JPH0618371Y2 - Development device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is applied to, for example, an electrostatic transfer copying machine or a laser printer, and is used for developing an electrostatic latent image or the like formed on a recording medium. The present invention relates to a developing device.

[Conventional technology]

In a copying machine or the like, toner made of a color pigment is attached to the electrostatic latent image for the purpose of visualizing the electrostatic latent image formed on the recording medium. In this case, in order to not only visualize the electrostatic latent image in black but also colorize it into each color, a plurality of developing devices containing toners of various colors are provided inside the copying machine. The developing device can be selected and used.

For example, in the case of forming a full-color image, a developing device containing cyan, magenta, yellow, and, if necessary, black toner is separately provided, and an electrostatic latent image on a recording medium that is color-separated through filters of each color is formed. Each color toner is developed, and each color toner is overlaid on the recording medium to obtain a full-color copy image.

Therefore, the developing device needs to be configured not to adhere to the toner electrostatic latent image when it is not used for development.

To prevent the toner of the developing device that is not used for development from adhering to the electrostatic latent image on the recording medium, conventionally, for example, the developing gap, that is, the distance between the recording medium and the developing portion of the developing device is changed. It is customary that the toner is not sent to the developing area facing the recording medium by switching.

[Problems to be solved by the invention]

However, in the configuration in which the development gap is switched as described above, if the development gap is not positioned accurately, the development condition tends to vary, and the image density tends to change, so that a normal image is formed. There was a problem that could not be.

Further, in the developing device adopting the magnetic brush developing method, the position of the magnet forming the developing unit is shifted so that the magnetic brush does not come into contact with the recording medium. When the position of the magnet shifts inside, not only the image density is changed, but when a two-component developer is used, the carrier adheres to the recording medium, resulting in a marked deterioration in image quality.

Therefore, a stirring roller is arranged in the developer supply passage for supplying the developer to the developing magnet roller which is disposed facing the recording medium and performs the development, and a slit is formed concentrically with the stirring roller on the outer periphery of the stirring roller. A cylindrical shutter is fitted, and the developer supply passage is closed or opened by a shutter mechanism whose rotation is controllable, while the developer sent through the developer supply device is transferred onto a recording medium by a developing magnet roller. It is conceivable that the electrostatic latent image is developed, and the developer after development is drawn up by the developing magnet roller and conveyed to a portion where the developer is stirred by the conveying magnet roller. This makes it possible to prevent the toner of the developing device, which is not used for development, from adhering to the electrostatic latent image on the recording medium without switching the developing gap.

Further, a toner concentration detecting sensor is provided in the developer supply passage between the shutter and the developing magnet roller, and the toner concentration detecting sensor detects a decrease in toner concentration in the developer sent to the developing magnet roller. By supplying the toner to the developer supply passage while the toner is being supplied, the image density can be kept constant.

However, the toner concentration detection sensor having the above configuration can detect the toner concentration when the developer is sent to the developing magnet roller and the magnetic brush is formed on the outer circumference of the developing magnet roller. After the completion, the shutter is closed to block the developer supply passage, and the developer existing in the developer supply passage between the shutter and the developing magnet roller is developed by the developing magnet roller and the conveying magnet roller. When the developer is no longer present after being returned to the agitating section, the toner concentration detection sensor cannot detect the toner concentration. Therefore, when the magnetic brush is formed, that is, when the developing time for one time is short, a decrease in toner concentration is detected by the toner concentration detecting sensor during the development, and the toner concentration is detected by the toner concentration detecting sensor. Even if the replenishment is started, if the developing time is short, the toner concentration detection sensor immediately becomes unable to detect the toner concentration, so the replenishment is interrupted in a short time, and the toner is sufficiently replenished. You will not have the time to do it.

In particular, in a full-color developing device, the developing time for one type of color, that is, the time during which the magnetic brush is formed, is extremely short, and at this time, the toner density detection sensor detects a decrease in toner density. However, it is very difficult to replenish the consumed toner amount in a short time.

Therefore, by predicting the toner consumption amount, if the toner concentration detection sensor detects a decrease in toner concentration at the end of one development, the toner concentration detection sensor cannot detect the toner concentration after development. It is conceivable that the toner can be replenished by the timer even in the case of the above.

However, if the timer circuit is configured to replenish a certain amount of toner after each drive system of the developing device is stopped, the replenished toner is not agitated at all, and at the time of the next development, the agitation failure, that is, the agitation failure. The charged toner causes problems such as a fogging phenomenon and toner scattering.

[Means for solving problems]

In order to solve the above-mentioned problems, the developing device according to the present invention includes a shutter that can open and close a developer supply passage to a developing unit that develops a recording medium, and a shutter that closes when the development is completed. A developer returning means for returning the developer existing in the developer supply passage between the shutter and the developing unit to the developer supply passage upstream of the shutter, and supplying the developer to the developing unit between the shutter and the developing unit. The toner concentration detection sensor for detecting the toner concentration in the developer and the toner replenishing means after the shutter is closed when the toner concentration detection sensor detects a level corresponding to a predetermined toner concentration reduction state at the end of development. And a timer circuit for controlling the time so as to replenish a predetermined amount of toner to the developer supply passage on the upstream side of the shutter,
There is a preliminary stirring roller for preliminarily stirring the toner replenished in the developing tank with the developer returned to the developer supply passage on the upstream side of the shutter by the developer returning means. It is characterized in that it is set to start in synchronism with the circuit, and after the toner replenishing means is stopped, the preliminary agitating roller is stopped with a certain delay.

[Action]

With the above configuration, when the toner concentration detection sensor detects a predetermined toner concentration decrease state at the end of development, even if the magnetic brush is not formed in the developing unit even if the shutter is closed and the magnetic brush is not formed in the developing unit, a certain amount of toner is discharged. Is replenished. As a result, even when the developing time is short, it is possible to replenish a constant amount of toner regardless of the developing time.

Moreover, since the preliminary stirring roller is activated in synchronization with the timer of the timer circuit, and the preliminary stirring roller is stopped after a certain time delay after stopping the toner replenishing means, the replenished toner is developed by the preliminary stirring roller. Pre-mixed with later developer. Therefore, it is possible to prevent fogging phenomenon and toner scattering due to poor toner stirring from occurring at the next development, the image quality is stabilized, and there is a fixed time delay when the timer is turned off and toner is not supplied. As a result, the preliminary stirring roller is also stopped, so that the stress of the developer due to stirring is suppressed to a minimum. In addition, all the toner replenished from the toner replenishing means is sufficiently agitated by the pre-agitating roller, which improves the power consumption of the toner and reliably avoids the fogging phenomenon and toner scattering due to the uncharged toner. Will be done.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

As shown in FIG. 1, inside the developing tank 1 in which the developer is stored, the developing tank 1 is disposed so as to face the photoconductor 3 as a recording medium,
A developing magnet roller 2 for developing a developer by forming a magnetic brush with a magnetic force to bring the developer into contact with an electrostatic latent image on the photoconductor 3 is rotatably attached. The developing magnet roller 2 constitutes a developing portion of the developing device, and has a rotatable cylindrical non-magnetic sleeve having an outer peripheral portion made of A or the like and is rotatable with respect to the developing tank 1. The non-magnetic sleeve is supported and is rotated by the driving force of the motor M3. Inside the non-magnetic sleeve, a magnet magnetized around each pole is fitted, and the S pole of this magnet forms the main pole and is fixed to the developing tank 1 so as to face the photoconductor 3. Has been done. By making the non-magnetic sleeve rotatable with respect to the magnet in the fixed state as described above, when the non-magnetic sleeve is rotated by the drive of the motor M3, the developer is magnetically attached to the surface of the non-magnetic sleeve. Is attracted to the surface of the photoconductor 3 and the developer is formed into a brush shape along the magnetic force of the main pole of the magnet facing the photoconductor 3. The magnetic brush rubs the electrostatic latent image formed on the photoconductor 3. As a result, the photosensitive member 3 is transferred to the photosensitive member 3, and the photosensitive member 3 is developed.

Above the developing magnet roller 2, a carrying magnet roller (developer returning means) 4 for carrying the developer drawn up after development to a portion where the developer is stirred is attached. The carrying magnet roller 4 has the same structure as the developing magnet roller 2 described above, and the non-magnetic sleeve of the carrying magnet roller 4 is rotated so that the non-magnetic sleeve of the carrying magnet roller 4 is not magnetized. The developer is conveyed while being magnetically attracted to the surface of the magnetic sleeve.

A scraper 6 for scraping off the developer on the surface of the non-magnetic sleeve is provided close to the top of the transport magnet roller. The scraper 6 is arranged in a downwardly inclined state from one end to the other end, and the other end of the scraper 6 is extended to a stirring section for stirring the developer.

Further, the developing tank 1 is provided with a toner hopper 7 communicating with the inside of the developing tank 1, and a toner replenishing roller 8 provided in the toner hopper 7 causes the toner contained in the toner hopper 7 to be removed from the developing tank 1. It is configured so that the developer can be supplied in a fixed amount to the developer supply passage therein. The toner replenishing roller 8 is rotated by the driving force of the motor M1, and the timer circuit 11 operates in response to a detection signal from a toner concentration detecting sensor 10 described later, so that the toner replenishing roller 8 is kept for a certain time.
Is configured to rotate so that the toner can be sent to the developer supply passage in the developing tank 1. The toner hopper 7, toner replenishing roller 8 and motor M1
The toner replenishing means 9 is constituted by.

On the scraper 6, a preliminary stirring roller 5 which is rotationally driven by a motor M2 is provided in close proximity to and rotatable. The preliminary agitating roller 5 preliminarily agitates the toner replenished in the developing tank 1 from the toner replenishing means 9, and agitates the developer scraped off by the scraper 6 from the conveying magnet roller 4 and the toner. While mixing. The developer containing the toner stirred by the preliminary stirring roller 5 is fed to the stirring section by the rotation of the preliminary stirring roller 5.

The above-mentioned stirring section is provided with a stirring roller 12 that is rotatably provided, and is fitted concentrically with the outer circumference of the stirring roller 12, and slits 13a and 13a are formed on opposing walls on the circumference.
And a cylindrical shutter 13 having. The agitating roller 12 is a preliminary agitating roller 5 in the middle of a developer supply passage for supplying the developer sent by the carrying magnet roller 4 to the developing magnet roller 2.
It is located on the lower side of. The shutter 13 and the stirring roller 12 are independently controlled in rotation, and the shutter 13 is driven by a shutter driving motor (not shown), while the stirring roller 12 is drivingly connected to the motor M3 of the developing magnet roller 2. There is. Then, as shown in FIG. 1, the slits 13a, 13a of the shutter 13 are formed.
Is set to open the developer supply passage, the supply of the developer to the developing magnet roller 2 is controlled, while the shutter 13 has an angle of about 90 from the state shown in FIG.
If it is set to a state where both the vicinity of the inlet and the vicinity of the outlet of the developer supply passage are closed by the wall portion of the non-slit portion after rotating by only °, the developer supply passage is blocked and the supply of the developer is stopped. Is configured.

Then, while the electrostatic latent image formed on the photoconductor 3 is being developed, only the developing device necessary for the shutter 13
Is set to an open state, the supply of the developer to the developing magnet roller 2 is continued, and when the development of the electrostatic latent image on the photoconductor 3 is completed and the shutter 13 is still open, the toner described later. The density detection sensor 10 detects the density of the toner, and then the shutter 13 is rotated about 90 ° to close the slits 13a of the shutter 13 by the curved portion 1a of the developing tank 1 and the partition member 14, while the shutter 13 is closed. The developer supply passage is shut off by the constituent wall portion and the supply of the developer to the developing magnet roller 2 is stopped by closing the shutter 13 as described above.

Further, in the developer supply passage between the shutter 13 and the developing magnet roller 2 serving as the developing section during the supply of the developing agent to the developing magnet roller 2, the developing agent attracted to the developing magnet roller 2 is developed. A regulating doctor grade 15 for regulating the amount of the developer is provided, and the regulating doctor grade 15 is a toner for detecting the concentration of the toner of the developer supplied to the developing magnet roller 2 which is the developing section. The density detection sensor 10 is attached.

A timer circuit 11 for time-controlling the toner replenishing means 9 (toner replenishing roller 8) for replenishing the toner is connected to the toner concentration detecting sensor 10 so that the toner supplied to the developing magnet roller 2 If the density is, for example, a certain value or less, the toner density detection sensor 10 detects a certain level (for example, High) and the timer circuit 1
1 is turned on, the motor M1 of the toner replenishing means 9 is driven for a preset time by the timer circuit 11, and the motor M2 of the preliminary stirring roller 5 is started in synchronization with the timer circuit 11 to start the motor. After M1 is stopped, the motor M2 is stopped with a certain delay. Therefore, the toner replenishing means 9
Can supply a certain amount of toner to the developer supply passage even after the shutter 13 is closed.

In the above configuration, when the non-magnetic sleeve of the developing magnet roller 2 is rotated in the arrow direction of FIG. 1 during development, the developer formed by being magnetically attracted to the surface of the non-magnetic sleeve. Magnetic brush rubs the electrostatic latent image formed on the photoconductor 3 to develop it.

The developed developer is drawn up by the developing magnet roller 2 and transferred to the carrying magnet roller 4. In the carrying magnet roller 4, the non-magnetic sleeve rotates in the direction of the arrow in FIG. 1, so the developer is carried while being magnetically attracted to the surface of the non-magnetic sleeve,
After that, the developer is scraped off from the surface of the non-magnetic sleeve by the scraper 6.

The developer scraped off by the scraper 6 is stirred by the preliminary stirring roller 5 rotating in the arrow direction, and then transferred to the stirring unit along the scraper 6.

In the stirring section, when the shutter 13 is rotated and set to the open state as shown in FIG. 1, the developer flows from the slit 13a on the inlet side of the shutter 13 into the stirring roller 12, where the developer is Is stirred. After that, the slit 13 on the exit side of the shutter 13 is moved by the stirring roller 12.
The toner is sent out from a, and the developer is sent to the developing magnet roller 2 through the developer supply passage and is again provided for development by the developing magnet roller 2 forming the developing portion.

Next, when finishing the development, the shutter 13 is set to about 90.
Rotate to block the developer supply passage. This allows
Since the developer is not sent to the developing magnet roller 2, the magnetic brush is not formed on the non-magnetic sleeve of the developing magnet roller 2, and therefore the photoreceptor 3 is not developed.

At the end of the development, as shown in FIGS. 2 and 3, after the development is completed (S1) and before the shutter 13 still blocks the developer supply passage, the toner concentration detection sensor 10 detects the toner. Is detected (S2), and the sensor level of the toner density detection sensor 10 at that time is, for example, Hi.
If it is gh, the shutter drive motor (not shown) is turned on for t ₁ = 0.5 seconds after the development end command signal is transmitted, and the shutter 13 is closed (S3).

After the shutter 13 is closed, the motor M3 is turned off after t ₂ = 1 second to stop the rotation of the developing magnet roller 2 and the stirring roller 12 (S4), and at the same time, the timer of the timer circuit 11 is turned on ( S5) The motor M1 is activated, the toner supply roller 8 is started, and toner supply is started (S6). Note that the toner replenishing roller 8 is started not after the developing magnet roller 2 is stopped but in response to the driving of the shutter 13, and when the output of the toner concentration detection sensor 10 is High, the toner replenishing roller 8 is started. May be. In this case, the preliminary stirring roller 5 may be restarted at the same time as the toner supply roller 8, or the rotation of the preliminary stirring roller 5 may be continuously driven.

As described above, the preliminary stirring roller 5 is continuously rotating, or if the rotation is temporarily stopped before that, the preliminary stirring roller 5 is restarted in synchronization with the turning on of the timer (S7). The preliminary stirring roller 5 is in a rotating state. In addition, since the timer of the timer circuit 11 operates during the preset time t ₃ = 1 second (S8), the motor M1 is turned off.
After F, the rotation of the toner replenishing roller 8 is stopped and the replenishment of toner is completed (S9). After the rotation of the toner replenishing roller 8 is stopped, the timer of the timer circuit 11 causes the motor M2 to be turned off after a further delay of t ₄ = 2 seconds by a preset time, thereby stopping the preliminary stirring roller 5 (S10). .

On the other hand, when the toner concentration detection sensor 10 does not reach a certain sensor level when detecting the toner concentration, the timer of the timer circuit 11 is in the OFF state, and the toner concentration is within the allowable range. Since the supply is not yet required, after closing the shutter 13 (S11),
All drive systems are stopped (S12), and the preliminary stirring roller 5
Is also not driven, so toner is not replenished.

[Effect of device]

As described above, the developing device according to the present invention includes the shutter that can open and close the developer supply passage to the developing unit that develops the recording medium, and the shutter and the developing unit when the shutter is closed after the development is completed. Between the shutter and the developing unit, and a developer returning means for returning the developer existing in the developer supplying passage between the shutter and the developing unit to the developer supplying passage upstream of the shutter. Toner concentration detecting sensor for detecting the toner concentration of the toner, and when the toner concentration detecting sensor detects a level corresponding to a predetermined toner concentration lowering state at the end of development, after the shutter is closed, a certain amount of toner is supplied by the toner supply means. And a timer circuit that controls the time so that the toner is replenished to the developer supply passage on the upstream side of the shutter. There is a preliminary stirring roller for preliminarily stirring the developer returned to the developer supply passage on the upstream side of the shutter by the developer returning means, and the preliminary stirring roller is activated in synchronization with the timer circuit and the toner is supplied. It is configured such that the pre-agitation roller is stopped with a certain delay after the supply means is stopped.

As a result, when the toner concentration detection sensor detects a toner concentration lowering state at the end of development, a constant amount of toner is replenished by the timer circuit even after the shutter is closed. It becomes possible to replenish the toner.

Moreover, since the preliminary agitating roller is activated in synchronization with the timer of the timer circuit, and the preliminary agitating roller is stopped after a certain time delay after stopping the toner replenishing means, the replenished toner is sufficiently supplied by the preliminary agitating roller. Is pre-stirred. Therefore, the charging power of the toner is improved, the fog phenomenon and the toner scattering due to the poor stirring of the toner are avoided, the image quality is stabilized, and the stress of the developer due to the stirring is suppressed to the minimum. Produce an effect.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is a vertical sectional view showing the overall construction of the developing device, and FIG. 2 shows the movement of each operating part of the developing device. The flowchart and FIG. 3 are the timing charts. 1 is a developing tank, 2 is a developing magnet roller (developing section),
3 is a photoconductor (recording medium), 4 is a magnet roller for conveyance (developer returning means), 5 is a preliminary stirring roller, 8 is a toner replenishing roller, 9 is a toner replenishing means, 10 is a toner concentration detection sensor, and 11 is a timer. Circuit, 12 is a stirring roller, 1
3 is a shutter, and M1, M2 and M3 are motors.

Claims (1)

[Scope of utility model registration request] 1. A shutter that can open and close a developer supply passage to a developing unit for developing a recording medium, and a developer supply passage between the shutter and the developing unit when the shutter is closed after development is completed. A developer returning means for returning the existing developer to the developer supply passage upstream of the shutter, and a toner concentration for detecting the toner concentration in the developer supplied to the developing unit between the shutter and the developing unit. When the detection sensor and the toner concentration detection sensor detect a level corresponding to a predetermined toner concentration reduction state at the end of development, a certain amount of toner is developed upstream of the shutter by toner replenishing means after the shutter is closed. A developing device having a timer circuit for controlling the time for replenishing the developer supply passage, wherein the toner replenished in the developing tank is protected by the developer returning means. The pre-agitating roller for pre-agitating the developer returned to the developer supply passage on the upstream side of the shutter is started in synchronization with the timer circuit and after the toner replenishing means is stopped. A developing device, characterized in that the pre-agitation roller is set to stop after a certain period of delay.