JP4809636B2 - Belt traveling device and image forming apparatus using the same - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer or a copying machine, and more particularly to a belt traveling apparatus having a function of correcting meandering of an endless intermediate transfer belt and an image forming apparatus using the same.

  In color image forming apparatuses such as printers and copiers, a plurality of photosensitive drums are arranged along the running direction of an endless intermediate transfer belt, and the electrostatic latent images formed on the respective photosensitive drums have different colors. A tandem method is known in which toner images of each color are formed by adsorbing toner, and the toner images of each color are sequentially transferred onto a transfer belt driven by a belt traveling device. As the endless transfer belt travels, a phenomenon occurs in which the endless transfer belt is biased or meanders in a direction perpendicular to the travel direction (width direction of the transfer belt). Since the meandering of the transfer belt causes misalignment of each toner image and causes deterioration in image quality, the tandem color image forming apparatus requires control to suppress the meandering of the transfer belt. .

  2. Description of the Related Art Conventionally, as a method for controlling the belt shift of an endless belt, a method for controlling an inclination angle of one roller with respect to a horizontal plane among a plurality of rollers that stretch the endless belt is known. This control method is less burdensome on the belt than the method of guiding the edge of the endless belt, and is superior in terms of belt durability, while detecting the predetermined position in the moving direction of the endless belt, A means for comparing with the set value is required, and there is a problem that it is difficult to control the belt deviation with a simple configuration with high accuracy.

  Patent Document 1 focuses on this problem, and in a device that controls the belt deviation by adjusting the inclination of the adjustment roller based on the belt position detected by the belt position detection means, the amount of inclination of the roller is determined as the belt position. A method of adjusting and controlling proportionally to the amount of fluctuation is proposed.

  According to this control method, even if the reference position of the adjustment roller is shifted from the center position when the actual belt shift is controlled, the inclination of the adjustment roller is controlled around the shifted position. The belt deviation of the belt is controlled with high accuracy.

  Such a control method requires a position detector for detecting the belt position of the belt width. For example, Patent Document 1 discloses a position detection sensor shown in FIG.

  The position detection sensor includes a light emitting unit 31 such as an LED and a light receiving unit 32 such as a photodiode across the belt edge 30a of the transfer belt 30. When the position of the belt edge 30a is shifted left and right, the light emitting unit 31 The amount of light applied to the light receiving unit 32 is changed, and the detection voltage of the light receiving unit 32 is also changed according to the position.

  FIG. 12 shows an example of the characteristics of such a sensor. The horizontal axis represents the belt position, and the vertical axis represents the detection voltage. As shown in the figure, the sensor characteristics have a region where the detection voltage is displaced almost linearly according to the belt position (sensor detection range) and a region where the detection voltage is constant regardless of the belt position. The center position of the detection range of the sensor is set as the belt reference voltage.

  The detection accuracy of each sensor is guaranteed by the manufacturer, but the guaranteed range is the detection range of the sensor shown in the figure. Since the detection accuracy is not guaranteed outside this range, sufficient detection accuracy cannot be ensured. there is a possibility.

  The sensor of FIG. 12 shows an example in which the reference position is set to 6.5 mm and, for example, a detection accuracy of ± 10 μm is guaranteed within a range of ± 1.0 mm around this position. In the present specification, a range in which the accuracy of the sensor is guaranteed in this way is referred to as a detection accuracy guaranteed range.

  By the way, in the belt running device used in the image forming apparatus as described above, when the casing is twisted due to aging, the edge position of the transfer belt protrudes from the detection accuracy guarantee range of the belt position detection sensor, Alternatively, the meandering speed of the transfer belt may be outside the specified range. As described above, when the detection accuracy of the running position of the transfer belt cannot be guaranteed, or when the meandering speed of the transfer belt increases and falls outside the specified range, there is a problem that the image quality at the time of image formation is deteriorated.

JP 2002-287527 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a belt traveling device and an image forming apparatus that solve the above-described conventional problems.

  Specifically, an object of the present invention is to provide a belt traveling device that can appropriately correct the meandering of the transfer belt even when the housing of the belt traveling device is twisted due to aging, etc. It is an object of the present invention to provide an image forming apparatus that stably forms the image.

In order to achieve the above object, the present invention provides an endless belt stretched around a plurality of rollers and any one of the plurality of rollers as a driving roller, and the belt is driven by the rotation of the driving roller. A drive means, a meandering correction roller that is one of the plurality of rollers, and a meandering correction means that corrects meandering in the width direction of the belt by adjusting the inclination of the meandering correction roller; and the width direction of the belt And a correction control unit for controlling the meandering correction unit based on a detection signal from the position detection unit. The correction control unit is based on a signal from the position detection unit. And calculating a first correction amount corresponding to a value proportional to the position in the width direction of the belt, and a second correction value corresponding to a value obtained by integrating the position in the width direction of the belt. Calculate the correction amount And, it means for the integral correction amount, when the widthwise position of the belt by judging means for judging whether or not within the predetermined range in the width direction of the position of the belt is determined in advance is within a predetermined range when it is determined holds the integral correction amount when said determined without integrating the widthwise position of the belt, and means for the integrating component correction amount and the third correction amount, wherein When the determination means determines that the position in the width direction of the belt is outside the predetermined range, the meander correction means is controlled based on a value obtained by adding the first correction amount and the second correction amount; One feature is that, when it is determined that the position in the width direction of the belt is within a predetermined range, the meandering correction means is controlled based on a value obtained by adding the first correction amount and the third correction amount. Have

Another feature of the present invention is that the detection accuracy guarantee range of the position detection means is −P to + P, and the amplitude of the edge position detection signal of the endless belt is Ed, −I> −P + Ed, + I <+ P−Ed. Sometimes, the predetermined range is represented by -I to + I.

Another feature of the present invention is that when the position in the width direction of the belt is within the range of −I to + I for a predetermined time, the position in the width direction of the belt is within the predetermined range by the determination unit. It is to be determined that there is.

  Another feature of the present invention resides in that an image forming apparatus is configured using the belt traveling device.

  According to the present invention, even when the casing of the belt traveling device is twisted due to aging, the meandering correction control in the width direction of the belt is performed within the detection accuracy guarantee range of the belt position detection sensor, and the meandering speed of the belt is also Since it can be suppressed within the specified range, it is possible to provide an image forming apparatus capable of stably forming a high-quality image.

  Hereinafter, an image forming apparatus using the belt traveling device according to the present invention will be described first, and then an embodiment of the belt traveling device according to the present invention and the configuration and operation of each part of the device will be described.

(1) Four-color full-color image forming apparatus FIG. 10 is a schematic diagram of a four-color full-color image forming apparatus according to the present invention. The image forming apparatus includes four image forming units 41 a, 41 b, 41 c, 41 d arranged along the traveling direction of the transfer belt 50.

  The image forming unit 41a includes a photosensitive drum 42a, a drum charger 43a, an exposure device 44a, a developing device 45a, a transfer device 46a, and a cleaning device 47a. The image forming units 41b to 41d are configured similarly.

  The image forming units 41a to 41d form images of different colors, for example, 41a is yellow, 41b is magenta, 41c is cyan, and 41d is black.

  The photosensitive drum 42a starts rotating in the direction of the arrow G based on an image forming operation start instruction from a controller (not shown), and continues rotating until the image forming operation ends. When the photosensitive drum 42a starts rotating, a high voltage is applied to the charger 43a, and negative charges are uniformly charged on the surface of the photosensitive drum 42a.

  When character data or graphic data converted into a dot image is sent from the controller (not shown) to the image forming apparatus as an on / off signal of the exposure device 44a, laser light is emitted from the exposure device 44a to the surface of the photosensitive drum 42a. A part to be irradiated and a part not to be irradiated are formed. When the portion where the charge is reduced on the photosensitive drum 42a reaches the position facing the developing unit 45a by the irradiation of the laser beam from the exposure device 44a, the portion where the charge is reduced on the photosensitive drum 42a is charged with a negative charge. A toner image of the finished toner is formed.

  When the toner image formed on the photosensitive drum 42a reaches the transfer device 46a, the toner image is transferred onto the transfer belt 50 rotating in the direction of arrow A by the action of a high voltage applied to the transfer device 46a. The The photosensitive drum 42a that has passed the transfer position is cleaned by the cleaning device 47a, and is prepared for the next image forming operation.

  The image forming operation is similarly performed in the image forming unit 41b following the image forming unit 41a, and the toner image formed on the photosensitive drum 42b is applied on the transfer belt 50 by the action of a high voltage applied to the transfer unit 46b. Transcribed. At this time, the timing at which the image formed by the image forming unit 41a and transferred onto the transfer belt 50 reaches the transfer device 46b and the toner image formed on the photosensitive drum 42b are transferred to the transfer belt 50. By matching the timing, the toner images formed by the image forming unit 41 a and the image forming unit 41 b overlap on the transfer belt 50. Similarly, a full color image is formed on the transfer belt 50 by superimposing the toner images formed by the printing units 41 c and 41 d on the transfer belt 50.

  At the same time when the full-color image reaches the paper transfer unit 49, the paper 48 conveyed in the direction of arrow H from the paper feed unit (not shown) of the image forming apparatus reaches the paper transfer unit 49 and is applied to the paper transfer unit 49. The full color image on the transfer belt 50 is transferred to the paper 48 by the action of the high voltage. When the paper 48 is conveyed to the fixing device 51, the toner image on the paper 48 is melted and fixed on the paper 48.

  On the other hand, after the full-color image passes through the paper transfer unit 49, toner that is not transferred adheres to the transfer belt 50, and the toner is cleaned by the belt cleaning mechanism 52.

(2) Configuration of Belt Traveling Device Next, an embodiment of the belt traveling device according to the present invention will be described with reference to FIG.

  As shown in FIG. 3, the belt running apparatus 1 of the present invention includes a transfer belt 2, a belt position detection mechanism 3, a belt meandering correction mechanism 13, a meandering correction control unit 23, and the like. The transfer belt 2 composed of an endless belt is stretched around a driving roller 8, a meandering correction roller 11, and driven rollers 12a to 12d. The drive roller 8 is connected to a belt drive motor 9, and the belt 2 travels when the motor 9 rotates. In the following description, the direction of arrow A in FIG. 3 is referred to as a belt traveling direction, and the direction of arrow B is referred to as a belt width direction.

  The belt position detecting mechanism 3 detects the meandering displacement amount of the transfer belt 2 in the belt width direction by detecting the edge position of the transfer belt 2, and the detection signal is applied to the meandering correction control unit 23. .

  On the other hand, the belt meandering correction mechanism 13 controls to correct the meandering of the transfer belt 2 by changing the inclination of the meandering correction roller 11. The inclination angle of the meandering correction roller 11 is controlled by the amount of rotation of the meandering correction motor 14, and the amount of rotation of the motor 14 is controlled by the meandering correction motor driving unit 15.

  The meandering correction control unit 23 receives the detection signal from the belt position detecting mechanism 3, advances a signal for instructing the meandering correction to the meandering correction motor driving unit 15, and instructs the driving motor driving unit 10 about the traveling speed of the belt 2. Send a signal.

  Details of the belt position detection mechanism 3, the belt correction meandering mechanism 13, and the meandering correction control unit 23 will be described in detail below.

(3) Belt position detection mechanism 3
FIG. 5 shows an embodiment of the belt position detecting mechanism 3, which includes a contact 4 made up of L-shaped members 4a and 4b and a displacement sensor 7 constituting belt position detecting means. The contact 4 is supported so as to be rotatable in the direction of arrow C around the support shaft 5. A spring 6 is attached to one member 4 b constituting the contact 4, and the other member 4 a is always in contact with the edge of the transfer belt 2 by its pulling force.

  On the other hand, a displacement sensor 7 constituting a belt position detecting means is disposed in the vicinity of the member 4b of the contactor 4. The displacement sensor 7 includes, for example, a light emitting unit made of a light emitting diode and a light receiving unit that receives reflected light. The displacement sensor 7 is configured to be able to detect the distance to the member 4b from the light receiving position of the reflected light in the light receiving unit.

  According to the above configuration, since the member 4a of the contact 4 is always in contact with the edge of the transfer belt 2, the contact 4 rotates in the direction of the arrow C in accordance with the meandering of the belt 2 and is displaced. Since the light receiving position of the reflected light in the light receiving portion of the sensor 7 changes, the meandering amount of the belt 2 can be detected as the signal magnitude of the displacement sensor 7.

  Since the edge of the transfer belt 2 is usually non-linear as shown by the solid line in FIG. 5 according to the cutting accuracy, the transfer belt 2 does not meander when the transfer belt 2 travels. Although the edge position signal of the transfer belt vibrates, the meandering correction control 23 of the present invention can perform meandering correction with high accuracy in such a case as described later.

(4) Belt meandering correction mechanism 13
FIG. 4 shows an embodiment of the belt meandering correction mechanism 13, which includes a swing arm 16, an eccentric cam 20, an eccentric cam position detection sensor 21, and the like. The swing arm 16 includes two members 16a and 16b. The end of one member 16b is connected to the end of the meandering correction roller 11, and the bearing 18 is fixed to the end of the other member 16a. . The members 16a and 16b are supported so that they can rotate integrally around the rotation shaft 17.

  A spring 19 is attached to the member 16 a of the swing arm 16, and the bearing 18 is always in contact with the eccentric cam 20 by its pulling force. The eccentric cam 20 rotates in the direction of arrow D around the rotation shaft provided at the eccentric position, and the rotation shaft is connected to the rotation shaft of the meandering correction motor 14 shown in FIG.

  An eccentric cam position detection sensor 21 is disposed in the vicinity of the eccentric cam 20 so that the reference position of the eccentric cam 20 can be recognized by detecting the position of the shielding plate 22.

  Next, the operation of the belt meandering correction mechanism 13 will be described. The control signal from the meandering correction control unit 23 in FIG. 3 is given to the meandering correction motor driving unit 15 to instruct the amount of rotation of the meandering correction motor 14. When the motor 14 is rotated by a predetermined amount, the eccentric cam 20 is also rotated in the direction of arrow D, and the bearing 18 is moved up and down in the direction of arrow E.

  When the bearing 18 moves upward, one end of the member 16a rotates upward about the shaft 17, and conversely, the end of the member 16b rotates downward about the shaft 17. Since the meandering correction roller 11 is connected to the end of the member 16b, when the end of the member 16b rotates downward, the correction roller 11 also changes downward in the direction of arrow F. Conversely, when the bearing 18 moves downward, the correction roller 11 moves upward in the arrow F.

  As shown in FIG. 3, one end of the meandering correction roller 11 is fixed, and the end to which the swing arm 16 is connected moves up and down, so that the meandering correction roller 11 is inclined according to the rotation amount of the motor 14. It will be. When the meandering correction roller 11 is inclined, the transfer belt 2 moves in the width direction according to the inclination angle.

  That is, the transfer belt 2 meanders due to unevenness of the belt width direction due to the twist of the belt body of the belt traveling device 1, but the meandering direction of the meandering correction roller 11 is inclined depending on the position of the eccentric cam 20. By controlling the angle, the meandering correction can be performed by making the tension of the transfer belt 2 in the belt width direction uniform.

(5) Meander correction control unit 23
Next, the meandering correction control unit 23 of the belt traveling device according to the present invention will be described. FIG. 1 is a block diagram of the meandering correction control unit 23 of the apparatus of the present invention, and FIG. In order to facilitate understanding of the invention, a block diagram of a conventional meandering correction control unit is shown in FIG. 6 and its operation explanatory diagram is shown in FIG. 7 and FIG. 8. First, FIGS.

  In FIG. 6, an edge detection signal of the transfer belt 2 is applied to the meandering correction control unit 23 from the displacement sensor 7 constituting the belt position detecting means. Since the edge of the transfer belt 2 is non-linear due to the problem of cutting accuracy as shown in FIG. 5, the edge position detection signal vibrates even if the transfer belt 2 does not meander, and the edge shown in FIG. The waveform is as shown by the dotted line. The transfer belt edge position detection signal is applied to the belt position calculation processing unit 24, and belt position calculation processing is performed from the edge position. For example, by taking an average of the edge position detection signals indicated by the dotted lines in FIG. 7A, the belt traveling position as indicated by the solid lines is calculated.

  A signal indicating the belt running position is applied to the proportional control unit 25 and the integral control unit 26, respectively. The proportional control unit 25 calculates a proportional correction amount by multiplying the belt running position by a proportional correction coefficient.

  On the other hand, the integration control unit 26 integrates a signal representing the belt running position, and then multiplies the integration correction coefficient to calculate an integral correction amount. The proportional correction amount and the integral correction amount are added to generate a correction signal, and the correction signal is applied to the meandering correction motor 14 via the meandering correction motor driving unit 15.

  FIG. 7 shows the operation when the meandering correction control unit 23 is configured as described above and only the proportional control is performed, and FIG. 8 shows the operation when the proportional integration operation is performed.

  7, (1) is the running position of the transfer belt 2 and the edge position of the transfer belt 2, (2) is the meandering speed of the transfer belt 2, and (3) is the eccentric cam 20 calculated by the proportional control unit 25 (FIG. The position of 4) is shown.

  Now, for example, a case is assumed where the housing of the belt traveling device 1 is twisted due to aging.

  In general, when the casing of the belt traveling device 1 is twisted, the driving roller 8, the driven rollers 12a to 12d, and the meandering correction roller 11 shown in FIG. 3 are inclined. Therefore, the tension of the transfer belt 2 in the belt width direction is not uniform. At this time, in order to make the tension of the transfer belt 2 in the belt width direction uniform, the position of the eccentric cam 20 needs to be, for example, Cp shown in (3) of FIG. However, in order to set the position of the eccentric cam 20 to Cp only by proportional control by the proportional control unit 25, the traveling position of the transfer belt 2 becomes Bp from the proportional correction amount calculation formula of the following formula (1).

Eccentric cam position Cp = proportional correction coefficient × belt traveling device Bp (1)
This belt travel position Bp is, for example, a position represented by Bp in (1) of FIG. Since the edge position of the transfer belt 2 vibrates with the amplitude Ed around the belt running position Bp as shown by the dotted line in (1), the edge position signal is partially detected by the displacement sensor 7. The accuracy guarantee range (−P to + P) will protrude.

  In this way, if the detection signal of the displacement sensor goes beyond the detection accuracy guarantee, the belt position cannot be detected accurately, and meandering due to improper correction occurs, so the quality of the image formed by the image forming apparatus is greatly reduced. Will do.

  On the other hand, FIG. 8 shows an operation when proportional integral control is performed by the meandering correction control unit 23. FIG. 8 also shows (1) the running position of the transfer belt 2, the edge position (2) of the transfer belt 2, the meandering speed (3) of the transfer belt 2, and the position of the eccentric cam calculated by proportional integral control.

  When the position of the eccentric cam 20 is adjusted by the proportional integral control signal, for example, even if the casing of the belt traveling device 1 is twisted and the driving roller 8, the driven rollers 12a to 12d and the meandering correction roller 11 are inclined, (1) in FIG. ), The traveling position of the transfer belt 2 can be kept near the target position. Therefore, even if the edge position of the transfer belt 2 vibrates with the amplitude Ed as shown by the dotted line in the figure, it is possible to keep the edge position signal within the detection accuracy guarantee range (−P to + P) of the displacement sensor 7. . However, in this case, the meandering speed of the transfer belt 2 shown in FIG. 2B may fall outside the specified range (−V to + V).

  That is, the eccentric cam 20 needs to be quickly operated so that the travel position of the transfer belt 2 becomes smaller when the travel position of the transfer belt 2 becomes larger than the target position. On the other hand, if the travel position of the transfer belt 2 becomes smaller than the target position, the eccentric cam 20 operates so that the travel position of the transfer belt 2 becomes larger. Therefore, the position of the eccentric cam 20 is as shown in (3) of FIG. Although it changes, in the position adjustment of the eccentric cam 20 by proportional-integral control, there is integration in the integration control unit 26, so the eccentric cam 20 operates with a delay with respect to fluctuations in the travel position of the transfer belt 2. Therefore, the running position of the transfer belt 2 vibrates near the target position as shown in FIG. 8 (1), and the meandering speed of the transfer belt 2 fluctuates greatly as shown in FIG. 8 (2). As a result, the meandering speed may fall outside the specified range (−V to + V).

  As described above, in the control by the conventional meandering correction control unit 23, the edge position of the transfer belt 2 may protrude from the detection accuracy guarantee range of the displacement sensor 7 in the case of proportional control, and the transfer belt 2 in the case of proportional integral control. Since the meandering speed may exceed the predetermined range, the image quality is deteriorated.

  On the other hand, in the present invention, the meandering correction control unit 23 is configured as shown in FIG. 1 so that the edge position of the transfer belt 2 is within the detection accuracy guarantee range (−P to + P) of the belt position detection sensor 7. The meandering speed of the transfer belt 2 is also controlled within a specified range (-V to + V).

  FIG. 1 differs from FIG. 6 in that an integral correction determination processing unit 27 is included in the integral control unit 26. The integral correction determination processing unit 27 determines whether or not the traveling position of the transfer belt 2 is within a predetermined range, and performs different processing depending on the result. It demonstrates using the flowchart of these.

  In step 100, an edge position signal of the transfer belt 2 is detected, and in step 101, the running position of the transfer belt 2 is calculated from this signal. In step 102, a proportional correction amount is calculated by multiplying the calculated belt travel position by a proportional correction coefficient.

  Next, in step 103, it is determined whether or not the calculated belt position is within a predetermined range (-I to + I). This predetermined range (-I to + I) is set by the following equation (2) based on the detection accuracy guarantee range (-P to + P) of the belt position detection sensor 7 and the amplitude Ed of the edge position detection signal of the transfer belt 2. .

-I> -P + Ed, + I <+ P-Ed (2)
The predetermined range (-I to + I) is a range provided to limit the integral correction amount according to the travel position of the transfer belt 2, and is referred to as an integral correction limit range.

  If the determination in step 103 is NO, the integration control unit 26 integrates the travel position information of the transfer belt 2 in step 104 and further multiplies the integral correction coefficient in step 105 to calculate an integral correction amount.

  On the other hand, if the determination in step 103 is YES, that is, if the travel position of the transfer belt 2 is within the integral correction limit range (−I to + I), the integration control unit 26 does not integrate the travel position of the transfer belt 2. The current integral correction amount is held, and the held value is set as the integral correction amount. Further, in step 107, the integral correction amount and the separately calculated proportional correction amount are added, and the meandering correction motor 14 is driven based on the added information, and the position of the eccentric cam 20 is adjusted (step 108).

  Next, the operation of the belt traveling device including the meandering correction control unit 23 according to the present invention will be described with reference to FIG.

  In the following description, the operation of the belt traveling device 1 when the power of the image forming apparatus is turned on will be described as an example. However, when the image forming apparatus starts image formation and when the belt traveling apparatus 1 is adjusted, it is not during image formation. Is the same operation. 2A shows the running position of the transfer belt 2 and the edge position of the transfer belt 2. FIG. 2B shows the meandering speed of the transfer belt 2. FIG. 2 shows the position of the eccentric cam 20 calculated by the proportional integral control. In each case, the horizontal axis indicates the passage of time. The range of (-I to + I) in (1) is the above-described integral correction limit range.

  When the power is turned on, the belt running position is outside the integral correction limit range (−I to + I), so that the process proceeds to steps 100, 101, 102, 103, 104, and 105 in FIG. A position control signal for the eccentric cam 20 is generated by the sum of the integral correction amounts. By this control, the belt running position gradually moves toward the target position (the center position between + P and -P) as in the conventional proportional integral control. When the belt running position falls within the range of (-I to + I), that is, when the belt edge position oscillating with the amplitude Ed falls within the range of (-P to + P), the meandering correction control process starts from step 103 in FIG. Proceed to step 106. In this case, since the signal indicating the belt edge position is oscillating, the determination in step 103 is YES when the traveling position of the transfer belt 2 is within the range of (−I to + I) continues for a predetermined time. The following process is performed.

  In step 106, the integral correction amount of the integral control unit 26 when the determination in step 103 becomes YES is held. Thereafter, in step 107, the position of the eccentric cam is determined by the sum of the held integral correction amount and the proportional correction amount. Generate a control signal. Accordingly, the integration operation by the integration control unit 26 as in the prior art prevents the eccentric cam 20 from operating late with respect to fluctuations in the travel position of the transfer belt 2, and the meandering speed of the transfer belt 2 is also shown in FIG. Thus, it falls within the specified range (+ V to -V).

  As will be apparent from the above description, the meandering correction control in the belt running device of the present invention is a control in which the running position of the transfer belt 2 falls within the integral correction limit range (−I to + I) by, for example, proportional integral control when the power is turned on. By doing so, at the time of image formation, the edge position of the transfer belt 2 is within the detection accuracy guarantee range (−P to + P) of the displacement sensor 7, and the detection accuracy of the running position of the transfer belt 2 can be ensured. . When the travel position of the transfer belt 2 is within the integral correction limit range (−I to + I), the position of the eccentric cam 20 is the sum of the proportional correction amount of the proportional control unit 25 and the integral correction amount held by the integral control unit 26. By calculating from the above, the position of the eccentric cam 20 at the time of image formation operates quickly with respect to the change in the travel position of the transfer belt 2, and vibration of the travel position of the transfer belt 2 can be suppressed. The meandering speed of 2 can be within the specified range (-V to + V).

  Therefore, even if the housing of the belt running device is twisted due to aging, etc., and the drive roller, driven roller, and meandering correction roller are inclined, the belt edge is outside the detection accuracy guarantee range of the sensor that detects the belt position, or the transfer belt It is possible to prevent the meandering speed from exceeding a predetermined range and to form a high-quality image.

It is a block diagram which shows the control part in the belt traveling apparatus which concerns on this invention. It is operation | movement explanatory drawing of the belt traveling apparatus which concerns on this invention. 1 is a schematic configuration diagram illustrating an embodiment of a belt traveling device according to the present invention. It is explanatory drawing of the belt meandering correction | amendment mechanism in the belt traveling apparatus which concerns on this invention. It is explanatory drawing of the belt position detection mechanism in the belt traveling apparatus which concerns on this invention. It is a block diagram which shows the structure of the conventional control part of a belt travel apparatus. It is operation | movement explanatory drawing of the conventional control part of a belt travel apparatus. It is operation | movement explanatory drawing of the conventional control part of a belt travel apparatus. It is a flowchart which shows the control flow of the control part of the belt traveling apparatus which concerns on this invention. 1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus using a belt traveling device according to the present invention. It is explanatory drawing which shows an example of an edge sensor. It is explanatory drawing of the detection guarantee range of a displacement sensor.

Explanation of symbols

1: belt running device, 2: transfer belt, 3: belt position detection mechanism,
4: contact, 5: spindle, 6: contact spring,
7: belt position detecting means (displacement sensor), 8: driving roller, 9: belt driving motor,
10: belt drive motor drive unit, 11: meandering correction roller,
12a to 12b: driven roller, 13: belt meandering correction mechanism,
14: Meander correction motor 15: Meander correction motor drive unit 16: Swing arm
17: Rotating shaft 18: Bearing 19: Swing arm spring
20: Eccentric cam, 21: Eccentric cam position detection sensor, 22: Shield plate,
23: meandering correction control unit, 24: belt position calculation processing unit,
25: proportional control unit, 26: integral control unit, 27: integral correction determination processing unit 30: transfer belt, 31: light emitting unit, 32: light receiving units 41a to 41d: image forming unit, 42a to 42a: photosensitive drum,
43a to 43d: chargers 44a to 44d: transfer units, 45a to 45d: developing units,
46a to 46d: transfer device, 47a to 46b: cleaning device, 48: paper,
49: Paper transfer device, 50: Transfer belt, 51: Fixing device, 52: Cleaning mechanism

Claims (6)

An endless belt stretched around a plurality of rollers;
Drive means for driving any one of the plurality of rollers as a drive roller and driving the belt by rotation of the drive roller;
Any one of the plurality of rollers is a meandering correction roller, and meandering correction means for correcting meandering in the width direction of the belt by adjusting the inclination of the meandering correction roller;
Position detecting means for detecting a position in the width direction of the belt;
A correction control unit for controlling the meandering correction means based on a detection signal from the position detection means,
The correction control unit calculates a first correction amount corresponding to a value proportional to the position in the width direction of the belt based on a signal from the position detection unit, and sets the proportional correction amount;
Means for calculating a second correction amount corresponding to a value obtained by integrating the position in the width direction of the belt, and setting the integral correction amount;
When the determining means for determining whether or not the position in the width direction of the belt is within a predetermined range, when the position in the width direction of the belt is determined to be within the predetermined range, the width direction of the belt wherein the integral correction amount holding, and means for the integrating component correction amount and a third correction amount when the determined position without integration,
When the determination means determines that the position in the width direction of the belt is outside the predetermined range, the meander correction means is controlled based on a value obtained by adding the first correction amount and the second correction amount. ,
When it is determined that the position in the width direction of the belt is within a predetermined range, the meandering correction unit is controlled based on a value obtained by adding the first correction amount and the third correction amount. Belt running device.   In claim 1, when the detection accuracy guarantee range of the position detection means is -P to + P, and the amplitude of the edge position detection signal of the endless belt is Ed, -I> -P + Ed, + I <+ P-Ed, The belt traveling device is characterized in that the predetermined range is represented by -I to + I.   3. The position of the belt in the width direction according to claim 2, wherein the position in the width direction of the belt is within a predetermined range by the determination means when the position in the width direction of the belt is within a range of -I to + I for a predetermined time. It is determined that the belt travel device. A belt traveling device that travels an endless transfer belt;
A plurality of image forming units arranged along the direction of the transfer belt;
In a color image forming apparatus for forming a color image by superimposing and transferring toner images of different colors formed by the plurality of image forming units onto the transfer belt,
The belt traveling device is
An endless belt stretched around a plurality of rollers;
Drive means for driving any one of the plurality of rollers as a drive roller and driving the belt by rotation of the drive roller;
Any one of the plurality of rollers is a meandering correction roller, and meandering correction means for correcting meandering in the width direction of the belt by adjusting the inclination of the meandering correction roller;
Position detecting means for detecting a position in the width direction of the belt;
A correction control unit for controlling the meandering correction means based on a detection signal from the position detection means,
The correction control unit calculates a first correction amount corresponding to a value proportional to the position in the width direction of the belt based on a signal from the position detection unit, and sets the proportional correction amount;
Means for calculating a second correction amount corresponding to a value obtained by integrating the position in the width direction of the belt, and setting the integral correction amount;
When the determining means for determining whether or not the position in the width direction of the belt is within a predetermined range, when the position in the width direction of the belt is determined to be within the predetermined range, the width direction of the belt Means for holding the integral correction amount at the time of the determination without integrating the position, and setting the integral correction amount as a third correction amount;
Determination means for determining whether or not the position in the width direction of the belt is within a predetermined range,
When the determination means determines that the position in the width direction of the belt is outside the predetermined range, the meander correction means is controlled based on a value obtained by adding the first correction amount and the second correction amount. ,
When it is determined that the position in the width direction of the belt is within a predetermined range, the meandering correction unit is controlled based on a value obtained by adding the first correction amount and the third correction amount. Color image forming apparatus.   In claim 4, when the detection accuracy guarantee range of the position detection means is -P to + P, and the amplitude of the edge position detection signal of the endless belt is Ed, -I> -P + Ed, + I <+ P-Ed, The color image forming apparatus, wherein the predetermined range is represented by −I to + I.   6. The position of the belt in the width direction according to claim 5, wherein the position in the width direction of the belt is within a predetermined range by the determination means when the position in the width direction of the belt is within a range of −I to + I for a predetermined time. And a color image forming apparatus.

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