JPH0962137A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the back surface fixing temperature reaching waiting time in a both-side printing mode by increasing the number of revolution of a cooling fan at the point of time when recording paper passes a fixing unit and making the temperature of the fixing unit reach the fixing set temperature in an early stage. SOLUTION: When a printing operation is started, the recording paper 10 or 13 is carried, and whether the recording paper 10 or 13 passes the fixing unit 17 or not is judged, and both-side mode flag is checked at the point of time when the recording paper 10 or 13 passes the fixing unit 17. When a both- side printing flag is set, the number of revolution of the cooling fan is increased, so that the recording paper 10 or 13 is carried to a both-side printing unit 24 and the recording paper 10 or 13 is inverted from the front surface to the back surface at the inside of the both-side printing unit 24. Although the fixing set temperature is made lower at the time of back surface fixing than that at the time of front surface fixing, it reaches the back surface fixing set temperature in the early stage by increasing the number of revolution of the cooling fan at the point of time when the fixing stage of the front surface is completed in the both-side printing mode, so that waiting time hardly occurs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus equipped with a double-sided printing unit capable of forming an image on the front surface and the back surface of a recording paper in a laser beam printer, a copying machine or the like.

[0002]

2. Description of the Related Art Conventionally, printers of various principles have been proposed as output terminals for personal computers, workstations, etc. In particular, laser beam printers (hereinafter referred to as LBP) using an electrophotographic process and laser technology are used for recording. It is highly popular in terms of speed and print quality, and is rapidly becoming popular. Further, in recent years, the number of printers compatible with double-sided printing, in which a double-sided unit is attached to the LBP and images are formed on both sides of the recording paper, has been increasing.

Generally, in an electrophotographic apparatus such as an LBP, after a photoconductor is charged by a charging device (charging step), an optical writing device such as a laser optical system is used as a recording means to form a photoconductor on the photoconductor. Writing (exposure step) is performed, and then a developing step, a transfer step, and a fixing step are performed to perform printing, and the recording paper is ejected outside the machine. When performing double-sided printing, the recording paper is conveyed into the double-sided printing unit after the fixing process, the front and back sides of the recording paper are reversed inside the double-sided printing unit, and then the recording paper is conveyed again into the machine, and the charging process and the exposure process are performed. After the development process, the transfer process, and the fixing process, the recording paper is ejected out of the machine to complete double-sided printing.

The operation of the conventional image forming apparatus will be described below. FIG. 3 is a block diagram of a conventional image forming apparatus,
FIG. 4 is a control block diagram of the conventional image forming apparatus, and FIG. 5 is a diagram showing a control flow of the conventional image forming apparatus.

In FIG. 3, reference numeral 1 denotes a photoconductor in which a photosensitive layer such as an organic photoconductor (OPC) is applied in a thin film on the outer peripheral surface of a Ni (nickel) belt base material. On the peripheral surface of the photoconductor 1, a charger 2, an exposure optical system 3,
A developing device 4, a transfer roller 5 and a static eliminator 6 are provided. A developing sleeve 7 is provided in the front part of the developing device 4.

The charger 2 comprises a charging wire 2a made of a tungsten wire or the like, a shield plate made of a metal plate, and a grid plate. By applying a high voltage to the charging line 2a, the charging line 2a causes corona discharge, and the photoconductor 1 is uniformly charged via the grid plate. An exposure light beam 8 is emitted from the exposure optical system 3. The exposure light beam 8 is obtained by subjecting an image signal from a gradation conversion device (not shown) to light intensity modulation or pulse width modulation by a laser drive circuit (not shown), and an electrostatic latent image is formed on the photoconductor 1. To do. The developing device 4 is always in contact with the photoconductor 1, and the developing sleeve 7 rotates in synchronization with the rotation of the photoconductor 1 to perform development.

Reference numeral 9 is a first recording paper cassette for accommodating the recording paper 10. The recording papers 10 are sent from the first recording paper cassette 9 one by one to the paper conveyance path 15 by the first paper feed roller 11. When the user selects paper feeding from the second recording paper cassette 12, the recording paper 13 is sent out to the paper conveyance path 15 by the second paper feed roller 14. 16 is the recording paper 10 or 13 fed from the first recording paper cassette 9 or the second recording paper cassette 12.
It is a sensor such as a photo interrupter for detecting the image forming process and serves as a reference for generating the image forming process timing.

Reference numeral 17 denotes a heating roller 18 having a heat source inside.
And a pressure roller 19 for fixing the toner image transferred onto the recording paper 10 or 13 to the recording paper 10 or 13 by pressure and heat accompanying the nip rotation of the heating roller 18 and the pressure roller 19. Let A fan (not shown) is provided near the fixing unit to suppress the temperature rise inside the machine, and is rotating at a certain number of rotations. Reference numeral 20 denotes a sensor such as a photo interrupter that determines whether the recording paper 10 or 13 has passed through the fixing unit 17. After that, the recording paper 10 or 13 is conveyed to the paper discharge unit 22 or 23 designated by the user.

Reference numeral 21 denotes a paper discharge unit for the recording paper 10 or 13, and a transport path switching unit for controlling the transport of the recording paper 10 or 13 to the double-sided printing unit 24. If face-up discharge is selected, the recording paper 10 or 13 is discharged to the face-up discharge unit 22, and if face-down discharge is selected, the recording paper 10 or 13 is discharged to the face-down discharge unit 23. To be done. If double-sided printing is selected, the recording paper 10 or 13 is conveyed into the double-sided printing unit 24.

With respect to the image forming apparatus having the above components, the relationship and operation of each component will be described below. The photoconductor 1 is driven by a drive source (not shown). In this state, first, the charging wire 2a in the charger 2 connected to the high voltage power source
Is applied with a high voltage to cause corona discharge, and the surface of the photoconductor 1 is uniformly charged to about -700V. Next, when the photosensitive member 1 is rotated to irradiate the uniformly charged surface of the photosensitive member 1 with the exposure beam 8 of the laser beam, the irradiated portion on the photosensitive member 1 loses the electric charge and an electrostatic latent image is formed. It is formed. On the other hand, the developing device 4 is always in contact with the photoconductor 1.

Immediately before the electrostatic latent image on the photosensitive member 1 reaches the developing position, the developing sleeve 7 having the toner on its surface is -3
A negative potential of about 00V is applied. If a negative charge is given to the toner in advance, the toner adheres only to the portion (electrostatic latent image portion) on the photoconductor 1 where the exposure light beam 8 is irradiated and the charge is removed, and the development is performed by the so-called negative-positive process.
The toner image thus formed is transferred to the transfer roller 5+
The first recording paper cassette 9 or the second recording paper cassette 1 is applied by applying a high voltage of about 1000 V and pressure.
The recording sheet 10 sent from the sheet 2 along the sheet conveying path 15
Or it is transferred to 13. When the transfer is completed, the charge on the photoconductor 1 is removed by the static eliminator 6.

Subsequently, the recording paper 10 or 13 on which the toner image is transferred is sent to a fixing unit 17, where it is fixed by the heat of the heating roller 18 and the nip pressure of the pressure roller 19, and a paper discharge unit designated in advance. The sheet is discharged to 22 or 23. The above operation completes the recording of one image. When double-sided printing is designated, the recording paper 10 or 13 that has passed through the fixing unit 17 is guided by the transport path switching unit 21 toward the double-sided printing unit 24. After reversing the front and back sides of the recording paper 10 or 13 inside the double-sided printing unit 24, the recording paper 10 or 13 is conveyed again into the machine, the image forming process is performed on the back surface, and after the fixing process is completed, a preset discharge is performed. It is discharged to the paper unit 22 or 23.

Next, the operation of the conventional image forming apparatus will be described in detail with reference to FIGS. 4 and 5. In FIG. 4, A
Is a CPU (central processing unit) having a fan drive unit B, a print mode determination unit C, a fixing temperature setting unit D, and a fixing temperature determination unit E. The fan drive unit B controls a fan drive unit F for suppressing an increase in the in-machine temperature due to heat generation during fixing. The print mode determination means C determines a signal from the print mode designating section G that designates double-sided printing or single-sided printing. Further, the fixing temperature setting means D sets the fixing temperature, and the fixing temperature determination means E inputs the actual temperature information of the fixing device heater from the fixing section H and manages the fixing temperature for the fixing section H. I is a ROM in which a program for controlling each of the above means is stored, and J is a RAM which is a work area for operating variables and the like necessary when executing the program.

Next, the operation flow of the conventional image forming apparatus will be described in detail with reference to FIG. First, the power of the entire image forming apparatus is turned on (step 2-1). Initial operation of each electrophotographic process for printing and warm-up of the fixing unit 17 are started (step 2-
2) Wait until these are completed (step 2-3).
When the initial of each electrophotographic process and the warm-up of the fixing unit 17 are completed, the image forming apparatus checks the print mode designation status (step 2-4). If the double-sided printing mode is designated, the double-sided mode flag is set (step 2-5), and if the single-sided mode is designated, the single-sided mode flag is set (step 2-6). After that, the image forming apparatus enters a print start request waiting state (step 2-
7).

When the print start request is issued, the image forming apparatus starts each print process (step 2-8) and starts the print operation. Now, when the printing operation is started, the recording paper 1
0 or 13 is conveyed, but the recording paper 10 or 1
3 determines whether or not the fixing unit 17 has passed, and waits until the fixing unit 17 passes (step 2-9). If the recording paper 10 or 13 has passed through the fixing unit 17, the double-sided mode flag is checked at that time (step 2-1).
0). If the double-sided printing flag is set, the recording paper 10 or 13 is conveyed to the double-sided printing unit 24 (st
ep2-11). Recording paper 10 in the double-sided printing unit 24
Or, the front and back sides of 13 are reversed, and the printing process on the back side is performed. However, when a toner image is formed on the back side and the recording paper 10 or 13 enters the fixing unit 17 again, the toner on the front side once fixed is heated. As a result, the toner comes into pressure contact with the pressure roller 19 which is heated by the heat of 18, so that a part of the toner on the surface adheres to the pressure roller 19 and the part where the toner has fallen off becomes a white spot, or the next recording is performed. A so-called hot offset state occurs in which the dropped toner adheres to the paper 10 or 13. In order to prevent this, it is necessary to set the fixing temperature lower when fixing the back surface than when fixing the surface. Therefore, the recording paper 10 or 13 is made to stand by until the backside fixing temperature is reached (step 2-1).
2).

When the backside fixing temperature is reached, the recording paper 10
Alternatively, 13 is again conveyed to the inside of the machine, and the back side printing process is executed (step 2-13). Although the subsequent processing is the same as that in the single-sided printing mode, the recording paper 10 or 13 is conveyed to the paper discharge unit 22 or 23 (step 2-14), and it is determined whether the printing is completed (step 2-15). If printing is completed, go to step 2-16. If the power is turned off, all the processing is ended, and if not turned off, step 2-1
If the power is turned off, the process is terminated, and if not turned off, the process returns to step 2-4. If printing is continued, the process returns to step 2-8.

[0017]

However, in the above-described conventional configuration, in the double-sided printing mode, the conveyance of the recording paper is temporarily stopped in the double-sided printing unit until the back side fixing set temperature is reached, which causes a problem that the printing speed is lowered. Had.

Therefore, an object of the present invention is to provide an image forming apparatus capable of reducing the waiting time for reaching the rear surface fixing temperature in the double-sided printing mode.

[0019]

In order to solve the above problems, in the present invention, when the recording paper passes through the fixing unit, the rotation speed of the cooling fan is increased so that the temperature of the fixing unit is set to early fixing. Temperature (Backside fixing temperature <Frontside fixing temperature)
To prevent the printing speed from decreasing.

[0020]

By the above means, it is possible to realize an image forming apparatus in which the printing speed does not decrease due to the waiting for the fixing temperature to be reached even when printing on both sides.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 is a control block diagram of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing a control flow of the image forming apparatus of an embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. It is a block diagram of an example image forming apparatus.

Since the structure of the image forming apparatus of the present invention shown in FIG. 3 is the same as that of the conventional example, detailed description thereof will be omitted. The block configuration of the image forming apparatus of the present invention shown in FIG. 1 has a fan rotation speed setting means K for changing the rotation speed of the fan.
Since it is the same as the conventional example except that is newly provided, detailed description thereof will be omitted.

Next, the operation flow of the image forming apparatus will be described in detail with reference to FIG. First, the power of the entire image forming apparatus is turned on (step 1-1). The initial operation of each electrophotographic process for printing and the warm-up of the fixing unit 17 are started (step 1-2),
Wait until these are completed (step 1-3). When the initial of each electrophotographic process and the warm-up of the fixing unit 17 are completed, the image forming apparatus checks the print mode designation status (step 1-4). If the duplex printing mode is specified, set the duplex mode flag (s
If the one-sided mode is designated, the one-sided mode flag is set (step 1-6). After this, the image forming apparatus enters a print start request waiting state (step 1-7).

When the print start request is issued, the image forming apparatus starts each print process (step 1-8) and starts the print operation. Now, when the printing operation is started, the recording paper 1
0 or 13 is conveyed, but the recording paper 10 or 1
It is determined whether or not the sheet No. 3 has passed the fixing unit 17, and waits until the sheet passes (step 1-9). If the recording paper 10 or 13 has passed through the fixing unit 17, the double-sided mode flag is checked at that time (step 1-1).
0). If the double-sided printing flag is set, the rotation speed of the cooling fan is increased (step 1-11) and the recording paper 10 or 13 is conveyed to the double-sided printing unit 24 (step).
p1-12).

In the double-sided printing unit 24, the front and back sides of the recording paper 10 or 13 are reversed, and the back side printing process is performed. However, a toner image is formed on the back side and the recording paper 10 or 13 rushes into the fixing unit again. Then, the toner on the surface once fixed receives the heat of the heating roller 18 and comes into pressure contact with the heated pressure roller 19, so that part of the toner on the surface adheres to the pressure roller 19 and the toner falls off. A so-called hot offset state occurs in which a portion becomes blank and the toner that has fallen off adheres to the next recording paper 10 or 13. In order to prevent this, it is necessary to set the fixing temperature lower when fixing the back surface than when fixing the surface. For this reason, the recording paper 10 or 13 is put on standby until the backside fixing temperature is reached (step 1-13). However, in the present embodiment, in the double-sided printing mode, since the rotation speed of the cooling fan is increased and the backside fixing set temperature is reached early at the time when the front side fixing process is completed, this waiting time hardly occurs.

When the backside fixing temperature is reached, the recording paper 10
Alternatively, 13 is again conveyed to the inside of the machine, and the back side printing process is executed (step 1-14). Although the subsequent processing is the same as that in the single-sided printing mode, the recording paper 10 or 13 is conveyed to the paper discharge unit 22 or 23 (step 1-15), and it is determined whether the printing is completed (step 1-16). If printing is completed, go to step 1-17. If the power is turned off, all the processing is ended, and if not turned off, step 1-1.
7. If the power is turned off, all the processes are terminated, and if not turned off, the process returns to step 1-4. If printing is continued, the process returns to step 1-8.

[0027]

According to the present invention, even in the double-sided printing mode, it is possible to prevent a decrease in printing speed due to waiting for the backside fixing temperature to be achieved, and to realize an image forming apparatus which is easy to use.

[Brief description of drawings]

FIG. 1 is a control block diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a control flow of the image forming apparatus according to the embodiment of the present invention.

FIG. 3 is a configuration diagram of an embodiment of the present invention and a conventional image forming apparatus.

FIG. 4 is a control block diagram of a conventional image forming apparatus.

FIG. 5 is a diagram showing a control flow of a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging device 3 Exposure optical system 4 Developing device 5 Transfer roller 6 Static eliminator 9 First recording paper cassette 10 Recording paper 11 First paper feeding roller 12 Second recording paper cassette 13 Recording paper 14 Second Paper feed roller 17 Fixing unit 18 Heating roller 19 Pressure roller 24 Double-sided printing unit A CPU (Central processing unit) B Fan drive means C Print mode determination means D Fixing temperature setting means E Fixing temperature determination means F Fan drive section K fan Rotation speed setting means

Claims (1)

[Claims] 1. A first roller and a second roller which are in pressure contact with each other for nipping and conveying a recording medium, and one of the first roller and the second roller is heated to a preset temperature. Heating means, a driving means for rotating the first roller and the second roller, a temperature detecting means for detecting the temperature of at least one of the first roller and the second roller, and heat from the heating means. And a fan for suppressing the temperature rise in the machine due to, the recording paper on which the toner is printed is passed between the first roller and the second roller to fix the toner on the surface of the recording paper, After that, it has a double-sided printing function of fixing the toner on the back surface of the recording paper by passing the recording paper which is reversed and the toner is printed on the back surface between the first roller and the second roller. Surface After the chromatography fixing, the image forming apparatus characterized by varying the rotational speed of the fan.