JP2002296961A - Image forming device and method for preventing recording paper from being stuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing a phenomenon that OHTs are stuck to each other on a paper ejection tray when recording paper is the OHT, and a method for preventing the recording paper from being stuck. SOLUTION: This image forming device is equipped with a transfer device transferring an unfixed developer image to the recording paper 2, and a fixing device 13 fixing the unfixed developer image on the recording paper 2 by heating the recording paper 2 carried from the transfer device while holding and carrying it. In the case of consecutively printing the OHT as the recording paper 2, throughput is restrained by making space between paper and paper longer than usual and also fixing temperature is appropriately controlled in the space between the paper and the paper.

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 such as a copying machine, a printer, a facsimile, etc. using an electrophotographic system having a heating type fixing device.

[0002]

2. Description of the Related Art An image forming apparatus for visualizing an image stored in a storage element by fixing it on a recording paper such as a printing paper as a developer is represented by a laser beam printer or a copying machine. It is widely used because of its quietness. The printing operation in such an image forming apparatus is carried out by a known electrophotographic technique, that is, through an exposure, development, and transfer process, to carry an image visualized by a toner on a recording paper such as a printing paper, and finally, the toner image is formed. The process is terminated by fixing the recording paper. For example, a laser beam printer has a configuration as shown in FIG.

FIG. 11 shows a main section of a laser beam printer 1 which is a conventional image forming apparatus. The laser beam printer 1 has a cassette 3 for accommodating a recording paper 2.
A pickup roller 4 for picking up the recording paper 2, a paper feed roller 5 for sending out the recording paper 2, and a conveyance roller 6 for conveying the recording paper 2 to a registration roller 9 described later, and a multipurpose tray (hereinafter MPT) for manual paper feeding (not shown) ) Is provided with an MPT paper feed roller 7 for sending out the recording paper 2. A registration roller front sensor 8 (hereinafter referred to as a pre-registration sensor) is provided between a position where the recording paper conveyance path from the cassette 3 and the recording paper conveyance path from the MPT merge and a registration roller 9 for synchronously conveying the recording paper 2. ) Is provided to detect that the recording paper 2 sent from the paper feed system has moved to the transport system.

On the other hand, an image forming section 11 for forming an image by a laser beam emitted from a laser scanner section 12 is disposed downstream of the registration roller 9, and a fixing device 13, which will be described in detail later, is further downstream of the image forming section 11. A fixing paper discharge roller 14, a face-down (hereinafter abbreviated as FD) conveyance roller 15, and an FD paper discharge roller 16 for feeding the processed recording paper 2 downstream are arranged, and the recording paper 2 is conveyed to an FD paper discharge tray 17. . The fixing device 13 includes a fixing roller 13b having a built-in fixing heater 13a, and a pressure roller 13c pressed against the fixing roller 13b. The fixing heater 13a heats the inner peripheral surface of the fixing roller 13b, and the heat is
The structure is such that the heat is transmitted to the front side by the heat conduction of 3b itself. A temperature sensor 13d such as a thermistor for measuring the surface temperature of the fixing roller 13b is arranged around the fixing roller 13b, and the temperature is controlled by a temperature control circuit (not shown) according to the measured surface temperature of the fixing roller 13b. The power supply to the heater 13a is controlled, and the surface temperature of the fixing roller 13b is automatically adjusted to a predetermined fixing temperature. The fed recording paper 2 is heated and pressed by the fixing roller 13b and the pressure roller 13c, and the image is fixed on the upper surface of the recording paper 2.

In an image forming apparatus such as a high-speed laser printer for continuously printing recording paper at a high speed, the recording paper 2 heated in the fixing process is discharged to the FD discharge tray 17 in a still hot state. When an OHT is used, it often occurs that the OHTs as recording paper stick to each other without completely drying the toner. Therefore, in the fixing process, the fixing temperature is set lower, or the fixing speed is reduced, or both are performed at the same time.
This prevents sticking between T's. Regarding this prior art, Japanese Patent Laid-Open Publication No. 2000-75584 discloses a fixing speed lower than usual and a printing temperature equal to a standby temperature in order to maintain good fixing performance irrespective of paper type. Alternatively, there is provided a color image forming apparatus having another mode of low-speed low-temperature fixing in which fixing is performed in the vicinity thereof.

[0006]

As described above, in the conventional image forming apparatus, as for the recording paper which may be stuck on the paper discharge tray such as the OHT, the time required for the recording paper to be cooled by the FD paper discharge tray. In order to take longer, the paper interval is made longer than usual. This makes it possible to prevent the recording paper from sticking, but the throughput is reduced, and the surface temperature of the fixing roller and the pressure roller is increased due to the long interval between the sheets, so that the fixing property is excessively increased. However, there is a problem that the original fixing control cannot be performed.

The present invention has been made in view of the above-mentioned circumstances, and when the recording paper is OHT,
It is an object of the present invention to provide an image forming apparatus and a method for preventing recording paper from sticking, which can prevent sticking between OHTs.

[0008]

The present invention can solve the above-mentioned problems by providing the following constitution.

(1) A transfer device for transferring an unfixed developer image onto recording paper, and heating while holding and transporting the recording paper conveyed from the transfer device, the unfixed developer image is transferred onto the recording paper. An image forming apparatus provided with a fixing device for performing fixing, in a case where continuous printing is performed using OHT as recording paper, the interval between the sheets is made longer than usual to suppress the throughput, and the fixing temperature is appropriately controlled between the sheets. An image forming apparatus comprising:

(2) In the case of continuous printing using OHT as recording paper, the interval between sheets is made longer than usual to suppress the throughput, the fixing temperature between the sheets is appropriately controlled, and the interval between the sheets is increased as the printing progresses. The image forming apparatus according to the above (1), wherein the length is increased.

(3) In the case of continuous printing using OHT as recording paper, the interval between the sheets is made longer than usual to suppress the throughput, and the fixing temperature between the sheets is appropriately controlled, and as the printing progresses, the fixing temperature is increased. The image forming apparatus according to the above (1), wherein the image forming apparatus is set at a low level.

(4) In the case of continuous printing using OHT as recording paper, the interval between sheets is made longer than usual to suppress throughput, the fixing temperature between sheets is appropriately controlled, and the sheet is discharged downstream of the fixing unit. The image forming apparatus according to the above (1), further comprising a fan for cooling the recording paper inside.

(5) In the case of continuous printing using OHT as recording paper, the throughput is suppressed by making the paper interval longer than usual, and the fixing temperature between the papers is appropriately controlled so that the OH
The image forming apparatus according to the above (1), wherein a reflection type photosensor is disposed upstream of the fixing device as the T detecting means.

(6) A transfer device for transferring an unfixed developer image onto recording paper, and heating while holding the recording paper conveyed from the transfer device while nipping and transporting, the unfixed developer image is transferred onto the recording paper. An image forming apparatus provided with a fixing device for fixing includes a step of detecting whether or not the recording paper is an OHT. When performing continuous printing using the OHT as the recording paper, the paper interval is made longer than usual to suppress the throughput. Along with
Providing a step of appropriately controlling the fixing temperature between the sheets, elongating the sheet as the printing progresses, or reducing the fixing temperature, and cooling the recording paper being discharged downstream of the fixing device. , And the recording paper is OH
In the case of T, a method for preventing sticking of recording paper, which can prevent mutual sticking phenomenon.

[0015]

Embodiments of the present invention will be described below.

FIG. 1 is a schematic cross-sectional view showing a basic overall configuration of a laser beam printer as an example of an image forming apparatus according to the present invention, and FIG. 3 is a partial detailed cross-sectional view from a fixing device to an FD discharge tray according to the first embodiment of the present invention. FIG. 4 is a flowchart illustrating a control operation of the first embodiment according to the present invention. FIG. 6 is a flowchart illustrating a control operation according to the second embodiment of the present invention. FIG. 6 is a schematic cross-sectional view illustrating an overall configuration of a laser beam printer according to a third embodiment of the present invention. FIG. 8 is a partial detailed cross-sectional view from the reflection type photosensor to the FD discharge tray in Example 3; FIG.
FIG. 10 is a schematic cross-sectional view showing the overall configuration of a laser beam printer according to a fourth embodiment of the present invention, FIG. 10 is a partial detailed cross-sectional view of the fourth embodiment according to the present invention, and FIG. FIG. 1 is a schematic cross-sectional view showing the overall configuration of a laser beam printer as an example of the first embodiment.

A description will be given in detail with reference to the drawings based on a plurality of embodiments.

(First Embodiment) First, a first embodiment according to the present invention will be described below with reference to the drawings.

The description of the same parts as in the conventional example will be omitted. As described in the conventional example, FIG. 1 is a schematic cross-sectional view showing the overall configuration of a laser beam printer 1 as an example of the image forming apparatus according to the present invention. FIG. 2 is a block diagram illustrating a main configuration of the first embodiment.

1 and 2, a laser beam printer 1 as an example of an image forming apparatus includes a fixing device 13, a display unit 26, a driving unit 27, a sensor group 28, various fans 29, and a controller 25 for controlling them. Have been.
Further, on the controller 25, a storage element 25a, a comparison circuit 25b, and the like are provided. The temperature data output from the fixing roller temperature sensor 13d and converted into a voltage value is compared with a voltage conversion value of a fixing temperature set value stored in the storage element 25a in the comparison circuit 25b, and the fixing temperature according to the setting is determined. It is possible to perform control.

FIG. 3 shows an example of an image forming apparatus from the fixing device 13 of the laser beam printer 1 to the FD paper discharge tray 1.
FIG. 7 is a cross-sectional view showing a part up to 7 in detail. Fixing device 1
Reference numeral 3 includes a fixing roller 13b having a built-in fixing heater 13a, and a pressure roller 13c pressed against the fixing roller 13b. The conveyed recording paper 2 is heated and pressed by the fixing roller 13b and the pressure roller 13c, and after the image is fixed on the upper surface of the recording paper 2, the paper is sent out to the paper discharge unit by the fixing paper discharge roller 14, and the FD is conveyed. Roller 15, FD discharge roller 1
After that, the sheet is discharged to the FD sheet discharge tray 17.

FIG. 4 shows a flowchart of a series of control operations in the first embodiment.

Here, the sequence for printing on plain paper is omitted for simplicity.

An OHT (Over
head Transparence Sheet) When is selected (step S102), the controller 25 reads the sheet interval setting value D _p of the address A _d of the memory device 25a (step S10
3) The pickup roller 4 is driven at the timing of the set value (step S104). For OHT,
By delaying the sheet feeding by the pickup roller 4 from the normal state, the throughput can be suppressed. Next, in the fixing process, a contact type temperature sensor 13 such as a thermistor is used.
d by comparing the fixing temperature T _o of the surface temperature T and OHT stored in the storage device 25a of the fixing roller 13b that is measured (step S105, step S106), T <
If T _o heat the fixing heater to light the heater or in intermittent lighting exceeds fixing temperature T _o of the OHT (step S107). If conversely T ≧ T _o off the heater (step S108), and not exceed the fixing temperature T _o of the OHT. And the fixing sheet discharge sensor 19
This fixing control is repeated until it is confirmed that OHT as recording paper has passed (step S109). When the fixing paper discharge sensor 19 confirms the passage of the recording paper, it is confirmed whether the next recording paper is waiting before the registration (step S110). If there is an OHT as the recording paper, it is set in the fixing process. The fixing control is repeated (step S105 and subsequent steps).

(Embodiment 2) Next, Embodiment 2 according to the present invention will be described with reference to the accompanying drawings.

The description of the same parts as in the conventional example will be omitted.

The basic structure is the same as that of the first embodiment, and a sectional view of the laser beam printer is shown in FIG.

FIG. 3 is a sectional view showing in detail a portion from the fixing device 13 of the laser beam printer 1 as an example of the image forming apparatus to the FD discharge tray 17. The fixing device 13 includes a fixing roller 13b having a built-in fixing heater 13a.
And a pressure roller 13c pressed against the fixing roller 13b
And a fixing roller temperature sensor 13d. The conveyed recording paper 2 includes a fixing roller 13b and a pressure roller 13c.
After the image is fixed on the upper surface of the recording paper 2, the recording paper 2 is sent to the paper discharge unit by the fixing paper discharge roller 14,
After passing through the FD transport roller 15 and the FD discharge roller 16, the FD
The paper is discharged to the paper discharge tray 17.

Also in the second embodiment, in the case of continuous printing using OHT as recording paper, the interval between the sheets is made longer than usual, and the fixing roller temperature is appropriately controlled between the sheets, so that the sheet is stuck on the FD discharge tray 17. The purpose is to prevent sticking. However, as the number of continuous prints increases, the temperature inside the machine rises as printing progresses,
It is difficult for the temperature of the recording paper after fixing to reach the FD discharge tray, and the possibility of sticking increases. In order to prevent this, control is performed to gradually increase the sheet interval as printing progresses. The paper interval is adjusted by changing the paper feed timing of the pickup roller 4.

FIG. 5 is a flowchart showing a series of control operations in this embodiment.

In the second embodiment, as in the first embodiment, a sequence for printing plain paper is omitted for simplification.

[0032] OHT is selected as the recording paper by the user (step S202), the controller 25 reads the sheet interval setting value D _p of the address A _d of the memory device 25a (step S203), the pickup roller driving its settings (Step S204). OH
In the case of T, the throughput can be suppressed by delaying the paper feed by the pickup roller 4 from the normal. Next, in the fixing process, the surface temperature T of the fixing roller 13b measured by the contact-type temperature sensor 13d such as a thermistor and the fixing temperature T of the OHT stored in the storage element.
_o (Step S205, Step S20)
6) to heat the fixing heater to if T <T _o light the heater or in intermittent lighting exceeds fixing temperature T _o of the OHT (step S207). If conversely T ≧ T _o off the heater (step S208), and not exceed the fixing temperature T _o of the OHT. This fixing control is repeated until the fixing paper discharge sensor 19 confirms that the recording paper has passed (step S209). When the fixing / discharge sensor 19 confirms that the recording paper has passed, it is confirmed whether or not the next recording paper is waiting before the registration (step S210). If there is a recording paper, the address next to the address _Ad of the storage element is determined. It reads the setting D _p between the paper stored in (step S21
1) The pickup roller is driven at the timing of the set value (from step S204).

Third Embodiment Next, a third embodiment according to the present invention will be described with reference to the accompanying drawings.

The description of the same parts as in the conventional example will be omitted.

FIG. 6 is a sectional view of the laser beam printer 1 according to the third embodiment.

The difference from FIG. 1 showing the basic configuration of the present invention is that a reflective photosensor 20 capable of automatically detecting OHT is arranged near the pre-registration sensor 8.

FIG. 7 shows the reflection type photo sensor 20 of the laser beam printer 1 as an example of the image forming apparatus.
FIG. 3 is a cross-sectional view showing a portion reaching a D paper discharge tray 17 in detail.

The reflection type photo sensor 20 comprises a sensor body 20a for emitting and receiving light and a prism 20b. If opaque paper such as plain paper passes, it will be shaded,
If the translucent OHT passes, the light is transmitted, so that the OHT can be determined. The fixing device 13 includes a fixing roller 13b having a built-in fixing heater 13a, a pressure roller 13c which is in pressure contact with the fixing roller 13b, and a fixing roller temperature sensor 1
3d. The conveyed recording paper 2 is heated and pressed by the fixing roller 13b and the pressure roller 13c, and after the image is fixed on the upper surface of the recording paper 2, the paper is sent out to the paper discharge unit by the fixing paper discharge roller 14, and the FD is conveyed. The sheet is discharged to an FD sheet discharge tray 17 via a roller 15 and an FD sheet discharge roller 16. Also in the third embodiment, when printing continuously using OHT as a recording sheet, the interval between the sheets is longer than usual to suppress the throughput, and the fixing roller temperature is appropriately controlled between the sheets, so that the FD discharge tray 17 is used. The purpose of the present invention is to prevent OHTs from sticking to each other. Since the suppression of the throughput is performed only after recognizing the OHT, the driving timing of the registration roller 9 is changed.

As the number of continuous prints increases, the internal temperature increases as printing progresses, so that the temperature of the recording paper after fixing is less likely to reach the FD discharge tray, and the possibility of sticking is high. Become. To prevent this, the temperature of the fixing roller, which was controlled lower than usual between sheets, is gradually changed to a lower value as printing proceeds.

FIG. 8 is a flowchart showing a series of control operations in this embodiment.

In the third embodiment, a sequence for printing plain paper for simplicity is omitted as in the above-described embodiment.

When it is detected that the reflection type photosensor 20 has passed through and the OHT has been fed (step S302), the registration roller drive is adjusted to the sheet interval at the timing of the set value (step S303). , The controller 25 sets the temperature T ₀ of the address _AT of the storage element 25a.
Is read (step S304). In the case of the OHT, the throughput can be suppressed by making the conveyance by the registration roller 9 slower than usual.

Next, in the fixing process, the surface temperature T of the fixing roller 13b measured by the contact type temperature sensor 13d such as a thermistor and the OH stored in the storage element 25a.
Compares the fixing temperature T _o of the T (step S305, step S306), and heats the fixing heater to if T <T _o light the heater or in intermittent lighting exceeds fixing temperature T _o of the OHT (step S307). Conversely, T ≧ T
If it is _o , the heater is turned off (step S308) and O
So as not to exceed the set fixing temperature T _o of HT. This fixing control is repeated until the fixing paper discharge sensor 19 confirms that the recording paper has passed (step S309). When the fixing / discharge sensor 19 confirms that the recording paper has passed, it is confirmed whether or not the next recording paper is waiting before the registration (step S31).
0), if there is recording paper, address A _{T of} storage element 25a
It reads the temperature setpoint T _o, which is stored in the next address (step S311), and repeats the set fixing control again at the fixing process (step S305 or later).

Embodiment 4 Next, Embodiment 4 according to the present invention will be described with reference to the accompanying drawings.

The description of the same parts as in the conventional example will be omitted.

FIG. 9 is a sectional view of the laser beam printer 1 in this embodiment.

The difference from FIG. 1 showing the basic configuration of the present invention is that the FD discharge roller 16 and the FD discharge tray 17
An anti-sticking fan 18 is provided to cool the recording paper 2 heated in the fixing process by blowing outside air.

FIG. 10 is a sectional view showing in detail a portion from the fixing device 13 of the laser beam printer 1 as an example of the image forming apparatus to the FD discharge tray 17.

In the fourth embodiment, similarly to the above-described embodiment, when performing continuous printing using OHT as a recording sheet, the interval between the sheets is made longer than usual, and the temperature of the fixing roller is appropriately controlled between the sheets. However, if the interval between recording sheets is longer than usual, the throughput is reduced, and the original performance of the printer cannot be exhibited. Therefore, by cooling the recording paper being discharged by using the sticking prevention fan 18, the cooling efficiency can be increased and the throughput can be kept from decreasing as much as possible. In this embodiment, the air volume of the sticking prevention fan 18 is kept constant, the interval between the recording sheets 2 to be fixed and discharged is increased, and the cooling time in the discharge tray 17 is increased. A flowchart of a series of control operations in the present embodiment is shown in FIG.

In the fourth embodiment, the sequence for printing plain paper is omitted for the sake of simplicity, as in the previous embodiment.

[0051] When the user by OHT is selected as the recording paper (step S102), the controller reads the sheet interval setting value D _p of the address A _d of the storage element (step S
103), the pickup roller is driven at the timing of the set value (step S104). Here, the sheet interval set value _Dp is a value shorter than the sheet interval set value in the first embodiment.

Next, in the fixing process, the surface temperature T of the fixing roller 13b measured by the contact type temperature sensor 13d such as a thermistor and the OH stored in the storage element 25a.
Compares the fixing temperature T _o of the T (step S105, step S106), and heats the fixing heater to if T <T _o light the heater or in intermittent lighting exceeds fixing temperature T _o of the OHT (step S107). Conversely, T ≧ T
If the _o to turn off the heater (step S108), O
So as not to exceed the set fixing temperature T _o of HT. This fixing control is repeated until the fixing paper discharge sensor 19 confirms that the recording paper has passed (step S109). When the fixing / discharge sensor 19 confirms that the recording paper has passed, it is confirmed whether or not the next recording paper is waiting before the register (step S11).
0), if there is a recording sheet, the fixing control set in the fixing process is repeated (step S105 and thereafter).

[0053]

As described above, the first embodiment according to the present application is described.
According to the invention, when continuous printing is performed using OHT as recording paper, the interval between sheets is made longer than usual to suppress the throughput, and the fixing temperature is appropriately controlled between the sheets, so that the OHT on the discharge tray is controlled. Sticking of each other can be prevented.

According to the second invention, in the first invention, when continuous printing is performed using OHT as recording paper, the paper interval is made longer than usual to suppress the throughput, and
An image forming apparatus capable of appropriately controlling a fixing temperature between sheets. The length of the sheet is increased as printing progresses. OHTs can be prevented from sticking together.

According to the third invention, in the first invention, when continuous printing is performed using OHT as recording paper, the paper interval is made longer than usual to suppress the throughput, and
An image forming apparatus capable of appropriately controlling the fixing temperature between sheets, and by lowering the fixing temperature as printing progresses, even if the number of continuous prints increases and the internal temperature rises, a discharge tray. OHTs can be prevented from sticking together.

According to the fourth aspect of the present invention, in the first aspect of the present invention, when printing continuously using OHT as recording paper, the interval between the sheets is made longer than usual to suppress the throughput, and the fixing temperature between the sheets is reduced. An image forming apparatus that can be appropriately controlled, in which a cooling fan is disposed between a downstream of a fixing device and a discharge tray to cool a recording sheet being discharged, thereby improving cooling efficiency and fixing process. In this case, it is possible to prevent OHTs from sticking to each other on the paper discharge tray without lowering the throughput as much as possible.

According to the fifth aspect, in the first aspect, when continuous printing is performed using OHT as recording paper, the interval between the sheets is made longer than usual to suppress the throughput, and the fixing temperature between the sheets is reduced. An image forming apparatus that can be appropriately controlled. By arranging a reflection type photo sensor upstream of a fixing device as an OHT detecting means, the OHT can be automatically detected, and a user's recording paper can be detected. Good printing is possible even if there is no designation or wrong designation.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a basic overall configuration of a laser beam printer as an example of an image forming apparatus according to the present invention.

FIG. 2 is a block diagram illustrating a configuration of a main part of a first embodiment according to the present invention.

FIG. 3 is a partial detailed cross-sectional view from a fixing device to an FD discharge tray according to the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating a control operation according to the first embodiment of the present invention.

FIG. 5 is a flowchart illustrating a control operation according to a second embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view illustrating the entire configuration of a laser beam printer according to a third embodiment of the present invention.

FIG. 7 is a partial detailed cross-sectional view from a reflection type photosensor to an FD discharge tray according to a third embodiment of the present invention.

FIG. 8 is a flowchart illustrating a control operation according to a third embodiment of the present invention.

FIG. 9 is a schematic cross-sectional view illustrating the entire configuration of a laser beam printer according to a fourth embodiment of the present invention.

FIG. 10 is a partial detailed sectional view of a fourth embodiment according to the present invention.

FIG. 11 is a schematic cross-sectional view showing the overall configuration of a laser beam printer as an example of an image forming apparatus in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus (laser beam printer) 2 Recording paper 3 Cassette 4 Pickup roller 7 MPT feed roller 8 Pre-registration sensor 9 Registration roller 11 Image forming unit 12 Laser scanner unit 13 Fixing device 13a Fixing heater 13b Fixing roller 13c Pressure roller 13d Fixing roller temperature sensor 14 Fixing discharge roller 15 FD transport roller 16 FD discharge roller 17 FD discharge tray 18 Sticking prevention fan 19 Fixing discharge sensor 20 Reflective photo sensor 25 Controller 25a Storage element 25b Comparison circuit 26 Display unit 27 Drive unit 28 Sensor group 29 Various fans

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 DA12 DC02 DE02 DE07 DE10 ED17 EE07 JA11 JB16 JC13 2H033 BA11 BA31 BA32 BA59 BB18 BB28 CA16 CA30 CA37

Claims (6)

[Claims] A transfer device for transferring an unfixed developer image onto a recording sheet; heating the recording sheet conveyed from the transfer device while nipping and conveying the fixing sheet to fix the unfixed developer image on the recording sheet; An image forming apparatus provided with a fixing device for performing continuous printing using OHT as recording paper, in which a sheet interval is made longer than usual to suppress throughput and
An image forming apparatus for appropriately controlling a fixing temperature between sheets. 2. When printing continuously using OHT as recording paper, the throughput is suppressed by making the paper interval longer than usual, and the fixing temperature between the papers is appropriately controlled so that the paper interval becomes longer as the printing progresses. The image forming apparatus according to claim 1, wherein: 3. When printing continuously using OHT as recording paper, the throughput is suppressed by making the paper interval longer than usual, and the fixing temperature between papers is appropriately controlled, and the fixing temperature is lowered as printing progresses. The image forming apparatus according to claim 1, wherein: 4. When continuous printing is performed using OHT as recording paper, the interval between sheets is made longer than usual to suppress throughput, the fixing temperature between the sheets is appropriately controlled, and the sheet is discharged downstream of the fixing device. 2. The image forming apparatus according to claim 1, further comprising a fan for cooling the recording paper. 5. When printing continuously using OHT as recording paper, the interval between sheets is made longer than usual to suppress the throughput, the fixing temperature between the sheets is appropriately controlled, and a fixing device is used as OHT detecting means. 2. The image forming apparatus according to claim 1, wherein a reflection type photo sensor is arranged upstream of the image forming apparatus. 6. A transfer device for transferring an unfixed developer image onto recording paper, and heating while holding and conveying the recording paper conveyed from the transfer device to fix the unfixed developer image on the recording paper. An image forming apparatus including a fixing device for detecting whether the recording sheet is an OHT or not;
In the case of continuous printing using OHT as recording paper, the paper interval is made longer than usual to suppress the throughput, and a step of appropriately controlling the fixing temperature between the papers is provided. Alternatively, the method includes a step of lowering the fixing temperature and a step of cooling the recording paper being discharged downstream of the fixing device. When the recording paper is an OHT, the recording paper is attached so as to prevent a mutual sticking phenomenon. Prevention method.