JPH03288167A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the breakage of a belt member by constituting either of an image carrying means and a transfer material carrying means of an endless belt member and a belt holding mechanism and forcibly giving biasing force to the belt member so that the belt member may be driven within a fixed position. CONSTITUTION:This device is provided with plural rotatable belt holding mechanisms 4-7 disposed a specified distance apart and the endless belt member 1 movably held by the mechanisms 4-7. A mark 2 is put on the belt member 1 and a mark detection means 130 is provided along a direction intersecting the moving direction of the member 1. Based on an output signal from the means 130, the relative positions of the mechanisms 4-7 are forcibly variably adjusted, and image forming timing for the respective image carriers 61-64 is adjusted based on the moving quantity or the moving speed of the mark 2 in the direction intersecting the moving direction of the belt member 1. Namely, the biasing force is forcibly given to the belt member 1, which is driven within the fixed moving range. Thus, the breakage of the belt member 1 is prevented.

Description

[Detailed Description of the Invention] Product No. 1 The present invention generally relates to an image forming apparatus, and specifically relates to:
In an image forming apparatus in which one or both of the image carrying means and the transfer material conveying means is constituted by a belt holding mechanism and an endless belt member, a biasing force is forcibly applied to the endless belt member. The present invention relates to an image forming apparatus that can reliably drive an image within a certain movement range.

As is well known, various types of image forming apparatuses have been developed that employ electrophotography or electrostatic recording in the 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 in place of photoreceptor drums, and improvements have also been made to transfer material transport mechanisms. Image forming apparatuses that employ endless belt members have been developed. In this way, image forming apparatuses that use endless belt members for the photoreceptor and other transfer material conveyance mechanisms have been able to improve many functions, but on the other hand, there are some problems unique to belt mechanisms. It is essential to have some means for suppressing the occurrence of belt deviation, meandering, etc. during driving, which are drawbacks. In other words, defects such as deviation and meandering when driving the belt are caused by problems such as the belt drive mechanism, the mechanical accuracy of the belt itself, changes in belt characteristics, and the fact that the transfer material rushes from the transfer material supply mechanism into the transfer material conveyance belt. It is impossible to suppress the belt from shifting or meandering without taking some measures, as it is caused by various forces applied from the outside, such as the vibrations of the conveyor belt. Met.

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 to be larger at the center than at both ends so that the roller member as a whole has a crown shape; ) A method of providing a guide groove on each roller member and providing a guide rib on the inner peripheral side of the endless belt member corresponding to the groove; (c) A method of writing a registration mark on the belt member and determining the relative positional deviation of this mark. (iv) A method in which a registration mark is written on the belt member and the relative position of the belt holding member is varied based on the relative positional deviation of this mark.

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 it is designed to prevent so-called permanent deformation of the belt member due to creep distortion while utilizing the distortion that occurs in the belt member, for example, when using a rubber belt, the rubber belt has low elasticity and low hardness 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 thicker, 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 belt destruction cannot be solved by this method.

Finally, the method (d) above is intended to have the belt move almost straight in the vicinity of the target position, as shown by the two-dot chain line in Fig. 8, but in reality, the belt does not move in a straight line due to changes in the relative position of the belt. It has been difficult to rotate the belt within a satisfactory range due to problems such as a delay in the response of the shift and the inability to follow the direction and degree of shift to minute changes in the relative position of the belt.

Therefore, it is an object of the present invention to forcibly apply a biasing force to an endless belt member to reliably drive this belt member within a certain range of movement, and to prevent permanent biasing of the belt member. It is an object of the present invention to provide an image forming apparatus that eliminates the drawbacks of the prior art, such as damage to the belt member, image distortion caused by using a material with sufficient elasticity, and increased transfer current.

The above objects are achieved by an 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. In an image forming apparatus including a conveyance means, at least one of the image bearing means and the transfer material conveyance means is moved by a plurality of rotatable belt holding mechanisms arranged at a predetermined distance and the belt holding mechanisms. an endless belt member capable of being retained;
A mark is provided on the endless belt member, and a mark detection means for detecting the mark along a direction transverse to the direction of movement of the endless belt member is provided, and the belt is held based on an output signal from the mark detection means. The relative positions of the mechanisms are forcibly and variably adjusted, and the timing of image formation on each of the image bearing means is determined based on the amount or speed of movement of the mark in a direction transverse to the direction of movement of the endless belt member. This is an image forming apparatus characterized by adjusting the following.

According to a preferred embodiment of the present invention, the positional deviation of the transferred image due to the deviation of the belt member is detected by the electric signal representing the amount of deviation of the belt member detected by the mark detection means, and when the belt member makes one revolution. The deviation speed of the belt member is determined based on the required time, and correction is made by adjusting the image forming timing for the image bearing means.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

In the image forming apparatus according to the present invention, at least one of the image carrying means and the transfer material conveying means included in the apparatus has a belt holding mechanism and an endless belt member, and the image carrying means includes: An image forming process from latent image formation to visible image formation is executed in the means, and the transfer material transport means transports the transfer material onto which the visible image on the image bearing means is transferred. 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. In the image forming apparatus of this embodiment, only the transfer material conveying means has a belt holding mechanism and an endless belt member. However, it goes without saying that only the image carrying means may have the same structure, or both means may have the same structure. Further, although four image bearing means are provided for color image formation, the invention is not limited to this, and 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), and then transferred to the transfer material (see FIG. (not shown). The belt 1 is wound around a driving roller 4, a tension roller 5, a correction roller 6, and a driven roller 7, which constitute a belt holding mechanism, and moves in the direction of the arrow in the figure.

Next, the image forming apparatus according to the present invention shown in FIG. 1 will be described with reference to FIG. 2 showing the detailed configuration of a belt and a belt holding mechanism, which is one of the main points of the present invention.

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 correction roller 6 corrects defects such as deviation and meandering occurring in the belt 1. One end of the rotation shaft of the correction roller 6 is supported by a pivot bearing 12, and the other end is supported by a bearing 9. There is. The bearing 9 is connected to a rod 11 coaxially connected to the operating shaft of an actuator 10, which is a variable adjustment means, and the operating shaft of the actuator 10 reciprocates along the belt 1 as indicated by X in FIG. When the bearing 9 is moved, the bearing 9 is configured to move along a slight arc along the correction roller 6 via the rod 11 as shown by AA' in FIG. That is, the correction roller 6
Since the pivot bearing 12 is fixed, the actuator 10 moves around the pivot bearing 12.
As a result of the operation, the other end side (that is, the bearing 9 side) is moved in an arc in the direction of the operating axis of the bearing 10 (direction along the belt 1) as shown by arrow A-A' in FIG. This allows the center axis of rotation of the correction roller 6 to form an arbitrary angle with the original position of the correction roller 6 in the direction along the belt 1. In this embodiment, a linear stepping motor is used as the actuator 10, and the movement amount of the rotation center axis of the correction roller 6 is set by the number of pulses of a drive command signal (pulse signal) output to this linear stepping motor. This can be easily done by varying the .

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 is a CCD (CCD) that senses the reflected light from the illumination means 13 that illuminates the belt along the direction transverse to the moving direction of the belt 1 and the sign 2 and converts it into an electrical signal. It is composed of a charge coupled device) 14. Of course, any label detection means can be used.

In the above configuration, when the actuator 10 is actuated to move the rotation center axis of the correction roller 6 from the original position C shown by the dotted line to the position C' shown by the solid line in the moving direction of the belt 1, for example, as shown in FIG. (This direction of movement is assumed to be the → direction). Since the correction roller 6 is at its original position, a twisting angle is created between it and the other rollers, so the winding position of the belt 1 is as shown in Fig. 3. As the belt 1 shifts from the position shown by the broken line to the position shown by the solid line in FIG. Conversely, if the center axis of rotation of the correction roller 6 is moved from the original position C shown by the dotted line in the direction opposite to the moving direction of the belt 1 (this movement direction is considered to be one direction), the correction roller 6 will also return to the original position. Since a twisting angle occurs between the belt 1 and the other rollers, the winding position of the belt 1 shifts from the position indicated by the broken line in Figure 3 to the outside (to the right) in the figure, and the belt 1 is biased in the opposite direction. Therefore, between the maximum deviation position in ten directions and the maximum deviation position in one direction in the belt movement range, the belt 1
If the position of is forced to move all the time, that is,
When one end of the belt 1 reaches the maximum deviation position in the ten directions, it is moved in one direction, and when the opposite end of the belt 1 reaches the maximum deviation position in one direction, it is moved in the ten directions, and so on. If the belt position is forcibly moved in a zigzag manner at a predetermined shifting speed, the belt l can always be driven within a certain range, as shown by the solid line in Figure 8, and accidents such as belt breakage can be avoided. This can be prevented.

For example, the forcible zigzag movement of the belt position may be
As shown in the figure, the maximum deviation position information in ten directions and the maximum deviation position information in one direction of the belt movement range are stored in advance in the memory 21, and the actuator 10 is operated to control the rotation center axis of the correction roller 6. move slowly at a predetermined speed. When the rotation center axis of the correction roller 6 moves in ten directions, the maximum offset position information in the ten directions is read out from the memory 21 to the comparison calculation circuit 20, and the position information of the marker 2 on the belt 1 detected by the CCD 14 is read out. The comparison result is O
The actuator 10 is driven in ten directions through the driver 23 until the As shown in FIG. 5-A, when one end of the belt reaches the maximum offset position in the ten directions, the comparison result of the comparison calculation circuit 20 becomes O, so the driver 23 moves the actuator 10 in the opposite direction (one direction). At the same time, the maximum offset position information in one direction is read from the memory 21 to the comparison calculation circuit 20, and is compared with the position information of the mark 2 on the belt detected by the CCD 14 as described above. In this state, when the opposite end of the belt reaches the maximum offset position in one direction as shown in FIG. The action will be repeated. (then,
The belt 1 moves in a zigzag manner between the maximum offset position in ten directions and the maximum offset position in one direction within the belt movable range, as shown by the solid line in FIG.

In FIG. 8, Δt indicates the time required to make one copy, and from this it can be understood that the shifting speed of the belt 1 is quite low.

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. 62-69203, the positional deviation 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 1 to make one revolution. The correction can be made by determining the deviation speed of the image forming apparatus and 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 has a belt holding mechanism and an endless belt member, but it is also possible to have only the image carrying means have the same structure, or Both the means and the transfer material conveying means may have a belt holding mechanism and an endless belt member. Furthermore, the present invention is not limited to color image forming apparatuses.

Furthermore, it goes without saying that the arrangement position of the correction roller, the means for moving the center axis of rotation of the correction roller, the direction of movement, etc. can be variously changed as necessary.

As mentioned above, according to the present invention, in an image forming apparatus in which at least one of the image carrying means and the transfer material conveying means is constituted by an endless belt member and a belt holding mechanism, the belt member Since the belt member is driven within a predetermined position by forcibly applying a biasing force to the belt member, the problem that the belt member remains permanently biased and the belt member is damaged does not occur. In addition, since there is no need to use a belt made of a material with sufficient elasticity, its wall thickness can be the same as before, and therefore there is no drawback that the image will be deformed when applied to a photoreceptor belt (or transfer material When applied to a conveyor belt, there are many remarkable effects such as no restriction on setting a large transfer current.

[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 perspective view illustrating how the belt shifts due to the action of the correction roller shown in FIG. 2. FIG. FIG. 4 is a block diagram showing an example of a control circuit that can be used in the image forming apparatus shown in FIG. 5-A and 5-B are schematic plan views illustrating a state in which the belt is deviated in the image forming apparatus of FIG. 1. FIG. FIG. 6 is a flowchart illustrating an example of a process for correcting misalignment of transferred images caused by belt misalignment. 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 diagram for explaining the difference in the belt skew state between the conventional image forming apparatus and the image forming apparatus according to the present invention. 0 4 0 1 0: Belt: Sign: Drive roller: Correction roller: Actuator: CCD (charge coupled device): Comparison calculation circuit: Memory: Sign detection means Section 4, Figure 6

Claims (1)

[Claims] 1) An image comprising 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 conveying means for conveying a transfer material to which the visible image on the image bearing means is transferred. In the forming apparatus, at least one of the image carrying means and the transfer material conveying means is movably held by a plurality of rotatable belt holding mechanisms arranged at a predetermined distance apart and the belt holding mechanisms. It has an endless belt member, a label is provided on the endless belt member, and a label detecting means for detecting the label along a direction transverse to the moving direction of the endless belt member, and The relative position of the belt holding mechanism is forcibly variably adjusted based on the output signal, and each of the above-mentioned An image forming apparatus characterized in that the timing of forming an image on an image bearing means is adjusted.