JPH0113101B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a copy density control and paper jam detection device for an electronic copying device.

When making copies using an electronic copying device, a developer container is filled with a mixture of toner and carrier in a certain ratio, and this developer is used to develop the electrostatic latent image on the photosensitive plate. As time progresses, the amount of toner in the developer in the developer container decreases, and thus the image density of the object to be developed decreases. To prevent this phenomenon, a toner replenishment container is installed and toner is sequentially replenished into the developer container at regular intervals, but since the amount of toner consumed differs depending on the document, the toner in the developer container is The amount decreases and the image density becomes inconsistent.

Therefore, various methods for controlling the supply of toner to the developing device have been proposed and put into practical use in order to keep the density of the copied image constant.

U.S. Pat. No. 3,348,522, U.S. Pat. No. 3,778,146, and U.S. Pat. No. 3,780,299 disclose that a standard electrostatic latent image is formed on the side edge of the photoreceptor drum away from the transfer area, and then developed. However, a method has been proposed in which the density of a developed image is measured and toner supply control is performed based on the measured value.

However, this known method has the disadvantage that toner density control is inaccurate because the standard image for toner supply control is formed at the side edge outside the area required for transfer.

Furthermore, the technique used in the above-mentioned toner density control, in which the photoreceptor drum is exposed to light and receives the reflected light, is also used to detect an error in separating the transfer paper from the photoreceptor drum, and the detection means is It is conceivable that it could be used for both purposes, but in the prior art, the toner density control detection means selected a side edge of the drum that was outside the required transfer area, that is, a position where the transfer paper could not be detected. It was not possible to use it for both purposes.

Therefore, the main object of the present invention is to solve the above-mentioned problems in the prior art.

Another object of the present invention is to provide a copy density control device capable of accurately controlling the density of a copy image.

Still another object of the present invention is to make it possible to use a detection means for toner density control, which in the prior art could not be used also for detecting transfer paper separation errors.

Another object of the present invention is to provide a toner concentration control device with a good S/N ratio.

The object of the present invention is to form a latent image of a toner density control image on a photoconductor at the front end or rear end outside the required transfer area with respect to the moving direction of the photoconductor, and within the required transfer area with respect to the direction perpendicular to the moving direction. A reference image is provided on the document table or document holding cover to form a toner density control image on the photoreceptor based on the reference image, and an infrared light is applied to the photoreceptor. a light-emitting element that emits light, a light-receiving element that receives reflected light from the light-emitting element, and an output voltage level from the light-receiving element generated in accordance with the toner density control image and a predetermined reference image density. The copy density is controlled using a means for comparing set levels and a control means for controlling toner replenishment operation according to the output generated by the comparison means, and the light emitting element and the light receiving element are used to control the copy density from the photoreceptor. This was achieved using a copying machine that is characterized by the ability to detect transfer paper separation failure.

In the apparatus of the present invention, when a patch for measuring toner density is placed in an area of the photoreceptor used for image formation, it is placed at a position immediately before image exposure on the surface of the photoreceptor to be used, thereby making it possible to detect the image to be transferred. It is even more effective because it measures the density of an equivalent toner image.

Furthermore, since the surface of the photoreceptor is irradiated with infrared rays, it is possible to prevent fatigue of the photoreceptor in areas other than the toner image patch area, and to reduce the memory effect of the photoreceptor without reducing the charging ability of the photoreceptor. Can be done. Therefore, even if a patch is installed in a tourist area, no damage will occur.

In the present invention, since a specific position on the photoreceptor does not become a reference position, the state of the toner transfer image can be measured more accurately.

The present invention will be explained below with reference to the illustrated embodiments.

First, an embodiment of a copying machine using a photoreceptor consisting of a rotating drum shown in FIGS. 1 to 3 will be described.

1 is a photoconductor consisting of a rotating drum installed in the frame of the machine, 1a is the area required for transfer of the photoconductor 1, and 1b is
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. There is.

6 is a document table; 7 is a 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.; The reference image 7 and the original on the original platen 6 are exposed onto the photoreceptor 1 in each exposure operation to form a latent image. 12 is a developer container 1 of the developing device 3;
A toner replenishment container is connected to the toner replenishment container 12 by an opening 14 on the top of the toner replenishment container 12, and toner is replenished from the toner replenishment container 12 to the developer container 13 by operating a swinging rod 15 provided in the container 12. be done. Reference numeral 16 denotes a transfer paper mounting table, and the transfer paper 17 placed on the mounting table 16 is fed one by one to the transfer unit 4 for each copy, the image on the photoreceptor is transferred to the transfer paper, and then separated. The toner is peeled off from the photoreceptor 1 by a separating device 18 such as a claw, and sent to a fixing device (not shown) via a conveying device 19 to be fixed.

20 is a light emitting element, 21 is a light receiving element, both elements 2
Reference numerals 0 and 21 are provided between the transfer unit 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 and strikes the light receiving element. The light is received at 21. Therefore, the toner control image 22 developed by the latent image of the reference image formed on the photoreceptor 1 passing through the developing device 3 receives light from the light emitting element 20 and is reflected by the light receiving element 21. reflect to. Further, when the transfer paper 23 that has passed through the transfer section 4 is not separated from the photoreceptor 1, it adheres to the photoreceptor 1, so that the transfer paper 23 can be detected.

24 and 25 are comparators built into a circuit consisting of a light emitting element 20, a light receiving element 21, etc.
is set by adjusting it with the variable resistor 26 so that the potential at point A and the potential at point B generated by the reflected light received from the image density at the toner standard (designated) density are equal. The toner control image 22 to be exposed and developed is irradiated with infrared light from the light emitting element 20, and the reflected light is received by the light receiving element 21.
A comparator determines whether the output voltage level at point A has become higher or lower than the set level, and depending on the signal, the swinging rod 15 of the toner supply container 12 is stopped or activated to remove the developer. Container 13
Controls toner supply inside the printer. Also, the comparator 25 is
The variable resistor 27 is adjusted and set so that when the transfer paper is separated well, that is, the potential at point A and the potential at point B' generated by the reflected light received from the surface of the photoreceptor 1 are equal. Separation or non-separation of the transfer paper is detected by emitting infrared light from the light-emitting element 20 for each copy, with timing shifted from density detection.If the transfer paper 23 cannot be separated from the photoreceptor 1, A Since the output voltage level at the point no longer matches the set level, the difference is determined and the drive mechanism is stopped.

Next, to explain the operation of the above-mentioned apparatus, the photoconductor 1 rotates for each copy, is first charged by the charging device 2, and then the document on the document table 6 is transferred to the photoconductor 1 by the exposure device 8. Area portion 1a is exposed. During this exposure, the exposure device 8 also exposes the shadow of the reference image 7 to the front end or rear end 1b of the photoreceptor 1 outside the required transfer area to form a latent image, and the developing device 3 The image and the latent image of the document are developed to form a toner control image 22 and an image of the document. The density of the image resulting from this development is developer container 1
It is determined by the amount of toner within 3.

When the photoconductor 1 further rotates and moves to the transfer section 4, the transfer required area portion 1a of the photoconductor 1 is transferred to the transfer paper 17 fed from the transfer paper mounting table 16 to the transfer section 4.
However, the toner control image 22 is not transferred to the transfer paper 17 because it is formed at the front end or rear end 1b outside the transfer area.

Therefore, when the photoreceptor 1 further rotates and the toner control image 22 moves to the detection section, the light emitting element 2
0, the reflected light is detected by the light receiving element 21, and the output voltage level is detected by the comparator 2.
4, and when the output voltage level becomes higher or lower, the swing rod 1 of the toner supply container 12 is
The operation of step 5 is stopped until the target copy image density is reached, or is started to control the amount of toner supplied into the developer container 13, so that an image with a constant density is always automatically obtained.

Then, the photoreceptor 1 further rotates, and the cleaning device 5 cleans the toner control image 22 and the original image remaining after the transfer, and the copying process can be performed again.

On the other hand, the transfer paper 17 on which the transfer has been performed is transferred to the separating device 1
8, the photoreceptor 1 is separated from the photoreceptor 1 by
is conveyed to a fixing device and fixed thereon. However, if the transfer paper 23 is moved without being separated by the separation device 19 and remains adsorbed to the photoconductor 1, the reflectance of the infrared light emitted from the light emitting element 20 changes in the detection section, so the light is received. Since the output voltage level of the element 21 changes, the change is detected by the comparator 25.
makes a judgment and stops the operation of the drive mechanism to prevent paper jams.

Next, in the embodiment shown in FIG. 5, the photoconductor 1 is provided on a belt 29 stretched between rollers 28, 28 instead of the photoconductor 1 consisting of a rotating drum, and its function is similar to that of the embodiment described above. It is similar to

[Brief explanation of drawings]

Figure 1 is a front view showing one embodiment of the present invention, Figure 2 is a front view showing one embodiment of the present invention;
The figure is a perspective view showing the state of toner concentration detection, FIG. 3 is a perspective view of the state of detecting poorly separated transfer paper, and FIG. 4 is a circuit showing an example of a device for detecting toner concentration and poorly separated transfer paper. FIG. 5 is a front view showing another embodiment. 1 is a photoreceptor, 1b is a front end or a rear end outside the required transfer area, 2 is a charging device, 3 is a developing device, 4 is a transfer section, 5 is a cleaning device, 6 is a document table, 7 is a reference image, 8
20 is an exposure device, 20 is a light emitting element, 21 is a light receiving element,
22 is a toner density control image, 23 is a transfer sheet with poor separation, and 24 and 25 are comparators.

Claims (1)

[Claims] 1 Place the document table so that the latent image of the toner density control image is formed on the photoconductor at the front end or rear end outside the required transfer area in the direction of movement of the photoconductor, and within the required transfer area in the direction perpendicular to the direction of movement. Alternatively, a reference image provided on the document holding cover, a light emitting element that irradiates infrared light onto the photoreceptor after passing through the transfer position and before reaching the cleaning position, and the light emitted from the light emitting element and reflected by the photoreceptor. a light-receiving element that receives reflected light from the toner density control image developed on the photoreceptor based on the reference image; and an output level and a reference density level from the light-receiving element that are generated in response to the reflected light from the toner density control image developed on the photoreceptor based on the reference image. a control means for controlling a toner replenishment operation in accordance with the output from the comparison means, and a control means for detecting poor transfer separation by comparing the output level from the light receiving element with a set level when the transfer separation is good. A copying machine characterized by having means for.