JPH0836292A - Developing device - Google Patents

Abstract

PURPOSE:To provide a developing device capable of increasing the leakage prevention effect of the developer at the time of the developer exchange operation and preventing the shifting to the printing operation in the state without fitting a toner 4 cartridge, in the developing device adopting the developer cartridge system. CONSTITUTION:At the time of replacing the developing cartridge 26, the developing cartridge 26 and the developer 26k are simultaneously replaced in a state of blocking the developer supply port 26c by the developer shutter 26d. When the toner cartridge 27 is not attached to the developing cartridge 26 and the developing shutter 26d is in a closed state, the toner concn. detecting container 26n inside becomes empty, hence on detecting about 0V, by the toner concn. detecting element 26f, the print operation is suspended while displaying 'toner cartridge unattached' on the operating panel in the printer main body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a developing device in an electrophotographic apparatus such as an optical printer or a copying machine using electrophotographic technology.

[0002]

2. Description of the Related Art A two-component developer in which toner and carrier are mixed at a predetermined ratio is used, and the electrostatic latent image surface is rubbed by a magnetic brush formed by adhering the developer to a magnetic developing roller. In a developing device for developing an electrostatic latent image, toner attached to the surface of a carrier is attracted to the electrostatic latent image and developed, and the toner consumed by this development is replenished from a toner cartridge.

In such a developing device, the carrier and toner rub against each other and the toner repeatedly adheres to the surface of the carrier, so that toner particles stick to the surface of the carrier (spent) or the carrier is peeled off to remove the carrier. The life of the developer is exhausted due to changes in surface characteristics or deterioration of toner charging characteristics due to carrier crushing and the like.

The life of the developer is affected by the physical properties of the toner and carrier, the amount of the developer, the structure of the apparatus, etc., but it generally corresponds to printing or copying of tens of thousands of pages.

When the life of the developer is exhausted, it is necessary to replace the developer contained in the developing device. However, the work of replacing the developer is considerably troublesome, and the developer replacement work is required. A technique for replacing the developing device itself has been proposed for the sake of simplicity.

However, when the developing device itself is replaced, new problems arise that replacement parts become expensive and it becomes difficult to accurately reproduce the facing gap between the developing roll and the electrostatic latent image. .

On the other hand, in this type of developing device, in order to realize clean toner replenishment work by the detachable toner cartridge, a shutter plate and a seal member are provided in the toner replenishing portion and the toner cartridge of the developing device. Also, a toner replenishing device has been proposed in which a seal member is interlocked with attachment / detachment of a toner cartridge (JP-A-4-12378).

By the way, in this toner replenishing device, since the shutter plate and the seal member are opened and closed in response to the detaching movement of the toner cartridge, it is possible to surely operate so as to prevent the toner leakage during the detaching movement process. It is necessary, and there is a problem that toner leakage occurs if there is a shift in operation timing, a shift in relative position of components, or the like.

However, it is extremely difficult to accurately move the member with which the toner comes into contact, and if the toner is caught and accumulated on the sliding portion, the accurate movement is hindered and the toner leaks.

[0010]

As described above, it is difficult for the toner replenishing device in the conventional developing device to reliably prevent the toner from leaking out. Therefore, even if the toner replenishing device is applied to the developer exchanging mechanism, the developing operation is not performed. Preventing drug leakage is difficult. When the developer leaks, the inside of the developing device becomes dirty, and when it adheres to the photoconductor, the carrier damages the photoconductive surface.

The object of the present invention is to enhance the effect of preventing developer leakage during developer replacement work in a developing device employing a developer cartridge system so that the developer whose life has expired can be replaced at low cost. It is therefore to provide a developing device having excellent device reliability, which does not shift to a printing operation without mounting a toner cartridge.

[0012]

[Means for Solving the Problems] The above-mentioned object is to hold the developer agitated in the developer accommodating space on the surface of the developing roll to act on the electrostatic latent image surface, and to finish the action on the electrostatic latent image surface. In a developing device having a structure in which the separated developer is separated from the surface of the developing roll and collected in the developer accommodating space, and the toner that has consumed toner is replenished with toner from a toner cartridge
A developing unit having a developing roll, a developer receiving port for receiving the developer to be held on the surface of the developing roll, a developer discharging port for discharging the developer separated from the developing roll, and the developing device receiving port. The developing unit is provided with a developer supply port formed at a position facing each other, a developer recovery port formed at a position facing the developer discharge port, and an agitation supply roll arranged in the developer accommodating space. A developer cartridge that is detachably engaged with the developer supply port to supply the developer to the developer receiving port and collect the developer discharged from the developer discharging port to the developer collecting port; A toner cartridge having a toner replenishing roll removably engaged with the developer cartridge to replenish the toner in the developer cartridge; and a toner cartridge for covering the developer supply port. The developer shutter and the developer shutter when the toner cartridge is attached to the developer cartridge are opened, the developer shutter is closed when the toner cartridge is removed from the developer cartridge, and the developer shutter is opened / closed in response to the attachment / detachment of the toner cartridge. In addition to the shutter driving means for detecting the opening and closing of the developer shutter, when the developer shutter is closed,
This is achieved by providing a means for displaying that the toner cartridge is not mounted on the operation panel of the printer body and stopping the printing operation.

[0013]

According to the present invention, when the life of the developer is exhausted, it is sufficient to replace the developer cartridge.

Further, the developer sent out by the agitating and supplying roll is piled up near the developer supply port of the used developing cartridge. When the developing cartridge is removed, the toner cartridge is previously removed to remove the developer. The developer supply port is closed by the developer shutter.

In addition, a toner cartridge is not installed,
When the developer shutter is closed, the printing operation is not performed.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 6 is a vertical cross-sectional side view of the color laser printer, in which the photosensitive belt 2 is stretched around rotating rolls 3, 4 and 5 and is rotatably held in the center of the printer body 1. There is.

The rotating roller 3 for driving the belt rotates so as to convey the photosensitive belt at a speed of about 70 mm / s.

The rotating rolls 3 and 4 are arranged so as to form a flat developing region on the photosensitive belt, and the rotating rolls 4 and 5 are arranged so as to form a toner image transfer region described later.

The rotating roll 3 guides the photosensitive belt 2 so as to form a stable exposure surface for scanning exposure, which will be described later.

Below the photosensitive belt 2, a corona discharge type charger 6, a laser beam scanning exposure unit 7 and a belt cleaner 16 are arranged.

The laser beam 7a generated from the scanning exposure unit 7 under the control of the video signal supplied from the higher-order image signal generator is directed in the direction crossing the surface of the photosensitive belt 2 which rotates along the surface of the rotating roll 3. 1.225ms
The surface of the photosensitive belt 2 is scanned and exposed by being repeatedly deflected in a cycle of, and an electrostatic latent image having a pixel density of about 300 dpi is formed in the rotating direction of the photosensitive belt 2.

On the upper side of the photosensitive belt 2, the developing devices 8 to 8 are arranged so as to face the developing area in which the photosensitive belt 2 rotates flat.
11 are detachably arranged, and the respective developing devices 8 to 11
The surface of the photosensitive belt 2 is rubbed with the developer magnetic brush formed in step 1 to develop the electrostatic latent image.

The developing device 8 uses a developer mixed with yellow (Y) color toner, the developing device 9 uses a developer mixed with magenta (M) color toner, and the developing device 10 uses. A developer mixed with cyan (C) color toner is used, and a developer mixed with black (K) color toner is used for the developing device 11.

Then, these developing devices 8 to 11 are selectively acted on the photosensitive belt 2 in accordance with the corresponding color of the electrostatic latent image to develop each electrostatic latent image into a toner image of the corresponding color. .

In order to develop each electrostatic latent image, one developing device 8 (9 to 11) is selected and acts on the photosensitive belt 2 for about 5 seconds.

The intermediate transfer drum 12 is arranged so as to rotate while being in contact with the photosensitive belt 2 positioned in the printer body 1 in the toner image transfer area, and the toner image formed on the surface of the photosensitive belt 2 is formed by this toner. Transferred in the image transfer area.

The intermediate transfer drum 12 also rotates at a speed of about 70 mm / s. This is a speed equal to the rotation speed of the photosensitive belt 2, and the movements of the photosensitive belt 2 and the intermediate transfer drum 12 are synchronized.

Around the periphery of the intermediate transfer drum 12, a pre-charging device 13, a transfer roll 14 and a drum cleaner 15 are arranged so as to face the outer peripheral surface of the intermediate transfer drum 12. The toner images are sequentially transferred so as to be polymerized to form a color toner image.

The precharger 13 is a corona discharger,
A corona discharge is generated by being urged to give a charge for supporting the transfer of the completed color toner image onto the recording paper 17 on the surface of the intermediate transfer drum 12.

The drum cleaner 15 is the intermediate transfer drum 12
Of the outer peripheral surface of the intermediate transfer drum 12 in the process of forming a color toner image by transferring a plurality of single-color toner images from the photosensitive belt 2 onto the intermediate transfer drum 12 in an overlapping manner. After the color toner image is transferred to the recording paper 17 and is moved to the outer peripheral surface of the intermediate transfer drum 12, it is in contact with the surface of the intermediate transfer drum 12 in order to remove the residual toner. To be operated.

The paper feed mechanism is installed in the space below the scanning exposure unit 7, and the recording paper 1 stored in the paper feed cassette 18 is provided.
7 is extracted by a paper feed roll 19 and sent out.

A registration roll 20 is provided between the paper feed roll 19 and the transfer roll 14 for aligning the conveyance timing of the color toner image formed on the surface of the intermediate transfer drum 12 with the recording paper 17 onto which the toner image is transferred. Paper feed roll 19
The conveyance timing of the recording paper 17 fed from the is adjusted and fed to the transfer roll 14.

The registration roll 20 holds the recording paper 17 at about 70.
It rotates so as to convey at mm / s (the same speed as the photosensitive belt 2).

A transport guide 21 is provided downstream of the transfer roll 14.
The printer main body 1 is provided with a fixing device 22 and a paper discharge roll 23, and a paper discharge tray 24 on which a printed matter (recording paper 17 having a toner image fixed) sent from the paper discharge roll 23 is placed.
Formed on the upper surface of the substrate.

The printer body 1 contains a control circuit device for controlling the operation of the color laser printer, but its illustration is omitted.

Next, the details of the developing devices 8 to 11 will be described. Since the four developing devices 8 to 11 have basically the same structure, the developing device 8 will be described as an example.

FIG. 1 shows a state in which the constituent parts of the developing device 8 are separated.

This developing device is provided with a developing unit 25 which is stationary for developing a developer by acting it on the photosensitive belt 2.
The developer mixed and charged by stirring is supplied to the developing unit 25, and the developer having completed the developing action is collected from the developing unit 25, and the developer is detachably engaged with the developing unit 25. A developer cartridge 26 and a toner cartridge 27 detachably engaged with the developer cartridge 26 so as to replenish the developer cartridge 26 with toner.

The developing frame 25e, which is the base of the developing unit 25, is a non-replaceable component fixed to the frame of the printer body 1, and is a developing roll 25a arranged to face the photosensitive belt 2 with a predetermined developing gap. And a carrier roll 25b, a developer receiving port 25f for receiving the developer 26k supplied from the developer cartridge 26 and giving it to the developing roll 25a, and a developer 26k magnetically held on the surface of the developing roll 25a. The spike-cutting blade 25c formed of a non-magnetic material that defines the height of the developing brush, and the developing roller 25a to the transport roller 25b.
It has a recovery guide 25d formed of a non-magnetic material for peeling off the developer 26k transferred to the transport roll 25b from the transport roll 25b, and a developer discharge port 25g for discharging the peeled developer 26k.

The developer cartridge 26 is the developing unit 2
The new developer 26k is stored in the developer accommodating container 26p in a new state, and the lower surface of the developer accommodating container 26p is closed by a seal that can be peeled off from the lateral direction. It is peeling. The developer container 26p is provided so that the developer does not spill when the developer cartridge 26 is transported.
By p, the packing means for the developer cartridge 26 can be simplified.

The developer cartridge 26 has a developer 26k.
A stirring screw 26b that stirs the toner to make the mixed state of the carrier and the toner uniform and frictionally charges the toner.
Further, while stirring the developer 26k, the developer supply port 26c
Agitating and supplying roll 26a for supplying the developer to the developer receiving port 25f of the developing unit 25, an engaging lever 26j for engaging a predetermined position of the developing unit 25, and a collecting guide 25d for peeling the developer from the conveying roll 25b and discharging the developer. Exit 25
The guide base 26i that receives the developer 26k discharged from the g through the developer recovery port 26s and guides it to the toner concentration detecting container 26n, the toner concentration detecting element 26f installed in the toner concentration detecting container 26n, and the support shaft 26q. The developer shutter 26 is supported by the spring and is biased by a spring so as to rotate counterclockwise to close the developer supply port 26c.
d, and a shutter lever 26e that operates in response to the attachment / detachment of the toner cartridge 27 to rotate about the support shaft 26r to open / close the developer shutter 26d.

The toner cartridge 27 is a replacement part that fits into the developer cartridge 26, and the lower surface of the new state is closed by a seal that can be peeled off by pulling out from the lateral direction.

The toner cartridge 27 is provided with a toner replenishing roll 27a and a toner stirring blade 27b, and an engaging stopper 27c for fitting and fixing the developer cartridge 26 at a predetermined position is provided.
When the toner concentration of the developer 26k in 6 falls below a predetermined concentration, the toner replenishing roll 27a rotates and the toner 2
7d is supplied into the developer cartridge 26.

In this developing device, as shown in FIG. 3, a developer cartridge 26 is mounted on the developing unit 25, fixed at a predetermined position by an engaging lever 26j, and a toner cartridge 27 is mounted on the developer cartridge 26. Then, it is fixed at a predetermined position by the engagement stopper 27c.

When the toner cartridge 27 is attached to the developer cartridge 26, the shutter lever 26e of the developer cartridge 26 is pushed down by the toner cartridge 27 to rotate counterclockwise about the support shaft 26r, and the developer shutter 26e is released. 26d is rotated about the support shaft 26q to open the developer supply port 26c.

As described above, since the developer shutter 26d is biased by the spring in the direction of closing the developer supply port 26c, the developer shutter 26d cannot be pushed down when the toner cartridge 27 is detached. It rotates counterclockwise so as to close the supply port 26c.

Further, as shown in FIG. 4, the developing unit 2
In the state where the toner cartridge 27 is attached to the developer cartridge 26 attached to the developer cartridge 5,
The engagement lever 26j of No. 6 cannot be released (the engagement lever 26j is released at the position shown in FIG. 1). That is, the toner cartridge 27 is pulled out, whereby the force of pressing down the shutter lever 26e of the developer cartridge 26 is released, and the developer shutter 26d closes the developer supply port 26c by the reaction force of the spring attached to the developer shutter 26d. In this state, the developer cartridge 26 is pulled out. Therefore, when the developer cartridge 26 is to be removed, the toner cartridge 27 is removed from the developer cartridge 26 to release the depression of the shutter lever 26e, and the developer shutter 26d is rotated by the spring force to develop the developer supply port 26c. Will be blocked. In this state, the engagement lever 26
Then, the developer cartridge 26 can be removed by raising the engaging lever 26j to release the fixing.

Since this is a known means, detailed description thereof will be omitted, but when the number of printed sheets reaches the end of the life of the developer, a message prompting the replacement of the developer is displayed on the operation panel of the printer body 1, and thereby the developer is replaced. Replacement work will be performed.

In this operation, as described above, by removing the toner cartridge 27 from the developer cartridge 26, the developer supply port 26c of the developer cartridge 26 is closed by the developer shutter 26d, and the developing unit is opened. The developer will not be spilled during the work of removing the developer cartridge 26 from 25.

When a new developer cartridge 26 is mounted in the developing unit 25, the developer container 26
By peeling off the seal that closes the lower surface of p, a new developer can be supplied to the developer accommodating space of the developer cartridge 26, which facilitates the developer replacement work.

The developing unit 25 is the most expensive component that needs to be maintained with high accuracy in the developing device. However, if the developer cartridge 26 is replaced as described above, the developing unit 25 will not work. Can be permanently installed and used.

The operating state of this developing device is shown in FIG.

Developer 26k in developer cartridge 26
Is a mixture of a magnetic carrier and an insulating toner, the carrier and the toner are uniformly mixed and stirred by a stirring screw 26b, and are supplied from a developer supply port 26c to a developing roller 25a in the developing unit 25 by a stirring supply roller 26a. .

The developing roll 25a is a stirring and feeding roll 26a.
Of the developer 26k held on its surface by the magnetic force of the developing roller 25a.
Is carried in the direction of arrow A while being cut into a predetermined thickness by the cutting blade 25d and rubs the photosensitive belt 2 to develop the electrostatic latent image formed on the surface of the photosensitive belt 2.

The developer 26k which has passed through the developing area is transferred from the developing roll 25a to the carrying roll 25b and carried to the upper part of the developing unit 25, and is peeled off from the carrying roll 25b by the peeling blade 25d and dropped. It is pushed out from the outlet 25g, guided from the developer recovery port 26s of the developer cartridge 26 to the guide base 26i, and recovered in the developer cartridge 26.

A part of the developer 26k guided by the guide base 26i flows into the toner concentration detecting container 26n, and the developer 26k is detected by the toner concentration detecting element 26f.
The toner density of is converted into a voltage and is constantly detected.

The voltage change detected by the toner concentration detecting element 26f with respect to the toner concentration of 1% of the developer 26k is 0.5 V, and when the toner concentration of the developer 26k is low,
The voltage detected by the toner concentration detecting element 26f becomes high,
If the toner concentration is high, the voltage will be low. That is,
When the voltage detected by the toner concentration detecting element 26f is higher than the predetermined voltage, the toner replenishing roll 27a in the toner cartridge 27 is rotated to replenish the toner 27d to the developer cartridge 26. In this embodiment, the predetermined voltage is set to 2.5 V and the control range of the toner concentration of the developer 26k is within ± 1%. Therefore, the voltage detected by the toner concentration detecting element 26f is usually 2V. 0.5 ± 0.5
Bolts (2-3 volts).

As shown in FIG. 2, the toner cartridge 2
If the developer 7 is forgotten to be mounted in the developer cartridge 26, the developer 26k in the toner concentration detection container 26n is discharged by the stirring screw 26b.

However, as described above, since the developer supply port 26c is blocked by the developer shutter 26d,
The developer 26k is not supplied to the developing roll 25a. Therefore, the developer 26k is not transported to the transport roll 25b either, and does not flow into the toner concentration detection container 26n.
As a result, the toner concentration detecting container 26n becomes empty, the toner concentration detecting element 26f detects about 0 volt, and "toner cartridge is not mounted" on the operation panel of the printer body.
Is displayed.

The control operation for detecting the toner concentration of the developer 26k of the toner concentration detecting element 26f and the non-mounting detection of the toner cartridge 27 will be described with reference to FIG.

When a print instruction is issued from the host, the developing device starts operation, and the toner concentration detecting element 26f detects the voltage. At this time, if the voltage V ₁ detected by the toner concentration detecting element 26f is V ₁ ≧ 0.5 V, the printer main body performs a series of printing operations such as charging, exposure, development, transfer and fixing.

After the printing operation is completed, the toner concentration detecting element 26f detects the voltage again. If the detected voltage V ₂ is V ₂ ≤2.5 V, it is determined that the toner concentration of the developer is equal to or higher than a predetermined level. Upon determination, the printer body is ready for the next print operation.

When V ₂ > 2.5 V, it is determined that the toner density of the developer is below a predetermined level, and the toner 27d is replenished from the toner cartridge 27. This operation is repeated until V ₂ ≤2.5 volts.

When the voltage V ₁ detected by the toner concentration detecting element 26f is V ₁ <0.5 V, there is no developer in the toner concentration detecting container 26n and the developer shutter is present.
26d is closed, that is, it is determined that the toner cartridge 27 is not installed, "toner cartridge is not installed" is displayed on the operation panel of the printer main body, and the printing operation is stopped.

In the above embodiment, the developer 26 is used as a means for detecting the opening / closing of the developer shutter 26d.
Toner concentration detecting element 26f for detecting the toner concentration in k
However, instead of this, the on / off operation is performed according to the opening / closing operation of the developer shutter 26d.
Changeover switch to turn off or developer shutter 26
You may make it use the light emitting / light receiving element etc. which turn on / off according to the opening / closing operation of d.

[0067]

According to the present invention, since it is sufficient to replace the developer cartridge when the life of the developer is exhausted, the cost is low, and the developing unit is still attached to the electrophotographic apparatus from the beginning of manufacture, and therefore, the electrostatic charge is eliminated. The facing gap with the latent image surface can be maintained with high accuracy, and therefore the developer can be replaced without degrading the developing performance.

Further, the developer sent out by the agitation supply roll is heaped up near the developer supply port of the used developing cartridge. However, when removing the developing cartridge, the toner cartridge is previously removed to remove the developer. Since the developer supply port is blocked by the developer shutter, there is no need to worry about spilling the developer inside the electrophotographic device during the replacement work to attach / detach the development cartridge to / from the development unit, and the replacement work can be performed cleanly. In addition, the spilled developer can eliminate the problem of damaging the electrostatic latent image surface.

In addition, the toner cartridge is not installed,
When the developer shutter is closed, the printing operation is not performed, so printing is not performed without the toner cartridge installed.Therefore, toner is scattered from the opening for replenishing toner from the toner cartridge. Therefore, the inside of the image forming apparatus is not polluted.

As shown in the illustrated embodiment, if the opening / closing detection of the developer shutter is performed by the toner concentration detecting element for detecting the toner concentration in the developer, the opening / closing detecting means of the developer shutter is newly added. Need not be provided,
The developing device can be made even cheaper.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional side view of a developing device according to the present invention with its constituent parts separated.

FIG. 2 is a vertical cross-sectional side view showing a state in which a developer cartridge 26 is attached to the developing unit 25 (a toner cartridge 27 is not attached) in the developing device according to the present invention.

FIG. 3 is a vertical cross-sectional side view showing a state in which a developer cartridge 26 and a toner cartridge 27 are attached to the developing unit 25 in the developing device according to the present invention.

FIG. 4 is an external perspective view of FIG.

FIG. 5 is a vertical cross-sectional side view showing an operating state of the developing device according to the present invention.

FIG. 6 is a vertical sectional side view of a color laser printer to which the developing device according to the present invention is applied.

FIG. 7 is a control operation flowchart of the color laser printer shown in FIG.

[Explanation of symbols]

2 ... Photosensitive belt, 8-11 ... Developing device, 25 ... Developing unit, 25a ... Developing roll, 25f ... Developer receiving port, 2
5 g ... Developer discharge port, 26 ... Developer cartridge, 26
a ... stirring supply roll, 26c ... developer supply port, 26d ...
Developer shutter, 26e ... Shutter lever, 26f
... toner concentration detecting element, 26n ... toner concentration detecting container,
26j ... Engaging lever, 26s ... Developer recovery port, 27 ... Toner cartridge, 27c ... Engagement stopper.

Claims (5)

[Claims] 1. A developer stirred in a developer accommodating space is held on the surface of a developing roll to act on the electrostatic latent image surface, and the developer which has finished acting on the electrostatic latent image surface is removed from the surface of the developing roll. In a developing device having a structure in which toner is peeled off and collected in the developer accommodating space, and the toner that has consumed toner is replenished with toner from a toner cartridge, the developing roll and the developer to be held on the surface of the developing roll A developing unit having a developer receiving port, a developer discharging port for discharging the developer separated from the developing roll, a developer supplying port formed at a position facing the developer receiving port, and the developer discharging port. A developer collecting port formed at a position opposite to the developer collecting port, and an agitating / supplying roll arranged in the developer accommodating space, and is detachably engaged with the developing unit so that the developer is supplied from the developer supplying port. A developer cartridge for supplying the developer to the inlet and collecting the developer discharged from the developer discharge port to the developer recovery port; and a developer cartridge that is detachably engaged with the developer cartridge. A toner cartridge having a toner replenishing roll for replenishing the toner; further, a developer shutter for covering the developer supply port; and a developer shutter when the toner cartridge is mounted on the developer cartridge to open the developer of the toner cartridge. In addition to the shutter driving means that closes the developer shutter when removing from the cartridge, opens and closes the developer shutter in response to attachment and detachment of the toner cartridge, the developer shutter is closed by detecting the opening and closing of the developer shutter. If the toner cartridge is not installed on the operation panel of the printer, Developing apparatus is characterized in that it comprises means to stop the printing operation and. 2. The developing device according to claim 1, wherein the means for detecting the opening / closing of the developer shutter is also used by the toner concentration detecting means in the developer. 3. The developing device according to claim 1, wherein the means for detecting the opening / closing of the developer shutter is a changeover switch which is turned on / off according to the opening / closing operation of the developer shutter. 4. The developing device according to claim 1, wherein the means for detecting the opening / closing of the developer shutter is a light emitting / receiving element which is turned on / off according to the opening / closing operation of the developer shutter. 5. An electrophotographic apparatus comprising the developing device according to claim 1.