JP2011039278A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce rotation torque of an entire apparatus, in an image forming apparatus that includes a plurality of image forming units, each of which has a releasing roller disposed in such a state that it is bitten into the surface of a developing roller. <P>SOLUTION: The image forming apparatus includes a plurality of image forming units 50, each of which includes: a developing roller 56 rotated while holding a developing liquid DL composed of a mixture of carrier liquid and toner particles; a corona discharger 57 for forming a toner particle layer TL by agglomerating, on the surface of the developing roller 56, the toner particles contained in the developing liquid DL carried by the developing roller 56; a cleaning blade 58 for scraping the developing liquid DL on the developing roller 56 while being brought into sliding contact with the developing roller 56; and the releasing roller 59 for releasing agglomeration of toner particles on the developing roller 56 by rotating in the same direction as the developing roller 56 in a state of being bitten into the surface of the developing roller 56. The image forming units 50 differ from one another in the biting amount of the releasing roller 59 into the developing roller 56. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image with a developer obtained by mixing toner particles (developer particles) in a carrier liquid.

  In general, in an image forming apparatus that forms an image with a developer obtained by mixing toner particles in a carrier liquid, a part of the developer carried on the developing roller is supplied to a photoconductor to form a toner image and develop. What remains on the roller is collected by a cleaning blade or the like and reused or discarded.

  In such an image forming apparatus, in order to uniformly supply toner particles to the electrostatic latent image on the photoreceptor, the toner particles in the developer are developed by, for example, discharging electric charges to the developer carried on the developing roller. Aggregates on the surface of the roller. For this reason, when the developer remaining on the developing roller is collected by the cleaning blade, the aggregated toner particles sometimes harden at the tip of the cleaning blade.

  Therefore, in order to solve this, a release roller is provided on the upstream side of the cleaning blade in the rotation direction of the developing roller, which is in sliding contact with the developing roller while rotating in the direction opposite to the moving direction of the surface of the developing roller. A configuration in which aggregation of toner particles is canceled is known (for example, see Patent Document 1).

Japanese Patent Laying-Open No. 2006-30719 (FIG. 16)

  By the way, it is easy to release the aggregation of the toner particles by disposing the release roller as described above so as to press more strongly against the developing roller. However, by causing the release roller to bite deeply into the developing roller, there arises a problem that the release roller becomes a resistance and the rotational torque of the developing roller increases.

  In particular, in a configuration including a plurality of developing rollers, such as an image forming apparatus that forms a color image, the rotational torque of each developing roller increases, so that the rotational torque of the entire apparatus increases, and a motor that is a driving source. There is a risk that a large load will be applied to the device or noise may be generated. In some cases, it is necessary to increase the size of the motor in order to cope with the load, which may lead to an increase in power consumption and an increase in motor driving sound.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the rotational torque of the entire apparatus in an image forming apparatus including a plurality of image forming units having release rollers arranged in a state of being bitten into the surface of the developing roller.

  In order to achieve the above object, an image forming apparatus of the present invention is an image forming apparatus that forms an image with a developer obtained by mixing developer particles in a carrier liquid, and that rotates while carrying the developer. A roller, aggregating means for aggregating developer particles contained in the developer carried on the developing roller on the surface of the developing roller, and cleaning that scrapes the developer on the developing roller in sliding contact with the developing roller. And a member, disposed upstream of the cleaning member in the rotation direction of the developing roller and downstream of the position facing the aggregating means, and rotates in the same direction as the developing roller in a state of biting into the surface of the developing roller. A plurality of image forming units having a release roller for releasing the aggregation of the developer particles on the developing roller. At least one blood bite amount of the release roller against the developing roller are different from each other from the other image forming units.

  According to the image forming apparatus configured as described above, at least one of the plurality of image forming units is different from the other image forming units in that the amount of biting of the release roller with respect to the developing roller is optimal for each image forming unit. The amount of biting can be set. Here, the toner particles are not completely the same in the components and amounts of pigments and charge control agents for each color, and the particle diameter, charging characteristics, viscosity when mixed in the carrier liquid, etc. are different for each color. It is difficult to make the conditions perfectly uniform. Therefore, according to the above-described image forming apparatus, for example, the amount of biting of the release roller is increased in an image forming unit that uses toner particles of a color that is strongly aggregated on the developing roller, and the release roller of other image forming units is used. Since the amount of biting can be reduced, the rotational torque required for driving the entire apparatus can be reduced.

  According to the image forming apparatus of the present invention, since at least one of the plurality of image forming units has a biting amount of the release roller with respect to the developing roller different from other image forming units, the optimum biting amount for each image forming unit. Thus, it is possible to reduce the rotational torque required for driving the entire apparatus.

1 is a diagram illustrating a schematic configuration of a color printer as an example of an image forming apparatus according to an embodiment of the present invention. It is an enlarged view of an image forming unit. FIG. 4 is an explanatory diagram (a) of aggregation of toner particles contained in the developer, and an explanatory diagram (b) when the voltage applied to the discharge wire is larger than in the case of (a). It is explanatory drawing of an effect | action of a cancellation | release roller. It is explanatory drawing of the amount of biting of a cancellation | release roller. FIG. 4 is a schematic diagram illustrating a biting amount of each release roller and an arrangement of image forming units in a color printer. It is explanatory drawing of the thickness of the carrier liquid layer formed on a developing roller, a photoreceptor drum, and an intermediate transfer belt. 4 is a table (a) to (d) showing an arrangement order of image forming units and a thickness of a carrier liquid layer formed on a developing roller, a photosensitive drum, and an intermediate transfer belt.

<Overall configuration of color printer>
Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, the direction will be described with reference to a user who uses the color printer 1 as an example of the image forming apparatus. That is, the right side in FIG. 1 is “front”, the left side is “rear”, the front side is “left”, and the back side is “right”. Also, the vertical direction in FIG.

  As shown in FIG. 1, the color printer 1 is an apparatus that forms an image with a developer DL, and a main body housing 10 includes a paper feeding unit 30, four LED units 40, and four (plural). An image forming unit 50, a transfer unit 60, and a fixing unit 70 are mainly provided. The developer DL of the present embodiment is a mixture of positively charged toner particles T (developer particles) and a non-volatile carrier liquid C (see FIG. 3).

  The paper feed unit 30 is provided in the lower part of the main body housing 10, and a paper feed tray 31 that accommodates the paper S, and a transfer position P (intermediate transfer belt 63 and secondary transfer from the paper feed tray 31). The sheet feeding mechanism 32 is mainly provided to convey the sheet to a nip position with the roller 65. The sheets S in the sheet feeding tray 31 are separated one by one by the sheet feeding mechanism 32 and conveyed to the transfer position P.

  The LED unit 40 is arranged to face the lower side of the photosensitive drum 51, and a plurality of light emitting units (LEDs) (not shown) are arranged at the tip in the axial direction (left-right direction) of the photosensitive drum 51. The LED unit 40 blinks the light emitting portion based on the image data to expose the surface of the photosensitive drum 51 that is uniformly charged by the charger 52, and the static electricity based on the image data is exposed on the photosensitive drum 51. An electrostatic latent image is formed.

  The image forming unit 50 is disposed above and below the paper supply unit 30 in the front-rear direction, and includes a photosensitive drum 51, a charger 52, a reservoir 53 for storing the developer DL, a supply roller 54, and an intermediate unit. A roller 55 and a developing roller 56 are mainly provided. The detailed configuration of the image forming unit 50 will be described later.

  The developer DL in the reservoir 53 is supplied to the developing roller 56 via the supply roller 54 and the intermediate roller 55 and is carried on the surface of the developing roller 56. The developer DL (toner particles T) carried on the surface of the developing roller 56 is supplied from the developing roller 56 to the electrostatic latent image on the photosensitive drum 51. As a result, the electrostatic latent image is visualized and a toner image is formed on the photosensitive drum 51.

  The transfer unit 60 is provided above the image forming unit 50, is stretched between the driving roller 61, the driven roller 62, and the driving roller 61 and the driven roller 62, and faces each photosensitive drum 51. An endless intermediate transfer belt 63 (intermediate transfer member) disposed, four primary transfer rollers 64 disposed opposite to the photosensitive drum 51 via the intermediate transfer belt 63, and driving via the intermediate transfer belt 63 A secondary transfer roller 65 disposed opposite to the roller 61 is mainly provided.

  The toner images of the respective colors formed on the photosensitive drums 51 are sequentially superimposed and transferred onto the intermediate transfer belt 63. The sheet S conveyed from the sheet feeding unit 30 passes between the intermediate transfer belt 63 and the secondary transfer roller 65 (transfer position P), so that the toner image on the intermediate transfer belt 63 is transferred to the sheet S. Transcribed.

  The fixing unit 70 is provided on the upper rear side of the transfer unit 60 and mainly includes a heating roller 71 and a pressure roller 72 that is disposed to face the heating roller 71 and presses the heating roller 71. The sheet S on which the toner image has been transferred passes between the heating roller 71 and the pressure roller 72 so that the toner image is thermally fixed, and is discharged onto the discharge tray 12 by the discharge roller 73.

<Detailed configuration of image forming unit>
Next, a detailed configuration of each part of the image forming unit 50 will be described. Each image forming unit 50 has substantially the same configuration except that the color of the toner particles T in the developer DL stored in the storage unit 53 is different.

  As shown in FIG. 2, the image forming unit 50 includes a corona discharge as an example of aggregating means in addition to the above-described photosensitive drum 51, charger 52, reservoir 53, supply roller 54, intermediate roller 55, and developing roller 56. An electric device 57, a cleaning blade 58 as an example of a cleaning member, and a release roller 59 are further provided.

  The photosensitive drum 51 is configured by forming a photosensitive layer on the surface (outer peripheral surface) of a cylindrical drum body having conductivity, and is upstream of the release roller 59 in the rotation direction of the developing roller 56 and a corona discharger. It is arranged downstream of the position facing 57. The developer DL remaining on the photosensitive drum 51 without being supplied to the intermediate transfer belt 63 is scraped and collected by the collecting blade 51B, and stored in a waste developer tank (not shown).

  The charger 52 is arranged to be opposed to the photosensitive drum 51 at a predetermined interval so as not to contact the photosensitive drum 51, and is configured to uniformly charge the surface of the photosensitive drum 51 by discharging electric charges to the photosensitive drum 51. Has been.

  The reservoir 53 stores the developer DL supplied from a known concentration adjusting unit 80 that adjusts the concentration of the developer DL (weight ratio of the toner particles T to the carrier liquid C).

  The supply roller 54 is a metal roller that rotates to carry the developer DL stored in the storage unit 53 on the surface and supply the developer DL to the intermediate roller 55.

  The intermediate roller 55 is a metal roller configured to be able to carry a predetermined amount of developer DL in a groove formed on the surface. By supplying the developer DL to the developing roller 56 via the intermediate roller 55, the supply amount of the developer DL to the developing roller 56 can be kept uniform. A liquid amount regulating blade 55B that scrapes off the developer DL is in sliding contact with the intermediate roller 55.

  The developing roller 56 is a roller that rotates while carrying the developer DL supplied from the intermediate roller 55 on its surface, and supplies the developer DL (toner particles T) to the photosensitive drum 51. The developing roller 56 (at least the surface of the roller portion) is formed of urethane rubber softer than the release roller 59 or the like.

  As shown in FIG. 3A, the corona discharger 57 is disposed opposite to the developing roller 56 at a predetermined interval so as not to contact the developing roller 56, and is a discharge wire stretched along the axial direction of the developing roller 56. 57A is mainly provided. The corona discharger 57 generates a corona discharge when a voltage is applied to the discharge wire 57A, and discharges the charge to the developer DL carried on the surface of the developing roller 56, thereby causing toner particles T contained in the developer DL. Are aggregated so as to be pressed toward the surface of the developing roller 56.

  As a result, the developer DL carried on the surface of the developing roller 56 is separated into a toner particle high concentration layer having a high toner particle T concentration (weight ratio) and a toner particle low concentration layer having a low toner particle T concentration. The In the following, for convenience of explanation, the toner particle high-concentration layer is referred to as a toner particle layer TL, and the toner particle low-concentration layer is referred to as a carrier liquid layer CL. The toner particles T are mixed with the carrier liquid C only by the difference (the toner particles T contained in the carrier liquid layer CL are not shown in FIG. 3).

  Returning to FIG. 2, the cleaning blade 58 is a member that slidably contacts the rotating developing roller 56 to scrape and collect the developer DL on the developing roller 56. The collected developer DL is returned to the density adjusting unit 80 and reused.

  The release roller 59 is a metal roller, and develops on the upstream side of the cleaning blade 58 in the rotation direction of the developing roller 56 and on the downstream side of the position facing the corona discharger 57 (the position in contact with the photosensitive drum 51). The roller 56 is arranged so as to bite into the surface. The release roller 59 is in sliding contact with the developing roller 56 while rotating in the same direction as the developing roller 56 to release the aggregation of the toner particles T on the developing roller 56.

  Specifically, as shown in FIG. 4, the toner particles T (developing liquid DL) that are not supplied to the photosensitive drum 51 and remain on the developing roller 56 collide with the release roller 59. At this time, the opposing surfaces of the developing roller 56 and the releasing roller 59 move in the opposite directions and rub against each other strongly, so that a part of the toner particles T aggregated on the surface of the developing roller 56 is scraped by the releasing roller 59. Taken, the aggregation is released and dispersed again in the carrier liquid C.

  Further, the remaining part of the aggregated toner particles T adheres to the surface of the release roller 59. Thereafter, the toner particles T adhering to the surface of the release roller 59 collide with the developing roller 56 and are scraped off, or collide with the toner particles T slipped between the developing roller 56 and the release roller 59. Aggregation is released and dispersed again in the carrier liquid C.

  Since the aggregation of the toner particles T on the developing roller 56 is released in this way, the toner particles T are prevented from being hardened at the tip of the cleaning blade 58 and the like. Will be able to.

  Such a release roller 59 can easily release the aggregation of the toner particles T by increasing the amount of biting into the developing roller 56. Here, the amount of biting (D) of the release roller 59 is, as shown in FIG. 5, the surface of the development roller 56 is recessed by pressing the release roller 59 against the development roller 56, and the release roller 59 The amount (the distance between A1 and A2) entering the developing roller 56 is assumed.

  As schematically shown in FIG. 6, in this embodiment, each image forming unit 50 is different from the other image forming units 50 in the amount of biting of the release roller 59 with respect to the developing roller 56. Specifically, in the four image forming units 50, the amount of biting of the release roller 59 with respect to the developing roller 56 is larger as the image forming unit 50 has a larger cohesive force of the corona discharger 57.

  Here, “the cohesive force is large” means that the ability of the toner particles T to aggregate on the surface of the developing roller 56 is large, and specifically, that the voltage applied to the discharge wire 57A is large. To do. As shown in FIG. 3B, when the voltage applied to the discharge wire 57A is increased, the amount of charge applied to the developer DL carried on the surface of the developing roller 56 is increased. It is possible to strongly aggregate toward the surface of 56. As a result, the thickness of the toner particle layer TL becomes thinner compared to the case where the voltage applied to the discharge wire 57A is small (see FIG. 3A) (note that the thickness of the toner particle layer TL is reduced). As a result, the carrier liquid layer CL is relatively thick.)

  Therefore, as shown in FIG. 6, in the four image forming units 50, the biting amount of the release roller 59 is set larger as the toner particle layer TL on the developing roller 56 is thinner. Specifically, the biting amount of the release roller 59 is set larger in the image forming unit 50 arranged on the front side (upstream side in the traveling direction of the intermediate transfer belt 63).

  As described above, since the release roller 59 can easily release the aggregation of the toner particles T by increasing the biting amount, the thickness of the toner particle layer TL on the developing roller 56 is thin (toner particle T By increasing the amount of biting in the image forming unit 50 (having a corona discharger 57 that strongly aggregates the toner particles), the aggregation of the toner particles T can be released more reliably.

  As a means for making the amount of biting of the release roller 59 different, for example, each image forming unit 50 is manufactured by changing the distance between the axes of the developing roller 56 and the release roller 59 for each unit, or for each unit. Alternatively, it may be manufactured by changing the spring pressure of the spring that presses the release roller 59 against the developing roller 56. Each image forming unit 50 is manufactured as a common component, and is provided with a configuration in which the distance between the axes of the developing roller 56 and the releasing roller 59 can be changed, or the spring pressure of the spring that presses the releasing roller 59 against the developing roller 56 The amount of biting in may be different by providing a configuration capable of changing the above and adjusting them.

  According to the color printer 1 of the present embodiment described above, each image forming unit 50 differs from the other image forming units 50 in that the amount of biting of the release roller 59 with respect to the developing roller 56 is optimal for each image forming unit 50. The amount of biting can be set. Thereby, for example, in each image forming unit 50, the amount of biting of each release roller 59 is set to the minimum value that can release the aggregation of the toner particles T, thereby reducing the rotational torque required for driving the entire apparatus. can do. As a result, it is possible to reduce the load applied to a drive source such as a motor to extend the life of the apparatus or to suppress the generation of noise. In addition, the motor can be miniaturized by reducing the load, and the power consumption and operation sound of the color printer 1 can be suppressed.

  In the present embodiment, the four image forming units 50 have a larger amount of biting as the image forming unit 50 having a larger cohesive force of the corona discharger 57. Therefore, the amount of biting of each release roller 59 is set to the minimum value as described above. It is possible to reliably cancel the aggregation of the toner particles T while setting. As a result, the rotational torque required for driving the entire apparatus can be reduced, and the developer DL can be satisfactorily collected by the cleaning blade 58.

  In FIG. 6, for convenience of explanation, the thickness of the toner particle layer TL and the carrier liquid layer CL and the amount of biting of the release roller 59 are highlighted. In FIG. 6, illustration of the toner particle layer formed on the photosensitive drum 51 and the intermediate transfer belt 63 is omitted, but the toner particle layer TL (toner particle T) is formed on the developing roller 56 from the photosensitive drum. The image is transferred to an exposed portion (exposed portion by laser light) on 51 and further transferred onto the intermediate transfer belt 63.

<Order of image forming units>
Next, the arrangement order of the image forming units 50 in the present embodiment will be described.
As shown in FIG. 7 (the toner particle layer is not shown), the inventors of the present application have (1) the thickness C ₂ of the carrier liquid layer CL formed on the photosensitive drum 51 is equal to the carrier on the developing roller 56. be approximately half the thickness _{C 1} of the liquid layer CL _{(C 2 =} C 1/2), and, (2) a carrier liquid layer toner image is formed on the intermediate transfer belt 63 after transfer CL the sum of the thickness C ₄ is the thickness C ₃ of the carrier liquid layer CL on the intermediate transfer belt 63 immediately before the toner image is transferred, the thickness C ₂ of the carrier liquid layer CL on the photosensitive drum 51 (C ₄ = (C ₃ + C ₂ ) / 2) is found as an experimental fact.

  According to this, when a plurality of image forming units 50 are arranged, as shown in FIG. 8A, the toner images are intermediately transferred in order from the image forming unit 50 having a thick carrier liquid layer CL on the developing roller 56. By arranging so as to transfer to the belt 63, the carrier on the intermediate transfer belt 63 after all the toner images have been transferred as compared with other arrangements (see FIGS. 8B to 8D). It is possible to reduce the thickness of the liquid layer CL. As a result, the amount of the carrier liquid C that moves from the intermediate transfer belt 63 to the paper S at the transfer position P (see FIG. 1) can be reduced, so that the fixability of the toner image transferred to the paper S can be improved. it can.

  Therefore, also in this embodiment, the four image forming units 50 are arranged so as to transfer the toner images to the intermediate transfer belt 63 in order from the thickest carrier liquid layer CL on the developing roller 56. .

  Specifically, as shown in FIGS. 1 and 6, the image forming unit 50 </ b> A having the largest carrier liquid layer CL on the developing roller 56 rotates in the clockwise direction in the figure starting from the transfer position P. The transfer belt 63 is disposed on the foremost side so as to transfer the toner image first. Next, the image forming unit 50B with the second thickest carrier liquid layer CL on the developing roller 56 is the second thickest image forming unit from the front side, and the image forming unit with the third thickest carrier liquid layer CL on the developing roller 56 is formed. 50C is arranged third from the front side. The image forming unit 50 </ b> D having the thinnest carrier liquid layer CL on the developing roller 56 is disposed on the rearmost side so as to transfer the toner image last to the intermediate transfer belt 63.

  Here, as shown in FIGS. 3A and 3B, when the carrier liquid layer CL on the developing roller 56 is thick, the toner particles T are strongly aggregated on the surface of the developing roller 56. Therefore, the thickness of the toner particle layer TL is relatively thin. Further, when the thickness of the carrier liquid layer CL on the developing roller 56 is thin, the toner particles T are not strongly aggregated on the surface of the developing roller 56, so the thickness of the toner particle layer TL is relatively thick. It has become.

  Therefore, in other words, the four image forming units 50 are arranged so as to transfer the toner images to the intermediate transfer belt 63 in order from the toner particles layer TL on the developing roller 56 having the smallest thickness (toner particles). The thinner the layer TL is, the more it is disposed on the front side). In the present embodiment, the image forming unit 50 having a thinner toner particle layer TL on the developing roller 56 (the corona discharger 57 has a larger cohesive force) has a larger biting amount of the release roller 59 with respect to the developing roller 56. It has become.

  From the above, when the arrangement order of the image forming units 50 is described in relation to the biting amount of the release roller 59, the four image forming units 50 are arranged in order of toner images in descending order of the biting amount of the release roller 59 with respect to the developing roller 56. Are transferred to the intermediate transfer belt 63 (the larger the amount of bite, the more the front side is disposed).

  As described above, according to the color printer 1 in which the four image forming units 50 (50A to 50D) are arranged, the rotational torque required for driving the entire apparatus can be reduced and the sheet S is further moved. Since the amount of the carrier liquid C can be reduced, the fixability of the toner image can be improved.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. About a concrete structure, it can change suitably in the range which does not deviate from the meaning of this invention.

  In the above-described embodiment, the four image forming units 50 have a release roller with respect to the developing roller 56 as the corona discharger 57 (aggregating unit) has a larger aggregating force (the toner particle layer TL on the developing roller is thinner). Although the amount of biting 59 was increased, it is not limited to this. For example, toner particles have different agglomeration conditions because the particle size, charging characteristics, viscosity when mixed in a carrier liquid, etc. differ from color to color due to differences in the components and amounts of pigments and charge control agents for each color. May not match. Therefore, due to the difference in cohesive force of the toner particles themselves, even if the cohesive force of the coagulating means is the same, the toner particle layer may be thinner than other toner particles, and the thickness of the toner particle layer may be reduced. . Therefore, the plurality of image forming units may increase the amount of biting of the release roller with respect to the developing roller as the cohesive force of the toner particles contained in the developing solution increases. In other words, the amount of biting of the release roller with respect to the developing roller may be increased as the image forming unit uses a developer containing toner particles that are strongly aggregated on the surface of the developing roller. According to this, for example, the amount of biting of the release roller is increased in an image forming unit that uses toner particles of a color that is strongly aggregated on the developing roller, and the amount of biting of the release roller is decreased in other image forming units. Therefore, the rotational torque required for driving the entire apparatus can be reduced.

  In the above embodiment, the four image forming units 50 have different amounts of biting by the release roller 59, but the present invention is not limited to this. For example, among the four image forming units 50, only the amount of biting of one release roller 59 may be different from the other three image forming units 50. Further, of the four image forming units 50, the two biting amounts may be large, and the remaining two image forming units 50 may be small. Further, among the four image forming units 50, one biting amount may be large, the other one biting amount may be small, and the remaining two biting amounts may be about the middle of the two.

  In the above-described embodiment, the corona discharge device 57 is illustrated as the aggregating unit so as to face the developing roller 56 with a predetermined interval therebetween, but is not limited thereto. For example, it may be a roller that rotates while being in contact with the developing roller and discharges electric charges to the developer carried on the surface of the developing roller by applying a voltage.

  In the above-described embodiment, the intermediate transfer belt 63 is exemplified as the intermediate transfer member. However, the intermediate transfer belt 63 is not limited thereto, and may be, for example, a roller-shaped intermediate transfer member.

  In the embodiment, the color printer 1 is exemplified as the image forming apparatus. However, the image forming apparatus is not limited to this, and may be, for example, a copying machine or a multifunction machine. In the above embodiment, an apparatus using positively charged toner particles T has been exemplified. However, the present invention is not limited to this, and the present invention can also be applied to an apparatus using negatively charged toner particles.

  Next, it was proved that the aggregation of the toner particles can be canceled by increasing the amount of biting of the release roller with respect to the developing roller under the condition that the toner particles contained in the developer are strongly aggregated on the surface of the developing roller. An experimental example will be described.

  In this experiment, using the image forming unit configured as shown in FIG. 2, white solid printing (printing performed without exposing the photosensitive drum) was performed under the following conditions, and the tip of the cleaning blade at this time The state of the nearby developer was observed. The results are shown in Table 1.

[Experimental conditions]
(1) Developing roller Material: Urethane rubber Diameter: 22mm
Development bias: 600V
Rotation speed: 180mm / sec
(2) Corona discharger Applied current: 15.0μA (Condition with low cohesive force)
: 22.4 μA (conditions where cohesive force is large)
(3) Release roller (no voltage is applied)
Material: Stainless steel Diameter: 8mm
Rotation speed: 180mm / sec
Biting amount: 110 μm, 130 μm or 230 μm
(4) Developer Toner particle concentration: 35% (weight ratio)

  In Table 1, “◯” means that the collected developer was flowing well on the cleaning blade, and “×” means that the developer was collected near the tip of the cleaning blade. Means that.

  As shown in Table 1, under the condition that the cohesive force of the corona discharger is small (toner particle cohesion is weak), the developer flowed satisfactorily on the cleaning blade at any biting amount. Accordingly, it was confirmed that the toner particle aggregation is released under the condition that the toner particle aggregation is weak even when the biting amount is 110 μm.

  On the other hand, when the corona discharger has a large cohesive force (toner particle cohesion is strong), if the amount of biting is small (110 μm, 130 μm), the developer may accumulate at the tip of the cleaning blade. When the amount was increased (230 μm), the developer flowed well on the cleaning blade. Accordingly, it was confirmed that the aggregation of the toner particles can be canceled by increasing the amount of biting of the release roller even under the condition where the aggregation of the toner particles is strong.

DESCRIPTION OF SYMBOLS 1 Color printer 50 Image forming unit 51 Photoconductor drum 56 Developing roller 57 Corona discharger 58 Cleaning blade 59 Release roller 63 Intermediate transfer belt C Carrier liquid DL Developer T Toner particle

Claims (3)

An image forming apparatus for forming an image with a developer obtained by mixing developer particles in a carrier liquid,
A developing roller that rotates while carrying the developer; aggregating means for aggregating developer particles contained in the developer carried on the developer roller on the surface of the developer roller; A cleaning member that scrapes off the developer on the roller, and is disposed on the upstream side of the cleaning member in the rotation direction of the developing roller and on the downstream side of the position facing the aggregating means, and bites into the surface of the developing roller. A plurality of image forming units having a release roller that rotates in the same direction as the developing roller and releases aggregation of developer particles on the developing roller;
At least one of the plurality of image forming units is different from other image forming units in the amount of biting of the release roller with respect to the developing roller.   2. The image forming apparatus according to claim 1, wherein the plurality of image forming units have a larger amount of biting of the release roller with respect to the developing roller as the aggregation force of the aggregation unit is larger. The developer particles provided in each of the plurality of image forming units, arranged upstream of the release roller in the rotation direction of the developing roller and downstream of the position facing the aggregating unit, are supplied from the developing roller. A photosensitive drum on which a developer image is formed;
An intermediate transfer member that is arranged to face each of the photosensitive drums and onto which a developer image on the photosensitive drum is transferred;
3. The image according to claim 2, wherein the plurality of image forming units are arranged so as to transfer a developer image to the intermediate transfer member in descending order of the amount of biting of the release roller with respect to the developing roller. Forming equipment.

Images