JPH04294377A - Fixing device - Google Patents

Abstract

PURPOSE:To eliminate the difference of glossiness and fixing property between the leading edge and the trailing edge of a transfer material caused by the lowering of the temperature of the surface of a roller at the time of fixing, to improve image quality and to lower a set temperature. CONSTITUTION:In a fixing device provided with at least a rotating body for fixing (fixing roller) 1 so that a fixed image is formed on the transfer material 11 by the rotating body for fixing, the difference of the glossiness and the fixing property between the leading edge and the trailing edge of the transfer material 11 is eliminated by making heating values given to the leading edge and the trailing edge of the transfer material 11 by the rotating body 1 equal, and a uniform image is obtained on all the surface of the transfer material 11.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to fixing devices for various image recording apparatuses such as copying machines and laser beam printers, and more particularly to fixing devices for fixing unfixed images by heat using a fixing roller.

0002

2. Description of the Related Art A conventional fixing device of this type uses a dry powder developer as shown in FIG. A heat roller fixing device that allows the recording material 103 loaded with the recording material 103 to pass therethrough is widely used. That is,
When the recording material 103 is conveyed, the fixing roller 100
The pressure roller 101 rotates at a constant speed, and the recording material 1
03 is heated and pressurized from both the front and back sides when passing between the fixing and pressure rollers 100 and 101, and the unfixed toner carried on the surface is melted and fixed.

0003

However, in the conventional heat roller type fixing device as described above, when the recording material 103 passes between the fixing roller 100 and the pressure roller 101 and fixing is performed, Applying a release agent and fixing by the recording material 103, pressure rollers 101,1
The heat of 02 is removed, and immediately before fixing, fixing, pressure roller 10
There was a large difference in the temperature of the roller surface immediately after fixing after 0 and 101 had rotated several times. For that purpose, recording material 103
The fixing temperature was different between the leading edge and the trailing edge, resulting in differences in image gloss, fixing performance, etc. In addition, even at the rear end of the recording material 103 where the temperature of the roller surface decreases, the temperature of the roller surface must be set high in order to perform sufficient fixing, which adversely affects the life of the roller and the temperature inside the machine. was giving.

An object of the present invention is to eliminate differences in gloss, fixability, etc. from the leading edge to the trailing edge of a recording material due to a drop in temperature of the surface of a rotating body such as a roller during fixing, and to improve image quality. It is an object of the present invention to provide a fixing device which can improve the temperature and lower the set temperature.

[0005]

[Means for Solving the Problems] The present invention has been made in order to solve the above-mentioned problems of the prior art, and its object is to provide at least a fixing rotary body, in which the fixing rotary body In a fixing device that forms a fixed image on a transfer material, a supply heat amount control means is provided to keep the amount of heat supplied from a fixing rotating body to the recording material substantially equal from the leading edge to the trailing edge of the recording material. It is characterized by

Preferably, the supplied heat amount control means supplements the supplied heat amount by bringing an external rotary member into heating contact with the fixing rotary member during fixing.

Further, the supply heat amount control means may gradually reduce the rotational speed of the fixing rotor and the pressurizing rotor during fixing.

Furthermore, the supply heat amount control means may be configured such that the amount of pressure applied to the fixing rotor and the heating rotor gradually increases during fixing.

[0009]

[Operation] In the fixing device configured as described above, the amount of heat supplied to the recording material by the supply heat amount control means is maintained approximately equal from the leading edge to the trailing edge of the recording material, and the amount of heat supplied to the recording material from the leading edge to the trailing edge of the recording material is It is possible to eliminate differences in gloss and fixability and obtain a uniform image over the entire surface of the recording material.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on the illustrated embodiments.

In FIG. 1 showing a fixing device according to a first embodiment of the present invention, this fixing device includes a fixing roller 1 as a rotatable fixing rotating body, and a pressure roller that rotates while being in pressure contact with the fixing roller 1. A pressure roller 2 as a pressure rotating body, a removable coating device 3 that supplies a release agent to the surface of the fixing roller 1, and toner and paper powder adhering to the surfaces of the fixing roller 1 and the pressure roller 2. A cleaning web 4 is configured to clean the . The fixing roller 1 has a structure in which the surface of a metal pipe is coated with silicone rubber or fluororubber. The pressure roller 2 is a metal roller provided with silicone rubber on its surface and coated with a fluororesin. Inside of fixing roller 1 or fixing roller 1 and pressure roller 2
A heater such as a halogen lamp is placed inside. Further, a thermistor 5 is in contact with the pressure roller 2, and the temperature of the roller is controlled by controlling the voltage applied to the heater via a temperature control circuit. These rollers 1 and 2 are rotatably supported by an apparatus main body (not shown) so as to be rotatable in the direction of the arrow. The coating device 3 includes a mold release agent tank 3a containing silicone oil as a mold release agent, a pumping roller 3b that pumps up the mold release agent from the mold release agent tank 3a, an application roller 3c that applies the mold release agent to the fixing roller 1, and a mold release agent. It consists of a blade 3d for controlling the amount of agent applied. The application roller 3c is rotatable, has a sponge rubber surface coated with silicone rubber, is removable from the fixing roller 1, and is coated with a release agent. The amount of the release agent applied is adjusted by the blade 3d, and the release agent is applied at a constant amount from the leading edge to the trailing edge of the transfer material. The cleaning web 4 has a nickel web 4a on the fixing roller 1 side, and a Nomex felt 4b on the pressure roller 2 side to clean the rollers.

In FIG. 1, reference numeral 8 denotes an external roller as supply heat amount control means that can be attached to and detached from the fixing roller 1, and a heater 10 such as a halogen lamp is disposed inside. A thermistor 9 is in contact with the external roller 8, and the temperature is controlled at a higher temperature than the fixing and pressure rollers 1 and 2 by controlling the voltage of the heater 10 via a temperature control circuit.

In this state, when the transfer material 11 as a recording material is conveyed to the fixing device via the entrance guide 6, the coating roller 3c contacts the fixing roller 1 and applies oil thereto. At this time, the fixing roller 1 is
The surface temperature of the fixing roller 1 decreases due to heat being taken away by the fixing roller 1. When the next fixing is performed, the heat of the fixing roller 1 is also taken away from the transfer material 11, and the surface temperature of the fixing roller 1 further decreases.

However, since the rotational speed, nip width, etc. of the fixing and pressure rollers 1 and 2 are constant, the transfer material 11 is fixed at the fixing position.
The amount of heat applied from the leading edge to the trailing edge gradually decreases, resulting in differences in gloss, fixability, etc. Particularly in the case of color images, differences in glossiness and fixability due to temperature differences from the leading edge to the trailing edge of the transfer material greatly affect the image quality. Therefore, when the surface temperature of the pressure rollers 1 and 2 decreases during fixing, the external roller 8 is brought into contact with the fixing roller 1, and the heat of the external roller 8 is applied to the fixing roller 1, thereby increasing the surface temperature of the fixing roller 1. It was possible to compensate for the decrease in temperature, eliminate the difference in roller surface temperature from the leading edge to the trailing edge of the transfer material, and achieve uniform gloss and fixing performance.

FIG. 2 is a control diagram showing a second embodiment of the present invention. The configuration is such that a variable speed device 20 is provided as a supply heat amount control means in place of the external roller 8 in FIG.

When the transfer material 11 is conveyed to the fixing device,
The temperature of the surface of the fixing roller 1 decreases due to the same process as described above, resulting in a difference in gloss and fixing performance between the leading edge and the trailing edge of the transfer material 11.

When the surface temperature of the fixing roller 1 is low, by slowing down the rotational speed of the fixing and pressure rollers 1 and 2 and increasing the time for applying heat, the same amount of heat as when the surface temperature is high can be applied to the transfer material 11. can be supplied to Therefore, by providing the speed variable device 20, the surface temperature of the fixing roller 1 decreases during fixing, as shown in FIG. By gradually slowing down the circumferential speed of the fixing and pressure rollers 1 and 2, a uniform image could be obtained from the leading edge to the trailing edge of the transfer material even if the temperature of the roller surface decreased. This also makes it possible to lower the temperature of the roller surface, which was set to ensure fixing performance at the rear end of the transfer material when fixing is performed at the same speed.

[0018]Although the specific configuration of the speed variable device is not shown, for example, the rotational speed of the motor itself may be controlled by a stepping motor or the like, or the speed may be adjusted using a stepless clutch. Alternatively, various known configurations can be adopted.

FIG. 3 is a control diagram showing a third embodiment of the present invention. The configuration is that a pressure device 4 is used instead of the external roller 1 in FIG.
0 is set. In the configuration of FIG. 1, the transfer material 11
When the transfer material 11 is conveyed to the fixing device, the temperature of the surface of the fixing roller 1 decreases due to the same process as described above, resulting in a difference in gloss and fixability between the leading edge and the trailing edge of the transfer material 11. Put it away. When the surface temperature of roller 1 is low,
In addition to increasing the time for supplying heat by slowing down the speed, by increasing the area to which heat is supplied, it is possible to supply the same amount of heat to the transfer material 11 as when the surface temperature is high.

Therefore, by providing a pressure device 40, the surface temperature of the roller 1 decreases during fixing, as shown in FIG. Gradually fix the pressure roller 1.
, 2 and the nip width, it was possible to obtain a uniform image from the leading edge to the trailing edge of the transfer material 11 even if the temperature of the roller surface decreased.

[0021] Furthermore, this makes it possible to lower the temperature of the roller surface, which was set to ensure the fixing performance at the rear end of the transfer material 11, when fixing is performed with the same amount of pressure. Ta.

Although the specific configuration of the pressure device 40 is not shown, various known configurations for adjusting the amount of pressure applied between the fixing roller 1 and the pressure roller 2 can be adopted.

[0023]

According to the present invention, when the surface temperature of the fixing roller decreases during fixing, the supply heat amount control means can equalize the amount of heat given by the fixing rotor at the fixing position from the leading edge to the trailing edge of the recording material. By doing so, the glossiness and fixing performance can be made uniform from the leading edge to the trailing edge of the recording material.

Particularly in color images, the difference in gloss from the leading edge to the trailing edge of the recording material had a great effect on the image, and this had a great effect on improving the image quality. Additionally, in the past, the surface temperature of the fixing rotor had to be set high to ensure fixing performance even at the trailing edge of the recording material, where the surface temperature of the fixing rotor decreased. By equalizing the amount of heat applied at the fusing position from the leading edge to the trailing edge of the material, this set temperature can be lowered, which is effective in extending the life of the fusing rotor and lowering the temperature inside the machine. Ta.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a fixing device according to a first embodiment of the present invention.

FIG. 2 is a control diagram of a fixing device according to a second embodiment of the present invention.

FIG. 3 is a control diagram of a fixing device according to a third embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of a conventional fixing device.

[Explanation of symbols]

1 Fixing roller 2 Pressure roller 3 Oil applicator 3a　Mold release agent tank 3b Pumping roller 3c Application roller 3d blade 4a Nickel web 4b Nomex felt 4 Web cleaning device 5 Thermistor 6 Entrance guide 7 Paper ejection guide 8 External roller 9 Thermistor

Claims (4)

[Claims] 1. A fixing device that includes at least a fixing rotary body and heats and fixes an unfixed image on a recording material with the fixing rotary body, wherein the amount of heat supplied from the fixing rotary body to the recording material is controlled. 2. A fixing device comprising: a means for controlling the amount of heat supplied to keep the amount of heat substantially equal from the leading edge to the trailing edge of the recording material. 2. The fixing device according to claim 1, wherein the supplied heat amount control means supplements the supplied heat amount by bringing an external rotating body into heating contact with the fixing rotary body during fixing. 3. The fixing device according to claim 1, wherein the supply heat amount control means gradually reduces the rotational speed of the fixing rotor and the pressure rotor during fixing. 4. The fixing device according to claim 1, wherein the supply heat amount control means gradually increases the amount of pressure applied by the fixing rotor and the pressurizing rotor during fixing.