JPH0792753A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device which can reduce the cost required for maintenance and is aimed to be miniaturized by feeding back the fluctuation of image density due to changes in the environment and aged deterioration, not only for ordinary images but for images transferred onto transfer materials. CONSTITUTION:The image forming device comprises a latent image forming means 3 for forming latent images of high and low density portions on an image carrier 1 on the basis of image data, a developing means 4 for developing the latent images of the high and low density portions formed on the image carrier 1 by the latent image forming means 3 using a developer, a sticking developer measuring means 5 for measuring the amount of developer of the high and low density portions which is stuck on the image carrier 1 through the development of the images by the developing means 4, and an image forming condition variation means for varying image forming conditions according to the value measured by the sticking developer measuring means 5, and also the sticking developer measuring means 5 is disposed on the back side of a conveying guide for transfer materials, and a window portion for measuring the amount of sticking developer is disposed over the transfer material conveying guide, and a protective cover for the sticking developer measuring means 5 is disposed on the window portion to serve also as a conveying guide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a color laser printer or a digital copying machine.

[0002]

2. Description of the Related Art As is well known, variations in image density in electrophotography are caused by changes and deterioration in image forming conditions due to environment and aging.

For this reason, in an analog copying machine as well as in a multi-tone printer or a digital copying machine, it is important to suppress the fluctuation of the image density and to stabilize the image density.

Particularly in a color printer, not only the density reproducibility but also the color reproducibility is affected, so that it can be said that stabilization of the image density is an indispensable requirement.

Therefore, conventionally, the materials and the process themselves are allowed to have these allowances, and instead of the maintenance method, as shown in Japanese Patent Application No. 4-255509 by the same applicant, the developer on the image bearing member is used. A method is disclosed which uses an adhesion amount measuring means.

[0006]

However, if the above-mentioned developer adhesion amount measuring means is simply arranged on the image carrier, the image carrier must be made large, and in order to downsize the apparatus, the conventional method is used. Need to be placed in the space.

Further, the printer output is obtained only by changing the developing bias, the charging grid bias, the laser power, or the like in accordance with the measured value of the developer adhesion amount on the image carrier by the developer adhesion amount measuring means. There is a problem that the stability of the image density transferred to the transfer material cannot be obtained.

Therefore, the present invention has been made in view of the above circumstances, and it is possible to feed back not only the image on the image carrier but also the transferred image to the transfer material, for the fluctuation of the image density due to changes in the environment and time. As a result, it is possible to provide an image forming apparatus aiming for downsizing without being dependent on maintenance, because it can be optimized in a cycle shorter than the maintenance cycle, stability of high image density can be achieved, the cost required for maintenance can be reduced. With the goal.

[0009]

In order to solve the above problems, the present invention provides a latent image forming means for forming a latent image of a high density portion and a low density portion on an image carrier based on image data, and this latent image. Developing means for developing a latent image of a high density portion and a low density portion on the image carrier formed by the forming means with a developer, and a high density portion and a low density portion adhered on the image carrier by the developing means. Developer adhesion amount measuring means for measuring the adhesion amount of the developer in the density portion,
The image forming condition changing unit changes the image forming condition based on the measurement value of the developer adhesion amount measuring unit. The developer adhesion amount measuring unit is arranged on the back surface of the transfer material transport guide and the transfer A window portion for measuring the amount of developer adhesion is arranged on the material conveyance guide, and a protective cover for the developer adhesion amount measuring means also serving as a conveyance guide is arranged in the window portion. .

The developer adhesion amount measuring means is also composed of control means for displaying a control panel or transmitting to a host according to the detection signal of the main body device, which also serves as paper detection means when a jam occurs.

Further, the developer adhesion amount measuring means also serves as a transfer density measuring means for measuring the density of the developer image transferred to the front surface of the transfer material, and measures the developer adhesion amount on the image carrier. The image forming changing unit changes the transfer bias according to the amount of change between the value and the measured value of the transfer density on the transfer material.

[0012]

According to the present invention, in the image forming apparatus in which the developer adhesion amount measuring means is arranged on the back side of the paper conveyance guide and the developer adhesion amount on the image carrier is measured to change the image forming condition. A window for measurement is arranged in the guide, and the window is provided with a transparent or openable cover that also serves as a paper transport guide. It is designed to prevent contamination.

Further, according to the present invention, the developer adhesion amount measuring means not only measures the developer adhesion amount on the image bearing member but also detects the paper when the main body of the apparatus detects a jam. It is possible to provide an image forming apparatus which has good operability for the user, such as returning operation, control panel display, or transmission to the host.

Further, in the present invention, the developer adhesion amount measuring means not only measures the developer adhesion amount on the image carrier, but also measures the transfer density on the transfer material or the toner adhesion amount of the transfer residual toner on the photoconductor. Since it can also be corrected to an appropriate transfer bias by not only forming an image on the image carrier but also maintaining the stability of the image on the transfer material, both can be measured by one measuring means. Therefore, it is possible to prevent a variation such as an individual difference of the measuring means from becoming a problem.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a laser printer to which the image forming apparatus according to the present invention is applied.

In FIG. 1, reference numeral 1 denotes a photosensitive drum as an image carrier, which is rotatably provided in the direction of arrow A.

The photosensitive drum 1 is an organic photosensitive member (OP
It is formed from a C) type photoconductive material.

Around the photosensitive drum 1, along the direction of rotation thereof, a charger 2 as a charging device, a laser optical system 3 as a latent image forming device, a developing device 4 as a developing device, and a developing device are sequentially installed. A toner adhesion amount measuring unit 5, which is an agent adhesion amount measuring means, a transfer charger 6, a peeling static eliminator 7, a cleaning device 8, and a static eliminator 9 are provided.

The photosensitive drum 1 rotates in the direction of arrow A in the figure, and the surface of the photosensitive drum 1 is negatively charged substantially uniformly by the charger 2 to -500 to -800 volts.

The laser beam 10 emitted from the laser optical system 3 exposes the surface of the photosensitive drum 1 according to image information to form an electrostatic latent image on the charging area.

After that, the electrostatic latent image is developed with a developer by the developing device 4, transferred onto the transfer material by the transfer charger 6, and the transfer material is peeled off from the photosensitive drum 1 by the peeling static eliminator 7.

The peeled transfer material is conveyed to the fixing device 12 by the conveying belt 11, the toner on the transfer material heated by the fixing device 12 is melted and fixed, and is discharged onto the paper discharge tray 13.

Further, after the transfer residual developer on the photoconductor drum 1 is cleaned by the cleaning device 8, the potential of the photoconductor drum 1 is removed by the static eliminator 9 and the printing routine as described above is repeated to stabilize. Printing is in progress.

(Embodiment 1) FIG. 2 is a block diagram of essential parts relating to the charging / exposure / developing means and the control means of the laser printer according to this embodiment.

In FIG. 2, the photosensitive drum 1 rotates counterclockwise in the drawing (in the direction of the arrow in the drawing).

The charger 2 is a scorotron charger mainly composed of a charging wire 14, a conductive case 15 and a grid electrode 16. The charging wire 14 is connected to a high-voltage power supply 17, and charges the surface of the photosensitive drum 1 by corona discharge.

The grid electrode 16 is connected to a high voltage power source 18 and controls the amount of charge on the surface of the photosensitive drum 1 by a grid bias voltage.

An electrostatic latent image is formed on the surface of the photosensitive drum 1 uniformly charged by the charger 2 by exposure of the modulated laser beam 10 from the laser optical system 3.

The gradation data buffer 19 stores gradation data from an external device or controller (not shown), corrects the gradation characteristics of the printer, and converts it into laser exposure time (pulse width) data. The laser drive current is modulated in accordance with the laser exposure time data from the gradation data buffer 19 so as to be synchronized with the scanning position of the laser beam 10, and the semiconductor laser (not shown) in the laser optical system 3 is driven.

As a result, the semiconductor laser emits light according to the exposure time data.

Further, the laser drive circuit 20 compares the output of a monitor light receiving element (not shown) in the laser optical system 3 with a set value, and controls the drive current to keep the output light quantity of the semiconductor laser at the set value. There is.

On the other hand, the pattern generation circuit 21 generates tone data of two different test patterns of low density and high density for measuring the toner adhesion amount.

The photosensitive drum 1 on which the electrostatic latent image is formed is developed by the developing device 4.

The developing device 4 is a two-component developing system in the embodiment shown in FIG. 1, that is, a developer consisting of toner and a carrier is stored, and the weight ratio of the toner to the developer (hereinafter referred to as toner concentration) is the toner concentration measurement. It is measured by the unit 22.

Then, the toner replenishing motor 2 for driving the toner replenishing roller 23 according to the output of the toner concentration measuring section 22.
4 is controlled so that the toner in the toner hopper 25 is replenished in the developing device 4.

In the present embodiment, the explanation is made on the two-component developing method, but it goes without saying that the developing method such as the one-component developing method or the liquid developing method does not cause any trouble in the present invention.

The developing roller 26 of the developing device 4 is connected to a high-voltage power supply 27 for developing bias and attaches toner to the image corresponding to the electrostatic latent image on the photosensitive drum 1.

Further, the control circuit 28 generates gradation data from the pattern generation circuit 21 at the end of the form-up processing after the power is turned on, so that the high / low / high / low level for measuring the toner adhesion amount on the photosensitive drum 1 can be obtained. Exposing the inside gradation pattern.

The output of the toner adhesion amount measuring unit 5 is digitized by the A / D converter 29 and input to the control circuit 30.

As shown in FIG. 3, a test pattern area corresponding to high density gradation data and a pattern area corresponding to low density gradation data are formed on the photosensitive drum 1 as shown in FIG. It

The control circuit 30 compares the output of the toner adhesion amount measuring unit 5 with a preset reference value, and according to the comparison result, the grid bias voltage of the charger 2 which is an image forming condition and the developing device. Processing for changing two of the developing bias voltages of No. 4 is performed.

At this time, the high-voltage power supplies 18 and 27 are controlled by output voltage control signals supplied from the control circuit 30 via the D / A converters 31 and 32, respectively.

FIG. 3 shows the structure of the toner adhesion amount measuring unit 5.

In FIG. 3, the light from the light source 33 is applied to the surface of the photosensitive drum 1, and the reflected light reflected by the photosensitive drum 1 or the toner that has been developed and adhered is photoelectrically converted by the photoelectric conversion unit 34. Is converted into a current according to
After further current / voltage conversion, A /
The signal is transmitted to the D converter 36 and taken into the control circuit 30 as a digital signal.

The light source 33 is current-driven by a light source drive circuit 37, and the light source drive circuit 37 is controlled by a control circuit 30 by an ON / OFF control or a signal for adjusting the amount of drive current to the light source 33.

Next, a method of changing the bias will be briefly described.

At the time of measuring the toner adhesion amount, the processes of charging, exposing, developing, cleaning, and discharging on the photosensitive drum are operated in the same manner as the normal image forming sequence, and the high density and low density generated by the pattern generating circuit 21 are generated. The image forming operation for the density test pattern is executed.

At this time, the grid bias voltage value and the developing bias voltage value of the charger 2 are set to predetermined values, respectively, and these values are the bias conditions that provide the standard gradation characteristic of normal temperature and normal humidity.

The size of the test pattern is a predetermined width centered on the center of the image area of the photosensitive drum 1 in the axial direction and a predetermined length in the rotation direction of the photosensitive drum 1.

The predetermined width corresponds to the position of the toner adhesion amount measuring unit 5 in the axial direction of the photoconductor drum 1, and the minimum size at which the detected spot size is not affected by the edge effect peculiar to electrophotography,
The predetermined length is set to the minimum size that does not affect the detection result by the influence of the edge effect and the response characteristics of the sensor.

In one embodiment of the present invention, the predetermined width is 1.5 to 5 mm larger than the detection spot size, and the predetermined length is the length which is detected by moving the detection spot size four times as long as one sensor time constant. Multiply the number of times by 1.5-5m
The length was set to m. When the toner adhesion amount is detected, the reflection amount of each test pattern is detected in synchronization with the arrival of the two test patterns at the position facing the toner adhesion amount measurement unit 5, and the toner adhesion amount measurement unit is also detected. Reference numeral 5 also detects the amount of reflected light in the undeveloped area of the photosensitive drum 1 at a predetermined timing.

The measured value detected above is converted into an A / D converter 29.
Is stored in the control circuit 30 via the, and the calculation result of a predetermined function relating to the optical reflectance with respect to the high-density and low-density portions based on the reflected light amount of the undeveloped area is used as the toner adhesion amount for each and The deviations are calculated by comparing the respective toner adhesion amounts.

In order for the deviation to be within the standard value range,
The sequence is repeated so that the grid bias voltage value and the developing bias voltage value are changed to fall within the standard value range. 4 and 5 and FIGS. 6 and 7 show examples when the above control is performed.

FIGS. 4 and 5 show examples in which the high density toner adhesion amount QH and the low density toner adhesion amount OL are lower than the respective target values QHT and QLT in a low temperature and low humidity environment.

FIGS. 6 and 7 show examples in which the high density toner adhesion amount QH and the low density toner adhesion amount QL in a high temperature and high humidity environment are both higher than the respective target values QHT and QLT.

The horizontal axes of FIGS. 4, 5, 6 and 7 represent the number of times of control, the vertical axes of FIGS. 4 and 6 represent the toner adhesion amount detection value, and the vertical axes of FIGS.

In this way, the number of control operations converges within the standard value with a relatively small number of times.

The above-described control example is an operation during warming up. In addition to this, for example, the toner adhesion amount measuring unit 5 is used when the photosensitive drum is rotated between paper sheets or before printing is started.
Finer control can be performed by performing abnormality monitoring by.

(Embodiment 2) FIG. 8 is an enlarged view around the toner adhesion amount measuring unit 5 in the laser printer shown in FIG. 1 to which the present invention is applied.

The toner adhesion amount measuring unit 5 is a paper conveyance guide 40.
By the holding member 48 on the opposite side of the photoconductor drum 1 of, that is, the back side of the paper transport surface 40a of the paper transport guide 40,
It is positioned so as to be positioned at an appropriate distance from the surface of the photoconductor drum 1 and fixedly arranged on the paper transport guide 40.

A window 40b is provided at the tip of the paper transport guide 40 so as not to block the light emitted from the toner adhesion amount measuring unit 5 to the photosensitive drum 1. When the toner image on the photoconductor drum 1 is transferred to the transfer material, the window 40b may damage the adhesion between the transfer material and the photoconductive drum 1 and cause image defects such as transfer marks. However, it is difficult to reduce the spot size of the sensor because it depends on the moving speed (process speed) of the photosensitive drum 1 and the sensor sensitivity to reduce the spot size of the sensor.

Therefore, in the present invention, as shown in FIG. 8, protection for the toner adhesion amount measuring section 5 which also serves as a paper conveyance guide and is made of a transparent material which transmits the light of the sensor made of acrylic or polycarbonate. Cover 41
By providing the above, it is possible to obtain a good image without the above-mentioned transfer marks and to protect the toner adhesion amount measuring unit 5 from dirt such as dust and toner, and the toner adhesion on the photosensitive drum 1 can be obtained. It enables stable measurement of the amount over a relatively long period of time.

Further, since the rib 41a of about 0.5 to 1 mm is formed on the protective cover 41 at a position avoiding the position where the light of the sensor passes, the rib 41a is formed by the tip of the transfer material when the transfer material passes. You can protect from scratches.

(Embodiment 3) FIG. 9 is another embodiment of the present invention and shows an enlarged view of the periphery of the toner adhesion amount measuring unit 5 as in the case of Embodiment 2.

As in the second embodiment, the toner adhesion amount measuring unit 5
Is the opposite side of the paper transport guide 40 to the photosensitive drum 1,
That is, the holding member 48 is positioned on the back side of the paper conveyance surface 40a of the paper conveyance guide 40 so as to be positioned at a proper distance from the surface of the photoconductor drum 1 and fixedly arranged on the paper conveyance guide 40.

A window 40b is provided at the tip of the paper transport guide 40 so as not to block the light emitted from the toner adhesion amount measuring unit 5 to the photosensitive drum 1. In the second embodiment, the transparent protective cover 41 is arranged, and the protection of the toner adhesion amount measuring unit 5 is almost complete.
For a long period of time, it is difficult to prevent the transparent protective cover 41 itself from being contaminated with toner, paper dust, etc., and maintenance is required by some method. For this reason, in the third embodiment, the transparent protective cover 41 is replaced by a protective cover 42 that also serves as a paper transport guide that can be opened and closed.

As a result, when the toner adhesion amount measuring unit 5 measures the toner adhesion amount on the photoconductor drum 1, the protective cover 42 is set to the open position with respect to the photoconductor drum 1, and the opening / closing operation is performed. It is possible to perform stable measurement for a long time regardless of the dirt of the free protective cover 42.

FIG. 9 shows a state in which the protective cover 42 is closed.

FIG. 10 shows an example of the opening / closing mechanism.

The protective cover 42, which also functions as an openable / closable paper conveyance guide, has an opening / closing fulcrum 42a held at the other end of a lever 48 supported by opening / closing fulcrum holding portions 40a provided at both ends of the paper conveyance guide 40. , And a protrusion 42b which is the point of action of opening and closing.

Further, in FIG. 10, reference numeral 43 is a solenoid for controlling the opening and closing of the protective cover 42, and 44 is engaged with the protrusion 42b of the protective cover 42 to move the protective cover 42 to the open position 42 '. It is a lever.

As described in the first embodiment, the protective cover 42 is opened during the warm-up, when the toner adhesion amount measuring unit 5 measures the distance between the sheets and the rotation of the photosensitive drum before the start of printing. By being in the state (position of 42 '), it is possible to perform an operation that does not hinder normal printing.

(Embodiment 4) Embodiment 4 relates to a further usage of the toner adhesion amount measuring unit 5 in the construction of Embodiment 3, in which the laser printer shown in FIG. 1 has a paper jam (hereinafter referred to as a jam). In case of occurrence of, the toner adhesion amount measuring unit 5 is used for paper detection.

Specifically, when the main body of the apparatus detects a jam, presence / absence of paper is detected in each of the aligning, toner adhesion amount measuring section, and paper discharge sensor sections to perform an appropriate jam restoration operation, control panel display, or It sends signals to the host computer.

FIG. 11 shows an example of a branch table of jam restoration operation after jam detection.

A, B, and C indicate the presence / absence of paper in each of the aligning, toner adhesion amount measuring unit, and paper ejection sensor unit (o is present, x is not present).

There are two jam recovery operation modes. One is a user jam elimination waiting state (1) by the jam display or the jam position display, and the other is the jam existing after the paper existing in the apparatus main body is discharged. If not, the printing operation starts again (2).

These two modes (1) and (2) are shown in FIG.
As shown in 1, the selection is made according to the jam condition.

FIG. 13B is a graph showing the sensor output by each gradation pattern, and the range of a in the graph shows the range of the sensor output when the paper is interposed between the sensor and the photoconductor. There is.

That is, since the paper is located at a position shorter than the focal length of the sensor and the light is scattered by the surface of the paper,
Since the sensor receives the scattered light, the sensor itself outputs in the halftone density range.

Therefore, when detecting the paper, there is a problem in what state the photosensitive drum is.

In reality, if there is no toner on the photosensitive member or if solid black is being developed, sensingo with a good S / N ratio is possible, but in reality it is said that solid black is developed. Since there are many system problems, it is possible to move the surface of the photoconductor on which the toner is not present to the sensor position by controlling the time from detecting the jam to stopping the rotation of the photoconductor. This makes it possible to detect paper.

(Fifth Embodiment) A fifth embodiment relates to a method of using the toner adhesion amount measuring unit 5 different from that of the fourth embodiment, and the toner adhesion amount measuring unit 5 is used for the toner adhesion of the toner image on the transfer material. The amount is also measured and controlled to an appropriate transfer bias.

FIG. 12 is a block diagram relating to the charging / exposure / developing / transfer means and the control means of the laser printer according to this embodiment. The portion relating to the transfer means is added to the block diagram of FIG. 2 in the first embodiment. It has been configured.

In FIG. 12, the photosensitive drum 1 rotates counterclockwise (in the direction of the arrow in the figure) with respect to the drawing.

The charger 2 is a scorotron charger mainly composed of a charging wire 14, a conductive case 15 and a grid electrode 16.

The charging wire 14 is connected to a high-voltage power supply 17, and the surface of the photosensitive drum 1 is charged by corona discharge.

The xelid electrode 16 is connected to a high voltage power source 18 and controls the amount of charge on the surface of the photosensitive drum 1 by a grid bias voltage.

An electrostatic latent image is formed on the surface of the photosensitive drum 1 uniformly charged by the charger 2 by exposure of the modulated laser beam 10 from the laser optical system 3.

The gradation data buffer 19 stores gradation data from an external device or controller (not shown), corrects the gradation characteristics of the printer, and converts it into laser exposure time (pulse width) data.

The laser drive circuit 20 uses the laser beam 10
The laser drive current is modulated in accordance with the laser exposure time data from the gradation data buffer 19 so as to be synchronized with the scanning position of, and the semiconductor laser (not shown) in the laser optical system 3 is driven.

As a result, the semiconductor laser emits light according to the exposure time data.

Further, the laser drive circuit 20 compares the output of the light receiving element for monitoring (not shown) in the laser optical system 3 with the set value, and controls the output current of the semiconductor laser to the set value by the drive current. There is.

On the other hand, the pattern generation circuit 21 generates tone data of test patterns having three different densities, namely, low density, high density and intermediate density for measuring the toner adhesion amount.

Now, the photoconductor drum 1 on which the electrostatic latent image is formed is developed by the developing device 4. The developing device 4 is a two-component developing system in the embodiment shown in FIG. 1, that is, a developer consisting of toner and carrier is stored, and the weight ratio of the toner to the developer (hereinafter referred to as toner concentration) is determined by the toner concentration measuring unit 22. To be measured.

Then, the toner replenishing motor 2 for driving the toner replenishing roller 23 in accordance with the output of the toner concentration measuring section 22.
4 is controlled so that the toner in the toner hopper 25 is replenished in the developing device 4.

It should be noted that although the description of the present embodiment is based on the two-component developing method, it goes without saying that the developing method such as the one-component developing method or the liquid developing method does not cause any problems in the present invention.

The developing roller 26 of the developing device 4 is connected to a high voltage power source 27 for developing bias, and makes toner adhere to the image corresponding to the electrostatic latent image on the photosensitive drum 1.

Then, the gradation pattern developed on the photosensitive drum 1 is transferred to a transfer sheet being conveyed by a transfer charger 6.
Is electrostatically transferred by and is fixed by a fixing device (not shown).

The corona wire 45 of the transfer charger 6 is connected to the high voltage power supply 46.

Further, the control circuit 30 generates gradation data from the pattern generation circuit 21 at a predetermined timing, so that the high, low, and middle floors for measuring the toner adhesion amount on the photosensitive drum 1 and the transfer paper are measured. Expose the tonal pattern.

The output of the toner adhesion amount measuring section 5 is digitized by the A / D converter 28 and input to the control circuit 30.

As a result of the above development, a test pattern area corresponding to high density gradation data and a test pattern area corresponding to low density gradation data are formed on the photosensitive drum 1 as shown in FIG. 13A. And a test pattern area corresponding to the grayscale data of the intermediate density.

The control circuit 30 stores the output of the toner adhering amount on the photosensitive drum 1 and the transfer paper of the toner adhering amount measuring unit 5, compares the difference in the value in each gradation pattern, and the comparison result. Accordingly, the image forming condition changing table stored in the control circuit 30 is used to change the corona wire voltage or current of the transfer charger 6 which is the image forming condition.

At this time, the high voltage power supply 46 is controlled by the output voltage or current control signal supplied from the control circuit 30 via the D / A converter 47.

Next, an example of the image forming condition changing sequence will be described with reference to the flowcharts shown in FIGS.

In the transfer bias changing mode in the present invention, the transfer toner and the amount of toner adhered on the photosensitive member are measured by the sensor, so that the transfer bias changing mode is executed at the time of predetermined double-sided printing.

For example, it may be performed at the end of warming-up after the power of the apparatus main body is turned on, or may be performed by keying in by a service person. Further, it may be performed at predetermined time intervals such as printing FAX transmission / reception information or predetermined printing by a printer. It is conceivable that the procedure is performed for each number of sheets, as shown in FIG.
Although an example including all is shown in FIG. 4, one or a plurality of optimum ones may actually be selected depending on the system of the apparatus.

That is, when the printer power is turned on and the printer is ready after the warming up, the transfer bias changing mode process is performed, and the counter and timer in the control circuit 30 are reset to be in the standby state.

Next, when the print request signal is received and the printing operation is performed, the number-of-printed-sheets counter is incremented.

At this time, when the print number counter reaches the predetermined print number, or when a predetermined time elapses before the print number counter reaches the predetermined print number, the transfer bias changing mode process is similarly performed.

At the end of warming up after the power is turned on, basically once a day is basically set,
In the case of every predetermined time, finer control is possible, but since one sheet of paper and toner are consumed, it becomes a problem if the frequency is too high.

In that respect, the method of incorporating the test pattern into the transmission / reception information printing when the FAX is installed is very effective.

Further, the method by a service person can greatly contribute to improvement of maintainability and reduction of service cost.

15 is a flowchart of the transfer bias changing mode in FIGS. 15 and 14.

The transfer bias changing mode is the following 5
It consists of steps.

(1) Test pattern image forming step (2) Double-sided printing step (3) Step of measuring toner adhering amount on photoconductor (4) Step of measuring toner adhering amount on transfer material (5) Bias changing step First, test In the pattern image forming step (1), each process of charging, exposing, developing, cleaning, and discharging is operated in the same manner as a normal image forming sequence, and each of high density, medium density, and low density generated by the pattern generation circuit 21 is generated. The image forming operation for the test pattern is executed.

Next, a single-sided printing operation (transfer / fixing / stacking of transfer materials) which is a double-sided printing step (2) is performed.
Until the transfer material is re-fed, the same test pattern image forming step (1) as described above is performed again.

Next, in the toner adhesion amount measuring step (3) on the photoconductor, the photoconductor drum is measured at a predetermined timing when the test pattern (high density, medium density, low density) reaches the toner adhesion amount measuring section 5. The reflected light amounts of the undeveloped surface of No. 1 and the high, middle and low density portions are detected and stored in the control circuit 30 via the A / D converter 28.

At this time, it is checked whether the reflected light amount is within a predetermined range, and if it is out of the range, it is judged to be abnormal and a sensor abnormality flag is set, and the control panel 2
It is displayed on the display section 9.

Next, the sheet is re-fed, which is the final step of the double-sided printing step, and the toner adhesion amount measuring step (4) on the transfer material is performed.
Then, at a predetermined timing when the test pattern (high density, medium density, low density) on the transfer material reaches the toner adhesion amount measuring section 5, the non-transferred surface of the transfer material and the high, middle and low density areas are reflected. The amount of light is detected and stored in the control circuit 30 via the A / D converter 28.

At this time, the sensor abnormality is similarly checked.

Further, the amount of reflected light on the photosensitive drum 1 is calculated by calculating a predetermined function relating to the optical reflectance for high, middle and low density areas with reference to the amount of reflected light on the undeveloped photosensitive member. It is calculated as (QH, QM, QL), and the process proceeds to the bias changing step (5).

FIG. 16 shows a flow chart of the bias changing step.

In the bias changing step, first, the amount of reflected light of the toner after fixing on the transfer material is converted from the amount of reflected light before fixing by a conversion table, and then the untransferred portion is transferred in the same manner as on the photosensitive drum. Adhesion amount (QTH, QTM, high / medium / low density part based on the amount of reflected light on the material
QTL) is calculated.

Next, the transfer efficiency (ηH, η
M, ηL) is calculated by the following (1), (2), (3).

ΗH = QTH / QH (1) ηM = QTM / QM (2) ηL = QTL / QL (3) Furthermore, whether or not the transfer efficiency at each of the above concentrations is within a prescribed value. After the judgment, the bias value is calculated if it is out of the standard value, and the bias is changed.

In the present embodiment, the predetermined standard value is determined by the following equations (4), (5) and (6).

ΗH, ηM, ηL ≧ 0.65 (4) MAX (η) -MIN (η) ≦ 0.15 (5) 0.8κ ≦ (ηL−ηH) / (ηM−ηH) ≦ 1 .2κ (6) However, MAX (η) and MIN (η) are transfer efficiency (η
The maximum and minimum values of (H, ηM, ηL) are shown.

That is, the expression (4) is applied to each transfer efficiency (η
H, ηM, ηL) is 0.6 or more, the difference between the maximum and minimum transfer efficiencies of equation (5) is within 0.15, and equation (6) is (η
L-ηH) and (ηM-ηH) have a ratio of 0.8κ and 1.2κ
It has become a standard between.

Κ takes a different value depending on the gradation pattern of the intermediate density.

[0133] Next, the transfer bias value (transfer flowing current value in the case of this embodiment: I _t [μA]) is calculated by the procedure shown in FIG. 17.

[0134] First, when less than 0.8κ in equation (6) condition is a function of the transfer efficiency eta in I _t values the current beta (eta)
And n = 1.

[0135] When exceeding the 1.2κ added alpha (eta) is a function of the transfer efficiency eta in I _t values of current.

[0136] Further, each (4), (5) when not satisfied the condition of Equation a function of its I _t values in the transfer efficiency ^{η (-1) n γ (η} ) and (-1) ⁿ [delta] (eta) Is added to derive the transfer bias value.

FIG. 18 shows an example of a reference transfer characteristic graph.

In the system showing the transfer characteristics as shown in FIG. 18, α (η), β (η), γ (η) and δ (η) which are functions of transfer efficiency for determining the transfer bias value are It has been confirmed by experiments that the following mathematical formula has a great effect on stability against the environment and long-term stability.

Α (η) = Kα × {(ηL−ηH) / (ηM−ηH)} / 1.2κ (7) β (η) = Kβ × 0.8κ / {(ηL−ηH) / ( ηM−ηH)} (8) γ (η) = Kγ × (MAX (η) -MIN (η)) / 0.05 (9) δ (η) = Kδ × (0.65-MIN (η )) / 0.65 (10) However, Kα, Kβ, Kγ, and Kδ are proportional constants. In this embodiment (embodiment 5), the toner adhesion amount measuring unit 5 is transferred to the toner adhesion amount on the photosensitive drum 1 and transferred. Also serves as a measure of the amount of toner adhering to the material.

Therefore, in the sensor shown in FIG. 8, the distance (optical path length) between the sensor and the object to be measured is ±, for example.
A predetermined accuracy such as 0.2 is required.

Therefore, there is a problem in measuring the toner adhesion amount on the transfer material 50. 19 (a),
As shown in FIG. 19B, FIG. 19A shows a state immediately after the transfer material reaches the photosensitive drum 1, and the sensor 5
The distance to the transfer material 50 at the point 5 ′ measured by is shorter than the distance to the photoconductor drum 1, and in such a state, the photoconductor drum 1 and the transfer material 50 are not in contact with each other. Becomes unstable.

However, as shown in FIG. 19B, when the rear end of the transfer material 50 reaches the transfer material 50, the transfer material 50 is almost in close contact with the photosensitive drum 1, so that the output of the sensor 5 is stable and accurate. It becomes possible to measure.

However, in the fifth embodiment of the present invention,
Since the test pattern must be transferred to the trailing edge of the transfer material to be measured in the transport direction, the leading edge is reversed during reprinting in double-sided printing operation. Must be done at the tip.

(Embodiment 6) Embodiment 6 relates to proper transfer bias control, which is different from Embodiment 5, in that a latent test pattern image of high, medium and low density formed on a photoconductor is formed. The amount of toner attached to the developed toner image is measured, and the amount of toner remaining after transfer is also measured to control the transfer bias to an appropriate level.

FIG. 20 is a block diagram relating to the charging / exposure / development / transfer means and the control means of the laser printer according to this embodiment. The block diagram of FIG. The arrangement of the portion 5 on the photosensitive drum 1 is different.

That is, the toner adhesion amount measuring unit 5 is arranged between the transfer charger 6 and the cleaning device 8.

The description of the block diagram is the same as that of the fifth embodiment, and will be omitted.

The main sequence for changing the image forming conditions in this embodiment is the same as that shown in the above-mentioned fifth embodiment (FIG. 14), so the explanation is omitted, but the sequence for changing the image forming conditions is as follows. Unlike the fifth embodiment, only the transfer bias changing mode in FIG. 14 is shown in the flowchart in FIG.

The transfer bias changing mode is set in the following 4
It consists of steps.

(1) Test pattern image forming step (2) Measurement step of toner adhesion amount (reference) on photoconductor (3) Measurement step of toner adhesion amount (transfer remaining) on transfer material (4) Bias changing step First, In the test pattern image forming step (1), each process of charging, exposure, development, cleaning, and charge removal operates in the same manner as a normal image forming sequence, and high density, medium density, and low density generated by the pattern generating circuit 21 are generated. The image forming operation is executed for each test pattern.

Next, in the toner adhesion amount measuring step (2) on the photoconductor, at a predetermined timing when the test pattern (high density, medium density, low density) reaches the toner adhesion amount measuring unit 5, the photoconductor drum is measured. The reflected light amounts of the undeveloped surface of No. 1 and the high, middle and low density portions are detected and stored in the control circuit 30 via the A / D converter 28.

At this time, it is checked whether the reflected light amount is within a predetermined range, and if it is out of the range, it is judged to be abnormal, and a sensor abnormality flag is set, and the control panel 2
It is displayed on the display section 9.

Next, the same test pattern image forming step (1) as described above is performed again, the transfer material is supplied to the photoconductor 1, and the test pattern (high density, medium density, low density) on the photoconductor 1 is obtained. ) Is transferred to the transfer material, the toner remaining on the photoconductor 1 reaches the toner adhesion amount measuring unit 5 at a predetermined timing, and the residual toner on the photoconductor surface and high / middle / low density portions is reflected. The amount of light is detected and stored in the control circuit 30 via the A / D converter 28.

At this time, the sensor abnormality is similarly checked.

Further, the amount of reflected light on the photosensitive drum 1 (reference and transfer residual) is a predetermined function related to the optical reflectance for high, middle and low density portions based on the amount of reflected light on the undeveloped photosensitive member. The calculation result of (1) is calculated as each adhesion amount, and the process proceeds to the bias changing step (4) (reference →
QH, QM, QL, transfer residue → QtH, QtM, Qt
L).

FIG. 22 shows a flowchart of the bias changing step.

In the bias changing step, first, the transfer efficiency (ηH, ηM, ηL) is calculated from the adhesion amount of each of the following (1
It is calculated by 1), (12) and (13).

ΗH = (QH-QtH) / QH (11) ηM = (QM-QtM) / QM (12) ηL = (QL-QtL) / QL (13) Further, transfer at each of the above-mentioned densities After determining whether the efficiency is within a predetermined specified value, if it is outside the standard value, a bias value is calculated and the bias is changed.

Further, after determining whether the transfer efficiency at each of the above-mentioned densities is within a predetermined standard value, if it is out of the standard value, a bias value is calculated and the bias is changed.

The flow up to the calculation of the bias value including the predetermined standard value is exactly the same as in the fifth embodiment.

[0161]

As described above, according to the present invention, the developer adhesion amount measuring means is arranged on the back side of the paper conveying guide, and the image formation condition is changed by measuring the developer adhesion amount on the image carrier. In the above-mentioned paper conveyance guide, a measurement window is provided, and the window is provided with a transparent or openable cover that doubles as a paper conveyance guide. It is possible to prevent the mixture of the developer and the developer.

Further, according to the present invention, not only the developer adhesion amount measuring means measures the developer adhesion amount on the image carrier but also the paper detection when the main body of the apparatus detects a jam, whereby the fine jam restoration is performed. It is possible to provide an image forming apparatus which is easy to operate for the user such as operation, control panel display, or transmission to the host computer.

Further, according to the present invention, the developer adhesion amount measuring means can measure not only the developer adhesion amount on the image carrier but also the transfer density measurement on the transfer material or the toner adhesion amount after transfer on the photosensitive member. By combining it, it is possible to correct to an appropriate transfer bias, and not only the image formation on the image carrier but also the stability of the image on the transfer material can be maintained. Since it also serves, it is possible to prevent variations such as individual differences in measuring means from becoming a problem.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a laser printer as an example of an image forming apparatus according to the present invention.

FIG. 2 is a block diagram of a charging / exposure / developing unit and a control unit of the laser printer according to the first exemplary embodiment.

FIG. 3 is a block diagram showing a configuration of a toner adhesion amount measuring unit.

FIG. 4 is a diagram illustrating an example of a change in toner adhesion amount according to the first exemplary embodiment.

FIG. 5 is a diagram showing an example of changes in bias values in FIG.

FIG. 6 is a diagram showing another example of changes in the toner adhesion amount according to the first embodiment.

FIG. 7 is a diagram showing an example of changes in bias values in FIG.

FIG. 8 is an enlarged view around the toner adhesion amount measuring unit of the laser printer according to the second embodiment.

FIG. 9 is an enlarged view of the vicinity of a toner adhesion amount measurement unit of a laser printer according to a third embodiment.

FIG. 10 is a diagram illustrating an example of an opening / closing mechanism of a protective cover of a toner adhesion amount measuring unit according to a third embodiment.

FIG. 11 is a diagram illustrating a branch of a jam restoration operation according to the fourth embodiment.

FIG. 12 is a block diagram of a charging / exposure / development / transfer unit of a laser printer and a control unit thereof according to a fifth embodiment.

FIG. 13 is a diagram showing high-, medium-, and low-density portions developed on a photosensitive drum, a toner adhesion amount measuring unit, and a relationship between sensor output and density.

FIG. 14 is a flowchart showing an image forming condition changing sequence in the fifth embodiment.

15 is a flowchart showing a processing operation of a transfer bias changing mode in FIG.

16 is a flowchart showing a bias changing step in FIG.

FIG. 17 is a flowchart showing the processing for determining the bias value to be changed in FIG.

FIG. 18 is a graph showing reference transfer characteristics in Example 5.

FIG. 19 is a diagram showing the position of the transfer material when measuring the toner adhesion amount on the transfer material in the fifth embodiment.

FIG. 20 is a block diagram of a charging / exposure / development / transfer unit of a laser printer and a control unit thereof according to a sixth embodiment.

FIG. 21 is a flowchart showing the processing operation of the transfer bias changing mode in the sixth embodiment.

22 is a flowchart showing a bias changing step in FIG. 21. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum (image carrier), 2 ... Charging device (charging means), 3 ... Laser optical system (exposure means), 4 ... Developing device (developing means), toner adhesion amount measuring unit, 6 ... Transfer charging device. , 8 ...
Cleaning device, 21 ... Pattern generating circuit, 28 ... A / D converter, 30 ... Control circuit, 17, 18, 27, 46 ... High-voltage power supply, 29 ... Control panel, 31, 32, 47 ... D
/ A converter, 40 ... Paper transport guide, 41 ... Protective cover (transparent), 42 ... Protective cover (openable / closable), 43 ... Solenoid, 44 ... Opening / closing lever, 48 ... Holding member, 50 ...
Transfer material.

Claims (11)

[Claims] 1. A latent image forming means for forming a latent image on an image carrier based on image data, and a developing means for developing the latent image on the image carrier formed by the latent image forming means with a developer. A developer adhesion amount measuring means for measuring the developer adhesion amount on the image carrier, an image forming condition changing means for changing the image forming condition according to the measurement value by the developer adhesion amount measuring means, and a transfer material image A carrier guide for carrying to the surface of the carrier, the developer adhesion amount measuring means is arranged on the back side of the carrier guide, and a window for measuring the amount of developer adhesion is formed on the carrier guide. The window has a transparent cover made of acrylic or polycarbonate or the like that also serves as a transport guide, and the transparent cover also serving as the transport guide has ribs formed on the side where the transfer material is transported. Image forming apparatus. 2. A latent image forming means for forming a latent image on an image carrier based on image data, and a developing means for developing the latent image on the image carrier formed by the latent image forming means with a developer. A developer adhesion amount measuring means for measuring the developer adhesion amount on the image carrier, an image forming condition changing means for changing the image forming condition according to the measurement value by the developer adhesion amount measuring means, and a transfer material image A carrier guide for carrying to the surface of the carrier, the developer adhesion amount measuring means is arranged on the back side of the carrier guide, and a window for measuring the amount of developer adhesion is formed on the carrier guide. The window has a cover that also serves as a conveyance guide, and the cover is openably and closably held with respect to the image carrier, and at least when the developer adhesion amount measuring means measures the density, it must be kept open. An image forming apparatus characterized by. 3. A latent image forming means for forming a latent image on the image carrier based on image data, and a developing means for developing the latent image on the image carrier formed by the latent image forming means with a developer. And an image forming condition changing means for changing an image forming condition according to a measurement value of the developer adhesion amount measuring means, and an image forming condition changing means for measuring a developer adhesion amount on the image carrier. In the apparatus, the developer adhesion amount measuring means is arranged on the opposite side of the image carrier from the transfer material conveyance path, and is disposed between the image carrier and the developer adhesion amount measuring means when a jam is detected in the apparatus body. An image forming apparatus, which also serves as a transfer material detecting unit for detecting the presence of the transfer material. 4. A latent image forming means for forming a latent image on an image carrier based on image data, and a developing means for developing the latent image on the image carrier formed by the latent image forming means with a developer. And an image forming condition changing means for changing an image forming condition according to a measurement value of the developer adhesion amount measuring means, and an image forming condition changing means for measuring a developer adhesion amount on the image carrier. In the apparatus, the developer adhesion amount measuring means is arranged on the opposite side of the image carrier from the transfer material conveyance path, and is disposed between the image carrier and the developer adhesion amount measuring means when a jam is detected in the apparatus body. The image forming apparatus also serves as a transfer material detecting unit that detects the presence of the transfer material at intermediate detection levels different from each other. 5. A latent image forming means for forming a latent image on an image carrier based on image data, and a developing means for developing the latent image on the image carrier formed by the latent image forming means with a developer. A developer adhesion amount measuring means for measuring a developer adhesion amount on the image carrier, and an image forming condition changing means for changing an image forming condition according to a measurement value by the developer adhesion amount measuring means, The developer adhesion amount measuring means is arranged on the opposite side of the image carrier with the transfer material conveyance path sandwiched between them, and the developer transferred to the front surface of the transfer material at the time of back surface printing during predetermined double-sided printing. It also serves as a transfer density measuring means for measuring the density of an image, and it functions as a transfer bias in accordance with the amount of change between the measured value of the amount of developer adhering on the image carrier and the measured value of the transfer density on the transfer material in printing a predetermined test pattern. An image forming apparatus characterized by changing the. 6. A latent image forming means for forming a latent image on an image carrier based on image data, and a developing means for developing the latent image on the image carrier formed by the latent image forming means with a developer. A developer adhesion amount measuring means for measuring a developer adhesion amount on the image carrier, and an image forming condition changing means for changing an image forming condition according to a measurement value by the developer adhesion amount measuring means, The developer adhesion amount measuring means is arranged on the opposite side of the image carrier with the transfer material conveyance path sandwiched between them, and the developer transferred to the front surface of the transfer material at the time of back surface printing during predetermined double-sided printing. It also serves as a transfer density measuring means for measuring the density of an image, and it functions as a transfer bias in accordance with the amount of change between the measured value of the amount of developer adhering on the image carrier and the measured value of the transfer density on the transfer material in printing a predetermined test pattern. And the specified double-sided printing is performed every predetermined time. An image forming apparatus comprising Ukoto. 7. A latent image forming means for forming a latent image on an image carrier based on image data, and a developing means for developing the latent image on the image carrier formed by the latent image forming means with a developer. A developer adhesion amount measuring means for measuring a developer adhesion amount on the image carrier, and an image forming condition changing means for changing an image forming condition according to a measurement value by the developer adhesion amount measuring means, The developer adhesion amount measuring means is arranged on the opposite side of the image carrier with the transfer material conveyance path sandwiched between them, and the developer transferred to the front surface of the transfer material at the time of back surface printing during predetermined double-sided printing. It also serves as a transfer density measuring means for measuring the density of an image, and it functions as a transfer bias in accordance with the amount of change between the measured value of the amount of developer adhering on the image carrier and the measured value of the transfer density on the transfer material in printing a predetermined test pattern. Change the value of the The developer deposition amount on the image carrier by the developing agent deposition amount measuring means measures the image forming apparatus characterized by performing measurements between the front surface printing and rear surface printing. 8. A test for measuring the transfer density at the front end when measuring the transfer density on the transfer material by the developer adhesion amount measuring means which also functions as the transfer density measuring means and when forming an image on the front surface. 7. The image forming apparatus according to claim 6, wherein the transfer density on the transfer material is measured at the rear end of the transfer material by performing pattern printing. 9. A latent image forming means for forming a latent image on an image carrier based on image data, and a developing means for developing the latent image on the image carrier formed by the latent image forming means with a developer. A developer adhesion amount measuring means for measuring a developer adhesion amount on the image carrier, and an image forming condition changing means for changing an image forming condition according to a measurement value by the developer adhesion amount measuring means, The developer adhesion amount measuring means is arranged between the transfer means and the cleaning means of the image carrier, and also serves as the transfer residual toner adhesion amount measuring means for measuring the toner adhesion amount of the transfer residual toner on the image carrier, and performs a predetermined test. An image forming apparatus, characterized in that a transfer bias is changed according to a change amount between a measured value of a developer adhesion amount on an image carrier and a measured value of a transfer residual toner adhesion amount in pattern printing. 10. A latent image forming means for forming a latent image on an image carrier based on image data, and a developing means for developing the latent image on the image carrier formed by the latent image forming means with a developer. A developer adhesion amount measuring means for measuring a developer adhesion amount on the image carrier, and an image forming condition changing means for changing an image forming condition according to a measurement value by the developer adhesion amount measuring means, The developer adhesion amount measuring means is arranged on the opposite side of the image carrier with the transfer material conveyance path sandwiched between them, and the developer transferred to the front surface of the transfer material at the time of back surface printing during predetermined double-sided printing. It also serves as a transfer density measuring means for measuring the density of an image, and it functions as a transfer bias in accordance with the amount of change between the measured value of the amount of developer adhering on the image carrier and the measured value of the transfer density on the transfer material in printing a predetermined test pattern. Change and the test pattern printing is High density portion and a low density portion and the image forming apparatus characterized by being composed of three patterns of the intermediate density portion. 11. A latent image forming means for forming a latent image on an image carrier based on image data, and a developing means for developing the latent image on the image carrier formed by the latent image forming means with a developer. A developer adhesion amount measuring means for measuring a developer adhesion amount on the image carrier, and an image forming condition changing means for changing an image forming condition according to a measurement value by the developer adhesion amount measuring means, The developer adhesion amount measuring means is arranged between the transfer means and the cleaning means of the image carrier, and also serves as the transfer residual toner adhesion amount measuring means for measuring the toner adhesion amount of the transfer residual toner on the image carrier, and performs a predetermined test. The transfer bias is changed according to the amount of change in the amount of developer adhered on the image carrier in pattern printing and the amount of change in the amount of residual toner adhered measured. Concentration part and An image forming apparatus characterized in that it is composed of three patterns of the intermediate density portion.