JP2806959B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus that develops with a two-component developer, such as a facsimile, a printer, and an electrophotographic copying machine.

(Prior art)

2. Description of the Related Art Conventionally, an image forming apparatus that forms a visible image by developing an electrostatic latent image with a two-component developer including a toner and a carrier, and transfers the visible image to transfer paper has been widely used.

In such a conventional image forming apparatus, a toner density based on a mixture ratio of a toner and a carrier of a two-component developer is set in advance and is used as data for image density control during image formation. Since the toner concentration of the two-component developer is not always constant, when the developer is replaced due to fatigue or the like, the toner concentration of the developer may be reset.

In setting and controlling the toner concentration, a toner concentration sensor provided in the developing device detects a toner concentration based on a mixture ratio of the toner and the carrier, and an operation is performed based on the detected data.

Generally, a magnetic sensor is used as the toner concentration sensor, and magnetically detects a mixing ratio between the toner and the magnetic carrier.

When setting the toner density, it is desirable that the developer be in a stable state. However, a two-component developer left for a long time has a low charge amount. To stabilize the charge amount, it is necessary to stir the developer in the developing device. For this reason, the toner density is set while the developing device is operating.

At the time of setting the toner density, as shown in FIG. 11, the photosensitive drum 51 is kept stopped, and the developing sleeve 52 is rotated. The toner is layered on the magnetic brush 53 formed on the developing sleeve 23, that is, the areas (areas indicated by oblique lines) 54, 55 before and after the photoconductor surface of the photosensitive drum 51 that comes into contact with the raised developer. However, even if the toner layer is cleaned in the cleaning step, the toner layer is not easily removed.
This toner layer causes a band-like background stain on the transfer paper during the actual copying operation. Since this toner layer can be removed by repeating the cleaning process, if the copy operation is not performed until the toner layer is removed, the background of the transfer paper can be prevented, but the copy is prohibited until the toner layer is removed.
That is the time loss.

In addition, since the magnetic brush continuously concentrates on a part of the stopped photosensitive drum, there is a difference in the surface properties due to filming of the drum between the photosensitive drum and other photosensitive members. It causes problems in terms of body life.

When the photosensitive drum 51 is stopped and the developing sleeve 52 is rotated, a pool of the developer is generated in the area A above the magnetic brush 53, and the inlet seal 56 of the developing device is damaged. The problem of scattering outside occurs. This usually occurs because the entrance seal 56 is set assuming that the photosensitive drum 51 rotates and there is no accumulation of agent.

Further, in the lower portion of the magnetic brush 53, the toner gradually drops in the B direction from the toner layer 55 attached to the photosensitive drum 53.
In particular, the toner and the photoreceptor are attracted by an intermolecular force, but easily fall because there is no electric attraction.

In the method of transferring to a transfer paper fixed to a transfer drum (not shown) in contact with the photosensitive drum 51, the toner attached to the photosensitive drum 51 adheres to the transfer drum film even when the transfer charger is OFF, and the transfer is performed. When the transfer paper is attached to the drum, the back surface of the transfer paper is stained. It is conceivable to provide a cleaner dedicated to the transfer drum in order to remove the back stain on the transfer paper. However, an extra space is required and there is a problem in cost.

[Problems to be solved by the invention]

An object of the present invention is to provide an image forming apparatus which solves the above-mentioned conventional problems, accurately detects the mixing ratio of toner and carrier, enables appropriate toner concentration setting, and does not stain the photoconductor at that time. Is an issue.

[Means for solving the problem]

According to the present invention, there is provided an image forming apparatus which forms a visible image by developing an electrostatic latent image with a two-component developer including a toner and a carrier according to the present invention. When the mixture ratio of toner and carrier is detected, the photoconductor for forming an electrostatic latent image, the cleaning device for the photoconductor, and the pre-cleaning device are operated to stabilize the operation of the photoconductor and the cleaning device. The problem is solved by operating the developing device later.

[Action]

According to the present invention, when the toner concentration is set, the photosensitive drum is rotated in addition to the developing device, and the cleaning device and the static eliminator for the photosensitive drum are operated.

According to the present invention, the magnetic brush by the developing sleeve of the developing device does not act locally on the photosensitive drum, but acts on the entire surface of the photosensitive drum of the photosensitive drum. Since the static eliminator is activated, the toner is not locally laminated,
Toner dropping is avoided without generating a toner reservoir.

〔Example〕

The details of the present invention will be described based on an embodiment shown in the drawings.

In FIG. 1, a copying machine as an example of an image forming apparatus utilizing the present invention exposes an image of a document on a contact glass 1 to a photosensitive drum 3 by an exposure optical device 2 and is charged by a charger 4. An electrostatic latent image is formed on the photosensitive drum 3. The electrostatic latent image is developed by a developing device 5, for example, a first developing device 5a having black toner and a second developing device 5b having, for example, three color toners, and is visualized. The visible image is transferred to a transfer paper fixed to a transfer drum 6 by a transfer charger 7.
Is transcribed under the action of

After the transfer, the photosensitive drum 3 is discharged by the pre-cleaning charge removing charger 13, is cleaned by the cleaning unit 8, and repeats the image forming process from charging.

In the case of color copying, for example, a color separation image of three colors is formed on the photosensitive drum 3 and is overlaid and transferred onto a transfer sheet fixed to the transfer drum 6. Therefore, one color copy is obtained by rotating the photosensitive drum 3 and the transfer drum 6 three times.

The leading end of the transfer paper supplied from a paper supply device 9 such as a paper supply cassette is clamped on the transfer drum 6 by a clamp device, and the entire transfer paper is electrostatically brought into close contact with the transfer drum 6 by the action of a transfer charger or the like. You. The transfer drum 6 carries out the transfer and the charge removal by the transfer charger 7 every one rotation.
Is repeated. After the transfer, the transfer paper is separated from the transfer drum 6, fixed by the fixing device 10, and discharged to the discharge tray 11.

The developing device 5 is configured as shown in FIG. 2, for example, in the case of the first developing device 5a. Although the detailed description of the second developing device 5b is omitted, it is basically the same as the first developing device 5a, except that it has a structure having three developing devices for three color toners. Only the difference.

In FIG. 2, a developer is accommodated in a developing device casing 21. A paddle 22 and a developing sleeve 23 are arranged in the developing device casing 21, and the developer pumped up by the paddle 22 is transported by the developing sleeve 23. In the developing sleeve 23, the developer is regulated to a certain layer thickness by the doctor 24 during the conveyance, and is supplied to the photosensitive drum 3, which is arranged to face the developing sleeve 23 with a predetermined gap,
The latent image on the photosensitive drum 3 is visualized.

The residual image agent after the development of the developing sleeve 23 is returned into the developing device casing 21. At this time, the developer separated from the developing sleeve 23 under the action of the magnetic shield plate 29 passes through the toner density sensor 25 and returns to the pumping position by the paddle 22.

A toner hopper 26 is exchangeably mounted on the developing device casing 21. Toner supply roller 27 from toner hopper 26
As a result, the toner is supplied into the developing device casing 21, and the toner is stirred and mixed by the agitator 28 in the developing device casing 21 and sent to the paddle 22 pumping position.

The developer casing 21 has an inlet seal 30 and a separator.
31, a pressure release filter 32 and the like are provided as needed.

When a replenishment signal is sent from the toner concentration sensor 25, a toner replenishment clutch (not shown) is turned on, the toner replenishment roller 27 is rotated, and the toner replenishment roller 27 is engaged by a seal 33 made of foamed polyurethane or the like. The toner is scraped off and falls into the developing device casing 21.

 A developing bias is applied to the developing sleeve 23.

The toner concentration sensor 25 is disposed at a position between the developing sleeve 23 and the paddle 22 of the developing device casing 21 and is formed as a magnetic sensor that detects the magnetic permeability within the detection range, thereby detecting the toner concentration at that time. You.

When the toner concentration sensor 25 provided in the developing device is a magnetic sensor, a change in the magnetic flux density due to a change in the mixing ratio of the toner and the magnetic carrier is detected as a change in the toner concentration by a detection unit in which the differential transformer is stored. . As shown in FIG. 3, the analog output signal of the magnetic sensor is
The data is input to a central control device (CPU) 37 via a digital conversion circuit (A / D converter) 36, and the control device performs toner density setting control.

As shown in FIG. 4, the control unit includes an operation unit having a numeric keypad, a number display unit, and the like; a switching unit for switching between a normal copy operation control mode and a toner density setting control mode; a toner supply detection unit; A central control unit CPU to which means, a timer for setting the stirring time of the developer stirring means, a non-volatile storage means (RAM), and a driver are electrically connected. The driver applies a bias to a main motor, a developing motor, a toner replenishing clutch for replenishing toner, a cleaning motor for driving a magnetic brush cleaning device as a cleaning means, and a magnetic brush roller for removing toner from a photoconductor. Control the output of the cleaning bias for cleaning, the adsorbing force of the toner adhering to the photoconductor, and the pre-cleaning charger for cleaning the photoconductor, and the developing bias for applying a bias to the developing roller. I do.

Toner density setting is performed by detecting toner density by a toner density sensor during the stirring state of the developer, sampling the density data by a CPU serving as a sample storage means, and as threshold data for density control to a non-volatile storage means. Store.

Hereinafter, the toner density setting control will be described with reference to the time charts of FIGS. 5 and 6 and the flowcharts of FIGS. 7 to 10.

5 and 7 in the toner density setting control mode.
Control based on the figure.

First, the switching means shown in FIG. 4 sets the toner density setting control mode. In this mode, a normal copy operation is not performed.

From this state, the toner density setting control mode is started by a key operation, for example, an operation of pressing down a copy start button of the operation unit (step 1).

When the toner density setting control mode is started, first, the main drum 47 for driving the photosensitive drum 3 is operated to rotate the photosensitive drum (step 2).

As the photosensitive drum rotates, the pre-cleaning charger is operated, and the cleaning means is operated by operating the cleaning bias and the cleaning motor for driving the cleaning roller (step 3).

After the operation of the photosensitive drum and the cleaning unit is stabilized, the developing bias and the developing motor of the developing device are operated to stir the developer (step 4).

At the same time, a timer for measuring the stirring time of the developer is started (step 5).

The timer is set so that the concentration setting timer operates during the stabilization time of the developer by the start of the timer.
The stirring stabilization time may be about 1 to 3 minutes for both monochrome images and color images.

While the developer is being stirred, the CPU appropriately samples the toner concentration detection data. When the timer completes the predetermined time (step 6), the final density sample data is stored in the non-volatile storage means as density control threshold data (D ₀ ) in the CPU (step 7). To stop the stirring of the developer. (Step 8).

After the stirring of the developer is completed, the cleaning bias and the cleaning motor are stopped (step 9), and the pre-cleaning charge elimination charger and the main motor are stopped, thereby terminating the toner density setting control mode (step 10).

After the end of the toner density setting control mode, the switching unit is returned to the original state, and the state of the image forming apparatus, for example, the copying machine is returned to the copy operation control mode.

When the copy operation control mode is switched by the switching means shown in FIG. 4, control is performed based on FIG. Start the copy operation control mode by pressing the copy start button on the operation unit (Step 1
1). Thus, various parts necessary for the copy operation are activated (step 12).

Sampling the toner density data (D _X) during the copy operation (step 13).

By comparing the sampled data D _X and pre-set by the non-volatile memory means the stored toner density control threshold data (D ₀₎ in CPU (step 14), there at D _0> D _X For example, the toner supply clutch is operated, and toner is supplied from the toner hopper by the toner supply roller (step 15).

Also, if the D ₀ <D _X, to stop the toner supply clutch (step 16).

As a result, the toner concentration of the developing device is controlled.

After the copying operation is stopped (step 17), the operations of the parts necessary for the copying operation are stopped (step 18).

Although a switch independent of the operation unit is provided as the switching means, for example, double pressing of a special key (operation key not used in a normal copy operation) in the operation unit, inputting of a code number by a numeric keypad, or a combination thereof Thus, a mode switching function can be provided by also using the switching means for another purpose.

The toner end control is performed according to the flow shown in FIG.

Press the copy start button on the operation unit to start copying in the copy operation control mode (step 2).
1), various parts necessary for the copy operation are activated (Step 2)
2).

If the toner supply clutch is continuously operated during the copy operation control (step 23), the toner supply time Tx is measured (step 24).

When the toner in the toner hopper runs out, the toner replenishment clutch operates continuously (step 25). For example, the time (T ₀ ) of the toner replenishment clutch that operates continuously for each copy is set to T ₀ or more. when the toner supply clutch is continuously actuated (step 26), to 0 to T _X terminates the measurement of the toner supply time (step 27). Then, 1 is counted up in the toner end counter _CX (step 28).

Compare the toner end setting counter C ₀ set in advance and the toner end counter C _X (step 29), when the C _X becomes C ₀ or more, and toner end.

When the toner end is reached, the copy operation control is stopped (step 30) so that the toner density of the developer does not decrease and the copy image quality is deteriorated even during the copy operation control (step 30). Turn on the display,
The subsequent copy operation is prohibited (step 31). Then, the toner end is stored in the non-volatile storage means (step
32).

When the toner supply clutch is changed from the operating state to the stopped state during the copy operation control (steps 23 and 25).
The measurement of the toner supply time is stopped, and the toner supply time T _{X is set} to 0.
And the toner end counter C _X is also set to 0 (step 3
3).

Toner end counter C _X is the toner end setting counter
If the _value is less than C0 (step 29), the copy operation control is continued unless the copy is stopped (step 34). If the copy is stopped (step 34), the copy operation control is stopped (step 35). The value of the toner end counter _CX at that time is stored in the non-volatile storage means (step 3
6) At the time of the next copy, the toner end count is continuously performed.

In the case of the toner end recovery mode, control is performed based on the flowchart of FIG. 10 and the time chart of FIG.

When the toner runs out, the toner in the toner hopper runs out, so that new toner must be supplied.

For example, there is a method of resetting the toner in the cartridge into the toner hopper, or a method of directly charging the toner into the hopper. At this time, the insertion / removal of the cartridge is detected by the toner supply detecting means (FIG. 4). Or opening and closing the cover, it is detected that new toner has been supplied.

In the embodiment of FIG. 4, a switch is used as the toner supply detecting means.

First, if it is in the toner end state (step 41), it is detected that new toner has been supplied by the toner supply means, and if it is detected that new toner has been supplied (step 4).
2), a toner end recovery mode is started (step 43).

When the toner end recovery mode starts, first, the main motor for driving the photosensitive drum is operated to rotate the photosensitive drum, and as the photosensitive drum rotates, the pre-cleaning static elimination charger is operated (step 44). Further, the cleaning means is operated by operating the cleaning motor for driving the cleaning roller and the cleaning bias (step 45).

After the operation of the photosensitive drum and the cleaning unit is stabilized, the developing bias and the developing motor of the developing device for stirring the developer and transporting the developer to the photosensitive drum are operated (Step 46).

After the developer in the developing device is in a stable stirring state, the CPU samples toner density data (D _X ) (step 47).

Sampled data Dx and threshold data for toner concentration control which have been set and stored in the nonvolatile storage means
And D ₀ is compared in CPU (step 48), for supplying toner by the toner supply roller from the toner hopper to operate the toner supply clutch if D _0> D _X (step 49).

At the same time, measurement of the toner supply recovery time T _RX is started (step 50). And comparing the toner supply recovery time T _RX and the toner replenishment recovery set time T _RO (step 51), even beyond the toner supply recovery set time T _RO if the toner supply clutch operating conditions, the toner supply recovery time The measurement is completed, and the value T _RX of the toner supply recovery time measuring device is set to 0 (step 52).

Thereafter, the stirring of the developer is stopped by stopping the developing motor and the developing bias (step 53).

After the stirring of the developer is completed, the cleaning motor and the cleaning bias are stopped (step 54), and the pre-cleaning charge removing charger and the main motor are stopped (step 55). In this case, even beyond the toner supply recovery set time, since the data D _X of the toner density does not reach the toner density control threshold data D _0, considered as the toner density is thin, not to release the toner end, again The toner end display is turned on to disable the copy operation (step 56).

This is used when a cartridge containing no toner is set or the user forgets to supply the toner.

Data D _X in the toner density of the toner concentration control threshold data D ₀ in step 48, if the D ₀ <D _X, stopping the toner replenishing clutch, ends the toner supply recovery time, the toner replenishing Set the recovery time measuring instrument value T _RX to 0
(Step 57).

After the toner replenishment clutch is stopped, the replenished toner is not sufficiently mixed with the developer. Therefore, the developer may be agitated for a time necessary to stabilize the charge amount. The developing motor and the developing bias are activated for that time.
Thereafter, the stirring of the developer is stopped by stopping the developing motor and the developing bias. (Step 58).

After the stirring of the developer is completed, the cleaning motor and the cleaning bias are stopped (step 59), and the rotation of the cleaning means and the photosensitive drum is stopped by stopping the pre-cleaning charge removing charger and the main motor (step 60). Then, in order to cancel the toner end data stored in the nonvolatile storage means, the value of the toner end counter _CX is set to 0 (step 61).

On the other hand, the toner end display and the copy prohibition display displayed on the operation unit are turned off, and the copy prohibition is released (step
62), the copying operation is normally performed, and the toner end recovery mode is terminated (step 63).

The setting of the toner density is automatically performed if the toner density setting mode is selected under the control of the control device.

When the automatic setting of the toner density and the toner end recovery control are performed while the transfer drum is kept in non-contact with the photosensitive drum, toner adhesion to the film of the transfer drum can be prevented, and furthermore, the transfer drum It is possible to prevent toner adhesion.

〔effect〕

According to the present invention, it is possible to prevent the transfer paper from being stained, to abolish or shorten the post-processing after the toner density setting and the toner end recovery, and to prevent the occurrence of uneven development.

Further, according to the present invention, the entrance seal of the developing device can be protected, the life of the photosensitive drum can be prolonged, and toner scattering can be prevented.

[Brief description of the drawings]

FIG. 1 is an overall schematic view of a copying machine using the present invention, FIG. 2 is a sectional view of a developing device, FIG. 3 is an output circuit diagram of a toner density detecting means, FIG. FIG. 5 is a time chart of the toner density setting control mode, FIG. 6 is a time chart of the toner end recovery mode, and FIGS.
FIG. 10 is a control flow diagram, and FIG. 11 is a diagram illustrating the relationship between a photosensitive drum and a developing sleeve when a conventional toner density is set. 3 photoreceptor 6 transfer drum 5 developing device 8 cleaning device 13 pre-cleaning static elimination charger 23 developing sleeve 25 toner concentration sensor

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shinichi 1-3-1 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-58-80677 (JP, A) JP-A Sho 62-75569 (JP, A) JP-A-63-210872 (JP, A) JP-A-62-109078 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/00 303 G03G 21/00 370-540 G03G 15/08-15/09 G03G 21/06-21/08

Claims (1)

(57) [Claims] 1. An electrostatic latent image comprising a toner and a carrier.
In an image forming apparatus that forms a visible image by developing with a component developer, the developer is exchanged / supplied in a non-image forming mode.
When detecting the mixture ratio of the toner and the carrier, the photosensitive member that forms the electrostatic latent image, the cleaning device for the photosensitive member, and the pre-cleaning static elimination device are operated.
An image forming apparatus, wherein the developing device is operated after the operation of the photosensitive member and the cleaning device is stabilized.