JPH07230211A - Developing device for image forming device - Google Patents

Abstract

PURPOSE:To provide a developing device, suitable for image forming device, which can obtain stable image quality and capable of switching the speed of an image forming process. CONSTITUTION:According to the switching of the speed of the image forming process, a value to be the reference value is selected from a toner concentration storage means 12, and toner concentration is controlled so as to have the reference value. Therefore, because the amount of toner which is supplied from a developer carrier 4 to an image carrier 1 is not influenced by a change in the speed of the image forming process, almost the same amount of toner can be always supplied to the image carrier 1 and stable image density can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for an image forming apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus for developing a latent image formed on an image bearing member by using a developer composed of toner and carrier, there is an image forming apparatus capable of switching the image forming process speed.

[0003]

However, in the conventional image forming apparatus capable of switching the image forming process speed, the rotation speed of the image carrier may be switched in accordance with the switching of the transfer speed of the transfer material. Since the relationship with the amount of toner supplied from the developer carrier to the image carrier was not considered, the number of processed pages per unit time increases, but the image carrier is carried from the developer carrier at each process speed. The amount of toner supplied to the body is different,
There is a problem that the image quality is not stable.

An object of the present invention is to provide a developing device which can obtain stable image quality and is suitable for an image forming apparatus capable of switching the image forming process speed.

[0005]

Means for Solving the Problems The above-mentioned object is to provide a means for changing the feed speed of a transfer material and a rotation speed of an image carrier in synchronism with each other, and a toner concentration storage means for preliminarily storing a plurality of toner concentrations as patterns. A means for selecting a toner density corresponding to the speed set by the speed changing means from the toner density storing means, a means for detecting an actual toner density, a toner density selected by the selecting means, and the detecting means. And a means for controlling the toner density to the toner density selected by the selecting means.

[0006]

According to the above construction, the reference value is selected from the toner concentration storage means in accordance with the switching of the image forming process speed, and the toner concentration is controlled to the reference value. The amount of toner supplied from the body to the image carrier is not affected by changes in the image forming process speed, and it is possible to always supply substantially the same amount of toner to the image carrier, and a stable image density can be obtained.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a photosensitive drum whose surface is photoconductively treated to become an image bearing member, which rotates in the direction of arrow a. Reference numeral 2 denotes a charger, which uniformly charges the surface of the photosensitive drum 1 to a predetermined polarity by corona discharge. An image exposure optical system 3 exposes the surface of the photosensitive drum 1 with a light image to form a charge latent image. Reference numeral 4 denotes a developing roll serving as a developer carrying member, which is composed of a magnetic roll 4a and a non-magnetic sleeve 4b rotating on the outer side thereof. It is formed. The non-magnetic sleeve 4b rotates in the direction of the arrow b, and the tip of the magnetic brush rubs the surface of the photosensitive drum 1 lightly to attach toner to the charge latent image and develop the image 6
To form. Denoted at 7 and 8 are transfer means for transferring a transfer material (paper or the like) 9. The transfer material 9 is driven in the direction of arrow c at a synchronous speed while temporarily contacting the surface of the photosensitive drum 1, and the transfer device 10 is also provided. The developed image 6 on the photosensitive drum 1 is transferred to the transfer material 9 by receiving the corona charge for transfer from the.

A drive source (not shown) for the photosensitive drum 1 and the conveying means 7 and 8 is connected to a speed switching mechanism 11 serving as a speed changing means. By adjusting the speed switching mechanism 11, the transfer speed of the transfer material 9 is adjusted. And the rotational speed of the photosensitive drum 1 can be changed synchronously. A plurality of toner densities are stored in advance in the toner density storage means 12, and when a speed is set by the speed switching mechanism 11, the toner density corresponding to the speed is selected by the selection means 13 from the toner density storage means 12. It On the other hand, inside the developing device 14, a detector 15 for detecting the toner concentration of the developer actually used in the developing process is provided. The toner concentration detected by the detector 15 is compared with the toner concentration reference value selected by the selection unit 13 by the control unit 16, and the toner concentration detected by the detector 15 is selected by the selection unit 13. When it is smaller than the reference value, the toner replenishment signal is issued from the control unit 16. After the toner replenishment signal is issued, the toner is automatically replenished from the toner replenishing means 17 to the developing device 14 based on this signal.

The control of the toner density when the image forming process speed is switched will be described with reference to FIG. 2, the horizontal axis represents the process speed by the peripheral speed ratio of the photosensitive drum 1 and the developing roll 4 (the larger the peripheral speed ratio, the lower the process speed), and the vertical axis represents the toner supply amount. There is. According to the present invention, as described above, the toner densities to be the plurality of reference values are set in advance in the toner density storage means 12, and any reference value can be selected according to the peripheral speed ratio. The toner supply amount from the roll 4 to the photosensitive drum 1 is determined by the toner concentration of the developer corresponding to the peripheral speed ratio. Therefore, taking the peripheral speed ratios S1 and S2 shown in FIG. 2 as an example, in the case of the peripheral speed ratio S1, the toner density corresponding to the peripheral speed ratio S1 is set so as to increase the toner density as shown in (a). In the case of the peripheral speed ratio S2, a toner density different from that in the peripheral speed ratio S1 is selected, and the toner density is set to be low as shown in (b). It is possible to make the amount of toner supplied from the developing roll 4 to the photosensitive drum 1 at the same level (A) during the development at the process speed.

Next, a comparison between the present invention and the prior art will be described with reference to FIG. 3 in relation to image density and toner density. In the prior art, the image density can be controlled only by a preset single toner density, so the image density only changes on the line B in the figure for each process speed, and the image density becomes stable. There wasn't. On the other hand, in the present invention, since the image density exists on the line C in the figure at any process speed, a constant image density can be obtained and stable image quality can always be secured.

[0011]

According to the present invention, in a developing device for forming a developed image on an image carrier by using a developer consisting of toner and carrier, the transfer speed of the transfer material and the rotation speed of the image carrier are synchronized. And means for shifting the toner density, a toner density storage means for preliminarily storing a plurality of toner densities in a pattern, a means for selecting the toner density corresponding to the speed set by the speed shifting means from the toner density storage means, and And a means for comparing the toner density selected by the selecting means with the toner density detected by the detecting means to control the toner density to the toner density selected by the selecting means. Since it is provided, even when the image forming process speed is switched, the toner supply amount from the developer carrying member to the image carrying member can be made almost always the same, It can be obtained those images quality.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a control operation of a toner ratio value of the present invention.

FIG. 3 is an explanatory diagram showing a relationship between the present invention and a conventional technique.

[Explanation of symbols]

11 is a speed switching mechanism, 12 is toner concentration storage means,
13 is selection means, 14 is a developing device, 15 is a detector, 16
Is a control unit, and 17 is a toner replenishing means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kotaro Yamada 1060 Takeda, Katsuta-shi, Ibaraki Hitachi Koki Co., Ltd. (72) Inventor Katsuhiro Shinohara 1060 Takeda, Katsuta-shi, Ibaraki Hitachi Koki Co., Ltd. (72) Inventor Kohei Katayama, 1060 Takeda, Katsuta, Ibaraki, Hitachi Koki Co., Ltd. (72) Minoru Murase, 1060, Takeda, Katsuta, Ibaraki, Hitachi Koki, Co., Ltd.

Claims (2)

[Claims] 1. A developing device for forming a developed image on an image carrier by using a developer composed of toner and carrier, and means for shifting the transfer speed of the transfer material and the rotational speed of the image carrier in synchronization with each other. A toner density storage means for storing a plurality of toner densities in a pattern in advance, a means for selecting a toner density corresponding to the speed set by the speed change means from the toner density storage means, and an actual toner density detection Means for comparing the toner density selected by the selecting means with the toner density detected by the detecting means, and controlling the toner density to the toner density selected by the selecting means. And a developing device of the image forming apparatus. 2. An image according to claim 1, wherein when the toner density detected by said detection means is lower than the toner density selected by said selection means, a toner replenishment signal is issued from said control means. Developing device of forming device.