JPH02267579A - Image recording device provided with heat roller fixing device - Google Patents

Abstract

PURPOSE:To constantly attain a stable fixing operation by switching the press- contacting force of a heat roller and a press-fixing roller to low when a set number of recording sheets of a prescribed size are fixed. CONSTITUTION:If the surface temperature of a heat roller is high at a point S and fixing is started at the press-contacting force PI, the surface temperature of the heat roller is gradually lowered as the recording sheets of the prescribed size are continuously fixed. Finally a set number n1 of recording sheets are fixed and the temperature arrives at a point C. Then, the press-contacting force is switched to a low pressure P2 at the point C. Thus since the press- contacting force when the recording sheet passes between the heat roller and a press-fixing roller is reduced, heat quantity taken away by the recording sheet is reduced. Resultantly, temperature lowering on a heat roller surface is stopped and the temperature on the heat roller surface is again in a rising condition. Therefore, the fixing operation is performed to the last (a point F) at the press-contacting force of the low pressure P2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image recording device that is used in an electrophotographic image recording device and is equipped with a heat roller fixing device that fuses and fixes a toner image on a transfer material. It is.

[Conventional technology]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A heat roller fixing device for an image recording apparatus such as a copying machine will be explained with reference to a sectional view shown in FIG.

52 is a heating element such as an infrared lamp, 54 is a thermocouple or thermistor, etc., and detects the surface temperature of the heat roller 51. The temperature sensor 53 is a pressure roller for sandwiching the recording paper between it and the heat roller 1 and allowing it to pass while applying a constant pressure, and is usually made of silicone rubber or a roller coated with silicone rubber. .

The recording paper on which the toner image has been formed is continuously inserted between the heat roller 51 and the pressure roller 53, where it is held and held while receiving heat, and a constant pressure is applied thereto. As a result, the toner is fused to the recording paper surface and fixed. The toner is thus fixed, but in order to keep the surface temperature of the heat roller 51 constant, the surface temperature of the heat roller 51 is detected, converted into a signal, and controlled.

[Problem that the invention seeks to solve]

An image recording device (including a fixing device using the heat roller);
In general, in a copying machine, if the copying speed is continuously increased, the amount of heat taken by the recording paper from the heat roller increases in proportion to the copying speed, so the surface temperature of the heat roller 51 decreases. The decrease in the surface temperature of the heat roller 51 also occurs depending on the pressure between the heat roller and the pressure roller, the room temperature, changes in the power supply voltage, and the type of recording paper It (thickness, paper quality, etc.). If the surface temperature of the heat roller 51 drops below a certain value, a good quality fixed image cannot be obtained, and in some cases, uneven fixing may occur, and unfixed recording paper may be sent out. was there.

For this reason, in order to maintain a sufficient temperature for fixing,
Temperature control is performed by preparing a heat source device with a large capacity. Even so, stable heat roller fixing is difficult to obtain.
There are problems such as the large size of the device and power supply.

[Means for solving problems]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate these drawbacks and provide an apparatus in which a toner image is always stably fixed by a heated roller.

The present invention achieves the above object by sandwiching and conveying a transfer material between a rotating heat roller having a built-in heating means and a pressure roller that presses the heat roller, and fixing the toner image attached to the transfer material. The image recording apparatus includes a detection device that directly or indirectly detects the temperature of the heat roller, and means for varying the pressure force of the pressure roller; When the number of sheets of transfer material (recording paper) of the same size reaches a set number, the pressing force of the heat roller and the pressure roller is switched to a second pressing force lower than the first pressing force to perform fixing. This is an image recording apparatus equipped with a heat roller fixing device. Also,
In the present invention, fixing is performed using the first pressure force until the first number of sheets is set within a certain time after the power is turned on, and after a certain period of time, the fixing is performed up to the second set value of the number of sheets. 1
This is an image recording apparatus equipped with the heat roller fixing device described in 1.

〔Example〕

Embodiments of the heat roller fixing device of the present invention will be described below with reference to the drawings.

FIG. 7 is a configuration diagram of an image recording apparatus (copying machine) equipped with a heat roller fixing device according to the present invention. First, an outline of the steps up to the fixing device in the copying machine will be explained.

The image carrier lO is charged by the charger 11, and the image carrier 1
The photoconductive surface on the 0 surface rotates while retaining charges in a negative manner, and reaches the exposure section 20. In the exposure section 20, light irradiated by a light source and reflected from the document is scanned by an optical system such as a mirror lens, and is incident on the photoconductive surface of the image carrier 10 to form an electrostatic latent image of the document image. This electrostatic latent image is developed in the developing section 30, and a toner image of the latent image is formed. In transfer N40, the toner image is transferred onto a synchronously fed transfer paper. The transfer paper on which the toner image has been transferred is separated from the image carrier lO by the separation electrode 41, conveyed by the conveyor belt 42, further thermally fixed by the heat roller fixing device 50 according to the present invention, and discharged outside the machine.

On the other hand, the transfer paper is separated by the separation electrode 41;
The image bearing member 10, carrying untransferred residual toner, reaches the cleaning device 43, where the residual toner on the image bearing member 10 is removed, and a new copy cycle is prepared.

FIG. 6 is a sectional view of a heat roller fixing device 5o according to the present invention. In the figure, 51 is a heat roller, and a halogen heater 52 is disposed inside the ripening roller 51. A heat roller 51 is provided below the heat roller 51 as an opposing roller.
A pressure roller 53 is provided for pressure-bonding. A transfer paper having a toner image is fed between the pair of rollers from the conveyor belt 42 side, and the toner image is passed toward the heat roller 51, thereby fixing the toner image on the transfer paper.

The heat roller 51 is a roller having an outer diameter of about 60+ mm and has a pipe-shaped metal core covered with a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) tube having a thickness of about 30 μLm.

The halogen heater 52 built into the heat roller 51 is
1500w and 600w located almost in the center of the heat roller 51
It is a W heater. The amount of heat generated by the heat roller 51 is
The peripheral surface temperature of the heat roller 51 is controlled to be maintained at around 200° C. during copying by temperature detection by a temperature sensor 54 disposed close to the shoulder surface of the heat roller 51 .

An oil application roller 5 is placed above the circumferential surface of the heat roller 51.
5 applies oil to the circumferential surface of the heat roller 51 while being pressed against the heat roller 51 by its own weight and spring and rotates as a result. Reference numeral 56 denotes an oil supply means for constantly supplying oil to the oil application roller 55, and an oil impregnated band 56B built in the box-shaped frame 56A slides on the circumferential surface of the oil application roller 55 to supply oil. A cleaning roller 57 made of foamed silicone rubber adsorbs and removes toner and the like adhering to the circumferential surface of the heat roller 51.

The pressure roller 53 is in pressure contact with the heat roller 51 from directly below and rotates counterclockwise. An auxiliary heating means 58 is disposed close to the circumferential surface of the pressure roller 53. The auxiliary heating means 58 has a built-in heater using a heating element, and controls the surface temperature of the pressure roller 53.

A transfer paper with a toner image transferred onto its upper surface is carried toward the pressure contact portion between the heat roller 51 and the pressure roller 53 from the direction of arrow A under the guidance of guide plates 501 and 502.

The transfer paper is held between the pressing portions of the rollers 51 and 53, and is conveyed in the direction of arrow B with pressing force applied thereto. On this occasion,
The toner on the transfer paper is melted by the heat generated by the heater 52 built into the heat roller 51, and both rollers 51.5
3, it is pressed and fixed onto the transfer paper. The transfer paper on which the toner image has been fixed is carried out from the pressure bonding portion of both rollers 51 and 52, peeled off from the circumferential surfaces of both rollers by separation claws 503 and 504, guided by guide members 505 and 506, and then transferred to the direction indicated by arrow B. It is discharged to the outside of the heat roller fixing device 50 in both directions.

FIG. 3 shows the relationship between the surface temperature change of the heat roller 51 and the pressing force, with time on the horizontal axis and temperature change on the vertical axis. As mentioned above, when recording paper is continuously inserted between the heat roller 51 and the pressure roller 53 and fixing is performed by applying pressure, the temperature of the surface of the heat roller decreases because the recording paper absorbs heat. descend. The temperature of this heat roller surface is usually 16
The temperature is about 0℃~2oo℃, and the roller pressure is 2kg/c.
+m to about 2.8 kg/cm is used.

Therefore, the size of the recording paper used (for example, A4 size) is set in advance through experiments, etc., and when fixing is performed with the pressure force PI of the heat roller 51 and the pressure roller 53, the size of the recording paper (A4 size) The extent to which the temperature of the heat roller 51 decreases depending on the number of sheets of recording paper fixed is measured. Based on this measurement result, both rollers 51
This recording paper size (A4 size) with the pressure force Pl of 153
Set the number nl of recording papers at which the temperature reaches a low temperature within the fixable range when fixing the recording papers. Then, until this standard number of sheets set value nl is reached, fixing is performed using the pressure force PI, and when this standard number of sheets exceeds the set value n1, the pressure force is switched to P2 and fixing is performed.

A mechanism for changing this pressure force is shown in FIGS. 1 and 2. A lever 101 is installed near the heat roller 51 and the pressure roller 53, and a rotatable transmission roller 102 is installed behind this lever. And the lever 101 is the support shaft 10
3 as a fulcrum and can move up and down. Further, the other end of the lever 101 is connected to an arm 110, which will be described later, by a tension spring 104. On the other hand, the cam 105 is integral with a rotating shaft 106 directly connected to the motor M2, and is capable of eccentric rotation. The cam 10 is brought into pressure contact with the transmission roller 102 at the circumferential surface.
The lever 1 is configured to be moved in the vertical direction by rotation of the lever 5.

A pressure roller 53 is attached to the lower arm +10 with Ill as the rotation axis, and the tip of the arm 110 rotates about the support shaft 112 and is movable in the vertical direction, and is attached to the frame of the fixing device. installed. Further, the tension spring 104 is connected to the lever 101 at the other end of the arm 110 through an arcuate long hole 113.

When the cam 105 is rotated by the driving force of the motor M2, the lever 101 is pushed up about the support shaft 103 via the transmission roller 102. Therefore, as shown in FIG. 2, the tension spring 104 stretches and pulls up the arm 110.

As a result, the crushing roller 53 is strongly pressed against the circumferential surface of the heat roller and the pressing force becomes high.

In this way, it is possible to change the pressing force depending on the rotational position of the cam 105. The drive motor M2 that rotates this cam 105 is controlled by the CPU. FIG. 5 shows a block diagram of the drive system of the image recording apparatus of the present invention.

As shown in FIG. 3, if the surface temperature of the heat roller 51 is high at five points and fixing is started with the pressure force pt, then as recording paper of this size (A4 size) is successively fixed, the heat roller The surface temperature gradually decreases and eventually reaches the set number n.
1 is fixed and reaches point C. Then, at this point C, the pressing force is switched to a low pressure of P2. By doing this, the pressing force when the recording paper passes between the heat roller 51 and the pressure roller 53 is reduced, and the amount of heat absorbed by the recording paper is reduced. That is, since the contact area between the circumferential surfaces of both rollers is reduced, the contact area and contact time between the recording paper and the heat roller are also reduced. In this way, the temperature decrease on the surface of the heat roller is interrupted, and the temperature on the surface of the heat roller rises again. Therefore, it is possible to fix up to & (point F) with this low pressing force P2.

Of course, the pressing forces Pi and P2 are each constant pressing forces, and the condition of PI≧P2 is required.

In fact, for example, P2'=T(0.5~0.7)x
P 1 is practical.

The number of sheets nLn2, n3 corresponding to each size of recording paper, for example, A4 size, 84 size, and A3 size, is set to the fourth value.
Make the settings as shown in the figure.

Next, by applying the present invention, we will explain the fusing table 1 at the initial stage of power-on: In an image recording device, copying, that is, fusing starts within a relatively short period of time after power is turned on, and cases in which fusing starts after a rather long period of time have elapsed. In detail, the fixing state is different depending on the case where the fixing state is set. That is, since heating of the heat roller 51 starts after the power is turned on, the heat roller 51 is not sufficiently warmed at the beginning. However, as time passes, the heat roller 51 becomes sufficiently heated, and the pressure roller 53 also rises in temperature.

Therefore, taking A4 size recording paper as an example, if fixing is to be started within a certain period of time, for example 30 minutes, after the power is turned on, fixing will be performed with the reference number of sheets set as 80 sheets. However, if you want to start fixing after this certain period of time (30 minutes) has elapsed, the standard number of recording paper settings should be set to 150 minutes.
Established as a sheet. After the reference number of sheets has been reached, fixing is continued by switching the pressing force according to the present invention as described above. By doing this, even when the heat roller 51 is being heated after the power is turned on, stable fixing can be performed by changing the set value of the number of recording sheets depending on the time. FIG. 4 shows an example of the relationship between the recording paper size and the reference sheet number setting value in this case.

The entire drive system of the image recording device is controlled by the CPU, but the motor Ml that drives the image carrier lO and the heat roller 51 and the motor M2 that drives the cam 105 are independent and are all controlled by the CPU at the same time. controlled by In addition, the standard number of sheets and recording paper size are also stored in the CPU memory, and the pressing force and temperature control are also controlled by the CPU.
It is configured to be controlled by the PU.

Note that it is also possible to selectively transmit the driving force of the heat roller 51 to the cam rotating shaft 106 via a clutch mechanism instead of the motor M2.

〔Effect of the invention〕

As described above, the heat roller fixing device of the present invention sets the recording paper size and number of sheets according to the temperature change of the heat roller, and switches the pressure of the roller accordingly, so as to always maintain an even image. , it became possible to stably obtain beautiful fixation. Furthermore, there is provided an image recording device equipped with a heat roller fixing device that can always perform stable fixing by changing the set value of the number of sheets when fixing is started within a certain period of time after turning on the power and after a certain period of time has elapsed. Now you can.

[Brief explanation of drawings]

Figures 1 and 2 show the mechanism for switching the pressing force of the pressure roller; sectional view, Figure 3 is a diagram showing temperature changes on the surface of the heat roller, and Figure 4 is a diagram showing changes in temperature of the recording paper size. A line diagram showing an example of the corresponding standard number of sheets setting, FIG. 5 is a control block diagram of the drive system of the image recording apparatus according to the present invention, FIG. 6 is a sectional view of the heat roller fixing device according to the present invention, and FIG. 7 1 is a sectional view showing an example of an image recording apparatus equipped with a heat roller fixing device according to the present invention. 50... Heat roller fixing device 51... Heat roller 52
...Halogen heater 53...Pressure Jl a -5
54...Temperature measurement unit 101...Lever 10
2...Transmission roller 103.112...Spindle 104...Tension spring 105...Cam 10
6.111...Rotation axis 110...Arm Ml
, M2... drive motor

Claims (2)

[Claims] (1) Equipped with a heat roller fixing device that sandwiches and conveys a transfer material between a rotating heat roller with a built-in heating means and a pressure roller that presses the roller, and fixes the toner image attached to the transfer material. The image recording apparatus includes a detection device that directly or indirectly detects the surface temperature of the heat roller, and means for varying the pressure force of the pressure roller, and has a transfer material recording paper of a preset size. , a heat roller fixing device configured to perform fixing by switching the pressure force of the heat roller and the pressure roller to a second pressure force lower than the first pressure force when a set number of sheets is reached. Image recording device. (2) Within a certain period of time after the power is turned on, fusing is performed using the first pressure force up to the first set number of sheets, and after a certain period of time, fusing is performed up to the second set number of sheets. An image recording apparatus comprising the heat roller fixing device according to claim 1.