JP2006201244A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a consumable item unit that copes with an environmental problem so as to prevent a rubbish increase after the expiration of the life time and is free from image quality degradation and other troubles when recycled, and to provide an image forming apparatus using the consumable item unit. <P>SOLUTION: After a replacement message is given due to the expiration of the life time of a developing unit, the main body of the image forming apparatus is operated to satisfy D<G<K or G<D<K, where the developing bias voltage applied to a developing roller is G (volt), a toner supply bias voltage applied to a toner supply roller is K, a doctor bias voltage applied to a doctor blade is D, and a combination of the application biases for regular printing is K<D<G. Thus, toner is affixed on the doctor blade. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a consumable unit that copes with an environmental problem that dust does not increase after the end of its life and does not cause troubles such as deterioration in image quality during reproduction, and an image forming apparatus using the consumable unit.

  Conventionally, there is an electrophotographic image forming apparatus (printer or copying machine) that forms an image using toner. In general, a main part of an image forming unit of the image forming apparatus includes a photosensitive unit centering on a photosensitive drum for forming an electrostatic latent image, and the electrostatic latent image is visualized (developed) with toner. A developing unit is detachably disposed.

  By the way, the above photoconductor unit is replaced with a new photoconductor unit when the photoconductor drum reaches the end of its life, and the used photoconductor unit is discarded when each part is damaged so that it cannot be reproduced. In the case of being collected in a recycling factory, a new photosensitive drum or other damaged member is replaced with a new member for reproduction.

  The developing unit is also designed so that the developing roller and other built-in members reach the end of their life when the toner in the interior is almost exhausted. Therefore, when the toner runs out, it is replaced with a new developing unit. The finished development unit is discarded when each part is damaged so that it cannot be regenerated, but when it is collected in the manufacturing factory or the reclaiming factory, it is disassembled and regenerated in combination with a usable member and a new member.

Such a unit is normally configured to be replaceable on the user side. Therefore, for a developing unit that has finished using toner, a new developing unit is purchased by the user and replaced with an old product. Is called. (For example, refer to Patent Document 1.)
JP 2004-085597 A ([Summary], FIG. 5)

  However, as described above, there is no problem when the material is collected and disassembled in a regular manufacturing factory of the image forming apparatus and then recombined with a usable member and a new member. However, there are some companies that simply fill the toner and resell it as it is without combining it with a new member that can be disassembled.

  In general, if a toner is simply filled without being combined with a new member that can be disassembled even after being collected, the image forming apparatus may be clogged with paper at a location that cannot be recovered, or the toner may still be present. In many cases, the quality of an image formed in a poorly printed state is deteriorated, and further problems such as scattering of toner and contamination of the fixing roller are adversely affected on the image forming apparatus main body.

  When such a problem occurs, the user issues a repair request by telephone or the like to the maker or dealer of the image forming apparatus. Based on this request, a service person or sales person of the manufacturer of the image forming apparatus or a store goes to the user, first checks the occurrence state of the trouble, and repairs the trouble.

  In this case, if the toner is still present but the printing state is bad and no trouble is found in any place other than the development unit, it is considered to be the responsibility of the manufacturer of the development unit. Depending on requirements, services such as free replacement of development units may be provided.

 When such a problem occurs, the developing unit itself is a genuine product and not a counterfeit product, so it is not known from the appearance whether it is a recycled product. Also, even if it is known that it is a resale product, it is not known whether it is from its own factory or a general recycling factory. Therefore, it is very difficult to determine whether the product is due to resold consumables or a malfunction on the image forming apparatus main body side.

  As described above, if the cause of the failure cannot be clearly specified, the responsibility for the occurrence of the failure is not only ambiguous, but the generated failure cannot be used for improvement or improvement of the apparatus. If the device cannot be improved or improved, similar problems may occur in the future.

  In such a case, as a result, it is often the case that the user misidentifies that the problem is caused by the main body of the image forming apparatus, not by the regenerated consumable unit (development unit in the above example). There is a problem that it leads to a down image of the forming apparatus manufacturer.

  An object of the present invention is to provide a consumable unit that copes with the environmental problem of not increasing dust after the end of its life and does not cause degradation of image quality and other troubles during reproduction. It is possible to realize the image forming apparatus used.

The configuration of the image forming apparatus according to the present invention will be described below.
The image forming apparatus of the present invention includes a developing hopper having an opening so as to face a photoconductor on which an electrostatic latent image is formed, and a non-covering portion provided so as to partially face the opening and accommodated in the developing hopper. A developing roller that holds the magnetic one-component toner on the surface and conveys the toner to apply it to the electrostatic latent image on the photoconductor, and the toner is developed upstream of the opening in the conveying direction of the developing roller. A doctor blade that regulates to form a thin layer on the roller, a toner supply roller that is disposed in the developing hopper and is in pressure contact with the developing roller on the upstream side in the transport direction of the developing roller from the doctor blade, and the opening The toner from the developing hopper is allowed to return to the developing hopper while being lightly pressed against the developing roller at the downstream side of the developing roller in the conveying direction of the developing unit. An image forming unit that is detachably attached to the apparatus main body, and a bias having the same polarity as the charging polarity of the toner so as to generate an electric field that maintains the toner carrying force with respect to the developing roller. A bias voltage applying means for applying a voltage between the developing roller and the doctor blade and between the developing roller and the toner supply roller; and a remaining amount of the nonmagnetic one-component toner stored in the developing hopper. An image forming apparatus comprising: a toner remaining amount detecting unit that detects; and a notification unit that notifies the replacement of the image forming unit when a predetermined toner remaining amount is reached based on detection by the toner remaining amount detecting unit. After the predetermined amount of toner is reached, the toner holding force on the developing roller is attenuated and toner is applied to the doctor blade. The bias voltage change control means for changing the bias setting by the bias voltage applying means to generate an electric field in the fixing direction, and the development process is operated for a predetermined time based on the bias setting set by the bias voltage change control means. Development process operation control means.

  In this image forming apparatus, for example, when the applied voltage to the developing roller is G volts, the applied voltage to the doctor blade is D volts, and the applied voltage to the toner supply roller is K volts, the bias is applied in normal printing. The relationship of the potential by the bias setting by the voltage application means is a relationship of “K <D <G”. In order to attenuate the toner carrying force with respect to the developing roller and generate an electric field in the direction in which the toner is fixed to the doctor blade. The relationship of the potential by the bias setting by the bias voltage applying means changed by the bias voltage change control means is set to be “D <G <K”.

  In this image forming apparatus, for example, when the applied voltage to the developing roller is G volts, the applied voltage to the doctor blade is D volts, and the applied voltage to the toner supply roller is K volts, The relationship of the potential by the bias setting by the bias voltage applying means is a relationship of “K <D <G”, and the toner holding force against the developing roller is attenuated to generate an electric field in the direction in which the toner is fixed to the doctor blade. The relationship of the potential by the bias setting by the bias voltage applying means changed by the bias voltage change control means may be set to satisfy “G <D <K”.

  According to the present invention, a consumable unit that has reached the end of its life must be disassembled and cleaned so that it cannot be regenerated. Therefore, when a consumable unit that has reached the end of its life is regenerated, it must be disassembled and cleaned before filling with toner. Rather than buying a disappointment that may arise from the need to disassemble and clean and only fill the toner, it is better to reassemble by combining the usable parts and new parts if you take the trouble of disassembling and cleaning anyway Therefore, not only remanufacturing at regular factories but also regenerators that can be used properly even when reclaiming at general remanufacturing factories, the occurrence of defects due to remanufactured products is drastically reduced. Can prevent the loss of credit.

Embodiments of the present invention will be described below with reference to the drawings.
(Embodiment 1)
FIG. 1 is a side sectional view schematically showing an internal configuration of an image forming apparatus according to an embodiment. An image forming apparatus 1 shown in FIG. 1 is a tandem full-color image forming apparatus, and is an image forming apparatus that is large enough to be placed on a desktop personal computer rack, for example.

  As shown in FIG. 1, the image forming apparatus 1 includes an open / close tray 3 on the front surface (right side of the figure) of the main body base 2, and a paper cassette 4 is detachably attached to the lower portion thereof. A large number of sheets are placed and accommodated in each.

  A power switch, an upper lid opening / closing switch, a liquid crystal display device, a plurality of input keys, and the like are disposed on the operation section 5 on the front upper surface of the main body base 2, and an upper lid 6 is disposed so as to cover almost the entire surface behind the power switch. ing. The upper lid 6 forms a discharge tray 7 with the rear surface together with the upper surface of the rear portion of the main body base 2, and opens and closes up and down with the hinge 8 as a fulcrum. Printed paper is discharged to the paper discharge tray 7 from a paper discharge port 9 above the rear portion.

  Further, inside the main body base 2, a conveying belt 11 formed in a flat loop shape in the front and rear directions is arranged substantially in the center with the conveying surface horizontal. The conveyor belt 11 is stretched between the driving roller 12 and the driven roller 13, is driven by the driving roller 12, and circulates in the counterclockwise direction in the drawing.

  The four photosensitive drums 14 (14m, 14c, 14y, 14k) are in contact with the upper circulation portion of the conveyance belt 11 and are multistage along the sheet conveyance direction (right to left in the drawing) of the conveyance belt 11. Are installed side by side.

  Around these photosensitive drums 14 (hereinafter, description will be made by assigning numbers only to various devices around the photosensitive drum 14m), the peripheral surface of the photosensitive drum 14 is surrounded in the clockwise direction, and the cleaner 15 Various devices such as a charger 16, an optical writing head 17, a developing unit 18, a developing roller 19, and a transfer device 21 are arranged.

  The transfer device 21 is in contact with the back surface of the upper circulation portion of the conveyance belt 11 and is in pressure contact with the lower peripheral surface of the photosensitive drum 14 via the conveyance belt 11. The optical writing head 17 is supported on the back surface of the upper lid 6 via the support member 22, and moves up and down along an arcuate locus along with the opening and closing of the upper lid 6. It is positioned at the position. Further, magenta, cyan, yellow, and black color toners are accommodated in the housings of the four developing units 18 corresponding to the four photosensitive drums 14m, 14c, 14y, and 14k, respectively.

  A standby roller pair 24 and a paper sensor 25 are arranged on the upstream side (right side in the drawing) of the transport belt 11 in the paper transport direction, the upstream branching sideways and down, and the paper feed roller 26 in the horizontal direction. , A separating member 27 and the aforementioned open / close sheet feeding tray 3 are disposed.

  Further, a feeding path 28 composed of two guide plates is formed below, and a pair of conveying rollers 29 is disposed at the upstream (downward) end portion thereof, below which the feeding end of the paper cassette 4 described above is provided. Is located. Above the paper feed end of the paper feed cassette 4, a paper feed roller 31 having a half-moon shaped cross section is disposed.

  On the other hand, on the downstream side of the conveyance belt 11 in the sheet conveyance direction, a sheet separation claw 32 is disposed in contact with the end portion thereof, and the fixing section 33 is disposed downstream thereof. The fixing unit 33 includes a heat fixing roller pair including a heat generation roller and a pressure roller inside a heat insulating casing, a fixing unit separation claw that is in pressure contact with the heat generation roller, an oil application roller, and the like.

  A paper discharge roller pair 34 is disposed downstream of the fixing unit 33, and a paper discharge path 35 that reverses from the top to the front is formed downstream thereof. A pair of paper discharge rollers 36 is disposed at the paper discharge port 9 at the end of the paper discharge path 35.

  Between the conveyor belt 11 and the paper cassette 4, an electrical unit 37 to which a predetermined number of circuit boards can be mounted is disposed. A control device composed of a plurality of electronic components is mounted on the circuit board of the electrical unit 37. This control device will be described later.

  FIG. 2 is a schematic enlarged sectional view showing the developing unit 18 taken out from the main body of the image forming apparatus 1 in some detail. In the figure, the photosensitive drum 14 is shown with a broken line for reference.

  As shown in the figure, in the normal state, the developing unit 18 is of course a sufficient non-magnetic one-component toner (hereinafter simply referred to as toner) for the upper toner hopper 39 as well as the lower developing hopper 38. Is housed.

  As the toner, as described above, the developing hopper 38 and the toner hopper 39 of the four developing units 18 corresponding to the four photosensitive drums 14 (14m, 14c, 14y, 14k) are provided with magenta, cyan, yellow, And black color toner are accommodated.

  Below the toner hopper 39 is disposed an agitator 41 that prevents the toner from coagulating and stirs the toner in the arrow direction in order to charge the toner with a weak negative potential. In addition, the developing hopper 38 is provided with an opening at a position facing the photosensitive drum 14, and the developing roller 19 is rotatably disposed in the opening.

As will be described in detail later, the photosensitive drum 14 is formed with an electrostatic latent image on the surface and rotates in the clockwise direction indicated by the arrow in the figure.
On the other hand, the developing roller 19 disposed in the opening of the developing unit 18, that is, the opening of the developing hopper 38 holds the non-magnetic one-component toner stored in the developing hopper 38 on the surface thereof. In order to apply the toner to the electrostatic latent image on the photosensitive drum 14, the toner on the surface is conveyed by rotating in the counterclockwise direction indicated by the arrow in the drawing.

  A doctor blade 42 is disposed on the upstream side of the developing roller 19 in the toner conveyance direction with respect to the opening. The doctor blade 42 contacts the surface of the developing roller 19 with a predetermined corner with a predetermined pressure, regulates the thickness of the toner that adheres to the surface of the developing roller 19 and is conveyed, The toner is formed into a predetermined thin layer.

  A toner supply roller 43 is disposed on the upstream side of the developing roller 19 in the toner conveyance direction with respect to the doctor blade 42. The toner supply roller 43 is made of, for example, conductive urethane sponge or the like, presses against the developing roller 19, rotates counterclockwise as indicated by an arrow in the figure to counter the rotation of the developing roller 19, and supplies toner to the developing roller 19. Supply while rubbing.

  Further, a regulating sheet member 44 is disposed on the downstream side in the toner transport direction of the developing roller 19 with respect to the opening portion of the developing hopper 38 so as to be pressed lightly against the developing roller 19. The restriction sheet member 44 allows the toner remaining on the developing roller 19 to return into the developing hopper 38 and at the same time restricts the toner from the developing hopper 38 from flowing out.

  In the developing hopper 38, a stirring member 45 with an encoder is disposed as a toner remaining amount detecting means for detecting the remaining amount of toner. When the remaining amount of toner in the developing hopper 38 becomes equal to or less than a predetermined amount, the stirring member 45 with the encoder has a remaining amount of toner less than or equal to a predetermined amount because, for example, the rotation becomes uneven or faster than normal rotation. This is notified to the control device.

  The control device blinks the warning light of the operation unit 5 or displays “no toner” on the display panel when the predetermined toner remaining amount is reached based on the detection of the remaining toner amount by the stirring member 45 with the encoder. For example, the user is notified of the replacement of the image forming unit 18.

  Further, a developing roller bias voltage is applied from the developing bias power source 46 to the developing roller 19, a doctor blade bias voltage is applied from the doctor blade bias power source 47 to the doctor blade 42, and toner A toner supply bias voltage is applied to the supply roller 43 from a toner supply bias power supply 48.

  These bias voltages, which will be described in detail later, are negative-polarity bias voltages having different potentials, and are developed between the developing roller 44 and the doctor blade 42 and between the developing roller 44 and the toner supply roller 43. An electric field that maintains the toner carrying force with respect to the roller 19 is generated.

  FIG. 3 is a circuit block diagram of the image forming apparatus 1 described above. As shown in FIG. 3, the circuit block has a central processing unit (CPU) 50 as a center, and an interface controller (I / F_CONT) 51 and a printer controller (PR_CONT) 52 connected to the CPU 50 via a data bus, respectively. , A printer printing unit 53, a ROM (read only memory) 54, an EEPROM (electrically erasable programable ROM) 55, an operation panel 56 of the operation unit 5, a bias power supply unit 57, and the like.

A system program is stored in the ROM 54, and the CPU 50 performs processing by controlling each unit in accordance with the system program.
That is, the I / F_CONT 51 converts print data supplied from a host device such as a personal computer into bitmap data and develops it in the frame memory 58. In the frame memory 58, a storage area is set for each of black (K), magenta (M), cyan (C), and yellow (Y), and data of each color is developed in a corresponding area.

The data developed in the frame memory 58 is output to the PR_CONT 52 and is output from the PR_CONT 52 to the printer printing unit 53.
The printer printing unit 53 is an engine unit, and under the control of the PR_CONT 52, an image having a rotational drive system including the photosensitive drum 14 to the transfer device 21 shown in FIG. It controls the drive output to the process load such as the forming unit, the conveyance mechanism composed of each unit that is rotationally driven, and the fixing unit 33 that is driven to generate heat and rotate.

  The black (K), magenta (M), cyan (C), and yellow (Y) data output from the PR_CONT 52 is sent from the printer printing unit 53 to the corresponding optical writing head 17 shown in FIG. Supplied.

  In addition to the developing bias power supply 46, the doctor blade bias power supply 47, and the toner supply bias power supply 48 shown in FIG. 2, the bias power supply unit 57 includes the transport belt 11, the charger 16, the transfer power supply (not shown). A bias power source to be applied to the device 21 or the like is connected.

  Next, the basic operation of the image forming apparatus 1 having the above configuration will be described. First, when the power is turned on and the number of sheets to be used, the print mode, and other specifications are input as a key input or a signal from the connected host device, printing (printing) is started.

  First, the sheet feeding roller 31 rotates once to take out the uppermost sheet stored in the sheet cassette 4 and feeds it to the standby roller pair 24 through the conveying roller pair 29 and the feeding path 28. Alternatively, the paper feed roller 26 feeds the uppermost sheet of the paper placed on the open / close paper feed tray 3 to the standby roller pair 24 in cooperation with the separating member 27. The paper sensor 25 detects the leading edge of the fed paper.

  The standby roller pair 24 temporarily stops its rotation, stops the paper advance, and waits for the conveyance timing. The drive roller 12 rotates counterclockwise and starts the circulating movement of the conveyor belt 11. Each photosensitive drum 14 is rotationally driven in the clockwise direction, and the peripheral devices are sequentially driven in accordance with the printing timing.

  The charger 16 applies a minus high voltage of, for example, “−1100 V” supplied from a charging power supply (not shown) to the photosensitive drum 14 while being pressed against and driven by the circumferential surface of the photosensitive drum 14. Due to the application of the high negative charge, the peripheral surface made of the insulating film of the photosensitive drum 14 is uniformly charged to a negative high potential of, for example, “−650 V” and initialized.

  The optical writing head 17 is disposed facing the photosensitive drum 14 while maintaining a predetermined distance. The optical writing head 17 performs exposure according to an image signal (printing information) on the peripheral surface of the photosensitive drum 14, and the potential of the exposed portion. Is attenuated to a potential of approximately “−50 V”, for example. As a result, an electrostatic latent image composed of a minus high potential portion that is substantially maintained at “−650 V” by the initialization charging and a minus low potential portion of “−50 V” by exposure is formed on the peripheral surface of the photosensitive drum 14. It is formed.

  The developing roller 19 is rotatably supported in the lower opening of the housing of the developing unit 18 and presses against the photosensitive drum 14, and the toner charged to a weak negative potential due to friction is opposed to the photosensitive drum 14. Rotate and transport. The developing roller 19 is applied with a developing bias having a negative intermediate potential of, for example, “−300 V” from the developing bias power source 46 shown in FIG.

  As a result, the developing roller 19 forms a potential difference of “−250 V” with the low potential portion of the “−50 V” electrostatic latent image. That is, the low potential portion of the electrostatic latent image forms a positive polarity potential relative to the developing roller 19.

  By the electric field due to this potential difference, the toner charged with a weak negative polarity is transferred to the low potential portion of the positive polarity of the electrostatic latent image on the photosensitive drum 14 (in the case of reversal development) to form a toner image (visualization). ,develop.

  At the timing when the leading edge of the developed magenta toner image on the peripheral surface of the photosensitive drum 14m, which is the most upstream in the paper conveyance direction, is rotated and conveyed to a portion facing the conveyance belt 11, printing of paper is started on the opposite portion. The standby roller pair 24 starts to rotate so as to match the position, and feeds the sheet toward the transport belt 11. The sheet is transported by the transport belt 11 to the first transfer portion formed by the photosensitive drum 14 m and the transfer device 21.

  The transfer unit 21 applies a transfer current output from a transfer bias power source (not shown) to the sheet via the transport belt 11 to transfer the magenta toner image on the photosensitive drum 14m to the sheet. Subsequently, the second transfer portion from the upstream side of the sheet conveyance direction by the photosensitive drum 14c and the transfer device 21 transfers the cyan toner image, and the third transfer portion by the photosensitive drum 14y and the transfer device 21 is the yellow toner. The image is transferred, and the most downstream transfer portion by the photosensitive drum 14k and the transfer device 21 transfers the black toner image.

  The sheet on which the four color toner images are transferred is separated from the transport belt 11 by the sheet separation claw 32 and is carried into the fixing unit 33. The fixing unit 33 presses and holds the sheet with the heat roller and the pressure roller, and applies heat and pressure to the sheet to discharge the toner image backward while fixing the toner image on the sheet. The sheet discharged from the fixing unit 33 is nipped by the pair of discharge rollers 34 and is continuously conveyed, guided upward along the discharge path 35, and further reversed to the front of the apparatus at the end to be discharged from the discharge port 9. And the toner image is discharged onto the paper discharge tray 7 with the toner image facing downward.

  By repeating the printing in this way, it is detected that the toner is consumed, and the toner in the developing hopper 38 is eventually reduced, and “no toner” is displayed on the operation panel 56. 18 exchanges are prompted.

  At this point, the toner is still left in the developing hopper 38 and can be used somewhat depending on the printing rate. This is designed as a slight margin for ensuring the print quality until the end of the life of the developing unit 18 becomes “no toner”.

  In this example, the margin amount of the toner at the time of “no toner” is utilized to cope with an environmental problem in which dust does not increase after the end of the life in the developing unit 18 that has reached the end of the life, and the image quality at the time of reproduction is reduced. A structure is built in the development unit 18 that forces it to be disassembled and cleaned before refilling with toner so that it becomes a consumable unit that does not cause degradation or other problems To do.

FIG. 4 is a diagram schematically illustrating the structure in the developing unit 18 that forces such disassembly and cleaning. This figure is an enlarged view of a contact portion between the developing roller 19 and the doctor blade 42.
In this example, the doctor blade 42 is made of stainless steel with a thickness of 0.1 mm, and the tip 42-1 is bent RO. 2. The bending angle is 65 degrees. The developing roller 19 is made of conductive urethane having a diameter of 19 mm and has a product hardness of 70 degrees. The contact angle between the doctor blade 42 and the developing roller 19 is about 25 degrees, and the contact pressure is 1600 g · f.

  The toner supplied from the toner supply roller 43 to the developing roller 19 is conveyed to a contact portion with the doctor blade 42. Normally, the toner that has been conveyed and passed through the doctor blade 42 is uniformly thinned to form a photosensitive drum. 14 and the developing roller 19 are conveyed to a developing unit facing each other.

  However, depending on the bias voltage applied to the toner supply roller 43 and the doctor blade 42, the toner is deposited on the portion A of the doctor blade 42 shown in FIG. .

  When the toner is fixed in this way, the toner conveyed later is blocked by the toner fixing portion 59 and cannot pass through the doctor blade 42, so that there is no toner on the developing roller 19. After this, even if the bias voltage is restored, the toner that is physically fixed does not return to the original state.

  Therefore, by constructing the structure of the toner fixing portion 59 between the doctor blade 42 and the developing roller 19 of the developing unit 18 that has reached the end of its life, when the developing unit 18 is filled with toner and reproduced, The developing unit 18 must be disassembled and the toner fixing part 59 must be cleaned in advance.

  In this way, the development unit that has reached the end of its life must be disassembled so that it cannot be regenerated unless it is cleaned. Therefore, if it takes some time to disassemble and clean it, it is better to reassemble it by combining it with a new member that can be used. However, since the reusable products that can be used properly are resold, the occurrence of defects due to the refurbished products is drastically reduced, thereby preventing the loss of trust from the user.

  By the way, regarding the construction of the toner fixing portion 59 between the doctor blade 42 and the developing roller 19 of the developing unit 18 whose lifetime has been exhausted in this way, the following experiments and observations and evaluations on the experimental results are described. Has been repeated.

  FIG. 5 is a chart showing such an experiment and the results of observation and evaluation for the experiment result. The chart 60 shown in the figure includes, from left to right, an experiment number column 61 indicating an experiment number, a developing bias column 62 indicating a voltage value G volts of a developing bias voltage applied from the developing bias power supply 46 to the developing roller 19, and toner. The supply bias field 63 indicating the voltage value K volts of the toner supply bias voltage applied from the supply bias power supply 48 to the toner supply roller 43, and the doctor blade bias voltage applied from the doctor blade bias power supply 47 to the doctor blade 42. A doctor bias field 64 indicating a voltage value D volts, and a toner layer state indicating an evaluation of a state of a toner layer formed on the developing roller 19 and a state where a toner fixing portion 59 is formed between the doctor blade 42 and the developing roller 19 It consists of column 65. The toner is usually charged to a weak negative potential by frictional charging.

  When it is detected that the toner in the developing hopper 38 is low and “no toner” is displayed on the operation panel 56, the developing bias voltage G is “−300 V” and the toner supply bias as in Experiment 1. When the voltage K is “−550 V” and the doctor blade bias voltage D is “−350 V”, the applied bias combination state “K <D <G” is set on the developing roller 19. The state of the toner layer is good.

  As in Experiment 2, the toner supply is performed without changing the doctor blade bias voltage such that the relationship between the bias voltages G, K, and D is “−300 V”, “−450 V”, and “−350 V”. It has been found that the state of the toner layer formed on the developing roller 19 becomes thin when the bias voltage for use is changed to a voltage that becomes an electric field in the direction of attracting the toner to the toner supply roller 43.

  Further, as in Experiment 3, the relationship between the bias voltages G, K, and D is “−300 V”, “−550 V”, “−350 V”, and the doctor blade without changing the toner supply bias voltage. It has been found that when the bias voltage for use is changed to a voltage that is an electric field in the direction of attracting the toner to the doctor blade 42, the state of the toner layer formed on the developing roller 19 also becomes thin.

  Then, as in Experiment 4, without changing the development bias voltage G and the doctor blade bias voltage D, the toner supply bias voltage K is changed to a voltage that becomes an electric field in a direction that attracts the toner to the toner supply roller 43 extremely. When the potential relationship is set to satisfy “D <G <K”, the amount of toner supplied onto the developing roller 19 is extremely reduced, and the toner is a portion A of the doctor blade 42 shown in FIG. The phenomenon of depositing on the toner and forming the toner fixing portion 59 began to occur.

  This is because when the amount of toner supplied onto the developing roller 19 becomes extremely small, the contact pressure between the toner and the doctor blade 42 becomes very high with respect to one toner, and the toner is deformed or crushed. It is considered that the toners accumulate and the accumulation grows and adheres to the doctor blade 42.

  Further, as in Experiment 5, without changing the doctor blade bias voltage, the developing bias voltage is increased in the minus direction from the normal value, and the toner supply bias voltage is also increased in the negative direction from the normal value. Even if the voltage is changed to a voltage that causes an electric field in an extremely attracting direction to 43 and the potential relationship is set to satisfy “G <D <K”, the toner is supplied onto the developing roller 19 as described above. The amount of toner became extremely small, and the phenomenon that the toner accumulated on the portion A of the doctor blade 42 shown in FIG. 4 and formed the toner fixing portion 59 began to occur.

  Therefore, after the developing unit has reached the end of its life and a message for replacing the developing unit is notified, the image forming apparatus 1 is operated, and the toner is attracted to the doctor blade or the toner supply roller as in Experiment 4 or Experiment 5 above. By applying a bias voltage that becomes an electric field in the direction between the developing roller and the developing roller, the toner fixing portion 59 can be formed in the portion A of the doctor blade 42 shown in FIG.

  As a result, when recycling consumable units that have reached the end of their lives, they must be disassembled and cleaned before filling them with toner. Rather than buying it, it is better to reassemble it by combining usable parts with new parts if it takes time to disassemble and clean it. As a result, the occurrence of problems due to the refurbished product is drastically reduced, thereby preventing the loss of trust from the user.

1 is a side sectional view schematically showing an internal configuration of an image forming apparatus in an embodiment. FIG. 2 is a schematic enlarged cross-sectional view showing a developing unit taken out from the image forming apparatus main body in some detail. 1 is a circuit block diagram of an image forming apparatus. It is a figure which illustrates typically the structure in the developing unit which forces decomposition and cleaning. 10 is a chart showing the results of observation and evaluation for experimental results for constructing a structure of a toner fixing portion between a doctor blade and a developing roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Main body base part 3 Opening / closing tray 4 Paper cassette 5 Operation part 6 Top cover 7 Paper discharge tray 8 Hinge 9 Paper discharge port 11 Conveying belt 12 Drive roller 13 Driven roller 14 (14m, 14c, 14y, 14k) Photosensitive drum DESCRIPTION OF SYMBOLS 15 Cleaner 16 Charger 17 Optical writing head 18 Developing unit 19 Developing roller 21 Transfer device 22 Support member 24 Standby roller pair 25 Paper sensor 26 Paper feed roller 27 Rolling member 28 Feeding path 29 Transport roller pair 31 Paper feed roller 32 Paper separation Claw 33 Fixing section 34 Paper discharge roller pair 35 Paper discharge path 36 Paper discharge roller pair 37 Electrical section 38 Developing hopper 39 Toner hopper 41 Agitator 42 Doctor blade 42-1 Tip 43 Toner supply roller 44 Regulator sheet member 45 Stirring member with encoder 46 Bias power for development 47 doctor blade bias power source 48 toner supply bias power source 50 CPU (central processing unit)
51 Interface Controller (I / F_CONT)
52 Printer Controller (PR_CONT)
53 Printer printing section 54 ROM (read only memory)
55 EEPROM (electrically erasable programable ROM)
56 Operation Panel 57 Bias Power Supply Unit 58 Frame Memory 59 Toner Adhering Unit 60 Observation and Evaluation Chart for Experimental Results 61 Experiment Number Field 62 Development Bias Field 63 Supply Bias Field 64 Doctor Bias Field 65 Toner Layer Status Field

Claims (3)

A developing hopper having an opening to face the photoreceptor on which the electrostatic latent image is formed;
A developing roller which is provided so as to partially face the opening and holds a non-magnetic one-component toner stored in the developing hopper on the surface and conveys the toner to apply to the electrostatic latent image on the photosensitive member; ,
A doctor blade that regulates the toner to form a thin layer on the developing roller on the upstream side of the opening in the transport direction of the developing roller;
A toner supply roller disposed in the developing hopper and in pressure contact with the developing roller on the upstream side in the transport direction of the developing roller with respect to the doctor blade;
A regulating sheet member that is lightly pressed against the developing roller downstream of the opening in the conveying direction of the developing roller and allows the toner to return into the developing hopper and at the same time regulates the outflow of toner from the developing hopper When,
An image forming unit that is detachable from the apparatus main body,
A bias voltage having the same polarity as the charging polarity of the toner is applied between the developing roller and the doctor blade and between the developing roller and the toner supply roller in order to generate an electric field for maintaining the toner carrying force on the developing roller. Bias voltage applying means to be applied;
Toner remaining amount detecting means for detecting the remaining amount of the non-magnetic one-component toner stored in the developing hopper;
In an image forming apparatus comprising: an informing means for informing the replacement of the image forming unit when a predetermined toner remaining amount is reached based on detection by the toner remaining amount detecting means;
After the predetermined toner remaining amount is reached, the bias setting by the bias voltage applying means is changed to attenuate the toner holding force on the developing roller and generate an electric field in the direction in which the toner is fixed to the doctor blade. Bias voltage change control means;
Development process operation control means for operating the development process for a predetermined time under the bias setting set by the bias voltage change control means;
An image forming apparatus comprising: When the applied voltage to the developing roller is G volts, the applied voltage to the doctor blade is D volts, and the applied voltage to the toner supply roller is K volts, the bias voltage is applied by the bias voltage applying means in normal printing. The relationship of the potential is “K <D <G”.
The relationship between the potentials by the bias setting by the bias voltage application means changed by the bias voltage change control means in order to attenuate the toner carrying force on the developing roller and generate an electric field in the direction in which the toner adheres to the doctor blade. Set so that D <G <K ”,
The image forming apparatus according to claim 1. When the applied voltage to the developing roller is G volts, the applied voltage to the doctor blade is D volts, and the applied voltage to the toner supply roller is K volts, the bias voltage is applied by the bias voltage applying means in normal printing. The relationship of the potential is “K <D <G”.
The relationship between the potentials by the bias setting by the bias voltage application means changed by the bias voltage change control means in order to attenuate the toner carrying force on the developing roller and generate an electric field in the direction in which the toner adheres to the doctor blade. Set so that G <D <K.
The image forming apparatus according to claim 1.

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