JPH08262819A - Image forming device - Google Patents

Abstract

PURPOSE: To obtain an image forming device usable for a long term by recording an image with an electrostatic charging voltage different from that at a normal recording time in the case the ratio of a black image in image data to be recorded is larger than the reference value of the black image ratio, that is, by adjusting/controlling the electrostatic charging voltage and recording the image to reduce load on an electrostatic charging part (electrostatic charger). CONSTITUTION: The ratio of the black image in the image data supplied to a printer part is measured by an image ratio measuring means for measuring the ratio of the black image in the whole original. In the case the measured ratio of the black image in the image data is equal to or below the reference value of the set black image ratio, the electrostatic charger 5, a transfer charger 8 and a separating charger are controlled by a CPU through each driving circuit so that recording may be executed by a voltage applied at the normal recording. In the case the measured ratio of the black image in the image data is larger than the set reference value, the electrostatic charger 5, the transfer charger 8 and the separating charger are controlled by the CPU through each driving circuit so that recording may be executed by a voltage different from the voltage applied at the normal recording.

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 provided with a printer section and a scanner section, and more particularly to an image forming apparatus using a so-called electrophotographic recording system.

[0002]

2. Description of the Related Art Conventionally, in image forming apparatuses such as copiers, facsimiles, printers, etc., an image forming apparatus using an electrophotographic recording method in which a semiconductor laser is driven to perform recording based on recorded image data is known. There is.

[0003]

However, in the above-mentioned conventional image forming apparatus, when a black image is recorded, particularly a so-called black solid image is formed, an image forming process (charging-exposure-developing-transfer-separation) is performed. Since it is necessary to maintain each part at a predetermined voltage, there have been problems such as a great amount of power consumption and shortened service life. The present invention has been made in view of the above problems, and according to the ratio of the black image of the image data supplied to the printer unit,
By adjusting the voltage (charging voltage, transfer voltage, separation voltage) of each of the charging section, the transfer section and the separation section in the image forming process, the load on each section during black image recording is reduced and the power consumption is reduced. An image forming apparatus that consumes less and can be used for a long period of time.

[0004]

In order to achieve the above object, the first invention of the present invention comprises a printer section for forming an image on a recording sheet, and a scanner section for reading an image of a document and replacing it with image data. In the image forming apparatus which is provided with the recording paper and the original on the same conveyance path, the reference value of the black image ratio for determining whether the recording is performed at the charging voltage during normal recording or the recording is performed by changing the charging voltage is set. Means to set,
If the black image ratio measuring means for measuring the black image ratio of the image data and the ratio of the black image of the previous period image data are higher than the reference value of the previous period black image ratio, the charging voltage is changed from that at the time of normal recording to perform recording. An image forming apparatus comprising: a control unit that controls the image forming apparatus. A second aspect of the invention is an image forming apparatus that includes a printer unit that forms an image on recording paper and a scanner unit that reads an image of a document and replaces it with image data, and conveys the recording paper and the document on the same conveyance path. A means for setting a reference value of a black image ratio for determining whether to perform recording at a transfer voltage during normal recording or to perform recording by changing the transfer voltage, and a black image ratio measuring means for measuring a black image ratio of image data And a control means for controlling recording by changing the transfer voltage from that in normal recording when the ratio of the black image in the previous period image data is larger than the reference value of the previous period black image ratio. It is a forming device. A third invention is a printer section for forming an image on a recording sheet,
In an image forming apparatus that includes a scanner unit that reads an image of a document and replaces it with image data, and conveys a recording sheet and a document on the same conveyance path, perform recording at the separation voltage during normal recording or change the separation voltage. A means for setting the reference value of the black image ratio that determines whether to perform recording, a black image ratio measuring means for measuring the black image ratio of the image data, and a ratio of the black image of the previous period image data is the reference of the previous period black image ratio. When the value is larger than the value, the image forming apparatus is provided with a control means for controlling the recording by changing the separation voltage from the normal recording.

[0005]

In the first invention, when the black image ratio of the image data to be recorded is larger than the reference value of the previous black image ratio,
That is, when recording a black solid image or an image with a large solid portion, recording is performed by changing the charging voltage from that during normal recording.
Recording is performed by adjusting and controlling the charging voltage, so the burden on the charging section (charging charger) is reduced and image formation that can be used for a long period of time is made compared to conventional image forming apparatuses that use an electrophotographic method with a constant charging voltage. A device can be provided. In the second invention, when the black image ratio of the image data to be recorded is larger than the reference value of the black image ratio in the previous period, that is, when a black solid image or an image having a large solid portion is recorded, the transfer voltage is normally recorded. Recording is performed by adjusting the transfer voltage, such as changing the recording from time to time, so that the load on the transfer unit (transfer charger) is reduced compared to the conventional image forming apparatus that uses an electrophotographic method with a constant transfer voltage. Therefore, an image forming apparatus that can be used for a long period of time can be provided. In the third invention, when the black image ratio of the image data to be recorded is larger than the reference value of the black image ratio in the previous period, that is, when a black solid image or an image having a large solid portion is recorded, the separation voltage is normally recorded. Since recording is performed by adjusting and controlling the separation voltage, such as changing the recording from time to time.
It is possible to provide an image forming apparatus that can be used for a long period of time by reducing the load on the separation unit (separation charger) as compared with the conventional image forming apparatus that uses an electrophotographic method with a constant separation voltage.

[0006]

The present invention will be described in detail below. FIG.
FIG. 1 is a schematic configuration diagram of a laser printer including a printer unit and a scanner unit, which is an embodiment of the present invention. The electrophotographic recording process adopted in the printer unit is known, and double-sided recording will be described based on the recording process. In the printer unit, the paper feed cassette C
The recording paper 3 fed from the sheet feeding roller 1 in the direction of the registration roller pair 2 is conveyed by the registration roller pair 2 to the drum-shaped photoconductor 4 at a timing. The photoconductor 4 is driven to rotate counterclockwise, and at that time,
The surface is charged by the charging charger 5 having a predetermined charging voltage, and the laser beam from the laser optical system 6 is irradiated to form an electrostatic latent image on the surface.

When the latent image passes through the developing section 7, the latent image is visualized by the toner under the action of the developing roller 7a, and the visible image is transferred to the recording paper 3 conveyed to the photoconductor 4 in a predetermined manner. The visible image on the recording paper 3 transferred by the transfer charger 8 having a voltage and separated from the photoconductor by the separation charger 21 having a predetermined separation voltage is fixed to the fixing roller pair 9a.
The image is fixed by the fixing device 9 having.

On the other hand, after the visible image is transferred, the cleaning device 12 removes the residual toner from the photoconductor 4, and the charge removal lamp P removes the electric charge. The toner removed from the photoconductor 4 is accommodated in the toner recovery tank 13 and recovered.

The recording paper 3 discharged from the fixing device 9 is rotated by a double-sided entrance guide 17 so that the double-sided conveyance roller pair 1
You are led to 8. The recording paper 3 is conveyed by the pair of double-sided conveyance rollers 18 to the pair of reversing rollers 19 rotating clockwise,
It passes through the inversion sensor 20. The recording paper 3 is the reversing sensor 20.
After a lapse of a predetermined time after passing through, the reversing roller pair 19 changes its rotation direction counterclockwise, and the recording sheet 3 is conveyed in the register roller pair 2 direction by the rotatable reversing guide 17 '.

The recording paper 3 again fed to the registration roller pair 2 is conveyed to the photosensitive member 4 by the registration roller pair 2 at a timing, and the toner is fixed on the recording paper 3 through the same procedure as above. To be done. At this time, the opposite side of the case where the sheet is fed from the sheet feeding roller 1 is in contact with the photoconductor 4, so that double sided recording is performed on the recording sheet 3. After passing through the fixing device 9, the double-sided recording paper 3 is guided by the double-sided entrance guide 17, discharged to the paper discharge unit 11, and stored.

C is provided downstream of the printer section in the recording paper feeding direction.
A scanner unit 26 having a reading head 25, which is a reading unit for reading image information including a CD (charge coupled device), is installed. The original document conveyed to the reading head 25 is sent out from the paper feed cassette C to the same conveyance path 27 as the recording paper by the rotation of the paper feed roller 1. Further, the arrangement of the scanner unit 26 is not limited to that shown in FIG. 1, and it is preferable that the scanner unit 26 is arranged near the developing unit 7 as an embodiment of the present invention. Moreover, it is also possible to arrange it in the vicinity of the transport path 27.

FIG. 2 is a block diagram showing an example of a control system of the laser printer of FIG. The controller 14 is connected to the external device 30 and sends image information to the printer device. The CPU 31 is a microcomputer that controls the printer device, is connected to the ROM 32 corresponding to each processing unit to execute the processing described later, and has a working RAM and the like. The main motor drive circuit 33 drives a main motor 34 that conveys the recording paper 3 and drives the fixing device 9 and the developing unit 7.

The polygon motor drive circuit 39 is a circuit for driving the polygon motor 40 of the laser optical system 6 and has a FG signal detection circuit for detecting the number of revolutions of the polygon motor 40. The paper feed clutch drive circuit 35 is provided for the recording paper 3
Paper feed clutch 36 for driving a paper feed roller for feeding
Drive. The registration clutch drive circuit 37 drives a registration clutch 38 that drives the registration roller pair 2. The charging charger drive circuit 49 drives the charging charger 5 with the charging voltage adjusted based on the image data to be recorded. The transfer charger drive circuit 50 drives the transfer charger 8 with the transfer voltage adjusted based on the image data to be recorded. Separation charger drive circuit 51
Drives the separation charger 21 with the separation voltage adjusted based on the image data to be recorded. The laser drive circuit 42 uses the image signal VIDEO generated from the image signal WDATA from the controller 14 to generate a laser signal from the laser device 4.
Drive 1 The optical writing signal control circuit 44 changes the main scanning synchronization signal LSYNC from the synchronization detection signal DETP obtained by the synchronization detector 43 in response to the rotation of the polygon motor 40.
The main scanning writing effective area signal LGATE and the sub-scanning writing effective area signal FGATE are obtained, and these signals are sent to the controller 14.

Further, the laser device 41 has a semiconductor laser section for outputting a laser beam in response to the driving of the laser drive circuit 42, and a light receiving element (not shown) provided for adjusting the light amount thereof.

The CPU 31 and the controller 14 are connected by a bidirectional serial interface composed of a reception data signal PERXD, a transmission data signal PERXD, a reception ready signal PEDTR, and a transmission ready signal PECTS.
The state of the printer device judged by U31 is the controller 1
4 and the controller 14 sends a command to control the printer device.

In the above arrangement, the CPU 31 informs the controller 14 that the printer is ready for recording operation. The controller 14 confirms that the recording operation is possible and issues a recording operation start command to the CPU 31.
Send to Upon receiving the recording operation start signal, the CPU 31 turns on the polygon motor drive signal PMST to immediately start the recording operation, and rotates the polygon motor 40. The polygon motor 40 outputs an FG pulse having a frequency corresponding to its rotation speed, and this pulse is detected by an FG signal detection circuit (not shown), and the polygon motor drive circuit 39 is detected.
Then, the rotation speed of the polygon motor is controlled so that it has the same frequency as the polygon motor reference clock PMCK. At the same time, the main motor drive signal MMST is turned on to rotate the main motor 34.

The controller 14 receives the recording density information input according to the switch operation of the external device or the operator depending on the image content regardless of the recording operation, and the CPU 14
A recording density designation command is transmitted to 31. In response to this, the CPU 31 sends a rotation speed control signal PMCON to the polygon motor drive circuit 39. RPM control signal PM
CON is a signal that determines the polygon motor reference clock PMCK, and is either the reference clock itself or a signal that selects one of a plurality of clocks provided in the polygon motor drive circuit 39 as the reference clock.

The polygon motor drive circuit 39 can stabilize the rotation of the polygon motor 40 by controlling the current to the polygon motor 40 so that the cycle of the FG pulse becomes a constant level. Therefore, the CPU 31 receives the recording density designation command, and then receives the rotation speed control signal PMCO.
By switching N, the number of rotations of the polygon motor 40 can be switched according to the designated recording density.

Further, the polygon motor drive circuit 39 turns on the polygon motor lock signal PMLK when the polygon motor 40 reaches the steady rotation speed corresponding to the recording density,
It is sent to the CPU 31. When the recording operation is started, the CPU 31 turns on the paper feed clutch drive signal FDCL, drives the paper feed roller 1, and conveys the recording paper 3 stored in the cassette C to the position of the registration roller pair 2. Then, after confirming that the polygon motor lock signal PMLK is turned on, the width scanning writing effective area signal FGATE is sent to the controller 14. The controller 14
The image signal WDATA is transmitted after a predetermined time in synchronization with the turning on of FGATE. CPU31 is FGA
TE is sent, and after a predetermined time, the registration clutch drive signal RGCL is turned on, the recording paper 3 is conveyed toward the recording position by the photoconductor 4, and an image is formed at the predetermined position on the recording paper.

When the FGATE signal is off, the CPU 31
Adjust the amount of laser light. The light amount signal fed back from the light receiving element of the laser device 41 is supplied to the laser driving circuit 4
It is compared with a predetermined level by a comparator in 2 and inputted to the CPU 31 as a binarized LDCT signal. CP
U31 changes the laser drive signal using digital-analog conversion, holds the laser light amount when the laser light amount reaches a predetermined value and the LDCT signal changes, and adjusts the laser light amount. Further, by irradiating the mirror on the rotating polygon motor 40 with the laser light, the synchronization detector 43 detects a synchronization signal of a constant cycle according to the rotation of the polygon motor 40.

The optical writing signal control circuit 44 inputs the synchronization detection signal DETP and generates an image writing clock WCLK synchronized with the DETP signal. At the same time, the WCLK signal is counted, and when the predetermined count is reached, the main scanning synchronization signal LSYNC and the main scanning writing effective area signal LGATE are generated. Further, the sub-scanning write effective area internal signal FSYNC from the CPU 31 is input and the sub-scanning writing effective area signal FGATE is generated in synchronization with the LSYNC signal. LGATE
Image signal WDATA from the controller 14 at the time of image writing in which the signal and the FGATE signal are turned on.
The laser device 41 in synchronization with the WCLK signal.
Laser drive circuit 4 by converting into a VIDEO signal for driving
Send to 2.

The exhaust (cooling) fan motor drive circuit 47 is
When the exhaust (cooling) fan motor 48 is driven and the device power is turned on, the exhaust (cooling) fan motor drive signal F is immediately output.
The MST is turned on, and the exhaust (cooling) fan motor 48 rotates. The rotation speed of the exhaust (cooling) fan motor 48 is F
The rotation speed is controlled by the MCON signal.

The scanner section 26 reads an original from the reading head 25, sends data to the controller 14 via the CPU 31, and performs data processing and storage. The document conveyance path at this time is the same as that at the time of printing operation.

The display device 49 informs a user or a service person of the state of the printer device by making characters, sounds, pictures and lights.

Referring to the flow chart of FIG. 3, in the present embodiment, particularly in the charging process, the transfer process and the separation process in the image forming process according to the ratio of the black image of the image data supplied to the printer unit. The control for adjusting the voltage (charging voltage, transfer voltage, separation voltage) of each part will be described.

First, in a standby state before recording, based on the size and resolution of the set original, the number of image data of the entire original and the voltages of the charging section, the transfer section and the separating section (charging voltage,
The transfer voltage, the separation voltage) is changed even during the normal recording to set the number of image data with respect to the number of image data of the whole document to be recorded. That is, the reference value of the black image ratio for determining whether to perform the recording at the voltage for the normal recording or to change the voltage during the normal recording is set in the CPU 31 in advance. (S1) Next, when the printing operation is performed, the black image ratio measuring means (not shown) for measuring the ratio of the black image in the entire document sheet measures the ratio of the black image in the image data supplied to the printer unit. To do. (S
2) It is measured by counting the data representing the black image. Further, the image data is stored in the scanner unit 2
It may be read in step 6 or input from the outside. Here, it is determined whether or not the ratio of the black image of the image data measured in (S2) is less than or equal to the reference value of the black image ratio set in (S1).
Compare and judge with. (S3)

As a result of the above (S3), if the black image ratio of the image data measured in (S2) is less than or equal to the reference value of the black image ratio set in (S1), recording is performed at the voltage for normal recording. As is the case, the charging charger 5, the transfer charger 8 and the separation charger 21 are driven by the drive circuits 49, 50 and 51.
It is controlled by the CPU 31 via. (S4) Then, a normal recording operation is performed. (S9)

As a result of the above (S3), when the black image ratio of the image data measured in (S2) is larger than the reference value of the black image ratio set in (S1), a voltage different from the voltage during normal recording is used. The charging charger 5, the transfer charger 8 and the separation charger 21 are controlled by the CPU 31 via the drive circuits 49, 50 and 51 so as to perform recording instead of. (S4) After the above (S4), it is determined whether or not all of the image data measured in (S2) are black. (S5) If all the image data is not black, the recording operation is executed. (S8) If all of the image data is black, the original image may not have been read correctly, so a warning message is displayed on the display device 49 to the user. (S6) After that, the user gives an instruction as to whether or not to perform the recording operation. (S7) If the recording operation is instructed, the recording operation is performed (S7).
8) If the recording operation is not instructed, the recording is not performed. (S9)

In the above (S1), the reference value of the black image ratio for determining whether to perform recording at the voltage for normal recording or to change the voltage during normal recording is the charging voltage, the transfer voltage, Each of the separation voltages may be set independently or may be set in common.

Further, prior to the voltage control of the above-mentioned respective parts, a reference value of a black image ratio for determining whether to perform recording with the laser output during normal recording or to suppress the laser output compared with during normal recording is set in advance. It may be set in the CPU 31, and when it is larger than the reference value, the same control as in (S1) to (S4) may be performed to perform recording with the laser output suppressed more than in normal recording.

[0031]

As described above, according to the first invention,
When the black image ratio of the image data to be recorded is higher than the reference value of the black image ratio in the previous period, that is, when a black solid image or an image with a large solid portion is recorded, the charging voltage is changed from that in normal recording and recording is performed. Recording is performed by adjusting the charging voltage, such as when performing charging. Therefore, compared to a conventional image forming apparatus using an electrophotographic method with a constant charging voltage, a charging unit (charging charger)
It is possible to provide an image forming apparatus that reduces the burden on the user and can be used for a long period of time. In the second invention, when the black image ratio of the image data to be recorded is larger than the reference value of the black image ratio in the previous period, that is, when the black solid image or the image having a large solid portion is recorded, the transfer voltage is normally recorded. Recording is controlled by adjusting the transfer voltage, such as changing the recording from time to time, so the load on the transfer unit (transfer charger) is reduced compared to the conventional image forming apparatus that uses an electrophotographic method with a constant transfer voltage. Therefore, an image forming apparatus that can be used for a long period of time can be provided. Third
In the invention, when the black image ratio of the image data to be recorded is larger than the reference value of the black image ratio in the previous period, that is, when a black solid image or an image with many solid portions is recorded, the separation voltage is set to be higher than that at the time of normal recording. Since recording is performed by adjusting and controlling the separation voltage, for example, by changing the recording, the burden on the separation unit (separation charger) is reduced compared to the conventional image forming apparatus that uses an electrophotographic method with a constant separation voltage. An image forming apparatus that can be used for a long period of time can be provided.

[0032]

[Brief description of drawings]

FIG. 1 is a schematic diagram of a laser printer including a printer unit and a scanner unit according to the present invention.

FIG. 2 is a control block diagram of the laser printer shown in FIG.

FIG. 3 is a control flow chart according to a ratio of a black image in image data of the present invention.

[Explanation of symbols]

5. Charger charger 8. Transcription charger 21. Separation charger 25. Read head 26. Scanner unit 31. CPU 49. Charging charger drive circuit 50. Transfer charger drive circuit 51. Separate charger drive circuit

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location G03G 21/00 370 B41J 3/00 D // B41J 2/30 3/10 114E

Claims (3)

[Claims] 1. An image forming apparatus, comprising: a printer section for forming an image on a recording sheet; and a scanner section for reading an image of a document and replacing it with image data, wherein the recording sheet and the document are conveyed on the same conveyance path. A means for setting a reference value of a black image ratio for determining whether to perform recording with a charging voltage during normal recording or to change the charging voltage, and a black image ratio measuring means for measuring a black image ratio of image data. When the ratio of the black image in the previous period image data is higher than the reference value of the previous period black image ratio, the image forming device is provided with a control means for controlling the recording by changing the charging voltage from that in the normal recording. apparatus. 2. An image forming apparatus, comprising: a printer section for forming an image on a recording sheet; and a scanner section for reading an image of a document and replacing it with image data, wherein the recording sheet and the document are conveyed on the same conveyance path. A means for setting a reference value of a black image ratio for determining whether to perform recording at the transfer voltage during normal recording or changing the transfer voltage, and a black image ratio measuring means for measuring the black image ratio of image data. If the ratio of the black image in the previous period image data is larger than the reference value of the previous period black image ratio, the image is characterized by including control means for controlling the recording by changing the transfer voltage to that in the normal recording. Forming equipment. 3. An image forming apparatus, comprising: a printer section for forming an image on a recording sheet; and a scanner section for reading an image of a document and replacing it with image data, wherein the recording sheet and the document are conveyed on the same conveyance path. A means for setting a reference value of a black image ratio for determining whether to perform recording at the separation voltage during normal recording or to perform recording by changing the separation voltage, and a black image ratio measuring means for measuring the black image ratio of image data. When the ratio of the black image in the previous period image data is larger than the reference value of the previous period black image ratio, the image forming is characterized by including control means for controlling the recording by changing the separation voltage from that in the normal recording. apparatus.