JPH0453984A - Image forming device - Google Patents

Abstract

PURPOSE:To more effectively change image quality with simple mechanism by linearly moving a developing device main body by a set of moving means. CONSTITUTION:When the developing device main body 41 is moved in a direction crossed with a line combining between the shaft centers of a photosensitive drum 2 and a developing sleeve 42 by the moving means T, and angle formed by the line combining between the shaft centers of the drum 2 and sleeve 42 with a main pole N1 is changed and the angle of the main pole is relatively changed. Therefore, the angle of the main pole is changed without changing the relative positions of plural magnetic poles of a magnet 43 fixedly arranged in the developing device main body 41 to the main device 41. Then, a distance between the shaft centers of the drum 2 and the sleeve 42 is changed with the movement of the main device 41. Consequently, a distance between opposed surfaces is changed. Thus, the image quality is effectively adjusted with the simple mechanism by changing two kinds of parameters.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an image forming apparatus to which the so-called Carlson process is applied, such as an electrostatic copying machine or a laser beam printer.

<Prior Art> Recently, there has been an increasing demand for an image forming apparatus that can satisfactorily reproduce completely different images such as solid images, images with many halftones such as photographs, and line images such as characters.

When a solid image is well reproduced, the shading of black and white becomes clear, but halftones become difficult to reproduce, and characters in a line image become thick.

On the other hand, when an image with many intermediate tones or a line image is well reproduced, the resulting image quality is contradictory in that it has rich gradation and edge effects, but the black and white shading is not clear.

In order to reproduce images of the contradictory quality described above well, it is necessary to adjust the toner adhesion conditions (
It is known that it is sufficient to change the development parameters (development parameters).

For example, as shown in FIG. 5, in an image forming apparatus equipped with a developing device 93 that electrostatically attaches toner to an electrostatic latent image formed on the surface of a photoreceptor drum 90 using a developing sleeve 91, the following is performed. It is possible to change each parameter.

(1) As shown by the black arrow in the figure, move the developing sleeve 91 in a direction parallel to the straight line shown by the chain double-dashed line connecting the axes of the developing sleeve 91 and the photoreceptor drum 90, and The distance between opposing surfaces (hereinafter referred to as rD-3 distance) α is changed. The smaller the D-5 distance α is, the better the image quality will be, with clear differences in shading, suitable for solid images, and the larger the D-3 distance a, the better the image will be, suitable for halftones and line images. , resulting in image quality with rich gradation that is faithful to the original.

■ In order to hold the developer on the surface of the developing sleeve 91, a plurality of magnetic poles Nl are arranged inside the developing sleeve 91.
, Sl..., a magnetic pole (hereinafter referred to as "main pole") N that faces the photoreceptor drum 90 and is involved in electrostatic adhesion of toner.
1 is shifted as shown by the white arrow in the figure, and the direction of the peak of the magnetic flux of the main pole N1 (indicated by the dashed-dotted arrow in the figure), the developing sleeve 91 and the photosensitive drum 90 are adjusted. The angle θ (hereinafter referred to as "main polar angle") with respect to the straight line connecting the axes of is changed. 20 The smaller the principal polar angle θ, the better the quality of the image with clear differences in shading, suitable for solid images.
The larger the principal polar angle θ, the higher the quality of the image, which is suitable for halftones and line images and has rich gradation that is faithful to the original.

C3) In order to regulate the amount of developer held by the developing sleeve 91, the distance between the developing sleeve 91 and the cutting plate 92 disposed near the developing sleeve 91 is changed to reduce the amount of developer retained by the developing sleeve 91. Change the retention amount.

In addition, each of the above parameters may be changed independently, but in order to change the image quality more effectively, two
It is preferable to change more than one type of parameter in a complex manner.

In addition, in the above figure, the -dotted chain line curve corresponds to each magnetic pole N.
It shows the magnetic force distribution of l, Sl...

<Problems to be Solved by the Invention> However, when changing the distance between D-5 in (1) and the distance between the panicle cutting plates 92 in (3) among the above parameters, it is necessary to change the distance between the developing sleeve 91 or the panicles. Since a slight movement of the cutting plate 92 greatly affects the image quality, a complicated and precise movement mechanism is required. Moreover, especially when changing the distance of the panicle cutting plate 92 in a, a moving mechanism must be provided within the developing device 93, which is unreasonable in terms of space. Furthermore, since the length of the cutting plate 92 is longer than the full width of the developing sleeve, if it is bent or distorted even slightly, the image quality will be uneven, and the image quality will not be uniform over the entire width of the formed image. There is also the problem of not being able to obtain it.

On the other hand, when changing the main pole angle θ of (2), in order to shift the position of the main pole N1, by interacting with this main pole N1, other It is necessary to shift the positions of magnetic poles Sl, N2...
For example, the developer pumping position by the magnetic pole s2, the magnetic pole S
3, the release position of the developer becomes blurred, and the circulation conditions of the developer inside the developing device change, resulting in developer retention, developer scattering from the lower part of the developing device, etc., and the formed image. This may cause image defects such as toner scattering and fogging.

Furthermore, in order to compositely change two or more types of parameters, multiple drive mechanisms corresponding to each parameter are required, which further complicates the surroundings of the developing device packed in a narrow space, increasing the possibility of malfunctions and There is a problem in that it causes an increase in costs.

The present invention has been made in view of the above circumstances, and
With a simpler mechanism, it is possible to compositely change two types of parameters other than the distance of the cutting plate, which may cause uneven image quality, and the above-mentioned method when changing each parameter is possible. without any inconvenience,
An object of the present invention is to provide an image forming apparatus that can adjust image quality.

Means for Solving the Problems> In order to solve the above problems, an image forming apparatus of the present invention has the following features:
A magnet having a plurality of magnetic poles is fixed to the developing device main body, and is arranged so as to be movable linearly in a direction intersecting the developing device main body or a straight line connecting the axes of the photoreceptor drum and the developing sleeve. It is characterized in that it includes a moving means for moving the developing device main body.

<Function> In the image forming apparatus of the present invention having the above configuration,
When the developer body is moved by the moving means in a direction that intersects the straight line connecting the axes of the photoreceptor drum and the developing sleeve, the angle of the straight line connecting the axes of the photoreceptor drum and the developing sleeve with respect to the main pole changes. As a result, the main polar angle changes relatively. Therefore, the main pole angle can be changed without changing the relative position of the plurality of magnetic poles of the magnet fixedly arranged on the developing device main body with respect to the developing device main body.

In addition, as mentioned above, the axis of the developing sleeve of the developing device main body that moves linearly and the axis of the photosensitive drum that is fixed at one point are related to the point and the straight line that passes near this point. Therefore, the distance between the axes of the photoreceptor drum and the developing sleeve changes as the developing unit body moves, and as a result, D-
The distance between S changes.

Furthermore, the amount of change in the D-S distance is proportional to the larger the intersection angle between the initial direction of the straight line connecting the axes of the photoreceptor drum and the developing sleeve and the moving direction of the developing unit body. Since the amount of movement is smaller than the amount of movement of the developing device main body, delicate adjustment of the distance between D and 8 is possible.

<Embodiment> An explanation will be given below with reference to the drawings showing an electrostatic copying machine as an embodiment of the image forming apparatus of the present invention.

As shown in FIG. 2, the electrostatic copying machine of this embodiment exposes and scans a document in the copying machine main body 1 to form an electrostatic latent image corresponding to the document image on the surface of a photoreceptor drum 2. an optical system 3 for forming the electrostatic latent image, a developing device 4 for developing the electrostatic latent image into a toner image, a transfer device 5 for transferring the developed toner image onto the surface of the paper P, and a paper feed cassette 11 or a manual feeder. It has a paper transport section 7 that discharges the paper P fed from the paper feed section 12 onto the paper discharge tray 13 via the transfer device 5 and the fixing device 6.

The developing device 4 includes a developing device main body 41 that accommodates a developer, and a developing device main body 41 that electrostatically applies toner to an electrostatic latent image rotatably disposed within the developing device main body 41, as shown in FIG. A cylindrical developing sleeve 42 for electro-deposition, and a magnet 43 disposed within the developing sleeve 42 and having a plurality of magnetic poles Nl, Sl, . . . for holding the developer on the surface of the developing sleeve 42. It is equipped with In addition, the developing device main body 4
1, a stirring means 44 for stirring the developer is arranged behind the developing sleeve 42, and a toner hopper 8 for replenishing toner is detachably mounted above the stirring means 44. . Furthermore, the developing sleeve 42
A panicle cutting plate 45 and a guide plate 46 are provided above. The cutting plate 45 is used to regulate the layer thickness (height of the magnetic brush) of the developer held around the developing sleeve 42, and also measures the magnetic permeability of the developer to determine the toner concentration. It also serves as a support for the sensor S for detection.

The guide plate 46 is provided to guide the developer that has passed through the sensor S to the stirring means 44 .

As shown in FIG. 1 (Tayama), the developing device main body 41 has a supporting shaft 47 provided coaxially with the developing sleeve 42, which is formed in the developing device receptacle 14 of the copying machine main body 1 in a substantially vertical direction. By fitting into the extending bearing groove 14a so as to be able to move up and down, It is supported so as to be movable in a direction intersecting the two-dot chain line on the side at an angle θ4.

Furthermore, an eccentric cam T1 of a moving means T for moving the developing device main body 41 in the specific direction is in contact with the bottom surface of the developing device main body 41. The moving means T includes the eccentric cam T1, a gear T3 attached to the eccentric shaft T2 of the eccentric cam T1, a gear T4 that meshes with the gear T3, and a stepping motor T5 that rotates the gear T4.

Further, a drum receiver 14b that contacts the outer peripheral surface of the photoreceptor drum 2 is fixed to the developer receiver 14, and also serves as a support for the photoreceptor drum 2.

In the image forming apparatus of this embodiment having the above configuration, when the stepping motor T5 is driven from the state where the developing device main body 41 is located at the lowest position as shown in FIG. 1 (mount A1) and FIG. , due to the rotation of the eccentric cam T1,
The developing device main body 41 is moved along the bearing groove 148 as shown in FIG.
It will rise to the highest position shown in +. Further, when the eccentric cam T1 is further rotated from this state, the developing device main body 41 is lowered to the original position shown in FIG. 3 along the bearing groove 14a.

FIG. 4(a) shows how the main polar angle and the D-S distance change when the developing device main body 41 is raised by the above mechanism.

That is, when the center of the developing sleeve 42 is linearly raised from Pl to P2 by raising the developing device main body 41, a straight line connecting the axes of the developing sleeve 42 and the photoreceptor drum 2, as shown by a two-dot chain line, is formed. The slope changes. On the other hand, −
As shown by the dotted chain arrow, the direction of the peak of the magnetic flux of the main pole N1 is always constant because the magnet 43 is fixed to the developing device main body 41, and the main pole angle changes relatively from θ1 to θ2. spread.

Therefore, the main polar angle can be changed without changing the circulation conditions of the developer within the developing device main body 41.

Further, due to the linear rise of the developing device main body 41, the center of the developing sleeve 42 moves in a direction away from the axis of the photosensitive drum 2, so the distance between D-5 is changed from α1 to α2.
It spreads to

The change in the distance between D and 3 will be explained using FIG. 4, which shows the relationship between a point and a straight line passing near this point.

In the figure, the distance α between D and 5 is calculated by the following formula.

γ α 1 m Co5　θ3 Further, the distance between D and 3 α2 is calculated by the following formula.

γ The above angle θ3 and angle (θ, +02−θl) are both 90
Since it is less than or equal to @, Cosθ3>Cos (θ, 1θ2−θ,), and as a result, α2>α1.

As described above, in this embodiment, the developing device main body 41 is moved in the initial direction of the straight line connecting the axes of the photosensitive drum 2 and the developing sleeve 42 (the direction of the lower two-dot chain line in FIG. 4 (al)). When the developing device main body 41 is raised linearly along the intersecting direction at the crossing angle θ4, the main polar angle becomes larger and the distance between D and S becomes larger. When the main polar angle is lowered, the main polar angle becomes smaller and
The distance between D and 8 becomes smaller. Therefore, by simply moving the developing device main body 41 in a straight line using one set of moving means T, it becomes possible to change the two parameters at the same time. Furthermore, as mentioned above, the larger the main polar angle, the higher the quality of the image, which is suitable for halftones and line images and is faithful to the original, with rich gradation, but the image density tends to decrease, and the D- The larger the distance between D and D, the higher the quality of the image becomes, with richer gradation, but the image density tends to decrease. The two parameters of increasing and decreasing the -S distance exhibit a synergistic effect, making it possible to change the image quality of the formed image more effectively.

Furthermore, in the above embodiment, the developing device main body 4 is oriented with respect to the initial direction of the straight line connecting the axes of the photosensitive drum 2 and the developing sleeve 42 (the direction of the lower two-dot chain line in FIG. 4 (al)).
In proportion to the crossing angle θ4 of the moving direction of step 1, the amount of increase α2−α1 in the distance between D and 3 becomes smaller than the amount of movement β of the developing device main body, making it possible to finely adjust the distance between D and S. becomes.

In the above embodiment, as described above, the photoreceptor is adjusted in the direction of movement of the developing device main body 41 so that the two parameters of increase/decrease in the main polar angle and increase/decrease in the distance between D-3 exhibit a synergistic effect. Whether the intersecting angle θ4 with respect to the straight line connecting the axes of the drum and the developing sleeve was set, or the intersecting angle is not limited to the angle in the embodiment. For example, fine adjustment of image quality becomes possible by setting the intersecting angle of the moving direction of the developing device main body 41 so that the above two parameters cancel each other out.

In the illustrated embodiment, an eccentric cam T1 is used as the moving means T for moving the developing device main body 41. In the present invention, for example, a mechanism for moving the developing device main body up and down by a combination of a rack and a pinion is used. It is also possible to employ moving means having a number of mechanisms, such as a mechanism for lifting the developing device body using a solenoid.

Although the illustrated embodiment shows an electrostatic copying machine, the configuration of the present invention can be applied to other image forming apparatuses such as laser beam printers.

In addition, various design changes can be made without changing the gist of the present invention.

<Effects of the Invention> The image forming apparatus of the present invention is configured as described above, and by linearly moving the developing device main body by a set of moving means, the main polar angle and the distance between D-5 can be adjusted. Since two parameters can be changed simultaneously, image quality can be changed more effectively with a simpler mechanism. In addition, the main pole angle can be changed without changing the relative position of the plurality of magnetic poles of the magnet fixedly arranged on the developing device body, so it is possible to change the main polar angle without changing the relative position with respect to the developing device body. without causing various inconveniences,
The main polar angle can be changed. Furthermore, the above D-S
The larger the intersecting angle between the initial direction of the straight line connecting the axes of the photoconductor drum and the developing sleeve and the moving direction of the developing device body, the greater the amount of change in the distance between them. Since the amount of movement is smaller than the amount of movement, it is possible to finely adjust the distance between D and 5.

Therefore, according to the image forming apparatus of the present invention, two types of parameters can be changed in a complex manner with a simpler mechanism, and various inconveniences that may occur when changing each parameter can be avoided. You can adjust the image quality without this happening.

Further, according to the image forming apparatus of the present invention, since an image quality faithful to the original can be obtained, a good image without deterioration can be obtained in so-called generation copying, such as recopying a copied image.

[Brief explanation of drawings]

FIG. 1 (b+ is a schematic front view showing the main parts of an electrostatic copying machine as an embodiment of the image forming apparatus of the present invention, FIG. 1 (b+ is a side view of the main parts described above, and FIG. FIG. 3(b) is a schematic diagram showing the internal structure of an electrostatic copying machine; FIG.
1) is an explanatory diagram illustrating the mechanism of parameter change in the above embodiment, and FIG. 5 is a sectional view showing the main part of the conventional example. 2... Photoreceptor, 41... Developing unit body, 43... Magnet, Sl, N2. S2゜T...Transportation means. 4...Developing device, 42...Developing sleeve, N1...Magnetic pole (main pole), S3...Magnetic pole, 2-...Photoreceptor 4...Developing device 41-...Developing device body 42 Developing sleeve T・-Moving means 2・Photoreceptor 4・・Developing device 41・・Developing device main body 42・・・Developing sleeve 43・・Magnet N1・・・Magnetic pole (main pole) ■ ...Movement means SL, N2, 52.53...Magnetic pole 2...-Photoreceptor 42--Image sleeve

Claims (1)

[Claims] 1. Equipped with a photoreceptor drum on which an electrostatic latent image is formed, and a developing device that develops the electrostatic latent image using toner,
The developing device includes a developing device main body that accommodates a developer containing toner, and a cylindrical developing sleeve rotatably disposed within the developing device main body for electrostatically adhering the toner to the electrostatic latent image. In an image forming apparatus including a magnet having a plurality of magnetic poles for holding developer on the surface of the developing sleeve, the magnet is fixed to the developing device main body, and the developing device main body is fixed to the developing device main body. , the image forming apparatus is arranged to be movable linearly in a direction intersecting a straight line connecting the axes of the photosensitive drum and the developing sleeve, and further includes a moving means for moving the developing device main body. Forming device.