JP4339079B2 - Transfer belt speed control method, transfer belt speed control apparatus, and image forming apparatus using the same - Google Patents

Description

The present invention relates to a transfer belt speed control method, a transfer belt speed control apparatus, and an image forming apparatus using the same.

  Conventionally, in order to control the conveying speed of a belt used in an image forming apparatus such as an image forming apparatus such as a printer, a copying machine, or a facsimile, an encoder disk (also referred to as a code wheel) is mounted on a roller that is slid in contact with the belt. And a structure in which a pulse is generated based on the rotation of the encoder disk using an encoder sensor facing the encoder disk, and the rotation of the roller is feedback-controlled based on this pulse (for example, , See Patent Document 1).

In addition, a technique for accurately matching the rotation center of the encoder disk and the rotation center of the rotation shaft is also known (see, for example, Patent Document 2).
JP 2002-248822 A JP 2001-227990 A

  By the way, in the case of a transfer belt used in an image forming apparatus, if the conveyance speed is not constant, image unevenness occurs. In particular, in the case of an image forming apparatus that forms a color image, if the transfer belt conveyance speed fluctuates, color misregistration occurs. Occurs and the image quality is degraded.

  Therefore, conventionally, a conveyance roller that is driven to rotate by a stepping motor and drives a transfer belt, and a conveyance shaft that has a rotation shaft, and an encoder disk is integrally fixed to the rotation shaft, and the transfer belt is in sliding contact with the outer peripheral surface. A speed control roller, an encoder sensor that faces the encoder disk and cooperates with the encoder disk to detect fluctuations in the transfer belt conveyance speed as fluctuations in the output pulse, and fluctuations in output pulses output from the encoder sensor. There is known a transfer belt speed control device including a feedback control circuit that drives and controls a stepping motor so that the transfer belt conveyance speed is constant.

  FIG. 1 shows this conventional transfer belt speed control apparatus. In FIG. 1, 1 is a transfer belt, 2 is a driving roller, 3 is a tension roller, 5 and 6 are driven rollers, 7 is a photosensitive drum for magenta (M), and 8 is a photosensitive drum for cyan (C). A photosensitive drum for yellow (Y), a photosensitive drum for black (BK), and a photosensitive drum for black (BK). Each photosensitive drum 7 to 10 is exposed by a known means. An electrostatic latent image is formed on 7-10, and toner is supplied by known means. A recording paper 11 is conveyed between the photosensitive drums 7 to 10 and the transfer belt 1, and toner is transferred to the recording paper 11 while the recording paper 11 is being conveyed, so that a color image is formed on the recording paper 11. The

  The drive roller 2 is driven by a drive mechanism. This drive mechanism is mainly composed of, for example, a stepping motor 12, an output gear 13, a timing belt 14, and a transmission gear 15 as a rotational drive source.

  The transfer belt 1 is in sliding contact with a conveyance speed control roller 16. The transport speed control roller 16 is provided between the tension roller 4 and the driven roller 6 on the side close to the driven roller 6.

  The transport speed control roller 16 has rotating shafts 17 and 18 at both ends thereof as shown in an enlarged view in FIG. The rotary shafts 17 and 18 are rotatably supported by bearings 19 and 20. The rotational centers of the rotary shafts 17 and 18 and the center of the virtual circle formed by the outer peripheral surface of the conveyance speed control roller are generally eccentric. The amount of eccentricity is within about 30 microns as a product tolerance.

  One rotating shaft 18 is provided with an encoder disk 21. As shown in FIG. 3, the encoder disk 21 is provided with a large number of slits 22 at equal intervals and radially in the circumferential direction. An encoder sensor 23 faces the rotation region of the slit 22.

  The encoder sensor 23 outputs a pulse based on the rotation of the encoder disk 21, and this output pulse is input to the feedback control circuit 24 shown in FIG. The feedback control circuit 24 counts the number of output pulses input per unit time, compares the counted number with the number of reference pulses, and drives and controls the stepping motor 12 so that the difference becomes zero.

  However, in this conventional transfer belt speed control device, as schematically shown in FIGS. 4 and 5, the rotation center Q2 of the encoder disk 21 coincides with the rotation center Q1 of the rotation shaft 18, If the center Q3 of the imaginary circle formed by the outer peripheral surface 16a of the conveyance speed control roller 16 and the rotation center Q1 of the rotary shaft 18 are eccentric, the inconvenience described below occurs.

  4 and 5, the symbol R1 is the amount of eccentricity between the rotation center Q1 of the rotating shaft 18 and the center Q3 of the imaginary circle of the conveyance speed control roller 16, and the symbol R3 is the imaginary amount of the conveyance speed control roller 3. The radius of the circle is shown, and the eccentricity R1 is exaggerated in FIGS.

  Assuming that the transfer speed of the transfer belt 1 is V and driven at a constant speed, when the transfer speed control roller 16 is at the rotational position shown in FIG. Since the rotation radius is (R3 + R1), the rotation angle θ1 per unit time (1 second) of the encoder disk 21 is as follows.

θ1 = V / (R3 + R1)
Therefore, the arc length X1 ′ of the encoder disk 21 per unit time is given by assuming that the radius of the encoder disk 21 is R2.
X1 ′ = R2 · θ1 = (R2 · V) / (R3 + R1)
On the other hand, when the transport speed control roller 16 is at the rotational position shown in FIG. 5, the rotation radius from the rotation center Q1 to the transfer belt 1 is (R3-R1). ) Per rotation angle θ2 is as follows.

θ2 = V / (R3-R1)
Therefore, the arc length X2 ′ of the encoder disk 21 per unit time is
X2 ′ = R2 · θ2 = (R2 · V) / (R3-R1)
That is, if the conveyance speed V of the transfer belt 1 is constant, the rotation angle of the rotating shaft 18 increases as the rotating radius decreases (the rotating speed of the rotating shaft 18 increases as the rotating radius decreases). The length X2 ′ is larger than the arc length X1 ′.

  Since the encoder disk 21 has slits 22 formed at equal intervals in the circumferential direction thereof, assuming that the transfer speed V of the transfer belt 1 is a constant speed, the transfer speed control roller 16 is at the rotational position shown in FIG. The number of pulses output by the encoder sensor 23 per unit time when the transport speed control roller 16 is at the rotational position shown in FIG. 5 with respect to the number of pulses output by the encoder sensor 23 per unit time. There are more.

  That is, when the transport speed control roller 16 is at the rotational position shown in FIG. 5, the encoder sensor 23 indicates that the transport speed control roller 16 is shown in FIG. 4 even though the transfer belt 1 is driven at a constant speed. When the number of pulses output is larger than the number of pulses that are output when in the rotational position and the transport speed control roller 16 is in the rotational position shown in FIG. 4, the encoder sensor 23 detects the transport speed control roller. 16 outputs a smaller number of pulses than when it is at the rotational position shown in FIG.

  Since the feedback control is performed depending on whether the number of output pulses is larger or smaller than the number of reference pulses, the transfer speed of the transfer belt 1 is increased when the number of pulses output from the encoder sensor 23 is larger than the number of reference pulses. If the number of pulses output from the encoder sensor 23 is smaller than the number of reference pulses, the transfer belt 1 is controlled so that the number of pulses output is reduced. The stepping motor 12 is driven and controlled so that the number of pulses output is increased when it is determined that the transport speed is low.

  Therefore, when the conveyance speed control roller 16 is at the rotational position shown in FIG. 5, the conveyance speed of the transfer belt 1 decreases, and when it is at the rotational position shown in FIG. 4, the conveyance speed of the transfer belt 1 increases. Thus, the feedback control is performed, and the conveyance speed control roller 16 includes a speed fluctuation component associated with its rotational position.

The present invention has been made in view of the above circumstances, and is used for transport speed control when the center of an imaginary circle formed by the outer peripheral surface of the transport speed control roller and the rotation center of the rotary shaft are eccentric. It is an object of the present invention to provide a transfer belt speed control method, a transfer belt speed control apparatus, and an image forming apparatus using the same, which can remove a speed fluctuation component associated with the rotational position of a roller as much as possible.

According to a first aspect of the present invention, there is provided a transfer belt speed control method, comprising: an encoder disk integrally provided on a rotation shaft of a transfer speed control roller; In what is detected as a change in the output pulse by using an encoder sensor facing and feedback-controlled so that the conveyance speed of the transfer belt becomes constant,
The transfer belt is located at a position eccentric from the rotation center of the rotation axis of the conveyance speed control roller and coincides with the center of an imaginary circle formed by the outer peripheral surface of the conveyance speed control roller. The encoder sensor is positioned on the side in sliding contact with the outer peripheral surface.

The transfer belt speed control device according to claim 2 has a drive roller that is driven to rotate by a stepping motor and drives the transfer belt, a rotary shaft, and an encoder disk is integrally fixed to the rotary shaft. A transfer speed control roller that is in sliding contact with the transfer belt, an encoder sensor that faces the encoder disk and detects a change in the transfer speed of the transfer belt as a change in an output pulse in cooperation with the encoder disk; A feedback control circuit that drives and controls the stepping motor so that the transfer belt conveyance speed is constant based on fluctuations in output pulses output from the encoder sensor,
The rotation center of the encoder disk exists at a position deviated from the rotation center of the rotation shaft of the transport speed control roller and coincides with the center of a virtual circle formed by the outer peripheral surface of the transport speed control roller, Is characterized in that the encoder sensor is positioned on the side in sliding contact with the outer peripheral surface.

  According to a third aspect of the present invention, in the transfer belt speed control device, the rotating shaft is supported by a bearing, and the encoder sensor is fixed to the bearing.

  5. The transfer belt speed control device according to claim 4, wherein a radius of the encoder disk is substantially coincident with a radius of the virtual circle, and the encoder sensor detects rotation of the encoder disk on an outer peripheral side of the encoder disk. It is characterized by.

  According to a fifth aspect of the present invention, the transfer belt speed control device according to the third aspect is used.

  According to the present invention, when the center of the imaginary circle formed by the outer peripheral surface of the conveyance speed control roller and the rotation center of the rotation shaft are decentered, the speed fluctuation component accompanying the rotation position of the conveyance speed control roller is reduced. It can be eliminated as much as possible.

  Hereinafter, a transfer belt speed control method, a transfer belt speed control apparatus, an image forming apparatus using the transfer belt speed control apparatus, and a conveyance speed control roller assembly according to the present invention will be described with reference to the drawings.

  FIG. 6 is a schematic view of a transfer belt speed control apparatus according to the present invention. The general configuration of the transfer belt speed control device is the same as that of the conventional transfer belt speed control device shown in FIG. 1, and therefore, the same components are denoted by the same reference numerals and detailed description thereof is omitted. The different parts will be mainly described below.

  Here, the encoder sensor 23 is composed of a transmissive photosensor, and is fixed to the bearing 20 as shown in an enlarged view in FIG. 7, and the transfer belt 1 is in sliding contact with the outer peripheral surface 16a of the conveyance speed control roller 16. Is provided. Toner speed preventing cover members 25, 25 are positioned and fixed to the transport speed control roller 16.

  The toner entry preventing cover member 25 includes a disk-like cover portion 25a for preventing the toner from entering the bearing 25 and a positioning cylinder portion 25b for positioning the encoder disk 21 in the axial direction. The encoder disk 21 is fixed to the end surface 25c of the positioning cylinder portion 25b by, for example, adhesion.

  As shown in an enlarged view in FIG. 8, the encoder disk 21 has a through hole 21a at the center thereof, and the rotation center Q2 of the encoder disk 21 is determined by surrounding the through hole 21a. A reference mark 26 for this purpose is formed.

  As shown in FIGS. 9 and 10 in an enlarged and schematic manner, the encoder disk 21 is arranged so that the rotation center Q2 coincides with the center Q3 of the virtual circle formed by the outer peripheral surface 16a of the conveyance speed control roller 16. It is attached.

  The alignment between the virtual circle center Q3 and the rotation center Q2 of the conveyance speed control roller 16 is performed using, for example, an alignment jig 27 shown in FIG. The positioning jig 27 is made of a surface plate having a V-shaped groove 28 shown in FIG.

  A reference transport speed control roller 16 'is placed on the surface plate. The axial end face of this reference transport speed control roller 16 'is imaged by an imaging camera 29 comprising a lens system 29a and a two-dimensional solid-state imaging device 29b shown in FIG. Then, the shape of the virtual circle on the outer peripheral surface 16a ′ of the reference transport speed control roller 16 ′ is analyzed, and the imaging camera 29 is moved so that the center Q3 of the virtual circle is located on the optical axis O of the imaging camera 29. Adjust the position. As a result, as shown in FIG. 13, the center Q3 of the reference transport speed control roller 16 'is positioned at the center O' on the monitor screen 30 of the imaging camera 29.

  Next, the conveyance speed control roller 16 in which the toner intrusion prevention cover member 25 and the encoder disk 21 are inserted through the rotary shaft 18 is placed on the alignment jig 27. Then, as shown in FIG. 14, the reference mark 26 is displayed on the monitor screen 30 of the imaging camera 29. The position of the encoder disk 21 is adjusted so that each reference mark 26 is equidistant from the center O ′ on the monitor screen 30. When each reference mark 26 is located at an equal distance from the center O 'on the screen, the encoder disk 21 is bonded and fixed to the end face 25c of the positioning cylinder portion 25b.

  Thereby, the center Q3 of the imaginary circle of the outer peripheral surface 16a of the conveyance speed control roller 16 and the rotation center Q2 of the encoder disk 21 coincide with each other to constitute a conveyance speed control roller assembly.

  Next, the reason why the encoder sensor 23 is provided on the outer peripheral surface 16a side in which the transfer belt 1 is in sliding contact will be described with reference to FIGS.

  9 and 10, the symbol R <b> 1 is between the rotation center Q <b> 1 of the rotation shaft 18 and the center Q <b> 3 of the virtual circle formed by the outer peripheral surface 16 a of the conveyance speed control roller 16, as in FIGS. 4 and 5. , R2 is the radius of the encoder disk 21, R3 is the radius of the virtual circle formed by the outer peripheral surface 16a of the transport speed control roller 16, and X1 is the rotational position of the transport speed control roller 16 shown in FIG. Is the arc length of the encoder disk 21 per unit time when the encoder disk 21 is rotated, and symbol X2 indicates that the encoder disk 21 rotates when the transport speed control roller 16 is at the rotational position shown in FIG. The arc length of the encoder disk 21 per unit time and the symbol θ1 when the transfer speed control roller 16 is in the rotational position shown in FIG. The rotation angle per unit time when the disk 21 is rotated, the symbol θ2 per unit time when the encoder disk 21 is rotated when the transport speed control roller 16 is at the rotation position shown in FIG. Is the rotation angle of the encoder disk 21.

As indicated by the solid line, when the encoder sensor 23 is provided on the side where the transfer belt 1 is in sliding contact, the transfer belt 1 is conveyed at the conveyance speed V.
When the transport speed control roller 16 is at the rotational position shown in FIG. 9, the rotational radius (moving radius) from the rotational center Q1 of the rotational shaft 18 to the transfer belt 1 is (R3 + R1). The rotation angle θ1 per time (1 second) is the same as described in FIG.
θ1 = V / (R3 + R1).

  On the other hand, the turning radius when one point G on the arc of the encoder disk 21 crosses the encoder sensor 23 is (R2 + R1).

Therefore, the arc length X1 of the encoder disk 21 per unit time is
X1 = (R2 + R1) · θ1 = (R2 + R1) · V / (R3 + R1)
On the other hand, when the conveyance speed control roller 16 is at the rotational position shown in FIG.
Since the rotation radius (moving radius) from the rotation center Q1 of the rotation shaft 18 to the transfer belt 1 is (R3-R1), the rotation angle θ2 per unit time (1 second) of the encoder disk 21 is shown in FIG. As shown,
θ2 = V / (R3−R1).

  On the other hand, the turning radius when the rotation G on the arc of the encoder disk 21 crosses the encoder sensor 23 is (R2-R1).

Therefore, the arc length X2 of the encoder disk 21 per unit time (1 second) of the encoder disk 23 is
X2 = (R2-R1) .theta.2 = (R2-R1) .V / (R3-R1)
On the other hand, as shown in FIGS. 15 and 16, when the encoder sensor 23 is provided on the side far from the outer peripheral surface 16 a with which the transfer belt 1 is slidably contacted with the rotary shaft 18 interposed therebetween, The arc length Y1 when the roller 16 is at the rotational position shown in FIG.
Y1 = (R2−R1) · θ1 = (R2−R1) · V / (R3 + R1).

On the other hand, the arc length Y2 when the transport speed control roller 16 is at the rotational position shown in FIG.
Y2 = (R2 + R1) · θ2 = (R2 + R1) · V / (R3−R1).

Here, the difference between the rotation radius R3 and the radius R2 of the encoder disk 21 is α, that is,
Let α = R3−R2.

If R2 is eliminated from the formulas of X1 and X2,
X1 = {1-α / (R3 + R1)} · V
X2 = {1-α / (R3-R1)} · V
From the above equations, when the difference between the arc length X1 and the arc length X2 is obtained,
X2−X1 = −2R1 · α · V / {(R3 + 1) · (R3-1)}
On the other hand, if R2 is deleted from the expressions Y1 and Y2,
Y1 = (R3-R1-α) · V / (R3 + R1)
Y2 = (R3 + R1-α) · V / (R3-R1)
From the above equations, when the difference between the arc length Y1 and the arc length Y2 is obtained,
Y2−Y1 = − {4R3 · R1 · V-2R1 · α · V} / {(R3 + 1) · (R3-1)}
As is apparent from this equation, when the encoder sensor 23 is provided on the side farther from the outer peripheral surface 16a with which the transfer belt 1 is in sliding contact with the rotation shaft 18, the numerator of the difference between the arc length Y1 and the arc length Y2 is obtained. The term “4R3 · R1 · V” appears in the term.

  Therefore, when the encoder sensor 23 is provided on the side where the transfer belt 1 is in sliding contact with the outer peripheral surface 16a of the conveyance speed control roller 16, the speed fluctuation component associated with the rotational position of the conveyance speed control roller 16 is 2R1 · α · V / {(R3 + 1) · (R3-1)}, when the encoder sensor 23 is provided on the side farther from the outer peripheral surface 16a with which the transfer belt 1 is slidably contacted with the rotary shaft 18 interposed therebetween, The maximum speed fluctuation component associated with the rotational position of the speed control roller 16 is {4R3 · R1 · V-2R1 · α · V} / {(R3 + 1) · (R3-1)}. Is provided on the side slidably contacting the outer peripheral surface 16a of the conveyance speed control roller 16, the encoder sensor 23 is located on the side farther from the outer peripheral surface 16a side on which the transfer belt 1 is slidably contacted with the rotary shaft 18 in between. The speed fluctuation component associated with the rotational position of the transport speed control roller 16 is smaller than that provided.

  This will be explained in terms of a physical phenomenon. When the encoder sensor 23 is provided on the side that is in sliding contact with the outer peripheral surface 16a of the conveyance speed control roller 16, the transfer belt control roller 16 is in the rotational position shown in FIG. When the conveyance speed V of 1 is constant, the rotation radius (R3 + R1) of the conveyance speed control roller 16 is larger than the rotation radius (R3-R1) at the rotation position shown in FIG. Although the rotation speed of the roller 16 decreases, the expected rotation angle θ1 ′ of the encoder disk 21 becomes larger than the actual rotation angle θ1, so that even if the rotation speed decreases, the number of pulses generated increases, while When the speed control roller 16 is at the rotational position shown in FIG. 10, the rotational radius (R3-R1) of the transport speed control roller 16 is at the rotational position shown in FIG. Is smaller than the rotation radius (R3 + R1) at that time, the rotation speed of the conveyance speed control roller 16 is increased, but the expected rotation angle θ2 ′ of the encoder disk 21 is smaller than the actual rotation angle θ2, so that the conveyance speed control is performed. Even if the rotational speed of the roller 16 is increased, the number of pulses generated is reduced, and the influence of the shaft runout of the encoder disk 21 on the rotary shaft 18 is cancelled.

  On the other hand, when the encoder sensor 23 is provided on the side far from the outer peripheral surface 16a with which the transfer belt 1 is slidably contacted with the rotation shaft 18, the conveyance speed control roller 16 is at the rotational position shown in FIG. When the conveyance speed V of the transfer belt 1 is constant, the rotation speed (R3 + R1) of the conveyance speed control roller 16 is larger than the rotation radius (R3-R1) at the rotation position shown in FIG. As the rotation speed of the control roller 16 decreases, the expected rotation angle θ1 ′ of the encoder disk 21 also becomes smaller than the actual rotation angle θ1, so that the number of pulses generated as the rotation speed decreases decreases. When the transport speed control roller 16 is in the rotational position shown in FIG. 16, the transport speed control roller 16 rotates halfway when the transport speed V of the transfer belt 1 is constant. Since the diameter (R3-R1) is smaller than the rotation radius (R3 + R1) at the rotation position shown in FIG. 15, the rotation speed of the conveyance speed control roller 16 is increased and the expected rotation angle θ2 of the encoder disk 21 is increased. Since 'also becomes larger than the actual rotation angle θ2, the number of pulses generated increases as the rotational speed increases, and the influence of the shaft runout of the encoder disk 21 on the rotary shaft 18 is amplified.

  Therefore, when the center Q3 of the imaginary circle formed by the outer peripheral surface 16a of the transport speed control roller 16 exists at a position eccentric from the rotation center Q1 of the rotation shaft 18 of the transport speed control roller 16, the rotation center of the encoder disk 21 It is desirable to make Q2 coincide with the center Q3 of the virtual circle and to position the encoder sensor 23 on the side where the transfer belt 1 is in sliding contact with the outer peripheral surface 16a.

  Next, the reason why it is preferable to make the rotation center Q2 of the encoder disk 21 coincide with the rotation center Q3 of the transport speed control roller 16 than to make the rotation center Q2 of the encoder disk 21 coincide with the rotation center Q1 of the rotary shaft 18. Will be described.

When the rotation center Q2 of the encoder disk 21 is made coincident with the rotation center Q1 of the rotary shaft 18, as shown in FIGS. 4 and 5, the difference between the arc length X1 ′ and the arc length X2 ′, X2′−X1 ′ is
X2'-X1 '=
= {2R3 · R1 · V-2R1 · α · V} / {(R3 + R1) · (R3-R1)}
Therefore, the rotation center Q2 of the encoder disk 21 is made to coincide with the center Q3 of the virtual circle formed by the outer peripheral surface 16a of the conveying speed control roller 16, and the encoder sensor 23 is moved to the outer peripheral surface of the conveying speed control roller 16 by the transfer belt 1. The speed variation associated with the rotational position of the transport speed control roller 16 is greater when the rotation center Q2 of the encoder disk 21 is made to coincide with the rotation center Q1 of the rotary shaft 18 when it is provided on the side that is in sliding contact with 16a. Ingredients are small.

  Here, when the encoder sensor 23 is provided on the side in sliding contact with the outer peripheral surface 16a of the transport speed control roller 16, the radius R2 of the encoder disk 21 is rotated by the virtual circle formed by the outer peripheral surface 16a of the transport speed control roller 16. If it is equal to the radius R3, that is, if the difference α between the rotation radius R3 and the radius R2 of the encoder disk 21 is “0”, the difference between the arc length X2 and the arc length X1 is 0, and the eccentric amount R1 Regardless, since the speed fluctuation component accompanying the rotation of the conveyance speed control roller 16 is eliminated, the radius R2 of the encoder disk 21 is preferably set to the radius R3 of the virtual circle, and the encoder sensor 23 is located on the outer peripheral side of the encoder disk 21. It is desirable to have a configuration that detects the rotation of the encoder disk 21. The speed control device of the transfer belt 1 having this configuration is particularly preferably used for a high-precision image forming apparatus that requires a clear color image.

It is a figure which shows schematic structure of the conventional conveyance speed control apparatus of a transfer belt. It is a side view which shows the state which made the bearing support the conventional roller assembly for conveyance speed control. It is a top view which shows an example of the encoder disk shown in FIG. It is a figure which shows a state when the rotation radius with respect to the transfer belt of the conventional conveyance speed control roller is in the maximum position. It is a figure which shows a state when the rotation radius with respect to the transfer belt of the conventional conveyance speed control roller is in the minimum position. It is a figure which shows schematic structure of the conveyance speed control apparatus concerning this invention. It is a side view which shows the state which made the bearing support the roller assembly for conveyance speed control concerning this invention. It is a top view of the encoder disk shown in FIG. FIG. 6 is a diagram illustrating a state when the rotation radius of the conveyance speed control roller according to the present invention is at a maximum position with respect to the transfer belt, and is a schematic diagram illustrating a state where the encoder sensor is positioned on the sliding contact side of the transfer belt. It is. FIG. 6 is a diagram illustrating a state when the rotation speed of the conveyance speed control roller according to the present invention is at a minimum position with respect to the transfer belt, and is a schematic diagram illustrating a state where the encoder sensor is positioned on the sliding contact side of the transfer belt. It is. It is a figure which shows the state which mounts the roller for reference | standard conveyance speed control on the positioning jig, and images with an imaging camera. It is the figure which looked at the state which mounted the reference | standard conveyance speed control roller in the alignment jig from the imaging camera side. It is a figure which shows the external appearance of the roller for the reference | standard conveyance speed control displayed on the screen of the monitor of an imaging camera. It is a figure which shows the external appearance shape of the roller for conveyance speed control displayed on the monitor screen of an imaging camera, Comprising: It is a figure which shows the state in which the encoder disk penetrated by the rotating shaft is displayed. It is a figure which shows a state when the rotation radius of the roller for conveyance speed control concerning this invention exists in the maximum position with respect to a transfer belt, Comprising: The encoder sensor was located on the opposite side with respect to the sliding contact side of a transfer belt It is a schematic diagram which shows a state. It is a figure which shows a state when the rotation radius of the roller for conveyance speed control concerning this invention exists in the minimum position with respect to a transfer belt, Comprising: The encoder sensor was located on the opposite side with respect to the sliding contact side of a transfer belt It is a schematic diagram which shows a state.

Explanation of symbols

1 ... transfer belt 2 ... drive roller 2
DESCRIPTION OF SYMBOLS 12 ... Stepping motor 16 ... Roller 16a for conveyance speed control ... Outer peripheral surface 18 ... Rotating shaft 21 ... Encoder disk 23 ... Encoder sensor 24 ... Feedback control circuit 24
Q1, Q2 ... Center of rotation Q3 ... Center

Claims (5)

Changes in the conveyance speed of the transfer belt driven by the drive roller are detected as fluctuations in the output pulse by using an encoder disk integrated with the rotation shaft of the conveyance speed control roller and an encoder sensor facing the encoder disk. In the transfer belt speed control method for feedback control so that the transfer belt conveyance speed is constant,
The transfer belt is located at a position eccentric from the rotation center of the rotation axis of the conveyance speed control roller and coincides with the center of an imaginary circle formed by the outer peripheral surface of the conveyance speed control roller. A method for controlling the speed of a transfer belt, wherein the encoder sensor is positioned on a side in sliding contact with the outer peripheral surface. A drive roller that is driven to rotate by a stepping motor and drives a transfer belt, and a conveyance speed control roller that has a rotary shaft, the encoder disk is fixed to the rotary shaft integrally, and the transfer belt is slidably contacted with the outer peripheral surface An encoder sensor that faces the encoder disk and detects fluctuations in the conveying speed of the transfer belt as fluctuations in output pulses in cooperation with the encoder disk, and based on fluctuations in output pulses output from the encoder sensor, In a transfer belt speed control device comprising a feedback control circuit that drives and controls the stepping motor so that the transfer speed of the transfer belt is constant.
The rotation center of the encoder disk exists at a position deviated from the rotation center of the rotation shaft of the transport speed control roller and coincides with the center of a virtual circle formed by the outer peripheral surface of the transport speed control roller, A speed control device for a transfer belt, wherein the encoder sensor is positioned on a side in sliding contact with the outer peripheral surface.   The transfer belt speed control device according to claim 2, wherein the rotation shaft is supported by a bearing, and the encoder sensor is fixed to the bearing.   The radius of the encoder disk is substantially matched with the radius of the virtual circle, and the encoder sensor detects the rotation of the encoder disk on the outer peripheral side of the encoder disk. Transfer belt speed control device.   An image forming apparatus using the speed control device for a transfer belt according to claim 3.

Images