JP2669612B2 - Electrostatic latent image developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to electrostatic latent image development for developing an electrostatic latent image formed on the surface of an electrostatic latent image carrier using an electrophotographic copying process or the like. It concerns the device. (Prior art and its problems) Conventionally, as one mode of the electrostatic latent image developing apparatus, Japanese Patent Application Laid-Open
There is one disclosed in JP-A-59-111664. This developing device generally has a developing sleeve having a built-in magnetic roller having a plurality of magnets therein, and a minute concave portion on the surface facing the developing sleeve and arranged in the toner supply opening of the toner storage tank. A supply roller,
A regulating blade that presses against the supply roller. That is, in this device, the uncharged toner stored in the toner storage tank is taken into the minute concave portion based on the rotation of the supply roller, and the portion other than the concave portion (convex portion) when passing through the pressure contact portion with the regulation blade is used. The toner held in (1) is scraped to regulate the toner supply amount. When the toner held on the surface of the supply roller reaches the toner supply area, which is a portion facing the developing sleeve, the toner is taken up by the magnetic brush on the developing sleeve and comes into contact with the carrier that constitutes the magnetic brush to reverse the carrier. A polar charge is provided. Then, the charged toner is conveyed to a portion (developing area) facing the photosensitive drum based on the rotation of the developing sleeve,
The electrostatic latent image formed on the surface of the photosensitive drum is developed. (Problems to be solved by the invention) However, in this toner, in the toner supply region, as described above, new toner is supplied from the supply roller to the developing sleeve, and the bias applied to the developing sleeve and the supplying roller is also increased. Excess charged toner on the developing sleeve is collected on the surface of the supply roller based on the voltage difference. Then, the collected charged toner is conveyed into the toner storage tank based on the rotation of the supply roller, and is again subjected to the blade scraping action at the pressing portion of the regulating blade. However, at this time, the charged toner contained in the concave portion is directly conveyed without being scraped by the blade,
The charged toner on the convex portion is scraped off by the blade and mixed into the uncharged toner in the toner storage tank, comes into contact with the uncharged toner, and both are electrically aggregated into a lump. Then, the agglomerated toner is held by the supply roller and supplied to the developing sleeve, and when the crushing effect on the developing sleeve is insufficient, the toner adheres to the surface of the photoconductor drum in the developing area as it is, and spots on the copied image, or This appears as a background fog, which causes a problem of deteriorating image quality. Also,
In the electrostatic latent image developing device, the toner is scattered or floating in the device due to the mechanical impact between the magnetic brush and the supply roller, and the same applies when the toner is reattached to the surface of the supply roller. (Means for Solving Problems) In order to solve the above problems, in the electrostatic latent image developing device according to the present invention, the minute irregularities on the surface of the supply roller are provided in a grid pattern, and the convex portions are in pressure contact with the regulating blade. The surface area should be 30% or less of the area of the toner transport area, and the depth of the concave portion should be 10 μm or less.
It was set to 50 μm. That is, the amount of charged toner that adheres to the convex portion of the supply roller and is sent into the toner storage tank is suppressed while maintaining the toner transportability of the supply roller. (Example) Hereinafter, the present invention will be described with reference to the drawings as an example. FIG. 1 shows a developing section of a copying machine equipped with a developing device (1) according to the present invention. The developing device (1) is a photosensitive drum (10).
0), which supplies toner to the electrostatic latent image of the copy image formed by charging and exposing the surface of the photoconductor drum (100) and visualizes it. Is what you do. The developing device (1) generally includes a developing sleeve (4) in a developing tank (2) composed of a casing (3) and a cover (3a) from the photosensitive drum (100) side to the right in order. ), A toner supply roller (12) is arranged, and a toner storage tank (22) is formed behind the toner supply roller (12). The developing sleeve (4) is a cylindrical body made of a conductive non-magnetic material such as aluminum, and has fine recesses formed on the surface by blasting, and the photosensitive drum is driven to rotate in the direction of arrow (a). It faces (100) with a developing gap (Ds) and can be driven to rotate in the counterclockwise direction [direction of arrow (b)]. A DC developing bias power source (5) (developing bias voltage: Vb) is connected between the developing sleeve (4) and the ground, and the negative side of the developing bias power source (5) is connected to the developing sleeve (4). Then, negative charges are stored on the surface of the developing sleeve (4). The magnetic roller (6) housed inside the developing sleeve (4) has a plurality of magnets whose magnetic poles are extended in the axial direction, and the magnetic poles are arranged so that the magnetic poles are alternately located at the S pole and the N pole at the outer peripheral portion. It is fixed in the state shown in FIG. A main developer stirring plate (7) attached to the cover (3a) faces the developing sleeve (4) above the photosensitive drum (100) side with a spike height regulating gap (Db). Also,
An auxiliary developer stirring plate (9) attached to the support portion (8) of the cover (3a) faces the diagonally upper right of the developing sleeve (4), and together with the main developer stirring plate (7), An empty space (11) is formed above the developing sleeve (4). A slit (10) is formed on the auxiliary developer stirring plate (9) in the axial direction of the developing sleeve (4). The toner supply roller (12) is formed of a conductive non-magnetic material such as aluminum, and as shown in FIG. 2, is located in the toner transport area (S) except the mirror surface portions (12a) and (12a) at both ends. Has a pattern (P) (see FIG. 3) of a grid-like minute concavo-convex pattern with a depth of about 30 μm formed by etching, and is parallel to the back side of the developing sleeve (4) with a supply gap (Dss). And can be driven to rotate in the direction of arrow (c). When the depth of the concave portion (Pa) of the fine concavo-convex pattern (P) is 10 μm or less, the toner supply amount becomes insufficient and an appropriate toner mixing ratio cannot be obtained.
If it is deeper than m, the pre-charging of the toner by the blade (18) becomes insufficient and the toner is solidified in the concave portion (Pa) (see FIG. 3), which causes image fog. The toner supply roller (12) is provided with an AC power supply (13),
Also, the toner supply roller (12) is grounded via a DC power source (14) and a pulsating recovery bias voltage in which AC is superimposed on DC is applied. A partition (1) is located above the rear side of the toner supply roller (12).
5) is mounted so that it can rotate around the support shaft (16),
The other end of a pressure contact spring (17), one end of which is attached to the upper rear end of the developing tank (3), is locked to the upper end of the partition wall (1).
5) is constantly urged in the direction of arrow (e), and the tip of the regulating blade (18) attached to the lower part of the partition wall (15) opposes the upper right diagonal of the toner supply roller (12) in the rotational direction. Light pressure contact. The regulating blade (18) and the auxiliary developer stirring plate (9) are connected by a sheet (19).
An empty space (20) is formed above the toner supply roller (12). Below the toner supply roller (12), a toner return prevention film (21) attached to the casing (3) is provided.
Are pressed along the rotation direction of the toner supply roller (12). The toner storage tank (22) is formed by partitioning the rear portion of the developing tank (3) by the partition wall (15), the regulation blade (18), the toner supply roller (12), and the toner return prevention film (21). A stirring rod (23) is attached to the inside of the toner storage tank (22) so as to be rotatable in the direction of the arrow (d). The operation of the developing device having the above configuration will be described. First, a starter made of a mixture of a negatively chargeable magnetic carrier and a positively chargeable insulating toner is loaded in the chamber (11) above the developing sleeve (4) and the toner supply roller (12), and the toner storage tank ( 22) Insulate the above-mentioned insulating toner. At this time, only the magnetic carrier may be loaded in the empty room (11) instead of the starter. This enables the developing device (1) to develop the electrostatic latent image. When a print switch (not shown) is turned on in this state, the developing sleeve (4), the toner supply roller (12) and the stirring rod (23) rotate in the directions of arrows (b), (c) and (d), respectively. As the developing device (1) operates as described above, the toner flows toward the toner supply roller (12) by the stirring action of the stirring rod (23) at the bottom portion of the toner storage tank (22), and the toner supply roller (12). (12) Mirror surface at both ends (12
The toner is taken in and filled in the surface minute recesses (Pa) of the toner carrying area (S) except for a) and (12a). The toner supplied to the toner supply roller (12) is conveyed in the direction of the arrow (c), and excess toner is scraped off when passing through the pressure contact portion of the regulation blade (18). The contact roller is triboelectrically charged to a positive polarity, and a thin layer of charged toner is formed on the surface of the supply roller (12). The toner retained on the surface of the supply roller (12) is carried to a portion [toner supply region (Y)] facing the developing sleeve (4), where the toner is retained on the developing sleeve (4). Supplied. At this time, excess toner on the developing sleeve (4) is collected by the toner supply roller (12).
The operation of supplying and collecting the toner will be described later in detail. The toner supplied to the developing sleeve (4) is conveyed in the direction of arrow (b) together with the carrier held on the peripheral surface of the developing sleeve (4), and the amount of the developer is increased by the auxiliary developer stirring plate (9). The part is closed. Then, the developer is pushed by the developer which will be conveyed later, warps up along the auxiliary developer stirring plate (9), passes through the slit (10), and is sent to the vacant chamber (11) on the downstream side. . The remaining developer passes through the gap between the auxiliary developer stirring plate (9) and the developing sleeve (4) and reaches the empty chamber (11) on the downstream side. The developer that has reached the empty room (11) is the main developer stirring plate (7).
It is blocked by, and along it, it rises while rotating counterclockwise in the vacant chamber (11), backflows and falls, and merges with the developer passing through the slit (10) and is mixed. . In this way, a part of the developer which is sufficiently mixed and stirred passes through the spike height regulating gap (Db) between the main developer stirring plate (7) and the developing sleeve (4) to form a magnetic brush,
The magnetic brush rubs the surface of the photoconductor drum (100) in the developing area (X) to develop and visualize the electrostatic latent image on the surface. After passing through the developing area (X), the developer remaining on the peripheral surface of the developing sleeve (4) continues to be the developing sleeve (4).
Is conveyed in the direction of the arrow (b) based on the rotation of the toner supply area (Y), which is a portion facing the toner supply roller (12).
, The developing sleeve (4) and the toner supply roller (1
The operation of supplying and collecting the toner is performed again between the steps 2) and 3). Then, when the toner supplied to the developing sleeve (4) reaches the empty chambers (20) and (11) again, the sufficiently mixed and stirred developer is uniformly replenished on the surface of the developing sleeve (4), The consumption pattern of the toner consumed in the previous development is erased. Hereinafter, the operation of supplying and collecting the toner in the toner supply area (Y) will be described. In the toner supply area (Y), the developing sleeve (4)
In the above, the developer is connected in a string along the magnetic field formed in the radial direction from the magnetic pole (N) of the magnetic roller (6) to form a magnetic brush. On the other hand, the surface minute recesses (Pa) of the toner supply roller (12) are filled with toner, and in particular, the charged toner contained in the surface is recessed between the toner supply roller (12) and the charged toner. The electrostatic attraction that acts is large. However, since the bias voltage (Vss + Vrms) obtained by superimposing the AC power supply (13) on the DC power supply (14) is applied to the toner supply roller (12), the charged toner is periodically supplied with the AC voltage (Vrms). It vibrates toward the developing sleeve (4) on the surface of the toner supply roller (12) according to the change. For this reason, the toner and the magnetic brush frequently contact each other, not to mention the toner located on the surface of the minute recess (Pa).
Even the toner located at the bottom of the minute recess (Pa) comes into contact with the magnetic brush, and the toner is efficiently scraped off by the magnetic brush. On the other hand, on the developing sleeve (4), the excess charged toner that is in contact with the carrier and is positively charged is based on the bias voltage difference applied to the developing sleeve (4) and the toner supply roller (12). Then, the toner is electrically sucked by the toner supply roller (12). The suction force acting here also changes cyclically under the influence of the AC power source (13), so that the electrostatic attraction of the excess toner is weakened and the excess toner is liable to peel off, and the excess toner is efficiently transferred to the toner supply roller (12). Well recovered. The charged toner collected by the toner supply roller (12) is
The toner adheres to the entire toner transport area (S) of the toner supply roller (12) and is transported to the toner storage tank (2) through the space between the toner return prevention film (21). As described above, the charged toner attached to the toner supply roller (12) is attached not only to the entire surface of the toner carrying area (S), that is, to the surface of the convex portion (Pb) as well as the concave portion (Pa). . Therefore, when the collected charged toner reaches the pressure contact portion of the regulation blade (18), the charged toner contained in the concave portion (Pa) is not subjected to the scraping action of the regulation blade (18) and is again supplied to the supply region (Y). The charged toner on the convex portion (Pb), although being conveyed to, is scraped off by the regulation blade (18) and falls into the toner storage tank (22) to be mixed with the uncharged toner. Then, the mixed charged toner is subjected to the stirring action by the stirring rod (23) together with the uncharged toner, and both are electrically aggregated into a lump. When such a phenomenon continues for a long period of time, a large amount of toner aggregates due to the collected charged toner is accumulated in the toner storage tank (22). However, in the developing device (1) according to the present invention,
From the following experiment in which the area of the convex portion (Pb) on the surface of the toner supply roller (12) was changed and the degree of fog appearing in the copied image was observed, the convex portion area was determined as the toner conveying area [= toner conveying area (S) Width x roller diameter (D) x π)]. Therefore, the amount of charged toner adhering to the surface of the convex portion (Pb) and mixed in the toner storage tank (22) is small,
Even if the agglomerates of charged toner and uncharged toner are supplied to the surface of the developing sleeve (4), the toner agglomerates on the developing sleeve (4) are sufficiently crushed by the sufficient crushing effect, and other toners are crushed. In the same manner as described above, a charge is applied and the resultant is subjected to ordinary development. For this reason, a copy image without spots and background fog can be obtained, and no dust is generated to contaminate the inside of the machine. Hereinafter, an experiment conducted by the present inventors will be described. The pattern of minute irregularities (P) is formed in a grid pattern, and the sizes of the concave portions (Pa) and the convex portions (Pb) are set to four types as shown in FIG. [Experimental conditions] a. Development sleeve (4) ・ Diameter …… 24.5mm ・ Rotational speed …… 200rpm ・ Development bias voltage (Vb) …… DC-200V b. Toner supply roller (12) ・ Diameter ...... 20mm ・ Rotation Number: 200 rpm-Recovery bias voltage (Vss) -DC-400V, AC 700V-AC frequency: 300Hz-Concave depth: 25μm-Supply roller convex area: Convex to toner transfer area (S) area Area (%) of part (Pb) (Refer to Fig. 3) Case 1 ... 11% 〃 2… 20 〃 〃 3… 31 〃 〃 4… 41 〃 ・ Small concavo-convex pattern (P) See Fig. 3 pattern column c. Gap ・ Development gap (Ds) …… 0.6mm ・ Head height regulation gap (Db) …… 0.45mm ・ Supply gap (Dss) …… 0.8mm d. Regulating blade (12a) ・ Thickness …… t = 150μm ・ Pressing force …… 0.7 g / mm [Experimental result] Copy under the above conditions, and observe the degree of background fog appearing in the copied image every 1,000 sheets. The results are shown in Figure 4. The rank of the background fog was set as follows. As is clear from FIG. 4, cases 1 and 2 (projection area: 1
In the case of 1,20%), even if 5,000 copies are made, there is almost no change in the fogging rank at the initial stage, and the value of "4.5" can be maintained. In case 3 (convex area: 31%), if the number of copies exceeds 3,000, a slight fog will appear on the background, but the fog rank will remain at "4" even after copying 5,000 copies. Yes, there is no problem in practice. However, in case 4 (convex area: 41%), fog gradually appears when the number of copies exceeds 1,000, and the fog rank reaches "3" at the end of copying 5,000,
Image quality deteriorates to the limit of practical use. From the above, the convex portion of the toner supply roller (12) (P
If the surface area b) is about 30% or less of the toner transfer area, a clear image free from fog can be obtained for a long period of time. On the contrary, if the surface area of the convex portion (Pb) is 30% or more of the toner transport area, the degree of fogging appearing on the image becomes worse as the number of copies increases. For this reason, it is necessary to remove the toner in the toner containing layer and load new toner every time when copying about 5,000 sheets. (Effects of the Invention) As is apparent from the above description, in the developing device according to the present invention, the area of the convex portion of the surface fine irregularities of the toner supply roller is 30% or less of the toner transport area. Therefore, the toner collected from the developing sleeve or the toner scattered and floating in the developing device is held by the convex portion on the surface of the supply roller and further scraped by the regulation blade, and the amount of the charged toner mixed in the toner storage tank is extremely large. Even if the developing device is used for a long time, the amount of charged toner deposited in the toner storage tank is small. Therefore, the amount of toner agglomerates mixed in the toner storage tank and combined with the uncharged toner is small, and even if the toner agglomerates are supplied onto the developing sleeve, the toner agglomerates are not formed. It is easily crushed by the developer conveyed above and is used for development together with other charged toner. Therefore, a clear image without spots and fog can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a developing device according to the present invention, FIG. 2 is a perspective view of a toner supply roller, and FIGS. 3 and 4 are experiments on fog by changing minute irregularities of the toner supply roller. It is a figure showing the result of having performed. 1 ... Developing device, 4 ... Developing sleeve, 6 ... Magnetic roller, 12 ... Toner supply roller, 18 ... Regulator blade, 22 ... Toner storage tank, P ... Small concavo-convex pattern, Pa ... Recessed portion, Pb: convex portion, S: toner transport area.

Continuation of front page        Panel     Referee Takehiko Takahashi     Judge Yuichi Ikeda     Judge Mizugaki                (56) References JP-A-59-210463 (JP, A)                 JP 57-185052 (JP, A)                 JP 59-189374 (JP, A)

Claims (1)

(57) [Claims] A developing roller having a plurality of magnets is made to face a supply roller having minute irregularities formed on the surface of the toner transport area, and the toner taken into the minute irregularities is supplied to the surface of the developing sleeve based on the rotation of the supply roller. On the other hand, in the electrostatic latent image developing device in which the toner supply amount is regulated by the regulation blade that is in pressure contact with the supply roller, the minute irregularities on the surface of the supply roller are provided in a grid pattern, and the convex portions that are in pressure contact with the regulation blade The surface area should be 30% or less of the area of the toner transport area, and the depth of the concave portion should be 10 μm to 50 μm.
An electrostatic latent image developing device characterized in that