JP2001051508A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce greasing or the excessive density of a formed image caused by forcibly supplying image forming substance from a replenishing port toward developer by executing reverse movement control that a developer carrier is endlessly moved in a direction opposite to a specified direction in specified timing. SOLUTION: When a developing sleeve 2 is reversely rotated by executing reverse rotation processing after printing operation is finished, the developer moving with the rotation of the sleeve 2 is carried to the vicinity of a toner replenishing port 7 after its layer thickness is regulated by a doctor blade 3 and a pre-doctor part 4 in this order. Since the pre-doctor part 4a regulates the layer thickness of the developer to be thicker than the blade 3, the developer A circulating in a developer storing part 9 is reversely moved to the vicinity of the port 7 by regulating the layer thickness of the developer in such an order. The developer reversely moved to the vicinity of the port 7 is retained in the vicinity of the port 7 and covers the port 7 when its retained amount becomes the specified one.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, a printer, and the like. More specifically, the present invention relates to an image forming apparatus for bringing an image forming substance into contact with a developer carried on a developer carrier to replenish the image forming substance. The present invention relates to an image forming apparatus that changes a contact state between a developer and an image forming substance near a replenishing port, and increases or decreases the amount of the image forming substance taken into the developer from the replenishing port by the change.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open Nos. 9-22178 and 9-197833 are known as developing devices for increasing or decreasing the amount of an image forming substance taken in.

[0003] In these developing devices, the contact state between the developer that rotates with a developing sleeve as a developer carrier and the toner as an image forming substance is changed in the vicinity of a toner supply port in accordance with the toner concentration of the developer. To change. Then, due to this change, the amount of toner taken in by the developer accompanying the developing sleeve near the toner supply port is increased or decreased. By increasing or decreasing the amount of toner taken in this way,
Even if a toner concentration sensor for detecting the toner concentration of the developer is not provided, the toner concentration of the developer at the developing position can be kept substantially constant.

Further, in these developing devices, the amount of developer stagnation around the developing sleeve is smaller than in a normal developing device having a toner density sensor.
As a result, it is not necessary to provide a stirring mechanism for stirring the developer around the developing sleeve, and the driving torque of the developing sleeve is reduced as compared with a normal developing device. If the stirring mechanism is omitted or the driving torque is reduced in this way, the configurations of the developing device and the image forming device can be simplified, and their size and cost can be reduced.

Further, in these developing devices, the toner replenished from the toner replenishing port is conveyed to the developing position without passing through the agitating mechanism, so that the residence time of the toner can be reduced. Thus, even when an image having a high image area ratio is formed, a sufficient amount of toner can contribute to development.

[0006]

However, in an image forming apparatus equipped with these developing devices, when an impact is given to the main body by a maintenance operation, a moving operation, or the like, the impact device is positioned near the toner supply port by the impact. A recoil is applied to the toner. Then, due to this reaction, the toner may be forcibly supplied from the toner supply port toward the developer. When the toner is forcibly supplied, the toner concentration of the developer increases more than necessary. This may cause a problem that a formed image is smeared or an image having an excessively high density is formed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to solve the problem of background contamination and formation caused by forcibly replenishing an image forming substance from a replenishing port toward a developer. An object of the present invention is to provide an image forming apparatus capable of reducing excessive image density.

[0008]

According to one aspect of the present invention, there is provided a developer carrying member which carries a developer and moves endlessly in a predetermined direction; A driving device for controlling the driving device, a driving control unit for controlling the driving device, a supply port for replenishing the developer carried on the developer carrier with an image forming substance, and a replenishing port carried on the developer carrier. A first regulating member that regulates the layer thickness of the developer on the downstream side in the predetermined direction from the supply port; and the additional regulation causes the developer to stay on the upstream side in the predetermined direction from the second regulating member. An agent container for accommodating a developer between the first regulating member and the second regulating member; and an additional regulation for further reducing the layer thickness further downstream in the predetermined direction than the first regulating member. A second regulating member, and the developer downstream of the second regulating member in the predetermined direction. A latent image carrier, which is arranged to face the carrier and carries the latent image, and the developer carried on the developer carrier according to the amount of the developer stagnating near the supply port. In an image forming apparatus that changes the contact state between the developer and the image forming substance and changes the amount of the image forming substance taken in from the supply port into the developer by the change, the developer carrier is moved at a predetermined timing. The drive control means is configured to execute reverse movement control for endlessly moving in a direction opposite to a predetermined direction.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, as the predetermined timing, the development of the latent image is terminated and the developer carrier is moved endlessly in the predetermined direction. The drive control means is configured to execute the reverse movement control immediately after stopping.

Further, the invention according to claim 3 further comprises a transfer means for transferring a visible image obtained by developing the latent image to a recording member directly or via an intermediate transfer member. 2. The image forming apparatus according to claim 1, wherein when performing the image forming operation, the endless movement of the developer carrier in the predetermined direction is stopped after the development of the recording member is completed. 3. When performing the image forming operation, the drive control means performs the reverse movement control immediately after terminating the development of the plurality of recording members and stopping the endless movement as the predetermined timing. Is constituted.

According to a fourth aspect of the present invention, in the case where the continuous image forming operation needs to be temporarily stopped, only the latent image being developed is developed and then the continuous image forming operation is performed. 4. The image forming apparatus according to claim 3, wherein the image forming operation is temporarily stopped. In the case where the continuous image forming operation is temporarily stopped, the developing of the latent image being developed is terminated as the predetermined timing. The drive control means is configured to perform the reverse movement control immediately after the endless movement of the developer carrier in the predetermined direction is stopped.

According to a fifth aspect of the present invention, in a case where an emergency stop of the development of the latent image occurs, the endless movement of the developer carrier in the predetermined direction is urgently stopped. Item 2. The image forming apparatus according to Item 2, 3 or 4, wherein the drive control means is configured to execute the reverse movement control immediately after the emergency stop of the endless movement as the predetermined timing. Is what you do.

Further, the invention of claim 6 is the invention according to claims 1, 2,
In the image forming apparatus of 3, 4, or 5, the endless movement amount of the developer carrier in the opposite direction is one of the developer carrier.
The drive control means is configured to perform the reverse movement control so as to be in a range from １ ／ to の of the endless movement amount per circumference.

The image forming apparatus according to claim 1, 2, 3, 4, 5, or 6, wherein the developer carried along with the developer carrier endlessly moving in the predetermined direction (hereinafter referred to as a normal direction) is the After the layer thickness is regulated by the first regulating member, the layer thickness is further regulated by the second regulating member. Then, after the latent image on the latent image carrier is developed at a developing position which is a position where the latent image carrier and the developer carrier are opposed to each other, the latent image carrier is transported to a position near a supply port. That is, the developer that rotates with the developer carrier is transported to the vicinity of the supply port after the layer thickness is regulated by the second regulating member. On the other hand, the developer regulated by the first regulating member comes to stay near the supply port, and
The developer regulated by the second regulating member is stored in the developer container. In the image forming apparatus having such a configuration,
For example, when the reverse movement control is performed at a predetermined timing, for example, immediately after the image forming operation is completed, the developer carrier is endlessly moved in the direction opposite to the normal direction at the timing (hereinafter, referred to as “removal”).
Reverse movement). When the developer carrier moves in the reverse direction in this way, the developer carried along with the developer carrier is conversely controlled in thickness in the order of the second regulating member and the first regulating member. It will be transported nearby. Since the first regulating member regulates the thickness of the developer thicker than the second regulating member, when the layer thickness of the developer is regulated in such an order, the developer contained in the developer accommodating portion is Moves backward to the vicinity of the supply port. In this way, the developer that has moved backward to the vicinity of the supply port stays in the vicinity of the supply port, and closes the supply port when a predetermined retention amount is reached. When the supply port is closed in this way, an image forming substance that is forcibly moved from the supply port toward the developer by applying a reaction can be sealed upstream of the supply port in the supply direction.

In particular, in the image forming apparatus according to the second aspect, the reverse movement control is performed immediately after the development of the latent image is completed and the endless movement of the developer carrier is stopped. By performing the reverse movement control in this manner, the next image forming operation can be waited in a state where the image forming substance is sealed upstream of the supply port in the supply direction. Therefore, even if a sudden situation such as contact between the main body of the image forming apparatus and a pedestrian, for example, giving a reaction to the image forming substance occurs during this standby, the image forming substance caused by the sudden occurrence occurs. Can be reduced.

In the image forming apparatus according to the third aspect, when a continuous image forming operation is performed, the reverse movement control is performed every time the development of the latent image on one recording member is completed. Instead, the reverse movement control is performed after the development of the latent images on all the scheduled recording members is completed.

In the image forming apparatus according to the fourth aspect of the present invention, since only the replenishing recording member and the image forming material have been lost, only the latent image under development is developed, and then a continuous image is formed. To suspend the image forming operation,
Immediately after the suspension, the reverse movement control is performed. By performing the reverse movement control as described above, even if the continuous image forming operation is temporarily stopped, the subsequent image forming operation can be waited in a state where the forced supply of the image forming substance can be reduced.

Further, in the image forming apparatus according to the fifth aspect, for example, a situation in which an emergency stop of the endless movement of the developer carrier occurs, such as a paper jam of a transfer sheet as a recording member, has occurred. Even when the endless movement is stopped urgently, the reverse movement control is performed immediately after the emergency stop. By performing the reverse movement control in this manner, even if the endless movement of the developer carrying member is urgently stopped, it is possible to wait for the resumption of the endless movement in a state where the forced supply of the image forming substance can be reduced. .

In particular, in the image forming apparatus according to the sixth aspect, a remarkable increase in the driving torque of the developer carrier and overflow of the developer caused by the execution of the reverse movement control are avoided. That is, by performing reverse movement control, the developer in the developer container is reversely moved to the vicinity of the supply port, and after the reverse movement control is continued even after the supply port is closed by the reversely moved developer, the supply port Is further increased in the vicinity of. When the amount of retained developer is increased in this manner, the driving torque of the developer carrier is significantly increased by the retained developer, or the developer is released from the developer carrier and overflows from the developing position. It causes so-called drug overflow. The inventors of the present invention have conducted intensive studies so that the amount of endless movement of the developer carrier in the opposite direction is within a range of １ ／ to の of the amount of endless movement per rotation of the developer carrier. By performing the reverse movement control, it has been found that such a remarkable increase in the driving torque and overflow of the agent can be avoided.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic printer as an image forming apparatus will be described below. First, the basic configuration of the printer will be described. FIG. 1 is a schematic configuration diagram showing a developing device and a photosensitive drum of the printer. In the figure, a photosensitive drum 1 as a latent image carrier is rotated clockwise in the figure by a driving force of a drum driving motor (not shown). Around the photosensitive drum 1, a developing device 10
In addition, a charging device (not shown), an optical writing unit, a charge removing device, a transfer device as a transfer unit, a drum cleaning unit, and the like are provided.

In the drawing, the surface of the photosensitive drum 1, which is driven to rotate clockwise, is neutralized when passing through the position facing the charge eliminator, and then moves to the position opposed to the charging device to uniformly move. Is charged. Then, when passing through the position facing the optical writing unit, the writing light generated based on the image information is irradiated, and the irradiation carries an electrostatic latent image. Thus, the photosensitive drum 1
The electrostatic latent image carried on the toner image is transferred to the developing device 10 by the rotation of the photosensitive drum 1 when the developing device 10 passes the developing position. Is developed. This toner image moves to a transfer position, which is a position facing the transfer device, as the photosensitive drum 1 rotates.

On the other hand, the printer includes a paper feeder (not shown) for storing transfer paper as a recording member, and a paper transport device for transporting the transfer paper discharged from the paper feeder to this transfer position. Have. The paper feeding device discharges the transfer paper housed therein to the paper transporting device at a predetermined timing. The transfer paper discharged in this way is sent to the transfer position by the paper transport device, and is superimposed on the toner image at the transfer position. A transfer bias power supply (not shown) is connected to the transfer device, and thereby a transfer electric field is formed between the transfer device and the photosensitive drum 1.
The toner image on the photosensitive drum is formed on the transfer paper by a synergistic effect of the transfer electric field and the pressing force between the photosensitive drum 1 and the transfer device. The transfer paper on which the toner image has been transferred in this manner is sent to a fixing device (not shown), where the toner image is fixed, and then conveyed out of the apparatus.

The photosensitive drum 1 that has passed the transfer position
When the toner passes through a position facing the drum cleaning unit, the residual toner on the surface is mechanically removed and cleaned. Then, it is moved again to a position facing the above-described static eliminator to eliminate the static charge, and is prepared for the next image formation.

The printer forms an image on transfer paper by a series of printing processes as described above.

Next, the developing device of the printer will be described in detail. Developing device 10 arranged on the side of photosensitive drum 1
Is provided with a toner hopper 5 as an image forming substance storage portion formed so as to be included in the developing casing 8. This toner hopper 5 containing toner T inside
Communicates with the toner supply port 7.

Inside the toner hopper 5, there is provided an agitator 6 as a conveying means which is rotated clockwise in the figure by the driving force of a developing main motor (not shown). The agitator 6 sends out the toner T stored in the toner hopper 5 toward the toner supply port 7 while stirring the toner T. The length of the agitator 6 is desirably set to such an extent that the tip of the agitator 6 does not touch the developer staying in the vicinity of the toner supply port 7 as shown in the agitator rotation orbit of FIG. With this setting, it is possible to avoid a shortage of magnetic carrier caused by scraping the magnetic carrier in the developer staying in the vicinity of the toner supply port 7 into the toner hopper 5 by the agitator 6.

On the side of the toner supply port 7, a developing sleeve 2 as a developer carrying member is provided. The developing sleeve 2 has a cylindrical nonmagnetic pipe 2b and four magnetic poles S, N, S, and N poles disposed inside the pipe 2b and extending in the pipe axis direction. And a magnet roller 2a having The pipe 2b is
It is rotated counterclockwise in the figure by the driving force of a developing main motor (not shown), and generates a two-component developer (hereinafter simply referred to as a developer) composed of a toner and a magnetic carrier by a magnetic force generated by a magnet roller 2a. Can be carried on the peripheral surface. Also, the magnet roller 2a
Is disposed inside the pipe 2b such that one N pole is opposed to a developing position which is a position where the photosensitive drum 1 and the developing sleeve 2 are opposed, and one S pole is opposed to the agent container casing 4. And is fixed inside the pipe 2b so as not to rotate with the rotation of the pipe 2b.

Around the pipe 2b, a doctor blade 3 as a second restricting member is provided upstream of the developing position in the rotation direction of the pipe 2b so as to maintain a predetermined gap between the distal end thereof and the surface of the pipe 2b. It is arranged in. A medicine container casing 4 is adjacent to the doctor blade 3 on the upstream side in the rotation direction of the pipe 2b. The agent container casing 4 has a pre-doctor portion 4a as a first regulating member at an end opposite to the doctor blade 3 side, and is larger than the gap between the tip of the pre-doctor portion 4a and the surface of the pipe 2b. The gap is maintained. Further, between the doctor blade 3 and the pre-doctor portion 4a, an agent accommodating portion 9 opening toward the developing sleeve 2 is formed. Further, the pre-doctor portion 4a is disposed so as to maintain a predetermined gap with a projecting portion 8a projecting from the bottom of the developing casing 8, and this gap is a communication space for communicating the toner supply port 7 with the toner hopper 5. It has become. The agent container casing 4 and the pre-doctor portion 4a may be formed by separate members.

The developer container 9 formed so as to open toward the developing sleeve 2 contains the circulating developer A therein. The circulating developer A rubs against the developer that moves so as to rotate with the developing sleeve 2 while the developing sleeve 2
The developer moves in the rotation direction, or moves in the opposite direction by being pushed by the subsequent developer while colliding with the doctor blade 3, thereby circulating in the developer container 9.

The above-mentioned communication space located between the projecting portion 8a of the developing casing 8 and the pre-doctor portion 4a is formed so as to be inclined downward from the toner hopper 5 side to the developing sleeve 2 side. By inclining the communication space in this way, vibration, uneven magnetic force distribution of the magnet roller 2a, scraping by the pre-doctor portion 4a, etc.
Even if the magnetic carrier is dropped from the developing sleeve 2 into this communication space, the magnetic carrier can be carried on the developing sleeve 2 again by the synergistic action of gravity and the magnet roller 2a. Thus, it is possible to prevent a decrease in the amount of magnetic carriers generated around the developing sleeve 2.

The toner T sent from the toner supply port 7 toward the developing sleeve 2 by the agitator 6 is taken into the developer on the developing sleeve 2.

The developer having thus taken in the toner T moves counterclockwise in the figure so as to rotate with the developing sleeve 2 (pipe 2b) and passes through the position facing the pre-doctor portion 4a. In addition, the thickness on the developing sleeve 2 is regulated. The developer removed from the developing sleeve 2 by this regulation stays in the vicinity of the toner supply port 7 or is carried again by the developing sleeve 2 and
a. On the other hand, the developer remaining on the developing sleeve 2 without being restricted by the pre-doctor portion 4a enters a position facing the above-described agent containing portion 9. Then, it rubs against the circulating developer A in the developer container 9,
The circulating developer A is taken in or the circulating developer A
While exchanging toner and magnetic carriers with
It is transported to the vicinity of the doctor blade 3.

As described above, the doctor blade 3 is disposed so as to maintain a gap smaller than the gap between the pre-doctor portion 4a and the developing sleeve 2 between the developing sleeve 2 and the developing blade 2. The thickness of the developer that moves so as to be entrained is further reduced. The developer removed from the developing sleeve 2 by this regulation is taken into the circulating developer A and circulates and moves in the developer container 9.
On the other hand, the developer remaining on the developing sleeve 2 without being restricted by the doctor blade 3 moves to the developing position so as to rotate with the developing sleeve 2.

A developing bias power supply (not shown) is connected to the developing sleeve 2, and a developing bias is applied by the power supply. At the developing position, a developing electric field is formed between the developing sleeve 2 and the electrostatic latent image carried on the photosensitive drum 1 by applying the developing bias. The developer that has moved to the developing position along with the developing sleeve 2 separates the toner from the magnetic carrier under the influence of the developing electric field and moves toward the electrostatic latent image on the photosensitive drum 1. Then, toner is attached to the electrostatic latent image, and the electrostatic latent image is developed into a toner image.

In the developing device 10 having such a configuration, when a large amount of toner is taken into the developer from the toner supply port 7, the toner concentration of the developer on the developing sleeve 2 increases. When the toner concentration of the developer increases in this manner, the toner concentration of the circulating developer A circulating in the agent container 9 also increases. Thus, the bulk of the circulating developer A in the developer container 9 increases. When the volume of the circulating developer A increases in this way, the developer that has entered the position facing the developer container 9 while rotating with the developing sleeve 2 is applied by contact with the circulating developer A. Transport resistance is increased. When the transport resistance increases in this manner, the developer that has been rotating along with the developing sleeve 2 causes a so-called ball-throwing phenomenon in which the circulating developer A is sequentially pushed out from the gap between the developing sleeve 2 and the doctor blade 3. . As the ball-throwing phenomenon progresses, as shown in FIG. 2, the amount of the developer remaining near the toner supply port 7 increases, and the toner supply port 7 is gradually closed. As a result, in the vicinity of the toner supply port, the state of contact between the developer rotating along with the developing sleeve 2 and the toner T supplied from the toner supply port 7 changes. Specifically, when the amount of retained developer in the vicinity of the toner supply port 7 increases, the area of contact between the developer T and the toner T that is being rotated together with the developing sleeve 2 decreases. When the contact area decreases, the amount of toner taken into the developer from the toner supply port 7 gradually decreases. That is, as the toner concentration of the developer rotating along with the developing sleeve 2 increases, the amount of toner taken into the developer from the toner supply port 7 decreases. When the amount of toner taken in decreases as described above, the toner concentration of the developer or the circulating developer A that is being rotated together with the developing sleeve 2 decreases, and the bulk thereof also decreases. As a result, the amount of the developer remaining in the vicinity of the toner replenishing port 7 is reduced. As a result, the toner replenishing port 7 closed by the developer is gradually opened, and the toner replenishing port 7 is opened. The amount of toner taken into the developer gradually increases.

As described above, in the present printer, the contact state between the developer and the toner T is changed according to the toner concentration of the developer on the developing sleeve 2, and the change in the amount of toner taken into the developer is caused by this change. Is increased or decreased. As a result, the toner concentration of the developer can be kept substantially constant even without a toner concentration sensor for detecting the toner concentration of the developer. Further, since the internal pressure of the developer can be increased in the agent container 9 to promote the frictional charging of the toner in the developer, a stirring paddle or a screw for promoting the frictional charging of the toner is not required. In addition, while the total amount of magnetic carrier used in a normal image forming apparatus is approximately 350 to 980 [g], the total amount used in the present printer is extremely small, 30 to 50 [g]. Therefore, the driving torque of the developing sleeve 2 can be greatly reduced, and the driving means of the developing sleeve 2 can be simplified.

Next, the control section of the printer will be described in detail. FIG. 3 is a block diagram showing a part of the electric circuit of the printer. As shown in the figure, the control unit 11 of the printer includes an image processing unit 12, a drum drive motor 13, a charging device 14, a light writing unit 15, a static elimination device 16, a transfer device 17, a drum cleaning unit 18, and a paper feeding device 1.
9, paper transport device 20, developing bias power source 21, transfer bias power source 22, developing main motor 23, developing clutch 2
4, an agitator clutch 25, a fixing device 26, a paper jam detection sensor 27, an operation display unit 28, a paper detection sensor 29 in the paper feeding device, and the like are connected.

The image processing unit 12 performs predetermined processing on an image signal sent from a personal computer (not shown) or the like, and then transmits the image signal to the control unit 11.

The developing clutch 24 turns on / off the transmission of the rotational driving force of the developing main motor to the developing sleeve 2 (pipe 2b).
To rotate or stop the developing sleeve.

Similarly, the agitator clutch 25 turns on / off the transmission of the rotational driving force of the developing main motor to the agitator 6. In the present printer, by separately providing the developing clutch 24 and the agitator clutch 25, the rotational driving of the developing sleeve 2 and the rotational driving of the agitator 6 can be individually turned ON / OFF.

The paper jam detection sensor 27 is connected to the paper conveying device 2.
0, and detects a paper jam of the transfer paper occurring therein.

The operation display section 28 is composed of a touch panel type liquid crystal display or the like, and displays various information on the display based on a signal from the control section 11 or displays various information on the control section 11 based on an operator's key operation. Or send a signal.

The paper detecting sensor 29 in the paper feeding device detects the transfer paper stocked in the paper feeding device 19.

As shown in FIG. 3, the control unit 11 has a CPU as a central processing unit, a ROM for storing invariable data such as control programs, and temporarily stores variable data such as operation data. And a RAM for performing the operation. When an image signal is received from the image processing unit 12, ON / OFF of driving of each device indicated by reference numerals 13 to 26 is performed.
By controlling OFF, a series of print processes (print operations) as described above are realized. Therefore, the control unit 11
Has a function as drive control means.

If the controller 11 detects a transfer paper jam based on the output from the paper jam sensor 27 during the printing operation, the paper jam is resolved. Emergency stop of print operation until
Further, when a continuous printing operation is performed on a plurality of transfer papers, for example, when “paper out” in the paper feeding device 19 is detected based on an output from the paper detection sensor 29 in the paper feeding device, Develops only the latent image under development and then temporarily stops the continuous printing operation. And
When the transfer paper is replenished to the paper feeding device 19 by the operator and “paper present” in the paper feeding device 19 is detected by the paper detection sensor 29 in the paper feeding device, the continuous printing operation which has been temporarily stopped is restarted. . The difference between the emergency stop and the temporary stop is that the former immediately stops the printing operation or the continuous printing operation, while the latter stops the continuous printing after the development of the electrostatic latent image being developed is completed. To stop the operation.

Various mechanical conditions in this printer are as follows. Gap GP between photosensitive drum 1 and developing sleeve 2 =
0.3 to 0.5 [mm] Gap G between developing sleeve 2 and doctor blade 3
D = 0.3 to 0.5 [mm] ・ Gap p between the developing sleeve 2 and the pre-doctor part 4a
GD = 0.6 to 1.4 [mm]-Diameter of developing sleeve 2 = 16 [mm]-Linear speed (rotation speed) of photoconductor drum 1 = 70 to 150
[Mm / sec] A ratio of the linear velocity of the pipe 2b to this linear velocity = 1.5 to 3.
0-Material of magnetic carrier = magnetite or iron-Average particle size of magnetic carrier = 30 to 100 (preferably 40 to 50) [μm]-Toner coverage of magnetic carrier = 50 to 120 [%]-Total amount of magnetic carrier = 30-50 [g] Amount of magnetic substance contained in toner T = 15-40 [wt%] Amount of silica contained in toner T = 0.5-1.0 [wt]
%] Amount of charge of toner T contributing to development = 10 to 30 [μc
/ G]

Next, the characteristic configuration of the printer will be described. FIG. 4 is a flowchart showing a part of the control performed by the control unit 11. In FIG. 4, the control unit 11 waits for reception of an image signal sent from the image processing unit 12 (s1 (step 1)). And
When this image signal is received (Y in s1), reference numerals 13 to 26 in FIG.
The control of the driving of each device indicated by is started (s2). When this printing operation has progressed to some extent, no abnormality has occurred (N in s3 and s4),
If the image signal for the next transfer sheet has not been received (N in s5), a print operation end routine is performed (s6). This print operation end routine is to discharge the transfer paper on which the toner image has been transferred and fixed,
This is a control routine for rotating the photosensitive drum 1 until the cleaning of the photosensitive drum 1 is completed. When the printing operation end routine is completed, the rotation of the photosensitive drum 1, the developing sleeve 2 (pipe 2b), and the agitator 6 is stopped.

After ending the print operation end routine, the control section 11 performs reverse rotation processing and then executes (s)
7) The control is returned to the start point of the main flow, and the reception of the image signal is again waited (s).
1). The reverse rotation process is a control for rotating the developing sleeve 2 in the reverse direction for a predetermined time by rotating the developing main motor 23 in the direction opposite to the normal direction and turning on the developing clutch 24.

As described above, if no abnormality occurs during the printing operation and the image signal relating to the next transfer sheet has not been received, the printing operation end routine and the reverse rotation control are executed. The print operation ends. And
By this printing operation, the toner image developed based on the image information is fixed on the transfer paper, and the transfer paper is discharged out of the machine. When the image signals for a plurality of transfer papers are continuously received, it is determined that the next print operation is necessary under the control of s5 (Y in s5), and the print operation for the next transfer paper is started. (S8). By starting the printing operation in this way, when the image signal is continuously received, the continuous printing operation is performed.

When the developing sleeve 2 rotates in the reverse direction by performing the reverse rotation process, the layer thickness of the developer that moves together with the developing sleeve 2 is regulated in the reverse order of the doctor blade 3 and the pre-doctor portion 4a. Then, the toner is conveyed to the vicinity of the toner supply port 7. Since the pre-doctor portion 4a regulates the thickness of the developer to be thicker than the doctor blade 3, when the layer thickness of the developer is regulated in this order, the circulating developer A in the Supply port 7
Will move backward to the vicinity of. In this way, the developer that has moved backward to the vicinity of the toner supply port 7 stays in the vicinity of the toner supply port 7 and closes the toner supply port 7 when it reaches a predetermined retention amount. When the toner supply port 7 is closed in this way, the toner T, which is forcibly moved from the toner supply port 7 toward the developer by applying a recoil, is confined to the toner hopper 5 side of the toner supply port 7. become. Even if a sudden situation such as contact between a pedestrian and the apparatus body occurs and a reaction is given due to a sudden situation such as the contact between the pedestrian and the apparatus body, the toner T sealed in the toner T is moved by the developer closing the toner supply port 7. Will be blocked. And, by being blocked in this way, forced replenishment to the developer is reduced.

The control unit 11 stops the printing operation after the toner T is thus sealed by performing the reverse rotation process. Therefore, the present printer waits for the next printing operation in a state where the toner T is sealed in the toner hopper 5 side from the toner supply port 7. Thus, when a print operation is on standby, even if a sudden situation such as giving a recoil to the toner T, such as contact between the apparatus main body and a pedestrian, occurs, This can reduce the forced supply of the toner T caused by this.

As described above, when a paper jam of the transfer paper is detected during this printing operation, the printing operation is stopped immediately. When a paper jam occurs, the transfer paper jammed in the paper transport device 20 is removed by the operator. However, when the transfer paper is removed, the printer body or the paper transport device 2 is operated by the operator.
The impact is applied to 0 or the like, and there is a high possibility that the toner T is forcibly supplied. Therefore, it is preferable to close the toner supply port 7 with the developer even when the printing operation is stopped immediately. Therefore, in the present printer, the control unit 11 is configured to execute the control from s9 to s14 so as to close the toner supply port 7 even when the printing operation is stopped urgently.

When the printing operation is urgently stopped (Y in s3), the control unit 11 first performs the same reverse rotation processing as in s7 to rotate the developing sleeve 2 in the reverse direction (s9), thereby replenishing the toner. The mouth 7 is closed with the developer. Then, after displaying necessary items such as "Please remove the paper jam, please remove it" on the display unit of the operation display unit 28 (s10), it is determined whether the printing operation can be resumed. A judgment is made (s11). Specifically, removal of the paper jam is confirmed based on the output from the paper jam detection sensor 27. Then, when it is determined that “restart is impossible” (N in s11), the control is looped to s11. This loop waits until the paper jam is removed. By the control from s9 to s11, even when the printing operation is stopped in an emergency, it is possible to wait for the restart of the printing operation with the toner supply port 7 closed with the developer.

If the control section 11 determines that "resume is possible" under the control of s11 (Y in s11), it cancels the display on the display section (s12), and then executes the sheet discharging process. (Step S13). By this paper discharging process, the transfer paper on which the transfer process in the paper transfer device, the transfer process of the toner image at the transfer position, the fixing process in the fixing device 26, and the like have been performed halfway is discharged outside the machine. Let it. Further, the printing operation that has been performed until immediately before the emergency stop is restarted from the beginning (s14). If the developing sleeve 2 that is rotating in the normal direction is urgently stopped and rotated in the reverse direction during the development, the developer is excessively conveyed to the developing position, resulting in the photosensitive drum 1
There is a high possibility that the background will be stained or the density of the toner image will be excessive. Therefore, when the printing operation is restarted after the emergency stop, a normal image is formed by discharging the transfer paper being conveyed and then performing the printing operation from the beginning.

As described above, when detecting "no paper" in the paper feeding device 19 during the continuous printing operation, the control section 11 develops only the latent image under development, and Pause the continuous printing operation. Even when the printer is temporarily stopped in this manner, an impact is applied to the printer main body, the sheet feeding device 19, and the like due to an operator's paper replenishing operation or the like, and there is a high possibility that the toner T is forcibly supplied. Therefore, even when the continuous printing operation is temporarily stopped, it is better to close the toner supply port 7 with the developer. Therefore, in the present printer, the control unit 11 is configured to execute the control from s15 to s19 so as to close the toner supply port 7 even when the continuous printing operation is temporarily stopped.

When the controller 11 determines that the continuous printing operation needs to be temporarily stopped due to the detection of "paper out" in s4 (Y in s4), the printing operation similar to s6 ends. A routine is performed (s15). According to this print operation end routine, the transfer paper on which the toner image on the photosensitive drum 1 is fixed is discharged out of the apparatus, and the continuous print operation is stopped as if it ended normally. However, the RAM of the control unit 11 still has the image information on the image to be output on another transfer sheet,
The continuous printing operation does not end normally.

After finishing the print operation end routine in s15, the control section 11 performs the same reverse rotation processing as in s7 and s9 to rotate the developing sleeve 2 in the reverse direction (s1).
6) This closes the toner supply port 7 with the developer. Next, after displaying necessary items on the display unit of the operation display unit 28, such as "Please replenish the transfer paper in the paper feeder," (s17), it is possible to resume the continuous printing operation. Judge whether or not (s
18). More specifically, replenishment of the transfer paper is confirmed based on the output from the paper detection sensor 29 in the paper feeder. And
When it is determined that "restart is impossible" (N in s18), the control is looped to s18. By this loop, it waits until the transfer paper is replenished. These s1
By the control from 5 to s18, even when the continuous printing operation is temporarily stopped, it is possible to wait for the continuous printing operation to be resumed with the toner supply port 7 closed with the developer.

When the control section 11 determines that "restart is possible" in the control in s18 (Y in s18), the control section 11 cancels the display on the display section (s19), and then executes the control in s5. Loop. With this loop, the continuous printing operation is restarted, and the printing operation on the next transfer sheet is started (s8).

In the printer according to the present invention, it is desirable that the developing sleeve 2 and the agitator 6 can be driven individually and that the agitator 6 is not rotated by the reverse rotation control. This is because, when the agitator 6 is rotated, the toner T in the toner hopper 5 is moved toward the toner supply port 7 by this rotation, which may cause unnecessary toner supply during the execution of the reverse rotation control. . However, if the rotational speed of the agitator 6 is extremely small and the moving force of the developer moving so as to close the toner supply port 7 by the reverse rotation of the developing sleeve 2 is larger than the conveying force of the toner T by the agitator 6. It is unlikely that unnecessary toner replenishment will occur during the execution of the reverse rotation control.

FIG. 5 is a graph showing the relationship between the toner concentration TC of the developer at the developing position and the elapsed time T. Specifically, the elapsed time T is defined as a period from the time when the printing operation of the present printer is stopped and a shock is applied to the stopped present printer to the time when the printing operation is started based on the reception of the image signal. Is the lapse of time. In FIG. 5, the graph indicates a change in the toner density TC in the present printer. The graph shows the change of the toner density TC in the conventional printer.

In the graphs (1) and (2), the toner density during the printing operation slightly increases or decreases during the printing operation. However, the range of this change is from the TC lower limit to
It is within the upper limit.

In the case of the conventional printer, when the first printing operation is stopped and the next printing operation is awaited, an impact is applied to the main body by a replacement operation of the developing device or a moving operation of the printer main body. Then (point B), the toner T is forcibly supplied from the toner supply port 7 to the developer on the developing sleeve 2. The developer that has forcibly taken in the toner T in this manner is transported to the developing position along with the developing sleeve 2 when the next printing operation is started. For this reason, in the conventional printer, when the next printing operation is started after an impact is applied to the printer body while the printing operation is stopped, as shown in the graph, the toner density TC at the developing position sharply increases. It rises and exceeds the TC upper limit. When the toner concentration TC exceeds the TC upper limit value in this way, background contamination or an image with an excessive ID is caused.

On the other hand, in the case of the printer according to this embodiment,
The next printing operation is awaited with the toner supply port 7 closed, and even if an impact is applied to the printer body while the printing operation is stopped, the toner is not forcibly supplied to the developer. . Therefore, even if the next printing operation is started after an impact is applied to the printer body during the stop of the printing operation, as shown in the graph, the toner concentration TC at the developing position may exceed the TC upper limit. Never.

FIG. 6 shows the relationship between the shutter performance of the toner supply port 7 by the developer and the reverse rotation speed of the developing sleeve 2 by performing the reverse rotation control, and the reverse rotation speed and the driving of the developing sleeve 2. It is a graph which shows the relationship with torque. As shown in the figure, when the reverse rotation speed of the developing sleeve 2 is smaller than 1/4 [rotation] due to the execution of the reverse rotation control, the shutter performance of the toner supply port 7 by the reversely moved developer rapidly deteriorates. . The reason why the shutter performance deteriorates is that the reverse rotation speed of the developing sleeve 2 is 1/4.
If the number of rotations is smaller than [rotation], a sufficient amount of the developer cannot be reversely moved from the developer container 9 toward the toner supply port 7. On the other hand, if the number of reverse rotations exceeds ［[rotation], the driving torque of the developing sleeve 2 exceeds the allowable limit. The reason why the driving torque exceeds the allowable limit is that the amount of the developer that is regulated by the doctor blade 3 and stays at the developing position is significantly increased. Further, when the amount of the developer that stays at the developing position increases as described above, the developer hardly receives the magnetic force of the magnet roller 2a, and the developer that detaches from the developing sleeve 2 appears. obtain. Therefore, it is desirable that the reverse rotation speed of the developing sleeve 2 by performing the above-described reverse rotation control be set in a range of １ ／ to ［[rotation]. Note that the graph shown in FIG. 7 is created based on the results measured under the mechanical conditions as described above.

As described above, according to the printer of the present embodiment, the toner T
Even if a sudden situation such as giving a recoil occurs, the forced replenishment of the toner T caused by the sudden situation can be reduced, and the ground caused by the situation occurring while waiting for the next printing operation can be reduced. Stain and excessive density of the toner image can be reliably reduced.

In this embodiment, the printer having the developing sleeve 2 as the developer carrier has been described. However, the present invention can be applied to an image forming apparatus having a developing carrier of another configuration such as an endless belt. is there.

Further, the printer for urgently stopping the printing operation based on the output of the paper jam detection sensor 27 has been described. For example, a door detection sensor for detecting the open state of the maintenance opening / closing door may be used. The present invention can also be applied to an image forming apparatus for urgently stopping a printing operation based on the output value of (i).

The printer for temporarily stopping the continuous printing operation based on the detection result of "paper out" in the paper feeding device 19 has been described. For example, the toner hopper 5 detachably mounted on the developing device 10 is described. The present invention is also applicable to an image forming apparatus that suspends a continuous printing operation based on “no toner” in the above.

[0069]

According to the first, second, third, fourth, fifth, or sixth aspect of the present invention, the supply port is closed at a predetermined timing so that the image forming substance is sealed upstream of the supply port in the supply direction. Therefore, an excellent effect that the replenishment of the image forming substance from the replenishing port toward the developer can be reduced at the timing, and the background contamination caused by the replenishment and the excessive density of the formed image can be reduced. is there.

In particular, according to the second aspect of the present invention, since the forced replenishment of the image forming substance caused during the standby of the next image forming operation can be reduced, the density of the formed image caused by the replenishment can be reduced. There is an excellent effect that excess can be surely reduced.

In particular, according to the third aspect of the present invention, when a continuous image forming operation is performed, the reverse movement control is performed after the development of the latent images on all the scheduled recording members is completed. Therefore, there is an excellent effect that it is possible to avoid a decrease in image forming speed caused by repeatedly performing the reverse movement control during the image forming operation.

According to the fourth aspect of the present invention, the continuous image forming operation can be waited in a state where the forced supply of the image forming material can be reduced, so that the image forming operation is temporarily stopped. There is an excellent effect that forced replenishment of the image forming substance which occurs when the replenishment is performed can be reduced, and background contamination and excessive density of the formed image caused by the replenishment can be reduced.

In particular, according to the fifth aspect of the present invention, in a state where forced replenishment of the image forming substance can be reduced, it is possible to wait for resumption of the endless movement of the developer carrier which has been stopped immediately. There is an excellent effect that forced replenishment of the image forming substance that occurs after the emergency stop of the endless movement can be reduced, and background contamination and excessive density of the formed image caused by the replenishment can be reduced.

In particular, according to the invention of claim 6, a remarkable increase in the drive torque of the developer carrying member and overflow of the developer caused by the execution of the reverse movement control are avoided, so that the increase in the drive torque and the overflow of the agent are prevented. There is an excellent effect that background stains and excessive density of the formed image can be reduced without occurrence.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a developing device and a photosensitive drum of a printer according to an embodiment.

FIG. 2 is an explanatory diagram illustrating a state in which a toner supply port of the developing device is closed.

FIG. 3 is a block diagram showing a part of an electric circuit of the printer.

FIG. 4 is a flowchart showing a part of control performed by a control unit of the printer.

FIG. 5 is a graph showing a relationship between a toner concentration of a developer and an elapsed time at a developing position in the developing device.

FIG. 6 shows a relationship between the shutter performance of the toner supply port of the developing device using the developer and the reverse rotation speed of the developing sleeve by performing the reverse rotation control, and the driving torque of the developing sleeve 2 and the reverse rotation speed. Graph showing the relationship.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 2 developing sleeve 2a magnet roller 2b pipe 3 doctor blade 4 agent housing casing 4a predoctor 5 toner hopper 6 agitator 7 toner supply port 8 developing casing 9 agent housing 10 developing device 11 controller 12 image processor Reference Signs List 13 Drum drive motor 14 Charging device 15 Light writing unit 16 Static eliminator 17 Transfer device 18 Drum cleaning unit 19 Paper feed device 20 Paper transport device 21 Developing bias power supply 22 Transfer bias power supply 23 Developing main motor 24 Developing clutch 25 Agitator clutch 26 Fixing device 27 Paper jam detection sensor 28 Operation display unit 29 Paper detection sensor in paper feeder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 21/14 G03G 15/08 507E 21/00 372 F term (Reference) 2C061 AP04 CF05 CF06 HJ03 HK06 HK11 2H027 DA04 DC14 DC18 DD07 DE07 ED10 ED17 EF09 EK07 2H077 AA14 AA18 AB04 AD06 AD13 AD16 AD18 AD35 BA07 DA10 DA43 DB01 EA03 EA16

Claims (6)

[Claims] A developer carrying member that carries the developer and moves endlessly in a predetermined direction; a driving device that moves the developer carrying member endlessly; a drive control unit that controls the driving device;
A supply port for replenishing the developer carried on the developer carrier with the image forming substance, and a layer thickness of the developer carried on the developer carrier downstream of the replenishment port in the predetermined direction. A first regulating member regulated by the first regulating member, a second regulating member additionally regulating the layer thickness further downstream in the predetermined direction than the first regulating member, and a second regulating member by the additional regulation. A developer accommodating portion for accommodating the developer stagnated on the upstream side in the predetermined direction between the first regulating member and the second regulating member; A latent image carrier that is arranged to face the developer carrier on the downstream side and carries a latent image, and the developer carrier is supported in accordance with an amount of the developer remaining near the replenishing port. The state of contact between the developer carried on the body and the image forming substance is changed, and this change causes the supply port to In the image forming apparatus that changes the amount of the image forming substance taken into the image material, the driving is performed so as to perform reverse movement control for endlessly moving the developer carrier in a direction opposite to the predetermined direction at a predetermined timing. An image forming apparatus comprising control means. 2. The image forming apparatus according to claim 1, wherein, as the predetermined timing, immediately after the development of the latent image is completed and the endless movement of the developer carrier in the predetermined direction is stopped. An image forming apparatus, wherein the drive control means is configured to perform reverse movement control. 3. A continuous image forming operation for a plurality of recording members, comprising a transfer means for transferring a visible image obtained by developing the latent image to a recording member directly or via an intermediate transfer member. 2. The image forming apparatus according to claim 1, wherein the endless movement of the developer carrier in the predetermined direction is stopped after the development of the recording members is completed. The drive control unit is configured to execute the reverse movement control immediately after the development of a plurality of recording members is completed and the endless movement is stopped as the predetermined timing. Image forming apparatus. 4. In a case where the continuous image forming operation needs to be temporarily stopped, the continuous image forming operation is temporarily stopped after only the developing latent image is developed. 4. The image forming apparatus according to claim 3, wherein, when the continuous image forming operation is temporarily stopped, the developing of the latent image during the development is terminated by the predetermined timing. An image forming apparatus, wherein the drive control means is configured to execute the reverse movement control immediately after stopping the endless movement in the direction. 5. An endless movement of said developer carrier in said predetermined direction is urgently stopped when an emergency stop of development of said latent image is required.
The image forming apparatus according to claim 1, wherein the drive control means is configured to execute the reverse movement control immediately after the emergency stop of the endless movement as the predetermined timing. 6. The image forming apparatus according to claim 1, wherein the amount of the endless movement of the K ぴ ぉ developer carrier in the opposite direction is the number of endless movements per rotation of the developer carrier. An image forming apparatus, wherein the drive control means is configured to perform the reverse movement control so as to fall within a range of １ ／ to の of the movement amount.