JP2906153B2 - Fixing control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to an image forming apparatus having a fixing section for sandwiching transfer paper such as a laser printer and a copying machine between a fixing roller and a pressure roller and fixing toner and the like to the transfer paper. The present invention relates to a fixing control device at the time of startup when the device is powered on.

(Prior art) Temperature control of the fixing unit when the power of an image forming apparatus such as a laser printer or a copying machine is turned on, or when the power is turned on again for a certain period of time after a failure such as curling or jam occurrence, and the apparatus is not used for a certain time. Was performed as follows.

As shown in FIG. 2, a fixing heater 1 is built in a cylinder of a fixing roller 1 and a transfer paper 4 is sandwiched between the fixing roller 1 and a pressing roller 3 to fix toner and the like by heating and pressing. Let it. The surface temperature of the fixing roller is detected by the thermistor 5, converted into a digital value and inputted to a microcomputer (CPU) 6, and compared with a reference voltage indicating a fixing temperature preset in the CPU 6, and reaches the fixing temperature. The CPU 6 controls so that the printing operation is performed when the printing is performed.

Illustrates this operation flow in Figure 3 was charged with an image forming apparatus and a power supply start start-up _{(POWER · ON) (S 1} ) together with the fixing motor heater 2 rotates the fixing roller is turned and at the same time the rotation operation (ON ) Is started (S ₂ ). Then, the temperature detection signal CPU6 is determined by (voltage) (S ₃₎ from the thermistor 5, the fixing condition if the fixing roller reaches a predetermined fixing temperature is in place as (OK), the startup startup the ready (S _4).

FIG. 4 shows a graph of actually measured fixing temperature data, in which the vertical axis represents the surface temperature (° C.) of the fixing roller, and the horizontal axis represents the elapsed time t (minutes). As can be seen from this graph, at the time of start-up, a certain time of about two minutes is required until a predetermined fixing temperature (about 176 ° C.) is reached, and the temperature is hardly stabilized.

(Problems to be Solved by the Invention) As described above, in the fixing unit, the temperature of the fixing roller is transferred by heat conduction to the pressure roller that is driven to contact with the fixing roller. The pressure roller is generally formed of an elastic member, such as rubber, for transferring the transfer paper 4, and it takes a considerably longer time for the pressure roller to be uniform at a predetermined temperature than for the fixing roller.

Therefore, when the image forming apparatus is started and started, idle rotation is performed for a short time (5 to 10 seconds) in order to equalize the heat amounts of the fixing roller and the pressure roller. It takes considerable time to become. If the temperature of the pressure roller is not made uniform, curling, jamming, and the like are likely to occur due to the temperature difference between the fixing roller and the pressure roller.

There is also a method of idling the fixing roller for a long time in order to make the temperature uniform, but this method has a disadvantage that the start-up time (warming-up time) is lengthened.

(Object of the Invention) It is an object of the present invention to provide a fixing control device capable of setting the temperatures of the fixing roller and the pressure roller to be uniform at an early stage and setting a fixing-possible temperature within a conventional startup time.

(Structure and Operation) In order to achieve the above object, the present invention provides a thermistor that detects the temperature of the fixing roller in a fixing unit that fixes a toner or the like to a transfer sheet by sandwiching the transfer sheet between the fixing roller and a pressure roller. A fixing unit that controls heating so that the temperature of the fixing roller becomes a set temperature based on the temperature detected by the thermistor, and that controls a rotation speed of the fixing roller. Means for setting the temperature to the temperature at the time of paper passing or a temperature higher than this temperature, and setting the rotational speed of the fixing roller to the rotational speed at the time of paper passing or a rotational speed higher than the rotational speed at the time of paper passing. Means for setting the rotation speed of the fixing roller and the set temperature of the fixing roller to be higher at the time of start-up by turning on the power of the image forming apparatus. And the set temperature.

According to the present invention, when the image forming apparatus is started up by turning on the power, the number of rotations of the fixing roller is rotated at a higher speed than during the steady paper feeding, so that the contact area between the fixing roller and the pressure roller is increased, and the fixing roller is added in a short time. A large amount of heat is transferred to the pressure roller side, thereby achieving a predetermined fixing temperature at an early stage and achieving uniformity.

Further, by setting the detection temperature of the fixing roller detected by the thermistor to a high temperature only at the time of startup and startup, the supply current to the heater is increased, and the fixing temperature is quickly set to a predetermined temperature. Aim for temperature uniformity.

(Embodiment) FIG. 1 shows an operation flow of an embodiment for carrying out the present invention.
At the same time as (ON) (S ₁ ), the CPU 6 sets the set temperature of the fixing roller to a temperature (for example, 210 ° C.) higher than the set temperature (for example, 176 ° C.) at the time of steady paper feeding. The set temperature is determined in consideration of the thickness of the pressure roller 3, where the pressure roller has a temperature uniformity mode ON state (S _2), as shown in FIG. 1, ON the heater 2 of the fixing roller 1 (S ₃ ), and further increase the speed of the driving motor of the fixing roller from the normal rotation.
And (S _4), the contact area of the fixing roller and the pressure roller a lot in a short time in the activation start-up time, perform an early uniform heat transfer to the pressing roller.

The CPU 6 determines from the detection signal (current) from the thermistor 5 whether the fixing condition of the roller for fixing and pressing is satisfied,
(S _5), conditions are in long as (S ₆ steady sheet passing mode equipped. That is, when the rotational speed of the drive motor of the set temperature and the fixing roller of the fixing roller at the time of steady sheet passing is lowered, the constant ready of the operation of the paper passing state becomes (S _7).

In the above operation, the CPU at startup and during normal paper feeding
Is performed by a detection signal from one thermistor, two temperature sensors may be independently provided to perform temperature control.

(Effects of the Invention) As described above, according to the present invention, when the image forming apparatus is started up, the number of rotations of the fixing roller is increased and the set temperature of the thermistor is increased. In this case, the temperature of the pressure roller can be made uniform more quickly and reliably, and the optimum fixing temperature can be obtained.

As a result, the temperature difference between the front and back surfaces of the transfer paper, which is generated particularly during the two-sided paper passing in the fixing unit, is eliminated, curling can be suppressed as much as possible, wrinkles and the like are less likely to occur, and good fixing and conveyance failure are eliminated. it can.

[Brief description of the drawings]

FIG. 1 is a diagram showing an operation flow of one embodiment for carrying out the present invention, FIG. 2 is a diagram showing a configuration of a fixing unit of an image forming apparatus in which the present invention is carried out, and FIG. FIG. 4 is a diagram showing an operation flow in a paper feeding preparation stage at the time, and FIG. 4 is a diagram showing a graph of actually measured fixing temperature data. DESCRIPTION OF SYMBOLS 1 ... Fixing roller, 2 ... Heater, 3 ... Pressure roller, 4 ... Transfer paper, 5 ... Thermistor, 6 ... Microcomputer (CPU).

Claims (1)

(57) [Claims] A thermistor for detecting the temperature of the fixing roller in a fixing unit for fixing toner and the like to the transfer sheet by sandwiching the transfer sheet between a fixing roller and a pressure roller; and performing the fixing based on the detected temperature of the thermistor. A heating unit that controls heating so that the temperature of the roller becomes a set temperature, and a control unit that controls the number of rotations of the fixing roller. Means for setting the temperature higher than the temperature, and means for setting the number of revolutions of the fixing roller to the number of revolutions at the time of paper passing or a number of revolutions higher than the number of revolutions at the time of paper passing. At the time of start-up by insertion, the rotation speed of the fixing roller and the set temperature of the fixing roller are set to be higher, and after a certain period of time, the rotation speed and the set temperature at the time of steady paper feeding are set. Fixing control device according to claim.