JP2790834B2 - Electrophotographic image forming apparatus - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical printer such as a laser printer, an electrophotographic copying machine, and an electrophotographic image forming apparatus such as a facsimile machine.

[Conventional technology]

2. Description of the Related Art Generally, in an electrophotographic image forming apparatus such as a laser printer, a series of process devices such as a photoconductor, a charging charger, a laser writing device, a developing device, a transfer charger, a discharge lamp, a fixing unit, and a cleaning unit are used. An image is formed on paper through an electrophotographic process.

By the way, among the above-mentioned process devices, the fixing unit includes a fixing roller for thermally fixing the toner image transferred from the photoreceptor surface onto the sheet, and a temperature for controlling the surface temperature opposite to the fixing roller. Detector (Thermistor)
Is fixedly installed.

The fixing roller has a built-in heater for heating its surface.

In such an image forming apparatus, when the power is turned on, the control circuit automatically supplies power to the heater, and the surface temperature of the fixing roller detected by the temperature detector is fixed at a predetermined temperature (for example, 160 ゜)
When the temperature reaches a predetermined temperature, image formation by the process device is permitted, and thereafter, the power supply to the heater is controlled to be on / off so as to maintain the predetermined temperature.

[Problems to be solved by the invention]

However, in such a conventional electrophotographic image forming apparatus, as long as the surface temperature of the fixing roller reaches a predetermined temperature, image formation is permitted regardless of the environmental temperature (in-machine temperature). When an image forming operation is performed by each process device other than the fixing unit in an environment (for example, 10 ° C. or less) before the process device is warmed, an image defect occurs and paper is wasted.

The present invention has been made in view of the above points, and has as its object to obtain good image quality from the first sheet after power-on even in a low-temperature environment.

[Means for solving the problem]

In order to achieve the above object, the present invention relates to an electrophotographic image forming apparatus including a fixing roller having a built-in heater and a temperature detector for detecting a surface temperature of the fixing roller. As shown in the figure, an energization time measuring means B for measuring the time after the power is turned on or the energization of the heater is started, and the temperature detected by the temperature detector A reaches a predetermined temperature at which fixing can be performed. A fixing roller temperature determining means C for determining whether or not the temperature has reached a predetermined temperature, and determining whether or not the time measured by the energizing time measuring means B is within a set time. The image forming apparatus further includes an image forming permission time determining unit D that outputs an image forming permission signal immediately if the time is within the set time, and outputs an image forming permission signal after a predetermined time if the time is not within the set time.

(Operation)

According to the image forming apparatus having the above-described configuration, when the environmental temperature is equal to or higher than the predetermined temperature, after the power is turned on or the power supply to the heater is started, the fixing roller temperature is set to the predetermined temperature at which the fixing can be performed within a set time. Therefore, the image formation permission time determination unit D determines the determination based on the determination result by the fixing roller temperature determination unit C and the measurement time by the conduction time measurement unit B, and immediately outputs an image formation permission signal.

However, if the environmental temperature is lower than the predetermined temperature, it takes more than a set time for the fixing roller temperature to reach the predetermined temperature. Therefore, the image formation permission signal is output after the waiting time for each process device to warm up), so that good image quality can be obtained even in a low temperature environment.

〔Example〕

Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

FIG. 2 is a sectional view showing a schematic configuration of a laser printer as an image forming apparatus embodying the present invention.

The laser printer 1 is provided with a detachable paper feed tray 2, a first paper discharge stacker 3 at the top, and a second paper discharge stacker 4 at the rear.

Normally, the first discharge stacker 3 is selected from the two discharge stackers 3 and 4. However, the second discharge stacker 3 is used in special cases such as when using easily curlable paper such as an envelope or postcard. Statka 4 is selected.

The paper discharge to the two paper discharge stackers is performed by the switching claw 5.
Can be switched by means of

Further, in the laser printer 1, a photosensitive drum 6, a charging charger 7, a laser writing device 8, a developing device 9, a transfer charging device 10, a fixing unit 11, a discharging lamp 12, Each processing device such as a cleaning unit 13 and the like, a paper feed unit including a paper feed roller 14 and a pair of registration rollers 15 and the like, and a paper discharge transport unit 16 including a transport roller and a paper guide plate are provided.

Note that the fixing unit 11 includes a fixing roller 11a, a temperature detector 11b installed facing the surface of the fixing roller 11a, and the like. The temperature detector 11b corresponds to the temperature detector A shown in FIG.

In the upper part of the laser printer 1, an in-machine cooling fan (ozone blowing fan) 17, a board for a printer controller 20 and an engine driver 30 are mounted.

 Next, the operation of each unit will be briefly described.

This laser printer is controlled by a printer controller
The printing is performed by the printer driver 20 based on data from the host system, and the engine driver 30 receives a print request signal from the printer controller 20 to start a printing operation.

Then, when the print sequence is started, paper feeding is started from the paper feeding tray 2 by the paper feeding roller 14 at a predetermined timing, and is temporarily stopped at a position where the leading end of the paper is held between the registration roller pair 15. In FIG. 2, the paper conveyance path is indicated by a virtual line with an arrow.

On the other hand, the photosensitive drum 6 rotates in the direction indicated by the arrow, and the electrophotographic process is performed.

That is, the photosensitive drum 6 is charged by the charging charger 7.
The surface of the photosensitive drum 6 is uniformly charged, and is irradiated with a laser beam modulated by a laser beam writing device 8 in accordance with a video signal from a printer controller 20 while being main-scanned in the axial direction of the photosensitive drum 6, and is exposed. An electrostatic latent image is formed on the photosensitive drum 6.

It is developed with a toner in a developing device 9 to make it a visible image, transferred by a transfer charger 10 to a sheet fed at a predetermined timing by a pair of registration rollers 15, and then transferred onto the transferred sheet. The visible image is fixed and heated by a fixing roller 11a in a fixing unit 11 controlled to be heated to about 160 ° C.

Then, the print paper exiting the fixing unit 11 is discharged to the first discharge stacker 3 via the second discharge stacker 4 or the discharge conveying section 16.

On the other hand, the photosensitive drum 6 after the transfer of the visible image is
12 to remove the surface charge, and the photosensitive drum 6
The upper residual toner is removed by the cleaning unit 13 and collected in the toner collection tank.

FIG. 3 is a circuit diagram showing an example of a fixing heater temperature control circuit.

The heater 40 is built in the above-described fixing roller 11a, and is energized from an AC power supply via a heater energization control circuit 41 to heat the fixing roller 11a.

The temperature detector 11b shown in FIG.
If you are using, since the vicinity disposed opposite the thermistor TH on the surface of the fixing roller 11a, accompanied connexion resistance value of the resistance value R _TH changes (temperature increase of the thermistor TH in accordance with the surface temperature R _TH is smaller).

Accordingly, the DC power supply Vcc is connected to the resistor R ₁ and the thermistor T.
H, and the magnitude of the current flowing to ground I changes through the resistor R _2.

Converts the current I to resistor R ₂ to the O connexion temperature detection voltage V _T, inputs it to the microcomputer 43 is converted into A / D converter 42 Niyotsu Te e.g. 8 bits of the digital signal (temperature detection signal) I do.

The capacitor C is provided for absorbing noise.

Microcomputer (hereinafter abbreviated as “CPU”) 43
Is composed of a CPU, a ROM, a RAM, a timer (counter), an I / O, and the like, and uses, for example, one provided on the substrate of the engine driver 30 in FIG.

The CPU 43 determines the fixing roller temperature based on the temperature detection signal from the A / D converter 42, controls the energization of the heater 40 by the heater energization control circuit 41, or energizes the heater 40 after the power is turned on or the heater 40 is energized. A time after the start is measured, a timing for permitting printing described later is determined, and a process of outputting a print permit signal is performed.

Therefore, in this embodiment, the CPU 43 also functions as the power-on time measuring means B, the fixing roller temperature determining means C, and the image forming permission timing means D shown in FIG.

The heater power supply control circuit 41 supplies an alternating current from an AC power supply (100 V) to the heater 40 via a switching element that is controlled to open and close by an on / off control signal from the CPU 43, for example, a solid state relay (SSR). .

Next, the operation of this embodiment thus configured will be specifically described with reference to FIG. 4 and FIG.

FIG. 4 is a flow chart showing the print permission time determination processing by the CPU 43 according to this embodiment, and FIG. 5 is a timing chart provided for a specific explanation of the processing.

That is, in Fig. 5 (a), and are for normal temperature environment (for example, when the outside air temperature exceeds 10 ° C),
Temperature change (rise) of the fixing roller surface with respect to the elapsed time when the heater fails in a low temperature environment (for example, 10 ° C or less)
(B) shows the output timing of the print permission signal (REDY) corresponding to (a) and (b) in FIG.

The routine shown in FIG. 4 is started at the same time when the power is turned on (power is turned on), and a timer (counter) in the CPU 43 is provided.
Start.

The memory in the CPU 43 stores in advance the elapsed times after power-on shown in FIG. 5 (a), T ₁ (for judging the heater-on timing), T ₂ (for judging the ambient temperature), and T ₃ (for judging the heater failure). )
And the predetermined time t ₃ when shown in (b), fixable predetermined temperature (in this example 160 ° C.) Yes stored set each data, the magnitude relation of T _1, T _2, T ₃ is T ₁ <T ₂ <T ₃ .

First, the elapsed time after power-on is T _1, to start power supply to the heater 40 by sending an ON signal to the heater energization control circuit 41 (heater ON).

And if in the case where the elapsed time after power-on, such the set time T ₃ connexion also fixing roller surface temperature is not the predetermined temperature, it is determined that the heater 40 is faulty (disconnection), it printer external Display on the display panel and proceed to the next process.

When fixing roller surface temperature before the predetermined temperature T ₃ has elapsed reaches a predetermined temperature (160 ° C.), then determines whether the elapsed time after power-on setting time T ₂ within.

If Yes, the print permission signal (RED
If it be set to "H" Y) permits the printing operation, has reached a predetermined temperature until T ₃ beyond If No to (T _2),
Then the print permission signal from wait until the predetermined time t ₃ has elapsed in the "H" to allow printing operation.

Therefore, in a low temperature environment, the fixing roller 11a
Also reaches a predetermined temperature surface temperature fixable, more so until a predetermined time t ₃ has elapsed not allowed printed, temperature around O connexion each process equipment to radiant heat from therebetween fixing roller 11a is raised As a result, the process equipment itself warms up, so that printing can be performed in an optimum state. That is, a stable optimal image can always be obtained without being affected by the temperature environment.

In this embodiment, the time after power-on is compared with each set time. Alternatively, the time after heater-on may be compared with each set time.

Further, in this embodiment, the environmental temperature compared by the connexion determined between the time and the predetermined time T ₂ of the up surface temperature of the power-on after the fixing roller reaches a predetermined temperature (160 ° C.), immediately or print Although permission is granted after the elapse of a predetermined time (delay time), for example, 0 to 10 ° C. is divided into five groups, and 0 ° C., 2
Five set times and five delay times corresponding to each set time are set in the CPU in accordance with the five-stage low-temperature environment of ℃, 4 ° C, 6 ° C, 8 ° C, and 10 ° C, and each set time is set. If the printing is permitted after a different delay time according to the result, the delay time can be minimized and the waiting time can be reduced.

Further, if the start time of the drive of the in-machine cooling fan 17 shown in FIG. 2 is delayed along with the delay of the time for permitting the printing, the rise in the temperature around the process equipment can be prevented, so that the temperature can be further reduced. It is valid.

Furthermore, in a low-temperature environment, the period of the preparation drive (warming-up) for accustoming the sequence devices including the process devices is made longer than usual, and the surface temperature of the fixing roller is made higher than usual only for a certain initial period (for example, 180 ° C.) is more effective.

Further, the present invention is not limited to a laser printer, but can be widely applied not only to other optical printers such as LED printers but also to other electrophotographic image forming apparatuses such as electrophotographic copying machines and facsimile machines.

〔The invention's effect〕

As described above, according to the present invention, good image quality can be ensured from the first sheet after power-on even in a low-temperature environment.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a basic configuration of the present invention, FIG. 2 is a sectional view showing a schematic configuration of a laser printer embodying the present invention, and FIG. 3 is a circuit showing an example of a fixing heater temperature control circuit of the same. FIG. 4 is a flow chart showing a print permission time determination process by the CPU of this embodiment, and FIG. 5 is a timing chart for specifically explaining the process. DESCRIPTION OF SYMBOLS 1 ... Laser printer, 6 ... Photoreceptor drum 7 ... Charging charger, 8 ... Laser writing device 9 ... Developing device, 10 ... Transfer charger 11 ... Fixing unit, 11a ... Fixing roller 11b ... Temperature detector (Thermistor TH) 20 Printer controller 30 Engine driver 40 Heater 41 Heater conduction control circuit 42 A / D converter 43 Micro computer (CPU)

Claims (1)

(57) [Claims] 1. An electrophotographic image forming apparatus comprising a fixing roller having a built-in heater and a temperature detector for detecting a surface temperature of the fixing roller. Energizing time measuring means for measuring a later time; fixing roller temperature determining means for determining whether or not the temperature detected by the temperature detector has reached a predetermined temperature at which fixing can be performed; When it is determined that the temperature has reached the predetermined temperature, it is determined whether or not the measurement time by the energization time measurement unit is within a set time, and if it is within the set time, an image formation permission signal is output immediately, and within the set time, An image forming permission time determining means for outputting an image forming permission signal after a lapse of a predetermined time if not provided.