JP2009048029A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of suppressing occurrence of void in a print image resulting from an agglomeration of developer. <P>SOLUTION: The magnetic member 9 of a developing member 6 for developing an electrostatic latent image by supplying developer, layered on the surface of a cylindrical member 10, to a photoreceptor 200 has a developer at magnetic poles N1, S2, S3, N2, and S1 in the rotating direction of the cylindrical member 10, with a position opposite the photoreceptor 200 as a base point. The end 70 of a thickness restricting member 7 which restricts the thickness of the layer of developer held and conveyed on the cylindrical member 10 to a constant thickness is fixed to a housing 2 by a fixing member 8 in the reverse direction to the rotation of the cylindrical member from the peak of the magnetic flux density of the second magnetic pole (S1) and within a range W in which the magnetic flux density of the magnetic pole is 50% or more of the peak of the magnetic flux density of the magnetic pole. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device, and more particularly to a developing device that is used in an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and that develops an electrostatic latent image formed on a photoreceptor.

  2. Description of the Related Art Conventionally, developing devices have been invented that are used in image forming apparatuses such as copying machines, facsimiles, and printers, and that develop an electrostatic latent image formed on a photosensitive member with a two-component developer using toner and carrier. As such a developing device, for example, a developing device as shown in Patent Document 1 has been invented. In addition to the device shown in Patent Document 1, there is a developing device 100 as shown in FIG.

  A developing device 100 shown in FIG. 5 includes a housing 101, and in the housing 101, a stirring member 102, a supply member 103, a magnetic member 104, a cylindrical member 105, a thickness limiting member 106, and A fixing member 107 is provided. In such a developing device 100, the developer filled in the housing 101, stirred by the stirring member 102 and supplied by the supply member 103 is stacked on the surface of the cylindrical member 105 by the magnetic force of the magnetic member 104. The The developer stacked on the surface of the cylindrical member 105 is conveyed to a position facing the photoreceptor 200 while being held on the surface of the cylindrical member 105 by the rotation of the cylindrical member 105. The developer stacked on the surface of the cylindrical member 105 is, in the course of conveyance, the end of the thickness limiting member 106 fixed to the casing 101 by the fixing member 107 at a predetermined distance from the surface of the cylindrical member 105. 1060 limits the layer thickness to a constant thickness.

As shown in FIG. 5, the thickness limiting member 106 has a leading end of the end 1060 that limits the thickness of the developer protruding from the leading end of the end 1070 of the fixing member 107 by a predetermined length L. The distance L between the tip of the end 1060 and the tip of the end 1070 is required to be shortened as the developing device 100 is downsized.
JP 2001-92249 A

  However, when the distance L between the distal end of the end portion 1060 of the thickness limiting member 106 and the distal end of the end portion 1070 of the fixing member 107 is shortened, the distance from the distal end of the end portion 1070 of the fixing member 107 to the surface of the cylindrical member 105 is increased. The distance also becomes shorter. When the distance from the tip of the end portion 1070 of the fixing member 107 to the surface of the cylindrical member 105 becomes shorter, the developer of the cylindrical member 105 scraped off by the end portion 1060 of the thickness limiting member 106 becomes the end portion of the fixing member 107. Aggregation tends to occur between 1070 and the surface of the cylindrical member 105. In the case of a developer that is used for printing a large number of recording papers, mixed with paper dust of the recording papers, and the toner is embedded in the carrier and the fluidity is deteriorated, this aggregation phenomenon becomes remarkable. When such developer aggregation with poor fluidity occurs, the aggregated developer blocks the developer conveyed from the rear in the rotational direction of the cylindrical member 105, and the developer is aggregated. The developer is not stacked on the surface of the cylindrical member 105 corresponding to. As a result, there is a problem that white linear color loss (hereinafter referred to as “white loss”) occurs in the recording paper transport direction in an image printed on the recording paper.

  SUMMARY An advantage of some aspects of the invention is that it provides a developing device capable of suppressing the occurrence of white spots in a printed image caused by aggregation of the developer.

  In order to achieve the above object, a developing device according to the present invention has a casing, a stirring member that stirs the developer filled in the casing, and a cylindrical shape, and is rotatable about an axis. A non-magnetic cylindrical member is provided coaxially on the outer periphery, and has a first magnetic pole that is one of the S and N poles having a magnetic flux density peak of 107 ± 5 mT at a position facing the photoreceptor. The other of the S and N poles having a magnetic flux density peak of 66 ± 5 mT at a position of 64 ± 5 ° in the reverse direction of the rotation of the cylindrical member with the magnetic flux density peak of the first magnetic pole as a base point The other of the S and N poles having a magnetic flux density peak of 63 ± 5 mT at a position of 84 ± 5 ° in the forward direction of rotation of the cylindrical member from the base point. A magnetic pole density at a position of 196 ± 5 ° in the forward direction from the base point. It has a fourth magnetic pole which is the other of the S and N poles whose peak is 50% to 80% of the magnetic flux density peak of the second magnetic pole, and 240 ± 5 in the forward direction from the base point. A fifth magnetic pole which is one of the S and N poles of polar magnetic force where the magnetic flux density peak is 50% to 70% of the magnetic flux density peak of the second magnetic pole at the position of °; A magnetic member that holds and conveys the developer stirred by the stirring member to the surface of the cylindrical member and supplies the developer to the photosensitive member, and the cylindrical member on the side of the cylindrical member where the stirring member is located. A thickness limiting member that is disposed at a predetermined distance from the surface of the member and that limits the thickness of the developer layer that is held and conveyed on the surface of the cylindrical member to a certain thickness; and the thickness limiting member; And a fixing member that is fixed to the housing.

  The “magnetic flux density peak” is a peak of the vertical component of the magnetic flux density caused by each magnetic pole of the magnetic member.

  According to the developing device of the present invention, the magnetic flux density peak of the fourth magnetic pole is 50% to 80% of the magnetic flux density peak of the second magnetic pole, and the magnetic flux density peak of the fifth magnetic pole is second. It is 50% to 70% of the peak of the magnetic flux density of the magnetic pole. Therefore, it is possible to suppress the occurrence of white spots in the printed image due to developer aggregation.

  Hereinafter, the developing device 1 according to the present invention will be described with reference to the drawings. The developing device 1 is used in an image forming apparatus such as a copying machine, a facsimile machine, or a printer. As shown in FIG. 1, the developing device 1 converts an electrostatic latent image formed on the surface of a photoconductor 200 into two components using toner and a carrier. Development is performed with a developer (hereinafter referred to as “developer”). The developing device 1 includes a housing 2. The developing device 1 includes stirring members 3 and 4, a supply member 5, a developing member 6, a thickness limiting member 7, and a fixing member 8 inside the housing 2.

  The agitating members 3 and 4 are in the shape of a screw in which a plate-like wing member is spirally wound around a rod-like member having a circular cross section, and the inside of the housing 2 is rotated by rotation about the axis of the rod-like member. The developer filled in is stirred.

  The developer filled in the housing 2 is composed of a toner that is a powder for coloring and a carrier that is a magnetic powder. The toner is made of, for example, a styrene acrylic resin or a polyester resin, and the carrier is made of, for example, a resin-coated magnetic material such as magnetite or ferrite.

  In the supply member 5, for example, only five wing members having a substantially triangular cross section are arranged in parallel with the axis of the rod member on the surface of the rod member having a circular cross section. The developed developer is supplied to the developing member 6 by rotation about the axis of the rod-shaped member.

  The developing member 6 is composed of a magnetic member 9 having a circular cross section and magnetism, and a cylindrical member 10 having a cylindrical shape and no magnetism. The magnetic member 9 is accommodated coaxially in the hollow portion of the cylindrical member 10. Further, the magnetic member 9 is fixed to the housing 2 at both ends in the longitudinal direction, and is not rotated around the axis. On the other hand, the cylindrical member 10 can rotate around an axis. The agitating members 3 and 4, the supply member 5 and the cylindrical member 10 are rotated about their respective axes by a driving force transmitted from a driving unit (not shown) provided in an image forming apparatus such as a copying machine. The

  The developing member 6 holds the developer supplied by the supply member 5 on the surface of the cylindrical member 10 by the magnetic force of the magnetic member 9, and conveys the held developer by the rotation of the cylindrical member 10 to be photosensitive. Supply to body 200.

  As shown in FIG. 2, the magnetic member 9 has five magnetic poles N1, S1, S2, S3, and N2 radially in the circumferential direction. Hereinafter, five magnetic poles N1 in the horizontal direction when the developing member 1 is attached to an image forming apparatus such as a copying machine, with the side on which the stirring members 3 and 4 of the magnetic member 9 are positioned as the base point P (0 °). , S1, S2, S3, N2 and the strength of the magnetic force will be described.

  First, the magnetic member 9 has a magnetic flux density peak of 107 ± 5 mT (milli-Tesla) at a position of 105 ± 5 ° in the forward direction of rotation of the cylindrical member 10 from the base point P (clockwise direction in FIGS. 1 and 2). ) N pole magnetic pole N1 (first magnetic pole). The “peak of magnetic flux density” means the peak of the vertical component of the magnetic flux density. The magnetic pole N <b> 1 is located at a location facing the photoconductor 200. Further, the magnetic member 9 includes an S magnetic pole S1 (second magnetic pole) having a magnetic flux density peak of 66 ± 5 mT at a position of 41 ± 5 ° in the forward direction of rotation of the cylindrical member 10 from the base point P. ing. (The peak position of the magnetic flux density of the magnetic pole S1 is 64 ± 5 ° in the reverse direction of the rotation of the cylindrical member 10 with reference to the peak position of the magnetic flux density of the magnetic pole N1.) Further, the magnetic member 9 is provided with an S magnetic pole S2 (third magnetic pole) having a magnetic flux density peak of 63 ± 5 mT at a position of 189 ± 5 ° in the forward direction of rotation of the cylindrical member 10 from the base point P. (The magnetic flux density peak position of the magnetic pole S2 is 84 ± 5 ° in the forward direction of rotation of the cylindrical member 10 with reference to the magnetic flux density peak position of the magnetic pole N1). 9 is the S pole where the peak value of the magnetic flux density is 50% to 80% of the peak value of the magnetic flux density of the magnetic pole S1 at a position of 301 ± 5 ° in the forward direction of the rotation of the cylindrical member 10 from the base point P. A magnetic pole S3 (fourth magnetic pole) is provided. (The magnetic flux density peak position of the magnetic pole S3 is 196 ± 5 ° in the forward direction of rotation of the cylindrical member 10 with reference to the magnetic flux density peak position of the magnetic pole N1.) Further, the magnetic member 9 is the N pole where the peak value of the magnetic flux density is 50% to 70% of the peak value of the magnetic flux density of the magnetic pole S1 at a position of 345 ± 5 ° in the forward direction of rotation of the cylindrical member 10 from the base point P. A magnetic pole N2 (fifth magnetic pole) is provided. (The peak position of the magnetic flux density of the magnetic pole N2 is 240 ± 5 ° in the forward direction of the rotation of the cylindrical member 10 with reference to the peak position of the magnetic flux density of the magnetic pole N1.) ± 5 ° and ± 5 mT in the values and magnetic flux density values are tolerances. FIG. 3 is an explanatory diagram showing the distribution of the vertical component of the magnetic flux density in the magnetic member 9 in which the magnetic poles are arranged in this way.

FIG. 3 is an explanatory diagram showing the distribution of the vertical component of the magnetic flux density in the magnetic member 9 in which the magnetic poles are arranged in this way. As can be seen from FIG. 3, the magnetic flux density peak value of the magnetic pole S3 is 50% to 80% of the magnetic flux density peak value of the magnetic pole S1, and the magnetic flux density peak value of the magnetic pole N2 is From 50% to 70% of the peak value of the magnetic flux density of S1.

  In such a magnetic member 9, the magnetic pole S <b> 3 functions to draw the developer supplied by the supply member 5 to the surface of the cylindrical member 10 to be laminated. Similarly, the magnetic pole N2 serves to draw and stack the developer supplied by the supply member 5 on the surface of the cylindrical member 10 and hold it on the surface. The magnetic pole S <b> 1 serves to hold the developer on the surface of the cylindrical member 10. Further, the magnetic pole N1 supplies toner contained in the developer held on the surface of the cylindrical member 10 to the surface of the photoconductor 200, and develops an electrostatic latent image formed on the surface of the photoconductor 200. To do. The magnetic pole S2 cancels the magnetic force of the magnetic pole S3 and works to peel off the developer held on the surface of the cylindrical member 10 from the surface of the cylindrical member 10 at the boundary of the magnetic force between the magnetic pole S2 and the magnetic pole S3. To do.

  On the side where the supply member 5 of the developing member 6 having such a magnetic member 9 is located, a thickness limiting member 7 is arranged. The thickness limiting member 7 is a long and narrow plate-like member, and is a fixing member in a state where an end portion 70 which is one long side of the plate is spaced from the surface of the cylindrical member 10 by a distance of 0.55 to 0.60 mm. 8 is fixed to the housing 2. The thickness limiting member 7 is configured such that the thickness of the developer stacked on the surface of the cylindrical member 10 by the magnetic poles S3 and N2 of the magnetic member 9 is changed to the end of the stacked developer as the cylindrical member 10 rotates. The thickness is limited to a predetermined thickness by scraping off at 70. Note that the fixing member 8 has the same length as the long side of the thickness limiting member 7, and the distance between the tip of the end 80 of the long side and the surface of the cylindrical member 10 is the end of the thickness limiting member 7. It is longer than the distance between the tip of the portion 70 and the surface of the cylindrical member 10.

  As described above, the developing device 1 of the present invention sets the magnetic flux density peak of the magnetic pole S3 to 50% to 80% of the magnetic flux density peak of the magnetic pole S1, and sets the magnetic flux density peak of the magnetic pole N2 to the peak of magnetic flux density of the magnetic pole S1. From 50% to 70%. According to such a developing device 1, it is possible to suppress the occurrence of white spots in the printed image due to the aggregation of the developer at the end portion 70 of the thickness limiting member 7 and the end portion 80 of the fixing member 8. The relationship between the magnetic flux density peak of the magnetic pole S1 and the magnetic flux density peaks of the magnetic pole S3 and the magnetic pole N2 has been derived by experiments. FIG. 4 is an explanatory diagram showing the values of the magnetic flux density peaks of the magnetic pole S3 and the magnetic pole N2 and the experimental conditions and data regarding the occurrence of white spots in the printed image.

  As shown in FIG. 4, the condition of the magnetic member 9 of the developing member 6 is changed to 1 to No. Eight, eight experiments were conducted. In these experiments, a developer whose fluidity is deteriorated by printing a solid image on 100,000 or more recording sheets is used. In addition, as a result of the experiment, if white spots occur when printing on less than 10000 (10k) sheets of recording paper, there is no effect to prevent the occurrence of white spots, and printing on 10000 (10k) or more sheets of recording paper. In the case where white spots occur, the effect of preventing the occurrence of white spots is assumed. The image printed on the recording paper in the experiment is also a solid image. Experiment No. 1, the position of the thickness limiting member 7 is set to a position of 9 ° in the forward direction of rotation of the cylindrical member 10 from the reference P (see FIG. 2). 2 to Experiment No. In 8, it is 17 degrees. When the position of the thickness limiting member 7 is 9 ° from the reference P, the end 70 of the thickness limiting member 7 is within the magnetic force range of the magnetic pole N2, and the magnetic flux density at the end 70 is the magnetic flux density of the magnetic pole N2. 20% of the peak. When the position of the thickness limiting member 7 is 17 ° from the reference P, the end portion 70 of the thickness limiting member 7 is within the range of the magnetic force of the magnetic pole S1, and the magnetic flux density at the end 70 is equal to that of the magnetic pole S1. It is 25% of the peak of magnetic flux density. In addition, No. 1 to No. In the condition of the magnetic member 9 of the developing member 6 in the experiment 8 (hereinafter referred to as “developing member condition”), the peak value of the magnetic flux density also changes for the magnetic poles other than the magnetic pole S3 and the magnetic pole N2. This is a change within tolerance and is not intended. The angle (position) of each magnetic pole is similarly changed within the tolerance range.

  Hereinafter, the condition that the magnetic flux density peak of the magnetic pole S3 is 50% to 80% of the magnetic flux density peak of the magnetic pole S1 is referred to as “condition 1”, and the magnetic flux density peak of the magnetic pole N2 is the magnetic flux density of the magnetic pole S1. The condition of 50% to 70% of the peak is called “condition 2”.

  No. The developing member condition of the experiment 1 is a condition in a conventional developing device. No. The developing member condition of Experiment 1 satisfies Condition 1 but does not satisfy Condition 2. As a result of the experiment, two white spots occurred in printing on the first recording sheet. Therefore, no. Under the developing member condition of Experiment 1, the effect of suppressing the occurrence of white spots was not obtained.

  No. The developing member condition of the experiment of No. 2 is that the peak value of the magnetic flux density of the magnetic pole N2 is No.2. The value is smaller than the value of the experiment of 1 and satisfies the condition 1 but does not satisfy the condition 2. As a result of the experiment, one white spot occurred in printing on the 9500 (9.5k) th recording paper. Therefore, no. Under the developing member conditions of Experiment 2, the effect of suppressing the occurrence of white spots was not obtained.

  No. The developing member condition of the experiment No. 3 is the peak value of the magnetic flux density of the magnetic pole S3. 2, the ratio of the peak value of the magnetic flux density of the magnetic pole N2 to the peak value of the magnetic flux density of the magnetic pole S1 (hereinafter simply referred to as “proportion”) It is made smaller than the value of the experiment of 2 and satisfies the conditions 1 and 2. As a result of the experiment, one white spot occurred in printing on the 17500 (17.5k) th recording paper. Therefore, no. With the developing member condition of Experiment 3, the effect of suppressing the occurrence of white spots was obtained.

  No. 4 to No. The developing member condition of the experiment 6 is such that the ratio of the peak value of the magnetic flux density of the magnetic pole S3 is constant, and the ratio of the peak value of the magnetic flux density of the magnetic pole N2 is sequentially reduced. No. 4 and no. The developing member conditions of the experiment of 5 satisfy the conditions 1 and 2, and The developing member condition of the experiment of 6 satisfies the condition 1 but does not satisfy the condition 2. As a result of the experiment, no. In the experiment No. 4, one white spot was generated by printing on the 20500 (20.5k) th recording paper, and an effect of suppressing the occurrence of white spot was recognized. No. In the experiment of No. 5, one white spot was generated by printing on the 19500 (19.5k) th recording paper, and an effect of suppressing the occurrence of white spot was recognized. On the other hand, no. In the experiment No. 6, “feed member pitch loss” occurred before the occurrence of white spots due to the aggregation of the developer. This supply member pitch omission means that a solid line image printed on recording paper has a white line perpendicular to the recording paper conveyance direction, and the pitch according to the interval between the five plate-like wing members of the supply member. It appeared in. This supply member pitch omission occurs due to a small amount of developer stacked on the surface of the cylindrical member 10 of the developing member 6.

  No. 7 and no. The developing member condition of the experiment No. 8 is such that the ratio of the peak value of the magnetic flux density of the magnetic pole N2 is constant, and the ratio of the peak value of the magnetic flux density of the magnetic pole S3 is not more than the lower limit and more than the upper limit of Condition 1. No. 7 and no. The developing member conditions of the experiment No. 8 both satisfy the condition 2 although the condition 1 is not satisfied. As a result of the experiment, no. In the experiment No. 7, “stirring member pitch loss” occurred before white spots due to developer aggregation. This stirrer pitch missing means that a solid white image appears diagonally due to a wing member spirally wound around the bar-shaped members of stirrers 3 and 4 on a solid image printed on recording paper. It is. This stirrer member pitch loss occurs due to a small amount of developer stacked on the surface of the cylindrical member 10 of the developing member 6. No. In the experiment No. 8, two white spots occurred when printing on the 6500th (6.5k) th recording paper, and the effect of suppressing the occurrence of white spots was not recognized.

  As described above, No. 1 that satisfies both Condition 1 and Condition 2 is satisfied. 3 to No. Only in the experiment No. 5, the effect of suppressing the occurrence of white spots due to the aggregation of the developer was recognized. Therefore, according to the developing device 1 of the present invention that satisfies both the conditions 1 and 2, the occurrence of white spots due to the aggregation of the developer can be suppressed.

  In addition, you may change the above-mentioned embodiment suitably in the range of the technical idea of invention. For example, in the above-described embodiment, the first magnetic pole (N1) and the fifth magnetic pole (N2) are N poles, the second magnetic pole (S1), the third magnetic pole (S2), and the first magnetic pole The four magnetic poles (S3) are the S poles, but the polarities of these magnetic poles may be reversed.

  The present invention is applicable to, for example, a developing device that is used in an image forming apparatus such as a copying machine, a facsimile machine, and a printer and develops an electrostatic latent image formed on a photosensitive member.

It is explanatory drawing which shows the structural example of the developing device 1 which concerns on this invention. It is explanatory drawing explaining the polarity and positional relationship of each magnetic pole with which the magnetic member 9 of the developing device 1 is provided. 4 is an explanatory diagram showing a distribution of vertical components of magnetic flux density in a magnetic member 9. FIG. It is explanatory drawing which shows the data of experiment. It is explanatory drawing which shows the structural example of the conventional developing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing apparatus 2 Housing | casing 3 Stirring member 4 Stirring member 5 Supply member 6 Developing member 7 Thickness limiting member 8 Fixed member 9 Magnetic member 10 Cylindrical member 200 Photoconductor

Claims (1)

A housing,
An agitating member for agitating the developer filled in the housing;
A non-magnetic cylindrical member having a columnar shape and rotatable about an axis is coaxially provided on the outer periphery, and the S pole and the N pole have a magnetic flux density peak of 107 ± 5 mT at a position facing the photoreceptor. The first magnetic pole is one of the poles, and the peak of the magnetic flux density is 66 at a position of 64 ± 5 ° in the reverse direction of the rotation of the cylindrical member with the peak of the magnetic flux density of the first magnetic pole as a base point. It has a second magnetic pole which is the other of the S and N poles of ± 5 mT, and the peak of the magnetic flux density is 63 at a position of 84 ± 5 ° in the forward direction of rotation of the cylindrical member from the base point. It has a third magnetic pole which is the other of the S and N poles of ± 5 mT, and the peak of the magnetic flux density is 196 ± 5 ° in the forward direction from the base point. The magnetic flux of the second magnetic pole It has a fourth magnetic pole that is the other of the S and N poles, which is 50% to 80% of the density peak. , One of S pole and N pole of polar magnetic force where the magnetic flux density peak is 50% to 70% of the magnetic flux density peak of the second magnetic pole at a position of 240 ± 5 ° in the forward direction from the base point. A magnetic member having a fifth magnetic pole as a pole, holding the developer stirred by the stirring member on the surface of the cylindrical member, and feeding the developer to the photoreceptor;
The thickness of the developer layer that is disposed on the side of the cylindrical member at a predetermined distance from the surface of the cylindrical member and is conveyed while being held on the surface of the cylindrical member. A thickness limiting member for limiting to a certain thickness;
And a fixing member that fixes the thickness limiting member to the housing.

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