JPH09269455A - Deflection mirror controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify constitution, to reduce a manufacturing cost and to enhance precision in adjustment also. SOLUTION: A deflection mirror controller is provided with a support side plate 32, an excentric cam 34 as an adjustment member and a stepping motor 36 as a drive source driving the excentric cam 34. A cam pivot 44 is formed on the support side plate 32, and the excentric cam 34 and an oblique teeth gear 46 are supported synchronously rotatably to the cam pivot 44. A worm gear 50 engaged with the oblique teeth gear 46 is attached to the rotary shaft of the stepping motor 36. A deflection mirror 26 is positioned so that its upper surface 26a and its front surface 26b are supported by leaf springs 40, 42 attached to the support side plate 32 in the recessed part 38 of the support side plate 32, and its lower surface 26d is supported by the excentric cam 34. The fine adjustment of the deflection mirror 26 in the y direction is performed by the rotation of the excentric cam 34.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling a deflection mirror in an electrophotographic apparatus, and more particularly to a deflection mirror control apparatus suitable for a full color electrophotographic apparatus having a plurality of photoconductors.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic system, if there is a size and a driving error of a mechanism, a toner image is formed at a position deviated from a position where the toner image is originally formed. Distortion or the like occurs. In particular, in a system in which each color image is transferred to a recording medium a plurality of times, such as a color electrophotographic apparatus, a relative positional deviation between the colors occurs as a new problem. Relative misregistration between colors is visually noticeable as color misregistration and significantly deteriorates image quality.

Particularly, in a full-color electrophotographic apparatus having a plurality of photoconductors, there are many factors for positional deviation, and it is said that the countermeasure is the most difficult. This type of full-color electrophotographic apparatus has a schematic structure, for example, as shown in FIG. As shown in FIG. 24, a plurality of image forming units are arranged along the sheet conveying path, and different colors are sequentially transferred each time the sheet passes through each image forming unit, and finally four colors are transferred. A color image is obtained by superposition. Each image forming unit includes a drum-shaped photoconductor (1 _BK , 1 _M , 1 _Y , 1 _C ) that functions as an image forming medium and a charging device (2 _BK , 2) arranged around these photoconductors. _M , 2
_Y , 2 _C ), exposure device, developing device (3 _BK , 3 _M , 3 _Y ,
3 _C ) etc. Each photoconductor (1 _BK , 1 _M ,
The surface of 1 _Y , 1 _C ) is uniformly charged by the charging device,
The exposure device exposes a pattern corresponding to the image to be output, and an electrostatic latent image is formed on the surface of each photoconductor (1 _BK , 1 _M , 1 _Y , 1 _C ). The electrostatic latent image is developed by a developing device to form a toner image, and the toner image is transferred onto a sheet. After transfer, photoconductor (1 _BK , 1
_The toner remaining on the surface of _M , 1 _Y , 1 _C ) is removed by a cleaning device (5 _BK , 5 _M , 5 _Y , 5 _C ).

The color-separated image signal obtained by the color image reading device 6 is subjected to color conversion processing by the image processing section 7 based on its intensity level, and black (BK), magenta (M), yellow (Y). ) And cyan (C) color image data. A laser scanner 8 is used as an exposure device.
The laser beam from the laser light source is reflected by the polygon scanner 9, and further the Fθ lens 10 _BK , 10 _M , 10
_Y , 10 _C , deflection mirrors 11 _BK , 11 _M , 11 _Y , 11
_The optical path is bent at _C and the photoconductor (1 _BK , 1 _M , 1 _Y , 1
The surface of _C ) is exposed. In this laser scanner 8, by a polygon scanner 9 is rotated, the main scanning is performed in the axial direction of the photosensitive member _{(1 BK, 1 M, 1} Y, 1 C), the photosensitive member (1 _BK, 1 _M, 1 _Y ,
By the rotation of 1 _C ), the sub-scan is performed in the direction orthogonal to the axial direction of the photoconductor. The alignment of each color is performed by the timing when the recording paper sent from the paper feed unit 12 is conveyed from the resist unit 13 to the transfer position of each color by the transfer belt 14 and the timing of each photoconductor (1 _BK , 1 _M , 1 _Y , 1). _C ) The exposure start time is set so that the timing at which the above image is moved to the transfer position is the same for all colors. After the transfer, it is sent to the paper output unit 15.

The types and causes of positional deviation occurring in such an image forming apparatus are mainly as follows. (A) Shift (constant deviation; FIGS. 25 (a), 25 (b),
(C)) It is caused by an exposure portion, a setting position of the photoconductor, an error in writing timing, and the like. In FIG. 25A, the writing start of the scanning line is deviated in the main scanning direction, FIG. 25B is the position of the scanning line deviated in the sub-scanning direction (paper conveyance direction), and FIG. 25C is the scanning line. The length is different. In the figure, a broken line L ₀ indicates a scanning line position that is originally written, and a solid line L ₁ indicates a scanning line that is deviated (the same applies hereinafter). Since these shifts are constant at any position on the image, the shifts can be eliminated by adjusting the writing timing of each color. (B) Skew (diagonal shift; FIG. 26) It is caused by a parallel error of the exposed portion, the photoconductor, and the transfer belt.
The scanning lines are written obliquely due to these factors. (C) Curvature (FIG. 27) Caused by a shape error of the toroidal surface of the Fθ lens. The image scanned due to this factor becomes curved. (D) Pitch unevenness (periodic deviation; FIG. 28) Due to uneven rotation of the photoconductor and the conveyance belt, unevenness of the scanning pitch interval occurs in the sub-scanning direction at the same cycle as the uneven rotation cycle. (E) Random (sudden and aperiodic) This is caused by vibration of the apparatus, slip of the transfer belt, and the like.

Generally, it is difficult to correct all of these positional deviations by one adjusting means, and various adjusting means have been studied for each positional deviation. Among these, the skew and pitch unevenness which are the objectives of the present invention will be described in detail.

(Regarding Skew) If there is an error in the parallelism between the deflection mirror and the photoconductor drums in the optical system, the inclinations of the main scanning lines differ for each color. At present, a serviceman manually adjusts the inclination of the deflecting mirror and the photosensitive drum to correct the deviation. (Regarding Pitch Unevenness) When there is unevenness in the driving of the photosensitive member or the like, a fluctuation in the scanning line interval having periodicity occurs in the sub-scanning direction. FIG. 29 is a graph showing an example of positional deviation variation of each color image in the sub-scanning direction. The horizontal axis l _f is the image position in the sub-scanning direction, and δ is the image positional deviation amount. Each color image has its own position variation periodic waveform. When these are overlapped, color shift occurs at each position in the sub-scanning direction, as shown in FIG. As one of the means for solving this problem, there is one that attempts to correct this deviation by changing the position of the deflecting mirror at the time of image formation and controlling the exposure position so as to cancel the position deviation. In order to actively correct the positional deviation, it is necessary to grasp the behavior of the positional deviation change in advance.

Both of the above two positional deviations (skew and pitch unevenness) can be corrected by controlling (adjusting) the position of the deflecting mirror in the optical system.
The driving elements proposed or generally considered as driving elements for moving the deflecting mirror are as follows. (A) piezo actuator which controls the position in the device, such as a piezoelectric actuator is capable of very fine movement control of several μm units, also it is possible high frequency control thousands H _z. (B) Position control is performed by the amount of screw advancement (Japanese Patent Laid-Open No. 7-248455) As shown in FIG. 31, a screw that rotates the stepping motor 80 in synchronization with the helical gear 84 via the worm gear 82 and the helical gear 84. To the support member 90 by the movement of the nut member 88 that is transmitted to the screw 86 and screwed into the screw 86.
The deflection mirror 92 supported by can be moved. In FIG. 31, reference numeral 94 is a leaf spring as a pressing member. In a mechanism using such a screw drive element, as shown in FIG. 32, since the movement amount of the deflection mirror 92 is proportional to the rotation angle θ _m of the motor output shaft, drive control is relatively easy. .

[0009]

However, in the case of using the above-mentioned piezo actuator, since it is necessary to secure an attachment structure that does not hinder the movement control of the piezo element, there is a concern that it is weak against disturbance such as vibration. There is. Moreover, since the piezo element returns to the original position when the power is turned off, it is necessary to set the initial position each time the power is turned on. Furthermore, it is difficult from the viewpoint of component cost. On the other hand, in the case of using screws, the cost of parts is difficult for screws with high precision pitch.

[0010]

In order to solve the above-mentioned problems of the prior art, the present invention grasps the necessary conditions therefor as follows.・ Small and highly accurate movement control is possible ・ High position retention and strong against disturbances such as vibrations ・ Since it controls multiple deflection mirrors, it is a simple structure that can be low cost ・ Especially correction of pitch unevenness However, since the movement is controlled over time during image formation, long-term drive stability is required. As a result of careful consideration, an "eccentric cam" was specified as an adjustment member to satisfy these conditions. It is a thing.

According to a second aspect of the present invention, from the viewpoint of widening the control range of the deflection mirror, in the configuration according to the first aspect, the control means for controlling the drive source is provided, and the amount for moving the deflection mirror is set. Is Δy, the moving angle of the eccentric cam is Δθ, the rotation angle of the eccentric cam from the home position is θ, and the eccentric amount of the eccentric cam is e, the control means is Δθ = sin- ¹ (sin θ + Δy / e) The configuration is such that control is performed through arithmetic processing based on the expression of −θ. According to the invention described in claim 3, from the viewpoint of reducing the drive error and avoiding the deterioration of the stability of the mechanism, in the configuration of claim 1, from the viewpoint of reducing the drive error, the support member, the eccentric cam, the drive A source is provided at each end of the deflection mirror, and the eccentric cam is independently driven at each end.

In a fourth aspect of the present invention, in order to realize a simple structure in which the inclination does not change when the parallel movement of the deflection mirror is performed, in the configuration of the third aspect, the one end of the deflection mirror is provided with the above-mentioned structure. An inclination holding mechanism is provided, which includes a pressing member that is provided so as to face the eccentric cam and is in point or line contact with the deflecting mirror, and an urging unit that urges the pressing member in a direction that always contacts the deflecting mirror. Is adopted. According to a fifth aspect of the invention, in order to prevent the contact position between the adjusting member and the deflection mirror from changing, in the configuration according to the first aspect, the contact surface of the eccentric cam with respect to the deflection mirror is formed in a tapered shape. There is a configuration that there is. According to the sixth aspect of the invention, in order to further improve the control accuracy of the deflecting mirror, means for newly forming a pattern for measuring the amount of misregistration between the colors at both ends in the main scanning direction, and each pattern. And a plurality of pattern detection means for detecting the amount of deviation of each color in the sub-scanning direction corresponding to, and based on the detection result from the pattern detection means, for a part or all of Appropriate approximation processing is performed, and based on the obtained data or approximation curve, the above equation Δθ = sin- ¹ (sinθ + Δ
y / e)-[theta] is obtained to control [Delta] y to control the drive source.

According to the seventh aspect of the invention, in order to accurately follow the movement amount of the deflection mirror to the movement ideal value, the above formula Δ
When the rotational movement position information of the eccentric cam is processed as the number of pulse trains based on θ = sin− ¹ (sin θ + Δy / e) −θ, the number of pulses corresponding to the above Δy is obtained at each predetermined time interval Δt, The control amount Δθ is determined by rounding off the fractional part. In the invention according to claim 8, in order to prevent the calculation error of the movement amount from being accumulated, in the configuration according to claim 7, each time interval Δ.
When the control amount Δθ for each t is determined, it is determined based on the absolute rotational movement position information based on the previous rotational movement position information and the positional information of the position of the angle θ (movement start position). ing. According to a ninth aspect of the present invention, in order to reliably perform control at predetermined time intervals, in the configuration according to the seventh or eighth aspect, timer means set to the predetermined time interval Δt is provided, and the control at each predetermined time interval Δt is performed. The configuration is such that information on the amount Δθ is calculated in advance and stored in a predetermined storage means, and the stored information is called as needed when the deflection mirror is moved.

According to a tenth aspect of the present invention, in the structure of the ninth aspect, within a difference time between the delay time such as the data calling from the storage means and the set time of the drive signal and the predetermined time interval Δt. The configuration is such that the movement of the eccentric cam is completed. According to the invention of claim 11, in order to eliminate an error due to backlash, in the structure of claim 6, when rotating in a direction opposite to the previous movement for the predetermined time interval Δt, a predetermined amount corresponding to backlash is generated. It is configured to return by Δθ of.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention (application example to a full-color electrophotographic apparatus using a plurality of photoconductors) will be described below with reference to FIGS. Since the outline of the full-color electrophotographic apparatus as an application target is the same as that shown in FIG. 24, only the main part of the optical system is shown. As shown in FIGS. 2 and 3, the laser beam from the laser light source is reflected by the polygon scanner 20, and the Fθ lenses 22, 24,
The deflection mirror 26 bends the optical path to expose the surface of the photoconductor. The deflection mirror 26 has one end side supported by the first deflection mirror control device 28 and the other end side supported by the second deflection mirror control device 30, and these two independent adjustment devices are used. The entire deflection mirror control device is configured.

The first deflection mirror control device 28 is roughly composed of a supporting side plate 32 as a supporting member, an eccentric cam 34 as an adjusting member, and a stepping motor 36 as a driving source. As shown in FIG. 1, the support side plate 32 has an L-shaped recess 3 that accommodates the end of the deflection mirror 26.
8 is formed and the upper surface 2 of the deflection mirror 26 is formed.
Leaf springs 40 and 42 for pressing 6a and the front surface 26b are provided. A cam support shaft 44 is integrally provided on the support side plate 32, and the eccentric cam 34 and the helical gear 46 are supported by the cam support shaft 44 so as to rotate synchronously. The stepping motor 36 is supported by a motor bracket 48 installed on the optical system base, and a worm gear 50 is directly connected to the output shaft of the stepping motor 36 and meshed with the above-mentioned helical gear 46. That is, the eccentric cam 34 is rotated with a certain reduction ratio by the rotation of the stepping motor 36. The deflection mirror 26 includes the leaf spring 4 described above.
0, 42, the rear surface 26c of the recess 3 of the support side plate 32
8, the lower surface 26d is supported by the eccentric cam 34, and is positioned by this four-sided support method.
The second deflecting mirror control device 30 also has the same configuration as the first deflecting mirror control device 28 except for a part (described later).

When the eccentric cam 34 rotates, the deflection mirror 2
The outer peripheral surface of the eccentric cam 34 that is in contact with 6 moves, and the deflection mirror 26 moves (adjusts) in the y direction (FIG. 1). The drive transmission configuration is not limited to this,
The combination of the worm gear 50 and the helical gear 46 has a merit that a large reduction ratio is provided and that the helical gear 46 does not rotate even if an unexpected external force is applied to the helical gear 50 side, and is a conventional means for fine position adjustment. . For example,
In the configuration of FIG. 1, the number of teeth z ₂ of the helical gear 46 is 40, the number of teeth z ₁ of the worm gear 50 is 1, and the stepping motor 36 is
If the step angle θm of the above is 15 ° and the eccentric amount e of the eccentric cam 34 is 1 mm, the average resolution yu becomes the following expression, and extremely high-resolution movement control is possible.

[Equation 1]

In the drive transmission system, backlash between gears causes a decrease in adjustment accuracy. In order to prevent this, in this embodiment, a torsion coil spring 52 is used, one end of which is an eccentric cam 34 and the other end is a supporting side plate. The eccentric cam 34 is provided with a unidirectional rotational force so that the tooth surface of the helical gear 46 is always in contact with the tooth surface of the worm gear 50. As a result, even if the eccentric cam 34 is rotated in the forward and reverse directions, backlash between gears does not occur, so that an adjustment error due to backlash can be eliminated. This is also a known means for highly accurate adjustment.

The relationship between the rotation angle of the eccentric cam 34 and the movement amount of the deflection mirror 26 is not linear, and the movement amount Δy / Δθ of the deflection mirror 26 with respect to the rotation amount of the eccentric cam 34 changes.
Therefore, in order to obtain the desired movement amount y, the eccentric cam 3
A means for determining or recognizing the initial position of 4 is required. The mechanism and means for setting the initial position of the eccentric cam 34 will be described below. As shown in FIG. 4, the deflection mirror control device in this embodiment includes a CPU 54 as a control means, and controls the stepping motor 36 based on an adjustment signal from the operation panel 56. The operation panel 56 includes an eccentric cam 3
A home position setting mode key 58 for setting the home position of No. 4 is provided. Further, as shown in FIG. 1, the eccentric cam 34 is provided with a positioning claw 60 (see FIG. 8), and correspondingly, the supporting side plate 32 is provided with a positioning pin 62.

When the home position setting mode key 58 is pressed, a pulse equal to or more than the motor drive pulse corresponding to the abutment of the positioning claw 60 and the positioning pin 62 is output by the CPU.
Sent from 54. As a result, the eccentric cam 34 rotates and the eccentric cam 34 continues to rotate even after the positioning claw 60 hits the positioning pin 62, the rated torque of the motor exceeds the drive torque of the eccentric cam 34, and the stepping motor 36 loses synchronization. . After the stepping motor 36 starts to step out, the positioning claw 60 and the positioning pin 62 are kept in contact with each other. Therefore, when the pulse transmission is completed, the positioning claw 60 and the positioning pin 62 are in the abutting rotational position. Thereafter, the CPU 54 gives a motor pulse corresponding to returning from the rotational position to the initial rotational position, and the eccentric cam 34 is reversed and positioned at the initial position (home position). With such a configuration, the home position can be set accurately without using a position detection sensor or the like.

The adjustment accuracy according to the above-described structure is governed by the roundness of the eccentric cam 34 except for the play of the eccentric cam 34 and the cam support shaft 44. However, the highly accurate eccentric cam 34 has a high accuracy. It can be manufactured at a lower cost than a screw, and since there is no equivalent to a nut member as compared with a screw method, the number of parts of the entire configuration is reduced, which can contribute to low cost.

Next, an embodiment corresponding to claim 2 will be described. When the rotation position as shown in FIG. 5 is set to the home position, the relationship between the rotation angle θ and the movement amount y of the deflection mirror 26 is given by the following equation. y = esin θ θ: cam rotation angle from home position e: cam eccentricity

FIG. 6 is a graph of the above equation, where the horizontal axis is θ and the vertical axis is y. The range of the graph is -90 ° ≤ θ ≥
90 ° and −e ≦ y ≧ e. Although y and θ have a substantially linear relationship near the home position, they cannot be regarded as a linear relationship at a position away from the home position. A method is conceivable in which the movement control stroke is set within a limited range near the home position when the movement control is performed, and the relationship between y and θ is regarded as linear. In this case, no special arithmetic processing is required, but the stroke that can be controlled for movement is considerably narrowed, and if the dimensional accuracy of each component involved in the installation of the deflection mirror 26 is made rough, this movement amount There is a concern that it will be insufficient. Further, if an attempt is made to secure a stroke by increasing the amount of eccentricity, the resolution for movement control becomes coarse and fine adjustment cannot be performed.

Therefore, when the adjustment signal is input, CP
U54 performs arithmetic processing based on the following equation, and the motor pulse step number corresponding to the rotation number obtained by this is transmitted from the CPU 54 to the stepping motor 36. Δθ = sin− ¹ (sin θ + Δy / e) −θ Δθ: moving angle As a result, a desired moving amount y of the deflection mirror 26 can be obtained at any position of the eccentric cam 34. Further, by adopting such a control method, the movement control stroke of the eccentric cam 34 can be fully used up to −90 ° ≦ θ ≧ 90 °. With the above configuration, the inclination of the deflection mirror 26 can be adjusted with high resolution, high accuracy, and large stroke.

Next, an embodiment corresponding to claims 3 and 4 will be described. The above-mentioned configuration is necessary for adjusting the inclination of the deflection mirror 26 in the main scanning direction, but in order to adjust the above-mentioned scanning line pitch unevenness in the sub-scanning direction, the deflection mirror 26 must be moved in parallel. I have to. A driving mechanism for displacing both ends of the deflection mirror 26 is required for the parallel movement, and for this purpose, a first deflection mirror control device 28 and a second deflection mirror control device 30 are provided. At the time of image formation, the first deflecting mirror control device 28 and the second deflecting mirror control device 30 displace the deflecting mirror 26 independently and with the same movement amount.

Further, in order to maintain the parallelism of the deflection mirror 26, a mechanism that does not cause angular displacement in the γ direction shown in FIG. 1 is required. If an angular displacement in the γ direction occurs due to some movement error, it will lead to an error in the optical path and correct adjustment will not be possible. More specifically, as shown in FIG. 7, when the deflection mirror 26 deviates from the original correct position (broken line) by an angle α in the γ direction (solid line), the writing position on the photoconductor 1 deviates by δ. In FIG. 7, when the distance ld from the deflection mirror 26 to the photoconductor 1 is 100 mm and an error of α = 0.1 ° occurs in the γ direction due to the movement control of the deflection mirror 26, the writing position error δ is Since the following formula is used, it is necessary to maintain the parallelism very accurately.

[Equation 2] Considering the fact that the optical path changes by 300 μm or more with a displacement of only 0.1 °, the optical path is corrected by changing the inclination of the deflecting mirror as in the technique described in Japanese Patent Laid-Open No. 7-248455. Can be said to be quite difficult in reality.

In order to deal with such a problem, in this embodiment, as shown in FIG. 2, in the second deflection mirror control device 30, a tilt holding mechanism 64 is provided in place of the plate spring 40. There is. As shown in FIG. 8, the tilt holding mechanism 64 includes a support shaft 66 integrally formed with the support side plate 32.
And the deflection mirror 26 rotatably supported by the support shaft 66.
Member 68 that makes point or line contact with the upper surface 26a of the
And a torsion coil spring 70 as an urging means having one end attached to the support side plate 32 and the other end attached to the pressing member 68. The pressing member 68 is always driven by the elastic force of the torsion coil spring 70. It is biased to come into contact with the deflection mirror 26.

The deflection mirror 26 is displaced and the pressing member 68 is moved.
The ridge line 68a (FIG. 1) of the pressing member 68 with respect to the deflection mirror 26 is parallel to the support shaft 66 in order to prevent the inclination of the deflection mirror 26 from changing even when is swung. With such a configuration, the pressing member 68 and the deflection mirror 26
Since the contact portion of the deflection mirror 26 does not change, the dimensional accuracy of the contact portion does not affect the parallelism of the deflection mirror 26. Further, since the movement stroke of the pressing member 68 is also minute, the influence of backlash is small. Here, the pressing member 68
The error amount of the writing position due to the error of the parallelism between the ridgeline 68a and the support shaft 66 will be calculated. 9 (a) and 9 (b),
The case where the angle between the ridgeline 68a of the pressing member 68 and the axis line 66a of the support shaft 66 is α ° is shown. In this case, the initial inclination error α is represented by the following equation. α = tan- ¹ (S / d) S: parallelism d: width of pressing member The tilt error at a certain rotational position is shown in FIGS. 9 (c) and 9 (d), and is represented by the following formula. α '= tan- ¹ (S' / d) = tan- ¹ (Scosψ /
d) ψ: The amount of change in the tilt due to the swing angle of the pressing member is given by the following formula.

(Equation 3) For example, if S: 0.1 mm, d: 15 mm, ψ: 10 °, the following results are obtained.

(Equation 4) Optical path length ld from the deflection mirror 26 to the photosensitive drum 1
If (Fig. 7) is 100 mm, the writing error δ
From the above equation, δ = 4 × 100 × sin (5.81 × 10 ⁻³ / 2) ≈
Since 0.02 mm = 20 μm, the parallel movement can be performed with considerable accuracy.

Next, an embodiment corresponding to claim 5 will be described. At the contact portion between the eccentric cam 34 and the deflection mirror 26,
As shown in FIG. 10, if the contact point P moves in the main scanning direction due to the inclination of the deflection mirror 26, a movement control error of the deflection mirror 26 will result. Therefore,
In this embodiment, as shown in FIG.
The contact surface 34a of No. 4 is formed in a tapered shape. In this way, the contact point P does not move in the main scanning direction,
An error based on this can be avoided.

Next, an embodiment corresponding to claim 6 will be described. The application target is a full-color electrophotographic apparatus using a plurality of photoconductors as in the above-mentioned embodiment, and the image forming process is the same, and therefore the description thereof is omitted. Since the outline of the configuration of the deflecting mirror control device is the same, the drawing corresponding to FIG. 2 is omitted. Further, in this embodiment, when the process linear velocity V = 180 [mm / s], the resolution in the sub-scanning direction is 1200 dpi, and the printing operation is performed by A4 size vertical feed (297 [mm]). Is assumed. Similar to the above embodiment, the stepping motor 36 is used as the drive source of the deflecting mirror 26, but a rotary encoder may be added to the DC motor to perform the positioning operation.

The deflection mirror control device in this embodiment is provided with a CPU 72 and the like as control means. CP
The U 72 controls various devices connected via the I / O port 75 according to a program stored in the ROM 74, and forms an image. Also, in the process, various data are stored in / called from the RAM 76.
The two stepping motors 36 as driving sources for the deflection mirror 26 are connected to the I / O port 75 via a motor driver 77. Also, an interrupt signal is output to the CPU 72 from a timer 78 as a timer means.
Further, the laser scanner 8 in this embodiment has a function as means for forming a pattern for measuring the amount of misregistration between the colors at both ends in the main scanning direction. As shown in FIG. 12, the measurement patterns 79, 79 are 5
After being optically written with a laser beam so as to have an equal interval for every 0 line, the transfer belt 1 is developed by a developing device.
4 is transferred to both ends in the main scanning direction. At both ends of the transfer belt 14 in the main scanning direction, two pattern detecting sensors (pattern detecting means) 73 corresponding to the respective patterns 79, 79 for detecting at least the deviation amount of each color in the sub scanning direction are installed. The pattern detection sensors 73, 73 of
A detection signal is output to the CPU 72 as shown in FIG.

Here, considering the linear velocity and the resolution, the interval Δd and the time difference Δt between the lines of the pattern 79 are Δd.
= 1059 [μm] and Δt = 5.88 [ms]. However, in reality, since there is an error in the parallelism between the deflection mirror and the photoconductor drums in the optical system, the image is skewed, and if there is unevenness in the drive of the photoconductor, the transfer belt, etc., pitch unevenness occurs, The detection result of the pattern interval from the pattern detection sensor 73 may not be Δd even if written at each time interval Δt.

A method of controlling the deflection mirror 26 based on the detection result of the pattern detection sensor 73 will be described below. It should be noted that although one color is described here, the same operation is performed for four colors, and thus a description of many colors will be omitted. Further, the left and right of the deflecting mirror 26 are independently driven, but this operation is also the same, so the description thereof is omitted.

The transfer belt 14 is moving in the direction of the arrow as shown in FIG. 12 or FIG. 24, and the measurement pattern 79 formed by the above method moves to the position of the pattern detection sensor 73. When the difference between the detection result of each line by the pattern detection sensor 73 and the above Δd is plotted,
As shown in FIG. However, since the detection result includes a measurement error as can be seen from FIG. 13, the misalignment on the image cannot be minimized by directly using it as the data for determining the control amount of the eccentric cam 34. .

Therefore, in order to reduce the influence of the pattern measurement error, it is decided to obtain a curve that is approximated up to the sixth-order term by using the least square method. A method of determining the approximate curve will be described based on the flowchart of the routine for determining the approximate curve shown in FIG. I = 0 in the main routine (not shown)
Therefore, i is incremented (Step
1). Next, the detection result of the pattern detection sensor 73 and Δd
Is compared (the difference is obtained) (Step 2), and the comparison result is stored in the RAM 76 (Step 3). Here, in the A4 size vertical feed direction, the space between every 50 lines is 2
Since 80 pieces will be created, it is determined whether i ≧ 280 (Step 4). As a result, if NO, Ste
If it is YES, the approximate curve δ = f (t) is obtained from the data for each Δt. In this embodiment, as described above, approximation is performed up to the sixth-order term by the method of least squares,
From the data of FIG. 13 f (t) = 2 * 10- 12 t 6 -10- 9 t 5 -
2 * 10- ⁷ t ⁴ + 0.0003t ³ -0.0741t ² + 4.947t. FIG.
Although only one cycle of the curve is shown in FIG.
The positional displacement of the upper pattern 79 means that this one cycle change is repeated (Step 5).

However, as shown in FIG. 15, in this embodiment, since the incident angle of the laser beam with respect to the deflection mirror 26 is 60 °, in order to cancel the deviation amount on the transfer belt 14, the deflection mirror 26 is canceled. Since the moving amount of 26 is δ / 2, as shown in FIG. 13, y = g (t),
In this case, g (t) = 8 * 10- ¹³ t ⁶ −6 * 10− ¹⁰ t ⁵ −9 * 10− ⁸
t ⁴ + 0.002t ³ −0.037t ² + 2.4737t (Step
6). In this embodiment, an approximated curve is obtained for all the detection results, but it is divided by a certain section and approximated,
Alternatively, the stepping motor 3 can be treated as discrete data by performing approximation from peripheral data of the result of interest.
6 may be drive-controlled.

Next, an embodiment corresponding to claims 7 and 8 will be described. FIG. 16 is an enlarged view of y = g (t) in FIG. 13, in which the eccentric cam 34 is now moved from a position of an angle θ _p (corresponding to a P pulse as a drive pulse) from HP (home position). To start the movement start origin O '
And Hereinafter, how to determine the control amount will be described based on the flowchart of the control amount determination routine of the eccentric cam 34 shown in FIG. First, in a main routine (not shown), when the CPU 72 receives an interrupt signal from the timer 78 set to Δt (= 5.88 ms) in advance, the CPU 72 executes a control amount determination routine.

In the control amount determination routine, since j = 0 in the main routine (not shown), j
Is incremented (Step 1). Then y = g
At (t), since t = j * Δt, y = (j) which is discrete data is obtained (Step).
2). Here, the amount n (j) representing how many stepping motor drive pulses y (j) is, n = h
It is calculated from (j) and y (j). However, since the gear reduction ratio is 40 and the unit step angle of the stepping motor 36 is 15 °, the following formula (A) h (j) = (180 / 0.375 π) * sin- ¹ { sin (0.375 pi / 180) * P + y (j) / e} -P ... (A) However, it is e = 1 (Step 3). Since n (j) has a fraction below the decimal point, it is rounded off to an integer value, and the obtained value is set to m (j) (Step 4).

Next, the line interval of the pattern 79, that is, the number of pulses corresponding to the control amount to move within Δt is Δn.
(J), the following formula (B) Δn (j) = m (j) −m (j−1) ... (B) is used to obtain (Step 5), and the obtained Δn (j) is RA.
It is stored in M76 (Step 6). In this example, 50
Since the correction is performed line by line, it will be performed 280 times within the vertical length of the A4 version, so it is determined whether i ≧ 280 (Step 7). If NO, jump to Step 1 and if YES. If it returns to the main routine.

In this way, the number of pulses for the control amount obtained from the approximate curve y (j) is rounded off, and as shown in equations (A) and (B), absolute pulses from the movement start origin are obtained. By determining the control amount in consideration of the number, it is possible to follow the approximate curve y (j) within 1/2 of the movement amount (= resolution) of the deflection mirror 26 corresponding to one drive pulse. Moreover, the error below the decimal point does not accumulate. FIG. 18 shows a flowchart of a mirror moving routine for actually moving the deflecting mirror 26. First, k is set to 0 in the main routine, so k is incremented (Step 1) and Δn
(K) is read from the RAM 76 (Step 2), Δn (k) is set in the motor driver 77 (Step 3),
A start signal is transmitted to the motor driver 77 to start the stepping motor 36 (Step 4), and the process returns.

Next, an embodiment corresponding to claim 9 will be described. Δt is determined by the sum of each of the time required to determine the control amount from the detection result, the data transfer time with the memory, the setting time of the control amount to the motor driver 77, and the time required to complete the movement of the stepping motor 36. For,
The smaller Δt is, the better the followability to the approximate curve y (t) is, and the positional deviation can be reduced. In this embodiment, FIG.
Δn (j) obtained in the control amount determination routine of
It is stored in M76 (Step 6), and when moving the mirror during image formation in the mirror moving routine shown in FIG. 18, Δn (j) is read from the RAM 76 (St).
ep2) Since the deflection mirror 26 is moved, it is possible to eliminate the time loss due to the calculation time as compared with the case where the deflection mirror 26 is sequentially calculated and moved when the deflection mirror 26 is moved.
Becomes smaller.

Next, an embodiment corresponding to claim 10 will be described. FIG. 19 shows the relationship between the setting of the number of moving pulses and the moving time in this embodiment on the time axis, and FIG.
The flowchart when setting 8 was shown. Timer 78
Is set to Δt (= 5.88ms), and the CPU 72
An interrupt signal is generated for the control amount determining routine, and the average sum of the data calling delay time on the memory and the delay time when setting the number of pulses for the motor driver 77 is Since it is 0.13 [ms],
Within the time obtained by subtracting the delay time from Δt (5.75 [ms])
The transmission pulse must be set so that the movement ends. In this way, by determining Δt in consideration of the time loss, the followability with respect to the approximate curve is improved, and the positional deviation can be reduced.

Next, an embodiment corresponding to claim 11 will be described. In this embodiment, the helical gear 84 and the worm gear 82 are used in the drive portion of the eccentric cam 34, but when moving in the opposite direction to the previous (i-1) th time, the backlash BL exists as shown in FIG. Therefore, the followability to the approximate curve is deteriorated. Therefore, in this embodiment, this backlash is removed. The pitch of the worm gear 82 corresponds to two drive pulses of the stepping motor 36. FIG. 22 shows a flowchart showing the operation for removing the backlash. First, it is determined whether or not the current moving direction is the reverse of the previous moving direction (Step 1). If NO, the process returns to the main routine, and if YES, two pulses are reversed (Step 1).
2) Return to the main routine. FIG. 23 shows a state in which the backlash BL has been removed by this. Since the backlash BL is removed, the approximate curve y
The followability with respect to (t) is improved, and the positional deviation can be reduced.

According to the first aspect of the invention, since the adjusting member is an eccentric cam, the structure can be simplified as compared with a driving form such as a screw and a lever, and highly accurate stepless adjustment can be performed. It can be performed, and the manufacturing cost can be reduced. According to the invention described in claim 2, since the rotation angle of the eccentric cam is controlled through a specific calculation process, the deflection mirror can be adjusted with high accuracy even at a rotation angle away from the home position. Therefore, the movement (adjustment) control range can be expanded.

According to the third aspect of the present invention, since the adjusting devices as the cam actuators are installed at both ends of the deflection mirror and driven independently, both the inclination correction of the deflection mirror and the parallel movement correction are performed. It can be carried out. According to the invention described in claim 4, since the tilt holding mechanism is provided at one end of the deflection mirror, it is possible to suppress the tilt change when the deflection mirror is moved in parallel, and perform highly accurate adjustment. You can According to the invention described in claim 5, since the contact surface of the eccentric cam with respect to the deflecting mirror has a taper, the contact point in the main scanning direction between the eccentric cam and the deflecting mirror does not change, and therefore highly accurate adjustment is possible. It can be performed.

According to the invention described in claim 6, since the influence of the pattern measurement error can be reduced by the appropriate approximation processing, the positional deviation can be reduced. According to the invention of claim 7, the error from the ideal movement value is within ½ of the movement amount of the deflection mirror corresponding to one rotation movement information pulse, so that the followability with respect to the ideal movement value becomes good. The position shift can be reduced. According to the invention of claim 8, when determining the control amount for each angular time interval, based on the previous rotational movement position information and the absolute rotational movement position information from the movement start position information. Since it is determined, the error due to rounding off after the decimal point is not accumulated, the followability with respect to the ideal movement value is improved, and the positional deviation can be reduced.

According to the ninth aspect of the invention, the control amount for each predetermined time interval is calculated in advance and stored in a predetermined storage means, and is called as needed when the deflecting mirror is moved. It is possible to reduce the predetermined time interval by eliminating time loss due to time. As a result, the followability with respect to the ideal movement value is improved, and the positional deviation can be reduced. According to the tenth aspect of the invention, since the movement of the eccentric cam is completed within the difference time between the delay time such as the set time of the drive signal and the predetermined time interval, the followability with respect to the ideal movement value becomes good. The position shift can be reduced. According to the eleventh aspect of the present invention, since the backlash is removed when rotating in the opposite direction to the previous time, the followability with respect to the ideal movement value is improved, and the positional deviation can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic side view of a deflection mirror control device showing an embodiment of the present invention.

FIG. 2 is a perspective view of the same.

FIG. 3 is a side view based on FIG.

FIG. 4 is a block diagram of control means and the like.

FIG. 5 is a diagram showing a home position of an eccentric cam.

FIG. 6 is a graph showing a relationship between displacement amounts of an eccentric cam and a deflection mirror.

FIG. 7 is a diagram showing an optical path error due to tilt movement of a deflection mirror.

FIG. 8 is a front view of the vicinity of the tilt holding mechanism as viewed obliquely from above.

FIG. 9 is a diagram showing a parallelism error between a pressing member and a support shaft in the tilt holding mechanism.

FIG. 10 is a diagram showing movement of a contact point in the main scanning direction between a deflection mirror and an eccentric cam.

FIG. 11 is a control block diagram of an embodiment corresponding to claims 6 to 11;

FIG. 12 is a perspective view showing a relationship between a measurement pattern on a transfer belt and a pattern detection sensor.

FIG. 13 is a diagram showing a relationship between measurement data obtained by a pattern detection sensor and its approximate curve.

FIG. 14 is a flowchart of an approximate curve determination routine.

FIG. 15 is a schematic diagram of a path of laser light.

FIG. 16 is an enlarged view of y = g (t).

FIG. 17 is a flowchart of a control amount determination routine.

FIG. 18 is a flowchart of a mirror movement routine.

FIG. 19 is a graph showing the relationship between the set time of the moving pulse number and the moving time on the time axis.

FIG. 20 is a flowchart of a timer setting routine.

FIG. 21 is a diagram showing backlash between a worm gear and a helical gear. ,

FIG. 22 is a flowchart of a backlash removal routine.

FIG. 23 is a diagram showing a state in which backlash is removed.

FIG. 24 is an overall view of a full-color electrophotographic apparatus using a plurality of photoconductors.

FIG. 25 is a diagram showing a shifted position shift image.

FIG. 26 is a diagram showing a positional shift image in which scanning lines are inclined.

FIG. 27 is a diagram showing a positional shift image in which a scanning line is curved.

FIG. 28 is a diagram showing a pitch unevenness image.

FIG. 29 is a graph showing misregistration for each color.

30 is a graph obtained by superimposing the graphs of the respective colors in FIG.

FIG. 31 is a schematic side view showing a conventional deflection mirror control device using screws.

FIG. 32 is a graph showing the relationship between the rotation angle of the motor output shaft and the movement amount of the deflection mirror in the conventional deflection mirror control device using screws.

[Explanation of symbols]

 26 Deflection Mirror 32 Support Side Plate as Supporting Member 34 Eccentric Cam as Adjusting Member 36 Stepping Motor as Driving Source 54 CPU as Control Unit 64 Tilt Holding Mechanism 68 Holding Member 70 Torsion Coil Spring as Biasing Means 73 Pattern Detection Means Pattern detection sensor 79 patterns

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiya Sato 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Inventor Yutaka Shio 10-3 Kitamura, Tottori City, Tottori Prefecture (72) Inventor Tomonori Yabuta 10-3 Kitamura, Tottori City, Tottori Prefecture, Ricoh Microelectronics Co., Ltd.

Claims (11)

[Claims] 1. A supporting member for supporting a deflecting mirror of an optical writing system in an electrophotographic apparatus, an adjusting member for contacting the deflecting mirror to change the inclination of the deflecting mirror in the main scanning direction, and driving the adjusting member. A deflection mirror control device including a drive source, wherein the adjusting member is an eccentric cam. 2. A control means for controlling the drive source, wherein the amount of movement of the deflection mirror is Δy, the moving angle of the eccentric cam is Δθ, and the rotation angle of the eccentric cam from the home position is θ. The deflection according to claim 1, wherein when the eccentric amount of the eccentric cam is set to e, the control means controls through an arithmetic processing based on an equation of Δθ = sin- ¹ (sinθ + Δy / e) -θ. Mirror controller. 3. The support member, an eccentric cam, and a drive source are provided at both ends of the deflection mirror, and the eccentric cam is independently driven at each end.
Deflection mirror control device described. 4. A pressing member which is provided at one end of the deflecting mirror so as to face the eccentric cam and is in point or line contact with the deflecting mirror, and a biasing member which constantly biases the pressing member in a direction of contacting the deflecting mirror. 4. The deflection mirror control device according to claim 3, further comprising an inclination holding mechanism including a means. 5. The deflection mirror control device according to claim 1, wherein a contact surface of the eccentric cam with respect to the deflection mirror is formed in a tapered shape. 6. A support member for supporting a deflecting mirror of an optical writing system in an electrophotographic apparatus, an adjusting member for contacting the deflecting mirror to change the inclination of the deflecting mirror in the main scanning direction, and driving the adjusting member. In the deflection mirror control device having a drive source, the adjusting member is an eccentric cam, and means for forming a pattern for measuring the amount of positional deviation between the colors at both ends in the main scanning direction, and each pattern. And a plurality of pattern detection means for detecting the deviation amount of each color in the sub-scanning direction corresponding to the above, and the drive source of the eccentric cam is Δθ = sin- ¹ (sinθ + Δy / e) -θ where Δθ: predetermined time Moving angle of eccentric cam within interval Δt Δy: moving amount of deflecting mirror within predetermined time interval Δt e: eccentric amount of eccentric cam Δt: unit time to complete moving amount Δy of eccentric cam The mirrors are independently controlled at both ends of the mirror through arithmetic processing based on the equation of the interval, and based on the detection result from the pattern detecting means, appropriate approximation processing is performed for a part or all of the above, A deflection mirror control device, characterized in that the drive source is controlled by obtaining Δy in the above formula Δθ = sin− ¹ (sin θ + Δy / e) −θ based on the obtained data or an approximated curve. 7. A supporting member for supporting a deflecting mirror of an optical writing system in an electrophotographic apparatus, an adjusting member for contacting the deflecting mirror to change the inclination of the deflecting mirror in the main scanning direction, and driving the adjusting member. In the deflection mirror control device having a drive source, the adjusting member is an eccentric cam, and means for forming a pattern for measuring the amount of positional deviation between the colors at both ends in the main scanning direction, and each pattern. And a plurality of pattern detection means for detecting the deviation amount of each color in the sub-scanning direction corresponding to the above, and the drive source of the eccentric cam is Δθ = sin- ¹ (sinθ + Δy / e) -θ where Δθ: predetermined time Moving angle of eccentric cam within interval Δt Δy: moving amount of deflecting mirror within predetermined time interval Δt e: eccentric amount of eccentric cam Δt: unit time to complete moving amount Δy of eccentric cam The mirrors are independently controlled at both ends of the mirror through arithmetic processing based on the equation of the interval, and the above equation Δθ = sin- ¹ (si
nθ + Δy / e) -θ, when the rotational movement position information of the eccentric cam is processed as the number of pulse trains, the number of pulses corresponding to the above Δy is calculated for each predetermined time interval Δt, and the decimal places are rounded off. A deflection mirror control device, characterized in that the control amount Δθ is determined by the following. 8. When determining the control amount Δθ for each time interval Δt, absolute rotational movement position information based on the previous rotational movement position information and the positional information of the position of the angle θ (movement start position) is also used. 8. The deflection mirror control device according to claim 7, wherein: 9. A timer means set to a predetermined time interval Δt is provided, information of the control amount Δθ for each predetermined time interval Δt is calculated in advance and stored in a predetermined storage means, and the stored information is deflected. 9. The deflection mirror control device according to claim 7, wherein the deflection mirror control device is called as needed when the mirror is moved. 10. A delay time such as a data calling from the storage means or a drive signal setting time, and the predetermined time interval Δ.
10. The deflection mirror control device according to claim 9, wherein the movement of the eccentric cam is completed within a time difference from t. 11. A predetermined Δ corresponding to a backlash when rotating in a direction opposite to the previous movement during a predetermined time interval Δt.
7. The deflection mirror control device according to claim 6, wherein the deflection mirror control device returns by θ.