JP2005300868A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the power consumption of a motor and the operating noise of the motor, in an image forming apparatus which includes a plurality of image carriers on the surface of which toner images are formed, an intermediate transfer body to which the toner images formed on the image carriers are transferred, carrier motors for rotating the image carriers, and a drive motor for rotating the intermediate transfer body, and which obtains a recorded image by transferring the toner images transferred to the intermediate transfer body onto a recording medium. <P>SOLUTION: At least one of image motors M1, M2 and the drive motor DM is composed of a DC brush-less motor. In the course of rising down the DC brush-less motor, the input of a command clock signal to the DC brush-less motor is stopped. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus for transferring a toner image formed on an image carrier to an intermediate transfer member, and transferring the toner image on the intermediate transfer member to a recording medium, and recording the toner image on the image carrier. The present invention relates to an image forming apparatus of a type that directly transfers to a recording medium that is carried and conveyed by a medium carrier.

  An image forming apparatus of the above type configured as a copying machine, a printer, a facsimile, or a multifunction machine having at least two of these functions is well known (see, for example, Patent Document 1). The former type of image forming apparatus that transfers a toner image on an image carrier to a recording medium via an intermediate transfer body is called an intermediate transfer type image forming apparatus, and directly records the toner image on the image carrier. The latter type of image forming apparatus that transfers to a medium is also referred to as a direct transfer type image forming apparatus. In any type of image forming apparatus, the image carrier is driven to rotate by a carrier motor, and the intermediate transfer member and the recording medium carrier are driven to rotate by a drive motor.

  Since the image carrier and the intermediate transfer member rotate while being in contact with each other, if the surface linear velocity of the image carrier and the intermediate transfer member is different, the surface of the image carrier and the surface of the intermediate transfer member are rubbed with each other. , Its wear is promoted. Therefore, conventionally, a stepping motor has been used as a carrier motor for rotationally driving the image carrier and a drive motor for rotationally driving the intermediate transfer member, respectively, and the number of input pulses is controlled so that the surface of the image carrier is intermediate The linear velocity on the surface of the transfer body was made to coincide. The same applies to an image forming apparatus of a direct transfer type using a recording medium carrier that rotates while contacting the image carrier instead of the intermediate transfer member.

  However, the stepping motor consumes a large amount of power and generates a large operating noise. Therefore, if a DC brushless motor is used as the carrier motor that rotationally drives the image carrier and the drive motor that rotationally drives the intermediate transfer member or the recording medium carrier, the occurrence of the above-described problems can be suppressed.

  However, conventionally, it is difficult to correctly control the rotational speed of the DC brushless motor when the DC brushless motor is started up and down. Therefore, when a DC brushless motor is used as the carrier motor and the drive motor, At the time of falling, there is a large difference in the surface speed between the image carrier and the intermediate transfer member, or between the image carrier and the recording medium carrier, which causes significant friction between them and shortens the service life. It was done. For this reason, conventionally, a stepping motor is usually used as the carrier motor and the drive motor. However, this has inevitably suffered from the disadvantage that the power consumption and the operating noise increase.

JP 2002-311672 A (page 6-7, FIG. 1)

  The present invention has been made on the basis of the above-described novel recognition. The object of the present invention is to achieve the above-described conventional technology even when a DC brushless motor is used as at least one of a carrier motor and a drive motor. An object of the present invention is to provide an image forming apparatus capable of effectively suppressing the above disadvantages.

  In order to achieve the above object, the present invention provides at least one image carrier on which a toner image is formed, an intermediate transfer member onto which the toner image formed on the image carrier is transferred, and rotating the image carrier. In the image forming apparatus, which has a driving motor for driving and a driving motor for rotating the intermediate transfer body, and transfers a toner image transferred to the intermediate transfer body to a recording medium to obtain a recorded image, the carrier At least one of the body motor and the drive motor is composed of a DC brushless motor, and the DC brushless motor is rotationally controlled by a command clock signal having a gradually increasing number of clocks when starting up, and is substantially constant during steady rotation. The rotation is controlled by the command clock signal of the number of clocks, and at the time of falling, the rotation is controlled by the command clock signal of the gradually decreasing clock number, In the course of the fall, it proposes an image forming apparatus, wherein the input of the command clock signal to the DC brushless motor is stopped (claim 1).

  Similarly, in order to achieve the above-mentioned object, the present invention carries at least one image carrier on which a toner image is formed and a recording medium carrying and transporting a recording medium onto which the toner image formed on the image carrier is transferred. In an image forming apparatus having a medium carrier, a carrier motor that rotationally drives the image carrier, and a drive motor that rotationally drives the recording medium carrier, at least one of the carrier motor and the drive motor The DC brushless motor is controlled by a command clock signal having a gradually increasing number of clocks at the time of startup, and is controlled by a command clock signal having a substantially constant number of clocks during steady rotation. During the fall, the rotation is controlled by a command clock signal with a gradually decreasing number of clocks, and during the fall, Input command clock signal to the DC brushless motor is proposed an image forming apparatus characterized by being stopped (claim 2).

  Further, in order to achieve the above object, the present invention provides at least one image carrier on which a toner image is formed, an intermediate transfer member onto which the toner image formed on the image carrier is transferred, and the image carrier. In the image forming apparatus, which has a carrier motor that rotates and a drive motor that rotates the intermediate transfer member, and obtains a recorded image by transferring the toner image transferred to the intermediate transfer member to a recording medium. At least one of the carrier motor and the drive motor is constituted by a DC brushless motor, and the DC brushless motor is controlled to rotate by a command clock signal having a gradually increasing number of clocks at the time of starting up, and substantially at the time of steady rotation. The rotation is controlled by a command clock signal with a fixed number of clocks, and at the fall, the rotation is controlled by a command clock signal with a gradually decreasing clock number. After completion the fall, carrier motor and the drive motor is proposed an image forming apparatus characterized by being reversed (claim 3).

  In order to achieve the above object, according to the present invention, at least one image carrier on which a toner image is formed, and a recording medium on which the toner image formed on the image carrier is transferred and carried. In an image forming apparatus having a medium carrier, a carrier motor that rotationally drives the image carrier, and a drive motor that rotationally drives the recording medium carrier, at least one of the carrier motor and the drive motor The DC brushless motor is controlled by a command clock signal having a gradually increasing number of clocks when the DC brushless motor is started up, and is controlled by a command clock signal having a substantially constant number of clocks during steady rotation. At the time of falling, the rotation is controlled by a command clock signal having a gradually decreasing number of clocks. Motor proposes an image forming apparatus characterized by being reversed (claim 4).

  Further, in the image forming apparatus according to claim 3 or 4, the input of the command clock signal to the DC brushless motor is stopped before the DC brushless motor stops the reverse rotation operation. (Claim 5).

  According to the present invention, since at least one of the carrier motor and the drive motor is composed of a DC brushless motor, the power consumption can be reduced, and the generation of operating noise can be suppressed.

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

  FIG. 1 is a schematic cross-sectional view showing an example of an intermediate transfer type image forming apparatus. In a main body 1, four image carriers 2Y, 2C, 2M, 2BK made of a drum-shaped photosensitive member and a support are provided. An intermediate transfer member 3 composed of an endless belt wound around rollers 4, 5 and 6 is disposed. Each image carrier 2Y to 2BK is rotationally driven in the clockwise direction in FIG. 1 by a carrier motor, which will be described later, with its surface abutting against the surface of the intermediate transfer member 3, and the intermediate transfer member 3 is also driven by a drive motor, which will be described later. It is rotationally driven in the direction of arrow A. The outer diameters of the plurality of image carriers 2Y to 2BK are all set equal.

  The configuration in which a toner image is formed on each image carrier 2Y, 2C, 2M, 2BK and the toner image is transferred to the intermediate transfer member 3 is substantially the same except that the color of the toner image is different. Therefore, only a configuration in which a toner image is formed on one of the image carriers 2Y and the toner image is transferred to the intermediate transfer member 3 will be described.

  An image forming means for forming a toner image on the surface of the image carrier 2Y is provided around the image carrier 2Y. When the image carrier 2Y is driven to rotate clockwise in FIG. The image carrier 2Y is charged to a predetermined polarity by a charging device including a charging roller 7 to which a voltage is applied. The charged image carrier 2Y is irradiated with a light-modulated laser beam L emitted from the optical writing device 8, thereby forming an electrostatic latent image on the image carrier 2Y. This electrostatic latent image is visualized as a yellow toner image by the developing device 9. Thus, a toner image is formed on the surface of the image carrier 2Y.

  A primary transfer device composed of a transfer roller 10 is disposed on the opposite side of the intermediate transfer body 3 from the image carrier 2Y, and a transfer voltage is applied to the transfer roller 10 to form the image on the image carrier 2Y. The toner image is transferred onto the intermediate transfer member 3 that rotates in the direction of arrow A. The transfer residual toner adhering to the image carrier 2Y after the toner image transfer is removed by the cleaning device 11. The cleaning device 11 has a cleaning blade 11A that presses against the surface of the image carrier 2Y, and the cleaning blade 11A scrapes off transfer residual toner to clean the surface of the image carrier.

  In the same manner as described above, a cyan toner image, a magenta toner image, and a black toner image are respectively formed on the image carriers 2C, 2M, and 2BK shown in FIG. 1, and these toner images are transferred to the yellow toner image. Then, the toner images are sequentially transferred onto the intermediate transfer body 3, and a composite toner image is formed on the intermediate transfer body 3. The transfer residual toner on each of the image carriers 2C, 2M, 2BK after the toner image transfer is removed by the cleaning device is the same as in the case of the first image carrier 2Y.

  On the other hand, a paper feed cassette 12 containing a recording medium P made of, for example, transfer paper or a resin sheet and a paper feed device 14 having a paper feed roller 13 are arranged at the lower part in the image forming apparatus main body 1. The uppermost recording medium P is sent out in the direction of arrow B by the rotation of the roller 13. The sent recording medium is transferred between a portion of the intermediate transfer member 3 wound around the support roller 4 at a predetermined timing by the registration roller pair 15 and a secondary transfer device including the transfer roller 16 placed on the support roller 4. To be sent to. At this time, a predetermined transfer voltage is applied to the transfer roller 16, whereby the composite toner image on the intermediate transfer body 3 is transferred to the recording medium P.

  The recording medium P to which the composite toner image has been transferred is further conveyed upward and passes between the fixing roller 18 and the pressure roller 19 of the fixing device 17. At this time, the toner image on the recording medium is fixed by the action of heat and pressure. Is done. The recording medium that has passed through the fixing device 17 is discharged by the paper discharge roller pair 20 to the paper discharge unit 21 at the top of the image forming apparatus main body 1. Further, the transfer residual toner adhering to the intermediate transfer body 3 after the toner image transfer is removed by the cleaning device 22. The cleaning device 22 shown here also has a cleaning blade 22 </ b> A that presses against the surface of the intermediate transfer body 3 and scrapes off transfer residual toner on the intermediate transfer body 3.

  In the intermediate transfer type image forming apparatus shown in FIG. 1, toner images of different colors are formed on a plurality of image carriers, and the toner images are transferred onto the surface of the intermediate transfer member 3 in an overlapping manner. A synthetic toner image is formed on the intermediate transfer body 3 and transferred to a recording medium. However, the image has only one image carrier and different colors on the surface of the image carrier. Toner images, for example, a yellow toner image, a cyan toner image, a magenta toner image, and a black toner image, are sequentially formed, and the respective toner images are transferred onto the intermediate transfer member and transferred onto the intermediate transfer member. The present invention can also be applied to an intermediate transfer type image forming apparatus configured to form an image and transfer the toner image onto a recording medium. In this case, only one image carrier is used.

  As described above, an intermediate transfer type image forming apparatus as an object of the present invention includes at least one image carrier on which a toner image is formed, and an intermediate transfer member on which the toner image formed on the image carrier is transferred. The toner image transferred to the intermediate transfer member is transferred to a recording medium to obtain a recorded image.

  On the other hand, FIG. 2 shows an example of a direct transfer type image forming apparatus. This image forming apparatus also has a plurality of image carriers 2Y, 2C, 2M, and 2BK configured as drum-shaped photoreceptors, and is wound around support rollers 4, 5, and 6 so as to face these image carriers. A recording medium carrier 3A composed of an endless belt that is hung is disposed. The outer diameters of the plurality of image carriers 2Y to 2BK are all set equal, and each of the image carriers 2Y to 2BK is driven to rotate in the clockwise direction in FIG. 2, and the recording medium carrier 3A is also in contact with these image carriers. However, it is rotationally driven in the direction of arrow A.

  A yellow toner image, a cyan toner image, a magenta toner image, and a black toner image are formed on the respective image carriers 2Y to 2BK in exactly the same manner as in the image forming apparatus shown in FIG. On the other hand, the recording medium P sent out from the paper feeding device 14 sequentially passes through the portions of the image carriers 2Y to 2BK while being supported on the recording medium carrier 3A, and at this time, formed on each image carrier. The transferred toner images are sequentially transferred onto the recording medium P. The synthesized toner image transferred to the recording medium P in this way is fixed to the recording medium by the fixing device 17. The recording medium P that has passed through the fixing device 17 is discharged onto the paper discharge unit 21. Further, the toner and paper dust adhering to the surface of the recording medium carrier 3 </ b> A are scraped and removed by the cleaning blade 22 </ b> A of the cleaning device 22.

  As described above, the direct transfer type image forming apparatus shown in FIG. 2 has the recording medium carrier 3A, and supports each image carrier 2Y while carrying and transporting the recording medium on the recording medium carrier 3A. The toner images on 2BK are transferred to the recording medium P. On the other hand, the intermediate transfer type image forming apparatus shown in FIG. 1 transfers the toner images formed on the image carriers 2Y to 2BK to the intermediate transfer body 3, and records the toner images on the intermediate transfer body. It is configured to transfer to the medium P. These are the only basic differences between the two. Each part in FIG. 2 corresponding to each part shown in FIG. 1 is denoted by the same reference numeral as that shown in FIG.

  Also, as a direct transfer type image forming apparatus, a recording medium in which toner images of different colors are sequentially formed on one image carrier, and each toner image is carried on a recording medium carrier and conveyed. An image forming apparatus of a type that sequentially superimposes and transfers is well known, and the present invention can also be applied to such an image forming apparatus. Further, a direct transfer type image forming apparatus that forms a single color toner image on one image carrier and transfers the toner image to a recording medium carried by the recording medium carrier to obtain a single color image is also used. The present invention can be applied.

  As described above, the direct transfer type image forming apparatus targeted by the present invention includes at least one image carrier on which a toner image is formed, and a recording medium on which the toner image formed on the image carrier is transferred. And a recording medium carrier that carries and conveys.

  Hereinafter, an intermediate transfer type image forming apparatus will be mainly described. However, each configuration according to the present invention can also be applied to a direct transfer type image forming apparatus.

  FIG. 3 is an explanatory diagram showing a drive system that rotationally drives the image carriers 2Y to 2BK and the intermediate transfer member 3 of the intermediate transfer type image forming apparatus shown in FIG. As can be seen from this figure, the intermediate transfer type image forming apparatus has carrier motors M1 and M2 for rotationally driving the image carriers 2Y to 2BK and a drive motor DM for rotationally driving the intermediate transfer body 3. Yes. In the example shown here, a carrier motor M1 that rotationally drives the image carriers 2Y, 2C, and 2M on which chromatic toner images are formed, and a carrier that rotationally drives the image carrier 2BK on which black toner images are formed. It has a motor M2. When it is necessary to identify these two carrier motors M1 and M2, the former will be referred to as a first carrier motor M1 and the latter as a second carrier motor M2.

  The direct transfer type image forming apparatus also includes a carrier motor that rotationally drives each of the image carriers 2Y to 2BK and a drive motor that rotationally drives the recording medium carrier 3A. These are configured in the same manner as the intermediate transfer type motors M1, M2, and DM described below, and operate in the same manner to rotationally drive the image carriers 2Y to 2BK and the recording medium carrier 3A.

  As shown in FIG. 3, gears 23Y, 23C, 23M, and 23BK arranged concentrically with the respective image carriers are integrally connected to the image carriers 2Y to 2BK, and these gears are identical to each other. It has a radius and the number of teeth is all set equal.

  Further, the intermediate gear 24 meshes with the gear 23Y connected to the image carrier 2Y and the gear 23C connected to the image carrier 2C, and both gears 23Y and 23C are driven and connected via the intermediate gear 24. Has been. The output gear 25 fixed to the output shaft of the first carrier motor M1 meshes with a gear 23C connected to the image carrier 2C and a gear 23M connected to the image carrier 2M. The output gear 26 fixed to the output shaft of the second carrier motor M2 meshes with a gear 23BK connected to the image carrier 2BK.

  When the first carrier motor M1 operates, the output gear 25 rotates counterclockwise in FIG. Therefore, both gears 23C and 23M engaged with the output gear 25 rotate in the clockwise direction in FIG. 3, so that the image carriers 2C and 2M rotate in the same direction as the gears 23C and 23M at the same rotational speed. To do.

  Further, the gear 23Y connected to the gear 23C via the intermediate gear 24 rotates in the clockwise direction in FIG. 3, and thereby the image carrier 2Y rotates at the same rotational speed in the same direction as the gear 23Y. The rotational speed of the image carrier 2Y is also the same as the rotational speed of the image carriers 2C and 2M.

  Further, when the second carrier motor M2 is operated, the output gear 26 rotates counterclockwise, and the gear 23BK engaged with the gear 26 is rotationally driven together with the image carrier 2BK in the clockwise direction. The image carrier 2BK rotates at the same rotational speed in the same direction as the gear 23BK.

  On the other hand, as shown in FIG. 3, a timing pulley 27 arranged concentrically with the support roller 4 around which the intermediate transfer body 3 is wound is integrally connected, and the output of the pulley 27 and the drive motor DM is integrated. An endless timing belt 29 is wound around a timing pulley 28 fixed to the shaft. When the drive motor DM is activated, the timing pulley 28 rotates counterclockwise in FIG. 3, and the rotation is transmitted to the timing pulley 27 via the timing belt 29, whereby the support roller 4 is the same as the pulley 27. It rotates counterclockwise at the same rotational speed as the pulley 27. As a result, the intermediate transfer member 3 is rotationally driven in the direction of arrow A. As described above, the image carriers 2Y to 2BK and the intermediate transfer member 3 are rotationally driven, and the above-described image forming operation is performed.

  In FIG. 3, the reference numeral 30 indicates a control circuit for controlling the rotation of the motors M1, M2, and DM, and the reference numerals 31 and 32 indicate drive circuits for the motors M1, M2, and DM. is there.

  Here, at least one of the carrier motors M1 and M2 and the drive motor DM is a DC brushless motor. In the illustrated example, the carrier motors M1 and M2 are DC brushless motors, and the drive motor DM is a stepping motor. In this way, the carrier motors M1 and M2 are constituted by DC brushless motors, so that the power consumption is reduced and the generation of the operation noise is suppressed as compared with the case where these motors M1 and M2 are constituted by stepping motors. can do.

  Both the carrier motors M1 and M2 and the drive motor DM may be constituted by DC brushless motors, and the above-described effects can be further enhanced. Nevertheless, in the image forming apparatus of this example, the reason why the stepping motor is used as the drive motor DM is as follows.

  In general, the intermediate transfer member 3 can be driven to rotate with a small power, like the recording medium carrier 3A shown in FIG. Therefore, it is sufficient to use a small motor as the drive motor DM. However, at the present stage, a small and low-priced DC brushless motor is not commercially available. Therefore, if a small stepping motor is used as the drive motor DM, the manufacturing cost of the image forming apparatus can be reduced. This is the reason why a small stepping motor is used as the drive motor DM.

  By the way, by controlling the number of input pulses, the stepping motor can correctly control the rotational speed of the motor at the time of starting up, at the time of falling, and even at the time of steady rotation after completion of starting up. Is possible.

  On the other hand, as described above, it is difficult for the DC brushless motor to correctly control the rotational speed of the DC brushless motor at the time of starting and falling to a desired value. If a DC brushless motor is used as the motor for driving the intermediate transfer member, the linear velocity on the surface of the image carrier that rotates while contacting each other and the linear velocity on the surface of the intermediate transfer member are greatly different at the time of start-up and fall. As a result, it has been considered that significant rubbing occurs between the surface of the image carrier and the surface of the intermediate transfer member, and the wear of the surface is promoted.

  However, as a result of recent studies, if the rotational speed of a DC brushless motor is controlled in accordance with a predetermined speed curve, the DC brushless motor can be controlled not only during its steady rotation but also during the startup and shutdown of the motor. It became clear that the rotation speed of the brushless motor can be controlled to a desired value. That is, a DC brushless motor that rotates at a rotational speed corresponding to the number of clocks of the command clock signal has a command clock having a clock number corresponding to a predetermined speed curve at the time of startup, steady rotation, and startup. The rotation is controlled by a signal. The number of clocks means the number of clocks generated per unit time.

  More specifically, data of a predetermined speed curve is stored in the memory 33 shown in FIG. 3, and a command clock signal corresponding to the speed curve is output from the control circuit 30, from the DC brushless motor. The carrier motors M1 and M2 formed are rotated at a rotation speed corresponding to the number of clocks. The feedback signals FB1 and FB2 output from the carrier motors M and M2 are compared with the command clock signal to control the rotation speed of the carrier motors M1 and M2. The feedback signals FB1 and FB2 are pulse signals corresponding to the rotation speeds of the carrier motors M1 and M2. It is also possible to detect a feedback signal from the rotation of elements driven by the respective carrier motors M1, M2, for example, the image carriers 2Y to 2BK.

  In the illustrated image forming apparatus, since the drive motor DM is a stepping motor, the drive motor DM is such that the linear velocity on the surface of the image carriers 2Y to 2BK is substantially equal to the linear velocity on the surface of the intermediate transfer member 3. A command clock signal having the number of clocks synchronized with the rotation of the motor may be input to the carrier motors M1 and M2. When starting up the DC brushless motor, the number of clocks of the command clock signal is gradually increased substantially continuously or stepwise, and when the motor is lowered, the number of clocks is gradually decreased substantially continuously or stepwise. During steady rotation of the motor, the rotation of the DC brushless motor is controlled by a command clock signal having a substantially constant number of clocks. In this way, by rotating the motors M1, M2, and DM in synchronization, the intermediate transfer member 3 and the image carrier that rotate while being pressed against each other even when the motors M1, M2, and DM are raised and lowered. 2Y to 2BK can rotate while contacting at almost the same surface linear velocity, and the surface can be prevented from being worn at an early stage.

  As described above, the rotation of the DC brushless motor is controlled by the command clock signal having a gradually increasing number of clocks when starting up, and the rotation is controlled by the command clock signal having a substantially constant number of clocks during steady rotation. Sometimes the rotation is controlled by a command clock signal having a gradually decreasing number of clocks. FIG. 4 is an explanatory diagram showing simplified speed curves of a drive motor DM made of a stepping motor and first and second carrier motors M1 and M1 made of a DC brushless motor. The vertical axis represents the rotation of the motor. Numbers are shown, and the horizontal axis shows time. The number of pulses at the start S of the drive motor DM shown in FIG. 4A is 786 PPS. The rotational speeds of the first and second carrier motors M1 and M2 shown in FIGS. 4B and 4C are controlled in accordance with the speed curve of the stepping motor shown in FIG. . Here, the rotation speed (rpm) of S1 and S2 at the start of the carrier motors M1 and M2 is 550.7 rpm. This is because the motors M1 and M2 cannot be rotated correctly even when a clock having a rotation speed equal to or lower than 1/4 of the rotation speed during steady rotation is given at the start of each carrier motor M1 and M2. .

  The time required for starting and lowering the first and second carrier motors M1 and M2 is 1000 msec, which is the same as that for the drive motor DM. The DC brushless motor normally completes startup in about 400 msec when the motor drive shaft load is 0.8 kgfcm. However, as shown in FIG. 4, the startup time of the carrier motors M1 and M2 is increased. By setting the lowering time to 1000 msec, which is significantly longer than 400 msec, the speed curve can be brought close to the speed curve of the drive motor DM consisting of a stepping motor with high accuracy, and the image carriers 2Y to 2BK and the intermediate transfer body 3 The surface rubbing can be effectively suppressed.

  By controlling the number of command clock signals supplied to the carrier motors M1 and M2 as described above, the image carriers 2Y to 2BK can be used not only at the time of steady rotation but also at the time of startup and shutdown of each motor. Can be made substantially equal to the surface linear velocity of the intermediate transfer member 3.

  Incidentally, the lowering of the carrier motors M1 and M2 is started at a predetermined timing as follows, for example. That is, as shown in FIG. 3, a feeler FM is provided on a gear 23M for a color image carrier on which a chromatic toner image is formed, in this example, an image carrier 2M on which a magenta toner image is formed. A feeler FBK is also provided in a gear 23BK that drives a black image carrier 2BK on which a black toner image is formed, and first and second sensors 34M and 34BK that detect the feelers FM and FBK are respectively provided. It is fixedly arranged. These sensors are, for example, photosensors. On the other hand, FIG. 5 is a graph in which the vertical axis indicates the number of clocks of the command clock signal to the carrier motors M1 and M2 and the number of rotations of these motors M1 and M2, and the horizontal axis indicates time. The clock number of the command clock signal to the carrier motors M1 and M2 is shown, and the broken line shows the rotation speed of the carrier motors M1 and M2. As shown in FIG. 5, after completion of the image forming operation, the carrier motor M1, at the time T1 when the first and second sensors 34M, 34BK shown in FIG. 3 detect the feelers FM, FBK, respectively. Reduction of the number of clocks of the command clock signal to M2 is started. Along with this, the carrier motors M1 and M2 start to decelerate, and the rotational speed of the drive motor DM shown in FIG. 3 also starts to decrease at the same timing as shown in FIG. As a result, when the motors M1, M2 and DM are lowered, the surface linear velocity of each of the image carriers 2Y to 2BK and the surface linear velocity of the intermediate transfer member 3 are controlled to be substantially the same, and finally these are stopped. To do.

  Assuming that the above control is performed every time the motors M1, M2 and DM are lowered, each image carrier is stopped while the same peripheral surface portion of each image carrier 2Y to 2BK is in contact with the intermediate transfer member 3. Will do. In this case, the surface linear velocities of the image carriers 2Y to 2BK and the intermediate transfer member 3 do not completely coincide with each other. At the time of stopping, there is a risk that the intermediate transfer member 3 receives a large frictional force, so that it is worn out early or damaged early.

  Therefore, in the image forming apparatus of this example, as shown in FIG. 5, the input of the command clock signal to the DC brushless motor is stopped in the middle of the lowering of the carrier motors M1 and M2 made of the DC brushless motor. Is done. In the example shown in FIG. 5, the input of command clock signals to the motors M1 and M2 is stopped at the time T2 when the rotational speeds of the carrier motors M1 and M2 reach 400 rpm. At this time, since the moment of inertia of the DC brushless motor is large, even if the input of the command clock signal to the DC brushless motor is stopped, the DC brushless motor does not immediately stop rotating at the time T2. After the time T2, the rotational speed is gradually decreased, and the rotation is stopped at the time T3. Moreover, since the carrier motors M1 and M2 are not controlled by the command clock signal after the time point T2, the rotational speeds of the carrier motors M1 and M2 after the time point T2 are not constant, and FIG. It varies as shown by the dotted line. The stop timing of the carrier motors M1 and M2 varies within a range indicated by δ in FIG. Therefore, as described above, even when the lowering of the carrier motors M1 and M2 is started at a predetermined timing, the same peripheral surface portion of each of the image carriers 2Y to 2BK is always in contact with the surface of the intermediate transfer member 3. In this state, the image carrier does not stop. For this reason, it is possible to prevent the same peripheral surface portions of the image carriers 2Y to 2BK from being worn out at an early stage or from being damaged at an early stage.

  Further, as shown in FIG. 6, the drive motor DM formed of a stepping motor has its rotational speed decreased more than before after the time T2 when the rotational speeds of the carrier motors M1 and M2 reach 400 rpm. The surface linear velocity of 2Y to 2BK and the surface linear velocity of the intermediate transfer body 3 are controlled to be substantially equal.

  By the way, in the image forming apparatus shown in FIG. 1, the cleaning device 11 for cleaning the surface of the image carrier after the transfer of the toner image has the cleaning blade 11A, but when the image carrier is stopped, the cleaning blade 11 If untransferred toner or paper dust accumulates between the leading edge of 11A and the surface of the image carrier, it becomes difficult to remove the toner or paper dust when the image carrier rotates next time. The same applies to the intermediate transfer member 3 and the cleaning blade 22A of the cleaning device 22.

  Therefore, in the image forming apparatus of this example, after completion of the lowering of the carrier motors M1 and M2 and the drive motor DM, the carrier motors M1 and M2 and the drive motor DM are in the opposite directions to those in the normal image forming operation. It is configured to reverse at low speed. The image carriers 2Y to 2BK shown in FIG. 1 are reversed in the counterclockwise direction in FIG. 1, and the intermediate transfer member 3 has a surface linear velocity substantially equal to the surface linear velocity of each image carrier, and an arrow A It reverses in the opposite direction. When such a configuration is adopted, the toner accumulated in the leading edge portions of the cleaning blades 11A and 22A when the transfer of the toner image from the image carrier to the intermediate transfer member 3 is completed and the image carrier and the intermediate transfer member are stopped. The paper powder is dispersed on the peripheral surface of the image carrier and the peripheral surface of the intermediate transfer member 3 by reversing the image carrier and the intermediate transfer member 3. Therefore, when the image carrier and the intermediate transfer member 3 are rotated with the next start of the image forming operation, the toner and paper dust can be efficiently removed by the cleaning blades 11A and 22A.

  FIG. 7 is a diagram showing an example of the relationship between the number of clocks of the command clock signal input to the carrier motors M1 and M2 during the above-described operation and the number of rotations of these motors M1 and M2, and a thick solid line indicates the number of clocks. The broken line indicates the rotational speed. In this example, as in the case of FIG. 5, the lowering of the carrier motors M1 and M2 is started at the time T1, and the command clock signal is input to the carrier motors M1 and M2 composed of DC brushless motors at the time T2. Is stopped, and the carrier motors M1 and M2 are stopped at time T3. Next, command clock signals start to be input to the carrier motors M1 and M2 at time T4, the motors M1 and M2 start reverse rotation, and command clock signals are input to the carrier motors M1 and M2 at time T5. After that, both carrier motors M1 and M2 continue to rotate due to inertia and the number of rotations thereof is decreased, and the rotation stops at time T6. Thus, also in this case, the input of the command clock signal to the DC brushless motor is stopped before the carrier motors M1 and M2 made of the DC brushless motor stop the reverse rotation operation. In the state where the same peripheral surface portion is in contact with the surface of the intermediate transfer member 3, the intermediate transfer member does not stop, thereby preventing early wear or damage to the surface of the intermediate transfer member.

  Also in this case, the rotational speed of the drive motor DM comprising the stepping motor is such that the surface linear velocity of the intermediate transfer member 3 is substantially the same as the surface linear velocity of each image carrier. The rotation is controlled in synchronization with the motor.

  The example in which the drive motor DM for driving the intermediate transfer body 3 is composed of a stepping motor and the carrier motors M1 and M2 for driving the intermediate transfer bodies 2Y to 2BK are composed of DC brushless motors has been described. The configuration can also be applied when the drive motor DM is a DC brushless motor and the carrier motors M1 and M2 are stepping motors. In this case, the drive motor DM is controlled in the same manner as the carrier motor described above, and the carrier motors M1 and M2 are controlled in the same manner as the drive motor described above. When the carrier motors M1, M2 and the drive motor DM are both DC brushless motors, these motors M1, M2, DM are controlled in the same manner as the carrier motor described above.

  Each configuration described above can also be applied to a direct transfer type image forming apparatus as described above. That is, even in the case of the direct transfer method, at least one of a carrier motor that rotationally drives the image carrier and a drive motor that rotationally drives the recording medium carrier comprises a DC brushless motor. Rotation is controlled by a command clock signal with a gradually increasing number of clocks at startup, rotation control is performed by a command clock signal with a substantially constant number of clocks at steady rotation, and command clocks with a gradually decreasing number of clocks at the time of startup The rotation is controlled by a signal. In addition, during the fall, the input of the command clock signal to the DC brushless motor is stopped. Further, the carrier motor and the drive motor can be reversely rotated after the completion of the fall, and at that time, before the DC brushless motor stops the reverse rotation operation, the command clock signal to the DC brushless motor is It can also be configured to stop input.

1 is a schematic cross-sectional view illustrating an example of an intermediate transfer type image forming apparatus. 1 is a schematic sectional view illustrating an example of a direct transfer type image forming apparatus. FIG. 2 is an explanatory diagram illustrating a drive system for an image carrier and an intermediate transfer member of the image forming apparatus illustrated in FIG. 1. It is a figure which shows an example of the control aspect of the rotation speed of a drive motor and a support body motor. It is explanatory drawing which shows an example of the control aspect at the time of fall of the support body motor which consists of DC brushless motors. It is explanatory drawing which shows an example of the control aspect at the time of fall of the drive motor which consists of a stepping motor. It is explanatory drawing which shows an example of the control aspect at the time of fall of the support body motor which consists of DC brushless motors, and reverse rotation.

Explanation of symbols

2Y, 2C, 2M, 2BK Image carrier 3 Intermediate transfer member 3A Recording medium carrier DM Drive motor M1, M2 Carrier motor P Recording medium

Claims (5)

At least one image carrier on which a toner image is formed, an intermediate transfer member to which the toner image formed on the image carrier is transferred, a carrier motor for rotationally driving the image carrier, and the intermediate transfer member An image forming apparatus that obtains a recorded image by transferring the toner image transferred to the intermediate transfer member to a recording medium,
At least one of the carrier motor and the drive motor is composed of a DC brushless motor, and the DC brushless motor is rotationally controlled by a command clock signal having a gradually increasing number of clocks when starting up, and during steady rotation, The rotation is controlled by a command clock signal having a substantially constant number of clocks, and at the time of a fall, the rotation is controlled by a command clock signal having a gradually decreasing number of clocks, and during the fall, the command clock to the DC brushless motor An image forming apparatus, wherein input of a signal is stopped. At least one image carrier on which a toner image is formed, a recording medium carrier that carries and transports a recording medium onto which the toner image formed on the image carrier is transferred, and rotationally drives the image carrier. In an image forming apparatus having a carrier motor and a drive motor that rotationally drives the recording medium carrier,
At least one of the carrier motor and the drive motor is composed of a DC brushless motor, and the DC brushless motor is rotationally controlled by a command clock signal having a gradually increasing number of clocks when starting up, and during steady rotation, The rotation is controlled by a command clock signal having a substantially constant number of clocks, and at the time of a fall, the rotation is controlled by a command clock signal having a gradually decreasing number of clocks, and during the fall, the command clock to the DC brushless motor An image forming apparatus, wherein input of a signal is stopped. At least one image carrier on which a toner image is formed, an intermediate transfer member to which the toner image formed on the image carrier is transferred, a carrier motor for rotationally driving the image carrier, and the intermediate transfer member An image forming apparatus that obtains a recorded image by transferring the toner image transferred to the intermediate transfer member to a recording medium,
At least one of the carrier motor and the drive motor is composed of a DC brushless motor, and the DC brushless motor is rotationally controlled by a command clock signal having a gradually increasing number of clocks when starting up, and during steady rotation, The rotation is controlled by a command clock signal having a substantially constant number of clocks, and at the time of falling, the rotation is controlled by a command clock signal having a gradually decreasing clock number. After the completion of the falling, the carrier motor and the drive motor are reversed. An image forming apparatus. At least one image carrier on which a toner image is formed, a recording medium carrier that carries and transports a recording medium onto which the toner image formed on the image carrier is transferred, and rotationally drives the image carrier. In an image forming apparatus having a carrier motor and a drive motor that rotationally drives the recording medium carrier,
At least one of the carrier motor and the drive motor is composed of a DC brushless motor, and the DC brushless motor is rotationally controlled by a command clock signal having a gradually increasing number of clocks when starting up, and during steady rotation, The rotation is controlled by a command clock signal having a substantially constant number of clocks, and at the time of falling, the rotation is controlled by a command clock signal having a gradually decreasing clock number. After the completion of the falling, the carrier motor and the drive motor are reversed. An image forming apparatus. The image forming apparatus according to claim 3 or 4, wherein the input of the command clock signal to the DC brushless motor is stopped before the DC brushless motor stops the reverse rotation operation.

Images