JP2004286898A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of stabilizing a developer feeding amount to a developing roll without reducing the life of a developer and obtaining images of high quality. <P>SOLUTION: In the developing device, the upstream side of a side face on which a minimum gap part between a regulating member and the developing roll 1 is formed is inclined from a segment drown from the center axis of the developing roll 1 to the minimum gap part to the downstream side of a developing roll rotating direction. In magnetic poles of the developing roll 1 which are arranged on the upstream side and downstream side of the regulating member, a ratio θ1/θ0 of an angle θ0 between the magnetic poles about the center axis of the developing roll 1 and an angle θ1 between the position of the minimum gap part of the regulating member and the developing roll 1 and the magnetic pole of the upstream side about the center axis of the developing roll 1 is set to 0.5 to 0.2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a developing device using a two-component developer in an image recording device such as an electrophotographic printer or a copying machine.
[0002]
[Prior art]
2. Description of the Related Art In an image recording apparatus such as an electrophotographic printer or a copying machine, a static potential is formed by forming an image forming portion at a predetermined potential VR and a non-image portion at a predetermined potential V0 on an image carrier called a photoreceptor rotating in one direction. An image visualizing agent called a toner is supplied from the developing device to the latent image to make the latent image a visible image, and the visible image is printed on recording paper. Conventionally, as a developing device applied to the electrophotographic method, a developing device using a two-component developer composed of toner and magnetic powder called a carrier has been frequently used.
[0003]
Normally, in this type of developing device, the toner in the developer and the carrier friction with each other by stirring the two-component developer in the developer accommodating section, and each is charged to a predetermined amount. The developer having a predetermined charge amount is guided from the developer accommodating portion to a developing member called a developing roll having a plurality of magnets therein. Here, the developer is held and conveyed by the rotation of the developing roll, and passes through a regulating member called a doctor blade provided in a part of the developing roll. At this time, the doctor blade has a polarity of a magnetic pole on the upstream side in the rotation direction of each developing roll with respect to the doctor blade in order to enhance developer transportability on each developing roll. It is arranged so that the polarity of the magnetic pole on the downstream side in the rotation direction is opposite to the polarity.
[0004]
Next, the developer regulated to a predetermined amount by the doctor blade is conveyed to a position where it comes into contact with the photoreceptor by rotation of the developing roll. At this time, a bias potential (hereinafter referred to as "developing bias") VB for applying only toner to the image forming portion on the photosensitive member is applied to the developing roll, and a visible image is formed on the image forming portion on the photosensitive member. It is formed.
[0005]
More specifically, a minimum gap (hereinafter, referred to as a developing gap) between the developing roll and the photosensitive member is formed in a portion of the developing roller near the developer and the photosensitive member. The developing gap depends on the magnitude of an electric field (hereinafter referred to as a developing electric field) for guiding toner formed by the developing bias from the developing roll to the photoreceptor. The smaller the developing gap, the stronger the developing electric field. Since the toner can be efficiently supplied to the photoreceptor with a lower developing bias, the developing gap is generally constituted by a gap of 1 mm or less (for example, see Patent Document 1).
[Patent Document 1]
Japanese Patent Publication No. 7-23976 (page 2-3)
[0006]
[Problems to be solved by the invention]
The developing gap is supplied with a developer that has passed through a minimum gap (hereinafter referred to as a doctor gap) formed by the doctor blade and the developing roll. For this reason, when the amount of the developer passing through the doctor gap is too large, a large amount of stress is applied to the developer when passing through the developing gap.
[0007]
In this case, in general, the doctor gap is made narrower than the developing gap, and the passing amount is suppressed. However, in recent years, the developing gap is often configured with a value smaller than 0.5 mm, and accordingly, the doctor gap needs to be a narrow gap of about 0.3 mm. However, narrowing the doctor gap leads to an increase in stress when the developer passes through the doctor gap, and there has been a problem that the life of the developer is reduced. Also, the accuracy of the doctor gap due to the eccentricity of the developing roll is about ± 0.1 mm, and in the narrow doctor gap of about 0.3 mm, the regulated amount of the developer fluctuates greatly, so that the stable supply of the developer can be achieved. It was difficult.
[0008]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a developing device capable of stably supplying a developer to a developing roll without reducing the life of the developer and obtaining a high-quality image.
[0009]
[Means for Solving the Problems]
The object of the present invention is that the upstream side of the side surface forming the minimum gap between the regulating member and the developing roll is rotated by a line drawn from the central axis of the developing roll toward the minimum gap. The angle θ0 between the magnetic poles of the magnetic poles of the developing roll, which is inclined to the downstream side in the direction and is located upstream and downstream of the regulating member, with respect to the central axis of the developing roll, This is achieved by setting the ratio θ1 / θ0 between the position of the minimum gap portion of the roll and the angle θ1 of the magnetic pole on the upstream side to the central axis of the developing roll from 0.05 to 0.2. .
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
A first embodiment of the present invention will be described mainly with reference to FIGS. FIG. 1 is an enlarged schematic view of a part of the developing device according to the first embodiment of the present invention, and FIG. 2 is a schematic diagram of the entire developing device.
[0011]
The present embodiment relates to a developing device 104 in which one developing roll 1 is installed so as to face an image carrier called a photoconductor 101. The developing roll 1 rotates in the forward direction with respect to the rotation of the photosensitive member 101 indicated by an arrow A in FIG. In the present embodiment, a drum-shaped photoconductor is used as the image carrier, but this may be a configuration such as a photoconductor belt that circulates on a specific track.
[0012]
In the developing device 104, a partition plate called a doctor blade 3 is arranged on the developing roll 1. As shown in FIG. 1, the doctor blade 3 regulates the passage amount of the developer 4 on the developing roller 1 to a predetermined value. The gap length is set to G1. Hereinafter, this gap is referred to as a doctor gap.
[0013]
In the embodiment shown in FIG. 1 or FIG. 2, the image visualizing agent called the developer 4 is a magnetic powder called a carrier and a powder that forms a visible image on the photoconductor 101 called a toner. The toner is mixed at a weight ratio of 2 to 10% of the total weight. In the present embodiment, since the toner 4 in the developer 4 is consumed only by the printing operation of the printing device (not shown), the weight ratio of the toner in the developer in the developing device 104 decreases. I do. For this reason, in the developing device 104 of this embodiment shown in FIG. 2, the mixing and stirring member 7 for mixing and stirring the toner 5 supplied from the toner storage and supply device 9 into the developing device 104 with the developer 4 is provided. Have been. The toner in the developer 4 is agitated by the mixing / stirring member 7, so that the toner rubs against a carrier or the like in the developer 4 and is charged to a predetermined value. The charge amount of the toner is -10 to -30 C / g in this embodiment.
[0014]
As shown in FIG. 2, the developing roll 1 has a magnet 20 fixed and installed in the order of S3 pole, N2 pole, S2 pole, N1 pole, S1 pole, N3 pole, and S4 pole. The developing roller 1 has a rotatable sleeve 21 on the outer periphery thereof. Therefore, the developer 4 in the vicinity of the developing roll 1 is attracted to the surface of the sleeve 21 by the magnetic pole S3 of the magnet 20, and the magnetic poles S3, N2, S2 with the rotation of the sleeve 21. Is transported to the vicinity of the doctor blade 3.
[0015]
Here, the developer 4 is regulated to a predetermined amount by passing through the doctor gap G1 at the regulation position J of the doctor blade 3 and passes through the magnetic pole N1 to the developing section of the developing roll 1 arranged at the magnetic pole S2. Led to. In the developing section of the developing roll 1, the image forming section and the non-image forming section of the surface of the photoreceptor 101 are adjusted to a predetermined potential before reaching the developing section by a charging and exposure process (not shown). A developing bias for supplying only toner from the developer on the developing roll 1 to the image forming portion of the photoreceptor 101 is applied to the developing roll 1 by a power source (not shown). As a result, a visible image is formed by the toner on the image forming portion on the photoconductor 101. Thereafter, the visible image on the photoconductor 101 is printed on a sheet by a transfer step (not shown), and is then fixed on the sheet by a fixing step (not shown).
[0016]
In the above-described series of printing operations, it is important for the developing device 104 to stably regulate the passage amount of the doctor blade 3 in order to obtain a predetermined developing performance. This will be described with reference to FIG.
[0017]
FIG. 3 shows the case where the doctor gap G1 is a parameter, the angle between the magnetic poles S2 and N1 with respect to the developing roll center C is θ0, and the angle between the magnetic pole S2 and the regulating position J with respect to the developing roll center C is θ1. Is the result of measuring the amount of developer passing through the doctor blade 3 when .theta.1 / .theta.0 is changed. The magnetic poles S2 and N1 are located upstream and downstream of the doctor blade 3, respectively. FIG. 4 shows the doctor gap G1 in the region (I) (where θ1 / θ0 is 0.4 to 0.6) and in the region (II) (where θ1 / θ0 is 0.05 to 0.2). The relationship between the amount of developer passing through the doctor blade 3 is shown.
[0018]
Usually, the restriction position J is set at the center of the magnetic poles S2 and N1, that is, in the region (I). This is because it has been empirically found that the passage amount of the developer is more stable at the center position than at the magnetic pole position. However, the passing amount in the area (I) is stable against the change of θ1 / θ0, but is larger than the other θ1 / θ0 positions. On the other hand, it was found that the area (II) had a passing amount of about half of the area (I). More specifically, when θ1 / θ0 is around 0.3, as in the case where G1 in FIG. 3 is 0.2 mm, the developer cannot pass through the doctor gap at all. Therefore, when θ1 / θ0 is around 0.3, the passing amount tends to be unstable. On the other hand, as shown in FIG. 4, in the region (II) where θ1 / θ0 is smaller than 0.2, the passing amount tends to change in proportion to the doctor gap, and the passing amount is stable.
[0019]
Next, the pressure applied to the developer 4 near the doctor blade will be described below. FIG. 8 shows the result of measuring the pressure applied to the doctor blade 3 with respect to θ1 / θ0 when the developing gap G1 is 0.6 mm. At this time, the pressure applied to the doctor blade 3 is applied by the developer 4 which passes through or is about to pass through the doctor blade 3, and it is considered that a pressure is also applied to the developer itself as a reaction force. In FIG. 8, the pressure is maximum when θ1 / θ0 near the magnetic pole is 0 and 1, and becomes minimum when θ1 / θ0 is 0.3. Therefore, although the amount of the developer passing near the magnetic pole is small, the pressure is nearly twice as large as that in the normally used region (I), which is not preferable because the life of the developer 4 is shortened. On the other hand, in the region (II) where θ1 / θ0 is 0.05 to 0.2, the pressure is almost the same as in the region (I) where θ1 / θ0 is 0.4 to 0.6, and the life of the developer is reduced. Considering that, the area (II) was found to be the optimal position.
[0020]
In the present embodiment, the regulating position J of the doctor blade 3 is set in the region (II) where the passing flow rate is small and the passing amount is stable with respect to the setting of the doctor gap, the doctor gap G1 is 0.6 mm, and the developing gap is 0.1 mm. It was adjusted to 5 mm. As a result, the same amount of passage as when the doctor gap G1 in the conventional region (I) is 0.3 mm can be obtained, and the stress applied to the developer in the developing gap does not increase.
[0021]
Further, in this embodiment, the upstream side surface 303 forming the minimum gap portion of the doctor blade 3 shown in FIG. 1 is pulled from the developing roll center C toward the regulating position J of the doctor blade 3. It is installed so as to be inclined downstream of the line segment L in the rotation direction of the developing roll (hereinafter, this is referred to as state (α)). As shown in an enlarged schematic view of a part of the developing device in another embodiment of FIG. 7, the upstream side surface 303 forming the minimum gap portion of the doctor blade 3 has the developing roll center C. From the line L drawn toward the regulating position J of the doctor blade 3 to the upstream side in the rotation direction of the developing roll (hereinafter referred to as state (β)). This is because a region where the amount of passage decreases as in (II) does not occur. This will be described with reference to FIG.
[0022]
FIG. 5 shows the results of measuring the amount of developer passing through the doctor blade 3 when θ1 / θ0 is changed in the states (α) and (β) when the doctor gap G1 is 0.6 mm. As a result, in the state (β), the passing amount is maximum when θ1 / θ0 is around 0.3, and the passing amount decreases as θ1 / θ0 approaches 0, and the passing amount in the region (II) becomes smaller. No reduced area occurs. This is because the space between the upstream side surface 303 of the doctor blade and the developing roll 1 is filled with the developer 4 just before the regulating position J, so that the pressure for passing through the doctor gap G1 is reduced. It is to increase.
[0023]
In consideration of the above, a state (state) is set in which the line L drawn from the center C of the developing roll toward the regulation position J of the doctor blade 3 is located on the downstream side in the rotation direction of the developing roll. (Α)), the developing device configuration in which the doctor blade 3 is installed in a region where θ1 / θ0 is 0.05 can reduce the amount of the developer passing without narrowing the doctor gap G1. The increase in stress when passing through the gap G1 is small, and the fluctuation of the regulated amount of developer due to the eccentricity of the developing roll 1 is small. As a result, the supply amount of the developer to the developing roller 1 was stabilized without shortening the life of the developer, so that a high quality image was obtained.
[0024]
A second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a schematic view showing a part of a developing device according to a second embodiment of the present invention.
[0025]
The present embodiment relates to a developing device in which two developing rolls 1 and 2 are installed so as to face the photosensitive member 101. Of the two developing rollers, the developing roller 2 rotates forward with respect to the rotation of the photosensitive member 101 indicated by an arrow A in FIG. The developing roller 1 rotates in the direction opposite to the rotation of the photosensitive member 101 and is arranged upstream in the rotation direction of the photosensitive member 101. In the present embodiment, a developing device having two developing rolls will be described. For example, a plurality of developing rolls are provided upstream of the developing roll 1 in the rotation direction of the photoconductor 101. Or a configuration having a plurality of developing rolls downstream of the developing roll 2 in the rotation direction of the photoconductor 101.
[0026]
In this embodiment, a doctor blade 3 is disposed between the developing roll 1 and the developing roll 2. As shown in FIG. 6, the doctor blade 3 regulates the amount of the developer passing over the developing rollers 1 and 2 to a predetermined value. , 2 are set to G1 and G2, respectively.
[0027]
In the present embodiment, the developer 4 is guided to the vicinity of the developing roll 2 from a mixing and stirring member (not shown). At this time, the developing roll 2 has N2 pole, S2 pole, N1 pole, S1 pole, N3 pole, and the developing roll 1 has N5 pole, S6 pole, N4 pole, S5 pole, and N6 pole. The developer 4 near the developing roll 2 is attracted by the magnetic pole N2 and is conveyed to the vicinity of the doctor blade 3 via the magnetic pole S2.
[0028]
Here, the developer 4 is regulated to a predetermined amount by passing through the doctor gap G2 at the regulation position J2 of the doctor blade 3, and passes through the magnetic pole N1 to the developing section of the developing roll 2 arranged at the magnetic pole S1. Be guided. At this time, part or all of the surplus developer due to the regulation of the amount of passage in the doctor blade 3 is attracted to the developing roll by the magnetic force of the magnetic poles S6 and N5, and the regulating position J1 of the doctor blade 3 is controlled. After passing through the doctor gap G1 and being regulated to a predetermined amount, it is guided via the magnetic pole N4 to the developing section of the developing roll 1 arranged at the magnetic pole S5.
[0029]
At this time, the upstream side wall surface of the doctor blade 3 is configured to incline downstream from a line drawn to the regulation positions J1 and J2 from the central axes of the developing rollers 1 and 2. The angles between the restriction positions J1 and J2 and the magnetic poles S6 and S2 located on the upstream side are the same as in the first embodiment in terms of the ratio between the angle between the magnetic poles S6 and N4 and the angle between the magnetic poles S2 and N1. It is set to be between 0.05 and 0.2.
[0030]
As a result, similarly to the first embodiment, the amount of the developer passing through the developing roller can be reduced without reducing the doctor gap, and the amount of the developer supplied to the developing roll can be reduced without reducing the life of the developer. Stable.
[0031]
【The invention's effect】
According to the present invention, the amount of developer passing through the developing roller can be reduced without narrowing the doctor gap, so that the amount of developer supplied to the developing roll can be stabilized without reducing the life of the developer, and high quality can be achieved. A developing device capable of obtaining a stable image can be provided.
[Brief description of the drawings]
FIG. 1 is an enlarged schematic view of a part of a developing device according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram of the entire developing device according to the first embodiment of the present invention.
FIG. 3 is a graph showing the relationship between θ1 / θ0 and the amount of passing developer in each doctor gap.
FIG. 4 is a graph showing a relationship between a doctor gap G1 and a passing amount of developer.
FIG. 5 is a graph showing the relationship between θ1 / θ0 and the amount of developer passing with respect to a doctor blade entrance state.
FIG. 6 is a schematic view illustrating a part of a developing device according to a second embodiment of the invention.
FIG. 7 is an enlarged schematic view of a part of the developing device in which the inclination of the doctor blade is changed in FIG. 1;
FIG. 8 is a graph showing a relationship between θ1 / θ0 and a pressure applied to a doctor blade.
[Explanation of symbols]
1, 2 development roll 3 doctor blade 4 developer 5 toner
7 Mixing and stirring member 9 Toner storage and supply device 101 Photoconductor 104 Developing device 20 Magnet 21 Three-blower

Claims (2)

A developing roll that includes a plurality of magnets therein, and that holds and conveys the developer by rotation to visualize an electrostatic latent image formed on the photoconductor, and is disposed close to the outer periphery of the developing roll. A developing device of a two-component developer type comprising a toner having a regulating member for regulating the transport amount of the developer and a carrier which is a magnetic powder, wherein a portion between the regulating member and the developing roll is provided. The upstream side of the side surface forming the minimum gap is inclined downstream from the line drawn from the central axis of the development roll toward the minimum gap in the rotation direction of the development roll, and the upstream side of the regulating member. The angle .theta.0 between the magnetic poles with respect to the central axis of the developing roll, the position of the minimum gap between the regulating member and the developing roll, and the upstream side of the magnetic pole of the developing roll located on the downstream side. Angle with respect to the central axis of the developing roll with respect to the magnetic pole Developing apparatus is characterized in the ratio .theta.1 / .theta.0 with .theta.1 be set from 0.05 to 0.2. 2. The developing device according to claim 1, wherein a minimum gap between the regulating member and the developing roll is set to be larger than a minimum gap between the photosensitive member and the vicinity of the developing roll.

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