JP2001183592A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problem that image quality varies with temperature variation. SOLUTION: This device is equipped with a deflecting means which deflects a light beam in a horizontal scanning direction, two light beam detecting means which detect the light beam deflected by the deflecting means at two positions on a horizontal scanning line, a means which measures the time difference from the detection of the light beam detected by one of the two light beam detecting means to the detection of the light beam by the other means, and a means 17 which corrects image formation conditions according to the time difference measured by this means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer,
The present invention relates to an image forming apparatus such as a facsimile and a printing machine.

[0002]

2. Description of the Related Art As an image forming apparatus, there is an electrophotographic image forming apparatus for forming an image on an image carrier using a light beam scanning device. JP-A-8-136838 discloses that
The purpose is to automatically correct the magnification when the scanning optical system changes due to environmental fluctuations, etc. The correction circuit controls the rotation speed of the polygon mirror via a polygon mirror drive circuit, and the magnification correction circuit controls the laser drive circuit via a phase synchronization circuit to control the phase of the laser beam, and the rotation speed of the photoconductor. An image forming apparatus in which the image forming apparatus is controlled by a main body drive circuit is described. However, Japanese Patent Application Laid-Open No.
No. 8 does not disclose correction based on fluctuations in detection results between two points (detection results between the start and end of scanning of a beam).

Japanese Patent Application Laid-Open No. Hei 5-72859 discloses a technique for processing image detection conditions inside and outside a device by a neural network to optimally control image forming conditions. An electrophotographic process control apparatus is described in which a surface potential, a test pattern density measurement result, and the like are processed by a neural network to correct process conditions such as a charging application bias and a developing bias.

Japanese Patent No. 2765626 discloses a technique for superimposing images created by a plurality of image forming units without misalignment.
An image forming apparatus that corrects an image forming position based on a result of reading the image is described.

Japanese Patent Application Laid-Open No. 11-55472 discloses that a plurality of light beams emitted from at least two or more light sources are distributed by one deflecting means so that two sets of light beams are opposite to each other in the sub-scanning direction. In a multicolor image forming apparatus that forms a multicolor image by irradiating a plurality of photoconductors arranged along the sub-scanning direction with these light beams so as to scan in the direction of A plurality of synchronization detection sensors provided outside the image forming area and used for determining an image writing start position in the main scanning direction on the plurality of photoconductors and respectively detecting a plurality of light beams from the deflecting unit; An end detection sensor provided at a scanning end end for detecting a light beam from the deflection unit, and a detection signal from the end detection sensor and a detection signal from the synchronization detection sensor. A scanning time measuring unit that counts a scanning time during which the light beam from the deflection unit scans from the synchronous detection sensor to the end detection sensor, a scanning time measured by the scanning time measuring unit, and a reference time as a reference. A shift amount calculating means for calculating a shift amount of a writing start position in the main scanning, and an image forming station on the opposite side to the image forming station which has counted the scanning time based on the shift amount calculated by the shift amount calculating means. There is described a multicolor image forming apparatus comprising: a read start timing shift means for shifting a read start timing of image data in a station.

Another object of the present invention is to automatically correct the magnification and the main scanning start position when the scanning optical system changes due to environmental fluctuations or the like. There has been proposed an image forming apparatus that detects a scanning period for scanning between two points by measuring the phases of a reference clock and a light beam detection signal, and corrects a magnification and a writing position in a main scanning direction based on a result of the detection.

[0007]

In an electrophotographic image forming apparatus, an electrostatic latent image is developed with a charged toner and transferred to an intermediate transfer member, transfer paper, or the like. There is a problem that a characteristic change occurs and image quality fluctuates. In addition, there is a problem that the image position fluctuates due to the thermal expansion of each part related to the conveyance unit and the image formation and the change in the characteristics of the optical components. In particular, in a color image forming apparatus that includes a plurality of image forming units and forms a full-color image by superimposing images of each color,
There is a problem that the relative fluctuation of the image position causes color unevenness and deteriorates the image quality. In some cases, a temperature sensor is provided in the apparatus for the purpose of correcting these, but it has been difficult to sufficiently stabilize image quality.

An object of the present invention is to provide an image forming apparatus capable of obtaining stable image quality without a large increase in cost. It is an object of the present invention to provide an image forming apparatus capable of obtaining stable image quality. It is an object of the present invention to provide an image forming apparatus capable of obtaining stable image quality even when the frequency of executing the correction mode is reduced. It is an object of the present invention to provide an image forming apparatus capable of obtaining stable image quality without particularly requiring a special cost increase. It is another object of the present invention to provide an image forming apparatus capable of obtaining stable image quality even when the frequency of executing the correction mode is reduced.

[0009]

According to a first aspect of the present invention, there is provided an image forming apparatus, comprising: scanning an image carrier on one or more image carriers by scanning a light beam modulated in accordance with an image signal; And a deflecting means for deflecting the light beam in the main scanning direction, and two light beams detecting the light beam deflected by the deflecting means at two positions on the main scanning line. Detection means, means for measuring the time difference between the detection of the light beam by one of the two light beam detection means and the detection of the light beam by the other of the two light beam detection means, and measurement by this means. Means for correcting the image forming conditions based on the time difference.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the correction of the image forming condition is a correction of a bias applied to a charging unit for charging the image carrier.

According to a third aspect of the present invention, in the image forming apparatus of the first aspect, the correction of the image forming condition is a correction of a bias applied to a developing unit for developing a latent image on the image carrier. It is.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the correction of the image forming condition is a correction of a toner density control value for a developing unit that develops a latent image on the image carrier. Things.

According to a fifth aspect of the present invention, in the image forming apparatus of the first aspect, the correction of the image forming condition is a correction of a bias applied to a transfer unit that transfers an image.

According to a sixth aspect of the present invention, in the image forming apparatus according to the first aspect, the correction of the image forming condition is a correction of a cooling capacity of a cooling unit that cools the image forming apparatus.

According to a seventh aspect of the present invention, in the image forming apparatus of the first aspect, the correction of the image forming condition is a correction of a writing image position of a writing unit that writes on the image carrier.

According to an eighth aspect of the present invention, in the image forming apparatus according to the first aspect, the image forming conditions are corrected by correcting a relative writing image position of a plurality of writing means for writing on a plurality of image carriers. It is something that is.

According to a ninth aspect of the present invention, in the image forming apparatus according to the first aspect, the correction of the image forming condition is performed by executing a correction mode.

According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the correction mode is a process control mode for creating and reading a test pattern.

According to an eleventh aspect of the present invention, in the image forming apparatus of the ninth aspect, the correction mode is to create and read a detection pattern for detecting a position of an image created by using a plurality of image carriers. This is a positioning mode for performing

The invention according to claim 12 is the invention according to claims 1 to 11
In the image forming apparatus according to any one of the above, the magnification of an image on the image carrier in the main scanning direction is also corrected based on the time difference.

The invention according to claim 13 is the invention according to claims 1 to 12
The image forming apparatus according to any one of the above, further comprising a storage unit for storing the variation of the time difference, wherein a correction method is learned based on the storage content of the storage unit.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of embodiments of the present invention, two examples of a conventional electrophotographic image forming apparatus will be described. FIG. 2 shows an example of an electrophotographic image forming apparatus. A sheet such as recording paper as a recording medium is fed from a sheet feeding device 1 as a sheet feeding unit to a sheet as a registration unit.
The sheet is fed to the pair of reciprocating rollers 2 and temporarily stopped with its leading end abutting against the reciprocating roller 2, and re-conveyance is started by the registration rollers 2 in conjunction with the image forming operation. The toner image on the photoreceptor 4 serving as an image carrier is transferred to the sheet on which the re-conveyance has been started by the transfer unit 3.
After the image is formed by fixing the toner image by fusing and pressing by the fixing unit 5, the toner image is discharged to the tray 7 by the paper discharging unit 6. Although the photoconductor 4 is a drum-shaped photoconductor, a belt-shaped photoconductor may be used.

The photoreceptor 4 is driven to rotate by a driving unit (not shown), the surface of the photoreceptor 4 is uniformly charged by a charging unit 8, and then exposed by a writing unit 9 to form an electrostatic latent image. The electrostatic latent image on the photoconductor 4 is developed into a toner image by the developing unit 10, and the toner image on the photoconductor 4 is transferred to the sheet by the transfer unit 3 as described above. After the toner image is transferred to the sheet, the transfer residual toner is removed from the photoreceptor 4 by the cleaning unit 11, and the electrostatic latent image is uniformly discharged by the discharging unit 12, and is supplied to the next image forming cycle.

Here, as the charging means 8, for example, a charging device of a roller charging type having a charging roller is used, and a charging bias is applied to the charging roller from a high voltage power supply unit to uniformly charge the photosensitive member 4. As the transfer unit 3, for example, a transfer device of a roller transfer system having a transfer roller is used, and a transfer bias is applied to the transfer roller from a high-voltage power supply unit to transfer the toner image on the photoconductor 4 to a sheet.

The developing means 10 is applied with a developing bias from a high-voltage power supply and uses a two-component developing type developing device which develops an electrostatic latent image on the photoreceptor 4 with a two-component developer composed of, for example, toner and carrier. Can be The writing means 9 deflects a light beam modulated by an image signal from a light source composed of, for example, a semiconductor laser in a semiconductor laser unit, through a collimator lens by a polygon mirror 9a as a deflecting means, and via a fθ lens 9b, Writing means comprising an optical scanning device for rotating the polygon mirror 9a by the motor 9c and scanning the light beam by the polygon mirror 9a so that the light beam is repeatedly scanned on the photosensitive member 4 in the main scanning direction. Is used.

The photosensitive member 4 and its peripheral parts 8 to 10;
Reference numerals 3, 11, and 12 constitute an image forming unit for forming an image on a sheet. The image forming unit includes a temperature detection sensor 13 for detecting a temperature near the charging unit 8 and a toner concentration of a developer in the developing unit 10 (mixing ratio of toner and carrier) so that the electrophotographic process can be stably performed. ), And an image density sensor 15 for optically detecting the amount of toner adhering to the photoreceptor 4. Process conditions of each unit described later are detected based on detection signals of these sensors. May be corrected. Although not shown, a surface potential sensor for measuring a charged surface potential on the photoconductor 4 or a humidity sensor for detecting humidity may be mounted and used for correction control of process conditions of each unit. In addition, a cooling fan 22 as a cooling unit is installed inside the device and cools the inside of the device.

FIG. 1 shows a control block configuration of the image forming apparatus. The image forming apparatus receives an instruction and data transfer from an image data generating apparatus 16 usually called a controller, and controls each unit of the apparatus to perform an image forming operation. The image forming control unit 17 is configured to be programmable by a one-chip microcomputer and its peripheral circuits,
Sensor signals from a temperature detection sensor 13 as a temperature detection unit, an image density sensor 15 as an image density detection unit, and a toner density sensor 14 as a toner density detection unit are given as input signals, and the input signals are appropriately processed. By controlling the high voltage power supply section 18 from the high piezoelectric key section 18 to the charging roller of the charging means 8, the developing device 10, the transfer means 3
The charging bias, the developing bias, the transfer bias, and the like for the transfer roller and the like are controlled.

The drive control unit 19 controls the drive motors of the paper feed unit 1, the image forming unit, the fixing unit 5, and the paper discharge unit 6, and the image formation control unit 17 controls the drive control unit 19 to control the drive sequence. Perform control. The image forming control unit 17 stores the operation history of the image forming apparatus, the sensor signal history, and the like in the operation storage unit 2 in order to control the operation state of the image forming apparatus.
Record at 0.

The image writing control unit 21 as a control means for controlling the writing means (optical writing means) 9 performs a writing sequence control according to the image data. However, since this writing sequence control requires high-speed processing, The image writing control unit 21 is configured by hardware. The image data generating device 16 includes an interface that transfers image data to the image writing control unit 21 and a communication interface that receives a request for an image forming operation and a notification of an operation state.

FIG. 3 shows an example of the relationship between the temperature and the charging potential of the photosensitive member 4 when a constant charging bias is applied to the charging means 8 of the roller charging type in the image forming apparatus.
Since the charging means 8 of the roller charging type uses a high-resistance rubber material in order to perform a uniform discharge in a gap near the contact portion with the photoconductor 4, the resistance value increases at low temperatures and 4
Tends to decrease in the charging potential. When the charging potential of the photoconductor 4 fluctuates, the photoconductor 4 causes an increase in toner adhesion on a background portion and a change in the amount of toner adhesion on a halftone portion and a solid image portion, causing a change in image density and a change in image quality. In order to avoid this, a constant charging bias to the charging means 8 is set to AC.
There has been an attempt to superimpose a current to eliminate the influence of fluctuations in the discharge start condition, but this has led to an increase in cost.

FIG. 4 shows an example of the relationship between the temperature of the developing device 10 of the two-component developing system and the toner charge amount in the image forming apparatus. The toner which is agitated and thinned in the developing device 10 and used for developing the latent image is frictionally charged in the process. However, in the developing device 10, the charge amount of the toner tends to decrease as the temperature increases. Such a tendency varies depending on the toner formulation, agitation, and the structure of thinning, but it is generally difficult to make the tendency invariant with temperature.

When the amount of toner charge increases, the amount of toner adhered to the same development potential (total amount of charge that can be developed on the photoreceptor) decreases, so that the developing ability decreases and image quality changes due to image density fluctuation. I will. In order to compensate for this, it is necessary to adjust the toner concentration with respect to the carrier, increase the developing bias, and increase the developing potential. In order to avoid this, an attempt has been made in the past to reduce the influence of fluctuations in developing ability by superimposing an AC current on the developing bias.
This has led to increased costs.

FIG. 5 shows an example of the relationship between the temperature of the transfer device 3 of the roller transfer type in the image forming apparatus and the optimum transfer current. The roller transfer type transfer device 3 has the same component configuration as that of the roller charging type charging device 8, and reduces the toner transfer rate, transfer dust, and worming by the same resistance value change as the roller charging type charging device 8 described above. The optimum constant current control point to be satisfied fluctuates. For this reason, when the transfer is performed by the transfer device 3 using a constant current control power supply of a constant value in the high voltage power supply unit 18, a decrease in image density due to a decrease in the transfer rate and a deterioration in image quality due to occurrence of abnormal images such as dust and worms. Occurred in some cases.

FIG. 6 shows an example of the temperature inside the apparatus and the operating state of the cooling fan 22 when the image forming operation is continuously performed in the image forming apparatus. As mentioned above,
Since a change in the temperature of the image forming unit affects a change in the image quality, it is desirable that the temperature change in the apparatus is stable. If the fan 22 is not operated, the temperature rise in the apparatus becomes steep after the operation of the apparatus is started, which is disadvantageous for image quality fluctuation. Further, in a normal image forming apparatus, the cooling fan is often operated continuously. However, the temperature inside the apparatus can be gradually increased after the operation is started, but the temperature inside the apparatus still fluctuates. Therefore, if a temperature sensor for measuring the temperature in the device is provided and the on / off control of the fan 22 is performed based on the measured temperature of the temperature sensor, the initial temperature rises after the operation starts, and the fan 22 is turned on. /
The OFF control can maintain the temperature in the apparatus at a uniform temperature, which is advantageous for stabilizing image quality.

FIG. 7 shows an example of a change in temperature and image position in the image forming apparatus. The leading edge margin of the sheet is formed by the sheet re-feeding start timing of the registration unit 2 and the writing operation start timing of the writing unit 9 after the sheet temporarily stops in a state where the sheet end abuts on the registration unit 2. If there is slight thermal expansion of the pair of registration rollers 2 used in the registration means, the time required for the sheet to reach the transfer position after re-feeding is accelerated, and the leading edge margin of the sheet tends to slightly widen.

FIGS. 8 and 9 show an example of the execution timing of the correction mode in the image forming apparatus and an example of the correction effect before and after the image density is corrected as the correction mode. The temperature fluctuation described with reference to FIGS. 3 to 6 can be corrected to some extent by using a measured temperature if a temperature sensor is arranged in the apparatus. Image quality fluctuates comprehensively due to various causes such as the situation and humidity. Therefore, a process control mode in which an image density sensor is used to more accurately detect and correct the actual image fluctuation will be described.

The image density sensor 15 is a reflection-type optical sensor that reads the amount of toner adhering to the photosensitive member 4 just before the transfer position. In the image density correction mode (process control mode), the image forming control unit 17 controls each unit of the apparatus to perform an image forming operation without performing sheet feeding, and is stored in the image writing control unit 21 in advance. The small halftone mark or solid density mark data (test pattern data) is transferred to the writing means 9 to form a mark on the photosensitive member 4 by a normal image forming operation. 4, the reflection density value obtained from the image density sensor 15 is detected during the time when the toner image corresponding to the mark or the background portion without the toner image passes the measurement position of the image density sensor 15, and the actual image density is detected. Is estimated.

If necessary, the image forming control unit 17 controls the toner supply (target toner density control value) from the high voltage power supply unit 18 or the toner supply unit to the developing unit 10 based on the detection result, thereby controlling various biases. And toner density, and repeatedly determine whether the image density has changed to the target image density, and perform the above-described mark formation and detection, and control of various biases and toner density so that the image density becomes the target image density. Do. The image forming control unit 17 controls the toner replenishing unit based on the input signal from the toner density sensor 14 so that the toner density of the developer in the developing unit 10 becomes the toner density control target value. The bias is switched in the reverse transfer direction to the transfer unit 3 so that the mark does not stain the transfer unit 3, and the toner on the photoconductor 4 is collected by the cleaning unit 11.

By executing the above-described correction mode (image density correction mode), the amount of toner adhered to a solid portion is reduced, and the density of a halftone portion and the amount of toner adhered to a solid portion are optimized.

Since the execution of the correction mode involves an image forming operation, it is desirable to execute the correction mode effectively. FIG. 8
(A), continuous image formation (printing)
It is often performed before or after the operation or during the image forming operation.
If the execution of the correction mode is the timing A before the image forming operation, the correction effect is quickly reflected in the subsequent image formation, and the correction effect against the environmental temperature change or the like is large, but a slight correction is performed before the first image forming operation. Mode execution time occurs.

If the execution of the correction mode is the timing B during the continuous image forming operation, the effect of correcting the image quality fluctuation caused by the temperature rise in the apparatus due to the continuous image forming operation is great, and the correction mode is set between the sheets (each sheet). , The correction mode can be executed without requiring a special correction mode execution time. If the execution of the correction mode is after the continuous image forming operation, when the image forming operation is started again within a short period after the execution of the correction mode, the timing A
The correction effect can be obtained without executing the correction mode, and the correction mode execution time does not hinder the image forming operation.

FIG. 10 shows an example of an electrophotographic full-color image forming apparatus in which image forming units for four colors are superposed. This full-color image forming apparatus forms a color image in which four images, for example, yellow (hereinafter referred to as Y), magenta (hereinafter referred to as M), cyan (hereinafter referred to as C), and black (hereinafter referred to as K) are superimposed. Has four image forming units 23Y, 23M, 23C and 23K.

The four image forming units 23Y, 23M, 2
3C and 23K are photosensitive members 2 as image carriers, respectively.
4Y, 24M, 24C, 24K, and charging means 25Y,
5M, 25C, 25K and developing means 26Y, 26M, 2
6C, 26K, transfer means 27Y, 27M, 27C, 2
7K, cleaning means 28Y, 28M, 28C, 2
8K, static elimination means 29Y, 29M, 29C, 29K,
Writing means 30Y, 30M, 30C, 30K, and toner density sensors 68Y, 68M, 68C, 68K for detecting the toner density (mixing ratio of toner and carrier) of the developer in developing means 26Y, 26M, 26C, 26K, respectively. Having.

Writing means 30Y, 30M, 30C, 30
For K, an optical scanning device including a laser beam scanning device is used. This laser beam scanning device 30Y, 30M,
Reference numerals 30C and 30K denote a semiconductor laser unit having a semiconductor laser and a collimator lens as light sources, and polygon mirrors 31Y, 31M, 31C and 3C as deflection means.
1K, and fθ lenses 32Y, 32M, 32C, and 32K. Each laser beam scanning device 30Y, 30M, 3
At 0C and 30K, the light beam (laser beam) emitted from the semiconductor laser passes through a collimator lens, and is reflected by polygon mirrors 31Y, 31M, 31C, and 31C.
The deflection scan is performed by 31K, and the fθ lenses 32Y and 32
M, 32C, and 32K, and the photoconductors 24Y, 24M, and 2
Scan over 4C, 24K. Here, polygon mirror 3
1Y, 31M, 31C and 31K are respectively driven to rotate by polygon motors 49Y, 49M, 49C and 49K, and the transfer belt 33 is wound around rollers 34 and 35 and is driven to rotate by a transport motor.

Each of the image forming sections 23Y, 23M, 23C, 2
In 3K, the photoconductors 24Y, 24M, 24C, 24
K is rotationally driven by a driving mechanism (not shown), and is uniformly charged by charging means 25Y, 25M, 25C, and 25K.
At 0M, 30C, and 30K, an electrostatic latent image is formed by scanning with laser beams modulated in accordance with image signals of Y, M, C, and K, respectively.

The photosensitive members 24Y, 24M, 24C, 24
The electrostatic latent images on K are developed by developing means 26Y, 26M,
The toner images are developed at 6C and 26K to form toner images of Y, M, C and K colors. Further, a sheet made of a recording paper or the like as a recording medium is fed from a paper feeding unit 39 to a pair of registration rollers 69 as a registration unit, and temporarily stopped with its leading end abutting against the registration roller 69 to form an image. The re-conveyance is started by the registration roller 69 in conjunction with the operation.
The sheet whose re-conveyance has been started is conveyed by the transfer belt 33 as recording medium conveying means. The sheet on the transfer belt 33 includes photoconductors 24Y, 24M, 24C,
The toner images of each color on 24K are transferred to transfer means 27Y, 27M,
The full-color image is formed by being sequentially superimposed and transferred by 27C and 27K, the full-color toner image is fixed by the fixing unit 36, and the tray 38 is discharged by the sheet discharging unit 37.
Is discharged to Also, the photoconductors 24Y, 24M, 24C,
24K is a cleaning unit 28Y after the transfer of the toner image.
28M, 28C, and 28K remove the residual toner and the like, and remove the charge by the charge removing means 29Y, 29M, and 29K.
The charge is removed by C and 29K to prepare for the next operation.

Here, the charging means 25Y, 25M, 25
For C and 25K, for example, a roller charging type charging device having a charging roller is used, and a charging bias is applied to the charging roller from a high-voltage power supply unit, and the photoconductors 24Y, 24M, and 24K are charged.
C and 24K are uniformly charged. Transfer means 27Y, 27
For M, 27C, and 27K, for example, a roller transfer type transfer device having a transfer roller is used, and a transfer bias is applied to the transfer roller from a high-voltage power supply unit so that the photoconductors 24Y and 24K
The toner images on M, 24C and 24K are transferred to a sheet. A developing bias is applied to the developing units 26Y, 26M, 26C, and 26K from a high-voltage power supply unit, and the developing units 26Y, 26M, 26C, and 26K use, for example, a two-component developer including a toner and a carrier.
A two-component developing type developing device for developing electrostatic latent images on 24C and 24K is used. A cooling fan (not shown) as a cooling unit cools the inside of the device.

FIG. 11 shows a control block configuration of the full-color image forming apparatus. The full-color image forming apparatus performs a full-color image forming operation by controlling each unit of the apparatus in response to an instruction and data transfer of the image data generating apparatus 41 usually called a controller, similarly to the image forming apparatus. The image forming control unit 42 is configured to be programmable by a microcomputer and its peripheral circuit, and is configured to detect a temperature detection sensor 43 as a temperature detection unit, and image density and background density on the photoconductors 24Y, 24M, 24C, and 24K. An image density detection unit 44 including a plurality of image density sensors to be detected, and toner density sensors 68Y, 68M, 68
A sensor signal from a toner density detecting unit 45 composed of C and 68K and an image position detecting unit 51 including an image position sensor 40 are provided as input signals. The input signals are appropriately processed to control the high voltage power supply unit 46. By doing so, the charging rollers of the chargers 25Y, 25M, 25C, 25K, the developing devices 26Y, 26M, 26C, 26
K, a charging bias, a developing bias, a transfer bias, and the like for the transfer rollers of the transfer units 27Y, 27M, 27C, and 27K are controlled.

The drive control unit 47 controls the drive motors of the paper feed unit 39, the image forming units 23Y, 23M, 23C, 23K, the fixing unit 36, and the paper discharge unit 37, and the image formation control unit 42 controls the drive control unit. The drive sequence control is performed by controlling 46. The image forming control unit 42 records the operation history of the image forming apparatus, the sensor signal history, and the like in the operation storage unit 48 in order to control the operation state of the image forming apparatus.

Writing means (optical writing means) 30Y, 30
The image writing control unit 50 as control means for controlling M, 30C, and 30K performs writing sequence control according to image data of each color. However, since this writing sequence control requires high-speed processing, the image writing control unit 50 is configured by hardware. The image data generation device 41 includes an interface that transfers image data to the image writing control unit 50, and a communication interface that receives a request for an image forming operation and a notification of an operation state.

In this full-color image forming apparatus, the image position of each color is determined by the writing means 30Y, 30M, 30C, 30K.
And even if the image position shift between the colors is as small as 0.1 mm due to slight temperature fluctuations of the support positions of the photoconductors 24Y, 24M, 24C, and 24K, the color quality changes and contours occur at the image boundaries, resulting in poor image quality. Is impaired. Therefore, the data of the position detection pattern of each color stored in advance in the image writing control unit 50 is written into the writing means 30Y, 30M, 30.
C, 30K, and the photosensitive member 24 in a normal image forming operation.
A position detection pattern of each color is formed outside the image forming area on Y, 24M, 24C, and 24K, and this is transferred to transfer means 27Y,
The image is transferred to the transfer belt 33 by 27M, 27C, and 27K, and the alignment state is detected by the image position detection unit 51 including the image position sensor 40. The image formation control unit 42 detects a positional deviation between the position detection patterns of each color. Correction of image forming timing and writing means 30Y, 30M, 30C, 3
A position adjustment mode for performing correction and the like of the 0K mounting position by controlling the mounting position adjusting means is performed.

FIG. 12 shows the position detection patterns 52Y, 52M, 52C, 52K of the respective colors formed on the transfer belt 33.
And an example of the image position sensor 40. Position detection pattern 5
2Y, 52M, 52C, and 52K are created as line images of adjacent colors. The image forming control unit 42 obtains a mutual line image 52Y, based on an input signal from the image position detection unit 51 at the timing when the position detection patterns 52Y, 52M, 52C, 52K pass on the detection surface of the image position sensor 40 together with the transfer belt 33. The distance between 52M, 52C, and 52K is calculated, and the positional deviation between the colors is detected from the deviation between this distance and the preset distance between the color line images.

Here, the position detection patterns 52Y, 52
Since M, 52C and 52K use horizontal line images parallel to the width direction (main scanning direction) of the transfer belt 33, it is possible to detect misregistration of each color in the sub-scanning direction. As a method for detecting the positional deviation in the main scanning direction between the colors, a position detection pattern of a vertical line image formed in parallel with the sub-scanning direction on the transfer belt 33 from an output signal of the image position sensor 40 as a CCD is used. There is a method of calculating the main scanning position, or calculating the positional deviation in the main scanning direction between the colors from the passing time of a position detection pattern having an oblique boundary on the transfer belt 33 on the detection surface of the image position sensor 40.

FIG. 13 shows an example of the relative displacement between the temperature of the full-color image forming apparatus and each color. In the full-color image forming apparatus, the higher the temperature, the more the photoconductors 24Y and 24
Since the position between M, 24C and 24K is enlarged, the relative position of each color is expanded. The correction mode is generally performed in the same manner as the correction mode shown in FIG. 8 of the image forming apparatus, and the effect and problem of executing the correction mode at timings A, B, and C are the same as those of the image forming apparatus. That is, in the correction mode, the image forming control unit 42 controls each unit of the apparatus to perform the image forming operation of each color without performing sheet feeding, and the small image stored in the image writing control unit 50 in advance. Write means 30Y, 30M, 30 for halftone mark and solid density mark data (test pattern data).
C, 30K, and the photosensitive member 24 in a normal image forming operation.
Marks are formed on Y, 24M, 24C, and 24K, and the image forming control unit 42 determines the photoconductors 24Y, 24M, 24C, and 24K.
Estimating the actual image density by detecting the reflection density value obtained from the image density sensor during the time when the toner image corresponding to the mark on K or the background portion having no toner image passes the measurement position of the image density sensor. I do. Then, if necessary, the image forming control unit 42 determines from the detection result the high-voltage power supply unit 46 and the toner replenishment unit from the developing devices 26Y, 26M, 26C,
The toner supply to 6K (toner density control target value) is controlled to control various biases and toner density, and it is repeatedly determined whether or not the image density has changed to the target image density. The formation and detection of the mark and the control of various biases and the toner density are performed so as to be as appropriate. Each of the developing units 26Y, 26M, 26C, and 26K is supplied with toner from a toner supply unit. Image formation control unit 42
Are the toner density sensors 68Y and 68Y for each image forming unit.
Based on an input signal from the toner density detecting unit 45 composed of M, 68C and 68K,
The control is performed so that the toner density of the developer in 0, 26Y, 26M, 26C, and 26K becomes the toner density control target value.

FIG. 14 shows an example of a writing unit having two synchronization detecting sections and an image writing control section used in the above-mentioned image forming apparatus and full-color image forming apparatus. The writing means is provided with a light beam detecting means including sensors 53 and 54 as a synchronization detecting unit for detecting a light beam (laser beam) before an image forming start position in the main scanning direction. 32Y, 32M, 32C, 32K
The laser beam transmitted through is reflected by mirrors 55 and 56, condensed by lenses 67 and 58, incident on sensors 53 and 54, and detected.

The laser beam is applied to the polygon mirrors 9a and 31.
By scanning at Y, 31M, 31C, 31K,
The sensors 53 and 54 detect the laser beams, respectively, and output laser beam detection signals DETP1 and DETP2. These laser beam detection signals DETP1 and DETP2 are sent to the magnification correction control unit 59. The magnification correction controller 59 has a function of generating a clock PCLK that determines the number of rotations of the polygon motors 9c, 49Y, 49M, 49C, and 49K. Further, the magnification correction control section 59 controls the clock PC
The time difference between the output signal DETP1 of the sensor 53 and the output signal DETP2 of the sensor 54 is measured by utilizing the fact that the image magnification in the main scanning direction changes according to the frequency of LK, and the frequency of the clock PCLK is varied based on the result. Magnification correction function for correcting image magnification in the scanning direction (magnification correction means)
Also have.

The clock PCLK subjected to the image magnification correction in the main scanning direction by the variable frequency in the magnification correction control section 59 is sent to the polygon motor drive control section 60 as drive control means. Polygon motor 9 at a rotational speed corresponding to the frequency of
c, rotate 49Y, 49M, 49C, 49K. The write clock generator 61 outputs the write clock W
CLK is generated and sent to the phase synchronous clock generator 62.

The phase synchronization clock generator 62 generates a clock VCLK synchronized with the synchronization detection signal DETP1 from the sensor 53 based on the write clock WCLK from the write clock generator 59, and operates as a light beam generator driving unit. It is sent to the LD drive unit 63. The LD driving unit 63 is a semiconductor laser (LD) unit 6 in the laser beam scanning device.
4 turns on the semiconductor lasers in the phase-locked clock generator 6
2 is controlled in accordance with an image signal synchronized with the clock VCLK from the second. Therefore, a laser beam modulated in accordance with an image signal from the semiconductor laser 64 is emitted through the collimator lens, and this laser beam is deflected by the polygon mirrors 9a, 31Y, 31M, 31C, and 31K and fθ lenses fθ lenses 9b, 32Y, 32M, 32
C, 32K via photoconductors 4, 24Y, 24M, 24
C, 24K will be scanned.

Fθ lenses 9b, 32Y, 32M, 32
Optical elements such as C and 32K cause thermal expansion and a change in the refractive index due to temperature fluctuations, causing fluctuations in the imaging position. This is remarkable in plastic lenses which have been widely used at low cost in recent years. In particular, the scanning width changes significantly due to a change in the shape in the lens longitudinal direction, and the image magnification changes. In order to correct this, this example detects the change in magnification with high accuracy by comparing the light input timings of the two synchronous detection units 53 and 54, and slightly corrects the rotation speed of the polygon motor to thereby increase the scanning speed. Is kept constant.

FIG. 15 shows an image writing control unit according to the first embodiment of the present invention. The first embodiment is an embodiment of the invention according to the first and second aspects of the present invention. FIG. 14 is a diagram showing a writing unit having two synchronization detecting units as shown in FIG. In the image forming apparatus shown in FIGS. 1 and 2, an image writing control unit as shown in FIG. 15 is used. The present inventor has pointed out that the change in the light input timing of the synchronization detection unit caused by the temperature fluctuation can be used not only as a signal for correcting the scanning speed but also as an index for detecting the temperature of an optical element represented by a lens. We paid attention to.

Therefore, in the first embodiment, the magnification correction control unit 5
9a has a function of generating a clock PCLK for determining the number of rotations of the polygon motor 9c.
The output signal DETP1 of the sensor 53 and the sensor 5
4 as well as a magnification correction function (magnification correction means) for correcting the image magnification in the main scanning direction by varying the frequency of the clock PCLK based on the measured time difference from the output signal DETP2. A time difference between the signal DETP1 and the output signal DETP2 of the sensor 54 is measured, a magnification correction value is calculated based on the time difference, and the magnification correction value signal EXLEV is output to the variation calculator 65.

The change amount calculation section 65 includes a magnification correction control section 59.
The magnification correction value signal EXLEV from “a” is appropriately stored in the magnification correction value storage unit 66 as a storage unit, and the magnification correction value signal EXLEV stored in the magnification correction value storage unit 66 and the current magnification correction control unit 59a are output. Magnification correction value signal EX
The amount of change is calculated from the LEV, and the calculation result is output via a correction signal output unit 67 to OPTT as a substitute index for temperature.
It is generated as an HM signal and output to the image formation control unit 17. The image formation control unit 17 utilizes the OPTTHM signal from the correction signal output unit 67 instead of the input signal from the temperature detection unit 13 (or utilizes the OPTTHM signal to improve the accuracy of the temperature detection unit 13). Control conditions.
For this reason, it is possible to better correct the image forming condition with respect to the temperature fluctuation of each unit.

The second embodiment of the present invention is an embodiment of the first and second aspects of the present invention, and is a part of the image writing control part and the image writing control part provided with two synchronization detecting parts as shown in FIG. In the full-color image forming apparatus shown in FIGS. 10 and 11 provided with the image writing control unit, an image writing control unit as shown in FIG. In the second embodiment, a magnification correction control unit 59a, a change amount calculation unit 65, and a magnification correction value storage unit 6 are provided for each of the image forming units 23Y, 23M, 23C, and 23K.
6. A correction signal output unit 67 is provided.

Each of the image forming units 23Y, 23M, 23C, 2
In 3K, the magnification correction control unit 59a has a function of generating a clock PCLK that determines the rotation speed of each of the polygon motors 49Y, 49M, 49C, and 49K, and the image magnification in the main scanning direction changes depending on the frequency of the clock PCLK. And the output signal DET of the sensor 53
The time difference between P1 and the output signal DETP2 of the sensor 54 is measured, and the frequency of the clock PCLK is varied based on the result to correct the image magnification in the main scanning direction. The OPTTHM signal from the correction signal output unit 67 is output to the image forming control unit 42. The image forming control unit 42 includes the correction signal output unit 6
7 is used in place of the input signal from the temperature detection unit 43 instead of the input signal from the temperature detection unit 43 (or the OPTTHM signal is used to improve the accuracy of the temperature detection unit 43), and the image forming conditions are controlled according to the magnification correction value signal EXLEV. I do. For this reason,
It is possible to better correct the image forming conditions with respect to the temperature fluctuation of each unit.

In the first and second embodiments, the magnification correction value signal E
Calibration between the change amount of the XLEV and the actual temperature may be fixed in advance using a conversion table or the like if there is no variation due to the manufacturing method. The conversion table or the like may be calibrated by measuring the change amount of the magnification correction value signal EXLEV below. Further, the present invention is applied for the purpose of detecting the temperature around the writing means when another temperature sensor such as a thermistor for measuring the temperature of the fixing means or a thermistor for measuring the temperature of the charging means is provided in the apparatus. In such a case, the apparatus itself may calibrate the change amount of the magnification correction value signal EXLEV and the actual temperature in the uniform temperature state.

Change amount calculation section 65, magnification correction value storage section 6
6. The correction signal output unit 67 includes the image formation control units 17 and 42.
Can be realized by software instead of the operation storage units 20 and 48, so that the magnification correction value signal EXLEV is directly input to the image formation control units 17 and 42 and the subsequent processing is realized by software. May be configured. A specific method of correcting the image forming conditions in the first and second embodiments will be described below.

The image forming control units 17 and 42 determine, for each image forming unit, the temperature detection result based on the magnification correction value signal EXLEV (OPTTHM signal from the correction signal output unit 67).
A built-in magnification correction value signal E as shown below
Charging bias power supply output control that holds the relationship between the XLEV and the applied charging bias of the charging bias power supply (power supply for applying a charging bias to each of the charging units 8, 25Y, 25M, 25C, and 25K) in the high-voltage power supply units 18 and 46 Based on the table, the charging bias power supply in the high voltage power supply sections 18 and 46 is controlled according to the magnification correction value signal EXLEV.

[0068] By correcting the charging bias in this manner, the photoconductors 4, 24Y, and 24, which are fixed at about 800V, are fixed.
M, 24C and 24K charged states can be realized. Charging means 8, 25Y, 25M, 25C, 25K and writing means 9,
Since 30Y, 30M, 30C, and 30K act on the photoconductors 4, 24Y, 24M, 24C, and 24K adjacently,
The positions are relatively close to each other, and the temperatures match well, which is preferable.

According to the first and second embodiments, one or a plurality of photosensitive members 4, 24Y and 24 as image carriers are scanned by scanning a light beam modulated in accordance with an image signal.
In an electrophotographic image forming apparatus for forming images on M, 24C and 24K, polygon mirrors 9a and 31Y as deflection means for deflecting the light beam in the main scanning direction are provided.
31M, 31C, 31K and the deflecting means 9a, 31
Sensors 53 and 54 as two light beam detecting means for detecting the light beams deflected by Y, 31M, 31C and 31K at two positions on the main scanning line, and one of the two light beam detecting means 53 and 54 The magnification correction control unit 59 as a means for measuring the time difference from the detection of the light beam by the other to the detection of the light beam by the other of the two light beam detection means 53 and 54, and the time difference measured by the means 59 A change amount calculation unit 65, a magnification correction value storage unit 66, a correction signal output unit 67,
Since the image forming control units 17 and 42 are provided, it is possible to effectively detect a change in image quality mainly due to a rise in temperature based on thermal expansion or a change in thermal refractive index of the optical element, and correct image forming conditions. Thus, stable image quality can be obtained without a large increase in cost.

According to the first and second embodiments, the correction of the image forming conditions is performed by the image carriers 4, 24Y, 24M, and 24M.
C, charging means for charging 24K, 25Y, 25M, 2
Since the correction of the bias applied to 5C and 25K is performed, the change in the charging potential caused by the change in the resistance value of the charging member mainly due to the temperature rise is effectively detected by the thermal expansion and the change in the thermal refractive index of the optical element. The charging bias can be corrected, and stable image quality can be obtained.

The third embodiment of the present invention is an embodiment of the first and third aspects of the present invention, in which a writing unit having two synchronization detecting units as shown in FIG. In the image forming apparatus shown in FIGS. 1 and 2 provided above, an image writing control unit as shown in FIG. 15 is used, and a magnification correction control unit 59a, a change amount calculation unit 65,
A magnification correction value storage unit 66 and a correction signal output unit 67 are provided.

Embodiment 4 of the present invention is an embodiment of the present invention according to claims 1 and 3, in which a writing means having two synchronization detecting sections as shown in FIG. In the full-color image forming apparatus shown in FIGS. 10 and 11 provided above, an image writing control unit as shown in FIG. 15 is used, and each image forming unit 23Y, 23
A magnification correction control section 59a, a change amount calculation section 65, a magnification correction value storage section 66, and a correction signal output section 67 are provided for each of M, 23C, and 23K.

In the third and fourth embodiments, the image forming control unit 17
Reference numeral 42 denotes a magnification correction value signal EXLEV for each image forming unit.
Temperature detection result (OPT from correction signal output unit 67)
From the THM signal, the following built-in magnification correction value signal EXLEV and a developing bias power supply (developing means 10, 26Y, 26M,
26C and 26K), based on a developing bias power output control table having a relationship with each applied developing bias.
Each applied developing bias of the developing bias power supply in 46 is controlled in accordance with the magnification correction value signal EXLEV.

[0074] By correcting the developing bias in this manner, the toner adhesion amount on the photoconductors 4, 24Y, 24M, 24C, and 24K can be made close to a constant amount. Photoconductor 4, 2
4Y, 24M, 24C, 24K and writing means 9, 30
Y, 30M, 30C, and 30K are adjacent to photoconductors 4, 2
Since it acts on 4Y, 24M, 24C, and 24K, it has a relatively close positional relationship, and the temperature is well matched, which is preferable.

According to the third and fourth embodiments, the image forming conditions are corrected by the image carriers 4, 24Y, 24M, 24M.
C, developing means 10, 26Y for developing a latent image on 24K,
Since the correction of the bias applied to 26M, 26C, and 26K is performed, a change in the toner charging ability of the developing member mainly due to a rise in temperature is effectively detected by the thermal expansion of the optical element or a change in the thermal refractive index, and the developing bias is detected. Can be corrected, and stable image quality can be obtained.

The fifth embodiment of the present invention is an embodiment of the first and fourth aspects of the present invention, in which a writing unit having two synchronization detecting units as shown in FIG. In the image forming apparatus shown in FIGS. 1 and 2 provided above, an image writing control unit as shown in FIG. 15 is used, and a magnification correction control unit 59a, a change amount calculation unit 65,
A magnification correction value storage unit 66 and a correction signal output unit 67 are provided.

The sixth embodiment of the present invention is an embodiment of the first and fourth aspects of the present invention, in which a writing unit having two synchronization detecting units as shown in FIG. In the full-color image forming apparatus shown in FIGS. 10 and 11 provided above, an image writing control unit as shown in FIG. 15 is used, and each image forming unit 23Y, 23
A magnification correction control section 59a, a change amount calculation section 65, a magnification correction value storage section 66, and a correction signal output section 67 are provided for each of M, 23C, and 23K.

In the fifth and sixth embodiments, the image forming control unit 17
Reference numeral 42 denotes a magnification correction value signal EXLEV for each image forming unit.
Temperature detection result (OPT from correction signal output unit 67)
THM signal), and a built-in magnification correction value signal EXLEV and developing means 10, 26Y,
The developing means 10, 26Y, 26M, 26C, 26C, 26K, 26K, 26C, and 26K are based on a toner concentration control target value table having a relationship with the toner concentration control target value of the developer in the developer.
The toner density control target value of the developer within 6K is corrected according to the magnification correction value signal EXLEV to perform toner density control.

[0079] Here, the developing means 10, 26Y, 26M, 26C, 26
K is supplied with toner from the toner supply unit. The image forming control units 17 and 42 are provided for each image forming unit based on input signals from the toner density detecting unit 14 including a toner density sensor and the toner density detecting unit 45 including toner concentration sensors 68Y, 68M, 68C and 68K. And the toner replenishing section is connected to the developing means 10, 26Y, 26M, 26C, 26K.
The control is performed so that the toner concentration of the developer inside the toner becomes the target value of the toner concentration control.

As described above, the toner density control is performed by correcting the target value of the toner density control.
The toner adhesion amounts on 24Y, 24M, 24C, and 24K can be made closer to a fixed amount. Developing means 10, 26Y,
26M, 26C, 26K and writing means 9, 30Y, 30
M, 30C, and 30K are adjacent to photoconductors 4, 24Y, 2
Since it acts on 4M, 24C, and 24K, it has a relatively close positional relationship, and the temperature is well matched, which is preferable. Further, as described above, by performing the correction of the developing bias and the correction of the target value of the toner density control in combination, more appropriate image density can be maintained, and the accuracy is expected to be improved, which is more preferable. In this case, each table needs to be set differently from the above-described embodiment, in consideration of the synergistic effect.

According to the fifth and sixth embodiments, the image forming conditions are corrected by the image carriers 4, 24Y, 24M and 24M.
C, developing means 10, 26Y for developing a latent image on 24K,
Since correction of the toner density control value (target value of toner density control) for 26M, 26C, and 26K is performed, the fluctuation of the toner charging ability of the developing member mainly due to the temperature rise is effected by the thermal expansion and thermal refractive index change of the optical element. And the toner density used for development can be corrected, and stable image quality can be obtained.

The seventh embodiment of the present invention is an embodiment of the present invention according to the first and fifth aspects, wherein a writing unit having two synchronization detecting units as shown in FIG. In the image forming apparatus shown in FIGS. 1 and 2 provided above, an image writing control unit as shown in FIG. 15 is used, and a magnification correction control unit 59a, a change amount calculation unit 65,
A magnification correction value storage unit 66 and a correction signal output unit 67 are provided.

Embodiment 8 of the present invention is an embodiment of the present invention according to claims 1 and 5, in which a writing means having two synchronization detecting sections as shown in FIG. In the full-color image forming apparatus shown in FIGS. 10 and 11 provided above, an image writing control unit as shown in FIG. 15 is used, and each image forming unit 23Y, 23
A magnification correction control section 59a, a change amount calculation section 65, a magnification correction value storage section 66, and a correction signal output section 67 are provided for each of M, 23C, and 23K.

In the seventh and eighth embodiments, the image forming control unit 17
Reference numeral 42 denotes a magnification correction value signal EXLEV for each image forming unit.
Temperature detection result (OPT from correction signal output unit 67)
From the THM signal), a magnification correction value signal EXLEV incorporated in advance as shown below and a transfer bias power supply (transfer means 3, 27Y, 27M,
Power supply for applying transfer bias to each of 7C and 27K)
, Based on the transfer bias power supply output control table having the relationship with each applied transfer bias.
The transfer bias applied by the transfer bias power supply is controlled in accordance with the magnification correction value signal EXLEV.

[0085] By correcting the transfer bias in this way, it is possible to make the dust, the worm, and the transfer rate in the image transfer close to the optimum. Since the transfer condition does not fluctuate very sensitively to the temperature, a suitable effect can be obtained to some extent by the rough prediction control from the temperature in the vicinity of the writing means, which is preferable.

According to the seventh and eighth embodiments, the correction of the image forming conditions is performed by the transfer means 3, 27Y, 2Y for transferring the image.
Since the bias applied to 7M, 27C, and 27K is corrected, a change in transfer performance caused mainly by a change in the resistance value of the transfer member due to a rise in temperature can be effectively detected by thermal expansion or a change in thermal refractive index of the optical element. As a result, the transfer bias can be corrected, and stable image quality can be obtained.

A ninth embodiment of the present invention is an embodiment of the first and sixth aspects of the present invention, in which a writing unit having two synchronization detecting units as shown in FIG. In the image forming apparatus shown in FIGS. 1 and 2 provided above, an image writing control unit as shown in FIG. 15 is used, and a magnification correction control unit 59a, a change amount calculation unit 65,
A magnification correction value storage unit 66 and a correction signal output unit 67 are provided.

The tenth embodiment of the present invention is an embodiment of the first and sixth aspects of the present invention, in which a writing unit having two synchronization detecting units as shown in FIG. In the full-color image forming apparatus shown in FIGS. 10 and 11, an image writing control unit as shown in FIG. 15 is used.
A magnification correction control unit 59a, a change amount calculation unit 65, a magnification correction value storage unit 66, and a correction signal output unit 67 are provided for each of 3M, 23C, and 23K.

In the ninth and tenth embodiments, the image forming control unit 1
Reference numerals 7 and 42 denote a built-in magnification correction value signal EXLEV and a fan output (the cooling fan 22 and the like) as described below from the temperature detection result (OPTTHM signal from the correction signal output unit 67) based on the magnification correction value signal EXLEV. Example 1
(The output for turning on / off the cooling fan within 0) based on the cooling means control table, when the temperature detection result is higher than the temperature reference value, the cooling fan 22 and the cooling fan in the tenth embodiment are turned on. Then, the cooling unit is controlled to turn off the cooling fan 22 and the cooling fan in the tenth embodiment when the temperature detection result is lower than the temperature reference value.

[0090] By performing such cooling unit control, the temperature around the image forming unit during operation can be made substantially constant. In the ninth and tenth embodiments, the on / off control of the cooling fan is performed. However, the rotation speed of the cooling fan is finely controlled according to the temperature, and the cooling fan is controlled in conjunction with the operation state to further stabilize. May be calibrated as follows.

According to the ninth and tenth embodiments, the correction of the image forming conditions is performed by correcting the cooling capacity of the cooling fan 22 as the cooling means for cooling the apparatus and the cooling capacity of the cooling fan in the tenth embodiment. The temperature rise in the device due to the above can be effectively detected by the thermal expansion and the change in the thermal refractive index of the optical element, and the ability of the cooling means can be corrected, and the temperature in the device can be stabilized and stabilized. Image quality can be obtained.

An eleventh embodiment of the present invention is an embodiment of the first and seventh aspects of the present invention, in which a writing unit having two synchronization detecting units as shown in FIG. In the image forming apparatus shown in FIGS.
An image writing control unit as shown in FIG. 15 is used, and a magnification correction control unit 59a and a change amount calculation unit 6 as in the first embodiment.
5, a magnification correction value storage unit 66 and a correction signal output unit 67 are provided.

The twelfth embodiment of the present invention is an embodiment of the first and seventh aspects of the present invention, in which a writing unit having two synchronization detecting units as shown in FIG. In the full-color image forming apparatus shown in FIGS. 10 and 11, an image writing control unit as shown in FIG. 15 is used.
A magnification correction control unit 59a, a change amount calculation unit 65, a magnification correction value storage unit 66, and a correction signal output unit 67 are provided for each of 3M, 23C, and 23K.

In Embodiments 11 and 12, the image forming control unit 1
Reference numerals 7 and 42 denote the relationship between the built-in magnification correction value signal EXLEV and the driving speed of the registration means as shown below from the temperature detection result (OPTTHM signal from the correction signal output unit 67) by the magnification correction value signal EXLEV. The speed control of the driving means for rotating and driving the registration rollers 2 and 69 as the registration means is performed in accordance with the magnification correction value signal EXLEV based on the registration means driving speed control table which holds the speed control of the registration means 2 and 69. I do.

[0095] By controlling the driving speed of the registration unit, the margin at the leading end of the sheet can be made substantially constant. Embodiments 11 and 12 are examples in which the linear velocity change due to thermal expansion of the registration rollers 2 and 69 is corrected. In an image forming apparatus in which the relationship between the temperature and the writing position fluctuation of the writing unit can be quantified in advance, the left end is used. Similarly, the variation in the writing position of the writing means may be corrected according to the temperature based on the temperature detection result by the magnification correction value signal EXLEV for the margin variation.

According to the eleventh and twelfth embodiments, the correction of the image forming conditions is performed by the image carriers 4, 24Y, 24M, and 2M.
Writing means 9, 30Y, 3 for writing to 4C, 24K
Since the correction of the writing image position of 0M, 30C, and 30K is performed, the fluctuation of the light beam path of the writing unit due to the temperature rise and the fluctuation of the image position due to the thermal deformation of the structural member are mainly determined by the thermal expansion and thermal refraction of the optical element. The image position can be corrected by effectively detecting the change in the rate, and stable image quality can be obtained.

The thirteenth embodiment of the present invention is an embodiment of the first and eighth aspects of the present invention, in which a writing unit having two synchronization detecting units as shown in FIG. In the image forming apparatus shown in FIGS. 10 and 11 provided above, an image writing control unit as shown in FIG. 15 is used,
As in the second embodiment, each of the image forming units 23Y, 23M, 23
For each of C and 23K, a magnification correction control section 59a, a change amount calculation section 65, a magnification correction value storage section 66, and a correction signal output section 67 are provided.

In the thirteenth embodiment, the image forming control unit 42
For each image forming unit, a built-in magnification correction value signal EXLE is obtained from a temperature detection result (OPTTHM signal from the correction signal output unit 67) based on the magnification correction value signal EXLEV.
V and the writing means 30Y, 30C, 30K, based on the image writing timing control table holding the relationship between the image writing timing of the writing means 30Y, 30M, 30C, 30K.
The image writing timings of M, 30C, and 30K are corrected according to the magnification correction value signal EXLEV.

The relationship between the magnification correction value signal EXLEV and the image writing timing of the Y color in the sub-scanning direction is, for example, as follows.

EXLEV (° C.) Image writing timing (μm) 0 to 10 +30 10 to 15 +20 15 to 200 0 20 to 25 -30 25 to 30 -70 30 to 40 -120 Example 13 is an image writing in the sub-scanning direction. In this example, the timing is corrected, but the image writing timing such as the main scanning direction and the skew may be corrected. By performing such correction of the image writing timing, it is possible to reduce the image position deviation in the sub-scanning direction. Example 1
In No. 3, since the image forming unit (excluding the writing unit) of each color is adjacent to the writing unit, it is possible to detect the temperature in the vicinity of the image forming unit (excluding the writing unit) of each color, and the temperature becomes uneven inside the apparatus. It is also preferable that appropriate image writing timing control corresponding to each color is performed even when the image is generated.

According to the thirteenth embodiment, the correction of the image forming conditions is performed by a plurality of image carriers 24Y, 24M, 24C,
A plurality of writing means 30Y, 30M for writing to 4K,
Since the correction of the relative written image position of 30C and 30K is performed, the image position of each of the plurality of image forming units is mainly changed due to the change in the optical path of the light beam of the writing unit or the thermal deformation of the structural member due to the temperature rise. Can effectively detect the relative color shift and impair the image quality due to the thermal expansion and thermal refractive index change of the optical element, and correct the relative image position of each color, and achieve stable image quality. Obtainable.

Embodiments 14 and 15 of the present invention
10 is an embodiment of the invention according to FIG. As described with reference to FIGS. 8 to 13, more accurate correction can be expected by performing a correction mode involving an image forming operation for measuring an image density value and an image position deviation value of each color. However, during the execution of the image forming operation for the correction, the normal image forming operation cannot be performed and the productivity is reduced. Therefore, the frequency of the image forming operation for the correction is preferably low. Therefore, in Embodiments 14 and 15, in the image forming apparatus shown in FIGS. 1 and 2 and in the full-color image forming apparatuses shown in FIGS. 10 and 11, as shown in FIG.
Determines from the temperature detection result (OPTTHM signal from the correction signal output unit 67) based on the magnification correction value signal EXLEV whether or not a temperature change exceeding a certain level has occurred, that is, (EXLEV value at the time of executing the previous correction mode) -Current EX
(LEV value)> 5 (° C.)
(EXLEV value at the time of execution of the last correction mode-current EX
If the absolute value of (LEV value)> 5 (° C.), the correction mode (process control mode) involving the image forming operation is executed as described above, and the EXLEV value at this time is stored.

As described above, since the correction mode is performed only when the temperature fluctuation is predicted to be equal to or more than the predetermined value, the unnecessary correction mode is not executed during the period when image formation is performed in a stable environment where correction is not required. Does not occur. Of course, the calibration may be performed so that the correction mode is also executed when detecting the output fluctuation of another sensor or predicting the temporal change due to the normal image forming operation time, in addition to the temperature fluctuation prediction. . In order to avoid sudden start of the correction mode, the timing for determining whether or not to start the execution of the correction mode is set to a timing that does not hinder the normal image forming operation as shown in A, B, and C of FIG. Is also good.

Further, since the correction mode is set to the process control mode, the overall fluctuation of the image forming section caused by the temperature fluctuation can be compared with the case where the charging means, the developing means, the transfer means and the like are individually and predictively corrected. As a result, optimum conditions can be selected from various image forming conditions, and the image density on the photoreceptor can be measured and confirmed, so that stable image formation can be performed more reliably.

According to the fourteenth and fifteenth embodiments, since the correction of the image forming conditions is performed in the correction mode, the fluctuation of the image quality mainly caused by the temperature rise is caused by the thermal expansion or the thermal refractive index change of the optical element. The frequency of execution of the correction mode is reduced by effectively detecting and determining whether or not it is necessary to execute at least the correction mode accompanying the image quality variation, and executing the correction mode appropriately when it is determined that the correction mode is necessary. However, stable image quality can be obtained.

Further, according to the fourteenth and fifteenth embodiments, since the correction mode is a process control mode in which a test pattern is created and read, the correction can be performed accurately, and the image quality deterioration caused by the density fluctuation can be achieved. Can be appropriately eliminated, and stable image quality can be obtained even when the frequency of executing the correction mode is reduced.

The sixteenth embodiment of the present invention is an embodiment of the present invention according to the eleventh embodiment, wherein the correction mode is the alignment mode in the fifteenth embodiment. Do. For this reason, the image forming units 23Y, 23M, 23C, 2
The relative position fluctuation of 3K is calculated using the magnification correction value signal EXLEV.
Temperature detection result (OPT from correction signal output unit 67)
Compared to the case of predictively correcting from the THM signal), the image position shift when the respective colors are superimposed can be measured and confirmed more reliably, and the image in which the position shift does not occur more reliably and stably can be confirmed. The formation can take place.

According to the sixteenth embodiment, in the fifteenth embodiment, the correction mode is different from that of the plural image carriers 4, 24Y, 2Y.
Since this is a positioning mode in which a detection pattern for detecting the position of an image created using 4M, 24C, and 24K is created and read, correction can be performed with high accuracy, and image quality degradation due to misalignment can be achieved. Can be appropriately eliminated, and stable image quality can be obtained even when the frequency of executing the correction mode is reduced.

The first to fifteenth embodiments are embodiments of the invention according to the twelfth aspect, and use two sensors 53 and 54 as a synchronous detecting means and a magnification correction control unit 59 for correcting image forming conditions and correcting magnification. Can be made common, and a more stable image forming apparatus can be realized without much cost increase. According to the fourteenth and fifteenth embodiments, since the correction mode is the process control mode, the overall variation of the image forming unit due to the temperature variation can be individually controlled by the charging unit, the developing unit, the transfer unit, and the like. Compared to the case of predictive correction, the optimum condition can be selected from various image forming conditions, and the image density on the photoreceptor can be measured and confirmed. Image formation can be performed.

According to Embodiments 1 to 15, the image carriers 4, 24Y, 24M, and
Since the magnification of the image on 24C and 24K is also corrected,
Changes in image quality mainly caused by temperature rise can be effectively detected by thermal expansion and thermal refractive index changes of optical elements, and magnification changes caused by optical element fluctuations can be corrected together, resulting in extra cost increase. , And stable image quality can be obtained.

The seventeenth and eighteenth embodiments of the present invention are as follows.
It is an Example of the invention which concerns on. In Embodiments 17 and 18, in Embodiments 14 and 15, the image forming control units 17 and 42 respectively provide the magnifications for each image forming unit during execution of the correction mode (process control mode) as shown in FIG. The temperature detection result (OPTTHM signal from the correction signal output unit 67) based on the correction value signal EXLEV and the photoconductors 4, 24Y, and 24 detected by the image density sensor
M, 24C, the image density on 24K and the operation recording unit 20,
Record at 48.

The image formation control units 17 and 42 provide, for each image formation unit, a temperature detection result based on the magnification correction value signal EXLEV recorded during execution of the process control mode (OPTTHM signal from the correction signal output unit 67: scanning time change amount).
And the photoconductors 4, 24Y detected by the image density sensor,
After the image density (image density change amount) on 24M, 24C, and 24K is collected to the extent that it can be correlated as shown in the graph, the process control mode is not performed, and
The learning result (the temperature detection result based on the magnification correction value signal EXLEV recorded in the operation recording units 20 and 48 (the correction signal output unit 6
7) and the image density on the photoconductors 4, 24Y, 24M, 24C, and 24K detected by the image density sensor) and the magnification correction value signal EXLEV from the correction signal output unit 67. Based on the temperature detection result (OPTTHM signal from the correction signal output unit 67), image forming conditions are predictively controlled according to the magnification correction value signal EXLEV.

More specifically, the image forming control units 17 and 42
The high-voltage power supply units 18 and 46 and the toner density control target value are obtained from the temperature detection result (OPTTHM signal from the correction signal output unit 67) based on the magnification correction value signal EXLEV from the correction signal output unit 67 based on the learning result. By controlling in accordance with the magnification correction value signal EXLEV, correction of the developing bias and correction of the toner density capable of controlling the image density are performed.

With such a configuration, it is possible to reduce the error in the control table caused by the variation between the image forming apparatuses and the installation environment of the image forming apparatuses in a learning manner. The method of performing the learning is not limited to only the linear approximation of the input and output as in the seventeenth and eighteenth embodiments. For example, the value of the control table is gradually changed.
Various methods can be selected. In addition, the image formation control units 17 and 42 detect the temperature based on the magnification correction value signal EXLEV (OPTTHM from the correction signal output unit 67).
Signal), various factors such as the output of other sensors, the operating state of the device, and the variation over time, etc., are comprehensively used as input signals to control the image forming conditions in a learning manner. It is possible and suitable.

According to the seventeenth and eighteenth embodiments, the operation recording units 20, 48 as storage means for storing the fluctuation of the time difference.
Since the correction method is learned based on the stored contents of the storage means 20 and 48, an appropriate correction method due to the variation between devices and the environment of the installation location is executed when the correction mode is executed. The result and the amount of change in the scanning time at that time are recorded, and a correction value based on the optimal amount of change for learning is predictively obtained to perform correction, thereby achieving stable image quality even when the frequency of executing the correction mode is reduced. Can be obtained.

The invention according to claim 13 can be applied to the first to thirteenth and sixteenth embodiments. Also,
The present invention is not limited to the above embodiment, and can be applied to other electrophotographic image forming apparatuses.

[0117]

As described above, according to the first aspect of the present invention, stable image quality can be obtained without a large increase in cost. According to the second aspect, stable image quality can be obtained. According to the third aspect, stable image quality can be obtained. According to the fourth aspect, stable image quality can be obtained.

According to the invention of claim 5, stable image quality can be obtained. According to the invention of claim 6, stable image quality can be obtained. According to the invention according to claim 7, stable image quality can be obtained. According to the invention of claim 8, stable image quality can be obtained. According to the ninth aspect, a stable image quality can be obtained even when the frequency of executing the correction mode is reduced.

According to the tenth aspect, a stable image quality can be obtained even if the frequency of executing the correction mode is reduced. According to the eleventh aspect, a stable image quality can be obtained even when the frequency of executing the correction mode is reduced. According to the twelfth aspect, a stable image quality can be obtained without particularly requiring a special cost increase. According to the thirteenth aspect, a stable image quality can be obtained even when the frequency of executing the correction mode is reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a control block configuration of an example of an electrophotographic image forming apparatus.

FIG. 2 is a cross-sectional view illustrating an example of the image forming apparatus.

FIG. 3 is a characteristic diagram illustrating an example of a relationship between a temperature and a charging potential of a photoconductor when a constant charging bias is applied to a charging unit of a roller charging type in the image forming apparatus.

FIG. 4 is a characteristic diagram illustrating an example of a relationship between a temperature of a two-component developing type developing device and a toner charge amount in the image forming apparatus.

FIG. 5 is a characteristic diagram illustrating an example of a relationship between a temperature of a transfer device of a roller transfer type in the image forming apparatus and an optimum transfer current.

FIG. 6 is a characteristic diagram illustrating an example of an internal temperature of the apparatus and an operation state of a cooling fan when image forming operations are continuously performed in the image forming apparatus.

FIG. 7 is a characteristic diagram illustrating an example of a change in temperature and image position in the image forming apparatus.

FIG. 8 is a timing chart illustrating an example of execution timing of a correction mode in the image forming apparatus.

FIG. 9 is a characteristic diagram illustrating an example of a correction effect before and after performing image density correction as a correction mode in the image forming apparatus.

FIG. 10 is a cross-sectional view illustrating an example of a full-color image forming apparatus in which image forming units for four colors are arranged in a superimposed manner.

FIG. 11 is a block diagram showing a control block configuration of the full-color image forming apparatus.

FIG. 12 is a top view illustrating an example of a position detection pattern of each color and an image position sensor formed on a transfer belt of the full-color image forming apparatus.

FIG. 13 is a characteristic diagram illustrating an example of a relative positional shift between a temperature and each color of the full-color image forming apparatus.

FIG. 14 is a diagram illustrating an example of a writing unit including two synchronization detection units and an image writing control unit used in the image forming apparatus and the full-color image forming apparatus.

FIG. 15 is a block diagram illustrating an image writing control unit according to the first embodiment of the present invention.

FIG. 16 is a diagram showing learning results of Examples 17 and 18 of the present invention.

FIG. 17 is a flowchart illustrating a processing flow of an image forming control unit according to Embodiments 14 and 15 of the present invention.

[Explanation of symbols]

3, 27Y, 27M, 27C, 27K Transfer means 4, 24Y, 24M, 24C, 24K Photoconductor 9, 30Y, 30M, 30C, 30K Writing means 9a, 31Y, 31M, 31C, 31K Polygon mirror 10, 26Y, 26M, 26C, 26K Developing means 17, 42 Image formation control unit 20, 48 Operation recording unit 22 Cooling fan 53, 54 Sensor 59 Magnification correction control unit 65 Change amount calculation unit 66 Magnification correction value storage unit 67 Correction signal output unit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiya Sato 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Inventor Kazuyuki Shimada 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Mitsuo Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo ・ Ricoh Co., Ltd. (72) Inventor Yuhisa Maeda 1-3-6, Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 2C362 BA50 BA52 BB30 BB32 BB34 BB37 BB39 BB40 BB42 BB43 CA22 CA39 CB73 CB80 DA32 2H045 AA01 BA22 BA34 CA88 DA41

Claims (13)

[Claims] 1. An electrophotographic image forming apparatus for forming an image on one or a plurality of image carriers by scanning a light beam modulated according to an image signal. Deflecting means for deflecting the light beam, and the light beam deflected by the deflecting means.
Two light beam detecting means for detecting a light beam at a location, and detecting the light beam on one of the two light beam detecting means;
An image forming apparatus comprising: means for measuring a time difference until a light beam is detected by the other of the two light beam detecting means; and means for correcting an image forming condition based on the time difference measured by the means. 2. The image forming apparatus according to claim 1, wherein the correction of the image forming condition is a correction of a bias applied to a charging unit for charging the image carrier. 3. The image forming apparatus according to claim 1, wherein the correction of the image forming condition is a correction of a bias applied to a developing unit for developing a latent image on the image carrier. apparatus. 4. The image forming apparatus according to claim 1, wherein the correction of the image forming condition is a correction of a toner density control value for a developing unit for developing a latent image on the image carrier. Forming equipment. 5. The image forming apparatus according to claim 1, wherein the correction of the image forming condition is a correction of a bias applied to a transfer unit for transferring an image. 6. The image forming apparatus according to claim 1, wherein the correction of the image forming condition is a correction of a cooling capacity of a cooling unit that cools the image forming apparatus. 7. The image forming apparatus according to claim 1, wherein the correction of the image forming condition is a correction of a writing image position of a writing unit that writes on the image carrier. 8. The image forming apparatus according to claim 1, wherein the correction of the image forming condition is a correction of a relative writing image position of a plurality of writing means for writing on a plurality of image carriers. Image forming apparatus. 9. The image forming apparatus according to claim 1, wherein the correction of the image forming condition is performed in a correction mode. 10. The image forming apparatus according to claim 9, wherein
The image forming apparatus is characterized in that the correction mode is a process control mode for creating and reading a test pattern. 11. The image forming apparatus according to claim 9, wherein
The image forming apparatus is characterized in that the correction mode is an alignment mode in which a detection pattern for detecting a position of an image created using a plurality of image carriers is created and read. 12. The image forming apparatus according to claim 1, wherein a magnification of an image on the image carrier in the main scanning direction is corrected in accordance with the time difference. . 13. The image forming apparatus according to claim 1, further comprising a storage unit for storing the change of the time difference, and learning a correction method based on the storage contents of the storage unit. An image forming apparatus.