JP2806617B2 - Method for adjusting meshing position between driving means and driven member for color image forming apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting a meshing position of a driving member and a driven member for a color image forming apparatus such as an electrophotographic color copying machine and a color printer.

(Prior Art) In such a color image forming apparatus, a plurality of image carriers such as photoconductors are juxtaposed, an electrophotographic process is performed on each image carrier to obtain a developed image of each color, and the developed image is transferred to a transfer material. The desired color image is obtained by transferring the image onto a transfer material conveyed by a means.

FIG. 10 shows a configuration diagram of a laser beam printer which is one type of this type of color image forming apparatus. The laser beam printer has three image forming units Pa, Pb, and Pc arranged side by side. The image forming units Pa, Pb, and Pc have dedicated photosensitive drums 1, 2, and 3, respectively. Around the photosensitive drums 1, 2, and 3, a dedicated laser beam exposure means 7, 8, 9 and a charging unit (not shown), an exposure unit, a developing unit, a transfer unit, a cleaning unit, and the like are included. Image forming process means are arranged.

On the other hand, below the photosensitive drums 1, 2, and 3, an endless belt 16 is provided.
Is provided, and the transfer material P supplied from a paper feeding device (not shown) is transferred by the transfer material transport means 13 to the transfer positions 25, 26, and 26 of the image forming units Pa, Pb, and Pc. 27
Is transported in the direction of the arrow shown in FIG.

In the laser beam printer having the above configuration, first, a visible image (yellow image) of yellow toner is formed in the first image forming unit Pa, and the visible image is transferred by the transfer material transporting means 13. The image is transferred at the transfer position 25.

On the other hand, while the visible image (yellow image) is being transferred to the transfer material P, a visible image (magenta image) of magenta toner is formed in the second image forming unit Pb. Transfer material P whose transfer is completed by Pa
Is carried into the transfer position 26 of the second image forming unit Pb, a magenta image is transferred to a predetermined position on the transfer material P.

Thereafter, similarly, a visible image (cyan image, black image) of a cyan toner and, if desired, a black toner is formed, and when the visible image is transferred onto the transfer material P, three colors or four colors are formed on the transfer material P. Color visible images are superimposed,
The transfer material P on which the transfer is completed undergoes image fixation by a fixing unit (not shown), and a desired color image is formed on the transfer material P. The photosensitive drums 1, 2, and 3 on which the transfer has been completed are cleaned by a cleaning unit (not shown) to remove residual toner, and are prepared for the subsequent latent image formation.

(Problems to be Solved by the Invention) By the way, the above-described color image forming apparatus such as a laser beam printer has an image forming unit for each color, which is advantageous for speeding up, and has a linear transfer path. It has the advantage of being adaptable to transfer materials such as thick paper and transparent film because it can be used, but in terms of how well it can register each color formed by different image forming units You have a problem to solve.

In order to solve the above problem, it has been proposed to drive a plurality of photosensitive drums with a single drive source via a worm and a worm wheel (see Japanese Patent Application Laid-Open No. 63-11967). In this proposal, the distance between the photosensitive drums is set so that the time interval for the transfer material to pass between the photosensitive drums is equal to an integral multiple of the drive unevenness period of the drive source (drive motor). The color shift is prevented by adjusting the phase of the position shift at each station caused by the unevenness.

However, according to the above proposal, rotation unevenness occurs in each photosensitive drum due to variation in accuracy of a driven member (here, a worm wheel) which receives a driving force from a driving source on the drum shaft. There is a problem that color shift occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a driving unit and a driven member for a color image forming apparatus capable of preventing a color shift from occurring and obtaining a high quality color image. An object of the present invention is to provide an engagement position adjusting method.

(Means for Solving the Problems) In order to achieve the above object, a method for adjusting the meshing position of a driving unit and a driven unit for a color image forming apparatus according to the present invention is performed by testing a plurality of rotatable image carriers. Forming a toner image of a pattern, transferring the toner image of the test pattern on the plurality of image carriers to a transfer material, and testing the plurality of tests corresponding to the plurality of image carriers on the transfer material. A step of reading a toner image of a pattern, a plurality of driven members provided on rotation axes of the plurality of image carriers, respectively, such that image expansion and contraction of the toner images of the test patterns match on a transfer material; Adjusting the meshing position with the driving means for driving the driven member.

(Operation) According to the present invention, the engagement position between the plurality of driven members and the driving unit is adjusted so that the image expansion and contraction of the toner image of each test pattern corresponding to the plurality of image carriers is matched on the transfer material. Therefore, it is possible to obtain a good image without positional deviation, that is, color deviation.

(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a configuration diagram of a photosensitive drum drive system of a laser beam printer according to the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is a perspective view of a main part of the laser beam printer.

The basic configuration of the laser beam printer will be briefly described with reference to FIG. 3. The laser beam printer has three image forming units Pa, Pb, and Pc arranged side by side.
Pa, Pb, and Pc are provided with dedicated photosensitive drums 1, 2, and 3 serving as image carriers. A dedicated image forming process means is arranged around each of the photosensitive drums 1, 2, and 3, and these image forming process means are laser beam exposing means 7, 8,
9. It is configured to include a charging unit (not shown), an exposure unit, a developing unit, a transfer unit, a cleaning unit, and the like.

On the other hand, below the photosensitive drums 1, 2, and 3, an endless belt 16 is provided.
Is provided, and the transfer material P supplied from a paper feeding device (not shown) is transferred by the transfer material transport means 13 to the transfer positions 25, 26, and 26 of the image forming units Pa, Pb, and Pc. 27
Is transported in the direction of the arrow shown in FIG.

Thus, in the present embodiment, each image forming unit Pa, Pb, Pc
The photosensitive drums 1, 2, and 3 have a driving motor 17 as a common driving source.
Is driven to rotate. That is, as shown in FIG. 1, a worm gear 1 is attached to a drive shaft 29 connected to the drive motor 17.
8, 19, 20 are engraved, and the worm gears 18, 19, 20 mesh with worm wheels 21, 22, 23 connected to the ends of the drum shafts 101, 102, 103 of the photosensitive drums 1, 2, 3. I have. Since the worm gears 18, 19, and 20 are integrally formed on the drive shaft 29, the worm gears 18, 19, and 20 are connected to the drive shaft 29.
Eccentricity is unlikely to occur between.

Accordingly, when the drive shaft 29 is rotationally driven by the drive motor 17, the rotation of the drive shaft 29 is transmitted through the worm gears 18, 19, 20 and the worm wheels 21, 22, 23 to the drum shafts 101, 102, 103.
The photosensitive drums 1, 2, and 3 supported on the drum shafts 101, 102, and 103 are driven to rotate at a predetermined speed.

Incidentally, the photosensitive drums 1, 2, and 3 are arranged at a predetermined distance from each other.
The time T ₁ , T ₂ during which the transfer material P passes between the transfer positions 25 and 26 and 26 and 27 of the adjacent photosensitive drums 1 and 2 and 2 and 3 is determined by the drive means comprising the drive motor 17 and the drive shaft 29. It is set to be equal to an integral multiple of the driving unevenness cycle. Therefore, the phases of the drive unevenness of the photosensitive drums 1, 2, and 3 caused by the drive unevenness of the drive units 17 and 29 coincide with each other.

Here, the details of the drive system of the photosensitive drums 1, 2, and 3 will be described with reference to FIGS.

In this embodiment, the drive shaft 29 is prevented from being deformed by the force applied to the worm gears 18, 19, 20 when the worm gears 18, 19, 20 are engaged with the worm wheels 21, 22, 23.
29 is a bearing for both ends of each worm gear 18, 19, 20 31, 32, 33, 3
It is supported at 4. The bearings 31, 32, 33, 34 are supported by bearing support members 35, 36, 37, 38, and the bearing support members 35, 36, 37, 38 are fixed to the main body side plate 40 (FIG. 2). reference). Note that the bearing support members 35, 36, 37, and 38 may be configured so that their positions can be adjusted with respect to the main body, so that the positions of the bearings 31, 32, 33, and 34 can be adjusted.

Worm wheels 21, 22, 23 and worm gears 18, 19,
A thrust force generated in the axial direction of the drive shaft 29 by meshing with the drive shaft 20 is received by a thrust receiving member 39 such as a circlip attached to an end of the drive shaft 29. The drum shaft
Worm wheels 21, 22, 23 fixed on 101, 102, 103
Is configured to be movable in the axial direction of each of the drum shafts 101, 102, 103 by means not shown, whereby the meshing positions of the worm gears 18, 19, 20 and the worm wheels 21, 22, 23 can be adjusted. .

Thus, in the present embodiment, the number of threads of each worm gear 18, 19, 20 is set to 4, the reduction ratio is set to 1/20, and the module is set to 1, and the pitch circle diameter of each worm wheel 21, 22, 23 is set. Is φ80
mm.

The diameter of the photosensitive drums 1, 2, and 3 is φ60mm, and the rotation speed is 30rpm.
Since the reduction ratio of the worm gears 18, 19, 20 and the worm wheels 21, 22, 23 is set to 1/20 as described above, the rotation speed of the drive motor 17 is 600 rpm.

Therefore, if the cumulative pitch error of the worm wheels 21, 22, 23 is, for example, 50 μm, the cumulative pitch error 50
Image displacement caused by μm is 50μm × φ60mm / φ8
0 mm = 37.5 μm.

As described above, by increasing the pitch circle diameter of the worm wheels 21, 22, 23, the worm wheels 21, 22,
It is possible to reduce the amount of image displacement caused by the 23 cumulative pitch errors.

In addition, the cumulative pitch error of each worm wheel 21, 22, 23 is measured in advance, and the phase of the image misregistration caused by the cumulative pitch error of the worm wheels 21, 22, 23 at each image station is adjusted to match the color. It is also possible to minimize the deviation.

FIG. 4 is a graph showing cumulative pitch errors of the worm wheels 21, 22, and 23. In this embodiment, each worm wheel
Since the number of teeth of 21, 22, and 23 is 80, the horizontal axis in FIG. 4 shows the number of teeth from a certain reference tooth to 80, and the vertical axis shows the cumulative pitch measured from the reference tooth. The error is shown. Normally, the cumulative pitch error is quantified by the value between the peaks shown in FIG. 4, but actually appears as a sine wave with one rotation of the gear from the reference tooth as one cycle.

Therefore, when a worm wheel with a cumulative pitch error of 50 μm is used, the positional deviation amount Δ of the image is as follows: Δ = 50/2 μm × 60/80 · sin θ = 18.75 sin θ μm where θ is an arbitrary tooth and the reference tooth The angle to make.

Can be expressed as

For example, the positional deviation of the image between the first station and the second station is a sine wave having a amplitude of 18.75 μm and a phase of 1
18.75 × 2 = 37.5μm when displaced by 80 ° (π)
Color shift occurs. In order to minimize the color shift due to the station difference, the phases of the image position shift curves of the stations may be matched.

 Here, how to adjust the phase will be described.

First, the worm wheel used at each station
The cumulative pitch errors of 21, 22, and 23 were measured, and reference teeth that could be approximated by a sine wave as shown in FIG. 4 were found.
Let n ₁ , n ₂ , n ₃ .

If the distance 1 between the photosensitive drums 1, 2, and 3 of each station is 150 mm, 150 / 60π × 80 teeth = 63.7 teeth ≒ 64 teeth, so there is a delay time between stations corresponding to 64 teeth.

Therefore, the worm wheels 21, 22, and 23 of each station may be shifted in the direction of delay by 64 teeth with respect to the rotation direction of the photosensitive drums 1, 2, and 3 and incorporated.

FIG. 1 shows how the worm wheels 21 and 22 of the first and second stations are assembled. First
When setting the reference tooth n ₁ stations of the worm wheel 21 in a position to mesh with the worm gear 18, the reference teeth n ₁ of the first station of the worm wheel 21 reference teeth n ₂ of the second station of the worm wheel 22, as shown From
The position is 64 teeth behind. Similarly, the worm wheel 23 of the third station is the same as the worm wheel of the first station.
From 21 to 128 teeth, 2nd station worm wheel 2
It is only necessary to incorporate n _{3 at a} position 64 teeth behind from 2.

Next, a description will be given of a method of reading an image expansion / contraction change from an output image and determining an engagement position between the worm gear and the worm wheel based on the result.

That is, in this method, a predetermined test pattern image is formed on each image carrier, the test pattern image is transferred to a transfer material to obtain a test pattern output image, the test pattern output image is read, and the image information is read. It is a method of calculating the amount of image position shift by analysis, analyzing the phase difference of the image expansion / contraction change on each image carrier from the image expansion / contraction change, and shifting the meshing position of the worm wheel and worm gear by the phase difference. .

 Hereinafter, the details will be described.

FIG. 5 is a plan view of an essential part showing an example of a test pattern image, for example, a pattern in which straight lines extending in the main scanning direction are arranged at 1 mm pitch in the sub-scanning direction on A3 size recording paper.

Such a test pattern image is output, and the positional deviation amount Δl of each line with respect to the nominal position is measured.

FIG. 6 is a graph showing an example of the measurement result of the positional deviation amount Δl. In FIG. 6, the horizontal axis represents the line number k of the test pattern line image, and the vertical axis represents the positional deviation amount Δl.
(Μm).

As shown in the figure, the positional deviation amount Δl is a periodic function with one rotation of the worm wheel as one cycle, and can be approximated by the following equation using a Fourier series.

_{Δl (θ) = a 0 +} a 1 cosθ + a 2 cos2θ + ... + a n cosnθ + b 0 + b 1 sinθ + b 2 sin2θ + ... + b n cosnθ ...... (1) The above equation is converted to the following equation Δl (θ) = a ₀ + c ₁ cos (θ + δ ₁ ) + c ₂ cos (2θ + δ
_{2) + ...... + c 2 cos} (nθ + δ n) ...... (2) next, k-th constants by the least squares method the positional shift amount of the line pattern as _{Δl k a 0, a m,} b m, a c _m When calculated, Here, comparing expressions (1) and (2), Here, one cycle of the worm wheel, that is, cycle 2π
Is c ₁ cos (θ + δ ₁ ), so that tan δ ₁ = −a ₁ / b ₁ , and the phase angle δ ₁ of the Δl curve can be calculated. Thus, the phase angle δ _{1 at} each image station is obtained from the test pattern output image at each image station.
Is determined.

The phase angle δ ₁ at the first station (Y image forming station) is set to δ ₁ (Y), and the second station and the third
The phase angle δ _{1 of the} station is δ ₁ (M), δ ₁ , respectively.
(C).

FIG. 7 is a diagram showing an example in which the positional shift amount Δl of the test pattern line output image is approximated by a Fourier series, and the vertical axis of the figure indicates the positional shift amount Δl.

In FIG. 7, .DELTA.l _Y represents the positional deviation fluctuation of the Y image (yellow image) formed in the first station, and .DELTA.l _M represents the second image.
The position deviation fluctuation of the M image (magenta image) formed by the station is shown. As is clear from the figure, in order to eliminate the color shift between the two, the phase angles δl _1Y and δl _1M
It is sufficient to form an image by matching the values.

FIG. 8 is a flowchart showing an example of a phase angle calculation procedure of each image station. In the figure, (1) to
(4) shows each step.

When calculating the phase angle [delta] _1, first, it outputs a test pattern image from the pattern generator (PG) (Step 1). This pattern generator may be provided in the ROM of the printer controller of the image forming apparatus, or may be external to the image forming apparatus.

Next, read the output image by the image reader (not shown) (Step 2), and calculates the position displacement amount .DELTA.l _k of each line of the test pattern image (Step 3). Incidentally, as the image reader, an image reader connected to the image forming apparatus may be used, or another image reader may be used.

In this way, the phase angle δ ₁ at each image station
Is calculated (step 4). For example, when the phase shift angles δ _1M and δ _1C of the second and third stations are made equal to δ _1Y using the first station as a reference station, the second station is (δ _1M −δ _1Y ). Then, the meshing position between the worm wheel and the worm gear may be shifted in the direction opposite to the rotation direction by (δ _1C -δ _1Y ).

In this embodiment, since the number of teeth of the worm wheel and 80 teeth, on the worm wheel, respectively, in the second station, in _{80/360 (δ 1M -δ 1Y} ) teeth third station, 80/360 ([delta] _1C −δ _1Y ) If only the teeth are displaced, the phase of the displacement Δl at each station matches.

As described above, the phase matching in the case where a plurality of photosensitive drums are driven by a single drive source via the worm gear and the worm wheel has been described. Phase can be adjusted.

FIG. 9 shows an example of this, according to which a drive pulley 40 on a drive motor output shaft (not shown), an input pulley 41 on the first station drum shaft, an input pulley 42 of the second station, and a third One timing belt 44 is wound around the input pulley 43 of the station, and the driving force of the driving motor is transmitted to each image station. In FIG. 9, reference numerals 45 and 46 denote idler pulleys.

Thus, also in the above configuration, by adjusting the meshing position between the input pulleys 41, 42, and 43, which are driven members, and the timing belt 44 as described above, the phase of the image misalignment amount Δl at each station is adjusted. Can prevent the occurrence of a so-called color shift.

(Effects of the Invention) As is apparent from the above description, according to the present invention, a plurality of driven members are provided such that the image expansion and contraction of the toner image of each test pattern corresponding to the plurality of image carriers matches on the transfer material. Since the engagement position between the member and the driving means is adjusted, a good image free from positional deviation, that is, color deviation can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a photosensitive drum drive system of a laser beam printer according to the present invention, FIG. 2 is a cross-sectional view taken along line II-II of FIG.
FIG. 3 is a perspective view of a main part of the laser beam printer, FIG. 4 is a graph showing a cumulative pitch error of the worm wheel, and FIG.
FIG. 6 shows an example of a test pattern image, FIG. 6 is a graph showing an example of a measurement result of a positional deviation amount, and FIG. 7 is a diagram showing an example of approximating the positional deviation amount of a test pattern line output image by a Fourier series. FIG. 8 is a flowchart showing an example of a phase angle calculation procedure of each image station, FIG. 9 is a view showing another embodiment of the photosensitive drum drive system, and FIG. 10 is a perspective view of a main part of a conventional laser beam printer. is there. 1, 2, 3 ... photosensitive drum (image carrier), 17 ... drive motor (drive means), 18, 19, 20 ... worm gear, 21, 22, 23 ...
… Worm wheel (driven member, 25, 26, 27… transfer position, 29… drive shaft (drive means), 40… drive pulley, 4
1, 42, 43 ... input pulley (driven member), 44 ... timing belt, Pa, Pb, Pc ... image forming unit.

Claims (3)

(57) [Claims] A step of forming a toner image of a test pattern on each of a plurality of rotatable image carriers; a step of transferring the toner images of the test pattern on the plurality of image carriers to a transfer material; Reading a toner image of each of the test patterns corresponding to the plurality of image carriers on a transfer material; and A plurality of driven members provided on the rotation shaft, and a step of adjusting a meshing position of a driving unit for driving the plurality of driven members; and a driving unit for a color image forming apparatus, comprising: A method for adjusting a meshing position with a driven member. 2. The method according to claim 1, wherein the driven member is a gear. 3. The method according to claim 1, wherein said driven member is a belt pulley. 3. The method according to claim 1, wherein said driven member is a belt pulley.