JP2009008716A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain the quantity of lubricant covering the surface of an electrostatic latent image carrier in proper quantity. <P>SOLUTION: This image forming device is provided with an electrostatic latent image carrier 4 which supports an electrostatic latent image on the surface, a development housing 19 which contains developer including a first toner in which addition quantity of the lubricant is more than predetermined quantity and a second toner in which addition quantity of the lubricant is less than the predetermined quantity, a developer carrier 80 which supplies the toner in the developer to the electrostatic latent image in a development region 85 and develops the electrostatic latent image, a cleaning blade 16 which scrapes off the toner on the electrostatic latent image carrier 4, a lubricant quantity detection means 100 which detects the quantity of the lubricant covering the surface of the electrostatic latent carrier 4, and a control part 70 which performs lubricant increase control so that the first toner is supplied to a non-image forming region on the surface of the electrostatic latent image carrier 4 from the developer carrier 80 and the quantity of the lubricant covering the surface of the electrostatic latent image carrier 4 is increased to be larger than first quantity when the quantity of the lubricant detected by the lubricant quantity detection means 100 is smaller than the first quantity. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus, and more particularly, to an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction machine having these functions combined.

  In an electrophotographic image forming apparatus, a technique for forming a lubricant film on the surface of the photoreceptor has been proposed in order to improve the transfer performance, cleaning performance, and durability of the photoreceptor.

  As a method of forming a lubricant film on the surface of the photoreceptor, a solid lubricant is pressed against a rotatable brush arranged so as to be in contact with the surface of the photoreceptor, and the lubricant scraped off by the brush is exposed to light. There are a method of applying to the body and a method of supplying the lubricant to the surface of the photosensitive member by developing using toner to which a lubricant is externally added.

  In the former method, since it is necessary to provide a coating device including a brush and a solid lubricant, the image forming apparatus is increased in size and the number of parts is increased. Therefore, it is preferable to employ the latter method from the viewpoint of saving space and reducing the number of parts.

  However, in the latter method, since the lubricant is supplied to the surface of the photoreceptor together with the toner used for development, the amount of lubricant supplied to the surface of the photoreceptor varies depending on the density of the image to be developed. Therefore, there is a possibility that a sufficient amount of lubricant cannot be supplied.

In view of such a problem, in the technique of Patent Document 1, a dedicated mode for supplying the lubricant to the surface of the photoconductor during non-image formation is set, and this dedicated mode is executed as necessary. Thus, a sufficient amount of lubricant can be supplied to the surface of the photoreceptor.
JP 2000-131003 A

  However, in the technique of Patent Document 1, when the dedicated mode is executed, the surface of the photoconductor may be covered with an excessive amount of lubricant. In this case, fine particles such as silica that function as a lubricant interposed between the photosensitive member and the cleaning blade cannot pass between the photosensitive member and the blade, and the frictional force between the photosensitive member and the blade increases. Abnormal wear of the blade may occur.

  Accordingly, an object of the present invention is to provide an image forming apparatus capable of maintaining an appropriate amount of lubricant covering the surface of an electrostatic latent image carrier such as a photoconductor.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
An electrostatic latent image carrier carrying an electrostatic latent image on the surface;
A developing housing containing a developer containing a first toner having an external addition amount of a lubricant equal to or greater than a predetermined amount and a second toner having an external addition amount of the lubricant smaller than the predetermined amount;
The developer is carried on the surface, and is arranged to face the electrostatic latent image carrier via a development region. In the development region, the toner in the developer is supplied to the electrostatic latent image to provide the static image. A developer carrying member that visualizes the electrostatic latent image;
A cleaning blade provided so as to be in contact with the electrostatic latent image carrier, and scraping off the toner on the electrostatic latent image carrier at a contact portion with the electrostatic latent image carrier;
Lubricant amount detection means for detecting the amount of the lubricant covering the surface of the electrostatic latent image carrier;
When the amount of lubricant detected by the lubricant amount detecting means is equal to or less than the first amount, the first toner is transferred from the developer carrier to the non-image forming area on the surface of the electrostatic latent image carrier. And a controller for performing a lubricant increase control for increasing the amount of the lubricant covering the surface of the electrostatic latent image carrier so as to be larger than the first amount. And

  The non-image forming area on the surface of the electrostatic latent image carrier referred to here is an area other than the area where image formation is performed, that is, the developer carrying body during non-image formation such as an inter-image sequence or an end sequence. This refers to the area that passes through the nip.

  According to the present invention, since the amount of lubricant covering the surface of the electrostatic latent image carrier can be maintained at an appropriate amount according to the detection result by the lubricant amount detection means, the durability of the electrostatic latent image carrier, transfer The durability of the cleaning blade in contact with the electrostatic latent image carrier can be improved while maintaining good performance and cleaning performance.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. In the following description, terms indicating a specific direction (for example, “up”, “down”, “left”, “right”, and other terms including them, “clockwise direction”, “counterclockwise” ”) Is used to facilitate understanding of the invention with reference to the drawings, and the present invention should not be construed as being limited by the meaning of these terms. Further, in the image forming apparatus and the developing apparatus described below, the same reference numerals are used for the same or similar components.

[1. Image forming apparatus]
FIG. 1 shows a schematic configuration of an image forming apparatus 2 according to an embodiment of the present invention. The image forming apparatus 2 is an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multi-function machine having a combination of these functions. Currently, various types of electrophotographic image forming apparatuses have been proposed. The illustrated image forming apparatus is a so-called tandem color image forming apparatus. However, the present invention is not applied only to this type of image forming apparatus. For example, a so-called four-cycle color image forming apparatus or a toner image on an electrostatic latent image carrier is directly applied to a recording medium. The present invention is equally applicable to a direct transfer type color image forming apparatus for transferring. Furthermore, the present invention can be applied to a monochrome image forming apparatus having only one developing device.

  The image forming apparatus 2 includes an image reading unit 20 for reading a document image and a printing unit 22 for printing the read image.

  The image reading unit 20 reads a document image into three colors of red (R), green (G), and blue (B) by a known mechanism, and reads yellow (Y), magenta (M), cyan ( C) and black (K) image data are created. In the figure, reference numeral 24 denotes a display unit for displaying various information relating to printing, and reference numeral 25 denotes a panel operation unit for performing a print start operation and various setting operations relating to printing. .

The print unit 22 includes an endless intermediate transfer belt 30 (corresponding to an intermediate transfer member in claims). A material having an electrical resistance of 1 × 10 ⁶ Ω / □ or more and 1 × 10 ¹³ Ω / □ or less is preferably used for the intermediate transfer belt 30. Specific examples of materials used for the belt 30 include, for example, , Polycarbonate, polyphenylene sulfide and the like. Further, as the intermediate transfer belt 30, a belt having a thickness of, for example, 50 μm or more and 150 μm or less is preferably used.

  The intermediate transfer belt 30 is wound around a plurality of rollers 32, 33 and 34. A roller 32 on the right side of the drawing is a drive roller that is drivingly connected to a motor (not shown), and the driving roller 32 connected to the motor rotates based on the driving of the motor to rotate the belt 30 and another roller 33 in contact with the belt 30. , 34 rotate counterclockwise in the figure.

  As the driving roller 32, one having an outer diameter of, for example, 12 mm or more and 30 mm or less is preferably used, whereby the size of the apparatus can be reduced. At least the surface of the driving roller 32 is made of a material having a large friction coefficient such as rubber or urethane, whereby the frictional force with the intermediate transfer belt 30 is increased, and the driving force is transmitted to the intermediate transfer belt 30 satisfactorily. it can.

  In addition, the intermediate transfer belt 30 is given a predetermined tension by a plurality of rollers 32, 33, and 34 in order to ensure a sufficient frictional force between the driving roller 32 and the intermediate transfer belt 30. The magnitude of tension applied to the intermediate transfer belt 30 is preferably 15N or more and 50N or less, for example.

  A secondary transfer roller 40 (corresponding to a secondary transfer member in claims) that presses the recording sheet 36 together with the belt 30 outside the belt portion supported by the drive roller 32 disposed on the right side in the drawing. Is provided. The secondary transfer roller 40 is arranged to be switchable between a position in contact with the outer peripheral surface of the belt 30 and a position separated from the outer peripheral surface of the belt 30. In a state where the secondary transfer roller 40 is in contact with the outer peripheral surface of the belt 30, the contact portion (nip portion) forms a secondary transfer region 41. As the secondary transfer roller 40, for example, an ion conductive roller is used, but an electronic conductive roller can also be used.

  A cleaning device 42 for the intermediate transfer belt is provided outside the belt portion supported by the roller 34 arranged on the left side in the drawing.

  Below the belt portion moving from the roller 34 on the left side to the roller 32 on the right side in the drawing, yellow (Y), magenta (M), cyan (C), black ( Four image forming units 3 (3Y, 3M, 3C, and 3K) that respectively create toner images of corresponding colors using the developer K) are arranged along the intermediate transfer belt 30.

  Each image forming unit 3 includes a cylindrical photosensitive member 4 as an electrostatic latent image carrier. The photosensitive member 4 is provided so as to be able to contact and separate from the intermediate transfer belt 30, and the primary transfer region 15 is formed at the contact portion in the contact state with the intermediate transfer belt 30. Around the photosensitive member 4, a charging device 8, an exposure device 10, a developing device 18, a primary transfer roller 14, and a photosensitive member cleaning blade 16 are arranged in this order along the rotation direction (clockwise direction in the drawing). Yes. The configuration of the developing device 18 will be described later.

  The primary transfer roller 14 is disposed inside the endless intermediate transfer belt 30. The primary transfer roller 14 is provided so as to be switchable between a state where it contacts the intermediate transfer belt 30 and clamps the belt 30 together with the photosensitive member 4 and a state where it is separated from the intermediate transfer belt 30. In a state where the primary transfer roller 14 presses the belt 30 together with the photoconductor 4, a primary transfer region 15 is formed at the nip portion between the belt 30 and the photoconductor 4. As shown in FIG. 2, a power source 64 as a primary transfer bias applying device is connected to the primary transfer roller 14 via a control circuit 66. When the power supply 64 is turned on, a polarity opposite to the normal charging polarity of the toner, specifically, for example, a positive primary transfer bias is applied to the primary transfer roller 14.

  Returning to FIG. 1, a control unit 70 is provided above the print unit 22 to control various operations related to printing.

  A paper feed cassette 44 as a paper feed device is detachably disposed below the print unit 22. The recording sheets 36 such as sheets stacked and accommodated in the sheet feeding cassette 44 are sent out one by one from the uppermost one to the conveying path 50 by the rotation of the sheet feeding roller 52 disposed in the vicinity of the sheet feeding cassette 44.

  A registration roller 54 for sending the recording sheet 36 to the secondary transfer area 41 at a predetermined timing is provided in the vicinity of the paper feed roller 52. A detection sensor 55 for detecting the leading edge of the recording sheet 36 is provided in the vicinity of the registration roller 54.

  The conveyance path 50 passes from the paper feed cassette 44 through the nip portion of the registration roller pair 54, the secondary transfer region 41, the nip portion of the fixing roller pair 56, and the nip portion of the paper discharge roller pair 60 to the print unit 22. It extends to the paper discharge unit 61 provided at the top.

  An example of the image forming operation in the full color mode will be described.

  First, red (R), green (G), and blue (B) image data obtained in the image reading unit 20 is subjected to predetermined data processing in the control unit 70, and yellow (Y) and magenta (M). , Cyan (C), and black (K) image data.

  The yellow, magenta, cyan, and black image data are stored in the image memory 72 in the control unit 70, and after a predetermined image correction for correcting the misalignment, a light source (not shown) provided in the exposure apparatus 10 is used. It is converted into a drive signal for causing light emission.

  In the print unit 22, first, in each image forming unit 3, the outer peripheral surface of the photosensitive member 4 that is rotationally driven at a predetermined peripheral speed is charged by the charging device 8, whereby the surface potential of the photosensitive member 4 (claims). For example, Vo is −600 V (see FIG. 3).

  Next, light is projected from the exposure apparatus 10 that has received the drive signal output from the control unit 70 onto the outer peripheral surface of the charged photoconductor 4 to form an electrostatic latent image. At this time, the electrostatic latent image portion on the surface of the photosensitive member 4 has a potential Vi (corresponding to the second potential in the claims) Vi on the same polarity side as the surface potential Vo and having an absolute value smaller than the surface potential Vo. Attenuates. Specifically, the potential Vi is set to −50 V, for example (see FIG. 3).

  Subsequently, the electrostatic latent image is made visible by the developer toner supplied from the developing device 18. When the toner image of each color formed on the photoconductor 4 in this way reaches the primary transfer region by the rotation of the photoconductor 4, yellow, magenta, cyan, and black are sequentially transferred from the photoconductor 4 to the intermediate transfer belt 30. Transferred (primary transfer) and overlaid.

  Untransferred toner remaining on the photoreceptor 4 without being transferred to the intermediate transfer belt 30 reaches the contact portion between the photoreceptor 4 and the cleaning blade 16 and is scraped off by the cleaning blade 16. It is removed from the outer peripheral surface.

  The superimposed four color toner images are conveyed to the secondary transfer region 41 by the intermediate transfer belt 30.

  On the other hand, the recording sheet 36 accommodated in the paper feed cassette 44 is sent out to the transport path 50 by the rotation of the paper feed roller 52 and is transported to the nip portion of the registration roller pair 54. The recording sheet 36 conveyed to the nip portion of the registration roller pair 54 is conveyed to the secondary transfer area 41 in accordance with the timing at which the toner image is conveyed to the secondary transfer area 41 by the intermediate transfer belt 30.

  When the recording sheet 36 is conveyed to the secondary transfer area 41, the toner image is transferred (secondary transfer) from the intermediate transfer belt 30 to the recording sheet 36. After the secondary transfer, the recording sheet 36 is conveyed to the nip portion of the fixing roller pair 56 further downstream of the secondary transfer area 41, and after the toner image is fixed by the fixing roller 56, the recording sheet 36 is discharged by the paper discharge roller 60. It is sent out to the paper section 61.

  Untransferred toner remaining on the outer peripheral surface of the intermediate transfer belt 30 without being transferred to the recording sheet 36 in the secondary transfer region 41 is removed from the intermediate transfer belt 30 by the cleaning device 42.

[2. Development device]
As shown in FIG. 2, the developing device 18 includes a developing housing 19 that accommodates the developer and various members, a first conveying roller 81 that carries the developer in the developing housing 19, a second conveying roller 82, and A developing roller 80 (corresponding to the developer carrying member in the claims).

  In the embodiment, a so-called two-component developer including a toner and a carrier is used as the developer accommodated in the developing housing 19. In the embodiment, the normal charging polarity of the toner is negative, the normal charging polarity of the carrier is positive, and the toner is electrostatically attached to the carrier. However, in the present invention, a so-called one-component developer containing no carrier can also be used.

  Various external additives are externally added to the toner, and the external additive includes a particulate lubricant to be supplied to the surface of the photoreceptor 4. As the lubricant, a material having a normal charging polarity opposite to that of the toner is used. That is, in the embodiment, the normal charging polarity of the lubricant is positive. As a specific material of the lubricant, for example, a fatty acid metal salt is used, and as a more specific material of the lubricant, for example, zinc stearate or calcium stearate can be mentioned. The external addition amount of the lubricant is different for each toner particle, and the charge amount of the toner is different depending on the external addition amount of the lubricant. Since the charging polarity of the lubricant is opposite to the charging polarity of the toner, the charge amount of the toner is smaller as the external additive amount of the lubricant is larger, and is increased as the external additive amount of the lubricant is smaller.

  The toner inside the developing housing 19 corresponds to a normally charged toner (a second toner in claims) having an external addition amount of a lubricant smaller than a predetermined amount (for example, 0.015 wt%) and having a regular charge amount. And a weakly charged toner (corresponding to the first toner in the claims) having an external additive amount of the lubricant equal to or greater than the predetermined amount and having a charge amount smaller than the regular charge amount. The charge amount of the normally charged toner is, for example, 30 to 40 μC / g, and the charge amount of the weakly charged toner is, for example, 20 μC / g or less.

  The first transport roller 81 and the second transport roller 82 are disposed to face each other via the first supply / recovery region 83, and the second transport roller 82 and the developing roller 80 are disposed in the second supply / recovery region 84. Are arranged opposite to each other. The developing roller 80 is disposed so as to face the developing area 85. The first transport roller 81, the second transport roller 82, and the developing roller 80 are rotatable in the counterclockwise direction in the drawing around the rotation axes parallel to each other.

  A power source (developing bias applying device) 86 is connected to the developing roller 80 via a control circuit 88. When the power supply 86 is turned on, a developing bias is applied to the developing roller 80, whereby an electric field that moves the toner carried on the developing roller 80 to the surface of the photosensitive member 4 between the developing roller 80 and the photosensitive member 4. Is formed. In the embodiment, the developing bias is configured by superimposing, for example, an AC voltage Vac of 1.5 kHz on a DC voltage Vdc of −400 V, for example, and the magnitude of the developing bias is the magnitude of the DC voltage Vdc (−400 V). It fluctuates periodically as the center.

  In the present invention, the magnitude of the DC voltage Vdc is a potential having a larger absolute value than the potential Vi of the electrostatic latent image portion on the surface of the photoconductor 4 and a smaller absolute value than the surface potential Vo of the photoconductor 4. If it exists, it is not limited to said magnitude | size. In the present invention, the developing bias does not necessarily have to be configured by superimposing the AC voltage Vac on the DC voltage Vdc, and may be configured only by the DC voltage Vdc.

  When developing is performed using the developing device 18 configured as described above, the developer accommodated in the developing housing 19 and carried on the first transport roller 81 causes the first transport roller 81 to rotate. It is transported to the supply / recovery area 83 and supplied to the second transport roller 82 in the first supply / recovery area 83. The developer supplied to the second transport roller 82 is transported to the second supply / recovery region 84 as the second transport roller 82 rotates, and is supplied to the developing roller 80 in the second supply / recovery region 84. . The developer thus carried on the developing roller 80 is transported to the developing area 85 as the developing roller 80 rotates, and in the developing area 85, the surface of the developing roller 80 and the electrostatic latent image portion on the surface of the photoreceptor 4 are conveyed. Only the toner of the developer (carrier and toner) carried on the developing roller 80 is selectively supplied to the electrostatic latent image portion on the surface of the photoconductor 4 by the electric field formed between the two. The developer that has not moved to the surface of the photoconductor 4 in the developing region 85 is transported to the second supply / recovery region 84 again by the rotation of the developing roller 80, and the second transport roller 82 in the second supply / recovery region 84. To be recovered. The developer collected on the second conveyance roller 82 is conveyed again to the first supply / recovery region 83 by the rotation of the second conveyance roller 82, and is transferred to the first conveyance roller 81 in the first supply / recovery region 83. To be recovered.

  As shown in FIG. 3, when development is performed in the image forming sequence, the surface potential Vo of the photoreceptor 4 is −600 V, and the potential Vi of the electrostatic latent image portion on the surface of the photoreceptor 4 is −50 V. The bias DC voltage Vdc is -400V. The toner on the developing roller 80 is not supplied to the non-latent image portion on the surface of the photoconductor 4 having a higher potential than the DC voltage Vdc, and the electrostatic latent on the surface of the photoconductor 4 having a lower potential than the DC voltage Vdc. The toner image is supplied only to the image portion, whereby a toner image is formed on the surface of the photoreceptor 4.

  When development is performed in this manner, the lubricant externally added to the toner is supplied to the surface of the photoconductor 4 together with the toner, but a part of the lubricant supplied to the surface of the photoconductor 4 is part of the toner. At the same time, the surface of the photoconductor 4 is scraped off by the cleaning blade 16, so that the amount of the lubricant covering the surface of the photoconductor 4 does not vary greatly. However, since the amount of lubricant covering the surface of the photoconductor 4 may become insufficient or excessive with the durability of the image forming apparatus 2, the image forming apparatus 2 according to the present invention includes the photoconductor 4. Lubricant amount detection means 100 (described later) for detecting the amount of lubricant covering the surface of the photosensitive member 4 is provided, and the control unit 70 lubricates the surface of the photoreceptor 4 according to the detection result by the lubricant amount detection means 100. Is configured to be controlled to an appropriate amount.

[3. Lubricant amount detection means]
Returning to FIG. 2, the lubricant amount detection unit 100 includes a friction coefficient detection unit 102 that detects the friction coefficient of the surface of the photoreceptor 4. The lubricant amount detection means 100 detects the amount of lubricant covering the surface of the photoconductor 4 by detecting that the friction coefficient of the surface of the photoconductor 4 is not less than the first reference value μ1 by the friction coefficient detection means 102. Of the lubricant covering the surface of the photosensitive member 4 by detecting that the friction coefficient of the surface of the photosensitive member 4 is not more than μ2 by the friction coefficient detecting means 102. It is configured to detect that the amount is greater than or equal to the second amount A2. Specific sizes of the first reference value μ1, the first amount A1, the second reference value μ2, and the second amount A2 will be described later.

  The friction coefficient detection means 102 is a drive motor (corresponding to the drive device in the claims) 90 that drives the photosensitive member to rotate, and a power supply (corresponding to the drive current supply device in the claims) that supplies the drive motor 90 with the drive current Id. 92) and an ammeter (corresponding to the drive current detection device in claims) 94 for detecting the magnitude of the drive current Id. The drive motor 90 is drivingly connected to the photoreceptor 4, and a power source 92 is connected to the drive motor 90 via an ammeter 94. When the power source 92 is turned on, the photoconductor 4 is rotationally driven by operating the drive motor 90, and at this time, the drive current Id flowing through the drive motor 90 is detected by the ammeter 94.

  The drive torque of the drive motor 90 varies according to the frictional force acting between the photosensitive member 4 and the cleaning blade 16, that is, the friction coefficient of the surface of the photosensitive member 4, and increases as the friction coefficient of the surface of the photosensitive member 4 increases. Become. The drive current Id is proportional to the rotational speed of the drive motor 90. Therefore, as the drive torque of the drive motor 90 is larger, that is, as the friction coefficient of the surface of the photoconductor 4 is larger, the drive current Id flowing through the drive motor 90 is smaller, and as the drive torque of the drive motor 90 is smaller, In other words, the smaller the friction coefficient of the surface of the photoconductor 4, the greater the drive current Id flowing through the drive motor 90 (see FIG. 11).

  The friction coefficient detecting means 102 detects that the driving current Id detected by the ammeter 94 is not more than the first current value I1, so that the friction coefficient of the surface of the photoconductor 4 is not less than the first reference value μ1. By detecting that the drive current Id detected by the ammeter 94 is equal to or greater than the second current value I2, the friction coefficient of the surface of the photoreceptor 4 is equal to or less than the second reference value μ2. It is configured to detect this. Specific sizes of the first current value I1 and the second current value I2 will be described later.

[4. Control of lubricant amount]
In order to control the lubricant covering the surface of the photoreceptor 4 to an appropriate amount, the control unit 70 performs lubricant increase control or lubricant decrease control as necessary during the inter-image sequence and the end sequence.

The lubricant increase control is a control in which weakly charged toner is supplied from the developing roller 80 to the surface of the photoconductor 4 to increase the amount of lubricant covering the surface of the photoconductor 4 to be larger than the first amount A1. It is. As shown in Table 1, when the amount of lubricant covering the surface of the photoreceptor 4 is insufficient, specifically, the amount of lubricant detected by the lubricant amount detecting means 100 is controlled by the lubricant increase control. This is done when the amount of A1 is less than or equal to A1. As described above, the fact that the amount of lubricant is not more than the first amount A1 is detected when the friction coefficient of the surface of the photoconductor 4 is not less than the first reference value μ1, and the friction coefficient of the surface of the photoconductor 4 is detected. Is equal to or greater than the first reference value μ1 is detected when the drive current Id is equal to or less than the first current value I1. That is, the lubricant increase control is performed when the drive current Id detected by the ammeter 94 is equal to or less than the first current value I1.

  In the embodiment, the first current value I1 is set to 0.07 A, the first reference value μ1 of the friction coefficient is set to 0.35, and the first amount A1 of the lubricant is equal to 100 K rotations of the photoconductor. The amount of lubricant consumed is 0.5 g / 100 Krot. The second current value I2 is 0.08 A, the second reference value μ2 of the friction coefficient is 0.3, and the second amount A2 of the lubricant is 0.2 g / 100 Krot. However, in the present invention, the first current value I1, the first reference value μ1, the first amount A1, the second current value I2, the second reference value μ2, and the second amount A2 are as described above. It is not limited to this.

  In the present embodiment, the relationship between the coefficient of friction of the photoreceptor surface shown in FIG. 8 and the durability of the photoreceptor, the relation between the coefficient of friction of the photoreceptor surface and the cleaning performance of the photoreceptor shown in FIG. 9, and FIG. Based on the relationship between the friction coefficient of the photoreceptor surface and the durability of the cleaning blade, the first reference value μ1 and the second reference value μ2 of the friction coefficient were set as described above. Specifically, FIG. 8 shows that as the coefficient of friction on the surface of the photoconductor 4 increases, the scraping amount α value on the surface of the photoconductor 4 increases and the durability of the photoconductor 4 deteriorates. FIG. 9A shows that when the friction coefficient of the surface of the photoconductor 4 is 0.26, even when the contact force of the cleaning blade 16 with respect to the surface of the photoconductor 4 is weak (for example, 15 N / m), FIG. 9B shows that the cleaning performance can be satisfactorily achieved by appropriately adjusting the angle with the tangent to the surface of the photoconductor 4. FIG. 9B shows the photoconductor when the coefficient of friction on the surface of the photoconductor 4 is 0.42. Even when the contact force of the cleaning blade 16 against the four surfaces is strong (for example, 32 N / m), the cleaning performance is deteriorated regardless of the angle between the end surface of the blade 16 and the tangent line of the surface of the photosensitive member 4. FIG. 10 shows that the wear amount of the cleaning blade increases remarkably when the coefficient of friction of the surface of the photoconductor 4 becomes a predetermined value or less, as represented by “x” in the figure. From the relationships shown in FIGS. 8 to 10, it is preferable to maintain the coefficient of friction of the surface of the photoconductor 4 in the range of 0.3 to 0.35. Therefore, the first reference value μ1 is set to 0.35. The second reference value μ2 was set to 0.3.

  Further, in the present embodiment, the first current value I1 and the second current value I2 are obtained from the relationship between the friction coefficient of the photosensitive member surface and the drive current Id shown in FIG. 11 (manufactured by Matsushita Electric Industrial Co., Ltd., brushless motor / DNQ12AS38W15 was used). Specifically, FIG. 11 shows that the drive current Id decreases as the friction coefficient of the surface of the photoreceptor 4 increases, and when the friction coefficient is 0.3, the drive current Id is 0.08 A, and the friction coefficient is 0. When it is 35, the drive current Id is 0.07 A. From this relationship, the first current value I1 was set to 0.07A, and the second current value I2 was set to 0.08A.

  As shown in FIG. 4, during the lubricant increase control, the control unit 70 performs control to increase the absolute value of the DC voltage Vdc of the developing bias by a predetermined magnitude. FIG. 4 shows only the aspect of the lubricant increase control performed during the inter-image sequence, but the lubricant increase control is similarly performed during the end sequence.

  Specifically, during the lubricant increase control, the development bias direct-current voltage Vd is controlled to increase by 100 V toward the negative polarity side. That is, the DC voltage Vd of the developing bias at the time of lubricant increase control is −500V. By controlling the developing bias in this manner, the difference between the magnitude of the DC voltage Vdc of the developing bias and the surface potential Vo of the photoconductor 4 is reduced, so that among the toner carried on the developing roller 80, the difference from the carrier A part of the weakly charged toner having a relatively weak adhesion moves from the developing roller 80 to the surface of the photoreceptor 4. At this time, the amount of toner supplied from the developing roller 80 to the photosensitive member 4 is the same as or substantially the same as that during development of an image having an image density of 2.5%. Note that the image density in this specification refers to the ratio S1 / S of the solid image S1 in the image forming region S.

  Since a lot of lubricant is externally added to the weakly charged toner, when the increase in the lubricant is controlled, a lot of lubricant is supplied to the surface of the photoreceptor 4 together with the weakly charged toner. The lubricant covering the surface increases so as to be greater than the first amount A1.

  When the lubricant increase control is performed, the photoconductor 4 is disposed away from the intermediate transfer belt 30. Thereby, it is possible to prevent the toner adhering to the surface of the photoreceptor 4 from being transferred to the intermediate transfer belt 30 by the lubricant increase control.

  However, during the lubricant increase control, the control unit 70 may control not to apply the primary transfer bias to the primary transfer roller 14 instead of separating the photoreceptor 4 from the intermediate transfer belt 30. Further, the toner adhering to the surface of the photoreceptor 4 can be prevented from being transferred to the intermediate transfer belt 30 by the lubricant increase control.

  In the lubricant reduction control, the amount of lubricant covering the surface of the photoconductor 4 is increased by supplying the regular charged toner to the surface of the photoconductor 4 and increasing the scraping force of the lubricant by the cleaning blade 16. It is the control which reduces so that it may become less than quantity A2. As shown in Table 1, in the lubricant reduction control, when the amount of lubricant covering the surface of the photoreceptor 4 is excessive, specifically, the amount of lubricant detected by the lubricant amount detecting means 100 is changed. Performed when the amount is equal to or greater than the second amount A2. As described above, the fact that the amount of the lubricant is equal to or greater than the second amount A2 is detected when the friction coefficient on the surface of the photoreceptor 4 is equal to or less than the second reference value μ2, and the friction coefficient on the surface of the photoreceptor 4 is detected. The second reference value μ2 is detected when the drive current Id is equal to or greater than the second reference value. That is, the lubricant reduction control is performed when the drive current Id detected by the ammeter 94 is equal to or greater than the second current value I2.

  As shown in FIG. 5, during the lubricant reduction control, the control unit 70 performs control to form an image having an image density of a predetermined level or more on the photoreceptor 4. FIG. 5 shows only the aspect of the lubricant reduction control performed during the inter-image sequence, but the lubricant reduction control is similarly performed during the end sequence.

  Specifically, at the time of lubricant reduction control, for example, an image having a 100% image density (a so-called solid image) is formed on the photoreceptor 4. However, the image formed during the lubricant reduction control is not limited to an image having an image density of 100% as long as the image has a high density (for example, 80% or more).

  By developing an image having a high image density in this way, a large amount of toner is supplied from the developing roller 80 to the surface of the photoreceptor 4. When the amount of toner on the photoconductor 4 increases due to this development, the scraping power of the lubricant by the cleaning blade 16 increases. The toner supplied to the surface of the photoconductor 4 by this development includes not only a regular charged toner but also a weakly charged toner, but the cleaning blade is more than the amount of lubricant supplied to the photoconductor 4 during development. Since the amount of the lubricant removed from the photoconductor 4 by 16 is increased, the lubricant reducing control is performed so that the lubricant covering the surface of the photoconductor 4 is less than the second amount A2. Decrease.

  In the lubricant reduction control, the photoconductor 4 is arranged away from the intermediate transfer belt 30 as in the lubricant increase control. Thereby, it is possible to prevent the toner adhering to the surface of the photoreceptor 4 from being transferred to the intermediate transfer belt 30 by the lubricant reduction control.

  However, during the lubricant reduction control, the control unit 70 may control not to apply the primary transfer bias to the primary transfer roller 14 instead of separating the photoreceptor 4 from the intermediate transfer belt 30.

  A specific example of the flow of each process for controlling an appropriate amount of lubricant covering the surface of the photoreceptor 4 during the image forming operation will be described with reference to the flowchart shown in FIG.

  As shown in FIG. 6, first, in step 1, it is determined whether or not the inter-image sequence is started. If it is determined in step 1 that the inter-image sequence has been started, the process proceeds to step 3. If it is determined in step 1 that the inter-image sequence has not been started, the process proceeds to step 2.

  In step 2, it is determined whether or not the end sequence has been started. If it is determined in step 2 that the end sequence has been started, the process proceeds to step 3. If it is determined in step 2 that the end sequence has not been started, the process returns to step 1.

  In step 3, the drive current Id flowing through the drive motor 90 for driving the photosensitive member 4 is detected by the ammeter 94, and the process proceeds to step 4.

  In step 4, it is determined whether or not the drive current Id is equal to or less than a first current value I1 (0.07 A in the embodiment). If it is determined in step 4 that the drive current Id is less than or equal to the first current value I1, the process proceeds to step 5, and if it is determined in step 4 that the drive current Id is greater than the first current value I1. , Go to step 6.

  In step 5, the above-described lubricant increase control is performed, and the amount of lubricant covering the surface of the photoconductor 4 is controlled to be larger than the first amount A1, and the process proceeds to step 8.

  In step 6, it is determined whether or not the drive current Id is equal to or greater than a second current value I2 (0.08 A in the embodiment). If it is determined in step 6 that the drive current Id is equal to or greater than the second current value I2, the process proceeds to step 7, and if it is determined in step 6 that the drive current Id is smaller than the second current value I2. , Go to Step 8.

  In step 7, the above-described lubricant reduction control is performed, and the amount of lubricant covering the surface of the photoreceptor 4 is controlled to be smaller than the second amount A2, and the process proceeds to step 8.

  In step 8, it is determined whether or not the inter-image sequence has been completed. If it is determined in step 8 that the inter-image sequence has been completed, the process proceeds to step 9. If it is determined in step 8 that the inter-image sequence has not been completed, the process returns to step 3.

  In step 9, it is determined whether or not the end sequence is completed. If it is determined in step 9 that the end sequence has ended, the process ends. If it is determined in step 9 that the end sequence has not ended, the process returns to step 3.

  As described above, in the lubricant increase control or the lubricant decrease control, the drive current Id is larger than the first current value I1 and smaller than the second current value I2 until the inter-image sequence or the end sequence ends. The process is repeated until the current value is reached, that is, until the amount of lubricant covering the surface of the photoreceptor 4 is greater than the first amount A1 and less than the second amount A2. By performing such control, the lubricant covering the surface of the photoconductor 4 is always controlled to an appropriate amount, and the durability, transfer performance, and cleaning performance of the photoconductor 4 are maintained well, and the durability of the cleaning blade 16 is maintained. Improvements can be made.

  While the present invention has been described with reference to the above-described embodiments, the present invention is not limited to the above-described embodiments.

  Using the image forming apparatus shown in FIG. 1 (process speed of 35 sheets / min), changes in the friction coefficient of the photoconductor with durability for each of Example 1, Example 2 and Example 3 having different development modes are shown. A test was conducted to confirm.

  As the photoreceptor, an overcoat layer made of a polycarbonate resin and having a surface roughness Rz of 0.06 to 0.08 was used. As the developer, a two-component developer containing toner and carrier was used, and as the external additive of the toner, a toner containing zinc stearate particles and silica fine particles was used.

  In Example 1, similar to the lubricant increase control in the above embodiment, the developing bias was increased by −100 V (see FIG. 4), and toner fogging was generated. In this toner fogging, the weakly charged toner on the developing roller is supplied to the photoconductor, and the amount of toner supplied is about the same as when developing an image with an image density of 2.5%.

  In Example 2, an image having an image density of 10% was developed. During this development, most of the toner supplied from the developing roller to the photosensitive member is regular charged toner.

  In Example 3, an image having an image density of 100% was developed as in the lubricant reduction control of the above embodiment. During this development, most of the toner supplied from the developing roller to the photosensitive member is regular charged toner.

  For each example, 5000 sheets of A4 paper were printed in a single-sheet intermittent mode under the conditions of an ambient temperature of 23 ° C. and a relative humidity of 65%, and the measurement of the coefficient of friction on the surface of the photoconductor was 500 sheets until 3000 sheets were printed. This was done every time, and after 3000 sheets, every 1000 sheets.

  To measure the coefficient of friction on the surface of the photoconductor, a portable tribometer (HEIDON Tribogear Muse TYPE: 94iII manufactured by Shinto Kagaku Co., Ltd.) is used. Measurements were made in contact with the body surface.

  As a result of the test, in Example 1, the friction coefficient on the surface of the photoreceptor tends to increase as the number of durable sheets increases. In Example 2, the friction coefficient on the surface of the photoreceptor is before and after the endurance. In Example 3, it was confirmed that the coefficient of friction on the surface of the photoreceptor tends to decrease as the number of durable sheets increases.

  From the results of Example 1, it can be inferred that the amount of lubricant covering the surface of the photoreceptor can be surely reduced by performing the lubricant reduction control according to the above-described embodiment. From the results of Example 3, it can be inferred that the amount of lubricant covering the surface of the photoreceptor can be reliably increased by performing the lubricant increase control according to the above-described embodiment.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to the present invention. It is a figure which shows the structure of an image creation part. 6 is a graph showing the relationship between the surface potential of a photoreceptor and the DC voltage of a developing bias. 6 is a graph showing the relationship between the potential on the surface of the photoreceptor and the DC voltage of the developing bias when lubricant increase control is performed. 6 is a graph showing the relationship between the potential on the surface of the photoreceptor and the DC voltage of the developing bias when lubricant reduction control is performed. It is a flowchart which shows the flow of each process for controlling the quantity of the lubricant which covers the photoreceptor surface. 6 is a graph showing the results of Test 1. 6 is a graph showing the relationship between the coefficient of friction on the surface of the photoreceptor and the amount of abrasion on the surface of the photoreceptor. 6 is a graph showing the relationship between the coefficient of friction on the surface of the photoreceptor and the cleaning performance of the photoreceptor. 6 is a graph showing the relationship between the coefficient of friction of the photoreceptor surface and the durability of the cleaning blade. 6 is a graph showing a relationship between a coefficient of friction on the surface of a photoconductor and a drive current flowing in a drive motor for driving the photoconductor.

Explanation of symbols

2: Image forming device, 4: Photoconductor, 8: Charging device, 10: Exposure device, 14: Primary transfer roller, 15: Primary transfer region, 16: Cleaning blade, 18: Developing device, 19: Developing housing, 30: Intermediate transfer belt, 36: recording sheet, 40: secondary transfer roller, 64: power supply, 66: control circuit, 80: development roller, 85: development area, 86: power supply, 88: control circuit, 90: drive motor, 92 : Power source, 94: Ammeter, 100: Lubricant amount detection means, 102: Friction coefficient detection means.

Claims (9)

An electrostatic latent image carrier carrying an electrostatic latent image on the surface;
A developing housing containing a developer containing a first toner having an external addition amount of a lubricant equal to or greater than a predetermined amount and a second toner having an external addition amount of the lubricant smaller than the predetermined amount;
The developer is carried on the surface, and is arranged to face the electrostatic latent image carrier via a development region. In the development region, the toner in the developer is supplied to the electrostatic latent image to provide the static image. A developer carrying member that visualizes the electrostatic latent image;
A cleaning blade provided so as to be in contact with the electrostatic latent image carrier, and scraping off the toner on the electrostatic latent image carrier at a contact portion with the electrostatic latent image carrier;
Lubricant amount detection means for detecting the amount of the lubricant covering the surface of the electrostatic latent image carrier;
When the amount of lubricant detected by the lubricant amount detecting means is equal to or less than the first amount, the first toner is transferred from the developer carrier to the non-image forming area on the surface of the electrostatic latent image carrier. And a controller for performing a lubricant increase control for increasing the amount of the lubricant covering the surface of the electrostatic latent image carrier so as to be larger than the first amount. An image forming apparatus.   The controller is configured to remove the second toner from the developer carrier when the amount of lubricant detected by the lubricant amount detector is equal to or greater than a second amount that is greater than the first amount. Lubricant reduction control for supplying to the non-image forming area on the surface of the electrostatic latent image carrier and reducing the amount of lubricant covering the surface of the electrostatic latent image carrier to be smaller than the second amount. The image forming apparatus according to claim 1, wherein: The lubricant amount detection means includes a friction coefficient detection means for detecting a friction coefficient of the surface of the electrostatic latent image carrier,
The lubricant amount detection means detects the amount of lubricant covering the surface of the electrostatic latent image carrier by detecting that the friction coefficient is equal to or greater than a first reference value by the friction coefficient detection means. Lubricant that covers the surface of the electrostatic latent image carrier by detecting that it is less than a first amount and detecting that the friction coefficient is less than or equal to a second reference value by the friction coefficient detector. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus detects that the amount is greater than or equal to the second amount. 4. The friction coefficient detecting means is
A driving device for rotationally driving the electrostatic latent image carrier;
A drive current supply device for supplying a drive current to the drive device;
A drive current detection device for detecting the magnitude of the drive current,
The friction coefficient detecting means detects that the friction coefficient is not less than the first reference value by detecting that the drive current detected by the drive current detecting device is not more than the first current value. Then, by detecting that the drive current detected by the drive current detection device is equal to or greater than a second current value that is greater than the first current value, the friction coefficient is less than or equal to the second reference value. The image forming apparatus according to claim 3, wherein the presence is detected. A charging device for charging the surface of the electrostatic latent image carrier to a first potential;
The surface of the electrostatic latent image carrier is irradiated with light to form an electrostatic latent image, and the potential of the electrostatic latent image portion is on the same polarity side as the first potential and from the first potential. An exposure apparatus that attenuates to a second potential having a small absolute value;
A developer bias comprising a DC bias having an absolute value smaller than the first potential and greater than the second potential, or a developer bias formed by superimposing an AC voltage on the DC voltage is applied to the developer carrier. A developing bias applying device that forms an electric field for moving toner from the surface of the electrostatic latent image to the electrostatic latent image portion between the electrostatic latent image carrier and the developer carrier,
The controller increases the absolute value of the DC voltage constituting the developing bias by a predetermined magnitude when performing the lubricant increase control, thereby removing the first toner from the developer carrier. The image forming apparatus according to claim 1, wherein the image forming apparatus is supplied to an electrostatic latent image carrier.   The controller, when performing the lubricant reduction control, develops the second toner by developing an image having a predetermined image density or more in the non-image forming area on the surface of the electrostatic latent image carrier. 6. The image forming apparatus according to claim 1, wherein the developer carrier is supplied to the electrostatic latent image carrier. An intermediate transfer member to which a toner image formed on the surface of the electrostatic latent image carrier is transferred;
The electrostatic latent image carrier is disposed so as to be able to contact and separate from the intermediate transfer member,
7. The control unit according to claim 1, wherein, when performing the lubricant increase control or the lubricant decrease control, the controller places the electrostatic latent image carrier away from the intermediate transfer member. An image forming apparatus according to claim 1. An intermediate transfer member to which a toner image formed on the surface of the electrostatic latent image carrier is transferred;
A transfer member for clamping the intermediate transfer member together with the electrostatic latent image carrier;
A transfer bias applying device that applies a transfer bias to the transfer member to form an electric field that moves toner from the surface of the electrostatic latent image carrier to the surface of the intermediate transfer member;
8. The control unit according to claim 1, wherein the control unit performs control so that the transfer bias is not applied to the transfer member when the lubricant increase control or the lubricant decrease control is performed. 9. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the lubricant contains a fatty acid metal salt.

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