JPH0527595A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent fluctuations in a toner replenishing quantity caused by a left standing time when a toner replenishing system is nonoperated. CONSTITUTION:A left standing timer is installed, and when a copying action is finished, the left standing timer is operated, to count the left standing time. On the other hand, a correcting coefficient corresponding to the left standing time counted when the starting button of a device is depressed, is determined, and when the number of video counts calculated by counting the output levels of each picture element of a digital picture signal, is converted into a toner replenishing time on a CPU 67, the toner replenishing time obtained in such a manner that the toner replenishing time on a conversion table is multiplied by the determined correcting coefficient to correct the left standing time, that is, the rotational frequency of a screw 62 is determined. When one toner image is formed, the screw 62 is rotated by the determined rotational frequency to replenish the toner, before the next toner image is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming for a copying machine, a printer, etc., such as an electrophotographic system or an electrostatic recording system in which a developer is attached to a latent image formed on an image carrier to make it a visible image. More specifically, the present invention relates to an image forming apparatus including a developer concentration control device that appropriately controls the toner concentration of a two-component developer.

[0002]

2. Description of the Related Art Generally, a two-component developer containing toner particles and carrier particles as a main component is used in a developing device provided in an electrophotographic or electrostatic recording type image forming apparatus. Particularly, in a color image forming apparatus that forms a full-color image or a multi-color image by an electrophotographic method, most developing apparatuses use a two-component developer from the viewpoint of image tint and the like. As is well known, the toner concentration (that is, the ratio of the weight of toner particles to the total weight of carrier particles and toner particles) of this two-component developer is a very important factor in stabilizing the image quality. The toner particles of the developer are consumed during development, and the toner concentration changes. Therefore, the developer concentration control device (ATR) is used to accurately detect the toner concentration of the developer at appropriate times, toner is replenished according to the change, and the toner concentration is constantly controlled to maintain the image quality. Need to hold.

FIG. 5 shows an example of the overall structure of an image forming apparatus equipped with a conventional developer concentration control apparatus, which is an electrophotographic digital copying machine in this example. First, the image of the document 21 is CC
An analog image signal read and obtained by D1 is amplified to a predetermined level by an amplifier 2 and is, for example, an 8-bit (0 to 255 gradation) digital image signal by an analog-digital converter (A / D converter) 3. Is converted to. Next, this digital image signal is supplied to a γ converter (a converter which is composed of a 256-byte RAM in this example, and which performs density conversion by a look-up table method) 5 and outputs γ.
After being corrected, the digital-analog converter (D / A converter) 9 is input. Here, the digital image signal is converted again into an analog image signal and supplied to one input of the comparator 11. The other input of the comparator 11 is supplied with a triangular wave signal of a predetermined cycle generated from the triangular wave generating circuit 10, and the analog image signal supplied to one input of the comparator 11 is compared with this triangular wave signal and pulsed. It is width modulated. This pulse-width-modulated binary image signal is directly input to the laser drive circuit 12 and used as an ON / OFF control signal for emission of the laser diode 13. The laser light emitted from the laser diode 13 is scanned in the main scanning direction by a well-known polygon mirror 14, passes through the f / θ lens 15 and the reflection mirror 16, and is rotated in the arrow direction. It will be illuminated above and will form an electrostatic latent image.

On the other hand, the photosensitive drum 17 is uniformly discharged by the exposing device 18, and is uniformly charged by the primary charging device 19, for example, to be negative. Then, upon receiving the above-mentioned laser light irradiation, an electrostatic latent image corresponding to the image signal is formed. This electrostatic latent image is developed into a visible image (toner image) by the developing device 20. This toner image is stretched between the two rollers 25 and 26, and is transferred to the transfer material 23 held on the transfer material carrying belt 27 which is endlessly driven in the direction of the arrow in the figure, and the transfer charger 22
Is transcribed by the action of. The residual toner remaining on the photosensitive drum 17 is then scraped off by the cleaner 24. Note that only one image forming station (including the photoconductor drum 17, the exposure device 18, the primary charging device 19, the developing device 20 and the like) is shown for simplification of description, but in the case of a color copying machine, For example, four image forming stations having the same configuration for each color of cyan, magenta, yellow, and black are sequentially arranged on the transfer material carrying belt 27 along its moving direction.

Further, in order to correct the toner density which has changed in the developing device 20 due to the development of the latent image, a video count type developer density control device is provided to control the output level of the digital image signal for each pixel. The toner has been added up and the toner is being predicted to be replenished. That is, the analog-digital converter 3
The output level of the image signal converted into a digital signal by each pixel is integrated, and this is converted into a video count number by the video counter 4 and sent to the CPU 6. The CPU 6 converts the video count number into a replenishment amount and sends it to the motor drive circuit 7 as a toner replenishment signal. The motor drive circuit 7 drives the motor 28 only for the time corresponding to the toner replenishment signal, and rotationally drives the toner conveying screw 30 in the toner replenishment tank 8 containing the toner 29 for the above predetermined time, and the toner replenishment tank 8 develops the toner. An appropriate amount of toner is replenished in the developing device 20 to keep the toner density in the developing device 20 constant.

[0006]

As described above, in the above-mentioned conventional developer concentration control device, the video count number obtained by integrating the output levels of the respective pixels of the digital image signal is uniquely converted into the toner replenishment amount. Since toner is being replenished, the toner replenishment amount for the same video count number is always the same amount. However, the toner accumulation state in the toner replenishment tank changes (for example, the density changes) depending on the length of time during which the copying operation is stopped, that is, the length of time that the toner replenishment system is inactive.
Therefore, if the video count number is uniquely converted to the toner replenishment amount as described above, there is a serious drawback that the replenishment amount varies even if toner is replenished for the same replenishment time due to the length of the standing time. there were.

Therefore, an object of the present invention is to control the developer concentration by correcting the toner replenishment time in accordance with the length of time the toner replenishment system is in the inactive state and preventing the toner replenishment amount from varying due to the time left. An image forming apparatus including the apparatus is provided.

[0008]

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention forms an electrostatic latent image corresponding to an image information signal on an image carrier, develops the electrostatic latent image with a two-component developer to form a visible image, and In an image forming apparatus for transferring an image to a transfer material, a toner replenishing means for replenishing the toner of the two-component developer and a toner replenishing means for operating the toner replenishing means according to the image density information of the image information signal to replenish the toner. A first developer concentration control device, and the first developer concentration control device
The image forming apparatus is characterized in that the operation time of the toner replenishing means operated by the developer concentration control device is corrected to replenish toner.

In one embodiment of the present invention, a second developer concentration control device for detecting the toner concentration of the two-component developer is provided, and the second developer concentration control device is operated at a predetermined timing. The toner replenishment error by the first developer concentration control device is corrected by the output signal from the lever of the second developer concentration control device according to the toner concentration.

[0010]

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

An image forming apparatus to which the present invention can be applied forms a latent image corresponding to an image information signal on an image carrier such as a photoconductor or a dielectric by an electrophotographic system, an electrostatic recording system, etc. The image is developed by a developing device using a two-component developer containing toner particles and carrier particles as main components to form a visible image (toner image), and the visible image is transferred to a transfer material such as paper, and a fixing unit. Any structure may be used as long as it is a permanent image.

First, the overall construction of an embodiment of an image forming apparatus according to the present invention will be described with reference to FIG. Although the present embodiment shows the case where the present invention is applied to an electrophotographic digital copying machine, it goes without saying that the present invention is equally applicable to other various image forming apparatuses such as an electrophotographic type and an electrostatic recording type.

In FIG. 1, an image of an original 31 to be copied is projected by a lens 32 onto an image pickup device 33 such as a CCD. The image pickup device 33 decomposes the image of the original 31 into a large number of pixels and generates a photoelectric conversion signal corresponding to the density of each pixel. The analog image signal output from the image pickup device 33 is sent to the image signal processing circuit 34, where it is converted into a pixel image signal having an output level corresponding to the density of the pixel for each pixel, and the pixel image signal is supplied to the pulse width modulation circuit 35. Sent.

The pulse width modulation circuit 35 forms and outputs a laser drive pulse having a width (time length) corresponding to the level of each input pixel image signal. That is, as shown in FIG. 3A, a wider drive pulse W is provided for a high-density pixel image signal, and a narrower drive pulse S is provided for a low-density pixel image signal. , A drive pulse I having an intermediate width is formed for the medium-density pixel image signal.

The laser drive pulse output from the pulse width modulation circuit 35 is supplied to the semiconductor laser 36, and the semiconductor laser 36 is caused to emit light for a time corresponding to the pulse width. Therefore, the semiconductor laser 36 is driven for a longer period of time with respect to the high-concentration pixels, and is driven for a shorter period of time with respect to the low-concentration pixels. Therefore, the photosensitive drum 40
The optical system described below exposes a high density pixel in a longer range in the main scanning direction and a low density pixel in a shorter range in the main scanning direction. That is, the dot size of the electrostatic latent image differs depending on the density of the pixel.
Therefore, of course, the toner consumption amount for the high density pixels is larger than that for the low density pixels. In FIG. 3D, the electrostatic latent images of low, medium and high density pixels are shown by L, M and H, respectively.

A laser beam 36a emitted from the semiconductor laser 36 is swept by a rotary polygon mirror 37, and a lens 38 such as an f / θ lens and a fixed mirror 39 for directing the laser beam 36a toward a photosensitive drum 40 which is an image carrier. Thus, a spot image is formed on the photosensitive drum 40. Thus, the laser beam 36a scans the drum 40 in a direction (main scanning direction) substantially parallel to the rotation axis of the photosensitive drum 40,
An electrostatic latent image will be formed.

The photosensitive drum 40 is an electrophotographic photosensitive drum that has amorphous silicon, selenium, OPC, etc. on its surface and rotates in the direction of the arrow. After being uniformly discharged by the exposure device 41, the primary charging device 42 is used. Are uniformly charged by. After that, the laser light modulated corresponding to the above-mentioned image information signal is exposed and scanned, whereby an electrostatic latent image corresponding to the image information signal is formed. This electrostatic latent image is reverse-developed by a developing device 44 using a two-component developer 43 in which toner particles and carrier particles are mixed, and a visible image (toner image) is formed. Here, the reversal development is a development method in which toner charged with the same polarity as the latent image is attached to a region of the photoconductor exposed to light to visualize the toner.
This toner image is stretched between two rollers 45 and 46,
It is transferred to the transfer material 48 held on the transfer material carrying belt 47 which is endlessly driven in the direction of the arrow in the figure by the action of the transfer charger 49.

Although only one image forming station (including the photosensitive drum 40, the exposure device 41, the primary charging device 42, the developing device 44, etc.) is shown for the sake of simplicity, the color image forming apparatus is not shown. In this case, for example, four image forming stations for each color of cyan, magenta, yellow, and black are sequentially arranged on the transfer material carrying belt 47 along the moving direction thereof, and on the photoconductor drum of each image forming station. An electrostatic latent image for each color obtained by color-separating the image of the original is sequentially formed, developed by a developing device having corresponding color toner, and sequentially transferred to a transfer material 48 which is held and conveyed by a transfer material carrying belt 47. Will be done.

The transfer material 48 to which the toner image is transferred is separated from the transfer material carrying belt 47 and conveyed to a fixing device (not shown) where it is fixed and converted into a permanent image. The residual toner remaining on the photosensitive drum 40 after the transfer is removed by the cleaner 50 after that.

An example of the developing device 44 is shown in FIG. As shown in the figure, the developing device 44 is arranged so as to face the photoconductor drum 40, and the inside thereof is a partition wall 5 extending in the vertical direction.
1, the first chamber (developing chamber) 52 and the second chamber (stirring chamber) 5
It is divided into three. A non-magnetic developing sleeve 54 that rotates in the arrow direction is arranged in the first chamber 52, and a magnet 55 is fixedly arranged in the developing sleeve 54. The developing sleeve 54 carries and conveys a layer of a two-component developer (including a magnetic carrier and a non-magnetic toner) whose layer thickness is regulated by a blade 56, and transfers the developer to the photosensitive drum 40 in a developing area facing the photosensitive drum 40. To develop the electrostatic latent image. In order to improve the developing efficiency, that is, the rate of applying toner to the latent image, a developing bias voltage in which a DC voltage is superimposed on an AC voltage is applied from a power source 57 to the developing sleeve 54.

Developer stirring screws 58 and 59 are disposed in the first chamber 52 and the second chamber 53, respectively. The screw 58 stirs and conveys the developer in the first chamber 52, and the screw 59 and the toner 63 supplied by the rotation of the conveying screw 62 from the toner discharge port 61 of the toner replenishing tank 60, which will be described later, and the inside of the developing device. Developer 43 in
And are conveyed by stirring to make the toner concentration uniform. The partition wall 51 has a first chamber 52 at the front and rear end portions in FIG.
And a second chamber 53 are connected to each other through a developer passage (not shown), and the first chamber in which the toner concentration is lowered due to the consumption of toner by the development due to the conveying force of the screws 58 and 59. The developer in 52 moves from one passage into the second chamber 53, and the developer whose toner concentration has recovered in the second chamber 53 moves from the other passage into the first chamber 52. There is.

The image signal processing circuit 34 is used to correct the changed developer density in the developing device 44 due to the development of the electrostatic latent image, that is, to control the amount of toner supplied to the developing device 44. The level of the output signal of is counted for each pixel. This counting is performed as follows in the embodiment of FIG.

First, the output signal of the pulse width modulation circuit 35 is supplied to one input of the AND gate 64, and this A
The clock pulse oscillator 65 is connected to the other input of the ND gate.
The clock pulse (the pulse shown in FIG. 3 (b)) is supplied. Therefore, from the AND gate 64, as shown in FIG. 3C, the number of clock pulses corresponding to the pulse width of each of the laser driving pulses S, I, and W, that is, the number of clock pulses corresponding to the density of each pixel. A pulse is output.
This clock pulse number is integrated by the counter 66 for each image, and the video count number is calculated. Therefore, the pulse integrated signal C ₁ (video count number) for each image from the counter 66 corresponds to the amount of toner consumed from the developing device 44 for forming one toner image of the original 31. There is.

Therefore, this video count number is calculated by the CPU 6
7 and store it in the RAM 68. CPU67
Has a conversion table showing the correspondence relationship between the video count number and the toner replenishment time. Based on the input video count number, toner 63 is replenished with an amount of toner 63 commensurate with the toner amount consumed from the developing device 44. The rotation driving time (that is, toner replenishment time) of the conveying screw 62 required to supply the toner from the tank 60 to the developing device is calculated, and the motor drive circuit 69 is controlled to drive the motor 70 only during the calculated time. Thus, in general, the higher the video count number, the longer the drive time of the motor 70, and the lower the video count number, the shorter the drive time of the motor 70.

The driving force of the motor 70 is transmitted to the carrying screw 62 through the gear train 71, and the carrying screw 6
2 conveys the toner 63 in the toner replenishing tank 60 to replenish the developing device 44 with a predetermined amount of toner. The toner is replenished every time the development of one image is completed.

However, as described above, without considering the length of time that the toner replenishment system is in the inoperative state,
If the video count number is uniquely converted to the toner replenishment amount, the toner accumulation state in the toner replenishment tank changes depending on the standing time, so that the toner replenishment amount changes at the same time and a replenishment error occurs.

For example, in this embodiment, a toner having a diameter of about 8 μm in which a color pigment is dispersed in polyester resin and silica is externally added is used. However, the toner 63 is rotated from the toner supply tank 60 shown in FIG. In an experiment using a replenishment system that replenishes the toner, the toner replenishment amount in the same time decreases linearly as the leaving time becomes longer, and the toner replenishing amount becomes constant when the leaving time becomes 15 hours or more,
It stopped changing. As is clear from this result, if the same video count number is uniquely converted into the same toner replenishment time without considering the leaving time, the replenishment amount will be different. Also, the video count is the toner supply amount (time).
However, there is a drawback that the toner replenishment amount cannot be easily determined unless it is uniquely converted.

Therefore, in this embodiment, a leaving timer is installed, and when the copying operation is completed, the leaving timer is operated to measure the leaving time. On the other hand, based on the above result, the leaving time as shown in FIG. And the correction coefficient are determined in advance, the correction coefficient corresponding to the standing time measured when the start button of the apparatus is pressed is determined from the relationship of FIG. 4, and the video count is converted into the toner replenishment time. , CPU
The toner replenishment time in the conversion table showing the correspondence relationship between the video count number and the toner replenishment time included in 67 is multiplied by this correction coefficient to determine the toner replenishment time in which the leaving time is corrected. Is configured so that the same amount of toner can be supplied. That is, it is possible to determine the correct toner replenishment amount in which the leaving time is uniquely corrected from the video count number. The correction coefficient at 15 hours was 1.5.

By the way, the output level of each pixel of the digital image signal obtained by photoelectrically converting the image of the original to be copied as described above is integrated, converted into a video count number, and converted into a supply amount. And predict the amount of consumption and develop unit 44
Unlike the case where the actual toner concentration of the developer is directly detected and the toner is replenished based on the toner concentration, the toner replenishment is a predicted replenishment.
4 when the amount of toner replenished from the toner replenishing tank 60 or the expected amount of toner consumption from the developing device 44 changes, and due to fluctuations in the consumption system and the replenishing system, the developer in the developing device 44 is changed. The toner concentration of 43, that is, the mixing ratio of the toner particles and the carrier particles gradually deviates from the initial setting value (specified value). If this deviation is not corrected, the toner density will largely deviate from the allowable range of the initial setting value.

Therefore, in the present embodiment, a second developer concentration control device is provided, and the second developer concentration control device is provided at a predetermined timing, for example, every time toner is replenished, or. The photoconductor drum 40 is activated at a timing such as after each copy operation is completed, or when the number of copies reaches a predetermined number, or when the number of video counts reaches a predetermined value, or the like. Form a reference image on top.

More specifically, a reference image signal generating circuit 72 for generating a reference image signal having a signal level corresponding to a predetermined density is provided, and the reference image signal from the generating circuit 72 is supplied to the pulse width modulation circuit 35. To generate a laser drive pulse having a pulse width corresponding to the predetermined density. The laser driving pulse is supplied to the semiconductor laser 36, the laser 36 is caused to emit light for a time corresponding to the pulse width, and the photosensitive drum 40 is scanned. (At this time, the counter 66 is not operated.) Thereby, the reference electrostatic latent image corresponding to the predetermined density is formed on the photosensitive drum 40, and the reference electrostatic latent image is developed by the developing device 44. To do. The patch-like reference toner image thus obtained is irradiated with light from a light source 73 such as an LED, and the reflected light is received by a photoelectric conversion element 74. Since the output signal of the photoelectric conversion element 74 corresponds to the density of the reference toner image, this output signal eventually corresponds to the actual toner density of the two-component developer in the developing device 44.

The output signal of the photoelectric conversion element 74 is supplied to one input of the comparator 75. A reference signal corresponding to the specified toner concentration of the developer 43 (toner concentration at the initial setting value) is input from the reference voltage signal source 76 to the other input of the comparator 75. Therefore, the comparator 75 compares the specified toner density with the actual toner density in the developing unit, and as a result of the comparison between the two input signals, the comparator 75 determines the actual amount of the developer 43 in the developing unit 44. An output signal indicating that the toner density is higher than a specified value or an output signal that indicates that the toner density is lower than the specified value is generated. If there is no difference between the two input signals, an output signal indicating that may be generated.

The output signal of the comparator 75 is supplied to the CPU 67. In this embodiment, the CPU 67 controls so as to correct the next toner replenishing operation in consideration of the measured standing time based on the output signal from the comparator 75. For example, when the actual toner concentration of the developer 43 detected by the photoelectric conversion element 74 is lower than the specified value, that is, when the toner is insufficiently supplied, the CPU 67 develops the insufficient toner. The screw 62 is operated to replenish the container 44. That is, the screw rotation time required to replenish the developing device 44 with the insufficient toner is calculated based on the output signal from the comparator 75, and the motor drive circuit 6
9 is controlled and the motor 70 is rotationally driven only for that time to supply the insufficient toner to the developing device 44. When the actual toner concentration of the developer 43 detected by the photoelectric conversion element 74 is higher than the specified value, that is, when the toner is excessively replenished, the CPU 67 outputs the output from the comparator 75. The amount of excess toner in the developer is calculated based on the signal. Then, in the subsequent image formation by the original, the toner is replenished so as to eliminate the excess toner amount, or the image is formed without replenishing the toner until the excess toner amount is consumed, that is, there is no toner. Replenishment forms an image to consume the excess toner amount, and when the excess toner amount is consumed, the toner replenishing operation is performed as described above.

As described above, by providing the second developer concentration control device and forming the reference image on the photoconductor drum 40 at a predetermined timing, the error of the amount of replenishment toner by the first developer concentration control device is increased. Can be corrected, and the toner density can always be maintained within the allowable range of the initial setting value.

The above control operation will be further described with reference to the flowchart of FIG.

First, when the start button is pressed to copy an original, the original is read in block S101 and a photoelectric conversion signal corresponding to the density of each pixel of the original image is generated. Next, in block S102, the output level of each pixel of the digital image signal is counted and integrated to calculate the video count number, which is sent to the CPU 67. Next, in block S103, the stand-by time measured by the stand-by timer from the end of the previously performed copy operation is read out to determine a correction coefficient corresponding to the length of this stand-by time, and in block S104, the CPU 67 converts the above-mentioned conversion. When converting the video count number to the toner replenishment time by referring to the table, the toner replenishment time is multiplied by the correction coefficient, and the toner replenishment time per image corresponding to the inputted video count number, that is, The rotation speed of the screw 62 is determined. For example, when the leaving time is 15 hours, the correction coefficient is 1.5 from the graph of FIG. 4, and the toner replenishment time determined from the normal video count is multiplied by 1.5. Then, in block S105, the copy operation is started, and the above-described image forming operations such as latent image formation, development, and transfer are executed. When one toner image is formed, the screw 62 is rotated by the number of rotations determined as described above to replenish toner before the next toner image is formed in block S106. Next, in block S107, the second developer concentration controller is operated to set the reference image to the photosensitive drum 4
0 to perform the above-mentioned operation. That is, it is checked whether the estimated replenishment amount obtained by converting the video count number into the toner replenishment time is correct in consideration of the leaving time, and if there is an error in the replenishment amount, corrective measures as described above are taken. To do. Next, decision block S1
At 08, it is determined whether or not the copy operation is completed. If it is completed (YES), the leaving timer is activated at block S109 to start measuring the leaving time when the toner replenishing system is inactive. Further, when the copy operation is not finished in the decision block S108 (NO), the leaving timer is not activated, and the process returns to the block S105 to continue the copy operation. Hereinafter, the same operation is repeated for each copy operation.

As described above, in this embodiment, the toner replenishment time calculated from the video count number in the CPU 67 is multiplied by the correction coefficient corresponding to the length of the leaving time to correct the variation of the toner replenishing amount due to the leaving time. Since the toner replenishment time is determined, there is an advantage that the toner can be replenished with high accuracy and the video count can be uniquely converted into the toner replenishment amount with high accuracy.

In the above embodiment, the toner replenishment time in which the variation of the toner replenishment amount due to the leaving time is corrected by multiplying the correction coefficient is used, and the toner is replenished with the same replenishment time for each copy operation even during continuous copying of the same document. However, during the continuous copy operation, the toner may be replenished in the normal toner replenishment time without multiplying the correction coefficient according to the standing time for the second and subsequent copy operations. Further, in the copying operation for the second and subsequent sheets of continuous copying, the toner may be replenished by the toner replenishment time multiplied by the correction coefficient smaller than that of the first sheet.

Further, in the above embodiment, the toner is replenished every time one toner image is formed. However, every time the copy number reaches a predetermined number, for example, 10 or the video count number reaches a predetermined value. The toner may be replenished collectively at each time. Of course, the toner replenishment time at this time is the replenishment time obtained by multiplying the normal toner replenishment time determined from the video count number by the correction coefficient according to the leaving time shown in the above embodiment.

Further, in the above embodiment, in order to measure the actual toner density of the developer in the developing device, a patch image is formed on the photosensitive drum and the density of this image is measured. Uses an inductance detection type developer concentration control device that detects the apparent magnetic permeability based on the mixture ratio of carrier and toner, and detects and corrects the actual toner concentration based on the change in the output as the second developer concentration control device. You may. Alternatively, the actual toner concentration of the developer can be measured by directly irradiating the developer on the developing sleeve or the like with light and measuring the reflected light. However, when the toner is colored black with carbon black, there is no great difference in the spectral reflectance between the toner and the carrier, and this method deteriorates the toner density detection accuracy, which is not preferable.

The present invention can also be applied to an image forming apparatus that performs the gradation expression of an image by the dither method. The present invention can also be applied to an image forming apparatus that forms a toner image based on an image information signal output from a computer or the like instead of copying a document. Further, it goes without saying that various modifications and changes can be made as necessary.

[0042]

As described above, according to the image forming apparatus of the present invention, the density information of the image of the image information signal is adjusted in accordance with the length of the leaving time in which the toner replenishing system is inactive. Since the determined toner replenishment time is corrected, it is possible to reliably prevent the variation of the toner replenishment amount due to the standing time. Therefore, there is a remarkable effect that the toner can be replenished with high accuracy and the toner concentration of the two-component developer can always be kept sufficiently within the allowable range of the initial setting value. Further, there is an effect that the density information of the image of the image information signal can be converted into a highly accurate toner replenishment amount that uniquely corrects the leaving time.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a schematic configuration of a developing device included in the image forming apparatus of FIG.

3 is a waveform diagram illustrating a method of counting density information of an image information signal in the image forming apparatus of FIG.

FIG. 4 is a characteristic diagram showing a relationship between a standing time and a correction coefficient for correcting a variation in toner replenishment amount during the same replenishment time.

FIG. 5 is a flow chart for explaining the basic operation of one embodiment of the present invention.

FIG. 6 is an explanatory diagram showing an overall configuration of an example of a conventional image forming apparatus.

[Explanation of symbols]

40 photoconductor drum 43 Two-component developer 44 Developer 60 toner supply tank 63 toner 65 clock pulse oscillator 66 counter 67 CPU 68 RAM 69 Motor drive circuit 70 motor 72 Reference image signal generation circuit 73 Light source 74 Photoelectric conversion element 75 Comparator 76 Reference voltage signal source

Claims (2)

[Claims] 1. An electrostatic latent image corresponding to an image information signal is formed on an image carrier, the electrostatic latent image is developed with a two-component developer to form a visible image, and the visible image is transferred. In the image forming apparatus for transferring to a material, a toner replenishing means for replenishing the toner of the two-component developer and a first toner replenishing means for activating the toner replenishing means according to the image density information of the image information signal. A developer concentration control device, and corrects the operation time of the toner replenishing device operated by the first developer concentration control device according to the length of time the toner replenishing device is not operating. Then, the image forming apparatus is characterized by replenishing toner. 2. A second developer concentration control device for detecting a toner concentration of the two-component developer is provided, and the second developer concentration control device is operated at a predetermined timing to obtain the second developer. 2. The image forming apparatus according to claim 1, wherein the toner supply error by the first developer density control device is corrected by an output signal from the density control device according to the toner density.