CN101379442B - Image forming device, image forming method, and image forming system - Google Patents

Abstract

The present invention provides an image forming apparatus, an image forming method, and an image forming system capable of properly preventing the occurrence of fog. The image forming apparatus has: an image carrier for carrying a latent image; a developer carrier having regularly arranged recesses on the surface, and the developer is transported to and from the carrier by being rotated while carrying the developer. the opposite position of the image body; an alternating voltage applying section that applies an alternating voltage to the developer carrier in order to develop the latent image by the developer transported to the opposite position, the The alternating voltage includes a first voltage for pushing developer from the developer carrier toward the image carrier, and a second voltage for pushing developer from the image carrier toward the developer carrier , here, the magnitude of the cycle of the alternating voltage is obtained by dividing the minimum width of the concave portion along the circumferential direction of the developer carrier by the moving speed of the developer carrier surface when the developer carrier rotates. Get the following value.

Description

Image forming apparatus, image forming method, and image forming system

technical field

The present invention relates to an image forming apparatus, an image forming method, and an image forming system.

Background technique

Image forming apparatuses such as laser printers are known. For example, the image forming apparatus has: an image carrier for carrying a latent image; and a developer carrier for carrying the developer to a relative position opposite to the image carrier by rotating the developer in a state of carrying the developer. . When an image signal or the like is sent from an external device such as a host computer, the image forming device develops the latent image carried by the image carrier with the developer transported to the relative position by the developer carrier to form a developer image, and The agent image is transferred to the medium, and finally an image is formed on the medium.

In addition, in the image forming apparatus described above, when the latent image is developed by the developer, there is a part for applying an alternating voltage to the developer carrier, the alternating voltage including: a first voltage for pushing the developer from the developer carrier to the image carrier; and a second voltage for pushing the developer from the image carrier to the developer carrier (refer to Japanese Patent Laid-Open No. Hei 5-142950 , JP-A-2004-219640 Bulletin).

Contents of the invention

On the surface of the developer carrier, regularly arranged recessed part.

However, the toner is easily embedded in the concave portion, and there is a tendency to deteriorate the rotatability of the toner in the concave portion. In addition, in an image forming apparatus having a charging member that comes into contact with the developer carrier to charge the developer carried by the developer carrier, the pressing force of the charging member on the developer is weakened in the concave portion (compared with the convex portion). , there is a possibility that triboelectrification cannot be properly performed.

Due to the above, the developer located in the recesses is likely to be insufficiently charged, and thus the toner becomes a cause of so-called fogging.

The present invention has been made in view of the above problems, and an object of the present invention is to appropriately prevent the occurrence of fog.

The present invention is mainly the following image forming apparatus. The image forming apparatus has: an image carrier for carrying a latent image; a developer carrier having regularly arranged recesses on the surface, and the developer is conveyed to and from the image carrier by being rotated while carrying the developer. on the opposite relative position; an alternating voltage applying section that applies an alternating voltage to the developer carrier in order to develop the latent image by the developer carried to the opposite position, the alternating The voltage includes: a first voltage for pushing the developer from the developer carrier to the image carrier; a second voltage for pushing the developer from the image carrier to the developer carrier; The magnitude of the period of varying voltage is equal to or less than a value obtained by dividing the minimum width of the concave portion in the circumferential direction of the developer carrier by the moving speed of the developer carrier surface when the developer carrier rotates.

Other characteristics of the present invention will be clarified by the description of this specification and the drawings.

Description of drawings

FIG. 1 is a diagram showing main components constituting a printer 10;

FIG. 2 is a block diagram showing a control unit of the printer 10 of FIG. 1;

FIG. 3A is a schematic diagram showing a photoreceptor 20 and a charging unit 30;

FIG. 3B is a schematic diagram showing a charging bias applied to the charging roller 31;

4 is a schematic diagram of a developing device;

Fig. 5 is a sectional view showing main constituent parts of the developing device;

FIG. 6 is a schematic perspective view of a developing roller 510;

FIG. 7 is a schematic front view of the developing roller 510;

FIG. 8 is a schematic diagram showing the cross-sectional shape of the groove portion 512;

Figure 9 is an enlarged schematic view of Figure 7;

FIG. 10 is a perspective view of the limiting scraper 560;

FIG. 11 is a perspective view of the bracket 526;

12 is a perspective view showing a state in which the bracket 526, the upper seal member 520, the regulating blade 560, and the developing roller 510 are assembled;

FIG. 13 is a perspective view showing a situation in which the bracket 526 is installed on the housing 540;

FIG. 14 is a schematic diagram showing a developing bias applied to the developing roller 510;

FIG. 15 is an explanatory diagram for explaining the advantages of the printer 10 of this embodiment;

Fig. 16A is a schematic diagram showing density unevenness caused by a developing bias;

Fig. 16B is a schematic diagram showing density unevenness caused by charging bias;

Fig. 16C is a schematic diagram showing a state in which the degree of density unevenness is enhanced;

FIG. 17 is a flowchart for explaining the operation of the printer 10 in this control;

18 is a graph showing the relationship between the type of medium and the moving speed V of the developing roller 510;

19A is a schematic diagram (part 1) showing changes of the developing roller 510 in the manufacturing process of the developing roller 510;

19B is a schematic diagram (part 2) showing changes of the developing roller 510 in the manufacturing process of the developing roller 510;

FIG. 19C is a schematic diagram (Part 3) showing changes of the developing roller 510 in the manufacturing process of the developing roller 510;

19D is a schematic diagram (Part 4) showing changes of the developing roller 510 in the manufacturing process of the developing roller 510;

FIG. 19E is a schematic view showing changes of the developing roller 510 in the manufacturing process of the developing roller 510 (Part 5);

FIG. 20 is an explanatory diagram for explaining rolling processing of the developing roller 510;

FIG. 21 is a flowchart for explaining a method of assembling the yellow developing device 54;

FIG. 22A is a diagram (part 1) showing changes in the surface shape of the developing roller 510;

FIG. 22B is a diagram (part 2) showing changes in the surface shape of the developing roller 510;

FIG. 22C is a diagram (part 3) showing changes in the surface shape of the developing roller 510;

Fig. 23A is a diagram (part 1) showing changes in developing bias voltage;

Fig. 23B is a graph (part 2) showing changes in developing bias voltage;

FIG. 24 is an explanatory diagram showing the external configuration of the image forming system;

FIG. 25 is a block diagram showing the configuration of the image forming system shown in FIG. 24 .

Label description

10 printer, 20 photoreceptor, 30 charging unit, 31 charging roller, 32 belt, 33 bearing, 34 spring, 35 cleaning roller, 40 exposure unit, 50YMCK developing unit, 50a central shaft, 51 black developing device, 52 magenta developing device , 53 Cyan developing device, 54 Yellow developing device, 55a, 55b, 55c, 55d holding part, 60 Primary transfer unit, 70 Intermediate transfer body, 75 Cleaning unit, 76 Cleaning blade, 80 Secondary transfer unit, 90 Fixing unit, 92 paper supply tray, 94 paper supply roller, 95 display unit, 96 registration roller, 100 control unit, 101 main controller, 102 unit controller, 112 interface, 113 image memory, 128YMCK developing unit drive control circuit, 129 charging unit control control circuit, 132 alternating voltage application part, 133 superimposed voltage application part, 510 developing roller, 510a central part, 510b shaft part, 512 groove part, 512a first groove part, 512b second groove part, 513 side surface , 514 bottom surface, 515 top surface, 520 upper seal member, 520a width direction end, 520b contact surface, 520c opposite surface, 524 upper seal pressure member, 526 bracket, 526a upper seal support part, 526b developing roller support part, 526c restricting blade support part, 530 toner container, 530a first toner container, 530b second toner container, 540 case, 542 upper case part, 544 lower case part, 545 partition wall , 546 Case sealing member, 550 Toner supply roller, 560 Restricting blade, 560a Front end, 562 Rubber part, 562a Contact part, 564 Rubber support part, 564a Thin plate, 564b Thin plate support part, 564c Longitudinal ends , 564d One end in the width direction, 564e The other end in the width direction, 572 Opening, 574 End sealing part, 576 Bearing, 600 Pipe fitting, 602 Flange press-in part, 604 Flange, 650 Round mold, 650a Convex part, 652 Round mold, 652a convex part, 680 groove, 700 image forming system, 702 computer, 704 display device, 706 printer, 708 input device, 708A keyboard, 708B mouse, 710 reading device, 710A floppy disk drive device, 710B CD-ROM drive device, 802 internal memory, 804 hard drive device, T toner

Detailed ways

At least the following matters are clarified from the description of this specification and the drawings.

The image forming device has:

An image-carrying body, used to carry a latent image;

a developer carrier having regularly arranged recesses on the surface, and carrying the developer to a relative position opposite to the image carrier by rotating the developer in a state of carrying the developer;

an alternating voltage applying section that applies an alternating voltage to the developer carrier in order to develop the latent image with the developer carried to the opposing position, the alternating voltage including: a first voltage , pushing the developer from the developer carrier to the image carrier; a second voltage, pushing the developer from the image carrier to the developer carrier;

Here, the magnitude of the period of the alternating voltage is obtained by dividing the minimum width of the concave portion in the circumferential direction of the developer carrier by the moving speed of the developer carrier surface when the developer carrier rotates. value below.

According to this image forming apparatus, occurrence of fog can be properly prevented.

Alternatively, the concave portion may be two types of helical grooves having different inclination angles with respect to the circumferential direction, and the two types of helical grooves intersect each other to form a lattice shape.

Alternatively, the developer carrier may have a rhombus-shaped top surface surrounded by the two kinds of spiral groove portions, and one of the two diagonal lines of the rhombus-shaped top surface is along the the circumferential direction.

Alternatively, the developer carrier may have a square top surface surrounded by the two types of spiral grooves.

In addition, the following mode may also be adopted, that is, the voltage applied to the developer carrier by the alternating voltage applying part is only the first voltage and the second voltage, and the alternating voltage applying part applies the voltages alternately. The first voltage and the second voltage.

Alternatively, the image carrier can be rotated, and the moving speed of the surface of the developer carrier when the developer carrier is rotated is the same as the speed of the image carrier when the image carrier is rotated. Surfaces move at different speeds.

At this time, the chargeability of the developer pulled back to the developer carrier side is good.

In addition, the following method can also be adopted, that is, the moving speed is variable, and when changing the moving speed, the size of the cycle of the alternating voltage is obtained by dividing the minimum width by the moving speed The value of the following way to change the size of the period of the alternating voltage.

In this case, regardless of the operating mode in which the image forming apparatus is executed, the above-described effect can be achieved, that is, the occurrence of fogging can be properly prevented.

Alternatively, the image forming apparatus may further include: a charging member that faces the image carrier and charges the image carrier; a superimposing voltage applying unit that superimposes a DC voltage and an AC voltage and For the charged part; the period of the alternating voltage is different from the value obtained by multiplying the period of the superimposed voltage by a natural number and the value obtained by dividing the period by a natural number.

At this time, in addition to properly preventing the occurrence of fog, the value obtained by multiplying the size of the cycle of the alternating voltage and the size of the cycle of the superimposed voltage by a natural number and dividing the size of the cycle by a natural number Since the obtained values are all different, it is possible to prevent the occurrence positions of the two kinds of density unevenness from continuously overlapping, and thus it is possible to suppress the conspicuousness of the density unevenness of the image.

Alternatively, the charging member may be a rotatable charging roller that faces the image carrier through a gap.

In this case, the effect of suppressing the conspicuous density unevenness of the image is more effective.

Alternatively, the image carrier can be rotated, and the alternating voltage applying unit alternately applies the first voltage and the second voltage for a predetermined time, and the image carrier rotation of the image carrier, if the portion of the image bearing member at the charging position charged by the charging member when the superimposing voltage applying portion starts applying the superimposing voltage is located by the developer transported to the opposite position At a developing position where development is performed, the alternating voltage application unit starts to apply the first voltage or the second voltage to the developer carrier.

In this case, the effect of suppressing the conspicuous density unevenness of the image is more effective.

Alternatively, the concave portion may be two types of helical grooves having different inclination angles with respect to the circumferential direction, and the two types of helical grooves intersect each other to form a lattice shape, and the The developer carrier has a square top surface surrounded by the two kinds of spiral groove portions, and the square top surface has one of two diagonal lines along the circumferential direction.

Image forming methods include the following methods:

The moving speed of the surface of the developer carrier having regularly arranged recesses on the surface is changed when the developer carrier is rotated while the developer carrier is rotated to carry the developer to the carrier image. body relative to the relative position;

The cycle of the alternating voltage is changed so that the size of the cycle of the alternating voltage is equal to or less than a value obtained by dividing the minimum width of the concave portion in the circumferential direction of the developer carrier by the changed moving speed. The magnitude of the alternating voltage includes: a first voltage to push the developer from the developer carrier to the image carrier; a second voltage to push the developer from the image carrier to the developer carrier;

According to the value obtained after the natural multiple of the period of the superimposed voltage by superimposing the DC voltage and the AC voltage and the value obtained after the natural number of the period is 1/2, both are the same as the changed period of the alternating voltage different conditions to change the size of the period of the superimposed voltage;

Applying the superimposed voltage with the period size changed to a charging member opposite to the image bearing body to charge the image bearing body;

Applying the alternating voltage with a changed cycle size to the developer carrier, the latent image carried by the image carrier is developed by the developer transported to the relative position.

According to the image forming method described above, even if the moving speed of the developer carrier is changed, it is possible to appropriately prevent the occurrence of fog and suppress the conspicuousness of uneven density of the image.

In addition, it is also possible to adopt a method in which the types of media on which images can be formed are plain paper and thick paper, and when an image is formed on the plain paper, the moving speed of the surface of the developer carrier is increased, and in the When forming an image on thick paper, the moving speed of the surface of the developer carrier is reduced.

In this case, even if the type of the medium is changed, it is possible to appropriately prevent the occurrence of fog and prevent the uneven density of the image from being conspicuous.

The image forming system has:

computer;

An image forming apparatus that can be connected to the computer, including: an image carrier for carrying a latent image; a developer carrier having recesses regularly arranged on the surface, and carrying the developer by rotating it in a state of carrying the developer to a relative position opposite to the image bearing body; an alternating voltage applying section that applies an alternating voltage to the developing in order to develop the latent image by the developer transported to the relative position a developer carrier, the alternating voltage comprises: a first voltage to push developer from the developer carrier to the image carrier; a second voltage to push developer from the image carrier to the developer Carrier; the magnitude of the period of the alternating voltage is obtained by dividing the minimum width of the concave portion in the circumferential direction of the developer carrier by the moving speed of the surface of the developer carrier when the developer carrier rotates value below.

According to this image forming system, occurrence of fog can be properly prevented.

Overall Configuration Example of Image Forming Apparatus

Hereinafter, a laser printer (hereinafter, also referred to as a printer) 10 as an image forming apparatus will be taken as an example, and its outline will be described with reference to FIG. 1 . FIG. 1 is a diagram showing main components constituting a printer 10 . In addition, in FIG. 1 , the vertical direction is indicated by arrows. For example, the paper feed tray 92 is arranged at the lower part of the printer 10 , and the fixing unit 90 is arranged at the upper part of the printer 10 .

As shown in FIG. 1 , the printer 10 of the present embodiment has: a charging unit 30; an exposure unit 40; a YMCK developing unit 50; A printing unit 60; an intermediate transfer body 70; a cleaning unit 75; and also has: a secondary transfer unit 80; a fixing unit 90; a display unit 95 as a user-facing notification member and composed of a liquid crystal panel; and controls the above-mentioned units, etc. A control unit 100 for managing the operation of the printer.

The photoreceptor 20 has a cylindrical conductive base material and a photosensitive layer formed on the outer peripheral surface of the conductive base material. The photoreceptor 20 can rotate around the central axis. In this embodiment, as shown in FIG. As indicated by the arrow, the photoreceptor 20 rotates clockwise.

The charging unit 30 is a device for charging the photoreceptor 20 . The charging unit 30 will be described in detail later. The exposure unit 40 is a device that forms a latent image on the charged photoreceptor 20 by irradiating laser light. The exposure unit 40 has a semiconductor laser, a polygon mirror, an F-theta lens, etc., and irradiates the charged photoreceptor 20 with modulated laser light based on an image signal input from a host computer such as a personal computer or word processor (not shown).

The YMCK developing unit 50 utilizes toner as an example of the developer contained in the developing device, that is, black (K) toner contained in the black developing device 51 , the toner contained in the magenta developing device 52 Magenta (M) toner, cyan (C) toner contained in the cyan developing device 53 , and yellow (Y) toner contained in the yellow developing device 54 make the photoreceptor 20 A device for developing latent images.

The YMCK developing unit 50 can move the four developing devices 51 , 52 , 53 , and 54 by rotating in a state where the four developing devices 51 , 52 , 53 , and 54 are attached. That is, the YMCK developing unit 50 holds the four developing devices 51, 52, 53, 54 by four holding parts 55a, 55b, 55c, 55d, and the four developing devices 51, 52, 53, 54 can be The center shaft 50a rotates around the center while maintaining its relative position. And, every time the image formation of one page is completed, the latent image formed on the photoreceptor 20 is selectively opposed to the photoreceptor 20 by the toner contained in each developing device 51 , 52 , 53 , 54 . Images are developed sequentially. The four developing devices 51 , 52 , 53 , and 54 can be attached and detached from the holding portion of the YMCK developing unit 50 , respectively. In addition, each developing device will be described in detail later.

The primary transfer unit 60 is a device for transferring the single-color toner image formed on the photoreceptor 20 to the intermediate transfer body 70. A full-color toner image is formed on the transfer body 70 . The intermediate transfer body 70 is an endless belt formed by providing a tin vapor-deposited layer on the surface of a PET film and laminating a semiconductive paint on the surface layer. speed rotary drive.

The secondary transfer unit 80 is a device for transferring a single-color toner image or a full-color toner image formed on the intermediate transfer body 70 to a medium such as paper, film, or cloth. The fixing unit 90 is a device for fusing and fixing a single-color toner image or a full-color toner image transferred onto a medium to form a permanent image.

The cleaning unit 75 is provided between the primary transfer unit 60 and the charging unit 30 and has a rubber cleaning blade 76 that contacts the surface of the photoreceptor 20 . After the toner image is transferred to the intermediate transfer body 70 , the cleaning blade 76 scrapes and removes the toner remaining on the photoreceptor 20 .

As shown in FIG. 2 , the control unit 100 is composed of a main controller 101 and a unit controller 102. An image signal and a control signal are input to the main controller 101, and the unit controller 102 controls all units according to an instruction based on the image signal and the control signal. The respective units and the like described above are described, thereby forming an image.

Next, the operation of the printer 10 configured as described above will be described.

First, when image signals and control signals from a host computer (not shown) are input to the main controller 101 of the printer 10 through the interface (I/F) 112, the unit controller 102 performs control, under which the photoreceptor 20 and the intermediate transfer body 70 are rotated. The photoreceptor 20 is sequentially charged by the charging unit 30 at the charging position while rotating.

As the photoreceptor 20 rotates, the charged area of the photoreceptor 20 reaches an exposure position, and a latent image corresponding to image information of a first color, eg, yellow Y, is formed in this area by the exposure unit 40 . In addition, with the YMCK developing unit 50 , a yellow developing device 54 containing yellow (Y) toner is located at a developing position opposite to the photoreceptor 20 . As the photoreceptor 20 rotates, the latent image formed on the photoreceptor 20 reaches a developing position, and is developed with yellow toner by the yellow developing device 54 . Thus, a yellow toner image is formed on the photoreceptor 20 . As the photoreceptor 20 rotates, the yellow toner image formed on the photoreceptor 20 reaches the primary transfer position, and is transferred onto the intermediate transfer body 70 by the primary transfer unit 60 . At this time, the primary transfer unit 60 is supplied with a primary transfer voltage having a polarity opposite to that of the charge polarity of the toner T (negative polarity in this embodiment). During this period, the photoreceptor 20 is in contact with the intermediate transfer body 70 , and the secondary transfer unit 80 is separated from the intermediate transfer body 70 .

For the second color, the third color, and the fourth color, the above-mentioned processes are sequentially performed by the respective developing devices, whereby the toner images of the four colors corresponding to the respective image signals are superimposedly transferred onto the intermediate transfer body 70 . A full-color toner image is thereby formed on the intermediate transfer body 70 .

As the intermediate transfer body 70 rotates, the full-color toner image formed on the intermediate transfer body 70 reaches the secondary transfer position, and is transferred onto the medium by the secondary transfer unit 80 . The medium is conveyed from the paper feed tray 92 to the secondary transfer unit 80 by the paper feed roller 94 and the registration roller 96 . In addition, during the transfer operation, the secondary transfer unit 80 is pressed against the intermediate transfer body 70 and a secondary transfer voltage is applied thereto.

The full-color toner image transferred to the medium is heated and pressurized by the fixing unit 90 to be fused and fixed on the medium.

On the other hand, the photoreceptor 20 scrapes off the toner T adhering to its surface by the cleaning blade 76 supported in the cleaning unit 75 after passing the primary transfer position, thereby preparing for charging to form the next potential. picture. The scraped toner T is recovered to a residual toner recovery unit included in the cleaning unit 75 .

A brief description of the control unit

Next, the configuration of the control unit 100 will be described with reference to FIG. 2 . The main controller 101 of the control unit 100 includes an image memory 113 , which is electrically connected to the host through the interface 112 and used for storing image signals input from the host. The unit controller 102 is electrically connected to each unit of the main body of the device (charging unit 30, exposure unit 40, YMCK developing unit 50, primary transfer unit 60, cleaning unit 75, secondary transfer unit 80, fixing unit 90, display unit 95). In connection, the state of each unit is detected by receiving signals from the sensors that these units have, and at the same time, each unit is controlled based on a signal input from the main controller 101 .

The YMCK developing unit driving control circuit 128 connected to the YMCK developing unit 50 has an alternating voltage applying part 132 (also simply referred to as a voltage applying part). In order to develop the latent image with the toner, the alternating voltage applying unit 132 functions as follows: applying an alternating voltage (hereinafter also referred to as developing bias voltage) to the developing roller 510 , between the developing roller 510 and the photoreceptor 20 to form an alternating electric field (details will be described later). In addition, a charging unit drive control circuit 129 connected to the charging unit 30 has a superimposed voltage applying unit 133 . In order to charge the photoreceptor 20 , the superimposed voltage applying part 133 plays the role of applying a superimposed voltage (hereinafter, also referred to as a charging bias voltage) to the charging roller 31 to form an alternating voltage between the charging roller 31 and the photoreceptor 20 . electric field.

Charge unit 30

Next, the charging unit 30 for charging the photoreceptor 20 will be described with reference to FIGS. 3A and 3B . FIG. 3A is a schematic diagram showing the photoreceptor 20 and the charging unit 30 . FIG. 3B is a schematic diagram showing a superimposed voltage applied to the charging roller 31 .

The charging unit 30 has: a charging roller 31 facing the photoreceptor 20 through a gap, rotatable as an example of a charging member for charging the photoreceptor 20; a cleaning roller 35 (not shown in FIG. 1 ), and The charging roller 31 abuts to clean the surface of the charging roller 31 . The charging roller 31 is configured by coating a conductive paint on the surface of a metal shaft. In addition, belts 32 that come into contact with the photoreceptor 20 are attached to both ends in the axial direction of the charging roller 31 . Since the outer diameter of the belt 32 is larger than that of the central portion of the charging roller 31 , a gap G is formed between the central portion and the photoreceptor 20 . Thus, the charging roller 31 charges the photoreceptor 20 in a non-contact state.

In addition, the charging unit 30 has a bearing 33 that rotatably supports the charging roller 31 , and a spring 34 that presses the charging roller 31 against the photoreceptor 20 through the bearing 33 . Then, the charging roller 31 is pressed against the photoreceptor 20 by the biasing force of the spring 34 , whereby the belt 32 comes into contact with the photoreceptor 20 .

Here, charging of the photoreceptor 20 will be described using FIG. 3B . When charging of the photoreceptor 20 is performed, a superimposed voltage (charging bias voltage) in which a DC voltage and an AC voltage are superimposed is applied to the charging roller 31 by the superimposed voltage applying portion 133 . Specifically, a voltage swinging between -540V and -620V (component of AC voltage) around -580V (component of AC voltage) is applied to charging roller 31 . In addition, the magnitude of the cycle of the charging bias (the magnitude of the cycle is denoted as T2) was 0.9 ms (millisecond).

developing device

Next, the developing device will be described using FIGS. 4 to 14 . Fig. 4 is a schematic diagram of a developing device. FIG. 5 is a cross-sectional view showing main components of the developing device. FIG. 6 is a schematic perspective view of the developing roller 510 . FIG. 7 is a schematic front view of the developing roller 510 . FIG. 8 is a schematic diagram showing a cross-sectional shape of the groove portion 512 . FIG. 9 is an enlarged schematic view of FIG. 7 , and is a view showing the groove portion 512 and the top surface 515 . FIG. 10 is a perspective view of the limiting scraper 560 . FIG. 11 is a perspective view of bracket 526 . FIG. 12 is a perspective view showing how the upper seal member 520 , the regulation blade 560 , and the developing roller 510 are assembled to the bracket 526 . FIG. 13 is a perspective view showing a state in which the bracket 526 is attached to the casing 540 . FIG. 14 is a schematic diagram showing a developing bias applied to the developing roller 510 . In addition, the cross-sectional view shown in FIG. 5 shows a cross-section of the developing device taken along a plane perpendicular to the longitudinal direction shown in FIG. 4 . In addition, in FIG. 5 , as in FIG. 1 , the vertical direction is indicated by arrows. For example, the central axis of the developing roller 510 is located below the central axis of the photoreceptor 20 . In addition, FIG. 5 shows a state where the yellow developing device 54 is located at a developing position facing the photoreceptor 20 . In addition, in FIGS. 6 to 9 , the dimensions of the groove portion 512 and the like are different from the actual size in order to be easily recognized in the drawings.

In the YMCK developing unit 50, there are provided a black developing device 51 containing black (K) toner, a magenta developing device 52 containing magenta (M) toner, and a cyan developing device 52 containing cyan (C) toner. The device 53 and the yellow developing device 54 containing the yellow (Y) toner have the same structure, so only the yellow developing device 54 will be described below.

The yellow developing device 54 has a developing roller 510 as an example of a developer carrier, an upper seal member 520 , a toner container 530 , a casing 540 , a toner supply roller 550 , a regulation blade 560 , a holder 526 and the like.

The developing roller 510 conveys the toner T to a relative position (developing position) facing the photoreceptor 20 by rotating while carrying the toner T. The developing roller 510 is a member made of aluminum alloy, iron alloy, or the like.

As shown in FIGS. 6 and 7 , in order to properly carry the toner T, the developing roller 510 has a groove portion 512 as an example of a concave portion on the surface of the central portion 510 a. In this embodiment, as the groove portion 512 , two kinds of spiral groove portions 512 having different winding directions are provided, that is, a first groove portion 512 a and a second groove portion 512 b. As shown in FIG. 7, the inclination angles of the first groove portion 512a and the second groove portion 512b with respect to the circumferential direction of the developing roller 510 are different from each other. The size of the acute angle formed by the length direction of the second groove portion 512b and the axial direction is about 45 degrees. In addition, as shown in FIG. 8, the width of the X direction of the first groove portion 512a and the width of the Y direction of the second groove portion 512b are about 50 μm, the depth of the groove portion 512 is about 7 μm, and the groove angle (in FIG. 8, The angle denoted by the symbol α) is about 90 degrees.

Moreover, the groove part 512 has the bottom surface 514 and the side surface 513, and in this embodiment, the inclination angle of the side surface 513 is about 45 degrees (refer FIG. 8).

As shown in FIG. 6 , FIG. 7 and FIG. 9 , the above-mentioned two types of spiral grooves 512 are regularly arranged on the surface of the central portion 510 a of the developing roller 510 , and intersect with each other to form a grid shape. Therefore, the diamond-shaped top surface 515 surrounded on four sides by the groove portion 512 forms a large number of meshes in the central portion 510a.

As mentioned above, in this embodiment, since the acute angle formed by the longitudinal direction of the first groove portion 512a and the axial direction and the acute angle formed by the longitudinal direction of the second groove portion 512b and the axial direction are both about is 45°, so the top surface 515 has a square planar shape, and one of the two diagonals of the top surface 515 is along the circumferential direction of the developing roller 510, and the other is along the axial direction. In addition, as shown in FIG. 8 , the length of one side of the square top surface 515 is about 30 μm.

Further, the developing roller 510 is provided with a shaft portion 510b supported via a bearing 576 by a developing roller supporting portion 526b of a holder 526 described later ( FIG. 12 ), thereby supporting the developing roller 510 rotatably. As shown in FIG. 5 , the developing roller 510 rotates in a direction (counterclockwise in FIG. 5 ) opposite to the rotation direction of the photoreceptor 20 (clockwise in FIG. 5 ). In addition, in this embodiment, when the developing roller 510 rotates, the moving velocity V of the surface of the developing roller 510 (ie, the linear velocity of the developing roller 510 on the surface of the developing roller 510 ) is 300 mm/s. In addition, when the photoreceptor 20 is rotated, the moving speed of the surface of the photoreceptor 20 (ie, the linear velocity of the photoreceptor 20 on the surface of the photoreceptor 20 ) is 210 mm/s, and the developing roller 510 is 210 mm/s with respect to the circumference of the photoreceptor 20 . The speed ratio is about 1.4.

In addition, there is a gap between the developing roller 510 and the photoreceptor 20 in a state where the yellow developing device 54 faces the photoreceptor 20 . That is, the yellow developing device 54 develops the latent image formed on the photoreceptor 20 in a non-contact state. In addition, in the printer 10 of this embodiment, when the latent image formed on the photoreceptor 20 is developed using a jumping developing method, an alternating electric field is formed between the developing roller 510 and the photoreceptor 20 (detailed later). illustrate).

The case 540 is manufactured by welding a plurality of integrally formed resin case parts, that is, an upper case part 542 and a lower case part 544 , and a toner container for accommodating the toner T is formed inside the case 540 . Agent containing body 530. The toner containing body 530 is divided into two toner containing portions, a first toner containing portion 530a and a second toner containing portion 530b, by a partition wall 545 inward from the inner wall (up and down in FIG. 5 ). direction) protrudes and serves to space the toner T. In addition, the upper parts of the first toner storage portion 530a and the second toner storage portion 530b communicate with each other, and the movement of the toner T is restricted by the partition wall 545 in the state shown in FIG. 5 . However, when the YMCK developing unit 50 is rotated, the toners accommodated in the first toner accommodating portion 530a and the second toner accommodating portion 530b are temporarily concentrated on the side of the communicating portion on the upper side of the developing position. , and when returning to the state shown in FIG. 5, these toners T will return to the first toner accommodating portion 530a and the second toner accommodating portion 530b after mixing. That is, the toner T in the developing device is appropriately stirred by the rotation of the YMCK developing unit 50 .

Therefore, in the present embodiment, no stirring member is provided in the toner container 530 , but a stirring member for stirring the toner T contained in the toner container 530 may be provided. In addition, as shown in FIG. 5 , the lower portion of the casing 540 (ie, the first toner accommodating portion 530 a ) has an opening 572 adjacent to which the developing roller 510 is disposed.

A toner supply roller 550 that supplies the toner T contained in the first toner accommodating portion 530 a to the developing roller 510 is provided in the above-mentioned first toner accommodating portion 530 a, And the toner T remaining on the developing roller 510 is peeled off from the developing roller 510 after the development. The toner supply roller 550 is made of polyurethane foam or the like, and contacts the developing roller 510 in an elastically deformed state. The toner supply roller 550 is disposed at the lower portion of the first toner accommodating portion 530a, and the toner T accommodated in the first toner accommodating portion 530a is transferred by the toner to the lower portion of the first toner accommodating portion 530a. The agent supply roller 550 supplies the developing roller 510 . The toner supply roller 550 is rotatable about a central axis located below the central axis of rotation of the developing roller 510 . In addition, the toner supply roller 550 rotates in a direction (clockwise in FIG. 5 ) opposite to that of the developing roller 510 (counterclockwise in FIG. 5 ).

The upper sealing member 520 abuts against the developing roller 510 along the axial direction of the developing roller 510, and after passing through the developing position, the upper sealing member 520 allows the toner T remaining on the developing roller 510 to move into the casing 540, and restricts the movement of the casing 540. The toner T inside the body 540 moves out of the casing 540 . The upper sealing member 520 is a sealing member made of polyethylene film or the like. The upper seal member 520 is supported by an upper seal support portion 526a of a holder 526 described later, and its longitudinal direction is arranged along the axial direction of the developing roller 510 (FIG. 12). The contact position where the upper seal member 520 contacts the developing roller 510 is located above the central axis of the developing roller 510 .

In addition, the upper seal member 520 is provided in a compressed state between the surface of the upper seal member 520 opposite to the contact surface 520b that contacts the developing roller 510 (this surface is also referred to as the opposite surface 520c) and the above-mentioned upper seal support portion 526a. There is an upper seal pressing member 524 made of elastic body such as foam ester (Moultoplain), and the pressing force of the upper seal pressing member 524 presses the upper seal member 520 toward the developing roller 510 side, whereby The upper seal member 520 is pressed against the developing roller 510 .

The regulating blade 560 penetrates from one axial end of the developing roller 510 to the other end, and abuts against the developing roller 510 through the abutting portion 562a to restrict the layer thickness of the toner T carried by the developing roller 510. The toner T carried by the roller 510 is charged. As shown in FIGS. 5 and 10 , this regulating scraper 560 has a rubber portion 562 and a rubber support portion 564 .

The rubber portion 562 is formed of silicone rubber, urethane rubber, or the like, and is in contact with the developing roller 510 .

The rubber support portion 564 includes a thin plate 564a and a thin plate support portion 564b, and supports the rubber portion 562 at one end portion 564d in the width direction thereof (ie, the end portion on the thin plate 564a side). The thin plate 564a is made of phosphor bronze, stainless steel, etc., and has elasticity. The thin plate 564 a supports the rubber portion 562 , and presses the rubber portion 562 against the developing roller 510 by its pressing force. The thin plate support portion 564b is a metal sheet disposed on the other end portion 564e in the width direction of the rubber support portion 564, and the thin plate support portion 564b is attached to the thin plate 564a in a state that supports the The end portion of the thin plate 564 a on the side opposite to the side supporting the rubber portion 562 .

In addition, the regulation scraper 560 is attached to the regulation scraper support portion 526c in a state in which both end portions 564c in the longitudinal direction of the thin plate support portion 564b are held by the regulation scraper support portion 526c of the bracket 526 described later. support.

The end portion of the blade 560 on the side opposite to the sheet supporting portion 564b, that is, the front end 560a is not in contact with the developing roller 510, and the portion (that is, the contact portion 562a) that is a predetermined distance from the front end 560a is not in contact with the developing roller 510. Contact to a certain extent. That is, the regulating blade 560 abuts on the developing roller 510 not on the edge but on the belly, and the layer thickness is regulated by the flat surface of the regulating blade 560 abutting on the developing roller 510 . In addition, the regulating blade 560 is arranged so that the front end 560 a thereof faces upstream in the rotation direction of the developing roller 510 , that is, so-called counter abuts. In addition, the abutting position of the regulating blade 560 abutting against the developing roller 510 is located below the central axis of the developing roller 510 , and is located below the central axis of the toner supply roller 550 . In addition, the restricting blade 560 abuts against the developing roller 510 in the axial direction of the developing roller 510 , thereby also serving to prevent leakage of the toner T from the toner container 530 .

In addition, as shown in FIG. 12 , an end seal member 574 is provided outside the rubber portion 562 of the regulating blade 560 in the longitudinal direction. The end sealing member 574 is formed of non-woven fabric, and is in contact with the axial end of the developing roller 510 along the peripheral surface of the developing roller 510, thereby preventing the toner T from leaking from between the peripheral surface and the housing 540. role.

The bracket 526 is a metal member for assembling various parts such as the developing roller 510, and as shown in FIG. The roller support portion 526b is provided outside the upper seal support portion 526a in the longitudinal direction (the axial direction) and intersects the longitudinal direction (the axial direction); the restricting blade support portion 526c is connected to the developing The roller support portion intersects and faces the longitudinal end portion of the upper seal support portion 526a.

12, the upper seal member 520 is supported at its widthwise end 520a (FIG. 5) by an upper seal supporting portion 526a, and the developing roller 510 is supported at its end by a developing roller supporting portion 526b.

Moreover, the regulation blade 560 is supported by the regulation blade support part 526c at the both end parts 564c of the longitudinal direction. The restriction scraper 560 is fixed to the bracket 526 by bolting to the restriction scraper support portion 526c.

In this way, as shown in FIG. 13 , the frame 526 assembled with the upper seal member 520 , the developing roller 510 , and the regulating blade 560 interposes the housing seal member 546 for preventing toner T from leaking from between the frame 526 and the housing 540 . (FIG. 5) and installed on the above-mentioned housing 540.

In the yellow developing device 54 configured as described above, the toner supply roller 550 supplies the toner T contained in the toner container 530 to the developing roller 510 . As the developing roller 510 rotates, the toner T supplied to the developing roller 510 reaches the abutting position of the regulating blade 560, and when passing through the abutting position, the layer thickness is regulated and negatively charged (negative electrode is charged). sex). The toner T on the developing roller 510 whose layer thickness is restricted and negatively charged is conveyed to a position opposite to the photoreceptor 20 (developing position) by further rotation of the developing roller 510, and is supplied to the relative position. The latent image formed on the photoreceptor 20 is developed.

Here, development of this latent image will be described using FIG. 14 . As described above, the printer 10 of the present embodiment uses the skip development method. When jump development is performed, an alternating voltage of a rectangular wave is applied to the developing roller 510 by the alternating voltage applying portion 132 . As shown in FIG. 14, the alternating voltage includes a first voltage V1 and a second voltage V2.

The first voltage V1 is a voltage for pushing toner from the developing roller 510 to the photoreceptor 20, and has a value of -900V. In this embodiment, as shown in FIG. 14 , when developing, the potential of the photoreceptor 20 is -500 V in the non-image portion (portion corresponding to a white image), and -500 V in the image portion (portion corresponding to a black image). is -50V, and since the toner is negatively polarized, when the first voltage V1 is applied to the developing roller 510, a toner is pushed from the developing roller 510 to form between the developing roller 510 and the photoreceptor 20. The electric field applied to the photoreceptor 20 moves the toner on the developing roller 510 toward the photoreceptor 20 .

On the other hand, the second voltage V2 is a voltage for pushing the toner from the photoreceptor 20 to the developing roller 510, and its value is 500V. When the second voltage V2 is applied to the developing roller 510 , an electric field is formed between the developing roller 510 and the photoreceptor 20 to push the toner from the photoreceptor 20 to the developing roller 510 , so that the toner on the photoreceptor 20 Move toward the developing roller 510 (pull back).

And, as shown in FIG. 14, since the first voltage V1 and the second voltage V2 are alternately applied by the alternating voltage applying part 132, when developing the latent image, the toner is alternately and repeatedly transferred from the developing roller 510 to the photoreceptor. 20 and the movement (return) from the photoreceptor 20 to the developing roller 510 .

In addition, in the present embodiment, both the time for which the alternating voltage application unit 132 continues to apply the first voltage V1 and the time for which the second voltage V2 is continuously applied are both 0.1 ms (milliseconds) (that is, the duty ratio is 50%). . Therefore, the magnitude of the period of the alternating voltage (the magnitude of the period is referred to as period T1) is 0.2 ms (millisecond) (see FIG. 14 ). In addition, the average voltage applied to the developing roller 510 by the alternating voltage applying portion 132 is greater than the potential of the non-image portion (-500V) and smaller than the potential of the image portion (-50V), and its value is -200V (=(-900+500) /2).

Due to the rotation of the developing roller 510 , the toner T on the developing roller 510 passing the developing position passes through the upper seal member 520 and is collected into the developing device without being scraped off by the upper seal member 520 . Also, the toner T remaining on the developing roller 510 is peeled off by the toner supply roller 550 .

Relationship Between the Width of the Groove 512 and the Period Size of the Alternating Voltage

As described above, considering that sufficient toner or the like can be carried on the surface of the developing roller 510 (in other words, the surface area of the surface on which the toner is carried is a sufficiently large value, etc.), sometimes the surface of the developing roller 510 Set the concave part of the regular configuration on it. The developing roller 510 of this embodiment is also provided with a groove portion 512 as an example of a concave portion.

However, the toner is easily inserted into the groove portion 512 , and there is a tendency for the toner toner to deteriorate in the groove portion 512 . In addition, as in the printer 10 of the present embodiment, when the regulating blade 560 is provided as a charging member that abuts on the developing roller 510 and charges the toner carried by the developing roller 510 , in the groove portion 512 (with top surface 515 ), the pressing force of the regulating blade 560 on the toner is weakened, and triboelectric charging may not be properly performed.

Due to the above, the toner located in the groove portion 512 tends to be insufficiently charged, and thus the toner becomes a factor of so-called fogging (caburi).

On the other hand, in the printer 10 of this embodiment, the magnitude (period T1) of the period of the alternating voltage (development bias) is the minimum width Lmin of the groove portion 512 in the circumferential direction of the development roller 510 divided by The moving speed V of the surface of the developing roller 510 when the developing roller 510 rotates is equal to or less than a value (T1≦Lmin/V). In the printer 10 of the present embodiment in which the width of the groove portion 512 and the cycle size of the developing bias satisfies the relationship described above, generation of fogging can be appropriately prevented.

Next, this will be described in more detail using FIGS. 9 and 15 . As described above, the surface of the developing roller 510 of this embodiment is provided with two types of spiral grooves 512 having different inclination angles with respect to the circumferential direction, and the two types of spiral grooves 512 intersect each other to form a lattice shape. In addition, the developing roller 510 has a square top surface 515 surrounded by the aforementioned two types of spiral grooves 512 , and one of two diagonal lines on the square top surface is along the circumferential direction ( FIG. 9 ). Furthermore, in such a developing roller 510 (as shown in FIG. 9 ), several widths such as width L1 and width L2 are defined for the width of the groove portion 512 along the circumferential direction of the developing roller 510, and the minimum width is as shown in FIG. 9 . Width Lmin (distance between AB in FIG. 9 ). In addition, the value of the width Lmin is about 70.71 μm.

As described above, the moving speed V of the surface of the developing roller 510 when the developing roller 510 rotates is 300 mm/s. Therefore, the value Lmin/V obtained by dividing the minimum width Lmin by the moving speed V of the surface of the developing roller 510 when the developing roller 510 rotates is about 0.236 ms (millisecond). Furthermore, as shown in FIG. 14 , since the magnitude of the period (period T1 ) of the developing bias is 0.2 ms, the present embodiment satisfies the relationship of T1≦Lmin/V.

Next, using FIG. 15 , it will be described why the occurrence of fog can be appropriately suppressed when such a relationship of T1≦Lmin/V is satisfied.

FIG. 15 shows two graphs (as an upper graph and a lower graph) and a time axis sequentially from top to bottom.

Here, the lower diagram of FIG. 15 shows which part of the developing roller 510 is located at a relative position to the photoreceptor 20 at a certain time t when the development of the latent image is performed. For example, when developing the latent image, if the part indicated by the symbol A in FIG. The portion indicated by the symbol B in FIG. 9 is located at the relative position. That is, the lower figure shows that it takes about 0.236 ms for the groove portion 512 (between A and B) of the developing roller 510 to pass through the relative position.

On the other hand, since the period (0.2 ms) of the developing bias is less than or equal to Lmin/V (0.236 ms), when the latent image is developed, the groove portion 512 (between A and B) of the developing roller 510 passes through the During the above relative position, one cycle of the developing bias is necessarily applied to the developing roller 510 (refer to FIG. 15 ).

That is, in the printer 10 of the present embodiment, while the groove portion 512 carrying a large amount of toner, which is the main cause of fogging, passes through the relative position, not only the The first voltage V1 that the roller 510 pushes toward the photoreceptor 20 is also reliably applied with the second voltage V2 that pulls the toner from the photoreceptor 20 back to the developing roller 510 . Therefore, the toner pull-back function of the second voltage V2 contributes to the pull-back development of the fogged toner that has moved from the groove portion 512 and adhered to the non-image portion (portion corresponding to a white image) of the photoreceptor 20 . Roller 510, so that the occurrence of fog can be properly prevented.

Density unevenness due to developing bias and charging bias

As described above, the alternating voltage (developing bias voltage) including the first voltage V1 and the second voltage V2 is applied to the developing roller 510, but it is well known that density unevenness occurs in an image due to the developing bias voltage. . In addition, the density unevenness tends to occur every cycle (period T1 ) of the developing bias. Similarly, a superimposed voltage (charging bias) in which a DC voltage and an AC voltage are superimposed is applied to the charging roller 31 , but it is well known that density unevenness occurs in an image due to the AC voltage component of the charging bias. In addition, the density unevenness tends to occur every cycle (period T2 ) of the charging bias. When the two kinds of density unevenness described above occur, if the occurrence positions of the two kinds of density unevenness overlap, the density unevenness becomes more prominent, and the density unevenness in the image becomes more conspicuous.

This phenomenon will be specifically described below using comparative examples shown in FIGS. 16A to 16C . Fig. 16A is a schematic view showing density unevenness due to a developing bias. Fig. 16B is a schematic diagram showing density unevenness due to charging bias. FIG. 16C is a schematic diagram showing a state in which the degree of density unevenness is enhanced.

As shown in FIG. 16A , density unevenness due to the developing bias occurs at predetermined intervals L1. The predetermined interval L1 is a value obtained by multiplying the moving speed of the photoreceptor 20 by the period T1 of the developing bias. Similarly, as shown in FIG. 16B , density unevenness due to charging bias occurs at predetermined intervals L2. The predetermined interval L2 is a value obtained by multiplying the moving speed of the photoreceptor 20 by the period T2 of the charging bias. Also, the above-mentioned two kinds of density variations occur independently.

In addition, when an image is formed, the first occurrence position of the density unevenness due to the developing bias and the first occurrence position of the density unevenness due to the charging bias sometimes overlap (area X1 surrounded by a dotted line in FIG. 16C ). When the occurrence positions of the two kinds of density unevenness overlap, the density unevenness becomes more remarkable. At this time, for example, when the period T1 of the developing bias is the same as the value obtained by dividing the period T2 of the charging bias by a natural number, the position where the density unevenness due to the charging bias occurs later will be the same as that caused by the developing bias. Since the occurrence positions of the resulting density unevenness tend to overlap continuously (area X2 surrounded by a dotted line in FIG. 16C ), the density unevenness becomes more prominent at predetermined intervals L2, and the density unevenness becomes particularly conspicuous.

In contrast, in the printer 10 of this embodiment, as shown in FIG. 3B and FIG. 14 , the period T1 (0.2 ms) of the above-mentioned developing bias is obtained by multiplying the period T2 (0.9 ms) of the charging bias by natural multiples. The value is different from the value obtained after dividing the natural number of the period T2. That is, T1 and T2 have a relationship of T1≠nT2 (here, n represents a natural number multiple or a fraction of a natural number). At this time, although the occurrence position of the density unevenness due to the developing bias and the occurrence position of the density unevenness due to the charging bias overlap sometimes, even if the occurrence positions of the two kinds of density unevenness overlap, they are the same as Unlike the case of the comparative example described above, it is possible to prevent successive occurrence positions of density unevenness due to developing bias and occurrence positions of density unevenness due to charging bias that occur subsequently. Therefore, it is possible to suppress the conspicuous density unevenness in the image.

In this way, in the printer 10 of the present embodiment, the period T1 of the developing bias and the period T2 of the charging bias satisfy the above-mentioned relationship, and it is possible to suppress conspicuous unevenness in image density.

Change control of cycle size of developing bias voltage and charging bias voltage

As described above, the printer 10 can form an image on a medium. Examples of the medium include special paper such as thick paper and OHP film, and plain paper. In addition, the printer 10 changes the processing speed of the printer (for example, the moving speed of the surface of the photoreceptor 20 , the moving speed V of the surface of the developing roller 510 , etc.) according to the type of media to appropriately form an image according to the type of media. Specifically, the printer 10 increases the processing speed when forming an image on plain paper, and decreases the processing speed when forming an image on special paper.

In addition, in the printer 10 of the present embodiment, in order to properly prevent the occurrence of fogging and prevent image density unevenness from being conspicuous, the processing speed of the printer is changed according to the type of the medium (as a result, the surface of the developing roller 510 The moving speed V is also changed), a control of changing the size of the cycle of the developing bias and the size of the cycle of the charging bias is performed. Specifically, the control unit 100 performs the following control: (1) changing the size of the cycle of the developing bias (hereinafter referred to as cycle T1 ) so that the cycle T1 of the developing bias is such that the groove portion 512 is aligned along the circumferential direction of the developing roller 510 The value obtained by dividing the minimum width Lmin by the above-mentioned moving speed V after the change is below; (2) Change the size of the period of the charging bias voltage (hereinafter referred to as period T2) so that the period T2 of the charging bias voltage is a natural number Both the value obtained by multiplying the period T2 and the value obtained by dividing the period T2 by a natural number are different from the period T1 after the change of the developing bias voltage.

Hereinafter, an example of the operation of the printer 10 during the control will be described using FIG. 17 . FIG. 17 is a flowchart for explaining the operation of the printer 10 during the control.

Various operations when the printer 10 executes these operations are mainly realized by the control unit 100 . In particular, in the present embodiment, it is realized by the CPU processing the program stored in the ROM. In addition, this program is composed of codes for performing various operations described below.

This control is executed when an image signal and a control signal are input into the printer 10 from a computer as an external device. This control signal includes information on the type of medium selected by the user (specifically, any one of "plain paper", "thick paper", and "transparency film").

First, the control unit 100 determines whether the media type included in the control signal matches a preset media type (here, "plain paper" is the preset media type) (step S102).

In this embodiment, the type of medium included in the control signal is "thick paper". At this time, since the type of medium (“thick paper”) contained in the control signal does not match the type of medium (“plain paper”) set in advance (step S102: No), the control unit 100 changes the processing speed (developing roller 510 moving speed V) (step S104).

FIG. 18 is a graph showing the relationship between the type of medium and the moving speed V of the developing roller 510 and the like, and is stored in the ROM or the like of the control unit 100 . As can be seen from the graph, the moving speed V of the developing roller 510 is 300 mm/s when forming an image on "plain paper", and 225 mm/s when forming an image on "thick paper". The moving speed V of the developing roller 510 when an image is formed on the film "is 150 mm/s.

Since the image is formed on "thick paper" in this embodiment, the control unit 100 changes the moving speed V of the developing roller 510 from 300 mm/s to 225 mm/s.

When the moving speed V of the developing roller 510 is changed, the control unit 100 changes the period T1 of the developing bias and the period T2 of the charging bias (steps S106, S108).

The graph shown in FIG. 18 shows the relationship between the kind of medium and the period T1 of the developing bias and the period T2 of the charging bias. For example, when the moving speed V of the developing roller 510 is 225 mm/s, the period T1 of the developing bias is 0.25 ms, and the period T2 of the charging bias is 1.1 ms. Also, as can be seen from the graph, the smaller the moving speed V of the developing roller 510 is, the larger the period T1 of the developing bias voltage and the period T2 of the charging bias voltage are.

In this embodiment, the moving speed V of the developing roller 510 is changed from 300 mm/s to 225 mm/s. Therefore, the control unit 100 changes the period T1 of the developing bias from 0.2 ms to 0.25 ms, and changes the period T2 of the charging bias from 0.9 ms to 1.1 ms as the moving speed V of the developing roller 510 changes.

However, as described above, when the moving speed V of the developing roller 510 is 300 mm/s, the period T1 (0.2 ms) of the developing bias and the period T2 (0.9 ms) of the charging bias have two expressions (namely, T1 ≤Lmin/V, and T1≠nT2). The period T1 of the developing bias and the period T2 of the charging bias are set so that the two expressions hold also when the moving speed V of the developing roller 510 is 225 mm/s and when the moving speed is 150 mm/s. Therefore, even if the moving speed V of the developing roller 510 is changed according to the type of the medium (for example, even if it is changed from 300 mm/s to 225 mm/s), the above two formulas (that is, T1≤Lmin/V, and T1 ≠nT2) changes the period T1 (0.25 ms) of the developing bias and the period T2 (1.1 ms) of the charging bias, so it is possible to properly prevent the occurrence of fog and suppress the conspicuousness of image density unevenness.

Next, returning to the flowchart shown in FIG. 17, the operation of the printer 10 in this control will be continued.

The control unit 100 applies a charging bias to the charging roller 31 to charge the photoreceptor 20 (step S110 ). In this embodiment, the photoreceptor 20 is charged by the superimposed voltage applying unit 133 applying the charging bias whose period T2 is changed to 1.1 ms in step S108 to the rotating charging roller 31 .

Next, the control unit 100 applies a developing bias to the developing roller 510 to develop the latent image on the photoreceptor 20 (step S112 ). In the present embodiment, the latent image is developed by applying the alternating voltage application unit 132 to the developing roller 510 in rotation by applying the developing bias whose period T1 is changed to 0.25 ms in step S106 .

In the above, the control unit 100 changes the moving speed V of the developing roller 510, but when the type of the medium included in the control signal matches the preset type of medium ("plain paper") (step S102: Yes), The control unit 100 does not change the moving speed V of the developing roller 510 . At this time, the control unit 100 also does not change the period T1 of the developing bias and the period T2 of the charging bias. That is, the moving speed V of the developing roller 510 was 300 mm/s, the period T1 of the developing bias was 0.2 ms, and the period T2 of the charging bias was 0.9 ms. Then, the superimposed voltage applying unit 133 applies a charging bias with a period T2 of 0.9 ms to charge the charging roller 31 (step S110), and the alternating voltage applying unit 132 applies a developing bias with a period T1 of 0.2 ms to make the latent image Develop (step S112).

In this case, since the above two expressions (that is, T1≦Lmin/V, and T1≠nT2) also hold, the occurrence of fog can be properly prevented and the image density unevenness can be suppressed from being conspicuous.

Manufacturing method of developing device

Here, a method of manufacturing the developing device will be described using FIGS. 19A to 21 . 19A to 19E are schematic diagrams showing changes of the developing roller 510 in the manufacturing process of the developing roller 510 . FIG. 20 is an explanatory view for explaining rolling processing of the developing roller 510 . FIG. 21 is a flowchart for explaining a method of assembling the yellow developing device 54 . In addition, when manufacturing the developing device, after the above-mentioned casing 540 , holder 526 , developing roller 510 , toner supply roller 550 , regulating blade 560 , etc. are manufactured separately, the developing device is assembled using these components. Here, regarding the manufacturing method of these components, first, the manufacturing method of the developing roller 510 will be described, and then the assembling method of the developing device will be described. Hereinafter, among the black developing device 51 , the magenta developing device 52 , the cyan developing device 53 , and the yellow developing device 54 , the yellow developing device 54 will be described as an example.

Manufacturing method of developing roller 510

Here, a method of manufacturing the developing roller 510 will be described using FIGS. 19A to 20 .

First, as shown in FIG. 19A, a pipe member 600 as a base material of the developing roller 510 is prepared. The wall thickness of the tube 600 is 0.5-3 mm. Next, as shown in FIG. 19B , flange press-fit portions 602 are formed at both end portions in the longitudinal direction of the pipe member 600 . The flange press-fit portion 602 is produced by cutting. Next, as shown in FIG. 19C , the flange 604 is press-fitted into the flange press-fitting portion 602 . In order to securely fix the flange 604 on the pipe fitting 600 , the flange 604 may also be glued or welded on the pipe fitting 600 after the flange 604 is pressed in. Next, as shown in FIG. 19D , centerless grinding is performed on the surface of the pipe member 600 pressed into the flange 604 . The centerless grinding is performed over the entire surface, and the ten-point average roughness Rz of the surface after the centerless grinding is 1.0 μm or less. Next, as shown in FIG. 19E , rolling processing is performed on the pipe member 600 press-fitted with the flange 604 . In this embodiment, so-called through feed rolling (also referred to as feed rolling, through feed rolling) processing using two round dies 650 and 652 is performed.

That is, as shown in FIG. 20, two circular dies 650, 652 arranged to clamp the above-mentioned pipe 600 as a workpiece are pressed against the pipe with a predetermined pressure (the direction of the pressure is indicated by a symbol P in FIG. 20 ). 600, in this state, the two round molds 650, 652 are rotated in the same direction (refer to FIG. 20). In through-feed rolling, by rotating the round dies 650, 652, the pipe 600 is rotated in the direction opposite to the rotation direction of the round dies 650, 652 (refer to FIG. to move in the indicated direction. Convex portions 650 a , 652 a for forming grooves 680 are provided on the surfaces of the round dies 650 , 652 , and the pipe 600 is deformed by the convex portions 650 a , 652 a to form the grooves 680 in the pipe 600 .

Then, after the rolling process is completed, the surface of the central portion 510a is plated with gold. In this embodiment, electroless Ni-P plating is used as the gold plating, but it is not limited to this, and hard chrome plating or electroplating may be used, for example.

Assembly method of yellow developing device 54

Next, a method of assembling the yellow developing device 54 will be described using FIG. 21 .

First, the casing 540, the holder 526, the developing roller 510, the regulating blade 560, and the like described above are prepared (step S2). Next, the regulating scraper 560 is fixed to the bracket 526 by bolting the regulating scraper 560 to the regulating scraper supporting portion 526c of the bracket 526 (step S4). In addition, before this step S4, the above-mentioned end seal member 574 is attached to the regulation scraper 560 in advance.

Next, the developing roller 510 is mounted on the holder 526 to which the regulating blade 560 is fixed (step S6). At this time, the developing roller 510 is attached to the bracket 526 so that the regulating blade 560 abuts against the developing roller 510 from one end portion to the other end portion in the axial direction. In addition, before this step S6, the above-mentioned upper sealing member 520 is mounted on the bracket 526 in advance.

Then, the bracket 526 mounted with the developing roller 510, the regulating blade 560, etc. is mounted on the housing 540 through the housing sealing member 546 (step S8), whereby the assembly of the yellow developing device 54 is completed. In addition, prior to this step S8, the above-mentioned toner supply roller 550 is mounted on the casing 540 in advance.

other implementations

As mentioned above, the image forming apparatus of the present invention has been described based on the above-mentioned embodiments, but the above-mentioned embodiments are only for facilitating understanding of the present invention, and do not limit the present invention. Needless to say, the present invention can be changed and improved without departing from the gist thereof, and the present invention includes their equivalents.

In the above-mentioned embodiments, an intermediate transfer type color laser printer has been described as an example of an image forming apparatus, but the present invention can be applied to color laser printers, monochrome laser printers, copiers, and facsimiles other than the intermediate transfer type. and other image forming devices.

In addition, the photoreceptor is not limited to a so-called photosensitive roller formed by providing a photosensitive layer on the outer peripheral surface of a cylindrical conductive base material, but may also be formed by providing a photosensitive layer on the surface of a belt-shaped conductive base material. And constitute the so-called photosensitive belt.

In addition, in the above embodiment, as shown in FIG. 3A, the charging member is a rotatable charging roller 31, and the charging roller 31 is opposed to the photoreceptor 20 through a gap (that is, the charging roller 31 is not in contact with the photoreceptor 20. The photoreceptor 20 is charged in a state), but it is not limited thereto. For example, the charging roller 31 may charge the photoreceptor 20 while being in contact with the photoreceptor 20 .

However, it is well known that when the charging roller 31 is not in contact with the photoreceptor 20 , that is, so-called non-contact charging, density unevenness due to charging tends to occur. Therefore, the effect of the printer 10 of the above embodiment in which the period T1 of the developing bias voltage and the period T2 of the charging bias voltage satisfy the relationship T1≠nT2, that is, the effect of suppressing the conspicuous unevenness of the image density, is more effective. In this respect, the above-described embodiment is more preferable.

In addition, in the above-described embodiment, as shown in FIG. 19 , the types of media on which images can be formed are plain paper and thick paper. When forming an image on the above-mentioned plain paper, the moving speed V of the surface of the developing roller 510 is increased (300mm /s), when forming an image on the above-mentioned thick paper, the moving speed V (150 mm/s) of the surface of the developing roller 510 is reduced, but it is not limited thereto. For example, the moving speed V of the developing roller 510 may also be changed according to the environment in which the printer 10 is installed.

When the moving speed V of the developing roller 510 is changed according to the type of the medium, the extent of the change tends to be large because images are formed according to the medium. Therefore, by changing the period T1 of the developing bias and the period T2 of the charging bias in accordance with the moving speed V of the developing roller 510, the above two expressions (that is, T1≦Lmin/V, and T1≠nT2) can be reliably made established. As a result, even if the type of the medium is changed, the occurrence of fog can be appropriately suppressed, and the density unevenness of the image can be suppressed from being conspicuous. In this respect, the above-described embodiment is more preferable.

In addition, in the above-mentioned embodiment, the concave portion is two types of spiral groove portions 512 having different inclination angles with respect to the circumferential direction of the developing roller 510, and the two types of spiral groove portions 512 intersect each other to form a lattice shape, but they do not limited to this. For example, the concave portion does not have to be groove-shaped. In addition, when the concave part is a groove part, the groove part does not need to be a spiral shape. In addition, only one type of groove portion may be provided as the concave portion.

In addition, in the above-mentioned embodiment, the developing roller 510 has the rhombus-shaped top surface 515 surrounded by the above-mentioned two kinds of spiral groove portions 512, and one of the two diagonal lines of the rhombus-shaped top surface 515 is along the circumferential direction. , but not limited to this. For example, as shown in FIG. 22A , the two diagonals on the top surface of the rhombus may not be along the above-mentioned circumferential direction.

In addition, in the above-described embodiment, the developing roller 510 has the square top surface 515 surrounded by the above-mentioned two kinds of spiral groove portions 512 , but the present invention is not limited thereto. For example, as shown in Figure 22B, the top surface may be a non-square rhombus. In addition, the top surface may not be a rhombus, for example, as shown in FIG. 22C , may also be a circle. In addition, FIGS. 22A to 22C are diagrams showing changes in the surface shape of the developing roller 510 (in addition, in each diagram, the above-mentioned minimum width Lmin is shown as reference information).

In addition, in the above-mentioned embodiment, the groove portion 512 includes the bottom surface 514 and the side surface 513, and the inclination angle of the side surface 513 is about 45° (refer to FIG. 8 ), but it is not limited thereto. For example, the inclination angle of the side surface 513 may also be about 90°.

In addition, in the above-mentioned embodiment, the voltage applied to the developing roller 510 by the alternating voltage application unit 132 is only the first voltage V1 and the second voltage V2, and the alternating voltage application unit 132 applies the first voltage V1 and the second voltage V2 alternately. , but not limited to this. For example, the alternating voltage application part 132 may apply the alternating voltage shown in FIG. 23A.

In addition, in the above-described embodiment, the duty ratio of the alternating voltage is 50%, but it is not limited thereto, and may be an alternating voltage as shown in FIG. 23B .

In addition, FIG. 23A and FIG. 23B are diagrams showing changes in alternating voltage (in addition, in each diagram, the size T1 of the above-mentioned period is shown as reference information).

In addition, in the above-mentioned embodiment, the moving speed of the surface of the developing roller 510 when the developing roller 510 rotates is different from the moving speed of the surface of the photoreceptor 20 when the photoreceptor 20 rotates. The speed of movement of the surface of the two is equal.

When the moving speed of the surface of the developing roller 510 when the developing roller 510 rotates is different from the moving speed of the surface of the photoreceptor 20 when the photoreceptor 20 rotates, compared with when the moving speeds of both surfaces are equal, the speed from the groove portion 512 Possibility that fog toner attached to the non-image portion (portion corresponding to a white image) of the photoreceptor 20 returns to the top surface 515 instead of the groove portion 512 when it is pulled back to the developing roller 510 side by the second voltage V2 Becomes high. Therefore, the chargeability of the returned toner is good, and in this respect, the above-described embodiment is more preferable.

Structure of image forming system, etc.

Hereinafter, an embodiment of an image forming system as an example of an embodiment of the present invention will be described with reference to the drawings.

FIG. 24 is an explanatory diagram showing the external configuration of the image forming system. The image forming system 700 includes a computer 702 , a display device 704 , a printer 706 , an input device 708 , and a reading device 710 . In the present embodiment, the computer 702 is housed in a mini tower type case, but it is not limited thereto. The display device 704 generally adopts a CRT (Cathode Ray Tube: cathode ray tube), a plasma display, or a liquid crystal display device, etc., but is not limited thereto. As the printer 706, the printer described above is used. In this embodiment, the input device 708 adopts a keyboard 708A and a mouse 708B, but it is not limited thereto. In this embodiment, the reading device 710 employs a floppy disk drive device 710A and a CD-ROM drive device 710B, but the present invention is not limited thereto. For example, other devices such as MO (Magneto Optical) disk drive or DVD (Digital Versatile Disk) may also be used.

FIG. 25 is a block diagram showing the configuration of the image forming system shown in FIG. 24 . An internal memory 802 such as a RAM and an external memory such as a hard disk drive 804 are also provided in a housing housing the computer 702 .

In the above description, an example in which the printer 706 is connected to the computer 702, the display device 704, the input device 708, and the reading device 710 to form an image forming system has been described, but the present invention is not limited thereto. For example, the image forming system may be composed of the computer 702 and the printer 706 , and the image forming system may not include any of the display device 704 , the input device 708 , and the reading device 710 .

In addition, the printer 706 may have the respective functions or a part of the mechanism of the computer 702 , the display device 704 , the input device 708 , and the reader device 710 , for example. As an example, the printer 706 may include an image processing unit that performs image processing, a display unit that performs various displays, and a recording medium loading and unloading unit for loading and unloading a recording medium on which images captured by a digital camera or the like are recorded. data.

The image forming system realized as above is superior to the conventional system as a whole.

Claims (14)

1. A laser printer, characterized in that, have: An image-carrying body for carrying a latent image; a developer carrier having regularly arranged recesses on the surface, and carrying the developer to a relative position opposite to the image carrier by rotating the developer in a state of carrying the developer; an alternating voltage applying section for applying an alternating voltage to the developer carrier in order to develop the latent image by the developer carried to the opposite position, the alternating voltage comprising: a first voltage for pushing developer from the developer carrier toward the image carrier, and a second voltage for pushing developer from the image carrier toward the developer carrier, Here, the magnitude of the period of the alternating voltage is obtained by dividing the minimum width of the concave portion in the circumferential direction of the developer carrier by the moving speed of the surface of the developer carrier when the developer carrier rotates. value below. 2. The laser printer according to claim 1, wherein: The recesses are two types of helical grooves having different inclination angles with respect to the circumferential direction, and the two types of helical grooves intersect each other to form a lattice shape. 3. The laser printer according to claim 2, wherein: The developer carrier has a rhombus-shaped top surface surrounded by the two kinds of spiral groove portions, and the rhombus-shaped top surface has one of two diagonal lines along the circumferential direction. 4. The laser printer according to claim 2, wherein: The developer carrier has a square top surface surrounded by the two kinds of spiral groove portions. 5. The laser printer according to any one of claims 1 to 4, wherein The voltage applied to the developer carrier by the alternating voltage applying section is only the first voltage and the second voltage, The alternating voltage applying unit alternately applies the first voltage and the second voltage. 6. The laser printer according to any one of claims 1 to 4, wherein The image carrier can be rotated, The moving speed of the surface of the developer carrier when the developer carrier is rotated is different from the moving speed of the surface of the image carrier when the image carrier is rotated. 7. The laser printer according to any one of claims 1 to 4, wherein The moving speed is variable, When changing the moving speed, the size of the cycle of the alternating voltage is changed so that the size of the cycle of the alternating voltage is equal to or smaller than a value obtained by dividing the minimum width by the moving speed. 8. The laser printer according to claim 1, wherein: Also includes: A charging member is opposed to the image bearing body and charges the image bearing body; a superimposed voltage applying unit that applies a superimposed voltage obtained by superimposing a DC voltage and an AC voltage to the charged part; The size of the cycle of the alternating voltage is different from the value obtained by multiplying the size of the cycle of the superimposed voltage by a natural number and the value obtained by dividing the size of the cycle by a natural number. 9. The laser printer according to claim 8, wherein: The charging member is a rotatable charging roller, The charging roller faces the image carrier with a gap therebetween. 10. The laser printer according to claim 8 or 9, characterized in that, The image bearing body can be rotated, The alternating voltage applying unit alternately applies the first voltage and the second voltage for a predetermined time, When the superimposed voltage application unit starts to apply the superimposed voltage, the part of the image carrier that is at the charging position by the charging member is positioned at the position that is charged by the conveyance along with the rotation of the image carrier. The alternating voltage application unit starts applying the first voltage or the second voltage to the developer carrier when the developing position where the developer at the opposite position is developed is reached. 11. The laser printer according to claim 8 or 9, wherein The concave portion is two types of helical grooves having different inclination angles with respect to the circumferential direction, and the two types of helical grooves intersect each other to form a lattice shape, The developer carrier has a square top surface surrounded by the two kinds of spiral groove portions, One of the two diagonals on the top surface of the square is along the circumferential direction. 12. An image forming method in a laser printer, characterized in that, Include the following steps: Changing the movement speed of the surface of the developer carrier when the developer carrier is rotated, the developer carrier having recesses regularly arranged on the surface, the developer is conveyed to the image carrier by rotating in a state of carrying the developer in relative relative position; The magnitude of the period of the alternating voltage is changed so that the magnitude of the period of the alternating voltage is not more than a value obtained by dividing the minimum width of the concave portion in the circumferential direction of the developer carrier by the changed moving speed , the alternating voltage includes: a first voltage for pushing the developer from the developer carrier to the image carrier; a second voltage for pushing the developer from the image carrier to the developer carrier; Change the size of the period of the superimposed voltage in which the DC voltage and the AC voltage are superimposed, so that the value obtained after multiplying the size of the period of the superimposed voltage by a natural number and the value obtained after dividing the size of the period by a natural number are all the same as the alternating current. The size of the period after the change of the variable voltage is different; Applying the superimposed voltage with the period size changed to a charging member opposite to the image bearing body to charge the image bearing body; Applying the alternating voltage with a changed cycle size to the developer carrier, the latent image carried by the image carrier is developed by the developer transported to the relative position. 13. The image forming method in the laser printer according to claim 12, wherein: The types of media on which images can be formed are plain paper and thick paper, When an image is formed on the plain paper, the moving speed of the surface of the developer carrier is increased, and when an image is formed on the thick paper, the moving speed of the surface of the developer carrier is decreased. 14. A laser printer system, characterized in that, have: computer; A laser printer, which can be connected to the computer, includes: an image carrier for carrying a latent image; a developer carrier having regularly arranged recesses on the surface, and transporting the developer to the In a relative position opposite to the image carrier; an alternating voltage applying section that applies an alternating voltage to the developer in order to develop the latent image by the developer transported to the relative position a carrier, the alternating voltage includes a first voltage for pushing developer from the developer carrier toward the image carrier, and a voltage for pushing developer from the image carrier toward the developer carrier The second voltage of the alternating voltage, the size of the cycle of the alternating voltage is the minimum width of the concave portion along the circumferential direction of the developer carrier divided by the movement of the surface of the developer carrier when the developer carrier rotates The resulting value for speed is below.

Images