JP2001253578A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device having high workability for users, and capable of forming images on a sheet with excellent image quality while preventing the weight of a frame from increasing. SOLUTION: A charging roller 22 serving as a charging means, a developing portion 23, and a cleaner blade 24 for photoreceptor are arranged respectively around a photoreceptor 21 along its rotational direction. A laser L is irradiated from an exposure portion 3 toward the outer periphery of the photoreceptor 21 to form an electrostatic latent image, and the image is developed by the developing portion 23 and primarily transferred onto an intermediate transfer belt 41. This process is carried out for each toner color, which is superimposed on the intermediate transfer belt 41 to form an color image, and the color image is transferred onto a sheet S in a secondary transfer area (transfer position) R2. A paper feeding cassette 6 for storing the sheet S is disposed above the image forming and transferring means which is formed as described above.

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 for taking out a sheet stored in a sheet cassette from the sheet cassette and transferring an image to the sheet at a predetermined transfer position.

[0002]

2. Description of the Related Art In an image forming apparatus of this type, as described in, for example, Japanese Patent Application Laid-Open No. 11-35209, a sheet cassette for storing sheets is arranged at the lowermost portion of the apparatus body, An image forming / transfer unit that forms an image at a position above the paper cassette and transfers the image to a sheet is disposed. In parallel with the formation of a color image on the intermediate transfer belt by the image forming / transferring means, the paper is taken out one by one from the paper feed cassette by the transporting means, transported to the gate roller and made to stand by. Thereafter, the standby paper is fed from the gate roller to the transfer position at an appropriate timing to transfer the color image formed on the intermediate transfer belt, and the transferred image is fixed by a fixing unit.

[0003]

When the paper feed cassette is arranged at the lowermost position as described above, the following problems occur. The first problem is that when replenishing paper in the paper cassette or replacing the paper cassette, the user must take a crouching posture. There is a problem of applying.

Further, in order to arrange the paper feed cassette in the apparatus main body, it is necessary to provide a paper feed cassette storage space. As a result, there is a problem that a relatively large space is formed at the lowermost portion of the main body frame of the apparatus, and a decrease in frame strength cannot be avoided. Further, since the image forming / transferring unit having a weight greater than that of the paper feed cassette is disposed above the paper feed cassette, the position of the center of gravity of the entire image forming apparatus is increased, and an excessive stress moment is easily applied. Combined with the decrease in strength, frame distortion is likely to occur, leading to a decrease in image quality.

Here, in order to prevent the image quality from deteriorating, for example, it is conceivable to reinforce the frame. However, another problem arises in that the weight of the entire apparatus increases due to the reinforcement of the frame.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is excellent in user's workability and can form an image on paper with excellent image quality while preventing an increase in frame weight. It is intended to provide a device.

[0007]

In order to achieve the above object, the present invention provides a main body frame, a paper cassette mounted on the main body frame while accommodating a plurality of sheets, and a paper cassette. A paper transporting means for removing the paper from the paper cassette and transporting the paper to a preset transfer position below the paper feed cassette; and supporting the main body frame at a position below the paper feed cassette to form an image. An image forming / transferring unit for transferring the image to a sheet conveyed to the transfer position by a conveying unit.

In the image forming apparatus configured as described above,
A paper feed cassette is disposed above the image forming / transferring means, so that, for example, paper supply to the paper feed cassette or replacement of the paper feed cassette can be performed at a higher position than in the conventional example. In addition, since the paper cassette is mounted on the main body frame in such an arrangement relationship, a storage space necessary for mounting the paper cassette is provided at a position above the main body frame. As described above, the frame strength is higher than when the storage space is provided at the lowermost portion of the main body frame. Further, the image forming / transferring unit having a weight greater than that of the sheet cassette is disposed at a lower position than the conventional example, thereby lowering the center of gravity of the entire apparatus, and the frame distortion due to the synergistic effect with the improvement of the frame strength described above. Is suppressed, and the image quality is improved.

Here, regarding the transfer position, the image forming /
Although it can be set at an arbitrary position in the transfer unit, especially when the transfer position is set to a position close to the paper feed cassette, the transport distance of the paper can be shortened, and the configuration of the transport unit is simplified, The occurrence of paper jam is effectively suppressed.

Further, in addition to setting the transfer position close to the paper feed cassette as described above, a fixing unit may be disposed near the downstream side of the transfer position in the sheet transport path. Is arranged at a position immediately below the sheet cassette, and the following operation is obtained. The paper may remain stored in the paper cassette for a long period of time. Here, if the paper feed cassette is arranged at the bottom of the apparatus as in the conventional example, the moisture content of the paper fluctuates due to environmental changes around the apparatus, especially humidity changes, and as a result, fusing performance fluctuates. May not be able to obtain good image quality. On the other hand, when the fixing unit is disposed immediately below the sheet cassette as described above, heat generated by the fixing unit is guided to the sheet cassette, and the paper in the sheet cassette is maintained at a stable humidity. As a result, the fixing performance is stabilized.

As described above, the fixing means is a heat generating portion.
An exposure unit and a development unit constituting the image forming / transfer unit may be arranged below the fixing unit in the height direction, and the exposure unit and the like are affected by heat generated by the fixing unit. And stable image quality can be obtained.

[0012]

FIG. 1 is a diagram showing one embodiment of an image forming apparatus according to the present invention. This image forming apparatus forms a full-color image by superimposing four color toners of yellow (Y), cyan (C), magenta (M), and black (K). When an image formation command (a signal indicating print content) is given to the control unit, each part of the engine unit is controlled in accordance with the command from the control unit to form an image on a sheet S such as a transfer sheet, a copy sheet, or an OHP sheet. An image corresponding to the command is formed.

In this image forming apparatus, the upper surface of the device case 1 functions as a standard paper discharge tray 11, and the paper S on which an image has been formed is discharged through a discharge port 12 opened on the upper surface side of the case 1. The sheets are ejected one by one to the standard ejection tray 11.

A main body frame for supporting or holding each part of the apparatus is provided inside the apparatus case 1. A photoreceptor 21 and a developing unit 23 constituting an image forming / transfer unit are attached to the main body frame as described later, and a paper feed cassette 6 is mounted above the image forming / transfer unit. . In addition, since the schematic configuration of the main body frame is clarified by showing the arrangement relation of these parts, the illustration of the main body frame in the figure is omitted.

The image forming / transfer means forms an image corresponding to an image forming command (a signal indicating the content of printing) on the intermediate transfer belt 41 and transfers the image to paper. In this image forming / transferring means, the image carrier unit 2
The toner image can be formed on the photosensitive member 21 of FIG. That is, the image carrier unit 2 includes a photoconductor 21 rotatable in the direction of the arrow in FIG. 1, and further includes a charging roller 22 as a charging unit, a developing unit around the photoconductor 21 along the rotation direction. Developing devices 23Y, 23C, 23
M, 23K, and a photoreceptor cleaner blade 24 are arranged, respectively.

In this apparatus, the charging roller 22 is connected to the photosensitive member 2
After the outer peripheral surface of the photosensitive member 21 is uniformly charged by contacting the outer peripheral surface of the photoconductor 1, a laser beam (light beam) L is irradiated from the exposure unit 3 toward the outer peripheral surface of the photoconductor 21. As shown in FIG. 1, the exposure section 3 includes a light emitting element 31 such as a semiconductor laser which is modulated and driven in accordance with an image signal, and a laser beam L from the light emitting element 31 is rotated by a high speed motor 32. Incident on a polygon mirror 33 to be formed. The laser light L reflected by the polygon mirror 33 is transmitted to the lens 34 and the mirror 3
5, the photosensitive drum 21 is scanned in the main scanning direction (a direction perpendicular to the plane of the drawing) to form an electrostatic latent image corresponding to an image signal. Reference numeral 36 denotes a horizontal synchronization reading sensor for obtaining a synchronization signal in the main scanning direction, that is, a horizontal synchronization signal HSYNC.

The electrostatic latent image thus formed is developed
Is developed with toner. That is, in this embodiment, as the developing unit 23, a developing unit 23Y for yellow, a developing unit 23C for cyan, a developing unit 23M for magenta, and a developing unit 23K for black are arranged along the photoconductor 21 in this order. Have been. These developing units 23Y and 23
Each of C, 23M, and 23K is configured to be able to freely contact and separate from the photoconductor 21, and the four developing units 23Y, 23M, 23C, and 23 according to instructions from the control unit.
B selectively contacts the photoconductor 21 and applies a high voltage to apply a toner of a selected color to the surface of the photoconductor 21 to apply electrostatic latent on the photoconductor 21. Reveals an image.

The toner image developed by the developing unit 23 is primarily transferred onto the intermediate transfer belt 41 of the transfer unit 4 in a primary transfer region R1 located between the black developing device 23K and the photosensitive member cleaner blade 24. Transcribed. Further, a photosensitive member cleaner blade 24 is disposed at a position advanced in the circumferential direction (the direction of the arrow in FIG. 1) from the primary transfer region R1.
After the primary transfer, the toner remaining on the outer peripheral surface of the photoconductor 21 is scraped off.

Next, the configuration of the transfer unit 4 will be described. In this embodiment, the transfer unit 4 includes a roller 4
2 to 47; an intermediate transfer belt 41 stretched over the rollers 42 to 47; a secondary transfer roller 48 for secondarily transferring the intermediate toner image transferred to the intermediate transfer belt 41 to the sheet S; Photoconductor 2 using two DC motors as drive sources
1 and a photoreceptor / belt drive unit (not shown) for rotatingly driving the intermediate transfer belt 41 in synchronization with the photoreceptor / belt drive unit. When the color image is to be transferred to the sheet S, the photosensitive member 2
The toner image of each color formed on the intermediate transfer belt 41
A color image is formed by being superimposed on the sheet, and the sheet S stored in the sheet cassette 6 is taken out by the conveying mechanism 7 and conveyed along the conveying path 71 to the secondary transfer area R2.
Further, a full-color image is obtained by secondary-transferring a color image onto the sheet S. Thus, in this embodiment, the secondary transfer region R2 corresponds to the “transfer position” of the present invention.

After the secondary transfer, the toner remaining on the outer peripheral surface of the intermediate transfer belt 41 is removed by a cleaner blade 491 provided on the belt cleaner 49. That is, the belt cleaner 49
Is disposed opposite to the roller 46 with the intermediate transfer belt 41 interposed therebetween. At an appropriate timing, the cleaner blade 491 comes into contact with the intermediate transfer belt 41 to scrape toner remaining on the outer peripheral surface thereof. Drop.

A sensor 40 for detecting a reference position of the intermediate transfer belt 41 is disposed near the roller 43, and a synchronization signal in a sub-scanning direction substantially orthogonal to the main scanning direction, that is, a vertical synchronization signal is provided. It functions as a vertical synchronization reading sensor for obtaining VSYNC.

The paper S on which the toner image has been transferred by the transfer unit 4 as described above is transported by the transport mechanism 7 along the transport path 71 to the fixing unit 5 disposed downstream of the secondary transfer area R2. Paper S
The upper toner image is fixed on the sheet S. Then, the paper S
Is further discharged to a standard paper discharge tray along the transport path 71.

As described above, according to this embodiment, since the paper feed cassette 6 is disposed above the image forming / transferring means, the following operational effects can be obtained. First, when replenishing paper to the paper cassette 6 or replacing the paper cassette 6, the user stands in a standing posture because the paper cassette 6 is arranged at a higher position than in the conventional example. Since the user can access the paper feed cassette 6, the physical load on the waist, knees, and the like can be reduced, and the workability of the user is improved. Further, it is also close to the standard paper output tray 11 from which the paper S on which the image has been formed is discharged,
Sheet replenishment and sheet removal frequently used by the user can be efficiently performed.

The storage space necessary for mounting the sheet cassette 6 is provided above the main body frame, and the frame strength is lower than when the storage space is provided at the bottom of the main body frame as in the conventional example. And the need for frame reinforcement is eliminated, making it possible to reduce the weight of the image forming apparatus.

Further, since the image forming / transferring means (weight unit) having a weight greater than that of the paper feed cassette 6 is arranged at a position lower than that of the conventional example, the center of gravity of the entire apparatus is lowered, and the above-mentioned frame strength is reduced. The image quality can be improved by suppressing the occurrence of frame distortion by a synergistic effect with the improvement of the image quality.

FIG. 2 is a diagram showing another embodiment of the image forming apparatus according to the present invention. This embodiment is significantly different from the previous embodiment in the following three points.

Difference (1): The transfer position (2
The next transfer area R2) is set near the inner bottom surface of the apparatus, whereas in the present embodiment, it is set near the sheet cassette 6. More specifically, as shown in FIG.
The sheet S taken out of the sheet cassette 6 is immediately looped in an inverted C-shape to be conveyed almost parallel to the lower surface of the sheet cassette 6, and the secondary transfer is performed in the middle of the parallel conveyance path 72. Have been. With such a configuration, the transport path 72 of the sheet S is significantly shortened as compared with the transport path 71 in the embodiment of FIG.

Difference (2): In this embodiment, the fixing unit 5 is disposed near the downstream side of the secondary transfer area (transfer position) R2 in the transport path 72, and the heat generated by the fixing unit 5 Is directly led to the paper feed cassette 6.

Difference (3): Further, in this embodiment,
As shown in FIG. 2, the photosensitive member 21, the developing unit 23, and the exposing unit 3 among the units constituting the image forming / transferring unit are arranged below the fixing unit 5 in the height direction (vertical direction in the drawing). ing.

Since the other configurations and operations are basically the same, they are denoted by the same reference numerals and description thereof is omitted.

An embodiment configured as described above (FIG. 2)
According to the third embodiment, in addition to the same operation and effect as obtained in the embodiment of FIG. 1, the operation and effect based on the above three differences are further provided. That is, the transfer path 72 is shortened by setting the transfer position (secondary transfer region R2) to a position close to the paper feed cassette 6, whereby the transfer mechanism 7 can be configured with fewer components (for example, rollers and guide plates). , The transport mechanism 7 can be simplified, and the occurrence of paper jam can be effectively suppressed.

Further, the fixing unit 5 is located near the downstream side of the transfer position (secondary transfer region R2) on the transport path 72 of the sheet S.
Are arranged, the fixing unit 5 is
Will be located immediately below. Therefore, the heat generated in the fixing unit 5 is guided to the sheet cassette 6 and
The paper S in the paper feed cassette 6 can be maintained at a stable humidity. As a result, the fixing performance can be stabilized, and an image can be formed with better image quality.

Further, in the image forming apparatus configured as described above, it is possible to preheat the paper S in the paper feed cassette 6 before performing image formation. By performing the preliminary heating, it is possible to prevent a temperature drop in a fixing process portion during continuous printing, and to speed up image formation.

Further, although the fixing unit 5 is a heat-generating part, the developing unit 23 and the exposure unit 3 are arranged below the fixing unit 5 in the height direction (vertical direction in FIG. 2). 23 and the like are less susceptible to the influence of heat generated in the fixing unit 5 (for example, thermal deformation), so that more stable image quality can be obtained.

The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the gist of the present invention. For example, in the above two embodiments, the image forming and
The transfer position is set at the lowermost portion and the uppermost portion, respectively. However, the transfer position is not limited to this, and the transfer position can be set to any position of the image forming / transferring portion.

In the above embodiment, the sheet feeding cassette 6
Is related to an image forming apparatus in which only one stage is provided. However, in an apparatus having a plurality of stages of sheet feeding cassettes, these sheet feeding cassettes The same effect can be obtained by arranging it at the upper position.

Further, in the above embodiment, the toner image on the photosensitive member 21 is transferred to the intermediate transfer belt 41. However, transfer media other than the intermediate transfer drum (transfer belt, transfer sheet, intermediate transfer belt, intermediate transfer sheet) The present invention is also applicable to an image forming apparatus that transfers a toner image to a reflective recording sheet or a transparent storage sheet. The above embodiment relates to a printer that forms an image based on an image forming command (a signal indicating the content of printing) from an external device such as a host computer, but the image forming apparatus is an image forming apparatus such as a copying machine or a facsimile machine. Includes general equipment. Further, the present invention can be applied to a printer, a facsimile apparatus, and a copying machine that employ a so-called tandem method as an image forming method. Further, the present invention can be applied to an image forming apparatus that transfers a toner image on a photoconductor to a sheet without forming an intermediate toner image.

[0038]

As described above, according to the present invention, since the paper feed cassette is disposed above the image forming / transferring means, for example, paper supply to the paper feed cassette or exchange of the paper feed cassette is performed. Can be performed at a higher position than in the conventional example, and paper replenishment and the like can be performed with excellent workability without imposing a physical burden on the user. In addition, since the paper cassette is configured to be mounted on the main body frame in such an arrangement relationship, a storage space necessary for mounting the paper cassette is provided above the main body frame, The frame strength can be increased as compared with the case where a storage space is provided at the lowermost portion of the main body frame as in the conventional example, and frame reinforcement is not required. Further, the image forming / transferring unit having a weight greater than that of the sheet cassette is disposed at a lower position than the conventional example, thereby lowering the center of gravity of the entire apparatus, and the frame distortion due to the synergistic effect with the improvement of the frame strength described above. Can be suppressed and the image quality can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a diagram illustrating another embodiment of the image forming apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 3 ... Exposure part 5 ... Fixing unit 6 ... Paper feed cassette 7 ... Conveying mechanism 21 ... Photoconductor 23 ... Developing part 23Y, 23C, 23M, 23K ... Developing device 71, 72 ... Conveying path R2 ... Second transfer area (transfer position ) S… Paper

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C059 AA05 AA09 AA21 AA22 AA26 AB01 2H032 AA05 AA15 BA01 BA03 BA09 BA15 BA21 BA23 2H071 BA04 BA22 DA02 DA08 DA09 DA12 DA15 DA22 DA23 3F343 FA02 FA09 FB01 GA01 GB01 HB03 HC02

Claims (4)

[Claims] 1. A main body frame, a paper feed cassette mounted on the main body frame while accommodating a plurality of papers, and taking out papers from the paper feed cassettes and placing the papers below the paper feed cassettes Transport means for transporting to a preset transfer position; and an image formed on the body frame supported by the main body frame at a position below the sheet feeding cassette, and the image being transferred to the transfer position by the transport means. An image forming apparatus comprising: an image forming / transfer unit for transferring an image. 2. The image forming apparatus according to claim 1, wherein the transfer position is set at a position close to the sheet feeding cassette in the image forming / transferring unit. 3. A transfer path for a sheet conveyed by the conveying means, which is disposed near the downstream side of the transfer position, passes through the transfer position, and applies heat to the sheet conveyed downstream to form a transfer image. The image forming apparatus according to claim 2, further comprising a fixing unit that fixes the sheet. 4. The image forming / transferring means includes: a photosensitive member;
An exposure unit that forms an electrostatic latent image on the photoconductor, and a development unit that develops the electrostatic latent image, wherein the exposure unit and the development unit are located below the fixing unit in the height direction. The image forming apparatus according to claim 3, wherein the image forming apparatus is disposed.