JPH06110290A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device capable of obtaining a high- definition color image by reducing the fluctuation of driving speed caused by backlash between a worm wheel and a worm as for an image forming device provided with three or more image forming mechanisms. CONSTITUTION:The driving mechanism of the image forming device is provided with plural worms 8BK, 8C, 8M and 8Y attached to a driving shaft 20 and meshing with the worm wheels 9BK, 9C, 9M and 9Y. The respective worms have a pair of tooth surfaces having different lead and lead angle, and are attached to be positionally adjusted in the shaft direction of the driving shaft.

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, and more particularly to an image forming apparatus having a plurality of image forming mechanisms for respectively forming images of different colors on an image carrier and forming a multicolor image. Regarding

[0002]

2. Description of the Related Art In recent years, image forming apparatuses for forming multicolored images have become widespread. This type of image forming apparatus
A plurality of image forming mechanisms each having an image forming function are provided, and each image forming mechanism has an image carrier. Conventionally, as a method of simultaneously driving a plurality of image carriers, as disclosed in, for example, Japanese Patent Publication No. 62-270957, a plurality of worms are provided on a common drive shaft and are connected to the image carriers. There is known a worm gear driving method in which a plurality of image bearing members are directly driven through a plurality of worm wheels that mesh with corresponding worms.

In the image forming apparatus of the type described above, a multicolor image is formed by sequentially superposing and transferring the images formed by the respective image forming mechanisms onto a single transfer material. Therefore, the image carrier of each image forming mechanism must be driven at a constant speed with high accuracy. Therefore, when adopting the worm gear driving method, the axial distance between each worm wheel and the worm is accurately adjusted to prevent fluctuations in the driving speed of the image carrier due to backlash between the worm wheel and the worm. Must be set.

[0004]

In the above-mentioned conventional structure, when the number of the image carrier and the worm wheel is two or less, the error in the axial distance between the worm wheel and the worm causes the drive shaft to have an error. It can be adjusted by moving in a direction perpendicular to the axis or by tilting the drive shaft. However, in an image forming apparatus including three or more image carriers and worm wheels,
When the two worm wheels have an inter-axis error, the error cannot be adjusted only by moving or inclining the drive shaft as described above. For this reason, backlash occurs in the meshing of the worm wheel and the worm that are attached with this inter-axis error, and the speed of the image carrier changes. As a result, a color shift occurs in the transferred image, making it difficult to form a highly vivid color image.

Further, in the conventional structure, when there are mounting errors of the worms mounted on the same drive shaft, that is, eccentricity or inclination with respect to the drive shaft, a plurality of worms can be driven uniformly. Can not. Therefore, there is a problem that a phase of the transferred image is shifted and a color shift occurs in the transferred image, and a highly vivid color image cannot be obtained.

Therefore, an object of the present invention is to reduce fluctuations in drive speed due to backlash between a worm wheel and a worm in an image forming apparatus provided with three or more image forming mechanisms, and to achieve high definition. An object is to provide an image forming apparatus capable of obtaining a color image.

[0007]

In order to achieve the above object, according to the image forming apparatus of the present invention, at least one of a plurality of worms attached to a drive shaft and meshed with a worm wheel is provided. The worm is composed of a lead and a pair of tooth surfaces having different lead angles. The at least one worm is attached to the drive shaft so that the position of the worm can be adjusted along the axial direction.

According to the image forming apparatus of the present invention,
The worm that meshes with the plurality of worm wheels is formed integrally with the drive shaft by cutting the drive shaft.

[0009]

As described above, since the lead and the pair of tooth surfaces having different lead angles are provided, the modules on both tooth surfaces of the worm are also different from each other. Therefore, if there is an axial error between the worm and the worm wheel, moving the worm along the axial direction of the drive shaft changes the tooth thickness of the worm that meshes with the worm wheel, and as a result, Axes between axes and backlash can be absorbed.

When the drive shaft is cut to form a worm, a plurality of worms can be formed without causing eccentricity or inclination of the worm with respect to the drive shaft, as compared with the case where an independent worm is attached to the drive shaft. It can be driven uniformly.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. As shown in FIG. 1, the color image forming apparatus according to this embodiment includes four sets of image forming mechanisms 10BK, 10C arranged side by side in the housing 30 in the horizontal direction.
It is equipped with 10M and 10Y. These image forming mechanisms 10BK, 10C, 10M, and 10Y form images of different colors, for example, black (BK), cyan (C), magenta (M), and yellow (Y) images. Since the image forming mechanisms 10BK, 10C, 10M, and 10Y have the same configuration, the image forming mechanism 10c will be described below as a representative and other image forming units will be described in order to simplify the description. The description of the mechanism is omitted. Note that the same parts of each image forming mechanism are given the same reference numerals, and in order to distinguish the image forming mechanisms of each color, subscripts (BK, C, M, Y) indicating each color are added to the reference numerals. There is.

The image forming mechanism 10C comprises a photosensitive drum 1C as an image carrier, a charger 2C, a developing device 3C, a cleaning device 4C, an exposure device 5C and a transfer device 6C. Then, a latent image of a cyan light image is formed by the exposure device 5C on the photoconductor drum 1C that is uniformly charged by the charging device 2C, and this latent image is developed by the developing device 3C, so that the latent image is formed on the photoconductor drum. A cyan image is formed.

Image forming mechanism 10BK, 10C, 10M, 1
Below 0Y, a conveying belt 26 as a conveying means extending along these image forming mechanisms is provided, and further, below the conveying belt, a sheet feeding cassette 23 is arranged. Then, the transfer sheet is sent out from the sheet feeding cassette 23 by the sheet feeding roller 24, the leading ends thereof are aligned by the registration rollers 25, and is sent to the transport belt 26 at the same timing.

The transfer sheets are formed on the photosensitive drums 1BK, 1C, 1M, 1M, 1M and 1M, on which the visible images are formed by the conveyor belts 26, respectively.
1Y is sequentially conveyed, and at that time, transfer devices 6BK, 6
By the actions of C, 6M, and 6Y, the visible images of the respective colors are sequentially superimposed and transferred onto the transfer paper. The transfer sheet onto which the visible image has been transferred is fixed by the fixing roller 27 of the fixing device, and is discharged onto the discharge tray 31 by the discharge roller 28. In addition,
The transfer sheet is electrostatically attracted to the transport belt 26, and thus is accurately transported at the same speed as the transport belt.

FIG. 2 shows four sets of image forming mechanisms 10BK and 10BK.
C, 10M, 10Y, especially the photosensitive drums 1BK, 1C,
It shows a drive mechanism for driving 1M and 1Y with high precision and at the same speed. The drive mechanism is the photosensitive drum 1BK, 1
Four worm wheels 9BK and 9 attached to C, 1M and 1Y drum shafts 7BK, 7C, 7M and 7Y, respectively.
C, 9M and 9Y, and a drive shaft 20 that extends horizontally below these worm wheels. Further, four worms 8BK, 8C, 8M and 8Y are attached to the drive shaft 20, and the corresponding worm wheels 9B are provided.
It meshes with K, 9C, 9M and 9Y. The drive shaft 20 is
It is configured by the motor shaft itself of a drive motor (not shown) or is connected to the motor shaft.

As shown in FIG. 3, in each worm,
The pitch ta of the tooth flank a is formed slightly smaller than the pitch tb of the tooth flank a, and the lead and lead angle of the tooth flank a are slightly changed from the lead and lead angle of the tooth b face.
As a result, the a-tooth surface module (ma = ta / π) is smaller than the b-tooth surface module (mb = tb / π), and the worm tooth thickness changes from the right end tooth to the left end tooth in the figure. It grows continuously as it goes. Each worm uses the intermediate tooth as the reference tooth R. In addition, the worms 8BK, 8C configured in this way,
8M and 8Y are attached to the drive shaft 20 such that their positions can be adjusted along the axial direction of the drive shaft.

When assembling the drive mechanism having the above structure, first, with reference to the reference teeth R of the worms 8BK, 8C, 8M, and 8Y, backlash should be prevented from occurring between the worms and the worm wheels facing each other as much as possible. Assemble the drive shaft 20, weem wheel and worm.

As shown in FIG. 4, in the assembled state, for example, the worm wheels 9BK and 9M and the worm 8 are
If the axial distance between BK and 8M deviates from the reference axial distance A by the errors B and C, backlash occurs between these worm wheels and worms, and the photosensitive drum Since the driving speeds of 1BK and 1M vary, it becomes difficult to form a good color image. Therefore, in this case, the worms 8BK and 8M are moved in the axial direction of the drive shaft 20, respectively, and the worm wheel 9BK,
Adjust the mounting positions of worms 8BK and 8M so that there is no backlash while changing the tooth thickness of the worm that meshes with 9M. As shown in FIG. 4, when the inter-axis distance is larger than the reference inter-axis distance A by the errors B and C, the worms 8BK and 8M are moved to the right by the adjustment amounts b and c, respectively, and the reference teeth R are removed. Backlash can be eliminated by engaging teeth with large tooth thickness with the corresponding worm wheels 9BK and 9M. On the contrary, when the inter-axis distance is smaller than the reference inter-axis distance A by the errors B and C,
Backlash can be eliminated by moving the worms 8BK and 8M to the left by the adjustment amounts b and c, respectively, and engaging the teeth having a tooth thickness smaller than the reference tooth R with the corresponding worm wheels 9BK and 9M. it can.

According to the color image forming apparatus constructed as described above, the four image forming mechanisms 10BK, 10C and 10C are provided.
The drive mechanism for driving M, 10Y is provided with four worms 8BK, 8C, 8M, 8Y mounted on the drive shaft 20 so as to be positionally adjustable along the axial direction of the drive shaft. It has different left and right tooth surfaces (a tooth surface, b tooth surface), and the tooth thickness changes continuously. for that reason,
These four worms 8 mounted on the same drive shaft
Even if BK, 8C, 8M, and 8Y have different backlashes, the backlash can be eliminated by adjusting the position of each worm. Therefore, the four image forming mechanisms can be driven with high accuracy at the same speed without causing fluctuations in the driving speed of the photosensitive drums of the image forming mechanisms. Therefore, it is possible to form a high-definition color image without color shift.

In the above embodiment, all four worms have left and right tooth flanks of different modules, but when three image forming mechanisms are provided, at least one worm is used. When four image forming mechanisms are provided as in the example, at least two worms are configured to have different tooth flanks of the module, and the remaining worms are configured to be normal worms having the same left and right tooth flank modules. You may do it.

For example, in the drive mechanism shown in FIG. 4, when the worms 8C and 8Y are worms having the same left and right tooth flank modules, and the remaining worms 8BK and 8M are the above worms having different left and right tooth flank modules. First,
Drive shaft 20, worm and worm wheel 9 to prevent backlash in worms 8C and 8Y
Assemble BK, 9C, 9M and 9Y. In this case, if the number of worms 8C and 8Y is two or less, the height or inclination of the drive shaft 20 can be adjusted to prevent the occurrence of backlash in these worms. If backlash occurs in the remaining worms 8BK and 8M in the assembled state, each worm 8B is processed by the same method as in the above-described embodiment.
Move K and 8M to adjust. Therefore, even with such a configuration, it is possible to realize a high-definition color image forming apparatus with no color misregistration, as in the above-described embodiment.

FIG. 5 shows a driving mechanism of a color image forming apparatus according to the second embodiment of the present invention. The same parts as those in the above-described embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

According to this embodiment, the worms 8BK, 8C, 8M and 8Y meshing with the corresponding worm wheels 9BK, 9C, 9M and 9Y are formed integrally with the drive shaft 20. That is, each worm is configured by cutting a tooth groove on the outer peripheral surface of the drive shaft.

According to the above construction, it is possible to prevent a mounting error such as an eccentricity, an inclination, etc., which occurs when a plurality of worms independent of the drive shaft are mounted on the drive shaft, and a phase shift between the plurality of worms. . Also, warm 8B
Since K, 8C, 8M and 8Y are formed integrally with the drive shaft 20, the photosensitive drums 1BK, 1C and 1C can be decelerated by one stage.
Can drive M, 1Y. Therefore, there is no factor of speed fluctuation among the plurality of worms 8BK, 8C, 8M, and 8Y, and each image forming mechanism can be accurately driven at the same speed. As a result, a high-definition color image without color misregistration can be obtained. Can be formed. Moreover, by reducing the number of parts, it is possible to simplify the assembly and reduce the manufacturing cost.

In the second embodiment described above, the worm is formed only in the portions meshing with the worm wheels 9BK, 9C, 9M and 9Y. However, as shown in FIG. A tooth groove may be cut on the outer peripheral surface of the drive shaft to form a single long worm. In this case, the same effect as that of the second embodiment can be obtained, and the processing of the portion between the adjacent worms is not required, and the processing of the worm is facilitated. Further, the drive shaft 20 can drive other components other than the image forming mechanism.

The present invention is not limited to the above-described embodiments, but can be variously modified within the scope of the present invention. For example, the driving mechanism may drive the developing roller of each image forming mechanism instead of the photoconductor drum.

[0027]

As described above, according to the present invention, it is possible to drive a plurality of image forming mechanisms with high accuracy at the same speed, and to form a highly vivid color image without color misregistration. A device can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view of a color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a side view schematically showing a drive mechanism.

FIG. 3 is a diagram schematically showing a tooth surface of a worm.

FIG. 4 is a side view of the drive mechanism in a state where backlash is adjusted.

FIG. 5 is a side view schematically showing a driving mechanism of the color image forming apparatus according to the second embodiment of the present invention.

FIG. 6 is a side view schematically showing a modified example of the drive mechanism in the second embodiment.

[Explanation of symbols]

1BK, 1C, 1M, 1Y ... Photosensitive drum, 7BK, 7C,
7M, 7Y ... drum shaft, 8BK, 8C, 8M, 8Y ... worm, 9BK, 9C, 9M, 9Y ... worm wheel, 1
0BK, 10C, 10M, 10Y ... Image forming mechanism, 20 ...
Drive shaft.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display part // B41J 3/54

Claims (2)

[Claims] 1. An image forming apparatus for forming a multicolor image, each of which has an image carrier and forms images of different colors on the image carrier, and at least 3 arranged side by side.
An image forming mechanism and a driving unit for driving the image forming mechanism, the driving unit including a worm wheel attached to each of the image forming mechanisms, and a drive shaft extending along the image forming mechanism, A plurality of worms each of which is attached to the drive shaft and meshes with the worm wheel, and at least one of the worms has a lead and a pair of tooth surfaces having different lead angles, and An image forming apparatus, wherein the position is adjustable along an axial direction of a drive shaft. 2. An image forming apparatus for forming a multicolor image, each of which has an image carrier and forms images of different colors on the image carrier, and at least 3 arranged in parallel.
An image forming mechanism and a driving unit for driving the image forming mechanism, the driving unit including a worm wheel attached to each of the image forming mechanisms, and a drive shaft extending along the image forming mechanism, An image forming apparatus comprising: a worm that is provided on the drive shaft and meshes with the plurality of worm wheels; and the worm is formed by cutting the drive shaft.