JP2002182458A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of stably forming an image even in aging by reducing the wear of a developing bias terminal part at a fixed position. SOLUTION: A printer 1 is equipped with a developing unit 40 capable of moving to a developing action position or a non-developing action position at the time of performing image forming action, and a developing bias applying part 102 applying developing bias to the unit 40 by a bias power source 105, and the unit 40 existing at the developing action position develops an electrostatic latent image on a photoreceptor drum 1 as a visible image. In the printer, a developing bias applying part 102 is equipped with the rotatable developing bias terminal part 106 coming into contact with the magnet roller shaft 98b of the unit 40 existing at the developing action position, supporting part 107 supporting the terminal part 106, and a compression spring 107a energizing the terminal part 106 and the supporting part 107 toward the direction of the shaft 98b of the unit 40.

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 printer, a facsimile, and the like. More specifically, the present invention relates to an image forming apparatus that sequentially moves a plurality of image forming means to a predetermined developing operation position. The present invention relates to an image forming apparatus including a movable image forming unit that develops an electrostatic latent image.

[0002]

2. Description of the Related Art A typical example of a color image forming apparatus for sequentially switching a developing device (image forming means) of a predetermined color on a photosensitive member (image carrier) to form an image is a rotatable revolver. And a color image forming apparatus having a unit.

In the image forming apparatus of the revolver developing type, a developing bias is usually applied only to a developing device at a developing operation position (image forming operation position). That is, the developing bias input portion of each developing device of the revolver developing device is connected to a bias power source fixedly arranged on the image forming apparatus main body side with the rotational movement of each developing device to the developing operation position, and a spring (elastic). (See JP-A-07-325480, etc.). Therefore, in such an image forming apparatus, the sliding between the developing bias terminal and the developing bias input section of each developing device is repeated by the switching movement of each color developing device to the developing operation position.

[0004]

However, as shown in FIG. 9, the developing bias terminal portion 201 urged by a spring toward the developing bias input portion of the developing device is connected to the developing bias input portion at a certain position. By repeating the sliding, the specific portion 20 of the developing bias terminal portion 201 is
There is a problem that 1a is worn away with time and is worn.

In particular, in a high-speed and high-durability machine, the developing bias terminal portion 101 is significantly worn, and the life of the developing bias terminal portion 100 is shortened. In addition, when carbon is used as the material of the developing bias terminal portion, the specific portion 101a of the developing bias terminal portion 100 is largely scraped, and the contact between the developing bias input portion and the developing bias terminal portion becomes unstable. There is a possibility that an abnormal image or a mechanical abnormal operation due to noise may occur.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of reducing abrasion of a developing bias terminal portion at a fixed position and performing stable image formation with time.

[0007]

According to the first aspect of the present invention, there is provided an image forming means which can be moved to an image forming operation position or a non-image forming operation position during an image forming operation, and a bias power supply to the image forming means. Developing bias applying means for applying a developing bias to the image forming apparatus, wherein the image forming means at the image forming operation position develops the electrostatic latent image on the image carrier as a visible image. A developing bias terminal portion which is in contact with the developing bias input portion of the image forming means and is rotatable when in the image forming operation position; And an elastic body which urges in a direction of the developing bias input section of the means.

According to the first aspect of the present invention, the developing bias terminal portion is made rotatable to prevent repeated sliding between the developing bias terminal portion and the developing bias input portion of the image forming means with time. Wear at a certain position can be prevented from occurring. In addition, since the occurrence of abrasion at a fixed position of the developing bias terminal portion can be prevented, the contact between the developing bias input portion and the developing bias terminal portion can be prevented from becoming unstable, so that a stable developing bias can be applied. Thus, stable image formation can be performed.

According to a second aspect of the present invention, in the first aspect, the rotation center axis of the developing bias terminal portion is
It is characterized by being substantially orthogonal to the moving direction of the developing bias input section of the image forming means.

[0010] According to the second aspect of the present invention, the first aspect is provided.
In addition to the same operation and effect as the invention described in the above, the developing bias input unit moves in the rotation direction of the developing bias terminal when the developing bias input unit of the image forming unit contacts the developing bias terminal unit when the developing bias input unit moves. The rotation of the developing bias terminal becomes smooth.

[0011] The invention according to claim 3 is the invention according to claim 1 or 2.
In the invention described in (1), the developing bias terminal portion is rotated in accordance with the contact due to the movement of the developing bias input portion of the image forming means.

According to the third aspect of the present invention, the first aspect is provided.
Or a rotation drive for rotating the developing bias terminal portion by rotating the developing bias terminal portion in accordance with the contact of the image forming means by the movement of the developing bias input portion. There is no need to separately provide a mechanism, and the configuration is simple.

The invention described in claim 4 is the first to third aspects of the present invention.
In the invention described in any one of the above, the biasing direction of the elastic body is 90 degrees or less with respect to the moving direction of the developing bias input unit at the contact start position between the developing bias terminal unit and the developing bias input unit of the image forming unit. It is characterized by having an angle.

According to the fourth aspect of the present invention, the first aspect is provided.
In addition to the same effects as those of the invention described in any one of (1) to (3), the biasing direction of the elastic body is set at an acute angle with respect to the moving direction of the developing bias input section of the image forming apparatus (biasing of the elastic body) By making the angle between the direction and the developing bias input section an acute angle), when the developing bias input section comes into contact with the developing bias terminal section (at the time of intrusion), the rotation center of the developing bias terminal section is strongly pressed against the support section. Therefore, the rotation of the developing bias terminal portion becomes smoother, and the wear of the rotation center of the developing bias terminal portion can be reduced.

Further, by making the angle between the biasing direction of the elastic body and the developing bias input section a narrow angle, the rate at which the shock when the developing bias input section enters the developing bias terminal section is absorbed by the elastic body. Therefore, the vibration caused by the impact can be reduced, and the jitter in the latent image writing portion on the image carrier, the transfer portion, and the like can be reduced.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a configuration diagram schematically showing a printer to which the present invention is applied. As shown in FIG. 1, a printer (image forming apparatus) 1 is capable of creating a color image and has a photosensitive drum 1 as an image carrier.

The photosensitive drum 1 is driven to rotate in the direction of arrow A, and a charging charger 2 as a uniform charging means is provided.
After being uniformly charged, the laser optical device 3 scans and exposes the image based on the upper part of the image to form an electrostatic latent image on the surface. Here, the image information to be exposed is monochrome image information obtained by decomposing a desired full-color image into yellow, magenta, cyan, and black color information. The electrostatic latent image formed on the photosensitive drum 1 is developed by yellow, magenta, cyan, and black toners as predetermined developers by a rotary developing device 4 to be described later. Each color image is formed.

Each color image formed on the photosensitive drum 1 is transferred onto the intermediate transfer belt 5 rotating in the direction of arrow B in synchronization with the photosensitive drum 1 for each of the single colors of yellow, magenta, cyan, and black. The next transfer charger 6 sequentially superimposes and transfers the images. The yellow, magenta, cyan, and black images superimposed on the intermediate transfer belt 5 are transferred from the automatic paper feed cassette 7 for both-sided copying and the manual paper feed tray 7a through the paper feed rollers 8, 8a and the registration roller 9 to the transfer unit. Is collectively transferred by the secondary transfer charger 11 onto the transfer paper 10 transported to the transfer paper. The transfer paper 10 after the transfer is fixed with the toner image by the fixing device 12 and is discharged out of the apparatus as a full-color print.

The toner on the photosensitive drum 1 which has not been transferred onto the intermediate transfer belt 5 is removed from the photosensitive drum 1 by the photosensitive cleaner 13 and the intermediate transfer which has not been transferred onto the transfer paper 10. The toner on the belt 5 is removed from the intermediate transfer belt 5 by the intermediate transfer belt cleaner 14.

Next, the rotary developing device 4 according to the present embodiment will be described. FIG. 2 is a cross-sectional view illustrating a bias applying unit that applies a developing bias to the developing unit.
FIG. 3 is an exploded perspective view of the rotary developing device, and FIG.
FIG. 5 is a cross-sectional view showing an internal structure of a developing unit of the rotary developing device. FIG. 5 is a view for explaining a revolver developing unit. FIG. 6 is a diagram schematically showing a drive system of the developing unit. FIG.

As shown in FIG. 3, the rotary type developing device 4
Developing units (image forming means) 40 each having a developing unit for each of four colors of black, cyan, yellow, and magenta, and having a substantially cylindrical outer periphery which is rotatably mounted around a central axis in the printer body. And four toner containers 41, 42, 43, and 44 corresponding to the respective developing devices and storing the black, yellow, magenta, and cyan toners, respectively, and at the front side of the developing device unit 40 in the center axis direction. A toner container unit 45 which is attached so as to be substantially coaxial and rotates integrally with the developing device unit 40 around the central axis, and in a state where the developing device unit 40 and the toner container unit 45 are carried, An accommodating base 46 slidable on the main body substantially parallel to the central axis, and a front supporting plate 48 of the accommodating base so as to cover the toner accommodating unit 45
And a cover 47 provided non-rotatably.
In the present embodiment, the revolver developing unit 20 is composed of the developing unit 40 and the toner container unit 45.

The revolver developing unit 20 includes
6 attached to the front support plate 48 so as to be freely rotatable.
One support roller 49 supports the disc-shaped front end wall 50 of the developing unit 40, and the center axis 52 of the tip taper protruded from the center of the disc-shaped rear end wall 51 of the developing unit 40.
Is rotatably supported by a center shaft insertion hole 54 formed in the rear side plate 53 so that the rotation axis of the photoreceptor drum 1 is adjusted in the printer body as shown in FIG. Are positioned at positions parallel to each other in substantially the same horizontal plane, and are rotatable.

As for details of a mechanism for rotatably supporting the revolver developing unit 20, as shown in FIG. 3, the housing 46 includes a front support plate 48, a rear support plate 55,
A front and rear end portion is fixed to both support plates 48 and 55, and a side cover 59 reinforced with connecting rods 56, 57 and 58 is provided. The front support plate 48 includes a revolver developing unit 20.
An insertion hole 60 into which the support roller 49 can be inserted is formed.
In addition, a toner supply roller driving motor 61 provided in the toner container unit 45 and a gear train driven by the motor 61 are attached.

An intermediate plate 63 is attached to the connecting rods 56 and 67 near the rear support plate 55, and a positioning pin is provided on the intermediate plate 63 so as to fit into a positioning hole 63a formed in the rear plate 53 of the main body. Have been. A base end of a bracket 64 holding a rotation positioning roller 66 is swingably attached to a positioning pin between the middle plate 63 and the rear support plate 55. The bracket 64 is urged by a spring 67 in a direction in which the rotary positioning roller 66 is fitted into a concave portion 65 formed at a predetermined location on the peripheral surface of the rear end wall 51 of the developing unit 40 (see FIG. 6). .

The main body front side plate 68 is formed with an insertion hole 69 into which the accommodating table 46 supporting the revolver developing device unit 20 can be inserted. The main body front side plate 68 and the main body rear side plate 5 are formed.
Up and down guides 70 and 71 for slidably supporting the accommodation table 46 are stretched between the upper and lower guides 3. Guided portions 72 and 73 are provided at the upper end and side portions of the side cover 59 of the accommodation base 46, respectively, as accommodation base portions guided by these guides 70 and 71. A guide pin groove 75 into which a guide pin 74 implanted upward in the guide 71 enters is formed on the lower surface.

In the above-described support mechanism for the revolver developing unit 20, when the housing 46 is inserted into the main body,
The tapered tip of the positioning pin protruding into the printer enters the positioning hole 63a of the main body rear side plate 53 immediately before the insertion of the housing table into the printer main body.
6. The rear support plate 55 and the bracket 64 are accurately positioned in the main body.

On the other hand, when the housing 46 is pulled out, the rear end of the revolver developing unit 20 supported by the rear plate 53 of the housing 46 has a tapered central shaft immediately before the main body of the housing 46 is completely inserted. 52 is lifted as it gradually enters the central shaft insertion hole 54, and when the insertion is completed, it is completely lifted from the rear support plate 55. And
After the front support plate 48 of the housing table 46 is completely inserted into the main body, the front support plate 48 is fixed to the main body front side plate 68 with screws 76 or the like.
As a result, the front end portion of the revolver developing unit 20 is supported by the support rollers 49 of the front support plate 48 of the accommodating table 46 accurately positioned on the main body, and is rotated by the main body rear side plate 53 via the central shaft 52. The rear end is freely positioned and becomes rotatable.

As shown in FIG. 6, the main body rear side plate 53 for rotationally driving the revolver developing unit 20 includes:
A revolver drive gear 78 driven by a revolver drive motor such as a stepping motor (not shown) is attached. This is the rear end plate 51 of the developing unit 40.
The rear end plate 51 fixed to the rear surface of the revolver by a screw or the like meshes with a revolver input gear 79 having substantially the same diameter as that of the revolver developing unit 40 to rotate. Further, a developing drive gear driven by a developing drive motor (not shown) is attached to the main body rear side plate 53 to drive a developing roller 84 and the like in the developing unit 40 described later.

Next, the developing unit 40 will be described with reference to FIGS. As shown in FIG. 4, the developing device unit 40 includes a partition wall provided between the front and rear end plates 50 and 51 having a substantially disk shape. The partition wall includes a hollow cylindrical portion 82 into which a cylindrical black toner bottle containing black toner can be inserted, and a space extending radially from the hollow cylindrical portion 82 to surround the hollow cylindrical portion 82 and are substantially circumferentially separated from each other. Same type 4
Developing device casing sections 83, 83 partitioned into two developing chambers
C, 83M, and 83Y.

In each of these developing chambers, a two-component developer composed of a carrier as a developer and toner of each color is accommodated. In FIG. 4, a developing operation position (image forming operation position) opposite to the photosensitive drum 1 is a developing chamber of a black developing device containing black toner and a carrier. The developing chamber of the yellow developing device containing the toner and the carrier, the developing room of the magenta developing device containing the magenta toner and the carrier, and the developing room of the cyan developing device containing the cyan toner and the carrier.

Since the internal structure of the four developing chambers is exactly the same, the internal structure will be described below with reference to the developing chamber at the developing operation position in FIG. In the internal structure of the other developing chamber at the position ()), the reference numerals of the corresponding members in the black developing chamber are given subscripts of Y, M, and C in order to distinguish the yellow, magenta, and cyan developing chambers. Signs are shown in the figure,
The description is omitted.

Referring to FIG. 4, in the black developing device at the developing operation position, an opening is formed in the developing device casing 83 toward the photosensitive drum 1, and the developing is performed so that a part is exposed through the opening. A developing roller 84 is provided in the room. In the developing chamber, a doctor blade 85 for regulating the amount of developer on the developing roller 84,
An upper transport screw 86 that transports a part of the developer pressed into the developing chamber at 5 from back to front along the central axis direction.
, A guide 87 and a stirring paddle 88 are provided.

The stirring paddle 88 includes a hollow cylindrical portion 89 having a plurality of developer discharge holes 89a formed therein and a hollow cylindrical portion 8 formed therein.
9, a plurality of agitating plate portions 90 extending radially from the peripheral surface, and a hollow cylindrical portion 89 accommodates a lower transport screw 91 for transporting the developer in a direction opposite to that of the upper transport screw 86. . In the developing device casing below the lower conveying screw 91, there are formed an agent outlet 92 used as an outlet for a deteriorated developer and an inlet for an unused developer (toner mixed). The outlet 92 is covered from outside by a cap 93 attached with a screw 94.

As shown in FIG. 5, the front ends of the upper and lower transport screws 86 and 91 extend to the outside of the front end wall 50 of the developing unit 40, and are transported to the extended portion by the upper transport screw 86. A drop portion 96 is provided for dropping the supplied developer onto the lower conveying screw 91 by its own weight. The developer conveyed to the front side by the guide 87 and the upper conveying screw 86 while being regulated by the doctor blade 85 drops through the falling portion 96 onto the conveying screw 91, and the effective width of the developing roller 84 by the lower conveying screw 91. After being transported into the developing chamber, the developer is discharged from the developer outlet of the hollow cylindrical portion 82 of the stirring paddle 88 into the developing chamber.

The developer discharged from the developer discharge port of the hollow cylindrical portion 82 of the stirring paddle 88 into the developer reservoir below the developing chamber is stirred by the rotation of the stirring paddle 88. Further, the front end portion of the transport screw 91 extends further forward than the falling portion 96, and each toner receiving case 91Y provided corresponding to each developing chamber of the toner container unit 45,
It extends to the inside of 91M, 91C, 110, specifically, below the toner supply roller 97 provided in these cases.

In FIG. 4, for example, the front and rear end walls for supporting the developing roller 84Y and the doctor blade 85Y of the yellow developing unit are configured as small end walls 104 which can be separated from the other front and rear end walls. This facilitates cleaning of the developing chamber and replacement of parts.

As shown in FIG. 3, the toner container unit 45 has a disk-shaped unit face plate 108 and a total of four toner receiving cases 91Y attached to the front surface of the unit face plate 108 so as to correspond to each developing device. , 91M,
91C and 110 are provided. The unit face plate 108 has a circular through hole (not shown) through which a cylindrical black toner container penetrates is formed at the center thereof, and each of the toner receiving cases 91Y, 91M, 91C, and 110 escapes from this through hole. Installed.

These four toner receiving cases 91
Y, 91M, 91C, 110, three color toner receiving cases 91Y, 91Y,
The toner receiving ports 91M and 91C face upward when the corresponding developing chambers are located at the developing operation position. Color toner containers 42, 43, and 44 of the same shape for the respective colors containing color toner are mounted on mounting portions around the toner receiving port.

On the other hand, the black toner receiving case 110 corresponding to the black developing device is provided with the color toner receiving case 9.
1Y, 91M, and 91C have color toner containers 42 and 4
It has a peripheral wall shape that is substantially the same as the overall peripheral wall shape of the two with the three and 44 attached. Then, at a position facing the center line of the revolver developing unit 20 on the peripheral wall portion having the same shape as the color toner receiving cases 91Y, 91M, and 91C, the toner receiving shape having a shape corresponding to the toner discharge port of the black toner container 41 is received. The mouth is formed.

The black toner container 41 has a cylindrical shape. A toner outlet is formed in a peripheral wall at one end in the longitudinal direction, and a ridge for feeding toner is provided on the inner peripheral surface from the other end. It is formed spirally toward the outlet side. Due to the spiral protrusion, during rotation of the black toner container 41,
The stored toner is sent from the rear end toward the front end, and the toner is supplied from the toner discharge port into the toner receiving port of the black toner receiving case 110.

The rear end of the black toner container 41 enters the hollow cylindrical portion 82 of the developing unit 40 through the central portion of the notch 47a for inserting the toner container formed in the cover 47. It is attached in a state where the front end is inserted until it is substantially flush with the front surface of the front end wall of each case of the toner container unit 45, for example.

Then, the black toner receiving case 11 shown in FIG.
As shown in FIG.
Inside each of Y, 91M, 91C and 110, a toner supply roller 97 is provided. The toner supply roller 97 is pivotally supported by the front end wall of the case 110 and the unit face plate 108. The shaft end of the toner supply roller 97 that is supported by the unit face plate 108 is
, And protrudes toward the developing unit 40 side, and a gear 197 is fixed to the protruding end.

The gear 197 meshes with a supply input gear (not shown) for driving input. Of the supply input gears provided for each toner supply roller 97, the toner supply roller 9 in the case corresponding to the developing device at the developing operation position
The gear corresponding to 7 meshes with a gear driven by a replenishing motor 61 (see FIG. 3) and is rotated by the motor 61. This toner supply roller 97
The toner that has dropped onto the lower transport screw 91 due to the rotation of the roller is transported into the developing chamber by the lower transport screw 91. The toner supply control is performed by the drive control of the supply motor 61 that drives the toner supply roller 97.

As shown in FIG. 6, each gear is provided on the rear side wall 51 of the developing unit 40. That is, the developing roller gear 9 is attached to the shaft end of the developing roller 84 which penetrates the rear side wall 51 and the like and projects to the rear side of the revolver input gear 79.
The upper and lower transport screw gears 99 and 100 are fixed to the shaft ends of the upper and lower transport screws 86 and 91 that protrude to the rear of the revolver input gear 79.

In FIG. 6, an idle gear 101 meshing with the developing roller gear 98 and the lower conveying screw 100 meshes with a developing output gear 81 mounted on the rear plate 53 of the main body and driven by a developing driving motor 80. Input gear 95 is attached to the rear side of the rear end wall 51 of the developing unit 40.

The revolver developing unit 20 is supported by the accommodating base 46 and inserted into the printer main body as described above, so that the developing output gear 81 on the main body side and the developing input gear 95 on the developing unit 40 side are connected. Are engaged. At the same time, the revolver input gear 79 of the developing unit 40 meshes with the revolver output gear 78 of the main body.

In FIG. 6, during the development, the development output gear 81
Are driven in the direction of arrow A in FIG. 6, and the upper and lower transport screw gears 99 and 100
Rotates, and the upper and lower transfer screws are driven to rotate. Also,
The developing roller gear 98 is rotated via the developing input gear 95, the lower conveying screw gear 100, and the idle gear 101, and the developing roller 84 is driven to rotate.

When the developing unit to be used is switched, the revolver output gear 79 driven by the above-described revolver driving motor is rotated in the direction of arrow B in FIG. 6 to rotate the developing unit 40 in the direction of arrow C. By letting
The developing device to be located at the developing operation position is switched, and a positioning roller 66 is inserted into a concave portion 65 formed at a predetermined position on the peripheral surface of the rear end wall 51 of the developing device unit 40 to be engaged therewith, thereby positioning the developing device unit 40. Do.

After this positioning, the developing drive gear 81
Is rotated in the direction of arrow A, a rotational moment indicated by arrow D acts on the developing unit 40. Therefore, the shape of the concave portion 65 and the urging force of the spring 67 for urging the rotational positioning roller 66 are set so that the developing unit 40 can be positioned against the rotational moment.

Here, in the present embodiment, a developing bias applying device (developing bias applying means) 102 is provided to satisfactorily apply a developing bias to the developing roller 84. That is, as shown in FIG. 2, the developing bias applying device 102 is located at a fixed position of the main body rear side plate 53 facing the end face of the roller shaft 98a of the developing roller 84 located at the developing operation position, and the bias circuit ( Bias power supply) 10
5, a developing bias terminal 106 for applying a developing bias, a guide member (supporting portion) 107 for rotatably supporting the developing bias terminal 106, and a magnet roller shaft for connecting the developing bias terminal 106 and the guide member 107 to each other. (Developing bias input section) 98b, and a compression spring 107 (elastic body) a for urging toward 98b.

In this embodiment, the developing roller gear 9
8, a magnet roller shaft 98b protruding from an end of the developing roller shaft 98a penetrates a hollow portion of the developing roller shaft 98a, and a power receiving terminal of the rotary developing device 4 in contact with the developing bias terminal portion 106. Department.

In the present embodiment, the developing bias terminal 106 is formed by hardening carbon with a binding material. Further, as shown in FIG.
06 is an outer peripheral portion 1 that contacts the magnet roller shaft 98b.
06a and a central projection 106b supported by the guide member 107 as a center of rotation, and moves from a developing operation position to a non-developing operation position (see arrow C) so that the magnet roller shaft 98b rotates by contact. It has become.

In this embodiment, as shown in FIG. 7, the biasing direction of the compression spring 107a (see arrow F) and the moving direction of the magnet roller shaft 98b (arrow C).
Is set to be an acute angle of 90 ° or less. That is, the urging direction of the compression spring 107a indicated by the arrow F is acute with respect to the moving direction of the magnet roller shaft 98b at the contact start position S between the developing bias terminal 106 and the magnet roller shaft 98b. Further, in order to make the rotation of the developing bias terminal 106 smooth, the projecting direction of the central projection 106 b of the developing bias terminal 106 is
The direction is substantially orthogonal to the moving direction of b.

By setting the biasing direction of the compression spring 107a at an acute angle with respect to the moving direction of the magnet roller shaft 98b, when the magnet roller shaft 98b comes into contact with the peripheral surface portion 106a of the developing bias terminal portion 106, as shown in FIG. (At the time of intrusion), it is possible to prevent the central protrusion 106b of the developing bias terminal 106 from being strongly pressed against the guide member 107, so that the rotation of the developing bias terminal 106 becomes smooth and the developing bias terminal 10
Wear of the central projection 106b of No. 6 can be reduced.

Further, by making the angle θ between the biasing direction of the compression spring 107a and the magnet roller shaft 98b an acute angle, the impact when the magnet roller shaft 98b enters the developing bias terminal 106 is reduced by the compression spring 107a. Since the ratio of absorption increases, the vibration due to the impact can be reduced, and the jitter in the transfer by the laser optical device 3 or the primary transfer charger 6 for writing the latent image on the photosensitive member 1 is reduced. be able to.

In the present embodiment, the guide member 107 is
It is made of a conductive and slidable material (sintered material or the like), and has a central protrusion 106 of the developing bias terminal 106.
By supporting b, the developing bias terminal 106 is rotatably supported. In addition, the guide member 107
It is housed in a case (not shown) attached to the rear side plate 53, and is slidably provided in the biasing direction of the compression spring 107a.

One end of the compression spring 107a is attached to the guide member 107, and the other end is connected to the bias power source 1
The power supply terminal 105a is attached to a power supply terminal 105a to which a voltage from the power supply terminal 05 is applied, and urges the developing bias terminal portion 106 and the guide member 107 in the direction of arrow F. Electrically connected. Therefore, the voltage from the bias power supply 105 is
The power is transmitted to the developing bias terminal 106 via the power supply side terminal 105a, the compression spring 107a, and the guide member 107. The developing bias terminal 106 is developed through the magnet roller 98b by contact with the magnet roller shaft 98b. A developing bias is applied to the roller 84.

As described above, in the present embodiment, the developing bias terminal 106 and the developing device unit 40 over time are made rotatable by making the developing bias terminal 106 rotatable.
It is possible to prevent the occurrence of abrasion at a certain position when the developing roller 84 repeatedly slides with the magnet roller shaft 98b. Further, since the occurrence of abrasion of the developing bias terminal portion 106 at a fixed position can be prevented, the unstable contact between the magnet roller shaft 98b and the developing bias terminal portion 106 can be prevented. In addition, stable image formation can be performed.

Further, when the developing bias terminal 106 rotates with the movement of the developing roller 84 by the movement of the magnet roller shaft 98b, the developing bias terminal 10 is rotated.
There is no need to separately provide a rotation drive mechanism for rotating the motor 6, and the configuration is simple. On the other hand, when the developing bias terminal 106 is rotated by obtaining a driving force from another driving mechanism, the developing bias terminal 1
By performing the rotation of No. 06, there is a possibility that abrasion may occur due to sliding at the center protrusion 106b which is the center of rotation of the developing bias terminal 106, and an attempt is made to reduce the number of rotations in order to prevent abrasion. In such a case, a speed reduction mechanism must be used, and the configuration becomes complicated.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the present embodiment, the developing bias terminal 106 is brought into contact with the magnet roller shaft 98b of the developing roller 84, but the present invention is not limited to this, and the developing bias terminal 106 is brought into direct contact with the developing roller shaft 98a. May be.

Although the present invention has been applied to the printer 1, the present invention is not limited to this. For example, a similar effect can be obtained by applying the present invention to a copying machine, a facsimile, or a multifunction peripheral thereof.

[0062]

According to the first aspect of the present invention, the developing bias terminal portion is made rotatable to prevent repeated sliding between the developing bias terminal portion and the developing bias input portion of the image forming means over time. In addition, it is possible to prevent the occurrence of wear at a certain position. In addition, since the occurrence of abrasion at a fixed position of the developing bias terminal portion can be prevented, the contact between the developing bias input portion and the developing bias terminal portion can be prevented from becoming unstable, so that a stable developing bias can be applied. Thus, stable image formation can be performed.

According to the second aspect of the present invention, the same effects as those of the first aspect of the invention can be obtained, and when the developing bias input section of the image forming means contacts the developing bias terminal section when the developing bias input section is moved, the developing bias input section is provided. Since the portion moves in the direction of rotation of the developing bias terminal, the rotation of the developing bias terminal portion becomes smooth.

According to the third aspect of the present invention, the same effects as those of the first or second aspect are attained, and the developing bias terminal portion rotates with the contact of the image forming means by the movement of the developing bias input portion. Thus, there is no need to separately provide a rotation drive mechanism for rotating the developing bias terminal section, and the configuration is simple.

According to the fourth aspect of the present invention, the same effects as those of the first to third aspects of the invention are obtained, and the biasing direction of the elastic body is changed by moving the developing bias input section of the image forming apparatus. When the developing bias input section comes into contact with the developing bias terminal section (at the time of rush), the angle is set to an acute angle with respect to the direction (the angle between the biasing direction of the elastic body and the developing bias input section is made acute). Since the rotation center of the developing bias terminal portion can be prevented from being strongly pressed against the support portion, the rotation of the developing bias terminal portion can be further smoothly performed, and the wear of the rotation center of the developing bias terminal portion can be reduced.

Further, by making the angle between the biasing direction of the elastic body and the developing bias input section a narrow angle, the ratio of the elastic body absorbing the shock when the developing bias input section enters the developing bias terminal section is reduced. Therefore, the vibration caused by the impact can be reduced, and the jitter in the latent image writing portion on the image carrier, the transfer portion, and the like can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a printer to which the present invention is applied.

FIG. 2 is a cross-sectional view illustrating a bias applying unit that applies a developing bias to a developing unit.

FIG. 3 is an exploded perspective view of the rotary developing device.

FIG. 4 is a cross-sectional view illustrating an internal structure of a developing unit of the rotary developing device.

FIG. 5 is a diagram for explaining a revolver developing unit.

FIG. 6 is a configuration diagram schematically showing a drive system of a developing unit.

FIG. 7 is an enlarged front view showing the vicinity of a developing bias terminal portion.

FIG. 8 is an enlarged perspective view showing a developing bias terminal portion and a guide member.

FIG. 9 is a perspective view showing a conventional developing bias terminal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Printer (image forming apparatus) 40 Developing unit (image forming means) 102 Developing bias applying device (developing bias applying means) 105 Bias power supply 106 Developing bias applying terminal portion 106b Central protrusion (rotation center axis) 107 Guide member (support) Part) 107a Compression spring (elastic body)

Claims (4)

[Claims] An image forming unit that can move to an image forming operation position or a non-image forming operation position during an image forming operation; and a developing bias applying unit that applies a developing bias to the image forming unit by a bias power supply. In an image forming apparatus in which an image forming unit at an image forming operation position develops an electrostatic latent image on an image carrier as a visible image, a developing bias applying unit is configured to develop the image forming unit when the image forming unit is at the image forming operation position. A developing bias terminal that is rotatable in contact with the bias input unit, a supporting unit that supports the developing bias terminal, and biases the developing bias terminal and the supporting unit toward the developing bias input unit of the image forming unit. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein a rotation center axis of the developing bias terminal section is substantially orthogonal to a moving direction of the developing bias input section of the image forming means. 3. The image forming apparatus according to claim 1, wherein the developing bias terminal rotates with a contact caused by movement of the developing bias input unit of the image forming unit. 4. The biasing direction of the elastic body has an angle of not more than 90 degrees with respect to the moving direction of the developing bias input portion at the contact start position between the developing bias terminal portion and the developing bias input portion of the image forming means. The image forming apparatus according to claim 1, wherein: