JPS5912466A - Density controller for developer - Google Patents

Abstract

PURPOSE:To detect toner density under no influence of the characteristics of a photosensitive material because a toner image is formed while charges given by an electrostatic charger are held as they are, by providing an insulator area to part of the photosensitive material and forming the toner image therein and measuring its density. CONSTITUTION:The density of the toner image in the insulator area 12 is measured to decide on whether the density of a developer is higher or lower than a reference value accurately. A photosensor is used to detect the density of the toner image in the area 12 at specific timing. A toner image density signal 17 is supplied to a comparator 18, which compares the voltage level with a reference voltage signal 21 outputted by a reference voltage generator 19. The comparator 18 generates a toner supplement signal 22 when judging that the reflection density of the toner image in the area 12 is lower than the reference value. A toner dispenser driving circuit 23 once supplied with the toner supplement signal 22 replenishes toner to the developer. Consequently, the density of the developer is controlled accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention applies to an electronic copying machine using a two-component developer ().
The present invention relates to a developer concentration control device.

In a two-component developing electronic copying machine, Kitria is used to
Boo is charged by friction and an electrostatic latent image is developed. In order to maintain the image density in a good state in this copying machine, it is necessary to appropriately replenish the developing device with 1 to toner to keep the density constant.

As a density control device used for this purpose, an i-position using a reference density patch is widely known.

In this apparatus, a base ring density patch set at a predetermined reflection li1 degree is placed on a part of the document table. When a copying operation is started, a toner image of (-) for the reference density patch is formed on the photosensitive material. In this case, the density of the 1 to toner image on the photosensitive material is detected using a reflection type photo sensor, and the amount of toner supplied to the Cuam device is controlled based on this.

However, when this device is used, the hot stone of the developer may not be controlled properly. The cause of this is said to be fluctuations in the potential of the electrostatic latent image with respect to the reference temperature patch portion. Photoconductors used as Zunawara photosensitive materials do not exhibit characteristics that are particularly sensitive to the environment or the degree of fatigue caused by their use, so the surface potential of the photosensitive material before development is within the standard m degrees. Fluctuations may also occur in the patch area.When the surface potential of the sensitive material changes, the degree of toner image produced by development changes accordingly.As a result, the density of the developer may be incorrectly detected. Therefore, the control will be performed incorrectly.

The present invention has 41 points as described above, and an object thereof is to provide a developer concentration control device that can accurately control the developer concentration regardless of the condition of the photosensitive material.

In the present invention, an insulator area is provided in a part of the photosensitive material, a toner image is formed on this insulator area, and the density is measured.
Ru. In this region, the charge applied by the charging device is retained as it is and a 1-toner image is created, so that the concentration of the developer can be stably measured.

The present invention will be described in detail below with reference to Examples.

FIG. 1 shows the main parts of a copying machine using the density control device of this embodiment. In this copying machine, a transparent original platen 2 on which the original m1 is placed is horizontally fixed to the soil part of the main body of the Hirakata machine (not shown). On the 4Z side of the document table 2, a long and narrow lamp 3 for irradiating the document is arranged horizontally to the document table 2. The lamp 3 and the first and second mirrors 4.5 are configured to reciprocate in the direction of the arrow in the figure, and the irradiation position of the original 1 is continuously changed from one end to the other end. The reflected light from the original 1 passes through the first mirror 4, the lens 6J'; J, and the second mirror 5, reaches the photosensitive drum 70, and forms an image. Around the photoreceptor drum 7, other parts such as a charger 8 for charging, a developer 9.1 to ner* for development, and a reciprocating type FO 1 to ZENRI 11 for detecting warm stones are arranged. has been done.

Now, when the illustrated start button 1 of this copying machine is pressed, the photosensitive drum 7 always starts rotating clockwise from its home position. With this, fluorescent light 3 starts lighting up at 'L'.
, the charger 8 starts discharging onto the photoreceptor drum 7. As shown in FIG. 2, the photosensitive drum 7 is partially coated with an insulator to form an insulator region 12 a3.

The charger 8 first charges the portion including the insulator region 12, and then the image region 13. Image area 13
At the timing when the leading end of the document 1 reaches the image forming position, optical components such as the lamp 3 start moving, and electrostatic latent images of the document 1 are sequentially formed in the image area 1Iili13. Each charged portion on the photoreceptor drum 7 is developed by a magnetic brush method by a developing roll 9.
A toner image is formed.

FIG. 3 shows the relationship between the developer's m degree, the sensitive material potential, and the 1-ner image m degree for the photosensitive drum used in this embodiment. Three curves shown in the figure 1
Numbers 4 to 16 represent different developer odors. Among them, curve 15 is an example when the developer concentration is appropriate, curve 14 is an example when the developer concentration is low, and curve 116 is an example when the developer concentration is low.
shows an example when the concentration is high. This figure shows that when the potential of the sensitive material applied during development is lower than a certain value (approximately 800 V in the figure), the toner image density (11 degrees of anti-DI) changes depending on the potential of the sensitive material. Recognize. In this region, the toner image density depends on both the sensitive material potential and the developer concentration, so as already pointed out, the toner image density
i! It is not possible to accurately determine the degree of i-agent compliance.

On the other hand, when development is performed on a portion where the potential of the sensitive material is higher than these values (approximately 800V to 1400V in the figure), the density of the tossed image depends only on the density of the developer. Assume that the insulator region 12 is charged to 1200V by the charger 8. The charge in this part remains unaffected by the environment, light, etc. As a result, by measuring the degree m of the toner image in the insulator region 12, it is possible to accurately determine whether the developer concentration is higher or lower than the reference value.

FO 1 to senry 11 detect the density of the toner image in the insulator region 12 at predetermined timing. As shown in FIG. 4, the toner@density signal 17 thus obtained is supplied to a comparator 18. The comparator 18 compares the voltage level with the M quasi-voltage signal 21 output from the reference voltage generator 19. The reference voltage signal 21 in this case is a signal at a voltage level corresponding to about 1.35 degrees of fouling of the toner image.

When it is determined that the inverse (1)l concentration of the tonneau image in the insulator region 12 is lower than the standard, the comparator 18 outputs a 1
- generates a replenishment signal 22. When the toner dispenser drive circuit 23 receives the toner replenishment signal 22, it drives a toner dispenser (not shown) to replenish the developer with toner. Since the detection of the degree of depth in the insulator region 12 is performed every copy 1→noise, the degree of S of the developer is always maintained at an ideal state.

FIG. 5 shows a modification of the present invention.

In this example, an insulator region 12 is provided at an end portion of the photosensitive drum 7 where no image is formed. In this case, the file A
1 to Hinley will also be placed at corresponding positions. According to this modification, an image can be formed at any rotational position of the photosensitive drum 7.

As explained above, according to the present invention, it is possible to detect 1.low density without being affected by the characteristics of the photosensitive material, which improves the accuracy of developer temperature control and produces high-quality copied images. Can you get it? In addition, since there is no need to place a reference temperature patch for density detection on the document table, the moving distance of the optical system or document table is short, and the time required for copying is shortened accordingly. There is also.

FIG. 1 is a block diagram showing the main parts of a copying machine according to an embodiment of the present invention, and FIG. FIG. 3 is a characteristic diagram of this photosensitive drum, and FIG. 4 is a perspective view of this example.
A block diagram showing the circuit parts used for one-time control,
FIG. 5 is a perspective view of a photosensitive drum according to a modified example.

7... Photosensitive drum 9... Developing roll 11... Photo sensor 1/12... Insulator area 18... Comparator 23. ...1~N dispenser drive circuit output
Attorney Fuji Xerox Co., Ltd. Representative Patent Attorney Umeo Yamauchi

Claims (1)

[Claims] In an electronic copying machine that uses a two-component developer to make copies, there is a charger that applies electricity (to an insulator area formed on a part of a sensitive material!) and a device that makes copies of the charged area. '] - Detects the density of the tonneau image obtained by developing it with a developing device used in A developer concentration control device characterized by comprising a temperature adjusting means for adjusting the toner temperature of the developer in the developing device based on a comparison result.