JPH08160751A - Developing device - Google Patents

Abstract

PURPOSE: To prevent toner from being attached and accumulated to/on a transfer roller by providing a developing device with a member executing such a control action that the bristle of the toner on a developing roller is prevented from becoming wider than the width of the recording paper so that it can be moved in a width direction according to the size of the recording paper. CONSTITUTION: When a motor 31 is rotated clockwise, a bristle cut plate 25 is wound up by a take-up pulley 28 because the winding-up force of the motor 31 is stronger than the force of the spiral spring 30 of a take-up reel 27. Thus, the level difference part 26 of the plate 25 is moved in a direction shown by an arrow B. That means, it is moved to an inner side in a sub-scanning direction and the head of the bristle is shaved by the wide width party. Then, a range L where the bristle 36 appears is made narrow. Besides, when the motor 31 is rotated counterclockwise, the plate 25 is rewound to the reel 27 by the force of the spring 30. Thus, the level difference part 26 of the plate 25 is moved to this side in the sub-scanning direction. Then, the range L where the bristle of the toner appears is made wide. Therefore, a fixed bristle cut plate 33 is fixed to a back side plate 24 at a middle position between an inner recording area and a paper reference position so that the bristle does not appear.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device. Specifically, a magnetic printing device or an electrostatic printing device that forms a magnetic or electrostatic latent image on the peripheral surface of a printing drum, visualizes the latent image with toner, and then transfers the toner image onto a recording sheet. The present invention relates to improvement of a developing device used in a copying apparatus.

[0002]

2. Description of the Related Art A magnetic printing apparatus will be described below as an example of the printing apparatus. 3 and 4 are Japanese Patent Publication No. 55-1738.
FIG. 3 is a schematic view of the apparatus, and FIG. 4 is an enlarged view of the developing apparatus. In FIG. 3, reference numeral 1 denotes a printing drum, and around the printing drum 1, a magnetic head 2, a developing device 3, a transfer roller 4, a cleaner 5, a degaussing head 6 and the like are sequentially arranged. A fixing roller 12 is arranged near the transfer roller 4.

When printing, the magnetic drum 2 is scanned in the sub-scanning direction (axial direction of the printing drum) while rotating the printing drum 1 in the direction of arrow A, and the peripheral surface of the printing drum 1 is scanned. A magnetic latent image corresponding to the image signal is formed on the upper surface. When the magnetic latent image reaches the developing device 3 as the drum rotates, the developing device 3 transfers the stored magnetic toner 7 to the transport roller 8 and the developing roller 3. The roller 9 supplies the image to the printing drum 1 to visualize the latent image. Then, after the visualized toner image is transferred onto the recording paper 11 by the transfer roller 4, the fixing roller 1
The heat fixing is performed by 2.

Next, details of the developing device will be described with reference to FIG. The transport roller 8 is a fixed magnet 13 magnetized as shown in the figure.
The pipe 14 rotates in the direction of arrow A around the outer periphery of the toner to adsorb the toner and supply the toner to the developing drum 9. The developing drum 9 is composed of, for example, a developing magnet 15 having a fixed magnetic pole arrangement as shown in the figure, and a developing pipe 16 rotating around the outer periphery thereof, and the developing pipe 16 is rotated in the direction of arrow B. Solid lines or dotted lines 17 and 18 having arrows indicate magnetic force lines, and the magnetic toners are arranged along the magnetic force lines to form a chain and receive a coupling force connecting to the front and rear magnetic toners. A state in which the toner particles connected in a chain form are cut into a uniform height on the developing pipe with a doctor blade is called a brush.

In this way, the printing drum 1 passes through the chains connected in a chain shape, and the magnetic latent image on the printing drum 1 having a magnetic attraction force larger than the chain-shaped coupling force produces magnetic toner. It is developed by adsorbing. in this case,
The magnetic latent image corresponding to black breaks the chain-like coupling and attracts the magnetic toner, but the part corresponding to white has no magnetic attraction force, so the magnetic toner is held by the developing roller by the chain-like coupling force and is transferred to the printing drum. It does not adhere to 1.

[0006]

In the above-mentioned conventional developing device, the toner is attracted to the image portion, but is not attracted to the non-image portion by the chain-like coupling force of the toner. However, since the toner spikes come into contact with the drum at high speed, the toner spikes are compressed, and at this time, a very small amount of toner adheres to the non-image area 19 of the printing drum 1 as shown in FIG.

If the area where the toner spikes appear in the sub-scanning direction is larger than that of the sheet 11a to be transferred, the trace amount of toner within the area of the sheet is transferred to the sheet 11a during the transfer process.
However, the trace amount of toner in the other range is attracted to the transfer roller 4. When printing is continuously performed in this state, the above-mentioned trace amount of toner adheres to and accumulates on the transfer roller 4. Then, when the paper 11b having a width larger than that of the above-mentioned paper 11a is passed next, the toner accumulated on the transfer roller is transferred to the back surface on which the toner is transferred, that is, the surface contacting the transfer roller 4.

That is, when a small sheet 11a is continuously fed, toner stains are transferred to the transfer roller 4 in a range exceeding the width of the sheet.
When the next large sheet 11b is passed, the back surface of the sheet is soiled. The magnetic printing device is required to print on various sizes of paper, and one of the features of the device is that it can print a large amount of paper in a short time. There should be no deterioration or stains on the paper. However, the conventional developing device has a problem that the paper is stained as described above.

In view of the above conventional problems, it is an object of the present invention to realize a developing device in which toner is not deposited and accumulated on a transfer roller even when sheets of various sizes are continuously fed, and the sheet is not contaminated. To do.

[0010]

According to the present invention, a latent image formed by recording means on the peripheral surface of a printing drum is visualized with toner, and the toner image is transferred onto recording paper. In the developing device of the copying apparatus, a member is provided that is movable in the width direction of the sheet according to the sheet size, so as to prevent the toner spikes on the developing roller contacting the printing drum from exceeding the width of the recording sheet. It is characterized by that.

Further, in addition to the above, the member for suppressing the toner bristles is in the form of a belt, and one end thereof is fixed to the take-up reel and the other end is fixed to the take-up pulley. By adopting this configuration, it is possible to obtain a developing device which does not stain the transfer roller without depositing toner on the transfer roller even when various sizes of paper are continuously passed.

[0012]

In the present invention, as shown in FIG. 1, with respect to the ears 36 of the magnetic toner formed on the peripheral surface of the developing roller 22, a member (ear cutting plate 25) for scraping off an unnecessary portion of the ears 36 is provided in the sub-scanning direction. Since it is provided so as to be movable, the bristle cutting plate 25 is moved according to the paper size, and the bristle of the toner is cut off so that the toner does not adhere to the non-image area. It will not adhere to. Therefore, the adhesion and accumulation of the toner on the transfer roller 21 is prevented, and thus the stain of the sheet is prevented.

[0013]

1 is a schematic view showing an embodiment of the present invention together with a printing drum. In the figure, 20 is a printing drum, 2
Reference numeral 1 is a transfer roller, and 22 is a developing roller of a developing device. The developing roller 22 is composed of a fixed developing magnet and a developing pipe provided on the outer periphery thereof, and is held by a front side plate 23 and a rear side plate 24 of the developing device, and the developing pipe is rotatable. ing. Further, reference numeral 25 denotes a member (hereinafter referred to as an ear cutting plate) for suppressing the ear of the magnetic toner, which is the main point of the present invention. The ear cutting plate 25 is formed of a flexible material in a band shape, and has a step portion 2 formed at a boundary between the wide portion and the narrow portion and the wide portion and the narrow portion.
6 and. One end of the cutting board 25 is fixed to the take-up reel 27, and the other end is fixed to the take-up pulley 28. In addition, this ear cutting board 25
The material must be non-magnetic, and thin plates such as plastic and stainless steel can be used.

The take-up reel 27 has a front side plate 23.
It is rotatably supported by a shaft 29 attached to and is urged by a spiral spring 30 to rotate in the direction of arrow A. The take-up pulley 28 is fixed to a rotary shaft 32 of a motor 31 installed on the rear side plate 24. A fixed spike cutting plate 33 is attached to the rear side plate 24 in the vicinity of the right end of the developing roller 22 (the paper transport reference side on the far side in the sub-scanning direction). Further, a sensor (for example, an optical sensor) 34 for detecting the stepped portion 26 of the spike cutting plate 25 is provided near the left side of the developing roller 22.

The operation of this embodiment thus constructed will be described with reference to FIG. The developing roller 22 has the magnetic toner 3 supplied on its peripheral surface by a toner carrying roller (not shown).
5 is adsorbed to form the ears 36 of toner, and is rotating in the direction of the white arrow. At this time, when the motor 31 is rotated in the clockwise direction, the winding force of the motor 31 exceeds the force of the spiral spring 30 of the take-up reel 27, so that the cutting board 25
Is wound up on the take-up pulley 28. As a result, in the ear cutting plate 25, the stepped portion 26 moves in the direction indicated by the arrow B, that is, in the sub-scanning direction (the rear side of the device), and the head of the ear is scraped off at the wide portion, and the ear 36 is formed. The appearing range L is narrowed.

When the motor 31 rotates counterclockwise, the spike cutting plate 25 is rewound on the take-up reel 27 by the force of the spiral spring 30. As a result, the stepped portion 26 of the bristle cutting plate 25 moves to the front side in the sub-scanning direction to widen the range L in which the ears of the toner appear. In addition, the fixed ear cutting board 33 on the back side
Does not need to be moved because all the sheets are conveyed with the end face on the back side as a reference. For this reason, the fixed edge cutting plate 33 is fixed to the rear side plate 24 at the intermediate position between the recording area on the back side and the paper reference position so that the toner spikes do not appear.

Next, the control of the cutting board 25 will be described. When the power is turned on, when the paper is selected, or when the paper is switched, the motor 31 rotates counterclockwise, the sensor 34 detects the step 26 of the spike cutting plate 25, and the step 26 is set as the origin. Return to position. Then, the size of the sheet is detected by the sheet size detecting means, the motor 31 rotates by an amount corresponding to the sheet, and the step portion 26 of the cutting board 25 is rotated.
To move. The movement amount according to the sheet will be described with reference to FIG.

2A and 2B are views for explaining the action of the ear cutting plate, where FIG. 2A is a relationship between the printing drum and the paper, and FIG. 2B is a relationship between the ear cutting plate and the ear in the case of a paper having a small width. , (C) show the relationship between the cutting board and the cutting edge in the case of a wide paper. Further, in (a), the right side of the printing drum 20 is the back side and the left side is the front side. There is a sheet conveyance reference on the back side, and the edge of both a small size a sheet and large b size sheet is aligned with this reference. Therefore, on the back side, the fixed spike cutting plate 33 cuts the spikes at the intermediate point P between the edge of the recording area and the edge of the paper.

On the front side, in the case of a small size paper of a size, as in (b), the spike cutting plate 25 moves its stepped portion 26 to the intermediate Q point between the end of the recording area and the end of the paper. Cut the ears and adjust ears 36 as shown. Further, in the case of a b-size paper having a large width, as shown in (c), the ear cutting plate 25 moves the stepped portion 26 to an intermediate R point between the edge of the recording area and the edge of the paper to perform the ear cutting. Adjust 36 as shown.

The movement amount of the cutting board 25 is ensured by the operating time of the motor 31. The means for securing this movement amount may be provided by providing a detection plate on a rotating member such as the motor shaft 32 or the take-up reel 27 for detection by a sensor, or may be specified by the number of pulses using a pulse motor. Although the above description has been made on the magnetic printing apparatus, the present invention can of course be applied to an electrostatic printing apparatus or the like.

[0021]

According to the present invention, a small amount of toner adhering to the non-image area of the drum is transferred to the transfer roller by automatically reducing the area in which the spikes of toner appear in the sub-scanning direction smaller than the size of the paper. The transfer roller can be prevented from adhering, and as a result, the transfer roller can be prevented from being soiled, so that the back soiling of various sizes of paper can be completely eliminated.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention together with a printing drum.

FIG. 2 is a view for explaining the action of the cutting board of the embodiment of the present invention.

FIG. 3 is a schematic view showing an example of a conventional magnetic printing apparatus.

FIG. 4 is a diagram showing a developing device as an example of a conventional magnetic printing device.

FIG. 5 is a diagram for explaining a problem to be solved by the invention.

[Explanation of symbols]

 20 ... Printing drum 21 ... Transfer roller 22 ... Developing roller 23 ... Developing device front side plate 24 ... Developing device rear side plate 25 ... Spike plate (member for suppressing spikes) 26 ... Step portion 27 ... Take-up reel 28 ... Take-up pulley 29 ... Shaft 30 ... Spiral spring 31 ... Motor 32 ... Rotating shaft 33 ... Fixed spike cutting plate 34 ... Sensor 35 ... Toner 36 ... Spike

Claims (2)

[Claims] 1. A developing device in a printing apparatus which visualizes a latent image formed by recording means on a peripheral surface of a printing drum with toner and transfers the toner image onto a recording sheet. A developing device, wherein a member that suppresses a brush of toner on a developing roller that comes into contact with a width of a recording sheet is provided so as to be movable in the width direction of the sheet according to the sheet size. 2. The developing device according to claim 1, wherein the member for suppressing the spikes of toner has a band shape, one end of which is fixed to a take-up reel and the other end of which is fixed to a take-up pulley. apparatus.