JP2002108166A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which prevents the printing length of a form from being made short even in the case of reduction of a roller diameter accompanied with use. SOLUTION: The image forming device is provided with a photoreceptor drum 13, an electrifying brush 14, an LED print head 16, a developing roller 18, a transfer roller 21, a heating roller 23, a press roller 25, etc. The form taken in from a paper supply cassette passes between the photoreceptor drum 13 and the transfer roller 21 and between the heating roller 23 and the press roller 25. A PSS 30 is arranged as a sensor on the entrance side to the transfer roller 21, and a PDS 31 is arranged as a sensor on the exit side from the press roller 25. The time in which the PDS 31 is turned on after turning-on of the PSS 30 in accordance with carrying of the form is measured, and this time is compared with a preliminarily stored table of correspondence between times and periods of a horizontal synchronizing signal, and the period of the horizontal synchronizing signal is changed to one corresponding to the measured time.

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 in which a printing length of a sheet is not reduced even if a roller diameter is reduced due to abrasion caused by contact with the sheet.

[0002]

2. Description of the Related Art In an electrophotographic printer, an image forming process is performed in synchronization with rotation of a photosensitive drum or a roller.

[0003]

By the way, since the rollers in the paper transport path are in direct contact with the paper,
The surface gradually scrapes due to friction with the paper, and the roller diameter gradually decreases. Since the number of rotations of the roller is constant, there is a problem in that, as the roller diameter gradually decreases, the paper transport distance per unit time decreases, and the print length of the paper becomes shorter.

This will be described in more detail with reference to FIG. 2 showing a schematic configuration diagram of a printer. In FIG. 2, the electrophotographic printer transfers an electrostatic latent image formed on the photosensitive drum 13 to a sheet (solid line) by a transfer roller 21 and transfers the electrostatic latent image to a sheet by a fixing device including a heating roller 23 and a press roller 25. Is to be established. Although not shown in FIG. 2, the paper is taken out one by one from a paper feed cassette by a pickup roller, and sent between the photosensitive drum 13 and the transfer roller 21 by a transport roller.

In particular, the photosensitive drum 13 and the transfer roller 2
1. Since the heating roller 23, the press roller 25, the pickup roller, the transport roller, and the like come into direct contact with the sheet, the surface gradually wears out due to friction with the sheet, and the roller diameter gradually decreases. Therefore, at first, the paper was securely transported for a predetermined distance by being gripped between the rollers.However, due to the decrease in the roller diameter, the paper transport distance became shorter than the predetermined length, and the printing length of the paper became shorter. Occurs.

The present invention has been made in view of such a problem, and provides an image forming apparatus in which the printing length of a sheet is not shortened even if the roller diameter is reduced with use. It is intended to be.

[0007]

According to a first aspect of the present invention, there is provided an image forming apparatus, comprising: a photosensitive member; a charger for uniformly charging the photosensitive member; and a horizontal synchronizing signal. An exposure unit that forms an electrostatic latent image on the photoconductor in synchronization with
A developing device that develops the electrostatic latent image formed on the photoconductor, a transfer device that transfers the developed image on the photoconductor to a recording medium,
It is characterized by comprising a transport mechanism for transporting the recording medium, a counter for counting the number of printed recording media, and a control unit for changing the cycle of the horizontal synchronization signal based on the count value of the counter.

In this apparatus, for example, the number of recording media (sheets) printed from the start of use of the apparatus to the present is counted by a counter, and the cycle of the horizontal synchronizing signal is changed according to this number. Can be prevented from becoming shorter. Specifically, the period of the horizontal synchronizing signal is lengthened with an increase in the number of prints, thereby compensating for a decrease in the transport speed of the recording medium due to a decrease in the roller diameter.

According to a second aspect of the present invention, there is provided an image forming apparatus comprising: a photosensitive member; a charger for uniformly charging the photosensitive member; and an exposure device for forming an electrostatic latent image on the photosensitive member in synchronization with a horizontal synchronization signal. Unit, a developing device for developing the electrostatic latent image formed on the photoconductor, a transfer device for transferring the developed image on the photoconductor to a recording medium, a conveyance mechanism for conveying the recording medium, and a conveyance A control unit that detects the recording medium transport speed of the mechanism unit and changes the cycle of the horizontal synchronization signal based on the detected transport speed.

In this apparatus, the transport speed of the recording medium (paper) in the transport mechanism is detected, and the cycle of the horizontal synchronizing signal is changed according to the transport speed. In other words, as the roller diameter decreases, the paper transport speed decreases accordingly, so that the period of the horizontal synchronizing signal is lengthened as the transport speed decreases.

Further, according to a third aspect of the present invention, there is provided an image forming apparatus, comprising: a photosensitive member; a charger for uniformly charging the photosensitive member; and an exposure device for forming an electrostatic latent image on the photosensitive member in synchronization with a horizontal synchronization signal. Unit, a developing device for developing the electrostatic latent image formed on the photoconductor, a transfer device for transferring the developed image on the photoconductor to a recording medium, a transport mechanism for transporting the recording medium, and an apparatus And a control unit that changes the cycle of the horizontal synchronizing signal based on the operation time counted by the timer.

In this apparatus, for example, the operation time from the start of use of the apparatus to the present is counted by a counter, and the cycle of the horizontal synchronizing signal is changed according to the operation time. This is because the roller diameter decreases as the apparatus is used, and the printing length of the recording medium (paper) becomes shorter. To prevent this, the longer the operation time, the longer the cycle of the horizontal synchronization signal. .

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to embodiments.

FIG. 1 (partial) and FIG. 2 (remaining part) are schematic structural views of an image forming apparatus according to the embodiment. This image forming apparatus is configured as a so-called multifunction machine having a facsimile function and a copy function. In FIG. 1, an MPU (control unit) 1, an NCU 2, a MODEM 3, a ROM 4 having a printing endurance table 4a, a RAM 5, an image It includes a memory (DRAM) 6, a CODEC 7, an operation unit 8, a scanner 9, an operation time counter 10, and a number counter 11. However, the operating time counter 10 and the number of sheets counter 11
May be provided either alone or both.
In addition, this apparatus transports a recording medium (paper) from a paper feed cassette (not shown) to a transport roller 32, a transfer roller 21, and a press roller 25, using an electrophotographic printer configured as shown in FIG. And a transfer mechanism unit.

The MPU 1 controls each unit constituting the apparatus, and also operates the apparatus for the operation time counted by the operation time counter 10, the number of sheets counted by the sheet counter 11, or the sensors (PSS30 and PDS31) described later. Has the function of changing the cycle of the horizontal synchronizing signal based on the transport speed of the sheet detected by the method.

The NCU 2 has functions for controlling connection with a telephone network (PSTN) and detecting transmission and reception of a dial signal corresponding to a telephone number (including a FAX number) of a destination. . MODEM3 is ITU
-T Recommendation T. 30 based on a facsimile transmission control procedure according to V.30. 17, V.I. 27ter, V.I. Modulation and demodulation of transmission / reception data according to 29 or the like are performed. Alternatively, in addition to these, The modulation and demodulation of the transmission / reception data according to C.34 are performed.

The ROM 4 stores a program for controlling the apparatus, and also stores a printing endurance table 4a to be described later with reference to FIGS. The RAM 5 temporarily stores data and the like. The image memory 6 temporarily stores received image data and image data read by the scanner 9. CODE
C7 transmits MH, M to transmit the read image data.
The received image data is encoded by the R, MMR method or the like, and decoded (decoded). The operation unit 8 is for the user to instruct facsimile transmission / reception, printing, and the like. The scanner 9 reads the image data of the original when performing a facsimile transmission.

The operating time counter 10 measures, for example, the usage time from the start of use of the apparatus to the present. The sheet counter 11 counts the number of sheets required for printing from the start of use of the apparatus to the present, for example.

The printer of this apparatus is provided with a printer control 12 for controlling each part of the printer in FIG. Inside the printer, a photosensitive drum 13 having a photoconductive film on the outer peripheral surface as a photosensitive member is arranged.
Is rotated by a drive source (not shown). A charging brush 14 is arranged around the photosensitive drum 13 as a brush roller type charger, and a predetermined bias voltage is applied to the charging brush 14 by a charging bias applying circuit 15. The charging brush 14 to which the bias voltage has been applied
While rotating, the outer peripheral surface of the photosensitive drum 13 is uniformly charged to about -750V.

The LED print head 16 as an exposure unit disposed around the photosensitive drum 13 has a large number of LEDs arranged side by side.
3 is irradiated with light to form an electrostatic latent image corresponding to image information on the outer peripheral surface.

Further, the developing device disposed around the photosensitive drum 13 is composed of a supply roller 17, a developing roller 18, a blade 19, a developing device bias application circuit 20, and the like. The supply roller 17 charges the toner from a toner case (not shown) containing the toner while the developing roller 18 is charged.
The developing roller bias application circuit 20 applies a predetermined bias voltage (−600) to the supply roller 17.
V to -700 V, preferably about -650 V). A predetermined bias voltage (−300 V to −400 V) is applied to the developing roller 18 arranged in contact with the supply roller 17 and the photosensitive drum 13 by a developing device bias applying circuit 20.
V, preferably -350 V).

The blade 19 elastically contacts the outer peripheral surface of the developing roller 18 to make the layer thickness of the toner adhered to the outer peripheral surface of the developing roller 18 uniform. 20 to a predetermined bias voltage (-600 V to -700 V, preferably about -650 V).
V) is applied.

Further, a transfer roller 21 as a transfer device disposed around the photosensitive drum 13 is disposed so as to be in contact with the outer peripheral surface of the photosensitive drum 13 across a sheet conveying path, and is driven by a driving source (not shown). Rotated. This transfer roller 2
1 is applied with a predetermined bias voltage by a transfer bias application circuit 22.

The fixing device disposed on the sheet feeding side of the sheet transport path includes a heating roller 23 having a heater, a heater driving circuit 24, a press roller 25, and the like. The heater of the heating roller 23 is heated to a predetermined temperature by a heater driving circuit 24. Heating roller 23 and press roller 25
Fixes the toner image on the sheet by heating and pressing the sheet after the transfer by the transfer roller 21.

In this apparatus, a memory removing brush 26 is arranged around the photosensitive drum 13. The memory removing brush 26 is for removing a toner image (memory image) remaining along the outline of the image on the outer peripheral surface of the photosensitive drum 13 even after transfer, and the memory removing brush 26 has a memory removing brush voltage applying circuit. 27 applies a predetermined bias voltage.

Further, this apparatus has a PSS 30 and a PSS 30 as sensors for detecting the recording medium conveying speed of the sheet conveying mechanism.
DS31 is arranged on the sheet feeding side and the sheet sending side of the sheet transport path. As described in the operation described later, the PSS 30 is turned on when a sheet is fed from a paper feed cassette (not shown), and the timer starts counting time simultaneously with the ON. The PDS 31 is turned ON when the sheet after the transfer is sent out, and at the same time as the ON, the timer stops counting time. The time from the start to the stop of this timer is treated as the paper transport speed.

In the image forming apparatus configured as described above, the operation other than the PSS 30 and the PDS 31 is well known.
Is uniformly charged to about -750 V, and the photosensitive drum 13
An electrostatic latent image corresponding to image information is formed on the photosensitive drum 1 by the LED print head 16 and the developing roller 18.
The toner is attracted to the electrostatic latent image on
A toner image is formed thereon. Then, the transfer roller 21
As a result, the toner image on the photosensitive drum 13 is transferred to a sheet. After the transfer, the sheet is heated and pressed by the heating roller 23 and the press roller 25, and the toner image is fixed on the sheet as a permanent image.

In this apparatus, in addition to the normal printing operation, the operation time counted by the operation time counter 10, the number of sheets counted by the sheet counter 11, or the sheet detected by the sensors (PSS30 and PDS31). , The cycle of the horizontal synchronization signal (HSYNC) is changed based on the transport speed. Since the horizontal synchronizing signal is generated by the MPU 1, the cycle can be easily changed, and the horizontal synchronizing signal from the MPU 1 is sent to the printer control 12.

The cycle of the horizontal synchronizing signal is set according to the number of prints as shown in the table of FIG. 7 for the number of prints, and is shown in FIG. It is set according to time as in the table, and in the case of operating time, it is set according to operating time as in the table of FIG. 7 to 9 are stored in the printing endurance table 4a of the ROM 4 as described above. The tables in FIGS. 7 to 9 are each divided into four stages, but it is needless to say that there may be five or more stages. The cycle of the horizontal synchronizing signal is changed as shown in FIG. 3 in the case of, for example, the number of prints, and is gradually increased as the number of prints increases.

Next, regarding the change processing of the horizontal synchronization signal,
This will be described with reference to the flowcharts of FIGS. The flowchart in FIG. 4 is based on the case where the number of prints is set as the change reference. Since the number of prints is small at the start of use of the apparatus (0 to n1), the horizontal synchronization signal is set to the initial value T0. After the start of use, in step ST1, the number of prints counted by the number counter 11 is read, and in step ST2, the read number of prints is compared with the value in the printing durability table of FIG.

In the next step ST3, it is determined whether or not the horizontal synchronizing signal needs to be changed. If the horizontal synchronizing signal needs to be changed, the process proceeds to step ST4, and if not, the process ends. In step ST4, the cycle is changed to the cycle of the horizontal synchronization signal set according to the number of prints, and the cycle is set again. For example, if the number of prints n is n1 <n ≦ n2
, The cycle of the horizontal synchronization signal is set to T1.

FIG. 5 is a flow chart in the case where the timer is used as a change reference.
Since the time until ON of S31 is short (t0), the cycle of the horizontal synchronization signal is set to T0. After the start of use, first, in step ST11, the timer T is reset, and in the next step ST12, the PSS 30 is turned off.
It is determined whether or not N has been reached. PSS30 if not yet
Waits until is turned on, and when turned on, step ST1
3 and the timer T is started. Next, in step ST14, it is determined whether or not the PDS 31 is turned on. If not, the process waits until the PDS 31 is turned on. If the PDS 31 is turned on, the process proceeds to step ST15 and the timer T is stopped.

Then, in step ST16, PS
The time from ON of S30 to ON of PDS31 is compared with the value in the printing durability table of FIG. Next step ST17
Then, as a result of the comparison, it is determined whether or not the cycle of the horizontal synchronization signal needs to be changed. If the cycle needs to be changed, the process proceeds to step ST18, and if not, the process ends. In step ST18, the period is changed to the cycle of the horizontal synchronization signal set according to the time t of the timer T.
For example, when the time t changes from t0 to t1, the cycle of the horizontal synchronization signal is set to T1.

The flow chart of FIG. 6 shows the case where the operating time is used as a change reference. Since the operating time tw0 is short at the beginning of use of the apparatus, the cycle of the horizontal synchronizing signal is set to T0. After the start of use, first, in step ST21, the operation time data counted by the operation time counter 10 is fetched,
In the next step ST22, the fetched operating time data is compared with the values in the printing durability table of FIG. And
In step ST23, it is determined whether or not it is necessary to change the cycle of the horizontal synchronization signal based on the comparison result. If it is necessary, the process proceeds to step ST24, and if not, the process ends. In step ST24, the period is changed to the cycle of the horizontal synchronization signal set according to the operation time tw. For example, when the operating time tw changes from tw0 to tw1, the cycle of the horizontal synchronization signal is set to T1.

In the above-described image forming apparatus, in particular, the photosensitive drum 13 and the transfer roller 2 located on the paper transport path
1, heating roller 23, press roller 25, transport roller 3
2. Although not shown, the pick-up roller for taking out the sheets one by one from the paper feed cassette and other transport rollers for feeding the taken-out paper to the transport roller 32 are worn out by direct contact with the paper as the apparatus is used. Although the roller diameter gradually decreases, the cycle of the horizontal synchronizing signal is gradually set longer according to the number of prints, time (paper transport speed), or operation time. Even if it is reduced from the beginning of use of the apparatus, the problem that the print length of the paper becomes short does not occur.

The change of the cycle of the horizontal synchronizing signal may be based on any one of the number of prints, the time, and the operating time, or may be a combination of two or more. In this case, the change is made when any one of the conditions is satisfied or when two or three conditions are simultaneously satisfied.

[0037]

As described above, according to the image forming apparatus of the present invention, in particular, the rollers located on the conveyance path of the recording medium are worn by direct contact with the recording medium, and the conveyance speed of the recording medium is reduced. However, since the period of the horizontal synchronizing signal is changed longer according to the decrease, the print length on the recording medium does not change.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a part of an image forming apparatus according to an embodiment.

FIG. 2 is a schematic configuration diagram of a remaining portion of the image forming apparatus.

FIG. 3 is a diagram illustrating a relationship between the number of prints and a cycle of a horizontal synchronization signal.

FIG. 4 is a flowchart illustrating a process of changing the cycle of a horizontal synchronization signal in accordance with the number of prints in the image forming apparatus.

FIG. 5 is a diagram showing a state in which PSS is turned on to PDS in the image forming apparatus
It is a flowchart which shows the process which changes the period of a horizontal synchronizing signal according to the time until it turns on.

FIG. 6 is a flowchart illustrating a process of changing a cycle of a horizontal synchronization signal according to an operation time in the image forming apparatus.

FIG. 7 is a table showing the number of prints and the cycle of a horizontal synchronization signal stored in a ROM in the image forming apparatus.

FIG. 8 shows P stored in a ROM in the image forming apparatus.
9 is a table of a time from SS on to PDS on and a cycle of a horizontal synchronization signal.

FIG. 9 is a table of operation time and a period of a horizontal synchronization signal stored in a ROM in the image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 MPU (control part) 4 ROM 4a Printing endurance table 10 Operating time counter 11 Number of sheets counter 13 Photosensitive drum (photoconductor) 14 Charging brush (charging device) 16 LED print head (exposure part) 18 Developing roller (developing device) 21 Transfer Roller (transfer unit) 23 Heating roller (fixing unit) 25 Press roller (fixing unit) 30 PSS (sensor) 31 PDS (sensor)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C162 AE04 AE10 AE19 AE28 AE47 AF13 AF41 AF69 AF82 AF90 FA17 2C362 BB32 BB37 BB42 BB48 CB51 CB60 2H027 DA20 DA39 DA45 DE07 ED04 ED16 EE01 EE02 EE07 EF09 2H076 AB

Claims (3)

[Claims] A photoconductor, a charger for uniformly charging the photoconductor, an exposure unit for forming an electrostatic latent image on the photoconductor in synchronization with a horizontal synchronization signal, and a photoconductor formed on the photoconductor. A developing device that develops the electrostatic latent image, a transfer device that transfers the developed image on the photoconductor to a recording medium, a transport mechanism that transports the recording medium,
An image forming apparatus comprising: a counter that counts the number of printed recording media; and a control unit that changes a cycle of a horizontal synchronization signal based on the count value of the counter. 2. A photoconductor, a charger for uniformly charging the photoconductor, an exposure unit for forming an electrostatic latent image on the photoconductor in synchronization with a horizontal synchronization signal, and a photoconductor formed on the photoconductor. A developing device that develops the electrostatic latent image, a transfer device that transfers the developed image on the photoconductor to a recording medium, a transport mechanism that transports the recording medium,
An image forming apparatus comprising: a control unit that detects a recording medium conveyance speed of a conveyance mechanism unit and changes a cycle of a horizontal synchronization signal based on the detected conveyance speed. 3. A photoconductor, a charger for uniformly charging the photoconductor, an exposure unit for forming an electrostatic latent image on the photoconductor in synchronization with a horizontal synchronization signal, and a photoconductor formed on the photoconductor. A developing device that develops the electrostatic latent image, a transfer device that transfers the developed image on the photoconductor to a recording medium, a transport mechanism that transports the recording medium,
An image forming apparatus comprising: a timer for counting an operation time of the apparatus; and a control unit for changing a cycle of a horizontal synchronization signal based on the operation time counted by the timer.