JP2022070577A - Developing unit and image forming apparatus - Google Patents

Abstract

To solve the problem in which a supply roller not only has a function to supply developer to a developing roller but has a function to scrape off a developer remaining on a surface of the developing roller; however, these functions are reduced with the lapse of an operating time, which causes a reduction in image quality.SOLUTION: A developing unit comprises: a developing roller 23 that supplies toner to a photoconductor drum 21 and develops a latent image on the photoconductor drum 21; and a supply roller 25 that is arranged in contact with the developing roller 23 to form a nip area, has a foam layer 52 on its surface, and supplies toner to the developing roller. The supply roller 25 has a rotation stress ratio of 0.97 or more and 1.23 or less and an outer diameter change amount of 0.03 [mm] or less.SELECTED DRAWING: Figure 2

Description

An embodiment of the present invention relates to a developing unit used in an electrophotographic printer, a copying apparatus, or the like, and an image forming apparatus including the developing unit.

An electrophotographic image forming apparatus includes a developing unit having a developer carrier for developing a latent image formed on the surface of the image carrier and a developer supplying member for supplying the developer to the developer carrier. (See, for example, Patent Document 1).

JP-A-2019-8140 (see, for example, FIG. 2)

The developer supply member has a function of not only supplying the developer to the developer carrier but also scraping off the developer remaining on the surface of the developer carrier, but these functions deteriorate with the lapse of use time. However, the image quality was deteriorated.

The developing unit of the embodiment of the present invention supplies a developer to the electrostatic latent image carrier and develops the latent image on the electrostatic latent image carrier, and the developing agent carrier and the developing agent carrier. Arranged so as to form a nip region in contact with the developer, the developer has an elastic layer on the surface, and the developer carrier is provided with a developer supply member for supplying the developer.
When a stainless steel indenter having an outer diameter of 16 [mm] and a length of 50 [mm] is pushed 0.73 [mm] into the surface of the end and center of the elastic layer in the extending direction of the nip region. The ratio of the stress at the end to the stress at the center is 0.97 or more and 1.23 or less.
A stainless steel indenter having a square surface having a side of 50 [mm] and a thickness of 10 [mm] having a polishing film having a grain size of 30 [μm] fixed to the surface was used to obtain the polishing film. When 0.73 [mm] is pushed into the elastic layer and the developer supply member is rotated at a peripheral speed of 136.1 [mm / sec],
The developer supply member when the indenter is separated 250 seconds after the indenter has reached 0.73 [mm] with respect to the outer diameter of the developer supply member before the indenter is pushed in. The amount of decrease in the outer diameter of the above is 0.03 [mm] or less.

Another developing unit according to the present invention is a developer carrier that supplies a developer to the electrostatic latent image carrier and develops a latent image on the electrostatic latent image carrier, and the developer carrier. It is arranged so as to form a nip region in contact with the developer, has an elastic layer on the surface, and includes a developer supply member for supplying the developer to the developer carrier.
When a stainless steel indenter having an outer diameter of 16 [mm] and a length of 50 [mm] is pushed 0.73 [mm] into the surface of the end and center of the elastic layer in the extending direction of the nip region. The ratio of the stress at the end to the stress at the center is 0.97 or more and 1.23 or less.
When a tensile test of JIS-K6251 was performed using a dumbbell No. 1 shape test piece formed of the material before the foaming treatment after vulcanization of the elastic layer, the elongation rate when the test piece broke ([[ %]) Divided by the stress at that time ([N / mm ² ]) shall be 72.6 [% / N / mm ² ] or more and 81.6 [% / N / mm ² ] or less. It is characterized by.

According to the embodiment of the present invention, it is possible to suppress the deterioration of the image quality due to the uneven supply of the developer due to the developer supply member and the occurrence of stains and blurring due to the deterioration of the scraping property of the developer.

It is a main part block diagram which shows schematic the main part structure of the printer provided with the development unit by embodiment of this invention. It is a schematic block diagram which shows typically the internal structure of the development unit together with the toner cartridge mounted on the development unit. It is a block diagram which shows the main part structure of the part related to this invention in the control system of a printer. It is an external view which shows the main part structure of the supply roller of Embodiment 1. FIG. It is a flowchart which shows the manufacturing method of a supply roller. It is a figure which shows the spectral intensity distribution obtained by the FT-IR (Fourier transform infrared spectroscopy) analysis of the conductive foam layer made of silicone rubber. It is a figure which shows the spectral intensity distribution obtained by the FT-IR analysis of the conductive foam layer made of urethane rubber. It is explanatory drawing which shows typically the state of the cell wall of the supply roller at the time of initial or continuous printing when the degree of elongation is less than 72.6%, or is more than 81.6%. It is explanatory drawing which shows typically the state of the cell wall of the supply roller at the initial stage or after the rotational stress test when the rotational stress attenuation rate is less than 27.0%, or is more than 31.0%. It is a figure which shows the shape of the test piece of the dumbbell No. 1 shape specified in JIS-K6251. It is a schematic block diagram which provides the explanation of the measuring method of the rotational stress attenuation rate of a supply roller. (A) is a schematic configuration diagram for explaining a measurement method of a simple wear test of a supply roller, and (b) is an external perspective view showing a configuration of an indenter. It is a flowchart which shows the measurement procedure of the outer diameter change amount and weight change amount of a supply roller 25. It is a schematic block diagram used for the explanation of the method of measuring the rotational stress ratio of a supply roller, (a) is a figure at the time of testing an end part, and (b) is a figure at the time of testing a central part. (A) is a diagram schematically showing an image when 2 × 2 (halftone) pattern printing is performed over substantially the entire area of the recording paper, and (b) is a partially enlarged view thereof. It is a characteristic graph which shows the relationship between the toner stirring coefficient k and the rotational stress ratio (B / A).

Embodiment 1.
FIG. 1 is a main part configuration diagram schematically showing a main part configuration of a printer provided with a developing unit according to an embodiment of the present invention.

As shown in FIG. 1, the printer 1 as an image forming apparatus has development units 2K, 2C, 2M, 2Y (particularly distinction) for each color of black (K), cyan (C), magenta (M), and yellow (Y). If it is not necessary to do so, it may be simply referred to as a development unit 2), toner cartridges 3K, 3C, 3M, 3Y for each color (may be simply referred to as toner cartridge 3 if there is no particular need to distinguish). A paper feed cassette 6 that stores and supplies a transfer unit 14, an exposure unit 5K, 5C, 5M, 5Y (may be simply referred to as an exposure unit 5 when it is not necessary to distinguish them), and a recording paper 10 as a recording medium. A fixing unit 7 or the like for fixing a toner image on the recording paper 10 is provided.

The developing unit 2 is transferred from the supply side (upstream side in the paper transport direction) to the discharge side (paper) along the transport path of the recording paper 10 by the transfer unit 14 (horizontal portion of the paper transport path 8 indicated by the alternate long and short dash line in the figure). The development unit 2K, the development unit 2C, the development unit 2M, and the development unit 2Y are arranged in this order toward the downstream side in the transport direction, and each of them is detachably configured with respect to the main body of the printer 1. It should be noted that, for each detachable or movable component such as the developing unit 2 of the printer 1, the portion excluding the component may be referred to as the printer 1 main body.

The toner cartridges 3K, 3C, 3M, and 3Y are toner storages that contain toners 40K, 40C, 40M, and 40Y as unused developing agents (sometimes referred to simply as toner 40 if it is not necessary to distinguish them). The unit 31K, 31C, 31M, 31Y (may be simply referred to as a toner storage unit 31 when it is not necessary to distinguish them) is provided. Then, each of the corresponding developing units 2K, 2C, 2M, and 2Y is detachably configured on the upper part, and the unused toner 40 is supplied to the corresponding developing unit 2 in a mounted state.

The developing units 2K, 2C, 2M, and 2Y all have the same structure, and the photosensitive drums 21K, 21C, 21M, 21Y as the electrostatic latent image carriers corresponding to each have the same structure (when there is no particular need to distinguish them). (Sometimes referred to simply as the photosensitive drum 21), charging rollers 22K, 22C, 22M, 22Y (sometimes simply referred to as charging rollers 22 when there is no particular need to distinguish), developing rollers 23K as a developer carrier. , 23C, 23M, 23Y (may be simply referred to as a developing roller 23 when it is not necessary to distinguish), developing blade 24K, 24C, 24M, 24Y (when it is not particularly necessary to distinguish, simply developing blade 24). (Sometimes referred to as supply roller 25), supply rollers 25K, 25C, 25M, 25Y as developer supply members (may be simply referred to as supply rollers 25 when there is no particular need to distinguish), cleaning blades 27K, 27C, 27M. , 27Y (may be simply referred to as cleaning blade 27 when it is not necessary to distinguish), and first transport unit 28K, 28C, 28M, 28Y (when it is not particularly necessary to distinguish, simply the first transport unit. 28) and the like.

As will be described later, each first transport unit 28 directs the waste toner removed by the corresponding cleaning blade 27 toward the upper side of the paper surface of FIG. 1 which is the axial direction of the photosensitive drum 21 (the positive direction of the Y axis which will be described later). To carry. The second transport unit 29 collectively transports the waste toner sent from each of the first transport units 28 to the waste toner container 32 arranged on the upstream side in the paper transport direction from the developing unit 2K. The waste toner container 32 accommodates the waste toner conveyed by the second transfer unit 29, and is detachably provided with respect to the printer 1 main body.

The X, Y, and Z axes in FIG. 1 have an X axis in the transport direction when the recording paper 10 passes through the four developing units 2, and a Y axis in the rotation axis direction of each photosensitive drum 21. The Z-axis is taken in the direction orthogonal to both of these axes. Further, when each axis of X, Y, and Z is shown in another figure described later, it is assumed that these axial directions indicate a common direction. That is, on the XYZ axes of each figure, the depiction portion of each figure indicates the arrangement direction when the printer 1 shown in FIG. 1 is configured. Further, here, it is assumed that the Z axis is arranged so as to be substantially in the vertical direction.

FIG. 2 is a schematic configuration diagram schematically showing the internal configuration of the developing unit 2 together with the toner cartridge 3 mounted on the developing unit 2. The configuration of the developing unit 2 will be further described with reference to the figure.

The developing unit 2 includes a photosensitive drum 21, a charging roller 22 that uniformly charges the surface of the photosensitive drum 21, and a toner 40 (FIG. 1) on an electrostatic latent image formed on the surface of the photosensitive drum 21 by the exposure unit 5 (FIG. 1). ), A developing roller 23 that regulates the layer thickness of the toner 40 supplied to the developing roller 23, a supply roller 25 that supplies the toner 40 to the developing roller 23, and a recording sheet 10 (FIG. 1). It is provided with a cleaning blade 27 for removing the toner 40 remaining on the photosensitive drum 21 without being transferred to the processing blade 27, and a first transport unit 28 for transporting the toner 40 removed by the cleaning blade 27 as waste toner.

The photosensitive drum 21 is composed of a conductive support and a photoconductive layer, and a blocking layer, a charge generation layer as a photoconductive layer, and a charge transport layer are sequentially laminated on a metal pipe such as aluminum as a conductive support. It is an organic photoconductor having a structure, and rotates in the direction of transporting the recording paper 10 in the positive direction of the X-axis (in the direction of the arrow in the figure).

The charging roller 22 is connected to a charging roller power supply 121 (FIG. 3) that applies a bias voltage having the same polarity as the toner 40, and is composed of a metal shaft and a semi-conductive rubber layer such as epichlorohydrin rubber. The surface of the photosensitive drum 21 is uniformly and uniformly charged by the applied bias voltage.

The developing roller 23 is connected to a developing roller power supply 122 (FIG. 3) that applies a bias voltage having either the same polarity as the toner 40 or the opposite polarity, and has a metal shaft, a semi-conductive urethane rubber layer, and a surface. It is composed of a processing layer and is arranged at a position where it comes into contact with the photosensitive drum 21 with a predetermined pressure contact amount, and rotates in the direction opposite to the rotation of the photosensitive drum 21 (in the direction of the arrow in the figure) with a predetermined peripheral speed ratio. Then, the charged toner 40 is adhered to the electrostatic latent image portion on the photosensitive drum 21 and developed by the applied bias voltage.

The developing blade 24 is connected to a developing roller power supply 122 or a supply roller power supply 123 (FIG. 3) to which a bias voltage having the same polarity as or opposite to that of the toner 40 is applied, and is the length of the developing roller 23. For example, a metal thin plate member having a width substantially the same as the width in the direction and having a thickness of 0.08 [mm]. Further, one end side is fixed, and the inner surface of the other end side slightly inside from the tip portion thereof is arranged so as to be in contact with the peripheral surface of the developing roller 23, and the developing roller 23 is arranged by the applied bias voltage and contact pressure. The toner 40 formed on the peripheral surface is charged to regulate the layer thickness.

The supply roller 25 is connected to a power supply 123 (FIG. 3) for a supply roller that applies a bias voltage having either the same polarity as the toner 40 or the opposite polarity, and is a metal shaft with a core metal 51 (FIG. 4). It is composed of a foam layer 52 (FIG. 4) as an elastic layer of the conductive foamed silicone sponge. The shaft is arranged parallel to the axis of the developing roller 23 at a position where it abuts with a predetermined pressure contact amount so as to form a nip region with the developing roller 23, and as shown by an arrow in the figure, with respect to the rotation of the developing roller 23. The toner is rotated in the same direction (opposite to the contact surface with the developing roller 23) with a predetermined peripheral speed ratio, and the toner replenished from the toner storage unit 31 included in the toner cartridge 3 by the applied bias voltage. 40 is supplied to the developing roller 23. Therefore, the nip region extends in the axial direction of the supply roller 25.

Further, the supply roller 25 charges the toner 40 by the contact frictional force with the developing roller 23, and scrapes off the undeveloped toner on the developing roller 23. The supply roller 25 will be described in detail later.

The cleaning blade 27 is a urethane rubber member arranged at a position where one end thereof abuts on the photosensitive drum 21 with a predetermined pressure contact amount. The first transport unit 28 transports the toner 40 and the deposits removed by the cleaning blade 27 as waste toner toward the upper side of the paper surface (plus direction of the Y axis) in FIG. 2 which is the axial direction of the photosensitive drum 21.

To the toner accommodating portion 38, the toner 40 supplied from the toner cartridge 3 mounted on the developing unit 2 via the toner supply port 35 is conveyed to the stirring member 37 to be agitated and to evenly level the toner 40 in the Y-axis direction. The screw 36 is arranged.

Specifically, the toner accommodating portion 38 has a length of 150.03 [mm] in the longitudinal direction and a length of 64.0 [mm] in the lateral direction, and has a length of the toner supply port 35 in the longitudinal direction. The length is 15.0 [mm] and the length in the lateral direction is 9.7 [mm]. Here, the ratio of the length in the longitudinal direction of the toner supply portion 35 to the length in the longitudinal direction of the toner accommodating portion 38 is 15.0 [mm] / 150.03 [mm] = 0.099. In the present embodiment, the toner supply unit 35 is arranged substantially at the center of the toner storage unit 38 in the longitudinal direction of the toner storage unit 38. Therefore, in the longitudinal direction of the toner accommodating portion 38, the toner supply port 35 is shorter than the toner accommodating portion 38, and the toner is not directly supplied to both ends of the toner accommodating portion 38. Further, since the toner supplied from the toner supply port 35 is evenly distributed in the Y-axis direction by the stirring member 37 and the transport screw 36, there is no configuration for transporting the toner from both ends of the toner accommodating portion 38 to the central portion. .. Therefore, the toner whose characteristics have changed as compared with the new toner, that is, the so-called deteriorated toner, tends to accumulate at both ends of the toner accommodating portion 38 due to the peeling of the external additive.

The developing unit 2, the toner cartridge 3, the waste toner container 32, and the like are all replacement units, and can be replaced when the toner is consumed or the components are deteriorated and the life is reached.

In FIG. 1, the exposure units 5K, 5C, 5M, and 5Y are LED heads including a light emitting element such as an LED (Light Emitting Diode) and a lens array, and correspond based on the print data input by the printer 1. The surfaces of the photosensitive drums 21K, 21C, 21M, and 21Y are each irradiated with light to attenuate the potential of the exposed portion to form an electrostatic latent image.

The paper cassette 6 accommodates the recording paper 10 in a stacked state inside, and is detachably attached to the lower part of the printer 1. At the upper part of the paper feed cassette 6 on the paper feed side, there is a paper feed section (not shown) equipped with a hopping roller or the like that separates the recording paper 10 one by one and feeds it to the paper transport path 8 (indicated by the alternate long and short dash line in the figure). It is arranged. A transport roller (not shown) is arranged at a key point of the paper transport path 8, and the recording paper 10 is sequentially transported to the downstream side.

The transfer unit 14 is paired with a transfer belt 9 that electrostatically attracts the recording sheet 10 and conveys it to the downstream side, a drive roller 11 that is rotated in the direction of an arrow by a drive unit (not shown) to drive the transfer belt 9, and a drive roller 11. The tension roller 12 on which the transfer belt 9 is stretched and the photosensitive drums 21K, 21C, 21M, and 21Y are arranged so as to face each other via the transfer belt 9 and rotate in the direction of the arrow to record a toner image. It is provided with transfer rollers 4K, 4C, 4M, and 4Y (may be simply referred to as transfer rollers 4 when it is not necessary to distinguish them) to be transferred to the paper 10.

A transfer roller power supply 124 (FIG. 3) for applying a bias voltage of opposite polarity to the toner 40 is connected to each transfer roller 4, and is formed on the corresponding photosensitive drum 21 by the applied bias voltage. The toner images are sequentially superimposed and transferred to the recording paper 10.

The fixing unit 7 is arranged on the downstream side of the developing unit 2 in the paper transport path 8, and includes a heating roller 7a, a pressure roller 7b, a thermistor (not shown), and a heating heater. In the heating roller 7a, for example, a hollow cylindrical core metal made of aluminum or the like is coated with a heat-resistant elastic layer of silicone rubber, and a PFA (tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer) tube is coated therein. Is formed by. A heating heater such as a halogen lamp is provided in the core metal.

The pressure roller 7b has a structure in which a heat-resistant elastic layer of silicone rubber is coated on a core metal made of, for example, aluminum, and a PFA tube is coated on the core metal, so that a pressure contact portion is formed between the pressure roller 7b and the heating roller 7a. It is arranged in. The thermistor is a means for detecting the surface temperature of the heating roller 7a, and is arranged in the vicinity of the heating roller 7a in a non-contact manner.

The surface temperature of the heating roller 7a is maintained at a predetermined temperature by a heating heater whose temperature is controlled by the fixing control unit 127 (FIG. 3) based on the surface temperature detected by the thermistor. When the recording paper 10 on which the toner image is transferred passes through the pressure contact portion formed by the temperature-controlled heating roller 7a and the pressure roller 7b, the toner image on the recording paper 10 is caused by the heat and pressure applied at the time of passing. Is established.

FIG. 3 is a block diagram showing a main configuration of a portion of the control system of the printer 1 related to the present invention. Hereinafter, this control system will be described with reference to FIGS. 1 and 2.

In the figure, the control unit 101 is composed of a ROM, a RAM, an input / output port, a timer, and the like, and receives print data and control commands from a higher-level device (not shown) via an I / F (Interface) control unit 111 to be a printer. 1 Control the entire sequence and perform printing operations. The reception memory 112 temporarily records the print data input from the host device via the I / F control unit 111, and the image data editing memory 113 receives the print data recorded in the reception memory 112 and the print data thereof. The image data formed by the editing process of the print data, that is, the image data is recorded.

The operation unit 114 includes an LED for displaying the state of the printer 1 and a switch and a display unit for giving an instruction from the operator to the printer, and the sensor group 115 includes various types for monitoring the operating state of the printer 1. The sensor includes, for example, a paper position detection sensor, a temperature / humidity sensor, a concentration sensor, and the like.

The charging roller power supply 121 applies a voltage to the charging roller 22 according to the instruction of the control unit 101 to charge the surface of the photosensitive drum 21, and the developing roller power supply 122 adheres the toner 40 to the electrostatic latent image. A predetermined voltage is applied to the developing roller 23, the power supply 123 for the supply roller applies a predetermined voltage to the supply roller 25 in order to supply the toner 40 to the developing roller 23, and the power supply 124 for the transfer roller is the photosensitive drum 21. A predetermined voltage is applied to the transfer roller 4 in order to transfer the toner image formed on the sheet to the recording paper 10. The voltage of the charging roller power supply 121, the developing roller power supply 122, and the supply roller power supply 123 can be changed according to the instruction of the control unit 101.

The fuse power supply 125 is a fuse power supply that allows a current to flow through a fast-acting fuse 130 that determines whether the developing unit 2 is an unused product, and the head drive control unit 126 is an image data recorded in an image data editing memory 113. Is sent to the exposure unit 5 to drive the light emission of the LED. The fixing control unit 127 heats and drives the heating heater of the fixing unit 7 to control the surface temperature of the heating roller 7a and controls the rotation of the pressure roller 7b in order to fix the transferred toner image on the recording paper 10. do.

The transport motor control unit 128 rotates and controls the paper transport motor 131 for transporting the recording paper 10, and the transport motor control unit 128 transports or stops the recording paper 10 at a predetermined timing according to the instruction of the control unit 101. Let me do it. The drive control unit 129 drives a drive motor 132 for rotating the photosensitive drum 21. When the drive motor 132 is rotationally driven by the drive control unit 129, the photosensitive drum 21 rotates in the direction of the arrow as shown in FIG. 2, and the charging roller 22, the developing roller 23, and the supply roller 25 rotate at predetermined positions, respectively. Rotate in the direction of the arrow at speed.

The dot counter 101a counts the number of dots required for printing from the image data editing memory 113, and the drum counter 101b counts the number of rotations of the photosensitive drum 21 rotated during the printing operation. The calculation unit 101c performs a calculation based on the temperature read from the sensor group 115 and the rotation speed of the drum counter 101b, and determines whether or not a rotation flag is generated.

FIG. 4 is an external view showing a main configuration of the supply roller 25 according to the first embodiment. The configuration of the supply roller 25 will be further described with reference to the figure.

The supply roller 25 has a core metal 51 of φ6 [mm] as a support shaft as a conductive support, and a foam layer 52 of φ13 [mm] and a length of 221.4 [mm] in the longitudinal direction is provided on the outside thereof. Is forming. Innumerable cells exist in the foam outer layer 52a and the inner inner layer 52b of the foam layer 52. The rubber material of the foam layer 52 includes urethane rubber, silicone rubber, EPDM rubber, acrylic rubber, ethylene propylene rubber, styrene butadiene rubber, acrylonitrile / butadiene rubber, butadiene rubber, isoprene rubber, acrylic rubber, chloroprene rubber, and butyl rubber. Etc. are used. In particular, in recent years, urethane-based and silicone-based products have become the mainstream.

The core metal 51 may be any metal as long as it has a predetermined rigidity and sufficient conductivity, and for example, iron, copper, brass, stainless steel, aluminum, nickel and the like are used. Further, a material other than metal can be used as long as it has conductivity and appropriate rigidity. For example, a resin molded product in which conductive particles are dispersed, ceramics, or the like can be used. Further, in addition to the roll shape, the pipe shape in the air may be used. Further, both ends of the core metal 51 may have gear mounting steps or may have pin holes, and in this case, both ends thereof may have a smaller diameter than the portion having the foam layer 52.

The outer diameter of the foam layer 52 may be constant in the axial direction, a crown shape in which the outer diameter decreases as it approaches the axial end of the supply roller 25, and an outer diameter as it approaches the axial end of the supply roller 25. It may have an inverted crown shape or a tapered shape in which the diameter increases, or a shape having different diameters at both ends, but for the reason described later, the inverted crown shape is preferable in this embodiment.

Next, a general manufacturing method of the supply roller 25 will be described. FIG. 5 is a flowchart showing a manufacturing method of the supply roller 25. First, a filler, a foaming agent and a cross-linking agent are added to the above-mentioned rubber material (step S101).

Fillers include reinforcing fillers and conductive fillers. As the reinforcing filler, for example, silica (aerosol silica or settling silica), reinforcing carbon black and the like can be used. As the conductive filler, for example, conductive carbon black, metal powder such as nickel, aluminum and copper, metal oxide such as zinc oxide, barium sulfate, titanium oxide, potassium titanate and the like are coated with tin oxide. Things can be used. Here, titanium, reinforcing carbon black, and conductive carbon black are used as the filler.

As the foaming agent, an azo compound-based foaming agent (here, azobisisobutynitrile: AIBN) is used. However, instead of the azo compound-based foaming agent, a bicarbonate-based, isocyanate-based, nitrite, hydradina derivative, azide compound-based foaming agent, or the like may be used.

As the cross-linking agent (vulcanizing agent), a peroxide and a sulfur-based vulcanizing agent are used. However, instead of these, hydrogensiloxane in the presence of a platinum catalyst, an isocyanate agent, or the like may be used.

A rubber material to which a filler, a foaming agent and a cross-linking agent are added is mixed and kneaded using a pressurized kneader, a mixing roll or the like (step S102).

The kneaded rubber composition is filled in an extrusion molding machine and extruded around the core metal 51 (step S103). As a result, a cylindrical rubber composition is formed on the surface of the core metal 51. Hereinafter, a material obtained by molding a rubber composition (rubber compound) on the surface of the core metal 51 is referred to as a roller body.

Next, the roller body thus formed is set in a heating furnace and heated to a temperature required for vulcanization of rubber (step S104). In this step (primary vulcanization step), vulcanization of rubber proceeds, but foaming does not occur.

After the primary vulcanization step, a pre-vulcanization step for foaming (step S105) is performed. In the pre-vulcanization step, the roller body is heated at a higher temperature than the above-mentioned primary vulcanization step. As a result, foaming occurs to form bubbles (cells), and vulcanization of rubber also proceeds. Step S105 and step S1207 described later are referred to as foaming treatment.

After the pre-vulcanization step, the roller body is taken out from the heating furnace, and the outer periphery of the foam layer of the roller body is roughly polished (step S106). Here, the range of the thickness number [mm] of the outer periphery (surface) of the foam layer is removed by rough polishing. In the primary vulcanization step and the pre-vulcanization step described above, a skin layer having small bubbles is formed on the outer periphery of the foam layer, and this skin layer is removed by rough polishing.

Then, the roughly polished roller body is set in the heating furnace, and the secondary vulcanization step (step S107) is performed. In the secondary vulcanization step, the roller body is heated to a temperature higher than the heating temperature in the primary vulcanization step. As a result, further foaming occurs, and vulcanization of rubber also proceeds.

In the secondary vulcanization step, since the skin layer is removed in advance, the bias (distortion) of the crosslinked state of the rubber is suppressed, and the bubbles are uniformly (that is, uniform in size over the entire surface of the foam layer). ) Can be formed. Further, in the secondary vulcanization step, the small molecule siloxane derived from silicone is removed by volatilization, but since the skin layer is removed from the surface of the foam layer as described above, the small molecule siloxane is effectively removed. can do.

After the secondary vulcanization step, the surface of the foam layer of the roller body is finished by polishing to obtain a predetermined outer diameter (step S108). As a result, the supply roller 25 having the conductive foam layer 52 formed on the surface of the core metal 51 is formed (step S109).

It is also possible to extrude the rubber pound into a tube shape in advance and heat it to vulcanize and foam it to form a sponge rubber tube, which is then covered with the core metal 51 to form the supply roller 25. At this time, if necessary, the core metal 51 and the conductive foam layer 52 may be fixed with an adhesive. In this embodiment, silicone rubber is used as the rubber material of the conductive foam layer 52. The foam layer 52 of the supply roller 25 using silicone rubber has a plurality of cells in an independent cell state. Since silicone rubber has closed cells, it is most preferable to use silicone rubber as a main component.

In the case of the conductive foam layer having open cells, the toner can penetrate deep into the bubbles, so that the toner may be clogged in the bubbles. Therefore, as the number of prints by the image forming apparatus increases, the amount of toner clogged in the bubbles increases, and as a result, the hardness and electrical resistance of the conductive foam layer increase, and image unevenness (cassoulet) due to insufficient supply of sonar occurs. It can occur. On the other hand, in the case of the conductive foam layer having closed cells, the toner does not penetrate deep into the bubbles, and the toner in the bubbles is less likely to be clogged. Therefore, even if the number of prints by the image forming apparatus increases, the hardness and electrical resistance of the conductive foam layer do not increase much, and the occurrence of image unevenness (cassoulet) is suppressed.

Here, a method for calculating the silicone ratio and the urethane ratio, which are the materials of the supply roller 25, will be described.

A square sample having a side of 1 [cm] was cut out from the conductive foam layer 52 of the supply roller 25, and FT-IR (Fourier transform infrared spectroscopy) analysis was performed. The analysis range was set to a wave number of 400 to 4000 [cm ^-1 ].

FIG. 6 is a diagram showing a spectral intensity distribution obtained by FT-IR (Fourier transform infrared spectroscopy) analysis of a conductive foam layer 52 made of silicone rubber. In FIG. 6, the peak of SiO ₂ is seen at the wave number 778 [cm ^-1 ], the peak of Si—O—Si is seen at the wave number 995 [cm ^-1 ], and the peak of SiC is seen at the wave number 1254 [cm ^-1 ]. Can be seen.

FIG. 7 is a diagram showing the spectral intensity distribution obtained by FT-IR analysis of the conductive foam layer 52 made of urethane rubber. In FIG. 7, the peak of CO is seen at the wave number 1721 [cm ^-1 ], and the peak of NH is seen at the wave number 2937 [cm ^-1 ].

Even if the conductive foam layer 52 of the supply roller 25 contains silicone rubber and another substance (for example, urethane rubber), the main component of the silicone rubber may be 50% by weight or more. Further, the silicone rubber may be a modified silicone rubber.

The supply roller 25 of the present embodiment limits the specific elements of the specifications of the foam layer 52 as described later, but here, various supply rollers are not limited thereto. Distinguished as 25', each element will be described below.

(About product hardness)
It is desirable that the conductive foam layer 52 of the supply roller 25'is used with a low hardness of Asker F hardness of 40 or more and 46 or less. This is because when the hardness of the supply roller 25'is higher than the above range, the graininess (dot formation) deteriorates due to the increase in the load of toner damage, and the wear of the toner and members increases because the pressure at the contact portion is increased. However, there is a drawback that it is not suitable for high durability. On the contrary, if it is lower than the above range, the amount of the foaming agent used for hardness adjustment becomes excessive and it is difficult to manufacture, and even if it is manufactured, the unevenness of the foaming state in the roller is large and the quality is not stable. Difficult to use.

A foaming agent such as AIBN (Azobisisobutyronirile) is used to adjust the hardness of the supply roller 25', and the hardness is adjusted by the amount of the foaming agent. By using the foaming agent, the foaming ratio of the sponge is increased, and it is possible to change the size of the foaming cell and the thickness of the cell wall.

(About stretchability)
The degree of elongation of the supply roller 25'in the solid state is within the range of 72.6 [% / N / mm ² ] or more and 81.6 [% / N / mm ² ] or less according to the test results described later. Is desirable. The degree of elongation here is the elongation rate [%] of the rubber test piece at the time of breaking when the solid is stretched in the tensile test, and the maximum stress (breaking strength) required to pull the solid to break it. Refers to the value divided by. It is considered that the higher this value is, the easier it is to expand in the rotation direction when compressed and rotated, and conversely, the lower this value is, the more difficult it is to extend in the rotation direction, and conversely, it is easy to break (wear). The method for measuring the degree of elongation will be described in detail later.

FIG. 8 is an explanatory diagram schematically showing the state of the cell wall of the supply roller 25'during initial or continuous printing when the elongation is less than 72.6% or exceeds 81.6%.

As shown in the figure, when the degree of elongation is less than 72.6 [% / N / mm ² ], the supply roller 25'when rotated while being niped with the developing roller (developer carrier) 23. The cell wall is hard to stretch, and the cell wall is easily torn, that is, easily worn by the pressure in the rotation direction. As a result, when the supply roller 25'is used, wear accelerates during continuous printing, the nip width with the developing roller 23 becomes smaller, and the undeveloped toner on the developing roller 23 cannot be scraped off, so that stains occur. do.

On the contrary, when the degree of elongation exceeds 81.6 [% / N / mm ² ], the supply roller is as shown in FIG. 8 when rotated while being niped with the developing roller (developer carrier) 23. The 25'itself is easy to stretch in the rotation direction, and the cell wall is laid down in the rotation direction during continuous printing, so that it is easy to settle. As a result, the stress in the vertical direction is reduced, and as a result, the stress on the developing roller 23 is reduced. Due to this cause, the undeveloped toner on the developing roller 23 cannot be scraped off, so that stains occur. From the above, it is desirable that the degree of elongation of the supply roller 25'in the solid state is within the range of 72.6 [% / N / mm ² ] or more and 81.6 [% / N / mm ² ] or less. It can be said that.

The term "dirt" as used herein means that the toner adheres to the background portion of the image, that is, the non-image portion of the printed matter, due to the toner having a higher charge amount than the normally charged toner, that is, the so-called overcharged toner. .. In the present embodiment, since the negatively charged toner is used, "dirt" is generated by the excessively negatively charged toner.

(About rotational stress attenuation rate)
The rotational stress attenuation rate of the conductive foam layer 52 of the supply roller 25'is preferably in the range of 27% or more and 31% or less according to the test results described later. The rotational stress damping rate referred to here refers to the damping rate with respect to the initial stress after the rotational stress test in which a metal indenter is pushed 0.73 mm into the foam layer 52 of the supply roller 25'and compressed and rotated for 6 hours. The method for measuring the rotational stress attenuation factor will be described in detail later.

FIG. 9 is an explanatory diagram schematically showing the state of the cell wall of the supply roller 25'after the initial or rotational stress test when the rotational stress attenuation rate is less than 27.0% or exceeds 31.0%. Is.

As shown in the figure, when the rotational stress attenuation rate is less than 27%, the supply roller 25'has a high hardness or is in a state of being hard to be deformed, so that the contact rotation with the developing roller (developer carrier) 23 is performed. Even at times, the 25'conductive foam layer 52 of the supply roller tries to maintain its pre-deformed shape. Therefore, strong pressure is applied to the contact member such as the developing roller 23, which causes a problem that the load torque of the photosensitive drum 21 increases. In addition, this may cause damage to the surface layer of the developing roller 23, causing filming of the developing roller 23 and the like, which may cause printing defects.

On the contrary, when the rotational stress attenuation rate exceeds 31%, the strainability of the supply roller 25'is poor, that is, the recovery of the elasticity of the pushed portion of the foam layer 52 is slow, so that it is easy to settle. After 6 hours, the contact pressure with the developing roller (developer carrier) 23 during rotation is weak, and the undeveloped toner of the developing roller 23 cannot be sufficiently scraped off, resulting in stains. From the above, it can be said that the rotational stress attenuation rate of the supply roller 25'is preferably 27% or more and 31% or less.

Here, the measurement results by the simple wear test adopted to specify the “wear (amount)” and the “settle” described above in detail will be described.

(About simple wear test)
In the simple wear test, the supply roller 25'before and after pressing the vicinity of the center of the rotating supply roller 25' against the metal indenter to which the wrapping film having a particle size of 30 [μm] (# 600) is attached for 250 seconds. It measures the weight and the outer diameter of the pressing part. The weight change of the supply roller 25'after the simple wear test is referred to as a weight change amount [g], and the outer diameter change amount of the indenter nip portion after the wear test is shown as an outer diameter change amount [mm]. The measuring method of the simple friction test will be described in detail later.

The weight change amount [g] can represent the wear amount of the conductive foam layer 52 of the supply roller 25'. This amount of weight change is generated by scraping (wearing) the cell wall of the foam layer 52 when the wrapping film is contact-rotated.

The outer diameter change amount [mm] can represent a state due to wear and a state due to settling of the conductive foam layer 52 of the supply roller 25'. When the amount of change in the outer diameter is large, there are a state where it is scraped due to wear and a state where the cell wall is lying down and settled. When the amount of change in weight of the foam layer 52 is large and the amount of change in outer diameter is large, it can be said that the influence of wear is strong. Further, when the amount of change in weight of the foam layer 52 is small, but the amount of change in outer diameter is large, it can be said that the outer diameter has become smaller because the cell wall is lying down and settled, although it is not worn.

According to the test results described later, it is desirable that the outer diameter change amount of the supply roller 25'at the nip portion before and after the simple wear test is 0.03 mm or less and the weight change amount is 0.07 g or less. If the provisions other than the above are specified, a state due to wear or settling occurs, and as described above, the residual toner of the developing roller (developer carrier) 23 after development cannot be sufficiently scraped off and stains occur. Resulting in. Therefore, it is desirable that the amount of change in the outer diameter of the supply roller 25'at the nip portion before and after the simple wear test is 0.03 mm or less and the amount of change in the weight of the supply roller 25'is 0.07 g or less.

(About rotational stress ratio)
The ratio B / A (rotational stress ratio) of the stress A [N] at the center and the stress B [N] at the ends when the supply roller 25'is rotating is 0.97 or more and 1.23 according to the test results described later. The following is desirable. The rotational stress here is based on the position where the metal roller of φ13.0 (mm) comes into contact with the outermost surface, and the metal indenter is pushed 0.73 mm onto the conductive foam layer 52 of the supply roller 25'from there. It refers to the maximum stress [N] when the roller is rotated when it is loaded. The rotational stress ratio refers to the ratio (B / A) of the rotational stress A [N] at the central portion and the rotational stress B [N] at the edges. The method for measuring the rotational stress ratio will be described in detail later.

When the rotational stress ratio exceeds 1.23, the pressure on the end side of the supply roller 25'is increased, which increases the torque load of the photosensitive drum 21 and the toner damage on the end side, resulting in graininess (dots). Deterioration of reproducibility) occurs.

When the rotational stress ratio is 0.97 or less, the nip width with the developing roller 23 becomes small, and the efficiency of supplying toner to the developing roller 23 and scraping off the residual toner of the developing roller 23 after development deteriorates. Further, as continuous printing is performed, the nip width with the developing roller 23 on the end side decreases due to wear on the supply roller 25'side, and the supplyability and scraping property further decrease, so that the durability of the developing unit 2 is reduced. The sex gets worse. In particular, when the drum count is 30 k or more, the toner supply on the end side of the supply roller 25'is uneven, and partial blurring occurs at the solid end. Further, the occurrence of this blurring is also due to a decrease in toner supply to the developing roller 23 because the deteriorated toner tends to accumulate at both ends due to the old toner being pushed into both ends. This tendency is particularly remarkable when the toner supply port 35 is provided near the center of the toner accommodating portion 38 as in the present embodiment. Further, in the present embodiment, the ratio of the toner supply port 35 in the longitudinal direction to the length of the toner accommodating portion 38 in the longitudinal direction is 0.099, but if the ratio becomes larger, the toner is supplied from the toner supply port. Since the property is improved, it is possible to further suppress the blurring.

As described above, the ratio B / A (rotational stress ratio) of the stress A [N] at the center and the stress B [N] at the ends during rotation of the supply roller 25'is 0.97 or more and 1.23 or less. desirable.

For example, by forming an inverted crown shape in which the outer diameter on the end side of the supply roller 25'is larger than that in the center portion and making the stress on the end portion higher than that in the center portion, the supply roller 25'side can be used over time for continuous printing. Since the decrease in the nip width with the developing roller 23 on the end side due to wear can be suppressed, the toner supply property is maintained and the life of the developing unit 2 becomes long. In addition, the larger the rotational stress ratio (closer to 1.23) within the specified range, the higher the agitation of the toner, so the end side where old toner tends to stay also tends to mix with the center side where there is a lot of fresh toner. Therefore, it is possible to obtain a high-quality image with a long life.

Next, each measurement method of the degree of elongation, the rotational stress damping rate, the simple wear test, and the rotational stress ratio will be described.

(Measurement method of elongation)
In the measurement of the degree of elongation, the material (solid rubber material) after vulcanization and before the foaming treatment of the rubber material constituting the conductive foam layer 52 of the supply roller 25'is used as shown in FIG. -A test piece 209 having a dumbbell No. 1 shape specified in K6251 was formed. The test piece 209 is a plate-shaped piece long in one direction, and has a parallel portion 209a in the center in the longitudinal direction and grip portions 209b at both ends in the longitudinal direction. The material after vulcanization and before the foaming treatment is a material after the vulcanization step of step S104 and before the pre-vulcanization step of step S105 in the manufacturing process described with reference to FIG.

In FIG. 10, numbers other than the reference numerals 209, 209a, and 209b represent dimensions, and the unit is [mm]. The total length of the test piece 209 is 120 [mm], and the distance between the marked lines is 80 [mm]. The width of the parallel portion 209a of the test piece 209 is 10 [mm], and the maximum width of each grip portion 209b is 25 [mm].

The test piece 209 was attached to a tensile tester, and a tensile test based on JIS-K6251 was performed. The gripping portions 209b at both ends of the test piece 209 were gripped by a pair of upper and lower chucks (grasping portions) of the tensile tester, and a tensile force was applied in the longitudinal direction. The distance between the chucks of the test piece 209 was set to 80 [mm]. The tensile speed by the tensile tester was set to 500 [mm / min].

When a tensile force is applied to the test piece 209 in this way and the test piece 209 breaks, the elongation rate of the test piece 209 is defined as the elongation rate E [%]. More specifically, the elongation ratio E [%] is the ratio of the length of the test piece 209 at break to the length 120 [mm] of the test piece 209 before tension.

Further, the stress at break of the test piece 209 measured by the load cell of the tensile tester is defined as the stress S [N / mm ² ].

Here, the value obtained by dividing the elongation rate E [%] of the test piece 209 at break by the stress S [N / mm ² ] at break is defined as the elongation degree [% / (N / mm ² )]. .. The higher the degree of elongation, the easier it is for the conductive foam layer 52 to expand and deform in the rotational direction when it is compressed and rotated, and the lower the degree of elongation, the more difficult it is for the conductive foam layer 52 to extend in the rotational direction, and when it deforms. It is considered that it is easily broken (weared).

(Measurement method of rotational stress attenuation rate)
A method for measuring the rotational stress attenuation rate of the supply roller 25'will be described with reference to FIG. FIG. 11 is a schematic configuration diagram for explaining a method for measuring the rotational stress damping rate of the supply roller 25'.

The measurement of the rotational stress damping rate of the supply roller 25'here was carried out using a compression tester manufactured by Instron (model name: INSTRON 5543A). As shown in FIG. 11, both ends of the core metal 51 of the supply roller 25'are rotatably placed on the rotary support member 201. In this state, the supply roller 25'is rotated at a rotation speed of 200 [rpm] (peripheral speed 136.1 [mm / sec]), and the foam layer 52 in the rotating state has a cross-sectional outer diameter of 16 [mm] and a length of 50 [. The indenter 205, which is a SUS cylinder of [mm], is pushed to 0.73 [mm] at a compression rate of 10 [mm / min] to bring it into a rotating state, and the state is maintained for 6 hours.

The rotational stress attenuation rate indicates how much the stress of the supply roller 25'after 6 hours is attenuated with respect to the initial stress. That is, the rotational stress attenuation rate can be expressed by the following equation.
Rotational stress damping rate [%] = (1- (Stress [N] of supply roller 25 after 6H]
/ Initial push-in stress [N]))) x 100

(Simple friction test method)
A measurement method of a simple wear test for measuring the amount of change in the outer diameter and the amount of change in the weight of the supply roller 25'will be described with reference to FIG. FIG. 12A is a schematic configuration diagram for explaining a measurement method for a simple wear test of the supply roller 25', and FIG. 12B is an external perspective view showing the configuration of the indenter 206.

The measurement of the simple wear test of the supply roller 25'here was carried out using a compression tester manufactured by Instron (model name: INSTRON 5543A). As shown in FIG. 12A, both ends of the core metal 51 of the supply roller 25'are rotatably placed on the rotary support member 201. In this state, the supply roller 25'is rotated at a rotation speed of 200 [rpm], and the indenter 206 is brought into contact with the foam layer 52 in the rotated state.

As shown in FIG. 12 (b), the indenter 206 has a square surface having a side of 50 [mm] and has a particle size of 30 on one surface of a metal plate 206a made of SUS having a thickness of 10 [mm]. A lapping (polishing) film (20 mm × 50 mm) 206b of [μm] (# 600) is attached by center distribution. The indenter 206 is applied to the foam layer 52 of the supply roller 25'rotating at a rotation speed of 200 [rpm] (peripheral speed 136.1 [mm / sec]) at a compression speed of 10 [mm / min]. Push it up to 73 [mm] and keep it in that state for 250 seconds.

FIG. 13 is a flowchart showing a procedure for measuring the outer diameter change amount and the weight change amount of the supply roller 25'. First, before the start of the simple wear test, the weight of the supply roller 25'(weight w1) is measured (step S201).

Next, the outer diameter (referred to as the outer diameter d1) of the supply roller 25'is measured (step S202). Further, in the contact region C (FIG. 12A) of the supply roller 25'with the indenter 206, the outer diameters were measured at 9 points at equal intervals in the axial direction, and the average value was obtained. An automatic roller diameter measuring device "RM202" manufactured by Apollo Seiko Co., Ltd. was used for measuring the outer diameter of the supply roller 25'.

Then, as described above, the supply roller 25'is rotated at a rotation speed of 200 [rpm] (peripheral speed 136.1 [mm / sec]), and the indenter 206 is pushed in at a speed of 10 [mm / min] to form a conductive foam layer. When it is pushed into 52 and the pushing amount reaches 0.73 [mm], the supply roller 25'is rotated for 250 seconds while maintaining that state, and the indenter 206 is separated from the conductive foam layer 52 (step S203).

In this state, the outer diameter of the supply roller 25'(referred to as the outer diameter d2) is measured (step S204), and the weight of the supply roller 25'(referred to as the weight w2) is further measured (step S205).
The method of measuring the weight and the outer diameter of the supply roller 25'is as described in steps S201 and S202.

From the weights w1 and w2 of the supply rollers 25 obtained in steps S201 and S205, the weight change amount (w1-w2) of the supply rollers 25'was obtained. The amount of weight loss of the supply roller 25 reflects the amount of wear of the supply roller 25'.

Further, the amount of change in the outer diameter of the supply roller 25'(d1-d2) was obtained from the outer diameters d1 and d2 of the supply rollers 25'obtained in steps S202 and S204. The amount of decrease in the outer diameter of the supply roller 25'reflects the amount of wear of the supply roller 25 and the degree of collapse of the cell wall (the degree of settling).

(Measurement method of rotational stress ratio)
Next, a method of measuring the rotational stress ratio of the supply roller 25'will be described with reference to FIG. 14A and 14B are schematic configuration diagrams for explaining a method for measuring the rotational stress ratio of the supply roller 25', FIG. 14A is a diagram for testing an end portion, and FIG. 14B is a diagram for testing a central portion. It is a figure at the time of testing.

The measurement of the rotational stress ratio of the supply roller 25'here was carried out using a compression tester manufactured by Instron (model name: INSTRON 5543A). As shown in FIG. 14, both ends of the core metal 51 of the supply roller 25'are rotatably placed on the rotary support member 201. In this state, the supply roller 25'is rotated at a rotation speed of 200 [rpm], and an indenter 205, which is a SUS cylinder having an outer diameter of 16 [mm] and a length of 50 [mm], is attached to the foam layer 52 in the rotated state. , Push to 0.73 [mm] at a compression speed of 10 [mm / min].

When pushing in, the position in contact with the outermost surface of the metal roller of φ13.0 [mm] is estimated as the reference height in advance, and from that reference height, the metal indenter 205 is applied to the conductive foam layer 52 of the supply roller 25'. Was pushed in 0.73 [mm] to measure. As shown in FIGS. 14A and 14B, the above measurement was performed on the central portion and the end portion side, and the maximum stress (rotational stress) from the rotating supply roller 25'was measured. At this time, the value obtained by dividing the rotational stress B [N] at the end by the rotational stress A [N] at the central portion was calculated as the rotational stress ratio (B / A).

In the present embodiment, the length of the foam layer 52 in the longitudinal direction is 221.4 mm, and the length of the indenter 205 in the longitudinal direction is 50 [mm]. Therefore, the measurement at the central portion referred to here is an indenter arranged in the central portion (position of 110.7 [mm] ± 20 [mm] from the end portion) in the longitudinal direction of the foam layer 52 by center distribution. This corresponds to arranging and measuring the central portion of 205 (position 25 [mm] from the end portion) so as to overlap each other.

Next, the extension degree of the supply roller 25'is 72.6 [% / N / mm ² ] or more and 81.6 [% / N / mm ² ] or less, and the rotational stress attenuation rate is 27% or more and 31% or less. , The printing test and the test result which became the basis for setting the rotational stress ratio to 0.97 or more and 1.23 or less will be described.

Table 1 lists 13 types of supply rollers 25'prepared as test samples with different specifications, Examples 1 to 6 and Comparative Examples 1 to 7, and the evaluation results of the printing test conducted using these. It was done.

As shown in the table, the supply rollers 25'as the 13 types of test samples of Examples 1 to 6 and Comparative Examples 1 to 7 have different degrees of elongation, rotational stress attenuation rate, and rotational stress ratio. Here, 13 types of supply rollers 25'as test samples will be described.

The supply roller 25'of Example 1 has an elongation degree of 81.6 [% / N / mm ² ], a rotational stress attenuation rate of 28 [%], and a rotational stress ratio of 1.23. The foam layer 52 is thicker on the edge side than in the central portion, the amount of wear on the rubber portion is small, the sample is not settled, and the toner is well agitated.
The supply roller 25'of Example 2 has an elongation degree of 72.6 [% / N / mm ² ], a rotational stress attenuation rate of 29 [%], and a rotational stress ratio of 1.23. The foam layer 52 is thicker on the edge side than in the central portion, the amount of wear on the rubber portion is small, the sample is not settled, and the toner is well agitated.
The supply roller 25'of Example 3 has an elongation degree of 81.6 [% / N / mm ² ], a rotational stress attenuation rate of 28 [%], and a rotational stress ratio of 0.97. The thickness of the foam layer 52 is the same as that of the central portion and the end portion, the amount of wear of the rubber portion is small, and the sample is not settled.

The supply roller 25'of Example 4 has an elongation degree of 72.6 [% / N / mm ² ], a rotational stress attenuation rate of 27 [%], and a rotational stress ratio of 1.09. The foam layer 52 is thicker on the edge side than in the central portion, the amount of wear on the rubber portion is small, the sample is not settled, and the toner is well agitated.
The supply roller 25'of Example 5 has an elongation degree of 72.6 [% / N / mm ² ], a rotational stress attenuation rate of 31 [%], and a rotational stress ratio of 0.98. This is a sample in which the amount of wear of the rubber part is small and there is no settling.
The supply roller 25'of Example 6 has an elongation degree of 75.6 [% / N / mm ² ], a rotational stress attenuation rate of 31 [%], and a rotational stress ratio of 1.22. It is a sample in which the amount of wear of the rubber portion is small, the sample is not settled, and the toner is well agitated.

The supply roller 25'of Comparative Example 1 has an elongation degree of 81.6 [% / N / mm ² ], a rotational stress attenuation rate of 28 [%], and a rotational stress ratio of 0.90. This is a sample in which the amount of wear of the rubber portion is small and the sample is not settled, but since the initial stress on the end side is low, the supply property is lowered when the rubber portion is worn on the end side during continuous printing.
The supply roller 25'of Comparative Example 2 has an elongation degree of 87.0 [% / N / mm ² ], a rotational stress attenuation rate of 33 [%], and a rotational stress ratio of 0.90. Since the degree of elongation is high and the amount of change in the outer diameter by the simple wear test is 0.05 [mm], it is a sample that is easily settled.
The supply roller 25'of Comparative Example 3 has an elongation degree of 65.8 [% / N / mm ² ], a rotational stress attenuation rate of 26 [%], and a rotational stress ratio of 1.01. This is a sample in which the amount of change in outer diameter by a simple wear test is 0.05 [mm] and the amount of change in weight is 0.30 [g], and the amount of wear of the rubber portion is large.

The supply roller 25'of Comparative Example 4 has an elongation degree of 65.8 [% / N / mm ² ], a rotational stress attenuation rate of 30 [%], and a rotational stress ratio of 1.10. This is a sample in which the amount of change in outer diameter by a simple wear test is 0.07 [mm] and the amount of change in weight is 0.21 [g], and the amount of wear of the rubber portion is large.
The supply roller 25'of Comparative Example 5 has an elongation degree of 69.4 [% / N / mm ² ], a rotational stress attenuation rate of 33 [%], and a rotational stress ratio of 1.03. This is a sample in which the amount of change in outer diameter by a simple wear test is 0.06 [mm] and the amount of change in weight is 0.19 [g], the amount of wear of the rubber portion is large, and the sample is easily settled.
The supply roller 25'of Comparative Example 6 has an elongation degree of 65.8 [% / N / mm ² ], a rotational stress attenuation rate of 24 [%], and a rotational stress ratio of 1.27. The amount of change in outer diameter by the simple wear test is 0.07 [mm], the amount of change in weight is 0.21 [g], and the amount of wear of the rubber portion is large.
The supply roller 25'of Comparative Example 7 has an elongation degree of 75.6 [% / N / mm ² ], a rotational stress attenuation rate of 28 [%], and a rotational stress ratio of 0.69. This is a sample in which the amount of wear of the rubber portion is small and the sample is not settled, but since the initial stress on the end side is low, the supply property is lowered when the rubber portion is worn on the end side during continuous printing.

Next, the image evaluation method will be described. For the image evaluation of the supply roller 25'here, an image evaluation device (C650dnw manufactured by Oki Data Corporation) having the same basic configuration as the printer 1 shown in FIG. 1 is used, and the supply roller 25 as a sample is used. I put on ´ and went. Therefore, it will be described with reference to the printer 1 shown in FIG. 1 as an image evaluation device.

Magenta (M) was used as the toner. This toner has a degree of cohesion in the range of 48 [%] to 56 [%] and a blow-off charge amount of 75 to 80 [μC / g], and the toner cartridge 3 is preliminarily charged with about 23.0 [g] of toner. ] ± 0.5 [g] was filled.

An image evaluation device equipped with a supply roller 25'to confirm the effect on blurring caused by insufficient toner supply due to wear of the supply roller 25'with time and stains caused by insufficient scraping of undeveloped toner. (Printer 1) was operated to perform a continuous printing test of 50,000 sheets.

The conditions for the continuous printing test are set as shown in (1)-(5) below.
(1) Printing speed: A4 vertical direction 35 [ppm]
(2) Number of continuous prints per day: 2,500 (do this for 20 days)
(3) Print pattern: 0.3 [%] (printed image density)
(4) A 2 × 2 (halftone) pattern and a solid pattern are printed before the start of printing 2,500 sheets and after the end of printing.
(5) Test environment: temperature 20 [° C], relative humidity 50 [%]

The image judgment was performed as follows.
A 2 × 2 (halftone) pattern and a solid pattern were printed before the start of printing 2,500 sheets and after the end of printing, and stains and blurring were judged. To determine the stain, when a 2 × 2 pattern is printed, it is confirmed whether excess toner is developed on the portion that is not originally printed on the upper end of the paper surface. When the solid pattern is printed, it is confirmed whether or not a whiteout image is generated from the vertical center to the lower end of the A4 paper. At this time, even if there is a partial white spot at the end, it is counted as occurring.
In the image determination, in the continuous printing test of 50,000 sheets of stains and blurs, those in which one or more of them occurred were judged as "x", and those in which neither of them occurred was judged as "◯".

Here, 2 × 2 (halftone) pattern printing and printed image density will be described. FIG. 15A is a diagram schematically showing an image 150 when 2 × 2 (halftone) pattern printing is performed over substantially the entire area of the recording paper 10, and FIG. 15B is a partially enlarged view thereof. It is a figure.

As shown in FIG. 15B, for example, when a 1-dot area having a resolution of 600 [dpi] is defined as 1 square and divided into 16 squares of 4 vertical dots and 4 horizontal dots, the divided area of each divided area is divided. For example, a fixing pattern is generated for 4 squares corresponding to 2 × 2 dots in the central portion.

In terms of print image density, printing with an area ratio of 100 [%] during full-scale solid printing in a printable range of a predetermined area (for example, one round of a photosensitive drum or one page of recording paper) is printed with an image density of 100 [%]. ], And the printing corresponding to the area of 1 [%] with respect to the printed image density of 100 [%] is referred to as the printed image density of 1 [%]. That is, the print image density is the following formula print image density = [Cm (i) / (Cd × C0)] × 100.
It is calculated by.
Cm (i): The number of dots actually used in printing when the photosensitive drum was rotated by Cd, that is, the number of exposed dots.
C0: The number of dots per rotation of the photosensitive drum, that is, dots that are possible per rotation of the photosensitive drum (potentially dots in printing) regardless of the presence or absence of exposure, and are assumed to be solid images (solid images). The number of dots used in the case.
Cd × C0 is the number of dots that can be (potentially dots in printing) when the photosensitive drum rotates by Cd.

Next, the toner agitation test will be described. In the toner agitation test of the supply roller 25'here, an image evaluation device (C650dnw manufactured by Oki Data Corporation) having the same basic configuration as the printer 1 shown in FIG. 1 is used, and the toner is supplied as a sample. The roller 25'was attached. Therefore, it will be described with reference to the printer 1 shown in FIG. 1 as an image evaluation device.

The entire upper end of the developing unit 2 (see FIG. 2) on which each supply roller 25'is mounted is hollowed out, and 2.5 [g] of cyan (C) toner is added to the range of 2.5 [cm] from both ends of the developing unit. Add (5 g in total). From there, the yellow (Y) toner 27 [g] is charged into the region (central portion) surrounded by the cyan toner. After the toner was added, vinyl was laid and mounted on the image evaluation device (printer 1) so that the toner would not leak from the hollowed out part.

The conditions for continuous printing are set as shown in (1)-(5) below.
(1) Printing speed: A4 vertical direction 35 [ppm]
(2) Number of continuous prints at one time: 500 sheets in total (3) Print pattern: 0.3 [%] (print image density)
(4) 2 × 2 (halftone) is printed before the start of continuous printing and after printing the 100th and 200th sheets.
(5) Test environment: temperature 20 [° C], relative humidity 50 [%]

The color agitation test will be described. Color difference ΔE (L * a * b) is measured using a branch school colorimeter X-Rite528 (X-Rite) near the end of 2x2 (halftone) printed before the start of continuous printing and on the 200th sheet. bottom. The slopes of the two points (a, b) before the start of continuous operation and the 200th sheet (a, b) were calculated as the toner stirring coefficient k. The higher the toner stirring coefficient, the more likely it is that the color will change. Therefore, it can be said that the higher the toner stirring coefficient, the higher the toner stirring property. Therefore, the toner agitation coefficient was used as an index of the toner agitation property this time.

FIG. 16 is a characteristic graph showing the relationship between the toner stirring coefficient k and the rotational stress ratio (B / A). As shown in the graph, the toner stirring coefficient k changes according to the rotational stress ratio (B / A), and the degree of elongation is 72.6 [% / N / mm ² ] or more and 81.6 [% / N /. In the case of the average of the group of mm ² ] or less, the rotational stress ratio (B / A) shows a curve that becomes the minimum at 0.97, and the toner stirring coefficient k increases or decreases at the boundary of 0.97. To increase. However, when the rotational stress ratio (B / A) is less than 0.97, unevenness occurs in the toner supply as described above.

Further, the toner stirring coefficient k increases as the rotational stress ratio increases when the rotational stress ratio exceeds 0.97. Further, as shown in the figure, the curve shown by the group average having an extension degree of 72.6 [% / N / mm ² ] or more and 81.6 [% / N / mm ² ] or less and an extension degree of 61.8 [% / mm / mm 2]. From the comparison with the curve shown by the group average of N / mm ² ] or more and 65.8 [% / N / mm ² ] or less, it can be seen that the larger the degree of elongation, the higher the toner stirring coefficient k tends to be.

The test results will be explained.
As shown in Table 1, compared to Examples 1 to 6 in which printing defects did not occur, in Comparative Examples 1 to 7, either one or more of blurring and stains occurred. From this result, the rotational stress ratio is 0.97 or more and 1.23 or less, and the degree of elongation is 72.6 [% / N / mm ² ] or more and 81.6 [% / N / mm ² ] or less. Moreover, it was found that good image evaluation results can be obtained when the rotational stress ratio is 0.97 or more and 1.23 or less.

The supply roller 25'of Comparative Example 1 had an elongation degree and a rotational stress attenuation rate within the specified ranges, but the rotational stress ratio was less than 0.97, and partial blurring occurred. This is because the nip width with the developer carrier is reduced on the end side from the initial stage due to wear due to continuous aging, so that the toner supply of the supply roller 25'is uneven, and the toner is sufficiently supplied to the developing roller 23. Because I couldn't do it.

In the supply roller 25'of Comparative Example 2, the degree of elongation, the rotational stress attenuation rate, and the rotational stress ratio are all out of the specified range. When the degree of elongation exceeds 81.6 [% / N / mm ² ], the supply roller 25'is likely to settle when rotated while being niped to the developing roller 23, and the stress on the developing roller 23 is increased. As a result, the residual toner of the developing roller 23 after development cannot be sufficiently scraped off, so that stains occur.

The supply roller 25'of Comparative Example 3 has an elongation degree and a rotational stress attenuation rate outside the specified range. When the degree of elongation is less than 72.6% [% / N / mm ² ], the nip width with the developing roller 23 is reduced due to wear over time due to contact rotation with the developing roller 23, resulting in development after development. Dirt is generated because the residual toner of the roller 23 cannot be sufficiently scraped off. In Comparative Example 3, the rotational stress ratio is within the specified range, but as described above, the specifications are such that it is easily worn, so that the influence of the decrease in the nip amount is high, and as a result, dirt is generated.

The extension degree of the supply roller 25'of Comparative Example 4 is out of the specified range. When the degree of elongation is less than 72.6 [% / N / mm ² ], the nip width with the developing roller 23 decreases due to wear over time due to contact rotation with the developing roller 23, as in the case of Comparative Example 3. As a result, the residual toner of the developing roller 23 after development cannot be sufficiently scraped off, so that stains occur. In Comparative Example 4, the rotational stress ratio and the rotational stress attenuation rate are within the specified ranges, but since the specifications are such that they are easily worn as described above, the influence of the decrease in the nip amount is large, and as a result, dirt is generated.

The supply roller 25'of Comparative Example 5 has an elongation degree and a rotational stress attenuation rate outside the specified range. When the degree of elongation is less than 72.6 [% / N / mm ² ], the nip width with the developing roller 23 decreases due to wear over time due to contact rotation with the developing roller 23, as in the case of Comparative Example 3. do. Further, since the rotational stress attenuation rate exceeds 31%, the recovery of the elasticity of the pushed portion of the foam layer 52 is slow, so that it is easy to settle, and the undeveloped toner of the developing roller 23 cannot be sufficiently scraped off, resulting in stains. Occur. In Comparative Example 5, although the rotational stress ratio is within the specified range, it is easily worn and settled as described above, so that the influence of these two points is large, and as a result, dirt is generated.

The supply roller 25'of Comparative Example 6 has an extension degree of less than 72.6 [% / N / mm ² ], a rotational stress attenuation rate of 27% or less, and a rotational stress ratio of more than 1.23, all of which are out of the specified range. It has become. Therefore, not only the stain is generated, but also the load applied to the photosensitive drum 21 increases. When the rotational stress ratio exceeds 1.23, the pressure on the end side of the supply roller 25'is stronger, the torque load of the photosensitive drum 21 is increased, the load on other contact members is also increased, and the durability of the developing unit 2 itself is increased. Also has an adverse effect.

The supply roller 25'of Comparative Example 7 had an elongation degree and a rotational stress attenuation rate within the specified ranges, but the rotational stress ratio was less than 0.97, and partial blurring occurred. This is because the nip width with the developer carrier is reduced on the end side from the initial stage due to wear due to continuous aging, so that the toner supply of the supply roller 25'is uneven, and the toner is sufficiently supplied to the developing roller 23. Because I couldn't do it.

With respect to Comparative Examples 1 to 7, the supply rollers 25'of Examples 1 to 6 did not show any image defects, and the images were good. Therefore, from the supply rollers 25'of Examples 1 to 6, the degree of elongation of the supply rollers 25'related to the toner scraping property, which can satisfy the toner scraping property and the toner supply property, and the supply roller 25 at the time of solidification. The rotational stress attenuation rate of the conductive foam layer 52, the rotational stress ratio related to the toner supply during durability and durability, and the numerical ranges of the outer diameter change amount and the weight change amount are as described above. Can be set to a range. Therefore, the supply rollers 25'of Examples 1 to 6 correspond to the supply rollers 25 of the present embodiment.

As described above, the supply roller 25 of the present embodiment uses silicone rubber as the foam layer 52 and has an elongation degree of 72.6 [% / N / mm ² ] or more and 81.6 [% / N] when solid. / Mm ² ] or less, the amount of change in outer diameter in the simple wear test is 0.03 mm or less, the amount of change in weight is 0.07 g or less, and the stress attenuation rate of the rubber part after 6 hours when the supply roller 25 rotates NIP. By setting the rotational stress ratio B / A of 27% or more and 31% or less, and the rotational stress (A) at the central portion and the rotational stress (B) at the end portion to 0.97% or more and 1.23 or less. It is possible to maintain the toner supply property and the toner scraping property up to a drum count of 50 k, and suppress the occurrence of stains and blurring.

Further, by setting the degree of elongation to 72.6 [% / N / mm ² ] or more and 81.6 [% / N / mm ² ] or less, supply roller wear debris is generated and supply is performed by the settling of the supply roller cell wall. Deterioration of image quality caused by the occurrence of unevenness is suppressed, and partial blurring is suppressed by setting the rotational stress ratio B / A to 0.97% or more and 1.23 or less.

Furthermore, by setting the amount of change in the outer diameter by the simple wear test to 0.03 mm or less, the amount of decrease in the outer diameter is large and the cell wall is lying down, that is, supply unevenness occurs due to the settling of the cell wall of the supply roller. It is suppressed, and partial blurring is suppressed by setting the rotational stress ratio B / A to 0.97% or more and 1.23 or less.

As described above, according to the developing unit of the present embodiment, it is possible to suppress the occurrence of stains and blurring in the printed image.

In the first embodiment according to the embodiment of the present invention described above, an example adopted for an image forming apparatus as a color printer is shown, but the present invention is not limited to this, and an image processing apparatus such as a copying machine, a facsimile, or an MFP is shown. Is also available. Further, although the color printer has been described, it may be a monochrome printer.

1 printer, 2 development unit, 3 toner cartridge, 4 transfer roller, 5 exposure unit, 6 paper feed cassette, 7 fixing unit, 7a heating roller, 7b pressure roller, 8 paper transfer path, 9 transfer belt, 10 recording paper, 11 Drive Roller, 12 Tension Roller, 14 Transfer Unit, 21 Photosensitive Drum, 22 Charging Roller, 23 Development Roller, 24 Development Blade, 25 Supply Roller, 27 Cleaning Blade, 28 1st Transport Section, 29 2nd Transport Section, 31 Toner Storage unit, 32 Waste toner container, 35 Toner supply port, 36 Conveyor screw, 37 Stirring member, 38 Toner storage unit, 40 Toner 51 Core metal, 52 Foam layer, 52a Foam outer layer, 52b Inner layer, 101 Control unit, 101a dot counter, 101b drum counter, 101c calculation unit, 111 I / F control unit, 112 reception memory, 113 image data editing memory, 114 operation unit, 115 sensor group, 121 charging roller power supply, 122 development roller power supply, 123 Power supply for supply roller, power supply for 124 transfer roller, power supply for 125 fuse, 126 head drive control unit, 127 fixing control unit, 128 transfer motor control unit, 129 drive control unit, 130 fast blow fuse, 131 paper transfer motor, 132 drive motor , 201 rotary support, 205 indenter, 206 indenter, 206a metal plate, 206b wrapping film, 209 test piece, 209a parallel part, 209b grip part.

Claims (6)

A developer carrier that supplies a developer to the electrostatic latent image carrier and develops a latent image on the electrostatic latent image carrier, and a developer carrier.
It is arranged so as to abut on the developer carrier to form a nip region, has an elastic layer on the surface, and includes a developer supply member that supplies the developer to the developer carrier.
When a stainless steel indenter having an outer diameter of 16 [mm] and a length of 50 [mm] is pushed 0.73 [mm] into the surface of the end and center of the elastic layer in the extending direction of the nip region. The ratio of the stress at the end to the stress at the center is 0.97 or more and 1.23 or less.
A stainless steel indenter having a square surface having a side of 50 [mm] and a thickness of 10 [mm] having a polishing film having a grain size of 30 [μm] fixed to the surface was used to obtain the polishing film. When 0.73 [mm] is pushed into the elastic layer and the developer supply member is rotated at a peripheral speed of 136.1 [mm / sec],
The developer supply member when the indenter is separated 250 seconds after the indenter has reached 0.73 [mm] with respect to the outer diameter of the developer supply member before the indenter is pushed in. A developing unit characterized in that the amount of decrease in the outer diameter of is 0.03 [mm] or less. A developer carrier that supplies a developer to the electrostatic latent image carrier and develops a latent image on the electrostatic latent image carrier, and a developer carrier.
It is arranged so as to abut on the developer carrier to form a nip region, has an elastic layer on the surface, and includes a developer supply member that supplies the developer to the developer carrier.
When a stainless steel indenter having an outer diameter of 16 [mm] and a length of 50 [mm] is pushed 0.73 [mm] into the surface of the end and center of the elastic layer in the extending direction of the nip region. The ratio of the stress at the end to the stress at the center is 0.97 or more and 1.23 or less.
When a tensile test of JIS-K6251 was performed using a dumbbell No. 1 shape test piece formed of the material before the foaming treatment after vulcanization of the elastic layer, the elongation rate when the test piece broke ([[ %]) Divided by the stress at that time ([N / mm ² ]) shall be 72.6 [% / N / mm ² ] or more and 81.6 [% / N / mm ² ] or less. A development unit featuring. The developing unit according to claim 1 or 2, wherein the developing agent supply member has an inverted crown shape. The developing unit according to any one of claims 1 to 3, wherein the developing agent supply member contains silicone as a main component. The developing unit according to any one of claims 1 to 4, wherein the elastic layer has an Asker F hardness of 40 or more and 46 or less. The developing unit according to any one of claims 1 to 5.
A transfer unit that transfers the developer image formed on the electrostatic latent image carrier to a medium, and
An image forming apparatus including a fixing unit for fixing a developer image transferred to the medium to the medium.

Images