JP2001042614A - Developing device and color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a satisfactory image provided with sufficient image density in a developing device, where a toner carrier is made to rotated so that it is moved from bottom to top in a developing range that faces with the image carrier. SOLUTION: In the developing device which carries out developing by making the toner carrier 21 of a roll state rotate, so that the carrier 21 is moved from the bottom to the top in the developing range that is faced with the image carrier 10, a pre-electrifying member 26 is installed so that it is in contact with the toner carrier in a position farther downstream in the rotating direction of the toner carrier than a toner feeding member 25 from which toner is fed to the toner carrier, a restricting member 27 is installed so that it is in contact with the bottom pat of the toner carrier farther downstream in the rotating direction of the toner carrier than the pre-electrifying member 26, conductivity is imparted to at least a part of the pre-electrifying member 26, where it is in contact with the toner carrier and so as to impress a bias voltage to this conductive part, making the toner electrified to a prescribed polarity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine or a printer, and a color image forming a color image by storing toners of different colors in such a developing device. Related to the forming device,
In particular, when only toner is used as the developer and the toner is guided to the developing area facing the image carrier by the toner carrier in the form of a roller, the development is performed in the developing area facing the image carrier. The toner carrier is rotated so as to move upward from, and a regulating member is provided below the toner carrier so that the amount of toner conveyed to the developing area by the toner carrier is regulated by the regulating member. The present invention relates to a developing device and a color image forming apparatus using such a developing device.

[0002]

2. Description of the Related Art Conventionally, as a developing device used in an image forming apparatus such as a copying machine or a printer, in addition to a two-component developing system using a toner and a carrier as a developer, a developing method using no carrier is used. 1 using only toner
A component developing system is known.

[0003] Here, a developer using only toner as a developer 1
As shown in FIG. 1, for example, as shown in FIG. 1, a toner t contained in a container 1 a of a device main body 1 is sent to a roller-shaped toner supply member 3 by a toner feed member 2. The toner supply member 3 is rotated to supply the toner t to the toner carrier 4 in the form of a roller. The toner t thus supplied is conveyed by the rotation of the toner carrier 4 and the toner carrier 4 is rotated. The regulating member 5 is pressed against the surface of the toner carrier 4 to regulate the amount of the toner t conveyed by the toner carrier 4 and to frictionally charge the toner t. The one in which t is guided to a development area facing the image carrier 6 by the toner carrier 4 to perform development has been used.

Here, in the conventional developing device, as shown in FIG. 1, in the developing region where the toner carrier 4 and the image carrier 6 are opposed to each other, the toner carrier 4 and the image carrier 6 are respectively positioned upward. Was rotating to move downward from

However, depending on the type of image forming apparatus, it may be necessary to move the above-described image carrier upward from below in the developing area. In particular, a plurality of developing apparatuses are provided with toners of different colors. In a color image forming apparatus provided with an intermediate transfer member for transferring a toner image formed on an image carrier in an overlapping manner when forming a color image by housing the image carrier, the image carrier is required to be compact. It was sometimes necessary to move the developing area upward from below.

Here, when the image carrier is moved upward from below in the developing area, the toner carrier is rotated so as to move downward from above in the developing area as described above. When the body and the image carrier are brought into contact with each other to develop the toner, the toner accumulates in an upstream portion where the toner carrier comes into contact with the image carrier, and the toner spills to the outside or fog occurs on the formed image. In the case where development is performed without bringing the toner carrier and the image carrier into contact with each other, there is a problem that a leak easily occurs between the toner carrier and the image carrier.

In recent years, Japanese Patent Application Laid-Open No. 8-29
As described in JP-A-7411, JP-A-9-244406, JP-A-10-171226, etc., the image carrier moves upward from below in the developing region where the toner carrier and the image carrier face each other. In such a case, there has been proposed a developing device in which the toner carrier rotates so as to move upward from below in the developing region.

Here, when the toner carrier is rotated so as to move upward from below in the developing area, a regulating member for regulating the toner supplied to the toner carrier may be provided on the lower side of the toner carrier. Needed.

However, when the regulating member is provided below the toner carrier, a certain amount of toner is separated from the toner carrier by its own weight before the toner supplied to the toner carrier is guided to the regulating member. And the sufficient amount of toner is not guided to the developing area, and the density of the formed image is reduced.

For this reason, as shown in Japanese Patent Application Laid-Open No. Hei 10-171226, the surface of the toner carrier is in contact with the surface of the toner carrier at a position upstream of the regulating member for regulating the amount of toner in the toner carrier. There is also proposed a device provided with a seal member so as to perform the above operation.

However, even when the sealing member is provided so as to be in contact with the toner carrier on the rotation direction upstream side of the toner carrier with respect to the regulating member, the toner is not sufficiently held by the toner carrier. However, there is a problem in that the toner drops away from the toner carrier before being guided to the position of the regulating member, and the density of the formed image still decreases. And so on.

[0012]

SUMMARY OF THE INVENTION According to the present invention, when a toner is guided by a rotating toner carrier to a developing region facing the image carrier to perform development, the developing region facing the image carrier is moved upward from below. And a regulating member provided below the toner carrier to regulate the amount of toner conveyed to the developing area by the toner carrier. It is an object of the present invention to solve the above-mentioned problem in the above.

That is, according to the present invention, in the developing device as described above, the toner supplied to the toner carrier is prevented from dropping away from the toner carrier before being guided to the regulating member, and a sufficient amount of toner is prevented. It is an object of the present invention to make it possible to obtain a good image having a sufficient image density without causing a decrease in density or blurring even when a solid image is formed, by causing the toner to be guided to a development area. Is what you do.

[0014]

In the developing device according to the present invention, in order to solve the above-mentioned problems, the toner is guided by a roller-shaped toner carrier to a developing area opposed to the image carrier. In the developing device that performs
The above-mentioned toner carrier is rotated so as to move upward from below in a developing area opposed to the image carrier, and a position on the downstream side in the rotation direction of the toner carrier with respect to a toner supply member for supplying toner to the toner carrier. The pre-charging member is provided so as to be in contact with the toner carrier, and is conveyed to the developing area by the toner carrier such that the pre-charging member contacts the lower portion of the toner carrier downstream of the pre-charging member in the rotation direction of the toner carrier. A regulating member that regulates the amount of toner to be supplied, imparts conductivity to at least a portion of the pre-charging member that contacts the toner carrier, and biases the conductive portion to charge the toner to a predetermined polarity. The voltage was applied.

Here, as in the developing device of the present invention, the pre-charging member is brought into contact with the toner carrier at a position downstream of the toner supply member for supplying the toner to the toner carrier in the rotation direction of the toner carrier. In the pre-charging member, at least a portion of the pre-charging member that is in contact with the toner carrier is provided with conductivity, and a bias voltage for charging the toner to a predetermined polarity is applied to the conductive portion. The supplied toner is appropriately pre-charged to a predetermined polarity by contact with the pre-charging member. Then, the toner thus pre-charged is held on the toner carrier by electrostatic force, and the toner drops away from the toner carrier before the toner is guided to the position of the regulating member by the toner carrier. Will be prevented.

Therefore, a sufficient amount of toner is guided to the position of the regulating member by the toner carrier, and the toner is appropriately regulated by the regulating member, so that an appropriate amount of toner is guided to the developing area. To obtain an image having a sufficient image density.

Further, in the developing device according to the present invention, at least a portion of the pre-charging member which contacts the toner carrier is frictionally charged to charge the toner to a predetermined polarity. When using a material positioned in the series, or when using a negatively charged toner, if at least a portion of the pre-charging member that contacts the toner carrier is formed of a material having a work function equal to or less than the toner, the toner carrying The toner supplied to the body is appropriately pre-charged to a predetermined polarity by contact with the pre-charging member, and a sufficient amount of toner is guided to the position of the regulating member by the toner carrier to appropriately As a result, an appropriate amount of toner is guided to the developing area to obtain an image having a sufficient image density, and a good image with less streak noise and the like. Obtained as to become.

Further, when the leading end of the pre-charging member is brought into contact with the toner carrier, if the surface roughness of the pre-charging member at the leading end contacting the toner carrier becomes too small, the toner on the surface of the pre-charging member may not be formed. The amount of toner that is not properly pre-charged due to slippage, is no longer sufficiently held by the toner carrier, falls away from the toner carrier before being guided to the position of the regulating member, and is guided to the developing area. And the density of the formed image decreases. On the other hand, if the surface of the pre-charging member at the leading end contacting the toner carrier is too rough, the amount of toner held and transported by the toner carrier due to the contact of the pre-charging member causes unevenness, and Density unevenness or the like occurs in the image to be reproduced. Therefore, the ten-point average roughness Rz of the surface where the pre-charging member is in contact with the toner carrier is defined as claim 4.
Is preferably set to 0.1 μm ≦ Rz ≦ 2.0 μm.

When the leading end of the pre-charging member is brought into contact with the toner carrier as described above, if the pressure contact force of the pre-charging member to be brought into contact with the toner carrier becomes weak, the toner is sufficiently pre-charged by the pre-charging member. The toner is no longer charged, is not sufficiently held by the toner carrier, and falls away from the toner carrier before being guided to the position of the regulating member, so that the amount of toner guided to the development area is reduced and formed. Image density decreases. On the other hand, if the pressure contact force of the pre-charging member to be brought into contact with the toner carrier becomes too strong, the toner having a large particle size does not pass through the pre-charging member, and only the toner having a small particle size is transported by the toner carrier. As a result, toner with a large particle size remains,
The quality of the image formed gradually changes. Therefore, when the tip of the pre-charging member is brought into contact with the toner carrier, it is preferable that the linear pressure of the pre-charging member with respect to the toner carrier be in the range of 0.1 to 4.0 gf / mm.

In the color image forming apparatus according to the present invention, a plurality of developing devices accommodating toners of different colors, and the toner images formed on the image carrier by these developing devices are transferred in a superimposed manner. In a color image forming apparatus provided with an intermediate transfer member, the above-described developing device of the present invention is used.

Each of the developing devices in the color image forming apparatus is provided with a developing device according to the present invention in which the toner carrier rotates so as to move upward from below in the developing region facing the image carrier. With the use of, it is possible to form an image having a sufficient image density by moving the image carrier from the bottom to the top in the development area, and, corresponding to the configuration of the color image forming apparatus,
The device can be made compact.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a developing device according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings.

In the developing device according to this embodiment,
A toner carrier 21 is provided so as to face the image carrier 10 with a small space therebetween, and the toner carrier 21 and the image carrier 10 are rotated in opposite directions to rotate the toner carrier 21 and the image carrier 10. The toner carrier 21 and the image carrier 10 are respectively moved upward from below in the development region where.

Further, in this developing device, the toner t is stored in the storing portion 20a of the device main body 20, and the toner feeding member 22 provided with the blade member 22a is rotatably provided.

Then, the toner feeding member 22 is rotated so that the toner t stored in the housing portion 20a by the blade member 22a of the toner feeding member 22 is supplied to the toner retaining portion 24 provided with the receiving member 23. I have to.

A toner supply member 25 in the form of a roller is provided in the toner retaining section 24 so as to be in contact with the toner carrier 21, and the toner supply member 25 is rotated in the same direction as the toner carrier 21. Thus, the toner supply member 25 and the toner carrier 21 are moved in the opposite direction at the contact portion, and the toner t is supplied from the toner supply member 25 to the toner carrier 21.

Further, one end of a plate-shaped pre-charging member 26 made of a conductive material is attached to the receiving member 23, and the pre-charging member 26 is rotated below the toner supply member 25 by rotating the toner carrier 21. The toner carrier 2 with respect to the toner supply member 25.
1 at the downstream side in the rotation direction, the leading end of the pre-charging member 26 is brought into contact with the pre-charging member 26 at an appropriate linear pressure along the axial direction of the toner carrier 21. A bias voltage for charging the toner t to a predetermined polarity is applied. In addition,
In the developing device of this embodiment, a gap of 1 mm or more is provided between both ends of the pre-charging member 26 and both side walls of the apparatus main body 20, and excessive toner t is removed from the accommodating portion 20 a of the apparatus main body 20 through the gap. To be returned inside.

When a bias voltage for charging the toner t to a predetermined polarity is applied to the pre-charging member 26 from the bias power supply 26a as described above, the toner carrier 21 is brought into contact with the pre-charging member 26. Is preliminarily charged to a predetermined polarity, and the preliminarily charged toner t is held on the toner carrier 21 by electrostatic force.

The lower portion of the toner carrier 21 downstream of the tip of the pre-charging member 26 in the rotation direction of the toner carrier 21 extends toward the upstream side in the rotation direction of the toner carrier 21. Plate-shaped regulating member 27
Is brought into contact with the toner carrier 21 so as to have an appropriate gap with the tip of the pre-charging member 26, and the toner t held by the toner carrier 21 by the electrostatic force as described above is regulated by the regulating member. 27. In this case, since the toner t is held on the toner carrier 21 by the electrostatic force as described above, the toner t is prevented from falling away from the toner carrier 21 before being guided to the regulating member 27, and is sufficiently reduced. A large amount of toner t
As a result, the toner t is guided to the position of the regulating member 27, and since the toner t is appropriately pre-charged to a predetermined polarity, the toner t is also prevented from adhering to the regulating member 27.

The regulating member 27 removes excess toner t from the toner carrier 21 to regulate the amount of toner t conveyed to the developing area and to regulate the amount of toner t.
Is charged. Note that this regulating member 27
The extra toner t released from the toner carrier 21 is guided downward through the gap, and is returned to the storage section 20a by a return roller 28 provided below the toner t.

Next, the toner t regulated and regulated by the regulating member 27 as described above is
1 to the developing area facing the image carrier 10,
In this development area, the toner carrier 21
And the image carrier 10 are respectively moved upward from below, and a developing bias voltage in which an AC voltage is superimposed on a DC voltage is applied from a developing bias power supply 29 to the toner carrier 21 so that the toner carrier 21 and the image carrier are An oscillating electric field is applied between the image bearing member 10 and the electrostatic latent image formed on the image bearing member 10 to supply toner t from the toner bearing member 21 to perform development. In this embodiment,
As described above, the development is performed with the toner carrier 21 and the image carrier 10 opposed to each other at a small interval in the development area, but the toner carrier 21 and the image carrier 10 are brought into contact with each other in the development area. It is also possible to cause the development.

After developing the electrostatic latent image formed on the image carrier 10 as described above, the toner carrier 2
The toner t remaining on the toner carrier 1 is returned to the apparatus main body 20, and at a position where the toner t remaining on the toner carrier 21 is returned to the apparatus main body 20, the sealing material 32 is pressed against the toner carrier 21 by the cushion material 31. Seal material 3
2, a voltage for removing the toner t is applied from the power supply 33 for removing the toner, so that the toner t remaining on the toner carrier 21 is removed.

Then, after the toner t remaining on the toner carrier 21 is neutralized, the toner t remaining on the toner carrier 21 is reversed at a portion where the toner t contacts the toner carrier 21 as described above. The toner is separated from the toner carrier 21 by the toner supply member 25 that moves in the direction, and is mixed with the toner t in the toner retaining section 24, and new toner t is supplied from the toner supply member 25 to the toner carrier 21 as described above. Let it be supplied.

Here, when the toner supply member 25 is moved in the direction opposite to the toner carrier 21 at the portion where the toner carrier 21 contacts as described above, the toner
5 is moved in the same direction as the toner carrier 21, only the toner t having a large particle diameter is detached from the toner carrier 21, and the toner t having a small particle diameter does not remain. 21 small toner t
The toner supply member 25 also ensures that the toner supply member 25 is separated from the toner carrier 21. For this reason, a large amount of the toner t having a small particle diameter is first used for development, and the ratio of the toner t having a large particle diameter in the storage portion 20a gradually increases.
The quality of the formed image does not change.

Next, in the developing device shown in FIG. 2, when the tip of the pre-charging member 26 is brought into contact with the toner carrier 21 to pre-charge the toner t as described above, the pre-charging member 26 An experiment in which the bias voltage applied from the bias power supply 26a is changed is performed to clarify the advantages of the developing device according to the embodiment of the present invention with reference to a comparative example.

(Experiment 1) In this experiment, a photosensitive drum having a diameter of 30 mm was used as the image carrier 10 and a toner carrier having a diameter of 16 mm was used as the toner carrier 21. The carrier 21 and the image carrier 10 are provided so as to face each other with an interval of 200 μm, and the toner carrier 21 and the image carrier 10 are rotated in opposite directions to rotate the toner carrier 21 and the image carrier 10. And the image carrier 1 in the development area where
0 is moved upward from below, and the peripheral speed v1 of the image carrier 10 is set to 160 mm / s.
The toner carrier 2 with respect to the peripheral speed v1 of the image carrier 10
The ratio θ (v2 / v1) of the peripheral speed v2 of 1 was set to 1.5.

Further, as the pre-charging member 26, S
A plate made of US made of SUS having a ten-point average roughness Rz of 0.5 μm on the surface in contact with the toner carrier 21 and a regulating member 27 made of SUS having a plate thickness of 0.3 mm is used. And a negatively chargeable toner having a weight average particle diameter of 8.0 μm was used as the toner t.

When the leading end of the pre-charging member 26 is brought into contact with the toner carrier 21 to pre-charge the toner t supplied to the toner carrier 21, the bias power source 26a supplies the pre-charging member In applying bias voltage Va to No. 26, the following Table 1
As shown in (1), in the first embodiment, the same bias voltage Va (Va = Vb) as the development bias voltage Vb applied to the toner carrier 21 from the development bias power supply 29 described above.
In the second embodiment, the developing bias power supply 29
Bias voltage V applied to toner carrier 21 from
While the bias voltage Va (Va = Vb−100 V) shifted by 100 V is applied to the − side which is the charging polarity of the toner t from b, in Comparative Example 1, the bias voltage Va is not applied to the pre-charging member 26. I made it.

Next, after the toner t supplied to the toner carrier 21 is preliminarily charged, the toner carrier 2
The toner t conveyed by 1 is regulated by the regulating member 27, and the toner t is frictionally charged so as to be guided to the developing area facing the image carrier 10.

The surface potential of the image carrier 10 is-
While a solid electrostatic latent image of 50 V is formed, the developing bias power supply 29
The peak-to-peak value Vpp is 16 at a DC voltage of -400V.
A developing bias voltage Vb on which an AC voltage having a frequency of 2 kHz at 00 V is superimposed is applied, and a toner t is supplied from the toner carrier 21 to the above-described electrostatic latent image portion formed on the image carrier 10, and each A solid image was formed.

Each solid image formed as described above was evaluated, and a solid image having a constant image density was obtained, and a solid image having a greatly reduced image density at the rear end was indicated by x. The results are shown in Table 1.

[0042]

[Table 1]

As is apparent from the result, when the tip of the pre-charging member 26 is brought into contact with the toner carrier 21 to pre-charge the toner t, the bias power source 26a supplies the pre-charging member 26 with the toner carrier 21. In the developing devices of Examples 1 and 2 to which the bias voltage Va for charging the toner t to a negative polarity was obtained, a good solid image without density reduction was obtained. In the developing device of Comparative Example 1 in which the bias voltage Va was not applied, the toner t in the toner carrier 21 was not appropriately precharged, and the toner t in the toner carrier 21 was separated before being guided to the regulating member 27. As a result, the amount of toner guided to the developing area was reduced, and the image density at the rear end of the solid image was greatly reduced.

(Experiment 2) In this experiment, the material of the surface of the pre-charging member 26 used in the above-described experiment 1 that is in contact with the toner carrier 21 was changed, and the work function Wf of the surface in contact with the toner carrier 21 was changed. However, as shown in Table 2 below, 4.2 eV, 4.6 eV, 5.0 eV, 5.2
The pre-charging member 26 having eV was used.

Here, in determining the work function Wf of the surface of the pre-charging member 26 which is in contact with the toner carrier 21, a contact potentiometer (SSVII-1 manufactured by Kawaguchi Electric Co., Ltd.)
0), the work function Wf of each surface was determined by measuring the contact potential difference with Au based on Au having a work function Wf of 4.9 eV. The work function Wf of the negatively chargeable toner was 5.0 eV.

The pre-charging member 26 having the work function Wf of the surface as described above is brought into contact with the toner carrier 21 to pre-charge the toner t supplied to the toner carrier 21. As in the case of the second embodiment, the bias power source 26a supplies the pre-charging members 26 with the developing bias power source 29 to the toner carrier 21.
A bias voltage Va (= Vb−100 V) shifted by 100 V to the − side of the charging polarity of the toner t from the developing bias voltage Vb to be applied to the toner t is pre-charged. After being pre-charged by the member 26, the toner carrier 2 is
1 regulates the amount of toner t conveyed.

The state of fixation of the toner t on the regulating member 27 which regulates the amount of the toner t conveyed by the toner carrier 21 in this way is examined. In the case of fixing to the regulating member, it is indicated by x, and is shown in Table 2 below.

[0048]

[Table 2]

As is apparent from the result, when the pre-charging member 26 is made of a material having a work function equal to or less than the work function of the toner t when the negative charging toner is used, the portion where the pre-charging member 26 comes into contact with the toner carrier 21 is formed. The toner t was negatively charged by the contact with the charging member 26, and the toner t did not adhere to the regulating member 27.

On the other hand, when the portion where the pre-charging member 26 contacts the toner carrier 21 is made of a material having a higher work function than the toner t, the pre-charging member 26
And the toner t charged to the opposite polarity is generated by the contact with
The toner t charged in the opposite polarity as described above is
And the toner t conveyed by the toner carrier 21 has streak-like unevenness, and streaky noise occurs in the formed image.

(Experiment 3) In this experiment, as the pre-charging member 26, a member made of a SUS plate was used as in the case of the above-mentioned experiment 1, while the pre-charging member 2 was used.
6 is the ten-point average roughness Rz of the surface in contact with the toner carrier 21.
Was changed in the range of 0.05 to 2.5 μm as shown in Table 3 below.

When the pre-charging members 26 are brought into contact with the toner carrier 21 to preliminarily charge the toner t supplied to the toner carrier 21, the second embodiment is used.
In the same manner as in the above case, the bias power from the bias power supply 26a to the pre-charging member 26 is set to 100 V on the negative side, which is the charging polarity of the toner t, with respect to the developing bias voltage Vb applied from the developing bias power supply 29 to the toner carrier 21. By applying the shifted bias voltage Va (= Vb−100 V),
The toner t held on the toner carrier 21 is pre-charged by each pre-charging member 26.

Next, after the toner t supplied to the toner carrier 21 is preliminarily charged as described above, the toner t conveyed by the toner carrier 21 is regulated by the regulating member 27, and the toner t is rubbed. Charge it,
When the transport unevenness of the toner t on the toner carrier 21 guided to the developing area facing the image carrier 10 and thus guided to the developing area facing the image carrier 10 is visually observed, there is no transport unevenness. ○, × when there is uneven transport
The results are shown in Table 3 below.

In the same manner as in Experiment 1 described above, a solid electrostatic latent image having a surface potential of −50 V is formed on the image carrier 10 while the developing bias power supply 29 supplies the toner carrier 21. Is applied with a developing bias voltage Vb in which an AC voltage having a peak-to-peak value Vpp of 1600 V and a frequency of 2 kHz is superimposed on a DC voltage of -400 V, and the electrostatic bias formed on the image carrier 10 is applied. The toner t was supplied to the latent image portion from the toner carrier 21 to form a solid image.

Then, each solid image formed in this manner was evaluated, and a solid image having a constant image density was obtained, and a solid image having a greatly reduced image density at the rear end was indicated by x. The results are shown in Table 3.

[0056]

[Table 3]

As is apparent from the result, the ten-point average roughness Rz of the front end portion brought into contact with the toner carrier 21 is 0.1%.
When the pre-charging member 26 having a range of about 2.0 μm is used, there is no unevenness in the amount of the toner t conveyed to the developing area by the toner carrier 21, and there is no density unevenness. An image was obtained, and a good solid image without a decrease in density was obtained.

On the other hand, when the pre-charging member 26 having a ten-point average roughness Rz of less than 0.1 μm at the tip portion contacting the toner carrier 21 is used, the toner carrier 2
The toner t in 1 is not properly pre-charged,
The toner t is not sufficiently held by the toner carrier 21, and the toner t falls away from the toner carrier 21 before being guided to the regulating member 27, and the amount of the toner t guided to the developing area is reduced. The density of the solid image decreased.
On the other hand, when a pre-charging member 26 having a ten-point average roughness Rz of more than 2.0 μm at the tip portion to be brought into contact with the toner carrier 21 is used, the pre-charging member 26 makes contact with the toner carrier 21 and conveys the toner. The amount of the toner t was uneven.

Next, a color image forming apparatus according to an embodiment of the present invention using the developing device described in the above embodiment will be specifically described with reference to the accompanying drawings.

Here, in the color image forming apparatus according to the first embodiment, as shown in FIG. 4, four developing devices A1 to A4 according to the above embodiment are used.
The three developing devices A1 to A4 contain toners of different colors of yellow, magenta, cyan, and black, and the four developing devices A1 to A4 are held by a rotating holder 40. The positions of A1 to A4 are changed, and the toner carrier 21 in each of the developing devices A1 to A4 is sequentially guided to a position facing the image carrier 10 so that the toner carrier 21 and the image carrier 10 face each other. In the region, the toner carrier 21 and the image carrier 10 move upward from below, respectively.

When a color image is formed by the color image forming apparatus of the first embodiment, for example, first, the toner carrier 21 of the first developing device A1 containing the yellow toner is replaced with the image carrier. 10 so that the image carrier 10 is rotated,
The surface of the image carrier 10 is uniformly charged by the charging device 41, and the thus-charged image carrier 10 is exposed by the exposure device 42 in accordance with an image signal. An electrostatic latent image is formed on the surface.

Next, in the developing area where the image carrier 10 on which the electrostatic latent image is formed and the toner carrier 21 of the first developing device A1 face each other, the toner carrier 2
1 and the image carrier 10 are respectively moved upward from below, and the yellow toner is supplied from the toner carrier 21 to the electrostatic latent image portion formed on the image carrier 10, and the image carrier 1
At 0, a yellow toner image corresponding to the electrostatic latent image is formed.

The yellow toner image thus formed on the image carrier 10 is transferred to an endless belt-shaped intermediate transfer member 43 stretched over the image carrier 10, and after the transfer, The yellow toner remaining on the image carrier 10 is removed from the image carrier 10 by the cleaning device 44.

Thereafter, the holder 40 is rotated to position the toner carrier 21 of the second developing device A2 containing the magenta toner next so as to face the image carrier 10. In the same manner as in the case of the first developing device A1, a magenta toner image is formed on the surface of the image carrier 10, and this magenta toner image is transferred to the intermediate transfer member onto which the yellow toner image has been transferred. On the other hand, the magenta toner remaining on the image carrier 10 after the transfer is removed from the image carrier 10 by the cleaning device 44.

By performing the same operation, a cyan toner image is formed on the surface of the image carrier 10 by the third developing device A3 containing the cyan toner, and the cyan toner image is formed. A black toner image is formed on the surface of the image carrier 10 by the fourth developing device A4 containing the black toner and transferred to the intermediate transfer member 43, and this cyan toner image is transferred to the intermediate transfer member 43 Is transferred to the intermediate transfer member 43, and thus the yellow, magenta, cyan,
The black toner images are transferred to form full-color toner images.

Then, a recording sheet 46 is transferred from a sheet cassette 45 provided below the color image forming apparatus by a feed roller 47 and an intermediate transfer member 43 and a transfer roller 48.
The full color toner image formed on the intermediate transfer member 43 is transferred to the recording sheet 46, and the full color toner image thus transferred on the recording sheet 46 is recorded by the fixing device 49. The sheet is fixed to the sheet 46 and discharged, while the intermediate transfer member 43 is not transferred.
The remaining toner is removed from the intermediate transfer member 43 by the cleaning device 50.

Further, in the color image forming apparatus according to the second embodiment, as shown in FIG. 5, four developing devices A1 to A4 in the above embodiment are used, and these four developing devices A1 to A4 are used. Yellow, magenta, cyan,
The four developing devices A1 to A4 are accommodated in the color image forming apparatus in order from the top while containing toners of different colors of black, and are opposed to the toner carrier 21 in each of the developing devices A1 to A4. The image bearing members 10 are respectively provided in the developing areas where the toner bearing members 21 and the image bearing members 10 face each other.
1 and the image carrier 10 move upward from below.

Further, an endless belt-shaped intermediate transfer member 43, which is vertically extended, is provided at a position opposite to each of the developing devices A1 to A4 with the image carrier 10 therebetween. Reference numeral 43 moves downward from above on the side in contact with each image carrier 10.

Here, when forming a color image by the color image forming apparatus of the second embodiment, the image carrier which is opposed to the toner carrier 21 of the first developing device A1 containing the yellow toner is used. By rotating 10, the surface of the image carrier 10 is uniformly charged by the charging device 41, and the image carrier 10 thus charged is exposed by the exposure device 42 in accordance with the image signal, An electrostatic latent image is formed on the surface of the image carrier 10.

Then, in the developing area where the image carrier 10 on which the electrostatic latent image is formed and the toner carrier 21 of the first developing device A1 face each other, the toner carrier 2
1 and the image carrier 10 are respectively moved upward from below, and the yellow toner is supplied from the toner carrier 21 to the electrostatic latent image portion formed on the image carrier 10, and the image carrier 1
At 0, a yellow toner image corresponding to the electrostatic latent image is formed.

Next, the yellow toner image thus formed on the image carrier 10 is transferred to the intermediate transfer member 43, and the yellow toner remaining on the image carrier 10 after the transfer is cleaned. The image carrier 10 is removed by the device 44.

Then, in the same manner as in the first developing device A1, the magenta color, the magenta color, and the image carrier 10 of the second to fourth developing devices A2 to A4, which are opposed to the toner carriers 21, respectively. A cyan and black toner image is formed, and the magenta, cyan, and cyan toner images thus formed on each image carrier 10 are formed.
The black toner image is sequentially transferred to the intermediate transfer body 43 to which the yellow toner image has been transferred as described above, and a full-color toner image is formed on the intermediate transfer body 43.

Thereafter, similarly to the above-described first color image forming apparatus, the recording sheet 46 is transferred from a paper cassette 45 provided below the color image forming apparatus to the intermediate transfer body 43 and the transfer roller 43 by a feed roller 47. The full color toner image formed on the intermediate transfer member 43 is transferred to the recording sheet 46, and the full color toner image thus transferred on the recording sheet 46 is fixed by the fixing device 49. The toner is fixed on the recording sheet 46 and discharged, and the toner remaining on the intermediate transfer member 43 without being transferred is removed from the intermediate transfer member 43 by the cleaning device 50.

[0074]

As described above in detail, in the developing device according to the present invention, the toner carrier is rotated so as to move upward from below in the developing area facing the image carrier.
A pre-charging member is provided so as to be in contact with the toner carrier at a position downstream of the toner supply member that supplies toner to the toner carrier in the rotation direction of the toner carrier. The contact portion is provided with conductivity, and a bias voltage for charging the toner to a predetermined polarity is applied to the conductive portion, so that the toner supplied to the toner carrier contacts the pre-charging member. As a result, pre-charging is appropriately performed to a predetermined polarity.

As a result, in the developing device according to the present invention, the toner thus preliminarily charged is held on the toner carrier by electrostatic force, and a sufficient amount of toner is guided to the position of the regulating member by the toner carrier. As a result, the toner is appropriately regulated, and an appropriate amount of toner is guided to the development area by the toner carrier and used for development, so that an image having a sufficient image density can be obtained.

In the developing device according to the present invention, at least a portion of the pre-charging member that contacts the toner carrier is frictionally charged to charge the toner to a predetermined polarity. When using a material positioned in the series, or when using a negatively charged toner, if at least a portion of the pre-charging member that contacts the toner carrier is formed of a material having a work function equal to or less than the toner, the toner carrying The toner supplied to the body is appropriately pre-charged to a predetermined polarity by contact with the pre-charging member, and a sufficient amount of toner is guided to the position of the regulating member by the toner carrier to appropriately In addition to being regulated, the toner is also prevented from adhering to the regulating member, and an appropriate amount of toner is guided to the development area and used for development, and an image having a sufficient image density Together to obtain, it became streaky good images without generation of noise and the like can be obtained.

When the pre-charging member is brought into contact with the toner carrier as described above, the ten-point average roughness Rz of the surface where the pre-charging member contacts the toner carrier is 0.1 μm ≦
When Rz ≦ 2.0 μm, the toner is appropriately pre-charged by the pre-charging member, and the toner conveyed by the toner carrier does not have unevenness, and has a sufficient image density. A good image without density unevenness can be obtained.

Further, in the color image forming apparatus according to the present invention, a plurality of developing devices accommodating toners of different colors and the toner images formed on the image carrier by these developing devices are transferred in an overlapping manner. In the color image forming apparatus provided with the intermediate transfer member, the developing device as described above in the present invention is used, so that the image carrier is moved from the lower side to the upper side in the developing area to obtain a sufficient image density. Image forming apparatus, and the apparatus can be made compact in accordance with the configuration of the color image forming apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a conventional developing device.

FIG. 2 is a schematic explanatory diagram of a developing device according to an embodiment of the present invention.

FIG. 3 is a schematic explanatory diagram of a color image forming apparatus according to the first embodiment of the present invention.

FIG. 4 is a schematic explanatory view of a color image forming apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Image carrier 21 Toner carrier 25 Toner supply member 26 Pre-charging member 26a Bias power supply 43 Intermediate transfer body A1-A4 Developing device t Toner

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 9, 2000 (200.6.9)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0060

[Correction method] Change

[Correction contents]

Here, in the color image forming apparatus according to the first embodiment, as shown in FIG. 3 , four developing devices A1 to A4 according to the above embodiment are used.
The three developing devices A1 to A4 contain toners of different colors of yellow, magenta, cyan, and black, and the four developing devices A1 to A4 are held by a rotating holder 40. The positions of A1 to A4 are changed, and the toner carrier 21 in each of the developing devices A1 to A4 is sequentially guided to a position facing the image carrier 10 so that the toner carrier 21 and the image carrier 10 face each other. In the region, the toner carrier 21 and the image carrier 10 move upward from below.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0067

[Correction method] Change

[Correction contents]

Further, in the color image forming apparatus according to the second embodiment, as shown in FIG. 4 , four developing devices A1 to A4 according to the above embodiment are used, and the four developing devices A1 to A4 are used. Yellow, magenta, cyan,
The four developing devices A1 to A4 are accommodated in the color image forming apparatus in order from the top while containing toners of different colors of black, and are opposed to the toner carrier 21 in each of the developing devices A1 to A4. The image bearing members 10 are respectively provided in the developing areas where the toner bearing members 21 and the image bearing members 10 face each other.
1 and the image carrier 10 move upward from below.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Ichiro Izumi 2-13-13 Azuchicho, Chuo-ku, Osaka City F-term in Osaka International Building Minolta Co., Ltd. 2H073 AA02 BA01 BA11 CA02 CA22 2H077 AC03 AD02 AD06 AD13 AD17 AD35 BA10 DB08 DB14 EA11 EA24 FA01 FA16 FA25 GA13

Claims (5)

[Claims] In a developing device for performing development by guiding a toner to a developing area facing an image carrier by a roller-shaped toner carrier, the toner carrier is disposed below a developing area facing the image carrier. The pre-charging member is provided so as to be in contact with the toner carrier at a position on the downstream side in the rotation direction of the toner carrier from the toner supply member that supplies the toner to the toner carrier. A regulating member that regulates the amount of toner conveyed to the developing area by the toner carrier so as to contact the lower portion of the toner carrier downstream of the pre-charging member in the rotation direction of the toner carrier is provided. At least a portion of the charging member that comes into contact with the toner carrier is provided with conductivity, and a bias is applied to the conductive portion to charge the toner to a predetermined polarity. A developing device, wherein a bias voltage is applied. 2. The developing device according to claim 1, wherein
A developing device, wherein at least a portion of the pre-charging member that comes into contact with the toner carrier is made of a material located in a triboelectric series for charging the toner to a predetermined polarity. 3. The developing device according to claim 1, wherein a negatively-charged toner is used as the toner, and at least a portion of the pre-charging member that comes into contact with the toner carrier is a toner work. A developing device comprising a material having a function or less. 4. The developing device according to claim 1, wherein the ten-point average roughness Rz of a surface of the pre-charging member in contact with the toner carrier is 0.1 μm ≦ Rz ≦
A developing device having a thickness of 2.0 μm. 5. A color image comprising a plurality of developing devices accommodating toners of different colors and an intermediate transfer member onto which a toner image formed on an image carrier by each of these developing devices is transferred in a superimposed manner. A color image forming apparatus, wherein the developing device according to any one of claims 1 to 4 is used as the developing device.