JP2000181164A - Image forming device - Google Patents

Abstract

(57) Abstract: Provided is an image forming apparatus that constantly maintains X, Y, and Z positioning of a write head correctly. A write head (58) is swingably attached to an upper lid member (44) via a head spring member (116), descends when the upper lid member (44) is closed, and abuts a pin (106) projecting below right and left ends. Is pressed against a receiving groove 108 of a positioning member 107 provided in a sub-frame unit 104 of a side frame 103 on a side of the apparatus main body to position in the X and Y directions, and a focus roller 113 provided at both ends is exposed to light. The Z-direction is determined by contacting the end peripheral surface of the body drum 52. The eccentricity of the photosensitive drum 52 is absorbed by the writing head 58 swinging via the focus roller 113. The positioning member 107 is positioned and supported by the support shaft 114 in the X and Y directions,
It swings following the swing of the write head 58.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus which always positions a writing head correctly with respect to an image carrier.

[0002]

2. Description of the Related Art Conventionally, there is an electrophotographic image forming apparatus as shown in a side sectional view of FIG. The image forming apparatus (main body device) 1 shown in FIG. 1 includes an upper cover 2 on an upper surface, and a detachable paper cassette 3 on a lower portion. A large number of sheets P are placed and stored in the sheet cassette 3. Top lid 2
Has a power switch, a liquid crystal display, a plurality of input keys, etc., which are not visible on the front side, but is obliquely downward on the rear side (left side in the figure). The paper ejection tray 2-1 is formed to incline backward. Inside the main body device 1, an image forming unit 5 is detachably provided at the front center thereof.

The image forming unit 5 is constructed around a photosensitive drum 6, and a cleaner 7 and an initialization charging brush 8 are assembled along a peripheral surface of a rear portion (left side in the figure) of the photosensitive drum 6. A developing device 9 is mounted on the front peripheral surface of the body drum 6. A developing roller 11 rotatably supported by an opening on the lower side surface of the developing device 9 is in pressure contact with the front peripheral surface of the photosensitive drum 6. A toner 12 is accommodated in the developing device 9, and a stirring member 13 is disposed so as to be buried in the toner 12. Image forming unit 5
13 is detachable from the main body device 1, and when mounted, FIG.
It is fixed to the position shown in.

In the main unit 1, a transfer unit 14 is provided at a position facing the lower surface of the photosensitive drum 6, and is fixed to the upper cover 2 at a position facing the upper surface of the photosensitive drum 6. A write head 15 is arranged. Write head 15
Is lowered as the upper lid 2 is closed from the open position shown by the two-dot chain line 2 'in the figure to the position shown by the solid line, and is positioned with respect to the photosensitive drum 6.

[0005] The upper and lower sides are located on the upstream side (right side in the figure) of the conveying path from the opposing portion (transfer portion) between the photosensitive drum 6 and the transfer device 14.
A carry-in guide path 16 composed of a plurality of guide plates is formed, and a conveying roller pair 17 is disposed upstream thereof. Transport roller pair 1
Upstream of 7, the guide path branches laterally and downwardly, and the lateral guide path directly serves as an insertion slot 18 for manual paper, and opens to the front of the main unit 1. A paper feed guide path 19 is formed below, and this paper feed guide path 19 is opened above the paper feed end of the paper cassette 3 described above. A paper feed roller 21 having a semicircular cross section is disposed above the paper feed end of the paper cassette 3 and located behind the opening (left side in the figure).

A fixing unit 22 is provided downstream from the transfer unit, and a conveyance guide path 23 is formed between the transfer unit and the fixing unit 22. The fixing device 22 includes a heating roller 24 surrounded by a housing made of a heat insulating member, and a pressing roller 25 pressed against the heating roller 24.

A discharge roller pair 26 is disposed immediately after the fixing unit 22, a discharge guide path 27 standing upward in an arc is disposed downstream of the discharge roller pair 26, and a discharge roller pair 28 is disposed at an upper end thereof. It is located above the rear end of the above-described paper discharge tray 2-1.
A motor 29 is disposed between the fixing device 22 and the inner wall of the rear surface of the main body device 1, and a driving force transmission system such as a gear or a toothed belt (not shown) is connected to the motor 29 to transmit power to each of the above-described portions. It is configured to be.

The operation of the image forming apparatus thus configured will be briefly described again with reference to FIG. In FIG. 13, when the power is turned on to the main unit 1 and the size, number of sheets, and other designations of the paper to be used are input as a key input or a signal from a host device to be connected, the motor 29 is turned on.
Is driven. The paper feed roller 21 makes one rotation, and feeds the uppermost sheet of the paper P loaded and stored in the paper cassette 3 to the transport roller pair 17 via the paper feed guide path 19. Alternatively, an appropriate sheet is manually fed from the insertion slot 18. The fed sheet P is transported by the transport roller pair 17 from the transfer unit to the fixing device 22.

Prior to this, the image forming unit 5 and the writing head 15 are driven in accordance with the printing timing. The photosensitive drum 6 rotates clockwise, the initialization charging brush 8 applies a uniform high negative charge to the peripheral surface of the photosensitive drum 6, and the writing head 15 applies an image to the peripheral surface of the photosensitive drum 6. Exposure is performed according to a signal to form a low potential portion. As a result, an electrostatic latent image composed of the high negative potential portion due to the initialization and the low negative potential portion due to exposure is formed on the peripheral surface of the photosensitive drum 6.

The developing roller 11 of the developing device 9 includes the stirring member 1
The toner 12 which is frictionally charged to a weak negative potential while being agitated by the toner 3 is electrostatically adsorbed on the peripheral surface and is rotationally conveyed to a pressure contact portion with the photosensitive drum 6, and the electrostatic latent of the photosensitive drum 6 is The toner 12 is transferred to the low potential portion of the image to form a toner image on the peripheral surface of the photosensitive drum 6 (reversal development).

At the timing when the leading end of the toner image on the peripheral surface of the photosensitive drum 6 is rotated and conveyed to the transfer portion, the paper roller pair 17 moves the paper P so that the printing start position of the paper P coincides with the transfer portion. P is carried in. Transfer device 14
Applies a positive charge to the paper P by corona discharge,
The toner image on the photosensitive drum 6 is transferred to the sheet P by the electric field due to the electric charge.

The paper P on which the toner image has been transferred is subsequently transported by the transport roller pair 17 and is transported into the fixing device 22. The fixing device 22 includes a heating roller 24 and a pressing roller 2.
5, the toner image is heat-fixed to the sheet P by heat and pressure while the sheet P is held and the conveyance is continued, and the sheet P is conveyed downstream.
The sheet P on which the image is fixed is sent out to the sheet discharge guide path 27 by the pair of discharge rollers 26, and is discharged by the pair of discharge rollers 28 onto the discharge tray 2-1 with the toner image facing down.

The writing head 15 includes a large number of light emitting elements extending in the longitudinal direction of the photosensitive drum 6 (rotational axis direction). The light emitting elements are arranged by the number corresponding to the maximum number of pixels in the main scanning direction of the image (the width direction of the paper), and the distance between the pixels (the arrangement interval of the light emitting elements) is one inch even if it is coarse. 300 to 4
Since the dots are extremely fine, that is, 00 dots, a stable image cannot be formed unless the relative position between the photosensitive drum 6 and the writing head 15 is constant. Therefore, it is necessary to position the relative position between the photosensitive drum 6 and the write head 15 in advance.

FIG. 14A is a front sectional view of a positioning mechanism of an image forming section in such an image forming apparatus, and FIG. 14B is an enlarged side sectional view of the mechanism. I have. That is, in order to position the relative position between the photosensitive drum 6 and the writing head 15 at a constant position, as shown in FIG. A receiving groove 32 having a V-shaped cross section is provided slightly below the inner wall, and supports the support shaft 6-1 of the photosensitive drum 6 to position the photosensitive drum 6.

On the other hand, a V-shaped receiving groove 33 for the write head 15 is provided above the receiving groove 32 on the inner wall. Support member 34 of write head 15
Is held by the upper lid 2 via a spring member 36, and when the upper lid 2 is closed, the write head 15 is lowered from above, and is provided so as to protrude downward from both ends of the support member 34 of the write head 15. The contact pin 35 is contacted with the receiving groove 33 and the write head 15 is moved to the photosensitive drum 6.
Are positioned with respect to.

FIG. 15 shows the attached pin 35 and the receiving groove 3.
It is an enlarged view of the contact part with No. 3. As shown in the figure, the tip of the attached pin 35 forms a circumferential surface or a spherical surface with a radius R. Therefore, the center θ of the circumference (or spherical surface) always keeps the same position with respect to the V-shape of the receiving groove 33 in contact. In addition, since the attached pin 35 is fixed to the writing head 15, the distance from the light emitting element 37 of the writing head 15 to the center θ of the tip of the attached pin 35 is always constant.

Therefore, if the mounting position of the photosensitive drum 6 to the main body device is set so that the peripheral surface of the photosensitive drum 6 is at the above-mentioned fixed position θ, the arrow A in FIGS. The write head 15 supported by the upper lid 2 via the support member 34 and the spring member 36 and lowered from above
However, even if the position is slightly shifted back and forth (left and right in FIG. 15) as shown by the double-headed arrow B in FIG. 15, the distance from the light emitting element 37 to the center θ of the tip of the attached pin 35, that is, the photosensitive drum 6 Since the distance to the peripheral surface is always constant,
There is no change in the exposure action, and a stable electrostatic latent image can be recorded.

FIGS. 16A and 16B show another example of the positioning mechanism. In this case, the support shaft 6'-1 of the one photosensitive drum 6 'is positioned by being supported by the bearing of the support frame 31' of the main unit in the same manner as described above.
The positioning of the other write head 15 'is performed by a roller 38 which comes into contact with the peripheral surface of the photosensitive drum 6'. The rollers 38 are disposed at both ends of a support member 34 'of the write head 15', and the support member 34 'is supported by the upper lid frame 2' via a spring member 36 '.

[0019]

However, FIG. 14 (a),
(b) and the positioning mechanism shown in FIG.
The write head 15 and the write head 15 can be fixed in position by the same apparatus main body frame 31, so that there seems to be no problem with respect to the change in position. However, in this case, although the urging force of the spring member 36 suppresses the lifting of the writing head 15, it does not work to suppress the photosensitive drum 6. Therefore, the nonmagnetic one-component toner 12 is used. When the developing roller 11 is pressed against the photosensitive drum 6 in the developing mode, the rotation of the developing roller 11 causes the support shaft 6 of the photosensitive drum 6 to rotate.
Problems such as floating of -1 occur. In other words, since the position of the write head 15 is fixed, as a result, the relative position with respect to the photosensitive drum 6 is deviated, causing a problem such as a focus failure or the like. Also,
Even if the support shaft of the photoconductor drum 6 does not float, if the photoconductor drum 6 itself is eccentric, the peripheral surface of the photoconductor drum 6 is deviated from the predetermined position θ.

On the other hand, the positioning mechanism shown in FIGS. 16 (a) and 16 (b) in which the roller 38 comes into contact with the peripheral surface of the photosensitive drum 6 ', even if the photosensitive drum 6' is eccentric, Is suitable for positioning in the Z direction (distance direction between the photosensitive drum and the write head), but a displacement occurs in the X direction (main scanning direction, left and right direction in FIG. 16A). In a tandem type color image forming apparatus in which a plurality of pairs of photosensitive drums and writing heads are provided in series, there is a problem that it is not possible to obtain an overlay accuracy of an image to be applied for each color.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances,
It is an object of the present invention to provide an image forming apparatus which always maintains X (main scanning direction), Y (sub scanning direction), and Z (distance between a photosensitive drum and a writing head) correctly.

[0022]

The structure of the image forming apparatus of the present invention will be described below. An image forming apparatus according to the present invention includes an image carrier having a circulating surface, a first body for disposing the image carrier, and a second body for positioning and supporting the image carrier on the first body. 1 supporting means, a second body connected to the first body at one end as a fulcrum and capable of opening and closing, and movably supported by the second body and attached to the image carrier when the two bodies are closed. A write head for writing image information in a direction substantially perpendicular to the direction of movement of the write head against the surface, first biasing means for biasing the write head in the image carrier direction, Positioning means for setting the facing state of the writing head and the image carrier in a predetermined relationship at the time of closing, wherein the positioning means is located at both ends in the orthogonal direction. Provided on the write head, each with a circle at the tip A pair of positioning projections having a surface or a spherical surface, and the first body or the first supporting means movably supported in a linear direction connecting a generatrix of the image carrier and a center of a rotation axis; A pair of head positioning members, each of which has a deep concave portion capable of accommodating the pair of positioning projections and accommodating the projections; , The first
A second urging means for urging the head positioning member in the direction of the write head with an urging force smaller than the urging force of the urging means; and a surface provided on the head positioning member or the write head, the surface of the image carrier. And a roller member rotatably abutting on both ends in the orthogonal direction to set a facing distance between the writing head and the image carrier.

The writing head is an optical writing head having a predetermined number of LED light emitting elements in a writing section. The head positioning member may be supported by a support shaft and urged by the first urging means, and may be moved in a direction urged by the second urging means. It is arranged to be swingable.

In the image forming apparatus, the image carrier, the first supporting means,
A tandem-type image forming apparatus including a plurality of image forming apparatus sections each including the write head, the first urging means, and the positioning means in a multistage manner in a flow direction of a processing step.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. In the following description, the image carrier includes, for example, a photosensitive drum 52, the first body includes, for example, an apparatus main body of the image forming apparatus 40, and the first support unit includes, for example, a sub-frame. The second body includes, for example, the upper cover member 44, the write head includes, for example, the write head 58, and the first biasing unit includes, for example, the head spring member 116, etc. The pair of positioning projections of the pair of head positioning members of the positioning means are, for example, abutment pins 106 and the like.
The deep concave portion of the pair of head positioning members of the positioning means includes, for example, a positioning member 107, a receiving groove 108, and the like, the second biasing means includes, for example, a spring member 115, and the roller member includes , For example, a focus roller 113 and the like.

FIG. 1 is a side sectional view schematically showing an internal configuration of an image forming apparatus having a positioning mechanism according to an embodiment. Note that since FIG. 3 is a cross-sectional view of the central portion, a positioning mechanism, which will be described in detail later, disposed on the side is not shown.

First, the overall configuration of the image forming apparatus will be described. The image forming apparatus 40 shown in FIG. 1 is a small-sized image forming apparatus that is large enough to be mounted on, for example, a desktop personal computer rack. The image forming apparatus (apparatus main body) 40 has an opening / closing tray 41 on the front surface (right side in the figure) and a detachable paper cassette 42 on the lower part. A large number of sheets 43 are placed and stored in the sheet cassette 42.

An upper cover member 44 is provided at the upper portion, and a paper discharge tray 45 is formed at the rear upper surface of the upper cover member 44 together with the rear upper surface of the apparatus main body 40. Front part 46 of device body 40
Is provided with an operation panel including a power switch, a liquid crystal display device, a plurality of input keys, and the like.

The drive roller 4 is located substantially at the center.
7 and a transport belt 49 for the paper circulating and held by the driven roller 48 are provided. Above the transport belt 49, four image forming units 51 (51a, 51b,
51c, 51d) are juxtaposed in a multi-stage manner in the sheet transport direction.

Each of the image forming units 51 includes a photosensitive drum 52 (hereinafter referred to as an image forming unit 51a).
Are attached to the image forming unit 51 so as to surround the photosensitive drum 52, and the cleaner 53 and the initialization charging brush 5 are provided.
4. Various devices such as a toner container 55 and a developing roller 56 are arranged.

A write head 58 disposed on the back surface of the upper cover member 44 via a support member 57 is inserted and disposed directly above the photosensitive drum 52 by closing the upper cover member 44. The write head 58 includes a number of LED light emitting elements. The upper lid member 44 is connected to the apparatus main body 40.
It opens and closes around the rear support shaft 59. The photosensitive drum 52 is in contact with the transport belt 49, and a transfer brush 61 is provided so as to face the photosensitive drum 52 from the back surface of the belt 49.

The image forming unit 51 is a detachable unit. By opening the upper cover member 44 and retreating the four write heads 58 obliquely upward, the upper space is opened, and the apparatus main body 40 is opened. It is in a state where it can be detached from or attached to. This facilitates replacement of the photosensitive drum with a new one after fatigue with time and maintenance in the event of a trouble such as a paper jam.

At the upstream end (right side in the drawing) of the transport belt 49 in the paper transport direction, a paper pressing roller 62 is disposed by pressing the driven roller 48 via the transport belt 49. On the upstream side, a standby roll pair 63 and a paper detection sensor 64 are arranged, and the upstream side branches laterally (in front of the apparatus) and downward, and in the lateral direction, a paper feed roller 65, a separating member 66,
And the above-mentioned opening / closing tray 41 is provided. Further, a transport path 67 composed of two guide plates is provided in a downward direction, and a feed roller pair 68 is provided at an upstream end thereof.
Below this, the paper feed end of the above-mentioned paper cassette 42 is located. A paper feed roller 69 is disposed above the paper feed end.

A separation claw 71, a fixing device 72, a pair of discharge rollers 73, and a switching lever 74 are provided downstream of the other conveyance belt 49 in the sheet conveyance direction. The fixing device 72 includes a pressure contact roller, a heat generating roller, a fixing separation claw, a peripheral cleaning device, an oil application roller, a thermistor, and the like, which are assembled in a heat insulating housing.

The switching lever 74 guides the sheet to the upper discharge path 75 when it is at the lower position as shown in the figure, and opens the sheet to the rear surface of the apparatus when it is turned upward. To the paper discharge port 76 to be processed. The above-described discharge path 75 is inverted from the upward direction of the apparatus main body to the front side, and a discharge roller pair 78 is formed in an upper discharge port 77 opened above a rear part of the discharge tray 45.
To communicate through.

The transport belt 49 and the paper cassette 42
Between them, a cleaner bottle 81 is provided detachably at the front. A blade scraper 82 is attached to the upper part of the cleaner bottle 81, and the tip of the blade scraper 82 contacts the surface of the lower circulating portion of the conveyor belt 49. Further, an electrical component unit 83 is provided at the rear. A circuit board on which a control device, which will be described in detail later, is mounted is disposed in the electrical component 83.

The image forming apparatus 40 is configured to be able to perform both monochrome printing and full color printing. For this purpose, the transport belt 49 is supported between the image forming units 51 a to 51 c by a fixed support roller 84 and a movable support roller 85. The fixed support roller 84 is rotatably fixed to the frame of the apparatus main body, and the movable support roller 85 is held at the other end of a beam-shaped support member 86 that rotates around the support shaft of the fixed support roller 84. .

A cam 87 slidingly contacts the lower portion of the beam-shaped support member 86, and selectively rotates left and right between a position shown in the figure and a position rotated 90 degrees clockwise. When the cam 87 rotates 90 degrees clockwise from the position shown in the figure, the beam-shaped support member 86 slightly rotates downward, and the movable support roller 85 moves downward. As a result, the photosensitive drums 52 of the image forming units 51a to 51c are released from the image forming by releasing the contact with the conveyor belt 49, and only the image forming unit 51d that is responsible for the image formation of the black toner is connected to the drive roller 47. An image can be formed by contacting the surface of the transport belt 49 which is supported between the fixed support rollers 84 and has a fixed position.

FIG. 2 is a diagram showing a system configuration of the image forming apparatus 40 described above. As shown in the figure, the image forming apparatus 40 includes an engine control unit 88 and a PPC color engine unit 89. Print data is input to the engine control unit 88 from the host computer 90.

The engine control unit 88 includes a CPU 9
3, ROM 94, RAM 95, EEPROM 96, video I / F control section 97, head control section 98, correction control section 9
9, an input / output control unit 101.

The CPU 93 performs system control of the entire image forming apparatus 40 of the present embodiment, and performs control according to a program stored in the ROM 94. RAM 95
Stores data generated during the control process of the CPU 93. An operation panel 102 is connected to the CPU 93, and a key operation signal is transmitted from the operation panel 102 to the CPU 9.
3 is output.

The EEPROM 96 stores correction values (adjustment values) and the like. The video data output from the host computer 90 is input to the video I / F control unit 97. The input video data is output to the head control unit 98 under the control of the video I / F control unit 97. The video I / F control unit 97 sends and receives various signals to and from the host computer 90 in addition to the above-described video data.

The head control section 98 converts the video data input from the video I / F control section 97 into the image forming unit 51.
a to 51d (hereinafter, the writing head 58 of the image forming unit 51a is referred to as an LED head Y58a, and the writing head 58 of the image forming unit 51b is referred to as a writing head 58).
Is the LED head M58b, the write head 58 of the image forming unit 51c is the LED head C58c, and the write head 58 of the image forming unit 51d is the LED head Bk58.
d), outputs yellow (Y) video data to the LED head Y58a, and outputs magenta (M) video data to the LED head M5.
8b, the cyan (C) video data is output to the LED head C58c, and the black (Bk) video data is output to the LED head Bk58d.

As described above, the image forming units 51a to 51a
The write head 58 supported and disposed on the upper lid member 44 corresponding to 1d forms a part of the PPC color engine unit 89 in FIG. The correction controller 99 adjusts the output light amount (light amount per unit time or lighting time) of the write head 58 based on the correction value stored in the EEPROM 96.

The operation of the image forming apparatus 40 thus configured will be described with reference to FIGS. 1 and 2 again. First, when the power is turned on and the number of sheets, the printing mode of a full-color image, and other designations are input by a key, the sheet feeding roller 69 makes one rotation and the uppermost part of the sheet 43 stored in the sheet cassette 42 is stored. Is taken out and fed toward the feed roller pair 68.

The feed roller pair 68 sandwiches the sheet 43,
The sheet is fed to the standby roller pair 63 via the conveyance path 67. Alternatively, the sheet feeding roller 65 feeds the sheet placed on the open / close tray 41 to the standby roller pair 63 in cooperation with the separating member 66. The fed paper 43 is detected by a paper detection sensor 64.
Is detected. The standby roller pair 63 temporarily stops rotating, abuts the leading end of the paper 43 on the holding portion, and waits until the transport timing.

The driving roller 47 starts rotating in the counterclockwise direction, and the driven roller 48 is driven to rotate in the counterclockwise direction. As a result, the upper circulating portion of the transport belt 49 abuts on the four photosensitive drums 52 and circulates in the counterclockwise direction as a whole. At the same time, the image forming units 51 are sequentially driven in synchronization with the printing timing, and the photosensitive drums 52 are sequentially driven to rotate clockwise in accordance with the driving.

First, the initialization charging brush 54
Initialization is performed by applying a uniform high charge to the peripheral surface of the photosensitive drum 52. The write head 58 performs exposure on the peripheral surface of the photosensitive drum 52 according to an image signal, and forms an electrostatic latent image by a high-potential portion due to the initialization and a low-potential portion whose potential is attenuated by the exposure. It is formed on the peripheral surface of the drum 52. The developing roller 56 transfers the toner supplied from the toner container 55 to the low potential portion of the electrostatic latent image, and
A toner image is formed (developed) on the peripheral surface.

The leading end of the toner image on the peripheral surface of the photosensitive drum 52 of the most upstream image forming unit 51 a is
The standby roller pair 63 starts rotating and moves the sheet 43 to the driven roller 4 so that the printing start position of the sheet 43 coincides with the point of rotation and conveyance to the point opposite to the sheet 43.
8 and the sheet pressing roller 62 are fed.

The driven roller 48 and the pressing roller 62 hold the fed paper 43 together with the transport belt 49 to
3 is conveyed. Even after the sheet 43 is released from being nipped by the driven roller 48 and the pressing roller 62, the sheet 43 is adsorbed on the transport belt 49 and is transported as it is. As the paper 43 is conveyed, the toner images are sequentially superimposed and transferred on the paper by an electric field formed between each of the photosensitive drums 52 and each of the transfer brushes 61.

The paper 43 onto which the toner images of four colors of Y (yellow), M (magenta), C (cyan) and Bk (black) are transferred is separated from the conveyor belt 49 by the separation claw 71 and the fixing device 72 It is carried in. After the toner image is fixed by heat and pressure by the fixing device 72, the sheet 43 is discharged outside the apparatus by the pair of discharge rollers 73 with the toner image facing upward from the rear discharge port 76. Alternatively, the toner image is discharged from the upper discharge port 77 onto the discharge tray 45 with the toner image facing down.

[0052] The blade scraper 82
The toner remaining on the surface (mainly at both ends) of the sheet 9 is scraped to clean the transport belt 49, and the scraped unnecessary toner is stored in the cleaner bottle 81.

When the monochrome image print mode is designated, as described above, the cam 87 rotates 90 degrees clockwise from the position shown in FIG. Drum 5 of image forming unit 51d
Only the image forming unit 2 contacts the transport belt 49 to form an image forming unit, and the remaining three image forming units 51a to 51c are stopped or driven idle. Other operations such as the conveyance of the paper 43, the formation of the electrostatic latent image, the development of the toner image, the fixing by heat and pressure, and the discharge of the paper on which the image has been formed are the same as those in the full-color image print mode described above. The same is true.

The photosensitive drum 52 is positioned by a support shaft held by a bearing of the apparatus main body 40 and a drum gear (not shown) of the photosensitive drum 52 engaging with a drive mechanism of the apparatus main body. The head 58 is attached to the upper lid member 44 and rotates about its support shaft 59 with opening and closing of the upper lid member 44, and the relative position with respect to the photosensitive drum 52 is unstable in this state.

On the other hand, in the tandem developing method as described above, if the print dot positions of the respective image forming units do not fall within half dots, moire fringes and the like are generated, and a clear print result is obtained. I can't get it. Therefore, the positions of the sheet 43, the photosensitive drum 52, and the write head 58 must be accurately determined.

However, in this case, if attention is paid to the overlap of the dot positions in the print result, even if the main scanning direction is oblique to the paper (inclined with respect to the width direction of the paper),
If the relative positions of the write head 58 and the photosensitive drum 52 can be matched so that the print dots of all the image forming units have the same inclination, then Y (yellow), M
If the output timings of the image formation of (magenta), C (cyan) and Bk (black) are electrically corrected and interpolation dots are inserted into the dots in the main scanning direction, the apparent displacement of the print dots can be eliminated. .

However, there is a limit to the control by the control unit, and from the viewpoint of shortening the processing time, it is preferable to perform mechanical positioning as much as possible, especially in a small machine. .

In the above-described image forming apparatus 40, the writing head 58 is positioned with respect to the photosensitive drum 52 by holding the support shaft of the photosensitive drum 52 and fixing and positioning the support shaft, that is, the photosensitive drum 52. Device main body 40
The drum shaft holding portion of the frame is provided with a receiving groove formed integrally therewith, and by closing the upper cover member 44, the head pin attached to the writing head 58 is fitted into the receiving groove to position the drum. Do.

This positioning is performed by adjusting the inclination of the write head 58 (the inclination of each write head in the paper advancing direction with respect to the width direction of the paper), and adjusting the position of the write head 58 in the main scanning direction (dots of the write head). In other words, three adjustments are to be performed, that is, an adjustment for maintaining the position of the photosensitive drum 52 and the writing head 58 constant. These three adjustments are performed by the receiving grooves.
Hereinafter, this will be described.

FIG. 3 is a plan sectional view showing components related to the photosensitive drum and the positioning mechanism of the image forming apparatus 40 cut at the center. FIG. 4 is a front view of the image forming apparatus 40. FIG. 4 is a cross-sectional view of a portion where a photosensitive drum is disposed.

FIG. 5A is an enlarged view of a portion indicated by a circle D in FIG. 3, FIG. 5B is an enlarged view of a portion indicated by a circle E in FIG.
(c) is a cross-sectional view of FIG. (a) or (b) viewed from the side. 3 and 5 (c), only the outline of the write head 58 is shown by a two-dot chain line.

In FIGS. 3, 4 and 5 (a), (b) and (c), a write head 58 (hereinafter, write head 1 in FIG. 14) is used.
5 and the support member 34 together, and the write head 15 of FIG.
As described above, also in this embodiment, the write head and the support member are collectively shown as a write head 58) is attached to the upper lid member 44 as described above (see FIG. 1). As shown in FIG. 5C, the write head 58 is swingable through the head spring member 116, and is not positioned in this state.

When the upper cover member 44 is closed, the write head 58 engages with a sub-frame unit 104 fixed to the side frame 103 on the main unit side, as described later, and moves the position in the X and Y directions. It is dispensed and the position is fixed.

That is, the write head 58 includes the abutting pins 1 vertically protruding from the left and right ends, respectively.
06, and these abutment pins 106 are in pressure contact with receiving grooves (concave recesses) 108 of positioning members 107 provided in the left and right subframe units 104, respectively. The above-described side frame 103 is fixed to a base 105, and a sub-frame unit 104 which is a device on the apparatus main body side fixed to the side frame 103.
Although not particularly shown, the positioning member 107 can be finely moved in the X direction and the Y direction. Thus, the write head 58 is positioned in the X direction and the Y direction.

On the other hand, with respect to the photosensitive drum 52, both ends 109-1 of the drum support shaft 109 are fitted into and engaged with the bearing portions 112 of the sub-frame unit 104, whereby the photosensitive drum 52 is positioned. I have. A write head 5 is provided above the peripheral surface of the end of the photosensitive drum 52.
Focus rollers 113 provided on the inner side of the abutment pins 106 at both ends of No. 8 abut. As a result, even if the rotation of the photosensitive drum 52 is eccentric, the write head 58 swings up and down following the displacement of the peripheral surface of the photosensitive drum 52 that rotates eccentrically. Therefore, the distance between the write head 58 and the peripheral surface of the photosensitive drum 52 is always kept constant. That is, the write head 58 is
The two are positioned in the Z direction.

On the other hand, the positioning member 107 is supported by being positioned in the X and Y directions by the support shaft 114. The center of the support shaft 114, the center of the hemisphere R at the tip of the abutment pin 106, and the peripheral surface of the photosensitive drum 52 are arranged on the same plane.

The positioning member 107 is urged in a counterclockwise direction by a spring member 115 so as to be rotatable. This biasing force is applied to the positioning member 10.
7, at the point of the receiving groove 108, the head spring member 116
Is set to be weaker than the urging force applied downward through the write head 58 and the butting pin 106. Thus, the positioning member 107 swings following the vertical swing of the write head 58.

That is, the write head 58 is positioned in the Z direction following the displacement of the rotating peripheral surface of the photosensitive drum 52, and swings up and down following the displacement of the peripheral surface of the photosensitive drum 52. Also, the receiving groove 10 of the positioning member 107
By virtue of 8, it is always maintained at a constant position in the X direction and the Y direction. It is questioned whether the positioning in the X direction and the Y direction by the receiving groove 108 may be displaced by the swing of the write head 58 and the positioning member 107, but the displacement in the X direction and the Y direction is It is a minute thing to ignore. Hereinafter, this will be described.

FIG. 6 (a) is a view in which the main part of FIG. 5 (c) is shown again, and FIG. 6 (b) is a view for explaining the displacement of the exposure point on the peripheral surface of the photosensitive drum. Here, the diameter of the photosensitive drum 52 is 30 mmφ, the diameter of the focus roller 113 is 8 mmφ, and the diameter of the hemisphere at the tip of the abutting pin 106 is 4 mmφ. First, as shown by a two-dot chain line 58 'in FIG. 6A, an exposure point 1 generated when the write head 58 is tilted 5 ° to the left.
The displacement of 17 is 0 in the X direction and 0.01 m in the Y direction.
m, Z direction = 0.012 mm, which can be said to be a negligible level.

Next, the support shaft 114 of the positioning member 107
From the center of the groove to the center of the receiving groove 108 = 32 mm
And When the positioning member 107 swings upward at an angle of 1 °, the displacement of the exposure point is X direction = 0, Y direction = 0.
005 mm (to the left in FIGS. 6 (a) and 6 (b)), the Z direction = 0, which is also a negligible level.

Although the focus roller 113 is attached to the write head 58 in the above embodiment, the attachment of the focus roller 113 is not limited to this.
FIGS. 7A, 7B, and 7C are diagrams showing examples in which a focus roller is attached to a positioning member. FIGS. 6 (a), 6 (b) and 6 (c) show FIG.
(a), (b), and (c) show cross-sectional views of the same portions. As shown in FIGS. 7A, 7B, and 7C, the focus roller 11
3 'is not the write head 58, but the positioning member 1
It is attached to a support arm 107-1 provided to project laterally (in the direction of the photoconductor drum) from 07 ', and is in contact with the peripheral surface of the end of the photoconductor drum 52. The configuration of the other parts is the same as in the case of FIGS.

As a result, the positioning member 107 'swings directly following the eccentricity of the photosensitive drum 52, and the writing head 58 swings according to the positioning member 107'. Also in this case, the displacement of the exposure point is negligible as described above.

In any of the above cases, the positioning member 1
07 (or 107 ′) is urged in the counterclockwise direction by the spring member 115, but a configuration in which the positioning member is formed of a resin having spring properties and the groove and the spring portion are integrated may be used. . Further, the rotation center of the positioning member is not limited to the Y direction as in the above two examples, and may have a rotation center in the X direction. Further, the floating groove may be movable up and down instead of swinging.

By the way, the arrangement density of the light emitting elements of the write head was about 300 dpi in the initial stage. Correspondingly, a high resolution arrangement of 1200 dpi is also possible.
On the other hand, the substrate of the light emitting element of the write head is easily affected by the environmental temperature.

FIGS. 8A and 8B are diagrams schematically showing expansion of the write head due to such environmental temperature. Same figure
(a) Part of the 300 dpi write head (left end)
The upper part shows a state at a temperature of 25 ° C., and the lower part shows a state at a temperature of 60 ° C. FIG. 3B shows a write head of 1200 dpi, and similarly shows a state at a temperature of 25 ° C. above and a state at a temperature of 60 ° C. below it.

As shown in FIGS. 7A and 7B, a dimensional difference of 40 μm occurs at each of the right and left ends of the write head. Assuming that the state at a temperature of 25 ° C. is standard, at a temperature of 60 ° C.,
In the case of a 300 dpi write head, as shown in FIG. 3A, approximately one light emitting element (corresponding to one dot of pixel) on the left and right respectively protrudes outward, and thus, 1200 dpi.
As shown in FIG. 1B, approximately three light-emitting elements on the left and right protrude outward, respectively.

The write head of 300 dpi is generally used for monochrome images, so there is no problem. However, the write head of 1200 dpi is used for printing a full-color image as described above.
Four write heads C, Y, and Bk are used in a multistage manner. Each of the write heads M, C, Y, and Bk has a different lighting ratio, and the degree of temperature rise also differs depending on whether it is close to or away from a heat-generating portion such as a fixing unit or a power supply in the apparatus main body. . Such a difference in the rise temperature appears as a shift of the printing dots.

In particular, when the size of the write head becomes about 300 mm, which corresponds to A3 size paper, about 100 μm elongation occurs at 60 ° C. as described above. That is, a color shift of 100 μm occurs in the printed image, which may cause image deterioration. Of course, there is a method of suppressing an increase in temperature by using an air cooling fan, but this method has various problems such as an increase in cost and generation of noise. In the present embodiment, this problem is solved by controlling print data.

FIG. 9 is a diagram showing a temperature detecting circuit provided in each image forming unit 51 for controlling print data. In the figure, the temperature change of the image forming unit 51 changes the electric resistance of the thermistor 118. Power supply VCC
The voltage at the branch point input to the A / D converter 119 and the thermistor 118 via the resistor R1 changes according to the change in the electrical resistance of the thermistor 118 corresponding to the temperature change.

This voltage value is converted into a digital signal by the AD converter 119 and input to the CPU 93 shown in FIG. The engine control unit 88 stores a correspondence table between the voltage value indicated by the digital signal and the temperature and a correspondence table between the temperature and the print control information in the EEPROM 96, and the CPU 93 performs correction control based on these tables. A PPC color engine unit 89 is controlled via a unit 99.

For example, if the voltage value of the digital signal output from the AD converter 119 indicates that the temperature of the image forming unit 51 is 60 ° C., as shown in FIG. Are excluded from the lighting drive, that is, they are turned off. Then, the fourth to 1197-th light-emitting elements on the inner side are driven for lighting.

At this time, the lighting information that should be given to the first to third light emitting elements is given to the fourth to sixth light elements, and the printing information is sequentially shifted in this way and given.
Decimate at appropriate places. That is, 2000
The print information for one piece is thinned out at equal intervals to 1194 pieces of print information, and is provided to 1194 light emitting elements. Then, the dot positions for thinning out the print information are changed for each print line. For example, the positions are sequentially changed to adjacent dot positions. Even if the print information is thinned out and printed as described above, it cannot be visually recognized at all.

Incidentally, as described above, the light emitting element of the write head is disposed on the LED chip (substrate). However, there is not a substrate as long as 300 mm, and a plurality of short LED chips are continuously arranged on a 300 mm write head. Each LED at this time
The accuracy of keeping the distance between chips correctly depends on the work accuracy of the chip mounting device (chip mounter).
It also depends on the cutting accuracy of the LED chip. Therefore, if there is a defect in the accuracy at the time of chip mounting by the chip mounting device, or if there is a defect in the cutting accuracy of the chip, the distance between a plurality of consecutively arranged chips is longer than the reference value. Cases occur.

FIGS. 10A and 10B are diagrams showing an example in which the distance between the chips is larger than the reference value and a printing state thereof. As shown in FIG. 7A, the distance between the adjacent chips C1 and C2 is longer than the standard distance t12.
The following problem occurs if the distance is 1 b extra. That is, the light emitting element L128 at the right end of the chip C1
When there is lighting data D128 and D129 across the light emitting element L1 at the left end of the chip C2, a blank portion (white printing) occurs between the chips regardless of the printing section.

As a method for solving this problem, the light amounts of the lighting data D128 and D129 are corrected by increasing the LED currents applied to the light emitting elements L128 and L1, and only this portion is corrected as shown in FIG. When printing with a high light intensity, the white print portion generated in FIG. 7A becomes black print, and the blank problem can be solved. However, as described above, the light intensity distributions of the lighting data D128 and D129 are larger than those of the other dots, which affects the print density and causes deterioration of the image.

FIG. 11 is a diagram showing an example of an auxiliary chip provided in a write head to solve the above problem. As shown in the figure, in the write head 58, an auxiliary chip 123 is provided between a chip 121 (C1) and a chip 122 (C2) which are wider than the standard. On the auxiliary chip 123, light-emitting elements 11 to 14 smaller than the light-emitting elements L1, L2 to L127 and L128 provided on the regular chip 121 or 122 are arranged at high density. These lighting drive circuits 124, 125 and 126
Is controlled by the head control unit 98 shown in FIG.

FIG. 12 shows a write head 58 having the above configuration.
FIG. 9 is a diagram showing a state of complementary printing by the following. As shown in the drawing, the light emitting element L128 at the right end of the chip C1 and the chip C
If there are lighting data D128 and D129 across the leftmost light emitting element L1, the light emitting elements 13 and 14 of the auxiliary chip 123 are turned on. In this case, the lighting control unit 99 converts the lighting data D129 into the light emitting element L of the chip 122 (C2) so that the density distribution indicated by the thick solid line in FIG.
1 and the light emitting elements 13 and 14 of the auxiliary chip 123. Thereby, the position of the print dot can be corrected and the light intensity can be corrected.

The position of each dot was determined by arranging an LED chip on the write head and then using a measuring jig to finely move the photo sensor in the main scanning direction to determine whether any of the light emitting elements were out of specification. Measure whether it is located at
The number can be controlled by writing the number of the light emitting element into the EEPROM 96 and mounting the EEPROM 96 in the image forming apparatus together with the write head.

[0089]

As described above in detail, according to the present invention, the receiving groove for positioning in the X direction and the Y direction is formed so as to be swingable following the displacement of the photosensitive drum in the Z direction. Positioning in three directions of X, Y, and Z can be accurately achieved with one receiving groove, thereby forming a high-quality image by keeping the writing head in the correct position with a simple positioning mechanism having a small structure. It is possible to provide an image forming apparatus that performs

[Brief description of the drawings]

FIG. 1 is a side sectional view schematically showing an internal configuration of an image forming apparatus having a positioning mechanism according to an embodiment.

FIG. 2 is a diagram illustrating a system configuration of the image forming apparatus of FIG. 1;

FIG. 3 is a plan sectional view showing components related to a photosensitive drum and a positioning mechanism in a state of being cut at the center of the image forming apparatus of FIG. 1;

FIG. 4 is a cross-sectional view of a portion where a photosensitive drum is provided, as viewed from the front of the image forming apparatus of FIG. 1;

5 (a) is an enlarged view of a portion indicated by a circle D in FIG. 3, (b) is an enlarged view of a portion indicated by a circle E in FIG. 4, and (c) is a view of (a) or (b) from the side. It is sectional drawing seen.

6 (a) is a diagram showing the main part of FIG. 5 (c) again, and FIG. 6 (b) is a diagram for explaining a displacement amount of an exposure point on the peripheral surface of the photosensitive drum.

FIGS. 7A, 7B, and 7C are diagrams showing examples in which a focus roller is attached to a positioning member.

FIGS. 8A and 8B are diagrams schematically showing expansion of a write head due to environmental temperature.

FIG. 9 is a diagram illustrating a temperature detection circuit provided in each image forming unit.

FIGS. 10A and 10B are diagrams illustrating an example in which the distance between chips is larger than a reference value and a printing state thereof.

FIG. 11 is a diagram showing a complementing method when the distance between chips is larger than a reference value.

12 is a diagram showing a corrected printing state in the configuration of FIG. 11;

FIG. 13 is a side sectional view showing an example of a conventional electrophotographic image forming apparatus.

14A is a front sectional view of a positioning mechanism of an image forming unit in a conventional image forming apparatus, and FIG.

FIG. 15 is an enlarged view of a contact portion between a contact pin provided with a conventional positioning mechanism and a receiving groove.

FIGS. 16A and 16B are views showing a positioning mechanism using rollers as another conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Top cover 2 'Top cover frame 2-1 Discharge tray 3 Paper cassette 4 Support shaft 5 Image forming unit 6, 6' Photoconductor drum 6-1 and 6'-1 Support shaft 7 Cleaner 8 Initialization charging brush Reference Signs List 9 developing device 11 developing roller 12 toner 13 stirring member 14 transfer device 15, 15 'writing head 16 carry-in guide path 17 carrying roller pair 18 insertion port 19 feed guide path 21 feed roller 22 fixing device 23 transport guide path 24 heat generating roller Reference Signs 25 Pressing roller 26 Discharge roller pair 27 Discharge guide path 28 Discharge roller pair 29 Motor 31, 31 'Support frame 32, 33 Receiving groove 34, 34' Support pin 35 Attached pin 36, 36 'Spring member 37 Light emitting element 40 Image forming apparatus (apparatus main body) 41 Opening / closing tray 42 Paper cassette 43 Paper 44 Top lid member 45 Discharge Paper tray 46 Front part of the apparatus main body 47 Drive roller 48 Follower roller 49 Conveying belt 51 (51a, 51b, 51c, 51d) Image forming unit 52 Photoconductor drum 53 Cleaner 54 Initializing charging brush 55 Toner container 56 Developing roller 57 Supporting member 58 Write head 58a LED head Y 58b LED head M 58c LED head C 58d LED head Bk 59 support shaft 61 transfer brush 62 paper press roller 63 standby roll pair 64 paper detection sensor 65 paper feed roller 66 separating member 67 feed path 68 feed roller Pair 69 Paper feed roller 71 Separation claw 72 Fixing device 73 Outgoing roller pair 74 Switching lever 75 Discharge path 76 Discharge port 77 Upper discharge port 78 Discharge roller pair 81 Cleaner bottle 82 Blade scraper 83 Electrical unit 84 Fixed support roller 85 Moving support roller 86 Beam support member 87 Cam 88 Engine control unit 89 PPC color engine unit 90 Host computer 93 CPU 94 ROM 95 RAM 96 EEPROM 97 Video I / F control unit 98 Head control unit 99 Correction control unit 101 Input / output control Unit 102 Operation panel 103 Side frame 104 Subframe unit 105 Base 106 Butt pin 107 Positioning member 108 Receiving groove (concave recess) 109 Drum support shaft 109-1 Shaft end 112 Bearing unit 113, 113 'Pin roller 114 Support shaft 115 Spring member 116 Head spring member 117 Exposure point 118 Thermistor 119 A / D converter 121, 122 LED chip 123 Auxiliary chip 124, 125, 126 Lighting drive circuit

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Makoto Asako 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Computer Co., Ltd. Tokyo Office (72) Inventor Yasushi Nakamura 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Computer Inside the Tokyo Office (72) Kenji Takano Inventor 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Computer Co., Ltd. Inside the Tokyo Office (72) Inventor Takashi Mohri 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Computer Co., Ltd. Within the Tokyo office (72) Inventor Kazutaka Otsuka 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Computer Co., Ltd. Tokyo office F-term (reference) 2H030 AA06 AA07 AB02 BB02 BB23 BB71 2H071 BA04 BA13 BA16 BA29 DA02 DA15 EA06 2H076 AB01 AB60 EA24

Claims (4)

[Claims] An image carrier having a circulating surface;
A first body for disposing the image carrier, first support means for positioning and supporting the image carrier on the first body, and openable and closable with one end serving as a fulcrum relative to the first body And a second body connected to the second body and movably supported by the second body, facing the image carrier when the two bodies are closed, and facing the image carrier along a direction substantially orthogonal to the direction of movement of the surface. A write head for writing information, a first urging means for urging the write head in the direction of the image carrier, and a facing relationship between the write head and the image carrier when the two bodies are closed in a predetermined relationship. A positioning means for setting, the positioning means being provided on the write head at both ends in the orthogonal direction, each having a circumferential surface or a spherical surface at a tip portion. Positioning projections, and the first body Alternatively, the first support means is movably supported in a linear direction connecting the generatrix of the image carrier and the center of the rotation axis, and is capable of accommodating the pair of positioning projections. A pair of head positioning members having a narrow recess for setting the positional relationship of the write head with respect to the first support unit in the moving direction and the orthogonal direction; and a biasing force smaller than a biasing force of the first biasing unit. A second urging means for urging the head positioning member in the direction of the writing head, and provided on the head positioning member or the writing head, and rotatably provided on both ends of the surface of the image carrier in the orthogonal direction. An image forming apparatus, comprising: a roller member that sets a facing distance between the writing head and the image carrier in contact therewith. 2. The image forming apparatus according to claim 1, wherein the writing head is an optical writing head having a predetermined number of LED light emitting elements in a writing unit. 3. The head positioning member is supported by a support shaft and biased by the first biasing means.
The image forming apparatus according to claim 1, wherein the image forming apparatus is arranged so as to be swingable in a direction urged by the urging means. 4. An image forming apparatus comprising the image carrier, the first supporting means, the writing head, the first urging means, and the positioning means, is provided in plural in a multistage manner in a flow direction of a processing step. 4. The image forming apparatus according to claim 1, wherein the image forming apparatus is a tandem type image forming apparatus.