JP3347226B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, a printer, and the like. The present invention relates to an image forming apparatus having a rotary developing device for performing development by moving a developing device used for a developing device to a predetermined developing position near a latent image carrier. In particular, the present invention relates to an image forming apparatus having a rotary developing device using non-magnetic one-component development for performing contact development on a photoconductor.

[0002]

2. Description of the Related Art For example, as an image forming apparatus of a color electrophotographic recording system, a rotating body is provided in close proximity to a photoreceptor, and a plurality of developing units using toners of different colors at predetermined positions of the rotating body. A developing device has been developed which has a rotary developing device that supports a developing device and sequentially rotates and transports each developing device to a developing position to develop a latent image on a photoreceptor with toner of each color (Japanese Patent Application Laid-Open No. H10-163873). (JP-A-61-151564, JP-A-63-91676, JP-A-63-177159, JP-A-61-209469, JP-A-5-158320).

[0003]

In an image forming apparatus having a rotary developing device of this type, for example, as described in Japanese Patent Application Laid-Open No. S61-151564, a rotary developing device is provided before the operation is started. Is controlled to rotate to a reference position which is a reference for driving the rotating body. However, assuming that the rotary developing device is simply rotated to the reference position, if the rotation angle to the reference position is 90 degrees or more, the developing roller of at least one developing device passes through the developing position facing the photoconductor. I do. During this passage, a part of the toner properly held on the developing roller is transferred to the photoconductor, and as a result, a portion of the toner layer on the developing roller with a small amount of toner in a horizontal band is generated. Was.
At this time, when an image is output, a portion having a low density is generated in a horizontal band shape. When two or more developing devices pass a developing position facing the photoconductor, 1
The toner transferred from the developing roller of the second developing device to the photoconductor adheres to the developing roller of the second developing device. For this reason, the toner of another color is mixed into the developing roller of the second developing device, and by repeating such an operation, the toner in each developing device is discolored by color mixture,
There is also a problem that a visible image of a predetermined color cannot be obtained.

Japanese Patent Application Laid-Open No. 63-91676 discloses that when a rotary developing device is rotated, a latent image carrier (photoconductor) is rotated before a predetermined developer conveying member (developing roller) reaches a developing position. There has been proposed an image forming apparatus characterized in that the image forming apparatus is made to perform the operation. In this image forming apparatus, the problem of color mixing is avoided, but if the rotation of the photoconductor continues at the time when the predetermined developing roller reaches the developing position, the surface area of the photoconductor opposed to the developing roller increases. Therefore, the amount of transfer of the toner on the developing roller to the photoconductor increases. As a result, the portion of the toner layer on the developing roller facing the photoreceptor becomes thinner and thinner, and a portion with less toner is generated in a horizontal band. At this time, when an image is output, a portion having a low density is generated in a horizontal band shape.

Japanese Patent Application Laid-Open No. 63-177159 discloses a repulsive electric field for a toner from a developing device toward a surface of an image carrier (photoreceptor) when the developing device is moved to a developing position and when the developing device is separated from the developing position. An image forming apparatus characterized by strengthening has been proposed. However, such control requires a control circuit for turning on / off the developing bias and a power supply capable of generating a different bias value during development and during movement. There was a problem that the size was increased and the cost was increased.

Japanese Unexamined Patent Application Publication No. 61-209469 discloses a method for avoiding a collision with a surrounding optical system or the like by a simple configuration when a developing device receiver supporting a plurality of developing devices is rotated. A developing device receiver that supports the developing device so as to be able to contact and separate from the carrier (photoreceptor); An image forming apparatus characterized by the following has been proposed. However, such a device has a problem that it is complicated and large, and increases the cost.

Japanese Patent Application Laid-Open No. 5-158320 discloses that a rotary developing device has a plurality of marks represented by a plurality of elements corresponding to a plurality of pieces of information relating to the rotary developing device, and reads at least one mark set. There has been proposed an image forming apparatus that moves at high speed without reading a mark set to a position near a position to be moved based on position information in a rotation direction determined from a reference position of a rotary developing device. . However, in this image forming apparatus, it is necessary to rotate the rotary developing device at a slow speed at which the mark can be detected until one mark set is read, during which the developing roller of one developing device faces the photosensitive member. At that time, a part of the toner properly held on the developing roller is transferred to the photoreceptor, and as a result, a portion of the toner layer on the developing roller with a small amount of toner in a horizontal band is generated. There was a defect.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and an object of the present invention is to allow a developing roller to rotate on a latent image carrier while rotating the rotor to a reference position in rotation about a rotation axis. An object of the present invention is to provide an image forming apparatus capable of reducing or preventing the occurrence of the abnormal image in a subsequent image forming operation due to opposition with a simple configuration.

[0009]

In order to achieve the above object, the image forming apparatus according to the first aspect of the present invention is used for development by rotating a rotating body having a plurality of developing devices arranged around a rotating shaft. The image forming apparatus includes a rotary developing device that performs development by moving a developing device to be developed to a predetermined developing position near a latent image carrier (hereinafter, referred to as an image forming apparatus having a basic configuration). If there is a replacement or maintenance work due to the life of the machine, or if the process of the image forming machine is stopped halfway due to jamming or non-feeding of the transfer paper, the rotation of the rotating In the state where the rotating body is rotated to one reference position in the rotation of and stopped at the reference position to prepare for the image forming operation, each developing unit is stopped at the reference position before the image forming operation is started. Genki It is characterized in that for the roller rotationally driven.

According to a second aspect of the present invention, in the image forming apparatus having the above-mentioned basic configuration, a developing roller and a replenishing roller for replenishing the developing roller with toner are provided in each developing device.
When a bias voltage applying device is provided between the developing roller and the replenishing roller for forming an electric field in a direction in which the toner is transferred from the developing roller to the replenishing roller, and replacement or maintenance work is performed due to the life of the developing device. Or, when the process of the image forming apparatus is stopped halfway due to clogging or non-feeding of the transfer paper, the rotating body is rotated to one reference position in the rotation around the rotation axis before starting the subsequent image forming operation. And stopped at the reference position to prepare for the image forming operation.In a state where the image forming apparatus is stopped at the reference position before the image forming operation is started, the electric field is formed in each developing device, and the developing roller and The supply roller is driven to rotate.

According to a third aspect of the present invention, in the image forming apparatus having the above-described basic configuration, a developing roller and a replenishing roller for replenishing the developing roller with toner are provided in each developing device.
When a bias voltage applying device is provided between the developing roller and the replenishing roller for forming an electric field in a direction in which the toner is transferred from the developing roller to the replenishing roller, and replacement or maintenance work is performed due to the life of the developing device. Or, when the process of the image forming apparatus is stopped halfway due to clogging or non-feeding of the transfer paper, the rotating body is rotated to one reference position in the rotation around the rotation axis before starting the subsequent image forming operation. Stop at the reference position to prepare for the image forming operation, before rotating the rotating body to the reference position in the rotation around the rotation axis to prepare for the image forming operation, in each developing device The electric field is formed, and the developing roller and the supply roller are driven to rotate.

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

According to the present invention, a part of the toner properly carried on the developing roller is not transferred to the latent image carrier.
Alternatively, even if the transfer is very small, or even if the transfer is performed, the toner layer on the developing roller is initialized, and as a result, the toner layer on the developing roller does not have a portion with a small amount of toner in a horizontal band, Or, even if it occurs, it is very slight, and when an image is output, a uniform and good image can be obtained without occurrence of a portion having a low density in a horizontal band shape.

[0018]

【Example】

Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an example of a full-color printer provided with a developing device according to the present invention. In the printer shown in FIG. 1, a belt-shaped photosensitive member (latent image carrier) 1 is uniformly charged by a charging roller, and is then scanned and exposed by a laser optical device 3 based on image information, thereby forming an electrostatic latent image on the surface. It is formed. Here, the image information to be exposed is monochromatic image information obtained by decomposing a desired full-color image into yellow, magenta, cyan, and black color information. The formed electrostatic latent image is developed with predetermined yellow, magenta, cyan, and black toners by a rotary developing device 4 described later, and an image of each color is formed on the photoconductor 1.

Photosensitive belt 1 rotating in the direction of arrow A in FIG.
The respective color images formed thereon are sequentially transferred onto the intermediate transfer belt 5 rotating in the direction of arrow B in the drawing in synchronization with the photoreceptor belt 1 for each of the single colors of yellow, magenta, cyan, and black. The yellow, magenta, cyan, and black images superimposed on the intermediate transfer belt 5 are transferred onto a transfer paper 11 that is conveyed to a transfer unit from a paper supply table 8 via a paper supply roller 9 and a registration roller 10 to transfer rollers 6. Are collectively transferred. After the transfer, the transfer paper 11 is fixed by the fixing device 7 to complete a full-color image.

FIG. 2 is a sectional view showing a schematic configuration of the developing device, FIG. 3A is a partially enlarged view of the developing device, and FIG.
Is a side view showing the internal structure of one developing unit in the developing device, and FIG. 4 is a perspective view of a rotating body in the developing device. The rotary (revolver-type, rotary-type) developing device 4 as a developing device according to the present invention includes:
It is arranged near the above-mentioned photoreceptor belt 1. 2, in the rotary developing device 4, casings 20 and 21 forming a rotating body are provided rotatably about a rotation center O, and the casings 20 and 21 are driven by a driving mechanism (not shown). It is rotated in the direction of arrow C. The casings 20 and 21 have a shape such that the developing device is divided into four parts.
Y, M, C, and K are formed.

FIG. 2 shows a state in which one developing unit 22Y is at the developing position. Each developing unit 22Y,
M, C, and K are provided with cylindrical developing rollers 23Y, M, C, and K as developer transport members. The developing rollers 23Y, 23M, 23C, and 23K are arranged so that a part of the developing rollers 23Y, M, C, and K is exposed to the outside through an opening 22a provided in the casing 20, and rotate in the direction of arrow D in FIG. Then, the corresponding electrostatic latent image is developed (see FIG. 3A). The developing unit of this embodiment is a developing device using a non-magnetic one-component developer, and contains yellow, magenta, cyan, and black toners in each unit. , And sequentially rotate the photosensitive belt 3
A full-color image is formed by developing the electrostatic latent image formed thereon and superimposing each developed image on the intermediate transfer belt 5 and the transfer paper 11 as described above.

Since the color developing units 22Y, M, C, and K have the same form and the same operation, only the one color developing unit 22Y will be described here. In FIG. 3A, the developing unit 22Y is disposed below the photoreceptor belt 1 as an electrostatic latent image carrier, and a non-magnetic image is formed on the electrostatic latent image formed on the photoreceptor 1 located above the developing unit 22Y. A toner as a one-component developer is supplied.

In FIG. 1, reference numeral 22 denotes a (yellow) developing unit, and this developing unit 22 is located at a developing position.
An opening 22a is formed in the upper part. In the opening 22a, a developing roller 23Y as a developer carrier is disposed so as to face the photoconductor so as to rotate in the same direction as the photoconductor moving direction at a predetermined peripheral speed ratio with the photoconductor. . Below the developing roller 23, a replenishing roller 31 as a toner supply member made of an elastic material such as foamed polyurethane rubs against the developing roller 23, and
Are provided so as to rotate in the same direction at the contact portion with the developing roller 23 at the rubbing portion with a predetermined peripheral speed ratio. A blade 32 made of an elastic material such as urethane rubber is provided near the opening 22a on the downstream side of the supply roller 31 in the moving direction of the developing roller 23 so that one end thereof is in contact with the developing roller 23. . In the drawing, reference numeral 33 denotes a screw-shaped first toner conveying member to be described later, which conveys the toner from the near side to the far side in the drawing.

On the front side of the developing device 23, a toner container 40 is provided as shown in FIGS. The toner conveying member 33 is a screw-shaped first toner conveying member. The toner conveying member 33 is disposed in parallel with the developing roller 23 and the replenishing roller 31 from the toner container 40 to the other side plate of the developing device 4. In cooperation with the developing roller 23 and the replenishing roller 31, the toner is rotated at a predetermined peripheral speed ratio so as to convey the toner from the side to the back side.
The casing 20 is disposed so that a part thereof is in contact with the supply roller 31. The toner transport member 33 is formed by the developing roller 23, the supply roller 31, and the casing 20.
Is formed around the toner conveying space 37.

Screw-shaped first toner conveying member 33
Is rotated at a predetermined peripheral speed ratio in conjunction with the developing roller 23 and the supply roller 31 so as to convey the toner from the near side to the far side of the drawing. With this rotation, the first toner conveying member 33 conveys the toner from the toner storage unit 40 into the toner conveying space 37 and supplies the toner onto the supply roller 31. The toner supplied on the supply roller 31 is supplied while being charged on the surface of the developing roller 23 by the supply roller 31, and is carried on the surface of the developing roller 23. The toner carried on the surface of the developing roller 23 is made into a uniform and thin layer of toner by the blade 32, and the electrostatic latent image formed on the surface of the photoconductor 1 is developed by contact or non-contact development.

By the way, the toner not used in the developing step is conveyed by the first toner conveying screw 33Y to the end of the developing unit opposite to the toner container 40Y. A toner circulating portion 34Y is provided outside the effective diameter portion in the axial direction of the developing roller 23Y and the supply roller 31Y at the end of the developing unit opposite to the toner container 40Y. The toner transported by the first toner transport screw 33Y to the toner circulating section 34Y falls to the lower portion of the yellow developing unit 22Y due to gravity.

Below the yellow developing unit 22Y, the second toner conveying screw 35Y is provided with the developing roller 2Y.
3Y, the supply roller 31Y, and the first toner conveying screw 33Y are disposed in parallel with each other, and are rotated so as to convey the toner in the opposite direction to the first toner conveying screw 33Y. To the toner container 40Y. First toner transport screw 33
By appropriately setting the transport amount of Y and the second toner transport screw 35Y, the toner can be supplied onto the supply roller 31Y without performing the toner amount detection and complicated supply amount control in the yellow developing unit 22Y. It is possible to provide a small-sized developing device having a large degree of freedom in layout and a small sectional occupation ratio with respect to the photoconductor. (Hereinafter, margin)

Incidentally, reference numerals 42Y, 42M and 42 in FIG.
C and 42K are development units 22Y and 22M, respectively.
22C, 22K toner storage units 40Y, 40M, 40
C, 40K, which are detachably attached to the toner cartridges 42Y, 42M, 42
C and 42K are always mounted and replaced when the developing device 4 is newly mounted and at the time of toner end, so that the toner container 40
A required amount of toner is accommodated in Y, 40M, 40C, and 40K.

Here, at times other than the image forming operation, that is, before and after the image forming operation, the developing device 4 waits and stops at the reference position of the developing device as shown in FIG.
In this embodiment, the developing roller 23 of the yellow developing device 22Y
A position where Y and the roller 23Y and 23K do not contact the photoconductor 1 at a substantially intermediate point between Y and the developing roller 23K of the black developing device 22K is set as a reference position. This is when the photosensitive member 1 is not operated.
This is a position where the photosensitive member 1 and the developing roller 23 are prevented from being deteriorated or damaged due to unnecessary contact between the photosensitive member 1 and the developing roller 23, and the toner is prevented from adhering or sticking outside a predetermined area.

When replacement or maintenance work is performed due to the life of the developing device, or when the process of the image forming device is stopped halfway due to clogging or non-feeding of the transfer paper, etc. In some cases, the positional relationship between each color of the developing device and the photoconductor becomes random.
In this case, it is necessary to rotate the developing device to the reference position of the developing device and stop the developing device before starting the image forming operation to prepare for the image forming operation.

However, if the developing roller of at least one developing unit passes through the developing position facing the photoreceptor during the rotation to the reference position, as described above, the developing roller is properly held on the developing roller during this passage. Part of the toner thus transferred is transferred to the photoreceptor, and as a result, a portion of the toner layer on the developing roller with a small amount of toner in a horizontal band is generated. Then, when the image is output at this time, the result is that a portion having a low density occurs in a horizontal band shape.

Therefore, in this embodiment, before the image forming operation is started, the developing device is rotated to the reference position and stopped, and thereafter, before the image forming operation is started, the developing roller and the replenishing roller are driven by the driving device (not shown). Is driven to rotate,
The disturbance of the toner layer on the developing roller is eliminated, and the toner layer is made uniform over the entire circumference of the developing roller.

In the following, when replacement or maintenance work is performed due to the life of the developing device, the positional relationship between each color of each developing device of the developing device and the photosensitive member becomes random, and before the image forming operation starts. Another embodiment in which the developing device is rotated to the reference position and stopped to prepare for an image forming operation is different from the embodiment, and the configuration and operation shown in FIGS. 1 and 4 are the same as those of the first embodiment. (Examples 2 to 12) will be described.

Embodiment 2 FIG. 6 is an explanatory view of an image forming apparatus according to another embodiment of the present invention. In this image forming apparatus, terminals 100 and 101 capable of applying different bias voltages to the developing roller and the replenishing roller are provided on the rotating body side for each developing unit, and a pair of fixed terminals 102 engaged with these terminals. , 103 are provided on the main body side. The fixed terminals 102 and 103 are connected to a developing roller bias power supply 104 and a supply roller bias power supply 105. Then, as described above, if the positional relationship between each color of each developing device of the developing device and the photoconductor becomes random, the developing device is rotated to the reference position of the developing device, stopped, and then developed. A bias voltage is applied to at least one of the supply rollers from the developing roller so that the developing roller and the supply roller are driven to rotate so that an electric field in a direction in which the toner is transferred from the roller to the supply roller is generated. For example, when the charge polarity of the toner is negative, -300 V is applied to the developing roller and 0 V is applied to the supply roller.
To rotate the developing roller and the supply roller. In this case, the toner layer is hardly formed on the developing roller over the entire circumference. Therefore, the top of the developing roller is initialized, and after the start of the image forming operation, a new toner layer is formed over the entire circumference of the developing roller, so that a uniform and good image can be output. The terminals 100, 10
1, 102, 103 and power supplies 104, 105,
When a bias is applied to the developing roller and the replenishing roller during the developing operation, the power supplies 104 and 105 are configured to generate a voltage used during the developing.

Embodiment 3 Next, still another embodiment will be described. In the present embodiment, for example, using the configuration of FIG. 6, if the positional relationship between each color of each developing unit of the developing device and the photoconductor becomes random as described above, the developing first A bias voltage is applied to at least one of the developing roller and the replenishing roller so that the developing roller and the replenishing roller are rotated to generate an electric field in a direction in which the toner is transferred from the roller to the replenishing roller. As a result, almost no toner layer is formed on the developing roller over the entire circumference. Thereafter, the developing device is rotated to the reference position of the developing device and stopped. With this control, while the developing device is rotated to the reference position of the developing device, there is no toner layer on the developing roller even if the developing roller faces the photoreceptor. Does not become non-uniform, and unnecessary toner does not adhere to the photoconductor.

Embodiment 4 Next, still another embodiment will be described. In this embodiment, as shown in FIG. 7, one of the support rollers 106 and 107 supporting the photosensitive belt 1 is movable. Then, as described above, when the positional relationship between each color of each developing device of the developing device and the photoconductor becomes random, while the developing device is rotated to the reference position of the developing device, as indicated by a broken line. Then, the support roller 106 is moved so that the photosensitive member and the developing roller do not come into contact with each other. In the illustrated example, the support roller 106 is moved by the combination of the solenoid 109 and the biasing spring 108s whose one end is locked to the shaft 106a of the support roller. However, another moving mechanism can be used.

Embodiment 5 Next, still another embodiment will be described. In the present embodiment, as shown in FIG. 8, a member 111 made of a permanent magnet is movably supported by an arm 110 inside the photoreceptor belt 1. Main photoreceptor belt 1
Is a ferromagnetic material because its base is made of nickel electroforming. And, as described above, when the positional relationship between each color of each developing device of the developing device and the photoconductor becomes random, while rotating the developing device to the reference position of the developing device,
As shown by the broken line, the support shaft 107a of the arm 110 is moved so that the photosensitive member 1 does not come into contact with the developing roller. Since the photoreceptor belt is supported with some slack, a part of the photoreceptor belt can be retracted as shown by a broken line even if the support roller of the photoreceptor is fixed.

Embodiment 6 Next, still another embodiment will be described. In this embodiment, as described above, if the positional relationship between each color of each developing device of the developing device and the photoconductor becomes random, the rotary developing device is moved to the reference position before the image forming operation is started. During the rotation, the photosensitive member is rotationally driven such that the moving speed of the surface of the developing roller facing the photosensitive member and the relative speed with respect to the photosensitive member surface are substantially zero. For example, in FIG. 9, if the developing device is rotated in the direction of arrow E, while the rotary developing device is rotated to the reference position, the moving speed of the surface of the developing roller facing the photoconductor, The photosensitive member is driven to rotate in the direction of arrow A so that the relative speed of the photosensitive member becomes substantially zero. With this control, the amount of transfer of the toner on the developing roller to the photoconductor can be considerably reduced as compared with the case where the relative speed is provided.

[Embodiment 7] Next, still another embodiment will be described. In this embodiment, as shown in FIG. 10, a gear 112 provided at the end of the developing roller is provided on the extension of the longitudinal end of the photoconductor at a position where the developing roller faces the photoconductor.
A rack 113 is provided separately from the photosensitive member so as to mesh with the photosensitive member. As described above, if the positional relationship between each color of each developing device of the developing device and the photoconductor becomes random, the rotary developing device is rotated to the reference position before the image forming operation is started. However, for example, when the rotary developing device is rotationally moved in the direction of arrow C, when the developing roller comes to a position facing the photosensitive member, the rack 113 and the gear 112 of the developing roller mesh with each other, and the developing roller And the relative speed between the surface of the developing roller and the surface of the photosensitive member becomes substantially zero. In this device, the amount of transfer of the toner on the developing roller to the photoreceptor can be considerably reduced as compared with the case where the speed is relative. During the image forming operation, the rack needs to be retracted so as not to bite.

[Embodiment 8] Next, still another embodiment will be described. In this embodiment, as described above, if the positional relationship between each color of each developing device of the developing device and the photoconductor becomes random, the rotary developing device is moved to the reference position before the image forming operation is started. During the rotation, the relative velocity between the surface linear velocity of the developing roller and the surface of the photoconductor is substantially zero.
The developing roller is rotated by a driving device (not shown).

Embodiment 9 Next, still another embodiment will be described. In this embodiment, as described above, if the positional relationship between each color of each developing device of the developing device and the photoconductor becomes random, the rotary developing device is moved to the reference position before the image forming operation is started. During the rotation, the photosensitive member is charged. The voltage applied to the charger may be the same as that used in the image forming operation, but a slightly lower voltage is more preferable because the amount of transfer of the toner on the developing roller to the photoconductor is reduced. For example, when the charging roller as in this embodiment is used, the image forming operation is -190.
0 V was applied, and -1200 V was applied while rotating the rotary developing device to the reference position.

[Embodiment 10] Next, still another embodiment will be described. In this embodiment, as described above, if the positional relationship between each color of each developing device of the developing device and the photoconductor becomes random, the rotary developing device is moved to the reference position before the image forming operation is started. During this rotation, a positive bias voltage is applied to the developing roller. For example, in this example using negatively charged toner, +400 V was applied to the developing roller.

[Eleventh Embodiment] Next, still another embodiment will be described. In this embodiment, as described above, if the positional relationship between each color of each developing device of the developing device and the photoconductor becomes random, the rotary developing device is moved to the reference position before the image forming operation is started. During the rotation, the photosensitive member was charged to a predetermined potential, and a predetermined bias voltage was applied to the developing roller. These applied voltages have good values during a normal image forming operation, and a simple power supply having only one output value can be used. The timing of application may be synchronized with the rotation of the developing device, and no new timing control is required.

Embodiment 12 Next, still another embodiment will be described. In this embodiment, as shown in FIG. 11, a ring-shaped mark 114 composed of a continuous gray scale (in which the optical density changes stepwise) is provided on the end face of the rotating body of the developing device. . A reflection type optical sensor 115 is provided inside the side plate of the image forming apparatus at a position corresponding to the mark 114, for example. In this image forming apparatus, the output value of the optical sensor 115 is detected when the power is turned on or when the cover is opened. If the value is a value corresponding to the reference value of the developing device, the rotation operation of the developing device is not started. However, as described above, when the positional relationship between each color of each developing device of the developing device and the photoconductor becomes random, the output value of the optical sensor 115 becomes a value corresponding to the reference value of the developing device. Is different and the mark is a continuous gray scale, so that the value and the rotation angle of the developing device to be rotated correspond one to one. Therefore,
If the output value of the optical sensor 115 is detected only once first, the rotation angle of the developing device to be rotated can be determined (for example, each density of the gray scale and the rotation angle up to the reference position are stored in a data table form). The rotation angle is obtained by looking up the data table using the detected density. Therefore, the developing device can be rotated to an appropriate reference position at the highest possible speed of the motor that rotates the developing device. Note that a color circle in which the balance of R, G, and B continuously changes in the circumferential direction can be used as the mark. In this case, the detector is C
A CD or the like may be used. Also in this case, each component value of RGB and the rotation angle of the developing device to be rotated correspond to one to one.

[0045]

According to the image forming apparatus of the first aspect, before the start of the image forming operation, the disturbance of the toner layer on the developing roller is eliminated, and the toner layer is made uniform over the entire circumference of the developing roller. Thus, a uniform and good output image can be obtained without generating a low density portion.

According to the image forming apparatus of the present invention, before the image forming operation is started, an electric field in a direction in which the toner is transferred from the developing roller to the supply roller is generated to initialize the developing roller. After the start of the operation, a new toner layer is formed over the entire circumference of the developing roller, and a uniform and good image can be output.

According to the image forming apparatus of the third aspect, before the image forming operation is started, before the rotating body is rotated to the reference position, an electric field is generated in a direction in which the toner is transferred from the developing roller to the supply roller. As a result, there is almost no toner on the developing roller, and then the rotating body is rotated to the reference position, so that unnecessary toner adhesion on the latent image carrier does not occur. After the start of the image forming operation, a new toner layer is formed over the entire circumference of the developing roller, so that a uniform and good image can be output.

[0048]

[0049]

[0050]

[0051]

[0052]

[Brief description of the drawings]

FIG. 1 is an overall schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of a developing device of the image forming apparatus.

FIGS. 3A and 3B are explanatory views of a developing unit in the developing device. FIGS.

FIG. 4 is a perspective view of a rotating body of the developing device.

FIG. 5 is an explanatory diagram of a home position of the rotating body.

FIG. 6 is a perspective view of a developing device of an image forming apparatus according to another embodiment.

FIG. 7 is a sectional view of a developing device of an image forming apparatus according to still another embodiment.

FIG. 8 is a sectional view of a developing device of an image forming apparatus according to still another embodiment.

FIG. 9 is a sectional view of a developing device of an image forming apparatus according to still another embodiment.

FIG. 10 is a sectional view of a developing device of an image forming apparatus according to still another embodiment.

FIG. 11 is a side view of a developing device of an image forming apparatus according to still another embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor belt (latent image carrier) 2 charging roller 3 laser optical unit 4 developing device 5 intermediate transfer belt 6 transfer roller 7 fixing unit 8 paper feed table 9 paper feed roller 10 registration roller 11 transfer paper 12 photoconductor cleaner 13 intermediate Transfer belt cleaner 20 Black developing unit casing 20a Casing opening 21 Developing unit casing 22 Developing unit 23 Developing roller 31 Supply roller 32 Developing blade 33 First transport member 34 Toner circulation unit 35 Second transport member 40 Toner container 41 Cover 42 Toner Cartridge

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuichi Ueno 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Ugitsu Fujishiro 1-3-6 Nakamagome, Ota-ku, Tokyo No. Ricoh Co., Ltd. (72) Inventor Chiyako Kobayashi Ricoh Co., Ltd. 1-3-6 Nakamagome, Ota-ku, Tokyo (56) References JP-A-63-178263 (JP, A) JP-A-63 JP-A-91676 (JP, A) JP-A-1-2577871 (JP, A) JP-A-62-192778 (JP, A) JP-A-5-307322 (JP, A) JP-A-4-177271 (JP, A) JP-A-61-151564 (JP, A) JP-A-61-217073 (JP, A) JP-A-3-81955 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/01-15/01 117 G03G 15/08-15/095

Claims (3)

(57) [Claims] A developing device used for development is moved to a predetermined developing position near a latent image carrier by a rotation of a rotator having a plurality of developing devices arranged around a rotation axis to perform development. When an image forming apparatus with a rotary developing device is used, when there is replacement or maintenance work due to the life of the developing device, or when the process of the image forming device is stopped halfway due to clogging or non-feed of the transfer paper Before starting the subsequent image forming operation, the rotating body is rotated to one reference position in rotation around the rotation axis and stopped at the reference position to prepare for the image forming operation. An image forming apparatus wherein the developing roller of each developing device is rotationally driven in a state where the developing roller is stopped at the reference position before the operation is started. 2. A developing device, which is used for development, is moved to a predetermined developing position near a latent image carrier by rotation of a rotating body having a plurality of developing devices arranged around a rotation axis to perform development. In the image forming apparatus having a rotary developing device, a developing roller and a replenishing roller for replenishing toner to the developing roller are provided in each developing device, and a toner is supplied between the developing roller and the replenishing roller in a direction from the developing roller to the replenishing roller. A bias voltage application device is provided to create an electric field in the direction in which the image is transferred.If there is replacement or maintenance work due to the life of the developing device, or if the transfer paper is jammed or not fed, the process of the image forming device If you stop halfway, the subsequent image forming operation start earlier, by rotating the rotating member to one <br/> reference position is stopped at the reference position in the rotation of the rotary axis, provided to the image forming operation Image forming, wherein the electric field is formed in each of the developing devices and the developing roller and the replenishing roller are rotationally driven in a state where the developing device is stopped at the reference position before the image forming operation is started. apparatus. 3. A developing device to be used for development is moved to a predetermined developing position near a latent image carrier by rotation of a rotating body having a plurality of developing devices disposed around a rotation axis, thereby performing development. In the image forming apparatus having a rotary developing device, a developing roller and a replenishing roller for replenishing toner to the developing roller are provided in each developing device, and a toner is supplied between the developing roller and the replenishing roller in a direction from the developing roller to the replenishing roller. A bias voltage application device is provided to create an electric field in the direction in which the image is transferred.If there is replacement or maintenance work due to the life of the developing device, or if the transfer paper is jammed or not fed, the process of the image forming device If you stop halfway, the subsequent image forming operation start earlier, by rotating the rotating member to one <br/> reference position is stopped at the reference position in the rotation of the rotary axis, provided to the image forming operation Before rotating the rotating body to a reference position in the rotation around the rotation axis for preparing for the image forming operation, the electric field is formed in each developing device, and the developing roller and the replenishing roller are formed. An image forming apparatus characterized by rotating the image forming apparatus.