JP6677930B2 - Developing device and image forming device - Google Patents

Description

  The present invention relates to a developing device and an image forming device.

  Conventionally, a developer carrier that carries a two-component developer composed of a magnetic carrier and a toner on the surface thereof is disposed to face a surface of the developer carrier with a predetermined gap, and is conveyed to a development area. 2. Description of the Related Art A developing device including a developer regulating member that regulates the amount of a developer is known.

  For example, Patent Document 1 discloses the following developing device. This developing device includes a developing carrier containing a magnetic pole generating means having a plurality of magnetic poles, and a round bar member made of a magnetic material, which is a developer regulating member. A magnetic field is generated between the layer thickness regulating pole and the round bar member by the magnetic pole generation means included in the development carrier, and a predetermined amount of spikes is generated in the developer on the development carrier, which is effective. The layer thickness is regulated. In this developing device, the maximum position of the magnetic flux density distribution in the normal direction of the layer thickness regulating pole, the so-called peak position, is a position away from the round bar member by a predetermined distance toward the downstream side in the rotation direction of the developing carrier. As a result, it is possible to reduce the accumulation of the developer on the downstream side of the round bar member in the rotation direction of the development carrier, and to reduce the image quality loss caused by the irregularly accumulated developer being used for development. I can do it.

  However, the developing device of Patent Document 1 uses a round bar member made of a magnetic material for the development regulating member. Therefore, in the principle of the round bar member made of a magnetic material, the developing device is located downstream of the round bar member in the rotation direction of the development carrier. It was not possible to completely prevent the generation of the agent pool generated on the side.

In order to solve the above-mentioned problem, the present invention provides a developer carrier having a magnetic field generating means for generating a plurality of magnetic poles , and a developing sleeve rotatable around the fixed magnetic field generating means. A cylindrical developer regulating member disposed opposite to the developer carrier to regulate the amount of developer carried on the developer carrier, and develops the electrostatic latent image formed on the image carrier. In the developing device,
The developer regulating member is a magnetic material on at least a part of the peripheral surface of the developer regulating member on the upstream side in the developer conveying direction of the developer carrier from a portion facing the developer carrier, is characterized in than said facing portion including a non-magnetic material on at least a portion of the downstream side in the developer transport direction.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the agent pool which arises downstream in a developer conveyance direction is suppressed, and a favorable image can be obtained.

FIG. 1 is a schematic configuration diagram illustrating a configuration of a main part of a color copying machine that is an image forming apparatus according to an embodiment. FIG. 2 is an enlarged sectional view illustrating an example of an image forming unit of the image forming apparatus. FIG. 4 is an explanatory diagram of a regulating member in a conventional developing device. FIG. 2 is a schematic configuration diagram illustrating an example of a regulating member in the developing device according to the first embodiment. Explanatory drawing which shows an example of a structure of the fixing part of the regulating member. 9 is a graph showing a relationship between a ratio of a magnetic member and a non-magnetic member and a gap or density unevenness between a developing roller and a regulating member. FIG. 5 is an explanatory diagram of a position of a boundary between a magnetic member and a non-magnetic member with respect to a developing roller. FIG. 9 is a schematic configuration diagram illustrating an example of a casing near a regulating member in the developing device according to the second embodiment. FIG. 13 is a schematic configuration diagram illustrating an example of a regulating member in a developing device according to a third embodiment.

Hereinafter, an embodiment in which the present invention is applied to a printer which is an electrophotographic image forming apparatus will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram illustrating a configuration of a main part of a color copying machine 100 that is an image forming apparatus according to the present embodiment.
As shown in FIG. 1, in a color copying machine 100 according to the present embodiment, a plurality of photosensitive drums 1a, 1b, 1c, 1d arranged opposite to an intermediate transfer belt 5 are individually provided with developing devices 4a, 4b, 4c, 4c. 4d. This is a so-called tandem-type color copying machine provided with an image forming unit for forming a single-color toner image on each photoconductor and sequentially transferring the single-color toner images to record a composite color image on a sheet.
The configuration of each image forming unit is the same except that the color of the toner used is different. Therefore, the following description will be made omitting the suffixes a, b, c, and d added to the end of the reference numeral of each member.

  As a specific operation of the image forming unit, first, a latent image is optically formed at a writing position by the writing unit 3 on the surface of the photosensitive drum 1 uniformly charged by the charging roller 2 serving as a charging unit. Then, a visualized image of the toner is formed by the developing device 4 as a developing unit. The toner image formed on the surface of the photosensitive drum 1 is temporarily transferred to the intermediate transfer belt 5 by the intermediate transfer belt transfer unit 12, and is transferred to the transfer paper conveyed through the registration roller pair 6 as a paper transfer unit. The toner image on the intermediate transfer belt 5 is transferred by the belt 7. The transfer paper onto which the toner image has been transferred is conveyed to fixing means 8 by a paper transfer belt 7, where the toner image on the transfer paper is fixed by heat and discharged outside the machine.

The untransferred toner on the photoconductor drum 1 that has not been transferred to the intermediate transfer belt 5 is scraped off from the photoconductor by the photoconductor cleaning blade 9. The residual charge on the photosensitive drum 1 is eliminated by the electricity elimination means to prepare for the next image forming operation.
The untransferred toner scraped off from the photoconductor drum 1 by the photoconductor cleaning blade 9 passes through a collected toner transport path 14 indicated by a broken line in the drawing and is stored in a waste toner storage container 15. Further, the untransferred toner on the intermediate transfer belt 5 and the toner of the pattern image for process control are also scraped off from the intermediate transfer belt 5 by the intermediate transfer cleaning blade 13, and similarly, the waste toner passes through the collected toner conveyance path 14. It is stored in the storage container 15.

Next, replenishment of the new toner to the developing device 4 will be described.
The new toner filled in the toner cartridge is supplied to the toner hopper 11 on the rear side of the machine main body by the toner supply device 10. The toner stored in the toner hopper 11 is rotated by rotating the toner supply screw in the toner hopper when the toner concentration in the developing device 4 is determined to be low by the toner concentration detecting means 21 shown in FIG. An appropriate amount of toner is supplied to the developing device 4 from inside the toner hopper. To detect the remaining amount of toner in the toner bottle, a remaining amount detection sensor for detecting the presence or absence of toner is disposed in the toner hopper. When this sensor detects that there is no toner, the toner supply device 10 is requested to supply toner. If the remaining amount detection sensor does not detect the presence of the toner even after requesting the supply of the toner for a predetermined time, it is determined that there is no remaining toner in the toner bottle.

Next, the configuration of the image forming unit will be described in detail.
FIG. 2 is an enlarged sectional view illustrating an example of an image forming unit of the image forming apparatus.
As shown in FIG. 2, the developing device 4 and the photosensitive drum 1 are, for example, a process cartridge integrally formed. This process cartridge is formed detachably with respect to the main body of the image forming apparatus by integrating the charging roller 2 and the photosensitive member cleaning blade 9 as cleaning means in addition to the photosensitive drum 1 and the developing device 4. .

  The developing device 4 is provided with a developing roller 16 for forming a toner image on the photosensitive drum 1 with respect to the electrostatic latent image optically formed by the writing unit 3. The developing roller 16 is a developer carrier that carries a two-component developer (hereinafter, referred to as a developer) including a toner and a magnetic powder carrier on the surface. On the upstream side of the developing area of the developing roller 16, a regulating member 17 which is a developing regulating member for regulating the amount of the developer on the developing roller to a predetermined amount is arranged. A two-component developer in which toner particles and magnetic particles (carrier) are mixed is contained in a developing tank portion in the developing device 4, and the developer is rotated by the two screw members 18 and 19 at a constant speed. The toner and the carrier are frictionally charged by agitation while circulating through the inside. The transport screw 18, which is one of the two screw members 18 and 19, supplies a part of the developer to the developing roller 16, and the developing roller 16 magnetically carries the developer and transports the developer. I do.

  Below the other screw 19 of the two screw members 18 and 19, a toner concentration detecting means 21 is disposed. The toner density in the developing tank is measured as needed by the toner density detecting means 21 and is controlled so that the toner density falls within an appropriate value. After the toner from the toner replenishing unit is once stored in the sub-hopper, when the toner concentration in the developing tank is detected to be low by the toner concentration detecting unit 21, the toner is rotated for a time converted by a predetermined conversion formula. An appropriate amount is supplied to the developing toner supply port 23 by the supplied toner supply screw 22.

In the present embodiment, the configuration of the developing device 4 is preferably as follows.
For example, the developer carrying amount per unit area on the developing roller 16 at a position facing the photoconductor is preferably 30 to 70 (mg / cm ² ), and more preferably 40 to 60 (mg / cm ² ). . If the developer carrying amount is less than 30 (mg / cm ² ), it is necessary to increase the electric field applied between the developing roller and the photoconductor, which is disadvantageous for carrier adhesion. On the other hand, when the developer carrying amount is more than 70 (mg / cm ² ), the filling density of the developer in the space between the photoreceptor and the developing roller increases, and the developer There is a tendency that stagnation occurs and the fluidity of the developer decreases. As the fluidity decreases, toner is not smoothly supplied to the electrostatic latent image on the photoreceptor, and image density reduction and density unevenness are likely to occur.

In this embodiment, when the peripheral speed of the developing roller 16 is Vs and the peripheral speed of the photosensitive member is Vp, it is desirable to adjust Vs / Vp to be in the range of 1.5 to 2.5. As a result, a high-quality image can be obtained. If Vs / Vp is lower than 1.5, the passage time of the developer passing through the electrostatic latent image is shortened, so that the developing ability is reduced. When an image having a large area is output, The image density is significantly reduced. It is known that an abnormal image occurs when Vs / Vp is higher than 2.5, that is, when the contact time between the developer and the electrostatic latent image is increased.
The abnormal image as used herein refers to a decrease in image density at the rear end of the solid image portion, image omission, particularly, image omission that is conspicuous at the rear end of the halftone image, and image density at the boundary between the solid image and the halftone image. Mean change. Each of these appears at a place where the latent image potential is different or at the boundary of the image density where the latent image potential changes discontinuously and abruptly. This is caused by the movement of the toner in the developer during the passage of the developer through the development nip and the transient phenomenon when the developer layer having the capacitance as a derivative in the first place passes through a different discontinuous development electric field. It is considered something.

  Furthermore, in the present embodiment, the developer has a toner concentration in a range of 5.0 to 9.0 (wt%), an average charge amount Q / M of 15 to 60 (−μC / g), and more preferably. It is desirable to use a carrier having a concentration of 20 to 40 (-μC / g) from the viewpoint of optimizing the coverage of the carrier with the toner and the fluidity of the developer. When the toner concentration is lower than 5.0 (wt%), the charge amount Q / M of the developer tends to increase, and it is necessary to set the developing potential for developing the electrostatic latent image on the photoconductor higher. And the life of the photoconductor may be shortened. Further, when the charge amount Q / M of the developer exceeds 60 (-μC / g), the possibility that the image density decreases is increased. When the toner concentration is higher than 9.0 (wt%), the charge amount Q / M of the developer tends to decrease. When the charge amount Q / M of the developer is less than 15 (−μC / g), toner scattering is apt to occur, and as the toner scattering level becomes worse, the so-called background stain, in which the image background is stained with toner, is reduced. This causes image quality degradation. Therefore, a developer having a toner concentration in the range of 5.0 to 9.0 (wt%) and an average charge amount Q / M of 15 to 60 (-μC / g) is used. As a result, stable image quality can be obtained over a long period of time even with a developer using a small particle size carrier and a small particle size toner.

The coverage of the carrier with the toner is 10 to 80%, preferably 20 to 60%. The coverage is calculated by the following equation.
Coverage (%) = (Wt / Wc) × (ρc / ρt) × (Dc / Dw) × (１ ／) × 100
In the above formula, Dc is the weight average particle diameter of the carrier (μm), Dw is the weight average particle diameter of the toner (μm), Wt is the weight of the toner (g), Wc is the weight of the carrier (g), and ρt is the toner true weight. The density (g / cm ³ ) and ρc represent the true carrier density (g / cm ³ ).
The weight average particle size is calculated based on the particle size distribution of particles measured on a number basis (the relationship between the number frequency and the particle size). In this case, the weight average particle size Dw is represented by the following equation.
Dw = {1 / {(nD3)} × {(nD4)}
In the above formula, D indicates the representative particle size (μm) of the particles present in each channel, and n indicates the total number of particles present in each channel. The channel indicates a length for equally dividing the particle size range in the particle size distribution map. In the present embodiment, a length of 2 μm is employed. The lower limit of the particle diameter stored in each channel was adopted as the representative particle diameter of the particles present in each channel.

  The developer used in the exemplary embodiment has a weight average particle diameter of the toner of 4.0 to 8.0 μm, and a ratio (Dw) between the weight average particle diameter (Dw) and the number average particle diameter (Dn) of the toner. / Dn) is preferably 1.20 or less. Although reducing the particle size of the toner is indispensable for increasing the resolution, as a side effect, the fluidity and the storage stability tend to be deteriorated. If the toner particle size is less than 4.0 μm, the fluidity of the developer is extremely deteriorated, and it is difficult to ensure a uniform toner concentration in the developer. In addition, the reduction in toner particle diameter tends to increase the coverage of the carrier. If the coverage is too high, there is a concern that acceleration of carrier contamination and toner scattering may occur.

  As a means for improving the fluidity of the toner and the developer, there is a method of adding a large amount of an additive to the toner. However, this method cannot be expected to be essentially improved because side effects occur. However, by making the particle size distribution of the toner uniform, the side effect of reducing the particle size of the toner can be overcome. That is, it is desirable that the weight average and number average particle diameter ratio Dw / Dn of the toner is close to 1. When the ratio is set to 1.20 or less, the effect of suppressing the deterioration of the fluidity can be obtained. In this case, the toner concentration can be made uniform. As described above, by setting the weight average particle diameter of the toner to 4.0 to 8.0 μm and the weight average to number average particle diameter ratio Dw / Dn to 1.20 or less, the image density stability is improved. As a result, the resolution can be improved, and a higher quality image can be obtained. By setting the ratio of the number of particles of 3 μm or less in the toner particle size distribution to 5% or less, the quality improvement effect in fluidity and storability is remarkable. Good levels are obtained.

  The particle size distribution of the toner can be measured by various methods. In the present embodiment, the measurement is performed by using a small-hole passage method (a Coulter counter method). As a measuring device, COULTERCOUNTERMODELTA2 (manufactured by Coulter Inc.) was used, and an interface for outputting a number distribution and a volume distribution was connected, and an aperture (pore) of 100 μm was used. As a measurement method, first, a toner measurement sample is dispersed in a surfactant added to an electrolytic aqueous solution. The dispersed sample is injected into another 1% NaCl electrolytic solution, and a current is passed between the electrodes through an electrolytic solution having electrodes placed on both sides of the aperture of the aperture tube. The particle size distribution of 2 to 40 μm particles is measured from the resistance change at this time, and the number average particle size and weight average particle size are determined from the average distribution.

  It is preferable to add a fluidity imparting agent to the toner. Various fluidity-imparting agents can be used, and it is preferable to use hydrophobic silica fine particles and hydrophobic titanium oxide fine particles in combination. In particular, when stirring and mixing are performed using particles having an average particle diameter of 50 (nm) or less, the electrostatic force with the toner and the van der Waals force can be reduced, and the fluidity of the toner can be improved. Can be planned. As a result, a desired charge level of the developer can be obtained, good image quality can be obtained, and the transfer residual toner can be reduced. Further, while the titanium oxide fine particles are excellent in environmental stability and image density stability, they tend to deteriorate charging start-up characteristics. Therefore, when the added amount of the titanium oxide fine particles is larger than the added amount of the silica fine particles, it is considered that the influence of the deterioration of the charging start-up characteristics is increased. However, when the addition amount of the hydrophobic silica fine particles is in the range of 0.3 to 1.5 (wt%) and when the hydrophobic titanium oxide fine particles is in the range of 0.2 to 1.2 (wt%), the charge rising characteristics are large. Even if copying is repeated without loss, stable image quality can be obtained, and toner scattering can be suppressed.

  Further, by adding hydrophobic silica having a large particle diameter having an average particle diameter of 80 to 140 (nm), the performance with respect to transferability and developability is further improved. In particular, the quality improvement effect is remarkable in a developer using a toner having a small particle diameter such as a toner having an average particle diameter of 7 (μm) or less. That is, the additive having a large particle size acts as a spacer between the toner particles, so that aggregation of the toner at the time of toner transfer compression and burying of the additive on the toner surface at the time of idle stirring of the developing machine can be suppressed. As a result, a solid image density unevenness due to transfer failure and a decrease in toner fluidity due to burying of the additive do not occur, and a high-quality image can be obtained over a long period of time.

The weight average particle diameter Dw of the carrier in the developer is 20 to 60 (μm), and more preferably 20 to 40 (μm). When the weight average particle diameter Dw of the carrier is larger than 60 (μm), the magnetic carrier holding force on the photoreceptor is strong and the carrier is hard to adhere, but the carrier surface area per unit weight is small. When the toner density is increased in order to obtain a high image density, the background smear rapidly increases. Also, when the dot diameter of the latent image is small, the variation in the dot diameter becomes large. On the other hand, when the weight average particle diameter Dw of the carrier is smaller than 20 μm, the magnetic moment per carrier particle is reduced, the magnetic carrier holding force on the developing roller is weakened, and carrier adhesion is likely to occur.
The magnetic moment per carrier particle when a magnetic field of 1000 · (10 ³ / 4π) [A / m] is applied is 70 (A · m ² / kg) or less. If the height is higher than this, the magnetic brush becomes hard, and it is easy to produce ear traces and blurred images. The lower limit is not particularly limited, but is usually about 50 (A · m ² / kg). If the magnetic moment is less than 50 (A · m ² / kg), the magnetic carrier holding force on the developing roller is reduced, and carrier adhesion is likely to occur.

  The magnetic moment of the carrier can be measured as follows. Using a BH tracer (BHU-60 / manufactured by Riken Denshi), 1.0 g of carrier particles are packed in a cylindrical cell and set in an apparatus. The magnetic field is gradually increased and changed to 3000 Oe, then gradually reduced to zero, and then the magnetic field in the opposite direction is gradually increased to 3000 Oe. After the magnetic field is gradually reduced to zero, a magnetic field is applied in the same direction as the first. In this manner, the BH curve is illustrated, and the magnetic moment of 1000 Oe is calculated from the figure.

Next, the structure of the regulating member 17 which is a developer regulating member and its surroundings will be described in detail.
The developing roller 16 includes a cylindrical developing sleeve made of a nonmagnetic material and a magnet 25 of a magnet roller as a magnetic field generating means fixed inside, and can freely rotate around the magnet. it can. In the magnet 25, a main pole (P1 pole) is arranged at a portion facing the photosensitive drum 1, and S poles and N poles are alternately arranged in a counterclockwise direction. Further, a magnetic pole of the same polarity is arranged adjacent to a position downstream of the portion facing the photosensitive drum 1 in the rotation direction of the developing roller 16 in order to separate the developer from the developing sleeve. The height (load amount) of the developer on the developing roller 16 is regulated by the regulating member 17 arranged in the developing case. An opening is provided at a portion of the main body case of the developing device where the developing roller 16 and the photosensitive drum 1 are opposed to each other. I have. The electrostatic latent image on the photosensitive drum 1 is developed by the toner on the developing roller 16 to become a toner image.

FIG. 3 is an explanatory view of a regulating member in a conventional developing device.
Conventionally, in a two-component developing method in which development is performed using a two-component developer containing toner and magnetic particles, a developer regulating member (hereinafter referred to as a regulating member) is used to adjust an appropriate amount of the developer in a development area. A predetermined gap is provided at a position facing the carrier. In recent years, since demands for downsizing and cost reduction of image forming apparatuses have been increasing, for example, not only a regulating member but also a member for attaching the regulating member is required, and a plate that requires a large arrangement space is required. There is an example in which a round bar-shaped restricting member is employed instead of the restricting member having a shape of a circle.

However, in a developing device using a cylindrical round bar member as the developer regulating member, the following problems occur depending on the material of the round bar member.
For example, when the round bar member is a non-magnetic material, as shown in FIG. 3A, the round bar member 117 and the developing roller 16 are combined with each other in order to obtain a desired developer regulated amount (hereinafter, a pumping amount). (Indicated by the arrow A in the figure) must be narrowed. For this reason, it is necessary to increase the precision of the parts, and the stress on the developer increases.
When the round bar member is made of a magnetic material, as shown in FIG. 3B, the developer magnetically attracted to the round bar member 217 moves downstream in the developer conveying direction indicated by a range B in the figure. Accumulates on the side, causing a reservoir of agent. When the agent pool collapses and is conveyed irregularly to the developing carrier, unevenness in the amount of pumping occurs, which causes deterioration in image quality and abnormal images.

  Therefore, in the developing device of the present embodiment, as shown in FIG. 3C, the material of the regulating member 17 is composed of a magnetic member 17a and a non-magnetic member 17b. Thus, the gap between the round bar member 117 indicated by the arrow C and the developing roller 16 can be set wider than the round bar member 117 illustrated in FIG. 3A, and also illustrated in FIG. It is possible to suppress the generation of the agent pool like the round bar member 217. Hereinafter, the embodiment will be described in detail.

[Example 1]
Next, a first example (hereinafter, referred to as an example 1) of the developing device according to the present embodiment will be described.
FIG. 4 is a schematic configuration diagram illustrating an example of the regulating member 17 of the developing device in the present embodiment.
As shown in FIG. 4, the regulating member 17 includes a magnetic member 17a and a non-magnetic member 17b. Specifically, the magnetic member 17a is arranged on the upstream side in the developer conveying direction, which is the rotation direction of the developing roller 16, and the non-magnetic member 17b is arranged on the downstream side in the developer conveying direction. By configuring the regulating member 17 in this manner, the gap between the developing roller 16 and the regulating member 17 necessary for obtaining a desired regulation amount can be widened by the magnetic member 17a disposed on the upstream side. it can. In addition, by disposing the non-magnetic member 17b on the downstream side, it is possible to suppress the generation of the agent pool generated by the regulating member formed only of the magnetic member.

  In addition, the regulating member 17 of the present embodiment bonds the magnetic member 17a and the non-magnetic member 17b, each of which is obtained by shaving a magnetic round bar member and a non-magnetic round bar member in half from a cylindrical shape. It is formed by things. The invention is not limited to this, and the magnetic member 17a and the non-magnetic member 17b that have been cut may be formed by magnetization.

FIG. 5 is an explanatory diagram illustrating an example of a configuration of a fixing portion of the regulating member 17.
Since the regulating member 17 of this embodiment has a biased magnetization characteristic, the regulating member 17 is easily rotated with respect to the developing device 4 by the influence of the magnet in the developing roller 16 or the pressure of the developer. If the regulating member 17 rotates, the original performance cannot be obtained. Therefore, in the present embodiment, the regulating member 17 is fixed as follows so as not to rotate. That is, as shown in FIG. 5, the end of the regulating member 17 is cut into a D shape, and a hole having the same shape as the D shape is also opened on the developing case 20 side. Then, by inserting the end of the regulating member 17 into the hole on the developing case 20 side, the regulating member 17 is fixed so as not to rotate.

Next, a comparative experiment using a regulating member of a different material will be described.
In this experiment, the comparison between the gap between the developing roller and the regulating member and the occurrence of density unevenness was performed using three regulating members having different materials. Specifically, the regulating member of Example 1 described with reference to FIG. 5, the regulating member of Comparative Example 1 in which the material of the regulating member is entirely formed of a magnetic member, and the comparative member in which the material of the regulating member is entirely formed of a non-magnetic member The regulating member of Example 2 was used.
In order to make the amount of the developer pumped up by the developing roller appropriate, it is necessary to adjust the gap between the developing roller and the regulating member. In this experiment, the gap of each regulating member was adjusted so that the amount of the developer pumped up to obtain a desired image was adjusted. Table 1 below shows the results of the test.

The criterion for determining the density unevenness is “」 ”when there is no problem, and“ × ”when it is not acceptable.
As shown in Table 1, in the regulating member of Comparative Example 1, density unevenness occurred due to the agent pool generated on the downstream side of the regulating member, and the density unevenness determination was “x”. Further, in the regulating member of Comparative Example 2, since the material was a non-magnetic member, no agent accumulation occurred, and the density unevenness determination was “「 ”. However, since the gap between the developing roller and the regulating member is 0.22 mm, and the design tolerance is strict at this value, it is difficult to actually mount the device.
On the other hand, with the regulating member of Example 1, the density unevenness determination was “○”. Further, the gap between the developing roller and the regulating member could be made almost the same width as in Comparative Example 1.

Next, the ratio between the magnetic member 17a and the non-magnetic member 17b in the regulating member 17 will be described.
FIG. 6 is a graph showing the relationship between the ratio of the magnetic member 17a and the non-magnetic member 17b and the gap or density unevenness between the developing roller and the regulating member.
In the regulating member 17 of this embodiment, the ratio of the magnetic member 17a and the non-magnetic member 17b is set to 50%, but either ratio may be increased.
For example, as shown in FIG. 6, as the ratio of the magnetic member to the ratio of the non-magnetic member increases, the gap between the developing roller and the regulating member can be widened, but it is difficult to suppress density unevenness. Conversely, as the ratio of the non-magnetic member to the ratio of the magnetic member increases, the gap between the developing roller and the regulating member becomes narrower, but density unevenness can be suppressed. Therefore, the ratio between the magnetic member and the non-magnetic member may be such that the gap between the developing roller and the regulating member and the density unevenness are within the allowable ranges.

Next, the position of the boundary between the magnetic member 17a and the non-magnetic member 17b with respect to the developing roller 16 (hereinafter simply referred to as the boundary of the member) will be described.
FIG. 7 is a diagram illustrating the position of the boundary between the magnetic member 17a and the non-magnetic member 17b with respect to the developing roller 16.
In the present embodiment, the closest position between the developing roller 16 and the regulating member 17 is arranged so as to be the boundary of the member, but the boundary of the member is inclined to either the upstream side or the downstream side in the developer conveying direction. You may.
For example, as shown in FIG. 7, when the boundary of the member is inclined upstream in the developer conveying direction with respect to the closest position between the developing roller 16 and the regulating member, the influence of the non-magnetic member 17b increases, Gap tends to occur. On the other hand, if the magnetic member 17a is tilted downstream in the developer transport direction, the influence of the magnetic member 17a becomes large, and the developer tends to accumulate downstream in the developer transport direction. Therefore, if the gap between the developing roller and the regulating member and the density unevenness are within the respective allowable ranges, the boundary range of the member may be inclined with respect to the closest position between the developing roller 16 and the regulating member 17. Good.

  In this embodiment, the upstream side of the regulating member 17 in the developer conveying direction is entirely formed of a magnetic member, and the downstream side is entirely formed of a non-magnetic member. However, at least the following configuration is sufficient. That is, on the peripheral surface of the regulating member, at least part of the upstream side in the developer conveying direction of the developer carrying member with respect to the portion facing the developer carrying member, the magnetic material is located downstream of the facing portion in the developer carrying direction. It is sufficient that at least a part of the side includes a magnetic material.

[Example 2]
Next, a second example (hereinafter, referred to as an example 2) of the developing device according to the present embodiment will be described.
The developing device of the present embodiment has the same configuration as the developing device 4 of the first embodiment except that the shape of the developing case is different. Therefore, the same parts as those of the developing device 4 of the first embodiment are denoted by the same reference numerals, and the description will be omitted.

FIG. 8 is a schematic configuration illustrating an example of a configuration of a casing near a regulating member of a developing device according to the second exemplary embodiment.
As shown in FIG. 8, in the developing device of the present embodiment, the developing case 28 extends to a position close to the regulating member 17 on the downstream side in the developer conveying direction. By forming the developing case 28 in such a shape, the agent accumulation region on the downstream side of the regulating member 17 in the developer conveyance direction can be geometrically closed, so that the agent accumulation can be further reduced.

[Example 3]
Next, a third example (hereinafter, referred to as an example 3) of the developing device according to the present embodiment will be described.
Note that the developing device of the present embodiment has the same configuration as the developing device 4 of the first embodiment except that the shape of the regulating member 27 is different. Therefore, the same parts as those of the developing device 4 of the first embodiment are denoted by the same reference numerals, and the description will be omitted.

FIG. 9 is a schematic configuration diagram illustrating an example of the regulating member 27 according to the third embodiment.
As shown in FIG. 9, in the regulating member 27 of the present embodiment, the shape of the non-magnetic member 27b is as follows. That is, the surface of the non-magnetic member 27b facing the developing roller 16 has a curved surface along the surface of the developing roller 16. With such a configuration, the agent accumulation region generated downstream of the regulating member 27 in the developer conveyance direction can be geometrically closed, and the agent accumulation can be further reduced.

What has been described above is merely an example, and each embodiment has a specific effect.
(Aspect A)
A developer carrying member such as a developing roller 16 including a magnetic field generating means such as a magnet 25 for generating a plurality of magnetic poles, carrying a two-component developer composed of a magnetic carrier and a toner on the surface and conveying the surface; A developer regulating member such as a cylindrical regulating member 17 which is disposed opposite to the developer carrying member and regulates the amount of the developer carried on the developer carrying member; In a developing device such as a developing device 4 that develops an electro-latent image, the developer regulating member is configured to develop the developing carrier more than a portion of the peripheral surface of the developer regulating member facing the developer carrier. A magnetic material is included in at least a part of the upstream side in the developer transport direction, and a magnetic material is included in at least a part of the downstream side in the developer transport direction than the facing portion.

In the developing device using the round bar member as the developer regulating member, the following problems occur depending on the material of the round bar member.
For example, when the round bar member is a non-magnetic material, the gap between the round bar member and the developer carrier must be narrowed in order to obtain a desired developer regulation amount (hereinafter, a pumping amount). Therefore, it is necessary to increase the precision of the parts, and the stress on the developer increases. Further, when the round bar member is a magnetic material, the developer magnetically attracted to the round bar member accumulates on the downstream side in the developer transport direction, and the agent accumulates. When the agent pool collapses and is conveyed irregularly to the developing carrier, unevenness in the amount of pumping occurs, which causes deterioration in image quality and abnormal images.

  In this aspect, the gap between the developer carrying member and the developer regulating member on the upstream side in the developer transport direction can be widened by forming the upstream side of the developer regulating member in the developer transport direction with a magnetic material. This makes it possible to increase the precision of parts and suppress stress on the developer. Further, since the downstream side of the developer regulating member in the developer conveying direction is formed of a non-magnetic material, the developer is not magnetically attracted to the developer regulating member at the downstream side of the developer conveying direction. It is possible to suppress accumulation of the agent that occurs on the downstream side in the developer conveying direction with respect to the agent regulating member. Therefore, it is possible to reduce unevenness in the amount of pumping that occurs when the agent pool collapses and is conveyed to the developing carrier, and it is possible to perform favorable image formation.

(Aspect B)
The developing device according to Aspect A is characterized in that the developer regulating member such as the regulating member 17 is fixed to an apparatus main body such as the developing case 20.
In this aspect, as described in the first embodiment, the developer regulating member can be fixed so as not to rotate, and the performance of the developer regulating member can be maintained.

(Aspect C)
In the developing device according to Aspect A or B, a part of a casing of an apparatus main body such as a developing case 28 disposed around the developer regulating member such as the regulating member 17 is moved in the developer conveying direction of the developer regulating member. Characterized in that it has a shape close to the surface on the downstream side.
In this aspect, as described in the second embodiment, since the agent accumulation region on the downstream side of the developer regulating member in the developer conveyance direction can be geometrically closed, the agent accumulation can be further reduced.

(Aspect D)
In the developing device according to any one of Aspects A to C, a downstream side of the developer regulating member such as the regulating member 27 in the developer transport direction has a shape along a surface of the developer carrying member such as the developing roller 16. It is characterized by the following.
In this aspect, as described in the third embodiment, the agent accumulation region on the downstream side of the developer regulating member in the developer conveyance direction can be geometrically closed, so that the agent accumulation can be further reduced.

(Aspect E)
In an image forming apparatus for forming an image by transferring an image obtained by developing a latent image formed on a latent image carrier by a developing device onto a recording material, the developing device may include any one of modes A to D It is characterized by using a developing device.
In the present embodiment, the unevenness of the pumping amount caused by the collapse of the agent pool and the conveyance to the developing carrier can be reduced, so that good image formation can be performed.

DESCRIPTION OF SYMBOLS 1 Photoconductor drum 2 Charging roller 3 Writing means 4 Developing device 5 Intermediate transfer belt 6 Registration roller pair 7 Paper transfer belt 8 Fixing means 9 Photoconductor cleaning blade 12 Intermediate transfer belt transfer means 16 Developing roller 17 Example 1, Example Control member 17a according to 2 Magnetic member 17b Non-magnetic member 20 Developing case 25 according to the first embodiment Magnet 27 Control member 27b according to the third embodiment Non-magnetic member 28 according to the third embodiment Developing case 100 according to the second embodiment Color copying Machine

JP 2008-275719 A

Claims (5)

A magnetic field generating means for generating a plurality of magnetic poles , and a developer carrier having a developing sleeve rotatable around the fixed magnetic field generating means ; and a developer carrier arranged opposite to the developer carrier. A developing device for developing an electrostatic latent image formed on the image carrier, the developing device comprising: a developing device for developing an electrostatic latent image formed on an image carrier; At least a portion of the peripheral surface of the developer regulating member on the upstream side of the developer carrier in the developer transport direction with respect to the portion facing the developer carrier is a magnetic material, and the developer transport is more than the facing portion. a developing device which comprises a non-magnetic material on at least a portion of the downstream side in the direction.   The developing device according to claim 1, wherein the developer regulating member is fixed to an apparatus main body.   3. The developing device according to claim 1, wherein a part of a casing of the apparatus main body disposed around the developer regulating member is close to a surface of the developer regulating member on a downstream side in the developer conveying direction. 4. A developing device characterized by having a shaped shape.   The developing device according to claim 1, wherein a downstream side of the developer regulating member in the developer conveying direction has a shape along a surface of the developer carrier. .   5. An image forming apparatus for forming an image by transferring an image obtained by developing a latent image formed on a latent image carrier by a developing device onto a recording material, wherein the developing device is used as the developing device. An image forming apparatus using the developing device according to claim 1.

Images