JP3584142B2 - Image forming device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic image forming apparatus, and more particularly to an image forming apparatus having excellent gradation stability of an output image.
[0002]
[Prior art]
Conventionally, a charging means, that is, an image bearing member, for example, an electrophotographic photosensitive drum, is uniformly charged by a primary charger, and a latent image is formed on the photosensitive drum by exposing the image by an exposing means. In an electrophotographic image forming apparatus that obtains an image by developing an image with a developing unit, when a high gradation characteristic is required, a sensor that detects the surface potential on the electrophotographic photosensitive drum is provided. A reference latent image pattern is formed separately from the image forming sequence, the area is detected, and based on the information, the voltage applied to the grid of the primary charger and the voltage of the DC component of the developing bias applied to the developing means are calculated. Controls such as setting to an optimum state are performed.
[0003]
By such control, it is possible to keep the range between the start point (point where toner adheres) and the end point (point where toner adheres maximally) for tone reproduction optimally.
[0004]
[Problems to be solved by the invention]
However, with the primary charger using the potential sensor and the control of the potential of the developing bias to secure the gradation range, it is fundamentally difficult to cope with the fluctuation over time in the development, and finally the recording material However, there is a problem that the image density range obtained by the method cannot be guaranteed.
[0005]
Further, the potential sensor used in this control has a higher cost than a jam detection sensor or the like used in the recording material conveyance path, and as a result, the production price of the product is increased.
[0006]
Accordingly, it is an object of the present invention to provide an image forming apparatus which can cope with time-dependent fluctuations in development, improves the gradation stability of an output image, and does not increase the manufacturing cost. .
[0007]
[Means for Solving the Problems]
The above object is achieved by an image forming apparatus according to the present invention. In summary, the invention relates to an image carrierChargeCharging means;Expose the image carrier charged by the charging meansExposure means;Develop the electrostatic latent image formed by the exposure unit with tonerAnd a developing unit.
The densities of a plurality of reference toner images formed by changing the developing conditions without changing the exposure conditions and the charging conditions are detected by the density detecting means, and the temporary developing conditions are determined in accordance with the detected densities. And
The density detecting means detects the densities of a plurality of reference toner images formed under a plurality of different developing conditions and charging conditions set according to the provisional developing conditions without changing the exposure conditions. The development and charging conditions according to the determined densityAn image forming apparatus characterized in that:
[0008]
According to a second aspect of the present invention, an image carrierChargeCharging means;Expose the image carrier charged by the charging meansExposure means;Develop the electrostatic latent image formed by the exposure unit with tonerAnd a developing unit.
The densities of a plurality of reference toner images formed by changing the charging conditions without changing the exposure conditions and the developing conditions are detected by the density detecting means, and the temporary charging conditions are determined in accordance with the detected densities. And
The density detecting means detects the densities of a plurality of reference toner images formed under a plurality of different developing conditions and charging conditions set in accordance with the provisional charging conditions without changing the exposure conditions. The development and charging conditions according to the determined densityAn image forming apparatus is provided.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.
[0012]
Example 1
FIG. 1 shows a schematic overall configuration of an embodiment of the image forming apparatus of the present invention. In this embodiment, the image forming apparatus is an electrophotographic multicolor image forming apparatus, which includes an image carrier that rotates in the direction of an arrow, that is, a photoconductor drum 1 in this embodiment, and a charging unit around it. A primary charger (charging means) 2, a rotary developing device (developing means) 3 having developing devices M, C, Y, and BK, a transfer charging means 4, a cleaning means 5, and a photosensitive drum 1. An exposure unit 6 such as a laser beam exposure device arranged above is provided. Next, an image forming procedure in the image forming apparatus having such a configuration will be described.
[0013]
As described above, the photosensitive drum 1 rotates in the direction of the arrow, and is uniformly charged by the primary charger 2. That is, in this embodiment, the primary charger 2 is a scorotron-type corona charger having a grid 2A, and a voltage set by the CPU 13 is applied to the grid 2A of the primary charger 2 from the DC high-voltage power supply 11. As a result, the surface of the photosensitive drum is uniformly charged.
[0014]
The image signal is converted into laser light via a laser driver (not shown) and a laser light source (not shown), and the laser light is reflected by the polygon mirror 7 and the mirror 8 and irradiated onto the photosensitive drum 1. . An electrostatic latent image is formed on the photosensitive drum 1 by scanning with the laser beam. The latent image on the photosensitive drum 1 is developed for each color by the developing device 3 to be a toner image. A developing bias voltage set by the CPU 13 is applied from the AC high-voltage power supply 12 to the developing means, particularly a developer carrier such as a developing sleeve disposed to face the photosensitive drum 1. FIG. 1 shows a development state in which the developing device Y is located at the development position and is developed with yellow toner.
[0015]
On the other hand, a recording material P such as a reflection type recording sheet or a transparent recording sheet is wound around a transfer drum 9 as a recording material carrier, and in this embodiment, Y (yellow), M (magenta), (Cyan) and BK (black) rotate one by one, and the toner image on the photosensitive drum is transferred onto the recording material P in a superimposed manner.
[0016]
When the transfer is completed, the recording material P is separated from the transfer drum 9 and is conveyed to a fixing unit 10 including a pair of fixing rollers, and the toner image on the recording material P is made into a permanent image (color image print).
[0017]
Further, the toner remaining on the photosensitive drum 1 without the transfer partition is wiped off by the cleaning means 5, and the photosensitive drum 1 is cleaned so as not to hinder the next image formation.
[0018]
As will be described in detail later, as shown in FIG. 1, around the photoconductor drum 1, a detection unit 14 for reading a reference patch image formed on the photoconductor drum 1 is further arranged. ing. In the present embodiment, the detecting unit 14 includes an LED 15 as an irradiating unit that emits near-infrared light (light having a main wavelength of about 950 nm), and a light-receiving unit that receives the near-infrared light reflected by the photosensitive drum 1. And an element (optical sensor) 16.
[0019]
FIG. 2 schematically shows an image signal processing circuit for obtaining a gradation image according to the present embodiment.
[0020]
According to the present embodiment, a luminance signal of an image is obtained by the CCD 21, and the luminance signal is converted into a digital signal by the A / D conversion circuit 22. In the obtained luminance signal, sensitivity variations of individual CCD elements are corrected by a shading circuit 23, and the corrected luminance signal is converted into a density signal by a LOG conversion circuit 24. The density signal thus obtained is converted by the LUT 25 obtained by inversely converting the γ characteristic of the printer so that the original image density and the output image density match. The converted signal is converted by the pulse width conversion circuit 26 into a signal corresponding to the dot width, and sent to the laser driver 27 of the exposure means. The signals are all processed as 256-bit signals of 8 bits.
[0021]
As described above, the image signal is converted into a laser beam through the laser driver and the laser light source (not shown), and the laser beam is scanned by the polygon mirror 7 to irradiate the photosensitive drum 1. As described above, a latent image having a gradation characteristic due to a change in dot area is formed on the photosensitive drum 1 by laser beam scanning, and a gradation image is formed through processes of development, transfer, and fixing.
[0022]
In this embodiment, the image forming apparatus includes a test pattern generator 29 as shown in FIG. FIG. 13 shows a state in which a specific pattern generated by the test pattern generator 29, that is, a reference patch image 121 is formed on the photosensitive drum 1.
[0023]
That is, the specific pattern 121 is formed at a position on the photosensitive drum 1 corresponding to the detection unit 14 including the LED 15 and the light receiving element (optical sensor) 16. The formed specific pattern 121 is irradiated with near-infrared light emitted by the LED 15, and the reflected light is received by the light receiving element, that is, the optical sensor 16.
[0024]
FIG. 3 shows a processing circuit for processing a signal from the detecting means 14, that is, the sensor 16.
[0025]
In this embodiment, near-infrared light incident on the sensor 16 is converted into an electric signal by the sensor 16, and the electric signal is converted into a digital signal by the A / D converter 41. Next, the digital signal is subjected to density conversion by the density conversion circuit 42, and the correction value is calculated by the correction value calculation circuit 43 of the correction value corresponding to the sensor individual in order to correct the deviation of the individual sensor based on the converted density value. The calculated value is sent to the CPU 13.
[0026]
Next, the developer used in each developing device will be described. In this embodiment, a two-component developer having a carrier and a toner is used as the developer because it is advantageous in color purity and transparency.
[0027]
Describing the toner, the toner used in the present embodiment is a yellow, magenta, cyan, and black toner formed by dispersing color materials of each color using a styrene-based copolymer resin as a binder.
[0028]
The spectral characteristics of the yellow, magenta, and cyan color toners are as shown in FIGS. 4 to 6 in this order, and the reflectance of near-infrared light (950 nm) is 80% or more.
[0029]
On the other hand, since the black toner uses carbon black as a coloring material, the reflectance of near-infrared light (950 nm) is about 10% as shown in FIG.
[0030]
The particle diameter of the used toner is 6 to 8 μm in volume average, and is obtained by a known pulverization method. In addition, it was confirmed that the same result was obtained with a toner polymerized by the suspension polymerization method.
[0031]
FIG. 14 shows the reflectance characteristics of the photosensitive drum 1. The reflectance of near infrared light (950 nm) is about 40%.
[0032]
FIG. 8 shows a relationship between the image density on the recording material P corresponding to the toner density on the photosensitive drum 1 and the output of the sensor 16. In this embodiment, the output of the sensor 16 in a state where the toner does not adhere to the photosensitive drum 1 is set to 2.5V.
[0033]
As can be seen from FIG. 8, as for the yellow, magenta, and cyan color toners, the reflected light amount from the photosensitive drum 1 increases as the image density increases, and the sensor output increases. On the other hand, for black, as the image density increases, the amount of light reflected from the photosensitive drum 1 decreases, and the sensor output decreases.
[0034]
By utilizing these relationships, it is possible to know the state of the output image without transferring the toner image to the recording material P from the sensor output even with toners having different reflection characteristics.
[0035]
FIG. 9 shows a control flowchart of the primary charger grid voltage (Vpri), the photosensitive drum surface potential, and the developing bias potential (Vdev) in this embodiment according to the present invention.
[0036]
This control is started when the main power supply of the image forming apparatus main body is turned on and an image can be formed, for example, when the fixing temperature reaches a specified temperature or immediately thereafter, and further, When a timer is set in the apparatus main body, the apparatus is started periodically, for example, every two hours. In other words, the apparatus is started at intervals such that the user does not know that the gradation characteristic of the image changes. It is desirable to make it.
[0037]
When this control is activated and started, the already registered Vpri1 and Vdev1 are set, and a patch image 1 having a density signal 144 level is formed (S91). Next, Vpri2 and Vdev2 are set, and a patch image 2 of a density signal 144 level is formed (S92). At this time, even if Vpri and Vdev are changed, the potential setting on the photoconductor drum 4 is not instantaneously switched due to the configuration of the image forming apparatus, but an inclined area in the middle of the change is generated. As shown in FIG. 13, the patch images 121 are formed at intervals.
[0038]
Next, Vpri3 and Vdev3 are set to form a patch image 3 of the density signal 144 level (S93).
[0039]
Ideally, it is considered desirable to form an image at a density signal level of 255. However, in this embodiment, the density signal is set at a level of 144. That is, if the density is too high, the reading resolution by the sensor 16 tends to decrease. Therefore, the density signal level is set to 144 levels. However, the density signal level is not limited to 144 levels.
[0040]
Further, the primary charger grid voltage (Vpri) and the developing bias potential (Vdev) will be described.
[0041]
FIG. 10 shows the relationship between the primary charger grid voltage (Vpri), the photosensitive drum surface potential, and the developing bias potential (Vdev). The solid line of V00 is the photosensitive drum surface potential after exposure when the image signal of 00h of this image forming apparatus is set. The solid line of VFF indicates the photosensitive drum surface potential after exposure when the image signal of FFh of the image forming apparatus is set. As the primary charger grid voltage (Vpri) increases, both VFF and V00 increase.
[0042]
A broken line in FIG. 10 indicates an optimum developing bias potential in the image forming apparatus. The difference between the broken line of the developing bias and the line of the VFF, that is, Vcont1, Vcont2, and Vcont3 in FIG. 10 is a value called a contrast potential. As the Vcont increases, the maximum density of the image forming apparatus increases. In a relationship.
[0043]
In the present embodiment, the characteristics shown in FIG. 10 are checked in advance, and the values of Vpri1, Vdev1, Vpri2, Vdev2, Vpri3, and Vdev3 are registered in a ROM (not shown) so that the values can be retrieved at any time. I do.
[0044]
Referring back to FIG. 9, the patch images 1, 2, and 3 formed as described above are read by the sensor 16 and converted into densities D1, D2, and D3 (S94). Next, Vpri and Vdev for obtaining the target density D = 1.5 are calculated and set (S95). In this embodiment, by setting the target density D of the 144 level to 1.5, the density of 1.6 can be indirectly achieved at the 255 level.
[0045]
A method for obtaining Vpri and Vdev will be described with reference to FIG. FIG. 11 is a graph in which the densities D1, D2, and D3 obtained in S94 are plotted against the primary charger grid voltage (Vpri).
[0046]
Here, it is checked which of the densities D1, D2, and D3 the target density 1.5 is, or whether the target density is 1.5 or less or D3 or more. In the present embodiment shown in FIG. 11, there is a target density of 1.5 between D2 and D3.
[0047]
Therefore, in this embodiment, Vpri of 440 V and Vdev of 400 V were set by linearly interpolating the data of Vpri2 and Vpri3 and the data of D2 and D3.
[0048]
In FIG. 9, it is determined whether or not the above sequence has been completed for all colors (S96), and a similar sequence for four colors is performed independently to determine and set Vpri and Vdev for each color. When all the colors have been completed, the present control ends.
[0049]
According to the above-described control of the present invention, since the setting of the density range to be ensured by the image forming apparatus is controlled by the toner image on the photosensitive drum 1 corresponding to the actual image density, the fluctuation of the density during development is sufficient. Can be set, and as a result, the gradation stability of the output image can be improved.
[0050]
Example 2
FIG. 12 shows a control flowchart of the primary charger grid voltage (Vpri), the photosensitive drum surface potential, and the developing bias potential (Vdev) in the second embodiment of the present invention.
[0051]
In the present embodiment, the control sequence is roughly divided into two blocks. That is, the flow on the left side of FIG. 12 and the flow on the right side. First, the control sequence shown by the flow on the left will be described.
[0052]
First, while the primary charger grid voltage is set to VpriA and the developing bias potential is changed to Vdev1, Vdev2, and Vdev3, 48-level thin patch images 1, 2, and 3 are formed (S121, S122, and S123). The positional relationship and sequence on the photosensitive drum 1 for creating a patch image are the same as in the first embodiment. FIG. 15 shows the state of the surface potential of the photosensitive drum 1 at this time. By switching the developing bias potential to Vdev1, Vdev2, and Vdev3, the contrast potential setting changes and the image densities of the patch images 1, 2, and 3 change as indicated by arrows.
[0053]
The image densities of the patch images 1, 2, and 3 are read by the sensor 16 and converted into densities D1, D2, and D3 (S124).
[0054]
The target density D, that is, VdevB, which is the target density set to the image density 0.4 in this embodiment, is obtained from the relationship between the densities D1, D2, and D3 by the same means as in the first embodiment, and this value is set. (S125).
[0055]
In this example, it can be seen that the target density was obtained under the conditions indicated by the mark X in FIG. 15, that is, at a developing bias potential of 400 V.
[0056]
When the above-described control sequence is completed for all colors (S126), the control sequence in the first block is completed, and the flow proceeds to the control sequence of the second block shown in the flow on the right side of FIG.
[0057]
In the control sequence in the first block, the control for guaranteeing the density of the low-density patch image is performed while the developing bias is applied. However, the meaning of this control is that the surface potential V00 when the image signal of 00h is drawn. And the optimum state of the developing bias potential Vdev, that is, the arrow G in FIG. If the relationship between the surface potential V00 and the developing bias potential Vdev is maintained, the gradation characteristics of the extreme highlight where the toner starts to adhere are indirectly maintained.
[0058]
Next, the control sequence shown by the flow on the right side will be described.
[0059]
First, Vpri4, Vpri5, Vpri6 and Vdev4, Vdev5, Vdev6 are set from VdevB determined by the control sequence shown in the flow on the left (S127). At this time, in this embodiment, as shown in FIG. 16, the intervals between Vpri4, Vpri4, Vpri, and 6 are set so that the difference between the surface potential V00 obtained by performing the 0-level laser exposure and the developing bias potential Vdev becomes G. It was set to open moderately.
[0060]
More specifically, the relationship between the primary charger grid voltage (Vpri) of V00 and the developing bias potential (Vdev) is checked in advance by a surface voltmeter, and the slope coefficient is registered in the ROM of the image forming apparatus. In addition, it was constructed so that it could be withdrawn at any time. Then
A patch image 4 of 144 levels is formed by Vpri4 and Vdev4 (S128),
A 144-level patch image 5 is formed with Vpri5 and Vdev5 (S129), and
A 144-level patch image 6 is formed with Vpri6 and Vdev6 (S130).
[0061]
The patch images 4, 5, and 6 are read by the sensor 16 and converted into densities D4, D5, and D6 (S131).
[0062]
The target density D, that is, VpriC and VdevC, which are the target densities set to the image density 1.4 in this embodiment, are obtained from the relationship with the densities D1, D2, and D3 by the same means as in the first embodiment. Is set (S132).
[0063]
When all the colors have been completed, the present control is completed (S133).
[0064]
According to the above-described control of the present invention, in the control sequence shown in the left flow, first, in order to guarantee the low density side, the relationship between V00 and the developing bias is temporarily set, and then the right flow is set. In the control sequence shown in (2), in order to guarantee the high density while maintaining the low density state, the relationship between the developing bias and the VFF is adjusted, and the two steps of the low density and the high density of the gradation are performed. The points can be controlled, and as a result, the gradation stability of the output image can be improved.
[0065]
In the present embodiment, the procedure of adjusting the high density after adjusting the low density is taken. However, it is needless to say that the same effect can be obtained in the order of adjusting the high density and then adjusting the low density in the reverse order. No.
[0066]
Example 3
FIG. 17 shows a control flowchart of the primary charger grid voltage (Vpri), the photosensitive drum surface potential, and the developing bias potential (Vdev) in the third embodiment of the present invention.
[0067]
In the present embodiment, the control sequence is roughly divided into two blocks. That is, the flow on the left side of FIG. 17 and the flow on the right side. First, the control sequence shown by the flow on the left will be described.
[0068]
First, with the developing bias potential set to VdevE and the primary charger grid voltages changed to Vpri7, Vpri8, and Vpri9, 144-level dark patch images 7, 8, and 9 are formed (S171, S172, and S173). The positional relationship and sequence on the photosensitive drum 1 for creating a patch image are the same as in the first embodiment. FIG. 18 shows the state of the surface potential of the photosensitive drum 1 at this time. By switching the primary charger grid voltage to Vpri7, Vpri8, Vpri9, the contrast potential setting changes and the image densities of patch images 7, 8, and 9 also change.
[0069]
The image densities of the patch images 7, 8, and 9 are read by the sensor 16 and converted into densities D7, D8, and D9 (S174).
[0070]
The target density D, that is, VpriF which is the target density set to the image density 1.4 in this embodiment is obtained from the relationship with the densities D7, D8, and D9 by the same means as in the first embodiment, and this value is set. (S175).
[0071]
In this example, it can be seen that the target density was obtained under the conditions indicated by the mark X in FIG. 18, that is, at the primary charger grid voltage of 400V.
[0072]
When the above-described control sequence is completed for all colors (S176), the control sequence in the first block is completed, and the process proceeds to the control sequence of the second block shown in the right-hand flow of FIG.
[0073]
In the control sequence in the first block, the control for guaranteeing the density of the high-density patch image is performed while the primary charger grid voltage is applied. The intent of this control is that the image signal of FFh (255 level) is output. The optimum state of the surface potential VFF and the developing bias potential Vdev when drawing, that is, the arrow H in FIG. 18 has been obtained. If the relationship between the surface potential VFF and the developing bias potential Vdev is maintained, the gradation characteristics of the high density portion where a large amount of toner adheres will be indirectly maintained.
[0074]
Next, the control sequence shown by the flow on the right side will be described.
[0075]
First, Vpri10, Vpri11, Vpri12 and Vdev10, Vdev11, Vdev12 are set from VpriF determined in the control sequence shown in the flow on the left (S177). At this time, in the present embodiment, as shown in FIG. 19, the intervals between Vpri10, Vpri10, Vpri12 and Vpri are set appropriately so that the difference between the surface potential VFF obtained by performing the laser exposure at the 255 level and the developing bias potential Vdev becomes H. Set to open.
[0076]
More specifically, the relationship between the grid voltage of the primary charger of the VFF and the developing bias potential is checked in advance with a surface voltmeter, and the coefficient of the slope is registered in the ROM of the image forming apparatus, and can be extracted at any time. It is configured as follows. Then
A patch image 10 of 48 levels is formed with Vpri10 and Vdev10 (S178),
A patch image 11 of 48 levels is formed by Vpri11 and Vdev11 (S179), and
A patch image 12 of 48 levels is formed by Vpri12 and Vdev12 (S180).
[0077]
The patch images 10, 11, and 12 are read by the sensor 16 and converted into densities D10, D11, and D12 (S181).
[0078]
The target density D, that is, VpriG and VdevG, which are the target densities set to the image density 0.4 in this embodiment, are obtained from the relationship with the densities D10, D11, and D12 by the same means as in the first embodiment. Is set (S182).
[0079]
When all the colors have been completed, the present control is completed (S133).
[0080]
According to the above-described control of the present invention, in the control sequence shown in the left flow, first, in order to guarantee the high density side, the relationship between VFF and the developing bias is temporarily set, and then the right flow is set. In order to guarantee the low density while maintaining the high density state, the control sequence shown in (2) adjusts the relationship between the developing bias and V00. The points can be controlled, and as a result, the gradation stability of the output image can be improved.
[0081]
In the description of each of the above embodiments, the photoconductor drum has been described as the image carrier, but a photoconductor belt, a photoconductor sheet, or the like may be used in addition. Also, an example has been described in which the toner image on the image carrier is optically detected by the optical sensor, but the transfer drum 9 as the recording material carrier is used as the image medium, and the patch image formed on this image medium is A similar effect can also be obtained by arranging a sensor capable of detecting the patch image and reading it in synchronization with the image position after forming the patch image, and performing a series of controls similar to the above-described embodiment. In this case, it is preferable to provide a step of cleaning the toner on the transfer drum 9 when the control is completed. Of course, other than the transfer drum, a transfer belt, a transfer sheet, or the like may be used as the recording material carrier.
[0082]
Further, in an image forming apparatus using a drum-shaped, belt-shaped or sheet-shaped intermediate transfer body, a sensor capable of detecting a patch image on the intermediate transfer body is arranged, and when a patch image is formed, it is located at the image position. A similar effect can be obtained by performing a series of controls similar to those in the above-described embodiment by reading in synchronization.
[0083]
Furthermore, as shown in FIG. 20, it goes without saying that the same control can be performed by a sensor 201 for detecting a toner image on a recording material and a sensor 202 for detecting a toner image immediately after fixing.
[0084]
【The invention's effect】
As described above, the present inventionAccording toIt is possible to cope with the fluctuation over time in development, to improve the gradation stability of the output image, and to achieve the effect of not increasing the manufacturing cost.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a first embodiment of an image forming apparatus of the present invention.
FIG. 2 is a block diagram illustrating a schematic configuration of an image signal processing circuit.
FIG. 3 is a block diagram illustrating transmission of a sensor output signal.
FIG. 4 is a spectral characteristic diagram of a yellow toner.
FIG. 5 is a spectral characteristic diagram of magenta toner.
FIG. 6 is a spectral characteristic diagram of a cyan toner.
FIG. 7 is a spectral characteristic diagram of a black toner.
FIG. 8 is a diagram illustrating a relationship between an output image density and a sensor output.
FIG. 9 is a flowchart showing a first embodiment of a control sequence according to the present invention.
FIG. 10 is a diagram showing a relationship between a primary charger grid voltage, a photosensitive drum surface potential, and a developing bias potential.
FIG. 11 is a diagram for finding an optimal primary charger grid voltage.
FIG. 12 is a flowchart showing a second embodiment of the control sequence according to the present invention.
FIG. 13 is a perspective view illustrating a configuration for reading a patch image on a photosensitive drum.
FIG. 14 is a graph showing a spectral reflection characteristic of the photosensitive drum.
FIG. 15 is a diagram showing a relationship between a primary charger grid voltage, a photosensitive drum surface potential, and a developing bias potential.
FIG. 16 is a diagram showing a relationship between a primary charger grid voltage, a photosensitive drum surface potential, and a developing bias potential.
FIG. 17 is a flowchart showing a third embodiment of the control sequence according to the present invention.
FIG. 18 is a diagram showing a relationship between a primary charger grid voltage, a photosensitive drum surface potential, and a developing bias potential.
FIG. 19 is a diagram showing a relationship between a primary charger grid voltage, a photosensitive drum surface potential, and a developing bias potential.
FIG. 20 is a schematic configuration diagram showing another embodiment of the image forming apparatus of the present invention.
[Explanation of symbols]
1 Photoconductor drum (image carrier)
2 Primary charger (charging means)
2A grid
3 Developing device (developing means)
4 Transfer charging means
5 Cleaning means
6 Exposure means
9 Transfer drum (recording material carrier)
10 Fixing means
11 Primary charger grid applied high voltage power supply
12 Development bias power supply
13 CPU
14 Detection means
15 LED (light irradiation means)
16 Light receiving element (optical sensor)

Claims (2)

An image forming apparatus having a charging unit that charges the image carrier, an exposure unit that exposes the image bearing member charged by the charging means, a developing means for developing the electrostatic latent image formed by the exposure means with toner, the At
The densities of a plurality of reference toner images formed by changing the developing conditions without changing the exposure conditions and the charging conditions are detected by the density detecting means, and the temporary developing conditions are determined in accordance with the detected densities. And
The density detecting means detects the densities of a plurality of reference toner images formed under a plurality of different developing conditions and charging conditions set according to the provisional developing conditions without changing the exposure conditions. An image forming apparatus for determining a developing condition and a charging condition according to the determined density . An image forming apparatus having a charging unit that charges the image carrier, an exposure unit that exposes the image bearing member charged by the charging means, a developing means for developing the electrostatic latent image formed by the exposure means with toner, the At
The densities of a plurality of reference toner images formed by changing the charging conditions without changing the exposure conditions and the developing conditions are detected by the density detecting means, and the temporary charging conditions are determined in accordance with the detected densities. And
The density detecting means detects the densities of a plurality of reference toner images formed under a plurality of different developing conditions and charging conditions set according to the provisional charging conditions without changing the exposure conditions. An image forming apparatus for determining a developing condition and a charging condition according to the determined density .

Images