JPS63173088A - Device for fixing image forming device - Google Patents

Abstract

PURPOSE:To shorten a warming-up time and to prolong the service life of a fixing roll by constituting a current supply control circuit so that the circuit is transferred at least from a warming-up mode to an idling mode while forecasting a response delay due to the heat capacity of a temperature detecting sensor. CONSTITUTION:When the detecting temperature of a temperature detecting sensor 30 reaches a detecting temperature T2 while forecasting the detecting temperature T2 of the sensor 30 at time t10 when the temperature of a fixing roll 10 reaches temperature T3 at which fixing is enable, current supply to a fixing heater 32 is turned off. If an initial leading temperature (temperature at the time of turning on a power supply) T1 is high, arriving time up to the objective temperature T3 is short and influence to exerted upon a constant is reduced, so that it is necessary to set up the T2 to a high value close to the T3. Thereby, the detecting temperature T1 of the sensor 30 at the time of turning on the power supply is read out and the temperature T2 corresponding to the detected temperature T1 is found out to change the operation starting level of the current supply control circuit 31. Consequently, the warming-up time can be shortened and the surface temperature of the fixing roll 10 can be controlled at the fixable temperature T3.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fixing device for an image forming apparatus such as an electronic copying machine, and more particularly to energization control of a fixing heater.

(Background of the Invention) An electronic copying machine exposes a charged photoreceptor (hereinafter, a photoreceptor drum will be explained as an example) to light according to document information to create a static image.
! Form a latent image and make it visible with toner,
This is a device that transfers and fixes this toner visible image onto transfer paper. In recent years, this type of electronic copying machine has been used in all fields of industry.

FIG. 4 is a diagram showing an example of the configuration of this type of electronic copying machine. When the operator presses a copy button (not shown), the device shown begins the copying process. That is, the photosensitive drum 1, which is rotating in the direction of the arrow, is rotated in the cleaning section 2 after the residual toner on the drum is removed by a blade.
A charging electrode 3 charges its surface with an electric charge.

Next, the charges on the photosensitive drum 1 are erased by the charge erasing section 4 . Thereafter, the charged area of the photosensitive drum 1 is exposed to light reflected by the original 6, and an electrostatic latent image of the original image is formed on the drum surface. That is, the original 6 is irradiated with light from the exposure unit 5, which is movable in the direction of the arrow shown in the figure, and the reflected light containing the original information reaches the photosensitive drum 1 via the mirror M1-M3 and the lens system. , the drum surface is exposed to light to form an electrostatic wI image on the drum surface. This electrostatic latent image is converted into a visible image by adsorption of toner in the developing section 7. Thereafter, the toner visible image on the drum surface is transferred to transfer paper (copy paper) by a transfer section 8.

After the transfer, the transfer paper is separated from the photosensitive drum 1 and sent to the fixing roller 10 by the transport mechanism 9. Then, the transfer paper is heated by the fixing row 510, the toner is fused to the transfer paper, and the copying process is completed.

A portion consisting of the exposure section 5 and the mirrors Mi, Mz, and Mi (the portion surrounded by a broken line) constitutes an optical unit 20, which can be moved in the direction of the arrow in the figure by a moving mechanism (not shown). It has become. Here, in order to always keep the optical path length constant, the first mirror M1 and the exposure section 5 are connected to the second mirror M1.
．． The third mirror M2 moves at twice the speed of Ml. Here, the light source 21 in the exposure device @5 is composed of, for example, a bar-shaped fluorescent light perpendicular to the paper surface.
The optical unit 20 can scan the entire surface of the original 6.

By the way, a fixing heater for heating the fixing roller 10 is provided inside the fixing roller 10, and is supplied with power from a power supply device (not shown). If the temperature of the fixing roller 10 is not constant, the degree of fixing of the copied image will vary depending on the transfer paper, resulting in an uneven image, which is undesirable.

Therefore, the temperature of the fixing roller is controlled to a predetermined value. This temperature control method includes, for example, on-off control. FIG. 5 is a diagram showing the operation mode of the on/off control, in which the vertical axis represents the temperature T detected by the temperature detection sensor attached to the fixing roller, and the horizontal axis represents the time t. Also, Tsl, Ta
2 are the energization stop temperatures of the idle link mode and copy mode, which will be described later, respectively, and Ta2. Ta2 is in idle link mode.

At the energization start temperature in copy mode, Tsl-Ta2. T
a2-Ta2 are the hysteresis widths of the idle link mode and copy mode, respectively.

Next, the on/off control shown in FIG. 5 will be explained.

At time to, the fixing heater is turned on. As a result,
The detected temperature gradually increases as shown in the figure. And time [1
When the detected temperature exceeds the energization stop temperature TS1, the energization to the fixing heater is turned off.

Even if the power is turned off, the detected temperature will rise for a while due to the heat capacity, but after that, the detected temperature will start to decrease.

Time 1. When the detected temperature falls below the energization start temperature TS2, the energization to the fixing heater is turned on again. The same operation is repeated below. At time t3, the copy button is pressed to start the copy process, and the power is stopped at FIA degree TSI.
, 1! The starting temperature Ts2 is also the set value Ts3 in the copy process. Changed to Ts4. The period from the time to to the time 1 when the energization stop temperature Ts1 is reached is the warming-up mode, the period from the time t1 to the time t3 at which the copy process starts is the fitting mode, and the period after time t3 is the copy mode.

(Problems to be Solved by the Invention) Incidentally, the temperature detection sensor used for such temperature control is coated with silicone rubber or the like in order to increase pressure contact with the fixing roller.

For this reason, the temperature detection sensor also has a considerable heat capacity, and the temperature detected by the temperature detection sensor is delayed due to a thermal time constant with respect to the temperature change of the fixing roller.

This delay due to the thermal time constant becomes a problem, particularly when the fixing roller is heated from a normal temperature atmosphere to a fixable temperature by turning on the power.

That is, if the fixing roller is heated until the temperature detected by the temperature detection sensor reaches the fixing temperature without considering this thermal time constant (assuming 7sl is equal to the fixing temperature), the fixing temperature O-
The actual temperature of the roller will be much higher than the fixing temperature, and extra heat will be added.

As a result, the warming-up time from turning on the power until informing the operator that fixing is possible becomes longer. In addition, because the constant @0-ra temperature becomes high, the toner re-adheres to the fixing roller (so-called hot offset), resulting in smeared images, deterioration of the performance of the fixing roller surface, and shortened lifespan. occurs.

The present invention has been made in view of these points, and
The purpose is to realize a fixing device for an image forming apparatus that can reduce warming-up time, provide high-quality images, and extend the life of the fixing roller.

(Means for Solving the Problems) The present invention solves the above-mentioned problems by fixing a toner image formed on a transfer paper using a fixing roller heated by a fixing heater. In the device, the surface 111 of the fixing roller! [In the fixing device, the energization control circuit includes a MArxAr upper sensor that outputs a signal related to the In anticipation of a response delay due to the heat capacity of the detection sensor,
The present invention is characterized in that it is configured to shift from at least a warming-up mode to an idling mode.

(Function) Since the energization to the fixing heater is carried out at one time according to the thermal time constant of the temperature detection sensor, the energization to the fixing heater is stopped before the temperature detected by the temperature detection sensor reaches the fixing temperature level of the fixing roller. It will be turned off.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram (also showing peripheral configurations) showing one embodiment of the present invention. Components that are the same as those in FIG. 4 are designated with the same numbers. In the figure, 30 is the fixing roller 10
A temperature detection sensor 31 outputs a detection signal related to the surface temperature of the temperature detection sensor 30, and is an energization control circuit that controls energization to the fixing heater 32 in accordance with the thermal time constant of the temperature detection sensor 30.

FIG. 2 shows the surface temperature of the fixing roller 10 and the temperature sensor 30.
2 is an explanatory diagram of changes in detected temperature over time, where actual mA indicates the surface temperature of the fixing roller 10, and broken line B indicates the temperature detection sensor 30.
The detected temperature is shown.

In the figure, Tl indicates the initial startup temperature, 3 indicates the fixing possible degree, 1. 1211 indicates the time when the surface temperature of the fixing roller 10 reaches temperature a T s, 1211 indicates the time when the temperature detected by the temperature detection sensor 30 reaches m degrees T3,
2 is time 1. T4 shows the surface temperature of the fixing roller 10 when the fixing heater 32 is energized and heated until time 12o.

That is, the surface temperature of the fixing roller 10 and the temperature detection sensor 30
There is a difference between the detected temperature and the actual temperature 1i1A and the broken line B in FIG. 2 due to the difference in thermal time constant.

Therefore, if the fixing heater 32 is energized and heated until the temperature detected by the temperature detection sensor 30 reaches T3 as in the conventional method, the temperature of the fixing roller 10 will reach T4.

Therefore, in the present invention, the temperature of the fixing roller 10 is the temperature T which allows fixing! The temperature detection sensor 30 at time tIO reaches
In anticipation of the detected temperature T2, when the detected temperature of the temperature detection sensor 30 reaches Tl, the power supply to the fixing heater 32 is turned off.

With this configuration, the warm-up time can be shortened from t to tIo compared to the conventional configuration,
The surface temperature of the fixing roller 10 can be controlled to the fixable temperature T3.

Note that if the initial startup temperature (temperature at power-on) T+ is high, the time to reach the target temperature T3 will be short, and therefore the influence on the time constant will be small, so it is necessary to set Tl close to Ts and high. Detected temperature T of the temperature detection sensor 30 when the power is turned on! The temperature T2 corresponding to the detected temperature Ts is determined by reading the temperature Ts, and the operation start level of the control circuit 31 is changed. A specific example is as follows. Fixable m II When Ts is 180°, if Ts<100°C, 1c is Tz-170°C, 10
If 0℃≦T2≦150℃, Tl-175℃, 15
If 0°C<TI, T2-180°C.

If selected in this way, NTl-3 at t2o-31 seconds
It can be shortened to tw-29 seconds at 0°C. Note that instead of dividing T1 into levels and setting T2 in stages as in this example, it may be changed continuously according to T1.

FIG. 3 is a flowchart showing the flow of such a series of operations. After starting energization, first the temperature detection sensor 30
Read the detected temperature T+ (step ■). The detected value T
Find T2 from 1 (step ■). Thereafter, the fixing heater 32 is energized and heated until the temperature detected by the temperature detection sensor 30 becomes equal to T2 (Step 2). Then, when the temperature detected by the temperature detection sensor 30 reaches T2, the heating of the fixing heater 32 is turned off (step (2)).

(Effects of the Invention) As described in detail above, according to the present invention, the warming-up time can be shortened, high-quality images without hot offset can be obtained, and the life of the fixing roller can be extended. The device can be realized.

[Brief explanation of the drawing]

FIG. 1 illustrates one embodiment of the present invention. FIG. 2 is a temperature change side view to explain the operation of FIG. 1, FIG. 3 is a flowchart to explain the flow of the operation of FIG. 1, and FIG. 4 is a configuration of the electronic copying machine. Figure 5 showing an example
The figure is a diagram showing an on/off control mode. 1... Photosensitive drum 2... Cleaning section 3
...Charged electrode 4...Charged eraser section 5...
Exposure section 6... Original 8... Transfer section
9... Conveyance mechanism 10... Fixing roller 2
0...Optical unit 21...Light source 30
... Temperature detection sensor 31 ... Energization control circuit 32
... Fixing heater patent applicant Roku Konishi Photo Industry Co., Ltd. Agent Patent attorney Fuji Ijima 1 person Figure 2 Figure 3

Claims (2)

[Claims] (1) A fixing device of an image forming apparatus that fixes a toner image formed on a transfer paper using a fixing roller heated by a fixing heater, and a temperature detection device that outputs a signal related to the surface temperature of the fixing roller. In the fixing device including a sensor and an energization control circuit that controls energization to the fixing heater based on the output of the temperature detection sensor, the energization control circuit may be configured to take into account a response delay due to the heat capacity of the temperature detection sensor. A fixing device for an image forming apparatus, characterized in that the fixing device is configured to shift from at least a warming-up mode to an idling mode. (2) The image forming apparatus according to claim 1, wherein the energization control circuit is configured to change the energization stop temperature when shifting from the warming-up mode to the idling mode in accordance with the initial startup temperature. fixing device.