JP2010145911A - Developer supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a satisfactory image by appropriately supplying developer. <P>SOLUTION: A conveying substrate (63) is provided with: a developer carrier member (62); and a conveying substrate (63). The conveying substrate (63) is provided with a vertical conveying member (63b) provided to stand so as to convey the developer (T) upward. The developer conveying substrate (62) is provided opposite the upper end (63b1) of the vertical conveying substrate (63b). A bias is applied between the vertical conveying substrate (63b) and the developer carrier member (62) so as to generate an electric field along which the developer T charged to a prescribed polarity is carried toward the developer bearing member (62) from the upper end (63b1) of the vertical conveying substrate (63b) toward the developer carrier member (62). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developer supply device configured to supply a powdery developer charged to a predetermined polarity to a supply target while being conveyed along an developer conveyance path by an electric field.

As this type of apparatus, those disclosed in Japanese Patent Application Laid-Open Nos. 60-115962, 11-84862, 2001-209246, 2002-287495, etc. are known. Yes. Such an apparatus includes a plurality of transport electrodes arranged along the developer transport direction, and is configured to transport the developer by an electric field generated by applying a drive voltage to the plurality of transport electrodes. .
Japanese Patent Application Laid-Open No. 60-115962 Japanese Patent Laid-Open No. 11-84862 JP 2001-209246 A JP 2002-287495 A

  In this type of apparatus, the developer having a poor charged state (including uncharged or charged with a polarity opposite to the desired polarity) is supplied to the supply target, or the developer stays in the supply path. Thus, when the supply state of the developer becomes defective, problems such as disorder of the formed image occur. Therefore, by appropriately supplying the developer in this type of apparatus, good image formation can be performed. The present invention has been made to cope with such a problem.

<Configuration>
A developer supply device that is an object of the present invention is configured to supply a powdery developer charged to a predetermined polarity to a supply target while being conveyed along the developer conveyance path by an electric field. . The developer supply device includes a developer carrying member and a transport substrate.

  The developer carrying member is a roller-shaped member having a cylindrical circumferential surface, and is provided to face the supply target. The transport substrate includes a plurality of transport electrodes arranged along the developer transport path, and development along the developer transport path is caused by an electric field generated when a voltage is applied to the transport electrodes. The developer is conveyed in the agent conveying direction.

  The transfer board includes a vertical transfer board. The vertical transport substrate is erected so as to transport the developer vertically upward as the developer transport direction.

  The transfer substrate may further include a bottom transfer substrate. The bottom conveyance substrate is provided so as to constitute the bottom surface of the developer storage unit. In addition, the bottom transport substrate is connected to the lower end portion so that the developer is charged by friction with the developer and the charged developer is transported toward the lower end portion of the vertical transport substrate. .

  The developer carrying member is provided to face the upper end portion of the vertical transport substrate.

  A bias is applied between the vertical transport substrate and the developer carrying member so that an electric field is formed from the upper end of the vertical transport substrate toward the developer carrying member for the developer charged to the predetermined polarity. Applied.

  A transport stop region where no electric field is generated for transporting the developer in the developer transport direction may be provided at the uppermost end of the vertical transport substrate.

  The transport stop region may be provided with a reverse feeding unit that generates an electric field for transporting the developer charged to the predetermined polarity downward. Specifically, for example, the reverse feeding unit may include a transport stop region electrode with a fixed potential. Alternatively, the reverse feeding section is applied with a plurality of alternating AC voltages whose traveling directions are opposite to those of the transport electrodes so as to generate an electric field for transporting the developer charged to the predetermined polarity downward. A transport stop region electrode may be provided.

<Action>
In this configuration, the developer is transported vertically upward as the developer transport direction by the vertical transport substrate along the developer transport path. Then, at the position where the upper end portion of the vertical transport substrate and the developer carrying member face each other, the developer charged to the predetermined polarity moves to the developer carrying member side by the bias. That is, the developer is carried on the peripheral surface of the developer carrying member.

  At this time, the developer having a poor charged state cannot be moved to the developer carrying member side by the action of the bias and falls downward. Alternatively, the developer having a poorly charged state falls downward in the transport stop area due to obstructing transport upward in the developer transport direction.

  This effectively suppresses the supply of the developer having a poor charged state to the supply target. That is, on the vertical transport substrate, the developer having a good charge state and a poor charge state is well selected.

  When the developer having a poor charged state falls so as not to collide with the vertical transport substrate (for example, vertically downward), the transport of the developer is disturbed on the vertical transport substrate (for example, the charged state) The accumulation or retention of the developer having a poor resistance on the vertical transport substrate, or the falling off of the developer having a good charged state from the vertical transport substrate, etc.) is suppressed as much as possible.

  When the transport substrate includes the bottom transport substrate, an electric field generated by the bottom transport substrate is in contact with the bottom transport substrate in the developer stored in the developer storage section. Thus, it is transported toward the lower end portion of the vertical transport substrate. Then, at the lower end portion, the developer is transferred from the bottom conveyance substrate to the vertical conveyance substrate.

  Therefore, even if there is no positive and mechanical charging operation (such as stirring) in the developer reservoir, the developer is charged by contact or friction with the bottom transport substrate. Thereby, the deterioration with time of the developer can be suppressed as much as possible. Further, the developer in the developer reservoir is fluidized favorably due to the falling of the developer having a poor charged state.

  According to the developer supply apparatus of the present invention having the above-described configuration, the developer is more appropriately supplied to the supply target, and thus good image formation is performed.

  Hereinafter, embodiments of the present invention (embodiments that the applicant considers best at the time of filing of the present application) will be described with reference to the drawings.

  In addition, the description about the following embodiment is specific to the extent possible, merely an example of the embodiment of the present invention in order to satisfy the description requirement (description requirement / practicability requirement) of the specification required by law. It is only what is described in. Therefore, as will be described later, it is quite natural that the present invention is not limited to the specific configurations of the embodiments described below. Various modifications that can be made to the present embodiment are listed together at the end, as they would interfere with the understanding of the consistent description of the embodiment if inserted during the description of the embodiment. .

<Configuration of laser printer>
FIG. 1 is a side view showing a schematic configuration of a laser printer 1 as an image forming apparatus to which an embodiment of the present invention is applied.

  Referring to FIG. 1, the laser printer 1 includes a paper transport mechanism 2, a photosensitive drum 3, a charger 4, a scanner unit 5, and a toner supply device 6.

  Sheet-like paper P is stored in a stacked state in a paper feed tray (not shown) provided in the laser printer 1. The paper transport mechanism 2 is configured to transport the paper P along a predetermined paper transport path PP.

  An electrostatic latent image carrying surface LS is formed on the peripheral surface of the photosensitive drum 3 as a supply target of the present invention. The electrostatic latent image carrying surface LS is formed as a cylindrical surface parallel to the main scanning direction (z-axis direction in the figure). The electrostatic latent image carrying surface LS forms an electrostatic latent image based on a potential distribution, and carries toner T (see FIG. 2) as a developer of the present invention at a position corresponding to the electrostatic latent image. Is configured to do.

  The photosensitive drum 3 is configured to be rotationally driven in a direction indicated by an arrow in the drawing (clockwise in FIG. 1) around a central axis C parallel to the main scanning direction. That is, the photosensitive drum 3 is configured so that the electrostatic latent image carrying surface LS can move along the sub-scanning direction orthogonal to the main scanning direction.

  The charger 4 is disposed so as to face the electrostatic latent image carrying surface LS. The charger 4 is a corotron type or scorotron type charger, and is configured so that the electrostatic latent image carrying surface LS can be uniformly positively charged.

  The scanner unit 5 is configured to generate a laser beam LB modulated based on image data. That is, the scanner unit 5 is configured to generate a laser beam LB having a predetermined wavelength band in which light emission ON / OFF is controlled depending on the presence or absence of pixels.

  Further, the scanner unit 5 is configured to image (expose) the generated laser beam LB at the scan position SP on the electrostatic latent image carrying surface LS. Here, the scan position SP is provided at a position downstream of the charger 4 in the rotation direction of the photosensitive drum 3 (direction indicated by the arrow in FIG. 1: clockwise in the drawing).

  Further, the scanner unit 5 moves (scans) the position where the laser beam LB is imaged on the electrostatic latent image carrying surface LS at a constant speed along the main scanning direction. An electrostatic latent image can be formed on the latent image carrying surface LS.

  The toner supply device 6 as the developer supply device of the present invention is disposed below the photosensitive drum 3 so as to face the photosensitive drum 3. The toner supply device 6 is configured to be able to supply the electrostatic latent image carrying surface LS in a charged state at the developing position DP. Here, the development position DP is a position where the toner supply device 6 faces the electrostatic latent image carrying surface LS. The detailed configuration of the toner supply device 6 will be described later.

  Next, the specific configuration of each part of the laser printer 1 will be described in more detail.

  The sheet transport mechanism 2 includes a pair of registration rollers 21 and a transfer roller 22.

  The registration roller 21 is configured so that the paper P can be sent out between the photosensitive drum 3 and the transfer roller 22 at a predetermined timing.

  The transfer roller 22 is disposed so as to face the electrostatic latent image carrying surface LS, which is the outer peripheral surface of the photosensitive drum 3, with the sheet P interposed therebetween at the transfer position TP. Further, the transfer roller 22 is configured to be rotationally driven in a direction (counterclockwise) indicated by an arrow in the drawing.

  The transfer roller 22 is connected to a bias power supply circuit (not shown). That is, a predetermined transfer bias voltage for transferring the toner (developer) attached on the electrostatic latent image carrying surface LS to the paper P is applied between the transfer roller 22 and the photosensitive drum 3. It has become.

<< Toner Supply Device >>
FIG. 2 is an enlarged side cross-sectional view of the toner supply device 6 shown in FIG. Referring to FIG. 2, the toner supply device 6 is configured to supply the charged toner T to the photosensitive drum 3 while being transported along the toner transport path TTP by an electric field.

  The toner box 61 forming the casing of the toner supply device 6 is a box-like member formed in an oval shape in a side sectional view, and its longitudinal direction is parallel to the vertical direction (y-axis direction in the figure). Is arranged. The toner box 61 contains toner T as a powdery dry developer. That is, the toner storage portion 61 a is formed by the space inside the semi-cylindrical lower end portion of the toner box 61. In this embodiment, the toner T is a positively chargeable, non-magnetic one-component black toner. An opening 61b is provided at the top of the toner box 61, that is, at a position facing the photosensitive drum 3.

  Inside the toner box 61 is housed a developing roller 62 as a developer carrying member of the present invention. The developing roller 62 is rotatably supported by the toner box 61. The developing roller 62 is a roller-like member having a toner carrying surface 62a that is a cylindrical circumferential surface, and is provided to face the photosensitive drum 3 at the opening 61b. That is, the toner box 61 is arranged such that the toner carrying surface 62a of the developing roller 62 is close to the electrostatic latent image carrying surface LS of the photosensitive drum 3 at the developing position DP with a gap of a predetermined interval (about 500 μm). The developing roller 62 is disposed.

  Inside the toner box 61, a transport substrate 63 is provided along the toner transport path TTP. The transport substrate 63 is fixed to the inner wall surface of the toner box 61. In the present embodiment, the transport substrate 63 includes a bottom transport substrate 63a, a vertical transport substrate 63b, and a recovery substrate 63c. The details of the internal configuration of the transfer substrate 63 (the bottom transfer substrate 63a, the vertical transfer substrate 63b, and the recovery substrate 63c) will be described later.

  The bottom conveyance substrate 63a is disposed at the bottom in the space inside the toner box 61 so as to form the bottom surface of the toner storage unit 61a. The bottom transfer board 63a is a concave curved portion bent in a semi-cylindrical shape in a side sectional view at the bottom of the transfer board 63, and is smoothly connected to the lower end of the vertical transfer board 63b. The bottom conveyance substrate 63a is connected to the lower end portion so as to convey the toner T in the toner storage portion 61a toward the lower end portion of the vertical conveyance substrate 63b.

  The vertical transport substrate 63b is formed in a flat plate shape, and is erected vertically so as to transport the toner T transferred from the bottom transport substrate 63a vertically upward.

  The upper end portion 63b1 of the vertical transport substrate 63b is a portion that defines the upstream end of the opening 61b of the toner box 61 in the toner transport direction TTD, and in the present embodiment, is approximately the same height as the center of the developing roller 62. Is provided. The upper end portion 63b1 is disposed so as to face the cylindrical toner carrying surface 62a of the developing roller 62 with a gap of a predetermined interval (about 300 μm).

  The collection substrate 63 c is provided to face the developing roller 62 on the opposite side of the upper end portion of the vertical conveyance substrate 63 b and the developing roller 62. In other words, the collection substrate 63c is disposed downstream of the opening 61b of the toner box 61 in the toner transport direction TTD. In the present embodiment, the end portion of the collection substrate 63c in the toner transport direction TTD is provided at a position corresponding to the lower end of the developing roller 62.

  The collection substrate 63c is configured to collect the toner T that has not been consumed at the development position DP from the development roller 62 and to convey the collected toner T toward the lower toner storage portion 61a. Specifically, the upper part of the collection substrate 63c is opposed to the developing roller 62 with a gap of a certain distance (a gap narrower than the gap between the photosensitive drum 3 and the developing roller 62 at the developing position DP: about 300 μm). As shown, it is bent into a concave curved surface. The lower end portion of the collection substrate 63c is provided so as to convey the toner T vertically downward.

  The bottom transfer board 63 a and the vertical transfer board 63 b in the transfer board 63 are electrically connected to the transfer power supply circuit 64. The recovery board 63c is electrically connected to the recovery power supply circuit 65. The developing roller 62 is electrically connected to the developing bias power supply circuit 66.

  The transport power supply circuit 64, the recovery power supply circuit 65, and the development bias power supply circuit 66 circulate the toner T in the toner transport direction TTD along the toner transport path TTP (the toner T in the toner storage unit 61a is transferred to the vertical transport substrate 63b. The toner T is transported to the upper end portion 63b1, and the toner T is transferred to the developing roller 62 side at the upper end portion 63b1 to be carried on the toner carrying surface 62a to the developing position DP, and is not consumed at the developing position DP. A voltage necessary to collect the toner T from the developing roller 62 and recirculate it to the lower toner reservoir 61a is output.

  Specifically, the carrier power supply circuit 64 outputs a rectangular wave AC voltage of 400 V to 1000 V (amplitude 600 V, DC offset 700 V) and 300 Hz. Further, the recovery power supply circuit 65 outputs a rectangular waveform AC voltage of −300 V to +300 V (amplitude 600 V, DC offset 0 V) and 300 Hz. Further, the development bias power supply circuit 66 outputs a rectangular wave AC voltage of −600 V to 1400 V (amplitude 2000 V, DC offset 400 V) and 1200 Hz.

  That is, the development bias power supply circuit 66 applies a bias between the vertical conveyance substrate 63b and the development roller 62 so that the positively charged toner T forms an electric field from the upper end 63b1 of the vertical conveyance substrate 63b toward the development roller 62. To be applied. The development bias power supply circuit 66 applies an output voltage (collection bias) with a larger amplitude than the recovery power supply circuit 65 and a frequency that is an integral multiple of the frequency of the output voltage of the recovery power supply circuit 65 to the developing roller 62. It has become.

  The recovery power circuit 65 applies an output voltage to the recovery substrate 63c so as to have an average potential (0V) lower than the potential (240V) of the exposure portion to which the toner T is supplied on the electrostatic latent image carrying surface LS. It has become. The outputs of the recovery power supply circuit 65 and the development bias power supply circuit 66 are set so that the electric field between the development roller 62 and the recovery substrate 63c is stronger than the electric field between the development roller 62 and the photosensitive drum 3. The voltage is set.

  In the space inside the toner box 61, a shielding plate 67 is disposed at a position below the developing roller 62 and close to the vertical conveyance substrate 63b. The shielding plate 67 is provided so that the toner T does not adhere to the developing roller 62 when the toner T rises in the space inside the toner box 61 by the operation of the transport substrate 63.

<<< Transport substrate >>>
FIG. 3 is an enlarged side sectional view of the transfer board 63 shown in FIG.

  Referring to FIG. 3, the transport substrate 63 is a thin plate-like member and has the same configuration as that of the flexible printed circuit board. Specifically, the transport substrate 63 includes a transport electrode 631, a transport electrode support film 632, a transport electrode coating layer 633, and a transport electrode overcoating layer 634.

  The transport electrode 631 (the transport electrode 631 in the bottom transport substrate 63a is referred to as the bottom transport electrode 631a, the transport electrode 631 in the vertical transport substrate 63b is referred to as the vertical transport electrode 631b, and the transport electrode 631 in the recovery substrate 63c is referred to as the recovery electrode 631c). A linear wiring pattern having a longitudinal direction parallel to the main scanning direction (that is, orthogonal to the sub-scanning direction), and is formed of a copper foil having a thickness of about several tens of μm. The plurality of transport electrodes 631 are arranged along the toner transport path TTP and are arranged in parallel to each other.

  Each of the plurality of transport electrodes 631 arranged along the toner transport path TTP is connected to the same power supply circuit every third. That is, the transfer electrode 631, connected to the power supply circuit VA, the transfer electrode 631, connected to the power supply circuit VB, the transfer electrode 631, connected to the power supply circuit VC, the transfer electrode 631, connected to the power supply circuit VD, and the power supply circuit VA. The transport electrodes 631, the transport electrodes 631, the transport electrodes 631,... Connected to the power circuit VC connected to the power supply circuit VB are sequentially arranged along the toner transport path TTP (note that these are connected. The power supply circuits VA to VD are components of the transport power supply circuit 64 and the recovery power supply circuit 65 in FIG.

  Here, FIG. 4 is a graph showing an example of output waveforms of the power supply circuits VA to VD shown in FIG. In the present embodiment, as shown in FIG. 4, each of the power supply circuits VA to VD is configured to output a drive voltage that is an AC voltage having substantially the same waveform. Further, the power supply circuits VA to VD are configured so that the phases of the waveforms of the voltages generated by the power supply circuits VA to VD are different by 90 °. That is, the voltage phase is delayed by 90 ° in order from the power supply circuit VA to the power supply circuit VD.

  In this way, the transport substrate 63 applies the drive voltage as described above to each transport electrode 631 and generates a traveling-wave electric field along the toner transport path TTP. The toner is transported in the toner transport direction TTD.

  The plurality of transport electrodes 631 are formed on the surface of the transport electrode support film 632. The transport electrode support film 632 is a flexible film and is made of an insulating synthetic resin such as a polyimide resin.

  The transport electrode coating layer 633 is made of an insulating synthetic resin. The transport electrode coating layer 633 is provided to cover the transport electrode 631 and the surface of the transport electrode support film 632 where the transport electrode 631 is provided.

  On the transport electrode coating layer 633, the transport electrode overcoating layer 634 (the transport electrode overcoating layer 634 on the bottom transport substrate 63a is the bottom overcoating layer 634a, and the transport electrode overcoating layer 634 on the vertical transport substrate 63b is vertical. The overcoating layer 634b and the transport electrode overcoating layer 634 on the collection substrate 63c are referred to as a collection overcoating layer 634c). That is, the above-described transport electrode coating layer 633 is formed between the transport electrode overcoating layer 634 and the transport electrode 631. The surface of the transport electrode overcoating layer 634 is formed as a smooth surface with very few irregularities so that the toner T can be transported smoothly.

  In the present embodiment, the vertical overcoating layer 634b and the recovery overcoating layer 634c are formed of the same material (polyester). As the material, a material in which the position in the triboelectric charge train is on the plus side, that is, the same polarity as the charging polarity of the toner T, is used with respect to the material (polyimide) constituting the bottom overcoating layer 634a.

  FIG. 5 is an enlarged side sectional view of the upper end portion 63b1 of the vertical transfer substrate 63b shown in FIG. Referring to FIG. 5, a transport stop region 635 is provided at the most downstream portion (uppermost end portion) of the upper end portion 63b1 in the toner transport direction TTD. In the present embodiment, the conveyance stop region 635 is formed in a range from the highest position of the vertical conveyance substrate 63b to a position closest to the toner carrying surface 62a. In the conveyance stop region 635, an electric field for conveying the positively charged toner T in the toner conveyance direction TTD is not generated.

  Specifically, a plurality of transfer stop region electrodes 636 are provided in the transfer stop region 635 of the present embodiment. Specifically, the transport stop region electrode 636 in this embodiment uses a part of the most downstream side in the toner transport direction TTD among the many transport electrodes 631 (see FIG. 3) provided on the vertical transport substrate 63b. Provided along the toner transport path TTP. That is, the transport stop region electrode 636 is a linear wiring pattern having a longitudinal direction parallel to the main scanning direction, and is formed of a copper foil having a thickness of about several tens of μm.

  Further, in the present embodiment, the plurality of transfer stop region electrodes 636 are applied with a multiphase AC voltage whose traveling direction is opposite to the applied voltage to the transfer electrode 631 shown in FIG. In other words, the transport stop area 635 is configured such that the toner T is transported in the direction opposite to the toner transport direction TTD.

<Description of laser printer operation>
Next, an outline of the operation of the laser printer 1 configured as described above will be described together with the operations and effects of the configuration of the embodiment with reference to the drawings as appropriate.

<< Paper feeding action >>
First, referring to FIG. 1, the leading edge of the paper P stacked on the paper feed tray (not shown) is sent to the registration roller 21. The registration roller 21 corrects the skew of the paper P and adjusts the conveyance timing. Thereafter, the paper P is fed to the transfer position TP.

<< Carrying of toner image on latent image forming surface >>
As described above, while the paper P is being conveyed toward the transfer position TP, an image of the toner T is carried on the electrostatic latent image carrying surface LS that is the circumferential surface of the photosensitive drum 3 as follows. Is done.

<<< Formation of electrostatic latent image >>>
First, the electrostatic latent image carrying surface LS of the photosensitive drum 3 is uniformly charged to the positive polarity by the charger 4.

  The electrostatic latent image carrying surface LS charged by the charger 4 is opposed to the scanner unit 5 (opposite) by the rotation of the photosensitive drum 3 in the direction (clockwise) indicated by the arrow in the drawing. It moves along the sub-scanning direction to a certain scanning position SP.

  At this scan position SP, the laser beam LB modulated based on the image information is applied to the electrostatic latent image carrying surface LS while being scanned along the main scanning direction. Depending on the modulation state of the laser beam LB, a portion where the positive charges on the electrostatic latent image carrying surface LS disappear is generated. As a result, an electrostatic latent image having a positive charge pattern (image-like distribution) is formed on the electrostatic latent image carrying surface LS.

  The electrostatic latent image formed on the electrostatic latent image carrying surface LS is moved to the developing position DP facing the toner supply device 6 by the rotation of the photosensitive drum 3 in the direction indicated by the arrow (clockwise) in the drawing. Move towards.

<<< Conveyance and supply of charged toner >>>
2 and 3, the toner T stored in the toner box 61 is charged by contact with the bottom overcoating layer 634a on the bottom transport substrate 63a, friction, or the like. The charged toner T that is in contact with or close to the bottom overcoating layer 634a on the bottom transport substrate 63a is transported in the toner transport direction TTD by the electric field generated by the voltage applied to the bottom transport electrode 631a, and is transferred to the vertical transport substrate 63b. Delivered.

  Here, in this embodiment, the downstream end of the bottom transport substrate 63a in the toner transport direction TTD, that is, the connection portion with the vertical transport substrate 63b is formed in a curved surface shape. Thereby, the transfer of the toner T from the bottom conveyance substrate 63a at the lower end portion of the vertical conveyance substrate 63b can be performed smoothly.

  The vertical transport substrate 63b transports the toner T delivered from the bottom transport substrate 63a at the lower end thereof vertically upward. At this time, unlike the bottom overcoating layer 634a in the bottom transport substrate 63a, the vertical overcoating layer 634b in the vertical transport substrate 63b has a low function of further positively charging the positively charged toner T being transported. Therefore, a change in the charging state of the toner T being conveyed on the vertical conveyance substrate 63b can be suppressed as much as possible.

  Referring to FIG. 5, toner T that is being transported on the vertical transport substrate 63b is mixed with toner that is in a poorly charged state (such as uncharged toner T ′ or reversely charged, ie, negatively charged toner T ″). However, in the configuration of the present embodiment, the well-charged toner T from which the poorly charged state is removed is carried on the toner carrying surface 62a of the developing roller 62 as follows.

  When the non-charged toner T ′ is conveyed vertically upward by the vertical conveyance substrate 63b, it falls downward from the vertical conveyance substrate 63b by the action of gravity. The negatively charged toner T ″ falls downward due to the bias between the vertical transport substrate 62b and the developing roller 62, the electric field generated in the transport stop region 635, and the action of gravity.

  Thereby, only the toner T having a good charged state is selectively conveyed toward the developing roller 62 and the developing position DP. That is, on the vertical conveyance substrate 63b, the toner T having a good charge state and a poor one are well selected.

  The toner T dropped downward from the vertical transport substrate 63b reaches the downstream end of the bottom transport substrate 63a in the toner transport direction TTD. As a result, the toner T in the toner reservoir 61a, which is near the end on the downstream side in the toner transport direction TTD of the bottom transport substrate 63a, is fluidized well, and the bottom overcoating layer 634a Charges well due to friction.

  As described above, in the toner supply device 6 of the present embodiment, the toner T can be obtained without forcibly (positively) charging the toner T in the toner storage unit 61a by a mechanical action by a stirring member, a blade, or the like. Is transported well. Therefore, the deterioration of the toner T with time can be suppressed as much as possible.

  In addition, the toner T that has fallen from the vertical conveyance substrate 63b and has a poorly charged state reaches the toner storage portion 61a, not the middle of the vertical conveyance substrate 63b. Accordingly, the transport of the toner T by the vertical transport substrate 63b is disturbed (for example, the toner T being transported in a well-charged state falls off from the vertical transport substrate 63b, or the vertical transport substrate of the toner T in a poorly charged state is transported. And the like are prevented as much as possible.

  As described above, the positively charged toner T is supplied to the development position DP. The electrostatic latent image formed on the electrostatic latent image carrying surface LS is developed with the toner T in the vicinity of the development position DP. That is, the toner T adheres to the portion on the electrostatic latent image carrying surface LS where the positive charge in the electrostatic latent image has disappeared. As a result, an image of toner T (hereinafter referred to as “toner image”) is carried on the electrostatic latent image carrying surface LS.

  The toner T on the toner carrying surface 62a that has passed through the development position DP (not consumed at the development position DP) moves to the collection substrate 63c side by the action of the collection bias described above. That is, the toner is recovered from the toner carrying surface 62a by the recovery substrate 63c.

  Here, in the present embodiment, an AC recovery bias is applied to the developing roller 62. The toner T in the vicinity of the toner carrying surface 62a of the developing roller 62 vibrates by the action of the AC component of the recovery bias. Due to this vibration, the toner T floating from the toner carrying surface 62a collides with the toner T carried (attached) on the toner carrying surface 62a. Due to such a collision, the toner T carried on the toner carrying surface 62a is likely to float from the toner carrying surface 62a.

  In the present embodiment, the average potential (0 V) of the recovery bias is set to a potential lower than the potential (240 V) of the exposed portion where the toner T is to be supplied on the electrostatic latent image carrying surface LS. Further, in the present embodiment, the electric field between the developing roller 62 and the collection substrate 63c is stronger than the electric field between the developing roller 62 and the photosensitive drum 3.

  Due to such a recovery bias, the toner T that has not been consumed from the portion of the toner carrying surface 62a that has passed through the development position DP is peeled off satisfactorily and moves toward the recovery substrate 63c. Therefore, the occurrence of ghost in the formed image is suppressed as much as possible.

  In the present embodiment, the amplitude of the recovery bias is set larger than the amplitude of the voltage applied to the recovery electrode 631c. For this reason, the recovery operation of the toner T from the toner carrying surface 62a as described above can be performed satisfactorily without increasing the voltage between the adjacent recovery electrodes 631c. Therefore, the insulation between the adjacent recovery electrodes 631c in the recovery substrate 63c can be ensured satisfactorily.

  Further, this recovery bias also serves as a bias for so-called jumping development at the development position DP. Accordingly, the recovery bias can be satisfactorily applied with a simple device configuration.

  The toner T that has moved from the toner carrying surface 62a to the collection substrate 63c is conveyed toward the lower toner reservoir 61a by an electric field generated by a voltage applied to the collection electrode 631c.

  Here, in the present embodiment, the frequency of the recovery bias is set to an integral multiple of the frequency of the voltage applied to the vertical transport electrode 631b and the recovery electrode 631c. Thereby, the recovery bias and the electric field for transporting the toner T on the recovery substrate 63c are well synchronized.

  The toner T is conveyed vertically downward at the lower end of the collection substrate 63c. At this time, the inertia in the same direction as the gravity acts on the toner T. Then, below the lower end portion of the collection substrate 63c, the toner T falls to the toner storage portion 61a by the action of gravity and inertia in the same direction as the gravity. Therefore, even if the collection substrate 63c is not provided until the toner storage portion 61a is reached, the toner T is favorably returned to the toner storage portion 61a.

<< Transfer of toner image from latent image forming surface to paper >>
Referring to FIG. 1, the toner image carried on the electrostatic latent image carrying surface LS of the photosensitive drum 3 as described above has a direction in which the electrostatic latent image carrying surface LS is indicated by an arrow in the drawing. By being rotated (clockwise), the sheet is conveyed toward the transfer position TP. At the transfer position TP, the toner image is transferred onto the paper P from the electrostatic latent image carrying surface LS.

<List of examples of modification>
Note that, as described above, the above-described embodiments are merely examples of typical embodiments of the present invention that the applicant has considered to be the best at the time of filing of the present application. Therefore, the present invention is not limited to the above-described embodiment. Therefore, it goes without saying that various modifications can be made to the above-described embodiment within the scope not changing the essential part of the present invention.

  Hereinafter, some typical modifications will be exemplified. In the following description of the modified examples, the same reference numerals as those in the above embodiment can be used for members having the same configuration and function as those described in the above embodiment. And about description of this member, the description in the above-mentioned embodiment shall be used in the range which is not technically consistent.

  However, it goes without saying that the modifications are not limited to those listed below. In addition, a plurality of modified examples can be applied in a composite manner as appropriate within a technically consistent range.

  The present invention (especially those expressed in terms of action and function in each component constituting the means for solving the problems of the present invention) is based on the description of the above embodiment and the following modifications. It should not be interpreted in a limited way. Such a limited interpretation, while improperly harming the applicant's interests (rushing to file under an earlier application principle), improperly imitates the patent for the protection and use of the invention Contrary to the purpose of the law, it is not allowed.

  (1) The application target of the present invention is not limited to a monochromatic laser printer. For example, the present invention can be suitably applied to a so-called electrophotographic image forming apparatus such as a color laser printer or a monochromatic and color copying machine. At this time, the shape of the photosensitive member may not be a drum shape as in the above-described embodiment. For example, a flat plate shape or an endless belt shape may be used. Further, as the exposure light source, other than the laser scanner (LED, EL (electroluminescence) element, phosphor, etc.) can be suitably used.

  Alternatively, the present invention is also suitably applied to an image forming apparatus of a system other than the above-described electrophotographic system (for example, a toner jet system that does not use a photoreceptor, an ion flow system, a multi-stylus electrode system, etc.). obtain.

  (2) The vertical transfer board 63b is only required to stand substantially along the vertical direction, and may be slightly inclined. Similarly, the lower end portion of the collection substrate 63c may be slightly inclined.

  (3) The center portion of the bottom transfer substrate 63a may be flat. That is, the curved portion of the bottom transfer substrate 63a may be only the connection portion with the lower end portion of the vertical transfer substrate 63b.

  (4) The terminal end of the recovery substrate 63c in the toner transport direction TTD may be connected to the bottom transport substrate 63a.

  (5) The shielding plate 67 can be omitted.

  (6) The configuration of the transfer substrate 63 is not limited to that of the above-described embodiment. For example, the transport electrode overcoating layer 634 can be omitted (in this case, the material selection of the transport electrode coating layer 633 is performed similarly to the material selection of the transport electrode overcoating layer 634 in the above-described embodiment). Alternatively, both the transport electrode coating layer 633 and the transport electrode overcoating layer 634 can be omitted by embedding the transport electrode 631 in the transport electrode support film 632.

  (7) Referring to FIG. 4, the waveform of the voltage generated by each of the power supply circuits VA to VD may be an arbitrary waveform such as a sine wave shape or a triangular wave shape other than a rectangular wave shape.

  In the above-described embodiment, four power supply circuits VA to VD are provided, and the phases of the voltages generated by the power supply circuits VA to VD are different by 90 °. However, the present invention is not limited to this, and for example, three power supply circuits may be provided, and the phases of the voltages generated by the respective power supply circuits may be different by 120 °.

  (8) The voltage applied to the developing roller 62 may be only a direct current component (including ground).

  (9) The photosensitive drum 3 and the developing roller 62 may be in contact with each other.

  (10) The potential of the transfer stop region electrode 636 may be fixed. In this case, the number of transfer stop region electrodes 636 may be one.

  (11) Other modifications not specifically mentioned are naturally included in the technical scope of the present invention within the scope not changing the essential part of the present invention.

  In addition, in each element constituting the means for solving the problems of the present invention, the elements expressed in terms of operation and function are the specific structures disclosed in the above-described embodiments and modifications, It includes any structure that can realize this action / function. Furthermore, the contents (including the specification and the drawings) of each publication cited in this specification can be incorporated as part of this specification.

1 is a side view showing a schematic configuration of a laser printer as an image forming apparatus to which an embodiment of the present invention is applied. FIG. 2 is an enlarged side sectional view of the toner supply device shown in FIG. 1. FIG. 3 is an enlarged side cross-sectional view of the transport substrate shown in FIG. 2. It is a graph which shows an example of the output waveform of each power supply circuit shown by FIG. It is the sectional side view to which the upper end part in the vertical conveyance board | substrate shown by FIG. 2 was expanded.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser printer 2 ... Paper conveyance mechanism 3 ... Photosensitive drum (supply object)
4 ... Charger 5 ... Scanner unit 6 ... Toner supply device (developer supply device)
21 ... Registration roller 22 ... Transfer roller 61 ... Toner box 61a ... Toner reservoir (developer reservoir)
61b ... Opening 62 ... Developing roller (developer carrying member)
62a ... toner carrying surface 63 ... transport substrate 63a ... bottom transport substrate 63b ... vertical transport substrate 63b1 ... upper end 63c ... recovery substrate 64 ... transport power circuit 65 ... recovery power circuit 66 ... development bias power circuit 67 ... shield plate 631 ... transport Electrode 631a ... Bottom transport electrode 631b ... Vertical transport electrode 631c ... Recovery electrode 632 ... Transport electrode support film 633 ... Transport electrode coating layer 634 ... Transport electrode overcoating layer 634a ... Bottom overcoating layer 634b ... Vertical overcoating layer 634c ... Recovery over Coating layer 635... Transport stop region 636... Transport stop region electrode C... Central axis DP... Development position LB .. laser beam LS. Transfer position TTD: Toner transport direction TTP Toner transport route

Claims (6)

In a developer supply apparatus configured to supply a powdery developer charged to a predetermined polarity to a supply target while being conveyed along a developer conveyance path by an electric field.
A roller-like member having a cylindrical circumferential surface, provided to face the supply target, a developer carrying member;
A plurality of transport electrodes arranged along the developer transport path are provided, and the electric field generated in response to voltage application to the transport electrodes causes the developer transport direction along the developer transport path in the developer transport direction. A transport substrate configured to transport the developer;
With
The transport substrate includes a vertical transport substrate erected so as to transport the developer vertically upward as the developer transport direction,
The developer carrying member is provided so as to face the upper end of the vertical transport substrate,
A bias is applied between the vertical carrying substrate and the developer carrying member so that an electric field is formed from the upper end portion of the vertical carrying substrate toward the developer carrying member for the developer charged to the predetermined polarity. A developer supply device, wherein the developer supply device is applied. The developer supply device according to claim 1,
The developer supply apparatus according to claim 1, wherein a transport stop region in which an electric field for transporting the developer in the developer transport direction is not generated is provided at an uppermost end portion of the vertical transport substrate. The developer supply device according to claim 2,
The developer supply device according to claim 1, wherein a reverse feed unit that generates an electric field for conveying the developer charged to the predetermined polarity downward is provided in the conveyance stop region. The developer supply device according to claim 3,
The developer supply apparatus according to claim 1, wherein the reverse feeding unit includes a conveyance stop region electrode having a fixed potential. The developer supply device according to claim 3,
The reverse feeding section is applied with a plurality of conveyance stops to which a multiphase AC voltage having a traveling direction opposite to that of the conveyance electrode is applied so as to generate an electric field for conveying the developer charged to the predetermined polarity downward. A developer supply apparatus comprising a region electrode. A developer supply device according to any one of claims 1 to 5,
The transfer substrate is
The developer is charged by friction with the developer, and connected to the lower end so as to convey the charged developer toward the lower end of the vertical conveyance substrate, and the bottom surface of the developer reservoir is A developer supply device, further comprising a bottom conveyance substrate provided to be configured.

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