contact with each other, a heating member for heating the fixing member, and a temperature for detecting the temperature of the fixing member. A detection unit, and a control unit for controlling the driving of the heating unit so that the temperature detected by the temperature detection unit falls within a predetermined temperature range, wherein the recording medium carrying the unfixed image is formed by the fixing unit and the pressing unit. In the fixing device in which the unfixed image is fixed on the recording medium by being nipped and conveyed by a nip and heated and pressurized, the fixing body and the pressurized body are detected by the temperature detecting means when the heating body is heated up. The rotation is started when the temperature reaches a predetermined temperature within the predetermined temperature range, and the pre-rotation is performed so that the recording medium is pre-rotated before reaching the nip of the recording medium. Temperature range After reaching the upper limit temperature is also achieved by a first aspect of the invention that are set to be continued until a predetermined time elapses.

Further, according to the present application, the above object is to provide an image forming apparatus for recording an image formed by a series of image forming processes on a recording medium, wherein the image forming apparatus includes the fixing device of the first invention. The invention is also achieved by the invention of the above.

That is, according to the first aspect of the present invention, when the fixing member and the pressure member are heated and heated by the heating member, the temperature detected by the temperature detecting means falls within a predetermined temperature range within the predetermined temperature range. , The preparatory rotation continues until the detected temperature reaches the upper limit temperature of the predetermined temperature range until a predetermined time elapses, and then the recording medium is passed through the nip.

In the second invention according to the present application, the temperature detected by the temperature detecting means when the fixing body and the pressurizing body start heating of the heating body is within a predetermined temperature range. , The preparatory rotation continues until the detected temperature reaches the upper limit temperature of the predetermined temperature range until a predetermined time elapses, and then the recording medium is passed through the nip.

[0014]

Embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic sectional view of such an image forming apparatus.

The image forming apparatus includes an image carrier 26,
A primary charger 20 for charging the surface of the image carrier 26, a laser 13 for performing an exposure process on the charged surface of the image carrier 26,
A developing device 21 for developing the latent image on the image carrier 26 as a toner image, a transfer charger 35 for transferring the toner image on the image carrier 26 to a recording medium, and a transfer material P as a recording medium that has undergone a transfer process And a fixing device 15 for performing a fixing process.

The image forming apparatus includes a control unit 16
The control device 16 controls the timing of the entire operation of the image forming apparatus. The control device 16 forms a toner image on the image carrier 26, and transfers the transfer material P at the portions of the separation charger 34 and the transfer charger 35. Transfer of the toner image to the fixing device 15
, The operation of forming a series of images such as fusing and fixing the toner image onto the transfer material P is collectively controlled.

Next, the operation of the image forming apparatus will be described.

In this image forming apparatus, first, the surface of the image carrier 26 rotating in the direction of the arrow shown in the figure is uniformly charged by the primary charger 20 disposed above the image carrier 26. .

The reflected light of the light emitted from the light source 10 to the original G is converted into a digital image signal through a reading device 11 and a control device 16 which is a control CPU, and is converted into a digital image signal. The laser 13 exposes the charged surface of the image carrier 26, and as a result, an electrostatic latent image is formed on the image carrier 26.

The electrostatic latent image is developed as a toner image by a developing device 21, and the toner image is transferred to a paper as a recording medium by a transfer charger 35. And is conveyed to the fixing device 15 along the conveyance path 25.

The paper that has passed through the transport path 25 passes through the guide 3 and is transferred to a fixing roller 4 as a fixing body incorporating a main heater 6 and a sub-heater 7 as appropriate heating bodies such as a halogen heater, and a fixing roller 4. The toner image is conveyed to a nip portion with a pressure roller 5 serving as a pressurizing member to be pressed, and when passing through the nip portion, the toner image is melt-fixed to the paper to form a hard copy and is carried out of the machine.

It is preferable that a fluororesin film such as PTFE is formed on the surface of the fixing roller 4 to prevent offset, and the pressing roller 5 is formed of an elastic material such as heat-resistant rubber. Preferably, a nip width is obtained.

A thermistor 8 as a temperature detecting means such as a thermistor or a thermocouple is disposed in contact with the outer peripheral surface of the fixing roller 4, and transmits the detection signal to a known control means (not shown). By controlling the output or applied voltage of the main heater 6 and the sub-heater 7 by the control means, the temperature of the outer peripheral surface of the fixing roller 4 is maintained within a predetermined temperature range in which the toner image can be melted. It has become.

The fixing roller 4 is formed by forming a heat-resistant elastic layer 42 with a thickness of about 0.1 to 1 mm on the outer peripheral surface of a metal hollow roller core 41 of aluminum, stainless steel, iron or the like. The resin layer 43 serving as a release layer is 1.0 to 40.
It is formed with a thickness of about μm.

The pressure roller 5 includes a metal roller core 51.
An elastic layer 52 of silicone rubber, fluorine rubber, fluorosilicone rubber or the like is relatively thick (for example,
(About 0 mm), and a fluororesin layer 53 as a release layer is formed thereon with a thickness of about 30 to 50 μm.

A cleaning device for removing foreign matters such as offset toner and paper dust adhering to the surface of the fixing roller 4 from the surface of the fixing roller 4 is provided above the fixing roller 4. The cleaning device is a nomex, a hymeron or the like. The cleaning web 70 made of the heat-resistant non-woven cloth is used.

This cleaning web 70 is usually made by mixing a high-temperature soft polyester fiber with an aromatic polyamide fiber to produce a nonwoven fabric having appropriate softness and strength. This nonwoven fabric has a viscosity of about 10,000 centistoxs. It uses a silicone oil impregnated at high temperature and rolled up.

The web pressing roller 65 is formed by coating a metal core with a heat-resistant rubber layer such as silicone rubber, and in order to obtain sufficient softness, a foaming agent is put in the rubber to form a sponge. is there. Rubber hardness is 10
20 ° (Asker-C) is used.

The web press roller 65 is rotatably supported at both ends by a bearing 72.
Foreign matter, such as offset toner and paper powder, adhered to the surface of the fixing roller 4 by pressing against the surface of the fixing roller 4,
Prevents offset.

The web take-up shaft 61 is rotated in the direction indicated by the arrow in the drawing by driving means (not shown), and the web feeding shaft 6 is rotated.
From 6 the cleaning web 70 is wound up by a predetermined amount per copy in synchronization with the copying operation.

A main heater 6 and a sub-heater 7 which are two heating source heaters are disposed in the fixing roller 4, and each of the main heater 6 and the sub-heater 7 has 8 heaters.
A 00W, 400W halogen heater is used.

Therefore, when the main power is turned on, the main heater 6 and the sub-heater 7 are turned on, and the temperature of the fixing roller 4 starts to rise.

When the main power supply is turned on in the morning, the main heater 6 and the sub-heater 7 are turned on, and the temperature of the fixing roller 4 starts increasing. When the thermistor 8 detects the surface temperature of the fixing roller 4 at 195 ° C., it receives a driving force of a driving motor (not shown) and performs preliminary rotation before the transfer material P reaches the nip. Pressure roller 5
(Hereinafter, referred to as pre-multi-rotation) is started.

The present embodiment is characterized in that after the thermistor 8 detects 200 ° C. as the surface temperature of the fixing roller 4, it is possible to copy after further extending the pre-multiple rotation for one minute.

During this time, the heater performs ON / OFF control so that the surface temperature of the fixing roller 4 is maintained at 200 ° C.

When the start button on the operation panel is pressed, copying is started at a speed of 60 sheets per minute. When the temperature of the fixing roller 4 is reduced to 170 ° C. by continuous copying, the speed is reduced to 50 sheets per minute. Roller 4
Is prevented from lowering, thereby preventing defective fixing.

After the temperature is raised to 200 ° C., which is the copy start temperature at the start-up of the morning, the pre-multiple rotation is forcibly extended, and the temperature of the pressure roller 5 is increased before the copy is started, so that the pressure of the fixing roller 4 is increased. The curl amount is reduced by reducing the temperature difference from the roller 5-, the temperature of the fixing roller 4 during continuous copying is suppressed, the fixing property is prevented from lowering, and it is possible until the down sequence starts. Increasing the number of copies also has the effect of improving productivity.

FIG. 3 shows the main heater 6 and the sub-heater 7 in the first embodiment at the start of the morning and after the start of copying.
FIG. 6 is a diagram for explaining a lighting sequence of FIG.

Here, experimental results regarding fixing performance, productivity, and stackability of the image forming apparatus according to the present embodiment will be described based on comparisons with comparative examples as shown in Table 1.

[0041]

[Table 1]

As shown in Table 1, in Comparative Example 1, when the surface temperature of the fixing roller 4 was detected to be 195.degree. C. at the start of the morning, the pre-multi-rotation was started, and after the temperature was increased to 200.degree. You can start.

In Comparative Example 2, when the surface temperature of the fixing roller 4 is detected to be 205 ° C. at the start-up in the morning, the pre-multi-rotation starts, and after the temperature is raised to 210 ° C., copying can be started.

Comparative Example 3 is the same as Comparative Example 1 with respect to the pre-multi-rotation start temperature and the copy start temperature, except that the temperature of the down sequence (the copy speed is reduced from 60 sheets per minute to 50 sheets) is 165 ° C. .

FIG. 4 is a diagram for explaining a lighting sequence of the main heater 6 and the sub-heater 7 at the start of the first morning and after the start of copying in Comparative Example 1.

In this experiment, regarding the fixing property, 1000 sheets of A4 size paper were continuously copied in a 15 ° C. environment.
The black image fixed on the paper was taken out at an interval of 0 sheets, rubbed with a predetermined sheet of paper for a specified number of times, and the density before and after was measured with a reflection densitometer.

Regarding productivity, A was measured at 15 ° C.
The time required when 1000 sheets of 4-size paper are continuously copied is shown.

Regarding the stacking performance, the maximum curl amount of 10 samples immediately after the ejection of 100 sheets of A4 size paper continuously extracted at an interval of 10 sheets in an environment of 30% and 80% was shown.

As a result, as shown in Table 1, Comparative Examples 1 to
In No. 3, there was a problem in any of the fixing property, the productivity, and the stacking property, but in the present embodiment, all were satisfied.

On the other hand, by extending the pre-multiple rotation, the warm-up time of this embodiment is longer than that of Comparative Examples 1 and 3, but is equal to the warm-up time of Comparative Example 2. It is.

[0051]

As described above, according to the first aspect of the present invention, the temperature detected by the temperature detecting means when the fixing body and the pressurizing body start heating of the heating body is the predetermined temperature. When the temperature reaches a predetermined temperature within the range, the rotation starts, and after the detected temperature reaches the upper limit temperature of the predetermined temperature range, the pre-rotation continues until a predetermined time elapses, and then the recording medium passes through the nip. To reduce the temperature of the fixing body during continuous fixing and to prevent the temperature difference between the fixing body and the pressure body, and reduce the warm-up time without impairing the fixing stability and productivity. In addition, curling of the recording medium after the fixing process can be suppressed.

According to the second invention of the present application,
The fixing body and the pressure body start rotating when the temperature detected by the temperature detecting means reaches a predetermined temperature within the predetermined temperature range at the time of heating up of the heating body, and the detected temperature falls within the predetermined temperature range. Even after the temperature reaches the upper limit temperature, the pre-rotation continues until a predetermined time elapses, and then the recording medium is passed through the nip. It is possible to prevent the temperature difference between the pressurizing members, shorten the warm-up time without impairing the fixing stability and productivity, and suppress the curling of the recording medium after the fixing process.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a schematic configuration of a fixing device provided in the image forming apparatus of FIG.

FIG. 3 is a diagram for explaining lighting timings of the heating element at the time of startup and after the start of fixing in the embodiment of the present invention.

FIG. 4 is a diagram for explaining lighting timing of a heating element at the time of startup and after the start of fixing in Comparative Example 1.

[Explanation of symbols]

 Reference Signs List 4 fixing roller (fixing member) 5 pressure roller (pressing member) 6 main heater (heating member) 7 sub heater (heating member) 8 thermistor (temperature detecting means) 15 fixing device

Claims (2)

[Claims] 1. A fixing member and a pressure member which rotate in pressure contact with each other, a heating member for heating the fixing member, a temperature detecting means for detecting a temperature of the fixing member, and a temperature detected by the temperature detecting means being a predetermined temperature. Control means for controlling the driving of the heating element so as to fall within the range, wherein the recording medium carrying the unfixed image is nipped and transported by a nip formed by the fixing element and the pressure element, and heated and pressed by heating and pressing. In the fixing device for fixing an unfixed image on the recording medium, the fixing member and the pressure member are arranged such that when the temperature detected by the temperature detecting means reaches a predetermined temperature within the predetermined temperature range at the time of heating up of the heating member. The rotation of the recording medium is pre-rotated so as to pre-rotate before reaching the nip of the recording medium, and the pre-rotation elapses a predetermined time after the detected temperature reaches the upper limit temperature of the predetermined temperature range. Until A fixing device characterized by being set to be continued. 2. An image forming apparatus for recording an image formed by a series of image forming processes on a recording medium,
An image forming apparatus comprising the fixing device according to claim 1.