JP3004136B2 - Electrophotographic printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
Sometimes called paper. ) And an electrophotographic printer using a heat roller fixing unit.

[0002]

2. Description of the Related Art In a conventional electrophotographic printer, every time data of one page is received and stored, the data is output, the processes of exposure, development and transfer are operated, and at the same time, the paper is conveyed. The pressure roller is opened just before the front perforation of the page where the transfer of the image is completed enters the nip portion of the fixing unit, and the pressure roller is closed immediately after the perforation passes through the nip portion,
The pressure roller is opened just before the rear perforation of the same page enters the nip portion of the fixing unit, and thereafter, if the data for the next page is received and accumulated before the transfer of the previous page is completed, the conveyance is continued. Then, control to repeat the transfer and the opening and closing of the pressure roller is performed.When the data of the next page is not received, the paper with the rear perforation of the page being transferred is positioned at the transfer position. Control is performed to stop the conveyance and open the pressure roller of the fixing unit.

The reason why the pressure roller of the fixing unit is opened while the perforations pass is to prevent the paper sheet from being fed by the roller and the tractor from accumulating a slight deviation, and the paper sheet from being peeled off by the tractor unit. This is to prevent the occurrence of dents and paper jams.

In the above-described conventional electrophotographic printer, as shown in FIG. 1A, the distance La between perforations (that is, the length of one page) is changed from the transfer position of the transfer unit 35 to the fixing unit 40. And only one type of paper 1A equal to the fixed distance Ls to the fixing position is used. In FIG. 1, 1, 1A, 1B, 1C are papers, 31 is a photosensitive drum,
Reference numeral 35 denotes a transfer unit, and reference numeral 40 denotes a fixing unit including a heating roller 41 and a pressure roller 42 that moves up and down.
Of a, 1b, and 1c, the shaded area indicates a predetermined attachment part, the solid line area indicates a transferred / unfixed part, and the chain line area indicates an untransferred part.

[0005]

Recently, there has been a demand for a printer that can use a sheet of paper having various page lengths (distance between perforations). However, when the data for the next page is not received at the end of the transfer for one page, according to the conventional control method of stopping the conveyance and opening the pressure roller of the fixing unit, the distance Ls between the transfer position and the fixing position is determined. Page length L different from
When using paper having b, Lc (however, Lb <Ls, Lc> Ls), various problems occur.

That is, as shown in FIG. 1 (b ₁ ), L
Last page (1b) received for paper 1B with b <Ls
When the transfer is stopped at the end of the transfer for one minute, the previous page (1
a) Stopping the paper conveyance during the fixing for
Of the page (1a) that has passed through the fixing unit 40, uneven fixing may occur on the printing surface, or the fixing unit 4
There is a problem that the unfixed toner on the page (1b) before passing through 0 scatters, and the print quality is deteriorated.

To avoid this problem, FIG.
_As shown in ₂ ), when the sheet is transported until the fixing of the page (1a) before the last page (1b) is completed, the transfer of the data received after the standby is started, and the start position of the next page (1c) is set. And paper must be discarded for one page (1c), which is a problem in terms of cost.

Further, in the case of Lc> Ls, (c
_As shown in ( ₁ ), there is a problem similar to that of (b ₁ ), and as shown in (c ₂ ), when fixing to the last page (1b), the paper of one page (1c) is likewise formed. To waste.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points. Even if continuous form papers having various page lengths are used, fixing can be performed for each page without causing fixing unevenness. An object of the present invention is to provide an electrophotographic printer using a heat roller fixing unit capable of maintaining print quality.

[0010]

In order to achieve the above object, according to the present invention, there is provided a page length input means for inputting a page length of a continuous form sheet currently used, and a page length input from the page length input means. Is the distance L from the transfer position to the fixing position.
When La is equal to La or Lb shorter than Ls, the transfer of the electrophotographic process is started together with the start of the forward conveyance of the sheet by the conveyance control means. (b) When Lc is larger than Ls, the conveyance control is started. Means for controlling the transfer of the electrophotographic process after the transfer of the difference (Lc-Ls) between Ls and Lc, and (a) when the page length input from the page length input means is (a) La, The paper transport starts at the same time as the transfer by the print control means.If there is received print data for the next page, the transport continues in the forward direction.If there is no received print data, the front perforation of the transferred page is the nip of the fixing unit. Transported to just before the section and stopped. (B) In the case of Lb,
The sheet conveyance is started simultaneously with the start of the transfer by the print control means, and if there is received print data for the next page, the conveyance in the forward direction is continued.If there is no received print data, the front perforation of the transferred page is the fixing section. After being transported in the forward direction until just before the nip portion and stopped, transported in the reverse direction by the difference (Ls-Lb) between Ls and Lb and stopped, and (c) when Lc, electrophotography Before the start of the transfer of the process, the sheet is transported in the forward direction by the difference (Lc−Ls) between Ls and Lc. At the start of the process, the front perforation of the transferred page passes through the fixing section. Lc difference (Lc-Ls)
After transporting the data in the forward direction, if there is received data for the next page, the transport in the forward direction is continued. Otherwise, the transport is stopped and the difference (Lc−Ls) is transported in the reverse direction. Immediately after the rear perforation of the page before the page transferred by the print control unit passes through the nip portion of the fixing unit, regardless of the size of the continuous report sheet used. And a fixing control unit for closing the pressure roller of the fixing unit and opening the pressure roller immediately before the rear perforation of the fixed page arrives at the nip.

[0011]

When data for the next page is continuously received at the time of transfer of one page, paper conveyance is continued irrespective of the size of the page length, and transfer is performed in accordance with the transfer and the page length. Opening and closing of the pressure roller of the fixing unit is repeatedly controlled.

When the page length is La which is equal to the distance Ls between the transfer position and the fixing position, and when data for the next page is not received at the time of transfer of one page, the data of the page currently being transferred is At the end of the transfer, the paper conveyance is stopped, and the pressure roller is opened.
Thereafter, when the data of the next page is received, the sheet conveyance is started and the fixing and the transfer are started almost simultaneously.

Next, when the page length is Lb smaller than Ls, and when the data of the next page is not received at the time of transfer of one page, even after the transfer of the page currently being transferred is completed, The conveyance of the sheet by the distance (Ls-Lb) is continued until the fixing of the previous page is completed, the conveyance is stopped at the end of the fixing, the pressure roller is opened, and the sheet is moved in the reverse direction by the distance (Ls-Lb). And stops, and waits for reception of data for the next page. Thereafter, when data for the next page is received, the transfer in the forward direction is started and the transfer is started. When the distance (Ls-Lb) is advanced, the pressure roller of the fixing unit is closed.

When the page length is Lc which is larger than Ls, and when the data of the next page is not received at the time of transfer of one page, the pressure of the fixing unit is set when the fixing of the previous page is completed. The roller is opened, the conveyance is continued until the transfer of the page currently being transferred is completed, the conveyance is stopped at the end of the transfer, and the paper is moved by a distance (Lc−
Ls), transported in the reverse direction and stopped, and wait for reception of data for the next page. Then, when the next page of data is received,
Close the pressure roller, start the forward conveyance, and set the distance (Lc−
Ls) Transfer is started when moving forward.

[0015]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a cross-sectional view schematically showing a configuration of an electrophotographic printer using continuous form paper and using a heating roller. The printer includes a transport unit 10 provided in the main body 100 for transporting the paper 1, a detection unit 20 for detecting the leading end of the paper 1 transported by the transport unit, and A transfer unit 30 for printing data received from the outside via the communication control unit 70 by electrophotography, a heat roller type fixing unit 40 for heating and fixing the toner image transferred onto the paper, and a fixing unit for the fixing unit. A contact / separation unit 50 for bringing the pressure roller 42 into and out of contact with the heating roller 41
And a control unit 60 that controls the transport unit 10, the transfer unit 30, the fixing unit 40, and the contact / separation unit 50 according to the presence or absence of the input from the detection unit 20 and the reception data.

The transfer section 10 includes a stepping motor (hereinafter simply referred to as a motor) 11 which can be rotated in the reverse direction, and a transfer section 3.
The tractors 12 and 13 are disposed before and after 0, a transport roller (not shown) disposed therebetween, and a discharge roller 14 disposed on the paper discharge side. The present invention has one feature in that a reversible motor is used as the motor 11. The transfer unit 30 has the same configuration as that of the related art, and includes a photosensitive drum 31 and a charger 32, an exposure unit 33, a developing unit 34, a transfer unit 35, and a cleaning unit 36 disposed around the photosensitive drum 31. Reference numeral 37 denotes a separator for bringing the sheet 1 into contact with the photosensitive drum 31 during transfer and separating the sheet 1 during non-transfer.

The fixing section 40 includes a heating roller 41 which is rotated in a predetermined direction by a motor (not shown), and a pressure roller 42 which freely rotates facing the heating roller 41. The pressure roller 42 is opened and closed with respect to the heating roller 41 by the contact / separation unit 50. The contact / separation part 50 is described in Japanese Patent Application
The one proposed in the specification of US Pat. No. 3,069,887 can be used. That is, the lever 52 is rotatably supported at one end with the shaft 51 as a fulcrum, the pressure roller 42 is supported at the other end of the lever, and the roller 53 is rotatably provided at an intermediate portion of the lever 52. A cam 54 corresponding to the peripheral surface of the roller 53 is provided above the sheet conveying surface, and the lever 52 is constantly urged upward by a spring 55. A driving source (not shown) is attached to the rotation shaft of the cam 54. It is configured by being connected. The drive source is, for example, a rotary solenoid or a motor that rotates 180 ° when energized, and the cam 54 is driven by 18 times each time a drive signal is input.
And a motor control circuit that rotates the motor until it is rotated by 0 °.

As shown in FIG. 2, the cam 54 is normally held in a state in which a low portion of the cam 54 is in contact with the roller 53. Therefore, the pressing roller 42 is pressed against the heating roller 41. However, when the driving source is driven by the control unit 60 described later, the cam 54 is rotated by 180 ° and the high portion thereof comes into contact with the roller 53, so that the pressing roller 42
Is moved downward to be separated from the heating roller 41. At this time, the sheet 1 is formed by a sheet guide portion 56 having a long arcuate curved surface which comes into contact with the heating roller contact surface side.
Since it is pulled in the direction away from the heating roller 41,
The heating roller 41 is separated from the heating roller 41 by a predetermined distance.

As shown in FIG. 3, the printer has a communication control unit 70 for receiving print data from a host computer, and an operation unit 80 such as a keyboard for inputting the page length of paper used in the printer. Having. The communication control unit 70, the operation unit 80, and the detection unit 20
0 is connected to the CPU 62 via the I / O unit 61. The CPU 62 also has a ROM 63 for storing a system program and an R for temporarily storing data.
A storage unit comprising an AM 64 is connected, and a reversible motor 11 of the transport unit 10 via an I / O unit 61.
The electrophotographic process unit of the transfer unit 30, the motor of the fixing unit 40, the heating roller 41, and the contact / separation unit 50 are connected.

As shown in FIG. 4, the CPU 62 of the control section 60 receives the print data sent from the host computer by the communication control
A function of converting the print data into a font data string using the character font data stored in the ROM 63 and outputting a control signal to the transfer unit 30 based on the converted font data string. Printing control means
621, and a page length set from the operation unit 80;
A conveyance control unit b622 for controlling the motor 11 of the conveyance unit 10 to rotate forward or reverse based on the input from the detection unit 20 and the presence or absence of the received data. The separation / separation control means 623 for bringing the sheet 1 into and out of the sheet 31 and the number of pulses given to the reversible motor 11 for the conveyance control and the perforation of the sheet 1 From the nip portion of No. 40 to a point where the length of the non-printing area provided before and after the sheet reaches 1/2 inch before the perforation passes a 通過 inch from the nip portion, the fixing section Pressure roller contact / separation control means 624 for opening the pressure roller 42 from the heating roller 41. The pressure roller contact / separation control means 624 opens the pressure roller 42 immediately before the perforation enters the nip of the fixing unit 40, and closes the pressure roller 42 again immediately after the perforation passes through the nip. Is controlled.

The functions of the print control means 621, the conveyance control means 622, the separator contact / separation control means 623, and the pressure roller contact / separation control means 624 of the CPU differ depending on the page length of the currently used sheet. The page length is input from the operation unit 80 after the printer is started. If a perforation sensor capable of reliably detecting the perforation of the sheet is devised, the transport device is started, Between the time when the perforation sensor detects one perforation and the time when the next perforation is detected, the conveyance control means b of the control unit 60 controls the conveyance unit 10.
The page length can be automatically set by the number of pulses given to the motor 11.

The page length of the paper used in the printer according to the present invention, that is, the distance between perforations is La, Lb, Lc.
(However, if the distance from the transfer position by the transfer unit 35 to the fixing position by the fixing unit 40 is Ls, La = Ls, L
b <Ls, Lc> Ls).
For each case where the page length of the paper used is La, Lb, Lc, the transport unit 10 and the transfer unit 3 by the control unit 60
0, the control of the contact / separation unit 50 and the operation by the control will be described with reference to FIGS.
A description will be given based on the flowchart of FIG.

[When the page length is La (= Ls)] As shown in FIG.
The control unit 60 executes the program to rotate the photosensitive drum of the transfer unit 30 (S11). When the page length of the paper 1A to be used is set to La equal to Ls shown in FIG. 5 (S1
In 2), it is checked whether or not there is received data to be printed in the storage unit (RAM 64) (S13). If so, the print control unit 621 starts exposure by the exposure unit 33 at a predetermined timing (S14). , Separator contact / separation control means 62
3 causes the separator 37 to approach the photosensitive drum side, and the conveyance control means 622 starts conveyance (S15). Then, the conveyance amount of the sheet 1A (FL) is alpha, ie FIG. 5 (a ₂₎ as shown in, one page non-printing area distance from the front side perforations (p ₁₎ to the tip of the print area (e.g., 1 / 2 inch),
At the point in time (Y in S16), the print control means 62
1 starts transfer, and the pressure roller contact / separation control means 624 rotates the cam 5 of the contact / separation unit 50 to a predetermined angle, closes the pressure roller 42 of the fixing unit, and starts fixing (S17). .

It is determined whether or not the data for the next page has been received and accumulated from this time until the exposure of the data for one page is completed, that is, whether or not to continue printing (S1).
8) If it has been received, that is, if printing is to be continued (Y in S18), process control such as exposure, development, and transfer by the transfer unit 30 (S19) is performed, and then the transfer is performed by the transfer control unit 621. It is determined from the number of pulses given to the motor 11 whether the carry amount FL is La-α, that is, whether the rear end of the print area of the previous page has passed the fixing position of the fixing unit (S110), and the fixing is performed. When the sheet passes through the position, the pressure roller contact / separation control means 624 controls the contact / separation unit 50 to open the pressure roller 42 of the fixing unit (S111). Further, it is checked whether or not the carry amount has reached La (S112). If the carry amount has reached La, that is, if one page length has been carried, the carry control means resets the carry amount count value FL to 0 when it reaches La. (S113), and jump to step S16.

As shown in FIG. 5 (a ₃ ), one of the sheets 1A
After the start of the transfer of the page (pn), the data of the next page (pn + 1) has not been received until the end of the transfer (N in S18).
), When the carry amount FL of the page (pn) currently being transferred (S114) has reached La-α (S115), that is, the front perforation of the transferred area is α more than the fixing position.
The pressure roller contact / separation control means 62
4 causes the contact / separation section 50 to separate the pressure roller 42 from the heating roller 41. That is, the fixing unit is opened (S116).
). When the carry amount FL becomes La (Y in S117), the carry control means 621 stops the carry, and at the same time, the separator contact / separation control means 623 separates the separator 37 from the photosensitive drum, and the carry control means The quantity count value (FL) is set to O, and the flow returns to step S13 to wait for data reception for the next page.

[When the page length is Lb (<Ls)] As shown in FIG.
The control unit 60 executes the program to rotate the photosensitive drum of the transfer unit 30 (S21), and the page length of the sheet 1B to be used is set to Lb smaller than Ls shown in FIG. 6 (S2).
In 2), it is checked whether or not there is received data to be printed in the storage unit (RAM 64) (S23). If there is received data, the print control means 621 starts exposure by the exposing device 33 at a predetermined timing (S23). Simultaneously with S24, the separator contact / separation control means 623 causes the separator 37 to approach the photosensitive drum side, and the conveyance control means 622 starts conveyance, and (S2)
5) At the time when the paper transport amount (FL) becomes equal to α, that is, the distance of the non-printing area from the front perforation of one page to the leading end of the printing area, the printing control means 621 starts the transfer, The pressure roller contact / separation control means 624
0 is rotated to a predetermined angle to close the pressure roller 42 of the fixing unit and start the fixing operation (S
21 to S27) when the page length is La (S11 to S1).
Same as 7).

Then, the paper transport amount FL is (Ls-Lb)
When the pressure becomes + α, the pressure roller contact / separation control means 624 closes the pressure roller 42 of the fixing unit and starts fixing. If the data for the next page has been received and accumulated until the exposure of the data for one page is completed (Y in S210), process control such as exposure, development, and transfer by the transfer unit 30 (S210).
After the step 211) is performed, it is determined whether the transport amount FL is Lb based on the number of pulses given to the transport motor 11 from the transport control unit 621.
That is, it is determined whether or not the one-page length has been transported (S21).
2) When Lb is reached, the transport control means 621 sets the transport amount count value FL to 0 (S213), and furthermore, the transport amount F
When L becomes (Ls−Lb) −α, that is, when the rear end of the print area of the previous page reaches the fixing position, the pressure roller contact / separation control unit 624 controls the contact / separation unit 50 to Then, the pressure roller 42 of the fixing unit is opened (S215), and thereafter, step S26 is performed.
Jump to The operation up to this is the case where the print data is continuously received and the conveyance of the paper is continued.
Since it is almost the same as the case a, it is not shown in FIG.

Then, for example, as shown in FIG.
During fixing of one page, before the exposure of page Pn is completed, the next page (Pn + 1)
In the case where there is no received data (N in S210), after the exposure control for the Pn page (S216) is completed, FIG. 6 (b ₂ )
As shown in (2), when the carry amount FL becomes Ls-α (Y in S217), that is, when the end of the print area of the previous page (Pn-1) reaches the stationary position, the separator contact / separation is performed. The control unit 623 separates the separator 37 from the photosensitive drum 31 to terminate the transfer, and the pressing roller contact / separation control unit 624 separates the pressing roller 42 of the fixing unit from the heating roller 41. 622 stops the conveyance (S218).

Subsequently, the transport control means 622 controls the motor 11
Is reversed (S219), and as shown in FIG. 6 (b3), when the carry amount FL in the reverse direction becomes (Ls-Lb)-. Alpha.
220) Y, that is, when the front perforation of the next page (Pn + 1) is reversely fed to a position that matches the transfer position, the reverse feeding is stopped, the transport amount FL is set to 0 (S221), and then the process proceeds to step S23. Jump to wait for the next page of data to be received.

Next, when data is received (Y in S23)
As shown in (b ₄ and b ₅ ) in FIG. 6, exposure is started again (S24), approach of the separator 37, and conveyance start (S2).
5), the transfer to the Pn + 1 page is started when the carry amount becomes α (S26, 27), and when (Ls−Lb) + α, the transfer to the previous page (Pn) is started as described above. The fixing is started (S28, 29).

[When the page length is Lc (> Ls)] When the page length is Lc which is longer than the distance Ls between the transfer position and the fixing position, the front of the page before the first page of the paper 1C is printed. Waiting for reception with the perforations matched with the fixing position.
Then, after the page length is set to Lc (S32), when print data is received (Y in S33), the separator 37 is moved closer to the photosensitive drum 31 and transport is started (S3).
4). Then, when the carry amount FL becomes α (Y in S35), the pressure roller 42 is closed, and fixing to the previous page is started (S36). Thereafter, exposure is started in accordance with a preset carry amount (S37), and transfer is started when the carry amount FL is (Lc-Ls) + α (S39). It is determined whether data exists (S310).
If there is, exposure control for the page is continued (S311),
When the transport amount is Lc-α (Y in S212), that is, immediately before the rear perforation of the previous page during fixing reaches the nip portion of the fixing portion (when the end of the printing area reaches the nip portion) ), The pressure roller 42 is opened (S313). Then, when the transport amount is Lc, that is, when the page length of one page is transported, the transport amount count value FL of the transport control means 621 is cleared to O, and the process jumps to step S35 to perform similar printing on the next page. Continue operation.

On the other hand, if the printing is not continued in step S310 (the print data for the next page is not received), the exposure control for the page currently being transferred (S316).
), When the carry amount FL becomes LC-α, that is, as shown in FIG. 7 (c ₁ ), the page (pn
When the end of the printing area of (-1) has passed the fixing position of the fixing section 40 (Y in S317), the pressure roller 42 is opened (S31).
8) When the transport amount further becomes Lc (S320),
When the carry amount count value FL is set to 0, and subsequently, the carry amount FL becomes (Lc-Ls) -α again (Y in S321),
That is, as shown in (c ₂ ) of FIG. 7, when the end of the print area of the page (Pn) currently being transferred has passed through the transfer position and the transfer has been completed, the conveyance of the sheet 1C is stopped and the separator 3 is stopped.
7 is separated from the photosensitive drum (S322).

Subsequently, the conveyance control means 621 controls the motor 11 of the conveyance section to rotate in the reverse direction to feed the paper in a reverse direction (S323).
When (S324) to the opposite direction conveying amount becomes {(Lc-Ls) -α} , i.e., as shown in FIG. 7 (c _3),
The reverse feed is stopped with the leading end of the print area of the page (Pn) for which transfer has been completed coincident with the fixing position, and the carry amount count value FL is cleared to 0 (S325).
Jump to 3 and wait for reception of the next data.

Next, when print data is received, the process proceeds to step S34, where the approach of the separator and the start of conveyance are performed as described above, and as shown in FIGS. 7 (c ₄ ) and (c ₅ ). When the leading end of the print area of the page (Pn) before the page (Pn + 1) to which the data is transferred reaches the fixing position (S
At 315 (Y), the fixing unit closes to start fixing, exposure for the data is started (S37), and when the leading end of the print area of the next page Pn + 1 reaches the transfer position (Y at S38), the transfer is started. After starting (S39), the same operation as described above is repeated.

[0035]

As described above, according to the present invention, even if continuous form paper having various page lengths is used, fixing can be performed for each page without causing fixing unevenness. Can be held.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a relationship between a page length of a sheet and a transport position for explaining a problem when a control method in a conventional electrophotographic printer is used.

FIG. 2 is a cross-sectional view illustrating a configuration of a general electrophotographic printer.

FIG. 3 is a schematic configuration diagram illustrating a control system.

FIG. 4 is a block diagram illustrating functions of a control unit that implements the present invention.

FIG. 5 is a schematic diagram for explaining control contents when the page length of a sheet is equal to a distance between a transfer position and a fixing position in the printer of the present invention.

FIG. 6 is a schematic diagram for explaining control contents when the page length of a sheet is smaller than a distance between a transfer position and a fixing position in the printer of the present invention.

FIG. 7 is a schematic diagram for explaining control contents when the page length of a sheet is larger than a distance between a transfer position and a fixing position in the printer of the present invention.

FIG. 8 is a schematic flowchart for explaining the operation of the printer according to the present invention when the page length of the sheet is equal to the distance between the transfer position and the fixing position.

FIG. 9 is a schematic flowchart for explaining the operation of the printer of the present invention when the page length of the sheet is smaller than the distance between the transfer position and the fixing position.

FIG. 10 is a schematic flowchart for explaining an operation when the page length of a sheet is larger than a distance between a transfer position and a fixing position in the printer of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 printer body 10 transport unit 20 paper detection unit 30 transfer unit 40 fixing unit 50 contact / separation unit 60 control unit 70 communication control unit 80 operation unit 62 CPU 621 print control unit 622 transport control unit 623 separator contact / separation control unit 624 pressure roller Contact / separation control means

Continued on the front page (72) Inventor Masatake Satake 4-3 Jonai, Hanamaki City, Iwate Prefecture Inside Shinko Works, Ltd. References JP-A-3-109579 (JP, A) JP-A-4-42282 (JP, A) JP-A-4-142564 (JP, A) JP-A-4-211973 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 11/00-11/70 G03G 15/00-15/20 G03G 21/14

Claims (1)

(57) [Claims] An electrophotographic printer using continuous form paper and a heat roller type fixing device, comprising: (a) a page length input means, a print control means, a transport control means, and a contact / separation control means. (B) the page length input means is for inputting a page length of a continuous form sheet currently used; and (c) the print control means is for the page length input from the page length input means to be: (A) When La is equal to the distance Ls between the transfer position and the fixing position, or when Lb is shorter than Ls, the transfer of the electrophotographic process is started together with the start of the forward transfer of the sheet by the transfer control means, and (b) L greater than Ls
c, the difference between Ls and Lc (L
(d) the transfer of the electrophotographic process is started after the transfer of (c-Ls), and (d) the transfer control means, when the page length input from the page length input means is (a) La, The sheet conveyance is started simultaneously with the start of the transfer by the print control means.If there is received print data for the next page, the conveyance in the forward direction is continued.If there is no received print data, the front perforation of the transferred page is immediately before the fixing device. (B) In the case of Lb, paper transport starts simultaneously with the start of transfer by the print control means, and if there is received print data for the next page, transport in the forward direction is continued. If not, the page is conveyed in the forward direction until the front perforation of the transferred page reaches just before the fixing device and stopped, and then conveyed in the reverse direction by the difference (Ls-Lb) between Ls and Lb and stopped. And (c) when Lc, the electrophotographic professional Before the start of the transcription of Sesame, the difference between Ls and Lc (Lc-L
s), and the front perforation of the transferred page passes through the fixing portion at the start of the process, and further, the difference (Lc−Ls) between Ls and Lc is further transported in the forward direction. Thereafter, if there is received data for the next page, the transport in the forward direction is continued, and if not, the transport is stopped, and the difference (Lc-Ls) is transported in the reverse direction and stopped. (E) The contact / separation control means is provided immediately after the rear perforation of the page preceding the page transferred by the print control means has passed through the fixing section, regardless of the size of the continuous form paper used. An electrophotographic printer, wherein the pressure roller of the fixing unit is closed, and the pressure roller is opened immediately before the rear perforation of the fixed page reaches the fixing unit.