JPH047510B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of controlling an electrostatic recording device such as an electrophotographic copying machine or an electrostatic printer. More specifically, there is a method for controlling an electrostatic recording apparatus that detects the density of a visible image obtained by developing a reference latent image formed on an image carrier and performs process control based on the detected image density information. Regarding improvements. Various control methods described above have been proposed in the past.
It has been put into practical use in some areas. Next, an embodiment of such process control will be explained. (1) Toner replenishment control After forming a reference latent image on the image carrier, it is developed to obtain a visible image, the image density is detected, and toner replenishment control is performed based on the detected image density information. . (2) Charge level control Based on the image density information described above, the image density is adjusted by controlling the corona discharge pressure that uniformly charges the image carrier. (3) Exposure amount control Image density adjustment is performed by controlling the image exposure light amount based on the image density information described above. (4) Development bias control Based on the image density information described above, the development bias voltage is controlled to adjust the image density. Among the process controls described above, toner replenishment control will be described below in relation to the prior art. Conventionally, in electrostatic recording devices, a toner replenishment control device that automatically controls the amount of toner supplied has been adopted as a device to maintain the image quality of the resulting copies, especially the density of the copied images, at a constant level. . To control the amount of toner supplied, there is a method to improve the stability of image quality by detecting changes in the amount of transmitted light, electrical resistance, magnetic resistance, etc. of the developer and maintaining the toner content in the developer at a constant level. However, in order to control toner replenishment, including the effects of deterioration of the developer and photoconductor, a part of the photoconductor is exposed to a standard amount of light.
There is also a toner replenishment control device that detects the density of a visible image (toner image) obtained by developing this, that is, a reference density image, and controls toner replenishment based on this detected information. The present invention is an improvement of this toner supply control device. A reference density image for controlling toner replenishment is formed on a photoconductor outside the effective image area of the document for each copy, and this reference density image is generally formed by a reflective sensor consisting of a light emitting element and a light receiving element. The concentration was being detected. This reference density image was formed as a toner image on the photoreceptor for each copy. This image is not transferred to the transfer paper, but advances almost as it is to the cleaning section, where it is removed by a cleaning device. Since the amount of toner that adheres at one time is large, in this case, the reference density image is usually formed on the image carrier as a reference density image of a predetermined size, and (1) there is a large amount of wasted toner consumption. . (2) Since the amount of toner to be removed increases in the cleaning section, the burden of cleaning increases, resulting in poor cleaning and early performance deterioration of the cleaning device. (3) Making it easier for photoreceptor memory to occur due to the reference density image. It had the following disadvantages. The present invention aims to eliminate the above-mentioned drawbacks, and the purpose is to form a reference latent image on an image carrier, and develop the reference latent image to obtain a reference visible image with a high density. In a control method for an electrostatic recording device that detects the density information of the reference visible image and replenishes toner based on the density information of the detected reference visible image, the reference visible image is formed every plurality of recording cycles, and the reference visible image is Comparing the density information with a preset setting value, and controlling the developing device to replenish toner when the density information of the reference visible image reaches the setting value,
When the density information of the reference visible image deviates from the set value by a large amount, another set value is set to increase the interval between the formation of the visible images, and compared with the density information of the reference visible image, the recording cycle is performed. This is achieved by a method for controlling an electrostatic recording device, which is characterized by controlling the interval at which visible images are formed. The present invention will be described in detail below with reference to the illustrated embodiments. FIG. 1 shows an embodiment of a copying machine using a photoreceptor consisting of a rotating drum and employs the control device of the present invention, and FIG. 2 is a perspective view showing the state of toner concentration detection on the photoreceptor drum. 1 is a photoconductor consisting of a rotating drum installed in the frame of the machine; 1a is the area of the photoconductor 1 required for transfer; 1b
is the front end or rear end of the photoreceptor 1 outside the required transfer area, and around the photoreceptor 1, a charging device 2, a developing device 3, a transfer section 4, and a cleaning device 5 are appropriately arranged in the machine frame. ing. 6 is a document table; 7 is a retractable reference image provided on the front end (or rear end) of the document table 6 or the document holding cover; 8 is an exposure device consisting of a light source 9, a mirror 10, a lens 11, etc.; 8, the reference image 7 in a fixed position and the original on the original platen 6 are exposed onto the photoreceptor 1 in each exposure operation to form a latent image. Reference numeral 12 denotes a toner replenishment container connected to the developer container 13 of the developing device 3 through an opening 14, and when a swinging rod 15 provided in the container 12 operates, the toner is supplied to the toner replenishment container. From container 12 to developer container 13
will be replenished. Reference numeral 16 denotes a transfer paper mounting table, and the transfer paper 17 placed on the mounting table 16 is transferred to the transfer unit 4 one by one for each copy.
The image on the photoreceptor is transferred to a transfer paper, which is separated from the photoreceptor 1 by a separation device 18 such as a separation claw, and transferred to a fixing device (not shown) via a conveyance device 19.
It is sent to and fixed. 20 is a light emitting element such as a light emitting diode, 21 is a light receiving element such as a phototransistor, and a quantum element 2
A photocoupler consisting of 0 and 21 is provided between the transfer section 4 and the cleaning device 5, and when, for example, infrared light is irradiated from the light emitting element 20 toward the photoreceptor 1, the infrared light is reflected by the photoreceptor 1. The light is received by the light receiving element 21. Therefore, the latent image of the reference image formed on the photoreceptor 1 passes through the developing device 3, and the developed reference density patch image 22 receives light from the light emitting element 20 and is reflected by the light receiving element. It is reflected to 21 and the concentration is detected. FIG. 3 shows one embodiment of the control circuit of the present invention, in which the reflection density of the reference density patch image 22 formed on the photoreceptor 1 is detected by the light receiving element 21 to obtain a detection signal V ₀ . The detection signal V ₀ is compared by comparators _{C 1} , C ₂ , and C 3 whose reference voltages are set to V 1 , V ₂ , and V ₃ (V ₁ > V ₂ > V ₃ ), respectively, and the detection signal _{V 0} is compared to the ports P ₁ and P of the CPU. ₂ , input to _P3 . When copying the first sheet, a reference density patch image 22 is formed on the photoreceptor 1, the image density is detected, and it is determined how many copies the patch image 22 should be formed on the photoreceptor 1 based on the detection signal. Table 1 is Part 1
This shows an example program.

[Table] P -Oki -Oki -Oki In other words, the patch image 22 is formed on the photoreceptor 1 every copy or every 1 to 3 copies according to the status of the ports P ₁ to P ₃ of the CPU, and the patch image density is detected. I'll do what I do. In Table 1, H indicates that the patch image density is low, and L indicates that the patch image density is high. Therefore, in the state (d), the patch image density is high and there is a lot of toner adhesion to the photoreceptor 1. Therefore, a patch image is formed every third copy to minimize toner adhesion to the photoreceptor 1. Reduce opportunities for In addition, in state (a), the patch image density is low, and if a high-density original is continuously copied in this state, the image density will drop significantly, so it is necessary to detect and constantly check the patch density after each copy. occurs. To avoid forming patch images, first
The reference image 7 in the figure may be retracted to a position where no image is formed, or the photoreceptor 1b corresponding to the reference image 7 may be
The portion may also be charged by the charging device 2 as desired. Furthermore, a charge erasing lamp may be provided between the exposure position and the development position, and the reference patch image may be erased by the lamp. In this embodiment, the processing means is controlled in response to input from port _P2 of the CPU to keep the image density constant. Here, assuming that the process means is toner replenishment, when the port _P2 is H, the image density is low, so a toner replenishment signal is generated, and when the port _P2 is L, the image density is high, so the toner replenishment signal is not generated. In the copying machine shown in FIG. 1, the swinging rod 15 is operated in response to a toner replenishment signal, and toner is replenished from the toner replenishment container 12 to the developer container 13. Although a plurality of analog comparators are used in this embodiment, it is also possible to digitize the patch image density detected by the AD converter and input it to the CPU for control without using the comparators. In this embodiment, the interval at which reference density patch images are intermittently formed is controlled in accordance with the density of the reference density patch images formed on the photoreceptor. The present invention, in which the reference density patch image is formed once for each multiple copy cycle, eliminates the above-mentioned drawbacks that occurred when the conventional patch image was formed once for each copy. ,
For example, when performing toner replenishment control, toner replenishment is performed at appropriate timing even though patch images are checked intermittently.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of a copying machine to which the present invention is applied, FIG. 2 is a perspective view showing the state of toner concentration detection on a photosensitive drum, and FIG. 3 is an embodiment of a control circuit of the present invention. This is an example. DESCRIPTION OF SYMBOLS 1... Photoreceptor, 2... Charging device, 7... Reference image, 20... Light emitting element, 21... Light receiving element, 22
...Reference density patch image.

Claims (1)

[Claims] 1. Forming a reference latent image on an image carrier, detecting the density of a reference visible image obtained by developing the reference latent image,
In a method for controlling an electrostatic recording device that replenishes toner based on density information of a detected reference visible image,
Forming the reference visible image every plurality of recording cycles, comparing the density information of the reference visible image with a preset setting value, and when the density information of the reference visible image reaches the setting value; In addition to controlling the developing device to replenish toner, when the density information of the reference visible image deviates from the set value by a large amount, another set value is set so as to widen the interval between the formation of the visible images, and the reference visible image is 1. A method of controlling an electrostatic recording device, comprising controlling an interval of visible image formation in a recording cycle by comparing density information of the visible image.