JPH0575812A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device whose operability for setting density is improved by enabling the adjustment of the density during the formation of an image. CONSTITUTION:A period during which primary electrification voltage in the process of the formation of the image and developing voltage are impressed. that is, the period during which one of the primary electrification driving signal of the output signal of a microcomputer 3 and a developing bias driving signal is turned ON is considered to be an image forming period, and when a picture density setting slide volume 1 is operated in this image forming period, and the digital data D2 of the microcomputer 3 is changed, the microcomputer 3 holds the digital data D3 to be outputted to a D/A converter 4, and changes the output digital data D3 in accordance with the input digital data D2 after the image forming period.

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, and more particularly to an image forming apparatus having an image density control function.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus, a slide volume for image density setting is used, a voltage controlled by the slide volume is directly input to a high voltage power supply circuit, and various voltages are controlled by the high voltage power supply circuit. By doing so, the image density is controlled. For example, as shown in FIG. 8, the image forming apparatus includes a host I / F circuit unit 130 that receives information from the host PC 110, a formatter unit 140 that expands print information of the host PC 110 into an image, and controls the engine unit 160, and an operator. Includes an operation panel unit 150 for operating the image forming apparatus and an engine unit 160 for controlling the electrophotographic process and printing the image information received from the formatter unit 140 on a sheet. Then, using the density adjusting volume (variable resistor) 172 incorporated in the engine section 160, the primary charging voltage and the developing voltage of the high-voltage power supply 171 are changed, and the toner density is adjusted at the stage of developing the toner on the photosensitive drum. The print density of the paper is adjusted by changing the intensity of the latent image on the photosensitive drum by changing the amount of laser light or changing the amount of laser light.

[0003]

However, in the above-mentioned conventional example, the voltage set by the density adjusting volume 172 is directly input to the high voltage power supply 171, and the toner density and the strength of the latent image are changed according to the input voltage. Thus, the image density is controlled, and if the density adjustment volume 172 is operated during image formation, the image density will change. Therefore, in order not to cause an image defect due to density adjustment during image formation,
Density adjustment volume 172 for laser beam printers, etc.
Is provided at a position where it cannot be operated during image formation, but there is a drawback in that the operability of the density adjustment volume 172 deteriorates at such a position.

In a system in which a plurality of operators use the host PC or a plurality of host PCs are connected, the value of the density adjustment volume 172 is checked every time and the operator or the host PC used last time changes the setting. In that case, there was the trouble of having to set again.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an image forming apparatus capable of adjusting the density during image formation and improving the operability of the density setting. ..

[0006]

[Means for Solving the Problems] and

In order to achieve the above object, the image forming apparatus of the present invention has the following constitution.

That is, in an image forming apparatus having an image density control function, density setting means for setting the density of an image formed on a recording medium, and image forming means for forming an image in accordance with the density set by the density setting means. Have.

Further preferably, according to a recognition means for recognizing a period for forming an image and a recognition result by the recognition means,
It further comprises storage means for storing the density set by the density setting means.

More preferably, the image forming means further comprises a storage means for storing a predetermined density, and when the density is not set by the density setting means, the image forming means forms an image according to the density stored in the storage means. Is characterized by.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings.

<First Embodiment> FIG. 1 is a schematic block diagram showing the arrangement of an image forming apparatus according to the first embodiment. In the figure, reference numeral 1 is an image density setting slide volume, and 2 is an AD converter. The voltage D1 controlled by the image density setting slide volume 1 is input, converted into a digital value D2, and output. A microcomputer 3 controls various operations of the laser beam printer. A DA converter 4 receives a digital value D3 output from the microcomputer 3, converts it into an analog voltage D4, and outputs it. Reference numeral 5 is a high-voltage power supply circuit, which is a primary charging voltage (HVD) used when forming an image.
C '), developing bias (HVDVP'), and transfer voltage (HVT ') are generated, and the image density is controlled.
6 is a photosensitive drum, 7 is a primary charging roller, 8 is a developing cylinder, and 9 is a transfer charging roller. A host computer 10 sends code information. A video controller 11 develops the code information sent from the host computer 10 into printable image information.

In the above structure, the microcomputer 3 turns on the ready (RDY) signal to the video controller 11 when the image forming is possible. When the video controller 11 confirms the ready signal, the image formation start command signal (hereinafter abbreviated as “print (PRNT) signal”) is sent to the microcomputer 3.
Is output. On the other hand, when this print signal is confirmed, the microcomputer 3 determines that the main motor drive signal (PMD
RV) is turned on to drive the main motor.

Next, when the main motor is driven, the photosensitive drum 6, the primary charging roller 7, the developing cylinder 8 and the transfer charging roller 9 start rotating in synchronization with this. After that, the microcomputer 3 turns on the primary charging drive signal, applies the primary charging voltage to the primary charging roller 7, and uniformly charges the surface of the photosensitive drum 6. The surface of the uniformly charged photosensitive drum 6 is irradiated with a laser beam modulated based on an image signal (VDO signal), and a latent image is formed on the surface of the photosensitive drum 6. The latent image formed on the surface of the photosensitive drum 6 is transferred onto the printing paper by the transfer charging roller 9 after a visible image is formed by the toner on the developing cylinder 8.

In the image forming process described above, the primary charging voltage (HVDC '), the developing bias (HVDVP'),
And a transfer voltage (HVT ') are respectively generated by the high voltage power supply circuit 5, and signals for controlling the output timing of each voltage are respectively a primary high voltage drive signal (HVDC signal), a developing bias drive signal (HVDVP signal), and a transfer high voltage control. Signals (HVT signals), and each signal is output from the microcomputer 3 at the timing shown in FIG.

The intermediate tap voltage D1 of the image density setting slide volume 1 is input to the AD converter 2, converted into digital data D2, and then input to the microcomputer 3. The microcomputer 3 outputs digital data D3 corresponding to the input digital data D2 to the DA converter 4, is converted into analog data D4, and is input to the high voltage power supply circuit 5. The high-voltage power supply circuit 5 controls the image density according to the input analog data D4. That is, the image density can be controlled by changing the potential difference between the surface potential of the photosensitive drum 6 and the amount of electric charge applied to the toner, that is, the potential of the developing cylinder 8. Therefore, in the high voltage power supply circuit 5, the input analog data D4 is input.
The image density is controlled by changing the potential difference between the primary charging voltage and the developing voltage in accordance with the above.

Therefore, when the image density is changed within the period ("T" shown in FIG. 2) in which the primary charging voltage and the developing voltage are applied in the image forming process, the potential difference between the primary charging voltage and the developing voltage is changed. Changes to a linear type, resulting in a defective image. In order to prevent this image defect, it is necessary to fix the potential difference between the primary charging voltage and the developing voltage during the period in which the primary charging voltage and the developing voltage are applied in the above-described image forming process.

A signal for controlling the output timing of the primary charging voltage (HVDC ') and the developing voltage (HVDVP') is
These are a primary charging drive signal (HVDC) and a developing bias drive signal (HVDVP), and these signals are output from the microcomputer 3. Further, by controlling the output timing of the digital data D3 output to the DA converter 4 by the microcomputer 3, the timing of changing the potential difference between the primary charging voltage and the developing voltage can be controlled. Therefore, the period during which the primary charging voltage and the developing voltage are being applied in the image forming process, that is, one of the primary charging driving signal and the developing bias driving signal, which are the output signals of the microcomputer 3, is on is the image forming period. During the image forming period, when the image density setting slide volume 1 is operated and the digital data D2 of the microcomputer 3 changes, the microcomputer 3
Holds the digital data D3 to be output to the DA converter 4, and the input digital data D2 after the image forming period described above.
By changing the output digital data D3 in accordance with the above, it is possible to prevent the above-mentioned image defect.

As a result, the image density setting slide volume 1 can be operated at any time regardless of whether it is during the image forming period, and can be arranged at a position with good operability.

<Second Embodiment> Next, the second embodiment of the present invention will be described.
Embodiments will be described below with reference to the drawings.

In this embodiment, the interface between the microcomputer 3 and the video controller 11 shown in FIG. 1 is used as a video interface, and the microcomputer 3 and the video controller 11 perform serial communication via the video interface. In this serial communication, the control information given from the video controller 11 to the microcomputer 3 is used as a command, and the status information given from the microcomputer 3 to the video controller 11 is used as a status, which are handled as information having a data length of 8 bits. Further, the video controller 11 is connected to the host computer 10 via the host interface, and is configured so that image density control information can be input from the host computer 10 via the host interface and the video interface.

With this configuration, setting means for setting the image density can be arranged on the host computer 10 side.

FIG. 3 is a schematic block diagram showing the structure of the image forming apparatus according to the second embodiment. In addition, the same reference numerals are given to those having the same functions as those in FIG.
The description is omitted. In FIG. 3, reference numeral 10 'is a host computer having an image density operating means corresponding to the above-mentioned image density setting slide volume 1.

First, the operator operates the host computer 1
When the image density operating means provided at 0'is operated, image density control information corresponding to the operation is sent to the host computer 1
0'is output to the video controller 11 via the host interface, and the video controller 11 outputs an image density control command according to the image density control information to the microcomputer 3 via the video interface. Next, the microcomputer 3 controls the output digital data D3 according to the image density control command. After that, the image density can be adjusted by the same processing as in the first embodiment.

In the image density control with the above-mentioned structure, the image density operation means can be operated at any time regardless of the state of the apparatus main body, so that the above-mentioned image defect can occur.
In order to prevent this image defect, even if the image density control command is input during the image forming period as in the first embodiment,
The microcomputer 3 does not execute this command, saves this command, and holds the digital data D3 to be given to the DA converter 4. Then, after the image forming period, by controlling the digital data D3 given to the DA converter 4 in accordance with the stored command data and controlling the image density, the above-mentioned image defect can be prevented.

In this embodiment, the case where the image density operation means is provided in the host computer 10 'has been described as an example, but since an operation panel (not shown) is usually connected to the video controller 11, the image density operation means is It is also possible to use an operation panel as the concentration operation means.

<Third Embodiment> Next, the third embodiment of the present invention will be described.
Embodiments will be described in detail below with reference to the drawings.

FIG. 4 is a schematic block diagram showing the structure of the image forming apparatus according to the third embodiment. As illustrated, the image forming apparatus 120 includes a host I / F circuit 130 for inputting print information sent from the host PC 110,
A formatter unit 140 that expands image information based on print information, an operation panel unit 150 that sets image density,
Engine unit 160 for printing by electrophotographic process
It consists of and. In addition, the formatter unit 140
Are CPU 141, RAM 142, ROM 143, buffer 144, video I / F circuit 145, NV
The engine unit 160 includes a RAM 146 and a CPU, R
One-chip microcomputer 161, which has a built-in AM, ROM, I / O port, etc., main motor 162, scanner motor 163, laser driver 164, fan motor 165,
The light receiving element 166, the thermistor 167, the paper sensor 168,
A fixing heater 169, a sheet feeding solenoid 170, a high voltage power source 171, a density adjustment D / A circuit 172, a toner cartridge 173 and the like are included.

In the above configuration, when print information including information such as paper setting information and density setting information is input from the host PC 110 to the formatter section 140 via the host I / F circuit 130, the CPU 141 causes the ROM 14 to operate.
The print information is judged according to the image developing program stored in No. 3, and the image information is developed and stored in the buffer 144. After that, when the expansion process ends, the video I / F circuit 1
A print start command is issued to the CPU 161 of the engine section 160 through 45. On the other hand, the CPU 161 starts up each unit of the engine unit 160, notifies the formatter unit 140 of the fact that paper has been fed and printing is possible.
As a result, the formatter unit 140 reads the image information from the buffer 144 in accordance with the horizontal synchronization timing,
The laser is blinked to start printing by the electrophotographic process.

At this time, as the density setting information, the initial value written in the ROM 143 of the formatter unit 140 is NV.
It is set in the RAM 146. Further, the operator can operate the operation panel unit 150 to set a desired density. On the other hand, when the density setting information is input from the host PC 110, the value is written in the RAM 142, and the density is adjusted according to the value. Then, when the printing is completed, the value is cleared. Also, the host PC 110
If the density setting information is not specified from, the above NVR
The density is adjusted according to the value set in the AM 146. Specifically, the CPU 141 determines whether or not the density setting information is input from the host PC 110, and if the density setting information is input, the engine unit 160 is output through the video I / F circuit 145.
Send the setting information to. And C of the engine section 160
The PU 161 sets the setting information in the density adjustment D / A circuit 172, and the primary charging voltage and the developing voltage in the high-voltage power supply 171 are changed according to the setting values, and the density is adjusted.

Further, the above-mentioned density setting information is realized by information of a plurality of byte strings, the first half byte pattern shows a density setting command, and the second half byte pattern shows a density setting value. That is, the CPU 141 judges the byte pattern and, when recognizing the density setting command, transmits the density setting value to the CPU 161 through the video I / F circuit 145. Then, the CPU 161 controls the density adjustment D / A circuit 172 according to the density setting value,
The toner density is controlled as shown in. Here, FIG.
FIG. 9 is a diagram showing characteristics of toner density, primary charging voltage, and developing voltage, and as shown in the drawing, the maximum density setting value (FFH) V
The density adjustment D / A circuit 172 is set so as to be Dh and Dl at h and the minimum (00H) Vl.

On the other hand, when the density setting command is not input, the CPU 141 reads the value of the NVRAM 146 and sets it as the default value. In this case, the density set value is calculated and set so as to have a desired density according to the density control voltage and the toner density having the characteristics shown in FIG. Further, as described above, the density setting value is not changed unless the user sets a particular value, and printing is performed with the density of that value.

As described above, when the host PC 110 sends a series of print information with the density setting information added, the density setting value becomes effective only when the print information is printed, and after the printing is completed. If there is no density setting information at the time of the next printing, printing is performed with the density of the default value.

<Fourth Embodiment> Next, a fourth embodiment according to the present invention.
Embodiments will be described below with reference to the drawings.

FIG. 7 is a schematic block diagram showing the arrangement of an image forming apparatus according to the fourth embodiment. In this embodiment, as shown in the figure, this device is connected to a plurality of host PCs, and has the same configuration as that of the third embodiment shown in FIG. In this configuration, for example, the density setting information set by the host PC (# 1) is
The density setting information is valid only for the host PC, and the density setting information is not applied to other host PCs. That is, the CPU 141 of the formatter unit 140 discriminates the recognition code of the host PC and the density setting information set by the host PC, and controls the toner density to be printed. Similarly, the density setting information is set in the NVRAM 146, and the next time print information is sent from the same host PC, if the density setting information is not set in the information, the density setting value is set in the NVRAM 146. Is read out to adjust the toner density.

As described above, when the image forming apparatus is connected to a plurality of host PCs, the identification code of the host PC and the density setting information are discriminated to make a pair, and the toner density is controlled based on the information. The toner density information set by a certain host PC can print without affecting other host PCs. If the identification code of the host PC and the toner concentration setting information cannot be discriminated, the toner concentration information set by one host PC is returned to the other host by returning the toner concentration information to the default value for each series of data printing. There is an effect that printing can be performed without affecting the PC.

In each of the above-described embodiments, the toner density is changed by controlling the primary charging voltage and the developing voltage. However, by changing the laser light amount and directly controlling the latent image appearing on the drum, the toner density is changed. It is also possible to change. In that case, the density adjustment D / A circuit 172 is used to control the variation in the characteristics of the laser, and the CPU 161 of the engine unit 160 executes the control to change the toner density.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0038]

As described above, according to the present invention,
It is possible to adjust the density during image formation and improve the operability of the density setting.

[Brief description of drawings]

FIG. 1 is a schematic block diagram illustrating a configuration of an image forming apparatus according to a first exemplary embodiment.

FIG. 2 is a timing chart showing an image forming period in the first embodiment.

FIG. 3 is a schematic block diagram showing a configuration of an image forming apparatus according to a second embodiment.

FIG. 4 is a schematic block diagram showing a configuration of an image forming apparatus according to a third embodiment.

[Figure 5]

FIG. 6 is a diagram showing a relationship between a density control voltage and a toner density characteristic.

FIG. 7 is a schematic block diagram showing a configuration of an image forming apparatus according to a fourth embodiment.

FIG. 8 is a schematic block diagram showing a configuration of a conventional image forming apparatus.

[Explanation of symbols]

 1 Slide Volume 2 AD Converter 3 Microcomputer 4 DA Converter 5 High Voltage Power Supply Circuit 6 Photosensitive Drum 7 Primary Charging Roller 8 Developing Cylinder 9 Transfer Charging Roller 10 Host Computer 11 Video Controller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenjiro Hori 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (3)

[Claims] 1. An image forming apparatus having an image density control function, comprising: density setting means for setting the density of an image formed on a recording medium; and image forming means for forming an image according to the density set by the density setting means. An image forming apparatus comprising: 2. A recognition means for recognizing a period for forming an image, and a storage means for storing the density set by the density setting means in accordance with the recognition result by the recognition means. The image forming apparatus according to claim 1. 3. A storage unit for storing a predetermined density, wherein the image forming unit forms an image according to the density stored in the storage unit when the density is not set by the density setting unit. The image forming apparatus according to claim 1.