JP2002225328A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an imaging apparatus in which a developer passage control member is protected against creep deformation and pressed against the developer carrier side with a stabilized pressure at the time of image recording operation. SOLUTION: The developer passage control member 4 for controlling passage of developer 8 through a plurality of small holes 23 arranged in array in the direction orthogonal to the carrying direction of developer, at the time of imaging operation, in response to an external signal is applied with a tension only at the time of imaging operation.

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 applied to a copying machine, a facsimile, a printer, and the like, and more particularly, to an image forming apparatus for ejecting a developer to a recording member to form an image.

[0002]

2. Description of the Related Art In recent years, in offices, with the improvement of personal computer capabilities and the advancement of network technology,
High-performance printers that can handle large volumes of documents,
Facsimiles and copiers are becoming widespread. On the other hand, color documents are also increasing due to the rapid spread of inkjet printers and the like. However, engines capable of outputting satisfactory black-and-white or color documents including printing speed are under development, and their appearance is expected.

One conventional image forming apparatus uses a direct marking method of forming an image directly on a recording member. For example, an image forming apparatus disclosed in JP-B-44-26333 proposes a developer injection type apparatus which is one of direct marking methods. This is because an image signal is input to an image signal electrode provided in a print head to generate an accelerating electric field, a charged developer passes through a small hole near the image signal electrode, and the developer is applied to a counter electrode. The recording material is caused to land on the recording member to form an image.

Here, an example of a print head will be described. FIG. 7 is a cross-sectional view illustrating a configuration of a recording portion of a conventional image forming apparatus. As shown in FIG. 7, the developing unit 1005 of this type of image forming apparatus 1001 is provided with a storage container 1003 and a developing roller 1004 that carries and transports toner (developer) on the peripheral surface thereof. I have. The developer supply unit 1005 includes a storage container 100.
The toner in the developing roller 10 is agitated to frictionally charge the toner.
A supply roller 1006 for supplying the toner to the toner supply unit 04 is provided.

[0005] In front of the developing roller 1004, a developer passage control member (recording head) 1007 having a small hole 1009 through which the developer passes is provided.

[0006] A transfer belt 1008 is provided so as to face the developing unit 1005. The back electrode 10 opposing the developing roller 1004 with the transfer belt 1008 and the developer passage control member 1007 interposed therebetween.
10 are provided.

[0007] The developer passage control member 1007 is formed of a flexible printed circuit board having flexibility. One end of the developer passage control member 1007
02 with a screw 1011 and the other end
And a tension spring 1012 is stretched between them. Thus, the developer passage control member 1007 is configured to be tensioned. This is because the developer passage control member 100
7 is to press the charged developer toward the surface of the developing roller 1011 which carries the charged developer. By this pressing, the distance between the image signal electrode on the developer passage control member 1007 and the developer on the surface of the developing roller 1004 is kept constant.

In this state, the developer passage control member 1007
An image signal is input to the image signal electrode provided in the first electrode to generate an accelerating electric field, and the charged developer is charged into the small hole 1 near the image signal electrode.
009, the developer is landed on a transfer belt as a recording member by a voltage applied to a back electrode 1010 as an opposite electrode, and an image is formed. Thus, the image signal electrode on the developer passage control member 1007 and the developing roller 10
By performing the image forming operation while keeping the distance between the surface of the developer 04 and the developer constant, a desired image can be surely formed.

[0009]

However, in the above-described prior art configuration, the developer passage control member 1007 is always tensioned by the tension spring 1012. That is, the developer passage control member 1007 is constantly stressed. For this reason, the developer passage control member 1
007 undergoes creep deformation and the developer passage control member 1
There is a possibility that the distance between the image signal electrode provided around the small hole 1009 on 007 and the developer on the surface of the developing roller 1004 changes. As a result, a problem of image quality deterioration may occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and prevents the developer passage control member from causing creep deformation and develops the developer passage control member with a stable pressure during image recording operation. It is an object of the present invention to provide an image forming apparatus capable of accurately forming an image by pressing the agent to the agent carrier side.

[0011]

According to the image forming apparatus of the present invention, when an image is formed on an image receiving medium, a plurality of small holes through which a charged developer passes are arranged in a direction perpendicular to the direction in which the developer is transported. The developer passage control member, which is formed in a shape and controls the passage of the developer through the small holes in response to an external signal, is tensioned so as to be pressed against the developer carrier that carries and transports the charged developer. Except when an image is formed on an image receiving medium, no tension is applied to the developer passage control member.

In this way, an appropriate tension can be applied to the developer passage control member during the image forming operation, so that an accurate image can be formed. In addition, the tension applied to the developer passage control member other than when an image is formed is formed. Can be reduced. That is, except when it is necessary to apply tension to the developer passage control member, the tension applied to the developer passage control member can be reduced. Accordingly, unnecessary stress is not applied to the developer passage control member, and creep deformation of the developer passage control member can be prevented.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to a first aspect of the present invention comprises a developer carrier for carrying and transporting a charged developer, and a line formed in a direction perpendicular to a direction in which the developer is transported. A plurality of small holes through which the developer is disposed and a control electrode for controlling the passage of the developer through the small holes by applying a voltage according to an external signal are formed. A developer passing control member, and an electric field for causing the developer to fly between the developer carrier and the image receiving medium on which the developer that has passed through the small hole adheres to the developer passing control member; A fixing means for fixing one end of both ends of the developer passage control member sandwiching a position of the developer passage control member facing the developer carrier to the device housing, The other end of the developer passage control member, Tension generating means for the image material passage control member to pull the developer carrier so as to press, and the tension generating means so as not to pull the developer passage control member except when forming an image on the image receiving medium, When an image is formed on an image receiving medium, a configuration is adopted in which the tension generating unit pulls the developer passage control member.

With this configuration, an appropriate tension can be applied to the developer passage control member when forming an image, so that an accurate image can be formed. In addition, when an image is not formed, a tension applied to the developer passage control member can be formed. Is reduced, so that excessive stress is not applied to the developer passage control member. Thus, creep deformation of the developer passage control member can be prevented, and an image can be formed accurately.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the control means controls the developer passage control immediately before a voltage is applied to the control electrode. The member is controlled so as to be pulled, and immediately after the voltage application to the control electrode is completed, the tension generating means is controlled so as not to pull the developer passage control member.

As described above, the period during which the developer passage control member is pulled is from immediately before the voltage is applied to the control electrode to immediately after the application of the voltage to the control electrode is completed. Pulling time can be minimized. Thereby, the stress applied to the developer passage control member can be minimized.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect or the second aspect, the tension generating means includes: a spring member connected to the other end of the developer passage control member; And a solenoid for pulling the spring member.

As described above, by employing a low-priced solenoid having a small device configuration as a tension generating means, a cost increase and a space increase can be suppressed.

Hereinafter, a configuration of an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG. Figure 1
1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to the embodiment. In FIG. 1, the right side is the front side of the image forming apparatus, and the left side is the rear side.

As shown in FIG. 1, the present image forming apparatus 100
A recording paper cassette 49 for storing recording paper 50 is arranged near the bottom surface of the main body case 3 and on the front side. A paper feed roller 51 is provided on the rear side of the recording paper cassette 49. The paper feed roller 51 is rotated clockwise by a drive unit (not shown), and feeds the uppermost recording paper 50 into the apparatus.

On the other hand, an image forming unit 2 is disposed above these paper feed mechanisms. The image forming unit 2
The image forming apparatus includes a developing unit 210 for forming an image of a plurality of colors and an image receiving unit 220 on which a single-color image formed by the developing unit 210 is superimposed.

In the developing unit 210, developer supply units (hereinafter referred to as developing units) 5a to 5d containing toners 8a to 8d, which are developers of four colors of yellow, magenta, cyan and black, are provided with openings on the right side. A flexible printed circuit board (hereinafter referred to as “FPC” (F
The head units 1a to 1d are referred to as "flexible printed circuits". The FPC head units 1a to 1d are provided in the FPC folder unit 36 provided in the developing unit 210.
It is configured so that it can be attached and detached. The inner wall surface of the FPC folder unit 36 has a shape corresponding to the developing devices 5a to 5d. The FPC folder unit 36 is attached to the main body case 3 via a hinge 37 so as to be freely opened and closed. The details of the FPC head units 1a to 1d will be described later.

The developing devices 5a to 5d are configured to be detachable from the FPC head units 1a to 1d, respectively.
The developing devices 5a to 5d are removed when replenishing the internal toners 8a to 8d, for example. A developing roller 1 carrying toners 8a to 8d is provided on the rear side inside the developing devices 5a to 5d.
1a to 11d are provided. Such a developing device 5a
Pressing portions 38a to 38d formed by springs and the like from the front side of developing devices 5a to 5d so that developing devices 5a to 5d are fixed at predetermined positions when FPC head units 5a to 5d are mounted on FPC head units 1a to 1d. Is pressed.

The image receiving unit 220 is formed by winding an endless transfer belt 7 as an image receiving medium around two belt rollers 29 and 30. The belt roller 30 is disposed above the uppermost FPC head unit 1a, and the belt roller 29 is disposed below the lowermost FPC head unit 1d. The belt roller 29 supports the transfer belt 7 and is connected to a drive motor (not shown) and functions as a drive roller for the transfer belt 7.

Back electrodes 6a to 6d are provided inside the transfer belt 7 arranged on the front side and at positions facing the developing rollers 11a to 11d, respectively. In other words, the developing rollers 11 a to 11 a
d and the back electrodes 6a to 6d face each other. The back electrodes 6a to 6d are formed in a circular cross section, that is, in a roller shape so as to smoothly contact the transfer belt 7.

A transfer roller 31 is provided at a position facing the belt roller 29. Transfer roller 31
Transfers the images of a plurality of colors formed on the transfer belt 7 to the recording paper 50 conveyed through the recording paper guide 32. Specifically, the toner constituting the image on the transfer belt 7 is electrically attracted to the transfer roller 31 side, and the image is recorded on the recording paper 50.
Transfer to

A fixing unit 54 composed of a fixing roller 59 and a heat roller 60 is provided in the direction of conveyance of the recording paper 50 by the transfer roller 31. Fixing roller 59
The recording paper 50 enters the contact surface between the sheet and the heat roller 60. The heat roller 60 applies heat to the recording surface of the recording paper 50, and the fixing roller 59 presses the recording paper 50 against the heat roller 60, whereby an image is fixed on the recording paper 50.

Further, the fixing roller 59 and the heat roller 60
The recording paper 50 discharged from the contact surface of the fixing unit 54 passes through a transport path 53 formed by the housing of the fixing unit 54. A pair of discharge rollers 55 is provided at the end of the transport path 53.
The discharge roller 55 is connected to the recording paper 50 conveyed through the conveyance path 53.
Is discharged outside the fixing unit 54.

A recording paper guide 56 is provided in the transport direction of the recording paper 50 discharged by the discharge roller 55.
The recording paper guide 56 regulates conveyance of the recording paper 50 discharged from the discharge roller 55 and discharges the recording paper 50.

Here, the structure around the developing unit 5 and the FPC head unit 1 which are members constituting the developing unit 210 will be described in detail with reference to FIG. FIG.
FIG. 3 is a partially enlarged view showing a configuration around a developing device and an FPC head unit when the image forming apparatus according to the embodiment is in a standby state and a stopped state. FIG. 2 shows a state in which the developing unit 5 is mounted at a predetermined position with respect to the FPC head unit 1 by the pressing unit 38.

As shown in FIG. 2, a developer passage control means for controlling the supply of the toner 8 from the developing device 5 to the transfer belt 7 side of the FPC head unit 1, that is, an FPC (insulating substrate) 4 as a recording head is provided. Installed. Specifically, one end of both ends of the FPC 4 sandwiching the position facing the developing roller 11 is fixed to the lower frame 61 of the FPC head unit 1 by a fixing screw 25. FP
The other end of C4 is a stay 62a at the tip of the upper frame 62.
One end of the tension spring (spring) 10 is attached to a spring attachment hole 201 formed near the front end of the other end. Further, the other end of the tension spring 10 is attached to a spring fixing arm 14 of a solenoid 15 provided on the upper frame 62. The tension spring 10 pulls the FPC 4 toward the front. Thus, the FPC 4 is attached to the upper frame 62 and the lower frame 61. The FPC 4 is made of a sheet-like flexible insulating material.

Further, the surface of the FPC 4 on the side of the developing device 5 (hereinafter referred to as the
A spacer 27 is fixed slightly above the axis of the developing roller 11 on the “back surface of the FPC 4”. The spacer 27 is in contact with the developing roller 11 and the FPC 4
The distance between the developing roller 11 and the developing roller 11 is kept constant. At the position corresponding to the axis of the developing roller 11 of the FPC 4, a number of small holes 23 are formed at a fine pitch along the width direction of the transfer belt 7.

Here, the structure around the small hole 23 formed in the FPC 4 will be described with reference to FIG. FIG. 3 is an enlarged view of the back surface of the FPC and the surface of the FPC on the transfer belt side (hereinafter, referred to as “front surface of FPC”) according to the embodiment.

As shown in FIG. 3, the back surface 263 of the FPC 4
Has a plurality of small hole rows 260 formed by the small holes 23 that have been drilled.
Are formed. Also, on the back surface 263 of the FPC 4,
A ring-shaped image signal electrode (control electrode) 261 is formed so as to surround each small hole 23. On the other hand, FPC4
An aperture electrode 262 is formed on the surface of the substrate.

Each image signal electrode 261 is similarly connected to the FPC 4
Are independently connected to an image signal output unit serving as an image signal voltage switching unit through a lead wire 300 wired on the back surface of the device. Normally, a voltage of 400 V or less is applied to the image signal electrode 261. In the present embodiment, a voltage of 300 V is applied for dot formation, and a voltage of -100 V for non-dot formation.

Now, returning to the description of the FPC head unit 1 with reference to FIG. Below the developing roller 11 of the developing device 5, a toner supply roller 13 is provided. The toner supply roller 13 stirs the toner stored in the developing device 5 to frictionally charge the toner and supplies the toner to the developing roller 11. Further, a toner regulating blade 12 is provided above the developing roller 11. The toner regulating blade 12
The toner layer carried on the developing roller 11 is regulated.

On the outer side of both ends in the axial direction of the developing roller 11, a regulating collar (shown in FIG. 1) as a first spacer means which comes into contact with the back electrode 6 to regulate the distance between the developing roller 11 and the back electrode 6 to be constant. Z) is provided. The regulating collar has an outer peripheral surface in contact with the back electrode 6 and an inner peripheral surface having an outer diameter portion of the developing roller 11 or an outer diameter of a coaxial guide shaft (not shown) extending to both sides from the developing roller 11. It is arranged in a state of contact with the part. In the regulating color, the distance between the back electrode 6 and the developing roller 11 is set to, for example, 150 to 1000 μm, and in this embodiment, to 350 μm.

A guide shaft coaxial with the developing roller 11 is provided to project from both ends of the FPC head unit 1. A drive gear (not shown) for transmitting a rotational driving force to the developing roller 11 is provided on at least one side of the guide shaft so as to rotate the developing roller 11 only in a counterclockwise direction as viewed in the drawing of FIG. It is arranged via a direction clutch (not shown). With this configuration, the developing devices 5a to 5d
When a gear train (not shown) at the preceding stage is engaged with the head unit 1a to 1d, the developing roller 1
1 is rotatably driven by a driving force of a separate driving means (not shown).

The developing roller 11 is made of aluminum,
It is made of a metal such as iron or an alloy. In this embodiment, an aluminum cylinder having an outer diameter of 20 mm and a thickness of 1 mm is used. The regulating blade 12 is made of an elastic member such as urethane, has a hardness of 40 to 80 degrees (JISK6301A scale), has a free end length (length of a portion protruding from the mounting portion) of 5 to 15 mm, and extends to the developing roller 11. The linear pressure of 5 to 40 g / cm is appropriate, and one to three layers of toners 8 a to 8 d are formed on the developing roller 11. In the present embodiment, the regulating blade 12 is electrically floated.

Further, the toners 8a to 8d are
Between the developing roller 11 and the regulating blade 12. In the present embodiment, a nonmagnetic material having a negative charge of −10 μC / g and an average particle diameter of 8 μm is used as the toner 8.

The supply roller 13 is formed by providing a synthetic rubber such as urethane foam on a metal shaft such as iron (diameter: 8 mm in the present embodiment) of about 2 to 6 mm, and has a hardness of 30 mm.
(Measured by a method according to JIS K6301A scale when processed into a roller shape), assists charging of toner 8 and controls supply. The amount of biting into the developing roller 11 is preferably about 0.1 to 2 mm.

Further, the developing roller 11, the toner supply roller 13, and the toner regulating blade 12 may be electrically grounded or applied with a DC or AC voltage. Further, the toner regulating blade 12 may be electrically floated.

On the other hand, the back electrode 6 functions as a counter electrode and forms an electric field between the back electrode 6 and the developing roller 11, and is made of a metal plate or resin in which conductive fillers are dispersed.
Although a DC voltage of about 500 to 2000 V is applied to the back electrode 6, a voltage of 1000 V is applied in the present embodiment.

When a voltage of 1000 V is applied to the back electrode 6, an electric field is generated between the back electrode 6 and the developing roller 11, and the toner carried on the developing roller 11 is attracted to the back electrode 6. However, in the present image forming apparatus 1, the image signal electrodes 2 provided on the FPC 4 are provided.
The toner passing through the small holes 23 is controlled by adjusting the voltage applied to 61. As a result, a desired recorded image is formed.

In order for the image forming apparatus 1 to form an image accurately, the distance between the image signal electrode 261 on the FPC 4 and the developer on the surface of the developing roller 11 must be kept constant. Pull one end of the FPC 4 with the tension spring 10,
By applying tension to the FPC 4, the FPC 4 is pressed against the surface of the developing roller 11. However, FP
Since C4 is made of a flexible print, that is, a flexible material, there is a possibility that creep deformation will occur if stress is constantly applied.

Therefore, the present invention prevents the creep deformation of the FPC 4 by making the tension applied to the FPC 4 variable and applying a strong tension to the FPC 4 only during image formation. Specifically, the tension applied to the FPC 4 is made variable by connecting a solenoid 15 to the tension spring 10.

Hereinafter, the control of the solenoid associated with the image forming operation of the image forming apparatus according to the above embodiment will be described. First, a configuration for controlling the solenoid 15 will be described with reference to FIG. FIG. 4 is a hardware block diagram of the image forming apparatus according to the embodiment.

The image forming apparatus 100 is provided with a CPU 401 as a main control unit. The CPU 401 operates according to a program stored in the storage unit. Also,
The image forming apparatus 100 includes a ROM 402 as a storage unit.
And a RAM 403 are provided. The ROM 402 is a nonvolatile read-only storage unit, and stores programs and various initial settings. Also, the RAM 403
Is a volatile rewritable storage means,
01 work memory.

Further, the image forming apparatus 100 is provided with an electrode control unit 404 and a back electrode control unit 405 for controlling the image forming operation. The electrode control unit 404
During the image forming operation, the voltage applied to the image signal electrode 261 is controlled to control the toner 8 passing through the small hole 23 of the FPC 4. The back electrode control unit 405 also draws the toner 8 to the back electrode 6 during image formation.
The voltage of the back electrode 6 is controlled.

The image forming apparatus 100 includes an FPC 4
Solenoid 15 to adjust the tension applied to
N, OFF control, that is, the solenoid 15
Is provided with a solenoid control unit 406 that controls the pulling.

Next, the image forming apparatus 1 at the time of image formation
The control of the solenoid 15 of 00 will be described with reference to FIG. FIG. 5 is a timing chart for explaining the solenoid control of the image forming apparatus according to the embodiment.

First, prior to forming an image, when the user inserts developing units 5a to 5d to predetermined positions of FPC head units 1a to 1d of main body case 3 and closes FPC folder unit 36, the FPC folder unit is closed. The pressing portions 38a to 38d attached to the inner surface of the pressing member 36 urge the developing devices 5a to 5d toward the back electrode 6 side.

This state is at the time of standby and stop of image formation. At this time, as shown in FIG. 2, the solenoid 15 is in an OFF state, that is, a state in which there is no suction force. In other words, there is no tension in which the solenoid 15 pulls the FPC 4 in the direction of arrow a. For this reason, as shown in FIG. 2, an interval is generated between the FPC 4 and the developing roller 11, and the pressing force of the FPC 4 on the developing roller 11 is lost. As described above, the external force applied to the FPC 4 is close to 0 during standby and stop of image formation. That is, the external force applied to the FPC 4 is minimized. As described above, before the image forming operation, the FPC 4
Not to put too much stress on Thereby, creep of the FPC 4 can be prevented.

Next, when moving to the image forming operation, as shown in FIG. 5, the solenoid control unit 406 turns on the solenoid 15 prior to the image recording operation. Then, a suction force is generated in the solenoid 15, and as shown in FIG. 6, the solenoid 15 pulls the FPC 4 through the tension spring 10 in the direction of arrow a. FIG. 6 is a partially enlarged view showing the configuration around the FPC head unit during the recording operation of the image forming apparatus according to the above embodiment.

As a result, as shown in FIG.
Is attracted to the developing roller 11 side. Thus, the outer peripheral surface of the developing roller 11 does not directly contact the FPC 4 but contacts the spacer 27. As a result, a pressing force F1 for pressing the FPC 4 from the back surface to the front surface via the spacer 27 is generated on the developing roller 11. As described above, the FPC 4 is pressed toward the developing roller 11 with the spacer 27 interposed therebetween. On the other hand, the pressing force F toward the developing roller 11 is also applied to the FPC 4.
A reaction force equal to 1 acts. By this pressing force F1,
The tension is applied to the FPC 4.

As described above, the FPC 4 and the developing roller 1
1 are pressed against each other with a spacer 27 interposed therebetween, so that the distance between the back surface of the FPC 4 and the outer peripheral surface of the developing roller 11 is maintained at the thickness of the spacer 27. The distance between the image signal electrode 261 and the toner layer on the developing roller 11 is determined by the film thickness of the spacer 27 and the insulating layer of the FPC 4. That is, a state where image formation can be performed accurately is achieved.

The image forming apparatus 100 shifts to the recording operation in this state. That is, the back electrode control unit 405 turns on the back electrode 6. Then, as shown in FIG. 5, the image signal electrode 261 is turned on in accordance with the image to be formed by the electrode control unit 404. In this way, an accurate image is formed.

When the formation of the desired image is completed,
As shown in FIG. 5, the solenoid control unit 406 turns off the solenoid 15. As a result, there is no force for the solenoid 15 to pull the tension spring 10 in the direction of arrow a, and the spring fixing arm 14 moves to the direction of arrow b. This state is a state where there is no tension applied to the FPC 4 by the solenoid 15.
That is, the external force applied to the FPC 4 is minimized. Thus, when the image forming operation is completed, F
By preventing excessive stress from being applied to the PC 4, creep of the FPC 4 can be prevented.

When the operation shifts to the image forming operation again, the solenoid control unit 406 turns on the solenoid 15.
Then, the spring fixing arm 14 is pulled to a state where accurate image formation can be performed as described above.

As described above, image formation is performed by fixing one end of the FPC 4 with the fixing screw 25 and pulling the other end with the solenoid 15 via the tension spring 10 as in the above embodiment. It is possible to reduce the tension applied to the FPC 4 from the tension spring 10 in addition to the case described above.
That is, the tension applied to the FPC 4 can be reduced except when it is necessary to apply the tension to the FPC 4. Therefore, unnecessary stress is not applied to the FPC 4, creep of the FPC 4 can be prevented, and deterioration of image quality due to deformation of the FPC 4 can be prevented.

When forming an image, the FPC 4 can be pressed toward the developing roller 11 with a stable pressure by turning on the solenoid 15. Accordingly, the distance between the image signal electrode 261 and the toner layer on the developing roller 11 is kept constant, and an image can be formed with high image quality.

In the above embodiment, the solenoid 15
The period during which the FPC 4 is pulled from the time immediately before the voltage is applied to the image signal electrode 261 to the time immediately after the voltage application to the image signal electrode 261 is completed can be minimized. Thereby, the stress applied to the FPC 4 can be minimized.

In the above embodiment, the solenoid 1 is used as tension generating means for varying the pulling force of the FPC 4.
By using 5, the external force applied to the FPC 4 can be easily controlled. In addition, by adopting an inexpensive solenoid 15 having a small device configuration, the cost increases,
Space increase can be suppressed. In the above embodiment,
Although the description has been given using the solenoid 15 as the tension generating means, any means other than the solenoid 15 can be applied as long as the tension can be varied with respect to the FPC 4.

Further, in the above-described embodiment, in order to form a color image, a plurality of developing units 5a to 5d accommodating developers 8a to 8d of four colors of yellow, magenta, cyan and black, and a plurality of developers Although the configuration includes the passage control member 4, a configuration in which a single developing device and a developer passage control unit are provided to perform monochrome recording may be used.

In the above embodiment, the electrode control unit 4
04, back electrode control unit 405, solenoid control unit 406
Has been described as a different configuration from the CPU 401, but the functions of the electrode control unit 404, the back electrode control unit 405, and the solenoid control unit 406 may be provided to the CPU 401.

[0066]

As described above, according to the present invention,
By reducing the tension applied to the developer passage control member except during the image recording operation, it is possible to prevent the developer passage control member from creeping and to apply an appropriate tension to the developer passage control member during the image recording operation. Thus, the developer passage control member can be pressed toward the developer carrier with a stable pressure. Thereby, an image can be formed accurately.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention;

FIG. 2 is a partially enlarged view showing a configuration around a developing device and an FPC head unit when the image forming apparatus according to the embodiment is in a standby state and when the image forming apparatus is stopped.

FIG. 3 shows the back surface of the FPC and the FPC according to the embodiment.
Enlarged view of PC on the transfer belt side

FIG. 4 is a hardware block diagram of the image forming apparatus according to the embodiment;

FIG. 5 is a timing chart for explaining solenoid control of the image forming apparatus according to the embodiment;

FIG. 6 is a partially enlarged view showing a configuration of a recording portion during a recording operation of the image forming apparatus according to the embodiment.

FIG. 7 is a partially enlarged view showing a configuration of a recording portion of a conventional image forming apparatus.

[Explanation of symbols]

 1a to 1d FPC head unit 4 FPC 5a to 5d Developing device 6 Back electrode 7 Intermediate image receiving belt 8a to 8d Toner 10 Tension spring 11 Developing roller 13 Supply roller 14 Spring fixing arm 15 Solenoid 23 Small hole 25 Fixing screw 27 Spacer 38a to 38d Pressing unit 100 Image forming device 261 Image signal electrode 401 CPU 404 Electrode control unit 405 Back electrode control unit 406 Solenoid control unit

Claims (3)

[Claims] 1. A developer carrier for carrying and transporting a charged developer, and a plurality of small holes through which the developer passes in a row arranged in a direction perpendicular to a direction in which the developer is transported, and a plurality of external holes. A control electrode for controlling the passage of the developer through the small holes by applying a voltage corresponding to a signal from the developer passage control member, and the developer passage control member A back electrode for generating an electric field for causing the developer to fly between the developer carrier and an image receiving medium on which the developer having passed through the small hole is attached; Fixing means for fixing one end of both ends of the developer passage control member across a position opposed to the developer carrier to an apparatus housing; and fixing the other end of the developer passage control member to the developer passage control member. A member presses the developer carrier. The tension generating means pulls the developer passing control member so as not to pull the developer passage control member except when forming an image on the image receiving medium, and when forming an image on the image receiving medium, the tension generating means Control means for pulling the developer passage control member,
An image forming apparatus comprising: 2. The control unit controls the tension generating unit to pull the developer passage control member immediately before a voltage is applied to the control electrode, and the voltage application to the control electrode is completed. 2. The image forming apparatus according to claim 1, wherein the tension generating unit controls the developer passage control member so as not to pull the member immediately after the tension. 3. The device according to claim 1, wherein the tension generating means includes a spring member connected to the other end of the developer passage control member, and a solenoid for pulling the spring member. 3. The image forming apparatus according to 2.