JPH0527597A - Image forming device - Google Patents

Abstract

PURPOSE:To calculate toner consumption by sufficiently reflecting a difference in the toner consumption caused by the difference in an image density level distribution. CONSTITUTION:A developer concentration controller 60 is composed of a data value selecting part 61 classifying each picture data of an inputted digital video signal into plural divisions with the values of each picture data, an accumulating part 62 accumulating the amount of the picture data of each selected division, a coefficient integrating part 63 multiplying cumulative values and proper coefficients (control constants) corresponding to each division, together, respectively, and an adding part 64 adding the multiplied value of respective cumulative values and coefficients to obtain the sum total, the picture data selected by the multiplication of the proper coefficient is weighted, the difference in the toner consumption caused by the difference in a density level distribution is accurately corrected, and the toner consumption is highly accurately calculated. A highly accurate toner replenishing signal based on the toner consumption is outputted to a toner replenishing system.

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.

Conventionally, as such a developer concentration control device, (1) a developer on a developing sleeve of a developing device is irradiated with near-infrared light by, for example, a light emitting diode, and the reflected light is detected by an optical sensor. , Compare the detection result with the reference value,
A photoelectric detection system in which toner is replenished in accordance with the difference, (2) A latent image of a constant image is actually formed on the photoconductor drum, and is developed into a visible image. For example, light is emitted from a light emitting diode or the like, and the reflected light is detected by an optical sensor to detect the density of a visible image,
An image forming system has been proposed in which the remaining amount of developer is detected from this detection result and toner is replenished.
Further, as being widely used in a digital image forming apparatus, (3) an analog image signal of a document image read by an image pickup device such as a CCD is converted into a digital image signal, and the digital image signal is converted pixel by pixel. There has been proposed a so-called video count type developer concentration control device that integrates output levels to calculate a video count number, converts the video count number into a supply amount, and supplies toner.

[0004]

However, the photoelectric concentration type developer concentration control device of the above (1) for detecting the near-infrared reflected light from the developer on the developing sleeve to detect the toner concentration of the developer. However, when a normal black toner is used, its light absorption region extends to the near-infrared region, so the measurement accuracy is extremely poor, and in the case of a black toner, the toner concentration cannot be controlled. is there.

Further, in the developer concentration control device of the image forming system of the above (2), which detects the toner concentration by detecting the reflected light from a constant visible image formed on the photosensitive drum, it scatters inside the device. Since the light emitting surface of the light emitting element and the light receiving surface of the optical sensor are contaminated by the developer, there are disadvantages that measurement error is large and accurate toner replenishment cannot be performed.

Furthermore, image data or a part thereof is accumulated to calculate a video count number, the video count number is converted into a toner replenishment amount to calculate a toner consumption amount, and toner corresponding to this is replenished. In the developer concentration control device of the above (3), since the difference in toner consumption amount due to the difference in image density level distribution is not taken into consideration, a replenishment error is likely to occur and stable high-precision toner replenishment cannot be performed. was there.

Therefore, an object of the present invention is to control the developer concentration capable of accurately calculating the toner consumption amount by sufficiently reflecting the difference in toner consumption amount due to the difference in the density level distribution of the image of the image information signal. 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 and develops the electrostatic latent image using a two-component developer containing toner and carrier as main components. In an image forming apparatus for forming a visible image, a toner replenishing means for replenishing the toner of the two-component developer and each image data of the image information signal is selected into a plurality of sections according to the data value, and each selected section Add appropriate weighting to the image data of
A developer concentration control device for determining a toner consumption amount, and generates a toner replenishment signal for operating the toner replenishing means based on the toner consumption amount determined by the developer concentration control device to replenish the toner. And an image forming apparatus.

In one embodiment of the present invention, the developer density control device includes means for selecting each image data of the image information signal into a plurality of sections according to the data value, and image data of each selected section. The toner consumption amount is composed of means for accumulating the respective numbers, means for multiplying each cumulative value by an appropriate coefficient corresponding to each category, and means for adding each multiplication value to obtain the sum thereof. Is calculated with high accuracy.

In another embodiment of the present invention, the developer density control device includes a look-up table for outputting the toner consumption amount corresponding to all the image data values of the digitized image information signal. When one image data is input to this look-up table, a signal representing the toner consumption amount corresponding to this one image data is output, and the toner consumption amount is calculated with high accuracy by the sum of them.

[0011]

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, or the like, and the latent image is formed by a toner. Any structure may be used as long as it is developed by a developing device using a two-component developer containing particles and carrier particles as a main component to form a visible image (toner image).

First, the overall construction of the first embodiment of the 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. 2, the image of the 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 sensor 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 each pixel, that is, a digital video signal. , To the pulse width modulation circuit 35.

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 video 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. 3B, 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.

Now, in order 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 replenished to the developing device 44, a developer concentration control device 60. Is provided, and a digital video signal which is an output signal from the image signal processing circuit 34 is input to the developer concentration control device 60.

The developer concentration control device 60 includes a data value selection unit 61, an accumulation unit 62, a coefficient integration unit 63, and an addition unit 64.
As will be described later, the input video signal is divided into a plurality of sections according to the value, weighted by multiplying by an appropriate coefficient (control constant), and the difference in the density level distribution of the image Correct the difference in toner consumption. Then, by taking the sum of them, the toner consumption amount required for forming the image is calculated with high accuracy, and this is output to the toner replenishment system as a toner replenishment signal. In this embodiment, the toner replenishment signal is supplied from the toner replenishing tank 67 to the developing device 44 in an amount corresponding to the amount of toner consumed from the developing device 44 when an image corresponding to the input video signal is formed. This corresponds to the rotation drive time of the conveying screw 68 (that is, the toner replenishment time) required for This toner replenishment signal is supplied to the motor drive circuit 69 to drive the motor 70 only during the calculated time. The driving force of the motor 70 is transmitted to the conveying screw 68 via the gear train 71, and the conveying screw 68 conveys the toner 66 in the toner replenishing tank 67 to replenish the developing device 44 with a predetermined amount of toner. .

More specifically with reference to FIG. 1, the developer concentration control device 60 divides the digital video signal input in the data value selection section 61 into a plurality of sections 1, 2 ,. .., n, and the accumulating unit 62 counts the number of video signals for each of the divided sections. The coefficient accumulation unit 63 multiplies and weights a certain fixed amount of each of these divisions by an appropriate coefficient (control constant) corresponding to each division, and the toner consumption due to the difference in the density level distribution of the image is consumed. Correct the difference in quantity accurately. The respective integrated values from the coefficient integrating section 63 are added by the adding section 64 to obtain the sum, the toner consumption amount is determined, and this is sent to the toner replenishing system as a toner replenishing signal to replenish the toner. Here, each classification category and the coefficient corresponding to each classification category are determined in advance as appropriate values from the relationship between the image density level distribution and the amount of developer consumed.

As described above, the output signal from the addition section 64 is supplied to the motor drive circuit 69 as a toner replenishment signal, and the motor 70 is driven to rotate the conveying screw 68 for the time determined as described above. The toner 66 is replenished from the toner replenishing tank 67 into the developing device 44 in an amount exactly corresponding to the consumption amount.

Next, a specific example of the developer concentration control device 60 described above will be described in detail with reference to FIGS. FIG. 4 shows all image data values of the input video signal from 00 _H to
FF _H , 00 _{H to} 3F _H , 40 _{H to} 7F
Data classification is performed on four categories _H , 80 _{H to} BF _H , and C0 _{H to} FF _H , and coefficients corresponding to the respective categories to be multiplied by the coefficient accumulating unit 63 are α, β, γ, and δ. This is the case. A histogram for each image data per image is considered to be as shown in FIG. 5, for example,
In this example, four categories of A, B, C and D are selected. In this example, the selection of the data value is performed by the decoder 14 decoding the upper 2 bits of the video signal in the data value selection unit 61 as shown in FIG. The output signals a to d from the decoder 14 are signals having only the meaning of whether or not the signals have been applied to their respective sections. These output signals a to d are respectively
It is supplied to one input of the D gates 15a to 15d. The other inputs of these AND gates 15a~15d is supplied with synchronizing pulses, thus, each logical product is taken, the signal C _K a~C _K d is generated. These signals C
_{K a to} C _k d are respectively input to the counters 16 a to 16 d of the accumulating unit 62 to count the number of signal values in each of the sections A, B, C and D. These counters 16a-1
After the number of signal values in each section is accumulated by 6d by a certain amount, a data output pulse is supplied to these counters 16a to 16d to calculate the accumulated values by the coefficient integrator 63.
Are supplied to the integrators 17a to 17d, and the counters 16a to 16d are reset to the initial state.
In the integrators 17a to 17d, the input cumulative value is multiplied by appropriate coefficients α, β, γ, and δ corresponding to the respective sorting categories, and weighted to determine the toner consumption amount due to the difference in the density level distribution of the image. Correct the difference accurately. The integrated values of the number of image data and the coefficients obtained for each of these sorting categories are sent to the adder 18 of the adder 64, and their sum is calculated. Since this total accurately represents the toner consumption amount consumed by the image accumulated in the accumulating unit 63, this toner consumption amount is sent to the toner replenishment system as a toner replenishment signal, and as described above, the toner consumption amount is accurately calculated. Supply the correct amount of toner.

FIG. 6 is a timing chart for further explaining the operation of the decoder 14 and the AND gates 15a to 15d. For example, the input video signal value is 5
1 _H , 38 _H , A5 _H , and C8 _H are the above-mentioned data value selection unit 6
The case where it is input to 1 is shown. Signal value 51 _H is in category B,
Since the signal value 38 _H corresponds to the section A, the signal value A5 _H corresponds to the section C, and the signal value C8 _H corresponds to the section D, the output signals a to d of the decoder 14 are as shown in FIG. Therefore, the outputs C _{K a to} C _K d of the AND gates 15 a to 15 d, which are the logical product of the output signals a to d of the decoder 14 and the synchronization pulse sent for each image data, are as shown in the figure. The area selection value based on the data will be determined.

As described above, in the present embodiment, the input video signal is divided into a plurality of sections according to the value, weighted by multiplying by an appropriate coefficient (control constant), and the sum of them is obtained. Since the toner consumption required to form the image is calculated, the difference in the toner consumption due to the difference in the density level distribution of the image is sufficiently reflected, and the toner consumption can be calculated with extremely high accuracy. . Since the toner replenishment system is operated by the highly accurate toner replenishment signal based on the toner consumption amount and the toner is replenished to the developing device 44, a replenishment error does not occur unlike the conventional case,
Therefore, there is an advantage that stable and highly accurate toner supply can be performed.

FIG. 7 is a flow chart of a second embodiment of the present invention when the control operation of the first embodiment is executed by software using a microcomputer.

First, when the start button is pressed to copy an original, the original is read in block S1,
A photoelectric conversion signal corresponding to the density of each pixel of the original image is generated. Next, in block S2, each video signal value of the digital pixel image signal obtained by signal processing the photoelectric conversion signal is stored in the image memory as image data. Next, in block S3, the first image data value d _im stored in the image memory is read out and stored in the working register, and in decision block S4, the image data value d _im stored in the working register is selected. That is, it is determined whether or not this image data value _dim is within the sorting section N, and if it is not within the section N (NO), the determination target is changed to the next sorting section N + 1 in block S5, and the determination block S4 is selected. It is again determined whether or not the image data value d _im is within the section N + 1.
This determination is repeated until the selection classification of the image data value _dim is determined. In the above judgment block S4, the classification is N
If it is determined (YES), the count value C _N of the section N is incremented by 1 in block S6, and if the selection section is determined to be N + 1 (YES), block S6 is determined.
At 6, the count value C _{N + 1} of the section N + 1 is incremented by 1, and so on. After the selection section of the first image data d _im is determined and the count value of the section is increased by 1, then the second image data d _{im + 1} is read from the image memory to the working register, and the same control operation is performed. Do.
Thereafter, the same control operation is sequentially performed on the remaining image data stored in the image memory, and the determination block S7 returns 1
When it is determined that the control operation for the image data for the image area is completed (YES), appropriate coefficients (for example, α, β, γ, δ described above) corresponding to the count value of each sorting section are determined in block S8. The toner amount consumed in one image area is calculated by multiplying and summing them, and this is output to the toner replenishing system as a toner replenishing signal. For example, if this toner replenishment signal is the drive time of the motor 70 for rotating the screw 68 of the toner replenishment tank 67 in FIG. 2, the copy operation is started and one image forming operation such as latent image formation, development, transfer, etc. is started. Is executed, the motor 70 is driven for the motor drive time determined in the block S8 to rotate the screw 68 to replenish toner from the toner replenishing tank 67 into the developing device 44. Hereinafter, the same control operation is repeated for each copy operation.

Thus, the toner can be replenished with high accuracy and stability, and the toner concentration of the developer can be maintained within a substantially constant range. Therefore, a high-quality image with stable density can always be obtained.

FIG. 8 shows a third embodiment of the present invention, in which a look-up table 20 for outputting the toner consumption amount corresponding to all video signal values is provided. The look-up table 20 uses, as an address, a video signal that has been digitized and subjected to appropriate image processing, and as data corresponding to the address, the toner consumption amount corresponding to all video signal values (as described above depending on the video signal value). A weighted value) is stored. When one image data (one video signal) is input to the lookup table 20, the toner consumption amount corresponding to the one image data is calculated. The signal representing is output from the look-up table 20. This output signal is the AND gate 21
One of the inputs, and the other input of the AND gate 21 is ANDed with the clock pulse supplied for each image data to determine the toner consumption amount for one image data. This determined toner consumption amount is added to the addition circuit 2
2 is added to the total amount of toner consumed by the video signal stored in the buffer 23 before that time. This addition output is again stored in the buffer 23, and addition with the toner consumption amount that arrives next is repeated.

The output signal representing the toner consumption amount from the adder circuit 22 is logically ANDed with the image area pulse indicating the end of the video signal group for one image area supplied from the control circuit (not shown) in the AND gate 24. , Therefore AN
A signal representing the total amount of toner consumed for one image area is output from the D gate 24 and sent to the toner replenishment system as a toner replenishment signal. When an image area pulse indicating the end of the video signal group for one image area is supplied to the AND gate 24, the toner consumption amount accumulated in the buffer 23 is reset to zero.

Also in this embodiment, the difference in the toner consumption amount due to the difference in the image density level distribution is sufficiently reflected by the look-up table, and the toner consumption amount can be calculated with extremely high accuracy, which is stable. There are advantages that the toner can be replenished with high accuracy and that the circuit configuration is simple.

The toner may be replenished every time one toner image is formed as described above. However, for example, every time when the number of copies reaches a predetermined number, it is appropriate to correspond to the count value of each sorting section. It is also possible to multiply by a certain coefficient and take the sum of them to generate a toner replenishment signal so that the toner is replenished collectively. In this way, when toner is replenished collectively, for example, when a replenishment system for replenishing toner from the toner replenishing tank by rotation of the conveying screw as shown in FIG. 2 is used, a small amount of toner is replenished. Since there is a possibility that an error will occur, there is much less room for error to be introduced, and there is an advantage that the replenishment accuracy is further improved.

In the above embodiment, the present invention is applied to the electrophotographic digital copying machine. However, the present invention is not limited to the electrophotographic digital copying machine and electrostatic recording type copying machine. It is equally applicable to image forming apparatuses such as printers. For example, the present invention can be applied to an image forming apparatus that performs grayscale representation of an image by a dither method, and also 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. The present invention can also be applied. Further, it goes without saying that various modifications and changes can be made to the configuration of the image forming apparatus, the developer concentration control apparatus, the control system, etc.

[0035]

As described above, in the image forming apparatus according to the present invention, the input digital image information signal is divided into a plurality of sections according to the signal value, and weighted by multiplying by an appropriate coefficient (control constant). The toner consumption required to form the image is calculated by taking the sum of the above, and the difference in the toner consumption due to the difference in the density level distribution of the image is sufficiently reflected, resulting in extremely high accuracy. It is possible to calculate the toner consumption amount. Since the toner replenishment signal is activated by the highly accurate toner replenishment signal based on the toner consumption amount to replenish the toner to the developing device, a replenishment error does not occur unlike the conventional case, and therefore a stable and high precision is obtained. There is a remarkable effect that the toner can be replenished and a stable image with high image quality and stable density can be always obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a developer concentration control device, which is a main part of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the overall configuration of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a waveform diagram showing a laser drive pulse and an electrostatic latent image that change according to density information of an image information signal in the image forming apparatus of FIG.

FIG. 4 is a block diagram showing a specific example of the developer concentration controller of FIG.

5 is a schematic diagram showing an example of a histogram of one image data input to the developer concentration control device of FIG.

FIG. 6 is a timing chart for explaining the operation of the developer concentration controller of FIG.

FIG. 7 is a flow chart for explaining the basic operation of the second embodiment of the present invention.

FIG. 8 is a block diagram showing a main part of a third embodiment of the present invention.

[Explanation of symbols]

20 lookup table 21, 24 AND gate 22 Adder circuit 23 buffers 34 Image signal processing circuit 35 Pulse width modulation circuit 40 photoconductor drum 43 Two-component developer 44 Developer 60 developer concentration control device 61 Data value selection section 62 Cumulative division 63 Coefficient accumulator 64 adder 66 toner 67 Toner supply tank 68 Conveyor screw 69 Motor drive circuit 70 motor

Claims (3)

[Claims] 1. A visible image is formed by forming an electrostatic latent image corresponding to an image information signal on an image carrier and developing the electrostatic latent image using a two-component developer containing toner and carrier as main components. In the image forming apparatus for forming, a toner replenishing means for replenishing the toner of the two-component developer and each image data of the image information signal is selected into a plurality of sections according to the data value, and the selected image data of each section And a developer concentration control device that determines the toner consumption amount by performing appropriate weighting on the toner consumption amount, and operates the toner replenishing means based on the toner consumption amount determined by the developer concentration control device. An image forming apparatus that generates a toner replenishment signal and replenishes toner. 2. The developer density control device comprises means for selecting each image data of the image information signal into a plurality of sections according to the data value thereof, and means for accumulating the number of image data of each selected section. 2. The image forming method according to claim 1, further comprising means for multiplying each accumulated value by an appropriate coefficient corresponding to each section, and means for adding each multiplied value to obtain a sum thereof. apparatus. 3. The developer concentration control device comprises a look-up table for outputting the toner consumption amount corresponding to all the image data values of the digitized image information signal. Image forming device.