JP2007164086A - Belt driving unit and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To bring about no difference in rotating speed between a first roller (driving roller) and a second roller (secondary transfer roller) as far as possible even when a belt driving unit is actuated. <P>SOLUTION: A belt driving controller 70 switches to use the output signal of a second sensor 6B (a sensor detecting the divisions of a scale of a rotary disk 81 fitted to the rotary shaft of the secondary transfer roller 22 driven by a secondary transfer motor 82) till the lapse of a sensor output switching predefined time after the belt driving motor 7 is actuated, and the output signal of a first sensor 6A (a sensor detecting the divisions of a scale of an intermediate transfer belt 10) after the lapse of the sensor switching predefined time to perform feedback control over the belt driving motor 7 respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a belt driving device for driving a belt, and an image forming apparatus such as a color printer or a color copying machine including the belt driving device.

  2. Description of the Related Art Conventionally, for example, a belt drive device that drives an intermediate transfer belt of an image forming apparatus has a seal-like scale seal formed with a large number of scales at intervals along the circumferential direction of the intermediate transfer belt. The scale seal of each scale seal is detected by one sensor (reflection photosensor) to obtain an output pulse, and the speed of the intermediate transfer belt is detected from the detection result, Based on the result, the belt drive motor for moving the intermediate transfer belt is feedback-controlled so that the intermediate transfer belt moves at an ideal speed (constant speed).

  However, when the seal-like scale seal as described above is applied over the entire circumference of the intermediate transfer belt, the seam between the front end and the rear end of the scale seal is inevitably a gap or overlap. Can do. And the detection pulse of the sensor which detected the joint location will have a pulse interval wide or narrow compared with the detection pulse in locations other than a joint.

  In this case, when feedback control is performed using the detection pulse, the control system determines that the belt speed has become slow in the part where the pulse interval is wide, although the belt speed has not slowed, Feedback control is performed so as to increase the belt speed suddenly. Also, in the part where the pulse interval is narrow, the control system judges that the belt speed has increased even though the belt speed has not increased, and performs feedback control so that the belt speed is suddenly decreased. It will end up. In particular, when the belt drive device is started (when the belt drive motor is started), there is a possibility that a problem that the belt drive motor does not start occurs.

Therefore, in the conventional belt driving device, as shown in Patent Document 1, for example, a home mark provided on an endless belt and a home sensor that detects the home mark prior to the timing at which the scale sensor reads the joint of the scale. When the detection output of the home sensor is received, the control by the first speed control device having the first scale sensor is invalidated, and the surface speed of the endless belt is controlled by the second speed control having the second scale sensor. There has also been proposed a system in which control for transferring to an apparatus is performed.
JP 2004-191845 A

In the above-described conventional example, if the joint location is detected when the belt drive motor is activated, the belt drive motor is not activated, so the sensor is switched. This is effective for the joint.
However, when the belt drive motor is activated (initially driven), that is, when the belt drive device is activated, a certain period of time is required until the drive (rotational speed) of the belt drive motor is stabilized. The drive roller (first roller) that moves the intermediate transfer belt and the secondary transfer roller (second roller) that contacts the outer peripheral surface of the intermediate transfer belt at a different position from the drive roller cause a difference in rotational speed. there were.

For example, FIG. 12 is a graph showing the locus until the driving of the belt driving motor is stabilized when the belt driving device is started.
Specifically, in FIG. 12, when the rotation speed of the secondary transfer roller is slower than that of the drive roller, the friction load of the intermediate transfer belt is correspondingly increased, and the load torque of the belt drive motor rotating the drive roller is Increased more than necessary, the motor itself is judged to be abnormal, and the belt drive is stopped. In addition, sagging of the intermediate transfer belt occurs between the driving roller and the secondary transfer roller. As a result, problems such as scratches on the intermediate transfer belt may occur, which may lead to image distortion. On the other hand, when the rotational speed of the secondary transfer roller is faster than that of the drive roller, the load torque of the belt drive motor that rotates the drive roller becomes smaller than necessary, and the motor itself is judged to be in an abnormal state. As a result, the belt drive is stopped or cannot be controlled.

  The present invention has been made in view of the above problems, and the first roller (driving roller) and the second roller do not cause the above-described problems even when the belt driving device is started. It is an object of the present invention to enable driving of a belt so that the rotational speed of the (secondary transfer roller) does not differ as much as possible (see FIG. 8).

In order to achieve the above object, the present invention provides a belt drive device and an image forming apparatus.
A belt driving device according to a first aspect of the present invention is a belt driving device for driving a belt, wherein the first driving means for supplying a driving force to a first roller that contacts the belt and moves the belt, and the first driving device. Secondary driving means for supplying driving force to the second roller that contacts the belt at a position different from one roller, rotational speed detecting means for detecting the rotational speed of the second roller, and provision to the primary driving means Belt driving control means for calculating driving force and instructing the driving force to the primary driving means to control driving of the belt is provided, and the belt driving control means is based on the detection value of the rotational speed detecting means. Driving force calculating means for calculating the driving force supplied to the primary driving means.

According to a second aspect of the present invention, there is provided a belt driving apparatus according to the first aspect, wherein the driving force calculating means sets the rotational speed at which the rising speeds of the first roller and the second roller coincide with each other to the primary driving means. It is calculated as the driving force to be provided to.
A belt driving device according to a third aspect of the present invention is the belt driving device according to the first or second aspect, wherein the rotational speed detecting means is a means for detecting the rotational speed of the second roller and outputting a corresponding pulse signal. A scale in which scales are formed at equal intervals along the circumferential direction of the belt, scale detection means for detecting scale marks and outputting corresponding pulse signals, pulse signals from the scale detection means or the rotation Sensor output switching means for switching the pulse signal from the speed detection means to be used for control by the belt drive control means, and the sensor output switching means from the start of the primary drive means to the completion of startup, The pulse signal from the rotation speed detection means is switched to be used for control by the belt drive control means.

According to a fourth aspect of the present invention, there is provided a belt driving device according to the third aspect, wherein the belt driving device according to the third aspect is provided with time measuring means for starting time measurement in response to activation of the belt driving device. The pulse signal from the rotation speed detecting means is used for the control by the belt drive control means when the time reaches the predetermined value until the time reaches a predetermined value. It is switched as follows.
A belt driving device according to a fifth aspect of the invention is the belt driving device according to the fourth aspect, wherein the predetermined value is a time required for the driving of the primary driving means and the second driving means to become stable. is there.

  A belt drive device according to a sixth aspect of the invention is a belt drive device for moving a belt at a constant speed, and a primary drive means for supplying a driving force to a first roller for moving the belt in contact with the belt; Secondary driving means for supplying a driving force to the second roller contacting the belt at a position different from the first roller, rotational speed detecting means for detecting the rotational speed of the secondary driving means, and the primary driving means; Belt driving control means for controlling the driving of the belt by instructing the driving force to be given to the primary driving means and controlling the driving of the belt, and detecting the rotational speed detecting means in the belt driving control means. Driving force calculation means for calculating the driving force to be supplied to the primary driving means based on the value is provided.

  According to a seventh aspect of the invention, in the belt driving device according to the sixth aspect, the driving force calculating means includes a reduction ratio between the second roller and the secondary driving means, and a detection value of the rotational speed detecting means. Based on the above, the rotational speed for matching the rotational speeds of the first roller and the second roller is calculated as the driving force to be provided to the primary driving means.

  An image forming apparatus according to an eighth aspect of the present invention is an image forming apparatus for forming an image by transferring an image on a transfer belt onto a recording medium, wherein the first roller moves the transfer belt in contact with the transfer belt Primary driving means for supplying a driving force to the roller, secondary driving means for supplying a driving force to the second roller contacting the outer peripheral surface of the transfer belt at a position different from the first roller, and an outer periphery of the second roller A third roller that is in contact with the inner peripheral surface of the transfer belt so as to face the surface, a rotational speed detecting unit that detects a rotational speed of the second roller, and a driving force applied to the primary driving unit. A recording medium is fed between the belt driving control means for instructing the driving force to the primary driving means to drive and control the transfer belt, the second roller and the third roller, and the transfer belt. Transfer the above image to the recording medium Provided a paper feed and discharge means for discharging the after, the belt drive control means, and calculates the driving force provided to the primary drive means based on the detected value of the rotational speed detecting means.

  According to the belt drive device of the present invention, the belt drive control means detects the rotation speed of the second roller (secondary transfer roller) that contacts the belt at a position different from the first roller (drive roller). Based on the detected value, the driving force to be supplied to the primary driving means for supplying the driving force to the first roller that contacts the belt and moves the belt is calculated, and the driving force is instructed to the primary driving means. Since the belt is driven and controlled, even when the belt driving device is activated, it is possible to minimize the difference in rotational speed between the first roller and the second roller. The image forming apparatus according to the present invention can reliably acquire a high-quality image by including the belt driving device.

Hereinafter, the best mode for carrying out the present invention will be specifically described with reference to the drawings.
FIG. 1 is a schematic view showing a belt driving device of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is an overall configuration diagram showing an example of the image forming device, and FIG. 3 is an intermediate view of the belt driving device of FIG. It is a top view which shows the scale provided on the transfer belt, and the 1st sensor which detects it.
The color copying machine shown as an example of the color image forming apparatus in FIG. 2 includes four drum-shaped photoreceptors 40Y, 40C, 40M, yellow (Y), cyan (C), magenta (M), and black (K). 40K (hereinafter simply referred to as photoconductor 40 if not specified), and each image provided on each photoconductor 40 is provided with a roller-like primary transfer device (primary transfer roller) 62. A tandem type image forming apparatus including an intermediate transfer belt 10 transferred at a next transfer position.

For example, as shown in FIG. 3, the belt driving device of this color copying machine has a scale 5 (a part of which is simplified in FIG. 1) composed of a large number of scales 5a in the circumferential direction of the surface (outer peripheral surface) of the intermediate transfer belt 10. For example, by sticking. A seam 11 (a gap in this example) is formed between the start end (front end) 11 a and the end end (rear end) 11 b of the scale 5. In addition, the scale 5 provided by sticking is also called a scale seal. The scale 5 may be directly formed on the surface of the intermediate transfer belt 10.
The scale 5a of the scale seal 5 is detected (detected) by a first sensor 6A, which will be described later, and the output value output by the belt drive control device 70 (belt drive control) shown in FIG. The belt drive control device 70 performs feedback control for moving (driving) the intermediate transfer belt 10 at a constant speed based on the output value.

In the feedback control, the scale 5a of the scale seal 5 is read (detected) by the first sensor 6A to calculate the actual speed of the intermediate transfer belt 10, and the speed of the intermediate transfer belt 10 according to the actual speed ( Hereinafter, the control is simply performed by correcting the belt speed to a target speed.
In the feedback control, the second sensor 6B is used in addition to the first sensor 6A. The first sensor 6 </ b> A is a scale sensor (scale detection means) that reads the scale 5 a of the scale seal 5. The second sensor 6B is a sensor (rotational speed detecting means) provided in the encoder 80 attached to the rotary shaft of the roller-shaped secondary transfer device (secondary transfer roller) 22 and is provided on a rotary disk described later. The scale on the scale (scale seal) is optically read. This scale may be formed directly on the rotating disk.

  For convenience of illustration, the sensor 6B is located outside the encoder 80, but is actually provided inside the encoder 80. Further, the scale 5 provided on the intermediate transfer belt 10 may be provided on the back surface (inner peripheral surface) thereof. Further, the scale of the scale 5 and the scale of the scale provided on the rotary disk of the encoder 80 may be formed by a number of slits or through holes in addition to a number of marks. However, it is necessary to use the 1st sensor 6A and the 2nd sensor 6B according to them. For example, when the scale is formed by a large number of marks, a light reflection type sensor is used, and when the scale is formed by a large number of slits or through holes, a light transmission type sensor is used.

FIG. 4 is a plan view showing a configuration example of a rotating disk provided in the encoder 80 attached to the secondary transfer roller 22.
The rotary disk 81 is provided with a scale seal 8 in which a large number of scales 8a (only a part of which is shown in FIG. 4) are written in a disk shape. Therefore, the second sensor 6B may have the same configuration as the first sensor 6A. In addition, an insertion hole 8b is formed in the rotary disk 81, and the rotary shaft of the secondary transfer roller 22 is inserted therein.

  This belt driving device also uses the pulse signal from the first sensor 6A (scale detecting means) or the pulse signal from the second sensor 6B (rotational speed detecting means) to feedback control the belt driving motor 7 (belt driving control device 70). A function (provided in the belt drive control device 70 in this embodiment) as a sensor output switching means for switching to be used for control.

In the color copying machine shown in FIG. 2, the copying machine main body 1 is placed on a paper feed table 2. A scanner 3 is mounted on the copying machine main body 1 and an automatic document feeder (ADF) 4 is mounted thereon.
In the copying machine main body 1, a transfer device 20 having an endless belt-like intermediate transfer belt 10 is provided at substantially the center thereof. The intermediate transfer belt 10 is stretched between a driving roller 9 and two driven rollers 15 and 16. It is constructed so as to rotate clockwise in FIG. The intermediate transfer belt 10 is configured so that residual toner remaining on the surface after image transfer is removed by a cleaning device 17 provided on the left side of the driven roller 15.

Above the linear portion spanned between the driving roller 9 and the driven roller 15 of the intermediate transfer belt 10, the four photoreceptors 40 described above are disposed along the moving direction of the intermediate transfer belt 10. Each of them is provided so as to be able to rotate counterclockwise in FIG. Each image (toner image) formed on each photoconductor 40 is sequentially transferred onto the intermediate transfer belt 10 in a superimposed state.
Around each drum-shaped photoconductor 40, a charging device 60, a developing device 61, a primary transfer roller 62, a photoconductor cleaning device 63, and a charge eliminating device 64 are provided. An exposure device 21 is provided above the photoconductor 40.

On the other hand, on the lower side of the intermediate transfer belt 10, a secondary transfer roller 22 serving as a transfer unit for transferring an image on the intermediate transfer belt 10 to a sheet P as a recording material is provided. The secondary transfer roller 22 is rotated by a driving force supplied by a secondary transfer motor 82 (secondary driving means).
A conveyance belt 24 is provided on the left side of the secondary transfer roller 22. The conveyor belt 24 is an endless belt that is stretched between the two rollers 23 and 23.
The secondary transfer roller 22 is pressed against (contacts) the driven roller 16 via the intermediate transfer belt 10, and the sheet P fed between the secondary transfer roller 10 and the intermediate transfer belt 10 is placed on the intermediate transfer belt 10. Toner images are transferred at once.

The conveyance belt 24 conveys the sheet after image transfer to the fixing device 25.
A fixing device 25 that fixes the toner image on the sheet P is disposed downstream of the conveying belt 24 in the sheet conveying direction, and a pressure roller 27 is pressed against the fixing belt 26 that is an endless belt.
A sheet reversing device 28 that reverses the sheet when forming images on both sides of the sheet is provided below the conveying belt 24.

Here, when making a color copy with this color copying machine, the user sets an original on the original table 30 of the ADF 4. Alternatively, the ADF 4 is opened and a document is set on the contact glass 32 of the scanner 3, and the ADF 4 is closed and pressed.
When a start switch (not shown) is pressed, when the document is set on the ADF 4, the document is fed onto the contact glass 32. When the document is manually set on the contact glass 32, the scanner 3 is immediately driven, and the first traveling body 33 and the second traveling body 34 start traveling. Then, light is emitted from the light source of the first traveling body 33 toward the document, and reflected light from the document surface is directed to the second traveling body 34, and the light is reflected by the mirror of the second traveling body 34. The light enters the reading sensor 36 through the imaging lens 35 and the content of the original is read.

Further, the intermediate transfer belt 10 starts to rotate by pressing the start switch described above. Further, at the same time, the respective photoreceptors 40 (40Y, 40C, 40M, and 40K) start rotating, and yellow (Y), cyan (C), magenta (M), and black (K) are placed on the respective photoreceptors 40. The operation of forming each monochrome image is started. The respective color images formed on the respective photoreceptors 40 are sequentially transferred in an overlapping state on the intermediate transfer belt 10 that rotates in the clockwise direction in FIG. 2, and a full-color composite color image is provided there. Is formed.
On the other hand, when the start switch described above is pressed, the paper feed roller 42 of the selected paper feed stage in the paper feed table 2 rotates, and the sheet P is fed from one selected paper feed cassette 44 in the paper bank 43. The paper is fed out, separated into one sheet by the separation roller 45, and conveyed to the paper feed path 46.

The sheet P is conveyed by a conveyance roller 47 to a paper feed path 48 in the copying machine main body 1, hits a registration roller 49 and temporarily stops.
In the case of manual sheet feeding, the sheet P set on the manual tray 51 is fed out by the rotation of the sheet feeding roller 50, and is separated into one sheet by the separation roller 52 and conveyed to the manual sheet feeding path 53. Then, it hits the registration roller 49 and temporarily stops.
The registration roller 49 starts to rotate at an accurate timing in accordance with the composite color image on the intermediate transfer belt 10, and the sheet P that has been temporarily stopped is placed between the intermediate transfer belt 10 and the secondary transfer roller 22. Send it in. Then, a color image is transferred onto the sheet P by the secondary transfer roller 22.

The sheet P on which the image has been transferred is conveyed to the fixing device 25 by the conveying belt 24, where the transferred image is fixed by applying heat and pressure. Thereafter, the sheet P is guided to the discharge side by the switching claw 55, discharged by the discharge roller 56 onto the discharge tray 57, and stacked there.
When the double-sided copy mode is selected, the sheet P on which an image is formed on one side is conveyed to the sheet reversing device 28 side by the switching claw 55, reversed there and led again to the transfer position, and this time the image is printed on the back side. After the formation, the paper is discharged onto a paper discharge tray 57 by a discharge roller 56.

  The first sensor 6A shown in FIG. 3 is disposed at the end in the belt width direction where the scale seal 5 (see also FIG. 5) provided on the entire surface of the intermediate transfer belt 10 can be read. The belt drive control device 70 shown in FIG. 6 calculates the actual speed of the intermediate transfer belt 10 from the information that the first sensor 6A has read (detected) the scale 5a of the scale seal 5, and according to the actual speed. Then, the speed of the intermediate transfer belt 10 is corrected to the target speed (basic speed) by controlling the belt drive motor 7.

FIG. 6 is a block diagram showing a configuration example of a control system of the color copying machine shown in FIG.
The belt drive control device 70 includes a central processing unit (CPU) having various determination and processing functions, a ROM storing each processing program and fixed data, and a RAM (non-volatile raw RAM) which is a data memory storing processing data. ), A timer circuit, and a controller using a microcomputer comprising an input / output circuit (I / O), and the functions according to the present invention (functions as driving force calculation means, sensor output switching means, and timing means) Can be realized.
The belt drive control device 70 is connected to the first sensor 6A, the second sensor 6B, the belt drive motor 7, and the secondary transfer motor 82 in order to enable the above-described feedback control of the belt speed.

This belt drive control device 70 exchanges the status of the main body operation and the status of the belt drive device (belt operation) with the main body control device 100 which controls the operation (main body operation) of the copying machine main body 1. .
The main body control device 100 can control the main body operation, that is, control to form a four-color toner image by optical writing based on the reading result by the reading sensor 36 of the scanner 3 (FIG. 2), development, and superposition intermediate transfer. In this manner, the reading sensor 36, the exposure device 21, and the image forming unit 18 are also connected. It is also connected to other loads such as various drive systems and various detection devices.

Next, the drive system of the intermediate transfer belt 10 and the belt speed detection system of the intermediate transfer belt 10 will be described.
As shown in FIG. 1, the rotational force (driving force) of the belt drive motor 7 is transmitted to a drive roller 9 that stretches the intermediate transfer belt 10 in a rotatable manner and drives the belt. The intermediate transfer belt 10 is a belt formed of, for example, fluorine-based resin, polycarbonate resin, polyimide resin, or the like, and an elastic belt in which all layers or a part of the belt is formed of an elastic member is used. .
The belt drive motor 7 is a primary drive unit, and rotates the intermediate transfer belt 10 in the direction indicated by the arrow C by supplying a drive force to the drive roller 9 and rotating the drive roller 9. The transmission of force may be direct or via a gear.

As described above, the scale seal 5 is formed on the entire surface of the intermediate transfer belt 10 over the entire circumference (only a part near the joint 11 is shown for convenience of illustration), but the belt width direction of the scale seal 5 is shown. This position is a position corresponding to the end of the photoconductor 40 and is located in the non-image forming area.
As shown in FIG. 5, the first sensor 6A is, for example, a reflective optical sensor including a pair of light emitting elements 6a and light receiving elements 6b, and irradiates the scale seal 5 from the light emitting elements 6a. The reflected light of the light is received by the light receiving element 6b, and at this time, different amounts of reflected light are detected between the scale 5a of the scale seal 5 and the portion 5b other than the scale.
That is, the first sensor 6A outputs a binary signal of High and Low due to a difference in reflectance that differs between the scale 5a of the scale seal 5 and the portion 5b other than the scale.

Here, for example, if the type of the first sensor 6A is a type that outputs a High signal when the light receiving element 6b receives light, the reflectance of the scale 5a of the scale seal 5 is higher than that of the portion 5b other than the scale. 5, the signal output from the first sensor 6 </ b> A is an output while the scale 5 a passes through the first sensor 6 </ b> A in the range of t in FIG. 5. Therefore, as the intermediate transfer belt 10 rotates, the output of the first sensor 6A repeats High and Low as shown in the figure depending on the presence or absence of the scale 5a passing through the detection range of the first sensor 6A.
Therefore, the moving speed (belt speed) of the surface of the intermediate transfer belt 10 can be calculated by obtaining the time T from when the signal changes from Low to High until when the signal changes from Low to High.

This is merely an example of a method for detecting the belt speed of the intermediate transfer belt 10, and it is possible to calculate the moving speed of the belt by reading the scale scale formed on the intermediate transfer belt 10. For example, any type of sensor or scale may be used, and any calculation method (detection method) may be used.
If the second sensor 6B has the same configuration as that of the first sensor 6A, the scale of the rotating disk can be read in the same manner as described above to detect the rotational speed of the secondary transfer roller 22.

Next, feedback control of the belt speed performed by executing the belt driving method for switching the outputs of the two sensors will be specifically described with reference to FIG.
FIG. 7 is a block diagram showing a detailed example of the control system of the belt driving device of this color copying machine.
In FIG. 7, reference numeral 110 denotes a drive transmission unit for transmitting the driving force of the belt drive motor 7 and includes a drive roller 9 and the like. Reference numeral 80 denotes an encoder, which includes the rotary disk 81 and the second sensor 6B attached to the rotary shaft of the secondary transfer roller 22 driven by the secondary transfer motor 82 as described above.

In addition to the controller 71 described with reference to FIG. 6, the belt drive control device 70 includes an input switch 72 that switches between the output signal (pulse signal) of the first sensor 6A and the output signal (pulse signal) of the second sensor 6B, A comparator 73 that compares a signal corresponding to the target speed (basic speed) V0 of the transfer belt 10 with a signal from the input switch 72 is provided.
In this belt drive control device 70, when a start signal is input from the main body control device 100, the input switch 72 switches the feedback signal to the FB loop signal, that is, the output signal of the second sensor 6B.

  As a result, the controller 71 activates the belt drive motor 7 and outputs an output signal of the second sensor 6B that reads the scale 8a of the scale seal 8 of the rotary disk 81 of the encoder 80 attached to the rotary shaft of the secondary transfer roller 22. Based on this, feedback control (start-up control) of the belt drive motor 7 is performed. At this time, the output signal of the second sensor 6B is compared with the signal corresponding to the preset target speed V0 via the input switch 72 by the comparator 73, and the output signal of the second sensor 6B indicates the target speed V0. Since data indicating whether the current speed is increasing or decreasing is output to the controller 71, the current (driving force) applied to the belt driving motor 7 is calculated and adjusted based on the data, so that the belt speed is set to the target speed. Increase (make constant speed).

  Then, it is necessary for the belt speed to rise to the target speed V0 after starting the belt drive motor 7 (required for the drive of the belt drive motor 7 and the secondary transfer motor 82 to become stable). Immediately after reaching the specified output switching time), the input switching device 72 switches the feedback signal to the speed control loop signal, that is, the output signal of the first sensor 6A in accordance with an instruction from the main body control device 100.

  Accordingly, the controller 71 performs feedback control for moving the intermediate transfer belt 10 at a target speed V0 at a constant speed based on the output signal of the first sensor 6A that reads the scale 5a of the scale seal 5 of the intermediate transfer belt 10. At this time, the output signal of the first sensor 6A is compared with the signal corresponding to the target speed V0 via the input switch 72 by the comparator 73, and the output signal of the first sensor 6A increases or decreases compared to the target speed V0. Since the data indicating whether the belt is running is output to the controller 71, the belt speed is controlled at a constant speed by calculating and adjusting the current applied to the belt drive motor 7 based on the data. That is, the belt speed is held at the target speed V0.

  However, when the joint of the scale seal 5 is detected from the output signal of the first sensor 6A, during the detection, adjustment of the current applied to the belt drive motor 7 based on the comparison result by the comparator 73 described above is prohibited, By using a dummy signal stored in a memory (for example, non-volatile raw RAM) not shown in advance without using the output signal of one sensor 6A, the speed before the detection of the joint is maintained. Or you may make it control the belt drive motor 7 using the technique described in Japanese Patent Application No. 2003-140376 previously submitted by the present applicant.

  The load driven by the belt drive motor 7 includes the secondary transfer roller 22 that contacts the intermediate transfer belt 10 in addition to the drive transmission unit 110 and the intermediate transfer belt 10. The secondary transfer roller 22 is driven by a secondary transfer motor 82. Therefore, since the driving source of the intermediate transfer belt 10 and the secondary transfer roller 22 is different, the surface of the intermediate transfer belt 10 may be rubbed by the secondary transfer roller 22. Therefore, in this embodiment, in order to prevent this problem, the belt drive motor 7 is controlled in accordance with the rising of the secondary transfer roller 22. For this reason, the time required for the secondary transfer roller 22 to rise (rise time) becomes the sensor output switching specified time, and the belt drive control device 70 uses the rise as the sensor output switching specified time in accordance with an instruction from the main body control device 100 in advance. If set, scratches due to rubbing of the surface of the intermediate transfer belt 10 can be avoided.

  Further, when the belt drive motor 7 is started and started up (the belt speed reaches the target speed) and the feedback control of the belt drive motor 7 is continued using the output signal of the second sensor 6B, It is necessary to switch to the output signal of the first sensor 6A at least before the operation of writing (forming) an image on the photoconductor 40 is started. This is because, when switching to the output signal of the first sensor 6A is performed during image writing on the photoconductor 40, slight speed fluctuations of the intermediate transfer belt 10 cause subtle speed fluctuations of the photoconductor 40. This is because the image writing positions of the photoconductors 40Y, 40M, 40C, and 40K are slightly rubbed to cause color misregistration.

  A drive transmission system (drive transmission unit) such as a gear may be provided between the secondary transfer roller 22 and the secondary transfer drive motor 82 that drives the secondary transfer roller 22. In this case, the current value (control value) given to the secondary transfer motor 82 by the controller 71 (CPU) in the belt drive control device 70 is corrected by the reduction ratio of the drive transmission system. That is, based on the reduction ratio and the output signal of the second sensor 6B, a current (current that matches the rotational speeds of the drive roller 9 and the secondary transfer roller 22) to the secondary transfer motor 82 is calculated.

Next, the relationship between the rotational speeds of the drive roller 9 and the secondary transfer roller 22 when the belt drive device is activated (rises) will be described with reference to FIG.
FIG. 8 is a diagram showing an example of the relationship between the rotational speeds of the drive roller 9 and the secondary transfer roller 22 when the belt drive device (belt drive motor 7) is started (rises).

In the conventional control, as described with reference to FIG. 12, the rotational speed difference between the driving roller 9 and the secondary transfer roller 22 is very large, which causes a problem.
In the control according to this embodiment, the rotational speed difference between the drive roller 9 and the secondary transfer roller 22 is very small. Therefore, the belt drive motor 7 does not have a load torque just below the motor output torque, and the intermediate transfer belt 10 does not bend, and the belt drive control device 70 is not abnormally processed due to an abnormal reduction of the load torque.

Next, feedback control (including sensor output switching processing) of belt speed at start-up performed by the belt drive control device 70 shown in FIG. 7 will be described with reference to FIG.
FIG. 9 is a flowchart showing an example of feedback control of the belt speed at the time of start performed by the belt drive control device 70 shown in FIG.
The belt drive control device 70 shown in FIG. 7 starts the processing routine shown in FIG. 9 by calling from a main routine (not shown). First, in step S1, it is determined whether or not the belt drive device (belt drive motor 7) is activated. to decide.

If it is not at the time of starting the belt driving device, the process directly returns to the main routine.
When the belt driving device is activated, the process proceeds to step S2, and the pulse signal (output voltage value) from the second sensor 6B of the encoder 80 attached to the rotating shaft of the secondary transfer roller 22 is converted into the belt speed. The input (sensor output) is switched so as to be used for feedback control, and the belt speed feedback control is performed based on the pulse signal from the second sensor 6B. At the time of starting the belt driving device, although not shown, time measurement (time measurement) is also started.

  Next, in step S3, it is determined whether or not the measurement time has reached the specified time (sensor output switching specified time). If the specified time has not been reached, the process returns to step S2 to perform feedback control of the belt speed. When the time is reached, the process proceeds to step 4 where the input is switched so that the pulse signal (scale signal) from the first sensor 6A is used for feedback control of the belt speed, and based on the pulse signal from the first sensor 6A. Then, feedback control of the belt speed is performed, and the process returns to the main routine.

FIG. 10 is a block diagram showing another detailed example of the control system of the belt driving device of this color copying machine, and the same reference numerals are given to the same parts as those in FIG.
In FIG. 10, reference numeral 83 denotes an FG (frequency generator) originally mounted in the secondary transfer motor 82, which corresponds to a rotational speed detecting means. Therefore, in this example, the output signal (pulse signal) of the FG is used as feedback.

Next, belt speed feedback control (including sensor output switching processing) at the time of startup performed by the belt drive control device 70 shown in FIG. 10 will be described with reference to FIG.
FIG. 11 is a flowchart illustrating an example of feedback control of the belt speed at start-up performed by the belt drive control device 70 illustrated in FIG. 10.
The belt drive control device 70 shown in FIG. 10 starts the processing routine shown in FIG. 11 by calling from a main routine (not shown). First, in step S11, it is determined whether or not the belt drive device (belt drive motor 7) is activated. to decide.

If it is not at the time of starting the belt driving device, the process directly returns to the main routine.
When the belt driving device is activated, the process proceeds to step S12, and the pulse signal from the FG 83 in the secondary transfer motor 82 that drives the secondary transfer roller 22 is input to be used for feedback control of the belt speed. (Sensor output) is switched, and feedback control of the belt speed is performed based on the pulse signal from the FG 83. At the time of starting the belt driving device, although not shown, time measurement is also started.

  Next, it is determined in step 13 whether or not the measurement time has reached the specified time. If the specified time has not been reached, the process returns to step S12 to perform feedback control of the belt speed, but if the specified time has been reached, the process returns to step S14. The input is switched so that the pulse signal (scale signal) from the first sensor 6A is used for belt speed feedback control, and the belt speed feedback control is performed based on the pulse signal from the first sensor 6A. And return to the main routine.

In this embodiment, the speed control of the intermediate transfer belt 10 is performed, but the position control of the intermediate transfer belt 10 may be performed.
Further, the functions as the controller 71, the input switching unit 72, and the comparator 73 described with reference to FIG. 7 or FIG. 10 are realized by the CPU (computer) in the controller 71 executing the program according to the present invention in the ROM. Is also possible. Thereby, the program can cause the CPU in the controller 71 to realize functions as a driving force calculating means, a sensor output switching means, and a time measuring means.

The program according to the present invention may be stored in the ROM from the beginning, but is provided by being recorded on a non-volatile recording medium (memory) such as a CD-ROM or flexible disk, SRAM, EEPROM, or memory card as a recording medium. You can also Each processing procedure described above can be executed by causing the CPU to execute a program recorded in the memory or causing the CPU to read and execute the program from the memory.
It is also possible to download the program from an external device that is connected to a network and includes a recording medium that records the program, or an external device that stores the program in a storage unit, and execute the program.

As described above, the embodiment in which the present invention is applied to the belt driving device for driving the intermediate transfer belt and the color copying machine including the belt driving device has been described. However, the present invention is not limited thereto, and other belts for image formation ( The present invention can also be applied to a belt drive control device that drives a photosensitive belt, a transfer belt, a transfer conveyance belt, or an image recording medium conveyance belt) and an image forming apparatus such as a color copying machine or a color printer including the belt drive control device.
That is, the example in which the present invention is applied to the belt driving device in the tandem type color copying machine in which the photosensitive pairs of the respective colors are arranged on the intermediate transfer belt has been described, but the image forming apparatus to which the present invention can be applied. The belt driving device is not limited to this configuration. As long as the image forming apparatus has a belt driving device that rotationally drives an endless belt stretched around a plurality of rollers by at least one of the rollers, it can be applied to any belt driving device. is there.

  As is apparent from the above description, according to the present invention, even when the belt driving device is activated, it is possible to minimize the difference in rotational speed between the first roller and the second roller. Become. Therefore, if this invention is utilized, the belt drive device which can implement | achieve stabilization of belt drive reliably can be provided. Further, by providing the belt driving device, it is possible to provide an image forming apparatus that can reliably acquire a high-quality image.

1 is a schematic diagram illustrating a belt driving device of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an overall configuration diagram illustrating an example of the image forming apparatus. FIG. 2 is a plan view showing a scale provided on an intermediate transfer belt of the belt driving device of FIG. 1 and a first sensor for detecting the scale. FIG. 2 is a plan view showing a configuration example of a rotating disk provided in an encoder attached to the secondary transfer roller 22 of FIG. 1. It is a figure which shows the binary sensor output signal which the 1st sensor of FIG. 3 detects and outputs the scale of a scale. FIG. 3 is a block diagram illustrating a configuration example of a control system of the image forming apparatus illustrated in FIG. 2.

3 is a block diagram illustrating a detailed example of a control system of a belt driving device of the image forming apparatus illustrated in FIG. 2. FIG. 3 is a diagram showing an example of a relationship between rotational speeds of a driving roller 9 and a secondary transfer roller 22 when the belt driving device (belt driving motor 7) shown in FIG. 2 is started. It is a flowchart which shows an example of feedback control of the belt speed at the time of starting which the belt drive control apparatus 70 shown in FIG. 7 performs. 3 is a block diagram showing another detailed example of a control system of the belt driving device of the image forming apparatus shown in FIG. 2. 11 is a flowchart illustrating an example of feedback control of a belt speed at start-up performed by the belt drive control device 70 illustrated in FIG. 10. It is a diagram which shows an example of the relationship between the rotational speed of the drive roller at the time of starting of the conventional belt drive device (belt drive motor) and the secondary transfer roller.

Explanation of symbols

5, 8: Scale seals 5a, 8a: Scale 6A: First sensor 6B: Second sensor 7: Belt drive motor 8b: Insertion hole 9: Drive roller 10: Intermediate transfer belt 11: Joint 15, 16: Driven roller 22: Secondary transfer roller 70: Belt drive controller 71: Controller 72: Input switch 73: Comparator 80: Encoder 81: Rotary disk 82: Secondary transfer motor 83: FG 100: Main body controller 110: Drive transmission unit

Claims (8)

A belt driving device for driving a belt,
Primary driving means for supplying a driving force to a first roller that moves the belt in contact with the belt, and a secondary for supplying a driving force to a second roller that contacts the belt at a position different from the first roller. A driving means; a rotational speed detecting means for detecting the rotational speed of the second roller; and a driving force to be supplied to the primary driving means, and calculating the driving force to the primary driving means to rotate the belt. Belt drive control means for driving control,
The belt drive apparatus according to claim 1, wherein the belt drive control means includes drive force calculation means for calculating a drive force to be supplied to the primary drive means based on a detection value of the rotation speed detection means. The belt drive device according to claim 1, wherein
The belt driving device according to claim 1, wherein the driving force calculating means calculates a driving force that provides the primary driving means with a driving force that matches rising speeds of the first roller and the second roller. The belt driving device according to claim 1 or 2,
The rotation speed detection means is means for detecting the rotation speed of the second roller and outputting a corresponding pulse signal,
A scale in which scales are formed at equal intervals along the circumferential direction of the belt, scale detection means for detecting scale marks and outputting corresponding pulse signals, pulse signals from the scale detection means or the rotation A sensor output switching means for switching the pulse signal from the speed detection means to be used for control by the belt drive control means; and
The sensor output switching means switches the belt signal from the rotation speed detecting means to be used for the control by the belt drive control means from the start of the primary drive means to the completion of rising. apparatus. The belt driving device according to claim 3, wherein
Providing a time measuring means for starting time measurement in response to the activation of the belt drive device;
The sensor output switching means outputs a pulse signal from the rotation speed detecting means until the time measured by the time measuring means reaches a predetermined value, and when the time reaches the predetermined value, a pulse signal from the scale detecting means. The belt drive device is switched to be used for control by the belt drive control means. The belt drive device according to claim 4, wherein
The belt driving apparatus according to claim 1, wherein the predetermined value is a time required for the driving of the primary driving means and the second driving means to become stable. A belt driving device for moving a belt at a constant speed,
Primary driving means for supplying a driving force to a first roller that moves the belt in contact with the belt, and a secondary for supplying a driving force to a second roller that contacts the belt at a position different from the first roller A driving means; a rotational speed detecting means for detecting the rotational speed of the secondary driving means; and a driving force to be supplied to the primary driving means, and calculating the driving force to the primary driving means to instruct the belt. Belt drive control means for controlling the drive,
The belt drive apparatus according to claim 1, wherein the belt drive control means includes drive force calculation means for calculating a drive force to be supplied to the primary drive means based on a detection value of the rotation speed detection means. The belt drive device according to claim 6, wherein
The driving force calculating means matches the rotational speeds of the first roller and the second roller based on a reduction ratio of the second roller and the secondary driving means and a detection value of the rotational speed detecting means. A belt driving device characterized in that the driving force to be calculated is calculated as a driving force to be supplied to the primary driving means. An image forming apparatus that forms an image by transferring an image on a transfer belt to a recording medium,
A primary driving means for supplying a driving force to a first roller that moves the transfer belt in contact with the transfer belt, and a second roller that contacts the outer peripheral surface of the transfer belt at a position different from the first roller. Secondary driving means for applying force, a third roller that contacts the inner peripheral surface of the transfer belt so as to face the outer peripheral surface of the second roller, and a rotational speed detection that detects the rotational speed of the second roller Means, a driving force to be supplied to the primary driving means, a belt driving control means for controlling the driving of the transfer belt by instructing the driving force to the primary driving means, the second roller and the first driving means. A paper supply / discharge means for supplying a recording medium between the three rollers and discharging the image after transferring the image on the transfer belt to the recording medium;
The image forming apparatus according to claim 1, wherein the belt drive control unit calculates a driving force to be supplied to the primary drive unit based on a detection value of the rotation speed detection unit.

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