Charging member, charging device, detachable body, and image forming apparatus

A charging member includes a contact section and a supported section. The contact section is in contact with a charged body. The supported section is integrated with the contact section and is supported by a support member. The supported section has a lower hardness than the contact section.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2012-183668 filed Aug. 22, 2012.

BACKGROUND

Technical Field

The present invention relates to charging members, charging devices, detachable bodies, and image forming apparatuses.

SUMMARY

According to an aspect of the invention, there is provided a charging member including a contact section and a supported section. The contact section is in contact with a charged body. The supported section is integrated with the contact section and is supported by a support member. The supported section has a lower hardness than the contact section.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention will be described below with reference to the drawings.

Configuration of Image Forming Apparatus10

First, the configuration of an image forming apparatus10will be described.FIG. 1schematically illustrates the configuration of the image forming apparatus10.

As shown inFIG. 1, the image forming apparatus10includes an image reading device500that reads an image of a document and an image recording device100that records the image onto a recording medium P. The image recording device100is capable of recording (forming) an image onto the recording medium P on the basis of image data of the document image read by the image reading device500or image data acquired from an external device of the image forming apparatus10.

Image Reading Device500

As shown inFIG. 1, the image reading device500includes an image-reading-device body502, a document transport device504that transports a document G, and an image reading section510that is provided within the image-reading-device body502and reads an image from the document G transported by the document transport device504.

The document transport device504has a document accommodation section (i.e., a document tray)506that can accommodate multiple documents G. Each document G accommodated in the document accommodation section (document tray)506is transported along a U-shaped path indicated by a direction of an arrow C so as to be output to a document output section508. In the image reading section510, light is emitted by a light emitting section512to the document G transported by the document transport device504and is reflected by the document G. The light is then focused on a detector518, such as a charge-coupled-device (CCD) image sensor, via multiple mirrors514and an imaging lens516. The focused light is detected by the detector518, whereby the image on the document G transported by the document transport device504is read in the image reading section510.

A transparent plate520is provided at an upper portion of the image-reading-device body502. An image of a document placed on this transparent plate520can also be read by the image reading section510. The document transport device504is attached to the image-reading-device body502in an openable-closable manner and functions as a holding cover that holds in place the document placed on the transparent plate520.

Image Recording Device100

As shown inFIG. 1, the image recording device100includes an image-recording-device body11that accommodates components therein. The image-recording-device body11contains therein an accommodation section12that accommodates recording media P, such as paper, an image forming unit60as an image forming section (i.e., an image recording section) that forms (records) an image onto each recording medium P, a fixing unit80as a fixing device that fixes the image formed on the recording medium P by the image forming unit60onto the recording medium P, a transport section16that transports the recording medium P from the accommodation section12to the image forming unit60, and a controller20that controls the operation of each section of the image recording device100. An output section18to which the recording medium P having the image fixed thereon by the fixing unit80is output is provided at an upper portion of the image-recording-device body11.

The image forming unit60is configured as a replaceable process cartridge and functions as an example of a detachable body that allows a photoconductor drum32, a charging device70, an exposure device36, and a developing device38, which will be described later, to be integrally attachable to and detachable from the image-recording-device body11(as an example of an image-forming-apparatus body). As shown inFIG. 2, the image forming unit60has an image-forming-unit body (i.e., a housing)60A that is attachable to and detachable from the image-recording-device body11. The image-forming-unit body60A is provided with the photoconductor drum32as an example of a charged body. The photoconductor drum32rotates in one direction (e.g., in the clockwise direction inFIG. 2).

In the following order from the upstream side of the photoconductor drum32in the rotational direction thereof, the photoconductor drum32is surrounded by the charging device70that electrostatically charges the photoconductor drum32, the exposure device36that exposes the photoconductor drum32electrostatically charged by the charging device70to light so as to form an electrostatic latent image on the photoconductor drum32, the developing device38that develops the electrostatic latent image formed on the photoconductor drum32by the exposure device36so as to form a black toner image, a transfer roller26as a transfer section that transfers the black toner image formed on the photoconductor drum32by the developing device38onto the recording medium P, and a removing device29that removes residual toner from the photoconductor drum32after the toner-image transfer process. A detailed configuration of the charging device70will be described later.

The developing device38includes transport members38B that transport a developer in the axial direction of the photoconductor drum32while stirring the developer, and a developing roller38A as a developer supply body that retains the developer transported by the transport members38B and supplies the developer to the photoconductor drum32.

As shown inFIG. 1, the exposure device36forms the electrostatic latent image on the basis of an image signal (i.e., image data) sent from the controller20. Examples of the image signal sent from the controller20include an image signal of the document image read by the image reading device500and an image signal acquired from the external device of the image forming apparatus10.

A toner cartridge58as a toner container that accommodates toner therein is provided above the exposure device36. The toner in the toner cartridge58is transported to the developing device38by a toner transport device (not shown).

The transfer roller26is opposed to the photoconductor drum32and nips the recording medium P together with the photoconductor drum32so as to transport the recording medium P upward. Furthermore, the transfer roller26receives a transfer voltage (i.e., a transfer bias) for transferring the toner image on the photoconductor drum32onto the recording medium P. A transfer position T where the toner image formed on the photoconductor drum32is transferred onto the recording medium P is formed between the transfer roller26and the photoconductor drum32.

As shown inFIG. 2, the removing device29is specifically constituted of a cleaning blade as a removing member that comes into contact with the photoconductor drum32so as to remove residual toner from the photoconductor drum32.

As shown inFIG. 1, the transport section16includes a feed roller46that feeds each recording medium P accommodated in the accommodation section12, a transport path48along which the recording medium P fed by the feed roller46is transported, and multiple transport rollers50that are arranged along the transport path48and transport the recording medium P fed by the feed roller46to the transfer position T.

The fixing unit80is disposed above the transfer position T (i.e., at the downstream side thereof in the transport direction) and fixes the toner image transferred on the recording medium P from the photoconductor drum32by the transfer roller26onto the recording medium P. An output roller52that outputs the recording medium P having the toner image fixed thereon onto the output section18is provided above the fixing unit80(i.e., at the downstream side thereof in the transport direction).

An inversion transport path37that inverts the recording medium P having the toner image fixed on one face thereof so as to transport the recording medium P again to the transfer position T is provided at the opposite side (i.e., the left side inFIG. 1) of the photoconductor drum32relative to the transfer roller26. When forming images onto both faces of the recording medium P, the recording medium P having the toner image fixed on one face thereof is guided to the inversion transport path37by being switched back by the output roller52so as to be transported again to the transfer position T.

Image Forming Operation

Next, an image forming operation (image recording operation) for forming (recording) an image onto the recording medium P in the image recording device100will be described.

In the image recording device100, a recording medium P fed from the accommodation section12by the feed roller46is transported to the transfer position T by the multiple transport rollers50.

In the image forming unit60, the photoconductor drum32is electrostatically charged by the charging device70and is subsequently exposed to light by the exposure device36, whereby an electrostatic latent image is formed on the photoconductor drum32. The electrostatic latent image is developed by the developing device38so that a black toner image is formed on the photoconductor drum32. This black toner image is transferred onto the recording medium P by the transfer roller26at the transfer position T.

The recording medium P having the toner image transferred thereon is transported to the fixing unit80, and the toner image is fixed onto the recording medium P by the fixing unit80. If an image is to be formed only on one face of the recording medium P, the recording medium P, after having the toner image fixed thereon, is output to the output section18by the output roller52.

If images are to be formed on both faces of the recording medium P, the recording medium P, after having the toner image fixed on one face thereof, is switched back by the output roller52and is inverted and transported to the inversion transport path37. Then, the recording medium P is transported again to the transfer position T from the inversion transport path37. At the transfer position T, an image is formed on the non-image-recorded face of the recording medium P in a manner similar to the above procedure. The recording medium P is then output to the output section18by the output roller52. Accordingly, the image forming operation is performed in the above-described manner.

An image recording device (image forming apparatus) to which the charging device70is applied is not limited to the image recording device100(image forming apparatus10) described above, and may alternatively be image recording devices (image forming apparatuses) of various types, such as a tandem-type image recording device (image forming apparatus) that forms a color image.

Configuration of Charging Device70

Next, the configuration of the charging device70will be described.FIG. 3is a cross-sectional view illustrating the configuration of the charging device70.

As shown inFIG. 3, the charging device70includes a charging blade72as an example of a charging member, a support member74that supports the charging blade72, a power source78that applies a charge voltage to the support member74, and electrically conductive paste76as an electrically conductive member.

The charging blade72includes an edge section72A (corner section) as an example of a contact section that is in contact with the photoconductor drum32(as an example of a charged member), and a supported section72B that is integrated with the edge section72A and is supported by the support member74.

The charging blade72is rectangular in a side view (i.e., a cross-sectional view) and has a thickness T ranging between, for example, 1 mm and 3 mm and a length L ranging between, for example, 9 mm and 15 mm. Furthermore, the charging blade72has a free length FL ranging between, for example, 7 mm and 10 mm. An amount H by which the charging blade72digs into the photoconductor drum32ranges between 0.5 mm and 2.0 mm. An angle θ of the charging blade72relative to the surface of the photoconductor drum32ranges between, for example, 10° and 25°.

The term “free length FL” refers to a length by which the charging blade72protrudes from a tip (i.e., the left tip inFIG. 3) of the support member74. Furthermore, referring toFIG. 3, the term “amount H by which the charging blade72digs into the photoconductor drum32” refers to a distance (in the radial direction of the photoconductor drum32) between an imaginary line I of the outer periphery of the photoconductor drum32and an edge S that penetrates into the imaginary line I, supposing that the photoconductor drum32is not present.

In a side view (i.e., a cross-sectional view), the edge section72A has a triangular shape with a length L1of, for example, 0.5 mm in the thickness direction of the charging blade72and a length L2of, for example, 2.5 mm.

The supported section72B has a lower hardness than the edge section72A. In other words, the edge section72A has a higher hardness than the supported section72B. The JIS-A hardness of the edge section72A may be 84° or higher. As will be described later, if the aforementioned hardness is lower than 84°, the charging would become non-uniform at the initial stage of operation due to vibration occurring in a portion of the edge section72A that is in contact with the photoconductor drum32.

The JIS-A hardness of the supported section72B may be 74° or lower. As will be described later, if the aforementioned hardness exceeds 74°, the charging non-uniformity would further deteriorate from the initial stage due to yielding of the charging blade72.

In this exemplary embodiment, the edge section72A has conductive properties, and the supported section72B has insulation properties, such that discharging toward the photoconductor drum32is performed at the edge section72A. In detail, discharging is performed at the downstream side (i.e., the right side inFIG. 3) of the photoconductor drum32in the rotational direction thereof relative to the portion (i.e., the edge S) of the edge section72A that is in contact with the photoconductor drum32.

The edge section72A is specifically composed of a rubber material having conductive properties. More specifically, the edge section72A is composed of a rubber material with a conductivity adding material, such as carbon or ion conductive material, dispersed therein. An example of the rubber material used includes polyurethane rubber. The term “conductive properties” in this case refers to a volume resistivity range of 1010Ωcm or lower. In view of performing discharging, the volume resistivity of the edge section72A may range between 104Ωcm and 108Ωcm.

The supported section72B is specifically composed of a rubber material having insulation properties. More specifically, the supported section72B is composed of a rubber material not having the aforementioned conductivity adding material dispersed therein. An example of the rubber material used includes polyurethane rubber. The term “insulation properties” in this case refers to a volume resistivity range of 1011Ωcm or higher.

Furthermore, the polyurethane rubber material used for forming each of the edge section72A and the supported section72B is, for example, a polyurethane composition containing polyisocyanate and polyol. The polyol used is, for example, polycaprolactonepolyol, polyester polyol, or polyether polyol.

The polyisocyanate used in the edge section72A is, for example, 1,5-naphthalene diisocyanate (NDI). A suitable polyol used relative to the 1,5-naphthalene diisocyanate (NDI) is polycaprolactonepolyol. 1,5-naphthalene diisocyanate (NDI) has a rigid structure and a sufficient crystalline height. By utilizing this structure for forming polyurethane, polyurethane with a high hardness is obtained.

The charging blade72is formed by, for example, the following manufacturing method and is integrally constituted of the supported section72B and the edge section72A that have different hardnesses.

The manufacturing method for the charging blade72includes, for example, using a first casting unit to supply a liquid material for the edge section72A to a corner area of a molding groove formed around the outer periphery of a rotating molding drum and then using a second casting unit to supply a liquid material for the supported section72B to the molding groove. Subsequently, a strip-shaped molded product obtained as a result of thermosetting the two liquid materials by using a heating device provided inside the molding drum is cut, whereby the charging blade72is obtained. The manufacturing method for the charging blade72is not limited to the one described above, and various kinds of manufacturing methods may be employed.

In the configuration using the charging blade72as in this exemplary embodiment, discharging is generally performed in an area (i.e., a discharge area) where the gap between the charging blade72and the photoconductor drum32is about 8 μm to 200 μm.

Therefore, in this exemplary embodiment, the amount H by which the charging blade72digs into the photoconductor drum32, the angle θ, the length L2, and so on are determined so that the gap between the edge section72A and the photoconductor drum32is within the aforementioned range and so that better processability is achieved for the charging blade72. A gap K (in the radial direction of the photoconductor drum32) between the photoconductor drum32and the downstream end (i.e., the right end inFIG. 3) of the edge section72A in the rotational direction of the photoconductor drum32is, for example, 1 mm.

In detail, at a position where the length L2from the edge S is about 500 μm, the gap between the edge section72A and the photoconductor drum32is about 200 μm, and discharging is made to occur at the edge-S side from the aforementioned 500 μm, position. Therefore, from the standpoint of maintaining a gap that allows for discharging, the length L2may be shorter than 2.5 mm and may be set in a range in which a gap that allows for discharging between the edge section72A and the photoconductor drum32can be maintained.

The length L2may be set to be longer from the standpoint of the processability of the charging blade72(i.e., the edge section72A). In this exemplary embodiment, the length L2is set to a sufficiently large value of 2.5 mm in view of better processability in the manufacturing process.

For suppressing charging non-uniformity caused by yielding, to be described later, the overall hardness of the charging blade72may be reduced by increasing the region of the supported section72B, and the length L2may be shortened.

The length L1is not limited to 0.5 mm mentioned above and may be, for example, smaller than or equal to half the thickness T of the charging blade72. If the length L1exceeds half of the thickness T of the charging blade72, the length L1would occupy a larger region of the supported section72B, thus making it difficult to maintain the overall hardness of the charging blade72to a low value. This would result in a reduced effect for suppressing charging non-uniformity caused by yielding.

The support member74is a tabular member extending longitudinally in the axial direction of the photoconductor drum32. The support member74has a function of supporting the charging blade72onto the image-forming-unit body (charging device body)60A (seeFIG. 2) and also functions as an electrode that receives a charge voltage from the power source78. The support member74is composed of, for example, metal or an alloy, such as a copper alloy or SUS, iron plated with chromium or nickel, or an electrically conductive material, such as synthetic resin.

The electrically conductive paste76functions as an electrically connecting member for electrically connecting the support member74to the discharge area in the charging blade72. In this exemplary embodiment, the edge section72A serves as the discharge area. The electrically conductive paste76extends from a back surface (i.e., a surface (upper surface inFIG. 3) opposite the photoconductor drum32) of the support member74to the edge section72A via an end surface (i.e., a left end surface inFIG. 3) of the support member74, a back surface (i.e., a surface (upper surface inFIG. 3) opposite the photoconductor drum32) of the charging blade72(i.e., the supported section72B), and an end surface (i.e., a left end surface inFIG. 3) of the charging blade72(i.e., the supported section72B).

Relationship Between Hardness of Charging Blade and Amplitude of Vibration at Edge and Relationship Between Hardness of Charging Blade and Charging Non-Uniformity at Initial Stage Caused by Edge Vibration

The following description relates to the relationship between the hardness of a charging blade and the amplitude of vibration occurring at the portion (i.e., the edge S) thereof in contact with the photoconductor drum32and the relationship between the hardness of the charging blade and charging non-uniformity at an initial stage caused by vibration occurring at the portion (i.e., the edge S) thereof in contact with the photoconductor drum32. The results obtained here correspond to a case where a single-layer charging blade82is used, as shown inFIG. 4. This single-layer blade is also composed of a rubber material having conductive properties. More specifically, the blade is composed of a rubber material with a conductivity adding material, such as carbon or ion conductive material, dispersed therein. An example of the rubber material used includes polyurethane rubber. The term “conductive properties” in this case refers to a volume resistivity range of 1010Ωcm or lower. In view of performing discharging, the volume resistivity may range between 104Ωcm and 108Ωcm.

As shown in a graph inFIG. 5A, the higher the hardness of the charging blade, the smaller the amplitude (vibration) at the edge S. Furthermore, as shown in a graph inFIG. 5B, the higher the hardness of the charging blade, the smaller the charging non-uniformity at the initial stage caused by vibration at the edge S. In the graphs inFIGS. 5A and 5B, an inflection point where the inclination changes corresponds to a JIS-A hardness of 84°. Specifically, in a charging blade with a JIS-A hardness of 84° or higher, the effect for suppressing charging non-uniformity at the initial stage caused by vibration at the edge S is high.

The term “charging non-uniformity at the initial stage” refers to charging non-uniformity at the initial stage of operation of the device (the same applies throughout this specification). The term “amplitude of vibration” inFIG. 5Acorresponds to a displacement amount (mm) of the edge S that vibrates in the radial direction of the photoconductor drum32as the photoconductor drum32rotates. The term “charging non-uniformity” in the graph inFIG. 5Bcorresponds to charging non-uniformity in the rotational direction of the photoconductor drum32and is measured by measuring the surface potential of the rotating photoconductor drum32(the same applies throughout this specification).

The vibration (amplitude) in this case corresponds to vibration occurring at the portion (i.e., the edge S) of the charging blade that is in contact with the photoconductor drum32. This portion is a very narrow area that has an effect on discharging. In other words, this vibration is different from high-frequency vibration occurring in a large area, as in a stick-slip phenomenon in a cleaning blade. A stick-slip phenomenon is a phenomenon in which a blade repeatedly undergoes a process of being deformed by being pulled downstream in the rotational direction of a photoconductor drum due to a frictional force between the blade and the photoconductor drum and then restoring its original form due to an elastic force of the blade.

Accordingly, it is obvious from the graphs inFIGS. 5A and 5Bthat the higher the hardness of the charging blade, the smaller the vibration occurring at the portion (i.e., the edge S) thereof in contact with the photoconductor drum32and the smaller the charging non-uniformity at the initial stage caused by the vibration.

Relationship Between Hardness of Charging Blade and Amount of Yielding in Charging Blade and Relationship Between Hardness of Charging Blade and how Much Charging Non-Uniformity has Deteriorated Since Initial Stage Due to Yielding

The following description relates to the relationship between the hardness of a charging blade and the amount of yielding in the charging blade and the relationship between the hardness of the charging blade and how much charging non-uniformity has deteriorated since the initial stage due to yielding. The results obtained here correspond to a case where the single-layer charging blade82is used, as shown inFIG. 4.

The term “yielding” refers to decreasing of the amount H by which the charging blade digs into the photoconductor drum32over time, and the term “amount of yielding” refers to an amount by which the aforementioned amount H has decreased with time (the same applies throughout this specification). The results here are obtained by measuring an amount of yielding after forming images on 30,000 recording media P and also by measuring how much the charging non-uniformity has deteriorated since the initial stage due to yielding.

As shown in a graph inFIG. 6A, the higher the hardness of the charging blade, the larger the amount of yielding. Furthermore, as shown in a graph inFIG. 6B, the higher the hardness of the charging blade, the larger the amount of deterioration in charging non-uniformity since the initial stage due to yielding. The amount of deterioration in charging non-uniformity since the initial stage due to yielding corresponds to a value obtained by subtracting the charging non-uniformity value at the initial stage shown inFIG. 5Bfrom the charging non-uniformity value after forming images on 30,000 recording media P.

The charging non-uniformity conceivably deteriorates with time due to the following reason. A pressure-contact force of the charging blade against the photoconductor drum32weakens due to yielding of the charging blade. This causes foreign matter, such as an external additive, contained in the toner on the photoconductor drum32to penetrate between the edge S of the charging blade and the photoconductor drum32and adhere to an area (i.e., a discharge surface) in the charging blade where discharging is performed for the photoconductor drum32. Therefore, the amount of deterioration in charging non-uniformity after forming images on 30,000 recording media P is expressed as an amount of deterioration in charging non-uniformity occurring due to the adhesion of foreign matter, such as an external additive, to the charging blade, which is caused by yielding of the charging blade.

In the graphs inFIGS. 6A and 6B, an inflection point where the inclination changes corresponds to a JIS-A hardness of 74°. Specifically, in a charging blade with a JIS-A hardness of 74° or lower, the effect for suppressing deterioration in charging non-uniformity caused by yielding is high.

Accordingly, it is obvious from the graphs inFIGS. 6A and 6Bthat the higher the hardness of the charging blade, the larger the amount of yielding in the charging blade and the larger the charging non-uniformity caused by the yielding.

Evaluations

With regard to each of charging blades according to an example and first to fourth comparative examples, the charging non-uniformity at the initial stage caused by vibration occurring at the portion (i.e., the edge S) of the edge section72A in contact with the photoconductor drum32, the amount of deterioration in charging non-uniformity occurring due to yielding after forming images on 30,000 recording media P from the initial stage, and the charging non-uniformity after forming images on 30,000 recording media P are evaluated.

Configuration of Charging Blade

In each of the first and second comparative examples, a single-layer charging blade is used, as shown inFIG. 4. The charging blade is composed of polyurethane rubber with an ion conductive material dispersed therein.

In each of the third and fourth comparative examples and the example, a double-layer charging blade constituted of the edge section72A and the supported section72B is used, as shown inFIG. 3. The edge section72A is composed of polyurethane rubber with an ion conductive material dispersed therein, and the supported section72B is composed of polyurethane rubber not having a conductivity adding material dispersed therein.

In each of the first to fourth comparative examples and the example, the charging blade used has a thickness T ranging between 1.5 mm and 3 mm and a free length FL ranging between 7 mm and 9 mm. Moreover, the amount H by which the charging blade digs into the photoconductor drum ranges between 0.5 mm and 2.0 mm, and the angle θ between the charging blade and the surface of the photoconductor drum ranges between 10° and 25°.

The JIS-A hardness of the charging blade according to each of the first to fourth comparative examples and the example is set as follows.

Third Comparative Example: 59° for Edge Section72A and 90° for Supported Section72B

Fourth Comparative Example: 63° for Edge Section72A and 81° for Supported Section72B

Example: 90° for Edge Section72A and 59° for Supported Section72B

Evaluation Results

As a result, in the first comparative example, the charging non-uniformity at the initial stage is small and is within a practicable charging non-uniformity range. However, the charging non-uniformity after forming images on 30,000 recording media P is large and exceeds the practicable charging non-uniformity range.

In the second to fourth comparative examples, the charging non-uniformity at the initial stage and the charging non-uniformity after forming images on 30,000 recording media P exceed the practicable charging non-uniformity range.

In contrast, in the example, the charging non-uniformity at the initial stage and the charging non-uniformity after forming images on 30,000 recording media P are within the practicable charging non-uniformity range.

In the evaluation results shown inFIG. 7, a circle indicates that the charging non-uniformity at the initial stage and/or the charging non-uniformity after forming images on 30,000 recording media P is/are within the practicable charging non-uniformity range, and an “x” indicates that the charging non-uniformity at the initial stage and/or the charging non-uniformity after forming images on 30,000 recording media P exceed or exceeds the practicable charging non-uniformity range.

Accordingly, by using a charging blade72in which the edge section72A has a higher hardness than the supported section72B, the charging non-uniformity at the initial stage caused by vibration of the charging blade72and the charging non-uniformity caused by yielding occurring in the charging blade72over time may be suppressed.

Charging Blade172According to First Modification

Next, a charging blade172according to a first modification will be described.FIG. 8is a cross-sectional view illustrating the configuration of the charging blade172according to the first modification. The following description will be directed to sections that are different from those of the aforementioned charging blade72. Furthermore, sections that have the same functions will be given the same reference numerals, and descriptions thereof will be omitted.

As shown inFIG. 8, in the charging blade172according to the first modification, the supported section72B is composed of a material having conductive properties. Specifically, like the edge section72A, the supported section72B is composed of a rubber material having conductive properties. More specifically, the supported section72B is composed of a rubber material with a conductivity adding material, such as carbon or ion conductive material, dispersed therein. An example of the rubber material used includes polyurethane rubber. The term “conductive properties” in this case refers to a volume resistivity range of 1010Ωcm or lower.

In this modification, the edge section72A is composed of polyurethane rubber with an ion conductive material dispersed therein. The supported section72B is composed of polyurethane rubber with carbon black dispersed therein.

The electrically conductive paste76extends from the back surface (i.e., the surface (upper surface inFIG. 8) opposite the photoconductor drum32) of the support member74to the back surface (i.e., the surface (upper surface inFIG. 8) opposite the photoconductor drum32) of the charging blade72(i.e., the supported section72B) via the end surface (i.e., the left end surface inFIG. 8) of the support member74.

A configuration not provided with the electrically conductive paste76is also permissible. With the electrically conductive paste76, an insulating material can be used as an adhesive layer (not shown) for adhering the support member74and the charging blade72to each other. The aforementioned adhesive layer may alternatively be composed of an electrically conductive material.

In view of performing discharging, the volume resistivity of the edge section72A may range between 104Ωcm and 108Ωcm. Furthermore, in order to achieve a function for supplying electricity to the edge section72A, the volume resistivity of the supported section72B may range between 103Ωcm and 106Ωcm.

Charging Blade272According to Second Modification

Next, a charging blade272according to a second modification will be described.FIG. 9is a cross-sectional view illustrating the configuration of the charging blade272according to the second modification. The following description will be directed to sections that are different from those of the aforementioned charging blade72. Furthermore, sections that have the same functions will be given the same reference numerals, and descriptions thereof will be omitted.

As shown inFIG. 9, in the charging blade272according to the second modification, an entire opposing surface72C (i.e., a surface opposite a supported surface (joined surface) supported by the support member74) of the supported section72B that faces the photoconductor drum32is integrally provided with the edge section72A. The supported section72B and the edge section72A are rectangular in a side view (i.e., a cross-sectional view).

For example, the edge section72A may have a thickness T1that is smaller than or equal to half the thickness T of the charging blade72. If the thickness T1exceeds half of the thickness T of the charging blade72, the thickness T1would occupy a larger region of the supported section72B, thus making it difficult to maintain the overall hardness of the charging blade72to a low value. This would result in a reduced effect for suppressing charging non-uniformity caused by yielding.

The electrically conductive paste76extends from an opposing surface (i.e., a surface (lower surface inFIG. 9) opposite the back surface) of the support member74that faces the photoconductor drum32to the edge section72A via a downstream end surface (i.e., a right end surface inFIG. 9) of the charging blade72(i.e., the supported section72B) in the rotational direction of the photoconductor drum32.

In view of performing discharging, the volume resistivity of the edge section72A may range between 104Ωcm and 108Ωcm. The supported section72B may have insulation properties since it does not have a function for supplying electricity to the edge section72A.

Charging Blade372According to Third Modification

Next, a charging blade372according to a third modification will be described.FIG. 10is a cross-sectional view illustrating the configuration of the charging blade372according to the third modification. The following description will be directed to sections that are different from those of the charging blade172according to the first modification. Furthermore, sections that have the same functions will be given the same reference numerals, and descriptions thereof will be omitted.

As shown inFIG. 10, in the charging blade372according to the third modification, the edge section72A has a triangular shape, in a side view (i.e., a cross-sectional view), with a length L1of, for example, 0.5 mm in the thickness direction of the charging blade372and a length L2of, for example, 0.25 mm. In other words, the length L2is shorter than that of the charging blade172(charging blade72) according to the first modification.

In the third modification, the edge section72A has insulation properties, and the supported section72B has conductive properties, such that discharging toward the photoconductor drum32is performed at the supported section72B.

In the third modification, the amount H by which the charging blade372digs into the photoconductor drum32, the angle θ, the length L2, and so on are determined so that the gap between the supported section72B and the photoconductor drum32allows for discharging (i.e., a gap of about 8 μm to 200 μm). A gap K (in the radial direction of the photoconductor drum32) between the photoconductor drum32and the upstream end (i.e., a left end inFIG. 10) of the supported section72B in the rotational direction of the photoconductor drum32is, for example, 50 μm. Therefore, discharging toward the photoconductor drum32is performed between the upstream end of the supported section72B in the rotational direction of the photoconductor drum32and an area where the gap between the supported section72B and the photoconductor drum32is equal to 200 μm.

The supported section72B is specifically composed of a rubber material having conductive properties. More specifically, the supported section72B is composed of a rubber material with a conductivity adding material, such as carbon or ion conductive material, dispersed therein. An example of the rubber material used includes polyurethane rubber. The term “conductive properties” in this case refers to a volume resistivity range of 1010Ωcm or lower. In view of performing discharging, the volume resistivity of the supported section72B may range between 104Ωcm and 108Ωcm.

The edge section72A is specifically composed of a rubber material having insulation properties. More specifically, the edge section72A is composed of a rubber material not having the aforementioned conductivity adding material dispersed therein. An example of the rubber material used includes polyurethane rubber. The term “insulation properties” in this case refers to a volume resistivity range of 1011Ωcm or higher.

In this exemplary embodiment including the third modification, insulation between the photoconductor drum32and the edge S (edge section72A) is maintained by a surface layer of the photoconductor drum32so that a leakage (i.e., an electrical breakdown) between the edge S and the photoconductor drum32is prevented from occurring. However, the edge S that vibrates by coming into contact with the rotating photoconductor drum32may possibly damage the surface layer of the photoconductor drum32. Even in that case, since the edge section72A has insulation properties in the third modification, the leakage (electrical breakdown) between the edge section72A and the photoconductor drum32may be suppressed. Furthermore, with the edge section72A having a high hardness in this exemplary embodiment, vibration thereof is minimized, whereby damage to the surface layer of the photoconductor drum32may be suppressed.

Furthermore, with the edge section72A having insulation properties, discharging occurring between the edge section72A and the photoconductor drum32is suppressed at the upstream side (left side inFIG. 10) of the edge S in the rotational direction. In other words, discharging is satisfactorily performed only at the downstream side of the edge S in the rotational direction of the photoconductor drum32.

Other Modifications

Although the image recording device100is equipped with the removing device29that removes residual toner from the photoconductor drum32, the charging blade72may alternatively be used as a removing device that removes residual toner from the photoconductor drum32. In this case, the removing device29is not provided, and the charging blade72is configured to serve both as a charging device and a removing device.

The present invention is not limited to the exemplary embodiments described above, and various modifications, alterations, and variations are permissible. For example, with regard to the modifications described above, multiple modifications may be combined where appropriate.