JP2942017B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic or electrostatic recording system for forming a visible image by attaching a developer to a latent image formed on an image carrier. The present invention relates to an apparatus, and more particularly, to an image forming apparatus having a developer concentration control unit for appropriately controlling the toner concentration of a two-component developer.

[0002]

2. Description of the Related Art Generally, a two-component developer mainly composed of toner particles and carrier particles is used in a developing device provided in an electrophotographic or electrostatic recording type image forming apparatus. In particular, in a color image forming apparatus that forms a full-color or multi-color image by an electrophotographic method, most developing devices use a two-component developer from the viewpoint of the tint of the image. As is well known, the toner concentration (that is, the ratio of the weight of the toner particles to the total weight of the carrier particles and the toner particles) of the 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. For this reason, the toner concentration of the developer is accurately detected in a timely manner by using the developer concentration control means (ATR), the toner is replenished in accordance with the change, the toner concentration is constantly controlled to be constant, and the image quality is improved. Need to be retained.

FIG. 7 shows an overall configuration example of an image forming apparatus having a conventional developer concentration control means, in this example, an electrophotographic digital copying machine. First, if the image of the original 21 is CC
An analog image signal read and obtained by D1 is amplified to a predetermined level by an amplifier 2, and is converted into a digital image signal of, for example, 8 bits (0 to 255 gradations) by an analog-digital converter (A / D converter) 3. Is converted to Next, the digital image signal is supplied to a γ converter (a converter constituted by a 256-byte RAM in this example and performing a density conversion by a look-up table method) 5 to be γ-converted.
After being corrected, it is input to a digital-analog converter (D / A converter) 9. Here, the digital image signal is converted into an analog image signal again 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 period generated from the triangular wave generating circuit 10. The analog image signal supplied to one input of the comparator 11 is compared with the triangular wave signal and pulsed. It is width modulated. The pulse width modulated binarized image signal is input to the laser drive circuit 12 as it is, and is used as an on / off control signal for light emission of the laser diode 13. The laser beam emitted from the laser diode 13 is scanned in the main scanning direction by a well-known polygon mirror 14, passes through an f / θ lens 15 and a reflection mirror 16, and rotates in the direction indicated by an arrow in FIG. Illuminated above to form an electrostatic latent image.

On the other hand, the photosensitive drum 17 is uniformly discharged by the exposure device 18 and is uniformly charged, for example, negatively by the primary charger 19. Thereafter, an electrostatic latent image corresponding to the image signal is formed by receiving the above-described laser light irradiation. This electrostatic latent image is developed into a visible image (toner image) by the developing device 20. This toner image is stretched between two rollers 25 and 26 and is transferred to a transfer material 23 held on a transfer material carrying belt 27 which is driven endlessly in the direction of the arrow in FIG.
Is transcribed by the action of The residual toner remaining on the photosensitive drum 17 is scraped off by the cleaner 24 thereafter. Although only a single image forming station (including a photosensitive drum 17, an exposing unit 18, a primary charging unit 19, a developing unit 20, and the like) is shown for simplicity of explanation, the case of a color image forming apparatus will be described. For example, the image forming stations for the respective colors of cyan, magenta, yellow, and black are sequentially arranged on the transfer material carrying belt 27 along the moving direction.

Further, in order to correct the changed toner density in the developing device 20 due to the development of the latent image, a video count type developer density control means is provided, and the output level of the digital image signal for each pixel is adjusted. Accumulation is performed and toner is replenished in a predictable manner. That is, the analog-digital converter 3
The output level of the image signal converted into a digital signal is integrated for each pixel, 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 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 for a time corresponding to the toner replenishment signal, and rotates and drives the toner conveying screw 30 in the toner replenishment tank 8 containing the toner 29 for the above-mentioned predetermined time. An appropriate amount of toner is replenished into the developing device 20 so that the toner density in the developing device 20 is kept constant.

[0006]

However, the conventional developer density control means does not directly detect the toner density of the developer, but converts the density information of the original image into a video count number and converts this into a replenishing amount. Since it is a predicted replenishment in which the toner is replenished by predicting the consumption amount, if the replenishment amount of the replenishment system and the consumption amount of the consumption system fluctuate, it cannot be dealt with. Due to these fluctuations, the toner concentration, that is, the mixture ratio of the toner particles and the carrier particles gradually deviates from the initial set value (specified value). For this reason, the conventional developer concentration control means has a serious drawback that the toner concentration greatly deviates from the allowable range of the initial set value.

Therefore, an object of the present invention is to provide a second developer concentration control means for directly detecting the toner concentration of a developer,
The second developer concentration control means is operated at a predetermined timing to correct an error occurring at the time of toner replenishment, so that the toner concentration of the two-component developer can always be maintained within the allowable range of the initial set value. An object of the present invention is to provide an image forming apparatus provided with a developer concentration control means.

[0008]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention uses a latent image forming means for forming an electrostatic latent image corresponding to an image information signal on an image carrier, and a two-component developer for forming the electrostatic latent image formed on the image carrier using a two-component developer. A toner supply unit for supplying toner to the development unit, a toner supply amount for one image based on image density information of the image information signal, and First developer concentration control means for actuating and replenishing toner; operating at a predetermined timing to detect the toner concentration of the two-component developer, and replenish or oversupply in accordance with a detection signal indicating the toner concentration. And a second developer density control means for generating an output signal representing the amount of toner of the image forming apparatus. Per image A surplus or shortage toner amount is determined, and in the case of excessive replenishment, the determined toner amount is subtracted from the toner replenishment amount per one image determined by the first developer concentration control means to replenish the toner. If the toner amount is insufficient, the determined amount of toner is added to the amount of toner replenishment per image determined by the first developer concentration control means, so that the first developer concentration control means 1 decided
Control means for correcting the toner supply amount per sheet image, wherein the first developer concentration control means controls the toner supply based on the toner supply amount per image corrected by the control means. An image forming apparatus characterized by operating a replenishing unit.

In one embodiment of the present invention, the second
A developer concentration control means for detecting a detection signal representing the toner concentration of the two-component developer by a predetermined reference value or a detection signal representing the toner concentration detected by the second developer concentration control means before the detection value. The difference value is provided to the control means as an output signal.

In another embodiment of the present invention, the control means includes a table for converting an output signal of the second developer density control means into image density information of the image information signal, and a table for converting the image information signal. There is a table for converting the density information of the image into a toner supply amount and a table for converting the output signal of the second developer concentration control means into the toner supply amount.

[0011]

Embodiments of the present invention will be described below in detail 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 photosensitive member or a dielectric by an electrophotographic system, an electrostatic recording system or the like. 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. Any configuration may be used as long as the image is a permanent image.

First, an overall configuration of an embodiment of an image forming apparatus according to the present invention will be described with reference to FIG. In this embodiment, the present invention is applied to an electrophotographic digital copying machine. However, it goes without saying that the present invention can be equally applied to various other image forming apparatuses of an electrophotographic type and an electrostatic recording type.

In FIG. 1, an image of a document 31 to be copied is projected by a lens 32 onto an image pickup device 33 such as a CCD. The image sensor 33 decomposes an original image into a number of pixels and generates a photoelectric conversion signal corresponding to the density of each pixel. The analog image signal output from the image sensor 33 is sent to an image signal processing circuit 34, where the image signal is converted into a pixel image signal having an output level corresponding to the density of the pixel. 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 applied to a high-density pixel image signal, and a narrower drive pulse S is applied to a low-density pixel image signal. , A drive pulse I having an intermediate width is formed for a 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 causes the semiconductor laser 36 to emit light for a time corresponding to the pulse width. Therefore, the semiconductor laser 36 is driven for a longer period of time for the high-density pixels, and is driven for a shorter period of time for the low-density pixels. Therefore, the photosensitive drum 40
By using the optical system described below, a longer range is exposed in the main scanning direction for high density pixels, and a shorter range is exposed in the main scanning direction for low density pixels. That is, the dot size of the electrostatic latent image differs according to the density of the pixel.
Therefore, it goes without saying that the toner consumption for the high density pixels is larger than that for the low density pixels. In FIG. 3D, the electrostatic latent images of the low, medium and high density pixels are indicated by L, M and H, respectively.

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

The photosensitive drum 40 is an electrophotographic photosensitive drum having amorphous silicon, selenium, OPC and the like on its surface and rotating in the direction of the arrow. Is charged uniformly. Thereafter, exposure scanning is performed with a laser beam modulated in accordance with the image information signal described above, whereby an electrostatic latent image corresponding to the image information signal is formed. This electrostatic latent image is reversely 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 a toner charged to the same polarity as the latent image is attached to a region of the photoconductor exposed to light, and the toner is visualized.
This toner image is stretched between two rollers 45 and 46,
The image is transferred onto a transfer material 48 held on a transfer material carrying belt 47 driven endlessly in the direction of the arrow by the action of a transfer charger 49.

The transfer material 48 onto which the toner image has been transferred is separated from the transfer material carrying belt 47, is conveyed to a fixing device (not shown), and is fixed to a permanent image. Further, the residual toner remaining on the photosensitive drum 40 after the transfer is removed by the cleaner 50 thereafter.

Although only a single image forming station (including a photosensitive drum 40, an exposing unit 41, a primary charging unit 42, a developing unit 44, and the like) is shown in FIG. In the case of (1), for example, 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, and a document is placed on the photosensitive drum of each image forming station. Are sequentially formed, developed by a developing device having a corresponding color toner, and sequentially transferred to a transfer material 48 held and conveyed by a transfer material carrying belt 47. Will be.

FIG. 2 shows an example of the developing device 44. As shown in the drawing, the developing device 44 is disposed so as to face the photosensitive drum 40, and the inside thereof has a partition wall 5 extending in the vertical direction.
1, a first chamber (developing chamber) 52 and a second chamber (stirring chamber) 5
It is divided into three. A non-magnetic developing sleeve 54 that rotates in the direction of the arrow is disposed in the first chamber 52, and a magnet 55 is fixedly disposed in the developing sleeve 54. The developing sleeve 54 carries and transports a layer of a two-component developer (including a magnetic carrier and a non-magnetic toner) whose thickness is regulated by a blade 56, and transfers the developer in a developing area opposed to the photosensitive drum 40. To develop the electrostatic latent image. In order to improve the development efficiency, that is, the rate at which toner is applied to the latent image, a development bias voltage in which a DC voltage is superimposed on an AC voltage is applied to the development sleeve 54 from a power supply 57.

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 communicates with the toner 63 supplied by the rotation of the conveying screw 62 from a toner discharge port 61 of a toner replenishing tank 60 which will be described later. Developer 43
Are agitated and conveyed to make the toner concentration uniform. The partition 51 has a first chamber 52 at the front and rear ends in FIG.
A developer passage (not shown) is formed to allow the first chamber and the second chamber 53 to communicate with each other. The toner is consumed by the development due to the conveying force of the screws 58 and 59, and the toner concentration is reduced. The developer in the second chamber 53 moves into the second chamber 53 from one passage, and the developer whose toner concentration has been recovered in the second chamber 53 moves into the first chamber 52 from the other passage. I have.

The image signal processing circuit 34 is used to correct the changed developer concentration 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. 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 an AND gate 64.
A clock pulse oscillator 65 is connected to the other input of the ND gate.
(Pulse shown in FIG. 3 (b)). Therefore, as shown in FIG. 3C, the AND gate 64 outputs a number of clock pulses corresponding to the respective pulse widths of the laser driving pulses S, I and W, that is, a number of clock pulses corresponding to the density of each pixel. A pulse is output.
The number of clock pulses is integrated by the counter 66 for each image, and the video count is calculated. The pulse integration 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 to form one toner image on the document 31. I have.

Therefore, the pulse integration signal C ₁ is sent to the CPU
The data is supplied to the RAM 67 and stored in the RAM 68. CPU6
Reference numeral 7 denotes a rotation driving time of the transport screw 62 required to supply the toner 63 in an amount corresponding to the toner amount consumed from the developing device 44 from the toner replenishing tank 60 to the developing device based on the pulse integration signal C _1. After the calculation, the motor driving circuit 69 is controlled to drive the motor 70 only during the calculated time. Thus, in general, if the pulse integration value is large, the driving time of the motor 70 is longer, and if the pulse integration value is small, the driving time of the motor 70 is shorter.

The driving force of the motor 70 is transmitted to the conveying screw 62 through a gear train 71,
Reference numeral 2 conveys the toner 63 in the toner replenishing tank 60 to replenish the developing device 44 with a predetermined amount of toner. This toner supply is performed each time the development of one image is completed.

By the way, the toner is supplied to the developing device based on the density information obtained by photoelectrically converting the image of the document to be copied as described above, because the actual toner density of the developer is directly detected and based on the detected density. Instead of replenishing toner.
Since this is a kind of speculative supply, as described above, the developing device 4
When the amount of toner replenished from the toner replenishing tank 60 to the toner supply unit 4 and the amount of toner consumed from the developing unit 44 change from the expected value, and the consumption system and the replenishment system change, the developer in the developing unit 44 is changed. 43 gradually deviates from the initial set value. If this deviation is not corrected, the toner density will deviate significantly from the allowable range of the initial set value.

For this reason, in the present embodiment, a second developer concentration control means is provided, and the second developer concentration control means is operated at a predetermined timing to form a reference image on the photosensitive drum 40. .

More specifically, a reference image signal generation 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 this generation circuit 72 is transmitted to the pulse width modulation circuit 35. To generate a laser drive pulse having a pulse width corresponding to the predetermined density. The laser drive pulse is supplied to the semiconductor laser 36, the laser 36 emits 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, a reference electrostatic latent image corresponding to the predetermined density is formed on the photosensitive drum 40, and this reference electrostatic latent image is developed by the developing device 44. I 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, the 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 a comparator 75. A reference signal corresponding to a specified toner density of the developer 43 (toner density at an initial set value) is input from the reference voltage signal source 76 to the other input of the comparator 75. Accordingly, since the comparator 75 compares the specified toner density with the actual toner density in the developing device, as a result of comparing the two input signals, the comparator 75 determines the actual toner density of the developer 43 in the developing device 44. An output signal indicating that the toner density is higher than the specified value or an output signal indicating that the toner density is lower than the specified value is generated. When there is no difference between the two input signals, an output signal indicating the difference may be generated. Comparator 7
The output signal of No. 5 is supplied to the CPU 67.

As shown in FIG. 4, in this embodiment, the CPU 67 determines the relationship between the output of the second developer concentration control means (the output of the comparator 75 in this embodiment) and the optical density, and the video count number, for example. A table 1 representing a relationship between an output level such as a gradation level and an optical density;
Table 2 showing the relationship between the output of the second developer density control means and the video count number based on the result of the above, and the toner supply between the formation of the toner image such as during continuous copying based on the video count data. 3 showing the relationship between the video count number and the toner replenishment time (replenishment amount)
And a table 4 representing the relationship between the output of the second developer concentration control means and the toner supply time from the tables 2 and 3.

Next, a CPU having the above tables 1-4
The control operation of the image forming apparatus of the present embodiment using the printer 67 will be described with reference to the flowchart of FIG.

First, when a start button is pressed to copy a document, the document is read as described above in block S101, and a photoelectric conversion signal corresponding to the density of each pixel of the document image is generated. Next, in block S102, the output level of each pixel is counted and integrated to calculate a video count. This pulse integrated value is
67, and in block S103, 1
The toner supply time per sheet image (the supply amount may be used), that is, the rotation speed of the screw 62 is determined, and the block S10 is executed.
4, a copying operation is started, and the above-described latent image formation, development,
An image forming operation such as transfer is performed. When one toner image is formed, before forming the next toner image in block S105, the screw 62 is rotated by the rotation speed determined as described above to supply toner. This toner image formation and toner supply operation is repeated for the number of copies set by the operator. Next, when the set number of copies have been completed in block S106, the second developer density control means operates in block S107, and forms a reference image on the photosensitive drum 40 as described above, and The actual toner concentration of the developer 43 is measured. Next, in a block S108, the measured value of the toner density is compared with a reference value to calculate the difference, and in a block S109, the difference value is calculated from the table 4 of the CPU 67 by using the excessive or insufficient toner per image. Convert to supply time. And
In the decision block S110, it is determined whether or not the toner is excessively replenished based on the comparison result. If the toner is excessively replenished (YES), the excessive toner per sheet calculated from the block S111 is calculated from the block S111. An instruction to subtract the replenishment time is given to the block S103, and the subtraction is performed from the toner replenishment time per one image calculated in the block S103 at the time of the next image forming operation. On the other hand, if it is determined in the determination block S110 that the toner supply is insufficient (NO), a command to add the insufficient toner supply time per sheet calculated in the block S109 is sent from the block S112. This is given to S103, and is added to the toner supply time per one image calculated in block S103 at the time of the next image forming operation. Hereinafter, the same operation is repeated.

As described above, in this embodiment, every time one copy operation (or continuous copy operation) is completed, the second developer density control means is operated, and the actual toner density of the developer at that time is operated. Is directly detected, the actual toner density is compared with a reference value to calculate the difference value, and the difference value is input to the CPU 67, and the excessive or insufficient toner replenishment per one image is performed by a table held by the CPU 67. Since the time (supply amount) is calculated and the toner supply time (supply amount) calculated at the time of the next image forming operation is corrected, there is an advantage that errors in the supply system due to the environment, aging, and the like can always be corrected. is there.

In the above-described embodiment, the actual toner density of the developer 43 in the developing device 44 measured in the block S108 is compared with a reference toner density value (initial setting value), and the difference value is used as a basis for one image. The excessive or insufficient toner replenishment time (replenishment amount) has been calculated, but as shown in the flowchart of FIG. 6, a block S1 for operating the second developer concentration control means before the block S104 for starting the copy operation.
13, the difference between the output values of the second developer density control means before and after one copy operation is obtained in block S108, and this difference value is determined by table 4 of the CPU 67 as excess or insufficient per one image. It is needless to say that the same control operation as in the above embodiment may be performed by converting to the toner supply time.

Further, instead of operating the second developer concentration control means every time one copy operation (or continuous copy operation) is completed as in the above embodiment, for example, once a day,
Even if the toner replenishment time (replenishment amount) is corrected, the intended purpose can be achieved. For example, the last data detected by operating the second developer concentration control means when the apparatus was turned off the day before, that is, the excessive or insufficient toner supply time (supply amount) for one image, The memory is stored, and when the apparatus is turned on the next day, the second developer concentration control means is operated to calculate an excessive or insufficient toner replenishment time per image, and a comparison between the two values is made. , The toner supply time (replenishment amount) may be corrected.

In a full-color copying machine or the like, the amount of toner replenishment differs for each color even if toner is replenished for a certain period of time due to differences in physical properties of toners of different colors. In this case, a correspondence table between the toner replenishment time and the toner replenishment amount is provided for each toner of each color, and the time for replenishing the toner of each color is determined with reference to this table, and the toner is replenished. In this case, the replenishment accuracy is improved.

In the above embodiment, the actual toner density of the developer in the developing device was measured by forming a patch image on the photosensitive drum and measuring the density of the image. The actual toner concentration of the developer can also be measured by directly irradiating the developer on the developing sleeve or the like with light and measuring the reflected light. However, if the toner is colored black with carbon black, there is no significant difference in the spectral reflectance between the toner and the carrier.
In this method, the detection accuracy of the toner density is poor. Therefore, when such a toner is used, the toner density can be measured with higher accuracy by using the above-described method based on the patch image. Further, it goes without saying that a good result can be obtained even if a method of detecting the toner concentration of the developer by changing the inductance is used as the second developer concentration control means.

Further, the present invention can be applied to an image forming apparatus which performs shading expression of an image by a dither method. The present invention is also applicable 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. Of course, as described above, the present invention can be applied to a color image forming apparatus. In this case, the above-described image forming unit may be provided for each color along the traveling direction of the transfer material carrying belt 47. However, the image of the document may be color-separated to form an image information signal for each color, and toner supply may be controlled for each color in the same manner as described above. The present invention is also applicable to a color image forming apparatus having a configuration in which a plurality of developing units are arranged around a photosensitive drum. Further, it goes without saying that various modifications and changes can be made as necessary.

[0040]

As described above, according to the image forming apparatus of the present invention, the second developer concentration control means is operated at a predetermined timing, and the actual toner concentration of the developer at that time is directly changed. Detected and calculates the excessive or insufficient toner replenishment time (replenishment amount) per one image from the actual change in toner density value, and calculates the toner replenishment time (replenishment amount) in the next image forming operation. The correction is performed by adding or subtracting the toner replenishment time (replenishment amount), which is easily corrected even when the replenishment amount of the replenishment system and the consumption amount of the consumption system fluctuate due to environment, aging, and the like. This has a remarkable effect that the toner concentration, that is, the mixing ratio of the toner particles and the carrier particles, can always be maintained within the allowable range of the initial set value (specified value).

[Brief description of the drawings]

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

FIG. 2 is a schematic sectional view illustrating 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 an explanatory diagram illustrating a table included in a control unit of the image forming apparatus in FIG. 1;

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

FIG. 6 is a flowchart for explaining a basic operation of another embodiment of the present invention.

FIG. 7 is an explanatory diagram illustrating an overall configuration of an example of a conventional image forming apparatus.

[Explanation of symbols]

 Reference Signs List 40 photosensitive drum 43 two-component developer 44 developing device 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

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 15/08-15/08 115 G03G 15/00 303 G03G 21/00 370-520 H04N 1/29

Claims (4)

(57) [Claims] 1. A latent image forming means for forming an electrostatic latent image corresponding to an image information signal on an image carrier, and developing the electrostatic latent image formed on the image carrier using a two-component developer. A developing unit, a toner replenishing unit that replenishes the developing unit with toner, and a toner replenishing amount per image determined based on image density information of the image information signal, and operating the toner replenishing unit. First developer concentration control means for replenishing toner; operating at a predetermined timing to detect the toner concentration of the two-component developer; and, based on a detection signal indicating the toner concentration, the amount of toner replenished or insufficient. And a second developer density control means for generating an output signal representing the following: a single image based on the output signal generated from the second developer density control means. Excess young per hit Determines the insufficient toner amount, and in the case of excessive replenishment, subtracts the determined toner amount from the toner replenishment amount per one image determined by the first developer density control means to determine the replenishment amount. In the case of (1), the determined amount of toner is added to the amount of toner replenishment per one image determined by the first developer density control means, thereby determining the toner amount by the first developer density control means. Control means for correcting the toner replenishment amount per one image, wherein the first developer concentration control means corrects the toner supply amount corrected by the control means.
An image forming apparatus, wherein the toner supply unit is operated based on a toner supply amount per sheet image. 2. An output of the second developer density control means is a detection signal representing a toner density of the second developer density control means, which is obtained by converting a detection signal representing a toner density to a predetermined reference value or a predetermined value. 2. The image forming apparatus according to claim 1, wherein the difference value is a difference value compared with a detection signal representing a toner concentration detected by the developer concentration control means. 3. A table for converting an output signal of the second developer density control means to image density information of the image information signal, and / or a toner image density information of the image information signal. A table for converting to a supply amount, and
2. The image forming apparatus according to claim 1, further comprising a table for converting an output signal of the second developer density control unit into a toner supply amount. 4. The image forming apparatus according to claim 1, wherein said second developer concentration control means is operated for each of a plurality of continuous copy operations.