JPH0455883A - image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] No. 1 The present invention generally relates to an image forming apparatus, and specifically:
One or both of the image carrying means and the transfer material conveying means is constituted by a belt-like endless moving body and an endless moving body holding mechanism that holds this endless moving body, and the belt-like endless moving body is forcibly moved by a pressure means. The present invention relates to an image forming apparatus in which a biasing force is applied to cause this endless moving body to reciprocate within a certain movement range.

2. Description of the Related Art As is well known, various types of image forming apparatuses have been developed that employ an electrophotographic method or an electrostatic recording method for an image forming process. Among these various types of image forming apparatuses, a photoreceptor drum is used as an image bearing means, and peripheral equipment such as a charger, an exposure means, a developer, a transfer material transport mechanism, etc. are installed around the photoreceptor drum. There is a set format. In recent years, in order to further improve the functions of photoreceptor drums, transfer material transport mechanisms, etc., endless belt members that carry photoreceptors have been adopted instead of photoreceptor drums, and transfer material transport mechanisms have been An image forming apparatus employing an endless belt member has also been developed. In this way, in image forming apparatuses that employ endless belt members for the photoreceptor and other transfer material conveyance mechanisms, it has become possible to improve the functions of the belt mechanism. It is essential to have some kind of means to suppress the occurrence of belt deviation and meandering during driving, which are unique defects.In other words, defects such as deviation and meandering during belt drive can be prevented by the belt drive mechanism, etc. , the mechanical accuracy of the belt itself,
This is caused by various forces applied from the outside, such as changes in the characteristics of the belt, vibrations of the conveyor belt caused when the transfer material enters the transfer material conveyor belt from the transfer material supply mechanism, and so on. It has been impossible to suppress the occurrence of belt deviation, meandering, etc. without providing such a belt.

Conventionally, the following method has been adopted as a means for correcting defects such as deviation or meandering of the belt. That is, (a) a method in which the diameter of the roller member that holds the endless belt member is set larger at the center than at both ends so that the roller member as a whole has a crown shape; (b) each method. A method of providing a guide groove on the roller member and providing a guide rib on the inner peripheral side of the endless belt member corresponding to the guide groove, (c) writing a registration mark on the belt member and checking the relative positional deviation of this mark. This is a method of correcting by applying optical feedback.

However, each of the above methods has drawbacks as described below. In other words, method (a) above is the most widely used correction method, but by making the roller member into a crown shape, the endless belt member is distorted and an internal stress difference is generated, thereby reducing the part of the belt. In order to suppress shifting, it is necessary to use a belt made of a material with sufficient elasticity. Furthermore, since the strain that occurs in the belt member is utilized to prevent so-called permanent deformation of the belt member due to creep distortion, for example, when using a rubber belt, it is necessary to use a rubber belt with low hardness and high elasticity as described above. It is necessary to use a material made of a similar material, and its wall thickness must also be set to satisfy mechanical strength. Therefore, it is not appropriate to apply the method (a) above to a photoreceptor belt, etc., since the image will be deformed due to distortion on the belt surface. Since the thickness of the belt must be increased, the transfer current must be set large, which is also not appropriate.

Next, in the method (b) above, the thrust force generated in the belt member is received by the end face of the guide rib to suppress the deviation of the belt member, so the accuracy of the guide rib provided on the belt member is This will determine the accuracy of the belt member movement speed control. However, it is technically very difficult to mount the guide ribs high on the inner circumferential side of the belt member with high precision, so the moving speed of the belt member cannot be controlled with high precision, and it is difficult for mass production. Not suitable.

Next, in the method (c) above, it takes time to perform feedback to adjust the optical system, so it is difficult to apply feedback every time image is formed, and furthermore, the belt may become permanently skewed. The problem of leading to belt failure remains unsolved with this method.

Therefore, an object of the present invention is to forcibly apply a biasing force to a belt-shaped endless moving body using a pressure means to cause the endless moving body to reciprocate within a certain movement range, and to permanently shift the endless moving body. It is an object of the present invention to provide an image forming apparatus which eliminates disadvantages such as destruction due to shifting, image distortion caused by using a material having sufficient elasticity, and increase in transfer current.

- The above-mentioned objects are achieved by the image forming apparatus according to the present invention. In summary, the present invention provides at least one image bearing means on which an image forming process from latent image formation to visible image formation is performed, and a transfer material for transporting a transfer material to which the visible image on the image bearing means is transferred. an endless moving body holding mechanism, wherein at least one of the image bearing means and the transfer material conveying means includes a belt-like endless moving body and a plurality of rotatable supports that hold the endless moving body. an image forming apparatus comprising: a pressurizing means for applying an adjustable tension to the belt-like endless moving body; and a mark provided on the belt-like endless moving body that moves across the moving direction of the belt-like endless moving body. a mark detecting means for detecting along the direction, and when one end of the belt-shaped endless moving body reaches one maximum offset position in a direction transverse to the moving direction, the pressurizing means A greater tension is applied to one side of the endless moving body than the opposite side, and when the opposite end of the belt-shaped endless moving body reaches the opposite maximum offset position, the pressing means A greater tension is applied to the opposite side of the endless moving body than the one side to forcibly reciprocate the belt-like endless moving body within a certain range of movement by the pressurizing means, and the marking The image forming apparatus is characterized in that the timing of image formation on each of the image bearing means is adjusted based on the amount of movement or the speed of movement of the belt-like endless moving body in a direction transverse to the movement direction. be.

According to a preferred aspect of the present invention, the positional shift of the image due to the deviation of the belt-like endless moving body is corrected by adjusting the position of the image relative to the image carrying means in accordance with a change in the pressure force or pressure balance on the belt-like endless moving body. This is corrected by adjusting the formation timing.

EMBODIMENT OF THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The image forming apparatus according to the present invention has a structure in which at least one of the image carrying means and the transfer material conveying means included in the apparatus includes a belt-like endless moving body and a holding mechanism that holds the endless moving body. , the image bearing means is one in which an image forming process from latent image formation to visible image formation is executed, and the transfer material conveying means is a transfer material to which the visible image on the image bearing means is transferred. It is used to transport. Since the functions of each of the above means are already well known, detailed explanation thereof will be omitted.

FIG. 1 is a schematic perspective view showing a first embodiment of an image forming apparatus according to the present invention. Although the structure includes a moving body holding mechanism, it goes without saying that only the image carrying means may have a similar structure, or both means may have a similar structure. Additionally, four image bearing means are provided for color image formation;
However, the present invention is not limited to this (the present invention can be applied to an image forming apparatus having an arbitrary number of image bearing means).

Since the image forming apparatus shown in FIG. 1 employs an electrophotographic image forming process, the four negatively charged photoreceptor drums 61 to 64 have a rotating polygon mirror 30 and reflecting mirrors 41 to 64.
A latent image of the image to be copied is formed through the image forming apparatus 52 and converted into a visible image by a developing device (not shown).
It is configured to be transferred onto a transfer material (not shown) conveyed by. The belt 1 has an endless moving body holding mechanism (
In this embodiment, the drive roller 4 constituting the belt holding mechanism)
, fixed roller 5, tension roller 6 and driven roller 7
and moves in the direction of the arrow shown in the figure.

Each of the rollers constituting the belt holding mechanism described above is rotatably supported, and the drive roller 4 and driven roller 7 are arranged in a corresponding relationship and both are fixed at a predetermined position. A drive motor 8 that rotates the drive roller 4 in the direction of arrow B in the figure is connected to the rotation shaft of the drive roller 4 . The tension roller 6 is disposed below the driven roller 7 in the figure, and is used to apply a predetermined tension to the belt 1 while correcting defects such as deviation and meandering of the belt 1. As shown in FIGS. 2 and 3, both ends of the rotating shaft of the tension roller 6 are supported by bearings 12a and 12b, respectively. These bearing bearings 12
a, 12b are connected to tension springs lla, llb, respectively, and tension springs lla, llb are connected to actuators 1.a, 12b, respectively. It is connected to Oa and 10b. The above tension roller 6, actuator 10
a, 10b, tension springs lla, 11b, bearings 12a, 12b, etc. constitute a pressure means for applying tension to the belt 1 in this embodiment.

In this embodiment, linear stepping motors are used as the actuators 10a and 10b, and the setting of the magnitude of the tension applied to the tension roller 6 is determined by the drive command signal (pulse signal) output to the linear stepping motor. This can be easily done by varying the number of pulses. Further, a suitable mark 2 such as a registration mark is provided on the belt 1, and this mark 2 is a mark that detects the mark on the belt along a direction transverse to the moving direction of the belt 1. It is detected by the detection means 130. In this embodiment, the sign detection means 130 includes an illumination means 13 that illuminates the belt along a direction transverse to the moving direction of the belt 1, and a CCD that senses reflected light from the sign 2 and converts it into an electrical signal.
(charge coupled device) 14. Of course, any label detection means can be used.

FIG. 3 is a plan view for explaining the principle of operation of applying tension to the belt 1 by the pressure means and correcting deviation, meandering, etc. of the belt 1. For example, as shown in the figure, the belt 1 is If it is off to the side (right side),
Activate the actuator 10a on the side to rotate its operating shaft 10.
Move a° in the direction of the arrow Y, and move the belt 1 from the A side to the B side (
Left side) Apply stronger tension. As a result, the belt 1 moves in the direction of the weaker tension, that is, in the direction of the arrow X (this direction is referred to as the child direction).

Further, when the belt 1 is biased toward the B side (left side) in the figure, the actuator 10b on the B side is operated to apply a stronger tension to the B side of the belt 1 than to the A side. As a result, the belt 1 moves to the A side where the tension is weaker (this direction is defined as one direction).

The present invention utilizes the above principle, and in this embodiment, a biasing force is forcibly applied to the belt 1 by the pressure means having the above structure, and the belt 1 is reciprocated within a certain range of movement.
This is to ensure reliable driving. That is, in the above configuration, when one end of the belt l reaches the maximum offset position in the child direction as shown in FIG. A greater tension is applied to the A side to forcibly move the belt 1 in one direction. Further, as shown in FIG. 4(B), when the opposite end of the belt 1 reaches the maximum offset position in one direction, the actuator 10a on the A side is actuated so that the A side of the belt 1 becomes larger than the B side. Apply tension to forcibly move the belt 1 in the child direction. If the belt position is constantly forced to reciprocate in a zigzag manner at a predetermined shift speed in this way, the belt 1 can always be driven within a certain range.
Accidents such as belt damage can be prevented.

The forcible reciprocating movement of the belt position can be carried out by storing in advance in the memory 21 the maximum deviation position information in the child direction and the maximum deviation position information in one direction of the belt movement range, as shown in FIG. 5, for example. , the moving direction of the belt position is detected by the CCD 14. As shown in FIG. 6, this CCD 14 has a large number of light-receiving elements a to k (actually, an even larger number of light-receiving elements are arranged) arranged in the direction across the belt 1. ) and (B), the elements a to k that receive the light reflected from the sign 2 on the belt 1 change depending on the movement of the belt position, so which light-receiving element generates the output? By detecting whether the belt is moving, the belt position can be accurately detected, and the direction of movement of the belt position can also be detected. When the belt position is moving in the child direction, the maximum deviation position information in the child direction is read out from the memory 21 to the comparator circuit 20 and compared with the position information of the marker 2 on the belt 1 detected by the CCD 14. , the comparison result is O
The A-side actuator 10a is held in the operating state through the driver 23 until the

As shown in FIG. 4(A), when one end of the belt reaches the maximum offset position in the child direction, the comparison result of the comparison calculation circuit 20 becomes 0, so the driver 23 moves the actuator 10a.
is deenergized to activate the actuator 10b on the B side, and at the same time, the maximum deviation position information in one direction is read out from the memory 21 to the comparison calculation circuit 20, and as described above, the information on the maximum deviation position in one direction is read out from the memory 21, and the information on the mark 2 on the belt detected by the CCD 14 is read out from the memory 21. It is compared with location information.

In this state, when the opposite end of the belt reaches the maximum offset position in one direction as shown in FIG. actuator], Oa is actuated, and the above-mentioned operation is repeated. Thus, the belt 1 reciprocates in a zigzag manner between the maximum offset position in the child direction and the maximum offset position in one direction within the belt movable range.

As described above, the deviation of the visible image transferred from each image bearing means (photosensitive drum in this embodiment) to the transfer material (approximately perpendicular to the conveyance direction of the belt 1) caused by the forced zigzag movement of the belt position As disclosed in, for example, Japanese Patent Application Laid-Open No. 62-692, O3, the displacement of each color in the direction is determined by the amount of deviation of the belt 1 read by the CCD 14 and the time required for the belt I to make one revolution. The deviation speed of the belt 1 is determined by the following, and the correction can be made by adjusting the image forming timing for each image carrying means based on the result. The above adjustment operation can be executed, for example, according to the flowchart shown in FIG.

In the above-mentioned embodiment, the shift speed of the belt 1 is kept constant and the image forming timing of each photoreceptor drum is corrected, but as shown in FIG.
CCD 14A to 1 dedicated to each photoreceptor drum near 64
4D may be provided, and these CCDs may be used to measure individual belt deviation amounts in each portion, and the measurement results may be individually fed back to the image forming timing of the corresponding photoreceptor drum. Note that the other configurations are the first
Since it is the same as the image forming apparatus shown in the figure, corresponding parts are given the same reference numerals and their explanation will be omitted.

With this configuration, even if the slippage speed of the belt 1 is not constant for some reason, it is possible to accurately correct the transfer image deviation, so that more precise transfer image deviation correction can be performed.

In the above embodiments, a case has been described in which the present invention is applied to an electrophotographic image forming apparatus, but the present invention can also be applied to an electrostatic recording type image forming apparatus. Further, in the image forming apparatus of the above embodiment, only the transfer material conveying means is configured to have an endless moving body holding mechanism and a belt-like endless moving body, but it is also possible to use a similar configuration for only the image carrying means, or Both the carrying means and the transfer material conveying means may be configured to have an endless moving body holding mechanism and a belt-like endless moving body. Further, the intermediate transfer belt may have a similar structure. Furthermore, the present invention is not limited to color image forming apparatuses. It goes without saying that the arrangement position of the tension roller, the means for applying tension to the tension roller, etc. can be variously changed as necessary.

As described above, according to the present invention, at least one of the image carrying means and the transfer material conveying means is constituted by a belt-like endless moving body and an endless moving body holding mechanism that holds this endless moving body. In this image forming apparatus, the endless moving body is configured to reciprocate within a certain movement range by forcibly applying a biasing force to the belt-like endless moving body, so that the endless moving body is permanently biased. The conventional disadvantage of being left untouched and being damaged does not occur. In addition, since it is not necessary to use an endless moving body made of a material with sufficient elasticity, its wall thickness can be the same as before, so there is no problem that the image will be deformed when applied to an endless moving body of an image carrier. First, even when applied to an endless moving body of a transfer material conveying means, there are many remarkable effects such as there is no restriction that the transfer current must be set large.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is a schematic perspective view showing the detailed configuration of a belt and a belt holding mechanism, which is the gist of the present invention and is employed in the image forming apparatus of FIG. 1. FIG. 3 is a schematic plan view for explaining the operating principle of applying tension to the belt by a pressure means to correct deviation, meandering, etc. of the belt. FIGS. 4A and 4B are schematic plan views illustrating a state in which the belt is shifted in the image forming apparatus shown in FIG. 1. FIGS. FIG. 5 is a block diagram showing an example of a control circuit that can be used in the image forming apparatus shown in FIG. FIGS. 6(A) and 6(B) are schematic diagrams for explaining the relationship between the light receiving element of the CCD and the mark on the belt. FIG. 7 is a schematic perspective view showing a second embodiment of the image forming apparatus according to the present invention. FIG. 8 is a flowchart illustrating an example of a process for correcting misalignment of transferred images caused by belt misalignment. 1: Belt 2: Sign 4: Drive roller 6: Tension roller 10a, 10b = Actuator 11, a, 11b: Tension spring 12a, 12b = Bearing bearing 1.4: CCD (charge coupled device) 20: Comparison Arithmetic circuit 21: Mesori 130: Sign detection means Fig. 3 1 Otsu Fig. 5

Claims (1)

[Scope of Claims] 1) At least one image bearing means on which an image forming process from latent image formation to visible image formation is performed, and a transfer material that conveys the transfer material to which the visible image on the image bearing means is transferred. an endless moving body holding mechanism, wherein at least one of the image bearing means and the transfer material conveying means includes a belt-like endless moving body and a plurality of rotatable supports that hold the endless moving body. an image forming apparatus comprising: a pressure means that applies adjustable tension to the belt-like endless moving body; and a pressurizing means that applies an adjustable tension to the belt-like endless moving body; a mark detecting means for detecting along the direction, and when one end of the belt-shaped endless moving body reaches one maximum offset position in a direction transverse to the moving direction, the pressurizing means A greater tension is applied to one side of the endless moving body than the opposite side, and when the opposite end of the belt-shaped endless moving body reaches the opposite maximum offset position, the pressing means A greater tension is applied to the opposite side of the endless moving body than the one side to forcibly reciprocate the belt-like endless moving body within a certain range of movement by the pressurizing means, and the marking The image forming apparatus is characterized in that the timing of image formation on each of the image bearing means is adjusted based on the amount of movement or the speed of movement of the belt-like endless moving body in a direction transverse to the movement direction.