JP2020118888A - Developer supply member, image forming unit, and image forming apparatus - Google Patents

Abstract

To make it possible to certainly improve image quality.SOLUTION: A surface cell diameter of a foam layer 76 of a developer supply member in pressure contact with and rotatably disposed on a developer carrier is 280 μm or more and 567 μm or less, and a cell diameter ratio γ representing the ratio of the surface cell diameter to an internal cell diameter in the foam layer 76 is 0.75 or more and 0.93 or less. A rubber total area ratio of a cell skeleton part from a surface layer 76a of the foam layer 76 to the depth of a distance defined according to a nip part area is 31.7% or more and 69.1% or less. Suppliability of developer to the developer carrier and scrapability of developer from the developer carrier in a state where the developer supply member is compressed can be increased.SELECTED DRAWING: Figure 1

Description

The present invention relates to a developer supply member, an image forming unit and an image forming apparatus.

2. Description of the Related Art Conventionally, an image forming apparatus such as a printer, a copying machine, a facsimile machine, a multi-function machine, for example, an electrophotographic printer is provided with an image forming unit, and the image forming unit includes a photosensitive drum, a charging roller, a developing roller, A supply roller as a developer supply member, a toner cartridge, and the like are provided. In the printer, the surface of the photosensitive drum uniformly charged by the charging roller is exposed by the LED head to form an electrostatic latent image, which is supplied from the toner cartridge to the developing roller via the supply roller. The toner is attached to the electrostatic latent image, the electrostatic latent image is developed, and a toner image is formed. The toner image is transferred to a sheet as a medium by a transfer roller and fixed by a fixing device, so that an image is formed on the sheet.

By the way, the supply roller has a function of supplying the toner to the developing roller and scraping the toner from the developing roller.

Therefore, the foam layer of the supply roller is formed of urethane rubber, the surface cell diameter which is a parameter of the foam layer is 180 [μm] or more and 280 [μm] or less, and the internal cell diameter is 280 [μm] or more, and , 650 [μm] or less and the surface area ratio of the cell skeleton portion is 30 [%] and 60 [%] or less, the image may be blurred or the paper may be stained. To improve the image quality (see, for example, Patent Document 1).

JP, 2017-134252, A

However, in the above-described conventional supply roller, the surface area ratio of the cell skeleton portion is a value that defines only the surface of the foam layer, that is, the surface layer, and the supply roller is actually pressed against the developing roller and compressed. Since it is not specified assuming the state of use, that is, the state of mounting, it is not possible to sufficiently supply the toner to the developing roller, and it is also impossible to sufficiently scrape the toner from the developing roller. Therefore, it is not possible to reliably prevent the image from being blurred or the paper to be soiled, and it is not possible to reliably improve the image quality.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a developer supply member, an image forming unit and an image forming apparatus that can solve the problems of the conventional supply roller and reliably improve the image quality.

Therefore, the developer supply member of the present invention is rotatably arranged in pressure contact with the developer carrying member in the image forming unit so as to form a nip region with the developer carrying member. There is.

The surface cell diameter of the foam layer is set to 280 [μm] or more and 567 [μm] or less.

Further, the cell diameter ratio, which represents the ratio of the surface cell diameter to the internal cell diameter in the foam layer, is set to 0.75 or more and 0.93 or less.

Then, the total rubber area ratio of the cell skeleton portion from the surface layer of the foamed layer to the depth of the distance defined according to the nip portion region is 31.7% or more and 69.1% or less. To be done.

According to the present invention, the developer supply member is rotatably arranged in pressure contact with the developer carrying member in the image forming unit, and forms a nip region with the developer supply member. There is.

The surface cell diameter of the foam layer is set to 280 [μm] or more and 567 [μm] or less.

Further, the cell diameter ratio, which represents the ratio of the surface cell diameter to the internal cell diameter in the foam layer, is set to 0.75 or more and 0.93 or less.

Then, the total rubber area ratio of the cell skeleton portion from the surface layer of the foamed layer to the depth of the distance defined according to the nip portion region is 31.7% or more and 69.1% or less. To be done.

In this case, the surface cell diameter of the foam layer is 280 [μm] or more and 567 [μm] or less, and the cell diameter ratio representing the ratio of the surface cell diameter to the internal cell diameter in the foam layer is 0.75 or more. And 0.93 or less, the total rubber area ratio of the cell skeleton portion from the surface layer of the foam layer to the depth of the distance defined according to the range of the nip portion region is 31.7% or more, In addition, since the content is 69.1% or less, the development in the state where the nip region is formed between the developer carrying member and the developer supply member, that is, the developer supply member is compressed. It is possible to improve the supply property of the developer to the developer carrier and the scraping property of the developer from the developer carrier.

Therefore, not only the developer can be sufficiently supplied to the developer carrier, but also the developer can be scraped off sufficiently from the developer carrier, so that the image is blurred or the medium is soiled. It can be surely prevented.

As a result, the image quality can be surely improved.

It is a conceptual diagram of the supply roller in the embodiment of the present invention. 1 is a schematic diagram of a printer according to an embodiment of the present invention. FIG. 3 is a schematic diagram of an image forming unit according to an embodiment of the present invention. 3 is a control block diagram of the printer according to the embodiment of the present invention. FIG. It is a figure which shows the evaluation result of the image when the printing experiment in embodiment of this invention is performed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this case, a supply roller as a developer supply member, an image forming unit (developing device), and a printer as an image forming device will be described.

2 is a schematic diagram of a printer according to the embodiment of the present invention, and FIG. 3 is a schematic diagram of an image forming unit according to the embodiment of the present invention. Since the image forming units 16Bk, 16C, 16M, and 16Y have the same structure, only the image forming unit 16Bk will be illustrated and described in FIG.

In the figure, 10 is a printer, and Cs is a housing of the printer 10, and a paper cassette 11 as a medium accommodating portion is detachably disposed below the housing Cs, and the paper cassette 11 serves as a medium. Paper P is stored. Adjacent to the front end of the sheet cassette 11, the sheets P are separated one by one, fed out in the direction of the arrow X, and fed by a hopping roller or the like (not shown) for feeding to the sheet conveyance path Rt1 as a medium conveyance path. A mechanism is provided.

The paper P fed into the paper transport path Rt1 is transported by a transport roller pair (not shown) by driving a paper transport motor 71 (FIG. 4) described later, and images of black, cyan, magenta, and yellow are formed. Is supplied to the image forming units 16Bk, 16C, 16M, and 16Y as an image forming unit that forms the image.

The image forming units 16Bk, 16C, 16M, and 16Y are detachably attached to the main body of the printer 10, that is, the apparatus main body Bd, and include the unit main body portion 37 and the toner cartridge 41 as a developer storage portion. The unit main body 37 is provided with the photosensitive drum 31 as an image carrier, and the toner as a developer of each color is stored in the accommodation chamber of the toner cartridge 41. A predetermined image forming unit of the image forming units 16Bk, 16C, 16M, and 16Y, in the present embodiment, the image forming unit 16Bk is disposed adjacent to the toner cartridge 41 and is a waste toner as a waste developer accommodating portion. A tank 43 is provided, and waste toner as waste developer is stored in the waste toner tank 43.

The unit main body portion 37 is rotatably disposed in contact with the photoconductor drum 31, the photoconductor drum 31, and a charging roller 32 as a charging device that uniformly charges the surface of the photoconductor drum 31, A developing roller 33, which is rotatably arranged in contact with the body drum 31, and which adheres toner to the electrostatic latent image as a latent image, is rotatably arranged in pressure contact with the developing roller 33. A supply roller 34 provided as a developer supply member for supplying toner to the developing roller 33, a developing blade 35 as a developer layer regulating member for uniformly thinning the toner supplied to the developing roller 33, and a developer. The toner remaining as an image on the photosensitive drum 31 after the transfer of the toner image is removed from the photosensitive drum 31 by a cleaning blade 36 as a cleaning member, and the toner scraped off by the cleaning blade 36 is used as a waste toner. The spiral 38 is provided as a transport member that transports the image forming unit 16Bk in the width direction.

The photosensitive drum 31, the charging roller 32, the developing roller 33, and the supply roller 34 are connected to a drive motor (drum motor) 72 (FIG. 4), which will be described later, as a drive unit for image formation, and the drive motor 72 is connected to the drive motor 72. It is rotated in the direction of the arrow by driving.

Then, the LED head 22 as an exposure device is disposed above the unit main body portion 37 of each of the image forming units 16Bk, 16C, 16M, and 16Y so as to face each photoconductor drum 31, and each of the LED heads 22 allows the LED head 22 to operate. The surface of the photoconductor drum 31 is exposed to form an electrostatic latent image. The LED head 22 includes an LED (Light Emitting Diode) as a light emitting element, a lens array, and the like.

A transfer unit u1 is disposed below the image forming units 16Bk, 16C, 16M, and 16Y in the apparatus body Bd, and the transfer unit u1 serves as a first roller (not shown) and a second roller. Transfer belt as a belt member stretched movably by a driven roller (not shown), a tension roller (not shown), the drive roller, the driven roller, and the tension roller, and electrostatically adsorbs and conveys the paper P as it travels. 17 and a transfer roller 21 as a transfer member, which is rotatably arranged so as to face the photoconductor drum 31 with the transfer belt 17 interposed therebetween and to be in pressure contact with the photoconductor drum 31.

In the image forming units 16Bk, 16C, 16M and 16Y, the surface of the photoconductor drum 31 is uniformly charged by the charging roller 32, exposed by the LED head 22, and an electrostatic latent image is formed on the surface of the photoconductor drum 31. Then, the developing roller 33 causes the toner supplied from the supply roller 34 to adhere to the electrostatic latent image, develops the electrostatic latent image, and forms a toner image on the surface of the photosensitive drum 31.

The sheet P supplied to the image forming unit 16Bk in the direction of the arrow Y is conveyed as the transfer belt 17 is moved, passes between the photosensitive drums 31 and the transfer rollers 21, and The transfer roller 21 sequentially transfers the toner images of the respective colors formed on the respective photoconductor drums 31 in the respective image forming units 16Bk, 16C, 16M and 16Y so as to be superposed on the paper P, and the color toner images are formed on the paper P. To form.

Subsequently, the paper P is supplied to the fixing device 18 as a fixing device arranged on the downstream side of the image forming unit 16Y in the paper transport path Rt1. The fixing device 18 includes a heating roller 18a serving as a first fixing member, a pressure roller 18b serving as a second fixing member that is pressed against the heating roller 18a to form a pressure contact portion, and the heating roller 18a. A non-illustrated thermistor or the like is provided as a temperature detection unit that is arranged in a non-contact manner and detects the temperature of the heating roller 18a. Inside the heating roller 18a, a heater such as a halogen lamp is provided as a heating body.

When the sheet P is supplied to the fixing device 18, the color toner image is heated by the heating roller 18a and pressed by the pressure roller 18b to be fixed on the sheet P, so that a color image is formed on the sheet P. To be done. Then, the sheet P discharged from the fixing device 18 is transported by a pair of transport rollers (not shown), then discharged to the outside of the apparatus main body Bd, and stacked on a stacker (not shown) formed on the top of the housing Cs.

In the apparatus body Bd, a waste toner carrying path 46 as a waste developer carrying device is arranged to extend below the image forming units 16Bk, 16C, 16M and 16Y. The waste toner carrying path 46 is formed along a frame (not shown), collects the waste toner carried by the spiral 38, carries it in the direction of arrow Z, and supplies it to the waste toner tank 43.

The photosensitive drum 31 is formed by sequentially coating a conductive support made of a metal pipe such as aluminum with a blocking layer and a photoconductive layer made of a charge generation layer and a charge transport layer.

The charging roller 32 is formed by coating a metal cored bar with a semiconductive rubber layer such as epichlorohydrin rubber, and is brought into contact with the photoconductor drum 31 with a predetermined pressure contact amount. It is rotated along with the rotation.

The developing roller 33 is formed by sequentially coating a metal cored bar with a urethane rubber layer having semiconductivity as an elastic layer and a surface treatment layer, and abuts on the photosensitive drum 31 with a predetermined pressure contact amount. Then, the photosensitive drum 31 is rotated at a predetermined peripheral speed ratio in a direction following the rotation of the photosensitive drum 31.

The developing blade 35 is made of, for example, a thin metal plate member having a thickness of 0.08 [mm] and a length substantially equal to the length of the developing roller 33 in the longitudinal direction. One end of the developing blade 35 in the lateral direction is fixed to a predetermined position of the frame of the unit main body 37, and the other end of the developing blade 35 has a surface slightly inward from the leading edge contacting the developing roller 33. To be made.

As will be described later, the supply roller 34 is formed by coating a metal cored bar with a rubber material, is brought into pressure contact with the developing roller 33 with a predetermined pressure contact amount, and forms a nip portion with the developing roller 33. A region is formed and rotated with respect to the rotation of the developing roller 33 in the counter direction (the same direction as the rotating direction of the developing roller 33) at a predetermined peripheral speed ratio.

The cleaning blade 36 is made of urethane rubber, and one end of the cleaning blade 36 is brought into contact with the photosensitive drum 31 with a predetermined pressure contact amount.

Each of the image forming units 16Bk, 16C, 16M, 16Y and the toner cartridge 41 is formed as a replacement unit and is replaced when the stored toner is consumed or the constituent parts are deteriorated.

In the fixing device 18, the heating roller 18a and the pressure roller 18b are each formed by coating a hollow cylindrical cored bar made of, for example, aluminum or the like with a heat resistant elastic layer made of silicone rubber. It is formed by coating a tube made of a fluororesin such as PFA (tetrafluoroethylene-perfluorolalkyl vinyl ether copolymer).

Next, the control device of the printer 10 will be described.

FIG. 4 is a control block diagram of the printer according to the embodiment of the present invention.

In the figure, 51 is a control unit including a CPU (microprocessor), ROM, RAM, input/output port, timer, etc., 52 is an interface (I/F) control unit, and the control unit 51 is a higher-level device. The print data and the control command are received from the host computer (not shown) via the interface control unit 52, the entire sequence of the printer 10 (FIG. 2) is controlled, and the printing operation is performed.

Further, 53 is a reception memory as a first storage device for temporarily recording the print data received by the control unit 51, and 54 is image data generated by editing the print data, that is, image data. Is an image data editing memory in which is recorded.

Reference numeral 57 denotes an operation/display unit including an LED as a display unit for displaying the state of the printer 10, a switch as an operation unit for an operator to input an instruction to the printer 10, and 58. The sensor group 58 is a sensor group including various sensors for monitoring the state of the printer 10. The sensor group 58 is formed on the paper P, a sensor for detecting the position of the paper P, a sensor for detecting temperature and humidity, and the like. It is composed of a sensor for detecting the density of an image.

Further, 61 is a power source for the charging roller that applies a voltage to the charging roller 32 based on the instruction of the control unit 51 to uniformly charge the surface of the photosensitive drum 31, and 62 is based on the instruction of the control unit 51. A developing roller power source for applying a voltage to the developing roller 33 to attach the toner to the electrostatic latent image on the photosensitive drum 31, and 63 applies a voltage to the supply roller 34 based on an instruction from the control unit 51 to perform development. A supply roller power supply that supplies toner to the roller 33, and a transfer roller power supply 64 that applies a voltage to the transfer roller 21 based on an instruction from the control unit 51 and transfers the toner image on the photosensitive drum 31 to the paper P. is there.

The charging roller power supply 61, the developing roller power supply 62, and the supply roller power supply 63 can change the voltage applied to the charging roller 32, the developing roller 33, and the supply roller 34 according to an instruction from the control unit 51.

Then, 66 sends the image data recorded in the image data editing memory 54 to the LED head 22, and a head drive control unit 67 for driving the LED head 22, and 67 fixes the transferred toner image on the paper P. Therefore, the fixing control unit 68 that controls the temperature of the heating roller 18a of the fixing device 18 is a conveyance motor control unit that controls the sheet conveyance motor 71 based on an instruction from the control unit 51.

A drive control unit 69 drives the drive motor 72 to rotate the photosensitive drum 31.

Next, the supply roller 34 will be described.

FIG. 1 is a conceptual diagram of a supply roller according to the embodiment of the present invention.

The supply roller 34 is made of an electrically conductive material, has a cylindrical shape as a support metal core 75, and is surrounded by the metal core 75 and is made of an electrically conductive material. A foam layer 76 having a surface layer (foam outer layer) 76a formed on the surface of the foam layer 76, and a foam inside (foam inner layer) formed inside the surface layer 76a. It consists of 76b. In the present embodiment, the core metal 75 has an outer diameter of 6 mm.

In the figure, the enlarged view G1 shows the total rubber area ratio of the cell skeleton px1 from the surface layer 76a to a depth of 100 [μm], and the enlarged view G2 shows the cell skeleton px2 from the surface layer 76a to a depth of 400 [μm]. Represents the total rubber area ratio.

Both ends of the cored bar 75 are projected from the foam layer 76, and a gear (not shown) for transmitting the rotation of the drive motor 72 (FIG. 4) to the supply roller 34 is attached to one end of the cored bar 75. A shaft sh1 is disposed at both ends of the core 75, and the supply roller 34 is rotatably supported by the unit main body 37 (FIG. 2) via the shaft sh1.

As the material of the foam layer 76, a rubber material such as silicone rubber, urethane rubber, EPDM rubber, acrylic rubber, ethylene propylene rubber, styrene/butadiene rubber, acrylonitrile/butadiene rubber, butadiene rubber, isoprene rubber, chloroprene rubber, or butyl rubber is used.

When silicone rubber is used among the rubber materials, the cells are formed independently of each other in the foam layer 76, so that it is difficult for the toner to enter the supply roller 34 and the toner is not supplied to the cells of the surface layer 76a. The toner stored in the cell can be efficiently discharged. Therefore, it is possible to improve the toner supply property to the developing roller 33. Further, the silicone rubber material has a property of dripping in the moving direction, and when the supply roller 34 is compressed and rotated with respect to the developing roller 33, the contact area between the supply roller 34 and the developing roller 33 becomes large. It is possible to enhance the scraping property of the toner from the developing roller 33.

Since silicone rubber has a lower mechanical strength than other rubber materials, it is easily worn and has low durability.

Further, when urethane rubber is used among the above rubber materials, the mechanical strength of urethane rubber is higher than that of other materials, so that abrasion of the supply roller 34 during continuous printing can be suppressed, and the developing roller can be suppressed. Not only can the durability of 33 be increased, but also the hardness of the foam layer 76 can be easily reduced, so the load applied to the image forming units 16Bk, 16C, 16M, 16Y, the printer 10, etc. can be reduced. It is possible to reduce energy consumption.

Since urethane rubber is often formed by connecting cells in the foam layer 76, the use of urethane rubber not only makes it easier for the toner to enter the supply roller 34 but also causes the surface of the supply roller 34, that is, In addition, the cells of the surface layer 76a of the foam layer 76 are likely to be clogged with the toner, and the toner supply property to the developing roller 33 becomes low.

Further, since the urethane rubber has a property of being crushed when compressed, the contact area with the developing roller 33 when the supply roller 34 is pressed against the developing roller 33 and rotated is reduced, and the toner from the developing roller 33 is scratched. Takenability will be low.

The material of the cored bar 75 may be a metal having a predetermined rigidity and sufficient conductivity, and for example, iron, copper, brass, stainless steel, aluminum, nickel or the like is used. Further, as a material other than metal, a material having a predetermined rigidity and sufficient conductivity, for example, a resin molded product in which conductive particles are dispersed, ceramics, or the like can be used. Further, the cored bar 75 can be formed in a roll shape, a pipe shape, or the like.

Next, a method of manufacturing the supply roller 34 will be described.

As the method of manufacturing the supply roller 34, a mold foaming method in which urethane rubber is integrally foamed with the core metal 75 in a cylindrical mold having a roller shape, and a urethane foam free-foaming to form a prismatic foam There is a manufacturing method of free foaming in which the outer periphery is polished after cutting out, passing the cored bar 75 through the hole formed in the foamed body.

Independent cells and communicating cells are formed in the foam layer 76 that is foamed in the method of manufacturing the mold foam. In this case, since the mold is used, it is not necessary to polish and finish the molded product, and it is possible to manufacture the supply roller 34 with small outer diameter deviation. On the other hand, cells having a large cell diameter and cells having a high degree of communication are formed in the foamed layer 76 foamed in the free foaming manufacturing method.

The shape of the supply roller 34 is generally a straight shape, but may be a crown shape or a taper shape in which the diameters of both ends are small, and further, the diameters of both ends may be different. ..

In the present embodiment, the hardness of the supply roller 34 is set to 26 [Asker F] or more and 38 [Asker F] or less. If the hardness of the foam layer 76 is high, the load applied to the toner is large, toner damage occurs, and not only graininess (dot formation due to granulation) occurs, but also the contact pressure with the developing roller 33 increases and the supply is increased. The roller 34 is worn and the durability of the supply roller 34 is lowered, the load applied to the image forming units 16Bk, 16C, 16M and 16Y is increased, and the image forming units 16Bk, 16C, 16M and 16Y are operated. It may be difficult to control.

The hardness of the supply roller 34 can be set by adjusting the amount of a foaming agent such as AIBN (isobisisobutylnitrile).

Further, by adjusting the amount of the foaming agent, it is possible to change the foaming ratio of the foamed layer 76 and change the cell diameter, the wall thickness of the cell, and the like.

In the present embodiment, urethane rubber is used as the rubber material of foam layer 76.

In the present embodiment, the surface cell diameter of the foam layer 76 is the first parameter, and the cell diameter ratio γ representing the ratio of the surface cell diameter to the internal cell diameter of the foam layer 76 is the second parameter. The total rubber area ratio of the cell skeleton portion from the surface layer 76a of the foam layer 76 to the depth of the distance defined according to the nip portion region, in the present embodiment, from the surface layer 76a to the depth of 400 [μm] The rubber total area ratio of the cell skeleton is defined as a third parameter, assuming a mounting state in which the supply roller 34 is pressed against the developing roller 33 and is compressed for use.

Next, each of the parameters will be described.
[Surface cell diameter]
The surface cell diameter refers to the cell diameter of the cells of the surface layer 76 a of the foam layer 76.

The surface cell diameter is a parameter for improving the toner supply property of the supply roller 34 to the developing roller 33 and the toner scraping property of the developing roller 33. If the surface cell diameter is unnecessarily small, the opening of the cell of the surface layer 76a of the foam layer 76 is small, so that the toner stored in the cell may not be discharged and the supplyability may be lowered.

On the other hand, if the surface cell diameter is unnecessarily large, the area of the cell skeleton portion of the surface layer 76a becomes small, the contact area with the developing roller 33 becomes small, and the scraping property of the toner from the developing roller 33 becomes low. As a result, the toner remaining on the developing roller 33 cannot be collected after the electrostatic latent image is developed, and excess toner may adhere to the paper P and stain the paper P. Therefore, in order to improve the toner supply property to the developing roller 33 and the toner scraping property from the developing roller 33, it is necessary to set the surface cell diameter to an appropriate value.
(Internal cell diameter)
The internal cell diameter refers to the cell diameter of the foam interior 76b of the foam layer 76.
(Cell diameter ratio γ)
The cell diameter ratio γ is the ratio of the surface cell diameter to the internal cell diameter, and the internal cell diameter refers to the cell diameter inside the foam body 76b.

The cell diameter ratio γ is represented by Do/Di when the surface cell diameter is Do and the internal cell diameter is Di, and the toner supply property to the developing roller 33 and the toner scraping property from the developing roller 33 are shown. It is a parameter to maintain continuously.

When the cell diameter ratio γ is unnecessarily small, the toner is not discharged from each cell of the surface layer 76a, the toner is likely to be clogged in the cell, and the toner supply property is deteriorated. Further, due to this, when the hardness of the foam layer 76 becomes high, the load applied to the toner becomes large, not only the toner damage occurs and the graininess occurs, but also the contact pressure with the developing roller 33 becomes high, and the supply roller 34 becomes high. The durability of the supply roller 34 becomes low due to wear, the load applied to the image forming units 16Bk, 16C, 16M, 16Y becomes large, and control for operating the image forming units 16Bk, 16C, 16M, 16Y is difficult. It becomes.

On the other hand, if the cell diameter ratio γ is unnecessarily large, the surface cell diameter is large, so that the contact area with the developing roller 33 becomes small and the scraping property of the toner from the developing roller 33 becomes low. As a result, the toner remaining on the developing roller 33 after development cannot be collected, and excess toner may adhere to the paper P and stain the paper P. Further, it is difficult to increase the cell diameter ratio γ more than necessary due to the characteristics of the urethane rubber used for the foam layer 76, the manufacturing method of the supply roller 34, and the like. From this, in order to improve the toner supply property to the developing roller 33 and the toner scraping property from the developing roller 33, it is necessary to set the cell diameter ratio γ to an appropriate value.
(Rubber total area ratio)
The rubber total area ratio is a parameter that represents the total area ratio of the cell skeleton portion within a predetermined range from the surface layer 76a of the foam layer 76, in the present embodiment, from the surface layer 76a to a depth of 400 [μm].

As described above, the larger the contact area with the developing roller 33 is, the higher the scraping property of the toner from the developing roller 33 is. Therefore, it is considered that the contact area of the skeleton portion of the surface cell is increased. When the supply roller 34 is pressed against the developing roller 33 and rotated, the supply roller 34 is compressed, and the contact area with the developing roller 33 includes not only the cell skeleton portion of the surface layer 76a but also the inner cell skeleton portion. The value is the total area of the nip area between the supply roller 34 and the developing roller 33.

Therefore, in order to enhance the scraping property of the toner from the developing roller 33, it is necessary to set the total rubber area ratio from the surface layer 76a to the depth of 400 [μm] to an appropriate value.

Next, an evaluation result of an image when a printing experiment is performed using a supply roller manufactured by making each parameter different will be described.

FIG. 5 is a diagram showing an evaluation result of an image when a printing experiment is performed in the embodiment of the present invention.

First, the supply roller used in the printing experiment will be described.

A printing experiment was performed using the supply rollers of Examples 1 to 4 and Comparative Examples 1 to 3.

Each of the supply rollers used in Examples 1 to 4 and Comparative Examples 1 to 3 had a straight shape. In addition, the method of manufacturing the supply roller of Examples 1 and 3 and Comparative Example 1 was mold foaming, and the method of manufacturing the supply roller of Examples 2 and 4 and Comparative Examples 2 and 3 was free foaming.

The supply rollers of Examples 1 to 4 and Comparative Examples 1 to 3 have hardness [Asker F], surface cell diameter Do [μm], internal cell diameter Di [μm], cell diameter ratio γ, and surface layer 76a to 100 [μm]. The total rubber area ratio [%] up to the depth of and the total rubber area ratio from the surface layer 76a to the depth of 400 [μm] are made different.
[Example 1]
The supply roller is manufactured by a mold foaming manufacturing method and has a hardness of 36 [Asker F], a surface cell diameter Do of 414 [μm], an internal cell diameter Di of 489 [μm], and a cell diameter ratio γ of 0.85. The total rubber area ratio from the surface layer 76a to the depth of 100 [μm] is 36.5 [%], and the total rubber area ratio from the surface layer 76a to the depth of 400 [μm] is 67.4 [%].
[Example 2]
The supply roller is manufactured by a free foaming manufacturing method, and has a hardness of 38 [Asker F], a surface cell diameter Do of 280 [μm], an internal cell diameter Di of 372 [μm], and a cell diameter ratio γ of 0.75. The total rubber area ratio from the surface layer 76a to the depth of 100 [μm] is 2.7 [%], and the total rubber area ratio from the surface layer 76a to the depth of 400 [μm] is 33.1 [%]. The total rubber area ratio from the surface layer 76a to the depth of 400 [μm] is about 10 times or more the total rubber area ratio to the depth of 100 [μm].
[Example 3]
The supply roller is manufactured by a mold foaming manufacturing method and has a hardness of 34 [Asker F], a surface cell diameter Do of 488 [μm], an internal cell diameter Di of 522 [μm], and a cell diameter ratio γ of 0.93. The total rubber area ratio from the surface layer 76a to the depth of 100 [μm] is 35.2 [%], and the total rubber area ratio from the surface layer 76a to the depth of 400 [μm] is 69.1 [%].
[Example 4]
The supply roller is manufactured by a free foaming manufacturing method, has a hardness of 26 [Asker F], a surface cell diameter Do of 567 [μm], an internal cell diameter Di of 702 [μm], and a cell diameter ratio γ of 0.81. The total rubber area ratio from the surface layer 76a to the depth of 100 [μm] is 1.5 [%], and the total rubber area ratio from the surface layer 76a to the depth of 400 [μm] is 31.7 [%]. The total rubber area ratio from the surface layer 76a to the depth of 400 [μm] is about 20 times or more the total rubber area ratio to the depth of 100 [μm].
[Comparative Example 1]
The supply roller is manufactured by a mold foaming manufacturing method and has a hardness of 41 [Asker F], a surface cell diameter Do of 293 [μm], an internal cell diameter Di of 361 [μm], and a cell diameter ratio γ of 0.81. The total rubber area ratio from the surface layer 76a to the depth of 100 [μm] is 49.6 [%], and the total rubber area ratio from the surface layer 76a to the depth of 400 [μm] is 70.7 [%]. The rubber area ratio up to the depth of 400 [μm] is the largest among the supply rollers of Examples 1 to 4 and Comparative Examples 1 to 3.
[Comparative Example 2]
The supply roller is manufactured by a free foaming manufacturing method, has a hardness of 26 [Asker F], a surface cell diameter Do of 702 [μm], an internal cell diameter Di of 732 [μm], and a cell diameter ratio γ of 0.96, The total rubber area ratio from the surface layer 76a to the depth of 100 [μm] is 3.3[%], and the total rubber area ratio from the surface layer 76a to the depth of 400 [μm] is 13.4[%]. The surface cell diameter Do and the cell diameter ratio γ are the largest among the supply rollers of Examples 1 to 4 and Comparative Examples 1 to 3.
[Comparative Example 3]
The supply roller is manufactured by a free foaming manufacturing method, has a hardness of 30 [Asker F], a surface cell diameter Do of 478 [μm], an internal cell diameter Di of 653 [μm], and a cell diameter ratio γ of 0.73. The total rubber area ratio from the surface layer 76a to the depth of 100 [μm] is 2.9%, and the total rubber area ratio from the surface layer 76a to the depth of 400 μm is 31.5%. The cell diameter ratio γ is the smallest among the supply rollers of Examples 1 to 4 and Comparative Examples 1 to 3.

Next, a method of measuring the first to third parameters will be described.
[Method of measuring surface cell diameter]
The surface cell diameter Do of the supply roller was measured by using a CCD camera (“Digital Microscope AR1260” manufactured by Precision Wave Co., Ltd.), focusing on the cell skeleton portion of the surface layer 76a of the supply roller at a magnification of 100 times.

At the position on the longitudinal direction at a distance of about 100 mm from the central portion of the supply roller to the end side, two positions at a distance of 180[°] on the circumferential direction of the supply roller are set as measurement positions, and 1 at each measurement position The measurement range was set within the [mm] square frame, and the major axis of all independent cells existing in the measurement range was measured, and the average value was defined as the surface cell diameter Do.
[Measuring method of internal cell diameter]
The inner cell diameter Di of the supply roller is 10 times the cell skeleton on the surface of the cut-out foam inside 76b by cutting out the inside of the foam 76b and using a CCD camera ("Digital Microscope AR1260" manufactured by Precision Wave Co., Ltd.). The measurement was performed by focusing at a magnification of 100 times.

At the position on the longitudinal direction at a distance of about 100 mm from the center of the supply roller to the end side, the two positions at a distance of 180[°] on the circumferential direction of the supply roller are set as the measurement positions, and 1 at each measurement position. The [mm] square frame was set as the measurement range, and the major axis of all the independent cells existing in the measurement range was measured, and the average value was defined as the internal cell diameter Di.
[Rubber total area ratio measuring method]
The rubber total area ratio γ was measured using a hybrid laser microscope (“OPTELICS” manufactured by Lasertec Corporation). Focusing on the cell skeleton of the surface layer 76a of the supply roller, the total rubber area ratio was measured for the cell skeleton at a depth of 100 [μm] and a depth of 400 [μm] from the core metal direction.

The supply rollers of Examples 1 to 4 and Comparative Examples 1 to 3 are manufactured by a mold foaming or free foaming manufacturing method. The supply rollers manufactured by the free foaming manufacturing method are finished by polishing the outer circumference. As a result, fluffing occurs from the supply roller manufactured by the mold foaming manufacturing method, and outer diameter runout of about 100 μm exists. If there is an outer diameter deflection, a measurement error will occur at each measurement location when the measurement is performed while focusing on the cell skeleton portion of the surface layer 76a. Therefore, in order to suppress the occurrence of a measurement error due to the outer diameter runout, the rubber surface area ratio was measured not from the surface layer 76a but from the surface layer 76a to a depth of 100 [μm].

However, since the supply roller is pressed against the developing roller 33 and rotated and compressed, it is preferable to measure the total rubber area ratio under the conditions assuming the mounting state of the supply roller 34.

Therefore, the total rubber area ratio from the surface layer 76a of the foam layer 76, which is the nip portion area with the developing roller 33, to a depth of 400 [μm] was also measured.

Next, a method of conducting a printing experiment will be described.

In conducting a printing experiment, an image forming unit equipped with each supply roller was mounted on a printer ("C542dn" manufactured by Oki Data Co., Ltd.), and the temperature was 23 ± 3 [°C] and the humidity was 55 ± 10 [%]. Printing was performed below and the image formed on the paper was evaluated.

The image to be evaluated is a magenta image, and the toner cartridge of the magenta image forming unit has a cohesion degree of 48% or more and 56% or less and a blow-off charge amount of 75[%]. About 30.0±0.5 [g] of magenta toner having a viscosity of not less than μC/g] and not more than 80 [μC/g] was filled. The image forming unit was idled once before the image was evaluated.

Next, the image evaluation result of the printing experiment will be described.

The image formed on the paper is a 2×2 (halftone) pattern image and a 100% solid image, and after printing, whether the image is blurred or not, and the paper is stained. It was judged whether or not.

In determining whether or not a blur has occurred in the image, when a solid image of 100 [%] is formed on the paper, it is determined whether or not the density lowers at the upper end and the lower end of the paper and the lower end of the paper. It was confirmed whether or not white spots occurred, and when at least one of the decrease in density and the white spots occurred, it was determined that the image had a blur.

In determining whether or not the paper is soiled, when a 2×2 pattern image is formed on the paper, it is confirmed whether toner adheres to a portion of the upper end of the paper where the image is not formed. It was determined that the paper was soiled when the paper was attached.

In the evaluation result of FIG. 5, when neither the image blurring nor the paper stain occurs, the result is “◯”, and when the image blurring or the paper stain occurs, the result is “Δ”. The case where both stains on the paper occurred was rated as x.

〔Measurement result〕
As shown in FIG. 5, in the supply rollers of Examples 1 to 4, neither image blurring nor paper stains occurred, and it is possible to suppress the occurrence of printing defects due to the supply roller. , Was able to improve the image quality. On the other hand, in the supply rollers of Comparative Examples 1 to 3, it is not possible to prevent at least one of image blurring and paper stains and to prevent printing defects due to the supply roller. , The image quality was degraded.
[Comparative Example 1]
The image is blurred. In the supply roller of Comparative Example 1, the total rubber area ratio of the cell skeleton portion from the surface layer to the depth of 400 [μm] is 70.7 [%], which is large. Therefore, since the contact area with the developing roller is large and the opening area of the cell on the surface layer is small, it is considered that the toner in the cell was not sufficiently discharged.
[Comparative Example 2]
The paper is dirty. In the supply roller of Comparative Example 2, the cell diameter ratio γ was 0.96, which was large, and the total rubber area ratio of the cell skeleton portion from the surface layer to the depth of 400 μm was 13.4 [%]. small. Therefore, it is considered that the contact area with the developing roller was small and the toner was not sufficiently scraped off from the developing roller.
[Comparative Example 3]
The image is blurred and the paper is dirty. In the supply roller of Comparative Example 3, the cell diameter ratio γ is 0.73, which is small, and the total rubber area ratio from the surface layer to the depth of 400 μm is 31.5 [%], which is small. Therefore, since the inner cell diameter Di is larger than the surface cell diameter Do, the toner easily enters the cells, the toner is not sufficiently discharged from the cells, the toner supply property is lowered, and the toner is sufficiently supplied to the developing roller. It is possible that it was not. Further, it is conceivable that the total area ratio of rubber from the surface layer to the depth of 400 [μm] is small, so the contact area with the developing roller is small and the toner was not sufficiently scraped off from the developing roller.

From this, in the supply roller 34 using urethane rubber as the material of the foam layer 76, neither the image blurring nor the paper stain occurs, and it is possible to suppress the occurrence of the print failure due to the supply roller 34. The above-mentioned parameters capable of improving the image quality can be set from the respective values of the first to fourth embodiments of FIG. 5 as follows.

That is, the surface cell diameter is set to 280 [μm] or more and 567 [μm] or less.

When the surface cell diameter is less than 280 [μm], the opening area of the cell is small, the toner that has entered the supply roller 34 is not discharged, and the toner supply property becomes low. On the other hand, when the surface cell diameter is larger than 567 [μm], the area of the cell skeleton of the surface layer 76a is small and the contact area with the developing roller 33 is small, so that the toner scraping property from the developing roller 33 becomes low.

The cell diameter ratio γ is set to 0.75 or more and 0.93 or less.

When the surface cell diameter ratio γ is less than 0.75, the surface cell diameter Do is smaller than the internal cell diameter Di, so that the cells of the surface layer 76a are likely to be clogged with toner, and the toner is less easily supplied to the developing roller 33. Get lower. When the cells are clogged with toner, the hardness of the supply roller 34 is increased, so that the load applied to the toner is increased, the toner is damaged, and the graininess is generated. In addition, the contact pressure is increased and the foaming is caused. The layer 76 and the like are worn and durability is reduced, and the torque required to operate the image forming units 16Bk, 16C, 16M, and 16Y is increased. On the other hand, when the cell diameter ratio γ is larger than 0.93, the area of the cell skeleton portion of the surface layer 76a is small and the contact area with the developing roller 33 is small, so that the toner scraping property from the developing roller 33 becomes low. As a result, the toner remaining on the developing roller 33 after development cannot be collected, and excess toner adheres to the paper P, causing the paper P to be soiled.

In addition, the total rubber area ratio of the cell skeleton portion from the surface layer 76a to a depth of 400 [μm] is set to 31.7% or more and 69.1% or less.

If the total rubber area ratio is less than 31.7 [%], the contact area with the developing roller 33 when the supply roller 34 is mounted and pressed against the developing roller 33 and rotated is small. Scraping property of the toner becomes low. On the other hand, when the total rubber area ratio is larger than 69.1 [%], the opening area of the cell of the surface layer 76a is small, the toner is likely to be clogged in the cell, and the toner supply property to the developing roller 33 becomes low.

As described above, in the present embodiment, the surface cell diameter of the foam layer 76 is set to 280 [μm] or more and 567 [μm] or less, and represents the ratio of the surface cell diameter to the internal cell diameter in the foam layer 76. The cell diameter ratio γ is set to 0.75 or more and 0.93 or less, and the rubber total area ratio of the cell skeleton portion from the surface layer 76a of the foam layer 76 to a depth of 400 [μm] is 31.7 [%. ] And 69.1[%] or less, the development is performed in the state where the nip area is formed between the developing roller 33 and the supply roller 34, that is, in the state where the supply roller 34 is compressed. The toner supply property to the roller 33 and the toner scraping property from the developing roller 33 can be improved.

Therefore, it is possible to sufficiently supply the toner to the developing roller 33 and to sufficiently scrape the toner from the developing roller 33, and it is possible to reliably prevent the image from being blurred or the paper P to be soiled. Can be prevented.

Therefore, the image quality can be surely improved.

Although the printer 10 is described in the present embodiment, the present invention can be applied to an image forming apparatus such as an MFP, a facsimile, and a copying machine.

It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

16Bk, 16C, 16M, 16Y Image forming unit 33 Developing roller 34 Supply roller 76 Foaming layer 76a Surface layer

Claims (13)

In a developer supply member that is rotatably disposed in pressure contact with a developer carrying member in an image forming unit and forms a nip area with the developer carrying member,
(A) The surface cell diameter of the foam layer is set to 280 [μm] or more and 567 [μm] or less,
(B) The cell diameter ratio that represents the ratio of the surface cell diameter to the internal cell diameter in the foam layer is 0.75 or more and 0.93 or less,
(C) The total rubber area ratio of the cell skeleton portion from the surface layer of the foam layer to the depth of the distance defined according to the nip portion area is 31.7% or more and 69.1% or less. A developer supply member characterized in that: The developer supply member according to claim 1, wherein the distance defined according to the nip area is 400 μm. The developer supply member according to claim 1, wherein the foamed layer has an internal cell diameter of 372 [μm] or more and 702 [μm] or less. The development according to claim 2, wherein the total rubber area ratio of the cell skeleton portion from the surface layer of the foam layer to a depth of 100 [μm] is 1.5% or more and 36.5% or less. Agent supply member. The developer supply member according to any one of claims 1 to 4, wherein the foam layer has a hardness of 26 [Asker F] or more and 38 [Asker F] or less. The developer supply member according to claim 1, wherein the foam layer is made of urethane rubber. The developer supply member according to any one of claims 1 to 6, wherein the developer carrying member is formed by coating a cored bar with an elastic layer. The developer supply member according to claim 1, wherein the foam layer is foamed in a mold. The developer supply member according to claim 1, wherein the foam layer is foamed by free foaming. 10. The degree of cohesion of the developer scraped off from the developer carrying member and supplied to the developer carrying member is set to 48 [%] or more and 56 [%] or less. The developer supply member according to. The blow-off charge amount of the developer scraped off from the developer carrying member and supplied to the developer carrying member is 75 [μC/g] or more and 80 [μC/g] or less. The developer supply member according to any one of 1. An image forming unit comprising the developer supply member according to claim 1. An image forming apparatus comprising the image forming unit according to claim 12.

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