JP2004249665A - Electrophotographic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adjust printing resolving power in an electrophotographic apparatus wherein an organic EL element is used in an exposure head. <P>SOLUTION: The electrophotographic apparatus has the exposure head 52 having first and second element rows 86a and 86b, wherein organic EL elements 86 are staggered in two rows, provided thereto so as to emit light at every row, photosensitive bodies 47Y, 47M, 47C and 47K on which electrostatic latent images are formed by the exposure light of the exposure head 52, a developing sleeve 49 for supplying toners to the electrostatic latent images to form toner images on the photosensitive bodies 47Y, 47M, 47C and 47K and a CPU 111 for selectively using a part or the whole of the element rows corresponding to a printing condition including printing resolving power designated by a user. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic apparatus having an exposure head in which a plurality of light emitting elements are linearly arranged.
[0002]
[Prior art]
Conventionally, a laser beam emitted from a laser light source is scanned using a rotating polygon mirror (polygon mirror) to form a latent image on a photoconductor, or an exposure head in which a plurality of light emitting elements are linearly arranged. 2. Description of the Related Art An electrophotographic apparatus having a configuration in which a latent image is formed on a photoreceptor by exposure is known.
[0003]
Among them, the electrophotographic apparatus equipped with an exposure head is advantageous in miniaturization because the optical system can be configured simply, and it is not restricted by the rotation speed of the rotating polygon mirror, so high speed can be achieved if the light intensity of the light emitting element is sufficient. It is also advantageous in terms of conversion.
[0004]
As a conventional exposure head, an LED head in which a number of minute LED elements are linearly arranged has been put to practical use. In general, high brightness can be obtained from an LED element. However, since the LED element is basically manufactured using a semiconductor process, the yield is rapidly deteriorated when an attempt is made to increase the length. Therefore, the integration degree of the light emitting element is, for example, at most 512 pixels per chip in the case of 1200 dpi (dot / inch). In order to realize a long exposure head because one chip is short as described above, it is necessary to accurately arrange a large number of chips in a line. Further, it is known that the LED head forms a PN junction for each LED element by a semiconductor process, so that the luminance variation is large (up to about ± 25% in one chip). In general, each LED element or a plurality of LED elements emit light in a predetermined sequence to control the current value for driving the LEDs based on the light amount correction data, or to adjust the light emission time. Control methods are known.
[0005]
On the other hand, as another example of an exposure head, an exposure head using an organic EL (electroluminescence) element in which a plurality of light emitting elements are linearly arranged is known.
[0006]
Since the organic EL element generates a small amount of heat, cooling radiating fins and the like can be eliminated, and the size of the exposure head itself can be reduced to, for example, about 3 mm or less.
[0007]
Note that Japanese Patent No. 3230450 discloses a printer head in which a plurality of light emitting elements are arranged in a staggered manner, and a printer to which the printer head is applied. In the printer disclosed in this document, an image is always formed by controlling all the light emitting elements regardless of image data to be printed.
[0008]
[Patent Document 1]
Japanese Patent No. 3230450
[0009]
[Problems to be solved by the invention]
In general, a printer connected to a network or the like and intended for output from a personal computer or the like is configured so that a printing resolution can be selected based on, for example, a user's designation, and even in an electrophotographic apparatus equipped with an exposure head, It is necessary to respond to the need to use a high-resolution mode, that is, a high-resolution mode, and a low-resolution mode, that is, a low-resolution mode.
[0010]
In general, printing at high resolution allows fine control of character edges and the screen for tone reproduction, so high-quality printing is possible.On the other hand, printing at low resolution is necessary for image data expansion processing. Since the data amount is reduced, for example, the time from when the print data (usually PDL: page description language) is transferred from the computer to the printer until the printing by the printer is completed is shortened.
[0011]
The user can select a high-resolution mode (high printing resolution and high image quality but takes time to complete printing) and a low-resolution mode (low printing resolution but time until printing completion) according to the required priority of image quality and printing speed. Can be shortened).
[0012]
Here, if the printing resolution can be selected, depending on the contents specified by the user, a case may occur in which only one of the plurality of light emitting element arrays is used. Specifically, in the case of an exposure head having a recording resolution of 1200 dpi when all the light emitting elements are used, all of the plurality of element rows are used in the high resolution mode, but the plurality of element rows are used in the low resolution mode of 600 dpi. In this case, for example, one of two rows is used.
[0013]
In this case, in the case of a device such as an organic EL element in which the amount of emitted light decreases as the cumulative lighting time increases, if only one of the plurality of element rows arranged in a staggered manner is continuously used, The light amount difference from the unused element row becomes large, which causes image quality deterioration.
[0014]
In addition, when the interval between the plurality of element rows arranged in a staggered manner is large, if the selected element row changes, the image forming position shifts in the sub-scanning direction.
[0015]
Further, in the case of a so-called tandem color printer in which a plurality of image forming stations including at least an exposure head are arranged in a row, the image forming position of each color is shifted depending on the selection of the light emitting element row.
[0016]
Therefore, an object of the present invention is to provide a technique capable of easily adjusting a printing resolution in an electrophotographic apparatus equipped with an exposure head having a plurality of light emitting element arrays.
[0017]
Another object of the present invention is to provide an electrophotographic apparatus capable of equalizing deterioration of an organic EL element in units of columns.
[0018]
Still another object of the present invention is to provide an electrophotographic apparatus capable of matching print positions in different element arrays.
[0019]
It is another object of the present invention to provide an electrophotographic apparatus capable of preventing color misregistration in color printing.
[0020]
[Means for Solving the Problems]
In order to solve this problem, an electrophotographic apparatus according to the present invention includes an element row in which light emitting elements are arranged in a plurality of rows in a staggered pattern, and the element rows are capable of emitting light for each row. Means, a photoreceptor on which an electrostatic latent image is formed by exposure light from the exposure means, a developing means for supplying toner to the electrostatic latent image to form a toner image on the photoreceptor, and a print resolution designated by a user And control means for selectively using a part or all of the element array according to printing conditions including
[0021]
As described above, since the light emitting elements are provided with a plurality of element rows arranged in a zigzag pattern, and a part or all of the element rows are driven by the control means, the recording resolution of the exposure head can be simplified. It becomes possible to adjust.
[0022]
Further, in order to solve this problem, in the electrophotographic apparatus of the present invention, the control unit controls the light emission period between the element arrays to be substantially equal in the low resolution mode using a part of the element arrays. Control.
[0023]
This makes it possible to equalize the deterioration of the light emitting elements in units of columns.
[0024]
Further, in order to solve this problem, in the electrophotographic apparatus of the present invention, the control means controls the exposure start timing so that the top margins of different element rows are the same in the low resolution mode. .
[0025]
This makes it possible to match the printing positions in different element rows.
[0026]
In order to solve this problem, in the electrophotographic apparatus of the present invention, a plurality of exposure means and development means are provided corresponding to each color toner, and the control means comprises the same element array of an exposure head corresponding to each color toner. Is used to perform printing.
[0027]
Thus, even if the element array to be used is switched, the writing start positions of the respective color image data become relatively the same, so that it is possible to prevent color misregistration in color printing.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
According to an aspect of the present invention, there is provided an exposure unit including a plurality of rows of light emitting elements arranged in a staggered pattern with respect to each other, and each of the element rows is capable of emitting light for each row. Photoreceptor on which an electrostatic latent image is formed by the exposure light of the means, developing means for supplying toner to the electrostatic latent image to form a toner image on the photoreceptor, and printing conditions including a print resolution specified by the user Control means for selectively using a part or all of the element array according to the above, wherein a plurality of element arrays in which light emitting elements are staggered with respect to each other. Since a part or the whole is driven by the control means, there is an effect that the recording resolution of the exposure head can be adjusted.
[0029]
According to a second aspect of the present invention, in the first aspect, the printing conditions include a low-resolution mode for forming an image at a low resolution and a high-resolution mode for forming an image at a high resolution. This mode is an electrophotographic device that uses a part of the element array in the low resolution mode, and uses the entire element array in the high resolution mode, and has the effect that the recording resolution of the exposure head can be adjusted. Have.
[0030]
According to a third aspect of the present invention, in the first or second aspect of the present invention, in the low resolution mode using a part of the element arrays, the control means is configured such that the light emission periods between the element arrays are substantially equal. This is an electrophotographic apparatus that performs control such that the deterioration of the light emitting elements can be equalized in units of columns.
[0031]
According to a fourth aspect of the present invention, in the third aspect of the present invention, the control means is an electrophotographic apparatus for switching an element array to be used in a page unit or a job unit in which printing is performed. Can be equalized in units of columns.
[0032]
According to a fifth aspect of the present invention, in the fourth aspect of the present invention, when switching the element row in page units, the control means may switch the element row different from the last element row used in the previous job. This is an electrophotographic apparatus that uses a column for the first page of the current job, and has an effect that deterioration of light emitting elements can be equalized for each column.
[0033]
According to a sixth aspect of the present invention, in the first aspect of the present invention, in the low-resolution mode, the control means is configured such that top margins of mutually different element rows are the same in the low resolution mode. This is an electrophotographic apparatus that controls the exposure start timing, and has the effect of making it possible to match the printing positions in different element rows.
[0034]
The invention according to claim 7 of the present invention is the electrophotographic apparatus according to claim 6, wherein the control means changes the setting of the top margin according to the distance between the element rows and the printing speed. This has the effect of making it possible to match the printing positions in the element rows.
[0035]
According to an eighth aspect of the present invention, in the invention according to any one of the first to seventh aspects, in the low resolution mode, the control means outputs different light amount correction data according to the selected element row. An electrophotographic apparatus that emits light from an element row by using the element row has an effect of making it possible to equalize the amount of light between the element rows.
[0036]
According to a ninth aspect of the present invention, in the invention according to any one of the first to eighth aspects, a plurality of exposing means and developing means are provided corresponding to each color toner, and the control means comprises: This is an electrophotographic apparatus that performs printing using the same element row of an exposure head corresponding to the above, and since the writing position of each color image data is the same, it is possible to prevent color misregistration in color printing. Have.
[0037]
According to a tenth aspect of the present invention, in the invention according to any one of the first to ninth aspects, in the low resolution mode, the control means controls data input to the element row, or This is an electrophotographic apparatus that controls a driver for driving the device array and selects an element row to emit light. Since a part or all of the plurality of element rows are driven by the control unit, the recording resolution of the exposure head is adjusted. It has the effect that it becomes possible.
[0038]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In these drawings, the same members are denoted by the same reference numerals, and redundant description is omitted.
[0039]
FIG. 1 is a schematic diagram showing a configuration of an electrophotographic apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory view showing a developing station in the electrophotographic apparatus of FIG. 1, and FIG. 3 is exposure in the electrophotographic apparatus of FIG. FIG. 4 is an explanatory view showing an internal structure of the head, FIG. 4 is an explanatory view showing an arrangement of organic EL elements as an exposure light source provided in the exposure head of FIG. 3, and FIG. 5 shows a configuration of a controller in the electrophotographic apparatus of FIG. FIG. 6 is a block diagram showing a configuration of an engine control unit in the electrophotographic apparatus of FIG. 1, FIG. 7 is a block diagram showing a configuration of a head control unit of FIG. 6, and FIG. 8 is a detail of an exposure head and a head control unit. FIG. 2 is a circuit diagram showing a configuration.
[0040]
Referring to FIG. 1, an electrophotographic apparatus 40 has a yellow developing station 41Y, a magenta developing station 41M, a cyan developing station 41C, and a black developing station 41K. A paper feed tray 43 for accommodating the recording paper 42 is provided above, and recording paper serving as a transport path of the recording paper 42 supplied from the paper feed tray 43 is provided at a location corresponding to each of the developing stations 41Y to 41K. The transport path 44 is vertically arranged from above to below.
[0041]
The developing stations 41Y to 41K form yellow, magenta, cyan, and black toner images in order from the upstream side of the recording paper transport path 44, and include photoconductors 47Y to 47K, a developing sleeve (not shown), and charging. It is an assembly of members for realizing a development process in a series of electrophotographic methods, such as a container (not shown).
[0042]
Now, the developing station 41 will be described in detail with reference to FIG. FIG. 2 is a diagram showing a structure around the developing station. The developing stations 41Y to 41K differ in the color of the filled developer, but since the configuration is the same regardless of the developing color, the description will be given without simplification of the color for simplicity.
[0043]
In FIG. 2, the inside of the developing station 41 is filled with a developer 45 which is a mixture of a carrier and a toner. Reference numerals 46a and 46b denote stirring paddles for stirring the developer 45. The rotation of the stirring paddles 46a and 46b causes the toner in the developer 45 to be charged to a predetermined potential by friction and circulates inside the developing station 41. The toner and the carrier are sufficiently stirred and mixed. Reference numeral 47 denotes a photosensitive member which is rotated in a direction D3 by a driving source (not shown). A charger 48 charges the surface of the photoconductor 47 to a predetermined potential. 49 is a developing sleeve (developing means), and 50 is a thinning blade. The developing sleeve 49 has a mag roll 51 in which a plurality of magnetic poles are formed. The layer thickness of the developer 45 supplied to the surface of the developing sleeve 49 is regulated by the thinning blade 50, and the developing sleeve 49 is rotated in a direction D4 by a driving source (not shown). As a result, the developer 45 is supplied to the surface of the developing sleeve 49, and the developer not transferred to the photoconductor 47 is collected in the developing station 41.
[0044]
52 is an exposure head (exposure means). The exposure head 52 according to the present embodiment is configured by arranging organic EL elements in a staggered pattern with respect to each other to form two element rows, and forms an electrostatic latent image having a maximum size of A4 on a photoconductor. Only the toner of the developer 45 supplied to the surface of the developing sleeve 49 adheres to this electrostatic latent image portion, and the electrostatic latent image is visualized. The details of the structure of the exposure head and the arrangement of the organic EL elements will be described later.
[0045]
53 is a supporting member for supporting the exposure head 52. Numeral 54 denotes a light quantity sensor constituted by a phototransistor or the like, which is arranged at an angle at which light emitted from the exposure head 52 and reflected on the surface of the photoconductor 47 is directly incident. A scattering plate (not shown) is provided on the surface of the light amount sensor 54 on which the light is incident. Even if the incident position of the light slightly changes due to, for example, the eccentricity of the photoconductor 47, the received light amount does not largely change. It has become. The light quantity sensor 54 has a characteristic that the output current changes linearly with respect to the received light quantity. By referring to the output of the light quantity sensor 54, the light emitting element (organic EL element) at a predetermined position of the exposure head 52 emits light. The amount of light can be detected.
[0046]
A transfer roller 55 is provided at a position opposing the recording paper transport path 44 with respect to the photoconductor 47, and is rotated in a direction D5 by a driving source (not shown). A predetermined transfer bias is applied to the transfer roller 55, and transfers the toner image formed on the photoreceptor 47 to the recording paper conveyed through the recording paper conveyance path 44.
[0047]
Hereinafter, the description will be continued by returning to FIG.
[0048]
Reference numeral 56 denotes a toner bottle which stores yellow, magenta, cyan, and black toners. A toner transport pipe (not shown) is provided from the toner bottle 56 to each of the developing stations 41Y to 41K, and supplies toner to the developing stations 41Y to 41K.
[0049]
Reference numeral 57 denotes a paper feed roller, which rotates in the direction D1 by controlling an electromagnetic clutch (not shown), and sends out the recording paper 42 loaded in the paper supply tray 43 to the recording paper transport path 44.
[0050]
A registration roller 58 and a pinch roller pair 59 are provided as a nip conveyance unit on the entrance side of the recording paper conveyance path 44 located between the paper supply roller 57 and the transfer portion of the yellowest development station 41Y at the uppermost stream. The registration roller 58 and the pinch roller pair 59 temporarily stop the recording paper 42 conveyed by the paper feed roller 57 and convey the recording paper 42 in the direction of the yellow developing station 41Y at a predetermined timing. By this temporary stop, the leading end of the recording paper 42 is regulated in parallel with the axial direction of the registration roller 58 and the pinch roller pair 59, thereby preventing the recording paper 42 from skewing.
[0051]
Reference numeral 60 denotes a recording paper passage sensor. The recording paper passage sensor 60 is constituted by a reflection type sensor (photo reflector), and detects the front end and the rear end of the recording paper 42 based on the presence or absence of reflected light.
[0052]
When the rotation of the registration roller 58 is started (power transmission is controlled by an electromagnetic clutch (not shown) to turn ON / OFF), the recording paper 42 is transported along the recording paper transport path 44 in the direction of the yellow developing station 41Y. However, starting from the rotation start timing of the registration roller 58, the writing timing of the electrostatic latent image by the exposure head (see reference numeral 52 in FIG. 2) mounted on each of the developing stations 41Y to 41K is independently controlled.
[0053]
A fixing device 62 is provided as a nip conveying means on the exit side in the recording paper conveying path 44 located further downstream of the blackest developing station 41K at the most downstream side. The fixing device 62 includes a heating roller 63 and a pressure roller 64. The heating roller 63 is a multi-layered roller composed of a heating belt, a rubber roller, and a core material (both not shown) in order from the surface. The heat generating belt is a belt having a three-layer structure, and includes a release layer, a silicone rubber layer, and a base material layer (both not shown) from the side closer to the surface. The release layer is made of a fluorine resin having a thickness of about 20 to 30 μm, and imparts release properties to the heating roller 63. The silicon rubber layer is made of about 170 μm silicon rubber, and gives the pressing roller an appropriate elasticity. The base layer is made of a magnetic material that is an alloy of iron, nickel, chromium, or the like.
[0054]
65 is a back core in which the exciting coil is included. Inside the back core 65, an exciting coil formed by bundling a predetermined number of copper wires (not shown) whose surface is insulated is extended in the rotation axis direction of the heating roller 63, and heated at both ends of the heating roller 63. The roller 63 is formed so as to rotate along the circumferential direction of the roller 63. When an alternating current of about 30 kHz is applied to the exciting coil from an exciting circuit (not shown) which is a semi-resonant type inverter, a magnetic flux is generated in a magnetic path formed by the back core 65 and the base layer of the heating roller 63. An eddy current is formed in the base layer of the heating belt of the heating roller 63 by this magnetic flux, and the base layer generates heat. The heat generated in the base material layer is transmitted to the release layer via the silicone rubber layer, and the surface of the heating roller 63 generates heat.
[0055]
Reference numeral 66 denotes a thermistor (Thermal Sensitive Resistor) provided as a temperature detecting unit for the heating roller 63. A thermistor is a ceramic semiconductor obtained by sintering at a high temperature using a metal oxide as a main raw material. It can measure the temperature of a contacted object by applying that the load resistance changes according to the temperature. . The output of the thermistor 66 is input to a control device (not shown), and the control device controls the power output to the excitation coil inside the back core 65 based on the output of the thermistor 66, and the surface temperature of the heating roller 63 becomes approximately 170 ° C. Control.
[0056]
When the recording paper 42 on which the toner image is formed passes through a nip formed by the heating roller 63 and the pressure roller 64 whose temperature is controlled, the toner image on the recording paper 42 is heated by the heating roller 63. The image is heated / pressed by the pressure roller 64 and a fixed image can be obtained.
[0057]
Reference numeral 67 denotes a recording paper trailing edge detection sensor for monitoring the discharge state of the recording paper 42. Reference numeral 71 denotes a toner image detection sensor. The toner image detecting sensor 71 is a reflection type sensor unit using a plurality of light emitting elements (both visible light) having different emission spectra and a single light receiving element. The image density is detected by utilizing the fact that the absorption spectrum differs depending on the image density. Further, since the toner image detecting sensor 71 can detect not only the image density but also the image forming position, in the electrophotographic apparatus according to the present embodiment, two toner image detecting sensors 71 are provided in the width direction of the apparatus, The image forming timing is controlled on the basis of the detection position of the image position shift amount detection pattern formed in (1).
[0058]
72 is a recording paper transport drum. The recording paper transport drum 72 is a metal roller whose surface is covered with rubber having a thickness of about 200 μm, and the recording paper 42 after fixing is transported along the recording paper transport drum 72 in the direction D2. At this time, the recording paper 42 is cooled by the recording paper transport drum 72 and transported while being bent in a direction opposite to the image forming surface. As a result, it is possible to greatly reduce the curl generated when a high-density image is formed on the entire surface of the recording paper. Thereafter, the recording paper 42 is conveyed in the direction D <b> 6 by the kick-out roller 74 and is discharged to the discharge tray 78.
[0059]
Reference numeral 73 denotes a face-down paper discharge unit. The face-down discharge unit 73 is configured to be rotatable around the support member 75, and when the face-down discharge unit 73 is opened, the recording paper 42 is discharged in the direction D7. When the face-down sheet discharge section 73 is closed, a rib 76 is formed on the back surface along the conveyance path so as to guide the conveyance of the recording sheet 42 together with the recording sheet conveyance drum 72.
[0060]
A driving source 77 employs a stepping motor in the present embodiment. By the drive source 77, a peripheral portion of each of the developing stations 41Y to 41K including a paper feed roller 57, a registration roller 58, a pinch roller pair 59, photoconductors 47Y to 47K and transfer rollers 55Y to 55K, a fixing device 62, a recording paper transport drum 72, the kick roller 74 is driven.
[0061]
Reference numeral 80 denotes a controller, which receives image data from a computer or the like (not shown) via an external network and generates printable image data.
[0062]
81 is an engine control unit. The engine control unit 81 controls the hardware and mechanism of the electrophotographic apparatus 40, forms a color image on the recording paper 42 based on the image data transferred from the controller 80, and performs overall control of the electrophotographic apparatus. .
[0063]
82 is a power supply unit. The power supply unit 82 supplies power of a predetermined voltage to the drive source 77, the controller 80, and the engine control unit 81, and also supplies power to the heating roller 63 of the fixing device 62. A so-called high-voltage power supply such as charging of the surface of the photoconductor 47, a developing bias applied to the developing sleeve (49 in FIG. 2, and a transfer bias applied to the transfer roller 55) is included in the power supply unit.
[0064]
Further, the power supply unit 82 includes a power supply monitoring unit 83 so that at least a power supply voltage supplied to the engine control unit 81 can be monitored. The monitor signal is detected by the engine control unit 81, and detects that the power supply switch is turned off or a drop in the power supply voltage at the time of a power failure or the like.
[0065]
Next, the configuration of the exposure head will be described with reference to FIG.
[0066]
As shown in FIG. 3, the exposure head 52 has a head support member 53 that supports the exposure head 52. The exposure head 52 includes an organic electroluminescence element (organic EL element) 86 as a light source, which is mounted on a base material 84 and hermetically sealed by a sealing material 85 provided on the head support member 53, A driver 87 is provided on 84 and supplies a voltage corresponding to the image data to the organic EL element 86 to emit light. Further, on the base material 84, a prism 88 for reflecting irradiation light from the organic EL element 86 and changing the optical path by 90 °, a fiber lens array 89 for transmitting and condensing light from the prism 88, and a fiber lens array 89 A cylindrical lens 90 for narrowing the light from the lens in the sub-scanning direction is mounted.
[0067]
As shown in FIG. 4, the organic EL elements 86 are arranged in a zigzag pattern with each other, and two element rows, that is, a first element row 86a and a second element row 86b are formed. The first and second element rows 86a and 86b can be turned on and off for each row, and a high-resolution mode for driving both element rows at the same time, that is, a high-resolution mode, and one of the element rows A low-resolution mode for driving only the pixel, that is, a low-resolution mode is realized.
[0068]
That is, in the present embodiment, the pitch of the organic EL element 86 in one element row in the main scanning direction is 1/600 inch, and the pitch of the organic EL element 86 when the two element rows in the main scanning direction are also combined. Is 1/1200 inch, and the pitch between the first element row 86a and the second element row 86b is 4/1200 inch. When the printing resolution under the printing conditions specified by the user is 1200 dpi (high resolution mode), both the first element row 86a and the second element row 86b are driven to form an image. In the case of 600 dpi (low-resolution mode), one of the first element row 86a and the second element row 86b is selectively driven to form an image. Thus, the printing resolution of the electrophotographic apparatus using the organic EL element 86 for the exposure head 52 is adjusted.
[0069]
The drive control of the organic EL element 86 is performed by a CPU 111 described later, including the case described below.
[0070]
Here, the numerical values such as the pitch in the present embodiment are examples, and the present invention is not limited to these numerical values. Further, the number of element rows is two in this embodiment, but may be three or more.
[0071]
As shown in the figure, the organic EL element 86 is elongated in the sub-scanning direction, and light emitted from the organic EL elements 86 in the first element row 86a and the second element row 86b is output by a single cylindrical lens 90. It is narrowed down in the scanning direction. Originally, light emitted from the organic EL element 86 by the fiber lens array 89 forms an erect equal-magnification image on the image plane of the photoconductor 47, but the cylindrical lens 90 has power only in the sub-scanning direction. Since the focal lengths of the main scanning side and the sub-scanning side are different, the light spot on the photoreceptor 47 contracts in the sub-scanning direction and expands in the main scanning direction (that is, the sub-scanning direction depends on the power of the fiber lens array 89 and the cylindrical Focusing is performed on the image plane of the photoconductor 47 by the power of the lens 90, but the focus position is intentionally shifted in the main scanning direction). Therefore, the photosensitive member 47 is designed so that a substantially square light spot is obtained on the image plane.
[0072]
Furthermore, since the individual light spots in the main scanning direction at this time are designed to be in contact with each other, the latent image in the main scanning direction will not be intermittent even if only one element row is used.
[0073]
Next, the configuration and operation of the controller in the electrophotographic apparatus according to the present embodiment will be described with reference to FIG.
[0074]
In FIG. 5, reference numeral 100 denotes a computer. The computer 100 transfers image data and print job information to the controller 80 via the network 101. 102 is a network interface. The controller 80 receives image data and print job information transferred from the computer 100 via the network interface 102, and transmits status information such as an error state of the electrophotographic apparatus to the computer 100.
[0075]
A CPU (control means) 103 controls the operation of the controller 80 based on a program stored in the ROM 104.
[0076]
A RAM 105 is used as a work area of the CPU 103, and temporarily stores image data and print job information received by the network interface 102, printable image data expanded in page units, and the like. You.
[0077]
Reference numeral 106 denotes an image processing unit. The image processing unit 106 performs image processing (conversion processing from printer language to raster data, color correction, page-by-page) based on the image data transferred from the computer 100 and print job information (both temporarily stored in the RAM 105). , Edge correction, screen generation, etc.) to generate image data to be printed, and store the image data in the RAM 105 again.
[0078]
Reference numeral 107 denotes a printer interface. Image data in page units stored in the RAM 105 is transferred to the engine control unit 81 via the printer interface 107.
[0079]
Next, the configuration and operation of the engine control unit will be described with reference to FIG.
[0080]
In FIG. 6, reference numeral 110 denotes a controller interface. The controller interface 110 receives image data in page units and print mode information transferred from the controller 80.
[0081]
Reference numeral 111 denotes a CPU (control means) which controls the operation of the printer engine based on a program stored in the ROM 112. A RAM 113 is used as a work area when the CPU 111 operates. Reference numeral 114 denotes a so-called rewritable nonvolatile memory such as an EEPROM. The non-volatile memory 114 stores, for example, life information such as the rotation time of the photoconductor 47 of the electrophotographic apparatus and the operation time of the fixing device 62, and the cumulative lighting value of the light emitting element described in detail later. 115 is a serial interface. Information from a group of sensors such as a recording paper passage sensor 60, a recording paper trailing edge detection sensor 67, and a light amount sensor 54 (see reference numeral 54 in FIG. 2), a power supply monitoring unit 83 (detects a decrease in power supply voltage, and operates the CPU 111 Before the operation stops, the cumulative value of the number of lighting of each light emitting element of the exposure head is stored in the nonvolatile memory 114.) The output of the serial conversion means (not shown) is converted into a serial signal of a predetermined cycle, Received at interface 115. The serial signal received by the serial interface 115 is read by the CPU 111 after being converted into a parallel signal. On the other hand, the start / stop of a drive source 77 for driving the paper feed roller 57, the photoconductors 47Y to 47K, the heating roller 63 of the fixing device 62, the recording paper transport drum 72, and the like, and the driving force for the paper feed roller 57 and the registration roller 58 A control signal to an actuator such as an electromagnetic clutch (not shown) for controlling transmission and a control signal for setting a potential of a high-voltage power supply such as a developing bias / transfer bias / charging potential are transmitted to the serial interface 115 as parallel signals. Sent. The serial interface 115 converts this parallel signal into a serial signal and outputs it to the actuator group. In the present embodiment, all sensor inputs and actuator control signal outputs that do not need to be detected at high speed are performed via the serial interface 115.
[0082]
On the other hand, an input from the toner image detection sensor 71 (an image displacement detection pattern needs a detection resolution of about 10 μm) that requires high-speed sampling is directly connected to an input terminal of the CPU 111.
[0083]
Reference numerals 120Y, 120M, 120C, and 120K denote head control units that control the driving of the exposure heads (see reference numeral 52 in FIG. 2) corresponding to each printing color. The head controllers 120Y to 120K include functions for controlling the exposure timing of the exposure head 52 and controlling the drive voltage of the organic EL elements mounted on the exposure heads 52Y to 52K. Reference numerals 121Y, 121M, 121C, and 121K denote buffer memories having a capacity of several lines. The image data transferred via the controller interface 110 is temporarily stored in buffer memories 121Y to 121K provided independently for each printing color. The image data stored in the buffer memories 121Y to 121K is transferred to exposure heads 52Y to 52K corresponding to respective print colors by a DMA circuit (not shown). Note that the buffer memories 121Y to 121K are configured by dual port RAMs, and are readable and writable by the CPU 111 via a path (not shown).
[0084]
Reference numerals 122Y, 122M, 122C, and 122K denote drivers, which are light-emitting elements 123Y to 123L, which are organic EL elements, based on control signals output from the head control units 120Y to 120K and image data transferred from the buffer memories 121Y to 121K. Drive 123K.
[0085]
Here, light emission control of the exposure head 52 by the CPU 111 will be described.
[0086]
In the low resolution mode, if one of the element rows is always selected and driven, the deterioration of the organic EL elements in the element row progresses more than the organic EL elements in the other element row. The light emission period between the element rows 86a and 86b is controlled so as to be substantially equal. That is, specifically, the element row to be driven is switched for each page on which printing is performed. However, even if the element row is switched in units of a plurality of pages or in units of jobs with one page being the minimum unit, the deterioration of the organic EL elements can be made uniform in units of columns.
[0087]
When the element row is switched on a page basis, an element row different from the last element row used in the previous job (for example, the first element row 86a used lastly in the last job) In this case, if the second element column 86b) is used for the first page of the current job, the two element columns are always used alternately, and the deterioration of the organic EL element is determined in units of columns. This is desirable because it is more uniform.
[0088]
If the power supply monitoring unit 83 described above detects that the power supply voltage has dropped beyond a predetermined range, the CPU 111 stores in the EEPROM 114 which element row was used for the last print page. Thus, not only when the power is normally turned off but also during a power failure, the element row to be used next can be correctly selected.
[0089]
Here, if the printing start position in the sub-scanning direction of the element rows different from each other, that is, the top margin is different, the printing position in the first element row 86a and the printing position in the second element row 86b are slightly different. Become. Therefore, in order to prevent this, in the low resolution mode, the CPU 111 controls the exposure start timing so that the top margins of different element rows are the same. That is, the setting of the top margin is changed according to the distance between the element rows and the printing speed.
[0090]
In a tandem-type electrophotographic apparatus in which a plurality of exposure heads 52, photoconductors 47, and developing sleeves 49 are provided for each color toner as in this embodiment, the same element row is used for all the exposure heads 52. Printing. That is, if the exposure head 52 for forming a yellow image uses the first element row 86a, and the exposure head 52 for forming a magenta image uses the second element row 86b, the elements driven by the printing colors are used. When the columns are changed, the writing positions of the respective color image data are different, so that a color shift corresponding to the interval between the element columns occurs. Therefore, in order to prevent such color shift in color printing, printing is performed by the CPU 111 using the same element array of the exposure head 52 corresponding to each color toner.
[0091]
Normally, the precision of the interval between the first element row 86a and the second element row 86b can be realized extremely high (depending on the precision of the mask at the time of element formation, and has a precision of substantially submicron order). Therefore, as long as the same element row is used for each print color, the state of color misregistration does not change even if the element row used is switched.
[0092]
By the way, since an evaporation process is used for manufacturing an organic EL element, luminance variation between adjacent pixels can be generally suppressed to be small. However, since the distance in the sub-scanning direction (that is, the distance between element rows) is larger than the pixel pitch in the main scanning direction, the light amount distribution in the main scanning direction differs for each element row. Therefore, in order to make the light amount uniform by performing light amount variation correction corresponding to each element line, the CPU 111 emits light in the element line using different light amount correction data according to the selected element line in the low resolution mode. It is desirable to make it.
[0093]
Next, the configuration of the head control unit 120 will be described in detail with reference to FIG. As shown in FIG. 6, there are actually four head control units for each printing color, but one head control unit will be described below for simplicity.
[0094]
In FIG. 7, reference numeral 130 denotes a head drive timing control unit. The head drive timing control unit 130 provides a buffer memory to the first driver 122a corresponding to the first element row 86a and the second driver 122b corresponding to the second element row 86b mounted on the exposure head 52. Control for holding one line of the image data sent from 121 and drive timing of the first and second element rows 86a and 86b are generated. The head drive timing controller 130 supplies the buffer memory 121 with a clock signal (CLK) for transferring image data and the address (ADDRESS) generated by the address generator 130a. In addition, the head drive timing control unit 130 outputs a clock signal (CLK) and other driver control signals to the first and second drivers 122a and 122b.
[0095]
Next, the driving of the exposure head 52 will be described in detail with reference to FIG.
[0096]
In FIG. 8, reference numeral 150 denotes 39 driver chips arranged linearly in the line direction. 151 is a 256-bit shift register provided for each driver chip 150; 152 is a 256-bit latch arranged corresponding to the shift register 151; 153 is an output signal of the latch 152 and strobe signals (STB) 1 to 13; A gate 154 that receives and operates is a driver transistor that turns ON / OFF based on an output signal of the gate 153, and 123 is an organic EL element that emits light based on a current driven by the driver transistor 154.
[0097]
The image data (DATA) output from the buffer memory 121 is transferred in bit units inside the shift register 151 in synchronization with the clock signal (CLK), and is output to the adjacent shift register 151 when the transfer of 256 bits is completed. You. When the image data (DATA) is sent to all the shift registers 151, the load signal (LOAD) is input to the latch 152, and the image data (DATA) in the shift register 151 is held in the latch 152 collectively.
[0098]
When the image data is latched, strobe signals (STB) 1 to 13 are sequentially output, and the image data (DATA) and the strobe signals (STB) 1 to 13 already held in the latch 152 are subjected to an AND operation at the gate 153. Then, when the strobe signals (STB) 1 to 13 become a predetermined logic (for example, High state), the driver transistor is turned on according to the latched image data, and a driving current is supplied to the organic EL element 123 so that the organic EL element 123 is driven. The EL element 123 lights up.
[0099]
Next, the head drive voltage setting unit 133 will be described. In the head drive voltage setting unit 133, reference numeral 156 denotes a DA converter, and 157 denotes a head power supply. The power supply voltage supplied to the entire driver transistor 154 is determined by setting a value from the CPU 111 to the DA converter 156. A driver current setting unit 158 is provided independently for each driver chip 150. The driver current setting unit 158 receives a line synchronization signal (LSYNC) and a clock signal (CLK), and can set a current value supplied to each driver chip 150 in synchronization with transfer of image data. ing.
[0100]
Next, selection of the first element row 86a and the second element row 86b will be described.
[0101]
There are two procedures for selecting an element row by the CPU 111.
[0102]
That is, in the first procedure, first, when the controller transfers a command including resolution information (high-resolution mode or low-resolution mode), the CPU 111 receives and analyzes the command. Here, the controller performs a resolution conversion process and outputs image data according to the resolution. Next, the CPU 111 operates the register of the head drive timing control unit 130 of the head control unit 120 to set the data transfer mode. When a high resolution (for example, 1200 dpi) is specified, the head drive timing control unit 130 controls the address generation unit 130a, and outputs the even-numbered image data to the first driver 122a and the odd-numbered image data to the first driver 122a. Is transferred to the second driver 122b (DMA transfer). When a low resolution (for example, 600 dpi) is specified, the head drive timing control unit 130 controls the address generation unit 130a and transfers image data of all addresses to the first driver 122a or the second driver 122b. I do.
[0103]
As described above, in the first procedure, the controller prepares image data corresponding to the resolution. Therefore, when two first and second element rows 86a and 86b are arranged in a staggered manner, as described above, in the low resolution mode, print data is input to only one of the element rows. In the high resolution mode, image data is divided into even addresses and odd addresses and input to each element row. In this procedure, although the processing in the head control unit 120 is complicated, when the resolution is low, the number of pixels to be processed is reduced, so that the time from when the controller starts the expansion processing to when printing is completed is shortened. There is an advantage.
[0104]
In the second procedure, first, when the controller transfers a command including resolution information, the CPU 111 receives and analyzes the command. Here, the controller does not perform the resolution conversion processing of the image data, and always outputs image data (for example, 1200 dpi) corresponding to the maximum resolution. Next, the CPU 111 operates the register of the head drive timing control unit 130 of the head control unit 120 to set the data transfer mode. When a high resolution (for example, 1200 dpi) is specified, the head drive timing control unit 130 controls the address generation unit 130a, and outputs the even-numbered image data to the first driver 122a and the odd-numbered image data to the first driver 122a. The data is transferred to the second driver 122b (DMA transfer), and both drivers are operated. When a low resolution (for example, 600 dpi) is designated, the head drive timing control unit 130 controls the address generation unit 130a, so that the image data of the even address is sent to the first driver 122a and the image data of the odd address is sent to the first driver 122a. DMA transfer to the second driver 122b. At this time, the head drive timing control unit 130 controls the supply of the STROBE signal to select a driver to be operated.
[0105]
As described above, in the second procedure, the controller always outputs the data of the maximum resolution together with the resolution information, and selects the driver by the STROBE signal. Therefore, when two first and second element rows 86a and 86b are arranged in a staggered manner, the operation of the driver that drives one element row is prohibited in the low resolution mode. In the high resolution mode, the operation of the driver for driving both element arrays is permitted. In this procedure, contrary to the first procedure, the processing of the head control unit 120 is simplified. However, since the controller always generates the image data having the maximum resolution, the expansion processing of the image data depends on the printing resolution. It is the same as the case of the maximum resolution (the printing speed does not change even if the printing resolution is lowered).
[0106]
In the above description, the case where the present invention is applied to a color electrophotographic apparatus has been described. However, the present invention can also be applied to a monochromatic electrophotographic apparatus such as black. Further, when applied to a color electrophotographic apparatus, the developed colors are not limited to four colors of yellow, magenta, cyan and black.
[0107]
【The invention's effect】
As described above, according to the present invention, since the light emitting elements are provided with a plurality of element rows that are mutually staggered, and a part or all of these element rows are driven by the control means, An advantageous effect is obtained that the recording resolution of the head can be easily adjusted.
[0108]
Further, in the low resolution mode in which some element arrays are used, if the light emission periods between the element arrays are controlled to be substantially equal, the deterioration of the organic EL elements can be equalized in units of columns. Is obtained.
[0109]
Further, in the low resolution mode, if the exposure start timing is controlled so that the top margins of the different element rows are the same, it is possible to obtain an effective effect that the printing positions of the different element rows can be matched. Can be
[0110]
In a configuration in which a plurality of exposure units and development units are provided for each color toner, the control unit performs printing using the same element row of the exposure head corresponding to each color toner. Since the data writing positions are the same, an effective effect of preventing color shift in color printing can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of an electrophotographic apparatus according to an embodiment of the present invention.
FIG. 2 is an explanatory view showing a developing station in the electrophotographic apparatus of FIG.
FIG. 3 is an explanatory diagram showing an internal structure of an exposure head in the electrophotographic apparatus of FIG.
FIG. 4 is an explanatory diagram showing an arrangement of organic EL elements as an exposure light source provided in the exposure head of FIG.
FIG. 5 is a block diagram showing a configuration of a controller in the electrophotographic apparatus of FIG.
FIG. 6 is a block diagram showing a configuration of an engine control unit in the electrophotographic apparatus of FIG.
FIG. 7 is a block diagram showing a configuration of a head control unit in FIG. 6;
FIG. 8 is a circuit diagram showing a detailed configuration of an exposure head and a head control unit.
[Explanation of symbols]
47Y, 47M, 47C, 47K photoreceptor
49 Developing sleeve (developing means)
52 Exposure head (exposure means)
86 Organic EL device
86a first element row
86b second element row
111 CPU (control means)
123Y, 123M, 123C, 123K Light emitting device (organic EL device)

Claims (10)

Exposure means in which the light-emitting elements are provided with element rows arranged in a plurality of rows in a staggered pattern, and the element rows are capable of emitting light for each row,
A photosensitive member on which an electrostatic latent image is formed by exposure light of the exposure unit,
Developing means for supplying toner to the electrostatic latent image to form a toner image on the photoconductor,
An electrophotographic apparatus comprising: a control unit for selectively using a part or all of the element array in accordance with printing conditions including a printing resolution designated by a user. The printing conditions include a low-resolution mode that is a mode for forming an image at a low resolution and a high-resolution mode that is a mode for forming an image at a high resolution, and the low-resolution mode uses a part of the element array. 2. The electrophotographic apparatus according to claim 1, wherein in the high resolution mode, all of the element rows are used. 3. The electronic device according to claim 1, wherein in the low resolution mode using a part of the element arrays, the control unit controls the light emission periods between the element arrays so as to be substantially equal. Photo equipment. 4. The electrophotographic apparatus according to claim 3, wherein the control unit switches the element array to be used in units of pages or jobs in which printing is performed. When switching the element array in page units, the control unit uses an element array different from the element array used at the end of the previous job for the first page of the current job. The electrophotographic apparatus according to claim 4. 6. The device according to claim 2, wherein the control unit controls the exposure start timing such that, in the low resolution mode, top margins of the element rows that are different from each other become the same. 7. Electrophotographic equipment. 7. An electrophotographic apparatus according to claim 6, wherein said control means changes a setting of a top margin according to a distance between the element rows and a printing speed. 8. The electronic device according to claim 1, wherein in the low resolution mode, the control unit causes the element array to emit light using different light amount correction data according to the selected element array. 9. Photo equipment. A plurality of the exposure means and the development means are provided corresponding to each color toner,
The electrophotographic apparatus according to any one of claims 1 to 8, wherein the control unit performs printing using the same element row of the exposure head corresponding to each color toner. The low-resolution mode controls the data input to the element array or controls a driver for driving the element array to select a light-emitting element array. The electrophotographic apparatus according to any one of claims 9 to 9.

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