JP2002108100A - Developing apparatus and magnetic roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make toner feeding quantity to a photoreceptor adjustable. SOLUTION: This magnetic roller 12 is composed by arranging seven electric magnets 122 (122-1 to 122-7) inside a sleeve 121 forming a hollow cylinder body. Each of the electric magnet units 122 is arranged so that the shaft of the electric magnet that is incorporated therein becomes orthogonal to the shaft center of the sleeve 121 and moreover so that one of the magnetic pole comes close to the sleeve 121. The polarity of electric magnet units is periodically changed at a specified speed by means of the electric magnet driving circuit 16 and a CPU 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to, for example, an electrophotographic apparatus, in which a magnetic developer stored in a storage container is carried on the surface of a developing roller, transported outside the storage container, and brought into contact with a photosensitive member. The present invention relates to a developing device for visualizing an electrostatic latent image formed on the photoconductor and a magnet roller suitable for such a developing device.

[0002]

2. Description of the Related Art As a developing method used in this type of developing apparatus, a one-component developer using a magnetic toner is used.
Component development method, consisting of non-magnetic toner and magnetic carrier 2
A two-component developing method using a component developer and a 1.5-component developing method using a 1.5-component developer composed of a magnetic toner and a magnetic carrier are known.

[0003] In any of these developing systems, basically, a magnetic force generated by a magnet disposed inside the developing roller causes the developer to adhere to the surface of the developing roller in a spike shape,
A so-called magnetic brush is formed. Then, the developer is supplied to the surface of the photoconductor by bringing the magnetic brush into contact with the surface of the photoconductor.

A permanent magnet is generally used as the magnet disposed inside the developing roller.

[0005]

The two-component development method and 1.5
In the case of the component developing method, only the toner is consumed in the developing operation, and the carrier is not consumed. For this reason, the ratio of the toner to the carrier decreases,
When the permanent magnet is used as described above, the developer in which the ratio between the carrier and the toner fluctuates is carried as it is on the developing roller and conveyed. As a result, the amount of toner supplied to the photoreceptor surface fluctuates, and the developing operation becomes unstable.

When the toner can be replenished, the carrier is repeatedly used for a long period of time, so that the carrier deteriorates due to mechanical contact or the like. For this reason, carrier exchange may be performed periodically. However, when the permanent magnet is used as described above, the developer is always attracted to the developing roller. Therefore, when replacing the carrier, an operation of removing the developer adsorbed by the developing roller is performed. This necessitates the necessity of replacing the carrier.

In any of the developing methods, since the developer contains a magnetic component, when the permanent magnet is used as described above, the developer is always attracted to the developing roller. For this reason, the amount of the developer adhering to the developing roller gradually increases and eventually becomes layered, which may make it difficult to form the magnetic brush satisfactorily.

Further, since the developer is always attracted to the developing roller as described above, the developer may remain on the developing roller for a long period of time. In this case, the stirring and friction become insufficient, and the charge amount of the toner becomes insufficient. As a result, the developing operation may become unstable.

The present invention has been made in view of such circumstances, and a first object of the present invention is to provide a developing device capable of adjusting a toner supply amount to a photosensitive member. It is in.

The second object of the present invention is to:
It is an object of the present invention to provide a developing device capable of renewing a developer attached to a developing roller.

[0011]

According to a first aspect of the present invention, a magnetic developer stored in a storage container such as a hopper is stored on a surface of a developing roller. In a developing device which is transported to the outside of the container and is brought into contact with the photoreceptor to visualize an electrostatic latent image formed on the photoreceptor, an electromagnet unit having a predetermined width along a roller longitudinal direction is used as the developing roller. A plurality of non-rotating magnet rollers are arranged along the circumferential direction of the roller in a state where only one of the magnetic poles is close to the roller surface, and the polarity of the magnetic poles of the plurality of electromagnet units is changed at a predetermined speed. Driving and controlling the plurality of electromagnet units so as to change periodically, for example, an electromagnet driving circuit and a CPU
And drive control means realized by the software processing of (1).

By taking such measures, a magnetic brush is formed on the surface of the magnet roller by the magnetic force generated by the plurality of electromagnet units, and the magnetic brush changes with the magnetic poles of the plurality of electromagnet units. Move on the surface of the magnet roller. By changing the speed at which the polarity of the magnetic pole of the electromagnet unit is changed, the moving speed of the magnetic brush changes. Therefore, the transport amount of the developer is variable.

According to a second aspect of the present invention, in the electromagnet unit according to the first aspect, a plurality of electromagnets having a width smaller than the predetermined width are arranged along the longitudinal direction of the roller.

By taking such measures, the electromagnets having a small width cooperate to realize a function as an electromagnet having a large width. Therefore, the loss for generating the magnetic force in the electromagnet unit is reduced, and the efficiency is improved.

According to a third aspect of the present invention, in addition to the first aspect, a developer containing the toner and the carrier is used in the developer stored in the storage container. A ratio determining unit such as a developer remaining amount monitoring unit that determines the ratio based on, for example, the remaining amount of the developer is provided, and the drive control unit determines the ratio between the toner and the carrier determined by the ratio determining unit. The speed at which the polarities of the magnetic poles of the plurality of electromagnet units are changed is changed according to.

By taking such a measure, the ratio between the toner and the carrier in the developer stored in the storage container is determined, and the speed at which the polarity of the magnetic poles of the plurality of electromagnet units is changed accordingly. Automatically adjusted.
Therefore, it is possible to stabilize the toner supply amount by automatically adjusting the developer conveyance amount so as to compensate for the change in the toner supply amount due to the change in the ratio between the carrier and the toner.

According to a fourth aspect of the present invention, the developing unit including the storage container and the magnet roller according to the first aspect of the present invention is separate from the control unit provided with the drive control means. When it is possible to arbitrarily connect the developing unit to the control unit,
Identifiers that differ depending on the type of the developing unit provided in the developing unit, and determine the type based on the identifier provided in the connected developing unit provided in the control unit, for example, Type determining means comprising identifier reading means and type determining processing means realized by software processing of a CPU, and the drive control means further comprises: The operation states of the plurality of electromagnet units are changed.

By taking such measures, the type of the mounted developer unit is determined based on the identifier provided in the developer unit, and the polarity of the magnetic poles of the plurality of electromagnet units is changed accordingly. The speed is adjusted automatically. Therefore, it is possible to stabilize the toner supply amount by automatically adjusting the developer conveyance amount so as to compensate for the difference in the toner supply amount for each type of the developing unit.

On the other hand, in order to achieve the second object, the fifth
The present invention relates to the electromagnet, wherein a magnetic force effective for supporting the developer in a predetermined region located inside the storage container on the surface of the magnet roller according to the first invention does not reach any of the electromagnet units. We decided to arrange units.

By taking such measures, the developer which has moved to a predetermined area where the magnetic force effective for supporting the developer does not reach any of the electromagnet units reduces the magnetic force attracted to the surface of the magnet roller. Loses and magnetically separates from the magnet roller. Therefore, it is possible to prevent the developer from remaining on the magnet roller.

According to a sixth aspect of the present invention, in addition to the fifth aspect of the present invention, a cleaning roller such as a small roller is provided in contact with the predetermined area on the surface of the magnet roller.

By taking such a measure, the developer which is magnetically separated from the magnet roller but remains on the surface of the magnet roller is scraped off by the cleaning roller. Therefore, it is possible to more reliably prevent the developer from remaining on the magnet roller.

In order to achieve the second object, the seventh object
According to the present invention, for example, a magnetic developer stored in a storage container such as a hopper is carried on the surface of a developing roller, transported to the outside of the storage container, and brought into contact with the photoconductor to form a static developer formed on the photoconductor. In a developing device for visualizing an electro-latent image, a magnet roller having a built-in electromagnet is used as the developing roller, and the electromagnet is turned off for a predetermined period at a predetermined timing, for example, every time a predetermined number of sheets are printed. There is provided drive control means for controlling the drive of the electromagnet, for example, the drive control means comprising an electromagnet drive circuit and drive control means realized by software processing of a CPU.

By taking such measures, the magnetic roller as the developing roller carries the magnetic developer by the magnetic force generated by the built-in electromagnet, but the electromagnet is turned off at a predetermined timing. As a result, the magnetic developer magnetically separates from the magnet roller. Therefore, it is possible to prevent the developer from remaining on the magnet roller.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a main configuration of an electrophotographic apparatus configured by applying the developing device according to the present embodiment.

As shown in FIG. 1, the electrophotographic apparatus of the present embodiment has a developing unit 1, a control unit 2, and a photosensitive member 3.

The developing unit 1 is a mechanism for executing a developing operation for visualizing an electrostatic latent image formed on the photosensitive member 3 by a charger and an exposure device (not shown). The developing unit 1 is detachably mountable to the main body of the electrophotographic apparatus provided with the control unit 2, and the mounting state is shown in the figure.

As shown in FIG. 1, the developing unit 1 includes a hopper 11, a magnet roller 12, a small roller 13,
Scraper 14, agitator 15, electromagnet drive circuit 16
And an identifier 17.

The hopper 11 is a hollow box having a width larger than the effective developing width in the depth direction of the drawing. Below the side wall of the hopper 11 located on the photoconductor 3 side with the developing unit 1 mounted, an opening is formed in the depth direction in the drawing, which extends over the effective developing width. A roller 12 is provided. The developer is stored in the internal space of the hopper 11. In addition,
The developer used in the developing device of the present embodiment is a two-component developer or a 1.5-component developer, and includes a carrier and a toner.

The magnet roller 12 includes seven electromagnet units 1 inside a hollow cylindrical sleeve 121.
22 (122-1 to 122-7). Each of the electromagnet units 122 has a plurality (n
) Are arranged along at least the effective development width along the longitudinal direction (axial direction) of the sleeve 121. In addition, each of the electromagnet units 122
The axis of each of the included electromagnets M is perpendicular to the axis of the sleeve 121, and one of the magnetic poles is arranged close to the sleeve 121. Further, as shown in FIG. 3, only the narrow angle between the electromagnet unit 122-1 and the electromagnet unit 122-7 is set to 90 °, and the narrow angle between the other adjacent units is set to 45 °. ing. And the magnet roller 12 having such a structure
As shown in FIG. 1, the narrow angle between adjacent units is 90
° and is fixed in a direction in which a portion set to be larger than the others (hereinafter, referred to as a non-magnetic force region) is located in the internal space of the hopper 11.

One of the features of the present invention is that the electromagnet unit 122 is configured by arranging a plurality of small electromagnets M. As a result, it is possible to reduce the loss due to the generation of the magnetic force as compared with the case where one large electromagnet is used, and it is possible to efficiently generate the magnetic force.

The small roller 13 is a cylindrical roller having a width comparable to that of the magnet roller 12 in the depth direction in the drawing, and is in contact with the magnet roller 12 in parallel with the magnet roller 12 and near the non-magnetic force region. It is arranged in the internal space of the hopper 11 in a state. The small roller 13 is rotated by a rotation drive mechanism (not shown).

The scraper 14 is a plate-shaped member having a width comparable to that of the small roller 13 in the depth direction of the drawing, and is provided inside the hopper 11 in parallel with the small roller 13 and in contact with the small roller 13. It is fixedly arranged in space.

The agitator 15 rotates in the space above the internal space of the hopper 11 to stir the developer.

The electromagnet drive circuit 16 drives a number of electromagnets M constituting each electromagnet unit 122 under the control of the control unit 2.

The identifier 17 is provided on the lower surface of the hopper 11 and indicates the type of the developing unit 1. This identifier 17
Can be realized by, for example, a projection having a different pattern for each type of the developing unit 1, or a signal generator for outputting a different signal for each type of the developing unit 1.

FIG. 4 is a circuit diagram showing a part of the configuration of the electromagnet drive circuit 16.

In this figure, seven electromagnet units 122 are shown.
2 shows a circuit for driving one electromagnet M included in each of them. In this figure, reference numeral MA denotes an electromagnet included in the electromagnet unit 122-1, reference numeral MB denotes an electromagnet included in the electromagnet unit 122-2, reference numeral MC denotes an electromagnet included in the electromagnet unit 122-3, and reference numeral MD Is an electromagnet included in the electromagnet unit 122-4, a symbol ME is an electromagnet included in the electromagnet unit 122-5, a symbol MF is an electromagnet included in the electromagnet unit 122-6, and a symbol MG is an electromagnet unit 122-7. Each of the included electromagnets is shown.

Thus, each electromagnet unit 122 has n
Since each electromagnet M is provided, the electromagnet drive circuit 16 is actually provided with n sets of circuits shown in FIG.

First, one electromagnet M included in each of the seven electromagnet units 122 is, as shown in FIG.
The winding directions of the coils match from the surface side of the magnet roller 12 toward the axis. The coil of each electromagnet M is connected between the axial ends of the electromagnets MA and MC, and the electromagnet M-
C, ME, front end portions, electromagnets ME, MG end portions on the axial side, electromagnets MB, MD end portions on the axial side,
The front ends of the electromagnets MD and MF are connected to each other. That is, electromagnets MA, MC, ME, MG
Are connected in series, and the electromagnet M-
Each coil of B, MD, and MF is connected in series.

Now, as shown in FIG.
Inverters 41, 41, 43, 44, 45, 46,
47, 48 and eight transistors 49, 50, 51,
52, 53, 54, 55, and 56.

The inverters 41 and 42 are connected in series, and the control signal φA is input to the upper inverter 41. The output of the inverter 41 is provided to the base of the transistor 49, and the output of the inverter 42 is provided to the base of the transistor 50.

The inverters 43 and 44 are connected in series, and the control signal φC is input to the upper inverter 43. The output of the inverter 43 is provided to the base of the transistor 51, and the output of the inverter 44 is provided to the base of the transistor 52.

The transistors 49 and 51 are of the npn type, and both have their emitters grounded. Transistor 5
Numerals 0 and 52 are pnp type, and both have an emitter connected to the power line. The collectors of the transistors 50 and 51 are both connected to the front end of the coil of the electromagnet MA. The collectors of the transistors 49 and 52 are
Both are connected to the front end of the coil of the electromagnet MG.

The inverters 45 and 46 are connected in series, and a control signal φB is input to the upper inverter 45. The output of the inverter 45 is provided to the base of the transistor 53, and the output of the inverter 46 is provided to the base of the transistor 54.

The inverters 47 and 48 are connected in series, and a control signal φD is input to the upper inverter 47. The output of the inverter 47 is supplied to the base of the transistor 55, and the output of the inverter 48 is supplied to the base of the transistor 56.

The transistors 53 and 55 are of the npn type, and both have their emitters grounded. Transistor 5
Reference numerals 4 and 56 denote a pnp type, both having an emitter connected to a power line. The collectors of the transistors 54 and 55 are both connected to the front end of the coil of the electromagnet MB. The collectors of the transistors 53 and 56 are
Both are connected to the axial end of the coil of the electromagnet MF.

As described above, the electromagnet drive circuit 16 is provided with n sets of circuits shown in FIG. 4, and these n sets of circuits have control signals φA, φB, φC, φD.
Are given in common.

Now, as shown in FIG. 1, the control unit 2
It has a CPU 21, a ROM 22, a RAM 23, an interface unit (IF unit) 24, and an identifier reading unit 25. These components are connected to each other via a system bus 26. When the developing unit 1 is mounted, the electromagnet drive circuit 16 provided in the developing unit 1 is also connected to the system bus 26.

The CPU 21 performs various control processes for realizing the operation as the electrophotographic apparatus by software processing based on the operation program stored in the ROM 22.

The ROM 22 stores the above-described operation program and other various data.

The RAM 23 temporarily stores data used when the CPU 21 performs various processes.

A host computer (not shown) is connected to the interface unit 24 and communicates with print data.

The identifier reading section 25 reads the identifier 17 provided in the mounted developing unit 1.

The processing means realized by the CPU 21 through software processing includes a developer remaining amount monitoring means, a type determination processing means, and a drive control means, in addition to a well-known general processing means in an electrophotographic apparatus.

Here, the developer remaining amount monitoring means is the hopper 1
The remaining amount of the developer stored in the printer 1 is monitored.

The type judgment processing means judges the type of the mounted developing unit 1 based on the result of reading by the identifier reading section 25.

The drive control means will be described later in consideration of the developer remaining amount monitored by the developer remaining amount monitoring means, the type determined by the type determination processing means, a data table prepared in the ROM 22, and the like. Performs an electromagnet drive control process.

Next, the operation of the electrophotographic apparatus configured as described above will be described. The operation relating to image formation is the same as that of a conventional general electrophotographic apparatus, and therefore, the description thereof is omitted, and here, control processing of the developing operation will be described.

First, in order to execute the developing operation, the CPU 2
1 is a control signal φA, at a switching cycle T as shown in FIG.
φB, φC, and φD are sequentially set to Low level.

When φA is at the low level, in the electromagnet drive circuit 16, the output of the inverter 41 is at the high level, the output of the inverter 42 is at the low level, the transistors 49 and 50 are turned on, and the electromagnets MA, MC, M−
A current is generated through E and MG, and these electromagnets are turned on. However, in the electromagnets MA and ME, the current flows from the roller surface side to the roller axis side, and in the electromagnets MC and MG, the current flows from the roller axis side to the roller surface side. As shown in FIG.
-E becomes "N" and electromagnets MC and MG become "S".

When φB is at the low level, in the electromagnet drive circuit 16, the output of the inverter 45 is at the high level, the output of the inverter 46 is at the low level, the transistors 53 and 54 are turned on, and the electromagnets MB, MD and M−
A current flows through F and these electromagnets are turned on. However, in the case of the electromagnets MB and MF, the current flows from the roller surface side to the roller axis side, and in the case of the electromagnet MD, the current flows from the roller axis side to the roller surface side. As shown, the electromagnets MB and MF are “N”, and the electromagnet MD is “S”.

When φC is at the low level, in the electromagnet drive circuit 16, the output of the inverter 43 is at the high level, the output of the inverter 44 is at the low level, the transistors 51 and 52 are turned on, and the electromagnets MA, MC, M−
A current is generated through E and MG, and these electromagnets are turned on. However, in the electromagnets MA and ME, the current flows from the roller axis to the roller surface, and in the electromagnets MC and MG, the current flows from the roller surface to the roller axis. As shown in FIG.
-E becomes "S" and electromagnets MC and MG become "N".

When φD is at the low level, in the electromagnet drive circuit 16, the output of the inverter 47 is at the high level, the output of the inverter 48 is at the low level, the transistors 55 and 56 are turned on, and the electromagnets MB, MD and M−
A current flows through F and these electromagnets are turned on. However, in the case of the electromagnets MB and MF, the current flows from the roller axis to the roller surface, and in the case of the electromagnet MD, the current flows from the roller surface to the roller axis. As shown, the electromagnets MB and MF become “S” and the electromagnet MD becomes “N”.

Thus, each electromagnet M is turned on / off at each switching cycle T, and the polarity of the magnetic pole is inverted each time it is turned on. Then, the electromagnet M whose polarity of the magnetic pole on the roller surface side is “N” or “S” is obtained by electromagnet MA → electromagnet MB → electromagnet MC → electromagnet MD → electromagnet ME → electromagnet M−
It changes every switching cycle T in the order of F → electromagnet MG.

Since the n electromagnets M in each electromagnet unit 122 are driven synchronously, each electromagnet unit 122 functions as one large electromagnet, and the magnetic polarity on the roller surface side is “N”. Or, the electromagnet unit 122 which is “S” is the electromagnet unit 122-1 → the electromagnet unit 122-2 → the electromagnet unit 122-3 → the electromagnet unit 122-4 → the electromagnet unit 122-5 → the electromagnet unit 122-6.
→ It changes every switching cycle T in the order of the electromagnet unit 122-7.

As a result, when the electromagnet unit 122-1 is turned on, the developer attracted to the surface of the magnet roller 12 by the magnetic force generated by the electromagnet unit 122-1 changes with the change of the electromagnet unit 122 that generates the magnetic force. The surface of the roller 12 moves in the counterclockwise direction in FIG. Therefore, the developer is supplied to the surface of the photoconductor 3. Note that a developing bias of a predetermined voltage (for example, -600 V) is applied to the sleeve 121, and the development of the electrostatic latent image formed on the photoconductor 3 is performed by the action of the developing bias.

Then, of the developer transported to the outside of the hopper 11, the toner that has not adhered to the carrier and the photosensitive member 3 moves on the magnet roller 12 as it is, and returns to the inside of the hopper 11. Then, the developer that has reached the position of the electromagnet unit 122-7 is not affected by the magnetic force generated by the electromagnet unit 122-1 because the distance between the electromagnet unit 122-7 and the electromagnet unit 122-1 is increased, and When the electromagnet unit 122-7 is turned off, it is magnetically separated from the magnet roller 12.

As described above, the gap between the electromagnet unit 122-7 and the electromagnet unit 122-1 is increased to form a non-magnetic force area, and the developer that has moved on the surface of the magnet roller 12 is once removed from the magnet roller 12. One of the features of the present invention is that the magnetic head is magnetically separated. As a result, it is possible to prevent the developer from adhering to the magnet roller 12, and to form a good magnetic brush.

Further, since the small roller 13 is in contact with and rotates at a position near the non-magnetic force area, the magnet roller 1 is only required when the electromagnet unit 122-7 is turned off.
2 is removed from the magnet roller 12.

The provision of the small roller 13 is also one of the features of the present invention. As a result, the developer that is magnetically separated from the magnet roller 12 but continues to adhere to the surface of the magnet roller 12 can be scraped off, and the developer can be more reliably separated from the magnet roller 12. It becomes possible.

The small roller 13 has a function of flowing the developer around and a function of frictionally charging the developer.

The above is the description of the magnet roller 1 of the present embodiment.
2 is the basic operation of the developer conveyance.

The CPU 21 does not always perform the control signal changing process for causing the developer to be transported as described above, but performs the following electromagnet control process separately to start the control signal changing process. Has stopped.

That is, when it becomes necessary to perform printing, the CPU 21 executes an electromagnet drive control process as shown in FIG.

In this electromagnet drive control processing, the CPU 2
First, the type 1 determines the type of the currently mounted developing unit 1 based on the output from the identifier reading unit 25 (step ST1). Here, the developing unit 1
TYPE1 and TYPE2 which have a difference such as a different mixing ratio between the carrier and the toner in the developer.
It is assumed that there are two types. Therefore, the CPU 21 determines whether the mounted developer unit 1 is TYPE1 or TYPE2 based on the determination result in step ST1 (step ST2), and further determines the remaining amount of the developer thereafter. It is checked whether the value is less than the threshold value (step ST3 or step ST4). The remaining amount of the developer is separately managed, for example, by using a sensor or managing the amount of toner used.

Here, the mounted developing unit 1
Is TYPE1 and the remaining amount of the developer is less than the threshold value, the CPU 21 sets the switching period T of the control signal to a predetermined value T1 (step ST5). If the mounted developer unit 1 is TYPE 1 and the remaining amount of the developer is equal to or larger than the threshold value, the CPU 21 sets the control signal switching cycle T to a predetermined value T2 (step ST2).
6). If the mounted developer unit 1 is TYPE2 and the remaining amount of developer is less than the threshold value, CP
U21 sets the control signal switching period T to a predetermined value T3 (step ST7). If the mounted developer unit 1 is TYPE2 and the remaining amount of the developer is equal to or larger than the threshold value, the CPU 21 sets the control signal switching cycle T to a predetermined value T4 (step ST8).

Thus, the switching cycle T of the control signal is changed and set according to the type of the mounted developer unit 1 and the remaining amount of the developer.

Subsequently, the CPU 21 starts the control signal changing process described above (step ST9). In the standby state, the CPU 21 maintains the control signal state at the time when the control signal change processing was previously stopped, and when starting the control signal change processing, the CPU 21 changes the control signal as described above from that state. Do.

As a result, the electromagnet unit 122 is driven at the switching period T changed and set as described above.

By the way, when the switching period T is shortened, the moving speed of the developer increases, and the transport amount of the developer increases. Conversely, if the switching period T is lengthened, the moving speed of the developer decreases, and the transport amount of the developer decreases. Therefore, the switching period T
Is changed, it is possible to adjust the transport amount of the developer.

Therefore, the predetermined values T1, T2, T3 and T4 are set in such a manner that the toner transport amount becomes a predetermined optimum amount in consideration of the mixing ratio of the carrier and the toner in the developer under each condition. By appropriately setting the amount of toner to be obtained, it is possible to transfer the toner with an appropriate amount of conveyance in response to a difference in the type of the developing unit 1 and a change in the mixing ratio of the carrier and the toner due to the decrease of the toner. Is performed.

As described above, one of the features of the present invention is to use the magnet roller 12 having the structure shown in FIG. 1 as a developing roller. Thus, it is possible to change the transport speed of the developer, and it is possible to adjust the toner supply amount to the photoconductor 3 by appropriately adjusting the speed. In addition, the adjustment of the toner supply amount does not require any mechanical change, and can be realized only by switching of the electrical control processing, so that it is very simple.

Further, in this embodiment, the change setting of the switching period T is automatically performed in consideration of the mixing ratio of the carrier and the toner, which is one of the features of the present invention. As a result, it is possible to always maintain an optimal development state without bothering the user.

In this embodiment, the type of the developing unit 1 is determined in order to determine the mixing ratio between the carrier and the toner, which is one of the features of the present invention. Thus, even when any of the two types of developing unit 1 having different mixing ratios of the carrier and the toner in the contained developer is mounted, it is possible to always maintain a state in which optimal development is performed. In the present embodiment, attention is paid only to the difference in the mixing ratio between the carrier and the toner due to the difference in the type of the developing unit 1. However, the embodiment is modified so as to take into account other conditions such as the magnetic force of the electromagnet M being different. It is possible.

The CPU 21 waits for the printing to be completed in such a state while performing the printing operation according to a well-known procedure (step ST10). When the printing is completed, the CPU 21 stops the control signal change processing (step ST11).

Subsequently, the CPU 21 checks whether or not the number of printed sheets has become equal to or more than a specified number of sheets since the cleaning operation described later was performed last time (step ST12). If the number of prints is equal to or more than the specified number, that is, every time a predetermined number of prints are performed, the CPU 21 sets all of the control signals φA to φD to High level for a predetermined time (step ST13).

As described above, it is one of the features of the present invention that the control signals φA to φD are all set to the High level for a predetermined time each time a predetermined number of prints are performed. As a result, all the electromagnet units 122 are turned off, so that the adsorption of the developer to the magnet roller 12 is temporarily released, and the formed magnetic brush is eliminated.
As a result, the magnetic brush is refreshed, and the developer adhering to the magnet roller 12 can be prevented from being layered.

Here, all the electromagnet units 122 are OF
In order to set F, it is possible to turn off all the electromagnet units 122 at the same time.
122-1 → Electromagnetic unit 122-2 →…… → Electromagnetic unit
It may be turned off gradually in the order of 122-7. By doing so, the developer that has already adhered to the surface of the magnet roller 12 is recovered in the hopper 11, and then all the electromagnet units 122 are simultaneously turned off, so that the scattering of the developer is prevented. It is possible to

The present invention is not limited to the above embodiment. For example, in the above embodiment, for the purpose of refreshing the magnetic brush formed on the surface of the magnet roller 12, (1) a non-magnetic force area is formed on the magnet roller 12.

(2) The small rollers 13 are provided.

(3) Every electromagnet unit 122 is turned off at a predetermined timing.

Although the following three means are taken, these means alone can realize the refreshing of the magnetic brush. Therefore, only one or two means may be taken.

In the above embodiment, the switching period T is set automatically. However, the user can specify the value of the switching period T and set the designated value as the switching period T to perform the manual setting. It may be possible.

In the above embodiment, two types of developing unit 1 can be used. However, it is also possible to adopt a configuration that can support three or more types of developing unit 1.
In this case, a set value as the switching cycle T corresponding to each type to be dealt with may be prepared in advance.

In the above-described embodiment, the switching cycle T is changed in two stages for determining whether the remaining amount of the developer is equal to or more than the threshold value for simplification of the description. As the number of steps increases, the developer can be transported with a more appropriate amount of developer transport according to the ratio between the carrier and the toner.

In the above embodiment, the timing of turning off all the electromagnet units 122 is managed based on the number of prints. However, the timing may be managed based on other information such as the elapsed time.

In the technique of refreshing the magnetic brush by turning off all the electromagnet units 122 shown in the above-described embodiment, if a magnet roller using an electromagnet is used, the developer is conveyed by rotating the roller. However, the present invention can be applied to the case where the composition is different or a one-component developer is used.

In the above embodiment, the electromagnet unit 1
Reference numeral 22 denotes a configuration in which a plurality of small electromagnets M are arranged, but it is also possible to use a single electromagnet having a large width comparable to the development width.

Since the number of electromagnet units and the positional relationship between them are different depending on the properties of the developer and other various conditions, the conditions can be appropriately changed in consideration of those conditions.

In the above embodiment, the control unit is used in common with the electrophotographic apparatus. However, the control unit may have a control unit unique to the developing device.

The magnet roller 12 having the structure shown in this embodiment can be used not only as a developing roller but also as another roller as long as it is a roller for conveying powdered magnetic material (not limited to developer). Is also applicable. Specifically, for example, application to a cleaning roller for removing the carrier adhered to the photoconductor from the photoconductor can be considered.

In addition, various modifications can be made without departing from the gist of the present invention.

[0105]

According to the first aspect of the present invention, an electromagnet unit having a predetermined width in the longitudinal direction of the roller is used as the developing roller along the circumferential direction of the roller with only one of its magnetic poles approaching the roller surface. Since a plurality of non-rotating magnet rollers arranged in a row are used, and the plurality of electromagnet units are driven and controlled so as to periodically change the polarity of the magnetic poles of the plurality of electromagnet units at a predetermined speed. By changing the speed at which the polarity of the magnetic pole of the electromagnet unit is changed, the moving speed of the magnetic brush can be changed. As a result, the transport amount of the developer becomes variable, and the toner supply amount to the photoconductor is reduced. It can be adjusted.

According to the second invention, the electromagnet unit according to the first invention is configured by arranging a plurality of electromagnets having a width smaller than the predetermined width along the longitudinal direction of the roller. Therefore, the loss for generating the magnetic force in the electromagnet unit is reduced, and the efficiency can be improved.

According to a third aspect of the present invention, in addition to the first aspect, the ratio between the toner and the carrier in the developer stored in the storage container is determined, and the polarities of the magnetic poles of the plurality of electromagnet units are determined accordingly. The speed of changing the toner is automatically adjusted, so that the amount of the developer transported is automatically adjusted so as to compensate for the change in the amount of toner supplied due to the change in the ratio of the carrier and the toner, thereby stabilizing the amount of toner supply. It becomes possible.

According to a fourth aspect of the present invention, the type of the mounted developer unit is determined based on the identifier provided in the developer unit, and the speed at which the polarities of the magnetic poles of the plurality of electromagnet units are changed is automatically adjusted accordingly. Since the adjustment is performed, it is possible to stabilize the toner supply amount by automatically adjusting the developer conveyance amount so as to compensate for the difference in the toner supply amount for each type of the developing unit.

According to the fifth aspect of the present invention, a magnetic force effective for supporting the developer in a predetermined area located inside the storage container on the surface of the magnet roller according to the first aspect of the invention is applied to any of the electromagnet units. Since the electromagnet unit is arranged so as not to exceed, the developer returning to the inside of the storage container after moving out of the storage container after moving on the surface of the magnet roller is returned from the magnet roller in the predetermined area. The developer is magnetically separated, so that the developer adhering to the developing roller can be renewed.

According to the sixth aspect of the invention, in addition to the fifth aspect of the present invention, since the cleaning roller is provided in contact with the predetermined area on the surface of the magnet roller, it is magnetically magnetized. The developer remaining on the surface of the magnet roller, which is removed from the surface of the magnet roller, is scraped off by the cleaning roller, so that the developer attached to the developing roller can be more reliably updated.

According to the seventh aspect, the magnet roller as the developing roller carries the magnetic developer by the magnetic force generated by the built-in electromagnet. By turning off the electromagnet at a predetermined timing, the magnet roller is turned off. The magnetic developer is magnetically separated from the magnet roller, thereby making it possible to renew the developer attached to the developing roller.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main configuration of an electrophotographic apparatus configured by applying a developing device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an electromagnet unit 122 in FIG.

FIG. 3 is a diagram showing a positional relationship of an electromagnet unit 122 in FIG.

FIG. 4 is a circuit diagram showing a configuration of a part of an electromagnet drive circuit 16 in FIG. 1;

FIG. 5 is a timing chart showing a timing relationship among control signals φA, φB, φC, and φD.

FIG. 6 is a diagram showing a state of a change in magnetic polarity on the roller surface side of each electromagnet.

FIG. 7 is a flowchart showing a processing procedure at the time of electromagnet drive control processing by a CPU 21 in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Developer unit 2 ... Control unit 3 ... Photoconductor 11 ... Hopper 12 ... Magnet roller 13 ... Small roller 14 ... Scraper 15 ... Agitator 16 ... Electromagnet drive circuit 17 ... Identifier 24 ... Interface part (IF part) 25 ... Identifier reading Part 26: System bus 41 to 48 ... Inverter 49 to 56 ... Transistor 121 ... Sleeve 122 (122-1 to 122-7) ... Electromagnet unit M ... Electromagnet

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 7/02 G03G 15/08 507A

Claims (8)

[Claims] An electrostatic latent image formed on a photoconductor is formed by carrying the magnetic developer stored in the storage container on the surface of a developing roller, transporting the developer to the outside of the storage container, and contacting the photoconductor. In the developing device for visualizing, as the developing roller, a plurality of electromagnet units having a predetermined width along the longitudinal direction of the roller are arranged along the circumferential direction of the roller in a state where only one of its magnetic poles is close to the roller surface. Drive control means for controlling the plurality of electromagnet units so as to periodically change the polarities of the magnetic poles of the plurality of electromagnet units at a predetermined speed using a non-rotating magnet roller. Developing device. 2. The developing device according to claim 1, wherein the electromagnet unit is configured by arranging a plurality of electromagnets having a width smaller than the predetermined width along a longitudinal direction of the roller. 3. A drive control unit comprising: a ratio determination unit configured to determine a ratio between the toner and the carrier in the developer stored in the storage container as a developer using a developer including a toner and a carrier; 2. The developing device according to claim 1, wherein a speed of changing polarities of magnetic poles of the plurality of electromagnet units is changed according to a ratio between the toner and the carrier determined by the ratio determining unit. 3. apparatus. 4. A developing unit including the storage container and the magnet roller and a control unit provided with the drive control means are separate bodies, and a plurality of types of developing unit are arbitrarily connected to the control unit. And different identifiers depending on the type of the developing device unit provided in the developing device unit, and the identifier provided in the control unit and provided in the connected developing device unit. Type determining means for determining the type of the electromagnet unit, wherein the drive control means changes the operating state of the plurality of electromagnet units according to the type of the connected developing device determined by the type determining means. The developing device according to claim 1. 5. The electromagnet unit is arranged such that a magnetic force effective for supporting the developer does not reach any of the electromagnet units in a predetermined region located inside the storage container on the surface of the magnet roller. The developing device according to claim 1, wherein: 6. The developing device according to claim 5, further comprising a cleaning roller disposed in contact with said predetermined area on the surface of said magnet roller. 7. A magnetic developer stored in a storage container is carried on a surface of a developing roller, transported to the outside of the storage container, and brought into contact with a photoconductor to form an electrostatic latent image formed on the photoconductor. In the developing device for visualization, a drive control means for controlling the electromagnet so as to turn off the electromagnet for a predetermined period each time a predetermined condition is satisfied, using a magnet roller having a built-in electromagnet as the developing roller is provided. A developing device. 8. An electromagnet unit having a predetermined width along a longitudinal direction of a hollow cylindrical sleeve is provided inside a hollow cylindrical sleeve along a circumferential direction of a roller with only one of its magnetic poles being close to the roller surface. A magnet roller characterized by being arranged in a plurality.