JP2853037B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus provided with a magnetic brush device.

[0002]

2. Description of the Related Art Among image forming apparatuses configured as an electrophotographic copying machine, a facsimile, a printer, and the like, when a dry developing apparatus using a powder developer is used, toner particles are contained in a casing of the developing apparatus. A two-component developer composed of a toner and a carrier containing only an auxiliary agent or a one-component developer composed of only a magnetic toner, and the developer carrying member that is driven to rotate the contained developer. To form and transport a magnetic brush of the developer, and develop the electrostatic latent image formed on the latent image carrier with the developer.

On the other hand, as a cleaning device for transferring the developed toner image on the latent image carrier to a transfer material and then cleaning the toner remaining on the latent image carrier, an agent comprising a cleaning sleeve which is driven to rotate is used. It is also known to use a magnetic brush cleaning device that forms a magnetic brush of a cleaning agent on a supporting member and conveys the cleaning agent, and cleans the residual toner on the latent image carrier with the cleaning agent.

The above-described developing device and magnetic brush cleaning device both constitute a magnetic brush device, and the configuration according to the present invention is applicable to both such a developing device and a cleaning device. is there.

FIG. 7 shows a conventional example of an image forming apparatus having a developing device of the above-described magnetic brush device. A two-component developer (not shown) among the above-described developers is housed in a casing 1 of the developing device, and the housed developer is pumped up while being stirred by the agent stirring member 2. Are supplied onto the developing sleeve 3. The developing sleeve 3, which is an example of the configuration of the developer carrying member, is located to face a drum-shaped photoreceptor 5, which is an example of a latent image carrier.

[0006] Inside the developing sleeve 3, for example, a pole from P ₁ to P _5-pole magnet 4 arranged in the circumferential direction is provided as shown, the developing sleeve 3 counterclockwise against the magnet 4 By rotating in the direction, the developer supplied onto the developing sleeve 3 is carried on the sleeve by magnetic force and is conveyed counterclockwise in the figure as a magnetic brush.
At this time, the electrostatic latent image formed on the surface of the photoconductor 5 is visualized as a toner image by the toner of the developer, and the developed toner image is transferred to the transfer paper S (FIG. 9).

In this example, the photosensitive member 5 rotates clockwise. Further, the developer can be transported by rotating the developing sleeve 3 and the magnet 4 together. In each case, the magnet 4
Is used to form a magnetic brush on the surface of the developing sleeve 3 which is an example of the agent carrying member, by magnetically supporting the developer which is an example of the agent.

In FIG. 7, reference numeral 6 designates a doctor member for regulating the layer thickness of the developer on the developing sleeve 3, and reference numeral 7 designates the developer scraped off by the doctor member 6 for transferring the developer. While moving in the axial direction of the
This is a separator for dropping to the side of. Reference numeral 8 denotes a toner supply roller for supplying the toner from the toner bottle 9 into the casing 1.

Incidentally, the above-mentioned casing 1 is open on the exposed side so that the portion of the peripheral surface of the developing sleeve 3 located on the side of the photoreceptor 5 is exposed. And
Among the casing ends of the developing casing 1 sandwiching the developing sleeve 3, a sealing member 11 is attached to a casing end on the upstream side in the rotation direction of the photoconductor 5, and the sealing member 11 is provided with a developer in the developing casing. The upper part of the opening is sealed so as not to scatter outside.

In order to achieve such a function, an end portion of the casing downstream of the photosensitive member 5 in the rotation direction, that is, a casing end surface 12 which forms a part of the developing casing 1 and is located opposite to the photosensitive member 5. Alternatively, such a seal member may be provided, but in this case, the seal member disturbs the toner image on the photoreceptor. Therefore, such a seal member is placed on this side. It is inappropriate to provide. For this reason, the casing end face 12 on the downstream side is simply kept close to and facing the photoconductor 5.

FIG. 8 shows a state in which the developer 13 on the developing sleeve 3 is moving toward the developing section 10. During such a movement, the developer wraps around the portion of the casing end face 12 and adheres and deposits on this portion. When the amount of deposition increases and comes into contact with the surface of the photoconductor 5, carriers in the agent adhere to the photoconductor.

FIG. 9 shows a state in which such a carrier C has adhered to the toner image T on the surface of the photoreceptor 5, and the toner image T is transferred to the transfer paper S. Then, the peripheral portion including the portion to which the carrier is attached becomes white. This causes a so-called white spot on the image.

As shown in FIG. 10, the developer passes between the casing end face 12 and the photoconductor 5, or the developer attached to the casing end face 12 scatters downward, and the scattered developer If the photoconductor adheres to the charge wire of the charger 18, a leak may occur between the photoconductor and the photoconductor.

In view of this, as shown in FIG. 11, a means is also provided in which the carrier is directly captured by a dedicated magnet 14 provided in the vicinity of the casing end face 12, and the captured material is periodically cleaned and removed. A configuration is also known in which a dedicated magnet is formed in a rotating roller shape, and a carrier attached to the peripheral surface is scraped by a blade. Further, as shown in FIG. 12, the width w of the casing end face is reduced,
Measures have been taken to make it difficult for carriers to be deposited on this part.

However, in the former countermeasure example, a dedicated magnet is required, which leads to an increase in apparatus cost, and also in FIG.
In the example shown in, periodic cleaning must also be performed. In the latter countermeasure example, it is possible to eliminate the accumulation of carriers, but the amount of developer passing between the end surface of the casing and the photosensitive member increases, so that the developer adheres to process equipment such as a charger, and the surrounding area also increases. With a developer.

The above-mentioned problem may occur in a developing device using a one-component developer composed of a magnetic toner. If the scattered toner adheres to the background portion of the photoreceptor, the problem that background fouling occurs may occur. I can't escape.

Further, the various problems described above also occur in the magnetic brush cleaning device in the same manner.

[0018]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus having a magnetic brush device which can prevent a large amount of agent from being deposited on the end face of a casing with a simple structure.

[0019]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an agent-carrying member which is positioned opposite to a latent image-carrying member and is rotationally driven; And a casing provided with an opening on the exposed side, and a magnet provided inside the agent carrying member, which forms a magnetic brush on the surface of the agent carrying member by magnetically supporting the agent on the surface of the agent carrying member. In the image forming apparatus provided with a magnetic brush device having the magnet, the magnet captures the agent on the casing end surface located opposite to the surface of the latent image carrier and draws the agent toward the agent carrying member side. The moving direction of the surface of the latent image carrier is arranged so as to exert a magnetic field which gradually increases from the casing end face portion farthest from the agent carrying member toward the casing end face portion closest to the agent carrying member to the casing end face. The width of the housing end face is 2m along
An image forming apparatus characterized by being set to m or more is proposed.

At this time, it is advantageous to determine the strength of the magnetic force of the magnet such that the strength of the magnetic field at the portion of the casing end face closest to the agent carrying member is at least 200 gauss.

In each of the above structures, it is desirable that the surface roughness of the end face of the casing is set to 3S or less.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. First, a developing device will be described as a magnetic brush device, and an embodiment of an image forming apparatus having such a developing device will be described.

FIG. 1 is a view showing a main part of the image forming apparatus. The image forming apparatus shown here is also located opposite a drum-shaped photosensitive member 5 which is an example of a latent image carrier, and An agent-carrying member configured as a developing sleeve 3 that is driven to rotate, and a casing 1 whose opening side is open so that a portion of the agent-carrying member located on the latent image carrier side is exposed.
A magnet brush device is provided inside the agent carrying member, and has a magnet 4 having a magnet 4 that forms a magnetic brush by carrying the agent magnetically on the surface of the agent carrying member.

[0024] In this _example, the magnet 4 made of P 1 to P ₅ pole (7) is held in non-rotating state with respect to the sleeve 3 to rotate. The casing end surface 22 on the downstream side in the rotation direction of the photoconductor 5 forms a rectangular flat surface that is longer in the axial direction of the photoconductor than the surface width W in the rotation direction of the photoconductor. The casing end face 22 forms a part of the casing 1 and the photosensitive member 5
And the casing end face 22
Are formed so as to move away from the developing sleeve 3 which is an example of the agent carrying member as going toward the downstream side in the rotation direction of the photoconductor. A portion of the casing end face 22 which is closest to the developing sleeve 3, in the illustrated example, the portion on the most upstream side in the photoconductor rotation direction is the portion A, and a portion farthest from the developing sleeve 3, that is, a portion on the most downstream side. It is set as part B.

Here, the feature of the present embodiment is that the developer is caught on the casing end face 22 by the developing sleeve 3.
Is applied to the magnet 4, particularly the P ₁ and P ₂ poles provided near the end face of the casing. That is, the magnet 4 provided inside the agent carrying member composed of the developing sleeve 3
A casing end surface portion furthest away from the developer carrying member so as to capture the agent on the casing end surface 22 located opposite to the surface of the latent image carrier and draw it toward the developer carrying member comprising the developing sleeve 3 The arrangement is such that a magnetic field gradually increasing from (B) to the casing end face portion (A section) closest to the agent carrying member is applied to the casing end face 22. Moreover, the width W of the casing end face 22 along the moving direction of the surface of the latent image carrier made of the photoconductor 5 is set to 2 mm or more.

The developer on the developing sleeve 3 moves in the direction of the arrow together with the developing sleeve. At this time, a part of the developer scatters toward the casing end face 22 and adheres to the casing end face 22. Or try to attach.
Therefore, for example, when the above-described magnetic field is formed in the region of the casing end face 22 by the lines of magnetic force indicated by reference numerals M, M1, M2,... In FIG. The carrier can be captured by the magnetic field, and rides on the lines of magnetic force to develop the developing sleeve 3.
And can be collected.

FIG. 3 shows that when the amount of Gauss, which is the strength of the magnetic field in the portion A, is changed, the amount of carriers scattered to the casing end face 22 and not attracted to the developing sleeve 3 but remaining on the casing end face 22 is reduced. This is an example of experimental data showing how the change occurs. When the magnetic field intensity of the portion A is smaller than 200 Gauss, the force of attracting the developing sleeve 3 is weak,
There is a risk that the remaining amount of the carrier will increase significantly. If it is more than that, the remaining amount of the carrier can be suppressed. This data example is for the case where the surface roughness of the casing end surface is about 10S.

The strength of the magnetic field of the portion A depends on various conditions, but if the strength of the magnet 4 is determined so as to be about 200 gauss or more as described above, the amount of carrier scattering can be effectively reduced. It can be reduced, and can be efficiently collected toward the developing sleeve. Of the casing end face 22,
The strength of the magnetic force of the magnet 4 is determined so that the strength of the magnetic field in the portion closest to the agent carrying member composed of the developing sleeve 3 is 200 gauss or more. The strength of the magnetic field varies depending on the scattering speed of the carrier, the distance between the end of the casing and the magnet, and the like.

In order to achieve such a function, magnetic poles near the casing end face 22, for example, P ₁ and P ₂ poles,
What is necessary is just to magnetize with the magnetic force intensity | strength which forms a magnetic field of such intensity. Of course, in this case,
The shapes of the P ₁ and P ₂ poles and the arrangement thereof are also taken into consideration.

FIG. 5 shows how the strength of the magnetic field at the end face of the casing from the portion A to the portion B changes when the set magnetic force of the P ₁ and P ₂ poles (FIG. 1) is changed in three stages. It shows whether or not. L ₁ is a case where the setting force is the largest,
L ₂ is a case than the set force it small, L ₃ is a case where the setting field is the smallest. When the set magnetic force is the smallest, that is, when the set magnetic force is such that the magnetic flux density of the part A is about 200 Gauss, the magnetic flux density of the part B is 50
It is about Gaussian. In this way, by gradually decreasing the strength of the magnetic field from the part A to the part B, and applying the magnetic field to the part B, the carrier wrapped around the part B is transferred to the developing sleeve side. Can be magnetically attracted.

On the other hand, assuming that the magnetic field becomes stronger toward section B,
The carrier is attracted to the side of the developing sleeve and cannot be collected to the developing sleeve side, and the carrier may be scattered below the part B.

FIG. 4 shows that the carrier C wrapped around the casing end face 22 is the developer magnetic brush 1 of the developing sleeve 3.
3 schematically shows an example of the state of being collected on the side of the casing 3. When the carrier attached to the casing end face 22 is slid and the carrier is separated from the casing end face 22 along the magnetic field lines M, for example, If the surface condition of the surface is rough, the carrier is less likely to slide on the surface and is less likely to be separated from the surface, so that the surface condition is desirably smooth. In view of such a point, the casing end face 2
The surface roughness of No. 2 is set to 10S or less, preferably 3S or less. At this time, it is convenient to apply a tape or the like to improve the smoothness and to make the surface flat.

By doing so, even if the carrier wraps around the casing end surface 22, the wrapped carrier can be efficiently drawn to the developing sleeve side. This makes it possible to more reliably prevent the carrier from coming into contact with the photoreceptor 5, thereby preventing the occurrence of white spots on the image.

FIG. 2 shows that the surface of the casing end face 22 is intentionally made uneven so that the carrier easily adheres to this face. When the surface width W (FIG. 1) is changed, the carrier trapping on the casing end is changed. FIG. 5 shows an example of an experimental result for confirming how the amount changes. FIG. As can be seen, if the surface width W is smaller than 2 mm, the carrier scattered by the centrifugal force due to the rotation of the developing sleeve 3 may jump out of the casing 1 so as to jump over the casing end face 22. That is, the carrier may be scattered to a place where the magnetic field does not reach without being captured by the casing end face 22, and may fall.

In view of such a point, the width W of the casing end face 22 along the moving direction of the surface of the photoreceptor 5 is set to 2 mm or more. With such a configuration, it is possible to secure a sufficient casing end face width W so that the developer scattered by the centrifugal force due to the rotation of the developing sleeve 3 does not jump over the casing end face 22, whereby the developer is retained on the casing end face 22, In addition, this can be reliably drawn into the casing 1 and the developer can be prevented from scattering outside the casing.

Since the other basic configuration is the same as that shown in FIG. 7, further description of the basic configuration will be omitted.

In the above-described embodiments, a developing device using a two-component developer consisting of a carrier and a toner is applied. However, a developing device using a one-component developer consisting of only a magnetic toner is used. The present invention is also applicable to an image forming apparatus having the same. Further, the present invention can also be applied to a developing device in which the developing sleeve is stopped and the magnet inside the developing sleeve is rotated, or the developing sleeve and the magnet are rotated together. Further, the present invention can be applied to the casing end surface on the upstream side in the rotation direction of the photoconductor where the conventional sealing member 11 (FIG. 7) is provided. Scattering can be prevented and cost reduction can be achieved.

The embodiment of the present invention applied to an image forming apparatus having a developing device as an example of a magnetic brush device has been described above. FIG. 6 shows a magnetic brush cleaning device as another example of the magnetic brush device. An embodiment in which the present invention is applied to an image forming apparatus having the same will be described.

In FIG. 6, a pre-cleaning charger 28 is provided so as to face the photoconductor 5 rotating in the direction of the arrow. A plurality of magnets 104 are provided inside the pre-cleaning charger 28 on the downstream side.
Cleaning sleeve 32 agent is a configuration example of a carrier is arranged (the individual magnets are denoted by the sign of P ₁ to P _6). In the illustrated example, the cleaning sleeve 3 is used.
2 is rotatably driven in the direction of the arrow by a drive motor (not shown) with respect to the fixed magnet 104.

When the toner remaining on the photoreceptor 5 reaches the site of the pre-cleaning charger 28 after the transfer of the toner visual image, the pre-cleaning charger 28 causes the toner to be easily cleaned by corona discharge. , A charge of a certain polarity (positive in the example in the figure) is applied.

On the other hand, a cleaning agent C1 comprising a cleaning carrier and toner is carried on the cleaning sleeve 32 by the magnetic force of the magnet 104, and a magnetic brush is formed by the carrier. In this way, the magnet 104 provided inside the cleaning sleeve 32 carries the cleaning agent C1 on its surface with a magnetic force to form a magnetic brush. Cleaning agent C
Numeral 1 is a powder of a carrier and a toner which are frictionally charged to different polarities, and particles of a carrier made of a magnetic material are carried on the sleeve 32 by magnetic force, and the toner is electrostatically attached to the particles.

The residual toner charged by the pre-cleaning charger 28 removes the residual toner from the cleaning sleeve 3.
When the cleaning toner reaches the cleaning area X opposite to the cleaning area 2, the residual toner is electrostatically transferred to the cleaning carrier having a negative charge on the cleaning sleeve 32 to which the bias voltage (negative in the illustrated example) is applied. Adheres with suction and mechanical scavenging forces. In this way, the toner on the photoconductor is removed and cleaning is performed.

Next, the carrier to which the toner has adhered is carried on the cleaning sleeve 32 by magnetic force, and is conveyed while forming a magnetic brush. The carrier is made of, for example, a metal and has a predetermined polarity (negative in the illustrated example). Is applied to the toner collecting roller 33 at a position facing the toner collecting roller 33, and at this time, the toner is electrostatically attached to the collecting roller 33. At that time, a certain amount of toner is left on the cleaning sleeve 32 side, and this is the cleaning agent C.
1 is the toner. A collection blade 34 made of an elastic rubber, an elastic metal plate, or the like comes into contact with the toner collection roller 33, whereby the toner adhered to the collection roller 33 is scraped down. The scraped toner is discharged out of the cleaning device by a discharging screw 35.

On the other hand, the cleaning agent C1 on the cleaning sleeve 32 is further conveyed, and the thickness of the agent C1 becomes, for example, about 0.5 to 2.0 mm at the doctor blade portion 36 formed by a part of the casing 101. And enters the cleaning area X again.

The magnetic brush device comprising the above-described magnetic brush cleaning device is also a photosensitive member 5 which is an example of a latent image carrier.
And a casing 101 having an opening on the exposed side so that a portion of the agent holding member located on the side of the latent image carrier is exposed. And a magnet 104 that is provided inside the agent carrying member, and forms a magnetic brush by carrying the agent C1 on the surface of the agent carrying member with a magnetic force. The magnet 104, in this example, mainly two magnetic poles P ₁ and P ₂ , captures the cleaning agent C 1 and attracts the cleaning agent C 1 toward the cleaning sleeve 32 with respect to the casing end face 122 forming a part of the casing 101. Is formed. That is, the magnet 10
Reference numeral 4 denotes an agent carrying member which captures the agent on the casing end face 122 located opposite to the surface of the latent image carrier comprising the photosensitive member 5 and draws the agent toward the agent carrying member comprising the cleaning sleeve 32. It is arranged so as to apply a magnetic field which gradually becomes stronger from the furthest casing end face portion (part B) to the casing end face portion (part A) closest to the agent carrying member to the casing end face 122. Moreover, the width W of the casing end face 122 along the moving direction of the surface of the latent image carrier made of the photoconductor 5 is set to 2 mm or more.

With the above configuration, the cleaning agent adheres and accumulates on the casing end face 122 and adheres to the photosensitive member 5 or the cleaning agent C1 scatters outside the casing 101, just like the embodiment described above. It is possible to prevent such a problem that the cleaning agent drops down or the scattered cleaning agent adheres to the pre-cleaning charger 28 to cause a leak with the photoconductor 5. Line M in FIG. 6 shows the lines of magnetic force formed between the magnet P ₁ and P _2.

Also, in the embodiment shown in FIG.
Of the casing end face 122, the cleaning sleeve 3
The strength of the magnetic force of the magnet 104 is set so that the strength of the magnetic field of the portion (A portion) closest to the agent carrying member composed of No. 2 is at least 200 gauss, and the casing end surface portion farthest from the cleaning sleeve 32, that is, The magnetic field is applied to the portion B. Further, there is no difference from the previous embodiment in that it is desirable to set the casing end face 122 to a surface roughness of 10S or less, particularly 3S or less, and to make the surface flat.

The present invention is naturally applicable to an image forming apparatus having a magnetic brush cleaning device for rotating the cleaning sleeve 32 and the magnet 104 together.
Also, the configuration according to the present invention can be adopted for the casing end surface of the other end 111 of the casing 101.

[0049]

According to the first aspect of the present invention, the magnet captures the agent on the casing end face located opposite to the surface of the latent image carrier and draws the agent toward the agent carrying member.
Since the magnetic field is arranged so as to exert a magnetic field which gradually increases from the casing end face portion farthest from the agent carrying member toward the casing end face portion closest to the agent carrying member to the casing end face, the agent on the casing end face is dispensed with the agent. It can be attracted by the magnetic force to the side of the supporting member, thereby preventing a large amount of agent from being deposited on the end face of the casing and preventing the deposited agent from adhering to the surface of the latent image carrier. Moreover, since the width of the casing end surface along the moving direction of the surface of the latent image carrier is set to 2 mm or more, the agent scattered by centrifugal force due to the rotation of the agent carrying member jumps over the casing end surface, It is possible to prevent the magnetic brush device from being scattered from between the end face of the casing and the latent image carrier and to prevent the surroundings from being contaminated with the agent.

According to the second and third aspects of the present invention, the above-described functions and effects can be more reliably achieved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of a developing device.

FIG. 2 is a diagram illustrating an example of a correlation between a width of a casing end face and an amount of carrier captured on the casing end face.

FIG. 3 is a diagram showing an example of how the carrier scattering amount changes when the Gaussian amount at the upstream end of the casing end surface is changed.

FIG. 4 is a perspective view of a peripheral portion of the casing end surface showing a state in which a carrier that has wrapped around the casing end surface is drawn toward the developing sleeve.

FIG. 5 is a diagram showing an example of how the strength of a magnetic field changes from an upstream end to a downstream end of a casing end surface when a magnetic force of a magnet in a developing sleeve is set in three stages.

FIG. 6 is a sectional view showing an embodiment in which the present invention is applied to an image forming apparatus having a magnetic brush cleaning device.

FIG. 7 is a diagram illustrating a conventional example of a developing device.

FIG. 8 is a configuration diagram around a developing unit for explaining a problem caused by a carrier deposited on an end surface of a casing coming into contact with a photoconductor.

FIG. 9 is a schematic diagram of a configuration around a transfer portion for explaining that a white spot on an image occurs due to a carrier adhered to a photoconductor.

FIG. 10 is a peripheral configuration diagram of a casing end surface for describing a problem that occurs when a developer scatters from between a casing end surface and a photoconductor.

FIG. 11 is a configuration diagram showing a conventional example.

FIG. 12 is a configuration diagram showing another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing 4 Magnet 13 Magnetic brush 22 Casing end face 101 Casing 104 Magnet 122 Casing end face W width

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Sho-62-19670 (JP, U) Japanese Utility Model Sho 63-62859 (JP, U) (58) Fields surveyed (Int. Cl. ⁶ , DB name) G03G 15/08-15/095 G03G 21/10-21/12

Claims (3)

(57) [Claims] An image bearing member which is positioned opposite to a latent image carrier and rotates
A driven Ru-carrying member, such portion located to the latent image bearing member of the agent carrying member is exposed, a casing having an opening the exposed side, is provided inside of the carrying member, the agent carrying member And a magnet that forms a magnetic brush by carrying an agent with a magnetic force on the surface of the image forming apparatus, wherein the magnet is located at an end surface of the casing that faces the surface of the latent image carrier. A magnetic field gradually increasing from the casing end surface portion farthest from the agent carrying member toward the casing end surface portion closest to the agent carrying member with respect to the casing end surface so as to capture the upper agent and draw it toward the agent carrying member side. And the width of the casing end surface along the moving direction of the surface of the latent image carrier is 2 mm.
mm. 2. The image forming apparatus according to claim 1, wherein the strength of the magnetic force of the magnet is determined such that the strength of the magnetic field at a portion of the casing end face closest to the agent carrying member is 200 gauss or more. 3. The image forming apparatus according to claim 1, wherein a surface roughness of an end face of the casing is set to 3S or less.