JP5585499B2 - Lubricant coating apparatus and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a lubricant coating device and an image forming apparatus provided in an image forming apparatus having an image bearing rotating body.

  An image forming apparatus such as an electrophotographic printer charges a photosensitive drum as an example of an image bearing rotator, and exposes the charged photosensitive drum to form an electrostatic latent image on the photosensitive drum. The electrostatic latent image formed on the photosensitive drum is developed to form a toner image, and the formed toner image is transferred to a recording sheet. Residual toner remaining on the photosensitive drum without being transferred to the recording sheet is removed by a cleaner. It is configured to be cleaned.

As a method for cleaning the residual toner, a configuration in which the tip of the cleaning blade is pressed against the surface of the rotating photosensitive drum and the residual toner on the photosensitive drum is scraped off is generally used.
When the cleaning blade is pressed against the surface of the photosensitive drum, if the frictional force between the photosensitive drum and the cleaning blade increases, the tip of the cleaning blade may be bent and deformed or damaged. . In addition, wear of the tip portion of the cleaning blade increases, and there is a possibility that a cleaning failure may occur in a period shorter than the assumed life.

As a method of preventing such a change, breakage, and increase in wear of the cleaning blade, there is a method of reducing the frictional force between the photosensitive drum and the cleaning blade by applying a lubricant to the photosensitive drum.
In Patent Document 1, a brush roller in contact with a solid lubricant is rotated, the solid lubricant is shaved by the brush roller, and the scraped lubricant powder is conveyed to the surface of the photosensitive drum in a state of being taken into brush fibers. A configuration in which lubricant powder is applied to a photosensitive drum is disclosed.

JP 2006-251751 A

However, the conventional configuration in which the lubricant powder as described above is scraped with a brush roller has a problem in that the efficiency of supplying the lubricant to the photosensitive drum is poor.
That is, brush fibers conventionally used for brush rollers are generally made of nylon or polyester, and the lubricant is made of zinc stearate. Nylon or polyester has a lower work function than zinc stearate. The work function indicates energy necessary for taking out electrons from the substance, and is known as a quantity indicating the ease of charging. The lower the work function, the easier the electrons are emitted and the more easily charged.

  When the work function of the brush fiber is lower than that of the lubricant, the brush fiber is positively charged and the lubricant powder is easily negatively charged due to friction when the solid lubricant is scraped off by the brush fiber. Since the charging polarity of the photosensitive drum is generally negative, when the lubricant powder is negatively charged with the same polarity as the photosensitive drum, the lubricant powder is removed from the brush fiber by the repulsive force of Coulomb. It becomes difficult to move to.

If it becomes difficult for the lubricant powder to move from the brush fiber to the photoconductor drum, the lubricant powder can be applied to the surface of the photoconductor drum when the tip of the brush fiber rubs against the surface of the photoconductor drum. Part of the powder is likely to remain on the brush fibers without moving to the photosensitive drum.
The fact that the lubricant powder is likely to remain on the brush fibers means that the amount of lubricant supplied to the photosensitive drum per rotation of the brush roller is reduced, and the efficiency of supplying the lubricant is poor. become. If the lubricant powder continues to remain on the brush fibers, the brush fibers will eventually become clogged with the lubricant powder, and the performance of the brush fibers will be reduced by scraping and transporting the solid lubricant, and the amount of lubricant supplied to the photosensitive drum Will decline early.

As a method for improving the supply efficiency of the lubricant powder as much as possible, for example, a negative bias voltage that is larger in absolute value than the residual potential (negative) of the photosensitive drum is applied to the brush roller, and the lubricant adhered to the brush fiber. A method for easily moving the powder to the photosensitive drum is conceivable.
However, this method increases the electric field strength at the tip of the brush fiber, and electric discharge easily occurs between the photosensitive drum even at a low voltage. When the electric discharge occurs, the brush fiber deteriorates, and the photosensitive member is deteriorated due to the deterioration of the brush fiber. This leads to an early decrease in the amount of lubricant powder supplied to the drum.

If the supply amount of the lubricant to the photosensitive drum is lowered at an early stage, the cleaning blade is easily damaged due to an increase in the frictional force between the photosensitive drum and the cleaning blade. Further, the lubricant is not limited to the cleaning property, and may be used for the purpose of improving the transfer property. In this case, if the lubricant cannot be stably supplied, the transfer property is deteriorated at an early stage.
The present invention has been made in view of the above problems, and a lubricant application device capable of stably supplying a lubricant to an image bearing rotating body such as a photosensitive drum over a long period of time, and the same An object of the present invention is to provide an image forming apparatus including the above.

  In order to achieve the above object, a lubricant application apparatus according to the present invention is provided in an image forming apparatus having an image bearing rotator, which scrapes off solid lubricant and applies the scraped lubricant powder to the peripheral surface of the image bearing rotator. Lubricant coating apparatus for coating, which is interposed between an image bearing rotator and a solid lubricant, scrapes the solid lubricant at the first position by rotation, and scrapes off the lubricant powder at the second position. A coating member that is applied to the peripheral surface of the coating member, and abuts against the rotating coating member at a position downstream of the second position and upstream of the first position along the rotation direction of the coating member to rub the coating member A friction charging member for charging, and the charging polarity of the lubricant powder scraped by the coating member charged by friction with the friction charging member as the material of the friction charging member, the coating member, and the solid lubricant is an image. Work with a polarity opposite to the charged polarity of the rotating carrier Wherein the ones of the magnitude of the number is selected.

Further, the charging polarity of the image bearing rotating body is negative, the work function of the coating member before the friction charging is φb, the work function of the friction charging member is φm, and the work function of the solid lubricant is φj. In this case, φm> φb and φj <(φm + φb) / 2 are satisfied.
Furthermore, the application member is made of a brush-like member.
Here, the coating member is characterized in that conductive brush fibers are provided around the core bar, and the core bar is grounded.

Further, the friction charging member is made of a resin containing fluorine.
Further, the image forming apparatus is provided with a cleaning member that contacts the peripheral surface of the image bearing rotator and removes toner remaining on the peripheral surface. It is characterized in that it contacts the circumferential surface of the image carrying rotator at a position downstream of the rotation direction of the image carrying rotator from the position in contact with the circumferential surface of the carrying rotator.

In addition, the coating member is disposed at a position downstream of the second position where the lubricant is applied to the circumferential surface of the image bearing rotator, and is in contact with the circumferential surface of the image bearing rotator. And a leveling member for leveling the lubricant applied to the image bearing rotating body by the coating member.
An image forming apparatus according to the present invention includes the above-described lubricant application device.

  In this way, the charging polarity of the lubricant supplied to the image bearing rotator becomes opposite to the charging polarity of the image bearing rotator, so that the lubricant is easily supplied to the image bearing rotator by the attractive force of Coulomb. In addition, since it is not necessary to apply a bias voltage to the coating member, it is possible to improve the supply efficiency of the lubricant as compared with the conventional case, and to supply the lubricant to the image bearing rotator stably over a long period of time. It becomes possible.

1 is a diagram illustrating an overall configuration of a printer. It is a figure which expands and shows the structure of the cleaner with which a printer is equipped. It is a schematic diagram which shows a mode that each of the friction charging member with which a cleaner is equipped, a brush fiber, and a solid lubricant is electrically charged. (A) is a schematic diagram which shows the magnitude | size of the work function of the friction charging member, brush fiber, and solid lubricant before friction charge, (b) and (c) are a mode that a work function changes a mode. FIG. It is a figure which shows the result of the experiment which shows whether the lubrication agent application was performed favorably in the structure of Examples 1, 2 and Comparative Examples 1-4.

Hereinafter, embodiments of a lubricant application device and an image forming apparatus according to the present invention will be described by taking a tandem color digital printer (hereinafter simply referred to as “printer”) as an example.
(1) Overall Configuration of Printer FIG. 1 is a diagram showing the overall configuration of the printer.
As shown in the figure, the printer forms an image by a known electrophotographic system, and includes an image forming unit 10, an intermediate transfer unit 20, a feeding unit 30, a fixing unit 40, and a control unit 50. When a print job execution instruction is received from an external terminal device (not shown) connected to a network (for example, a LAN), a color image composed of yellow, magenta, cyan, and black colors is received based on the instruction. Perform formation. Hereinafter, the reproduction colors of yellow, magenta, cyan, and black are represented as Y, M, C, and K, and Y, M, C, and K are added as subscripts to the numbers of the components related to the reproduction colors.

The image forming unit 10 includes image forming units 10Y, 10M, 10C, and 10K corresponding to Y to K colors.
The image forming units 10Y to 10K include photosensitive drums 11Y to 11K as image bearing rotators, chargers 12Y to 12K disposed around the image forming units, exposure units 13Y to 13K, and developers 14Y to 14K. Cleaners 16Y to 16K are provided, and Y to K color toner images are formed on the photosensitive drums 11Y to 11K.

  The intermediate transfer unit 20 includes an intermediate transfer belt 21 that circulates in the direction of the arrow in the drawing, rollers 22, 23, and 24 that stretch the intermediate transfer belt 21, and the photosensitive drums 11 </ b> Y to 11 </ b> K via the intermediate transfer belt 21. Primary transfer rollers 15 </ b> Y to 15 </ b> K that are in contact with the roller, a secondary transfer roller 25 that is in contact with the roller 22 via the intermediate transfer belt 21, and a cleaner 26 that removes residual toner on the intermediate transfer belt 21. .

The feeding unit 30 feeds the paper S as a recording sheet stored in the paper feed cassette 35 one by one toward the transport path 37, and the fed paper S on the transport path 37. A conveyance roller pair 32 for conveyance and a timing roller pair 33 for taking a timing for sending the conveyed paper S to the secondary transfer position 29 are provided.
The fixing unit 40 presses the fixing roller and the pressure roller to ensure a fixing nip and heats the fixing roller with a heater to maintain a temperature necessary for fixing.

  The control unit 50 converts an image signal from an external terminal device into a digital signal for Y to K colors, and generates a drive signal for driving the laser diodes arranged in the exposure units 13Y to 13K. The laser diodes of the exposure units 13Y to 13K are driven for each image forming unit by the generated drive signal, the laser beam L is emitted, and the photosensitive drums 11Y to 11K are exposed and scanned.

Before the exposure scanning, the photosensitive drums 11Y to 11K are uniformly charged by the chargers 12Y to 12K, and electrostatic latent images are formed on the peripheral surfaces of the photosensitive drums 11Y to 11K by the exposure of the laser beam L. An image is formed.
The photosensitive drums 11Y to 11K have a charging characteristic of being charged with a negative (negative) polarity. The photosensitive drums 11Y to 11K are negatively charged by the chargers 12Y to 12K, and an image is formed by the laser beam L. The part to be exposed is exposed.

Each electrostatic latent image is developed with toner by developing units 14Y to 14K. Here, toner having a negative charge polarity is used, and a so-called reversal development method is used. The toner images of the respective colors are primarily transferred onto the intermediate transfer belt 21 by electrostatic force acting between the primary transfer rollers 15Y to 15K and the photosensitive drums 11Y to 11K.
Since van der Waals force is acting between the photosensitive drum and the toner, there are few toners (residual toner) that cannot be electrostatically transferred to the intermediate transfer belt 21 among the toner particles constituting the toner image. However, it exists.

The residual toner is removed by the cleaners 16Y to 16K. A lubricant is applied to the peripheral surfaces of the photosensitive drums 11Y to 11K after the residual toner is removed by lubricant application portions (described later) provided in the cleaners 16Y to 16K.
The image forming operations for the respective colors on the photoconductive drums 11Y to 11K are executed at different timings so that the toner images are superimposed and transferred at the same position on the intermediate transfer belt 21. The respective color toner images transferred onto the intermediate transfer belt 21 are moved to the secondary transfer position 29 as the intermediate transfer belt 21 rotates.

In synchronization with the timing of the image forming operation, the sheet S is fed from the feeding unit 30 via the timing roller pair 33, and the sheet S includes the intermediate transfer belt 21 and the secondary transfer roller 25. Each color toner image on the intermediate transfer belt 21 is secondarily transferred onto the sheet S all at once by electrostatic force acting between the secondary transfer roller 25 and the roller 22.
The sheet S that has passed through the secondary transfer position 29 is conveyed to the fixing unit 40, and when passing through the fixing nip, the toner image is heated and pressurized to be fixed on the sheet S, and then passed through the discharge roller pair 38. Are discharged and stored in the storage tray 39.

(2) Configuration of Cleaners 16Y to 16K FIG. 2 is an enlarged view showing the configuration of the cleaner 16Y, and also shows the photosensitive drum 11Y, the charger 12Y, and the like arranged around the cleaner 16Y. . Since the cleaners 16Y to 16K are basically the same in configuration, the configuration of the cleaner 16Y will be described here, and the description of the other cleaners 16M to 16K will be omitted.

  As shown in the figure, the cleaner 16Y includes a cleaning blade 61, a recovery screw 62, a brush roller 63, a solid lubricant 64, a friction charging member 65, a holder 66, a compression spring 67, and a leveling blade. 68 and the like, and these members are supported by the housing 60. Here, the brush roller 63 and the frictional charging member 65 to the leveling blade 68 constitute the lubricant application portion 69. Each member excluding the compression spring 67 is elongated along the axial direction of the photosensitive drum 11Y, and its axial length is at least longer than the printing width. A plurality of compression springs 67 are arranged at intervals along the axial direction.

  The cleaning blade 61 is formed by processing polyurethane rubber into a sheet shape, and the tip of the cleaning blade 61 is applied to the circumferential surface of the photosensitive drum 11Y in a direction (counter direction) opposite to the rotating direction (drum rotating direction) of the photosensitive drum 11Y. In contact therewith, the residual toner T on the photosensitive drum 11Y is scraped off. The residual toner T thus scraped off is sent to a recovery screw 62, and is transported to a waste toner recovery box (not shown) by the recovery screw 62 and recovered.

  The brush roller 63 (application member) is a roll-shaped brush member in which brush fibers 72 are provided around a metal core 71, and is positioned downstream of the cleaning blade 61 in the drum rotation direction. The brush portion of the brush fiber 72, which is interposed between the drum 11Y and the solid lubricant 64 and faces the circumferential surface of the photosensitive drum 11Y, abuts on the circumferential surface of the photosensitive drum 11Y, and the circumferential surface of the photosensitive drum 11Y. Apply lubricant to

The metal core 71 rotates in a direction opposite to the drum rotation direction at a position where the brush fiber 72 abuts on the peripheral surface of the photosensitive drum 11 </ b> Y by a driving force from a driving unit (not shown) to constitute the brush fiber 72. The rotational speed of the core metal 71 is defined so that the linear velocity along the rotation direction of the core metal 71 at the tip of the brush bristles is higher than the speed of the peripheral surface of the photosensitive drum 11Y.
Here, the conductive polyethylene fiber is used for the brush fiber 72, and the base of each brush hair constituting the brush fiber 72 is grounded via the cored bar 71.

The brush hair is made of 2 to 15 denier (D) synthetic fibers, the height of the brush hair is about 2 to 8 mm, and the number per unit area (plant density) is 50,000 to 300,000 (pieces). The electrical resistance value is about 10 ⁶ to 10 ¹⁰ [Ω].
The solid lubricant 64 is obtained by melt-molding metal soap powder, and zinc stearate is used here.

  The holder 66 holds the solid lubricant 64, and the compression spring 67 applies an urging force for pressing the solid lubricant 64 against the brush roller 63 via the holder 66. The solid lubricant 64 pressed against the brush roller 63 is scraped off by the brush hairs of the brush fibers 72 as the brush roller 63 rotates. The scraped lubricant powder is conveyed to the photosensitive drum 11Y in a state of being taken into the brush fibers 72, and is applied to the photosensitive drum 11Y.

In the present embodiment, for the brush fibers 72, the solid lubricant 64, and the friction charging member 65, the scraped lubricant powder is charged to a positive polarity opposite to the negative polarity that is the charging polarity of the photosensitive drum 11Y. A material with a work function magnitude is selected.
By charging the lubricant powder to a positive polarity, not only mechanical lubricant powder is supplied by rubbing when the brush fibers 72 of the brush roller 63 rub against the peripheral surface of the photosensitive drum 11Y, but also electrostatic Thus, the lubricant powder can be supplied by being attracted to the photosensitive drum 11Y, and the supply efficiency of the lubricant can be improved as compared with the conventional case. The reason for this will be described later.

The frictional charging member 65 is around the brush roller 63, and along the rotation direction of the brush roller 63, is more than a contact position P2 (corresponding to a position where the lubricant is applied) where the brush roller 63 contacts the photosensitive drum 11Y. It is located at a contact position P3 that is downstream and upstream from the contact position P1 at which the brush roller 63 contacts the solid lubricant 64.
The friction charging member 65 has a surface made of PTFE (polytetrafluoroethylene), and the surface abuts against the brush fiber 72 in a state of slightly biting into the brush fiber 72 of the rotating brush roller 63, so that the brush fiber. 72 is triboelectrically charged. Here, the brush fibers 72 are frictionally charged to a positive polarity depending on the work functions of the friction charging member 65 and the brush fibers 72.

  The leveling blade 68 is formed by processing polyurethane rubber into a sheet shape, and is disposed at a position downstream of the brush roller 63 in the drum rotation direction. The tip of the leveling blade 68 is in contact with the peripheral surface of the photosensitive drum 11Y in the counter direction. The lubricant powder applied on the body drum 11Y is leveled to form a film of lubricant powder on the photoreceptor drum 11Y. A film formed of lubricant powder made of zinc stearate is characterized by high releasability and a low friction coefficient, high transferability and cleaning properties, and the peripheral surfaces of the cleaning blade 61 and the photosensitive drum 11Y. And the wear of the peripheral surface of the photosensitive drum 11Y can be suppressed, and the life of each member can be extended.

(3) Regarding setting of work function FIG. 3 is a schematic view showing a state in which each of the friction charging member 65, the brush fiber 72, and the solid lubricant 64 is charged, and FIG. FIG. 4B and FIG. 4C schematically show how the work function changes. FIG. 4B and FIG. 4C are schematic views showing the work functions of the friction charging member 65, the brush fibers 72, and the solid lubricant 64. FIG.

As shown in FIG. 3, the tip of each bristle (hereinafter referred to as “brush bristle tip”) 73 constituting the brush fiber 72 by the rotation of the brush roller 63 passes through the contact position P <b> 3 with the frictional charging member 65. In doing so, the brush bristle tip 73 is frictionally charged to a positive polarity by friction between the bristle tip 73 and the frictional charging member 65.
In a state where the bristle tip 73 is frictionally charged to a positive polarity, the brush bristle tip 73 and the solid lubricant 64 are brought into contact with the solid lubricant 64 when passing through the contact position P1. The solid lubricant 64 is scraped off by friction and the scraped lubricant powder J is frictionally charged to a positive polarity.

The lubricant powder J frictionally charged to the positive polarity passes through the contact position P1, and is conveyed toward the contact position P2 between the brush roller 63 and the photosensitive drum 11Y in a state of being taken into the brush fiber 72. .
Since the charging polarity of the photosensitive drum 11Y is negative as described above, and negative residual charges often remain even after cleaning, the lubricant powder J frictionally charged to positive polarity is In addition to the mechanical application by the brush fibers 72 being rubbed against the peripheral surface of the photosensitive drum 11Y at the contact position P2, electrostatic application by being attracted to the photosensitive drum 11Y by the action of Coulomb's attractive force. Is done.

The reason why the lubricant powder J is charged in the positive polarity as described above depends on the work functions of the friction charging member 65, the brush fiber 72, and the solid lubricant 64.
As shown in FIG. 4A, when the work function of the frictional charging member 65 before frictional charging is φm, the work function of the brush fibers 72 is φb, and the work function of the solid lubricant 64 is φj, ) And (Formula 2).

φm> φb (Formula 1)
φj <φave (Formula 2)
Here, φave = (φm + φb) / 2.
FIG. 4B is a diagram showing how the work function of the frictional charging member 65 and the bristle tip 73 changes due to the frictional charging of the frictional charging member 65 and the bristle tip 73.

  According to the above (Equation 1), there is a relationship of the work function φm of the friction charging member 65> the work function φb of the brush fiber 72, so that the friction between the friction charging member 65 and the brush bristle tip 73 is higher than the friction charging member 65. Electrons at the bristle tip 73 having a low work function move to the frictional charging member 65. Due to the movement of the electrons, the brush bristle tip portion 73 changes from an electrically stable state to a state where electrons are insufficient, and is charged positively, the work function increases to φave, and the work function φj of the solid lubricant 64 increases. It will be in a higher state.

  Here, the work function φave is expressed by [(φm + φb) / 2], and the work functions of both the frictional charging member 65 and the brush bristle tip 73 change to the same magnitude due to the movement of electrons due to frictional charging. Shows its size. Since electrons move due to a difference in work function between two different members, the same work function means that no further movement of electrons is performed.

The work function of the bristle tip 73 changes to φave due to frictional charging with the frictional charging member 65, and the bristle tip 73 passes through the contact position P3 (FIG. 3) after frictional charging, that is, with the frictional charging member 65. After that, in a state where the work function is φave, the solid lubricant 64 is scraped when passing through the contact position P1 toward the contact position P1 with the solid lubricant 64.
FIG. 4C is a diagram showing how the work functions of the brush bristle tip 73 and the lubricant powder J change due to friction when the brush bristle tip 73 scrapes the solid lubricant 64.

  According to the above (Equation 2), there is a relationship of work function φave of the brush bristle tip 73 after frictional charging> work function φj of the solid lubricant 64, and the brush bristle tip 73 after frictional charging is the frictional charging member 65. The electrons are deprived by frictional charging, and the electrons are deprived from the lubricant powder J scraped by friction between the brush bristle tip 73 and the solid lubricant 64 in an attempt to return to the original stable state. . That is, the electrons of the lubricant powder J move to the brush bristle tip 73.

As a result, the lubricant powder J is electrically stable from the state where it is electrically stable, and becomes positively charged. Due to the movement of electrons from the lubricant powder J to the brush bristle tip, the work function of the brush bristle tip 73 becomes lower than that immediately after frictional charging with the friction charging member 65, and approaches the stable state before friction charging. Become.
As shown in FIG. 3, the brush bristle tip 73 conveys the positively charged lubricant powder J to the contact position P2 with the photosensitive drum 11Y and applies it to the photosensitive drum 11Y. It contacts the peripheral surface of the photosensitive drum 11Y.

  Since the photoconductor drum 11Y often has a negative residual charge as described above, electrons may move from the photoconductor drum 11Y to the brush bristle tip 73 during the contact. If the brush bristle tip 73 at that time has fewer electrons than the stable state, it returns to the stable state due to the movement of the electrons. When excessive electrons are supplied, the electrons are gradually dropped to the ground via the grounded metal core 71, thereby preventing excessive electrons from being accumulated in the brush bristle tip 73.

As a result, after the brush bristle tip 73 returns to the stable state before the frictional charging, the brush roller 63 reaches the contact position P3 with the friction charging member 65 by one rotation of the brush roller 63, and when the brush bristle tip 73 passes through the contact position P3, the friction is again generated. It is charged to a positive polarity by frictional charging with the charging member 65.
As described above, the cycle from when the bristle tip 73 is frictionally charged by the frictional charging member 65 to when the brush bristle tip 63 is returned to the position of the frictional charging member 65 by one rotation of the brush roller 63 is one of the brush fibers 72. By repeating the brush bristles for each rotation of the brush roller 63, the lubricant powder J is supplied to the photosensitive drum 11Y in a state of being positively charged which is the opposite polarity to the charging polarity of the photosensitive drum 11Y. Will be able to.

Here, the electrons existing in the frictional charging member 65 are prevented from continuing to accumulate in the frictional charging member 65 by being dropped from the brush fiber 72 to the ground through the cored bar 71 when the rotation of the brush roller 63 is stopped. .
(4) About the result of an experiment of lubricant application evaluation FIG. 5 is a diagram showing the result of an experiment showing whether or not the lubricant application was successfully performed in the configurations of Examples 1 and 2 and Comparative Examples 1 to 4. .

Each column of the friction charging member, application brush, and lubricant shown in the figure shows the material used and the magnitude of the work function, and the column of brush voltage application indicates whether or not a voltage is applied to the brush roller. The column of the lubricant application evaluation shows the evaluation before the endurance and after the endurance, in this case, after the printing of 10, 200,000 and 300,000 sheets.
(4-1) Experimental conditions The magnitude of the work function shown in the figure indicates a value measured by ultraviolet electron spectroscopy (UPS measurement method), and here, ESCALab200R manufactured by VG Scientific was used. Specifically, ultraviolet He-I was irradiated, kinetic energy was measured between 20 and 50 eV, the valence band level bandwidth was determined, and the HOMO level was determined by the ultraviolet He-I energy.

The experimental machine was based on Bizhub Pro 6501P (A4 paper: 65 sheets / min, 600 dpi) manufactured by Konica Minolta, and the friction charging member, application brush, and lubricant were replaced with the materials of the above-described Examples and Comparative Examples. A product was prepared and used as an experimental machine for each example.
Except for the material of the fiber, the coating brush is made of conductive fiber having a fiber thickness of 6 dtex and a fiber resistance of 10 ⁸ Ω, a metal core with an outer diameter of 6 mm, and a brush outer diameter of 0.5 mm. Used was a roll of 12 mm (fiber height 2.5 mm) and a fiber density of 120 KF / inch ² . The solid lubricant used was a solidified zinc stearate, and was brought into contact with the application brush by a pressing spring so that the pressing force was 6 N / m.

  The friction charging member was arranged so as to be frictionally charged with the brush fibers of the application brush using a fixed member made of PTFE on the surface in contact with the application brush. In addition, although the amount of biting of the friction charging member with respect to the application brush is 1 mm, the friction charging member of the friction charging member is prevented so that the friction charging member does not work as so-called flicker, where the brush fibers are scraped against the edge of the friction charging member. The biting amount is zero at the upstream end (corresponding to the inlet where the brush fibers enter the triboelectric charging region) and the downstream end (corresponding to the outlet where the brush fibers exit the triboelectric charging region) of the region in contact with the application brush. I have to.

As a leveling member, polyurethane rubber is held on a sheet metal with a thickness of 2 mm and a protrusion amount of 8 mm, the contact angle with respect to the photosensitive drum is 10 °, and the contact force is within the range of 10 N / m to 30 N / m. It adjusted so that it might become. A polyurethane rubber having a hardness of 62 to 78 degrees and a rebound resilience of 8 to 45% (both measured values at 25 ° C.) was used.
The lubricant application evaluation was performed using the coefficient of friction of the photosensitive drum as a substitute measurement value for each durable sheet. This is because maintaining the target coefficient of friction can be regarded as equivalent to maintaining the target value by applying the lubricant.

  Here, “before durability” indicates the result after printing 100 sheets when printing 100 sheets in order to apply a certain amount of lubricant to the photosensitive drum prior to the experiment. This pre-endurance printing was performed by continuously printing 100 images with a density corresponding to 1% of each color in an environment of 23 ° C. and 55% RH. The lubricant was applied to the photosensitive drum by this 100-sheet continuous printing. After the lubricant was applied, the friction coefficient was measured.

The friction coefficient is measured by attaching a flannel cloth (cotton 100%) to a friction coefficient measurement probe of HEIDON's Tribogear Muse 94i. If the friction coefficient is less than 0.3, ○, 0.3-0. If it was 4, it evaluated as (triangle | delta), and 0.4 or more evaluated as x.
Durability was performed by printing 100,000, 200,000, and 300,000 continuous grid line images (blue) corresponding to 20% for each color under an environment of 23 ° C. and 55% RH. The lubricant evaluation method at the end of continuous printing for each number of sheets was performed by measuring the same coefficient of friction as before the endurance. In addition, although it measured about each color of Y-K, the same result was obtained by any color.

(4-2) Experimental results Examples 1 and 2 satisfy the above (Equation 1) and (Equation 2), respectively, and the evaluation results are all good before and after endurance. The required amount of lubricant could be continuously applied to the photosensitive drum.
On the other hand, Comparative Example 1 satisfies (Equation 1), but does not satisfy (Equation 2), and does not satisfy (Equation 2). Becomes lower than the work function φj of the solid lubricant 64, and makes the polarity of the lubricant powder J negative. For this reason, the target lubricant application amount could not be supplied, and the evaluation result was x.

Comparative Example 2 is a configuration that does not satisfy (Expression 1) but satisfies (Expression 2).
The fact that (Equation 1) is not satisfied means that the work function φb of the brush fiber 72 is higher than the work function φm of the friction charging member 65, and the brush bristle tip 73 is frictionally charged by the friction charging member 65. At this time, in order to take electrons from the frictional charging member 65, the brush bristle tip 73 is charged with a negative polarity.

  On the other hand, since (Formula 2) is satisfied, the polarity of the lubricant powder J can be made positive, and the lubricant powder J can be applied to the photosensitive drum. However, although it can be applied initially, since the polarity of the brush bristle tip 73 after frictional charging is negative, the positive lubricant powder J is gradually accumulated in the brush fibers 72, and the accumulated amount increases. Eventually, the brush fiber 72 becomes clogged with the lubricant powder J, and the lubricant application function is lowered.

Therefore, in Comparative Example 2, the evaluation result was ◯ before the endurance, but as the endurance progressed, the evaluation result shifted from Δ to ×, and a necessary amount of lubricant was applied over a long period of time. Could not continue to apply to drum.
Comparative Example 3 is a configuration that does not include the friction charging member 65, and the charging polarity of the lubricant powder J is determined by the work function of the brush fibers 72 and the lubricant. In Comparative Example 3, since the work function φb of the brush fibers 72 <the work function φj of the lubricant, there is a relation that the charge polarity of the lubricant powder J is negative. As a result, a required amount of lubricant could not be continuously applied to the photosensitive drum over a long period of time.

  The comparative example 4 has a configuration in which the friction charging member 65 is not provided and a negative voltage is applied to the brush roller 63. Since the friction charging member 65 is not provided, the charging polarity of the lubricant powder J is determined by the work function of the brush fibers 72 and the lubricant. In Comparative Example 4, since the work function φb of the brush fiber 72 <the work function φj of the lubricant, there is a relation that the charge polarity of the lubricant powder J is negative. Further, the negative voltage applied to the brush roller 63 is set to an absolute value larger than the negative residual potential of the photosensitive drum.

  Lubricant powder J scraped off by the brush roller 63 due to the potential difference generated between the brush roller 63 and the photosensitive drum causes the peripheral surface of the photosensitive drum to be in contact position P2 where the brush roller 63 contacts the peripheral surface of the photosensitive drum. On the other hand, by applying a negative voltage to the brush roller 63, the electric field strength becomes strong at each brush bristle tip 73 and discharge easily occurs, and the deterioration of the brush fibers 72 is likely to proceed at an early stage. Become.

For this reason, the evaluation result was ○ before endurance or immediately after the start of endurance, but as the endurance progressed, the evaluation result shifted from △ to ×, and as a result, the necessary amount of lubricant was exposed over a long period of time. Could not continue to apply to body drum.
As described above, in the present embodiment, the friction charging member, the brush fiber, and the solid lubricant are made of materials satisfying the above (formula 1) and (formula 2), so that a voltage is applied to the brush roller. Therefore, it is possible to continue supplying the required amount of lubricant powder to the photosensitive drum over a long period of time. By reducing the friction coefficient, the cleaning blade can be prevented from being worn or damaged, and the life of the cleaning blade can be extended. At the same time, the life of the photosensitive drum can be extended by improving the transferability and cleaning performance and suppressing the progress of the wear on the peripheral surface of the photosensitive drum.

<Modification>
As described above, the present invention has been described based on the embodiment. However, the present invention is not limited to the above-described embodiment, and the following modifications may be considered.
(1) In the above embodiment, the example in which the brush roller 63 is used as an application member for scraping the solid lubricant 64 and applying the shaved lubricant powder J to the photosensitive drum has been described. Not limited to. For example, a sponge-like thing, the roller which provides roughness, such as a micro unevenness | corrugation, can also be used for a surrounding surface.

(2) In the above embodiment, the configuration example in which the brush roller 63 rotates in the direction opposite to the rotation direction of the photosensitive drum 11Y at the position P2 that is the contact position with the photosensitive drum 11Y has been described. For example, it may be configured to rotate in the same direction.
In the case of this configuration, the frictional charging member 65 is disposed around the brush roller 63 at a position downstream of the contact position P2 and upstream of the contact position P1 in the rotation direction of the brush roller 63. The rotation direction of the brush roller 63 is determined as a suitable direction depending on the apparatus configuration.

  (3) In the above embodiment, the example in which the friction charging member 65 is made of PTFE, the brush fiber 72 (application member) is made of polyethylene, and the solid lubricant 64 is made of zinc stearate has been described. The material is not limited to this. As the coating member, the friction charging member, and the solid lubricant, materials having a work function satisfying the above (Formula 1) and (Formula 2) can be selected and used.

Within the range satisfying the above (Formula 1) and (Formula 2), for example, a polyester resin fiber, an acrylic resin fiber, or a metal fiber can be used as the coating member. Further, the configuration of the brush may be a woven brush obtained by winding a woven base fabric around a cored bar, or may be an electrostatic flocking brush for flocking a cored bar by electrostatic attraction force.
For example, instead of the solid lubricant 64 instead of zinc stearate, a fatty acid metal salt such as magnesium stearate or lithium stearate can be used.

Furthermore, although PTFE is used as the friction charging member, general resins containing fluorine, such as PFA (perfluoroalkoxyalkane), ETFE (ethylene-tetrafluoroethylene copolymer), PVDF (polyvinylidene fluoride), PFEP (perfluoroethylene propene). Copolymer) or the like.
In the above, (Equation 1) and (Equation 2) are used. For example, each material of the application member, the friction charging member, and the solid lubricant is caused by friction between the application member, the friction charging member, and the solid lubricant. A configuration in which the charge polarity of the lubricant powder scraped off by the coating member charged to the opposite polarity to the charge polarity is selected from those having a work function magnitude that is opposite to the charge polarity of the image bearing rotating body. Then, the lubricant can be applied under the same conditions as in the above embodiment.

(4) In the above embodiment, the frictional charging member 65 is disposed at a position where the frictional charging member 65 bites into the tip 73 of the brush fiber 72 of the brush roller 63. The biting amount is set to a value suitable for the device configuration.
(5) In the above embodiment, the example in which the lubricant applying device according to the present invention and the image forming apparatus including the lubricant applying device are applied to a tandem color digital printer or the like has been described, but the present invention is not limited to this. Regardless of color or monochrome image formation, any configuration can be applied to a copying machine, FAX, MFP (Multiple Function Peripheral), etc., as long as the lubricant is applied to the surface of the image bearing rotating body. In addition, the configuration example in which the image bearing rotator is a photosensitive drum has been described, but the image bearing rotator is not limited to a drum shape, and may be a belt shape, for example. Furthermore, although the configuration example in which the lubricant application unit 69 is provided in the cleaner 16Y has been described, a configuration in which the lubricant application unit 69 is disposed separately from the cleaner 16Y may be employed. Further, the lubricant application unit (apparatus) may be configured to include at least the brush roller 63 and the friction charging member 65.

  Further, the configuration example in which the cleaning blade 61 is used as a cleaning member for removing the residual toner on the photosensitive drum has been described. However, the configuration is not limited to the blade shape, but may be another shape. In this case, an increase in frictional force between the cleaning blade 61 and the peripheral surface of the photosensitive drum 11Y may not be a problem. Even in such a case, for example, the transferability can be improved over a long period of time by the stable supply of the lubricant. There is an effect that can be done.

  Further, the configuration example using the roller-shaped chargers 12Y to 12K as the charging member has been described. Further, the example in which the leveling blade 68 is used as the leveling member for leveling the lubricant applied to the peripheral surface of the photosensitive drum 11Y has been described. For example, a roller-shaped one can also be used.

Needless to say, the material, size, electrical resistance value, and the like of each member described above are not limited to those described above, and suitable materials, sizes, and the like are determined according to the apparatus configuration.
Further, the contents of the above embodiment and the above modification may be combined.

  The lubricant application apparatus according to the present invention is useful as a technique for applying a lubricant to an image bearing rotating body provided in an image forming apparatus.

11Y, 11M, 11C, 11K Photosensitive drums 12Y, 12M, 12C, 12K Charging roller 61 Cleaning blade 63 Brush roller 64 Solid lubricant 65 Friction charging member 68 Leveling blade 69 Lubricant application part 71 Core metal 72 Brush fiber 73 Brush Hair tip J Lubricant powder

Claims (8)

A lubricant application device that is provided in an image forming apparatus having an image bearing rotating body, scrapes a solid lubricant, and applies the scraped lubricant powder to the peripheral surface of the image bearing rotating body,
An application member interposed between the image bearing rotator and the solid lubricant, scraping the solid lubricant at the first position by rotation, and applying the scraped lubricant powder to the peripheral surface of the image bearing rotator at the second position;
A friction charging member that contacts the rotating application member at a position downstream of the second position and upstream of the first position along the rotation direction of the application member to frictionally charge the application member;
As the materials for the friction charging member, the coating member, and the solid lubricant, the charging polarity of the lubricant powder scraped by the coating member charged by friction with the friction charging member is opposite to the charging polarity of the image bearing rotating body. A lubricant application device characterized in that a work function having such a magnitude is selected. When the charging polarity of the image bearing rotor is negative, the work function of the coating member before the friction charging is φb, the work function of the friction charging member is φm, and the work function of the solid lubricant is φj,
The lubricant application device according to claim 1, wherein φm> φb and φj <(φm + φb) / 2 are satisfied. The application member is
The lubricant application device according to claim 1 or 2, comprising a brush-like member. The application member is
The lubricant application device according to claim 3, wherein conductive brush fibers are provided around the core metal, and the core metal is grounded. The friction charging member is:
It consists of resin containing a fluorine, The lubricant supply apparatus of any one of Claims 1-4 characterized by the above-mentioned. The image forming apparatus is provided with a cleaning member that contacts the circumferential surface of the image bearing rotating body and removes toner remaining on the circumferential surface,
The application member is
6. The cleaning member is in contact with the circumferential surface of the image carrying rotator at a position downstream of the rotational direction of the image carrying rotator relative to the position where the cleaning member is in contact with the circumferential surface of the image carrying rotator. The lubricant application device according to any one of the above.   The application member is disposed at a position downstream of the second position where the lubricant is applied to the peripheral surface of the image bearing rotator in the rotational direction of the image bearing rotator, and is in contact with the peripheral surface of the image bearing rotator. The lubricant application device according to any one of claims 1 to 6, further comprising a leveling member for leveling the lubricant applied to the image bearing rotating body by the member.   An image forming apparatus comprising the lubricant application device according to claim 1.

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